聚合物共混体系阻隔模型和计算机模拟

为了研究聚合物共混体中分散相的形态和分布对共混物阻隔性能的影响，本文建立了分子扩散通过聚合物共混体系一般化的数学模型，并由蒙特卡罗方法模拟共混分散体系的分布，经计算机模拟计算后，得到片状的分散相具有较好的阻隔效果，该结论与实验结果相符。     

基于隐式积分的树叶形变快速仿真

针对秋天树叶形变过程的仿真问题,在双层质点-弹簧模型的基础上,提出一种半过程半物理的树叶形变快速仿真算法.由于同时调节叶肉和叶脉弹簧系数会使得树叶形变不易控制,因此对叶脉和叶肉分开进行模拟:为叶脉设计一种目标形态,叶脉形变序列的中间形态可以通过对初态和终态的插值得到,叶肉会在叶脉形变引发的弹簧力的牵引下发生相应的形变,质点-弹簧系统会在阻尼的作用下趋于稳定,上述过程是一个不断循环迭代的过程;针对显式积分求解器求解时间过长和不稳定的缺点,采用大时间步长的隐式积分求解器以显著地提高系统的稳定性和求解效率.算法分析和实验结果表明,该算法可以稳定、快速、逼真地模拟秋天树叶老化过程中几何形态的变化过程.     

虚拟手术中心脏跳动仿真技术研究

提出一种可实时运行的基于示例形状匹配的心脏跳动仿真方法,该方法通过简单的示例形态来控制心脏跳动过程中发生的形变行为。形变描述符被用来唯一定义形变对象的形变,并利用该描述符将形变优选空间表示为示例形态的线性组合。在每个时间步长中,当前的形变描述符被线性投影到示例歧管上,然后当计算目标位置时其被用于修改每个局部区域的静止形态。实验证明该方法能够真实地反映心脏的形变效果,达到实时模拟心脏跳动的目的。     

高分子复合材料电镜负片多功能测量统计软件

从电镜照片考查多相聚合物中分散相的分散情况是研究高分子复合材料结构与性能关系的重要手段。本文提供的软件具有16种测量统计功能。它可准确迅速地对由128×128个点组成的负片数字图像作任意指定区域的自动处理。补偿“漏点”,剔除“小杂点”。经设置图像考核达到实用要求。该软件亦可应用于聚合工程及其它学科涉及的有关颗粒工程研究。     

玉米叶片形态的几何造型研究

为了更好地进行玉米叶片几何造型模拟，基于对玉米叶片形态建成过程的观测研究，首先提取了玉米叶片形态结构和形态建成过程的主要特征，然后构建了参数化的玉米叶片几何模型。该模型用较少几个具有较明确的生物学意义的形态参数，就可实现玉米叶片形态和形变过程的矢量化，再结合VC 和OpenGL，就可在计算机上重现玉米叶片的虚拟生长，模拟结果表明，图像上的效果、产生的数据和实际叶片基本一致，从而为相关领域研究者提供了一个可视化的玉米叶片模型。该模型结构简单、易于交互、真实感强，可较好地模拟玉米叶片建成过程中的形态变化特征。     

未来的开发工具

在积极准备新操作系统发布的过程中微软公司为其它软件开发商们提供了大量能开发在此操作系统之上应用程序的工具。软件开发商需要可与现有的及之前平台相兼容的新工具否则他们编写新功能无法得以实现。但是这些工具本身就缺少了此平台的相关信息。     

聚合物挤出在线超声监测传感器研究

共混聚合物在挤出过程中需要对其在螺杆挤出机机筒内的混合状态实时监测,针对这一情况,设计了由超声探头、聚醚醚酮(PEEK)缓冲杆和冷却装置组成的超声传感器,并将其应用于螺杆挤出机中聚合物的混合状态监测.文章分析了钢杆和PEEK杆超声波信噪比情况,PEEK缓冲杆具有较高的信噪比.本文的研究说明设计的传感器结构适合于较低温度的聚合物混合状态的在线监测.     

