聚合物加工中分散相形态变化的计算机模拟

为了控制聚合物共混物在加工中的相形态,就必须了解其形态变化的规律。通过对两相不相容聚合物共混过程的分析,编制了聚合物共混过程中形态变化的模拟软件ＰＢＭ。此软件可直观地显示共混过程中分散相形态的变化,包括孤立分散相液滴的形变和破裂,共混后分散相形态的松驰过程,以及整个分散体系中多粒子的形变、破裂和凝聚过程。此软件可对聚合物共混过程起一定的指导作用。     

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。     

高聚物数据库中数据的评选,加工及关联

本文着重讨论了高聚物数据库中收入的数据类型,数据评选的原则,数据的加工及关联。高聚物数据库中收入了1989年之前在22种主要期刊上公开发表的关于聚合物、高分子溶液及聚合物共混体系相平衡方面的主要数据类型。为提高数据的可使用性,高聚物数据库中收入的高分子溶液无限稀释数据及汽-液平衡数据加工为考虑气相非理想性影响的溶剂无限稀释活度系数和溶剂活度。本文还讨论了将UNIQUAC模型推广应用于高分子溶液汽-液平衡数据的关联。     

中讯还在“守株待兔”

在把员工的工作场面展示给外界时，中讯软件集团董事长王志强通常都是一副志得意满的样子。弧形的办公室分布着一行一行的办公桌，没有任何阻隔，看起来似乎没有尽头。     

聚合物注射成型保压分析研究进展

本文综述了聚合物注射成型保压分析的理论模型及其描述方程，并对今后的发展方向进行了展望，保压过程是一个非等温过程，熔体具有可压缩性，弹性的影响不应忽略，对于结晶聚合物，应考虑结晶对压力分布和温度分布的影响。     

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.     

UNIFAC-ZM活度系数模型预测聚合物溶液中溶剂扩散系数

根据Vrentas-Duds自由体积理论，结合基于UNIFAC活度系数模型，在较宽的浓度范围内预测了聚合物溶液中小分子的扩散行为。对某些聚合物体系，计算结果和实验数据基本一致。表明UNIFAC-ZM模型可代替Flory-Huggins方程用于预测聚合物溶液中小分子扩散系数。调节自由体积模型中的指前因子D0数值可改善预测结果。     

硅橡胶材料填充改性的相行为模拟研究

结合推广的Flory-Huggins理论和Monte carlo方法,模拟了由气相白炭黑和改性气相白炭黑填充的硅橡胶的相行为,获得了填料与聚硅氧烷的相互作用能分布曲线,配位数及相图。相图和热力学分析表明,经六甲基二硅氮烷改性的气相白炭黑与聚硅氧烷的相容性和共混体系的稳定性得以明显提高。     

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。     

液态金属填充型聚合物基导热材料的研究进展

集成电路技术的进步不断推动着芯片向高集成度和高性能的方向发展,随之而来的高密度热流带给芯片热管理的挑战也日益严峻。聚合物由于具有柔软的力学性能,且易于加工,十分适合作为电子产品中的导热材料。目前,聚合物的导热性能较低,向其中填充高导热填料,制备高导热的聚合物基复合材料是实现其工业化应用的主要手段。该文综述了近年来以液态金属为填料的聚合物基导热材料的研究现状及应用。液态金属在聚合物基体中的结构分布可分为非连续分布、单向连续分布及三维连续分布。针对不同液态金属分布结构的聚合物基复合材料,结合前人的研究工作,该文分别介绍了热界面材料传热机理,聚合物基液态金属的相关制备方法,所得复合材料的导热特性以及其面临的技术瓶颈。最后,对液态金属填充型聚合物基导热材料的未来研究方向进行了展望。     

Harmless delays and global attractivity for nonautonomous predator-prey system with dispersion

In this paper, we consider a nonautonomous predator-prey model with dispersion and a finite number of discrete delays. The system consists of two Lotka-Volterra patches and has two species: one can disperse between two patches, but the other is confined to one patch and cannot disperse. Our purpose is to demonstrate that the time delays are harmless for uniform persistence of the solutions of the system. Furthermore, we establish conditions under which the system admits a positive periodic solution which attracts all solutions.     

一种高效的有向栅栏修补算法

栅栏覆盖是有向传感器网络覆盖控制的研究热点之一,但有向栅栏空洞问题仍是一个研究空白.分析栅栏空洞的几何性质,根据栅栏空洞的虚拟圆和外接圆,创建转动修补区域模型(RRR);提出一种基于转动修补区域的栅栏修补方法(EBarR),利用转动修补区域,确定移动节点修补目标位置和目标感知方向,分布式选择能耗最小节点修补栅栏空洞,延长网络寿命.仿真结果证明,EBarR修补算法可以节能高效地修补有向栅栏空洞.本文的研究对提升无线传感器网络的性能具有重要的理论与实际意义.     

