2008
Authors
de Sousa, M;
Publication
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS
Abstract
When developing applications with high integrity requirements, the choice of programming language is of utmost importance. In fact, IEC 61508 includes a table with suggested programming languages for each SIL (Safety Integrity Level). The languages defined in IEC 61131-3 are included in this table, but are only highly recommended for the higher SILs if a subset of the languages are used. In this paper we propose restrictions and changes to the IEC 61131-3 languages that constitute a subset of the languages with the objective of making them appropriate for the development of high integrity applications.
2008
Authors
Santos, AA; de Sousa, M;
Publication
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS
Abstract
The IEC 61499 standard defines function blocks with which distributed control applications may be developed, and how these are interpreted and executed. With the distributed nature of the control application, many issues also need to be taken into account. In this paper we propose a replication management framework for IEC 61499 applications, and discuss some mechanisms and protocols that may be used for this purpose.
2008
Authors
Barbosa, M; Farshim, P;
Publication
Proceedings of the 2008 ACM Symposium on Information, Computer and Communications Security, ASIACCS '08
Abstract
Certificateless cryptography inherits a solution to the certificate management problem in public-key encryption from identity-based techniques, whilst removing the secret key escrow functionality inherent to the identity-based setting. Signcryption schemes achieve confidentiality and authentication simultaneously by combining public-key encryption and digital signatures, offering better overall performance and security. In this paper, we introduce the notion of certificateless signcryption and present an efficient construction which guarantees security under insider attacks, and therefore provides forward secrecy and non-repudiation. Copyright 2008 ACM.
2008
Authors
Matos, MA; Gouveia, EM;
Publication
IEEE TRANSACTIONS ON POWER SYSTEMS
Abstract
The idea behind the first proposal of the fuzzy power flow (FPF) was to analyze the impact of the uncertainties in load and generation at the power flow level, when no statistical information is available. Further development of the field addressed the optimal power flow problem and the use of fuzzy methodologies to help planners of the composite generation-transmission system. In a market environment, transmission system adequacy may be defined as the ability of the system to meet reasonable demands for the transmission of electricity. The starting point of this paper is that FPF can be used as a tool to quantify this adequacy, without the need of making too many assumptions about load and generation uncertainties. However, some changes in the basic concept of the FPF are needed in order to accomplish this task-part of this paper is devoted to the description of the adequate formulation. We will also show that this formulation can be used both in the normal operation situation and in the reliability evaluation of the transmission system. An illustrative example completes this paper.
2008
Authors
Mendes, JM; Rodrigues, A; Leitao, P; Colombo, AW; Restivo, F;
Publication
EDOCW: 2008 12TH ENTERPRISE DISTRIBUTED OBJECT COMPUTING CONFERENCE WORKSHOPS
Abstract
Automation systems are changing from the centric-controlled approach to a more flexible and autonomous behavior. The contribution to this philosophy comes from several technologies, including service-oriented concepts. This work focus on some open points of enhanced communication and control patterns and presents it in form of a multi-use communication module. For the development of such systems, the SOA4D implementation of Device Profile for Web Services (DPWS) was used. The specified communication structure that works on top of the DPWS toolkit can be integrated in software applications targeting but not limited to embedded devices. The resulting interaction patterns also establish a-stronger association to real life services and define flexible communication routines between service requester and provider.
2008
Authors
Valente, JMS; Alves, RAFS;
Publication
COMPUTERS & OPERATIONS RESEARCH
Abstract
In this paper, we consider the single machine scheduling problem with quadratic earliness and tardiness costs, and no machine idle time. We propose several dispatching heuristics, and analyse their performance on a wide range of instances. The heuristics include simple and widely used scheduling rules, as well as adaptations of those rules to a quadratic objective function. We also propose heuristic procedures that specifically address both the earliness and the tardiness penalties, as well as the quadratic cost function. Several improvement procedures were also analysed. These procedures are applied as an improvement step, once the heuristics have generated a schedule. The computational experiments show that the best results are provided by the heuristics that explicitly consider both early and tardy costs, and the quadratic objective function. Therefore, it is indeed important to specifically address the quadratic feature of the cost function, instead of simply using procedures originally developed for a linear objective function. The heuristics are quite fast, and are capable of quickly solving even very large instances. The use of an improvement step is recommended, since it usually improves the solution quality with little additional computational effort.
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