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龙羊峡水库蓄水对水温的净影响 被引量:15
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作者 隋欣 杨志峰 《水土保持学报》 CSCD 北大核心 2004年第4期154-157,共4页
分析水库蓄水对水温的影响对于研究水库气候效应,探讨水库建设对水生生物和下游农作物灌溉的影响具有重要意义。本文建立了计算分层型水库对水温净影响的数学模型,并利用龙羊峡水库和下游河道实测水温和气温成果,在深入分析了龙羊峡水... 分析水库蓄水对水温的影响对于研究水库气候效应,探讨水库建设对水生生物和下游农作物灌溉的影响具有重要意义。本文建立了计算分层型水库对水温净影响的数学模型,并利用龙羊峡水库和下游河道实测水温和气温成果,在深入分析了龙羊峡水库水温类型和水温铅直分布规律的基础上,采用该模型计算了龙羊峡水库蓄水对坝前和下游河道水温的净影响。与传统的差值法相比,该模型引入了基于气温与水温相关关系的修正因子,扣除了自然因素引起的水温背景值的变化,可以获得更为准确的计算结果。 展开更多
关键词 龙羊峡水库 蓄水量 水温 净影响
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考虑用户意愿的符号网络净积极影响力最大化问题
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作者 宗金醒 帅天平 《哈尔滨商业大学学报(自然科学版)》 CAS 2023年第5期604-611,共8页
影响力最大化是近年来广泛研究的社交网络的核心问题.然而之前的研究较少考虑用户的意愿以及用户之间的友好或敌对关系.因此综合考虑这些因素,针对符号网络提出了考虑用户意愿的净积极影响力最大化问题,该问题可以描述如下:利用符号网... 影响力最大化是近年来广泛研究的社交网络的核心问题.然而之前的研究较少考虑用户的意愿以及用户之间的友好或敌对关系.因此综合考虑这些因素,针对符号网络提出了考虑用户意愿的净积极影响力最大化问题,该问题可以描述如下:利用符号网络来刻画用户具有友好(积极)和敌对(消极)关系的社交网络,每个用户对传播的信息有自己的意愿,目标是要从网络中选择k个用户,使得最终的净积极影响的用户数量最多.通过对问题的细致分析,建立了考虑用户意愿的传播模型,证明了该模型下净积极影响力最大化问题是非次模和非单调的,随后给出了基于概率驱动的结构感知的求解算法,通过在三个数据集上的实验表明,利用提出的算法找到的种子集有更好的净积极影响力. 展开更多
关键词 符号网络 积极影响 消极影响 积极影响 概率驱动结构感知算法 用户意愿
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基于突发事件影响下的逐步灰色预测
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作者 韩旭 郏然然 《科技风》 2019年第15期198-199,共2页
灰色预测模型是一种小样本的简单预测模型,但简单的灰色预测模型已经不适合当今日新月异的时代。本文以海南省限购政策对商品房价格的影响为例,基于灰色预测模型,对突发事件影响下的灰色预测模型进行分析讨论,建立事件发生后的时间净影... 灰色预测模型是一种小样本的简单预测模型,但简单的灰色预测模型已经不适合当今日新月异的时代。本文以海南省限购政策对商品房价格的影响为例,基于灰色预测模型,对突发事件影响下的灰色预测模型进行分析讨论,建立事件发生后的时间净影响值下的逐步灰色预测模型。 展开更多
关键词 灰色预测 时间净影响 逐步灰色预测
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我国自然旅游资源私有化后果动态管理研究 被引量:5
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作者 黄向 保继刚 Stephen Smith 《软科学》 CSSCI 2008年第4期88-92,共5页
通过对"自然旅游资源私有化(NBTRP)"现象的机会和危险分析。NBTRP产生的影响既有正面影响也有负面影响,因此"NBTRP净影响监管模型"被设计用以动态综合评价目标目的地NBTRP的成效。
关键词 自然旅游资源私有化 净影响 监管模型
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Purification Effects of Aquatic Vegetations on Lake Wetland Water Environment and Analysis of the Influencing Factors in Hongze Lake 被引量:3
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作者 赵洪波 吴睿 卡林 《Agricultural Science & Technology》 CAS 2012年第1期211-216,共6页
[Objective] To study the purification effect of plant community on wetland water environment in Hongze Lake, and to provide references to the ecological restoration of this area. [Methed] The typical lakeside zone of ... [Objective] To study the purification effect of plant community on wetland water environment in Hongze Lake, and to provide references to the ecological restoration of this area. [Methed] The typical lakeside zone of Hongze Lake Wetland National Nature Reserve was taken as the study area. Through the field survey based on environmental characteristics of aquatic areas and non-aquatic areas, combined with laboratory test, the content changes of nutrients (N and P), COD (chemical oxygen demand) and SD (transparency) levels in the water body of lake wetland were measured; the purification effect of the lake wetland ecosystem in the growth process of aquatic vegetation was quantitatively analyzed, and possible influ- encing factors were discussed. [Result] Aquatic vegetation could remove the TN, TP, COD, Chla in wetland water environment and had obvious effects on the changes of SD content. Competition between aquatic plants can inhibit the growth of algae and relieve the eutrophication of water body. [Conclusion] This study provided theoretical basis for ecological restoration and enhancement of self-purification capability in the lakeside zone of Hongze Lake. 展开更多
