1,721,746 research outputs found
Decay times of an N-normal-mode system
No full textWe derive a general closed-form expression for the decay times at the N-normal modes for a system of coupled oscillators, described by a set of linear differential equations. The formula is helpful to study the sensitivity of resonant gravitational-wave antenna and, more generally, in matching mechanical or electrical resonant systems. © 1993 Società Italiana di Fisica
Mechanical thermal noise in coupled oscillators
No full textA correct prediction of the thermal noise spectrum is crucial to design properly gravitational wave detectors which are intrinsically limited by this kind of fluctuation. The off-resonance slope of the spectrum can be predicted using the fluctuation-dissipation theorem and it must be consistent and compatible with the spectrum obtained through the normal mode representation. We investigate this comparison leading to a deeper understanding of the thermal noise prediction tools
Test mass suspensions
No full textIn this chapter we describe the designs used for the suspension systems for Advanced LIGO and Advanced Virgo, which support the test masses that serve as the mirrors for the interferometers. These systems are attached to the last stage of the seismic isolation systems for the detectors. Their designs are chosen to minimize thermal noise, residual seismic noise and technical noise, while allowing control of position and orientation of the test masses, and enabling the interferometers to function. Advanced LIGO and Advanced Virgo differ in their approach to seismic isolation and control. Thus, although the final stages of the suspension systems have clear similarities, there are significant differences in the overall suspension systems. Hence we discuss the designs of the two systems separately. In a concluding section we compare the two systems and note that although the two projects have taken different approaches in certain areas, there are key concepts that show similarities and that both designs should meet their requirements
Anelastic; elastic properties of a synthetic monocrystal of bismuth germanate Bi4Ge3O12 at low temperatures
No full textDevelopment of a lumping methodology for the analysis of the excited states in plasma discharges operated with argon, neon, krypton, and xenon
Full text linkIn this paper, a methodology is presented to compute the plasma properties (e.g.,, density and temperature) accounting for the dynamics of the excited states. The proposed strategy applies to both zero-dimensional (0D) models and multidimensional fluid and hybrid codes handling low-pressure (<50 mTorr) plasma discharges filled with argon, neon, krypton, and xenon gases. The paper focuses on two main aspects: (i) a lumping methodology is proposed to reduce the number of reactions and species considered in order to keep at bay the computational cost without a major loss of accuracy; (ii) the influence that different datasets of cross sections have on the results has been assessed. First, the lumping methodology has been implemented in a 0D model accounting for singly charged ions, neutrals, along with 1s and 2p excited states (Paschen notation). Metastable and resonant are treated as two separate species within the 1s energy level respectively). The results have been benchmarked against those obtained treating each energy level of the excited states as an individual species. Differences lower than 1% have been obtained. Second, the results of the 0D model have been compared against measurements of electron density and temperature performed on an inductively coupled plasma. Numerical predictions and experiments present a disagreement up to 20%-30%, which is comparable to the uncertainty band of the measurements. Finally, the lumping strategy has been implemented in a 2D fluid code to assess its computational affordability, and the results have been compared against the experiments as well. A variance up to 30% in electron density and temperature is registered adopting different datasets of cross sections
Single device telemetric algorithm for absolute position measurement using a CCD camera.
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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