bluuebunny/crossref_metadata_2025 huggingface dataset:
A posteriori error estimator for harmonic A‐φ formulation
Authors: Tang Zuqi , Le Menach Yvonnick , Creuse Emmanuel , Nicaise Serge , Piriou Francis , Nemitz Nicolas
Published: July 2013

Purpose

In this paper, the aim is to propose a residual‐based error estimator to evaluate the numerical error induced by the computation of the electromagnetic systems using a finite element method in the case of the harmonic A‐φ formulation.

Design/methodology/approach

The residual based error estimator used in this paper verifies the mathematical property of global and local error estimation (reliability and efficiency).

Findings

This estimator used is based on the evaluation of quantities weakly verified in the case of harmonic A‐φ formulation.

Originality/value

In this paper, it is shown that the proposed estimator, based on the mathematical developments, is hardness in the case of the typical applications.
Model of dynamic operation of stepper linear reluctance motor based on field approach
Authors: Mikołajewicz Jacek
Published: July 2013

Purpose

The aim of this paper is to analyse the influence of various methods of controlling a stepper linear reluctance motor on the dynamic parameters of this motor.

Design/methodology/approach

Construction, principle of working, and mathematical model of a four‐band stepper linear reluctance motor are shortly discussed. In order to elaborate an effective tool for motor performance analysis, a circuital approach was applied. To increase model accuracy, major parameters of the model (main self‐ and leakage inductances) were calculated on the basis of a 3D electromagnetic field distribution using Finite Element Method (FEM). The nonlinearity of the core was taken into account. Elaborated mathematical model was implemented in MatLab‐Simulink environment. Selected results of investigations are presented.

Findings

The elaborated mathematical model and the review of control methods are very useful for analysis of dynamic operation of stepper linear reluctance motors.

Originality/value

The paper provides a review of control methods of stepper linear reluctance motors.
Impact of windings switching on torque‐speed curves of PM BLDC motor
Authors: Krykowski Krzysztof , Hetmańczyk Janusz , Makieła Dawid
Published: July 2013

Purpose

When phase windings of brushless DC motor are switched, additional voltage drops across inductances of main circuit appear. These drops lead to, among other effects, increase of torque‐speed curve slope. The discussed research has been aimed at working out a simple and precise method of identifying torque‐speed characteristic of PM BLDC motor. The elaborated method takes into account the influence of windings switching and motor inductances on motor torque‐speed characteristic. In order to assess the results, extensive test simulations of models implemented in Matlab/Simulink software have been run. Results of analysis and test simulations have been compared with lab test results of two real PM BLDC motors.

Design/methodology/approach

Analytical calculations take into consideration phenomena occurring during windings switch‐overs and impact of inductance on emerging voltage and rotational speed drops. It has been pointed out that on account of main circuit inductance, the average value of source current is less than average value of equivalent current generating electromagnetic torque. For analysis sake it has been assumed when windings are being switched‐over the current is kept constant; the motor parameters have also been assumed to be constant.

Findings

A novel and accurate method of determining torque‐speed characteristics of PM BLDC motor has been worked out. This method has been investigated with the help of motor computer models implemented in Matlab/Simulink software and the obtained results have been subsequently compared with results of laboratory tests of two commercially available PM BLDC motors.

Research limitations/implications

The object of the research was brushless DC motor with permanent magnet excitation. The impact of windings switch‐overs on torque‐speed curves of the motor has been analysed. Analytical method which makes it possible to determine torque‐speed curve of this motor very easily has been elaborated. Computer model of PM BLDC motor for Matlab/Simulink software has also been worked out. Extensive simulations helping to verify the proposed method have been run. Results of analysis and simulation tests have been verified by means of laboratory tests of two commercially available PM BLDC motors.

Practical implications

PM BLDC motors are used more and more widely. The new method of determining PM BLDC motors torque‐speed curves will facilitate analysis and design of drive systems utilizing these motors and will also speed up calculations.

Originality/value

The presented method of determining torque‐speed curves of PM BLDC motor is novel and much more precise than methods commonly used nowadays. Recognized methods usually neglect impact of inductance on motor properties.
Evaluating performances of electric machines supplied by the sinusoidal and pulse width modulated voltages
Authors: Štumberger Gorazd , Štumberger Bojan , Stojan David , Plantić Željko , Deželak Klemen , Čemažar Matjaž , Dolinar Drago
Published: July 2013

Purpose

Many authors reported the decrease of performances when electric machines and electromagnetic devices were supplied by pulse width modulated (PWM) voltages. However, these statements are rarely supported by measurements performed under fair conditions. The aim of this paper is to compare the performances of a single‐phase transformer and a three‐phase permanent magnet synchronous motor (PMSM) supplied by sinusoidal and PWM voltages and to find a way to evaluate the decrease of performances when PWM voltages are applied.

