共查询到20条相似文献，搜索用时 31 毫秒
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贾珍珍 《湖南农业大学学报(自然科学版)》2016,(6):118-121
以美国国防高级研究计划局（DARPA）为例，从DARPA对信息技术的领域分布、技术潜能与影响方面，对美国信息技术的发展情况进行探讨，并在最后提出信息技术对于我国军事技术发展的有关思考。 相似文献
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Sagdeev RZ Linkin VM Kerzhanovich VV Lipatov AN Shurupov AA Blamont JE Crisp D Ingersoll AP Elson LS Preston RA Hildebrand CE Ragent B Seiff A Young RE Petit G Boloh L Alexandrov YN Armand NA Bakitko RV Selivanov AS 《Science (New York, N.Y.)》1986,231(4744):1411-1414
The VEGA balloons made in situ measurements of pressure, temperature, vertical wind velocity, ambient light, frequency of lightning, and cloud particle backscatter. Both balloons encountered highly variable atmospheric conditions, with periods of intense vertical winds occurring sporadically throughout their flights. Downward winds as large as 3.5 meters per second occasionally forced the balloons to descend as much as 2.5 kilometers below their equilibrium float altitudes. Large variations, in pressure, temperature, ambient light level, and cloud particle backscatter (VEGA-1 only) correlated well during these excursions, indicating that these properties were strong functions of altitude in those parts of the middle cloud layer sampled by the balloons. 相似文献
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Lally VE 《Science (New York, N.Y.)》1967,155(3761):456-459
Superpressure GHOST balloons are being launched from Christchurch, New Zealand, to determine their life, stability, and clustering characteristics at several altitudes. Thtee separate balloons have flown for more than 6 months at 200 millibars, proving capability of the long life that had been hoped for at such middle altitudes and providing preliminary trajectory data for the Southern Hemisphere. Icing problems at lower altitudes have not yet been solved. We expect future flight durations of several years at higher altitudes. If successful, the new balloons will be useful platforms for experimenters concerned with study of large-scale and long-term effects in the stratosphere. 相似文献
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Seven balloons were launched successfully from Ascension Island in January 1969. The balloons, flown at altitudes of 20 and 24 kilometers, will make possible a detailed analysis of the stratospheric circulation near the equator and will hopefully lead to an understanding of the quasi-biennial stratospheric oscillation in the tropics. 相似文献
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与探空气球测风相比,风廓线雷达具有快速、连续、时空分辨率高、无需施放探空气球等优点。分析局地暴雨过程中的风廓线雷达资料的特点,提取降水信号,使风廓线雷达资料在短时强降水监测和预报中发挥作用具有十分重要的意义。华北区域的一次实例验证表明,风廓线雷达在暴雨预报中有很好的应用效果。 相似文献
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Linkin VM Kerzhanovich VV Lipatov AN Shurupov AA Seiff A Ragent B Young RE Ingersoll AP Crisp D Elson LS Preston RA Blamont JE 《Science (New York, N.Y.)》1986,231(4744):1420-1422
Thermal structure measurements obtained by the two VEGA balloons show the Venus middle cloud layer to be generally adiabatic. Temperatures measured by the two balloons at locations roughly symmetric about the equator differed by about 6.5 kelvins at a given pressure. The VEGA-2 temperatures were about 2.5 kelvins cooler and those of VEGA-1 about 4 kelvins warmer than temperatures measured by the Pioneer Venus Large Probe at these levels. Data taken by the VEGA-2 lander as it passed through the middle cloud agreed with those of the VEGA-2 balloon. Study of individual frames of the balloon data suggests the presence of multiple discrete air masses that are internally adiabatic but lie on slightly different adiabats. These adiabats, for a given balloon, can differ in temperature by as much as 1 kelvin at a given pressure. 相似文献
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Preston RA Hildebrand CE Purcell GH Ellis J Stelzried CT Finley SG Sagdeev RZ Linkin VM Kerzhanovich VV Altunin VI Kogan LR Kostenko VI Matveenko LI Pogrebenko SV Strukov IA Akim EL Alexandrov YN Armand NA Bakitko RN Vyshlov AS Bogomolov AF Gorchankov YN Selivanov AS Ivanov NM Tichonov VF Blamont JE Boloh L Laurans G Boischot A Biraud F Ortega-Molina A Rosolen C Petit G 《Science (New York, N.Y.)》1986,231(4744):1414-1416
A global array of 20 radio observatories was used to measure the three-dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the Venus atmosphere near Venus midnight by the VEGA spacecraft on 11 and 15 June 1985. Initial analysis of only radial velocities indicates that each balloon was blown westward about 11,500 kilometers (8,000 kilometers on the night side) by zonal winds with a mean speed of about 70 meters per second. Excursions of the data from a model of constant zonal velocity were generally less than 3 meters per second; however, a much larger variation was evident near the end of the flight of the second balloon. Consistent systematic trends in the residuals for both balloons indicate the possibility of a solar-fixed atmospheric feature. Rapid variations in balloon velocity were often detected within a single transmission (330 seconds); however, they may represent not only atmospheric motions but also self-induced aerodynamic motions of the balloon. 相似文献
