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The stronger activity of poly(vinylidene difluoride) (PVDF; C2H2F2), related with its high dielectric constant and its ferromagnetic behavior, puts it into the kinds of materials with novel mechani...

Thermoelectric effects have attracted wide attention in recent years from physicists and engineers. In this work, we explore the self-similar patterns in the thermoelectric effects of monolayer graphene-based structures, by using the quantum relativistic Dirac equation. The transfer matrix method has been used to calculate the transmission coefficient. The Landauer–Büttiker formalism and the Cutler–Mott formula were used to calculate the conductance, the Seebeck coefficient, and the power factor. We find self-similar behavior and the scale factors between generations in transport and thermoelectric properties. Furthermore, we implement these scale invariances as general scaling rules. We present a new analytical demonstration of self-similarity in the Seebeck coefficient. These findings can open outstanding perspectives for experimentalists to develop thermoelectric devices.

Periodic superlattices constitute ideal structures to modulate the transport properties of two-dimensional materials. In this paper, we show that the tunneling magnetoresistance (TMR) in phosphorene can be tuned effectively through periodic magnetic modulation. Deltaic magnetic barriers are arranged periodically along the phosphorene armchair direction in parallel (PM) and anti-parallel magnetization (AM) fashion. The theoretical treatment is based on a low-energy effective Hamiltonian, the transfer matrix method and the Landauer–Büttiker formalism. We find that the periodic modulation gives rise to oscillating transport characteristics for both PM and AM configurations. More importantly, by adjusting the electrostatic potential appropriately we find Fermi energy regions for which the AM conductance is reduced significantly while the PM conductance keeps considerable values, resulting in an effective TMR that increases with the magnetic field strength. These findings could be useful in the design of magnetoresistive devices based on magnetic phosphorene superlattices.

The effects of contact voltage and hydrostatic pressure on subband structure and optical transitions in GaAs delta-Field Effect Transistor (δ-FET) are theoretically studied. The electronic structure of δ-FET under hydrostatic pressure is determined by solving the Schrodinger equation using a theoretical model at low pressure. It is found that the subband energies and intersubband optical absorption on δ-FET are quite sensitive to the contact voltage and applied hydrostatic pressure. Wherein, a blue-shifting as hydrostatic pressure increases and a red-shifting as the contact potential increases, are shown. Our results could be important for infrared optical device applications and useful in the design of devices based on contact voltage and hydrostatic pressure-dependent optical processes.

The effects of the interlayer distance on the nonlinear optical properties of n-type quadruple δ-doped GaAs quantum well were theoretically investigated. Particularly, the absorption coefficient and the relative refraction index change were determined. In the effective mass approach and within the framework of the Thomas–Fermi theory, the Schrödinger equation was resolved. Thereby, the subband energy levels and their respective wave functions were calculated. The variations in the nonlinear optical properties were determined by using the density matrix solutions. The achieved results demonstrate that the interlayer distance causes optical red-shift on nonlinear optical properties. Therefore, it can be deduced that the suitably chosen interlayer distance can be used to tune optical properties within the infrared spectrum region in optoelectronic devices such as far-infrared photo-detectors, high-speed electronic-optical modulators, and infrared lasers.

The study presents the hybridization of global sensitivity analysis with data-driven techniques to evaluate the Mexican electricity market interaction and assess the impact of individual parameters concerning locational marginal prices. The study case pertains to Yucatan, Mexico's electricity grid and market characteristics. A comparison of three artificial intelligence techniques in the electricity market is presented to forecast electricity prices in real-time market conditions. The study contemplates exogenous input parameters classified as regional, operational, meteorological, and economic indicators. A sensitivity analysis was carried out to the model with the best performance of the Artificial Intelligence techniques. The results showed that the impact of the variables fluctuates according to market and consumption conditions. In this study, the most relevant variables were electricity generation (17.06%), fossil fuel costs (natural gas 12.54% and diesel 8.63%), load zone (11.17%), and the day of the year (8.51%). From the qualitative point of view, the complex behavior of the parameters was analyzed; moreover, the quantitative results weighted the relevance of the variables in the Locational Marginal Prices. The meteorological and economic parameters allow assessing the environment where it interacts and serves as an instrument for decision-making in the planning of the energy sector. The presented methodology can be implemented as an alternative tool for market participants to analyze electricity prices.

