• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 12
  • 5
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 34
  • 34
  • 30
  • 6
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 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.
31

Global and Local Buckling Analysis of Stiffened and Sandwich Panels Using Mechanics of Structure Genome

Ning Liu (6411908) 10 June 2019 (has links)
Mechanics of structure genome (MSG) is a unified homogenization theory that provides constitutive modeling of three-dimensional (3D) continua, beams and plates. In present work, the author extends the MSG to study the buckling of structures such as stiffened and sandwich panels. Such structures are usually slender or flat and easily buckle under compressive loads or bending moments which may result in catastrophic failure.<div><br><div>Buckling studies of stiffened and sandwich panels are found to be scattered. Most of the existed theories employ unnecessary assumptions or only apply to certain types of structures. There are few unified approaches that are capable of studying the buckling of different kinds of structures altogether. The main improvements of current approach compared with other methods in the literature are avoiding unnecessary assumptions, the capability of predicting all possible buckling modes including the global and local buckling modes, and the potential in studying the buckling of various types of structures.<br></div><div><br></div><div>For global buckling that features small local rotations, MSG mathematically decouples the 3D geometrical nonlinear problem into a linear constitutive modeling using structure genome (SG) and a geometrical nonlinear problem defined in a macroscopic structure. As a result, the original structures are simplified as macroscopic structures such as beams, plates or continua with effective properties, and the global buckling modes are predicted on macroscopic structures. For local buckling that features finite local rotations, Green strain is introduced into the MSG theory to achieve geometrically nonlinear constitutive modeling. Newton’s method is used to solve the nonlinear equilibrium equations for fluctuating functions. To find the bifurcated fluctuating functions, the fluctuating functions are then perturbed under the Bloch-periodic boundary conditions. The bifurcation is found when the tangent stiffness associated with the perturbed fluctuating functions becomes singular. Moreover, the arc-length method is introduced to solve the nonlinear equilibrium equations for post-local-buckling predictions because of its robustness. The imperfection is included in the form of geometrical imperfection by superimposing the scaled buckling modes in linear perturbation analysis on mesh.<br></div><div><br></div><div>Extensive validation case studies are carried out to assess the accuracy of the MSG theory in global buckling analysis and post-global-buckling analysis, and assess the accuracy of the extended MSG theory in local buckling and post-local-buckling analysis. Results using MSG theory and extended MSG theory in buckling analysis are compared with direct numerical solutions such as 3D FEA results and results in literature. Parametric studies are performed to reveal the relative influence of selective geometric parameters on buckling behaviors. The extended MSG theory is also compared with representative volume element (RVE) analysis with Bloch-periodic boundary conditions using commercial finite element packages such as Abaqus to assess the efficiency and accuracy of the present approach.<br></div></div>
32

"Manifestações psicopatológicas não-psicóticas em uma amostra da comunidade chinesa da cidade de São Paulo" / Non-psychotic psychopathologic manifestations in a sample of the Chinese community in the city of São Paulo

