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脲酶抑制剂对石灰性土壤尿素转化及N_2O排放的影响 被引量:19
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作者 李君 刘涛 褚贵新 《农业环境科学学报》 CAS CSCD 北大核心 2014年第9期1866-1872,共7页
通过研究脲酶抑制剂对土壤中尿素转化的影响,揭示土壤各形态氮对N2O的贡献,为控制石灰性土壤氮素损失及提高氮肥利用率提供理论依据。在室内恒温培养条件下(25℃),研究了正丁基硫代磷酰三胺(NBPT)、醋酸棉酚、硫代硫酸铵3种脲酶抑... 通过研究脲酶抑制剂对土壤中尿素转化的影响,揭示土壤各形态氮对N2O的贡献,为控制石灰性土壤氮素损失及提高氮肥利用率提供理论依据。在室内恒温培养条件下(25℃),研究了正丁基硫代磷酰三胺(NBPT)、醋酸棉酚、硫代硫酸铵3种脲酶抑制剂对石灰性土壤各形态氮素转化与脲酶抑制率的影响,同时在人工气候室(昼夜)通过Unisense N2O微电极法对各处理土壤N2O浓度进行了原位实时监测。结果表明:尿素施入土壤1 d后50%已迅速水解,3d后完全水解。1~14d各脲酶抑制剂均可显著抑制尿素水解,尿素+NBPT处理的土壤尿素残留量显著高于其他处理,其脲酶抑制率为33.6%;NBPT处理的土壤NH4^+-N含量低于其他各处理(P〈0.05),在第7d分别比尿素、尿素+硫代硫酸铵、尿素+醋酸棉酚处理的降低了64.8%、63.5%、70.9%。土壤N2O浓度在第1~4 d较低,第4d后迅速上升,第6 d升至峰值,随后呈明显下降趋势(第6~9 d)。第9~14d各处理N2O的排放表现为尿素〉尿素+醋酸棉酚〉尿素+硫代硫酸铵≥尿素+NBPT。各形态氮与N2O浓度的通径系数分别为NO3^--N(0.641)〉NH4^+-N(0.356)〉Urea-N(0.255),通径相关和线性相关均表明NO3^--N含量与N2O浓度呈显著正相关,是制约N2O排放的主导因素。石灰性土壤施用脲酶抑制剂可抑制土壤尿素水解转化,有效降低土壤N2O浓度,3种脲酶抑制剂中NBPT效果最佳。 展开更多
关键词 石灰性土壤 N2O浓度 unisense N2O微电极 脲酶抑制剂 尿素
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Theory of Point Contact Restraint and Qualitative Analysis of Robot Grasping 被引量:7
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作者 熊有伦 《Science China Mathematics》 SCIE 1994年第5期629-640,共12页
This paper presents a geometrical representation of robot grasping and a definition of "relative form closure" of point contact restraint based on the concepts of positive linear combination,affine combinati... This paper presents a geometrical representation of robot grasping and a definition of "relative form closure" of point contact restraint based on the concepts of positive linear combination,affine combination,convex combination,etc.in the screw space.The dual equivalence theorem,topological equivalence theorem and algebraic equivalence theorem are derived from the defined restraint cone and freedom cone in the dual screw spaces.A J0-function method of computer-aided grasp planning is implemented more efficiently than other proposed methods.The states of restraint and instantaneous motion of a rigid body grasped by a set of point contacts are specified by the unisense degrees of freedom and unisense degrees of restraint.Finally,a quality measure of robot grasping is provided for the synthesis procedure of relatively form-closed grasp. 展开更多
关键词 ROBOT GRASPING mechanism form CLOSURE unisense degree of FREEDOM
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