Electron transport in a silicene structure, composed of a pair of magnetic gates, is studied in a ferromagnetic and antiferromagnetic configuration. The transport properties are investigated for asymmetrical external effects like an electrostatic potential, a magnetic field and for asymmetrical geometric structure. This theoretical study, has been done using the matrix transfer method to calculate the transmission, the conductance for parallel and antiparallel magnetic alignment and the tunneling magnetoresistance (TMR). In Particular, we have found that the transmission, conductance and magnetoresistance oscillate as a function of the width of barriers. It is also found that a best control and high values of TMR spectrum are achieved by an asymmetrical application of the contact voltage. Besides, we have shown that the TMR is enhanced several orders of magnitude by the combined asymmetrical magnetization effect with an adequate applied electrostatic potential. Whereby, the asymmetrical external effects play an important role to improve TMR than symmetrical ones. Finally, the giant TMR can be flexibly modulated by incident energy and a specific asymmetrical application of control voltage. These results could be useful to design filters and digital nanodevices.

Thomas Fermi (TF) approach was used to represent a model for the n-type quadruple δ-doped (QDD) system in GaAs. This is the first physical model in the literature for the QDD system. The energies, the wave functions and the Fermi energy (EF) were calculated. These calculations were performed for different density of impurities in the doped layer (N2D) and for different separation distances (d) between the doped layers. Preliminary results show that the value of the Fermi level for the first proposed model is well below its expected value. This observation is exploited for a second model consistent with the expected values of the EF. Our results indicate that there is a limit at the bottom of the potential profile for a multilayered doped delta system. This has a great importance for calculations in optoelectronic and transport properties.

The electronic structure and the transport phenomena of δ-MIGFETs have been studied in an AlxGa1−xAs host matrix. The subband structure and mobility calculations were performed within the effective mass approximation and relative mobility formula, respectively. Both the electronic structure and the transport properties are calculated as dependent on the applied magnetic field (B), the aluminum molar fraction (x) and the contact voltage in one of the gates (VC1). It was found that the mobility and conductivity are enhanced by increasing the magnetic field for appropriate aluminum molar fraction and contact voltage. In particular, the mobility (conductivity) is improved almost 26% (32%) for VC1 = 900 meV (850 meV), x = 0.2, and B = 20 T.

Car accidents is a major source of congestion that affect the traffic dynamic especially in urban network. In this paper, we studied the impact of evacuation time ( T ) of damaged cars and transmission probability ( r ) on traffic characteristics when a car accident occurs at the intersection of two roads. Traffic is temporary stuck for T time steps then the vehicles involved in collision will be removed from the system. Simulation results show the existence of a critical evacuation time (injection rate α ) after which the variation of injection rate (evacuation time) hasn’t any effect on neither the flow nor the probability of accidents P a c . Moreover, when α ≤ 0 . 02 or α > 0 . 1 , the system exhibits a second order transition from Low Density Phase (LDP) to High Density Phase (HDP). However, the transition is of first order when 0 . 02 i α ≤ 0 . 1 . Furthermore, car accidents take place if α is higher than a critical value α c . This value does not depend on T when T 40 or T > 60 . Nonetheless, it depends strongly on T if 40 ≤ T ≤ 60 . The effects of the transmission probability and the probability to have a collision p’ are also studied. Likewise, different phase diagrams of the system are discussed.

