基于实例的GIS数据库模式匹配方法     

王育红  陈军 《武汉大学学报(信息科学版)》2008,33(1):46-50

针对空间数据库的特点,提出了一种改进的基于实例的层次式模式匹配方法,并解决了实体对应关系的自动建立、要素类相似性计算、属性相似性计算等问题.最后,通过实验验证了该方法的有效性.  相似文献   

Modelling of the vertical fluxes of nitric acid,ammonia, and ammonium nitrate     

Gerhard Kramm  Ralph Dlugi 《Journal of Atmospheric Chemistry》1994,18(4):319-357

Results from numerical investigations regarding the exchange of HNO₃, NH₃, and NH₄NO₃ between the atmosphere and the biosphere are presented. The investigations were performed with a modified inferential method which is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these nitrogen compounds. This modified inferential method calculates the micrometeorological quantities (such as the friction velocity and the fluxes of sensible and latent heat), the height-invariant fluxes of the composed chemically conservative trace species with group concentrationsc ₁=[HNO₃]+[NH₄NO₃] (total nitrate),c ₂=[NH₃]+[NH₄NO₃] (total ammonia), andc ₃=[HNO₃]-[NH₃] as well as the fluxes of the individual nitrogen compounds. The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The modified inferential method requires only the data of wind velocity, temperature, humidity and concentrations (HNO₃, NH₃, and NH₄NO₃) measured at a reference height by stations of a monitoring network.  相似文献   

地理学的特点     

李容全  邱维理 《地理与地理信息科学》2006,22(6):79-82

现代地理学强调过程与演变的研究,在定量研究方面取得了显著的进步。但在热衷于建立各种模型时,地理学的特点或性质却被忽视,这在国内尤其明显。认识地理学的本质特点,对于学习地理学、发展地理学科和从事地理学研究非常重要。地理学的特点可概括为4方面:即地理学是“研究行星地球表面的科学”、“研究关系的科学”、“强调位置的科学”和“考察分布的科学”。这4个方面缺少任何一方,都不能反映有别于其他任何学科的地理学自身的特点。  相似文献   

Tectonic relation between northeastern China and the Korean peninsula revealed by interpretation of GRACE satellite gravity data   总被引：2，自引：0，他引：2  

Sungchan Choi  Chang-Whan Oh  Herrmann Luehr 《Gondwana Research》2006,9(1-2):62

The major continental blocks in northeastern Asia are the North China block and the South China block, which have collided starting from the Korean peninsula. Geologic and geophysical interpretations reveal a well defined suture zone in northeastern China from Qinling through Dabie to Jiaodong. The discovery of high-pressure metamorphic rocks in the Hongseong area of the Korean peninsula, prominent evidence for the collision zone, indicates extension of the collision zone in northeastern China into the Korean peninsula. Interpretation of the GRACE satellite gravity dataset shows two prominent structural boundaries in the Yellow Sea. One extends from the Jiaodong Belt in eastern China to the Imjingang Belt in the Korean peninsula. The other extends from near Nanjing, eastern China, to Hongseong. Tectonic movement in or near the suture zone may be responsible for seismic activity in the western Korean peninsula and the development of the Yellow Sea sedimentary basin.  相似文献   

Seaweed floristic studies along tsunami affected Indian coasts: A litmus test scenario after 26th December 2004     

Vaibhav A Mantri 《Journal of Earth System Science》2006,115(3):371-378

On 26th December 2004, the world witnessed the devastating power of tsunami, affecting many countries, bordering the Indian Ocean region. This has caused significant changes in the shallow and intertidal regions of the Indian coast, especially the Andaman and Nicobar Islands, Tamil Nadu, Kerala and Pondicherry. The baseline data on biomass availability and distribution of benthic intertidal seaweed species were collected immediately after this catastrophic event by spot surveying 11 selected localities of the above-mentioned regions. In all, 45 species belonging to 31 genera were recorded during the present survey, the maximum number of seaweed species were recorded at Thirumullavarum, Kerala with the minimum at Car Nicobar, Andaman and Nicobar Islands. A very different trend was observed in the case of biomass availability at some locations which was due to the influence of habitat suitability over the tsunami damage. The details of this study have been provided in the present communication  相似文献   

Townsend's Hypothesis, Coherent Structures And Monin–Obukhov Similarity     

K. G. McNaughton  Yves Brunet 《Boundary-Layer Meteorology》2002,102(2):161-175

Townsend's hypothesis states that turbulence near a wall can be divided into an activepart that transports momentum, and an inactive part that does not, and that these twokinds of turbulence do not interact. Active turbulence is generated by wind shear and has properties that scale on local parameters of the flow, while inactive turbulence isthe product of energetic processes remote from the surface and scales on outer-layerparameters. Both kinds of motion can be observed in the atmospheric surface layer, soMonin–Obukhov similarity theory, which is framed in terms of local parameters only,can apply only to active motions. If Townsend's hypothesis were wrong, so that activeand inactive motions do interact in some significant way, then transport processes nearthe ground would be sensitive to outer-layer parameters such as boundary-layer depth,and Monin–Obukhov theory would fail.Experimental results have shown that heat transport near the ground does depend onprocesses in the outer layer. We propose a mechanism for this whereby inactive motionsinitiate active, coherent ejection/sweep structures that carry much of the momentum andheat. We give evidence that the inactive motions take the form of streak patterns of fasterand slower air, and argue that these are induced by the pressure effects of large eddiespassing overhead. The streak pattern includes regions where faster streams of air overtakeand engulf slower-moving streaks. Transverse vortices form across the spines of the streaksat these places and some of them develop into horseshoe vortices. These horseshoe vorticesgrow rapidly and are rotated forward in the sheared flow so they soon contact the ground,squirting the air confined between the legs of the horseshoe vortex outwards as a forcefulejection. This model is consistent with a wide range of results from the field and laboratoryexperiments. Heat transport is significantly affected, so undermining the dimensionalassumptions of Monin–Obukhov similarity theory.  相似文献   