Design/methodology/approach

In order to perform a fair comparison between performances of the tested objects supplied by sinusoidal and PWM voltages, an experimental system was built. It contains a single‐phase and a three‐phase linear rectifier for supply with sinusoidal voltages and an H‐bridge inverter and a three‐phase inverter for supply with PWM voltages. The tests and measurements were performed on a single‐phase transformer and three‐phase PMSM, where different constant loads and different modulation frequencies were used. The test conditions were identical for the supply by sinusoidal and PWM voltages. The measured data, used for the evaluation of performances, were the input and output power and the time behaviours of currents and voltages together with their THDs.

Findings

The results presented in the paper clearly show that the efficiency of the singe‐phase transformer and three‐phase PMSM decreases with the increasing level of voltage THD. To properly determine the THD of PWM voltage, the sampling frequencies above 1 MHz and special equipment are normally required. However, if the modulation frequency is not too high, also the current THD, which can be easily determined, can be used to evaluate the decrease of efficiency in the case of supply by PWM voltages.

Originality/value

The results presented in the paper clearly show that the efficiency of the singe‐phase transformer and three‐phase PMSM decreases with the increasing level of voltage THD.
Sizing of active power filters using some optimization strategies
Authors: Grabowski Dariusz , Maciążek Marcin , Pasko Marian
Published: July 2013

Purpose

The change in the way of active power filters (APF) location can lead to overall cost reduction due to less number or less power of APFs required. The goal of this paper was to minimize the APF currents what is equivalent to solution with less apparent power of installed devices. The next step consists in development of new methods of APF optimal location.

Design/methodology/approach

Some scripts integrating optimization and harmonic analysis methods in Matlab and PCFLO software environments have been developed in order to achieve the goal.

Findings

Solution to the minimization problem determines the current spectrum of an APF connected to a selected system bus in accordance with some optimization strategies which among others enable minimization of THDV coefficients.

Research limitations/implications

The APF control algorithm defined in the frequency domain and based on given current spectrum could lead to some problems with synchronization between APF instantaneous current and compensated current waveforms.

Originality/value

There are many papers on APFs but usually systems in which an APF is connected near a nonlinear load are analyzed. Some attempts to solve the more complex problems of synchronized multipoint compensation have been already made but there is still no generally accepted and commonly used solution.
Improved iron loss calculation for non‐centered minor loops
Authors: Fratila Mircea , Benabou Abdelkader , Tounzi Abdelmonaïm , Dessoude Maxime
Published: July 2013

Purpose

Pulse width modulated (PWM) inverters are widely used to feed induction motors for variable speed applications. The use of PWM power supplies induces additional magnetic losses in the magnetic circuit of the electrical machine. The aim of this paper is to present a novel analytical approach to account for these losses.

Design/methodology/approach

The methodology proposed here consists in identifying the analytical method with a static Preisach hysteresis model. The Preisach model was validated by comparing it with measurements obtained from an Epstein frame. Then, the results obtained with this approach were compared with a basic analytical method that is widely used.

Findings

The authors' model provides a fast way for estimating the minor loop iron losses introduced by static convertors. They compared the proposed model with another analytical model (J. Lavers model) for different wave forms. One can observe that the J. Lavers model overestimates the iron losses introduced by the non‐centred minor loops.

Originality/value

In this paper, an improved analytical model is presented which estimates the non‐centred minor loop iron losses. In order to do a precise estimation of the iron loss introduced by the minor loops, the authors' model takes into account the position and the size of the minor loop. The proposed model is identified from a static Preisach model.
Hysteresis curves of a resistance spot welding transformer
Authors: Petrun Martin , Chwastek Krzysztof , Dolinar Drago
Published: July 2013

Purpose

The aim of the paper is to provide a simple and reliable hysteresis model for prediction of magnetization curves of a resistance spot welding transformer (RSWT) core, operating in a wide range of flux densities and excitation frequencies.

Design/methodology/approach

The hysteresis model considered in the paper is the T(x) description advanced by J. Takács. Three options to extend the model to the dynamic magnetization conditions are considered. The excitation conditions differ from those prescribed by international standards.

Findings

The quasi‐static Takács model combined with a fractional viscosity equation similar to that proposed by S.E. Zirka outperforms other considered options. The effect of eddy currents may be considered as a disturbance factor to the frequency‐independent quasi‐static hysteresis loop.