This paper theoretically investigates the impact of aperiodic sequences in the ballistic transport and thermoelectric effect in silicene gated superlattices. In our analysis, we have implemented the well-known Fibonacci, Thue–Morse, and triadic Cantor type sequences. The transfer matrix technique and the Landauer–Butikker formalism are used to calculate the transmission probability and the conductance, respectively. The Cutler–Mott formula is employed to estimate the Seebeck coefficient, and the thermoelectric power factor is then obtained. We found that the transmission minibands of aperiodic superlattices exhibit a much more fragmented structure in comparison to that reported in the periodic case. Consequently, the conductance curve presents a more pronounced oscillating shape, which improves the thermoelectric properties. In particular, the Seebeck coefficient has reached values up to 78.2 mV/K for Fibonacci, 233.0 mV/K for Thue–Morse, and 436.3 mV/K for Cantor. In addition, the power factor has been substantially increased, reaching peaks of approximately 8.2, 50.2, and 2.1 nW/K 2 for the mentioned sequences, respectively. The best results were obtained for s p i n d o w n ( s p i n u p) charge carriers in the K ( K ′) valley. Besides, an additional improvement is obtained by considering superior generations of the aperiodic sequences. Finally, our findings are supported through the redistribution of the density of the states, which is induced by the aperiodicity of the nanostructure as well as by the low-dimensionality of the thermoelectric device.

The electronic, magnetic and optical properties of phosphorene monolayer adsorbed with Ti, S and co-adsorbed with (Ti,S) atoms were studied using the density functional theory. We utilized two different approaches: Density functional tight binding (DFTB) and full potential linearized augmented plane wave (FP-LAPW) within the generalized gradient approximation (GGA) for the exchange correlation potential. We find that the three cases S, Ti and (Ti,S) adsorbed in the phosphorene monolayer materials exhibit a spin polarization moment due to the hybridization of 3 p -S, 3 d -Ti and 3 p states of the phosphorene material. Moreover, for the case of Ti and (Ti, S) adatoms, a half metallic characteristic with 100% spin polarization at the Fermi level is present, while for S adatoms the Fermi level is located between bands. Furthermore, we show that these materials exhibit outstanding optical properties such as a high absorption and low reflectivity in the visible light range. A higher absorption and reflectivity are denoted for (Ti,S) co-adatoms phosphorene compared to pristine case. Also, we find the largest values of absorption for S adatoms phosphorene from 628 to 675 nm for zigzag direction. These materials have potential for applications in optoelectronic, photoelectric and spintronic devices.

Unavoidable structural disorder associated with the variation of the widths of barriers and wells as well as the heights of barriers in superlattices of 2D materials can affect considerably electronic transport and related phenomena. In this work, we study the impact of structural disorder on the electronic transport and thermoelectric properties of gated silicene superlattices (GSSLs). A low-energy effective Hamiltonian has been used to describe electrons in silicene. The transfer matrix approach, the Landauer–Buttiker formalism and the Cutler–Mott formula have been implemented to obtain the transport and thermoelectric properties. In particular, the conductance, Seebeck coefficient and power factor are investigated in ordered and disordered GSSLs. The results show that disorder related to the width of barriers-wells is not equivalent to the one associated to the height of barriers. The former barely changes the transport and thermoelectric coefficients at low energy, while the latter greatly affects them in the whole energy range. We also assess the disorder associated to the on-site potential of silicene layers, finding that its influence is limited. So, our results indicate that in the design and fabrication of GSSLs a precise control of the height of the barriers is required in order to have and preserve good thermoelectric properties.

Traffic control at intersections in urban conditions directly influences the CO2 emissions in their proximity. Improving traffic control at an intersection is another way to reduce vehicular emissions and creating a positive impact on the environment. Roundabout intersection excepted to reduce the CO2 emissions as a result of reducing the vehicle idling time and delays. The purpose of this paper is to investigate the CO2 emissions in a roundabout intersection using a cellular automata model. The roundabout system is composed of the circulating lane and entry/exit lanes, where the entry/exit lanes are controlled by a set of traffic signals (Sn) operating in a fixed-time T. We explore numerically the dependence of the total CO2 emission rate on the injection and extraction rates. Surprisingly, even a small number of vehicles that break the rules of entrance to the circulating lane can affect the CO2 emissions on the roundabout system. Furthermore, we found that the variation of the number Sn, as well as the cycle time play an important role in the variation of the CO2 emissions. Macroscopic and microscopic analyses are conducted to understand the effect of the various parameters on the CO2 emissions in the roundabout system.

