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991.
基于遥感与GIS技术的城镇体系空间特征的分形分析--以绍兴市为例 总被引:20,自引:5,他引:15
在遥感技术与GIS技术的支持下,采用分形几何理论对绍兴市城镇体系空间结构特征和形态特征进行分析,探讨城镇体系的演化规律。研究表明,绍兴市城镇体系无论在空间结构上还是在空间形态上都具有分形特征。城镇分布密度由绍兴市区向周围逐渐衰减,且分布不均衡,具有向交通线集中的趋势,形成了优化的空间结构。但1984~1997年间,空间结构的演化趋向于围绕绍兴市在半径方向上均匀分布,分形特性减弱。此外,各城镇基本是以各自的中心逐渐向外扩展,空间关联性大致不变。空间形态则日趋复杂,稳定性越来越低,发展的随意性越来越大。绍兴市区这一特点更明显。 相似文献
992.
Characteristics and formation causes of Qingdao Cold Water Mass 总被引:2,自引:0,他引:2
In this work,the main characteristics of the Qingdao Cold Water Mass were studied by using“the comparison analysis method”based on 1980 temperature,salinity and dissolved oxygen data on the western South Yellow Sea.The formation cause of the water mass was analyzed based on February of 1959 temperature and salinity data for this area and on some other authors’studies.The results showed that the Qingdao Cold Water Mass has growing and vanishing processes:appears in the last ten days of March;has stable pattern in April;is biggest in its area in May;becomes small in its area in June;vanishes in July.It comes from the northem Shandong Coastal Water and is characterized by low temperature and salinity and high disolved oxygen.The mass is formed under the joint effects of anticyclonic circulation and solar radiation. 相似文献
993.
Djuro Novakovic Christopher D. White Rucsandra M. Corbeanu William S. Hammon III Janok P. Bhattacharya George A. McMechan 《Mathematical Geology》2002,34(7):857-893
Ground-penetrating radar (GPR) surveys, outcrop measurements, and cores provide a high-resolution 3D geologic model to investigate the hydraulic effects of shales in marine-influenced lower delta-plain distributary channel deposits within the Cretaceous-age Ferron Sandstone at Corbula Gulch in central Utah, USA. Shale statistics are computed from outcrop observations. Although slight anisotropy was observed in mean length and variogram ranges parallel and perpendicular to pale of low
, the anisotropy is not statistically significant and the estimated mean length is 5.4 m. Truncated Gaussian simulation was used to create maps of shales that are placed on variably dipping stratigraphic surfaces interpreted from high-resolution 3D GPR surveys, outcrop interpretations, and boreholes. Sandstone permeability is estimated from radar responses calibrated to permeability measurements from core samples. Experimentally designed flow simulations examine the effects of variogram range, shale coverage fraction, and trends in shale coverage on predicted upscaled permeability, breakthrough time, and sweep efficiency. Approximately 1500 flow simulations examine three different geologic models, flow in the 3 coordinate directions, 16 geostatistical parameter combinations, and 10 realizations for each model. ANOVA and response models computed from the flow simulations demonstrate that shales decrease sweep, recovery, and permeability, especially in the vertical direction. The effect on horizontal flow is smaller. Flow predictions for ideal tracer displacements at Corbula Gulch are sensitive to shale-coverage fraction, but are relatively insensitive to twofold variations in variogram range or to vertical trends in shale coverage. Although the hydraulic effects of shale are statistically significant, the changes in flow responses rarely exceed 20%. As a result, it may be reasonable to use simple models when incorporating analogous shales into models of reservoirs or aquifers. 相似文献
994.
The directionality of thermal radiance of a homogeneous isothermal non-black plane surface is totally decided by its directional emissivity, which depends on the complex dielectric constant and roughness of surface. It can be expressed by This paper proves that it is necessary to express emissivity by a matrix when a target becomes an inhomogeneous non-isothermal open complex with complicated inner geometric structure. The matrix describes the inner radiative interaction among components accurately and also expresses its thermal radiative directionality and structural characteristics completely. Advantages of matrix expression are as follows: first, the physical mechanics of effective emissivity of an open complex is described in a simple and perfect way; second, it becomes easy to understand the principle and method to retrieve components temperature from multi-angle thermal remotely sensed data; and third, the differences of directionalities between an open complex and a homogeneous isothermal non-black plane body are expressed by just using an effective emissivity matrix instead of an emissivity vector. Formula in classic physics is only the special case of matrix expression; therefore, the matrix is a universal unconditional expression to describe the directionality of thermal radiance. 相似文献
995.
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998.
华北地区地震异常前兆信息场演化特征及其与地震关系的研究 总被引:7,自引:1,他引:6
在对地震异常前兆信息量先前研究的基础上,进一步给出了描述各种地震异常前兆信息量的普适性综合数学表达式.从大量震例资料入手,再次研究了地震异常延续有效性的问题,进而建立了地震异常持续有效时间与延续有效时间的数学关系式.收集整理了1980~1997年华北地区水化、形变、地磁、应力、水位、地电等371个观测项目、上百万个前兆观测数据,对每一观测项目逐一计算了它们的地震异常前兆信息量.研究了华北地区近20年的地震异常前兆信息场的演化特征及其与地震的关系,建立了华北地区Ms≥5地震的中短期综合预报指标体系,经R值评分检验,表明该地震综合预报指标体系在中短期地震预测中具有一定效果. 相似文献
999.
Based on self-organizing map, a method that can perform cluster analysis and discrimination analysis in one step is proposed in this paper. Using the proposed method, one can view the relative topological relationships of input patterns, determine the proper number of clusters, and assign unknown patterns to known clusters without losing any information of input patterns. Regarding the capability of determining the proper number of clusters, the proposed method is superior to conventional cluster analysis. The discrimination results also show that the assignments of unknown patterns to known clusters are reasonable using the proposed method. The advantages of the proposed method are also demonstrated by an application to the hydrological factors affecting low-flow duration curves in southern Taiwan. 相似文献
1000.
Excessive inputs of phosphorus and nitrogen are the main reasons of eutrophication of inland waters and coastal areas. Large efforts have been made to control phosphorus, but the measures to reduce nitrogen emissions failed at least partly. While it was possible to reduce nitrogen emissions from industry and municipal wastewater treatment plants, diffuse sources are showing only very minor decline. Examples of limnetic, marine and coastal systems are given to review the current knowledge about nitrogen transformation and the effects of nitrate in the environment. When N is the limiting nutrient in a particular water body, this does not necessarily mean that phytoplankton is controllable by NO3– removal. In systems with problems due to a high redox‐sensitive internal phosphorus load and under certain constraints, nitrate may be used as an ecotechnological measure to prevent anaerobic phosphorus release from sediments. Model simulations are used to demonstrate this. A schematic model of redox‐mediated temporal phosphorus storage in riverine lake sediments with short retention time is proposed. We conclude that while anthropogenic nitrogen emissions are a global problem, no fast and simple single solution exists. Additional nitrogen removal in wastewater treatment will have no effect, as long as diffuse sources and nitrate concentrations in groundwater remain at a high level. Emission reductions should be achieved in an integrated way, taking direct and indirect effects into account. In this sense, case by case decisions and a new definition of “sensitive areas” are required. 相似文献