Research limitations/implications

The combined approach yields in most cases a satisfactory agreement between theory and experiment. For highest frequency considered in the paper (1 kHz) excessive “heels” were observed in the modelled loops. This artifact may be reduced by the introduction of a more complicated relationship for the viscous term. Future work shall be devoted to this issue.

Practical implications

The combined Takács‐Zirka model is a useful tool for prediction of magnetization curves of a RSWT core in a wide range of flux densities and excitation frequencies.

Originality/value

The usefulness of the Takács description has been verified in a practical application. The model is able to predict magnetization curves under non‐standard excitation conditions.
SMA actuators: theory, performance curves and design problems
Authors: Kluszczyński Krzysztof , Kciuk Marek
Published: July 2013

Purpose

The main purpose of the paper is to develop model basing on the modified and properly‐adopted Fermi‐Dirac equation which combines proper accuracy with adequate simplicity as well as to show how steady state and transient curves resulting from this model can be applied for solving design task.

Design/methodology/approach

The standard Fermi‐Dirac equation was modified and extended. Full performance cycle for the SMA actuator was characterized by double‐valued function describing the actuator activation and the actuator deactivation. All these functions and parameters can be easily determined by analysis of measurement data or with use of Hooke‐Jeeves optimization algorithm.

Findings

SMA linear actuator can be used in mechatronic systems as a special non‐standard drive when ultra‐light mass and very simple mechanical construction of power feed system is required. The proposed steady‐state and transient performance curves as well as operation diagram constitute sufficient base for effective designing SMA drive systems.

Research limitations/implications

The greatest disadvantage of a SMA actuator is long time of deactivation resulting from slow self‐cooling process. As far as efficiency is concerned as essential factor for choosing the most suitable linear actuator, there is no sense to take into account a linear SMA actuator because of its very low efficiency.

Practical implications

Designer can use performance curve which determines proper length of SMA actuator and range of its motion. The proposed model can be implemented in SMA drive control unit for controlling position of the actuator.

Originality/value

Similarities between change of martensitic phase during transition process and probability P of electron energy level distribution described by the Fermi‐Dirac two‐variable equation were taken into account. Such an approach seems to express in the most suitable way the physical nature of m‐a transition. The authors decided to extend concept (proposed in Jayender et al.) and to adopt the Fermi‐Dirac equation for describing behaviour of a SMA linear actuator.
Identification of current flow depending on the mechanical deformation in a stranded cable
Authors: Zeroukhi Youcef , Napieralska Juszczak Ewa , Komeza Krzysztof , Morganti Fabrice , Vega Guillaume
Published: July 2013

Purpose

In the majority of devices for measuring the resistance of wires or cables, the supplying voltage is applied via some clamping arrangement. Thus, current enters the bundle of conductors through the side surface of the outside wire. The purpose of this project was to establish the distance from the supplying point after which the current may be considered to be uniform and normal to the cable cross‐section.

Design/methodology/approach

When current passes from one wire to another, the crucial parameter is the resistance of the contact region. The paper presents a method by which this region can be identified and relevant resistance measured. A comprehensive simulation was conducted for different types of wires and cables to assess the influence of design parameters on the current distribution and uniformity.

Findings

The distance from the current entry point (the clamps) to the position where current density may be considered uniform has been established. This has facilitated estimating recommended positions of voltage taps with reference to current taps.

Practical implications

The look‐up tables and graphs allow adjustments to the position of the taps and/or correction of the measured results.

Originality/value

The original contribution of this paper is in the way the contact region is identified where current passes from one wire to another. Original relationships have been proposed showing the relationship between contact resistance and the design parameters of the cable and mechanical stress.
Information needs analysis of the aerospace discipline
Authors: Du Weichun , Song Shuang
Published: July 2013

Purpose

The purpose of this paper is to identify the core literature of aerospace studies and the databases necessary to ensure its coverage in a collection for aerospace scientists. The paper also aims to examine whether China has different needs from other countries.

Design/methodology/approach

A sequence of bibliometric analyses was used. Institutions and countries with high aerospace research productivity were identified from 4,290 papers published in “aerospace engineering” journals in Science Citation Index. Journal papers cited in these papers (14,618 extracted from 17,015 citations in all) were analyzed to discover the core source journals for aerospace research. The availability of the core journals in online databases determined necessary library provision for aerospace research.