This paper presents the design and implementation of a system to monitor the energy quality using ATmega2560 microcontroller embedded in the Arduino MEGA board. The proposed system is capable of acquiring voltage and current signals at sampling rate of up to 22 kHz simultaneously, and through digital processing obtains the basic parameters of the electrical signal. The samples obtained are possible to send, at various transmission rates, through the USB port to the computer. The components used in the realization are of low cost compared with the existing equipment at commercial level. The reliability of the system is validated by comparing the results with electrical metrology equipment. Keywords-- Real-time Monitoring, Open Source microcontroller, Basic electrical parameters measurements

Ballistic electron transport in a silicene structure, composed of a pair of magnetic gates, in the ferromagnetic and an-tiferromagnetic configuration is studied. This theoretical study has been done using the matrix transfer method to calculate the transmission, the conductance for parallel and antiparallel magnetic alignment and the magnetoresistance. Results show that conductance and magnetoresistance oscillate as a function of the length between the two magnetic domains. The forbidden transmission region also increases as a function of the barrier separation distance.

This paper presents the recognition of myoelectric signal's algorithm design thru artificial neural network architecture, for the manufacture of a prototype of human hand prosthesis. At the beginning of the project the myoelectric sensor was designed to help capture the signals that correspond to the movement of each finger of a human hand. A database was generated with captured myoelectric signals, which was used for the training of artificial neural networks (ANN), obtaining the weights and bias. The performance of the architecture was evaluated with statistical criteria for the validation of ANN, comparing between simulated data and experimental data. It was found, that the best architecture in this project has 7 neurons in the hidden layer, one in the output layer and 96% correlation coefficient, this architecture is the number 7 in Table 1 which contains a performance report learning algorithm of the different architectures proposed.

The application of the Thomas-Fermi method to calculate the electron spectrum in quantum wells formed by highly doped n-Si quantum wires is presented under finite temperatures where the many-body effects, like exchange, are taken into account. The electron potential energy is calculated initially from a single equation. Then the electron energy sub-levels and the wave functions within the potential well are simulated from the Schr?dinger equation. For axially symmetric wave functions the shooting method has been used. Two methods have been applied to solve the Schr?dinger equation in the case of the anisotropic effective electron mass, the variation method and the iteration procedure for the eigenvectors of the Hamiltonian matrix.

In the framework of the Thomas–Fermi (TF) approach, a model for the p-type double-δ-doped (DDD) system in GaAs is presented. This model, unlike other works in the literature, takes into account that the Poisson equation associated with the system is nonlinear. The electronic structure is calculated for heavy and light holes. The changes in the electronic structure result of the distance d between the doped layers are studied. In particular, the relative absorption coefficient as well as the relative refractive index change is calculated as a function of the incident photon energy for heavy holes. The effect of the interlayer distance exhibits, in the absorption coefficient, a red shift of the peak position and a decrease in amplitude when the distance increases. In addition, the relative refractive index change node has a red shift as well as the interlayer distance increases. The calculations show that the effect of the separation between layers has a greater influence on the linear terms. These results are very important for theoretical calculations and engineering of optical and electronic devices based in δ-doped GaAs.

The superposition principle is one of the cornerstones of physics. In low-dimensional systems, it is routinely used to model the potential profile. That is the case of coupled [Formula: see text]-doped quantum wells, for which, several works have studied the transport and optoelectronic properties. However, the Poisson equation determines the potential profile is not linear, and the superposition principle is not at all valid. The aim of this work is to correct some of the inconsistencies of the mentioned models for coupled [Formula: see text]-doped quantum wells. In the framework of Thomas–Fermi approximation, we calculated the potential profile, the wave functions, the energy values and the relative absorption coefficient for the double system compared to an isolated delta system in terms of impurity density and distance between [Formula: see text]-wells. We found a red shifting in the absorption coefficient when the interlayer distances increase, in addition, an enhancement in the absorption coefficient is detected for a specific separation distance. Our results agree with ab-initio calculations reported for the electronic structure.

