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Iztok Hafner, 2011, undergraduate thesis

Abstract: Uporabnost kompleksnih podatkov, med katerimi so zelo pomembne ontologije, je v veliki meri odvisna od njihove ustrezne vizualizacije. Vizualizacija kompleksnih podatkov ni trivialno opravilo in zahteva dobro premišljen koncept ter implementacijo z ustreznim orodjem, ki po možnosti omogoča tudi objavo na svetovnem spletu. Eno takih orodij naj bi bilo tudi Processing, zato ga bomo v diplomi podrobno spoznali. Processing omogoča razvijanje grafično bogatih aplikacij. Temelji sicer na platformi Java, vendar vpeljuje svoj inovativen način razvoja grafičnega uporabniškega vmesnika. Ogledali si bomo tudi sestrski projekt okolja Processing, imenovan Processing.JS, ki omogoča prenos Processing aplikacij na splet z možnostjo izvajanja kot popolne HTML5 spletne aplikacije. Ker se bomo lotili vizualizacije ontologij, bomo pregledali še koncepte semantičnega spleta in preučili standarde, ki semantični splet omogočajo. S pomočjo pridobljenih znanj se bomo nato osredotočili na razvoj Processing aplikacije, ki bo iz izbrane ontologije razbrala pomembne podatke in jih grafično prikazala ter tako omogočila uporabniku njihovo lažje interpretiranje.
Keywords: vizualizacija podatkov, okolje Processing, ontologija, JavaScript, semantični splet
Published: 26.09.2011; Views: 1270; Downloads: 106
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Analysis of growth models for batch kefir grain biomass production in RC1 reaction system
Marko Tramšek, Andreja Goršek, 2008, original scientific article

Abstract: This work describes the statistical analysis of three mathematical models, modified for describing the kefir grain biomass growth curve. Experimental data of time-dependent kefir grain mass increase were used. The propagation was performed in RC1 batch reaction system under optimal bioprocess parameters (temperature, rotational frequency of stirrer, glucose mass concentration) using traditional cultivation in fresh, high-temperature, pasteurized whole fat cow's milk. We compared values of biological parameters obtained by applying the nonlinear regression of experimental data in logistic, Gompertz and Richards models. The most statistically appropriate model was determined using the seven statistical indicators. We established that the kefir grain biomass growth curve during batch propagation under optimal bioprocess conditions can be most successfully described using the Gompertz growth model.
Keywords: chemical processing, milk products, kefir grain growth, process parameters, design of experiments, modeling, mathematical models, Gompertz growth model, RC1
Published: 31.05.2012; Views: 1792; Downloads: 64
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Kefir grains production - An approach for volume optimization of two stage bioreactor system
Andreja Goršek, Marko Tramšek, 2008, original scientific article

Abstract: The main objective of the present study was to design a continuous two-stage bioreactor system for kefir grains production. Based on the experimental data of time-depended kefir grain mass increase and average pH profile during kefir grains batch propagation, parameters of predictive growth and exponential pH models were initially estimated. Afterwards, the non-linear programming (NLP) optimization problem for estimating the optimal volumes of two unequal in series connected continuously stirred tank bioreactors (CSTB) has been developed. The NLP problem is based on criterion of minimal total holding time (MTHT), kefir grain mass balances in CSTB and parameters of the growth and pH models. The results showed that novel kefir grains production plant with two-stage continuous operation, at capacity, qm,KG,pr=3 kgh-1 and conversion, Xo,2=0.980, would primarily require investment in two CSTB with V1=5.93 m3 and V2=5.62 m3, respectively. Technological and economical authorization for a two-stage continuous bioreactor system was mainly confirmed with a more than five times lower total bioreactor volume compared to one-stage plant.
Keywords: chemical processing, bioprocesses, milk products, kefir grains production, bioreactor design, modeling, optimization
Published: 31.05.2012; Views: 1861; Downloads: 70
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Analysis of neuromuscular disorders using statistical and entropy metrics on surface EMG
Rok Istenič, Prodromos A. Kaplanis, Constantinos S. Pattichis, Damjan Zazula, 2008, original scientific article

