MATERIAL MODELLING FOR TRANSIENT DYNAMIC ANALYSIS OF REINFORCED CONCRETE STRUCTURES

Reinforced concrete is a composite structural material which has been the subject of extensive research since it was first used. When considering the rational properties, the research has mainly centred on the behaviour of the concrete, that of the reinforcing steel and the interaction between the steel and the surrounding concrete subject to static loading. The behaviour of reinforced concrete, and, in particular, that of the concrete itself when subject to dynamic loading has been less thoroughly studied. This paper proposes a material model for the concrete which includes the effect of high strain rate upon both the stiffness of the material and upon the crushing strength. It proposes expressions for the yield and failure surfaces of the concrete which account for the effects of high strain rate and then incorporates this material model into an existing finite element program to compare with a series of test results. The paper illustrates that this improved material model can now produce a displacement/time history for reinforced concrete elements which is very close to that observed in tests on elements which are far outside the elastic range.     

蒙脱土的价电子结构与其同晶置换

为研究蒙脱土结构与其性能的关系,根据蒙脱土的晶体结构,设定其结构单元,运用"固体与分子经验电子理论(EET)"对蒙脱土的价电子结构进行计算.研究表明:与理想蒙脱土相比,八面体中0.66个铝被镁同晶置换后蒙脱土结构单元的结合能基本不变,且与氧桥相连的四面体和八面体中主要键的共价电子分布差距变小;蒙脱土3个亚层之间的作用力比片层之间的分子间作用力大两个数量级,证明了蒙脱土的3个亚层结构稳定;在极性介质中可以改变蒙脱土片层间距,但其3个亚层不易分离.     

加强氢能和燃料电池研究的国际合作——第三届广州国际燃料电池会议回顾

介绍了第三届广州国际燃料电池会议的情况,150多人参加了会议,提交了论文89篇。会议期间召开了中英双边座谈会。本次会议对加强国际合作起了重要作用。     

Characteristics of High- and Low-Fat Bologna Sausages as Affected by Final Internal Cooking Temperature and Chilling Storage

A study was made of the effect that final internal processing temperature (63, 70 and 78°C) and chilling storage (2°C) exerted on the characteristics (cooking loss, purge loss, colour, Instron texture profile analysis) of high-fat (242 g kg⁻¹) and low-fat (100 g kg⁻¹) bologna sausage. High-fat sausages were harder and chewier than low-fat sausages. Lower fat contents were accompanied by a significant reduction in the cooking loss and purge loss. Binding properties were not affected ( P> 0·05) by final internal cooking temperature. In general, Hunter colour parameter a values were higher in low-fat samples subjected to a high final internal cooking temperature than in those cooked up to only 63°C. High internal temperatures produced harder meat emulsions, an effect which was more pronounced in high-fat than in low-fat sausages. Cohesiveness and springiness of sausages was not affected ( P> 0·05) by heat treatment. There were no major variations in textural parameters as a result of chilled storage.     

粉末冶金多孔材料性能研究

为了研究多孔结构的渗透特性和机械性能,采用粉末冶金模压烧结技术制备微孔尺寸约5μm不锈钢、高温合金和铜合金非等厚回转体多孔发汗结构,研究了其微孔分布均匀性、气体渗透性能和力学性能与孔隙率的关系,渗透率随孔隙率增大而增大,强度随孔隙率增大而降低,除铜合金外,延伸率随孔隙率增大而降低。金属粉末冶金多孔材料可用于热防护结构的发汗冷却。     

生产工艺对NTC热敏电阻粉料可重复性的影响

NTC粉料的可重复性,取决于粉料加工结果的可重现性和稳定性。故从控制粉料球磨粒度和球磨均匀性的角度,对粉料加工过程中的关键工序进行改良和精确控制,实施主料–掺杂–主料的配料次序,采用圆球状锆质磨介,并根据材料体系区分不同的预烧温度,采用(或者接近)临界球磨速度磨料等一系列改良措施,从而获得(1.0±0.2)μm的可控粒度范围粉料,达到粉料具有良好可重复性的目的。     

