• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.354-362
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• 2016

PURPOSE. The trueness and precision of acquired images of intraoral digital scanners could be influenced by restoration type, preparation outline form, scanning technology and the application of power. The aim of this study is to perform the comparative evaluation of the 3-dimensional reproducibility of intraoral scanners (IOSs). MATERIALS AND METHODS. The phantom containing five prepared teeth was scanned by the reference scanner (Dental Wings) and 5 test IOSs (E4D dentist, Fastscan, iTero, Trios and Zfx Intrascan). The acquired images of the scanner groups were compared with the image from the reference scanner (trueness) and within each scanner groups (precision). Statistical analysis was performed using independent two-samples t-test and analysis of variance (${\alpha}=.05$). RESULTS. The average deviations of trueness and precision of Fastscan, iTero and Trios were significantly lower than the other scanners. According to the restoration type, significantly higher trueness was observed in crown and inlay than in bridge. However, no significant difference was observed among four sites of preparation outline form. If compared by the characteristics of IOS, high trueness was observed in the group adopting the active triangulation and using powder. However, there was no significant difference between the still image acquisition and video acquisition groups. CONCLUSION. Except for two intraoral scanners, Fastscan, iTero and Trios displayed comparable levels of trueness and precision values in tested phantom model. Difference in trueness was observed depending on the restoration type, the preparation outline form and characteristics of IOS, which should be taken into consideration when the intraoral scanning data are utilized.

• 한국정보통신학회논문지
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• 제7권3호
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• pp.532-543
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• 2003

본 논문은 저작권보호를 위해 디지털영상의 라벨링을 위한 reversible DTCNN(discrete-time cellular neural network) 구조를 제안한다. 이러한 저작권보호 라벨링을 위해서 2차원 이진 pseudo 랜덤 영상열에 사용할 수 있는 새로운 reversible DTCNN의 구조와 개념을 설명하고 이에 대한 복잡행위를 보여주기 위해 reversible DTCNN의 서로 다른 방법들의 예시를 들어 설명한다. 또한 서로 다른 2진영상인 원영상과 복사된 영상은 서로 다른 2진 랜덤 영상키를 사용한다. 이 영상키는 원영상을 스크램블하는데 사용된다. 따라서 reversible DTCNN를 다시 역변환시켜서 저작권보호가 라벨링된 영상으로부터 복사된 영상임을 찾아낼 수 있다. 그러나 이러한 동영상을 처리하는 데는 S/W에서는 많은 시간이 소요되므로 고속 DTCNN 칩을 사용하여 실시간에서 동영상이나 비디오영상을 저작권보호를 위한 라벨링에 사용할 수 있으며, 이러한 결과를 컴퓨터에서 시뮬레이션됨을 보인다.

• 방송공학회논문지
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• 제20권5호
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• pp.667-675
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• 2015

고화질, 고품질 방송에 대한 관심이 크게 증가하면서 영상 신호 뿐만 아니라 음향 신호의 고품질화를 요구하는 목소리도 높아지고 있다. 음향 신호의 고품질화에 기여하는 요소 중 하나는 가령, 10.2채널, 22.2채널 등과 같은 재생 채널 수의 확장이지만 이는 많은 수의 스피커를 설치해야만 하는 문제점이 발생한다. 이와 같은 문제를 해결하기 위한 한 가지 방법으로 전방 스피커 어레이를 통한 입체 음향 재생 방식을 들 수 있는데 본 논문에서는 스피커 어레이 기반 음장 재생 방식인 음장합성 기술 (Wave Field Synthesis, WFS)에 대한 소개 및 이론적인 분석을 하고 이 기술로 구현한 전방 스피커 어레이 시스템의 입체 음향 재현 성능을 확인하기 위한 주관 청취 평가 결과를 제시한다. 결론적으로, WFS에 기반한 전방 스피커 어레이 재생 방식이 디스크리트 5.1채널 재생 방식과 비교하여 만족스러운 음장감을 제공한다는 것을 알 수 있었다.

