• Restorative Dentistry and Endodontics
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• 제43권1호
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• pp.9.1-9.6
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• 2018

The objective of this case report is to introduce a simple technique for simultaneously taking a closed-mouth impression and functionally generated path (FGP) for a full coverage crown restoration. A monolithic zirconia crown was the restoration of choice. An alginate impression of the abutment tooth was taken to fabricate a custom-made closed-mouth impression tray covering the abutment tooth and the adjacent teeth. The tray had an FGP table and an abutment tray in cameo and intaglio surfaces, respectively. The impression was taken with silicone impression material after adjusting the abutment tray and inscribing the FGP using self-curing acrylic resins. Plaster casts were made from the impression, and a zirconia crown was fabricated. The crown was cemented to the abutment tooth with minimal adjustments. This simple technique resulted in a well-fitting crown that accounted for mandibular movements. Using the custom closed-mouth impression tray incorporating an FGP table simultaneously aids in fabricating an accurately fitting restoration that incorporates harmonious mandibular movements using a single impression capture.

• 한국정보처리학회논문지
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• 제5권5호
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• pp.1333-1344
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• 1998

마이크로 커널 기반 운영체제는 종래의 통합커널에 비해 비교적 속도가 늦지만 운영체제 모듈성, 이식성 측면에서 장점이 있어 다중컴퓨터 시스템에 적합하다. 다중컴퓨터 시스템용 운영체제가 시스템의 기능을 원활하게 수행할 수 있도록 하기 위해서는 부트 시의 정보를 이용하여 처리기의 각 장치 및 메모리를 시스템에 알맞게 초기화하여야 할 것이다. 본 논문에서는 OSF/1 AD3를 기반으로 한 운영체제인 고속병렬컴퓨터의 OSF/1 AD3 MISIX 마이크로 커널 초기화에 대해 기술한다. 클러스터링 기반 고속병렬처리 시스템인 고속병렬컴퓨터의 초기화를 부트, 하드웨어 관련 초기화, 메모리 주소공간 구축 등의 관점에서 기능을 소개하고, 이를 시험한 내용을 시험 환경을 바탕으로 기술한다. 구현된 마이크로 커널은 운영체제 이식 작업의 일부로 4개의 처리기를 갖는 단일노드 시스템에서 시험이 이루어졌다.

• Tribology and Lubricants
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• 제30권2호
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• pp.108-115
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• 2014

The friction behaviors of bulk amorphous thermal spray coating (BAC) and second phase-reinforced composite coatings using a high velocity oxy-fuel spraying process were investigated using a ball-on-disk test rig that slides against a ceramic ball in an atmospheric environment. The surface temperatures were measured using an infrared thermometer installed 50 mm from the contact surface. The crystallinities of the coating layers were determined using X-ray diffraction. The morphologies of the coating layers and worn surfaces were observed using a scanning electron microscope and energy-dispersive spectroscopy. The results show that the friction behavior of the monolithic amorphous coating was sensitive to the testing conditions. Under lower than normal loads, a low and stable friction coefficient of about 0.1 was observed, whereas under a higher relative load, a high and unstable friction coefficient of greater than 0.3 was obtained with an instant temperature increase. For the composite coatings, a sudden increase in friction coefficient did not occur, i.e., the transition region did not exist and during the friction test, a gradual increase occurred only after a significant delay. The BAC morphology observations indicate that viscous plastic flow was generated with low loads, but severe surface damage (i.e., tearing) occurred at high loads. For composite coatings, a relatively smooth surface was observed on the worn surface for all applied loads.

• 대한기계학회논문집A
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• 제40권3호
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• pp.267-273
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• 2016

본 연구에서는 부분 안정화 지르코니아(Z)와 자기치유능력을 부여하기 위하여 SiC와 $TiO_2$를 첨가한 5종류의 복합 지르코니아(ZS, ZST1, ZST2, ZST3, ZST5)를 소결하여, 기계적 특성과 열처리에 의한 균열 치유 가능성을 평가하였다. 6종류 지르코니아 세라믹스의 비커스 경도는 큰 차이가 없으며, 부분 안정화 지르코니아에 SiC 첨가(ZS)는 급격한 굽힘강도의 저하가 나타났지만, $TiO_2$의 첨가(ZST1, ZST2, ZST3, ZST5)는 강도가 향상하였다. 이는 SiC 및 $TiO_2$의 첨가의 따른 결정화의 영향이라 판단된다. 최고 굽힘 강도를 나타내는 균열 치유 조건에서 지르코니아 단상체는 비커스 균열이 남았으나, SiC가 첨가된 4종류는 비커스 균열이 관찰되지 않아 균열이 치유되었다.

• 대한기계학회논문집A
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• 제32권11호
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• pp.1003-1009
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• 2008

In this study, liquid phase sintered SiC (LPS-SiC) materials were made by hot pressing method. The particle size of nano-SiC powder was 30nm. Alumina ($Al_2O_3$), yttria ($Y_2O_3$) and silica ($SiO_2$) were used for sintering additives. To investigate effects of $SiO_2$, ratios of $SiO_2$ contents were changed by five kinds. Materials have been sintered for 1 hour at $1760^{\circ}C$, $1780^{\circ}C$ and $1800^{\circ}C$ under the pressure of 20MPa. The system of sintering additives which affects a property of sintering as well as the influence depending on compositions of sintering additives were investigated by measurement of density, mechanical properties such as flexural strength, vickers hardness and sliding wear resistance were investigated to make sure of the optimum condition which is about matrix of $SiC_f$/SiC composites. The abrasion test condition apply to load of 20N at 100RPM for 20min. Sintered density, flexural strength of fabricated LPS-SiC increased with increasing the sintering temperature. And in case of LPS-SiC with low $SiO_2$, sliding wear resistance has very excellent. Monolithic SiC $1800^{\circ}C$ sintering temperatures and 3wt% have excellent wear resistance.

