Papers by Keyword: Radiation

Abstract: Animal and plant products subjected to various doses of radiation were examined to measure the concentration of quinoid radiotoxins (QRTs) by the indirect hemagglutination (IHA) test using anantibody diagnosticum produced on the basis of immunoglobulin obtained through the hyperimmunization of sheep with a quinoid radiotoxin of plant origin. The irradiation of plant raw materials was performed in the "Issledovatel" gamma ray facility at a dose of 0.4 kGy. It has been found that the titers of radiotoxinsin the irradiated products depend on the type of product, the radiation dose as well as the length of the post-irradiation storage period. With the doses designated, in compliance with the technology, to extend the shelf life of potatoes and onions, the titer sranged from 1:8 to 1:74.7 in potatoes and from 1:10.7 to 1:85.3 in onions between days 3 and 30 after the radiation exposure. In the wheat and oats grains irradiated at doses of 0.3 and 0.7 kGy this indicator was 1:6.7-1:37.3. Between days 2 and 21 after the exposure to a dose of 25 kGy, QRT titers in the grainsranged from 1:21.3 to 1:53.3, against the titers of 1:0.7-1:2 in the non-irradiated grains. The titers of radiotoxins in the meat exposed to the doses of 10 and 20 kGy were 1:6.7-1:26.7 between days 3 and 30 after the radiation exposure. QRT levels in animal internal organs (liver) were greaterby 1-2 log2 than those in the meat. Elevated QRT levels in all of these irradiated products were recorded within the initial 45 days after the radiation exposure. On day 60, radiotoxin titers were at the same level as the control products.

Abstract: The paper proposes the method of stress calculation in three-layer protecting structures of nuclear reactors under thermal and radiation effects. We consider the case of a plane deformed state. One-dimensional axisymmetric finite elements are used. The effect of indirect material heterogeneity on the stress-strain state of the structure is investigated.

Abstract: Heat exchange through infrared radiation in air layers located inside building envelopes may be significantly modified in case of use of aluminium foil coatings therein. The intensity of conductive, convective and radiative heat exchange in these structures depends on the thickness of the air layer and the temperature difference on its surfaces. Generally speaking, application of aluminium foil in air layers of a building envelope improves its thermal insulation capacity. However, assessment of efficiency of such a solution and determination of the thermal resistance value of a given structure is often incorrectly determined and assumed for design calculations. The article analyzes the instructions and principles of determination of thermal insulation capacity of unventilated air layers. Provisions of two standards have been compared with results of tests of air layer parameters. The effect of different factors on heat exchange and insulation capacity of air layers with reflective coatings has been considered and assessed.

Abstract: The resistance of some compounds to conventional treatments engenders the search for alternative methods, such as photo-oxidation. Antibiotics and photo-producers are found in the environment, indicating that these compounds are persistent. This work had as its goal to investigate the photo-oxidation of the antibiotic named tetracycline hydrochloride adsorbed in montmorilloniteclay (VHS) and into aqueous suspension. In order to irradiate the interaction products 0,03g were weighed and put in a petri dish to be collected on pre-determined times. The extraction of the drug was made by adding 10 mL of distilled water and put on the ultrasound for 2 hours. The suspensions were prepared by using 200 mL of the concentration from 25mgL^-1 of tetracycline in 1gL^-1 g of clay in a borosilicate reactor. This system was stirred in the dark during 1 hour in order to achieve its balance. The samples were radiated by using an Ultra-Vitalux UV lamp, with 300 W for 2 hours. The kinetics were followed through UV-Vis spectroscopy, monitored in 359 nm, in the maximum wavelength of the drug. The suspensions showed a degradation twice as fast when compared to the interaction product, for the rate of degradation of this system was 24%. This decrease on the concentration may have been caused by the hydroxyl radicals generated by the photolysis of the iron hydroxide II. Hence, one concludes that in the case of the system in suspension it was more effective to the photo-oxidation of this antibiotic. Although, there is the need for increasing the exposure time of the interaction product in order to verify possible structural changes of this system by DRX.

Abstract: This study aims to explore modification of polyaniline nanofiber through grafting polymerization to increase its solubility and processability for application in aqueous environment. Grafting via electron beam radiation procedure is extremely productive in terms of time consumption and environmental friendliness. In this work, acrylic acid was grafted on to polyaniline nanofiber using electron beam irradiation. The influence of altering the electron beam power from 2-3 MeV, radiation dosage from 5-25 kGy, acrylic acid concentration from 10-100% and soaking time from 2-24 hours during graft polymerization were studied over the grafting percentage (%G). Grafting parameter was determined by weight changes before and after grafting procedure. Grafted polyaniline is characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA). Formation of new peak at 1700 cm-1 for FTIR spectroscopy analysis of grafted polyaniline confirmed grafting has taken place during irradiation.