Wang, Yuan Pang 14 March 2003 (has links)
Introdução: Os transtornos mentais que ocorrem na comunidade e em culturas diversas são temas de grande interesse frente às constantes transformações sociais no mundo. A mudança do foco de pesquisa para os transtornos freqüentes na comunidade possibilitou aperfeiçoamentos metodológicos e desenvolvimento de instrumentos sensíveis para a sua detecção. A inclusão da variável cultural no estudo da psiquiatria, por sua vez, questiona o universalismo psicopatológico, a taxonomia ocidental e o diagnóstico de síndromes culturalmente específicas. Uma amostra desta visão psiquiátrica, ancorada na questão cultural e de transtornos da comunidade, são as pesquisas envolvendo neurastenia, um transtorno neurótico comum entre os chineses. O presente trabalho é um estudo observacional e transversal dos transtornos mentais comuns entre os indivíduos chineses da comunidade. Objetivo: Avaliar a psicopatologia não-psicótica dos chineses residentes na cidade de São Paulo, através de instrumentos padronizados. Material e Método: Os sujeitos da comunidade (n = 211), chineses e seus descendentes, preencheram um questionário de auto-avaliação e foram entrevistados por pesquisadores treinados. Os instrumentos utilizados foram: Chinese Health Questionnaire (CHQ-12), Escala de Sintomas Físicos, Escala de Eventos Vitais, Inventário de Depressão de Beck (BDI), Inventário de Ansiedade Traço-Estado (IDATE) e Schedule for Clinical Assessment in Neuropsychiatry (SCAN). Os dados foram analisados através de estatística descritiva, análise univariada (testes de qui-quadrado, Fisher e t de Student), análise multivariada (regressão logística), análise da curva ROC, análise fatorial exploratória (CHQ-12) e análise de correlação. Resultados: A probabilidade dos indivíduos pontuar alto no CHQ-12 ou ser casos prováveis de transtornos mentais comuns associou ao fato de ser do sexo feminino (OR = 2,31; IC95%: 1,12–4,75) e fluentes em chinês mandarim (OR = 3,37; IC95%: 1,68–6,78). Além disso, aqueles sujeitos com queixas físicas (OR = 4,20; IC95%: 1,70–10,40), relato de eventos-vitais no último ano (OR = 4,91; IC95%: 1,51–16,00) e pontuação alta no BDI (OR = 1,29; IC95%: 1,20–1,41) também tiveram maior chance de apresentar transtornos. O coeficiente de consistência interna &#61537; de Cronbach do CHQ-12 foi de 0,71 e a correlação item-total variou de 0,25 a 0,55, mostrando boa fidedignidade e homogeneidade deste instrumento. Adotando SCAN como critério-padrão, o melhor ponto de corte de CHQ-12 foi 2/3. Os seguintes indicadores de validade foram calculados a partir deste critério: sensibilidade 75%, especificidade 71%, valor preditivo positivo 55%, valor preditivo negativo 86% e taxa de classificação incorreta 28%. A curva ROC foi utilizada para avaliar a capacidade discriminante do instrumento, tendo uma área sob a curva de 0,728. O questionário CHQ-12 também se correlacionou significativamente com Escala de Sintomas Físicos (p < 0,005), Escala de Eventos Vitais (p < 0,005), BDI (p < 0,0005) e IDATE (p < 0,05). Na análise fatorial exploratória, três dimensões psicopatológicas explicaram 47,8% da variância total do CHQ-12. O conteúdo sintomatológico avaliado por este instrumento pode ser descrito como tridimensional, contendo fator somático, depressivo e de preocupação. As entrevistas do SCAN (n = 25) geraram diagnósticos de distimia, depressão e insônia não orgânica (CID-10). Os item-grupos “mau funcionamento subjetivo" (p < 0,005) e “características especiais de depressão" (p < 0,005) predominaram no perfil sintomatológico dos casos positivos de SCAN. Conclusão: Os transtornos mentais comuns predominantes na comunidade chinesa de São Paulo são os transtornos neuróticos, muito sugestivos de neurastenia. Os sujeitos chineses da comunidade apresentam uma psicopatologia própria, semelhante àquela dos indivíduos do seu país de origem. O CHQ-12 é um instrumento de rastreamento culturalmente sensível, que apresenta evidências de confiabilidade e validade para ser aplicado em outras populações de chineses. / Introduction: Community and culturally specific mental disorders have attracted much interest lately as a consequence of the constant social changes in the world. The shift of research focus to community-specific disorders has permitted methodological improvements and the development of tools for their detection. The inclusion of the cultural variable in the study of psychiatry questions psychopathological universality, Western taxonomy, and the diagnosis of culturally specific syndromes. The research of neurasthenia, a common neurotic disorder among the Chinese, is an example of the psychiatric approach based on cultural issues and on community disorders. This is an observational and transversal study of the common mental disorders among Chinese individuals in the community. Objective: to assess the non-psychotic psychopathology of the Chinese who live in the city of São Paulo, using standardized instruments. Materials and Methods: Individuals of the community (n = 211), Chinese and their descendants, filled out a self-evaluation questionnaire and were interviewed by trained researchers. The instruments used were: Chinese Health Questionnaire (CHQ-12), Physical Symptom Scale, Life Event Scale, Beck Depression Inventory (BDI), Trait-State Anxiety Inventory (STAI), and Schedule for Clinical Assessment in Neuropsychiatry (SCAN). The data were analyzed with descriptive statistics, univariate analysis (chi-square, Fisher and Student’s t tests), multivariate analysis (logistic regression), ROC curve analysis, exploratory factor analysis (CHQ-12), and correlation analysis. Results: The likelihood of an individual scoring high in CHQ-12 or having a probable common mental disorder is associated to the fact of being female (OR = 2.31; 95% CI: 1.12–4.75) and fluent in Mandarin Chinese (OR = 3.37; 95% CI: 1.68–6.78). Moreover, those with physical complaints (OR = 4.20; 95% CI: 1.70–10.40), reporting life events in the previous year (OR = 4.91; 95% CI: 1.51–16.00) and scoring high in BDI (OR = 1.29; 95% CI: 1.20–1.41) also had a greater likelihood of presenting disorders. CHQ-12’s Cronbach’s &#61537; coefficient of internal consistency was 0.71 and the item-total correlation ranged from 0.25 to 0.55, showing that this instrument is reliable and homogeneous. Using SCAN as a standard criterion, the best cut-off point for CHQ-12 was 2/3. The other validity indicators were calculated based on that criterion: sensitivity 75%, specificity 71%, positive predictive value 55%, negative predictive value 86%, and misclassification rate 28%. ROC curve was used to evaluate the discriminating capacity of the instrument, having an area under the curve of 0.728. CHQ-12 questionnaire also correlated significantly with the Physical Symptom Scale (p < 0.005), Life Event Scale (p < 0.005), BDI (p < 0.0005), and STAI (p < 0.05). In the exploratory factor analysis, three psychopathologic dimensions explained 47.8% of the total variance of CHQ-12. The symptomatological content evaluated by this instrument may be described as three-dimensional, including somatic, depressive and preoccupation factors. SCAN interviews (n = 25) led to diagnoses of dysthymia, depression and non-organic insomnia (ICD-10). The item-groups “poor subjective functioning" (p < 0.005) and “special features of depression" (p < 0.005) prevailed on the symptomatological profile of SCAN-positive cases. Conclusion: the most common mental disorders in São Paulo’s Chinese community are the neurasthenia-like neurotic disorders. The individuals of the Chinese community presented a unique psychopathology, resembling that of their country of origin. CHQ-12 is a culturally sensitive screening instrument, which seems to be reliable and valid enough to be used in other Chinese populations.
33

