Effect of nucleating agent on the isothermal crystallization kinetics of PHBV

The crystallization behavior of PHBV, poly(beta -hydroxybutyrate-co-beta -hydrxyvalerate), with nucleating agents under isothermal conditions was investigated. A differential scanning calorimeter was used to monitor the crystallization process from the melt. During isothermal crystallization, the dependence of relative degree of crystallinity on time was described by the Avrami equation. It has been shown that the addition of BN and Tale causes a considerable increase in the overall crystallization rate of PHBV but does not influence the Avrami exponent n, mechanism of nucleation and spherulite growth mode of PHBV. A little of nucleating agent will increase the crystallization rate and decrease the fold surface free energy sigma (e), remarkably. The effect of BN is more significant than that of Talc.

Polyaniline as marine antifouling and corrosion-prevention agent

Conductive polyaniline was found to have special marine antifouling property. The coating from conducting polyaniline and epoxy resin(or polyurethane) can last 6-9 months in Southern China sea, i.e., less than 10% of the coating surface was fouled during this period. The conducting polyaniline has special synergetic antifouling effect on other antifouling agents like cuprous oxide or 4, 4'-dichlorodiphenyltrichloroethane. The conductivity of the polyaniline was found to be extremely important for its antifouling effect. Moreover, employing aliphatic polyamine as solvent of emeraldine base and curing agent of epoxy resin, a new technique to process corrosion prevention coating containing emeraldine base was developed, therefrom the emeraldine base and epoxy resin was in molecular level blending. This technique was solvent free and extremely effective, i.e., only 1wt% of emeraldine base in the coating can have good corrosion prevention property.

Liquid crystalline polymer as a processing agent in blends of poly(ether-ketone)/LCP70

Blends of a liquid crystalline thermotropic copolyester (LCP70) and an amorphous phenolphthalein based poly(ether-ketone)(PEK-C) with two viscosities were prepared by melt blending. The blends' morphology, rheological and mechanical properties were investigated by DSC, SEM, mechanical and rheological tests. It was observed that the optimum composition of the PEK-C/LCP70 blend was 10 wt% LCP for both mechanical and rheological properties. When the LCP content was less than 10%, the LCP phase existed as finely dispersed fibrous domains with a diameter of about 1 mu m in the matrix, and both tensile and flexural properties were improved. In contrast, when the LCP content reached 20% or more, the LCP domains coalesced to ellipsoidal particles with a diameter of about 5 mu m, and the mechanical properties decreased as a result. It is demonstrated that pure PEK-C with a high viscosity which was difficult to process by melt extrusion, could be extruded conveniently when 10% LCP70 was incorporated. It is emphasized that LCP not only can be used as a reinforcing phase but also an effective processing agent for engineering thermoplastics, especially for those with high viscosity and narrow processing window. (C) 1997 Elsevier Science Ltd.

Properties of ethylene-propylene copolymer/PA-1010 blends using ethylene-propylene copolymer-graft-acrylic acid as a compatibilizing agent

The modification of ethylene-propylene copolymer (EP) has been accomplished by radical EP-graft-acrylic acid (EP-g-AA) has been used to obtain ternary PA/EP/EP-g-AA blends by melt mixing. Different blend morphologies were observed by scanning electron microscopy; the domain size of the EP-dispersed phase in the polyamide 1010 matrix of compatibilized blends decreased compared with that of uncompatibilized blends. It is found that EP-g-AA used as the third component has a profound effect on the mechanical properties of the resulting blends. This behavior has been attributed to serious chemical interactions taking place between the two components. Thermal analysis shows that some thermal properties of PA in compatibilized PA/EP/EP-g-AA changed because of chemical reactions taken place during the blending process. Wide angle x-ray diffraction measurements also confirmed this result. (C) 1996 John Wiley & Sons, Inc.

New antibiotic with typical plant anthraquinone structure obtained studying terrestrial and marine Streptomycetes

In our screening for new antibiotics from bacteria, the streptomycete isolate M097 from Jiaozhou Bay in China was found to produce aloesaponarin II (1a) and 1,6-dihydroxy-8-hydroxymethyl-anthraquinone (2). Similarly, a terrestrial streptomycete GW24/1694 produced 1a and its methyl ether, the new compound 1-hydroxy-6-methoxy-8-methyl-anthraquinone (1b). All structures were derived by spectrochemical analysis and by comparison with reference data. The results showed that the marine streptomycete isolate M097 and the terrestrial streptomycete GW24/1694 could be a promising material for studying the biosynthetic pathway of polyketides.

Concurrence of cat and tet genes in multiple antibiotic-resistant bacteria isolated from a sea cucumber and sea urchin mariculture farm in China

A basic understanding of abundance and diversity of antibiotic-resistant microbes and their genetic determinants is necessary for finding a way to prevent and control the spread of antibiotic resistance. For this purpose, chloramphenicol and multiple antibiotic-resistant bacteria were screened from a mariculture farm in northern China. Both sea cucumber and sea urchin rearing ponds were populated with abundant antibiotic-resistant bacteria, especially marine vibrios. Sixty-five percent chloramphenicol-resistant isolates from sea cucumber harbored a cat gene, either cat IV or cat II, whereas 35% sea urchin isolates harbored a cat gene, actually cat II. The predominant resistance determinant cat IV gene mainly occurred in isolates related to Vibrio tasmaniensis or Pseudoalteromonas atlantica, and the cat II gene mainly occurred in Vibrio splendidus-like isolates. All the cat-positive isolates also harbored one or two of the tet genes, tet(D), tet(B), or tet(A). As no chloramphenicol-related antibiotic was ever used, coselection of the cat genes by other antibiotics, especially oxytetracycline, might be the cause of the high incidence of cat genes in the mariculture farm studied.

