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Article
Publication date: 1 March 1996

H.K. Tang and Brian Lee

Programmable electronics are particularly susceptible to transients, a form of electromagnetic interference. The widespread use of programmable electronics in many…

1157

Abstract

Programmable electronics are particularly susceptible to transients, a form of electromagnetic interference. The widespread use of programmable electronics in many mass‐produced products, industrial systems and safety‐critical applications is a cause for concern over their reliability. Neglecting transients’ effect in the initial product specification stage increases significantly the possibility of having to redesign a product late in its development cycle, with all its serious consequences. Deals first with the nature of transients and transient faults in programmable electronics, then elaborates on transients’ effects on reliability and discusses the related management issues.

Details

International Journal of Quality & Reliability Management, vol. 13 no. 2
Type: Research Article
ISSN: 0265-671X

Keywords

Article
Publication date: 5 May 2022

Adel Oubelaid, Nabil Taib and Toufik Rekioua

The purpose of this paper is the investigation of a new coordinated switching strategy to improve the transient performance of a fuel cell (FC)- supercapacitor (SC…

Abstract

Purpose

The purpose of this paper is the investigation of a new coordinated switching strategy to improve the transient performance of a fuel cell (FC)- supercapacitor (SC) electric vehicle. The proposed switching strategy protects FCs from large currents drawn during abrupt power variations. Furthermore, it compensates the poor FC transient response and suppresses the transient ripples occurring during power source switching instants.

Design/methodology/approach

Coordinated power source switching is achieved using three different transition functions. Vehicle model is fractioned into computational and console subsystems for its simulation using real time (RT) LAB simulator. Blocs containing coordination switching strategy, power sources models and their power electronics interface are placed in the computational subsystem that will be executed, in RT, on one of real time laboratory simulator central processing unit cores.

Findings

Coordination switching strategy resulted in reducing transient power ripples by 90% and direct current (DC) bus voltage fluctuations by 50%. Switching through transition functions compensated the difference between FC and SC transient responses responsible for transient power ripples. Among the three proposed transition functions, linear transition function resulted in the best transient performances.

Originality/value

The proposed coordinated switching strategy allows the control of the switching period duration. Furthermore, it enables the choice of adequate transition functions that fit the dynamics of power sources undergoing transition. Also, the proposed switching technique is simple and does not require the knowledge of system parameters or the complex control models.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 41 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 26 January 2022

Xinyi Jiang, Yanfeng Chen, Bo Zhang and Dongyuan Qiu

This paper aims to present a simplified method to analyze the transient characteristics of a fractional-order very high frequency (VHF) resonant boost converter. The…

Abstract

Purpose

This paper aims to present a simplified method to analyze the transient characteristics of a fractional-order very high frequency (VHF) resonant boost converter. The transient analytical solutions of state variables obtained by this method could be used as a guide for parameter design and circuit optimization.

Design/methodology/approach

The VHF converter is decoupled into a simplified equivalent circuit model and described by the differential equation. The solution of the simplified equivalent circuit model is taken as the main oscillation component of the transient state variable. And the equivalent small parameter method (ESPM) and Kalman filter technology are used to solve the differential equation of the converter to obtain the steady-state ripple component. Then, by superimposing the abovementioned two parts, the approximate transient analytical solution can be acquired. Finally, the influence of the fractional order of the energy storage elements on the transient process of the converter is discussed.

Findings

The results from the proposed method agree well with those from simulations, which indicates that the proposed method can effectively analyze the transient characteristic of the fractional-order VHF converter, and the analytical solution derived from the proposed mathematical model shows sufficient accuracy.

Originality/value

This paper proposes for the first time a method to analyze the transient characteristics of a fractional-order VHF resonant boost converter. By combining the main oscillated solution derived from the simplified equivalent circuit model with the steady-state solution based on ESPM, this method can greatly reduce the computation amount to estimate the transient solution. In addition, the discussion on the order of fractional calculus of energy storage components can provide an auxiliary guidance for the selection of circuit parameters and the study of stability.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 41 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 7 June 2018

Sonia Bensemmane, Marc Ohana and Florence Stinglhamber

Prior research has conceptualized workplace justice as a stable variable over time changing from one individual to another. However, it can be assumed that perceptions of…

Abstract

Purpose

Prior research has conceptualized workplace justice as a stable variable over time changing from one individual to another. However, it can be assumed that perceptions of organizational justice fluctuate within the same person over the course of a few weeks or months due to different events at work. Specifically, the purpose of this paper is to suggest that transient overall team justice is predictive of employee’s transient thriving at work (i.e. the experience of vitality and learning at work). In addition, the authors examined transient self-efficacy as an underlying mechanism of this relationship.

Design/methodology/approach

A total of 395 individuals completed a first general questionnaire and then completed an online questionnaire over four waves of survey.

Findings

Results of hierarchical linear models indicated that transient overall team justice positively predicts transient individual’s self-efficacy, which, in turn, positively predicts transient individual’s thriving at work.

Research limitations/implications

Overall, a dynamic approach of organizational justice capturing variability in justice perceptions certainly enlarges our understanding of the concept and its outcomes.