In this paper, we proposed a model based on the connected vehicles to control the traffic flow at the intersection. To evaluate this model, we studied its impact on the flux and the probability of accidents at the intersection. On the one hand, simulation results showed that the increase in the number of connected vehicles decreases the congestion coefficient and enhances the traffic situation in the system. On the other hand, connected vehicles reduce the probability of accidents at the intersection. In this way, the vehicle intersection (central controller) communication can decrease the congestion and enhance road safety, especially in the intermediate and high traffic conditions.

We have theoretically calculated the effects of hydrostatic pressure on subband structure and optical transitions in n -delta-doped quantum well (DDQW) in GaAs for different values of energy. The electronic structure of DDQW under the hydrostatic pressure is determined by solving the Schrodinger equation and a simple algebraic method. From our calculations, it is found that the subband energies and intersubband optical absorption is quite sensitive to the applied hydrostatic pressure. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons.

According to the scaling-down theory, the ALD-FET (Atomic Layer Doping-Field Efiect Transistor) structure has attracted a lot of attention in view of its uses for developing devices with very short channels and for achieving very-high-speed operation. Therefore, there is a strong need to obtain an accurate understanding of carrier transport (mobility and conductivity) in such devices. In this work, we report the carrier transport based on the electronic structure of devices. Our results include analytical expressions of both mobility and conductivity. Our analytical expressions for the mobility and conductivity allow us to analyze transport in ALD-FET. We report regions where this device operates in digital and analogue mode. These regions are delimited in terms of intrinsic and extrinsic parameters of the system. The width of the Ohmic region as well as the NDR (Negative Difierential Resistance) properties of the system are also characterized.

Using the cellular automata Nagel–Schreckenberg (NaSch) model, we numerically study the impact of traffic lights on the probability of car accidents ([Formula: see text]) at the intersection of two roads. It is found that, the probability [Formula: see text] is more stable with variation of the green light ([Formula: see text]) when the symmetric lights are adopted. Moreover, simulation results show the existence of a critical time [Formula: see text], below which ([Formula: see text]) [Formula: see text] increases as the injection rate ([Formula: see text]) increases, however, above which ([Formula: see text]) the growing of [Formula: see text] has for effect the decrease of [Formula: see text]. Furthermore, the decrease of [Formula: see text] is almost always accompanied by a loss of the flux, especially with asymmetrical lights. To overcome this problem, we proposed a strategy that can greatly increase the flux and keep the probability [Formula: see text] as small as possible, especially for the low and high injection rates.

Low-dimensional thermoelectricity opens the possibility of improving the performance and the efficiency of thermoelectric devices by redistributing the electron density of states through the reduction of dimensionality. In this work, we explore this possibility in silicene by reducing its dimensionality through the periodic arrangement of gated electrodes, the so-called gated silicene superlattices. Silicene electrons were described quantum relativistically. The transmission, conductance, and thermoelectric properties were obtained with the transfer matrix method, the Landauer-Buttiker formalism, and the Cutler-Mott formula, respectively. We find that the redistribution of the density of states together with the intrinsic characteristics of silicene, the local bandgap and the large spin-orbit coupling, contribute to the enhancement of the thermoelectric properties. In particular, the Seebeck coefficient and the power factor reach values of a few mV/K and nW/K 2. These findings in conjunction with the low thermal conductivity of silicene indicate that silicene-based nanostructures could be the basis of more efficient thermoelectric devices.

Various feedback strategies are proposed to improve the traffic flow. However, most of these works did not take road safety into consideration. In this paper, we studied the impact of four feedback strategies on the probability of rear-end collisions ([Formula: see text]). We proposed a new feedback strategy named Accidents Coefficient Feedback Strategy (ACFS) in which dynamic information can be generated and displayed on a board at the entrance of two-route scenario with intersection to help drivers to choose the appropriate road. This new strategy can greatly improve road safety and make the flow smooth as possible at the same time. Moreover, the impact of the intersection and boundary rates ([Formula: see text] and [Formula: see text]) on [Formula: see text] is also studied.

