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1.
Synthesis of regional networks for biomass and biofuel production
Hon Loong Lam, 2010, doktorska disertacija

Opis: This thesis presents two different approaches to the synthesis of regional networks for biomass and biofuel production and supply: Mathematical Programming and Graph Theoretic approach. The optimisation criterion for both approaches is the maximisation of profit. The first approach is based on a generic optimisation model of biomass production and supply networks. This superstructure approach is based on a flexible number of network layers: plantation, collection using a pre-treatment, process, and consumption. A Mixed Integer Linear Programming (MILP) model has been successfully developed during this work. However, the solution of this biomass production network model is very challenging due to the large sizes of the networks and the number of interconnections. The huge number of redundant variables reduces model efficiency (time taken to solve the model and the interpretation of the results). This model when representing very large size networks cannot be solved over a reasonable time even by professional mathematical programming software tools. Several model-size reduction techniques are therefore proposed for the solution of large-scale networks. In particular, methods are proposed for (i) reducing the connectivity within a biomass supply chain network by setting the maximum allowable distance between the supply zones to the collection centres, (ii) eliminating unnecessary variables and constrains to reduce the zero-flows in the full model, and (iii) aggregating the network and hence the synthesis process by merging the collection centres. The network synthesis is also carried out by P-graph (Process Graph) tools. P-graph is a directed bipartite graph, having two types of vertices — one for operating units and another for those objects representing material or energy flows/quantities. In this procedure, firstly a maximum feasible superstructure for biomass production network is generated from which the optimal structure is then selected by the Branch and Bound method. This graph-based method clearly shows where, how, and what kind of material and energy carriers will be transferred from one supply chain layer to another. In order to test the efficiency of the model, a small regional renewable network problem was solved using both methods. Their performances were tested and the results confirmed the applicability on a regional scale. The proposed model-size reduction techniques were also tested. A large-scale regional case study was created to demonstrate these techniques. The results are very positive and some suggestions for future work are given in the conclusion.
Ključne besede: Biomass and bioenergy network synthesis, Model-size reduction techniques, Mathematical Programming, MILP, P-Graph
Objavljeno: 06.01.2011; Ogledov: 2462; Prenosov: 83
.pdf Celotno besedilo (4,25 MB)

2.
Analysis of growth models for batch kefir grain biomass production in RC1 reaction system
Marko Tramšek, Andreja Goršek, 2008, izvirni znanstveni članek

Opis: 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.
Ključne besede: chemical processing, milk products, kefir grain growth, process parameters, design of experiments, modeling, mathematical models, Gompertz growth model, RC1
Objavljeno: 31.05.2012; Ogledov: 1688; Prenosov: 42
URL Povezava na celotno besedilo

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Development of a mathematical model for the heat transfer of the system man - clothing - environment
Jelka Geršak, Milan Marčič, 2007, izvirni znanstveni članek

Opis: The paper presents the development of a mathematical model of the heat transfer from the human body to the environment air that can be solved on a PC. The advantage of the presented heat transfer model is the ability of a fast evaluation of the heat transfer for various textile materials incorporated ino the clothing system under different ambient conditions.
Ključne besede: textiles, garment properties, heat transfer, mathematical model
Objavljeno: 31.05.2012; Ogledov: 929; Prenosov: 36
URL Povezava na celotno besedilo

5.
The calculation of thermal conductivity, viscosity and thermodynamic properties for nanofluids on the basis of statistical nanomechanics
Jurij Avsec, Maks Oblak, 2007, izvirni znanstveni članek

Opis: The paper features the mathematical model of calculation of thermophysical properties for nanofluids on the basis of statistical nanomechanics. Calculation of properties for nanofluids for real substances is possible by the classical and statistical mechanics. Classical mechanics has no insight into the microstructure of the substance. Statistical mechanics, on the other hand, calculates the properties of state on the basis of molecular motions in a space, and on the basis of the intermolecular interactions. The equations obtained by means of classical thermomechanics are empirical and apply only in the region under observation. The main drawback of classical thermomechanicsis that it lacks the insight into the substance of microstructure. Contrary to classical mechanics, statistical mechanics calculates the thermomechanic properties of state on the basis of intermolecular and intramolecular interactions between particles in the same system of molecules. It deals with the systems composed of a very large number of particles. The results of the analysis are compared with experimental data and show a relatively good agreement. The analytical results obtained by statistical mechanics are compared with the experimental data and show relatively good agreement.
Ključne besede: statistical thermodynamics, thermophysical properties, viscosity, thermal conductivity, thermodynamic properties, mathematical model, nanofluids, statistical nanomechanics
Objavljeno: 31.05.2012; Ogledov: 1204; Prenosov: 38
URL Povezava na celotno besedilo

