• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.50-55
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• 2009

In this paper, a distributed amplifier is designed using distributed network synthesis that provides the optimum absorption capability of a capacitance. Transfer functions of filters, which consist of the amplifier, are synthesized by a low-pass Chebyshev approximation. Capacitances that a filter network can absorb are calculated as a function of its minimum insertion loss(MIL) and ripple. Active devices in a distributed amplifier are modeled as equivalent circuits by using their S-parameters, and their equivalent capacitances are absorbed into filter structures by properly adjusting the MIL and ripple of a transfer function. As an application example, a distributed amplifier with the gain of about 12.5dB is designed that operates over the frequency range between 0.1 and 7.5GHz. Experimental results prove that distributed network synthesis, which considers capacitance absorption capability, is useful to the design of distributed amplifiers.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.866-872
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• 2009

The effects of magnetic powder thickness on electromagnetic wave absorption characteristics in Fe-6.5Si-0.9Cr (wt%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The atomized FeSiCr powders were milled by using attritor for 12, 24, and 36 h, powder thickness changed from $40{\mu}m$ to $3{\mu}m$ upon 36 h milling. The composite sheet, including thinned magnetic flakes, exhibited higher power loss in the GHz frequency range as compared with the sheets having thick flakes. Moreover, both the complex permeability and the loss factor increased with the decrease in thickness of the alloy flakes. Therefore, the enhanced power loss property of the sheets containing thin alloy flakes was attributed to the flakes of high complex permeability, especially their imaginary part. Additionally, the complex permittivity was also increased with the reduction of flake thickness, and this behavior was considered to be helpful for improvement of the electromagnetic wave absorption characteristics in the composite sheets, including thin alloy flakes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.132-136
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• 2004

열 증착 방법을 이용하여 copper(II)-phthalocyanine(CuPc) 박막을 glass 기판 위에 제작하였다. 열처리 조건은 $150^{\circ}C$에서 후열(annealing) 처리 하는 방식과 예열하는 두 가지 방식으로 달리하였다. 제작된 박막의 전기전도도를 평가하기 위해 마이크로웨이브 근접장 효과를 이용한 근접장 현미경(near-field scanning microwave microscope)을 이용하여 비파괴적인 방식으로 CuPc 박막의 반사계수(reflection coefficient)를 측정하였다. CuPc 박막의 전기전도도 특성을 UV 흡수도를 통한 에너지 밴드갭의 shift 현상과 관련지어 설명하고 또한 x-ray diffraction(XRD) data를 통해 박막의 결정 특성과 비교하였다. 박막 표면 특성은 SEM(scanning microscope microscopy)을 통해 관측하였다. 열처리 조건에 따른 CuPc 박막의 전기전도도 특성은 후열 처리한 박막의 경우 예열 처리한 박막보다 전기 전도 특성이 향상되었음을 관측할 수 있었다.

• Journal of the East Asian Society of Dietary Life
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• v.11 no.2
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• pp.131-139
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• 2001

The physicochemical and sensory characteristics of brown rice flakes by different processing conditions such as flaking Process and their heat treatments were investigated to establish the brown rice flake processing procedure. To successfully make the compressed rice grain type flakes, the most appropriate water steeping conditions were 5 hours at 60'C. The brown rice flakes by compressed flaking procedure and heat treatment with microwave toasting showed the best crispiness-texture that tested from textrometer or sensory evaluation, and there was no significant difference between the source of rice varieties. The water absorption index(WAI) of tested flakes were negatively correlated with the water soluble index( WSI) and positively correlated with bowl life. The flakes made by compressed flaking procedure and heat treatment with microwave toasting showed longer bowl life, which is the length of the time that the cereal can retain its crispness after being soaked in milk.

