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281.
石油安全指标体系与综合评价 总被引:11,自引:3,他引:8
为科学评价我国石油安全的程度,从国内资源禀赋、国内生产能力、国际市场可得性和国家应急保障能力等4个方面,设计了石油安全评价指标体系。采用德尔菲法、主成分分析法,选取储采比、储量替代率、石油消费对外依存度、石油进口集中度、国际原油价格和国内石油储备水平等6个个指标,构成一个新的综合指标:石油安全度,用其对我国石油安全形势进行定量评价。将石油安全度的安全警戒划分为五级:I级1~0.8,基本安全;II级0.8~0.6,弱安全;III级0.6~0.4,不安全;Ⅳ级0.4~0.2,很不安全;V级0.2以下,严重不安全。1993-2004年,我国石油安全度为0.54~0.75,处于弱安全到不安全之间。 相似文献
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本文根据在安宁河流域实施高产高效种植模式的实践,就高产高效栽培的功能目标和技术调控等问题进行了探讨。作物高产高效种植集生物、环境、经济、技术于一体,其中,技术居主导地位,对整个组合进行调控,使之按高产稳产优质低耗高效的目标发展。社会的需求量、农民的积极性、生态良性性、环境吻合性和能量高效转化性是评价高产高效种植模式功能目标的原则。系统的调控机制有三个层次,即自然调控、直接调控、间接调控。农业科技通过生态环境调控、输入输出调控、物种结构调控、综合关系调控等途径实现调控机制。科学技术的选择原则是:生物生理生态适应性、自然环境吻合性、社会经济允许性、配套有序整体性和推广普及性。 相似文献
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ABSTRACT. In the last decade much research has been devoted to applying the systems analysis approach to water resources problems. A popular research goal has been determination of the “best” method of operating a multipurpose reservoir. The goal of this study was to derive the economically optimum flood control diagram for a multipurpose reservoir by systems analysis. The technique employed to optimize the flood control diagram was programmed so that the optimization process could be applied to other multipurpose reservoirs. Two computer programs developed at the U.S. Army Corps of Engineers' Hydrologic Engineering Center were utilized with modifications to simulate the operation of Folsom Reservoir in central California. Economic analyses were incorporated along with an optimization technique into the reservoir operations program; and the resultant program was capable of routing a sequence of monthly reservoir inflows, computing benefits for various flood control diagrams (as dictated by the optimization procedure), and selecting the economically optimum flood control diagram. The univariate gradient technique was the optimization procedure employed. The two computer programs are on file at the Hydrologic Engineering Center in Davis, California. 相似文献
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The relevant velocity that describes transport phenomena in a porous medium is the pore velocity. For this reason, one needs not only to describe the variability of transmissivity, which fully determines the Darcy velocity field for given source terms and boundary conditions, but also any variability of the pore volume. We demonstrate that hydraulically equivalent media with exactly the same transmissivity field can produce dramatic differences in the displacement of a solute if they have different pore volume distributions. In particular, we demonstrate that correlation between pore volume and transmissivity leads to a much smoother and more homogeneous solute distribution. This was observed in a laboratory experiment performed in artificial fractures made of two plexiglass plates into which a space-dependent aperture distribution was milled. Using visualization by a light transmission technique, we observe that the solute behaviour is much smoother and more regular after the fractures are filled with glass powder, which plays the role of a homogeneous fault gouge material. This is due to a perfect correlation between pore volume and transmissivity that causes pore velocity to be not directly dependent on the transmissivity, but only indirectly through the hydraulic gradient, which is a much smoother function due to the diffusive behaviour of the flow equation acting as a filter. This smoothing property of the pore volume-transmissivity correlation is also supported by numerical simulations of tracer tests in a dipole flow field. Three different conceptual models are used: an empty fracture, a rough-walled fracture filled with a homogeneous material and a parallel-plate fracture with a heterogeneous fault gouge. All three models are hydraulically equivalent, yet they have a different pore volume distribution. Even if piezometric heads and specific flow rates are exactly the same at any point of the domain, the transport process differs dramatically. These differences make it important to discriminate in situ among different conceptual models in order to simulate correctly the transport phenomena. For this reason, we study the solute breakthrough and recovery curves at the extraction wells. Our numerical case studies show that discrimination on the basis of such data might be impossible except under very favourable conditions, i.e. the integral scale of the transmissivity field has to be known and small compared to the dipole size. If the latter conditions are satisfied, discrimination between the rough-walled fracture filled with a homogeneous material and the other two models becomes possible, whereas the parallel-plate fracture with a heterogeneous fault gouge and the empty fracture still show identifiability problems. The latter may be solved by inspection of aperture and pressure testing. 相似文献
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289.
河蚬资源的开发与养殖技术 总被引:3,自引:0,他引:3
本文分析了河蚬的养殖现状和经济价值,并根据河蚬的生物学特性,阐述了其养殖技术要点。 相似文献
290.
川西平原比利时杜鹃商品化盆栽技术 总被引:7,自引:0,他引:7
本文结合川西平原的气候特点和多年栽培实践,阐述了比利时杜鹃的生物学特性及生志习性,提出了特别是元旦、春节等节日用花的商品化盆栽技术要求. 相似文献