• Journal of Oral Medicine and Pain
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• v.26 no.4
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• pp.395-406
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• 2001

지난 수십년동안, 다양한 레이저기기를 이용하여 치아 경조직에 대한 응용 실험을 수행되었다. 그러나, 발생한 주요한 문제는 열발생과 플라즈마 형성과 같은 부작용이 지속된다는 점이었다. 실망스러운 실험결과에 따라 치아 삭제에 대한 레이저의 응용에 대한 연구가 거의 진행되지 못하였다. 본 연구의 목적은 국내에서 처음으로 개발된 얼비움레이저기기를 사용하여 다양한 에너지 수준과 다양한 펄스빈도에서 법랑질의 삭제율을 비교하고자 하였다. 본 연구에 사용된 레이저기기는 국내에서 최초로 개발된 $2.94{\mu}m$ 펄스를 $250{\mu}s$ 방출하는 얼비움야그레이저 기기이다. 기기의 에너지는 20 mJ에서 350 mJ까지 다양하게 방출하며, 최대 출력은 3.5 W이다. 22개의 치아를 에폭시 레진에 포매하고 경화하였다. 치아의 법랑질을 회전 다이아몬드 칼을 흐르는 물과 함께 사용하여 협측 또는 설측으로 평탄하게 삭제하였다. 제작된 법랑질표면은 6개의 구획으로 구분하여 에너지 수준과 펄스빈도에 따라 조사하였다. 본 연구에서 사용된 표본 수는 132개이며, 삭제율을 조사하기 위한 모든 표본은 22개의 실험 군으로 분류하였다. 실험결과는 다음과 같다. 1. 에너지 수준간에는 유의한 삭제율의 차이가 있었다. 2. 40 및 80 mJ로 조사한 경우에는 펄스빈도 간에 차이가 없었지만, 120 mJ의 출력으로 동일한 에너지를 조사한 경우에는 20 Hz가 40 또는 80 mJ로 조사한 경우 보다 가장 삭제효과가 높았다. 3. 연속조사 한 경우 조사시간 경과에 따라 법랑질의 삭제율은 증가되지 않았다. 결론적으로 효과적으로 법랑질을 삭제하기 위해서는 적절한 에너지와 펄스의 레이저를 사용해야 하며, 또한 항상 정확한 초점거리를 유지해야 할 것으로 사료된다.

• 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.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.272-285
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• 2003

This study was conducted to observe the microscopic structures of cavities formed after ablation of primary teeth, permanent teeth, enamel and dentin in using a bur and cavities formed after ablation using laser and the following results were obtained after comparing the effects of ablation. Using a #330 bur and Er:YAG laser irradiated at 150 mJ, 200 mJ, 250 mJ and 300 mJ all at the frequency of 5 Hz, 1 mm enamel and dentin samples were ablated and the ablation time was measured. In order to measure the surfaces ablated, 5 each of primary teeth and permanent teeth were ablated using a #330 bur and Er:YAG laser at 150 mJ, 200 mJ, 250 mJ and 300 mJ for 1 sec and the cross section and vertical section were observed. The following results were obtained : 1. Cutting time of Er:YAG laser was longer than that of conventinal high-speed bur regardless of teeth type. 2. Cutting on enamel, Cutting time of conventional high-speed bur in deciduous teeth was longer than in permanent teeth(P<0.05). But Er:YAG laser was not showed any difference between the deciduous and permanent teeth(P>0.05). 3. Cutting on dentin, Cutting time of conventional high-speed bur in permanent teeth was longer than deciduous teeth. Er:YAG laser of 150 mJ, 5 Hz in permanent teeth was longer than in deciduous teeth(p<0.05). But laser of other power did not showed mean difference. 4. The cavity surface treated with the convetional high-speed bur revealed a relatively flat appearance, almost covered with a debris-like smear layer. Cavity wall showed striped appearance because of blade of bur. 5. The cavity surface treated by the Er:YAG laser system was irregular or rough surface with the absence charring, carbonization, or cracking of the dentin. In addition, there was an absence of a smear layer. Cavity floor was round and relatively smooth. According to these results, cutting time of Er:YAG laser was almostly same in permanent and deciduous teeth, but more effective in dentin than enamel. Cutting the sample, Er:YAG laser was needed more time than conventional bur. But SEM findings suggested that laser device produced favorable surface characteristic(i.e, no smear layer, irregular surface, cracking).

