Ratcheting Behavior of Weld Joints Under Uniaxial Cyclic Loading Using Miniature Specimen

Because of the size limitation of weld joints in different regions, the traditional standard bar specimen is not suitable to investigate the mechanical properties of weld joints. In this study, miniature specimens were extracted from specific regions(base metal, weld metal, and three heat-affected zones) of API X80 and X70 weld joints. Uniaxial tensile tests were conducted to obtain the mechanical properties of different regions, and then uniaxial ratcheting tests were conducted to investigate the ratcheting behaviors of the different regions under the same peak and nominal stresses. Under both the tensile tests and ratcheting tests, the weld joints exhibit heterogeneous results, such as different mechanical properties and ratcheting behaviors, which were region dependent. Furthermore, the yield strength and yield-to-tensile strength ratio contribute differently to the ratcheting response.     

水稻珠心细胞的超微结构及酸性磷酸酶活性的动态变化

水稻在大孢子发生期间,珠心细胞保留了较多的分生组织细胞的特征:其细胞形态规则,细胞质浓厚,富含核糖体。核糖体游离于细胞质中,或附着于内质网及核外膜上。酸性磷酸酶的反应产物主要位于小液泡中,偶见于高尔基潴泡及小泡中。随着胚囊的分化,在珠心的内层出现一系列复杂的变化:①在细胞的液泡化过程中,频繁并持续地发生液泡对细胞质组分的吞噬,导致大液泡的形成,其中有很多的酸性磷酸酶反应产物。大液泡的进一步扩大和继后的破裂,引起细胞的解体;②粗面内质网槽库彭大并对细胞质进行分隔与吞噬,在核周腔内出现膜束縛内含物;③质膜与细胞壁分离,二者之间有大量的小泡及酸性磷酸酶反应产物。最后珠心细胞的原生质强烈收缩,转化为无结构的电子致密的残迹。     

将农杆菌Ti质粒携带的外源基因转入水稻细胞

未经特殊处理的农杆菌C58C1Rif~r菌株,与籼稻悬浮培养细胞共培养时,很少见有细菌的附着,也观察不到纤维丝的形成。但经复合酚类化合物预处理的菌株,与籼稻培养细胞在普通培养液,特别是在复合诱导培养液(培养过的番茄下胚轴切段、胡萝卜细胞及农杆菌的培养滤液)中共培养时,均可发现有较多的细菌附着于水稻细胞表面,并且菌体周围有纤维丝的形成。在复合处理组中,位于pGV3850:1103neo嵌合质粒T-DNA上的NPTⅡ基因及NOS基因在籼稻培养细胞中获得了转移与表达。     

南海季风低压的活动及其降水分析

本文对1973～1986年在南海生成的季风低压的时空分布、路径及其降水特征等进行了统计分析和天气学研究。选择1986年6月下旬和1985年8月中旬两个季风低压过程,对其物理量作了计算,讨论了季风低压登陆后各物理量对降水造成的影响。     

Intersections of two offset parametric surfaces based on topology analysis

Conventional methods for solving intersections between two offset parametric surfaces often include iteratively using computationally expensive SSI (surface/surface intersections) algorithm. In addition, these methods ignore the relations between the intersection curves of parametric surfaces with different offset distances. The algorithm presented in this paper, makes full use of the topological relations between different intersection loops and calculates intersection loops with the help of previously calculated intersection loops. It first pre-processes two parametric surfaces to obtain the characteristic points, called topology transition points (TTPs), which can help in the subsequent finding of the topologies of the intersection curves. Then these points are categorized into several distinct groups, and we can determine the calculation strategy for searching initial points by analyzing the properties of these TTPs on the surfaces. Hence, all intersection curves can be marched from initial points by the tracing algorithm. The proposed algorithm could calculate intersection curves robustly and effectively, and has been tested to be capable of overcoming the degenerate conditions such as loop and singularities leaking that occur frequently in conventional algorithms. Project supported by the National Research Foundation for the Doctoral Program (No. 2000033554) of Higher Education of China and the Natural Science Foundation of Zhejiang Province, China (No. 6001107)     

论我国现代职业教育体系的构建

从宏观角度分析了我国职业教育体系的现状,指出目前我国职业教育体系存在的主要问题,探讨现代职业教育体系的主要特点及构建现代职业教育体系的理论依据,并提出建立我国现代职业教育体系的对策和建议.     

美国高校价值观教育主要路径

20世纪80年代后,伴随着美国社会道德状况的恶化和价值观危机的显现,价值观教育在美国高校中呈现出日渐复苏的迹象。在具体实施价值观教育的过程中,美国高校探索出了课程教学的路径、社会服务的路径、品格塑造的路径以及多元整合的路径。尽管很多美国高校在价值观教育的路径选择方面进行了有益探索,但是在价值观教育的核心理念和“顶层设计”方面仍然存在诸多问题。     

析张爱玲小说与五四新小说的关联

中国现代小说从诞生时已经沿着两条道路行走,即形成了所谓"雅"、"俗"两种类别的小说模式。二十世纪四十年代,两条道路合流交叉的倾向日趋明显,张爱玲的小说成为雅俗合流之中一道亮丽的风景。本文通过分析其小说集《传奇》对五四新小说的若干元素的吸取、融会,欲辨析其间对雅文学承继与融合的种种表征,借此总结其创作经验,为中国现代小说发展提供借鉴。     

用好养好黑土地的科技战略思考与实施路径——中国科学院“黑土粮仓”战略性先导科技专项的总体思路与实施方案

"黑土地保护与利用科技创新工程(黑土粮仓)"战略性先导科技专项(A类)是中国科学院实施"黑土粮仓"科技会战,深入贯彻落实习近平总书记关于"把黑土地用好养好"系列指示精神的核心抓手。该专项立足国家粮食安全战略目标,针对东北黑土地保护与利用面临的关键科学技术难题,根据问题导向、创新引领和示范带动的思路,以"目标清、可考核、用得上、有影响、推得开、留得下"为原则,开展黑土地保护与利用的核心技术攻关和区域适宜性模式示范,致力于形成用好养好黑土地的系统解决方案,服务国家粮食安全产业带建设和现代农业发展。     

现代渔业创新发展亟待链条设计与原创驱动

现代渔业是对传统渔业在国民经济发展中作用的重新定位,与农、林、牧业共同构成陆海统筹的国家粮食安全保障体系,发展现代渔业对实现新空间和新资源拓展,确保国家粮食安全的实施具有重大意义。文章从近海环境、渔业资源以及捕捞、养殖、加工等方面分析了我国渔业发展现状,阐述了通过贯穿产业链、问题链、创新链、任务链和价值链的全链条设计,实现现代渔业转型升级、创新兴业的发展理念;从重大科学问题、重大技术瓶颈和四大创新工程等方面,阐释了通过原创驱动实现现代渔业跨越发展的途径;提出了现代渔业的发展思路和发展建议,以期为我国现代渔业科技创新与产业发展提供参考。