Percorrer por autor "Santos, Rui"
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- Accuracy measures for binary classification based on a quantitative variablePublication . Santos, Rui; Felgueiras, Miguel; Martins, João Paulo; Ferreira, LilianaThe identification of the right methodology to perform binary classification based on an observed quantitative variable is usually a complex choice. Thus, the use of appropriate accuracy measures is crucial. In fact, the ROC curve reveals a lot of information about the accuracy of the applied methodology for all the possible values of the cut-point. In particular, the integral and partial areas under the ROC curve are widely used. The φ index, in which sensitivity equals specificity, may also be applied. Nevertheless, the accuracy at one specific cut-point may be sufficient to assess the accuracy in some applications. Therefore, different ways to define the optimal cut-point may be applied, such as the maximization of the Youden index, the maximization of the concordance probability or the minimization of the distance to the point with absence of misclassification. To compare the adequacy of these measures, a simulation study was performed under different scenarios. The results highlight the advantages and disadvantages of each procedure and advise the use of the φ index.
- Alternative heavy tailed models in seismologyPublication . Felgueiras, Miguel; Martins, João; Santos, RuiGreat earthquakes are commonly considered as the ones with moment magnitude (Mw ) above or equal to 8.0. Since these earthquakes can destroy entire communities located near the epicentre, the search of physical laws that explain the energy released by them is an important issue. There is a connection between the radiated energy of an earthquake, its magnitude and its seismic moment (M 0). Thence, when fitting a heavy or an extremely heavy tailed distribution to a seismic moment dataset, we are in fact adjusting a mathematical model which explains the amount of energy released by these great seisms. Therefore, the main goal of this work is to study the more appropriated Pareto based models (the most used family in this field) when explaining the seismic moment of the great earthquakes. With this purpose in mind, we selected two different catalogs that accommodate recent events and are considered more accurate than other catalogs used in previous works. We conclude that the traditional Pareto distribution remains a good choice to deal with this kind of data, but Log-Pareto lead to higher p-values and Location-scale Pareto is better fitted to the biggest events.
- Commingled and disarticulated human remains related to 1755 Lisbon earthquake: Height estimation from incomplete and complete femoral bonesPublication . Matos, Sofia; Flamino, Carolina Barroso; Borges, Guilherme; Francisco, Inês; Tropa, Madalena; Cruz, Tiago; Bento, Beatriz; Santos, Rui; Pereira, Cristiana PalmelaIntroduction: In Forensic Medicine, the estimation of the stature often has a crucial role in the reconstruction phase of disjointed populations. The femur, being the longest bone in the human body, is usually the most reliable source in height estimation. However, in these populations, intact femurs are hardly ever found, making it necessary to use femur fragments for the same purpose. Aim: This investigation aims to estimate the stature of the catastrophic population concerning the earthquake that occurred in Lisbon, in 1755. Materials and Methods: The study was conducted on 8 whole femurs and 21 fragments, which were measured and weighted. These measurements were applied in a regression formula, obtained from the gathered research, in order to estimate the stature of the population. Results: The results showed that, for the whole femur, the corresponding height varies between 147.96 cm and 168.82 cm. For the fragments, the obtained estimates vary between 151.96 cm and 174.96 cm. Conclusion: The methods used proved to be reliable in estimating the length of the femur, as well as in deducting the height of individuals through this bone, allowing the study of these parameter's evolution in generations.
- Cut-off for the legal ages in the Portuguese Population by Third Maturity Index: Measures of AccuracyPublication . Pereira, Cristiana Palmela; Rodrigues, Ana; Santos, Adriana; Salvado, Francisco; Santos, Rui; Cameriere, RobertoObjectives: The aim of this study is to estimate the cut-off points for the Portuguese legal ages through the I3M, and to compare them with the methods of Demirjian, Nolla and Moorrees. Design: The lower third molars were analyzed on 348 orthopantomography's aged between 12 and 23 years in a Portuguese Population. The images were analyzed by ImageJ and the cut-off points were calculated for the respective legal ages of 14, 16, 18 and 21 years old. Results: The correlation between age and the I3M was 0.862, whereas with Demirjian's stadiums, Nolla's stages, and Moorrees’ stages the correlation coefficients were 0.863, 0.842 and 0.844, respectively. For the cut-off point of 0.08 for the age of 18, a sensitivity of 78.99 %, specificity of 93.48 %, an accuracy of 88.54 %, a positive predictive value of 86.24 % and a posteriori Bayes probability of 92.82 %. The cut-off points established for the ages of 14, 16, 18 and 21 years for the Portuguese population achieved an accuracy of 83.67 %, 85.67 %, 88.54 % and 87.11 %, respectively. Conclusion: Demirjian's method and Cameriere's method attain quite similar results. In certain ages, the methods of Nolla and Moorrees show higher sensitivity or higher specificity when compared to Cameriere's method, however this last method is more stable in terms of reliability and more suitable to use in the Portuguese population.
