Search results

1 – 10 of 165
To view the access options for this content please click here
Article
Publication date: 28 October 2014

Ryszard Szupiluk and Tomasz Ząbkowski

The purpose of this paper is to propose a noise identification method for data without temporal structure, in which application of typical mathematical white or colored…

Abstract

Purpose

The purpose of this paper is to propose a noise identification method for data without temporal structure, in which application of typical mathematical white or colored noise models is very limited due to observation order requirements. The method is used to identify the destructive elements and to eliminate them what finally brings prediction improvement.

Design/methodology/approach

The paper concerns noise detection problem presented in the framework of ensemble methods via blind signals separation. The authors utilize the Extended Generalized Lambda Distribution (EGLD) model to compare the signals with the target.

Findings

The authors proposed novel signals similarity measure which is based on the EGLD system. The authors showed that it can be applied for data with or without time structure, as well as for data which are mutually uncorrelated. It turned out that method is effective for noise identification and can be an alternative, in many cases, to correlation approach, particularly for noise identification problems.

Originality/value

In this method the improvement of prediction results is associated with elimination of the real physical factors rather than mathematical averaging in terms of arbitrary assumed distributions. In this approach, it does not matter what is the structure of aggregated models, what significantly distinct this approach from such techniques as boosting or bagging, in which the aggregation process applies to the models of similar structure. For this reason the methodology is focussed on physical noises elimination from predictions and it is complementary to the other ensemble approaches.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 10 May 2019

Peterson Owusu Junior, George Tweneboah, Kola Ijasan and Nagaratnam Jeyasreedharan

This paper aims to contribute to knowledge by investigating the return behaviour of seven global real estate investment trusts (REITs) with respect to the appropriate…

Abstract

Purpose

This paper aims to contribute to knowledge by investigating the return behaviour of seven global real estate investment trusts (REITs) with respect to the appropriate distributional fit that captures tail and shape characteristics. The study adds to the knowledge of distributional properties of seven global REITs by using the generalised lambda distribution (GLD), which captures fairly well the higher moments of the returns.

Design/methodology/approach

This is an empirical study with GLD through three rival methods of fitting tail and shape properties of seven REIT return data from January 2008 to November 2017. A post-Global Financial Crisis (GFC) (from July 2009) period fits from the same methods are juxtaposed for comparison.

Findings

The maximum likelihood estimates outperform the methods of moment matching and quantile matching in terms of goodness-of-fit in line with extant literature; for the post-GFC period as against the full-sample period. All three methods fit better in full-sample period than post-GFC period for all seven countries for the Region 4 support dynamics. Further, USA and Singapore possess the strongest and stronger infinite supports for both time regimes.

Research limitations/implications

The REITs markets, however, developed, are of wide varied sizes. This makes comparison less than ideal. This is mitigated by a univariate analysis rather than multivariate one.

Practical implications

This paper is a reminder of the inadequacy of the normal distribution, as well as the mean, variance, skewness and kurtosis measures, in describing distributions of asset returns. Investors and policymakers may look at the location and scale of GLD for decision-making about REITs.

Originality/value

The novelty of this work lies with the data used and the detailed analysis and for the post-GFC sample.

Details

Journal of European Real Estate Research , vol. 12 no. 3
Type: Research Article
ISSN: 1753-9269

Keywords

To view the access options for this content please click here
Article
Publication date: 28 September 2021

Pooja Dhiman and Amit Kumar

The purpose of this paper is to investigate the performance of a turbine structure of the oil and gas Egyptian company in terms of reliability, mean time to failure…

Abstract

Purpose

The purpose of this paper is to investigate the performance of a turbine structure of the oil and gas Egyptian company in terms of reliability, mean time to failure (MTTF), mean time to repair (MTTR) and mean time between failures (MTBF) under fuzzy environment and working criteria. This paper examines the impact of the failure of various components on the complete turbine structure of the oil and gas system.

Design/methodology/approach

To overcome the problem of uncertain behavior of available data for various components, the right triangular generalized fuzzy number (RTrGFN) is proposed to be taken into the account to express the uncertainty which attains some tolerance in data. Furthermore, reliability indices are calculated with the help of the Lambda Tau method and the arithmetic operations on right generalized triangular fuzzy numbers (RTrGFN).

