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71.
Pushover analysis is a tool to study the inelastic behavior of structures under strong seismic action. The 3D-pushover analysis was performed to analyze the inelastic lateral-torsional coupled response of multistory asymmetric structures. The symmetric frame and frame-wall systems were studied in this paper, and the capability curve of the top displacement and base shear,the story drift and the position of rotation center were compared with reference to corresponding symmetric structures. The characters of inelastic response of multistory asymmetric structures were found. The conclusion provides reference for performance-based seismic design of asymmetric structures. 相似文献
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“层流型”分草曲面用于覆盖免耕播种机的研究 总被引:8,自引:3,他引:8
运用流体力学基本原理对分草曲面的工作流场、秸秆覆盖层的连续介质属性,以及曲面用于分草、防堵的机理进行了研究。采用“环槽试验方法”测定秸秆层的“相当粘度”,将分草曲面视为绕流物体,提出“层流型”曲面分草器最具良好的绕流性能,宜用作覆盖免耕播种机的防堵装置。本文并对5种流线的流速变化特征及其绕流特性进行了分析研究,提出抛物线与双曲线最宜用作分草曲面的流线。 相似文献
77.
农业机械中型面无键联接技术 总被引:1,自引:0,他引:1
论述了型面无键联接的含义及型面联接的DG(等距)型廓形曲线,探讨了型面无键联接曲线的方程;并介绍了型面无键联接在喷粉喷雾机、收割机、拖拉机和摘棉机等农业机械中的应用,提出了在机械传动中实现无键联接的途径。 相似文献
78.
P. J. T. Van Bakel 《Irrigation and Drainage Systems》1988,2(2):125-137
The use of drainage systems for supplementary irrigation is widespread in The Netherlands. One of the operating policies is to raise the surface water level during the growing season in order to reduce drainage (water conservation) or to create subsurface irrigation. This type of operation is based on practical experience, which can be far from optimal.To obtain better founded operational water management rules a total soil water/surface water model was built. In a case study the effects of using the drainage system in a dual-purpose manner on the arable crop production were simulated with the model. Also, the operational rules for managing this type of dual-purpose drainage systems were derived.The average annual simulated increase in crop transpiration due to water conservation and water supply for subsurface irrigation are 6.0 and 5.4 mm.y–1, respectively. This is equivalent with 520 × 103 and 460 × 103 Dfl.y–1 for the pilot region (2 Dfl 1 US $). The corresponding investments and operational costs are 600 × 103 Dfl and 9 × 103 Dfl.y–1 for water conservation and 3200 × 103 Dfl and 128 × 103 Dfl.y–1 for subsurface irrigation. Hence, water conservation is economically very profitable, whereas subsurface irrigation is less attractive.Comparing the management according to the model with current practice in a water-board during 1983 and 1986 learned that benefits can increase with some 50 and 500 Dfl per ha per year, respectively. 相似文献
79.
Infiltration characteristics for border strip irrigation at two sites with swelling clay soils were examined. Volume infiltrated was calculated from flow onto the field monitored with flow meters; depth of water in the soil estimated from soil samples taken before and after irrigation; and the advance profile which was used to calculate the volume infiltrated with time. Volume infiltrated was compared with volume of cracks before irrigation.Linear advance and observed crack closing supported the hypothesis that infiltration approached zero after about 10 min. Volume of cracks was less than 20% of the volume infiltrated. Wetting front was 3–10 times greater than depth of observed surface cracks. There was no significant correlation between intake opportunity time and depth of infiltration, but elevation irregularities were related to infiltration. 相似文献
80.