排序方式: 共有29条查询结果,搜索用时 15 毫秒
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武汉市近年水田生产机械化发展存在系列服务,相对集中,人畜混合三种类型地区。农机部门为水田机械化发展做了大量的管理,引导工作。进一步发展需继续深入贯彻的农业“两法”,建立农机服务市场,依靠科技进步。 相似文献
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ZHANG Chun xun 《保鲜与加工》2003,(4):155-158
To supply an even more amplitude background for the analysis on the quality of the structure of Chongqing, this paper analyzed the altitudes of employment structure and production value structure among three industry structures in Chongqing, then an static and dynamic comparison with other countries of DIFFERENT levels on the basis of grasping Chongqing's status in Western Area. An structural explanation of ChongQing's economy development stage aiming at giving an even more amplitude background to analyze the essence of its industrial structure. 相似文献
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罗泽xun 《东北林业大学学报》1990,18(4):99-105
兔形目(Lagomorpha)按传统分类习惯被划分为兔类(Harcs)、穴兔类(Rabbits)和鼠兔类(Pikas)三大类群,已得到国际公认。但是,兔类实际上仅是一个属——兔属(Lepus)。按过去的分类系统,划归在兔亚科(Lcporinae)中,丝毫体现不出兔类在兔形目中作为三大类群之一的分类地位。然而,若结合生态与形态一并研究,则发现兔类与穴兔类初生的幼兔形态与生态明显有异:兔类终生在地面生活,初生的幼兔全身具毛,眼睁开,不久便能走路;为避天敌,需迅速奔跑,后腿变长,而奔跑中需氧多,后鼻孔变宽(翼内窝的宽度大)。穴兔类产仔在地下洞穴中,初生幼兔没毛,闭着眼,不会走动;避天敌主要靠迅速钻洞,奔跑慢,后鼻孔窄。它们生态与形态差异如此之大,在相似性大,而差异性小的野兔来说,应作为演化中新变所产生的新征。兔属可独立成亚科,称兔亚科为宜。穴兔类中,古兔亚科(Palacolaginae)自成独立亚科;其余的穴兔类应另立一新亚科,为穴兔亚科(Rabbitinae, nom. nov.)。 相似文献
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This paper focuses on the design of eleven rollers straightener. An elastic plastic FEM model is introduced to cope with the difficulty of pre estimating the performance of straightening during the design process. To obtain straightening force, stress, strain, elastic plastic ratio, relations between reduction amount of roller and roughness of plate per square meter, a three dimensional element model is established and straightening process is simulated. In addition, an experiment is conducted to measure the reduction amount of roller and the roughness of plate per square meter. It is shown that the results of numerical simulation are consistent with the experimental results. The developed computing model can provide essential references for the optimization of straightener. 相似文献
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The virtual environment is the important and indispensable part of virtual reality The method of modeling virtual environment is studied and discussed, based on the research of the basic theory and key technology of virtual reality. Taking the indoor virtual environment modeling as an example, the whole design object, design idea, design rules and the key technologies of indoor virtual environment modeling is dissertate systematically. The modeling objects are reusable and interactive owing to the adaptation of object-oriented and agent-oriented techonlogy. The actual scene is classified according to structure and layer so as to the scene was managed effectively and displayed more quickly. So the system had the properties of immersion, interaction and imagination at some extent. 相似文献
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In the ironmaking process, it is essential that sinter and feed of blast furnace are established economically and reasonably. Taking some steel company for example, the best economical condition for feed of blast furnace is comprehensively considered from technologic demand and economic efficiency. According to LP and based on practice and trial, aimed function and confined condition is confirmed, computation programs are made by Matlab while realizing optimization feed. The blast furnace material balance and heat balance are calculated by program with visual interface. Thus, we can directly judge rationality of optimization. The results show that LP is effective method to realize feed of blast furnace. 相似文献