Modeling of the elastic mechanical behavior of thin compliant joints under load for highest-precision applications

For the most demanding measurement tasks in force metrology flexure hinges in compliant mechanisms represent a key component. To enhance the mechanical properties of devices like weighing cells, the ability of precise modeling of flexure hinges is essential. The present scientific work focuses on the modeling of the mechanical behavior of a single flexure hinge subjected to geometric deviations and non-ideal loading conditions as those encountered in weighing cells. The considered hinge has a semi-circular contour and a large width compared to its minimum notch height. This geometry is modeled using the finite element method. Requirements for a trustworthy and efficient computation are elaborated under the consideration of geometric deviations for later parametric studies. Analytical expressions found in the literature are compared to numerical results to prove the validity of their assumptions for thin hinges. The model is used for studying the deviation of the stiffness in non-ideal flexure hinges. Sources of deviation are identified and described by parameters. The range of values for each parameter is chosen on the basis of available manufacturing technology. Influential parameters are identified through a sensitivity analysis. The effect of loading conditions is studied in the context of the application in weighing cells. For the enhancement of the overall sensitivity, the stiffness of the flexure hinges can be reduced. One option, the alteration of the geometry by adding a flexure strip in the center of the semi-circular flexure hinge is studied in comparison to existing analytical equations. The effects of ground tilts for a single loaded flexure hinge are investigated as a foundation for future modeling of a tilt insensitive state of a weighing cell mechanism (autostatic state). By adjusting the vertical position of the center of mass of the lever, the tilt sensitivity can be reduced to zero. An approach to find the position for this state is presented considering the numerical limitations of finite element modeling. Using this approach, the variation of the sought position is evaluated for different values of the design parameters.Tesi

Feasibility of near infrared spectroscopy in stroke patients

Introduction Stroke is the main cause of death in Portugal. It is a severe pathology with a sudden onset and with a very high demand in both time and money from the families of the affected patients and from health organizations and social services. Inexpensive and practical diagnostic tools that will assist in early detection and treatment are the source of numerous studies. The physiology behind a stroke is a sudden ischemic event in the brain. Near infrared spectroscopy (NIRS) is a non-invasive mean of measuring cerebral perfusion in real time. Due to its rapid and recent development few data exists about its applicability. Since NIRS detects oxygen levels that are supposedly low due to oligemia in infarcted areas, our study tried to ascertain the significance of NIRS measurements in stroke patients. Objectives -Determine which systemic factors influence rSO2 values. -Determine NIRS viability in diagnosing and monitoring stroke patients by comparing their values with those of healthy individuals using the reference value of 60 rSO2. -Determine if NIRS is capable of influencing therapeutical changes in those monitored. Methodology This is a prospective study where we used NIRS EQUANOX® technology with 4 sensors: 2 Frontal 2 supra-auricular to compare cerebral oxygen values of rSO2 in a control sample of 60 healthy persons from two retirement homes from the geographical area of Covilhã, Portugal and compared them with 128 stroke patients hospitalized in the Centro Hospitalar Cova da Beira (CHCB). We also collected data consisting of: risk factors, imagiological studies and vital signs. The hospitalized patients were monitored twice on the first day and then once daily during the following four consecutive days for a total of five days. The results were analyzed using SPSS ® software - version 17 for Windows ® and were considered significant at p < 0.05. We resorted to the tests of independence Chi-square and Mann Whitney U to analyze the relationships between variables. Results Our study revealed that the hospitalized stroke patients had higher rSO2 values than healthy individuals from retirement homes, and that these higher values decreased along the week they were hospitalized. We also found that the lesion side diagnosed by CT scan had higher rSO2 values than the contralateral healthy side. We did not find any association between: stroke risk factors and rSO2 readings, use of thrombolysis and rSO2 measurements, the imagiological exams and rSO2 readings (CT, TU and CU) and no association between age or gender with rSO2 levels

How earnings announcement impact Faang stock prices?

