• Restorative Dentistry and Endodontics
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• 제46권2호
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• pp.16.1-16.11
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• 2021

Objectives: The aim of this study was to evaluate the shaping ability of the TruShape and Reciproc Blue systems and the apical extrusion of debris after root canal instrumentation. The ProTaper Universal system was used as a reference for comparison. Materials and Methods: Thirty-three mandibular premolars with a single canal were scanned using micro-computed tomography and were matched into 3 groups (n = 11) according to the instrumentation system: TruShape, Reciproc Blue and ProTaper Universal. The teeth were accessed and mounted in an apparatus with agarose gel, which simulated apical resistance provided by the periapical tissue and enabled the collection of apically extruded debris. During root canal preparation, 2.5% sodium hypochlorite was used as an irrigant. The samples were scanned again after instrumentation. The percentage of unprepared area, removed dentin, and volume of apically extruded debris were analyzed. The data were analyzed using 1-way analysis of variance and the Tukey test for multiple comparisons at a 5% significance level. Results: No significant differences in the percentage of unprepared area were observed among the systems (p > 0.05). ProTaper Universal presented a higher percentage of dentin removal than the TruShape and Reciproc Blue systems (p < 0.05). The systems produced similar volumes of apically extruded debris (p > 0.05). Conclusions: All systems caused apically extruded debris, without any significant differences among them. TruShape, Reciproc Blue, and ProTaper Universal presented similar percentages of unprepared area after root canal instrumentation; however, ProTaper Universal was associated with higher dentin removal than the other systems.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.632-637
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• 2021

현재 미래의 건설 산업 기술을 발전시키고자 최근 미래 산업으로 각광받고있는 3D 프린팅을 이용한 콘크리트의 시공기술을 활용하여 구조물을 건설하는 연구가 국내외 건설업계 및 학계에서 활발히 진행되고 있다. 하지만 현재 개발되고 있는 3D 프린팅 기술은 적합한 시공기술, 콘크리트 재료 자체의 물성이 사용기준에 미치지 못하고 실제 현장에서 적용하기가 어려운 상황이다. 또한 시공된 구조물에 대한 내구성 관리 및 유지관리를 위한 연구가 필요한 실정이다. 본 연구에서는 Material extrusion 방식으로 출력한 3D 프린팅 콘크리트를 각각의 적층 방향 X, Y, Z축으로 나누어 측정한 압축강도와 휨강도를 기존의 몰드에 제작한 시험체와 비교 분석하였다. Test direction II Z축의 시험체의 압축강도가 나머지 Test direction I, III Y축, X축의 시험체에 비하여 8~10%의 높은 강도를 발현하였고 몰드 제작 시험체와 비교하였을 경우 4%가량 낮은 강도를 발현하였다. 휨강도 측정결과 재령 28일 기준으로 Test direction II Z축 방향의 시험체의 휨강도가 Test direction I, III Y축, X축의 시험체에 비하여 5~7%의 높은 강도를 발현하였고 몰드 제작 시험체와 비교하였을 경우 2%가량 낮은 강도를 나타내었다.

• 산업기술연구
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• 제17권
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• pp.213-218
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• 1997

This study is concerned with characteristics of bending collapse of aluminum members with multi-cell section. Aluminum is light so it is compatible of being used for vehicle structures members. Bending collpase behaviors of aluminum members with multi-cell section are very complex and tension failure mode are occured in experiment. In this paper, the aluminum members are modeled to be able to represent the tension failure mode and, characteristics of bending collapse of aluminum members with multi-cell section by experimental method are compared with the results of PAM-CRASH.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 추계학술대회 논문집
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• pp.157-164
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• 1994

Finite element analysis of material deformation is successfully utilized to understand metal forming processes such as forging, extrusion and deep drawing. However, such analysis involves contact problems; a free node touches a die surface and a contact node slips along the die surface. In the present investigation, appropriate contact algorithms were developed assuming that a three dimensional surface can be divided into bilinear patches and that nodal velocities are linear during an incremental time. The algorithms were coded into a computer program and tested for a simple surface. Comparison of the test result with that obtained from a commercial code is presented and discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.616-618
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• 2000

