Light scattering by an elongated particle: spheroid versus infinite cylinder

Using the method of separation of variables and a new approach to calculations of the prolate spheroidal wave functions, we study the optical properties of very elongated (cigar-like) spheroidal particles. A comparison of extinction efficiency factors of prolate spheroids and infinitely long circular cylinders is made. For the normal and oblique incidence of radiation, the efficiency factors for spheroids converge to some limiting values with an increasing aspect ratio a/b provided particles of the same thickness are considered. These values are close to, but do not coincide with the factors for infinite cylinders. The relative difference between factors for infinite cylinders and elongated spheroids (a/b \ga 5) usually does not exceed 20 % if the following approximate relation between the angle of incidence $\alpha (in degrees)$ and the particle refractive index m=n+ki takes the place: \alpha \ga 50 |m-1| + 5 where 1.2 \la n \la 2.0 and k \la 0.1. We show that the quasistatic approximation can be well used for very elongated optically soft spheroids of large sizes.Comment: 12 pages, 7 figures, Accepted by Measurement Science and Technology (special OPC issue

Utilization of the wastes of vital activity

The recycling of wastes from the biological complex for use in life-support systems is discussed. Topics include laboratory equipment, heat treatment of waste materials, mineralization of waste products, methods for production of ammonium hydroxide and nitric acid, the extraction of sodium chloride from mineralized products, and the recovery of nutrient substances for plants from urine

Analysis of the process of immersion of kernels in liquids with different specific mass

In a grain pile there is material other than grain including poisonous ergot sclerotia. Grain and sclerotia of ergot by linear dimensions and speed of soaring have similar characteristics. Complete separation of grain from ergot by these properties in a single process is impossible. Cleaning seeds from ergot sclerotia with the specific mass less than the specific mass of grain is possible in a salt solution. To mechanize the separation of ergot sclerotia from rye seeds by the wet method, there is an urgent need in the development of an appropriate device. Under study was an immersion in water (ρzh = 1.0∙103 kg/m3 ) and aqueous solutions of sodium chloride (NaCl) with a specific mass ρzh = 1.09∙103 and 1.15∙103 kg/m3 of individual rye grains with their specific mass ρz = 1.2...1.5∙103 kg/m3 , length lz = 5.0...10.0 10-3 m, width в = 1.4...3.6∙10-3 m and thickness δ = 1.2...3.5∙10-3 m. Theoretical studies were carried out on the basis of mathematical modeling methods using the laws of hydrodynamics, which were confirmed by experimental studies with winter rye grains of the Falenskaya 4 variety with a specific mass ρz = 1.1...1.3 103 kg/m3 , length lz = 5.0...8.0∙10-3 m, width в = 1.4...3.6∙10-3 m and thickness δ = 1.2...3.5∙10-3 m. It has been established that the calculated values of the immersion velocity of cylindrical kernels and spheroidal kernels in comparison with the experimental values in water (ρzh = 1.0∙103 kg/m3 ) is not more than 2%, and in aqueous solutions of sodium chloride (NaCl) the specific mass ρzh = 1.09∙103 and 1.15∙103 kg/m3 – 7 and 10%, respectively. This approach to determining the speed of immersion of grain in liquid can be used in the development of the machine for cleaning grain according to specific mass using wet method to substantiate its structural and technological parameters

Optical properties of dust

http://arxiv.org/abs/0808.4123Except in a few cases cosmic dust can be studied in situ or in terrestrial laboratories, essentially all of our information concerning the nature of cosmic dust depends upon its interaction with electromagnetic radiation. This chapter presents the theoretical basis for describing the optical properties of dust -- how it absorbs and scatters starlight and reradiates the absorbed energy at longer wavelengths.Partial support by a Chandra Theory program and HST Theory Programs is gratefully acknowledged