• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제24권1호
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• pp.103-119
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• 2020

In this work, the hydromagnetic and thermal characteristics of natural convection flow in a vertical parallel plate micro-porous-channel with suction/injection is analytically studied in the presence of Hall current by taking the temperature jump and the velocity slip at the wall into account. The governing equations, exhibiting the physics of the flow formation are displayed and the exact analytical solutions have been obtained for momentum and energy equations under relevant boundary conditions. The impact of distinct admissible parameters such as Hartmann number, Hall current parameter, permeability parameter, suction/injection parameter, fluid wall interaction parameter, Knudsen number and wall-ambient temperature ratio on the flow formation is discussed with the aid of line graphs. In particular, as rarefaction parameter on the micro-porous-channel surfaces increases, the fluid velocity increases and the volume flow rate decreases for injection/suction.

• 한국소음진동공학회논문집
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• 제21권6호
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• pp.553-561
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• 2011

A theoretical approach is carried out to predict the quality factors of flexible modes of a microcantilever on a squeeze-film. The frequency response function of an inertially-excited microcantilever beam is derived using an Euler-Bernoulli beam theory. The external force due to squeeze-film phenomenon is developed from the Reynolds equation. Slip boundary conditions are employed at the interfaces between the fluid and the structure to consider the gas rarefaction effect, and pressure boundary condition at both ends of fluid analysis region is enhanced to increase the exactness of predicted quality factors. To the end, an approximate equation is derived for the first bending mode of the microcantilever. Using the approximate equation, the quality factors of the second and third bending modes are calculated and compared with experimental results of previously reported work. The comparison shows the feasibility of the current approach.

• 천문학회보
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• 제35권2호
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• pp.46.2-46.2
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• 2010

A magnetosonic wave is a longitudinal wave propagating perpendicularly to the magnetic fields and involves compression and rarefaction of the plasma. Lee and Kim (2000) investigated the theoretical solution for the evolution of nonlinear magnetosonic waves in the homogeneous space which adopt the approach of simple waves. We confirm the solution using a one-dimensional MHD code with Total Variation Diminishing (TVD) scheme. Then we apply the solution for the solar wind profiles. We examined the properties of nonlinear waves for the various initial perturbations at near the Lagrangian (L1) point. Also we describe waves steepening process while the shock is being formed by assuming different timescales for a driving source.

• Restorative Dentistry and Endodontics
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• 제42권1호
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• pp.65-71
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• 2017

A revascularization procedure was shown to be the best alternative therapy for immature teeth with necrotic pulp and apical infection. A 12 year old female with a history of trauma to her upper central incisor and a sinus tract was referred for endodontic treatment. She was an active orthodontic patient and had undergone regenerative endodontic treatment for the past 2 years. Clinical examination revealed no response to sensibility, percussion, and palpation tests. The preoperative radiograph showed an open apex and apical rarefaction. The case was diagnosed as previously treated tooth with asymptomatic apical periodontitis. Regenerative endodontic retreatment was performed, and the case was followed for 3 years. Clinical, radiographic, and cone-beam computed tomography follow-up examination revealed an asymptomatic tooth, with evidence of periapical healing and root maturation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.309-317
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• 2012

Recent years have witnessed the use of micro shock tube in various engineering applications like micro combustion, micro propulsion, particle delivery systems etc. The flow characteristics occurring in the micro shock tube shows a considerable deviation from that of well established conventional macro shock tube due to very low Reynolds number and high Knudsen number effects. Also the diaphragm rupture process, which is considered to be instantaneous process in many of the conventional shock tubes, will be crucial for micro shock tubes in determining the near diaphragm flow field and shock formation. In the present study, an axi-symmetric CFD method has been applied to simulate the micro shock tube, with Maxwell's slip velocity and temperature jump boundary conditions. The effects of finite diaphragm rupture process on the flow field and the shock formation was investigated, in detail. The results show that the shock strength attenuates rapidly as it propagates through micro shock tubes.

• 한국자기학회지
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• 제5권5호
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• pp.695-701
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• 1995

Fundamental issues and general procedures of modeling the head disk interface (HDI) in order to provide design criteria for future ultra-low flying sliders are given. Intermittent contact and gaseous rarefaction effects are discussed using nonconventional kinetic theory. To illustrate the simulation results, we modeled IBM 3370 taper flat sliders and positive/negative "bow tie" sliders. Several alternative HDI concepts for future disk drives - viscoelastic bearings, a hybrid system, and contact recording - are also briefly discussed.

