bluuebunny/crossref_metadata_2025_split huggingface dataset:
FE analysis of electromagnetic field coupled with fluid dynamics in an MR clutch
Authors: Jędryczka Cezary 
Published: August 2007

PurposeThe aim of this paper is to find an accurate model for the finite element analysis of coupled phenomena in the dynamic operation of a magnetorheological clutch (MR CLUTCH).Design/methodology/approachThe rheological properties of magnetorheological fluid (MRF) depend on magnetic field distribution. Therefore, the field‐circuit model of electromagnetic phenomena is coupled with the fluid motion model of MRF. The finite element method and time stepping algorithm are used to solve the examined problem. The eddy currents in massive conducting elements are taken into consideration. In order to include the nonlinearity of ferromagnetic core and non‐linear rheological properties of MRF, the Newton procedure is applied. This procedure is joined with the block‐over relaxation algorithm in order to reduce calculation time.FindingsThe proposed method gives sufficient accuracy of coupled electromagnetic and magnetorheological phenomena analysis. The comparison between measured and calculated clutching torque values shows a good agreement.Research limitations/implicationsThermal and hysteresis effects are not taken into account.Originality/valueThe presented approach can be useful for designing and optimizing MRF devices with axial symmetry. The accurate finite‐element model of coupled electromagnetic and mechanical phenomena is used as a tool for the analysis of MR device dynamic operation.
The calculation of the classical loss as well as the excess loss in the soft magnetic materials under the rotational magnetisation
Authors: Anuszczyk Jan , Gmyrek Zbigniew , Zwoliński Grzegorz 
Published: August 2007

PurposeThe calculation of the power loss in the core of the electrical machines is a special problem. In some areas of the electrical machine core the magnetic fields are neither unidirectional nor sinusoidal. This paper seeks to discuss the rotational power loss calculation methodology.Design/methodology/approachThe proposed methodology is based on the calculation of the field quantities Bx and By. In this methodology the rotational power losses are calculated employing the empirical approach directly from these quantities. Moreover, the computational model is the most important element of the proposed methodology because it utilises the FEM to the calculations of the hodographs of the flux density vector in each mesh element.FindingsThe paper formulates the dependence of the rotational power losses from the B vector hodograph shape.Research limitations/implicationsExperimental verification will still be needed as to the accuracy of the model and the applicability to the various magnetic materials.Practical implicationsThe paper provides an easy mathematical method to the iron loss calculation, under the rotational magnetisation, the excess loss included.Originality/valueThe analytical model, as presented here, is applicable to the iron loss calculation under the rotational magnetisation in devices that have complicated geometrical shapes.
Eddy current losses in permanent magnets of the BLDC machine
Authors: Miljavec Damijan , Zidarič Bogomir 
Published: August 2007

PurposeThis study aims to calculate eddy current losses in permanent magnets of BLDC machine in the generator mode of operation with no‐load.Design/methodology/approachStator slot openings and special design of the stator poles cause changes in the magnetic flux density changes in permanent magnets. The stator windings are not connected to an outer source and no currents flow in them. The induced eddy currents in permanent magnets are dependent solely on the stator geometry. Analytical approach to calculate the eddy current density distribution in permanent magnets is based on known distribution of magnetic flux density in the air‐gap of BLDC. The magnetic flux density distribution is obtained from magneto‐static finite element model of BLDC. For verification of analytical approach the eddy current density distribution in permanent magnets is also calculated by magneto‐transient finite element model of BLDC.FindingsThe eddy current losses in PM obtained with the FEM indicate additional heating of the BLDC machine at high rotational speeds even when it operates at no load. When some special stator designs (the side of the air gap) are needed, the losses in PMs and their heating increase.Research limitations/implicationsTo get more precise results, the proposed analytical method for eddy current losses calculation in PM should be further analyzed. More geometric parameters of the BLDC design should be introduced to analytical formulations, especially those which affect variations in reluctance.Practical implicationsWhen some special stator designs (the side of the air gap) are needed, the losses in PMs should be observed. This is particularly recommended at higher rotation velocities. Any kind of magnetic flux density change induces eddy currents and together with them also power losses. These losses give rise to additional heating of PM. With this, the temperature‐dependent working characteristic of PM (second quadrant of the B‐H curve) moves toward the coordinate origin point. The overall machine performance is reduced. The presented work gives the view about happenings in permanent magnets regarding induced eddy current losses. It is a useful tool for fast estimation and reduction of eddy current losses in PM due to stator geometry.Originality/valueThe value of the paper is the closed view about happenings in permanent magnets regarding induced eddy currents and the calculation of eddy current losses in rotor permanent magnets of BLDC due to stator design. The originality is in the analytical approach to calculate the eddy current losses based only on known magneto‐static flux density distribution in air‐gap of BLDC.
A finite element analysis of spatial solitons in optical fibres
Authors: Nicolet A. , Drouart F. , Renversez G. , Geuzaine C. 
Published: August 2007

