Effect of the initial structure on the behaviour of Chlef sandNoureddine Della
, Ahmed Arab
, Mostefa Belkhatir
, Hanifi Missoum
, Claude Bacconnet
, Daniel Boissier
, 2010, original scientific article
Abstract: It has been known for many years that initial structure, plays an important part in the results of laboratory testing of natural of silty sands. For this purpose, a series of monotonic undrained triaxial compression tests were carried out on samples composed of Chlef sand with 0.5% non-plastic silt content using two depositional methods (dry funnel pluviation and wet deposition) at different initial relative density (RD= 29%, 50% and 80%). All specimens were subjected to isotropic consolidation of 50 kPa, 100 kPa and 200 kPa. It was found that the initial structure of the soil influences considerably the undrained shear response in terms of maximal deviatoric stress, peak strength and excess pore water pressure.
Keywords: liquefaction, sand, dry funnel pluviation, wet deposition, density, deviatoric stress, pore pressure
Published: 11.06.2018; Views: 410; Downloads: 51
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The action of a laser on an aluminium targetVišnja Henč-Bartolič
, Tonica Bončina
, Suzana Jakovljević
, Davor Pipić
, Franc Zupanič
, 2008, original scientific article
Abstract: A nitrogen laser beam (337 nm, 6 ns (FWHM), (3.2 [plus minus] 0.2) mJ) was focused with a quartz lens (f = 100 mm) onto an aluminium target in air at normal pressure. The laser irradiation and plasma explosion caused a modification to the Al surface and the deposition of a thin film (droplets) onto a glassy carbon plate. The irradiated target and the deposited material were studied with a scanning electron microscope (SEM) and a focused-ion-beam (FIB) device. A crater surrounded by a rim was produced on the spot of maximum irradiation on the aluminium target. The crater, very deep in comparison to its width and thickness, was presumably caused by the Kelvin-Helmholtz and the Rayleigh-Taylor instabilities. The temperatures of the electron and the massive particles were explained.
Keywords: aluminium, laser ablation, thin film deposition, instabilities, temperatures
Published: 23.03.2017; Views: 647; Downloads: 72
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Energy metabolism, growth performance, body composition, meat quality and boar taint compounds in immunocastrated pigsNina Batorek Lukač
, 2015, doctoral dissertation
Abstract: In recent years, immunocastration, a vaccination against gonadotropin releasing hormone, has been proposed as an alternative to surgical castration of intact male pigs without anaesthesia. However, the effects of immunocastration on metabolic changes, nutritional requirements and growth potential have not been quantified. Thus in the present thesis, the meta-analytical approach was used to quantitatively synthesize the effects of immunocastration and four studies were conducted to evaluate the effects of quantitative and qualitative feed restriction on growth performance, heat production and energy metabolism, carcass and meat quality. Results show that boar taint compounds are dramatically reduced in immunocastrates, still they remain slightly higher than in surgical castrates. Immunocastrates are less feed efficient, fatter but grow more rapidly and may have better meat quality than entire males. Compared to surgical castrates, immunocastrates have superior performance with no difference in meat quality. It is more economical to fatten immunocastrates than surgical castrates, but production costs and carcass quality are less favourable than in entire males because of the huge increase in voluntary feed intake during the weeks preceding slaughter. Applying quantitative feed restriction after active immunization did not significantly affect growth performance or carcass composition; however, restrictively fed immunocastrates were closer to entire males, whereas ad libitum fed immunocastrates were closer to surgical castrates. Meat quality is also unchanged by the restriction. However, higher incidence of carcass lesions in restricted immunocastrates together with higher plasma cortisol level indicates more aggression prior to slaughter and can be considered as a negative aspect of the quantitative restriction. Total heat production, assumed to be the major factor contributing to the differences in feed efficiency of pigs, is changed after the immunocastration. Additional energy retained due to higher feed intake is directed towards lipid deposition. Increased fatness of immunocastrates is a result of increased daily lipid deposition caused by higher energy intake, lower fasting heat production and improved energy retention. Hence, dietary energy intake should be limited after immunocastration. Moreover, according to the results of the nitrogen balance study, dietary crude protein content could also be decreased. By reducing net energy concentration of the diet up to 10 % using higher fibre content, similar energy efficiency (gain to net energy intake ratio) may be achieved, with an advantage in terms of reduced lipid deposition, and no effect on growth rate after effective immunization. This is particularly important when immunocastrated pigs are fattened to higher body weights, i.e. when longer delays between full immunization and slaughter are practiced.
Keywords: pig, immunocastration, growth performance, carcass characteristics, meat quality, heat production, lipid metabolism, fat deposition, feed restriction
Published: 27.07.2015; Views: 1687; Downloads: 137
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Wear resistance of coke-crushing hammersFranc Zupanič
, 2013, original scientific article
Abstract: This work investigated several methods for improving the wear resistance of the 42CrMo4 tool steel used for coke-crushing hammers. The methods embraced heat treatment for obtaining different combinations of strength and ductility of the bulk steel, and surface-engineering processes comprising TiN thin-film deposition using magnetron-sputtering, nitriding and WC/Ni weld deposit surfaced by gas metal arc (GMA) method. The wear-resistance was tested under industrial conditions. Oil quenching and tempering significantly increased the wear resistance in comparison to the as-received condition. Conversely, nitriding and TiN-hard coating did not show any significant improvement. WC/Ni weld deposit provided the best protection against wear, which was caused predominantly by hard abrasive particles present in the coke.
Keywords: zvarni spoj, mikrostrukture, obrabna odpornost, toplotna obdelava, obraba, kladivo, weld deposition, microstructure, impact coke crusher, heat treatment, wear, hammer
Published: 10.07.2015; Views: 1109; Downloads: 52
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APPLYING THE GRAIN-BOUNDARY DIFFUSION PROCESS USING ELECTROPHORETIC DEPOSITION TO SELECTED REGIONS OF A Nd-Fe-B MAGNETBlaž Goričar
, 2014, master's thesis
Abstract: This Master's thesis research is about the localized coercivity enhancement of Nd-Fe-B magnets, which are used in electric motors. Computer simulations show, that when magnets operate at high temperatures, they experience large demagnetizing fields. However, this happens only on specific parts of the body of the magnet. The demagnetization can be prevented by locally enhancing the coercivity only on these specific parts. The goal of this Master’s thesis was to research the localized coercivity enhancement by creating a magnet, where one half would have different magnetic properties compared to the other half.
Commercially available Nd-Fe-B magnets were bought from Shin-Etsu, Japan. The magnetic properties of the magnets were measured on two very different devices – the permeameter and the vibrating sample magnetometer. The demagnetization curves were compared. The coercivity of the magnet was improved with the electrophoretic deposition of dysprosium on the surface. The dysprosium then diffused, at high temperature, from the surface to the inside of the magnet along the grain boundaries. The microstructure of the magnet was analysed on the scanning electron microscope, while the content of the elements was quantitatively analysed with the EDS method.
The demagnetization curves of both devices were comparable. The grain-boundary diffusion process of dysprosium with the electrophoretic deposition increased the coercivity of the magnet by 25 %, without any significant loss in remanence. The research on the localized grain-boundary diffusion was first done with measurements on the vibrating sample magnetometer and then confirmed with the Hall probe. We discovered that one part of the magnet could have different magnetic properties compared to the other half. There was a clear border between the two.
Keywords: Nd-Fe-B magnet, coercivity, magnetic properties, electrophoretic deposition, grain-boundary diffusion process.
Published: 09.09.2014; Views: 1633; Downloads: 94
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