• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1408-1411
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• 2002

In this paper, we propose a method that converts motion vectors on MPEG coded domain as a uniform set, independent of the frame type and the direction of prediction, and directly utilizes these normalized motion vectors for understanding video contents. This frame-type-independent motion vectors are utilized as feature information for image retrieval or moving object tracking on compressed domain. By simulation, we evaluate the effectiveness of the proposed method and compare its performance to the conventional method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.377-378
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• 2006

The proposed method measures the correlation maps of SVD that are used to interpret data relations and structures between the original image and the distorted image. It seems that the SVD results can be used to assist us in gaining information about covariance structure of two images. This method is able to work in the complete absence of any digital watermark or signature. The effectiveness of this method is seen through testing the robustness against JPEG compression.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.894-897
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• 2000

In this paper, we present a content-based image retrieval method that is less sensitive to some rotations and translations of an image by using the fuzzy region segmentation. The algorithm retrieves similar images from a database using the two features of color and color spatial information. To index images, we use the average coordinates of color distribution to obtain the spatial information of each segmented region. Furthermore, we also propose the alternative to the ripple phenomenon, which is occurred in the conventional fuzzy region segmentation algorithm.

• 천문학회보
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• 제46권2호
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• pp.61.1-61.1
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• 2021

Squeezed light는 중력파 검출기의 양자 잡음을 줄여 측정의 민감도를 향상시키기 위해 사용하는 양자 광원이다. Squeezed light는 광학적 손실에 민감하기 때문에 중력파를 측정하기 위해서는 정밀한 mode matching이 필요하다. 하지만 mode mismatching은 실제 실험 상황에서 동적으로, 그리고 무작위로 나타나므로 정밀하게 조정하기 어렵다. Mode mismatching에 견고한 squeezed light를 만들기 위해서는 multimode squeezed light가 필요하다. Multimode squeezed light를 만드는 방법으로 는 self-imaging cavity를 이용하여 생성하는 방법이 대표적으로 알려져 있다. 이 발표에서는 self-imaging cavity 기반으로 만든 optical parametric oscillator(OPO) 에서 생성된 squeezed light가 기존 OPO로 생성한 squeezed light 보다 여러 spatial mode mismatching (위치, 방향, 크기 빗맞음)에 대해 견고함을 소개한다.

• Journal of the Optical Society of Korea
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• 제18권3호
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• pp.256-260
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• 2014

Columnar-structured cesium iodide (CsI) scintillators doped with thallium (Tl) are frequently used as x-ray converters in medical and industrial imaging. In this study we investigated the imaging characteristics of CsI:Tl films with various reflective layers-aluminum (Al), chromium (Cr), and titanium dioxide ($TiO_2$) powder-coated on glass substrates. We used two effusion-cell sources in a thermal evaporator system to fabricate CsI:Tl films on substrates. The scintillators were observed via scanning electron microscopy (SEM), and scintillation characteristics were evaluated on the basis of the emission spectrum, light output, light response to x-ray dose, modulation transfer function (MTF), and x-ray images. Compared to control films without a reflective layer, CsI:Tl films with reflective layers showed better sensitivity and light collection efficiency, and the film with a $TiO_2$ reflective layer showed the best properties.

• Korean Journal of Radiology
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• 제20권1호
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• pp.18-33
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• 2019

In this study, we summarize the clinical role of magnetic resonance imaging (MRI) in the diagnosis of patients with malignant uterine neoplasms, including leiomyosarcoma, endometrial stromal sarcoma, adenosarcoma, uterine carcinosarcoma, and endometrial cancer, with emphasis on the challenges and disadvantages. MRI plays an essential role in patients with uterine malignancy, for the purpose of tumor detection, primary staging, and treatment planning. MRI has advanced in scope beyond the visualization of the many aspects of anatomical structures, including diffusion-weighted imaging, dynamic contrast enhancement-MRI, and magnetic resonance spectroscopy. Emerging technologies coupled with the use of artificial intelligence in MRI are expected to lead to progressive improvement in case management of malignant uterine neoplasms.

• Applied Microscopy
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• 제45권1호
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• pp.23-31
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• 2015

Dark field (DF) transmission electron microscopy image has become a popular characterization method for two-dimensional material, graphene, since it can visualize grain structure and multilayer islands, and further provide structural information such as crystal orientation relations, defects, etc. unlike other imaging tools. Here we present microstructure of graphene, particularly, using DF imaging. High-angle grain boundary formation wass observed in heat-treated chemical vapor deposition-grown graphene on the Si substrate using patch-quilted DF imaging processing, which is supposed to occur by strain around multilayer islands. Upon the crystal orientation between layers the multilayer islands were categorized into the oriented one and the twisted one, and their local structure were compared. In addition information from each diffraction spot in selected area diffraction pattern was summarized.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1990년도 추계학술대회
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• pp.19-23
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• 1990

A new technique for reducing the susceptibility artifact in gradient echo imaging which uses a tailored RF pulse is proposed. It is applied to the case of imaging where artifacts and distortions arise due to the high local magnetic field inhomogeneity i. e., the susceptibility. The signal loss and void phenomena due to susceptibility in a voxel are studied and a correction method using a tailored RF pulse is proposed. Applications of this method in imaging are given and experimental results obtained using an human volunteer with a 2.0 T KAIS NMR system are presented.

• 대한방사성의약품학회지
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• 제1권1호
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• pp.46-52
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• 2015

Herein we present the synthesis of $^{68}Ga$-labeled gold nanoparticles for in vivo PET imaging. A novel chelator DTPA-Cys was easily prepared from diethylenetriaminepentaacetic dianhydride in high yield. The ${\alpha}_v{\beta}_3$ integrin receptor targeted gold nanoparticle probe was synthesized by using DTPA-Cys, polyethylene glycol and cRGD peptide. $^{68}Ga$ labeling of cRGD conjugated gold nanoparticle was carried out at $40^{\circ}C$ for 30 min. Observed radiochemical yield was more than 75% as determined by radio-TLC and the probe was purified by centrifugation. In vitro stability test showed that 90% of $^{68}Ga$-labeled gold nanoparticle probe was stable in FBS for 1 h. Those results demonstrated that $^{68}Ga$-labeled gold nanoparticle could be used as a potentially useful probe for specific tumor imaging.

• Applied Microscopy
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• 제46권3호
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• pp.164-166
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• 2016

Electron channeling contrast imaging (ECCI) is a powerful analyzing tool for identifying lattice defects like dislocations and twin boundaries. By using diffraction-based scanning electron microscopy technique, it enables microstructure analysis, which is comparable to that obtained by transmission electron microscopy that is mostly used in defect analysis. In this report, the optimal conditions for investigating crystal defects are suggested. We could obtain the best ECCI images when both acceleration voltage and probe current are high (30 kV and 20 nA). Also, shortening the working distance (6 mm) enhances the quality of defect imaging.