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Article
Publication date: 25 February 2020

Renato Vieira, Paulo Carreira, Pedro Domingues and Antonio Aguiar Costa

Despite the continuous development of Building Information Modeling (BIM) standards, not all of its dimensions are supported to the same extent. This is the case of Building…

848

Abstract

Purpose

Despite the continuous development of Building Information Modeling (BIM) standards, not all of its dimensions are supported to the same extent. This is the case of Building Automation Systems (BAS) in which the features that are limited mostly to physical setup of devices are supported. These are largely insufficient to support modeling automation scenarios. The purpose of this article is to clarify the gap in the state of the art and define the need for further developments.

Design/methodology/approach

This article explores the existing gap in the literature and discusses the hypothesis of extending BIM to a wider support of BA concepts. Based on an assessment of scientific and technical literature, this study elicits the information requirements of BA and performs a gap analysis with current BIM standards, such as Industry Foundation Classes (IFC).

Findings

Our findings lead us to conclude that there is a lack of completeness regarding features from BAS automation and management levels. Furthermore, it is shown that IFC is the most adequate data model to cover BAS without losing its purpose, but there is still a considerable work that needs to be addressed in future research.

Originality/value

BIM standards such as IFC position themselves as natural candidates for modeling and exchanging information regarding BA. However, the extent to which BIM supports automation features has never been rigorously analyzed. This article explores the existing gap in the literature and discusses the hypothesis of extending BIM to a wider support of BA concepts. Based on an assessment of scientific and technical literature, this study elicits the information requirements of BA and performs a gap analysis with current BIM standards such as IFC.

Details

Engineering, Construction and Architectural Management, vol. 27 no. 6
Type: Research Article
ISSN: 0969-9988

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Article
Publication date: 7 September 2015

M. Schrittwieser, O. Bíró, E. Farnleitner and G. Kastner

The purpose of this paper is to approximate the convective heat transfer using a few non-dimensional parameters in the design process of large synchronous machines. The computed…

124

Abstract

Purpose

The purpose of this paper is to approximate the convective heat transfer using a few non-dimensional parameters in the design process of large synchronous machines. The computed convective wall heat transfer coefficient can be used in circuit models or can be defined in numerical heat conduction (HC) models to compute the thermal field in the solid domains without the time consuming computation of the fluid domain.

Design/methodology/approach

Computational fluid dynamics (CFD) has been used to include a wide range of different designs, operating conditions and cooling schemes to ensure accurate results for a wide range of possible machines. Neural networks are used to correlate the computed heat transfer coefficients to various design parameters. The data set needed to define the weights and bias layers in the network has been obtained by several CFD simulations. A comparison of the evaluated solid temperatures with those obtained using the conjugate heat transfer (CHT) method has been carried out. The results have also been validated with calorimetric measurements.

Findings

The validation of the HC model has shown that this model is capable of yielding accurate results in a few minutes, in contrast to the several hours needed by the CHT solution. The workflow to determine the convective heat transfer in a specific part of an electrical machine has been also been established. The approximation of the convective wall heat transfer coefficient is shown to be obtainable in sufficient detail by using a neural network.

Research limitations/implications

The paper describes a method to approximate the convective heat transfer accurately in a few seconds, which is very useful in the design process. The heat convection can then be characterized in a HC model including the solid domains only. The losses can be defined as sources in the solid domains, e.g. copper and iron, obtained by electromagnetic calculations and the thermal field can hence be easily computed in these parts. This HC model has the main advantage that the time consuming computation of the fluid domain is avoided.

Originality/value

The novelty in this work is the approximation of the convective heat transfer by using a neural network with an accuracy of less than 5 percent as well as the development of a HC model to compute the temperature in the solid domains. The investigations presented pinpoint relevant issues influencing the thermal behavior of electrical machines.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 5
Type: Research Article
ISSN: 0332-1649

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Book part
Publication date: 30 August 2019

Md. Nazmul Ahsan and Jean-Marie Dufour

Statistical inference (estimation and testing) for the stochastic volatility (SV) model Taylor (1982, 1986) is challenging, especially likelihood-based methods which are difficult…

Abstract

Statistical inference (estimation and testing) for the stochastic volatility (SV) model Taylor (1982, 1986) is challenging, especially likelihood-based methods which are difficult to apply due to the presence of latent variables. The existing methods are either computationally costly and/or inefficient. In this paper, we propose computationally simple estimators for the SV model, which are at the same time highly efficient. The proposed class of estimators uses a small number of moment equations derived from an ARMA representation associated with the SV model, along with the possibility of using “winsorization” to improve stability and efficiency. We call these ARMA-SV estimators. Closed-form expressions for ARMA-SV estimators are obtained, and no numerical optimization procedure or choice of initial parameter values is required. The asymptotic distributional theory of the proposed estimators is studied. Due to their computational simplicity, the ARMA-SV estimators allow one to make reliable – even exact – simulation-based inference, through the application of Monte Carlo (MC) test or bootstrap methods. We compare them in a simulation experiment with a wide array of alternative estimation methods, in terms of bias, root mean square error and computation time. In addition to confirming the enormous computational advantage of the proposed estimators, the results show that ARMA-SV estimators match (or exceed) alternative estimators in terms of precision, including the widely used Bayesian estimator. The proposed methods are applied to daily observations on the returns for three major stock prices (Coca-Cola, Walmart, Ford) and the S&P Composite Price Index (2000–2017). The results confirm the presence of stochastic volatility with strong persistence.

Details

Topics in Identification, Limited Dependent Variables, Partial Observability, Experimentation, and Flexible Modeling: Part A
Type: Book
ISBN: 978-1-78973-241-2

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Article
Publication date: 9 September 2013

Maximilian Schrittwieser, Oszkár Bíró, Ernst Farnleitner and Gebhard Kastner

The purpose of this work is to propose a numerical method based on computational fluid dynamics (CFD) for reconstructing the heat transfer inside electrical machines. The used…

279

Abstract

Purpose

The purpose of this work is to propose a numerical method based on computational fluid dynamics (CFD) for reconstructing the heat transfer inside electrical machines. The used conjugate heat transfer (CHT) method takes heat convection and heat conduction into account to determine the temperature rise and the thermal losses in stator duct models of large hydro generators. Three different test cases are studied with different slot section components. The numerical models are validated with measurement data for a range of different mass flow rates.

Design/methodology/approach

The work presented is based on the combination of two complementary approaches, namely numerical simulation and measurements. The measured data for the air mass flow and the heat losses are used as boundary conditions for the identification of the temperature distribution in the solid and fluid domains (using a commercial software for CFD). The CHT method is an additional application of CFD and is used to solve the energy equations in the solid domains. Therefore, it is possible to define a thermal source in the solid domains.

Findings

The data obtained by the numerical computation are compared with measurement data for different mass flow rates of the cooling fluid. The quality of the computed values depending on the different mass flow rates shows a good agreement with the measured data. The temperature distribution in the solid domains depending on different material properties is also pointed out in this investigation.

Research limitations/implications

The topic describes a method for solving the heat transfer in the fluid as well as the solid domains. The losses can be defined as sources in the solid domains, e.g. copper and iron, obtained by electromagnetic calculations. This boundary condition defines the situation more accurately than, for example, a constant value of the heat flux or the temperature at the walls like in common used CFD simulations. Another advantage of CFD over other approaches is the consideration of the actual wall heat transfer coefficient.

Originality/value

The presented investigations show relevant issues influencing the thermal behaviour of electrical machines.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 9 February 2023

Mahdi Ghaemi Asl, Rabeh Khalfaoui, Hamid Reza Tavakkoli and Sami Ben Jabeur

This study aims to investigate the relationship between stock markets, environmental, social and governance (ESG) factors and Shariah-compliant in an integrated framework.

590

Abstract

Purpose

This study aims to investigate the relationship between stock markets, environmental, social and governance (ESG) factors and Shariah-compliant in an integrated framework.

