Beichuan Yan and Richard Regueiro
This paper aims to present performance comparison between O(n2) and O(n) neighbor search algorithms, studies their effects for different particle shape complexity and…
Abstract
Purpose
This paper aims to present performance comparison between O(n2) and O(n) neighbor search algorithms, studies their effects for different particle shape complexity and computational granularity (CG) and investigates the influence on superlinear speedup of 3D discrete element method (DEM) for complex-shaped particles. In particular, it aims to answer the question: O(n2) or O(n) neighbor search algorithm, which performs better in parallel 3D DEM computational practice?
Design/methodology/approach
The O(n2) and O(n) neighbor search algorithms are carefully implemented in the code paraEllip3d, which is executed on the Department of Defense supercomputers across five orders of magnitude of simulation scale (2,500; 12,000; 150,000; 1 million and 10 million particles) to evaluate and compare the performance, using both strong and weak scaling measurements.
Findings
The more complex the particle shapes (from sphere to ellipsoid to poly-ellipsoid), the smaller the neighbor search fraction (NSF); and the lower is the CG, the smaller is the NSF. In both serial and parallel computing of complex-shaped 3D DEM, the O(n2) algorithm is inefficient at coarse CG; however, it executes faster than O(n) algorithm at fine CGs that are mostly used in computational practice to achieve the best performance. This means that O(n2) algorithm outperforms O(n) in parallel 3D DEM generally.
Practical implications
Taking for granted that O(n) outperforms O(n2) unconditionally, complex-shaped 3D DEM is a misconception commonly encountered in the computational engineering and science literature.
Originality/value
The paper clarifies that performance of O(n2) and O(n) neighbor search algorithms for complex-shaped 3D DEM is affected by particle shape complexity and CG. In particular, the O(n2) algorithm outperforms the O(n) algorithm in large-scale parallel 3D DEM simulations generally, even though this outperformance is counterintuitive.
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Beichuan Yan and Richard Regueiro
The purpose of this paper is to extend complex-shaped discrete element method simulations from a few thousand particles to millions of particles by using parallel computing on…
Abstract
Purpose
The purpose of this paper is to extend complex-shaped discrete element method simulations from a few thousand particles to millions of particles by using parallel computing on department of defense (DoD) supercomputers and to study the mechanical response of particle assemblies composed of a large number of particles in engineering practice and laboratory tests.
Design/methodology/approach
Parallel algorithm is designed and implemented with advanced features such as link-block, border layer and migration layer, adaptive compute gridding technique and message passing interface (MPI) transmission of C++ objects and pointers, for high performance optimization; performance analyses are conducted across five orders of magnitude of simulation scale on multiple DoD supercomputers; and three full-scale simulations of sand pluviation, constrained collapse and particle shape effect are carried out to study mechanical response of particle assemblies.
Findings
The parallel algorithm and implementation exhibit high speedup and excellent scalability, communication time is a decreasing function of the number of compute nodes and optimal computational granularity for each simulation scale is given. Nearly 50 per cent of wall clock time is spent on rebound phenomenon at the top of particle assembly in dynamic simulation of sand gravitational pluviation. Numerous particles are necessary to capture the pattern and shape of particle assembly in collapse tests; preliminary comparison between sphere assembly and ellipsoid assembly indicates a significant influence of particle shape on kinematic, kinetic and static behavior of particle assemblies.
Originality/value
The high-performance parallel code enables the simulation of a wide range of dynamic and static laboratory and field tests in engineering applications that involve a large number of granular and geotechnical material grains, such as sand pluviation process, buried explosion in various soils, earth penetrator interaction with soil, influence of grain size, shape and gradation on packing density and shear strength and mechanical behavior under different gravity environments such as on the Moon and Mars.
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Lili Qian, Chunhui Zheng, Jinwei Wang, María de los Ángeles Pérez Sánchez, Eduardo Parra López and Hanliang Li
This study aims to explore how tourists construct destination images in the context of dark tourism and reveals the relationships between on-site experience, destination image and…
Abstract
Purpose
This study aims to explore how tourists construct destination images in the context of dark tourism and reveals the relationships between on-site experience, destination image and behavioural intention.
Design/methodology/approach
The earthquake-ravaged county town of Beichuan in China was chosen as the study site. The study collected 298 viable questionnaires from tourists. Partial least squares structural equation modelling was performed to explore the relationships between the variables of on-site experience, destination image and behavioural intention.
Findings
The study identified four dimensions of dark tourism destination image (TDI) from its attribute and functional perspective. It found that “image of memorial place” and “image of educational place” were the most perceptual images and positively related with most subdimensions of on-site experience and behavioural intention. “Image of leisure place” and “image of landscapes of fear” were less perceived by tourists and negatively related with some subdimensions of on-site experience and behavioural intention.
