• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.570-577
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• 2001

Three-dimensional time-dependent flow past a circular cylinder is numerically investigated using direct numerical simulation for Reynolds number 280 and 300. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme and the pressure and viscosity terms are applied by the 4th order central difference. And in spanwise, Navier-Stokes equation is distributed using of Spectral Method. At Reynolds number 259 the two-dimensional wake becomes linearly unstable to a second branch of modes with wavelength about 1.0 diameters at onset (B-mode). Present results of three-dimensional effects of in wake of a circular cylinder is represented with spanwise and streamwise vorticity contours as Reynolds numbers.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.80-84
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• 1996

This paper aims at reviewing the Possibility application over normal or abnormal, detection used by AE and the wear characteristics of grinding process. In this study, when diamond bur in dentistry with chosen grinding conditions were tuned at grinding. The variation of grinding resistance and hE signal is detected by the use of AE measuring system. The tests are carried out in accordance with diamond burs and workpiece; arcyl and bovine. According to the experiment results, the following can be expected; AE has the possibility to detect the state normality and abnormality. However, the grinding resistance measuring can find it difficult to detect it. It can be accurately excerpted from AE occurrence pattern in contact start point of diamond bur and bovine, grinding condition and derailment point. It is known that AE$\_$rms/ is well compatible with grinding resistance. According to the increase of the material removal rate, the specific energy of the diamond bur is inclined to decrease and the grinding resistance has a tendency to increase.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.148-154
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• 1999

This study was carried out to verify grinding performance of dental diamond bur and investigate the possibility of AE application in dentistry field. Workpieces were made of acryl and bovine respectively for the experiments in this study. Grinding test was conducted to get the data of grinding resistance and specific grinding energy of four different types of diamond bur by using tool dynamometer. AE signal was acquired to verify grinding process in the AE measuring system. Tool wear was observed to find parameters about grinding characteristics of diamond bur by means of SEM picture. It was found that the wear of dental diamond bur could be detected with polishing of grinding material, removal of adhesive parts, wear of particles neighboring cutting nose, loss of material and elevation of temperature. The wear of B, C, D type diamond bur is due to wear and fracture of grain size. Abnormal state can be found through the behavior of AE signal in the grinding working. As a result, it is expected that forecast of abnormal state is possible using AE equipments under real time process.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.34-35
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• 2013

In this study, the ultra high strength concrete which have 80, 130, 180MPa took the heat from 20℃ to 700℃ and the 0, 20% stress in normal condition's to evaluate stress-strain, residual compressive strength and thermal expansion deformation were evaluated. The heating speed of specimen was 0.77℃/min 20~50℃, 50℃ before the target temperature, and the other interval's heating speed was 1℃/min. As a result, the stress-strain curve of non-load specimen showed the liner behavior at high temperature when the specimen's strength increased more. If ultra high strength concrete got loads, its compressive strength tended to decrease different from the normal strength concrete. The thermal expansion deformation was expanded from a vitrification of quartz over 500℃. however, over the 600℃, it was shrinked because of the dehydration of the combined water.

• 한국가구학회지
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• 제28권3호
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• pp.198-206
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• 2017

In this study, analysis of the cultural effects on design expressions and comparative analysis of designers' cultural background on their expression methods were implemented. The purpose of this study is to help the professionals and learners who pursue towards cultural designs in the design field utilize this research work as reference data and academic materials, and to contribute to the development of designs in the Eastern cultures. The author compared the differences between the viewpoints depending on background, either the Eastern or the Western culture, based on the existing studies and literatures, and analyzed the relationship between the viewpoints and expressions. Also, analyses of the expression methods related with cultural viewpoints and design viewpoints were conducted, especially with analysis of works of Uchida Shigeru from the East and Berner Panton from the West. Although both of their works were produced contemporarily and expressed with similar techniques, each of the conceptual approaches to their works represents different characteristics of the cultural viewpoint. Such a finding suggests that the approach to the design process should take place in a different way based on its cultural background, and it is accordingly required to seek for a new method for cultural design process.

• 한국정밀공학회지
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• 제14권12호
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• pp.66-72
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• 1997

This paper aims at reviewing the possibility application over normal or abnormal, detection used by AE and the wear characteristics of grinding process. In this study, when diamond bur in dentistry with chosen grinding conditions were tuned at grinding. The variation of grinding resistance and AE signal is detected by the use of AE measuring system. The tests are carried out in accordance with diamond burs and workpiece: arcyl and bovine. According to the experiment results, the following can be expected: AE has the possibility to detect the state normality and abnormality. Hpwever, the grinding resistance measuring can find it difficult to detect it. It can be accurately excepted from AE occurrence pattern in contact start point of diamond bur and bovine, grinding condition and derailment point. It is known that AErms is well compatible with grinding resistance. According to the increase of the material removal rate, the specific energy of the diamond bur is inclined to dectease and the grinding resistance has a tendency to increase.

