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471.
SVG作为移动互联时代获得各种丰富图形信息的有效表达方法,已成为LBS中空间信息表达与描述的热点应用之一,但目前的研究大多没有考虑多源数据格式向SVG格式转换后的图像质量评价问题。针对多源空间数据向SVG格式转换方法和转换效果评价技术,本文设计了栅格数据和矢量数据向SVG格式转换的表达方法,分别利用直接载入栅格图像和编程实现矢量数据转换的方法实现了多源空间数据向SVG格式的有效转换;从定性与定量相结合的角度分析了转换前后的图像质量,设计了角点检测评价指标和流程,提出了基于Harris角点检测的SVG转换前后图形几何质量的评价方法。实验证明:SVG格式比较适用于位置服务中对空间数据尤其是矢量数据的表达,经过SVG转换后的图像,无论是栅格数据还是矢量数据都具有较高的图像质量,且栅格数据的转换效果相对略差于矢量数据;验证了一种基于SVG的移动位置空间服务信息表达和组织模式,对普及和强化SVG在位置服务系统中的应用具有一定的推动作用。 相似文献
472.
Performance of a regional climate model (RCM), WRF, for downscaling East Asian summer season climate is investigated based on 11-summer integrations associated with different climate conditions with reanalysis data as the lateral boundary conditions. It is found that while the RCM is essentially unable to improve large-scale circulation patterns in the upper troposphere for most years, it is able to simulate better lower-level meridional moisture transport in the East Asian summer monsoon. For precipitation downscaling, the RCM produces more realistic magnitude of the interannual variation in most areas of East Asia than that in the reanalysis. Furthermore, the RCM significantly improves the spatial pattern of summer rainfall over dry inland areas and mountainous areas, such as Mongolia and the Tibetan Plateau. Meanwhile, it reduces the wet bias over southeast China. Over Mongolia, however, the performance of precipitation downscaling strongly depends on the year: the WRF is skillful for normal and wet years, but not for dry years, which suggests that land surface processes play an important role in downscaling ability. Over the dry area of North China, the WRF shows the worst performance. Additional sensitivity experiments testing land effects in downscaling suggest the initial soil moisture condition and representation of land surface processes with different schemes are sources of uncertainty for precipitation downscaling. Correction of initial soil moisture using the climatology dataset from GSWP-2 is a useful approach to robustly reducing wet bias in inland areas as well as to improve spatial distribution of precipitation. Despite the improvement on RCM downscaling, regional analyses reveal that accurate simulation of precipitation over East China, where the precipitation pattern is strongly influenced by the activity of the Meiyu/Baiu rainfall band, is difficult. Since the location of the rainfall band is closely associated with both lower-level meridional moisture transport and upper-level circulation structures, it is necessary to have realistic upper-air circulation patterns in the RCM as well as lower-level moisture transport in order to improve the circulation-associated convective rainfall band in East Asia. 相似文献
473.
Summary The diurnal variations of water vapor in central Japan were investigated with GPS-derived precipitable water (PWV) and surface
meteorological data as classified to three kinds of locations. Twenty-five clear days in central Japan in August 2000 were
investigated to clarify the role of water vapor in the nocturnal maximum in the diurnal cycle of convective rainfall. The
diurnal variations of PWV and some meteorological factors were composite during the selected days at 6 stations. The PWV shows
a clear diurnal cycle with the amplitude of 3.4 mm to 8.8 mm and changes little during the period from the morning to noon.
The daily amplitude of PWV is the largest in basin and smallest in plain although mean of PWV keeps high value in plain. A
typical feature of the diurnal variation in central Japan is a maximum appearing in the evening. The time of maximum is from
1800 LST to 2000 LST, and minima appears at noon nearly in mountainous area and basin, while in early morning in plain. The
diurnal maximum of PWV appears earlier in mountainous region than in plain.
A diurnal cycle of specific humidity can be observed in all locations, and the amplitude in mountainous region is especially
large compared with that in basin and plain. It is important to notice that there are remarkable differences in specific humidity
among the six stations. The results suggest that the diurnal variation of PWV seems to be strongly affected by the local thermal
circulations generated by the topography around these stations. The moisture transport causes the differences in phase of
the diurnal cycle of PWV between different locations as well as the phase difference in precipitation. A very clear diurnal
variation in surface air temperature is similar to that of solar radiation, with a minimum in the morning and a maximum in
early afternoon. Maximum of surface wind speed are corresponded to peak of precipitation very well. It can be concluded that
the amplitude of solar radiation increases with altitude as opposed to the situation of PWV generally.
The precipitation observed frequently in the evening also shows a similar diurnal variation to that of the PWV, indicating
the peak of precipitation appearing in late afternoon or in the evening over central Japan. Meanwhile the PWV reaches its
nocturnal maximum. There is a good relationship between the diurnal cycle of observed precipitation and that of the PWV.
Authors’ addressess: Guoping Li, Department of Atmospheric Sciences, Chengdu University of Information Technology, #3 Section
3, Ren Min Nan Road, Chengdu, Sichuan 610041, P.R. China; Dingfa Huang, Department of Surveying Engineering, Southwest Jiaotong
University, Chengdu, China; Fujio Kimura, Tomonori Sato, Institute of Geoscience, University of Tsukuba, Tsukuba, Japan. 相似文献
474.
475.
