• Maxillofacial Plastic and Reconstructive Surgery
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• 제37권
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• pp.9.1-9.7
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• 2015

Background: This study are to identify the symptomatic changes and condylar stability after 2 jaw surgery without preceding treatments for Temporomandibular joints(TMJ) in class III patients with the TMJ symptoms; and to assess therapeutic effect of 2 jaw surgery and the necessity of preceding treatment for alleviation of TMJ symptoms. Methods: 30 prognathic patients with preexisting TMJ symptoms were divided into 2 groups according to presence or absence of preceding treatments before the surgery. We evaluated symptomatic changes on both TMJ by questionnaires and clinical examinations. And we reconstructed 3D cone beam computed tomography images before 2 jaw surgery, immediately after the surgery, and 6 months or more after the surgery with SimPlant software, and analyzed the stability of condylar position on 3D reconstruction model. Significances were assessed by the Wilcoxon signed rank test on SPSS ver. 20.0. Results: Both groups had favorable changes of TMJ symptoms after orthognathic surgery. And postoperative position of condyle had good stability during follow-up period. Conclusion: 2 jaw surgery without preceding treatments for TMD can have therapeutic effect for TMD patients with class III malocclusion.

• 한국재료학회지
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• 제15권6호
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• pp.361-369
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• 2005

InP(100) crystal surface was irradiated by ion beams with low energy $(180\~225\;eV)$ and high flux $(\~10^{15}/cm^2/s)$, Self-organization process induced by ion beam was investigated by examining nano structures formed during ion beam sputtering. As an ion source, an electrostatic closed electron Hall drift thruster with a broad beam size was used. While the incident angle $(\theta)$, ion flux (J), and ion fluence $(\phi)$ were changed and InP crystal was rotated, cone-like, ripple, and anistropic nanostrucuture formed on the surface were analyzed by an atomic force microscope. The wavelength of the ripple is about 40 nm smaller than ever reported values and depends on the ion flux as $\lambda{\propto}J^{-1/2}$, which is coincident with the B-H model. As the incident angle is varied, the root mean square of the surface roughness slightly increases up to the critical angle but suddenly decreases due to the decrease of sputtering yield. By the rotation of the sample, the formation of nano dots with the size of $95\~260\;nm$ is clearly observed.

• 한국도로학회논문집
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• 제14권3호
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• pp.49-58
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• 2012

1986년 AASHTO 설계법에서 회복탄성계수를 이용한 다짐관리 기법이 제안된 이후, 국내외에서 경험적 설계법에서 역학적-경험적 설계법으로 전환되고 있다. 10여년의 연구결과 노상 다짐관리는 기존의 다짐도와 평판재하시험에서 평판재하시험 및 소형 충격 재하시험, 동적 콘 관입시험으로 전환되어질 예정이다. 본 연구에서는 노상 재료의 물성치와 구조해석을 통해 한국형 도로포장 설계법에서 제시된 회복탄성계수 예측식을 검증하였으며, 실제 평판재하시험, 소형충격재하시험, 동적 콘 관입시험등의 현장시험을 통해 경험적 모델로 추정된 회복탄성계수와 현장 탄성계수 측정값간의 상관관계식들을 개발하였다. 또한 제안된 상관관계를 이용하여 현장시험을 통한 노상의 다짐관리방안을 제안하였다.

• Journal of Periodontal and Implant Science
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• 제50권3호
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• pp.146-158
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• 2020

Purpose: The aim of this study was to investigate and identify the main causes of periodontal tissue change associated with labial gingival recession by examining the anterior region of patients who underwent orthodontic treatment. Methods: In total, 45 patients who had undergone orthodontic treatment from January 2010 to December 2015 were included. Before and after the orthodontic treatment, sectioned images from 3-dimensional digital model scanning and cone-beam computed tomography images in the same region were superimposed to measure periodontal parameters. The initial labial gingival thickness (IGT) and the initial labial alveolar bone thickness (IBT) were measured at 4 mm below the cementoenamel junction (CEJ), and the change of the labial gingival margin was defined as the change of the distance from the CEJ to the gingival margin. Additionally, the jaw, tooth position, tooth inclination, tooth rotation, and history of orthognathic surgery were investigated to determine the various factors that could have affected anterior periodontal tissue changes. Results: The mean IGT and IBT were 0.77±0.29 mm and 0.77±0.32 mm, respectively. The mean gingival recession was 0.14±0.57 mm. Tooth inclination had a significant association with gingival recession, and as tooth inclination increased labially, gingival recession increased by approximately 0.2 mm per 1°. Conclusions: In conclusion, the IGT, IBT, tooth position, tooth rotation, and history of orthognathic surgery did not affect labial gingival recession. However, tooth inclination showed a significant association with labial gingival recession of the anterior teeth after orthodontic treatment.

• 한국화재소방학회논문지
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• 제34권4호
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• pp.59-68
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• 2020

본 연구에서는 축소모형을 이용한 철도터널의 화재안전성 평가 실험시 필요한 축소모형 철도차량의 화재에 대한 설계를 수행하였다. 기존의 철도터널 축소모형 실험시 활용된 방법의 단점을 극복하기 위하여 화재부력을 위하여서는 메탄올 화원을 이용하였으며, 연기 가시화를 위하여서는 스모크카트리지를 활용하여 철도차량 화재를 모사하였다. 지하철 철도차량의 열방출률의 모사를 위하여 다양한 메탄올 연료 팬에 대하여 콘칼로리미터(ISO 5660) 및 저울을 이용하여 열방출률을 측정하였다. 설계된 축소모형 철도차량 화원을 이용하여 축소모형 철도터널에서의 임계속도를 측정하였다. 화재 임계속도는 축소모형 터널 상부에서의 온도 및 레이져를 이용한 가시화 측정결과 등을 종합적으로 검토하여 선정하였다.

