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21.
????????????????Kullback-Leiber???????????????Bayes?????????????????????Σ?????????????￡??????????????????????????????????????????????????3??????????Kullback-Leiber????????????????????????б???????÷???????????????????????????Ч???? 相似文献
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地理加权回归是常用的空间分析方法,已广泛应用于各个领域,但利用此方法进行回归分析前,往往忽略了对设计矩阵进行局部多重共线性的诊断,从而导致对模型的估计不准确。因此,本文在引入了全局模型的多重共线性诊断方法的基础上,对这些方法进行了改进,改进后构建了加权方差膨胀因子法和加权条件指标方法——分解比法,用于诊断地理加权回归模型设计矩阵的多重共线性问题。实验结果表明,多重共线性不存在于全局模型,而可能存在于局部模型中,构建的两种方法能够有效地诊断地理加权回归模型的多重共线性问题,且加权条件指标方法——分解比法比加权方差膨胀因子法在诊断多重共线性问题上更有优势。 相似文献
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阐述了私募股权投资的估值问题.首先简要介绍了投资组合问题的发展历史与研究成果.接着较为详细地论述了私募股权投资的估值问题的研究现状,包括有限合伙人的投资组合选择,以及对投资企业的价值评估体系和评估方法的研究,并给出了所要研究的模型,即含有未支撑风险的私募股权投资模型.最后给出所要研究模型在通胀环境、Knight不确定环境下以及跳扩散环境下的拓展框架. 相似文献
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集合卡尔曼滤波 (the Ensemble Kalman Filter,简称EnKF) 中将预报集合的统计协方差作为预报误差协方差,但该估计可能严重偏离真实的预报误差协方差,影响同化精度。基于极大似然估计理论,发展了一种优化预报误差协方差矩阵的实时膨胀方法,即MLE (the Maximum Likelihood Estimation) 方法。利用蒙古国基准站Delgertsgot (简称DGS站) 观测资料,基于EnKF方法和MLE方法,在通用陆面模式 (the Common Land Model,简称CoLM) 中同化了地表温度和10 cm土壤温度观测资料,建立了土壤温度同化系统。结果表明:MLE方法对地表温度和各层土壤温度 (尤其深层土壤温度) 的估计比EnKF方法准确。考虑到浅层和深层土壤温度的差别,在实施MLE方法时对浅层和深层土壤温度采用了不同的膨胀因子。对比膨胀因子为单一标量时的结果,多因子膨胀能缓解深层土壤温度的不合理膨胀,改善同化效果。 相似文献
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Raymond A. Duraiswami Gauri Dole Ninad Bondre 《Journal of Volcanology and Geothermal Research》2003,121(3-4):195-217
The pahoehoe–aa transition for a flow exposed near Bodshil village from the western part of the Deccan Volcanic Province (DVP) is reported for the first time. The 1-km-long Bodshil flow issued as a small sheet from a pre-existing lobe. Near the source, the crust is characterised by numerous squeeze-ups. A number of gaping fractures, parallel to sub-parallel to the flow direction, are exposed on the surface in the medial portion of the flow. About 800 m away, the flow completely transforms to slabby pahoehoe. The terminal portion of the flow is characterised by concentrations of slabs, blocks and lava balls. The size and concentrations of the slabs and lava balls appear to increase along the length of the flow. Petrographic studies reveal a dominant hypohyaline texture. The flow core is coarse and is characterised by plagioclase set in a glassy matrix. The presence of clinopyroxene in addition to plagioclase and glass distinguishes the crust and interslab crust from the core. On the basis of mineralogy, a temperature range of 1146±15°C to 1169±15°C is inferred for the Bodshil flow. Increased vesicle deformation across the transition is discernible and an average D-value of <0.4 indicates moderate strain rates during emplacement. In light of the morphology and petrography, the cooling history and the mode of emplacement of the Bodshil flow is discussed. The flow originated as a small toe at the leading edge of a pahoehoe flow, and grew into a sheet by the mechanism of inflation. Continuous inflation caused the brittle crust to uplift and produce a network of inflation clefts that were subsequently occupied by squeeze-ups. Temporary stagnation of the flow due to cessation of lava supply or storage allowed the crust to grow and thicken. Renewed movement of the stored and cooled lava to the flow front at a fairly high volumetric rate was responsible for the initial disruption of the crust. High rates of crustal disruption induced higher rates of degassing and cooling, which resulted in rapid crystallisation of the fluid core. Increase in crystallinity lead to the onset of yield strength, and it is envisaged that at least the terminal parts of the flow behaved as a Bingham fluid. The Bodshil flow is unique to the DVP because it is the first to record slabby pahoehoe and provide evidence for the incipient transformation of basaltic lava from pahoehoe to aa. 相似文献
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The 1990 Kalapana flow field is a complex patchwork of tube-fed pahoehoe flows erupted from the Kupaianaha vent at a low effusion rate (approximately 3.5 m3/s). These flows accumulated over an 11-month period on the coastal plain of Kilauea Volcano, where the pre-eruption slope angle was less than 2°. the composite field thickened by the addition of new flows to its surface, as well as by inflation of these flows and flows emplaced earlier. Two major flow types were identified during the development of the flow field: large primary flows and smaller breakouts that extruded from inflated primary flows. Primary flows advanced more quickly and covered new land at a much higher rate than breakouts. The cumulative area covered by breakouts exceeded that of primary flows, although breakouts frequently covered areas already buried by recent flows. Lava tubes established within primary flows were longer-lived than those formed within breakouts and were often reoccupied by lava after a brief hiatus in supply; tubes within breakouts were never reoccupied once the supply was interrupted. During intervals of steady supply from the vent, the daily areal coverage by lava in Kalapana was constant, whereas the forward advance of the flows was sporadic. This implies that planimetric area, rather than flow length, provides the best indicator of effusion rate for pahoehoe flow fields that form on lowangle slopes. 相似文献
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