华北旱作农业地带立体农业开发的方向和途径──以河北省滦平县为例     

田中洋介  石敏俊  李桂森  汪洪清  王旭 《资源科学》1996,(6)

本文为中国科学院科技扶贫滦平开发试验站＂燕山东段北麓生态经济沟综合技术研究＂课题中农业经营、农村经济方面的调查研究报告。主要内容是运用农业经营学的分析方法，分析华北旱作农业地带土地利用、农业经营方式和农户经济的动态及存在问题，提出今后立体农业开发的方向和有关对策。  相似文献   

A tree-shaped motion strategy for robustly executing robotic assembly tasks     

Yusuke BOTA  Hajime MIZUYAMA  Akio NODA  Tatsuya NAGATANI  Ken-ichi TANAKA 《浙江大学学报(A卷英文版)》2010,11(12):986-991

An assembly robot needs to be capable of executing an assembly task robustly under various uncertainties.To attain this goal,we use a task sequence tree model originally proposed for manual assembly.This model regards an assembly task under uncertainties as a transformation of the contact state concept.The concept may contain several contact states with probabilities but these are transformed through a series of task elements into the contact state concept having only the goal state at the end.The transformed contact state concept can be classified according to the terminal condition of each task element.Thus,the whole assembly task can be designed as a tree-shaped contingent strategy called a task sequence tree.This paper proposes a systematic approach for reconfiguring a task sequence tree model for application to a robotic assembly task.In addition,by taking a 2D peg-in-hole insertion task to be performed by a robot equipped with a force sensor as an example,we confirm that the proposed approach can provide a robust motion strategy for the task and that the robot can actually execute the task robustly under bounded uncertainty according to the strategy.  相似文献   

Science Letters:Preparation, crystallization and preliminary X-ray diffraction analysis of PH1948, predicted RNA methyltransferase from Pyrococcus horikoshii     

GAO Yong-gui  YAO Min  TANAKA Isao 《Journal of Zhejiang University. Science. B》2005,6(6)

RNA methyltransferase is responsible for transferring methyl and resulting in methylation on the bases or ribose ring of RNA, which existed widely but mostly remains an open question. A recombinant protein PH1948 predicting RNA methyltransferase from Pyrococcus horikoshii OT3 has been crystallized. The crystals of selenomethionyl PH1948 belong to space group C2, with unit-cell parameters a=207.0 (A),b=43.1 (A), c= 118.2 (A), β=92.1°, and diffract X-rays to 2.2(A) resolution. The VM value was determined to be 2.8(A)3/Da, indicating the presence of four protein molecules in the asymmetric unit.  相似文献   

战后日本小学理科课程的修订     

刘继和  田中实 《外国教育研究》2002,29(8):38-40

文章以日本小学理科教学大纲（理科的目标和内容）为线索，简要系统地回顾了战后日本小学理科课程七次修订的历史，阐述了日本小学新理科课程的基本理念。  相似文献