Beginning in the late '30s, stock market event studies intend to provide more information about market movements and behavior, around the major events during the year, allowing market players to make better and more sustained investment decisions. This paper analyzes how the FAANG stocks behave when quarterly earnings announcement results are reported. To answer this question, we compare the performance of 7 different announcements for each firm, by the calculation of the abnormal returns, using 3 different normal models with 2 different extensions, and test the statistical robustness with 4 different statistical tests. Our results showed different price reactions around events, but consistent high abnormal returns on an individual event and period analysis on the day after the announcement. Results also revealed that on a multi-period analysis, the stocks are not consistently positive or negative, leading to symmetric high abnormal returns and a low percentage of abnormal performance. At the same time, on a multi-event analysis, results, by type of news, show significant under and overreactions on the stock market price movements. However, the efficient market hypothesis is not consistent when the news, resulting from the announcement, incorporate the stock price. From a safety perspective, this study emphasizes on the necessity to consider the impact of quarterly earnings announcement reports, on FAANG stock prices, and consequently on market players’ investment decisions.Com início no final dos anos 30, os estudos sobre eventos nos mercados de capitais surgem com o intuito de proporcionar mais informação sobre os movimentos e o comportamento do mercado, em torno dos maiores eventos anuais, permitindo aos players de mercado tomar decisões de investimento mais sustentadas. Esta tese analisa como é que as ações FAANG reagem, quando é anunciado o relatório dos resultados trimestrais das empresas. Para conduzir a análise, iremos comparar a performance de 7 anúncios, diferentes para cada empresa, através do cálculo dos abnormal returns, utilizando 3 modelos normais com 2 extensões diferentes, e testar a robustez estatística através de 4 testes. Os resultados demonstram diferentes reações dos preços em torno dos eventos. Mais precisamente, abnormal returns elevados e consistentes, no dia após o anúncio, numa análise individual. Os resultados também revelaram que, numa análise de vários períodos, as ações não apresentam consistência positiva ou negativa, levando a abnormal returns simétricos e uma percentagem reduzida de abnormal performance. Ao mesmo tempo, numa análise multi-eventos, os resultados, de acordo com o tipo de notícias, são significativamente baixos e demonstram reações exageradas nos movimentos de preço no mercado acionista. No entanto, a Hipótese de Mercado Eficiente não é consistente quando as notícias relacionadas com os anúncios trimestrais incorporam o preço da ação. De forma geral, o estudo enfatiza a necessidade de considerar o anúncio dos resultados trimestrais nos preços das ações FAANG e, consequentemente, nas decisões de investimento dos players de mercado

