• 한국광학회:학술대회논문집
• /
• 한국광학회 2002년도 하계학술발표회
• /
• pp.162-163
• /
• 2002

1-D photonic band-gap structure is identified in a cholesteric liquid crystal system. The optical transmission spectrum is measured and compared with the theoretical analysis. Nonlinear transmission is measured near the band edge. Also 3-D photonic band-gap structures are fabricated from dielectric colloidal polystyrene beads through a centrifuge method. The fabricated photonic crystals exhibit opalescent colors under white light and show a clear diffraction peak dependent on the incident angle of the light beam. Also the scanning electron microscope image was taken to verify the face-centered cubic crystal structure. Bragg's law and Snell's law are employed to describe the position of angle resolved diffraction peaks. It was shown that the optically deduced effective refractive index and lattice constants were in good agreement with the crystal structure identified by scanning electron microscope.

• 대한기계학회논문집B
• /
• 제27권2호
• /
• pp.251-258
• /
• 2003

Natural gas hydrates typically contain 85 wt.% water and 15 wt.% natural gas, and commonly belongs to cubic structure I and II. When referred to standard conditions, 1㎥ solid hydrates contain up to 172N㎥ of methane gas, depending on the pressure and temperature of production. Such large volumes make natural gas hydrates can be used to store and transport natural gas. So, the tests were performed on the formation of natural gas hydrate is governed by the pressure, temperature, gas composition etc. The results show that the formation pressure of structure II is lower about 65% and the solubility is higher about 3 times than that of structure I.

• Bulletin of the Korean Chemical Society
• /
• 제35권11호
• /
• pp.3299-3302
• /
• 2014

The In2S3 thin films of tetragonal structure and In2O3 films of cubic structure were synthesized by a spin coating method from the organometallic compound precursor triethylammonium indium thioacetate ($[(Et)_3NH]^+[In(SCOCH_3)_4]^-$; TEA-InTAA). In order to determine the electron mobility of the spin-coated TEA-InTAA films, thin film transistors (TFTs) with an inverted structure using a gate dielectric of thermal oxide ($SiO_2$) was fabricated. These devices exhibited n-channel TFT characteristics with a field-effect electron mobility of $10.1cm^2V^{-1}s^{-1}$ at a curing temperature of $500^{\circ}C$, indicating that the semiconducting thin film material is applicable for use in low-cost, solution-processed printable electronics.

• 한국생산제조학회지
• /
• 제9권3호
• /
• pp.69-75
• /
• 2000

The object of the research is to estimate for pearlite structure of quenched carbon steels. The effects of temperature on physical properties metallic structures and the latent heat by phase transformation were considered. In this study a set of constitutive equations relevant to the analysis of thermo-elasto plastic materials with pearlite phase transformation during quenching process way presented on the basis of continuum thermo-dynamics. The iso-thermal transformation curve of the SM50C was formlated by cubic spline curve. The formulated equations of evolution in pearlite transformation was used for structure analysis. The volume fraction of pearlite was obtained from the results of calculated metallic structure by Finite element equation.

• 한국세라믹학회지
• /
• 제28권11호
• /
• pp.859-864
• /
• 1991

High quality lead titanate thin films were fabricated by spin coating on a silicon substrate. The resulting dried gel layers were uniform in thickness through 2$\times$2 $\textrm{cm}^2$ area, and polycrystalline perovskite structures developed almost crack free with a heat treatment above 50$0^{\circ}C$ in films with thickness above 360 nm. Metastable pyrochlore structures were observed in films with thickness of 160 nm when heat treated at 500 and $600^{\circ}C$, but these structure did not appear in films with thickness of 360 nm. The thickness dependence in crystal structure of films was studied. by varying the substrate condition and analyzing the interface between the film and substrate. In native oxide films on silicon stbstrates, amorphous dried gel layers were heterogeneously nucleated. Metastable cubic pyrochlore structure could be crystallized in amorphous native oxide.

• 한국분말재료학회지
• /
• 제11권3호
• /
• pp.242-246
• /
• 2004

FePt nanoparticles for high-density magnetic recording media were synthesized by the simultaneous chemical reduction of Fe(acac) $_2$ and Pt(acac) $_2$ with 1,2-hexadecanediol as the reducing reagent. TEM images showed that the shape of as-synthesized FePt nanoparticle was spherical and average particle size was 3 nm. Also, SAD pattern showed that crystal structure was disordered FCC (face centered cubic). These FCC structured nanoparticles were transformed FCT (face centered tetragonal) structure by annealing at 55$0^{\circ}C$ for 30 min in Ar atmosphere. XRD analysis revealed that as-synthesized FePt nanoparticles were transformed from disordered FCC to ordered FCT. Finally, the coercivity of 2 kOe for FePt nanoparticles with FCT structure was obtained by VSM measurement.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
• /
• pp.445-450
• /
• 1997

