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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.
11

Estudo dos fatores de risco associados às infecções pelo HIV, hepatite B e C e sífilis e suas prevalências em população carcerária de São Paulo / Study of prevalence and risk factors associated with hiv infection, hepatitis B and C and syphilis in a prison population of Sao Paulo State

Maerrawi, Ilham El 20 December 2012 (has links)
INTRODUÇÃO: Infecções pelo HIV, HBV, HCV e Treponema pallidum encontram no sistema prisional um ambiente favorável para suas propagações e representam grave problema de saúde pública. Neste estudo buscamos conhecer o perfil epidemiológico dos reeducandos de uma unidade prisional e a dinâmica do seu comportamento associado às infecções estudadas. Foram medidas as prevalências dessas infecções e suas coinfecções, investigados os potenciais fatores de risco, assim como medido o padrão de uso de drogas no presídio com ênfase no crack. MÉTODOS: Estudo epidemiológico transversal realizado de fevereiro a dezembro de 2007, na Penitenciária I de São Vicente. Realizada uma análise descritiva utilizando medidas de frequência, médias e desvio padrão. Foram considerados apenas os diagnósticos sorológicos para definição das infecções. Utilizado o OR (odds ratio) como medida de associação com nível de significância de 5% (?). Utilizada a regressão logística para estimar OR ajustado por algumas variáveis. RESULTADOS: Participaram das entrevistas 546 (84,1%) reeducandos e 514 (94,1%) realizaram as sorologias. Apresentaram um perfil jovem com idade média de 29,8 anos. 52,0% (283) referiram relacionamento conjugal com média de dois filhos. Declararam ser de cor parda 51,5% (280). O tempo médio de prisão foi de 10,5 anos. As prevalências identificadas foram: HIV 1,8% [IC95% = 0,1- 3,3], HBV 21,0% [IC95% = 17,8-25,1], HCV 5,3% [IC95% = 3,5-7,6], e 5,3% [IC95% =3,5-7,6] para a infecção pelo Treponema pallidum. Os fatores de risco associados com a infecção pelo HIV foram: uso de droga injetável (OR=15,38), > 30 anos (OR=13,3), uso de cocaína na vida (OR= 5,36) e uso de crack na vida (OR= 5,21). Nas análises multivariadas as variáveis que se mantiveram associadas com o HBV foram: uso de droga injetável (OR=3,36), ter referido DST (OR= 2,28), > de 30 anos (OR=1,86) e mais de cinco anos de prisão (OR= 2,17); com o HCV foram: uso de droga injetável (OR=9,65), uso de maconha na prisão (OR=2,91) e idade >30 anos (OR=8,41); com o Treponema pallidum foram: relação homossexual (OR=11,92) e ter referido sífilis (OR=10,88). As prevalências das coinfecções foram: 0,8% [IC95%= 0,2-2,0] para HIV/HBV, 1,4% [IC95%=0,5-2,8], para HBV/Treponema pallidum, 1,8% [IC95%= 0,8-3,3] para HBV/HCV, e para a tripla infecção 0,4% [IC95%= 0,5-1,4]. Confirmaram o uso de crack na vida 25,0% (136) dos entrevistados. Idade média de início de uso de drogas ilícitas foi de 15,4 anos. Na prisão, o uso de álcool foi relatado por 8,4% (45), tabaco por 62,0% (318), maconha por 36,5 % (194), cocaína por 9,0% (48), e crack por 11,7% (15), sendo seu uso diário referido por 2,3% (3). Uso de drogas injetáveis na vida foi referido por 5,9% (32) e nenhum uso nos últimos seis meses. As situações de violência relacionadas com drogas para 14,3% (28) foram de ameaças de morte, 16,7% (57) agressões físicas e 27,3% (3) sofreram agressão sexual. Para 15,8% (30) o crack esteve relacionado com estas situações. O seu uso com outras drogas foi referido por 41,5% (54). CONCLUSÃO: As prevalências encontradas na população confinada continuam maiores que as observadas na população geral. O consumo de drogas e praticas sexuais desprotegidas foram mantidas no período de confinamento. O tempo de confinamento mostrou-se fator importante na análise de risco. Os fatores de riscos