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Article
Publication date: 29 August 2019

Song Gao, Jory Seguin, Wagdi G. Habashi, Dario Isola and Guido Baruzzi

This work aims to describe the physical and numerical modeling of a CFD solver for hypersonic flows in thermo-chemical non-equilibrium. This paper is the second of a…

Abstract

Purpose

This work aims to describe the physical and numerical modeling of a CFD solver for hypersonic flows in thermo-chemical non-equilibrium. This paper is the second of a two-part series that concerns the application of the solver introduced in Part I to adaptive unstructured meshes.

Design/methodology/approach

The governing equations are discretized with an edge-based stabilized finite element method (FEM). Chemical non-equilibrium is simulated using a laminar finite-rate kinetics, while a two-temperature model is used to account for thermodynamic non-equilibrium. The equations for total quantities, species and vibrational-electronic energy conservation are loosely coupled to provide flexibility and ease of implementation. To accurately perform simulations on unstructured meshes, the non-equilibrium flow solver is coupled with an edge-based anisotropic mesh optimizer driven by the solution Hessian to carry out mesh refinement, coarsening, edge swapping and node movement.

Findings

The paper shows, through comparisons with experimental and other numerical results, how FEM + anisotropic mesh optimization are the natural choice to accurately simulate hypersonic non-equilibrium flows on unstructured meshes. Three-dimensional test cases demonstrate how, for high-speed flows, shocks resolution, and not necessarily boundary layers resolution, is the main driver of solution accuracy at walls. Equally distributing the error among all elements in a suitably defined Riemannian space yields highly anisotropic grids that feature well-resolved shock waves. The resulting high level of accuracy in the computation of the enthalpy jump translates into accurate wall heat flux predictions. At the opposite end, in all cases examined, high-quality but isotropic unstructured meshes gave very poor solutions with severely inadequate heat flux distributions not even featuring expected symmetries. The paper unequivocally demonstrates that unstructured anisotropically adapted meshes are the best, and may be the only, way for accurate and cost-effective hypersonic flow solutions.

Originality/value

Although many hypersonic flow solvers are developed for unstructured meshes, few numerical simulations on unstructured meshes are presented in the literature. This work demonstrates that the proposed approach can be used successfully for hypersonic flows on unstructured meshes.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 2
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 21 June 2019

Jory Seguin, Song Gao, Wagdi George Habashi, Dario Isola and Guido Baruzzi

This paper aims to describe the physical and numerical modeling of a new computational fluid dynamics solver for hypersonic flows in thermo-chemical non-equilibrium. The…

Abstract

Purpose

This paper aims to describe the physical and numerical modeling of a new computational fluid dynamics solver for hypersonic flows in thermo-chemical non-equilibrium. The code uses a blend of numerical techniques to ensure accuracy and robustness and to provide scalability for advanced hypersonic physics and complex three-dimensional (3D) flows.

Design/methodology/approach

The solver is based on an edge-based stabilized finite element method (FEM). The chemical and thermal non-equilibrium systems are loosely-coupled to provide flexibility and ease of implementation. Chemical non-equilibrium is modeled using a laminar finite-rate chemical kinetics model while a two-temperature model is used to account for thermodynamic non-equilibrium. The systems are solved implicitly in time to relax numerical stiffness. Investigations are performed on various canonical hypersonic geometries in two-dimensional and 3D.

Findings

The comparisons with numerical and experimental results demonstrate the suitability of the code for hypersonic non-equilibrium flows. Although convergence is shown to suffer to some extent from the loosely-coupled implementation, trading a fully-coupled system for a number of smaller ones improves computational time. Furthermore, the specialized numerical discretization offers a great deal of flexibility in the implementation of numerical flux functions and boundary conditions.

Originality/value

The FEM is often disregarded in hypersonics. This paper demonstrates that this method can be used successfully for these types of flows. The present findings will be built upon in a later paper to demonstrate the powerful numerical ability of this type of solver, particularly with respect to robustness on highly stretched unstructured anisotropic grids.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 8 May 2017

Hongwei Wang, Song Gao, Pei Yin and James Nga-Kwok Liu

Comparative opinions widely exist in online reviews as a common way of expressing consumers’ ideas or preferences toward certain products. Such opinion-rich texts are key…

Abstract

Purpose

Comparative opinions widely exist in online reviews as a common way of expressing consumers’ ideas or preferences toward certain products. Such opinion-rich texts are key proxies for detecting product competitiveness. The purpose of this paper is to set up a model for competitiveness analysis by identifying comparative relations from online reviews for restaurants based on both pattern matching and machine learning.

