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分析了梅港站多年洪水流量水位关系,得出信江尾闾相同洪水流量下水位逐年抬高的结果,通过方案比较选择了信江尾闾整治实施方案。 相似文献
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本文就引黄工程系统实现办公自动化管理的必要性、办公自动化系统的建设目标以及办公自动化系统设计应遵循的原则、方案设计、设备选型、应用系统建设等方面,阐述了引黄工程办公自动化系统的方案构想。 相似文献
66.
More work is needed on devising practical, but theoretically well-founded procedures for doing object-oriented database (OODB) design [17]. Design procedures should also be flexible enough to take into account various application characteristics (such as whether objects are very large or are read-only). In this paper, we present and discuss an OODB design procedure that addresses these problems. The procedure is practical in the sense that it is based on a common family of conceptual models and in the sense that it does not expect users to supply esoteric, difficult-to-discover, and hard-to-understand constraints (such as multivalued dependencies), nor does it make hard-to-check and easy-to-overlook assumptions (such as the universal relation scheme assumption). At the same time, the procedure is well-founded and formal, being based on NNF (Nested Normal Form [21]), a new theoretical result that characterizes properties of interest in designing complex objects. It is also adaptable to various applications characteristics. 相似文献
67.
聚乙烯装置改扩建挤压造粒设备布置的优化 总被引:1,自引:0,他引:1
结合工艺流程和工程设计经验,阐述了PE改造过程中造粒系统的设备布置方案的要点及相关注意事项。 相似文献
68.
三峡工程导流底孔长管方案研究 总被引:1,自引:0,他引:1
三峡大坝河床溢流坝段内设有泄洪深孔、表孔和第三期导流底孔。后者系三期导流时用以泄水和实现围堰挡水发电的主要建筑物,孔口尺寸为6m×8.5m,进出口均为56.0m,型式有短管和长管两种。导流孔上游短管为管长16.09m,下游明流段98.78m;长等方案是上游管长77m,下游明渠长33m。短管方案由于坝体挖空大不利施工和坝体应力条件不良等而选用长管方案。长管方案在闸门布置、体型、水力学特征等四方面均能解决好。 相似文献
69.
J. R. Douglas 《河流研究与利用》1988,2(3):309-321
The River Severn is the longest of Britain's regulated rivers: this chapter describes the geography of the river's catchment area, from its source in central Wales to the Bristol Channel where it flows into the sea. It then considers the historical development of the Severn as a water resource, culminating in the construction of Llyn Clywedog and more recently the Shropshire Groundwater Scheme to augment low river flows and support greatly increased abstractions. Plans for even more substantial development of the resource system appropriate to the rapid demand growth of the 1960s and early 1970s are discussed. Practical experience in regulating flows in the river gained during the drought of 1976 is described and used to explain recent developments in the practice and monitoring of river regulation. 相似文献
70.
Polymorphic type-checking in scheme 总被引:1,自引:0,他引:1
This paper presents a type-inference system for Scheme that is designed to be used by students in an introductory programming course. The major goal of the work is to present a type system that is simple enough to be used by beginner students, yet is powerful enough to express the ideas of polymorphism, abstract data types (ADTs), and higher-order procedures. The system also performs some rudimentary syntax checking. The system uses subtyping, but only in a primitive fashion. It has a type datum which is a supertype of all types, and a type poof which is a subtype of all types. It uses intersection types to control the use of datum and to generate simple but accurate types. 相似文献