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Artículos publicados en: 2022

Distributed generation in low-voltage DC systems by wind energy in the Baja California Peninsula, Mexico
Energy
https://doi.org/10.1016/j.energy.2021.122530
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%.
Numerical-analytical solutions of the fractional point kinetic model with Caputo derivatives
Annals of Nuclear Energy
https://doi.org/10.1016/j.anucene.2021.108745
Marco A. Polo Labarrios 1 , Francisco Godínez 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.
Modeling a multi-layered blockchain framework for digital services that governments can implement
Journal of Intelligent & Fuzzy Systems
https://doi.org/10.3233/JIFS-219244
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

Keywords:
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.
An analytical Survey of Attack Scenario Parameters on the Techniques of Attack Mitigation in WSN
Wireless Personal Communications
https://doi.org/10.1007/s11277-021-09107-6
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
https://doi.org/10.1109/TAC.2021.3075179
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
https://doi.org/10.1109/TAC.2021.3066581
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.
Unit commitment for multi-terminal VSC-connected AC systems including BESS facilities with energy time-shifting strategy
International Journal of Electrical Power & Energy Systems
https://doi.org/10.1016/j.ijepes.2021.107367
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
https://doi.org/10.1016/j.ijepes.2021.107469
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
https://doi.org/10.1016/j.ijthermalsci.2021.107358
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
https://doi.org/10.1016/j.atmosres.2021.105888
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
https://doi.org/10.1016/j.dib.2022.107853
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
https://doi.org/10.1016/j.matlet.2021.131414
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
https://doi.org/10.1016/j.epsr.2022.107771
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
https://doi.org/10.1016/j.ijheatmasstransfer.2022.122522
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
https://doi.org/10.1016/j.nucengdes.2021.111599
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
https://doi.org/10.1016/j.ijnonlinmec.2021.103833
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
https://doi.org/10.1140/epjp/s13360-022-02407-1
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 Lambarri 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

Keywords:
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
https://doi.org/10.1007/s40430-022-03385-2
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.
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
https://doi.org/10.1007/s12665-021-10137-3
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
https://doi.org/10.5194/hess-26-975-2022
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

Keywords:
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??
A Hamiltonian control approach for electric microgrids with dynamic power flow solution
Automatica
https://doi.org/10.1016/j.automatica.2022.110192
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
https://doi.org/10.1016/j.coesh.2022.100346
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
https://doi.org/10.1016/j.euromechflu.2022.01.001
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
https://doi.org/10.1016/j.procs.2022.01.202
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
http://dx.doi.org/10.22201/fca.24488410e.2022.3090
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.
Power system coherency assessment by the affinity propagation algorithm and distance correlation
Sustainable Enegy, Grids and Networks
https://doi.org/10.1016/j.segan.2022.100658
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
https://doi.org/10.1016/j.solener.2022.02.014
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
https://doi.org/10.1016/j.asej.2021.06.027
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
https://doi.org/10.1016/j.epsr.2022.107868
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
https://doi.org/10.1016/j.procs.2022.01.201
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
https://doi.org/10.1016/j.epsr.2022.107819
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
Mathematics
https://doi.org/10.3390/math10050841
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.