Novel antifouling and antimicrobial compound from a marine-derived fungus Ampelomyces sp.

In this study, using a bioassay-guided isolation and purification procedure, we obtained 3-chloro-2,5-dihydroxybenzyl alcohol from a marine-derived Ampelomyces species that effectively inhibited larval settlement of the tubeworm Hydroides elegans and of cyprids of the barnacle Balanus amphitrite. The inhibitive effect on larval settlement was nontoxic and the EC50 of 3-chloro-2,5-dihydroxybenzyl alcohol ranged from 3.19 mu g ml(-1) to 3.81 mu g ml(-1) while the LC50 was 266.68 lambda g ml(-1) for B. amphitrite cyprids; EC50 ranged from 0.67 mu g ml(-1) to 0.78 mu g ml(-1), and LC50 was 2.64 mu g ml(-1) for competent larvae of H. elegans, indicating that inhibitive effect of this compound was nontoxic. At a concentration of 50 mu g per disc, this compound showed strong inhibitive effects on the growth of 13 out of 15 marine bacterial species tested in disc diffusion bioassay. Overall, the high inhibitory activities against bacteria and larval settlement as well as the non- or low-toxic nature of this compound to the barnacle and polychaete larvae suggest this compound could be a potent antifoulant and/or antibiotic.

基于粗糙集和多Agent系统的知识挖掘

通过优化知识表达系统中条件属性对决策属性的依赖度,深入研究了粗糙集并与多Agent系统相结合。利用离散粒子群算法,提出一种基于粒子群优化的粗糙集知识约简算法,该算法解决了启发式算法无法全局搜索进行约简的问题。最后通过在矿井中调度信息的应用验证了有效性。

BDI Agent的人机智能结合方法

在网络遥操作中存在着由于操作者的操作负担过重或长时间操作而引起的误操作问题,提出以著名的BDIAgent模型为基础,通过引入中断机制,将反映操作者智能决策的操作目标、操作意图与BDIAgent推理产生的目标、意图进行结合的方法,为解决Agent智能的局限性和操作者的误操作问题,提供了一种人机接口方法,实现了人机智能结合.给出了中断的引入方法和操作者操作目标、操作意图中断响应原理,用形式化模型描述了人机智能决策选取目标和意图的过程.该人机智能结合方法在网络遥操作RoboCup中型足球机器人系统中得到了应用.

基于Agent的网络遥操作机器人系统控制研究

为了充分发挥智能机器人的自主性和人的主观能动性,实现通过网络遥操作非结构化环境下的智能机器人,提出了一种基于Agent的网络遥操作机器人控制系统结构,分析了控制系统中各部分的功能,给出了系统中各个Agent的实现方法。该控制方法已通过仿人形机器人的遥操作控制实验得到了验证。

基于agent及holon的可重构生产线实现技术

以大批量制造的生产线制造系统为背景,研究基于agent与holon智能制造思想体系的可重构生产线制造系统实现技术,以提高生产线柔性与可重构能力为目标·深入分析了多agent制造及holonic制造模式体系下智能单元自主决策、协商合作在制造系统环境中的实现与运行机制,在以机械加工线和装配线为代表的不同的工程实际背景与应用环境下该思想体系目前的具体应用情况与实现技术·指出该思想体系面向具体工程背景的有效实施应用是理论研究的关键·最后以某汽车变速器装配生产线制造系统为应用实例,从其规划设计与运行角度,分析了可重构生产线系统的框架设计及具体实现技术与方法·

基于多Agent可重构机器人控制方法的研究

根据多 Agent理论中的协商、合作机制和可重构机器人结构的分布性 ,将集中式的机器人控制分配到一组关节 Agent中 ,每个 Agent控制机器人的一个关节 ,使用这种分布式方法 ,得到了一种新的通用机器人控制方法 ,即将关节机器人的复杂控制转换为多个简单子系统的控制 ,该方法可应用于具有不同构型的机器人系统 ,特别适用于可重构模块化机器人的控制。利用微分运动理论提出了一种新的决策方法 ,便于 Agent之间的合作与协商。仿真实验结果表明该方法是一种可行的机器人控制方法

基于Agent的分布式多机器人系统建模及分析

进行一个多装配机器人系统 DAMAS的模型研究 ,介绍离散事件动态系统的重要建模工具 Petri网 ,提出解决模型复杂性的有效方法 ,建立了系统中各个 Agent及整个系统的 Petri网模型 ,对这些模型及相互间的交互模型进行了重要的活性和有界性分析 ,对多机器人系统的协作机制进行了验证分析。

基于Agent的机器人新型控制器模型研究

进行了基于Agent的机器人新型控制器模型研究 ,在指出传统机器人控制器的缺陷基础上首先介绍了机器人控制器适应先进制造要求的发展方向 ,在此基础上详细介绍了提出的基于Agent的机器人新型控制器模型 ,对于开发未来的开放化机器人控制器具有重要的指导意义。

网络环境下基于Agent的多机器人协调与路径规划

本文针对基于Ａｇｅｎｔ的分布协作式多机器人装配系统——ＤＡＭＡＳ的特点，在原有工作的基础上，提出了网络环境下基于Ａｇｅｎｔ的路径规划思想，重新定义Ａｇｅｎｔ各功能模块的内容，建立系统中的通讯机制．同时，介绍了系统进行路径规划的工作过程，给出了路径规划器的规划算法