• 한국광학회지
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• 제13권1호
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• pp.79-83
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• 2002

회전항을 첨가한 임의 위상판(random phase mask; RPM)을 이용하여 광학상 암호화 장치의 암호화수준을 향상시키는 방법을 제시하였다. 이중 임의 위상판으로 암호화된 광학상은 광굴절 LiNbO$_3$:Fe 결정에 기록되고 위상공액파를 이용하여 재생하였으며, 세기변조 함수를 이용하여 아날로그 입력상에 대한 암호화 수준을 분석하였다.

• Tribology and Lubricants
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• 제16권5호
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• pp.317-323
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• 2000

The film thickness and shape of elastohydrodynamic lubrication is measured by optical interferometer, which is the most precise method for EHL film measurement. However, the interpretation of the image pattern from optical viscometer is not simple for two-dimensional shape. A newly developed method of image processing makes it possible to evaluate the film thickness and shape in every point of contact region with two dimensional aspects. In this study, we captured the film shape of EHL film by the monochromatic incident light and analyzed the film thickness with the image processing method, which uses phase shift method. From the values of intensity in fringes, the qualitative feature of film thickness in the contact area are obtained by using Zernike polynomial

• Corrosion Science and Technology
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• 제23권2호
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• pp.113-120
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• 2024

An attempt was made to apply digital image correlation (DIC) strain analysis to in-situ scanning electron microscopy (SEM) observations of bending deformation to quantify local strain distribution inside a ZnMgAl-alloy coating in deformation. Interstitial-free steel sheets were hot-dipped in a Zn-3Mg-6Al (mass%) alloy melt at 400 ℃ for 2 s. The specimens were deformed using a miniature-sized 4-point bending test machine inside the SEM chamber. The observed in situ SEM images were used for DIC strain analysis. The hot-dip ZnMgAl-alloy coating exhibited a solidification microstructure composed of a three-phase eutectic of fine Al (fcc), Zn (hcp), and Zn2Mg phases surrounding the primary solidified Al phases. The relatively coarsened Zn₂Mg phases were locally observed inside the ZnMgAl-alloy coating. The DIC strain analysis revealed that the strain was localized in the primary solidified Al phases and fine eutectic microstructure around the Zn₂Mg phase. The results indicated high deformability of the multi-phase microstructure of the ZnMgAl-alloy coating.

• 한국전자파학회논문지
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• 제28권7호
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• pp.580-583
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• 2017

항공기 탑재형 SAR에서 요동보상 후 남아있는 잔여 오차 및 공간 가변적 오차 등으로 인해 품질이 저하된 SAR 영상을 보상하기 위한 분할처리 기반 자동초점 기법을 제시한다. Spotlight SAR는 공간 분할하고, Stripmap SAR는 시간 분할한 뒤, 분할된 데이터에 대해 영상을 생성한 후, 추정된 오차의 적합성 분석과정이 포함된 구역 자동초점 기법(Autofocus)를 수행한다. 또한 분할된 영상에서 위상오차 추정이 되지 않아 보상이 되지 않는 경우에는 인접한 분할 영상의 위상오차에 가중치를 부여하여 보상하는 과정을 통해 전체 영상의 화질을 향상시키는 방법을 제시한다.

• 한국방사선학회논문지
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• 제3권2호
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• pp.23-26
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• 2009

본 연구는 향상된 중심배열 정렬 위상 펼침 방법(ICASPL)을 제안하고 자기공명 위상 영상을 재구성하여 성능을 평가하였다. 제안된 방법을 수행하기 위해 2% 한천젤에 0.6mM/l를 첨가한 팬텀을 제작하여 임상용젠작하5T 자기공명영상와젠상용화된 무릎코일을 이용하여 MR위상영상을 얻었다. 획득된 k 공간 자료는 PC로 옮긴 뒤 매트랩 프로그램을 이용하여 영상을 재구성하였다. 제안된 ICASPU의 오차를 2차 회귀분석읕 이용하여 기존의 중심배열 정렬 위상 펼침과 비교 평가하였다. 그 결과 기존의 ICASPU방법에 비해 제안된 ICASPU방법이 5배 정도 오차가 향상된 것을 확인할 수 있었다. 본 연구는 향상된 중심배열 정렬 위상 펼침 방법을 이용한 위상영상 펼침의 유용성을 확인하였으며, 향후 위상 정보를 포함한 영상 적용에 매우 유용할 것이라 기대된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4508-4530
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• 2021

