• 한국표면공학회지
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• 제50권6호
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• pp.460-464
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• 2017

As increasing thermal efficiency of the gas turbine, the performance improvement of thermal barrier coatings is also becoming important. Ytrria stabilized zirconia(YSZ) is the most popular materials for ceramic top coating because of its low thermal conductivity. In order to enhance the performance of thermal barrier coatings for hot sections in the gas turbine, suspension plasma spraying was developed in order to feed nano-sized powders. YSZ coatings formed by suspension plasma spraying showed better performance than YSZ coatings due to its exclusive microstructure. In this research, two YSZ coatings were deposited by suspension vacuum plasma spraying at 400 mbar and 250 mbar. Microstructures of YSZ coatings were analyzed by scanning electron image(SEM) on each spraying conditions, respectively. Crystalline structure transformation was not detected by X-ray diffraction. Thermal conductivity of suspension vacuum plasma sprayed YSZ coatings were measured by laser flash analysis. Thermal conductivity of suspension vacuum plasma sprayed YSZ coatings containing horizontally oriented nano-sized pores and vertical cracks showed $0.6-1.0W/m{\cdot}K$, similar to thermal conductivity of YSZ coatings formed by atmospheric plasma spraying.

• 한국정보통신학회논문지
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• 제8권2호
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• pp.379-385
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• 2004

일반 의료기관에서의 PACS를 이용한 효율적인 환자 영상의 관리가 늘어가고 있다. 그런 환경하에서 환자의 사생활 보호와 의료영상 자체의 소유권, 재산권의 여부 및 데이터 변형 여부의 판별이 중요시된다. 의료데이타의 보호를 위해 디지털 워터마킹이 사용되며, 본 논문에서는 RST공격에 강인한 워터마킹 기법을 제안한다. 기존에 제안된 기하학적 변형에 강인한 워터마킹 기법중에서 Log-Polar변환과 Fourier-Mellin 변환을 이용한 방법은 영상에 가해진 RST공격을 영상의 좌표변환과 DFT의 순환적 이동 특성을 이용하여 강인성을 확보한다. 하지만 실제적 구현에서 원영상과 워터마크의 손실이 문제 시 된다. 본 논문에서는 반지름-위상 Look Up Table을 이용하여 좌표변환 시 발생하는 손실을 막으면서 회전에 강인한 워터마킹 기법을 제안한다.

• 한국산학기술학회논문지
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• 제7권6호
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• pp.1231-1236
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• 2006

영상의 화질을 개선하기 위한 많은 방법 중 비교적 간단하게 사용되는 방법 중 하나는 영상의 대비를 조절하는 것이다. 이러한 대비를 조절하는 방법 중 하나인 히스토그램 균등화는 영상 계조도 값의 분포를 균등 분포로 변환함으로써 화질을 개선한다. 그러나, 기존의 방법은 영상의 히스토그램 분포가 몇개의 계조도 값에 군집화되어 있다면 영상의 계조도가 과도하게 변하는 단점을 갖는다. 본 논문은 그레이스케일 영상에 대해 히스토그램의 형태를 고려해서 가우시안 함수에 기반한 히스토그램 매칭 방법을 제안한다. 제안된 방법은 영상이 과도하게 밝아지는 것을 제한하고 히스토그램의 분포가 몇 개의 계조도에 군집화되어 있는 영상에서의 에지 및 어두운 부분의 자세한 정보를 표현하는데 우수한 성능을 나타내었다.

• 한국정밀공학회지
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• 제21권11호
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• pp.69-74
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• 2004

This paper presents ESPI system for the measurement of thermal expansion coefficient of STS430 up to 1,00$0^{\circ}C$ . Existing methods, strain gauge and moire have the limitation of contact to object and do not supply the coefficient up to 80$0^{\circ}C$ . There needs to measure the data up to 80$0^{\circ}C$, because heat resistant materials have high melting temperature up to 1,000'E In previous studies related to thermal strain analysis, the quantitative results have not reported by ESPI at high temperature, yet. In-plane ESPI and vacuum chamber for the reduction of air turbulence and oxidation are designed for the measurement of the coefficient up to 1,00$0^{\circ}C$ and speckle correlation fringe pattern images are processed by commercial image filtering tool-smoothing, thinning and enhancement- to obtain quantitative results, which is compared with references data. The comparison shows two data are agreed within 4.1% blow $600^{\circ}C$ however, there is some difference up to $600^{\circ}C$. Also, the incremental ratio of the coefficient is changed up to 80$0^{\circ}C$ . The reason is the phase transformation of STS430 probably begins at 80$0^{\circ}C$

• 한국산학기술학회논문지
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• 제6권4호
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• pp.291-295
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• 2005

본 논문은 변형된 2-D PCA를 이용한 얼굴 인식 방법에 대하여 제안한다. 기존의 PCA는 1 차원 벡터들로 공분산 행렬을 구하는 반면에 2-D PCA는 2 차원 영상을 직접적으로 이용하여 공분산 행렬을 구한 후 그것의 고유값에 따른 고유벡터를 구하여 특징 벡터들을 추출한다. 제안 방법은 두 개의 공분산 행렬들을 이용하여 선형 변환 행렬을 구하는 변형된 2-D PCA 방법을 적용하여 얼굴을 인식한다. 실험 결과는 2-D PCA 보다 제안된 방법이 $1\%$ 정도 얼굴 인식률이 더 좋으며, 안정된 인식률을 보여준다.

