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951.
K M Deeley M L Duldig J E Humble 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):1049-1052
The relativistic solar particle event of 4 May 1960, resulting in a cosmic ray ground level enhancement, occurred well before modern analysis techniques were available. We have located surviving data from 23 neutron monitors and have used these to estimate the spectrum, mean arrival direction and particle pitch angle distribution as the event progressed. We find that the apparent particle arrival direction was at equatorial latitudes, over northern South America, in contrast to contemporary analyses that proposed it to be over North America. Our modified power law spectra are broadly consistent with earlier results. Data from stations above sea level need to be corrected for altitude using a two-attenuation length technique. The standard method involves comparison of data from two relatively close stations at significantly different altitude. We have shown that this method may be unreliable in cases, such as this, of quite sharp anisotropy. 相似文献
952.
Maneuvering target tracking using extended Kalman filter 总被引:1,自引:0,他引:1
Cortina E. Otero D. D'Attellis C.E. 《IEEE transactions on aerospace and electronic systems》1991,27(1):155-158
A numerically well-conditioned, quasi-extended Kalman filter is proposed. The filter is numerically described. The simulation results presented show that the estimation performance of the quasi-extended filter is superior, for short distances, compared with the widely used linear tracking filters. In addition, the simplicity of the quasi-extended filter makes it very easy to implement 相似文献
953.
Fontana R.J. Richley E.A. Beard L.C. Barney J. 《Aerospace and Electronic Systems Magazine, IEEE》2004,19(5):36-41
Under Phase I of the Defense Advanced Research Projects Agency (DARPA) Networking in Extreme Environments (NETEX) initiative, Multispectral Solutions, Inc. (MSSI) was tasked with the development of a general-purpose, ultrawideband hardware simulator capable of reproducing a wide variety of ultrawideband (UWB) waveforms. The simulator, with UWB outputs from baseband through millimeter wave, was to be used for the purpose of electromagnetic susceptibility testing of legacy military radio, radar, and positioning systems. The ultimate goal of this portion of the Phase I program was the quantitative determination of those UWB parameters (e.g., frequency, power, pulse rate, pulse shape, dithering, etc.) which had the least impact on the operational performance of legacy designs. This describes the development of the MSSI NETEX UWB simulator (BFP1000). 相似文献
954.
S Philosoph-Hadas H Friedman S Meir R Berkovitz-SimanTov I Rosenberger A H Halevy P B Kaufman P Balk E J Woltering 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(5):921-932
The negative gravitropic response of cut flower stalks is a complex multistep process that requires the participation of various cellular components acting in succession or in parallel. The process was particularly characterized in snapdragon (Antirrhinum majus L.) spikes with regard to (1) gravity stimulus perception associated with amyloplast reorientation; (2) stimulus transduction mediated through differential changes in the level, action and related genes of auxin and ethylene and their possible interaction; (3) stimulus response associated with differential growth leading to stalk curvature; (4) involvement of cytosolic calcium and actin cytoskeleton. Results show that the gravity-induced amyloplast reorientation, differential over-expression of two early auxin responsive genes and asymmetrical distribution of free IAA are early events in the bending process. These precede the asymmetrical ethylene production and differential stem growth, which was derived from initial shrinkage of the upper stem side and a subsequent elongation of the lower stem side. Results obtained with various calcium- and cytoskeleton-related agents indicate that cytosolic calcium and actin filaments may play essential roles in gravitropism-related processes of cut flower stalks. Therefore, modulators of these two physiological mediators may serve as means for controlling any undesired gravitropic bending. 相似文献
955.
V N Sychev E Y Shepelev G I Meleshko T S Gurieva M A Levinskikh I G Podolsky O A Dadasheva V V Popov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(9):1529-1534
Since 1990, the orbital complex MIR has witnessed several incubator experiments for determination of spaceflight effects on embryogenesis of Japanese quail. First viable chicks who had completed the whole embryological cycle in MIR microgravity hatched out in 1990; it became clear that newborns would not be able to adapt to microgravity unaided. There were 8 successful incubations of chicks in the period from 1990 to 1999. In 1995-1997 the MIR-NASA space science program united Russian and US investigators. As a result, experiments Greenhouse-1 and 2 were performed with an effort to grow super dwarf wheat from seed to seed, and experiment Greenhouse-3 aimed at receiving two successive generations of Brassica rapa. But results of these experiments could not be used for definitive conclusions concerning effects of spaceflight on plant ontogenesis and, therefore, experiments Greenhouse-4 and 5 were staged within the framework of the Russian national space program. The experiments finally yielded wheat seeds. Some of the seeds was left on the space station and, being planted, gave viable seedlings which, in their turn, produced the second crop of space seeds. 相似文献
956.
