• 대한치과보철학회지
• /
• 제43권6호
• /
• pp.717-726
• /
• 2005

Statement of problem. One of the common problems of provisional crown and fixed partial denture materials is that when they are subjected to constant loads for a long period of time, they exhibit a dimensional change (creep). Purpose. The aim of this study was to investigate the viscoelastic behaviour of polymer-based provisional crown and fixed partial denture materials with time at constant compressive load. Material and methods. Three dimethacrylate-based materials (Protemp 3 Garant, Temphase, Luxatemp) and one monomethacrylate-based material (Trim) were selected. Dimensional changes of the specimens were recorded by a LVDT to evaluate their viscoelastic behavior and creep strain. For all specimens, two loading procedures were used. At first, static compressive stress of 4 MPa was applied for 30 minutes and followed by 1 hour of strain recovery. Then, after 24 hours of water storage, the specimens were loaded again. The creep values between materials were statistically analyzed using one-way ANOVA and multiple comparison $Scheff\acute{e}$ test. Independent samples t-test was also used to identify the difference of creep strain between first and secondary loading conditions at the significance level of 0.05. Results. Following application of the first loading, Trim showed the highest maximum creep strain (32.7%) followed by Luxatemp, Protemp 3 Garant and Temphase, with values of 3.78%, 2.86% and 1.77%, respectively. Trim was significantly different from other materials (P<0.05), while there were no significant differences among Luxatemp, Protemp 3 Garant and Temphase (P>0.05). The highest recovery and permanent set of Trim, were significantly different from those of others (P<0.05). At the secondary loading of the dimethacrylate-based materials, creep deformation, recovery and permanent set decreased and the percentage of recovery increased, while in Trim, all values of the measurements increased. This result showed that the secondary loading at 24 hours produced a significant creep magnitude. Conclusion. The dimethacrylate-based provisional crown and fixed partial denture materials showed significantly higher creep resistance and lower deformation than the monomethacrylate-based material. Thus, monomethacrylate-based materials should not be used in long-term stress-bearing situations.

• 한국주조공학회지
• /
• 제36권5호
• /
• pp.159-166
• /
• 2016

The microstructural evolution of a cast Ni base superalloy, IN738LC, has been investigated after long term exposure at several temperatures. Most of the fine secondary ${\gamma}^{\prime}$ particles resolved after 2000 hour exposure at $816^{\circ}C$. At higher temperatures of $871^{\circ}C$ and $927^{\circ}C$, secondary ${\gamma}^{\prime}$ resolved after 1000 hours of exposure, and cuboidal primary ${\gamma}^{\prime}$ grew with exposure time. During the thermal exposure, ${\sigma}$ phase formed at all tested temperatures, and ${\eta}$ phase was observed around interdendritic regions due to carbide degeneration. The influence of microstructural evolution during thermal exposure on the mechanical properties has been analyzed. The effects of ${\gamma}^{\prime}$ particle growth are more pronounced on the high temperature creep properties than on the room temperature tensile properties.

• 설비공학논문집
• /
• 제24권6호
• /
• pp.467-475
• /
• 2012

Recently, residents have been spending almost 90% of their time indoors, which presents a higher risk from inhalation of pollutants than when spending time outdoors. Therefore, controlling indoor air quality became important. It is reported that the lung diseases and mortality for occupants are increased when there is high density of ozone which is one of the pollutants among the indoor air. In addition, the reactions between ozone and building materials produce VOCs and formaldehyde. The studies to eliminate the ozone by building materials have been actively investigated. However, ozone removal and secondary pollutants from ozone reactions with building materials have not been reported in Korea. For this reason, the aim of this study is to introduce ozone removal by HVAC filters, various building materials, and eco-friendly building materials including the quantity of secondary pollutant emissions.

• 공업화학
• /
• 제26권3호
• /
• pp.287-293
• /
• 2015

본 논문은 층상구조에 기반을 둔 리튬 2차 전지용 양극 활물질 관련 기술에 대한 특허정량분석에 관한 것으로, 우리나라 356건, 미국 1,628건, 일본 2,915건, 유럽 439건, PCT (WO) 611건 등 등록/공개된 5,000여 건의 특허를 분석하였다. 본 특허정량분석을 통해 1991년도부터 2013년까지의 리튬 코발트 개량기술, 대체 기술의 경향을 분석하였으며, 우리나라, 미국, 일본 유럽 등 주요국별로 리튬이차전지 기술의 특허 점유율을 구하였다. 그중 차세대 리튬이차전지 기술로 부상하고 있는 구조 혼합 기술 관련 특허는 2000년에 다수 출원되기 시작하여 2005년도에는 SANYO (34.5% 점유), SONY (17.5% 점유), LG (7% 점유) 및 SAMSUNG (5.5% 점유)을 필두로 많은 특허가 출원되었다. 마지막으로 성분계별 공정 분포도를 버블차트로 작성하여 분야별 연구 집중도를 확인하였다.

