一类混合Ramsey数

设a(G)表示图G的点荫度,m为正整数,H为连通图,混合Ramsey数v(a;m;H)被定义的为最小的正整数P,使得对任意P阶图G则有a(G)≥m或者H包括于G^-。本文给出了v(a;m;H)的一种计算方法,并对图Cn和轮Wn确定了v(a;n;Cn)和v(a;m;Wn)的值。     

超硬砂轮修整的研究——制动式整形器的理论与实践

超硬砂轮修整的困难,是生产上推广应用的主要障碍之一。本文对制动式整形器进行了理论上的分析,并进行了实验。找出了影响整形效率和整形精度的规律,提出了制动式整形器合理使用的方法和适合的参数。整形器价格低廉,可直接在生产上使用,是一种有效的整形工具。     

Hydrogels based on physiologically clotted fibrin–gelatin composites

Fibrin–gelatin composite (PFG) films were prepared and crosslinked with glutaraldehyde as reported by us previously. These composites were graft‐copolymerized with poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(2‐hydroxypropyl methacrylate) (PHPMA) with a potassium persulfate and sodium metabisulfite redox initiation system. The graft copolymers (PFG‐HEMA and PFG‐HPMA) were characterized for their percentage of grafting, percentage of equilibrium water content, and percentages of free water and bound water. The chemical composition and thermal, mechanical, morphological, and surface characteristics were also evaluated. The optimum conditions for obtaining a maximum percentage of grafting were standardized. PFG and its graft copolymers exhibited higher equilibrium water contents ranging from 60 to 77% when compared with those of HEMA and HPMA homopolymers. DSC studies revealed increased freezing water contents and decreased bound‐water contents for the graft copolymers when compared with those of PFG alone. These properties improved the efficacy of hydrogels. PFG demonstrated better mechanical properties as compared with its graft copolymers. This may be attributed to the alkaline reaction conditions wherein protein hydrolysis of PFG would have occurred thereby reducing the overall strength of the graft copolymers. IR and scanning electron microscopic studies confirmed the grafting of PHEMA and PHPMA onto PFG. Contact‐angle studies revealed increased polarity for graft copolymers, which is a symbol for increased hydrophilicity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2241–2252, 2004     

THE EFFECT OF THE CBN WHEEL DRESSING AND THE GRAIN HEIGHT PROTRUDING FROM THE BOND ON THE GRINDING PERFORMANCE

CBN (Cubic Boron Nitride) is a highly efficient abrasive and has unique properties (highhardness, high thermal stability and high chemical inertia). As early as 1969 CBN Wheels had al-ready been made and showed excellent performance for grainding high speed steels and othermaterials hard to be ground. So far, however, CBN Wheels are still not popularly utilized in theindustry, the writer considers the main reason being the inadequate study for practical applica-tions and especially the suitable dressing technique. The dressing of resinoid CBN Wheels discussed in the paper, is different from that ofconventional ones. It has to be divided into two operations, truing and sharpening, each of whichhas its specific and independent functions. A simple dressing method with a lot of informationsuitable for production is studied; finally, the grain height protruding from the bond is taken asan index for evaluating the dressing results, and the effect of grain height on the grinding per-formance is discussed. By selecting proper conditions according to the workpiece requirements, abetter technical and economical benifit can be obtained.     

Dual‐Functional Dextran‐PEG Hydrogel as an Antimicrobial Biomedical Material

Microbial infections continually present a major worldwide public healthcare threat, particularly in instances of impaired wound healing and biomedical implant fouling. The development of new materials with the desired antimicrobial property to avoid and treat wound infection is urgently needed in wound care management. This study reports a novel dual‐functional biodegradable dextran‐poly(ethylene glycol) (PEG) hydrogel covalently conjugated with antibacterial Polymyxin B and Vancomycin (Vanco). The hydrogel is designed as a specialized wound dressing that eradicates existing bacteria and inhibits further bacteria growth, while, ameliorating the side effects of antibiotics and accelerating tissue repair and regeneration. The hydrogel exhibits potent antibacterial activities against both gram‐negative bacteria Escherichia coli (E. coli) and gram‐positive bacteria Staphylococcus aureus (S. aureus) with no observable toxicity to mouse fibroblast cell line NIH 3T3. These results demonstrate the immense potential of dextran‐PEG hydrogel as a wound dressing healthcare material in efficiently controlling bacteria growth in complex biological systems.     

女性服装购买与穿着行为的类型划分

以问卷调查为基础，采用因子分析和聚类分析的方法，将女性服装购买与穿着行为划分为“热衷时尚”、“讲究高档”、“回避过时”和“慎重理智”四个因子，将消费者划分为慎重理智型、漠不关心型、流行追随型、讲究身份型、追求时髦型和保守计划型６种基本类型．通过相关分析知各类型消费者在个人基本属性、购买服装时对服装属性的重视程度、购买场所选择、流行信息来源、流行采用时机和采用动机、着装态度、年置装费以及生活方式等方面都存在显著差异．这些差异可作为服装企业制订市场营销策略的依据．     

基于MAP-PRF复合的新型创口敷料合成及毒性研究

针对创口处理和修复中保护创面、防止感染和促进愈合等问题,基于仿生合成MAP粘合材料防水、快速闭合创口及生物源PRF快速止血、促进愈合的特性,设计并合成一种新型MAP-PRF复合创口敷料。采用^1H NMR表征材料结构,UV-Vis验证MAP聚氨酯侧链邻二酚粘合单元引入,GPC表征聚合材料分子量分布。细胞毒性分析和热分析数据表明:MAP-PRF复合材料的热稳定性良好、毒性低,可进一步用于生物医药领域的软组织快速粘合修复及硬组织粘接。     

果树根外追肥应把握的技术要点浅析

本文作者紧密结合本地实际，详细阐述了对果树进行根外追肥实践中应把握好根外追肥的种类、浓度、部位、时期及防止产生的肥害等技术要点和应注意的五个方面问题，对当前开展的建生态市、产无害果活动有一定借鉴和指导意义。     

中国大陆与香港服装穿着习惯比较研究

对中国６个大区的６大中心城市及香港地区消费者的穿着习惯进行了系统调查和研究，发现中国大陆各中心城市消费者穿着习惯基本趋同，与香港地区消费者穿着习惯差异越来越小，但在牛仔服装的消费方面，中国大陆与香港等发达地区相比较，尚有一定的差异．     

A New Method for Dressing Fine Grain Diamond Wheels——the Soft-Elastic Dressing Method

IntroductionInrecentyears,ceramicshavebeenmuchmorewidelyusedinthefieldsofoptics,electronics,abrasion-resistancepartsandthermalresistanceparts.Ceramicsareveryhardandchemicallyinert,havehighthermalresistance,highabrasionresistanceandlowelectricalconductivity.Buttheyareratherdifficulttomachinebecauseoftheirhardnessandbrittleness.Grindingwithfinegraindiamondwheelsisanefficientmethodforpreciseandultra-precisemachiningofceramics.Beforegrinding,thefinegraindiamondwheelrequiresdressing.Thedressingpro…