基于模糊控制的齿轮传动系统振动主动控制与仿真

基于集中质量法建立了由一对渐开线直齿圆柱齿轮组成的传动系统3自由度数学模型.采用一种主动控制结构,使主动控制力以更直接的方式来控制齿轮啮合点由于传动误差而引起的振动.通过压电堆作动器输出的位移控制齿轮轴的弯曲振动,以抑制齿轮传动误差,进而达到控制齿轮传动系统振动噪声的目的.在Matlab/Simulink环境中设计模糊...     

计算机基础课程考试系统的设计与实现

探讨计算机基础课程考试系统的设计和实现方法.系统使用Visual Basic 6.0开发前台应用程序,使用Access 2000进行后台数据库设计.系统包括管理员和考生两大模块,分别实现考试系统的维护管理和考生完成考试过程,系统具有维护简单、使用方便等特点,并实际应用于计算机基础教学中.     

无源射频识别标签整流电路的分析与设计

整流电路的设计是无源射频识别(RFID)标签的关键技术之一.基于两种传统的整流电路,分析影响其输出电压和能量转换效率(PCE)的几个因素,在此基础上提出了一种改进的整流电路.该电路采用栅极交叉连接的结构来消除天线到芯片的阈值电压压降,并通过增加两个MOS管作为开关来抑制芯片到天线的电荷回流.电路的设计仿真结果显示,该整流电路具有较高的输出电压和PCE.     

企业核心能力生成机理的研究

企业获得长久竞争优势的途径是提高核心能力,运用企业能力结构图来阐述企业学习、核心能力与长久竞争优势之间的联系,构建了多层回路模型来阐明规范、能力与战略三个学习回路之间的逻辑关系,指出各学习回路内部要素之间的相互作用促进了企业核心能力的形成。     

考虑碰撞安全性的电动客车车身截面尺寸优化

针对承载式车身结构的客车在正面碰撞中安全性较差的问题,结合有限元网格变形技术对客车前端管梁结构进行碰撞安全性和轻量化多目标优化设计。建立了客车碰撞分析有限元模型并对碰撞后的评价指标进行了分析,选取了在正面碰撞中吸能量占比较大的管梁结构作为优化区域,以选取出的管梁截面的长度、宽度和厚度作为设计变量,引入驾驶舱4个关键位置的侵入量、前端结构的吸能量、峰值侵入速度和设计区域总质量作为优化响应,通过灵敏度分析得到各设计变量对优化响应的贡献度值,基于熵权法和TOPSIS综合权重方法,筛选出对优化响应综合贡献度较高的设计变量,最后结合拉丁超立方实验设计、响应面法(RSM)和NSGA-Ⅱ算法对客车前部区域结构进行了多目标优化,研究结果表明：多目标优化后,驾驶员胸部生存空间提升6.28%,腿部生存空间提升9.7%,选取点峰值侵入速度降低6.1%,客车前端吸能结构吸能量提升8.3%,同时实现客车前端结构质量减轻15.187kg,减重率为6.58%。     

A Comprehensive Review of Rosmarinic Acid: From Phytochemistry to Pharmacology and Its New Insight

Polyphenolic acids are the widely occurring natural products in almost each herbal plant, among which rosmarinic acid (RA, C₁₈H₁₆O₈) is well-known, and is present in over 160 species belonging to many families, especially the Lamiaceae. Aside from this herbal ingredient, dozens of its natural derivatives have also been isolated and characterized from many natural plants. In recent years, with the increasing focus on the natural products as alternative treatments, a large number of pharmacological studies have been carried out to demonstrate the various biological activities of RA such as anti-inflammation, anti-oxidation, anti-diabetes, anti-virus, anti-tumor, neuroprotection, hepatoprotection, etc. In addition, investigations concerning its biosynthesis, extraction, analysis, clinical applications, and pharmacokinetics have also been performed. Although many achievements have been made in various research aspects, there still exist some problems or issues to be answered, especially its toxicity and bioavailability. Thus, we hope that in the case of natural products, the present review can not only provide a comprehensive understanding on RA covering its miscellaneous research fields, but also highlight some of the present issues and future perspectives worth investigating later, in order to help us utilize this polyphenolic acid more efficiently, widely, and safely.     

Development of a ~3He Gas Filling Station at the China Spallation Neutron Source

At the China Spallation Neutron Source(CSNS), we have developed a custom gas-filling station, a glassblowing workshop, and a spin-exchange optical pumping(SEOP) system for producing high-quality ~3He-based neutron spin filter(NSF) cells. The gas-filling station is capable of routinely filling ~3He cells made from GE180 glass of various dimensions, to be used as neutron polarizers and analyzers on beamlines at the CSNS. Performance tests on cells fabricated at our gas-filling station are conducted via neutron transmission and nuclear-magneticresonance measurements, revealing nominal filling pressures, and a saturated ~3He polarization in the region of 80%, with a lifetime of approximately 240 hours. These results demonstrate our ability to produce competitive NSF cells to meet the ever-increasing research needs of the polarized neutron research community.     

Oblique Perforation of Thick Metallic Plates by Rigid Projectiles

Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.The English text was polished by Keren Wang     

Optimization of Multi-Criteria Experiments with Fuzzy Results

Introduction To reach a best quality product, experiments and an op- timized design of experiments are required in an inte- grated quality management system. The best quality level of a manufacturing process or product is defined not only by one, but by m…     

心肌组织力学行为的测试系统

为方便与准确定量地研究心肌组织主动力与被动力的性质,在综合现代实验力学中的光测、电测和步进电机控制等技术的基础上开发了两套实验测试系统。这两个系统也可用于一般生物软组织性质的研究。论述了这两套测试系统各自的工作原理,介绍了硬件和软件的组成部分和功能,以及关键部位力传感器的设计和标定。介绍了心肌力学性质测试的一般方法,初步得到了心肌组织的被动力和主动力的基本性质,和现有的理论模型进行了拟合和比较,表明这两套系统可以完成心肌组织的生物力学性质的测试。