En prensa  2022  2021  2020  2019  2018  2017  2016  2015 

Artículos publicados en: 2022

Finding evidence of an ancient platform through magnetometry in Huexotla, Central Mexico
Archaeological Prospection
Denisse L. Argote Espino 1 , Alberto Juárez Osnaya 1 , Alejandro García Serrano 2
1 Instituto Nacional de Antropología e Historia, Dirección de Estudios Arqueológicos
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Archaeological prospection, Central Mexico, geophysical survey, Huexotla, magnetometry, sacred precinct
Abstract: The archaeological zone of Huexotla, east of Mexico Basin, was part of the Acolhuacan lordship, associated to the Mexica domain in the Postclassical period. In this site, several structures have been partially explored, some of which are open to the public. Recent explorations led to the hypothesis that the structures of La Estancia, the Wall and the Community were part of a more complex space that formed the Sacred Precinct of the city. In order to test this postulate, magnetometry was conducted in three areas of the site. By processing Total Field and Vertical Gradient magnetic data, we were able to identify and understand the distribution of underground features like walls, floors and platforms, aiding in the determination of potential excavation areas. Processing the magnetic data with the application of the analytic signal operator allowed more information to be acquired for the recognition of structures of interest. The geophysical results were correlated with the outcomes of archaeological excavations in three structures, confirming the existence of architectural patterns that were not previously detected and supporting the thesis proposed for the ceremonial enclosure.
Dynamic stability of a parallel kinematic machine
Journal of Applied Research and Technology
Ricardo Yáñez Valdez 1 , Jorge A. Téllez Galván 1 , Marcelo López Parra 1 , Leonardo Urbiola Soto 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Chatter, cutting force, parallel kinematic machine, parallel mechanism, stability lobe diagram
Abstract: Machine tool chatter causes machining instability, surface roughness, and tool wear in metal cutting processes. A stability lobe diagram based on the theory of regenerative vibration is an effective tool to predict and control the chatter. This paper presents the advances in the mechanical design of a parallel kinematic machine tool. The features that make it ideal for machining tasks, and that make unique in its own way, are highlighted. In addition, the description of the progress of this work will be focused on the analysis of the stability limitation for machining systems to derive the stability lobe diagram with modal analysis of the spindle. A vibratory model is developed by adding cutting forces and including analytical equations for the depth of cut and for the cutting speeds, both depending on the frequency of vibration. A step-by-step procedure provides a stability lobe diagram. The results show that it is relatively easy to provide a relationship between depth of cut and spindle speed. In turn, it makes it easy to compare machining processes under different cutting parameters and conditions.
Fully Developed Temperature Profile for a Power-Law Laminar Nanofluid Flow in a Circular Duct Subject to a Uniform Heat Flux
Nanoscience and Technology: An International Journal
Jorge Armando Ojeda 1 , Federico Méndez Lavielle 2
1 Universidad de Colima, Facultad de Arquitectura y Diseño
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Nanofluid, power-law, circular duct, convection, laminar flow
Abstract: In the present work, we develop a theoretical analysis of a fully developed laminar nanofluid flow in a circular duct in a steady state subject to a uniform heat flux condition. The rheological behavior of the base fluid is described with the aid of the power-law model and the nanofluid properties such as dynamic viscosity, thermal conductivity, density, and specific heat are assumed as constants for a fixed value of the volumetric fraction. An analytical solution can be obtained based on the mean temperature concept. The Nusselt number was defined and depends on the dimensionless parameter of the viscosity and the power-law index. The main results reveal that for a maximum value of the volumetric fraction, the Nusselt number decreases drastically for shear-thinning base fluids, whereas for shear-thickening base fluids it tends asymptotically to a constant value. For an increase in the volumetric fraction value, the dimensionless velocity profiles have shown lower values for shear-thinning base fluids and the dimensionless temperature profiles present a greater difference between the dimensionless wall temperature and the nanofluid stream temperature.
Assessment of vulnerability to water shortage in the municipalities of Mexico City
Boletin de la Sociedad Geologica Mexicana
Alma R. Huerta Vergara 1 , Saúl Arciniega Esparza 2 , Adrián Pedrozo Acuña 3 , Arnoldo Matus Kramer 4 , Eduardo Vega López 5
1 Universidad Nacional Autónoma de México, Posgrado en Ciencias de la Sostenibilidad
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Comisión Nacional del Agua, Instituto Mexicano de Tecnología del Agua
4 ITHACA Environmental
5 Universidad Nacional Autónoma de México, Facultad de Economía

Keywords: Water vulnerability, water supply, exposure, adaptive capacity, urbanization, Mexico City.
Abstract: Water issues in Mexico City have been severe during the last years due to population increase, forcing external water sources to meet water demands. This research aims to evaluate the evolution of water vulnerability in the sixteen municipalities of Mexico City in the years 2005, 2010, and 2015. This vulnerability has increased in the last decades due to the combination of several problems such as lack of maintenance in the water infrastructure (eg. water leaks), aquifer overexploitation, uncontrolled city growth, rainwater and wastewater expelled from the basin without the intention of using it. For the vulnerability assessment we used a combination of indicators that respond to its three dimensions: 1). Exposure (urbanization, population, and economic units), 2). Sensitivity (reports of leaks, shortages, and poor water quality) and 3). Adaptive capacity (wastewater treatment, water availability, and GDP). The municipalities identified with very high vulnerability in the three years of study (2005, 2010, and 2015) were Iztapalapa, Gustavo A. Madero, and Tlalpan joined these during 2015. In contrast, those with the lowest vulnerability were Milpa Alta, Magdalena Contreras, and Cuajimalpa; the latter stepped down from having Low to Very Low vulnerability between 2005 and 2010-2015. Between these two classifications, we have the Municipalities that reveal high, moderate, and low vulnerability. The results highlight that all municipalities must prevent water leaks to achieve increasingly sustainable management of the liquid, especially Gustavo A. Madero, Iztapalapa, and Tlalpan. Suggesting that harmonized action among all of them will help accelerate goal achievement. Still, citizen action will play a leading role in maintaining care and water usage levels when promoted and encouraged adequately. At the end of the lecture, the reader would be able to discuss if a series of social elements (like the indicators proposed in this work) construct water vulnerability or depend on the quantity of water the cities receive. Also, they will understand their role in water management and have factors to evaluate vulnerability in other regions.
On Active Vibration Absorption in Motion Control of a Quadrotor UAV
Francisco Beltran Carbajal 1 , Hugo Yañez Badillo 2 , Rubén Tapia Olvera 3 , Antonio Favela Contreras 4 , Antonio Valderrabano González 5 , Irvin López García 1
1 Universidad Autónoma Metropolitana, Unidad Azcapotzalco
2 Tecnológico Nacional de México, Tecnológico de Estudios Superiores de Tianguistenco
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería
4 Tecnológico de Monterrey, Escuela de Ingeniería y Ciencias
5 Universidad Panamericana, Facultad de Ingeniería

Keywords: Vibration control, dynamic vibration absorbers, aerial vehicles; quadrotor, motion tracking control
Abstract: Conventional dynamic vibration absorbers are physical control devices designed to be coupled to flexible mechanical structures to be protected against undesirable forced vibrations. In this article, an approach to extend the capabilities of forced vibration suppression of the dynamic vibration absorbers into desired motion trajectory tracking control algorithms for a four-rotor unmanned aerial vehicle (UAV) is introduced. Nevertheless, additional physical control devices for mechanical vibration absorption are unnecessary in the proposed motion profile reference tracking control design perspective. A new dynamic control design approach for efficient tracking of desired motion profiles as well as for simultaneous active harmonic vibration absorption for a quadrotor helicopter is then proposed. In contrast to other control design methods, the presented motion tracking control scheme is based on the synthesis of multiple virtual (nonphysical) dynamic vibration absorbers. The mathematical structure of these physical mechanical devices, known as dynamic vibration absorbers, is properly exploited and extended for control synthesis for underactuated multiple-input multiple-output four-rotor nonlinear aerial dynamic systems. In this fashion, additional capabilities of active suppression of vibrating forces and torques can be achieved in specified motion directions on four-rotor helicopters. Moreover, since the dynamic vibration absorbers are designed to be virtual, these can be directly tuned for diverse operating conditions. In the present study, it is thus demonstrated that the mathematical structure of physical mechanical vibration absorbers can be extended for the design of active vibration control schemes for desired motion trajectory tracking tasks on four-rotor aerial vehicles subjected to adverse harmonic disturbances. The effectiveness of the presented novel design perspective of virtual dynamic vibration absorption schemes is proved by analytical and numerical results. Several operating case studies to stress the advantages to extend the undesirable vibration attenuation capabilities of the dynamic vibration absorbers into trajectory tracking control algorithms for nonlinear four-rotor helicopter systems are presented.
Effect of oils on the transmission properties of a terahertz photonic crystal
Applied Optics
Dahí Ludim Hernández Roa 1 , Yesenia A. García Jomaso 1 , Neil C. Bruce 1 , Jesús Garduño Mejía 1 , Oscar Pilloni 2 , Laura Oropeza Ramos 3 , Carlos Gerardo Treviño Palacios 4 , César L. Ordoñez Romero 5 , Armando M. Velázquez Benítez 1 , Naser Qureshi 1
1 Universidad Nacional Autónoma de México, Instituto de Ciencias Aplicadas y Tecnología
2 Universidad Nacional Autónoma de México, Instituto de Ingeniería
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería
4 Instituto Nacional de Astrofísica ?ptica y Electrónica
5 Universidad Nacional Autónoma de México, Instituto de Física

Abstract: The transmission properties of a photonic crystal immersed in several different oils have been characterized using terahertz time domain spectroscopy in the spectral range of 0.3??1.5 THz. As in previous works, oil samples can be distinguished using terahertz transmission measurements. When the same oils are introduced into a photonic crystal, we find that the effective refractive index of the photonic crystal is sensitive to the properties of the oils and shows differences not seen in bulk measurements. These effects are described in detail and have potential applications in both the sensing of very small volumes of oils and in the fine control of the refractive indices of photonic crystals.
Estudio numérico-experimental del campo de velocidades en un canal rectangular con curvatura compuesta y ancho variable en 2DH
Tecnología y Ciencias del Agua
José Luis Aragón Hernández 1 , Christian Alberto Caballero Coranguez 2 , Amado Abel Jiménez Castañeda 2 , Moisés Berezowsky Verduzco 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Instituto de Ingeniería

Keywords: Canal curvo, modelación numérica bidimensional horizontal, hidrodinámica, turbulencia, separación de flujo
Abstract: Se presenta un análisis de la aproximación obtenida con los sistemas de modelación matemática HEC-RAS, Iber y Telemac??Mascaret para el cálculo del campo de velocidades en un canal de sección rectangular con curvatura compuesta y ancho variable; en el canal se desarrollaron corrientes secundarias y separación de flujo; los tres modelos son de uso libre y se basan en la hipótesis de flujo bidimensional horizontal (2DH). Se utilizan las ecuaciones de Saint Venant en cada modelo matemático para calcular la hidrodinámica y la turbulencia. El campo de velocidades se determina a partir de mediciones físicas en un canal de laboratorio con un velocímetro Doppler acústico (Micro-ADV 16 MHz) y se compara con los campos de velocidades calculados con los sistemas de modelación matemática (HEC-RAS, Iber y Telemac??Mascaret). Se presenta un análisis de errores, con el objetivo de determinar el grado de aproximación obtenido con cada sistema de modelación, y la discusión de los factores y fenómenos observados en el laboratorio, esto permite tener conocimiento sobre la complejidad en la naturaleza de los flujos turbulentos en canales con curvaturas fuertes. Se encontró que los tres modelos, en general, tienen un comportamiento similar y aceptable, con una aproximación promedio superior al 93 %; en cambio, en un análisis por sección, en una zona de recirculación, se observó separación del flujo y alta turbulencia (procesos físicos de la dinámica del fluido que los modelos empleados no pueden reproducir de forma adecuada); la aproximación promedio disminuye hasta el 82.5 %.
Distributed generation in low-voltage DC systems by wind energy in the Baja California Peninsula, Mexico
Rodolfo Farías Miranda 1 , Nadia Maria Salgado Herrera 2 , Osvaldo Rodríguez Hernández 2 , Juan Ramón Rodríguez Rodríguez 3 , Miguel Robels 2 , Dante Ruiz Robles 4 , Vicente Venegas Rebollar 1
1 Tecnológico Nacional de México, Campus Morelia
2 Universidad Nacional Autónoma de México, Instituto de Energías Renovables
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería
4 Universidad Nacional Autónoma de México, Escuela Nacional de Estudios Superiores Unidad Juriquilla

