The effects of AC and DC on cooling rate, solute distribution and nugget shape after solidification, which are responsible for microstructure of the fusion zone, during resistance spot welding are realistically and extensively investigated. The finite difference method is used to predict transport variables in workpieces and electrodes during heating, melting, cooling and freezing periods. The model accounts for electromagnetic force, heat generations at the electrode-workpiece interface and faying surface between workpieces, and dynamic electrical resistance including bulk resistance and contact resistances at the faying surface and electrode-wokpiece interfaces, which are function of hardness, temperature, electrode force, and surface condition. The computed results show that in contrast to DC, using AC readily produces the nugget in an ellipse shape. Deficit and excess of solute content occur in a thin layer around the boundary and interior of the nugget, respectively. The effects of dynamic electrical resistance subject to AC (Alternative current) on transport variables, cooling rate, solute distribution and nugget shape after solidification during resistance spot welding are realistically and extensively investigated. The model accounts for electromagnetic force, heat generation and contact resistances at the faying surface and electrode-workpiece interfaces and bulk resistance in workpieces. Contact resistance are comprised of constriction and film resistances, which are functions of hardness, temperature, electrode force and surface condition. The computed results show that the weld nugget readily occurs by increasing constriction resistance and Curie temperature. High Curie temperature enhances convection and solute mixing, and readily melts through the workpiece surface near the electrode edge. Aside from finding the significant effect of Curie temperature on resistance spot welding, this study indicates that any mean (For example, adjusting solute content) to reduce Curie temperature can be a new way to control weld quality.

Abstract Dynamic electrical resistance during resistance spot welding has been quantitatively modeled and analyzed in this work. A determination of dynamic resistance is necessary for predicting the transport processes and monitoring the weld quality during resistance spot welding. In this study, dynamic resistance is obtained by taking the sum of temperature dependent bulk resistance of the workpieces and contact resistances at the faying surface and electrode-workpiece interface within an effective area corresponding to the electrode tip where welding current primarily flows. A contact resistance is composed of constriction and film resistances, which are functions of hardness, temperature, electrode force, electrical resistivity and surface condition. Unsteady, axisymmetric transport of mass, momentum, energy, species, and magnetic field intensity with a mushy-zone phase change in workpieces and temperature, and magnetic fields in electrodes during resistance spot welding, are systematically investigated. Electromagnetic force, joule heat, heat generation at the electrode-workpiece interface and faying surface between workpieces, different properties between phase, and geometries of electrodes are taken into account. The predicted nugget thickness and dynamic resistance versus time show quite good agreement with available experimental data. Excluding expulsion, the dynamic resistance curve can be divided into four stages. A rapid decrease of dynamic resistance in stage 1 is attributed to decreases in film resistances at the faying surface and electrode-workpiece interface. In stage 2, the increase in dynamic resistance results from the primary increase of bulk resistance in the workpieces and an increase of the sum of contact resistances at the faying surface and electrode-workpiece interface. Dynamic resistance in stage 3 decreases, because increasing rate of bulk resistance in the workpieces and contact resistances decrease. In stage 4 decrease of dynamic resistance is mainly due to the formation of the molten nugget at the faying surface. The molten nugget is found to occur in stage 4 rather than stage 2 or 3 as qualitatively proposed in the literature. The effects of different parameters on the dynamic resistence curve are also presented. Besides, electromagnetic force effect on velocity field of molten nugget was proven to be crucial. Higher current, smaller magnetic diffusivity and decreasing the radius of electrode tip will lead to high current density around the corner between electrode and workpiece. Sometimes the corner of electrode and surface of workpieces will be melted due to local high current density.

Exercise-induced hypoalgesia (EIH) denotes the phenomenon wherein physical activity induces a diminished sensitivity to pain, holding significant implications for pain management modalities. This investigation sought to evaluate the reproducibility of pressure pain thresholds (PPT) subsequent to dynamic resistance exercise and juxtapose PPT measurements during periods of quiet rest against those immediately post-exercise. A cohort of five healthy participants underwent three separate sessions, wherein PPT assessments were conducted pre- and post-exercise. Findings revealed a nuanced reliability in PPT measures during EIH evaluation, necessitating judicious interpretation due to the constrained sample size. Comparative analyses with antecedent research underscored discernible disparities in exercise intensities and methodological approaches, accentuating the imperative of considering idiosyncratic responses and procedural distinctions. Despite inherent limitations, notably the modest sample size, this inquiry furnishes valuable insights into the intricacies of EIH assessment, elucidating the complexities inherent in advancing knowledge within the domain of pain modulation research. Prospective investigations with larger and more heterogeneous cohorts are imperative to fortify the dependability and generalizability of findings in this realm.