Findings

The most productive aerospace research institutions are in China and the USA. Journals are the most important information resources. While 20 per cent of cited journals were discipline‐specific, 80 per cent were in related fields. Chinese researchers had similar resource needs to researchers from other countries. To provide for aerospace research, a library collection needs to include the databases of the field, and commercial and open access journals that cover aerospace engineering, related disciplines and the sciences in general.

Originality/value

The paper reveals the characteristics of the literature of the aerospace discipline for the first time. It identifies the core journals used by aerospace researchers and the bundle of online resources necessary to adequately provide for research in the field. The technique used can be applied to other disciplines.
Logistics alliance management capabilities: where are they?
Authors: Brekalo Lisa , Albers Sascha , Delfmann Werner
Published: July 2013

Purpose

– Due to the continued high failure rate of logistics alliances, the purpose of this paper is to propose incorporating the widely neglected dynamic capabilities approach into the explanation of logistics alliance performance.

Design/methodology/approach

– The authors identify specific characteristics of logistics alliances that are used to argumentatively develop a framework of logistics alliance management capabilities.

Findings

– We propose an initial framework of logistics alliance management capabilities, based on the dynamic capabilities approach of strategic management, with the aim of improving logistics alliance success.

Research limitations/implications

– The presented framework offers a basis for a wider range of empirical studies. Qualitative researchers are encouraged to further specify and better understand the sub-processes that underlie logistics alliance management capabilities in different alliance settings. Quantitative studies could help to reliably assess the differences and performance implications of these capabilities.

Practical implications

– The authors
'
conceptualization supports managers in their relevant strategic and organizational attempts to enhance logistics alliance success.

Originality/value

– This paper contributes to the logistics literature by making a more general yet established construct accessible to logistics scholars and practitioners. The roots of the authors
'
logistics alliance management capabilities construct in dynamic capabilities provide a framework that is new and potentially more comprehensive than the collection of somewhat isolated alliance success factors that have hitherto been proposed in the logistics literature.
The impact of dependence and trust on supply chain integration
Authors: Zhang Min , Huo Baofeng
Published: July 2013

Purpose

– The purpose of this paper is to investigate the joint influence of dependence and trust in supply chain relationships on supply chain integration (SCI) and financial performance.

Design/methodology/approach

– This study develops a dependence-trust-SCI-performance model and tests it using structural equation modeling based on empirical data collected from 617 manufacturers in China.

Findings

– The results show that trust with customers/suppliers significantly influences SCI. Although dependence on customers/suppliers has no direct effect on SCI, it improves SCI indirectly through trust with customers/suppliers. Both supplier integration and customer integration significantly improve financial performance.

Practical implications

– This study suggests that manufacturers should manage dependence and trust in supply chain relationships simultaneously to enable SCI. When there is high-level dependence on customers/suppliers, manufacturers should invest resources to develop trust with those customers/suppliers. Moreover, to achieve a better financial performance, manufacturers should integrate with both customers and suppliers.

Originality/value

– This study contributes to the literature by providing empirical evidence regarding the direct effect of trust on SCI, and the indirect influence of dependence on SCI through trust. This extends extant knowledge regarding the joint impact of dependence and trust on SCI. Hence, both researchers and practitioners should pay attention to interdependence among different relationship management practices. Moreover, this study also empirically supports the argument that SCI improves firms
'
financial performance.
The confidence factor in pricing: driving firm performance
Authors: Liozu Stephan M. , Hinterhuber Andreas
Published: July 2013

Purpose

The purpose of this paper is to identify a set of specific activities and a set of competencies associated with above‐average firm performance.

Design/methodology/approach

Quantitative survey of 748 respondents.

Findings

It was found that four key competencies differentiate high performing from low performing companies: organizational confidence; pricing capabilities; organizational change capacity; and championing behaviors by top management. The research also identifies a set of specific activities that are linked with superior firm performance: activities directed at the improvement of pricing effectiveness (e.g. trainings, pricing tools; pricing performance reviews); improvements in product differentiation and product quality (e.g. through innovation and research aimed at identifying and creating customer value); increased sense of organizational confidence (e.g. optimism, resilience, “can do”‐attitude); improved support of top management; improved ability to stick to list prices and minimization of discounting behaviors; and finally, enhanced cultural adaptability to respond to changing market conditions.

Research limitations/implications

Through a quantitative research design, the authors document the link between pricing capabilities, organizational confidence and superior firm performance.

Practical implications

The authors identify both specific activities, as well as higher order competencies, practising managers need to develop in order to increase firm performance via pricing. Taking a hypothetical company as example, the authors' data show that, on average, a one point improvement on a seven‐point scale in organizational confidence leads to a 4 per cent improvement in return on sales.

