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Article
Publication date: 7 August 2017

Qiao Wang, Wei Zhou, Yonggang Cheng, Gang Ma and Xiaolin Chang

Domain integrals, known as volume potentials in 3D elasticity problems, exist in many boundary-type methods, such as the boundary element method (BEM) for inhomogeneous…

Abstract

Purpose

Domain integrals, known as volume potentials in 3D elasticity problems, exist in many boundary-type methods, such as the boundary element method (BEM) for inhomogeneous partial differential equations. The purpose of this paper is to develop an accurate and reliable technique to effectively evaluate the volume potentials in 3D elasticity problems.

Design/methodology/approach

An adaptive background cell-based domain integration method is proposed for treatment of volume potentials in 3D elasticity problems. The background cells are constructed from the information of the boundary elements based on an oct-tree structure, and the domain integrals are evaluated over the cells rather than volume elements. The cells that contain the boundary elements can be subdivided into smaller sub-cells adaptively according to the sizes and levels of the boundary elements. The fast multipole method (FMM) is further applied in the proposed method to reduce the time complexity of large-scale computation.

Findings

The method is a boundary-only discretization method, and it can be applied in the BEM easily. Much computational time is saved by coupling with the FMM. Numerical examples demonstrate the accuracy and efficiency of the proposed method..

Originality/value

Boundary elements are used to create adaptive background cells, and domain integrals are evaluated over the cells rather than volume elements. Large-scale computation is made possible by coupling with the FMM.

Details

Engineering Computations, vol. 34 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 13 June 2016

Matthew Valasik, Shannon E. Reid and Matthew D. Phillips

The purpose of this paper is to examine the impact of the temporary disbandment of a gang unit on collecting gang intelligence and arresting gang members in one of the Los…

Abstract

Purpose

The purpose of this paper is to examine the impact of the temporary disbandment of a gang unit on collecting gang intelligence and arresting gang members in one of the Los Angeles Police Department’s Community Policing Areas.

Design/methodology/approach

An interrupted time series methodology (ARIMA) is utilised to examine 1,429 field interview cards and 1,174 arrests of gang members that occurred from 1 January 2010 to 31 December 2011 within one police division.

Findings

Results indicated that the dismantling of the gang unit negatively impacted the collection of intelligence on gang members by officers, regardless of whether the officers were officially serving in the gang unit. Suppression efforts by gang unit officers also resulted in a sustained decline.

Originality/value

Given that many urban centres have specialised gang units, this study demonstrates how organisational turnover or disbandment of a gang unit negatively impacts a department’s ability to deal with local gang issues. Furthermore, these finding suggest that police organisations should consider such ramifications on intelligence-based policing activities.

Details

Journal of Criminological Research, Policy and Practice, vol. 2 no. 2
Type: Research Article
ISSN: 2056-3841

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Article
Publication date: 15 June 2015

Wei Zhou, Gang Ma, Xiao-Lin Chang and Yin Duan

The purpose of this paper is to discretely model rockfill materials considering the irregular shape of the particles and their crushability. The scientific goal was to…

Abstract

Purpose

The purpose of this paper is to discretely model rockfill materials considering the irregular shape of the particles and their crushability. The scientific goal was to investigate the influence of particle crushability and shape on the mechanical behavior of rockfill materials.

Design/methodology/approach

The method of generating irregular-shaped particles was based on the observation that most rockfill grains can be approximately circumscribed by an ellipsoid. Two shape descriptors were used to make the virtual particles closely replicate the geometric features of natural rockfill grains. The combined finite-discrete element method (FDEM) was used to numerically simulate a drained, tri-axial compression test. The particle assemblies were subjected to tri-axial compression under strain controlled conditions while a constant confining pressure was maintained.

Findings

The non-breakable particles showed a remarkable ability to dilate as a result of a higher inter-particle locking effect. Dilation forces the particles to move from a lower potential energy state to a higher potential energy state, which causes the micro-structure to become less stable, resulting in a dramatic decline in the angle of friction from the peak state to the residual state. In addition, the elongated particles enhance the interlocking effect, but breakage is also more likely to occur. The net effect of those two mechanisms controls the overall shearing resistance of rockfill materials.

