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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
511

Studium fyzikálně-chemických vlastností povrchově modifikovaného oxidu wolframu / Studium fyzikálně-chemických vlastností povrchově modifikovaného oxidu wolframu

Polášek, Jan January 2016 (has links)
This work can be divided into two parts. In the first part, we examine possibilities of preparation of monocrystalline tungsten and tungsten oxide nanoclusters by means of magnetron sputtering with gas aggregation. Clusters are prepared in the non-reactive (Ar) and reactive (Ar + O2) atmosphere and heated after the deposition or during the flight by IR radiation. Influence of oxygen in the aggre- gation process was described and possibilities of generating crystalline tungsten and tungsten oxide clusters were found. In the second part, we study reactivity of tungsten oxide layers, pure and doped with rare metals (Pt, Au), deposited on the silicon wafer and etched carbon, towards partial methanol oxidation. Influence of carbon substrate and metal doppants on reactivity was found and described, along with mofrological and chemical changes that occurs in the sample during the proces. 1
512

Konceptstudie e-metanol i Norra Sverige / Concept study e-methanol in Northern Sweden

Sahlén, Ronja January 2022 (has links)
Användandet av fossila bränslen som energikälla leder till stora utsläpp av växthusgaser och klimatförändringar, vilket börjar bli ett hot som växer sig större för varje år. Genom att använda e-bränslen kan man ersätta fossila bränslen, minska utsläppen av växthusgaser och lyckas uppnå klimatmålen. Examensarbetet specialiserade sig på produktion av e-metanol som är en slutprodukt av e-bränslen. Syftet var att undersöka förutsättningarna för ett ekonomiskt, tekniskt och säkerhetsmässigt hållbart Power-to-X koncept i form av en e-metanolanläggning i Norra Sverige. Detta gjordes genom att ta fram mass- och energibalans för metanolproduktion, dimensionera och genomföra en ekonomisk analys för en e-metanolanläggning. För dimensionering undersöktes metanolbehovet och vad nuvarande konventionella metanolanläggningar producerar. En teknisk kartläggning av e-metanolproduktion och olika elektrolys-tekniker utfördes, för att uppskatta en genomförbar storlek av e-metanolanläggning i Norra Sverige. För examensarbetet utfördes inte en teknisk kartläggning för koldioxidavskiljning, CO2-råvaran valdes att köpas in som en driftskostnad. Ett förenklat flödesschema togs fram med vald PEM-elektrolysteknik och direkt CO2-hydrering baserad på liknande studier inom metanolproduktion. För ekonomiska analysen utvärderades anläggningens totala kapitalinvesteringskostnad och driftskostnad för metanolproduktion och elektrolysör separat. Kostnaden för utrustningen inom metanolproduktionen togs från studier med ett liknande flödesschema. Utrustningen som beaktades var kompressorer, värmeväxlare, reaktor, separator och destillation. Efterfrågan på förnybar metanol i Sverige och resten av världen är stor och förväntas fortsätta att öka, för att användas i flera tusentals vardagsprodukter, inklusive plast, färg, kosmetiska och bränslen. För e-metanolanläggningen krävs det stora mängder el och vatten till elektrolysören och koldioxid för metanolproduktionen. En e-metanolanläggning med 500 kton/år i kapacitet, anses vara fullt genomförbar att realisera i Norra Sverige. Tekniken finns för att kunna skapa den mängd CO2 och H2 som anläggningen kräver. Största svårigheten är att få råvarorna, CO2 och H2, till en rimlig kostnad och kapital för att bygga anläggningen. Vidare är det osäkert ifall det finns tillräckligt med förnybar CO2 från netto CO2-neutrala källor i Norra Sverige. Den totala kapitalkostnaden för denna storlek uppskattades till 1,61 miljarder SEK fördelat på tre konstruktionsår, vilket till största del bestod av kostnaden för elektrolysören med 72 %. Den totala driftskostnaden uppskattades till 1,74 miljarder SEK per år, vilket till största del bestod av kostnaden för elektriciteten med 72 %, där majoriteten gick till elektrolysören. Priset på CO2 har en stor inverkan beroende på val av källa och teknik för koldioxidavskiljning. Dessa kostnader är en uppskattning och kan vara högre för ett verkligt fall, när skatter, plats etc. tas i hänsyn och när elprisets variation är medräknat. E-metanol kan bli konkurrenskraftig med fossil metanol om kostnaden för elektrolysören och elpriset, skulle minska avsevärt och ifall det finns tillräckligt med förnybar CO2 tillgängligt.
513

