The study of a dynamic dial-a-ride problem under time-dependent and stochastic environments

This paper studies a dynamic dial-a-ride problem bearing complex constraints on a time-dependent network. A flexible scheduling scheme is proposed to dynamically cope with different stochastic events, such as the travelling time fluctuation, new requests, absences of customers, vehicle breakdowns, cancellations of requests, traffic jams and so on. A fast heuristic is proposed to re-optimize the schedule when a new event occurs. This heuristic consists of a properly organized local search strategy and uses a secondary objective function to drive the search out of local optima. Intensive computational simulations were carried out to evaluate the performance of this scheduling scheme and the influence of different stochastic factors. The simulation results of different scenarios with different percentage of dynamic requests reveal that this scheduling scheme can generate high quality schedules and is capable of coping with various stochastic events.     

Damage detection in plates structures based on frequency shift surface curvature

This paper presents a novel damage detection method for plate structures based on the curvature of frequency shift surface (FSS). Unlike other commonly used vibration properties like mode shapes which have low accuracy in practice; this method uses the FSS curvature to improve the accuracy because the measurement of frequency gives better accuracy. Furthermore, it is found that the local damage will only cause local change on the FSS curvature which can be considered as abnormality because the FSS curvature of an intact plate is smooth according to the assumption that intact plate structures are often homogenous and smooth. To avoid the usage of prior knowledge of the health structure, the curve fitting technique based on local regression is adopted to simulate the FSS curvature for the intact state so that only the data from the damaged plate structure is required. Compared with traditional methods, this method is more sensitive and accurate.     

Determining charge transport pathways through single porphyrin molecules using scanning tunneling microscopy break junctions

Charge transport in a porphyrin with four identical pyridyl substituents, 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP), was investigated using the scanning tunneling microscopy break junction method. To determine the dominant pathway, we studied two structurally similar porphyrins, o-DPyP and p-DPyP. Our experiments reveal that charge transport through TPyP in a break junction configuration does not follow the traditional assumption, i.e., the shortest path between the neighboring side groups. Instead, the charge transport pathway was dominated by the farthest anchoring groups. Furthermore, these single molecule experiments can distinguish between the two structural isomers, which is important in molecular discrimination, porphyrin chemistry, and molecular electronics.     

Preparation of dually, pH- and thermo-responsive nanocapsules in inverse miniemulsion

pH- and thermo-sensitive nanocapsules were successfully synthesized via inverse miniemulsion copolymerization of N-isopropyl acrylamide (NIPAM), N,N'-methylene bisacrylamide (MBA), and a functional monomer, 4-vinyl pyridine (4-VP). The size and size distribution of nanocapsules were measured by dynamic light scattering (DLS). The particle morphology was observed by transmission electron microscopy (TEM). The final morphology of particles was strongly influenced by the hydrophobicity of functional monomers. The use of a hydrophilic functional monomer, acrylic acid, led to the formation of solid particles, while the use of the more hydrophobic functional monomer, 4-VP, resulted in the formation of nanocapsules. The particle morphology, size, and size distribution were investigated in terms of the content of 4-VP, MBA, and the type and content of surfactant. The pH- and thermo-sensitivities were characterized by measuring the size variation with the change of temperature and pH. The organic-inorganic nanocapsules were prepared by coating a layer of silica particles on the surface of the sensitive nanocapsules.     

普通物理利用逐章研讨模式,培养学生思考能力

为了利用有限的教师资源,提高学生对普通物理学习的参与度,培养学生的思考能力,提出了一种逐章研讨的教学模式.在每章课堂教学内容完成后,要求学生结合该章内容,利用该章的物理原理讲解一个身边可以找到的实例,或者利用该章知识提出一种新设计、新发明.经过两个大班的尝试,学生们积极参与,不同学科背景的学生表现了不同的特点,明显增强了学生对物理课程的兴趣.经过尝试,学生在课堂学习时更加投入,加强了对物理理论的思考和理解.     

基于哈特曼-夏克波前传感器的模糊图像复原方法

离焦模糊图像的清晰度较低,因此必须对其进行复原。传统方法通常采用圆盘或高斯函数来近似离焦造成的点扩散函数,复原效果不够理想。为此,提出利用哈特曼-夏克波前传感器探测离焦波前,根据所得波前计算光学系统的点扩散函数,并采用Richardson-Lucy算法对模糊图像进行复原。搭建了实验用的光学系统,采集了离焦模糊图像以及相应的波前信息,获得了清晰的复原图像,并利用客观图像评价方法对退化图像和复原图像进行了评价,同时与传统方法得到的复原图像进行了比较。实验结果表明,该方法能精确重建点扩散函数,有效提高图像的质量。     

数字图象清晰度评价函数研究

分析了梯度函数、频谱函数和熵函数在自动对焦技术中的作用,并研究了评价函数的性能.实验表明,梯度函数具有运算速度快的优点,适用于需要实时成象的场合;而频谱函数具有灵敏度高、曲线尖锐的特点,能够满足高精度的要求.     

Automatic tailoring and transplanting: a practical method that makes virtual screening more useful

Docking-based virtual screening of large compound libraries has been widely applied to lead discovery in structure-based drug design. However, subsequent lead optimizations often rely on other types of computational methods, such as de novo design methods. We have developed an automatic method, namely automatic tailoring and transplanting (AutoT&T), which can effectively utilize the outcomes of virtual screening in lead optimization. This method detects suitable fragments on virtual screening hits and then transplants them onto a lead compound to generate new ligand molecules. Binding affinities, synthetic feasibilities, and drug-likeness properties are considered in the selection of final designs. In this study, our AutoT&T program was tested on three different target proteins, including p38 MAP kinase, PPAR-α, and Mcl-1. In the first two cases, AutoT&T was able to produce molecules identical or similar to known inhibitors with better potency than the given lead compound. In the third case, we demonstrated how to apply AutoT&T to design novel ligand molecules from scratch. Compared to the solutions generated by other two de novo design methods, i.e., LUDI and EA-Inventor, the solutions generated by AutoT&T were structurally more diverse and more promising in terms of binding scores in all three cases. AutoT&T also completed the assigned jobs more efficiently than LUDI and EA-Inventor by several folds. Our AutoT&T method has certain technical advantages over de novo design methods. Importantly, it expands the application of virtual screening from lead discovery to lead optimization and thus may serve as a valuable tool for many researchers.     

敲击扫描式梁式结构损伤检测方法

受到啄木鸟敲击树干找虫子等敲击现象的启发,论文针对梁式结构提出了一种敲击扫描式损伤检测方法.基于对敲击扫描过程的理论探讨,我们得到了该方法的灵敏度表达式,从而为该方法找到了可靠的理论基础.数值模拟和简单实验表明,该方法不但简单易行,而且在有干扰的环境下也可以有效地检测出结构的损伤.     

大型空间结构的热-动力学耦合问题及其有限元分析

论文对辐射换热条件下闭口薄壁杆件与单枝开口薄壁杆件的瞬态温度场问题,提出了一种一维傅立叶温度有限元,克服了传统一维温度单元只能计算薄壁杆截面平均温度的缺点,通过增加结点摄动温度自由度的方法,该一维单元能计算杆截面的温度分布.在此一维温度单元与梁位移单元相协调的基础上,进一步发展了大型空间结构热诱发振动稳定性判据与热颤振响应有限元计算方法.对于柔性空间结构发展了考虑几何非线性的热-结构动力学耦合有限元计算方法,成功地对这类结构的热动力屈曲问题进行了数值模拟.