• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.26-31
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• 2012

We have proposed a metamaterial lens that enables sub-wavelength focusing, which is shorter than an operating wavelength. Our lens is a two dimensional array of a unit cell consisting of a metallic dual-plate printed on a dielectric substrate. The unique dual-plate structure provides negativeness both in permittivity and permeability, with no help from conventional additional structures, which are normally printed on the opposite of metallic patterns. Therefore, we can focus a source (or an image) in a tiny distance shorter than the free space wavelength (${\lambda}$) at the frequencies of interest. Furthermore, since the proposed geometry does not need separate supplementary structures to acquire negative permittivity or permeability, our lens is much simpler than conventional metamaterial lenses, which is a strong point in practical applications. We have validated sub-wavelength focusing ability in a 6 GHz frequency band through an experiment of near field scanning, which provided the width of about 0.19 ${\lambda}$ at a half maximum of a peak value of an measured image. The width of the focused image through the lens is more than 4 times shorter than that without the lens, which confirms the validity of our design approach.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.110-119
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• 2017

This paper describes a CMOS image sensor (CIS) with dual correlated double sampling (CDS) and column-parallel analog-to-digital converter (ADC) and its measurement method using a field-programmable gate array (FPGA) integrated module. The CIS is composed of a $320{\times}240$ pixel array with $3.2{\mu}m{\times}3.2{\mu}m$ pixels and column-parallel 10-bit single-slope ADCs. It is fabricated in a $0.11-{\mu}m$ CIS process, and consumes 49.2 mW from 1.5 V and 3.3 V power supplies while operating at 6.25 MHz. The measured dynamic range is 53.72 dB, and the total and column fixed pattern noise in a dark condition are 0.10% and 0.029%. The maximum integral nonlinearity and the differential nonlinearity of the ADC are +1.15 / -1.74 LSB and +0.63 / -0.56 LSB, respectively.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.132-141
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• 1998

Particle image velocimetry(PIV), a planar measuring technique, is an efficient tool for studying the complicated flow field such as in-cylinder flow, and intake port flow. PIV can be also used for analyzing the integral length scale of turbulence, which is a measure of the size of the large eddies that contain most of the turbulence kinetic energy. In this study, dual color scanning PIV was designed and demonstrated by using a rotating mirror and a beam splitter. This PIV system allowed enlargement of flexibility in the intensity of vectors to be calculated by spatial filtering technique, even in combustion chamber with high velocity gradient and high vorticity$({\sim}1000s^{-1})$. A new color image processing algorithm was developed, which was used to find the direction of particle movement directly from the digital image. These measuring techniques were successfully applied to obtaining the turbulence intensity (~0.1m/s) and the turbulent integral length scale of vorticity(~1mm).

• 한국추진공학회지
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• 제11권3호
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• pp.50-57
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• 2007

Particle Image Velocimetry(PIV) 및 Dual-mode Phase Doppler Anemometry(DPDA) 기법을 적용하여 소형 액체로켓엔진에 사용되는 인젝터의 분무특성 규명을 위한 연구를 수행하였다. PIV 측정법으로 순간평면 이미지를 획득하여 분무 거동을 정성적으로 예측하고, 분사각 관련 인젝터 성능평가 기법을 수렵하였다. 또, DPDA 측정법을 통해 액적의 속도와 크기 등의 분무거리에 따른 변이를 정량화하고, 인젝터의 미립화 성능을 관찰하였다. 본 연구의 궁극적인 목적은 분무특성에 대한 명확한 이해를 통해 개발하고자 하는 새로운 인젝터의 설계변수 도출 및 분무성능 평가기준을 마련하기 위함이다.

• 인터넷정보학회논문지
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• 제22권3호
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• pp.37-43
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• 2021

본 논문에서는 모바일 환경에서 실시간으로 전면과 후면 카메라의 객체를 인식하여 객체 픽셀의 영역을 분할하고 이미지 처리를 통해 합성하는 방법을 연구하였다. 이를 위해 Apple사의 iOS에서 제공하는 듀얼 카메라에 DeepLabV3 머신러닝 모델을 적용하여 객체를 분할하였다. 또한 이미지 합성 및 후처리를 위해 Apple사의 코어 이미지와 코어 그래픽 라이브러리를 이용하여 영역의 배경 제거 및 합성 방식을 제안하고 구현하였다. 또한, 이전 연구에 비해 CPU 사용량을 개선하였고 깊이와 DeepLabV3의 처리 속도를 비교하여 처리 결과에 영향을 주는 요소를 분석하였다. 마지막으로 이 두 방식을 활용한 카메라 애플리케이션을 개발하였다.

