不完备系统多准则决策的云PDR方法

针对多准则决策问题的意义以及经典粗糙集方法在不完备系统方案排序问题中的不足,在前人基于概率优势关系(PDR)排序方法的基础上,结合云理论提出了基于云概率优势关系的不完备系统多准则决策方法,即云PDR排序法。将期望、熵、超熵等参数引入PDR方法,充分考虑了决策的模糊性、波动性和随机性,评价过程和结果更加客观全面。以煤炭资源型城市为例进行应用研究,获得其中各城市发展水平及其波动情况的排序,并通过与其他方法结果的比较验证了本文方法的优势与有效性。     

打车软件混合随机均衡模型时间可靠性研究*

为了探究打车软件出现后对乘客打车行为的影响,揭示是否使用打车软件对乘客候车时间长短的变化规律,基于路网混合随机均衡模型理论,在考虑打车软件对出租车司机搜索行为影响和随机变化的OD对需求条件下,构建基于弹性需求的打车软件随机用户均衡模型;然后结合乘客等车、司机空驶时间和可靠性计算模型,引入连续平均（MSA）算法和随机路径流量分配（Dial）算法进行求解;最后通过算例验证了所建模型和算法的有效性。研究结果表明不同需求弹性下、是否使用打车软件对会乘客候车时间及候车时间可靠性产生明显的差异。     

基于高斯曲率的蛋白质嵌入到对称低温电镜密度图的方法

为了解决低温电镜三维重构得到的对称生物大分子三维结构分辨率低的问题,提出一种新的基于高斯曲率计算的自动化的方法.通过计算生物分子表面的高斯曲率和优化模型等数学方法把单个蛋白质或其他亚基嵌入到对称的低温电镜密度图中,通过计算蛋白质和对称低温电镜密度图的离散高斯曲率来定义特征点,对低温电镜密度图,利用K-means分类来定义相应的特征点.用均方根偏差值、曲率的交叉关联系数和优化模型来匹配对应的特征点,用最小二乘法计算旋转矩阵和平移向量.最后,用同样的方法把其他部分也嵌入到对称的生物大分子中.给出了椭球体x~2+y~2/2+z~2/3=1的解析高斯曲率和数值计算的高斯曲率的比较、蛋白质1DOR的高斯曲率计算和特征点的计算结果、蛋白质1DOR和2REC的分子装配结果可视化.数值实验结果表明所提出来的一系列的方法是准确和有效的.     

基于Zigbee技术的船舶机舱监控系统的设计

针对船舶机舱监控系统中的布线复杂、通讯盲区等问题,以机舱主要电气设备的温度监测为研究对象,提出和设计基于ZigBee技术以CC2430为核心的无线监控系统,在ZigBee协议的基础上完成软件的设计.     

Alignment control for a long span urban rail-transit cable-stayed bridge considering dynamic train loads

In this paper, bridge alignment control with considering dynamic train loads was experimentally and theoretically investigated. Analytical process of bridge dynamics and the self-adaptive Kalman filter bridge alignment control method with considering the dynamic train loads were briefly introduced. The static measurement, the dynamic test, the field alignment measurement as well as the finite element analysis (FEA) of the second longest rail transit cable-stayed bridge in the world were carried out. Based on the results, the train dynamic load effect on the bridge alignment was obtained quantitatively. Subsequently, alignment control of the rail transit bridge with considering this effect using a self-adaptive Kalman filter method was analyzed. The results show that: (a) the dynamic train loads have effects on alignment control of the bridge and therefore cannot be neglected; (b) the self-adaptive Kalman filter method is applicable and reliable for alignment control of bridges during construction. The analytical method and whole process contribute to develop a related specification and further engineering applications.     

Thermal analysis of a solar parabolic trough receiver tube with porous insert optimized by coupling genetic algorithm and CFD

In this paper, the heat transfer enhancement in a solar parabolic trough receiver tube with porous insert and non-uniform heat flux condition was investigated. A new optimization method, which couples genetic algorithm (GA) and computational fluid dynamics (CFD) based on Socket communication, was proposed to optimize the configuration of porous insert. After the acquisition of the optimal porous inserts, some performance evaluation criterions such as synergy angle, entransy dissipation and exergy loss were introduced to discuss the heat transfer performance of the enhanced receiver tubes (ERTs) with optimal and referenced porous inserts. The results showed that, for a large range of properties of porous insert (including porosity and thermal conductivity) and Reynolds number, the heat-transfer performance of ERT with porous insert optimized by GA is always higher than that of the referenced ERTs. Better heat-transfer performance can further improve the solar-to-thermal energy conversion efficiency and mechanical property of the solar parabolic trough receiver. When some porous materials with high thermal conductivity are adopted, ERT can simultaneously obtain perfect thermal and thermo-hydraulic performance with using the same optimized porous insert, which cannot be achieved by using the referenced porous insert. In the view of those introduced evaluation criterions, using the optimized porous insert can obtain better synergy performance and lesser irreversibility of heat transfer than using the referenced porous insert. Entransy dissipation per unit energy transferred and exergy loss rate have equivalent effects on the evaluation of irreversibility of heat transfer process. These evaluation criterions can be used as optimization goals for enhancing the comprehensive performance of the solar parabolic trough receiver.     