High Tc superconductors are enabling in the generation of extremely high magnetic fields. Flux pumping is a promising technology which can be used to operate HTS magnets without significant loss. In this decade, several HTS flux pumps based on travelling magnetic waves have been developed, yet their physics is still unclear. This thesis established a framework in the area of flux pumping for HTS coils. It revealed the underlying physics of existing travelling wave flux pumps, which is an important theoretical contribution. Based on the thorough understanding of flux pumping mechanism, the author proposed two novel types of flux pumps. The new inventions make flux pumping much easier, more controllable, and much less energy consuming. These flux pumps may promote the future applications of HTS magnets. This thesis can be a guidebook for researchers and engineers in developing flux pumps.

Sammanfattning: Bakgrund: Långvarig ospecifik ländryggssmärta medför stora problem och lidande på ett individuellt plan, men påverkar även samhället då det medför stora kostnader för sjukvården. Dynamisk styrketräning av rygg och bål är ett vanligt behandlingsalternativ. Under de senaste fem åren har det ej genomförts någon litteraturstudie som sammanställer denna träningens effekt på upplevd smärtintensitet. Därmed finns det ett kliniskt värde för fysioterapeuter att litteratur sammanställs.  Syfte: Syftet med denna litteraturstudie var att sammanställa, värdera och jämföra forskningsresultat av dynamisk styrketräning för bål och rygg som behandling för personer med långvarig ospecifik ländryggssmärta och dess effekt på upplevd smärta. Metod: En litteraturstudie genomfördes i databaserna PubMed och PEDro. Samtliga sökträffars titel och abstrakt granskades, studier med potential att möta inklusionskriterier granskades därefter i fulltext varefter relevanta studier slutgiltigen inkluderades. Studier kvalitetsgranskades enligt PEDro-scale och resultatets tillförlitlighet sammanvägdes med GRADEstud. Resultat: 12 RCT-studier identifierades och granskades. Kvalitetsgranskning visade att 9 studier höll hög kvalitet. Studier med hög kvalitet evidensgraderades enligt GRADEstud, där två subgrupperingar identifierades. Dynamisk träning håller en låg (++) tillförlitlighet avseende effekt på upplevd smärta. Resultaten varierade avseende effekt på smärta, utfall och studierna hade olika upplägg vilket har bidragit till att tillförlitligheten bedöms som låg.  Konklusion: Dynamisk styrketräning av rygg och bål tycks inte vara mer effektiv än annan träning för att minska upplevd smärta för personer med långvarig ospecifik ländryggssmärta. / Abstract: Background: Chronic non-specific low back pain causes major problems and suffering for individuals, but also affects society as it entails large costs for healthcare. Dynamic strength-training of the core is a common treatment. In the last five years, no literature study has been conducted. There is a clinical value for physiotherapists in compiling literature for this treatment method. Objective: The purpose of this literature study was to compile, evaluate and compare research results of dynamic strength training for the core as a treatment for people with long-term non-specific low back pain and its effect on perceived pain. Method: A literature study was conducted in the databases PubMed and PEDro. Title and abstract of all studies were examined, studies that met inclusion criteria were examined in full text, after which relevant studies were included.  Studies were quality reviewed according to PEDro-scale and the result reliability was weighed with GRADEstud. Results: 12-RCT studies were included. Quality review showed that 9 studies maintained a high level. High quality studies were graded with GRADEstud, two subgroups were identified. Dynamic strength-training maintains a low (++) reliability regarding the effect on perceived pain. The results varied regarding effect on perceived pain and the studies had different setups which contributed to the low reliability. Conclusion: Dynamic strength-training of the back and core does not seem to be more effective than other training to reduce perceived pain for persons with chronic non-specific low back pain.

