1,721,352 research outputs found
Going 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
Updates on the Multi-channel LYRA ASIC for X/γ- ray Detection Instrument onboard HERMES Space Mission
No full textSIRIO: A High-Speed CMOS Charge-Sensitive Amplifier for High-Energy-Resolution X-γ Ray Spectroscopy with Semiconductor Detectors
No full textA fully integrated pulsed reset charge-sensitive amplifier (CSA) optimized for low-capacitance (< 100 fF) radiation detectors was developed on a 0.35- mu ext{m} low-noise CMOS technology. The CSA was successfully tested with a collimated 10-mm2 silicon drift detector (SDD) and extensively characterized. The experimental setup and the achieved spectrometry results with SDD are described for triangular and trapezoidal shaping filters with peaking times ranging from {t_{mathrm {peak}}=0.1!-!12.8,,mu ext {s}} at an operating temperature of -35 °C. With a minimum equivalent noise charge (ENC) of 3.4 electrons rms measured at t_{mathrm {peak}} = 5.6,,mu ext{s} with the SDD connected, corresponding to a pulser linewidth of 29.9 eV full-width at half-maximum (FWHM), the presented results are among the best recorded for integrated CSA designs. The measured ENC at t_{mathrm {peak}} = 0.1,,mu ext{s} is of 8.1 e- rms (70.7 eV FWHM) corresponding to 138.4 eV FWHM on the 5.9 keV 55Fe line. The open-input rise time is below 10 ns and the pulsed reset speed of 4 keV/ns allows a full recovery from a saturated output voltage in 63 ns. These latter results, together with the low-noise performance at short peaking times, make this preamplifier best suited for high-count rate spectroscopy applications that require a research-grade performance, such as in instrumentation for X and gamma spectroscopy and imaging for synchrotron radiation facilities, as well as other scientific or industrial applications
Dynamic range enhancement circuit and characterization of non-stationary gain effects in pulsed-reset charge sensitive amplifiers
No full textExcess noise and spectra distortion in pulsed-reset charge sensitive amplifiers due to non-stationary gain: analytical model and Monte Carlo simulations
No full textMulti-symplectic Lie Group Thermodynamics for Covariant Field Theories
No full textWe propose a multi-symplectic generalisation of Souriau’s Lie group thermodynamics for first order parametrised classical field theories. A new notion of general covariant Gibbs state functional is defined in terms of the multi-momentum map associated to the lifted action of the diffeomorphisms group on the fields extended phase space. We elaborate on the use of such functional toward a covariant statistical mechanic description of fully constrained field theories, at the crossroad between geometrical methods and information theory
Comparison of conventional and hybrid density functional approaches. Cationic hydrides of first-row transition metals as a case study
No full textCovariant momentum map thermodynamics for parametrized field theories
No full textA general-covariant statistical framework capable of describing classical fluctuations of the gravitational field is a thorny open problem in theoretical physics, yet ultimately necessary to understand the nature of the gravitational interaction, and a key to quantum gravity. Inspired by Souriau's symplectic generalization of the Maxwell-Boltzmann-Gibbs equilibrium in Lie group thermodynamics, we investigate a space-time-covariant formulation of statistical mechanics for parametrized first-order field theories, as a simplified model sharing essential general covariant features with canonical general relativity. Starting from a covariant multi-symplectic phase space formulation, we define a general-covariant notion of Gibbs state in terms of the covariant momentum map associated with the lifted action of the diffeomorphisms group on the extended phase space. We show how such a covariant notion of equilibrium encodes the whole information about symmetry, gauge and dynamics carried by the theory, associated with a canonical spacetime foliation, where the covariant choice of a reference frame reflects in a Lie algebra-valued notion of local temperature. We investigate how physical equilibrium, hence time evolution, emerges from such a state and the role of the gauge symmetry in the thermodynamic description
Analytical Model of the Discharge Transient in Pulsed-Reset Charge-Sensitive Amplifiers
No full textA study of the reset transient of charge-sensitive amplifiers operating with a pulsed switch in parallel to the feedback capacitance is presented. Analytical models have been developed for amplifiers in both linear and slew rate regimes during the reset phase. The models predict the time interval required to reset the amplifier that, in most cases, significantly differs by the simple discharge of the feedback capacitance through the switch resistance and strongly depends on the open-loop gain and bandwidth of the core amplifier and on the input capacitance. The models also quantitatively predict spurious voltage transients at the preamplifier's input and possible ringings at the output, as a function of the main general parameters of the circuit. A case application study of the presented model is proposed for low-capacitance detectors, such as semiconductor drift detectors or small pixel detectors
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