Keywords: Distributed renewable energy access, Low-voltage direct current, Wind energy conversion system, Dual active bridge, Small signal model, Real-time validation
Abstract: Mexico's national electric grid comprises ten regional systems, with one isolated in the south of the Baja California Peninsula. In addition, providing electricity access remains a challenge in the country. Therefore, distributed renewable energy solutions are relevant to satisfy the electricity demand and promote grid development. Distributed renewable energy access (DREA) based on a wind energy conversion system integrated into low-voltage direct current (LVDC) networks is presented. The DREA is analysed and simulated under wind speed conditions measured and recorded for one year at Baja California Sur. A representative variability is applied to five type-4 wind turbines based on wind speed turbulence intensity analysis. The generated power is transferred through a bidirectional dual active bridge converter, controlled by a novel small-signal model using a single closed-loop proportional-integral control, owing to its modularity, power density, and ability to transfer power from LVDC to high-voltage direct current. The effectiveness and robustness of the proposed DREA are assessed via a complete mathematical model, corroborated by the simulation results in MATLAB-Simulink®, and validated by experimental results using the real-time simulator Opal-RT Technologies® and laboratory prototyping. The results indicate a DC-link voltage compensation and integration of a power capacity of 150 kW in the LVDC networks with an efficiency of 94%.
The Risk Atlas of Mexico City, Mexico: a tool for decision??making and disaster prevention
Natural Hazards
David Alberto Novelo Casanova 1 , Gerardo Suárez 1 , Enrique Cabral Cano 1 , Enrique Antonio Fernández Torres 1 , ?scar Arturo Fuentes Mariles 2 , Emre Havazli 3 , Miguel A. Jaimes 2 , Erika D. López Espinoza 4 , Ana Lillian Martín Del Pozzo 1 , Wendy V. Morales Barrera 5 , Hipólito L. Morales Rodríguez 2 , Amiel Nieto Torres 1 , Sergio R. Rodríguez Elizarrarás 5 , Darío Solano Rojas 6 , Víctor M. Velasco Herrera 1
1 Universidad Nacional Autónoma de México, Instituto de Geofísica
2 Universidad Nacional Autónoma de México, Instituto de Ingeniería
3 University of Miami, Rosenstiel School of Marine and Atmospheric Science
4 Universidad Nacional Autónoma de México, Centro de Ciencias de la Atmósfera
5 Universidad Nacional Autónoma de México, Instituto de Geología
6 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Mexico City, Hazard, Vulnerability, Risk, Risk Atlas, Disaster prevention, Mexico
Abstract: We present a Risk Atlas of Mexico City based on a Geographical Information System (RA-GIS). We identified the prevalent social risk to the more relevant hazards in Mexico City (CDMX): earthquakes, volcanic eruptions, floods, landslides, forest fires, and land subsidence. A total of 274 shape-file maps were generated in this project. Seismic hazard was estimated for return periods (RP) of 20, 125, 250, and 475 years. Three areas in central and northwestern CDMX were identified along the Younger Chichinautzin Monogenetic Volcanic Field with a high probability of forming a new volcano. Subsidence is concentrated to the east and southeast of CDMX, where subsidence rates are among the highest worldwide. Flooding events were estimated for RP of 2, 5, 10, 50, and 100 years, and most of them are concentrated in the central and northern sectors of the city. During the dry season (December??April), southern CDMX has very high probability of forest fire occurrence. There is high susceptibility of landslides on the west and southwest of the city. The goals of this RA-GIS are to provide a tool to the local and federal authorities and all organizations responsible for disaster prevention and mitigation to: (1) improve the knowledge of the potential physical and social impact of local hazards; (2) provide elements for disaster prevention, mitigation, preparedness, and response; (3) benefit decision-makers with robust risk data; (4) provide information for land-use planning; and (5) support further research to reduce the impact of disasters caused by natural phenomena.
Numerical-analytical solutions of the fractional point kinetic model with Caputo derivatives
Annals of Nuclear Energy
Marco A. Polo Labarrios 1 , Francisco Antonio Godínez Rojano 2 , Sergio Quezada García 3
1 Universidad Iberoamericana, Departamento de Física y Matermáticas
2 Universidad Nacional Autónoma de México, Instituto de Ingeniería
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Reactor dynamics, Fractional neutron point kinetic equations, Anomalous diffusion exponent, Caputo fractional derivative, Laplace Transform method, Chebyshev polynomials
Abstract: Novel solutions to the fractional neutron point kinetic equations in terms of Caputo derivatives are obtained for three different cases: 1) constant reactivity; 2) cold startup process of a Pressurized Water Reactor; and 3) start-up of a nuclear reactor. Numerical-analytical solutions for the first and second cases are achieved via Laplace transform technique with Talbot's method for the numerical inversion of the transformed equations. Analytical solutions for the third case are constructed by a collocation method using Chebyshev polynomials. The solutions predict inertia effects observed as a growth in neutron density up to reaching a peak and then a gradual decrease followed by a series of oscillations until reaching a steady state. This behavior, on the one hand, is accentuated as the fractional order decreases, and on the other hand, it is reconciled with the fact that the propagation speed of the neutrons within the reactor is finite.
A Novel GaN-Based Solid-State Circuit Breaker with Voltage Overshoot Suppression
IEEE Transactions on Industrial Electronics
Gabriel E. Mejía Ruiz 1 , Mario Roberto Arrieta Paternina 1 , Alejandro Zamora Méndez 2 , Julio Cesar Rosas Caro 3 , Guillermo Bolivar O. 4
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Michoacana de San Nicolás de Hidalgo, Facultad de Ingeniería Electrica
3 Universidad Panamericana, Facultad de Ingeniería
4 Corporación Universitaria Minuto de Dios, Facultad de Ingeniería

Keywords: Gallium nitride FETs, overcurrent protection, short-circuit protection, solid-state circuit breaker, voltage overshoot suppression, snubber circuit
Abstract: This paper proposes a novel ultra-Fast self-powered bidirectional solid-state circuit breaker (SSCB) with voltage overshoot suppression that uses gallium nitride (GaN) switches with very low conduction losses. This SSCB can be used in low and medium AC/DC networks for both short-circuit protection and overcurrent protection. An exhaustive methodology for RCD snubber design applied to SSCBs is provided. A comprehensive review of the technical literature is presented exhibiting that the proposed SSCB reduces conduction losses and detection time in comparison with other similar SSCBs. The performance features of the proposed SSCB are verified through the functional tests that are carried out employing a hardware-implemented prototype. Experimental results confirm that our proposal is able to detect and process the short-circuit failure in 282ns; the authors have not found any faster results in the literature.
Modeling a multi-layered blockchain framework for digital services that governments can implement
Journal of Intelligent & Fuzzy Systems
Fernando Rebollar 1 , Rocío Aldeco Pérez 2 , Marco A. Ramos 1
1 Universidad Autónoma del Estado de México, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Abstract: The general population increasingly uses digital services, meaning services which are delivered over the internet or an electronic network, and events such as pandemics have accelerated the need of using new digital services. Governments have also increased their number of digital services, however, these digital services still lack of sufficient information security, particularly integrity. Blockchain uses cryptographic techniques that allow decentralization and increase the integrity of the information it handles, but it still has disadvantages in terms of efficiency, making it incapable of implementing some digital services where a high rate of transactions are required. In order to increase its efficient, a multi-layer proposal based on blockchain is presented. It has four layers, where each layer specializes in a different type of information and uses properties of public blockchain and private blockchain. An statistical analysis is performed and the proposal is modeled showing that it maintains and even increases the integrity of the information while preserving the efficiency of transactions. Besides, the proposal can be flexible and adapt to different types of digital services. It also considers that voluntary nodes participate in the decentralization of information making it more secure, verifiable, transparent and reliable.
A System Identification-Based Modeling Framework of Bidirectional DC-DC Converters for Power Grids
Journal of Modern Power Systems and Clean Energy
Gabriel E. Mejía Ruiz 1 , Mario Roberto Arrieta Paternina 1 , Juan Ramón Rodríguez Rodríguez 1 , Juan Manuel Ramírez Arredondo 2 , Alejandro Zamora Méndez 3 , Guillermo Bolivar O. 4
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Instituto Politécnico Nacional, Centro de Investigación y de Estudios Avanzados
3 Universidad Michoacana de San Nicolás de Hidalgo, Facultad de Ingeniería Electrica
4 Corporación Universitaria Minuto de Dios, Facultad de Ingeniería

Keywords: Dual active bridge, eigensystem realization algorithm, generalized average model, power converters identification, power converter modeling
Abstract: This paper proposes a systematic identification framework founded on the eigensystem realization (ER) to precisely model electronic power converters. The proposed framework furnishes an energy-based optimal reduction method to precisely identify the power converters' dynamics from simulated or actual raw data measured at the converter's ports. This approach does not require any prior knowledge of the topology or converter internal parameters to derive the system modal information. The proposed method's accuracy and feasibility are exhaustively evaluated via simulations and practical tests on a software-simulated and hardware-implemented dual activebridge (DAB) converter under steady-state and transient conditions. After different comparisons against the Fourier series-based generalized average model, the switching model, and experimental measurements; the proposed method attains a root mean square error less than 1% concerning the actual raw data and a computational effort reduction of 8.6 times regarding the Fourier-based model.
An analytical Survey of Attack Scenario Parameters on the Techniques of Attack Mitigation in WSN
Wireless Personal Communications
Karen Ávila 1 , Paul Sanmartin 2 , Daladier Jabba Molinares 1 , Javier Gómez 3
1 Universidad del Norte
2 Universidad Simón Bolívar
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Security, WSN, Attacks in wireless sensor networks, IoT, Sybil, Wormhole, Selective forwarding, Sinkhole
Abstract: Wireless sensor networks (WSN) were cataloged as one of the most important emerging technologies of the last century and are considered the basis of the Internet of Things paradigm. However, an undeniable disadvantage of WSN is that the resources available for these types of networks, such as processing capacity, memory, and battery, are usually in short supply. This limitation in resources implements security mechanisms a difficult task. This work reviews 93 recent proposals in which different solutions were formulated for the different attacks in WSN in the network layer; in total, 139 references were considered. According to the literature, these attacks are mainly Sybil, wormhole, sinkhole, and selective forwarding. The main goal of this contribution is to present the evaluation metrics used in the state of the art to mitigate the Sybil, wormhole, sinkhole, and selective forwarding attacks and show the network topologies used in each of these proposals.
Continuous Sliding-Mode Output-Feedback Control for Stabilization of a Class of Underactuated Systems
IEEE Transactions on Automatic Control
Luis Ovalle 1 , Héctor Ríos 1 , Miguel Llama 1 , Leonid Fridman Golredich 2
1 Instituto Tecnológico de la Laguna, División de Estudios de Posgrado e Investigación
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Underactuated Systems, Output-Feedback Stabilization, Sliding-Mode control
Abstract: This paper presents a robust output-feedback control scheme for the stabilization of a class of non-linear underactuated mechanical systems in presence of coupled disturbances. The scheme is based on the so-called coupled sliding-mode control, i.e., no transformation into the normal form is required. The proposed output approach is composed of a Super-Twisting Controller and a High-Order Sliding-Mode Observer that robustly stabilize the origin of the system asymptotically. All of the results are proven by Lyapunov approaches. The proposed approach is validated by means of simulations and experimental results on a 4 degrees of freedom (DOF) underactuated crane.
Conditions of self-oscillations in generalized Persidskii systems
IEEE Transactions on Automatic Control
Jian Wang 1 , Jesús Mendoza Avila 2 , Denis Efimov 3 , Alexander Aleksandrov 4 , Leonid Fridman Golredich 2
1 Hangzhou Dianzi University, School of Automation
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Villenueve d'Ascq, Nord Europe Center
4 St. Petersburg State University, Faculty of Applied Mathematics

Keywords: Lyapunov methods, Oscillators, Stability analysis, Nonlinear dynamical systems, Trajectory, Robustness, Sliding mode control
Abstract: For a class of generalized Persidskii systems, whose dynamics are described by superposition of a linear part with multiple sector nonlinearities and exogenous perturbations, the conditions of practical stability, instability and oscillatory behavior in the sense of Yakubovich are established. For this purpose the conditions of local instability at the origin and global boundedness of solutions (practical input-to-state stability) are developed in the form of linear matrix inequalities. The proposed theory is applied to investigate robustness to unmodeled dynamics of nonlinear feedback controls in linear systems, and to determine the presence of oscillations in the models of neurons.
Adaptive sliding mode control with guaranteed performance based on monitoring and barrier functions
International Journal of Adaptive Control and Signal Processing
Víctor Hugo Pereira Rodrigues 1 , Liu Hsu 1 , Tiago Roux Oliveira 2 , Leonid Fridman Golredich 3
1 Federal University of Rio de Janeir, Department of Electrical Engineering
2 State University of Rio de Janeiro, Department of Electronics and Telecommunication Engineering
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: barrier function, monitoring function, norm observer and global tracking, output feedback, slidingmode control
Abstract: This paper proposes a new adaptive sliding mode control approach via output feedback for a class of nonlinear systems. The sliding-mode based controller can deal with parametric uncertainties and (un)matched disturbances with unknown upper bounds. Finite-time convergence of the tracking error to a predefined neighborhood of the origin of the closed-loop system is proved with guaranteed transient and steady-state performance. Basically, the novelty of our result lies on combining two important adaptation tools: monitoring and barrier functions. The adaptation process is divided into two stages, where an appropriate monitoring function allows for the specification of performance criteria during the transient phase, while the barrier function ultimately confines the tracking error within a small residual set in steady state. Simulation results including an application to Anti-lock Braking System illustrate the advantages of the proposed adaptive control strategy.
Unit commitment for multi-terminal VSC-connected AC systems including BESS facilities with energy time-shifting strategy
International Journal of Electrical Power & Energy Systems
Juan S. Guzmán Feria 1 , Luis Miguel Castro González 1 , José Horacio Tovar Hernández 2 , Néstor González Cabrera 1 , Guillermo Gutiérrez Alcaraz 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Instituto Tecnológico de Morelia, Posgrado en Ingeniería Eléctrica

