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Home>Products>Journal and Reviews>I.RE.Mo.S.>Latest issue
International Review on Modelling and Simulations - February 2009 - Papers
International Review on Modelling and Simulations - Papers
by M.T. Abakar, J.J. Rousseau, Y. Mahamoud, T. Rouiller, B. Allard Vol. 2. n. 1, pp. 1-7
Abstract - A general
method for thermal modelling of magnetic components used in power
electronics is presented. The paper is composed of two parts. The first
one is subtitled Theoretical issues and concerns an approach for thermal
modelling. The objectives of this work are presented, the assumptions
are justified and the proposed thermal approach is developed and
discussed. In a second paper entitled Experimental determination of the
model parameters the proposed method will be applied to determine the
thermal equivalent circuit of a magnetic component. Comparisons between
experimental results and simulation will be carried out in order to
validate the approach. For thermal modelling the following rules have
been defined:An easy-to-use model; An accurate model (better than a few
degrees). The thermal model must be able to determine average
temperatures of windings and magnetic core respectively, and the input
data are both magnetic and copper losses. The nodal method is considered
and equivalent circuits are constructed. The model is composed of many
thermal elements (resistors and capacitors) that represent thermal
exchanges into and outside the component. To validate the model a
thermal measurement equipment was also developed and some measurements
have been performed. A good agreement is found between the model and the
measurements.
Keywords: Power electronics, Magnetic components, Heat transfer, Thermal modelling.
Vol. 2. n. 1, pp. 8-11
Abstract - A low power fast adder circuit, suitable for implementation in deep submicron CMOS technologies is presented. It is done by design of full adder subcomponents. One subcomponent is an optimized version of a common circuit, and the second is a newly designed circuit. The results of HSPICE simulations, which are performed in 90nm PTM (Predictive Technology Model), are presented for subcomponents and the resulted full-adder circuit. HSPICE simulation results show great improvements for this new presented circuit. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Deep submicron CMOS technology, Static power consumption, Adder subcomponents.
Vol. 2. n. 1, pp. 12-17
Abstract - This paper proposes new and non-traditional approaches for power system fault calculations. The numerical algorithm is based on a finite element technique (FET) procedure. The finite element technique so far used for numerical analysis of continuum field problems here has been adapted to power system fault studies. The numerical procedure is very efficient, numerically stable and generally applicable. From the point of view of computational complexity and from the pedagogical point of view, novel computational method is very simple and suitable for the power system fault calculations. As the power system has been built assembling the three phase finite elements, the solution of the fault studies is natural and straightforward. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Numerical analysis, Finite element technique, Fault studies.
Vol. 2. n. 1, pp. 18-24
Abstract - This paper presents a new methodology that allows selecting and ranking critical contingencies for voltage stability in Power Systems, redefining the branch participation factor. This method uses the modal analysis of the reduced Jacobian matrix, as well as the partition of the system in multiple areas. Furthermore, it is shown how to use this method to analyze, rank and select critical contingencies with N-2 criteria. Moreover, this method allows analyzing the impact of contingencies in a determined area over another area. The proposed methodology can be used to study the ranking and contingencies assortment with voltage stability criteria, potential and dangerous contingencies in the case of cascading events and, even more, the impact of contingencies between neighbours interconnected systems, for instance, international interconnections. Also, this paper shows the computing time employed by the proposed method. This methodology has been tested in the IEEE 118 nodes system. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Contingencies Ranking, Nodal Analysis, Voltage Security Indexes, Voltage Stability.
Vol. 2. n. 1, pp. 25-34
Abstract - Dynamic model of a 500 W hybrid energy system is presented in this paper. This parallel operation of wind turbine, battery, photo voltaic array and proton exchange membrane fuel-cell (PEMFC) is discussed to show the advantages of named devices cooperation. This kind of hybrid system is completely stand-alone, reliable and has high efficiency. In order to minimize sudden variations in voltage magnitude ultra-capacitors are proposed. Also Power converter and inverter are used to produce ac output power. Dynamics of fuel-cell component such as double layer capacitance are also taken into account. Control scheme of fuel-cell flow controller and voltage regulators are based on PID controllers. Finally Dynamic response of the system to some step changes in energy sources and load demand are presented. Simulation results show the ability of the system in adapting itself to sudden changes and new conditions. Combination of PV and wind renewable sources is made the advantage of using this system in regions which have higher wind speeds in the seasons that suffers from less sunny days and visa versa. It can also easily be used in communities remote from electrical grid. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Hybrid energy systems, Wind energy, Fuel cells, Battery, Photovoltaic, Dynamic modeling of energy systems, Control and simulation.
