• 한국정밀공학회지
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• 제13권11호
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• pp.46-56
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• 1996

Planarization technique is rapidly recognized as a critical step in chip fabrication due to the increase in wiring density and the trend towards a three dimensional structure. Global planarity requires the preferential removal of the projecting features. Also, the several materials i.e. Si semiconductor, oxide dielectric and sluminum interconnect on the chip, should be removed simultaneously in order to produce a planar surface. This research has investihgated the development of the chemical mechanical polishing(CMP) machine with uniform pressure and velocity mechanism, and the pad insensitive to pattern topography named hard grooved(HG) pad for global planarization. Finally, a successful result of uniformity less than 5% standard deviation in residual oxide film and planarity less than 15nm in residual step height of 4 inch device wafer, is achieved.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.554-560
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• 2008

In posterior maxilla, it is difficult to achieve primary stability of implants due to sinus pneumatization, alveolar bone loss, and low bone quality. The accurate and objective primary stability assessment is important for good prognosis of implants. Purpose: The aim of this study was to assess the primary stability of the non-submerged, internal type implants with maxillary sinus augmentation using deproteinized bovine bone mineral by a resonance frequency analyzer, when residual alveolar bone height is under 8mm Materials and methods: A total of 20 implants was placed into 5 grafted maxillary sinuses in 5 patients. Deproteinized bovine bone mineral (Bio-$Oss^{(R)}$) was used as graft material. SS II implants (diameter 4.1mm, and length 11.5mm, SLA suface)) were placed. All of the patients received maxillary sinus graft procedure by 1-step technique. Residual bone height was $1.3{\sim}7.8mm$ (mean 4.4mm) measured by panorama radiography. After implant placement, RFA was measured at 4,8,12,20 weeks. The results were divided into 2 groups; RFA value under 4mm and over 5mm of bone height. It was statistically analyzed. Results: 1. The primary stability of implants was increased with time 2. The RFA value was above 65 ISQ at 12 weeks 3. There was no correlation between RFA and residual alveolar bone height in maxillary sinus augmentation by 1-step technique. Conclusion: 1-step surgical procedure is a feasible option for patients with as little as 4mm residual alveolar bone height, when utilizing non-submerged, internal type implants with xenografts.

• 한국추진공학회지
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• 제2권1호
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• pp.31-40
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• 1998

고강도 알루미늄 대형 링롤재의 급냉 및 요소제거 후 발생하는 잔류응력을 2차원 및 3차원 유한요소 해석하였고, 3단계 절단법에 의해 측정된 변형율과 ABAQUS의 요소제거 기능을 이용한 해석값을 직접 비교하였다. 급냉후 잔류응력 해석결과는 2단 과시효후 측정값과 비슷한 경향을 보였으나 그 절대값의 차이가 크게 나타났다. 이는 링 시편의 높이가 작아 측정값이 부정확하였기 때문이며, 링의 높이를 증가시켜 높이방향으로 균일한 응력분포를 갖도록 하면 그 차이가 감소될 것으로 판단된다. 잔류응력을 측정하는 3단계 절단 과정을 모사한 3차원 해석결과와 측정된 변형율을 직접 비교함으로써 실험과 해석의 정확성을 향상시킬 수 있도록 하였다. 이로부터 잔류응력이 내재하고 형상이 복잡한 대형 알루미늄 구조물의 기계가 공에 의한 변형을 정확히 예측할 수 있는 기반을 마련하였다.

• Geomechanics and Engineering
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• 제19권2호
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• pp.105-114
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• 2019

In this paper, simulation tests were conducted with similar materials to study the distribution of residual voids in longwall goaf. Short-time step loading was used to simulate the obvious deformation period in the later stage of arch breeding. Long-time constant loading was used to simulate the rheological stage of the arch forming. The results show that the irregular caving zone is the key area of old goaf for the subsidence control. The evolution process of the stress arch and fracture arch in stope can be divided into two stages: arch breeding stage and arch forming stage. In the arch breeding stage, broken rocks are initially caved and accumulated in the goaf, followed by the step deformation. Arch forming stage is the rheological deformation period of broken rocks. In addition, under the certain loads, the broken rock mass undergoes single sliding deformation and composite crushing deformation. The void of broken rock mass decreases gradually in short-time step loading stage. Under the water lubrication, a secondary sliding deformation occurs, leading to the acceleration of the broken rock mass deformation. Based on above research, the concept of equivalent height of residual voids was proposed, and whose calculation equations were developed. Finally, the conceptual model was verified by the field measurement data.

• Structural Engineering and Mechanics
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• 제77권6호
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• pp.819-830
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• 2021

To evaluate the performance of concrete load bearing walls in a structure under horizontal loads after being exposed to real fire, two steps were followed. In the first step, an experimental study was performed on the thermo-mechanical properties of concrete after heating to temperatures of 200-1000℃ with the purpose of determining the residual mechanical properties after cooling. The temperature was increased in line with natural fire curve in an electric furnace. The peak temperature was maintained for a period of 1.5 hour and then allowed to cool gradually in air at room temperature. All specimens were made from calcareous aggregate to be used for determining the residual properties: compressive strength, static and dynamic elasticity modulus by means of UPV test, including the mass loss. The concrete residual compressive strength and elastic modulus values were compared with those calculated from Eurocode and other analytical models from other studies, and were found to be satisfactory. In the second step, experimental analysis results were then implemented into structural numerical analysis to predict the post-fire load-bearing capacity response of the walls under vertical and horizontal loads. The parameters considered in this analysis were the effective height, the thickness of the wall, various support conditions and the residual strength of concrete. The results indicate that fire damage does not significantly affect the lateral capacity and stiffness of reinforced walls for temperature fires up to 400℃.

