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291.
Katsuyuki Noguchi Andreas Richter Heinrich Bovensmann Andreas Hilboll John P. Burrows Hitoshi Irie Sachiko Hayashida Yu Morino 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We have conducted a feasibility study for the geostationary monitoring of the diurnal variation of tropospheric NO2 over Tokyo. Using NO2 fields from a chemical transport model, synthetic spectra were created by a radiative transfer model, SCIATRAN, for summer and winter cases. We then performed a Differential Optical Absorption Spectroscopy (DOAS) analysis to retrieve NO2 slant column densities (SCDs), and after converting SCDs into vertical column densities (VCDs), we estimated the precision of the retrieved VCDs. The simulation showed that signal-to-noise ratio (SNR) ? 500 is needed to detect the diurnal variation and that SNR ? 1000 is needed to observe the local minimum occurring in the early afternoon (LT13–14) in summer. In winter, the detection of the diurnal variation during LT08–15 needs SNR ? 500, and SNR ? 1000 is needed if early morning (LT07) and early evening (LT16) are included. The currently discussed sensor specification for the Japanese geostationary satellite project, GMAP-Asia, which has a horizontal resolution of 10 km and a temporal resolution of 1hr, has demonstrated the performance of a precision of several percent, which is approximately corresponding to SNR = 1000–2000 during daytime and SNR ? 500 in the morning and evening. We also discuss possible biases caused by the temperature dependence of the absorption cross section utilized in the DOAS retrieval, and the effect of uncertainties of surface albedo and clouds on the estimation of precisions. 相似文献
292.
This paper describes some new concepts in dealing with the circuitry for Loran-C automatic timing systems. The conventional analog techniques associated with phase-adjusting networks have been replaced by an incremental digital phase-shifting device. The Loran-C period generator includes facilities for delay compensation by means of an epoch monitor producing a 1-Hz output coincident with the master station TOC (time of coincidence). The required initial time information has to be accurate within ± 20 ms. The automatic format identification and decoding equipment together form a system which takes into account the information of every Loran-C pulse. Owing to the use of digital signal treatment, the synchronization accuracy is limited only by the resolution of the incremental phase shift. The automatic cycle selection device is based on sampling techniques where the derivative of the envelope is calculated. The time of coincidence has to be precalculated and fed into the thumbwheel memory of the epoch monitor, which is automatically initiated when the synchronizing operations are concluded. For VLBI purposes and transcontinental use, the accuracy of this system will be better than 1 ?s when post corrections, supplied by the U.S. Naval Observatory, are taken into account. 相似文献
293.
N. Wichaipanich P. Supnithi T. Tsugawa T. Maruyama T. Nagatsuma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
In this work, the foF2 and hmF2 parameters at the conjugate points near the magnetic equator of Southeast Asia are studied and compared with the International Reference Ionosphere (IRI) model. Three ionosondes are installed nearly along the magnetic meridian of 100°E; one at the magnetic equator, namely Chumphon (10.72°N, 99.37°E, dip angle 3.0°N), and the other two at the magnetic conjugate points, namely Chiang Mai (18.76°N, 98.93°E, dip angle 12.7°N) and Kototabang (0.2°S, 100.30°E, dip angle 10.1°S). The monthly hourly medians of the foF2 and hmF2 parameters are calculated and compared with the predictions obtained from the IRI-2007 model from January 2004 to February 2007. Our results show that: the variations of foF2 and hmF2 predicted by the IRI-2007 model generally show the similar feature to the observed data. Both parameters generally show better agreement with the IRI predictions during daytime than during nighttime. For foF2, most of the results show that the IRI model overestimates the observed foF2 at the magnetic equator (Chumphon), underestimates at the northern crest (Chiang Mai) and is close to the measured ones at the southern crest of the EIA (Kototabang). For hmF2, the predicted hmF2 values are close to the hmF2(M3000F2OBS) during daytime. During nighttime, the IRI model gives the underestimation at the magnetic equator and the overestimation at both EIA crests. The results are important for the future improvements of the IRI model for foF2 and hmF2 over Southeast Asia region. 相似文献
294.
