航海问卷调查中不完全数据的补缺方法研究

探讨期望最大化(Expectation Maximization,EM)算法在处理不完全数据统计中的应用,通过EM补缺,扩大统计样本数量,以避免航海科研中常常发生的问卷调查数据的缺失而造成统计分析的困难,从而提高了参数估计精度。然后运用电子表格方法对一个实例进行描述、建模和求解,避免了繁琐的计算和编程工作,为广大航海科研与实践管理工作者提供一种方便、有效的数据处理方法。     

一种新型的船舶航行试验系统

船舶航行实验是船舶完工以后,验收时按规定进行交船试验的重要部分。传统的试验方法是通过GPS定位、人工测量和记录,再进行分析,耗费许多人力、物力。本试验方法是在GPS定位技术、电子海图技术、计算机处理技术基础上设计的新型试验系统。在航行试验时由GPS获取实时的位置信息,将位置信息显示到电子海图上,另外由数据库存储试验数据,试验结束时由计算机自动处理得出试验结果并可打印。使用情况表明该系统可以准确、方便地完成航行试验,试验结束后还可以离线分析,为未来的船舶设计积累相关的资料。     

论遥感数据的模糊不确定性及基于Rough集的处理方法

从遥感信息的处理过程、遥感信息的本身特点以及遥感成像3个方面论证遥感数据的不确定性。造成遥感数据不确定性的主要因素包括:图像的几何畸变、传感器系统工作不稳定、遥感数据分类的准确率、遥感统计模式识别、外界条件影响、误差积累等。遥感数据模糊不确定性则来自于数据边界判别、数据的复杂性、遥感成像技术水平和遥感影像解释等方面。提出用Rough集理论处理遥感数据的模糊不确定性的方法,并以一矿区的TM图像为例,分析开采沉陷形态。分析结果与实地情况吻合,表明用Rough集理论处理,简单直观,结果更具有科学性和合理性。     

The Mercator global ocean operational analysis system: Assessment and validation of an 11-year reanalysis

This paper presents Prototype Système 2 Global (PSY2G), the first Mercator global Ocean General Circulation Model (OGCM) to assimilate along-track sea level anomaly (SLA) satellite data. Based on a coarse resolution ocean model, this system was developed mainly for climatic purposes and will provide, for example, initial oceanic states for coupled ocean-atmosphere seasonal predictions. It has been operational since 3 September 2003 and produces an analysis and a two-week forecast for the global ocean every week. The PSY2G system uses an incremental assimilation scheme based on the Cooper and Haines [Cooper, M., Haines, K., 1996. Data assimilation with water property conservation. J. Geophys. Res., 101, 1059-1077.] lifting–lowering of isopycnals. The SLA increment is obtained using an optimal interpolation method then the correction is partitioned into baroclinic and barotropic contributions. The baroclinic ocean state correction consists of temperature, salinity and geostrophic velocity increments and the barotropic correction is a barotropic velocity increment. A reanalysis (1993–2003) was carried out that enabled the PSY2G system to perform its first operational cycle. All available SLA data sets (TOPEX/Poséïdon, ERS2, Geosat-Follow-On, Jason1 and Envisat) were assimilated for the 1993–2003 period. The major objective of this study is to assess the reanalysis from both an assimilation and a thermodynamic point of view in order to evaluate its realism, especially in the tropical band which is a key region for climatic studies. Although the system is also able to deliver forecasts, we have mainly focused on analysis. These results are useful because they give an a priori estimation of the qualities and capabilities of the operational ocean analysis system that has been implemented. In particular, the reanalysis identifies some regional biases in sea level variability such as near the Antarctic Circumpolar Current, in the eastern Equatorial Pacific and in the Norwegian Sea (generally less than 1 cm) with a small seasonal cycle. This is attributed to changes in mean circulation and vertical stratification caused by the assimilation methodology. But the model's low resolution, inaccurate physical parameterisations (especially for ocean–ice interactions) and surface atmospheric forcing also contribute to the occurrence of the SLA biases. A detailed analysis of the thermohaline structure of the ocean reveals that the isopycnal lifting–lowering tends to diffuse vertically the main thermocline. The impact on temperature is that the surface layer (0–200 m) becomes cooler whereas in deeper waters (from 500 to 1500 m), the ocean becomes slightly warmer. This is particularly true in the tropics, between 30°N and 30°S. However it can be demonstrated that the assimilation improves the variability in both surface currents and sub-surface temperature in the Equatorial Pacific Ocean.     

TDCS的D/D结合及交叉互控方案

不同制式TDCS的结合有2种方式：D／D结合方式和交叉互控方式。就这2种结合方式的目的、结构、原理、技术要点进行了分析和讨论，并根据在成都铁路局应用的经验，实际比较了其优缺点，旨在为同类系统的实现提供参考。     

列车气动试验数据的知识化研究

采用基于专家库逻辑推理的试验数据知识提取方法来发现和挖掘试验数据。构建基于规则表示的特征关联专家库,建立列车气动试验数据知识化提取系统模型,采用面向对象的程序设计思想初步实现了这一系统,在试验数据处理的实践中逐步实现"试验数据可视化 知识提取 试验报告"的信息智能反馈。     

LBS空间数据内容与管理方法

LBS空间数据的管理和数据库建立是LBS定位服务系统的核心。本文在论述了LBS系统各个部分的构成的基础上,探讨了LBS空间数据库管理的具体内容,设计了基于Oracle Spatial对象关系型数据库的LBS空间数据存储与管理的方法,设计和开发了面向对象的空间数据引擎,研究了LBS数据通过空间数据引擎上传到Oracle Spatial的技术。     

基于OLAP的数据仓库模型的探讨

随着跨领域产业的出现和各领域知识的互相渗透,企业决策所需要的数据量越来越庞大。一个企业的数据仓库包含了该企业运作的所有历史数据,有效地构建和使用数据仓库为企业人做出决策提供更优越的平台。本文提出基于OLAP的数据仓库的设计方案,并对雪花模式和星型模式的优缺点进行详细论述。     

轨道质量指数计算问题的探讨

由于缺乏去除功能,轨检车检测信号中存在的噪音包含在轨道质量指数(TQI)检测结果中,不利于轨道质量状态的客观评价,并影响编制维修计划。为此,提出在轨检车主机中,将1m轨向和低速时轨向作为噪音处理、将相邻检测数据差大于4mm时作为噪音处理的两种方法,并针对后种方法处理噪音不彻底的问题,提出将波形整体作为噪音处理的方法。考虑到主机传输到编辑机中的数据中仍会存在噪音并需进行人工删除的实际,提出在编辑机中重新计算各单项不平顺标准差与TQI的算法。结果表明:上述去除噪音的方法可行有效,可以大大提高TQI计算精度。     

一种柴油机台架试验数据采集系统的设计

利用信息技术实现柴油机台架试验的自动测试和数据采集,使性能试验的精确度及工作效率大大提高。介绍一种船舶柴油机台架试验中的数据采集系统。经现场试验,证明该系统工作稳定可靠,满足实用要求。