• 한국생산제조학회지
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• 제19권2호
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• pp.251-259
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• 2010

It is presented in this study a new efficient intelligent machining strategy, which can be used to remove the uncut volume at the boundary region of curved surfaces caused by cutter interference. The geometric form definitions and recognition of topological features of the surface triangulation mesh are used to generate cutter paths along successive and interconnected steepest pathways, that minimize the cusp height left after flat end milling. In order to machine the uncut volume gradually, the z-map cutter centers are adjusted to avoid cutter interference for the 6 kinds of avoidance types. And then, the generative subsequent paths are sequenced to determine the second step cutter paths for the next uncut volume. For the 2 kinds of test models with convex and concave surface region, the implemented software algorithm is evaluated by investigating the residual swelling of uncut volume for each machining step.

• 터널과지하공간
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• 제13권5호
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• pp.362-372
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• 2003

시멘트가 사용된 이래로 수많은 콘크리트 구조물들이 건설되어 왔으나 그 수명은 콘크리트의 특성으로 인해 한계가 있다고 할 수 있다. 이로 인하여 불가피하게 보수 보강의 필요성이 나타나며 최근까지 많은 방법들이 개발되어 적용되고 있다. 본 연구에서는 압축공기식 치핑머신과 앵커핀을 사용하여 노후화된 콘크리트를 보수 보강하는 새로운 방법을 적용하여 노후화된 콘크리트와 신선한 콘크리트의 접합면에 대한 역학적 특성을 밝히고자 하였다. 콘크리트 노후부를 제거하기 위한 방법으로 치핑머신을 사용한 경우와 브레이커를 사용한 경우를 비교한 결과 최대점착력에서는 치핑머신이, 잔류점착력에서는 브레이커를 사용한 경우가 높게 나타났다. 접합면에 치핑머신으로 요철을 준 결과, 최대점착력은 평평한 접합면의 경우에 비하여 30 mm 요철심도에서는 14%, 50 mm에서는 22%의 증가를 보였다. 앵커핀은 잔류점착력을 증가시키고 전단파단 이후 슬립을 억제하는 효과를 보였으며, 인장강도를 32% 정도 증가시키는 효과를 나타내었다. 요철과 앵커핀을 복합적으로 적용한 결과 최대점착력은 접합면이 없는 신선한 콘크리트의 77%에 이르렀고 잔류점착력은 신선한 콘크리트의 180%에 이르는 높은 효과를 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.459-464
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• 2001

The main object of this study is to develop a reliable FEM simulation technique for the analysis of Steel D&I Can bodymaking process using ABAQUS software. The body making process includes drawing, redrawing, 3 step ironing, doming. The newly developed FEM code in this research is based on the previous research achievement of POSCO for the drawing, redrawing and ironing process. The analysis is performed using two dimensional axisymmetric elements to analyze the punch force, the height of can, the distribution of residual stress and strain. The effect of blank thickness, gap of ironing die is also analyzed.

• 한국산림과학회지
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• 제112권1호
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• pp.83-92
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• 2023

본 연구는 국가산림자원조사 자료를 활용하여 우리나라 혼효림에 대한 산림 입지조건을 탐색하고 임분의 생장 및 수확량을 추정하기 위하여 수행되었다. 혼효림의 생장은 흉고직경, 수고, 흉고단면적을 변수로 하는 Chapman-Richards 모델을 적용하여 식을 도출하였으며, 수확량은 흉고단면적, 지위지수, 임령, 입목밀도 등의 인자를 단계적회귀분석 적용으로 회귀식을 도출하였다. 국내 혼효림은 다양한 입지에 생육하고 있었는데, 기후대별로는 온대중부권역에 과반수 이상이 분포하고 있었으며, 해발고별로는 101~400 m 지역에 약 62%가 분포하는 것으로 나타났다. 임령을 설명변수로 하는 혼효림 생장모형의 적합도(FI)는 흉고직경 0.32, 수고 0.22, 흉고단면적 0.18로 도출되어, 다소 낮은 적합도 값을 갖는 것으로 나타났다. 그러나 추정식의 실측치와 추정치 간의 관계 그래프 및 잔차 등을 고려할 때, 임령을 설명변수로 이용하는 추정모형의 사용은 특별한 문제가 없을 것으로 판단되었다. 혼효림의 수확모형은 여러 생장인자 중 흉고단면적(BA), 지위지수(SI), 임령(Age)이 단계적으로 투입되는 회귀식 Stand volume =-162.6859+6.3434 ∙ BA+9.9214 ∙ SI+0.7271 ∙ Age이 도출되었으며, 식의 설명력 (R²)은 약 96% 였다. 앞서 도출된 최적의 생장 및 수확모형을 이용하여 임시 임분수확표가 만들어 졌다. 또한 임시 임분수확표 자료를 활용하여 혼효림의 재적수확최대벌기령을 도출하였다.