N F Mikhaylenko S K Sytnik E K Zolotareva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(5):1007-1010
Photochemical characteristics and lipid composition of thylakoid membranes from 12 day-old pea leaves that were exposed to slow clino-rotation were examined and compared with a vertical control. Proton permeability of thylakoid membranes was estimated from light-induced proton uptake (delta H+) and post-illumination proton efflux in chloroplast suspensions. The delta pH magnitude was calculated from the level of light-induced quenching of 9-aminoacridine fluorescence. Proton permeability of thylakoid membranes increased during exposure to clino-rotation. When subsequently transferred to darkness, proton efflux increased almost 2-fold in clinorotated leaves. The results were compared with data on pigment and polar lipid composition of photosynthetic membranes in clino-rotated and control plants. It was concluded that both the increase of proton permeability and the decrease of polar lipid content in chloroplasts were induced by clino-rotation. 相似文献
957.
An environmental control system (ECS) being developed under the title of energy efficient environmental control system is described. The ECS is a closed-loop, electrically driven, vapor cycle system. The vapor cycle will have a compressor driven by a variable speed, high-voltage dc motor. The reasons for selecting this type of system are discussed here. Breadboard testing of a variable speed compressor to demonstrate the feasibility of such an approach has been completed. The testing results were used to develop a preliminary design of a prototype compressor. In future phases of the program, the prototype compressor will be developed; a prototype system will be constructed and laboratory tested; and finally the prototype system will be flight demonstrated. 相似文献
958.
Garry E. Hunt 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):75-84
In this paper we describe the Interactive Planetary Image Processing System (IPIPS) which was developed originally for studies of planetary meteorology and oceanography and is now used to support remote sensing studies in all areas of earth sciences. The computing machinery, the image display systems and the programming that unites them into an interactive research and analysis tool are described. We present some results from our recent research activities and also outline the role of IPIPS in the Imperial College and University of London teaching programme. 相似文献
959.
O A Troshichev E S Gorshkov S N Shapovalov V V Sokolovskii V V Ivanov V M Vorobeitchikov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(7):1619-1624
Variations of the gravitational field affected by the Sun and the Moon while the Earth's moving along the orbit seem to be a powerful source of many rhythmical processes typical of biochemical processes. Studies carried out in AARI revealed the obvious relationships between the dynamics of some biochemical reactions and lambda(D)-function describing the regular variations of the gravitational field under combined influence of the Sun and the Moon. The following of them are examined as examples: the rate of the unithiol oxidation in vitro, concentration of the thiol compounds in human urine, some hematological indicators (rate of the erythrocytes sedimentation, hemoglobin content). Compatibility of run of the biochemical indicators and lambda(D)-function is indicative of essential influence of the regular variations of the gravitational field on rhythmics of the biochemical processes. As this takes place, the solar activity acts like to the instability factor. Balance of the solar activity effects and the varying gravitational field effect alter in time depending on location in the solar activity cycle. 相似文献
960.
Bellegarda J.R. Titlebaum E.L. 《IEEE transactions on aerospace and electronic systems》1991,27(1):30-39
A formalism is presented for the analysis of general frequency hop waveforms, such as those suitable for use in coherent active radar and sonar echolocation systems as well as multiple-access spread-spectrum communications. This formalism is based on the concept of coincidence, or `hit', between two frequency hopping patterns. The collection of all possible hits, together with their locations, is recorded in time-frequency space, which produces the high array associated with the two patterns considered. If the code length is sufficiently small with respect to the time-bandwidth product chosen, the hit array can be viewed as a digital representation of the corresponding ambiguity function. Salient properties of the hit array formalism are derived, including simple relationships between hit arrays resulting from basic symmetry-preserving transformations. These properties make it possible to predict the performance of a given set of frequency hop waveforms directly from the associated set of frequency hopping patterns 相似文献