Liu H. Ghafoor A. Stockmann P.H. 《IEEE transactions on aerospace and electronic systems》1992,28(2):324-334
The Gram-Schmidt orthogonalization (GSO) algorithm has excellent numerical performance and is readily applicable to systolic implementations such as in a field of adaptive cancellation systems. A modified GSO algorithm for a fully adaptive array is proposed and computer simulations show that the proposed algorithm gives superior performance. A systolic implementation of the proposed GSO algorithm for fully adaptive array is presented. A feedback mode GSO algorithm for use with analog weights is also presented and has been shown to have excellent performance in the presence of weight errors 相似文献
295.
M P R Waligórski M Hollmark B Lind I Gudowska 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(6):1378-1382
Based on irradiation with 45 MeV/u N and B ions and with Co-60 gamma rays, cellular parameters of Katz's track structure model have been fitted for the survival of V79-379A Chinese hamster lung fibroblasts. Cellular parameters representing neoplastic transformations in C3H10T/1/2 cells after their irradiation with heavy ion beams, taken from earlier work, were also used to model the radiation hazard in deep space, following the system for evaluating, summing and reporting occupational exposures proposed in 1967 by a subcommittee of NCRP. We have performed model calculations of the number of transformations in surviving cells, after a given fluence of heavy charged particles of initial energy 500 MeV/u, penetrating thick layers of cells. We take the product of cell transformation and survival probabilities, calculated along the path lengths of charged particles using cellular survival and transformation parameters, to represent a quantity proportional to the \"radiation risk factor\" discussed in the NCRP document. The \"synergistic\" effect of simultaneous charged particle transfers is accounted for by the \"track overlap\" mode inherent in the model of Katz. 相似文献
296.
297.
298.
P. Ajith Kumar Shashi Kumar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Prolonged exposure of the microscopic outer layer of the lunar surface to the space environment leads to the maturation of the surface. Maturation can be quantified and it may be expressed in terms of optical maturity (OMAT). Optical maturity estimations are very much helpful in the identification and mapping of the major minerals present on the lunar regolith. Estimation of the maturation and mineral mapping using remote sensing techniques are achieved, by coupling spectral reflectance of the lunar surface with an optimized origin. The present work estimates the optical maturity and Ferrous oxide content of the Goldschmidt and Schrodinger craters, through the recalibration of the classical method of Lucey et al. (2000a) with an origin of (0.08, 1.18) and Moon Mineralogy Mapper (M3) data. The overall recalibration results assure that the craters are highly matured. 相似文献
299.
Gorczynski RM Gorczynski CP Gorczynski LY Hu J Lu J Manuel J Lee L 《Acta Astronautica》2005,56(9-12):890-899
We examined expression of genes associated with cytokine production, and genes implicated in regulating bone metabolism, in bone stromal and osteoblast cells incubated under standard ground conditions and under conditions of neutral buoyancy, and in the presence/absence of serum from normal or sleep-deprived mice. We observed a clear interaction between these two conditions (exposure to neutral buoyancy and serum stimulation) in promoting enhanced osteoclastogenesis. Both conditions independently altered expression of a number of cytokines implicated in the regulation of bone metabolism. However, using stromal cells from IL-1 and TNFx cytokine(r) KO mice, we concluded that the increased bone loss under microgravity conditions was not primarily cytokine mediated. 相似文献
300.
U. Villante M. De Lauretis P. Francia M. Vellante A. Piancatelli 《Space Science Reviews》2006,122(1-4):107-117
We review the results obtained in the frequency range of Pc3 (22-100 mHz) and Pc4 (7-22 mHz) pulsations at Italian Antarctic stations in the southern polar cap (“Mario Zucchelli”, at Terra Nova Bay, TNB, 80˚.S; “Concordia”, the Italian/French base at Dome C, DMC, 89˚.S). The absence of a midnight enhancement in the pulsation power suggests a negligible substorm influence at extreme latitudes, while the sharp noon enhancement, which appears only at TNB, is determined by the closer proximity of the station to cusp related phenomena. The relationship between the frequency of the band-limited signals and the interplanetary magnetic field strength, the cone angle influence, and the higher correlation of the Pc3 power with the solar wind speed in the morning hours suggest a global scenario in which upstream waves would be mainly responsible for the mid-frequency activity in the polar cap. However, the polarization pattern is odd with respect to the predictions for tailward propagating modes. 相似文献