Vol. 2. n. 1, pp. 35-41
Abstract - This paper tries to develop the concept of the dual structure for a skewed motor. In a dual structure method there is no skew, therefore the known drawbacks of the skewing is prevented. This idea can be used for both of the skewed rotor and stator. In the first part of the paper the Dual structure for a BLDC motor is discussed. In this case, it is desired to find a method for cogging torque reduction without deteriorating the trapezoidal shape of back- EMF. In the second part a dual structure for a PMSM is derived. In this case, it is necessary to find a cogging torque reduction method which makes the back-EMF shape closer to a sine shape. The simulation result by finite element shows a considerable reduction in the cogging torque of the motors in each part. Moreover the simulation verifies the quality of back-EMF shape in each case. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Permanent Magnet Motors, Finite Element Methods, Brushless Rotating Machines.
Vol. 2. n. 1, pp. 42-48
Abstract -
Joule losses are the major ones in an electric machine. They are the
principal origin of overheat that can cause the destruction of machine’s
constituents. In this paper, we consider to reduce Joule losses in a
linear reluctant stepping motor by tow complementary steps. By the first
one, Joule losses reduction resulted of dental geometrical dimensions
modification. Numerical simulations have served to present losses
fluctuations as a function of tooth width. The critical of the resulted
curves permitted to extract the most appropriate dimensions which
minimize Joule losses with respecting the magnetic constraints. By the
second step, Joule losses reduction is based on magnetomotive force
analysis. The dynamic insufficiencies resulted of the magnetomotive
force reduction had been disappeared by the migration to a more perfect
hybrid structure. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Force, Joule losses, Magnetomotive force, Clutter, Overheat, Local saturation.
Vol. 2. n. 1, pp. 49-56
Abstract - In this work, a reliable multi-agents system is proposed for on-line Fault Detection and Isolation in case of faults affecting sensors and actuators. In this approach various model based diagnostic methods are combined. In fact, two detection methods are used, the first is based on binary logic and the second is based on a fuzzy approach. Besides, four isolation methods are used. The first is based on fault signature principle. The second is based on fuzzy logic. The third and the fourth are based respectively on Probabilistic Neural Networks (PNN) and Multi-Layer Perceptron (MLP). Each agent is specialized on a specific method for detection or isolation. Agents cooperate and negotiate to ensure efficient fault detection and isolation. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Fault Detection and Isolation, Diagnosis, Multi-agents systems, Cooperation, Negotiation.
Vol. 2. n. 1, pp. 57-66
Abstract - The
geometric variations of a product depend strongly on the quality of
realization of all its components. The geometrical defects which appear
during the machining range are tacked in account by the means of the
machining simulation according to a given model. The machining
simulation contributes to the manufacturing specifications by detailing
the effects of the manufacturing errors on the requirements to respect.
These requirements consist essentially on the imposed dimensional and
geometrical specifications.The developed method is focused on the
geometrical machining simulation in order to establish manufacturing
specification in three directions. The proposed method is based on a
modeling of the different setups of the machining range by the means of
a graph representation. A formal writing of the machining simulation
based on the small displacement torsor is proposed. The developed method
leads to the calculation of the three-dimensional manufacturing errors
on machined surfaces. Then, tolerances on production dimensions can be
calculated in three directions. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Manufacturing simulation, Small displacement torsor, Three-dimensional manufacturing errors.
