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11.
Effect of AlTi5B1 and AlSr10 additions on the fluidity of the AlSi9Cu3 alloy
Matej Steinacher, Franc Zupanič, Mitja Petrič, Primož Mrvar, 2014, original scientific article

Abstract: This work studies the effect of the AlTi5B1 and AlSr10 additions on the fluidity and the solidification time of the AlSi9Cu3 casting alloy. The fluidity was investigated by determining the flow length in a spiral-shaped mould. The solidification time was measured with a thermocouple positioned at the ingate bottom. An individual pouring into the preheated (200 °C) metallic mould was done at different pouring temperatures ((640, 670, 700, and 710) °C). In all the cases, the fluidity was improved with the increasing pouring temperatures. An addition of the AlTi5B1grain refiner to the basic alloy reduced both the grain size and the fluidity, whilst the solidification time was similar to that of the basic alloy. On the other hand, an addition of the AlSr10 modifier refined the ßSi eutectic phase, increased the fluidity and prolonged the solidification time in comparison to the basic alloy. The fluidity was proportional to the solidification time. Thus, by carrying out a simple thermal analysis and determining the solidification time, it is possible to predict the fluidity.V delu je predstavljen vpliv dodatkov AlTi5B1 in AlSr10 na livnost in strjevalni čas livne aluminijeve zlitine AlSi9Cu3. Livnost smo preiskovali z merjenjem dolžine toka taline v kovinski kokili s spiralno livno votlino, medtem ko smo strjevalni čas merili s termoelementom, ki je bil vstavljen na dnu lijaka. Talino smo pri različnih livnih temperaturah ((640, 670, 700 in 710) °C) ulivali v predgreto kokilo (200 °C). Livnost je v vseh primerih naraščala z naraščanjem livne temperature. Dodatek udrobnilnega sredstva AlTi5B1 k osnovni zlitini je zmanjšal tako velikost kristalnih zrn kot livnost, medtem ko je bil strjevalni čas podoben kot v osnovni zlitini. Dodatek modifikatorja AlSr10 je zmanj{al velikost evtektične faze ßSi, povečal livnost ter podaljšal strjevalni čas v primerjavi z osnovno zlitino. Livnost je bila sorazmerna strjevalnemu času, tako da lahko z enostavno termično analizo in določanjem strjevalnega časa napovemo livnost preiskovane zlitine.
Keywords: AlSi9Cu3 alloy, grain refinement, modification, fluidity, solidification time
Published: 15.03.2017; Views: 407; Downloads: 53
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12.
Modification of PET-polymer surface by nitrogen plasma
Rok Zaplotnik, Metod Kolar, Aleš Doliška, Karin Stana-Kleinschek, 2011, original scientific article

Abstract: Low pressure weakly nitrogen plasma was applied for incorporation of nitrogen-containing functional groups onto poly(ethylene terephthalate) - PET polymer. Nitrogen plasma was created in an electrode-less radiofrequency discharge at the nominal power of 200 W and the frequency of 27.12 MHz. Nitrogen molecules entered the discharge region were highly excited, partially dissociated and weakly ionized. Transformation into the state of plasma allowed for creation of chemically reactive particles with a high potential energy while the kinetic energy remained close to the value typical for room temperature. The chemical reactivity allowed for rapid functionalization with nitrogen-rich functional groups. The appearance of these groups was monitored by X-ray photoelectron spectroscopy - XPS. The polymer surface was quickly saturated with nitrogen indicating that the modification was limited to an extremely thin surface film.
Keywords: poly(ethylene terephthalate), nitrogen plasma, surface modification, functional groups, X-ray photoelectron spectroscopy
Published: 17.03.2017; Views: 329; Downloads: 61
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13.
Adapted user-centered design
Emilija Stojmenova Duh, Bojan Imperl, Tomaž Žohar, Dejan Dinevski, 2012, original scientific article

Abstract: Being familiar with all the benefits of e-Health and the strategic plan for the Slovenian health sectors informatization, Telekom Slovenia and the Faculty of Medicine from the University of Maribor, along with other partners, have initiated an e-Health project. The project group is developing various e-Health services that are based on modern ICT (information and communications technology) solutions and will be available on several screens. In order to meet the users needs and expectations and, consequently, achieve the high acceptance of e-Health services, the user-centered design (UCD) approach was employed in the e-Health project. However, during the research it was found that conventional UCD methods are not completely appropriate for older adults: the target population of the e-Health services. That is why the selected UCD methods were modified and adapted for older adults. The modified UCD methods used in the research study are presented in this paper. Using the results of the adapted UCD methods, a prototype for a service named MedReminder was developed. The prototype was evaluated by a group of 12 study participants. The study participants evaluated the MedReminder service as acceptable with a good potential for a high adoption rate among its target population, i.e., older adults.
Keywords: ICT, e-Health, MedReminder, user-centered design, modification, adaptation, older adults
Published: 21.06.2017; Views: 284; Downloads: 58
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14.
Protein adsorption on various plasma-treated polyethylene-terephthalate substrates
Nina Recek, Morana Jaganjac, Metod Kolar, Lidija Milković, Miran Mozetič, Karin Stana-Kleinschek, Alenka Vesel, 2013, original scientific article