identificados aparecem como importantes indicadores para a estruturação de estratégias de controle dessas infecções junto à população confinada. / INTRODUCTION: Infection by HIV, HBV, HCV and Treponema pallidum are common in the prison system due to an environment favorable to their propagation and represent a serious public health problem. This study aims to understand the epidemiological profile of the inmates in a prison unit and the behaviors associated with the infectious diseases studied. We estimated the prevalence of these infections and their co-infections, investigated potential risk factors, as well as identified the pattern of drug use in prison, especially crack use. METHODS: A cross-sectional epidemiological study conducted from February to December 2007 at the São Vicente Penitentiary . A descriptive analysis using frequency measures, means and standard deviations was conducted. We considered only the setting for serological diagnosis of infections. Odds ratio (OR) with a significance level of 5% (?) was used as a measure of association and a logistic regression was applied to estimate adjusted OR for some variables. RESULTS: A total of 546 prisoners were interviewed (84.1%). Of these, 514 (94.1%) underwent serological analysis. Results showed a profile of young men with an average age of 29.8 years. Fifty-two percent (283) reported marital relationship with an average of two children, and 51.5% (280) reported being of mixed ethnicity. The average time of arrest was 10.5 years. The prevalences were identified: HIV 1.8% [95% CI = 0.1 - 3.3], HBV 21.0% [95% CI 17.8 to 25.1], HCV 5.3% [95% CI = 3.5 to 7.6] and 5.3% [95% CI = 3.5 to 7.6] for infection with Treponema pallidum. The risk factors associated with HIV infection were injected-drug use (OR = 15.38), > 30 years (OR = 13.3), cocaine use (OR = 5.36) and use of crack during lifetime (OR = 5.21). According to multivariate analyzes, variables associated with HBV were: injected-drug use (OR = 3.36), reported any STD (OR = 2.28), > 30 years (OR = 1.86) and more than five years in prison (OR = 2.17); the variables associated with HCV were: injected-drug use (OR = 9.65), marijuana use in prison (OR = 2.91) and age> 30 years (OR = 8.41); the variables associated with Treponema pallidum were: homosexual intercourse (OR = 11.92) and have referred syphilis (OR = 10.88). The prevalence of co-infections were 0.8% [95% CI = 0.2 to 2.0] for HIV / HBV, 1.4% [95% CI = 0.5 to 2.8] for HBV / Treponema pallidum, 1.8% [95% CI = 0.8 to 3.3] for HBV / HCV infection and for the triple infection 0.4% [95% CI = 0.5 to 1.4]. Average age of onset of illicit drug use was 15.4 years. The use of crack during lifetime was reported by 25.0% (136) of respondents. In prison, alcohol use was reported by 8.4% (45), tobacco by 62.0% (318), marijuana by 36.5% (194), 9.0% for cocaine (48), and crack by 11.7% (15), with the daily use of crack reported by 2.3% (3). Injected-drug use during lifetime was reported by 5.9% (32), but no use in the last six months was reported. Drug-related violence episodes reported were death threats 14.3% (28), 16.7% (57) assaults and 27.3% (3) suffered sexual assault. To 15.8% (30) of the respondents, crack use was associated with violence episodes. The use of crack-cocaine in association with other drugs was reported by 41.5% (54). CONCLUSION: The prevalence found in the confined population is still larger than those observed in the general population. Drug use and unprotected sexual practices were maintained during the period of confinement. The confinement time proved to be an important factor in the analysis of risk of infection. The identified risk factors appear to be important indicators for developing strategies to control these infections in the prison environment.
12