A Membrane Separation Process for Biodiesel Purification

Saleh, Jehad January 2011 (has links)
In the production of biodiesel via the transesterification of vegetable oils, purification to international standards is challenging. A key measure of biodiesel quality is the level of free glycerol in the biodiesel. In order to remove glycerol from fatty acid methyl ester (FAME or biodiesel), a membrane separation setup was tested. The main objective of this thesis was to develop a membrane process for the separation of free glycerol dispersed in FAME after completion of the transesterification reaction and to investigate the effect of different factors on glycerol removal. These factors included membrane pore size, pressure, temperature, and methanol, soap and water content. First, a study of the effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was performed using a modified polyacrylonitrile (PAN) membrane, with 100 kD (ultrafiltration) molecular weight cut off for all runs at 25°C. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME. The mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated (or raw) FAME. The size of the droplets and the free glycerol separation both increased with increasing water content of the FAME. Next, three types of polymeric membranes in the ultrafiltration range with different molecular weight cut off, were tested at three fixed operating pressures and three operating temperatures (0, 5 and 25oC) to remove the free glycerol from a biodiesel reactor effluent. The ASTM standard for free glycerol concentration was met for the experiments performed at 25°C. The results of this study indicate that glycerol could be separated from raw FAME to meet ASTM and EN standards at methanol feed concentrations of up to 3 mass%. The process was demonstrated to rely on the formation of a dynamic polar layer on the membrane surface. Ceramic membranes of different pore sizes (0.05 µm (ultrafiltration (UF) range) and 0.2 µm (microfiltration (MF) range)) were used to treat raw FAME directly using the membrane separation set up at temperatures of 0, 5 and 25°C. The results were encouraging for the 0.05 µm pore size membrane at the highest temperature (25°C). The effect of temperature on glycerol removal was evident from its relation with the concentration factor (CF). Higher temperatures promoted the achievement of the appropriate CF value sooner for faster separation. Membrane pore size was also found to affect separation performance. A subsequent study revealed the effect of different variables on the size of the glycerol droplets using dynamic light scattering (DLS). A key parameter in the use of membrane separation technology is the size of the glycerol droplets and the influence of other components such as water, methanol and soaps on that droplet size. The effect of water, methanol, soap and glycerol on the size of suspended glycerol droplets in FAME was studied using a 3-level Box-Behnken experimental design technique. Standard statistical analysis techniques revealed the significant effect of water and glycerol on increasing droplet size while methanol and soap served to reduce the droplet size. Finally, a study on the effect of trans-membrane pressure (TMP) at different water concentrations in the FAME phase on glycerol removal using UF (0.03 µm pore size, polyethersulfone (PES)) and MF (0.1 and 0.22 µm pore sizes, PES) membranes at 25, 40 and 60°C was performed. Results showed that running at 25°C for the two membrane types produced the best results for glycerol removal and exceeded the ASTM and EN standards. An enhancement of glycerol removal was found by adding small amounts of water up to the maximum solubility limit in biodiesel. An increase in temperature resulted in an increase in the solubility of water in the FAME and less effective glycerol removal. Application of cake filtration theory and a gel layer model showed that the gel layer on the membrane surface is not compressible and the specific cake resistance and gel layer concentration decrease with increasing temperature. An approximate value for the limiting (steady-state) flux was reported and it was found that the highest fluxes were obtained at the lowest initial water concentrations at fixed temperatures. In conclusion, dispersed glycerol can be successfully removed from raw FAME (untreated FAME) using a membrane separation system to meet the ASTM biodiesel fuel standards. The addition of water close to the solubility limit to the FAME mixture enables the formation of larger glycerol droplets and makes the separation of these droplets straightforward.
514

Synthetic Routes to Crystalline Complex Metal Alkyl Carbonates and Hydroxycarbonates via Sol–Gel Chemistry—Perspectives for Advanced Materials in Catalysis

