• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.4
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• pp.300-309
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• 1996

The electric and magnetic fields radiated by lightning discharges are significantly changeable in amplitude and time, one of the topics concerning electromagnetic compatibility of modern electronic systems is the efficient and economic protection against transient voltages caused by not only by direct but also by nearly lightning strokes. In this paper, in order to obtain the detailed informations about lightning electromagnetic impulse waveforms, the electric and magnetic fields radiated by lightning discharges in the summer of 1995 were measured by a fast electric antenna and a loop-type magnetic field sensor, and their charac- teristics were presented and analyzed. The signals of the electric and magnetic fields were re- corded continuously by a transient digitizer having a resolution of 12 bit and a memory capacity of 5000 point and using a sampling time of 200 ns. The electric and magnetic field waveforms associated with lightning return strokes are significantly different with those of intracloud discharges. The magnetic fields radiated by intracloud lightning discharges have essentially the same waveforms as the electric field when the lightning discharhes are at distance of 50 km or more. Also the main frequency components of the electric and magnetic fields radiated by lightning discharges range from a few kHz to several hundred kHz.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.1
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• pp.20-34
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• 2003

Novel methods producing supplementary and prosthetic material by cutting or discharge processing via computer design have been proposed as alternatives for traditional casting methods and are being utilized for commercial purposes. The CAD/CAM system used in dentistry can be classified into three-dimensional input of target values, restoration design, and material processing. The marginal fidelity in production of In-Ceram core has important clinical implications and is a key consideration issue in CAD/CAM production as well. Through this research, the author arrived at the following conclusion aaer conducting comparison analysis of marginal fidelities between the In-Ceram core produced via CAD/CAM and that produced through the traditional method ; 1. In the cases of mesial, distal, and lingual margins, the core margins via CAD/CAM produced lower values than those via the traditional method, but the differences were found to be statistically insignificant. 2. In the case of labial flange, the core margins via CAD/CAM produced lower values than those via the traditional method and the differences were found to be statistically significant. (p<0.05) 3. In comparision with overall marginal fidelity, the core margins via CAD/CAM produced lower values than those via the traditional method, but the differences were found to be statistically insignificant. 4. Among the core margins produced via the traditional method did not have statistically significant differences but fir those produced via CAD/CAM had statistically significant differences between labial and lingual sides and between labial and mesial sides. (p <0.05).

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.28-31
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• 2002

Filmless full-PACS in korea has rapidly been growing, since government had supported collaborative PACS project between industry and university hospital in late of 1995. At the same time, a small company had started PACS business, while the Korea PACS society was being formed. In the beginning, PACS societies had focused on developing peripheral solutions such as DICOM gateway for image acquisition, x-ray film digitizer, and viewing software for research or management of personal image data, while Samsung Medical Center had started installing an imported partial PACS system which had recently upgraded with a new system. In similar time frame, a few hospitals had started developing and installing domestic large scale full-PACS system. Several years later, many hospitals have installed full-PACS system with national policy of reimbursement for PACS exams in November 1999. It is believed that Korea is the first country that adopted PACS reimbursement for filmless full-PACS as a national policy. Both experiences of full-PACS installation and national policy generated tremendous intellectual and technological expertise about PACS at all levels, clinical, hospital management, education, and industrial sectors. There are currently three types of PACS system which includes domestic, imported, and hybrid PACS system with imported solution for core system and domestic solution for peripheral system. There are more than 20 domestic PACS companies and they have now enough experiences so that they are capable of installing a truly full-PACS system for large-scale teaching hospitals. PACS societies in Korea understand how to design, implement, install, manage, sustain, and provide good services for large-scale full-PACS. PACS society has also strength for the highest integration technology of the Hospital Information. However, further understanding and timely implementation of continuously evolving international standard and integrated healthcare enterprise concepts may be necessary for international leading of PACS technologies for the future.

• Journal of radiological science and technology
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• v.33 no.3
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• pp.173-178
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• 2010

In projection radiography, two types of digital imaging systems are currently available, computed radiography (CR) and digital radiography (DR): a difference between them can be stated in terms of dose and image quality. In the Department of Radiology our hospital, a flat-panel DR equipment (Digital diagnost, Philips) and two CR systems (ADC Compact plus digitizer, AGFA) are employed. Eight standard radiographic examinations (Skull AP, Skull LAT, Chest PA, Chest LAT, Abdomen AP, L-spine AP, L-spine LAT, Pelvis AP) were considered: doses delivered to patients in terms of both entrance skin dose (ESD) were calculated and compared in order to study the dosimetric discrepancies between CR and DR. Assessment of image quality is undertaken by Consultant Radiologists to ensure that the quality criteria for diagnostic radiographic images of the European guidelines were met. Results showed that both ESD in DR are lower than that in CR; all images met the criteria in the European Guidelines for both modalities and were used for reporting by the radiologists. Since the operators are the same and the image quality is comparable in both modalities, this study shows that in the considered examinations, DR can perform better than CR from a dosimetric point of view.

• Journal of the Korean Association of Geographic Information Studies
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• v.5 no.4
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• pp.45-55
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• 2002

The purpose of this study is to suggest the way of analyzing land uses to utilize GIS in the field of urban planning. The Saga Land Information System was built in early 1990s. The building data were inputted by house investigation map(1/1,000) using digitizer. And urban planning basis investigation data in 1994 were utilized as the attribute data. Also, by calculating specialization factor, we distinct the characteristic of every land use of the city, and it compares every land use zone. This study calculated and compared an observation frequency and an expectation frequency of every building use and land use zone. We found that the use of the building tend to be controlled and guided by the land use zone.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.1
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• pp.95-122
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• 1990

This study was done to analyze the occlusal curve as one of the factors to be considered for maintenance of occlusal stability in the orthodontic and prosthodontic treatments. Sixty gnathological casts we.e obtained from 43 subjects with normal occlusion and 17 subjects with some of temporomandibular disorders. The occlusal surfaces of gnathologic casts were duplicated by using a Color kit SK-700 and tile reference points of X, Y coordinates were digitized by using the Summagraphic digitizer and 18AT computer system. The Z coordinates of cusp height were measured by 0.01mm measurable caliper. The mathematical computer program of least square method was used to analyze the occlusal curve arranged by three dimensional coordinates of X, Y, Z. The following results were obtained : 1. The occlusal curve of buccal and lingual cusp tips was fitted to the ellipse, and the occlusal curve of anterior teeth was fitted to a part of the circle in the analysis of conic sections. 2. The radius of Spee's curve showed individual differences, but was average 98.7mm in male subjects and 93.7mm in female subjects. 3. The radius fo Spee's curve according to the half of canine width showed the least coefficient of variation. 4. The radius of Spee's curve was not significantly relative to the lateral occlusal contacts on laterotrusion and the absence or presence of temporomandibular disorders. 5. The radius of Wilson's curve showed individual difference and the size of radius was followed by the order of 1st premolar, 2nd premolar, 2nd molar and 1st molar.

• Progress in Medical Physics
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• v.29 no.2
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• pp.53-58
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• 2018

This paper evaluates patient-specific quality assurance (PSQA) in the treatment of small and multiple tumors by the CyberKnife system with fixed collimators, using an ion chamber and EBT3 films. We selected 49 patients with single or multiple brain tumors, and the treatment plans include one to four targets with total volumes ranging from 0.12 cc to 3.74 cc. All PSQA deliveries were performed with a stereotactic dose verification phantom. The A16 microchamber (Standard Imaging, WI, USA) and Gafchromic EBT3 film (Ashland ISP Advanced Materials, NJ, USA) were inserted into the phantom to measure the point dose of the target and the dose distribution, respectively. The film was scanned 1 hr after irradiation by a film digitizer scanner and analyzed using RIT software (Radiological Imaging Technology, CO, USA). The acceptance criteria was <5% for the point dose measurement and >90% gamma passing rate using 3%/3 mm and relative dose difference, respectively. The point dose errors between the calculated and measured dose by the ion chamber were in the range of -17.5% to 8.03%. The mean point dose differences for 5 mm, 7.5 mm, and 10 mm fixed cone size was -11.1%, -4.1%, and -1.5%, respectively. The mean gamma passing rates for all cases was 96.1%. Although the maximum dose distribution of multiple targets was not shown in the film, gamma distribution showed that dose verification for multiple tumors can be performed. The use of the microchamber and EBT3 film made it possible to verify the dosimetric and mechanical accuracy of small and multiple targets. In particular, the correction factors should be applied to small fixed collimators less than 10 mm.