• 한국정보통신학회논문지
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• 제12권11호
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• pp.2050-2056
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• 2008

본 논문은 스테레오 라인 CCD와 광원을 이용한 2차원 평면에서 이동객체를 인식하고 이동경로를 추적하는 시스템 구현이다. 시스템 구현은 카메라 이미지를 직접 처리하는 대신 두개의 라인 CCD 센서와 입력된 라인 이미지의 밝기를 비교하여 2차원 거리를 측정한다. 알고리듬은 이동객체감지, 경로추적과 좌표변환 기법을 적용한다. 객체의 이동경로를 효과적으로 감지하기 위하여 측정된 거리의 신뢰성을 평가하는 알고리즘을 개발하였다. 시스템을 구현하여 실험한 결과 5mm 인식율과 100ms 주기 이상의 이동객체경로 추적이 가능하였다.

• 대한두개안면성형외과학회지
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• 제19권4호
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• pp.275-278
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• 2018

Trichoblastic carcinoma usually occurs as a malignant transformation of the trichoblastoma, but is very rare. A 25-year-old man was admitted with trichoblastoma in the nuchal area with frequent recurrences since birth. The preoperative neck magnetic resonance image revealed lobulated soft tissue lesions involving superficial fascia and infiltrating into both proximal trapezius muscles. In our department, wide excision and reconstruction with a free anterolateral thigh flap were performed. Histological examination revealed skin adnexal carcinoma, originating from the hair follicles, consistent with trichoblastic carcinoma. There was no palpable mass 5 years postoperatively, and there was no recurrence on follow-up positron emission tomography-computed tomography. Trichoblastic carcinomas are rare and difficult to diagnose, but histopathological findings include atypical basaloid keratinocytes with crowded, hyperchromatic nuclei, and increased mitotic activity. The presence of hypercellular stroma is a criterion for distinguishing trichoblastic carcinoma from basal cell carcinoma. A rare giant trichoblastic carcinoma was reported, which was the biggest one in the literature.

• Smart Structures and Systems
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• 제23권4호
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• pp.359-371
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• 2019

As part of a structural health monitoring system, the relative geometric relationship between a ship and bridge has been recognized as important for bridge authorities and ship owners to avoid ship-bridge collision. This study proposes a novel computer vision method for the real-time geometric parameter identification of moving ships based on a single shot multibox detector (SSD) by using transfer learning techniques and monocular vision. The identification framework consists of ship detection (coarse scale) and geometric parameter calculation (fine scale) modules. For the ship detection, the SSD, which is a deep learning algorithm, was employed and fine-tuned by ship image samples downloaded from the Internet to obtain the rectangle regions of interest in the coarse scale. Subsequently, for the geometric parameter calculation, an accurate ship contour is created using morphological operations within the saturation channel in hue, saturation, and value color space. Furthermore, a local coordinate system was constructed using projective geometry transformation to calculate the geometric parameters of ships, such as width, length, height, localization, and velocity. The application of the proposed method to in situ video images, obtained from cameras set on the girder of the Wuhan Yangtze River Bridge above the shipping channel, confirmed the efficiency, accuracy, and effectiveness of the proposed method.

• Smart Structures and Systems
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• 제31권4호
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• pp.409-419
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• 2023

Structural integrity can be accessed from dynamic deformations of structures. Moreover, dynamic deformations can be acquired from non-contact sensors such as video cameras. Kanade-Lucas-Tomasi (KLT) algorithm is one of the commonly used methods for motion tracking. However, averaging throughout the extracted features would induce bias in the measurement. In addition, pixel-wise measurements can be converted to physical units through camera intrinsic. Still, the depth information is unreachable without prior knowledge of the space information. The assigned homogeneous coordinates would then mismatch manually selected feature points, resulting in measurement errors during coordinate transformation. In this study, a two-stage optimization method for video-based measurements is proposed. The manually selected feature points are first optimized by minimizing the errors compared with the homogeneous coordinate. Then, the optimized points are utilized for the KLT algorithm to extract displacements through inverse projection. Two additional criteria are employed to eliminate outliers from KLT, resulting in more reliable displacement responses. The second-stage optimization subsequently fine-tunes the geometry of the selected coordinates. The optimization process also considers the number of interpolation points at different depths of an image to reduce the effect of out-of-plane motions. As a result, the proposed method is numerically investigated by using a truss bridge as a physics-based graphic model (PBGM) to extract high-accuracy displacements from recorded videos under various capturing angles and structural conditions.

• 자원환경지질
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• 제56권4호
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• pp.397-408
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• 2023

A total of 64 specimens of trace fossils were collected from the Jinju Formation of the construction site of Jinju Aviation Industrial Complex, and from the Haman Formation of Namhae Gain-ri fossil site. The fossils are continuously and regularly meandering sine-curve in shape. The fossil varies in morphology: width between 0.2 and 5.6 mm, wavelength between 1.5 and 28 mm, and amplitude between 0.9 and 7.9 mm; the Jinju specimens are commonly wider than the Haman ones. The ratio of wavelength to amplitude is more or less regular regardless of width of the specimen, and the linear correlation of the ratios shows that the Jinju specimens fit better than the Haman specimens. Taking all morphometric parameters, specimens in all size ranges are temporarily identified as ichnospecies Cochlichnus anguineus. In order to obtain more distinct and clearer images of Cochlichnus, we selected two specimens and applied a new imaging technology RTI. For photography of the trace fossils, 50 to 80 images were taken per set with photometric lighting close to the surface and horizontally. RTI technology clearly showed that the images of tiny fossils were improved: the surface contrast become sharper and messy and unnecessary information disappeared. Currently, RTI technology is used in many fields including preservation of cultural properties and archaeology. As a consequence, we hope to apply this technique to the field of paleontology, especially to the study of trace fossils of very small size.