Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

English (EN)·Polski (PL)·Yкраїнський (UK)
Przejdź do strony domowej biblioteki Centralna Biblioteka Wojskowa Link otwiera się w nowym oknie Logo biblioteki Prolib Integro - strona głównaCentralna Biblioteka Wojskowa

Wyszukujesz frazę "Diffusion" wg kryterium: Wszystkie pola

  Lista filtrów
Wyrównaj
Wyświetlanie 1-15 z 18
Tytuł:
Some remarks on positron/positronium diffusion models
Autorzy:
Świątkowski, W.
Powiązania:
https://bibliotekanauki.pl/articles/148428.pdf
Data publikacji:
2003
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
diffusion
diffusion length
positron
positronium
Opis:
Positrons thermalized near the sample boundary (as well as Ps atoms formed in the sample) can reach the boundary as a result of diffusive movement. Observations of such effects as positron reemission or positron surface trapping as well as positronium emission allow one to calculate respective diffusion lengths. From the presented analysis it follows that some models used in such calculations give quite wrong results.
Źródło:
Nukleonika; 2003, 48, 3; 141-144
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The quantum diffusion of carbon in alfa-iron in low temperature
Autorzy:
Dąbrowski, L.
Andreev, A.
Georgiev, M.
Powiązania:
https://bibliotekanauki.pl/articles/147484.pdf
Data publikacji:
2006
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
carbon
diffusion
tunneling
adiabatic
polaron
Opis:
Recent experimental data on the diffusion coefficient of carbon in á-iron below liquid nitrogen temperature (LNT) question the classical approach to the observed temperature dependence. As the temperature is lowered below LNT, the diffusion constant tends to a nearly temperature-independent value rather than continuing its activated trend. The low temperature branch is apparently characteristic of a quantum mechanical process dominated by tunneling in ground state. Concomitantly we apply an occurrence-probability approach to describing the overall temperature dependence as a single continuous rate. Within the adiabatic approximation the electronic eigenvalue depending parametrically on the nuclear coordinates is taken to be the potential energy to control the motion of the nuclei. The resulting rate involves all horizontal-tunneling energy-conserving elastic transitions at the quantized energy levels of the migrating atom. A small though not negligible slope in the temperature dependence as the temperature is raised below 100 K is dealt with by complementing for the rate of a parallel one-phonon inelastic-tunneling process in excess to the basic elastic-tunneling rate. Our combined approach agrees well with the experimental data. In particular, the frequency of the coupled vibration is obtained virtually identical to the carbon vibrational frequency from inelastic neutron scattering data. The migrational barrier is also found to be within the limits expected for alfa-iron.
Źródło:
Nukleonika; 2006, 51, 2; 93-99
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solution of diffusion-advection equation of radon transport in many-layered geological media
Autorzy:
Yakovleva, V. S.
Parovik, R. I.
Powiązania:
https://bibliotekanauki.pl/articles/148852.pdf
Data publikacji:
2010
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
radon
diffusion
advection
transport
modeling
soil
Opis:
Radon transport modeling in geological media is an important tool for solving problems and tasks of radioecology and geophysics. Comparison of radon field time series obtained by numerical and experimental methods is one of the most common and widely applicable ways to analyze the influence of state and variability of meteorological, electrical and actinometric parameters of atmosphere, cosmic weather factors, variations of deflected mode of geological medium on the level and variations of radon field. The solutions of stationary and non-stationary diffusion-advection equations of radon transport in many-layered geological media by numerical methods, notably by integro-interpolation method (balance method) are presented. The peculiarity of radon transport in many-layered media is taken into account in the developed numerical model. This peculiarity is connected with the transport equation coefficients which can change very rapidly at the border of two adjacent layers, i.e. they can be discontinuous at the borders of each layer that can be caused by parameters of soils greatly differing in value (density, porosity, radium content, diffusion and emanation coefficients). The present work is provided with an example of application of the developed numerical model for solving a practical problem on assessment of influence of deep seated uranium-containing rock on the value of radon volumetric activity at the depth of less-than or equal to 1 m. The article considers non-stationary numerical model calculations showing at what time moments the distribution curves of radon volumetric activity coincide with stationary regime of radon transport in geological media. The validity of the developed numerical solution has been confirmed by these calculations.
Źródło:
Nukleonika; 2010, 55, 4; 601-606
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simultaneous measurement of Cr, Mn and Fe diffusion in chromium-manganese steels
Autorzy:
Dudała, J.
Gilewicz-Wolter, J.
