Physiological sources of variation in chemical defense ofOreina gloriosa (Coleoptera: Chrysomelidae)

The defensive secretion of the alpine chrysomelidOreina gloriosa is a complex mixture of mainly cardenolides and tyrosine betaine. Individually sampled secretions of adult laboratory-reared and field-collected beetles were analyzed by reverse-phase HPLC; 16 secretion components were quantified. Quantities and concentrations of different components were significantly affected by the age, sex, and reproductive status of individual beetles. Aging was correlated with marked increases (up to 4.4-fold) and decreases (up to 2.7-fold) of quantities and concentrations of several components. Differences between the sexes were smaller, but quantities of all components and concentrations of several components were larger in laboratory-reared females than in males. There was less of one component of the secretion in mated than unmated females, but the concentrations of four secretion components were higher (up to 1.6-fold) in mated females.     

Aging and moisture effects on the tensile properties of starch/poly(hydroxyester ether) composites

The effects of starch and aging on the mechanical properties of starch/poly(hydroxyester ether) (PHEE) composite materials were characterized. Native or modified cornstarches were extruded with PHEE. Composites were aged for up to 20 months at either 23°C and 50% relative humidity (RH) or over calcium sulfate to keep the composites dry. The tensile strength (TS) of the composites was affected by the type of starch filler that they contained. Composites containing native or crosslinked starch had significantly greater TS than composites containing octenylsuccinated starch. It was thought that the octenylsuccinate modification of the starch granule affected the adhesion between the starch and PHEE. Aging the composites at 50% RH had a significant effect on the mechanical properties of the composites, with TS and Young's modulus (YM) significantly decreasing and the elongation to break significantly increasing after 20 months of storage. Composites stored at 50% RH absorbed water, which caused changes in the mechanical properties by plasticizing PHEE. Composites containing poly(lactic acid) and PHEE did not experience large reduction in TS and YM when aged at 50% RH, even though they also absorbed water. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3332–3339, 2006     

影响氯磺化聚乙烯/丁腈橡胶共混物耐热老化性能的因素

研究了氯磺化聚乙烯(CSM)和丁腈橡胶(NBR)的共混比、硫黄用量、炭黑、防老剂及软化剂诸因素对CSM/NBR共混物耐热老化性能的影响。结果表明,将CSM与NBR共混,可以改善NBR的耐热老化性能,当CSM/NBR共混比(质量比)为50/50时,耐热老化性能得到显著提高。适当减少硫黄用量,有利于保持较高的耐热老化性能,硫黄用量以0.25~0.75份为宜。炭黑用量对共混物的耐热老化性能有影响,随着炭黑N 550用量的增加,老化后的力学性能保持率先增加后减小。防老剂NBC的耐热老化效果较好。软化剂选用邻苯二甲酸二丁酯或邻苯二甲酸二辛酯时,CSM/NBR共混物具有较好的耐热老化性能。     

基质沥青老化行为与老化机理

在环境作用下沥青易产生静态硬化和氧化硬化,使沥青的流变特性发生改变,而严重影响沥青路面的耐久性,如何合理评价和选择沥青对确保路面使用品质至关重要.通过3种不同基质沥青的组分分析和不同老化状态下沥青的常规试验(针入度、软化点和延度试验)、SHRP试验(DSR(Dynamic Shear Rheometer)和BBR(Bending Beam Rheometer)试验)结果比较,结合FTIR(Fourier Transform Infrared)红外光谱试验结果,分析了不同老化状态下基质沥青的老化特性和机理.结果表明,常规试验可用来描述基质沥青老化前后性能变化,但它只能提供特定温度荷载频率下的试验信息,而SHRP试验可全方位反映沥青老化对沥青流变行为的影响,建议采用SHRP流变学指标特别是BBR试验结果评价沥青的老化特性.     

