• 대한전자공학회논문지
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• 제23권6호
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• pp.936-943
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• 1986

The lasing wavelengths and gain characteristics of the array modes of channel-substrate planar(CSP) lasers are presented. The gain values of array modes are determined from the complex coupling coefficients calculated using the fields of neighborig elements of the array. The computations show that for index guided lasers which have fields that are almost real valued, or have only slight phase curvature, the highest order array mode will have preferred oscillation. The inphase or fundamental mode, which produces only one major lobe in the far-field radiation pattern, will have the lowest modal gain of all array modes. Some of the devices discussed have modal gain differences of less than 10 cm**-1 between the highest and fundamental modes. For optical field confinement factors of about 20%, this gain difference corresponds to avtive layer gains of approximately 50**-1.

• 동력기계공학회지
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• 제14권3호
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• pp.46-51
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• 2010

A torsional guided wave was applied to detect a defect in petrochemical pipes. Phase and group velocity dispersion curves for the longitudinal and torsional modes of the inspected pipe were presented for the theoretical analysis. It was found through mode shape analysis that there was mode conversion when torsional wave is incident at an asymmetric defect. An artificial notch was fabricated in the pipe and the detectability was examined from the distance 2m of the end of the pipe by using magnetostrictive sensors. The relativities between the amplitude of the reflected signal and the size of the defect was examined. It was shown that the T(0,1) mode could be used for the long range inspection for the petrochemical pipes.

• 센서학회지
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• 제30권3호
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• pp.131-138
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• 2021

The optimization of the specifications of vertical silicon on insulator (SOI) slot optical waveguides suitable for integrated-optical biochemical sensors was performed through computational analysis of the confinement factor of the guided mode distributed in the slot in addition to analytical examination of the TE mode. The optimized specifications were confirmed based on sensitivity in terms of the change in the refractive index of the biochemical analyte. When the slot width, rail width, and height were set to 120 nm, 200 nm, and 320 nm, respectively, the confinement factor was evaluated to be about 56% and the sensitivity was at least 0.9 [RIU/nm].

• Clinical Pain
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• 제20권1호
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• pp.7-14
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• 2021

Musculoskeletal ultrasound has evolved as the essential tool to diagnose and guide intervention procedures in people with neuromusculoskeletal conditions. Image optimization and understanding device operations are core components for ultrasound guided intervention procedure training. All ultrasound machines share the common operative features and there are various buttons for the features in the device control panel. Ultrasound "knobology" refers to the thorough understanding of imaging optimization. This review addressed basic information for the transducers, depth setting, gain and focus control, different modes focusing on brightness and doppler modes.

• Current Optics and Photonics
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• 제6권2호
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• pp.129-136
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• 2022

We propose a photonic crystal fiber (PCF) with a slotted porous core and elliptical-hole cladding, for high birefringence in the terahertz regime. Asymmetry in the guided mode is obtained mainly by using arrays of elliptical air holes in the TOPAS^® polymer cladding. We investigate the tradeoff between several structural parameters and find optimized values that can have a high birefringence while satisfying the single-mode condition. The optical properties in the terahertz regime are thoroughly analyzed in numerical simulations, using a full-vector finite-element method with the perfectly-matched-layer condition. In an optimal design, the proposed photonic crystal fiber shows a high birefringence of 8.80 × 10^-2 and an effective material loss of 0.07 cm^-1 at a frequency of 1 THz, satisfying the single-mode-guidance condition at the same time. The proposed PCF would be useful for various polarization-management applications in the terahertz range.

• 대한방사선치료학회지
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• 제21권2호
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• pp.67-74
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• 2009

목 적: 전립선암 환자를 대상으로 kV 콘빔CT를 이용한 영상유도방사선치료 시 촬영조건에 따른 인체의 각 장기들에 미치는 흡수선량(absorbed dose)과 유효선량(effective dose)을 비교 평가해 보고자 한다. 대상 및 방법: 환자를 대상으로 직접 실험할 수 없으므로 인체의 구성과 조직이 흡사한 인체 모형 팬텀(Anderson rando Phantom, Alderson Research Laboratories Inc., USA)과 전산화 단층 모의치료기(Lightspeed RT CT, GE, USA)를 이용하여 국제 방사선 방호 위원회(International Commission on Radiological Protection, ICRP)에서 권고된 신체 내 중요 장기들을 묘사하였다. 팬텀 내부의 묘사된 주요 장기에 선량 측정을 위하여 열형광선량계(TLD 100 Lif rods, Harshaw Chemical Co., USA)를 1~8개 삽입한 후 팬텀의 중심을 전립선에 위치시키고, On board imager (OBI) System이 부착된 의료용 선형 가속기(Clinac iX, Varian, USA)를 이용하여 두 가지 촬영모드인 표준모드(Standard-mode, A-mode)와 저선량모드(Low-dose mode, B-mode)에서 kV 콘빔 CT 촬영을 각 3회씩 반복해서 측정하였다. 결 과: 인체 모형 팬텀을 이용하여 전립선암 환자를 대상으로 한 kV 콘빔 CT 촬영을 시행한 결과 전립선, 방광, 직장에 대한 흡수선량은 A-mode인 경우 각각 5.5 cGy/1회, 6.5 cGy/1회, 5.7 cGy/1회, B-mode인 경우 1.1 cGy/1회, 1.3 cGy/1회, 1.2 cGy/1회 결과를 보였다. 각 장기에 대한 조직가중치를 고려한 유효선량은 A-mode와 B-mode에서 19.1 mSv, 4.4 mSv의 결과로 나타났다. kV 콘빔CT 촬영 시 인체에 미치는 유효선량을 측정한 결과, 전립선암 영상유도방사선치료 시 A-mode 콘빔CT는 B-mode 콘빔CT보다 환자가 받는 선량이 약 4배 이상 증가하는 것을 알 수 있었다. 결 론: 그러므로 전립선암 영상유도방사선치료 시 환자가 받는 치료 이외의 선량을 고려했을 때 가능한 B-mode 또는 낮은 촬영 조건을 설정하여 환자가 받는 치료이외선량을 가능한 한 줄일 필요가 있다고 사료된다.

