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Primerjava pretočnih šifrirnikov podatkov na modulu STM32f411
Filip Horvat, 2020, diplomsko delo

Opis: V diplomskem delu smo se posvetili preučevanju vede kriptografije in šifrirnih algoritmov. Pogledali smo si delovanje pretočnih šifrirnikov, natančneje dveh algoritmov projekta eStream. Opisali smo delovanje algoritmov Salsa20/ChaCha20 in Grain v1. Njuno delovanje smo preverili na mikrokrmilniku STM32F411. Implementacijo algoritma Salsa20/ChaCha20 smo našli v knjižnici STM CryptoLib. Algoritma Grain v1 prej omenjena knjižnica ne vsebuje, zato smo ga implementirali sami. Na koncu smo primerjali njuni hitrosti šifriranja s tremi video datotekami različnih velikosti. Ugotovili smo, da se naša implementacija algoritem Grain v1 precej počasneje šifrira in dešifrira podatke kot Salsa20/ChaCha20.
Ključne besede: kriptografija, pretočni šifrirni algoritmi, eStream, ChaCha20, Grain v1, STM32F411, STM CryptoLib
Objavljeno: 04.11.2020; Ogledov: 102; Prenosov: 13
.pdf Celotno besedilo (1,37 MB)

Determining the grain size distribution of granular soils using image analysis
Nihat Dipova, 2017, izvirni znanstveni članek

Opis: Image-processing technology includes storing the images of objects in a computer and processing them with the computer for a specified purpose. Image analysis is the numerical expression of the images of objects by means of mimicking the functioning of the human visual system and the generation of numerical data for calculations that will be made later. Digital image analysis provides the capability for rapid measurement, which can be made in near-real time, for numerous engineering parameters of materials. Recently, image analysis has been used in geotechnical engineering practices. Grain size distribution and grain shape are the most fundamental properties used to interpret the origin and behaviour of soils. Mechanical sieving has some limitations, e.g., it does not measure the axial dimension of a particle, particle shape is not taken into consideration, and especially for elongated and flat particles a sieve analysis will not yield a reliable measure. In this study the grain size distribution of sands has been determined following image-analysis techniques, using simple apparatus, non-professional cameras and open-code software. The sample is put on a transparent plate that is illuminated with a white backlight. The digital images were acquired with a CCD DSLR camera. The segmentation of the particles is achieved by image thresholding, binary coding and particle labeling. The geometrical measurements of each particle are obtained using an automated pixel-counting technique. Local contacts or limited overlaps were overcome using a watershed split. The same sample was tested by traditional sieve analysis. An image-analysis-based grain size distribution has been compared with a sieve-analysis distribution. The results show that the grain size distribution of the image-based analysis and the sieve analysis are in good agreement.
Ključne besede: image analysis, image processing, grain size, sand
Objavljeno: 18.06.2018; Ogledov: 464; Prenosov: 61
.pdf Celotno besedilo (1,27 MB)
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Probabilistic study of the phenomenon of crushed grains using the model of Weibull
Kheffache Toufik, Melbouci Bachir, 2012, izvirni znanstveni članek

Opis: The crushing of grains in a granular medium is a very important phenomenon; it is a source of both physical and mechanical changes to these materials. A statistical study of the mechanical properties of a material was used to characterize the distribution and fracture mechanics in order to quantify the evolution of these distributions with sample sizes (grains and whole grains). This work presents the results of an experimental study made on the crushing of individual grains of limestone and samples consisting of multiple grains subjected to a uniaxial loading in order to highlight the influence of the loading and the grain size on the rate of crushing. A statistical study using the Weibull method allowed us to model the problem and quantify the rate of breakage for the two cases. The results obtained show that the rate of deflection depends on the grain size and the intensity of the applied load. Statistical modelling using the Weibull method gave us acceptable results in both cases.
Ključne besede: grain, sample, crushing, statistical study
Objavljeno: 13.06.2018; Ogledov: 321; Prenosov: 39
.pdf Celotno besedilo (335,52 KB)
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Mean grain size as a function of spectral amplitude: a new regression law for marine sediment cores
Nelly Zanette, Darinka Battelino, 2017, izvirni znanstveni članek

