Formal analysis on an extended security model for database systems

In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security model for database systems is pro- posed. According to this method, an analysis by using Coq proof assistant to ensure the correctness and security of the extended model is introduced. Our formal security model has been verified secure. This work demonstrates that our verification method is effective and sufficient.     

Temperature Distribution in a Long-Span Aircraft Hangar

Long-span aircraft hangars have features which differ from other large structural systems. The temperature stresses due to temperature variations often greatly impact the mechanical performance of the structure. The paper presents an analysis of the heat transfer processes and factors which influence the temperature distribution. The AMECO-A380 aircraft hangar at the Beijing Capital International Airport was selected as a practical example to illustrate the use of finite volume analysis to calculate the temperature field taking into account meteorological conditions, solar radiation, heat convection, etc. The temperature distribution and the variation of the length of the upper and lower chords of the grid structure roof were analyzed to develop guidelines for the temperature distributions in very large aircraft hangars. The results show that the temperature effect will be large for long-span hangars, and the temperature stresses due to nonuniform temperatures should be analyzed to guarantee the structural safety of large aircraft hangars.     

双护盾全断面掘进机卡机事故处理方案

通过介绍双护盾全断面掘进机的卡机过程,分析了掘进机卡机的原因,提出了卡机脱困的方案,介绍了卡机的初步判定方法。     

钢纤维增强钢丝网混凝土T形梁的抗弯试验研究

钢纤维增强钢丝网混凝土(FC)是一种新型的高强复合材料.为了解FC受弯构件的抗弯性能,文中进行了12根复合材料T形梁的抗弯试验,对构件的开裂及发展情况以及正截面抗弯承载力进行了对比分析.在此基础上,给出了T形梁正截面承载力的计算公式,并对影响FC受弯构件抗弯承载力的因素进行了分析.试验结果表明,钢纤维与钢丝网的复合能起到显著的增强效果,有效地提高钢筋混凝土受弯构件的抗裂性能和抗弯承载力.     

介孔材料-酸性红12染料分子体系动力学模型的建立和模拟

以酸性红12作为多苯环长链发色有机物的代表,通过对有效扩散系数的测定,确定其在介孔材料颗粒体上的吸附等温式和平衡接近率随时间变化的关系.利用非稳态扩散传质与非稳态热传导过程类比速率方程相似的特点,应用Peterson的热传导近似公式,用计算机求解超越方程,得到了酸性红12在介孔复合材料颗粒内的有效扩散系数并进行了拟合验证,得出该传质过程的主要作用力类型.     

基于图式理论的大学英语欣赏教学法

现代图式理论自发展以来广泛使用英语教学。欣赏教学法就是以图式理论为基础。以欣赏为辅助手段的教学方法,适用于我国大学英语教学。教师通过引导学生进行欣赏和创作,激活已有图式、建立新的图式。本文以一次课堂教学为例,表现了欣赏教学法的多种实现途径。     

现代主义与后现代主义辨析——以电影《广岛之恋》、《疯狂的石头》为例

对于现代主义、后现代主义的异同,仅从理论上分析和概括是不够的,而且这也容易使理论显得空泛而缺少根基。文章以电影《广岛之恋》、《疯狂的石头》为例,从故事主题、时空观、艺术表现手法三个方面辨析了现代主义与后现代主义具体而实在的联系和区别。     

Evaluation of a 3dVAR system for the South China Sea

The authors evaluate a three-dimensional variational （3dVAR） system for the South China Sea （SCS） in this study. The assimilation method applied in the system takes into consideration error correlation along each ground track and uses recursive filter for optimiza- tion. Data from three R/V cruises during the spring and summer of 1998 and the summer of 2000 are used to evaluate the system. The root-mean-square error and bias are reduced significantly and when the altimeter data are assimilated, the distribution of the error is much closer to the Gaussian distribution. Precipitation and river discharge in the southwestern SCS are reproduced, and the variability of sea surface height is efficiently transferred to the subsurface. The 3dVAR system performs well for each of the three cruises, suggesting that it is steady for routine usage.     

论两汉妇女孝行为发生机制

两汉时代,孝道成为家庭伦理的核心、社会道德规范,深刻影响了人们的行为.因此,两汉孝子辈出、孝行兴盛.作为孝的实践主体之一的妇女,分别以女儿、儿媳的身份尊敬、赡养长辈,在孝伦理实践中扮演着重要角色.两汉女孝,形式多样.就其行为的发生机制来看,既有内在的精神动因,又有外在的社会动力.