Hanf, Schirin, Lizandara-Pueyo, Carlos, Emmert, Timo Philipp, Jevtovikj, Ivana, Gläser, Roger, Schunk, Stephan Andreas 10 October 2023 (has links)
Metal alkoxides are easily available and versatile precursors for functional materials, such as solid catalysts. However, the poor solubility of metal alkoxides in organic solvents usually hinders their facile application in sol–gel processes and complicates access to complex carbonate or oxidic compounds after hydrolysis of the precursors. In our contribution we have therefore shown three different solubilization strategies for metal alkoxides, namely the derivatization, the hetero-metallization and CO2 insertion. The latter strategy leads to a stoichiometric insertion of CO2 into the metal–oxygen bond of the alkoxide and the subsequent formation of metal alkyl carbonates. These precursors can then be employed advantageously in sol–gel chemistry and, after controlled hydrolysis, result in chemically defined crystalline carbonates and hydroxycarbonates. Cu- and Zn-containing carbonates and hydroxycarbonates were used in an exemplary study for the synthesis of Cu/Zn-based bulk catalysts for methanol synthesis with a final comparable catalytic activity to commercial standard reference catalysts.
515

Electrocatalytic and fuel processing studies for portable fuel cells

Matter, Paul H. 08 August 2006 (has links)
No description available.
516

Spectroscopic Studies and Reaction Mechanisms of Small Molecule Oxidation over Metal Oxide-Supported Catalysts

Sapienza, Nicholas Severino 02 January 2024 (has links)
Chemical warfare agents are a toxic class of compounds that are incredibly harmful to human health. Methods of detoxification and decontamination currently exist, however they all suffer from problems that involve logistical transport or involve technologies that directly address liquid threats instead of vapors. One promising method of detoxification involves the oxidation of these compounds into less-harmful species. The relatively large chemical size and complexity of modern-day chemical warfare agents, however, precludes a straightforward analysis of the chemical transformations that take place on novel decontaminating materials. Additionally, a fundamental understanding of reaction mechanisms that occur on novel material surfaces is required before improved materials can be developed. To this end, the oxidation of three simpler, smaller organic molecules were studied over a variety of materials in order to build up a chemical understanding of the systems under study. The photoepoxidation of propene into propene oxide was observed to readily occur over an in-house developed dual titania-silica catalyst created by atomic layer deposition. The subsequent photoinduced degradation of produced propene oxide was observed to occur over the novel catalyst. Next, the oxidation of CO was studied over a Pt/TiO2 catalyst while in the presence of humidity. The addition of water was shown to enable an alternative, low energy pathway that closely followed the water gas shift, but ended upon the production of stable surface-bound formates. Gaseous oxygen was found to subsequently oxidize these surface formates into the full oxidation product, CO2. Next, the oxidation of methanol was studied over the same Pt/TiO2 catalyst. It was discovered that the water produced when methanol initially adsorbs to the catalyst surface is responsible for unlocking the oxidative capacity of the material. Finally, a custom packedbed reactor was designed and built that enabled unique experimental capabilities not yet available in commercial systems, and will be used in the future to directly test the oxidative capabilities of novel materials for chemical warfare agent destruction. / Doctor of Philosophy / The chemical interactions and reactions that occur between gases and surfaces are incredibly important for a multitude of technologies employed by governments, militaries, and citizens alike. The precise methods in which these gases interact with materials of interest determine whether said material can be used in a catalytic fashion. Much like how an automobile catalytic converter does not have to be replaced each time the vehicle is started; a catalyst is able to be used repeatedly without loss of function. Catalysts in general are unique in that they function to create or allow for chemical reactions to proceed through alternative, lower energy pathways that are more likely to occur under milder environmental conditions. In order to understand the chemical reactions that occur on a catalyst, a combination of specialized spectroscopic methods was used that allowed for tracking the precise chemical bonds that were formed or broken during reaction. A few different model chemical reactions are explored in this work, ranging from the conversion of carbon monoxide into CO2, and the oxidation of methanol, a small alcohol commonly found in fuel cells. The experimental techniques employed herein allowed for precise chemical mechanisms to be tracked, and the information gained will certainly be useful for the design of next-generation materials by future research.
517