Abstract: Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper describes the effect of electron beam irradiation on the nanoindentation creep of unfilled and glass fiber filled polypropylene (25%). nanoindentation creep were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β – radiation (0, 30, 45 and 60 kGy). The purpose of the article is to consider to what extent the irradiation process influences the resulting nanoindentation creep measured by the DSI method. The unfilled and filled polypropylene tested showed significant changes of indentation creep. The measured results indicate, that electron beam irradiation is very effective tool for improvement of creep properties of unfilled and filled polypropylene. The nanoindentation creep after irradiated unfilled Polypropylene was decreased up to 16 % (filled polypropylene was decreased up to 9%) compared to non-irradiated surface. These changes were examined and confirmed by Gel content.

Abstract: The main objective of this work is to study the thermal exchanges in a habitable enclosure located in a desert region of Algeria (Adrar). This latter is considered as an air volume of parallelepiped shape limited by horizontal and vertical flat walls. The walls are the only capacitive elements of the enclosure. They are thermally coupled by convection and radiation and are the seat of conductive flux. The external facades of the enclosure are the seat of a convective flux with the external air and radiative exchanges with the environment (ground and sky). Openings (cracks, sealing defects, infiltration orifices, renewal orifices, etc.) allow the air to circulate inside the habitable enclosure and between the inside and the outside. Thermal exchanges are studied using the balance equations established at each wall of the enclosure. These equations have been discretized by an implicit finite difference method. The systems of algebraic equations thus obtained have been solved by the Gauss algorithm using the nodal method. The effects of the outdoor ambient temperature, the density of the incident solar flux on the facades and the orientation of the habitable enclosure in the meridian plane on the temperature distributions of the internal walls and the filled air in the enclosure havec been analyzed on the basis of recent climate data measured at the ADRAR Saharan Renewable Energy Research Unit. An analysis of the evolution of the internal ambient temperature as a function of the wind exposure factor of the heated space and of the degree of leaktightness of the doors and windows was also carried out at the end of this work. An acceptable agreement was found between the numerical results and those measured by the radiometric station. Moreover, the results obtained show that the building material used in this region causes undesirable overheating due to its thermal inertia.

Abstract: In this analysis, effects of viscous dissipation and thermal radiation on an electrically conducting boundary layer flow, heat and mass transfer of a fluid through a porous medium over a stretching sheet in the presence of heat source/sink is considered. The symmetry groups admitted by the corresponding boundary value problem are obtained by using symmetric transformations. These transformations are used to convert the partial differential equations of the governing equations into self-similar non-linear ordinary differential equations. These transformed ODEs are solved by employing Runge-Kutta fourth order with shooting method. Numerical results obtained for different thermo-physical parameters characterizes the flow phenomena are drawn graphically and effects of various physical parameters on velocity, temperature and concentration profiles are discussed. Numerical computation for skin friction, Nusselt number and Sherwood number are also obtained and presented in Tables.

Abstract: The hydromagnetic peristaltic motion of Carreau and Casson nanofluids flow in an irregular channel in the presence of diffusion thermo (Soret) and thermo diffusion (Dufour) impacts has been examined. The effect of thermal radiation is incorporated in the energy equation and velocity slip included in the boundary conditions. The dimensionless governing equations for the flow, fluid temperature and nanoparticle concentration are acquired for the suppositions of low Reynolds number and large wavelength. Resulting flow problem has been solved numerically. Outcome of emerging sundry variables on these three flow profiles are graphically analyzed. Axial velocity enhances near the walls of the irregular channel to the mounting values of Hartmann number where as the velocity declines in the central part of the irregular channel. Temperature magnifies considerably with the boosting values of Dufour number. Impact of Soret number decays concentration. Also, a comparative study is made for the numerical results of axial velocity with the existing reports. In addition the numerical results of the friction factor, energy and mass transfer rates for both Carreau and Casson nanofluids are analyzed through the tables.

Abstract: A numerical study of a natural convection flow coupled with radiation was carried out in a double-skin façade. The solar radiation flux to which the double-skin façade is subjected has been chosen for a cold season month (φ = 66.9 W/m² ). The double-skin façade is installed on a building whose interior temperature is 293 K given that the temperature at the inlet in winter conditions is 255 K. This study focuses on 5 different widths of the double-skin façade (4, 6, 8, 10 and 12 cm). Three-dimensional numerical simulations have been carried out for a steady and turbulent flow. Transport equations of mass, momentum and energy are solved numerically using finite volume method. Velocity and temperature profiles show the differences between all the above mentioned 5 cases in order to highlight the optimal width of the double-skin façade.