Crematocrito de la leche materna en madres eutroficas y desnutridas

Objetivo: Comparar y analizar el valor calórico, medido por crematocrito, del calostro materno en mamás lactantes eutróficas y desnutridas y determinar si existe un riesgo de presentar un valor calórico bajo en la leche de una madre expuesta a desnutrición en comparación a una eutrófica. Material y Método: El diseño del estudio es de tipo analítico, Ambispectivo y de cohorte. Se incluyo a 93 participantes conformados por madres lactantes de recién nacidos a término del Hospital Chulucanas de Piura en el periodo Octubre 2022 - Marzo 2023, que cumplieron con los criterios de selección. Fueron clasificadas en dos grupos como eutróficas (n: 62) y desnutridas (n:31) según el Índice de Masa Corporal en 2 ocasiones, en el primer trimestre de la gestación y en el puerperio inmediato. Se recolectaron los datos mediante la historia clínica y la entrevista a la mamá; se procesó la muestra de calostro materno en un laboratorio para el cálculo y análisis del Crematocrito y valor calórico. Los datos que se obtuvieron se procesaron en Excel y en el paquete estadístico IBM SPSS 26 y MEDCALC. Resultados: Se tuvieron 31 madres lactantes con valor calórico bajo,34 con normal y 28 con elevado. Al asociar las características somatometrícas el peso y el IMC en el primer trimestre sí estuvieron asociados a presentar un valor calórico bajo, normal o elevado. En el puerperio al evaluar la asociación el peso y el IMC en madres lactantes con valor calórico bajo fue menor en comparación al de madres con valor calórico normal y elevado. Por ello hay diferencia significativa. La leche materna que tiene un valor calórico bajo presento un menor Crematocrito, menor columna de crema, pero presentaron una mayor columna de suero en comparación a las que presento un valor calórico normal y elevado. Se encontró una correlación positiva que demuestra que la madre presenta mayor crematocrito y valor calórico en su leche cuando más IMC presente en el puerperio (p <0.0001). El punto de corte obtenido para establecer IMC materno en el primer trimestre de la gestación como predictor diagnóstico de leche materna con valor calórico bajo en el puerperio fue IMC < 20.78, presentando una (sensibilidad 100%) y (especificidad 100%) para predecir diagnóstico de leche materna con valor calórico bajo en el puerperio. La diferencia entre ambos estados nutricionales con respecto al valor calórico, Crematocrito, columna de crema y columna de suero demuestra que si hay significancia estadística (p < 0,05). En el cálculo del riesgo relativo de bajo valor calórico en la leche materna del puerperio inmediato en gestantes con desnutrición materna en el primer trimestre hallamos que la desnutrición materna presenta un riesgo de 4 veces presentar bajo valor calórico de la leche materna en el puerperio inmediato en comparación de las madres que presentan un peso eutrófico en el primer trimestre de la gestación . Mediante análisis multivariado utilizando regresión lineal múltiple. Se hallo un modelo predictivo donde por cada kg/m2 al cuadrado que gana la gestante en el primer trimestre del embarazo gana 0,7% de crematocrito y 51 k/cal de valor calórico en su leche materna en el puerperio inmediato, ello ajustado por variables clínicas y sociodemográficas. Conclusiones: Las características somatometrícas que presenta la madre en el primer trimestre y en el puerperio inmediato están asociadas al nivel del valor calórico de la leche materna. El Crematocrito, la columna de crema y la de suero están asociados al nivel del valor calórico de la leche materna en el puerperio inmediato. Que el nivel del valor calórico y el Crematocrito se correlacionan de manera positiva. Donde a mayor IMC materno puerperal, mayor valor calórico y Crematocrito en su leche. El punto de corte del IMC materno menor de 20.78 en el primer trimestre de embarazo predice con una especificidad de 100% y sensibilidad de 100% un nivel de valor calórico bajo de la leche materna en el puerperio inmediato. Las madres que presentan desnutrición en el puerperio inmediato presentan un menor valor calórico, Crematocrito, columna de crema pero mayor columna de suero en su leche. La desnutrición materna presenta un riesgo de 4 veces presentar bajo valor calórico de la leche materna en el puerperio inmediato en comparación de las madres que presentan un peso eutrófico en el primer trimestre de la gestación. Se obtuvo un modelo predictivo donde por cada kg/m2 que gana la gestante en el primer trimestre del embarazo gana 0,7% de crematocrito y 51 K/cal de valor calórico en su leche materna en el puerperio inmediato, ello ajustado por variables clínicas y sociodemográficas.Objective: To compare and analyze the caloric value, measured by crematocrit, of maternal colostrum in eutrophic and malnourished lactating mothers and determine if there is a risk of presenting a low caloric value in the milk of a mother exposed to malnutrition compared to a eutrophic one. Material and methods: Method: The study design was analytical, ambispective and cohort. 93 participants were included, made up of breastfeeding mothers of term newborns at the Chulucanas Hospital in Piura during the period October 2022 - March 2023, who met the selection criteria. They were classified in two groups as eutrophic (n: 62) and malnourished (n:31) according to the Body Mass Index on two occasions, in the first trimester of gestation and in the immediate puerperium. Data were collected through clinical history and maternal interview; the maternal colostrum sample was processed in a laboratory for the calculation and analysis of the Crematocrit and caloric value. The data obtained were processed in Excel and in the statistical package IBM SPSS 26 and MEDCALC. Results: There were 31 lactating mothers with low caloric value, 34 with normal and 28 with high. When associating the somatometric characteristics, weight and BMI in the first trimester were associated with presenting a low, normal or high caloric value. In the postpartum period, when evaluating the association, the weight and BMI in lactating mothers with low caloric value was lower compared to that of mothers with normal and high caloric value. Therefore there is a significant difference. Breast milk that has a low caloric value presented a lower Crematocrit, lower cream column, but presented a higher serum column compared to those that presented a normal and high caloric value. A positive correlation was found that shows that the mother has a higher crematocrit and caloric value in her milk when more BMI is present in the puerperium (p <0.0001). The cut-off point obtained to establish maternal BMI in the first trimester of pregnancy as a diagnostic predictor of breast milk with low caloric value in the puerperium was BMI < 20.78, presenting a (100% sensitivity) and (100% specificity) to predict diagnosis. of breast milk with low caloric value in the puerperium. The difference between both nutritional states with respect to caloric value, Crematocrit, cream column and serum column shows that there is statistical significance (p < 0.05). In calculating the relative risk of low caloric value in breast milk in the immediate postpartum period in pregnant women with maternal malnutrition in the first trimester, we found that maternal malnutrition presents a 4-fold risk of presenting low caloric value of breast milk in the immediate postpartum period in comparison of mothers with eutrophic weight in the first trimester of pregnancy. By multivariate analysis using multiple linear regression. A predictive model was found where for each kg/m2 squared that the pregnant woman gains in the first trimester of pregnancy, she gains 0.7% of crematocrit and 51 k/cal of caloric value in her breast milk in the immediate postpartum period, adjusted by clinical and sociodemographic variables. Conclusions: The somatometric characteristics presented by the mother in the first trimester and in the immediate puerperium are associated with the level of the caloric value of breast milk. Crematocrit, cream column and serum column are associated with the level of the caloric value of breast milk in the immediate puerperium. That the level of caloric value and Crematocrit are positively correlated. The higher the puerperal maternal BMI, the higher the caloric value and the higher the Crematocrit in her milk. The cut-off point of maternal BMI less than 20.78 in the first trimester of pregnancy predicts with a specificity of 100% and sensitivity of 100% a low caloric value of breast milk in the immediate puerperium. Mothers who present malnutrition in the immediate puerperium present a lower caloric value, Crematocrit, cream column but higher serum column in their milk. Maternal malnutrition presents a 4 times higher risk of presenting low caloric value of breast milk in the immediate puerperium compared to mothers who present a eutrophic weight in the first trimester of gestation. A predictive model was obtained where for each kg/m2 gained by the pregnant woman in the first trimester of pregnancy, she gains 0.7% of crematocrit and 51 K/cal of caloric value in her breast milk in the immediate puerperium, adjusted for clinical and sociodemographic variables.Tesi

