Specific interactions in blends containing Chitosan and functionalized polymers. Molecular dynamics simulations

Chitosan (CS)/poly(vinyl alcohol) (PVA) and Chitosan/poly(2-hydroxyethyl methacrylate) (P2HEM) blends have been studied through molecular dynamic simulations. In a previous work it was found miscibility between these polymers and it was attributed to hydrogen bonding formation. However, the experimental information obtained was not enough to know which of the interacting groups of Chitosan, i.e. -CH₂OH or -NH₂, are responsible of the interaction. Therefore, we have performed molecular dynamics simulation runs of 1 ns in order to calculate radial distribution functions (RDF) for the groups tentatively involved in the interaction. The results are correlated with our previous experimental data. This way, we have obtained a more precise conclusive information about the interactions involved as function of the blends composition. For low compositions of PVA and P2HEM the interaction is predominantly with the hydroxymethyl groups of CS while as the composition of PVA and P2HEM increases, the interaction with the amine groups increases.     

Terminal velocity of non-spherical particles falling through a Carreau model liquid

A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured.     

动态汽车衡测量结果的不确定度评定

本文主要介绍了在动态汽车衡的试验过程中不确定度来源,并以动态试验为例重点介绍了计算各分量的标准不确定度、合成标准不确定度以及扩展不确定度的方法.     

Dynamic modes of Ti combustion in a coflow of N<Subscript>2</Subscript>-Ar mixture

Combustion of bulk density Ti powder (containing 20 wt % TiN as a diluent) in a coflow of N₂-Ar mixture was investigated upon variation in the nitrogen content of the gaseous mixture. The obtained data are believed to open up new horizons for fabrication of layered and composite ceramics by infiltration-mediated combustion.      

A multi-agent architecture for dynamic scheduling of steel hot rolling

Steel production is a complex process and finding coherent and effective schedules for the wide variety of production steps, in a dynamic environment, is a challenging task. In this paper, we propose a multi-agent architecture for integrated dynamic scheduling of the hot strip mill (HSM) and the continuous caster. The scheduling systems of these processes have very different objectives and constraints, and operate in an environment where there is a substantial quantity of real-time information concerning production failures and customer requests. Each process is assigned to an agent which independently, seeks an optimal dynamic schedule at a local level taking into account local objectives, real-time information and information received from other agents. Each agent can react to real-time events in order to fix any problems that occur. We focus here, particularly, on the HSM agent which uses a tabu search heuristic to create good predictive–reactive schedules quickly. The other agents simulate the production of the coil orders and the real-time events, which occur during the scheduling process. When real-time events occur on the HSM, the HSM agent might decide whether to repair the current schedule or reschedule from scratch. To address this problem, a range of schedule repair and complete rescheduling strategies are investigated and their performance is assessed with respect to measures of utility, stability and robustness, using an experimental simulation framework.     

动态多目标决策问题的灰色分析方法

将用于固定时间截面下静态多目标决策的灰色关联理论推广到动态情形，引入局部理想最优效果和整体理想最优效果的概念，提出一种新型的动态多目标决策问题的灰色关联模型，并通过算例说明该方法的合理可行性。     

TCP/IP网络的动态模型描述

拥塞现象成为TCP/IP网络发展面临的一个重要问题。因此，拥塞控制对TCP/IP网络的鲁棒性和稳定性具有重要作用。目前，网络拥塞控制策略主要包括两类：端到端的控制机制，如TCP拥塞控制算法；网络内部的主动队列管理(AQM)策略。但由于缺乏对网络系统动态特性的了解，这些拥塞控制策略大都基于专家经验，并没有建立完整的理论分析框架。为此，本文从数据流的角度出发，通过建立网络基本单元状态方程模型来实现IP网络系统的数学解析模型，然后用混杂系统来描述TCP带有拥塞控制策略的数据传输过程，建立了TCP/IP网络的动态模型，为网络系统中动态性能的分析、拥塞控制策略的设计奠定了基础。实验结果表明，该数学模型与NS仿真实验的结果相一致。     

The Effect of Structural Defects on the Thermal Conductivity of ZnS, ZnSe, and CdTe Polycrystals

ZnS, ZnSe, and CdTe polycrystals are experimentally investigated. Mechanisms are treated which restrict the thermal conductivity in samples prepared by recrystallization pressing and by deposition from the vapor phase and subjected to additional strain. Anomalies are observed on the temperature dependences of the thermal resistance of investigated samples, which are due to the special features of their phonon spectra and to the variation of the contribution made by longitudinal and transverse phonon branches to the heat transfer in the Debye temperature region and higher.     

Evaluating dynamic performance: The influence of salient Gestalt characteristics on performance ratings.

It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aspects of rapid crack propagation in silicon

Fracture experiments with silicon specimens in recent years have shown the need for a new approach to the analysis of rapidly propagating cracks in single crystals. Behaviour and phenomena have been revealed that fracture in these materials is rather different from the fracture of both amorphous and polycrystalline materials. We show that continuum mechanics is insufficient for analyzing crack propagation in single crystals since it is unable to consider atomistic‐scale phenomena. Accordingly, we describe basic phenomena associated with rapid crack propagation in silicon : (i) anisotropic velocity‐dependent R‐curve behaviour, as a key phenomenon dictating atomistic scale behaviour, (ii) crack deflection from one cleavage plane to another as a mesoscopic scale phenomenon in single‐crystal fracture, (iii) the Rayleigh surface wave speed as the limiting crack tip velocity is re‐examined, (vi) the lowest crack velocity in brittle crystals is examined, and finally (v) the interaction between crack path and preferred cleavage planes in single crystals is depicted.