The Effect of Changes in Environmental Conditions on the Mechanical Behaviour of Selected Paint Systems

ABSTRACT

The impact of relative humidity (RH) and temperature variation on the mechanical behaviour of paintings on canvas was investigated, based on the various environmental recommendations that are applied by museums and institutions worldwide. Paint samples were constructed based on the works of twentieth-century artists such as Soulages and Riopelle. The various samples are based on criteria such as paint media, additives, pigment type, canvas type, thickness, type of application, and drying time. Once they are fully dry, paint films behave as elastic, viscoelastic, or viscoplastic materials depending on the chemical nature of their components. These properties, as well as tensile strength, were determined by a series of tensile tests. Other samples were included, originating from discarded oil paintings on canvas from the seventeenth and nineteenth centuries. To carry out mechanical tests under controlled conditions of temperature and RH, a climatic chamber was built around the column of a universal testing machine. Samples were submitted to stress relaxation tests to observe their response to changes in environmental conditions. RH was increased from 20 to 90% and temperature from 15 to 60°C. Reactivity diagrams were drawn based on the results. The endurance limit under mechanical fatigue was determined from the diagrams and helped define the risks associated with each painting type when exposed to the accepted environmental recommendations.     

反证法的逻辑原理及其在图论中的应用

本文系统地介绍了反证法的逻辑原理、种类、图论证明中运用反证法导致矛盾的类型，以及在图论证明中在什么情况下运用反证法较为适宜等问题，使读者对反证法及反证法在图论中的应用有一个全面的认识．     

我国小麦期货市场有效性的实证分析

主要探讨了小麦现货价格和期货价格是否存在短期均衡关系以及小麦期货市场是否有效的问题。通过定量性研究发现,我国小麦期货价格和现货价格之间不存在均衡关系;小麦期货市场不具有价格发现功能,即小麦期货市场处于无效状态。由此,针对性地对小麦期货市场的有效性提出了一些建议。     

大学生恋爱心理归因分析

目前，大学生谈恋爱的现象已经十分普遍，并且已经成为困扰大学生的主要心理问题之一，这对大学生的综合发展十分不利。在阐述大学生的恋爱心理，并根据人们常见的归因偏向对大学生的恋爱心理做出分析的基础上，有针对性地提出了教育对策。     

差热分析在物化实验中的应用

介绍两个以差热分析为实验手段的物化实验，并讨论它的优点。     

名称理论的现代发展

现代逻辑产生以来,在名称问题上的学术争议发生在描述理论和因果历史理论之间。塞尔被简单地归于前一流派,这是不适当的:从塞尔对名称理论所包含的两个问题的区分来看,他的成就值得特殊对待。通过探究描述理论和因果历史理论各自的成就与不足,可系统把握现代名称理论的发展脉络。     

处理Word文档中图表的技巧及实践

Word文档中要加入图表时 ,通常用Word的绘图工具和表格菜单命令来绘制这些图表。实际应用中存在如下问题 :(1 )画好的图表在排版时常常发生“错位”现象 ,需反复对图表进行调整 ,甚至需要重新绘制 ;(2 )图表插入的位置很难变动 ;(3)绘制的图形会产生庞大的字节数 ,占用很大有存储空间等等。文章介绍了一些处理技巧与实践 ,供参考     

基于CMM/CMMI的DP过程实施方法及其WEB实现

CMM/CMMI的关注点在于过程改进,即通过改进过程来改进产品。但CMM/CMMI只描述了一个成熟组织应具有的软件过程能力,却没有指出如何取得这种能力的具体方法。由于没有过程能力的具体实施方法及缺乏支持工具,一些通过CMM/CMMI的企业的过程能力并未达到预期效果。针对这一问题,对如何实现CMM/CMMI中原因分析与解决方案过程域的主要目标进行了深入分析,提出一种简洁、易实施并具有一定通用性的缺陷预防(Defect Prevention,DP)实施方法,并介绍了基于该方法的DP过程支持工具的WEB实现。     

玩忽职守罪构成论

玩忽职守罪的行为与结果之间是部分具有因果关系的,因而不能仅以行为与结果之间是否有因果关系来判断犯罪的成立,否则不能制止国家机关工作人员的渎职行为,保护公民的合法权益,维护社会秩序的稳定。     

Testing for invariance in a structural model of academic achievement across underachieving and non-underachieving students

This work aimed to test the invariance of a causal structural model of the determinants of academic achievement in underachieving and non-underachieving students. A theoretical model of the relationships between personal, social, and familial variables and academic performance was derived empirically using data from a large sample obtained in a previous study, prior to testing for invariance across the two student groups. Underachieving students were identified using the Rasch model procedure. The sample comprised 259 underachieving and 258 non-underachieving students. The latter were selected randomly from a large non-underachieving sample of Spanish secondary education students. For model comparisons between groups, multiple-group causal structural analyses were performed, following a sequence of nested models with increasing constraints. The results showed a good fit of the model in both groups, although about half of the parameters were not invariant across groups. Underachieving students were characterized by their lack of learning strategies, an academic self-concept that exerted less influence on achievement, and a positive effect of the parent-school relationship on academic performance/achievement. Non-underachieving students were characterized by their use of metacognitive strategies, which led to higher academic achievement, a greater effect of self-concept on their achievement, the perception of parental support leading to higher performance, and the positive effects of peer acceptance on academic achievement.