Qing Li, Grant P. Steven and Y.M. Xie
Most engineering products contain more than one component or structural element, a consideration that needs to be appreciated during the design process and beyond, to…
Abstract
Most engineering products contain more than one component or structural element, a consideration that needs to be appreciated during the design process and beyond, to manufacturing, transportation, storage and maintenance. The allocation and design of component interconnections (such as bolts, rivets, or springs, spot‐welds, adhesives, others) usually play a crucial role in the design of the entire multi‐component system. This paper extends the evolutionary structural optimization method to the generic design problems of connection topology. The proposed approach consists of a simple cycle of a finite element analysis followed by a rule‐driven element removal process. To make the interconnection elements carry as close to uniform a load as possible, a “fully stressed” design criterion is adopted. To determine the presence and absence of the interconnection elements, the usage efficiencies of fastener elements are estimated in terms of their relative stress levels. This avoids the use of gradient‐based optimization algorithms and allows designers to readily seek an optimization of connection topology, which can be implemented in their familiar CAD/CAE design platforms. To demonstrate the capabilities of the proposed procedure, a number of design examples are presented in this paper.
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Qing Li, Grant P. Steven, Osvaldo M. Querin and Y.M. Xie
This paper shows how the evolutionary structural optimization (ESO) algorithm can be used to achieve a multiple criterion design for a structure in a thermal environment. The…
Abstract
This paper shows how the evolutionary structural optimization (ESO) algorithm can be used to achieve a multiple criterion design for a structure in a thermal environment. The proposed thermal ESO procedure couples an evolutionary iterative process of a finite element heat conduction solution and a finite element thermoelastic solution. The overall efficiency of material usage is measured in terms of the combination of thermal stress levels and heat flux densities by using a combination strategy with weighting factors. The ESO method then works by eliminating from the structural domain under‐utilized material. In this paper, a practical design example of a printed circuit board substrate is presented to illustrate the capabilities of the ESO algorithm for thermal design optimization in multiple load environments.
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K.A. Proos, G.P. Steven, O.M. Querin and Y.M. Xie
In continuation of the recent development of Evolutionary Structural Optimisation (ESO) applied to the simultaneous objective to maximise the natural frequency and to minimise the…
Abstract
In continuation of the recent development of Evolutionary Structural Optimisation (ESO) applied to the simultaneous objective to maximise the natural frequency and to minimise the mean compliance, presents the Multicriteria ESO optimisation of two new criteria. This has been done with the use of four different multicriteria methods. Three examples have been used to verify the usefulness and capability of these methods applied to ESO in the context of the aforementioned criteria. Concluded that the ESO weighting method is proficient in presenting the designer with a range of options (of Pareto attribute) taking into account multiple criteria, and the global criterion method has the tendency to produce shapes and topologies that resemble that of the weighted 50 per cent: 50 per cent method. Likewise, the logical OR operator method produced designs that corresponded directly to those of 100 per cent stiffness weighted criteria. No clear resemblance could be concluded with the case of the logical AND operator method.
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In this paper, the future trends and challenges of financial risk management are considered. First, the historical developments and current status of financial risk management are…
Abstract
In this paper, the future trends and challenges of financial risk management are considered. First, the historical developments and current status of financial risk management are assessed. Then, key features of the financial industry in the digital economy are discussed. It is argued that the technology innovations, particularly in computing and telecommunication, will continue to have an important influence on the future development of financial risk management. Based the past and present of financial risk management as well as the general trends in the financial industry, some future trends and challenges of financial risk management in the digital economy are discussed. Finally, some implications for financial institutions, corporations and emerging economies are given.
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– This paper aims to investigate the volatility transmission and dynamics in China Securities Index (CSI) 300 index futures market.
Abstract
Purpose
This paper aims to investigate the volatility transmission and dynamics in China Securities Index (CSI) 300 index futures market.
