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Kinetics of supercritical carbon dioxide extraction of borage and evening primrose seed oil
Petra Kotnik, Mojca Škerget, Željko Knez, 2006, izvirni znanstveni članek

Opis: 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.
Ključne besede: chemical processing, high pressure technology, supecritical CO2, seed oil extraction, evening primrose, borage, free fatty acids, kinetics, modeling
Objavljeno: 31.05.2012; Ogledov: 902; Prenosov: 7
URL Celotno besedilo (0,00 KB)

Freedom of speech in the 21st century: universal principles have local contents
Melita Zajc, 2009, recenzija, prikaz knjige, kritika

Ključne besede: free market economy, knowledge society
Objavljeno: 31.05.2012; Ogledov: 616; Prenosov: 5
URL Celotno besedilo (0,00 KB)

Grafting of cotton with [beta]-cyclodextrin via poly(carboxylic acid)
Bojana Vončina, Alenka Majcen Le Marechal, 2005, izvirni znanstveni članek

Opis: Cyclodextrins are cyclic oligosaccharides. Cyclodextrin molecules can form inclusion complexes with a large number of organic molecules. The properties of cyclodextrins enable them to be used in a variety of different textile applications. Cyclodextrins can act as auxiliaries in washing and dyeing processes, and they can also be fixed onto different fiber surfaces. Because of the complexing abilities of cyclodextrins, textiles with new functional properties can be prepared. Poly(carboxylic acid)s such as 1,2,3,4-butane tetracarboxylic acid (BTCA) are well-known non-formaldehyde crosslinking reagents. BTCA has four carboxylic acid groups, which can react with hydroxyl groups of cellulose and form stable ester bonds. We crosslinked -cyclodextrin molecules on hydroxyl groups of cellulose via BTCA.
Ključne besede: textile fibres, chemical modification, beta cyclodextrines, butane tetracarboxylic acid, BTCA, FTIR, host-guest systems, formaldehyde-free crosslinking reagents
Objavljeno: 01.06.2012; Ogledov: 974; Prenosov: 17
URL Celotno besedilo (0,00 KB)

Bojan Miličević, 2012, diplomsko delo

Opis: Diplomsko delo opisuje strojno opremo plovila AR.Drone. Opisani so elementi, ki so nameščeni na plovilu, njihove lastnosti, komunikacija med plovilom in klientom. Nameščene kamere na plovilu omogočajo prepoznavanje oznak drugih plovil, ter orientacijo v okolju. Med letenjem plovila poteka prenos navigacijskih podatkov in podatkov slike oz. videa preko brezžičnega omrežja. Za upravljanje plovila uporabljamo napravo z operacijskim sistemom android, ki komunicirata preko brezžičnega omrežja. V sami aplikaciji pa lahko prilagajamo nastavitve upravljanja plovila. Klient se direktno poveže na strežnik, ki je implementiran na AR.Drone. AR.Drone ima implementiran standard IEEE 802.11 g/n za brezžično povezavo. V diplomskem delu smo preučili možnost priklopa plovila na standard IEEE 802.15.4.
Ključne besede: plovilo AR.Drone, operacijski sistem Android, aplikacija AR.Free Flight
Objavljeno: 26.11.2012; Ogledov: 851; Prenosov: 75
.pdf Celotno besedilo (2,03 MB)

Tine Curk, 2012, magistrsko delo

Opis: A grafted polymer layer can be used to prevent the deposition of colloidal particles on a solid surface. This thesis presents Monte Carlo simulations of hard-sphere colloids pushed to a polymer brush under the influence of external fields (e.g. gravity). For weak fields colloids can not penetrate the brush and the effective potential acting on a single colloid is approximately quadratic. The phase diagram of three-dimensional hard-sphere colloids, that in one dimension are constrained to a plane by a harmonic potential, is presented. Under the influence of sufficiently strong external fields colloids penetrate the brush and form internally ordered, columnar structures that span the polymer layer. The morphology of the patterns that form depends sensitively on the strength of the applied field. We propose a simple phenomenological theory that accounts for the main characteristics of the observed behaviour. The present results suggest a simple experimental method to determine the surface polymer coverage.
Ključne besede: Soft Matter, Monte Carlo Method, Wang-Landau Algorithm, Free Energy, Polymer Brush, Colloids, Ordering
Objavljeno: 04.03.2013; Ogledov: 1184; Prenosov: 48
.pdf Celotno besedilo (6,75 MB)

