识别出层压板小质量冲击下发生分层扩展时的接触力有助于确定导致其损伤的外物冲击能量。由解析模型的分析可知,局部接触刚度降低会引起接触力的突降,而整体弯曲刚度的降低不会产生这个响应特征,只会导致接触力峰值的降低。研发了小质...识别出层压板小质量冲击下发生分层扩展时的接触力有助于确定导致其损伤的外物冲击能量。由解析模型的分析可知,局部接触刚度降低会引起接触力的突降,而整体弯曲刚度的降低不会产生这个响应特征,只会导致接触力峰值的降低。研发了小质量冲击试验机,对层压板进行多个能量下的小质量冲击试验,由冲击头的响应和层压板冲击点的挠度测量接触力。发现产生明显分层损伤时,接触力在理论的分层阈值处有明显下降,随后继续升高,这种现象可作为冲击中分层扩展的识别方法;由冲击点挠度测量接触力时,为了捕捉到突降信号,采样频率需达到200 k Hz,否则只会得到接触力曲线斜率发生变化的结果。展开更多
A growth chamber study was conducted to determine the relationships between the supply of soil available nitrogen (N) and sulfur (S) and canola (Brassica napus) and wheat (Triticum aestivum L. 'Biggar') N and ...A growth chamber study was conducted to determine the relationships between the supply of soil available nitrogen (N) and sulfur (S) and canola (Brassica napus) and wheat (Triticum aestivum L. 'Biggar') N and S uptake and yield in three Western Canadian soils. The suitability of one-hour burial with an anion exchange membrane (AEM) was assessed for its utility as a quick test of the available N:S balance in the soil. Canola and wheat were grown on a Luvisolic soil low in available S and on Brown and Black Chernozemic soils low in both available N and S, with different rates and combinations of N and S fertilizers applied. AEM burial was used to assess soil available nitrate and sulfate supply rates after fertilization. Dry matter yield and N and S concentrations in plant tissues were determined after 6 weeks of growth. The soil available N:S ratio determined by AEM burial closely reflected the relative supplies of available N and S as revealed in the N:S ratios of plant tissue dry matter. The highest yields were achieved where the available N:S ratio in soil and plant tissue ranged from 5 to 13. Thus, a one-hour burial of an AEM probe in the field may be a useful tool to quickly test if a balanced N and S supply is present in the soil for optimum crop yield.展开更多
文摘识别出层压板小质量冲击下发生分层扩展时的接触力有助于确定导致其损伤的外物冲击能量。由解析模型的分析可知,局部接触刚度降低会引起接触力的突降,而整体弯曲刚度的降低不会产生这个响应特征,只会导致接触力峰值的降低。研发了小质量冲击试验机,对层压板进行多个能量下的小质量冲击试验,由冲击头的响应和层压板冲击点的挠度测量接触力。发现产生明显分层损伤时,接触力在理论的分层阈值处有明显下降,随后继续升高,这种现象可作为冲击中分层扩展的识别方法;由冲击点挠度测量接触力时,为了捕捉到突降信号,采样频率需达到200 k Hz,否则只会得到接触力曲线斜率发生变化的结果。
基金Project supported by the Potash and Phosphate Institute of Canada (PPIC).
文摘A growth chamber study was conducted to determine the relationships between the supply of soil available nitrogen (N) and sulfur (S) and canola (Brassica napus) and wheat (Triticum aestivum L. 'Biggar') N and S uptake and yield in three Western Canadian soils. The suitability of one-hour burial with an anion exchange membrane (AEM) was assessed for its utility as a quick test of the available N:S balance in the soil. Canola and wheat were grown on a Luvisolic soil low in available S and on Brown and Black Chernozemic soils low in both available N and S, with different rates and combinations of N and S fertilizers applied. AEM burial was used to assess soil available nitrate and sulfate supply rates after fertilization. Dry matter yield and N and S concentrations in plant tissues were determined after 6 weeks of growth. The soil available N:S ratio determined by AEM burial closely reflected the relative supplies of available N and S as revealed in the N:S ratios of plant tissue dry matter. The highest yields were achieved where the available N:S ratio in soil and plant tissue ranged from 5 to 13. Thus, a one-hour burial of an AEM probe in the field may be a useful tool to quickly test if a balanced N and S supply is present in the soil for optimum crop yield.