基于蔡氏电路混沌系统的图像加密方法

鉴于低维混沌加密存在密钥空间相对较小的局限性,基于三维蔡氏电路混沌系统的图像空域置乱加密方法可避免该局限性.利用产生的混沌序列,经过预处理生成置乱索引矩阵用于图像加密.该方案密钥敏感性高,可实现多幅图像的并行加密,是一种具有较高的安全性,加密效率高,且易于实现的图像加密算法.     

基于开物2000的调浆配料系统设计与实现

以某企业的调浆配料生产流程为基础,介绍了基于开物2000开发的离散数字控制系统的设计原理及其实现过程。该系统硬件搭配合理,程序设计模块化,控制精度高,可靠性良好。     

Cyclides in pure blending I

In this paper, we study blends between natural quadrics using both Dupin ring cyclides and parabolic cyclides. We present a new definition of a pure cyclide blend that we believe will help ensure the blend surface is useful to a designer. This definition will force the construction of nonsingular cyclide blends, deliberately excluding cyclide joins and singular surfaces. Further, we study the implications of the cyclide blend definition on the position of the quadrics in a blend and on the properties of the blending cyclide's extreme circles. This is the first part of a two part paper.     

Structural and water diffusion of poly(acryl amide)/poly(vinyl alcohol) blend films: Experiment and molecular dynamics simulations

To study the effects of composition ratios and temperature on the diffusion of water molecules in PVA/PAM blend films, five simulation models of PVA/PAM with ten water molecules at different composition ratios (4/0, 3/1, 2/2, 1/3, 0/4) were constructed and simulated by using a molecular dynamics (MD) simulation. The diffusion behavior of water molecules in blends were investigated from the aspects of the diffusion coefficient, free volume, pair correlation function (PCF) and trajectories of water molecules, respectively. And the hydrophilicity of blend composite was studied based on the contact angle and equilibrium water content (EWC) of the blend films. The simulation results show that the diffusion coefficient of water molecules and fractional free volume (FFV) of blend membranes increase with the addition of PAM, and a higher temperature can also improve the diffusion of water molecules. Additionally, the analysis of PCFs reveals the main reason why the diffusion coefficient of water in blend system increases with the addition of PAM. The measurement results of contact angle and EWC of blend films indicate that the hydrophilicity of blend films decreases with the addition of PAM, but the EWC of blends increases with the addition of PAM.     

Reduction of train-induced building vibrations by using open and filled trenches

A numerical investigation on the effectiveness of open and in-filled trenches in reducing the building vibrations due to passing trains is presented. Particularly, a two-dimensional soil-structure system containing the cross-section of a railway embankment, the underlying soil, a trench barrier and a nearby six-storey building is considered. For the analysis, a time domain coupled boundary element-finite element algorithm is employed. Unlike most of the previous formulations, this model completely considers the soil-structure interaction effects and directly determines the effect of the wave barrier on the structural response. The effects of geometrical and material properties of the trench and its backfill material on the structural response are investigated. The results point out that using a trench barrier, a reduction level up to 80% of the building vibrations and internal forces can be achieved. Increasing the depth or the width of a trench may improve its reduction effect and a softer backfill material results in a better isolation effect.     

Thin‐film barriers using transparent conducting oxides for organic light‐emitting diodes

Abstract— This study covers thin‐film barriers using inorganic barriers of transparent conducting oxides (TCOs) such as zinc oxide (ZnO) and indium tin oxide (ITO). The TCOs were fabricated using a sputtering method with a process gas of pure argon at room temperature. ITO showed better properties as a barrier than the ZnO and exhibited the electronic performance necessary to perform additional functions. The ITO has superior barrier performance because it has a lower crack density due to its partial amorphous phase. For organic/inorganic multilayer barriers, the organic underlayer decreased the water‐vapor transmission rate (WVTR) more than the organic upper layer, indicating that the planarization effect was important in reducing the WVTRs. The results of this organic/ITO multilayer barrier study are expected to be useful in finding a practical solution to OLED encapsulation.     

一类带时滞与扩散的食物链离散系统的定性分析(英文)

本文研究了捕食者固定在一个地点且不能分开,而被捕食者可以分布在两个地点的一类带时滞与扩散的食物链离散系统。证明了在相应条件下系统的持久性,并给出了一个例子说明了结果可靠性。进一步,如果假设系统是周期的,得到了其正周期解的全局面吸引性的新的判定标准。     

曙光5000高性能计算机Barrier网络的设计

为优化Barrier操作的性能,提高大规模并行计算应用在曙光5000系统中的执行效率,文中提出了一种基于硬件的Barrier加速设计.该设计是采用树形Barrier算法,通过增强曙光5000互联网络交换芯片的功能,实现低延迟、可扩展、高可靠和可管理的Barrier网络.该网络支持并发16个Barrier操作,可在Fat-Tree拓扑环境下实现较低的Barrier操作延迟.相比已有实现,是更适合Fat-Tree拓扑的设计方案.理想情况下,1024个节点的同步操作在1.7μs内完成.根据Barrier操作归约和分发过程的特点,分别采用请求应答和超时催促两种机制,为Barrier操作的可靠性提供保障.以该设计实现的Barrier网络原型系统已通过FPGA验证.