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铁路起重机回转小车轨道制造技术研究及应用
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作者 陈喜 《起重运输机械》 2023年第6期64-69,共6页
铁路起重机型号、规格逐渐向大型、重型结构方向发展,小车的体积和质量也随之变大。在保证小车结构、起升速度、回转运行速度、吊装载荷不变的情况下,为实现系统运行平稳、提高精度的要求,对相关结构制造提出了更高要求。回转轨道及反... 铁路起重机型号、规格逐渐向大型、重型结构方向发展,小车的体积和质量也随之变大。在保证小车结构、起升速度、回转运行速度、吊装载荷不变的情况下,为实现系统运行平稳、提高精度的要求,对相关结构制造提出了更高要求。回转轨道及反滚轮轨道作为回转小车系统的核心部件,是保证小车系统在复杂工装下能平稳运行的关键。其中,回转轨道的耐磨性能和尺寸精度以及回转轨道和反滚轮轨道组合精度要求高,文中通过下料、制造、安装技术与材料的选择方面以及焊接技术方面的优化改进,采取有效的控制措施,并结合具体项目中的实践论证,提高了轨道尺寸精度、轨道硬度,延长了轨道使用寿命,整体制造水平得到了提升,质量得到了改善。 展开更多
关键词 铁路起重机 回转轨道 反滚轮轨道 耐磨钢 制造技术 焊接技术
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Think Tanks in the United States: The Evolution and Evolving Roles
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作者 Jiangli Su 《Sociology Study》 2016年第3期176-185,共10页
Think tanks as an important force in the policy making field in the United States have strengthened their visibility and expanded their influence in recent decades. This paper contends that the historical and politica... Think tanks as an important force in the policy making field in the United States have strengthened their visibility and expanded their influence in recent decades. This paper contends that the historical and political climate of the United States has fostered the development of think tanks and they will continue to exert their influence in the policy making field of the United States. It mainly examines the history of American think tanks and the roles they have been performing during more than one hundred years' evolution. In the twenty-first century, in a more and more flattering world, policy issues become increasingly complicated, therefore think tanks are indeed fixtures of American policy making scene. They play six major roles (1) source for policy idea; (2) venue for communicating and initiating new policy ideas; (3) source for personnel; (4) educating and informing the public; (5) evaluator of government policies; and (6) Track lI diplomacy. 展开更多
关键词 Think tanks policy making public policy industry policy idea revolving door track II
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地球白天何时离太阳最近
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作者 周教生 雷桂林 郑卓 《甘肃联合大学学报(自然科学版)》 2006年第3期45-47,共3页
根据地球绕太阳公转和自转的数据,计算出临界点,进而定性地阐明了人们在早晨、中午和傍晚看太阳远近的规律.
关键词 地球自转 地球公转 椭圆轨道 临界点
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