Digital Simulation

The statistics of isotropic homogeneous decaying at moderately large Reynolds number are studied in detail using a Fourier-space band-filtering method on flow fields obtained by direct numerical simulation. Two distinct aspects of the non-Gaussianity of the turbulent field are ...

The working principles and design equations of four different isolated, bi-directional DC to DC converter topologies (a dual active bridge converter, a series resonant converter and two multiple stage topologies) for a 2 kW bi-directional battery charger that can be operated in a wide input and output voltage range are presented in this paper. The results of a detailed mathematical

Abstract-this paper presents a study of the approaches taken to model and simulate power systems of an industrial plant. Even the best-designed electric systems occasionally experience short-circuits resulting in abnormally high currents. To predict the behavior of these short ...

The increasing utilization of photovoltaic (PV) solar systems in distributed (or dispersed) generation systems imposes new requirements for the operation and management of the distribution grid, especially when high penetration levels are achieved. Under this scenario, the power electronics technology plays a vital role in managing an effective grid integration of the PV system, since it is subject to requirements related not only to the intermittent source itself but also to its effects on the grid operation. This paper proposes an improved structure of power conditioning system (PCS) for the grid integration of PV solar systems. The topology employed consists of a three-level cascaded Z-source inverter and allows the flexible, efficient and reliable generation of high quality electric power from the PV array. A full detailed model is described and its control scheme is designed. Validation of models and control schemes is carried out through digital simulations using the MATLAB/Simulink environment.

A technique for image encryption using fractional Fourier transform (FRT) and radial Hilbert transform (RHT) is proposed. The spatial frequency spectrum of the image to be encrypted is first segregated into two parts/channels using RHT, and image subtraction technique. Each of these channels is encrypted independently using double random phase encoding in the FRT domain. The different fractional orders and random phase masks used during the process of encryption and decryption are the keys to enhance the security of the proposed system. The algorithms to implement the proposed encryption and decryption scheme are discussed, and results of digital simulation are presented.

In 1926, the young Piero Bottoni painted a series of watercolor studies entitled Cromatismi architettonici. They are almost unique in the Italian urban studies, proposing color gradations as a key to " symphonic " orchestrating the redevelopment of urban street fronts.

A model is developed for industrial natural gas steam reformers with top-fired and side-fired furnance design. The one-dimensional heterogeneous model for catalyst tubes takes into account the intra-particle diffusion resistances. Two approximations are used for the computation of the effective diffusivities via the Stefan-Maxwell equations. The two-point boundary value differential equations for the catalyst pellets are solved by a novel efficient and modified orthogonal collocation technique. The performance of the model has been checked in the case of two industrial reformers used in the ammonia and methanol industries in Egypt and Saudi Arabia.On a mis au point un modàle pour des réformeurs industriels à la vapeur et au gaz naturel dont la conception du four prévoit une alimentation dans la partie supérieure du réformeur ou la partie latérale. Le modèle hétérogène unidimensionnel pour des tubes de catalyseur tient compte des résistances de diffusion intraparticulaire. Deux approximations sont utilisées pour le calcul des diffusivités efficaces via les équations de Stefan-Maxwell. Les équations différentielles de la valeur limite à deux-points pour les pastilles de catalyseur sont résolues par une nouvelle technique de collocation orthogonale efficace modifiée. On a vérifié la performance du modèle dans le cas de deux réformeurs industriels utilisés dans les industries de l'ammoniac et du méthanol en Égypte et en Arabie Saoudite.

An inherent numerical problem associated with the fully explicit pseudospectral numerical simulation of the incompressible Navier-Stokes equation for viscous flows with no-slip walls is described. A semi-implicit scheme which circumvents this numerical difficulty is presented. In this algorithm the equation of continuity rather than the Poisson equation for pressure is solved directly. Pseudospectral formulation of the channel flow problem using Fourier series and Chebyshev polynominals expansions is given for this scheme. An example demonstrating the applicability of the method is given.

This study, carried out in cooperation with ESSAIM, Ecole Superieure des Sciences Appliquees pour l'Ingenieur, Mulhouse in France, was aimed at developing accurate mathematical models of some types of tyre, in order to analyze their influence on vehicle dynamics. The complete vehicle was studied under dynamic conditions, to quantify the influence of all factors, such as rolling forces, aerodynamic forces and many others, acting on their components on torque distribution and vehicle dynamics. Mathematical models for two common types of vehicle, namely front and rear wheel drive, each ones equipped with the different types of tyre, were developed. Both models were used to simulate the behaviour of a real vehicle, developing complete simulation software, developed in Matlab-Simulink environment at MIPS, Modelisation Intelligence Processus Systemes. Therefore, this car model, running on a straight and curve track, was also developed, to get a qualitative insight of the influence of ...

This paper proposes a novel control system for control of a hybrid wind/photovoltaic (PV) farm utilization with alternative power source for DC type loads. A controller consisting of six different loop controllers is mainly used to regulate the DC-DC converter to reduce a weighted total sum of all loop errors, to mainly track a given speed reference trajectory depicting the

In the past decades, the power quality (PQ) has become a critical issue in highly automated industries and sensitive load centers. The voltage quality is the most important part of the PQ for customers. The voltage disturbances in the form of voltage sags, swells and harmonics can cause huge financial losses. In the past few years, the power electronic solutions have been proposed to avoid these problems. The dynamic voltage restorer (DVR) is one of the solutions. This paper proposes a new topology for single-phase DVR which is able to compensate multiple voltage disturbances and limit the downstream fault currents with a simple topology. The proposed DVR is based on the single-phase direct ac/ac converter which is energized from the main grid. As a result, there is no need for energy storage elements and dc link capacitors. The proposed topology can deal with high voltage with low voltage rating switches. Therefore, the switches can be IGBTs without needing an auxiliary forced commutation circuit as in thyristors which are high voltage switches. The performance of the proposed topology is validated by digital simulations and a laboratory scale prototype implementation.► A new topology for dynamic voltage restorer (DVR) is proposed. ► The proposed topology is based on single-phase direct ac/ac converter. ► The proposed topology does not require energy storage elements. ► The DVR compensates multiple voltage disturbances and limits the downstream fault currents. ► The proposed topology can operate in high voltage networks with low voltage rating switches.