From Algebraic Riccati equations to unilateral quadratic matrix equations: old and new algorithms

The problem of reducing an algebraic Riccati equation $XCX-AX-XD+B=0$ to a unilateral quadratic matrix equation (UQME) of the kind $PX^2+QX+R$ is analyzed. New reductions are introduced which enable one to prove some theoretical and computational properties. In particular we show that the structure preserving doubling algorithm of B.D.O. Anderson [Internat. J. Control, 1978] is nothing else but the cyclic reduction algorithm applied to a suitable UQME. A new algorithm obtained by complementing our reductions with the shrink-and-shift tech- nique of Ramaswami is presented. Finally, faster algorithms which require some non-singularity conditions, are designed. The non-singularity re- striction is relaxed by introducing a suitable similarity transformation of the Hamiltonian

Nonsymmetric algebraic Riccati equations associated with an M-matrix: recent advances and algorithms

We survey on theoretical properties and algorithms concerning the problem of solving a nonsymmetric algebraic Riccati equation, and we report on some known methods and new algorithmic advances. In particular, some results on the number of positive solutions are proved and a careful convergence analysis of Newton\u27s iteration is carried out in the cases of interest where some singularity conditions are encountered. From this analysis we determine initial approximations which still guarantee the quadratic convergence

From hysteria to somatic symptom disorders: Searching for a common psychopathological ground

After decades of manifold contributions aimed at defining hysteria, somatisation and conversion, such syndromes are still neglected and their nosographical definition is debated. The DSM and the ICD have undergone major changes, but their clinical utility with regards to these syndromes is still questionable. On the contrary, the Diagnostic Criteria for Psychosomatic Research represents a useful clinical instrument since it translates psychosocial variables derived from psychosomatic research into operational tools. The present paper offers an overview on the psychopathological description of syndromes such as alexithymia, hypochondriasis, health anxiety, thanatophobia, conversion symptoms, anniversary and reaction which are frequent in clinical practice, but often misdiagnosed due to their absence in the DSM and the ICD. In addition, the influence of culture and cultural changes on the modifications of psychopathological manifestations is described as a further possible source of misdiagnosing and underreporting. New psychopathologies (e.g., multiple chemical sensitivity, orthorexia/vigorexia) that resemble conversion and/or somatisation have been developed, but neither is included in nosography nor taught to clinicians. The aim of the present paper is thus to describe psychopathological manifestations of somatic symptoms and related disorders to help clinicians formulate their diagnosis on the presence of signs and symptoms that can be elicited during a clinical visit, rather than by way of exclusion of other organic or psychiatric disease only

Os desertos habitados: Estado Novo, colonialismo, memória e patrimônio em perspectiva comparada

O presente artigo objetiva discutir a recorrência de algumas narrativas como forma de justificativa para a exploração de povos e territórios colonizados. Estabelece-se uma análise comparativa entre governos estadonovistas no Brasil e em Portugal a partir da exploração de conteúdos de duas revistas de propaganda dos regimes, bem como de discursos científicos, buscando ressaltar sua consonância com os conceitos de colonialismo interno e colonialidade do poder. Finalmente, procura-se apontar algumas recorrências contemporâneas em relação à utilização das mesmas narrativas e criticar a produção de silenciamentos e de esquecimentos em relação às memórias relativas aos povos nativos e às políticas coloniais.L’article cherche à discuter la référence continue aux récits historiques pour justifier la soumission des peuples et des lieux colonisés. Il compare des publications de relations publiques des Estados Novos du Brésil et du Portugal, mettant en évidence des cadres d’interprétation savants utilisant des concepts tels que le colonialisme intérieur et la colonialité. Il pointe ensuite les utilisations récentes de ces mêmes cadres, afin de critiquer la façon dont les peuples autochtones sont réduits au silence, soumis à l’oubli, par le biais de politiques colonialistes.The paper aims at discussing the continuous reference to historical narratives to justify the submission of colonized people and places. It compares a couple of New State (Estado Novo) PR publications, from Brazil and Portugal, highlighting scholarly interpretive frameworks using such concepts as inner colonialism and coloniality. It then points to recent uses of the same frameworks, in order to criticize the ways native people are silenced, submitted to oblivion, through colonialist policies

Mutual visibility by luminous robots without collisions

We consider the Mutual Visibility problem for anonymous dimensionless robots with obstructed visibility moving in a plane: starting from distinct locations, the robots must reach, without colliding, a configuration where no three of them are collinear. We study this problem in the luminous robots model, in which each robot has a visible light that can assume colors from a fixed set. Among other results, we prove that Mutual Visibility can be solved in SSynch with 2 colors and in ASynch with 3 colors. If an adversary can interrupt and stop a robot moving to its computed destination, Mutual Visibility is still solvable in SSynch with 3 colors and, if the robots agree on the direction of one axis, also in ASynch. As a byproduct, we provide the first obstructed-visibility solutions to two classical problems for oblivious robots: collision-less convergence to a point (also known as near-gathering) and circle formation