DSpace community: 電機工程學系

Zernike moment and local distribution fitting fuzzy energy-based active contours for image segmentation

title: Zernike moment and local distribution fitting fuzzy energy-based active contours for image segmentation abstract: 摘要： This paper presents a new region-based active contour model for extracting the object boundaries in an image, based on techniques of curve evolution. The proposed model introduces an energy functional that involves intensity distributions in local image regions and fuzzy membership functions. The local image intensity distribution information used to guide the motion of the contour, in the paper, is derived by Hueckel operator in the neighborhood of each image point. The parameters of Hueckel operator are estimated by a set of orthogonal Zernike moments before curve evolution. Meanwhile, the fuzzy membership functions are used to measure the association degree of each image pixel to the region outside and inside the contour. To minimize the energy functional, instead of solving the Euler–Lagrange equation of the underlying problem, the paper employs a direct method to compute the energy alterations. As a result, the model can deal with images with intensity inhomogeneity. In addition, the model effectively alleviates the sensitivity to contour initialization. Moreover, the model reduces computational cost, avoids problems associated with choosing time steps as well as allows fast convergence to the segmentation solutions. Experimental results on synthetic, real images and comparisons with other models show the desired performances of the proposed model. 其他題名： SIViP 出版者： London: Springer London 出版日期： 2014-01 出處： Signal, image and video processing, 2014-01, Vol.8 (1), p.11-25 版權： Springer-Verlag London 2012 識別號： ISSN: 1863-1703 識別號： EISSN: 1863-1711 識別號： DOI: 10.1007/s11760-012-0415-0

Yellow-emitting Si-doped GaN: Favorable characteristics for intermediate band solar cells

title: Yellow-emitting Si-doped GaN: Favorable characteristics for intermediate band solar cells abstract: 摘要： The photovoltaic performance of a GaN p-n-n homojunction is characterized using the air-mass (AM) 1.5G solar spectrum and a 532-nm green laser. The n-type active region is doped with Si in order to create an intermediate band for sub-bandgap photon absorption. When the doping level in the active region increases from 0 (unintentionally doped) to n=1×1018cm−3, the short-circuit current density (Jsc) under illumination by the green laser is noticeably reduced, whereas the Jsc under AM1.5G is significantly enhanced by 90%. The results indicate that the Si-induced intermediate band is partially filled, a key feature favored by intermediate band solar cells. •GaN p-n-n homojunction solar cells are designed and fabricated to demonstrate the capability of sub-bandgap photon absorption.•The n-type active region is doped with Si in order to create an intermediate band.•Under the illumination of AM 1.5G, the short-circuit current density is significantly enhanced by 90% with increased Si-doping in the active region.•The partially filled intermediate band is confirmed with a two-photon absorption measurement. 出版者： Elsevier B.V 出版日期： 2015-01 出處： Solar energy materials and solar cells, 2015-01, Vol.132, p.544-548 資源來源： Elsevier ScienceDirect Journals Complete 版權： 2014 Elsevier B.V. 識別號： ISSN: 0927-0248 識別號： EISSN: 1879-3398 識別號： DOI: 10.1016/j.solmat.2014.10.008

X-band voltage-controlled oscillator with built-in envelope detection

title: X-band voltage-controlled oscillator with built-in envelope detection abstract: 摘要： A wide‐tuning‐range X‐band voltage‐control oscillator (VCO) with built‐in envelope detectors is designed and measured. The VCO is implemented using a 0.18‐μm CMOS technology. The VCO core is composed of a cross‐coupled pair and a parallel‐LC resonator. The variable capacitance is implemented using MOS varactors. Large varactor capacitance and small transistor size are used to reduce the tuning‐range degradation due to the parasitic capacitance of the cross‐coupled pair and buffer amplifier. Each single‐ended output of the differential buffer amplifier is connected to a Greinacher voltage doubler, which serves as an envelope detector that senses the output power of the VCO and translates it into a dc voltage. The chip area of the VCO is 1.25 × 0.6 mm2. The measured frequency tuning range and FoMT (at 1‐MHz offset) are 31.7% and −192.5 dBc/Hz, respectively. The relation between the VCO output power and detector output voltage is characterized. Using the relation, the envelope detectors can be used for real‐time monitoring of the power level at any location in a chip, providing built‐in self‐test capability. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:11–14, 2014 其他題名： Microw. Opt. Technol. Lett 出版者： New York: Blackwell Publishing Ltd 出版日期： 2014-01 出處： Microwave and optical technology letters, 2014-01, Vol.56 (1), p.11-14 資源來源： Wiley Online Library - AutoHoldings Journals 版權： Copyright © 2014 Wiley Periodicals, Inc. 識別號： ISSN: 0895-2477 識別號： EISSN: 1098-2760 識別號： DOI: 10.1002/mop.27985 識別號： CODEN: MOTLEO

Wide-stopband Wilkinson power divider with bandpass response

title: Wide-stopband Wilkinson power divider with bandpass response abstract: 摘要： A wide-stopband Wilkinson power divider with bandpass response and good isolation is presented. A 3-terminal, 2-pole bandpass filter and two 3-pole lowpass filters are used to replace the two quarter-wavelength transformer in a conventional Wilkinson power. The divider consists of two shorted-circuited half-wavelength stepped-impedance resonators and two 3-pole microstrip stepped-impedance lowpass filters. Thus, the divider achieves not only a bandpass response but also a very wide stopband. For the upper stopband performance, the rejection level is >10 dB up to 22.2 times the centre frequency. 出版者： Stevenage: The Institution of Engineering and Technology 出版日期： 2014-01-02 出處： Electronics letters, 2014-01, Vol.50 (1), p.39-40 資源來源： Wiley Online Library (Open Access collection) 版權： The Institution of Engineering and Technology 版權： 2020 The Institution of Engineering and Technology 版權： 2015 INIST-CNRS 版權： Copyright The Institution of Engineering & Technology Jan 2, 2014 識別號： ISSN: 0013-5194 識別號： ISSN: 1350-911X 識別號： EISSN: 1350-911X 識別號： DOI: 10.1049/el.2013.3264 識別號： CODEN: ELLEAK