Effect of surface roughness on rarefied-gas heat transfer in microbearings

In this Letter, the rarefaction and roughness effects on the heat transfer process in gas microbearings are investigated. A heat transfer model is developed by introducing two-variable Weierstrass-Mandelbrot (W-M) function with fractal geometry. The heat transfer problem in the multiscale self-affine rough microbearings at slip flow regime is analyzed and discussed. The results show that rarefaction has more significant effect on heat transfer in rough microbearings with lower fractal dimension. The negative influence of roughness on heat transfer found to be the Nusselt number reduction. The heat transfer performance can be optimized with increasing fractal dimension of the rough surface. © 2012 Elsevier B.V. All rights reserved.

Detection of large-scale concrete columns for automated bridge inspection

There are over 600,000 bridges in the US, and not all of them can be inspected and maintained within the specified time frame. This is because manually inspecting bridges is a time-consuming and costly task, and some state Departments of Transportation (DOT) cannot afford the essential costs and manpower. In this paper, a novel method that can detect large-scale bridge concrete columns is proposed for the purpose of eventually creating an automated bridge condition assessment system. The method employs image stitching techniques (feature detection and matching, image affine transformation and blending) to combine images containing different segments of one column into a single image. Following that, bridge columns are detected by locating their boundaries and classifying the material within each boundary in the stitched image. Preliminary test results of 114 concrete bridge columns stitched from 373 close-up, partial images of the columns indicate that the method can correctly detect 89.7% of these elements, and thus, the viability of the application of this research.

Large Scale Column Detection for Bridge Inspection

Manually inspecting bridges is a time-consuming and costly task. There are over 600,000 bridges in the US, and not all of them can be inspected and maintained within the specified time frame as some state DOTs cannot afford the essential costs and manpower. This paper presents a novel method that can detect bridge concrete columns from visual data for the purpose of eventually creating an automated bridge condition assessment system. The method employs SIFT feature detection and matching to find overlapping areas among images. Affine transformation matrices are then calculated to combine images containing different segments of one column into a single image. Following that, the bridge columns are detected by identifying the boundaries in the stitched image and classifying the material within each boundary. Preliminary test results using real bridge images indicate that most columns in stitched images can be correctly detected and thus, the viability of the application of this research.

Slip flow and heat transfer in microbearings with fractal surface topographies

The effects of random surface roughness on slip flow and heat transfer in microbearings are investigated. A three-dimensional random surface roughness model characterized by fractal geometry is used to describe the multiscale self-affine roughness, which is represented by the modified two-variable Weierstrass- Mandelbrot (W-M) functions, at micro-scale. Based on this fractal characterization, the roles of rarefaction and roughness on the thermal and flow properties in microbearings are predicted and evaluated using numerical analyses and simulations. The results show that the boundary conditions of velocity slip and temperature jump depend not only on the Knudsen number but also on the surface roughness. It is found that the effects of the gas rarefaction and surface roughness on flow behavior and heat transfer in the microbearing are strongly coupled. The negative influence of roughness on heat transfer found to be the Nusselt number reduction. In addition, the effects of temperature difference and relative roughness on the heat transfer in the bearing are also analyzed and discussed. © 2012 Elsevier Ltd. All rights reserved.

A coordination-based approach to elasticity of floppy and stiff random networks

We study the role of connectivity on the linear and nonlinear elastic behavior of amorphous systems using a two-dimensional random network of harmonic springs as a model system. A natural characterization of these systems arises in terms of the network coordination relative to that of an isostatic network $\delta z$; a floppy network has $\delta z<0$, while a stiff network has $\delta z>0$. Under the influence of an externally applied load we observe that the response of both floppy and rigid network are controlled by the same critical point, corresponding to the onset of rigidity. We use numerical simulations to compute the exponents which characterize the shear modulus, the amplitude of non-affine displacements, and the network stiffening as a function of $\delta z$, derive these theoretically and make predictions for the mechanical response of glasses and fibrous networks.

Optimal data fitting on lie groups: A coset approach

This work considers the problem of fitting data on a Lie group by a coset of a compact subgroup. This problem can be seen as an extension of the problem of fitting affine subspaces in n to data which can be solved using principal component analysis. We show how the fitting problem can be reduced for biinvariant distances to a generalized mean calculation on an homogeneous space. For biinvariant Riemannian distances we provide an algorithm based on the Karcher mean gradient algorithm. We illustrate our approach by some examples on SO(n). © 2010 Springer -Verlag Berlin Heidelberg.

基于参数化求和不变量与特征重整的形状匹配

从特征提取和特征匹配两方面考虑,提出了一种鲁棒的形状匹配方法。首先,基于求和不变量,设计了基于面积的形状参数化和归一化方法,提出了参数化求和不变量,该不变量基于形状局部描述且采用积分算子计算,具有较好的鲁棒性和仿射不变性。然后,为进一步提高形状匹配的鲁棒性,在特征匹配上,分析了参数化求和不变量的先验信息,设计了基于特征重整的匹配距离函数,并通过动态规划进行实现。仿真实验表明了所提方法的有效性。

Effect of annealing on the deformation mechanism of a styrene/n-butyl acrylate copolymer latex film investigated by synchrotron small-angle X-ray scattering

The deformation mechanism of a styrene/n-butyl acrylate copolymer latex film subjected to uniaxial tensile stress was studied by small-angle X-ray scattering. The influence of annealing at 23, 60, 80, and 100 degrees C for 4 h on microscopic deformation processes was elucidated. It was demonstrated that the microscopic deformation mechanism of the latex films transformed gradually from nonaffine deformation behavior to affine deformation behavior with increasing annealing temperature.

In Situ Observation of Tensile Deformation Processes of Soft Colloidal Crystalline Latex Fibers

The deformation mechanism or styrene/n-butyl acrylate copolymer latex films with fiber symmetric crystalline structure subjected to uniaxial stretching was studied using synchrotron small-angle X-ray scattering technique. The fibers were drawn at angles or 0, 35, and 55 degrees with respect to the Fiber axis. In all cases, the microscopic deformation within the crystallites was Found to deviate from affine deformation behavior with respect to the macroscopic deformation ratio. Moreover, the extent of this deviation is different in the three cases. This peculiar behavior can be attributed to the relative orientation of the (111) plane of the crystals, the plane of densest packing, with respect to the stretching direction in each case. When the stretching direction coincides with the crystallographic (111) plane, which is the case for stretching directions of 0 and 55 degrees with respect to the fiber axis, the microscopic deformation deviates less from affine behavior than when the stretching direction is arbitrarily oriented with respect to the crystallographic (111) plan.

Fractal roughness characterization of super-ground Mn-Zn ferrite single crystals

The surface of superground Mn-Zn ferrite single crystal may be identified as a self-affine fractal in the stochastic sense. The rms roughness increased as a power of the scale from 10(2) nm to 10(6) nm with the roughness exponent alpha = 0.17 +/- 0.04, and 0.11 +/- 0.06, for grinding feed rate of 15 and 10 mu m/rev, respectively. The scaling behavior coincided with the theory prediction well used for growing self-affine surfaces in the interested region for magnetic heads performance. The rms roughnesses increased with increase in the feed rate, implying that the feed rate is a crucial grinding parameter affecting the supersmooth surface roughness in the machining process.

