压电驱动器发热测量和幅值误差补偿研究

本文用一种新的方法量化了压电驱动器的发热问题,并分析了发热对压电驱动器运动幅值的影响,实验研究了产生发热问题的原因:驱动频率、驱动电压幅值、压电驱动器的体积表面积比、负载,实验表明电流的峰峰值是压电驱动器温度有效的测量指标,通过电流测量实现压电驱动器的过热保护,补偿由于发热引起的驱动器振动幅值变化,补偿后的定位精度可以提高近三分之二。     

家庭服务机器人现状与展望

家庭服务机器人具有辅助人类从事家务劳动、提高人们居家生活质量等优势,已经得到千家万户的认可,逐步成为人们日常生活的重要组成部分.根据家庭服务机器人的智能化程度和用途将家庭服务机器人分为初级小家电类机器人、幼儿教育娱乐类机器人、人机互动式机器人.依据家庭服务机器人的功能特征分析其研究现状,并且分析3类机器人所应用的关键技...     

Rational Design of Metal Oxide-Based Heterostructure for Efficient Photocatalytic and Photoelectrochemical Systems

Solar-driven photo-to-chemical conversion is an interesting approach for energy harvesting and storage with high sustainability. To achieve high photo-to-chemical conversion efficiency, it is important to develop cost-effective and stable catalysts with high activity. Metal oxides provide an interesting platform for the development of efficient catalysts owing to their abundance, high stability, and tunable band edges. Their performance highly depends on the rational design of heterostructures with engineered electronic structures, modified charge migration behavior, tailored interfacial properties, and amplified electromagnetic fields. All these enable the achievement of efficient light harvesting, promoted charge separation and transport, and accelerated surface reactions. Herein, a recent study on rationally designed metal oxide heterostructures for enhancing photo-to-chemical energy conversion via photocatalytic and photoelectrochemical systems is reviewed. The approaches to enhance their conversion efficiency are as follows: 1) surface modification via loading of plasmonic metals and other photosensitizers; 2) surface regulation, including morphology, defect, and dopants; 3) interfacial assembly with metal oxides, other metal compounds, and metal-free materials. Moreover, the underlying reaction mechanisms of metal oxide-based heterostructures and how they affect the energy conversion efficiency are discussed. Finally, the challenges and perspectives on the development of metal oxide-based heterostructures and associated photo-to-chemical devices are presented.     

Dopamine-containing gadolinium complex as magnetic resonance imaging contrast agent

Gadolinium diethylenetriamine-pentaacetic bisdopamide (Gd-DTPA-2DA) was synthesized by the incorporation of dopamine to diethylenetriaminepentaacetic acid (DTPA) and further reaction with gadolinium chloride. In vitro and in vivo properties were also evaluated. Gadolinium complex Gd-DTPA-2DA possessed higher relaxation effectiveness and less cytotoxicity to HeLa cells than that of Gd-DTPA. Moreover, Gd-DTPA-2DA greatly enhanced the contrast of MR images of the brains, provided prolonged intravascular duration, and produced highly contrasted visualization of the brain.     

基于小波分形技术提取发动机曲轴轴承故障特征

利用小波技术对发动机曲轴轴承振动信号进行分解,对特定层的信号进行重构,并计算重构信号的分形维数,来实现发动机曲轴不同技术状态下特征提取。实验结果表明,特定频率带振动信号的分形维数更能敏感反应发动机曲轴轴承技术状态,它可以作为诊断发动机曲轴轴承故障的一个重要特征量。     

Unlabeled PCA-shuffling initialization for convolutional neural networks

In order to obtain prominent recognition accuracy convolutional neural networks (CNNs) need large amounts of labeled data to initialize network parameters. However, there exist two open problems, i.e., the uncertainties of the initialized effects and the limited labeled data To address the problems, we propose a novel method named UPSCNNs, which uses unlabeled data to perform Principal Component Analysis (PCA) and shuffling initialization for CNNs, composed of four steps, i.e. sampling the input images, calculating the sampling sets with PCA and initializing and shuffling the convolutional kernels. In cases with the same network architecture and activation function, i.e., Rectified Linear Units, we conduct the comparative experiments on three image datasets, i.e., STL-10, CIFAR-10(I) and CIFAR-10(II). In terms of accuracy, we find (1) the novel method increases by 4-20 percent in comparison to other weight initialization methods, e.g., Msra initialization, Xavier initialization and Random initialization and (2) an increase of 1-3 percent is obtained with unlabeled data than with only labeled data The results indicate that our method can make full use of unlabeled data for initializing CNNs to achieve good recognition effectiveness.     

