• 한국통신학회논문지
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• 제39A권2호
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• pp.86-91
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• 2014

Holographic data storage (HDS) has a number of advantages, including a high transmission rate through the use of a charge coupled device array for reading two-dimensional (2D) pixel image data, and a high density capacity. HDS also has disadvantages, including 2d intersymbol interference by neighboring pixels and interpage interference by multiple pages stored in the same holographic volume. These problems can be eliminated by modulation codes. We propose a 7/9 error-correcting modulation code that exploits a Viterbi-trellis algorithm and has a code rate larger (about 0.778) than that of the conventional 6/8 balanced modulation code. We show improved performance of the bit error rate with the proposed scheme compared to that of the simple 7/9 code without the trellis scheme and the 6/8 balanced modulation code.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 자성 및 자성재료 국제학술대회
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• pp.14-14
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• 2011

Limited understanding of the surface properties of $Pt_3Ni$ for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) has motivated the study of magnetic properties and electronic structures of Pt segregated $Pt_3Ni$ (111) surface during adsorption of oxygen molecule on it. The first principle method based on density functional theory (DFT) is carried out. Nonmagnetic Pt has induced magnetic moment due to strong hybridization between Ni 3d and Pt 5d. It is found that an oxygen molecule prefers bridge site with Pt rich subsurface environment for adsorption on the surface of Pt segregated $Pt_3Ni$ (111). It is seen that there is very small charge transfer from $O_2$ to Pt. The curve of energy versus magnetic moment of the oxygen explains the magnetic moments in transition states. We found the dissociation barrier of 1.07eV significantly higher than dissociation barrier 0.77eV on Pt (111) suggesting that the dissociation is more difficult on Pt segregated $Pt_3Ni$ (111) surface. The spin polarized densities of states are presented in order to understand electronic structures of Pt and $O_2$ during the adsorption in detail.

• Journal of Advanced Marine Engineering and Technology
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• 제30권8호
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• pp.927-933
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• 2006

The structural and electrical characteristics of PLZT thin films fabricated onto $Pt/IrO_2/Ir/Ti/SiO_2/Si$ substrates by a pulsed laser deposition were investigated to develop the high dielectric thin films for capacitor layer of semiconductor memory devices The slim region 14/50/50 PLZT thin films were fabricated by PLD and estimated the characteristics for memory application 14/50/50 PLZT thin films have crystallize into perovskite structure at the $600^{\circ}C$ deposition temperature, 200 mTorr of oxygen pressure, and 2 $J/cm^2$ of laser energy density. In this condition PLZT thin films had the dielectric constant as high as 985, storage charge density 8.17 ${\mu}C/cm^2$ and charging time 0.20 ns. Leakage current density was less than $10^{-10}A/cm^2$ up to 5 V bias voltage.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권3호
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• pp.114-119
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• 2005

We investigated compatibilizing effects of electrical properties such as charge distributions and electrical breakdown in blends of low density polyethylene (LDPE) / polystyrene (PS) with poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), the triblock copolymer. The blends with $70\;wt\%$ of LDPE and $30\;wt\%$ of PS were prepared through a melt blending in a batch type kneader at a temperature of $220^{\circ}C$ when the SEBS content increased up to $10\;wt\%$. Scanning electron microscopy (SEM) was investigated for observation of morphology of LDPE / PS blends increasing SEBS contents. The morphological observation showed that addition of SEBS results in the domain size reduction of the dispersed PS phase and a better interfacial adhesion between LDPE and PS phases. Measurements of space charge distributions for blends was carried out with pulsed electroacoustic (PEA) method. It was possible to observe that the amount of charge storage in the LDPE / PS blends decreased wiか increasing of SEBS content. The location of SEBS at a domain interface enables charges to move from one phase to the other via domain interface and results in a indicative decrease in the amount of space charge for the LDPE / PS blends with SEBS. Electrical breakdown strength of these blends was observed. It was found that the maximum breakdown strength of the blend was 51.55 kV/mm. These results were better than 38.38 kV/mm of LDPE used electrical insulator for cables and were caused by crystalinity of blends. Because the crystalinity of blends were lower than LDPE, electrical breakdown strength of LDPE / PS blends is higher than that of LDPE. We evaluated the possibility of these blends for insulating material substituted LDPE.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.285-295
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• 2021