Keywords: AC/DC networks, Battery energy storage systems, Mixed-integer linear programming, Shift factors, Unit commitment, VSC stations
Abstract: This paper proposes a novel modelling framework for Unit Commitment (UC) studies in multi-terminal VSC-connected AC grids. Battery Energy Storage Systems (BESS) are also considered with an energy time-shifting strategy whose charge and discharge modes are defined within the 24-hour planning horizon to promote a high competition level of energy trading in the power grid. The entire transmission network is formulated by shift factors and power losses of AC/DC branches and VSC units are included by piecewise linear functions. Thus, this novel UC approach retains a mixed-integer linear programming model with a high modelling versatility for arbitrary hybrid power grids accommodating any number of VSC stations and BESS units. The method described in this paper enables the optimal generation scheduling combined with the charge and discharge BESS modes. Its applicability is confirmed using two case studies, one featuring a four-terminal VSC-HVDC system with two BESS, and another characterised by seven VSC-connected AC systems with five BESS. To validate the proposed method, results are compared against those furnished by the classic UC representing the network through nodal equations. It is concluded that both methods favourably agree with each other as the errors are inferior to 2%. The usefulness of the proposed method to the real-time operation of AC/DC grids with BESS facilities is valuable.
Decentralized robust state estimation of multimachine power systems
International Journal of Electrical Power & Energy Systems
Natanael Vieyra Valencia 1 , Jesús Álvarez 2 , Paul Rolando Maya Ortíz 3
1 Universidad Nacional Autónoma de México, Posgrado en Ingeniería Eléctrica
2 Universidad Autónoma Metropolitana, Departamento de Procesos e Hidráulica
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Decentralized dynamic state estimation, Multimachine power system, Nonlinear interconnected system, Geometric estimator, Extended kalman filter, Synchronous generator
Abstract: The problem of online estimating the states of nonlinear (NL) Multimachine Power Systems (MPSs) is addressed within a constructive framework that combines notions and tools from electrical engineering and nonlinear estimation theory. First, the standard NL centralized model is realized as a set of linear decentralized robustly observable models, with augmented states that capture nonlinearity, parameter error, and intermachine state interaction. Then, based on the observability property of the decentralized model, a robustly convergent linear Geometric (Luenberger-like with integral action) estimator with simple tuning is constructed. With respect to previous MPS estimation techniques, the novelties are: (i) from a theoretical perspective, the comprehensiveness of the methodology, with model design, solvability in terms of observability, and robust functioning criteria coupled with a simple tuning scheme, and (ii) from an industrial applicability viewpoint, an online computation load considerably smaller than the one of the NL Extended Kalman Filter (EKF), and a tuning scheme appreciably simpler than the one of the NL sliding mode perturbation observer (SMPO). The proposed design methodology is illustrated through numerical simulation with a representative case example.
Doubly conjugate asymptotic analysis for the temperature and electric fields in a combined gel and stratum corneum system
International Journal of Thermal Sciences
Edgar Ali Ramos Gómez 1 , José Joaquín Lizardi Del Ángel 2 , Federico Méndez Lavielle 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Autónoma de la Ciudad de México, Colegio de Ciencia y Tecnología

Keywords: Skin electroporation, Joule heating effect, Conjugate double problem, Theoretical predictions
Abstract: In the present work, we study with the aid of regular perturbation techniques under what physical conditions, the thermal and electrical simultaneous interactions that occur between a gel and a stratum corneum of the skin, can operate in direct contact to avoid possible damage to the human skin. This doubly conjugate asymptotic analysis was formulated in terms of a pair of dimensionless conservation equations for the energy and electrical charge in each medium and it was solved by using asymptotic perturbation techniques, identifying a dimensionless parameter, denoted as , that measures the competition of electrical conductivities in the two medium affected by the electrical pulse. Because the electrical conductivity of the stratum corneum is very small, this parameter assumes usually very large values compared with unity and the theoretical predictions show the relevance that this parameter has on the increment of the temperature in both media. Therefore, we consider that this parameter can guide a positive performance of this class of medical treatments based on electric signals because delimits, under transient conditions, up to where the simultaneous presence of thermal and electrical effects control the reversible skin electroporation. The asymptotic analysis was validated with experimental data of other authors and a numerical solution of the full governing equations.
Large diurnal wind variability over the western and northern Campeche Bank caused by the low latitude of the Yucatan Peninsula and its interaction with Easterlies
Atmospheric Research
María Eugenia Allende Arandía 1 , Jorge Zavala Hidalgo 2 , Rosario Romero Centeno 2 , Gemma L. Franklin 1 , Nidia Taylor Espinosa 2 , María Elena Osorio Tai 3
1 Universidad Nacional Autónoma de México, Instituto de Ingeniería
2 Universidad Nacional Autónoma de México, Instituto de Ciencias de la Atmósfera y Cambio Climático
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Large wind variability, Easterlies, Diurnal signal, Campeche Bank, Breeze extension, Breeze circulation cell
Abstract: The northern and western Campeche Bank have an intense diurnal cycle with a significant offshore extension. Wind observations along the coast of the southern Gulf of Mexico, confirm that the breeze phenomenon occurs with great intensity and extension. To analyze this mesoscale phenomenon, a numerical simulation of high spatial-temporal resolution was performed using the Weather Research and Forecasting model (WRF). Diurnal wind components were fitted to a sinusoidal function, and the resulting parameters were used to obtain monthly elliptical hodographs. The greatest amplitude of the diurnal signal occurred in April, at the cays and islands, whereas in the continental region the amplitude of the diurnal component was greatest on the northern and western coasts of the Yucatan Peninsula. The large amplitude of this diurnal wind component is determined by a combination of different factors: the latitude, the geographical configuration of the southern Gulf of Mexico, the orography, the dominant easterly winds, and the development of an intense thermal contrast. Regarding the analysis of the wind components, a strong asymmetry was found between the sea-breeze and the land-breeze. Sea breeze winds are intense over the ocean, exceeding 10 ms??1 at 100 km from the coastline. The friction effect over land is also perceptible, reducing the wind magnitude by more than 6 ms??1. The formation of a breeze cell circulation with opposing easterly winds creates a strong convergence zone. It was found that the Yucatan Peninsula location, due to its relatively low latitude and altitude, in combination with the predominant easterly winds, favors these dynamics.
Numerical simulation data and FORTRAN code to compare the stress response of two transversely isotropic hyperelastic models in ABAQUS
Data in Brief
Carlos Castillo Méndez 1 , Armando Ortiz Prado 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Finite element, UMAT subroutine, Hyperelasticity, Anisotropic invariants
Abstract: We present the numerical simulation data obtained by implementing a user material subroutine (UMAT) in the finite element commercial package ABAQUS. The simulation data correspond to the stress response of two transversely isotropic hyperelastic models on homogeneous and non-homogeneous deformations. First model is proposed in the co-submitted article [1] and depends on both anisotropic invariants ( and ) to describe the fiber reinforcement. The second model is the Holzapfel-Gaser-Ogden (HGO) model described in [2], that only depends on the anisotropic invariant . Since the first model is not found in the ABAQUS material library, we present a FORTRAN code for a UMAT subroutine. In addition, we introduce in detail the steps to implement the material models using the attached files in ABAQUS.
Determination of optimal electrochemical parameters to reproduce copper artistic patina on quaternary alloys
Materials Letters
Jesús Rafael González Parra 1 , Alba Covelo Villar 1 , Miguel Ángel Hernández Gallegos 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Patina, Electrochemical impedance spectroscopy, Bronze, Corrosion, Surfaces
Abstract: A copper patina provides both a pleasing aesthetical appearance and corrosion protection to artistic artworks so the electrochemical features for restoring metallic artifacts need to be studied. In this study, the potentiodynamic scan rate consisting of 0.5, 1, 3, 5, 7 10 mV/s to develop artistic patinas on a quaternary copper alloy was studied. The results obtained by SEM/EDS indicate that the patina on the surface is a porous layer mainly composed of copper/chloride corrosion products. The X-Ray analysis identified the formation of nantokites and atacamites depending on the scan rate that was applied. The morphology appearance shows a greenish patina and a more porous structure for scan rates lower than 5 mV/s. Polarization curves and electrochemical impedance spectroscopy determined that the corrosion protection increases at lower scan rates due to higher barrier properties of the patina layer.
An asymptotic and algebraic estimation method of harmonics
Electric Power Systems Research
Francisco Beltran Carbajal 1 , Rubén Tapia Olvera 2 , Antonio Valderrabano González 3 , Hugo Yáñez Badillo 4
1 Universidad Autónoma Metropolitana, Unidad Azcapotzalco
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Universidad Panamericana, Facultad de Ingeniería
4 Tecnológico de Estudios Superiores de Tianguistenco, Departamento de Investigación

Keywords: Harmonic distortion, Harmonic estimation, On-line parameter estimation, Algebraic identification
Abstract: A new on-line and time-domain parameter estimation approach of harmonics in electric power system signals is introduced. The developed parametrical identification perspective is based on asymptotic and algebraic estimation techniques, and vibrating signal modeling. Specified harmonics and DC offset component of some measured distorted oscillating signal are reconstructed asymptotically. In this fashion, closed-form explicit formulae to compute into a small window of time, algebraically, on-line and in time-domain, the parameters of amplitude, frequency and phase of harmonics are then derived. Analytical, numerical and experimental results of six and twelve pulses converter reveal the effectiveness and efficiency of the proposed selective estimation approach for harmonics and corresponding parameters of measured oscillating electric signals into an operating frequency bandwidth. Among others, synchronization of power converters or switches to grid without the use of filtering can be achieved with this strategy.
Thermodiffusive effect on the local Debye-length in an electroosmotic flow of a viscoelastic fluid in a slit microchannel
International Journal of Heat and Mass Transfer
A. Hernández 1 , José Carlos Arcos Hernández 1 , J. Martínez Trinidad 1 , Oscar Eladio Bautista Godínez 1 , Salvador Sánchez 2 , Federico Méndez Lavielle 3
1 Instituto Politécnico Nacional, Escuela Superior de Ingeniería Mecánica y Eléctrica
2 Universidad Nacional Autónoma de México, Instituto de Ciencias Aplicadas y Tecnología
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Local Debye-length, Thermodiffusion, Viscoelastic fluid, Electroosmotic flow, Soret effect
Abstract: This work theoretically studies the influence of the thermodiffusive effect on the local Debye length thickness in a purely electroosmotic flow in a parallel flat plate microchannel. An imposed electric field between the ends of the microchannel interacts with an ionized viscoelastic fluid causing Joule heating, which induces a temperature gradients along the microchannel, affecting the fluid??s physical properties, and in a notable manner, the ionic distribution into the electric double layer (EDL), resulting in thermodiffusion. Consequently, an induced pressure field counterbalances the axial variation of the plug-like electroosmotic velocity to maintain the fluid mass continuity. Also, the ionic distribution and electrical potential based on the non-isothermal Poisson-Boltzmann equation are modified. To estimate the local Debye length thickness, the coupled set of the Poisson-Boltzmann, momentum, and energy equations are solved numerically in the limit of the lubrication approximation theory (LAT). Our results indicate that the thermodiffusion has an important effect on the thickness of the local Debye-length, particularly in the warm zone of the fluid. Besides, the ionic response to thermal fields is given by a positive Soret coefficient, which indicates that the ionic particles move from warm to cold regions in the fluid, giving place to a thinner Debye length and lower ionic concentration around the warming zone; this migration of ions confirms that the dimensionless mass-flow rate is affected with the Soret coefficient compared with the non-thermodiffusion case.
Neutronic and thermohydraulic analysis of a SMR-PWR core with TRISO fuel based on a 2n multifactorial analysis
Nuclear Engineering and Design
Jesús Rosales 1 , Juan Luis François Lacouture 1 , Annie Ortiz 2 , Carlos García 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad de La Habana, Insituto Superior de Tecnologías y Ciencias Aplicadas

