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Shape optimization of truss-stiffened shell structures with variable thickness
Marko Kegl, Boštjan Brank, 2006, original scientific article

Abstract: This paper presents an effective approach to shape optimal design of statically loaded elastic shell-like structures. The shape parametrization is based on a design element technique. The chosen design element is a rational Bézier body, enhanced with a smoothly varying scalar field. A body-like designelement makes possible to unify the shape optimization of both pure shells and truss-stiffened shell structures. The scalar field of the design element is obtained by attaching to each control point a scalar quantity, which is an add-on to the position and weight of the control point. This scalar field is linked to the shell thickness distribution, which can be optimized simultaneously with the shape of the shell. For linear and non-linear analysis of shell structures, a reliable 4-node shell finite element formulation is utilized. The presented optimization approach assumes the employment of a gradient-based optimization algorithm and the use of the discrete method of direct differentiation to perform the sensitivity analysis.Four numerical examples of shell and truss-stiffened shell optimization are presented in detail to illustrate the performance of the proposed approach.
Keywords: mechanics of structures, shape optimization, shells, trusses, Bézier body, numerical methods, optimum design
Published: 30.05.2012; Views: 1099; Downloads: 65
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Software and equipment for remote testing of sensors
Barbara Brezovec, Vojko Matko, 2007, original scientific article

Abstract: An improved approach for remote testing of elements and systems is presented in this article. To ensure high reliability of products, tests must be done in the production phase to detect possible errors in working mode. Because environmental testing involves long-term processes the possibility of remote observation and remote controlling of tests is very useful solution. The concept is to connect the testing chamber with a personal computer, create a reliable driver and control it remotely over the local network or Internet from other client. It is designed for performing tests on wide area of sensors and sensor based systems.
Keywords: sensors reliability, testing methods, remote control, virtual instruments
Published: 31.05.2012; Views: 1118; Downloads: 162
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Parameter identification of the Jiles-Atherton hysteresis model using differental evolution
Matej Toman, Gorazd Štumberger, Drago Dolinar, 2008, original scientific article

Abstract: In this paper, parameters of the Jiles-Atherton (J-A) hysteresis model are identified using a stochastic search algorithm called differential evolution (DE). The J-A hysteresis model's parameters are identified by DE in such a way, that best possible agreement is obtained between the measured and model calculated hysteresis loops. This agreement is furthermore increased by improving the J-A hysteresis model. The improvement is achieved by replacing a constant pinning parameter in the J-A hysteresis model with a variable one. Here, the variable pinning parameter is written as a function of a magnetic field. Bz DE identified parameters are used in the J-A hysteresis model, which is included in the dynamic model of a single-phase transformer. The effectiveness of the improved J-A hysteresis model and parameters identification approach is verified with experiments and simulations.
Keywords: Jiles-Atherton model, J-A hysteresis model, magnetic hysteresis, optimization methods, parameters estimation, single-phase transformer
Published: 31.05.2012; Views: 1239; Downloads: 32
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Adapting prosody in a text-to-speech system
Janez Stergar, Caglayan Erdem, 2010, independent scientific component part or a chapter in a monograph

Keywords: stochastic methods, databases, phonetic transcription
Published: 31.05.2012; Views: 912; Downloads: 58
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The role of computer-aided chemical engineering education within the european Bologna three- cycle study system
Zdravko Kravanja, Jiri Klemeš, 2011, published scientific conference contribution

Abstract: Universities around Europe are currently adopting the new Bologna three-cycle study system and most of Chemical Engineering departments have already developed new study programs accordingly. In this respect, two main questions have been posed in order to reorganize current chemical engineering study programs: i) which skills and knowledge, common to all chemical engineers, should not be ignored whilst developing new chemical engineer curricula, and ii) which are the other chemical engineering topics, engineering fields, and nonengineering knowledge necessary for engineers to manage those problems of specific current and future (bio)chemical and process related industries. One of the aims of this presentation is to discuss basic learning outcomes, and recommended topics common to all chemical engineers, especially relating to those process systems engineering aspects to be embedded within new study programs requiring the use of computer-aided methods and tools during chemicalengineering education. The uses for these methods and tools will be discussed shortly, among them the development of new computer-aided methods and tools, multimedia internet-based teaching and learning programs, and cyberinfrastrucure-based virtual libraries.
Keywords: Bologna study system, computer-aided education, chemical engineering core curriculum, program outcomes, computer-aided methods and tools
Published: 01.06.2012; Views: 1296; Downloads: 53
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Concentration of free fatty acids in rapeseed oil
Petra Kotnik, Mojca Škerget, Željko Knez, 2012, published scientific conference contribution

Keywords: materials, methods, vegetable oils
Published: 01.06.2012; Views: 1011; Downloads: 13
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Boundary domain integral method for high Reynolds viscous fluid flows in complex planar geometries
Matjaž Hriberšek, Leopold Škerget, 2005, original scientific article

Abstract: The article presents new developments in boundary domain integral method (BDIM) for computation of viscous fluid flows, governed by the Navier-Stokes equations. The BDIM algorithm uses velocity-vorticity formulation and is basedon Poisson velocity equation for flow kinematics. This results in accurate determination of boundary vorticity values, a crucial step in constructing an accurate numerical algorithm for computation of flows in complex geometries, i.e. geometries with sharp corners. The domain velocity computations are done by the segmentation technique using large segments. After solving the kinematics equation the vorticity transport equation is solved using macro-element approach. This enables the use of macro-element based diffusion-convection fundamental solution, a key factor in assuring accuracy of computations for high Reynolds value laminar flows. The versatility and accuracy of the proposed numerical algorithm is shown for several test problems, including the standard driven cavity together with the driven cavity flow in an L shaped cavity and flow in a Z shaped channel. The values of Reynolds number reach 10,000 for driven cavity and 7500 for L shapeddriven cavity, whereas the Z shaped channel flow is computed up to Re = 400. The comparison of computational results shows that the developed algorithm is capable of accurate resolution of flow fields in complex geometries.
Keywords: fluid mechanics, numerical methods, boundary domain integral method, algorithms, incompressible fluid flow, Navier-Stokes equations, velocity vorticity formulation, segmentation technique, driven cavity flow
Published: 01.06.2012; Views: 1105; Downloads: 44
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Modelling of surface crack growth under lubricated rolling-sliding contact loading
Boštjan Zafošnik, Zoran Ren, Jože Flašker, Gennady Mishuris, 2005, original scientific article

Abstract: The paper describes modelling approach to computational simulation of surface crack growth subjected to lubricated rolling-sliding contact conditions. The model considers the size and orientation of the initial crack, normal and tangential loading due to rolling-sliding contact and the influence of fluid trapped inside the crack by a hydraulic pressure mechanism. The motion of the contact sliding load is simulated with different load cases. The strain energy density (SED) and maximum tangential stress (MTS) crack propagation criteria are modified to account for the influence of internal pressure along the crack surfaces due to trapped fluid. The developed model is used to simulate surface crack growth on a gear tooth flank, which has been also experimentally tested. It is shown that the crack growth path, determined with modified crack propagation criteria, is more accurately predicted than by using the criteria in its classical form.
Keywords: fracture mechanics, numerical methods, contact loading, finite element analysis, internal pressure, maximum tangential stress, strain energy density, surface crack growth
Published: 01.06.2012; Views: 1606; Downloads: 53
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