高超音速零攻角尖锥边界层转捩的机理

先计算出高超音速零攻角尖锥边界层的定常层流流场．然后在计算域的入口引入两组有限幅值的T-S波扰动,对空间模式的转捩过程进行了直接数值模拟．分析了转捩过程的机理,发现平均流剖面稳定性的变化是其关键．并进一步讨论了不同模态初始扰动在高超音速尖锥边界层中的演化规律．     

像平面式干涉成像光谱仪光程差分析与计算

像平面式干涉成像光谱仪的光程差(OPD)线性度与光谱及图像重建精度直接相关。分析了光程差产生原理,通过分别对单个像面的正离焦及负离焦部分光程差进行讨论,给出了像平面式干涉结构在单侧及双侧离焦模式下的光程差表达式,并对两者在不同波长满足奈奎斯特条件时的光程差及其非线性残差进行仿真,并通过实验验证。仿真结果表明:系统在两种工作模式下的光程差非线性残差均随像面夹角增加而增大,单侧离焦模式零级点两侧光程差不对称,且负离焦部分残差较小;双侧离焦模式零级点两侧光程差对称,但非线性残差大于前者。实验结果表明,当工作波长较短时(如紫外),单侧离焦模式负离焦部分在实际应用中可认为满足光程差线性分布关系。     

NUMERICAL INVESTIGATION OF EVOLUTION OF DISTURBANCES IN SUPERSONIC SHARP CONE BOUNDARY LAYERS

The spatial evolution of 2-D disturbances in supersonic sharp cone boundary layers was investigated by direct numerical simulation (DNS) in high order compact difference scheme. The results suggested that, although the normal velocity in the sharp cone boundary layer was not small, the evolution of amplitude and phase for small amplitude disturbances would be well in accordance with the results obtained by the linear stability theory (LST) which supposes the flow was parallel. The evolution of some finite amplitude disturbances was also investigated, and the characteristic of the evolution was shown. Shocklets were also found when the amplitude of disturbances increased over some value.     

张力结构的非线性有限元分析

张力结构中的索结构分析通常采用非线性二节点直线或二次曲线单元，但是在大跨度结构，尤其是索弯顶结构的分析中，常用的单元已不能满足精度的要求，本文提出了考虑自重作用下有初始垂度的五结点非线性空间曲线元模型，放弃了一些特殊的假定，考虑了应变表达式中高阶量的影响，推导出了适合于弹性大位移几何非线性分析的Ｌａｇｒａｎｇｄ方程及其切线刚度矩阵，编制了相应的计算程序。     

脉冲激光作用下的量子定位实验方案的设计及分析

基于量子相干和量子空间定位的原理,设计了量子空间定位的实验方案.讨论了在脉冲激光作用下,由第二类自发参量下转换所产生的纠缠光子对的光谱特征、对应的相干函数特点以及对量子定位的影响.结果表明,随着激光脉冲宽度的增加,纠缠光子对的相干性减小,量子定位的测量准确度降低.     

Poor rich demarcation of Matthew effect on scale-free systems and its application

In a scale-free network,only a minority of nodes are connected very often,while the majority of nodes are connected rarely. However,what is the ratio of minority nodes to majority nodes resulting from the Matthew effect In this paper,based on a simple preferential random model,the poor-rich demarcation points are found to vary in a limited range,and form a poor-rich demarcation interval that approximates to k/m ∈ [3,4]. As a result,the (cumulative) degree distribution of a scale-free network can be divided into three intervals: the poor interval,the demarcation interval and the rich interval. The inequality of the degree distribution in each interval is measured. Finally,the Matthew effect is applied to the ABC analysis of project management.     

Mass spectrum and strong decays of strangeonium in a constituent quark model

In this work we calculate the mass spectrum of strangeonium up to the 3D multiplet within a nonrelativistic linear potential quark model.Furthermore,using the obtained wave functions,we also evaluate the strong decays of the strangeonium states with the ^3P_0 model.Based on our successful explanations of the well established states φ(1020) , φ(1680) , h_1(1415) , f'_2(1525) ,and φ_3(1850) ,we further discuss the possible assignments of strangeonium-like states from experiments by combining our theoretical results with observations.It is found that some resonances,such as f_2(2010) and f_2(2150) ,listed by the Particle Data Group,and X(2062) and X(2500) ,newly observed by BESIII,may be interpreted as strangeonium states.The possibility of φ(2170) as a candidate for φ(3S) or φ(2D) cannot be excluded.We expect our results to provide useful references for looking for the missing s\bar{s} states in future experiments.     

常见黄瓜病害的多光谱诊断

为了实现可靠的植物病虫害诊断,文章提出把光谱分析技术和多光谱成像技术相结合的方法用于常见的红粉、黑星、白粉、褐斑和霜霉五种黄瓜病害的识别研究。实验采用窄带多光谱成像技术在标准观测环境下获取患病黄瓜叶面的14个可见光通道和近红外通道、全色通道的多光谱图像。利用距离法、光谱角度匹配法和相关系数法对病斑样本的光谱信息进行学习分类。对于实验提出的七种分类情况,通过距离法和相关系数法组合筛选,对红粉、白粉、黑星和白板的分类正确率达100％,对霜霉及无病的分类正确率达80.00％和93.33％,平均分类正确率为81.90％。实验结果表明,光谱分析方法和多光谱成像技术结合能全面、快速、精确提取植物病害的信息,实现分类,为对植物病害进行快速、准确和非破坏性诊断提供技术支持。     

四边型弯张换能器特性研究及宽带设计

四边型弯张换能器通常工作带宽较窄,为了提高带宽性能,对四边型弯张换能器振动及辐射特性进行了研究,重点分析壳体结构参数对换能器发送电压响应的影响。根据分析结果提出了拓宽换能器工作带宽的方法,利用有限元软件进行了仿真计算并制作了四边型弯张换能器样机。测量得到在2.4~5 kHz的频率范围内,换能器的最大发送电压响应值达到140 dB,带内起伏4 dB,有限元仿真结果与实验结果吻合较好。研究结果表明设计的四边型弯张换能器不仅能够低频工作,并且可以在小尺寸下实现大功率发射,同时还具备宽带发射特性。     

Approximating the CIECAM02 color appearance model by means of neural networks

An artificial neural network used to realize the approximating problem of the color appearance model (CAM) CIECAM02 in color management is demonstrated. GretagMacbeth ColorChecker Charts, which now axe widely used in calibration of digital camera, are chosen as samples to implement the forward and reverse color appearance models. When the predictive results are evaluated, for forward model, the output color appearance space is converted to the uniform color space based on CAM and is evaluated, while for reverse model, because the prediction precision is insufficient, we try to convert the color appearance space, which is the cylinder space, to the cube space similar to the red, green, and blue (RGB) space, and the results show that the precision is obviously improved.