Originality/value
To our knowledge, this study is the first attempt to explore the complex mechanisms of dark TDI formation with the framework of “on-site experiences–destination images–behavioural intentions”. By identifying tourists’ most and least perceptual images and their effective antecedents and consequences help to reconcile and manage the controversial and contradictory images of a dark tourism destination.
摘要
目标
本文探讨了游客如何建构黑色旅游目的地形象, 进一步研究了游客现场体验、目的地形象、行为意愿之间的作用关系。
设计/方法
以汶川地震重灾区北川老县城遗址为案例地, 本研究收集了游客结构化问卷298份, 采用偏最小二乘结构方程模型(PLS-SEM)分析了游客现场体验、目的地形象和行为意愿各维度之间的作用关系。
研究发现
从目的地属性和功能角度, 本文区分了黑色旅游目的地形象四个维度。研究发现“纪念地形象”和“教育地形象”是游客感知最强的两大维度, 与绝大多数游客现场体验和行为意愿的维度呈显著正向影响关系。 “休闲地形象”和“恐惧景观形象”, 游客感知较弱, 与现场体验和行为意向的一些维度呈负向影响关系。
创新/价值
本文首次利用“现场体验-目的地形象-行为意愿”这一研究框架, 揭示黑色旅游目的地形象的复杂生成机制。通过识别游客感知最强和最弱的形象维度, 揭示其前因与后果, 有助于调和与管理有争议和矛盾的黑色旅游目的地形象。
Propósito
Este estudio explora cómo los turistas construyen la imagen del destino en el contexto del turismo oscuro, revelando las relaciones entre experiencias en el lugar, imágenes del destino e intenciones de comportamiento.
Diseño/metodología/enfoque
El terremoto que devastó la ciudad del condado de Beichuan en China fue elegido lugar de estudio por sus peculiaridades para el desarrollo del destino oscuro. El estudio recopiló 298 cuestionarios viables de turistas. Se planteo un modelo de ecuaciones estructurales (PLS-SEM) para explorar las relaciones entre las variables de experiencias en el lugar, imágenes de destino e intenciones de comportamiento.
Hallazgos
El estudio identificó cuatro dimensiones de la imagen del destino turístico oscuro desde su atributo y perspectiva funcional. De igual forma, se encontró que la “imagen del lugar conmemorativo” y la “imagen del lugar educativo” eran las imágenes más perceptivas y estaban relacionadas positivamente con la mayoría de los subdimensiones de las experiencias en el lugar e intenciones de comportamiento. Los turistas percibieron menos la “imagen de un lugar de ocio” y la “imagen de paisajes de miedo” y se relacionaron negativamente con algunos subdimensiones de las experiencias en el lugar e intención de comportamiento.
Originalidad/valor
Hasta donde sabemos, este estudio es el primer intento de explorar el complejo mecanismo en la formación de TDIs oscuros con el marco de “experiencias en el lugar- imágenes de destino – intenciones de comportamiento”. Al identificar las imágenes más o menos perceptivas de los turistas, y sus antecedentes y consecuencias efectivos, ayuda a conciliar y gestionar las imágenes controvertidas y contradictorias de un destino turístico oscuro.
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Richard Regueiro, Zheng Duan and Beichuan Yan
– The purpose of this paper is to develop a concurrent multiscale computational method for granular materials in the quasi-static loading regime.
Abstract
Purpose
The purpose of this paper is to develop a concurrent multiscale computational method for granular materials in the quasi-static loading regime.
Design/methodology/approach
Overlapped-coupling between a micropolar linear elastic one-dimensional (1D) mixed finite element (FE) model and a 1D chain of Hertzian nonlinear elastic, glued, discrete element (DE) spheres is presented. The 1D micropolar FEs and 1D chain of DEs are coupled using a bridging-scale decomposition for static analysis.
Findings
It was found that an open-window DE domain may be coupled to a micropolar continuum FE domain via an overlapping region within the bridging-scale decomposition formulation for statics. Allowing the micropolar continuum FE energy in the overlapping region to contribute to the DE energy has a smoothing effect on the DE response, especially for the rotational degrees of freedom (dofs).
Research limitations/implications
The paper focusses on 1D examples, with elastic, glued, DE spheres, and a linear elastic micropolar continuum implemented in 1D.
Practical implications
A concurrent computational multiscale method for granular materials with open-window DE resolution of the large shearing region such as at the interface with a penetrometer skin, will allow more efficient computations by reducing the more costly DE domain calculations, but not at the expense of generating artificial boundary effects between the DE and FE domains.
Originality/value
Open-window DE overlapped-coupling to FE continuum domain, accounting for rotational dofs in both DE and FE methods. Contribution of energy from micropolar FE in overlap region to underlying DE particle energy.