亚历山大藻分子鉴定和荧光原位杂交检测方法研究

近年来，世界沿海国家有害赤潮发生的频率、规模及危害都有上升趋势，有害赤潮已经成为重要的近海环境问题之一。要有效防范有害赤潮带来的危害效应，建立和发展可靠、有效的赤潮监测手段非常重要。目前，对于赤潮藻种的监测主要依靠显微观察的方法，在实际应用中经常遇到困难。首先，亲缘关系相近的物种在形态上差异很小，如甲藻门亚历山大藻属的一些种类，仅细胞壁上个别甲片的结构有细微差别，并且这些形态学指标还容易受环境条件及生长阶段的影响。另外，这种以形态学为基础的分析方法，分析速度慢、耗时长，对操作人员的要求较高，难以满足浮游植物种群动力学监测“量大、连续”的要求。因此，本研究将分子生物学的技术和方法应用于赤潮监测，力求提高赤潮藻种鉴定的准确性和检测工作的效率。 亚历山大藻是一类重要的有害赤潮藻，该藻属中一些产毒特性差别很大的藻种，单从表形特征难以明确区分，从而限制了基于形态观察的监测技术的应用。本研究中，我们尝试应用分子生物学技术与方法，开展了该藻属藻种分子鉴定和荧光原位杂交检测方法的研究。在亚历山大藻的分子鉴定方面，我们采用了核糖体RNA基因（rDNA）序列分析的方法，首次测定了9株分离自中国沿海的（以及实验室保有的其它两株）亚历山大藻的rDNA序列全长，其中包括核糖体小亚基（SSU）rDNA、大亚基（LSU）rDNA、5.8S rDNA及内转录间隔区（ITS）区序列。序列分析结果显示，这些藻株包含了5种核糖体类型，分别是塔玛复合种亚洲温带（Temperate Asian）核糖体类型（TSC-TA），塔玛复合种西欧（West European）核糖体类型（TSC-WE），相关亚历山大藻（A. affine）核糖体类型（AF），微小亚历山大藻（A. minutum）葡萄牙（Portugal）核糖体类型（M-PO）和微小亚历山大藻新西兰（New Zealand）核糖体类型（M-NZ）。将测获的rDNA序列划分为若干保守性不同的区段，分别进行系统发育分析（结合GenBank数据库中保存的其它亚历山大藻相关序列）。结果显示，LSU rDNA D1-D2区是对该藻属藻种进行分子鉴定和系统发育研究的较好区段。同时，为解决建立亚历山大藻克隆培养的困难，我们应用单细胞rDNA序列分析方法，对亚历山大藻单个细胞直接进行了种类鉴定。结果表明，该方法适用于不同生活史阶段的亚历山大藻。 在亚历山大藻的检测技术方面，我们进一步扩展和完善了针对完整细胞的荧光原位杂交检测方法。首先，通过对不同核糖体类型藻株rDNA序列信息的对比分析，针对各自特异的序列位点，设计了特异性rRNA标记探针。经荧光原位杂交实验检验，实现了对5种核糖体类型亚历山大藻的特异性标记。其中，针对WE、M-PO及M-NZ核糖体型的特异性探针为首次获得，另外两个探针是针对TA和AF核糖体类型rRNA新的位点所设计。同时，对影响探针标记效果的诸多因素进行了分析和探讨。此外，在2007年春季长江口海域赤潮调查中，首次应用特异性核酸探针和荧光原位杂交检测方法，调查了该海域亚历山大藻的丰度。结果表明，在4月4日-4月10日的样品中，亚历山大藻达到了较高的密度，最高密度达到103cells/L。同时发现，实验中样品的保存方法有待改进。随后的研究表明，盐醇固定方法及多聚甲醛/甲醇固定方法，可以较好的保持rRNA不被降解并适宜杂交（至少3个月时间）。 总之，本研究首次测定并分析了11株亚历山大藻（9株分离自中国沿海）的rDNA全序列信息。在此基础上，获得了5种核糖体类型亚历山大藻的特异性rRNA标记探针，其中3种为首次获得。另外，实验证明，单细胞rDNA分析技术和荧光原位杂交检测方法，在自然水体中亚历山大藻的直接鉴定及丰度调查中，均具有良好的应用前景。这一工作为我国近海亚历山大藻的鉴定和检测提供了理论依据和方法学基础，希望对该藻赤潮的监测工作有推动作用。 关键词：亚历山大藻 遗传探针 rRNA rDNA 荧光原位杂交 系统发育

