排序方式: 共有28条查询结果,搜索用时 15 毫秒
21.
The speedily expanding Internet is in the process of transforming the technological, economic, and policy bases for nation-state regulation of telecommunications, including space-based satellite networks. Deployment of the packet-switched Internet has accelerated the liberalization of telecommunications markets and has led to far-reaching regulatory restructuring and policy shifts regarding state ownership and control of networks and information flows. As space-based GMPCS networks become integral parts of the globalizing Internet infrastructure, the state-centric legal paradigm requiring state “authorization and continuing supervision” of space activities by “non-governmental entities” stipulated under Article VI of the OST and associated treaties forming the outer space legal regime will be called increasingly into question. This paper examines the technological, economic/trade, and security issues that question whether the existing state-centric paradigm for regulating Internel-based GMPCS satellite systems will remain in legal phase with emerging liberalized regulatory regimes for terrestrial Internet-based infractructures. 相似文献
22.
Tom Gehrels Larry Esposito 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):67-71
We report results from analysis of data from Pioneer Saturn's Imaging Photopolarimeter. These include the discovery of a new ring and satellite, the structure of the atmosphere of Saturn and Titan, the inhomogeneous nature of Saturn's rings, and a model for the rings' formation and bimodal particle size distribution. 相似文献
23.
Ye Zhang Jade Q. Clement Daila S. Gridley Larry H. Rodhe Honglu Wu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Extrapolation of known radiation risks to the risks from low dose and low dose-rate exposures of human population, especially prolonged exposures of astronauts in the space radiation environment, relies in part on the mechanistic understanding of radiation induced biological consequences at the molecular level. While some genomic data at the mRNA level are available for cells or animals exposed to radiation, the data at the protein level are still lacking. Here, we studied protein expression profile changes using Panorama antibody microarray chips that contain antibodies to 224 proteins (or their phosphorylated forms) involved in cell signaling that included mostly apoptosis, cytoskeleton, cell cycle and signal transduction. Normal human fibroblasts were cultured until fully confluent and then exposed to 2 cGy of 150 MeV protons at high-dose rate. The proteins were isolated at 2 or 6 h after exposure and labeled with Cy3 for the irradiated cells and with Cy5 for the control samples before loading onto the protein microarray chips. The intensities of the protein spots were analyzed using ScanAlyze software and normalized by the summed fluorescence intensities and the housekeeping proteins. The results showed that low dose protons altered the expression of more than 10% of the proteins listed in the microarray analysis in various protein functional groups. Cell cycle (24%) related proteins were induced by protons and most of them were regulators of G1/S-transition phase. Comparison of the overall protein expression profiles, cell cycle related proteins, cytoskeleton and signal transduction protein groups showed significantly more changes induced by protons compared with other protein functional groups. 相似文献
24.
Pierre Y. Bely Holland C. Ford Richard Burg Larry Petro Rick White John Bally 《Space Science Reviews》1995,74(1-2):101-112
The tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips to 8 km in the polar regions. This makes the cold, dry and nonturbulent lower stratosphere accessible to tethered aerostats. Tethered aerostats can fly as high as 12 km and are extremely reliable, lasting for many years. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first in the Arctic (near Fairbanks, Alaska) and, potentially, later in the Antarctic, to operate a new technology 6-meter, diluted aperture telescope with diffraction-limited performance in the near infrared. Thanks to the low ambient temperature (220 K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2 to 3 micron band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 microns, the combination of high resolution images and a very dark sky make it the spectral region of choice for observing the redshifted light from galaxies and clusters of galaxies at moderate to high redshifts.Affiliated to the Astrophysics Division, Space Science Department, European Space Agency 相似文献
25.
The Sasakawa International Center for Space Architecture (SICSA) is undertaking a multi-year research, planning and design study that is exploring near- and long-term commercial space development opportunities. The central goal of this activity is to conceptualize a scenario of sequential, integrated private enterprise initiatives that can carry humankind forward to Mars. Each development stage is planned as a building block to provide the economic foundation, technology advancements and operational infrastructure to support others that follow. This report presents fundamental issues and requirements associated with planning human Mars initiatives that can transfer crews, habitats and equipment from Earth to Mars orbit, deliver them to the planet's surface, and return people and samples safely back to Earth. The study builds in part upon previous studies which are summarized in SICSA's: Commercial Space Development Plan and the Artificial Gravity Science and Excursion Vehicle reports. Information and conclusions produced in this study provide assumptions and a conceptual foundation for a subsequent report titled The First Mars Outpost: Planning and Concepts. 相似文献
26.
杨玉梅 《华北航天工业学院学报》2000,10(2):32-34
互斥方案决策时,运用净现值和内部收益率指标,经常遇到结论相矛盾的情况,本文主要应用方案重复法和投资增额评价法解决这一问题。 相似文献
27.
John O. Goldsten Edgar A. Rhodes William V. Boynton William C. Feldman David J. Lawrence Jacob I. Trombka David M. Smith Larry G. Evans Jack White Norman W. Madden Peter C. Berg Graham A. Murphy Reid S. Gurnee Kim Strohbehn Bruce D. Williams Edward D. Schaefer Christopher A. Monaco Christopher P. Cork J. Del Eckels Wayne O. Miller Morgan T. Burks Lisle B. Hagler Steve J. DeTeresa Monika C. Witte 《Space Science Reviews》2007,131(1-4):339-391
A Gamma-Ray and Neutron Spectrometer (GRNS) instrument has been developed as part of the science payload for NASA’s Discovery
Program mission to the planet Mercury. Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) launched
successfully in 2004 and will journey more than six years before entering Mercury orbit to begin a one-year investigation.
The GRNS instrument forms part of the geochemistry investigation and will yield maps of the elemental composition of the planet
surface. Major elements include H, O, Na, Mg, Si, Ca, Ti, Fe, K, and Th. The Gamma-Ray Spectrometer (GRS) portion detects
gamma-ray emissions in the 0.1- to 10-MeV energy range and achieves an energy resolution of 3.5 keV full-width at half-maximum
for 60Co (1332 keV). It is the first interplanetary use of a mechanically cooled Ge detector. Special construction techniques provide
the necessary thermal isolation to maintain the sensor’s encapsulated detector at cryogenic temperatures (90 K) despite the
intense thermal environment. Given the mission constraints, the GRS sensor is necessarily body-mounted to the spacecraft,
but the outer housing is equipped with an anticoincidence shield to reduce the background from charged particles. The Neutron
Spectrometer (NS) sensor consists of a sandwich of three scintillation detectors working in concert to measure the flux of
ejected neutrons in three energy ranges from thermal to ∼7 MeV. The NS is particularly sensitive to H content and will help
resolve the composition of Mercury’s polar deposits. This paper provides an overview of the Gamma-Ray and Neutron Spectrometer
and describes its science and measurement objectives, the design and operation of the instrument, the ground calibration effort,
and a look at some early in-flight data. 相似文献
28.
位于美国加利福尼亚州沃兰西亚的TA制造公司研制出一种可恢复飞机防火墙的完整性并保护表面不受火和热的破坏的密封胶.这种防火密封胶和隔热混合物叫做"快速密封胶"(英文商标为FASTBLOCKTM ).它可以迅速密封防火墙结构的隙缝,并保护表面不受火和热的破坏. 相似文献