• 멤브레인
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• 제27권4호
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• pp.350-357
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• 2017

본 연구는 열유도 상분리법(thermally induced phase separation, TIPS)을 사용하여, 수처리 분리막에 적용하기 위해, 응고조의 온도 및 열용량의 변화에 따른 분리막의 모폴로지 변화를 관찰하였다. 분리막을 제조하기 위한 소재로는 기계적 물성과 내화학성이 우수한 poly(vinylidene fluoride)(PVDF)와 실리카를 이용하였고, 희석제로는 dioctyl phthalate (DOP), dibutyl phthalate (DBP)를 사용하였다. 다양한 응고액의 열용량 변화에 따른 구조 변화 관찰을 위하여 SEM 이미지를 관찰하였다. 열용량이 증가할수록 PVDF의 결정화 속도가 느려져 큰 기공을 나타내며 열용량이 작을수록 결정화 속도가 증가하여 작은 기공이 생기는 것을 확인하였다.

• 한국세라믹학회지
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• 제42권8호
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• pp.537-541
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• 2005

Silicon nitride is one of the most successful engineering ceramics, owing to a favorable combination of properties, including high strength, high hardness, low thermal expansion coefficient, and high fracture toughness. However, the impact damage behavior of $Si_3N_4$ ceramics has not been widely characterized. In this study, sphere and explosive indentations were used to characterize the static and dynamic damage behavior of $Si_3N_4$ ceramics with different microstructures. Three grades of $Si_3N_4$ with different grain size and shape, fine-equiaxed, medium, and coarse-elongated, were prepared. In order to observe the subsurface damaged zone, a bonded-interface technique was adopted. Subsurface damage evolution of the specimens was then characterized extensively using optical and electron microscopy. It was found that the damage response depends strongly on the microstructure of the ceramics, particularly on the glassy grain boundary phase. In the case of static indentation, examination of subsurface damage revealed competition between brittle and ductile damage modes. In contrast to static indentation results, dynamic indentation induces a massive subsurface yield zone that contains severe micro-failures. In this study, it is suggested that the weak glassy grain boundary phase plays an important role in the resistance to dynamic fracture.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1394-1397
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• 2006

Polymer Dispersed Liquid Crystal (PDLC) films, of which the liquid crystal has negative dielectric anisotropy, were prepared from the phase separation between MJ001317 and a variety of compositions of resins by common polymerization induced phase separation method. In this work, the effects of resin compositions have been systematically investigated and it was found that the morphology and size of droplet, which is closely related to electro-optic properties, mainly depend on the rate of polymerization and cross-linking density for each resin composition. The reverse mode PDLC films from this newly developed formulation containing TPGDA/EHA/HMPPO showed the good off-state transmittance, contrast ratio (19/1), and relatively low driving voltage(10V).

• 한국전기전자재료학회논문지
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• 제28권3호
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• pp.160-164
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• 2015

In this study, $(1-x)Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3+xCeMnO_3$ (x= 0~0.02) ceramics were prepared by Columbite precursor method. The phase structure, ferroelectric and piezoelectric properties were systematically investigated. It was found that PMW-PNN-PZT possessed superior electrical properties due to its composition close to the MPB (morphotropic phase boundary). Coercive electric field of 10.05 [kV/cm] and density of 7.88 [$g/cm^3$] were obtained when the substitution amount of $CeMnO_3$ is x=0.02. In contrast, specimens with x=0.01 showed the mechanical quality factor($Q_m$) of 1,091 and the electromechanical coupling factor($k_p$) of 0.613.

• Journal of the Optical Society of Korea
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• 제17권3호
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• pp.262-268
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• 2013

We study the focusing properties of a two-dimensional square-lattice photonic crystal (PC) comprising silica and germanium partitioned cylinders in air background. The finite difference time domain (FDTD) method with periodic boundary condition is utilized to calculate the dispersion band diagram and the FDTD method incorporating the perfectly matched layer boundary condition is employed to simulate the image formation. In contrast to the common square PCs in which the negative refraction effect occurs in the first photonic band without negative phase propagation, in our suggested model system, the frequency with negative refraction exists in the second band and in near-infrared region. In this case, the wave propagates with a negative phase velocity and the evanescent waves can be supported. We also discuss the dependency of the image resolution and its location on surface termination, source location, and slab thickness. According to the simulation results, spatial resolution of the proposed PC lens is below the radiation wavelength.

• 한국발생생물학회지:발생과생식
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• 제10권2호
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• pp.79-84
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• 2006

제주 연안에 서식하는 용치놀래기, 어렝놀래기, 황놀래기, 놀래기를 대상으로 체장에 따른 성 분포와 생식소의 성 특성을 조직학적으로 탐색하여 성 전환 양상을 조사 비교하였다. 용치놀래기, 어렝놀래가, 황놀래기, 놀래기는 자성선숙형 자웅동체어로 조직학적 관찰 결과 정소조직(정자형성부위)이 퇴화기 난소의 전역에 출현하는 혼재형 2에 속하는 어종이었다. 용치놀래기, 황놀래기 그리고 놀래기는 1차 수컷과 2차 수컷이 존재하는 복웅성 어류이고, 조사된 어렝놀래기는 암컷이 수컷으로 성 전환된 2차 수컷만이 출현하는 단웅성 어류로 사료된다.

• 한국재료학회지
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• 제26권1호
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• pp.13-16
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• 2016

Morphology and formation processes of lamellar grain boundaries in titanium rich binary TiAl intermetallics were studied. TiAl alloys containing aluminum content of 44 to 48 at.% were induction-heated to 1723 K followed by helium-gas-quenching at various temperatures. For the Ti-44%Al, few lamellae were observed in samples quenched from higher than 1473 K. Although small peaks of beta phase were detected using X-ray diffraction, only the ordered hexagonal phase (${\alpha}_2$) with clear APB contrast was observed in TEM observation. For the Ti-48 at.%Al alloy, almost no lamellar structure, and straight grain boundaries were observed in samples quenched from higher than 1623 K. The formation of lamellae along grain boundaries was observed in the sample quenched from 1573 K. The fully lamellar microstructures with serrated boundaries were observed in samples quenched from lower than 1473 K. It was found that the formation of ${\gamma}$ platelets took place at higher temperatures in Ti-48 at.%Al than in Ti-44 at.%Al. Although the size of the serration is different, serrated lamellar grain boundaries could be obtained for all alloy compositions employed. The serration appeared to be due to the grain boundary migration induced by precipitation and growth of ${\gamma}$. Differences in transformation characteristics with aluminum content are discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.562-564
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• 2001

Transformation of molecular film occurs only usually in air-water interface, 2 dimensions domain's growth and crash are achieved. Organic matter thin film that accumulate molecular film in archaism board only that consist of growth of domain can understand correct special quality of accumulation film supplying information about fine structure and properties of matter of device observing information and so on that is surface forward player and optic enemy using AFM one of SPM application by nano electronics. The stable images are probably due to a strong interaction between the monolayer film and glass substrate. We are unable to obtain molecule resolution in images of the films but did see a marked contrast between images of the bare substrate and those with the network structure film deposited onto it. Formation that prevent when gas phase state and liquid phase state measure but Could know organic matter that molecules form equal and stable film when molecules were not distributed evenly. and accumulated in solid state only.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1618-1620
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• 2002

Transformation of molecular film occurs only usually in air-water interface, 2 dimensions domain's growth and crash are achieved. Organic matter thin film that accumulate molecular film in archaism board only that consist of growth of domain can understand correct special quality of accumulation film supplying information about fine structure and properties of matter of device observing information and so on that is surface forward player and optic enemy using AFM one of SPM application by nano electronics. The stable images are probably due to a strong interaction between the monolayer film and glass substrate. We are unable to obtain molecule resolution in images of the films but did see a marked contrast between images of the bare substrate and those with the network structure film deposited onto it. Formation that prevent when gas phase state and liquid phase state measure but Could know organic matter that molecules form equal and stable film when molecules were not distributed evenly, and accumulated in solid state only.

• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.707-711
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• 2006

ZnO was doped up to 0.3 wt% for improving the electrical properties of lead-free $[Li_{0.04}(Na_{0.44}Ko_{0.52})-(Nb_{0.86}\;Ta_{0.10}\;Sb_{0.04})]O_3$ piezoelectric ceramics. The ceramics were fabricated with the conventional sintering processes. Crystal structure of the samples was tetragonal phase regardless of ZnO amount. However, the piezoelectric properties were varied with the ZnO amount. The electro-mechanical coupling factor $(k_p)$ was with the ZnO amount up to 0.2 wt% but decreased with the further addition. the maximum value of $k_p$ was 0.475. Density, piezoelectric charge constant and relative dielectric constant was also showed maximum value at 0.2 wt%. The maximum values are $4.75g/cm^3$, 275 pC/N, 1403, respectively. In contrast, the mechanical quality factor $(Q_m)$ was not varied with increasing the ZnO addition up to 0.2 wt% but rapidly increased at 0.3 wt%.