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Quantitative examination of process parameters during kefir grain biomass production
Andreja Goršek, Marko Tramšek, 2007, kratki znanstveni prispevek

Opis: This article examines the propagation of kefir grains in fresh HTP whole fat cows' milk, with some additions (glucose and bakers yeast). The objective of our work was an experimental determination of the various process parameters relative influence on the propagation and daily kefir grain increase mass, using the Taguchi method for experimental design. The effects of medium temperature, glucose mass concentration, bakers yeast mass concentration and the rotational frequency of the stirrer at four levels were studied. Orthogonal array layout of L16 was selected for the proposed experimental design. All experiments were performed in an automated laboratory reaction calorimeter RC1 (Mettler-Toledo) with the same milk (3.5 % fat). The gravimetric method was used to determine daily kefir grain mass increases. Relative contributions of the proposed influencing process parameters on the daily kefir grains increase mass were estimated by analysis of the variance (ANOVA). The highest increase (51.5 %) was found at the rotational frequency of the stirrer 90 (1/min), at glucose mass concentration 20 g/L, and at mediumtemperature 24 °C. Within the observed range of yeast mass concentrationthis process parameter was found to be insignificant compared to others. The rotational frequency of the stirrer has the highest relative influence on the daily kefir grains increase mass (37.3 %) while glucose mass concentration and medium temperature have lower ones, 18.8 % and 9.9 %, respectively. The remaining fraction represents error influence. The main reason for its relatively high value (34.0 %) is that kefir grains are bulky and awkward to handle. This fact confirms the importance of optimal kefir grains production management.
Ključne besede: chemical processing, milk products, kefir, kefir grain growth, process parameters, design of experiments, Taguchi method, RC1
Objavljeno: 31.05.2012; Ogledov: 1670; Prenosov: 33
URL Povezava na celotno besedilo

Determination of the process parameters relative influence on k[sub]La value using Taguchi design methodology
Marko Tramšek, Andreja Goršek, 2007, izvirni znanstveni članek

Opis: This article describes experimental determination of the relative impact of significant process parameters that influence volumetric oxygen mass transfer coefficient (kLa) using Taguchi design methodology. For this purpose an automated RC1 reaction calorimeter (Mettler-Toledo), which was originally developed for chemical processes, was modified for the bioprocesses. Simple fermentation using Baker's yeast was studied to illustrate the design procedure. Orthogonal array L25 was selected for the proposed design and ANOVA method was used for recognizing the relative influence of the process parameters. Within the observed range of temperature (?), fermentation media volume (VFM), and yeast mass concentration (?Y), these process parameters were found to be unimportant compared to the volumetric air flow rate (qV,a) and rotational frequency of the stirrer (fm). The qV,a had a substantial effect on the kLa value (89.2 %) and the fm had just a small one (3.6 %), meanwhile the remain fraction to 100 % represents error. The results refer strictly to the selected case study. Anyhow, the proposed procedure shows that application of the Taguchi approach for analyzing the oxygen mass transfer based on the experimental data obtained from a highly-automated laboratory reactor appears to have potential usage in general biopharmaceutical process design.
Ključne besede: bioprocess parameters, mass transfer, volumetric oxygen mass transfer coefficient, process parameters, Taguchi method, analysis of variance
Objavljeno: 31.05.2012; Ogledov: 1535; Prenosov: 25
URL Povezava na celotno besedilo

In-situ investigation of sucrose hydrolysis - successful link between design of experiment, RC1 and reactIR system
Katja Zajšek, Andreja Goršek, 2008, izvirni znanstveni članek

Opis: The main purpose of this work was combining the modern laboratory equipment (RC1 reaction calorimeter and ReactIRTMiC10 reaction analysis system) and the concept of the Taguchi fs design of experiment to determine the relative influence of important process parameters affecting the sucrose hydrolysis. The reaction was catalyzed by strong acidic cation-exchange resin Amberlite IR-120 in H+ form. Four process parameters, including reaction temperature (.), sucrose mass concentration (fÁS), catalyst mass concentration (fÁC) and the rotational frequency of the stirrer (fm) at four levels were considered in this study. Relative contributions of the proposed influencing process parameters on hydrolysis time were estimated by analysis of the variance (ANOVA). The results showed that . had a substantial effect on the reaction time (78,3 %), the fm and fÁC had a smaller ones (7,9 % and 6,4 %, respectively), meanwhile the remain fraction to 100 % represents error (7,4 %). The optimum conditions, where the time required for complete sucrose hydrolysis would be the shortest, are: .= 79 Ključne besede: sucrose hydrolysis, catalyst, Taguchi method, in-situ FTIR, reaction calorimeter RC1
Objavljeno: 31.05.2012; Ogledov: 1335; Prenosov: 30
URL Povezava na celotno besedilo

