共查询到20条相似文献,搜索用时 15 毫秒
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Stüeken E. E. Som S. M. Claire M. Rugheimer S. Scherf M. Sproß L. Tosi N. Ueno Y. Lammer H. 《Space Science Reviews》2020,216(3):1-17
Space Science Reviews - The Ionospheric Connection Explorer (ICON) mission makes measurements in near-Earth space that provide knowledge of the state of the ionosphere. From the vantage of... 相似文献
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Lawrence M. Widrow Dongsu Ryu Dominik R. G. Schleicher Kandaswamy Subramanian Christos G. Tsagas Rudolf A. Treumann 《Space Science Reviews》2012,166(1-4):37-70
We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark–hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars are discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a?Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium. 相似文献
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作为两颗"伽利略在轨验证元素"(GIOVE)试验卫星中的第一颗,Giove-A,于2005年12月28日当地时间上午11时19分在哈萨克斯坦拜科努尔航天中心发射升空,经过"弗雷盖特"(Fregat)上面级火箭的三次点火后,这颗由英国萨里卫星技术公司制造的试验卫星被送入了高23230千米、倾角56度的轨道. 相似文献
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本文摘编自上海人民出版社出版的《天高歌长--我的飞机设计师生涯》一书的第三章"雏鹰展翅"。本书作者曾负责中国第一架喷气式飞机、第一架批生产的中国型号、第一架超音速飞机、以及20世纪内我国设计的最大飞机等机型的总体设计。书中记述了作者自幼年起的成长道路以及参与这些工程的经历和体会 相似文献
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Remote sensing is viewed as a complete system for observing and managing man's environment on Earth. The sensing portion of the system consists of space, air, and ground observing platforms, sensors, communications, computational capabilities and interpretation, and recognition algorithms. The data are put to use using environmental models, geographic information systems, and management models. Progress and potentials in each of these system elements are reviewed and projected. Existing and potential uses are sketched and certain institutional, diplomatic, and national security issues are identified. Some underlying reasons for belief in continued progress are mentioned and the need for certain crucial choices in the future stated which will determine which of a number of possible futures will be realized. 相似文献
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2008年6月29日,首架国产新型涡桨支线飞机“新舟”600在中国一航西安飞机工业(集团)有限责任公司(以下简称一航西飞)总装厂房顺利下线,这是一航西飞涡桨支线“新舟”系列飞机的最新成员,也是一航西飞为实现“新舟”系列化发展而迈出的第一步。 相似文献
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Simon Glover 《Space Science Reviews》2005,117(3-4):445-508
In this review, I survey our current understanding of how the very first stars in the universe formed, with a focus on three
main areas of interest: the formation of the first protogalaxies and the cooling of gas within them, the nature and extent
of fragmentation within the cool gas, and the physics – in particular the interplay between protostellar accretion and protostellar
feedback – that serves to determine the final stellar mass.
In each of these areas, I have attempted to show how our thinking has developed over recent years, aided in large part by
the increasing ease with which we can now perform detailed numerical simulations of primordial star formation. I have also
tried to indicate the areas where our understanding remains incomplete, and to identify some of the most important unsolved
problems. 相似文献
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旭日初升创新之始 1951年4月17日,中央人民政府革命军事委员会和政务院颁发了《关于航空工业建设的决定》,由此,新中国航空工业以航空工业管理局的身份获得了"准生证",并开始了混沌初生的艰苦创业阶段.当时的航空工业全部的"家当"不过是由从空军移交过来的16家设备陈旧、规模偏小、厂房简陋的维修工厂.当年的中国航空工业是依照"边修理、边建设"的战略,从修理飞机和发动机开始起家的. 相似文献
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The year 2008 marked the one hundredth anniversary of the observational discovery by George Ellery Hale of magnetic field in sunspots (Hale in Astrophys. J. 28:315–343, 1908). This observation, the first to suggest a direct link between the best-known variable features on the Sun and magnetism, started a line of research that has widened considerably over the last 100 years and is continuing today. Knowledge about all aspects of the Sun has increased in a remarkable way over the past few decades. Variations in the appearance of the Sun and its corona, as well as deeper sources of quasi-regular and chaotic changes that make up solar variability have been extensively documented by both ground-based and space-based solar observatories. It has been recognized that solar magnetism is the key phenomenon that drives solar variability. The workshop devoted to the origin and dynamics of solar magnetism held in the International Space Science Institute in Bern, Switzerland, from 21 to 25 January 2008 reviewed the status of the field and has led to this volume that brings together the best available knowledge and understanding of solar magnetism 100 years after Hale’s pioneering paper. This introductory paper gives an outline of the history of research into solar variability up to the work of Hale and his colleagues. The achievements of the past decades are discussed extensively in the other contributions to this volume. 相似文献
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Despite much recent theoretical and observational progress in our knowledge of the early universe, many fundamental questions remain only partially answered. Here, we review the latest achievements and persisting problems in the understanding of first cosmic structure formation.This revised version was published online in July 2005 with a corrected cover date. 相似文献
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美国空军在今年9月首次使用人造合成燃料在一架B-52上进行了试飞.这是合成燃料在飞行器上的首次应用,对未来航空燃料的发展具有重大意义. 相似文献
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《中国民用航空》1998,(11)
The57-yearoldPhilippineAirlines(PAL),whichclosedatmidnightSept.23,leftwithadebtof$2.1billion,andbecameAsia'sfirstflagcarriertofallvichnitothereces5ionthathadgrippedthetfavelindustryformorethanayear-Butitsproblemswentdeeperthantherecession.TheycenteredonyearsofdistrustbetweenmanagementandlabOLAlthoughitreopenedonOct.7atlast,itisstillhardtoanticipatetheairiineswillbecomeaflashingphoenixagain.Afterathree-yearbattle,billionaireLucioTanachievedcontroloftheairlineinJunel996andembarkedonanambit… 相似文献
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6月17日,珠海保税区摩天宇航空发动机维修有限公司迎来了第50台发动机进厂维修。来自中国南方航空集团北方航空公司编号为V11081的V2500发动机成为珠海摩天宇所维修的第50台发动机,将进行全面大修。珠海摩天宇是德国MTU航空发动机公司和中国南方航空公司各占50%股份的合资企业,总投资额为1.89亿美元。珠海摩天宇公司于2003年年初宣布投产营运,受“非典”的影响,真正的业务发展始于2003年下半年。在短短的一年内,珠海摩天宇的CFM56-3和V2500发动机的维修相继获得了中国民航总局(CAAC)、欧洲联合航空局(JAA)和美国联邦航空局(FAA)三大… 相似文献
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上世纪五六十年代,能当上八级技工(高级工)是工人师傅们一辈子孜孜追求的目标之一。当年,从学徒、初级技工(1-3级工)、中级技工(4-6级工)、锤炼到高级技工(7-8级工),没有十多年光阴是拿不下来的。再往上一级,则是技师职称。据悉,目前全国民航系统只有32位安检技师。 相似文献
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The radar cross section of a flat plate has a sin x/x lobe structure. If a synthetic-array radar flies past the plate the resulting image is dependent upon what part of this lobe structure is sampled. When the plate is parallel to the flight path, the image is a line as wide as the plate. If the plate is not parallel, only the discontinuities at the ends of the plate are visible in the image. 相似文献