Decay and environmental studies on southern pine

Dahlen, Joseph Martin 10 December 2010 (has links)
This work focused on decay and dimensional stability of southern pine lumber and environmental issues associated with emissions released during kiln drying of southern pine. In one study decking boards were treated with a 3% resin acid solution to increase the dimensional stability. The boards were placed on a roof and weathered for two years. The increased water repellency reduced moisture gain following summer rainstorms by one-third compared to untreated matched samples, this significantly reduced splitting by half and cupping by one-third. In one study decking boards from matched samples were weathered for two years in the roof setup described above, and in a fungal ground proximity test. The ground proximity samples had slightly more decay than the roof samples. Correlation between decay ratings for the matched samples was 37%, suggesting above-ground decay susceptibility is dependent on the macro- and micro-environment. Decay in roof exposure was modeled based on moisture content factors, whereas decay in ground proximity was modeled by the resin and fatty acids. One study tested pole sections with varying amounts of sapwood, heartwood, and knots dried in a pilot-scale kiln. A sample of the kiln exhaust was measured for volatile organic compounds. Emissions from poles were similar to clear lumber. Emissions from heartwood poles were less than for heartwood lumber, perhaps due to the poles’ sapwood band. The final study was conducted with clear and knotty lumber kiln dried to below 8% moisture content using three kiln schedules. Wood dried to this lower moisture content is used in interior applications or exported. During drying, a sample of the kiln exhaust was analyzed for total VOCs, and a sample of the kiln exhaust was collected and analyzed for hazardous air pollutants via gas chromatography and spectrophotometry. For all three kiln schedules, mills would reach 10 tons of methanol and thus must comply with maximum achievable control technology standards before reaching 25 tons of methanol, formaldehyde, acetaldehyde, acrolein, and propionaldehyde.
518

A techno-economic assessment of Steam-methane reforming to methanol : Comparative analysis of CO2 and Syngas to methanol / En teknoekonomisk utvärdering av ång-metanomformning till metanol : Jämförande analys av CO2 och Syngas till metanol

