• 한국산업정보학회논문지
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• 제24권5호
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• pp.129-137
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• 2019

정보 기술의 발전에 따라 유비쿼터스 컴퓨팅 기술이 대두되고 있다. 이에 맞춰 디바이스의 소형화와 사용자의 편리성을 증대시키기 위한 여러 연구가 진행되고 있다. 그중 몇몇의 제안된 디바이스들은 사용자가 착용해야 한다는 점과 손에 들고 동작시켜야 한다는 불편함이 있다. 본 논문에서는 이러한 불편함을 해결하기 위해 텔레비전 시청 시 사용할 수 있는 가상 버튼을 제안하였다. 텔레비전을 통해 영상 시청 시 전방에서 사용자가 영상을 시청한다는 점을 이용해 카메라를 TV 상단에 설치하여 카메라가 머리 위쪽을 촬영하게 한다. 촬영된 영상에서 배경과 손 영역을 분리하여 검출하고, 검출된 손 영역에 외곽선을 검출한 후 손가락의 끝점을 검출한다. 손가락의 끝점을 검출하면 전방을 촬영하고 있는 영상 상단에 가상 버튼 인터페이스가 출력되며 검출된 손가락의 끝점이 포인터가 되어 위치정보를 갖고 버튼 안쪽에 위치할 경우 버튼이 동작한다.

• Archives of Plastic Surgery
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• 제50권4호
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• pp.335-339
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• 2023

It is undeniable that a significant number of patients who want to improve their facial appearance is increasingly interested in nonsurgical procedures. Without a doubt, the use of autologous fat could not be left out as a magnificent alternative for nasal modeling simply because of four influential factors: ease of collection, compatibility, the temporality of the results, and safety. This work describes an innovative alternative technique for nasal modeling using micrografts enriched with adipose-derived mesenchymal stem cells (ASCs). With this technique, fat was collected and divided into two samples, nanofat and microfat. Nanofat was used to isolate the ASCs; microfat was enriched with ASCs and used for nasal modeling. Lipoinjection was performed in a supraperiosteal plane on the nasal dorsum. Through a retrolabial access, the nasal tip and base of the columella were lipoinjected. We consider that nonsurgical nasal modeling using micrografts enriched with ASCs can be an attractive and innovative alternative. This technique will never be a substitute for surgical rhinoplasty. It can be performed in a minor procedure area with rapid recovery and return to the patient's daily activities the next day. If necessary, the procedure can be repeated.

• 한국해양공학회지
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• 제27권3호
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• pp.67-72
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• 2013

In this study, numerical analyses that considered the dynamic interaction effects between the flow and a turbine were carried out to investigate the power output performance of an H-type Darrieus turbine rotor, which is one of the representative lifting-type vertical-axis tidal-current turbines. For this purpose, a commercial CFD code, Star-CCM+, was utilized for an example three-bladed turbine with a rotor diameter of 3.5 m, a solidity of 0.13, and the blade shape of an NACA0020 airfoil, and the optimal tip speed ratio (TSR) and corresponding maximum power coefficient were evaluated through exhaustive simulations with different sets of flow speed and external torque conditions. The optimal TSR and maximum power coefficient were found to be approximately 1.84 and 48%, respectively. The torque and angular velocity pulsations were also investigated, and it was found that the pulsation ratios for the torque and angular velocity were gradually increased and decreased with an increase in TSR, respectively.

• 한국염색가공학회지
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• 제29권4호
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• pp.256-267
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• 2017

The purpose of this study was to analyze the functional ingredients of Perilla Frutescens L. Britt extracts and to confirm the possibility of producing PVA nanofibers using extracts. Distilled water, 3% aqueous sodium hydroxide solution and ethanol were used as extraction solvents. The electrospinning was carried out at a PVA concentration of 12%, an applied voltage of 10 kV and a tip to collector distance of 15cm. The contents of volatile substances, essential oils, total polyphenols and flavonoids of the extracts were measured to examine the constituents of functional materials. Flavor components and esters were identified in 3% sodium hydroxide and ethanol extracts. The content of polyphenols and flavonoids in ethanol extracts was higher than that of medicinal plants. 1wt.% of Tween 20 was added to disperse the essential oil components of the ethanol extract. Addition of a dispersant made it possible to produce a homogeneous mixture by having some compatibility with the ethanol extracts and the PVA molecule. When the concentration of the ethanol extract was 0.25 and 0.5wt%, relatively uniform PVA nanofiber having an average diameter of 350 to 365nm could be produced. The results of FT-IR, XRD and DSC analysis confirmed that Perilla Frutescens L. Britt ethanol extract was well mixed with PVA molecules and was electrospun.

