低温液体管路输送中几个问题的分析

对低温液体传输过程中气体置换、预冷过程、竖直管道中间歇泉现象、盲支管填充时和阀门开启时的不稳定现象作了较详细分析,指出了其可能造成的危害,并提出了相应的解决方法。     

低温液体充填管路的数值计算

在低温液体的管路输送中,充填过程是一个使管路热负荷大幅减少的预冷却阶段,了解其特征规律非常重要。本文通过建立一维模型,对水平液氢加注管的预冷过程进行了数值计算,求得了各时刻管路的壁温分布,以及预冷却过程所用的时间。初步分析了低温液体充填管路过程中,管壁与工质的温度分布特点,以及管路长度、管径与加注流量对预冷却时间的影响。     

空分装置低温液体离心泵防“气蚀”措施的探索和研究

阐述了空分装置中低温液体泵的"气蚀"产生原因及泵本身的特性。通过分析、试验、探索和研究,与之对应提出了在设计低温液体泵进、出口管路系统时,通过一些注意事项,改进设计思路,预防"气蚀"现象的发生,进而提出了低温液体泵的防"气蚀"控制措施。     

间歇泉现象研究对低温推进剂加注系统的启示

通过对国内外研究现状的归纳与分析,介绍了关于间歇泉研究的进展和成果,并对抑制间歇泉方法进行了对比分析,阐述了各种方法适用于低温加注系统可行性,并提出了开展低温加注系统间歇泉研究的思路,为低温加注间歇泉危害性分析以及加注系统设计等方面的研究提供了理论支撑,为以后的研究奠定了基础。     

低温盲支管诱发水击振动的实验研究

低温加注管路系统难以避免存在盲支管结构,当系统中发生参数突变时,会存在诱发低温盲支管填充水击振动现象。本文从实验角度探索诱发低温盲支管填充水击振动的成因,结果表明:当盲支管处于热态时,通过对盲支管进行排气扰动,可诱发低温液体填充盲支管水击振动;管路系统的背压越高,盲支管水击振动压力值越大。     

凹形液氮管道排空过程分析

低温液体的管路排空为低温工程界常见问题,对安全产生重要影响。为了解低温液体管路排空过程,文中使用常温的氮气对充满液氮的管道进行吹除排空。采用流体力学与两相流的理论计算得到液氮排空过程的参数变化,并分析了不同的氮气温度、流量对液氮排空的影响。结果表明,对于复杂管路建议采用较大质量流量以及较高温度的气源进行低温液体的排空。     

新型的轻便自动输液装置

本文介绍了我们研制的新型轻便自动输液装置.它不需要电能和压缩气体能,仅利用虹吸再气化原理,靠低温液体气化后体积膨胀数百倍而产生的压力来输送液体.装置全重2.5kg结构简单轻巧,主要工作部分为三个气动单向阀和一个气化室系统.该装置已成功地用于低温物理,低温电子学和红外技术的实验中,小规模地从杜瓦容器向实验装置输送液氮、液氦和液空.一次驱动,便能自动输送5—10升液体;根据需要,还可循环驱动以输送更多的液体.     

低温输送系统的CO_2冷凝真空绝热方案研究

采用在真空夹层中充注纯度不高的一般工业用 CO2 的方法 ,来研究不同充注压力及不同绝热层材料下低温输送管路中的 CO2 冷凝真空绝热问题 ;分析了 CO2 纯度对绝热层真空度的影响。测量并计算了管路内充满液氮后真空绝热层的真空度、真空绝热层外壁壁温和绝热层的表观导热率。结果表明 ,在低真空绝热夹层中充注工业用 CO2 后 ,得到的真空绝热层绝热效果良好 ,能够满足一般的低温输送管路需求。     

低温管路预冷过程的实验研究

搭建了低温管路预冷过程实验台,并对不同管长和不同入口压力下低温管路预冷过程中压力和温度的变化情况进行了实验研究。结果表明,管路较长时,不稳定现象表现得更加剧烈,管路预冷时间变长,并会产生更大的压力峰值。     

超导体在低温液体泵中的应用研究与发展现状

由于低温液体泵固有的低温工作环境可为超导材料提供冷却条件而省去制冷系统,将超导材料应用于低温液体泵具有显著优势。本文针对高可靠性低温液体泵在低温流体输送中的应用需求,介绍了传统低温液体泵的应用背景及其存在的问题; 总结了国内外超导技术应用于低温液体泵的研究现状,详细讨论了低温泵用超导电机、低温泵用超导磁悬浮轴承和其他结构超导低温泵的研究热点和发展趋势; 在此基础上,提出一种轴向磁通盘式电机驱动的超导磁悬浮低温潜液泵。其离心泵叶轮和盘式电机转子在超导磁悬浮轴承系统的悬浮支撑下可实现无接触转矩传动和无摩擦旋转运行,该新型结构超导磁悬浮低温潜液泵在结构上具有独特优势,其研发对推动超导低温液体泵技术具有促进作用。     

Optical solitons and complexitons of the Schrödinger–Hirota equation

The Schrödinger–Hirota equation governs the propagation of optical solitons in a dispersive optical fiber. In this paper, this equation will be solved by the ansatz method for bright and dark 1-soliton solution. The power law nonlinearity will be assumed. By using the tanh method, some additional solutions will be derived. Finally, the numerical simulations will be given.     

