• Journal of architectural history
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• v.8 no.2 s.19
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• pp.109-118
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• 1999

The purpose of this paper is to apply Stephen C. Pepper's contextualism to architecture: to interpret the former in the light of architectural theory, and ultimately to liberate architecture from the Western 'Idea' and return it to its context. The major concepts of Pepper used in the paper are quality, texture, spread, change, fusion, strand and context. Pepper's contextualism makes us realize that architecture cannot be separated from its context where human beings, history, neighborhood, and nature are all interpenetrating, and create a quality. Contextualism thus teaches us to make an effort to understand the region where we belong, and to create an architectural device that interrelates form and function of an architecture with its space-time environment, or its strand, texture and context.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.187-190
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• 2002

Confocal microscopy is very popular technology in bio-medical inspection due to its ability to reject background signals and to measure very thin slide of thick specimens, which is called optical sectioning. But intensity of detected signal in fluorescence type confocal microscopy is so small that only 0.2% of emitted fluorescence light can be detected in the best case. In this paper, we proposed the reflecting optical system to improve the detection intensity and designed the optical system by optimal design method. At the end of the paper, we analyzed the characteristics of the proposed reflecting optical system.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.321-324
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• 2004

We used BV CCD images to study the dynamical substructures of three globular clusters - M5, NGC6934, NGC7006 - analyzing the radial variations of ellipticity and position angle from the point spread function stellar photometry and the ellipse surface photometry. Several populations were classified by the brightness on color-magnitude diagrams of each globular cluster. Ellipse analyses to the images, removed stars of each population from the original images of the clusters, show radial variations in ellipticity and position angle, with the amount of $0.01\~0.25$ in ellipticity and $+90\~-90$ degrees in position angle up to roughly three times of half light radius $(r_h)$. It is also apparent that there are no significant discrepancies in the dynamical substructures beyond $r_h$ among the different populations. However, dynamical substructures on the central region (i.e., inner than $\~r_h$) reflect the contributions of populations of bright red giant stars and horizontal branch stars.

• Journal of Multimedia Information System
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• v.5 no.2
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• pp.79-82
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• 2018

Due to the handheld holding of smartphones and the presence of light leakage and non-balanced contrast, the detection of the retina area in smartphone-captured fundus images is more challenging than retinography-captured fundus images. This paper presents a computationally efficient image processing pipeline in order to detect and enhance the retina area in smartphone-captured fundus images. The developed pipeline consists of five image processing components, namely point spread function parameter estimation, deconvolution, contrast balancing, circular Hough transform, and retina area extraction. The results obtained indicate a typical fundus image captured by a smartphone through a D-EYE lens is processed in 1 second.

• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.165-172
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• 1996

A scanning slot digital mammography system Luing a plastic scintillating fiber screen (SFS) is currently being developed To improve the x-ray interaction efficiency and absorption efficiency of an SFS, high Z elements can be added into the scintillating fiber core. In this paper, we investigated theoretically the zero spatial frequency detective quantum efficiency, DQE(0), and modulation transfer function, MTF(f), of three 2 cm thick SFSs made of polystyrene, polystyrene loaded with 5% by weight of lead, and polystyrene Loaded with 10% by weight of tin scintillating fibers. X-ray interaction efficiency, scintillating light intensity distributions and line spread functions were generated using Monte Carlo simulation. DQE(0) and MTF(f) were computed for x-ray energies ranging from 15 to 50 keV. Loading high Z elements into the SFS markedly increased the DQE(0). For x-ray energies used for mammovaphy, DQE(0) values of both high Z element loaded SFSs are about a factor of three higher than the DQE(0) of an Min-R screen. At mammographic x-ray energies, MTF(f) values of all three SFSs are Venter than 50% at 25 Ip/mm spatial frequency, and were found to be dominated by the 20 um individual scintillating fiber diameter used The results show that both hiP DQE(0) and spatial resolution can be achieved with the high Z element loaded SFSs, which make these SFSs attractive for use in a scanning slot detector for digital mammography.

• Current Optics and Photonics
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• v.6 no.2
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• pp.171-182
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• 2022

A single-photon laser and mid-wave infrared (MWIR) common aperture optical system was designed and developed to detect and range a long-distance civil aviation aircraft. The secondary mirror of the Ritchey-Chretien (R-C) optical system was chosen as a dichroic lens to realize the design of a common aperture system for the laser and MWIR. Point spread function (PSF) ellipticity was introduced to evaluate the coupling efficiency of the laser receiving system. A small aperture stop and narrow filter were set in the secondary image plane and an afocal light path of the laser system, respectively, and the stray light suppression ability of the small aperture stop was verified by modeling and simulation. With high-precision manufacturing technology by single point diamond turning (SPDT) and a high-efficiency dichroic coating, the laser/MWIR common aperture optical system with a 𝜑300 mm aluminum alloy mirror obtained images of buildings at a distance of 5 km with great quality. A civil aviation aircraft detection experiment was conducted. The results show that the common aperture system could detect and track long-distance civil aviation aircraft effectively, and the coverage was more than 450 km (signal-to-noise ratio = 6.3). It satisfied the application requirements for earlier warning and ranging of long-range targets in the area of aviation, aerospace and ground detection systems.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.56.4-57
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• 2017

The Schwarzschild-Chang off-axis telescope is a "linear astigmatism-free" confocal system. The telescope comprises two pieces of aluminum-alloy freeform mirrors that are fabricated with diamond turning machine (DTM) process. We designed optomechanical structures where optical components in the telescope system can be adjustable on a linear stage. Optomechanical deformation caused by the weight of system itself and its temperature variation is analyzed by the finite element analysis (FEA). The results show that the deformation is estimated in the tolerance range. For the optic-axis alignment of telescope system, three-point alignment (TPA) method is chosen. The TPA method uses three parallel lasers and a plane mirror. Point source images were taken from collimated light and field observation. The performance of optical system was tested by point spread function and aberration measurement of the point sources.

