• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.4
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• pp.433-440
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• 2016

This paper proposes a method of minimizing total energy consumption of IoT environment when communication devices in the network share the information directly. The proposed method reduces total number of transmission for the information sharing by using an effective network coding-based technique which dynamically selects a node and a data packet for each transmission. Simulation results show that the proposed method has better performance than an existing network coding-based method selecting transmission node in fixed order, a network coding-based method selecting transmission node in random order, and a uncoded method selecting transmission node in random order.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.960-964
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• 2005

In this paper, we dealt with a partial discharge(PD) measurement method that has been accepted as an effective and non-destructive technique to estimate insulation performance of low-voltage electric and electronic devices. The PD measurement system Is composed of a coupling network, a low noise amplifier, and associated electronics. h shielded box Is adopted to make a better measurement environment against around noise. A low cut-off frequency of the coupling network estimated by a sinusoidal wave input was 125 kHz (-3 dB). Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 10 mV/pC. In an application test oil a low-voltage three phase Induction motor (5 HP), we could detect 0.53 pC level of partial discharge at the applied voltage of AC 650 $V_{peak}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.662-665
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• 2002

The microwave dielectric properties and the microstructures of $Tm_2O_3$-modified $BiNbO_4$ ceramics were investigated. $Bi_{(1-x)}Tm_xNbO_4$ ceramics combined with orthorhombic and triclinic phases were identified at sintering temperatures of $920{\sim}960^{\circ}C$. The apparent density decreased slightly with the increasing Tm content. Regardless of the Tm content the dielectric constant $(\varepsilon_r)$ of all compositions except x=0.1 in $Bi_{(1-x)}Tm_xNbO_4$ ceramics saturated at the range of 42~44. The $Q{\times}f_0$ values of 6,000-12,000(GHz) were obtained for all compositions when the sintering temperatures were in the range of $920{\sim}960^{\circ}C$. The temperature coefficient of the resonant frequency$(\tau_f)$ can be also adjusted with increasing the amount of the doped Tm from a positive value of $+15ppm/^{\circ}C$ to a negative value of $-20ppm/^{\circ}C$. The $Bi_{(1-x)}Tm_xNbO_4$ ceramics can be possibly applied to multilayer microwave devices with low processing temperatures.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.53-58
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• 2016

Because a progressive tax of home electricity rates is charged and a continuous rise of industrial electricity rates is expected in order to solve the global warming, the high oil prices and the serious power shortage problem, the efforts to apply the energy storage systems which can significantly improve the energy usage efficiency to the smart grid are trying newly. In this study, characteristics of the secondary battery which can be used as energy storage devices, the structure and operation principle of a lithium-ion battery, and the concept of energy storage systems are research and analyzed. In addition, in this paper, the base technologies which are required to apply to the energy storage system to electric power system are established by studying about installation location and application methodology of energy storage system to electric power system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.906-911
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• 2004

In this paper, we used only PR as etching mask, while it used usually Cr/AU as etching mask, and in order to fabricate a photosensor has the increased sensitivity, we investigated on the sensitivity of general type and p-i-n type diode. we designed microchannel size width max 10um, min 5um depth max 10um, reservoir size max 100um, min 2mm. Fabrication of microfluidic devices in glass substrate by glass wet etching methods and glass to glass fusion bonding. The p-i-n diode has higher sensitivity than photodiode. Considering these results, we fabricated p-i-n diodes on the high resistive($4k{\Omega}{\cdot}cm$) wafer into rectangle and finger pattern and compared internal resistance of each pattern. The internal resistance of p-i-n diode can be decreased by the application of finger pattern has parallel resistance structure from $571\Omega$ to $393\Omega$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.615-624
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• 2017