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Beichuan Yan, Richard A. Regueiro and Stein Sture
The purpose of this paper is to develop a discrete element (DE) and multiscale modeling methodology to represent granular media at their particle scale as they interface solid…
Abstract
Purpose
The purpose of this paper is to develop a discrete element (DE) and multiscale modeling methodology to represent granular media at their particle scale as they interface solid deformable bodies, such as soil‐tool, tire, penetrometer, pile, etc., interfaces.
Design/methodology/approach
A three‐dimensional ellipsoidal discrete element method (DEM) is developed to more physically represent particle shape in granular media while retaining the efficiency of smooth contact interface conditions for computation. DE coupling to finite element (FE) facets is presented to demonstrate initially the development of overlapping bridging scale methods for concurrent multiscale modeling of granular media.
Findings
A closed‐form solution of ellipsoidal particle contact resolution and stiffness is presented and demonstrated for two particle, and many particle contact simulations, during gravity deposition, and quasi‐static oedometer, triaxial compression, and pile penetration. The DE‐FE facet coupling demonstrates the potential to alleviate artificial boundary effects in the shear deformation region between DEM granular media and deformable solid bodies.
Research limitations/implications
The research is being extended to couple more robustly the ellipsoidal DEM code and a higher order continuum FE code via overlapping bridging scale methods, in order to remove dependence of penetration/shear resistance on the boundary placement for DE simulation.
Practical implications
When concurrent multiscale computational modeling of interface conditions between deformable solid bodies and granular materials reaches maturity, modelers will be able to simulate the mechanical behavior accounting for physical particle sizes and flow in the interface region, and thus design their tool, tire, penetrometer, or pile accordingly.
Originality/value
A closed‐form solution for ellipsoidal particle contact is demonstrated in this paper, and the ability to couple DE to FE facets.
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María de-Miguel-Molina, Daniel Catalá-Pérez, Blanca de-Miguel-Molina and Virginia Santamarina-Campos
Haiqing Hu and Tian Wu
Strengthening the combination of technology and finance can significantly promote the development of economy and society. Urbanization is a crucial standard to measure the…
Abstract
Strengthening the combination of technology and finance can significantly promote the development of economy and society. Urbanization is a crucial standard to measure the economic and social development of a country and region, and urban regional planning based on science and technology finance has always been the focus of both domestic and foreign research institutions. Thus, this paper takes Mianyang, the first city of science and technology, as the object of research, and from the angle of the development process of Mianyang, investigates the three stages of the construction and development of this science and technology city. This study analyzes the characteristics of regional planning of Mianyang City and sums up the idea of relying on the old city to build another new district, which boosts the development of science and technology as well as the economy. From two specific angles (i.e., urban spatial function region planning and urban and rural planning), this paper thoroughly studies a multiscale planning scheme of Mianyang’s urban area in recent years by researching the local policy, system, finance, and society. Empirical measurement proves that reasonable planning and construction of the science and technology city Mianyang can accelerate the development process of the western region, effectively promoting the economic development of the surrounding areas of Sichuan and remarkably improving the overall quality of the regional economy of both Chongqing and Sichuan Provinces.
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Kayode D. Aleshinloye, Emrullah Erul, Adetola A. Omitola, Juliana Rodrigues Vieira Tkatch and Aysegul Gunduz Songur
Residents’ understanding of the development and promotion of dark tourism cannot be universally assumed due to cultural and traditional disparities across different geographical…
Abstract
Purpose
Residents’ understanding of the development and promotion of dark tourism cannot be universally assumed due to cultural and traditional disparities across different geographical regions. Using the social exchange theory (SET) and the cognitive appraisal theory (CAT) as the theoretical baseline for exploring the residents’ cultural perception of dark tourism development and promotion. The purpose of this study is twofold: first, to comprehend the residents’ perspectives about the meaning, values and cultural interpretation of dark tourism; second, to explore the residents’ attitudes from both an emotional and economic interface to dark tourism development and promotion in their community.
Design/methodology/approach
Using a qualitative approach with purposive and snowball sampling strategies, 25 semi-structured interviews were conducted with residents or natives of the Jesse community, selected from both within and outside the community.
Findings
Our research revealed that the residents’ emotions about the fire disaster transcend the prospect of economic empowerment the dark tourism concept could bring to the community. Besides, the respondents struggled to understand the meanings of dark tourism, but the younger respondents tended to welcome the idea more than the older ones.
Practical implications
The study findings emphasized the importance of stakeholders in engaging the residents in designing and managing community tourism initiatives. This will prevent conflict with cultural traditions and ensure tourism sustainability.
Originality/value
A novel study using the SET and CAT models to examine community perspectives on dark tourism from sub-Sahara Africa, providing an alternative viewpoint to Western interpretations and representation.