Originality/value

Our research highlights which organizational competencies drive firm performance. Specifically this research is the first quantitative survey which documents a positive relationships between organizational confidence and firm performance.
Gift‐giving among adolescents: exploring motives, the effects of givers' personal characteristics and the use of impression management tactics
Authors: Segev Ruth , Shoham Aviv , Ruvio Ayalla
Published: July 2013

Purpose

Previous research on impression management explored motives, the use of impression management tactics and the influence of personality characteristics on the tendency to engage in impression management. The purposes of this research are to examine gift‐giving behavior among adolescents based on the building blocks of impression management theory, the ways that personality characteristics motivate gift‐givers to engage in active and defensive impression management and how the use of impression management tactics (i.e. similarity‐conformity and target‐enhancement) are reflected in their gift‐giving behavior.

Design/methodology/approach

A convenience sample of 141 adolescences was used in a quantitative study. Self‐report questionnaires were distributed to adolescents of different ages (13‐16), with students from diverse social strata. Students were asked to recall a recent peer gift‐giving experience and to refer to it when answering the questions which covered motives for gift‐giving, personality characteristics, and the characteristics of the gift.

Findings

The authors' study shows that personality characteristics such as public self‐consciousness, self‐monitoring, and self‐esteem are positively related with gift‐giving motives. Additionally, gift‐giving motives are positively related with the use of similarity‐conformity and target‐enhancement tactics. Finally, the use of impression management tactics reflects adolescents' special characteristics, such as their tendency towards conformism, important role of peers in their lives, and their high need to protect and nurture these social resources.

Originality/value

This research explored the instrumental role of gift‐giving among adolescents and contributes to the existing literatures on gift‐giving, impression management, and adolescents' consumer behavior.
Examination of work task and criteria choices for the relevance judgment process
Authors: Taylor Arthur
Published: July 2013

Purpose

The purpose of this paper is to better understand the dynamic nature of the relevance judgment process and the influence of work task on that process.

Design/methodology/approach

The empirical study reported here examined the information seeking behavior of a group of undergraduate college students assigned a set of research assignments (work tasks). Subjects recorded their selection of documents used for an assignment and the criteria used to judge those documents relevant. Statistical analysis was used to associate relevance judgments and the criteria used to make those judgments with work tasks.

Findings

Findings indicate a strong statistical association between work task and criteria used to judge relevance. Findings also include identification of specific criteria used to judge relevance and the relative importance of those criteria based on frequency of selection of criteria for a work task.

Research limitations/implications

Findings provide additional insights into the dynamic nature of the relevance judgment process. Relevance judgment influences revealed in these findings in the form of criteria used to make relevance judgments further explicate the relevance judgment process and provide suggestions for the improvement of information retrieval systems and information literacy efforts.

Originality/value

Understanding the relevance judgment process is critical to understanding information behavior in general. Few studies have examined relevance criteria selections as part of the relevance judgment process and fewer still have studied these selections in relation to work tasks. A better understanding of this relationship is an essential part of understanding the dynamic nature of the relevance judgment process and its influences.
Online copyright protection and innovation
Authors: Tian Dexin , Chao Chin‐Chung
Published: July 2013

Purpose

This study aims to explore the policy‐making mechanism of the Organisation for Economic Co‐operation and Development (OECD) on innovation and the US practice in identifying policies on online copyright protection and innovation. The research findings provide valuable implications for emerging economies like China.

Design/methodology/approach

For data collection, this study adopted field observation of online interactions. Guided by the democratic paradigm of the civil society, state, and market and the theory of the government's roles as a broker, advocator, and facilitator, thematic analysis was applied to analyze the 150 purposively selected comments of US internet stakeholders for emerging themes and implications.

Findings

While the USA exemplified the OECD guidance by reaching out to all internet stakeholders, most of whom call for a neutral internet and reduce innovation barriers through technological and market solutions, the US online copyright protection policies are expected to bring incentives fairly to all internet stakeholders rather than the historically weighted copyright holders and content industries.

Originality/value

This study is the first academic effort in exploring the US practice of the OECD innovation guidelines by identifying online copyright and innovation policies. The implications of this study are valuable to not only the internet policy‐makers of the OECD member countries but also emerging economies, especially like China which desires long‐term innovation but keeps censoring the internet with its growing firewall.
Binomial option pricing models for real estate development
Authors: Shen Jianfu , Pretorius Frederik
Published: July 2013

Purpose

The purpose of this paper is to construct option pricing models for real estate development by considering and incorporating institutional arrangements, direct interactions and financial constraints in the model. It extends the application of real option theory from the framework borrowed from financial option pricing, and considers the case where a development company has restrictions from outside environment and financial constraint. It explores the effects of these additional practical factors on real asset project value and development timing. This paper makes contributions to bridge the theoretical models and practical applications.

