Charge Transportation and Chirality in Liquid Crystalline Helical Network Phases of Achiral BTBT-Derived Polycatenar Molecules

First examples of multichain (polycatenar) compounds, based on the π-conjugated [1]benzothieno[3,2-b]benzothiophene unit are designed, synthesized, and their soft self-assembly and charge carrier mobility are investigated. These compounds, terminated by the new fan-shaped 2-brominated 3,4,5-trialkoxybenzoate moiety, form bicontinuous cubic liquid crystalline (LC) phases with helical network structure over extremely wide temperature ranges (>200 K), including ambient temperature. Compounds with short chains show an achiral cubic phase with the double network, which upon increasing the chain length, is at first replaced by a tetragonal 3D phase and then by a mirror symmetry is broken triple network cubic phase. In the networks, the capability of bypassing defects provides enhanced charge carrier mobility compared to imperfectly aligned columnar phases, and the charge transportation is non-dispersive, as only rarely observed for LC materials. At the transition to a semicrystalline helical network phase, the conductivity is further enhanced by almost one order of magnitude. In addition, a mirror symmetry broken isotropic liquid phase is formed beside the 3D phases, which upon chain elongation is removed and replaced by a hexagonal columnar LC phase.     

Source time reversal (STR) method for linear elasticity

We study the problem of source reconstruction for a linear elasticity problem applied to seismicity induced by mining. We assume the source is written as a variable separable function $\mathit{f}\left(\mathit{x}\right)g\left(t\right)$. We first present a simple proof a local decay result for elasticity in the case of homogeneous media. We then extend the source time reversal method, originally developed for acoustic waves, to an elastic system of waves. Additionally, we present a fast reconstruction implementation for large data sets. This is especially useful in the elastic case, in which the numerical cost is higher than in fluid acoustics. We complement this work with several 2D and 3D numerical experiments and an analysis of the results.     

镜面杂质与水汽吸放对露点仪影响的实验研究

显微成像露点仪在研制和测试过程中发现镜面杂质和内腔材质吸放水汽等影响测量精度的问题。针对镜面杂质对显微成像露点仪测量的影响开展了镜面图像特征的实验研究，结果表明：镜面杂质点处露珠凝结具有优先性，且反复凝结消散后镜面出现杂质沉降现象。针对水汽吸放对显微成像露点仪的影响开展了水汽释放与吸附效应的实验研究，结果表明：当温度发生变化时，显微成像露点仪感应舱内壁氧化铝材质存在释放（或吸附）水汽现象，使得显微成像露点仪测量值偏大（或偏小）。研究结果为露点仪在功能设置及镜面与腔体材料选择方面提供了参考。     

Principle of a two-output-difference interferometer for removing the most important interference distortions

This paper presents a two-output-difference interferometer for removing the most important interference distortions caused by nonlinear detectors. These distortions can be removed not only because the resulting interferogram is composed of the difference between the signals of the two detectors, but also because the modulated signals at each output have the same amplitude and opposite phases. Due to the use of two corner-cube mirrors fixed as a single moving element, the tilt and shearing problem will disappear. The effect of the corner-cube mirror deviation angle and the plane mirror tilt angle are investigated in detail, and the formulas of their tolerance are derived by means of modulation depth and phase error. The advantage of the interferometer enables it to be suitable for Fourier transform spectrometers.     

Structural parameter design method for a fast-steering mirror based on a closed-loop bandwidth

When a fast-steering mirror (FSM) system is designed, satisfying the performance requirements before fabrication and assembly is vital. This study proposes a structural parameter design approach for an FSM system based on the quantitative analysis of the required closed-loop bandwidth. First, the open-loop transfer function of the FSM system is derived. In accordance with the transfer function, the notch filter and proportional-integral (PI) feedback controller are designed as a closed-loop controller. The gains of the PI controller are determined by maximizing the closed-loop bandwidth while ensuring the robustness of the system. Then, the two unknown variables of rotational radius and stiffness in the open-loop transfer function are optimized, considering the bandwidth as a constraint condition. Finally, the structural parameters of the stage are determined on the basis of the optimized results of rotational radius and stiffness. Simulations are conducted to verify the theoretical analysis. A prototype of the FSM system is fabricated, and corresponding experimental tests are conducted. Experimental results indicate that the bandwidth of the proposed FSM system is 117.6 Hz, which satisfies the minimum bandwidth requirement of 100 Hz.     

