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1 – 6 of 6Yunqiao Dong, Zhengxu Tan, Hengbo Sun and Fengwei Yuan
In traditional methods, a one-directional distance transformation is employed to eliminate the near-singularity in the radial direction. However, when the projection point of the…
Abstract
Purpose
In traditional methods, a one-directional distance transformation is employed to eliminate the near-singularity in the radial direction. However, when the projection point of the source point is near the boundary of the integral element, the near-singularity in the circumferential direction still exists, resulting in large errors in the numerical results. The purpose of this paper is to propose a bi-directional distance transformation for the elimination of near-singularities in two directions arising from the irregular integral element.
Design/methodology/approach
The sources of the circumferential near-singularity caused by irregular sub-triangular element are analyzed in this paper. A bi-directional distance transformation based on the (a, β) transformation is proposed to eliminate the near-singularities in the two directions. The (a, β) transformation is initially introduced to separate the integral variables and streamline the implementation of subsequent transformations. In the transformed (a, β) coordinate system, a new distance transformation applied in the circumferential direction is constructed.
Findings
With the proposed method, the radial and circumferential near-singularities are eliminated using two different distance transformations, respectively. Thus, accurate calculations of the nearly singular integrals can be achieved, irrespective of the shape of the integral element.
Originality/value
Numerical examples are presented to calculate the nearly singular integrals of different orders over both the linear integral element and the quadratic integral element. Comparative studies demonstrate that the proposed method significantly improves the accuracy of these calculations.
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Jianming Zhang, Lei Han, Yudong Zhong, Yunqiao Dong and Weicheng Lin
This paper aims to propose a boundary element analysis of two-dimensional linear elasticity problems by a new expanding element interpolation method.
Abstract
Purpose
This paper aims to propose a boundary element analysis of two-dimensional linear elasticity problems by a new expanding element interpolation method.
Design/methodology/approach
The expanding element is made up based on a traditional discontinuous element by adding virtual nodes along the perimeter of the element. The internal nodes of the original discontinuous element are referred to as source nodes and its shape function as raw shape function. The shape functions of the expanding element constructed on both source nodes and virtual nodes are referred as fine shape functions. Boundary variables are interpolated by the fine shape functions, while the boundary integral equations are collocated on source nodes.
Findings
The expanding element inherits the advantages of both the continuous and discontinuous elements while overcomes their disadvantages. The polynomial order of fine shape functions of the expanding elements increases by two compared with their corresponding raw shape functions, while the expanding elements still keep independence to each other as the original discontinuous elements. This feature makes the expanding elements able to naturally and accurately interpolate both continuous and discontinuous fields.
Originality/value
Numerical examples are presented to verify the proposed method. Results have demonstrated that the accuracy, efficiency and convergence rate of the expanding element method.
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Jianming Zhang, Pan Wang, Chenjun Lu and Yunqiao Dong
The purpose of this paper is to preset a spherical element subdivision method for the numerical evaluation of nearly singular integrals in three-dimensional (3D) boundary element…
Abstract
Purpose
The purpose of this paper is to preset a spherical element subdivision method for the numerical evaluation of nearly singular integrals in three-dimensional (3D) boundary element method (BEM).
Design/methodology/approach
In this method, the source point is first projected to the tangent plane of the element. Then two cases are considered: the projection point is either inside or outside the element. In both cases, the element is subdivided into a number of patches using a sequence of spheres with decreasing radius.
Findings
With the proposed method, the patches obtained are automatically refined as they approach the projection point and each patch of the integration element is “good” in shape and size for standard Gaussian quadrature. Therefore, all kinds of nearly singular boundary integrals on elements of any shape and size with arbitrary source point location related to the element can be evaluated accurately and efficiently.
Originality/value
Numerical examples for planar and slender elements with various relative location of the source point are presented. The results demonstrate that our method has much better accuracy, efficiency and stability than conventional methods.
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Yuan Li, J. Zhang, Yudong Zhong, Xiaomin Shu and Yunqiao Dong
The Convolution Quadrature Method (CQM) has been widely applied to solve transient elastodynamic problems because of its stability and generality. However, the CQM suffers from…
Abstract
Purpose
The Convolution Quadrature Method (CQM) has been widely applied to solve transient elastodynamic problems because of its stability and generality. However, the CQM suffers from the problems of huge memory requirement in case of direct implementation in time domain or CPU time in case of its reformulation in Laplace domain. The purpose of this paper is to combine the CQM with the pseudo-initial condition method (PICM) to achieve a good balance between memory requirement and CPU time.
Design/methodology/approach
The combined methods first subdivide the whole analysis into a few sub-analyses, which is dealt with the PICM, namely, the results obtained by previous sub-analysis are used as the initial conditions for the next sub-analysis. In each sub-analysis, the time interval is further discretized into a number of sub-steps and dealt with the CQM. For non-zero initial conditions, the pseudo-force method is used to transform them into equivalent body forces. The boundary face method is employed in the numerical implementation. Three examples are analyzed. Results are compared with analytical solutions or FEM results and the results of reformulated CQM.
Findings
Results demonstrate that the computation time and the storage requirement can be reduced significantly as compared to the CQM, by using the combined approach.
Originality/value
The combined methods can be successfully applied to the problems of long-time dynamic response, which requires a large amount of computer memory when CQM is applied, while preserving the CQM stability. If the number of time steps is high, then the accuracy of the proposed approach can be deteriorated because of the pseudo-force method.
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Jiangfeng Ye, Yunqiao Wu, Bin Hao and Zusheng Chen
The purpose of this study is to investigate the relationships between two types of informal ties and radical innovation in the context of China’s university spin-offs and the…
Abstract
Purpose
The purpose of this study is to investigate the relationships between two types of informal ties and radical innovation in the context of China’s university spin-offs and the moderating roles of knowledge breadth and depth in such relationships.
Design/methodology/approach
A systematic review of literature on informal ties, internal knowledge base and radical innovation provides the theoretical foundation of the research framework and hypotheses. Using a sample of 158 China’s university spin-offs, the authors conduct a regression analysis on the theoretical framework and hypotheses.
Findings
The results show that business and university ties are positively related to radical innovation. Moreover, the effects of business and university ties on radical innovation are contingent on knowledge breadth and depth in opposite ways. In particular, the positive effect of business ties on radical innovation depends significantly on internal knowledge depth rather than on knowledge breadth, and the positive effect of university ties on radical innovation will be affected by internal knowledge breadth rather than knowledge depth.
Practical implications
Managers of university spin-offs must examine informal ties they already have and identify their nature, content and embedded advantages and promptly adjust their strategy of informal ties to adapt to their firms’ internal knowledge base.
Originality/value
This study highlights the positive role of managers’ personal connections with different external parties in facilitating radical innovation and advances the understanding of informal ties by proposing that the effects of informal ties on radical innovation are contingent on a firm’s internal knowledge base in the context of China’s university spin-offs.
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Lin Gui, Zhendong Yin and Huihua Nie
The stability maintenance system has played an essential role in maintaining social stability although it also has brought about social problems worthy of attention. Admittedly…
Abstract
Purpose
The stability maintenance system has played an essential role in maintaining social stability although it also has brought about social problems worthy of attention. Admittedly compensation-based stability maintenance policy can address the appeals of citizens whose rights are infringed and the dissolving effect in the provision of compensation can save the cost of stability maintenance but such stability maintenance system lacks equilibrium.
Design/methodology/approach
The establishment of a strict assessment system for stability maintenance performance can encourage the stability maintenance authorities to eliminate the “fuse effect” as much as possible and ensure the effective implementation of the stability maintenance system. However, the rigorous stability maintenance performance assessment also provides the possibility for profit-driven petitions.
Findings
Due to the continuous accumulation of social dissatisfaction and the lack of stability maintenance equilibrium in the implementation of the compensation-based stability maintenance policy, public governance will fall into a stability maintenance paradox of “greater instability resulting from stability maintenance”.
Originality/value
The provision of sufficient means for the people to protect their interest by implementing measures such as strengthening the rule of law mechanisms is the key to achieve long-term social stability.
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