Opis: Geophysics has been developed in order to supply indicative estimations in soil mechanics like the grain size distribution of finely grained soils as day, silt and fine sands. The paper describes the attempt to characterize porous and saturated marine sediments with a non destructive technique which is the acoustic wave, in order to determine the correlation with geotechnical measurements. The characterization of physical parameters of marine sediments was based on research methods which permit to describe the parameters defining different types of sediment and zones of sedimentation; to determine fundamental parameters that influence the propagation of the acoustic waves in saturated and porous means; to define quick and indicative methods for characterization of physical parameters of analysed means. The acoustic measurements were carried out at SACLANT-NATO of La Spezia (I), where the Vertical Multi Sensor Core Logger (V-MSCL) was used. The results of acoustic tests were compared to the grain size curves of the sediments and the propagation characteristics such as velocity, density, porosity and absorption of experimentally determined data. The analyses are based 011 various mathematical models presented in. literature, in order to predict and to describe physical mechanisms of the wave propagation using a simplification of the sediment structure. The target of the study was to determine a new mathematical law that linked the mean grain size to a directly measurable parameter such as the spectral amplitude, and to offer the possibility to obtain the first indicative value of the sediment mean grain size. The determined exponential law represents an innovative and quick approach to determine a physical characteristic of saturated and porous sediments such as the grain size in a non destructive way based on the spectral analysis of the wave propagation form.
Ključne besede: soil mechanics, marine sediments, finely grained soil, acoustic waves, grain size curve
Objavljeno: 17.05.2018; Ogledov: 493; Prenosov: 50
.pdf Celotno besedilo (437,86 KB)
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Grain amaranth as an alternative and perspective crop in temperate climate
Silva Grobelnik Mlakar, Matjaž Turinek, Manfred Jakop, Martina Bavec, Franc Bavec, 2010, pregledni znanstveni članek

Opis: As a consequence of globalisation and industrialisation of agriculture, global food security has become increasingly dependent on only a handful of fertilisation and energy high demanding plant species. This involution has increased the vulnerability of agriculture, reduced genetic diversity, provoked some environmental problems and impoverished the human diet. The mentioned facts stimulate the retrieving of alternative crops into the production. The present paper briefly describes crop importance, botany, nutritional value and utilisation of grain amaranth (Amaranthus spp.), one of the alternative crops discussed in the book Organic Production and Use of Alternative Crops. The immediate objective of this paper is to present information gained as a result of a national project on grain amaranth.
Ključne besede: grain amaranth, nutrition value, utilisation
Objavljeno: 29.03.2018; Ogledov: 596; Prenosov: 96
.pdf Celotno besedilo (172,19 KB)
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Microstructure of NiTi orthodontic wires observations using transmission electron microscopy
Janko Ferčec, Darja Jenko, Borut Buchmeister, Franc Rojko, Bojan Budič, Borut Kosec, Rebeka Rudolf, 2014, izvirni znanstveni članek

Opis: This work presents the results of the microstructure observation of six different types of NiTi orthodontic wires by using Transmission Electron Microscopy (TEM). Within these analyses the chemical compositions of each wire were observed in different places by applying the EDS detector. Namely, the chemical composition in the orthodontic wires is very important because it shows the dependence between the phase temperatures and mechanical properties. Micro- structure observations showed that orthodontic wires consist of nano-sized grains containing precipitates of Ti2Ni and/or TiC. The first precipitated Ti2Ni are rich in Ti, while the precipitated TiC is rich in C. Further investigation showed that there was a difference in average grain size in the NiTi matrix. The sizes of grains in orthodontic wires are in the range from approximately 50 to 160 nm and the sizes of precipitate are in the range from 0,3 μm to 5 μm.
Ključne besede: orthodontic wires, nickel-titanium orthodontic wire, NiTi wire, shape memory alloys, SMA wires, microstructure, transmission electron microscopy, TEM, average grain size
Objavljeno: 03.07.2017; Ogledov: 622; Prenosov: 77
.pdf Celotno besedilo (869,15 KB)
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Impact energy analysis of quenched and tempered fine grain structural steel specimens after weld thermal cycle simulation
Marko Dunđer, Tomaž Vuherer, Ivan Samardžić, 2014, izvirni znanstveni članek

Opis: The paper presents impact energy results of thermal cycle simulated specimens of quenched and tempered fine grain structural steel S960QL. These results are obtained by examining notched Charpy specimens. Upon performed metallographic analysis and measured hardness, total impact energy is separated into ductile and brittle components.
Ključne besede: quenched and tempered fine grain structural steel, welding thermal cycle, impact energy, cooling time t8/5
Objavljeno: 03.07.2017; Ogledov: 567; Prenosov: 74
.pdf Celotno besedilo (1,18 MB)
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Fatigue crack initiation from microstructurally small Vickers indentations
Tomaž Vuherer, Andrej Godina, Zijah Burzić, Vladimir Gliha, 2007, izvirni znanstveni članek