多孔硅基微型 Bragg 光学传感器的理论和应用研究

对多孔硅基微型光学传感器的可制备性进行了理论分析,说明只要选择合适的腐蚀条件,采用交替改变电流密度的方法就可以得到折射率随深度交替变化的多层多孔硅结构,即 Bragg 反射镜,同时可实现了反射谱峰位可调。提出了Bragg 反射镜的理论模型,对其布拉格中心波长,半峰全宽以及光强反射率进行了理论计算,得出了高低折射率之比、层数与光强反射率之间的关系,并对实际情况进行了说明。最后,简单介绍了 Bragg 反射镜在气体/液体传感器及光学微腔中的应用,有一定的应用价值。     

基于影像源法的基坑开挖引起的土体水平位移预测

基坑开挖将使土体产生附加水平位移,过大的水平位移会使邻近地下结构物受到破坏。基于影像源法,并充分发挥基坑围护结构易于实测的优势,推导了在基坑开挖下的坑外土体水平位移半解析式,分析中,通过定义土体的不均匀收敛系数,考虑了当前研究中大都忽略的土体收敛非均匀性,与实际情况更接近。同工程实测数据的对比验证了所提方法的准确性。进一步参数分析表明:不考虑土体收敛非均匀性的坑外土体水平位移计算值同实测相比,会低估上部土体水平位移,高估下部土体水平位移,因而同实测出现一定偏差,且当土体愈靠近基坑,偏差愈明显,可见考虑土体的非均匀收敛愈有必要。计算发现,当不均匀系数介于3～6时,计算结果同实测吻合较好。本文研究成果可为预测基坑开挖诱发土体水平位移提供一种新的探究思路。     

群井降水的实用计算方法

基坑开挖或施行人工挖孔桩常常需要进行人工降水。对于群井降水问题，由于存在着很多的渗流急变区，常规的数值解法费工耗时。通过应用镜像叠加法改造渗流场的边界条件，推导任意层地基在任意矩形平面边界条件下群井降水近似解的计算通式，设计通用程序，为解决工程问题提供实用的快速计算方法。     

YG8材料ELID磨削过程中法向磨削力的研究

在线电解修整(Electrolytic In-Process Dressing,ELID)磨削方法由于其高效的镜面磨削效率而被广泛应用于硬、脆性材料的镜面磨削加工。在精密平面磨床上加装喷嘴电解ELID磨削系统,进行了硬质合金材料YG8的ELID磨削试验研究。实验分析了磨削力与输出电压、脉冲频率、脉冲电流占空比、砂轮转速、工作台进给速度及磨削深度等ELID磨削工艺参数变化的影响关系。同时,在相同的磨削参数下,对ELID磨削和普通磨削条件下的磨削力进行对比分析。试验结果表明:ELID磨削能明显降低磨削力,与普通磨削相比较,能更好地实现YG8的超精密磨削加工。     

机载小型化快速反射镜用微位移测量传感器设计

为了实现机载小型化FSM的闭环控制,设计了一款小体积、高精度、高环境适应性的微位移测量传感器。首先根据位移传感器的技术原理和机载FSM的应用需求,提出了微位移测量传感器的主要设计指标。然后,分别对微位移测量传感器的发光元件、密珠滑轨、测量光栅和接收元件等进行了详细设计与选择。其中,高精度密珠滑轨的采用不仅减小了测量过程中的附加阻力,而且使光栅副的运动更加精准;光栅副通光窗口的引入、独特零件编码的设计、裂相法信号提取方式的采用,保证了微位移测量传感器的高低温性能。最后,针对微位移测量传感器在机载小型化FSM上的应用效果进行了理论分析与实验检测。结果显示:机载小型化FSM的方位指向误差不超过3.4″,俯仰指向误差不超过3.8″,证明了专用型微位移测量传感器高精度、高分辨力和高响应速度的技术特点,满足机载小型化FSM的应用需求。