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151.
利用国内大型风沙物理风洞实验模拟沙尘暴电现象,研究风沙起电机理,结果表 明,不同风速下不同沙粒会产生不同极性的电场强度和电位效应,风沙电随风速增大而增强 ,且随沙粒度增大而减小. 在沙漠区的16m,8m,4m和1m高度上观测到27次不同沙尘暴天气 过程的电场和风速随时间变化. 结果表明, 在晴天4个高度上的电场均为小正电场值,电场 随高度降低而减小,最大电场强度在5kV/m以下,日风速变化对各层电场起伏没有较大影响 . 有沙尘天气,各高度上的电场强度随风速变化而变化. 16m高度上电场均为负值,平均值 为 -20kV/m;中层8m 电场一般为较高正电场值,达到10~40kV/m,与16m高度上电场呈反相 关;下层1m 电场值变化一般很小,在1kV/m以下. 在强沙尘暴天气4个高度上的电场均为负 电值,电场值随高度降低而减小,16m高度上最大平均电场强度达到-200kV/m以上,瞬时值 超过 -2500kV/m,与晴天电场矢量相反. 相似文献
152.
153.
利用改进后的《出纳日记账处理系统》,按支出科目的类、款、项进行分类,登记零余额账户的银行存款日记账,达到《气象部门财政国库管理制度改革试点资金支付管理办法实施细则》关于登记银行日记账簿的要求。 相似文献
154.
We have successfully ported an arbitrary high-order discontinuous Galerkin method for solving the three-dimensional isotropic elastic wave equation on unstructured tetrahedral meshes to multiple Graphic Processing Units (GPUs) using the Compute Unified Device Architecture (CUDA) of NVIDIA and Message Passing Interface (MPI) and obtained a speedup factor of about 28.3 for the single-precision version of our codes and a speedup factor of about 14.9 for the double-precision version. The GPU used in the comparisons is NVIDIA Tesla C2070 Fermi, and the CPU used is Intel Xeon W5660. To effectively overlap inter-process communication with computation, we separate the elements on each subdomain into inner and outer elements and complete the computation on outer elements and fill the MPI buffer first. While the MPI messages travel across the network, the GPU performs computation on inner elements, and all other calculations that do not use information of outer elements from neighboring subdomains. A significant portion of the speedup also comes from a customized matrix–matrix multiplication kernel, which is used extensively throughout our program. Preliminary performance analysis on our parallel GPU codes shows favorable strong and weak scalabilities. 相似文献
155.
Muñoz-Barbosa A Gutiérrez-Galindo EA Daesslé LW Orozco-Borbón MV Segovia-Zavala JA 《Marine pollution bulletin》2012,64(2):405-409
In 1992 and 2004, heavy metals concentrations were measured in surficial sediments from Todos Santos Bay, located in Ensenada, Baja California, Mexico. The aim was to search for relationships between metal enrichment factors and a biological adverse effects index. Unlike Ni, the elements Cd, Cu and Zn showed significant correlations (p<0.05) between enrichment factors and the biological adverse effects index. Cu showed a 0.74:1 relationship, which means that any enrichment above 0.74 could represent biological adverse effects. On the other hand, Cd and Zn enrichments must be >5.5 and >1.5, respectively, in order for the sediments to be considered toxic. In general, data showed that most of the metal concentrations in Todos Santos Bay sediments could not cause adverse effects to biota. Only Ensenada's harbor and the zone next to a dredging dumping site showed metal enrichments that could be toxic. 相似文献
156.