• Korean Journal of Digital Imaging in Medicine
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• v.10 no.2
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• pp.23-31
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• 2008

Computed radiography(CR) has been widely used in the field of diagnostic radiography since digital X-ray image was introduced. The imaging performance of CR system was studied by analyzing the digital image data of the CR images which are the outcomes of the whole imaging system composed of image plate(IP), laser digitizer, analoge-digital convertor, and a given image processing unit. In this study, we used a conventional CR system made by Agfa. From the flat field image of 150$\times$150 image pixels, signal-to-noise ratio(SNR) was calculated. SNR of the CR image increases in proportion to logarithm value of the X-ray exposure irradiated on the IP. SNR is less than about 6 at the exposure below 0.2mR and is more than 10 at the exposure above 0.54mR. In our study, most of images obtained by the smaller exposures less than 2.0mR can not be readable. In general, the minimum value of the SNR ranges from 3 to 5. We obtained modulation transfer function(MTF) by analyzing the bar pattern image which was made under conditions as follows: X-ray tube potential was 55kVp, the IP exposure was 0.54 mR, and the distance between X-ray source to IP was 2m, where bar pattern was located on the IP. MTF is 23% at 2.5lp/mm spatial frequency. Provided that the MTF of noise equivalent modulation is 10%, the CR system has the limiting spatial resolution of 3.2lp/mm. If the image sharpness is evaluated by the spatial frequency where MTF is 50%. the corresponding spatial frequency is 0.5$\sim$0.75lp/mm. MTFA(Modulation Transfer Function Area) is 1.0lp/mm. Compared with the Fuji CR whose MTFA is 1.1lp/mm, Agfa CR in this study shows almost same MTFA performance.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.1
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• pp.71-92
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• 1999

This study is to analyze the stress and displacement on the jaws during the bilateral and unilateral clenching task on three dimensional finite element model of the dentated skull. For this study, the computed tomography(G.E.8800 Quick, USA) was used to scan the total length of human skull in the frontal plane at 1.9mm intervals. The CAD data were extracted from the tomograms through digitizer(Summa Sketch III, USA) and then reconstructed by means of the spline method in the CAD program. In this project, a commercial software I-DEAS(Master Series ver-sion 3.0, SDRC Inc, USA) was used for three-dimensional stress analysis on the finite element model. which consists of articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. The results are as follows. ; 1. During the bilateral clenching, each major muscle forces caused high stresses on various areas of skull: masseter muscle on articular disc and teeth ; temporal muscle on mandible and periodontal ligament ; medial pterygoid muscle on the temporomandibular joint. During the unilateral clenching, masseter muscle induced the maximum stress ; medial pterygoid muscle the minimum stress. 2. During the bilateral clenching, higher compressive stresses on articular disc were generated by the masseter muscle and higher deformation occurred on the most front outer sites. And during the unilateral clenching, temporal muscle and medial pterygoid muscle exerted their forces to twist temporomandibular joint area of the balancing side and induced a higher compressive stresses on the front outer sites of articular disc. 3. During the bilateral clenching, the masseter muscle bended the mandible outwardly, and then caused tensile stresses on the lingual surface of mandibular symphysis. And the medial pterygoid muscle caused tensile stresses on the labial surface of mandibular symphysis. 4. When each muscles were simultaneously applied on jaws, a high stress and displacement took place on mandible rather than on the maxilla. Also, a high stress and displacement took place during the unilateral clenching rather than during the bilateral clenching.

• Journal of Periodontal and Implant Science
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• v.24 no.1
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• pp.165-177
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• 1994

To investigate the depth of the root concavity and root surface area of the maxillary first premolar, 40 maxillary first premolars were used. All the teeth which extracted because of advanced periodontal disease and orthodontic treatment procedure, were sectioned every 1.5mm from cementoenameljunction to the apex with hard tissue microtome. Each sectioned root was taken photograph with slide film, and projected for measuring with a calibrated digital Curvi-Meter. The root surface area, percentage of the RSA and the linear variation of the RSA were calibrated for each 1.5mm section. Linear variation of the depth of root concavity was measured on mesial and distal root surface for each section using computer-aided digitizer. The results were as follows. 1. The total mean root length of maxillary first premolar was 13.48mm. Mean buccal root length of 2-rooted tooth was 12.59mm, mean palatal root length was 12.73mm, and mean root length of single rooted tooth was 13.78mm. 2. The total mean root surface area of maxillary first premolar was $194.17mm^2$, mean root surface area for 2-rooted tooth was $205.97mm^2$ and mean root surface area for single rooted tooth was $188.49mm^2$. 3. It was 59.93% of the total root surface area that the area from CEJ to coronal 6mm. And, the coronal half of the root length accounted for approximately 71.76% of the total root surface area. 4. Most deepest concavity of the mesial root surface was 0.65mm at apical 3.0mm, 4.5mm level in maxillary first premolar. And, that of the distal root surface was 0.37mm at apical 4.5mm level. 5. All of the maxillary first premolar had mesial root surface concavity. This mesial root surface concavity appeared to be more pronounced in 2-rooted tooth than single rooted tooth.