• Journal of Oral Medicine and Pain
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• v.30 no.3
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• pp.375-381
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• 2005

Er:YAG laser has been considered a promising alternative to dental drill and many researches indicate that adjustment to variable parameters, including water flow rate, pulse energy and pulse repetition rate, can be made to improve ablation ability and efficiency of the laser. Of these parameters, addition of water spray during irradiation has been thought to ablate dental hard tissue more rapidly and safely. The purpose of this study was to investigate tooth ablation amount by Er:YAG laser irradiation as related to varied water flow rates added and, ultimately to find the most effective water flow rate for ablation. In addition, the temperature change of pulp chamber during irradiation was also monitored on the irradiated and opposite pulpal walls, respectively. An Er:YAG laser with contact mode was employed. Extracted human molars were split into two pieces for ablation experiment. Pulse energies of 200 and 300 mJ with a pulse repetition rate of 20 Hz and 5 water flow rates (1.6, 3.0, 5.0, 7.0, and 10.0 ml/min) were applied. Each irradiation was performed for 3 seconds. According to these parameters, experimental groups were divided into 10 subgroups which consisted of 5 specimens. For temperature experiment, another 5 tooth-specimens were prepared in the manner that pulp chamber was open through access cavity preparation and two temperature-measuring probes were placed respectively on the irradiated and the opposite walls of pulp chamber. From the experiment on ablation amount related to different water flow rates, it was shown that the least water flow rate of 1.6 ml/min ablated more than any other water flow rates (p<0.000). When the irradiation for 3 seconds, combined with the pulse repetition time of 20Hz and the water flow rate of 1.6 ml/min was done to tooth specimen, the temperature rise was not noticeable both on the irradiated and the opposite pulpal walls (less than 3$^{\circ}C$) and there was no significant difference in temperature rise between the two pulse energies, 200 and 300 mJ. From the results of this study, it is suggested that tooth ablation with Er:YAG laser can be done effectively and safely at a energy between 200 and 300 mJ/pulse and a pulse repetition rate of 20 Hz when the lasing is conjugated with the water flow rate of 1.6ml/min.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.9
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• pp.9-13
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• 2010

In this thesis, we develop and analyze the beamforming algorithm which has two constraints to combat the signal cancellations. Through the simulation results, it is shown that the proposed scheme is more efficient compared with the spatial averaging method for preventing signal cancellation and eliminating interfering signal.

• Journal of Oral Medicine and Pain
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• v.31 no.3
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• pp.223-229
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• 2006

The objectives of this study was to investigate the amount of tooth ablation and the change of intrapulpal temperature by Er:YAG laser as it relates to pulse energy and pulse repetition rate at the identical power and, thereby, to reveal which of the two parameters strongly relates with ablation efficiency and intrapulpal temperature. Extracted healthy human molar teeth were sectioned into two pieces and each specimen was irradiated within the combination of pulse energy and pulse repetition time at the same power of 3W; $300mJy{\times}10Hz$ group, $200mJy{\times}15Hz$ group, and $150mJy{\times}20Hz$ group. Each specimen comprised ten tooth specimens. A laser beam with conjunction of a water flow rate of 1.6 ml/min was applied over enamel surfaces of the specimens during 3 seconds and the ablation amount was determined by difference in weight before and after irradiation. To investigate the temperature change in the pulp according to the above groups, another five extracted healthy human molar teeth were prepared. Each tooth was embedded into resin block and the temperature-measuring probes were kept on the irradiated and the opposite walls in the dental pulp during lasing. When the power was kept constant at 3W, ablation amount increased with pulse energy rather than pulse repetition rate (p=0.000). Although intrapulpal temperature increased with pulse repetition rate, there were no significant differences among the groups and between the irradiated and the opposite pulpal walls, except at a condition of $150y{\times}20Hz$ (p=0.033). Conclusively, it is suggested that ablation efficacy is influenced by pulse energy rather than pulse repetition rate.

• Korean Journal of Cognitive Science
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• v.7 no.1
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• pp.5-35
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• 1996

This paper addresses an one-pass parallel thinning algorithm which shows effectiveness in both accuracy and speed. The proposed method is based on parallel iterative boundary removal.Image connectivity are preseved and the algorithms performance is compared to other algorithms especially to parallel thinning algorithm which is the best parallel algorithm have been proposed.Evaluation result shows that the proposed algorithm compare favorably to others.The result shows exact thinning free from one pixel boundary noise and free from distortion of shape.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.728-734
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• 2001

The purpose of this study was to investigate the effects of Er:YAG laser on cutting of efficacy of enamel and dentin in primary and permanent teeth. We used the enamel and dentin specimens of human teeth which contain the physiologic saline and maintain the pulpal pressure in dentinal tubules. Each specimen was exposed to Er:YAG laser with non-contact mode under different treatment condition of irradiation energy, pulse repetition rate. We investigated the cutting efficacy of Er:YAG laser by Scanning Intensity Microscopy, and obtained following results. 1. Cutting volume of enamel and dentin in primary and permanent teeth were increased by increasing the irradiation energy, pulse repetition rate. 2. Cutting volume of primary teeth was larger than that of permanent teeth. 3. Cutting volume of dentin was larger than that of enamel in primary and permanent teeth. From these results, Er:YAG laser would be more effective in cutting dentin than enamel, and in cutting primary teeth than permanent teeth for clinical application.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.615-617
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• 2009