平纹织物复合材料横向力学性能研究

通过对平纹织物复合材料的横向拉压试验, 分析了产生各种破坏现象的微观机理。横向压缩过程中,在与水平面成45°方向剪切破坏的同时还出现层间裂纹。由于两个方向上纱线的弯曲程度不同, 破坏形式有很大差异, 不同自由边处的纱线界面存在不同程度的剪切破坏, 并表现出不同的边缘效应。借助显微镜观察和基于代表体积单元的数值模拟对这些现象进行了分析, 发现高度不均匀的内部波纹纱线结构在横向压缩下产生的层间剪切应力是出现横向裂纹的主要原因。      

红外辐射材料的研究及其在武钢工业炉上的应用

从高温工业炉强化炉内辐射传热过程的角度出发,分析了工业炉应用红外辐射材料的重要意义。在红外辐射材料的研究、涂料节能机理的研究和实际应用技术的研究等方面,系统地介绍了武钢的研究和实际应用情况。根据武钢20多年的实际应用经验,针对不同工业炉具体的工况条件,合理选择性能优良的红外辐射涂料,能够取得良好的节能、增产和延长炉子使用寿命的效果。     

仿生葫芦储热单元潜热蓄热堆积床数值研究

在碳达峰与碳中和的“双碳”能源背景下,传统封装相变材料（PCM）的储热单元与潜热储热堆积床（LHTES）系统无法满足当前的储热需求,而仿生学在储热领域的应用,可以为二者储热效率的提升提供一种全新的思路。为此,提出一种仿生葫芦结构的新型储热单元以增加传热面积,提高LHTES系统的热性能。优化仿生葫芦单元结构的尺寸参数对单元熔融特性的影响,确定最优熔融特性的尺寸参数。分析传统球形和仿生葫芦LHTES的温度分布、液相率、蓄热能力等性能指标的影响。结果表明,葫芦结构可提升14.5%的单元换热面积,与传统模型相比,仿生模型液相率和储热完成率最大可分别提升12.67%和6.2%。在此基础上,分析入口温度和流速对系统性能的影响,结果表明,进口温度对系统的储热性能影响较大,进口温度增大15 K,堆积床系统的储热时间比原来缩短59.6%。该研究可为优化LHTES系统、提高实际条件下的热性能提供参考。     

On the Effect of pH,Temperature, and Surfactant Structure on Bovine Serum Albumin–Cationic/Anionic/Nonionic Surfactants Interactions in Cacodylate Buffer–Fluorescence Quenching Studies Supported by UV Spectrophotometry and CD Spectroscopy

Due to the fact that surfactant molecules are known to alter the structure (and consequently the function) of a protein, protein–surfactant interactions are very important in the biological, pharmaceutical, and cosmetic industries. Although there are numerous studies on the interactions of albumins with surfactants, the investigations are often performed at fixed environmental conditions and limited to separate surface-active agents and consequently do not present an appropriate comparison between their different types and structures. In the present paper, the interactions between selected cationic, anionic, and nonionic surfactants, namely hexadecylpyridinium chloride (CPC), hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol sorbitan monolaurate, monopalmitate, and monooleate (TWEEN 20, TWEEN 40, and TWEEN 80, respectively) with bovine serum albumin (BSA) were studied qualitatively and quantitatively in an aqueous solution (10 mM cacodylate buffer; pH 5.0 and 7.0) by steady-state fluorescence spectroscopy supported by UV spectrophotometry and CD spectroscopy. Since in the case of all studied systems, the fluorescence intensity of BSA decreased regularly and significantly under the action of the surfactants added, the fluorescence quenching mechanism was analyzed thoroughly with the use of the Stern–Volmer equation (and its modification) and attributed to the formation of BSA–surfactant complexes. The binding efficiency and mode of interactions were evaluated among others by the determination, comparison, and discussion of the values of binding (association) constants of the newly formed complexes and the corresponding thermodynamic parameters (ΔG, ΔH, ΔS). Furthermore, the influence of the structure of the chosen surfactants (charge of hydrophilic head and length of hydrophobic chain) as well as different environmental conditions (pH, temperature) on the binding mode and the strength of the interaction has been investigated and elucidated.