Keywords: SMR, TRISO, Packing fraction, Serpent, Ansys CFX
Abstract: The study of small modular reactors has generated increasing interest in recent years in the international scientific community. Their applications and versatility make them an attractive option among candidates considered in generation III+ and IV. Additionally, the modeling and study of TRISO fuel in PWR-type modular reactors constitutes a challenge and opens new possibilities for its use. In this work, new studies are carried out on the conceptual design of SMR with TRISO fuel. Through a multifactorial statistical analysis, the influence of the enrichment, the packing fraction, and the kernel size on the multiplicative properties of the TRISO fuel is quantitatively evaluated. Once done, a core configuration is established with the aim that it can remain critical for approximately four years, without the need of refueling. Based on two models, one neutronic in Serpent and one thermohydraulic in Ansys CFX, the performance of the designed reactor is studied, and the results obtained when using a packing matrix composed of graphite and other composed of SiC are compared. To carry out this simulation, power correlations as a function of the height of the fuel assembly and temperature-dependent correlations are obtained for the fuel zone that is composed of the TRISO particles dispersed in the packing matrices. Temperature distributions in the fuel, clad, gap and coolant for the critical assembly were obtained.
Role of anisotropic invariants in numerically modeling soft biological tissues as transversely isotropic hyperelastic materials: A comparative study
International Journal of Non-Linear Mechanics
Carlos Castillo Méndez 1 , Armando Ortiz Prado 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Anisotropic invariants, Soft tissues, Hyperelasticity, Transversely isotropic, Finite element
Abstract: Fiber-reinforced biological soft tissues are often modeled as anisotropic hyperelastic materials. Four strain invariants can be used to define a strain energy function for soft tissues reinforced with a single fiber family: two isotropic invariants and two anisotropic invariants . Invariant is often omitted in the strain energy functions to simplify the problem mathematically. In this study, the implications of using only or the use of both anisotropic invariants in the numerical modeling of soft tissues were analyzed. A simple modification to the Holzapfel??Gasser??Ogden (HGO) model is proposed by adding a term that contains invariant . Material parameters were calculated by fitting the models with experimental data of uniaxial traction in the tibialis anterior tendon tissue of rats. General analytical solutions for the simple load scenarios were obtained. Such solutions are taken as a reference point to measure the precision of the numerical results obtained in the finite element simulations. The main differences between the models were observed in the shear behavior. The proposed model predicts three different shear responses (two responses with fiber reinforcement and one isotropic response), while the HGO model predicts two equal isotropic responses and only one with fiber reinforcement. Two sets of simple shear experimental data on a fiber-reinforced elastomer material were used to verify the shear stress prediction of the models. The experimental data show that the three shear behaviors are different; thus, the HGO model offers a limited description of the shear behavior. Furthermore, analytical solutions and experimental data suggest that invariant is related to the elastic energy of the fibers when the material is subjected to shear in a direction parallel to the fibers. The models for non-homogeneous deformations were also compared. For this comparison, an irregular geometry was implemented in ABAQUS, and the traction and shear conditions were simulated by changing the fiber inclination. The most critical difference was found when the shear was parallel to the direction of the fiber and the minor difference when the fiber was at 45° to the load force.
Gamma-ray flux measurement and geotechnical studies at the selected site for the LABChico underground laboratory
The European Physical Journal Plus
Alexis Aguilar Arevalo 1 , Xavier Bertou 2 , Carlos Canet Miquel 3 , Miguel Angel Cruz Pérez 4 , Alexander Deisting 5 , Adriana Dias 5 , Juan Carlos D' Olivo 1 , Francisco Favela Pérez 1 , Estela A. Garcés 6 , E. González García 7 , Adiv González Muñoz 6 , Jaime Octavio Guerra Pulido 7 , Javier Mancera Alejandrez 7 , Daniel José Marín Lámbarri 6 , A. M. Martínez Mendoza 6 , Mauricio Martínez Montero 1 , Jocelyn Monroe 5 , Sean Paling 8 , Simon Peeters 9 , Paul Scovell 8 , Cenk Türko?lu 9 , I. G. Vallejo Castillo 7 , Eric Vázquez Jáuregui 6 , Joseph Walding 5
1 Universidad Nacional Autónoma de México, Instituto de Ciencias Nucleares
2 Centro Atómico Bariloche
3 Universidad Nacional Autónoma de México, Centro de Ciencias de la Atmósfera
4 Universidad Nacional Autónoma de México, Programa de Posgrado en Ciencias de la Tierra
5 University of London, Royal Holloway
6 Universidad Nacional Autónoma de México, Instituto de Física
7 Universidad Nacional Autónoma de México, Facultad de Ingeniería
8 Boulby Mine, Boulby Underground Laboratory
9 University of Sussex, Department of Physics and Astronomy

Abstract: The γ-ray flux inside La Quaalude mine, the selected site for the construction of the underground laboratory LABChico in Mexico, is reported for energies below 3 MeV. Data were recorded with a 0.669 kg thallium-activated sodium iodide (NaI) crystal detector deployed for 3.6 hr. The detector response was calculated via Monte Carlo simulations with GEANT4 and validated against point-like calibration sources, and the γ-ray spectrum was extracted using an unfolding technique. The γ-ray flux above 250 keV and below 3 MeV is 0.1768 γ/cm2/s. The two most intense γ-rays in the natural radioactive background, 40K and 208Tl, were identified. The flux measured for these isotopes is 0.0363 ± 0.0020 γ/cm2/s and 0.0016 ± 0.0005 γ/cm2/s, respectively. A γ-ray spectrometry analysis of rock samples showed 674.0 ± 2.0 Bq/kg, 24.0 ± 0.1 Bq/kg, and 17.7 ± 0.2 Bq/kg, of 40K, 232Th, and 238U, respectively. These results are compared with deep underground facilities such as SURF, SNOLAB, Boulby, Modane, and Gran Sasso, with differences observed mainly due to the rock composition. Geotechnical studies of the mine and its rock composition are also reported.
Electroosmotic flow in a thin microchannel under the influence of some thermal electrokinetic effects
Journal of the Brazilian Society of Mechanical Sciences and Engineering
Edgar Ali Ramos Gómez 1 , César Treviño 2 , Federico Méndez Lavielle 1 , José Joaquín Lizardi Del Ángel 3
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Facultad de Ciencias
3 Universidad Autónoma de la Ciudad de México, Colegio de Ciencia y Tecnología

Keywords: Electrokinetics effects, Joule heating, Variable properties
Abstract: In this work, we predict for a laminar electroosmotic flow in a thin microchannel, the impact that has some non-isothermal electrokinetics effects when the Debye length and the fluid viscosity are both temperature-dependent functions. The motion of the electroosmotic flow is caused with the aid of an external and uniform electric field. The presence of this electric source over the fluid pattern translates into continuous action of the Joule heating, causing a non-isothermal electroosmotic flow. The influence of the above non-isothermal effects conducts to include important temperature gradients in the momentum equations such that induced pressure gradients along the microchannel are established which in turn changes drastically the velocity field. Relevant variables such as the dimensionless volumetric flow rate show different values in comparison with the purely isothermal electroosmotic flow.
Risk assessment of land subsidence and associated faulting in Mexico City using InSAR
Natural Hazards
Enrique Antonio Fernández Torres 1 , Enrique Cabral Cano 1 , David Alberto Novelo Casanova 1 , Darío Solano Rojas 2 , Emre Havazli 3 , Luis Salazar Tlaczani 1
1 Universidad Nacional Autónoma de México, Instituto de Geofísica
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 California Institute of Technology, Jet Propulsion Laboratory

Keywords: Land subsidence, InSAR, Risk assessment, Socioeconomic vulnerability, Surface faults, México
Abstract: Land subsidence and associated faulting have affected Mexico City (CDMX), Mexico, for more than 100 years. However, despite the extensive research on land subsidence in CDMX, very few investigations focus on characterizing its socioeconomic risk due to land subsidence. In this article, we present Mexico City??s socioeconomic risk map due to land subsidence and associated faulting, combining our data from a land subsidence characterization based on InSAR processing with a socioeconomic vulnerability assessment. Our results show two high subsidence velocity areas. The largest area is located in the northeast sector of CDMX and the neighboring State of Mexico suburbs, where the maximum subsidence rate reaches up to 423 mm/year. We also found that 40.4% of the total cumulative length of land subsidence-associated faults correspond to high 15.6% and very high 24.8% classes of subsidence horizontal gradient. Our results demonstrate a spatial correlation between areas of high subsidence rate and horizontal gradient with high and very high socioeconomic vulnerability zones. Under this scenario, 9% of the urbanized areas, about 70.7 km2, are exposed to high and very high land subsidence socioeconomic risk where approximately 12.6% of the CDMX population lives.
Arsenic and lead in the soils of San Antonio??El Triunfo mining district, B.C.S., México: a human health risk assessment
Environmental Earth Sciences
Ernesto Hernández Mendiola 1 , Francisco Martín Romero 1 , Diana Meza Figueroa 2 , Griselda Berenice Hernández Cruz 3 , L. Gerardo Martínez Jardines 1 , Violeta Espino Ortega 3
1 Universidad Nacional Autónoma de México, Instituto de Geología
2 Universidad Nacional Autónoma de México, Laboratorio Nacional de Geoquímica y Mineralogía
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Bioaccessibility, Geoavailability, Solid particles, Fine soil fraction, Carcinogenic and non-carcinogenic risks, Arsenic, Lead
Abstract: The MD SA-ET in Baja California Sur, Mexico, had over 200  years of intermittent mining activities. Studies in the area have reported Pb, Cd, Zn, and As dispersion from waste to soils, sediments, and groundwater, suggesting that even after all this time, biogeochemical processes have not completely mitigated the risk. Furthermore, evaluating how the fine particles in soils could control the human health risk by geochemical and mineralogical mechanisms has not yet been initiated. This study discusses the geoavailability and bioaccessibility based on the environmental and human health risks in an arid environment where the population is currently exposed to abandoned mining waste. The results show that urban soils (US) and stream sediments (SS) have very high total concentrations of As and Pb, but with low geoavailability, suggesting low environmental risk. Despite this, bioaccessibilities up to 100% were observed for As and Pb in the US, suggesting high risks for the inhabitants of San Antonio and El Triunfo towns. The blood Pb levels and the carcinogenic risk for As exposure assessed here show maximum values of 115.77 µgPb  dL??1 and 85 ? 10??4, respectively, which exceed the recommended limits according to USEPA. Chemical identification of microparticles (< 250  μm) by SEM??EDS shows bright metal solids with high iron content, commonly interpreted as iron oxide. However, it was possible to identify microparticles (< 5  μm) rich in Fe associated with ultrafine particles (< 1  μm) with high Pb and As contents. We conclude that differences between the geoavailability and bioaccessibility for soils and sediments in this study indicate that the solid microphases (possible Fe-oxides and oxyhydroxides) present in the fine soil fraction from MD SA-ET may control the geoavailability and bioavailability of As and Pb, as well as the environmental and human health risks.
Remote sensing-aided rainfall??runoff modeling in the tropics of Costa Rica
Hydrology and Earth System Sciences
Saúl Arciniega Esparza 1 , Christian Birkel 2 , Andrés Chavarría Palma 2 , Berit Arheimer 3 , José Agustín Breña Naranjo 4
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 University of Costa Rica, Department of Geography and Water and Global Change Observatory
3 Swedish Meteorological and Hydrological Institute
4 Comisión Nacional del Agua, Instituto Mexicano de Tecnología del Agua

Abstract: Streamflow simulation across the tropics is limited by the lack of data to calibrate and validate large-scale hydrological models. Here, we applied the process-based, conceptual HYPE (Hydrological Predictions for the Environment) model to quantitatively assess Costa Rica's water resources at a national scale. Data scarcity was compensated for by using adjusted global topography and remotely sensed climate products to force, calibrate, and independently evaluate the model. We used a global temperature product and bias-corrected precipitation from Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) as model forcings. Daily streamflow from 13 gauges for the period 1990??2003 and monthly Moderate Resolution Imaging Spectroradiometer (MODIS) potential evapotranspiration (PET) and actual evapotranspiration (AET) for the period 2000??2014 were used to calibrate and evaluate the model applying four different model configurations (M1, M2, M3, M4). The calibration consisted of step-wise parameter constraints preserving the best parameter sets from previous simulations in an attempt to balance the variable data availability and time periods. The model configurations were independently evaluated using hydrological signatures such as the baseflow index, runoff coefficient, and aridity index, among others. Results suggested that a two-step calibration using monthly and daily streamflow (M2) was a better option than calibrating only with daily streamflow (M1), with similar mean Kling??Gupta efficiency (KGE?????0.53) for daily streamflow time series, but with improvements to reproduce the flow duration curves, with a median root mean squared error (RMSE) of 0.42 for M2 and a median RMSE of 1.15 for M1. Additionally, including AET (M3 and M4) in the calibration statistically improved the simulated water balance and better matched hydrological signatures, with a mean KGE of 0.49 for KGE in M3??M4, in comparison to M1??M2 with mean KGE??
Flow patterns of multiple axial-radial impellers for potential use in aerated stirred tanks
Chemical Engineering & Technology
David Posadas Navarro 1 , Carlos Alberto Palacios Morales 2 , Abel Blancas Cabrera 3 , Mauricio A. Trujillo Roldán 4 , Martín Salinas Vázquez 4 , Gabriel Ascanio 1
1 Universidad Nacional Autónoma de México, Instituto de Ciencias Aplicadas y Tecnología
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Universidad Nacional Autónoma de México, Instituto de Investigaciones Biomédicas
4 Universidad Nacional Autónoma de México, Instituto de Ingeniería

