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1.
In urban environments, one major concern with deep excavations in soft clay is the potentially large ground deformations in and around the excavation. Excessive movements can damage adjacent buildings and utilities. There are many uncertainties associated with the calculation of the ultimate or serviceability performance of a braced excavation system. These include the variabilities of the loadings, geotechnical soil properties, and engineering and geometrical properties of the wall. A risk‐based approach to serviceability performance failure is necessary to incorporate systematically the uncertainties associated with the various design parameters. This paper demonstrates the use of an integrated neural network–reliability method to assess the risk of serviceability failure through the calculation of the reliability index. By first performing a series of parametric studies using the finite element method and then approximating the non‐linear limit state surface (the boundary separating the safe and ‘failure’ domains) through a neural network model, the reliability index can be determined with the aid of a spreadsheet. Two illustrative examples are presented to show how the serviceability performance for braced excavation problems can be assessed using the reliability index. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
2.
Noriaki Kimura 《Journal of Oceanography》2007,63(4):685-694
This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea
ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special
Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic
processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and
sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important
role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both
advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift.
Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind
speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge. 相似文献
3.
Abstract. Annual growth rates of gorgonians in the Indo-Pacific region are reported ror the first tinie. A method of measuring gorgonian growth using periodic photographic monitoring that is sensitive to horizontal growth and changes in growth foci but that does not require tedious underwater measurements is applied. Growth parameters of five species of gorgonians from three Families ( Plexauridae. Melithaeidae . and Subergorgiidae ) were monitored over a period of 18 months using this method. Growth rates ranged from 2.30 cm a-1 to 7.88 cm. a -1 in the highly sedimented waters of Singapore. The maximum number of branches added per year ranged from 1.7 to 14.5. 相似文献
4.
Toshimichi Ito Arata Kaneko Hiroyuki Tsubota Noriaki Gohda 《Journal of Oceanography》1994,50(4):465-477
The localized near-bottom water with silica content higher than that in the adjacent shelf water was observed to exist at the eastern margins of the East China Sea continental shelf. The core of the high silica water possessed the silica content corresponding to that in the Kuroshio at depths greater than on the shelf. The mixing analysis of water masses using temperature (T) and silica (Si) showed that the core water can be produced through the vertical mixing of intermediate water of the Kuroshio deeper than 100 m. This study provides us a conclusion that the intermediate water of the Kuroshio is strongly mixed on the shelf slope and then upwelled to form the ridge-like distribution of water masses with low temperature and high silica content at the shelf edge. 相似文献
5.
Analysis of snowpack dynamics during the spring melt season for a sub‐alpine site using point measurements and numerical modeling
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Snowpack dynamics through October 2014–June 2017 were described for a forested, sub‐alpine field site in southeastern Wyoming. Point measurements of wetness and density were combined with numerical modeling and continuous time series of snow depth, snow temperature, and snowpack outflow to identify 5 major classes of distinct snowpack conditions. Class (i) is characterized by no snowpack outflow and variable average snowpack temperature and density. Class (ii) is characterized by short durations of liquid water in the upper snowpack, snowpack outflow values of 0.0008–0.005 cm hr?1, an increase in snowpack temperature, and average snow density between 0.25–0.35 g cm?3. Class (iii) is characterized by a partially saturated wetness profile, snowpack outflow values of 0.005–0.25 cm hr?1, snowpack temperature near 0 °C, and average snow density between 0.25–0.40 g cm?3. Class (iv) is characterized by strong diurnal snowpack outflow pattern with values as high as 0.75 cm hr?1, stable snowpack temperature near 0 °C, and stable average snow density between 0.35–0.45 g cm?3. Class (v) occurs intermittently between Classes (ii)–(iv) and displays low snowpack outflow values between 0.0008–0.04 cm hr?1, a slight decrease in temperature relative to the preceding class, and similar densities to the preceding class. Numerical modeling of snowpack properties with SNOWPACK using both the Storage Threshold scheme and Richards' equation was used to quantify the effect of snowpack capillarity on predictions of snowpack outflow and other snowpack properties. Results indicate that both simulations are able to predict snow depth, snow temperature, and snow density reasonably well with little difference between the 2 water transport schemes. Richards' equation more accurately simulates the timing of snowpack outflow over the Storage Threshold scheme, especially early in the melt season and at diurnal timescales. 相似文献
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回顾分析Matilda医院超速CT室筛选首批病人中99例中国人资料,很明显从通常采用130-100Hounsfield单位作为检出冠状血管钙化的基数应用至中国人身上其阈值数目需要降低,同时,我们也发现如果病人年龄按每10年范围分组(21-30,30-40,41-50,51-60)而计算其超速CT的钙化指数会较随机男女一起按平均计算更易区分其差异.进一步分析显示,男性中年时候超速CT指数已达最高值,而女性则晚10年方达最高值,因此,为了更易探测冠脉循环内钙化倾向应作出超速CT检出钙化的指数数目.这些实践经验对动脉粥样硬化过程的预测或预防有实际意义. 相似文献
9.
Quaternary loess deposits containing charcoal and in situ organic matter constituents from Banks Peninsula, New Zealand, were subjected to various physical and chemical treatments before radiocarbon assay. A stepwide procedure was used in which each component was radiocarbon dated before and after the treatments were applied. The criterion adopted for judging the effectiveness of a treatment is an increase in the radiocarbon age of loess layer. On this basis the oldest and therefore the most reliable date was obtained from the intra-loess charcoal and its humic acid extract. By comparison, the radiocarbon ages of organic matter constituents of the whole or partitioned loess were much younger, and are considered to represent only average ages for the particular layers concerned. No advantage was gained by dating the carbon-enriched clay-humus fraction as opposed to whole loess samples. There is an apparent conflict between our dates and current interpretation of loess stratigraphy and chronology in the South Island of New Zealand, which requires further investigation. This uncertainty apart, the upper layers of multiple loess deposits are clearly much older than earlier reports indicate, and it follows that the correlation of these deposits with late-glacial events both within and beyond New Zealand is even more tenuous and unreliable than previously thought to be the case. 相似文献
10.
Goh Onitsuka Akihiko Morimoto Tetsutaro Takikawa Atsushi Watanabe Masatoshi Moku Yutaka Yoshikawa Tetsuo Yanagi 《Estuarine, Coastal and Shelf Science》2009,81(3):401-408
The relationship between island-induced cyclonic eddies and chlorophyll a (chl-a) was investigated using field data and satellite images in the eastern channel of the Tsushima Straits. The maximum chl-a concentration around the leeward eddy of the Tsushima Islands was two or three times greater than that of outside the eddy. Two different mechanisms of chl-a enhancement associated with island-induced cyclonic eddies were found in the post-bloom periods. In summer, when nutrients were depleted in the surface layer, eddy pumping increased the nutrient supply in the euphotic zone, resulting in enhanced chl-a around the shallow thermocline near the eddy core. In late autumn, when the mixed layer deepened over the euphotic zone, the mixed layer depth became shallow due to the doming effect of the cyclonic eddy, therefore, the improved irradiance condition led to an increase in the chl-a concentration in the surface mixed layer. Nighttime satellite visible images showed a number of fishing vessels in the lee region of the Tsushima Islands, implying that the enhanced phytoplankton biomass may have resulted in good feeding conditions for fishes and squids in the Tsushima Straits. 相似文献