Estudo dos fatores de risco associados às infecções pelo HIV, hepatite B e C e sífilis e suas prevalências em população carcerária de São Paulo / Study of prevalence and risk factors associated with hiv infection, hepatitis B and C and syphilis in a prison population of Sao Paulo State

Ilham El Maerrawi 20 December 2012 (has links)
INTRODUÇÃO: Infecções pelo HIV, HBV, HCV e Treponema pallidum encontram no sistema prisional um ambiente favorável para suas propagações e representam grave problema de saúde pública. Neste estudo buscamos conhecer o perfil epidemiológico dos reeducandos de uma unidade prisional e a dinâmica do seu comportamento associado às infecções estudadas. Foram medidas as prevalências dessas infecções e suas coinfecções, investigados os potenciais fatores de risco, assim como medido o padrão de uso de drogas no presídio com ênfase no crack. MÉTODOS: Estudo epidemiológico transversal realizado de fevereiro a dezembro de 2007, na Penitenciária I de São Vicente. Realizada uma análise descritiva utilizando medidas de frequência, médias e desvio padrão. Foram considerados apenas os diagnósticos sorológicos para definição das infecções. Utilizado o OR (odds ratio) como medida de associação com nível de significância de 5% (?). Utilizada a regressão logística para estimar OR ajustado por algumas variáveis. RESULTADOS: Participaram das entrevistas 546 (84,1%) reeducandos e 514 (94,1%) realizaram as sorologias. Apresentaram um perfil jovem com idade média de 29,8 anos. 52,0% (283) referiram relacionamento conjugal com média de dois filhos. Declararam ser de cor parda 51,5% (280). O tempo médio de prisão foi de 10,5 anos. As prevalências identificadas foram: HIV 1,8% [IC95% = 0,1- 3,3], HBV 21,0% [IC95% = 17,8-25,1], HCV 5,3% [IC95% = 3,5-7,6], e 5,3% [IC95% =3,5-7,6] para a infecção pelo Treponema pallidum. Os fatores de risco associados com a infecção pelo HIV foram: uso de droga injetável (OR=15,38), > 30 anos (OR=13,3), uso de cocaína na vida (OR= 5,36) e uso de crack na vida (OR= 5,21). Nas análises multivariadas as variáveis que se mantiveram associadas com o HBV foram: uso de droga injetável (OR=3,36), ter referido DST (OR= 2,28), > de 30 anos (OR=1,86) e mais de cinco anos de prisão (OR= 2,17); com o HCV foram: uso de droga injetável (OR=9,65), uso de maconha na prisão (OR=2,91) e idade >30 anos (OR=8,41); com o Treponema pallidum foram: relação homossexual (OR=11,92) e ter referido sífilis (OR=10,88). As prevalências das coinfecções foram: 0,8% [IC95%= 0,2-2,0] para HIV/HBV, 1,4% [IC95%=0,5-2,8], para HBV/Treponema pallidum, 1,8% [IC95%= 0,8-3,3] para HBV/HCV, e para a tripla infecção 0,4% [IC95%= 0,5-1,4]. Confirmaram o uso de crack na vida 25,0% (136) dos entrevistados. Idade média de início de uso de drogas ilícitas foi de 15,4 anos. Na prisão, o uso de álcool foi relatado por 8,4% (45), tabaco por 62,0% (318), maconha por 36,5 % (194), cocaína por 9,0% (48), e crack por 11,7% (15), sendo seu uso diário referido por 2,3% (3). Uso de drogas injetáveis na vida foi referido por 5,9% (32) e nenhum uso nos últimos seis meses. As situações de violência relacionadas com drogas para 14,3% (28) foram de ameaças de morte, 16,7% (57) agressões físicas e 27,3% (3) sofreram agressão sexual. Para 15,8% (30) o crack esteve relacionado com estas situações. O seu uso com outras drogas foi referido por 41,5% (54). CONCLUSÃO: As prevalências encontradas na população confinada continuam maiores que as observadas na população geral. O consumo de drogas e praticas sexuais desprotegidas foram mantidas no período de confinamento. O tempo de confinamento mostrou-se fator importante na análise de risco. Os fatores de riscos identificados aparecem como importantes indicadores para a estruturação de estratégias de controle dessas infecções junto à população confinada. / INTRODUCTION: Infection by HIV, HBV, HCV and Treponema pallidum are common in the prison system due to an environment favorable to their propagation and represent a serious public health problem. This study aims to understand the epidemiological profile of the inmates in a prison unit and the behaviors associated with the infectious diseases studied. We estimated the prevalence of these infections and their co-infections, investigated potential risk factors, as well as identified the pattern of drug use in prison, especially crack use. METHODS: A cross-sectional epidemiological study conducted from February to December 2007 at the São Vicente Penitentiary . A descriptive analysis using frequency measures, means and standard deviations was conducted. We considered only the setting for serological diagnosis of infections. Odds ratio (OR) with a significance level of 5% (?) was used as a measure of association and a logistic regression was applied to estimate adjusted OR for some variables. RESULTS: A total of 546 prisoners were interviewed (84.1%). Of these, 514 (94.1%) underwent serological analysis. Results showed a profile of young men with an average age of 29.8 years. Fifty-two percent (283) reported marital relationship with an average of two children, and 51.5% (280) reported being of mixed ethnicity. The average time of arrest was 10.5 years. The prevalences were identified: HIV 1.8% [95% CI = 0.1 - 3.3], HBV 21.0% [95% CI 17.8 to 25.1], HCV 5.3% [95% CI = 3.5 to 7.6] and 5.3% [95% CI = 3.5 to 7.6] for infection with Treponema pallidum. The risk factors associated with HIV infection were injected-drug use (OR = 15.38), > 30 years (OR = 13.3), cocaine use (OR = 5.36) and use of crack during lifetime (OR = 5.21). According to multivariate analyzes, variables associated with HBV were: injected-drug use (OR = 3.36), reported any STD (OR = 2.28), > 30 years (OR = 1.86) and more than five years in prison (OR = 2.17); the variables associated with HCV were: injected-drug use (OR = 9.65), marijuana use in prison (OR = 2.91) and age> 30 years (OR = 8.41); the variables associated with Treponema pallidum were: homosexual intercourse (OR = 11.92) and have referred syphilis (OR = 10.88). The prevalence of co-infections were 0.8% [95% CI = 0.2 to 2.0] for HIV / HBV, 1.4% [95% CI = 0.5 to 2.8] for HBV / Treponema pallidum, 1.8% [95% CI = 0.8 to 3.3] for HBV / HCV infection and for the triple infection 0.4% [95% CI = 0.5 to 1.4]. Average age of onset of illicit drug use was 15.4 years. The use of crack during lifetime was reported by 25.0% (136) of respondents. In prison, alcohol use was reported by 8.4% (45), tobacco by 62.0% (318), marijuana by 36.5% (194), 9.0% for cocaine (48), and crack by 11.7% (15), with the daily use of crack reported by 2.3% (3). Injected-drug use during lifetime was reported by 5.9% (32), but no use in the last six months was reported. Drug-related violence episodes reported were death threats 14.3% (28), 16.7% (57) assaults and 27.3% (3) suffered sexual assault. To 15.8% (30) of the respondents, crack use was associated with violence episodes. The use of crack-cocaine in association with other drugs was reported by 41.5% (54). CONCLUSION: The prevalence found in the confined population is still larger than those observed in the general population. Drug use and unprotected sexual practices were maintained during the period of confinement. The confinement time proved to be an important factor in the analysis of risk of infection. The identified risk factors appear to be important indicators for developing strategies to control these infections in the prison environment.
13

Extension de la méthode SmEdA par la prise en compte des matériaux dissipatifs en moyennes fréquences / Extension of the SmEdA method by taking into account dissipative materials at medium frequencies