Keywords: Aerated stirred tank, axial-radial impeller, flow fields, fluid mechanics, PIV
Abstract: The hydrodynamics of a stirred tank equipped with multiple hybrid impellers (ARIs) has been experimentally characterized. They were coaxially placed to agitate a viscous Newtonian fluid under gassed conditions. Experiments were performed using the particle image velocimetry technique (PIV) and flow fields were reported in terms of the velocity magnitude, vertical currents, turbulent intensity, and strain rates. For comparison purposes, impellers providing radial flow (Rushton turbines) and axial flow (pitched blade turbines) were also tested. Results show that hybrid impellers provided a uniform flow distribution throughout the tank at moderate strain rates, which make them an attractive alternative for fermentation processes with shear-sensitive cultures and viscous liquids.
A Hamiltonian control approach for electric microgrids with dynamic power flow solution
Sofía Ávila Becerril 1 , Gerardo Espinosa Pérez 1 , Juan E. Machado 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 University of Groningen, Faculty of Science and Engineering

Keywords: Microgrid control, Passivity-based control, Hamiltonian systems
Abstract: In this paper, a control scheme for islanded electric microgrids is proposed. Exhibiting a dynamical structure and based on passivity, cascaded systems, and input-to-state stability arguments, the asymptotic stability properties of the closed-loop system are formally established to guarantee that voltage regulation and a power network balance are achieved. In contrast to other approaches, the controller design considers the differential??algebraic structure of the system obtained by the explicit inclusion of the network??s dynamic, the existence of both a grid-forming and grid-following nodes, and the highly nonlinear structure of the power balance equations.
Implications of unconventional oil and gas development on groundwater resources
Current Opinion in Environmental Science & Health
Saúl Arciniega Esparza 1 , Antonio Hernández Espriú 1 , Michael Young 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 The University of Texas at Austin, Jackson School of Geosciences

Keywords: Shale gas, Hydraulic fracturing, Groundwater, Water stress
Abstract: An intensification of water use per well for hydraulic fracturing (HF) has been observed in different regions of the U.S. during the last 20 years. Water-scarce regions undergoing the most intensive unconventional reservoir development also face water and wastewater management issues to support HF activities. In this review, we analyze the current state of water use related to HF, focusing on the implications of shale gas development on groundwater resources within water-limited regions in the U.S. Recent concerns of HF water management highlight the importance of wastewater treatment and reuse to decrease the dependence on freshwater sources and to minimize the hazards of wastewater disposal.
Non-isothermal effects in the slippage condition and absolute viscosity for an electroosmotic flow
European Journal of Mechanics - B/Fluids
Edgar Ali Ramos Gómez 1 , César Treviño 2 , José Joaquín Lizardi Del Ángel 3 , Federico Méndez Lavielle 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Facultad de Ciencias
3 Universidad Autónoma de la Ciudad de México, Colegio de Ciencia y Tecnología

Keywords: Electroosmotic flow, Joule effect, Non-isothermal effects, Slip condition
Abstract: In this work, we have developed a novel asymptotic analysis using perturbation techniques for an electroosmotic flow in a rectangular microchannel, considering that the absolute viscosity is a function of temperature; a situation that affects also the slip condition at the walls of the microchannel, . The physical importance of this temperature dependence is based on the presence of the applied external electric field on the electrolyte solution, which originates the Joule heating effect that disturbances the isothermal hydrodynamic behavior. The above leads to a significant increase of the volumetric flow rate for this non-isothermal condition in comparison to the purely isothermal electroosmotic flow. This result is simultaneously controlled by the heat losses to the ambient and the slip effect: the lower the presence of the heat dissipation mechanism on the outer walls of the microchannel and the higher the sliding condition, the higher the values of the volumetric flow rate. The above trend differs substantially from the isothermal case and finds its justification in the recognition of the presence of the Joule heating effect that induces significant longitudinal and transverse temperature gradients along the microchannel. Considering the proper limitations of the asymptotic analysis, we compare the present asymptotic results with a full numerical solution of the governing equations, which are composed of the continuity, momentum, and energy equations for the electrolyte flow, together with the Poisson??Boltzmann.
A new telesurgery generation supported by 5G technology: benefits and future trends
Procedia Computer Science
Emmanuel Mendoza Navarro 1 , Adrielly Nahomee Ramos Álvarez 1 , Francisca Irene Soler Anguiano 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Telesurgery, 5G, Robotic System
Abstract: Telesurgery is a medical practice that has been developed for the last two decades. The idea is very simple, a highly trained surgeon performs a surgical intervention on a patient while being away from the operating room. The surgery execution is done through two principal equipment: a robotic one installed in the operating room and a remote station from which the surgeon controls the robot. The communication between both parties is established through a specialized internet connection. The research and development of these remote surgery systems have been revolutionizing the medicine praxis due to its multiple benefits. During the last years, these systems have substantially improved many of their main limiting aspects, furthermore, the incorporation of 5G technology is a booster in telesurgery possibilities. Nonetheless, telesurgery benefits are not available for everyone because telesurgery requires high-cost equipment incorporation, specialized facilities and staff. This is the main reason for which health systems in developing countries dismiss its application. As a result, this paper explains telesurgery with a brief historical review and future trends of this technology and also presents a value proposition that may facilitate telesurgery practice in remote medical units. Focusing on the implementations and benefits that 5G technology can provide to the development of telesurgery as a development opportunity medical praxis linked to the accelerated growth of high-speed networks in the connected world.
Cognitive evaluation of capital structure: Effect of cognitive factors on the debt ratio in Mexican construction industry
Contaduría y Administración
José Anselmo Pérez Reyes 1 , Ananya Rajagopal 2 , Montserrat Reyna Miranda 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Anáhuac, Facultad de Economía y Negocios

Keywords: capital structure, cognitive finance, cost of capital, debt ratio, decision-making process, leverage
Abstract: This study analyzes the impact of the construct of the capital structure on the observed debt ratio of an organization, in terms of the new approach of Cognitive Finance (Pérez et al, 2019) within the construction industry in Mexico. Using exploratory factor analysis and structural equation model (SEM), latent variables of capital structure from the responses to an instrument applied to 154 CFOs of construction companies in Mexico. Then a non-parametric correlation test is performed, to measure the impact of each latent variable on the observed debt-to-equity ratio. The study finds that concerns about the political environment, the trust from clients and suppliers, among other variables, have an impact in the decision-making process of construction CFOs related to the debt-to-equity ratio, in addition to those variables stablished by Traditional Financial Theory. The results suggest that unobservable variables must be considered to gain a deeper understanding of the decision-making process and that an integral vision to consider the study of the motivations that are behind of the observable financial behavior is necessary.
Physical and chemical evolution of the largest monogenetic lava field in the Central Andes: El Negrillar Volcanic Field, Chile
Journal of Volcanology and Geothermal Research
Daniela Parra Encalada 1 , Patricia Larrea 1 , Camila Loaiza 1 , Rubén Cartagena 1 , Sergio Salinas 2 , Benigno Godoy 1 , Pablo Grosse 3 , Petrus Le Roux 4
1 Universidad de Chile, Facultad de Ciencias Físicas y Matemáticas
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Fundación Miguel Lilo
4 University of Cape Town, Department of Geological Sciences

Keywords: Mafic to intermediate volcanism, Paleoreconstruction, Volumetric rates, Morphometric and rheological calculations, Altiplano-Puna plateau, Central Volcanic Zone
Abstract: El Negrillar volcanic field is one of the most voluminous monogenetic volcanic fields so far identified in the Central Volcanic Zone (CVZ) of the Andes: its lava field comprises 84 eruptive phases from 35 small eruptive centers. The study of this volcanic field offers a unique opportunity to assess the volumetric, morphometric, rheological, and compositional evolution of the effusive activity in an entire monogenetic cluster; the great extent and exposure of these small eruptive centers is difficult to observe in other monogenetic volcanoes from the Central Volcanic Zone, as they normally appear as isolated vents or in small clusters (< 3 eruptive centers) with less associated eruptive phases. Our methodology utilizes GIS mapping tools to outline the different eruptive phases of El Negrillar to create a detailed lava flow map, allowing us to estimate the volume emitted by each eruptive center. This analysis was also possible through the paleoreconstruction of the buried lava flows, allowing the determination of the variation in the magma supply. This yielded a total bulk volume of ~7.6?km3 (6.8?km3 DRE, considering the low vesicle abundance of the eruptive products), which exceeds by more than one order of magnitude the volume emitted by other monogenetic centers from the Salar de Atacama region (e.g., El País lava flow, Tilocálar Norte, Tilocálar Sur, La Albondiga and Cerro Overo). We also determined the composition of the entire effusive activity of El Negrillar; andesitic magmas represent more than 46 vol% of the lava field. We identify three main clusters (i.e., Northern El Negrillar (NEN), Central El Negrillar (CEN), and Southern El Negrillar (SEN)), that revealed a compositional variation together with a change in the calculated morphometrical and rheological parameters, implying the existence of a local trend within the monogenetic lava field. The NEN cluster represents the most differentiated magmatism in the field, characterized by amphibole-rich lavas with almost absent olivine, and the highest crystallinity and vesicle content, which led to an effusive activity sustained for more than 3?years, with lava accumulation predominating over its transport, leading to the shortest and thickest flows of the field. The presence of ??cauliflower shape bombs? in an early stage of one of its eruptive centers indicates that the NEN cluster may have been influenced by environmental factors leading to an early explosive episode during its activity. On the contrary, the SEN cluster represents the less differentiated magmatic activity of the field, characterized by olivine-rich lavas with almost absent amphibole, low crystallinity, and poor vesicles content, which along with a large magma supply led to effusive activity sustained for approximately two years where the lava flows achieved the longest distances in the field. The CEN cluster is compositionally closer to the SEN, but morphometrical and rheologically resembling to the NEN, suggesting that it represents an intermediate behavior between the other two clusters.
Power system coherency assessment by the affinity propagation algorithm and distance correlation
Sustainable Enegy, Grids and Networks
José Ortiz Bejar 1 , Mario Roberto Arrieta Paternina 2 , Alejandro Zamora Méndez 3 , Lucas Lugnani 4 , Eric Tellez 5
1 Universidad Michoacana de San Nicolás de Hidalgo
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Universidad Michoacana de San Nicolás de Hidalgo, Facultad de Ingeniería Electrica
4 University of Campinas, Department of Electrical Engineering
5 Centro de Investigación e Innovación en Tecnologías de la Información y Comunicación