关键词 Aquatic vegetation Water environment Purification effect Influencing factors
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The Soil Moisture and Net Primary Production Affected by CO_2 and Climate Change Using a Coupled Model
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作者 PENG Jing DAN Li 《Atmospheric and Oceanic Science Letters》 CSCD 2014年第4期269-274,共6页
In this paper, a coupled model was used to estimate the responses of soil moisture and net primary production of vegetation(NPP) to increasing atmospheric CO2 concentration and climate change. The analysis uses three ... In this paper, a coupled model was used to estimate the responses of soil moisture and net primary production of vegetation(NPP) to increasing atmospheric CO2 concentration and climate change. The analysis uses three experiments simulated by the second-generation Earth System Model(CanESM2) of the Canadian Centre for Climate Modelling and Analysis(CCCma), which are part of the phase 5 of the Coupled Model Intercomparison Project(CMIP5). The authors focus on the magnitude and evolution of responses in soil moisture and NPP using simulations modeled by CanESM, in which the individual effects of increasing CO2 concentration and climate change and their combined effect are separately accounted for. When considering only the single effect of climate change, the soil moisture and NPP have a linear trend of 0.03 kg m–2 yr–1 and –0.14 gC m–2 yr–2, respectively. However, such a reduction in the global NPP results from the decrease of NPP at lower latitudes and in the Southern Hemisphere, although increased NPP has been shown in high northern latitudes. The largest negative trend is located in the Amazon basin at –1.79 gC m–2 yr–2. For the individual effect of increasing CO2 concentration, both soil moisture and NPP show increases, with an elevated linear trend of 0.02 kg m–2 yr–1 and 0.84 gC m–2 yr–2, respectively. Most regions show an increasing NPP, except Alaska. For the combined effect of increasing atmospheric CO2 and climate change, the increased soil moisture and NPP exhibit a linear trend of 0.04 kg m–2 yr–1 and 0.83 gC m–2 yr–2 at a global scale. In the Amazon basin, the higher reduction in soil moisture is illustrated by the model, with a linear trend of –0.39 kg m–2 yr–1, for the combined effect. Such a change in soil moisture is caused by a weakened Walker circulation simulated by this coupled model, compared with the single effect of increasing CO2 concentration(experiment M2), and a consequence of the reduction in NPP is also shown in this area, with a linear trend of-0.16 gC m-2 yr-2. 展开更多
关键词 increasing atmospheric CO2 climate change soil moisture net orimarv oroduction coupled model
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资源约束下的投资优化模型
