• Investigative Magnetic Resonance Imaging
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• 제21권1호
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• pp.20-27
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• 2017

Purpose: To evaluate quantification results of single breath-hold (SBH) magnetic resonance (MR) cine imaging compared to results of conventional multiple breath-hold (MBH) technique for left ventricular (LV) function in patients with cardiac arrhythmia. Materials and Methods: MR images of patients with arrhythmia who underwent MBH and SBH cine imaging at the same time on a 1.5T MR scanner were retrospectively reviewed. Both SBH and MBH cine imaging were performed with balanced steady state free precession. SBH scans were acquired using temporal parallel acquisition technique (TPAT). Fifty patients ($65.4{\pm}12.3years$, 72% men) were included. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), myocardial mass, and LV regional wall motion were evaluated. Results: EF, myocardial mass, and regional wall motion were not significantly different between SBH and MBH acquisition techniques (all P-values > 0.05). EDV, ESV, and SV were significant difference between the two techniques. These parameters for SBH cine imaging with TPAT tended to lower than those in MBH. EF and myocardial mass of SBH cine imaging with TPAT showed good correlation with values of MBH cine imaging in Passing-Bablok regression charts and Bland-Altman plots. However, SBH imaging required significantly shorter acquisition time than MBH cine imaging ($15{\pm}7sec$ vs. $293{\pm}104sec$, P < 0.001). Conclusion: SBH cine imaging with TPAT permits shorter acquisition time with assessment results of global and regional LV function comparable to those with MBH cine imaging in patients with arrhythmia.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2007년도 학술대회
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• pp.66-66
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• 2007

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2007년도 학술대회
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• pp.72-72
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• 2007

• 한국전자파학회논문지
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• 제8권3호
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• pp.264-272
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• 1997

본 논문에서는 리액턴스 소자률 갖는 전기적 소형다이폴 안테나의 강제 공진특성을 해석하고 있다. 이론 해석 에는 다이폴 안테나에 흐르는 전류분포에 관한 적분방정식을 풀기 위해 모멘트 법을 적용했으며, 강제 공진특성 을 검토하기 위하여 급전점 및 장하점에 착목한 2단자 동가 회로망으로부터 안테나가 강제적으로 공진하도록 하는 리액턴스의 값을 결정하는 결정방정식을 도출하고 있다. 공진특성의 해석결과 리액턴스 소자를 적절히 조절 하면 안테나가 강제적으로 공진하며, 강제 공진에는 직렬공진 및 병렬공진의 두 가지 종류가존재한다는 것을 밝 히고 있다. 또한, 이들 강제 공진특성을 미지 주파수의 측정에 이용할 수 있다는 것을 원리적인 변을 중심으로 이 론적으로 검토하고 있다.

• 한국전자파학회논문지
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• 제20권1호
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• pp.83-90
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• 2009

본 논문에서는 상호 평행하는 두 개의 도체 평판의 슬릿을 통한 전자파 투과 문제를 고려하였다. TM 편파된 평면파가 슬릿에 입사되었을 때 각 슬릿의 등가 자류를 미지수로 하는 결합 적분방정식을 유도하고 모멘트 방법으로 풀어 수치해석하였다. 슬릿의 폭, 도체 평행 평판의 간격, 평면파의 입사각, 슬릿간 변위 등에 따른 슬릿을 통해 투과된 전력의 변화를 계산하였다. 두 슬릿간 변위가 반 파장의 정수배에 근접할 때 투과 공진(최대 전력 투과)현상이 관찰되었다. 슬릿의 폭과 도체판 간격이 파장에 비해 매우 좁은 경우 투과 전력의 최대치는 슬릿의 폭과 입사각도에 무관하게 일정함을 확인하였다. 또한, 제안된 구조에서 일어나는 투과 공진 현상의 원리를 단순화된 구조와 등가회로를 통해 설명하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1140-1142
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• 1995

The transformer is fabricated with two piezoelectric vibrator with the divided electrodes and adhesive insulator. We applied the electric input to the driving vibrator in parallel and connect the output voltage to the generating vibrator in series to the resistor load near its fundamental resonance frequency. Then we investigate output voltage in series twice as large as in parallal. Moreover we investigate the load characteristics at resonance frequencies under various resistor and the frequency characteristics near the resonance frequency under no load. Its equvalent circuit is derived from the Mason's model of a thickness-driven piezelectric vibrator. By its equevalent circuit, symbolic expressions for input impedances, voltage ratios, resonance frequencies, and bandwidths have been derived. The values calculated from those symbolic exprssions are shown to agree well with the measurement values.

• 한국소음진동공학회논문집
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• 제21권3호
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• pp.258-263
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• 2011

The direction of the cutting tool plays a critical role in elliptical vibration cutting(EVC) where the cutting tool cuts workpiece in a trochoidal motion. In this study, EVC cutting device was developed using two parallel piezoelectric materials and it was observed that the rotation direction of the tool reverses as the EVC device undergoes resonance at which either flexural(cutting direction) or longitudinal( thrust direction) mode shapes occurs. To analytically explain reversal of the rotation direction, kinematic motion analysis of the tool was modified to incorporate amplification of the vibration amplitude and phase introduced by resonance. It successfully demonstrated, through Matlab simulation, reversal of the rotation direction of the cutting tool as the excitation frequency increases beyond resonance frequencies at which either flexural or longitudinal vibration occurs.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.401-406
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• 1994

A magnetic resonance neurography technique for exclusive imaging of nerve networks is proposed. In the proposed technique, the anisotropy of diffusion coefficients of the molecules inside nerve cells was utilized to effectively suppress the magnetic resonance signal radiating from ones other than nerve tissues. Two images were obtained with diffusionweighting magnetic field gradients applied in the parallel and perpendicular directions with respect to the nerve orientation. One image was then subtract- ted from the other to form the neurogram. Experimentally obtained neurograms of the squld are presented.

• 한국자기학회지
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• 제5권5호
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• pp.524-527
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• 1995

The temperature dependence of spin wave mode separation in amorphous $Co_{89.5}Zr_{10.5}$ thin film has been investigated at temperatures between 100 K and 300 K. The magnetization and the spectroscopic splitting factor were obtained for the main resonance mode in parallel and perpendicular magnetic field. ${\Delta}H_{2-3}$, the difference between resonance field of mode 2 and the resonance field of mode 3, increases with decreasing temperature. The linewidth increases for all the modes with decreasing temperature. Especially in mode 3 it increases rapidly below 200 K. This phenomenon could be caused by the increase of exchange stiffness constant or the decrease of surface magnetic anisotropy constant with decreasing temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.22-25
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• 1987

New measurement method of coupled transmission line characteristics is described. This method presents precision calculated values of even- and odd-mode impedances and effective dielectric constants of mictostrip parallel coupled lines from the scalar quantities obtained by transmission coefficients at two different resonance frequencies. Measured impedances and effective dielctric constants are good agreement with predicted values.