Student Number : 9811923K - PhD thesis - School of Mechanical Engineering - Faculty of Engineering and the Built Environment / Methods are presented for obtaining models used for predicting welded sample resistance and effective weld current (RMS) for desired weld diameter (weld quality) in the resistance spot welding process. These models were used to design predictive controllers for the welding process. A suitable process model forms an important step in the development and design of process controllers for achieving good weld quality with good reproducibility. Effective current, dynamic resistance and applied electrode force are identified as important input parameters necessary to predict the output weld diameter. These input parameters are used for the process model and design of a predictive controller. A three parameter empirical model with dependent and independent variables was used for curve fitting the nonlinear halfwave dynamic resistance. The estimates of the parameters were used to develop charts for determining overall resistance of samples for any desired weld diameter. Estimating resistance for samples welded in the machines from which dataset obtained were used to plot the chart yielded accurate results. However using these charts to estimate sample resistance for new and unknown machines yielded high estimation error. To improve the prediction accuracy the same set of data generated from the model were used to train four different neural network types. These were the Generalised Feed Forward (GFF) neural network, Multilayer Perceptron (MLP) network, Radial Basis Function (RBF) and Recurrent neural network (RNN). Of the four network types trained, the MLP had the least mean square error for training and cross validation of 0.00037 and 0.00039 respectively with linear correlation coefficient in testing of 0.999 and maximum estimation error range from 0.1% to 3%. A prediction accuracy of about 97% to 99.9%. This model was selected for the design and implementation of the controller for predicting overall sample resistance. Using this predicted overall sample resistance, and applied electrode force, a second model was developed for predicting required effective weld current for any desired weld diameter. The prediction accuracy of this model was in the range of 94% to 99%. The neural network predictive controller was designed using the MLP neural network models. The controller outputs effective current for any desired weld diameter and is observed to track the desired output accurately with same prediction accuracy of the model used which was about 94% to 99%. The controller works by utilizing the neural network output embedded in Microsoft Excel as a digital link library and is able to generate outputs for given inputs on activating the process by the push of a command button.

A Reabilitação Cardíaca (RC) composta de exercícios puramente dinâmicos (EPD) tem sido fortemente recomendada para pacientes com doença arterial coronariana (DAC). Contudo, os exercícios resistidos devem ser incluídos como parte de um programa formal, uma vez que contribuem para promover ganhos nas atividades de vida diária e assim na qualidade de vida (QV). Estudos recentes têm mostrado que a magnitude das respostas metabólicas e autonômicas cardíacas durante o exercício resistido dinâmico (ERD) também está associada com a determinação do limiar de anaerobiose (LA), o qual é um importante parâmetro para determinar a intensidade no EPD. Diante disso, não há informações sobre essas respostas metabólicas e autonômicas no ERD, para pacientes com DAC. Adicionalmente, pouco é sabido acerca da avaliação da funcionalidade/incapacidade percebidos por estes pacientes já incluídos em programas formais de RC, podendo ampliar informações para a tomada de decisões neste processo. Portanto, este estudo propõe ampliar o corpo do conhecimento acerca de duas vertentes, sendo uma mais fisiológica e outra abordagem mais ampliada, contendo aspectos bio-psico-sociais, Objetivamos 1) Determinar o LA pela variabilidade da frequência cardíaca (VFC) durante um protocolo de ERD, numa população diagnosticada com DAC, participante de um programa de RC composto somente de EPD; e 2) Aplicar a CIF (Classificação Internacional de Funcionalidade, Incapacidade e Saúde), tendo como base a vinculação da mesma com a QV auto-percebida, com o propósito de investigar se o programa formal de RC pode produzir impacto nos desfechos multidemensionais de funcionalidade e incapacidade. Vinte pacientes (idade: 63±7 anos) com DAC (FEVE: 60±10%), apresentando boa capacidade funcional e bom prognóstico, realizaram um protocolo de ERD incremental no leg-press. O protocolo iniciava em 10% de l-RM (repetição maxima), com subsequêntes aumentos de 10% até a exaustão física. A variabilidade da frequência cardíaca (VFC), através dos indices lineares (rMSSD e RMSM) e