内骨架6鸭舌一次冲裁成形模具结构的改进

内骨架6鸭舌冲裁成形时,原使用的是对产品采用多次冲裁,导致累积误差,且容易漏冲,效益较低。经改进工艺及模具后,采用自动哈夫一次冲裁成形,产品精度得到很大提高。希望对模具设计人员有一定的帮助和指导作用。     

缸筒存在半孔滚压中滚压工具的磨损分析及改善研究

针对在缸筒存在半孔的滚压工艺的推广过程中,出现的滚压头滚子与支撑心轴急剧磨损情况,进行理论分析以及失效状况的汇总。通过改变滚压头的受力状况和使用环境等,提高滚压头使用寿命,为油缸内壁存在半孔的滚压工艺的推广及滚压头使用寿命提升总结了经验。     

高频宽带晶体滤波器的研制

在目前获得高频钽酸锂晶体谐振器较难的情况下,该文以石英晶体为材料,通过化学腐蚀法,将谐振器的基波频率从45 MHz提高到63 MHz,并采用在传统差接桥型电路中插入LC调谐回路的电路展宽方式,将石英晶体滤波器的相对带宽从0.3%拓展到1%。基于该法研制出相对带宽约1%的63 MHz晶体滤波器,其带宽大于600 kHz,损耗为4 dB。     

Cooperative Hybrid‐ARQ Protocols: Unified Frameworks for Protocol Analysis

Cooperative hybrid‐automatic repeat request (HARQ) protocols, which can exploit the spatial and temporal diversities, have been widely studied. The efficiency of cooperative HARQ protocols is higher than that of cooperative protocols because retransmissions are only performed when necessary. We classify cooperative HARQ protocols as three decode‐and‐forward‐based HARQ (DF‐HARQ) protocols and two amplified‐and‐forward‐based HARQ (AF‐HARQ) protocols. To compare these protocols and obtain the optimum parameters, two unified frameworks are developed for protocol analysis. Using the frameworks, we can evaluate and compare the maximum throughput and outage probabilities according to the SNR, the relay location, and the delay constraint. From the analysis we can see that the maximum achievable throughput of the DF‐HARQ protocols can be much greater than that of the AF‐HARQ protocols due to the incremental redundancy transmission at the relay.     

单调荷载下的砂土宏观和细观力学性状关联度试验研究

基于压缩试验的细观观测,研究了土体宏观力学性状和颗粒细观参数的定量关系。通过对单调压缩荷载下砂土颗粒的运动分析,研究了砂土颗粒的长轴L、短轴B、y轴投影长度、形心x坐标与形心y坐标5个细观力学指标与宏观力学性状孔隙比的关联,提出细观力学参数与孔隙比的量化计算式。依据中砂半模压缩试验结果修正了量化计算式,砂样顶面圆心处^#1观测点的计算孔隙比e小于砂样底面圆心处^#2观测点的e;砂样1/2高度水平面上,环刀与砂样中轴线间距离的中点^#3观测点的e小于环刀内侧壁处^#4观测点的e,根据计算结果绘出各观测点的e–p曲线。各观测点的计算孔隙比表明,观测点位置影响了颗粒运动及孔隙比变化。通过对砂土细观力学性状与孔隙比之间关联度的试验研究,从散体细观力学出发,提出了一种基于试验的土体宏、细观力学性状相关联的研究方法。     

双闭环反馈控制半桥DC-DC变换器设计

桥式拓扑广泛用于直流供电电压高于晶体管的安全耐压值的离线式变换器中,针对双闭环反馈控制半桥DC-DC变换器电路,为了得到稳定的直流电压、电流输出,采用电压闭环回路和电流闭环回路的反馈放大最终实现对半桥开关PWM波信号的控制,进而影响半桥变换器的轮流导通MOS开关管的导通占空比的方法,通过闭环网络仿真实验和硬件电路功率实验,验证了双闭环反馈控制可以满足半桥电路3.6 kW功率输出的要求.     

Polymers for use in drug delivery—property and structure requirements

The purpose of this paper is to discuss some of the requirements placed on materials needed for improved administration of drugs. Emphasis is placed on macromolecules that need to be designed and prepared to perform specific pharmacological functions, particularly to act as vehicles for delivering drugs to specific locations within the body. After introducing the reasons for more selective drug delivery, and explaining the rationale for using macromolecules, practical examples of results with linking drugs to polymers, modifying polymers to increase their biological compatibility, attachment to polymers of groups that could mediate their specific recognition, modification of proteins with polymers, and the use of polymer complexes will be given to indicate the areas of need for further development of pharmaceutically useful macromolecules.     

Principle and basic characteristics of linear synchronous motor with half‐wave rectified self excitation

This paper presents the principle and basic characteristics of a novel linear synchronous motor based on “half‐wave rectified self excitation principle.” The field winding is short circuited through a diode and the armature winding consists of conventional three‐phase windings. If the amplitude of the balance three‐phase currents is modulated by an alternating wave with bias frequency, the produced magnetomotive force pulsates at the bias frequency and moves at the synchronous velocity. This pulsating magnetomotive force induces the electromotive force with a bias frequency in the field winding. The field excitation is obtained by rectifying the electromotive force with the diode in the field winding. In this paper, the authors design and build an experimental machine and confirm its basic characteristics. They also deduce the performance equations and investigate the thrust ripple reduction. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(1): 82–90, 2008; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20684     

利用X射线法测定淬回火GCr15钢的硬度

研究了淬回火GCr15钢洛氏硬度与马氏体(211)晶面X射线半高宽间的关系，用数理统计方法对实验数据进行了分析。结果表明，洛氏硬度与半高宽间存在良好的相关性，相关系数约为0．973；建立了洛氏硬度与半高宽间的线性均方回归方程，利用该方程可预测淬回火GCr15钢的硬度。     

PyroCrack1-1型裂解炉在乙烯装置上的应用

为降低乙烯装置能耗，消除装置隐患、增加效益，提高企业的市场竞争力，中国石油吉林石化公司有机合成厂在2004年乙烯装置改造中，新建了2台林德PyroCrack1-1型裂解炉。该型裂解炉采用双辐射段炉膛，单对流段设计，可在一侧炉膛烧焦的同时，另一侧进行裂解。文中从设备结构、工艺操作、检查维护等方面对PyroCrack1-1型裂解炉进行了介绍。PyroCrackl-1型裂解炉的投用，既满足了乙烯装置平稳运行的要求，同时又兼顾了节能和装置后续发展的需求。