Optimal design of a piezoelectric smart structure is studied for cabin noise control. A cubic shaped acoustic cavity with a flat plate which covers one side is taken as the problem. The sensor signal is returned to the actuator through a negative gain. The acoustic cavity is modeled using the modal approach which represents the pressure fields in the cavity as a sum of mode shapes of the cavity with unknown coefficients. By using orthogonality of the mode shapes of the cavity, finite element equation for the structure with the influence of the acoustic cavity is derived. The objective function is the average pressure at a certain region, so-called silent zone, in the cavity and the design variables are the locations and sizes of the piezoelectric actuator and sensor. The optimal design is performed at several frequencies and the results show a remarkable noise reduction.

• Transactions on Electrical and Electronic Materials
• /
• 제16권2호
• /
• pp.86-89
• /
• 2015

Uniform ZrO₂ nanoballs were synthesized at 700℃ using the inverse replication method through a colloid-imprinted carbon (CIC) template. The structural, dielectric, and conducting properties of the ZrO₂ nanoballs were investigated and compared with those of ZrO₂ film prepared by sol-gel method and powdered ZrO₂ chemical. Both the monoclinic and cubic phases were found in the ZrO₂ balls and film but the ZrO₂ chemical showed a monoclinic phase, where the cubic structure is known to be formed at above 2,300℃. ZrO₂ nanoballs showed the lower dielectric property of k = 21.2 at 1 MHz because the 8-coordinated cubic phase in the ZrO₂ nanoball produced lower polarization than the polarization of the 7-coordinated monoclinic ZrO₂ chemical (k = 23.6). The dielectric stability was maintained in each ZrO₂ ball, film, and chemical under the applied forward and reverse voltage range (−5 to +5 V) at 1 MHz. The ionic conductivities were 7.86 × 10⁻⁸/Ω·cm for ZrO₂ nanoballs, 3.29 × 10⁻⁸/Ω·cm for ZrO₂ chemical, and 6.70 × 10⁻⁵/Ω·cm for the thickness of 1,053 nm ZrO₂ film at room temperature with the electronic contribution being less than 0.006%.

• 한국산학기술학회논문지
• /
• 제13권9호
• /
• pp.4139-4145
• /
• 2012

본 논문에서는 향후 태양전지 반사방지막에 적용여부를 알기 위하여 굴절률 분포에 따른 반사방지막의 성능을 분석하였다. 기존논문에서 제시되었던 1차, 3차 및 5차 함수의 굴절률 분포를 6층 구조의 두께 180 nm 반사방지막에 적용하고 각 굴절률 분포에 대한 반사율을 계산하고 비교하였다. 또한 새로운 구배형 굴절률(graded index) 구조를 제안하였고, 제안한 구조와 기존의 1차, 3차 및 5차 함수의 반사율과 비교하였다. 그 결과로써, 굴절률 분포가 고차 함수로 갈수록 반사율이 대체적으로 감소하였고, 구배형 굴절률 분포의 경우는 짧은 파장대(500 nm ~ 700 nm 이하)에서는 1차, 3차 및 5차 함수보다 더 높은 반사율을 보였고, 긴 파장대(700 nm 이상 ~ 800 nm)에서는 더 낮은 반사율을 보였다. 따라서 긴 파장대에서는 구배형 굴절률 분포가 기존의 1차, 3차, 5차 함수인 경우보다 더 좋은 반사방지막이 될 수 있다는 것을 발견했고, 이 결과는 긴 적색 가시광선에서 적외선 영역에 적용되는 광소자 및 광필터에 적용 가능하리라 판단된다.

• 한국시뮬레이션학회논문지
• /
• 제29권3호
• /
• pp.41-48
• /
• 2020

본 논문에서는 고속도로 통행량을 보다 정확하게 예측하기 위한 새로운 방법으로 통행량에 대한 누적분포함수를 이용한 동적 예측 알고리즘을 제시한다. 여기서 누적분포함수의 근사함수를 수치적 방법인 내츄럴 큐빅 스플라인(natural cubic spline) 보간법과 레벤버그-마쿼트(Levenberg-Marquardt) 방법을 통해 얻는다. 이 알고리즘은 금융수학에서 활용하는 누적 분포함수를 이용한 난수 생성 알고리즘을 통행량 예측에 알맞도록 새롭게 구조화한 것이다. 이 알고리즘으로 고속도로 통행량을 시뮬레이션하면 실제 통행량과 매우 흡사한 결과를 얻을 수 있음을 확인할 수 있다. 따라서 이 알고리즘은 고속도로뿐만 아니라 통행량 예측이 필요한 다양한 분야에서 활용할 수 있는 새로운 알고리즘이다.