Effect of Water on the Physicomechanical Properties of Composites Containing Secondary Polyethylene and Linen Yarn Production Waste

The effect of the amount of absorbed water on the physicomechanical indices (tensile modulus, tensile strength, and ultimate strain) of composites based on secondary polyethylene (SPE) of two trademarks and linen yarn production waste (LW), both with and without a coupling agent (diphenylmetane diisocyanate - DIC), is evaluated. It is shown that the strength properties considerably depend on the time of water sorption and on the blend composition. The tensile strength decreases with increased amount of absorbed water (with increased time of exposure to distilled water) and with increased content of LW in the composites. This can be explained by the plasticizing effect of water molecules, which is confirmed by the increase in the ultimate strain of specimens after their exposure to water. The slight increase in the strength observed for the systems modified with DIC is probably caused by cross-linking of the free diisocyanate in the system under the action of moisture. The diisocyanate intensifies the interfacial interaction and retards the water-sorption process. Therefore, the resulting strength indices of these systems are higher than those of the unmodified compositions.     

A local breakdown property of robust tests in linear regression

The breakdown slope, as a useful summary measure of local stability for estimators and test statistics, has been studied recently by He, Simpson, and Protnoy (1990, J. Amer. Statist. Assoc., 85). It is shown here that all regression estimates based on residuals alone in linear models have zero breakdown slopes in contamination neighborhoods, even though they can have breakdown points as high as one-half. The breakdown functions of tests based on the S-estimation are investigated. It is also shown that the Generalized M-estimators can have better local breakdown robustness. One way to obtain regression estimators with desirable local and global breakdown properties is discussed.     

环境激素对人体健康的影响

环境激素是环境中存在的能干扰生物系统或过程产生异常效应的物质;它能干扰生物体内激素,损害人类的生殖机能或引发肿瘤等,对人类的生存与健康构成严重威胁;防治环境激素的根本对策是杜绝其产生的源头.     

Synthesis and Crystal Structure of [(NH_4)_6][Gd_2Mo_(36)O_(112)(H_2O)_(20)]·52H_2O

1 INTRODUCTION There is considerable interest in the heteropolymetalates in view of their potential applications in many fields, such as, catalysis, biology, medicine, magnetochemistry, and materials science[1～5]. It has been well- known that the rare earth elements are highly oxophilic and the anion of polyoxomolybdates have oxygen-rich composition, which can be used as synthons for the construction of novel heteropolymetalates. Since the structure of polyoxoanion 36-molybdate Mo36O1128…     

起落架结构参数对飞机机轮摆振的影响

建立了飞机机轮摆振运动方程,详细研究了起落架三个重要结构参数;稳定距、支柱刚度和减摆器传动系统扭转刚度对飞机机轮摆振的影响,考虑了各参数之间的耦合作用,严格区分“轮胎型”摆振和“结构型”摆振,并分别予以研究,所得结论为新机防摆设计和现役飞机防摆维护提供了理论依据。     

半参数非线性模型的统计诊断与影响分析

本文系统研究了半参数非线性回归模型的统计诊断与影响分析方法;得到了一系列诊断统计量,两个实际数值例子验证了本文给出的诊断方法的有效性。     

痕量锗的HG-ICP测定及介质对其测定的影响的研究

采用氢化物发生-电感耦合等离子体原子发射光谱法测定痕量锗的方法,系统地考察了不同酸介质、NaBH₄浓度及共存元素的影响,确定了最佳测定条件。方法的检出限为0.2 ng·mL-1,精密度为0.9%。用环境标准物质进行对照,其测定值均在给定的标准范围之内。并且针对反应介质对锗测定的影响,进行了详尽的研究。     

光谱法研究1-萘酚、2-萘酚与瓜环的包结作用

用荧光光谱、紫外吸收光谱法研究了瓜环与1-萘酚、2-萘酚的相互作用,考察了pH对体系的影响。结果表明,1-萘酚、2-萘酚与六元、七元瓜环都不发生作用,而与八元瓜环发生相互作用,形成物质的量比为1∶1的稳定包结配合物。用荧光法测定1-萘酚、2-萘酚与八元瓜环包结配合物的稳定常数为4.2×104 L·mol-1和1.6×104 L·mol-1,紫外光谱法测定的稳定常数为4.2×104 L·mol-1和5.4×104 L·mol-1;在酸性和中性条件下1-萘酚、2-萘酚与八元瓜环发生包结作用,形成稳定包结物,而在强碱性条件下不发生包结作用。     

Evaluation of the thermophysical and heating properties of a composite rubber membrane with energy harvesting purposes

This paper evaluates the thermal behaviour of recycled rubber membranes from End of Life Tyres (ELTs) reinforced with steel wool fibres, and their potential use as solar collectors. The thermophysical and heating properties of the rubber membranes with different steel wool fibre contents were evaluated. The thermal performance of a solar collector prototype manufactured with these membranes was also evaluated. It was proven that the addition of metallic fibres can increase the amount of heat absorbed and the heating rate in the membranes. However, fibre addition over 0.5%/v does not contribute to an increase in the temperature reached. A solar collector prototype fabricated with rubber membranes with 0.5%/v of fibres can transmit the heat absorbed by the membrane to the water, reaching a temperature of 45 °C, thus demonstrating that it can be used as new sustainable construction material for energy harvesting applications.     

2-Dimensional and computational analysis of the 1H NMR spectrum of the bis(2,2′-bipyridine)carbonatocobalt(III) ion†

The use of COSzY and NOESY ¹H NMR techniques allows for the assignment of ¹H NMR chemical shifts for the bis(2,2′-bipyridine)carbonatocobalt(III) ion. These assignments are further confirmed by DFT GIAO-NMR calculations using the model chemistry B3LYP/6-31G(d,p) and invoking the IEF-PCM representing acetone. These computations also allow for initial quantification of a cis influence on the chemical shift due to anisotropic ring currents and a much less pronounced trans influence on the chemical shift due to inductive effects. The computational model employed is also compared to previously accepted models for anisotropic effects.