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1.
Yield strength modelling of formed material using evolutionary computational method
Leo Gusel, Rebeka Rudolf, 2009, original scientific article

Abstract: In this paper we propose an evolutionary computation approach for the modelling of yield strength in formed material. One of the most general evolutionary computation methods is genetic programming, which was used in our research. Genetic programming is an automated method for creating a working computer program from a problemćs high-level statement. Genetic programming does this by genetically breeding a population of computer programs using the principles of Darwinianćs natural selection and biologically inspired operations. During our research, material was cold formed by drawing using different process parameters and then determining yield strengths (dependent variable) of the specimens. On the basis of a training data set, various different genetic models for yield strength distribution were developed during simulated evolution. The accuracies of the best models were proved by a testing data set and comparing between the genetic and regression models. The research showed that very accurate genetic models can be developed by the proposed approach.
Keywords: metal forming, yield strength, genetic programming, modelling
Published: 31.05.2012; Views: 1169; Downloads: 21
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2.
Strength mismatch effect on yield load in X-shaped weldment with centre crack
Dražan Kozak, Nenad Gubeljak, Jožef Predan, Franjo Matejiček, 2004, published scientific conference contribution

Abstract: This paper provides yield load solutions for single edged fracture toughness specimen subjected to bending SE (B) with present X-shaped weld joint. The weld centre crack is located in the overmatch weld part. The corresponding fully plastic yield loads were obtained directly by plain strain FEM analysis for five characteristic a/W ratios: 0,1;0,2;0,3;0,4 and 0,5. Also, the influence of the sistematically varied weld root width 2H on the fracture behaviour has been evaluated. It was found that yield load decreases with the increasing weld root, because the undermatched region ahead the crack tip plays the dominant role.
Keywords: fracture mechanics, X-shaped welded joints, centre crack, strength mismatching, plastic yield load, constraint effects
Published: 01.06.2012; Views: 872; Downloads: 21
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3.
Optimal reactor systems for Van de Vusse reaction scheme with multicomponent feed
Duško Bikić, Branko Butinar, Peter Glavič, 2002, original scientific article

Abstract: In the present paper, product yield in the Van de Vusse reaction scheme with multicomponent feed has been studied. The optimal reactor structures have been found by investigating optimality conditions. The optimum product yield and criteria for selecting an appropriate reaction system have been obtained as functions of kinetic parameters. On the basis of optimization results the parameter space has been classified into regions indicating optimum reactor structure.
Keywords: optimal reactor structure, optimum product yield, multicomponent feed, parameter space, Van der Vusse reaction
Published: 01.06.2012; Views: 1342; Downloads: 37
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4.
Modeling of forming efficiency using genetic programming
Miran Brezočnik, Jože Balič, Zlatko Kampuš, 2001, original scientific article

Abstract: This paper proposes new approach for modeling of various processes in metal-forming industry. As an example, we demonstrate the use of genetic programming (GP) for modeling of forming efficiency. The forming efficiency is a basis for determination of yield stress which is the fundamental characteristic of metallic materials. Several different genetically evolved models for forming efficiency on the basis of experimental data for learning were discovered. The obtained models (equations) differ in size, shape, complexity and precision of solutions. In one run out of many runs of our GP system the well-known equation of Siebel was obtained. This fact leads us to opinion that GP is a very powerful evolutionary optimization method appropriate not only for modeling of forming efficiency but also for modeling of many other processes in metal-forming industry.
Keywords: metal forming, yield stress, forming efficiency, mathematical modeling, adaptation, genetic methods, genetic algorithm, genetic programming, artificial intelligence, process optimisation
Published: 01.06.2012; Views: 936; Downloads: 36
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5.
Agronomic characteristics, potential utilisation and quality of grain amaranth Amaranthus cruentus L.
Silva Grobelnik Mlakar, 2012, dissertation

