• The Journal of Advanced Prosthodontics
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• 제13권5호
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• pp.269-280
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• 2021

PURPOSE. The objective of this study was to evaluate the effect of thickness reduction and fatigue on the failure load of monolithic zirconia crowns. MATERIALS AND METHODS. 140 CAD-CAM fabricated crowns (3Y-TZP, inCorisTZI, Dentsply-Sirona) with different ceramic thicknesses (2.0, 1.5, 1.0, 0.8, 0.5 mm, respectively, named G2, G1.5, G1, G0.8, and G0.5) were investigated. Dies of a mandibular first molar were made of composite resin. The zirconia crowns were luted with a resin composite cement (RelyX Unicem 2 Automix, 3M ESPE). Half of the specimens (n = 14 per group) were mouth-motion-fatigued (1.2 million cycles, 1.6 Hz, 200 N/ 5 - 55℃, groups named G2-F, G1.5-F, G1-F, G0.8-F, and G0.5-F). Single-load to failure was performed using a universal testing-machine. Fracture modes were analyzed. Data were statistically analyzed using a Weibull 2-parameter distribution (90% CI) to determine the characteristic strength and Weibull modulus differences among the groups. RESULTS. Three crowns (21%) of G0.8 and five crowns (36%) of G0.5 showed cracks after fatigue. Characteristic strength was the highest for G2, followed by G1.5. Intermediate values were observed for G1 and G1-F, followed by significantly lower values for G0.8, G0.8-F, and G0.5, and the lowest for G0.5-F. Weibull modulus was the lowest for G0.8, intermediate for G0.8-F and G0.5, and significantly higher for the remaining groups. Fatigue only affected G0.5-F. CONCLUSION. Reduced crown thickness lead to reduced characteristic strength, even under failure loads that exceed physiological chewing forces. Fatigue significantly reduced the failure load of 0.5 mm monolithic 3Y-TZP crowns.

• 비교문화연구
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• 제30권
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• pp.73-95
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• 2013

The purpose of this paper look at the basis of the cultural differences of Korea and Japan by comparing the view about the death. Firstly, in terms of language to express the death, Korea can be summarized 'doragada (go back) Japan can be summarized sayonara(goodbye). Koreans' view about the death is that life and death are not separated and death is the start of another life not the end of existence through 'doragada' Japanese accept death as the order of the universe and the order of nature with resignation. At this time resignation means that Japanese accept the sad feeling to sublimate aesthetically while mourning the death Secondly The view about the death of Sunbee in the Joseon era and Japanese Samurai who were the traditional ideal figures is compared. The Sunbee dies from a justification and the Samurai die from the honor on the other hand. Unconditionally, the sunbee was not loyal to an individual but they thought significantly of the fidelity about the joint value. Unlike this, Japanese Samurai laid stress on the loyalty toward their lord and sacrifice. They selected the death conclusively when this fidelity was suspected. Thirdly the view about the death of Korea and Japan is summarized to the aesthetics of the survival and the aesthetics of the death. Korean saw the death negatively and regard exceedingly the extension of life, they preceded to survive in all kinds of difficulties. On the contrary, Japanese see it positively. They beautified the death and sublimated with the aesthetics. they pursue the nature of the life through the death. Finally, the basic difference of the korean and Japanese culture originate from the view about the death that is, the difference of the values about the life and death.

• 한국해양공학회지
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• 제32권6호
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• pp.492-501
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• 2018

The following results were obtained from a series of studies to accumulate data to reduce the coefficient of friction for press dies by performing tribological tests before and after the UNSM treatment of SM45C. The UNSM-treated material had a nano-size surface texture, high surface hardness, and large and deep compressive residual stress formation. Even when the load was doubled, the small amount of abrasion, small weight of the abrasion, and width and depth of the abrasion did not increase as much as those for untreated materials. When loads of 5 N, 7.5 N, and 10 N were applied to the untreated material of SM45C, the coefficient of friction was approximately 0.76-0.78. With the large specimen, a value of 0.72-0.78 was maintained at a load of 50 N despite the differences in the size of the wear specimen and working load. Tribological tests of large specimens of SM45C treated with UNSM under tribological conditions of 100 N and 50 N showed that the frictional coefficient and time constant stably converged between 0.7 and 0.8. The friction coefficients of the small specimens treated with UNSM showed values between 0.78 and 0.75 under 5 N, 7.5 N, and 10 N. The friction coefficients of the SM45C treated with UNSM were comparable to each other.