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.190-192
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• 2018

최근 딥 러닝 기술의 발전이 가속화됨에 따라, 기존의 알고리즘과 융합하여 뛰어난 성능 향상을 보이는 연구가 급격히 증가하고 있다. 본 논문에서는 딥 러닝을 이용하여 HEVC 로 압축된 동영상의 일부 프레임의 삭제여부를 검출하는 알고리즘을 제안한다. 영상의 삭제 정보가 포함되어 있는 HEVC 의 부호화 파라미터를 추출하여 간단한 전 처리 과정을 통해 데이터의 크기를 효과적으로 압축한 뒤, 동영상의 시간적 특성을 고려할 수 있도록 CNN 네트워크를 구성한다. 실험 결과, 효과적으로 다양한 압축 환경에 강인한 영상 삭제 검출 성능을 보이는 것을 확인하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10c
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• pp.287-290
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• 2006

플래시 메모리는 동작 특성상 메모리 영역에 대한 덮어쓰기(overwrite)가 불가능하고 메모리 쓰기를 위해서는 삭제(erase) 연산을 반드시 먼저 수행해야 한다. 삭제 연산은 읽기 연산에 비해 많은 시간이 소요되므로 될수록 줄이는 것이 플래시 메모리의 수행 성능 향상에 유리하다. 본 논문에서는 플래시 메모리에 대한 삭제 횟수를 줄이기 위해 데이터베이스 페이지에 대한 쓰기 연산을 지연하는 지연쓰기 기법을 제안한다. 이 기법은 페이지에 대한 갱신이 일어날 때 페이지캐시 내의 해당 페이지에 대해서는 갱신을 수행하되 그것을 유발한 레코드 연산(레코드 삽입, 갱신, 삭제)은 별도의 지연쓰기 큐에 기록한다. 그리고 레코드 연산이 지연쓰기 큐에 저장되어 있는 동안에는 해당 페이지에 대한 갱신은 보류한다. 만약 해당 페이지를 다시 읽어야할 필요가 있을 때에는 지연 쓰기 큐에 저장된 갱신 정보와 병합하여 갱신된 페이지를 페이지 캐시에 적재한다. 이는 갱신되는 페이지의 개수와 단일 페이지에 대한 갱신 횟수를 감소시키는 효과를 가져온다. 따라서 플래시 메모리의 삭제 및 쓰기 연산을 감소시켜 데이터베이스 시스템의 수행성능을 향상시키게 된다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.01a
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• pp.345-348
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• 2022

본 논문에서는 유체 시뮬레이션(Fluid simulation)중 화염에서 표현되는 불똥 입자(Fire-flake particle)의 생성, 움직임과 삭제를 효율적으로 학습하고 표현할 수 있는 인공지능 기법에 대해 소개한다. 유체 시뮬레이션을 계산하기 위해서는 일반적으로 수치해석학과 같은 학문의 이해가 필요하며 불똥이나 거품과 같은 유체의 2차 효과(Secondary effect)는 기반유체(Underlying fluids)를 통해 추출되기 때문에 복잡하고 계산양이 많아진다. 이러한 문제를 완화하고자 본 논문에서는 인공신경망을 이용한 분류 모델 학습을 통해 격자 내에서 표현되어야 하는 불똥 입자의 생성을 학습하고, 다항 회귀 모델 학습을 통해 불똥 입자의 움직임을 예측한다. 또한, 불똥 입자가 삭제되어야하는 상태를 네트워크 학습을 통해 얻어내며, 수명(Lifespan) 임계값 조절하여 다양한 장면에서 불똥을 제어할 수 있다. 결과적으로 화염의 움직임을 기반으로 불똥의 움직임을 복잡한 수학식이나 디자이너에게 의존하지 않고 인공지능 학습을 통해 쉽게 제어하고 예측하는 결과를 보여준다.

• Smart Media Journal
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• v.4 no.2
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• pp.26-33
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• 2015

In this paper, we propose an efficient automatic pedestrian removal system from a frame in a video sequence. It firstly finds pedestrians from the frame using a Histogram of Oriented Gradient(HOG) / Linear-Support Vector Machine(L-SVM) classifier, searches for proper background patches, and then the patches are used to replace the deleted pedestrians. Background patches are retrieved from the reference video sequence and a modified feather blender algorithm is applied to make boundaries of replaced blocks look naturally. The proposed system, is designed to automatically detect object and generate natural-looking patches, while most existing systems provide search operation in manual. In the experiment, the average PSNR of the replaced blocks is 19.246

• 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 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.

• 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.