• 한국전자파학회논문지
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• 제27권9호
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• pp.817-824
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• 2016

본 논문에서는 KSTAR의 ECEI(Electron Cyclotron Emission Imaging) 장치에 사용되는 100 GHz 미니렌즈의 성능을 향상하기 위해 변형된 타원형 렌즈 안테나 설계를 제안하고 있다. 기존 타원형 렌즈 구조의 밑면에 반구형 렌즈를 추가하고, 이 반구형 렌즈의 끝점에 100 GHz CPS 다이폴 안테나를 위치하게 하였다. 기하광학적 설계를 통해 안테나에서 방사된 전자파가 반구형 렌즈의 표면에서 전반사가 일어나도록 함으로써 안테나 패턴이 주빔 방향으로 집속되는 효과를 나타나게 하였다. 이 설계의 유효성은 3차원 EM 시뮬레이터로서 확인하였다. 제안된 반구형렌즈가 추가된 타원형 렌즈의 안테나 이득은 23.8 dB인데, 기존의 타원형 렌즈에 비해 2.2 dB 향상되었으며, 사이드 로브 레벨은 E-plane과 H-plane에서 2.6 dB, 3.4 dB 감소하였음을 확인하였다.

• 한국음향학회지
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• 제32권6호
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• pp.502-508
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• 2013

본 논문에서는 1-3 복합체 형태의 전도성 후면층을 이용한 2D 배열 초음파 트랜스듀서를 설계 및 제작하고 그 특성을 평가하였다. 1-3 복합체 형태의 전도성 후면층은 일반적인 재료를 사용해 널리 쓰이는 1-3 복합체 공정을 통하여 제작되었다. 본 연구의 대상이 되는 2D 배열 트랜스듀서는 4,096개의 구동 소자로 이루어져 있고, 각 소자의 중심주파수 및 비대역폭은 각각 3.5 MHz 및 60 % 이상을 목표로 설계하였다. 제작된 트랜스듀서는 중심주파수 및 비대역폭 목표치를 만족하였으며, 전체 구동 소자간의 특성도 0.81 dB 이내로 균일하였다. 따라서 본 연구에서 제시한 전도성 후면층의 2D 배열 초음파 트랜스듀서에 대한 적용 가능성이 검증되었다.

• Korean Journal of Radiology
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• 제20권1호
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• pp.102-113
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• 2019

Objective: To assess the accuracy and potential bias of computed tomography (CT) ventricular volumetry using semiautomatic three-dimensional (3D) threshold-based segmentation in repaired tetralogy of Fallot, and to compare them to those of two-dimensional (2D) magnetic resonance imaging (MRI). Materials and Methods: This retrospective study evaluated 32 patients with repaired tetralogy of Fallot who had undergone both cardiac CT and MRI within 3 years. For ventricular volumetry, semiautomatic 3D threshold-based segmentation was used in CT, while a manual simplified contouring 2D method was used in MRI. The indexed ventricular volumes were compared between CT and MRI. The indexed ventricular stroke volumes were compared with the indexed arterial stroke volumes measured using phase-contrast MRI. The mean differences and degrees of agreement in the indexed ventricular and stroke volumes were evaluated using Bland-Altman analysis. Results: The indexed end-systolic (ES) volumes showed no significant difference between CT and MRI (p > 0.05), while the indexed end-diastolic (ED) volumes were significantly larger on CT than on MRI (93.6 ± 17.5 mL/m² vs. 87.3 ± 15.5 mL/m² for the left ventricle [p < 0.001] and 177.2 ± 39.5 mL/m² vs. 161.7 ± 33.1 mL/m² for the right ventricle [p < 0.001], respectively). The mean differences between CT and MRI were smaller for the indexed ES volumes (2.0-2.5 mL/m²) than for the indexed ED volumes (6.3-15.5 mL/m²). CT overestimated the stroke volumes by 14-16%. With phase-contrast MRI as a reference, CT (7.2-14.3 mL/m²) showed greater mean differences in the indexed stroke volumes than did MRI (0.8-3.3 mL/m²; p < 0.005). Conclusion: Compared to 2D MRI, CT ventricular volumetry using semiautomatic 3D threshold-based segmentation provides comparable ES volumes, but overestimates the ED and stroke volumes in patients with repaired tetralogy of Fallot.

• 천문학회보
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• 제43권2호
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• pp.32.3-32.3
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• 2018

We use the synthetic light-cone from the cosmological hydrodynamical simulation Horizon-AGN to produce a mock photometric galaxy catalogue on the redshift range 0

• 인포메이션 디스플레이
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• 제5권2호
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• pp.27-32
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• 2004

• 한국위성정보통신학회논문지
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• 제8권2호
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• pp.68-73
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• 2013

최근의 3D 입체 영상 관련 기술의 발달은 스마트폰을 포함한 모바일 단말에서도 3D 입체 영상 서비스의 상용화를 가능하게 하고 있다. 스마트폰에서의 3D 입체 영상 서비스는 무안경 3D 디스플레이와 스테레오스코픽 3D 기술을 이용하고 있으며, 스테레오스코픽 이미지 관련 기술들은 지속적으로 활발히 연구가 진행되고 있다. 3D 입체 영상 서비스를 위하여 각각 다른 표준 H.264/AVC, H.264/AVC SEI, H.264/MVC가 MPEG에서 제정되었다. 본 논문에서는 최근 새롭게 대두되고 있는 모바일 단말에서의 스테레오스코픽 3D 기술의 발전과 특히 안드로이드 폰에서의 3D 서비스를 위한 비데오 포맷과 기능들에 초점에 맞추어 기술적 특성에 관한 분석을 행함으로서 그 활용성을 확인하였다.