Design/methodology/approach

Real estate development is modelled in the binomial option pricing framework with the considerations of time‐to‐build, foregone rent if delaying, institutional environment and capital budgeting. The investment timings are derived from the models and sensitivity analysis is conducted to explore the effects of these factors.

Findings

Apart from the factors in traditional option pricing theory, this paper confirms that the contractual covenants, positive synergies between properties and financial status of the firm, which enhance or restrict real flexibility embedded in the development land, influence project value and investment timing. Numerical examples illustrate the effects of these factors. It is argued that the valuation of real options should place emphasis on industry‐specific characteristics and start from the perspective of the firm rather than individual options.

Practical implications

The models constructed in this paper and the results can be directly used in the practical real estate development.

Originality/value

This paper incorporates many practical factors in real estate development which are not investigated in previous studies. It values the option project from the firm perspective rather than project perspective as previous studies. It also shows the effects of institutional arrangement and firm factors on project value and development timing.
Antecedents and evolution of the Bartlett and Ghoshal transnational typology
Authors: Rašković Matevž , Makovec Brenčič Maja , Jaklič Marko
Published: July 2013

Purpose

The purpose of this paper is to systematically describe the evolution of Bartlett and Ghoshal's transnational typology within an appropriate historical context, and to additionally review key antecedent works of other authors who contributed to its evolutionary nature.

Design/methodology/approach

The paper presents a comprehensive review of the literature by combining an evolutionary perspective with a Chandlerian business history approach.

Findings

The paper shows how Bartlett and Ghoshal's transnational solution concept was developed in light of the global economic changes of the 1970s and 1980s, as well as the managerial and strategic challenges faced by US MNCs. It shows how the transnational solution concept should not be seen as a single work, but rather the outcome of an academic discourse which lasted over a decade. The review of Bartlett and Ghoshal's stream of work since the mid 1980s also shows how the transnational solution concept developed gradually into its present form and through the integration of several antecedent concepts.

Originality/value

This paper describes not just the actual evolution of Bartlett and Ghoshal's transnational typology, but also systematically identifies and analyzes key antecedent works by other authors. This analysis has been overlooked and is at the same time key to the understanding of their typology. The employed evolutionary and business history perspectives within this paper are new to the international management literature. They should be especially valuable for graduate students and scholars who employ Bartlett and Ghoshal's typology, or anyone who wishes to understand theZeitgeistof the time articulated by this seminal work, which will soon celebrate its 25th anniversary.
Generalized magneto‐thermo‐microstretch elastic solid under gravitational effect with energy dissipation
Authors: Othman Mohamed I.A. , Atwa Sarhan Y. , Jahangir A. , Khan A.
Published: July 2013

Purpose

The purpose of this paper is to study the effect of gravity on the general model of the equations of generalized magneto‐thermo‐microstretch for a homogeneous isotropic elastic half‐space solid whose surface is subjected to a mode‐I crack. The problem is in the context of the Green and Naghdi theory of both types (II and III).

Design/methodology/approach

The normal mode analysis is used to obtain the expressions for the displacement components, the force stresses, the temperature, the couple stress and the microstress distribution.

Findings

The variations in variables against distance components are given graphically in 2D and 3D.

Practical implications

The linear theory of elasticity is of paramount importance in the stress analysis of steel, which is the commonest engineering structural material. To a lesser extent, the linear elasticity describes the mechanical behavior of the other common solid materials, e.g. concrete, wood and coal. However, the theory does not apply to the behavior of many of the newly synthetic materials of the elastomer and polymer type, e.g. polymethyl‐methacrylate (Perspex), polyethylene and polyvinyl chloride.

Originality/value

Comparisons are made with the results in the presence and absence of gravity and initially applied magnetic field with two cases: the first for the generalized micropolar thermoelasticity elastic medium (without stretch constants) between both types (II, III); and the second for the generalized magneto‐thermoelastic medium with stretch (without micropolar constants) between both types (II, III).
Fatigue behavior and damage mechanism of carbon/carbon composites: a review
Authors: Yang Xi , Li Hejun , Zhang Shouyang , Yu Kuahai , Wang Zhi
Published: July 2013

Purpose

This paper aims to review the research status of fatigue behavior and fracture mechanism for C/C composites.