• 한국재료학회지
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• 제22권2호
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• pp.71-77
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• 2012

When a new bonding agent using coal ash is utilized as a substitute for cement, it has the advantages of offering a reduction in the generation of carbon dioxide and securing the initial mechanical strength such that the agent has attracted strong interest from recycling and eco-friendly construction industries. This study aims to establish the production conditions of new hardening materials using clean bottom ash and an alkali activation process to evaluate the characteristics of newly manufactured hardening materials. The alkali activator for the compression process uses a NaOH solution. This study concentrated on strength development according to the concentration of the NaOH solution, the curing temperature, and the curing time. The highest compressive strength of a compressed body appeared at 61.24MPa after curing at $60^{\circ}C$ for 28 days. This result indicates that a higher curing temperature is required to obtain a higher strength body. Also, the degree of geopolymerization was examined using a scanning electron microscope, revealing a micro-structure consisting of a glass-like matrix and crystalized grains. The microstructures generated from the activation reaction of sodium hydroxide were widely distributed in terms of the factors that exercise an effect on the compressive strength of the geopolymer hardening bodies. The Si/Al ratio of the geopolymer having the maximum strength was about 2.41.

• 대한소아치과학회지
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• 제44권1호
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• pp.82-88
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• 2017

본 연구의 목적은 0.2% 클로르헥시딘이 함유된 $Peak^{(R)}$ Universal Bond (PUB)의 우치 상아질에서의 전단결합강도를 알아보는 것이다. 30개 우치의 상아질 시편을 10개씩 세 군으로 나누어 I군에는 $Adper^{TM}$ Single Bond Universal (SB)를 적용하였고 II군에는 $Consepsis^{(R)}$를 처리한 이후 SB를 적용하였고 III군에는 PUB를 적용하고 $Filtek^{TM}$ Z-350 XT B3 shade를 충전후 각각의 전단결합강도를 비교 평가하였다. 그 결과 산부식 후 $Consepsis^{(R)}$를 사용하는 것은 상아질의 전단결합강도에 있어 통계학적으로 유의한 차이를 보이지 않았다(p > 0.05). SB에 $Consepsis^{(R)}$를 적용하거나 적용하지 않은 것의 전단결합강도와 PUB의 전단결합강도는 통계학적으로 유의한 차이를 보였다(p < 0.05).

• Journal of Applied Biological Chemistry
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• 제54권1호
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• pp.67-70
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• 2011

The roots of Glycyrrhiza uralensis Fisch. were extracted with 30% aqueous ethanol (EtOH), and the concentrated extract was partitioned with n-hexane, chloroform ($CHCl_3$), ethyl acetate (EtOAc), n-butanol (n-BuOH), and $H_2O$, successively. From the $CHCl_3$ fraction, four flavonoids were isolated through the repeated silica gel ($SiO_2$), octadecyl silica gel (ODS), and Sephadex LH-20 column chromatographies (c.c.). According to the results of spectroscopic data including nuclear magnetic resonance spectrometry (NMR), electron ionization mass spectrometry (EI/MS), and infrared spectroscopy (IR), the chemical structures of the compounds were determined as glabrol (1), abyssinone II (2), glabridin (3), and isoliquiritigenin (4). The flavonoids were evaluated for cytotoxic effect against human cancer cell lines, HCT-116, HepG2, HeLa, SK-OV-3, SK-BR-3, MCF-7, and SK-MEL-5. Especially, glabrol (1) and glabridin (2) showed $IC_{50}$ values of lower than $25{\mu}M$.

• 콘크리트학회논문집
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• 제25권1호
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• pp.107-114
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• 2013

이 연구는 고속비상체의 충돌 및 에멀젼 폭약에 의한 폭발조건에서 섬유보강 콘크리트의 내충격 성능을 실험적으로 평가하는 것으로 목적으로 하였으며, 고속 충격시험은 비상체의 충돌속도는 약 350 m/s이며, 폭발실험은 시험체 표면에 폭약을 접촉시킨 상태에서 실시하였다. 그 결과, PVA, PE 및 강섬유의 혼입에 의한 섬유보강 콘크리트 시험체의 휨인장성능 증가는 고속충격 및 접촉폭발에 의한 배면파괴를 억제시켰다. 콘크리트의 내충격 성능에 있어서 배면파괴 억제는 압축강도에 비하여 휨인장성능의 영향을 크게 받는 것으로 나타났다. 또한, 고속충돌 및 접촉폭발에 의해 발생하는 콘크리트 시험체의 파괴패턴은 매우 유사한 것을 알 수 있었으며, 고속비상체에 의한 충돌실험을 통해 접촉폭발상황에 대한 시험체의 파괴패턴의 유추가 가능할 것으로 판단된다.