The aim of this PhD thesis is to find out mechanisms of the ripple initiation and formation in the chromium thin film on the glass substrate. To learn to control the ripple formation and to apply it for fabrication of diffraction gratings. In this thesis, the experimental and theoretical results of new self-organization effect of the metal thin film on the glass substrate under irradiation with a sequence of partially overlapping laser pulses are presented. The method for formation of the regular ripples and results on investigation of diffractive properties of the self-organized gratings is presented. Different types of metals are used in experiments in order to understand the reasons of regular structure formation in chromium film. A diverse behavior of the films under laser irradiation is observed depending on the metal when burst of partially overlapping pulses was applied. Experimental data is compared with simulations based on different physical phenomena in order to develop and confirm a model of ripple formation in thin chromium film under its irradiation with pulses of a nanosecond laser. The Plateau-Rayleigh instability of the cylindrical ridge formation during laser ablation appears to be the most probable process responsible for initiation of the ripple formation. The Marangoni convection of the molten metal from hot areas to cold is the stabilizing process of steady ripple formation. / Disertacijos darbo tikslas yra suprasti pagrindinius fizikinius mechanizmus, lemiančius raibulių susidarymą. Išmokti kontroliuoti raibulių formavimąsi. Panaudoti raibulių formavimąsi difrakcinių gardeliu gamybai. Rasti sąlygas, kada raibulių formavimosi galima išvengti, siekiant sumažinti kodinės stiklinės liniuotės periodą. Ištirti galimą raibulių formavimąsi skirtingų metalų dangose. Šioje daktaro disertacijoje pristatomi eksperimentiniai ir teoriniai rezultatai naujo savi-organizacijos reiškinio metalo dangos ant stiklo padėklo nanosekundinio lazerio į juostą sufokusuoto pluošto spinduliuotės poveikyje. Pristatomas naujas difrakcinių gardelių formavimo metodas panaudojant metalo savitvarką. Siekiant suprasti kas inicijuoja raibulių formavimąsi ir ar jis įmanomas visiems metalams, dangos apdribimas persiklojančiais lazerio impulsais aštriai į juostą sufokusuotu lazerio pluoštu išbandytas skirtingiems metalams. Skirtingas dangos elgesys stebimas kiekvienam metalui. Nagrinėjami pagrindiniai fizikiniai mechanizmai sukeliantys griežtai periodinių raibulių formavimąsi. Parodoma, kad raibulių formavimosi pradžia atsiranda dėl Plato-Reilio nestabilumo cilindrinės užvartos susidarymo metu. Taip pat parodoma, kad Marangoni konvekcija skystame metale yra pagrindinė jėga, lemianti nusistovėjusį periodinių raibulių formavimąsi.

Disertacijos darbo tikslas yra suprasti pagrindinius fizikinius mechanizmus, lemiančius raibulių susidarymą. Išmokti kontroliuoti raibulių formavimąsi. Panaudoti raibulių formavimąsi difrakcinių gardeliu gamybai. Rasti sąlygas, kada raibulių formavimosi galima išvengti, siekiant sumažinti kodinės stiklinės liniuotės periodą. Ištirti galimą raibulių formavimąsi skirtingų metalų dangose. Šioje daktaro disertacijoje pristatomi eksperimentiniai ir teoriniai rezultatai naujo savi-organizacijos reiškinio metalo dangos ant stiklo padėklo nanosekundinio lazerio į juostą sufokusuoto pluošto spinduliuotės poveikyje. Pristatomas naujas difrakcinių gardelių formavimo metodas panaudojant metalo savitvarką. Siekiant suprasti kas inicijuoja raibulių formavimąsi ir ar jis įmanomas visiems metalams, dangos apdribimas persiklojančiais lazerio impulsais aštriai į juostą sufokusuotu lazerio pluoštu išbandytas skirtingiems metalams. Skirtingas dangos elgesys stebimas kiekvienam metalui. Nagrinėjami pagrindiniai fizikiniai mechanizmai sukeliantys griežtai periodinių raibulių formavimąsi. Parodoma, kad raibulių formavimosi pradžia atsiranda dėl Plato-Reilio nestabilumo cilindrinės užvartos susidarymo metu. Taip pat parodoma, kad Marangoni konvekcija skystame metale yra pagrindinė jėga, lemianti nusistovėjusį periodinių raibulių formavimąsi. / The aim of this PhD thesis is to find out mechanisms of the ripple initiation and formation in the chromium thin film on the glass substrate. To learn to control the ripple formation and to apply it for fabrication of diffraction gratings. In this thesis, the experimental and theoretical results of new self-organization effect of the metal thin film on the glass substrate under irradiation with a sequence of partially overlapping laser pulses are presented. The method for formation of the regular ripples and results on investigation of diffractive properties of the self-organized gratings is presented. Different types of metals are used in experiments in order to understand the reasons of regular structure formation in chromium film. A diverse behavior of the films under laser irradiation is observed depending on the metal when burst of partially overlapping pulses was applied. Experimental data is compared with simulations based on different physical phenomena in order to develop and confirm a model of ripple formation in thin chromium film under its irradiation with pulses of a nanosecond laser. The Plateau-Rayleigh instability of the cylindrical ridge formation during laser ablation appears to be the most probable process responsible for initiation of the ripple formation. The Marangoni convection of the molten metal from hot areas to cold is the stabilizing process of steady ripple formation.

