• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.107-110
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• 1997

We generated a diffraction free beam from Nd:YAG laser with an NBUR (negative branch unstable ring) resonator. The field inside the resonator had a plane wavefront and a homogeneous intensity distribution and the output beam through a scraper mirror of an annular type was used as a source. The outpur beam had an inner radius of 2.5 mm and an outer radius of 5 mm. In this experiment, we used a Fourier transformation lens with the focal length of 5 m to observe the far-field pattern. The lens was placed at a distance of the focal length from the scraper mirror and we found that the beam did not show any noticable diffraction over the distance of 13 m from the lens.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.6
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• pp.886-898
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• 1995

One of the ways to measure the distance in the computer vision is to use the focus and defocus. There are two methods in this way. The first method is caculating the distance from the focused images in a point (MMDFP: the method measuring the distance to the focal plane). The second method is to measure the distance from the difference of the camera parameters, in other words, the apertures of the focal planes, of two images with having the different parameters (MMDCI: the method to measure the distance by comparing two images). The problem of the existing methods in MMDFP is to decide the thresholding vaue on detecting the most optimally focused object in the defocused image. In this case, it could be solved by comparing only the error energy in 3x3 window between two images. In MMDCI, the difficulty is the influence of the deflection effect. Therefor, to minimize its influence, we utilize two differently focused images instead of different aperture images in this paper. At the first, the amount of defocusing between two images is measured through the introduction of regularization and then the distance from the camera to the objects is caculated by the new equation measuring the distance. In the results of simulation, we see the fact to be able to measure the distance from two differently defocused images, and for our approach to be robuster than the method using the different aperture in the noisy image.

• Journal of Korean Society for Quality Management
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• v.42 no.4
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• pp.617-632
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• 2014

Purpose: This study aims to explore the relationship between the focal firm's interdepartmental cooperation and new product development (NPD) performance with focus on the moderating effect of environmental uncertainty. The basic hypothesized model is that there are positively associated relationships. Methods: The proposed research model was tested using structural equation modeling with 601 responses from multi-functional and multiple respondents in Korean manufacturing firms. Multi-group SEM analyses were conducted to explore the degree to which the hypothesized model was equivalent for different levels of environmental uncertainty. Results: Interdepartmental cooperation between R&D and production is positively associated with NPD performance under both higher and lower environmental uncertainties, while one between R&D and marketing is positively associated under only higher environmental uncertainty. Conclusion: This paper determined that NPD performance is positively correlated with R&D-production cooperation in a focal firm, and the relationship between R&D-marketing cooperation and NPD performance is positively moderated by level of environmental uncertainty. Consequently, this study suggests that it is always important for firms to put much effort on R&D-production cooperation for a better NPD performance, while R&D-marketing cooperation should be enhanced especially under higher environmental uncertainty than lower.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.66.2-66.2
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• 2016

KASI and NAOJ are making collaborating efforts to implement faster mapping capability into the new 275-500 GHz Atacama Submillimeter Telescope Experiment focal plane array (FPA). Feed horn antenna is one of critical parts of the FPA. Required fractional bandwidth is almost 60 % while that of traditional conical horn is less than 50 %. Therefore, to achieve this wideband performance, we adopted a horn of which the corrugation depths have a longitudinal profile. A profiled horn has features not only of wide bandwidth but also of shorter length compared to a linear-tapered corrugated horn, and lower cost fabrication with less error can be feasible. In our design process the flare region is represented by a cubic splined curve with several parameters. Parameters of the flare region and each dimension of the throat region are optimized by a differential evolution algorithm to keep >20 dB return loss and >30 dB maximum cross-polarization level over the operation bandwidth. To evaluate RF performance of the horn generated by the optimizer, we used a commercial mode matching software, WASP-NET. Also, Gaussian beam (GB) masks to far fields were applied to give better GB behavior over frequencies. The optimized design shows >23 dB return loss and >33 dB maximum cross-polarization level over the whole band. Gaussicity of the horn is over 96.6 %. The length of the horn is 12.5 mm which is just 57 % of the ALMA band 8 feed horn (21.96 mm).

