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郭越凡 CAPOCASA Eleonora EISENMANN Marc FLAMINIO Raffaele LEONARDI Matteo TACCA Matteo 肇宇航 李木子 吕振伟 《天文学进展》2019,(1)
随着技术的发展,下一代引力波探测器的激光功率将得到进一步提高。大光斑半径的应用也将使探测器的热噪声进一步降低,因此,量子噪声将成为在全频段限制引力波探测器灵敏度的首要因素。作为目前最有保障的一种降低量子噪声的技术,频率相关压缩态很可能将被应用于下一代所有引力波探测器中~([1])。频率相关压缩态可以通过将频率不相关压缩态与滤波腔相结合而产生。基于滤波腔具有的频率响应特性,这一技术的应用可以使低频波段的辐射压噪声有效降低,同时实现高频波段散粒噪声的降低,从而实现全探测频段灵敏度的提升。基于日本KAGRA引力波探测器的设计,我们预计将9dB压缩度的压缩态与周损失为8×10~(-5)的300m滤波腔相结合,可以使探测器灵敏度在全探测频段提高1倍。此实验于2015年开始,目前滤波腔的安装调试已经基本完成,得到的结果基本与实验前的模拟相符合。与频率不相关压缩态光学实验台的安装过程也已经过半,通过温度和控制回路的调制,二次谐波腔的转化率已经超过50%。 相似文献
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数字图像压缩方法在天文上的应用 总被引:1,自引:0,他引:1
概述了数字图像压缩技术在天文领域应用的必要性。针对天文观测的特点和研究的需要,经过研究、分析和比较,提出了天文图像压缩的可行方案。通过应用计算机编程及压缩实验并给出相应的结果。 相似文献
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本文研究了数字图象压缩的方法、分类和原理以及该技术在天文领域应用的必要性。针对天文观测的特点和需要,经过分析比较,提出了天文图象压缩的可行性方案。通过应用计算机编程、压缩实验得到相应结果。文中对天文数字图象分别进行了以下压缩方法实验:无失真压缩中的哈夫曼编码和位平面编码;限失真压缩中的离散余弦变换编码及混合编码等。其压缩比分别可达到2—4.5(无失真压缩)和10—30(限失真压缩)。图像压缩所需时间随使用的计算机而异。文中详细列出各种压缩方法的实验结果。 相似文献
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极端质量比旋进系统是空间引力波探测器最重要的波源之一。对引力波的探测需要高精度波形模版。当前主流的极端质量比旋进系统引力波计算模型中,人们一般将小质量天体当作试验粒子进行计算,而忽略了其结构及自身引力对背景引力场的影响。利用Mathisson-Papapetrou-Dixon方程研究延展体在弯曲时空中的运动,以及小天体自旋和质量多极矩对引力波信号识别产生的影响。结果表明,质量比在10?6-10?4范围的旋进系统,其自旋达到很大时,自旋对延展体的轨道运动有不可忽略的影响;在质量比10?4-10?2区间内,需要考虑中心黑洞潮汐作用导致的白矮星形变;在质量比大于10?4,且白矮星自旋很大时,其自旋产生的形变会对小天体轨道运动产生不可忽略的影响。大质量黑洞潮汐作用导致的恒星级黑洞或中子星产生的形变可以忽略,中子星和黑洞的自旋会对轨道运动产生不可忽略的影响,而自旋产生的四极矩对轨道运动不产生影响。 相似文献
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本文研究了数字图象压缩的方法,分类和原理以及该技术在天文领域应用的必要性。针对天文观测的特点和需要。经过分析比较,提出了天文图象压缩的可行性方案。通过应用计算机编程压缩实验得到相应结果。 相似文献
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概述了数字图像压缩技术在天文领域应用的必要性。针对天文观测的特点和研究的需要,经过研究,分析和比较,提出了天文图像压缩的可行方案。通过应用计算机编程及压缩实验给出相应的结果。 相似文献
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GRS 1915+105是银河系内的低质量黑洞X射线双星,其能谱和黑洞自旋已经得到了广泛的研究.自2018年6月开始,其X射线流量下降到了低流量水平,其间偶尔会产生多波段的耀发.利用Insight-HXMT(Insight-Hard X-ray Modulation Telescope,简称为慧眼)卫星在2020年8月30日到2020年10月13日之间对GRS1915+105的观测数据,研究了其能谱特性,发现在此次爆发过程中, X射线能谱可以用一个康普顿化的多温黑体谱很好地拟合.整个爆发的硬度强度图(Hardness-Intensity Diagram, HID)一直处于软态.采用GRS1915+105的最新动力学参数M=12.4-1.8+2.0M⊙, i=60°±5°, D=8.6-1.6+2.0kpc (M、M⊙、i和D分别表示黑洞质量、太阳质量、盘倾角和距离),得到其无量纲黑洞自旋a*的一个下限a*> 0.9990,确认了GRS 1915+105是一个具有极端自旋的黑洞.考虑本地吸收体的... 相似文献
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《Chinese Astronomy and Astrophysics》1982,6(2):121-125
Methods of calculating atomic partition functions and previous results are reviewed. Using the method given by de Jager and Neven(1960), the partition functions for Li I, Li II, Be I, Be II, CI, CII, OI, O II, Ne I, Ne II, Na I, Na II are calculated for 2000 K < T < 10000 K, ?3 < 1g Pe < +6. The results are given in TABLES 2-8. 相似文献
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Based on measurements performed by the Hydrogen Deuterium Absorption Cell (HDAC) aboard the Cassini orbiter, Titan’s atomic hydrogen exosphere is investigated. Data obtained during the T9 encounter are used to infer the distribution of atomic hydrogen throughout Titan’s exosphere, as well as the exospheric temperature.The measurements performed during the flyby are modeled by performing Monte Carlo radiative transfer calculations of solar Lyman-α radiation, which is resonantly scattered on atomic hydrogen in Titan’s exosphere. Two different atomic hydrogen distribution models are applied to determine the best fitting density profile. One model is a static model that uses the Chamberlain formalism to calculate the distribution of atomic hydrogen throughout the exosphere, whereas the second model is a Particle model, which can also be applied to non-Maxwellian velocity distributions.The density distributions provided by both models are able to fit the measurements although both models differ at the exobase: best fitting exobase atomic hydrogen densities of nH = (1.5 ± 0.5) × 104 cm−3 and nH = (7 ± 1) × 104 cm−3 were found using the density distribution provided by both models, respectively. This is based on the fact that during the encounter, HDAC was sensitive to altitudes above about 3000 km, hence well above the exobase at about 1500 km. Above 3000 km, both models produce densities which are comparable, when