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Article
Publication date: 14 November 2008

L. Kolev

To suggest a polynomial complexity method for determining the range of real eigenvalues in the case of the generalized eigenvalue problem when the elements of the matrices…

372

Abstract

Purpose

To suggest a polynomial complexity method for determining the range of real eigenvalues in the case of the generalized eigenvalue problem when the elements of the matrices involved are independent intervals.

Design/methodology/approach

The basic approach is to make use of approximate interval solutions as regards the right and left eigenvectors of the eigenproblem considered, the so‐called outer solutions, in order to determine the range.

Findings

First, a new method for computing the outer solutions has been suggested. The main result of the paper, however, is the development of a simple method for determining the range of the real eigenvalues. Unlike the known general‐purpose methods that have exponential complexity, the present range determination method is much simpler as its complexity is only polynomial.

Research limitations/implications

The method is applicable if certain sufficient conditions reported in the paper are satisfied (an incomplete quadratic system is to have a positive solution and the signs of the outer solutions should satisfy a complete or partial invariance).

Practical implications

The method guarantees reliable numerical results when the original eigenproblems contain interval uncertainties as is, strictly speaking, most often the case in practice.

Originality/value

To the best of the author's knowledge, the present paper suggests, for the first time, a simple method of polynomial complexity for solving the problem considered which is inherently a NP‐hard problem (of exponential complexity).

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 27 no. 6
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 3 May 2013

Lubomir Kolev

The purpose of this paper is to suggest a polynomial complexity method for determining the range of the active and reactive power consumed in AC uncertain parameter circuits whose…

103

Abstract

Purpose

The purpose of this paper is to suggest a polynomial complexity method for determining the range of the active and reactive power consumed in AC uncertain parameter circuits whose uncertain parameters are given as intervals.

Design/methodology/approach

First, the original problem is formulated as a corresponding interval quadratic range determination (IQRD) problem. Next, it is shown that the IQRD problem can be transformed equivalently into an interval linear range determination (ILRD) problem.

Findings

An efficient numerical method for solving the associated ILRD problem has been developed, capable of tackling the present active (or reactive) power range problem. It is based on the use of the outer solution y of an associated interval linear system defining the constraints in the ILRD problem.

Research limitations/implications

The method yields the exact active and reactive power range if the number of the components yi of y containing zero is relatively small (which is most often the case); otherwise, it provides tight outer bounds on the ranges sought.

Practical implications

The present method can be an alternative to the widely used Monte‐Carlo method since the former method provides exact (within rounding errors) results or tight outer approximations for lesser computation times.

Originality/value

To the best of the author's knowledge, the present paper suggests, for the first time, a simple interval analysis method of polynomial complexity for solving the problem considered which is inherently a NP‐hard problem (of exponential complexity).

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 30 July 2018

Adnan Enshassi, Abed Ayash and Sherif Mohamed

The purpose of this paper is to investigate the factors driving Palestinian construction contractors to implement energy management strategies during the execution of construction…

374

Abstract

Purpose

The purpose of this paper is to investigate the factors driving Palestinian construction contractors to implement energy management strategies during the execution of construction projects.

Design/methodology/approach

The study was conducted by administering a questionnaire that comprised 26 drivers for adopting energy management strategies. Data were collected from 67 contractors in the Gaza Strip. Factor analysis was adopted to explore the underlying relationships among the identified drivers.

Findings

Drivers were grouped into one of the four categories: economic and financial, institutional and legal, organisational and managerial and educational and informational. The results revealed that the majority of the respondents were of the view that economic and financial factors were the most important factors driving the adoption of energy management strategies by construction companies in the Gaza Strip. Of the economic and financial drivers, the cost savings derived from the adoption of energy management strategies was considered the most important item. Energy management education and training programmes are scarce in the Gaza Strip, and local contractors have no formal energy management education and training. The government needs to allocate sufficient funds for policy implementation and regulation enforcement.

Research limitations/implications

Difficulties in accessing energy management data are deemed as a limitation to this study, as the topic of energy management in the construction has received no or very little academic attention so far.

Practical implications

This study provides a valuable reference for studying ongoing research in the practice of energy management development in other industries and locations. The priority of the drivers for energy management will help the local contracting companies to focus on weak and strong points of the company for energy use development to remove these weak points and invest in strong points. This paper results can increase the encouragement for greater social responsibility of the contracting organisations towards energy use. Government and concerned organisations can get benefits from the identified factors in encouraging contractors to adopt energy management strategy in their projects.

Originality/value

This study is the first investigation of energy management aspects in a local construction industry, especially from contracting organisations.

Details

Journal of Financial Management of Property and Construction, vol. 23 no. 3
Type: Research Article
ISSN: 1366-4387

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Article
Publication date: 12 July 2011

Michał Tadeusiewicz and Stanisław Hałgas

The purpose of this paper is to develop a method for finding all the DC solutions in nonlinear circuits with the thermal constraint.

157

Abstract

Purpose

The purpose of this paper is to develop a method for finding all the DC solutions in nonlinear circuits with the thermal constraint.

