热轧薄板钢焊接区组织与性能分析

采用包钢CSP（Compact Strip Production）薄板坯连铸连轧工艺生产L245钢为原料进行螺旋焊管焊接生产,针对生产中焊缝裂纹问题对焊缝区的形貌、组织进行了观察,并对焊缝进行拉伸性能和X射线检验。分析表明,母材与热影响区的交界处（即偏向热影响区的“过渡区”）是L245焊管力学性能最脆弱处,珠光体的形貌是影响其拉伸性能的关键因素。     

DM6446视频处理系统的硬件电路设计

本文介绍了一种基于TI公司双核心处理器芯片TMS320DM6446的硬件电路系统.通过74AVC 16T245 DGGR,进行逻辑电平转换,降低了成本,与传统的CPLD电平转换方法相比,可以使布板布线更加紧凑,降低硬件的设计难度,成品效果好,跟踪算法在该硬件系统运行后,其处理速度可以达到26帧/s,而DSP占用率仅为5...     

60GHz无线通信系统在PPM调制下的信道容量分析

本文主要研究60GHz无线通信系统在高斯信道下的香农信道容量及在脉冲位置调制(MPPM)下的信道容量。理论分析与推导得到香农信道容量与传输距离的关系函数,由MPPM调制原理及高斯信道的数学模型推导系统在MPPM调制下信道容量与信噪比、信道容量与通信距离间的函数关系,利用Matlab仿真,得到不同条件下的关系曲线。研究结果表明,60GHz无线通信系统在高斯信道下的信道容量是通信距离和信噪比的函数,该系统更适合于短距离无线通信。高进制的PPM调制能够显著的提高系统数据传输速率,当数据率相同时,高进制调制的PPM能够提供的可靠通信距离更远。     

HFC-245fa聚氨酯硬泡的粘接性能研究

通过合成新型聚醚多元醇 ,对交联剂和催化剂的选择等试验 ,有效地改善了HFC 2 45fa聚氨酯硬泡的粘接性能 ,满足了冰箱冰柜生产对聚氨酯硬泡粘接强度的要求。研制生产的HFC 2 45fa组合聚醚发泡特性及发泡制品的性能均达到了CFC— 11型同类产品水平。     

3+1 architects

Without the predominance of a single presiding tradition of modern architecture in Estonia, the way has been clear for a younger generation of architects to make their mark. Andres Kurg describes the work of 3+1 architects, who launched their career in the mid-1990s with an Estonian Embassy in Vilnius, Lithuania. Through their trend-setting domestic work, they have proved able to appeal to a new wealthy client base, while also developing their own interests in programme and architecture's relationship to the physical landscape. Copyright © 2007 John Wiley & Sons, Ltd.     

60 GHz超高速无线网络接入机制研究

首先介绍了工作在60 GHz频段、支持1 Gbit/s以上数据速率的IEEE 802.15.3c标准和IEEE 802.11ad标准草案规定的无线接入机制的基本原理,然后对它们的特点和性能进行了详细的对比分析。研究结果显示:2种无线接入机制都采用了TDMA+CSMA/CA的混合机制,但各有所长;IEEE 802.11ad接入机制兼容性更好,能达到更高的数据速率,然而原理更复杂;IEEE 802.15.3c接入机制实现相对简单,同样也能达到Gbit/s级别的数据速率。最后,对全文进行总结并指出了未来的研究方向。     

