146 research outputs found
On a generalization of the Constantin–Lax–Majda equation
No full textWe present evidence on the global existence of solutions of De Gregorio's equation, based on numerical computation and a mathematical criterion analogous to the Beale-Kato-Majda theorem. Its meaning in the context of a generalized Constantin-Lax-Majda equation will be discussed. We then argue that a convection term, if set in a proper form and in a proper magnitude, can deplete solutions of blow-up
Preskušanje tekstilij za konfekcijske izdelke : diplomsko delo visokošolskega strokovnega programa
No full textStudy of carboxymethyl cellulose fibres and nano-hydroxyapatite electrospinning process
No full textV razvitem svetu je tkivni inženiring vedno bolj pomembno področje, saj se zaradi boljšanja življenjskega standarda in razvoja v zdravstvu prebivalstvo stara. Za izdelavo kostnih implantatov materiali potrebujejo posebne lastnosti, ki jih je mogoče doseči le s kreiranjem novih materialov z uporabo različnih tehnologij. Ena izmed možnosti je uporaba nanotehnologije, s katero lahko izdelamo nanokompozitna vlakna. Ena od možnih uporab so biorazgradljivi polimeri, kot je karboksimetil celuloza, in delci hidroksiapatita, ki spada med kalcijeve fosfate in je najboljši sintetiziran približek naravnim trdim tkivom v človeškem telesu.
V nalogi smo se osredotočili na študij elektropredenja karboksimetilceluloznih nanovlaken z vključenimi delci nano-hidroksiapatita za uporabo na področju tkivnega inženiringa. Sintetizirali smo nanodelce hidroksiapatita po obarjalni metodi in jih okarakterizirali. S postopkom elektropredenja smo izdelali karboksimetilcelulozna nanovlakna. Pri tem smo optimizirali postopek elektropredenja s stališča uporabljene predilne raztopine, parametrov predenja in okoljskih parametrov na podlagi analize z vrstično elektronsko mikroskopijo (SEM).
Ugotovili smo, da je najprimernejša predilna raztopina iz kombinacije raztopine natrijeve soli karboksimetil celuloze (NaCMC) s koncentracijo 7 ut. % in raztopine poli(etilen oksida) (PEO) s koncentracijo 5 ut. % v razmerju R (NaCMC : PEO) = 50 : 50. Optimalni parametri elektropredenja so električna napetost 65 kV in razdalja med elektrodama 150 mm. Relativna zračna vlažnost v prostoru ne sme presegati 50 %. V optimalno raztopino smo dodali različne koncentracije delcev nano-hidroksiapatita (nHAp) in izpredli nanokompozitna vlakna pri optimalnih pogojih elektropredenja. Na podlagi SEM analize delcev in analize z dinamičnim sipanjem svetlobe (DLS) smo pokazali, da imajo delci široko porazdelitev velikosti. Prisotni so nanodelci ter številni aglomerati delcev velikosti nekaj μm. Izvedli smo termogravimetrično analizo (TGA) nanokompozitnih vlaken in ugotovili, da odstotek anorganskega ostanka po segrevanju narašča proporcionalno z večanjem koncentracije dodanih delcev nano-hidroksiapatita, s čimer smo potrdili prisotnost delcev v vlaknih. Pripravili smo elektropredena karboksimetilcelulozna nanokompozitna vlakna z vključenimi delci nano-hidroksiapatita.In the developed world tissue engineering has become an increasingly important area, because population is aging due to the improvements of the standard of living and developments in medicine. For the manufacturing of bone implants materials require special properties which are achievable through creation of new materials using different technologies. One of the possibilities is the use of nanotechnology, where we can create nanocomposite fibres. Biodegradable polymers such as carboxymethyl cellulose and hydroxyapatite particles, which belong to the group of calcium phosphates and are the best synthetic approximation to natural hard tissues in human body, are suitable for these applications.
In our study we have focused our attention on the studies of carboxymethyl cellulose nanofibres with nano-hydroxyapatite particles electrospinning process for the use in the field of tissue engineering. We have synthesized hydroxyapatite nanoparticles via precipitation method and have characterized them. We have prepared carboxymethyl cellulose nanofibres via electrospinning process and optimized the process from the standpoint of used spinning solution, electrospinning parameters and environmental parameters on the basis of scanning electron microscope (SEM) micrographs.