6.
Diesel and biodiesel fuel spray simulations
Primož Pogorevc, Breda Kegl, Leopold Škerget, 2008, izvirni znanstveni članek

Opis: This paper deals with the investigation of the influential parameters of a mathematical spray breakup model using different fuels. Beside injection system measurements, fuel physical properties and injection process characteristics were measured, because they are necessary for the spray simulation input. For validation purposes, spray was injected into motionless air at atmospheric pressure and room temperature and filmed with a high-speed camera. Spray macrocharacteristics have been determined on the recorded images. Using the simulation program, the injection processes for diesel, biodiesel, and their 50% blend B50 have been simulated. Spray mathematical model parameters were tuned based on the experimentally gained results. Primary breakup model parameters showed the biggest impact on the spray characteristics and were therefore expressed using the fuel physical properties, the injection process characteristics, and the working regime parameters. Spray simulations into the combustion chamber were made in the end. All of these results are presented and discussed in this paper.
Ključne besede: fuel spray, spray breakup, biodiesel fuel, fuels, numerical simulations, mathematical model
Objavljeno: 31.05.2012; Ogledov: 860; Prenosov: 35
URL Povezava na celotno besedilo

7.
The combined analysis of phonon and electron heat transfer mechanism on thermal conductivity for nanofluids
Jurij Avsec, 2008, izvirni znanstveni članek

Opis: The paper features the mathematical model representing the analytical calculation of phonon and electron heat transfer analysis of thermal conductivity for nanofluids. The mathematical model was developed on the basis of statistical nanomechanics. We have made the detailed analysis of the influence of temperature dependence on thermal conductivity for nanofluids. On this basis are taken into account the influences such as formation of nanolayer around nanoparticles, the Brown motion of solid nanoparticles and influence of diffusive-ballistic heat transport. The analytical results obtained by statistical mechanics are compared with the experimental data and they show relatively good agreement.
Ključne besede: statistical nanomechanics, phonons, electron heat transfer, nanofluids, thermal conductivity, thermodynamic properties, mathematical model, statistical nanomechanics
Objavljeno: 31.05.2012; Ogledov: 1212; Prenosov: 39
URL Povezava na celotno besedilo

8.
Adaptive control for power system stability improvement
Jožef Ritonja, 2010, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Ključne besede: synchronous generator, control functions, mathematical model, voltage control
Objavljeno: 31.05.2012; Ogledov: 1994; Prenosov: 40
URL Povezava na celotno besedilo

9.
Intellectual capital - developmental resource of logistic companies for the 21st century
Ratko Zelenika, Drago Pupovac, 2003, pregledni znanstveni članek

Opis: On the basis of relevant scientific research this paper systematically and concisely elaborates the interaction between intellectual capital and logistic services production. Full attention is given to intellectual capital as a factor in effective creation of the logistic processes or in other words, to prove the statement that the first place for achieving competitive advantages in the global and/or regional market of logistic services belongs to knowledge used to produce or improve the existent logistic systems and to create new ones.Further, the paper deals with the tasks of creative logistic managers as open, dynamic and stochastic systems based on knowledge or the creation of universal logistic model determined by the fact that intellectual capital and technological paradigm create the way to new logistic paradigm.Special attention is paid to building and presenting a mathematical model for measuring the intellectual capital as well as the success of its use in different logistic companies.
Ključne besede: traffic, transport, logistics, developement, intellectual resources, logistic model, mathematical model
Objavljeno: 02.06.2017; Ogledov: 200; Prenosov: 35
.pdf Celotno besedilo (2,38 MB)
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10.
A sensitivity model and repeatability of recipe colour
Boris Sluban, Olivera Šauperl, 2001, izvirni znanstveni članek

Opis: The paper briefly describes a mathematical model of the colorant mixture colour sensitivity to concentration errors and the numerical estimates of the related quantities. Features of the theoretical model are illustrated with the results of a number of numerical experiments in which the optical data of a few basic dyes applied to textile fabric were used to predict the sensitivities of recipes for sets of target colours spaced regularly in the colour solid. The rest of the article deals with the question whether the predicted values of recipe colour sensitivity provide useful information about the repeatability of recipe colour. The results of a few groups of laboratory experiments involving the textile fabric dyeing with basic dyes have been analysed with this question in mind.
Ključne besede: textile dyeing, basic dyes, recipe colour, colour, color repeatability, colour sensitivity, concentration errors, mathematical model
Objavljeno: 05.07.2017; Ogledov: 175; Prenosov: 45
.pdf Celotno besedilo (88,81 KB)
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