High-speed photographic observation of collapse of two cavitation bubbles

Cavitation as a hydrodynamic phenomenon exists widely in water conservancy, shipbuilding, chemical and many other industries. Previous cavitation bubble dynamic studies mainly focused on single cavitation bubbles and their interaction with the wall. This paper studies the interaction between two cavitation bubbles under conditions with or without a wall. The results show that if the inception of two cavitation bubbles is not synchronized, the cavitation bubble of early inception collapse backwards the cavitation bubble of later inception; if the inception of two cavitation bubbles is synchronized, the two bubbles collapse towards each other; if a wall exists nearby, no matter whether the line connecting the centers of the two cavitation bubbles is vertical or parallel to the wall, the two cavitation bubbles collapse towards each other and then gradually merge, and the merged collapse body quickly moves to the wall. It is suggested that, as the number of cavitation bubbles increases, the cavitation erosion effect is not simply increased proportionally. Instead, mutual inhibitory effect may be demonstrated.     

An experimental investigation on acoustic emission characteristics of sandstone rockburst with different moisture contents

Rockburst occurred frequently during deep mining in China. The mechanism of rockburst is very complicated and related to many factors. In order to investigate the influence of moisture contents of rockmass on rockburst, we conducted a series of laboratory rockburst experiments of sandstone under three different moisture contents by the Modified True-Triaxial Apparatus (MTTA), in which the acoustic emission (AE) system was employed to monitor the internal damage of rock mass. A high-speed video camera was utilized to record the detail of rockburst. Based on the experimental results, the AE characteristics, such as AE count, AE energy, and AE frequency, were analyzed. The rockburst process, type, and indensity under different moisture contents were discussed. The research results show that with the increase of moisture contents, rock strength was soften, the elastic and the cumulative damage of the rock were reduced, resulting in a gradual decrease in AE cumulative counts and cumulative energy over the course of rockburst. This study provides an experimental basis and reference for better understanding to the rockburst mechanism and control.     

Taming complexity in nonlinear dynamical systems by recycled signal

In this paper, the impacts of the recycled signal on the dynamic complexity have been studied theoretically and numerically in a prototypical nonlinear dynamical system. The Melnikov theory is employed to determine the critical boundary, and the statistical complexity measure (SCM) is defined and calculated to quantify the dynamic complexity. It has been found that one can switch the dynamics from the periodic motion to a chaotic one or suppress the chaotic behavior to a periodic one, merely via adjusting the time delay or the amplitude of the recycled signal, therefore, providing a candidate to tame the dynamic complexity in nonlinear dynamical systems.     

Analytical investigation on thermal-induced warpage behavior of ultrathin chip-on-flex (UTCOF) assembly

The serious warpage issues of ultrathin chip-on-flex (UTCOF) assembly induced by mismatched thermal stresses have greatly affected the mechanical stability and reliability of emerging ultrathin chip packaging technology. Currently, a theoretical prediction as a convenient and straightforward approach is still lacked for describing effectively the thermal-mechanical behavior of UTCOF during the adhesive curing and cooling process. In consideration of the adhesive thickness approximating to ultrathin chip and flexible substrate thickness, we develop a layerwise-model of ultrathin chip-adhesive-flex structure under plain strain condition, where the behavior of thick adhesive bonding can be described precisely through increasing the subdivided mathematical plies. Further, the analytical results show that the concave and convex forms of ultrathin chip warpage yield at the end of the curing and cooling process respectively. Meanwhile, the effects of its structure dimensions and material properties are also revealed for discussing a way to relieve the extent of ultrathin chip warpage. Additionally, in order to verify the validity of the theoretical prediction, we also introduce the corresponding numerical technique and experimental method. These results suggest that a kind of rigid and ultrathin flexible substrate such as metal foil should be adopted for small warpage of ultrathin assembly.