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Mechanical behaviour of photopolymer cell-size graded triply periodic minimal surface structures at different deformation rates
Yunus Emre Yilmaz, Nejc Novak, Oraib Al-Ketan, Hacer Irem Erten, Ulas Yaman, Anja Mauko, Matej Borovinšek, Miran Ulbin, Matej Vesenjak, Zoran Ren, 2024, izvirni znanstveni članek

Opis: This study investigates how varying cell size affects the mechanical behaviour of photopolymer Triply Periodic Minimal Surfaces (TPMS) under different deformation rates. Diamond, Gyroid, and Primitive TPMS structures with spatially graded cell sizes were tested. Quasi-static experiments measured boundary forces, representing material behaviour, inertia, and deformation mechanisms. Separate studies explored the base material’s behaviour and its response to strain rate, revealing a strength increase with rising strain rate. Ten compression tests identified a critical strain rate of 0.7 s−1 for “Grey Pro” material, indicating a shift in failure susceptibility. X-ray tomography, camera recording, and image correlation techniques observed cell connectivity and non-uniform deformation in TPMS structures. Regions exceeding the critical rate fractured earlier. In Primitive structures, stiffness differences caused collapse after densification of smaller cells at lower rates. The study found increasing collapse initiation stress, plateau stress, densification strain, and specific energy absorption with higher deformation rates below the critical rate for all TPMS structures. However, cell-size graded Primitive structures showed a significant reduction in plateau and specific energy absorption at a 500 mm/min rate.
Ključne besede: cellular materials, triply periodical minimal surface, photopolymer, mechanical properties, strain rate, experimental compressive testing, computer simulations
Objavljeno v DKUM: 22.05.2024; Ogledov: 134; Prenosov: 7
.pdf Celotno besedilo (9,33 MB)
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Perspectives on the introduction of computer-supported real laboratory exercises into biology teaching in secondary schools : teachers as part of the problem
Andreja Špernjak, Andrej Šorgo, 2009, izvirni znanstveni članek

Opis: Computer supported virtual and real laboratories are recognized as tools that can help in raising the quality of biology instruction, and raising development competences in students. Yet biology teachers have been treating the computer as typewriter, as a source of information and as a tool for communication, all of which usages are common to all subjects. The uses of ICT that can significantly help in developing scientific literacy and that are primary tools in science teaching - such as the use of data loggers - are only rarely on the syllabus. The lack of equipment is not the most important reason for failure to use such applications; instead, this is probably due to teachers' attitudes, opinions and knowledge. Students cannot be recognized as an obstacle in working with ICT. Lawer secondary school students aged between 10 and 14 performed three laboratory exercises (Activity of yeast, Gas exchange in breathing, Heart rate) using three different methods: classic, computer-supported and virtual laboratory. As a result of testing, we know that all three methods are suitable even for younger students. When students were asked which method they liked the most, their first choice was computer-supported laboratory, followed by classic laboratory, with virtual laboratory in the third place.
Ključne besede: education, biology, secondary education, computer-supported laboratory, laboratory work, ICT, simulations
Objavljeno v DKUM: 15.12.2017; Ogledov: 1706; Prenosov: 118
.pdf Celotno besedilo (783,64 KB)
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Buckling behavior of cold-formed studs with thermal perforations
Marsel Garifullin, Alexey Sinelnikov, Maria Bronzova, Boštjan Kovačič, Rok Kamnik, 2016, objavljeni znanstveni prispevek na konferenci

Opis: Studies have shown that the optimal structural scheme for low-rise buildings that meets all regulatory requirements is a frame system. In this connection, thin-walled cold-formed steel (CFS) profiles seem to be the best material for constructing light steel framed (LSF) walls. The framework of LSF walls is usually constructed from CFS C-shaped profiles. To increase the thermal effectiveness of a wall, CFS profiles usually have thermal perforations and thus are called thermoprofiles. However, these openings have a negative impact on bearing capacity of profiles and require accurate evaluation. In this article a relatively new reticular-stretched thermoprofile with diamond-shaped openings is considered. The article deals with the buckling analysis of perforated CFS C-sections subjected to compression.
Ključne besede: structural engineering, steel structures, computer simulations, nonlinear model
Objavljeno v DKUM: 29.08.2016; Ogledov: 1291; Prenosov: 407
.pdf Celotno besedilo (2,85 MB)
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Computer Modelling of Porous Composite Structures with Advanced Pore Morphology
Aljaž Kovačič, 2016, doktorska disertacija