Sörensson, Oskar January 2024 (has links)
As society grapples with challenges of net zero emission, one big remaining challenge is heavy and aviation traffic due to the associated challenge of electrifying these sectors. One potential solution for this is E-fuels. E-fuels are hydrocarbon produced from electrolysis hydrogen and carbon dioxide that receive all their energy from renewable non-organic sources. The simplest E-fuel is methanol. Currently methanol is mainly produced from syngas derived from natural gas reforming also known as steam-methane reforming (SMR). A SMR process break down methane into hydrogen, CO2, and CO with the uses of steam. This syngas is then hydrogenated and forms methanol. One alternative production route to the classic syngas hydrogenation is to capture CO2 and add electrolysis hydrogen and then hydrogenate the mixture to from E-methanol.  This thesis aims to compare the traditional production method with joint SMR-flue gas CO2 hydrogenation plant as well as a direct air capture (DAC) CO2 hydrogenation plant. This comparison will be evaluated by their engineering performance, economic performance, and environmental performance.  This evaluation is done with process simulations in Chemcad as well as Excel. In Chemcad the desulfurization step, SMR, carbon capture, and distillation is simulated. The hydrogenation reactors are simulated in Excel with kinetic data. This process data in the foundation of the engineering performance and is used to determine hydrogen and carbon utilization along with energy and water demand. For the economic evaluation CAPEX is calculated from prices of related units adjusted for size and inflation. The OPEX is based on simulation data and modelled in Excel along with net present value (NPV). The environmental performance focuses on global warming potential as well as fossil resources depletion (FD).  The DAC system has both the highest hydrogen and carbon utilization at 98% and 96,9% respectively but suffer from the highest energy and water demand. Both flue gas method and syngas method have similar hydrogen utilization at around 83,5%, but they differ significantly with carbon utilization with 87,2% and 64,7 respectively. The syngas method has the highest net profit per ton methanol along with the highest NPV and the lowest CAPEX cost out of all three methods. The flue gas method still produces a net profit, but significantly lower than the syngas method. Its CAPEX is also significantly higher than its NPV. The DAC system as negative net profit as well as the highest CAPEX by a wide margin. The environmental impact of the flue gas system is significantly lower than that of the syngas route with less than a fourth of the CO2 eq. emissions. It also has a lower FD due to its higher carbon utilization which results in a higher yield methanol per ton natural gas.  Whilst the flue gas hydrogenation has several advantages over the syngas route and the economic improvements with better optimization for the carbon capture units would bring the net profit per ton methanol more in line with the syngas route, as of today it still is not economically defensible. / När samhället kämpar med utmaningarna kring nettonollutsläpp, kvarstår en stor utmaning inom tung- och flygtrafik på grund av den associerade svårigheten med att elektrifiera dessa sektorer. En potentiell lösning för detta är E-bränslen. E-bränslen är kolväten producerade från elektrolysväte och koldioxid som får all sin energi från förnybara icke-organiska källor. Den enklaste E-bränslen är metanol. För närvarande produceras metanol främst från syntes gas som kommer från naturgasreformering, även känd som ångmetanreformering (SMR). En SMR-process bryter ner metan till väte, CO2 och CO med hjälp av ånga. Denna syntes gas får sedan genomgå hydrering för att bilda metanol. Ett alternativa till denna produktionsmetod är att fånga CO2 och tillsätta elektrolysväte och sedan låta blandningen hydrera för att bilda E-metanol.  Detta examensarbete syftar till att jämföra den traditionella produktionsmetoden med en gemensam SMR-rökgas-CO2-hydreringanläggning samt en direkt luftinfångning (DAC) CO2-hydreringanläggning. Denna jämförelse kommer att utvärderas utifrån deras tekniska prestanda, ekonomiska prestanda och miljöprestanda.  Denna utvärdering görs med processimuleringar i Chemcad samt Excel. I Chemcad simuleras avsvavlingssteget, SMR, koldioxidsinfångning och destillation. Hydreringsreaktorerna simuleras i Excel med kinetiska data. Processdata från dessa simuleringar utgör grunden för den tekniska prestandan och används för att bestämma väte- och kolutnyttjande tillsammans med energi- och vattenbehov. För den ekonomiska utvärderingen beräknas CAPEX från priser på relaterade enheter justerade för storlek och inflation. OPEX baseras på simuleringsdata och modelleras i Excel tillsammans med nettonuvärde (NPV). Miljöprestandan fokuserar på den globala uppvärmningspotentialen samt utarmningen av fossila resurser (FD).  DAC-systemet har både den högsta väte- och kolutnyttjande på 98 % respektive 96,9 %, men lider av det högsta energi- och vattenbehovet. Både rökgasmetoden och syntesgasmetoden har liknande väteutnyttjande på cirka 83,5 %, men de skiljer sig betydligt när det gäller kolutnyttjande med 87,2 % respektive 64,7 %. Syntesgasmetoden har den högsta nettoförtjänsten per ton metanol samt det högsta NPV och den lägsta CAPEX-kostnaden av alla tre metoder. Rökgasmetoden ger fortfarande en nettoförtjänst, men betydligt lägre än syntesgasmetoden. Dess CAPEX är också betydligt högre än dess NPV. DAC-systemet har negativ nettoförtjänst samt den högsta CAPEX med en bred marginal. Miljöpåverkan från rökgassystemet är betydligt lägre än den från syntes gas metoden med mindre än en fjärdedel av CO2-ekvivalenta utsläpp. Det har också en lägre FD på grund av sitt högre kolutnyttjande vilket resulterar i ett högre utbyte av metanol per ton naturgas.  Trots att rökgashydrering har flera fördelar över syntesgasvägen och de ekonomiska förbättringarna med bättre optimering för koldioxidavskiljningsenheterna som skulle få nettoförtjänsten per ton metanol mer i linje med syntesgasvägen, är metoden fortfarande inte ekonomiskt försvarbart i dagsläget.
519

Experimental comparison of heat pipes and thermosyphons containing methanol and acteone

Strain, Jana 26 April 2017 (has links)
The cold chain industry has a need for a standalone, electricity independent cooling unit that is used for both storage of warehouse product and on deliveries [1]. Mixed temperature fresh and frozen food deliveries are problematic without the distributor having specialized duel compartment refrigerated trucks [2]. These trucks permanently reduce the available capacity for payload delivery [2]. It would be valuable to the cold chain industry to have a passive, independent, storage unit that can be moved using a forklift and placed anywhere within a reefer or warehouse [1]. This versatile unit is a simple mechanical system, but presents a complicated thermal problem. One of the design challenges is to thermally isolate the load from the environment and to maintain thermal conditions for a specified length of time. A proposed storage system uses heat pipes to connect the cargo compartment to a heat sink containing solid CO2. Heat pipes are a simple, passive, and quiet way to transfer heat. Heat pipe design and theory is an active area of research with numerous papers in the literature; however, there is less reported about the actual process of manufacturing. This thesis investigates a new potential application of heat pipes, with a focus on the manufacturing process and experimental performance. A total of four heat pipes and two thermosyphons are created using acetone and methanol as the working fluids, and copper and aluminum as the heat pipe housing. Performance is compared to an insulated copper tube with the same outer dimensions, where the primary performance metric is steady-state thermal resistance. In addition, transient performance is quantified as well as the temperature distribution along the outer in the evaporator, adiabatic and condenser regions. Results show that the prototypes made out of copper reached steady-state faster than the aluminum pipes, while also having a smaller temperature differential between the evaporator and condenser. Methanol and acetone have similar performance over the temperature ranges of 198 K to 358 K. The best performing prototype is a copper thermosyphon containing methanol which achieves an effective thermal resistance of 2.0 K/W with an applied load of 40.7 W, when the condenser is cooled with dry ice in acetone. When cooled with ice water the copper thermosyphon achieves an effective thermal resistance of 0.5 K/W with a load of 40.7 W. / Graduate / 0548 / jstrain@uvic.ca
520