não-lineares (SD1, SD2, SD1/SD2), bem como o lactato sanguíneo, foram determinados no repouso e durante o ERD. Funcionalidade e incapacidade do grupo foram avaliadas através da aplicação do Processo de Vinculação entre o SF-36 com a CIF. ANOVA para medidas repetidas, análise de Bland-Altman, coeficientes de correlação de Pearson e estatística descritiva foram empregados. Admitiu-se nível de significância de 95%. Foram encontradas significativas alterações na VFC e lactato sanguíneo a partir de 30% de 1-RM (p<0.05). Análise de Bland-Altman revelou boa concordância entre limiar de lactato (LL) e limiar de rMSSD (LrMSSD), e de SD1 (LSD1). As cargas relativas obtidas (a partir de 1-RM) no LL, LrMSSD e LSD1 não diferiram (29%±5; 28%±5; 29%±5, respectivamente). A vinculação entre o SF-36 e a CIF permitiu detalhar uma relação de \"Funções corporais\" e principalmente as \"Atividades e Participações\" acometidas pela doença, bem como o grau de problemas/prejuízo destas, mesmo após o programa de RC. Concluímos que o uso da VFC durante o ERD poderia ser um método não-invasivo viável na prática clínica para determinar o LA em pacientes com DAC, auxiliando na definição de parâmetros de intensidade de exercício seguros e apropriados. Além disso, a funcionalidade e incapacidade de pacientes coronariopatas, percebidos sob o seu próprio ponto de vista, poderiam ser avaliadas utilizando-se o SF-36 sob o escopo da CIF, adicionando informações complementares ao processo da RC. / Cardiac Rehabilitation (CR) composed of dynamics purely exercises (DPE) has been strongly recommended for patients with coronary artery disease (CAD). However, resistance training should be included as part of a formal program, since they contribute to promote gains in daily activities and thus the quality of life (QoL). Recent studies have shown that the magnitude of the cardiac, metabolic, and autonomic responses during dynamic resistance exercise (DRE) is associated with the determination of the anaerobic threshold (AT), which is an important parameter to determine the intensity during DPE. Therefore, there is no information about these metabolic and autonomic responses in resistance exercise for patients with CAD. In addition, little is known about the assessment of functioning/disability perceived by these patients already included in formal CR programs, which may extend information for decision-making in this processo Therefore, this study proposes to extend the body in the knowledge of two approaches, with a more physiological and other broader approach, containing bio-psycho-social aspects. We aimed to 1) Determine the A T by heart rate variability (HRV) during an DRE protocol in a population diagnosed with CAD who participated in a CR program with DPE only; and 2) Apply the ICF (International Classification of Functioning, Disability and Health), based on the binding of the same with self-perceived QoL (SF-36), in order to investigate whether the formal RC program may have an impact on multidemensionais outcomes of functionality and disability. Twenty men (age: 63±7 years old) with CAD (LVEF: 60±10%), with good functional capacity and good prognosis, underwent a DRE incremental protocol on leg press until maximal exertion. The protocol began at 10% of 1-RM (repetition maximum), with subsequent increases of 10% until maximal exhaustion. Heart rate variability (HRV) indices from Poincaré plots (SD1, SD2, SD1/ISD2) and time domain (rMSSD and RMSM), as well as blood lactate were determined at rest and during PRE. Functioning and disability were assessed by the linking process between the SF-36 and the ICF. ANOVA for repeated measures, Bland-Altman analysis, Pearson correlation coefficients, and descriptive statistics were used for statistical analysis. The significance level accepted was 95%. Significant alterations in HRV and blood lactate were observed from 30% of 1 RM (p<0.05). Bland- Altman analysis demonstrated a consistent agreement between blood lactate threshold (LT) and rMSSD threshold (rMSSDT) and LT with SD1 threshold (SD1T). Relative values of 1-RM in all LT, rMSSDT and SD1T did not differ (29% ± 5 vs 28% ± 5 vs 29% ± 5, respectively). Finally, the assessment of functioning and disability using the SF-36 and ICF, allowed to list in more detail the \"Body functions\" and especially the \"Activities and Participation\" affected by the disease, as well as the degree of problems/impairments of these aspects, even after the RC program. In conclusion, HRV during DRE could be a feasible noninvasive method in clinical settings to determine AT in CAD patients for planning safe and appropriaje exercise intensities during CR. Moreover, the functioning and disability of coronary patients, perceived under their own point of view, could be assessed using the SF-36 under the scope ofthe lCF, adding supplementary information to the CR process.

