Extraction and verification of coherent structures in near-wall turbulence

According to the characteristics of coherent structures in near-wall turbulence, an accurate extraction and verification method is developed based on wavelet transform (WT) and correlation analysis in this paper. At first, the fluid field of a turbulent boundary layer is measured precisely in a gravitational low-speed water tunnel. On the basis of the distribution of the coherent structures, velocity data of three test points are selected and analyzed, whose dimensionless heights are 20.8, 33.5, and 42.6. According to the frequency range of power spectrum density (PSD), coherent and incoherent structures are both extracted from the original signals using continuous and orthogonal wavelet transforms. To confirm the validity of the extracted signals, the probability density function (PDF) of each extracted signal is calculated. The result demonstrates that the incoherent structures obey the Gaussian distribution, while the coherent structures deviate from the Gaussian distribution. The PDFs of the coherent structures and the original signals are similar, which shows that the coherent structures make most contributions to the turbulence. For further verification, a correlation parameter between coherent and incoherent structures is defined, which evidently proves the validity of the extraction method in this paper.     

肌红蛋白力致去折叠的全原子分析

位于脊椎动物骨骼肌中的肌红蛋白在生命过程中扮演着重要角色，其折叠过程依赖于血红素的绑定.本文着重于肌红蛋白在力的作用下去折叠过程的全原子统计分析.结果表明血红素不仅具有生物学上的功能，而且决定其去折叠的动力学过程.在血红素不存在的情况下，肌红蛋白的力致去折叠过程存在一个中间态，其构象不同于化学变性剂所导致的去折叠中间态，发现新的中间态.结论与相关实验结果相符，揭示了肌红蛋白力致去折叠的一般机制.     

实验室天体物理的验证特例:W43A磁喷流

利用神光II号八路激光与平面Al靶相互作用产生双等离子体喷流.利用阿尔芬-欧拉磁流体动力学标度变换理论产生的喷流与天体环境下形成的W43A喷流进行比较.发现在实验室中直接测量的喷流物理量经过变换后,与天文观测数据极其相似,同时提出重联电场对喷流的形成与准直存在直接的影响.     

基于稀疏表示的可见光遥感图像飞机检测算法

为解决当前遥感图像飞机检测方法在复杂背景下准确率低,实现旋转不变困难的问题,结合图像稀疏表示原理,提出一种基于稀疏表示的飞机检测算法.该算法首先利用飞机是刚性目标且具有明显几何外观的特点,构建飞机几何原子库;然后建立飞机轮廓几何逼近的最优化方程,在稀疏表示原理框架下,得到飞机轮廓最优的几何部件组合;最后,以星型结构的部件模型为框架,生成待检测图像的目标显著图并根据显著图定位出飞机.实验结果表明,稀疏表示方法能自适应选取飞机部件,部件数目较少且不易受光照、颜色和复杂背景的影响.与现有算法相比,本文算法准确率达90%以上,检测速度有较大的提高.     

基于局部相关性的遥感图像全色锐化算法

为了增强多光谱图像的空间分辨率同时避免出现严重的光谱扭曲,对插值放大后的多光谱图像和原始全色图像分别作相同层数的非下采样轮廓波变换分解.在相应低频子带中,分别选取以待融合像素点为中心,大小为5×5的滑动窗口,计算待融合像素点的局部相关系数与四阶相关系数.如果局部相关系数大于四阶相关系数,说明该位置上的地物存在相似的光谱特征,因此用全色图像的高频系数替代多光谱图像的高频系数;反之,保持多光谱图像的高频系数不变.最后将多光谱图像的低频系数和替换后的高频系数进行非下采样轮廓波逆变换得到融合图像.采用Landsat 7遥感图像,对比给出了本文与现有同类最新文献融合结果及其主客观评价指标.实验结果表明,本文算法在提高空间分辨率与保持光谱信息两个方面都具有较好的效果.     

基于可能度的三角模糊数互补判断矩阵排序方法

研究了决策信息为三角模糊数形式给出的互补判断矩阵排序问题.根据三角模糊数互相比较的可能度公式,提出一种基于可能度的三角模糊数互补判断矩阵的排序方法.该方法思路清晰、合理,计算简洁,易于上机实现.最后算例分析表明,该方法是可行、有效的.     

基于内生创新溢出的企业低成本产品定位与定价博弈分析

通过引入一类企业的有效创新贡献水平函数,应用三阶段博弈模型分析了创新溢出内生时双寡头企业的产品定位和定价决策问题.研究发现,双寡头企业产品的均衡定位是功能非替代率的增函数;企业间的产品差异随功能非替代率的增大而增加,内生溢出却随之增大而减小;如果从两企业均衡定位处稍微减小它们之间的差异程度,则产业利润将减少,而社会福利是否减小与单位产品的功能非替代率的取值有关.     

我国A股房地产板块羊群效应研究

借助CSAD模型、马尔科夫转换模型和GARCH模型的研究结果表明我国A股房地产板块存在明显的羊群效应且存在如下特点:非对称性,扩张期较衰退期更为显著;规模差异性,大盘股较中小盘股更为显著;房地产调控政策影响的非对称性,紧缩政策较之宽松政策会诱发更加明显的羊群效应;产业链传染性,上下游行业中的羊群效应产生影响.非系统性风险和系统性风险都对A股房地产板块羊群效应产生了促进影响,且系统性风险的影响较大.     

Hydrodynamic Properties of Fe3O4 Kerosene-Based Ferrofluids with Narrow Particle Size Distribution

We investigate the hydrodynamic properties of Fe3O4 kerosene-based ferrofluids with narrow particle size distribution. The ferrofluids are synthesized by improving chemical coprecipitation technique. A narrow distribution of 8.6-10.8nm particle sizes is obtained from the magnetization curve with the free-form model based on the Bayesian inference theory. The fitting result is consistent with average particle size obtained from x-ray diffraction. With the increase of applied magnetic field and magnetic particle concentration, apparent viscosity of ferrofluids increases. At concentration 4.04%, the type of flow for the ferrofluid transforms from Newtonian to Bingham plastic fluid as the applied magnetic field increases.     

Study on CYCIAE-100 radiation field and residual radioactivity

The accelerators should be properly designed to make the radiation field produced by beam loss satisfy the dose limits. The radiation field for high intensity H^－ cyclotron includes prompt radiation and residual radiation field. The induced radioactivity in accelerator components is the dominant source of occupational radiation exposure if the accelerator is well shielded. The source of radiation is the beam loss when cyclotron is operating. In this paper, the radiation field for CYCIAE-100 is calculated using Monte Carlo method and the radioactive contamination near stripping foil is studied. A method to reduce the dose equivalent rate of maintenance staff is also given.