Design/methodology/approach

The authors define the sub-category of comparative sentences according to Chinese linguistics. Classification rules are set up for each type of comparative relations through class sequence rule. To improve the accuracy of classification, a comparative entity dictionary is then introduced for further identifying comparative sentences. Finally, the authors collect reviews for restaurants from Dianping.com to conduct experiments for testing the proposed model.

Findings

The experiments show that the proposed method outperforms the baseline methods in terms of precision in identifying comparative sentences. On the basis of such comparison-rich sentences, product features and comparative relations are extracted for sentiment analysis, and sentimental score is assigned to each comparative relation to facilitate competitiveness analysis.

Research limitations/implications

Only the explicit comparative relations are discussed, neglecting the implicit ones. Besides that, the study is grounded in the assumption that all features are homogeneous. In some cases, however, the weights to different aspects are not of the same importance to market.

Practical implications

On the basis of comparative relation mining, product features and comparative opinions are extracted for competitiveness analysis, which is of interest to businesses for finding weakness or strength of products, as well as to consumers for making better purchase decisions.

Social implications

Comparative relation mining could be possibly applied in social media for identifying relations among users or products, and ranking users or products, as well as helping companies target and track competitors to enhance competitiveness.

Originality/value

The authors propose a research framework for restaurant competitiveness analysis by mining comparative relations from online consumer reviews. The results would be able to differentiate one restaurant from another in some aspects of interest to consumers, and reveal the changes in these differences over time.

Details

Industrial Management & Data Systems, vol. 117 no. 4
Type: Research Article
ISSN: 0263-5577

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Book part
Publication date: 4 December 2020

Marko Jakšič and Marko Budler

Outsourcing of business-logistics services is a well-established business practice that allows an outsourcer to obtain the services or products from a logistics-service…

Abstract

Outsourcing of business-logistics services is a well-established business practice that allows an outsourcer to obtain the services or products from a logistics-service provider (LSP). The outsourcer can order a range of logistics services, including but not limited to warehousing, transportation, and forwarding. The outsourcers had traditionally focused on service-provider selection criteria such as costs, quality, and responsiveness while having devoted considerably less attention to how sustainably the practices are carried out. Past research identified different external and internal motivators that facilitate consideration of sustainability in selection of the service providers, whereas the current study investigates the outsourcers’ perception of importance of environmental sustainability in adoption of green logistics practices and selection of LSPs. We use a vantage point of outsourcers (“buyers”) to conduct the quantitative research based on a survey conducted on large manufacturing companies. The findings reveal a (mis)match between the perception of importance and realized inclusion of environmental-sustainability criteria. Ultimately, this study finds a link between the levels of perception and rate of adoption, and provides recommendations for the future adoption of environmental-sustainability criteria in the selection of the LSPs.

Details

Challenges on the Path Toward Sustainability in Europe
Type: Book
ISBN: 978-1-80043-972-6

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Article
Publication date: 13 April 2010

Liang Zhang, Song-bai Xue, Li-li Gao, Yan Chen, Sheng-lin Yu, Zhong Sheng and Guang Zeng

The purpose of this paper is to investigate the effects of minor addition of the rare earth (RE) element cerium, Ce, on the microstructures and creep properties of…

Abstract

Purpose

The purpose of this paper is to investigate the effects of minor addition of the rare earth (RE) element cerium, Ce, on the microstructures and creep properties of Sn-Ag-Cu solder alloys.

Design/methodology/approach

The pure Sn, Sn-Cu alloy, Sn-Ag alloy and Cu-Ce alloy were used as raw materials. Sn-Ag-Cu alloys with different contents of RE Ce were chosen to compare with Sn-Ag-Cu. The raw materials of Sn, Sn-Cu alloy, Sn-Ag alloy, Cu-Ce alloy were melted in a ceramic crucible, and were melted at 550°C ± 1°C for 40 minutes. To homogenize the solder alloy, mechanical stirring was performed every ten minutes using a glass rod. During the melting, KC1 + LiCI (1.3:1), were used over the surface of liquid solder to prevent oxidation. The melted solder was chill cast into a rod.

