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41.
The vaporization behavior of boron phosphate has been studied by using Knudsen effusion mass spectrometry. The vapor over BPO(4) consists of B(2)O(3), P(4)O(10), PO(2), BPO(4) (platinum cell) and B(2)O(3), PO, PO(2), BPO(3), BPO(4) (molybdenum cell). Standard enthalpies of formation and atomization (kJ/mol) were derived for BPO(4) (g) (-1000 +/- 15 and 2863 +/- 16) and for BPO(3) (g) (-731 +/- 15 and 2347 +/- 16), respectively. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
42.
Microwave heating of ceramic composites 总被引:1,自引:0,他引:1
The microwave heating of a ceramic composite is modelled andanalysed. The composite consists of many small ceramic particlesembedded in a ceramic cement. The composite is assumed to bewell insulated, and each particle is assumed to be in imperfectthermal contact with the surrounding cement. Based on thesetwo assumptions an asymptotic theory exploiting the small Biotnumber and small non-dimensional contact conductance is developed.Our asymptotic theory yields a set of nonlinear partial differentialequations which govern the temperature in the composite. Theseare reduced to a set of coupled nonlinear ordinary differentialequations in which the surface area of each particle entersas a parameter. Recent experiments with such composites haveshown that the steady-state temperature of the composite isstrongly dependent upon the radii of the embedded particles.Our model captures this effect. In fact, our analysis showsthat the assumption of imperfect thermal contact between theparticles and the ceramic cement is essential for this trendto be established. 相似文献
43.
Simple models of a reflection nebula in the form of a plane-parallel slab containing smooth spherical solid particles in submicron
size range have been considered. Single scattering has been assumed. The effect of varying the composition and size distribution
function of the grains have been brought out in the calculations using Mie theory of scattering. The analytical part of the
geometry of the problem has been treated quite rigorously and the resulting expression for nebular intensity has been presented
in a somewhat new form. In this paper, the case of the star behind the nebula has been examined.
A comparison of the theoretical results with the observations of the Merope nebula shows that the dirty ice grains with index
of refraction about 1·3–0·1i and size parametera
0 = 0·5μ give reasonable agreement with the colours. Simultaneously, the polarization in the visual and blue wavelength bands agree
approximately up to offset angle of 6 minutes of arc. The larger offset angles pose an intriguing problem. The general trends
of nebular colours and polarization with variation of real and imaginary parts of index of refraction and the size distribution
parameter have been tabulated to serve as a guide for further study of reflection nebulae with the star in the rear.
A part of this work was presented at the first scientific meeting of the Astronomical Society of India, held on 27 and 28
February 1974 at Hyderabad.
An erratum to this article is available at . 相似文献
44.
用本实验室合成的Ca0.80Zn0.20Te多晶料为原料,采用改进的布里奇曼法在镀碳和未镀碳的石英安瓿中生长出Ca0.80Zn0.20Te晶锭。使用X射线衍射仪对合成产物及晶锭进行了分析,生长晶体的X射线衍射峰尖锐,摇摆谱对称,表明晶锭的结晶性能较好;用IRPrestige-21红外光谱仪分析了晶体的红外透射光谱,测试结果表明安瓿镀碳后生长的晶体位错密度小,均匀性较好,电阻率优于未镀碳安瓿生长的晶体;晶体的蚀坑密度在10^3-10^4cm^-2之间,比未镀碳安瓿生长的晶体低1个数量级。 相似文献