"Manifestações psicopatológicas não-psicóticas em uma amostra da comunidade chinesa da cidade de São Paulo" / Non-psychotic psychopathologic manifestations in a sample of the Chinese community in the city of São Paulo

Yuan Pang Wang 14 March 2003 (has links)
Introdução: Os transtornos mentais que ocorrem na comunidade e em culturas diversas são temas de grande interesse frente às constantes transformações sociais no mundo. A mudança do foco de pesquisa para os transtornos freqüentes na comunidade possibilitou aperfeiçoamentos metodológicos e desenvolvimento de instrumentos sensíveis para a sua detecção. A inclusão da variável cultural no estudo da psiquiatria, por sua vez, questiona o universalismo psicopatológico, a taxonomia ocidental e o diagnóstico de síndromes culturalmente específicas. Uma amostra desta visão psiquiátrica, ancorada na questão cultural e de transtornos da comunidade, são as pesquisas envolvendo neurastenia, um transtorno neurótico comum entre os chineses. O presente trabalho é um estudo observacional e transversal dos transtornos mentais comuns entre os indivíduos chineses da comunidade. Objetivo: Avaliar a psicopatologia não-psicótica dos chineses residentes na cidade de São Paulo, através de instrumentos padronizados. Material e Método: Os sujeitos da comunidade (n = 211), chineses e seus descendentes, preencheram um questionário de auto-avaliação e foram entrevistados por pesquisadores treinados. Os instrumentos utilizados foram: Chinese Health Questionnaire (CHQ-12), Escala de Sintomas Físicos, Escala de Eventos Vitais, Inventário de Depressão de Beck (BDI), Inventário de Ansiedade Traço-Estado (IDATE) e Schedule for Clinical Assessment in Neuropsychiatry (SCAN). Os dados foram analisados através de estatística descritiva, análise univariada (testes de qui-quadrado, Fisher e t de Student), análise multivariada (regressão logística), análise da curva ROC, análise fatorial exploratória (CHQ-12) e análise de correlação. Resultados: A probabilidade dos indivíduos pontuar alto no CHQ-12 ou ser casos prováveis de transtornos mentais comuns associou ao fato de ser do sexo feminino (OR = 2,31; IC95%: 1,12–4,75) e fluentes em chinês mandarim (OR = 3,37; IC95%: 1,68–6,78). Além disso, aqueles sujeitos com queixas físicas (OR = 4,20; IC95%: 1,70–10,40), relato de eventos-vitais no último ano (OR = 4,91; IC95%: 1,51–16,00) e pontuação alta no BDI (OR = 1,29; IC95%: 1,20–1,41) também tiveram maior chance de apresentar transtornos. O coeficiente de consistência interna &#61537; de Cronbach do CHQ-12 foi de 0,71 e a correlação item-total variou de 0,25 a 0,55, mostrando boa fidedignidade e homogeneidade deste instrumento. Adotando SCAN como critério-padrão, o melhor ponto de corte de CHQ-12 foi 2/3. Os seguintes indicadores de validade foram calculados a partir deste critério: sensibilidade 75%, especificidade 71%, valor preditivo positivo 55%, valor preditivo negativo 86% e taxa de classificação incorreta 28%. A curva ROC foi utilizada para avaliar a capacidade discriminante do instrumento, tendo uma área sob a curva de 0,728. O questionário CHQ-12 também se correlacionou significativamente com Escala de Sintomas Físicos (p < 0,005), Escala de Eventos Vitais (p < 0,005), BDI (p < 0,0005) e IDATE (p < 0,05). Na análise fatorial exploratória, três dimensões psicopatológicas explicaram 47,8% da variância total do CHQ-12. O conteúdo sintomatológico avaliado por este instrumento pode ser descrito como tridimensional, contendo fator somático, depressivo e de preocupação. As entrevistas do SCAN (n = 25) geraram diagnósticos de distimia, depressão e insônia não orgânica (CID-10). Os item-grupos “mau funcionamento subjetivo” (p < 0,005) e “características especiais de depressão” (p < 0,005) predominaram no perfil sintomatológico dos casos positivos de SCAN. Conclusão: Os transtornos mentais comuns predominantes na comunidade chinesa de São Paulo são os transtornos neuróticos, muito sugestivos de neurastenia. Os sujeitos chineses da comunidade apresentam uma