Theory and design of a tapered line distributed photodetector

We present the theory and design of a tapered line distributed photodetector (TLDP). In the previously demonstrated velocity-matched distributed photodetector (VMDP), high electrical bandwidth is achieved by proper termination in the input end to absorb reverse traveling waves, sacrificing one-half of the quantum efficiency. By utilizing the tapered line structure and phase matching between optical waves and microwaves in our analyzed structure, a traveling-wave photodetector is more realizable and ultrahigh bandwidth can be attained due to removal of the extra input dummy load that sacrifices one-half of the total quantum efficiency. To investigate the advantages of TLDP over VMDP, we calculate their electrical bandwidth performances by using an analytic photodistributed current model. We adopted low-temperature-grown (LTG) GaAs-based metal-semiconductor-metal (MSM) traveling-wave photodetectors as example unit active devices in the analytic bandwidth calculation for their high-speed and high-power performances. Both VMDP and TLDP in our simulation are assumed to be transferred onto glass substrates, which would achieve high microwave velocity/impedance and make radiation loss negligible. The simulated bandwidth of a properly designed LTG GaAs MSM TLDP is /spl sim/325 GHz, which is higher than the simulated bandwidth of the LTG GaAs MSM VMDP with an open-circuit input end (/spl sim/240 GHz) and is almost comparable to the simulated bandwidth of an input-terminated LTG GaAs MSM VMDP (/spl sim/330 GHz). This proposed method can be applied to the design of high-bandwidth distributed photodetectors for radio-frequency photonic systems and optoelectronic generation of high-power microwaves and millimeter waves.     

吐丝圈径对大规格高碳盘条组织性能的影响

计算与分析了斯太尔摩冷线上盘条的吐丝圈径、搭接密度及"佳灵"装置横向布风曲线之间的关系,研究了吐丝圈径的大小对大规格82B盘条组织和性能的影响,确定了大规格82B盘条最小吐丝圈径应为980mm.     

网络化制造中基于STEP-NC的编程方法

STEP-NC是由欧美提出的新的数控接口标准，目的是取代旧的数控标准ISO6983。本文首先分析了STEP-NC的两种应用标准：ISO14649（ARM）和STEPAP238（AIM），并且分析了Part21和Part28的应用领域及Part21文件格式和其中的信息产生方法。然後介绍了ST-Developer环境下ROSEC＋＋颠库编程接口及其应用程序的早、晚编联方式，并且以此为基础设计了整个程序的编程流程，重点介绍了工艺规划设计。最后给出了在C＋＋编程环境下利用ROSE库函数写入形成STEP AP238文件的方法。     

桩帽处理对灌注桩高应变检测的影响

本文给出砼灌注桩高应变检测中桩帽的施工工艺 ,并讨论其对测试结果的影响。     

Interface characteristics and mechanical properties of carbon fibre reinforced copper composites

Interface characteristics of carbon fibre reinforced copper matrix composites materials with various interface states and their effect on the flexural strength of composites have been studied. Interfacial states are mechanical bonding, dissolution bonding and reaction bonding. To a certain extent, raising the interfacial strength enables an increase in the flexural strength due to prevention of carbon fibre being pulled out under low stress during fracture process of composites. Raising the interfacial bondage strength, causes the brittleness of composites to increase; the fracture surface of composites is converted from a fibre pull-out model to a fibre even model. While strengthening the interface bondage, the extent of chemical reaction and dissolution at the interface must be controlled to avoid degrading the carbon fibre.     

炉衬产生的氧对真空钢液脱氮的动力学影响

采用 99.99%氧化镁砂捣打炉衬的 2 0kg真空感应炉 ,研究了超低碳钢熔炼时炉衬产生的氧对真空钢液脱氮的影响。试验结果表明 :钢液中氧含量在 1 2 0× 1 0 - 6 时 ,脱氮的限制性环节是界面化学反应 ;随炉衬中氧的逸出 ,当钢液中氧含量在 5 1 0×1 0 - 6 时 ,真空钢液脱氮处于界面化学反应和液相边界层扩散控制的边缘区域 ,脱氮速率降低     

乙烯装置中汽油分馏塔设计浅析

对汽油分馏塔的技术特点进行了分析,对急冷油系统的设计和汽油分馏塔的内件选择和设计进行了分析和讨论.     

Slow eroding biodegradable multiblock poloxamer copolymers

Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol^?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of an interpenetrating polymer network composed of poly(methacrylic acid) and poly(vinyl alcohol)

Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry