Another Avenue for Anatomy of Income Comparisons : Evidence from Hypothetical Choice Experiments

September 2010, Revised December 2010, Secondly Revised November 2011, Thirdly Revised May 2012, Fourthly Revised March 2013

Pulsations in main sequence OBAF-type stars

CONTEXT: The third Gaia data release provides photometric time series covering 34 months for about 10 million stars. For many of those stars, a characterisation in Fourier space and their variability classification are also provided. This paper focuses on intermediate- to high-mass (IHM) main sequence pulsators (M ≥  1.3 M⊙) of spectral types O, B, A, or F, known as β Cep, slowly pulsating B (SPB), δ Sct, and γ Dor stars. These stars are often multi-periodic and display low amplitudes, making them challenging targets to analyse with sparse time series. AIMS: We investigate the extent to which the sparse Gaia DR3 data can be used to detect OBAF-type pulsators and discriminate them from other types of variables. We aim to probe the empirical instability strips and compare them with theoretical predictions. The most populated variability class is that of the δ Sct variables. For these stars, we aim to confirm their empirical period-luminosity (PL) relation, and verify the relation between their oscillation amplitude and rotation. METHODS: All datasets used in this analysis are part of the Gaia DR3 data release. The photometric time series were used to perform a Fourier analysis, while the global astrophysical parameters necessary for the empirical instability strips were taken from the Gaia DR3 gspphot tables, and the v sin i data were taken from the Gaia DR3 esphs tables. The δ Sct PL relation was derived using the same photometric parallax method as the one recently used to establish the PL relation for classical Cepheids using Gaia data. RESULTS: We show that for nearby OBAF-type pulsators, the Gaia DR3 data are precise and accurate enough to pinpoint them in the Hertzsprung-Russell (HR) diagram. We find empirical instability strips covering broader regions than theoretically predicted. In particular, our study reveals the presence of fast rotating gravity-mode pulsators outside the strips, as well as the co-existence of rotationally modulated variables inside the strips as reported before in the literature. We derive an extensive period–luminosity relation for δ Sct stars and provide evidence that the relation features different regimes depending on the oscillation period. We demonstrate how stellar rotation attenuates the amplitude of the dominant oscillation mode of δ Sct stars. CONCLUSIONS: The Gaia DR3 time-series photometry already allows for the detection of the dominant (non-)radial oscillation mode in about 100 000 intermediate- and high-mass dwarfs across the entire sky. This detection capability will increase as the time series becomes longer, allowing the additional delivery of frequencies and amplitudes of secondary pulsation modes

Nonlinear FET modeling from a single NVNA measurement by nonlinear function sampling

We propose an automatic method for FET quasi-static (QS) modeling based on just one full-swing, full-bandwidth (BW) Nonlinear Vector Network Analyzer (NVNA) measurement under a specific two-tone excitation. The procedure leverages on a newly defined Nonlinear Function Sampling (NFS) operator and on 2D time-domain waveform analysis, allowing for model identification by just solving a system of linear equations. The model has been validated under continuous-wave (CW) operation at 2.5 and 5 GHz, and for 3rd-order intermodulation distortion (IM3) prediction at 2.5 GHz

Measurement-Based FET Analytical Modeling Using the Nonlinear Function Sampling Approach

A novel and fast method for the measurement-based identification of an analytical field-effect transistor (FET) compact model from large-signal waveforms is presented. Based on a two-tone two-port experiment, a recently published nonlinear function sampling (NFS) operator providing the samples of the FET state functions in the voltage domain is here exploited, for the first time, to extract an equivalent-circuit model. The approach is demonstrated on a 250-nm gallium nitride (GaN)-on-silicon carbide (SiC) high-electron-mobility transistor (HEMT) at 2.5 and 5 GHz

Automatic Extraction of Measurement-Based Large-Signal FET Models by Nonlinear Function Sampling

A new method is proposed for the accurate experimental characterization and fully automated extraction of compact nonlinear models for field-effect transistors (FETs). The approach, which leads to a charge-conservative description, is based on a single large-signal measurement under a two-tone sinusoidal wave excitation. A suitable choice of tone frequencies, amplitudes, and bias allows to adequately characterize the transistor over the whole safe operating region. The voltage-controlled nonlinear functions describing the two-port FET model can be computed over an arbitrarily dense voltage domain by solving an overdetermined system of linear equations. These equations are expressed in terms of a new nonlinear function sampling operator based on a biperiodic Fourier series description of the acquired frequency spectra. The experimental validation is carried out on a 0.25- mu ext{m} gallium nitride (GaN) on silicon carbide (SiC) high-electron-mobility transistor (HEMT) under continuous-wave (CW) and two-tone excitation (intermodulation distortion test)