psicopatologia própria, semelhante àquela dos indivíduos do seu país de origem. O CHQ-12 é um instrumento de rastreamento culturalmente sensível, que apresenta evidências de confiabilidade e validade para ser aplicado em outras populações de chineses. / Introduction: Community and culturally specific mental disorders have attracted much interest lately as a consequence of the constant social changes in the world. The shift of research focus to community-specific disorders has permitted methodological improvements and the development of tools for their detection. The inclusion of the cultural variable in the study of psychiatry questions psychopathological universality, Western taxonomy, and the diagnosis of culturally specific syndromes. The research of neurasthenia, a common neurotic disorder among the Chinese, is an example of the psychiatric approach based on cultural issues and on community disorders. This is an observational and transversal study of the common mental disorders among Chinese individuals in the community. Objective: to assess the non-psychotic psychopathology of the Chinese who live in the city of São Paulo, using standardized instruments. Materials and Methods: Individuals of the community (n = 211), Chinese and their descendants, filled out a self-evaluation questionnaire and were interviewed by trained researchers. The instruments used were: Chinese Health Questionnaire (CHQ-12), Physical Symptom Scale, Life Event Scale, Beck Depression Inventory (BDI), Trait-State Anxiety Inventory (STAI), and Schedule for Clinical Assessment in Neuropsychiatry (SCAN). The data were analyzed with descriptive statistics, univariate analysis (chi-square, Fisher and Student’s t tests), multivariate analysis (logistic regression), ROC curve analysis, exploratory factor analysis (CHQ-12), and correlation analysis. Results: The likelihood of an individual scoring high in CHQ-12 or having a probable common mental disorder is associated to the fact of being female (OR = 2.31; 95% CI: 1.12–4.75) and fluent in Mandarin Chinese (OR = 3.37; 95% CI: 1.68–6.78). Moreover, those with physical complaints (OR = 4.20; 95% CI: 1.70–10.40), reporting life events in the previous year (OR = 4.91; 95% CI: 1.51–16.00) and scoring high in BDI (OR = 1.29; 95% CI: 1.20–1.41) also had a greater likelihood of presenting disorders. CHQ-12’s Cronbach’s &#61537; coefficient of internal consistency was 0.71 and the item-total correlation ranged from 0.25 to 0.55, showing that this instrument is reliable and homogeneous. Using SCAN as a standard criterion, the best cut-off point for CHQ-12 was 2/3. The other validity indicators were calculated based on that criterion: sensitivity 75%, specificity 71%, positive predictive value 55%, negative predictive value 86%, and misclassification rate 28%. ROC curve was used to evaluate the discriminating capacity of the instrument, having an area under the curve of 0.728. CHQ-12 questionnaire also correlated significantly with the Physical Symptom Scale (p < 0.005), Life Event Scale (p < 0.005), BDI (p < 0.0005), and STAI (p < 0.05). In the exploratory factor analysis, three psychopathologic dimensions explained 47.8% of the total variance of CHQ-12. The symptomatological content evaluated by this instrument may be described as three-dimensional, including somatic, depressive and preoccupation factors. SCAN interviews (n = 25) led to diagnoses of dysthymia, depression and non-organic insomnia (ICD-10). The item-groups “poor subjective functioning” (p < 0.005) and “special features of depression” (p < 0.005) prevailed on the symptomatological profile of SCAN-positive cases. Conclusion: the most common mental disorders in São Paulo’s Chinese community are the neurasthenia-like neurotic disorders. The individuals of the Chinese community presented a unique psychopathology, resembling that of their country of origin. CHQ-12 is a culturally sensitive screening instrument, which seems to be reliable and valid enough to be used in other Chinese populations.
34

