bluuebunny/crossref_metadata_2025 huggingface dataset:
Geometrical and positional optimization of the forward swept lift producing surfaces in 3D flow domains
Authors: Vatandas Ergüven
Published: October 2007

Purpose

This paper seeks to outline a forward swept wing (FSW) design problem to reduce the optimization time and cost and to compare it with previous backward swept wing (BSW) results to see the differences.

Design/methodology/approach

Dynamic mesh technique was used in the design of a transonic FSW by coupling it with heuristic algorithms. To obtain the initial FSW mesh from BSW domain, a modified dynamic mesh method was developed. It was also compared with experimental results.

Findings

It is observed that the drag coefficient can be reduced by 15 percent in 500 calculations while the lift coefficient is tried to be close to the design value determined at the beginning as a design constraint. Especially, the taper ratio change direction differs from previous BSW optimization.

Originality/value

It is the first time that the dynamic mesh technique is used for obtaining the mesh structures of the new FSW members through genetic optimization. A modified dynamic mesh was used to convert BSW domain to FSW, which means a huge movement for the cells. A physical model of initial FSW is also produced for wind tunnel and tested.
Effect of SiO2 nano‐particulates on corrosion behaviour of Ni‐W/SiO2 nanocomposite coatings
Authors: Yao Yingwu
Published: October 2007

Purpose

This paper aims to study the effect of SiO2 nano‐particulates on the corrosion behaviour of Ni‐W/SiO2 nanocomposite coatings.

Design/methodology/approach

Weight loss measurements, electrochemical measurements and scanning electron microscope were used to study the corrosion behaviour of Ni‐W/SiO2 nanocomposite coatings in NaCl solution.

Findings

The incorporation of SiO2 nano‐particulates into the Ni‐W alloy matrix significantly increased the corrosion resistance. The improvement in corrosion resistance was due to the SiO2 nano‐particulates acting as physical barriers to the corrosion process by filling in crevices, gaps and microscopic holes on the surface of the Ni‐W alloy.

Originality/value

This study highlights the use of nano‐particulates for the control of Ni‐W alloy coating corrosion and opens a new route for industry in the anti‐corrosion field.
Thermal ageing of barrier pigment paint films
Authors: Angeles M.E. , Magaña C.R. , Vázquez F.S. , Rodríguez F.J.
Published: October 2007

Purpose

The purpose of this paper is to evaluate the behaviour of commercial organic coatings in two proposed short time accelerated ageing methods.

Design/methodology/approach

Two cycles of accelerated ageing at different temperatures have been set out: dry heating and heating in immersion (humid). The dry ageing was carried out by warming up the film continuously over a 24 h period at three temperatures: 65, 85 and 100°C, until completion after ten days; the humid ageing was carried out by submerging some film samples in hot brine and maintaining them submerged for 24 h at 45, 65 and 85°C.

Findings

DSC and FTIR techniques reported that the coating suffered an “over‐cured” process after being submitted to the dry cycle. The films submitted to wet ageing developed micro‐cracks. Both ageing cycles caused physical degradation and a little sign of chemical degradation as shown by SEM observations.

Practical implications

The ageing cycles could be applied to organic coatings, maybe varying the temperatures according to the Tg of the resins employed, as well as the ageing time according to the hardness and resistance of the coatings.

Originality/value

The ageing cycles were proposed after a long review of the literature and the conditions employed were short enough for rapid evaluation and long enough to promote the degradation of the films.
Evaluation of pipeline corrosion in sour‐gas environment
Authors: Olorunniwo Olusegun E. , Imasogie Benjamin I. , Afonja Adeniyi A.
Published: October 2007

Purpose

This paper seeks to describe the adoption and implementation of a cost‐effective gas pipeline corrosion monitoring and control procedure for use in natural gas infrastructural facilities in sub‐Saharan Africa.

Design/methodology/approach

The incidence and severity of pipeline corrosion in a major gas production facility were monitored using a combination of instrumented field survey (potential measurements, line currents and soil resistivity measurements) and microscopic evaluation (OM and SEM) techniques. Portable field survey equipment with appropriate circuitry, contactors and sensors for potential, line current and soil resistivity measurements were used to make the field measurements. The equipment was standardized and calibrated for use in the service environment. The field survey data were superimposed on common plots in order to obtain clearer and complementary information on possible corrosion hotspots and damage locations along the submerged pipelines. Metallographic examination of the samples collected from the field was carried out to establish the type of corrosion attacks and mode of failure of the pipeline material.

Findings

It was established that a combination of corrosion‐related damage occurred as a result of localized attack over time. The investigation procedure was cost‐effective and can be used to determine which pipeline structures are protected and to gauge with a high degree of precision the integrity of the submerged pipeline.

Research limitations/implications

In the future, the procedure could be fully automated for routine on‐line/on‐site monitoring of gas pipelines in a sour‐gas environment.

Practical implications

The paper presents a useful database for the selection and/or design of corrosion‐resistant materials for use in sour‐gas environments and data for a comprehensive corrosion monitoring and control program in the peculiar service environment of sub‐Saharan Africa, for improved performance, productivity, personnel safety and reduced operating costs.

Originality/value

The information is useful to on‐site engineers and operators of gas‐production facilities, particularly in sub‐Saharan Africa, for designing and implementing cost‐effective corrosion monitoring and control programs.
Removal of Pb++ in presence of surfactants
Authors: El‐Batouti Mervette
Published: October 2007

Purpose

The object of the present work is to study the kinetics of removal of Pb++ on zinc rods in the presence and absence of three surface active substances (SAS) at different concentrations of SAS and different temperatures.

Design/methodology/approach

The paper uses a range of recently published (1973‐2003) works, which aim to provide practical and theoretical information about lead, which is a very toxic metal.

Findings

Lead tends to accumulate a sediment, from which it can be released by various processes of remobilization and in many cases it enters the food chain and is concentrated in fish and other edible organisms. The reaction can be considered as taking place via six steps.

Research limitations/implications

The work is a list of recent papers which have been published in different European journals and magazines.

Practical implications

The determination of change of Pb++ concentrations was carried out using a Perkin‐Elmer atomic absorption Spectrophotometer.

Originality/value

The rate of PbII/Zn cementation reaction in the presence of surfactants as non‐ionic (Triton‐X‐100), anionic (SDS) and cationic (CTAB) decreased compared with the blank solution (lead nitrate solution). The order of decreasing rate was as follows: Triton‐X‐100 > CTAB > SDS. The rate of cementation was increased by temperature and the value of ΔE* ranged between 27 and 33 kJmol−1, which indicated that the reaction is a diffusion‐controlled process. The presence of two different SAS in the solution is more effective than the presence of one only.
Electrochemical study of nanocrystalline plasma electrolytic carbonitriding of CP‐Ti
Authors: Aliofkhazraei M. , Salasi M. , Sabour Rouhaghdam A. , Taheri P.
Published: October 2007

Purpose

The aim of this paper is to obtain optimal corrosion resistance of certain differently treated samples by investigation of their electrochemical properties.

Design/methodology/approach

Nanocrystalline plasma electrolytic carbonitriding (PEC/N) treatments were applied on the surface of commercially pure titanium in a glycerol bath with different additives. The carbonitriding process was performed in a glycerol bath with different additives such as carbamide, natrium nitrate and triethanolamine. The effects of electrolyte composition on chemical composition and corrosion resistance of the PEC/N films were examined by means of X‐ray diffraction, scanning electron microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy in a Ringer solution.

Findings

The results showed that the PEC/N films obtained in solutions with triethanolamine (T‐film) had better corrosion resistance. All coated samples had a better electrochemical behaviour compared with the untreated substrate. Different nano‐structures and morphologies were obtained by different additives in electrolyte.

Practical implications

The results obtained in this research into nanocrystalline PEC/N can be used wherever good corrosion and wear resistance with the highest efficiency is required.

Originality/value

The speed of treatment by this technique makes this method very suitable for the industrial surface treatment of different components.
Dietary assessment, anthropometric measurements and nutritional status of Greek professional athletes
Authors: Papandreou Dimitrios , Eystathiadis Panagiotis , Bouzoukiu Vassiliki , Hassapidou Maria , Tsitskaris George , Garefis Andreas
Published: October 2007

Purpose

The purpose of this study is to examine the anthropometric characteristics and to assess dietary intakes of professional athletes, of four different sporting teams, in Northern Greece.

Design/methodology/approach

Height and weight was measured using stasiometer and a scale devise, respectively. Body fat was measured using bioelectrical impedance analysis with multiple frequencies. A five‐day questionnaire was used to assess the dietary intakes of athletes. The sample consisted of male and female athletes, of ten volleyball and 21 basketball players, 20 weightlifters and 31 distance runners.

Findings

Distance runners had the lower percentage of body fat and volleyball players the higher ones. In men, basketball players reported the lowest amounts for energy intake (1,900 kcal/day) and for carbohydrates (2 g/kg). In women, the lowest carbohydrate intake was reported in volleyball players. Volleyball men players consumed the highest amount of fat 110 g/day or 1.4 g/kg. Protein intakes were below the recommended values for weightlifters and distance runners for both male and female subjects.

Practical implications

The study indicated dietary problems that could limit the performance of the Greek athletes and calls for nutrition monitoring and assessment.

Originality/value

The article should be of value to nutritionists, athletes and coaches.
Mix flexibility and volume flexibility in a build‐to‐order environment
Authors: Salvador Fabrizio , Rungtusanatham Manus , Forza Cipriano , Trentin Alessio
Published: October 2007

Purpose

This paper aims to investigate the factors enabling or hindering the simultaneous pursuit of volume flexibility and mix flexibility within a supply chain through the lens of a manufacturing plant seeking to implement a build‐to‐order (BTO) strategy.

Design/methodology/approach

To accomplish this empirical investigation, an in‐depth case study involving a manufacturing plant and its supply chain was designed. Prior to primary and secondary data collection, this research setting had already decided to implement a BTO strategy and had, moreover, carefully assessed several practices for BTO strategy implementation, as well as their interactions.

Findings

The studied case suggests that a number of approaches typically used to increase volume flexibility, actually negatively affect mix flexibility and vice versa. The existence of such trade‐offs may ultimately inhibit the implementation of a BTO strategy and this was the case in the studied company. Nevertheless, empirical evidence also suggests that, to some extent, volume flexibility and mix flexibility may be achieved synergistically, as initiatives such as component standardization or component‐process interface standardization would improve both volume flexibility and mix flexibility.

Research limitations/implications

The pursuit of volume flexibility and mix flexibility in implementing a BTO strategy in a specific setting and from primarily an operations management perspective was investigated. As such, the findings can be complemented by viewing the case study results through the lens of other established general management theories or by replicating the study in different research settings.

Originality/value

While past research informs us about how manufacturing firms can successfully achieve mix flexibility or volume flexibility, there are few insights for understanding how volume flexibility and mix flexibility can both be simultaneously achieved within a manufacturing plant and its supply chain. This research fills this gap in the literature and contributes to the development of a theory of BTO strategy implementation, especially in terms of volume flexibility, mix flexibility and their interactions.
Modularization and the impact on supply relationships
Authors: Howard Mickey , Squire Brian
Published: October 2007

Purpose

This paper aims to examine the role of product architecture in supply chain design. Specifically, it seeks to resolve confusion over the impact of modularisation on supplier relationship management. On the one hand, the introduction of modularisation suggests that buyer and supplier firms should move towards greater collaboration in order to co‐develop products and reduce interface constraints. On the other hand, the standardisation of interfaces suggests that buyer firms could introduce a “black box” approach to component design, holding suppliers at arm's‐length and reducing dependence. These conflicting views form the focus of the research: under what conditions does modularity lead to increasing collaboration?

Design/methodology/approach

The data are drawn from UK manufacturing firms across eight industry sectors using a sample from the Conquest Business Media database. Three hypotheses are tested through a three‐step hierarchical regression analysis.

Findings

The findings provide support for the notion that product modularization will lead to greater levels of buyer‐supplier collaboration, but that this relationship is mediated by relationship‐specific assets and information sharing.

Originality/value

The paper supports the argument that modularised components require collaborative sourcing practices in order to co‐develop products and reduce interface constraints. This suggests that outsourcing requires a high level of integration, creating dependencies between firms representing considerable investment in equipment and sharing through proprietary information systems. As interest in build‐to‐order supply chains and flexible product architecture grows; this emphasizes the importance of specifying the exact nature of relationship processes without stifling product innovation.
A strategic model for agile virtual enterprise partner selection
Authors: Sarkis Joseph , Talluri Srinivas , Gunasekaran A.
Published: October 2007

Purpose

This paper aims to provide a practical model usable by organizations to help form agile virtual enterprises. The model helps to integrate a variety of factors, tangible and intangible, strategic and operational, for decision‐making purposes.

Design/methodology/approach

A comprehensive development of factors is determined from the literature and an analytical network process (ANP) methodology is introduced for decision model development. An illustrative example is presented.

Findings

The results provide a robust model that will aid decision makers and agile virtual enterprise brokers form partnerships within these organizational structures.

Research limitations/implications

The paper introduces a conceptual model with an illustrative validating example. A practical application and reapplication of the model are required to further validate the model. ANP can require significant managerial input for its application, potentially causing fatigue for decision makers.

Practical implications

Practical implications include a partner selection tool and framework for decision makers. The model may be easily tweaked by the elimination or addition of decision factors and their relationships.

Originality/value

The paper is useful to practitioners and organizations seeking to manage partnership formation of agile virtual enterprises, an emerging organizational form. This work expands the number of factors and interrelationships among these factors that no other model has explicitly addressed for the agile virtual enterprise formation situation.
On the temporal and spatial fourth‐order finite volume velocity de‐averaging for unsteady incompressible flows simulation
Authors: Trindade J.M.F. , Pereira J.C.F.
Published: October 2007

Purpose

This paper aims to focus on the temporal and spatial fourth‐order finite volume discretization of the incompressible form of the Navier‐Stokes equations on structured uniform grids. The main purpose of the paper is to assess the accuracy enhancement with the inclusion of a high‐order reconstruction of the point‐wise velocity field on a fourth‐order accurate numerical scheme for the solution of the unsteady incompressible Navier‐Stokes equations.

Design/methodology/approach

The present finite volume method uses a fractional time‐step for decoupling velocity and pressure. A Runge‐Kutta integration scheme is implemented for integrating the momentum equation along with a polynomial interpolation and Simpson formula for space‐integration. The formulation is based on step‐by‐step de‐averaging process applied to the velocity field.

Findings

The reconstruction of the point‐wise velocity field on a higher‐order basis is essential to obtain solutions that effectively stand for a fourth‐order approximation of the point‐wise one. Results are provided for the Taylor vortex decay problem and for co‐ and counter‐rotating vortices to assess the increase in accuracy promoted by the inclusion of the high‐order de‐averaging procedure.

Research limitations/implications

High‐order reconstruction of the point‐wise velocity field should be considered in high‐order finite volume methods for the solution of the unsteady incompressible form of the Navier‐Stokes equations on structured grids.

Practical implications

The inclusion of a high‐order reconstruction of the point‐wise velocity field is a simple and effective method of enhancing the accuracy of a finite volume code for the computational fluid dynamics analysis.

Originality/value

The paper develops an improved version of a fourth‐order accurate finite volume projection method with the inclusion of a high‐order reconstruction step.
Analysis of dynamic stresses in Kaplan turbine blades
Authors: Zhou Lingjiu , Wang Zhengwei , Xiao Ruofu , Luo Yongyao
Published: October 2007

Purpose

Some comparison of unsteady flow calculation and the measured stress showed that the dynamic stresses in blades are closely related to hydraulic instability. However, few studies have been conducted for the hydraulic machinery to calculate dynamic stresses caused by the unsteady hydraulic load. The present paper aims to analyse the stresses in blades of a Kaplan turbine.

Design/methodology/approach

By employing a partially coupled solution of 3D unsteady flow through its flow passage, the dynamic interaction problem of the blades was analyzed. The unsteady Reynolds‐averaged Navier‐Stokes equations with the SST κ‐ω turbulence model were solved to model the flow within the entire flow path of the Kaplan turbine. The time‐dependent hydraulic forces on the blades were used as the boundary condition for the dynamics problem for blades.

Findings

The results showed that the dynamic stress in the blade is low under approximately optimum operating conditions and is high under low‐output conditions with a small guide vane opening, a small blade angle and a high head.

Research limitations/implications

It is assumed that there is no feedback of blade motion on the flow. Self‐excited oscillations are beyond the scope of the present paper.

Originality/value

The authors developed a code to transfer the pressure on blades as a boundary condition for structure analysis without any interpolation. The study indicates that the prediction of dynamic stress during the design stage is possible. To ensure the safety of the blades it is recommended to check the safety coefficient during the design stage for at least two conditions: the 100 percent output with lower head and the 50 percent output with the highest head.
Control of cyclic variations by computing the cycle‐to‐cycle air‐fuel ratio by neuro fuzzy technique
Authors: Robinson Y. , Dhandapani S.
Published: October 2007

Purpose

The problem of cyclic variation has been an interesting area of research and has been investigated by many researchers. It is more severe in the case of two‐stroke engines compared with four‐stroke engines. One of the reasons for these cycle‐to‐cycle variations is the variations in the air‐fuel ratios of individual cycles and, if these values of individual cycle air‐fuel ratios are available by some means, they can be used for controlling the cyclic variations. The purpose of this paper is to find a technique to predict the air‐fuel ratio of the individual cycles and use the same for reducing cyclic variations.

Design/methodology/approach

In this work, a neuro‐fuzzy model was developed using MATLAB software to compute the air‐fuel ratio of the individual cycles based on the relationship between the air‐fuel ratio and the combustion parameters such as those indicating mean effective pressure (IMEP), crank angle occurrence of peak pressure, and angles of different percentages of heat releases. In‐cylinder pressure traces of 1,000 continuous cycles were measured using a Personal Computer (PC)‐based data acquisition system and an investigation was carried out. The readings were taken for two modes of operations, namely gasoline carburetion and electronic gasoline injection. The engine was loaded by an eddy current dynamometer. The air‐fuel ratio was varied from rich to lean by adjusting the fuel quantity in the carburetion mode and adjusting the pulse width (measure of quantity of fuel to be injected) in the injection mode, at constant throttle. The cyclic variation was identified by the variations in the peak pressures and IMEPs of the individual cycles. The stored data were given as input to the developed neuro‐fuzzy model and, using SIMULINK, the air‐fuel ratios of individual cycles were obtained. These predicted values are fed to the electronic control module (ECM) (meant for injecting the fuel) for refining the pulse width to get cyclic variations reduced.

Findings

Results show that cyclic variation increases when the mixture becomes lean. It was also found that cyclic variation in an injected engine was less in comparison with the carbureted engine, as the precise control of air‐fuel mixture was possible in the case of the injected engine.

Research limitations/implications

The technique used in this work may be modified to give more precise pulse width by incorporating various other parameters like exhaust temperature, etc. Future research may be focused to incorporate this system in a moving vehicle to get more fuel efficiency and fewer emissions.

