Environmentally-induced stone decay: the cumulative effects of crystallization–hydration cycles on a Lincolnshire oopelsparite limestone     

Belinda J. Colston  David S. Watt  Helen L. Munro   《Journal of Cultural Heritage》2001,2(4)

An investigation has been undertaken at St Andrew’s church, Walpole St Andrew, Norfolk, to establish the underlying causes of the observed stone decay to the upper parts of the six stone piers. The stone decay was first recorded in the early 1930s. The salt-contaminated masonry within the church has been shown to undergo severe salt decay during the summer, with little damage occurring over the winter months. The south aisle piers have been shown to decay 2.5 times faster than the north aisle piers. Although crystallization–hydration cycles have been identified, the rate of decay is at its greatest when the cycling is relatively infrequent. This was not the expected trend. Furthermore, it has been shown that during extended periods where the ambient relative humidity is less than 75%, the rate of decay reaches a maximum. It is the length of this ‘drying’ period that apparently has the greatest influence on the rate of decay and could explain the significant difference in the rate of decay between the south and north aisle piers. The results have serious implications for passive conservation, where it is often recommended to lower the ambient relative humidity to well below the equilibrium relative humidity of the salt contaminant, to avoid crystallization–hydration cycles. Since, at the time of building, the church was situated on the coast, it is possible that the sodium chloride contamination occurred during the building process (1440–1520), particularly since the area was prone to sea-flooding at this time. Alternatively, the salt could have been applied as a treatment during the general restoration of 1897. Whatever the source of the salt, it seems likely that the ambient environment was changed by the insertion of a sealed floor in 1897, which could account for the onset of the salt decay.  相似文献   

关于解决我国股市股权分置问题之拙见     

姚德奎 《渭南师范学院学报》2005,20(4):23-25

我国股市现存的制度性缺陷属于历史遗留问题,其中最大的缺陷———股权分置如今已经成为股市长期稳定发展的最大障碍。全流通不是解决股权分置的一个好办法。解决股权分置暨解救处于危局中的股市,可以通过尝试把国有股转换为优先股,依靠国家政策的力量拯救股市。  相似文献   

以整体性环境叙事构建中国绿色国际传播体系——以《中国日报》“北向追象”报道为例     

吴沁宇  韦清琦 《传媒观察》2022,(1)

《中国日报》于2021年夏开始的对云南亚洲象北行的专题英文报道,利用多平台综合信息展示了中国环保实践,在全球广受好评。本次报道与习近平总书记构建中国话语和中国叙事体系的理念十分相符,其中生态理念的本土特质得到凸显,官民一体的形象得到了积极塑造,而中国科技能力的展现也融入了一个好故事的解说之中。中国当代的环境叙事必须反映人与自然的生命共同体与人类命运共同体的完整结合;"北向追象"所构造的具有中国特色的环境叙事之所以取得了很好的外宣效果,跟其紧扣这一完整性的表达密不可分,对于今后的国际传播工作也提供了颇多启示。  相似文献   

电子政府府际信息共享环境的构成与作用机制研究     

韩刚 《情报学报》2008,27(5)

信息生态理论认为,组织的信息行为可以从其环境特征中找到依据。本文以信息生态范式为方法论指导,首先从层次、内容、稳定性三个维度揭示了电子政府府际信息共享环境的构成以及构成要素之间的相互关系;其次,指出不同类型环境构成要素的作用机制是不同的,提出了锁定机制、权威机制、触发机制、博弈机制和选择机制五种不同环境作用机制,并分别对其作用机理以及相互关系进行了分析。环境构成和作用机制的研究结论初步回答了这样两个重要的问题:什么因素影响着电子政府府际信息共享行为?是如何影响的?本文的结论可以为电子政府府际信息共享管理提供理论支持。  相似文献   

基于属性值偏好矩阵的协同过滤推荐算法   总被引：7，自引：2，他引：5  

李聪  梁昌勇 《情报学报》2008,27(6)

传统的协同过滤推荐算法面临用户评分数据稀疏性和冷启动问题的挑战.针对上述问题,提出了基于属性值偏好矩阵的协同过滤推荐算法,首先采用奇异值分解(SVD)对用户-项目评分矩阵降维得到目标用户的初始邻居用户集,生成新的用户-项目评分矩阵;然后将用户评分映射到相应的项目属性值上,生成每个用户的属性值偏好矩阵,并基于属性值偏好矩阵进行用户相似性度量,从而缓解了评分数据稀疏性;将新项目的属性值与用户的属性值偏好矩阵进行匹配,从而找出匹配度最高的前N个用户作为新项目的推荐受众.实验结果表明了该算法的有效性.  相似文献   

基于信息使用环境理论的引用行为研究:参考文献分析的视角     

谢娟  成颖  孙建军  柯青 《中国图书馆学报》2018,44(5):59-75

目前,学术界多开展引用动机和引文功能的相关研究,但对于引用偏好等引用行为却关注较少。基于Taylor的信息使用环境理论,本研究采用参考文献分析方法,全面揭示了施引者引用行为的特征和影响因素。研究将信息使用环境理论中的前三类要素分别通过学者特征、组织环境及论题进行定义,采用参考文献分析法提取第四类要素;随机抽取论文样本,针对上述四类特征进行编码并通过统计分析探讨影响施引者引用行为的因素。研究发现:学者的年龄、性别、教育水平、学术年龄、职业角色、职称、所属机构的类型和层次以及所从事的研究主题和类型,都能对质量、语种、数量、信息资源类型、论文新旧的引用偏好产生显著影响。研究表明:信息使用环境理论和参考文献分析法在引用行为研究中具有适用性。表4。参考文献47。  相似文献   

The Stability Evaluation and Prospects about Environment Engineering Geological in Coastal Zone     

MA Xue-ying 《环球赛鸽科技》2014,(24)

  相似文献   

Green inclusion: biophilia as a necessity     

Alexandros Stavrianos 《British Journal of Special Education》2016,43(4):416-429

This article argues that there is a strong link between the pedagogy for inclusion and the pedagogy of environmental education and tries to identify any benefits that could be acquired by pupils when the school system tries to use environmental educational programmes to promote inclusion. The idea of promoting a school yard into a school garden is given as an example. The article suggests that outdoor education experiences can facilitate positive development of self‐esteem, peer to peer socialisation as well as teacher–student relationships and a positive attitude towards school. One might conclude that the rationale behind environmental education has much to offer to all of our pupils.  相似文献   

不具传递性偏好的效用函数表示     

计伟 《贵阳金筑大学学报》2012,(1):9-11

主要是对参与人的被选方案集作些规定以及不具传递性的偏好作一些限制,得到了一些效用函数表示结果,统一和推广了许多已知结果。  相似文献   

论在中学化学教学中如何渗透绿色、环保教育          下载免费PDF全文

庄萍  毛云  强娜 《惠州学院学报》2006,26(6):123-128

从梳理中学化学教材中绿色、环保教育的知识点入手, 在课堂教学过程、研究性学习、实验课及课外活动等四个方面阐述了中学化学教育渗透绿色、环保教育的具体做法。  相似文献