Investigation of the nonlinear optical response of novel azobenzene-iminopyridine derivatives and the dynamic heterogeneities of water / methanol mixtures / Etude de la réponse optique non linéaire de nouveaux dérivés d'azobenzène-iminopyridine et des hétérogénéités dynamiques des mélanges eau/méthanol

Kerasidou, Ariadni 09 October 2015 (has links)
Cette étude est divisée en deux parties: l'analyse des propriétés optiques non linéaires (NLO) de nouveaux dérivés pi-conjugués d’Azobenzène Iminopyridine et les hétérogénéités dynamiques (DH) des mélanges eau/méthanol. La première partie a été réalisée en utilisant la technique Z-scan ainsi que les techniques de génération de deuxième et troisième harmoniques (SHG/THG). Communément, l'optique non linéaire est le domaine de l'optique qui étudie l'interaction de la lumière avec un système matériel et les changements induits dans les propriétés optiques des matériaux parun champ électromagnétique intense. La non-linéarité réside dans le fait que la réponse du matériau ne dépend pas linéairement de l'intensité du champ électrique. Les matériaux qui possèdent une forte réponse non linéaire sont très utiles pour la photonique et l'optoélectronique. Ils peuvent être utilisés comme limiteurs optiques pour protéger les détecteurs de faisceaux laser de haute intensité, également comme commutateurs optiques, portes optiques logiques, etc., avec un objectif ultime qui est le traitement de signal optique et la fabrication d'ordinateurs optiques. La deuxième partie a été réalisée au moyen de calculs informatiques et plus particulièrement de simulations de dynamiques moléculaires dans l'eau, dans le méthanol et dans des mélanges eau/méthanol à différentes températures. La simulation par ordinateur est un outil très approprié pour explorer les liquides, également dans la plage de régime en surfusion, sans les limitations du processus de nucléation qui a lieu dans l'expérience réelle. Lorsque la température diminue les liquides surfondus subissent a minima une augmentation exponentielle de leur viscosité (Arrhenius). Cette grande modification des propriétés detransport apparaît bien que la structure ne change que légèrement avec la température. / This study is divided into two parts: the investigation of the nonlinear optical (NLO) properties of new (pi)- conjugated Azobenzene Iminopyridine derivatives and the Dynamic Heterogeneities (DH) of water/methanol mixtures. The first part was achieved employing Z-scan, Second and Third Harmonic Generation (SHG/THG) techniques. Generally, nonlinear optics is the domain of optics that studies the interaction of light with a material system and the changes resulted in the optical properties of the materials by an intense electromagnetic field. The nonlinearity lies in the fact that the material response does not depend linearly on the intensity of the electric field. Materials with significant nonlinear response are very useful for photonics and optoelectronics. They can be used as optical limiters to protect sensitive detectors of high-intensity laser beams, as well as optical switches, optical logic gates and etc., with an ultimate objective the processing of optical signal and manufacture of optical computers. The second part was done via computer calculationsand more specifically Molecular Dynamic Simulations in water, methanol and water/methanol mixtures at different temperatures. Computer simulation is a very suitable tool for exploring liquids, also in the range of the supercooled regime, without the limitations of the nucleation process, which takes place in the real experiment. Supercooled liquids undergo an exponential (Arrhenius) or even larger increase of their viscosity, when the temperature decreases. This large modification of the transport properties appear while the structure only slightly changes with temperature.

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