用快速特性粘度法研究聚碳酸酯的热降解机理

通过快速特性粘度法研究聚碳酸酯(PC)在恒温条件下降解不同时间的粘均分子量，进而研究其降解机理和动力学方程．认为PC的整个降解过程可分为吸收氧气、酯交换和自由基反应3个阶段．对第1阶段——吸氧阶段和第2阶段——酯交换阶段的降解机理和动力学方程进行了详细的研究．     

Academic motivation in university: The role of basic psychological needs and identity formation.

This study was an investigation of the relationship between psychological need fulfillment, psychosocial development, and academic motivation in university students. Two models were tested. The 1st model, derived from developmental theories, proposed that basic psychological needs of autonomy, competence, and relatedness would predict identity and intimacy achievement, which would, in turn, predict academic intrinsic motivation. A 2nd model, based on self-determination theory, proposed that identity and intimacy would predict academic motivation and that this relationship would be mediated by basic psychological needs. Results from path analyses supported the model derived from self-determination theory over the model derived from developmental theories. Competence and identity were found to be the 2 constructs most strongly associated with academic motivation. These findings support the view that identity formation plays a critical role in facilitating academic motivation in university. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

不同因素对钼及钼合金塑脆性能影响的研究

钼及其合金具有很好的高温强度和抗腐蚀性等优异性能,广泛应用于众多高科技领域.综述了C、N、O杂质元素、掺杂元素和稀土氧化物、常规的K、Si、Al、Ca、Mg、Fe等元素以及织构等因素对钼及钼合金塑脆性能的影响,总结了提高钼合金塑性的基本方法和规律.同时指出钼及钼合金今后研究的重点是提高合金的横向塑性,以使其得到更广泛的应用.     

Correlation between the intergranular brittleness and precipitation reactions during isothermal aging of an Fe–Ni–Mn maraging steel

Evolution of the intergranular brittleness of an Fe–10Ni–7Mn (weight pct) maraging steel was correlated with precipitation reactions during isothermal aging at 753 K. Intergranular brittleness of the Fe–Ni–Mn steel raises after aging treatment which occurs catastrophically at zero tensile elongation in the underaged and peakaged steels. The intergranular failure is attributed to grain boundary weakening due to the formation of coarse grain boundary precipitates associated with solute-depleted precipitate-free zones during isothermal aging. Further, evidences of planar slip bands were found within the grains of a peakaged specimen loaded by tensile deformation. Those inhomogeneously deformed bands were identified to apply large strain localization in the soft precipitate-free zones at grain boundaries which is assumed to fascinate microcracks initiation at negligible macroscopic strains in the underaged and peakaged steels. During further aging, concurrent reactions including (i) overaging of matrix precipitates, (ii) spheroidization of grain boundary precipitates, (iii) growth of precipitate-free zone in width and (iv) diffusional transformation to austenite take place which increase tensile ductility after prolonged aging.     

Charismatic leadership and tacit knowledge sharing in the context of enterprise systems learning: the mediating effect of psychological safety climate and intrinsic motivation

Drawing upon charismatic leadership and intrinsic motivation theory, we developed a theoretical model to examine the impact mechanism of leader charisma on individuals’ tacit knowledge-sharing behaviour in the context of an Enterprise Systems learning team. We conducted a survey-based field study to examine the theoretical model and hypotheses. A total of 153 questionnaires were distributed to employees from more than 20 branches of the Beidahuang Group in China and 117 valid questionnaires were returned. Results from partial least squares analysis suggest that leader charisma has a strong influence on psychological safety climate, which in turn has a positive impact on individuals’ intrinsic motivation and their tacit knowledge-sharing behaviour. Our research findings unpack the impact mechanism of charismatic leadership on tacit knowledge sharing, and provide guidelines for the team leader to exhibit charismatic leadership traits in order to promote a psychological safety climate and facilitate an effective knowledge sharing of enterprise systems.     

