Modeling of turbidity dynamics caused by wind-induced waves and current in the Taihu Lake   总被引：3，自引：0，他引：3  

Ting-feng WU  Bo-qiang QIN  Guang-wei ZHU  Meng-yuan ZHU  Wei LI  Cheng-mei LUAN 《国际泥沙研究》2013,28(2):139-148

A simple turbidity model was developed with a sound physical basis based on in situ high-frequency observations of short-term, strong wind-induced sediment suspension in Taihu Lake, China. The validation results show that the model could successfully simulate turbidity caused by strong wind events, despite the relatively poor simulation accuracy for high values of turbidity caused by the entrainment of cyanobacteria by turbulence. The in situ observations and model simulation results indicate that the wind waves were within a narrow spectral band, with spectral energy mainly distributed within the 0.28–0.75 Hz band on opposite sides of the peak frequency. These high-frequency and low-energy wind waves are sensitive to depth filtering. However, the average depth of the lake is only 1.9 m, and wind waves still represent the main force of sediment suspension at the sediment-water interface. Moreover, lake currents were of significance to the maintenance of background turbidity in calm waves or ripples and in the determination of critical shear stress. By considering the spatial distribution of hydrodynamics and sediment, the model can be used to simulate the turbidity of the entire lake as well as boundary conditions for three-dimensional numerical models.  相似文献   

极地标本资源共享平台系统设计与实现   总被引：2，自引：0，他引：2       下载免费PDF全文

程文芳  张洁  夏明一  张北辰 《极地研究》2013,25(2):185-196

为了解决分布存储在全国各地的极地标本样品资源共享的问题,基于Python语言设计了具有数据发布、资源检索和申请审批等功能的极地标本资源共享平台信息系统,实现了极地标本样品的有效管理,目前已成功应用并对外服务。本文通过对系统重要功能模块的阐述介绍了系统设计与实现,最后对海量视频、查询推荐、图片检索、资源数据链等方面的问题进行了讨论。  相似文献   

A review of: “National Transfer Format,Release 1.0, January, 1987.” By THE WORKING PARTY TO PRODUCE NATIONAL STANDARDS FOR THE TRANSFER OF NATIONAL DIGITAL MAP DATA. (Southampton: The NTF Secretariat,Ordnance Survey, 1987. [Pp. 191: appendices and looseleaf annex.]     

HAROLD MOELLERING 《International journal of geographical information science》2013,27(3):289-292

Metonymically used location names (toponyms) refer to other, related entities and thus possess a meaning different from their literal, geographic sense. Metonymic uses are to be treated differently to improve the performance of geographic information retrieval (GIR). Statistics on toponym senses show that 75.06% of all location names are used in their literal sense, 17.05% are used metonymically, and 7.89% have a mixed sense. This article presents a method for disambiguating location names in texts between literal and metonymic senses, based on shallow features.

The evaluation of this method is two‐fold. First, we use a memory‐based learner (TiMBL) to train a classifier and determine standard evaluation measures such as F‐score and accuracy. The classifier achieved an F‐score of 0.842 and an accuracy of 0.846 for identifying toponym senses in a subset of the CoNLL (Conference on Natural Language Learning) data.

Second, we perform retrieval experiments based on the GeoCLEF data (newspaper article corpus and queries) from 2005 and 2006. We compare searching location names in a database index containing both their literal and metonymic senses with searching in an index containing their literal senses only. Evaluation results indicate that removing metonymic senses from the index yields a higher mean average precision (MAP) for GIR. In total, we observed a significant gain in MAP: an increase from 0.0704 to 0.0715 MAP for the GeoCLEF 2005 data, and an increase from 0.1944 to 0.2100 MAP for the GeoCLEF 2006 data.  相似文献   

Modelling the temporal element in land information systems     

STEPHEN PRICE 《International journal of geographical information science》2013,27(3):233-243

Abstract

This paper considers the use of a modern programming language (Modula-2) to develop a data model for a lot-based land information system. The emphasis is on the importance of maintaining the history of the lots, and a data model is developed which incorporates the history of each lot.  相似文献   

The design and implementation of SPIRIT: a spatially aware search engine for information retrieval on the Internet     

Ross S. Purves  Paul Clough  Christopher B. Jones  Avi Arampatzis  Benedicte Bucher  David Finch 《International journal of geographical information science》2013,27(7):717-745

Much of the information stored on the web contains geographical context, but current search engines treat such context in the same way as all other content. In this paper we describe the design, implementation and evaluation of a spatially aware search engine which is capable of handling queries in the form of the triplet of ?theme??spatial relationship??location?. The process of identifying geographic references in documents and assigning appropriate footprints to documents, to be stored together with document terms in an appropriate indexing structure allowing real‐time search, is described. Methods allowing users to query and explore results which have been relevance‐ranked in terms of both thematic and spatial relevance have been implanted and a usability study indicates that users are happy with the range of spatial relationships available and intuitively understand how to use such a search engine. Normalised precision for 38 queries, containing four types of spatial relationships, is significantly higher (p<0.001) for searches exploiting spatial information than pure text search.  相似文献   