On the nonlinear dynamics of a single degree of freedom oscillator with a time-varying mass

In this paper the forced vibrations of an undamped single degree of freedom oscillator with a time varying mass will be studied. An initial value problem for an oscillator equation with a Rayleigh type of nonlinearity will be formulated, and by applying a straight-forward perturbation method the problem will be solved approximately. The approximations of the solutions will be used to construct a map. By using this map the stability properties of the solutions can be determined. The stability properties of the nonlinear problem will be compared to those for the linear problem, which have been studied earlier in the literature. The instability regions in the parameter space and some phase-space figures for the nonlinear problem will be computed numerically. It will also be shown how the behaviour of the solutions changes when the instability regions in the parameter space are crossed.     

An LCD for the multimedia network age: Polymer stabilized FLCD

Liquid crystal displays (LCDs) will be classified into miniature displays, reflective type, projection type, direct view type, and holography type. All of these LCDs will be widely utilized in the coming multimedia network era. Along with this trend, in the first part of this paper we will discuss the social background of this research. We will place an emphasis on a polymer stabilized (PS) FLCD that is featured by fast response speed (40 microseconds), high contrast (230: 1) with grayscale, wide viewing angle, and high resolution (400 lp/mm). The PS-FLCD will be promising technology for displaying a moving video image in the multimedia network era.     

Recent advances in optical bistability

In this paper, recent advances in optical bistability and gating of semiconductors will be reviewed. Nonlinear mechanisms responsible for switching will be described. The advantages of nonlinear etalons for massive parallelism and current problems in performing such operations will be mentioned.     

Feasibility study for the use of PADC as a radiation detector for living cell cultures

In the framework of an ESA project, a microbiological experiment in space is planned. In this experiment a cell culture will be exposed to cosmic radiation onboard a spacecraft. Because the living cell culture will be directly on a nuclear track detector stack, this detector will be submitted to a different environment than normally used. The temperature will be 37°C and the culture will be in a biological growth medium. Tests have been conducted to assess the possible use of PADC in these conditions. For this, a series of alpha irradiated detectors have been exposed for different periods of time (up to 1 month) to these ‘biological’ conditions. The radiological properties as well as the mechanical properties (swelling…) have been investigated. Results show no influence of the biological environment on the PADC, which makes it useable under these circumstances.     

One-Dimensional Group III-Nitrides: Growth,Properties, and Applications in Nanosensing and Nano-Optoelectronics

This review will give a brief introduction to the growth and characterization methods of both binary and ternary compounds, in particular those exhibiting one-dimensionality, of the family to orient the readers about the material system to be discussed. A section will deal with the size and shape selection in group III nitride nanomaterials with a stress on intriguing morphologies such as nanowires, nanotips, and nanobelts. Complex structures, such as hierarchical and core-shell structures, will be introduced. Optical, electrical, and mechanical property, such as hardness, will be discussed in a greater detail, distinguishing the bulk from the nano wherever possible. Available models of electrical conduction and photoconduction in nanomaterials and their dependence on the actual size of the objects will be presented and compared. Optical properties of ensemble and single nanostructures, wherever possible, will be addressed in detail. The section on application will focus mainly on the sensor applications, including chemical sensors, gas sensors, and biosensors, with a thrust on DNA sensing. Because popular applications such as light-emitting diodes (LEDs) and field effect transistors (FETs) have already been reviewed extensively, only major contributions to this field—for example, nano-LEDs—will be discussed. Some recent advances in the group III-nitride materials family will be presented that will indicate future directions of research in this area.     

Quark confinement and curved spaces

In this work it will be shown how quark confinement appears when wave equations derived in curved spaces are considered. First, the equations and their solutions for Coulomb-like potentials will be presented, and then, how this theory leads to quark confinement. A comparison between different models of confinement will also be made. Arrival of the final proofs: 6 December 2005     

SHMFF去离子水冷却系统制冷升级改造设计

稳态强磁场实验装置去离子水冷却系统是保障水冷磁体稳定运行的必要技术装备系统之一。由于越来越多科学实验的开展,冷冻水蓄冷量不足的问题凸显,严重制约了水冷磁体的运行机时。本文介绍了去离子水冷却系统升级改造的方案设计及具体措施。采用优化设计的布水器,将现有蓄冷量增加一倍;为维持较短的制冷时间,新增大温差离心式冷水机组,与现有制冷机组并联使用;为了改善制冷系统的高耗能特性,增加闭式冷却塔在秋冬季节使用,系统可根据不同的湿球温度及回水温度,选择不同的制冷模式,让其取代冷水机组或其部分负荷使用,实现节能的目的。     

Effect of the glottal source and the vocal tract on the partials amplitude of vibrato in male voices

In this paper the production of vocal vibrato is investigated. The most relevant features of the acoustical vibrato signal, frequency and amplitude variations of the partials, will be related to the voice production features, glottal source (GS) and vocal tract response (VTR). Unlike previous related works, in this approach, the effect on the amplitude variations of the partials of each one of the above-mentioned voice production features will be identified in recordings of natural singing voice. Moreover, we will take special care of the reliability of the measurements, and, to this aim, a noninteractive vibrato production model will be also proposed in order to describe the vibrato production process and, more importantly, validate the measurements carried out in natural vibrato. Based on this study, it will be shown that during a few vibrato cycles, the glottal pulse characteristics, as well as the VTR, do not significantly change, and only the fundamental frequency of the GS varies. As a result, the pitch variations can be attributed to the GS, and these variations, along with the vocal tract filtering effect, will result in frequency and amplitude variations of the acoustic signal partials.