• 전자공학회논문지A
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• 제32A권1호
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• pp.70-78
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• 1995

In order to implement broadband RAM's(Radar Absorbing Materials) made up of multiple dielectricl layers, the design variables such as the dielectrci constaints, the depths and the loss tangents of dielectric are optimized. The wave impedances regarding the reflective wave are found in dielectrics, input impedances and reflection coefficients with multiple dielectric layers are derived from the transmission line circuit theory. Finally, minimum average reflective power and optimum design variables are obtained by applying the numerical technique, called modified Powell method. In case of four dielectric layers with inequality constraints in design variables, a quite favourable and feasible result with the total depth of 1.1 cm, the average reflective power of 0.85% over the bradband frequency range is obtained for a specific example.

• Journal of the Optical Society of Korea
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• 제18권2호
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• pp.101-109
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• 2014

In this paper, four apodization functions are proposed for silicon-on-insulator (SOI) strip waveguides with sidewall-corrugated gratings. The effects of apodization functions on the full width at half maximum (FWHM), the side-lobe level, and the reflectivity of the reflection spectrum are studied using the coupled-mode theory (CMT) and the transfer-matrix method (TMM). The results show that applying proposed apodization functions creates very good filtering characteristics. Among investigated apodized waveguides, the apodization functions of Polynomial and z-power have the best performance in reducing side-lobes, where the side-lobe oscillations are entirely removed. Four functions are also used for precise adjustment of the bandwidth. Simulation results show that the minimum and maximum values of the FWHM are 0.74 nm and 8.48 nm respectively. In some investigated functions, changing the apodization parameters decreases the reflectivity which is compensated by increasing the grating length.

• 제어로봇시스템학회논문지
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• 제12권6호
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• pp.554-560
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• 2006

In this paper, we propose the topological map building method about unknown environment using the ultrasonic sensors. An ultrasonic sensor inherently has the range error due to the specular reflection. To decrease this error, we estimate the obstacle states(position and velocity) using the local minimum sensor values and Jacobian. Estimated states are used to avoid the obstacles and build the topological map similar to the type that human being memorizes an environment. When a mobile robot is faced with three problems(comer way, cross way and dead end), it senses the movable directions using FIS(Fuzzy Inference System). Among these directions, it can select the target direction using binary decision tree(Turn Side Selector). Proposed algorithm has been verified with three simulations and three implementations.

• Journal of Magnetics
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• 제21권2호
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• pp.187-191
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• 2016

Retrieving the equivalent electromagnetic parameters (permittivity and permeability) plays an important role in the research and application of metamaterials. Frequency dispersion of magnetic permeability has been theoretically predicted in a metamaterial composed of cut wire pairs (CWP) separated by dielectric substrate on the basis of circuit theory. Magnetic resonance resulting from antiparallel currents between the CWP is observed at the frequency of minimum reflection loss (corresponding to absorption peak) and effective resonator size can be determined. Having calculated the circuit parameters (inductance L, capacitance C) and resonance frequency from CWP dimension, the frequency dispersion of permeability of Lorentz like magnetic response can be predicted. The simulated resonance frequency and permeability spectra can be explained well on the basis of the circuit theory of an RLC resonator.

• Journal of Magnetics
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• 제14권1호
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• pp.31-35
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• 2009

Herein, the Magneto-Optical Kerr Effect (MOKE) signal enhancement in nanostructures in investigated. It is well known that the MOKE signals of ferromagnetic thin films are enhanced with an additional dielectric layer due to multiple reflections. The MOKE signal is modulated with the additional dielectric layer thickness and is at a maximum when reflectivity is at a minimum. This is not always true in the nanostructures due to the contribution from the non-magnetic substrate portion, especially when substrate reflectivity is minimized and the dependence of the additional dielectric layer thickness for the nanostructure is changed in the case of the continuous thin film. We showed that the MOKE signal for nanostructures could be enhanced with a properly designed, dielectric layer in addition to the anti-reflection coated substrates.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.468-478
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• 2020

The wave interaction problem with a vertical slotted breakwater, consisting of impermeable upper, lower parts and a permeable middle part, has been studied theoretically. An analytical model was presented for the estimation of reflection and transmission of monochromatic waves by a slotted breakwater. The far-field solution of the wave scattering involving nonlinear porous boundary condition was obtained using eigenfunction expansion method. The empirical formula for drag coefficient in the near-field, representing energy dissipation across the slotted barrier, was determined by curve fitting of the numerical solutions of 2-D channel flow using CFD code StarCCM+. The theoretical model was validated with laboratory experiments for various configurations of a slotted barrier. It showed that the developed analytical model can correctly predict the energy dissipation caused by turbulent eddies due to sudden contraction and expansion of a slotted barrier. The present paper provides a synergetic approach of the analytical and numerical modelling with minimum CPU time, for better estimation of the hydrodynamic performance of slotted breakwater.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2006년도 추계학술대회
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• pp.75-79
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• 2006