Large-eddy simulations are conducted to investigate the effects of the incoming turbulent structure of the flow on pollutant removal from an ideal canyon. The target canyon is a two-dimensional street canyon with an aspect ratio of 1.0 (building height to street width). Three turbulent flows upwind of the street canyon are generated by using different block configurations, and a tracer gas is released as a ground-level line source at the centre of the canyon floor. Mean velocity profiles for the three flows are similar, except near the roof. However, the root-mean-square values of the velocity fluctuations and the Reynolds shear stress increase with the friction velocity of the incoming turbulent flow. The spatially-averaged concentration within the canyon decreases with increasing friction velocity. Coherent structures of low-momentum fluid, generated above the upwind block configurations, contribute to pollutant removal, and the amount of pollutant removal is directly related to the size of the coherent structure. 相似文献
476.
Agawa gold prospect, located in Yamaguchi Prefecture, southwestern Japan, is a small prospect, where placer gold has been explored and mined since the 17th century. We investigated the prospect to clarify the genesis of the deposit based on the geology, hydrothermal alteration, geochronology, and ore mineralogy. The main mineralized zone of the prospect has a horizontal and vertical extensions of 500 m and 100 m, respectively, and a width of less than 100 m. Gold mineralization in the prospect occurs as dissemination and stockwork veinlets in the intensely sericitized rocks at the apical part of the Agawa dioritic porphyry intrusion at 86.5–88.5 Ma. Mineralization is typified by at least three stages – an early stage characterized by the occurrence of pyrrhotite and native gold; a middle stage by chalcopyrite; and a late stage by pyrite–bornite. Mineral assemblage and fluid inclusion microthermometry estimation suggest a trend of decreasing temperatures from 400°C to 160°C at a constant sulfur fugacity. The mineralizing fluids formed by the mixing of a hypogene fluid of possibly magmatic origin with an external lower‐temperature and lower‐salinity fluid. The mixing process decreased the temperature and salinity of the fluid, resulting in the precipitation of sulfides, native gold and Bi–Te alloys and sulfosalts. The magnetite‐series signature of the Agawa porphyry and related molybdenite‐bearing mineralization indicate that the plutonism of the San‐in granitoids belt extends to the westernmost end of the Honshu Island. The compiled geochronology and distribution of the metallic deposits in the southwestern Japan arc show that transition from ilmenite‐series to magnetite‐series plutonism started earlier in the west, and shifted eastwards with time during the period from Late Cretaceous to Paleogene. 相似文献
477.
Manganese oxides precipitated from aerated well sea water at the Marine Science Museum, Tokai University, have been analyzed chemically and mineralogically. The ratios are lower in todorokite than in birnessite but these minerals have similar contents of minor transition metals, which can be taken up additionally from sea water after the precipitation of Mn oxides. On the basis of these results, the genesis of Mn minerals is discussed in relation to marine Mn nodules. 相似文献
478.
Yudai Sato Kazuhiko Kano Takeshi Ohguchi Teiji Yamazaki Kenshiro Ogasawara 《Sedimentary Geology》2009,220(3-4):218
The Early Miocene Tateyamazaki Dacite infills a 3.2 km diameter caldera. It comprises poorly sorted, massive, biotite-bearing dacite pumice lapilli tuff, in which huge blocks of densely welded dacite lapilli tuff, basaltic andesite lava, and other lithologies are commonly set. Dense blocks are variably cracked and intruded by the host lapilli tuff. Sparse blocks of bedded lapilli tuff and tuff are variably disaggregated to intermingle with the host rocks or are plastically deformed into irregular shapes. Rootless tuff veins millimeters to 30 cm thick are developed within the host rocks, mainly dipping at 10–30°, and are locally branched and mutually cut to form a network. Where thicker, they are stratified and locally carry accidental fragments. Accidental lapilli up to 2 or 3 cm wide and 30 cm long are locally set in near-vertical and variably sinuous arrays. Although poorly defined they are reminiscent of fluid escape structures. The host pumice lapilli tuff, however, retains in part a thermal remnant magnetization (TRM) vector stable at temperatures above 280 °C. Blocks in the caldera fill also retain TRM but the vectors are rotated significantly from those of the host pumice lapilli tuff and the adjacent volcanic rocks. Tateyamazaki Dacite is thus likely to have been emplaced at high temperatures, and intermingled with shattered basement rocks and ambient water to be partly liquefied within the caldera immediately after or during the caldera-forming eruption. 相似文献
479.
High-pressure experiments have been carried out at 11-22 kbar and 900-1200°C using a piston cylinder apparatus to constrain the thermal peak condition of a granulite characterized by the mineral assemblage of orthopyroxene+sillimanite+quartz from McIntyre Island, Enderby Land, East Antarctica. The bulk composition of the starting material is 85 wt.% McIntyre granulite+15 wt.% sillimanite. At 11 kbar, orthopyroxene, sillimanite and quartz are stable below 1000°C. At 1050°C sillimanite does not appear, and sapphirine coexists with orthopyroxene and quartz. These experimental results indicate that the McIntyre granulite has undergone the ultra high-temperature metamorphism at 1000-1050°C represented by the diagnostic mineral assemblage of orthopyroxene, sillimanite and quartz. 相似文献
480.
递归网格排序算法sort-tile -recursivestr是一种性能优良的静态变体其构建效率高效查询性能较为优良但是没有很好的兼顾到数据本身的聚集特性 hilbert曲线具有较好的数据聚集特性但是存在一定信息的丢失 本文利用hilbert曲线的聚集性来提高str-树的数据聚集性能提出了一种基于hilbert编码的str索引改进算法并在改进中弥补信息丢失的问题 算法首先按照mbr的hilbert值进行排序根据节点容量生成子节点形成各聚类中心针对hilbert异常值采用距离约束条件进行处理迭代以上过程生成hilbert str-树 研究结果表明该算法的查询效率优于str-树和r树 相似文献