We have determined that the most appropriate spinning solution is a combination of natrium salt of carboxymethyl cellulose (NaCMC) solution with a 7 wt. % concentration and poly(ethylene oxide) (PEO) solution with a 5 wt. % concentration with the ratio R (NaCMC : PEO) = 50 : 50. Optimal electrospinning parameters are 65 kV voltage and 150 mm distance between electrodes. Relative humidity should not exceed 50 %. We added different concentrations of nano-hydroxyapatite (nHAp) particles in the optimal spinning solution and electrospun nanocomposite fibres under optimal electrospinning conditions. SEM micrographs and dynamic light scattering (DLS) analysis of particles have shown the particles\u27 wide size distribution. There are both nanoparticles and agglomerates of micro dimensions present. We carried out thermogravimetric analysis (TGA) of the nanocomposite fibres and seen that the percentage of the inorganic residue increases proportionally with the increasing concentrations of nano-hydroxyapatite particles added to spinning solutions, what confirms the presence of particles in the fibres. We have prepared electrospun carboxymethyl cellulose nanocomposite fibres with added nano-hydroxyapatite particles
STUDY OF PRE-TREATMENT AND COATING OF REGENERATED CELLULOSE FIBRES WITH NANO PARTICLES
No full textCilj naloge \u27\u27Študij predobdelave in oplaščanja regeneriranih celuloznih vlaken z nano delci\u27\u27 je razvoj postopkov za oplaščanje celuloznih vlaken s funkcionalnimi nano delci, ki bi obstoječemu naboru lastnosti teh materialov dodali nove. Uporabili smo viskozna vlakna, ki smo jih oplaščali z delci silicijevega dioksida (SiO2) in železovega oksida-magnetita (Fe3O4). Raziskava je bila razdeljena v tri delepredobdelava viskoznih vlaken z namenom aktivacije njihove površine ter povečanja pornega sistema s čimer izboljšamo adhezijo delcev in omogočimo njihovo rast v notranjosti vlaken. V drugem delu smo raziskali sintezo delcev magnetita ter lastnosti nastalih delcevsintezne postopke smo primerjali z vidika njihove primernosti v kombinaciji s celuloznimi substrati. Tretji del je zajemal oplaščanje vlaken z delci silicijevega dioksida in magnetita po različnih postopkih. Z nabrekanjem v vodnih raztopinah natrijevega hidroksida različnih koncentracij smo odprli strukturo vlaken, s postopki sušenja z zamrzovanjem (liofilizacija) pa smo to povečanje pornega sistema ohranili, v primerjavi s sušenjem na zraku ali pri povišanih temperaturah. Raziskali smo vpliv postopkov predobdelav na nadmolekulsko strukturo vlaken, povečanje njihovega pornega sistema, na elektrokinetične lastnosti (površinski potencial) ter mehanske lastnosti. Povečanje deleža por je odvisno od uporabljene koncentracije natrijevega hidroksida in postopka zamrzovanjavišje koncentracije so v tem pogledu bolj učinkovite, vendar povzročajo znatnejše poslabšanje mehanskih lastnosti vlaken. Za nadaljnje postopke oplaščanja smo uporabili vlakna, nabrekana v 5 ut.% NaOH, ki smo jih počasi zamrzovali in liofilizirali. Podrobna raziskava sinteze delcev magnetita je zajemala variiranje molarnih koncentracij raztopin prekurzorjev ter njihovih razmerij, ter načina dodajanja komponent v reakcijski sistem. Spremljanje poteka reakcij in nastanka magnetita v posameznih fazah dodajanja reagentov oz. v določenih pH področjih ter analiza magnetnih lastnosti nastalih delcev je bila osnova za izbiro postopkov za kasnejše oplaščanje celuloznih vlaken. Koloidne lastnosti pripravljenih disperzij magnetita so bile raziskane s stališča njihove elektroforetične mobilnosti in velikosti delcev. Oplaščanje regeneriranih celuloznih vlaken z nano delci je potekalo po postopku in situ formacije delcev na površini vlaken za oba sistema delcev ter v primeru magnetita tudi z adsorpcijo delcev iz predhodno pripravljene disperzije. Aktivirana površina liofiliziranih vlaken diktira nastanek homogenih in gostejših plasti nano delcev v primerjavi z neenakomerno pokritimi površinami in aglomerati na zraku sušenih vlaken oz. vlaken brez predhodnega nabrekanja. Postopek liofilizacije pa omogoča v primeru delcev silicijevega oksida tudi njihovo rast v notranjosti vlaken. Lastnosti pripravljenih kompozitnih vlaken (viskozna vlakna z nano delci), ki so posledica anorganske faze, so v veliki meri izrazitejše v primeru liofiliziranih vlakenstopnja zaščite proti vnetju vlaken in posledičnem temperaturnem razpadu, ki jo dajejo delci silicijevega dioksida ter vrednosti nasičene magnetizacije, ki jo prispevajo delci magnetita so višje pri vlaknih, ki smo jih pred nanosom delcev liofilizirali.Aim of the presented thesis is a development of procedures for coating of regenerated cellulose fibres with functional nano particles, which can add new properties to these fibres. We have used viscose fibres, which were coated with silicon dioxide particles (SiO2) and iron oxide-magnetite particles (Fe3O4). Research work was divided into three partspre-treatment of viscose fibres with an aim to activate their surface and to enlarge their pore system, which would enhance the adhesion of particles to the fibres’ surface and allow them to also