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排序方式: 共有108条查询结果,搜索用时 562 毫秒
51.
A new model of albedo and emissivity of the martian seasonal caps represented as porous CO2 slabs containing spherical voids and dust particles is described. In the model, a radiative transfer model is coupled with a microphysical model in order to link changes in albedo and emissivity to changes in porosity caused by ice metamorphism. The coupled model is capable of reproducing temporal changes in the spectra of the caps taken by the Thermal Emission Spectrometer onboard the Mars Global Surveyor and it can be used as the forward model in the retrievals of the caps' physical properties (porosity, dust abundance, void and dust grain size) from the spectra. Preliminary results from such inversion studies are presented. 相似文献
52.
Nurur Rahman †‡ Janusz Krywult Patrick M. Motl Piotr Flin Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2006,367(2):838-850
We have made a comparative study of morphological evolution in simulated dark matter (DM) haloes and X-ray brightness distribution, and in optical clusters. Samples of simulated clusters include star formation with supernovae feedback, radiative cooling and simulation in the adiabatic limit at three different redshifts, z = 0.0, 0.10 and 0.25. The optical sample contains 208 Abell, Corwin & Olowin (ACO) clusters within redshift, z ≤ 0.25 . Cluster morphology, within 0.5 and 1.0 h −1 Mpc from cluster centre, is quantified by multiplicity and ellipticity.
We find that the distribution of the DM haloes in the adiabatic simulation appears to be more elongated than the galaxy clusters. Radiative cooling brings halo shapes in excellent agreement with observed clusters; however, cooling along with feedback mechanism makes the haloes more flattened.
Our results indicate relatively stronger structural evolution and more clumpy distributions in observed clusters than in the structure of simulated clusters, and slower increase in simulated cluster shapes compared to those in the observed one.
Within z ≤ 0.1 , we note an interesting agreement in the shapes of clusters obtained from the cooling simulations and observation. We also note that the different samples of observed clusters differ significantly in morphological evolution with redshift. We highlight a few possibilities responsible for the discrepancy in morphological evolution of simulated and observed clusters. 相似文献
We find that the distribution of the DM haloes in the adiabatic simulation appears to be more elongated than the galaxy clusters. Radiative cooling brings halo shapes in excellent agreement with observed clusters; however, cooling along with feedback mechanism makes the haloes more flattened.
Our results indicate relatively stronger structural evolution and more clumpy distributions in observed clusters than in the structure of simulated clusters, and slower increase in simulated cluster shapes compared to those in the observed one.
Within z ≤ 0.1 , we note an interesting agreement in the shapes of clusters obtained from the cooling simulations and observation. We also note that the different samples of observed clusters differ significantly in morphological evolution with redshift. We highlight a few possibilities responsible for the discrepancy in morphological evolution of simulated and observed clusters. 相似文献
53.
Janusz Sylwester Zbigniew Kordylewski Stefan Płocieniak Marek Siarkowski Mirosław Kowaliński Stanisław Nowak Witold Trzebiński Marek Śtęślicki Barbara Sylwester Eugeniusz Stańczyk Ryszard Zawerbny Żaneta Szaforz Kenneth J. H. Phillips František Fárník Anatolyi Stepanov 《Solar physics》2015,290(12):3683-3697
54.
J. Kaluzny I. B. Thompson W. Krzeminski A. Schwarzenberg-Czerny 《Monthly notices of the Royal Astronomical Society》2006,365(2):548-554
We present the results of a photometric survey for variable stars in the central region of the nearby globular cluster NGC 6397. Time-series photometry was obtained for 30 variable objects. The sample includes 12 new objects, of which six show periodic light curves and two are eclipsing binaries of unknown period. Six variables possess certain and three possess likely X-ray counterparts detected with the Chandra observatory. Among them, four are cataclysmic variables and one is a foreground eclipsing binary. The cataclysmic variable CV2 exhibited a likely dwarf nova type outburst in 2003 May. The cataclysmic variable CV3 was observed at 18.5 < V < 20.0 during five observing runs, but went into a low state in 2003 May when it reached V > 22 . We have found that the light curve of the optical companion to the millisecond pulsar PSR J1740−5340 exhibits noticeable changes of its amplitude on a time-scale of a few months. A shallow eclipse with Δ V = 0.03 mag was detected in one of the cluster turn-off stars suggesting the presence of a large planet or brown dwarf in orbit. 相似文献
55.
56.
