Surface oil flow technique and liquid crystal thermography for flow visualization in impulse,wind tunnels

This paper describes flow visualization techniques employing surface oil flow and liquid crystal thermography suitable for use in impulse wind tunnels. High spatial resolution photographs of oil flow patterns and liquid crystal thermograms have been obtained within test times ranging from 7 to 500 ms and have been shown to be very useful for revealing the detailed features of 3-D separated flow. The results from oil flow patterns, liquid crystal thermograms, schlieren photographs and heat flux measurements are shown to be in good agreement.     

SWT-120风洞稳定段的性能测量

在普通超音速风洞中,由于受到噪声干扰,很难进行有效的边界层转捩特性试验研究,针对超声速流动特点发展较低噪声风洞十分必要,而稳定段设计的好坏直接影响到下游试验段噪声水平。本文介绍一座低噪声风洞稳定段的结构和性能测量结果。先对稳定段的结构设计做了简单介绍,然后对实验结果进行分析,实验结果表明在大角度扩散段内装置孔锥,稳定段安装消音夹层和阻尼网组等部件后,气流的速度脉动和压力脉动明显降低,其中压力脉动降低一个量级,速度脉动为1%。进一步优化设计和改进工艺,速度脉动还可进一步降低。测量结果表明SWT-120稳定段的设计是成功的,对我们以后发展更高性能的静风洞有借鉴和参考价值。     

Effect of thermal annealing on the ac impedance of Co/Al2O3/Co/Al2O3/Co double-barrier MTJs

Double-barrier magnetic tunnel junctions (DBMTJs) were prepared from Co(75 nm)/Al₂O₃(2.3 nm)/Co(5 nm)/Al₂O₃(2.3 nm)/Co(50 nm) sputtering pentalayer films. The ac electrical properties of as-deposited DBMTJs and those annealed in a vacuum at 100–350 °C for 30 min were then investigated using a complex impedance spectroscopic technique. The ac impedance responses as a function of annealing temperature were further analyzed based on Maxwell's layered dielectric barrier and Maxwell–Wagner capacitor models after considering the DBMTJs as having double-capacitor-type structures. The effect of thermal annealing on the ac transport behavior of the DBMTJs was interpreted by examining the equivalent electric circuits fitted to Nyquist plots of each different sample. The effects were found to be due to changes in the structural characteristics in both bulk and interface morphologies of Co and Al₂O₃ layers. The structural morphology determined the different ac transport modes that occurred in the DBMTJs.     

Determination of probe spacings for the precise evaluation of electrical characteristics of a magnetic tunnel junction by in-house current-in-plane tunneling measurements

Magnetic tunnel junctions have not been easily accessible for research because of not only their complicated fabrication processes but also side effects induced during the fabrication. The method utilizing arrays composed of in-line four-point probes with various spacings is promising as an alternative to the fabrication method. We found in the current-in-plane tunneling measurement that the determination of the probe spacing is the most important to evaluate the characteristics of magnetic tunnel junctions. Our simulation indicates that if one would choose at least more than three sets of an array with probe spacings centered at the spacing at which the maximum current-in-plane tunneling magnetoresistance is observed, the statistics should become improved resulting in the accurate evaluation of the properties of tunnel junctions. We also found that the suitable probe spacings with a change in the resistance of electrodes are not as sensitive as those with a change in the RA of the tunnel junction. Our results alert that the failure of selecting suitable probe spacings observes no tunneling signals because tunneling is very sensitive to the resistances of the tunnel junction and electrodes, which makes the current-in-plane tunneling method useless.     

横截面积参数对钛氧化物忆阻器导电特性的影响

纳米钛氧化物忆阻器的导电过程因自身参数的改变及不同机理的共存而呈现复杂特性,但现有研究缺乏针对横截面积参数的改变对忆阻器导电特性影响的讨论.基于杂质漂移及隧道势垒机理,本文分析了忆阻器导电过程,研究了横截面积参数与导电过程中各关键物理要素间的关联,并基于此,分别研究了钛氧化物横截面积及隧道势垒横截面积的改变对忆阻器导电特性的影响,分析了两者的区别与联系.验证了两种机理共存情况下,相对于钛氧化物横截面积的改变,隧道势垒横截面积的改变是引发忆阻器导电特性变化的主要因素,且是导致忆阻器非理想导电特性的可能因素.研究成果有助于进一步解释忆阻器导电过程的复杂性,并为优化忆阻器模型的构建提供依据.     

Neural Networks Predict Protein Folding and Structure: Artificial Intelligence Faces Biomolecular Complexity

Abstract

In the genomic era DNA sequencing is increasing our knowledge of the molecular structure of genetic codes from bacteria to man at a hyperbolic rate. Billions of nucleotides and millions of aminoacids are already filling the electronic files of the data bases presently available, which contain a tremendous amount of information on the most biologically relevant macromolecules, such as DNA. RNA and proteins. The most urgent problem originates from the need to single out the relevant information amidst a wealth of general features. Intelligent tools are therefore needed to optimise the search. Data mining for sequence analysis in biotechnology has been substantially aided by the development of new powerful methods borrowed from the machine learning approach. In this paper we discuss the application of artificial feedforward neural networks to deal with some fundamental problems tied with the folding process and the structure-function relationship in proteins.     

典型高层住宅建筑风压分布特性的试验研究

在大气边界层风洞中对某高层住宅建筑模型进行了风压分布风洞试验,分析了单体及受扰后建筑表面风压的分布特性.结果表明:凹形立面同高度处风压的相关性高,双层悬挑屋檐中,上层受负风压控制,下层受正风压控制,顶部玻璃挡板也受正风压控制;建筑物的风压分布受周边建筑及地形的干扰后产生较大变化,尤其是1倍于干扰物高度范围内,脉动风压的...     

径向谐和激励下圆形隧道衬砌的动力稳定性

对径向谐和激励下圆形隧道的动力稳定性进行了研究,从动荷载下衬砌结构的振动方程出发,得到了隧道衬砌动力失稳临界频率计算公式,对可能影响隧道衬砌动力稳定性的因素进行了参数分析,探讨了系统参数,如地基土的性质、衬砌径厚比、外激励的性质以及系统的阻尼对衬砌动力稳定性的影响.计算结果表明:隧道周围土体的性质以及系统阻尼对衬砌的动...     

高速公路长隧道出口段驾驶人视觉特征变化规律

为改善高速公路长隧道出口段信息认知舒适性和行车安全,应用中型客车进行实际隧道环境行车试验,研究了驾驶人在隧道出口段的视觉变化特征。将隧道出口段选定为洞内200m至洞外200m范围,采用眼动测试装置记录行车过程中驾驶人视觉特征参数,运用BP神经网络模拟视觉特征参数变化,建立出口区段驾驶人注视时间、注视次数和扫视幅度等参数变化的网络模型。结果表明:从驾驶人发现隧道出口起,随着与隧道出口的逐渐接近,注视时间不断减少,注视次数亦减少,而扫视幅度逐渐增加;出隧道后注视次数增加,注视时间稍微增加,洞外扫视幅度大于隧道内,但变化幅度较小。     

肘部骨关节病变所致肘管综合征的手术治疗

目的:探讨尺神经沟扩大成型术治疗肘部骨关节炎、类风湿性关节炎所致的肘管综合征的疗效。方法:对11例肘管综合征患者行手术治疗,应用尺神经修复后功能评定试用标准和Lascar分级法评价疗效。结果:中度患者4例,术后优良率100%,重度患者7例,术后优良率86%。结论:尺神经沟扩大成型术方法简单易行,安全性高,疗效满意。