Parametric regression models for recurrent events analysis based on Chen distribution

In this paper, two parametric regression models based on Chen dis tribution are proposed for situations where recurrent events have the same or dif ferent risks of occurrence. Inference is based on a maximum likelihood approach, which ensures consistent parameter estimators. However, since in recurrent event data there is within-subject correlation, the “one step” jackknife estimator is used. An application on a real data set is also provided for illustrative purposes.info:eu-repo/semantics/publishedVersio

Efeito de tratamentos de pressão e temperatura no abrolhamento da batata (Solanum tuberosum)

Mestrado em Química e Qualidade dos AlimentosEste trabalho teve como objectivo estudar o efeito de tratamentos físicos de pressão e de temperatura no abrolhamento de tubérculos de batata. Verificouse que tratamentos de pressão de 1000 e 500 atm, aplicados durante 10 minutos, inibiram o abrolhamento de tubérculos, durante pelo menos 43 dias, quando estes eram armazenados em condições ambientais, enquanto um tratamento de 300 atm (10 minutos) retardou substancialmente o abrolhamento. Tratamentos de pressão a 300 e 500 atm (5, 5+5 e 10 minutos), demonstraram ter pouco efeito no abrolhamento, mas algum efeito no desenvolvimento dos brolhos, quando os tubérculos foram armazenados em câmara, com temperatura e humidade relativa controladas e luz difusa. Tratamentos térmicos de 60ºC, 65ºC, 70ºC e 75ºC de curta duração (3 e 5 minutos), demonstraram inibir o abrolhamento durante pelo menos 43 dias. Os mesmos tratamentos aplicados durante 1 minuto, retardam o abrolhamento. Tratamentos térmicos entre 5ºC e – 20ºC, com duração entre 1-5 minutos, não causaram nenhum efeito apreciável no abrolhamento. Tratamentos combinados de pressão (150 e 300 atm, 10 minutos) e temperatura (60ºC e 65ºC, 1 minuto), aplicados sequencialmente, causaram uma inibição pronunciada do abrolhamento na presença de luz, sendo o efeito inibidor dos tratamentos combinados, superior ao dos tratamentos aplicados individualmente. Nos tratamentos combinados, verificou-se que a aplicação de temperatura seguida de pressão, parece ter um efeito inibidor do abrolhamento superior, em relação à aplicação dos mesmos tratamentos, mas aplicando primeiro pressão seguida de temperatura. Quando o efeito dos tratamentos combinados no abrolhamento foi estudado na ausência de luz, verificou-se um efeito inibidor dos tratamentos no abrolhamento muito superior ao verificado na presença de luz. Na ausência de luz, os resultados obtidos indicam que, quando se aplica pressão primeiro, seguida de temperatura, os efeitos inibidores no abrolhamento são um pouco superiores, quando comparados com o tratamento em que se aplica primeiro temperatura. Deste modo, o efeito inibidor no abrolhamento de tubérculos de batata, causado por tratamentos térmicos (entre 60º-75ºC) de curta duração (1-5 minutos), tratamentos de pressão (300-1000 atm, 5-10 minutos) e tratamentos combinados de pressão e temperatura, poderá ser de interesse e potencial, para aplicação a nível industrial e fundamental, para, respectivamente, controlar o abrolhamento e estudar o mecanismo da quebra de dormência e início do abrolhamento.The aim of this work was to study the effect of physical treatments of high pressure and temperature on the sprouting of potato tubers. Is was verified that high pressure treatments of 1000 and 500 atm, applied during 10 minutes, could inhibit the sprouting, for at least 43 days, when the tubers were stored at environmental conditions, while a high pressure treatment of 300 atm (10 minutes) reduced substantially the sprouting. High pressure treatments of 300 and 500 atm (5, 5+5 and 10 minutes), showed only a slight effect on sprouting inhibition, but some inhibitory effect on sprout development, when the tubers were stored under controlled conditions of temperature and relative humidity and diffuse light. Short time (3 and 5 minutes) thermal treatments at 60ºC, 65ºC, 70ºC and 75ºC, were able to inhibit the sprouting for at least 43 days. The same treatments applied during 1 minute, still slowed down sprouting. Thermal treatments between 5ºC and – 20ºC, (1-5 minutes), showed no substantial effect on sprouting. Sequentially combined thermal (60ºC and 65ºC, 1 minute) and high pressure (150 and 300 atm, 10 minutes) treatments, caused a pronounced inhibition on sprouting, in the presence of light, being the inhibitory effect of the combined treatments higher than that caused by the treatments applied individually. In the combined treatments, it was verified a higher sprouting inhibitory effect, when temperature was applied first followed by pressure, compared to the treatments when pressure was applied first. When the effect of the combined treatments was studied in the absence of light, the sprouting inhibitory effect was more pronounced than that observed in the presence of light. In the absence of light, the results showed a slight higher inhibitory effect on sprouting, when pressure was applied first. In this way, the potato tuber sprouting inhibitory effect caused by short time (1- 5 minutes) thermal treatments (between 60º-75ºC), high pressure treatments (300-1000 atm, 5-10 minutes) and pressure/temperature combined treatments, can have interest and potential for industrial application and fundamental studies, for, respectively, control and study the mechanism of potato tuber internal dormancy break and sprouting initiation