Heike Marlene Anna Ehmann, 2012, doktorska disertacija

Opis: The goal of this thesis is the structuring of cellulose nanocrystals using different organofunctional silane compounds and different cationic species to prepare highly functional materials with tailored properties. In addition different new aspects and approaches for the structural characterization of functionalised cellulose nanocrystals (CNC) functionalised with different organofunctionalalkoxysilanes as well as cationic species have been introduced. Cellulose nanocrystals (CNC) are prepared using three different acidic conditions to hydrolyse microcrystalline cellulose (MCC). The sulphuric acid hydrolysis introduces highly negative charged sulphate groups on the CNC. The aqueous nanocrystalline cellulose suspensions (aNCS) are analysed in terms of ζ-potential related to the pH and concentration to investigate the stability while dynamic light scattering (DLS) is used to investigate the size distribution. The hydrochloric acid hydrolysis in contrast only removes the amorphous regions but the so obtained CNC are less stabilized (decreased ζ-potential) and tend to agglomerate very fast. The use of the mixture of both acids (HCl and H2SO4) during the hydrolysis of MCC introduces less sulphate groups compared with the sulphuric acid hydrolysis. AFM investigations show that the shapes of the CNC are highly influenced by the hydrolysis conditions. While the shape of the H2SO4 hydrolysed CNC is rod like, while the shape of the other two CNC samples is more spherical in nature. One of the major topic in this work is the analysis of aNCS in aqueous solutions by small angle x-ray scattering (SAXS). The use of the generalized indirect Fourier transformation (GIFT) method allows the analysis of these systems and structural properties such as shape, size and surface charge of aNCS can be assessed. Using this kind of characterisation it can be seen that the shape of the H2SO4 hydrolysed CNC is definitely rod like while the other CNC sample can be described with spheres. In addition to the aNCS characterisation different substrates (Si-wafer, glass slides, polystyrene, etc.) are equipped with aNCS using a variety of different deposition methods (e.g. spin coating, solution casting, dip coating). The resulting films are studied in terms of morphology AFM, SARFUS and SEM. Sophisticated scattering techniques are employed for surface structural characterisation as grazing incidence small angel x-ray scattering. The determination of surface free energies allows conclusions about the hydrophilicity and hydrophobicity as well as the interaction capacity with different liquids. It can be seen that besides the hydrophilic nature of the CNC also hydrophobic interactions are present. The highly negative charged CNC sample which was prepared using sulphuric acid hydrolysis is found to be best suitable for the further hybridization with different organofunctional silanes and for the layer by layer approach (LBL) with different cationic species. The organofunctionalalkoxysilanes which were used in this study can be divided into three groups (e.g filler, surface functionalisation silanes, cross linking silanes). Depending on the nature of the organic residue the silanes are capable to introduce functionalities with enhanced hydrophobic and olephobic properties. The surface energies are investigated using contact angle method, while the surface energies are calculated using three different model approaches (OWRK, Wu, Acid-Base). The most increased hydrophobic and oleophobic properties were measured for trimethylfluorophenylsilantriol (PFTEOS). The morphology of the coated silanes is investigated using SAFRUS technique. It can be seen that nearly all silanes can be coated as homogeneous films onto different substrates (Si-wafer, SURFs, glass slides) with different methods (spin coating, solution casting). The macroscopic appearance of solution casted silanes is investigated using optical microscopy. The differences of the structural nature of the so obtained coatings and detaching films were investigated...
Ključne besede: Cellulose nanocrystals, sol-gel chemistry, organofunctionalalkoxysilanes, hybrid materials, small angle x-ray scattering, generalized indirect Fourier Transformation, quartz crystal microbalance dissipation, surface free energy, surface functionalisation, layer by layer
Objavljeno: 28.11.2012; Ogledov: 1234; Prenosov: 72
.pdf Celotno besedilo (8,59 MB)

Aja Lovrec, 2014, magistrsko delo

Opis: There are different ways of perceiving and understanding humour. Some people comprehend the content on the internet social sites as humorous, others as hateful. The aim of this master’s thesis is to raise awareness of hate speech on the internet. The survey was designed for the purpose of highlighting the difference between hate speech and humour in the example of internet memes. There were 513 Slovene participants answering the questionnaire on how they understand selected internet memes – as humour or as hate speech. The sample of English native speakers was smaller (57 respondents), yet enough to compare the results based on different independent variables (English language proficiency and gender). It was confirmed that there is a thin line between hate speech and humour. Some memes that were considered humorous for Slovene respondents were understood as offensive for English native speakers. We concluded that the level of English proficiency does not significantly influence considering memes as humorous or hate speech. The independent variable of gender has some influence on the respondens perception of a meme as humorous or hateful. Based on the survey analysis, it is concluded that memes which might be perceived as hate speech could also be understood as humorous due to the general purpose of a meme (memes are meant to be humorous and funny).
Ključne besede: hate speech, humour, internet memes, human rights, free speech
Objavljeno: 08.10.2014; Ogledov: 1144; Prenosov: 154
.pdf Celotno besedilo (5,17 MB)

On cube-free median graphs
Boštjan Brešar, Sandi Klavžar, Riste Škrekovski, 2003

Opis: Naj bo ▫$G$▫ mediansk graf brez 3-kocke. Pokazano je, da velja ▫$frac{k}{2} ge sqrt{n}-1 ge frac{m}{2sqrt{n}} ge sqrt{s} ge r-1$▫, kjer so ▫$n, m, s, k$▫ in ▫$r$▫ števila točk, povezav, kvadratov, ▫$Theta$▫-razredov in število povezav najmanšega ▫$Theta$▫-razreda grafa ▫$G$▫. Enakosti so dosežene natanko tedaj, ko je ▫$G$▫ kartezični produkt dveh dreves istega reda. Obravnavan je tudi polinom kock medianskih grafov in pokazano je, da lahko ravninske medianske grafe brez 3-kocke prepoznamo v linearnem času.
Ključne besede: matematika, teorija grafov, medianski graf, kartezični produkt, prepoznavni algoritem, mathematics, graph theory, median graph, cube-free graph, Cartesian product, recognition algoritem
Objavljeno: 10.07.2015; Ogledov: 222; Prenosov: 3
URL Celotno besedilo (0,00 KB)

Relaxing linear matrix inequalities noncommutatively
Igor Klep, 2010, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: linear matrix inequality (LMI), completely positive, semidefinite programming, Positivstellensatz, Gleichstellensatz, archimedean quadratic module, free positivity
Objavljeno: 10.07.2015; Ogledov: 111; Prenosov: 2
URL Celotno besedilo (0,00 KB)

Relaxing LMI Domination Matricially
Igor Klep, 2010, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: linear matrix inequality (LMI), completely positive, semidefinite programming, Positivstellensatz, Gleichstellensatz, archimedean quadratic module, free positivity
Objavljeno: 10.07.2015; Ogledov: 112; Prenosov: 2
URL Celotno besedilo (0,00 KB)

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