Design/methodology/approach

The proposed approach employs an algorithm for finding all the DC solutions without thermal constraint, including a new contraction and elimination method, an efficient method for tracing characteristics expressing voltages and power in terms of temperature, and electrical analog of the chip thermal behavior.

Findings

The paper brings a method that guarantees finding all the DC solutions, considering thermal behavior of the chip, in mid‐scale practical transistor circuits.

Originality/value

A new contraction and elimination method, being the core of the algorithm for finding all the DC solutions, is proposed. An approach enabling us to consider a feedback between the power dissipated inside the chip and the temperature, which affects the circuit parameters and consequently the solutions is developed.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 October 2006

G. Spagnuolo

To introduce an interval arithmetic (IA)‐based approach to tolerance analysis and design and to yield evaluation. The technique distinguishes itself by its reliability in the…

158

Abstract

Purpose

To introduce an interval arithmetic (IA)‐based approach to tolerance analysis and design and to yield evaluation. The technique distinguishes itself by its reliability in the detection of even non convex and/or non simply connected regions of acceptability.

Design/methodology/approach

Range methods, and IA among them, inherently allow the evaluation of an overestimation of the true range spanned by a performance function of a given system because of variation of its parameters values. Such a feature is of great help in performing the robust design of any system, that is, in doing the placement of the design set within the region of acceptability, even in the presence of tolerances and parameters values drifts.

Findings

The IA‐based branch and bound numerical procedure proposed in the paper has shown its reliability and robustness during the tolerance analysis of systems exhibiting quite involved regions of acceptability.

Research limitations/implications

Many remarks are reported in the paper to complete the research and extend it to a larger class of problems.

Practical implications

The procedure might be built into simulation environments in order to help the designer in dominating tolerances effects.

Originality/value

This paper shares in suggesting the use of a powerful tool, i.e. range methods, in the area of tolerance design and reliability.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 25 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 December 2005

M. Tadeusiewicz and S. Hałgas

Showing both theoretically and experimentally that the Newton‐Raphson algorithm is a very efficient tool for computing the transfer factor characteristic of AM detectors.

469

Abstract

Purpose

Showing both theoretically and experimentally that the Newton‐Raphson algorithm is a very efficient tool for computing the transfer factor characteristic of AM detectors.

Design/methodology/approach

An equation which describes the diode and transistor AM detectors has been investigated. Using elementary techniques of mathematical analysis, some theoretical properties of the equation have been formulated and convergence of the Newton‐Raphson algorithm has been proved.

Findings

It is shown that the Newton‐Raphson algorithm is an efficient tool for tracing the transfer factor characteristics of both diode and transistor AM detector. The convergence of this algorithm is proved and a comparison with SPICE simulation is made. Furthermore, the diode and transistor AM detectors have been built up and validating measurements have been carried out. The comparison shows that the algorithm proposed in the paper computes the characteristics fast achieving good accuracy.

Research limitations/implications

The results obtained are limited to those described in the paper diode and transistor AM detectors.

Originality/value

Some properties of the nonlinear equation describing the AM detectors are formulated and convergence of the Newton‐Raphson algorithm to a unique solution is proved.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 September 2018

Snehashish Chakraverty and Nisha Rani Mahato

In structural mechanics, systems with damping factor get converted to nonlinear eigenvalue problems (NEPs), namely, quadratic eigenvalue problems. Generally, the parameters of…

315

Abstract

Purpose

In structural mechanics, systems with damping factor get converted to nonlinear eigenvalue problems (NEPs), namely, quadratic eigenvalue problems. Generally, the parameters of NEPs are considered as crisp values but because of errors in measurement, observation or maintenance-induced errors, the parameters may have uncertain bounds of values, and such uncertain bounds may be considered in terms of closed intervals. As such, this paper aims to deal with solving nonlinear interval eigenvalue problems (NIEPs) with respect to damped spring-mass systems having interval parameters.

Design/methodology/approach

Two methods, namely, linear sufficient regularity perturbation (LSRP) and direct sufficient regularity perturbation (DSRP), have been proposed for solving NIEPs based on sufficient regularity perturbation method for intervals. LSRP may be used for solving NIEPs by linearizing the eigenvalue problems into generalized interval eigenvalue problems, and DSRP may be considered as a direct solution procedure for solving NIEPs.

Findings

LSRP and DSRP methods help in computing the lower and upper eigenvalue and eigenvector bounds for NIEPs which contain the crisp eigenvalues. Further, the DSRP method is computationally efficient compared to LSRP.

Originality/value

The efficiency of the proposed methods has been validated by example problems of NIEPs. Moreover, the procedures may be extended for other nonlinear interval eigenvalue application problems.