Atmospheric nitrogen inputs into the North Sea: effect on productivity     

Gerrit de Leeuw  Lucinda Spokes  Tim Jickells  Carsten Ambelas Skjth  Ole Hertel  Elisabetta Vignati  Susanne Tamm  Michael Schulz  Lise-Lotte Srensen  Britta Pedersen  Laura Klein  K. Heinke Schlünzen 《Continental Shelf Research》2003,23(17-19):1743

The ANICE (Atmospheric Nitrogen Inputs into the Coastal Ecosystem) project addressed the atmospheric deposition of nitrogen to the North Sea, with emphasis on coastal effects. ANICE focused on quantifying the deposition of inorganic nitrogen compounds to the North Sea and the governing processes. An overview of the results from modelling and experimental efforts is presented. They serve to identify the role of the atmosphere as a source of biologically essential chemical species to the marine biota. Data from the Weybourne Atmospheric Observatory (UK) are used to evaluate the effect of short episodes with very high atmospheric nitrogen concentrations. One such episode resulted in an average deposition of 0.8 mmol N m⁻² day⁻¹, which has the potential to promote primary productivity of 5.3 mmol C m⁻² day⁻¹. This value is compared to long-term effects determined from model results. The total calculated atmospheric deposition to the North Sea in 1999 is 948 kg N km⁻¹, i.e. 0.19 mmol N m⁻² day⁻¹ which has the potential to promote primary productivity of 1.2 mmol C m⁻² day⁻¹. Detailed results for August 1999 show strong gradients across the North Sea due to adjacent areas where emissions of NO_x and NH₃ are among the highest in Europe. The average atmospheric deposition to the southern part of the North Sea in August 1999 could potentially promote primary production of 2.0 mmol C m⁻² day⁻¹, i.e. 5.5% of the total production at this time of the year in this area of the North Sea. For the entire study area the atmospheric contribution to the primary production per m² is about two-third of this value. Most of the deposition occurs during short periods with high atmospheric concentrations. This atmospheric nitrogen is almost entirely anthropogenic in origin and thus represents a human-induced perturbation of the ecosystem.  相似文献   

The colonization of periphytic diatom species on artificial substrates in the Ashar canal, Basrah, Iraq   总被引：1，自引：0，他引：1  

H.A. Hameed 《Limnologica》2003,33(1):54-61

Studies have been conducted between March 1993 and March 1994 in the Ashar canal, a backwater of the Shatt al-Arab River, Iraq. Using artificial substrates, the colonization and development of seventy-five diatom species belonging to twenty genera could be revealed. Taxa apportionment varied seasonally as well as within each season. A few species have been found during all experiments. These are Amphora ovalis, Bacillaria paradoxa, Cocconeis placentula var. euglypta, Cyclotella meneghiniana, Cymbella ventricosa, Navicula tripunctata var. schizonemoides, Rhoicosphenia curvata, and Synedra ulna. The occurrence of B. paradoxa in Experiment 1 (March-April 1993) and Experiment 4 (end of January to beginning of March 1994) was higher than 50%. Similarity of species increased towards the end of each season, and the communities from experiments 1 and 4 were more similar than others. The experiments also suggest that week 4 represents the equilibrium phase while week 6 reflects the increase in biological interactions. The results could also indicate the sequence of primary colonizers and the community development towards the equilibrium.  相似文献   

影像匹配中几种相似性测度的分析   总被引：8，自引：3，他引：8  

山海涛  郭建星  耿则勋 《测绘信息与工程》2003,28(4):11-13

对基于灰度影像匹配中的几种相似性测度进行了研究，分析了每种测度的直观意义、限制条件以及改进措施，最后通过实验结果验证了上述结论。  相似文献   

特定基准下的异常位移诊断   总被引：1，自引：0，他引：1  

独知行  欧吉坤  柴艳菊  韩保民 《武汉大学学报(信息科学版)》2003,28(5):569-572

针对地壳运动和变形研究中存在的位移资料的参考基准、异常位移等问题，主要讨论了位移资料特定基准的转换和异常位移诊断的数学模型——特定基准转换模型为七参数相似变换模型，转换保持了变形体内部相对位置关系不变，并使转换后的位移矢量更能体现区域内的相对运动信息；异常位移诊断采用拟准检定法(QUAD)，在选定拟准观测的情况下，使得位移真误差具有明显的分群性；模拟算例结果显示，本文采用的线性变换模型、粗差拟准检定法都表现出很好的效果。  相似文献