Originality/value

After calibration using a few micro-parameters, the combined FDEM was able to reproduce the typical behavior of rockfill materials without requiring a description of the complex relationship that exists between constituents; this relationship must be described in continuum mechanics. The simulation results showed that this approach is predictive. The combined FDEM also provides an opportunity for a quantitative study of the micro-structure of granular materials, and this study will help us to better understand the mechanical characteristics of rockfill materials.

Details

Engineering Computations, vol. 32 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 4 July 2016

Wei Zhou, Wei Yuan, Gang Ma and Xiao-Lin Chang

The purpose of this paper is to propose a novel combined finite-discrete element method (FDEM), based on the cohesive zone model, for simulating rockslide problems at the…

Abstract

Purpose

The purpose of this paper is to propose a novel combined finite-discrete element method (FDEM), based on the cohesive zone model, for simulating rockslide problems at the laboratory scale.

Design/methodology/approach

The combined FDEM is realized using ABAQUS/Explicit. The rock mass is represented as a collection of elastic bulk elements glued by cohesive elements with zero thickness. To reproduce the tensile and shear micro-fractures in rock material, the Mohr-Coulomb model with tension cut-off is employed as the damage initiation criterion of cohesive elements. Three simulated laboratory tests are considered to verify the capability of combined FDEM in reproducing the mechanical behavior of rock masses. Three slope models with different joint inclinations are taken to illustrate the application of the combined FDEM to rockslide simulation.

Findings

The results show that the joint inclination is an important factor for inducing the progressive failure behavior. With a low joint inclination, the slope failure process is observed to be a collapse mode. As the joint inclination becomes higher, the failure mode changes to sliding and the steady time of rock blocks is shortened. Moreover, the runout distance and post-failure slope angle decrease as the joint inclination increases.

Originality/value

These studies indicate that the combined FDEM performed within ABAQUS can simulate slope stability problems for research purposes and is useful for studying the slope failure mechanism comprehensively.

Details

Engineering Computations, vol. 33 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 14 April 2014

Yujia He

Rare earths are essential materials for many high-tech industries critical to both economic development and national defense. China, the world's dominant supplier of rare…

Abstract

Purpose

Rare earths are essential materials for many high-tech industries critical to both economic development and national defense. China, the world's dominant supplier of rare earths, has recently been imposing stricter controls over its production and export. The purpose of this paper is to examine the domestic roots of the changes in China's rare earth industry production and exports in its three-decade rise to the current global monopoly.

Design/methodology/approach

This paper adopts the historical institutionalism approach to analyze the trajectory of industry and trade development. The author analyzes data collected from government whitepapers and reputed scholarly and news sources.

Findings

This paper argues that the Chinese rare earth industry has gone through three periods of development, in which the state attempted to control the market and industry through reformulating rules and institutions to achieve state goals. Domestic state institutions, combined with macroeconomic environment and state governance strategy shaped the three-decade experience of rare earth industry and trade development in China.

Originality/value

This paper builds on existing findings about Chinese state regulations to provide a novel analytical framework to analyze the role of the state in industry and trade development in the rare earth industry. The focus on a single strategic industry seldom studied in the current literature also provides ample empirical value to further scholarly understanding about this industry.

Details

International Journal of Emerging Markets, vol. 9 no. 2
Type: Research Article
ISSN: 1746-8809

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Book part
Publication date: 13 July 2020

Abeer Salem

This chapter suggests a perspective on dealing with the future as dealing with uncertainty, which necessitates an alteration of the current learning paradigm and the…

Abstract

This chapter suggests a perspective on dealing with the future as dealing with uncertainty, which necessitates an alteration of the current learning paradigm and the adoption of a model that, not only accommodates, but also anticipates and embraces diversity, variety, and differences in knowledge. It calls for a model that moves beyond pre-determined content and learned solutions to seeding creativity and cultivating improvization. It approaches education as lifelong learning, as necessarily transformative, creative and authentic. It posits that dealing with the uncertainties of the future requires the acquisition of skills of mitigation and improvization that anticipate, not only mitigate; but to acquire the ability to see and create opportunities out of uncertainty. It endeavors to explore the ways by which higher education can address the need for facing the uncertainties of the future and the complexity of the sustainability challenges.

