A Current Amplifier Circuit and Control Strategy Based on FPGA

With the extensive application of electric vehicles, energy storage systems and other power electronic equipment, the research on large capacity controllable current source will be an important direction in the future. This paper proposes controllable current source controlled by a full digitally hysteresis current based on field programmable gate array(FPGA), in which the single phase full bridge topology is adopted as the main circuit of current source. The two levels and three levels hysteresis current control strategies are analyzed and compared with the platform of PSCAD/EMTDC. The user defined component was adopted to realize the two difference control strategies with fortran language program. The simulation results verified that the two levels hysteresis current control strategy is much more fit for the controllable current source. Finally, a prototype is designed and fulfilled and it is controlled by the digitally controller with FPGA. The hysteresis current control is realized by FPGA controller with VHDL programming. The experimental results show that the researched hysteresis current control technology is effective for the current amplifier

Gyrotron Development at High Order Modes

The present work has been characterized by higher order modes in the cavities of the Gyrotron; they are capable of producing RF plasma by developments of it. It uses for fusion systems. We choose the TE31,8 mode in our study. The main problem of gyrotron is the device of the thermal cavity loading. The problem of the thermal loading is solved when any parasitic modes suppress, absence of desired modes; the thermal loading is increased when the high power tube of gyrotron operation is unstable. The mathematical interaction model contains equations that describe the electron motion and the field profiles of the transferred electric modes of the resonator, these are interacting with electrons based on the finite difference method that has been designed to study the starting current, the frequency, quality factor and calculates the roots of the Bessel function by the program we designed in Fortran language. They are used to calculate the operation frequency. Good agreement is between our results and the previous published results both confirm the accuracy of the performance of the designed program.

Chemical detection of certain greenhouse gases by the LIDAR Technique

The aim of this study is to detect the chemical elements of the greenhouse effect from the LIDAR signal. Using a digital program developed by Fortran language, and based on spectral data. In the present work, The LIDAR sample is clearly contains water vapor and carbon dioxide. According to our results, the content of the sample with methane and the non-detection of nitrogen oxide, due to the absence of its absorption signal in the spectral range of the experimental signal. Carbon dioxide is one of the most dangerous greenhouse gases, our results show that 1 mole of this gas requires 1.45 moles of water vapor.

ELECTRICAL POTENTIAL BETWEEN NON-PARALLEL FLAT ELECTRODES – SIMULATION OF A CELL USED WITH TOMATO

The equipotential lines of the field generated by the cell used in dielectric measurements of whole fruit tomato are plotted. This cell consists of two inclined electrodes, at inverse potentials, and is an adaptation made in the Dielectric Laboratory of the cell used by Varlan-Sansen. To obtain the graphs, the Laplace equation was solved by finite differences and a program in Fortran language was written, which performs the calculations by numerical iteration. The field generated by the cell at different electrode separation distances was analyzed.

Normal contact performance of mortise and tenon joint: theoretical analysis and numerical simulation

This article aims to investigate the contact characteristics of mortise and tenon (M&T) joints in the traditional timber structures. In particular, the normal embedded compressive contact between contact surfaces of M&T joint was investigated. Based on basic contact theory and contact characteristics between mortise and tenon, a normal elasto-plastic contact model, which can reflect the real normal contact behavior of M&T joints in traditional wooden structures, was proposed. Coulomb friction contact was utilized to describe the tangential slipping characteristics of the contact surfaces. Micro-morphology scanning tests of wood samples with different roughness were carried out to determine the parameters involved in the normal contact model. The normal contact model subroutine of M&T joint was compiled by FORTRAN language, implemented into ABAQUS through user-defined interface (UINTER). Then the proposed model was verified by shear tests of wood contact surfaces considering different normal pressures. Finally, a finite element model (FEM) of straight tenon joint subjected to cyclic reversed loading, based on the proposed normal elasto-plastic contact model, was developed, and a FEM considering normal “hard contact” between the contact surfaces, was also performed. The simulation results were validated by the experimental results. Results showed that the user-defined normal elasto-plastic contact FEM was more in line with the actual force state and mechanical behavior of M&T joints, which can more accurately predict the failure modes and simulate the hysteretic behavior of M&T joints, compared to the FEM considering normal “hard contact” of the contact surfaces.