Vol. 2. n. 1, pp. 67-71
Abstract - An elasto-plastic incremental finite element computer code baptized SEMA "Static Explicit Method Analysis" is developed to simulate the clinch joining process. The FE code is based on an Updated Lagrangian scheme. The used resolution method is based on an explicit static approach. The integration of the elasto-plastic behavior law is realized with an algorithm of Simo and Taylor. The tools are represented by plane facets. A 4-node axisymetric element is used with one-point reduced integration method and hourglass control. The results will be compared to those computed using the static implicit method (computer code ABAQUS) and those obtained by experimental measurements. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: FEM, Numerical simulation, Clinching, Contact, Large deformation.
Vol. 2. n. 1, pp. 72-77
Abstract - The common ability of the riblets or grooved surfaces to reduce turbulent skin friction has been well demonstrated over the latest years for numerous flow conditions. In this paper, turbulent flow simulation was performed in periodic channel with longitudinal grooved wall. Blade and V grooves are examined. The numerical approach was carried out by FLUENT code adopting both Large Eddy Simulation (LES) and Reynolds Stress Model (RSM). The numerical study investigated in the case of low Reynolds number to ascertain riblets efficiency is given. Drag reduction is found to be in good agreement with the available data. Moreover, typical features related to the effects of grooved surface on the behavior of turbulent secondary motion are provided. It is shown that, LES and RSM can reproduce such phenomena over grooved wall. Furthermore, eddy viscosity variation is provided by comparison between smooth and grooved wall. However, the RSM is clearly superior for situations in which the anisotropy of turbulence has a dominant effect on the mean flow. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Grooved surfaces, Large Eddy Simulation (LES), Riblets, Reynolds Stress Model (RSM).
by T. Descamps, L. Van Parys Vol. 2. n. 1, pp. 78-87
Abstract - Widely used for light frame structures or for heavy laminated wood structures, dowel-type fasteners are largely used in timber construction. The purpose of this work is to develop a tool for the semi-rigid analysis and design of such joints. After a short description of common semi-rigid modeling of timber plane frames, a method for an efficient study of joints built with dowel-type fasteners is proposed and developed. This method consists in the introduction of a specific finite element called "Finite Semi-Rigid Element" between the ends of the jointed members. This joint element consists of two nodes, each with three degrees of freedom. During the FE analysis, these nodes are simply tied with common beams elements. The stiffness of the FSRE is computed from the geometry of the joints and non-linear embedding stiffness of all fasteners. As among all connections, slender dowel-type fasteners present some advantages (ductility and cost), this work focused on the study of nailed joints. To validate the finite element modeling, a simple column in compression was studied. Experimental results of a splice joint in bending are presented and compared with numerical analysis results. Finally, to underline interests of finite semi-rigid studies, a frame structure has been studied. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Finite element, Joint, Semi-rigid, Stiffness, Timber.
by Anastasia K. Papadopoulou Vol. 2. n. 1, pp. 88-92
Abstract - For
analysis of a column the finite element method can be used. The
behaviour of a steel column which is exposed to fire is examined. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Fire, Heat Conduction, Plastic Hinges, Step-By-Step Algorithm, Steel Column, Thermal Expansion, Truss Model.
by Souheďl El Alimi, Cécile Münch, Abbčs Azzi, Patrick Bégou, Sassi Ben Nasrallah Vol. 2. n. 1, pp. 93-97
Abstract - This paper presents Large Eddy simulations of a compressible turbulent flow through a duct of square cross-section with a discrete heating source on its bottom wall. The potential interest is related to numerous engineering applications. In the first part of this study, a non heated duct was considered. Tow values of Reynolds number are investigated (Re=8000 and Re=10000). The secondary flow characteristic of this type of flow was highlighted and the intensification of turbulent structures with the Reynolds number was revealed. In the second part, the effect of the discrete heating source is studied without considering gravity effects. It was found that the coherent turbulent structures are enhanced in size and a strong intensification of ejection and sweeps phenomenon are shown at the level of the heating source. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Large Eddy Simulations, Turbulence, Computational fluid mechanics, Secondary flow, Discrete heating source.
