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。     

路桥试验室仪器设备期间核查制约因素剖析

论述了仪器设备期间核查的目的和必要性,并对“如何理解、如何进行、如何看待”三个制约路桥试验室仪器设备期间核查的因素进行了剖析。     

Comparison of data envelopment analysis and deterministic parametric frontier approaches: an application in the Norwegian road construction sector

This paper analyzes efficiency in the Norwegian road sector by using two competing methods. The first is Data Envelopment Analysis (DEA), while the second is Deterministic Frontier Analysis (DFA) with a Cobb‐Douglas kernel specification. Both approaches show similarities with respect to efficiency distribution. The rock‐blasting sectors potential for efficiency improvement is in the range 19–59 percent. Both approaches demonstrate decreasing return to scale properties for the average unit. There is a significant correlation between size and efficiency indicating that larger units perform better than smaller ones. Precautionary blasting mainly performed in densely populated areas is also found to explain much of the variations in efficiency scores. Any policy implication should therefore carefully examine exogenous factors. The main difference between the two approaches, which can be explained by the number of parameters to be determined, concerns level of scores rather than their distribution. However, there are arguments that advocate DEA rather than DFA in the rock‐blasting sector.     

The net incidence of transit subsidies: a case study

The purpose of this paper is to investigate the net incidence of government subsidies to a transit system (i.e., the net impact of who pays and who benefits from transit subsidies). Rather than considering the U.S. transit subsidy program in the aggregate, the net incidence of subsidies to a particular transit system — Tidewater Regional Transit (TRT) — is analyzed. The paper concludes that the net incidence of the TRT subsidy program is progressive. Furthermore, the paper provides a methodology that can be used for investigating the net incidence of government subsidies to other transit systems.