利用压电薄膜设计体积位移传感器

以不同边界条件的振动板为例,提出利用模态方法和分部积分方法设计PVDF传感器测量体积位移。模态正交性设计方法只能满足单一边界条件振动板结构体积位移的测量,而根据分部积分方法设计得到的PVDF传感器,适合一定边界范围的振动板的体积位移测量,并且所设计的PVDF传感器形状与激励力性质(类型、位置和频率范围)以及振动板本身的材料特性无关。     

固定挤压垫的优化设计

综合分析了杯碗式固定挤压垫实际密封效果差的原因，针对固定挤压垫的结构进行了改进。并介绍了国外最新推出的几种固定挤压垫。     

涂装检查基本数学计算

介绍了防腐蚀涂料涂装中的基本数学计算内容，包括单位换算、温度换算、面积计算、膜厚计算以及涂料用量和价格计算等。     

DBP和NA在发射药中扩散性能的分子动力学模拟

针对钝感剂在发射药贮存期间的扩散迁移影响发射药服役寿命的问题,采用分子动力学模拟(MD模拟)比较了小分子邻苯二甲酸二丁酯(DBP)、聚新戊二醇己二酸酯(NA)在发射药体系中的扩散系数,探究了温度和硝化甘油(NG)含量对DBP、NA在双基发射药中扩散的影响,并分析了扩散机理.结果表明:5℃时DBP和NA在NC基体中的扩散能力相当,扩散系数均在10-12 m2·s-1数量级,25℃时DBP与NA的扩散系数分别为1.13×10-11 m2·s-1和5.13×10-12 m2·s-1,65℃时DBP与NA的扩散系数分别为1.88×10-11 m2·s-1和7.57×10-12 m2·s-1,85℃时DBP与NA的扩散系数分别为3.42×10-11 m2·s-1、1.11×10-11 m2·s-1,在相同温度下,钝感剂扩散系数的大小顺序为DBP>NA,这说明NA具有较好的抗迁移特性,该特性在高温时更为凸显;从微观角度分析温度对扩散机理的影响为:高温使原子间氢键作用峰值减小,即DBP、NA与NC的相互作用力减弱,并且体系的自由体积分数也变大,增大了分子运动的有效活动空间,更有利于DBP、NA扩散.DBP、NA的扩散能力随着增塑剂NG含量的增加而增强,添加NG使得DBP、NA与NC的相互作用减弱,因此DBP、NA运动更活跃,扩散能力增强.     

Modeling the occupant evacuation of the mass rapid transit station using the control volume model

In this study, a control volume model is applied to simulate the process of evacuation in mass rapid transit (MRT) station using different scenarios. The control volume model assumes that each individual is an independent particle. When the evacuation occupant flow is larger than the capacity of the exit so that a virtual closed surface called the control surface that can be formed by connecting the waiting occupants at the exit. The change of the control volume is dependent on the transient number of the waiting occupants only. Based on the homogeneous flow with neglecting the behavior of the individual, the dynamic change of the evacuation occupant at the exit of the platform and the concourse can be formulated and analyzed. In addition, the number and capacity of the exits used in the total evacuation time analysis were measured with the aid of video recording and on-site observations. Using the control volume model, the dynamic characteristics of the evacuation process at each time-step for each of the exits are calculated and discussed. Comparisons are also made with the results found from other studies and NFPA 130.     

An exact method for determining local solid fractions in discrete element method simulations

A novel solid fraction algorithm is presented which accounts for the partial volume of a sphere straddling cuboidal bin boundaries. The algorithm accounts for spheres intersecting a single plane (face), two perpendicular planes (edge), or three perpendicular planes (corner). Comparisons are made against the more common algorithm in which the solid fraction is determined by assigning the sphere's total volume to the bin in which the sphere's center of volume (COV) is located. Bin size‐to‐sphere diameter ratios >30 must be used to give errors <5% when using the traditional method when applied to simple cubic (SC) and hexagonal packing assemblies. Bin size‐to‐sphere diameter ratios larger than five are required for random sphere packings. Although time averaged solid fraction measurements are similar using either the exact or COV solid fraction schemes, the scatter in the COV method is much larger than for the exact method. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture Substrates

Thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non‐covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels’ physico‐chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties.     

Modelling of wall heat transfer using modified conduction transfer function, finite volume and complex Fourier analysis methods

The original conduction transfer function (CTF) method (which was derived from the EnergyPlus source codes), and the present modified CTF method (which uses a higher order discretisation scheme for the surface heat flux as well as finer grids at the layer boundaries for multi-layer constructions) were used to calculate wall surface heat fluxes based on monitored wall surface temperatures as the inputs. At the same time, the finite volume method and the matrix method (based on the complex Fourier analysis) were also used for the numerical predictions. The matrix transfer method was updated to treat the non-linear long wave length thermal radiation and proved to be consistent with the results from the finite volume method for all wall types ranging from single-layer wall, two-layer wall with air gap, cavity brick wall and brick veneer wall. Numerical predictions using the matrix transfer method, the conduction transfer function method and the finite volume method were compared with the long period measurements for single- or multi-layer materials with and without air gaps. At the same time, CTF coefficients for modified CTF methods were tabulated and analysed for all computational cases in this study.     

厚层稠油油藏直平组合火驱机理研究与试验

针对厚层稠油油藏常规直井火驱火线超覆严重、纵向动用程度差、采出程度低等问题,采用数值模拟方法,明确直平组合火驱中火线波及规律,分析直井、水平井在不同阶段的生产特征,明确直井、水平井作用机理.研究结果表明:采用直平组合火驱的井网模式改变了原有直井的火驱流场,起到向下牵引火线作用,提高了纵向波及体积;采用直平组合式井网进行...     

LiNbO3晶体中引入π位相差实现选择性擦除

在晶体中进行大容量多重体存储 ,需要对晶体中记录数据进行修改 ,这就使得选择性擦除必不可少。介绍了铌酸锂晶体中实现选择性擦除的原理 ,着重介绍了在物光和参考光中引入π位相差的几种方法 ,通过引入π位相差来记录互补全息图 ,利用全息图及其他的互补全息图的非相干叠加来消除原全息图对晶体折射率的调制 ,从而实现对未定影全息图的选择性擦除。实现了在晶体中某一数据页面内部分数据的擦除 ,并从理论上对实验结果进行了分析。并给出了在某一数据页面内进行部分擦除的实验结果