Stęgowski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/148882.pdf
Data publikacji:
2005
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
radiotracers
diffusion
steel
spectrum
artificial neural networks
Opis:
The paper presents an application of multitracer method to diffusion measurement in Cr-Mn steels. Radioisotope tracers of chromium 51Cr, manganese 54Mn and iron 59Fe were used simultaneously in the diffusion process. Measurements of gamma-ray spectra and the proper analysis enabled evaluation of concentration distribution for each tracer. As a new tool, artificial neural networks (ANN) method was used for analysis of spectra. The proper solution of the diffusion model was applied to the experimental tracers' distribution data and diffusion coefficients were determined.
Źródło:
Nukleonika; 2005, 50, 2; 67-71
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A study of cerium extraction by TBP and TODGA using a rotating diffusion cell
Autorzy:
Bromley, M. A.
Boxall, C.
Powiązania:
https://bibliotekanauki.pl/articles/148471.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
SACSESS
TBP
TODGA
rotating diffusion cell (RDC)
separation
extraction
Opis:
For the study of the coupled interfacial-mass transfer kinetics of, inter alia, TBP, TODGA, CyMe4-BTBP and CyMe4-BTPhen based solvent extraction processes, a new rotating diffusion cell (RDC) apparatus has been established at Lancaster University. RDC studies of Ce(IV)/TBP and Ce(III)/TODGA extraction systems have been undertaken in order to improve the understanding of the chemical and kinetic processes involved. In each case, an interesting dependency on local hydrodynamics at the solution phase boundary with results suggesting that the organic extractant molecules migrate into the aqueous phase in order to capture Ce.
Źródło:
Nukleonika; 2015, 60, No. 4, part 2; 859-864
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diffusion of helium in the perfect uranium and thorium dioxide single crystals
Autorzy:
Dąbrowski, L.
Szuta, M.
Powiązania:
https://bibliotekanauki.pl/articles/147700.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
uranium
thorium dioxide
diffusion
tunneling
DFT+U
generalized gradient approximation (GGA)
potential barrier
incorporated helium
Opis:
We present quantum-mechanical evaluation of helium diffusion coefficient in the crystalline UO2 and ThO2. Parameters assignment of Schrödinger’s equation were done using the crystal field potentials which were obtained applying the density functional theory (DFT). “Ab initio” calculations were performed using the Wien2k program package. To compute the unit cell parameters the 13 atom super-cell was chosen. Applying two-site model we evaluated the time for an over-barrier jump and diffusion of interstitial He. The obtained values for diffusion coefficient are compared with the experimentally obtained values and with the theoretical values of other authors. In addition, it is simultaneously shown that helium diffusion in these materials is a quantum diffusion.
Źródło:
Nukleonika; 2013, 58, 2; 295-300
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of low temperature diffusion of carbon in martensite by Mössbauer spectroscopy and X-ray diffraction
Autorzy:
Jabłońska, A.
Dąbrowski, L.
Suwalski, J.
Neov, S.
Powiązania:
https://bibliotekanauki.pl/articles/147492.pdf
Data publikacji:
2006
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
martensite
diffusion coefficients
Mössbauer specroscopy
X-ray studies
Opis:
Martensite containing 0.87 wt.% carbon was studied by Mössbauer spectroscopy at temperatures, T = 10, 15, 25, 40 and 78 K and by X-ray diffraction at T = 78 K in the course of 35 days. Samples in the form of 30 mm thick foil of pure carbon martensite with enhanced tetragonality were synthesized applying non-standard technology. The measured by X-rays (c/a - 1) ratio varies within the limits 0.044-0.055 by pulsations with a period of few hours. According to Kurdimov’s model any changes in tetragonality of martensite are fully related to the passage of carbon atoms from Oc to Oa and Ob octahedral sites or vice versa. Pulsations of the central and satellite sextets were observed by Mössbauer spectroscopy. In accordance with the conventional interpretation of satellites, these pulsations result from different spatial distribution of carbon around the Fe atoms in the diffusion process. The data of (c/a - 1) pulsations were used to determine the diffusion coefficient below 78 K. The measured diffusion coefficient of carbon in a-iron below 78 K contradicts the classical approach to the observed temperature dependence. As the temperature is lowered below 78 K, the diffusion constant approaches the nearly temperature-independent value. The low temperature branch is apparently characteristic of a quantum mechanical process dominated by tunnelling in the ground state.
Źródło:
Nukleonika; 2006, 51, 2; 101-104
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
In situ measurement of diffusivity
Autorzy:
Berne, P.
Pocachard, J.