• Korean Journal of Optics and Photonics
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• v.6 no.2
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• pp.165-171
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• 1995

Infrared-Radio frequency double resonance (IRRFDR) and Infrared-Microwave double resonance (IRMWDR) spectroscopy have been used to probe a level of A symmetry for $CD_{3}$OH. Double resonance spectra of $CD_{3}$OH have been investigated over the range of 940 to 1020 $cm ^{-1}$ . Twenty K-type doublet transitions have been observed in both the radio frequency region, which covers 50 MHz to 1 GHz, and the microwave region, which covers 8 GHz to 12 GHz. The results propose new assignments of infrared (IR) absorption transitions and far-infrared (FIR) laser emission lines. These involve torsional excited levels and CO stretch states. Measurements of the A state splitting have permitted the determination of the asymmetry splitting parameters $S^{o}$(n, K) and $^{co}$ (n, K) for (n, K)=(0.3) and (1.3)

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.261-266
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• 1997

Nonevasive multifrequency microwave radiometry using coaxial waveguide antenna has been investigated for a homogeneous and four layer human body model. The coupling between coaxial waveguide antenna and a biological object was analyzed by use of the finite-difference time-domain(FDTD) method to obtain the absorbed power patterns in the media. The object studied in this paper was a homogeneous and four-layered lossy medium. The specific absorption rates(SAR) distribution which was corresponding to the temperature distribution was calculated in each region by use of the steady-state response in FDTD method. The SAR pattern of 1.2GHz was compared with that of 1.8GHz.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.3 no.2
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• pp.40-45
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• 1992

A simple emission model applicable for low scattering (scattering << absorption) anisotropic layer is developed and applied to the interpretation of measurements of microwave emission from row crops. The vegetation layer of row crops is modeled as a random slab embedded with small spheroid with major axis aligend paralel to the crop-row direction. The total emission is given in a simple algebraic form based on the zero-order radiative transfer theory. The single scattering albedo for spheroid and its polarimetric phase function are presented. The effects of layer azimuthal dependence on emission are accounted for by using an anisotropic albedo in the zero-order transfer theory. The developed emission theory favorably compares with the brightness temperature measured over soybeans canopy.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.39-46
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• 2004

Removal efficiencies for diesel fuel and diesel hydrocarbons ($C_10$∼$C_22$) using microwave-enhanced SVE process were evaluated with dry and moist soil, respectively. Diesel removal rates of microwave-enhanced SVE process were 7 times for dry soil and 1580 times for moist soil as great as those of the SVE process without microwave heating. High dielectric property of water contents may accelerate the absorption of microwave energy into soil and thus vaporized the diesel fuel components drastically. The diesel removals were 67.7∼78.4% for $C_10$ and $C_12$, and 0∼18.5% for $C_14$∼$C_22$ for dry and moist soil with SVE process only. On the other hand, dry soil with microwave-enhanced SVE process showed 89.3∼99.4% removal for $C_10$ to and $C_12$ and 35.6∼67.0% for hydrocarbons over $C_14$. All hydrocarbons ($C_10$∼$C_22$) studied were significantly removed (93.6∼99.8%) for moist soil with microwave-enhanced SVE process.

• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.843-850
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• 1991

There is a growing demend for absorptive electromagentic shielding materials for wide band frequency application. In this study, the absorber which consists of a rubber plus Ni-Zn ferrite which have been prepared by direct-wet method. A rubber ferrite composite for electromagnetic shielding, it is most importan facter the homogeneous ultra fine size and high dispersitive ferrite powder. Direct-wet method and solid-solid reaction method for preparing of ultra fine ferrite powder was used. It has been experimentally verified that the powder which prepared by direct-wet method was very fine and almost same size spherical powder, the composite ferrite have excellent electromagnetic wave absorption in X-band.

• CELLMED
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• v.6 no.1
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• pp.3.1-3.4
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• 2016

Consumption of herbal products from the medicinal plants contaminated with heavy metals can cause serious consequences on human health. This is a major concern for traditional and herbal medicine. The present study was carried out to analyze and quantify the levels of six potentially toxic heavy metals namely arsenic, lead, cadmium, mercury, chromium and nickel in ten important Indian medicinal herbs. The air dried raw herbs were processed by microwave assisted wet digestion and analyzed by using atomic absorption spectrophotometer equipped with graphite tube atomizer. Except the chromium content in three plants, all the levels of six heavy metals analyzed were found to be quite below the permissible limits in all the ten raw medicinal herbs analyzed. The present work implies that, regular and systematic screening of raw medicinal herbs is necessary to check the levels of the heavy metal contaminants before using them for consumption or preparation of herbal formulations so that the possible contamination cannot cumulate up to the finished products.