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1.
The influence of electrogalvanic device on scaling
Marjana Simonič, Irena Ban, 2013, izvirni znanstveni članek

Opis: The use of an electrogalvanic device for scale neutralisation is descibed in this paper. Physico-chemical analyses were performed before and after the treatment. The results were compared with those obtained by using magnetic water treatment device. By measuring some individual parameters and the implementation of chemical analysis, the satisfactory functioning of the electrogalvanic device was demonstrated. The quality of drinking water did notchange much after the water treatment method. The results of determination of calcium carbonate saturating index showed that the raw drinking water is incarbonate equlibrium as well as both treated water samples. The calcite/aragonite ratio was studied by means of microscopy and X-ray powder diffraction. Inspection of crystals formed during the experiments with microscopy indicated that aragonite crystal structure of the precipitates prevailed over the calcite stucture. The diffractograms showed that the share of aragonite increased after using the electrogalvanic device compared with raw drinking water samples where the share of calcite was higher.
Ključne besede: water treatment, electrogalvanic device, calcite, aragonite
Objavljeno: 03.04.2017; Ogledov: 38; Prenosov: 0
.pdf Polno besedilo (1,40 MB)

2.
Characterization of Slovenian coal and estimation of coal heating value based on proximate analysis using regression and artificial neural networks
Darja Kavšek, Adriána Bednárová, Miša Biro, Roman Kranvogl, Darinka Brodnjak-Vončina, Ernest Beinrohr, 2013, izvirni znanstveni članek

Opis: Chemical composition of Slovenian coal has been characterised in terms of proximate and ultimate analyses and the relations among the chemical descriptors and the higher heating value (HHV) examined using correlation analysis and multivariate data analysis methods. The proximate analysis descriptors were used to predict HHV using multiple linear regression (MLR) and artificial neural network (ANN) methods. An attempt has been made to select the model with the optimal number of predictor variables. According to the adjusted multiple coefficient of determination in the MLR model, and alternatively, according to sensitivity analysis in ANN developing, two descriptors were evaluated by both methods as optimal predictors: fixed carbonand volatile matter. The performances of MLR and ANN when modelling HHV were comparable; the mean relative difference between the actual and calculated HHV values in the training data was 1.11% for MLR and 0.91% for ANN. The predictive ability of the models was evaluated by an external validation data set; the mean relative difference between the actual and predicted HHV values was 1.39% in MLR and 1.47% in ANN. Thus, the developed models could be appropriately used to calculate HHV.
Ključne besede: Slovenian coal, higher heating value, HHV, regression, artificial neural network
Objavljeno: 03.04.2017; Ogledov: 22; Prenosov: 0
.pdf Polno besedilo (749,77 KB)

3.
A kinetic study on drinking water denitrification using a membrane bioreactor
Andreja Goršek, Marjana Simonič, Aleksandra Petrovič, 2015, izvirni znanstveni članek

Opis: This study determines the basic parameters of Monod kinetics for microbial growth within a membrane bioreactor using the Zenon ZeeWeed 10 MBR system. The influent nitrate concentration was kept at 70 ± 2 mg L-1 NO3ˉ. During the experiments a constant concentration of activated sludge was maintained at approximately 0.76 g L-1 under anoxic conditions. Sucrose was added to the activated sludge as a carbon source. The Monod kinetic parameters were calculated by numerical interpolation, by considering experimental data. The maximum specific growth rate of the biomass was determined to be 0.31 h-1, half-saturation constant 5.4 mg L-1, and yield coefficient 0.35 mg biomass mg-1 COD. Afterwards, a dynamic simulation was performed within the calculated parameters. The dynamic concentration profiles for substrate and biomass were determined at different dilution rates within the range of 0.8 to 5 d-1.
Ključne besede: kinetics, denitrification, drinking water, membrane bioreactor, sucrose
Objavljeno: 03.04.2017; Ogledov: 22; Prenosov: 0
.pdf Polno besedilo (1,68 MB)

4.
Prediction of wine sensorial quality by routinely measured chemical properties
Adriána Bednárová, Roman Kranvogl, Darinka Brodnjak-Vončina, Tjaša Jug, 2014, izvirni znanstveni članek

