• The Journal of Advanced Prosthodontics
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• 제3권3호
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• pp.140-144
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• 2011

PURPOSE. Finite element study on the effect of abutment length and material on implant bone interface against dynamic loading. MATERIALS AND METHODS. Two dimensional finite element models of cylinderical implant, abutments and bone made by titanium or polyoxymethylene were simulated with the aid of Marc/Mentat software. Each model represented bone, implant and titanium or polyoxymethylene abutment. Model 1: Implant with 3 mm titanium abutment, Model 2: Implant with 2 mm polyoxymethylene resilient material abutment, Model 3: Implant with 3 mm polyoxymethylene resilient material abutment and Model 4: Implant with 4 mm polyoxymethylene resilient material abutment. A vertical load of 11 N was applied with a frequency of 2 cycles/sec. The stress distribution pattern and displacement at the junction of cortical bone and implant was recorded. RESULTS. When Model 2, 3 and 4 are compared with Model 1, they showed narrowing of stress distribution pattern in the cortical bone as the height of the polyoxymethylene resilient material abutment increases. Model 2, 3 and 4 showed slightly less but similar displacement when compared to Model 1. CONCLUSION. Within the limitation of this study, we conclude that introduction of different height resilient material abutment with different heights i.e. 2 mm, 3 mm and 4 mm polyoxymethylene, does not bring about significant change in stress distribution pattern and displacement as compared to 3 mm Ti abutment. Clinically, with the application of resilient material abutment there is no significant change in stress distribution around implant-bone interface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.193-197
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• 2008

Array of micro-dimple on polyoxymethylene (POM) surface was fabricated using Q-switched Nd:YAG laser and its characteristics were studied in terms of heat affected zone (HAZ), dimple geometry, and the effect of specimen surface roughness. Process parameters such as lamp current, process time, and the stream of air in order to minimize HAZ and flow of molten polymer into cavity were extensively studied in this work. Dimple geometry was further investigated by 3-D optical microscopy to provide deep insight into morphological analysis near the dimples. This paper also presents the applicapability of micro-dimples in polymeric tribological system, such as a thrust bearing. Micro-dimples were expected to provide low coefficient of friction and enhanced lubricity at the sliding interface.

• Structural Engineering and Mechanics
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• 제70권5호
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• pp.591-600
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• 2019

Steel tubular buckling controlled braces are well known as being simple, practical and cost-effective lateral force resisting systems. Although these system features have gained the attention of the researchers over the last decade, steel tubular buckling controlled braces currently have limited application. Indeed, only a few steel tubes tightly encased within each other exist in the steel industry. In this paper, a new and practical design method is proposed in order to better promote the widespeared application for current steel tubular buckling controlled brace applications. In order to reach this goal, a holed-adapter made with polyoxymethylene adaptable to all round and square steel sections, was developed to use as infiller. The research program presents designing, producing and displacement controlled cyclic loading tests of a conventional tubular brace and a buckling controlled composite brace. In addition, numerical analysis was carried out to compare the experimental results. As a result of the experimental studies, buckling was controlled up to 0.88 % drift ratio and the energy dissipation capacity of the conventional tubular brace increased 1.46 times due to the proposed design. The main conclusion of this research is that polyoxymethylene is a highly suitable material for the production of steel tubular buckling controlled braces.

• Tribology and Lubricants
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• 제25권3호
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• pp.141-149
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• 2009

The effect of micro-cavities fabricated using laser surface texturing (LST) technique on polyoxymethylene (POM) surface was studied in terms of heat affected zone (HAZ), cavity geometry, surface roughness, deformation of cavity along with sliding cycles, and tribological characteristics. Cavity process parameters were lamp current, process time, and the stream of air used to minimize the flow of molten polymer into cavity. Especially, the deformation of cavity geometry was extensively studied to provide deep insight into morphological analysis of the cavities. Also, this paper presents the behavior of friction and wear of POM specimens as a function of sliding cycles.

