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531.
Auto-temperature-controlled ventilation embankment is an effective engineering measure for “cooling roadbed”. Practice proves that this new method can sufficiently make use of natural cold energy. It has the advantages of higher efficiency, better cooling effect and feasibility in engineering practice, and wider application in various environment, etc. And also, it is comparatively cheap in project cost. Through practice in the field for half a year, the testing results show that, with the application of auto-temperature-controlled system, the artificial permafrost table has been raised by 65 cm. The artificial permafrost table was basically at the embankment bottom, and the action of freeze-thaw circle on engineering stability was effectively avoided. In the month with highest ground temperature, in the scope with 1–4 m in depth, including the majority of the embankment and the upper part in the original seasonal layer, the ground temperature decreased by 0.7°C. Through thermal flux calculation in the original seasonal layer, in the month with the maximum thermal flux coming into permafrost, it is found that the thermal flux reduces nearly by half. Coming into the cooling period for nearly a month, the ground temperature in entire auto-temperature-controlled embankment is close to zero, and the foundation is at negative temperature. But in a large region in the embankment and foundation the ground temperature was over 0°C and varied from 0°C to0.39°C in ordinary ventilation embankment. 相似文献
532.
Zhang Xiaoliang 《中国地震研究》2004,18(2):161-170
On the basis of Discontinuous Deformation Analysis (DDA), and considering the moderate intrusion of specific block boundaries to different extents, the first-order block motion model is established for the northeastern margin of Qinghai-Xizang(Tibet) block and the kinematical model for depicting deformation of small regions as well by using GPS observations of three periods (1991, 1999 and 2001). By simulating, we obtained the motion features of the firstorder blocks between the large WWN faults on the sides of the studied region, the distribution features of the principal strain rate field and the inhomogeneous motion features with spacetime of the faults in the northern boundary of the Qinghai-Xizang (Tibet) block. 相似文献
533.
534.
几种空气质量预报方法的预报效果对比分析 总被引:9,自引:0,他引:9
目前应用于我国各个城市空气质量预报业务的预报方法主要有三种 :数值模式预报、统计预报和综合经验预报。这几种预报方法都有其各自的优势 ,同时也存在一些不足。应用以上方法对天津市市区进行空气质量业务预报 ,通过实测资料与预报结果进行对比分析 ,给出这几种方法在天津市区空气质量预报中的预报效果客观评价。 相似文献
535.
用远场辐射场反演云闪放电参数 总被引:2,自引:0,他引:2
用地面电磁场遥感闪电放电参数无论是在实际应用还是理论研究中都具有重要意义。文中基于电流传输线模式 ,提出了一种用单站远场VLF/LF辐射场反演云内放电参数的简便方法。当传输线电流从底部传播到顶部的时间只有几微秒时 ,整个传输线的VLF/LF辐射可以近似成偶极子辐射 ,即远场辐射场与电流的时间变化率和传输线长度的乘积成正比。因此 ,对远场辐射场做时间积分就能获得完整的电流矩波形 (上升沿有所加宽 ) ,而且传输线模式中的重要参数 ,电流从底部传播到顶端经历的时间 ,也可以近似地用辐射场时间积分幅度与辐射场幅度之比来估计。这一方法具有估计云闪双极性大脉冲辐射过程的放电参数的潜力。 相似文献
536.
