2,647 research outputs found
Dynamic Thermal Analysis of a Power Amplifier
This paper presents dynamic thermal analyses of a power amplifier. All the
investigations are based on the transient junction temperature measurements
performed during the circuit cooling process. The presented results include the
cooling curves, the structure functions, the thermal time constant distribution
and the Nyquist plot of the thermal impedance. The experiments carried out
demonstrated the influence of the contact resistance and the position of the
entire cooling assembly on the obtained results.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Analysis of short-term dynamic in vivo response of E. coli to alternative substrate perturbations
Passively viewing negatively valenced baby faces attenuates left amygdala activity in healthy females scoring high on 'Harm Avoidance'
HOUSEHOLDS' EXPERIENCES WITH THE RED IMPORTED FIRE ANT IN SOUTH CAROLINA
The red imported fire ant (Solenopsis invicta), abbreviated as RIFA, is believed to have been brought by accident to Mobile, Alabama in the 1930s via ship ballast from South America. The RIFA was first reported in Charleston and Orangeburg counties in South Carolina in 1952 and has since spread to all 46 counties in the state. The RIFA has had adverse impacts on the environments it has infested. In natural environments, the young of ground-nesting insects, reptiles, birds and mammals are subject to RIFA predation. In agriculture, the RIFA damages crops and livestock. The RIFA poses a health threat to humans, as it is aggressive and has a venomous sting. To learn more about the current impacts of the RIFA, a random sample of South Carolina households was conducted between November 1998 and January 1999. This report summarizes the survey results.Environmental Economics and Policy,
Syntheses and Properties of Two-Dimensional, Dicationic Nonlinear Optical Chromophores Based on Pyrazinyl Cores
Six new dicationic 2D nonlinear optical (NLO) chromophores with pyrazinyl-pyridinium electron acceptors have been synthesized by nucleophilic substitutions of 2,6-dichloropyrazine with pyridyl derivatives. These compounds have been characterized as their PF_6^â salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Large red shifts in the intense, Ď â Ď* intramolecular charge-transfer (ICT) transitions on replacing âOMe with âNme_2 substituents arise from the stronger Ď-electron donor ability of the latter. Each compound shows a number of redox processes which are largely irreversible. Single crystal X-ray structures have been determined for five salts, including two nitrates, all of which adopt centrosymmetric packing arrangements. Molecular first hyperpolarizabilities β have been determined by using femtosecond hyper-Rayleigh scattering at 880 and 800 nm, and depolarization studies show that the NLO responses of the symmetric species are strongly 2D, with dominant âoff-diagonalâ β_(zyy) components. Stark (electroabsorption) spectroscopic measurements on the ICT bands afford estimated static first hyperpolarizabilities β_0. The directly and indirectly derived β values are large, and the Stark-derived β_0 response for one of the new salts is several times greater than that determined for (E)-4â˛-(dimethylamino)-N-methyl-4-stilbazolium hexafluorophosphate. These Stark spectroscopic studies also permit quantitative comparisons with related 2D, binuclear RuII ammine complex salts
Thermodynamics of trajectories of the one-dimensional Ising model
We present a numerical study of the dynamics of the one-dimensional Ising
model by applying the large-deviation method to describe ensembles of dynamical
trajectories. In this approach trajectories are classified according to a
dynamical order parameter and the structure of ensembles of trajectories can be
understood from the properties of large-deviation functions, which play the
role of dynamical free-energies. We consider both Glauber and Kawasaki
dynamics, and also the presence of a magnetic field. For Glauber dynamics in
the absence of a field we confirm the analytic predictions of Jack and Sollich
about the existence of critical dynamical, or space-time, phase transitions at
critical values of the "counting" field . In the presence of a magnetic
field the dynamical phase diagram also displays first order transition
surfaces. We discuss how these non-equilibrium transitions in the 1 Ising
model relate to the equilibrium ones of the 2 Ising model. For Kawasaki
dynamics we find a much simple dynamical phase structure, with transitions
reminiscent of those seen in kinetically constrained models.Comment: 23 pages, 10 figure
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