The United States Food and Drug Administration is responsible for ensuring US residents receive safe and effective medicines. Since blood levels of drugs are correlated with pharmacological effect, FDA closely regulates how those blood levels are measured. The FDA has established requirements for bioanalytical analyses such as minimum method validation, SOP, and reporting criteria. The FDA also has standards for computer validation which must be followed to ensure the data are reliable. Data presented to the Agency are scrutinized to ensure they are accurate and a true reflection of the raw data generated in a study. To verify the quality of data, FDA has developed an inspection program. The specific requirements of the FDA related to bioanalysis will be discussed.

• 지구물리와물리탐사
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• 제13권4호
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• pp.323-329
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• 2010

동해 울릉분지에서 가스하이드레이트 탐사를 목적으로 획득된 탄성파 중합 자료에 다음 세 가지의 디컨볼루션을 적용하여 지층경계면을 분해하는 특성을 분석하였다: (1) 트레이스별 최소위상 스파이킹 디컨볼루션 (2) 트레이스 평균 최소위상 디컨볼루션 (3) 검층자료를 이용한 디컨볼루션. 트레이스별 최소위상 스파이킹 디컨볼루션의 경우 수직 분해능은 증가하지만 수평 연장성이 감소하는 경향을 보였다. 각 트레이스에서 구한 최소위상 파형요소를 평균하여 구한 대표 파형요소를 이용하는 두 번째 방법은 전체적으로 트레이스별 스파이킹 디컨볼루션의 결과와 비슷하지만 해저면 모방 반사면이 보다 연속적이고 일관된 결과를 보이며 하부 반사면들이 더 뚜렷하게 나타난다. 세 번째 방법의 결과는 쇄설류 퇴적체 내부가 좀 더 상세하게 나타나며 해저면과 해저면 모방 반사면의 파형이 이상적 영위상 형태를 보이며 반사면의 연속성이 향상되었음을 보여준다. 이러한 특성은 가스하이드레이트 안정영역의 하부경계를 지시하는 해저면 모방 반사면의 진폭특성분석과 퇴적상 해석을 향상시키므로 탐사 지역의 가스하이드레이트 분포와 자원량을 정확히 추정하는 데에 도움을 준다.

• 한국음향학회지
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• 제16권3호
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• pp.45-50
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• 1997

쐐기각이 다른 4종류의 쐐기형 수중음파 흡수타일을 설계, 제작하고 각각의 흡음타일에 대한 반사음장의 크기를 측정하였다. 흡음타일의 정면에서 측정한 반사음장의 크기는 실험한 4개의 타일중 쐐기의 꼭지각이 30$^{\circ}$일 때 최소값을 갖고 120$^{\circ}$일 때 최대값을 가졌다. 쐐기형 흡음타일의 꼭지각이 클수록 그 반사계수가 증가되는 것을 확인하였다. 또한 본 실험에 사용된 10kHz~30kHz 주파수 범위에서 쐐기각이 같은 흡음판에 의한 반사음장의 크기는 주파수와 무관하였다. 그리고 쐐기형 흡음타일 후면에서 측정한 반사음장의 크기는 흡음판의 형태와 실험에 사용된 주파수들에 무관한 일정한 값을 가졌다. 쐐기형 흡음타일의 반사음장에 대한 측정값과 수치모델에 의한 계산값은 대체로 잘 일치하였다.

• 한국재료학회지
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• 제13권6호
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• pp.389-393
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• 2003

The effect of antireflection layer on the reduction of optical loss has been investigated in Si photodiodes detecting red light with central wavelength of 670 nm. The theoretical analysis showed minimum reflection loss of 6% for the $SiO_2$thickness of about $1100∼1200\AA$ in the $SiO_2$-Si system with the single antireflection layer and no reflection loss for the X$N_3$N$_4$$SiO_2$thickness of $2000\AA$/$1200\AA$ in the $Si_3$$N_4$$SiO_2$-Si system with double antireflection layer. In our experiments, Si photodiodes with the web-patterned $p^{＋}$-shallow diffusion region were fabricated by bipolar IC process technology and the devices were classified into three kinds according to the structure of $Si_3$$N_4$/$SiO_2$antireflection layer. The fabricated devices showed maximum spectral response in the optical spectrum of 650∼700 nm. The average photocurrents of the devices with the $Si_3$$N_4$$SiO_2$thickness of $1000\AA$/X$SiO\AA$, and $2000\AA$$1800\AA$ under the incident power, of -17 dBm were 3.2 uA, 3.5 uA and 3.1 uA, respectively.