• 한국재료학회지
• /
• 제13권9호
• /
• pp.581-586
• /
• 2003

3%C-18%Cr-1%Mo-2%Ni-1%Mn high chromium cast iron was casted and destabilized at temperatures of 900, 1000 and $1100^{\circ}C$ for 1, 2, 4 and 8hr under $N_2$atmosphere to observe the effect of destabilization temperature and time on the carbide and matrix structures. In as-cast condition, the microstructure consisted of $M_{ 7}$$C_3$ carbides and matrix structures which were composed of 91.50% austenite and 8.50% martensite. Numerous fine secondary carbides were observed in the specimens destabilized at $900^{\circ}C$ for 1, 2, 4 and 8hr. But, the number of secondary carbides were much reduced with the increased destabilization temperature. More austenite was formed in the matrix with the higher destabilization temperature. The amounts of austenite in the matrix were 4.23% at $900^{\circ}C$, 29.68% at $1000^{\circ}C$ and 66.51% at$ 1100^{\circ}C$, respectively. However, the effect of destabilization time on the secondary carbide and matrix was very weak compared with that of destabilization temperature. The ranges of the amount of austenite in the matrix from 1hr to 8hr destabilization heat treatment were: 3.95%-4.35% at $900^{\circ}C$, 28.89%-30.15% at $1000^{\circ}C$ and 65.13%-67.12% at $1100^{\circ}C$, respectively. The variation ranges were very narrow. The equilibrium concentration of C and Cr in austenite was already reached within 1hr during destabilization heat treatment. After an attainment of the equilibrium concentration of C and Cr in austenite, no more secondary carbide was precipitated from the matrix.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2015년도 임시총회 및 하계학술연구발표회
• /
• pp.187-188
• /
• 2015

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
• /
• pp.76-76
• /
• 2004

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.1445-1447
• /
• 2008

Micro crystal structure of polycrystalline MgO film is controlled by adjusting the energy of particles arrived at the substrate during deposition. The change of crystal structure affects on the total area of (200) surface where the oxygen vacancies are formed easily, resulting in the change of secondary electron emission (SEE) coefficient($\gamma$).

• 한국초지조사료학회지
• /
• 제20권1호
• /
• pp.13-18
• /
• 2000

An efficient method for Agrobacterium-mediated transformation of forage crop alfalfa (Medicago sativa L.) was established using secondary somatic embryogenic calli. Agrobacterium tumefaciens strain EHAlOl and a binary vector pIG121-Hm which has selection markers for kanamycin and hygromycin have been shown to be an efticient materials for alfalfa transformation. The secondary somatic embryogenic calli originated from hypocotyl explants of alfalfa were efficient infection materials for Agrobacterium EHAlOl and normally germinated into plantlets. The introduced gene (GUS) was constitutively expressed in all tissues of transgenic alfalfa with different expression levels. These results indicate that the use of pIG121-Hm vector, Agrobacterium EHAlOl and improved culture system of callus facilitate the transformation of alfalfa. (Key words : Agrobacterium, Alfalfa, Gene transfer, Transformation)

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.232-236
• /
• 2004

The fracture characteristics of unidirectional composite single-lap bonded joints were investigated experimentally and numerically. The effects of bonding method, surface roughness, bondline thickness and the existence of fillet on the failure characteristics and strength of bonded single-lap joints were evaluated experimentally. The failure process, failure mode and the behavior of load-displacement curve was apparently different according to bonding method. The failure load of the specimen co-cured without adhesive was definitely superior to other types of specimens but the specimens co-cured with adhesive film had a less strength than secondary bonded specimens. In the secondary bonded specimens, the lower value of surface roughness and existence of fillet improved the strength of specimens. The strain energy release rates calculated by geometric nonlinear finite element analyses and Virtual Crack Closure Technique for the secondary bonded specimens considering the three types of initial cracks - comer crack, edge crack and delamination crack - were consistent with the test results.