Design/methodology/approach
This paper applies the bivariate Constant Conditional Correlation (CCC) and Dynamic Conditional Correlation (DCC) Generalized Autoregressive Conditional Heteroskedasticity (GARCH) models using high frequency data. Estimates for the bivariate GARCH models are obtained by maximising the log-likelihood of the probability density function of a conditional Student’s t distribution.
Findings
This empirical analysis yields a few interesting results: there is a one-way feedback of volatility transmission from the CSI 300 index futures to spot returns, suggesting index futures market leads the spot market; volatility response to past bad news is asymmetric for both markets; volatility can be intensified by the disequilibrium between spot and futures prices; and trading volume has significant impact on volatility for both markets. These results reveal new evidence on the informational efficiency of the CSI 300 index futures market compared to earlier studies.
Originality/value
This paper shows that the CSI 300 index futures market has improved in terms of price discovery one year after its existence compared to its early days. This is an important finding for market participants and regulators. Further, this study considers the volatility response to news, market disequilibrium and trading volume. The findings are thus useful for financial risk management.
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Rubén Ansola, Estrella Veguería, Javier Canales and Cristina Alonso
– This paper aims to show an evolutionary topology optimization procedure for the design of compliant electro-thermal mechanisms.
Abstract
Purpose
This paper aims to show an evolutionary topology optimization procedure for the design of compliant electro-thermal mechanisms.
Design/methodology/approach
The adopted methodology is based in the evolutionary structural optimization (ESO) method. This approach has been successfully applied by this group for compliant mechanisms optimization under directly applied input loads and simple thermal loads. This work proposes an extension of this procedure, based on an additive version of the method, to solve the more complicated case of electro-thermal actuators optimum design, based on Joule's resistive heating.
Findings
Examples solved for the design of plane compliant mechanisms are presented to check the validity of this technique. The designs obtained are compared favorably with results obtained by other authors to illustrate and validate the method, showing the viability of this technique for the optimization of compliant mechanisms under electro-thermal actuation.
Research limitations/implications
This investigation is based on and additive version of the evolutionary method. Since this approach does not have the capability to remove material it could be combined with the classic element rejection evolutionary method to overcome these deficiencies, developing an improved bi-directional algorithm, which should be analyzed and applied for these types of designs in future works.
Practical implications
Electro-thermal actuators have widespread use in MicroElectroMechanical Systems applications. Since these elements cannot be manufactured using typical assembly processes compliant mechanisms optimization play a crucial role for their successful design. The proposed methodology could help engineers to rapidly conceive complex and efficient actuators.
Social implications
The topology optimization procedure developed in this paper enables systematic design of these devices, which can result in a save of manufacturing time and cost.
Originality/value
Most applications of the ESO method have considered maximum stiffness structure design, and even if it has been successfully applied to some other optimum material distribution problems, electro-thermal actuators design has not been considered yet. This paper shows that this methodology could be useful also in the design of electro-thermal compliant mechanisms, and provides engineers with a very simple and practical alternative design tool.
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Rubén Ansola, Estrella Vegueria and Javier Canales
The purpose of this paper is to describe an element addition strategy for topology optimization of thermally actuated compliant mechanisms under uniform temperature fields.
Abstract
Purpose
The purpose of this paper is to describe an element addition strategy for topology optimization of thermally actuated compliant mechanisms under uniform temperature fields.
Design/methodology/approach
The proposed procedure is based on the evolutionary structural optimization (ESO) method. In previous works, this group of authors has successfully applied the ESO method for compliant mechanism optimization under directly applied input loads. The present paper progresses on this work line developing an extension of this procedure, based on an additive version of the method, to approach the more complicated case of thermal actuators.
Findings
The adopted method has been tested in several numerical applications and benchmark examples to illustrate and validate the approach, and designs obtained with this method are compared favorably with the analytical solutions and results derived by other authors using different optimization methods, showing the viability of this technique for uniformly heated actuators optimization.