Keywords: Coherency, Affinity propagation, Clustering, Phasor measurement units, Frequency, Slow coherency
Abstract: This paper assesses the coherency in power systems employing the affinity propagation (AP) algorithm with different distance metrics and quality measurements. This assessment allows determining the appropriate metric to cluster a frequency dataset that possesses coherent patterns. Thanks to the AP method does not require initialization for the number of clusters, its convergence characteristics guaranteed by the optimization process, and its capacity for using different distance metrics as input, the AP is adopted to identify and distinguish such coherent patterns that embody the collective motion of an operative area in a power system. The AP method is a data-driven method that uses an affinity matrix as input, i.e., the square matrix computed with pairwise distances. Since the distance function significantly impacts the quality of the resulting clustering, this contribution evaluates three different distance metrics, distance correlation, and the results are compared using four cluster indexes. The data collection is constituted by a set of frequency signals and the representative objects are the nodes identified as the center of each operative area. This contribution presents experimental results using simulated signals with added noise and real event signals captured by 94 PMUs. We found that our proposed strategy achieves highly competitive results for identifying coherent generator and non-generator buses in large-scale power systems.
Advanced three-stage photovoltaic system phasor model for grid integration dynamic studies
Solar Energy
Jesús H. Sánchez 1 , Luis Miguel Castro González 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Electrical network, DC/DC boost converter, Dynamic simulations, Phasor modeling, Photovoltaic systems, Voltage source converter
Abstract: As the penetration of photovoltaic (PV) generation increases at different system voltage levels, their impact on the power grid operation and control is more important to analyze. Hence, suitable PV models must be developed with which it is possible to carry out dynamic analysis for fair-sized electrical networks. This is a demanding task, computationally-wise, for detailed switching-based PV models using small numerical integration steps required by the associated power electronic devices. In this sense, an advanced three-stage PV system phasor model is proposed in this paper whose hallmark resides in the proper characterization of the PV arrays and DC/DC converter through a nonlinear potential regression technique in combination with the generatrix method. As a result, the PV operating surfaces, as function of irradiance and temperature, can be determined and used for the calculation of virtual resistances relating to the PV optimal operation and internal power losses. The virtual resistances are seamlessly combined with a developed AC/DC converter phasor model for efficient dynamic simulations of electrical networks. The new PV model has been thoroughly validated using Simscape Electrical of Simulink where an electrical network with one PV system is dynamically simulated. The outcomes of the developed model are compared to those obtained from switching-based PV models based on different maximum power tracking strategies, i.e., the incremental conductance (IC) and perturbation and observation (P&O) algorithms. The impact of the PV system on the power grid operation and the accuracy of results are assessed, demonstrating that the proposed model favorably agrees with the benchmark switching-based PV models as errors inferior to 2 % are obtained. Furthermore, it is confirmed that the new PV system model enables faster dynamic simulations than what it is possible to achieve with switching-based models since it is 28.82 times faster than the PV model based on the IC algorithm and 31.80 times faster than that using the P&O technique.
Study of a current multilevel converter as an interconnection element for PV systems
Ain Shams Engineering Journal
Rafael Jesús Hernández 1 , V. Cárdenas 2 , Gerardo Espinosa Pérez 3 , R. Álvarez Salas 1 , H. Miranda Vidales 1
1 Universidad Autónoma de San Luis Potosí, Facultad de Ingeniería
2 Universidad Autónoma de San Luis Potosí, Centro de Investigación y Estudios de Posgrado
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Current source converter, Multilevel current rectifier, PV system
Abstract: The present paper focuses on the use of the Multilevel Current Rectifier topology as an interconnection element between PV systems and the network or loads. In order to properly use the converter in connection with the PV system, several subjects such as the compatibility with the maximum power point tracking and the compatibility between the converter and the PV array must be taken into account. Compatibility between the converter and the PV array can be achieved by ensuring at least the maximum power point is a point that the converter can work with. In this sense, this work focuses on the operating conditions to guarantee the compatibility with the PV array. The main results are an analytical and experimental characterization of the operating range of the system using the Multilevel Current Rectifier. This operating range has a precision of 1%. Leading to the conclution that not only the converter is a viable option, but also that the theory and methodology used can be extrapolated to another topologies.
On the modelling of DC microgrids for steady-state power flow studies
Electric Power Systems Research
Luis Miguel Castro González 1 , Cristóbal Ramírez Ramos 1 , Jesús H. Sánchez 1 , Daniel Guillén Aparicio 2
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Tecnológico de Monterrey, Ingeniería Eléctrica y Electrónica

Keywords: BESS, Cogeneration, Distributed generation, Power flows, Microgrids, PV systems, Wind generators
Abstract: This paper introduces a comprehensive modelling framework for power flow studies of DC microgrids (MG). Suitable AC/DC and DC/DC converter models based on voltage source converters and dual-active bridges are firstly derived. In turn, these are seamlessly combined with battery energy storage systems (BESS) and distributed generators (DG) such as cogeneration, wind generators and photovoltaic systems to give rise to a complete MG representation. The hallmark of this formulation is that all MG component models are derived following basic principles of operation in steady-state in such a way that their internal variables are calculated during the iterative process. The method features a unified formulation through the widely-used power injection concept. For validity purposes, a 13-node MG comprising three DG, two DC/DC converters and one BESS is studied considering both grid-connected and island operation modes. The same MG model was implemented in Matlab/Simscape Electrical using detailed models. Both solutions are shown to agree well with each other since errors inferior to 1% and 2% were obtained for nodal voltages and power flows, respectively. A 118-bus MG including 15 DG units, 5 DC/DC converters and 4 BESS was additionally studied to confirm the practicality of the new approach in larger MG facilities.
Data science - time series analysis of oil & gas production in mexican fields
Procedia Computer Science
María de los Ángeles Sánchez Morales 1 , Francisca Irene Soler Anguiano 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Oil, Gas, Production, Time Series Analysis, Seasonal, Non-Seasonal Methods, ARIMA, SARIMA Methods
Abstract: Nowadays, large industries of financial, technological, manufacturing, energetic, and service sectors have accomplished the incorporation of Data Science in their operations, processes, and work structures, obtaining significant improvements in their productivity and service potentials. Whereby the oil and gas industry should not be foreign to this science that aids the decision-making processes using the acquired information by extracting massive, structuring data, combining statistics, mathematics, and informatics. Since the variations in petroleum and gas offer and demand are strongly related to the changes in prices, the use of Data Science intends to administer and reduce the risks provoked by the processes and decisions related to every step of the industry??s chain value. Oil and gas exploration, extraction, development, and production generate considerable amounts of data created by different means, lacking order and precision. Hence, data analysis provides formality to the experiments in this area, improving productivity alternatives and creating innovation opportunities. The present paper objective is to comprehend the production fluctuation trends to understand the possible behaviour of future productions in three Mexican fields with the highest petroleum and gas production, Maloob, Zaap, and Ayatzi for petroleum and Ku, Akal, and Maloob for gas, through the application of a Time Series Analysis to each one of them.
Short-term generation capacity expansion planning considering multi-terminal VSCsingle bondHVDC links using a linear programming framework improved by shift factors
Electric Power Systems Research
Luis Miguel Castro González 1 , Néstor González Cabrera 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: AC/DC systems, Generation capacity expansion planning, VSC-HVDC links, Linear programming, Shift factors
Abstract: This paper describes the modelling of short-term generation capacity expansion planning (GCEP) for multi-terminal VSC-based HVDC transmission systems. The GCEP formulation is based on a mixed-integer linear programming (MILP) framework where transmission losses are considered by piecewise linearisation. As opposed to existing methods, the present GCEP formulation is based on shift factors which enable the representation of the hybrid AC/DC grids including VSC stations. This way new power generation investments can be efficiently determined at any of the VSC-connected AC systems. This new method lies in sharp contrast with the so-called classic GCEP method where the system nodal power balances are formulated using the voltage phase angles as decision variables thus increasing the model complexity. Indeed, to determine the GCEP investments, the present model aimed to multi-terminal HVDC links only uses AC/DC transmission line losses, power generations and projected generating power plants as decision variables. The new GCEP formulation is compared to the classic method using two compelling multi-terminal VSCsingle bondHVDC test systems for validity and applicability purposes. Results show that the proposed formulation reduces the simulation running time by more than 80%, compared to the standard model, accompanied by acceptable accuracy of results since errors inferior to 5% are obtained.
Reversible Data Hiding with a New Local Contrast Enhancement Approach
Eduardo Fragoso Navarro 1 , Manuel Cedillo Hernández 2 , Francisco Javier García Ugalde 1 , Robert Morelos-Zaragoza Ascanio 3
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Instituto Politécnico Nacional, Escuela Superior de Ingeniería Mecánica y Eléctrica
3 San Jose State University, College of Engineering

Keywords: Contrast enhancement, histogram shifting, information security, image processing
Abstract: Reversible data hiding schemes hide information into a digital image and simultaneously increase its contrast. The improvements of the different approaches aim to increase the capacity, contrast, and quality of the image. However, recent proposals contrast the image globally and lose local details since they use two common methodologies that may not contribute to obtaining better results. Firstly, to generate vacancies for hiding information, most schemes start with a preprocessing applied to the histogram that may introduce visual distortions and set the maximum hiding rate in advance. Secondly, just a few hiding ranges are selected in the histogram, which means that just limited contrast and capacity may be achieved. To solve these problems, in this paper, a novel approach without preprocessing performs an automatic selection of multiple hiding ranges into the histograms. The selection stage is based on an optimization process, and the iterative-based algorithm increases capacity at embedding execution. Results show that quality and capacity values overcome previous approaches. Additionally, visual results show how greyscale values are better differentiated in the image, revealing details globally and locally.
Thermal analysis using induction and concentrated solar radiation for the heating of metals
Results in Engineering
Armando Rojas Morin 1 , Yolanda Flores Salgado 2 , Omar Álvarez Brito 3 , Alejandro Jaramillo Mora 1 , Arturo Barba Pingarrón 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Dirección General de Tecnologías de la Información y Comunicación
3 Universidad Nacional Autónoma de México, Instituto de Energías Renovables

Keywords: Solar energy and electric induction coupling, Metal piece heating, Exergy analysis
Abstract: It is described the thermal analysis of a cylindrical workpiece involving the coupling of two heat sources. Induction heating was applied, which generated Eddy currents that circulated through the workpiece and heated the material surface. Also, concentrated solar energy heating was applied at the top of the workpiece, which generated a heat flux from the Fresnel lens concentrator. The formulation for the transient heat transfer analysis is presented. A numerical simulation for solving Maxwell's equations along with coupled and transient heat transfer conditions was developed using COMSOL Multiphysics®. The temperature distribution of the cylindrical workpiece was obtained, and the heating time was also determined. Subsequently, we compared this simulation and the experimental test. The experimental results show that for the coupling induction and concentrated solar energy, the temperature reaches its maximum faster than induction or concentrated solar energy alone. This kind of proposed alternative system can be useful for time and energy reduction for industrial heat treatments like annealing, precipitation hardening, quenching and tempering, isothermal treatments of ferrous and non-ferrous alloys.
Analysis of the effect of cationic ratio Bi3+/Fe3+ on the magnetic and multiferroic properties of BiFeO3 nanoparticles synthesized using a sonochemical-assisted method
Ceramics International
R.L. Palomino Resendiz 1 , Ana María Bolarín Miró 1 , F. Pedro García 2 , Félix Sánchez De Jesús 1 , J.P. Espinós Manzorro 3 , Claudia Alicia Cortés Escobedo 4
1 Universidad Autónoma del Estado de Hidalgo, Área Académica de Ciencias de la Tierra y Materiales
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Universidad de Sevilla, Instituto de Ciencia de Materiales de Sevilla
4 Instituto Politécnico Nacional, Centro de Investigación e Innovación Tecnológica

Keywords: Multiferroic ceramic, Bismuth ferrite (BiFeO3) nanoparticles, Magnetoelectric materials, Sonochemical synthesis, X-ray photoelectron spectroscopy
Abstract: This study examined the effects of the cationic ratio of Bi3+/Fe3+ via X-ray photoelectron spectroscopy (XPS) on the magnetic and multiferroic properties of BiFeO3 nanoparticles synthesized using a sonochemical-assisted method. X-ray diffraction revealed the successful synthesis of single-phase BiFeO3 powder after annealing the sonicated material at 723 K. The powder was composed of agglomerates of rounded particles with a mean particle size of 35 nm. XPS was performed to determine the Bi3+/Fe3+ ratio as a function of the heat treatment process and its relationship with secondary phases, which can modulate the magnetic properties of the nanopowders. The cationic ratio obtained by XPS confirmed that the powders obtained at 623 and 923 K have excess Bi3+ and Fe3+, respectively, which induces the formation of Bi24Fe2O39 and Bi2Fe4O9 as the majority phases. Powder annealing at 723 K revealed a ferromagnetic order with specific magnetization of 1.8 Am2/kg. This ferromagnetic behavior was preserved after applying spark plasma sintering (SPS) at 923 K. By contrast, conventional sintering at 1023 K promotes antiferromagnetic order. In addition, the dielectric properties of the ceramic material of the sintered powders showed a behavior related to a typical ferroelectric material.
Interaction between long water waves and two fixed submerged breakwaters of wavy surfaces
Wave Motion
Eric Gustavo Bautista Godínez 1 , S. Bahena Jiménez 1 , A. Quesada Torres 1 , Federico Méndez Lavielle 2 , E. Arcos 3
1 Instituto Politécnico Nacional, Escuela Superior de Ingeniería Mecánica y Eléctrica
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería
3 Tecnológico de Estudios Superiores de Huixquilucan, División de Ingeniería Civil