Abstract: This paper introduces the surface electromyogram (EMG) classification system based on statistical and entropy metrics. The system is intended for diagnostic use and enables classification of examined subject as normal, myopathic or neuropathic, regarding to the acquired EMG signals. 39 subjects in total participated in the experiment, 19 normal, 11 myopathic and 9 neuropathic. Surface EMG was recorded using 4-channel surface electrodes on the biceps brachii muscle at isometric voluntary contractions. The recording time was only 5 seconds long to avoid muscle fatigue, and contractions at fiveforce levels were performed, i.e. 10, 30, 50, 70 and 100 % of maximal voluntary contraction. The feature extraction routine deployed the wavelet transform and calculation of the Shannon entropy across all the scales in order to obtain a feature set for each subject. Subjects were classified regarding the extracted features using three machine learning techniques, i.e. decision trees, support vector machines and ensembles of support vector machines. Four 2-class classifications and a 3-class classification were performed. The scored classification rates were the following: 64+-11% for normal/abnormal, 74+-7% for normal/myopathic, 79+-8% for normal/neuropathic, 49+-20% for myopathic/neuropathic, and 63+-8% for normal/myopathic/neuropathic.
Keywords: surface electromyography, neuromuscular disorders, neuropathy, myopathy, EMG signals, signal processing, wavelet transform, metrics
Published: 31.05.2012; Views: 1048; Downloads: 20
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Heat integration between two biodiesel processes using a simple method
Anita Kovač Kralj, 2008, original scientific article

Abstract: Biodiesel is a clean-burning alternative fuel, produced from domestic, renewable resources. Biodiesel can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modification. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics. This paper presents heat integration between two biodiesel processes. Biodiesel can be produced by the esterification of different fatty acids (high and low boiling point) with alcohols. This simple method for heat integration is based on three possible steps. Simultaneous integration between processes can be performed using a stagewise model with a mixed integer nonlinear programming (MINLP) algorithm (step 3), which can include alternatives suggested by pinch analysis of heat transfer between the processes (step 2). The internal integration of individual processes can be performed in step 1. The fraction can be calculated for maximum integration between processes. Integration between the processes can be carried out using all three steps or by the first and third steps or by the last step only, depending on the problems' complexities. This method includes streams of different processes which are heated or cooled using a utility only. The existing heaters and coolers can be left unchanged in their original processes or can be used for integrating heat between processes, with hot and cold utilities being saved. This approach is illustrated by integrating two simulated biodiesel processes.The objective was to maximize additional annual profit for integration between processes by USD8300/a.
Keywords: chemical processing, biodiesel producing, heat integration, nonlinear programming
Published: 31.05.2012; Views: 1187; Downloads: 43
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Kinetics of supercritical carbon dioxide extraction of borage and evening primrose seed oil
Petra Kotnik, Mojca Škerget, Željko Knez, 2006, original scientific article

Abstract: In the present work, high-pressure extraction of borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.) seed oil, containing the valuable -linolenic acid (GLA), has been investigated. Extraction was performed with supercritical carbon dioxide on a semi-continuous flow apparatus at pressures of 200 and 300 bar, and at temperatures of 40 and 60 °C. A constant flow rate of carbon dioxide in the range from 0.17 to 0.20 kgžhwas maintained during extraction. The extraction yields obtained using dense CO2 were similar to those obtained with conventional extraction using hexane as solvent. The composition of extracted crude oil was determined by GCanalysis. The best results were obtained at 300 bar and 40 °C for both seed types extracted, where the quality of oil was highest with regard to GLA content. The evening primrose seed oil extracted with supercritical fluid extraction was particularly rich in unsaturated fatty acidsČ up to 89.7 wt-% of total free fatty acids in the oil. The dynamic behavior of the extraction runs was analyzed using two mathematical models for describing the constant rate period and the subsequent falling rate period. Based on the experimental data, external mass transfer coefficients, diffusion coefficients and diffusivity in solid phase were estimated. Results showed good agreement between calculated and experimental data.
Keywords: chemical processing, high pressure technology, supecritical CO2, seed oil extraction, evening primrose, borage, free fatty acids, kinetics, modeling
Published: 31.05.2012; Views: 1179; Downloads: 55
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Particle formation using supercritical fluids
Željko Knez, 2006, review article