Experimental design of crystallization processes using Taguchi method
Miran Hvalec, Andreja Goršek, Peter Glavič, 2004, izvirni znanstveni članek

Opis: Crystallization has become one of the most important unit operation in the chemical industries. The need to reduce the time from product discovery to market introduction is an inherent concern. In order to achieve the prescribedproduct quality characteristics, the process of engineering experimentation has to be optimized. Therefore, an experimental design method for crystallization processes is presented in this paper. Initially, the standardized Taguchi method was used to plan a minimum number of experiments. After identifying the working levels of the design factors and the main performance characteristics of the product under study, the method can be successfully applied to the crystallization processes. The simultaneous variations of the main crystallization parameters and their interactions were investigated using orthogonal array technique. A statistical analysis of 'signal-to-noise' ratio was followed by performing a variance analysis. After developing some special criteria, which depend on performance objectives, the optimal levels of the design factors were determined. Crystallization of $KNO_3$ with desirable particle size as a performance characteristic was used to illustrate the design procedure. The effects of rotational frequency of the stirrer, linear cooling rate and added admixture on final particle size were studied. In order to keep the selected parameters constant during the experiment and to ensure reproduction of entire experiment the automated reaction calorimeter RC1 was used.
Ključne besede: crystallization, particle size, Taguchi method
Objavljeno: 01.06.2012; Ogledov: 1474; Prenosov: 56
.pdf Celotno besedilo (701,22 KB)
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Effect of solid state fermentation medium optimization on Pleurotus ostreatus laccase production
Nataša Belšak, Andrej Gregori, Maja Leitgeb, Dušan Klinar, Štefan Čelan, 2015, izvirni znanstveni članek

Opis: The objective of this work was to increase laccase production by Pleurotus ostreatus PLAB through culture medium optimization using solid-state culture conditions. Increased laccase activity was obtained through the design of experiments (DOE) using the Taguchi orthogonal array (OA). Seven factors, viz. lignocellulose, glucose, yeast extract, peptone, $KH_2PO_4$, $MgSO_4$ · $7H_2O$ and $MnSO_4$ · $H_2O$ at three levels and pH at two levels with OA layout of L18 ($2^1 × 3^7$) were selected for the proposed experimental design using Minitab 17 software. Data analysis showed that lignocellulose (20%) and glucose (10 g $L^{–1}$) had a positive effect, whereas $KH_2PO_4$, $MgSO_4$ · $7H_2O$ and $MnSO_4$ · $H_2O$ did not have a significant effect on laccase production. Taguchi OA analysis showed that pH 6, lignocellulose 20%, glucose 10 g $L^{–1}$, yeast extract 6 g $L^{–1}$, peptone 15 g $L^{–1}$, $KH_2PO_4$ 3 g $L^{–1}$, $MgSO_4$ · $7H_2O$ 0.5 g $L^{–1}$ and $MnSO_4$ · $H_2O$ 0.1 g $L^{–1}$ were the optimal conditions to maximize laccase production. The model predicted a 30.37 U $g^{–1}$ dry wt., which agreed with the experimentally obtained laccase activity 29.15 U $g^{–1}$ dry wt. at optimal conditions.
Ključne besede: Taguchi method (DOE), orthogonal array, optimization, Pleurotus ostreatus, laccase production, solid state fermentation
Objavljeno: 18.08.2017; Ogledov: 479; Prenosov: 176
.pdf Celotno besedilo (126,99 KB)
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Optimization of machining parameters for turning operation with multiple quality characteristics using Grey relational analysis
Franko Puh, Zoran Jurković, Mladen Perinic, Miran Brezočnik, Stipo Buljan, 2016, izvirni znanstveni članek

Opis: Optimization of machining processes is essential for achieving of higher productivity and high quality products in order to remain competitive. This study investigates multi-objective optimization of turning process for an optimal parametric combination to provide the minimum surface roughness (Ra) with the maximum material-removal rate (MRR) using the Grey–Based Taguchi method. Turning parameters considered are cutting speed, feed rate and depth of cut. Nine experimental runs based on Taguchi’s L9 (34) orthogonal array were performed followed by the Grey relational analysis to solve the multi- response optimization problem. Based on the Grey relational grade value, optimum levels of parameters have been identified. The significance of parameters on overall quality characteristics of the cutting process has been evaluated by the analysis of variance (ANOVA). The optimal parameter values obtained during the study have been validated by confirmation experiment.
Ključne besede: ANOVA, Grey relational analysis, multi-objective optimization, Taguchi method, turning
Objavljeno: 12.07.2017; Ogledov: 357; Prenosov: 234
.pdf Celotno besedilo (487,53 KB)
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