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41.
42.
Roberto F. Viotti Lucio Angelo Antonelli Sonja Rebecchi Corinne Rossi 《Journal of Astrophysics and Astronomy》2002,23(1-2):19-22
We have investigated with BeppoSAX the long term behaviour of the harder X-ray component of the supposed supermassive binary
system η Car along its 5.52 year cycle. We have found that in March 1998 during egress from the last December 1997 eclipse,
this component was the same as outside eclipse, but for a large (×3.5) increase of NH
h
, that can be attributed to the presence or formation of opaque matter in front of the source near periastron. Unexpectedly,
at that time the iron 6.7 keV emission line was 40% stronger. BeppoSAX has for the first time found ahard X-ray tail extending to at least 50 keV, that cannot be adequately fitted with an additional hotter thermal component. The 2–100 keV
spectrum of η Car is instead well fitted with an absorbed powerlaw spectrum with photon index 2.53, suggesting non-thermal
emission as an alternative model for the core source. 相似文献
43.
A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems, one EA type and two EB type eclipsing binaries (one of them could be a W UMa system), and seven pulsating stars including three candidates of δScuti stars. 相似文献
44.
45.
本文对Osherovich的黑子返回磁通量模型作了适当的修改,使用黑子中心作为边界条件,用五种观测结果,导出了理论模型所需的五个主要参量,用半经验方法求得了黑子静力学模型的磁场、压力和温度等物理量.将此模型应用于一个中等大小的圆形对称黑子,可得到一个特解,结果发现我们的模型既能满足黑子的磁性质,同时又能满足合理的热力学量分布. 相似文献
46.
介绍了MATLAB语言特点和系统建模方法的基本理论.根据南海气象数据的实际建模处理过程,给出了建模的详细步骤及其MATLAB实现过程以及MATLABTM的主要实现程序.试验讨论和结果表明利用MATLAB语言可以方便地对南海气象数据用系统建模方法进行建模和处理,MATLAB在运用系统建模法处理南海气象数据方面具有明显的优越性. 相似文献
47.
48.
Calibrating the GOCE accelerations with star sensor data and a global gravity field model 总被引:1,自引:0,他引:1
A reliable and accurate gradiometer calibration is essential for the scientific return of the gravity field and steady-state
ocean circulation explorer (GOCE) mission. This paper describes a new method for external calibration of the GOCE gradiometer
accelerations. A global gravity field model in combination with star sensor quaternions is used to compute reference differential
accelerations, which may be used to estimate various combinations of gradiometer scale factors, internal gradiometer misalignments
and misalignments between star sensor and gradiometer. In many aspects, the new method is complementary to the GOCE in-flight
calibration. In contrast to the in-flight calibration, which requires a satellite-shaking phase, the new method uses data
from the nominal measurement phases. The results of a simulation study show that gradiometer scale factors can be estimated
on a weekly basis with accuracies better than 2 × 10−3 for the ultrasensitive and 10−2 for the less sensitive axes, which is compatible with the requirements of the gravity gradient error. Based on a 58-day data
set, scale factors are found that can reduce the errors of the in-flight-calibrated measurements. The elements of the complete
inverse calibration matrix, representing both the internal gradiometer misalignments and scale factors, can be estimated with
accuracies in general better than 10−3. 相似文献
49.
基于SAR干涉点目标分析技术的城市地表形变监测 总被引:1,自引:0,他引:1
通过深入研究干涉点目标的相位模型,提出基于空间搜索的邻近点目标干涉相位差解缠方法,用以计算点目标的地形残差和线性形变,以及分离点目标大气延迟相位和非线性形变相位的时空域滤波方法,解决干涉点目标分析中的关键问题.最后,以苏州地区地表沉降监测为应用试验,利用形成的SAR干涉点目标形变信息提取技术,获取苏州市区1992-2002年间的地表沉降信息.研究结果与已有文献记录保持比较好的一致性,证明SAR干涉点目标技术完全可以发展成为应用于城市地表形变监测的实用化技术.Abstract: Interferometric point target analysis (IPTA) is one of the latest developments in radar interferometric processing. It is achieved by analysis of the interferometric phases of some individual point targets, which are discrete and present temporarily stable backscattering characteristics, in long temporal series of interferometric SAR images. This paper analyzes the interferometric phase model of point targets, and then addresses two key issues within IPTA process. Firstly, a spatial searching method is proposed to unwrap the interferometric phase difference between two neighboring point targets. The height residual error and linear deformation rate of each point target can then be calculated, when a global reference point with known height correction and deformation history is chosen. Secondly, a spatial-temporal filtering scheme is proposed to further separate the atmosphere phase and nonlinear deformation phase from the residual interferometric phase. Finally, an experiment of the developed IPTA methodology is conducted over Suzhou urban area. Totally 38 ERS-1/2 SAR scenes are analyzed, and the deformation information over 3 546 point targets in the time span of 1992-2002 are generated. The IPTA-derivecl deformation shows very good agreement with the published result, which demonstrates that the IPTA technique can be developed into an operational tool to map the ground subsidence over urban area. 相似文献
50.
Kazuo Abe 《Journal of Oceanography》2008,64(6):961-967
From August 2006 to August 2007, the concentrations of dissolved silica (Si(OH)4) were monitored in the surface water of Urasoko Bay and the mouth of the stream that runs into the bay. Urasoko Bay is located
on the northern coast of Ishigaki Island, Okinawa, Japan, which is in a subtropical area of the North Pacific Ocean and is
surrounded by a relatively poorly developed fringing reef. Added to these samples were freshwater from the upstream area and
brackish water that exudes at the beach site, which were collected from April to June 2007. Rainwater samples were also collected
during the study period. The concentration of Si(OH)4 generally decreased from upstream to the bay site, and, on clear days, Si(OH)4 data from all study sites (the bay, beach, stream mouth, and upstream) plotted against salinity fell on a single straight
line. When the influence of rainwater was, the results were scattered below the straight line, which suggests dilution by
rainwater with a much lower Si(OH)4 concentration. These findings show that offshore seawater, rainwater, and upstream freshwater regulate the concentration
of Si(OH)4 in the surface water of Urasoko Bay. 相似文献