Keywords: Long waves, Plate, Wavy surface, Domain perturbation method, Wave reflection
Abstract: In this work, we carried out an asymptotic analysis, up to the second order in a regular expansion, of the interaction between linear long waves and two submerged breakwaters of wavy surfaces, which obey a sinusoidal profile. The governing equations are expressed in their dimensionless version. The boundary conditions at the breakwaters surfaces are non-homogeneous; therefore, they are linearized using the domain perturbation method. Breakwaters with wavy surfaces generate larger reflection coefficient values than those obtained for breakwaters with flat surfaces. The largest values of this coefficient are obtained when the breakwater??s length is of the same order of magnitude as the wavelength. The asymptotic solution is compared with classical analytical solutions and the results are in good agreement. The present asymptotic solution can be used as a practical reference for the selection of the geometric configuration of a submerged floating breakwater under shallow flow conditions.
Volume reduction of water samples to increase sensitivity for radioassay of lead contamination
Applied Water Science
Alexis Aguilar Arevalo 1 , Carlos Canet Miquel 2 , Miguel Angel Cruz Pérez 3 , Alexander Deisting 4 , Adriana Dias 4 , Juan Carlos D' Olivo 1 , Francisco Favela Pérez 1 , Estela A. Garcés 5 , Adiv González Muñoz 5 , Jaime Octavio Guerra Pulido 6 , Javier Mancera Alejandrez 6 , Daniel José Marín Lámbarri 5 , Mauricio Martínez Montero 1 , Jocelyn Monroe 4 , Sean Paling 7 , Simon Peeters 8 , Paul Scovell 7 , Cenk Türko?lu 8 , Eric Vázquez Jáuregui 5 , Joseph Walding 4
1 Universidad Nacional Autónoma de México, Instituto de Ciencias Nucleares
2 Universidad Nacional Autónoma de México, Centro de Ciencias de la Atmósfera
3 Universidad Nacional Autónoma de México, Programa de Posgrado en Ciencias de la Tierra
4 University of London, Royal Holloway
5 Universidad Nacional Autónoma de México, Instituto de Física
6 Universidad Nacional Autónoma de México, Facultad de Ingeniería
7 Boulby Mine, Boulby Underground Laboratory
8 University of Sussex, Department of Physics and Astronomy

Keywords: Lead-210, Lead in drinking water, World Health Organisation, Radioassay, Volume Reduction
Abstract: The World Health Organisation (WHO) presents an upper limit for lead in drinking water of 10 parts per billion ppb. Typically, to reach this level of sensitivity, expensive metrology is required. To increase the sensitivity range of low-cost devices, this paper explores the prospects of using a volume reduction technique of a boiled water sample doped with Lead-210 (210 Pb), as a means to increase the solute??s concentration. 210Pb is a radioactive lead isotope and its concentration in a water sample can be measured with e.g. High Purity Germanium (HPGe) detectors at the Boulby Underground Germanium Suite. Concentrations close to the WHO limit have not been examined. This paper presents a measurement of the volume reduction technique retaining 99±(9)% of 210Pb starting from a concentration of 1.9?10??6 ppb before reduction and resulting in 2.63?10??4 ppb after reduction. This work also applies the volume reduction technique to London tap water and reports the radioassay results from gamma counting in HPGe detectors. Among other radio-isotopes, 40K, 210Pb, 131I and 177Lu were identified at measured concentrations of 2.83?103 ppb, 2.55?10??7 ppb, 5.06?10??10 ppb and 5.84?10??10 ppb in the London tap water sample. This technique retained 90±50% of 40K. Stable lead was inferred from the same water sample at a measured concentration of 0.012 ppb, prior to reduction.
Effect of curing post-treatment time on mechanical properties and stress distribution of adhesively bonded dissimilar steel-aluminum joints
The International Journal of Advanced Manufacturing Technology
Celso E. Cruz González 1 , Benjamín Vargas Arista 2 , Saúl Daniel Santillán Gutiérrez 3 , Arturo Barba Pingarrón 3 , Isidro Guzmán Flores 4
1 Centro de Ingeniería y Desarrollo Industrial, Dirección de Ingeniería Mecánica
2 Tecnológico Nacional de México, Instituto Tecnológico de Tlalnepantla
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería
4 Universidad Autónoma de Coahuila, Facultad de Sistemas

Keywords: Adhesive bonding, Dissimilar joints, Curing, Single lap shear testing, Adhesive fracture
Abstract: Adhesive bonding is a joining technology gaining popularity in automotive and aeronautic industries because it allows weight reduction, adhesive bonds and adhesive dissimilar materials joining which could be part of assembly to be welded to other structure, resulting in thermal cycle that could affect mechanical properties. Dissimilar joints between plates of dual-ten 590/600 dual phase high strength steel and AA6061T6-590 aluminum alloy bonded by MP55420 adhesive were analyzed by means of computational stress analysis, single lap shear testing, failure analysis, thermo-gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Results indicated that after curing at 175 ??C during 75 and 120 min, stiffness (measured as Young modulus) increased, ductility was reduced, two principal decomposition stages of mass loss were located from 200 to 500 ??C in TGA graphs, and there was no significant change in adhesive chemistry considering FTIR curves. Moreover, maximum load of single lap shear specimens was reduced, color adhesive changed from bright to dark amber, as well as joints failed by adhesive mechanism surpassing shear-strain limit as curing time increased. Computational stress analysis showed that peak normal and shear stresses were generated on both edges of adhesive joints after post-treatment time increased.
Evidence of magnetodielectric coupling in bismuth doped lanthanum ferrite obtained by high-energy ball milling
Physica B: Condensed Matter
Lucía I. Olivares Lugo 1 , Félix Sánchez De Jesús 1 , O. Rosales González 1 , Claudia Alicia Cortés Escobedo 2 , Arturo Barba Pingarrón 3 , Ana María Bolarín Miró 1
1 Universidad Autónoma del Estado de Hidalgo, Área Académica de Ciencias de la Tierra y Materiales
2 Instituto Politécnico Nacional, Centro de Investigación e Innovación Tecnológica
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Bi doped LaFeO3, Multiferroic material, Dielectric properties, Perovskite, LaFeO3, Magnetodielectric coupling
Abstract: In this study, the effects of Bi3+ doping of LaFeO3 on the crystal structure and the multiferroic properties of La1??xBixFeO3 (0.0 ? x ? 0.5, ?x = 0.1) are analyzed. Moreover, the magnetodielectric coupling in these materials is discussed. At low doping levels (x ? 0.3 mol), the orthorhombic LaFeO3 stabilizes, and at high bismuth contents (x ? 0.4), the orthorhombic BiFeO3 is formed, which was confirmed by determining the Néel temperature (623 K??823 K). The magnetic behavior of the samples shows antiferromagnetic order for all compositions. All the samples showed high relative permittivity values, which increased by doping with Bi3+. Furthermore, the presence of Bi decreased the dielectric dissipation factor, which is attributed to low-crystal-structure distortion. Finally, magnetodielectric coupling in these multiferroic materials is reported for the first time, as observed through changes in the relative permittivity under different applied fields and frequencies.
Exergy analysis of the Mexican energy sector
Sustainable Energy Technologies and Assessments
Daniel Alejandro Pacheco Rojas 1 , Gabriel León De los Santos 1 , Cecilia Martín del Campo 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Exergy analysis, Energy quality, Exergy Factor, Energy sector analysis, Sustainability indicators
Abstract: This paper proposes a step-by-step, replicable methodology for analyzing the exergy characteristics of a country??s energy system. It introduces a set of indicators comparable to those commonly used to describe national energy systems: (1) exergy intensity (2) exergy destruction per capita, (3) exergy destruction per gross domestic product (GDP), (4) exergy efficiency, and (5) exergetic cost. The energy efficiency of the energy sector in Mexico was roughly 20% lower than energy efficiency, with substantially less improvement over the 15 years from 2013 to 2018. This difference arises from a strong dependency on fossil fuels and associated exergy destruction, which is not immediately apparent when taking only an energy perspective. The economic value of exergy destruction could represent 2.9 % of GDP in Mexico. A decreasing trend in the final exergy consumption is not necessarily reflected in lower exergy destruction. Those indicators provide information about the Jevons?? paradox. And it points to substantial room for efficiency improvements in the energy sector, with important implications for greenhouse gas emissions. Applying the exergy perspective will allow policymakers to understand better opportunities to unlock new efficiencies and improve the sustainability of Mexico??s energy system and those of other countries.
Comparison of Estimates of the Excitation Force for Fault Diagnosis in a Wave Energy Converter
Alejandro González Esculpi 1 , María Cristina Verde Rodarte 1 , Paul Rolando Maya Ortíz 2
1 Universidad Nacional Autónoma de México, Instituto de Ingeniería
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Fault diagnosis, excitation force estimation, unknown input observer, wave energy converter, renewable energy
Abstract: This work analyzes the effect of estimating the excitation force in a model-based fault diagnosis (FD) of a wave energy converter (WEC). This force is a non-measurable variable related to the elevation of the sea waves at the location of the floater through a non-causal kernel function. Hence, two strategies are studied here: real-time estimates from predicted wave elevation and smoothed estimates from available measurements. To compare the performance of FD schemes based on each estimate, one considers faults in the damping subsystems of a WEC based on the Archimedes wave swing prototype. The FD scheme is also composed of an unknown input observer for fault detection and an estimator of the magnitude of the faults. Numerical simulations with irregular sea waves show improved diagnosis with smoothed estimates of the excitation force, at the expense of introducing some time delay.
Thermal impact induced by the environment in the transport of heavy oils in offshore insulated pipelines: Evaluation of heat transfer
Journal of Petroleum Science and Engineering
R. Flores Quirino 1 , O. Pastor Reyes 1 , Juan Pablo Aguayo Vallejo 1 , Gabriel Ascanio 1 , Federico Méndez Lavielle 2 , José Federico Hernández Sánchez 1 , Salvador Sánchez 1
1 Universidad Nacional Autónoma de México, Instituto de Ciencias Aplicadas y Tecnología
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Viscous flow, Conjugate heat transfer, Insulated pipeline, Thermal dependent properties, Dynamic viscosity, Heavy oil
Abstract: In this work, the non-isothermal transport of heavy oils in offshore insulated pipelines is theoretically analyzed. Here, because heavy oils show poor thermostability in terms of the dynamic viscosity, the evaluation of the two physical phenomena involved in the mentioned process (flow hydrodynamics and heat transfer) must be carried out in a coupled manner. In addition, if the performance of this type of transport system is considered, and a novel numerical approach is employed, the present mathematical formulation allows defining the relationship between flow assurance and the thermal impact induced by certain environmental conditions. The above is the main contribution of this work, which is achieved by obtaining the results considering an eigenvalue condition, and making the numerical scheme a useful tool to determine an adequate thermal shielding. First, the heat transfer in the transport system is estimated for given thermal??hydrodynamic conditions, and then, the numerical algorithm corrects the thermal shielding (insulation thickness) in such a way that the flow rate is preserved. In summary, the main results indicate that, when a section of the pipeline has a deficient thermal shielding, the flow hydrodynamics receives a considerable thermal impact, causing a significant reduction in the flow rate. Instead, when the thermal shielding is improved, the flow rate increases as the heat flux that is emitted by the pipeline to the environment is confined. Unfortunately, introducing a strong thermal shielding along the entire length of the pipeline implies an excessive use of thermal insulation (cost??benefit); therefore, rational and adequate use of thermal insulation barriers is the most appropriate condition. Such a conclusion is demonstrated by comparing the two study cases using the same amount of thermal insulation (value of the Graetz??Nusselt relationship); here, the flow rate increases more than double for the case as the thermal shielding is numerically corrected, in comparison to the case when the thermal insulation thickness is constant.
Modelling of renewable energy power plant controllers for steady-state studies using an extended power flow formulation
International Journal of Electrical Power & Energy Systems
Rubén A. Reyes Zamora 1 , Pedro F. Rosales Escobedo 1 , Luis Miguel Castro González 2 , Judith Paniagua Ramírez 1 , A. Ruelas 1 , A. Acuña 1 , J. A. Suastegui 1
1 Universidad Autónoma de Baja California, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Droop control, Power flow analysis, Power plant controllers, PV power plants, Wind power plants
Abstract: The increasing penetration of large-scale wind and photovoltaic plants has created new challenges for the secure and reliable operation of power systems. To face these challenges, these renewable plants are composed of numerous inverter-based resources that use centralized controllers to satisfy grid code requirements related to frequency and voltage control, both under dynamic and steady-state conditions. In this paper, an extended power flow formulation is proposed for the steady-state modelling of power plant controllers along with their power flow controls including those associated with droop control, suitable for any plant topology and number of regulation devices. The effectiveness of this modelling approach is validated against WECC generic models using dynamic simulations in PSS®E. For this purpose, a 13-bus 5-generator test system representing a 100-MW renewable power plant is studied. The accuracy of the introduced formulation is demonstrated since it presents absolute errors smaller than 0.2% between both fundamentally different methods. Additionally, the well-known IEEE RTS-96 test system is used to model 29 power plant controllers with 93 generators, thus showing the practicality of the proposed formulation. It can be envisaged that this timely tool is valuable for power system operation and expansion planning considering large-scale variable renewable energy power plants.
A Lipschitz continuous sliding mode control for implicit systems
European Journal of Control
Praveen Babu 1 , Debbie Hernández 2 , Bijnan Bandyopadhyay 3 , Leonid Fridman Golredich 4
1 Indian Institute of Technology Bombay, Systems and Control Engineering
2 Instituto Tecnológico de Estudios Superiores de Monterrey, Escuela de Ingeniería y Ciencias
3 Indian Institute of Technology, Systems and Control Engineering
4 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Implicit systems, Sliding mode control, Sliding surface, Lipschitz continuous control
Abstract: In this paper, implicit systems with uncertain input matrix subjected to matched Lipschitz disturbances are considered. For such kind of systems a Lipschitz continuous control, achieving admissible solutions for implicit systems is proposed. The developed methodology consists of two steps. In the first step a stable sliding surface is designed after transforming the original system into a regular like form. Then a first order sliding mode controller through an integrator is designed which will ensure finite-time convergence to the sliding manifold and the exponential convergence to the origin in spite of the presence of Lipschitz disturbances and uncertain input matrix.
Hydrodynamic cavitation through a bio-inspired fast-closing plunger mechanism: experiments and simulations
Bioinspiration & Biomimetics
Francisco Antonio Godínez Rojano 1 , José Enrique Guzmán Vázquez 1 , Martín Salinas Vázquez 1 , Rogelio Valdés 2 , Carlos Alberto Palacios Morales 3 , Oscar Chávez 4
1 Universidad Nacional Autónoma de México, Instituto de Ingeniería
2 Universidad Iberoamericana, Departamento de Estudios en Ingeniería para la
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería
4 Instituto Tecnológico de Chihuahua, División de Estudios de Posgrado e Investigación