正态资料下采用α'调整作为国际多中心临床试验目标区有效性研究的桥接方法

目的: 探讨新药在国际多中心临床试验（MRCT）中，以正态资料为主要疗效终点、目标区采用调整后的检验水准α'作为决策依据方法的可行性和α'的合理取值，确定目标区样本量的比例，为MRCT在目标区通过审批提供参考。方法: 利用Monte Carlo法模拟优效性设计和目标区不同规模MRCT的数据模型，在检验水准α=0.05水平上显示试验组优于对照组的前提下，目标区采用调整后检验水准α'作为决策依据的条件Ⅰ型错误率（CFPR）、条件检验效能（CP）随目标区样本量占MRCT样本量占比K的变化情况。结果: 目标区CFPR和CP随着α'的增加而增加，K值越大，相应的目标区CFPR也越高。当K<30%和α'<0.5时，基本可以控制目标区CFPR不超过0.5；当K≤15%和α'=0.5时，即使f=1.0，CP依然很低不足0.76；当K=20%，如果f>0.8，则目标区CP可超过0.70；当K=25%，如果f>0.8，目标区CP可超过0.75；当K=30%，只要f=0.7，目标区CP就能维持在0.80以上；当K=50%时，f即使只有0.5，目标区CP依然可以达到0.80以上。结论: 本研究提出的方法容易理解，便于操作，尤其对于f≥0.7的情形有较好表现。     

铣削高强度钢刀具磨损有限元仿真研究

高强度钢作为难加工材料的一种,对其进行高效加工一直是工业难题.本文使用DEFORM-3D有限元仿真软件,选用不同铣削用量,通过单因素试验方法模拟了高强度钢的铣削过程,分析了刀具磨损形貌特征,得出了铣削用量对刀具磨损的影响规律.通过对刀具前刀面不同磨损程度区域取点并绘制铣削温度曲线图得出结论:刀具磨损程度越剧烈,铣削温度...     

Application of time–temperature–stress superposition principle on the accelerated physical aging test of polycarbonate

The effect of physical aging on the polymer mechanical properties is very important for long‐term safety assessment of engineering application. In this paper, the physical aging tests of polycarbonate (PC) were conducted systemically under different temperature and uniaxial tensile stress level. It was shown that both temperature and stress have obvious accelerated effect on the physical aging of PC. The higher the temperature and stress level are, the faster the aging process is. To predict the long‐term behavior after physical aging using the short‐term test results of PC, the elongation‐at‐break was chosen as the index of the severity of physical aging. An Arrhenius‐type time–temperature–stress superposition principle (TTSSP) was proposed to evaluate long‐term performance using short‐term test data. Using the proposed method, time and cost can be dramatically reduced for the assessment of long‐term physical aging performance of polymeric material. POLYM. ENG. SCI., 55:2215–2221, 2015. © 2015 Society of Plastics Engineers     

一种基于网形结构矩阵的配电网故障定位改进算法研究

作为故障定位的核心部分,故障定位算法的准确性与实时性非常重要。本文针对配网的各种故障情况以及不同的运行方式,在前人研究的基础上,提出一种新的算法。该算法以矩阵分析为基础,根据FTU上传的故障信息,仅选择包含故障信息的线路参与计算。算法可以根据配电网实际的运行方式形成相应的网络描述矩阵,能够实现普通树状网及开环运行环网的故障定位需求。通过Delphi语言编程实现该算法,证明了算法在定位方面的准确性,为其在实际工程的应用提供了理论依据。