This paper describes the recent research and technical trend of power cable system. Compact sizing with long length and large capacity is the main trend of the power cable. From the manufacturing process to the monitoring of the underground power line, various new techniques are being developed for reliability and high quality such as in-line monitoring system, triple common extrusion, PD measurement system, new type completion test, etc.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.505-511
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• 1998

Production technologies for aluminum rolling stocks are mainly related to welding of aluminum alloys. Automatic welding of extrusion profiles and control of welding deformations are the important contents of the production technologies. Another production technology other than welding is the technique for surface treatment of aluminum carbody. In this paper, problems caused during construction of the test carbody are described and the remedies for the problems are suggested. The accumulated experiences and systematic data will be helpful for the mass production of aluminum rolling stocks in the furture.

• 한국표면공학회지
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• 제43권6호
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• pp.278-282
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• 2010

In this research, the friction and wear characteristic behaviors of coating materials of TiAlN and CrAlN were investigated. The wear test was conducted in air and un-lubricated state using the reciprocating friction wear tester. Temperature were 50 and $120^{\circ}C$, and load were 3, 7, and 11 kgf for tests. By comparing the coefficient of friction and observing the wear microstructure, the friction and wear characteristic behaviors of TiAlN and CrAlN coating layers on SKD61 were investigated. The coefficient of friction of CrAlN coating was lower than that of TiAlN at all conditions. Therefore, CrAlN was suggested to be more advantageous coating than TiAlN for the extrusion mold of aluminum.

• 한국주조공학회지
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• 제21권6호
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• pp.359-365
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• 2001

The superplastic behavior of whisker reinforced aluminum alloy matrix composites fabricated by squeeze casting as one of high pressure routes was investigated. The preforms of ${\alpha}-Si_3N_4$ and ${\beta}-SiC$ whiskers without any binder as a reinforcement were used. The matrix materials were 2024 and 7075 aluminum alloys. For the purpose of optimum superplastic condition, respectively, the whiskers volume fraction, extrusion temperature, tensile test temperature and initial strain rate were changed. Fracture surface of tested specimens were observed by SEM. By the results, it became possible to produce superplastic composites by applying only a hot extrusion process to composites obtained by the squeeze casting. The superplastic composites developed are ${\alpha}-Si_3N_4w/7075$, ${\alpha}-Si_3N_4w/2024$ and ${\beta}-SiCw/2024$ systems at high strain rate.

• 한국생산제조학회지
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• 제20권6호
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• pp.785-792
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• 2011

Equal channel angular(ECA) pressing is the established processing technique in which a polycrystalline metal is pressed through the die to achieve a very high plastic strain. Therefore, the capability to produce an ultra-fine grain size in the materials is provided. To investigate that mechanical properties at elevated temperature have the ultrafine grain ECA pressing, experiments were conducted on an Al-4.8% Mg-0.07% Mn-O.06% Si alloy. After having been solution treated at 773K for 2hrs, the billet for ECA pressing was inserted into the die. And it was pressed through two channel of equal to cross section intersecting at a 90 degree angle. The billet can be extrude repeatedly because of 1:1 extrusion ratio. Since the billet is passed through the cannel for 2 times, a large strain is accumulated in the alloy. The tensile tests on elevated temperature were carried out with initial strain rate of $10^{-3}s^{-1}$ at eight temperature distributed from 293K to 673K.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.41.2-41.2
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• 2010

In this work, HAp-(t-ZrO2) ceramic composites of biomimic artificial bone were fabricated by multi-extrusion process in order to replace nature bone. HAp-(t-ZrO2) and graphite powders were mixed separately with ethylene vinyl acetate (EVA) and stearic acid using shear mixer. Extruded HAp-(t-ZrO2) filaments and carbon filaments were arranged in the die to fabricate the first pass filament. The first pass filaments were arranged in the same die with a central carbon core for making the space for spongy bone. Burning out and sintering processes were performed to remove the binder and lubricant. The microstructure channel diameter was researched around $300{\mu}m$. Microstructure analysis was carried out by OM, SEM, and $\mu$-CT. Compressive strength was investigated for the artificial bone. Some preliminary bio-compatibility test was evaluated.