Dust sediments collected from 1995 to 1998 in Beijing, Dunhuang, Inner Mongolia, Kashi, the Kunlun Mountains, Lanzhou, Ningxia, the Taklimakan Desert, and Xi‘an, China, were characterized in terms of their physical, chemical, and mineralogical properties. Most aerosols and dust analysed ranged in texture from silty clay to clay loam. Their median particle diameters (Mds) generally ranged between 5 to 63μm,coinciding with those of loess from central China and the finest sand from northwestern China. The dust sediments were characterized by a predominance of SiO2 and Al2O3, followed by K2O. Their SiO2/Al2O3and K2O/SiO2 molar ratios ranged from 5.17 to 8.43 and from 0.009 to 0.0368, respectively. The mass concentration spectrum during a dust storm showed a single peak, rather than the triple peak generally observed under clear sky conditions. The dominant minerals were chlorite, illite, calcite, and dolomite.These physical, chemical, and mineralogical properties were consistent with those of aeolian soils and loess in western and central China. The results suggest that aerosols and fine-gained fractions of dust sediments collected in northern China are mainly composed of soil material transported from the arid and semiarid regions of China and Mongolia by prevailing winds. The rate of deposition and properties of dust falling on eastern China were strongly influenced by meteorological conditions, season, latitude, longitude, and altitude of the sampling sites. 相似文献
537.
The present paper focuses on land cover dynamics pattern in Balkhila sub-watershed situated in Garhwal Himalayas. This study
contributes example from human shaped ecosystem in mountainous regions where fragmentation of natural resources is active.
The remote sensing and GIS has been used to understand the land cover dynamics along the topography. The results report that
the land cover dynamics is dependent on the aspect due to sun illumination. The altitude and slope are no more a barrier for
resource extraction and the human activity zone is shifting towards higher altitudes and slopes. The changes are also defined
along the road and settlements. 相似文献
538.
R. Ramakrishnan S. Manthira Moorthi N. Padmanabhan P. Gupta 《Journal of the Indian Society of Remote Sensing》2004,32(1):103-111
Panchromatic data of pixel resolution 5.8 m obtained from IRS-1C and IRS-1D satellites proved to be very useful for mapping
purposes. One of the popular data product is the 70 km swath mosaic which is covered by a combination of 3 CCD line sensors,
each with 4096 pixels. Each CCD-line sensor with different imaging times causes geometric problems of mosaicing three strips
data together. In this paper, we propose the details of the design elements of system that caters to the need for accurate
and automatic multi strip image registration without any second resampling of the data. The systematic geometric correction
grid mapping is improved to facilitate accurate mosaicing by automatic image registration task that makes use of the overlap
data within image strips and image registration is achieved up to sub-pixel level. 相似文献
539.
A complete dismembered sequence of ophiolite is well exposed in the south Andaman region that mainly comprises ultramafic
cumulates, serpentinite mafic plutonic and dyke rocks, pillow lava, radiolarian chert, and plagiogranite. Pillow lavas of
basaltic composition occupy a major part of the Andaman ophiolite suite (AOS). These basalts are well exposed all along the
east coast of southern part of the south AOS. Although these basalts are altered due to low-grade metamorphism and late hydrothermal
processes, their igneous textures are still preserved. These basalts are mostly either aphyric or phyric in nature. Aphyric
type exhibits intersertal or variolitic textures, whereas phyric variety shows porphyritic or sub-ophitic textures. The content
of alkalies and silica classify these basalts as sub-alkaline basalts and alkaline basalts. A few samples show basaltic andesite,
trachy-basalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt
samples are probably derived from similar parental magmas. Al2O3/TiO2 and CaO/TiO2 ratios classify these basalts as high-Ti type basalt. On the basis of these ratios and many discriminant functions and diagrams,
it is suggested that the studied basalts, associated with Andaman ophiolite suite, were derived from magma similar to N-MORB
and emplaced in the mid-oceanic ridge tectonic setting. 相似文献
540.
This article deals with women's use of public space and sense of place in El Raval, a neighbourhood located in the historical
center of Barcelona. Attention will be paid to discover to what degree the existence of a quality public space fosters the
creation of socially meaningful places, thus contributing to the construction of womens sense of place and urban identities.
A qualitative approach, based on direct observation and in-depth interviews with women living in the neighbourhood, has allowed
us to capture the main aspects of the building of a sense of place and belonging, that is the use of public space and facilities,
the attitude towards living in the neighbourhood, etc.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献