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1.
SISTEMI ZA OKREVANJE PO KATASTROFAH Z UPORABO STREŽNIŠKIH OBLAKOV
Rok Dimec, 2009, diplomsko delo

Opis: V diplomski nalogi so opisani načini okrevanja po katastrofi, zaščite računalniške infrastrukture in podatkov ter lastnosti sodobnih podatkovnih centrov. Opisani so sodobni pristopi k tem problemom, izvedeni s pomočjo tehnologij spletnih storitev in izvajanja v oblaku. Predstavljeni so trije ponudniki na tem področju, ki nudijo najem strojne opreme za izvajanje in razvoj aplikacij, ki jo prilagodimo svojim potrebam ter tako izkoristimo visoko odzivnost in zmogljivost. Naštete so tako prednosti, kakor tudi slabosti teh tehnologij in s primerom prikazano delovanje aplikacije na Google App Engine infrastrukturi.
Ključne besede: podatkovni center, okrevanje, katastrofa, izvajanje v oblaku, spletne storitve, Google App Engine, Amazon, Force.com
Objavljeno: 24.04.2009; Ogledov: 1904; Prenosov: 171
.pdf Celotno besedilo (4,70 MB)

2.
On the local variation of the crack driving force in a double mismatched weld
Jožef Predan, Nenad Gubeljak, Otmar Kolednik, 2007, izvirni znanstveni članek

Opis: A material inhomogeneity in the direction of crack extension causes a difference between the near-tip crack driving force, Jtip, and the nominally applied far-field crack driving force, Jfar. This difference can be quantified by a material inhomogeneity term, Cinh, which is evaluated by a post-processing procedure to a conventional finite element stress analysis. The magnitude of the material inhomogeneity term is evaluated for cracks in an inhomogeneous welded joint made of a high-strength low-alloy steel. Both a crack proceeding from the under-matched (UM) to the over-matched (OM) and from the OM to the UM weld metal are treated. The effects of the inhomogeneity of the different material parameters (modulus of elasticity, yield strength, and strain hardening exponent) on Cinh and Jtip are systematically studied. The results demonstrate that the material inhomogeneity term is primarily influenced by the inhomogeneity of the yield strength. A crack growing towards an OM/UM interface experiences an accelerated crack growth rate or a pop-in, an UM/OM interface leads to a reduced crack growth rate or a crack arrest. The application of global assessment methods of the mismatch effect which are included in the Engineering Treatment Model (ETM) or in the Structural Integrity Assessment Procedures for European Industry (SINTAP) is discussed.
Ključne besede: crack driving force, material inhomogeneity, mismatched weld, interface, J-integral, finite element modeling
Objavljeno: 31.05.2012; Ogledov: 909; Prenosov: 45
URL Povezava na celotno besedilo

3.
Adaptive self-learning controller design for feedrate maximization of machining process
Franc Čuš, Uroš Župerl, 2007, izvirni znanstveni članek

Opis: An adaptive control system is built which controlling the cutting force and maintaining constant roughness of the surface being milled by digital adaptation of cutting parameters. The paper discusses the use of combining the methods of neural networks, fuzzy logic and PSO evolutionary strategy (Particle Swarm Optimization) in modeling and adaptively controlling the process of end milling. An overall approach of hybrid modeling of cutting process (ANfis-system), used for working out the CNC milling simulator has been prepared. The basic control design is based on the control scheme (UNKS) consisting of two neural identificators of the process dynamics and primary regulator. Experiments have confirmed efficiency of the adaptive control system, which is reflected in improved surface quality and decreased tool wear.
Ključne besede: end milling, adaptive force control, artificial intelligence, optimisation, adaptive control systems
Objavljeno: 31.05.2012; Ogledov: 899; Prenosov: 19
URL Povezava na celotno besedilo

4.
Optimization of extrusion process by genetic algorithms and conventional techniques
Zoran Jurković, Miran Brezočnik, Branko Grizelj, Vesna Mandić, 2009, izvirni znanstveni članek

Opis: The purpose of this research is the determination of the optimal cold forward extrusion parameters with the minimization of tool load as objective. This paper deals with different optimization approaches in order to determine optimal values of logarithmic strain, die angle and friction factor with the purpose to find minimal tool loading obtained by cold forward extrusion process. Two experimental plans based on factorial design of experiment and orthogonal array have been carried out. Classical optimization, according to the response model of extrusion forming force, and the Taguchi approach are presented. The obtained extrusion force model as the fitness function was used to carry out genetic algorithm optimization. Experimental verification of optimal forming parameters with their influences on the forming forces was also performed. The experimental results show an improvement in the minimization of tool loading. The results of optimal forming parameters obtained with different optimization approaches have been compared and based on that the characteristics analysis (features and limitations) of presented techniques.
Ključne besede: metal forming, forward extrusion force optimization, design of experiments, Taguchi approach, genetic algortihm
Objavljeno: 31.05.2012; Ogledov: 1024; Prenosov: 50
.pdf Celotno besedilo (469,47 KB)
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5.
Use of AFM force spectroscopy for assessment of polymer response to conditions similar to the wound, during healing
Uroš Maver, Tina Maver, Andrej Žnidaršič, Zdenka Peršin, Miran Gaberšček, Karin Stana-Kleinschek, 2011, izvirni znanstveni članek

