Abstract
This paper presents a Variable Structure Adaptive Backstepping Controller (VS-ABC) for linear plants with arbitrary relative degree, using only input/output measurements. In order to improve the transient response, switching laws are proposed in the adaptive backstepping approach via modular design, instead of the integral adaptive laws. Furthermore, simplified algorithms are presented for the VS-ABC, motivating applications on industrial environments. Simulation results for an unstable system with relative degree three are shown.

Abstract
The most popular weight restrictions are assurance regions (ARs), which impose ratios between weights to be within certain ranges. ARs can be categorized into two types: ARs type I (ARI) and ARs type II (ARII). ARI specify bounds on ratios between input weights or between output weights, whilst ARII specify bounds on ratios that link input to output weights. DEA models with ARI successfully maximize relative efficiency, but in the presence of ARII the DEA models may under-estimate relative efficiency or may become infeasible. In this paper we discuss the problems that can occur in the presence of ARII and propose a new nonlinear model that overcomes the limitations discussed. Also, the dual model is described, which enables the assessment of relative efficiency when trade-offs between inputs and outputs are specified. The application of the model developed is illustrated in the efficiency assessment of Portuguese. secondary schools.

Abstract
Software tools in education became popular since the widespread of personal computers. Engineering courses lead the way in this development and these tools became almost a standard. Engineering graduates are familiar with numerical analysis tools but also with simulators (e. g. electronic circuits), computer assisted design tools and others, depending on the degree. One of the main problems with these tools is when and how to start use them so that they can be beneficial to students and not mere substitutes for potentially difficult calculations or design. In this paper a software tool to be used by first year students in electronics/electricity courses is presented. The growing acknowledgement and acceptance of open source software lead to the choice of an open source software tool - Scilab, which is a numerical analysis tool - to develop a toolbox. The toolbox was developed to be used as standalone or integrated in an e-learning platform. The e-learning platform used was Moodle. The first approach was to assess the mathematical skills necessary to solve all the problems related to electronics and electricity courses. Analysing the existing circuit simulators software tools, it is clear that even though they are very helpful by showing the end result they are not so effective in the process of the students studying and self learning since they show results but not intermediate steps which are crucial in problems that involve derivatives or integrals. Also, they are not very effective in obtaining graphical results that could be used to elaborate reports and for an overall better comprehension of the results. The developed tool was based on the numerical analysis software Scilab and is a toolbox that gives their users the opportunity to obtain the end results of a circuit analysis but also the expressions obtained when derivative and integrals calculations, plot signals, obtain vector diagrams, etc. The toolbox runs entirely in the Moodle web platform and provides the same results as the standalone application. The students can use the toolbox through the web platform (in computers where they don't have installation privileges) or in their personal computers by installing both the Scilab software and the toolbox. This approach was designed for first year students from all engineering degrees that have electronics/electricity courses in their curricula.

Abstract
In this paper we address the accurate estimation of the frequency of sinusoids of natural signals such as singing, voice or music. These signals are intrinsicly harmonic and are normally contaminated by noise. Taking the Cramér-Rao Lower Bound for unbiased frequency estimators as a reference, we compare the performance of several DFT-based frequency estimators that are non-iterative and that use the rectangular window or the Hanning window. Tests conditions simulate harmonic interference and two new ArcTan-based frequency estimators are also included in the tests. Conclusions are presented on the relative performance of the different frequency estimators as a function of the SNR. ©2010 IEEE.

Abstract
The effects of the delta meson on the dynamical instabilities of cold and warm nuclear and stellar matter at subsaturation densities are studied in the framework of relativistic mean-field hadron models (NL3, NLp and NLp delta) with the inclusion of the electromagnetic field. The crust-core transition density and pressure are obtained as a function of temperature of beta-equilibrium matter with and without neutrino trapping. The distillation effect is discussed. For beta-equilibrium matter with trapped neutrinos the pasta phase disappears for T> 13.2 MeV (NLp and NLp delta) or T> 11.6MeV (NL3). For neutrino free matter the non-homogeneous phase does not exist for T>3MeV. The delta meson has a larger effect in neutron rich matter, larger densities and smaller temperatures. It reduces the extension of the spinodal. The distillation effect is stronger for larger densities and smaller temperatures. The delta meson increases the distillation effect, for larger densities. NL3 predicts larger clusters compared with the other two parametrizations, and a smaller extension of the non-homogeneous phase for all temperatures. At the transition densities, the NLp and NLp delta predict clusters with the double of the size as compared with an intermediate density. Constraints at finite temperature on the EOS are required.

Abstract
In this paper it is presented a study were the Rough Set Theory is applied to evaluated a set of the new severity index. The developed methodology produces a classification of the system operation in four possible states: normal, alert, emergency (emergency I and emergency II). The states can be classified as secure, that correspond to the normal state and insecure for the remaining ones. Severity indices are used to represent the impact of the reliable contingencies in electric power system Security studies. In this study the severity index are used to classify and ranked the contingencies. This methodology was applied to the 118IEEE busbar test power network, and the results obtained are analyzed. Finally, some conclusions that provide a valuable contribution to the understanding of the power system security analysis are pointed out. © 2010 IEEE.