Opis: Advanced pore morphology (APM) structures are composite metal foams, which are assembled from a large number of small spherical elements with cellular structure, and are bonded into a composite with polymeric adhesive. The result of such composition is a wide spectrum of achievable mechanical behaviour in APM structures. To explore their full potential, efficient computational models are needed, which allow for simple parameter variation. Unfortunately, the current computer models do not allow for efficient simulations of porous composite structures with advanced pore morphology, as they employ complex discretisation approaches. A new approach to simulation is presented in this work, based on the discrete particle method (DPM), where every element of APM structure is discretised with a single node. This enables more efficient simulations of APM structures, while still allowing for simple variation of structural parameters. The DPM method was augmented with constitutive models of normal and tangential contact behaviour of APM elements and bonds between them, which were formulated based on an extensive experimental study of APM structure's geometry and mechanical behaviour. Consequently, the models enable simulations of large APM structure's behaviour by modelling the contact behaviour of individual elements. The implementation of new models was verified on a set of analytically solvable examples, and the accuracy of the models was validated with very good correspondence between computational and experimental results. Moreover, the models were validated on a wide set of examples, also taking into account the various strain rates and the absence of the bonds. The applicability of new models was demonstrated in a comprehensive parametrical study, where the influential structural parameters and properties were identified for low and high strain rate deformations. The study also demonstrated the possibility of customising the mechanical behaviour with property gradation, and with introduction of regular, as well as geometrically complex APM element assemblies. The possibility of coupled discrete particle method and finite element method simulations was also addressed. The newly developed models represent a breakthrough in the field of computational investigation of APM structures, and provide for simpler and more efficient investigations of APM structures in the future.
Ključne besede: Metal foams, advanced pore morphology, composite materials, mechanical properties, contact modelling, discrete particle methods, computer simulations
Objavljeno v DKUM: 11.03.2016; Ogledov: 2521; Prenosov: 239
.pdf Celotno besedilo (44,29 MB)

Chiral discrimination in mobile phases for HPLC
Renato Lukač, Andrew J. Clark, Syma Khalid, Alison Rodger, Alan Snedden, P. Mark Rodger, 2002, izvirni znanstveni članek

Opis: In this paper we present an algorithm and some preliminary results of a computer simulation study designed to elucidate the molecular interaction mechanisms associated with chiral discrimination in chiral high performance liquid chromatography (HPLC). Molecular dynamics simulations have been performed on a novel active stationary phase constituent based on disaccharides and a model analyte in a typical solvent used as mobile phase in chiral HPLC. The results are interpreted in terms of typical binding geometries and energies found from the simulations. This paper provides basic algorithms for predicting enantiometric selectivity and for investigating the implications for choice of parameters such as solvent polarity and temperature for optimising chiral HPLC separations
Ključne besede: physical chemistry, liquid crystals, liquid chromatography, computer simulations, spectroscopy
Objavljeno v DKUM: 07.06.2012; Ogledov: 2118; Prenosov: 57
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Lower secondary school students' attitudes toward computer-supported laboratory exercises
Andreja Špernjak, Miro Puhek, Andrej Šorgo, 2010, izvirni znanstveni članek

Opis: In Science teaching laboratory work is recognized as one of the cornerstones. In school science laboratory work computers can be used as computer supported laboratory (real) and as virtual laboratory. In the first case "real" laboratories involve bench top experiments utilizing data acquisition systems while "virtual" laboratory entails interactive simulations and animations. Lower secondary school students in age between 11 and 15 performed three laboratory exercises (Activity of yeast, Gas exchange in breathing, Heart rate) as classic, computer-supported and virtual laboratory. As a result of testing we know that all three methods are suitable even for younger students. When they were asked which method they liked the most, their first choice was computer-supported laboratory, followed by classic laboratory, and virtual laboratory at the end. Additionally recognized weak and strong sides of used methods are discussed.
Ključne besede: education, biology, computer-supported laboratory, simulations, secondary schools
Objavljeno v DKUM: 07.06.2012; Ogledov: 2289; Prenosov: 106
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