The preparation and evaluation of salt forms of linogliride with reduced solubilities as candidates for extended release

Salts of linogliride with reduced solubilities were prepared and evaluated as potential candidates for extended-release oral dosage forms. A once-daily dose of 300–800?mg was intended. Seven acids were selected: p-acetamidobenzoic, benzoic, p-hydroxybenzoic, 3-hydroxy-2-naphthoic, 1-napsylic, pamoic, and p-toluenesulfonic acids but only four salts were able to be prepared in suitable quantities for evaluation: linogliride pamoate, p-hydroxybenzoate, 3-hydroxy-2-naphthoate, and 1-napsylate. The pH-solubility profiles of the four new salts, free base, and fumarate salt were compared over the pH 1.43–8.3 range and the intrinsic dissolution rates of the four new salts and the free base were determined at pH 1.43, 4.4, and 7.5. The range of the pH-solubility profile and intrinsic dissolution rates of the p-hydroxybenzoate salt were less than the free base and fumarate and higher than the other three new salts. The pH-solubilities and intrinsic dissolution rates of the 1-napsylate salt were pH-independent. The solubilities and intrinsic dissolution rates of the pamoate and 3-hydroxy-2-naphthoate were higher at pH 1.4–3.4 than at higher pH. At pH 4.4 and higher, the solubilities were essentially the same, in the 1–2?mg/mL range. The intrinsic dissolution rates were also very low and not very different. Dissolution studies with capsules containing 800?mg doses of the pamoate, 1-napsylate, free base, and fumarate performed in a dissolution medium of pH beginning at 2.2 and ending at 6.8 demonstrated that the pamoate and 1-napsylate salt forms dissolved slower and could be useful as extended-release forms.     

导静电防腐涂料的研究进展

导静电防腐涂料是随着科技的进步而迅速发展起来的一种功能性涂料,要求涂料兼具导静电和防腐蚀性能,广泛应用于电子电器、航空航天、石油化工等众多领域。然而,目前我国的导静电防腐涂料还存在无法兼顾导电性和防腐性,以及成本高等问题,综合性能尚不理想,因此研究并提升其综合性能成为该类涂料发展的技术关键。本文论述了本征型与添加型导静电防腐涂料的发展现状,以及各个类型的优缺点,展望了导静电防腐涂料的未来发展前景。     

AFM imaging and nanoindentation of polymer of intrinsic microporosity PIM-1

Polymers of intrinsic microporosity (PIMs) have promising gas adsorption properties for potential applications such as incorporation into high-pressure hydrogen storage tanks in an effort to increase the storage capacity or decrease the operating pressure. Such applications require detailed mechanical characterisation and determination of the structure-properties relationships to enable optimisation of the interface between the polymer and the tank. In this study, we show that Atomic Force Microscopy (AFM) nanoindentation can be used to determine the elastic modulus of cast PIM-1 films and that this property is depth-dependent. Average values of elastic modulus obtained experimentally were 1.87 GPa and are compared with elastic tensile modulus and storage tensile modulus obtained in previous studies. In addition, Scanning Electron Microscopy (SEM) and AFM imaging was performed to investigate the surface structure of the cast PIM-1 film, which has been shown to be highly granular.     

The effects of social messaging on students' learning and intrinsic motivation in peer assessment

This study aims to gain a better understanding of how the newly arisen social messaging may impact the practice of peer assessment. Seventy-nine ESL (English as second language) students reviewed each other's English essays in three peer assessment groups: a three-member group using wiki (wiki group), a three-member group using social messaging (small messaging group), and a six-member group using social messaging (big messaging group). Data analysis suggested that peer assessment facilitated by social messaging can be at least of the same effectiveness as wiki-facilitated peer assessment on ESL students' writing skills and intrinsic motivation. In addition, the findings indicated that students in the small messaging group outperformed students in the big messaging group on essay writing and reported a significantly higher rating on perceived competence, a positive indicator of the behavioural measures of intrinsic motivation, than students in the big messaging group.     

基于Evans截割模型的镐型截齿峰值截割力的计算

为了能对镐型截齿在平面截割截槽对称条件下的峰值截割力进行较为准确的预测,基于Evans的截割模型,通过分析截割时齿头的锥形表面因岩石的夹制效应而接触应力分布有所不同,理论推导出了一个新的峰值截割力计算公式以及公式应满足的截割边界条件。相比现有其他截割力计算公式,除了考虑截齿半锥角θ、煤岩抗拉强度σt及齿岩之间摩擦因数f等参数的影响,且将煤岩的脆性指数m引入其中,计算结果与试验值更为接近。公式所应满足的截割边界条件,可用截深h和加载位置与相邻自由边界垂直距离s比值的最低限值smin/h表示,且值大小受截齿半锥角θ影响较小,而主要与煤岩脆性指数m有关,当m介于5~15时,smin/h介于2~3,符合既有试验所得结果。所得公式和结论可为进一步分析和推导镐型截齿在实际采掘条件下包含更多参数的峰值截割力提供理论基础和指导。