Opis: The resistivity of coarse grain steel against crack initiation in the presence of micro defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as an artificial micro defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses.
Ključne besede: welded joints, micro defect, coarse grain HAZ, crack initiation, crack growth, stress concentration, fatigue limit, Vickers, residual stresses
Objavljeno: 03.07.2017; Ogledov: 607; Prenosov: 81
.pdf Celotno besedilo (1,02 MB)
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Microstructural and phase analysis of CuAlNi shape-memory alloy after continuous casting
Mirko Gojić, Stjepan Kožuh, Ivan Anžel, Gorazd Lojen, Ivana Ivanić, Borut Kosec, 2013, izvirni znanstveni članek

Opis: The results of the characterization of a CuAlNi shape-memory alloy after continuous casting technology are shown. Using this procedure a bar with a diameter of 8 mm was manufactured. After solidification of the alloy the microstructure characterization was carried out using optic microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) methods. Our results showed that the as-cast alloy consisted of the parent β1 and β1’ martensite phases. The martensite phase primary as the needle-like inside grains was observed. Martensite laths have different orientations inside particular grains. It was found that the average grains size is 98.78 µm. The grain diameter near to the external surface is higher than in the center. The average hardness of the alloy was 275 HV1.
Ključne besede: shape memory alloys, martensite, continuous casting, grain size
Objavljeno: 16.03.2017; Ogledov: 582; Prenosov: 76
.pdf Celotno besedilo (1,28 MB)
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Effect of AlTi5B1 and AlSr10 additions on the fluidity of the AlSi9Cu3 alloy
Matej Steinacher, Franc Zupanič, Mitja Petrič, Primož Mrvar, 2014, izvirni znanstveni članek

Opis: This work studies the effect of the AlTi5B1 and AlSr10 additions on the fluidity and the solidification time of the AlSi9Cu3 casting alloy. The fluidity was investigated by determining the flow length in a spiral-shaped mould. The solidification time was measured with a thermocouple positioned at the ingate bottom. An individual pouring into the preheated (200 °C) metallic mould was done at different pouring temperatures ((640, 670, 700, and 710) °C). In all the cases, the fluidity was improved with the increasing pouring temperatures. An addition of the AlTi5B1grain refiner to the basic alloy reduced both the grain size and the fluidity, whilst the solidification time was similar to that of the basic alloy. On the other hand, an addition of the AlSr10 modifier refined the ßSi eutectic phase, increased the fluidity and prolonged the solidification time in comparison to the basic alloy. The fluidity was proportional to the solidification time. Thus, by carrying out a simple thermal analysis and determining the solidification time, it is possible to predict the fluidity.V delu je predstavljen vpliv dodatkov AlTi5B1 in AlSr10 na livnost in strjevalni čas livne aluminijeve zlitine AlSi9Cu3. Livnost smo preiskovali z merjenjem dolžine toka taline v kovinski kokili s spiralno livno votlino, medtem ko smo strjevalni čas merili s termoelementom, ki je bil vstavljen na dnu lijaka. Talino smo pri različnih livnih temperaturah ((640, 670, 700 in 710) °C) ulivali v predgreto kokilo (200 °C). Livnost je v vseh primerih naraščala z naraščanjem livne temperature. Dodatek udrobnilnega sredstva AlTi5B1 k osnovni zlitini je zmanjšal tako velikost kristalnih zrn kot livnost, medtem ko je bil strjevalni čas podoben kot v osnovni zlitini. Dodatek modifikatorja AlSr10 je zmanj{al velikost evtektične faze ßSi, povečal livnost ter podaljšal strjevalni čas v primerjavi z osnovno zlitino. Livnost je bila sorazmerna strjevalnemu času, tako da lahko z enostavno termično analizo in določanjem strjevalnega časa napovemo livnost preiskovane zlitine.
Ključne besede: AlSi9Cu3 alloy, grain refinement, modification, fluidity, solidification time
Objavljeno: 15.03.2017; Ogledov: 622; Prenosov: 73
.pdf Celotno besedilo (642,42 KB)
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