Practical implications

The design of vehicle and engine should be slightly modified to incorporate the ECM and various sensors.

Originality/value

The originality in this paper is that a new technique was developed to find the air‐fuel ratio of individual cycles. This will be useful for the engine manufacturers and for those researchers doing research on the engine side.
The customer‐led bank: how to retain customers and boost top‐line growth
Authors: Symonds Matt , Wright Tim , Ott John
Published: October 2007

Purpose

Banks have worked hard to improve their bottom‐line performance by focusing relentlessly on cutting costs. The effort made banks leaner, but essential as those efficiency gains have been, they did little to reduce costly customer defections. This article demonstrates that banks' long‐term growth and profitability hinge on their ability to attract and retain loyal customers and describes the key disciplines they need to master to become customer‐led organizations.

Design/methodology/approach

The article is based on the results of a global benchmarking survey of senior executives and customers at 30 major retail banks serving 170 million clients in 15 countries to ascertain what factors they saw to be most important to the success of strategies to promote organic revenue and profit growth.

Findings

The study revealed that the best‐performing banks garner the highest marks across the entire spectrum of managing the customer relationship. On average, banks that excel across all dimensions of acquiring and retaining loyal customers outgrow their peers and boost their return on equity.

Originality/value

Putting customer loyalty at the heart of their growth efforts requires banks to nurture the faithful core of their customer base and hone their skills for spotting and attracting the right new customers. The article describes how banks can design the right propositions by identifying target segments and crafting experiences to delight them, deliver on these promises by focusing the entire company on them, and use customer metrics to refine their products and services and develop organizational capabilities to delight customers again and again.
Overcoming change fatigue: lessons from Glasgow's National Health Service
Authors: MacIntosh Robert , Beech Nic , McQueen Juli , Reid Ian
Published: October 2007

Purpose

This paper explores the practicalities of organizational change in complex settings where much change has already occurred. It therefore offers insights into tackling and overcoming change fatigue.

Design/methodology/approach

The paper uses a longitudinal study of change within a healthcare organization. The paper draws on interviews, focus groups and observations during a 2.5‐year long action research project.

Findings

The paper reports findings on the speed at which change takes place, the importance of communication and the burden placed on senior officers during such communication and consultation processes, the use of appropriate external resources and expertise, the benefits of sharing best practice across sectors and the role of academic researchers in change processes.

Originality/value

The paper offers valuable insights to those charged with effecting organizational change in change fatigued settings.
Issue or problem? Managing the difference and averting crises
Authors: Jaques Tony
Published: October 2007

Purpose

Modern managers are expected to deal with a wide range of problems – only some of which are properly defined as organizational issues. The purpose of this paper is to distinguish true issues from other day to day problems and to offer guidelines to a strategic approach for identifying and managing such issues.

Design/methodology/approach

The paper briefly introduces the established discipline of issue management with criteria and examples to illustrate how issues differ from general business problems. Six key guidelines are then introduced to ensure that organizational responses to issues are focused on a single objective, which is aligned with overall strategy, which addresses the issue in a manner which is clear, unambiguous and easily communicated, and which has proper support from top management.

Findings

It is too easy to develop an issue response which simply meets the need for action or which assigns responsibility solely to the public affairs or communication function. To be effective issue management requires a cross‐functional approach aligned to organizational strategy and with hands‐on commitment by the managers most directly impacted.

Originality/value

By exploring the vital link between issue management and strategic planning the paper demonstrates that issue management must directly involve line managers and offers practical guidelines for how managers can positively influence setting strategic objectives to deliver bottom line results.
Creating value through acquisitions
Authors: Jackson Stuart E.
Published: October 2007

Purpose

Acquisitions can be a powerful tool to achieve growth, enter new markets and expand the range of a firm's capabilities. But with the highly competitive market for acquisitions and the correspondingly high acquisition prices, all too often transactions fail to create value for shareholders. Does this mean companies should avoid acquisitions and focus solely on organic growth? If acquisitions are to be part of a company's growth strategy, how can management identify which targets have the potential to more than justify the required investment and create value. In this article, the author shows how the discipline of strategic market position (SMP) can be used to test whether a proposed acquisition will really improve a company's overall competitive position and enhance its ability to deliver strong profitability for the future.

Design/methodology/approach

Using the example of Northrop Grumman, the author shows how to apply a four‐part “SMP test” to assess potential deals.

Findings

The example serves to illustrate how a merger to increase scale within a broad industry may contribute little to improved performance, but an acquisition of a company with distinctive, but complementary capabilities targetting a shared set of customer needs can deliver a very successful outcome. In particular, the author discusses the case of Northrop's acquisition of Ryan Aeronautical, a supplier of unmanned aircraft. The deal enabled Northrop to win new contracts worth many times the acquisition cost for Ryan.

Originality/value

The lesson is that if acquirers understand the true strategic value of an asset, measured in terms of stronger SMP and increased revenues, and/or higher profitability for the combined organization, then they can identify situations when the value opportunity will more than offset the premium required to complete the transaction.
The effect of molecular mean‐field interaction on remanent magnetism
Authors: Takacs J.
Published: October 2007

Purpose

The paper aims to take a critical view of the Wholfarth's assumption and the Henkel plots as the measure of molecular mean‐field interaction in magnetic materials. At the same time it seeks to formulate the effect of the molecular field interaction on the anhysteretic remanence.

Design/methodology/approach

Based on the recently verified Bosorth's original definition of anhysteretic state, the paper verifies Wohlfarth's conjecture. By including the molecular field interaction into the effective field expression it formulates the hysteretic and anhysteretic remanent behavior of the magnetic material.

Findings

The hysteretic and anhysteretic character of the material can be formulated up to and beyond the Barkhausen jump. The paper also points out that, the now verified, Wholfarth's conjecture is applicable to not only major hysteresis loops but also to symmetrical minor loops as well, within the same set. By doing so it removes the uncertainty surrounding its mathematical formulation.

Research limitations/implications

In the light of these findings the conjecture's relation to multi‐phase magnetic materials has to be investigated in the future.

Originality/value

The formulation of the hyteretic and anhysteretic remanent character can provide a graphical interpretation of the materials behavior. The paper demonstrate how the Henkel plots, based on the Wholfarth's conjecture, used as an indicator of the magnitude of the molecular interaction, can be simplified to the benefit of the theoretical and practical users.
Modeling dc gain performance of 4H‐SiC BJTs
Authors: Fardi Hamid Z.
Published: October 2007

Purpose

To model the differential dc gain, base resistance, and current voltage performance of 4H‐Silicon Carbide (SiC) bipolar junction transistors (BJT) operating at and above room temperature. Accurate modeling will result in improved process efficiency, interpretation of experimental data, and insight into device behavior.

Design/methodology/approach

The PISCES two dimensional device simulation program is used to allow for modeling the behavior of 4H‐SiC BJT. The physical material parameters in PISCES such as carrier's mobility and lifetime, temperature dependent bandgap, and the density of states are modified to accurately represent 4H‐SiC. The simulation results are compared with the measured experimental data obtained by others. The comparisons made with the experimental data are for two different devices that are of interest in power electronics and RF applications.

Findings

The simulation results predict a dc current gain of about 25 for power device and a gain of about 20 for RF device in agreement with the experimental data. The comparisons confirm the accuracy of the modeling employed.

Research limitations/implications

The simulated current‐voltage characteristics indicate that higher gain may be achieved for 4H‐SiC transistors if the leakage current is reduced.

Practical implications

The simulation work discussed in this paper complements the current research in the design and characterization of 4H‐SiC bipolar transistors. The model presented will aid in interpreting experimental data at a wide range of temperatures.

Originality/value

This paper reports on a new model that provides insight into the device behavior and shows the trend in the dc gain performance important for the design and optimization of 4H‐SiC bipolar transistors operating at or above the room temperature.
On the analysis and control of four‐switch three‐phase inverter fed brushless motor drives
Authors: Guermazi Abdessatar , Sahbi Mariem , Masmoudi Ahmed , Elantably Ahmed
Published: October 2007

Purpose

This paper aims at the improvement of the cost‐effectiveness of brushless DC motor (BDCM) drives integrated in electric and hybrid propulsion systems.

Design/methodology/approach

The cost‐effectiveness improvement is gained through the reduction of the topology of the inverter in the armature which turns to have two legs (four switches) rather than three legs (six switches) in conventional inverters. This has been made possible thanks to the availability of the battery pack in automotive applications.

Findings

It has been found that the four‐switch three‐phase inverter (FSTPI) fed BDCM drive has almost the same performance as the six‐switch three‐phase inverter (SSTPI) fed BDCM.

Research limitations/implications

This works should be extended by an experimental validation of the established results.

Practical implications

The reduction of the topology of the inverter in the armature of the BDCM opens up crucial cost benefits especially in large‐scale production industries, such as the automotive one.

Originality/value

The implementation of a simple self‐control strategy in a FSTPI fed BDCM drive yields almost the same dynamic and steady state performance as those obtained by a SSTPI fed BDCM drive. An analytical assessment of the steady state features of the FSTPI‐fed BDCM drive has been confirmed by simulation.
CAD‐oriented signal and noise modeling of mm‐wave FETs: a wave approach
Authors: Abdipour Abdolali , Moradi Gholamreza
Published: October 2007

Purpose

The purpose of this paper is to present computer‐aided simultaneous signal and noise modeling and analysis for mm‐wave field‐effect transistors (FETs) based on scattering parameters approach.

Design/methodology/approach

A mm‐wave FET is modeled as three active‐coupled transmission lines, and the developed wave approach is applied to this model to calculate both signal and noise performances of the device.

Findings

The measurements show a good match with the calculated data from the point of view of both signal and noise performances of the device.

Originality/value

This CAD‐oriented analysis and modeling can be easily applied to the mm‐wave simulators to improve the simultaneous signal and noise optimization, modeling and analysis of mm‐wave devices, especially for traveling wave transistors in which the distributed model seems to be more exact than the usual lumped models. Also the proposed routine compared to the admittance approach is conceptually more compatible with scattering representations of active and passive circuits. The developed algorithm has been applied successfully to mm‐wave MESFETs and HEMTs.
Epileptic seizure characterization by Lyapunov exponent of EEG signal
Authors: Osowski Stanislaw , Swiderski Bartosz , Cichocki Andrzej , Rysz Andrzej
Published: October 2007

Purpose

The purpose of this paper is to develop the new method of estimation of the short‐term largest Lyapunov exponent of electroencephalogram (EEG) waveforms for the detection and prediction of the epileptic seizure.

Design/methodology/approach

The paper proposed the modifications concerned with the way of selection of the segments of EEG waveforms taking part in estimation of Lyapunov exponent, as well as determination of the distances between two time series. The proposed method is based on Kolmogorov‐Smirnov test of similarity of two vectors. Through the application of this test more accurate and less parameterized approach to the estimation of the short‐term largest Lyapunov exponent of EEG waveforms has been obtained.

Findings

The results of performed experiments have shown that in most cases our modified method has outperformed the classical procedure, leading to more stable results, closer to the neurologist indications. The analysis of the data has proved that the change of the largest Lyapunov exponent provides a lot of information regarding the epileptic seizure. The minimum value of Lyapunov exponent indicates fairly well the seizure moment. The Tindex applied for few different electrode sites can provide good advanced prediction of the incoming epileptic seizure.

Practical implications

After additional experiments this method may find practical application for supporting the medical diagnosis of the epilepsy.

Originality/value

The proposed modification of the estimation of the short‐term largest Lyapunov exponent of the EEG waveforms eliminates some arbitrarily chosen parameters tuned by the user and leads to more accurate estimate. Such estimation results are better suited for the characterization of the epileptic activity.
Sensorless‐estimation of induction motors in wide speed range
Authors: Bogosyan Seta , Barut Murat , Gokasan Metin
Published: October 2007

Purpose

The purpose of this paper is to improve performance in the estimation of velocity and flux in the sensorless control of induction motors (IMs) over a wide speed range, including low and zero speed.

Design/methodology/approach

Temperature and frequency dependent variations of stator (Rs) and rotor (R′r) resistances are very effective on estimation performance in sensorless control over a wide speed range. To this aim, an extended Kalman filter (EKF) is designed, which estimates the stator resistance,Rs, load torque,tL, velocity and flux. To provide robustness againstR′rvariations, the extended model is also continuously updated withR′rvalues from a look‐up table, built via EKF estimation.

Findings

As demonstrated by the experimental results, the estimated states and parameters undergo a very short transient and attain their steady‐state values accurately, with no need for signal injection due to the inherent noise introduced by EKF.

Originality/value

The value of this study is in the development of an EKF‐based scheme, which solves theRs−R′restimation problem in IM sensorless control. The successful experimental results obtained with the combined EKF and look‐up table approach also offer a solution to all EKF‐based estimation schemes which involve a high number of estimated parameters, hence, compromising estimation accuracy.
A mathematical approach for studying interconnected earthing systems inside MV networks
Authors: Campoccia Angelo , Riva Sanseverino Eleonora , Zizzo Gaetano
Published: October 2007

Purpose

The purpose of this paper is to define a new methodology for studying interconnected earthing system inside unearthed medium voltage (MV) networks.

Design/methodology/approach

The developed methodology is based on the division of the MV network into simpler sub‐systems and its resolution using a multiport approach.

Findings

The methodology has been applied to various situations giving precious information on the behaviour of the interconnected earthing systems. The comparison between the results of the simulations and measurements done on a really existing network has shown that the methodology is able to provide accurate results.

Research limitations/implications

Some factors can influence the precision of the methodology. Indeed, for a correct simulation of the system it is necessary to know several electrical and geometrical parameters, often obtainable with difficulty.

Practical implications

Utilities are quite interested in this topic. The study of interconnected earthing systems in MV networks with the purpose of identifying safe extended areas named Global Earthing Systems has important management and economic consequences.

Originality/value

The paper presents a new analysis methodology applicable to MV networks that surpasses the limits of the analysis methodology generally applied for the study of the same topic in high voltage networks.
The Crout version of ILU preconditioning applied to the fast‐multipole method for solving large‐scale electromagnetic open PEC problems
Authors: Yu Yiqiang , McCowen Andy
Published: October 2007

Purpose

The purpose of this paper is to investigate and analyze the efficiency and stability of the implementation of the Crout version of ILU (ILUC) preconditioning on fast‐multipole method (FMM) for solving large‐scale dense complex linear systems arising from electromagnetic open perfect electrical conductor (PEC).

