• The Journal of Advanced Prosthodontics
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• 제6권5호
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• pp.361-371
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• 2014

PURPOSE. In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown. MATERIALS AND METHODS. The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and $30^{\circ}$ oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA). RESULTS. As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at $30^{\circ}$, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually. CONCLUSION. The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the $30^{\circ}$ oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study.

• 한국해양공학회지
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• 제26권5호
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• pp.1-4
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• 2012

A energy saving device "Crown duct" has been developed and its efficiency gain has been verified experimentally in the towing tank of SSPA. The preswirl stator is well known as one of energy saving devices, which recovering the rotational energy of propeller slipstream. Crown duct has two functions of recovers the rotational energy by three blades on top of duct and of flow concentration by semi-duct. The model tests showed 4.4% efficiency gain with Crown Duct at full load condition and 6.9% at ballast condition compared with the bare hull ones for the middle class tanker.

• 대한기계학회논문집
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• 제16권8호
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• pp.1451-1457
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• 1992

본 연구에서는 작업롤의 온도분포를 정상 상태에서 롤의 길이 방향만을 고려 한 경우에 대하여 구한 다음 Fouries 급수로 전개하여 이 온도분포에 따른 작업롤의 축대칭 3차원 열-탄성문제를 해석함으로서 롤의 크라운 양과 열응력을 구하여 이 결과 를 유한요소법에 의한 결과와 비교 검토 하였다.

• 대한치과보철학회지
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• 제45권1호
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• pp.12-20
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• 2007

Purpose: The purpose of this study was to compare the fracture strength of the zirconia monolithic all-ceramic crowns according to the thickness (0.5mm, 0.8mm, 1.1mm) and metal-ceramic crowns (1.0mm, 1.5mm) Material and method: Twelve crowns for each of 3 zirconia crown groups were fabricated using CAD/CAM system (Kavo, Germany) and twelve crowns for each of 2 metal-ceramic crown groups were made by the conventional method. All crowns were luted to the metal dies using resin cement. Half of the specimens were exposed to thermocycling ($5-55^{\circ}C$, 1 Hz) and cyclic loading (300,000 cycles, 50N). Subsequently, all crowns were mounted on the testing jig in a universal testing machine. The load was directed at the center of crown with perpendicular to the long axis of each specimen until catastrophic failure occurred. Analysis of variance and Tukey multiple comparison test (P<.05) were used for statistical analysis of all groups, and paired t-test (P<.05) was followed for statistical comparison between each groups' fracture load before and after cyclic loading. Results: 1. The fracture strength of the zirconia monolithic crowns and the metal-ceramic crown increased as thickness increased (P<.05). 2. The cyclic loading and thermocycling significantly decreased the fracture strength of the zirconia monolithic crowns (P<.05). 3. The standard deviation of fracture strength of the zirconia monolithic crowns was very low. Conclusion: The fracture strength of the zirconia monolithic crowns for the posterior area tends to be higher with thickness increased and 0.8mm or over in thickness is recommended to have similar or over the fracture strength of metal-ceramic crowns.

• 구강회복응용과학지
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• 제25권1호
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• pp.1-12
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• 2009

이 논문의 목적은 시멘트 층 내의 응력분포에 대해 금관의 물성과 시멘트의 물성 및 교합력의 방향이 미치는 영향을 이차원 유한요소분석으로 조사하는 것이다. Chamfer 변연을 가지는 23개의 하악 제1대구치 모델을 상정하였다. 금관의 재질은 제 3형 금합금, Ni-Cr 합금, 세라믹, 복합레진 등 4가지이며, 시멘트의 재질은 인산 아연 시멘트와 글라스 아이오노머 시멘트 등 2가지이다. 치축과 평행하게 또는 경사지게 하여 1N 단위로 금관에 하중을 가했다. 시멘트층의 응력은 금관 변연이 다른 곳보다 더 높았다. 치축에 평행한 하중이 치축에 경사진 하중보다 더 높은 응력을 발생시켰다. 경도가 더 큰 금관은 시멘트 층 내에서 더 높은 응력을 나타냈으며, 더 높은 응력은 더 큰 Young's modulus을 나타냈다.

• 한국산림과학회지
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• 제101권2호
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• pp.244-250
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• 2012

본 연구의 목적은 강원도 양양지역에 분포하는 소나무림을 대상으로 지상부 바이오매스와 수관층 연료특성에 대하여 분석하고자 하였다. 연구대상지는 강원도 양양군 현남면 하월천리 일대 소나무림으로 선정하였으며, 총 13본의 표본목을 벌채하여 분석하였다. 본 연구 결과에 의하면, 양양지역 소나무림의 줄기밀도($g{\cdot}cm^{-3}$)는 0.347~0.409, 지상부 바이오매스 확장계수는 1.251~1.419의 범위로 나타났다. 지상부 연료량은 총 $161.6Mg{\cdot}ha^{-1}$로 나타났으며, 줄기 $126.4Mg{\cdot}ha^{-1}$, 가지 $29.3Mg{\cdot}ha^{-1}$, 잎 $5.9Mg{\cdot}ha^{-1}$로 나타났다. 수관층 연료특성 인자에 관한 연구에서는 수관화 확산 시 연소될 수 있는 연소가능 연료(잎~1 cm이하 가지)의 비율은 45.2%로 나타났고, 연료량을 수관체적으로 나눈 연소가능 연료밀도($kg{\cdot}m^{-3}$)는 평균 0.178로 나타났다. 본 연구의 결과는 소나무림의 바이오매스 및 탄소 흡수량 추정과 수관화 위험성을 연료적 관점에서 평가하는데 있어 유용한 기초자료가 될 것으로 사료된다.

