祁连山区黑河流域季节冻土时空变化研究

季节冻土的时空变化对地—气水热交换、地表能量平衡、地表水文过程、生态系统及碳循环等有着非常重要的影响.利用黑河流域11个气象站40多年的气温数据和5 cm深度处的土壤温度数据,建立了月平均气温与土壤冻结天数之间的关系.同时应用月平均气温与冻结天数的相关关系和5 km网格化月平均气温及30 m分辨率的DEM数据,编制了黑河流域逐月季节冻土分布图,并按其空间分布特征,将逐月地表冻融状态划分为:完全冻结、不完全冻结和不冻结3种.系统研究了黑河流域2000-2009年逐月季节冻土分布及冻结概率的时空变化特征.在季节分配上,黑河流域完全冻结面积最大值出现在1月;不完全冻结面积最大值在11月;而不冻结面积最大值在6月和7月.在年际变化上,完全冻结状态的离差值在冷季变化大,暖季变化小;不完全冻结状态在一年的回暖期和降温初期,年际变化较大;不冻结状态分别在4月和10月变化较大.冻结概率在1月达到最大值,6月和7月降低到最小值.在空间分布上,黑河流域季节冻土的逐月分布与变化和冻结概率主要受海拔高度控制,纬度的影响次之.     

Short Term and Short Range Seismicity Patterns in Different Seismic Areas of the World

The aim of this work is to quantitatively set up a simple hypothesis for occurrence of earthquakes conditioned by prior events, on the basis of a previously existing model and the use of recent instrumental observations. A simple procedure is presented in order to determine the conditional probability of pairs of events (foreshock-mainshock, mainshock-aftershock) with short time and space separation. The first event of a pair should not be an aftershock, i.e., it must not be related to a stronger previous event. The Italian earthquake catalog of the Istituto Nazionale di Geofisica (ING) (1975–1995, M 3.4), the earthquake catalog of the Japan Meteorological Agency (JMA) (1983–1994, M 3.0) and that of the National Observatory of Athens (NOA) (1982–1994, M 3.8) were analyzed. The number of observed pairs depends on several parameters: the size of the space-time quiescence volume defining nonaftershocks, the inter event time, the minimum magnitude of the two events, and the spatial dimension of the alarm volume after the first event. The Akaike information criterion has been adopted to assess the optimum set of space-time parameters used in the definition of the pairs, assuming that the occurrence rate of subsequent events may be modeled by two Poisson processes with different rates: the higher rate refers to the space-time volume defined by the alarms and the lower one simulates earthquakes that occur in the nonalarm space-time volume. On the basis of the tests carried out on the seismic catalog of Italy, the occurrence rate of M 3.8 earthquakes followed by a M 3.8 mainshock within 10 km and 10 days (validity) is 0.459. We have observed, for all three catalogs, that the occurrence rate density for the second event of a couple (mainshock or aftershock) of magnitude M₂ subsequent to a nonaftershock of magnitude M₁ in the time range T can be modeled by the following relationship: (T, M₂) = 10^{a + b(M1 - M2)} with b varying from 0.74 (Japan) to 1.09 (Greece). The decrease of the occurrence rate in time for a mainshock after a foreshock or for large aftershocks after a mainshock, for all three databases, obeys the Omori's law with p changing from 0.94 (Italy) to 2.0 (Greece).     

基于可靠度理论的滑坡稳定性及其影响因素分析

基于可靠度理论,利用Morgenstern-Price法、Ordinary法、Bishop法和Janbu法等4类极限平衡方法对台州市北水南调工程朱溪引水段Ⅷ号滑坡的稳定性进行了分析,设计了最不利组合、最有利组合、平均值组合的确定性分析方案,目的是为可靠度计算结果提供对比基准;设计了Monte-Carlo循环次数为5 000,50 000,500 000,5 000 000次等4种计算工况,岩土参数的概率分布函数为正态分布、三角形分布和均匀分布等3种情况,方差等于0.5,1.0,2.0,3.0,4.0,5.0倍初始实验方差等6种计算方案,岩土参数间相关性在-1.0～1.0间按0.25等幅变化的9种情况。研究发现,循环次数仅对安全系极值有较大影响,对可靠度指标影响不大;分布函数和数据离散性均会对结果精度造成影响;参数相关性仅对失效概率造成较大影响。     

Theoretical Study on Stochastic Modeling of Combined Gravity-Magnetic-Electric-Seismic Inversion and Its Application

