32 research outputs found
Delelopment system of administrative station management for computer-based train radio communication
Mathematical modeling of extraction process for biporous medium and analyze of pressure in particles and extraparticle space
Обґрунтовано математичну модель процесу відтиску матеріалів рослинного походження у одновимірній постановці. Середовище, що піддається відтиску, представляється у вигляді біпористої системи, системою міжчастинкових та внутрішньочастинкових просторів. Сформульовано рівняння фільтрації-консолідації з відповідними початковими та крайовими умовами як для міжчастинкового, так і внутрішньочастинкового просторів у припущенні, що для матеріалів рослинного походження, міжчастинковий шар пор володіє малою місткістю, а пори в частинках – високою. Проведено числове моделювання профілів тисків в мікро- та макро порах біпористого середовища для двох матеріалів з різними степенями попередньої деформованості внутрішньої структури. Отримані результати вказують на відтермінування падіння значення тиску в частинці та уповільнення процесу консолідації для менш деформованого середовища.During solid-liquid expression, the porous layer formed by a whole fruit or fragmentized material is subjected to unidirectional or complex compression in industrial presses. Such compression can be carried out under constant or variable parameters (pressure, deformation rate). Physical model of solid-liquid expression from liquid containing materials is presented in one-dimensional formulation. The layer of sliced cellular material is conceptualized as a double porosity system with extraparticle and intraparticle networks for liquid flowing. The liquid flowing occurs inside the particles (intraparticle space), outside the particles (extraparticle space) and between these two spaces. The sliced particles are rectangular parallelepipeds separated by the porous network. The extraparticles network forms the first porosity with low storage capacity and high hydraulic permeability. The sliced liquid containing particles form a second porosity with high storage capacity and low hydraulic permeability. The filtration-consolidation equations with corresponding initial and boundary conditions were formulated for both extraparticle and intraparticle networks. The extraparticle network was supposed to form the first porosity level, while the intraparticle network forms a second porosity. Using obtained numerical solutions, the liquid pressure distributions inside of porous particles and in the extraparticle space were calculated. The pressure distribution curves are presented in function of time and dimensionless geometrical coordinates. Computational modeling of pressure profiles in macro- and micropores versus time for different layer sections was done for plant material with two different compressibility-permeability characteristics corresponding different degrees of tissue destroying. Results show the delayed pressure drop in the intraparticle network and retardation of consolidation kinetics for the less destroyed plant tissue due to the lower value of consolidation coefficient. Therefore, the degree of destroying of cellular tissue can influence importantly on the pressure profiles and retardation of pressure drops inside the porous particles
The Competitive Diffusion of Gases in a Nanoporous Zeolite Using a Slice Selection Procedure
The study of the co-diffusion of several gases through a microporous solid and of the resulting
instantaneous distribution (out of equilibrium) of the adsorbed phases is particularly important in
many fields, such as gas separation, heterogeneous catalysis, etc. Classical H NMR imaging is a
good technique for visualizing these processes but, since the signal obtained is not specific for each
gas, each experiment has to be performed several times under identical conditions, and each time
with only one incompletely deuterated gas. In contrast, we have proposed a new NMR imaging
technique (based on the so-called NMR slice selection procedure) which gives a signal
characteristic of each adsorbed gas. It can therefore provide directly, at every moment and at every
level of the crystallite bed, the distribution of several gases competing in diffusion and adsorption.
Solutions to the direct and inverse problems are based on Heaviside’s operational method and
Laplace integral transformation. New procedures for identifying diffusion coefficients for co-
diffusing components (benzene and hexane) in intra- and intercrystallite spaces were implemented,
using high-speed gradient methods and mathematical diffusion models, as well as the NMR spectra
of the adsorbed mass distribution of each component in the zeolite bed. These diffusion coefficients
were obtained as a function of time for different positions along the bed. Benzene and hexane
concentrations in the inter- and intracrystallite spaces were calculated for every position in the bed
and for different adsorption times