13,284 research outputs found
Note: Contrast enhancement and artifact suppression in computed tomography using sinogram normalization
No full textThe intensity and direction of the incident beam at the sample position in synchrotron full-field transmission X-ray microscopy is subject to change. Incident-beam fluctuation in computed tomography results in significant contrast degradation of the reconstructed image. In the present study, we devised a simple method by which that problem could be corrected using sinogram normalization. According to our results, the image contrast was improved by 13%, and the artifacts were suppressed. © 2018 Author(s).11Nsciescopu
Gold-conjugated protein nanoarrays through block-copolymer lithography: From fabrication to biosensor design
No full text
Topological criterion for selection of quintic Pythagorean-hodograph Hermite interpolants
No full textChoi, Hyeong In; Farouki, Rida T.; Kwon, Song-Hwa; Moon, Hwan Pyo. (2006). Topological criterion for selection of quintic Pythagorean-hodograph Hermite interpolants. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/4320
Highly Efficient Single-Stage DAB Microinverter Using a Novel Modulation Strategy to Minimize Reactive Power
No full textThis article proposes a highly efficient single-stage dual-active-bridge (DAB) microinverter with a novel modulation strategy to minimize the reactive power flow of DAB converter. Using the proposed modulation, the DAB microinverter achieves good controllability and high efficiency with the following features. First, the variable-frequency control algorithm linearizes the nonlinear function of the phase shift angle, enabling a simple closed-loop control for the sinusoidal trajectory tracking. Second, the proposed modulation strategy minimizes the reactive power flow during the switching period while guaranteeing the zero-voltage-switching (ZVS) turn-on of all switches. With minimized reactive power, current stress and power losses are significantly reduced. Thus, the DAB microinverter achieves a maximum efficiency of 96.87%. Third, the proposed phase shift angles and switching frequency are obtained in an analytic form, thereby that they are computationally simple and easy to implement. The operation principle of the proposed modulation strategy is theoretically analyzed and verified. Experimental results based on a 330-W prototype module are conducted to evaluate the performance of the proposed inverter and to verify the analysis.11Nsciescopu
High-Efficiency Two-Stage Three-Level Grid-Connected Photovoltaic Inverter
No full textThis paper proposes a high-efficiency two-stage three-level grid-connected photovoltaic (PV) inverter. The proposed two-stage inverter comprises a three-level step-up converter and a three-level inverter. The three-level step-up converter not only improves the power-conversion efficiency by lowering the voltage stress but also guarantees the balancing of the dc-link capacitor voltages using a simple control algorithm; it also enables the proposed inverter to satisfy the VDE 0126-1-1 standard of leakage current. The three-level inverter minimizes the overall power losses with zero reverse-recovery loss. Furthermore, it reduces harmonic distortion, the voltage ratings of the semiconductor device, and the electromagnetic interference by using a three-level circuit configuration; it also enables the use of small and low-cost filters. To control the grid current effectively, we have used a feed-forward nominal voltage compensator with a mode selector; this compensator improves the control environment by presetting the operating point. The proposed high-efficiency two-stage three-level grid-connected PV inverter overcomes the low efficiency problem of conventional two-stage inverters, and it provides high-power quality with maximum efficiency of 97.4%. Using a 3-kW prototype of the inverter, we have evaluated the performance of the model and proved its feasibility.113sciescopu
High-Efficiency Bridgeless Single-Power-Conversion Battery Charger for Light Electric Vehicles
No full textCharging batteries of light electric vehicles require chargers with high efficiency and a high power factor. To meet this need, this paper presents a bridgeless single-power-conversion battery charger composed of an isolated step-up ac-dc converter with a series-resonance circuit. The bridgeless configuration reduces the conduction losses associated with the input diode rectifier, and the series-resonance circuit reduces the reverse-recovery losses of the output diodes by providing zero-current switching. In addition, direct and series-resonance current injections enable bidirectional core excitation by the transformer, thereby allowing high-power capability. The control algorithm derived from feedback linearization is also developed, which allows the proposed charger to correct the power factor and regulate the output power in a single-stage power conversion. This simple circuit structure leads to high efficiency and a high power factor. The theoretical concepts of the proposed charger are verified experimentally using a 1.7-kW prototype.11Nsciescopu
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