高速水流中旋涡空化所引起的空蚀和振动

为了研究旋涡空化所引起的空蚀和振动观象以及二者的关系,采用高速摄影的方法,观察了发生在射流放水阀山部的空化形态。采用快速富里叶变换（FFT）分析了空化所引起的振动。采用失重法,进行了空蚀实验。结果表明,旋涡空化能引起严重的空蚀和剧烈的振动。在旋涡空化发展的个同阶段,其所导致的振动和空蚀呈观了个同的特性。当Sσ>0.74时,随空化数的变化,振动和空蚀呈现了相同的变化趋势,但是,在0.50<σ<0.74的范围内,振动和空蚀呈现了相反的变化趋势。这是由于水流中空化旋涡的数目和形态随空化数的变化,以及旋涡空化引起振动和空蚀的机理不同所造成的。     

Application of Tikhonov regularization method to wind retrieval from scatterometer data Ⅱ: cyclone wind retrieval with consideration of rain

According to the conclusion of the simulation experiments in paper I, the Tikhonov regularization method is applied to cyclone wind retrieval with a rain-effect-considering geophysical model function (called GMF+Rain). The GMF+Rain model which is based on the NASA scatterometer-2 (NSCAT2) GMF is presented to compensate for the effects of rain on cyclone wind retrieval. With the multiple solution scheme (MSS), the noise of wind retrieval is effectively suppressed, but the influence of the background increases. It will cause a large wind direction error in ambiguity removal when the background error is large. However, this can be mitigated by the new ambiguity removal method of Tikhonov regularization as proved in the simulation experiments. A case study on an extratropical cyclone of hurricane observed with SeaWinds at 25-km resolution shows that the retrieved wind speed for areas with rain is in better agreement with that derived from the best track analysis for the GMF+Rain model, but the wind direction obtained with the two-dimensional variational (2DVAR) ambiguity removal is incorrect. The new method of Tikhonov regularization effectively improves the performance of wind direction ambiguity removal through choosing appropriate regularization parameters and the retrieved wind speed is almost the same as that obtained from the 2DVAR.     

氘离子束轰击石墨引起化学腐蚀的实验进展

在ＳＭＦ－８００ 石墨第一壁化学腐蚀温度特性的实验研究基础上,进一步测试了Ｇ３ 石墨、ＳＭＦ－８００ 高纯石墨和硼化石墨,以及ＳｉＣ涂层等在１．３μＡ／３ｋｅＶ 氘离子束轰击下化学腐蚀的温度特性。从中优选出Ｃ２Ｂ１０Ｈ１２ 氦辉光放电法制取的ＳＭＦ－８００ 石墨硼化层,它具有最佳的抗化学腐蚀性能。其ＣＤ４ 产额较ＳＭＦ－８００ 高纯石墨的降低一个数量级以上,ＣＤ４ 产额峰值温度下移至６５０Ｋ附近。用小角度转动样品法,初步观察了氘离子束轰击下石墨释放ＣＤ４ 的角分布特性,为托卡马克先进偏滤器实验中确立ＣＤ４ 辐射区的定位及其控制等可行性进行了探索     

基于级联神经网络的实用型三维复合不变性多目标识别

以三 飞机模型作为待识别目标,模型真实场景,对用于多目标分类识别的级联神经网络重新进行了研究。实验发现畜产品上降的主要原因是实际采集的目标发生的复杂畸变与计算机模拟产生的效果并不一样。用采集得到的目标图像作为训练样本,对网络重新构造和训练,取得了好的实验结果。分析了其中涉及到目标定位、图像分割等图像预处理问题,提出了一种基于二值图像开矿学腐蚀运算的快速目标检测位法,可快速有效地对目标进行检测定 。     

Erosion in conical diffusers in particulate-laden cavitating flow

This paper highlights the serious damage that can occur in diffusing sections of pipework in which a cavitating particulate-laden fluid is flowing. The combined effects of particle erosion and cavitation are shown to remove considerably more material than would be expected from summing the effects of the individual mechanisms. It is demonstrated that, to be sure of avoiding this accelerated surface erosion, the transition from a smaller flow section to a larger one needs to be an abrupt expansion. If pressure recovery is important, a possible design solution is proposed. In the case of swirling flow, the expansion again needs to be abrupt. Evidence was also obtained which showed that, by allowing air to be entrained into the low pressure region in the flow, the cavitation and the erosion can be substantially reduced.     

Model Study of Basin Soil Loss (BSL) in the Loess Plateau of China (Ⅰ)

Rain is the main motive force of erosion in the Loess Plateau of China. The relationship between rain and basin soil loss (BSL) is the base for establishing BSL model. Based on areo image interpretation, site investigation and analysis of 30-year rain-hydrological data of the study area——the Gushanchuan River Basin which is a branch of the middle reaches of the Yellow River basin as well as one of the intense erosion centres, the BSL features have been revealed. According to the features, the structure of the BSL model is proposed as follows: C·R =S, where C, R and S represent the factor of underlayer, rain and BSL quantity, respectively.Then by using the methods of multivariate statistical analysis, the dominant rain specific elements that affect the BSL and the corresponding formula of the relationship between rain and BSL have been determined as P_m and I_a, and respectively. With this formula the BSL quantity of every rainfall can be estimated. The estimated accuracy can be satisfied after correc     

Temperature and density profiles of magnetically rotating arcs burning in contaminated argon

Spectroscopic measurements on copper vapors emitted by the cathode are presented for magnetically rotating arcs in a coaxial copper electrode geometry. The maximum temperature of a 100-A arc column burning in contaminated argon is shown to be lower than 8000 K. A maximum Cu density of 5 × 10²¹ in m^–3 is observed when argon is contaminated with 1% CO, while it is larger than 10²² m^–3 with 1% nitrogen contamination. The copper vapors emitted by the cathode explain the low temperatures observed. Cases of surface control of the arc velocity at the cathode and radial losses of copper vapors out of the arc column are observed front specific parameters describing the arc profiles. Evidence is given for a copper ion recombination zone extending 2 mm from the cathode in the nitrogen contamination case.     

Room-temperature surface-erosion route to ZnO nanorod arrays and urchin-like assemblies

A solution surface-erosion route was successfully employed to produce one-dimensional (1D) ZnO nanostructures. ZnO nanorod arrays and three-dimensional urchin-like assemblies could be selectively obtained with different manipulations. In this process, zinc foil was introduced to an organic solution system and acted both as a reactant and substrate to support the 1D nanostructures obtained. This method, without any template, apparatus, surfactants, or additional heterogenous substrates, has greatly simplified the preparation of oriented 1D ZnO nanostructures. In particular, this simple route could be carried out at room temperature over a period as short as several minutes, thus it could be conveniently transferred to industrial applications. The possible formation mechanism, erosion process, and influence factors were also investigated.     

Analysis of the Initial Slope of the Small‐Angle Scattering Correlation Function of a Particle

The small‐angle scattering correlation function of a particle γ(r) results from scattering experiments. This function possesses a well‐defined slope γ′(0) at the origin. This slope is defined by the particle volume V and the whole surface area S of the particle via γ′(0) = –S/(4V). In this paper it is demonstrated that this slope defines the mean chord length of the particle, . This theorem involves non‐convex particles, especially the case of particles with hollow parts. Consequently, for a large class of particle shapes the mean chord length is defined in terms of V and S. This extension of the Cauchy theorem is developed by closer analysis of the set covariance C(r), of the small‐angle scattering correlation function γ(r), and of the so‐called linear erosion P(r) near the origin r→0. The cases of a single hollow sphere, of two touching spheres, and of the single hollow cylinder are discussed.