冰川运动速度研究: 方法、变化、问题与展望

冰川流速是表征冰川运动的重要参数之一,对于冰川动力学、气候变化以及物质平衡等研究具有重要意义。冰川流速的影响因素多样,其中气象因子主要是通过改变冰川物质平衡、活动性以及水力特征来对冰川运动产生影响,所以冰川流速也可能与气象因子一样具有季节性差异。基于2017-11-06—2020-11-02期间31景哨兵1号（Sentinel-1）雷达影像,采用外部数字高程模型（digital elevation model,DEM）辅助的偏移量追踪法对中国西藏自治区昌都市八宿县境内然乌湖流域的雅弄冰川进行了冰川表面流速提取,并结合研究区冰舌面积变化以及气象因子（平均气温、降水量、降雪日数以及平均日照数）对雅弄冰川流速季节性变化进行了分析。结果表明：雅弄冰川流速分布呈现中上部流速高而下部流速低的特点,且冰川中部主流线流速明显高于两侧速度。30组冰川流速变化具有明显的季节性,夏季流速高而冬春季流速低。与流速变化相同,冰舌面积变化同样具有季节性差异,冬季面积明显大于夏季面积。与气象影响因子对比分析发现,气温、降水以及日照均对冰川表面流速具有正效应,促进冰川运动,而降雪抑制了部分热量及辐射传递,进而抑制了冰川融水过程,减缓了冰川运动。在气象因子影响力上,气温对冰川运动的效应最明显,降雨次之,日照影响最小。     

卫星跟踪卫星技术的进展及应用前景

卫星跟踪卫星技术被认为是 2 1世纪初最有价值和应用前景的高效重力探测技术 ,旨在测定中长波重力场的精细结构及时间相依变化。本文首先简要阐述卫星跟踪卫星技术的发展背景及概况 ,其次介绍目前已经实施和将要实施的卫星跟踪卫星计划 CHAMP和 GRACE的进展情况 ,最后讨论该技术在精化地球重力场和研究相关地学问题中的应用前景。     

动态非线性滤波模型非线性强度的曲率度量及其应用

基于微分几何的两种曲率——参数影响曲率和固有曲率,给出了定量描述非线性滤波问题的非线性强度的方法,分别采用扩展Kalman滤波方法和Unscented Kalman滤波方法进行了模拟实验。结果验证了这些曲率确实能够度量非线性滤波问题的非线性强度,且能够评估非线性滤波算法的状态估计性能。     

Development of FBMINC model for particle diffusion in fluids

An accurate particle tracking method using FBMINC （new fractional Brownian motion） is outlined. It generates non-Fickian diffusion rather than Fickian diffusion as traditional particle tracking model does. The FBMINC model is based on fractional Brownian motion （fl3m） which is generalization of regular Brownian motion. The two models of fBms （FBM model and FBMINC model） were explored and the differences of the two models are compared from the three aspects： the standard deviation of each step, the small memory and the effect of the number of particles in the cloud. The results show the FBMINC model is a better model as it produces more accurate statistics. The effect of simple shear dispersion for both Brownian and fBm was investigated. The power law scaling of fBm shear dispersion was correctly identified. In addition, a scaling coettieient was found numerically. The FBMINC model is then used for producing both superdiffusive and subdiffusive particle paths, therefore, the non-Fickian diffusion of soil particle clouds can be modelled. The particle clouds represent soil contaminant are released in an idealised coastal bay and the fBm particle tracking method is used for simulation the particle cloud spreading in the bay. There is a noticeable increase in the spreading rate of the cloud. In addition, owning to the spreading rate of the cloud, a noticeable part of it has escaped the bay area and transported downstream. The variation of the Hurst exponent can lead to an area of the flow being affected by a contaminant cloud which is not picked up by the regular Brownian motion models. The purpose of this paper is to bring soil transport engineers a new angle on soil particle transport research in fluids. Using FBM1NC particle tracking model allows more flexibility in simulation of diffusion in soil contaminant spread in coastal bay or ocean surface.     

GIS数据辅助下的线状目标自动提取

首先介绍了遥感影像中线状目标骨架自动提取的意义和研究现状，然后结合老的GIS数据，提出了一种算法来实现遥感影像中线状目标骨架的自动提取，算法主要包括影像预处理、GIS数据与影像的配准、骨架跟踪、编组连接与数据简化等步骤。最后又利用遥感影像和相应的GIS数据进行了实验，实验证明了算法的可行性和有效性。     

风暴分类识别技术在人工防雹中的应用

利用新一代多普勒天气雷达资料,在风暴跟踪识别算法的基础上,发展了风暴分类技术,以提高人工防雹作业指挥的效率。首先以SCIT算法为基础,结合风暴的结构特征,综合利用雷达、探空资料,自动提取风暴结构特征指数;其次采用基于决策树模型的风暴自动分类技术,将风暴按强度分为雷雨云、单体风暴、多单体风暴和强风暴;最后根据风暴强度、高度和位置等属性,对有可能产生冰雹的单体,结合GIS,自动对下游方向或附近作业点进行预警或输出作业参数。通过对2006—2014年期间重庆、辽宁大连和河南三门峡三地发生的较为典型的31次冰雹天气过程、182站次冰雹样本的检验来看:该方法通过对风暴按强度、垂直结构等综合属性进行分类,能有效提高冰雹识别的命中率、降低空报率,其中强风暴的命中率能达到100%,空报率仅为11.4%。能有效提高人工防雹作业的自动化程度,对防雹作业的科学决策有着重要参考作用。     

电力系统潮流量的微机快速跟踪测量

提出了一种电力系统潮流量的快速跟踪测量方法，其响应时间只有一个采样时间间隔。实验表明，其准确度可满足实用要求。     

Flounders follow the tides to feed: Evidence from ultrasonic tracking in an estuary

Ultrasonically tagged flounders were tracked in the estuary of the River Bann, Northern Ireland, for periods of between 2 and 12 h (11 fish for a total of 92 h and 2·5 km), during their summer residence. Positions were determined by triangulation with two receivers.All fish remained within 400 m of the release point; on average flounders moved about 270 m during one tidal cycle, equivalent to 830 body lengths, or just over 1 body length per minute. Movements were most likely at dusk, but other parameters were not contingent upon time of day, although no data were gathered at dawn. Frequency, direction, distance, speed and duration of movement and turn rate were all significantly contingent upon state of the tide. The movement data are interpreted in terms of feeding behaviour, supported by results from other parts of the study. At high tide flounders made active but meandering searches for food on the inundated mudflats. Similar but faster searches heading downstream on falling tides reflected (a) completion of feeding while littoral invertebrates were still available and (b) avoidance of stranding. Flounders made infrequent but long and linear passages downstream at low tide, when they tended to bury themselves at the edge of the main channel where there was little food. Subsequently, the fish followed the rising tide upstream so that the cycle of movements kept most fish in the same area of the estuary in the short term. It is suggested that tolerance of changing salinities enables flounders, more than other flatfish species, to exploit dense populations of estuarine intertidal invertebrates as food.     

风暴单体识别与跟踪(SCIT)算法评估

利用兴义新一代多普勒天气雷达复合体扫资料及WSR-88D提供的风暴单体识别与跟踪(SCIT)算法对2007-2008年发生在贵州省黔西南地区的40次天气过程个例进行验证、分析,分别从单体识别、单体跟踪评估、单体位置预报、单体算法评估效果与季节关系分析、单体算法评估效果与距离关系分析、冰雹暴雨评估对比分析6个方面进行评估、分析。在充分考虑了当地地理环境、气候背景的前提下对算法评估不太理想的情况进行了误差分析,并进行了算法补偿,提出了解决的办法,一是降低识别阈值,将SCIT的7个反射率阈值降低一个等级,二是提取反射率因子垂直梯度,用上述两个改进方法对2007-2008年的40次天气过程重新进行评估,并与算法改进前的评估效果进行对比检验,结果表明,算法改进后评估效果有所提高。     

Algorithms and Software for Meteor Detection

An ever increasing variety of electronic instrumentation is being brought to bear in meteor studies and analysis, with unique meteor detection challenges arising from the attempt to do automated and near real-time processing of the imagery. Recent algorithm developments in the literature have been applied and implemented in software to provide reliable meteor detection in all-sky imagers, wide-field intensified video, and narrow field-of-view telescopic systems. The algorithms that have been employed for meteor streak detection include Hough transforms with phase coded disk, localized Hough transforms with matched filtering, and fast moving cluster detection. They have found application in identifying meteor tracks in the Spanish Fireball Network all-sky images, detailed analysis of video recordings during the recent Leonid meteor storms, and development of a detection/cueing technology system for rapid slew and tracking of meteors.