taking into account the measurement uncertainty.The inferred exobase density using the Chamberlain profile is a factor of about 2.6 lower than the density obtained from Voyager 1 measurements and much lower than the values inferred from current photochemical models. However, when taking into account the higher solar activity during the Voyager flyby, this is consistent with the Voyager measurements. When using the density profile provided by the particle model, the best fitting exobase density is in perfect agreement with the densities inferred by current photochemical models.Furthermore, a best fitting exospheric temperature of atomic hydrogen in the range of TH = (150-175) ± 25 K was obtained when assuming an isothermal exosphere for the calculations. The required exospheric temperature depends on the density distribution chosen. This result is within the temperature range determined by different instruments aboard Cassini. The inferred temperature is close to the critical temperature for atomic hydrogen, above which it can escape hydrodynamically after it diffused through the heavier background gas. 相似文献
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Brian A. Tinsley 《Planetary and Space Science》1973,21(4):686-691
This note critically examines the relative importance of several effects which influence the diurnal variation of atomic hydrogen abundance near the critical level.It is pointed out that the neglect of exospheric hydrogen in a recent theoretical treatment causes an overestimation of the diurnal variation at high exospheric temperatures, and an underestimation at low exospheric temperatures. The fluxes due to lateral flow are large compared to other fluxes only to the extent that the actual diurnal variation is very different from the diurnal variation corresponding to zero net lateral flow, which does not seem to be the case in the real atmosphere. Two effects which are probably important are charge exchange reactions with thermal oxygen ions, resulting in a diurnal exchange with the plasmasphere; and charge exchange reactions with high velocity protons, resulting in enhanced escape and diurnal variation. 相似文献
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P. Mészáros 《Astrophysics and Space Science》1968,2(4):510-519
We discuss the distribution of dust and atomic hydrogen in and around a small dark cloud near Ophiuchi. Although the obscuration reaches values as high as 8 magnitudes, the values ofN
H derived inside the cloud do not differ markedly from those found at nearby, less obscured points. At low values of the obscuration, dust and hydrogen isophotes show satisfactory agreement, i.e.,N
H increases withN
G. However, we find thatN
H starts decreasing for sufficiently large values ofN
G. In the entire range of optical extinctions investigated our observations are satisfied by an expression of the typeN
H=AN
G exp (-BN
G). Interpretation of this relationship suggests that an appreciable part of the hydrogen has been converted to molecular form inside the cloud. A tentative method for calculating the time elapsed since the conversion process began is proposed.Contribution No. 2 from the Argentine-Carnegie Radio Astronomy Station of the Instituto argentino de Radioastronomía and the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. 相似文献
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Vladimir Escalante 《Planetary and Space Science》1992,40(12):1705-1717
Effective radiative recombination coefficients are calculated for atomic oxygen using an atomic model potential to obtain accurate non-hydrogenic transition probabilities of singly excited states. Results are presented for many lines for temperatures up to 3000 K. Simple analytic fits are given which are accurate for most lines. 相似文献
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E.C. Zipf 《Planetary and Space Science》1985,33(11):1303-1307
The single and double ionization of atomic oxygen by electron impact has been studied, and the energy dependence of the specific ionization cross-section, σ(O+) and σ(O2+), has been measured from 40 to 300 eV using a high-density atomic oxygen source not contaminated by metastable O(1D) or O(1S) atoms. 相似文献
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