基于丝网传感器的气水两相流流型转换测量

两相流流型有助于两相流体结构与运动规律的研究,是开展气水两相流研究的基础。为了探究各种流型之间转换过程中的流体动力学现象,利用丝网传感器(Wire Mesh Sensor,WMS)通过对50 mm内径的垂直管道不同流动条件下各种流动形态的空隙率、气泡分布及其变化过程成像测量表明在水相表观流速不变,气相表观流速增加的条件下,从泡状流到弹状流过渡过程中,均匀分布的离散小气泡密度逐渐增加,管道中心气泡浓度逐渐高于管壁,管道中心小气泡开始碰撞聚合形成大气泡;随着水相表观流速减小,进一步增加气相表观流速,弹状大气泡破裂成若干不规则气泡,向下一个流型过渡。     

虚拟手术中血流特效场景仿真的研究

血流特效场景可以增强虚拟手术的真实感。虚拟手术中的血流特效场景包括了有交互的血液模拟及血管壁模拟。首先基于光滑粒子流体动力学,使用Physx物理引擎模拟血液流动的物理形态,并利用Screen Space Flow算法对血流表面进行实时渲染。然后基于质点-弹簧模型,提出使用Physx物理引擎模拟可交互、有弹性形变及可切割的血管壁。最后实现两个实验场景:场景一实现肺动脉内大规模血液流动的特效;场景二实现在用户交互下的血管壁形变和切割,并通过触发事件实现血管壁破裂流血的特效。实验结果表明,该血流及血管壁模拟方法在40 000个粒子下仍能保证实时绘制,满足虚拟手术的需求。     

填料粒子尺寸对聚合物共混体系力学性能的影响研究

聚合物填料的分布、形状、大小对冻胶的力学性能有重要影响,本文应用有限元方法对简化的微观材料结构进行力学分析,建立了聚合物和填料粒子共混的有限元模型。     

Simultaneous visualization of the flow inside and around droplets generated in microchannels

This paper reports the visualization of droplet formation in co-flowing microfluidic devices using food-grade aqueous biopolymer–surfactant solutions as the dispersed droplet phase and sunflower oil as the continuous phase. Microparticle image velocimetry and streak imaging techniques are utilized to simultaneously recover the velocity profiles both within and around the dispersed phase during droplet formation and detachment. Different breakup mechanisms are found for Newtonian–Newtonian and non-Newtonian–Newtonian model water-in-oil emulsions, emphasizing the influence of process and material parameters such as the flow rates of both phases, interfacial tension, and the elastic properties of the non-Newtonian droplet phase on the droplet formation detachment dynamics.     

Lattice Boltzmann simulation of the dispersion of aggregated particles under shear flows

The lattice Boltzmann method (LBM) for multicomponent immiscible fluids is applied to simulations of the deformation and breakup of a particle-cluster aggregate in shear flows. In the simulations, the solid particle is modeled by a droplet with strong interfacial tension and large viscosity. The van der Waals attraction force is taken into account for the interaction between the particles. The ratio of the hydrodynamic drag force to cohesive force, I, is introduced, and the effect of I on the aggregate deformation and breakup in shear flows is investigated. It is found that the aggregate is easier to deform and to be dispersed when I is over 100.     

Smoothed Particle Hydrodynamics (SPH) simulation of a high-pressure homogenization process

High-pressure homogenization is a widely used process in the food, pharmaceutical, and cosmetic industry for producing emulsions. Because of small dimensions and high velocities, the experimental and numerical investigation of such a process is challenging. Hence, the development of products is mostly based on trial and error. In this paper, simulations of a generic high-pressure homogenization process using the Lagrangian, mesh-free smoothed particle hydrodynamics (SPH) method are presented and compared to experimental findings using Micro-Particle Image Velocimetry (μ-PIV). The SPH code has been developed and validated with the scope of simulating technical relevant multi-phase problems (Höfler et al. 2012). The present simulations cover the investigation of two different dynamic viscosities of the dispersed phase as well as different droplet trajectories. The comparison between the simulations and the experiments focusses on the velocity distribution of the continuous phase and the droplet deformation and breakup. In both cases a qualitatively good agreement is observed, demonstrating the ability of our SPH implementation for simulating technical relevant two-phase flows.     

An investigation on the mechanism of droplet formation in a microfluidic T-junction

This paper reports the findings of a numerical investigation on the droplet break-up in a microfluidic T-junction. The numerical flow visualization of the droplet formation process is validated with the experimental flow visualization. From the computational results, we show that the pressure profile of the dispersed phase and the continuous phase in the squeezing regime changes as the droplet break-up process proceeds. The assumption taken by other researchers that the dispersed phase pressure profile, during the droplet formation process at a T-junction, remains constant and only the continuous phase pressure changes according to the blockage of the channel is proved to be invalid. We provide new insights on the pressure difference between the dispersed phase and the continuous phase during the droplet break-up process and show that the minimum pressure difference happens at the last moment of the droplet break-up and not during the second and third stage of the droplet formation mechanism in the squeezing regime as suggested by other researchers.     