Opis: Force spectroscopy is a very promising technique for the evaluation of interactions within different environments. Knowledge about them is especially important during the design and preparation of those modern wound dressings in contact with a changing wound-environment over a prolonged time. Such exposure can cause a drastic decrease in the materialćs mechanical performance, and can lead to degradation, thus lowering the success of any healing process. Our study tries to establish a model system, which would enable us to assess the applicability of the mentioned technique for the evaluation of any interaction changes between polymer molecules and a chosen surface, after exposure to different environments. Our proposed experimental setup consists of two representative polymers, a model silicon surface, and two solutions of various pHs and ionic strengths, respectively. Within the chosen range of parameters, we are confident that we can prove the usefulness of force spectroscopy for further research into polymer suitability, for the development of novel wound dressings.
Ključne besede: force spectroscopy, AFM, wound dressings, polymer materials, model system
Objavljeno: 01.06.2012; Ogledov: 1059; Prenosov: 49
.pdf Celotno besedilo (316,48 KB)
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6.
Combined feedforward and feedback control of end milling system
Franc Čuš, Uroš Župerl, Jože Balič, 2011, izvirni znanstveni članek

Ključne besede: machining, force control, neural networks
Objavljeno: 01.06.2012; Ogledov: 741; Prenosov: 14
URL Povezava na celotno besedilo

7.
Optical properties of plastically deformed copper : an ellipsometric study
Nebojša Romčević, Rebeka Rudolf, J. Trajić, M. Romčević, B. Hadžić, Dana Vasiljević-Radović, Ivan Anžel, 2011, izvirni znanstveni članek

Opis: In this paper the results of optical properties investigations on plastically deformed copper are presented. The optical properties of the plastically deformed copper were studied using spectroscopic ellipsometry in the ultraviolet-visible (UV-VIS) range. Chemically pure copper was deformed by applying the Equal Channel Angular Pressing (ECAP) technique. During the last decade, equal-channel angular pressing procedure was used for the fabrication of ultrafine-grained metals and alloys. The plastic deformation of metallic materials leads to the production of bulk nano-scale structures with ultrafine grains and cross-sections, which remain about equal before and after deformation. The parameters of the sample were calculated using a two-film model together with the Bruggeman effective medium approximation.
Ključne besede: ellipsometric spectroscopy, atomic force microscopy, copper, amorphisation
Objavljeno: 01.06.2012; Ogledov: 1040; Prenosov: 33
.pdf Celotno besedilo (354,12 KB)
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8.
9.
Fuzzy control strategy for an adaptive force control in end-milling
Uroš Župerl, Franc Čuš, Matjaž Milfelner, 2005, izvirni znanstveni članek

Opis: This paper discusses the application of fuzzy adaptive control strategy to the problem of cutting force control in high speed end-milling operations. The research is concerned with integrating adaptive control with a standard computer numerical controller (CNC) for optimising a metal-cutting process. It is designed to adaptively maximise the feed-rate subject to allowable cutting force on the tool, which is very beneficial for a time consuming complex shape machining. The purpose is to present a reliable, robust neural controller aimed at adaptively adjusting feed-rate to prevent excessive tool wear, tool breakage and maintain a high chip removal rate. Numerous simulations and experiments are conducted to confirm the efficiency of this architecture.
Ključne besede: automatic control, end milling, adaptive force control, fuzzy adaptive control
Objavljeno: 01.06.2012; Ogledov: 1095; Prenosov: 48
URL Povezava na celotno besedilo

10.
On fracture behaviour of inhomogeneous materials - a case study for elastically inhomogeneous bimaterials
Otmar Kolednik, Jožef Predan, G.X. Shan, N.K. Simha, Franz Dieter Fischer, 2005, izvirni znanstveni članek

Opis: This paper presents a case study, examining the influence of a sharp bimaterial interface on the effective crack driving force in a fracture mechanics specimen. The inhomogeneity of the elastic modulus in linear elasticand non-hardening and hardening elastic-plastic bimaterials is considered. The interface is perpendicular to the crack plane. The material properties and the distance between the crack tip and the interface are systematically varied. The effect of the material inhomogeneity is captured in form of a quantity called "material inhomogeneity term",▫$C_inh$▫. This term can be evaluated either by a simple post-processing procedure, following a conventional finite element stress analysis, or by computing the J-integral along a contour around the interface, ▫$J_int$▫. The effective crack driving force,▫$J_tip$▫, can be determined as the sum of ▫$C_inh$▫ and the nominally applied far-field crack driving force, ▫$J_far$▫. The results show that ▫$C_inh$▫ can be accurately determined by both methods even in cases where ▫$J_tip$▫-values are inaccurate. When a crack approaches a stiff/compliant interface,▫$C_inh$▫ is positive and ▫$J_tip$▫ becomes larger than ▫$J-far$▫. A compliant/stiff transition leads to a negative ▫$C_inh$▫, and ▫J_tip$▫ becomes smaller than ▫$J_far$▫. The material inhomogeneity term, ▫$C_inh$▫, can have the same order of magnitude as ▫$J_far$▫. Based on the numerical results, the dependencies of ▫$C_inh$▫ on the material parameters and the geometry are derived. Simple expressions are obtained to estimate ▫$C_inh$▫.
Ključne besede: mechanics of structures, fracture toughness, inhomogeneous materials, J-integral, crack driving force, interface, material force
Objavljeno: 01.06.2012; Ogledov: 786; Prenosov: 9
URL Povezava na celotno besedilo

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