Design/methodology/approach

The fatigue behavior is related to many factors. The mechanical and physical properties were compared to evaluate the effect of fatigue under various experimental conditions, including different load type, loading frequency and stress ratio. Special attention is put on the high‐temperature fatigue research.

Findings

The strength has improved by fatigue loading. And most researchers considered that the weaken interface was the main reason for fatigue enhancement. However, the research on high‐temperature fatigue behavior is especially scarce.

Originality/value

This review provides a guideline on the current and future research on fatigue behavior of C/C composites.
Optimization of process parameters in electro chemical machining (ECM) using DFA‐fuzzy set theory‐TOPSIS for titanium alloy
Authors: Santhi M. , Ravikumar R. , Jeyapaul R.
Published: July 2013

Purpose

The purpose of this paper is to present a new method to optimize the electro chemical machining process parameters for titanium alloy (Ti6Al4V).

Design/methodology/approach

The desirability function analysis (DFA), fuzzy set theory with trapezoidal membership function and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method are used to optimize the electro chemical machining process parameters for titanium alloy (Ti6Al4V). In recent years, the utilization of titanium and its alloys, especially of Ti6Al4V materials, in many different engineering fields has undergone a tremendous increase. The ECM process has a potential in the machining of Ti6Al4V. The machining parameters such as electrolyte concentration, current, applied voltage and feed rate with multiple responses such as material removal rate (MRR) and surface roughness (SR) are considered. Experimental work is carried out on Ti6Al4V using second order central composite rotatable design. The two responses are converted into global knit quality index using DFA. Fuzzy set theory with trapezoidal membership function is used to convert all machining parameters and responses into fuzzy values. Then a TOPSIS approach which determines the optimal machining parameters in terms of higher closeness coefficient is proposed to optimize the machining parameters of ECM for titanium alloy. Finally, ANOVA is performed to investigate the significance of each machining parameter and to identify the most influencing factor which affects the process responses.

Findings

The optimal machining parameters for ECM process are determined using desirability function analysis, fuzzy set theory and TOPSIS.

Originality/value

A new method is proposed to optimize the electro chemical machining process parameters for titanium alloy.
An integrated model for effective knowledge management in Chinese organizations
Authors: An Xiaomi , Deng Hepu , Wang Yiwen , Chao Lemen
Published: July 2013

Purpose

The purpose of this paper is to provide organizations in the Chinese cultural context with a conceptual model for an integrated adoption of existing knowledge management (KM) methods and to improve the effectiveness of their KM activities.

Design/methodology/approaches

A comparative analysis is conducted between China and the western world based on a comprehensive document analysis from key databases available. In total, four critical dimensions, which are identified through the review of the related literature including observation, methodology, systems and applications, are used in the analysis for addressing the questions of why, what, how, and where in KM.

Findings

The paper rationalizes the need for this study in conformity with the emerging trend of an integrated use of diverse KM methods and approaches for effective KM in organizations. Further, a reference model for the integrated adoption of existing KM methods is developed with respect to the characteristics of the Chinese culture for improving the effectiveness of KM activities in the organizations. Such a model can adequately address the questions of why, what, how, and where in KM in Chinese organizations to the best of Chinese collective interest, which provides more comprehensive and unified KM views, activities, processes and technologies for collaborative innovation in Chinese organizations.

Originality/value

This paper is the first of its kind to systematically review existing KM methods and approaches with respect to the perspectives of observations, methodologies, systems and applications for effective KM in Chinese organizations.
Toll‐deficient Drosophila is susceptible to Pythium insidiosum infection
Authors: Zanette Régis A. , Santurio Janio M. , Loreto Érico S. , Alves Sydney H. , Kontoyiannis Dimitrios P.
Published: July 2013

There is a paucity of animal models of pythiosis, a life‐threatening disease of humans and animals, the immunopathogenesis of which is poorly understood. A pythiosis model was developed by injecting Toll (Tl)‐deficient Drosophila melanogaster flies with Pythium insidiosum zoospores. The infected Tl mutant flies had significantly lower survival rates (73.7%) than did control flies. This study reveals the important role of Tl pathway activation in fly immune response to pythiosis.
Partitioning net interactions among plants along altitudinal gradients to study community responses to climate change
Authors: Michalet Richard , Schöb Christian , Lortie Christopher J. , Brooker Rob W. , Callaway Ragan M.
Published: July 2013

Altitudinal gradients provide a useful space‐for‐time substitution to examine the capacity for plant competition and facilitation to mediate responses to climate change. Decomposing net interactions into their facilitative and competitive components, and quantifying the performance of plants with and without neighbours along altitudinal gradients, may prove particularly informative in understanding the mechanisms behind plant responses to environmental change.

