亲水性和疏水性微管道中流动滑移特性的实验研究

通过对微圆管道内表面进行界面性质处理，研究了不同界面性质对去离子水在内径50μm微管道中的流动滑移特性的影响。通过实验，在微圆管道内表面自组装一层疏水性单分子octadecyltrichlorosilane（OTS）膜来改变界面性质，并采用体积法测量压力驱动下微圆管道中去离子水的流量，观察去离子水在亲水性和疏水性表面微圆管道中的流动滑移情况。结果表明，去离子水在亲水性表面流动的压力一流量特性仍符合经典的Navier—Stokes方程，而去离子水在疏水性表面管道中流动时，其流量明显增大，说明去离子水在疏水性表面微圆管道中的流动出现了表面滑移。其原因是，疏水性表面使微管道表面的粗糙度降低，微管道表面产生微气泡或低密度液体而引起流动滑移。     

亲/疏水性不同壁面组成微通道的深宽比与通道内液体的自发毛细流动

研究了聚合物芯片上由亲/疏水性不同壁面组成的微通道内流体的流动行为。为了实现该类微通道内液体的自发毛细流动和被操作液体的自发毛细输运,根据系统总表面自由能极小原理,提出了微通道内毛细输运自发实现时微通道的临界深宽比条件。在以二聚二甲基硅氧烷(PDMS)和玻璃为材料的微流控芯片上进行了三面疏水一面亲水微通道内水的毛细输运实验。针对165μm,200μm和265μm3种深度的通道,理论计算的临界深宽比为0.5,而实验得到的值分别为0.4714,0.4878和0.4818,实验结果与理论预测结果基本相符,从而验证了由亲疏水性不同的壁面组成的微通道内毛细输运自发实现的临界深宽比条件。     

超疏水表面的减阻研究

为探索超疏水表面的减阻机制,利用位错刻蚀法在铝板上制备出接触角为156°、滚动角小于5°的超疏水表面,并分别以具有超疏水表面和亲水表面的铝板为基板,构建了两种流动状态可视化测试的微粒子图像测速(Particle Image Velocimetry ,PIV)微通道,通过PIV粒子图像测试技术对水在超疏水微通道和亲水微通道中的速度流动情况进行实验测定与对比,得出超疏水表面确实有减阻效果,最大减阻效果可达8.72%,并从多角度进行了解释分析.     

超疏水表面减阻特性的研究进展

超疏水表面具有减阻效果,在提高管道传输效率、降低水下航行体和微流体器件中流动阻力等方面有着广阔的应用前景。介绍超疏水表面的制备、滑移理论以及减阻特性的研究,讨论微尺度下表面润湿性、表面微结构和流场流动状态对壁面减阻的影响,对超疏水壁面减阻的物理机制进行总结,并指出气体层不连续模型和气穴模型是分别适用于光滑疏水表面和带微结构超疏水表面的减阻模型。介绍超疏水表面减阻特性的一些应用,提出将超疏水表面应用到微流体系统中面临的问题,如微通道壁面疏水性的制备及其减阻效果的耐久性。     

界面性质对流动滑移特性影响的实验研究

采用分子自组装技术在微圆管道内壁生成一层单分子Octadecyltrichlorosilane(OTS)膜来改变其界面性质,使亲水性管道表面变成疏水性表面。利用亲水性和疏水性表面内径50μm的微管道,通过测量其流量的方法观察了去离子水在不同界面性质表面的管道中的流动滑移情况。实验结果表明,在亲水性表面管道中,去离子水流动的压力-流量关系符合经典的Navier-Stokes方程;去离子水在自组装一层单分子OTS膜管道流动时,由于去离子水在斥水性微管道中的流动出现了表面滑移,其流量增大约8%,去离子水流动的压力-流量关系不再符合经典的Navier-Stokes方程。     

单细胞捕捉微流控芯片设计及流场分析

聚合物单细胞捕获微流控芯片中流场分布对细胞捕获有着重要意义,是芯片结构设计的一个关键因素.在聚合物单细胞捕获微流控芯片中,不同尺寸微坝结构对细胞捕获效率有影响.针对成骨细胞的捕获与培养设计了3种尺寸的微坝结构,并对成骨细胞捕获和培养过程芯片内部流场进行了模拟分析,模拟结果显示下端开口尺寸为10μm的微坝结构内部流速最小,故其流体对细胞产生的作用力越小,细胞变形程度越小,细胞越容易被留在微坝中,从而被捕获.为之后的实验提供了一定的指导作用.     

微通道中电渗流滑移现象的数值模拟

为了研究疏水表面微通道中电渗流(EOF)的输运及滑移特性,针对具有特定滑移长度的疏水表面微通道,建立了微通道EOF的控制方程。基于有限元分析方法对微通道EOF进行了数值模拟,分析了微通道高度、外加电场强度和固液界面边界滑移长度等对EOF的影响。结果表明,疏水表面和亲水表面微通道EOF的瞬态过程相似,稳态时间尺度在毫秒量级,大小与微通道尺度的平方成正比,符合黏性扩散定律;EOF速度大小与电场强度和边界滑移长度成正比,与微通道高度无关。     

两种液体在微圆管道内流动特性的试验研究

随着微机电系统的不断发展,作为微机电系统的一个重要的分支,微流体系统越来越引起许多科学家的重视和研究,但是微流体系统不是简单的在尺度上面的减小,而是随着尺度的减小,流动的特性也会发生变化。在宏观中可以忽略的因素在微观中可能会占主导作用。在本文章中,主要是实验的形式对微观流动特性进行了研究,测试液体是两种介质(水和硅油),采用的不同的微管内径13μm,20μm,50μm和100μm,长度为40mm。实验结果表明,在此实验条件下,液体的流动压力和流量仍呈现线性关系,与宏观大管道的理论预想基本相同,宏观管道内采用的N—S方程在此实验条件仍可适用。     

基于DMD无掩膜光刻快速制作亲疏水图案化表面

亲疏水图案化表面在表面张力限制的微流控技术中能够发挥显著作用。常见的方法在制作表面的微图案时都需要实物掩模版,这类方法不具备灵活调节制造亲疏水表面微图案的形状与尺寸的能力,并且因制作掩膜而导致制作成本和时间成本都很高。因此,提出了基于DMD无掩膜光刻技术快速制作亲疏水图案化表面的方法并可用于自组装微液滴阵列。该方法利用DMD无掩膜曝光系统进行加工,一步成型地完成了亲疏水图案化表面的疏水处理和微图案化处理。这种方法无需实物掩模,能够灵活调控加工表面疏水图案的形状与尺寸,工艺简单快捷,降低了制作成本。     

微结构表面上流体流动的数值模拟

根据固液界面的复合接触模式,考察了液体在光栅表面上的流动.运用二阶中心差分方法对Navier-Stokes方程进行离散求解,采用了零滑移和零剪切交错边界条件,开发了一个用于计算二维流动参数的计算系统.运用该系统对二维管道进行了模拟,得到了管道内流体的速度分布和压强分布,并计算了管道的减阻情况.计算结果与以往类似结果对比说明了系统的理论基础和实施方案的正确性;计算结果表明,流体在光滑与光栅结构表面构成的管道中的压强分布存在一定差异,光栅结构表面具有一定的减阻性能.最后,通过对不同的表面结构参数进行数值实验,得出了用于减阻衡量的关系式.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.