Opis: The determination of the sensorial quality of wines is of great interest for wine consumers and producers since it declares the quality in most of the cases. The sensorial assays carried out by a group of experts are time-consuming and expensive especially when dealing with large batches of wines. Therefore, an attempt was made to assess the possibility of estimating the wine sensorial quality with using routinely measured chemical descriptors as predictors. For this purpose, 131 Slovenian red wine samples of different varieties and years of production were analysed and correlation and principal component analysis were applied to find inter-relations between the studied oenological descriptors. The method of artificial neural networks (ANNs) was utilised as the prediction tool for estimating overall sensorial quality of red wines. Each model was rigorously validated and sensitivity analysis was applied as a method for selecting the most important predictors. Consequently, acceptable results were obtained, when data representing only one year of production were included in the analysis. In this case, the coefficient of determination (R2) associated with training data was 0.95 and that for validation data was 0.90. When estimating sensorial quality in categorical form, 94 % and 85 % of correctly classified samples were achieved for training and validation subset, respectively.
Ključne besede: overall sensorial quality, prediction, Slovenian wine, artificial neural networks, multivariate data analysis
Objavljeno: 03.04.2017; Ogledov: 29; Prenosov: 0
.pdf Polno besedilo (1,02 MB)

5.
Priprava feritov MnZn s hidrotermalno obdelavo oksidov
Darko Makovec, Andrej Žnidaršič, Mihael Drofenik, 2004, izvirni znanstveni članek

Opis: V članku poročamo o rezultatih raziskovalnega dela v okviru sodelovanja med Institutom "Jožef Stefan" in tovarno ISKRA Feriti, d.o.o., v katerem smo razvili nov postopek za masovno pripravo MnZn-feritov, ki temelji na pripravi feritnih prahov s hidrotermalno obdelavo izhodnih oksidov. Z omenjeno metodo smo dobili feritne prahove, ki so po fazni sestavo podobni tistim, pripravljenim po klasičnem keramičnem postopku. Priprava prahov po hidrotermalni metodi je zahtevala prilagoditev celotnega tehnološkega procesa priprave feritov. Prednost hidrotermalne metode pred klasičnim keramičnim postopkom je predvsem v manjši porabi energije, saj poteka termična obdelava oksidne mešanice pri relativno nizkih temperaturah (260 [kompozitum]C - 320 [kompozitum]C) ter bistveno krajših časih, hkrati pa se je izkazalo, da imajo hidrotermalni prahovi velik potencial pri pripravi feritov MnZn z izboljšanimi lastnostmi.
Ključne besede: priprava prahov, hidrotermalna sinteza, magnetni materiali, feriti MnZn
Objavljeno: 27.03.2017; Ogledov: 18; Prenosov: 0
.pdf Polno besedilo (182,35 KB)

6.
Synthesis of nanocrystalline nickel-zinc ferrites within reverse micelles
Vuk Uskoković, Mihael Drofenik, 2003, izvirni znanstveni članek

Opis: Nanocrystalline nickel-zinc ferrites were synthesized via a reverse micelle microemulsion route. The precursor cations were precipitated in the microemulsion system CTAB/1-hexanol/water. A subsequent oxidizing reaction was used to synthesize the nickel-zinc ferrite. The obtained nanoparticles were less than 20 nm in size.
Ključne besede: nanomaterials, ferrite, powders synthesis, microemulsion, reverse micelle
Objavljeno: 23.03.2017; Ogledov: 66; Prenosov: 0
.pdf Polno besedilo (109,33 KB)

7.
Sinteza magnetnih nanodelcev, funkcionaliziranih s tanko plastjo silike
Stanislav Čampelj, Darko Makovec, Marjan Bele, Mihael Drofenik, Janko Jamnik, 2007, izvirni znanstveni članek

Opis: V prispevku opisujemo pripravo maghemitnih nanodelcev prevlečenih s siliko. Postopek je potekal v treh ločenih stopnjah. V prvi smo delce sintetizirali s koprecipitacijo ionov Fe[na]{2+} in Fe[na]{3+}. V drugi smo delce prevlekli s citronsko kislino, da bi preprečili aglomeracijo, in jih dispergirali v vodi. Uspešnost dispergiranja smo spremljali z ugotavljanjem masnega deleža delcev, dispergiranih v vodi. Vsebnost delcev je odvisna od pH-vrednosti pri kateri secitronska kislina adsorbira na površini in koncentracije raztopljene citronske kisline. Tretja stopnja postopka je vsebovala prevlačenje nanodelcev s siliko, ki je potekalo v vodni suspenziji. Ključnega pomena za uspešno prevlačenje nanodelcev s siliko je stabilnost suspenzije nanodelcev oblečenih s citronsko kislino.
Ključne besede: maghemit, nanodelci, citronska kislina, silika, vodna suspenzija
Objavljeno: 23.03.2017; Ogledov: 56; Prenosov: 0
.pdf Polno besedilo (731,75 KB)

