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 two-part…
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
Keywords
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 code uses…
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
Keywords
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 proxies…
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
Keywords
Kajal Sitlani, Abhineet Saxena, Deepti Sharma and Garima Pancholi
Organizations’ culture and environment create a remarkable influence on the minds of the employees. Employees spend a lot of time at the workplace; hence, it is essential to take…
Abstract
Organizations’ culture and environment create a remarkable influence on the minds of the employees. Employees spend a lot of time at the workplace; hence, it is essential to take care of their happiness. Stressful workplace environment reduces the job satisfaction of employees which eventually leads to mental health issues. The study focuses on mapping the publication trends on happiness of employees at their workplace over the years. The mapping was done with the help of Scopus and VOSviewer. The study takes into consideration the research publication on workplace happiness since 2013 from Scopus database using ‘Employee Happiness at Workplace’ which showed around 104 publications related to happiness till Sept 2022. The database was refined and further analyzed by VOSviewer version 1.6.16. Though much research has been done on employee happiness and lot many scales are developed on the happiness index, but bibliometric analysis is yet to be carried out on workplace happiness, it's development, forms and factors. This analysis will bridge the gap of researchers and provide them directions to carry on the research for future.
Details
Keywords
The aim of this paper is to provide a narrative review of previous research on tourism demand modelling and forecasting and potential future developments.
Abstract
Purpose
The aim of this paper is to provide a narrative review of previous research on tourism demand modelling and forecasting and potential future developments.
Design/methodology/approach
A narrative approach is taken in this review of the current body of knowledge.
Findings
Significant methodological advancements in tourism demand modelling and forecasting over the past two decades are identified.
Originality/value
The distinct characteristics of the various methods applied in the field are summarised and a research agenda for future investigations is proposed.
目的
本文旨在对先前关于旅游需求建模和预测的研究进行叙述性回顾并对未来潜在发展进行展望。
设计/方法
本文采用叙述性回顾方法对当前知识体系进行了评论。
研究结果
本文确认了过去二十年旅游需求建模和预测方法论方面的重要进展。
独创性
本文总结了该领域应用的各种方法的独特特征, 并对未来研究提出了建议。
Objetivo
El objetivo de este documento es ofrecer una revisión narrativa de la investigación previa sobre modelización y previsión de la demanda turística y los posibles desarrollos futuros.
Diseño/metodología/enfoque
En esta revisión del marco actual de conocimientos sobre modelización y previsión de la demanda turística y los posibles desarrollos futuros,se adopta un enfoque narrativo.
Resultados
Se identifican avances metodológicos significativos en la modelización y previsión de la demanda turística en las dos últimas décadas.
Originalidad
Se resumen las características propias de los diversos métodos aplicados en este campo y se propone una agenda de investigación para futuros trabajos.
Details
Keywords
Previous theoretical and empirical literature has advocated growth in the access and use of flexible working arrangements by establishing their link with individual and especially…
Abstract
Previous theoretical and empirical literature has advocated growth in the access and use of flexible working arrangements by establishing their link with individual and especially parental subjective well-being. Given this, the current research investigates impact that their own or their partners’ transition to flexitime and teleworking has on parental subjective well-being. The cross-partner dimension has not been explored yet by prior studies. Measures for cognitive, subjective well-being include satisfaction with life overall, satisfaction with the amount of leisure time, and satisfaction with health. Ordered logit longitudinal models are estimated using Understanding Society data from 2009 to 2019. Corroborating prior studies, the current analysis finds that mothers’ transition to flexitime and teleworking has a positive impact on their leisure time and health satisfaction. For fathers, switching to telework improves satisfaction with their amount of leisure time, while adopting flexitime can take a toll on self-reported health satisfaction. However, contrary to expectations, mothers’ move to teleworking can be injurious for fathers’ life satisfaction levels, yet fathers’ adoption of flexitime fosters mothers’ satisfaction with their leisure time amount.
Details
Keywords
Olivia Kyriakidou, Joana Vassilopoulou and Dimitria Groutsis
The unanticipated disruption caused by the ongoing coronavirus pandemic led to the extensive use of flexible working arrangements. In such a boundaryless work environment, however…
Abstract
The unanticipated disruption caused by the ongoing coronavirus pandemic led to the extensive use of flexible working arrangements. In such a boundaryless work environment, however there are significant concerns, especially around inclusivity and discrimination. Given the increasing concerns surrounding hybrid and remote work settings, the authors investigated whether the extent of working in substantially flexible working arrangements relates to employees’ perceived ostracism and inequality, distinguishing between working from home, in a hybrid mode or from the office. In addition, the authors theorised that in flexible working arrangements, high-quality leader relationships, such as leader–member exchange (LMX) and servant leadership are likely to reduce perceptions of ostracism and inequality. Based on a survey of 161 professionals, who worked to varying degrees in flexible working arrangements, the authors found that employees who worked extensively in a hybrid mode were less likely to report experiences of ostracism and inequality in comparison to employees who worked mainly from home or in an office. Furthermore, a moderation analysis showed that the effects of LMX and servant leadership on perceptions of ostracism and inequality were much stronger for individuals who work in hybrid working arrangements than those who work at the office or from home. This research makes an important contribution to our understanding of how different degrees of flexible working arrangements affect employees by demonstrating the role of high-quality leader relationships in reducing perceptions of ostracism and inequality at different degrees of work flexibility.
Details
Keywords
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…
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
Keywords
Ada T. Cenkci, Megan S. Downing, Tuba Bircan and Karen Perham-Lippman
XiYue Deng, Xiaoming Li, Zhenzhen Chen, Mengli Zhu, Naixue Xiong and Li Shen
Human group behavior is the driving force behind many complex social and economic phenomena. Few studies have integrated multi-dimensional travel patterns and city interest points…
Abstract
Purpose
Human group behavior is the driving force behind many complex social and economic phenomena. Few studies have integrated multi-dimensional travel patterns and city interest points to construct urban security risk indicators. This paper combines traffic data and urban alarm data to analyze the safe travel characteristics of the urban population. The research results are helpful to explore the diversity of human group behavior, grasp the temporal and spatial laws and reveal regional security risks. It provides a reference for optimizing resource deployment and group intelligence analysis in emergency management.
Design/methodology/approach
Based on the dynamics index of group behavior, this paper mines the data of large shared bikes and ride-hailing in a big city of China. We integrate the urban interest points and travel dynamic characteristics, construct the urban traffic safety index based on alarm behavior and further calculate the urban safety index.
Findings
This study found significant differences in the travel power index among ride-sharing users. There is a positive correlation between user shared bike trips and the power-law bimodal phenomenon in the logarithmic coordinate system. It is closely related to the urban public security index.
Originality/value
Based on group-shared dynamic index integrated alarm, we innovatively constructed an urban public safety index and analyzed the correlation of travel alarm behavior. The research results fully reveal the internal mechanism of the group behavior safety index and provide a valuable supplement for the police intelligence analysis.