• 한국항공우주학회지
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• 제31권2호
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• pp.41-50
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• 2003

본 논문에서는, 병렬 다중 프런트 해법을 이용한 비선형 병렬 구조해석 과정을 소개하고 이의 응용예제로써 2차원 및 3차원 균열 모델에서의 손상 국부화를 모사하였다. 비선형 유한요소 해석과 연속체 손상역학과 관련된 병렬 알고리듬을 구현하였고, 비선형 손상해석에서 사용되는 많은 변수들을 저장하기 위해서는 메모리가 많이 필요하므로 이를 줄이는 방안을 고려하였다. 그리고 손상 진전으로 인한 변형도 연화가 발생할 때 해를 구하기 위해 사용한 Riks의 연속법도 병렬 계산에 맞도록 수정하였다. 수치예제로써, 최대 약 1백만 자유도를 가진 모델들을 사용하여 손상 국부화 문제를 해석하였는데, 이 예제에서 비선형 병렬 알고리듬의 병렬효율과 자유도 변화에 따른 균열 끝단에서의 손상 변화를 살펴보았다.

• The Journal of Advanced Prosthodontics
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• 제2권4호
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• pp.134-141
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• 2010

PURPOSE. The objective of this study was to evaluate fracture strength of collarless metal-ceramic FPDs according to their metal coping designs. MATERIALS AND METHODS. Four different facial margin design groups were investigated. Group A was a coping with a thin facial metal collar, group B was a collarless coping with its facial metal to the shoulder, group C was a collarless coping with its facial metal 1 mm short of the shoulder, and group D was a collarless coping with its facial metal 2 mm short of the shoulder. Fifteen 3-unit collarless metal-ceramic FPDs were fabricated in each group. Finished FPDs were cemented to PBT (Polybutylene terephthalate) dies with resin cement. The fracture strength test was carried out using universal testing machine (Instron 4465, Instron Co., Norwood MA, USA) at a cross head speed of 0.5 mm/min. Aluminum foil folded to about 1 mm of thickness was inserted between the plunger tip and the incisal edge of the pontic. Vertical load was applied until catastrophic porcelain fracture occurred. RESULTS. The greater the bulk of unsupported facial shoulder porcelain was, the lower the fracture strength became. However, there were no significant differences between experimental groups (P > .05). CONCLUSION. All groups of collarless metal-ceramic FPDs had higher fracture strength than maximum incisive biting force. Modified collarless metal-ceramic FPD can be an alternative to all-ceramic FPDs in clinical situations.

• Geomechanics and Engineering
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• 제15권4호
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• pp.927-935
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• 2018

The mechanical behavior of the brittle material samples containing the internal and edge cracks are studied under direct shear tests. It is tried to investigate the effects of stress interactions and stress intensity factors at the tips of the pre-existing cracks on the failure mechanism of the bridge areas within these cracks. The direct shear tests are carried out on more than 30 various modeled samples each containing the internal cracks (S models) and edge cracks (E models). The visual inspection and a low power microscope are used to monitor the failure mechanisms of the tested samples. The cracks initiation, propagation and coalescences are being visualized in each test and the detected failure surfaces are used to study and measure the characteristics of each surface. These investigations show that as the ratio of the crack area to the total shear surface increases the shear failure mode changes to that of the tensile. When the bridge areas are fixed, the bridge areas in between the edge cracks have less strength than those of internal cracks. However, the results of this study show that for the case of internal cracks as the bridge area is increased, the strength of the material within the bridge area is decreased. It has been shown that the failure mechanism and fracture pattern of the samples depend on the bridge areas because as the bridge area decreases the interactions between the crack tip stress fields increases.