• 대한기계학회논문집A
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• 제39권8호
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• pp.781-785
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• 2015

엔지니어링 플라스틱(Engineering Plastic ; EP)에 대한 내구성 평가를 위해 현재 새롭게 국내에서 개발한 초음파 피로시험법을 이용하여 EP 중에서도 결정화 속도가 빠르고 결정화도가 높은 범용 POM(Polyoxymethylene) 소재에 대한 초음파 가속피로시험 거동을 평가하고자 하였다. 이에 본 연구에서 사용된 POM 소재의 밀도는 $1.37g/cm^3$, 동탄성계수는 3.49 GPa 로 측정되었으며, 초음파피로시험 20kHz, 응력비 R= -1 의 판상시편 두께 (4t, 7t, 10t)에 따른 피로수명평가 결과 전체 응력진폭 5.0~6.0MPa 부위에서 피로한도를 확인하였다. 피로시험 후 파단 면을 관찰한 결과 7t, 10t 두께 시편의 크랙 시작위치에서 미소 공동들이 서로 연결된 형태의 잔금(crazing) 균열현상으로 파단된 dimple 구조형상을 전자현미경을 통해 확인할 수 있었다.

• 대한방사선기술학회지:방사선기술과학
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• 제40권1호
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• pp.13-18
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• 2017

본 논문은 GATE (geant4 application for tomographic emission) 시뮬레이션을 이용하여 다양한 모양과 재질의 팬텀에서 CTDI (computed tomography dose index)를 평가하였다. GATE 시뮬레이션은 실린더 기둥, 타원 기둥과 육각 기둥 형태와 물, PMMA (polymethyl methacrylate), polyethylene 그리고 polyoxymethylene 재질의 다양한 지름(1 ~ 50 cm)의 팬텀을 모사하여 $CTD_{I100center}$ 값을 비교하였다. 120 kV, 200 mAs에서 실린더 기둥, 타원 기둥과 육각 기둥의 $CTDI_{100center}$ 값은 각각 11.1, 13.4 그리고 12.2 mGy이었다. 이 결과는 동일 볼륨이지만 팬텀의 형태에 따라 $CTDI_{100center}$ 값의 차이가 있음을 알 수 있다. 그리고 물, PMMA 그리고 polyoxymethylene 팬텀의 $CTDI_{100center}$ 값을 비교했을 때 물질의 밀도가 높을수록 상대적으로 $CTDI_{100center}$ 값이 낮게 측정되었다. 하지만 polyethylene의 경우 지름이 15 cm ($CTDI_{100center}$ : 35.0 mGy) 이 상에서는 PMMA 보다 $CTDI_{100center}$ 값이 증가하였다. 그리고 30 cm ($CTDI_{100center}$ : 17.7 mGy) 이 상의 지름에서는 물 보다 더 높은 $CTDI_{100center}$ 값을 보였다. 본 실험을 통해 팬텀의 재질 및 모양에 따른 $CTDI_{100center}$ 값을 GATE 시뮬레이션을 이용하여 평가하였다. CT 선량 평가시 다양한 재질 및 인체에 가까운 모양의 팬텀을 사용함으로써 좀 더 정확한 환자선량을 평가할 수 있을 것이다.

• 대한치과교정학회지
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• 제37권5호
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• pp.341-350
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• 2007

본 실험은 마찰력을 줄이고 물리적 성질을 개선하여 최근에 개발된 수 종의 심미 브라켓들과 교정 탄선간에 발생하는 마찰력의 크기를 측정, 비교해 보고자 하였다. 일반 슬롯의 세라믹 브라켓인 Inspire, Signature III와 Cristaline V, 스테인레스 스틸 (SS) 슬롯을 가진 세라믹 브라켓인 Clarity, 골드 슬롯을 가진 Luxi II, polyoxymethylene 계열의 플라스틱 브라켓인 Brillant, SS 슬롯을 가진 컴파짓 브라켓인 Spirit MB, 금속 브라켓인 Integra를 사용하여 018"원형의 교정 탄선에 $0^{\circ}$, $4^{\circ}$, $8^{\circ}$의 tip angulation을 부여하고 elastic module로 결찰한 뒤 인공 타액 상태에서 활주이동 할 때의 운동 마찰력을 측정하였다. 연구 결과 슬롯에 silica 처리된 세라믹 브라켓 (CR)이 유의하게 낮은 마찰력을 보였고 (p < 0.05), 단결정 세라믹 브라켓이 (IN) 유의하게 큰 마찰력을 보였다 (p < 0.05). 플라스틱 브라켓인 polyoxymethylene 계열의 BR이 낮은 마찰력 양상을 보였고 이는 금속 브라켓과 유사하였다. 모든 브라켓에서 브라켓-탄선 각도가 증가함에 따라 유의하게 마찰력이 증가하였으나 주사전자현미경상에서 탄선이나 브라켓에 손상은 발견되지 않았다. 마찰력의 양상이 브라켓의 재질로 추측할 수 있는 것과는 다르게 나타난 결과로 보건대 심미 브라켓이 스테인레스 스틸 브라켓에 비해 마찰력 면에서는 오히려 우수하거나 큰 차이가 없으므로 임상적으로는 마찰력은 크게 고려하지 않아도 되겠다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.153-153
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• 2016