• 영미문화
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• 제16권2호
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• pp.71-88
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• 2016

Cormac McCarthy's The Road depicts a post-apocalyptic future in which the time and reason of catastrophe are not specified, but it can be seen to project the contemporary social and ethical concerns in the dismal setting. In this respect, the journey the man and boy depart for to the South is on one hand a journey to seek a warmer place to support their lives in the literal sense and, on the other hand, a journey to seek 'what a human being is' in the devastated world in a metaphorical sense since they face extremely harsh and tremendously poignant conditions in which their creed as human beings is tested. This paper aims to explore the hazards of the current society that the text criticizes and the morality and ethical values to be preserved and pursued. The second chapter examines how the text describes the contemporary crisis through the dark and coldness of the land and its sterility. The land produces almost nothing as the entire surface was scorched and is now covered with thick ashes. It shows perfectly a destroyed and irrecoverably frozen land. Throughout this desolate and ruined land, the atrocity and violence of the survivors goes beyond the limit. Ravaging strangers and plundering villages are widely spread. These conditions mirror the apparent selfishness and immorality of the recent society. The third chapter analyzes the man's inconsistent or dualistic narrative on the good. He knows what the good is but doesn't allow the boy to demonstrate the good behavior on others. His conflict is rooted in his hope to protect his son from being attacked by others. Therefore it can be interpreted that the meaning and orders of living in this post-apocalyptic period are uncertain and indecisive. The fourth chapter examines the belief the man and the boy clings to. Unlike the man's contradictory decisions, he shows definite firmness to be 'the good' by not eating people and carrying 'the fire.' Until he dies, the man endeavors to protect his son and have him acquire the moral conviction and strength to carry the fire in the world. In conclusion, the text reads the current society critically and highlights the importance of the humanity that must not be discarded throughout the generations.

• Journal of Korean Dental Science
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• 제15권1호
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• pp.61-67
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• 2022

Purpose: This study aimed to evaluate the accuracy of bite registration using intraoral scanner based on data trimming strategy for fremitus teeth. Materials and Methods: A reference model was designed by Medit Model Builder software (MEDIT Corp., Seoul). Tooth number 24 and 25 were separated as dies and tooth number 26 was prepared for full-coverage crown. Those were printed using a 3D printer (NextDent 5100). The scanning procedure was performed by a single trained operator with one intraoral scanner (i700; MEDIT Corp.). The scanning groups were divided as follows: group 1 (G1), no fremitus; group 2 (G2), 0.5 mm buccal fremitus in the maxillary left first and second premolar; and group 3 (G3), 1.5 mm buccal fremitus in the maxillary left first and second premolar. Each group was scanned 10 times and were analyzed using the reference model data. Surface-based occlusal clearance was analyzed at the prepared tooth to evaluate accuracy. Result: Mean values of control group (G1) were 1.587±0.021 mm. G2 showed similar values to those from the control group (1.580±0.024 mm before trimming strategy and 1.588±0.052 mm after trimming strategy). G3 showed significantly greater values (1.627±0.025 mm before trimming strategy and 1.590±0.024 mm after trimming strategy) and the differences were found between trimming strategy (P=0.004). Conclusion: Bite trimming strategy for fremitus teeth is a reliable technique to reduce inaccuracies caused by the mobility at maximum intercuspation.

• Tribology and Lubricants
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• 제39권5호
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• pp.190-196
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• 2023

Anti-adhesion coatings are very important in the processing of adhesive materials such as optical clear adhesive (OCA) films. Choosing the appropriate release coating material for dies and tools can be quite challenging. Hydrophobic surface treatment is usually performed, and its performance is often estimated by the static water contact angle (CA). However, the relationship between the release performance and the CA is not well understood. In this study, the water CAs of surfaces coated with anti-adhesion materials and the peel strengths of the acrylic-based adhesive films are evaluated. STC5 and SUS304 are selected as the base materials. Base materials with different surface roughnesses are produced by hairline finishing, mirror-polishing, and end milling. Four fluoropolymer compounds, including a self-assembled monolayer, are selected to make the base surface hydrophobic. Static, advancing, and receding CAs are mostly increased due to the coating, but the CA hysteresis is found to increase or decrease depending on the coating material. The peel strengths all decreased after coating and are largely dependent on the coating material, with significantly lower values observed for fluorosilane and perfluoropolyether silane coatings. The peel strength is observed to correlate better with the static CA and advancing CA than with the receding CA or hysteresis. However, it is not possible to accurately predict the anti-adhesion performance based on water CA alone, as the peel strengths are not fully proportional to the CAs.

• 마이크로전자및패키징학회지
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• 제29권4호
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• pp.41-47
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• 2022