• 한국컴퓨터정보학회논문지
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• 제17권12호
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• pp.219-228
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• 2012

본 논문에서는 키넥트의 3차원 영상정보를 이용하여 손가락 움직임을 검출하고 이 정보를 이용하여 종이건반 피아노를 구현하는 방법을 제안한다. 키넥트의 컬러영상과 깊이영상을 이용하여 먼저 건반 식별을 위해 필요한 건반 패턴 정보와 사용자의 종이건반 누름 여부를 판정하기 위한 건반깊이 정보를 검출한다. 배경의 깊이정보를 이용하여 입력된 깊이정보로부터 손 영역을 검출할 경우 종이건반과 접촉한 손가락 끝부분이 잘려나가는 문제를 해결하기 위해 스킨 컬러를 이용하여 정확도를 향상시켰다. 그리고 면적을 이용한 외곽선 검출과 convex hull 알고리즘을 이용하여 손가락 끝점을 검출하고 건반 패턴 정보와 비교하여 건반 누름을 판정하였다. 본 논문에서 제안하는 방법을 이용하여 종이건반 피아노 성능평가를 수행한 결과 높은 검출 정확도를 보였다. 구현된 종이건반 피아노 기능을 활용하여 피아노 연주 입력장치를 구현함으로써 PC기반 피아노 연주시스템 구현의 편리성을 보였으며 악기 초보자가 PC 기반 피아노 연주 학습에 사용자 인터페이스로 활용할 수 있는 가능성을 확인하였다.

• Tribology and Lubricants
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• 제31권6호
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• pp.264-271
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• 2015

Adhesion force of nanomaterials such as nanoparticle, nanowire, and nanorods should be significantly considered for its mechanical applications. However, examination of the adhesion force is limited since it is technically challenging to carry out experiments with such small objects. Therefore, in this work, molecular dynamics simulation (MDS) was conducted to determine the adhesion force between a nanowire and a flat surface, which could not be readily assessed through experiments. The adhesion force of a cylindrical-shaped nanowire was assessed by performing MDS and applying an equation of Van der Waals interaction. Simulation was conducted in two steps: indentation of a spherical tip on the flat surface and indentation of a cylinder on the flat surface, because the purpose of the simulation was comparing the results of the simulation and calculation of the Van der Waals interaction equation. From the simulation, Hamaker constant used for the equation of Van der Waals interaction was determined to be 2.93 °ø 10?18 J. Using this constant, the adhesion force of the nanowire on the flat surface was readily estimated by calculating Van der Waals equation to be approximately 65~89 nN with respect to the diameter of the nanowire. Moreover, the adhesion force of the nanowire was determined to be 52~77 nN from the simulation It was observed that there was a slight discrepancy (approximately 15~25%) between the results of the simulation and the theoretical calculation. Thus, it was confirmed that the calculation of Van der Waals interaction could be utilized to assess the adhesion force of the nanowire.

• 대한기계학회논문집A
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• 제38권2호
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• pp.121-127
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• 2014

단층 그래핀 시트(Single layer graphene sheet, SLGS)의 찢어짐 모드(모드 III) 파괴 예측을 위한 원자 기반 미세결합요소모델이 개발되었다. 이 모델은 그래핀 시트의 최대 변형률 관계를 예측하기 위해 수정된 모스포텐셜을 사용한다. 면외 전단하중 조건에서 그래핀의 모드 III 파괴를 광범위한 분자역학(Molecular mechanics, MM) 시뮬레이션으로 조사하였다. 분자역학은 원자의 균열선단 근처 원자의 변위를 설명하기 위해 사용되었고, 선형탄성파괴역학은 이 영역 바깥의 영역을 설명하기 위해 사용되었다. 해석 결과 분자역학 방법이 SLGS의 전단 물성 계산뿐만 아니라 armchair 및 zigzag 방향 모드 III 파괴인성 연구에도 단순하면서도 신뢰할만하다는 것을 보여준다. SLGS 의 모드 III 파괴인성은 zigzag 방향에 대해 $0.86MPa{\sqrt{m}}$, armchair 방향에 대해 $0.93MPa{\sqrt{m}}$로 예측되었다.