亚历山大藻（非PSP产毒株）毒理的初步研究

本文以一株不产PSP毒素的相关亚历山大藻（AC-1）为对象，研究了该藻株对褶皱臂尾轮虫、卤虫、黑褐新糠虾急性毒性效应和对糠虾的慢性毒性影响，同时对AFT毒素成分进行了研究，研究结果如下： 通过相关亚历山大藻（AC-1）对褶皱臂尾轮虫、卤虫、黑褐新糠虾的急性毒性影响研究，发现随着相关亚历山大藻（AC-1）密度的升高，轮虫、卤虫、糠虾的存活率逐渐降低，其96hLC50分别为：1500cells/ml，90cells/ml，5000cells/ml。比较研究三种生物对相关亚历山大藻（AC-1）敏感性可以看出，三种生物对该藻的敏感性顺序为：卤虫>轮虫>糠虾。 相关亚历山大藻（AC-1）对黑褐新糠虾的生长及种群繁殖有显著影响，我们发现在密度为50cells/ml藻液中，糠虾的繁殖就受到了不利影响。实验进行到63d结束时，糠虾日最高产虾数、总产幼虾数、总产虾天数都明显减少，初次产虾时间推迟，繁殖中断增加。且该藻对黑褐新糠虾亲虾的存活、生长也有一定的影响，糠虾亲虾的存活率为对照的71%，而体长和体重分别为对照组的87.3%和97.8%，但差异尚不显著（P>0.05）。 研究相关亚历山大藻（AC-1）各组分的毒性（藻液、藻细胞重悬液、藻细胞培养过滤液、内容物），发现藻液和藻细胞重悬液对褶皱臂尾轮虫种群数量及轮虫、卤虫、糠虾的存活率均有显著影响，表明相关亚历山大藻活体藻细胞的毒性最强。过滤液和内容物也显著降低了轮虫和卤虫的存活率，其对糠虾也有影响，但不显著，表明AFT毒素可能来源于细胞内，能分泌到细胞培养液中。 研究相关亚历山大藻（AC-1）AFT毒素的热稳定性、酸碱稳定性、去蛋白组分毒性、分子量范围、极性、多糖组分鉴定，表明AFT毒素为极性较强的多糖类物质，对热和酸碱是稳定的，其分子量范围在5K~50K之间。 以上结果表明相关亚历山大藻（AC-1）虽然不产生PSP毒素，但能产生极性多糖类毒素，对甲壳类等浮游动物的种群数量和资源补充产生不利影响。本研究为以后进一步研究AFT毒素的作用机制和毒素的化学结构奠定了基础，为全面评价亚历山大藻赤潮的危害提供了科学依据。

基于仿射不变特征的图像匹配

图像匹配是计算机视觉中的一个重要研究领域，无论在民用还是军用上都有着重要的应用价值。本文以研究室国防重点预研究项目自动目标识别为背景，采用图像匹配方法，实现飞行器定位导航。具体工作流程是：事先利用侦察手段获取飞行器途经下方的地物景象(基准图)并存于飞行器载计算机中，然后当携带相应传感器的飞行器飞过预定的位置范围时，拍摄当地的地物景象(实时图)，将实时图和基准图在飞行器载计算机中进行匹配比较，可确定当前飞行器的准确位置，完成定位导航功能。 由于对同一场景使用相同或不同的传感器(成像设备)，以及在不同条件下(天候、照度、摄像位置和角度等)成像的复杂性和多样性等困难的存在，传统的相关匹配方法对上述困难的克服在方法原理上存在先天不足，所以无法胜任。故本文采用的方法是基于局部不变量特征的图像匹配。局部不变量特征因为能更灵活地描述图像，有效地处理图像复杂和遮挡问题，所以基于局部不变量特征的图像匹配方法对于视点的大变化，图像背景变化，以及目标场景识别等都有较好的效果。 基于局部不变量特征的图像匹配方法的步骤通常分为三部分：(1)用图像区域检测算子提取图像相关区域，(2)构造合适的特征描述区域，(3)选择特征相似度度量准则实现图像区域特征的匹配。本文详细研究了最大稳定极值区域 (MSER)方法，在此基础上进行了改进，具体工作如下：(1)利用高斯核函数对图像平滑采样，建立图像的高斯尺度空间，(2)在图像的高斯尺度空间中，利用MSER检测算子检测出图像在不同尺度下的所有仿射相关区域，(3)由于区域不规则，再用仿射不变的椭圆拟合并归一化，这时所有的区域仅存在旋转的不同，(4)用SIFT特征描述图像区域，得到所有区域的128维特征向量集。(5)采用欧式距离度量特征间的相似度，以最近邻和次近邻的比值作为特征匹配准则进行匹配。 本论文的主要研究工作在于把图像的高斯尺度空间引入到MSER算法中，进而大大改善了MSER算法对于图像的尺度变换、仿射变换以及图像模糊的性能。由于建立了高斯尺度空间，增加了MSER检测算子检测的范围，所以使得改进算法的性能得到了改善。论文第四章给出四组实验，分别为尺度变换，仿射变换，图像模糊和大视点变换。最后通过对匹配结果正确数量和错误数量的统计，论证了改进方法的性能要好于MSER算法。通过对算法复杂度的分析，得出虽然在改进算法引入了图像的高斯尺度空间，但是算法复杂度却并未增加，与MSER算法相同，为O(nloglogn)。