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1.
The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research 总被引:2,自引:0,他引:2
Pollock C.J. C:son-Brandt P. Burch J.L. Henderson M.G. Jahn J.-M. McComas D.J. Mende S.B. Mitchell D.G. Reeves G.D. Scime E.E. Skoug R.M. Thomsen M. Valek P. 《Space Science Reviews》2003,109(1-4):155-182
Energetic Neutral Atom (ENA) imaging has contributed substantially to substorm research. This technique has allowed significant advances in areas such as observation and quantification of injected particle drift as a function of energy, observation of dynamics in the tail that are directly related to the effects of imposed (growth phase) and induced (expansion phase) electric fields on the plasma, the prompt extraction of oxygen from the ionosphere during substorms, the relationship between storms and substorms, and the timing of substorm ENA signatures. We present discussion of the advantages and shortcomings of the ENA technique for studying space plasmas. Although the technique is in its infancy, it is yielding results that enrich our understanding of the substorm process and its effects. 相似文献
2.
H Rahmann R Hilbig J Flemming K Slenzka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(6-7):121-124
This study presents qualitative and quantitative data concerning gravity-dependent changes in the swimming behaviour of developing cichlid fish larvae (Oreochromis mossambicus) after a 9 resp. 10 days exposure to increased acceleration (centrifuge experiments), to reduced gravity (fast-rotating clinostat), changed accelerations (parabolic aircraft flights) and to near weightlessness (2nd German Spacelab Mission D-2). Changes of gravity initially cause disturbances of the swimming performance of the fish larvae. With prolonged stay in orbit a step by step normalisation of the swimming behaviour took place in the fish. After return to 1g earth conditions no somersaulting or looping could be detected concerning the fish, but still slow and disorientated movements as compared to controls occurred. The fish larvae adapted to earth gravity within 3-5 days. Fish seem to be in a distinct early developmental stages extreme sensitive and adaptable to altered gravity; However, elder fish either do not react or show compensatory behaviour e.g. escape reactions. 相似文献
3.
K L Kohlmann P Westgate A Velayudhan J Weil A Sarikaya M A Brewer R L Hendrickson M R Ladisch 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(1-2):251-265
A large amount of inedible plant material composed primarily of the carbohydrate materials cellulose, hemicellulose, and lignin is generated as a result of plant growth in a Controlled Ecological Life-Support System (CELSS). Cellulose is a linear homopolymer of glucose, which when properly processed will yield glucose, a valuable sugar because it can be added directly to human diets. Hemicellulose is a heteropolymer of hexoses and pentoses that can be treated to give a sugar mixture that is potentially a valuable fermentable carbon source. Such fermentations yield desirable supplements to the edible products from hydroponically-grown plants such as rapeseed, soybean, cowpea, or rice. Lignin is a three-dimensionally branched aromatic polymer, composed of phenyl propane units, which is susceptible to bioconversion through the growth of the white rot fungus, Pluerotus ostreatus. Processing conditions, that include both a hot water pretreatment and fungal growth and that lead to the facile conversion of plant polysaccharides to glucose, are presented. 相似文献
4.
Lenz R. Schuler K. Younis M. Wiesbeck W. 《Aerospace and Electronic Systems Magazine, IEEE》2006,21(5):30-33
In April 2006, the TerraSAR-X satellite was launched. This paper describes the development of a novel and highly integrated, digitally-controlled active SAR system calibrator (DARC). It consists of both an active transponder path for absolute radiometric calibration and a calibrated receiver chain for antenna pattern evaluation of the satellite antenna. A total of 16 active transponder and receiver systems and 17 receiver-only systems will be fabricated for a calibration campaign in 2006. 相似文献
5.
A problem of determining a shape of the airfoil being streamlined by a potential incompressible inviscid flow is solved by
the successive approximation method using a specified chord velocity diagram. It is shown that a closed airfoil that possesses
a specified chord velocity diagram can be constructed with a sufficient accuracy; if the chord diagram is unsuccessfully specified,
the closed airfoil may prove to be not univalent, that is, physically unrealizable. 相似文献
6.
Garenaux K. Merlet T. Alouini M. Lopez J. Vodjdani N. Boula-Picard R. Fourdin C. Chazelas J. 《Aerospace and Electronic Systems Magazine, IEEE》2007,22(2):3-8
Radar systems require transmission of very high purity signals. Photonics is now mature enough to achieve analog transmission with very low noise, strong immunity, and wide-bandwidth even in harsh environments. We present our recent developments of optimized optical links dedicated to radar and multifunction systems 相似文献
7.
Search and rescue satellite aided tracking (SARSAT) depends on the processing of emergency locator transmitter (ELT) signals which are received by a satellite in low polar orbit. Since the signal from a distressed vehicle is normally immersed in a background of other ELT signals (false alarms), interference, and noise, different methods of spectral estimation can provide advantages in estimating carrier frequency. A comparison between average spectrum and minimum spectrum for several real signals is provided here. 相似文献
8.
The robustness of a moving-bank multiple model adaptive estimator/controller to order reduction in the controller design model is examined. It is shown that the adaptive mechanism and bank-moving logic are not confounded by the effects of unmodeled higher order modes of a large flexible spacestructure. Control characteristics are achieved that are essentially equivalent to those of an artificially informed benchmark controller 相似文献
9.
This paper discusses and evaluates two innovative SETI education programs conducted at the University of Western Sydney, viz: the SETI Pathways Program and the Life in the Universe Curriculum Project. 相似文献
10.
Bucci N.J. Nespor J.D. Urkowitz H. Mokry D. Brown R. Baldygo W. 《Aerospace and Electronic Systems Magazine, IEEE》1995,10(8):37-43
A major technology barrier to the application of pulse compression for the meteorological functions required by a next generation ATC radar is range/time sidelobes which mask and corrupt observations of weak phenomena occurring near areas of strong extended meteorological scatterers. Techniques for suppressing range sidelobes are well known but without prior knowledge of the scattering medium's velocity distribution their performance degrades rapidly in the presence of Doppler. Recent investigations have presented a “doppler tolerant” range sidelobe suppression technique. The thrust of the work described herein is the extension of previous simulations to actual transmitted dispersed/coded waveforms using the S-band surveillance radar located at Rome Laboratory Surveillance Facility. The objectives of the experiment are: 1) to extend the verification of the simulation of the Doppler tolerant technique; and 2) to demonstrate that the radar transmitter, waveform generator, and receiver imperfections do not significantly degrade resolution, performance or reliability of meteorological spectral moment estimates 相似文献