by S. Ktata, K. Ouni, N. Ellouze Vol. 2. n. 1, pp. 98-104
Abstract - This paper introduces an effective technique for the compression of ECG signals. The technique is based on MEZW. The EZW compression algorithm for the one dimensional signal was originally derived for image compression based Shapiro’s EZW algorithm. The MEZW apply the chosen threshold values or the expression in order to specify that the significant transformed coefficients are greatly significant. The threshold is applied for different wavelet types in biorthogonal and orthogonal class. The performance of ECG compression algorithm is measured by its ability to minimize distortion while retaining all clinically significant features of the signal. A CR of 88 to 1 is achieved with PRD less than 4%. The algorithm is compared to an alternative compression algorithm based on the discrete wavelet transform. Experiments on selected records from the MIT-BIH database reveal that the proposed method is significantly more efficient in compression. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Compression algorithms, Electrocardiogram, Wavelet transforms, EZW, MEZW.
by B. Yagoubi, M. Daoud, A.Khaled Vol. 2. n. 1, pp. 105-108
Abstract - We have applied a continuous wavelet transform, in particular the Morlet wavelet, to the heart rate variability (HRV) to study the autonomous nervous system (ANS) behaviours and to show the advantage of the wavelet transform method over the spectral analysis. The RR intervals data were taken from the HRV signals of young and old men watching a fantasy film. The results obtained using the Morlet wavelet transform were compared to those obtained by spectral analysis. We have concluded that the study using the wavelet transform is more complete than using the spectral analysis method, that is the sympathetic and the parasympathetic activities can be localised in time during the test period. It seems, in this study, that the sympathetic activity is generally dominant for the old men, whereas in the case of the young men the ANS activity is very unstable throughout the whole time of the film reflecting, probably their ordinary behaviours. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: ANS, HRV, Wavelet transform.
Vol. 2. n. 1, pp. 109-112
Abstract - Fractal analysis is a mathematical model used to describe structures and textures. Fractal analysis has been applied to trabecular patterns in digital radiographs, to estimate changes in bone architecture and density as in osteoporosis. There are different methods for the estimation of fractal dimension (FD) from bone radiographs, some more successful than others, while some give conflicting results. That is why we decided to compare the sensitivity of three FD methods for predicting change in bone quality using simulated digital radiographs. Performances of three fractal analysis methods for predicting change in bone quality using simulated digital radiographs, was tested using two sets of simulated images. The first set contained 5 images of structures varying in boundary thickness to simulate varying degrees of bone density. The second set contained 5 images of the same structure but with the addition of different noise levels. Comparison of the performance of the three FD methods tested here indicates that the Tile method is the most appropriate method for the estimation of changes in bone density, since it accurately produces a corresponding decrease or increase in FD values, and it is not sensitive to noise levels in the digital images. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Fractals, Osteoporoses, Digital radiograph, Noise, Fourier analysis.
Vol. 2. n. 1, pp. 113-117
Abstract - This paper presents the analysis and the synthesis models of voiced sound, using the autoregressive (AR) method. The analysis model is used to extract the sound source (excitation glottic signal), an application to detect and compare the pitch of voiced sounds. However, the synthesis model is used to extract the spectrum and to detect the formants of corresponding sounds, which are pronounced by normal man, man with defective audition (deaf, deep deaf) and other affected by tracheotomy. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Cepstral, Cumulant, Defective audition, Spectrum, Tracheotomy, Pitch.
Vol. 2. n. 1, pp. 118-123
Abstract - This paper proposes a novel technique to detect ventricular fibrillation (VF). The Creighton University ventricular tachyarrhythmia database (CU) and MIT-BIH arrhythmia database were used in this investigation. Three studied features including mean frequency (FM), peak frequency (FP), and spectrum width (SW) which were used in this investigation were derived from the wavelet power spectrum. The Bayesian classifier was employed to classify between sinus rhythm group (SN) and VF group (VF). The results show that the wavelet power spectrum of SN trace are broader than VF’s spectrum. The SW feature performs as the best quality feature in this study. The area under receiver operating characteristic (ROC) curve for SW was 96. The classification with FP and SW achieved the highest performance was 960.2% specificity obtained at 930.2% sensitivity. This investigation exhibits that the wavelet marker has potential to improve an accuracy algorithm for VF detecting. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Ventricular Fibrillation, Detection, Wavelet Transform, Bayesian Classifier.
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