Improved Methods for Network Screening and Countermeasure Selection for Highway Improvements

Raihan, Md Asif 07 September 2018 (has links)
Network screening and countermeasure selection are two crucial steps in the highway improvement process. In network screening, potential improvement locations are ranked and prioritized based on a specific method with a set of criteria. The most common practice by transportation agencies has been to use a simple scoring method, which, in general, weighs and scores each criterion and then ranks the locations based on their relative overall scoring. The method does not deal well with criteria that are qualitative in nature, nor does it account for the impacts of correlation among the criteria. The introduction of Analytic Hierarchy Process (AHP) provides agencies with a method to include both quantitative and qualitative criteria. However, it does not address the issue on correlation. This dissertation explores the use of both Analytic Network Process (ANP) and Fuzzy Analytic Network Process (FANP) for their potential capabilities to address both issues. Using urban four-lane divided highways in Florida for bicycle safety improvements, both ANP and FANP were shown to provide more reasonable rankings than AHP, with FANP providing the best results among the methods. After the locations are ranked and prioritized for improvements, the next step is to evaluate the potential countermeasures for improvements at the selected top-ranked locations. In this step, the standard practice has been to use Crash Modification Factors (CMFs) to quantify the potential impacts from implementing specific countermeasures. In this research, CMFs for bicycle crashes on urban facilities in Florida were developed using the Generalized Linear Model approach with a Zero-Inflated Negative Binomial (ZINB) distribution. The CMFs were tested for their spatial and temporal transferability and the results show only limited transferability both spatially and temporally. The CMFs show that, in general, wider lanes, lower speed limits, and presence of vegetation in the median reduce bicycle crashes, while presence of sidewalk and sidewalk barrier increase bicycle crashes. The research further considered bicycle exposure using the bicycle activity data from the Strava smartphone application. It was found that increased bicycle activity reduces bicycle crash probabilities on segments but increases bicycle crash probabilities at signalized intersections. Also, presence of bus stops and use of permissive signal phasing at intersections were found to increase bicycle crash probabilities.

Page generated in 0.1291 seconds