PurposeThis paper concerns the study of non‐linear effects in optical fibres with a core made of a Kerr type medium. The aim is to propose an algorithm to find spatial solitons, i.e. solutions with a harmonic behaviour in time and along the fibre but with a field distribution in the cross‐section corresponding to a self‐trapped propagation of the electromagnetic field.Design/methodology/approachThe field is supposed to be harmonic in time and along the direction of invariance of the fibre but inhomogeneous in the cross‐section. This modifies the refractive index profile of the fibre (a step‐index one in this study). A scalar model of the fibre, together with the finite element method (that is well suited to deal with inhomogeneous media), is used and a new iterative algorithm is proposed to obtain the non‐linear solutions. An adaptive meshing is necessary to guarantee the accuracy of the model.FindingsThe new algorithm converges to self‐coherent solutions that are different from those obtained via a fixed power algorithm. The equivalents both of a fundamental mode and of a second order mode are studied.Originality/valueThe approach acknowledges the findings of the previously known spatial solitons (with a slight modification of the algorithm) together with a new family of solutions. It opens a new field of investigation to understand this whole family of non‐linear solutions as it shows that only a small part of them was known up to now.
Modeling the frequency response of p+InP/n−InGaAs/n+InP photodiodes with an arbitrary electric field profile
Authors: Manuel Torres Pereira Jorge 
Published: August 2007

PurposeThis paper seeks to present a numerical model which is used to obtain the transit time limited frequency response of p‐i‐n photodiodes with an arbitrary electric field profile. The effect of the absorption layer width and bias voltage on the frequency response is also investigated.Design/methodology/approachThe absorption region is divided into any desired number of layers and the continuity equations are solved, for each layer, assuming that within the layer the carriers' drift velocities are constant. The frequency response of the multilayer structure is calculated from the response of each layer using matrix algebra.FindingsThe numerical results agree well with those from the experiment. It is seen that the results, assuming the saturation drift velocities, are usually overestimated especially for low values of the bias voltage or high values of the absorption region width.Research limitations/implicationsThe numerical method under study neglects the capacitive effects which may determine the frequency response of very short devices. In this case a more complete treatment, including also the displacement current, should be carried out.Practical implicationsSoftware development for the design of multilayer photodiodes with optimized frequency response.Originality/valueTo the best of one's knowledge this is an original report of the application of this numerical method to the calculation of the frequency response of p‐i‐n photodiodes. The numerical method, being able to treat in a simple way multilayer structures with any electric field profile, is a very powerful tool in the development of software for the design of efficient photodiodes of various types.
A method for optimization of the working point of the N‐phase (N+1)‐wire systems with nonlinear loads
Authors: Debowski Krzysztof , Pasko Marian 
Published: August 2007

PurposeThe paper proposes to deal with the problems concerning the N‐phase (N+1)‐wire system with sinusoidal voltage sources and nonlinear loads. In the model of the N‐phase voltage source the inner impedance has been included. The problem of the optimization of working conditions of the system is a minimization of RMS value of its line currents as well as their distortions caused by nonlinear loads.Design/methodology/approachThe solution of this problem is based on the frequency domain. It is obtained by means of Lagrange's multipliers and the suitable measurement experiment.FindingsAfter optimization source currents are sinusoidal with minimized RMS values. After connection of the designed compensator to the system under research the phase currents are equal to determined active currents.Research limitations/implicationsThis method can be used for some classes of nonlinear loads, i.e. for systems with inertialess (non‐reactive) elements, which consume the active power of the basic harmonic of the voltage source and where the currents of the system are periodical. The mentioned power is an additional constraint of the presented minimization.Practical implicationsThe working point of the system can be obtained by means of the compensator LC, RLC or (RLC,‐R). It will always be a linear one and its structure consists of two components: elements with parameters determined for the basic harmonic and the filter for elimination of the higher harmonics caused by nonlinear loads.Originality/valueThe presented method has been generalized for N‐phase (N+1)‐wire systems.
Energy controlled shunt active power filters
Authors: Szromba Andrzej 
Published: August 2007