The inverse spinel Cobalt ferrite (CoFe₂O₄, CFO) is considered to be a promising alternative to commercial graphite anodes for lithium ion batteries (LIBs). However, the further development of CFO is limited by its unstable structure during battery cycling and low electrical conductivity. In an effort to address the challenge, we construct three-dimensional hierarchical flower-like CFO nanoclusters (CFO NCs)-decorated carbonized cotton carbon fiber (CFO NCs/CCF) composite. This structure is consisted of microfibers and nanoflower cluster composited of CFO nanoparticle, in which CCF can be used as a long-range conductive matrix, while flower-like CFO NCs can provide abundant active sites, large electrode/electrolyte interface, short lithium ion diffusion path, and alleviated structural stress. As anode materials in LIBs, the flower-like CFO NCs/CCF exhibits excellent electrochemical performance. After 100 cycles at a current density of 0.3 A g^-1, the CFO NCs/CCF delivers a discharge/charge capacity of 1008/990 mAh g^-1. Even at a high current density of 15 A g^-1, it still maintains a charge/discharge capacity of 362/361 mAh g^-1.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.181.1-181.1
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• 2014

Supercapacitor is attracting growing attention for a promising energy conversion and storage device because of its desirable electrochemical properties such as rapid charge-discharge rate, high power density and long cycle life. Three-dimensional (3D) metal nanostructure has been widely studied since it can provide efficient charge transport along the 3D network in many device applications. In this work, we fabricated well-ordered 3D nickel (Ni) nanostructures using 3D-arrayed polystyrene nano-opal substrates. We also fabricated half-cell supercapacitors by electrodepositing $RuO_2$ onto these nanostructured Ni current collectors and investigated their morphological and electrochemical properties.

• 한국재료학회지
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• 제27권5호
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• pp.248-254
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• 2017

In the present work, graphene powder was synthesized by laser scribing method. The resultant flexible light-scribed graphene is very appropriate for use in micro-supercapacitors. The effect of the laser scribing process in reducing graphene oxide (GO) was investigated. GO was synthesized using a chemical mixture of GO solution; then, it was coated onto a LightScribe DVD disk and laser scribed to reduce GO and create laser-scribed graphene (LSG). The CV curves of pristine rGO at various scan rates showed that the ultimate product possesses the ability to store energy at the supercapacitor level. Charge-discharge curves of pristine rGO at two different current densities indicated that the specific capacitance ($C_m$) increases due to the reduction of the discharge current density. Finally, the long-term charge-discharge stability of the LSG was plotted and indicates that the specific capacitance decreases very slightly from its primary capacitance of ${\sim}10F\;cm^{-3}$ and that the cyclic stability is favorable over 1000 cycles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.335-338
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• 2000

Carbon is an attractive candidate for use in eletrochemical supercapacitors that depend on charge storage in the electrode/electrolyte international double layer. Property of an electrical double layer capacitor depend both on the technique used to prepare the electrode and on the current collector structure. The study is to research that V$_2$O$_{5}$-flyash-AC composite electrode for supercapacitor. The discharge capacitance of V$_2$O$_{5}$-flyash-AC(70wt%) in 1st and 50th cycle was 18.6F/g and 15.13F/g at current density of 0.5mA/cm$^2$. The discharge process of V$_2$O$_{5}$-flyash (3 : 97)-AC composite electrode is larger than that others.thers.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.32-53
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• 2022

Although lithium-ion batteries are currently the most reliable power supply system for various mobile applications, further improvement in energy density is still required as the need for batteries in large energy-consuming devices is rapidly growing. However, in the anode, the most widely commercialized graphite-based anode materials almost face theoretical limitations. In addition, sodium-ion batteries have been actively studied to replace expensive charge carriers with cheaper ones. Accordingly, conversion-based materials have been extensively studied as high-capacity anode materials in both lithiumion batteries and sodium-ion batteries because their theoretical capacity is twice or thrice higher than that of insertion-based materials. This review will provide a comprehensive understanding of conversion-based materials, including basic charge storage behaviors, critical drawbacks that should be overcome, and practical material design for high-performance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.241-241
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• 2010

New non-volatile memory with high density and high work-function metal nano-dots, MND (Metal Nano-Dot) memory, was proposed and fundamental characteristics of MND capacitor were evaluated. In this work, nano-dot layer of FePt with high density and high work-function (~5.2eV) was fabricated as a charge storage site in non-volatile memory, and its electrical characteristics were evaluated for the possibility of non-volatile memory in view of cell operation by Fowler-Nordheim (FN)-tunneling. Here, nano-dot FePt layer was controlled as a uniform single layer with dot size of under ~ 2nm and dot density of ${\sim}\;1.2{\times}10^{13}/cm^2$. Electrical measurements of MOS structure with FePt nano-dot layer shows threshold voltage window of ~ 6V using FN programming and erasing, which is satisfied with operation of the non-volatile memory. Furthermore, this structure provides better data retention characteristics compared to other metal dot materials with the similar dot density in our experiments. From these results, it is expected that this non-volatile memory using FePt nano-dot layer with high dot density and high work-function can be one of candidate structures for the future non-volatile memory.