Ecohydrological evolution model on riparian vegetation in hyperarid regions and its validation in the lower reach of Tarim River 总被引:1,自引:0,他引:1
The evolution of the ecohydrological system driven by external climatic forcing and internal feedbacks between vegetation and hydrology, which is more remarkable in arid and semiarid regions, has attracted substantial research attention in recent years. To examine critically the state‐of‐the‐art assumptions and dynamic equations used in the evolution study of an ecohydrological system, the rule of proceeding from simplicity to complexity should be followed. The riparian vegetation ecohydrological system in hyperarid regions (e.g. the lower Tarim River) can serve as a starting point given its simplicity, which has been seldom examined before in terms of system evolution. Further, the water transfer practice from 2000 to 2006 in the lower Tarim River serves as a valuable prototype experiment for model validation. This is because the remarkable changes in groundwater and vegetation in the area have taken place within a shorter period and thus can be easily observed. In the present study, the ecohydrological evolution model on riparian vegetation (ERV model) in hyperarid regions was proposed by coupling groundwater movement and vegetation dynamics. In the ERV model, the groundwater table serves as a critical feedback variable that determines the vegetation dynamics (colonization and mortality) and is determined by vegetation transpiration other than groundwater movement. The monitored groundwater table by wells and satellite‐observed vegetation coverage from the Moderate Resolution Imaging Spectroradiometer are used for model validation. The simulation results show the good performance of the ERV model with uncalibrated parameters. It was also calibrated manually using a multiobjective method, and the fine‐tuned parameters are close to the uncalibrated ones, indicating the robustness of the model. The analysis shows further that the increased evapotranspiration is substantially due to the water transfer and thus the vegetation growth, which implies the importance of ecohydrological coupling for long‐term hydrological modelling. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
157.
地震信号检测是进行各种地震数据分析和处理的首要任务,STA/LTA方法具有算法简单、便于实时处理等特点,被广泛应用于地震信号检测.结合实际震例数据研究STA/LTA方法进行地震信号检测的各种影响因素,得到该方法进行检测时最合理的参数设置范围. 相似文献
158.
根据汶川地震序列,选出距离合适、波形相关性较好的事件作为震源阵,联合永久台阵(那曲、和田台阵),进行震源阵与固定台阵组合研究,计算其台阵响应.结果表明,地震序列可以形成震源阵,按照地震台阵的特殊方法进行研究,可以提高信噪比,为揭示地下精细结构提供条件. 相似文献
159.
We established a line (screened) of Portunus trituberculatus by selectively breeding individuals that survived from challenge with Vibrio alginolyticus, and compared the response of screened and unscreened (control) P. trituberculatus challenged with V. alginolyticus. We measured superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase, and peroxidase activity and the content of hemocyanin in the plasma and phenoloxidase activity in serum. The cumulative survival rate after 24-h challenge with V. alginolyticus was significantly higher in the screened crabs than in the unscreened crabs (P<0.05). T-SOD and PO activity were significantly lower in the screened stock than in the unscreened stock (P<0.05). POD, CAT, and ACP activity and hemocyanin content were significantly higher in the screened stock than in the unscreened stock. Our results suggest that the screened stock was more resistant to infection. Furthermore, the indices we measured may be used to evaluate the health state of P. trituberculatus. 相似文献
160.
利用2000-2010年16 d合成的MODIS/[NDVI]数据,结合植被异常指数、趋势线分析和Hurst指数等分析方法,对新疆伊犁河谷植被覆盖的时空变化特征进行了分析。结果表明:(1) 伊犁河谷内植被覆盖随海拔增高而先增加后减小,最高植被覆盖区位于2 000~2 500 m的高程带;2000-2010年伊犁河谷各高程带内植被覆盖整体下降趋势明显,但海拔低于1 000 m的高程带除外。(2)受干湿环境影响,伊犁河谷全区平均被植异常指数最高值出现在降水最多的2002年,最低值出现在降水最少的2008年,但不同区域植被异常指数的变化存在较大差异。(3)伊犁河谷内植被覆盖增加和减小的区域分别占总面积的4.09%和19.34%,增加区域主要位于伊犁河两岸的平原区,减小区域主要位于乌孙山两端以及伊犁河谷周围海拔2 000 m左右的低山区域;变标度极差分析结果表明,伊犁河谷内植被覆盖年际变化呈现很强的持续性,未来一定时间内将保持现有变化趋势不变。 相似文献