Dynamic test method for determining the thermal performances of heat pipes

With a view toward shortening the necessary time to examine the thermal performances of heat pipes, a novel dynamic test method is originated and compared to the conventional steady-states test. A set of dynamic parameters of thermal performances of heat pipes is ideated from the observed transient phenomenon. Bending angles, fill ratios, and shapes of heat pipes are investigated in order to study their influences on the thermal performances of heat pipes for both steady-state and dynamic tests. A model based on the investigated dynamic test is established to explain the experimental results. Experimental results demonstrate that deformation of heat pipes would damage the thermal performances of heat pipes most significantly. Larger fill ratios would increase the operation limitations but also lead to less sensitive temperature responses of heat pipes. The parameters and the influences of factors between the steady-state test and the dynamic test are found to be remarkably analogous. As a consequence, the dynamic test can be adopted instead of the steady-state test to determine the thermal performance of heat pipes when high efficiency is of prior concern.     

The use of a grey-based Taguchi method for optimizing multi-response simulation problems

Simulation modelling is a widely accepted tool in system design and analysis, particularly when the system or environment has stochastic and nonlinear behaviour. However, it does not provide a method for optimization. In general, problems contain more than one response, which are often in conflict with each other. This article proposes a grey-based Taguchi method to solve the multi-response simulation problem. The grey-based Taguchi method is based on the optimizing procedure of the Taguchi method, and adopts grey relational analysis (GRA) to transfer multi-response problems into single-response problems. A practical case study from an integrated-circuit packaging company illustrates that differences in performance of the proposed grey-based Taguchi method and other methods found in the literature were not significant. The grey-based Taguchi method thus provides a new option when solving a multi-response simulation-optimization problem.     

The Aso-Bridge coseismic landslide: a numerical investigation of failure and runout behavior using finite and discrete element methods

The complex coseismic process of the Aso-Bridge landslide during the main shock of the 2016 Kumamoto Earthquake was investigated. Finite element analysis and discrete element analysis considering vertical seismic accelerations (VSA) were conducted to explore the salient features of the prefailure mechanism and postfailure kinematic process of the coseismic landslide associated with the initiation time and kinematic runout behavior, respectively. Two seismic input conditions, one involving only horizontal seismic accelerations (HSA), and the other accounting for both HSA and VSA, were used to assess the influence of VSA from the prefailure to postfailure regimes. First, satisfactory agreement between the study and the published results in terms of landslide initiation time was obtained. As revealed by the rapid change of source displacement (RCSD), VSA did not alter landslide initiation time; however, it significantly increased the RCSD approximately 2-fold, which provided a clear initiation time. At landslide initiation, the estimated average velocities in a vertical direction increased approximately 16-fold (from −0.011 to −0.174 m/s) by accounting for VSA. Second, the results suggested that VSA had a trivial influence on runout behavior in the postfailure regime, given that such behavior was dominated by the collision and free fall during the sliding as well as the terrain features. With an average velocity of 21.34 m/s, the sliding source ultimately reached the riverbank within 21 s. The paper demonstrates that a combination of FEA and DEA can be used to investigate the coseismic process of the Aso-Bridge landslide and lead to satisfactory agreement with the event. Our comprehensive analysis provides insight into the role of VSA in earthquake-induced landslides.

     

双向选择排序算法

为丰富O(n²)阶排序算法的种类,以更好地服务于教学科研和日常应用,提出了一种新的排序算法-双向选择排序算法.通过数学方法分析得知:该算法的时间复杂度为O(n²),空间复杂度为O(1).通过实验对比得知:在相同条件下,该算法的运行时间平均为冒泡排序的27%、简单选择排序的62%、直接插入排序的88%.     

液相前驱体浸渗技术调控陶瓷材料组成和特性的研究进展

液相前驱体浸渗是一种能够引入含量和分布可控的外来组元的工艺. 本文综述了浸渗技术的研究情况, 着重从传质机理研究使用的坯体和前驱体的种类与特性方面, 分析了该工艺的特点, 揭示了如何通过控制浸渗工艺参数实现对最终材料成份与性能的调控. 已有的研究表明, 作为一种普适性的方法, 浸渗工艺有望推广到其它材料体系中去, 而且在实现块体均匀少量掺杂、表面强化、梯度与功能材料的制备方面具有独特的优势及发展前景.     

Relaxed observer-based controller design method of discrete-time multiplicative noised LPV systems via an extended projective lemma

ABSTRACT

The aim of this paper is to discuss a relaxed observer-based control problem of multiplicative noised Linear Parameter Varying (LPV) systems with unmeasurable states. For discussing the problem, positive definite matrices without neglecting any element are employed to construct a novel parameter-dependent Lyapunov function. Based on the Lyapunov function, some relaxed sufficient conditions are derived to hold the freedom in searching feasible solutions. Furthermore, an extended projective lemma is developed to convert those conditions into Linear Matrix Inequality (LMI) form. Solving these LMI conditions, controller gain and observer gain can be simultaneously obtained in one-step procedure via using convex optimization algorithm. Therefore, an observer-based controller can be established to guarantee the asymptotical stability of the multiplicative noised LPV systems in the sense of mean square. At last, two numerical examples are used to show effectiveness and applicability of the proposed design method.     

Optimization method for the inverse problem of reconstructing the source term in a parabolic equation

This work investigates the inverse problem of reconstructing a spacewise dependent heat source in the parabolic heat equation using a final temperature measurement. Such problem has important application in a large field of applied science. On the basis of the optimal control framework, the existence and necessary condition of the minimizer for the cost functional are established. The global uniqueness and stability of the minimizer are deduced from the necessary condition. The Landweber iteration algorithm is applied to the inverse problem and some numerical results are presented for various typical test examples.     

Reconstruction of a space and time dependent heat source from finite measurement data

This paper deals with an inverse problem of determining a heat source function in heat conduction equations when the solution is known in a discrete point set. Being different from other ordinary inverse source problems which are often dependent on only one variable, the unknown coefficient in this paper not only depends on the space variable x, but also depends on the time t. On the basis of the optimal control framework, the inverse problem is transformed into an optimization problem. The existence and necessary condition of the minimizer for the cost functional are established. The convergence of the minimizer as the mesh parameters tend to zero is also proved. The conjugate gradient method is applied to the inverse problem and some typical numerical experiments are performed in the paper. The numerical results show that the proposed method is stable and the unknown heat source is recovered very well.