O ensaio de simples reconhecimento com o SPT é um dos mais utilizados para investigação do subsolo nos EUA e no Brasil. Os dados obtidos com este ensaio dinâmico, tais como o índice de resistência à penetração NSPT, classificação do solo e nível freático são usados por diferentes métodos para estimativa de capacidade de carga de fundações rasas e profundas. Para um mesmo solo, o índice NSPT pode ser diferente se diferentes equipamentos forem usados devido ao fato de que diferentes equipamentos de SPT mostram diferentes níveis de eficiência. Em vista disso, uma alternativa para estimar a eficiência do ensaio SPT é utilizando-se o ensaio de prova de carga estática sobre o amostrador. Este ensaio foi implementado para poder avaliar a eficiência do ensaio SPT. Para este fim, foram executados 13 ensaios dinâmicos e 13 ensaios estáticos no campus experimental do Laboratório de Engenharia Civil da UNESP (Bauru). Para estimar a eficiência do ensaio SPT através do ensaio dinâmico, um sistema de aquisição analógico-digital foi utilizado para obter registros de aceleração e força na seção localizada junto ao amostrador SPT. O ensaio dinâmico foi modificado para utilizar várias energias potenciais nominais do martelo e sistemas de elevação. A determinação da eficiência do ensaio através da execução da prova de carga estática foi obtida com base no princípio de Hamilton. Adicionalmente, realizando-se a comparação entre o comportamento de carregamento dinâmico e estático, pode-se obter a resistência estática do sistema amostrador-solo. Esta resistência é calculada utilizando a base de dados obtidas no campo e a aplicação de vários métodos de estimativa como: Aoki et al.(2007), De Souza (2009) e Odebrecht (2003). Os resultados da estimativa da eficiência através do ensaio de prova de carga estática sobre o amostrador mostraram-se consistentes em relação aos valores obtidos com o ensaio dinâmico. Concluiu-se que a execução do ensaio de prova de carga estática sobre, o amostrador é uma alternativa simples e econômica para obter a eficiência do SPT. / The Standard Penetration Test, SPT, is one of the most used one for subsoil information in the USA and Brazil. The data obtained in this dynamic test, such as the penetration resistance index, NSPT, the soil classification and phreatic level are used by different methods to estimate the shallow and deep foundations load capacity. For the same soil, the index NSPT can be different if different equipments are used, because different SPT equipments show different efficiency levels. Having this in mind, an alternative to estimate the essay efficiency of the SPT test is using the static load test (SLT) to the sampler. This test was implemented in order to evaluate the efficiency of SPT. To do so, 13 dynamic tests and 13 static tests were performed in the experimental campus of the State University of São Paulo at Bauru (Unesp- Bauru-Brazil). To estimate the efficiency of the SPT test through the dynamic test, a data acquisition system was used to register accelerations and forces at the located section close to the sampler SPT. The dynamic test was modified so that it would be possible to use many nominal potential energy of the hammer and elevation systems. The estimation of the efficiency made through the SLT tests was based on Hamilton\'s principle. Furthermore, by comparing the dynamic and static behavior, we can get the soil-sampler interface static resistance. This resistance is calculated by using the field data through various estimation methods such as Aoki\'s (2007), De Souza\'s (2009) and Odebrecht\'s (2003). The estimates of the efficiency obtained through SLT test were found to be consistent with those obtained through the SPT modified tests. We conclude that SLT is a simple and non-expensive alternative to obtain the efficiency of SPT equipment.

