热电材料中的晶格热导率

随着可再生能源及能源转换技术的快速发展, 热电材料在发电及制冷领域的应用前景受到越来越广泛的关注。发展具有高热电优值材料的重要性日益突出, 如何获得低晶格热导率是热电材料的研究重点之一。本文阐述了热容、声速及弛豫时间对晶格热导率的影响, 介绍了本征低热导率热电材料所具有的典型特征, 如强非谐性、弱化学键、本征共振散射及复杂晶胞结构等, 并分析了通过多尺度声子散射降低已有热电材料晶格热导率的方法, 其中包括点缺陷散射、位错散射、晶界散射、共振散射、电声散射等多种散射机制。此外, 总结了几种预测材料最小晶格热导率的理论模型, 对快速筛选具有低晶格热导率的热电材料具有一定的理论指导意义。最后, 展望了如何获得低热导率热电材料的有效途径。     

基于深度学习的fMRI数据分析在偏头痛研究中的应用

偏头痛作为一种常见的疾病,发病概率高,致病机理尚不明确,并且临床缺乏有效的诊断手段.运用功能核磁共振成像技术获取被试脑功能数据,然后通过深度学习中自动编码器,自动提取数据特征,并结合各种机器学习算法,预测偏头痛,为临床诊断提供参考依据.用深度学习提取数据特征,训练分类器,能达到更好的分类效果.深度学习算法可以在传统模板获取初步特征之后,进一步提取更加精细有效的特征,在预测偏头痛上获得更好的分类性能.     

Structures and Properties of New Cadmium(II) and Copper(II) Metal–Organic Frameworks Based on Flexible Bridged 1,4-bi(1H-imidazol-1-yl)butane Ligand

Two new metal–organic frameworks (MOFs) based on cadmium(II) ions, 1,2-benzenedicarboxylic acid (BDC), flexible ligand 1,4-bi(1H-imidazol-1-yl)butane (BIIM), coordinated water molecules, [(BIIM)(BDC)(H₂O)Cd]_3n (1) and copper(II) ions, BIIM, coordinated water, free thiophene-2,5-dicarboxylate (TDC), free water, {[(BIIM)₄(H₂O)₄Cu₂]·(TDC)₂·(H₂O)₁₂}_n (2) are prepared and characterized by X-ray diffraction, thermal gravimetric analysis (TGA), infrared (IR) spectrum and the photoluminescence property for complex (1). The X-ray diffraction analysis reveals that the structures of complexes 1 and 2 are 2D structures through the C–H···π stacking interactions (for 1) and the BIIM bridging connections (for 2). The IR spectrum for 1 and 2 are presented in the paper, for 1, the strong peaks at 1399 and 1573 cm^?1 are owing to the carboxylic CO₂ ^? symmetry and asymmetry stretching vibrations of BDC. The features of the IR spectrum are consistent with the single crystal structures. The TGA reveal the water is the first lost material from complex, then the ligands removed, and finally the residues of these two complexes are the metal oxide.     

一种合成孔径雷达用的光学处理器

本文介绍由三个透镜组成的对合成孔径雷达数据进行现场处理的光学处理器。它具有轻便、灵活、容易调整、适应范围大和便于装拆的特点。     

Tribological behaviours of an ion sulphurisation layer on steels

A sulphide layer with a certain thickness was made on the surface of 1045 and 52100 steels by means of a low temperature ion sulphurisation process. Tribological behaviours of the sulphide layers were investigated on a SRV reciprocating wear tester under dry and paraffin oil lubrication conditions. SEM equipped with EDX was used to analyse the morphologies and compositions of wear scars and wear debris. Sulphide layers showed remarkable friction-reducing effects and obvious wear-resistance. With the increase in thickness of the sulphide layer, its operational period was extended, but its friction coefficient was unchanged greatly. Under the same experimental conditions, the operational period of the sulphide layer on 52100 steel was longer than that on 1045 steel, and the wear-resistance of the former was better. The wear mechanism of the sulphurised surface is discussed.     

