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1 – 10 of over 56000Weihua Zhang, Yuanchen Zeng, Dongli Song and Zhiwei Wang
The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system. This paper aims to…
Abstract
Purpose
The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system. This paper aims to define and substantiate the assessment of the structural integrity and dynamical integrity of high-speed trains in both theory and practice. The key principles and approaches will be proposed, and their applications to high-speed trains in China will be presented.
Design/methodology/approach
First, the structural integrity and dynamical integrity of high-speed trains are defined, and their relationship is introduced. Then, the principles for assessing the structural integrity of structural and dynamical components are presented and practical examples of gearboxes and dampers are provided. Finally, the principles and approaches for assessing the dynamical integrity of high-speed trains are presented and a novel operational assessment method is further presented.
Findings
Vehicle system dynamics is the core of the proposed framework that provides the loads and vibrations on train components and the dynamic performance of the entire vehicle system. For assessing the structural integrity of structural components, an open-loop analysis considering both normal and abnormal vehicle conditions is needed. For assessing the structural integrity of dynamical components, a closed-loop analysis involving the influence of wear and degradation on vehicle system dynamics is needed. The analysis of vehicle system dynamics should follow the principles of complete objects, conditions and indices. Numerical, experimental and operational approaches should be combined to achieve effective assessments.
Originality/value
The practical applications demonstrate that assessing the structural integrity and dynamical integrity of high-speed trains can support better control of critical defects, better lifespan management of train components and better maintenance decision-making for high-speed trains.
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Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the…
Abstract
Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore aims to give the reader an encyclopaedic view on the subject. The bibliography at the end of the paper contains 2,025 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1992‐1995.
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This paper gives a bibliographical review of the finite element and boundary element parallel processing techniques from the theoretical and application points of view. Topics…
Abstract
This paper gives a bibliographical review of the finite element and boundary element parallel processing techniques from the theoretical and application points of view. Topics include: theory – domain decomposition/partitioning, load balancing, parallel solvers/algorithms, parallel mesh generation, adaptive methods, and visualization/graphics; applications – structural mechanics problems, dynamic problems, material/geometrical non‐linear problems, contact problems, fracture mechanics, field problems, coupled problems, sensitivity and optimization, and other problems; hardware and software environments – hardware environments, programming techniques, and software development and presentations. The bibliography at the end of this paper contains 850 references to papers, conference proceedings and theses/dissertations dealing with presented subjects that were published between 1996 and 2002.
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Abstract
Considering the randomness of physical parameters of structural material, dynamic characteristic topology optimization mathematical model based on reliability of planar continuum structures is built in this paper. In which topology information variables of the structure are taken as design variables, minimizing the mean value of total structural weight as objective function and satisfying the reliability requirement of structural dynamic characteristic as constraints. In the process of optimization, the ESO method based on probability is adopted as solution strategy. At the same time, distribution function method is utilized to convert the reliability constraints into conventional constraints formally. A square thin plate with four sides fixed is used as an example to demonstrate the rationality and validity of the presented model.
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Presents a review on implementing finite element methods on supercomputers, workstations and PCs and gives main trends in hardware and software developments. An appendix included…
Abstract
Presents a review on implementing finite element methods on supercomputers, workstations and PCs and gives main trends in hardware and software developments. An appendix included at the end of the paper presents a bibliography on the subjects retrospectively to 1985 and approximately 1,100 references are listed.
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This paper aims to explain how the dynamic demand environment influences strategic firm behavior along an industry’s evolutionary path. A conceptual gap concerning the influence…
Abstract
Purpose
This paper aims to explain how the dynamic demand environment influences strategic firm behavior along an industry’s evolutionary path. A conceptual gap concerning the influence of demand-side environmental factors (vis-à-vis changes in technology and policy) on firms’ strategic choices motivates the theory developed herein. The paper’s contribution to the literature on “evolutionary perspective in strategy” also addresses an important gap in the emerging literature on “strategy dynamics”.
Design/methodology/approach
The conceptual framework in this paper features a dynamic demand environment that provides the structural context for firms’ strategic choices. It conceptualizes demand-side competence as a mediating firm-specific construct to explain the endogenous relationship between the characteristics of the demand environment and firms’ path dependent demand-side investments.
Findings
A review of the literature on evolutionary perspective in strategy reveals an important conceptual gap concerning the structural determinants of dynamic firm behavior. There is no explanation of the endogenous relationship between dynamic demand structure, firms’ dynamic demand-side competence, and temporally heterogeneous strategic choices.
Originality/value
The demand-side explanation of how idiosyncratic firm behavior is endogenously determined, with both structural characteristics (demand structure) and firm competences (demand-side competence), addresses an important conceptual gap. The novelty of the theory developed herein lies in its explication of the effect of dynamic demand environment on the evolution of idiosyncratic strategic firm behavior – entry, investment and exit – along the evolutionary path of an industry. The theory developed herein not only explains the effect of both determinants of idiosyncratic strategic firm behavior – the external industry environment (dynamic market structure) and internal firm environment (dynamic firm competences) – but also explains how the determinants evolve along the industry’s lifecycle.
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Victor Aguirregabiria and Arvind Magesan
We derive marginal conditions of optimality (i.e., Euler equations) for a general class of Dynamic Discrete Choice (DDC) structural models. These conditions can be used to…
Abstract
We derive marginal conditions of optimality (i.e., Euler equations) for a general class of Dynamic Discrete Choice (DDC) structural models. These conditions can be used to estimate structural parameters in these models without having to solve for approximate value functions. This result extends to discrete choice models the GMM-Euler equation approach proposed by Hansen and Singleton (1982) for the estimation of dynamic continuous decision models. We first show that DDC models can be represented as models of continuous choice where the decision variable is a vector of choice probabilities. We then prove that the marginal conditions of optimality and the envelope conditions required to construct Euler equations are also satisfied in DDC models. The GMM estimation of these Euler equations avoids the curse of dimensionality associated to the computation of value functions and the explicit integration over the space of state variables. We present an empirical application and compare estimates using the GMM-Euler equations method with those from maximum likelihood and two-step methods.
