热致性液晶聚合物种类对环氧树脂性能的影响研究

利用自行合成的多种热致性高分子液晶聚合物对CYD -12 8环氧树脂进行共混改性 ,用FTIR方法研究了液晶聚合物对环氧树脂固化反应程度的影响 ,用DSC、TGA研究了液晶聚合物对环氧树脂固化物Tg 和热失重温度的影响 ,测试了共混物的力学性能 ,并用扫描电镜观察了共混物冲击断面的形貌。结果表明 :端基含有活性反应基团的液晶聚合物可以提高固化反应程度、提高固化物的韧性和强度 ,同时还使固化物的Tg 和热失重温度提高 ,SEM观察表明 ,加入液晶聚合物的材料断裂面面积增大 ,逐渐出现韧性断裂的特征。

浅谈膜式燃气表的性能与检定技术方法

随着中国经济的快速增长,国民的生活质量有了明显的提升,膜式燃气表在人们的生产和生活中的作用越来越重要,它已被广泛应用于各个领域和各个行业,只有保证燃气表计量的准确性,才能得到广大群众的认可,因此要求计量检定人员,应该在熟悉燃气表工作原理的基础上,弄清燃气表的各项指标,在实际应用中必须有熟练的技术人员,以保证燃气表结算的准确性。本文在介绍燃气表的种类与性能、燃气表检定工作原理基础上,论述了膜式燃气表的检定技术,旨在为膜式燃气表的使用和检定贡献自己的一份力量。

浅析缓冲器在电梯安全保护中的作用

在国家整体经济持续发展背景下,逐渐迈进城镇化的发展进程,一些高层建筑的不断建设与兴起,促使电梯成为人们实际生活与生产中十分重要的运输工具。目前,社会对电梯的使用数量有很大的需求,因此也提高了电梯的使用标准,促使运输安全成为人们重点关注的话题。从电梯安全保护情况分析,缓冲器发挥至关重要的作用,属于电梯设施中不可缺少的组成部分,对电梯设备的整体运行安全性起到积极的影响,保护人们的使用安全。

骨传导技术在消防装备中的应用

消防战士在灭火、抢险中急需一种既把繁多的单兵装置组合一体又可解放双手使用器械的单兵作战装置。文章介绍了骨传导技术的种类功能、主要性能、简易判断方法以及骨传导器件在高端及特殊场合的使用。

Patterns of species diversity and functional diversity of breeding birds in Hangzhou across an urbanization gradient

Given the rapid rise in human population and increasing urbanization,it is important to understand their potential impacts on biodiversity.From March 2007 to August 2007,we conducted bird surveys in 90 strip transects,each 3 km long and 100 m wide,along a gradient of urbanization in Hangzhou,China.This gradient spanned a range of urbanization levels including urban areas,rural-urban continuum areas,farming areas,mixed forest/farming areas and forested areas.We recorded 96 breeding bird species and classified them into nine functional groups based on nesting requirements.The nine functional groups consisted of canopy nesters,shrub nesters,canopy/shrub nesters,natural cavity nesters,building nesters,natural cavity/building nesters,ground nesters,water surface nesters and parasitic nesters.Species and functional diversities were estimated based on the Shannon-Wiener index.Environmental data of each transect as human disturbance,vegetation cover and building index were also measured,and a synthetic urbanization index of each transect was introduced based on these data.We used regression analyses to model the relationship of species abundance,species diversity,functional abundance and functional diversity with this synthetic index.The results show that urbanization significantly reduces species richness,species diversity,functional richness and functional diversity,but the specific patterns differed.The relationship between species abundance/species diversity and urbanization is linear.In contrast,the relationship between functional diversity and urbanization was quadratic.In other words,with increased urbanization,functional diversity declined only slightly at first but then dropped at an accelerating rate.This implies that,although moderate urbanization reduces species diversity of breeding birds,it affects functional diversity of breeding birds only slightly in Hangzhou.The regression analysis of species diversity and functional diversity suggests a quadratic relationship between species diversity and functional diversity,i.e.,a linear relationship between species diversity and functional diversity can only exist at low diversity levels across urbanization gradients and increasing species abundance does not lead to an increase in functional diversity at the highest diversity levels.

塑料王特种工程塑料——氟塑料

简述特种工程塑料—氟塑料的研究开发历程和主要种类性能及其应用。

中低压电缆头安装施工中常用的带材及绕包注意事项

本文详谈了中低压电缆头安装施工中常用的带材及绕包注意事项：绕包前将电缆绕包部位清洁干净，避免有杂质存在而影响胶带的操作与效果；要求均匀拉伸100%，便其层间产生足够的粘合力，并消除层间气隙；采用半重叠法绕包；绕包厚度按照附件安装工艺要求执行；绕包结束后，用双手挤压绕包部位，直至完全自粘。

轻合金材料的应用及发展

随着能源、资源和环境问题的日渐突出,以铝合金、镁合金、钛合金为代表的轻合金材料应用越来越广泛,轻合金材料已经成为与人类生活、生产和社会发展密不可分的重要材料。文章介绍了轻合金材料的基本概念,综述了轻合金材料的种类、性能及其在社会各方面的应用,并对轻合金材料的发展前景进行了展望。

Identification of Rhodiola species by using RP-HPLC

An approach was established using RP-HPLC (reversed-phase high-performance liquid chromatography) to identify ten species of Rhodiola, R. coccinea A. Bor, R. junggarica C.Y. Yang et N.R. Cui spn., R. heterodonta A. Bor, R. linearifolia A. Bor, R. pamiro alaiucm A. Bor, R. kaschgarica A. Bor, R. litwinowii A. Bor, R. gelida schrenk, R. rosea L. and R. quadrifide Fisch et Mey collected from the Tianshan Mountains areas of China. Chromatograms of alcohol-soluble proteins, generated from these ten Rhodiola spp. were compared. Each chromatogram of alcohol-soluble proteins came from a single seed of one wild species only. The results showed that when using a Waters Delta Pak. C18, 5 μm particle size reversed phase column (150 mm×3.9 mm), a linear gradient of 22%?55% solvent B with a flow rate of 1 ml/min and a run time of 67 min, the chromatography gave optimum separation of Rhodiola alcohol-soluble proteins. Chromatogram of each species was different and could be used to identify those species. Cluster analysis of genetic similarity coefficients of 37% to 60% showed a medium degree of genetic diversity among the species in these eco-areas. Cluster analysis showed that the ten species of Rhodiola can be divided into four clusters and yielded the general and unique biochemical markers of these species. RP-HPLC was shown to be a rapid, repeatable and reliable method for Rhodiola species identification and analysis of genetic diversity.

Iron Regulation of Wetland Vegetation Performance Through Synchronous Effects on Phosphorus Acquisition Efficiency

Iron-rich groundwater flowing into wetlands is a worldwide environmental pollution phenomenon that is closely associated with the stability of wetland ecosystems. Combined with high phosphorus(P) loading from agricultural runoff, the prediction of the evolution of wetland vegetation affected by compound contamination is particularly urgent. We tested the effects of anaerobic iron-rich groundwater discharge in a freshwater marsh by simulating the effect of three levels of eutrophic water on native plants(Glyceria spiculosa(Fr. Schmidt.) Rosh.). The management of wetland vegetation with 1–20 mg/L Fe input is an efficient method to promote the growth of plants, which showed an optimum response under a 0.10 mg/L P surface water environment. Iron-rich groundwater strongly affects the changes in ecological niches of some wetland plant species and the dominant species. In addition, when the P concentration in a natural body of water is too high, the governance effect of eutrophication might not be as expected. Under iron-rich groundwater conditions, the δ^(13)C values of organs were more depleted, which can partially explain the differences in δ^(13)C in the soil profile. Conversely, the carbon isotope composition of soil organic carbon is indicative of past changes in vegetation. The results of our experiments confirm that iron-rich groundwater discharge has the potential to affect vegetation composition through toxicity modification in eutrophic environments.

Highly Dispersed Pt Species with Excellent Stability and Catalytic Performance by Reducing a Perovskite-Type Oxide Precursor for CO Oxidation

A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of citrate acid complexa-tion combined with impregnation. In a nanocrystallite of LaCOl-xPtxO3, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, CO temperature-programmed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo0.95Pt0.05O3/ SiO2 catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 ℃ for 250 h with complete CO conversion.