• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.225-226
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• 2004

• Proceedings of the Korean Magnestics Society Conference
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• 2015.05a
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• pp.144-144
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• 2015

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.270-271
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• 2000

Among many optical modulators, we are interested in traveling-wave(TW) multiple quantum well(MQW) electro-absorption modulator which can be used for wide-band applications, covering DC to 30GHz or higher frequencies. In this study, we simulate a 1.3mm InGaAs/lnGaAsP TW MQW EAM using the 3D Finite Difference-Time Domain (FDTD) method. We identify that several geometric factors affect Microwave charateristics. Our calculated data provide useful information to optimize and fabricate ridge-type TW CPW EAM.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.3
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• pp.3-10
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• 1993

As a method to measure the absorbing characteristics of microwave absorber, various microwave measuring method can be used fundamentally. There is, however, a big problem in measuring errors, since the wavelength of microwave such as used for radar is very short. Therefor, this research aimed to design and fabricate a converting adaptor of 20mm .PHI. coaxial tube from a type-N connector to coaxial tube and to use it for evaluating absorption characteristics of microwave absorbor. Furthemore, the measurements of absorbing characteristics and material constants have been perfomed and reviewed, which were carried out by using the coaxial and by using rectangular waveguide, respectively. As a result, the validity of the proposed measuring method has been conformed. In this paper, a preliminary evalua- tion on the characteristics of the electromagnetic wave absorbor for X-band radar designed and fabricated for a laboratory use is performed by reflected power method near to a pratical use. Then for field test by using X-band radar is carried out with real target of $1.2m\times1.2m$ in size. As the result of the above, the usefullness of the designed and fabricated electromagnetic wave absorber in paint type for X-band radar has been confirmed.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.183-196
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• 2020

This study aimed to recover native gold from the concentrate using microwave-nitric acid leaching and magnetic/hydro separation experiments. The insoluble-residue was filtered from leaching solution through microwave-nitric acid leaching experiment. As a result of the atomic absorption spectrometer(AAS) analysis of the filtered leaching solution, it was discovered that Au content was not eluted at all and it was observed from the back scattered electron(BSE) image that native gold was liberated in the insoluble-residue. When magnetic/hydro separation experiments were applied for the insoluble-residue, magnetic and non magnetic minerals were separtated from insoluble-residue. Magnetite was recovered from the magnetic minerals and as a result of applying the hydro separation experiment again for the non-magnetic mineral, native gold was recovered. The native gold was identified through the X-ray diffraction(XRD) analysis and BSE image.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.62-66
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• 2009

The soft magnetic FeSiCr were processed the ball-mill for 30 hours and the shape of FeSiCr particles was changed from sphere to flake type, which was observed using scanning electron microscope. The complex permittivity and permeability spectra and reflection loss of FeSiCr-rubber composite was measured using Network Analyzer in order to investigate the relationship between the microwave absorption and the material constants. The matching frequency shifted toward lower frequency range with microwave absorber thickness, and microwave absorber with FeSiCr-rubber composite showed a maxium reflection loss of -8.3 dB at 1.86 GHz for a 1.3 mm thickness.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.45-54
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• 2004

Microwave characteristics of ridge type CPW traveling-wave(TW) electroabsorption modulator and photodetector are affected by the thickness of intrinsic layer, width of guiding layer, and the separation of signal and ground electrodes. These factors are determined effective index of microwave and characteristic impedance due to changing of capacitance(C) and inductance(L) of device. However, conventional equivalent circuit of TW-structure is approximated to microstrip and CPW transmission line by distribution of electric and magnetic fields, respectively. In this paper, we analyzed microwave characteristics of TW-structure and found more accurate value of C and L by using finite difference time domain (FDTD) method. These values are adopted circuit element of equivalent circuit. Microwave characteristics obtained by the FDTD and equivalent circuit model show good agreement.

• Journal of Magnetics
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• v.14 no.4
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• pp.155-160
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• 2009

This study examined the effects of a decrease in thickness of magnetic alloy flakes on the electromagnetic wave absorption characteristics of nanocrystalline $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ (at.%) alloy flakes/polymer composite sheets available for a quasi-microwave band. The thickness of FeCuNbSiB alloy flakes decreased to 1-2 $\mu$m with increasing milling time up to 24 h, and the composite sheet including alloy flakes milled for 24 h exhibited considerably enhanced power loss properties in the GHz range compared to the sheets having non-milled alloy powders. Although a considerable increase in loss factor upon milling was observed in the narrow frequency range of 4-6 GHz, there was no correlation between the complex permeability and flake thickness. However, the complex permittivity increased with increasing milling time, and there was good agreement between the milling time and the frequency dependences of the complex permittivity and power loss.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.8
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• pp.1968-1973
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• 2013

We present the enhancement of narrowband modulation response of an optical source by integrating a dual-electrode distributed feedback (DFB) laser with an electro-absorption modulator (EAM). The dual-electrode DFB laser exhibits a multiple optical modes owing to a self-pulsation in GHz range. By modulating the laser and modulator sections of the integrated device simultaneously, 20-dB of narrowband modulation response enhancement at 6 GHz with 7-GHz tuning range has been observed.

• Korean Journal of Metals and Materials
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• v.46 no.1
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• pp.44-51
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• 2008

The effects of magnetic powder size 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 composite sheet including small magnetic flakes with the size less than $26{\mu}m$ exhibited high power loss in the GHz frequency range as compared with the sheets having large alloy flakes of $45{\sim}75{\mu}m$. Moreover, both the complex permeability and the loss factor increased with the decrease in size of the alloy flakes. The large power loss of the sheets containing small magnetic flakes was attributed to the high complex permeability, especially their imaginary part. The high complex permeability of the sheets composed of small flakes was considered to be due to the highly thin shape of the flakes inducing low eddy-current loss.