Design/methodology/approach

The FMM is employed to reduce the computational complexity of the matrix‐vector product and the memory requirement of the impedance matrix. The numerical examples are initially solved by the quasi‐minimal residual (QMR) method with ILUC preconditioning. In order to fully investigate the performance of ILUC in connection with other iterative solvers, a case is also solved by bi‐conjugate gradient solver and conjugate gradient squared solver with ILUC preconditioning.

Findings

The solutions show that the ILUC preconditioner is stable and significantly improves the performance of the QMR solver on large ill‐conditioned open PEC problems compared to using ILU(0) and threshold‐based ILU (ILUT) preconditioners. It dramatically decreases the number of iterations required for convergence and consequently reduces the total CPU solving time with a reasonable overhead in memory.

Practical implications

The preconditioning scheme can be applied to large ill‐conditioned open PEC problems to effectively speed up the overall electromagnetic simulation progress while maintaining the computational complexity of FMM. More complex structures including wire‐PEC junctions and microstrip arrays may be addressed in future work.

Originality/value

The performance of ILUC has been previously reported only on preconditioning sparse linear systems, in which the ILU preconditioner is constructed by the ILUC of the coefficient matrix (e.g. matrix arised from two‐dimensional finite element convection‐diffusion problem) and subsequently applied to the same sparse linear systems; so it is important to report its performance on the dense complex linear systems that arised from open PEC electromagnetic problems. In contrast, the preconditioner is constructed upon the near‐field matrix of the FMM and subsequently applied to the whole dense linear system. The comparison of its performance against the diagonal, ILU(0) and ILUT precoditioners is also presented.
Effects of moisture and freeze‐thaw cycling on the quality of rice‐hull‐PE composite
Authors: Wang W.H. , Wang Q.W. , Xiao H. , Morrell J.J.
Published: October 2007

Purpose

To investigate the effects of moisture and freeze‐thaw cycling on the absorption and flexural properties of rice‐hull‐polyethylene (PE) composite.

Design/methodology/approach

Various rice‐hull‐PE composite specimens were submerged in water at various temperatures and subjected to various freeze‐thaw cycles. Various characterisations including water absorption, bending strength and stiffness, Fourier transform infrared spectroscopy and scanning electron microscope imaging were performed.

Findings

High temperatures accelerated the water sorption of the rice‐hull‐PE composite and increased the equilibrium moisture content. The uncoated surface was not significantly more easily permeated than the coated surface, contrary to expectations. However, more water was absorbed from the cut surface than from the original extruded surface. This was attributed to the tiny checks left on the surface by the sawing action, which indicated the importance of protecting the original surface layer from scraping or other damage. Bending strength and stiffness of the rice‐hull‐PE composite decreased significantly after the freeze‐thaw cycling treatment. The modulus of elasticity decreased more than the modulus of rupture. Compared to the effect of water immersion alone, freeze‐thaw cycling treatment slightly accelerated this decrease.

Research limitations/implications

The results of this study were obtained from accelerated laboratory experiments. Further research could be carried out to evaluate the properties of this rice‐hull‐PE composite in practical application.

Practical implications

The research revealed a possible degradation in quality when the rice‐hull‐PE composite is used in moist or freezing conditions. The resin layer on the extruded surface provides an important protection.

Originality/value

In China, rice‐hull powder is widely used as a reinforcing component in plastic composite. However, the durability of rice‐hull/PE composites has rarely been investigated. Results from this study will help users apply rice‐hull‐PE composites correctly and encourage the development of other agro‐fibre/polymer materials.
Synthesis of calixarene derivatives and their anticorrosive effect on steel in 1M HCl
Authors: Benabdellah M. , Souane R. , Cheriaa N. , Abidi R. , Hammouti B. , Vicens J.
Published: October 2007

Purpose

To evaluate the effect of synthesised calixarenes as new inhibitors on the corrosion of steel in HCl media at various temperatures.

Design/methodology/approach

Calixarenes have been synthesised and tested as corrosion inhibitors. Gravimetric technique and potentiodynamic polarisation and impedance spectroscopy methods were used.

Findings

Calixarenes exhibited a good inhibition. Their efficiency decreases slightly with temperature.

Research limitations/implications

It was found that the inhibition efficiency increases with the concentration of inhibitors to reach 92 per cent at 10−4M.

Practical implications

The efficiency of calixarene derivatives increases with the concentration and falls slowly with temperature to attain 84 per cent at 353 K range. Calixarenes can be used in chemical cleaning and pickling processes.

Originality/value

The originality of this work is to find an inhibitor to give protection close to 100 per cent.