Dynamic behavior and sound transmission analysis of a fluid-structure coupled system using the direct-BEM/FEM

A direct-BEM/Fem method was proposed to analyze the vibration and acoustic radiation characteristics of a submerged structure. Model parameters of the structure and the fluid-structure interaction due to surrounding water were analyzed by using FEM and direct BEM. Vibration velocity of the outer hull surface and underwater sound pressure were computed through modal superposition technique. The direct-BEM/FEM method was first validated by analyzing a submerged cylindrical shell, then was used to analyze the vibro-acoustic behavior of a submarine stern structure. The results have demonstrated the direct-BEM/FEM method is more effective than FEM in computing the underwater sound radiation of the stern structure.  

分子模拟在生物化学中的应用实例

分子模拟是一种描述和模拟分子和分子体系运动状态和性质的方法.随着电子计算机技术的飞速发展,分子模拟进入了一个前所未有的新时代.在此之前,人们只能通过机械模型和纸笔计算进行简单的分子模拟,现在通过利用电子计算机人们可以做更为复杂、更为全面的分子模拟.本文通过两个实例来简单阐述了分子模拟在生物化学中的应用.一则是通过模拟膦酰基氧化腈和丙乙腈的1,3偶极环加成反应过程,用密度泛函理论方法在B3LYP/6-31G(d,p)水平上解释了得到2∶1的加成产物的现象,来解释1,3偶极环加成反应得到2:1加成产物的现象.一则是通过结构生物信息学的方法建立H5N1高致病性禽流感病毒蛋白的三维结构,模拟其与一些药物分子的相互作用,研究H5N1的活性中心.  

Blind restoration of real turbulence-degraded image with complicated backgrounds using anisotropic regularization

This paper proposes a novel blind image restoration method based on estimating the point-spread functions by using two real turbulence-degraded images as input. The non-negative constraint and the spatial correlation are transformed mathematically into the penalty terms and added to the objective function. An anisotropic and nonlinear regularization function is proposed to adequately punish the differences of the point spread functions (PSFs) in the process of optimization estimation. Some definitions of weighted second-order differences are given and a fast method to construct the matrix of second-order weighted gradient operator is derived. The PSF values can be quickly estimated. With the estimated PSFs, the true images can be recovered by non-blind restoration methods. Experiment results for the restoration of real turbulence-degraded images with complicated backgrounds support the effectiveness of this proposed method.  

LNG船用超低温球阀的低温应力分析及数值模拟

应用有限元分析软件分别对通径为DN15的LNG船用超低温球阀在超低温条件下的应力进行分析。研究了球阀的阀杆、阀颈、阀盖等部件的应力在低温下的数值。研究结果显示出了球阀在低温下的应力集中部位,并提出了改进措施。为超低温球阀的结构设计提供了理论指导。  

Contrast Adaptation Decreases Complexity in Retinal Ganglion Cell Spike Train

The difference in temporal structures of retinal ganglion cell spike trains between spontaneous activity and firing activity after contrast adaptation is investigated. The Lempel-Ziv complexity analysis reveals that the complexity of the neural spike train decreases after contrast adaptation. This implies that the behaviour of the neuron becomes ordered, which may carry relevant information about the external stimulus. Thus, during the neuron activity after contrast adaptation, external information could be encoded in forms of some certain patterns in the temporal structure of spike train that is significantly different, compared to that of the spike train during spontaneous activity, although the firing rates in spontaneous activity and firing activity after contrast adaptation are sometime similar.  

Near field acoustic solution of a rotating point source in frequency domain

I.IntroductionAerodyntalcnoiseofturbomaChinrynotoalythectstheenvironmentbutalsosometimesresultsinstructuredamage.Aeroacoustics,asaintewhsciPlineofacousticsandaerodynamics,isattractingmorandmoreatteDtionandresearch.TherearetwoimportalltcontentsonthenoiseproducingmechAnsmsinaeroacousticproblem.OneisaboutthesourcesofnoiseinturbomachinryGenetallytherearethreetyPesofsources:thickness,forceandturbulencestress,correspondingrespectivelyTomonopole,dipoleandquadruplesourcesThelatertwokindsofsourcesh…  

Design of fly's-eye lens for LCOS laser display

Design of optical system in laser display has always been an important research topic. From the aspect of decreasing the system volume and improving the light efficiency, it can be found that when the size of fly's-eye lens and the value of f/# are definite, the more fly's-eye arrays there are, the more useful it will be to the decrease of the optical engine size, which means that more honeycombs on fly's-eye lens and better dodging effect can be more beneficial for the decrease of the system size. After the optimal design for the rectangular elements on sub-fly's-eye lens and then doing 4000 ray tracing, the light transmittance turns out to be good with little parasitic light and scattering light.  

Parallel detection and quantitative analysis of specific binding of proteins by oblique-incidence reflectivity difference technique in label-free format

In this work, we parallelly detected the specific binding between microarray targets including 12 different kinds of proteins and the probe solution containing five corresponding antibodies and quantitatively analyzed the interactions between CDH13 and solution phase anti-CDH13 at six different probe concentrations by oblique-incidence reflectivity difference (OIRD) method in label-free format. The detection sensitivity reached 10 ng/mL. The experimental results indicate that the OIRD method is a promising and competing technique not only in research work but also in clinic.  

Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification

Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992,optical parametric chirped pulse amplification(OPCPA)became the most promising method for the amplification of broadband optical pulses.In the meantime,we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers.The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level.Meanwhile,the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field.In this paper,we overview the basic principles,trends in development,and current state of the ultrashort and laser systems based on OPCPA,respectively.  

Calculation and analysis of Mueller matrix in light scattering detection

A new criterion for target detection and identification is proposed to realize metal/dielectric identification and recognition based on Mueller matrix analysis. By using randomly rough surfaces as targets, numerical calculations are used to prove the robustness and accuracy of the criterion. Moreover, to the best of our knowledge, this is the first time to successfully explain the criterion by theoretical analysis. We believe the work orovides an important reference for polarization imaging in laser radar and remote sensing, and so on.