• 비파괴검사학회지
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• 제34권1호
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• pp.23-30
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• 2014

$SiC_f$/SiC 복합재를 제작하여, $SiC_f$/SiC 복합재의 섬유배향 방향에 따르는 마모 특성을 평가하고, 마모시에 발생하는 탄성파를 검출하고 분석하였다. $SiC_f$/SiC 복합재는 섬유의 종 횡방향에 의한 마찰계수와 마모손실은 비슷하였으나, 섬유의 수직방향은 가장 작은 값을 나타내었다. 이것은 섬유의 취성 특성 때문이라 판단되며, 마모손실과 마찰계수는 정비례의 관계를 나타내었다. SiC 단상재의 탁월주파수는 58.6 kHz를 나타내고, $SiC_f$/SiC 복합재의 탁월주파수는 117.2와 136.7 kHz였다.

• 한국환경복원기술학회지
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• 제11권5호
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• pp.92-103
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• 2008

Development of new approaches to achieve naturally good ecological potential of forest road cut-slope by making the best use of advantages of gabion systems with vegetation base materials to prevent slope failure and erosion, in the area with highly erodible soil. As a result on the type analysis of gabion systems already installed in road cut-slopes, gabion systems were generally established to prevent slope failure. Existing gabion systems can be divided into monolithic and modular system and can be divided into ten subtypes according to the purpose of establishment and combination of other measures. As a result on the monitoring of erosion amount from forest road cut-slopes in the test applications, the order of erosion amount from largest to smallest is as follows : the curved road cut-slope site where normal gabion system was established ($7,911cm^3$); the control site ($7,632cm^3$); the straight road cut-slope site where normal gabion system was established ($7,301cm^3$); the curved road cut-slope site where the new gabion system was established ($5,684cm^3$); and the straight road cut-slope site where the new gabion system ($5,325cm^3$). Therefore, the result shows that the new gabion system is more effective than the normal gabion system to reduce erosion amount from forest ! road cut-slopes. During the study period, vegetation coverages of the straight and curved road cut-slope site where the new gabion system was established were about 45% and about 36%, so average vegetation coverage of the sites where the new gabion systems was established was higher than the sites where the normal gabion systems was established. Therefore, it was concluded that the new gabion system can be more effective for cut-slope revegetation.

• 한국산학기술학회논문지
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• 제15권8호
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• pp.4713-4716
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• 2014

알루미늄과 알루미늄 합금 제품의 고급화로 완벽한 알루미늄 용탕의 탈 가스 처리가 요구되고 있다. 탈 가스 처리를 위한 기존의 방법을 보면, 알루미늄 용탕 파우더와 약품 공급기로 이젝선하는 방법과 가스 취입 관을 사용하여 아르곤가스와 질소 또는 염소가스를 투입하는 방법 등이 사용되고 있다. 그러나 이 방법들은 작업도 어렵고, 염소와 불화물질 유해가스가 대단히 많이 발생하여 공해문제를 유발하는 문제점이 있으며 효과도 일정하지 않고, 과도한 처리시간으로 작업능률이 낮아지는 문제점도 있다. 가장 치명적인 문제점은 알루미늄 용탕과 약품의 반응으로 인한 많은 양의 찌꺼기의 생성과 더불어 금속의 손실 및 내화재의 수명감소를 야기하는 것이다. 이러한 문제점을 개선하기 위하여 본 연구에서는 기존에 알루미늄 연속제조를 위해 6단계 공정을 거처야 생산이 가능했던 부분을 이번에 개발한 3가지 공정만으로도 생산이 가능하게 알루미늄 연속 주조의 용탕과 탈 가스 장치의 일체화에 통한 기술을 개발에 관한 연구이다.

• 한국주거학회논문집
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• 제19권1호
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• pp.57-66
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• 2008

In the past, strong social bands, which had spontaneous communities, existed in Korean traditional society. However, while it's developing through industrialization; monolithic apartment houses were introduced which causes less interaction between neighbors. With the growing attention to the higher living quality, various schemes to revitalize the community spirits have been groped, including to improve in hardhearted neighborhood relationships and to cope with the dreariness in the city. With the development of the internet and the spread of 'digital home', the communities in cyber space have been especially revitalized since the information-oriented society. In a move to strengthen the communities in apartment complexes, this study tries to find the revitalization scheme for virtual communities in apartment complexes by analyzing the contents of its web sites and understanding the world of virtual community. These are compared and analyzed. The related virtual communities ("cafe" or "blogs") are also analyzed. The results are as follows. 1) There are some differences among the contents provided by apartment virtual community developing companies, still, it could be categorized into four types; "apartment complex introduction and management information" "community revitalization" "living guide" "individual services" 2) The contents provided by self-organized communities of residents neither require additional charge nor special membership for information while the formation is not systematized. 3) In the comparison of apartment virtual community developing companies with residents self-organized communities, "apartment complex introduction and management information" on freeboard, notice, request and Q&A, and "community revitalization" on communication board are both provided throughout the web sites. 4) The contents provided by apartment virtual community developing companies makes the information available in a wide range with managers, on the other hand, self-organized communities emphasize on showing attachment and concern of residents and requiring communications between neighborhoods.

• The Journal of Advanced Prosthodontics
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• 제6권6호
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• pp.456-461
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• 2014

PURPOSE. Translucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate. MATERIALS AND METHODS. Two commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05). RESULTS. High translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis. CONCLUSION. Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.