基于弯曲激波特征线法的两级压缩内收缩流场设计与分析

进气道是超声速飞行器的关键部件,设计核心是无黏超声速流场的确定,而波系结构又直接决定了流场的性能。考虑到实际应用价值,基于给定激波的超声速流场反设计至关重要。传统单道入射波的流场结构简单,压缩效率不高,且传统特征线法(method of characteristics,MOC)无法获得高阶的气动参数。为了拓展设计思路,首先利用弯曲激波特征线法展示了内收缩超声速流场不同的单元过程,随后基于此法提出了一种已知入射和反射激波的两级压缩内收缩流场的概念及反设计方法。基于此法设计的基准流场与数值模拟结果吻合良好,双入射激波可以提高压缩效率并缩短长度,能够实现波系结构和出口参数的分布可控,在非均匀来流条件下也能得到相应型面。在给定激波的条件下,求解分析了一系列具有中心体的轴对称流场,讨论入射和反射激波激波角分布对流场气动参数和几何参数的影响。弯曲激波特征线法的精确性和有效性使其成为平面/轴对称超声速流场反设计的良好候选。

多媒质区域中电磁波传播的时域特征波模拟

将时域特征波法用于模拟多媒质区域的电磁波传播。与时域有限差分法相比 ,时域特征波法在处理媒质交界面和吸收边界上具有优越性。

特大型钢吊箱在波浪荷载作用下动力响应研究

采用子空间迭代得到了特大型钢吊箱结构的各阶频率和振型,并采用特征波法分析了其按余弦规律变化的波浪荷载作用下的动力响应。结果表明:规则余弦波浪对结构动力响应的影响较小。建议在设计钢吊箱时,可以在静力分析的基础上适当乘以一个放大系数来考虑动力的影响。

基于实时动态在线模拟的城市供水管道泄漏监测系统研究

供水管道漏损现象极为普遍,而传统的泄漏监测方法存在难以及时发现并定位泄漏等困难。因此,研发出可实时监测管道运行状况并判别和定位泄漏的相关技术,对保障供水安全有着重要的意义。本文采用波特征法求解管道瞬态数理模型,提出了一种基于实时动态在线模拟的城市供水管道泄漏监测方法,并将该方法应用于相关软件的开发中。初步模拟对比显示,该软件可准确判别泄漏并进行泄漏点的精准定位,未来可将其应用于实际工程中。

无创连续血压测量技术的研究进展

本文介绍了无创连续血压测量技术的重要性,重点分析了动脉张力法、容积补偿法、脉搏波速传导法和脉搏波特征参数测定法的原理、研究现状及难点,并根据研究现状对无创血压测量技术的发展提出了展望。

OBC水陆检数据合并处理技术

估算标定因子、海水深度和海底反射系数三个参数是OBC水陆检数据合并处理技术的关键步骤。针对常规方法确定这三个参数费时和精度低的缺陷,本文采用相关特征匹配法匹配水陆检数据、相关函数特征法直接计算标定因子、波场延迟特征法直接计算海底反射系数、分段归一化相关谱法直接计算海水深度和海水双程旅行时,对水中检波器数据和陆地检波器数据进行合并处理。合并后数据不但消除了海水鸣震多次波干扰,而且保留了陆检数据的低频成分和水检数据的高频成分,有效拓宽了海底电缆数据的有效频带,提高了地震资料的信噪比和分辨率。实例处理结果说明了方法的有效性和实用性。

Wavelet matrix transform for time-series similarity measurement

A time-series similarity measurement method based on wavelet and matrix transform was proposed,and its anti-noise ability,sensitivity and accuracy were discussed. The time-series sequences were compressed into wavelet subspace,and sample feature vector and orthogonal basics of sample time-series sequences were obtained by K-L transform. Then the inner product transform was carried out to project analyzed time-series sequence into orthogonal basics to gain analyzed feature vectors. The similarity was calculated between sample feature vector and analyzed feature vector by the Euclid distance. Taking fault wave of power electronic devices for example,the experimental results show that the proposed method has low dimension of feature vector,the anti-noise ability of proposed method is 30 times as large as that of plain wavelet method,the sensitivity of proposed method is 1/3 as large as that of plain wavelet method,and the accuracy of proposed method is higher than that of the wavelet singular value decomposition method. The proposed method can be applied in similarity matching and indexing for lager time series databases.

Feature spectrum extraction of human fingernails based on LCTF multispectral imaging

A multispectral imaging system consisting of liquid crystal tunable filter(LCTF)and charge coupled device(CCD)camera was used to collect the images of fingernail samples at intervals of 10 nm during the spectral range of 450-1 000 nm,and a multispectral image of human fingernails containing 56 bands was obtained.The accurate reflectivity information of fingernails was obtained through referring whiteboard comparative measurement method.Principal component analysis(PCA)and band index method were used to reduce the dimension of the sample images respectively and two feature spaces were obtained.Spectral angle mapping(SAM)was used to classify human fingernails in these two feature spaces.The classification accuracy were above 92.5%and 82.9%respectively.Therefore,the feature space obtained by the PCA can be used as the characteristic spectrum of human fingernails,which provides a reliable basis for the analysis of multispectral spectrum of fingernails and human health assessment in the future.

Integrability Test and Spatiotemporal Feature of Breather-Wave to the （2＋1）-Dimensional Boussinesq Equation

Painleve integrability has been tested for （2＋1）D Boussinesq equation with disturbance term using the standard WTC approach after introducing the Kruskai＇s simplification. New breather solitary solutions depending on constant equilibrium solution are obtained by using Extended Homoclinic Test Method. Moreover, the spatiotemporal feature of breather solitary wave is exhibited.

Wave interaction with a two-layer porous breakwater in the presence of step-type bottom

Oblique wave interaction with a two-layer breakwater consisting of perforated front and back wall in the presence of bottom undulations is analyzed.Wave characteristics are studied in the framework of small-amplitude wave theory,and Darcy’s law is used for flow past porous structures.The varying bottom topography spanned over a finite interval connected by two semi-infinite intervals of uniform water depths.Eigenfunction expansion method is used to handle the solution in the regions of uniform bottom and a modified mild-slope equation along with jump conditions is employed for varying bottom topography.Reflection,transmission,and wave energy dissipation coefficients are obtained numerically by applying the matrix method to understand the effects of several physical quantities such as wavenumber,porosity,and angle of incidence.The transmission coefficient reduces significantly and the wave energy dissipation is high for the present model.Also,Bragg scattering is analyzed in the presence of step-type rippled bottom and presented in this paper.