Today distributed data storage service are being widely used. However lack of proper means of security makes the user data vulnerable. In this work, we propose a Randomized Block Size (RBS) model for secure data storage in distributed environments. The model work with multifold block sizes encrypted with the Chinese Remainder Theorem-based RSA (C-RSA) technique for end-to-end security of multimedia data. The proposed RBS model has a key generation phase (KGP) for constructing asymmetric keys, and a rand generation phase (RGP) for applying optimal asymmetric encryption padding (OAEP) to the original message. The experimental results obtained with text and image files show that the post encryption file size is not much affected, and data is efficiently encrypted while storing at the distributed storage server (DSS). The parameters such as ciphertext size, encryption time, and throughput have been considered for performance evaluation, whereas statistical analysis like similarity measurement, correlation coefficient, histogram, and entropy analysis uses to check image pixels deviation. The number of pixels change rate (NPCR) and unified averaged changed intensity (UACI) were used to check the strength of the proposed encryption technique. The proposed model is robust with high resilience against eavesdropping, insider attack, and chosen-plaintext attack.

• 한국음향학회지
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• 제29권8호
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• pp.509-515
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• 2010

본 논문은 충분한 음원 너비 (Apparent Source Width)와 스테레오 이미지 품질 (Stereophonic Image Quality)을 확보하는 모노-스테레오 업믹스 기법을 제안한다. 모노 신호의 분석을 위해 높은 계수의 비음수 행렬 분해가 사용된다. 그 결과로\ 나온 분해된 음원들은 음조성 (Tonality)에 의하여 타악기 (Percussive)와 음조 (Tonal) 그룹으로 분류된다. 두 그룹 중 하나는 바로 스테레오 채널로 들어가는 반면 나머지 하나는 디코릴레이터를 통과하여 들어가게 된다. 청취 평가 결과 제안한 방법은 충분한 음원 너비와 스테레오 음상을 제공할 뿐만 아니라 기존의 방법에 비해 음색 변화도 감소하는 종합적으로 향상된 성능을 보여주었다.

• 한국가시화정보학회지
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• 제19권1호
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• pp.28-35
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• 2021

In this study, an image processing method for the measurement of two-phase bubbly flow is developed. Shadowgraphy images obtained by high-speed camera are used for analysis. Some bubbles are generated as single unit and others are overlapped or clustered. Single bubbles can be easily analyzed using parameters such as bubble shape, centroid, and area. But overlapped bubbles are difficult to transform clustered bubbles into segmented bubbles. Several approaches were proposed for the bubble segmentation such as Hough transform, connection point method and watershed. These methods are not enough for bubble segmentation. In order to obtain the size distribution of bubbles, we present a method of splitting overlapping bubbles using watershed and approximating them to ellipse. There is only 5% error difference between manual and automatic analysis. Furthermore, the error can be reduced down to 1.2% when a correction factor is used. The ellipse fitting algorithm developed in this study can be used to measure bubble parameters accurately by reflecting the shape of the bubbles.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1998년도 추계학술발표 논문집
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• pp.111-115
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• 1998

A phase-shifting projection moire method particularly intended for high-speed three-dimensional shape reconstruction of diffuse objects is presented. Emphasis is on realization of phase-shifting fringe analysis in projection moire topography using a set of line grating pairs designed to provide different phase shifts in sequence. Further a time-integral fringe capturing scheme is devised to remove undesirable high frequency original grating patterns in real-time without time-consuming software image processing. Finally the performances of the proposed method are discussed with measurement results.

• 대한의용생체공학회:의공학회지
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• 제33권4호
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• pp.169-176
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• 2012

Tumor cell morphology is closely related to its migratory behaviors. An active tumor cell has a highly irregular shape, whereas a spherical cell is inactive. Thus, quantitative analysis of cell features is crucial to determine tumor malignancy or to test the efficacy of anticancer treatment. We use 3D time-lapse phase-contrast microscopy to analyze single cell morphology because it enables to observe long-term activity of living cells without photobleaching and phototoxicity, which is common in other fluorescence-labeled microscopy. Despite this advantage, there are image-level drawbacks to phase-contrast microscopy, such as local light effect and contrast interference ring. Therefore, we first corrected for non-uniform illumination artifacts and then we use intensity distribution information to detect cell boundary. In phase contrast microscopy image, cell is normally appeared as dark region surrounded by bright halo ring. Due to halo artifact is minimal around the cell body and has non-symmetric diffusion pattern, we calculate cross sectional plane which intersects center of each cell and orthogonal to first principal axis. Then, we extract dark cell region by analyzing intensity profile curve considering local bright peak as halo area. Finally, we calculated the Fourier descriptor that morphological characteristics of cell to classify tumor cells into active and inactive groups. We validated classification accuracy by comparing our findings with manually obtained results.