Hwang, HaDong 05 June 2015 (has links)
Le projet CLIC (City Lightweight Innovative Cab) dans lequel s’inscrit cette thèse de doctorat vise à développer une cabine de camion allégée sans dégrader les performances vibratoires et acoustiques. Pour cela il est nécessaire d’établir dans un premier temps un modèle de prédiction vibroacoustique du système couplé structure/espace intérieur incluant l’influence des matériaux dissipatifs (amortissement ou absorption) dans le domaine des moyennes fréquences. Les méthodes basées sur les éléments finis et les approches statistiques les plus couramment utilisées étant peu adaptées pour ce domaine de fréquence (coût de calcul important, méthodes peu flexibles), nous utiliserons le formalisme de la méthode SmEdA (Statistical modal Energy distribution Analysis). L’objectif principal de cette thèse de doctorat est dès lors, d’étendre cette méthode à la prise en compte de l’effet d’amortissement induit par des matériaux dissipatifs. La méthodologie se divise en trois étapes: 1. Les modèles équivalents des matériaux dissipatifs sont établis: (1) un modèle de plaque équivalent pour décrire la plaque amortie par un ou plusieurs patch(s) viscoélastique(s) et (2) un modèle de fluide équivalent pour décrire un matériau poreux agissant dans la cavité. 2. Chaque sous-système amorti est modélisé par éléments finis. Les méthodes MSE (Modal Strain Energy) et MSKE (Modal Strain Kinetic Energy) sont ensuite utilisées pour estimer les facteurs de perte modaux de chaque sous-système. 3. Le calcul SmEdA est effectué sur le système couplé en prenant en compte les facteurs de pertes modaux de chaque sous-système estimés dans la deuxième étape. Le point d’excitation est appliquée à la plaque, en supposant la force stationnaire et large bande. Afin de valider la méthodologie proposée un cas semi-complexe composé d’une plaque rectangulaire couplée à une cavité parallélépipédique est considéré. Ce système peut être utilisé pour étudier l’interaction vibroacoustique entre la structure de la cabine et l’intérieur de l’habitacle. Deux cas d’amortissement sont étudiés pour le système semi-complexe plaque-cavité: (1) un cas où la plaque est amortie avec un (ou plusieurs) patch(s) viscoélastique(s) et (2) un cas où un matériau poreux est placé dans la cavité. Le problème vibroacoustique est pour chaque cas modélisé suivant les trois étapes proposées et analyses dans le formalisme de la méthode SmEdA. Les résultats sont ensuite comparés au cas de référence (sans matériau dissipatif). La dernière partie de la thèse porte sur la validation expérimentale pour chaque cas test de la méthodologie numérique proposée. a mobilité d’éntrée, la puissance injectée et les énergies des sous-systèmes sont comparées aux prédictions numériques. Enfin les facteurs de pertes modaux des sous-systèmes estimés par les méthodes MSE et MSKE sont comparés aux résultats expérimentaux obtenus par la méthode d’analyse modale à haute résolution (méthode ESPRIT). / The project CLIC (City Lightweight Innovative Cab) aims to develop a lighter-weighted truck that maintains NVH performances of the initial design. This PhD research is then to establish a vibroacoustic prediction model of a complex structure-bounded fluid system (cabin structure coupled to cabin space) including dissipative treatments (damping or absorbing materials) for the mid-frequency domain. Since most commonly used element based and statistical methods are not suitable for this frequency domain, a proper prediction tool, which should be flexible in modeling capabilities and feasible in computational cost, must be implemented. The SmEdA (Statistical modal Energy distribution Analysis) method is considered in this thesis to comply with these requirements. The main objective of this research is to extend this method for taking account of the damping effect induced by dissipative materials. Development and validation of the methodology are carried out. 1. Dissipative materials are represented by simplified equivalent models: (1) the equivalent single layer model for describing the plate covered with a viscoelastic layer and (2) the equivalent fluid model for describing a porous material into the cavity. 2. Each subsystem including the equivalent models of the dissipative materials is modeled with FEM(Finite Element Model). The FE matrices including the energy dissipation are then computed. The MSE (Modal Strain Energy) and MSKE (Modal Strain Kinetic Energy) methods are used to estimate the modal damping loss factor of each subsystem mode. 3. The SmEdA calculation is performed on a whole system considering the modal damping loss factors estimated in the second step for each subsystem. The power is injected into the plate at a localized point by the stationary white noise force and subsequently, the SmEdA parameters are computed. To validate the proposed methodology, laboratory test cases of the structure-fluid problem composed of a rectangular plate coupled to a parallelepipedic cavity are considered. Such system can be used to study the vibroacoustic interaction between structure and fluid. Two damped test cases of the plate-cavity system are studied: (1) a system with a viscoelastic damping pad on the plate and (2) a system with a composite fibre in the cavity. The damped test cases are modeled following the three steps and are analyzed in the framework of SmEdA. The results are then compared to the original case with no damping treatment. The last part of the thesis presents an experimental validation of the numerical computation results on each test case. Measured quantities such as input mobility, injected power and subsystem energies are compared to the numerical predictions. The modal damping loss factors of the damped subsystems estimated with MSE and MSKE methods are compared to the experimental results estimated by a high-resolution modal analysis method (ESPRIT method).
14

