云南土壤水分自动站观测值的业务化检验及其标准     

鲁韦坤  李湘  朱斌 《气象科技》2015,43(2):202-206

按照土壤水分自动站业务化检验标准对云南2010年建立的20个土壤水分自动站观测值进行了业务化检验,其中17个站点通过业务化检验。为评估业务检验合格站点的数据质量,对检验时段人工对比观测数据进行分析,由于检验时段多分布在雨季,大部分土壤层观测数据的样本标准差较小,导致检验后干季时的土壤自动站与人工观测结果误差较大。将各站点的土壤体积含水量绝对误差转换成土壤相对湿度误差后,土壤相对湿度误差值大于等于10%的土层占有效检验总数的24.4%;误差值小于6%的只占总数的41.2%。分析认为当前土壤水分自动站业务化检验的评判标准值得商榷和论证。  相似文献   

Monitoring of seismic events from a specific source region using a single regional array: A case study     

S.?J.?GibbonsEmail author  T.?Kv?rna  F.?Ringdal 《Journal of Seismology》2005,9(3):277-294

In the monitoring of earthquakes and nuclear explosions using a sparse worldwide network of seismic stations, it is frequently necessary to make reliable location estimates using a single seismic array. It is also desirable to screen out routine industrial explosions automatically in order that analyst resources are not wasted upon detections which can, with a high level of confidence, be associated with such a source. The Kovdor mine on the Kola Peninsula of NW Russia is the site of frequent industrial blasts which are well recorded by the ARCES regional seismic array at a distance of approximately 300 km. We describe here an automatic procedure for identifying signals which are likely to result from blasts at the Kovdor mine and, wherever possible, for obtaining single array locations for such events. Carefully calibrated processing parameters were chosen using measurements from confirmed events at the mine over a one-year period for which the operators supplied Ground Truth information. Phase arrival times are estimated using an autoregressive method and slowness and azimuth are estimated using broadband f{-}k analysis in fixed frequency bands and time-windows fixed relative to the initial P-onset time. We demonstrate the improvement to slowness estimates resulting from the use of fixed frequency bands. Events can be located using a single array if, in addition to the P-phase, at least one secondary phase is found with both an acceptable slowness estimate and valid onset-time estimate. We evaluate the on-line system over a twelve month period; every event known to have occured at the mine is detected by the process and 32 out of 53 confirmed events were located automatically. The remaining events were classified as “very likely” Kovdor events and were subsequently located by an analyst. The false alarm rate is low; only 84 very likely Kovdor events were identified during the whole of 2003 and none of these were subsequently located at a large distance from the mine. The location accuracy achieved automatically by the single-array process is remarkably good, and is comparable to that obtained interactively by an experienced analyst using two-array observations. The greatest problem encountered in the single array location procedure is the difficulty in determining arrival times for secondary phases, given the weak Sn phase and the complexity of the P-coda. The method described here could be applied to a wide range of locations and sources for which the monitoring of seismic activity is desirable. The effectiveness will depend upon the distance between source and receiver, the nature of the seismic sources and the level of regional seismicity.  相似文献   

Local Sensitivity Analysis of a Numerical Model of Volcanic Plinian Columns through Automatic Differentiation     

Isabelle Charpentier  Juan Manuel Espíndola 《Mathematical Geology》2005,37(1):95-113

Numerical simulation of geological phenomena are nowadays widely used to understand them. A good example are the numerous codes developed to model mass motion in different processes. Such models are approximations to the real phenomena because the physical conditions are simplified or because the values of the parameters intervening in the modeling are known only approximately. For this reason, an obligatory step in the application of these models is the assessment of their sensitivity to changes in the parameters. Sensitivity analysis is also required to evaluate the influence of the different input variables in the outcome of the model. In general this analysis is carried out by repeated computation of the model to different sets of input variables and settings of the model. A more fruitful procedure to carry out such analysis can be achieved by automatic differentiation. In this paper we illustrate such approach through its application to the model of an eruptive plinian column. The results of the analysis allow to assess, in a systematic and efficient manner, the relevance of the different boundary values and parameters of the model. The analysis reveals the effects on velocity, temperature, gas fraction, radius and ultimately column height, by changes in their boundary value (i.e. at the vent). The effect of changes in the value of the gas constants, density of pyroclasts and specific heat of the erupted material is also evidenced. Alternatively, the results can be regarded as a mean to estimate the values of the variables for different set of boundary values without recurring to new runs of the model. Automatic differentiation is shown to be a convenient scheme to obtain derivatives of model variables. This type of analysis forms in addition the basis for further work in inversion schemes.  相似文献   

气象服务文本产品的自动生成   总被引：2，自引：0，他引：2  

张京江  谭晓光 《气象科技》2004,32(Z1):36-39

目前气象信息文本的自动生成技术主要有2种基于文字替换的CWF(Computer-Worded Forecasting)技术和基于知识库的KBTG(Knowledge-Based Text Generation)技术.使用CWF技术进行文本的自动生成,技术较成熟、容易实现.文中阐述了使用CWF技术进行文本的自动生成过程中涉及的3个关键技术①自动、定时生成预报文本;②定义预报文本的输出格式;③使预报文本的表达更接近自然语言.  相似文献   

水下机器人运动的S面控制方法   总被引：32，自引：4，他引：32  

刘学敏  徐玉如 《海洋工程》2001,19(3):81-84

由于水下机器人的强非线性以及系统存在不确定性，同时考虑到港湾环境下水声的噪声大，因此，水下机器人进行精确作业时的运动控制一直是其实用化过程中困扰人们的问题，通常水下机器人的控制方式有PID控制器，神经网络控制器和模糊逻辑控制器三种，但是，由于这三种方法在实际应用中都存在一些参数难以确定的缺陷，为了解决这一问题，本文从模糊逻辑控制方式出发，借鉴PID控制的结构形式，推导出一种全新而简单有效的控制方法，定义为S面控制法，从水下机器人的水池试验和海上实验来看，不论是定点的控制精度还是运动过程中的控制效果都较令人满意，尤其是在风浪，潮流都比较大的海上实验中得到验证，鲁帮性很好。  相似文献   

柱对称双浮子波能装置散射问题的解析方法     

吴必军  郑永红  游亚戈  孙晓燕  陈勇 《海洋学报》2004,26(3):115-125

通过构造绕射势特解的一种新表达式,基于特征函数展开法提出了线性入射波作用下柱对称双振荡浮子波能装置散射问题的一种新的表达式,并在此基础上计算了垂向波浪激励力.从速度势的求解过程可知,绕射势和辐射势的计算量相当,但垂向波浪激励力的计算比采用Haskind关系方法简单得多,两种方法的结果一样.另外对不同工况下垂向波浪激励力的变化趋势进行了分析.  相似文献   

柔性尾鳍推进装置的机构综合与优化设计   总被引：1，自引：0，他引：1  

陈先国  向忠祥 《海洋技术学报》1997,16(3):32-37

根据柔性尾鳍推进装置所需达到的性能特性要求，本文对该装置进行了机构综合与优化设计，以改善其水动力性能，提高其推进效率。  相似文献   

状态空间模型在海洋波能转换系统中的应用 Ⅱ.单个矩形振荡浮子装置运动受力分析的解析方法     

郑永红  游亚戈  沈永明  吴必军  刘荣 《海洋学报》2004,26(1):113-124

对线性入射波作用下的矩形振荡浮子运动受力分析给出了一种新的解析方法.对该方法首先采用特征函数展开法得到绕射速度势的一种新解析式,然后直接由绕射势和入射势来计算波浪激励力.与经典方法相比可以看出,对于立面二维问题,由于绕射势和辐射势的计算量相当,因此该方法比过去常用的解析法更为简单.为了验证方法的正确性,采用该方法对过去文献介绍的经典算例进行了计算,得到了与过去方法完全一致的结果,从而证明该方法是正确的.  相似文献   

电子海图数据的自动更新     

李忠新 《海洋测绘》2005,25(4):56-57

介绍了中国海事电子海图数据发布现状，结合IHO电子海图数据保护方案(S-63)，提出了一种新的电子海图数据自动更新机制。  相似文献   

BD卫星星间链路定轨结果及分析   总被引：3，自引：3，他引：0  

宋小勇  毛悦  冯来平  贾小林  姬剑锋 《测绘学报》2017,46(5):547-553

我国新一代北斗导航系统试验卫星搭载了高精度星间链路载荷并已经得到了实测数据。本文给出了星间链路数据预处理方法,并介绍了星间链路数据独立定轨和星间Ka测量与L波段数据联合定轨的方法和初步结果。利用3颗试验卫星和1个地面Ka站在轨试验,结果表明:独立采用星间链路定轨,其结果 R方向误差小于0.5m;星间链路数据与L波段数据联合定轨,其对L波段定轨结果有显著改善,轨道R方向误差小于0.3m;星间测量设备时延标校精度优于0.1m。  相似文献