Morphology,crystal structure and hydration of calcined and modified anhydrite

The effects of calcination and modification on the morphology （shapes and textures） and crystal structure of anhydrite powders were studied. The results show that, calcination at 100℃ causes anhydrite to disintegrate into smaller crystals, accompanied by a slight in- crease in d-spacing. Without calcination and modification, the solidification time and curing time of anhydrite are 15 and 77 h, respectively. After the treatment, however, the solidification time and curing time are shortened significantly to 9.5 and 14 rain, respectively. The com- pressive and flexural strengths of hydration products made from the treated anhydrite reach 10.2 and 2.0 MPa, respectively. The much shorter solidification and curing time make it possible to use anhydrite as a building and construction material.     

基于全量补偿算法的结构损伤识别

频率和振型是反应结构动力特性的主要模态参数,文中对损伤结构的频率和振型进行了研究。通过实测损伤结构的频率和振型,利用矩阵理论修正理论有限元模型,使之与实测损伤结构的频率和振型一致;将修正的理论有限元模型表达成单元刚度矩阵与损伤因子的线性组合,把损伤识别问题转化为组合系数的识别问题。给定损伤因子的合理取值范围,用优化方法求解损伤因子。通过对十跨桁架结构的数值仿真,仅用结构的前5阶频率和振型就能很好的识别结构的损伤,且该方法不需要对实测振型进行归一化处理,具有较强的实用性。     

一种改进的ViBe目标检测算法

现有ViBe目标检测算法存在误检率高,得到的结果噪声较大的问题。为此本文提出了一种将判定阈值自适应规则与优化结果反馈机制相结合的改进算法。该算法首先使用样本自身统计值作为阈值进行目标检测;接着对检测结果进行去噪、形态学处理等优化处理;最后将优化后的检测结果反馈给背景模型更新过程使检测更精确。与传统的ViBe算法相比,本文算法可更精确的提取出运动目标,误判率低,过检率较原始算法降低10%-20%。实验结果证明了该算法的有效性。     

The relation between the parabolic rate constants for the internal oxidation of binary alloys in terms of weight gain or thickness

A calculation of the parabolic rate law for internal oxidation in binary alloys expressed in terms of weight gain shows that its dependence on the concentration of the most-reactive component is different from that predicted by the classical Wagner treatment for the rate constant expressed in terms of thickness of the internal oxidation zone. It is shown that the ratio between the two rate constants for a given system is a very sensitive function of the concentration of the reactive element in the alloy.     

Mechanical nondiscoloring and antistretching photonic crystal films based on Zn2+ coordination and hydroxypropyl methylcellulose

Mechanical nondiscoloring and antistretching photonic crystal (PC) films, especially those with stable structure colors during deformation, have great potential applications in wearable display devices, decoration, and packaging. Here, PC films with antistretching and invariant structural colors during deformation were prepared, by combining Zn²⁺ coordinated elastic material and hydroxypropyl methylcellulose (HPMC) with polystyrene@silica (PS@SiO₂) colloidal crystals. The PC films release energy by forming local fractures at a microscopic level during the straining process but the lattice spacing and effective refractive index of the local array do not change. According to the Bragg law, the structure color remains unchanged. The introduction of HPMC gave the PC films excellent tensile properties, and the maximum tensile strength reached 10 MPa. And after 100 times of stretching, bending and compression cycles, the structural color remained unchanged.     

Effect of hollow glass beads on density and mechanical properties of silicone rubber composites

In this work, low density hollow glass beads (HGB)/silicon rubber (SR) composites were prepared by solution method and flocculation process. The prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, tensile test, and friction test. The results show that the densities of SR composites decrease from 1.140 to 0.792 g/cm³ with the addition of HGB. By comparing theoretical density with true density, it can be estimated that the ratio of shattered HGB increase from 8.79% to 24.76%. Especially, the mechanical properties of SR composites were improved by surface modification of HGB. By adding surface-modified HGB at 5 and 10 wt%, the tensile strengths of SR composites were enhanced by 17.8% and 28.2%, respectively. In addition, tear strength, shore A hardness, compression set, and friction property were significantly ameliorated. Furthermore, the mechanism of surface-modified HGB in mechanical properties was analyzed.     

A Cross-sectional Study on the Relationship Between Homocysteine and Lipid Profiles Among Chinese Population from Hunan

Previous studies have explored the relationship between homocystein (Hcy) and lipid profiles. However, the results from these studies have been inconsistent. The current study investigated the correlation between Hcy and lipid profiles in Chinese community-based population. The participants were composed of 4012 Chinese people aged 30–92 years old, who were recruited from rural and urban communities in the Hunan Province. Non-parametric test and logistic regression were used to examine the distribution of Hcy and lipid profiles (triglyceride [TG], total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C]) and the relationship between them. The median age of subjects was 54.50 years old, and 40.98% were male. Median Hcy was 13.20 μmol/L, and 35.39% had hyperhomocysteinemia (HHcy). Median TG was 1.51 mmol/L, TC was 4.77 mmol/L, LDL-C was 2.62 mmol/L, and HDL-C was 1.27 mmol/L. In multivariable logistic regression analysis, HHcy was associated with high levels of TG (OR_male = 2.240, p < 0.001; OR_female = 2.539, p < 0.001), TC (OR_male = 2.237, p < 0.001; OR_female = 2.202, p < 0.001), and LDL-C (OR_male = 1.413, p = 0.010; OR_female = 1.617, p < 0.001) in the different sexes population and low level of HDL-C in females (OR = 1.326, p = 0.023) after adjusting for confounders. HHcy was independently associated with an increasing risk of low HDL-C among females. The regression analysis showed that HHcy was also associated with hypertriglyceridemia, hypercholesterolemia, and high level of LDL-C in males and females from Chinese community-based population, which provides a basis for the treatment and prevention of abnormal lipid metabolism.     

Analysis and simulation of the grinding process. Part II: Mechanics of grinding

This paper is the second of three parts which describe the analysis and simulation of the grinding process. Generation of the workpiece surface depends on the interactions between the grains of the wheel and the workpiece. The grinding wheel surface generated by dressing was simulated by the method described in Part I. This part describes a method to investigate the process of grinding by simulating the cutting action of every grain which engages with the workpiece. Grinding forces are analysed by simulating the force on each grain which passes a section of the workpiece. The simulated workpiece surface shows features which are similar in nature to the experimental results. A more extensive comparison of simulated and experimental grinding behaviour is presented in Part III.     

Improvement of SiC_p Reinforced Cast AluminiumComposites by the ROC Method

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CHANGE OF CARBON CONTAMINATION DURING URANIUM REFINING

<正> 铀的精炼一般用石墨坩埚,由于石墨与铀的相互作用,使铀中含碳量增加,精炼过程的温度、时间等因素无疑将影响铀液增碳。为了解决这一问题,曾进行了如下的实验。 于内径3cm高7cm的石墨坩埚内加入约540g铀块,置小型熔炼装置内,通中频电源加热,分别于1320和1410℃保温,炉内保持5×10~(-2)mn Hg真空。用光学高温计测量坩埚底部小孔的温度,并以Pt-PtRh热电偶浸入熔池进行校对,测温误差为±10℃。于恒温保持期间,每隔一定时间,通过炉顶上的取样活塞,在不破坏炉内真空的条件下从坩埚中取出分析试样8—10g,供定碳用。碳的分析误差为±10％。