Design/methodology/approach

The authors employ the multivariate factor stochastic volatility (mvFSV) framework to extract the volatility of the different sectoral indices. Based on this evidence, the authors employ the quantile vector autoregressive (QVAR) approach to examine the dynamic spillover connectedness among the aforementioned indices.

Findings

The study emphasizes the following major findings: (1) significant time-varying spillover connectedness across quantiles, (2) bidirectional and asymmetric spillover effect among the ESG index and the other sectoral indices, (3) the strength of spillover connectedness is time-varying across quantiles, (4) based on the perspective of portfolio optimization, ESG market is a significant strong forecasting contributor to conventional and Shariah-compliant markets, (5) overall, the findings point out serious quantile pass-through effect among ESG index and the other sectoral indices during the COVID-19 health crisis.

Originality/value

This study extends the previous literature in the following ways. First, to the best of the researchers’ knowledge, none of the existing studies have investigated the relationship between stock markets, ESG factors and Shariah-compliant in an integrated framework. Second, this study extends the previous scholarships by applying the mvFSV. Third, the authors propose a new rolling version to estimate dynamic spillovers, namely the rolling-window quantile VAR method. This approach provides a great advantage in computing the dynamics of return and variance spillover between variables in terms not only of the overall factor but also of the net (pairwise) aspect.

Details

International Journal of Emerging Markets, vol. 19 no. 11
Type: Research Article
ISSN: 1746-8809

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Abstract

Details

Essays in Honor of Cheng Hsiao
Type: Book
ISBN: 978-1-78973-958-9

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Article
Publication date: 25 February 2022

Zhenkuo Ding, Man Hu and Sheng Huang

The purpose of this paper is to examine the influence of bilateral political relations on the completion stage premium of cross-border mergers and acquisitions(CSPCMA) and the…

585

Abstract

Purpose

The purpose of this paper is to examine the influence of bilateral political relations on the completion stage premium of cross-border mergers and acquisitions(CSPCMA) and the moderating roles of cultural distance, trade openness and the nature of firm ownership for this relationship.

Design/methodology/approach

Based on a sample of 401 cross-border mergers and acquisitions (M&A) conducted by Chinese companies from 1995 to 2019 in the Statistical Data Center (SDC), this article used weighted least squares (WLS) to empirically test the impact of bilateral political relations between countries on the CSPCMA.

Findings

The better the target country of entry’s bilateral political relations with China, the lower the premium of the transaction price paid by Chinese companies at the completion stage of cross-border M&A. Among the moderators, the study found cultural distance positively moderates the relationship between bilateral political relations between countries and CSPCMA. The degree of trade openness of the target country negatively moderates the relationship between bilateral political relations between countries and CSPCMA. The negative relationship between bilateral political relations between countries and CSPCMA is stronger when the acquirer is a state-owned enterprise (SOE).

Originality/value

The findings of this study not only add to the knowledge about the relationship between bilateral political relations and corporate cross-border M&A premiums, but also have managerial implications for Chinese corporate managers to sustainably reduce corporate cross-border M&A premiums.

Details

Cross Cultural & Strategic Management, vol. 29 no. 2
Type: Research Article
ISSN: 2059-5794

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Article
Publication date: 15 January 2024

Shalini Velappan

This study aims to investigate the co-volatility patterns between cryptocurrencies and conventional asset classes across global markets, encompassing 26 global indices ranging…

104

Abstract

Purpose

This study aims to investigate the co-volatility patterns between cryptocurrencies and conventional asset classes across global markets, encompassing 26 global indices ranging from equities, commodities, real estate, currencies and bonds.

Design/methodology/approach

It used a multivariate factor stochastic volatility model to capture the dynamic changes in covariance and volatility correlation, thus offering empirical insights into the co-volatility dynamics. Unlike conventional research on price or return transmission, this study directly models the time-varying covariance and volatility correlation.

