Variable abstraction and approximations in supervisory control synthesis

This paper proposes a method to simplify Extended Finite-state Automata (EFA) in such a way the least restrictive controllable supervisor is preserved. The method is based on variable abstraction, which involves the identification and removal of irrelevant variables from a model. Variable abstraction preserves controllability, and the paper shows how approximations can be used to ascertain least restrictiveness of the synthesis result. The approach has the modelling benefits of Extended Finite-state Automata, leads to optimal control solutions, and reduces the synthesis cost. An example of a manufacturing system illustrates the contributions

Androgen replacement therapy in men: current evidence and controversy

A queda dos níveis séricos de testosterona em homens de idade avançada – conhecida como andropausa ou hipogonadismo tardio – pode ser responsável por vários aspectos no declínio da qualidade de vida de homens idosos: disfunção erétil, diminuição da libido, redução de força física e energia, sarcopenia, osteopenia, fadiga e até depressão. Muitos de tais sinais e sintomas representam as mesmas alterações habitualmente atribuídas ao processo de envelhecimento. Quando um paciente se apresenta com esses sintomas, deve-se suspeitar do diagnóstico de hipogonadismo, sendo recomendada a dosagem de níveis séricos de testosterona. Homens sintomáticos apresentando níveis séricos de Testosterona total abaixo de 300 ng/ml são candidatos a terapia de reposição de testosterona. Evidências atuais indicam que, quando selecionados corretamente, pacientes que recebem reposição de testosterona se beneficiam de melhora na libido, na função erétil, em qualidade de vida nos aspectos gerais e nos quesitos ligados à vida sexual, bem como na densidade óssea e no ganho de massa muscular. No entanto, pacientes com níveis fisiológicos de Testosterona que recebem hormônio exógeno, visando atingir níveis supra-fisiológicos, podem enfrentar efeitos colaterais graves tais como atrofia testicular e alterações comportamentais, como agressividade exacerbada. Deve-se notar que a reposição de testosterona, independentemente da idade e de níveis séricos hormonais pré-tratamento, leva a prejuízo na fertilidade masculina, um fenômeno que pode ser transitório ou persistente. Em pacientes que possuem desejo reprodutivo, a reposição direta de testosterona não deve ser indicada, devendo-se levar em consideração outras opções como o citrato de clomifeno, de ação central. O efeito da reposição de testosterona no risco de câncer de próstata e no risco cardiovascular é ainda controverso; homens com hipogonadismo que sabidamente possuem câncer de próstata ou alto risco vascular devem ser examinados individualmente de modo a terem seus riscos estratificados e mitigados.The decline in Testosterone (T) levels in the ageing male - known as andropause or late-onset hypogonadism - may be responsible for several aspects of quality of life decline in older men: erectile dysfunction, impaired libido, decreased strength and energy, sarcopenia, osteopenia, fatigue and even depression in some cases. Many of these signs and symptoms represent the same alterations that are usually attributed to the process of ageing. When some individual presents with such symptoms, hypogonadism should be suspected, and serum T level should be evaluated. Men who are symptomatic and present low levels of serum Testosterone (generally below 300 ng/ml) are candidates for T replacement therapy. Current evidence shows that, when correctly selected, patients receiving T replacement may benefit from improvement in libido, erectile function, overall and sexual related quality of life, bone density and muscle mass. Conversely, patients with physiological circulating levels of T who receive hormone, aiming at supraphysiologic levels, may face severe side effects, including testicular atrophy and behavioral changes. Of note, T replacement, regardless of age and pre-therapy levels, leads to fertility impairment which can be transient or persistent. Direct testosterone replacement should not be indicated in men who wish to conceive children, although other options are available. The effect of Testosterone replacement on prostate cancer and on cardiovascular risk is still controversial; hypogonadal men known to have prostate cancer or high cardiovascular risk should be examined individually to have their risks stratified and mitigated

Generalised verification of the observer property in discrete event systems

The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system

Generalised verification of the observer property in discrete event systems

The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system

Verification of the observer property in discrete event systems

The observer property is an important condition to be satisfied by abstractions of Discrete Event System (DES) models. This technical note presents a new algorithm that tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure, called OP-Verifier, can be applied to (potentially nondeterministic) automata, with no restriction on the existence of cycles of 'non-relevant' events. This procedure has quadratic complexity in the number of states. The performance of the algorithm is illustrated by a set of experiments