Details

Introduction to Sustainable Development Leadership and Strategies in Higher Education
Type: Book
ISBN: 978-1-78973-648-9

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Abstract

Details

Reference Reviews, vol. 31 no. 8
Type: Research Article
ISSN: 0950-4125

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Article
Publication date: 6 January 2020

Rui Wang, Haiou Zhang, Wang Gui-Lan and Xushan Zhao

The wire and arc additive manufacturing (WAAM) is a promising technology, but the parts are mostly manufactured on the plane and along the vertical direction. The purpose…

Abstract

Purpose

The wire and arc additive manufacturing (WAAM) is a promising technology, but the parts are mostly manufactured on the plane and along the vertical direction. The purpose of this paper is to propose a cylindrical slicing and manufacturing method.

Design/methodology/approach

For revolved parts, e.g. blades of a propeller, instead of planes, a series of cylindrical surfaces intersect with the STL model of the part. The generated slicing layers lie on the cylindrical surface, and then these spatial contours are unfolded onto the plane by the use of the cylindrical coordinate system. A deposition system based on an NC machine is established to examine deposition paths. The temperature and stress of part of two deposition orders are analyzed using the finite element method.

Findings

The scan parallel path and contour offset path are not suitable to fabricate blades directly. The hybrid of two types of paths and the hybrid of skeleton and contour offset paths are capable of forming blades without gaps. Deposition symmetrically can decrease the deformation of the propeller.

Originality/value

The slicing algorithm is simply implemented and practicable for any parts. The recognition of gaps and supplementary skeleton path can guarantee the full deposition of contour offset paths.

Details

Rapid Prototyping Journal, vol. 26 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Content available
Article
Publication date: 25 May 2020

Palitha Konara, Zita Stone and Alex Mohr

The authors combine options logic with transaction cost economics to explain why firms maintain, divest or buy out their international joint ventures (IJVs). It is…

Abstract

Purpose

The authors combine options logic with transaction cost economics to explain why firms maintain, divest or buy out their international joint ventures (IJVs). It is suggested that a decline in environmental risk and higher partner-related risk makes a firm more likely to acquire an IJV but less likely to divest an IJV. The study also investigates how IJV age moderates the effects of a decline in environmental risk and higher partner-related risk.

Design/methodology/approach

The study employs competing risks analyses to examine the drivers of different termination outcomes using a dataset consisting of 459 IJVs in the People's Republic of China, of which 110 were either acquired or divested by their foreign parent.

Findings

The study finds that changes in environmental risk and partner-related risk affect how firms terminate their IJVs in the People's Republic of China. Specifically, the authors find that the effect of exogenous and endogenous risk are more pronounced for the acquisition of IJVs than for the divestment of IJVs.

Research limitations/implications

The study contributes to international marketing research by complementing options logic with transaction cost economics to provide a theoretical explanation of the different ways in which IJVs in the People's Republic of China are terminated.

Practical implications

IJVs continue to be an important yet often unstable method to serve international markets. Our findings increase managers' awareness of the effect that two important sources of risk may have on the termination of IJVs in the People's Republic of China.

Originality/value

The study provides novel insights into the effect that changes in exogenous and endogenous risk have on a firm's choice of termination mode drawing on novel data on the different ways in which foreign firms have terminated their IJVs in the Peoples' Republic of China.

Details

International Marketing Review, vol. 37 no. 6
Type: Research Article
ISSN: 0265-1335

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Article
Publication date: 31 January 2011

David Pyrooz, Scott Decker and Mark Fleisher

This article examines a range of issues associated with gangs in incarcerated settings. We begin by examining the similarities and differences between street and prison…

Abstract

This article examines a range of issues associated with gangs in incarcerated settings. We begin by examining the similarities and differences between street and prison gangs, and differentiating them from other types of criminal groups. Next, we focus on the emergence and growth of gangs in prison, including patterns and theoretical explanations. Importantly, we draw theoretical linkages between differing perspectives on gang emergence and gang violence. We also present administrative and official responses to gangs in prison. Finally, we discuss the movement from prison to the street, examining the difficulties that former prisoners face when re‐entering communities.

Details

Journal of Aggression, Conflict and Peace Research, vol. 3 no. 1
Type: Research Article
ISSN: 1759-6599

Keywords

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