某轻型卡车驾驶室地板强度分析研究与改进

以某轻型商用卡车驾驶室地板频繁发生开裂故障为背景,对该品牌商用车驾驶室地板强度进行故障原因分析及优化设计.首先对轻卡地板驾驶室进行CAE建模与仿真,使用电测法测得该轻型商用卡车道路行驶过程中各个测点的应变时域数据.计算结果表明,CAE计算仿真结果应力极值达160.7 MPa,电测法测得相同部位的应力极值达250.3 MPa,都远超驾驶室材料屈服强度极限.然后在此基础上判别问题性质,对翻转机构进行受力分析和计算,计算结果显示两侧扭矩极限理论差值仅为3424.2 N·m,判断开裂原因为驾驶室本体强度过低.最终在试验及理论分析的基础上,提出增加加强板及焊缝和增加结构胶两种结构强度优化措施,并进行多方面对比分析,为后续工程结构优化与强度分析提供参考依据.     

为实时业务提供QoS保证的MAC机制性能研究

分析的MAC机制在IEEE802．11DCF机制的基础上提供了QoS增强。由于实时业务对时延要求敏感。因而提出的实时业务分析模型并未考虑退避重传。和尽力而为业务相比较。实时业务获得了高的饱和吞吐量和低的接入延时，但是以较高的帧丢失率为代价。为了保证实时业务的QoS要求，使用QoS参数P0．Qos来限制帧丢失率。经过分析得出，在保证帧丢失率上限和最大吞吐量的条件下，可求得最优初始窗口，获得较好的网络性能。     

4H-SiC monolithic Darlington transistors with slight current gain drop at high collector current density

Profit from high current gain features, 4 H-Si C power Darlington transistor has the capacity for handling high current transmission. In this paper, monolithic Darlington transistors were fabricated using a simultaneous formation process for both n-type(emitter) and p-type(base) ohmic contact. The isolated device shows current gain of 1061 and 823 with collector current density(JC) increasing from 200 to 800 A/cm2, exhibiting a slight current gain drop at high JC. By extracting the interface state density(Dit) between Si O2 and p-type 4 H-Si C, it is found that this advantage owes to the improvement of the shallow bulk minority carrier lifetime in base region. Furthermore, ISE-TCAD(technology computer aided design) simulation was carried out to study the relationship between base minority lifetime and the current gain, from which the total base minority lifetime is estimated to be 48 ns. The open base breakdown voltage(BVCEO) is 850 V at a leakage current of 2 μA due to the electric filed crowding at the isolation bottom between drive bipolar junction transistor(BJT) and output BJT. To solve this, non-isolated devices were also fabricated with improved BVCEOof 2370 V, indicating the superior potential of 4 H-Si C monolithic Darlington transistors for high power application, while the current gain is deceased to 420, which needs further improvement.     

不同时期汉语散文的字同现网络之研究

基于汉语4个不同时期:古代汉语、魏晋南北朝的汉语、近代汉语以及现代汉语的散文,文中建立了字同现网络,并研究了它们的统计特征.研究发现99.6%的网络具有无标度特性,95.0%的网络具有小世界特性.该研究从复杂网络的角度揭示了汉语语言的发展不是平稳的,同时还揭示了不同时期中文文章的异同.在汉语语言学的研究中,对魏晋南北朝时期的文学是属于古代汉语还是近代汉语一直存在很大的争议.研究结果表明,魏晋南北朝时期网络的统计数据与其他时期的统计数据之间的确存在明显的不同,且魏晋南北朝时期的文学属于近代汉语似乎更合理.     