Research limitations/implications
As a simple initial approach, this research considers only uniform heating of the system, while many thermal actuators are heated nonuniformly. Future works will be based on electrothermal actuation, and nonuniform Joule heating will be considered as well, which might lead to more elegant and efficient solutions.
Practical implications
Compliant micromechanisms that are responsible for movement play a crucial role in microelectromechanical systems (MEMS) design, which cannot be manufactured using typical assembly processes and may not make use of traditional hinges or bearings. The topology optimization method described in this paper enables the systematic design of these devices, which can result in reduced conception time and manufacturing cost.
Originality/value
The ESO method has been successfully applied to several optimum material distribution problems, but not for thermal compliant mechanisms. Even if most applications of this method have been oriented for maximum stiffness structure design, this paper shows that this computation method may be also useful in the design of thermal compliant mechanisms and provides engineers with a very simple and practical alternative design tool.
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Langnan Chen, Steven Li and Weibin Lin
The opening up of B-share markets to domestic investors in 2001 is a landmark event in the development of the Chinese stock markets. This chapter aims to assess the possible…
Abstract
The opening up of B-share markets to domestic investors in 2001 is a landmark event in the development of the Chinese stock markets. This chapter aims to assess the possible changes in the market mechanism associated with this important event. A VECM-DCC-MVGARCH model is employed to investigate the market integration process in Chinese stock markets around the opening up of the B-share market to domestic investors. Our empirical results reveal that the Chinese stock markets were segmented before the opening up whereas they were integrated to some extent in the long-run after the opening up of B-share markets. Moreover, it is also found that A-share markets played a dominant role on the information flows between A-share and B-share markets; the short-run information flows between A-share and B-share markets were more rapid after the opening up of B-share markets.
The purpose of this paper is to investigate whether existing capital structure target adjustment models are able to identify whether companies adjust their capital structures…
Abstract
Purpose
The purpose of this paper is to investigate whether existing capital structure target adjustment models are able to identify whether companies adjust their capital structures towards an (unobservable) target.
Design/methodology/approach
Existing capital structure target adjustment models are applied to a specific dataset by using different regression techniques (ordinary least square, fixed effect, Fama‐MacBeth, least square dummy variable “corrected”, SYS‐GMM).
Findings
Existing capital structure target adjustment models are not able to identify whether companies adjust their capital structures towards a target or not. They might indeed indicate target adjustment behaviour when companies' capital structures actually move away from their targets.
Research limitations/implications
As target adjustment behaviour is often used as support for the trade‐off and against the pecking order theory, the “horse race” between both theories seems still to be open.
Originality/value
This paper highlights some of the fallacies of existing capital structure target adjustment models and demonstrates that the results obtained by those models can be highly misleading.
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Jie Liu, Guilin Wen, Qixiang Qing, Fangyi Li and Yi Min Xie
This paper aims to tackle the challenge topic of continuum structural layout in the presence of random loads and to develop an efficient robust method.
Abstract
Purpose
This paper aims to tackle the challenge topic of continuum structural layout in the presence of random loads and to develop an efficient robust method.
Design/methodology/approach
An innovative robust topology optimization approach for continuum structures with random applied loads is reported. Simultaneous minimization of the expectation and the variance of the structural compliance is performed. Uncertain load vectors are dealt with by using additional uncertain pseudo random load vectors. The sensitivity information of the robust objective function is obtained approximately by using the Taylor expansion technique. The design problem is solved using bi-directional evolutionary structural optimization method with the derived sensitivity numbers.
Findings
The numerical examples show the significant topological changes of the robust solutions compared with the equivalent deterministic solutions.
Originality/value
A simple yet efficient robust topology optimization approach for continuum structures with random applied loads is developed. The computational time scales linearly with the number of applied loads with uncertainty, which is very efficient when compared with Monte Carlo-based optimization method.