• Proceedings of the Korean Society of Laser Processing Conference
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• 2005.11a
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• pp.37-41
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• 2005

When screen size of the Flat Panel Display (FPD) becomes larger, the traditional photo-lithography using photomasks and UV lamps might not be possible to make patterns on Photo Resist (PR) material due to limitation of the mask size. Though the maskless photo-lithography using UV lasers and scanners had been developed to implement large screen display, it was very slow to apply the process for mass-production systems. The laser exposure system using 405 nm semi-conductor lasers and Digital Micromirror Devices (DMD) has been developed to overcome above-mentioned problems and make more than 100 inches FPD devices. It makes very fine patterns for full HD display and exposes them very fast. The optical engines which contain DMD, Micro Lens Array (MLA) and projection lenses are designed for 10 to 50 ${\mu}m$ bitmap pattern resolutions. The test patterns for LCD and PDP displays are exposed on PR and Dry Film Resists (DFR) which are coated or laminated on some specific substrates and developed. The fabricated edges of the sample patterns are well-defined and the results are satisfied with tight manufacturing requirements.

• Journal of ILASS-Korea
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• v.28 no.1
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• pp.32-42
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• 2023

In this study, spray characteristics of n-heptane and propane were investigated under different injection pressure using various imaging techniques such as Mie-scattering, DBI (diffuse back-illumination), and Schlieren imaging techniques. NI compact RIO system was used to control a test injector. Spray penetration length, length-to-width ratio and number of black pixels were calculated by using MATLAB software to compare spray characteristics of each fuel. Longer spray penetration length and higher length-to-width ratio were observed in propane spray because of flash boiling caused by high saturated vapor pressure. Spray collapse occurred in propane spray due to the high plume-to-plume interaction. Moreover, rapid evaporation occurred in propane spray, so that nozzle tip wetting could not be observed. Rapid evaporation of propane also caused fewer residual droplets compared to n-heptane spray. Therefore, propane is advantageous in reducing the generation of soot emission from large droplets that are not atomized. However, additional evaluation should be conducted considering combustion efficiency and the possibility of deposits by nozzle tip icing during fuel injection.

• Imaging Science in Dentistry
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• v.50 no.1
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• pp.15-22
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• 2020

Purpose: This study was conducted to objectively and subjectively compare the accuracy and reliability of 2-dimensional(2D) photography and 3-dimensional(3D) soft tissue imaging. Materials and Methods: Facial images of 50 volunteers(25 males, 25 females) were captured with a Nikon D800 2D camera (Nikon Corporation, Tokyo, Japan), 3D stereophotogrammetry (SPG), and laser scanning (LS). All subjects were imaged in a relaxed, closed-mouth position with a normal smile. The 2D images were then exported to Mirror^® Software (Canfield Scientific, Inc, NJ, USA) and the 3D images into Proplan CMF^® software (version 2.1, Materialise HQ, Leuven, Belgium) for further evaluation. For an objective evaluation, 2 observers identified soft tissue landmarks and performed linear measurements on subjects' faces (direct measurements) and both linear and angular measurements on all images(indirect measurements). For a qualitative analysis, 10 dental observers and an expert in facial imaging (subjective gold standard) completed a questionnaire regarding facial characteristics. The reliability of the quantitative data was evaluated using intraclass correlation coefficients, whereas the Fleiss kappa was calculated for qualitative data. Results: Linear and angular measurements carried out on 2D and 3D images showed excellent inter-observer and intra-observer reliability. The 2D photographs displayed the highest combined total error for linear measurements. SPG performed better than LS, with borderline significance (P=0.052). The qualitative assessment showed no significant differences among the 2D and 3D imaging modalities. Conclusion: SPG was found to a reliable and accurate tool for the morphological evaluation of soft tissue in comparison to 2D imaging and laser scanning.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.965-970
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• 2012

In this study, the water distribution in the cathode side of a direct methanol fuel cell (DMFC) is visualized using a neutron imaging technique at the Neutron Radiography Facility (NRF), KAERI. It is difficult to quantify the water content in the cathode side because of $CO_2$ gas. A compared open circuit voltage (OCV) image, relative $CO_2$, and water distribution can be visualized by the neutron imaging technique. This means that the neutron imaging technique is useful for the optimization of the flow field design and the establishment of water management, and, in turn, for the improvement of the cell performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.456-459
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• 2004

Analog film/screen systems have been being changed to a digital x-ray imaging device using direct conversion materials. Photocoductors for a direct detection flat-panel imager require high x-ray absorption, ionization and charge collection, low leakage current and large area deposition. In this work, $HgI_2$ films with excellent properties for x-ray detector were deposited by screen printing method. The thickness of $HgI_2$ film was about $150\;{\mu}m$. The passivation layer is fabricated using a-Se and parlyene, the both fabrication $HgI_2$ film were compared for analyzing the leakage current reduction. We measured electrical properties-leakage current, photosensitivity, SNR though I-V measurement, As the result, $HgI_2$ film using a-Se passivation layer had the greater

• Imaging Science in Dentistry
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• v.34 no.4
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• pp.185-190
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• 2004