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作者 龚刚 聂晶 《数理统计与管理》 CSSCI 北大核心 2003年第z1期56-61,共6页
资源约束下的投资问题在决策中很常见.本文提出运用边际净现值比较的思想来解决资源约束下多项目多地区投资决策问题的观点,并且尝试用"区域影响力系数"来衡量区域经济规模对投资项目的影响.在此基础上建立了资源约束下的投... 资源约束下的投资问题在决策中很常见.本文提出运用边际净现值比较的思想来解决资源约束下多项目多地区投资决策问题的观点,并且尝试用"区域影响力系数"来衡量区域经济规模对投资项目的影响.在此基础上建立了资源约束下的投资优化模型,并给出解决此类问题的方法. 展开更多
关键词 边际现值 区域影响力系数 资源约束
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Analysis of the influence of collection purification filtration system of channel upon groundwater quality about freeway
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作者 QIN Ren-jie ZHANG Bao-jing LIU Zhao-hui 《Journal of Environmental Science and Engineering》 2009年第7期1-5,共5页
At present, it is usually used the method that elevating the height of embankment to design passages of freeway to avoid transverse traffic disturbance in plain areas of China. But when design low embankment, it is di... At present, it is usually used the method that elevating the height of embankment to design passages of freeway to avoid transverse traffic disturbance in plain areas of China. But when design low embankment, it is difficulty for drainage or setting passages and culverts. Hengshui to Darning freeway in Hebei provence (Heng-Da freeway) is one section of Dalian to Guangzhnu freeway. This paper analyzes the characteristic of climate, geology, hydrology and low water table, good permeability stratum soil and its little and mass rain fall and deep drinking water well in the plain areas of North China when design low embankment of Heng-Da freeway, puts forward the drainage methods of water collecting filtration system to solve the drainage problem of passages and culverts, aiming at the type and the measures of the pollution on the surface, the channel collection purification infiltration system of highway uses the single composite technology of aerobic and oxygen to digest - precipitation-absorption of artificial materials percolation of soil to deal with the pollution of the rain on the road (the composite technology use the vermiculite as the material of infiltration), which be controlled in the drinking range of the water standard. It not only efficiently solved the problem of water collected in the channel, but also supplied the groundwater. It has reached the environment-friendly road construction purpose of the sustainable development of highway construction, "environment friendly" and "resource conservation". 展开更多
关键词 plain areas of North China FREEWAY low embankment VERMICULITE collection purification infiltration system
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某深埋分岔隧道空间荷载结构计算方法 被引量:14
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作者 丁文其 郑康成 金威 《中国公路学报》 EI CAS CSCD 北大核心 2016年第2期90-97,共8页
为了对分岔隧道毛洞数值模型作进一步优化,考虑施工措施和过程,建立精细化模型,对分岔隧道进行了有限元数值分析计算,并与毛洞开挖结果对比,总结得到分岔隧道荷载空间分布规律,根据岩体松动范围、衬砌内力和衬砌表面接触压力在隧道纵向... 为了对分岔隧道毛洞数值模型作进一步优化,考虑施工措施和过程,建立精细化模型,对分岔隧道进行了有限元数值分析计算,并与毛洞开挖结果对比,总结得到分岔隧道荷载空间分布规律,根据岩体松动范围、衬砌内力和衬砌表面接触压力在隧道纵向上的变化规律,引入净距影响系数,在《公路隧道施工技术细则》连拱隧道荷载计算方法的基础上进行改进,得到分岔隧道荷载计算新方法——空间荷载结构法,并应用于三维壳单元隧道荷载结构模型。结果表明:随着隧道净距的增大,塌落荷载值逐渐减小并因此产生隧道纵向上的弯矩;该方法计算得到的衬砌受力更符合分岔隧道实际受力情况。 展开更多
关键词 隧道工程 深埋分岔隧道 空间荷载结构法 隧道影响系数
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