• 한국광학회지
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• 제17권4호
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• pp.342-346
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• 2006

공진 파장 대역에서의 소멸비가 전기적으로 조절되는 폴리머 링 레조네이터를 제안하고 구현하였다. 이 소자는 버스 도파로에 결합된 링 도파로와 링의 바깥 쪽 클래딩 영역에 형성된 전극으로 이루어져 있다. 전극에 전력이 인가되면 열광학 효과에 의하여 폴리머의 굴절률이 감소하여 링 도파모드의 구속이 강해지며, 이 모드가 느끼는 등가 유효굴절률이 감소하게 된다. 결과적으로 링의 전파손실이 감소하게 됨에 따라 레조네이터의 소멸비가 변하게 된다. 측정된 소자의 특성을 살펴보면, 전력을 12mW까지 인가함에 따라 소멸비는 약 9dB 정도 증가하였는데, 이것은 링 도파로의 전파손실이 약 80dB/cm 감소한 것에 해당된다.

• 한국인터넷방송통신학회논문지
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• 제17권3호
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• pp.209-214
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• 2017

비대칭 다층 유전체 격자구조에 입사된 평면파는 대칭 격자구조와 같이 공간 고조파들을 생성한다. 이 성분들 중에 특정 공간 고조파는 GMR 특성으로 알려진 강한 공진 산란 변화를 겪는다. 본 논문에서는 이러한 효과를 명확히 분석하기 위하여 고유치 문제에 기인한 정확한 등가전송선로 이론(RETT)을 사용하여 격자 영역 내부의 공진현상과 분산특성을 분석하였다. 그 결과, 산란 공진의 peak에서 격자구조에 의하여 발생한 반사 모드와 격자구조에서 전송되는 누설 모드가 거의 일치한다는 것을 알 수 있었다. 따라서 누설파의 자유 공명 특성과 관련된 GMR 효과가 비대칭 다층 유전체 격자구조에서도 발생한다는 것을 확인하고 일반화하였다. 전형적인 격자의 공진특성을 보여주는 정량적인 수치해석 결과가 주어졌으며 TE, TM 모드가 반사면에 수직 입사된 특수한 경우도 논의하였다.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.249-257
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• 2013

This study newly presents a synthetic phase tuning technique to suppress the unwanted torsional mode while enhancing the desired torsional mode in a pipe. Specifically, we aim at the enhancement of the first torsional mode and the suppression of the undesired, second torsional mode. Earlier efforts were to enhance the desired wave mode only in the hope that the enhancement results in the suppression of the unwanted wave mode. Unlike these efforts, the suggested technique makes the complete cancellation of the unwanted wave mode but it is shown to enhance the desired first mode for torsional wave problems. In the present study, the synthetic phase tuning is developed for the cancellation of the unwanted wave mode, meaning that the number of necessary experimental equipments is reduced. Simulation and experiment were carried out to check the effectiveness of the proposed method. As an application of the suggested technique, we investigated the reflection and mode conversion characteristics of the first torsional mode according to the step thickness variation in a stepped pipe.

• 비파괴검사학회지
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• 제31권3호
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• pp.271-277
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• 2011

This study presents a nondestructive test for underwater PVC pipes. To use guided ultrasonic waves, specially denoted by cylindrical Lamb waves, a test setup was made in a water tank using the pitch and catch mode and specimens were made to give artificial cutouts located in the circumferential direction of the pipes. Total three states of damaged levels were considered to see how the guided waves interact with the defects. For the experimental adjustments, three different pipe diameters (60, 90, 114 mm) were tested, and two factors - incident angle (10 and $40^{\circ}$) and distance (50 and 200 mm) - were tried. From the results, regardless of the diameters and two experimental factors, it is shown that the degrees of defects were recognized through amplitude and arrived time of the very first part of the received cylindrical Lamb waves. Between amplitude and arrived time, it is found that the amplitude gives more sensitive results.