Originality/value

The study contributes to understand why even employees who feel generally treated with justice by their team may experience from time to time low levels of thriving at work because of a recent unjust treatment from the team and a decrease of their subsequent self-efficacy.

Details

Journal of Managerial Psychology, vol. 33 no. 2
Type: Research Article
ISSN: 0268-3946

Keywords

Article
Publication date: 13 November 2007

Jian Tang, Xiang Cui, Lei Qi, Tiebing Lu, Lin Li, Puxuan Zhu, Guang Yang and Weizhen Zhang

The purpose of this paper is to present a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference…

Abstract

Purpose

The purpose of this paper is to present a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference generated in the pipelines due to the inductive coupling in the fault‐to‐ground condition of power lines in close proximity.

Design/methodology/approach

Based on finite difference‐time domain method, an improved method is proposed to calculate transient inductive interference in underground metallic pipelines due to a fault in nearby power lines. The frequency‐dependent problem in the analysis of transient interference is solved in phase domain. Compared with the traditional method, the disposal of phase‐modal transformation matrices’ frequency‐dependent characteristic is avoided and the calculation is simplified by using vector fitting approach and recursive algorithm greatly in the proposed method.

Findings

A novel improved method is proposed to calculate transient induced voltage distribution along underground metallic pipelines due to a fault in nearby power lines. Results show that the peak value of transient induced voltage at the most critical point is about 1.15 times of the magnitude in the steady state without the fault removed and the analysis of transient inductive interference is necessary in the fault‐to‐ground case of power lines.

Practical implications

In order to mitigate the interference from power lines to nearby pipelines, pipelines should be good grounded and positioned as far away from the power line as possible. In high soil resistivity areas, the common corridor should be avoided.

Originality/value

The paper presents a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference generated in the pipelines due to the inductive coupling in the fault‐to‐ground condition of nearby power lines. The proposed method is general and can also be applied to other transient interference studies such as crosstalk problems of communication networks and interference between power lines and aboveground pipelines or communication cables. Effects of various parameters upon the inductive interference generated in underground pipelines due to a fault in nearby power lines are analyzed to be a guide for controlling the inductive interference.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 3 May 2016

Nicola Massarotti, Michela Ciccolella, Gino Cortellessa and Alessandro Mauro

The purpose of this paper is to focus on the numerical analysis of transient free convection heat transfer in partially porous cylindrical domains. The authors analyze the…

Abstract

Purpose

The purpose of this paper is to focus on the numerical analysis of transient free convection heat transfer in partially porous cylindrical domains. The authors analyze the dependence of velocity and temperature fields on the geometry, by analyzing transient flow behavior for different values of cavity aspect ratio and radii ratio; both inner and outer radius are assumed variable in order to not change the difference ro-ri. Moreover, several Darcy numbers have been considered.

Design/methodology/approach

A dual time-stepping procedure based on the transient artificial compressibility version of the characteristic-based split algorithm has been adopted in order to solve the transient equations of the generalized model for heat and fluid flow through porous media. The present model has been validated against experimental data available in the scientific literature for two different problems, steady-state free convection in a porous annulus and transient natural convection in a porous cylinder, showing an excellent agreement.

Findings

For vertically divided half porous cavities, with Rayleigh numbers equal to 3.4×106 for the 4:1 cavity and 3.4×105 for the 8:1 cavity, the numerical results show that transient oscillations tend to disappear in presence of cylindrical geometry, differently from what happens for rectangular one. The magnitude of this phenomenon increases with radii ratio; the porous layer also affects the stability of velocity and temperature fields, as oscillations tend to decrease in presence of a porous matrix with lower value of the Darcy number.

Research limitations/implications

A proper analysis of partially porous annular cavities is fundamental for the correct estimation of Nusselt numbers, as the formulas provided for rectangular domains are not able to describe these problems.

Practical implications

The proposed model represents a useful tool for the study of transient natural convection problems in porous and partially porous cylindrical and annular cavities, typical of many engineering applications. Moreover, a fully explicit scheme reduces the computational costs and ensures flexibility.

Originality/value

This is the first time that a fully explicit finite element scheme is employed for the solution of transient natural convection in partially porous tall annular cavities.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 15 February 2013

Kam C. Chan, Feida Zhang and Weining Zhang

The purpose of this paper is to study the relationship between institutional holdings and analyst coverage in the context of the heterogeneous nature of institutional investors.

1263

Abstract

Purpose

The purpose of this paper is to study the relationship between institutional holdings and analyst coverage in the context of the heterogeneous nature of institutional investors.

Design/methodology/approach

Similar to prior studies (e.g. Ke and Ramalingegowda; Ramalingegowda and Yu), this paper obtains institutional investors' trading classifications (transient, dedicated, and quasi‐indexing) from Brian Bushee directly. To examine the hypotheses, the paper uses a two‐step instrumental variable approach demonstrated in O'Brien and Bhushan to mitigate the simultaneity relationship between the change in analyst coverage and the change in the number of heterogeneous institutional investors.