• 한국운동역학회지
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• 제21권5호
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• pp.511-520
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• 2011

The purpose of this study was to provide scientific information to track and field coaches and athletes through the analyses of the biomechanics characteristics of the top 4 sprinters in the men's 100 m final in the IAAF World Championships Daegu 2011. Twelve video cameras (Sony, Japan) were used to capture the mid portion of the race (40 m - 70 m) with a sampling frequency of 60Hz. Biomechanical variables including the right ankle, knee and hip angles, the trunk angle, and the velocity of center of mass (COM) in the running direction, were calculated with the Kwon 3D program (Visol, Korea). Correlation coefficients between the COM velocity and each variables were calculated using Matlab 2008a (MathWorks, USA) at an alpha level of 0.05. The findings indicated that Yohan Blake (JAM) showed greater range of motion at the ankle and hip. Walter Dix(USA) showed greater knee and trunk movement, and Kim Collins (SKN) showed more dorsi-flexed and extended trunk angles during the race. Finally, Christophe Lemaitre (FRA) showed more plantar-flexed ankle with a less trunk motion, throughout the analyzed race.

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.252-256
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• 2017

PURPOSE. This in vitro study aimed to analyze and compare the reproducibility of zirconia and lithium disilicate crowns manufactured by digital workflow. MATERIALS AND METHODS. A typodont model with a prepped upper first molar was set in a phantom head, and a digital impression was obtained with a video intraoral scanner (CEREC Omnicam; Sirona GmbH), from which a single crown was designed and manufactured with CAD/CAM into a zirconia crown and lithium disilicate crown (n=12). Reproducibility of each crown was quantitatively retrieved by superimposing the digitized data of the crown in 3D inspection software, and differences were graphically mapped in color. Areas with large differences were analyzed with digital microscopy. Mean quadratic deviations (RMS) quantitatively obtained from each ceramic group were statistically analyzed with Student's t-test (${\alpha}=.05$). RESULTS. The RMS value of lithium disilicate crown was $29.2\;(4.1){\mu}m$ and $17.6\;(5.5){\mu}m$ on the outer and inner surfaces, respectively, whereas these values were $18.6\;(2.0){\mu}m$ and $20.6\;(5.1){\mu}m$ for the zirconia crown. Reproducibility of zirconia and lithium disilicate crowns had a statistically significant difference only on the outer surface (P<.001). The outer surface of lithium disilicate crown showed over-contouring on the buccal surface and under-contouring on the inner occlusal surface. The outer surface of zirconia crown showed both over- and under-contouring on the buccal surface, and the inner surface showed under-contouring in the marginal areas. CONCLUSION. Restoration manufacturing by digital workflow will enhance the reproducibility of zirconia single crowns more than that of lithium disilicate single crowns.

• 방송공학회논문지
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• 제17권4호
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• pp.684-694
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• 2012

수중 환경에서 물과 부유물에 의한 빛의 감쇄와 산란은 수중 영상의 색상을 열화시키고 가시성을 저하시키는 주요 원인이 된다. 이러한 수중 산란광은 피사체와의 거리의 함수로 표현되므로 깊이 정보는 빛의 전달률을 계산하기 위한 중요한 정보를 제공한다. 본 논문에서는 깊이 영상을 이용하여 전달률을 측정하고 이를 기반으로 영상의 각 화소에 존재하는 산란에 의한 열화값을 제거함으로써 수중 스테레오 영상의 가시성을 개선하는 방법을 제안한다. 제안하는 방법은 제거해야 하는 열화값이 영상의 화소값 보다 크지 않도록 보정하여 가사성 개선 시 나타날 수 있는 부분적인 영상 왜곡을 방지한다. 또한 수중 스테레오 영상의 심각한 문제점 중의 하나인 색상 불균형을 효과적으로 보정하여 가시성 개선 후 좌, 우 영상의 동일성을 유지한다. 실험 결과는 다양한 환경의 수중 영상에 대하여 제안하는 가시성 개선 후 색대비가 영상에 따라 5%에서 14%이상 향상되었음을 보여준다.

• 한국운동역학회지
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• 제27권1호
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• pp.35-43
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• 2017