PurposeShunt active power filters are used to decrease or almost eliminate non‐active currents flowing through the supply source. Numerous control methods of active filters have been proposed in many papers. The aim of this paper is to demonstrate a simple but very effective method of obtaining the compensated load active current.Design/methodology/approachThe method allows one to control the shunt active power filter only by monitoring energy stored in the filter. Based on the introduced generic structure of the filter the changes of filter energy are examined in order to obtain the reference current for the filter compensation action.FindingsThis presented method can be implemented to nearly all structures of active filters. It is suitable not only for the single‐phase but also for the three‐phase circuit. Such energy‐controlled filters may be built on the basis of voltage‐ and current‐source inverters as well.Originality/valueThis paper provides an alternative approach to address the problem of the shunt active filter control method. The paper shows that monitoring the filter's energy suffices for proper control of the filter compensation action.
Improved MRAS‐type speed estimator for the sensorless induction motor drive
Authors: Orlowska‐Kowalska T. , Dybkowski M. 
Published: August 2007

PurposeThis paper aims to obtain an accurate and robust estimation method of the rotor flux and speed for the sensorless induction motor (IM) drive.Design/methodology/approachThe reduced order observer has been used as an online tuned rotor flux model in the model reference adaptive system (MRAS) concept applied for the IM speed estimation. The output of this observer was used also as a feedback signal required in the direct field‐oriented control (DFOC) structure of the IM.FindingsIt is shown that a new rotor flux and speed estimator are more robust to motor parameter changes in comparison with the classical MRAS estimator and can work stably in the DFOC structure, in the wide speed range, even for relatively high (50 per cent) identification errors of equivalent circuit parameters of the IM.Research limitations/implicationsThe investigation looked mainly at the estimation accuracy performance and whole system stability while economic issues will still need to be addressed.Practical implicationsThe proposed new improved MRAS speed estimator can be easily realised using modern digital signal processors. The implementation was tested in an experimental set‐up with floating point DSP used as the system controller. The fixed‐point realisation needs to be developed to obtain the practical application in the industrial drive systems.Originality/valueThe application of the reduced order flux observer as a tuned flux model in the MRAS type speed estimator instead of the simple, but very sensitive to motor parameter uncertainties, current flux model, enables much better accuracy and stability of the rotor speed estimation in the complex DFOC structure than in the case of classical MRAS estimator.
Application of neuro‐fuzzy techniques to robust speed control of PMSM
Authors: Pajchrowski Tomasz , Zawirski Krzysztof , Brock Stefan 
Published: August 2007

PurposeThe purpose of the paper is to find a simple structure of speed controller robust against drive parameter variations. Application of neuro‐fuzzy technique in the controller of PI type creates proper nonlinear characteristics, which ensures controller robustness.Design/methodology/approachThe robustness of the controller is based on its nonlinear characteristic introduced by neuro‐fuzzy technique. The paper proposes a novel approach to neural controller synthesis to be performed in two stages. The first stage consists in training the neuro‐fuzzy system to form the proper shape of the control surface, which represents the nonlinear characteristic of the controller. At the second stage, the PI controller settings are adjusted by means of the random weight change procedure, which optimises the control quality index formulated in the paper. The synthesis is performed using simulation techniques and subsequently the behavior of a laboratory speed control system is validated in the experimental setup. The control algorithms of the system are performed by a microprocessor floating point DSP control system.FindingsThe proposed controller structure with proper control surface created by the neuro‐fuzzy technique guarantees expected robustness.Research limitations/implicationsThe proposed controller was tested on a single machine under well defined conditions. Further investigations are required before any industrial applications can be made.Practical implicationsThe proposed controller synthesis and its results may be very helpful in the robotic system where changing of system parameters is characteristic for many industrial robots and manipulators.Originality/valueThe original method of robust controller synthesis was proposed and validated by simulation and experimental investigations.
Logistics collaboration in supply chains: practice vs. theory
Authors: Sandberg Erik 
Published: August 2007