• Journal of Information Processing Systems
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• 제18권3호
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• pp.319-331
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• 2022

The capability to examine an X-ray image is so far a challenging task. In this work, we suggest a practical and novel algorithm based on image fusion to inspect the issues such as background noise, blurriness, or sharpness, which curbs the quality of dual-energy X-ray images. The current technology exercised for the examination of bags and baggage is "X-ray"; however, the results of the incumbent technology used show blurred and low contrast level images. This paper aims to improve the quality of X-ray images for a clearer vision of illegitimate or volatile substances. A dataset of 40 images was taken for the experiment, but for clarity, the results of only 13 images have been shown. The results were evaluated using MSE and PSNR metrics, where the average PSNR value of the proposed system compared to single X-ray images was increased by 19.3%, and the MSE value decreased by 17.3%. The results show that the proposed framework will help discern threats and the entire scanning process.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.254-259
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• 2001

There are advantages in the installation of dual subsea pipelines over two separate single lines. In many case it can reduce the cost for trench, back-filling and installation. However the installation of dual pipelines often requires technical challenges. Dual Pipelines should be placed to be stable to external loading not only during the installation but also in the design life. Dual pipelines in trench can reduce the influence of external forces. To investigate applied forces as slope changes, number of experiments are conducted with PIV (Particle Image Velocimetry) in a circulating water channel. Numerical approaches are also made to compare with experimental results. The velocity fields around dual pipelines in trench are investigated and analysed. Comparison of both results show similar pattern of flow around dual pipelines. it is proved that the trench slope affects the pipeline stability significantly. The results can be applied in the stability design of dual pipelines in trench section. The complex flow patterns can be referenced effectively linked in the understanding of fluid around circular bodies in trench.

• 한국측량학회지
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• 제33권6호
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• pp.517-526
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• 2015

Among the various image fusion or pan-sharpening methods, those wavelet-based methods provide superior radiometric quality. However, the fusion processing is not only simple but also flexible, since many low- and high-frequency sub-bands are often produced in the wavelet domain. To address this issue, a novel DT-CWT (Dual-Tree Complex Wavelet Transform) proportional to the fusion method by a WZP (Wavelet Zero-Padding) is proposed. The proposed method produces a single high-frequency image in the spatial domain that is injected into the LRM (Low-Resolution Multispectral) image. Thus, a wavelet domain fusion can be simplified to spatial domain fusion. In addition, in the proposed DT-CWTP (DT-CWT Proportional) fusion method, it is unnecessary to decompose the LRM image by adopting WZP. The comparison indicates that the proposed fusion method is nearly five times faster than the DT-CWT with SW (Substitute-Wavelet) fusion method, meanwhile simultaneously maintaining the radiometric quality. The conducted experiments with WorldView-2 satellite images demonstrated promising results with the computation efficiency and fused image quality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.452-472
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• 2019

Most existing wavelet-based multiplicative watermarking methods are affected by geometric attacks to a certain extent. A serious limitation of wavelet-based multiplicative watermarking is its sensitivity to rotation, scaling, and translation. In this study, we propose an image watermarking method by using dual-tree complex wavelet transform with a multi-objective optimization approach. We embed the watermark information into an image region with a high entropy value via a multiplicative strategy. The major contribution of this work is that the trade-off between imperceptibility and robustness is simply solved by using the multi-objective optimization approach, which applies the watermark error probability and an image quality metric to establish a multi-objective optimization function. In this manner, the optimal embedding factor obtained by solving the multi-objective function effectively controls watermark strength. For watermark decoding, we adopt a maximum likelihood decision criterion. Finally, we evaluate the performance of the proposed method by conducting simulations on benchmark test images. Experiment results demonstrate the imperceptibility of the proposed method and its robustness against various attacks, including additive white Gaussian noise, JPEG compression, scaling, rotation, and combined attacks.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.45-46
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• 2006

In this paper, a dual stage servo mechanism has been developed for image tracking system to improve transient control performances such as small rise time, small overshoot, small settling time, etc. A secondary stage, a platform, actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. In this mechanism, the gimbal provides large range but slow motion and the platform provides small range but fast positioning. A sliding mode control is applied to the platform positioning to attain robust performances and stability in the presence of the disturbance related to dynamic coupling of the gimbal and the platform. Results from experiments illustrate that the suggested dual stage mechanism controlled by the sliding mode control is effective in improving transient responses and attenuating the disturbance related with dynamic coupling.