Influence of Surface Stress on Frequency of Microcantilever-Based Biosensors (vol 10, pg 307, 2004)

Microcantilever-based biosensors have been found increasing applications in physical, chemical, and biological fields in recent years. When biosensors are used in those fields, surface stress and mass variations due to bio-molecular binding can cause the microcantilever deform or the shift of frequency. These simple biosensors allow biologists to study surface biochemistry on a micro or nano scale and offer new opportunities in developing microscopic biomedical analysis with unique characteristics. To compare and illustrate the influence of the surface stress on the frequency and avoid unnecessary and complicated numerical solution of the resonance frequency, some dimensionless numbers are derived in this paper by making governing equations dimensionless. Meanwhile, in order to analyze the influence of the general surface stress on the frequency, a new model is put forward, and the frequency of the microcantilever is calculated by using the subspace iteration method and the Rayleigh method. The sensitivity of microcantilever is also discussed. (19 refs.)

Cloning and sequencing of the phycocyanin gene from Spirulina maxima and its evolutionary analysis (vol 14, pg 307, 2002)

The geneswere cloned for the two apoprotein subunits, alpha and beta, of phycocyanin from the cyanobacterium Spirulina maxima (=Arthrospira maxima) strain F3. The alpha- and beta-subunit gene-coding regions contain 489 bp and 519 bp, respectively. The beta-subunit gene is upstream from the alpha-subunit gene, with a 111-bp segment separating them. Similarities between the alpha-subunits of S. maxima and nine other cyanobacteria were between 58% and 99%, as were those between the beta-subunits. The maximum similarity between the alpha- and beta-subunits from S. maxima was 27%.

Flow-Induced Vibrations Of A Cylinder With Two Degrees Of Freedom Near Rigid Plane Boundary

Based on similarity analyses, the flow-induced vibrations of a near-wall cylinder with 2 degrees of freedom are investigated experimentally by employing a hydroelastic apparatus in conjunction with a flume. The cylinder's vibration amplitude, vibration frequency and vortex shedding frequency were measured and analyzed. The effects of gap-to-diameter ratio (e,ID) upon the vibration responses are further investigated. The experimental results indicate that, when the reduced velocity (Vr) is small (e.g. Vr = 1.2 similar to 2.6), only streamwise vibration occurs, and its frequency is quite close to its natural frequency in still water. When increasing Vr (e.g. Vr > 3.4), both streamwise and transverse vibrations of the near-wall cylinder may occur. In the examined range of gap-to-diameter ratio (0.42 < e(0)/D < 2.68), 2 vibration stages (in terms of Vr) of streamwise vibrations usually exist: First Streamwise Vibration (FSV) and Second Streamwise Vibration (SSV). In the SSV stage, the vortex shedding frequency may either undergo a jump to that of the streamwise vibration, or stay consistent with that of the transverse vibration. The amplitudes of transverse vibration are usually much larger than those of streamwise vibration for the same value of e(0)/D. The maximum amplitudes of both streamwise and transverse vibration get larger with the increase of e(0)/D (0.42 < e(0)/D < 2.68).

Proper orthogonal decomposition of oscillatory Marangoni flow in half-zone liquid bridges of low-Pr fluids

Proper orthogonal decomposition (POD) using method of snapshots was performed on three different types of oscillatory Marangoni flows in half-zone liquid bridges of low-Pr fluid (Pr = 0.01). For each oscillation type, a series of characteristic modes (eigenfunctions) have been extracted from the velocity and temperature disturbances, and the POD provided spatial structures of the eigenfunctions, their oscillation frequencies, amplitudes, and phase shifts between them. The present analyses revealed the common features of the characteristic modes for different oscillation modes: four major velocity eigenfunctions captured more than 99% of the velocity fluctuation energy form two pairs, one of which is the most energetic. Different from the velocity disturbance, one of the major temperature eigenfunctions makes the dominant contribution to the temperature fluctuation energy. On the other hand, within the most energetic velocity eigenfuction pair, the two eigenfunctions have similar spatial structures and were tightly coupled to oscillate with the same frequency, and it was determined that the spatial structures and phase shifts of the eigenfunctions produced the different oscillatory disturbances. The interaction of other major modes only enriches the secondary spatio-temporal structures of the oscillatory disturbances. Moreover, the present analyses imply that the oscillatory disturbance, which is hydrodynamic in nature, primarily originates from the interior of the liquid bridge. (C) 2007 Elsevier B.V. All rights reserved.

平板集热器铁管板式集热板的最佳化

本文利用平板集热器管板式集热板的最佳化数学模型,计算得到了我国目前应用较广泛的铁管板式集热板的最佳化参数——在最小成本/效率参数时的最佳管间距、最佳板厚以及最佳管径。

无限长带状收缩的磁流体力学平衡和稳定

<正> 一、引言 由于拉长截面环形等离子体在实验中有较好的稳定性,因此不少受控理论工作者对它的磁流体力学平衡、稳定进行了研究。因其几何形态复杂,在过去的工作中都认为等离子体紧贴导体壁,实际上在等离子体与导体壁之间总有一低密度区——“真空区”存在,本文的目的就是讨论这种自由边界等离子体的平衡、稳定性质。因为在带状收缩演化早期,本质上是一个一维问题,其半高与半宽之比也很大,有的达10—14,因此文中取一无限长的中空圆管作为高度拉长带状收缩的近似,并根据[4]中的实验结果,

Explorations of electric-current system in solar active regions .1. Empirical inferences of the current flows

