救援延迟效应如何影响政府企业救灾合作？基于微分博弈的研究

“政府主导、社会参与”的政企协同救灾成为我国救灾体制改革的方向。通讯中断以及运输路网的破坏经常导致救援的延迟,在救援延迟的应急场景下政企协同合作的救援效率一定高于自发救援吗？针对自发救援和协同合作两种救援模式,考虑救援延迟效应,构建了政企救灾合作的微分博弈模型,分析救援延迟对政企救灾策略的影响,以及政府成本补贴对提高协同救灾的适用条件。最后结合云南鲁甸地震的案例加以验证。结果表明,当延迟时间小于某阈值时,协同救援才更有效率。与自发救援相比,协同救援下政府救灾投入量随延迟时间急剧上升,而企业投入量变化较小。企业单位收益系数可作为衡量灾害严重程度的指标,数值越大,政府承担企业的救灾成本补贴比例越大。     

防洪风险分析中改进的组合分布模型研究

洪水变量分布的选择是防洪风险分析中的一个重要工作 ,目前常用 P- 分布来描述洪水的随机特性 .建立在组合分布模型的基础上 ,本文提出了改进的组合分布模型 ,给出了不同情况下求最优分界点的模型 .实例计算表明 ,改进的组合分布模型在理论和应用上都优于原始分布 ,它能较好地反映洪水的风险     

基于合作博弈的非常规突发极端洪水灾害风险应急金融服务供应链协调

根据非常规突发极端洪水灾害风险的特点,从服务供应链视角,提出非常规突发极端洪水灾害风险应急金融服务供应链的管理框架,分析此供应链的结构和内涵.分析此应急金融服务供应链中各参与人的利益关系式与和谐阈值,利用合作博弈理论,建立基于传统Shapley值合作博弈模型,有效解决应急金融服务供应链中成员经营性政府、保险公司和公众三者之间的协调问题.     

赣江流域水体无机氮分布特征

于2006年1月和7月对赣江流域地表水进行了系统采集,分析研究了水体中各形态无机氮分布特征,结果表明,赣江水体中主要的氮素形式是NO-3-N,枯水期赣江流域NO-3-N、DIN从上游至下游呈明显的上升趋势,NH 4-N变化不明显.丰水期从上游至下游NO-3-N含量逐渐降低,但降幅不大,而NH 4-N和DIN在中游含量最低,下游最高.主要支流中枯水期以袁水NO-3-N和DIN含量最高,赣江中支NH 4-N含量为全流域最大值,而丰水期以禾水NO-3-N为流域最高值.赣江主干流丰水期各形态无机氮含量明显低于枯水期.氮污染较重的袁水的输入致使G38(樟树)处氮含量明显高于其它地方.     

城市防洪工程效益不确定性研究

城市防洪工程所能发挥的防洪效益受洪水发生情况、灾害指标等多种因素的影响，所有这些影响因素都具有不确定性。因此，工程所发挥的防洪效益也具有不确定性。基于这种分析，文章建立了估计防洪效益的随机模型。     

Remark on strong martingales and the linear embedding of tactics

It is shown that 2-parameter strong martingales in the sense of Walsh can be transformed into 1-parameter martingales by the “embedding of tactics” and can be characterized by this property.     

Extreme value processes and the evaluation of risk in flood analysis

A analysis of hydrological risk is presented associated with decisions based on stochastic flood models. The maxima of a stream-flow are described by a marked Poisson process with a cyclic trend and exponentially distributed marks. Typical design criteria like the expected largest exceedance of a fixed level in a given period are derived from the extreme value process. The approach adopted is based on the whole record of flood data, which consists of the number, the occurrence times and the exceedances of the maxima in the observation period. Thus, compared to the series of largest annual exceedances more information is extracted. This yields an improvement in the evaluation of risk.     

Practical Extreme Value Modelling of Hydrological Floods and Droughts: A Case Study

Estimation of flood and drought frequencies is important for reservoir design and management, river pollution, ecology and drinking water supply. Through an example based on daily streamflow observations, we introduce a stepwise procedure for estimating quantiles of the hydrological extremes floods and droughts. We fit the generalised extreme value (GEV) distribution by the method of block maxima and the generalised Pareto (GP) distribution by applying the peak over threshold method. Maximum likelihood, penalized maximum likelihood and probability weighted moments are used for parameter estimation. We incorporate trends and seasonal variation in the models instead of splitting the data, and investigate how the observed number of extreme events, the chosen statistical model, and the parameter estimation method effect parameter estimates and quantiles. We find that a seasonal variation should be included in the GEV distribution fitting for floods using block sizes less than one year. When modelling droughts, block sizes of one year or less are not recommended as significant model bias becomes visible. We conclude that the different characteristics of floods and droughts influence the choices made in the extreme value modelling within a common inferential strategy.This revised version was published online in March 2005 with corrections to the cover date.     

Two-dimensional coupled mathematical modeling of fluvial processes with intense sediment transport and rapid bed evolution

Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime, for which traditional decoupled mathematical river models based on simplified conservation equations are not applicable. A two-dimensional coupled mathematical model is presented, which is generally applicable to the fluvial processes with either intense or weak sediment transport. The governing equations of the model comprise the complete shallow water hydrodynamic equations closed with Manning roughness for boundary resistance and empirical relationships for sediment exchange with the erodible bed. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method, along with the HLLC approximate Riemann Solver, is adapted to solve the governing equations, which can properly resolve shock waves and contact discontinuities. The model is applied to the pilot study of the flooding due to a sudden outburst of a real glacial-lake. Supported by the National Basic Research and Development Program of China (973 Program) (Grant No. 2007CB14106), the National Natural Science Foundation of China (Grant No. 50459001), and the Key Project of Chinese Academy of Sciences (Grant No. KZCX3-SW-357-02)     

罕见灾难事件的福利减损效应研究

通过修正随机消费函数,构建了包含罕见灾难状态的理论模型,并根据中国经验消费数据测算了罕见灾难事件对国民福利的减损效应.研究发现:罕见灾难事件对国民经济福利的减损效应相当大,在合理的参数范围内,为通常意义上的经济波动福利减损效应的数十倍.罕见灾难事情的持续时间越长,福利减损效应越显著.相应的防灾减灾措施,可以有效降低灾难风险,进而提升灾难发生期的国民经济福利.因此,科学制定合理的宏观经济政策是必要的,其作用主要体现于缩短国民经济处于罕见灾难状态的时长、降低可避免的罕见灾难发生的概率以及减轻罕见灾难发生后经济衰退的幅度.