排序方式： 共有45条查询结果，搜索用时 15 毫秒
41.
Uniformly Redundant Arrays (URA's) are two–dimensional binary arrays with constant sidelobes of their periodic autocorrelation function. They are widely agreed upon to be optimum mask patterns for coded aperture imaging, particularly in imaging systems with a cyclic coded mask. In this paper, a survey of all currently known construction methods for URA's is given and the sizes and open fractions of the arrays resulting from each construction method are pointed out. Alternatives to URA's for situations in which a URA does not exist, are discussed. 相似文献
42.
Assimilating along-track SLA data using the EnOI in an eddy resolving model of the Agulhas system 总被引：1，自引：1，他引：0
Björn C. Backeberg François Counillon Johnny A. Johannessen Marie–Isabelle Pujol 《Ocean Dynamics》2014,64(8):1121-1136
The greater Agulhas Current is one of the most energetic current systems in the global ocean. It plays a fundamental role in determining the mean state and variability of the regional marine environment, affecting its resources and ecosystem, the regional weather and the global climate on a broad range of temporal and spatial scales. In the absence of a coherent in-situ and satellite-based observing system in the region, modelling and data assimilation techniques play a crucial role in both furthering the quantitative understanding and providing better forecasts of this complicated western boundary current system. In this study, we use a regional implementation of the Hybrid Coordinate Ocean Model and assimilate along-track satellite sea level anomaly (SLA) data using the Ensemble Optimal Interpolation (EnOI) data assimilation scheme. This study lays the foundation towards the development of a regional prediction system for the greater Agulhas Current system. Comparisons to independent in-situ drifter observations show that data assimilation reduces the error compared to a free model run over a 2-year period. Mesoscale features are placed in more consistent agreement with the drifter trajectories and surface velocity errors are reduced. While the model-based forecasts of surface velocities are not as accurate as persistence forecasts derived from satellite altimeter observations, the error calculated from the drifter measurements for eddy kinetic energy is significantly lower in the assimilation system compared to the persistence forecast. While the assimilation of along-track SLA data introduces a small bias in sea surface temperatures, the representation of water mass properties and deep current velocities in the Agulhas system is improved. 相似文献
43.
C.S. Möller U. Fritze–V. Alvensleben K.J. Fricke D. Calzetti 《Astrophysics and Space Science》2001,276(2-4):799-806
As a tool for interpreting nearby and high-redshift galaxy data from the optical to K-band we present our chemically consistent spectrophotometric evolutionary synthesis models. These models take into account
the increasing initial metallicity of successive stellar generations using recently published metallicity-dependent stellar
evolutionary tracks, stellar yields and model atmosphere spectra. The influence of the metallicity is analysed. Dust absorption
is included on the basis of gas content and abundance as it varies with time and galaxy type. We compare our models with IUE
template spectra and are able to predict UV fluxes for different spectral types. Combining our models with a cosmological
model we obtain evolutionary and k corrections for various galaxy types and show the differences from models using only solar metallicity input physics as a
function of redshift, wavelength band and galaxy type.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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45.
G. Asencio–Cortés S. Scitovski R. Scitovski F. Martínez–Álvarez 《Earth Science Informatics》2017,10(3):303-320
The prediction of earthquakes is a task of utmost difficulty that has been addressed in many different ways. However, an initial definition of the area of interest is needed, with adequate catalogs. In this work, different seismogenic zones proposals in the Republic of Croatia are studied, in terms of predictability. Such zones have been characterized with widely used seismicity parameters. Later, studies based on training and test sets properties as well as the quality of the data involved are carried out. The studies presented in this work analyze the prediction performance across the earthquake magnitude time series of the target seismogenic zones. Results show that specific prediction techniques could be used in some zones to improve earthquake magnitude prediction. 相似文献