Abstract: Protein adhesion and cell response to plasma-treated polymer surfaces were studied. The polymer polyethylene terephthalate (PET) was treated in either an oxygen plasma to make the surface hydrophilic, or a tetrafluoromethane CF4 plasma to make the surface hydrophobic. The plasma source was radiofrequency (RF) discharge. The adsorption of albumin and other proteins from a cell-culture medium onto these surfaces was studied using a quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The cellular response to plasma-treated surfaces was studied as well using an MTT assay and scanning electron microscopy (SEM). The fastest adsorption rate was found on the hydrophilic oxygen plasma-treated sample, and the lowest was found on the pristine untreated sample. Additionally, the amount of adsorbed proteins was higher for the oxygen-plasma-treated surface, and the adsorbed layer was more viscoelastic. In addition, cell adhesion studies support this finding because the best cell adhesion was observed on oxygen-plasma-treated substrates.
Keywords: oxygen and fluorine plasma treatment, polymer surface modification, protein adsorption, cell adhesion, quartz crystal microbalance, QCM
Published: 22.06.2017; Views: 277; Downloads: 204
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15.
Chemical modification and characterization of the surface of polysulfone membranes
Irena Kukovičič, Robert Šoster, Milan Brumen, Volker Ribitsch, D. Wiegel, K. Arnold, Črtomir Stropnik, 2000, original scientific article

Abstract: Asymmetric porous membranes were prepared from polysulfone by a wet-phase separation procedure. Different chemical modifications were applied to the upper membrane surface, i.e. the surface which was exposed to interaction with nonsolvent (water) in the coagulation bath during the membrane formation. The membrane surface was modified by the series of Friedel-Crafts electrophilic substitutions of aromatic rings in the polysulfone molecules. As a reagent 1-chlorodecane or propylene oxide dissolved in hexane and $AlCl_3$ as a catalyst were used. In the former case a hydrophobic and in the latter one a hydrophilic coating was achieved, respectively. The membrane surface was also modified by sulfonization with sulfuric (VI) acid water solution; in this way negative charges were introduced at the membrane surface. The membranes, unmodified and chemically modified, were characterized by measuring the membrane thickness, the deionized water flux through the membrane, the zeta potential and contact angle. The specific chemical modifications of the membrane surface affect the water flux, the zeta potential and contact angle values whereas the membrane thickness remains unchanged. These effects are interpreted in terms of hydrophilicity and hydrophobicity, changes of the membrane surface charge and the thickness of shear layer at the membrane surface, all with respect to the particular modification applied. Reaction with 1-chlorodecane gave a hydrophobic surface by nonpolar $–(CH_2)_9-CH_3$ groups and reaction with propylene oxide gave a hydrophilic surface with polar group $-CH(CH_3)-CH_2-OH$. The surface of sulfonized polysulfone membranes contained ionizable ($-SO_3H$) functional groups.
Keywords: polysulfone, chemical modification, Friedel-Crafts electrophilic substitution, sulfonization, hydrophylicity, hydrophobicity
Published: 17.08.2017; Views: 494; Downloads: 53
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16.
Modification of polyamide knitted fabric using different zeolites
Alenka Ojstršek, Tomaž Fakin, Karin Stana-Kleinschek, Darinka Fakin, 2017, original scientific article

Abstract: The aim of this research was to apply three different types of zeolites and the combination thereof in the form of a very fine powder, together with different chemicals and additives on polyamide knitted fabric according to an industrially acceptable exhaustion procedure in order to study changes in the morphology, optical properties and wettability of surfaces. Zeolites were analysed using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and gas physiosorption. Additionally, the morphology of zeolite-coated surfaces was examined closely using SEM, while changes in molecular-chemical level were examined by means of IR spectroscopy. Optical properties were studied using CIE colour measurement and diff use reflectance profi le determination, while the hydrophilic/hydrophobic character was examined using goniometry. The obtained results show the suitability of the employed exhaustion procedure, depending on the type of zeolite and the composition of the treatment bath. The results also provided evidence of the enhanced wettability of PA fabrics using 4A and 13X zeolites in combination with selected additives.
Keywords: zeolites, polyamide fibres, exhaustion, surface modification, wettability
Published: 31.08.2017; Views: 353; Downloads: 227
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17.
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