Made available in DSpace on 2014-12-17T15:01:55Z (GMT). No. of bitstreams: 1 MariaCPAM_Tese.pdf: 1121548 bytes, checksum: 75f9a451aff8c4991fa41301b935efcc (MD5) Previous issue date: 2001-07-05 / The heavy metals are used in many industrial processes and when discharged to the environment can cause harmful effects to human, plants and animals. The adsorption technology has been used as an effective methodology to remove metallic ions. The search for new adsorbents motivated the development of this research, accomplished with the purpose of removing Cr (III) from aqueous solutions. Diatomite, chitosan, Filtrol 24TM and active carbon were used as adsorbents. To modify the adsorbent surface was used a bicontinuous microemulsion composed by water (25%), kerosene (25%), saponified coconut oil (10%) and as co-surfactant isoamyl or butyl alcohols (40%). With the objective of developing the best operational conditions the research started with the surfactant synthesis and after that the pseudo-ternary diagrams were plotted. It was decided to use the system composed with isoamyl alcohol as co-surfactant due its smallest solubility in water. The methodology to impregnate the microemulsion on the adsorbents was developed and to prepare each sample was used 10 g of adsorbent and 20 mL of microemulsion. The effect of drying time and temperature was evaluated and the best results were obtained with T = 65 ?C and t = 48 h. After evaluating the efficiency of the tested adsorbents it was decided to use chitosan and diatomite. The influence of the agitation speed, granule size, heavy metal synthetic solution concentration, pH, contact time between adsorbent and metal solution, presence or not of NaCl and others metallic ions in the solution (copper and nickel) were evaluated. The adsorption isotherms were obtained and Freundlich and Langmuir models were tested. The last one correlated better the data. With the purpose to evaluate if using a surfactant solution would supply similar results, the adsorbent surface was modified with this solution. It was verified that the adsorbent impregnated with a microemulsion was more effective than the one with a surfactant solution, showing that the organic phase (kerosene) was important in the heavy metal removal process. It was studied the desorption process and verified that the concentrated minerals acids removed the chromium from the adsorbent surface better than others tested solutions. The treatment showed to be effective, being obtained an increase of approximately 10% in the chitosan s adsorption capacity (132 mg of Cr3+ / g adsorbent), that was already quite efficient, and for diatomite, that was not capable to remove the metal without the microemulsion treatment, it was obtained a capacity of 10 mg of Cr3+ / g adsorbent, checking the applied treatment effectiveness / Os metais pesados s?o utilizados em muitos processos industriais e, quando descartados ao meio ambiente, podem ocasionar efeitos prejudiciais aos seres vivos. O processo de adsor??o vem sendo utilizado como metodologia eficaz para a remo??o de ?ons met?licos. A busca por novos adsorventes motivou o desenvolvimento deste trabalho, realizado com o objetivo de remover Cr (III) de solu??es aquosas. Utilizou-se como adsorventes: diatomita, quitosana, Filtrol 24TM e carv?o ativo. Empregou-se como agente modificador dos adsorventes uma microemuls?o bicont?nua composta de ?gua (25 %), querosene (25 %), ?leo de coco saponificado (10 %) e cotensoativo (?lcool isoam?lico ou but?lico, 40 %). Com o objetivo de obter as melhores condi??es operacionais partiu-se da obten??o do tensoativo e obteve-se os diagramas pseudotern?rios. Resolveu-se empregar o sistema contendo o ?lcool isoam?lico devido sua menor solubilidade em ?gua. Desenvolveu-se a t?cnica de impregna??o da microemuls?o sobre os adsorventes e, para o preparo de cada amostra, empregou-se 10 g de adsorvente e 20 mL de microemuls?o. Avaliou-se o efeito do tempo de secagem e da temperatura, obtendo-se os melhores resultados com T = 65 ?C e t = 48 h. Ap?s avaliar a efici?ncia dos adsorventes testados resolveu-se utilizar a quitosana e a diatomita e avaliou-se a influ?ncia da velocidade de agita??o, granulometria, concentra??o, pH, presen?a de outros c?tions met?licos (cobre e n?quel) e NaCl na solu??o e o tempo de contato do adsorvente com a solu??o de metal. Obteve-se as isotermas de adsor??o e testou-se os modelos de Freundlich e Langmuir, que correlacionou melhor os dados. Com o