• 대한치과기공학회지
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• 제38권3호
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• pp.143-149
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• 2016

Purpose: The purpose of this study is to evaluate the effect of two different oblique mechanical loading to occlusal surfaces of cement retained implant on the stress distributions in surrounding bone, using 3-dimensional finite element method. Methods: A 3-dimensional finite element model of a cement retained implant composed of three unit implants, simplified ceramic crown and supporting bone was developed according to the design of ement retained implant for this study. two kinds of surface distributed oblique loads(100 N) are applied to following occlusal surfaces in the single crowns; 1) oblique load on 2 occlusal points(50N for each buccal cusp, 2 buccal cusps exist), 2) oblique load on 4 occlusal points(25N for each buccal and lingual cusp, 2 buccal and 2 lingual cusps exist) Results: The results of the comparison of the stress distributions on surrounding bone are as follows. In the condition of oblique load on 2 occlusal points, VMS was 741.3 Mpa in the M1(Ø$4.0{\times}13mm$) model and 251.2 Mpa in the M2(Ø$5.0{\times}13mm$) model. It means the stress on the supporting bone is decreased. The results of oblique load on 4 occlusal points are similar to this one. Conclusion: Increasing the diameter of the implant fixture is helpful to distribute the stress on the supporting bone. Also, to obtain the structural stability of the supporting bone, it is effective to distribute the load evenly on the occlusal surface of crown in producing single crown implant.

• 대한치과보철학회지
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• 제28권2호
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• pp.199-215
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• 1990

This study was to analyze the stress distribution of implant and supporting tissue in $Br{\aa}nemark$ osseointegration implant. The analysis has been conducted by using the axisymmetric finite element method and type of model according to crown material. Tests have been performed at 1 kg load on central fossa of crown portion. Each type of model was designed differently according to crown material. 1) Porcelain fused to metal crown(Model A) 2) Composite resin veneered crown(Model B) 3) Acrylic resin veneered crown(Model C) 4) Type III gold crown(Model D) The displacements and stresses of implant and supporting structures were analyzed to investigate the influence of the type of crown material. The results were obtained as follows : 1. Displacement of implant was shown uniformly downward displacement in all models and abutments were observed distally downward displacement. 2. In supporting tissues, stress was concentrated on the crest of compact bone and the spongy bone below implant. 3. The PFM and the type III gold crown showed the largest concentration of stress at the crest of compact bone and the spongy bone below implant, respectively. Acrylic resin artificial teeth and composite resin veneered crown indicated almost the same distribution of stress. 4. The gold screw, the abutment screw and the top of abutment showed the concentration of stress in implants of every model.

• 한국산림과학회지
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• 제99권1호
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• pp.52-56
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• 2010

본 연구에서는 우리나라에서 수관화에 취약하다고 밝혀진 소나무림을 대상으로 수관층의 연료특성을 잎과 가지 굵기 별로 구분하여 수분함량, 연료밀도로 제시하고자 하였다. 이를 위해 대구 팔공산에서 소나무 10그루를 벌채하여 각 부위별로 건중량을 측정하였다. 분석결과 수관층 살아 있는 부위의 평균 수분함량은 53%, 죽은 부위는 15.3%였으며, 생엽의 수분함수율은 평균 56%이었다. 수관화 확산시 실제적으로 연소되는 잎과 직경 1 cm 이하의 가지를 합한 연료량은 전체 바이오매스에서는 16.2%, 수관층 바이오매스에서는 55%를 차지하였다. 수관 연료밀도는 평균 0.24 kg/$m^3$이었으며, 잎과 1 cm 굵기 이하의 가지를 합한 유효 수관연료밀도는 0.1325 kg/$m^3$이었다.

• 한국해양공학회지
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• 제28권1호
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• pp.1-5
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• 2014

Chosun University, in cooperation with SPP shipyard, has developed an energy saving device based on a new concept: "Crown Duct." Crown Duct is composed of a semi-duct with short struts inside and outside the duct. Theoretical calculations for two different designs were carried out using the CFD code "Ship Flow." The design selected from these two different forms by the CFD code analysis was tested in a towing tank at SSPA. The results showed about 4% efficiency gain under a full-load condition and about 7% gain under a ballast condition in the towing tank test.