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Dynamic capabilities are regarded as the bedrock of businesses that survive in a dynamic environment. Building upon the social capital theory, the purpose of this paper is to…
Abstract
Purpose
Dynamic capabilities are regarded as the bedrock of businesses that survive in a dynamic environment. Building upon the social capital theory, the purpose of this paper is to investigate the nexus between dynamic capabilities and social capital in family businesses.
Design/methodology/approach
The study adopted a quantitative approach. As there is no formal business database available in China, the study followed a snowball sampling procedure. In total, 628 useful responses were gathered.
Findings
The study echoes the call of Arregle et al. (2007) for understanding family business’s internal sources of competitiveness and the role of social capital. Results show that the three dimensions of social capital, namely, structural, cognitive, and relational capital, influence dynamic capabilities of family businesses.
Research limitations/implications
The lack of an official business database in China made the conventional representative sample survey used in the West difficult to replicate. Furthermore, empirical data were collected from different regions of China; regional cultures and different levels of economic development across the regions might influence the social capital-dynamic capabilities connection, but these were not examined in the current study.
Originality/value
The study integrates two significant but disconnected research streams, i.e. social capital and dynamic capabilities. Furthermore, the study shows how different dimensions of social capital influence dynamic capabilities. Research findings derived may contribute to the entrepreneurial debate as to why some family businesses can survive in the dynamic environment while others cannot.
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Hongyue Zhao, Chuang Shi, Hongwei Guo and Rongqiang Liu
In order to make the aperture of spatial deployable antenna larger, this paper proposed the study on a spatial annular tensegrity structure with 100 m large scale, which could be…
Abstract
Purpose
In order to make the aperture of spatial deployable antenna larger, this paper proposed the study on a spatial annular tensegrity structure with 100 m large scale, which could be one of the ideal solutions to improve the dimension of the antenna. This study is aiming to figure out the dynamic characteristic of ultra-large annular tensegrity and address the problem of insufficient rigidity with local modes that many ring truss-type deployable antenna structures have faced.
Design/methodology/approach
This work is carried out based on the nonlinear dynamic modelling when fully considering the effect of bending and torsion deformation of beams, as well as the pretension of cables. Additionally, the structural stability analysis based on the proposed stability criterion is also presented to evaluate the tensegrity configuration with different distribution of cable groups.
Findings
This research results verify that the modified structure with radial ribs could eliminate the effect of the local vibration mode on stiffness and is suitable to meet the requirements of the annular tensegrity structure. Additionally, the calculation results demonstrate that the structural configuration of annular tensegrity with 36 groups of cables which share the nodes with radial ribs is more appropriate to enhance the stiffness and structural stability.
Originality/value
A new large annular tensegrity structure with radial ribs and tensioned cables is proposed. Based on the proposed structural configuration, the positive definiteness of the tangent stiffness matrix is carried out as the criterion of stability and the composition of the analytical expression of the tangent stiffness matrix is analyzed. Four levels of tensegrity structure stability have been carried out and the influence of the structural parameters on the stability and the rigidity has been analyzed. A scaled-down prototype is developed to verify the feasibility of the design of the hoop-column-rib configuration by the deployment and dynamic experiment.
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Timo Rogge, Ricarda Berger, Linus Pohle, Raimund Rolfes and Jörg Wallaschek
The purpose of this study a fast procedure for the structural analysis of gas turbine blades in aircraft engines. In this connection, investigations on the behavior of gas turbine…
Abstract
Purpose
The purpose of this study a fast procedure for the structural analysis of gas turbine blades in aircraft engines. In this connection, investigations on the behavior of gas turbine blades concentrate on the analysis and evaluation of starting dynamics and fatigue strength. Besides, the influence of structural mistuning on the vibration characteristics of the single blade is analyzed and discussed.
Design/methodology/approach
A basic computation cycle is generated from a flight profile to describe the operating history of the gas turbine blade properly. Within an approximation approach for high-frequency vibrations, maximum vibration amplitudes are computed by superposition of stationary frequency responses by means of weighting functions. In addition, a two-way coupling approach determines the influence of structural mistuning on the vibration of a single blade. Fatigue strength of gas turbine blades is analyzed with a semi-analytical approach. The progressive damage analysis is based on MINER’s damage accumulation assuming a quasi-stable behavior of the structure.
Findings
The application to a gas turbine blade shows the computational capabilities of the approach presented. Structural characteristics are obtained by robust and stable computations using a detailed finite element model considering different load conditions. A high quality of results is realized while reducing the numerical costs significantly.
Research limitations/implications
The method used for analyzing the starting dynamics is based on the assumption of a quasi-static state. For structures with a sufficiently high stiffness, such as the gas turbine blades in the present work, this procedure is justified. The fatigue damage approach relies on the existence of a quasi-stable cyclic stress condition, which in general occurs for isotropic materials, as is the case for gas turbine blades.
Practical implications
Owing to the use of efficient analysis methods, a fast evaluation of the gas turbine blade within a stochastic analysis is feasible.
Originality/value
The fast numerical methods and the use of the full finite element model enable performing a structural analysis of any blade structure with a high quality of results.
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