Findings

The study uncovers pronounced co-volatility movements between cryptocurrencies and specific indices such as GSCI Energy, GSCI Commodity, Dow Jones 1 month forward and U.S. 10-year TIPS. Notably, these movements surpass those observed with precious metals, industrial metals and global equity indices across various regions. Interestingly, except for Japan, equity indices in the USA, Canada, Australia, France, Germany, India and China exhibit a co-volatility movement. These findings challenge the existing literature on cryptocurrencies and provide intriguing evidence regarding their co-volatility dynamics.

Originality

This study significantly contributes to applying asset pricing models in cryptocurrency markets by explicitly addressing price and volatility dynamics aspects. Using the stochastic volatility model, the research adding methodological contribution effectively captures cryptocurrency volatility's inherent fluctuations and time-varying nature. While previous literature has primarily focused on bitcoin and a few other cryptocurrencies, this study examines the stochastic volatility properties of a wide range of cryptocurrency indices. Furthermore, the study expands its scope by examining global asset markets, allowing for a comprehensive analysis considering the broader context in which cryptocurrencies operate. It bridges the gap between traditional asset pricing models and the unique characteristics of cryptocurrencies.

Details

Studies in Economics and Finance, vol. 41 no. 5
Type: Research Article
ISSN: 1086-7376

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Article
Publication date: 7 September 2015

Stephan Klomberg, Ernst Farnleitner, Gebhard Kastner and Oszkár Bíró

The purpose of this paper is to carry out an analytical approximation model (heat transfer model (HTM)) for the calculation of the heat transfer coefficient at the end winding…

103

Abstract

Purpose

The purpose of this paper is to carry out an analytical approximation model (heat transfer model (HTM)) for the calculation of the heat transfer coefficient at the end winding bars of large hydro generators. These coefficients are needed for lumped parameter thermal models in the design process.

Design/methodology/approach

The computational fluid dynamics simulation in combination with conjugate heat transfer (CHT) validates the accuracy of the HTM. The theoretical approach describes the formulation of the heat transfer coefficient and the Gauss-Newton method has been applied to find the coefficients of the approximation model.

Findings

The paper describes the new analytical approximation model for the heat transfer coefficient at the end winding bars of hydro generators and shows also the validation to simulation results.

Originality/value

The analytical approximation model for the heat transfer coefficient at the end winding bars has been described and a comparison with CHT results has shown a good agreement.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 6 July 2015

Stephan Klomberg, Ernst Farnleitner, Gebhard Kastner and Oszkár Bíró

The purpose of this paper is to present a new computational fluid dynamics model for large electrical machines to simulate the heat transfer at specific components to the…

141

Abstract

Purpose

The purpose of this paper is to present a new computational fluid dynamics model for large electrical machines to simulate the heat transfer at specific components to the appropriate ventilation method. The most damageable parts for overheating in generators are the end winding bars, pole windings and stator ducts.

Design/methodology/approach

The reduced model introduced is basically derived from the state-of-the-art pole section model (PSM) and enables faster computations for heat transfer and cooling simulations of electrical machines. The fundamentals of the two methods and the grid generation are described. Two PSMs and four different reduced models are presented and compared among each other to tune the reduced model.

Findings

As a topic of outstanding interest in large hydro generators, the heat transfer at the end winding bars is solved with the aid of the reduced model. This slot sector model (SSM) has been validated and the computation time has been reduced enormously in comparison to the state-of-the-art PSM.

Research limitations/implications

The heat transfer has been carried out only for the end winding region of large hydro generators. The effect of the reduced model on the pole sections and stator ducts has not been investigated. Nevertheless, the reduced model is also valid for large motors.

Practical implications

This reduced model can finally be used for parametric studies with different cooling schemes and boundary conditions in the design process.

Originality/value

The comparison of various SSMs to PSMs shows an acceptable accuracy of the reduced model in combination with a rather low computation time. Due to modeling one slot only, the MFR-MP approach is an adequate and fast analyzing method for this kind of model structure.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 4
Type: Research Article
ISSN: 0332-1649

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