8.
Synthesis comparison and characterization of chitosan-coated magnetic nanoparticles prepared with different methods
Gordana Hojnik Podrepšek, Željko Knez, Maja Habulin, 2014, izvirni znanstveni članek

Opis: In this study, magnetic maghemite nanoparticles were prepared with the coprecipitation method, due to its simplicity and productivity. Thereafter, chitosan-coated magnetic nanoparticles were synthesized with three different methods, the micro-emulsion process, the suspension cross-linking technique and the covalent binding. Subsequently, a comparison of the used methods was done using various analyses such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC), vibrating-sample magnetometry (VSM) and dynamic light scattering (DLS). The characterization results from Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) indicated a successful binding of chitosan on the magnetic nanoparticles. SEM pictures showed that spherical structured particles with an increased particle size were obtained as the chitosan layer around the particles was increased. Considering that the magnetic-separation technique has the advantages of rapidity, high efficiency, cost-effectiveness and lack of negative effect on the biological activity, these carriers may be applied in enzyme immobilization.
Ključne besede: magnetic nanoparticles, chitosan, surface functionalization
Objavljeno: 23.03.2017; Ogledov: 57; Prenosov: 0
.pdf Polno besedilo (1022,83 KB)

9.
Efekt PTKU v močno donorsko dopirani keramiki BaTiO[spodaj]3
Nina Ule, Darko Makovec, Mihael Drofenik, 2000, izvirni znanstveni članek

Opis: Navadno izdelujejo upore s pozitivnim temperaturnim koeficientom upornosti (PTK-upore) s sintranjem nizko donorsko dopiranega BaTiO3 na zraku. Koncentracija donorja ne sme preseči kritične velikosti (-0,3 mol.% med sintranjem na zraku), ki povzroči zaustavitev pretirane rasti zrn med sintranjem. S sintranjem v redukcijski atmosferi lahko povišamo kritično koncentracijo donorja, in tako dobimo močno donorsko dopiran BaTiO3 z grobo zrnato mikrostrukturo. V grobo zrnatem BaTiO3 lahko s poznejšo reoksidacijo z žganjem na zraku uravnavamo PTKU-efekt. V tem delu so predstavljeni rezultati raziskave PTKU-efekta v keramikah BaTiO3, dopiranih s koncentracijami La od o do 20 ml.%. Vzorci so bili sintrani v redukcijski mešanici N2 z 1 % H2 in pozneje reoksidirani z žganjem na zraku.
Ključne besede: polprevodni BaTiO3, donorsko dopiranje, električne lastnosti, PTKU-efekt, mikrostruktura
Objavljeno: 17.03.2017; Ogledov: 114; Prenosov: 2
.pdf Polno besedilo (344,81 KB)

10.
Priprava nanokompozita za biomedicinske aplikacije
Stanislav Čampelj, Darko Makovec, Luka Škrlep, Mihael Drofenik, 2008, izvirni znanstveni članek

Opis: Kompozitni nanodelci, ki vsebujejo superparamagnetno maghemitno jedro, prevlečeno s tanko plastjo amorfnega silicijevega oksida so zelo obetaven material za uporabo v biomedicini. Magnetno jedro omogoča manipulacijo z delci z zunanjim magnetnim poljem, medtem ko plašč amorfnega silicijevega oksida omogoča vezavo različnih molekul na njihovo površino. Vezava različnih organskih molekul, na primer zdravilnih učinkovin, zahteva pripravo nanodelcev, ki imajo na površini sloj funkcionalizacijskih molekul z različnimi funkcionalnimi skupinami. Funkcionalizacijo nanodelcev smo dosegli s kovalentno vezavo različnih silanskih molekul: (3-aminopropil)trietoksisilan (APS) in viniltrietoksisilan (VTS), na njihovo površino. Reakcija je potekla v mešanici etanola, v katerem je bila predhodno raztopljena izbrana silanska molekula, in stabilne vodne suspenzije kompozitnih nanodelcev. Vezavo različnih silanskih molekul na površino nanodelcev smo spremljali z elektrokinetičnimi meritvami in s konduktometrično meritvijo koncentracije molekul na njihovi površini. Izkazalo se je, da lahko vežemo na delce molekule APS v površinski koncentraciji, ki se sklada s koncentracijo silanolnih skupin na površini amorfnega silicijevega oksida.
Ključne besede: nanodelci, nanokompoziti, silani, zeta-potencial, funkcionalizacija
Objavljeno: 17.03.2017; Ogledov: 98; Prenosov: 5
.pdf Polno besedilo (133,68 KB)

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