无铅封装中镀覆层对PBGA耐湿热可靠性的影响

随着电子产业中无铅替代有铅的迫切要求,无铅产品的应用越来越广泛,多种材料在无铅电子封装中的应用,使得界面反应与含铅产品相比更为复杂.通过对PBGA器件与不同表面镀层(OSP,ENIG)的PCB板互连形成的SnAgCu焊点,在高湿和炎热条件下的可靠性进行研究.试验结果表明:焊点的寿命在使用ENIG镀层时比使用OSP镀层时更长,说明焊点的可靠性与界面金属间化合物类型密切相关;试验后期还发现器件本身最易产生裂纹的地方位于芯片(DIE)、粘接层材料(DA)和塑封材料(EMC)交界处的芯片以及芯片和DA材料交界处的芯片上,主要是因为芯片与聚合物材料间不能形成过渡层,芯片应力无法得到松弛.     

非线性微分动力学模型的沥青老化行为

为了研究沥青的老化行为及抗老化性能,将沥青进行旋转薄膜烘箱老化（RTFOT）和60℃烘箱老化试验,并从不同使用年限的路面回收老化的沥青,采用非线性微分动力学模型对不同老化方式的沥青粘度进行拟合,根据模型参数讨论了沥青在不同老化条件下的性质变化和老化速率,并分析了老化机理的差异。结果表明,非线性微分模型可以有效地模拟沥青室内和野外老化进程,模型参数L和r可以实现对老化状态和老化速率的量化。不同老化温度下,沥青都有其对应的极限老化状态。RTFOT老化与野外老化的极限老化程度约为60℃烘箱老化的4～5倍,RTFOT老化6h与野外老化6a的老化效果接近,延时的RTFOT老化方法可以模拟实际路面沥青的长期老化。     

比例失效率模型的年龄性质及反失效率加型脆弱模型的年龄性质和随机序比较

分析了比例失效率模型的一些随机序关系,分别讨论了一维反失效率加型脆弱模型的一些年龄性质和随机序关系,最后给出了多维反失效率乘型脆弱模型的一些随机序关系．     

浅谈居住区规划设计中人口老龄化问题

人口老龄化是社会发展的必然趋势.随着计划生育的实施、医疗事业的加强、人口死亡率的下降,人口寿命的延长,老年人占人口的比重逐渐上升,我国社会正处于老龄化的过程中.因此,按照老年人的生理、心理和社会特征来规划和建设属于他们的居住环境,充分弥补年老者减退或丧失的各种机能,改善当前居住环境中存在的种种缺陷和不足,创造适合老年人...     

老龄化社会背景下独生子女养老问题研究

我国正处在老龄化社会的快速发展阶段,人口结构发生了很大的变化：“421”的家庭结构,已经使第一代独生子女面临着巨大的养老压力。在构建社会主义和谐社会的背景下,旧的养老模式已经不能适应社会发展的需要;转变传统养老观念,调整现有养老政策,探索以网络为载体的新型养老模式,是解决我国老龄化社会养老问题的出路所在。     

网络生态40年：立克里德的预言及互联网之趋“老”

立克里德1968年关于网络生态的预言正在变为现实。作为新媒体的互联网不仅改变了原有的媒体格局,而且影响了人们的生产方式和生活方式,甚至转变了人们有关自身存在的观念。在考察网络生态时,必须注意到它所包含的文化与反文化的矛盾、正视互联网发展所面临的问题,并理解互联网趋“老”的必然性。趋“老”的涵义之一,是指互联网在网络生态中所占地位的变化,即从相对新的媒体转变为相对旧的媒体,表现在产业链、用户群、媒体声望、主导价值取向、管理方式、社会印象等方面。“老”不仅是积以时日,而且是日益成熟。与时光相伴的“老”不可避免,问题在于这种过程性变化是进入化境,还是导致衰朽。我们的任务不是否认互联网趋“老”的事实,而是努力使这种变化有利于网络生态、媒体生态以至于整个人文生态的建设。为此,要提倡老实诚恳地办网、上网,以增进网络公信力,老练周到地应对信息“洪水”,以增进网络净化力,老成持重地处理各种矛盾,以增进网络亲合力。