공정제어분야의 분산제어시스템에서는 다양한 종류의 알람과 이벤트가 발생한다. 하지만 적용 분야에 따른 규격화된 알람 형식이 없기 때문에 매번 재정의를 하거나 프로그램의 대규모 수정을 해야 한다. 이러한 문제점을 해결하고자 알람 서버의 엔진은 변형 없이 알람 메시지 맵을 정의함으로써 다중 알람 발생자에서 발생하는 이벤트와 알람을 관리하며, 조건에 따른 자동 인지 및 삭제가 가능하도록 하며, 다중 알람 뷰어를 통해 사용자 인지, 삭제, 이력 조회 등이 가능하도록 하는 알람 서버를 설계하고자 한다. 본 논문에서는 알람 메시지 맵을 통한 신규 알람 등록을 자유롭게 하며, 다중 알람 발생자와 다중 알람 뷰어의 서비스를 위한 대규모 알람 서버를 설계하고자 한다.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.683-693
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• 2001

The purpose of this study was to evaluate the effects of Er:YAG laser on cutting efficacy and its histologic findings. Dentin specimens of human premolars and molars were used and irradiated by Er:YAG laser with noncontact handpiece type delivery system under different treatment condition of irradiation time. Cavity pattern and volume were evaluated to determine the cutting efficacy and following results were obtained. 1. Cutting volume of sound dentin was getting larger with time immersed in water increase 2. With the condition of irradiation (150mJ, 10Hz, 30sec), surface irregularity was more increased in sound dentin comparing to carious dentin. For the light microscopic examination, dentinal tubules were opened and ash flecks and cracks were noted with inconsistence of dentinal tubules. 3. In case of 30 sec. irradiation in carious dentin, dark zone was limited to small focus whereas 1 min. irradiation, more wider, and cracks were noted in the perpendicular to direction of dentinal tubules. For the 2 min. irradiation, cavity was the widest and more cracks were found.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.39-48
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• 2016

In this study, it can be shortened tunnel construction work period by introducing a single-shell tunnel does not placing the secondary concrete lining, a global research trend, reduction of the cost of the lining placement and number of benefits that can ensure the safety of long-term tunnel with a single shell it was to study the tunnel method. First, we analyze the design and construction practices relating to delete lining of the domestic design and construction practices and a comprehensive analysis of the stability study found a rock in good condition interval (1~3 grades), we propose that the lining uninstalled. In the case of domestic changes on the ground floor is very heavy underfoot conditions many so tunneling method by single shell as ground conditions are good and one preferred the water points that apply in less soil, the soil health and poor sections (4~5 grades) reflecting with respect to the concrete lining that is expected reasonable.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.32-44
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• 2001

The purpose of this study was to investigate the effects of Er : YAG laser on cutting efficacy and temperature changes of dentin. We used the dentin specimens of human premolars and molars which contain the physiologic saline and maintain the pulpal pressure in dentinal tubules. Each specimen was exposed to Er : YAG laser with non-contact handpiece type delivery system under different treatment condition of irradiation energy, pulse repetition rate, and exposure time. Two procedures were conducted by the presence of water flow during lasing. The specimens were grouped by thickness of dentin. We investigated the cavity pattern, volume, and temperature change of dentin specimen to determine the cutting efficacy and temperature rise of Er : YAG laser, and obtained following results. 1. Cutting volume of dentin was increased by increasing the irradiation energy, pulse repetition rate, and exposure time(P<0.05). 2. Margins of abulated cavities were sharp and clean and floors of cavities were conical in shape and showing smooth surfaces. Upper diameter of abulated cavities were increasing as laser parameter of irradiation energy, pulse repetition rate, and exposure time were increased. A few cracks were observed on abulated surfaces under treatment condition of laser parameter with 150mJ, 5Hz, and 5sec. 3. Temperature was increased as laser parameter of irradiation energy, pulse repetition rate, and exposure time were increased, and temperature rise was decreased as dentin thickness was increased(P<0.05). 4. Temperature rise was decreased under water flow compared with no water flow during laser exposure(P<0.05). From these results, we think that the method of using a Er:YAG laser would be effective and safe in cutting dentin for clinical application.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.06a
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• pp.403-406
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• 2001

문제은행 시스템은 피험자의 조건에 따라 데이터베이스에서 문항을 추출하여 가상공간에서 평가를 수행한다. 가상 공간에서의 평가는 피험자에게 적용하는 경우 출제 빈도에 따라 운항의 난이도 및 변별력에 영향을 주게 된다 출제 빈도에 따라 난이도나 변별력이 낮아지는 문항은 출제를 제한하는 기준이 필요하다. 본 논문에서는 문항 사후 난이도와 문항 변별도를 기반으로 하여, 문항 차분 난이도를 주기적으로 측정하고 난이도 차이가 일정 수준 이상이 되는 문항에 대해 출제를 제한하는 방안과 전체 피험자에 대한 운항의 변별력을 측정하러 변별력이 떨어지는 문항을 출제자에게 문항을 수정하게 하거나 삭제하도록 하는 방안들 제안한다.