This study investigated the various physical and electrical effects of silicon direct bonding. Direct bonding means the joining of two wafers together without an intermediate layer. If the surfaces are flat, and made clean and smooth using HF treatment to remove the native oxide layer, they can stick together when brought into contact and form a weak bond depending on the physical forces at room temperature. An IR camera and acoustic systems were used to analyze the voids and bonding conditions in an interface layer during bonding experiments. The I-V and C-V characteristics are also reported herein. The capacitance values for a range of frequencies were measured using a LCR meter. Direct wafer bonding of silicon is a simple method to fuse two wafers together; however, it is difficult to achieve perfect bonding of the two wafers. The direct bonding technology can be used for MEMS and other applications in three-dimensional integrated circuits and special devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.86-90
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• 2017

This work reports the phase-change behavior and thermal stability of doped GeSbTe/GeSbTe bilayers. We prepared the bilayers using RF sputtering, and annealed them at annealing temperature ranging from $100^{\circ}C$ to $400^{\circ}C$. The sheet resistance of the bilayer decreased and saturated with increasing annealing temperature, and the saturated value was close to that of pure GeSbTe film. The surface of the bilayer roughened at $400^{\circ}C$, which corresponds to the surface roughening of doped GeSbTe film. Mixed phases of face-centered cubic and hexagonal close-packed crystalline structures were identified in the bilayers annealed at elevated temperature. These results indicate that the phase-change behavior of the bilayer depends on the concurrent phase-transitions of the two GeSbTe-based films. The dopants in the doped GeSbTe film were diffused out at annealing temperatures of $300^{\circ}C$ or higher, which implies that the thermal stability of the bilayer should be considered for its application in phase-change electronic devices.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.1-10
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• 2018

In cognitive radio (CR), secondary users (SUs) are able to sense the absence of primary users (PUs) in the spectrum. Then, SUs use this information to opportunistically access the licensed spectrum in the PUs' absence. In this paper, we present an implementation of real-time video transmission with spectrum-sensing between two points using GNU Radio and a National Instruments 2900 Universal Software Radio Peripheral (USRP). In our project, spectrum-sensing is implemented at both transmitter and receiver. The transmitter senses the channel, and if the channel is free, a video signal (which could be a real-time signal from a video file) will be modulated and processed by GNU Radio and transmitted using a USRP. A USRP receiver also senses the channel, but in contrast, if the channel is busy, the signal is demodulated to reproduce the transmitted video signal. This project brings in several challenges, like spectrum-sensing in the devices' environment, and packets getting lost or corrupted over the air.

• Transactions on Electrical and Electronic Materials
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• v.16 no.1
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• pp.37-41
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• 2015

The most common structure of the current transformer (CT) consists of a length of wire wrapped many times around a silicon steel ring passed over the circuit being measured. Therefore, the primary circuit of CT consists of a single turn of the conductor, with a secondary circuit of many tens or hundreds of turns. The primary winding may be a permanent part of the current transformer, with a heavy copper bar to carry the current through the magnetic core. However, when the large current flows into a wire, it is difficult to measure its magnitude of current because the core is saturated and the core shows magnetic nonlinear characteristics. Therefore, we proposed a newly designed CT which has an air gap in the core to decrease the generated magnetic flux. Adding the air gap in the magnetic path increases the total magnetic reluctance against the same magnetic motive force (MMF). Using a ferrite core instead of steel also causes the generation of low magnetic flux. These features can protect the magnetic saturation of the CT core compared with the steel core. This technique can help the design of the CT to obtain a special shape and size.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.3-6
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• 2009

Aluminum nitride (AIN) thin films were deposited on a polycrystalline 3C-SiC intermediate layer by a pulsed reactive magnetron sputtering system. Characteristics of the AIN/SiC heterostructures were investigated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The columnar structure of AIN thin films was observed by FE-SEM. The surface roughness of AlN films on the 3C-SiC buffer layer was measured using AFM. The XRD pattern of AlN films on SiC buffer layers was highly oriented at (002). Full width at half maximum (FWHM) of the rocking curve near (002) reflections was $1.3^{\circ}$. The infrared absorbance spectrum indicated that the residual stress of AIN thin films grown on SiC buffer layers was nearly negligible. The 3C-SiC intermediate layers are promising for the realization of nitride based electronic and mechanical devices.