Journal Information
ISSN / EISSN : 1109-9445 / 2415-1513
Total articles ≅ 29
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Oscar Secundino-Sánchez, José F. Sánchez-Ramírez, Joel Diaz-Reyes

TiO2 nanofibres were synthesised by means of the electrospinning technique, which were annealed at high temperatures to achieve the crystalline phase transformation. The chemical stoichiometry of electrospun TiO2 nanofibres was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. TEM images show clearly the formation of TiO2 nanofibres that exhibit a homogeneous and continuous aspect without the presence of crystalline defects, whose surface morphology depends strongly on the annealing temperature. The crystalline phase transformation was studied by Raman spectroscopy, which revealed that annealed TiO2 nanofibres showed a crystalline phase transformation from pure anatase to, first a mix of anatase-rutile, then pure rutile as the annealing temperature increased, which was corroborated by X-ray diffraction and high-resolution TEM microscopy. The average grain size, inside the nanofibres, increased with the crystalline phase transformation from 10 to 24 nm for anatase-TiO2 and from 30 to 47 nm for rutile-TiO2, estimated by using the Scherrer-Debye equation. The band gap energy (Eg), obtained from optical absorption spectra, decreases monotonically, where a local minimum is observed at 700 °C, which is ranged in 3.75  Eg  2.42 eV, caused by the anatase → rutile crystalline phase transformation. The photoluminescence shows that radiative bands present a gradual red-shift as the annealing temperature increases due to the continuous change of Eg.
Minsha Shah, Hitesh Mandaliya, Lavkesh Lachhvani, Manu Bajpai, Rachana Rajpal

Microcontroller based trigger control circuit for fast pulsing of electrode potentials on wide range of time scales has been designed, installed, and tested for electron plasma experiments which are carried out in partial toroidal trap SMall Aspect Ratio Toroidal Electron plasma EXperiment in C – shaped geometry (SMARTEX – C), a device to create and confine non-neutral plasma (electron plasma). The sequence of trap operation is inject-hold-dump for which electrodes need to be pulsed with applied voltages at a high switching speed of few nanoseconds. Also this sequence of operation needs to be controlled over a very wide range of time scales from few microseconds to few seconds. As the available COTS (Commercial-Off-The-Shelf) high voltage DC power supplies generally do not provide this feature of fast switching at nanosecond time scale, MOSFET based circuit is developed which provides fast switching in the range of 20 – 100 nanoseconds of high voltages (200Vdc - 500Vdc) of multiple electrodes. The timing pulse widths of these trigger pulses are controlled using a microcontroller-based circuit. This experimental set-up also requires the triggering of a high current dc power supply used for an Electro-magnet (Toroidal Field Coil) to generate a toroidal magnetic field, at the start of this experiment. For this purpose, a Silicon Controlled Rectifier (SCR) based circuit is used. The gate pulse to trigger the SCR circuit is also generated from this microcontroller-based circuit. National Instrument’s LabVIEW software based Graphical User Interface (GUI) is developed for triggering the SCR and electrodes with a programmable time period through the serial link.
Chang-Ju Wu, I-Fong Chen, Chia-Mei Peng, Wen-Yi Tsai, Jwo-Shiun Sun

In this letter, the design of a compact planar Fractal-shaped O-ring monopole antenna based on the Sierpinski carpet concept is studied and proposed for modern broadband wireless applications. The planar fractal-shaped O-ring monopole antenna is on the basis of Sierpinski category construction and then modifies the state of the plane inward with a radius of 27mm over the two iterations. The antenna structure is low profile and easy to be fabricated, and it has performed the simulation and measurement with the result VSWR ≤ 2 that can achieve a wide impedance bandwidth 636% from the frequency band 1.57GHz ~ 10GHz. The geometric scale factor of the Sierpinski fractal is according to the same scale element that defines the geometrical self-similarity. In our experiments, the results show that use of fractal-shaped O-ring into monopole antenna structure can effectively improve input impedance matching, and obtain a larger bandwidth and better radiation pattern, while also having predictable multi-band characteristics.
Nihar Jouti Sama, Manash Pratim Sarma

OP-AMPs finds applications in different domains of electronics engineering including communications. There has been several OP-AMP configurations realized in the last decades for different target applications. But with the evolution of communication standards, to meet the demand for high data rate over the years, requirement for a high frequency and high BW OP-AMP is gaining attention. This makes the design challenge much higher. This paper presents a two-stage CMOS amplifier which uses frequency compensation method to facilitate higher BW. Different parameters like Gain, Gain band width product (GBWP), Phase Margin and Total Power dissipation are considered in this design. A step-by-step procedure for an efficient amplifier design is followed using frequency compensation. We have achieved a gain-bandwidth product (GBWP) of 110 MHz that is capable of driving large capacitive loads. It also achieves 77.7 dB gain with a phase margin of 60o.
Marcelo G. Cendoya, Graciela M. Toccaceli