- Dental Age Assessment by I2M and I3M: Portuguese Legal Age Thresholds of 12 and 14 Year OldsPublication . Augusto, Diana; Pereira, Cristiana Palmela; Rodrigues, Ana; Cameriere, Roberto; Salvado, Francisco; Santos, RuiObjective: Better understanding of dental age assessment may help in cases of age estimation in Forensic Clinics. The first aim was to provide essential information on method reliability for upcoming studies using dental age assessment by second molar index (I2M), and third molar index (I3M) for age estimation on legal ages of 12 - 14 years. The second aim was to document forensic method outcomes of the Demirjian method which has already been used in forensic clinic. Material and methods: Two samples were used for this purpose: for I2M, 633 orthopantomographs (270 females / 363 males), the age range from 7 to 17 years and for I3M, 471 orthopantomographs (253 females / 218 males), the age range from 10 to 23 years, from the database population of Lisbon North University Hospital Center, approved by the Ethic Committee. Results: The I3M cut-off point (1.133) for 12- year-olds obtained better results than the cut-off point stated by the I2M (0.135). Besides, I2M cut-off point (0.001) for 14- year- olds showed better results when compared with the cut-off point (0.705) established by the I3M. Both methods are reliable for the legal age thresholds of 12 and 14 years. However, using I2M and I3M allows us to vary the cut-off value to privilege sensitivities or specificity, depending on which is more appropriate to the intended application. Conclusions: The accuracy (88.94%) of I3M obtained better results for the 12- year- old cut-off point (1.133) and the accuracy (90.21%) of the I2M performed better for the 14- year- old cut-off point (0.001).
- Discrete Compound Tests and Dorfman’s Methodology in the Presence of MisclassificationPublication . Santos, Rui; Martins, João Paulo; Felgueiras, MiguelCompound tests can be used to save resources for classification or estimation purposes in clinical trials and quality control. Nevertheless, the methodologies that are usually applied are restricted to qualitative group tests. Moreover, when quantitative compound tests are applied the problem is to ascertain whether the amount of some substance of any individual in the group is greater or lower than a prefixed threshold. An overview of the applications of the discrete compound tests highlights the advantages (to save resources) and disadvantages (higher probability of misclassification), and suggests criteria to assess the suitability of applying Dorfman’s methodology.
- Estimation Through Array-Based Group TestsPublication . Oliveira Martins, João Paulo; Felgueiras, Miguel; Santos, RuiPooling individual samples for batch testing is a common procedure for reducing costs. The recent use of multidimensional array algorithms, due to the emergence of robotic pooling, is an innovative way of pooling. We show that the two-dimensional array-based group tests can provide accurate estimates for the prevalence rate even for situations in which the traditional estimators, applied to one-dimensional arrays, are not valid. Hence, a computational script was developed to determine which prevalence rate estimate minimizes the sum of the squared deviations between the number of observed and expected rows and columns whose pooled sample had a positive test result. © 2017, National Statistical Institute. All rights reserved.
- Evaluation of an educational project for the development of the autonomy of life in young people leaving residential carePublication . Santos, Rui; Margarido, Cristóvão; Pocinho, Ricardo; Silva, Tânia; Póvoa, VanessaOne of the protection measures provided to at-risk children and young people in Portugal is residential care. Residential care facilities foster children and young people from unstructured families, providing them with conditions that may allow to enhance their full development, including their education, well-being and preparation for life autonomy. Projet' Ar-te is an intervention project developed at Casa do Canto, under the direction of the Portuguese Association for the Rights of Minors and the Family - CrescerSer, financed from 2012 to 2015 through the "Children and Youth at Risk"Program of Fundação Calouste Gulbenkian. The main objectives of this project were the creation of the Life Skills Development Program (PDCV) and the Support and Monitoring Structure (ESAAC) for the young people leaving residential care, in order to provide them with a close affective rear, helping to face the challenges and difficulties they encounter successively outside the residential care facility. Through ethnobiographic interviews with two young women experiencing the project for one year, the aim was to understand their perceptions regarding two moments: the residential care period and the experiences after leaving Casa do Canto through the support provided by the ESAAC Structure. The results showed that participation in the project activities provided significant moments during residential care, which seem to have an important impact on the autonomy strategies adopted by young women after leaving the facility.
- Exploring Pareto scale mixturesPublication . Felgueiras, Miguel; Santos, RuiPareto scale mixtures can be used to obtain distributions with heavier tails. An explanation of this model properties is provided, together with a discussion about the parameters estimation. Finally, a real data application is presented, consisting in the larger earthquakes seismic moment modeling.
- Extensions of Dorfman’s TheoryPublication . Santos, Rui; Pestana, Dinis; Martins, João PauloEconomic impact of composite sampling is investigated in the realistic framework of tests with positive probability of false positive and of false negative results. Sensitivity and specificity when pooling samples are also discussed, using rarefaction as a framework.
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