A review of Cox' s model extensions for multiple events

In longitudinal studies, it is usual that a given subject can experience several failures. To analyse multiple failure-time data, we reviewed some extensions of Cox's regression model, which were proposed by: Prentice, Williams and Peterson (PWP); Andersen and Gill (AG); Wei, Lin e Weissfeld (WLW); and Lee, Wei and Amato (LWA). Our main goal is to underline the differences between these extensions, through a brief but careful description, providing also some guidance on how to choose the proper model for each situation. The guidelines presented in this work revealed to be a useful pointer to easily choose the most suitable model. Secondarily, we used the survsim and the survival R packages to illustrate the practical implementation of these models.info:eu-repo/semantics/publishedVersio

A influência das características geomecânicas dos maciços fracturados no desvio da perfuração

A perfuração é uma das operações envolvidas no desmonte de rocha com explosivos. A forma como esta operação é executada é determinante para o sucesso do desmonte. Quando é realizada correctamente o desmonte produz superfícies limpas com o mínimo de sobrescavação e perturbação. A selecção das ferramentas de perfuração é um dos factores preponderantes para os custos do desmonte de maciços rochosos. A forma como a perfuração é executada é determinante para a boa fragmentação do maciço rochoso. Este estudo irá centrar‐se na perfurabilidade do maciço, linearidade dos furos e desenvolvimento de metodologias do ciclo de perfuração. O objectivo geral deste trabalho é demonstrar a interdependência entre os parâmetros geológicos e geotécnicos do maciço rochoso e as tecnologias de perfuração de forma a optimizar tanto técnica como economicamente. O controlo geomecânico do desmonte do maciço rochoso através de uma perfuração alinhada é salientado com o intuito de uma abordagem de geoengenharia integrada nos maciços rochosos.Drilling is one of the unit operations involved in rock fragmentation by blasting. The way this operation is conducted determines the success of the rock fragmentation. When correctly performed, these blasts can produce very clean faces with a minimum of over‐break and disturbance. The wear of drilling tools in quarrying has always been a predominant factor for the costs of hard rock excavation. The way drilling is conducted determines the success of the rock fragmentation. This study will focus in the rock mass drillability, straight holes, and in the development of drilling cycle methodologies. The main goal of this work is to present the potential interdependency between geological and geotechnical parameters of rock masses and drilling technologies, in order to optimize drilling both technically and economically. The selected study area – Serdedelo Quarry (Ribeira, Ponte de Lima), NW Portugal – is located near regional faults. The geomechanical control of rock mass blasting by aligned drilling features is outlined in order to address an integrated geoengineering rock masses approach

Um olhar sobre o desenvolvimento de modelos de sobrevivência para acontecimentos recorrentes

info:eu-repo/semantics/publishedVersio

Modelos paramétricos flexíveis para acontecimentos recorrentes

Neste trabalho, s˜ao propostas duas classes de modelos pa ram´etricos para analisar o tempo entre acontecimentos recorrentes, utilizando splines c´ubicos restritos. As classes de modelos diferem no modo como se lida com a dependˆencia entre acontecimentos. Al´em disso, ambas as classes s˜ao caracterizadas por uma transforma¸c˜ao da fun¸c˜ao de sobrevivˆencia, atrav´es da fun¸c˜ao de liga¸c˜ao log-log ou −logit. De forma a ilustrar a metodologia proposta, efetua-se uma aplica¸c˜ao a um conjunto de dados reais sobre a recorrˆencia de cancro da bexiga. Os resultados revelam que o uso de splines c´ubicos res tritos permite modelar de forma flex´ıvel e adequada o tempo entre acontecimentos sucessivos.info:eu-repo/semantics/publishedVersio

