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981.
982.
锦州湾沾污沉积物急性毒性的海洋端足类检验 总被引:13,自引:1,他引:12
1992年9月 ̄1993年1月对锦州湾沾污沉积物的海洋端足类急性毒性效应进行了研究。从锦州湾湾顶到湾口沿西南--东北方向每2km等距离采集27个表层沉积我校 品,应用海洋端足类A mpelisca abdita对这些样品进行了10d直流式急性毒性检验,检验指标为死亡率。结果表明,五里河河口处受试生物死亡率最高,为100%,从湾顶该河口处沿东北方向随着距离增加,死亡率逐渐递减,笔架山处最低,仅为2. 相似文献
983.
M. D. Trifunac S. S. Ivanov M. I. Todorovska E. I. Novikova A. A. Gladkov 《Soil Dynamics and Earthquake Engineering》1999,18(3):375
This article explores the possibility to measure deformations of building foundations from measurements of ambient noise and strong motion recordings. The case under study is a seven-storey hotel building in Van Nuys, California. It has been instrumented by strong motion accelerographs, and has recorded several earthquakes, including the 1971 San Fernando (ML=6.6, R=22 km), 1987 Whittier–Narrows (ML=5.9, R=41 km), 1992 Landers (ML=7.5, R=186 km), 1992 Big Bear (ML=6.5, R=149 km), and 1994 Northridge (ML=6.4, R=1.5 km) earthquake and its aftershocks (20 March: ML=5.2, R=1.2 km; 6 December, 1994: ML=4.3, R=11 km). It suffered minor structural damage in 1971 earthquake and extensive damage in 1994. Two detailed ambient vibration tests were performed following the Northridge earthquake, one before and the other one after the 20 March aftershock. These included measurements at a grid of points on the ground floor and in the parking lot surrounding the building, presented and analyzed in this article. The analysis shows that the foundation system, consisting of grade beams on friction piles, does not act as a “rigid body” but deforms during the passage of microtremor and therefore earthquake waves. For this geometrically and by design essentially symmetric building, the center of stiffness of the foundation system appears to have large eccentricity (this is seen both from the microtremor measurements and from the earthquake recordings). This eccentricity may have contributed to strong coupling of transverse and torsional responses, and to larger than expected torsional response, contributing to damage during the 1994 Northridge, earthquake. 相似文献
984.
This article demonstrates how system identification techniques can be successfully applied to a soil-structure interaction system in conjunction with the results of the forced vibration tests on the Hualien large-scale seismic test structure which was recently built in Taiwan for an international joint research. The parameters identified are the shear moduli of several near-field soil regions as well as Young's moduli of the shell sections of the structure. The soil-structure interaction system is represented by the finite element method combined with infinite element formulation for the unbounded layered soil medium. Preliminary investigations are carried out on the results of the static stress analysis for the soil medium and the results of the in-situ tests to divide the soil-structure system into several regions with homogeneous properties and to determine the lower and upper bounds of the parameters for the purpose of identification. Then two sets of parameters are identified for two principal directions based on the forced vibration test data by minimizing the estimation error using the constrained steepest descent method. The simulated responses for the forced vibration tests using the identified parameters show excellent agreement with the test data. The present estimated parameters are also found to be well compared with the average value of those by other researchers in the joint project. 相似文献
985.
986.
百余年的ENSO事件与北京汛期旱涝的统计关系 总被引:11,自引:0,他引:11
利用王绍武等人最近对近百年ENSO事件及强度的研究结果,对ENSO事件与北京汛期相当暴雨日数的统计关系进行分析,表明,ENSO事件与北京沁期旱涝存在较复杂的统计关系,ENSO事件的性质,强度,起始季节和持续时间长短等与汛期旱涝的对应关系是复杂的。根据1867-1998年的ENSO事件和同期北京汛期相当暴雨日数资料,给出一些统计结果。 相似文献
987.
厄尔尼诺海区海温季节预测比较 总被引:1,自引:0,他引:1
余锦华 《南京气象学院学报》1999,22(3):374-380
利用奇异值分解方法建立多项线性统计气候预测模型,对厄尔尼诺海区各季节海温进行了短期气候预测试验,并采用历史资料独立样本检验的方法,评定不同预报时效的预报技巧。结果表明,不同海区各季节的预报效果相差很大。赤道西太平洋( Nino 4区)有最高的可预报性,在夏季末做冬季海温预报的技巧最高,多数条件下,这个区域的预报性能比较稳定。以海温和南方涛动指数作因子场的预报效果最好,大部分预报以单季的海温和南方涛动指数为预报因子效果较好,但有些预报以连续2季或3季的海温和南方涛动指数作预报因子的预报效果更好。 相似文献
988.
钟元 《热带气象学报(英文版)》1999,5(1):67-75
Statistical study is first performed of the efficiency of the technique of statistical interpretation using the products of NWP. The result shows that the application of the technique has improved the predictabilily of predictors in objective forecasting of tropical cyclone motion, increased the forecasting skill of models and extended the valid period of forecast. Then a discussion is made of some technical problems in the application in the motion forecasting, suggesting: a large sample of data and perfect forecast method be employed in constructing objective forecast models for tropical cyclone motion, predictors be included that are so finely built that they reflect all synoptic features and physical quantity fields and NWP products be used and corrected that are available at multiple times. It is one of the effective ways to improve the skill and stability of the forecast by composite use of outcomes from various forecasting models. 相似文献
989.
990.
钢屈服—摩擦复合耗能器的性能研究 总被引:6,自引:1,他引:5
本文提出了“综合利用不同耗能原理和机制来设计新型耗能器”的思想,研究开发了钢屈服-摩擦复合耗能器,并对其进行了性能试验和对比试验,考察了耗能器的工作性能和耗能性能。给出了耗能器的恢复力模型,研究结果表明,钢屈服-摩擦复合耗能器利用钢屈服滞回和摩擦两种机制耗能,具有稳定的工作性能,耗能能力强且可调节,构造简单,形状紧凑,体积小,造价低,制作与安装方便,是一种有广阔应用前景的新型耗能减震装置。 相似文献