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271.
陡坡带构造演化史研究对断陷湖盆具有重要意义,平衡剖面技术在面积(体积)守恒的基础上为恢复构造演化史提供了一种科学合理的技术方法。通过对东濮凹陷兰聊陡坡带进行平衡剖面法构造演化史恢复,再现了兰聊断层的活动规律及其对东濮断陷湖盆发展演化的控制作用,明确了东濮凹陷早第三纪层序地层发育特征、坡折带类型及其对砂砾岩扇体的控制作用,指出了隐蔽油气藏发育的有利层段和分布的有利地区。  相似文献   
272.
For parasitoids, host finding is a central problem that has been solved through a variety of behavioural mechanisms. Among species in which females do not make direct contact with hosts, as is the case for many dipteran parasitoids, eggs must be laid in an appropriate part of the host habitat. The asilid fly Mallophora ruficauda lays eggs in clusters on tall vegetation. Upon eclosion, pollen-sized larvae fall and parasitize soil-dwelling scarab beetle larvae. We hypothesized that wind dissemination of M. ruficauda larvae is important in the host-finding process and that females lay eggs at heights that maximize parasitism of its concealed host. Through numerical and analytical models resembling those used to describe seed and pollen wind dispersal, we estimated an optimal oviposition height in the 1.25- to 1.50-m range above the ground. Our models take into account host distribution, plant availability and the range over which parasitic larvae search for hosts. Supporting our findings, we found that the results of the models match heights at which egg clusters of M. ruficauda are found in the field. Generally, work on facilitation of host finding using plants focuses on plants as indicators of host presence. We present a case where plants are used in a different way, as a means of offspring dispersal. For parasitoids that carry out host searching at immature stages rather than as adults, plants are part of a dissemination mechanism of larvae that, as with minute seeds, uses wind and a set of simple rules of physics to increase offspring success.  相似文献   
273.
Floodplain management programs have been adopted by more than 85% of local governments in the nation with designated flood hazard areas. Yet, there has been little evaluation of the influence of floodplain policies on private sector decisions. This article examines the degree to which riverine floodplain management affects purchase and mitigation decisions made by owners of developed floodplain property in ten selected cities in the United States. We find that the stringency of such policies does not lessen floodplain property buying because of the overriding importance of site amenity factors. Indeed, flood protection measures incorporated into development projects appear to add to the attractiveness of floodplain location by increasing the perceived safety from the hazard. Property owner responses to the flood hazard after occupancy involve political action more often than individual on-site mitigation. Floodplain programs only minimally encourage on-site mitigation by the owner because most owners have not experienced a flood and many are unaware of the flood threat. It is suggested that floodplain programs will be more effective in meeting their objectives if they are directed at intervention points earlier in the land conversion process.  相似文献   
274.
紧急避难场所优化布局理论研究   总被引:4,自引:0,他引:4  
建设应急避难场所是国际社会应对突发性事件的一项灾民安置措施,同时也是现代化大城市用于民众躲避地震、火灾、爆炸、洪水等重大自然灾害的安全避难场所.本文在对避难场所规划原则、城市避难场所布局、选址及其要求进行分析的基础上,提出了城市避难场所数量、容量的确定路线,并对避难场所布局优化进行了研究,提出了网络优化模型,并结合实际应用对其进行了一定的完善.  相似文献   
275.
针对基于距离约束的井下定位算法本身存在的近似误差,尤其在锚点附近定位误差较大的问题,通过改进算法,引入1个误差系数ω,并以此为依据,来选取误差较小的边作为定位信息来源,同时引入修正系数ε来进行修正分割点,使其更加接近于垂足,以此来减少定位的误差。仿真结果表明:改进算法的平均定位误差远小于原定位算法,约为1/4;改进算法的最大误差小于1.5 m、最小误差为0.2 m;改进算法不仅定位精度优于原定位算法,且计算复杂度较低,更加适用于深井环境定位。  相似文献   
276.
利用GIS实现江苏省地表水省控断面管理   总被引:3,自引:1,他引:3  
江苏省环境监测中心开发的环境数据可视化地理信息系统是根据断面管理功能,在建立符合管理需求的各类断面图层基础上.采用通用软件开发平台和专业的GIS工具软件相集而成。该系统具有水环境信息的空间查询、表达、统计和绘图等功能.可使环境管理综合决策部门直观、有效地进行水环境质量管理。  相似文献   
277.
278.
鉴于我国应急物资的多部门分散管理与分散储备的特点,研究了区域性应急物资储备体系构建中的应急物资储备级库协同选址问题。为了实现应急物资在不同级库间的协同储备管理与分散优化调拨,建立了应急物资储备级库选址的协同优化模型。用启发式算法通过MATLAB编程来实现,并用算例进行了验证。  相似文献   
279.
为了更加合理的选择拆旧地块,以辽宁省桓仁县华莱镇为例,通过实际分析与特尔菲法选取14个评价指标,通过层次分析法确定指标的权重,采用加权指数和法计算评价得分,并运用累积曲线分级法将评价对象分为四类区域。结果表明最适宜拆旧区占居民点总面积的4.14%,适宜拆旧区占居民点总面积的6.16%,不适宜拆旧区占居民点总面积的31.91%,最不适宜拆旧区占居民点总面积的57.79%。  相似文献   
280.
Natural weathering processes are significant mechanisms that noticeably affect the fundamental nature of incineration ash residues. To provide a greater understanding of these processes, a MSWI (mono)landfill site in the north east of the US was selected as the target for systematic investigation of the natural weathering of bottom ash residues. Samples of various ages were collected from locations A (1 yr), B (10 yrs), C (13-14 yrs) and D (20 yrs) of the landfill in 2009. We investigated the phase transformation of the collected bottom ash particles, neoformation processes as well as the behavior and distribution of certain heavy metals (Cu, Pb, Zn, Ni, and Cr) in the neoformed phases using optical microscopy, SEM-EDX, and bulk examinations. Key findings: at the preliminary stage, the waste metallic particles (Al, Fe, and Cu) and unstable minerals such as lime, portlandite, ettringite and hydrocalumite convert to oxide and hydroxide (hydrate) phases, calcite, alumina gel and gypsum. At the intermediate stage, the decomposition of melt products including magnetite spinels and metallic inclusions is triggered due to the partial dissolution of the melt glass. At the longer time horizon it is possible to track the breakdown of the glass phase, the extensive formation of calcite and anhydrite, Al-hydrates and more stable Fe-hydrates all through the older ash deposits. Among the dominant secondary phases, we propose the following order based on their direct metal uptake capacity: Fe-hydrates>Al-hydrates>calcite. Calcite was found to be the least effective phase for the direct sorption of heavy metals. Based on overall findings, a model is proposed that demonstrates the general trend of ash weathering in the landfill.  相似文献   
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