Findings

It is found that the microstructure exhibits smaller grains and the Ag3Sn/Cu6Sn5 intermetallic compound (IMC) phases are modified in matrix with the addition of Ce. In particular, the addition of 0.03 wt.% Ce to the Sn-Ag-Cu solder can refine the microstructures and decrease the thickness of the IMC layers of Sn-Ag-Cu solder alloys. Meanwhile, thermodynamic analysis showed that these phenomena could be attributed to the reduction of the driving force for Cu-Sn IMC formation due to the addition of Ce. Results calculated using the thermodynamic method are close to the above experimental data. Thus, the optimum content of Ce in Sn-Ag-Cu solder alloys should be about 0.030 percent. Additionally, the effect of Ce on the creep rupture life of Sn-Ag-Cu soldered joints was studied. It was found that the creep rupture life may be increased up to 7.5 times more than that of the original Sn-Ag-Cu alloy, when Ce accounts for 0.030 percent.

Originality/value

This paper usefully investigates the effects of the RE cerium (Ce), on the microstructures and creep properties of Sn-Ag-Cu solder alloys, optimizing the quantity of Ce in the Sn-Ag-Cu solder alloy through a thermodynamic method and by creep-rupture life testing.

Details

Soldering & Surface Mount Technology, vol. 22 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 25 February 2020

Lucas Silvestre de Carvalho, Nelson Oliveira Stefanelli, Lilian Carolina Viana, Diogo de Siqueira Camargo Vasconcelos and Bruno Garcia Oliveira

This paper aims to investigate the main associations between research regarding innovation and green supply chain management (GSCM).

Abstract

Purpose

This paper aims to investigate the main associations between research regarding innovation and green supply chain management (GSCM).

Design/methodology/approach

For this the study sought to (1) present the most cited authors in the area; (2) demonstrate the main localities that develop research with this focus; (3) list the main journals with the published research on the themes. The methodology used was a bibliometric survey using the Scopus database as the data source. The VOSviewer® software was used to perform the analysis of the database from the respective DOI® of each article.

Findings

As results of the research, it is possible to demonstrate the existence of an agglomeration of countries that are interrelated in the development of research on these themes, especially China, the United States and the United Kingdom as the main foundations of this center.

Originality/value

This paper evidences the direction of scientific research within the analyzed area, demonstrating where there is convergence for innovation in actions related to GSCM. This guidance may demonstrate possible existing and unexplored gaps so that researchers can direct future research or check gaps to be filled by the development of new processes.

Details

Management of Environmental Quality: An International Journal, vol. 31 no. 2
Type: Research Article
ISSN: 1477-7835

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Book part
Publication date: 15 January 2010

Moshe Ben-Akiva

Purpose: This chapter introduces a choice modeling framework that explicitly represents the planning and action stages of the choice process.Methodology: A discussion of…

Abstract

Purpose: This chapter introduces a choice modeling framework that explicitly represents the planning and action stages of the choice process.

Methodology: A discussion of evidence from behavioral research is followed by the development of a discrete choice modeling framework with explicit planning and action submodels. The plan/action choice model is formulated for both static and dynamic contexts; where the latter is based on the Hidden Markov Model. Plans are often unobservable and are treated as latent variables in model estimation using observed actions.

Implications: By modeling the interactions between the planning and action stages, we are able to incorporate richer specifications in choice models with better predictive and policy analysis capabilities. The applications of this research in areas such as driving behavior, route choice, and mode choice demonstrate the advantages of the plan/action model in comparison to a “black box” choice model in terms of improved microsimulations of behaviors that better represent real-life situations. As such, the outcomes of this chapter are relevant to researchers and policy analysts.

Details

Choice Modelling: The State-of-the-art and The State-of-practice
Type: Book
ISBN: 978-1-84950-773-8

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Article
Publication date: 7 August 2017

Yuchen Lin, Yangbo Song and Jinsong Tan

As an important participant in capital market, institutional investors play a principal role in improving corporate governance. Most existing studies have focused on…

Abstract

Purpose

As an important participant in capital market, institutional investors play a principal role in improving corporate governance. Most existing studies have focused on institutional ownership and its economic consequences. Nevertheless, they have not provided sufficient insight on the governance behavior of institutional investors as well as the underlying incentive mechanism. This paper aims to analyze the governance role of institutional investors in information disclosure and provide related evidence.