Findings

This paper explores the reliability of a repairable 3 out of 4 structure of turbines and along with the other parameters namely MTTF, MTTR and MTBF; under a fuzzy environment. Failure rates and repair times are expected to be exponential. The ranking of components of the structure is being found to decide the priority for maintenance.

Originality/value

This paper investigates the performance of the system with different spread/tolerance like 15%, 25% and 50% of crisp data. It helps to predict realistic results in the range value. To enhance the system's performance, the most important item of the system requires greater attention. For this, the authors find the sensitive part by ranking. For ranking, an extended approach has been developed to find the sensitive unit of the system by using the right triangular generalized fuzzy number. This paper explores the most and least sensitive component of the system, which helps the maintenance department to plan the maintenance action.

Details

Journal of Quality in Maintenance Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2511

Keywords

To view the access options for this content please click here
Article
Publication date: 12 February 2019

Komal

The purpose of this paper is to analyze the fuzzy reliability of the compressor house unit (CHU) system in a coal fired thermal power plant under vague environment by…

Abstract

Purpose

The purpose of this paper is to analyze the fuzzy reliability of the compressor house unit (CHU) system in a coal fired thermal power plant under vague environment by reducing the accumulating phenomenon of fuzziness and accelerating the computation process. This paper uses different fuzzy membership functions to quantify uncertainty and access the system reliability in terms of different fuzzy reliability indices having symmetric shapes.

Design/methodology/approach

This study analyses the fuzzy reliability of the CHU system in a coal fired thermal power plant using Tω-based generalized fuzzy Lambda-Tau (TBGFLT) technique. This approach applies fault tree, Lambda-Tau method, different fuzzy membership functions and α-cut coupled Tω-based approximate arithmetic operations to compute various reliability parameters (such as failure rate, repair time, mean time between failures, expected number of failures, availability and reliability) of the system. The effectiveness of TBGFLT technique has been demonstrated by comparing the results with results obtained from four different existing techniques. Moreover, this paper applies the extended Tanaka et al. (1983) approach to rank the critical components of the system when different membership functions are used.

Findings

The adopted TBGFLT technique in the present study improves the shortcomings of the existing approaches by reducing the accumulating phenomenon of fuzziness, accelerating the computation process and getting symmetric shapes for computed reliability parameters when different membership functions are used to quantify data uncertainty.

Originality/value

In existing fuzzy reliability techniques which are developed for repairable systems either triangular fuzzy numbers, triangle vague sets or triangle intuitionistic fuzzy sets have been used for quantifying uncertainty. These approaches do not examine the systems for components with different membership functions. The present study is an effort in this direction and evaluates the fuzzy reliability of the CHU system in a coal fired thermal power plant for components with different membership functions. This is the main contribution of the paper.

Details

International Journal of Quality & Reliability Management, vol. 36 no. 5
Type: Research Article
ISSN: 0265-671X

Keywords

To view the access options for this content please click here
Article
Publication date: 1 December 2001

George J. Klir

Presents an overview of currently recognized theories of imprecise probabilities and their possible extensions. It is shown how the theories are ordered by their levels of…

Downloads
451

Abstract

Presents an overview of currently recognized theories of imprecise probabilities and their possible extensions. It is shown how the theories are ordered by their levels of generality. A summary of current results regarding measures of uncertainty and uncertainty‐based information is also presented.

Details

Kybernetes, vol. 30 no. 9/10
Type: Research Article
ISSN: 0368-492X

Keywords

To view the access options for this content please click here
Book part
Publication date: 12 September 1997

Carlos F. Daganzo

Abstract

Details

Fundamentals of Transportation and Traffic Operations
Type: Book
ISBN: 978-0-08-042785-0

To view the access options for this content please click here
Article
Publication date: 1 March 1985

Vinicio Magi and Gaetano Vacca

A new implementation of the implicit lambda scheme recently proposed by other authors is provided. One‐dimensional compressible non‐isentropic flows inside four different…

Abstract

A new implementation of the implicit lambda scheme recently proposed by other authors is provided. One‐dimensional compressible non‐isentropic flows inside four different nozzles and Fanno and Rayleigh's subsonic/ supersonic flows are computed, which demonstrate the superior efficiency and accuracy of the present formulation.