L245MB钢铸坯高温强度与弹性性能研究

 从显微结构到宏观结构上认识铸坯的高温性能演变规律，对铸坯的性能与质量控制具有重要意义。应用Gleeble热/力模拟试验机对L245MB钢铸坯在不同冷却速率下的高温强度演变规律进行了试验研究；采用EMTO第一性原理计算软件研究分析了不同晶体结构与磁性状态下铁基体相体模量B、单晶弹性常数c′与c44、多晶杨氏模量E、体系磁矩μ等随温度的演变规律。结果表明，冷却速率对铸坯高温强度演变的影响较小；高温强度在Ae3及TC温度附近发生转折，TC～Ae3温度区间呈现“平台”，抗拉强度平均演变速率为0.008 MPa/℃，屈服强度为0.076 MPa/℃。铸坯热塑性在TC～Ae3温度范围出现不同程度的下降，断面收缩率在800 ℃左右最小，为59.02%～62.79%；二冷低延性区的温度范围随冷却速率增加而增大，矫直区表面温度应控制在850 ℃以上以避免裂纹产生。铁基体相弹性性能参数随磁性状态及晶体结构的转变而变化，磁性状态的转变对c′、c44、E影响较大，晶体结构的转变对B影响较大；FM向PM转变时c′和E分别下降了64.09%和10.33%，c44提升了57.82%，bcc向fcc结构转变时B降幅达34.38%。结合分析了铁基体的单晶弹性常数c′、多晶杨氏模量E演变与铸坯高温强度演变间的联系，提供了从显微晶体结构性能参数推测分析铸坯宏观性能演变的思路，为第一性原理方法在钢铁材料高温力学性能中的研究应用提供基础。     

Modification of polymers for cardiovascular applications—some routes to bioactive hydrophilic polymers

This paper is concerned with the activation of platelets by polymers, a key-process in the behaviour of prosthetic devices in contact with blood. Platelets are activated by contact with many different types of polymer surfaces, which must therefore be regarded as thrombogenic. Two procedures for reducing thrombogenicity are discussed: (i) the chemical attachment of inhibitors of platelet aggregation and (ii) gross modification of the nature of the surface, e.g. by making it more hydrophilic. For purposes of (i) the potent prostaglandin analogue BW 245C has been used, while for (ii) grafting of poly(ethylene glycol) (PEG) has been explored. Both methods give greatly reduced platelet adhesion inin vitro tests. The second part of the paper deals with the properties of adducts of inhibitors of platelet aggregation (BW 245C, dipyridamole) with water-soluble macromolecules [poly(N-vinyl pyrrolidone), PEG, dextran]. Adducts have been synthesized with terminal and side-chain coupling. On adduction the two inhibitors mentioned show opposite types of behaviour: the molar activity of BW 245C is dramatically reduced, but that of dipyridamole is significantly increased. Remarkable synergistic effects have been recorded for BW 245C adducts. These observations are interpreted in terms of differences in stereochemistry in the drug-receptor interactions. Appropriate chemical techniques for coupling are outlined, attention being drawn to the special uses of haloalkyl- and haloacyl-isocyanates and 2-isocyanatoethyl methacrylate as reagents.     

三维射线跟踪预测模型在5.8GHz的实验验证

验证了一种用于无线信道特性预测的三维射线跟踪模型的计算方法.在 5.8GHz分别用不同的天线对视线和非视线两大类情形进行了仿真和测量,结果表明测量值和仿真值一致.     

基于0.18-μm锗硅BiCMOS工艺的60 GHz匹配型高隔离小型化变压器巴伦

介绍了一种工作在60 GHz频率的具有输出端口间高隔离和全端口匹配特性的小型化变压器巴伦芯片,该芯片采用0.18-μm锗硅BiCMOS工艺设计并加工。通过在60 GHz变压器巴伦的输出端口之间引入隔离电路,提高巴伦的隔离度性能并改善输出端口匹配性能;在此基础上,提出了一种基于左手材料传输线的隔离电路,能大大改善传统隔离电路中分布式传输线尺寸大的问题;为了进一步实现巴伦的小型化,在设计中采用了负载电容补偿技术,同时能改善变压器巴伦输入端口的匹配性能。设计的巴伦芯片经过电磁场仿真,其结果与在片测试结果有较高的一致性,验证了提出的设计方法,设计的巴伦芯片具有全端口匹配和输出端口间高隔离度的特性。基于实测结果,在60 GHz频率处,设计的巴伦芯片实现了超过25 dB的输出端口隔离度和优于18 dB的输出端口回波损耗,且占用尺寸极小,仅为0.022 mm²。