Design/methodology/approach

The authors propose a novel theory to analyze the institutional investors’ behavior of active governance and shows that such behavior significantly improves the quality of corporate information disclosure. The authors then conduct an empirical test by using the hand-collected data of institutional investors’ corporate visits during 2009-2014 in ChiNext.

Findings

This paper finds that the firms visited by institutional investors are more likely to have a greater tendency of disclosing more information than the firms that have never been visited. In particular, a higher frequency of visits or a larger number of participating institutional investors leads to a higher degree of disclosure. Consistent with the notion that on-site visits endow institutional investors with more frequent and active interaction with the firms, the authors find that the results are stronger for firms which are visited on-site, when compared with other information acquisition activities such as online meetings, conference calls and investor meetings. In addition, the effect of a site visit is greater when the site visit is conducted by securities companies or funds rather than insurance companies or QFIIs. Finally, the test of the direction of causality suggests that visits conducted by institutional investors leads to more information disclosure, rather than the reverse. Collectively, these results show that institutional investors’ participation enhances corporate information disclosure.

Originality/value

This paper explores the internal mechanism that institutional investors affect corporate governance by improving information disclosure through their corporate visits. This is the first study to investigate the influence of institutional investors’ corporate visits and their economic consequences.

Details

Nankai Business Review International, vol. 8 no. 3
Type: Research Article
ISSN: 2040-8749

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Article
Publication date: 11 January 2021

Ruting Huang and Xin Yao

The purpose of this paper is to investigate the decision behaviors and channel coordination of a sustainable three-echelon supply chain with retailer-led game setting.

Abstract

Purpose

The purpose of this paper is to investigate the decision behaviors and channel coordination of a sustainable three-echelon supply chain with retailer-led game setting.

Design/methodology/approach

The authors develop game-theoretic models to examine the decision behaviors of channel members in a three-echelon supply chain consisting of one supplier, one distributor and one dominated retailer. The authors first formulate two models for centralized decision and decentralized decision. And then this paper proposes sub-supply chain coordination and a two-tariff contract to coordinate the full supply chain. Finally, some management insights are obtained with a case study.

Findings

The authors find that when faced with environmentally conscious consumers, the channel members can benefit from higher greening level; however, higher cost of green technologies would have negative impacts on manufacturer's effort. The analysis also shows that cooperation among players can improve the supply chain performance and help with environmental improvement.

Research limitations/implications

The findings provide important managerial insights for the three-echelon supply chain to achieve sustainable goals where the retailer bears the environmental responsibility. However, this paper also has some limitations with assuming risk-neutral channel members and symmetric information.

Originality/value

The findings of the study contribute to coordination and collaboration in sustainability of supply chains. The results provide important managerial insights for the three-echelon supply chain to achieve sustainable goals.

Details

Journal of Enterprise Information Management, vol. 34 no. 1
Type: Research Article
ISSN: 1741-0398

Keywords

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Article
Publication date: 25 August 2020

Lutz Bellmann and Olaf Hübler

It is analyzed whether working from home improves or impairs the job satisfaction and the work–life balance and under which conditions.

Abstract

Purpose

It is analyzed whether working from home improves or impairs the job satisfaction and the work–life balance and under which conditions.

Design/methodology/approach

Blocks of influences on job satisfaction and work–life balance – personal traits, job characteristics, skills and employment properties – are estimated separately and in combination. To select the variables, the least angle regression is applied. The entropy balancing approach is used to determine causal effects. The study investigates whether imbalances are determined by private or job influences, whether firm-specific regulations and the selected control group affect the results and whether it only takes place during leisure time.

Findings

No clear effects of remote work on job satisfaction are revealed, but the impact on work–life balance is generally negative. If the imbalance is conditioned by private interests, this is not corroborated in contrast to job conditioned features. Employees working from home are happier than those who want to work at home, job satisfaction is higher and work–life balance is not worse under a strict contractual agreement than under a nonbinding commitment.

Originality/value

A wide range of personality traits, skills, employment properties and job characteristics are incorporated as determinants. The problem of causality is investigated. It is analyzed whether the use of alternative control and treatment groups leads to different results. The empirical investigation is based on new German data with three waves.

Details

International Journal of Manpower, vol. 42 no. 3
Type: Research Article
ISSN: 0143-7720

Keywords

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