The radiating part of circular sources

An analysis is developed linking the form of the sound field from a circular source to the radial structure of the source, without recourse to far-field or other approximations. It is found that the information radiated into the field is limited, with the limit fixed by the wavenumber of source multiplied by the source radius (Helmholtz number). The acoustic field is found in terms of the elementary fields generated by a set of line sources whose form is given by Chebyshev polynomials of the second kind, and whose amplitude is found to be given by weighted integrals of the radial source term. The analysis is developed for tonal sources, such as rotors, and, for Helmholtz number less than two, for random disk sources. In this case, the analysis yields the cross-spectrum between two points in the acoustic field. The analysis is applied to the problems of tonal radiation, random source radiation as a model problem for jet noise, and to noise cancellation, as in active control of noise from rotors. It is found that the approach gives an accurate model for the radiation problem and explicitly identifies those parts of a source which radiate.Comment: Submitted to Journal of the Acoustical Society of Americ

Upper limit to ΩB\Omega_B in scalar-tensor gravity theories

In a previous paper (Serna & Alimi 1996), we have pointed out the existence of some particular scalar-tensor gravity theories able to relax the nucleosynthesis constraint on the cosmic baryonic density. In this paper, we present an exhaustive study of primordial nucleosynthesis in the framework of such theories taking into account the currently adopted observational constraints. We show that a wide class of them allows for a baryonic density very close to that needed for the universe closure. This class of theories converges soon enough towards General Relativity and, hence, is compatible with all solar-system and binary pulsar gravitational tests. In other words, we show that primordial nucleosynthesis does not always impose a very stringent bound on the baryon contribution to the density parameter.Comment: uuencoded tar-file containing 16 pages, latex with 5 figures, accepted for publication in Astrophysical Journal (Part 1

Ten Years' Experience with the Swiss National Bank's Monetary Policy Strategy

In December 1999 the Swiss National Bank (SNB) abandoned monetary targeting and introduced a new monetary policy strategy. The cornerstones of the new framework are an explicit definition of what the SNB considers to be price stability, a forecast of inflation over a three-year horizon, and a target range for the three-month Swiss franc Libor. The strategy lived up to expectations in every respect and contributed to strengthening the SNB's credibility. In particular, the new framework's flexibility proved successful in times of financial stress. The term reference interest rate contains an automatic monetary stabilizer that has insulated the nonfinancial sector from much of the turbulence. The major challenge lying ahead is sustained accuracy in the assessment of future inflation

Influence of Wear on the Sizing Layer and Desizing of Single Carbon Fibre-to-Fibre Friction

Carbon fibres are sized for use in the reinforcement of composite materials. The purposes for sizing include improving yarn cohesion, which is necessary for the weaving process, and increasing the adhesion between the fibres and the matrix. Nevertheless, during weaving, some fibrillation can occur, and that has detrimental effects on the weaving productivity and on the composite's properties. The purposes of this research were: (a) to determine whether abrasive wear between sliding fibres would modify the sizing and (b) to study the influence of sizing on the friction between fibres. The same type of carbon fibre was subjected to different desizing processes. The coefficient of friction between single fibres was obtained before and after desizing. The effects of sizing and sliding distance on frictional behaviour were investigated, and are related to the observed the wear of sizing layer. In fact, it increased with sliding distance and induced a decrease in the coefficient of friction. Moreover, an efficient desizing process induced a decrease of the coefficient of friction

Performance of the new ACR/EULAR classification criteria for systemic sclerosis in clinical practice