To decouple the inherent responses of species to climate from the responses of plant–plant interactions to climate, we conducted a meta‐analysis. Using data from 16 alpine experiments, we tested if changes in net interactions along altitudinal gradients were due to a change in the performance of target species without neighbours (i.e. environmental severity effects only) or with neighbours (neighbour trait mediated effects).

There was a global shift from competition to facilitation with increasing altitude driven by both environmental severity and neighbour trait effects. However, this global pattern was strongly influenced by the high number of studies in mesic climates and driven by competition at low altitude in temperate climates (neighbour trait effect), and facilitation at high altitude in arctic and temperate climates (environmental severity effect).

In Mediterranean systems, there was no significant effect of competition, and facilitation increased with decreasing altitude. Changes in facilitation with altitude could not unambiguously be attributed to either neighbour trait effects or environmental severity effects, probably because of the opposing stress gradients of cold and aridity in dry environments.

Partitioning net interactions along altitudinal gradients led to the prediction that climate change should decrease the importance of facilitation in mesic alpine communities, which might in turn exacerbate the negative effects of climate change in these regions. In xeric climates, the importance of facilitation by drought‐tolerant species should increase at low altitudes which should mitigate the negative effect of climate change. However, the importance of facilitation by cold‐tolerant species at high altitudes may decrease and exacerbate the effects of climate change.
Bidirectional trophic linkages couple canopy and understorey food webs
Authors: Giery Sean T. , Lemoine Nathan P. , Hammerschlag‐Peyer Caroline M. , Abbey‐Lee Robin N. , Layman Craig A.
Published: July 2013

Cross‐system resource flux is a fundamental component of ecological systems. Allochthonous material flows generate trophic linkages between adjacent food webs, thereby affecting community structure and stability in recipient systems.

We investigated cross‐habitat trophic linkages between canopy and understorey food webs in a terrestrial, wooded, ecosystem in South Florida, USA. The focal community consisted of three species of Anolis lizards and their prey. We described interspecific differences among Anolis species in the strength and routing of these cross‐habitat flows using stable isotope analysis, stomach content analysis and habitat use data.

All three Anolis species in this study consumed different prey and occupied vertically distinct arboreal habitats. Despite these differences, carbon isotope and stomach content analysis revealed strong integration with understorey and canopy food webs for all Anolis species. Modes of resource flux contributing to the observed cross‐habitat trophic linkages included prey movement and the gravity‐driven transport of detritus.

Our study shows that terrestrial systems are linked by considerable bidirectional cross‐system resource flux. Our results also suggest that considering species‐specific interactions between predator and prey is necessary to fully understand the diversity of material and energy flows between spatially separated habitats.
Foraging and vulnerability traits modify predator–prey body mass allometry: freshwater macroinvertebrates as a case study
Authors: Klecka Jan , Boukal David S.
Published: July 2013

Predation is often size selective, but the role of other traits of the prey and predators in their interactions is little known. This hinders our understanding of the causal links between trophic interactions and the structure of animal communities. Better knowledge of trophic traits underlying predator–prey interactions is also needed to improve models attempting to predict food web structure and dynamics from known species traits.

We carried out laboratory experiments with common freshwater macroinvertebrate predators (diving beetles, dragonfly and damselfly larvae and water bugs) and their prey to assess how body size and traits related to foraging (microhabitat use, feeding mode and foraging mode) and to prey vulnerability (microhabitat use, activity and escape behaviour) affect predation strength.

The underlying predator–prey body mass allometry characterizing mean prey size and total predation pressure was modified by feeding mode of the predators (suctorial or chewing). Suctorial predators fed upon larger prey and had ˜3 times higher mass‐specific predation rate than chewing predators of the same size and may thus have stronger effect on prey abundance.

Strength of individual trophic links, measured as mortality of the focal prey caused by the focal predator, was determined jointly by the predator and prey body mass and their foraging and vulnerability traits. In addition to the feeding mode, interactions between prey escape behaviour (slow or fast), prey activity (sedentary or active) and predator foraging mode (searching or ambush) strongly affected prey mortality. Searching predators was ineffective in capturing fast‐escape prey in comparison with the remaining predator–prey combinations, while ambush predators caused higher mortality than searching predators and the difference was larger in active prey.

Our results imply that the inclusion of the commonly available qualitative data on foraging traits of predators and vulnerability traits of prey could substantially increase biological realism of food web descriptions.