Simulação térmica transiente de paredes de edifícios : um modelo para análise e validação de programas comerciais

Dissertação de mestrado integrado em Engenharia MecânicaA plataforma legislativa Nacional relativa ao desempenho energético dos edifícios, designada por Sistema Nacional de Certificação Energética e da Qualidade do Ar Interior nos Edifícios (SCE), tem por base a Diretiva 2002/91/CE (atualizada em 2010) e inclui o Regulamento dos Sistemas Energéticos e de Climatização em Edifícios (RSECE). Este regulamento obriga à simulação térmica dinâmica e detalhada de grandes edifícios novos utilizando softwares acreditados pela norma ANSI/ASHRAE 140-2004. Para os grandes edifícios existentes é obrigatória a realização de uma auditoria energética no prazo máximo de seis anos a qual, na maioria dos casos, também envolverá a referida simulação térmica. Prevê-se assim um grande crescimento na utilização de softwares comerciais pelo que haverá interesse em desenvolver uma ferramenta simplificada que permita a sua análise e validação, dado que aqueles utilizam modelos cuja precisão por vezes se desconhece. No trabalho presente foi desenvolvido um modelo, através do método dos volumes finitos, para a simulação térmica transiente de uma parede exterior dum edifício, o qual servirá de base para a criação de um programa de cálculo dinâmico das cargas térmicas num edifício simplificado, cujos resultados permitirão uma fácil comparação com os softwares comerciais. O modelo foi desenvolvido de raíz em ambiente MatLab e permite a definição de uma parede multi-camada, para além de incluir condições de fronteira avançadas, quer para a superfície interior, quer para a superfície exterior. Neste caso, é possível introduzir perfis horários para a temperatura exterior do ar e radiação solar incidente, sendo ainda consideradas as trocas de calor por radiação em separado com o chão e com o céu. Os resultados preliminares vieram demonstrar a importância da localização do isolamento na inércia térmica da parede, bem como a relevância da radiação solar incidente. Em algumas situações surgiram problemas de convergência numérica com origem nas condições-fronteira radiativas.The Portuguese legislation for the Energy Performance and Certification of Buildings is based on the European directive 2002/91/EC (with a recast in 2010), and includes the Regulation for the Energy and Air-conditioning Systems of buildings (RSECE). The latter requires all new large buildings to validate a dynamic and detailed thermal simulation using software solutions qualified by the standard ANSI/ASHRAE 140-2004. Also, all existing large buildings must undergo an energy audit within six years and, in most cases, this will also result in the need for a detailed thermal simulation. Therefore, a large increase in the use of commercial software packages is expected in the near future, so that there is the need for a simplified tool that will allow, by comparison, a better understanding in the analysis and validation of these products. In this work, by using the finite volume methodology, a model was developed for the transient thermal simulation of a building wall. The work will be the basis for a software code that will enable the dynamic thermal-load evaluation of a simplified building. The results will allow an easy comparison with the commercial software packages. The model was developed in the MATLAB® environment, allows the introduction of a multilayer wall and includes advanced boundary-layer conditions, both for the interior and exterior wall surfaces. In the latter it is possible to use hourly profiles as inputs for the external air temperature and solar radiation. The heat-transfer by long wave radiation is separately treated from wall to floor and wall to sky. The preliminary results demonstrate the importance of the insulation location in the inertial behavior of the wall, as well as the incident solar radiation in the resulting heat-fluxes. Some numerical convergence problems arose, due to particular irradiative boundary-layer conditions that will require a detailed analysis