prop?sito de verificar se o emprego de uma solu??o de tensoativo forneceria resultados semelhantes, tratou-se o adsorvente com esta solu??o e verificou-se que o adsorvente impregnado com a microemuls?o foi mais efetivo, comprovando que a fase org?nica (querosene) era importante para o processo. Estudou-se o processo de dessor??o e verificou-se que os ?cidos minerais concentrados eluiam melhor o cromo. O tratamento mostrou-se eficaz obtendo-se um aumento na capacidade de adsor??o de cromo de aproximadamente 10 % para a quitosana (132 mg de Cr3+/ g adsorvente), que j? era bastante eficiente, e, para a diatomita, que n?o era capaz de remover o metal, obteve-se uma capacidade de 10 mg de Cr3+/g adsorvente, comprovando a efic?cia do tratamento aplicado

In der Gitterquantenchromodynamik sind der Einsatz von unphysikalisch großen Quarkmassen und die Extrapolation von Ergebnissen zu physikalischen Massen signifikante systematische Fehlerquellen. In dieser Arbeit wird die praktische Durchführbarkeit numerischer Simulationen der Quantenchromodynamik mit physikalisch leichten up und down Quarkmassen unter Verwendung der Wilson twisted mass Diskretisierung untersucht. Simulationen im Regime physikalisch leichter Quarkmassen sind jedoch einerseits numerisch sehr aufwendig, können andererseits aber auch durch das Auftreten großer Diskretisierungsartefakte nicht praktikabel sein. Anhand von Simulationen mit massendegenerierten dynamischen up und down Quarks wird dargestellt dass die Erweiterung der twisted mass Fermionwirkung durch den Sheikholeslami-Wohlert Term es ermöglicht physikalisch leichte Quarkmassen zu erreichen. Es wird gezeigt, dass die Simulationen stabil sind und dass die Parameter der diskretisierten Theorie so gewählt werden können, dass das geladene Pion seine physikalische Masse annimmt. Ferner wird dargestellt, dass auch die Parameter für eine Simulation mit dynamischen massendegenerierten up und down quarks sowie nichtdegenerierten strange und charm Quarks schrittweise auf ihre physkalischen Werte gesetzt werden können. Um das Verhalten von Observablen bei physikalischer Quarkmasse zu untersuchen, werden Massen und Zerfallskonstanten von pseudoskalaren Mesonen mit up, down sowie strange und charm Valenzquarks berechnet. Die Ergebnisse stimmen größtenteils überein mit den phänomenologischen Werten, obwohl weder Kontinuumslimes noch die Extrapolation zu unendlichem Volumen durchgeführt werden. Renormierte leichte, strange und charm Quarkmassen werden über Interpolationen in hadronischen Observablen berechnet und stimmen ebenso größtenteils mit phänomenologischen Werten und anderen Ergebnissen aus der Gitter-QCD überein. / In computer simulations of Lattice Quantum Chromodynamics, the usage of unphysically large quark masses and the subsequent extrapolation of results to the physical value of the quark masses are major sources of systematic uncertainty. In this thesis, the feasibility and practicality of numerical simulations of Quantum Chromodynamics with physically light up and down quarks using the Wilson twisted mass quark discretisation are explored. Working in this regime is complicated firstly by the numerical expense of these simulations and secondly by the presence of potentially large lattice artefacts. The twisted mass discretisation is affected by an unphysical mass difference between the charged and neutral pions, rendering simulations at the physical charged pion mass infeasible if this mass splitting is too large. With the aim of reducing it, the Sheikholeslami-Wohlert term is added to the twisted mass fermion action and simulations with mass degenerate up and down quarks are then performed as a proof of concept. It is demonstrated that these simulations are stable and that the parameters of the lattice theory can be successfully tuned to correspond to the physical charged pion mass. Subsequently, the parameter tuning for simulations with mass degenerate up and down quarks as well as strange and charm quarks is explored and it is shown that it can be carried out in steps. As benchmark observables, the masses and decay constants of pseudoscalar mesons with light, strange and charm valence quarks are calculated and seen to largely reproduce their phenomenological values, even though continuum and infinite volume extrapolations are not performed. Light, strange and charm quark mass estimates are determined based on this data and also seen to coincide with phenomenological and other lattice determinations.