Details

Engineering Computations, vol. 2 no. 3
Type: Research Article
ISSN: 0264-4401

To view the access options for this content please click here
Article
Publication date: 1 February 1977

Snowden E. Bunch

Introduction Many recent articles on monetary economics devote considerable effort to empirically testing various current theories of money demand. Their authors search…

Abstract

Introduction Many recent articles on monetary economics devote considerable effort to empirically testing various current theories of money demand. Their authors search for new and better proxies to give empirical content to ‘demand‐for‐money’, ‘income’, and ‘interest‐rate’ magnitudes, standard components of money demand equations. They consider questions of which interest rate to choose from among the manifold, and whether to use Ml or perhaps some other money supply measure to represent ‘demand‐for‐money’. But these economists do not exert the same effort when giving specific form to general money demand functions. The usual research practice is to rather arbitrarily express estimating equations in either a linear or a log‐log functional form (1).

Details

Studies in Economics and Finance, vol. 1 no. 2
Type: Research Article
ISSN: 1086-7376

To view the access options for this content please click here
Article
Publication date: 12 July 2013

Manjit Verma, Amit Kumar and Yaduvir Singh

The purpose of this paper is to present a new methodology, named vague lambda‐tau, used for reliability analysis of a combustion system, which could be used for managerial…

Abstract

Purpose

The purpose of this paper is to present a new methodology, named vague lambda‐tau, used for reliability analysis of a combustion system, which could be used for managerial decision making and future system maintenance strategy.

Design/methodology/approach

This paper involves the qualitative and quantitative analysis of a combustion system. In qualitative analysis, the Petri net model is obtained from its equivalent fault tree and in quantitative analysis, the reliability parameters are evaluated using vague lambda‐tau methodology. Further, a decision support system based on vague sets is developed to overcome the limitations of traditional risk analysis.

Findings

The reliability parameters (such as expected number of failures, mean time between failures, availability, and reliability) of the compressor system are evaluated. The proposed, vague sets‐based reliability analysis and risk analysis not only overcome the limitations associated with traditional approaches but also integrate the confidence level of domain experts and expert's experience, in a more flexible and realistic manner.

Originality/value

Instead of fuzzy sets, this paper used vague sets for reliability analysis with Petri net modelling because in real life problems, there may be hesitation regarding the belongingness of an object to a set or not. In fuzzy set theory, there is no means to incorporate such type of hesitation.

To view the access options for this content please click here
Article
Publication date: 21 August 2009

Komal, S.P. Sharma and Dinesh Kumar

The purpose of this paper is to present a hybridized technique for analyzing the behavior of an industrial system stochastically utilizing vague, imprecise, and uncertain…

Abstract

Purpose

The purpose of this paper is to present a hybridized technique for analyzing the behavior of an industrial system stochastically utilizing vague, imprecise, and uncertain data. The press unit of a paper mill situated in a northern part of India, producing 200 tons of paper per day, has been considered to demonstrate the proposed approach. Sensitivity analysis of system's behavior has also been done.

Design/methodology/approach

In the proposed approach, two important tools namely traditional Lambda‐Tau technique and genetic algorithm have been hybridized to build genetic algorithms‐based Lambda‐Tau (GABLT) technique to analyze the behavior of complex repairable industrial systems stochastically up to a desired degree of accuracy. This technique has been demonstrated by computing six well‐known reliability indices used for behavior analysis of the considered system in more promising way.

Findings

The behavior analysis results computed by GABLT technique have reduced region of prediction in comparison of existing Lambda‐Tau technique region, i.e. uncertainties involved in the analysis are reduced. Thus, it may be a more useful analysis tool to assess the current system conditions and involved uncertainties. The paper suggested an approach to improve the system's performance.

Originality/value

The paper suggests a hybridized technique for analyzing the stochastic behavior of an industrial subsystem by computing six well‐known reliability indices in the form of fuzzy membership function.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 2 no. 3
Type: Research Article
ISSN: 1756-378X

Keywords

1 – 10 of 165