Abstract: The present thesis is based on a survey of literature on grain amaranth (i); an experiment aimed at defining allelopathic potential of grain amaranth (ii); pot experiments conducted to determine the effect of various soil and climatic conditions on percentage of live seed emergence (PLSE) and seedling weight of four amaranth species (iii); a pot experiment conducted to study the effect of drought – induced at different phenological stages – on growth, yield performance, and leaf gas exchange (iv); a four-year field experiment conducted to investigate the effects of sowing date and nitrogen fertilisation on yields, protein content and amino acid composition (v); and on experiments with various amaranth-containing composite flours conducted to evaluate the rheological properties of dough (vi), and baking performance and sensory characteristics of resulted breads (vii). The survey of literature summarizes grain amaranth importance, botany, nutritive value and properties of crop processed as food (i). The seeds of garden cress were germinated with aqueous extracts of pigweed (A. retroflexus) and grain amaranth prepared from fresh roots, stems, leaves, and inflorescence with seeds, used either undiluted or at varying concentrations (ii). Although all the extracts delayed germination, leaf extracts of both species and inflorescence extracts of grain amaranth proved the most potent. Compared to pigweed, grain amaranth, which is known for its phytotoxic activity, exerted an even stronger inhibitory effect. The results of pot experiments (iii) revealed that the 15 mm sowing depth gave the highest seedling weight on sand and the highest PLSE on loam. A. caudatus gave the highest PLSE whereas A. cruentus gave the lowest PLSE but the heaviest seedlings. PLSE was severely reduced on the loam where topsoil crusting occurred after a decrease in soil moisture content, but not on the silt loam even when dry conditions were maintained throughout the experiment. PLSE was above 80 % with temperatures > 21 °C. Light regime with 12 h illumination gave the highest PLSE. In the greenhouse pot experiment (iv) amaranth plants were exposed to different soil water regimes: constant adequate moisture (W1), drought throughout the growing period (W2), drought initiated at crop inflorescence formation (W3), drought until inflorescence formation (W4), and drought from the beginning of inflorescence formation to the beginning of flowering (W5). Water shortage during inflorescence formation (W3 and W5) appeared to be critical, but soil drying after sowing until the beginning of inflorescence formation (W4) showed a pronounced ability to restore net photosynthesis, and provoke and improve the assimilate allocation to the aboveground biomass, particularly grain. In the field experiment (v) two sowing dates, May and June, and three target levels of soil mineral nitrogen (Nmin) were tested. There was a lower grain yield, higher protein content in grain, and lower EAA in grain protein of plants sown in June. Nmin target value of 140 kg N ha–1 raised grain yield, protein concentration in grain, and maintained the content of EAA in protein. The composite flours were made by mixing 0, 10, 20, and 30 % (w/w) wholegrain amaranth flours with refined wheat, refined spelt, or wholegrain spelt as basic flours. By increasing the amaranth replacement ratio, the gelatinisation temperature, water absorption, development time, and stability increased, whereas the dough softening was only slight. The amaranth addition strengthened the dough (vi). Composite breads made with 10 % amaranth flour had higher (refined wheat and spelt) or unaltered (wholegrain spelt) volume and specific loaf volume than sole basic flours. Samples made from refined spelt flour and samples with 10 % amaranth addition were considered as good, with slight deviation in quality (vii). According to the information obtained in the scope of investigation, grain amaranth is recognised as a perspective crop suitable for production of highly nutritive food also under our conditions.
Keywords: Amaranthus cruentus, allelopathy, growth, yield, protein, Nmin, amino acids, photosynthesis, drough, composite flours, rheological properties, sensory analysis
Published: 23.10.2012; Views: 2303; Downloads: 152
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Determining energy production of CdTe photovoltaic system
Jan Šlamberger, Peter Virtič, 2013, original scientific article

Abstract: This paper presents a method for determining energy production of Cadmium-Telluride photovoltaic system, which has a different working performance than the most used Silicon photovoltaic systems. The main difference is sensitivity to the temperature and the solar irradiance. The CdTe cells are less sensitive to the temperature and in contrast to the Si Cells they have a higher efficiency at lower irradiance.
Keywords: photovoltaic module, energy production, annual energy yield, Cadmium-Telluride
Published: 10.07.2015; Views: 523; Downloads: 25
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