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91.
In this study, a capillary barrier system was designed and tested for an arid land environment. To simulate arid land conditions
of high temperature and sub-irrigation systems, the barrier was subjected to thermal and hydraulic gradients in opposite directions;
to test the barrier system under these severe conditions, an experimental apparatus was designed and fabricated. The multilayer
capillary barrier consisted of three layers made of silica sand, a mixture of sand and bentonite in equal portions, and a
mixture of clay (25%) and aggregate (75%). Several one dimensional coupled heat and moisture tests were performed. Temperature
variations along the thickness of the barrier were recorded as a function of time, and at the end of each test, the barrier
was sliced into small sections, for the determination of volumetric water content as a function of distance from the heat
source. The experimental results were discussed in view of the barrier's intended purpose of its ability to store moisture
for long time durations.
Coupled heat and moisture flow equations were developed and solved numerically via a finite difference method. Diffusivity
parameters were calculated by using experimental results, a numerical model, and Powell's conjugate directions method of nonlinear
optimization. The model was calibrated and the results were discussed. Good agreement between calculated and experimental
results was obtained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
92.
93.
一种组合优化的多边形化简方法 总被引:2,自引:0,他引:2
以多边形轮廓为目标 ,依据曲线特征点将其分解为一系列的弯曲特征 ,并对此弯曲特征集实施组合优化 ,将入围弯曲首尾相连 ,即可得到最终的化简结果 相似文献
94.
95.
分析了自动气象站分钟雨量资料获取与转换的必要性,介绍了雨量资料获取的思路与具体方法.通过这种方法,实现了商丘市所有自动气象站雨量资料的共享,并与GPRS、GSM乡级自动雨量站资料进行融合. 相似文献
96.
This short note reviews our thinking on how IGGOS can best achieve a high status within the set of global monitoring programmes. If such a high status can be obtained, then the importance of geodetic networks and services will be recognized more widely, and their activities will consequently be better resourced in the long term. One particular aspect concerns how IGGOS can complement the roles of the various IGOS partners within global monitoring. The different ways in which IGGOS can contribute to IGOS are outlined. 相似文献
97.
The GGOS as the backbone for global observing and local monitoring: A user driven perspective 总被引:1,自引:0,他引:1
A key geodetic contribution to both the three Global Observing Systems and initiatives like the European Global Monitoring for Environment and Security is an accurate, long-term stable, and easily accessible reference frame as the backbone. Many emerging scientific as well as non-scientific high-accuracy applications require access to an unique, technique-independent reference frame decontaminated for short-term fluctuations due to global Earth system processes. Such a reference frame can only be maintained and made available through an observing system such as the Global Geodetic Observing System (GGOS), which is currently implemented and expected to provide sufficient information on changes in the Earth figure, its rotation and its gravity field. Based on a number of examples from monitoring of infrastructure, point positioning, maintenance of national references frames to global changes studies, likely future accuracy requirements for a global terrestrial reference frame are set up as function of time scales. Expected accuracy requirements for a large range of high-accuracy applications are less than 5 mm for diurnal and sub-diurnal time scales, 2–3 mm on monthly to seasonal time scales, better than 1 mm/year on decadal to 50 years time scales. Based on these requirements, specifications for a geodetic observing system meeting the accuracy requirements can be derived. 相似文献
98.
A detailed receiver function image of the sedimentary structure in the Bohai Bay Basin 总被引:5,自引:0,他引:5
Tianyu Zheng 《Physics of the Earth and Planetary Interiors》2005,152(3):129-143
If the site at which receiver functions are constructed is filled by sediments, then the waveforms from these receiver functions are dominantly controlled by the sedimentary structures within the first few seconds after the direct P arrival. Based on this observation, waveform data collected at 44 temporary seismic stations have been used to image the sedimentary structure of the Bohai Bay Basin, a major continental petroliferous basin in Eastern China. An adapted hybrid global waveform inversion method was applied to the receiver functions to extract structural information beneath each of the stations. The derived S-velocity structure provides for the first time, a basin-scale seismic image of detailed sedimentary stratification. The sedimentary cover of the basin is about 2-12 km thick, consisting of Cenozoic, Mesozoic, and Paleozoic strata from top to bottom. The structural features presented in the S-velocity image coincide quite well with the depression-uplift type of tectonic system in the Bohai Bay Basin. The reconstructed morphology of the sedimentary layers provides seismological evidence for the two-stage evolution of the intracontinental basin that were caused by an intensive tectonic regime transition in late Mesozoic immediately following the lithospheric reforming of the Eastern China continent. 相似文献
99.
Jiang Jiayu Fu Shouxian Li Jiuling 《应用地球物理》2005,2(4):241-246
Branching river channels and the coexistence of valleys, ridges, hiils, and slopes'as the result of long-term weathering and erosion form the unique loess topography. The Changqing Geophysical Company, working in these complex conditions, has established a suite of technologies for high-fidelity processing and fine interpretation of seismic data. This article introduces the processes involved in the data processing and interpretation and illustrates the results. 相似文献
100.
Global ocean circulation models usually lack an adequate consideration of high-latitude processes due to a limited model domain
or insufficient resolution. Without the processes in key areas of the global thermohaline circulation, the characteristics
and flow of deep and bottom waters cannot be modeled realistically. In this study, a high-resolution (~20 km) ocean model
focused on the Weddell Sea sector of the Southern Ocean is combined with a low-resolution (2° × 2°) global ocean model applying the state estimation technique. Temperature, salinity, and velocity data on two Weddell Sea
sections from the regional model are used as constraints for the large-scale model in addition to satellite altimetry and
sea-surface temperatures. The differences between the model with additional constraints and without document that the Weddell
Sea circulation exerts significant influence on the course of the Antarctic Circumpolar Current with consequences for Southern
Ocean water mass characteristics and the spreading of deep and bottom waters in the South Atlantic. Furthermore, a warming
trend in the period 1993–2001 was found in the Weddell Sea and adjacent basins in agreement with float measurements in the
upper Southern Ocean. Teleconnections to the North Atlantic are suggested but need further studies to demonstrate their statistical
significance. 相似文献