grow in the inside of fibres. Second part is concerned with the magnetite particles’ synthesis and their propertiessynthesis procedures were compared from the viewpoint of their suitability to be combined with cellulose fibres. Third part deals with the coating of fibres with silicon dioxide and iron oxide-magnetite particles with different procedures. Swelling of fibres in aqueous solutions of sodium hydroxide opens their fibrillar structure, while freezing and freeze-drying retains this enlargement of the pore system, in contrast with conventional air or elevated temperature drying. Effect of different pre-treatment procedures on fibres’ supramolecular structure, enlargement of their pore system, surface potential and mechanical properties was investigated. Degree of enhancement of the pore system depends on the used concentration of sodium hydroxide and type of freezinghigher alkali concentrations are more effective, but at a cost of extensive decrease of mechanical properties’ values. For coating with nano particles, fibres, swollen in 5 w.% NaOH and slowly frozen prior to freeze-drying, were used. Analysis of magnetite particles’ synthesis comprised of variations of molar concentrations of precursor solutions as well as different addition protocols of reactants into the reaction system. Following the synthesis and evolution of particles’ formation in different stages of synthesis procedure i.e. at different pH values and analysis of particles’ properties was basis for choosing the synthesis routes for subsequent coatings of fibres. Colloidal properties of prepared dispersions were investigated from a viewpoint of particles’ electrophoretic mobility and their sizes. Coating of fibres was carried out with an in situ formation of particles in presence of fibres and in the case of magnetite, also with an adsorption of particles from a pre-prepared dispersion. Activated surface of viscose fibres dictates the formation of surface layers of particleshomogenous and densely packed layers are formed, while air-dried fibres exhibit unevenly covered surfaces and aggregates of particles. Freeze-dried fibres also enable, in the case of silicon dioxide, their growth in the interior of fibres. Properties of prepared composite fibres (viscose fibres with nano particles), which result from the presence of inorganic phase, are more pronounced with freeze-drying pre-treatmentdegree of combustion prevention and subsequent temperature degradation, which is yielded with silica particles and saturation magnetization values, contributed by magnetite particles
Dealing the Majda Koren’s literature works at the classroom teaching in the primary school
No full textChildren’s literature comprises a complex of belles-lettres texts, written by adult authors who establish a dialogue with a child in this way. The author's self-understanding or how the adults see the dialogue with the child is seen in literary works and autopoetics. The latter is about the author's explanation of their own view on young adult literature creation. Children’s literature is very diverse, considering the perspective from which the author presents the textual reality.
In my thesis I researched the prevailing perspectives in literary works of Majda Koren, and how the pupil's feedback differs based on different perspectives.
The introductory part is focused on presenting the Slovene children’s literature writer Majda Koren and her literary work.
In the central part various perspectives that are characterized in young adult literature are presented, and Koren's works are analyzed according to the prevailing perspective. I figured out that the perspective of reconciliation is prevailent in her works, which means that the author identifies herself with the child's soul and mostly writes about the troubles of heroes that prevent the children’s world to be like they want it to be.
In the final part lesson plans for four literary works of Majda Koren are written. I carried out the lessons in the 5th grade of primary school. The students’ feedback to the discussed works was positive, but it differed according to the perspective. They liked works with the realistic perspective and a hero they could identify with the most.
With every discussed literary work pupils were also recreating literary works. The easiest for them was to write fantasy texts – about themselves as the allmighty hero who solves all the problems. Somewhat harder for them was to describe real events that they experienced, because they could not use their imagination in this case.
In the end I did an interview with Majda Koren
Priprava celuloznih nanokompozitnih vlaken : diplomsko delo univerzitetnega študijskega programa
No full textKationsko izmenjevalna polipropilenska vlakna : diplomska naloga univerzitetnega študija
No full textMedlaboratorijsko preskušanje ploskih tekstilij : diplomsko delo visokošolskega strokovnega programa
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Študij vpliva postopkov obdelave na lastnosti viskoznih tkanin : diplomsko delo univerzitetnega študija
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