用RCR特征和NN识别实时手绘工程草图

针对实时手绘工程草图(简称手绘草图)的识别，引入草图重心、重径距和正规化重径(RCR)等图形特征概念，提出手绘草图的神经网识别方法．该方法以图素具有统计意义的正规化重径作为特征、以图素交叉方式组织正规化重径的值作为学习样本，应用弹力传播的Rprop算法训练BP神经网，一次训练即可得到能够识别任意倾角和位置手绘草图图素的识别器．从而达到了理想的识别效果．     

一种三自由度并联机器人机构的运动学分析

1引言 并联机器人具有输出精度高、结构刚性好、承载能力强、部件简单及运动学反解简单等许多串联机器人所没有的优点,近年来引起了机器人研究者的高度重视.其中,六自由度并联机器人方面的研究已比较深入和成熟.三自由度并联机器人是一种很有实用前景的机器人,也越来越多地引起人们的注意.三自由度并联机器人包括平面三自由度并联机器人,球面三自由度并联机器人和空间三自由度并联机器人.球面三自由度并联机器人能够实现运动平台三维转动,是一种角台形式,由静角台、动角台和三组具有一定弧度的连杆架和连杆构成,各联接处均采用转动副.这种机构结构复杂、设计困难。     

脉冲爆震发动机试验模型测控系统设计与实现

针对新型推进系统脉冲爆震发动机试验模型的多通道高速采集和实时控制的要求,设计并实现了发动机的实时测控系统．并重点介绍了系统的软硬件体系结构以及抗干扰、网络通讯及数据库存储等关键技术;经实际应用表明。系统实时性强,可靠性高,满足试验模型对高速采集和控制时间的要求。     

基于盲源分离和时频分析的漏磁信号处理

利用独立分量分析的冗余取消特性,对多维加噪声观测信号进行盲源分离,得到源观测信号,实现噪声的有效消除,文章中应用此方法处理了仿真漏磁缺陷信号,实验结果表明:该除噪方法能极大提高漏磁信号的信噪比,且其效果要优于小波变换除噪方法.漏磁缺陷信号在时域上波形非常相似,很难加以分辨,而它们的危害性却大不相同,文章对裂纹和凹坑缺陷信号进行小波包分解,根据信号特征自适应的产生一组最优基来表征信号,分析这两种缺陷的时频特性,准确识别出这两种缺陷.     

光纤AM CATV外调制发射技术

就光纤AMCATV外调制发射机的关键问题，即光源的选择、调制器的选择、非线性补偿、限幅失真抑制及CSO和CTB的闭环控制进行了较全面的论述。     

景海高速公路全—强风化花岗岩隧道塌方机理分析与处置

景海高速公路宾房2#隧道洞室围岩主要为中风化花岗岩,顶板为全—强风化花岗岩,具有浅埋、富水、自稳能力极差、遇水流塑性强、施工扰动作用下围岩液化现象明显等特点.该文从地质、施工、自然等多方面对隧道塌方进行分析,并提出一套隧道塌方综合治理措施.采用FLAC3D对治理地表注浆段进行了数值模拟,通过计算结果和现场K31+565...     

High-Efficiency Power Amplifier Using Novel Dynamic Bias Switching

A novel bias-switching scheme for a high-efficiency power amplifier is proposed. Two voltage levels for the drain bias of the RF power amplifier are generated using a combination of a class E dc/ac inverter and a class E rectifier with offset voltage. When signal peaks occur, the output of the class E dc/ac inverter is rectified and the rectified dc is added to the offset voltage by the class E rectifier, which boosts the drain bias of the RF power amplifier. Except during peaks, the drain bias of the RF power amplifier is connected to the offset voltage directly. Since the efficiency when there are no peaks is very high due to the direct connection between the offset voltage and drain bias, the overall efficiency of the RF power amplifier can be improved dramatically in high peak-to-average power ratio (PAPR) systems. The measured results show that the drain bias of the RF power amplifier is boosted up to approximately 1.8 times the offset voltage when the RF peaks generate. The overall efficiency of the proposed bias-switching amplifier is improved by 62% compared to that of the fixed bias amplifier in high PAPR systems     

Quantification of micro-cracks on the bending surface of roll formed products using the GTN model

With the rising interest in lightweight construction, the usage of high strength steel has increased remarkably during the last years. Unfortunately, there is manufacturing problem: high strength steel has a higher occurrence rate of cracks than mild steel. The Gurson-Tvergaard-Needleman (GTN) model is used to precisely predict the occurrence of cracks in roll forming. The flow stress and the GTN material parameters are identified using a load-displacement curve obtained from tensile test. In detail, the material parameters that have to be determined were selected and based on this 3-level orthogonal array is made. The coefficients of the objective function are derived using the response surface method with the orthogonal array based on the simulation results. The material parameters are obtained by minimizing the objective function and determined by comparing the simulation and test results. The reliability of the material parameters determined by the tensile test increased through cross-validation using the bending test. The roll forming simulation with the determined parameters is fulfilled, and the experiments are performed to determine the occurrence of micro-cracks according to bending angles. Micro-cracks are quantified by comparing the void volume fraction (f) from the GTN model, and the micro-cracks on the surface are measured using a scanning-electron-microscope.