• Korean Journal of Materials Research
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• v.2 no.4
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• pp.293-297
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• 1992

The magnetic properties of the amorphous Fe/sub 32/Ni/sub 36/Cr/sub 14/P/sub 12/B/sub 6/ has been studied by Mossbauer spectroscopy in the temperature range of 88-400K. The analysis of the spectrum of B8K, the magnetic hyperfine field and quadrupole splitting are found to be 140.5kOe and almost zero, which means that the magnetic hyperfine field is randomly oriented with respect to the principal axes of the electric field gradient, respectively. The values of quadrupole splitting in paramagnetic phase with Tc=280K are independent on the changes of temperature. Debye temperature is found to be about 288k from the analysis of recoilless fraction.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.112-113
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• 2002

최근에 극초단 고출력 레이저가 개발됨에 따라 이에 의한 강한 비선형 현상중의 하나인 고차 조화파(high-order harmonics)의 발생이 가능하게 되었다. 조사 레이저와 원자 간의 결맞는 과정에 의해서 생성된 고차 조화파는 레이저와 같은 좋은 결맞음과 펨토초 이하의 아주 짧은 펄스폭을 가질 수 있기 때문에 플라즈마 진단, 극자외선 광원을 이용한 비선형 광학, 아토초 영역의 물리적 현상을 관측하는데 아주 유용한 광원이 될 것으로 여겨져 오고 있다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.279-280
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• 2008

극자외선 영역(${\lambda}$=13.5 nm)에서 기하학적 그림자 효과를 줄이기 위해 ITO 박막을 RF 스퍼터링을 사용하여 증착하였다. 이를 러더퍼드 후방산란 분석법과 X-선 반사율 분석법을 이용하여 극 자외선 영역에서 ITO 박막의 광학상수를 결정하였다.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.185-189
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• 2002

Mignetron sputter 장비를 이용하여 극자외선 노광공정용 Mo/Si 다층박막을 증착하였다. 증착 시편과 동일한 조건에서 수행된 시뮬레이션과 측정된 반사도 값을 비교하였고, d-spacing, 밀도, interface layer, 입사각 둥이 반사도에 어떠한 영향을 미치는지에 대하여 고찰하였다. 또한 측정된 반사도 그래프에 근접한 조건을 조사하였다. 이를 통하여 Mo/Si 다층박막의 반사도에 영향을 미치는 인자들과 그 영향에 대하여 알 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1170-1179
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• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI for the whole operating conditions of various wind speeds using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Because there is no experimental data about wind turbine noise, we first of all compared aerodynamic performance such as shaft torque and power with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. As the wind speed increases, the overall sound pressure level and the sound pressure level by the quadrupole and dipole source show a increasing tendency. Also, sound pressure level is proportional to $r^{-2}$ in the near field and $r^{-1}$ in the far field according to the increase of distance from the center of hub of wind turbine. According to 2 times increase of distance, sound pressure level is reduced by about 6dB.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.1-8
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• 1994

A five mirror system with a reduction magnification(M=+1/5) is designed for DUV optical lithography. First, for spherical mirror systems, the numerical solutions of all zero 3rd order aberrations are derived and the 3-dimensional shape of the solution-domain is obtained. In these solutions, we select solutions which have as less residual aberrations and smaller central obscurration as possible and the aspherization is carried out to the last two spherical mirrors to obtain a system that has as higher NA as possible. Finally we obtain the system of which NA is 0.45, the central obscuration is about 25% and the resolution is about 650 cycles/mm at the 50% MTF value criterion and the depth of focus of 0.8${\mu}m$ for the nearly incoherent illumination (${\sigma}$=1.0) and the wavelength of 0.193${\mu}m$ (ArF excimer laser line).

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.53-53
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• 2010