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In June 1985, two instrumented balloons were placed in the atmosphere of Venus as part of the VEGA mission. Each balloon traveled about 30 percent of the way around the planet at a float altitude near 54 kilometers. In situ sensors measured pressure, temperature, vertical wind velocity, cloud particle backscatter, ambient light level, and frequency of lightning. A ground-based network of 20 radio antennas tracked the balloons by very long baseline interferometry (VLBI) techniques to monitor the Venus winds. The history, organization, and principal characteristics of this international balloon experiment are described. 相似文献
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Wilkinson DT 《Science (New York, N.Y.)》1986,232(4757):1517-1522
The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation-bumpiness on the sky at angular scales of about 10 arc minutes. They have not yet been seen. 相似文献
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数据库培训是数据库试用、购买、使用过程中重要的环节。针对数字环境下的数据库培训工作,指出面临的挑战,拿出解决的对策。旨在促进高校图书馆电子期刊数据库培训工作的合理发展。 相似文献
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Linkin VM Kerzhanovich VV Lipatov AN Pichkadze KM Shurupov AA Terterashvili AV Ingersoli AP Crisp D Grossman AW Young RE Seiff A Ragent B Blamont JE Elson LS Preston RA 《Science (New York, N.Y.)》1986,231(4744):1417-1419
The VEGA balloons provided a long-term record of vertical wind fluctuations in a planetary atmosphere other than Earth's. The vertical winds were calculated from the observed displacement of the balloon relative to its equilibrium float altitude. The winds were intermittent; a large burst lasted several hours, and the peak velocity was 3 meters per second. 相似文献
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Chatterjee R 《Science (New York, N.Y.)》2006,313(5794):1730-1735
Science and the National Science Foundation announce the winners and honorable mentions in the categories of photography, illustration, informational graphics, noninteractive multimedia, and interactive multimedia in this year's Science and Engineering Visualization Challenge. 相似文献
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Atmospheric burnup of the cosmos-954 reactor 总被引：2，自引：0，他引：2
Krey PW Leifer R Benson WK Dietz LA Hendrikson HC Coluzza JL 《Science (New York, N.Y.)》1979,205(4406):583-585
On 24 January 1978 the Russian satellite Cosmos-954 reentered the atmosphere over northern Canada. By use of high-altitude balloons, the atmosphere was sampled during 1978 up to an altitude of 39 kilometers to detect particulate debris from the reactor on board the satellite. Enriched uranium-bearing aerosols at concentrations and particle sizes compatible with partial burnup of the Cosmos-954 reactor were detected only in the high polar stratosphere. 相似文献
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H Koenig 《Science (New York, N.Y.)》1969,164(877):310-312
Fluorocitrate, a Krebs cycle inhibitor, induices neurons to rapidly expel multitudinous lysosomes, mitochondria, and other cytoplasmic constituents into their axons. After convulsive seizures commence, spectacular axonal balloons develop owing to obstruction of axonal flow by "log jams" of extruded organelles. A swelling of neuronal mitochondria is apparently responsible for the disgorgement of cytoplasmic material into axons. 相似文献
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Blamont JE Young RE Seiff A Ragent B Sagdeev R Linkin VM Kerzhanovich VV Ingersoll AP Crisp D Elson LS Preston RA Golitsyn GS Ivanov VN 《Science (New York, N.Y.)》1986,231(4744):1422-1425
Both VEGA balloons encountered vertical winds with typical velocities of 1 to 2 meters per second. These values are consistent with those estimated from mixing length theory of thermal convection. However, small-scale temperature fluctuations for each balloon were sometimes larger than predicted. The approximate 6.5-kelvin difference in temperature consistently seen between VEGA-1 and VEGA-2 is probably due to synoptic or planetary-scale nonaxisymmetric disturbances that propagate westward with respect to the planet. There is also evidence from Doppler data for the existence of solar-fixed nonaxisymmetric motions that may be thermal tides. Surface topography may influence atmospheric motions experienced by the VEGA-2 balloon. 相似文献
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哈维氏弧菌的血清型与菌苗抗原性的关系 总被引：2，自引：0，他引：2
采用不同血清型哈维氏弧菌Vibrio hanwyi624、809和106等3个菌株，制备成福尔马林灭活菌苗，注射接种大黄鱼4周后，通过血清中凝集、交叉凝集抗体效价测定以及活菌攻毒试验，证明了3个菌株制备的菌苗抗原性存在差异。 相似文献
20.
Rats never before exposed to opioids rapidly learned to press a lever for microinjections of morphine into the ventral tegmental area. Challenge by a narcotic antagonist produced no signs of physical dependence. Dependence was not seen after long-term morphine infusions into the ventral tegmentum but was seen after similar infusions into the periventricular gray region. Thus a major rewarding property of morphine is independent of the drug's ability to produce physical dependence. These data challenge models of drug addiction that propose physical dependence as necessary for the rewarding effects of opioids. 相似文献