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1.
A novel approach for assuring and following inoculum activity during kefir grains growth studies : application of dynamic pH profiles
Marko Tramšek, Andreja Goršek, 2007, izvirni znanstveni članek

Opis: The profiles of kefir grains growth curves strongly depend on bioprocess conditions and inoculum viability. Therefore, accurate growth curve studies require the use of optimally active kefir grains as inoculum. Accordingly, the main objective of our study was experimental optimization of classic kefir grains activation procedure and afterwards, comparison among growth curves of differently activated kefir grains. For this purpose some experiments were initially performed in computer-controlled RC1 reactor provided data of dynamic pH profiles during batch propagation of differently activated grains. Experimental data were mathematically analyzed and using the special methodology of minimizing the absolute deviation of pH(t) profiles the minimal time for grains activation was determined. We established that optimal inoculum activity could be ensured only by the kefir grains, which were previously activated at least over eleven successive days. In the second part of research the growth curve of optimally activated kefir grains was constructed using experimental measurements and fitted with Gompertz model. The present results were compared with the results obtained by our previous study, where classically activated grains were used. We established that, inspite of equal daily kefir grain mass increase, considerable difference in growth curves of differently activated kefir grains exist.
Ključne besede: chemical processing, kefir grains, growth curve, minimal activation time, dynamic pH profiles, Gompertz model
Objavljeno: 31.05.2012; Ogledov: 1067; Prenosov: 42
.pdf Celotno besedilo (384,93 KB)
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Context-dependent factored language models
Gregor Donaj, Zdravko Kačič, 2017, izvirni znanstveni članek

Opis: The incorporation of grammatical information into speech recognition systems is often used to increase performance in morphologically rich languages. However, this introduces demands for sufficiently large training corpora and proper methods of using the additional information. In this paper, we present a method for building factored language models that use data obtained by morphosyntactic tagging. The models use only relevant factors that help to increase performance and ignore data from other factors, thus also reducing the need for large morphosyntactically tagged training corpora. Which data is relevant is determined at run-time, based on the current text segment being estimated, i.e., the context. We show that using a context-dependent model in a two-pass recognition algorithm, the overall speech recognition accuracy in a Broadcast News application improved by 1.73% relatively, while simpler models using the same data achieved only 0.07% improvement. We also present a more detailed error analysis based on lexical features, comparing first-pass and second-pass results.
Ključne besede: speech recognition, factored language model, dynamic backoff path, word context, inflectional language, morphosyntactic tags
Objavljeno: 26.06.2017; Ogledov: 475; Prenosov: 169
.pdf Celotno besedilo (1,17 MB)
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5.
Container throughput forecasting using dynamic factor analysis and ARIMAX model
Marko Intihar, Tomaž Kramberger, Dejan Dragan, 2017, izvirni znanstveni članek

Opis: The paper examines the impact of integration of macroeconomic indicators on the accuracy of container throughput time series forecasting model. For this purpose, a Dynamic factor analysis and AutoRegressive Integrated Moving-Average model with eXogenous inputs (ARIMAX) are used. Both methodologies are integrated into a novel four-stage heuristic procedure. Firstly, dynamic factors are extracted from external macroeconomic indicators influencing the observed throughput. Secondly, the family of ARIMAX models of different orders is generated based on the derived factors. In the third stage, the diagnostic and goodness-of-fit testing is applied, which includes statistical criteria such as fit performance, information criteria, and parsimony. Finally, the best model is heuristically selected and tested on the real data of the Port of Koper. The results show that by applying macroeconomic indicators into the forecasting model, more accurate future throughput forecasts can be achieved. The model is also used to produce future forecasts for the next four years indicating a more oscillatory behaviour in (2018-2020). Hence, care must be taken concerning any bigger investment decisions initiated from the management side. It is believed that the proposed model might be a useful reinforcement of the existing forecasting module in the observed port.
Ključne besede: container throughput forecasting, ARIMAX model, dynamic factor analysis, exogenous macroeconomic indicators, time series analysis
Objavljeno: 12.12.2017; Ogledov: 418; Prenosov: 152
.pdf Celotno besedilo (1,33 MB)
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6.
A 3D nonlinear dynamic analysis of a rock-fill dam based on IZIIS software
Violeta Mircevska, Vladimir Bickovski, Mihail Garevski, 2007, izvirni znanstveni članek

Opis: This paper treats the 3D nonlinear dynamic behavior of a rock-fill dam based on the Mohr-Coulomb failure criterion. The dam is situated in a steep, narrow, “V-shaped” rigid canyon. The concept of a massless rock foundation is treated, for which a certain part of the rock is included in the model. The dam-rock interface was modeled by contact elements, which allowed certain relative displacements between the two media of different stiffnesses. The generation of the 3D mathematical model was related to the topology of the terrain, and the nonlinear dynamic response was based on the "step-by-step" linear-acceleration direct-integration method, making use of the Wilson-θ method. The convergence process was in accordance with the Newton-Raphson method. First, the initial static effective stresses existing in the conditions of the established stationary filtration through the clayey core were defined. The analysis was based on an original FE program for the static and dynamic analyses of rock-fill dams, as well as a FE program for the solution of the stationary filtration process through the clayey core. The dynamic response of the 3D model of the dam was defined for the effect of harmonic excitations. Dynamic analyses in the linear and nonlinear domains were performed for the purpose of comparing the results. The time histories of the linear and nonlinear responses were defined for selected sections and nodes of the model, the tension cut-off zones, the plastic deformations, and the stress-shear strain relationships. The coefficient against the sliding of the potential sliding surfaces was also defined. It can be concluded that 3D analyses as well as a nonlinear material treatment of the soils built in the dam are imperative for a proper assessment of the stability of rock-fill dams situated in narrow canyons.
Ključne besede: automatic generation of 3D model, rock-fill dam, nonlinear dynamic analysis, elastic perfectly plastic criterion, tension cutoff, cracking zones, plastic deformations, stability
Objavljeno: 18.05.2018; Ogledov: 614; Prenosov: 36
.pdf Celotno besedilo (923,69 KB)
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7.
A comparison of linear and nonlinear seismic tunnel-ground interaction analyses
Elefterija Zlatanović, Marina Trajković-Milenković, Dragan Lukić, Stanko Brčić, Vlatko Šešov, 2016, izvirni znanstveni članek

Opis: In order to study the effects of a seismically induced tunnel–ground interaction, two-dimensional numerical analyses are performed using the sofware ANSYS. The study employs a coupled beam–spring model subjected to earthquake loading that is simulated under pure shear conditions and determined by a free-field ground-response analysis using the code EERA. The properties of the soil material are considered as both linear and nonlinear. The results obtained by linear dynamic analyses are compared with state-of-practice analytical elastic solutions. A comparison of the results of both linear and nonlinear analyses is also performed, and significant differences, as well as important factors influencing the tunnel–ground interaction for both cases, are evaluated.
Ključne besede: circular tunnel, linear/nonlinear soil behaviour, beam–spring model, plane-strain conditions, simplified dynamic FE analysis, soil–structure interaction
Objavljeno: 18.06.2018; Ogledov: 151; Prenosov: 14
.pdf Celotno besedilo (1,57 MB)
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