The impact of the Bell system breakup on DP disaster recovery planning

The breakup of the Bell Telephone System in the United States has created new data processing disaster recovery planning problems. Where disaster recovery plans exist they assume that the communications common carrier will independently handle the restoration of data communications during the disaster recovery process. That is no longer true. Existing plans should be revised to reflect this new disaster recovery situation.     

Iterative design and testing within the software development life cycle

The activity of testing begins during system development and spans all subsequent phases. Some system development lifecycles describe testing which is performed after the coding phase, but this may cause the software to be delivered without sufficient testing. In this paper, we present a software system development lifecycle model, called the Test design Stages Processed model (TSP model), in which we emphasize that iterative test design stages should be incorporated at each phase of the software development lifecycle. When a phase is completed, testing of the phase should also be completed at that time. Within this paper we have added unit, integration and system testing processes into BoochÕs micro–design process to generate a new designs and test model. This shows the process of iterative and incremental software development. Comparing this with our model, we explain how the TSP model can be used for developing and testing an object-oriented software system.     

Printing of polymer thin‐film transistors for active‐matrix‐display applications

Abstract— We present a process for active‐matrix flat‐panel‐display manufacture based on solution processing and printing of polymer thin‐film transistors. In this process, transistors are fabricated using soluble semiconducting, conducting, and dielectric polymer materials. Accurate definition of the transistor channel and other circuit components are achieved by direct ink‐jet printing combined with surface‐energy patterning. We have used this process to create 4800‐pixel 50‐dpi active‐matrix backplanes. These backplanes were combined with polymer‐dispersed liquid crystal to create the first ink‐jet‐printed active‐matrix displays. Our process is, in principle, environmentally friendly, low temperature, compatible with flexible substrates, cost effective, and advantageous for short‐run length and large display sizes. As well as polymer‐dispersed liquid crystal, this technology is applicable to conventional liquid‐crystal and electrophoretic display effects.     

Software development for reliable software systems

The process of software development has a major influence on the reliability of a software system. The reliability of a software system can be improved by eliminating all the errors that occur during its development. This paper presents, from a tutorial point of view, a methodology of software development that can minimize the number of errors in a system when the system is being developed. The three phases of software development viz. requirements analysis, design, and implementation are examined to find out what needs to be done in each phase, how the end result of each phase can be verified for correctness, and how the form in which information is passed between each phase can be improved. This discussion is directly applicable to the development of small software systems and programs.     

Nanoparticles in polymer-matrix composites

Regarding the development of nanoparticles for polymer matrix composites the particle/agglomerate size and particle/agglomerate distribution in the composites, respectively, is often crucial. This is exemplarily shown for, e.g. optical applications with measurements of refractive index and transmittance. Classical blending techniques, where nanoparticles are dispersed in polymers or resins, are compared to a combination of a special gas-phase synthesis method with subsequent in-situ deposition of nanoparticles in high-boiling liquids. The particles/agglomerates were characterized regarding particle size and particle size distribution using transmission electron microscopy and dynamic light scattering. Additionally, important material properties like mechanical properties, relevant for application, or like viscosity, relevant for processing, are determined. It is shown, that with in-situ dispersed nanoparticles synthesized in a microwave plasma process composites with finely dispersed particles/agglomerates are attainable.     

Analysis of the demolding forces during hot embossing

Hot embossing is one of the main processing techniques for polymer microfabrication, which helps the LIGA (UV-LIGA) technology to achieve low cost mass production. When hot embossing of high aspect ratio microstructures, the deformation of microstructures usually occurs due to the demolding forces between the sidewall of mold inserts and the thermoplastic (PMMA). The study of the demolding process plays a key role in commercial manufacturing of polymer replicas. In this paper, the demolding behavior was analyzed by Finite element method using ABAQUS/Standard. Simulation identified the friction force caused by interface adhesion and thermal stress due to shrinkage between the mold and the polymer as the main sources of the demolding forces. Simulation also showed that the friction force made a greater contribution to the deformation than thermal stress, which is explained in the accompanying theoretical analysis. To minimize the friction force the optimized experiment was performed using PTFE (Teflon) as anti-adhesive films and using Ni-PTFE compound material mold inserts. Both lowered the surface adhesion energy and friction coefficient. Typical defects like pull-up and damaged edges can be reduced.