Dissolved air and water in lubricants used in oil injected screw air compressors and the impacts of these in the compressor performance.

Berle, Axel Gunnar 23 September 2008 (has links)
Power dispersion within oil injected screw air compressors : The PhD-work shows the power dispersion within the oil- and air circuits of oil injected screw air compressors for the working pressures (Pd), where Pd has been tested for Pd ≤ 8,5 bar (a) and Pd ≤14,0 bar(a) respectively. The executed test runs with mineral oil have further confirmed the suppliers quoted performance data within stated tolerances. For comparison of the compressor performance with type of lubricant, the performance tests have been repeated with the four most common types of lubricants, which today are commercialised for screw air compressors. The selected lubricants hold the same cinematic viscosity (ISO VG 46), but the lubricants diverge in question of solubility of air and in formation of air bubbles during the compression cycle. These phenomenas confirm deviations in prevailing viscosity in the oil film and demonstrate that the performance data vary slightly with selected type of lubricant. The tests have proven that the air, which dissolve in the lubricant during the compression cycle will not degas during the resting period in the air/oil receiver, nor will the miniscule air bubbles degas due to their low ascending speed. This means that the content of dissolved air and air bubbles in the oil in the receiver becomes the most elevated within the system and where the temperature is the highest within the compressor cycle. Further is the resting period of the oil in the receiver extreme long in relation to the over all operating cycle of the oil. The conclusion is that the destruction (oxidation) of the oil is taking place in the oil/air receiver and nowhere else within the system. To counteract the oxidation and other destructive processes in the oil circuit « additives » are introduced in the oil. So are e.g. anti-oxide additives reducing the formation of peroxides and are by this reducing the oxidation velocity of the oil until the additives have been consumed. These additives are reducing the oxidation velocity of the lubricants, but will as well, due to the increased polarity caused by the additives, increase the content of dissolved water in the oil. However, this increased content of dissolved water is (strongly) reducing life of the roller bearings. The measured quantities of dissolved water in the lubricants (after the executed tests) have been compared with achieved bearing life from tests executed by others. The PhD work is finally summarizing that the only method to strongly reduce the destruction of the lubricant is to immediately separate off the oil from the compressed air at exit of the compressor. In addition, the today's « dumped » power in the oil cooler can be recovered to increase the available pneumatic power by some 25-30%. Assumingly, this increase in working temperature of the pneumatic air will, in addition increase the efficiency in applied pneumatic tools.
15