Powiązania:
https://bibliotekanauki.pl/articles/148818.pdf
Data publikacji:
2005
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
diffusion
porous media
in situ measurement
Opis:
The mechanism of molecular diffusion controls the migration of contaminants in very low-permeability porous media, like underground facilities for the storage of hazardous waste. Determining the relevant diffusion coefficients is, therefore, of prime importance. A few techniques exist for the in situ measurement of that quantity, but they suffer from many handicaps (duration, complexity and cost of the experiments). We propose here two innovative methods that have some potential to improve this situation. So far, we have found them feasible on the basis of design calculations and laboratory experiments. This work is presently protected by a patent.
Źródło:
Nukleonika; 2005, 50, 1; 3-7
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical study on extraction of tritium generated in HMR by way of system composed of EXEL-process and thermal diffusion column cascade
Autorzy:
Shimizu, M.
Takeshita, K.
Powiązania:
https://bibliotekanauki.pl/articles/146995.pdf
Data publikacji:
2002
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
chemical exchange reaction
heavy water
isotope separation
thermal diffusion
trickel-bed reactor
tritium
Opis:
A new tritium extraction system composed of a trickle-bed hydrogen/water isotopic exchange column using a hydrophobic Pt-catalyst combined with an SPE-water electrolyser (EXEL-process) and a thermal diffusion column cascade was proposed for the removal of tritium from heavy water irradiated in HMR ((Heavy Water Moderated Power Reactor), volume of heavy water = 140 m3 and mean neutron flux = 5×1013 n/cm2s). Numerical study on the extraction of tritium from the heavy water was carried out and the dimensions of proposed system were determined under the conditions that the concentration of tritium in the heavy water was kept less than 2.5 Ci/lHW. The calculation results indicated that the proposed system was designed practically.
Źródło:
Nukleonika; 2002, 47,suppl.1; 89-93
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of temperature distribution of fuel, clad and coolant in the VVER-1000 reactor core during group-10 control rod scram by using diffusion and point kinetic methods
Autorzy:
Rahgoshay, M.
Rahmani, Y.
Powiązania:
https://bibliotekanauki.pl/articles/146827.pdf
Data publikacji:
2007
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
point kinetic
diffusion
COSTANZA-R,Z
VVER-1000
control rod
RELAP5
Opis:
In this paper, through the application of two different methods (point kinetic and diffusion), the temperature distribution of fuel, clad and coolant has been studied and calculated during group-10 control rod scram, in the Bushehr Nuclear Power Plant (Iran) with a VVER-1000 reactor core. In the reactor core of Bushehr NPP, 10 groups of control rods are used of which, group-10 control rods contain the highest amount of injected negative reactivity in terms of quantity as compared to other groups of control rods. In this paper we explain impacts of negative reactivity, caused by a complete or minor scram of group-10 control rods, on thermoneutronic parameters of the VVER-1000 nuclear reactor core. It should be noted that through these calculations and by using the results, we can develop a sound understanding of impacts of this controlling element in optimum control of the reactor core and, on this basis, with careful attention and by gaining access to a reliable simulation (on the basis of results of calculations made in this survey) we can monitor the VVER-1000 reactor core through a smart control system. In continuation, for a more accurate survey and for comparing results of different calculation systems (point kinetic and diffusion), by using COSTANZA-R,Z calculation code (in which neutronic calculations are based on diffusion model) and using WIMS code at different areas and temperatures (for calculation of constant physical coefficients and temperature coefficients needed in COSTANZAR, Z code) for the VVER-1000 reactor core of Bushehr NPP, calculation of temperature distribution of fuel elements and coolant by using diffusion model is made in the course of group-10 control rods scram and afterwards.
Źródło:
Nukleonika; 2007, 52, 4; 159-165
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vlasov plasma description of pair plasmas with dust or ion impurities
Autorzy:
Atamaniuk, B.
Turski, A. J.
Powiązania:
https://bibliotekanauki.pl/articles/146468.pdf
Data publikacji:
2012
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
pair plasmas
fractional diffusion
Vlasov plasmas
Opis:
The paper contains a unified treatment of disturbance propagation (transport) in the linearized Vlasov electron-positron and fullerene pair plasmas containing charged dust impurities, based on the space-time convolution integral equations. An initial-value problem for Vlasov-Poisson/Ampčre equations is reduced to the one multiple integral equation and the solution is expressed in terms of forcing function and its space-time convolution with the resolvent kernel. The forcing function is responsible for the initial disturbance and the resolvent is responsible for the equilibrium velocity distributions of plasma species. By use of resolvent equations, time-reversibility, space-reflexivity and the other symmetries are revealed. The symmetries carry on physical properties of Vlasov pair plasmas, e.g., conservation laws. Properly choosing equilibrium distributions for dusty pair plasmas, we can reduce the resolvent equation to: (i) the undamped dispersive wave equations, (ii) wave-diffusive transport equation, and (iii) diffusive transport equations of oscillations. In the last case, we have to do with anomalous diffusion employing fractional derivatives in time and space.
