The mechanism of the deposition of pyrolytic carbons

The changes in crystallite-preferred orientation, distribution of 0.1–1.0-μm diameter pores, density, growth feature shape, and crystallite arrangement that occur with changes in the conditions of pyrolytic carbon deposition in a fluidized bed of particles are studied. Based on these changes a deposition mechanism is proposed wherein changes in the crystallite-preferred orientation and the pore distribution are controlled by the relative concentrations of two depositing components, which are solid particles and molecular species. Changes in the crystallite arrangement, and thereby the density, are controlled by changes in the reaction probability of the planar hydrocarbon molecules with the carbon surface.     

Graphite—the most fascinating nuclear material

A review is made of the behaviour of graphite subjected to irradiation in nuclear reactors with particular emphasis on the dimensional changes of graphite crystallites and their relationship to the macroscopic dimensional changes of polycrystalline graphites. The theory of the formation of the lattice defects responsible for these changes is examined and deficiencies in present knowledge highlighted.     

火灾对施工中系杆拱桥混凝土箱梁性能的影响分析

为了研究系杆拱桥火灾后混凝土和箱梁损伤程度的大小和性能的变化,针对火灾后一座1～64 m系杆拱桥的过火结构进行检测和分析,并现场取样对火灾过程中混凝土箱梁温度场、混凝土受损程度、火灾后混凝土微观结构等进行实验分析,得到系杆拱桥在遭受火灾后各项性能的变化,为桥梁火灾检测提供一种可靠的的检测方案和检测依据,得到高温后混凝土性能变化,同时建立该桥的有限元模型,模拟得到的火灾后系杆拱桥承载力及变形等性能的变化情况和实测结果基本一致,为桥梁火灾后受损情况鉴定提供了一种可行的有限元模拟方法.     

Time dependent effects of pressure on the shear modulus of polypropylene

The time dependent changes in the shear modulus of polypropylene have been followed subsequent to both step and ramp changes in pressure for pressures up to 400 MN/m². Although the changes in pressure (p-jumps) are accompanied by transient heating effects which complicate the interpretation of the results; large changes in modulus can be seen at times of up to three hours after the pressure change. At these times the effects of temperature changes would be expected to be negligible. The results are consistent with the expected changes of free volume occurring during the dilatational creep under pressure, and lend no support to the ‘microstress’ theory recently proposed.     

Variations of fatty acid composition of erythrocyte and plasma lipids in the rat during the first period of life

The changes occurring in the fatty acid composition of the erythrocyte lipids during the first weeks of life were studied in the rat. The major changes consisted of a progressive decrease in oleic acid and a progressive increase in linoleic acid. A lower but significant increase in arachidonic acid was also observed. These changes are not related to variations in erythrocyte age; rather, they appear to be related to the age of the animal. Since somewhat similar changes were observed in the fatty acid composition of the major lipid classes of plasma during the first weeks of life, the possibility that these variations could account for the changes in the fatty acid composition of erythrocyte lipids was considered. Some support to this possibility was found in the results of experiments in which erythrocytes taken from 15-day-old rats were incubated with plasma taken from newborn rats. The changes in the fatty acid composition of erythrocytes and plasma lipids do not appear to be dependent on dietary lipids, since they occur during the suckling period, i.e., before the rats begin to ingest the pelleted diet which presents a fatty acid pattern completely different to that of the dams' milk.     

On the adsorption and redox catalysis of the oxalate anion and oxalato complexes on gold and metal-modified gold electrodes

The influence of foreign metal deposits (both upd- and opd-deposits) on a gold electrode on the rate of the redox reaction iron(II)/(III) oxalate has been studied with AC impedance measurements. An attempt has been made to rationalise observed changes in the rate of reaction in terms of changed metal-redox reactant interactions. Results obtained so far do not indicate significant changes in the adsorptive interaction as evidenced with Surface Enhanced Raman Spectroscopy despite the fact, that metal-adsorbate bands are pronounced. No correlations between band positions and their changes and changes of the catalytic activity could be observed.     

对塑料密度测试结果变化的分析

本文针对塑料密度测试结果的几点变化进行分析;密度梯度柱的配置、试验样品的处理过程、样品的制备过程、载荷等、实验环境、化验员的操作、数据的处理等将影响实验结果。     

磷石膏在低浓度硫酸中的溶解及相态变化

湿法磷酸生产过程副产大量磷石膏,因其含有较多杂质而无法直接利用,目前可采用硫酸酸浸处理提高磷石膏品质。为弄清酸浸过程中石膏的溶解性能和结晶形态的变化,本文探讨了在0～80 ℃、0～30%的硫酸浓度条件下,磷石膏在硫酸溶液中的溶解度大小、结晶形貌、物相组成及结晶水含量的变化情况。实验结果表明,磷石膏在硫酸溶液中的溶解度随温度升高而升高,在80 ℃时达最大;随浓度升高呈先升后降的变化,在硫酸浓度为10%时溶解度最大。硫酸浓度小于10%时,磷石膏中二水硫酸钙溶解,但无新相生成,其形貌变化不大;硫酸浓度大于10%时,二水硫酸钙溶解,同时再结晶转化成无水硫酸钙,最终导致磷石膏形貌和相态发生了改变,溶解度随硫酸浓度升高而降低。     

A note on volume changes in the lime-silica reaction

Volume changes occuring during the formation of calcium hydrosilicate phases in autoclaved quartzlime products have been calculated. An increase in the volume of the solid phase (and a corresponding decrease in porosity) occurs with the formation of C-S-H(II) and C-S-H(I) and is followed by a subsequent decrease in the volume of the solid phase with the formation of tobermorite, gyrolite or xonotlite. These changes correspond to strength changes in the system.     

氟化钙与硫酸在393．15K和553．15K时的焓变，自由能变与熵变值

对ＣａＦ２（ｃ）＋Ｈ２ＳＯ４（１）＝２ＨＦ（ｇ）＋ＣａＳＯ４（ｃ）反应在３９３．１５Ｋ（１２０℃）及５５３．１５Ｋ（２８０℃）时的焓变值、自由能变值及熵变值，进行了详细计算，得到了良好的结果。     

缓凝剂对水泥浆中自由水状态演变的影响

用低场核磁共振技术考察了HN-1型缓凝剂对水泥浆体中可蒸发水的横向弛豫时间(T2)及状态演变过程的影响。结果表明:在初始水化阶段的150 min内,水泥浆GR(添加缓凝剂HN-1的水泥净浆)的弛豫峰峰形和峰顶位置均无明显变化,水泥浆G(纯水泥净浆)的弛豫峰峰形变窄且峰顶位置从2.15 ms迁移至0.95 ms,说明缓凝剂HN-1主要通过改变水泥浆体中不同状态水的存留时间来改变其水化进程。随养护时间的延长,硬化水泥石W0.44和WR0.5中可挥发水弛豫峰分布范围分别从0.11~4.75 ms变为0.08~0.58 ms、0.24~4.23 ms变为0.11~2.35 ms,总体趋向于短弛豫时间,表明水泥石中毛细水逐渐向凝胶水和物理结合水转化,水泥石养护龄期延长至25 d时,其内部凝胶结构水含量超过90%。利用XRD考察了缓凝剂对水泥浆水化产物的影响,结果表明:缓凝剂只改变水泥浆水化过程,对最终水化产物晶型及晶型结构不存在任何影响。     

2001年我国涂料行业生产经营形势分析

对国内工业企业、石化和涂料行业的经济指标完成情况进行了比较 ,对行业内 36家企业经济指标作了汇总 ,并分析了华东、中南、华北及中西部等地区的涂料工业发展趋势 ,指出了 2 0 0 1年涂料行业的三大变化是 :体制创新 ,技术创新和营销模式的变革     

Lipids and the pill

The widespread use of anovulatory compounds and the well-known effects of sex hormones on various aspects of metabolism prompted this review of our work and the work of others on observed changes in lipid metabolism resulting from the administration of oral contraceptives and their components. In the rat, female sex hormone administration results in a decreased plasma cholesterol level, an accumulation of cholesterol in liver and a decreased hepatic cholesterol biosynthesis. On the other hand, cholesterol biosynthesis is enhanced in ovaries and adrenals. There is also a diminished alpha lipoprotein content and a corresponding decrease in the alpha/beta lipoprotein ratio. In some cases these changes are comparable to those observed during pregnancy. The results of sex hormone administration to women are more variable. In this case the most often observed effect is hypertriglyceridemia. Changes in lipoprotein content and distribution are also evident and may be the result of changes in metabolism in the liver, e.g., lipid synthesis or lipid transport from liver to plasma and tissues, or both. Many of these changes may be mediated indirectly through the action of estrogenprogestin on other hormones. In both species the effects of oral contraceptives are attributable principally to the estrogen component. The combination of estrogen with progestin compounds, which constitutes the oral contraceptive, modifies the effects of estrogen administered alone.     

压力降法在循环冷却水系统黏泥监控中的应用

介绍使用生物膜监测仪在循环水系统开展黏泥监控的原理、安装及使用情况。随着中水在天津石化公司化工厂循环水系统的大量使用,进行生物黏泥监控显得尤为重要。而生物膜监测仪主要是通过压力降原理来监测冷却水系统中的沉积产物,随着监测管内沉积物的变化,其压力降值也不断变化,通过实际应用表明,生物膜监测仪能有效地反映循环冷却水系统黏泥沉积情况,其压降值明显地随着循环水中异养菌、温度、浊度的变化而发生变化．因此在实际操作中具有很强的指导意义。     

The effects of weathering on the mechanical performance of automotive paint systems

The durability of automotive paint systems continues to be a great concern to both auto companies and their coating suppliers. Recent advances in assessing the durability of coatings by measuring weathering-induced chemical composition changes have greatly increased our ability to discern superior from inferior coatings. However, different coatings will likely tolerate different amounts of weathering-induced chemical composition changes while still maintaining their mechanical integrity. Thus, a means of linking chemical composition changes to changes in relevant mechanical properties would be highly desirable. The fracture energy, the amount of mechanical energy required to propagate a crack in a material, is a sensitive measure of the brittleness of a material and is relevant to a number of potential failure mechanisms in automotive paint systems. The fracture energy of clearcoats can vary widely depending on the formulation of the clearcoat (initial chemical composition and additive package) and on the amount of weathering. Weathering embrittles most coatings. Weathering-induced changes in the fracture energy are related to chemical composition changes occurring in the clearcoat. Because the brittlest materials will not crack without an applied stress, the stress distribution in complete paint systems as a function of weathering must also be known to accurately anticipate mechanical failures. Measuring thermoelastic constants of individual layers allows for computation of the stresses in complete paint systems. Stresses tend to increase with weathering. The presence of flaws in the clearcoat changes the stress distribution dramatically. Coupled with fracture energy measurements, the stress measurements provide additional insight into paint system failure mechanisms.     

工学结合视野下高职公共英语课程改革中的四个转变

工学结合的高职英语课程改革过程中,要特别注意以下四个转变,即师生角色的转变、教材的转变、教学过程的转变、教学评价的转变。只有落实了这四个转变,才能推进课程改革实践向纵深发展。     

Microstructural and bulk property changes in hardened cement paste during the first drying process

This paper reports the microstructural changes and resultant bulk physical property changes in hardened cement paste (hcp) during the first desorption process. The microstructural changes and solid-phase changes were evaluated by water vapor sorption, nitrogen sorption, ultrasonic velocity, and ²⁹Si and ²⁷Al nuclear magnetic resonance. Strength, Young's modulus, and drying shrinkage were also examined. The first drying process increased the volume of macropores and decreased the volume of mesopores and interlayer spaces. Furthermore, in the first drying process globule clusters were interconnected. During the first desorption, the strength increased for samples cured at 100% to 90% RH, decreased for 90% to 40% RH, and increased again for 40% to 11% RH. This behavior is explained by both microstructural changes in hcp and C–S–H globule densification. The drying shrinkage strains during rapid drying and slow drying were compared and the effects of the microstructural changes and evaporation were separated.     

Evaluation of the starch fraction in corn products consumed regionally

The purpose of this study was to evaluate through conventional analytical procedures, the degree of modification of the starch fraction of regional products based on corn, such as grits, flours, precooked grits, flakes, precooked flour, "frangollo" and "locrillo." Based on the interpretation of changes in the starch fraction, the following conclusions are reached. Corn grits, flours, "frangollo" and "locrillo" are raw corn products subjected to physical processes such as shelling, degermination and size reduction. They do not show changes in their physicochemical characteristics. Precooked grits present certain structural modification (among others, changes in their rheologic behavior) and partial molecular change (among others, changes in the insoluble carbohydrate fraction), indicating that they have been subjected to processes wherein factors such as temperature, moisture and/or pressure intervene. Corn flakes and precooked flours show a high enzyme digestibility and a high degree of change in their functional properties (mainly, in regard to solubility, absorption and viscosity). These changes indicate modification at granular and molecular level.     

Conformational changes in the induction period of crystallization as measured by FT-IR

The isothermal crystallization behaviors of poly(bisphenol A-co-decane ether) (BA-C10) at different temperatures were studied in situ by means of Fourier transform infrared spectroscopic (FT-IR) measurements. Conformational changes during the induction period were investigated in details. The results suggest that conformational changes of polymer chains always take place before the start of changes in the characteristic FT-IR peaks of the crystalline phase.     

Changes in the Reflectivity and Color Characteristics of Microcellular Foamed Plastics

As the use of plastics has increased in various industries, research on microcellular plastics has increased as well. The microcellular foaming process helps produce lighter plastic and reduces material consumption. This process also affects the optical properties. The primary purpose of this study is to measure the visible changes occurring in polymer samples by comparing changes in the samples before and after the microcellular foaming process. To measure the changes in color characteristics, colored PC samples were utilized for the experiments. Changes in the color characteristics were indicated using the Munsell color system.