Purpose: To compare the diagnostic accuracy for the detection of root fractures in CMOS-based digital periapical images with conventional film-based periapical images. Materials and Methods: Sixty extracted single-root human teeth with closed apices were prepared endodontically and divided into two groups; artificially induced vertical root fracture group and control group. All radiographs were obtained using the paralleling technique. The radiographs were examined by 4 observers three times within a 4 week interval. Receiver operating characteristic (ROC) analysis was carried out using data obtained from four observers. Intra- and inter-examiner agreements were computed using kappa analysis. Results: The area under the ROC curve (Az) was used as an indicator of the diagnostic accuracy of the imaging system. Az values were as follows: direct-digital images; 0.93, film-based images; 0.92, and inverted digital images; 0.91. There was no significant difference between imaging modalities (P<0.05). The kappa value of inter-observer agreement was 0.42 (range: 0.28-0.60) and intra-observer agreement was 0.57 (range: 0.44-0.75). Conclusion : There is no statistical difference in diagnostic accuracy for the detection of vertical root fractures between digital periapical images and conventional periapical images. The results indicate that the CMOS sensor is a good image detector for the evaluation of vertical root fractures.

• Journal of the Korean Society of Radiology
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• v.2 no.4
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• pp.33-40
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• 2008

Images acquired by a digital X-ray imaging system are inherently degraded due to system degradation process and additive noise sources. The system degradation in image quality is typically described as the system response function characterized by the modulation transfer function (MTF) and the noise term described as the noise power spectrum (NPS). In this case, we can restore the blur image as close as possible to the original image by using modified filtering designed for digital imaging system, as we know more precisely about the MTF and the NPS. In this paper, by performing simulation, we tried to restore blurred images taken from a digital X-ray imaging system based upon conventional filtering techniques such as a direct-inverse filtering, limited-inverse filtering, or a Wiener filtering, and evaluated the characteristics of the image restoration.

• The korean journal of orthodontics
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• v.45 no.3
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• pp.105-112
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• 2015

Objective: A recently developed facial scanning method uses three-dimensional (3D) surface imaging with a light-emitting diode. Such scanning enables surface data to be captured in high-resolution color and at relatively fast speeds. The purpose of this study was to evaluate the accuracy and precision of 3D images obtained using the Morpheus 3D$^{(R)}$ scanner (Morpheus Co., Seoul, Korea). Methods: The sample comprised 30 subjects aged 24.34 years (mean $29.0{\pm}2.5$ years). To test the correlation between direct and 3D image measurements, 21 landmarks were labeled on the face of each subject. Sixteen direct measurements were obtained twice using digital calipers; the same measurements were then made on two sets of 3D facial images. The mean values of measurements obtained from both methods were compared. To investigate the precision, a comparison was made between two sets of measurements taken with each method. Results: When comparing the variables from both methods, five of the 16 possible anthropometric variables were found to be significantly different. However, in 12 of the 16 cases, the mean difference was under 1 mm. The average value of the differences for all variables was 0.75 mm. Precision was high in both methods, with error magnitudes under 0.5 mm. Conclusions: 3D scanning images have high levels of precision and fairly good congruence with traditional anthropometry methods, with mean differences of less than 1 mm. 3D surface imaging using the Morpheus 3D$^{(R)}$ scanner is therefore a clinically acceptable method of recording facial integumental data.

• Imaging Science in Dentistry
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• v.43 no.1
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• pp.37-44
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• 2013

Purpose: The aim of this study was to analyze three-dimensional images of the arterial supply to the temporo-mandibular joint. Materials and Methods: Ten patients (five men and five women, mean age 36 years) without signs or symptoms of temporomandibular disorders, who underwent contrast-enhanced computed tomographic (CT) scanning with intravenous contrast, were studied. The direct volume rendering technique of CT images was used, and a data set of images to visualize the vasculature of the human temporomandibular joint in three dimensions was created. After elaboration of the data through post-processing, the arterial supply of the temporomandibular joint was studied. Results: The analysis revealed the superficial temporal artery, the anterior tympanic artery, the deep temporal artery, the auricular posterior artery, the transverse facial artery, the middle meningeal artery, and the maxillary artery with their branches as the main arterial sources for the lateral and medial temporomandibular joint. Conclusion: The direct volume rendering technique was found to be successful in the assessment of the arterial supply to the temporomandibular joint. The superficial temporal artery and maxillary artery ran along the lateral and medial sides of the condylar neck, suggesting that these arteries are at increased risk during soft-tissue procedures such as an elective arthroplasty of the temporomandibular joint.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.176-176
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• 2007

Flat-panel direct conversion detectors used in compound substance of semiconductor are being studied for digital x-ray imaging. Recently, such detectors are deposited by physical vapor deposition(PVD) generally. But, most of materials (HgI2, PbI2, TlBr, PbO) deposited by PVD have shown difficult fabrication and instability for large area x-ray imaging. Consequently, in this paper, we propose applicable potentialities for screen printing method that is coated on a substrate easily. It is compared to electrical properties among semiconductors such as $HgI_2$, $PbI_2$, PbO, HgBrI, InI, and $TlPbI_3$ under investigation for direct conversion detectors. Each film detector consists of an ~25 to $35\;{\mu}m$ thick layer of semiconductor and was coated onto the substrate. Substrates of $2cm{\times}2cm$ have been used to evaluate performance of semiconductor radiation detectors. Dark current, sensitivity and physics properties were measured. Leakage current of $HgI_2$ as low as $9pA/mm^2$ at the operation bias voltage of ${\sim}1V/{\mu}m$ was observed. Such a value is not better than PVD process, but it is easy to be fabricated in high quality for large area x-ray Imaging. Our future efforts will concentrate on optimization of growth of film thickness that is coated onto a-Si TFT array.