Ag sintering technologies have received great attention as it was applied to the inverter of Tesla's electric vehicle Model III. Ag sinter bonding technology has advantages in heat dissipation design as well as high-temperature stability due to the intrinsic properties of the material, so it is useful for practical use of SiC and GaN devices. This study was carried out to understand the sinter joining temperature effect on the robust Ag sintered joints in air without pressure within 10 min. Electroplated Ag finished Cu dies (3 mm × 3 mm × 2 mm) and substrates (10 mm × 10 mm × 2 mm) were introduced, respectively, and nano Ag paste was applied as a bonding material. The sinter joining process was performed without pressure in air with the bonding temperature as a variable of 175 ℃, 200 ℃, 225 ℃, and 250 ℃. As results, the bonding temperature of 175 ℃ caused 13.21 MPa of die shear strength, and when the bonding temperature was raised to 200 ℃, the bonding strength increased by 157% to 33.99 MPa. When the bonding temperature was increased to 225 ℃, the bonding strength of 46.54 MPa increased by about 37% compared to that of 200 ℃, and even at a bonding temperature of 250 ℃, the bonding strength exceeded 50 MPa. The bonding strength of Ag sinter joints was directly influenced by changes in the necking thickness and interfacial connection ratio. In addition, developments in the morphologies of the joint interface and porous structure have a significant effect on displacement. This study is systematically discussed on the relationship between processing temperatures and bonding strength of Ag sinter joints.

• Design & Manufacturing
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• 제17권4호
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• pp.63-71
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• 2023

In order to increase the extrusion production speed of aluminum, extrusion die cooling technology using liquid nitrogen has recently attracted a lot of attention. Increasing the extrusion speed increases the temperature of the bearing area of extrusion dies and the extrusion profile, which may cause defects on the surface of extruded profile. Extrusion die cooling technology is to directly inject liquid nitrogen through a cooling channel formed between the die and the backer inside the die-set. The liquid nitrogen removes heat from the die-set, and gaseous nitrogen at the exit of the channel, covers the extrusion profile of an inert atmosphere reducing the oxidation and the profile temperature. The aim of this study is to evaluate the cooling capacity by applying die cooling to extrusion of Al-Mn-based aluminum alloy flat tubes, and to investigate the effects of die cooling on the change in extrusion characteristics of flat tubes. Cooling capacity was confirmed by observing the temperature change of the extrusion profile depending on whether or not die cooling is applied. To observe changes in material characteristics due to die cooling, surface observation is conducted and microstructure and precipitate analysis are performed by FE-SEM on the surface and longitudinal cross section of the extruded flat tubes.

• 논리연구
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• 제7권2호
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• pp.15-46
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• 2004

표면은 서로 접촉하고 있는 두 개의 사물의 공통의 경계여야 한다; 그러므로 물의 표면은 물의 부분도 아니고 공기의 부분도 아니며, 또 이들 사이에 끼워진 그 어떤 물체도 아니다. 그렇다면 공기와 물을 갈라놓은 것은 무엇인가? 공기도 물도 아니며 실체가 없는 공동의 경계가 있어야만 한다는 것은 필연적이다. 왜냐하면 양자 사이에 끼워진 물체는 이들의 접촉을 막을 것이고, 물과 공기의 경우 이런 일은 일어나지 알고 있으며 그 어떤 매개체의 삽입 없이 접촉하고 있기 때문이다.

• 대한치과보철학회지
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• 제48권1호
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• pp.1-7
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• 2010

연구 목적: 본 연구에서는MAD/MAM 시스템으로 제작된 지르코니아 코어를 통상적인 방법으로 제작된 금속-도재관 코어와 CAD/CAM 시스템으로 제작된 코어와의 변연부 적합도를 비교 분석해 보고자 한다. 연구 재료 및 방법: 레진치를 전부 도재관 제작을 위한 형태로 삭제하고, 이를 복제하여 석고 모형을 제작하였다. 석고 모형에 대해 금속-도재관, CAD/CAM ($Cercon^{(R)}$), 3종의 MAD/MAM 시스템 ($Ceramill^{(R)}$, $Rainbow^{(TM)}$, $Zirkonzhan^{(R)}$)으로 각각 10개의 코어를 제작하였다. 제작된 코어를 다이에 합착하여 광학 현미경 상에서 50배율로 변연 간격을 관찰, 계측하였다. 측정된 결과는 one-way ANOVA test로 분석하고, Tukey's HSD test로 사후검정 하였다. 결과: 각 시스템에서 변연 간격의 평균과 표준 편차는 금속-도재관 코어 $51.97{\pm}23.38{\mu}m$, $Cercon^{(R)}$ $62.16{\pm}25.88{\mu}m$, $Ceramill^{(R)}$ $67.64{\pm}40.38{\mu}m$, $Rainbow^{TM}$ $125.07{\pm}42.19{\mu}m$, $Zirkonzhan^{(R)}$ $105.02{\pm}44.61{\mu}m$로 측정되었다. 결론: 금속-도재관 코어나 CAD/CAM에 비해 MAD/MAM 방식으로 제작된 코어의 변연 간격이 큰 것으로 나타났다 (P < .05). MAD/MAM 시스템 내에서도 $Ceramill^{(R)}$, $Zirkonzhan^{(R)}$, $Rainbow^{TM}$ 순으로 변연 간격이 작은 것으로 측정되었으며, 이중 $Ceramill^{(R)}$은 CAD/CAM 시스템인 $Cercon^{(R)}$과 변연 간격에 유의차가 없었다.