• 한국자원식물학회지
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• 제30권5호
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• pp.481-488
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• 2017

전통민속식물지식이 빠르게 사라져 가는 상황에서 전통식물지식에 대한 기초조사를 통한 기록이 매우 중요한 과제가 되었다. 민속식물학 조사에서 조사강도와 민속식물정보, 식물종 정보의 증가에 관련성은 가장 중요한 과제이다. 본 연구에서는 국립수목원에서 발간된 자료를 이용하여 한반도 민속식물에 대한 메타 데이터를 DB화하여 분석하였다. 전통민속식물지식의 종풍부도에 추정은 ACE, Chao1, Chao 2, ICE, Jack 1, Jack 2, Bootstrap 등의 추정식을 이용하여 제시하였다. 종누적곡선 분석에서 지역별 종누적이 다른 양상을 보여 강원도의 누적곡선은 상대적 샘플링 노력이 더 필요하며충남 지역의 경우 조사 강도에 비해 일찍 수평선에 점근하는 특성을 보여 이지역의 조사 강도가 실제 정보량의 증가에 비해 높았다. 식용, 약용, 공예용 등의 종풍부도는 남녀간의 지식이 분포가 차이가 있음을 확인하였다. 주변환경의 식물상과 비교분석을 통해 일부 지역의 경우 민속식물조사가 상대적으로 조사량이 부족하고 추가 조사시 더 다양한 종이 발굴 될 것으로 예상된다.

• 대한소아치과학회지
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• 제49권4호
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• pp.468-480
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• 2022

이 연구의 목적은 구개측 및 협측 변위를 보이는 상악 영구 견치에서 차단적 유견치 발치의 효과를 평가하고, 치료 결과에 영향을 미치는 임상적 및 방사선학적 인자를 분석하는 것이다. 상악 영구 견치의 맹출 경로가 근심 및 교합면 방향을 향하면서 치관의 일부가 인접치 치근과 중첩된 것으로 진단된 환자 중 해당 부위의 상악 유견치를 발치한 86명의 환자의 97개의 상악 영구 견치를 연구 대상으로 하였다. 97개의 변위된 상악 영구 견치 중 64개(66.0%)가 유견치 발치만으로 인접 측절치 치근에서 완전히 벗어났다. 상악 영구 견치의 협-구개측 변위 방향, 치관첨의 수평 및 수직적 위치, 치근단 폐쇄 여부, 유견치의 치근단 방사선투과상 여부, 인접 측절치의 쐐기모양 여부가 치료 결과에 유의미한 영향을 미쳤다.

• Restorative Dentistry and Endodontics
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• 제39권2호
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• pp.120-125
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• 2014

Use of an apical plug in management of cases with open apices has gained popularity in recent years. Biodentine, a new calcium silicate-based material has recently been introduced as a dentine substitute, whenever original dentine is damaged. This case report describes single visit apexification in a maxillary central incisor with necrotic pulp and open apex using Biodentine as an apical barrier, and a synthetic collagen material as an internal matrix. Following canal cleaning and shaping, calcium hydroxide was placed as an intracanal medicament for 1 mon. This was followed by placement of small piece of absorbable collagen membrane beyond the root apex to serve as matrix. An apical plug of Biodentine of 5 mm thickness was placed against the matrix using pre-fitted hand pluggers. The remainder of canal was back-filled with thermoplasticized gutta-percha and access cavity was restored with composite resin followed by all-ceramic crown. One year follow-up revealed restored aesthetics and function, absence of clinical signs and symptoms, resolution of periapical rarefaction, and a thin layer of calcific tissue formed apical to the Biodentine barrier. The positive clinical outcome in this case is encouraging for the use of Biodentine as an apical plug in single visit apexification procedures.

• Imaging Science in Dentistry
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• 제47권2호
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• pp.129-133
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• 2017

Dentinogenesis imperfecta is a dominant autosomal hereditary disorder of dentin formation that affects the deciduous and permanent teeth. Its etiology is characterized by inadequate cell differentiation during odontogenesis. The clinical characteristics of dentinogenesis imperfecta are discolored teeth with a translucency that varies from gray to brown or amber. Radiographically, the teeth exhibit pulp obliteration, thin and short roots, bell-shaped crowns, and periapical bone rarefaction. The aim of this report was to present a case of dentinogenesis imperfecta type II that was followed up over a 17-year period. This report also presents scanning electron microscopy images of the enamel and dentin, showing that both were altered in the affected teeth. The disease characteristics and the treatments that were administered are reported in this study to guide dentists with respect to the need for early diagnosis and adequate follow-up to avoid major sequelae.