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971.
972.
Teresita Heredia Ana G. Elias 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The precipitation over Tucuman (26.8°S; 65.2°W), which is representative of the Northwestern region of Argentina, is analyzed in search of an association with solar and geomagnetic activity, with the purpose of contributing to the controversial issue on the connection between climate variation and anthropogenic vs. natural forcing. Monthly time series of precipitation, sunspot number (Rz), and aa index were used for the period 1884–2010. A wavelet analysis was performed first which, due to the time series length, shows significant results only for periodicities lower than 32 years. Due to the transient character and non-constant phase of the results, any sustained wavelet coherence between precipitation and either sunspots or aa could be noticed. Moving averages and correlations were also assessed. The 11 and 22-year running mean of precipitation is positively correlated to Rz and aa when the whole period of analysis is considered. However, a shift in the long-term behavior of precipitation is noticed around 1940, which implies different correlation values with Rz and aa when the period before or after this year are considered. The solar cycle length is also considered for this statistical study and partly confirms the results obtained with Rz and aa. We propose plausible physical explanations based on geomagnetic activity and total solar irradiance effects over atmospheric circulation that could support the statistical result. A deeper analysis and broader geographical coverage is needed in order to detect a connection between precipitation and solar variability discernible from greenhouse gases effects. We emphasize the idea of the importance of recognizing and quantifying the different forcing acting on precipitation (or any other climate parameter), which sometimes can be barely evident from a solely statistical analysis. 相似文献
973.
S.R. Sanderson J.M. Austin Z. Liang F. Pintgen J.E. Shepherd H.G. Hornung 《Progress in Aerospace Sciences》2010,46(2-3):116-131
We note the common existence of a supersonic jet structure locally embedded within a surrounding transonic flow field in the hitherto unrelated phenomena of unstable gaseous detonation and hypervelocity blunt body shock wave interaction. Extending prior results that demonstrate the consequences of reduced endothermic reaction rate for the supersonic jet fluid in the blunt body case, we provide an explanation for observations of locally reduced OH PLIF signal in images of the keystone reaction zone structure of weakly unstable detonations. Modeling these flow features as exothermically reacting jets with similarly reduced reaction rates, we demonstrate a mechanism for jetting of bulk pockets of unreacted fluid with potentially differing kinetic pathways into the region behind the primary detonation front of strongly unstable mixtures. We examine the impact of mono-atomic and diatomic diluents on transverse structure. The results yield insight into the mechanisms of transition and characteristic features of both weakly and strongly unstable mixtures. 相似文献
974.
The multicriteria optimization problem on joint choice of a carrier aircraft and main design parameters of an air launcher
decoy are considered. The estimation of the design parameter values for the aerial decoy is based on the statistical data
processing with the use of the methods for constructing nonlinear regression. The result of solving this problem is a set
of Pareto-optimal geometry characteristics of the carrier aircraft and aerial decoy. A person who is responsible for decision-making
should choose the most reasonable variant from these characteristics. An example of solving the problem is presented. 相似文献
975.
Jose Alvarez-Ramirez Juan C. EcheverriaEduardo Rodriguez 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Several studies have suggested that the Sun and Moon cycles affect the Earth climatic dynamics. Nevertheless, there is a long-standing controversy whether solar variability and tides can significantly generate climate change, and how this may occur. Spectral analysis of climatic indices has provided only indirect evidences of the effects of solar–tidal periodicities in the Earth climate. This work addresses the issue by considering the dynamics of the daily North Atlantic Oscillation index over the period from 1950 to 2009. In contrast to previous studies, this work proposes that external cycles can be detected in the autocorrelation dynamics rather than in the raw North Atlantic Oscillation index series. Here, the R/S-scaling analysis is used to quantify, via the so-called Hurst exponent, the presence of autocorrelations along the studied years. Fourier analysis scan of the autocorrelation series thus show two prominent spectral components near (±3%) the lunar tidal 4.425 and the solar 11 years cycles. Intermediate spectral components near 6.4, 7.75 and 8.9 years are proposed to be, at least partially, a result of energy capture from internal mechanisms into cycles resulting from the nonlinear resonance of the fundamental solar–tidal cycles. The dominant effect of the solar variability is clarified by showing that in about 70% of the studied period the sunspot number and the Hurst exponent phases are synchronized, indicating that a higher solar activity enhances the North Atlantic Oscillation index predictability. 相似文献
976.
V.V. Paznukhov V.G. Galushko B.W. Reinisch 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
A technique for studying ionospheric wavelike phenomena, primarily AGW/TID events, is developed based on the solution of the problem of radio wave propagation in ionospheric plasma disturbed by wavelike processes. A perfectly reflecting surface model is used for representing TIDs propagating at ionospheric heights. This technique is a generalization of the Frequency-and-Angular Sounding (FAS) method developed earlier for oblique TID diagnostics using transmitters of opportunity. Trial measurements were made in November 2003 with two DPS-4 systems at Millstone Hill Observatory, providing experimental validation of the developed method by comparing the results of disturbance diagnostics to those simultaneously obtained with the original (oblique) FAS method. The TID parameters recovered during the November 2003 campaign suggest that the observed disturbances predominately propagated equatorward which likely indicates their sources to be in the auroral region. The equatorward propagating AGW/TIDs are typical for disturbed geomagnetic conditions which were observed during the campaign. Implementation of the generalized FAS technique in the DPS sounder allowed development of a dedicated data acquisition system for ionospheric disturbance diagnostics. Routine measurements with the developed technique using the existing world-wide network of Digisondes (GIRO) will make it possible to conduct large-scale studies of the AGW/TID phenomena. 相似文献
977.
Performance of 10- and 20-target MSE classifiers 总被引:2,自引:0,他引:2
Novak L.M. Owirka G.J. Brower W.S. 《IEEE transactions on aerospace and electronic systems》2000,36(4):1279-1289
MIT Lincoln Laboratory is responsible for developing the ATR (automatic target recognition) system for the DARPA-sponsored SAIP program; the baseline ATR system recognizes 10 GOB (ground order of battle) targets; the enhanced version of SAIP requires the ATR system to recognize 20 GOB targets. This paper presents ATR performance results for 10- and 20-target mean square error (MSE) classifiers using high-resolution SAR (synthetic aperture radar) imagery. 相似文献
978.
D Leugner T Streibel H Rocher G Reitz W Heinrich 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1998,22(4):511-515
Stacks of CR-39 plastic nuclear track detectors were mounted inside the MIR-station during the EUROMIR-94-mission. We present LET-spectra determined separately for long range cosmic ray heavy ions and for short range target fragments produced in nuclear interactions of cosmic rays and measured charge distributions for relativistic and stopping particles. 相似文献
979.
An elastically supported, tuned gyroscope is a complex device, but experience has shown that it can be represented by mathematical models by means of which practically all of its characteristic errors can be analyzed and predicted with good accuracy. The gyro angular transfer function, derived in [1], serves as an excellent basis of evaluation of errors due to asymmetries of the gimballing system and effects of rotor angular offsets. The gyro translational transfer function, derived in this paper, may be used in the analysis of errors caused by linear acceleration inputs. 相似文献