我国农产品物流存在的问题与发展对策

伴随农业经济的快速发展,我国农产品物流规模急剧扩大。在快速增长的过程中,我国农产品物流存在着体制不完善、决策不科学、技术水平低和地域差异大等问题,需要通过制定发展规划、提高技术水平、树立现代物流观念等措施来促进我国农产品物流的发展。     

CS3000 DCS系统升级改造案例与分析

集散控制系统(DCS)被广泛应用于石油化工生产.随着现代工业控制技术的不断更新换代,为保证控制系统运行的稳定性和可靠性,系统的升级改造是必然的趋势.以CENTUM CS3000 DCS系统为例,对控制系统升级改造的原因和必要性进行了分析,对控制系统升级方案和具体的实施方法进行了详细的描述.工业控制系统通过升级改造后,系统的硬件和软件的兼容性、可靠性将大为提高.     

“十一五”中国节能工作和铜的消费应用

节约资源,提高能源利用效率是中国经济发展的基本国策。在这个发展理念下制定的“十一五”规划将对铜行业有利有弊,但总体前景应是乐观的。随着电力、建筑、家电、汽车等行业的发展,中国铜消费量在2011年预计达到609.6万t,中国铜工业面临新的机遇与风险并存的发展时期。     

Calibration of the Weibull stress scale parameter, σu, using the Master Curve

This work proposes that the Weibull stress scale parameter, σ_u, increases with temperature to reflect the increasing microscale toughness of ferritic steels caused by local events that include plastic shielding of microcracks, microcrack blunting, and microcrack arrest. The Weibull modulus, m, then characterizes the temperature invariant, random distribution of microcrack sizes in the material. Direct calibration of σ_u values at temperatures over the DBT region requires extensive sets of fracture toughness values. A more practical approach developed here utilizes the so-called Master Curve standardized in ASTM Test Method E1921-02 to provide the needed temperature vs. toughness dependence for a material using a minimum number of fracture tests conducted at one temperature. The calibration procedure then selects σ_u values that force the Weibull stress model to predict the Master Curve temperature dependence of K_Jc values for the material. At temperatures in mid-to-upper transition, the process becomes more complex as fracture test specimens undergo gradual constraint loss and the idealized conditions of high-constraint, small-scale yielding assumed in E1921-02 gradually degenerate. The paper develops the σ_u calibration process to incorporate these effects in addition to consideration of threshold toughness effects and the testing of fracture specimens with varying crack-front lengths. Initial illustrations of the calibration process for simpler conditions, i.e. 1T crack-front lengths, use the temperature dependent flow properties and a range of toughness levels for an A533B pressure vessel steel. Then using the extensive fracture toughness data sets for an A508 pressure vessel steel generated recently by Faleskog et al. [Engng. Fract. Mech., in press], the paper concludes with calibrations of both m and σ_u over the DBT region and assessments of the Master Curve calibration approach developed here.     

Oracle 9i高级复制技术及其应用

Oracle9i针对分布式计算的需要，提供了一套功能强大的数据复制解决方案。概述了Oracle数据复制的分类、Oracle高级复制的发展及应用。介绍了Oracle9i高级复制技术中常用的基本概念、特点以及创建高级复制环境的过程，最后用一个实例说明了实体化视图复制并给出了部分脚本。Oracle9i高级复制技术支持多种应用，提高了应用系统的性能，并能更好地实现分布式计算。     

浅谈我国电网调度自动化“九五”期间的技术政策

“九五”是本世纪的最后5年，是我国电网调度自动化发展的关键时期。我国电网调度自动 化系统与国际先进水平的主要差距是综合应用水平低，其关键在于自动化基础设施质量较差 ， 电力系统基础数据不完整、不准确。加强基础建设，提高应用水平，为电网商业化运营服务 ，是“九五”期间我国电网调度自动化的中心工作。文中结合“八五”期间我国电网调度自 动化的工作实践和“九五”的发展要求，从11个方面谈了对《全国电网调度自动化 “九五”规划纲要》技术政策的认识     

江苏电力会议电视系统"十一五"期间的规划思考

随着会议电视重要性的不断提高,如何加强系统的稳定性和可靠性,提高系统的技术性能和音视频质量,以及提升系统的应用水平和范围是会议电视系统发展面临的主要问题。文章根据江苏电力会议电视系统网络的现状以及存在的问题,就“十一五”期间系统的改进和演变过程进行了阐述,并对高清晰会议电视系统的技术体制进行了简要分析。     

基于SNMP的一种Subagent模型的设计与实现

提出了基于SNMP协议的被管对象的一种比较通用的Subagent模型，该Subagent帮助网络管理站收集被管对象的可管信息，并在必要时发送告警信息给网络管理站。     

On Improvement of Methods for Experimental Determination of Strength Characteristics of NPP Component Materials

The methods for experimental determination of strength characteristics as per applicable standards have been reviewed. For some structural steels used in NPP facilities, the influence of loading parameters and specimen geometry are allowed for during the assessment of static fracture toughness (K_Ic, J_Ic). Recommendations are given on the setting of cycling conditions for fracture toughness testing of standard specimens with and without crack-guiding lateral grooves. The authors substantiate the applicability of the Master Curve method to determination of fatigue strength of small specimens with subsequent use of the results for calculating brittle fracture resistance of reactor pressure vessel materials in the welded joint.     

地理信息系统在城市环境规划中的应用

地理信息系统技术应用于环境规划工作具有多方面的优越性,能够进行规划信息管理、规划方案比较、评价与决策支持、规划图件制作等工作,基于地理信息系统建立城市环境规划信息系统是加强环境管理有力的技术支持.