As gravity field,magnetic field,electric field and seismic wave field are all physical fields,their object function,reverse function and compound function are certainly infinite contiuously differentiable func-tions which can be expanded into Taylor (Fourier) series within domain of definition and be further reduced in-to solving stochastic distribution function of series and statistic inference of optimal approximation,This is the basis of combined gravity-magnetic-electric-seismic inversion built on the basis of separation of field and source gravity-magnetic difference-value(D-value)trend surface,taking distribution-independent fault sys-tem as its unit,depths of seismic and electric interfaces of interests as its corresponding bivariate compound re-verse function of gravity-magnetic anomalies and using high order polynomial(high order trigonometric func-tion)approximating to its series distribution,The difference from current dominant inversion techniques is that,first,it does not respectively create gravity-seismic,magnetic-seismic deterministic inversion model from theoretical model,but combines gravity-magnetic-electric-seismic stochastic inversion model from stochastic model;second,after the concept of equivalent geological body being introduced,using feature of independent variable of gravity-magnetic field functions,taking density and susceptibility related to gravity-magnetic func-tion as default parameters of model,the deterministic model is established owing to better solution to the con-tradictioc of difficulty in identifying strata and less test analytical data for density and susceptibility in newly explored area;third,under assumption of independent parent distribution,a real modeling by strata,the prob-lem of difficult plane closure arising in profile modeling is avoided,This technology has richer and more detailed fault and strata information than sparse pattern seismic data in newly explored area,successfully inverses and plots structural map of Indosinian discontinuty in Hefei basin with combined gravity-magnetic-electric-seismic inversion,With development of high precision gravity-magnetic and overall geophysical technology,it is certain for introducing new methods of stochastic modeling and computational intelligence and promoting the develop-ment of combined gravity-magnetic-electric-seismic inversion to open a new substantial and promoting the develop-ment of combined gravity-magnetic-electric-seismic inversion to open a new substantial path.     

泥沙起动概率的高速摄影测量方法

为了通过实验测量泥沙起动概率,基于封闭槽道内开展的泥沙起动实验,系统论述了基于高速摄影的起动概率测量方法所涉及的起动概率定义、相机采样频率、图像处理方法、起动比例与运动比例的关系等关键问题.根据泥沙在水流紊动猝发作用下起动的物理机制,定义实测起动概率为单个紊动猝发周期内,从一定面积床面上冲刷外移的泥沙比例.根据推移质运动概念模型,提出高速图片拍摄间隔应小于推移质运动的中间时间尺度,以捕获泥沙的每一次起动.在高速图像处理时,通过连续两帧图片之间的灰度差实现运动比例的无偏差提取.进一步分析表明,运动泥沙可处于起动、止动或滑翔状态,运动比例等于起动比例、止动比例和滑翔比例之和,起动比例与运动比例之比等于两张图片之间的时间间隔除以推移质运动的中间时间尺度.基于上述关键技术,将高速摄影测量方法用于泥沙起动概率的测量,结果表明,临界起动水流条件时,床沙处于少量起动现象,对应的临界起动概率与窦国仁所推导的2.28%接近.     

一种适用于极区的横轴墨卡托海图

极区位于高纬度地区,极区航海图投影采用墨卡托投影时,图上极区附近变形较大,在极点处变形达到无穷大;采用极球面投影时,图上恒向线不是直线;心射切面投影不是正形投影,不能直接在图上量取方位和距离;兰伯特正形投影图上,经度是由角度表示,而不是真的经度;采用横轴墨卡托投影时,几乎所有的经线以及纬线在图上为曲线。以上常用的海图投影不利于船舶在极区安全航行,也不利于航海人员进行海图作业。针对此问题,将构建的伪经纬线网与经纬线网进行转换,通过Matlab得到基于伪经纬线网的横轴墨卡托投影图,此图具有类似于墨卡托海图的特点,图上极区变形失真小,图上伪经纬线的特点可方便极区海图作业。     

船舶定线制在海图上的表示方法分析

详细介绍了船舶定线制的起源以及在国内的应用情况,结合实例分析船舶定线制的完整体系,提出自己的分类方法,重点探讨船舶定线制这种复杂要素在海图上的表示原则和方法,以及如何在航海通告中明确表述该要素。     

基于电子海图的智能潜水器路径规划研究

随着地理信息系统技术的发展,电子海图作为一种专门的电子地图也越来越成熟。电子海图中提供了详细而准确的海洋环境信息。利用电子海图的环境建模和考虑海流因素的遗传搜索策略为解决大范围海洋环境下智能潜水器全局路径规划提供了一个新的方法。利用电子海图中的信息对智能潜水器的工作环境进行环境建模,以遗传多目标优化算法为搜索策略进行全局路径规划,并考虑海流因素对潜水器的影响,使潜水器在航行时可充分利用海流的能量。通过仿真试验对环境建模和路径规划进行了验证。该方法具有很好的实用性。     

模糊划分矩阵在岩土参数概率分布中的应用

讨论如何在小样本条件下用已有的过程经验与试验资料确定岩土参数概率分布,用模糊划分矩阵与BAYES方法相结合,给出由小样本试验数据确定岩土参数的概率分布。     

Evaluation of wave impact loads on caisson breakwaters based on joint probability of impact maxima and rise times

When waves break against seawalls, vertical breakwaters, piers or jetties, they abruptly transfer their momentum into the structure. This energy transfer is always spectacular and perpetually unrepeatable but can also be very violent and affect the stability and the integrity of coastal structures. Over the last 15 years, increasing awareness of wave-impact induced structural failures of maritime structures has emphasised the need for a more complete approach to dynamic responses, including effects of impulsive loads. At the same time, movement of design standards toward probabilistic approaches requires new statistical tools able to account for uncertainties in the variability of wave loading processes. This paper presents a new approach to the definition of loads for use in performance design of vertical coastal structures subject to breaking wave impacts.