Abstract: Particle formation and the design of solid particles and powdery composites with unique properties is at the moment one of major the developments of supercritical fluid (synonyms: dense gases, dense fluids, high pressure) applications. Conventional well-known processes for the particle-size redistribution of solid materials are crushing and grinding (which for some compounds are carried out at cryogenic temperatures), air micronization, sublimation, and recrystallization from solution. There are several problems associated with the above-mentioned processes. Some substances are unstable under conventional milling conditions, in recrysfallization processes the product is contaminated with solvent and waste solvent streams are produced. The application of supercritical fluids may overcome the drawbacks of conventional processes, and powders and composites with special characteristics can be produced. Several processes for the formation and design of solid particles using dense gases have been studied intensively. The unique thermodynamic and fluid-dynamic properties of supercritical fluids can also be used for the impregnation of solid particles, for the formation of solid powderous emulsions, particle coatings, e.g. for the formation of solids with unique properties for use in different applications. This review will focus on the fundamentals and on recent advances of particle formation and design processes using supercritical fluids on their applications and the technological advantages and disadvantages of various processes.
Keywords: chemical processing, high pressure technology, supercritical CO2, proteinase, thermal stability, pressure stability, enzyme activity, water content, dense gases
Published: 31.05.2012; Views: 1333; Downloads: 32
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The lipase-catalyzed synthesis of fatty acid fructose esters in organic media and in supercritical carbon dioxide
Saša Šabeder, Maja Leitgeb, Željko Knez, 2006, original scientific article

Abstract: Sugar fatty acid esters are biodegradable surface active compounds in foodstuffs and cosmetics or pharmaceuticals. They have potential in replacing pollutant chemically synthesized surfactants. The enzymatic synthesis of fructose palmitate catalyzed by Candida antarctica B lipase was performed in different organic media in a batch react at atmospheric pressure. The influence of the organic solvent and temperature on the esterification was studied. Since supercritical carbon dioxide (SC CO2) has several advantages over organic solvents, such as high reaction rate, high mass transfer, non-toxicity, non flammability and low price, it was also chosen as a reaction medium for fructose palmitate production. The influence of temperature on immobilized lipase activity was studied at 10 MPa and the results were compared to the results obtained from reactions performed at atmospheric pressure under the same reaction conditions. The highest conversion (67%) was obtained after 24 hours of reaction in SC C02 at 80°C. A change of the particle size distribution and morphology of the untreated lipase and lipase treated with 2-methyl 2-butanol and SC C02 was observed. This article was presented at 1st SEECChE, held in Belgrade, September 25-28, 2005
Keywords: chemical processing, high pressure technology, supercritical CO2, lipase catalyzed syntheses, esterification, fructose palmitate, biocatalysts, lipase, Candida antarctica B
Published: 31.05.2012; Views: 1463; Downloads: 196
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Enzyme-catalyzed reactions in different types of high-pressure enzymatic reactors
Mateja Primožič, Maja Leitgeb, Muzafera Paljevac, Željko Knez, 2006, original scientific article

Abstract: The enzyme-catalyzed hydrolysis of carboxy-methyl cellulose (CMC) was performed in three different types of reactors; in a batch stirred-tank reactor (BSTR) operating at atmospheric pressure, in a high-pressure batch stirred-tank reactor (HP BSTR) and in a high-pressure continuous tubular-membrane reactor (HP CTMR). In the high-pressure reactors aqueous SC C02 was used as the reaction medium. The aim of our research was optimization of the reaction parameters for reaction performance. All the reactions were catalyzed by cellulase from Humicola insolens. Glucose production in the high-pressure batch stirred-tank reactor was faster than in the BSTR at atmospheric pressure. The optimal temperature for the reaction performed in the BSTR at atmospheric pressure was 30°C, while the optimal temperature for the reaction performed in SC C02 was 32°C. The influence of the application of tubular ceramic membranes in the high-pressure reaction system was studied on the model reaction of CMC hydrolysis at atmospheric pressure and in SC C02. The reaction was catalyzed by cellulase from Humicola insolens covalently linked to the surface of the ceramic membrane. The hydrolysis of CMC in SC C02 and at atmospheric pressure was performed for a long time period. The reaction carried out in SC C02 was more productive than the reaction performed at atmospheric pressure.
Keywords: chemical processing, enzymatic reaction, cellulase, supercritical carbon dioxide, high-pressure batch reactor, high-pressure membrane reactor
Published: 31.05.2012; Views: 1135; Downloads: 163
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