固体氧化物燃料电池力学性能和形变行为研究

通过流延成型、丝网印刷和共烧结法成功制备了阳极支撑的平板式固体氧化物燃料电池(SOFCs)。采用陶瓷样品同轴环施力方式和双扭法测试单电池的抗弯强度和断裂韧性分别为156.69 MPa与2.51 MPa•m^1/2。当阳极支撑体由陶瓷(NiO/YSZ)还原为金属陶瓷(Ni/YSZ), 其抗弯强度和断裂韧性分别为104.48 MPa与3.95 MPa•m^1/2。同时电池的弯曲变形测试表明: 单电池经过阳极还原后弯曲变形程度变大, 平整化压力从电池阳极还原前的108 N增加至184 N, 而电池抵抗破裂能力增强。本研究显示, 随着阳极支撑体还原后单电池的断裂韧性显著提高, 将有效减缓其弯曲变形所引起的不利影响, 改善单电池的综合力学性能。     

基于改进势场栅格法的清洁机器人路径规划算法研究

针对人工势场法中机器人在障碍物附近震荡而无法到达目标点、存在陷阱区域、临近的障碍物之间不能发现路径等问题,提出了一种改进的势场栅格算法.结合牛耕式全覆盖路径规划算法使机器人在已知环境势场模型中快速静态规划出全局最优清扫路径,通过激光雷达与势场合力运算使其具备无碰撞的避障能力.在实际系统的实验验证结果表明,本算法能够使清洁机器人以更短路径遍历环境及增强避障能力,提高了清洁机器人的安全性与工作效率,具有实际应用价值.     

基于HALCON的双目视觉系统标定

论文对现有的双目视觉标定方法进行论述,阐述了双目视觉系统的原理,深入的介绍了双目视觉系统标定的原理,方法。此外,针对如何使用HALCON软件进行双目标定进行了详细的论述,分析了面阵摄像机的标定过程,该方法简单易行,充分发挥了HALCON的函数库功能,提高了标定精度和计算速度,而且具有良好的跨平台移植性。     

The fretting wear-resistant properties of steel with ion-sulphuration+shop-peening and shot-peening+ion-sulphuration duplex treatments

The fretting wear-resistant properties of ion-sulphuration+shot-peening and shot-peening+ion-sulphuration duplex-treated coatings on 1045 steel substrate were investigated. The results show that the fretting wear-resistance of shot-peening+ion-sulphuration coating was better than that of the ion-sulphuration+shot-peening coating. The fretting wear process of the duplex-treated coatings in the gross slip regime could be described as the sulphuration coatings playing an important lubricating role in the incubation period. Then a series of changes took place continuously and alternatively on the contact surfaces, including adhesion, material transfer, oxidation, delamination of the oxide layer and degradation. In the last stage, the trapping, pulverization and elimination of debris restrained the adhesion between the contact surfaces and led to a decrease in the friction coefficient.     

医疗大数据隐私保护多关键词范围搜索方案

随着医疗信息系统的急速发展,基于医疗云的信息系统将大量电子健康记录（EHRs）存储在医疗云系统中,利用医疗云强大的存储能力和计算能力对EHRs数据进行安全与统一的管理.尽管传统加密机制可以保证医疗数据在半诚实云服务器中的机密性,但对加密后的EHRs数据执行安全、快速、有效的范围搜索,仍是一个有待解决的关键问题.提出一种支持多关键词范围搜索的可搜索加密方案：利用向量积保持加密机制实现复杂查询结构的可搜索加密,可支持连接关键词查询、范围查询以及通配符的查询;通过随机化构建搜索索引和搜索陷门,实现搜索模式隐藏,达到搜索语句的隐私保护;采用矩阵哈达马积缩小所需密钥矩阵的维度.理论分析和实验结果表明：该方案在达到医疗数据隐私保证的同时,对用户的检索策略也进行了有效的隐私性保护,有效提高了检索效率,降低了创建索引及陷门所用时间,实现了多用户多文件下医疗数据的范围搜索能力.