• Current Optics and Photonics
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• 제2권2호
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• pp.172-178
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• 2018

We propose a precise 3D endoscopic technique for medical and industrial applications. As the 3D measuring principle, the continuously scanning structured illumination microscopy (CSSIM), which enables to obtain 3D sectional images by the synchronous axial scanning of the target with the lateral scanning of the sinusoidal pattern, is adopted. In order to reduce the size of the probe end, the illumination and detection paths of light are designed as coaxial and a coherent imaging fiber bundle is used for transferring the illumination pattern to the target and vice versa. We constructed and experimentally verified the proposed system with a gauge block specimen. As the result, it was confirmed that the 3D surface profile was successfully measured with $16.1{\mu}m$ repeatability for a gauge block specimen. In order to improve the contrast of the sinusoidal illumination pattern reflected off on the target, we used polarizing optical components and confirmed that the visibility of the pattern was suitable in CSSIM.

• Current Optics and Photonics
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• 제6권6호
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• pp.619-626
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• 2022

In this study, we develop a three-dimensional (3D) terahertz time-of-flight (THz-TOF) imaging technique with a large depth range, based on asynchronous optical sampling (ASOPS) methods. THz-TOF imaging with the ASOPS technique enables rapid scanning with a time-delay span of 10 ns. This means that a depth range of 1.5 m is possible in principle, whereas in practice it is limited by the focus depth determined by the optical geometry, such as the focal length of the scan lens. We characterize the spatial resolution of objects at different vertical positions with a focal length of 5 cm. The lateral resolution varies from 0.8-1.8 mm within the vertical range of 50 mm. We obtain THz-TOF images for samples with multiple reflection layers; the horizontal and vertical locations of the objects are successfully determined from the 2D cross-sectional images, or from reconstructed 3D images. For instance, we can identify metallic objects embedded in insulating enclosures having a vertical depth range greater than 30 mm. For feasible practical use, we employ the proposed technique to locate a metallic object within a thick chocolate bar, which is not accessible via conventional transmission geometry.

• Journal of Magnetics
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• 제21권2호
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• pp.281-285
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• 2016

The purpose of study was to evaluate SNR and CNR with different contrast agent contents (1.0 mmol/mL gadobutrol and 0.5 mmol/mL gadoterate meglumine) for spin echo (SE) and 3-dimension contrast-enhanced fast field echo (3D CE-FFE) pulse sequences. In this study, we compared the SNR and the CNR between 0.5 mmol/mL gadoterate meglumine and 1.0 mmol/mL gadobutrol according to the concentration of contrast agent in brain MRI. When we compared between SE and 3D CE-FFE pulse sequences, the higher SNR and CNR using 3D CE-FFE pulse sequence can be acquire regardless of contrast agent contents. Also, a statistically significant difference was found for SNR and CNR between all protocols. In conclusion, our results demonstrated that the SNR and CNR have not risen proportionately with contrast agent contents. We hope that these results presented in this paper will contribute to decide contrast agent contents for brain MRI.

• Korean Journal of Radiology
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• 제22권8호
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• pp.1266-1278
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• 2021

Objective: We aimed to compare the aortic valve area (AVA) calculated using fast high-resolution three-dimensional (3D) magnetic resonance (MR) image acquisition with that of the conventional two-dimensional (2D) cine MR technique. Materials and Methods: We included 139 consecutive patients (mean age ± standard deviation [SD], 68.5 ± 9.4 years) with aortic valvular stenosis (AS) and 21 asymptomatic controls (52.3 ± 14.2 years). High-resolution T2-prepared 3D steady-state free precession (SSFP) images (2.0 mm slice thickness, 10 contiguous slices) for 3D planimetry (3DP) were acquired with a single breath hold during mid-systole. 2D SSFP cine MR images (6.0 mm slice thickness) for 2D planimetry (2DP) were also obtained at three aortic valve levels. The calculations for the effective AVA based on the MR images were compared with the transthoracic echocardiographic (TTE) measurements using the continuity equation. Results: The mean AVA ± SD derived by 3DP, 2DP, and TTE in the AS group were 0.81 ± 0.26 cm², 0.82 ± 0.34 cm², and 0.80 ± 0.26 cm², respectively (p = 0.366). The intra-observer agreement was higher for 3DP than 2DP in one observer: intraclass correlation coefficient (ICC) of 0.95 (95% confidence interval [CI], 0.94-0.97) and 0.87 (95% CI, 0.82-0.91), respectively, for observer 1 and 0.97 (95% CI, 0.96-0.98) and 0.98 (95% CI, 0.97-0.99), respectively, for observer 2. Inter-observer agreement was similar between 3DP and 2DP, with the ICC of 0.92 (95% CI, 0.89-0.94) and 0.91 (95% CI, 0.88-0.93), respectively. 3DP-derived AVA showed a slightly higher agreement with AVA measured by TTE than the 2DP-derived AVA, with the ICC of 0.87 (95% CI, 0.82-0.91) vs. 0.85 (95% CI, 0.79-0.89). Conclusion: High-resolution 3D MR image acquisition, with single-breath-hold SSFP sequences, gave AVA measurement with low observer variability that correlated highly with those obtained by TTE.