A very attractive and relatively simple option to simulate a DC-DC converter is to use a hybrid model. In this case, the need to use very small simulation steps (as those necessary to simulate models carried out at the physical level) is avoided. Furthermore, unlike the averaged state-space models, it has the advantage that the model is valid throughout the entire working range of the converter and for both conduction modes (continuous and discontinuous). By simulating several renewable energy conversion systems incorporating DC-DC converters, the authors have discovered the true potential of this modeling method. Despite its inherent advantages, this approach to DC-DC converters simulation is not as widely adopted as it should be. This work tries to encourage the reader of its use in certain typical situations. In this article the implementation of the hybrid model of the DC-DC Buck-Boost converter, using Statechart techniques, is performed. This model was written in the Stateflow language, a tool from the MATLAB®/Simulink environment, and allowed the creation of a building block formed by the described converter model with adequate interfaces to the SimPowerSystem and Simulink environments. The block is validated by comparing simulation results, realized under different operating conditions, with calculations done employing well-known and proven formulas. As an example of the use of the presented block, a buck-boost DC-DC converter with voltage and current control loops is simulated, corroborating its correct performance
Alexander Zemliak, Fernando Reyes, Olga Felix

An analog circuit design methodology based on applications of control theory is the basis for constructing an optimal or quasi-optimal design algorithm. The main criterion for identifying the required structure of the algorithm is the behavior of the Lyapunov function, which was decisive for the circuit optimization process. The characteristics of the Lyapunov function and its derivative are the basis for finding the optimal structure of the control vector that determines the structure of the algorithm. A block diagram of a quasi-optimal algorithm that implements the main ideas of the methodology is constructed, and the main characteristics of this algorithm are presented in comparison with the traditional approach
Tarkeshwar C. Patil

In this paper, ferromagnetic Schottky contacts for GaN based spin injection are being studied. The electrical characterization of this Co/n-GaN and Fe/n-GaN Schottky contacts showing the zero-bias barrier height comes closer to unity as the temperature is increased. Also, the Richardson constant is extracted for this Schottky contact. Both the zero-bias barrier height and the Richardson constant are verified both experimentally as well as theoretically. Thus, this Schottky contacts will serve as spin injector for GaN based spin devices specifically for GaCrN based devices
Felix Sadyrbaev, Inna Samuilik, Valentin Sengileyev

We consider mathematical model of genetic regulatory networks (GRN). This model consists of a nonlinear system of ordinary differential equations. The vector of solutions X(t) is interpreted as a current state of a network for a given value of time t: Evolution of a network and future states depend heavily on attractors of system of ODE. We discuss this issue for low dimensional networks and show how the results can be applied for the study of large size networks. Examples and visualizations are provided
Adel Elgammal, Tagore Ramlal

This article forecasts the performance of smart-grid electrical transmission systems and integrated battery/FC/Wind/PV storage system renewable power sources in the context of unpredictable solar and wind power supplies. The research provided a hybrid renewable energy sources smart grid power system electrical frequency control solution using adaptive control techniques and model predictive control (MPC) based on the Multi-Objective Practical Swarm Optimization Algorithm MOPSO. To solve the problems of parameter tuning in Load Frequency Control, the suggested adaptive control approach is utilized to accomplish on-line adjustment of the Load Frequency Control parameters. During the electrical grid's integration, the system under investigation is a hybrid Wind/PV/FC/Battery smart grid with variable demand load. To achieve optimal outcomes, all of the controller settings for various units in power grids are determined by means of a customized objective function and a particle swarm optimization method rather than a regular objective function with fluctuating restrictions. To suppress the consumption and generation balance, MPCs were designed for each of the Storage Battery, Wind Turbine Generation, and the model Photovoltaic Generation. In addition, demand response (real-time pricing) was used in this scheme to reduce the load frequency by adjusting the controlled loads. The suggested control strategy is evaluated in the Simulink /MATLAB environment in order to analyse the suggested approach's working in the power system, as well as its effectiveness, reliability, robustness, and stability. The simulation findings show that the proposed control method generally converges to an optimal operating point that minimises total user disutility, restores normal frequency and planned tie-line power flows, and maintains transmission line thermal restrictions. The simulation results further indicate that the convergence holds even when the control algorithm uses inaccurate system parameters. Finally, numerical simulations are used to illustrate the proposed algorithm's robustness, optimality, and effectiveness. In compared to previous methodologies, the system frequency recovers effectively and efficiently in the event of a power demand disturbance, as demonstrated. A sensitivity test is also performed to assess the suggested technique's effectiveness.
Chang-Ju Wu, I-Fong Chen, Chia-Mei Peng, Jwo-Shiun Sun

In this letter, a single layer dual-polarization printed bow-tie slot broadband antenna with C-band stop is presented. The proposed antenna consists of two pairs of mirror-symmetric and mutually perpendicular bow-tie slots with two coplanar waveguide (CPW)-fed. The proposed antenna has a very simple structure and the measured results demonstrate the antenna performance can be achieved a wide impedance bandwidth 79.1% for | S11 | and | S22 | ≦ -10dB from 1.3 ~ 3 GHz and 62.3% from 5.25 ~ 10 GHz, which has been implemented the operating band for GPS (1575MHz), WLAN band (2.4GHz and 5.8GHz), and 6 GHz unlicensed spectrum (5.925 ~ 7.125 GHz), UWB band (3.1 ~ 10.6 GHz), LTE Upper band (LTE, 1710 ~ 2690 MHz) applications. The measured in-band isolation performance between the two ports | S21 | ≦ -15.5dB from 1.4 ~ 3 GHz, and | S21 | ≦ -21dB from 5 ~ 10 GHz is significantly achieved and the radiation pattern, peak gain, and efficiency of the proposed antenna are measured as well. In the end, the simulated and measured radiation patterns are compared.
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