Abstract
Most power systems are nowadays operated very near to their operating limits due to increase in consumption, while economic and environmental constraints have limited construction of new generation facilities and lines. This paper is devoted to the analysis of the ULTC effect in the dynamic voltage stability of an electric power network. Usually substations are provided with transformers with tap-changers facilities. It was long believed that transformers with tap-changers could eliminate or minimize effectively voltage instabilities. In this study it is shown the influence of the ULTC in the voltage instability for some situations in the analysed power network. It was used the BPA test power network. A severe contingency situation was simulated. The automatic voltage regulators of the generating units and the turbine speed governors will be modelled. The simulation results were obtained using the commercial transient software package EUROSTAG. Finally some conclusions that provide a better understanding of the voltage collapse phenomena are pointed out.

Abstract
Distributed real time system is a technology that is become widely used in diverse areas of application, including systems in vehicles, aircraft, locomotives, among others. Great part of these applications is considered critic. Hereupon, such systems must be predictable in relation to its logical result and its temporal behavior, same in operating under failure having to provide tolerances. Distributed real time system requires the use of deterministic and reliable communications mechanisms. A high trend in the automotive area is the replacing of great part of the mechanical andlor hydraulic systems for electronic systems, so called control-by-wire. To reach the objectives of the control-by-wire systems, it is necessary the use of distributed real time systems with fault tolerant properties. This work presents a study about the communication requirements in x-by-wire systems. A theoretic content and a detailed study of temporal property of the CAN and TTP/C network communication are presented in the environment of simulation of the x-by-wire system.

Abstract
In this paper we describe the algorithms used in the external tracking system of the Isurus AUV. By listening to the acoustic signals exchanged between the vehicle and the beacons of the acoustic navigation network, the tracking system is able to obtain distance measurements from the vehicle to each beacon, that are then used to compute the vehicle horizontal position. Several error sources make these measurements inadequate to be used for computing the vehicle position by a simple triangulation technique. The tracking algorithms described here are able to reject highly erroneous measurements, producing position estimates with a satisfactory degree of accuracy. Copyright © 2004 IFAC

Abstract
Workflow management systems are increasingly being used to support business processes. Methodologies have been proposed in order to derive workflow process definitions from business models. However, these methodologies do not comprise access control aspects. In this paper we propose an extension to the Work Analysis Refinement Modelling (WARM) methodology, which also enables to determine workflow access control information from the business process model. This is done by identifying useful information from business process models and showing how it can be refined to derive access control information. Our approach reduces the effort required to define the workflow access control, ensures that authorization rules are directly related to the business and aligns access control with the information system architecture that implements the business process.

Abstract
The in-situ investigation and characterization of ISC'2 experimental site comprised the application of several geophysical borehole, penetration and surface methods, namely S waves high resolution shallow reflection (SHRR), ground penetrating radar (GPR), P and S waves seismic cross-hole (CH), downhole (DII), refraction, electrical resistivity, as well as geotechnical tests, namely SPT, CPT, DMT, among others. The site, located within the campus of Faculty of Engineering of the University of Porto (FEUP), is geologically fortned by an upper layer of heterogeneous residual granite soil overlaying rather weathered granite contacting a gneissic migmatite. Direct and indirect results from some of the referred surveys are compared between them and with some of the available geological and geotechnical information, in particular hereby (Part II), those obtained from SHRR, GPR, and CH seismic tests. The integration of the available information was then used to build a tentative geological interpretation model. One of the objectives of this component of the global study, hereby presented, was to evaluate the possibility of obtaining valid infortnation from a single technique, particularly, S waves shallow reflection.

Abstract
The number of successful missions with autonomous underwater vehicles (AUVs) has been increasing steadily during the last few years, validating this emerging technology as an e cient tool for underwater sampling. At the same time it has served to envisage their operation in more demanding scenarios. This paper presents results from environment monitoring missions with an AUV and new mission concepts for the operation of one or multiple AUVs. These new concepts are the natural evolution of previous work and also the response to the requirements of some of the identi ed scenarios. For each type of mission, solutions for navigation, control, coordination, and communications are presented. © 2004 IFAC