M. Filomena Teodoro

Analytical and numerical investigation of mixed-type functional differential equations

This paper is concerned with the approximate solution of a linear non-autonomous functional differential equation, with both advanced and delayed arguments. We search for a solution x(t), defined for t@?[-1,k], (k@?N), that satisfies this equation almost everywhere on [0,k-1] and assumes specified values on the intervals [-1,0] and (k-1,k]. We provide a discussion of existence and uniqueness theory for the problems under consideration and describe numerical algorithms for their solution, giving an analysis of their convergence.

Finite element solution of a linear mixed-type functional differential equation

This paper is devoted to the approximate solution of a linear first-order functional differential equation which involves delayed and advanced arguments. We seek a solution x, defined for t ∈ (0, k − 1],(k ∈ IN ), which takes given values on the intervals [ − 1, 0] and (k − 1, k]. Continuing the work started in previous articles on this subject, we introduce and analyse a computational algorithm based on the finite element method for the solution of this problem which is applicable both in the case of constant and variable coefficients. Numerical results are presented and compared with the results obtained by other methods.

Empirical Studies in User Experience of an Emergency Management System

A system designed following usability principles, and considering users preferences and expectations ensures a high quality of user experience, which is particularly important when the system is used to support complex tasks. That is the case of emergency response operations’ coordination and execution. This work, conducted using an action research methodology, addresses challenges faced by the THEMIS project team during the conceptualization, design and implementation of an emergency management intelligent system, aiming to support disaster response operations and to improve the planning and execution efforts in disaster and crisis’ scenarios.

Perception about pediatric hypertension

Pediatric hypertension is prevalent and it may appear silently in childhood where the diagnosis is based on regular blood pressure measurements, which vary with age, sex, and height. It can progress to adulthood and be associated with potentially severe organ damage, so it is important to be aware of its existence and apply an early intervention. To evaluate the populations knowledge of the disease, we provided a questionnaire to the caregivers of pediatric patients at the Hospital de Santa Maria and the results were statistically analyzed in order to infer possible associations between sociodemographic variables (age, sex, race, residence, graduation level, and occupation) and theoretical knowledge of the disease. There were significant statistical associations between age, graduation level, and occupation with the knowledge of the possible silent emergence of the disease in childhood, the existence of risk factors, and the age from which the blood pressure should be checked. In this preliminary study, we used an experimental questionnaire. We employed generalized linear models to obtain statistical models. In future research, we will use more elaborate techniques, such as multivariate analysis (factorial analysis, correspondence analysis), as well as other suitable methods for analyzing the data obtained.

Modelling a nonlinear MTFDE from acoustics

The main interest of this work is to compute a approximate solution of equations with equal delay and advance which often appear in models from applied sciences. In this article, we consider a special case of a nonlinear forward-backward which models the vibration of some elastics tissues in physiology, just as the vocal fold mucosa. The oscillation as superficial wave propagating through the tissues in the direction of the flow is described by the considered equation. The approximation of solution is obtained using a non regular mesh instead a regular one as presented in [1] where is adapted an numerical scheme based on algorithms introduced in [2, 3] using collocation, finite element method, method of steps and Newton’s method3 are used.

An Issue About the Existence of Solutions for a Linear Non-autonomous MTFDE

This article is concerned with the existence of solution of a certain non-autonomous linear delayed-advanced differential equation. The main objective is to provide the proof of a theorem introduced in Lima et al. (J. Comput. Appl. Math. 234(9):2732–2744, 2010) about existence of solution of a class of mixed-type functional differential equations (MTFDEs). It is an effort to complete the theoretical basis of some computational methods introduced earlier to solve numerically such equations, which were deduced making use of that theorem.

Approximating a Retarded-Advanced Differential Equation Using Radial Basis Functions

In last years we have got the approximation of the solution of a linear mixed type functional differential equation, considering the autonomous and non-autonomous case by collocation, least squares and finite element methods considering a polynomial basis. The present work introduces a numerical scheme using collocation and radial basis functions to solve numerically the non-linear mixed type equation with symmetric delay and advance. The results are similar using collocation, B-splines and exponential radial functions. The preliminary results are promising, but more simulations using different basis of radial functions are needed.

Time Series Data Mining for Energy Prices Forecasting: An application to real data

Recently, at the 119th European Study Group with Industry, the Energy Solutions Operator EDP proposed a challenge concerning electricity prices simulation, not only for risk measures purposes but also for scenario analysis in terms of pricing and strategy. The main purpose was short-term Electricity Price Forecasting (EPF). This analysis is contextualized in the study of time series behavior, in particular multivariate time series, which is considered one of the current challenges in data mining. In this work a short-term EPF analysis making use of vector autoregressive models (VAR) with exogenous variables is proposed. The results show that the multivariate approach using VAR, with the season of the year and the type of day as exogenous variables, yield a model that explains the intra-day and intra-hour dynamics of the hourly prices.

Approximating a nonlinear advanced-delayed equation from acoustics

We approximate the solution of a particular non-linear mixed type functional differential equation from physiology, the mucosal wave model of the vocal oscillation during phonation. The mathematical equation models a superficial wave propagating through the tissues. The numerical scheme is adapted from the work presented in [1, 2, 3], using homotopy analysis method (HAM) to solve the non linear mixed type equation under study.

Performance Analysis of a GPS Equipment

In emerging economies the easiest way to ensure the geodetic support still is the static relative positioning (SRP) using a single reference station. This technique provides surveyors the ability to determine the 3D coordinates of a new point with centimeter-level accuracy. The objective of this work is to evaluate GPS SRP regarding accuracy, as the equivalent of a real time kinematic (RTK) network and to address the practicality of using either a continuously operating reference stations (CORS) or a passive control point for providing accurate positioning control. The precision of an observed 3D relative position between two global navigation satellite systems (GNSS) antennas, and how it depends on the distance between these antennas and on the duration of the observing session, was studied. We analyze the performance of the software for each of the six chosen ranges of length in each of the four scenarios created, considering different intervals of observation time. An intermediate inference level technique (Tamhane and Dunlop, Statistics and data analysis: from elementary to intermediate, Prentice Hall, New Jersey, 2000), an analysis of variance, establishes the evidence of relation between observing time and baseline length.