This paper proposes a 4.3 kW three-phase integrated PFC AC-AC resonant inverter for Induction Heating (IH) Application. This converter is composed by three independent resonant inverters with non-smoothed DC link that...
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This paper proposes a 4.3 kW three-phase integrated PFC AC-AC resonant inverter for Induction Heating (IH) Application. This converter is composed by three independent resonant inverters with non-smoothed DC link that achieves high power factor operation. The magnetic coupling of the three coils was modeled by using the impedance matrix for characterizing the resonant behavior of the arrangement. The coils arrangement with weak coupling between coils is applied for induction water heater. Experimental results validate the modes of operation with ZVS and the converter performance in the entire power input range (PF and THD).
In this paper, a Four-Port AC/DC-DC/AC conversion system is proposed using two full-bridge converters and a high-frequency transformer following the principle of Dual Active Bridge Converter. Two full-bridge AC/DC sin...
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In this paper, a Four-Port AC/DC-DC/AC conversion system is proposed using two full-bridge converters and a high-frequency transformer following the principle of Dual Active Bridge Converter. Two full-bridge AC/DC single-phase converters are connected by coupling their boost inductance to create a high-frequency transformer of the resulting proposed converter. The isolated power transfer between converters is controlled by the duty cycles and the phase-shift applied to the primary and secondary of the split transformer. The boundaries of the switching modes and the power transferred through the high-frequency transformer were obtained analytically. The system feasibility was validated by simulations and by a 300 W prototype with 94.9% maximum efficiency.
Nonreciprocal devices – in which light is transmitted with different efficiencies along opposite directions – are key technologies for modern photonic applications, yet their compact and miniaturized implementation ...
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This paper proposes three unidirectional ac-dc conversion power systems for wind energy conversion system (WECS) applications. These topologies are based on Vienna rectifiers and have reduced number of controlled swit...
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This paper proposes three unidirectional ac-dc conversion power systems for wind energy conversion system (WECS) applications. These topologies are based on Vienna rectifiers and have reduced number of controlled switches, which allows reduce size, costs and is still possible to obtain low current harmonic distortion. They are composed of a series connection of two three-phase converters associated to a permanent magnet synchronous machine (PMSM) by an open-end winding (OEW) configuration. Compared with the three-phase rectifier with reduced number of controlled switches, proposed topologies offer a higher levels-per-switch ratio, allowing to achieve a sinusoidal converter current with same or lower harmonic content. Besides this, they can offer lower switch blocking voltage. These characteristics make them very interesting options to the manufacturers due to reduced costs and better power quality offered. The system model, PWM technique and control strategy are discussed. Simulation and experimental results are provided in order to validate their performance and feasibility.
Phonons, or vibrational quanta, are behind some of the most fundamental physical phenomena in solids, including superconductivity, Raman processes, and broken-symmetry phases. It is therefore of fundamental importance...
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Controlling and guiding optical spins and pseudospins over an interface is of great importance in the emerging fields of spintronics and valleytronics, holding the promise for new degrees of freedom in the quest for e...
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Controlling and guiding optical spins and pseudospins over an interface is of great importance in the emerging fields of spintronics and valleytronics, holding the promise for new degrees of freedom in the quest for efficient information transport. Here we explore the general possibilities offered by metasurfaces to route optical momentum, spin and helicity through surface waves. We show how anisotropy and bianisotropy can be engineered to impart extreme directionality to local spin excitations. While most previous works have focused on out-of-plane spins, in-plane excitations have become particularly important for valleytronic applications relying on two-dimensional materials, and they offer specific challenges addressed here with suitably engineered nonlocality in metasurfaces.
We leverage aperiodic temporal modulations and nonreciprocity to realize PT-symmetric phenomena without the need for gain and loss provided by external mechanisms. We develop our approach using a general coupled-mode ...
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We leverage aperiodic temporal modulations and nonreciprocity to realize PT-symmetric phenomena without the need for gain and loss provided by external mechanisms. We develop our approach using a general coupled-mode framework, and verify our results via detailed simulations in a conservative electronic circuit, demonstrating wave phenomena such as scattering PT-phase transition and anisotropic transmission resonances in a Hermitian system. Our concept opens the possibility of implementing PT-symmetric phenomena without gain, with applications in sensing, communications, and a broad range of quantum physics.
Purpose To develop and characterize individualized dose and quality measures at organ level compared to their generic counterparts across a clinical CT dataset. Materials and methods The study included 9801 chest-abdo...
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Purpose To develop and characterize individualized dose and quality measures at organ level compared to their generic counterparts across a clinical CT dataset. Materials and methods The study included 9801 chest-abdomen-pelvis and abdomen-pelvis CT exams (7,763 patients, mean age, 56 ± 17 years; 4113 women) representing 20 unique protocols. For each exam, patient-specific organ dose of all radiosensitive organs was estimated using a validated method by generating personalized computational phantoms and Monte Carlo simulations. Effective dose ( E OD ) was calculated by weighted sum of the organ doses. Liver dose, O D liver , noise in the liver, N liver , and observer model detectability, d ′ , were assessed within the liver as examples of individualized, organ-based image assessment measurements. The organ-based measurements ( O D liver , E OD , and N liver ) were compared to their generic counterparts: ssize-specific ddose estimates (SSDE), effective dose based on dose length product ( E DLP ), and whole-body noise ( N global ), respectively. Results Generic dose values were substantially higher than individualized estimates for SSDE vs. O D liver (median of all exams: 51.2 %, p < 0.001) and E DLP vs. ED OD (median: 41.0 %, p < 0.001). N global was generally lower than N liver (median: −7.2 %, p < 0.001). The correlation relationships of E OD and d ′ were substantially varied ( R 2 range: 0–0.5) for different patient sizes and scan parameters. Conclusions Demonstrated across a population of exams, individualized organ-based measurements of dose and quality are feasible. Generic measures cannot fully represent individualized organ-based values. The correlation relationships between individualized dose and image quality values varies for different vendors and protocols, implying imaging optimization is best when done semi-independently for each factor using individualized measurements.
This paper presents the use of an active series compensator to improve the performance of wind energy conversion systems (WECS) using a grid-connected doubly-fed induction generator (DFIG) during grid disturbances. Th...
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ISBN:
(数字)9781728158266
ISBN:
(纸本)9781728158273
This paper presents the use of an active series compensator to improve the performance of wind energy conversion systems (WECS) using a grid-connected doubly-fed induction generator (DFIG) during grid disturbances. The series active compensator is based on a two-level three-phase inverter cascaded with three H-bridge inverters operating with floating capacitors and without using injection transformer. The converter operating principles and control strategies are discussed. Steady-state simulations were obtained for the DFIG with constant torque. Experimental results are also presented. It was verified that the proposed system is able to maintain sinusoidal and compensated voltages on the DFIG stator windings, even during a distorted grid voltage sag event.
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