지표위의 어떤 지점에서의 지구자기의 수평분력 방향과 진북방향 사이의 각을 편각(Declination)이라고 정의한다. 쉽게 말하면 편각은 나침반의 자침이 가러 키는 방향과 진북방향과의 사이 각을 말한다. 대부분의 사람들은 나침반의 자침이 북자기극(North magnetic pole)을 가러킨다고 잘못알고 있다. 지구 다이나모설(Geodynamo theory)에 의하면 주로 철(약 90%)로 구성된 외핵 속에서 계속 생성 유지되고 있는 복잡한 (각각 나선형(helical)의 회전축에 대체로 평행하거나 평행하지 않은) 대류(Convection currents)에 수반하는 전류가 복잡한 지구자기장을 형성한다. 지표상에서 측정한 지구자기장의 자료를 Spherical harmonic analysis 으로 분석하면 한 개의 커다란 쌍극자(Dipole) (Inclined geocentric dipole 또는 주된 자기장(Main field) 이라고 부름), 적도쌍극자(Equatorial dipole), 4극자 (Quadrupoles), 8극자(Octupoles) 등의 여러 개의 크고 작은 쌍극자들의 총합이 지구자기장의 근원인 것처럼 해석되고 있다. 어떤 지점에서의 지구자기장의 방향은 외핵에서 생성된 천체 자기장에서 Main field를 제거한 나머지 자기장과, 상부 맨틀(upper mantle), 지각 및 지표상에 존재하는 인공 물체 또는 암석 및 광석 등의 잔류자기 및 유도자기 그리고 지형 등의 영향으로 결정된다. 어떤 지점에서의 지구자기장의 방향은 태양풍(Solar wind)과 전리층 사이의 상호작용 등의 외부자장(external field)의 영향도 받는다. 비쌍극자 자장(Non-dipole field)은 지표상에서 측정되는 총자기장에서 외핵에서 생성된 주된 자기장(Main field) 즉, 지구의 회전축에서 약 11.5도 기울어진 쌍극자 자장을 제거하고 남는 자기장을 말한다. 따라서 편각은 비쌍극자자장의 영향을 가장 많이 받는다. 비쌍극자 자장은 정지한 상태의 자장(standing field) 과 매년 서쪽으로 약 0.2도 움직이는 Westward drift하는 자장으로 크게 두 가지로 구분된다. 쌍극자 자장의 방향은 매우 느리게 변하지만 그 세기는 현재 비교적으로 빠르게 약해지고 있다. 비교적으로 매우 빠르게 변하는 비쌍극자 자장의 변화를 영년변화(Secular variation) 이라고 한다.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.113-119
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• 2009

$^{57}Fe_xCu_{1-x}O$(x = 0.0, 0.02) powders were prepared by sol-gel method and their crystallographic and magnetic hyperfine properties have been studied using X-ray diffraction and $M{\ddot{o}}ssbauer$ spectroscopy (MS). The crystal structure of the samples is found to be monoclinic without any secondary phases and their lattice parameters increase with increasing annealing temperature ($T_A$), which is attributed to an increase in oxygen-vacancy content. MS measurements at room temperature indicate that $Fe^{3+}$ ions substitute $Cu^{2+}$ sites and ferromagnetic phase grow with increasing $T_A$. Magnetic hyperfine and quadrupole interactions of $^{57}Fe_{0.02}Cu_{0.98}O$ ($T_A=500^{\circ}C$) in the antiferromagnetic state at 17 K have been studied, yielding the following results: $H_{hf}=426.94\;kOe$, ${\Delta}E_Q=-3.67\;mm/s$, I.S.=0.32 mm/s, ${\theta}=65^{\circ}$, ${\phi}=0^{\circ}$, and ${\eta}=0.6$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.845-851
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• 2014

Dielectrophoresis (DEP) is defined as the motion of suspended particles in solvent resulting from polarization forces induced by an inhomogeneous electric field. DEP has been utilized for various biological applications such as trapping, sorting, separation of cells, viruses, nanoparticles. However, the analysis of DEP trapping has mostly employed the period-averaged ponderomotive forces while the dynamic features of DEP trapping have not been attracted because the target object is relatively large. Such approach is not appropriate for the nanoscale analysis in which the size of object is considerably small. In this study, we thoroughly investigate the dynamic response of trapping to various system parameters and its influence on the trapping stability. The effects of particle conductivity on its motion are also focused.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.663-669
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• 2016

A terahertz asymmetric split-loop resonator (ASLR) was analyzed for use in high-sensitivity sensing applications. Its structural asymmetricity induces an asymmetric Fano resonance which has a high quality factor compared to the symmetric eigen-resonance. The variations of the resonant frequency, transmission coefficient, and quality factor of the ASLR in the eigen and Fano resonances are analyzed as a function of its structural asymmetricity. Also, the surface current densities on the ASLR in both resonances are calculated to analyze the main cause of the variations of its transmission characteristics. The surface current of the ASLR in the eigen resonance shows a dipole resonance, which increases the radiation loss and reduces the quality factor. On the other hand, the surface current of the ASLR in the Fano resonance shows a trapped or quadrupole mode which has a low radiation loss. Therefore, the ASLR operated in the Fano resonance has a high quality factor. Terahertz, high-performance filters and high sensitivity sensors can be developed based on our analysis results of the ASLR having a high quality factor. These high-performance devices based on terahertz metamaterials could increase the adoption of terahertz industrial applications.