Locating place names from place descriptions     

Maria Vasardani  Stephan Winter  Kai-Florian Richter 《International journal of geographical information science》2013,27(12):2509-2532

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一种温度相关的HY-2A散射计地球物理模型函数     

陈克海  解学通  张金兰  郑艳 《热带海洋学报》2022,41(2):90-102

利用散射计测量海面后向散射系数, 并通过地球物理模型函数(geophysical model function, GMF)反演得到海面风场。目前散射计风场反演所采用的GMF一般只考虑雷达极化方式、雷达入射角、风速和相对风向对海面后向散射系数的影响, 而相关研究表明海表温度(sea surface temperature, SST)对Ku波段散射计风场反演具有不可忽略的影响。文章利用海洋二号A卫星散射计(Haiyang-2A Scatterometer, HY2A-SCAT)后向散射系数观测值、欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts, ECMWF )再分析风矢量和SST数据, 采用人工神经网络方法, 建立起一种SST相关的GMF (TNGMF)。对TNGMF进行分析后发现, 海面后向散射系数随着SST的增加而增加, 并且其增加幅度与雷达极化方式、风速有关。为了对比, 文章使用相同数据集和相同方法建立了不包含SST的GMF (NGMF), 将美国国家航天航空局散射计-2 (National Aeronautics and Space Administration Scatterometer-2, NSCAT2) GMF、TNGMF和NGMF分别用于HY2A-SCAT风场反演实验。试验结果表明, 采用NSCAT2 GMF、NGMF反演得到的风速在低温时系统性偏小, 在高温时系统性偏大; 而TNGMF可较好地纠正SST对风速偏差均值的影响, 从而提高反演风场质量。  相似文献   

新源县复杂地形下的风电场风场结构特征分析     

艾力亚尔.艾海提  买买提艾力.买买提依明  刘军建  马玉芬  刘宗会  王豫 《沙漠与绿洲气象(新疆气象)》2024,18(5)

利用新源县风电场周边气象站及测风塔观测资料、ERA5-Land再分析资料和数值模拟结果,分析新源县风电场的风场结构特征。结果表明：（1）风电场周边气象站的逐小时10m风速均呈现出早、晚偏低,中午偏高的变化规律。喀拉布拉镇站和公安农场站的风向主要以东风和南风为主,肖尔布拉克沟站的风向则以南风为主。测风塔4302的风速随着高度变化不明显。测风塔4301-4306均存在南风和北风,但各风向占比有一定差异。随高度升高,测风塔南风风向呈现出东南转西南的趋势。（2）ERA5-Land资料不能很好地再现研究区域风场变化。（3）数值模拟的风场变化具有一定山谷风特征。夜间的风向以东南风为主,白天则低海拔河谷地带风吹向山顶,北部谷风逐渐主导东北风向。20时,风电场区域主要以西北风为主。  相似文献   

Wind technologies: Opportunities and barriers to a low carbon shipping industry     

《Marine Policy》2017

The abatement potential of wind technologies on ships is estimated to be around 10–60% by various sources. To date there has been minimal uptake of this promising technology, despite a number of commercially available solutions that have been developed to harness this free and abundant energy source. Several barriers have been referred to in the literature that inhibit uptake of energy efficiency measures in shipping. This paper provides a systematic analysis of the viability of wind technology on ships and the barriers to their implementation, both from the perspective of the technology providers and technology users (ship owner–operators), using the survey and the deliberative workshop method. The data generated from these methods is analysed using the qualitative content analysis method. The results show that whilst there is renewed interest in wind power, there are several common economic barriers that are hindering the mass uptake of wind technologies. Our analysis shows that third party capital is a plausible solution to overcoming the cost of capital, split incentives and information barriers that have contributed to inhibiting the uptake of wind technology in the shipping industry.  相似文献   

一次短时暴雨WP-3000边界层风廓线雷达回波分析   总被引：2，自引：0，他引：2  

郑石  黄兴友  李艳芳 《辽宁气象》2011,(3):6-11

运用风廓线雷达产品等对2010年7月20日南京浦口区短时暴雨过程进行分析。结果表明：根据风廓线雷达产品和多普勒雷达产品在暴雨过程中的表现特征,发现在整个降水过程的不同时间段,风廓线雷达产品的水平风廓线、信号噪声比、垂直气流和折射率结构常数,以及多普勒雷达产品的基本反射率、风廓线等均表现出非常明显的特征,并且两者产品有着较好的对应关系。利用雷达回波图像可以直观反映降水过程中大气的变化情况,证明了风廓线雷达产品对暴雨等强对流天气预测作用显著。  相似文献