排序方式: 共有89条查询结果,搜索用时 194 毫秒
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P. Jakobsson D. Malesani J. Hjorth J.P.U. Fynbo B. Milvang-Jensen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We describe the current status and recent results from our Swift/VLT legacy survey, a VLT Large Programme aimed at characterizing the host galaxies of a homogeneously selected sub-sample of Swift GRBs. The immediate goals are to determine the host luminosity function, study the effects of reddening, determine the fraction of Lyα emitters in the hosts, and obtain redshifts for targets without a reported one. The main effort so far has been the definition of a very carefully selected sample, obeying strict and well-defined criteria: 68 targets in total. Among the preliminary results is a large optical detection rate, the lack of extremely red objects (only one possible case in the sample) and an update of the Swift GRB redshift distribution with 〈z〉∼2.0. 相似文献
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Because of its chemical and radiative properties, atmospheric ozone constitutes a key element of the Earth’s climate system.
Absorption of sunlight by ozone in the ultraviolet wavelength range is responsible for stratospheric heating, and determines
the temperature structure of the middle atmosphere. Changes in middle atmospheric ozone concentrations result in an altered
radiative input to the troposphere and to the Earth’s surface, with implications on the energy balance and the chemical composition
of the lower atmosphere. Although a wide range of ground- and satellite-based measurements of its integrated content and of
its vertical distribution have been performed since several decades, a number of uncertainties still remain as to the response
of middle atmospheric ozone to changes in solar irradiance over decadal time scales. This paper presents an overview of achieved
findings, including a discussion of commonly applied data analysis methods and of their implication for the obtained results.
We suggest that because it does not imply least-squares fitting of prescribed periodic or proxy data functions into the considered
times series, time-domain analysis provides a more reliable method than multiple regression analysis for extracting decadal-scale
signals from observational ozone datasets. Applied to decadal ground-based observations, time-domain analysis indicates an
average middle atmospheric ozone increase of the order of 2% from solar minimum to solar maximum, which is in reasonable agreement
with model results. 相似文献
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CCSDS(Consultative Committee for Space Data Systems,空间数据系统咨询委员会)SLE(Space Link Extension,空间链路拓展)网络协议体系模型中,一个服务实例只支持建立一个物理通信链路,造成上层应用与下层链路耦合过强,存在一定的安全隐患。针对此问题,设计了基于冗余连接机制的SLE网络协议体系模型,该模型在现有的SLE网络协议体系模型中增加了逻辑连接层,支持单一服务实例同时使用多个物理链路进行空间数据传输,可根据多连接状态重新设计TML(Transport Mapping Layer,传输映射层)状态变换关系以及数据传输模式。该模型能够兼容现有的SLE网络传输体系模型,提高SLE服务的可靠性。 相似文献
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L11前后机身下大梁对接设计,除综合考虑其强度和工艺性外,更主要的是确定大梁的对接形式,布置相应的承力构件,以便减轻结构重量,本文简要介绍了对接设计情况。 相似文献
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介绍美军现役主要战术数据链及美军针对四代机的数据链改进和试验情况,分析美军第四代战斗机的技战术性能,得到美军对下一代数据链建设方向的重点,对我军今后数据链建设具有借鉴意义,从而更有针对性地加强我军的数据链建设,提高我空军的整体战斗力。 相似文献
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结合空地通信系统的设计,简要分析了空地通信链路的特性,介绍了用分集技术改善空地通信链路抗衰落能力的方法。 相似文献