关于树的Large Laplace谱扰动

讨论树在添加一条边后其Laplace谱发生的扰动，刻画了满足如下条件的匹配数为2或3的树：添加一条边后所有变化的特征值以整数增加．对于每个μ≥2(或n≥5)，构造了一个匹配数为μ(或顶点数为n)的树，以满足上述性质．     

Advances in Tube Hydroforming - An Enabling Technology for Low-Mass Vehicle Manufacturing-Material, Lubrication, Loading, Simulation Issues, and Alternatives

The tube hydroforming process (THF) has recently found a wide application opportunity in the automotive industry, and is of increasing interest to other industries as well. The increased interest stems from the fact that, through the THF process, manufacturers are able to produce complex, consolidated,lightweight parts with reduced number of post-processing than through alternative metal forming techniques.In order to fully realize the benefits of this technology, various aspects have been under investigation in academia and industry world-wide. In this paper, effect of loading path, incoming material variation, and lubrication on the robustness of the hydroforming process and final part specifications are summarized based on previous experimental and computational work. In addition, the simulation of hydroforming and examples are presented in comparison with experimental findings. Briefly, results emphasized the importance of the loading path design whereas material variation within the experimentally tested range was not found to be significantly effective on the final part specifications. Selection of a lubricant for hydroforming of a frame rail part was presented demonstrating several aspects of lubrication selection methodology. Results of friction experiments show that only thickness, axial feeding, and force measurements are good indications of lubricant performance as these are found to be strongly discriminative.     

奇异型随机控制中的一个变分方程问题

讨论了一类带停时的奇异型随机控制问题中的一个变分方程问题,并且在两种不同的情况下给出了该变分方程的解,即为一阶连续可导凹函数,并在两种情况下给出了此函数的具体形式.     

高强混凝土立方体强度变异系数的商榷

对《混凝土结构设计规范》GB50010—2002所给变异系数的合理性进行了研究,发现规范所给变异系数偏大且过于粗略;在《混凝土结构设计规范》GBJ10—89的背景材料和清华大学叶列平等人的建议的基础上计算出了C50～C80级高强混凝土的标准差和变异系数,对结果存在的局部不合理进行了调整,并把调整后的结果和规范GB50010—2002所给变异系数以及几个工程实例的统计参数进行了比较,发现调整后的结果与工程实际统计数据比较接近,用于高强混凝土结构可靠度分析、高强混凝土某些强度指标的确定以及施工过程中高强混凝土配合比强度的确定时,比规范GB50010—2002所给变异系数要更适合.     

城市区域水土作用与土细观结构变异的试验研究

城市区域的水土作用因城市建设引发地下水“变异”而加剧．水土作用使土结构发生变化从而影响到土强度变化．文中将土的结构划分为微观、细观与宏观结构三层次．并定义了细观结构的物理涵义．通过细观结构变异试验以及SEM、X射线衍射、CT、STM等四种测试方法运用,表明在城市常温、常压、缓慢的地下水变异环境下,细观结构是水土相互作用发生、发展的“平台”及主要场所．研究所用方法与结果可用于预测因地下水环境变异引起的土体结构变异或引起土体污染后土体性质变化的趋势,进而为建筑环境的岩土环境稳定性做出评价和预测．     

向量值函数的有界变差

向量值函数的有界变差与弱有界变差是等价的，强有界变差一定是有界变差的，反之不然．文中还指出强、弱有界变差的条件，及特殊情形下强、弱有界变差可以等价．     

An integrative estimation model of summer rainfall-band patterns in China

Three variation indices are defined to objectively and quantitatively represent fluctuations of three rainfall-band patterns in summers in China for the period from 1951 to 2005, and the variation features of these indices are analyzed on both of interdecadal and interannual scales. A new method is proposed to establish an integrative estimation model based on the analysis of rainfall-band indices, and the model is applied to air, ocean factors to estimate their roles on variations of three rainfall-band patterns on different time-scales. The tests of estimation effects show that the fluctuations of three rainfall-band patterns are composed of variations on both significant inter-decadal and interannual scales, of which the interannual variation is mainly influenced by the Elnino/Lanina events, the East Asia monsoon and the ridge locations of subtropical high pressures in western pacific, while the interdecadal variation is mainly controlled by the Pacific decadal oscillation and interdecadal oscillations of the Arctic oscillation, ENSO, Nino3 sea surface temperature and summer monsoon. The estimated results from the integrative estimation model of rainfall-band patterns suggest that the way of estimation first according to each time scale of both the interdecadal and interannual scales, then estimating with an integration, which is proposed in this paper, has an obvious improvement on that without separation of time scales.     

CLM4.5对中国区域夏季土壤湿度的模拟研究

利用CESM(Community Earth System Model)框架最新发布的陆面模式CLM4.5模拟得到中国区域1991~2010年7月份0~10 cm的土壤湿度数据集;并以中国农作物生长发育和农田土壤湿度旬值数据集的土壤湿度作为实测值,与模拟结果进行了比较分析。结果表明CLM4.5能够揭示中国区域7月份0~10 cm土壤湿度的空间分布特征,与实测数据土壤湿度的年际变化趋势保持着较好的一致性。利用曼-肯德尔法进行突变现象检测表明,模拟和实测得到的二十年的土壤湿度在华北、东北地区有逐年减小的趋势,尤其是东北地区土壤变干现象尤为明显;而华东、华中地区的土壤湿度以2~3年为周期增减,并没有一个持续稳定的变化趋势。CLM4.5模拟的土壤湿度值普遍偏高,最大偏差超过0.1 mm3·mm-3,这可能与模式的参数化方案有关,在以今后的研究中有待进一步探索。     

土壤重金属与土壤理化性质的空间变异及研究

对研究区的部分土壤理化性质及土壤重金属的空间变异特性进行了分析,均表现出一定的空间变异性,并通过克里格插值得到它们的空间分布格局,表现出了一定的相似性,说明土壤理化性质与土壤重金属在空间分布上存在一定的相关性;通过对它们之间的空间相关性分析,表明克里格插值结果与实际计算结果是一致的,结果表明,土壤有机质、pH及各粒级含量土壤与Cu,Hg,As含量的相关性显著,与Zn,Pb和Cr为中等相关,且均为正相关,而与Cd的相关性不显著.在实际生产中,可以通过土壤部分理化性质来估计土壤重金属的分布特征.     

地磁太阴日变化L的M2潮变化特征

用M2潮引起的地磁太阳日变化L的谐波分析方法,计算了佘山地磁台的磁偏角、水平和垂直分量L的谐波系数。分离出海洋和电离层发电机对L的贡献,讨论了太阳活动对地磁太阳日变化的影响,并把结果与国外部分台站的结果进行了对比分析。