• 한국지구과학회지
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• 제38권2호
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• pp.115-128
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• 2017

아소 화산은 일본 규슈 중앙부에 위치하며, 세계에서 가장 큰 칼데라 화산중의 하나이다. 나카다케 분화구는 아소 칼데라의 중앙 화구군에서 유일한 활동적인 화산체이다. 2016년 10월 8일 아소 산에서 36년 만에 폭발적인 분화가 발생하였으며, 분연주가 11 km 상공까지 상승하였고 화산재는 최대 300 km 떨어진 지역에서도 확인되었다. 본 연구에서는 미국 USGS에서 개발한 Ash3D모델을 이용하여 2016년 10월 8일의 분화에서 발생한 화산재의 확산과 침적에 대한 수치모의를 실시하였다. 수치모의 결과 분화에 의해 발생한 화산재는 아소 칼데라 화산의 동쪽과 북동쪽으로 확산되어 우리나라에는 피해를 주지 않는 것으로 나타났으며, 동북동 방향으로 최대 400 km 이상 먼 곳까지 침적되는 것으로 나타났다. 본 연구의 수치모의 결과는 관측 확인된 화산재 침적 결과와 대체로 일치하였다. 빠른 화산재 재해 예보를 위하여 Ash3D를 이용한 수치모의가 유용하게 쓰일 수 있을 것이다.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.179-190
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• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• 대한기계학회논문집B
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• 제35권8호
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• pp.799-804
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• 2011

본 논문에서는 자연채광 시스템 LFLP(Linear Fresnel Light Pipe)와 DBLP(Double Blind Light Pipe)시스템을 비교하였다. LFLP시스템은 평행한 빛을 선형프레넬렌즈를 이용하여 선형 형태로 빛으로 집광하여 자연채광에 이용하는 시스템이며, DBLP시스템은 베네시안 형태의 블라인드를 이용하여 빛을 반사시켜 자연채광에 이용하는 시스템이다. DBLP시스템은 LFLP시스템을 개선한 것으로 시스템 앞쪽에 위치한 블라인드는 태양의 고도에 따른 빛을, 뒤쪽에 위치한 블라인드는 태양의 방위각에 따른 빛을 변광부로 반사시키도록 설계 되었다. DBLP시스템의 변광부는 콘모양으로 이루어 져 있으며 블라인드에 의해 반사된 빛을 산광부로 보내주는 역할을 하며, 산광부로 들어온 빛은 실내조명에 사용된다. 따라서 맑은날(clear sky)을 기준으로 두 시스템의 효율을 비교하면 DBLP시스템이 LFLP시스템보다 세배 높게 나오는 것으로 나타났다.

• 한국추진공학회지
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• 제5권1호
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• pp.18-25
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• 2001

2차 가스 분사 추력벡터 제어 성능 해석을 위한 체계적인 수치계산을 수행하였다. 분사위치와, 노즐 팽창각이 압력비, 추력비, 비추력비 및 축추력 증대와 같은 전체 성능 파라미터에 미치는 2차 분사의 효과를 고찰하였다. 2차 제트 분사에 의한 복잡한 노즐 배기 유동에 대한 수치 해석은 Baldwin-Lomax 난류 모델을 포함하는 비정상 3차원 레이놀즈 평균 Navier-Stokes 방정식을 이용하여 수행하였고, 팽창 팽착반각이 $9.6^{\cire}$인 로켓 노즐에서의 2차 공기분사에 대해 적용, 실험값과 비교, 검증 하였다. 전체 성능 파라미터에 대한 결과로서 주 노즐의 하류에 2차 분사구를 위치시키는 것이 반사 충격파의 발생을 방지하며, 넓은 적용범위에 대하여 효율적이고 안정한 추력 방향제어에 적합한 것으로 나타났다.

• 천문학회보
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• 제36권1호
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• pp.39.2-39.2
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• 2011

In this study we have examined the occurrence probability of solar proton events (SEPs) and their peak fluxes depending two CME parameters, linear speed and angular width. For this we used the NOAA SPE events and their associated CME data from 1997 to 2006. As a result, the probability strongly depends on two parameters as follows. In the case of halo CME whose speed is equal to and faster than 1500km/s, 36.1% are associated with SPEs but in the case of partial halo CME ($120^{\circ}{\leq}AW$ < $359^{\circ}$) whose speed is $400{\leq}V$ < $1000km/s$, only 0.9% are associated with SPEs. When we consider only front-side CMEs, 45.3% are associated with SPEs in the first case and 1.8% are associated with them in the second case. Both of whole CME data group and front-side CME data group have similar tendencies. The probabilities are different as much as 4.9 to 23 times according to the CME speed and 1.6 to 6.5 times to the angular width. We have also examined the relationship between CME speed and proton peak flux as well as its dependence on angular width (partial halo CME and halo CME), longitude (east, center, and west) and direction parameter (< 0.4 and {\geq} 0.4). Our results show that the relationships strongly depend on longitude as well as direction parameter. In addition, the relationship using the radial CME speed based on a cone model has a higher correlation coefficient than that using the projected CME speed.