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61.
A. M. Cherepashchuk 《Astrophysics and Space Science》2006,304(1-4):263-266
Line profiles and radial velocity curves for optical stars in X-ray binaries are calculated taking into account ellipticity of the optical star and X-ray heating effect. 相似文献
62.
Limitations Of The Tangent Plane Approximation For Wide-field Imaging Using The Mauritius Radio Telescope 总被引:1,自引:0,他引:1
The Mauritius Radio Telescope (MRT) is a Fourier synthesis, non-coplanar T array. The primary objective of the telescope is
to survey the southern sky at 151.5 MHz in the declination range -70° to -10°. Due to non-coplanarity, wide-field imaging and deconvolution of wide field images made using MRT are challenging problems
in applications of radio interferometric techniques. This paper discusses the usefulness and limitations of the tangent plane
approximation in transforming the measured visibilities to wide field images and in estimating the point spread function (PSF)
required for the deconvolution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
63.
64.
Ferrian magnesian spodumene was synthesized in the MLFSH system at P=0.4 GPa, T=700 °C, fO2=NNO+2.3. The space group at room T is P21/c [a=9.638(3) ?, b=8.709(2) ?, c=5.258(2) ?, β=109.83(3)∘, V=415.2 ?3]. The structure is topologically equivalent to that of ferrian spodumene, LiFeSi2O6, and has two symmetrically independent tetrahedral chains, A and B, and two independent octahedral sites, M1 and M2. The
crystal-chemical composition was determined combining EMP, SIMS and single-crystal XRD analysis, yielding M2(Li0.85Mg0.09Fe2+
0.06) M1(Fe3+
0.85Mg0.15)Si2O6. Li is ordered at the M2 site and Fe3+ is ordered at the M1 site, whereas Mg (and Fe2+) distribute over both octahedral sites. Structure refinements done at different temperatures (25, 70, 95, 125, 150 and 200
°C) allowed characterization of a reversible displacive P21/c→C2/c transition at 106 °C. Previous HT-XRD studies of Li-clinopyroxenes had shown that the transition temperature is inversely related to the size of the M1 cation.
For the crystal of this work, the aggregate ionic radius at M1 is longer than that of ferrian spodumene, for which the transition
temperature is −44 °C. The higher transition temperature observed can only be explained on the basis of the shorter aggregate
radius at the M2 site (due to the presence of Mg substituting after Li), in keeping with the results obtained for ferromagnesian
P21/c pyroxenes. The effects of all the chemical substitutions must be considered when modelling transition temperatures and
thermodynamic behaviour in clinopyroxenes.
Received: 7 May 2002 / Accepted: 23 October 2002 相似文献
65.
钻石与合成立方氧化锆外观相似,在没有鉴定仪器的条件下,使用10倍放大镜和肉眼观察颜色、光泽、色散、瑕疵、加工工艺、腰围等,辅以透字试验、亲油性实验、称重、测量直径等简单方法即可将钻石与合成立方氧化锆快速鉴别。 相似文献
66.
区域矿产资源经济综合评价是矿产普查与勘探学科和地质经济学科中十分重要的新分支.本文侧重讨论了区域矿产资源经济综合评价中的评价指标体系的构造、评价指标效果值的确定、综合评价方法和计算机评价系统的建立等问题. 相似文献
67.
设计了三条路线合成了席夫碱冠醚2,3:10,11-二苯并-1,12,15-三氧杂-5,8-二氧-2,3:4,5:8,9:10,11-十七环四烯(DTDC),并通过红外、紫外、伏安法等手段对产品的性状进行了表征。结果表明,设计的路线都是可行的,且具有简便、产物纯度高等优点。 相似文献
68.
The P21/mC2/m displacive phase transition in the synthetic end-member amphibole Na NaMg Mg5 Si8 O22 (OH)2 has been studied by monitoring changes in unit-cell parameters and the intensities of superlattice reflections at 25–400 °C. This amphibole allows investigation of the effects of compositional variations at the A- and B-group sites upon the transition. Polynomial fitting of a 24 Landau potential to the evolution of the order parameter with T yielded a T
c of 257 ± 3 °C, and Landau coefficients compatible with a second-order transition. Structure refinement of single-crystal data collected at 25, 140, 270 and 370 °C allowed modelling of the structural changes as a function of T and symmetry. Crystal-chemical analysis suggests that differences in T
c in cummingtonites and in the crystal of this work depend mainly upon the relations between the aggregate ionic radii of the B- and C-group cations.
Electronic Supplementary Material: of Table 5 is available in the online version of this article at http://dx.doi.org/10.1007/s00269-003-0348-9 相似文献
69.
设计了一种基于正交调制原理的数字频率特性测试仪,系统用稳态响应法测量电路的频率特性.单片机作为主控芯片,完成系统的总体控制及数字信号处理;使用集成的直接数字频率合成芯片输出全频率范围内的正弦波.系统对待测电路的输入信号及其输出响应采样,经数字信号处理后,获得电路的幅频特性和相频特性.设计的测试仪测某RLC网络,中心频率的相对误差小于0.2%,有载品质因数相对误差小于1.25%,最大电压增益大于-1 dB.频率特性测试仪输入输出阻抗均为50 Ω,幅频误差绝对值小于0.5 dB,相频误差绝对值小于3°,测试仪能满足微机械谐振传感器特征参数测试需求. 相似文献