47 documents found, page 1 of 5
Stochastic differential equations mixed model for individual growth with the in...
Jamba, Nelson T.; Filipe, Patrícia A.; Jacinto, Gonçalo; Braumann, Carlos A.In early work we have studied a class of stochastic differential equation (SDE) models, for which the Gompertz and the Bertalanffy-Richards stochastic models are particular cases, to describe individual growth in random environments, and applied it to model cattle weight evolution using real data. We have started to work on these type of models considering that the model parameters are fixed, i.e. the same for ...
Estimation for stochastic differential equation mixed models using approximatio...
Jamba, Nelson T.; Jacinto, Gonçalo; Filipe, Patrícia A.; Braumann, Carlos A.We used a class of stochastic differential equations (SDE) to model the evolution of cattle weight that, by an appropriate transformation of the weight, resulted in a variant of the Ornstein-Uhlenbeck model. In previous works, we have dealt with estimation, prediction, and optimization issues for this class of models. However, to incorporate individual characteristics of the animals, the average transformed siz...
A temporal analysis on patient and health service delays in pulmonary tuberculo...
Chakma, Bhaswar; Gomes, Dulce; Filipe, Patrícia A.; Soares, Patrícia; de Sousa, Bruno; Nunes, CarlaAn exploratory analysis was performed, trends of both delays were studied, and 36 months forecasts were generated. We used the permutation test to test differences between groups and the Seasonal and Trend decomposition using Loess (STL) method and Autoregressive Integrated Moving Average (ARIMA) models for forecasting for both Health and Patient delays. We used data from notified PTB cases in mainland Portugal...
Profit Optimization of Cattle Growth with Variable Prices
Jacinto, Gonçalo; Filipe, Patrícia A.; Braumann, Carlos A.We apply a class of stochastic diferential equations to model the growth of individual animals in randomly fuctuating environments using real weight data of males of the Mertolengo cattle breed. The use of these more realistic models can help farmers to optimize their proft. To this end we obtain the probability distribution, the frst two moments and others quantities of interest of the proft obtained by raisin...
Likelihood Function through the Delta Approximation in Mixed SDE models
Jamba, Nelson T.; Jacinto, Gonçalo; Filipe, Patrícia A.; Braumann, Carlos A.Stochastic differential equations (SDE) appropriately describe a variety of phenomena occurring in random environments, such as the growth dynamics of individual animals. Using appropriate weight transformations and a variant of the Ornstein–Uhlenbeck model, one obtains a general model for the evolution of cattle weight. The model parameters are \alpha, the average transformed weight at maturity, \beta, a growt...
Structured Additive Regression Modeling of Pulmonary Tuberculosis Infection
de Sousa, Bruno; Pires, Carlos; Gomes, Dulce; Filipe, Patrícia A.; Costa-Veiga, A; Nunes, CarlaTuberculosis (TB) is one of the top 10 causes of death and the leading cause from a single infectious agent (above HIV/AIDS). In 2017, the World Health Organization (WHO) estimated 10.0 million people developed TB and 1.3 million deaths (range, 1.2–1.4 million) among HIV-negative people with an additional 300 000 deaths from TB (range, 266 000–335 000) among HIVpositive people. Studies that understand the socio...
Time series analysis of Luanda road accidents, deaths and injureds
Alberto, Manuel; Gomes, Dulce; Filipe, Patrícia A.In this work, time series models are applied to explain and forecast the rate of traffic accidents, deaths and injureds in Luanda, Angola. Monthly Luanda data from 2002 to 2015 are used to fit models and to make predictions. Road accidents in Angola are currently one of the major causes of death in the country. Particularly Luanda, the capital, is the province that shows the highest rate in terms of accidents, ...
A time series approach to road accidents in Angola from 2002 to 2015
Alberto, Manuel; Gomes, Dulce; Filipe, Patrícia A.Road accidents are now a major health problem worldwide, and particularly in Angola, where they are currently one of the major causes of death in the country. Over the time horizon under study, from 2002 to 2015, the average growth rate of road accidents was 7.3\% and for both deaths and injured was 11.7\%. In the present work, we have characterize the trend of the road accidents, deaths and injured in Angola u...
STAR Modeling of Pulmonary Tuberculosis Delay-Time in Diagnosis
de Sousa, Bruno; Gomes, Dulce; Filipe, Patrícia A.; Areias, Cristiana; Briz, Teodoro; Pires, Carlos; Nunes, CarlaUnderstanding what characterizes patients who suffer great delays in diagnosis of pulmonary tuberculosis is of great importance when establishing screening strategies to better control TB. Greater delays in diagnosis imply a higher chance for susceptible individuals to become infected by a bacilliferous patient. A Structured Additive Regression model is attempted in this study in order to potentially contribute...
Equações diferenciais estocásticas na modelação do crescimento individual em am...
Filipe, Patrícia A.Este estudo centra-se na análise de modelos de crescimento individual em ambiente aleatório. Para tal, foram descritos modelos mais gerais de equações diferenciais estocásticas. Apresentamos o caso em que existe uma unica forma funcional para descrever a din^amica m edia da curva de crescimento completa e generalizamos para o caso multif asico, em que consideramos que o coe ciente de crescimento assume valores ...