In this paper we explore techniques to identify sources of electric current systems and their channels of flow in solar active regions. Measured photospheric vector magnetic fields (VMF) together with high-resolution white-light and H filtergrams provide the data base to derive the current systems in the photosphere and chromosphere. Simple mathematical constructions of fields and currents are also adopted to understand these data. As an example, the techniques are then applied to infer current systems in AR 2372 in early April 1980. The main results are: (i) In unipolar sunspots the current density may reach values of 103 CGSE, and the Lorentz force on it can accelerate the Evershed flow, (ii) Spots exhibiting significant spiral pattrn in the penumbral filaments are the sources of vertical major currents at the photospheric surface, (iii) Magnetic neutral lines where the transverse field was strongly sheared were channels along which strong current system flows, (iv) The inferred current systems produced oppositely-flowing currents in the area of the delta configuration that was the site of flaring in AR 2372.

带空腔爆轰加载装置对驱动飞片的影响

结合实验和数值模拟技术 ,研究了在炸药透镜和飞片之间引入空腔对爆轰躯体的定量影响。计算和实验结果基本一致 ,表明引入空腔的爆轰加载装置可以推动厚度 6mm以上的厚飞片 ,并可以避免飞片中出现层裂现象 ,从而可以实现较低的冲击压力和较长的压力脉宽 ,在推动厚飞片和较严格地控制作用时间方面也有明显的优点

可压涡卷空间演化的迎风紧致差分数值模拟

从数值算法的耗散和色散特征的时空全离散Fourier分析出发，通过直接求解二维非定常可压Navier-Stokes方程，将发展的5阶迎风紧致差分格式用于无约束可压平面受迫剪切层中基频涡卷空间演化过程的数值模拟。采用被动守恒标量等方法显示了基频涡卷的饱和、一次对并、二次对并等现象，据此探讨了入口来流亚谐扰动引起的初值效应问题，表明可压大尺度涡结构空间演化形态与受迫扰动方式之间存在关联。

中国科学院力学研究所2001年度科研状况与主要进展

<正>2001年是跨入新世纪的第一年,也是“十五”的第一年．在此年度,力学所的科研工作在诸多层面上都取得了重要的突破和进展．

中国科学院力学研究所2005年科技工作回顾

2005年，力学所经历了几件大事：一是完成了中国科学院知识创新工程试点二期的总结和创新三期筹划，并顺利通过了现场评估，为进入2006年开始的创新三期奠定了坚实基础；二是成功举办丁“庆祝力学研究所建所50周年暨钱学森回国50周年大会”；二是在国家和（部门）重点实验室的评估中，我所非线性力学国家重点实验室和高温气体动力学重点实验室被评为数理科学“良好类”实验室．

基于槽道流LES数据库的湍流猝发检测

采用大涡模拟方法,在与两种Reynolds数情形的DNS结果进行充分验证的基础上,获得了不同Reynolds数情形槽道湍流的可靠LES数据库,由此可进一步得到任意Reynolds数时速度剖面、湍流强度、剪应力等统计量的时空分布以及猝发结构的时空特征.基于这些可靠的LES数据库,利用条件采样方法检测猝发事件的时空尺度,并提出由喷发事件时间间隔概率分布曲线确定组合参数对传统的条件采样方法进行改进,以避免检测结果的误差.检测结果表明,引入组合参数后,湍流猝发周期对门限的依赖性得到显著改善.同时,对猝发事件的空间分布进行检测,得到了平均猝发面积比.通过比较不同Reynolds数的结果发现,Reynolds数对平均猝发周期和平均猝发面积比的影响不大.

Numerical Simulation of R-M Instability

In order to capture shock waves and contact discontinuities in the field and easy to program with parallel computation a new algorithm is developed to solve the N-S equations for simulation of R-M instability problems. The method with group velocity control is used to suppress numerical oscillations, and an adaptive non-uniform mesh is used to get fine resolution. Numerical results for cylindrical shock-cylindrical interface interaction with a shock Mach number Ms=1.2 and Atwood number A=0.818, 0.961, 0.980 (the interior density of the interface/outer density p(1)/p(2) = 10, 50, 100, respectively), and for the planar shock-spherical interface interaction with Ms=1.2 and p(1)/p(2) = 14.28are presented. The effect of Atwood number and multi-mode initial perturbation on the R-M instability are studied. Multi-collisions of the reflected shock with the interface is a main reason of nonlinear development of the interface instability and formation of the spike-bubble structures In simulation with double mode perturbation vortex merging and second instability are found. After second instability the small vortex structures near the interface produced. It is important factor for turbulent mixing.

Subsonic interface crack with crack face contact

A steady-state subsonic interface crack propagating between an elastic solid and a rigid substrate with crack face contact is studied. Two cases with respective to the contact length are considered, i.e., semi-infinite and finite crack face contact. Different from a stationary or an open subsonic interface crack, stress singularity at the crack tip in the present paper is found to be non-oscillatory. Furthermore, in the semi-infinite contact case, the singularity of the stress field near the crack tip is less than 1/2. In the finite contact case, no singularity exists near the crack tip, but less than 1/2 singularity does at the end of the contact zone. In both cases, the singularity depends on the linear contact coefficient and the crack speed. Asymptotic solutions near the crack tip are given and analyzed. In order to satisfy the contact conditions, reasonable region of the linear contact coefficient is found. In addition, the solution predicts a non-zero-energy dissipation rate due to crack face contact.