推拉式气垫运载平台推拉机构受力分析与计算     

张兰义  桑兰芬  陈吉清  杨永海  姚圣卓 《农业机械学报》2003,34(1):1-4

在总体方案设计的基础上探讨了推拉式气垫运载平台推拉机构的受力问题，提出基本假设，建立了工作负载与作业环境以及功能技术指标的数学关系，提出关键部件的设计准则和结构型式，拟定出力学谐调条件。通过3种典型工况的受力分析。推导出杆系结点力的计算公式，以模型样机为具体实例，进行了设计计算。  相似文献   

Effect of Field Drainage on Root Lodging Tolerance in Direct-Sown Rice in Flooded Paddy Field     

《Plant Production Science》2013,16(4):255-261

Abstract

To elucidate the effect of drainage of paddy fields on root lodging tolerance in direct-sown rice, we measured the pushing resistance (R), diameter of hill at the base (Dm), shoot dry weight (Ws) and root dry weight (Wr), in rice varieties grown using several irrigation management schemes that differed in the frequency and length of field drainage during the growing season. Soil hardness was also monitored to investigate the relationship between the variance of soil physical properties caused by different irrigation treatments and root lodging tolerance. Pushing resistance moment (Rh), i.e., product of pushing resistance (R) and height of pushed part of hill (h), showed higher values in rice grown in fields drained more frequently or for longer periods. A similar pattern was found in rice grown in field plots where root penetration to the subsoil layers was prevented by laying an unwoven cloth between the topsoil and subsoil layers. Higher values for pushing resistance efficiency based on root dry weight (Kr : Rh/Wr/Dm) were also found in plots subjected to more frequent or prolonged drainage, irrespective of rice variety. Soil hardness was progressively increased by each field drainage during the growing season, and showed a highly significant relationship with Kr. The above results suggest that field drainage increases the root lodging tolerance in direct-sown rice through improvement of anchoring ability caused by increased soil hardness.  相似文献