Objective: The purpose of this study was to determine how gaze angle affects muscle activity and kinematic variables during treadmill walking and to offer scientific information for effective and safe treadmill training environment. Method: Ten male subjects who have no musculoskeletal disorder were recruited. Eight pairs of surface electrodes were attached to the right side of the body to monitor the upper trapezius (UT), rectus abdominis (RA), erector spinae (ES), rectus femoris (RF), bicep femoris (BF), tibialis anterior (TA), medialis gastrocnemius (MG), and lateral gastrocnemius (LG). Two digital camcorders were used to obtain 3-D kinematics of the lower extremity. Each subject walked on a treadmill with a TV monitor at three different heights (eye level; EL, 20% above eye level; AE, 20% below eye level; BE) at speed of 5.0 km/h. For each trial being analyzed, five critical instants and four phases were identified from the video recording. For each dependent variable, one-way ANOVA with repeated measures was used to determine whether there were significant differences among three different conditions (p<.05). When a significant difference was found, post hoc analyses were performed using the contrast procedure. Results: This study found that average and peak IEMG values for EL were generally smaller than the corresponding values for AE and BE but the differences were not statically significant. There were also no significant changes in kinematic variables among three different gaze angles. Conclusion: Based on the results of this study, gaze angle does not affect muscle activity and kinematic variables during treadmill walking. However, it is interesting to note that walking with BE may increase the muscle activity of the trapezius and the lower extremity. Moreover, it may hinder proper dorsiflexion during landing phase. Thus, it seems to reasonable to suggest that inappropriate gaze angle should be avoided in treadmill walking. It is obvious that increased walking speed may cause a significant changes in biomechanical parameters used in this study. It is recommended that future studies be conducted which are similar to the present investigation but using different walking speed.

• 한국화재소방학회논문지
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• 제28권6호
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• pp.22-27
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• 2014

본 연구에서는 Fuel bed를 이용한 실험을 통하여 지표화 확산에 의한 온도 분포, 화염 높이, 복사열, 확산속도 등을 측정하였다. 실험 변수로는 수종, 풍속 및 경사도 등을 사용하였다. 수종으로는 침엽수종인 소나무 낙엽과 활엽수종인 굴참나무 낙엽을 사용하였다. 풍속은 터널식 방 구조에서 간이풍속 장치를 이용하여 1 m/s, 3 m/s, 5 m/s 풍속을 조절하여 실험하였다. 경사도는 Fuel bed의 기울기를 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 변화시켜 가며 조절하였다. 온도 분포 및 확산속도를 측정하기 위하여 K-type 1.6 mm 열전대를 35개를 격자모양으로 배치하였다. 측정을 위하여 복사열량계를 사용하였으며 이외에도 비디오 카메라 및 열화상 카메라를 사용하였다.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.105-113
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• 2009

The performance of a direct-injection type diesel engine often depends on the strength of swirl or squish, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the combustion in the cylinder was affected by the mixture formation process. In this paper, combustion process of biodiesel fuel was studied by employing the piston which has several grooves with inclined plane on the piston crown to generate swirl during the compression stroke in the cylinder in order to improve the atomization of high viscosity fuel such as biodiesel fuel and toroidal type piston generally used in high speed diesel engine. To take a photograph of flame, single cylinder, four stroke diesel engine was remodeled into two stroke visible engine and high speed video camera was used. The results obtained are summarized as follows; (1) In the case of toroidal piston, when biodiesel fuel was supplied to plunger type injection system which has very low injection pressure as compared with common-rail injection system, the flame propagation speed was slowed and the maximum combustion pressure became lower. These phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of swirl groove piston, early stage of combustion such as rapid ignition timing and flame propagation was activated by intensifying the air flow in the cylinder. (3) Combustion process of biodiesel fuel was improved by the reason mentioned in paragraph (2) above. Consequently, the swirl grooves would also function to improve the combustion of high viscosity fuel.

• 한국운동역학회지
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• 제15권4호
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• pp.169-179
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• 2005

In the 500m short track speed skating, the matter of who reaches the first corner first can important factor since each competitor races with all speed from the start to the first line. A filed study was attempted to kinematical estimation six female foreign skaters, who participated in the 500m female final round competition, and two Korea skates during the World Short track Skating Championship. The three dimensional motion analysis with DLT method was executed using four video cameras for analyzing the actual competition situation. In point of analyzing the actual competition situation, it is expected that skaters and coaches the effective informations, and the following conclusions are drawn; The elapsed time by phase in start motion of the foreign skaters appeared shorter those of Korea skaters, so the start training of Korea skaters should be strengthed. Also the displacement of C.G in the foreign skaters appeared shorter displacement than those of Korea skaters. Especially in the starting position, the foreign skaters are superior to Korea skaters in displacement of first(left) and next following stroke(right). The velocity of C.G and maximum velocity of skate blade of foreign skaters art faster than those of Korea skaters. And the foreign skaters show the superior early velocity change. Both of leaning body angle, and left and knee angle of the foreign skaters lead to positive point of having the propulsive force in the early starting position. Observing in the most prominent feature of foreign and Korea skaters in start phase, foreign skaters skate quickly the third stroke. These features of Korea skaters would appear disadvantage of location selection in entering the coner course.