PurposeThis paper aims to present results from a survey that investigates the situation in real world supply chains concerning logistics collaboration.Design/methodology/approachBased on supply chain management literature, a questionnaire was developed covering important topics from the literature. The questionnaire was sent to the logistics manager at Swedish manufacturing companies and a net response rate of 37.8 percent (177/482) was achieved. Apart from purely descriptive statistics, factor analysis, cluster analysis, analysis of variance (ANOVA), and cross tabulations with χ 2 tests were used for the analysis.FindingsFrom the results, three major conclusions are drawn. First, there is a clear relationship between the intensity of the collaboration and the positive effects experienced from the collaboration. Second, the results indicate that top management is an important driver for higher intensity collaboration. Third, there are serious differences between supply chain management (SCM) theory and practice, due to the absence of strategic elements in the collaboration and the different ways in which supplier and customer collaborations are managed.Research limitations/implicationsRelated to SCM theory, the lack of strategic elements in the collaboration might prevent or decrease the expected positive effects of the collaboration. It is therefore important to increase the strategic level component in the collaboration. Top management involvement is likely to be important to achieve this and hence more research on the topic is suggested.Originality/valueThe study presents a broad overview concerning logistics collaboration that covers many of the most important supply chain management issues. In addition, their relationship is discussed.
A STOPE model for the investigation of compliance with ISO 17799‐2005
Authors: Saad Saleh Mohamed , Alrabiah Abdullah , Haj Bakry Saad 
Published: August 2007

PurposeWith the widespread of e‐services, provided by different organizations at the internal intranet level, the business extranet level, and the public internet level, compliance with international information security management standards is becoming of increasing importance for establishing a common and safe environment for such services. The purpose of this paper is to examine the development of a mathematical model that enables the investigation of compliance of organizations with the widely acknowledged international information security management standard ISO 17799‐2005.Design/methodology/approachThe model is based on the strategy, technology, organization, people and environment – STOPE – framework that provides an integrated well‐structured view of the various factors involved. The paper addresses the use of the model for practical investigations; it describes a practical example illustrating possible practical results.FindingsThe results show the strengths and the weaknesses of compliance, with the standard, at different levels: from the level of the measures associated with each of the “131” standard protection controls, up to the level of the STOPE domains.Originality/valueThe paper addresses the use of a mathematical model for practical investigations of compliance with the international information security management standard.
Personalized biometric key using fingerprint biometrics
Authors: Thian Song Ong , Teoh Beng Jin Andrew , Connie Tee 
Published: August 2007

PurposeThis paper aims to address some of the practical and security problems when using fingerhash to secure biometric key for protecting digital contents.Design/methodology/approachStudy the two existing directions of biometric‐based key generation approach based on the usability, security and accuracy aspects. Discuss the requisite unresolved issues related to this approach.FindingsThe proposed Fingerhashing approach transforms fingerprint into a binary discretized representation called Fingerhash. The Reed Solomon error correction method is used to stabilize the fluctuation in Fingerhash. The stabilized Fingerhash is then XORed with a biometric key. The key can only be released upon the XOR process with another Fingerhash derived from an authentic fingerprint. The proposed method could regenerate an error‐free biometric key based on an authentic fingerprint with up to 99.83 percent success rate, leading to promising result of FAR = 0 percent and FRR = 0.17 percent. Besides, the proposed method can produce biometric keys (1,150 bit length) which are longer in size than the other prevailing biometric key generation schemes to offer higher security protection to safeguard digital contents.Originality/valueOutlines a novel solution to address the issues of usability, security and accuracy of biometric based key generation scheme.
Making a life or making a living?
Authors: Zhang Y. , Straub C. , Kusyk S. 
Published: August 2007

PurposeThe contemporary managerial work place is changing; baby boomers, the globalization and an increased participation of females in the workforce is redefining what value systems future managers’ will hold. This paper aims to build upon the traditional research on work ethics which focused primarily on working individuals. It seeks to explore future managers’ value systems on life vs work, in a cross‐national context.Design/methodology/approachPreviously validated questionnaires, containing 33 work–life values, were completed by business students in two French‐speaking regions of the world: Paris (France) and Quebec (Canada). Factor analysis was employed to examine the underlying value structure of work and life.FindingsFive factors emerged, two pertaining to work context, two to life context and one general factor as following: Extrinsic and intrinsic work context, social/society and ego/self‐life context and creativity. Subsequently, a comparison along these values is made between the two regions. Gender differences were also tested along these values. Results show differences in the value systems of these future managers based on region and gender, despite their common French language.Originality/valueThe paper provides a discussion of implications of the findings, within a context of ethics and social responsibility in reference to the stakeholder model.