• Journal of The Korean Astronomical Society
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• v.33 no.2
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• pp.89-95
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• 2000

As an efficient method to detect blending of general gravitational microlensing events, it is proposed to measure the shift of source star image centroid caused by microlensing. The conventional method to detect blending by this method is measuring the difference between the positions of the source star image point spread function measured on the images taken before and during the event (the PSF centroid shift, ${\delta}{\theta}$c,PSF). In this paper, we investigate the difference between the centroid positions measured on the reference and the subtracted images obtained by using the difference image analysis method (DIA centroid shift, ${\delta}{\theta}$c.DIA), and evaluate its relative usefulness in detecting blending over the conventional method based on ${\delta}{\theta}$c,PSF measurements. From this investigation, we find that the DIA centroid shift of an event is always larger than the PSF centroid shift. We also find that while ${\delta}{\theta}$c,PSF becomes smaller as the event amplification decreases, ${\delta}{\theta}$c.DIA remains constant regardless of the amplification. In addition, while ${\delta}{\theta}$c,DIA linearly increases with the increasing value of the blended light fraction, ${\delta}{\theta}$c,PSF peaks at a certain value of the blended light fraction and then eventually decreases as the fraction further increases. Therefore, measurements of ${\delta}{\theta}$c,DIA instead of ${\delta}{\theta}$c,PSF will be an even more efficient method to detect the blending effect of especially of highly blended events, for which the uncertainties in the determined time scales are high, as well as of low amplification events, for which the current method is highly inefficient.

• Progress in Medical Physics
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• v.8 no.2
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• pp.67-76
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• 1997

We studied optical behavior of scintillation light generated in NaI(TI) crystal using Monte Carlo simulation method. The simulation was performed for the model of NaI(TI) scintillator (size: 60 mm ${\times}$ 60 mm ${\times}$ 6 mm) using an optical tracking code. The sensitivity as a function of surface treatment (Ground, Polished, Metal-0.95RC, Polished-0.98RC, Painted- 0.98RC) of the incident surface of the scintillator was compared. The effects of NaI(TI) scintillator thickness and the refractive index of light guide optically coupling between the NaI(TI) scintillator and photomultiplier tube (PMT) were simulated. We also evaluated intrinsic position resolution of the system by calculating the spread of scintillation light generated. The sensitivities of the system having the surface treatment of Ground, Polished, Metal-0.95RC, Polished-0.98RC and Painted-0.98RC were 70.9％, 73.9％, 78.6％, 80.1％ and 85.2％, respectively, and the surface treatment of Painted-0.98RC allowed the highest sensitivity. As increasing the thickness of scintillation crystal and light guide, the sensitivity of the system was decreased. As the refractive index of light guide increases, the sensitivity was increased. The intrinsic position resolution of the system was estimated to be 1.2 mm in horizontal and vertical directions. In this study, the performance of NaI(TI)-PMT detector system was evaluated using Monte Carlo simulation. Based on the results, we concluded that the NaI(TI)-PMT detector array is a favorable configuration for small gamma camera imaging breast tumor using Tc-99m labeled radiopharmaceuticals.

• The Journal of the Korea Contents Association
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• v.10 no.6
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• pp.329-335
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• 2010

Digital imaging detectors can use a variety of detection materials to convert X-ray radiation either to light or directly to electron charge. Many detectors such as amorphous silicon flat panels, CCDs, and CMOS photodiode arrays incorporate a scintillator screen to convert x-ray to light. The digital radiography systems based on semiconductor detectors, commonly referred to as flat panel detectors, are gaining popularity in the clinical & hospital. The X-ray detectors are described between a-Silicon based indirect type and a-Selenium based direct type. The DRS of detectors is used to convert the x-ray to electron hole pairs. Image processing is described by specific image features: Latitude compression, Contrast enhancement, Edge enhancement, Look up table, Noise suppression. The image features are tuned independently. The final enhancement result is a combination of all image features. The parameters are altered by using specific image features in the different several hospitals. The image in a radiological report consists of two image evaluation processes: Clinical image parameters and MTF is a descriptor of the spatial resolution of a digital imaging system. We used the edge test phantom and exposure procedure described in the IEC 61267 to obtain an edge spread function from which the MTF is calculated. We can compare image in the processing parameters to change between original and processed image data. The angle of the edge with respect to the axes of detector was varied in order to determine the MTF as a function of direction. Each MTF is integrated within the spatial resolution interval of 1.35-11.70 cycles/mm at the 50% MTF point. Each image enhancement parameters consists of edge, frequency, contrast, LUT, noise, sensitometry curve, threshold level, windows. The digital device is also shown to have good uniformity of MTF and image parameters across its modality. The measurements reported here represent a comprehensive evaluation of digital radiography system designed for use in the DRS. The results indicate that the parameter enables very good image quality in the digital radiography. Of course, the quality of image from a parameter is determined by other digital devices in addition to the proper clinical image.