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41.
42.
雹云识别是一个多参数的模式识别问题,应用物元可拓思想将单参数雹云识别的不相容性转化为相容性问题。在与成都地区雹云识别的物元可拓模型进行对比后,根据低纬高原地形及气候特点,通过适当增加参数,构造完成低纬高原雹云识别的物元可拓模型,以此进行雹云识别,准确率达86%以上。 相似文献
43.
采用Green函数、保角映射等方法分析SH波上方垂直入射时弹性半空间中椭圆形弹性夹杂与任意方位裂纹的相互作用。首先,求解含椭圆形弹性夹杂的弹性半空间内任意一点承受时间谐和出平面线源荷载作用时的位移基本解,即Green函数,再结合裂纹切割法构造裂纹,得到SH波上方垂直入射时椭圆夹杂和裂纹同时存在条件下的位移场与应力场。作为算例,给出大量的数值结果,探讨不同参数情况下弹性夹杂周边动应力集中系数(DSCF)、地表位移及裂纹尖端动应力强度因子(DSIF)的分布规律,结果表明不同参数的变化会对三者的分布带来一定的影响。 相似文献
44.
浅埋隧道围岩应力场的计算复变函数求解法 总被引:2,自引:1,他引:1
对于受地表边界和地面荷载影响的浅埋隧道的围岩应力场,由于在数学处理上存在一定的困难,很难用解析解来进行分析,而通常采用边界元或有限元的数值方法来解答。为了求解浅埋隧道的应力场,采用边界配点来确定边界条件,同时用保角映射将一个含圆孔的半无限空间区域映射为圆环域,然后把这个区域内的解析函数展开成Laurent级数的形式,利用Muskhelishvili的复变函数理论和最小二乘法来确定解析函数的各项系数,从而求得浅埋隧道围岩压力的半数值、半解析解,最后通过算例给出了围岩应力的分布情况。计算结果表明,该方法计算精度高、计算量小,具有应用价值。 相似文献
45.
半无限含水层中带衬砌隧洞渗流解析研究 总被引:3,自引:0,他引:3
现有关于半无限含水层中隧洞渗流的解析解不能考虑衬砌部分排水的特性。假定土体和衬砌均为饱和均匀连续介质,采用土体与衬砌分算;利用复变函数解决孔口问题基本方法,对土体采用共形映射坐标变换,将土体中的渗流方程转换为与衬砌部分类似的二维Laplace方程圆环域的Dirichlet问题;通过Fourier解法,根据边界条件并利用流量连续条件,求得半无限空间中带衬砌隧洞渗流量和衬砌周边水头解析解答。分析了径深比、土体与衬砌渗透系数相对值、内壁水压力等因素对渗流量和衬砌周边水头的影响,并与数值算例进行了比较。结果表明,对浅埋隧洞该解析解仍具有较好的精度,是简便、实用的计算方法。 相似文献
46.
The longest total solar eclipse during the 21st century occurred in South and East Asia on July 22, 2009. Ionospheric response to this rare total solar eclipse which was observed right from the time of sunrise in the Indian zone, has been studied in terms of the total electron content (TEC) obtained from three global positioning system (GPS) receivers located at Udaipur, Hyderabad and Bengaluru, and electron density obtained using space based GPS-Radio Occultation technique. The study reveals significant reductions in the electron density and TEC that persisted up to 2 h past the last contact even during early morning eclipse. These observations imply that during the early morning eclipse, the production and loss of ionization dominate over the plasma transport processes. 相似文献
47.
综合运用保角变换、镜像反映愿理,势的叠加原理以及等值渗流阻力等数学和渗流力学分析方法,推导出裸眼系列完井方式下叠武分支水平井的产能解析公式,当分支数目为1时,所推导的解析公式退化为著名的Borisov公式.分析了影响其产能的几个重要因素,从而为该类型分支井的完井方案设计提供参考依据.经研究发现,完井筛管挡砂精度越高,相比水平井,叠式分支水平井产能损失相对越少;叠武分支水平井的产能受其在上下封闭边界油藏中垂向位置的影响较小;相比微元段模型,解析模型预测的产能偏高,引入校正系数后可减小偏差. 相似文献
48.
49.
Low-frequency variability of the North Equatorial Current bifurcation in the past 40 years from SODA 总被引:1,自引:1,他引:0
The low-frequency variability of the North Equatorial Current (NEC) bifurcation during 1958 to 2001 was investigated with the Simple Ocean Data Assimilation (SODA) 2.0.2 dataset.In agreement with recent observations,the NEC bifurcation latitude (NBL) shifted northward as depth increases, from about 12.7°N near the surface to about 17.1°N at depths around 500 m for the annual average. This study reveals that the interannual variations of NBL,with five years period,mainly focused on the upper 500 m with amplitude increasing as depth increased.The NBL shifted southward in the past 40 years,which was more significant in the subsurface at more than -0.02°/a.The NBL manifests itself in the transports of NMK (NEC-Mindanao Current (MC)-Kuroshio) system in strong relationship with MC (0.7) and Kuroshio (-0.7).The EOF analysis of meridional velocity off the Philippine coast shows that the first mode,explaining 62% of variance and 5 years period,was highly correlated with the southward shift of NBL with coefficient at about 0.75.The southward shift of NBL consists with the weakening of MC and strengthening of Kuroshio,which exhibited linear trends at -0.24Sv/a and 0.11Sv/a.Both interannual variation and trend of NBL were closely related to the variation of NMK system. 相似文献
50.
Sílvia Santos Joana F.M.F. Cardoso Célia Carvalho Pieternella C. Luttikhuizen Henk W. van der Veer 《Estuarine, Coastal and Shelf Science》2011
Monthly investment in soma and gonads in the bivalve Scrobicularia plana is described for three populations along its distributional range: Minho estuary, Portugal; Westerschelde estuary, The Netherlands and Buvika estuary, Norway. Seasonal cycles in body mass (BMI), somatic mass (SMI) and gonadal mass (GMI) indices were observed for all populations. In Portugal, BMI and SMI peaked in mid-autumn, while in The Netherlands both indices were at their highest in mid-spring. Norway showed a different pattern with two distinct peaks: one in mid-autumn and a second peak in spring. GMI reached maximum values in July in Portugal and Netherlands and in June in Norway. Overall, mean BMI and SMI were lower in Portugal while mean GMI was lower in Norway. The spawning period lasted the whole summer in Portugal, but was shorter (only two months) in The Netherlands and Norway. The reproductive investment in The Netherlands was significantly higher than in Portugal and Norway, with the lowest values being observed in Norway. Differences in annual cycles between populations were attributed to environmental factors, namely temperature and food availability. Temperature seems important in shaping the reproductive pattern with more northern populations showing shorter reproductive periods starting later in the year, and a lower reproductive output. In addition, winter water temperatures can explain the lower mean body and somatic mass values observed in Portugal. Food availability influenced the physiological performance of the species with peaks in somatic mass coinciding with phytoplankton blooms. This relation between physiological performance and environmental factors influences S. plana distribution, densities and even survival, with natural consequences on its commercial importance. 相似文献