Findings

The findings suggest that such relations are different among transient, dedicated, and quasi‐indexing institutional investors. Specifically, there are three major results. First, a change to the number of analyst coverage has the lowest impact on the change in the number of dedicated institutional investors. Second, a change in the number of transient institutional investors has a higher impact on change in analyst coverage than those for change in the number of dedicated and quasi‐indexing institutional investors. Third, changes to analysts' buy or sell recommendations have the least impact on the change in the number of dedicated institutions, relative to transient and quasi‐indexing institutions.

Research limitations/implications

The findings suggest that institutional investors are not homogeneous. Research studies on institutional investors need to disentangle the differences among different types of institutions.

Originality/value

The paper provides a comprehensive study on different institutional investors and analyst coverage. The findings show the complex nature of the interaction between institutional investors and analyst coverage.

Details

Review of Accounting and Finance, vol. 12 no. 1
Type: Research Article
ISSN: 1475-7702

Keywords

Article
Publication date: 7 June 2011

Juan Wang

The aim of this paper is to examine how informed traders, i.e. transient institutional investors that actively trade on information to maximize investment profits, use…

Abstract

Purpose

The aim of this paper is to examine how informed traders, i.e. transient institutional investors that actively trade on information to maximize investment profits, use insider trading signals in addition to accounting numbers to mitigate future abnormal returns.

Design/methodology/approach

Using a sample of 44,843 firm‐quarters from 1988 to 2001 in the USA, the paper examines how informed investors use insider trading signals and the extent to which the use of these signals by informed investors impacts insiders' future abnormal returns from trading.

Findings

This study finds that the change in transient institutional ownership in the next‐quarter is positively associated with net insider trading in the current quarter, after controlling for accounting information (including total accruals, unexpected earnings, etc.). In addition, this study finds that insider profits decrease in transient institutional ownership, consistent with the notion that trading by informed investors limits insider profits.

Research limitations/implications

The institutional ownership data are only available on a quarterly basis, which may not capture institutional investors' immediate response to insider trading signals.

Originality/value

This study provides systematic evidence on how informed traders use insider trading signals. This study adds to existing knowledge of the information environment of institutional investors by showing that transient institutional investors use insider trading signals in addition to accounting information in making investment decisions. Moreover, this study contributes to the literature on the determinants of insider profits by providing evidence that informed trading by investors has incremental power to explain insider profits.

Details

International Journal of Accounting & Information Management, vol. 19 no. 2
Type: Research Article
ISSN: 1834-7649

Keywords

Article
Publication date: 14 July 2022

Chuanbao Nie, Bowen Fu and Qiang Gao

This paper aims to develop an efficient numerical method for nonlinear transient heat conduction problems with local radiation boundary conditions and nonlinear heat sources.

Abstract

Purpose

This paper aims to develop an efficient numerical method for nonlinear transient heat conduction problems with local radiation boundary conditions and nonlinear heat sources.

Design/methodology/approach

Based on the physical characteristic of the transient heat conduction and the distribution characteristic of the Green’s function, a quasi-superposition principle is presented for the transient heat conduction problems with local nonlinearities. Then, an efficient method is developed, which indicates that the solution of the original nonlinear problem can be derived by solving some nonlinear problems with small structures and a linear problem with the original structure. These problems are independent of each other and can be solved simultaneously by the parallel computing technique.

Findings

Within a small time step, the nonlinear thermal loads can only induce significant temperature responses of the regions near the positions of the nonlinear thermal loads, whereas the temperature responses of the remaining regions are very close to zero. According to the above physical characteristic, the original nonlinear problem can be transformed into some nonlinear problems with small structures and a linear problem with the original structure.

Originality/value

An efficient and accurate numerical method is presented for transient heat conduction problems with local nonlinearities, and some numerical examples demonstrate the high efficiency and accuracy of the proposed method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 30 November 2021

Yuan Chen, Hao Shang, Xiaolu Li, Yuntang Li, Bingqing Wang and Xudong Peng

The purpose of this paper is to investigate the influence rule and mechanism of three degrees of freedom film thickness disturbance on the transient performance of spiral…

Abstract

Purpose

The purpose of this paper is to investigate the influence rule and mechanism of three degrees of freedom film thickness disturbance on the transient performance of spiral groove, upstream pumping spiral groove dry gas seal (UP-SDGS) and double-row spiral groove dry gas seal (DR-SDGS).

Design/methodology/approach

The transient performance of spiral groove, UP-SDGS and DR-SDGS are obtained by solving the transient Reynolds equation under different axial and angular disturbance coefficients. The transient and steady performance of the above-mentioned DGSs are compared and analyzed.

Findings

The film thickness disturbance has a remarkable impact on the sealing performance of DGS with different structures and the calculation deviations of the leakage rate of the UP-DGS will increase significantly if the film thickness disturbance is ignored. The axial and angular disturbance jointly affect the film thickness distribution of DGS, but there is no significant interaction between them on the transient sealing performance.

Originality/value

The influence mechanism of axial disturbance and angular disturbance on the transient performance of typical SDGSs behavior has been explained by theory. Considering small and large disturbance, the interaction between axial disturbance and angular disturbance on the transient performance have been studied.

Details

Industrial Lubrication and Tribology, vol. 74 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

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