Polyoxymethylene copolymer (POM-C) is an attractive and widely used engineering thermoplastic across many industrial sectors owing to outstanding physical, mechanical, self-lubricating and chemical properties. In this research work, the POM-C blocks were irradiated with 1 MeV electron beam energy in five doses (100, 200, 300, 500 and 700 KGy) in vacuum condition at room temperature. The tribological and physico-chemical properties of electron beam irradiated POM-C blocks have been analyzed using Pin on disk tribometer, Raman spectroscopy, SEM-EDS, Optical microscopy, 3D Nano surface profiler system and Contact angle analyzer. Electron beam irradiation at a dose of 100 kGy resulted in a decrease of the friction coefficient and wear loss of POM-C block due to well suited cross-linking, carbonization, free radicals formation and energetic electrons-atoms collisions (physical interaction). It also shows lowest surface roughness and highest water contact angle among all unirradiated and irradiated POM-C blocks. The irradiation doses at 200, 300, 500 and 700 kGy resulted in increase of the friction coefficient as compared to unirradiated POM-C block due to severe chain scission, chemical and physical structural degradation. The electron beam irradiation transferred the wear of unirradiated POM-C block from the abrasive wear, adhesive wear and scraping to mild scraping for the 1 MeV, 100 kGy irradiated POM-C block which is concluded from SEM-EDS and Optical microscopic observations. The degree of improvement for tribological attribute relies on the electron beam irradiation condition (energy and dose rate).

• 국제학술발표논문집
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• The 10th International Conference on Construction Engineering and Project Management
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• pp.1081-1087
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• 2024

The construction of 3D Printed Concrete (3DPC) structures, particularly in reinforced concrete, still poses challenges due to constraints in construction methods. Additionally, the unique mixture design of 3DPC typically results in noticeable drying shrinkage. Utilizing short fibers for fiber reinforcement is a reliable approach that may replace reinforcing steel and address the challenge of volume stability. In this study, polypropylene (PP) fibers and polyoxymethylene (POM) fibers were incorporated into the total volume of concrete at additional percentages of 0.5%, 1.0%, and 1.5% to printed the specimen. While ensuring printability, various experiment were conducted to evaluate compressive strength, flexural strength, anisotropy, and drying shrinkage,to ensure the impact of fiber type and content on the mechanical properties and drying shrinkage of 3DPC. The results indicate that 3DPC exhibits significant strength loss after fiber addition, with loss percentages approximately ranging from 5% to 55% for compressive strength and 9% to 57% for flexural strength. The extent of loss improves with increasing PP fiber content, while the strength of POM fibers continues to decline with increased usage. Furthermore, significant anisotropy is observed in 3DPC after fiber addition, with compressive strength relations appearing as X > Y ≈ Z in various directions, while flexural strength relations are demonstrated as Y ≈ Z > X. Concerning drying shrinkage, the addition of 1.0% POM fibers proves most effective in inhibiting drying shrinkage, reducing shrinkage by approximately 6% at the age of 56 days. In contrast, the presence of PP fibers, regardless of quantity, adversely affects drying shrinkage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.989-992
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• 2004

A new method is proposed to fabricate a reusable qualtz master with order of 100 nm dot pattern on its surface. Some fabrication conditions such as dose are investigated to find optimal condition. This reusable qualtz master is used directly as a stamper to injection mold the dot patterns. Polycarbonate and Polyoxymethylene are used as molding materials and the effect of the mold temperature is also investigated to see the moldabilty of the injection molding for very fine dot features.