3,485 research outputs found
State feedback linearized model for phase-controlled series-parallel resonant converters
This paper proposes a linearized large-signal state space model for phase-controlled series-parallel resonant converter. The model combines multiple-frequency and average state-space modeling techniques to generate a universal model with DC state variables that are easier to control compared to the fast resonant tank dynamics. In order to perform linearization, the proposed model utilizes a state feedback scheme from output filter inductor current. The model also serves as a tool for large signal prediction/estimation of converter state variables. The model accuracy was verified by comparing with a detailed switching model of the converter built in MATLAB simulation environment
New insulating phases of two-dimensional electrons in high Landau levels: observation of sharp thresholds to conduction
The intriguing re-entrant integer quantized Hall states recently discovered
in high Landau levels of high-mobility 2D electron systems are found to exhibit
extremely non-linear transport. At small currents these states reflect
insulating behavior of the electrons in the uppermost Landau level. At larger
currents, however, a discontinuous and hysteretic transition to a conducting
state is observed. These phenomena, found only in very narrow magnetic field
ranges, are suggestive of the depinning of a charge density wave state, but
other explanations can also be constructed.Comment: 5 pages, 5 figure
The Complex Topology of Chemical Plants
We show that flowsheets of oil refineries can be associated to complex
network topologies that are scale-free, display small-world effect and possess
hierarchical organization. The emergence of these properties from such man-made
networks is explained as a consequence of the currently used principles for
process design, which include heuristics as well as algorithmic techniques. We
expect these results to be valid for chemical plants of different types and
capacities.Comment: 7 pages, 5 figures and 1 tabl
Pediatric Psychologists’ Career Satisfaction: 2015 Society of Pediatric Psychology Workforce Survey Results.
Little is known about the career satisfaction of pediatric psychologists, who specialize in psychological research, teaching, and clinical service in the context of pediatric health care. As part of the larger Society of Pediatric Psychology Workforce Survey and in collaboration with the American Psychological Association Center for Workforce Studies, this study aimed to (1) describe the career domains which pediatric psychologists perceive to be important and their satisfaction in each domain, and (2) compare satisfaction of pediatric psychologists across work settings, number of positions, appointment duration, professional roles, career stage, academic rank, and gender. Responses from 336 pediatric psychologists demonstrated high career satisfaction. Domains of career satisfaction that received mean scores indicating high importance include balance of work and personal lives, peer/collegial support, and flexibility and choice in the workplace, but on average respondents reported being only somewhat satisfied in these domains. Total satisfaction scores were significantly higher among pediatric psychologists in 9–10-month appointments, primarily research careers, and at higher academic ranks, but scores were similar across employment settings and genders. To enhance career satisfaction and retention, pediatric psychologists may seek additional mentorship or explore new employment roles, and administrators and managers may consider adopting workplace policies or making environmental changes that could address specific areas of need
Isotope Effect in the Presence of Magnetic and Nonmagnetic Impurities
The effect of impurities on the isotope coefficient is studied theoretically
in the framework of Abrikosov-Gor'kov approach generalized to account for both
potential and spin-flip scattering in anisotropic superconductors. An
expression for the isotope coefficient as a function of the critical
temperature is obtained for a superconductor with an arbitrary contribution of
spin-flip processes to the total scattering rate and an arbitrary degree of
anisotropy of the superconducting order parameter, ranging from isotropic
s-wave to d-wave and including anisotropic s-wave and mixed (s+d)-wave as
particular cases. It is found that both magnetic and nonmagnetic impurities
enhance the isotope coefficient, the enhancement due to magnetic impurities
being generally greater than that due to nonmagnetic impurities. From the
analysis of the experimental results on La-Sr-Cu-M-O high temperature
superconductor, it is concluded that the symmetry of the pairing state in this
system differs from a pure d-wave.Comment: 4 pages, 3 figure
Efficient Selfconsistent Calculations of Multiband Superconductivity in UPdAl
An efficient physically motivated computational approach to multiband
superconductivity is introduced and applied to the study of the gap symmetry in
a heavy-fermion, UPdAl. Using realistic pairing potentials and accurate
energy bands that are computed within density functional theory,
self-consistent calculations demonstrate that the only accessible
superconducting gap with nodes exhibits d-wave symmetry in the
representation of the point group. Our results suggest that in a
superconductor with gap nodes the prevailing gap symmetry is dictated by the
constraint that nodes must be as far as possible from high-density areas
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