New FORTRAN meanline code for investigating the volute to rotor interspace effect on mixed flow turbine performance

Mixed flow turbines are widely used in several industrial applications covering turbomachinery, automotive engineering and electricity production. For decades, it is well known that mixed flow turbines are a seat of several loss phenomena such as the volute to rotor interspace loss, subject of this paper. Commonly, the meanline approach is the first step solution for building a preliminary design of such turbines and estimating subsequent losses. The accuracy of the code used in the meanline modeling is crucial for building an optimized turbine design with a minimized loss generation. This paper presents an improved validated meanline code, written in the newest object-oriented version of the FORTRAN language, for turbomachinery performance prediction. Unlike commercially available codes, the code allows the calculation of the rotor passage loss coefficient given the turbine expansion ratio without the need for additional test data. The standard deviation value between the code and test data is less than 10%, for all studied cases which ensure the validity of the developed model. Then, the developed code is exploited to investigate the effect of the volute to rotor interspace geometry on the loss generation and performance of a mixed flow turbine. Indeed, a performance distribution over a wide range of rotational speed and an energy loss breakdown are depicted and discussed showing a significant impact of the volute to rotor interspace. The results revealed an improvement in the turbine efficiency up to 2.9% with a volute to rotor interspace radii ratio of 0.59 at 80% of the design speed.

Application of Direct Integration Methods in the solution of a nonlinear beam problem

This work applies different numerical methods involved in the solution of a nonlinear clamped beam problem. The methodology used in the discretization of the dynamic problem is based on the Finite Element Method (FEM), followed by mode superposition, where a localized nonlinearity is applied at the free end of the beam. The solution of the nonlinear problem is performed by five different integration methods. The solution code is implemented in FORTRAN language, validated with ANSYS and the dynamic response and the graphs are obtained with the help of MATLAB software. The work shows the convergence of the implemented methods with various validation problems.

A fast spectral conjugate gradient method for solving nonlinear optimization problems

<span>This paper proposes a new spectral conjugate gradient (SCG) approach for solving unregulated nonlinear optimization problems. Our approach proposes Using Wolfe's rapid line scan to adjust the standard conjugate descent (CD) algorithm. A new spectral parameter is a mixture of new gradient and old search path. The path provided by the modified method provides a path of descent for the solution of objective functions. The updated method fits the traditional CD method if the line check is correct. The stability and global convergence properties of the current new SCG are technically obtained from applying certain well-known and recent mild assumptions. We test our approach with eight recently published CD and SCG methods on 55 optimization research issues from the CUTE library. The suggested and all other algorithms included in our experimental research were implemented in FORTRAN language with double precision arithmetic and all experiments were conducted on a PC with 8 GB ram Processor Intel Core i7. The results indicate that our proposed solution outperforms recently reported algorithms by processing and performing fewer iterations in a shorter time.</span>

A comparison between the presence and absence of virtual viscosity in the behaviour of the two phase flow interface

In this paper, a numerical study is performed in order to investigate the effect of the virtual viscosity on simulation of separated two-phase flow of gas-liquid. The governing equations solved by shock capturing method which can provide predicting the interface without the flow field solving. In this work, in order to calculate the numerical flux term, first-order centred scheme (Force scheme) was applied cause of its accuracy and appropriate validation. Analysis approves that the obtained stability range of this research is consistent with the classic Kelvin-Helmholtz instability equation only for the long wavelength with small amplitude. Results reveal that when the wavelengths are reduced, the specified range is not consistent and wavelength affects on instability range and it is over predicted. An algorithm for water faucet problem was developed in Fortran language. Short wavelength perturbations induce unbounded growth rates and make it impossible to achieve converging solutions. The approach taken in this article has been to adding virtual viscosity as a CFD technique, is used to remedy this deficiency.

MODELAGEM DA EMISSÃO DE LUZ BRANCA CONTÍNUA POR CONVERSÃO ASCENDENTE DE ENERGIA EM NANOMATERIAIS

In the last decade, the emission of continuous bright white light by nanomaterials of metal oxides has been observed when excited with lasers in the near infrared region. However, the origin of this phenomenon of emission of continuous white light by upconversion of energy is not yet established. Therefore, in this work, we aimed at developing a quantitative model based on the power balance equation to describe this process considering thermal emission as the main mechanism for white light generation. The model was implemented in the Rates program, in Fortran language, to solve differential equations using the 4th order Runge-Kutta method with an adaptive time step. The results show that the proposed model is adequate for the description of the most relevant features of this phenomenon, which allows its use in the design of new materials and to improve experimental conditions.