A crescente exigência do setor automotivo por maior produtividade com redução de custos, aliada aos novos materiais que compõe as carrocerias e seus revestimentos, levou ao estudo da correlação da resistência dinâmica, força de expansão térmica e indentação, com a formação do ponto de solda, a fim de qualificar e controlar a soldagem por resistência a ponto. Para o estudo ter validade prática a qualificação da solda, os parâmetros de soldagem e corpos de prova foram definidos conforme norma AWS-SAE D8-9M 2002. Os corpos de prova para os ensaios foram retirados das chapas que compõe uma carroceria veicular. O cabeçote de soldagem foi projetado e construído seguindo os padrões de máquinas industriais. Os instrumentos de medição foram desenvolvidos especificamente para atender as condições industriais da soldagem por resistência. Os ensaios simularam as variações de parâmetros e produção dos pontos de solda conforme ocorre na indústria automobilística. As análises foram realizadas através da comparação gráfica e matemática do comportamento das grandezas medidas com a qualificação dimensional do ponto. A correlação, apresentada, distingue chapas de espessuras diferentes, materiais de revestimento, variação de parâmetros, erros de posicionamento (ponto torto), expulsão de material (flash), variações na formação do ponto (undersize) e o mais importante, desgaste dos eletrodos. Esta correlação permite criar um sistema de qualificação e controle do ponto de solda. / The growing demand from the automotive sector for greater productivity, reduced costs, combined with new materials that make up their bodies and coats, led to the study of the correlation of the dynamic resistance, thermal force expansion and indentation, with the formation of the spot weld, in order to qualify and control the resistance spot welding. For the study to be valid practicing the qualification of spot weld, welding parameters and specimens were define according AWS - 9M SAE D8 2002 standard. The specimens for testing were removed from the sheets that make up a vehicle body. The welding head was designed and built according the standards of industrial machinery. Measuring instruments were developed specifically to meet the conditions of industrial resistance welding. The tests simulated the variations of parameters and production of welding spots as occurs in automotive industry. The analyzes were performed through the graphical comparison and mathematical behavior of measured quantities with dimensional spot qualification. The correlation presented distinguishes sheets of different thicknesses, coating materials, variation of parameters, positioning errors (crooked point), expulsion of material (flash), variations in spot formation (undersize) and most important, wear of the electrodes. This correlation allows to create a system of qualification and control of the spot welding.

A crescente exigência do setor automotivo por maior produtividade com redução de custos, aliada aos novos materiais que compõe as carrocerias e seus revestimentos, levou ao estudo da correlação da resistência dinâmica, força de expansão térmica e indentação, com a formação do ponto de solda, a fim de qualificar e controlar a soldagem por resistência a ponto. Para o estudo ter validade prática a qualificação da solda, os parâmetros de soldagem e corpos de prova foram definidos conforme norma AWS-SAE D8-9M 2002. Os corpos de prova para os ensaios foram retirados das chapas que compõe uma carroceria veicular. O cabeçote de soldagem foi projetado e construído seguindo os padrões de máquinas industriais. Os instrumentos de medição foram desenvolvidos especificamente para atender as condições industriais da soldagem por resistência. Os ensaios simularam as variações de parâmetros e produção dos pontos de solda conforme ocorre na indústria automobilística. As análises foram realizadas através da comparação gráfica e matemática do comportamento das grandezas medidas com a qualificação dimensional do ponto. A correlação, apresentada, distingue chapas de espessuras diferentes, materiais de revestimento, variação de parâmetros, erros de posicionamento (ponto torto), expulsão de material (flash), variações na formação do ponto (undersize) e o mais importante, desgaste dos eletrodos. Esta correlação permite criar um sistema de qualificação e controle do ponto de solda. / The growing demand from the automotive sector for greater productivity, reduced costs, combined with new materials that make up their bodies and coats, led to the study of the correlation of the dynamic resistance, thermal force expansion and indentation, with the formation of the spot weld, in order to qualify and control the resistance spot welding. For the study to be valid practicing the qualification of spot weld, welding parameters and specimens were define according AWS - 9M SAE D8 2002 standard. The specimens for testing were removed from the sheets that make up a vehicle body. The welding head was designed and built according the standards of industrial machinery. Measuring instruments were developed specifically to meet the conditions of industrial resistance welding. The tests simulated the variations of parameters and production of welding spots as occurs in automotive industry. The analyzes were performed through the graphical comparison and mathematical behavior of measured quantities with dimensional spot qualification. The correlation presented distinguishes sheets of different thicknesses, coating materials, variation of parameters, positioning errors (crooked point), expulsion of material (flash), variations in spot formation (undersize) and most important, wear of the electrodes. This correlation allows to create a system of qualification and control of the spot welding.