Technologie vstřikování zkušebních těles z termoplastů / Technology of injection molding of thermoplastic test specimens

Khamzin, Yersin January 2021 (has links)
The diploma thesis focuses on the optimization of technological parameters of plastic injection molding and the study of the influence of technological parameters on the quality of molded test specimens’ type 1A. The quality of molded parts for 3 types of polypropylene (PP) with different melt flow rate (Mosten GB 002, Mosten GB 218, Mosten MA 230) and 1 type of polystyrene (PS) (Krasten PS GP 154) was evaluated in terms of dimensional stability and weight. The contribution of software for modeling the plastic injection molding process was evaluated in this work. SOLIDWORKS Plastics software was used to optimize technological parameters. The construction of the bodies, mold and cooling system was constructed, and test bodies were produced on the basis of parameters obtained from the simulation of the injection molding process. Their quality parameters were compared with a 3D model and for each of the studied materials the optimal technological parameters were selected in terms of quality and the degree of influence of individual injection parameters on the quality of moldings was evaluated. The accordance of the results of the theoretical simulation with the real experiment was proved and a computational module independent of the optimized quality parameters, generally suitable for optimizing the quality parameters of the injected parts, was developed.
16

Dinàmica no lineal de sistemes làsers: potencials de Lyapunov i diagrames de bifurcacions

Mayol Serra, Catalina 04 March 2002 (has links)
En aquest treball s'ha estudiat la dinàmica dels làsers de classe A i de classe B en termes del potencial de Lyapunov. En el cas que s'injecti un senyal al làser o es modulin alguns dels paràmetres, apareix un comportament moltmés complex i s'estudia el conjunt de bifurcacions.1) Als làsers de classe A, la dinàmica determinista s'ha interpretat com el moviment damunt el potencial de Lyapunov. En la dinàmica estocàstica s'obté un flux sostingut per renou per a la fase del camp elèctric.2) Per als làsers de classe A amb senyal injectat, s'ha descrit el conjunt de bifurcacions complet i s'ha determinat el conjunt d'amplituds i freqüències en el quals el làser responajustant la seva freqüència a la del camp extern. 3) S'ha obtingut un potencial de Lyapunov pels làsers de classe B, només vàlid en el cas determinista, que inclou els termes de saturació de guany i d'emissió espontània.4) S'ha realitzat un estudi del conjunt de bifurcacions parcial al voltant del règim tipus II de la singularitat Hopf--sella--node en un làser de classe B amb senyal injectat.5) S'han identificat les respostes òptimes pels làsers de semiconductor sotmesos a modulació periòdica externa. S'han obtingut les corbes que donen la resposta màxima per cada tipus de resonància en el pla definit per l'amplitud relativa de modulació i la freqüència de modulació. / In this work we have studied the dynamics of both class A and class B lasers in terms of Lyapunov potentials. In the case of an injected signal or when some laser parameters are modulated, and more complex behaviour is expected, the bifurcation set is studied. The main results are the following:1) For class A lasers, the deterministic dynamics has been interpreted as a movement on the potential landscape. In the stochastic dynamics we have found a noise sustained flow for the phase of the electric field. 2) For class A lasers with an injected signal, we have been able to describe the whole bifurcation set of this system and to determine the set of amplitudes frequencies for which the laser responds adjusting its frequency to that of the external field. 3) In the case of class B lasers, we have obtained a Lyapunov potential only valid in the deterministic case, including spontaneous emission and gain saturation terms. The fixed point corresponding to the laser in the on state has been interpreted as a minimum in this potential. Relaxation to this minimum is reached through damped oscillations. 4) We have performed a study of the partial bifurcation set around the type II regime of the Hopf-saddle-node singularity in a class B laser with injected signal. 5) We have identified the optimal responses of a semiconductor laser subjected to an external periodic modulation. The lines that give a maximum response for each type of resonance are obtained in the plane defined by the relative amplitude modulation and frequency modulation.

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