酚醛树脂基活性炭微球的电化学性能研究Ⅰ.酚醛树脂基微球制备过程的研究

选用线型酚醛树脂为原料，采用乳化法可制得微球。为了揭示微球的成型，考察了在制备过程中酚醛树脂乙醇溶液的浓度、搅拌速率、成球终温、固化剂及表面活性剂的数量对酚醛树脂基微球的影响。研究结果表明：微球球径随着树脂溶液浓度的降低而减小，亦随搅拌速率的降低而减小；当搅拌速率为400r／min左右，表面活性剂的浓度在0．28mol／L～0．74mol／L，固化剂量的质量分数为6．0％(基于酚醛树脂)时，可得到球形度良好的微球。在高于树脂软化点以上成球终温对成球影响不大。     

液态金属离子源发射系统电场的模拟分析

发射系统是液态金属离子源的关键部件之一，它的性能的优劣直接影响到整个离子源的工作稳定性和可靠性。因而对其发射系统进行仿真分析，可以很好地指导液态金属离子源的设计制造。本文采用国际上重视的动态喷流柱模型，利用模拟电荷法对液态金属离子源的发射系统的电场进行了计算分析，画出了发射尖端电场强度随不同参数变化的曲线，得出发射尖端表面场强与球冠半径、发射体突出臂长度密切相关，而与引出电极的结构关系甚小的结论，因此液态金属离子源发射特性（如角电流强度）的改善，必须在发射尖的设计制作上下功夫。从而为液态金属离子源的设计提供了一个有效的辅助工具。     

Stress recovery in geometrically nonlinear membranes by a Hu-Washizu finite element formulation

A class of mixed finite elements based on the Hu-Washizu functional is introduced as a strategy to reduce the spurious stress phenomena encountered with standard or displacement-based formulations for geometrically exact membranes. Selected examples compare the performance of this class of elements with that of the standard formulation and demonstrate that reduction of spurious stresses is obtained and that the stresses are more accurate than those optimally sampled in the standard formulation.     

Liquid helium cryostat for SQUID-based MRI receivers

We describe a liquid helium cryostat, developed to cool SQUID-based receivers in low field MRI systems. The cryostat has a 4 L liquid helium capacity, a hold time of over 3 days and accommodates 10 cm diameter receiver coils. New vacuum insulation methods reduce the noise level by at least an order of magnitude compared to existing commercial designs. The minimum detectable field at 425 kHz, with a 5 cm diameter circular coil, was estimated to be 0.018 fT/Hz^1/2 from Q-factor measurements and 0.035 fT/Hz^1/2 by direct measurement with a SQUID amplifier. Further measurements indicated that most of this field noise probably originates with dielectric losses in the cryostat’s fibreglass shells.     

Microprocessor controlled three-way catalyst efficiency monitoring system

The present paper describes a new design for a microcontrolled three-way catalyst efficiency monitoring system. The system is based on the Motorola 68HC11e2 microprocessor and utilizes the differential signal from a pair of thermocouples installed at the catalyst outlet and inlet sections. This signal is processed in real time using an appropriate statistical algorithm and the corresponding results are compared to experimentally determined limiting values to assess the current state of the catalyst efficiency during driving conditions. The result of this comparison is presented on an LCD display as an A, B, C, or FAIL catalyst condition signal. The system can be readily installed and can operate on new and used cars provided that the type of catalyst used has been experimentally tested to provide the necessary limiting values that characterize its relative levels of efficiency. It can also be reprogrammed and calibrated via a RS232C serial interface.     

Bistable C1 ferroelectric liquid crystal device for e-paper application

Recent progress in both low pretilt and high pretilt defect-free C1 surface stabilized ferroelectric liquid crystal (SSFLC) devices for e-paper application is reviewed. First, by using numerical calculation to investigate the balance between surface azimuthal anchoring energy and bulk elastic energy within the confined chevron layer geometry of C1 and C2, we found it is possible to achieve a zigzag-free C1 state by low azimuthal anchoring alignment with a low pretilt angle. The critical azimuthal anchoring coefficient for defect-free C1 state is calculated. Its relationship with elastic constants, chevron angle, and surface topography effect are also discussed. Second, by using 5° oblique SiO deposition alignment, a defect-free, large memory angle, high contrast ratio, and bistable C1 SSFLC display, which has potential for electronic paper applications has also been developed. The electro-optical properties and bistability of this device have been investigated. Various aspects of defect control are also discussed.     

液氮汽车的研究

液氮汽车作为一种环保交通工具 ,与电动汽车相比 ,具有很多优点 ,亦是当前环保汽车的一大发展趋势。目前国内对液氮汽车的研究基本上还是空白 ,国外的研究也是刚刚起步。文章在阐述液氮汽车研究现状的同时 ,得出现有液氮汽车系统中存在的主要问题 ,并提出解决现有问题的技术措施 ,探索新型循环系统的原理以及各关键部件和过程的优化模型 ,为实用且环保的液氮汽车的发展提供理论依据     

一起低温液体贮槽制造过程爆裂事故分析

通过一起固定式低温绝热液体贮槽夹层气压试验时内壳发生失稳变形 ,导致外壳爆裂的事故原因分析 ,证明此类容器在制造过程应严格控制内壳的成型尺寸和焊缝残余应力 ,并加强对夹层气压试验、抽真空检漏的工艺程序监控。