Droplet transfer model for laser-enhanced GMAW

Laser-enhanced gas metal arc welding (GMAW) is a recent modification of conventional GMAW. It applies a low power laser to the droplet to obtain an auxiliary detaching force to help the detachment and achieve controlled metal transfer. As a primary parameter that affects the process and weld quality, the size of the droplet needs to be monitored and controlled. However, its direct measurement requires a high-speed camera and is not preferred in a manufacturing site because of its high cost and complicated system structure. Soft-sensing method was thus proposed as an alternative to obtain it in real time. Laser power intensity, wire feed speed and welding voltage were identified as the major parameters that determine the droplet size and were thus selected as the auxiliary variables to estimate the primary parameters: size and transfer rate of the droplet. Least squares (LS) regression equation, back-propagation neural network (BPNN), particle swarm optimization-based back-propagation neural network, and three swarm cooperative particle swarm optimization-based back-propagation neural network (TSCPSO-BPNN) models were established from the collected data. Simulation results were analyzed and compared among these models. It was found that the selected auxiliary variables were closely related to the primary variables. Droplet size and transfer rate estimates made based on the TSCPSO-BPNN model are similar to those based on LS regression equation. After dimension reduction, the LS equation can be simpler than TSCPSO-BPNN model while the accuracy is sufficient and meets the requirement for future control. The estimation by LS method could thus be utilized in the control of the laser-enhanced GMAW.     

红曲酯化菌21-3制曲试验

红曲酯化菌21-3具有较强的酯化力，将其应用于制曲生产试验。结果表明：21-3能在培曲过程和培制成曲中较好地生长繁殖；对大生产制曲工艺参数温度、水分和酸度等均无影响；可提高曲块的糖化力、液化力和发酵力，还可大幅度提高曲药的酯化力。（孙悟）     

基于卷积码的Turbo码交织器的设计

以（３７,２１）ＰＳＣ码为例,提出对基于卷积码的Ｔｕｒｂｏ码的交织器的设计方案,并推广到一般的ＲＳＣ码．分析了该交织对Ｔｕｒｂｏ码距离谱的影响．给出了动用该交织后分量码的选取原则．可以看到,该交织器设计方案在误比特率为１０＾－５时将产生明显的作用．     

Digital Twin for Human-Robot Interactive Welding and Welder Behavior Analysis

This paper presents an innovative investigation on prototyping a digital twin(DT)as the platform for human-robot interactive welding and welder behavior analysis.This humanrobot interaction(HRI)working style helps to enhance human users'operational productivity and comfort;while data-driven welder behavior analysis benefits to further novice welder training.This HRI system includes three modules:1)a human user who demonstrates the welding operations offsite with her/his operations recorded by the motion-tracked handles;2)a robot that executes the demonstrated welding operations to complete the physical welding tasks onsite;3)a DT system that is developed based on virtual reality(VR)as a digital replica of the physical human-robot interactive welding environment.The DT system bridges a human user and robot through a bi-directional information flow:a)transmitting demonstrated welding operations in VR to the robot in the physical environment;b)displaying the physical welding scenes to human users in VR.Compared to existing DT systems reported in the literatures,the developed one provides better capability in engaging human users in interacting with welding scenes,through an augmented VR.To verify the effectiveness,six welders,skilled with certain manual welding training and unskilled without any training,tested the system by completing the same welding job;three skilled welders produce satisfied welded workpieces,while the other three unskilled do not.A data-driven approach as a combination of fast Fourier transform(FFT),principal component analysis(PCA),and support vector machine(SVM)is developed to analyze their behaviors.Given an operation sequence,i.e.,motion speed sequence of the welding torch,frequency features are firstly extracted by FFT and then reduced in dimension through PCA,which are finally routed into SVM for classification.The trained model demonstrates a 94.44%classification accuracy in the testing dataset.The successful pattern recognition in skilled welder operations should benefit to accelerate novice welder training.     

炮塔回转座圈滚道中频淬火的工艺实践

根据某军品炮塔回转座圈滚道中频淬火的特点,通过对滚道淬火工艺及座圈变形的研究,得出减小座圈变形的淬火工艺参数及工艺方法,为炮塔座圈的生产提供了技术保障。     

红曲酯化菌21-3选育及特性研究

以本所分离保藏的9株红曲霉为出发菌株，经紫外线诱变，选育出性能稳定、酯化力强的红曲酯化菌21-3（Monascus pilosus），酯化力约为低温曲和次高温曲的2．1倍，约为高温曲的12．5倍。试验表明：能促进己酸、丁酸及混合酸与乙醇的酯化作用，生成的酯类物质均为己酸乙酯，且酯化能力极强。在培养基中加入适量乙醇，有利于21-3的生长，加入适量乳酸或与乳酸菌共生，有利于酯化酶的合成。