Modelos de sobrevivência aplicados à análise de acontecimentos múltiplos

Na modela¸c˜ao de acontecimentos m´ultiplos, uma abor dagem muita utilizada consiste em desenvolver extens˜oes do modelo semiparam´etrico de Cox. Contudo, quando se considera que o co nhecimento da distribui¸c˜ao do tempo ´e importante para o estudo, a abordagem param´etrica revela-se mais adequada. Neste trabalho, s˜ao apresentados dois novos modelos param´etricos baseados na dis tribui¸c˜ao de Weibull (modelos WNE e WE), como alternativas a duas das extens˜oes do modelo de Cox para acontecimentos recorren tes (modelos AG e PWP). De forma a ilustrar as diferen¸cas entre estas duas abordagens, ´e considerado um exemplo de aplica¸c˜ao com dados simulados. Os resultados obtidos com os modelos propostos permitem acrescentar mais duas op¸c˜oes ao leque de escolhas de mo delos para acontecimentos recorrentes.info:eu-repo/semantics/publishedVersio

The Extended Chen-Poisson Lifetime Distribution

A three-parameter lifetime distribution is proposed, named extended Chen-Poisson distribution, by compounding the Chen and zero-truncated Poisson distributions. The new distribution belongs to the unified Poisson family, where both distributions of the minimum and maximum are merged into one. Several properties of the distribution are studied. The proposed distribution is quite flexible since it accommodates different complex hazard shapes. Inference is based on the maximum likelihood method in the presence of a right-censoring mechanism. A simulation study is performed to evaluate the properties of the parameters estimators. Two real lifetime data sets are analysed for purposes of comparison with other generalizations of the Chen distribution, as well as with other members of the unified Poisson family. The obtained results allow to highlight the potential of the new distribution

Evaluation of the maize ( Zea mays L.) diversity on the Archipelago of Madeira

Abstract The variability of 43 open-pollinated populations of maize (Zea mays L.), representing a wide range of ecological conditions on the Archipelago of Madeira, was evaluated based on the morphological and reproductive traits. Individual data of 41 traits related to earliness, plant and tassel structure and the shape of the ear and grain were analysed using multivariate analysis. The populations belonging to two major maize varieties were grouped into four groups by their degree of dissimilarity, based on discriminant analysis. The dissimilarity of these groups was confirmed by the values of the Tukey test. The racial rank of these groups was proposed and a brief description of the maize landraces was presented. This work represents the first morphological characterization and analysis of diversity of maize germplasm for the Archipelago of Madeira where the traditional agricultural practices are still keeping this Portuguese region free from corn hybrids. The description of the Madeiran corn landraces allows us to preserve the existing corn biodiversity and could be used for their registration as conservation landraces or for conservation and breeding proposes worldwide

EcoGreenRoof – EGR: Eco-materials Development for Green Roofs

The project EcoGreenRoofs - EGR aims to develop ecological substrates for application in green roofs, which include in their formulation industrial waste of organic and inorganic base. The substrates are tentatively produced exclusively from industrial waste and / or materials derived from waste treated, and tested at a facility to be studied, developed and built on pilot scale. The substrates produced will be tested under real conditions for their validation and inherent production process. This project aims also to evaluate the commercialization of substrates by analyzing the technical, economic and environmental components. The project is being carried out in co-promotion by two enterprises, one with know-how in the execution of green roofs (Neoturf) and the other with knowledge to implementation of industrial solutions aiming waste management (W2V), and by two SI & I entities with the knowledge and means to develop waste recovery studies (CVR) and roof solutions (Itecons).This work has been co-financed by Compete 2020, Portugal 2020 and the European Union through the European Regional Development Fund – FEDER within the scope of the project EGR - EcoGreenRoof: Desenvolvimento de eco-materiais para coberturas verdes (POCI-01-0247-FEDER- 033728)