Objective. The preliminary classification criteria for SSc lack sensitivity for mild/early SSc patients, therefore, the new ACR/EULAR classification criteria for SSc were developed. The objective of this study was to evaluate the performance of the new classification criteria for SSc in clinical practice in a cohort of mild/early patients. Methods. Consecutive patients with a clinical diagnosis of SSc, based on expert opinion, were prospectively recruited and assessed according to the EULAR Scleroderma Trials and Research group (EUSTAR) and very early diagnosis of SSc (VEDOSS) recommendations. In some patients, missing values were retrieved retrospectively from the patient's records. Patients were grouped into established SSc (fulfilling the old ACR criteria) and mild/early SSc (not fulfilling the old ACR criteria). The new ACR/EULAR criteria were applied to all patients. Results. Of the 304 patients available for the final analysis, 162/304 (53.3%) had established SSc and 142/304 (46.7%) had mild/early SSc. All 162 established SSc patients fulfilled the new ACR/EULAR classification criteria. The remaining 142 patients had mild/early SSc. Eighty of these 142 patients (56.3%) fulfilled the new ACR/EULAR classification criteria. Patients with mild/early SSc not fulfilling the new classification criteria were most often suffering from RP, had SSc-characteristic autoantibodies and had an SSc pattern on nailfold capillaroscopy. Taken together, the sensitivity of the new ACR/EULAR classification criteria for the overall cohort was 242/304 (79.6%) compared with 162/304 (53.3%) for the ACR criteria. Conclusion. In this cohort with a focus on mild/early SSc, the new ACR/EULAR classification criteria showed higher sensitivity and classified more patients as definite SSc patients than the ACR criteri

Representação política em Althusius e Hobbes

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas, Programa de Pós-Graduação em Filosofia, Florianópolis, 2012Pretende-se investigar o surgimento da ideia de representação política nos primórdios da era moderna, no período de transformação gradativa dos reinos feudais em Estados nacionais. O estudo será realizado pelo confronto das teorias de Johannes Althusius e Thomas Hobbes. O primeiro é autor de Política e um defensor da soberania popular e da responsabilidade dos representantes ante os representados. Ele recorre à representação tanto como forma expressiva da vontade do povo quanto como meio de controle da atuação dos governantes. Concebe a sociedade com base em grupos, como reunião interativa de associações, que se iniciam no núcleo familiar estendido, característico do medievo, e progressivamente alcançam as relações complexas dos estamentos sociais sob um rei ou imperador. O tema em Hobbes será fundado no Leviatã, onde a representação é um instrumento de unificação pacificadora. Partindo da diversidade de vontades de indivíduos considerados como originalmente livres e iguais, os quais em função de seu próprio poder lutam por tudo que querem, Hobbes deseja demonstrar que só pela renúncia e transferência irrevogável destes direitos naturais ilimitados para um soberano absoluto é que os homens podem estabelecer um Estado. Ser representado é o caminho para construir uma vida boa numa sociedade em que todos devem submeter-se incondicionalmente a um representante onipotente. Na parte final, a leitura crítica e historicamente situada destas obras-primas será seguida de análise conceitual apoiada em Hanna Pitkin e seu The Concept of Representation.Abstract : In this essay I intend to investigate the emerging of the idea of political representation in the early stages of modern era, during the period of gradual transformation of feudal kingdoms into national States. This study will be accomplished by confronting the theories of Johannes Althusius and Thomas Hobbes. The first is the author of the Politics, a defender of the popular sovereignty, and of the responsibility of the representatives in view of the represented. He resorts to representation as much as in a way to express people's will, as in a way to control the governor's actions. He conceives society as being group-based, as an interactive reunion of associations that start in the extended nuclear family, characteristic of the medieval, and progressively reaches the complex relations of the social estates under a king or an emperor. The same theme in Hobbes will be found in the Leviathan, where the representation is an instrument of pacifying unification. Starting from the diversity of the individuals' wills considered originally as being free and equals, whom because of their own power will fight for everything they want, Hobbes wishes to demonstrate that only through the irrevocable renounce and transference of these unlimited natural rights to an absolute sovereign is that men can establish a State. Being represented is the only path to construct a good life in a society where everyone must submit unconditionally to an omnipotent representative. In the final part of this essay the critical and historically situated reading of these two masterpieces will be followed by a conceptual analysis backed in Hanna Pitkin's book The Concept of Representation