Jakub Jirásek Lada Hýlová Martin Sivek Janusz Jureczka Karel Martínek Ivana Sýkorová Mark Schmitz 《International Journal of Earth Sciences》2013,102(4):989-1006
The Main Ostrava Whetstone (MOW) is an important lithostratigraphic horizon of the Late Carboniferous sedimentary fill of the late Palaeozoic foreland Upper Silesian Basin. It is the largest and best-identified volcanogenic horizon in the basin, reaching thicknesses of 15.3 m and occupying an area of ca 2,973 km2 and a volume after lithification of 9.24 km3. It consists of volcanic materials transported to the basin probably by an aeolian process. Just after sedimentation, these materials were redeposited a short distance away in a shallow water environment. Granularity corresponds to a range from argillaceous siltstones to fine-grained sandstones. The components are dominated by glass shards replaced by clay minerals (mixed illite–smectite structures) in addition to quartz of volcanogenic and terrigenous origins. Sanidine and a plagioclase close to albite are also present. The sedimentary structures, micro-structures and composition of the MOW indicate variable and dynamic hydrodynamic conditions. The MOW represents a series of flooding events, which could be connected with unusual rainfall. Such major flooding events were most likely induced by volcanic eruptions. The available drill-core log data were used to construct a digital model of the whetstone, which showed an east–west zonality in the thicknesses, with the majority being synsedimentary. CA-TIMS U–Pb dating the volcanogenic zircons yields an age of 327.35 ± 0.15 Ma. The source location of the volcanogenic material is not clear; however, it is presumed to have been located in the west of the Upper Silesian Basin. 相似文献
57.
GPS-derived height changes in diurnal and sub-diurnal timescales 总被引:1,自引:0,他引:1
This paper describes the research concerning precise short-time GPS solutions conducted in the Centre of Applied Geomatics,
Military University of Technology, Warsaw, Poland. The data from ASG-EUPOS (Polish Active Geodetic Network) was processed
using Bernese 5.0 software and EPN (EUREF Permanent Network) standards and models. In this study, the adapted 3-hour observation
window is shifted every hour for obtaining hourly geocentric coordinates in ITRF2005 reference frame. The adjusted network
consisted of over 130 stations from Poland and the neighbouring countries, the period covered observations collected from
June 2008 through June 2010. These two years of observations allowed for examining short-period oscillations which were found
to be closely related to the tidal (dynamic) frequencies. The analysis of the residua from the IERS2003 tidal model was performed
using the least squares method with the Eterna software. It confirmed the existence of significant (several millimetres) oscillations
in the frequencies corresponding to S1, K1 and K2. The paper describes the idea of data processing and analysis, presents
the results of vertical (the Up component) oscillations in main tidal frequency bands, and also includes discussion of possible
explanation of the existence of short-period oscillations in the GPS precise solutions and the possibility of propagation
of short-period oscillations into long-period spurious changes in the daily (standard) GPS solutions. 相似文献
58.
Monika B. Kalinowska Paweł M. Rowiński Janusz Kubrak Dorota Mirosław-Świątek 《Acta Geophysica》2012,60(1):214-231
The problem of two-dimensional mathematical modelling of heated cooling water discharges into running waters is considered
in the paper. Two models — one for the evaluation of 2D turbulent velocity field and the other, developed by authors of the
study, for 2D heat transport in open-channels — were used in the calculations. Relevant scenarios of the spread of heated
water discharged from a designed gas-stem power plant to be constructed at the Vistula River were presented. Environmentally
most friendly variant of the discharge of the thermal pollution was selected from among four various variants. 相似文献
59.
Fast direct GPS P-Code acquisition 总被引:5,自引:0,他引:5
GPS P-Code has a higher chipping rate, better accuracy, and anti-jamming property than C/A code. Traditionally, GPS P-Code acquisition depends on handover from C/A code. This potentially needs long acquisition time. Moreover, when C/A code is not available, it is no longer possible to acquire GPS P-Code through handover from C/A code. The purpose of this paper is to describe a new overlap average method to facilitate hardware design of fast direct P-Code acquisition. It allows the rapid code phase search to acquire GPS P-Code signals, and also decreases the hardware resource requirement. The small size FFT in the proposed methods is very promising for fast FPGA hardware system design using FFT cores. The simulation results and theoretical analysis are included demonstrating the overall performance of the proposed method.
相似文献
Jing PangEmail: Phone: +1-916-2784549Fax: +1-916-2787215 |
60.