Keywords: Hydrodynamic, cavitations, bio-inspired, fast-closing plunger mechanism, experiments, simulations
Abstract: Experimental and numerical results are reported for the internal and external flow fields evolving in a bio-inspired snapping plunger. The experimental evidence underlines the nature of the dynamic-coupling between the processes taking place inside and outside the device. Two main structures dictate the properties of the external flow field: a strong jet which is followed by a vortex ring. Internally, complex patterns of cavitating structures are simultaneously produced in the chamber and the venturi-like conduit. We find the cavitation cycle to be suitably described by the Rayleigh??Plesset model and, thus, proceed to characterize the coupling of both fields in terms of the fluctuations of the velocity. All main parameters, as well as the energy released to the fluid during the collapse, are found to be within the same order-of-magnitude of previously known experimental results for isolated bubbles of comparable size.
Experimental Study of the Influence of CH4and H2on the Conformation, Chemical Composition, and Luminescence of Silicon Quantum Dots Inlaid in Silicon Carbide Thin Films Grown by Remote Plasma-Enhanced Chemical Vapor Deposition
ACS Omega
Rodrigo León Guillén 1 , Ana Luz Muñoz Rosas 1 , Jesús A. Arenas Alatorre 1 , Juan Carlos Alonso Huitrón 2 , Ana Laura Pérez Martínez 3 , Arturo Rodríguez Gómez 1
1 Universidad Nacional Autónoma de México, Instituto de Física
2 Universidad Nacional Autónoma de México, Instituto de Investigaciones en Materiales
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Abstract: Silicon carbide (SiC) has become an extraordinary photonic material. Achieving reproducible self-formation of silicon quantum dots (SiQDs) within SiC matrices could be beneficial for producing electroluminescent devices operating at high power, high temperatures, or high voltages. In this work, we use a remote plasma-enhanced chemical vapor deposition system to grow SiC thin films. We identified that a particular combination of 20 sccm of CH4 and a range of 58??100 sccm of H2 mass flow with 600 °C annealing allows the abundant and reproducible self-formation of SiQDs within the SiC films. These SiQDs dramatically increase the photoluminescence-integrated intensity of our SiC films. The photoluminescence of our SiQDs shows a normal distribution with positive skewness and well-defined intensity maxima in blue regions of the electromagnetic spectrum (439??465 nm) and is clearly perceptible to the naked eye.
Physical impact of a surfactant on the nonlinear oscillations of a microbubble considering a dynamic surface tension and subject to an external acoustic field
Physical Review Fluids
César Yepez Terreros 1 , Jorge Luis Naude De la Llave 1 , Federico Méndez Lavielle 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Abstract: The dynamics of microbubbles under the action of external acoustic forces has become particularly important in several applications. In this work, we are particularly interested in studying the transport of surfactant molecules to the surface of an oscillating microbubble, considering the impact that the dynamic surface tension and temporal evolution of the radius of the microbubble has when an acoustic pressure as a driving force is used to promote the nonlinear oscillations. The resulting governing equations to predict the radius of the microbubble and the evolution of the surfactant at the surface are written in dimensionless form. For these equations, we identify two fundamental dimensionless parameters: the Gibbs elasticity E, and the cohesive (or repulsive) parameter K. Using the physical domain 0?E?10 and ??13.2?K?13.2, and considering that the diffusive Péclet number is large, as occurs in some applications, the surfactant concentration equation is solvable by using a similarity transformation, whereas the Rayleigh-Plesset-type equation that includes the influence of the previous parameters E and K is solved by the fourth-order Runge-Kutta method. When the numerical predictions are compared with the well-known cases E=K=0, strong deviations reveal that the oscillation mechanisms can be significantly altered.
Impact of viscous dissipation on the conjugate heat transfer between the walls of a porous microchannel
Physica Scripta
Ian Guillermo Monsivais Montoliu 1 , Federico Méndez Lavielle 1 , José Joaquín Lizardi Del Ángel 2 , Edgar Ali Ramos Gómez 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Autónoma de la Ciudad de México, Colegio de Ciencia y Tecnología

Keywords: Microchannel heat sinks, viscous dissipation, freefem
Abstract: In this work, the finite element method was used to study numerically the viscous dissipation that occurs when a Newtonian fluid circulates through a porous microchannel that operates as a heat sink, in which a constant heat flux is applied from the outer walls of the porous microchannel into the fluid. Taking into account that this is a conjugate problem, where the temperature fields of both the porous medium and the wall are unknown, there are two well-known asymptotic limits in the literature that allow us to obtain the solution for this problem: the first one is the thermally thick wall limit $\left(\gamma /{\beta }_{w}^{2}=1\right)$, which has been widely studied previously by other authors; the second one is the thermally thin wall limit $\left(\gamma /{\beta }_{w}^{2}=25\right)$, where the longitudinal effects of heat conduction in the microchannel wall are considerably more important than the ones occurring in the transverse direction. Therefore, in this study, we analyze the competition between these effects and viscous dissipation, as well as the influence that both have on the temperature profiles of the fluid and the wall. The results show that for Br ? 0.1, a notable temperature increase occurs in the system, which offers interesting results that have not been reported in the literature yet, because from ? = 0.6 (Br = 0.1), there is a higher temperature in the center of the microchannel than in the vicinity of the wall; that is, the fluid temperature is higher at η = 0 with respect to the temperature value at η = 1. This situation becomes more evident as the Brinkman number increases; for example, for Br = 1, the temperature in the center of the microchannel increases up to 23% with respect to the fluid temperature at the wall. Finally, the decrease of the Darcy number does not have a considerable effect on the temperature profiles.
Development and characterization of sealed anodizing as a corrosion protection for AA2024-T3 in saline media
Materials Today Communications
Alba Covelo Villar 1 , Sandra Rodil 2 , X. R. Nóvoa 3 , Miguel Ángel Hernández Gallegos 1
1 Universidad Nacional Autónoma de México, Facultad de Ingeniería
2 Universidad Nacional Autónoma de México, Instituto de Investigaciones en Materiales
3 Universidad de Vigo, ENCOMAT Grupo

Keywords: Anodized aluminum, Sealants solutions, Fluoropolymer, Corrosion protection, XPS, SECM
Abstract: In the present investigation, a new processing route of anodized aluminum AA2024 was developed by incorporating a hydrophobic top sealant to increase the anti-corrosion properties of the substrate in saline media. Different sealant solutions (boiling water, potassium dichromate, and cerium nitrate) were used after the sealing treatment. The surface structure was characterized by water contact angle, atomic force microscopy (AFM), and scanning electron microscopy (SEM) measurements, while the composition was assessed by X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) evaluated the anticorrosive properties. The microhardness properties were assessed with Vickers testing. Each hydrophobic treatment notably improved the corrosion resistance of the AA2024; however, the cerium nitrate system obtained the best results, given that the morphology of the hydrophobic structure generated lower surface defects with high impedance values and, consequently, very low current. The microhardness properties were positively increased after the surface modification, thus, the hydrophobic sealant improved simultaneously both electrochemical and mechanical properties. The XPS identified the presence of fluorotriethoxysilane as the chemical compound responsible for the hydrophobic properties.
Finite-Time State Observer for a Class of Linear Time-Varying Systems With Unknown Inputs
IEEE Transactions on Automatic Control
Jorge Dávila Montoya 1 , Markus Tranninger 2 , Leonid Fridman Golredich 3
1 Instituto Politécnico Nacional, Sección de Estudios de Posgrado e Investigación
2 Graz University of Technology, Institute of Automation and Control
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Keywords: Robust observers, finite-time observers, time-varying systems, unknown inputs, high-order sliding modes
Abstract: A finite-time observer for a class of linear time-varying systems with bounded unknown inputs is presented in this note. The design of the observer exploits structural properties of the system and, through a linear operator, allows applying the robust exact differentiator in a block form without requiring additional stabilizing terms. The proposed observer provides an exact estimate of the states after a finite transient time despite the possible instability of the system and the effects of bounded unknown inputs.
Contextual Isotope Ranking Criteria for Peak Identification in Gamma Spectroscopy Using a Large Database
IEEE Transactions on Nuclear Science
Alexis Aguilar Arevalo 1 , Xavier Bertou 2 , Carlos Canet Miquel 3 , Miguel Angel Cruz Pérez 4 , Alexander Deisting 5 , Adriana Dias 5 , Juan Carlos D' Olivo 1 , Francisco Favela Pérez 1 , Estela A. Garcés 6 , Adiv González Muñoz 6 , Jaime Octavio Guerra Pulido 6 , Javier Mancera Alejandrez 6 , Daniel José Marín Lámbarri 6 , Mauricio Martínez Montero 1 , Jocelyn Monroe 5 , Sean Paling 7 , Simon Peeters 8 , Paul Scovell 7 , Cenk Türko?lu 8 , Eric Vázquez Jáuregui 6 , Joseph Walding 5
1 Universidad Nacional Autónoma de México, Instituto de Ciencias Nucleares
2 Centro Atómico Bariloche
3 Universidad Nacional Autónoma de México, Centro de Ciencias de la Atmósfera
4 Universidad Nacional Autónoma de México, Programa de Posgrado en Ciencias de la Tierra
5 University of London, Royal Holloway
6 Universidad Nacional Autónoma de México, Instituto de Física
7 Boulby Mine, Boulby Underground Laboratory
8 University of Sussex, Department of Physics and Astronomy

Keywords: Gamma-ray spectroscopy, heuristic algorithms, isotope identification, ranking
Abstract: Isotope identification is a recurrent problem in γ spectroscopy with high-purity germanium detectors. In this work, new strategies are introduced to facilitate this type of analysis. Five criteria are used to identify the parent isotopes making a query on a large database of γ lines from a multitude of isotopes producing an output list whose entries are sorted so that the γ lines with the highest chance of being present in a sample are placed at the top. A metric to evaluate the performance of the different criteria is introduced and used to compare them. Two of the criteria are found to be superior than the others: one based on fuzzy logic and another that makes use of the γ relative emission probabilities. A program called histoGe implements these criteria using an SQLite database containing the γ lines of isotopes which was parsed from WWW Table of Radioactive Isotopes. histoGe is Free Software and is provided along with the database so they can be used to analyze spectra obtained with generic γ -ray detectors.
Design, Growth, and Characterization of Crystalline Copper Oxide p-Type Transparent Semiconductive Thin Films with Figures of Merit Suitable for Their Incorporation into Translucent Devices
Crystal Growth and Design
María del Pilar Aguilar Del Valle 1 , Luis Fernando Garrido 1 , Juan Carlos Alonso Huitrón 2 , Luis Augusto Terrones Pacheco 1 , Héctor Cruz Manjarrez 1 , José Reyes Gasga 1 , Ana Laura Pérez Martínez 3 , Arturo Rodríguez Gómez 1
1 Universidad Nacional Autónoma de México, Instituto de Física
2 Universidad Nacional Autónoma de México, Instituto de Investigaciones en Materiales
3 Universidad Nacional Autónoma de México, Facultad de Ingeniería

Abstract: The development of high-performance p-type transparent conductive oxides (TCOs) is a scientific challenge. Cupric oxide (CuO) and cuprous oxide (Cu2O) are attractive candidates for manufacturing p-type TCOs due to their optoelectronic properties. However, tailoring the copper oxide optical absorption and sheet resistance using scalable and simple synthesis methods is not easy. This work presents a straightforward and highly reproducible methodology based on DC sputtering plus thermal treatments to manufacture copper oxide p-type TCOs with optimal figures of merit. We demonstrate that a low-temperature long-time annealing is capable of changing the conductivity and average transmittance of a determined copper oxide TCO. Our proposed long thermal treatment produces a decrease in the TCO average transmittance from 82 to 67%, but, in return, it generates an increment in the conductivity of 3 orders of magnitude from 2.5 ? 10??5 S/cm up to 0.048 S/cm. We estimate that these p-type TCOs could be used to build diverse translucent experimental devices where a p??n heterojunction is required.