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.140-140
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• 2001

We present two cases of surgically proven focal nodular hyperplasia whou underwent tri contrast-enhance MR imaging using gadolinium chelates, mangafodipir trisodium, and ferumoxides After the unehanced MR images were obtained, dynamic gadolinium-enhanced T1-weighted imagi were performed, then mangafodipir enhanced and ferumoxides-enhanced images were obtained. In one case, the mass was isointense on both T1- and T2-weighted images on the unehanced M images, iso and slightly hyperintense on ferumoxides-enhanced FSE and GRE images, strong hyperintense on the mangafodipir enhanced and gadolinium enhanced arterial phase images. In th other case, the mass was isointense on T2-weighted and hypointense on T1-weighted image isointense on ferumoxides-enhanced images, and hyperintense on mangafodipir enhanced an gadolinium enhanced arterial phase images. Triple contrast enhanced MR images were useful correctly diagnose these two cases preoperatively.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.3
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• pp.299-305
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• 2015

In this paper, we propose a simple and low-cost fabrication method of polymer microlens using solvent-vapor-assisted reflow (SVAR). Metal molds for replication of polymer were fabricated using micro milling and the cylindrical shape of polymer was imprinted using hot-embossing process. The cylindrical shape of polymer was changed to hemispherical lens shape by SVAR. The characteristics of fabricated microlens were evaluated according to the condition of SVAR such as temperature and time. The focal length of polymer microlens could be controlled more easily in low-temperature and long-time condition than in high-temperature and short-time condition. That is, the level of concentrated light to focal point could be improved through the control of temperature and time. Also, we confirmed that toluene was more appropriate solvent than acetone in fabrication of PMMA polymer microlens using SVAR.

• Archives of Plastic Surgery
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• v.38 no.1
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• pp.69-72
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• 2011

Purpose: Myositis ossificans is a benign condition of heterotopic bone formation that still requires more of its pathologic explanation. The lesions are localized predominantly to the high-risk sites of injury, involving flexor muscles of the upper limbs and thigh, but rarely in the head and neck area. Methods: A case of a 44-year-old male patient presented with a palpable hard mass on nasal dorsum. The patient experienced a similar lesion on upper limb few years ago. On computed tomographic image, the lesion presented focal definite increase in opacity compatible to adjacent bone densitiy on nasal dorsum. Results: The lesion was excised under open rhinoplasty incision. The pathologic report revealed focal bone formation and calcification within skeletal muscle. Conclusion: We describe a unique and only case of a myositis ossificans on nasal dorsum which is indifferent from previous concept.

• Investigative Magnetic Resonance Imaging
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• v.20 no.1
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• pp.75-79
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• 2016

We report a case of perivalvular abscess in a 66-year-old man with infective endocarditis, diagnosed by late gadolinium-enhanced (LGE) cardiovascular magnetic resonance (CMR) imaging. No clinical features suspicious of infective endocarditis were noted, however, transthoracic echocardiography revealed non-specific echogenic focal wall thickening at mitral-aortic intervalvular fibrosa. Perivalvular abscess in the aortic valve was demonstrated as focal wall thickening between the anterior mitral leaflet and the non-coronary cusp of the aortic valve with peripheral enhancement and central low signal intensity on LGE CMR imaging. Other features suggestive of infective endocarditis, such as neither vegetation nor valvular perforation were present. The perivalvular abscess did not grow after intensive intravenous antibiotics therapy, and the patient was discharged without surgical treatment. CMR with LGE provided an early accurate diagnosis of perivalvular abscess. The diagnosis of perivalvular abscess using LGE CMR imaging was not previously reported in Korea.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.2
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• pp.150-153
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• 2009

Xanthogranulomatous pyelonephritis is an uncommon chronic renal infection, which is usually found on middle-aged women and is rare in infant. Sometimes it forms focal mass like lesion of kidney with pathologically characteristic lipid-laden macrophage. A 1-month female infant was admitted for fever and moaning sound. On work-up of urinary tract infection, abdomen ultrasonography and computed tomography revealed a large mass on the upper portion of right kidney and PET/CT showed homogeneously increased $^{18}F$-FDG uptake. The radical nephrectomy of right kidney was performed and histology revealed a focal xanthogranulomatous pyelonephritis. To our knowledge, this is the first report presenting the finding of $^{18}F$-FDG PET/CT in the childhood xanthogranulomatous pyelonephritis.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.248-253
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• 2004

We propose a near- field scanning optical interferometer (NSOI) based on the facet reflection of a nano-sized moveable tapered optical fiber. The interferometer can measure the position and the wave-front of a focused spot simultaneously. The interfering fringes are generated by the reflected beams from the sample surface and from the fiber facet. The wave-front analysis at the focusing position is obtained by using a phase shifting technique with a four-step algorithm. It is found that the resolution for controlling the focal position of our proposed NSOI is less than λ/3 and the measured wave-front aberration at the focal position is in good agreement with the ones obtained by a Twyman-Green interferometer.