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Article
Publication date: 31 October 2023

Yongyuan Ma and Liguo Xue

Today's business world has been tarnished with numerous corporate irresponsible behaviors. It is thus of great importance for firms to carry out crisis management on the condition…

591

Abstract

Purpose

Today's business world has been tarnished with numerous corporate irresponsible behaviors. It is thus of great importance for firms to carry out crisis management on the condition of corporate social irresponsibility (CSI). Taking a contingent social media crisis management perspective, the authors aim to investigate the relation between CSI and firm value while also examining the moderating effects of being known in social media and generalized favorability in social media on this relation.

Design/methodology/approach

The empirical analysis conducted in the authors' research is based on a sample of 203 CSI events that occurred within publicly listed firms in China between 2011 and 2015. During the process of the authors' data collection, the authors initially verified the occurrence of CSI events in publicly listed firms by reviewing reports from reputable sources such as the 21st Century Business Herald and China Securities Journal. Subsequently, the authors collected the information pertaining to media coverage of these CSI events from the China Core Newspapers Full-text Database (CCND). Additionally, the authors obtained the remaining data from reliable sources such as Guba, the China Stock Market and Accounting Research Database (CSMAR) and the Chinese News Analytics Database (CNAD). To test the authors' hypotheses, the event study and multiple-regression analysis methods are adopted.

Findings

The authors find CSI generates a negative impact on firm value. Moreover, while being known in social media strengthens the negative relation between CSI and firm value, generalized favorability in social media weakens such relation.

Research limitations/implications

There are two streams of limitations that present promising avenues for future studies. Theoretically, the authors explore the mechanisms of CSI affecting firm value from a contingent social media crisis management perspective. Consequently, the authors' study does not encompass other potential mechanisms that may exist in the CSI–firm value linkage. In terms of empirical analysis, three issues arise that provide opportunities for further investigation. First, the authors have not accounted for all potential factors that could influence the link between CSI and firm value. Second, the authors' data are subject to limitation since it comes from manual collection. At last, because the authors confirm the sample based on the actual CSI events of publicly listed firms in China, the authors' sample size is small.

Originality/value

The authors' findings contribute to a more comprehensive understanding of the relation between CSI and firm value, as well as effective strategies for responding to CSI through the utilization of social media. Consequently, the authors' results have the potential to stimulate further research on the implications of CSI and the management of corporate crises through social media platforms.

Details

Management Decision, vol. 61 no. 12
Type: Research Article
ISSN: 0025-1747

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Article
Publication date: 5 April 2022

Yuquan Ni, Nannan Sun, Guixiang Zhu, Shujie Liu, Jun Liu and Guangneng Dong

This paper aims to study different morphology Cu6Sn5 effect on Babbitt alloy tribological properties.

192

Abstract

Purpose

This paper aims to study different morphology Cu6Sn5 effect on Babbitt alloy tribological properties.

Design/methodology/approach

Different morphology Cu6Sn5 of Babbitt was conducted by different cooling modes. Bare Babbitt was marked by Babbitt-0, Babbitt modified by first cooling mode (marked by Babbitt-1) and Babbitt modified by second cooling mode (marked by Babbitt-2). The microstructure and microhardness of specimens were tested. Then, tribological properties of Babbitt-0, Babbitt-1 and Babbitt-2 were performed by reciprocating mode under lubricated condition.

Findings

The results showed that shape Cu6Sn5 of Babbitt was changed from mixed needle and star-like shape to short rod-like or granular shape. The microhardness of Babbitt-1 was highest than that of Babbitt-0 and Babbitt-2. Compared with Babbitt-0 and Babbitt-2, tribological properties of Babbitt-1 were better under lubricated condition due to short rod-like and sparse distribution of Cu6Sn5. Moreover, the simulation result of strain and stress of Babbitt-1 was lowest than that of Babbitt-0 and Babbitt-2.

Originality/value

Different morphology (shape and distributed) of Cu6Sn5 was obtained by different cooling modes. Modulated different forms of Cu6Sn5 around SnSb was beneficial to improve Babbitt alloy tribological properties.

Details

Industrial Lubrication and Tribology, vol. 74 no. 5
Type: Research Article
ISSN: 0036-8792

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Book part
Publication date: 28 October 2019

Erwin Dekker and Stefan Kolev

In this chapter it is argued that the future of Austrian economics is best sought in the field of philosophy, politics, and economics (PPE), with a strong and diverse connection…

Abstract

In this chapter it is argued that the future of Austrian economics is best sought in the field of philosophy, politics, and economics (PPE), with a strong and diverse connection with civil society. The authors demonstrate the limitations inherent in the discipline of economics for Austrian economists, which consist of its narrowness as well as its near-exclusive focus on improving government policies. The authors suggest that the burgeoning field of PPE is a more natural home, and one that provides the great continuity with the broad social philosophical origins of the Austrian School. The chapter emphasizes the comparative strength of Austrian economics in direct relation to the public as well as civil society organizations, compared to the purely academic nature of many other economic schools and fields. But the authors warn against a too narrow ideological or too concentrated financial relationship with a small set of civil society organizations. The chapter illustrates some of the dangers and opportunities through a comparative history vis-à-vis the evolution of ordoliberal political economy in Germany.

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