低温旋转阀脉冲管制冷机实验研究

本文讨论了一种可适用于气体液化的新型脉冲管制冷系统：在该系统中,回热器被间壁式换热器所取代。切换阀置于脉冲管冷端,和脉冲管作为一个整体,起气体膨胀机的作用。我们建立了相应的实验装置以测量整个系统的性能．利用空气作介质,系统进出口温降为６３．６Ｋ,绝热膨胀效率可达４２％。利用氦气作工质,脉冲管冷端最低温度达１６０Ｋ,每１Ｋ有０．７５Ｗ的制冷量。     

高压联合进汽阀门三维粘性流场数值分析

本文采用多分区 ＳＩＭＰＬＥＣ算法对 ６００ ＭＷ汽轮机高压联合进汽阀门内部复杂流动进行了三维粘性数值分析。流场计算结果表明总压损失主要集中在调节阀喉口附近。调节阀阀碟前后的两股高速气流在阀碟的正上方位置相碰引起较大的掺混损失;气流经过调节阀喉口后,附面层急剧增厚,形成一层较厚的沿管壁的低总压区。计算得到的流场特性为即将开展的阀门结构优化设计提供了重要依据。     

新型滴定管的研制与应用

介绍了一种新型滴定管的结构,特点是及使用方法,通过数理统计对新型滴定管与经典滴定管平行测定结果进行了比较。新型滴定管具有较好的精密度、准确度和操作性能,克服了经典滴定管活塞易渗漏、易产生气泡、装液困难、近终点液滴不易控制及酸碱不通用的缺点。     

利用液晶光阀实现道路光学图象的实时边界提取

本文利用45°水平定向扭曲向列相液晶光阀的非线性输入输出特性,实验研究了道路光学图象的实时边界提取,效果很好.与数字边界提取相比,光阀边界提取的最大优势在于,处理与图象大小无关,时间少于15ms(即光阀的响应时间),可以达到实时操作,而且可以用白光做输入光源.     

Numerical study on effects of check valve closure flow conditions on pressure surges in pumping station with air entrainment

This paper proposes a numerical procedure to better compute the characteristics of pressure surges when check valves close under different flow conditions in a pumping station. Studies have shown that the effects of check valve closure on the pressure transients are predominantly dependent on the magnitude and gradient of the flow velocities immediately downstream of the check valve at the instant of valve closure. Through the present study, it was noted that the transient flow velocities near the check valve of a fluid system are also dependent on the characteristics of the air entrained into the fluid system. An improved numerical computational procedure for the fluid system with air entrainment under different transient conditions downstream of the check valve is also proposed in this paper. With a fluid system operating within the critical range of air entrainment values, the present analysis showed that there is a possibility of ‘high pressure surges’ when the check valves were closed at flow rates other than the positive flow conditions. This phenomenon was confirmed through field observations. This study thus concludes that a detailed numerical transient analysis of the fluid system, with various assumed amounts of entrained air, is necessary whenever there is the possibility of air entrainment into the fluid system, and that the flow conditions at the instant of check valve closure need to be modelled. Copyright © 2001 John Wiley & Sons, Ltd.     

三通道气相色谱法测定炼厂气组成

炼厂气是炼油工艺产生的各种气体的混合物,采用四阀六柱将炼厂气分离分解为3部分,以双TCD+FID检测器3通道气相色谱法快速分析炼厂气.FID通道用于分析烃类,一个TCD通道分析永久性气体和硫化物,另一个TCD通道分析氢气,采用面积归一化法定量计算分析结果.用该法测定了3种标准气体,测定值与标准值基本一致,测定结果的相对标准偏差小于8％.该法适用于测定包括液化气、烟气、裂解气等组分相近的样品组成.     

一种双蒸发器制冷系统调节性能的研究

在冻干装置中,一般采用一机双蒸发温度制冷系统。对双蒸发器表面温度的控制直接影响冻干的质量。文中对双蒸发器在冻干工艺中的调节性能进行了实验研究:首先,分析了针型阀门的开度对双蒸发器的影响;其次,分析了蒸发压力调节阀对于双蒸发器表面温度的调节特性;最后,通过实验得出了冷阱表面化霜时的温度控制曲线。     

实时三维经食管超声心动图诊断人工机械瓣卡瓣的应用价值

目的探讨实时三维经食管超声心动图（RT-3D-TEE）诊断人工机械瓣卡瓣的临床应用价值。方法回顾性分析10例经手术证实为人工机械瓣卡瓣患者的RT-3D-TEE资料,其中二尖瓣位7例,主动脉瓣位3例。结果机械瓣开放幅度明显减小8例;人工机械瓣呈固定半开放状态2例,瓣口流速增快并有中量反流;见低回声附着于瓣环5例,4例瓣环处见稍高回声赘生物,1例瓣柱结构模糊。手术证实血栓形成6例,肉芽组织增生2例,伴有纤维组织侵入1例,人工机械瓣瓣柱断裂1例。结论RT-3D-TE可对人工机械瓣卡瓣及其原因进行较准确评价。     

Liquid Crystals: A Bibliography for 1975

Abstract

The static dielectric constants of biphenyl-4-p-n-alkoxybenzoates have been measured as functions of temperature. The dielectric anisotropy (δ?) for the successive homologues (hexyl to undecyl) shows an alternation similar to that exhibited by the nematic-isotropic transition temperature (T _NI). The dispersion of ?_∥ in the frequency range of 0.1-15 MHz has been studied for four successive members of biphenyl-4-p-n-alkoxybenzoates (heptyl to decyl derivatives) as well as of trans-p-n-alkoxy-α-methyl-p'-cyanophenyl cinnamates (eighth to eleventh members). For both series the relaxation frequency (f _R) and the frequency of dielectric isotropy (f _o) evaluated at a common relative temperature show an alternation similar to T _NI. For any given compound the Arrhenius plots for f _R and f _o give the same value of the activation energy (W). In the case of the biphenyl esters the vaue of W is the same for the seventh and eighth members, but increases for the higher members which exhibit a smectic phase at lower temperatures. On the contrary for cinnamic acid esters W is found to be the same for all homologues irrespective of whether the nematic phase is preceded by a smectic phase or not.     

截止阀启闭过程内部瞬态流动特性

为分析截止阀启闭过程内部的瞬态流动特性,基于N-S方程和标准的κ-ε湍流模型,通过自定义函数(UDF)和C++语言编程给定阀芯的运动规律,采用动网格技术对截止阀进行了瞬态的全三维湍流数值模拟,得到阀芯在不同运动时刻的瞬态流场,阀芯在运动过程中受到的流体挤压效应是影响截止阀性能的主要原因。截止阀瞬态的全三维数值研究具有较高的可靠性,数值结果为进一步研究截止阀的性能提供重要理论依据。