Using the Nagel-Schreckenberg model, we investigate the flow characteristics in a traffic circle system, where the entry lanes are controlled by traffic lights operating in a fixed-time ([Formula: see text]. We considered four different strategies to control traffic coming from [Formula: see text] entry lanes. We found that depending on the strategy used, four distinct traffic phases can appear in the circulating lane of the traffic circle, namely free flow, congestion, maximum current, and gridlock. Also, we investigate the origin of the gridlock phase in both cases (i.e. with/without traffic lights). Furthermore, the lengths of queues of stopped vehicles in the entry lanes were studied. We found that the traffic flow behavior on the exit/entry lanes depends strongly on the flow characteristics at the circulating lane as well as traffic lights strategy. To improve the operation of the traffic circle system, we have studied the time delay between the traffic lights to switch where all entry lanes go red, which allowing vehicles to clear the circulating lane.

In this paper, we propose a stochastic cellular automata model to study the traffic behavior at a single-lane roundabout. Vehicles can enter the interior lane or exit from it via [Formula: see text] intersecting lane, the boundary conditions are stochastic. The traffic is controlled by a self-organized scheme. It has turned out that depending on the rules of insertion to the roundabout, five distinct traffic phases can appear, namely, free flow, congestion, maximum current, jammed and gridlock. The transition between the free flow and the gridlock is forbidden. The density profiles are used to study the traffic pattern at the interior lane of the roundabout. In order to quantify the interactions between vehicles in the interior lane of the roundabout, the velocity correlation coefficient (VCC) is also studied. Besides, the spatiotemporal diagrams corresponding to the entry/exit lanes are derived numerically. Furthermore, we have investigated the effect of displaying signal ([Formula: see text], as the [Formula: see text] decreases, the maximum current increases at the expense of the free flow and the jamming phase. Finally, we have investigated the effect of the braking probability [Formula: see text] on the interior lane of the roundabout. We have found that the increase of [Formula: see text] raises the spontaneous jam formation on the ring. Thus, enlarges the maximum current and the jamming phase while the free flow phase decreases.

The objective of this work is to analyze electronic transport phenomena, due to ionized impurity scattering in δ-MIGFET (Delta-Multiple Independent Gate Field Effect Transistor). In this work, we report theoretical results for electronic transport in a delta-MIGFET using the device electronic structure and analytical expression of mobility and conductivity. The results show that the analytical mobility and conductivity are a good way to analyze Received 13 August 2010, Accepted 14 October 2010, Scheduled 10 November 2010 Corresponding author: Outmane Oubram (oubram@uaem.mx). † Also with Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, Mexico D.F 04510, Mexico.

The influence of hydrostatic pressure on the low-temperature electron conductivity in n-type GaAs δ-doped single quantum wells is studied. The effect of the pressure on the electron mobility is described via a relative quantity that is proportional to the ratio between the results for P ≠ 0 and P = 0. Calculation is performed using an analytical description taking explicitly into account the dependence upon P of the main input parameters; i.e. effective mass and dielectric constant. It is shown that the effect of hydrostatic pressure is to increase the low-temperature resistivity of the two-dimensional electron gas in the system.

The first calculation of mobility and conductivity between source and drain as function of gate voltage in a δ-doped Field Effect Transistor is presented. The calculation was performed with a model for the δ-FET that was shown in (1). The mobility was calculated using a phenomenological expression that was presented in (2). That expression does not have empirical form, neither empirical parameter. For the first time a phenomenological expression of the conductivity is presented, which is derived from the mobility expression. The conductivity shows three different regions: a parabolic region and two linear regions. The parabolic region represents the region at which the conduction channel begins to close. On the other hand, the mobility shows a more different behavior. In the mobility there are four regions. These regions correspond to the disappearance of the different conduction channels that form the subbands of the delta- doped quantum well. The different behavior between mobility and conductivity relies on the depletion of the delta-doped quantum well as the gate potential grows.

This work presents a development kit to simulate the behavior of load flow an Voltage Stability of a power system. The network is designed and implemented to be useful as a tool in engineering studies and laboratory practices; also the measurement of steady state is compared with its digital behavior simulation using Power World software. The system configuration has been extracted from one similar typical network used in the literature of power systems. Basically it has an infinity bus, two generators, loads, six transmission lines that permit also synchronization tests and making digital and analog measurements. The generators, loads as a constant impedance (resistors, capacitors and reactors) and the infinity bus belong to a Lab-Volt commercial brand, transmission short line models are designed using easy acquisition materials. In addition the use of a digital instrument of AEMC series permits the capture of information.

The combined effects of hydrostatic pressure and voltage contact on subband structure and optical transitions in GaAs delta-MIGFET (Delta-Multiple Independent Gate Field Effect Transistor) have been theoretically studied. Results obtained show the optical absorption is quite sensitive to the applied hydrostatic pressure and contact voltage. These can be suitable for good optical performance and various infrared optical device applications and can be easily obtained by tuning the voltage contact and hydrostatic pressure strength.

Esta investigación presenta la simulación de las sobretensiones ocurridas durante una maniobra de mantenimiento en un compensador estático de potencia reactiva de 230 kV. El incorrecto funcionamiento de un interruptor de potencia causa una falla catastrófica que incluye la explosión y el incendio del equipo. La Información obtenida de investigaciones previas, donde se analizan los estados estable y transitorio del compensador, no toma en cuenta la combinación del comportamiento del compensador y la fallida operación de los medios de desconexión. La incorrecta apertura de uno de los polos del interruptor de potencia del compensador provoca sobretensiones interesantes las cuales están relacionadas con las componentes armónicas de tensión y corriente generadas por un elemento clave de la falla: el reactor controlado por tiristores. En este trabajo se utiliza el Software Alternative Transients Program (ATP) para modelar el compensador y obtener el cálculo de las sobretensiones transitorias. Se analizan las frecuencias naturales y el espectro armónico de las señales manejadas por el compensador. Con la ayuda de una videograbación se muestran imágenes reales de los arcos eléctricos generados debido a las sobretensiones. Este estudio se realiza por primera vez en este compensador estático y la información resultante es de mucha utilidad futura para el diseño eléctrico y la planificación de la operación de las redes de potencia.

We study the resonant tunneling effects through double barrier graphene systems (DBGSs). We have considered two types of DBGSs in order to take into account or rule out Klein tunneling effects: (1) the well-known and documented electrostatic-barrier structures (EBSs) created by means of electrostatic probes that act perpendicularly to the graphene sheet; and (2) substrate-barrier structures (SBSs) built sitting the graphene layer on alternating substrates, such as SiO2 and SiC, which are capable of non-open and open an energy bandgap on graphene. The transfer matrix approach is used to obtain the transmittance, linear-regime conductance, and electronic structure for different set of parameters such as electron energy, electron incident angle, barrier, and well widths. Particular attention is paid to the asymmetric characteristics of the DBGSs, as well as to the main differences between Klein and non-Klein tunneling structures. We find that: (1) the transmission properties can be modulated readily changing...

The influence of hydrostatic pressure on the electron states and low-temperature mobility in n-type GaAs δ-doped single quantum wells is studied. Values of hydrostatic pressure consider are below the so-called Γ-X crossover, keeping all attention in the electronic properties at the Brillouin zone center. The effect of the pressure on the electron mobility is described via a relative quantity that is proportional to the ratio between P ≠ 0 and zero pressure results. Calculation is performed using an analytical description of the potential energy function profile, based on the Thomas-Fermi approach, taking explicitly into account the dependence upon P of the main input parameters: effective masses and dielectric constant. The relative mobility increases for higher values of P. The cases of zero and finite -although small- temperature are studied, showing that the influence of T is mainly to lower the values of the relative mobility in the entire range of P considered. Numerical results are reported for a two-dimensional density of ionized impurities equals to 7.5 × 1012 cm-2.