Źródło:
Nukleonika; 2012, 57, 2; 317-319
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Radon film-badges versus existing passive monitors based on track etch detectors
Autorzy:
Tommasino, L.
Powiązania:
https://bibliotekanauki.pl/articles/148898.pdf
Data publikacji:
2010
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
radon
radon monitor
diffusion chamber
film badge
absorption
adsorption
Opis:
New methods and apparatus for the passive sampling of radon are introduced in the present paper. These samplers are based on the sorption of radon by layers of different types of solids. These solid layers result in sources of alpha, beta or gamma radiations, which can be detected by any passive or real-time detector, thus obtaining a variety of new radon monitors. By way of example, by facing one of said layers against a nuclear track detector, it is possible to obtain a compact radon film-badge. This film badge makes it finally possible to solve most of the shortcomings of existing passive monitors, based on track detectors, for the measurements of short- and long-term exposures of radon in air, in water, and in soils. These devices can be easily implemented by any existing radon service just as a back-up technology, with little or no change of the presently-used passive monitors.
Źródło:
Nukleonika; 2010, 55, 4; 549-553
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A laboratory facility (RTD) to study radon transport through modeled soil bed: results of preliminary measurements
Autorzy:
Kozak, K.
Mazur, J.
Hovhannisyan, H.
Powiązania:
https://bibliotekanauki.pl/articles/148126.pdf
Data publikacji:
2009
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
radon
transport
facility
diffusion
Opis:
The paper describes a laboratory facility (radon transport device – RTD) which makes it possible to study radon transport. The measuring position is a vertical cylindrical vessel with a height of 202 cm and a diameter of 24 cm. It can be filled with sand, gravel or other soil materials to be studied. The facility is providing radon gas from the source to the studied material and making it possible to measure radon concentration at different vertical distances from the source. The parameters of the medium (temperature, humidity) can be measured at the same time. The preliminary measurements using the RTD with sand as medium are presented.
Źródło:
Nukleonika; 2009, 54, 3; 193-198
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computation of the effect of pH on spur chemistry in water radiolysis at elevated temperatures
Autorzy:
Swiatla-Wojcik, D.
Powiązania:
https://bibliotekanauki.pl/articles/147674.pdf
Data publikacji:
2008
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
effect of pH
radiolysis of water
elevated temperatures
diffusion-kinetic calculations
Opis:
Diffusion-kinetic model has been employed to calculate the effect of pH and associated ionic strength on the primary yields in the radiolysis of water from ambient temperature to 200°C. Account has been taken of the effect of ionic strength, I, up to 0.1 molźdm-3 in both acidic and alkaline solutions resulting from the addition of H+ and OH-,assuming the counter ions have unit charge. The primary yields are essentially independent of pH for I ? 10-4. AboveI = 10-4 molźdm-3 the primary yields of e-aq and H2 in acidic solutions decrease whereas the primary yields of the H atom, hydroxyl radical and hydrogen peroxide increase. At I >10-3 molźdm-3 in alkaline solutions, the OH radical and hydrogen peroxide are partially converted into Oo- and HO-2 , respectively. Increases in the total yields GoOH + GOo- and Ge-aq + GHo and a decrease in GH2O2 + GHO-2 have been found with increasing pH. At elevated temperatures the effect of pH is diminished. The temperature effect on the primary yields in acidic and alkaline solutions is nearly the same as in neutral water.
Źródło:
Nukleonika; 2008, 53, suppl. 1; 31-37
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of the free volume sizes and shapes determined from crystallographic and PALS data
Autorzy:
Tydda, M.
Jasińska, B.
Powiązania:
https://bibliotekanauki.pl/articles/146378.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
benzenediols
free volume
molecular crystals olanzapine
positron annihilation
positronium
positronium diffusion coefficient
Opis:
Two different classes of molecular crystals were investigated. The first group was benzenediols, which are characterized by the same chemical composition but a different organization of their crystallographic structures; all of the compounds from this group have only one kind of free volumes. The second class was represented by olanzapine, which has more complex chemical composition and two kinds of free volumes in the structure. The o-Ps lifetime values determined from positron annihilation lifetime spectroscopy (PALS) measurements agree quite well with those calculated for sizes found from crystallographic data for benzenediols (agreement within 10% of the lifetime values). For olanzapine, a good agreement is observed in the case of cuboidal free volumes, while for the other kind of void, the agreement is less satisfactory. Positronium diffusion coefficient determined from o-Ps redistribution in olanzapine agrees with these found for polymers.
Źródło:
Nukleonika; 2015, 60, No. 4, part 1; 771-775
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies