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온라인매체 활용 교육과 가상⋅증강현실 활용 교육에 대한 교사의 TPACK 수준 비교
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(기아자동차)RV종합배선도
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Coastal-Zone Trace-Element Fluxes in the Sea of Japan
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Spacer-mediated display of active lipase on the yeast cell surface
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The Effect of Topiramate on Hippocampal Neuronal Death and Expression of Glutamate Receptor in Kainate-induced Status Epilepticus Model
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번역노걸대박통사범례(飜譯老乞大朴通事凡例)가 부재된 원본(源本) 『번역노걸대(飜譯老乞大)』^ 『번역박통사(飜譯朴通事)』에 대한 연구
- 검색키워드
- 저자 : Jungwhan Son (검색결과 3 건)
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Optimization of Envelope Tracking Power Amplifier for Base-Station Applications
Jungjoon Kim,Jungwhan Son,Seunghoon Jee,Seokhyeon Kim,Bumman Kim IEEE 2013 IEEE transactions on microwave theory and techniqu Vol.61 No.4
<P>We have proposed two methods of enhancing efficiency of an envelope tracking power amplifier (ET PA) from an interlock operation. The first is the utilization of sinking current. The sinking current is a critical efficiency reduction factor since it is a wasted power. To reduce the sinking current, the gate bias of the power amplifier (PA) is increased so that the sinking current is delivered to the PA and is utilized for amplification. The other one is the RF input shaping method. The input signal of ET PAs is a modulated RF signal, and the signal does not guarantee fully saturated operation of the PA at all power levels due to <I>g m</I> nonlinearity of a device. To obtain the maximum efficiency for all of the envelope voltage, we have found the optimum RF input conditions and applied it to the input of the PA. To verify the methods, the proposed ET PA is implemented using a Cree CGH40045 GaN HEMT. For a long-term evolution 5-MHz signal with 6.5-dB peak-to-average power ratio, the PA delivers power-added efficiency of 58.76% with 40.14-dBm output power at 889 MHz.</P>
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Saturated Power Amplifier Optimized for Efficiency Using Self-Generated Harmonic Current and Voltage
Jungjoon Kim,Jangheon Kim,Junghwan Moon,Jungwhan Son,Ildu Kim,Seunghoon Jee,Bumman Kim IEEE 2011 IEEE transactions on microwave theory and techniqu Vol.59 No.8
<P>A saturated power amplifier (PA) optimized for efficiency is described. As a PA is driven into saturated operation, the current source of the device generates a large third harmonic current, which creates a quasi-rectangular current waveform. The large nonlinear output capacitor of the transistor generates a second harmonic voltage with a very small third harmonic component. The second harmonic voltage is in-phase with the fundamental voltage, making a half-sine wave voltage waveform with voltage peaking. These waveforms are similar to those of a class F<SUP>-1</SUP> . The fundamental load at the intrinsic device is resistive with the output capacitance tuned out, which is identical to the class F<SUP>-1</SUP> case. However, the required harmonic impedances are just larger than the impedance levels of the output capacitance for both the second and third harmonics. Therefore, the circuit topology is similar to that of a class E amplifier, which is very simple. The PA implemented using a GaN HEMT delivers the expected good performance using the simple circuit topology.</P>
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Breast PET CT 영상 재구성 변화에 따른 대조도 대 잡음비와 신호 대 잡음비의 비교평가
이재영(JeaYoung Lee),이을규(EuKyu Lee),김기원(KiWon Kim),정회원(HoiWoun Jeong),유광열(KwangYeul Lyu),박훈희(HoonHee Park),손진현(JinHyun Son),민정환(JungWhan Min) 대한방사선과학회(구 대한방사선기술학회) 2017 방사선기술과학 Vol.40 No.1
본 연구는 양전자 컴퓨터단층촬영(Positron Emission Computed Tomography; PET-CT) 유방암 영상에서 질환관 심영역(Region of Interest; ROI)의 대조도 대 잡음비(Contrast to Noise Ratio; CNR)와 신호 대 잡음비(Signal to Noise Ratio; SNR)를 재구성 기법별로 측정 평가하여 통계적 분석을 하고자 하였다. 연구대상은 서울소재 대학병원에서 유방 양전자 컴퓨터단층촬영(Breast PET-CT)을 검사한 환자 100명이다. 측정방법은 ImageJ 프로그램을 사 용하여 표본의 인구사회학적 특성, 영상 재구성 기법별 유방암의 SNR과 CNR의 평균값, 95% 신뢰구간 값, SNR과 CNR의 평균차이 값 등을 분석하였다. SPSS Statistics21 통계프로그램으로 ANOVA 분석을 하였으며 p<0.05에서 유의한 것으로 판단하였다. 영상 재구성 기법별 분석결과는 CNR과 SNR 모두 TrueX_TOF, Iterative, Iterative-TOF, FBP-TOF 순으로 높은 값을 나타냈다(p<0.05). CNR과 SNR수치로 영상 재구성 기법의 특징을 조합하여 PET/CT 검사의 정확성과 편의성을 제공할 것이라 사료된다. The purpose of this study was to measure contrast to noise ratio (CNR) and signal to noise ratio (SNR) according to change of reconstruction from region of interest (ROI) in breast positron emission tomography- computed tomography (PET-CT), and to analyze the CNR and SNR statically. We examined images of breast PET-CT of 100 patients in a University-affiliated hospital, Seoul, Korea. Each patient’s image of breast PET-CT were calculated by using ImageJ. Differences of CNR and SNR among four reconstruction algorithms were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p<0.05). We have analysis socio-demographical variables, CNR and SNR according to reconstruction images, 95% confidence according to CNR and SNR of reconstruction and difference in a mean of CNR and SNR. SNR results, with the quality of distributions in the order of PSF_TOF, Iterative and Iterative-TOF, FBP-TOF. CNR, with the quality of distributions in the order of PSF_TOF, Iterative and Iterative-TOF, FBP-TOF. CNR and SNR of PET-CT reconstruction methods of the breast would be useful to evaluate breast diseases.
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