• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.24-25
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• 2006

High-Speed Centrifugal Compaction Process is one of slip-using compacting method originally developed for processing of oxide ceramics. In this study, we apply the HCP to ultra-fine (0.1 micron) WC powder. Organic liquid of heptane was chosen as dispersing media to avoid possible oxidation of WC. The mixing apparatus was a key to obtain dense compacts. Only the slips mixed by high energy planetary ball mill were packed up to 55% by the HCP, and sintered to almost full density at 1673 K without any sintering aids. This sintered compact marked Vickers hardness of Hv 2750 at maximum.

• Proceedings of the Korean Magnestics Society Conference
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• 1999.10a
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• pp.28-29
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• 1999

• Journal of Powder Materials
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• v.17 no.6
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• pp.443-448
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• 2010

The $\beta$ phase Ti-Nb-Sn-HA bio materials were successfully fabricated by high energy mechanical milling and pulse current activated sintering (PCAS). Ti-6Al-4V ELI alloy has been widely used as biomaterial. But the Al has been inducing Alzheimer disease and V is classified as toxic element. In this study, ultra fine sized Ti-Nb-Sn-HA powder was produced by high energy mechanical milling machine. The $\beta$ phase Ti-Nb-Sn-HA powders were obtained after 12hr milling from $\alpha$ phase. And ultra fine grain sized Ti-Nb-Sn-HA composites could be fabricated using PCAS without grain growth. After sintering, the microstructures and phase-transformation of Ti-Nb-Sn-HA biomaterials were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The relative density was obtained by Archimedes principle and the hardness was measured by Vickers hardness tester. The $\beta$-Ti phase was obtained after 12h milling. As result of hardness and relative density, 12h milled Ti-Nb-Sn-HA composite has the highest values.

• Proceedings of the Korean Magnestics Society Conference
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• 2010.06a
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• pp.70-71
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• 2010

In this study, We fabricated FePt-based perpendicular patterned media using a selective combination of E-beam lithography and either Ar plasma etching (deposition-first process) or FePt lift-off (deposition-last process). We employed the deposition-last process to avoid chemical and structural disordering by impinging Ar ions (deposition-first process). For a patterned medium with 100 nm patterns made by this process, the out-of-plane coercivity was measured to be 5 fold larger than its in-plane value. The deposition-last process may be a promising way to achieve ultra-high density patterned media.

• Transactions of the Society of Information Storage Systems
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• v.3 no.2
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• pp.94-112
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• 2007

Nano-sized inverted domain dots in ferroelectric materials have potential application in ultrahigh-density rewritable data storage systems. Herein, a data storage system is presented based on scanning non-linear dielectric microscopy and a thin film of ferroelectric single-crystal lithium tantalite. Through domain engineering, we succeeded to form an smallest artificial nano-domain single dot of 5.1 nm in diameter and artificial nano-domain dot-array with a memory density of 10.1 Tbit/$inch^2$ and a bit spacing of 8.0 nm, representing the highest memory density for rewritable data storage reported to date. Sub-nanosecond (500psec) domain switching speed also has been achieved. Next, long term retention characteristic of data with inverted domain dots is investigated by conducting heat treatment test. Obtained life time of inverted dot with the radius of 50nm was 16.9 years at $80^{\circ}C$. Finally, actual information storage with low bit error and high memory density was performed. A bit error ratio of less than $1\times10^{-4}$ was achieved at an areal density of 258 Gbit/inch2. Moreover, actual information storage is demonstrated at a density of 1 Tbit/$inch^2$.

• Journal of Powder Materials
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• v.16 no.6
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• pp.403-409
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• 2009

Plasma spray forming is recently explored as a near-net-shape fabrication route for ultra-high temperature metals and ceramics. In this study, monolithic tungsten has been produced using an atmospheric plasma spray forming and subsequent high temperature sintering. The spray-formed tungsten preform from different processing parameters has been evaluated in terms of metallurgical aspects, such as density, oxygen content and hardness. A well-defined lamellae structure was formed in the as-sprayed deposit by spreading of completely molten droplets, with incorporating small amounts of unmelted/partially-melted particles. Plasma sprayed tungsten deposit had 84-87% theoretical density and 0.2-0.3 wt.% oxygen content. Subsequent sintering at 2500$^{\circ}C$ promoted the formation of equiaxed grain structure and the production of dense preform up to 98% theoretical density.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.16-22
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• 2013

This paper presents the analysis and optimization of air-core permanent magnet linear synchronous motor with overlapping concentrated windings to achieve high thrust density, high thrust per copper losses and low thrust ripple. For the motor design, we adopt equivalent magnetizing current (EMC) method to analyze the magnetic field and give analytical formulae for calculation of motor parameters such as no-load back EMF, dynamic force, thrust density and thrust per copper losses. Further, we proposed a multi-objective optimization by genetic algorithm to search for the optimum parameters. The design optimization is verified by 2-D Finite Element analysis (FEA).

• Journal of Electrochemical Science and Technology
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• v.3 no.1
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• pp.14-23
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• 2012

Increasing demand of energy, the depletion of fossil fuel reserves, energy security and the climate change have forced us to look upon alternate energy resources. For today's electric vehicles that run on lithium-ion batteries, one of the biggest downsides is the limited range between recharging. Over the past several years, researchers have been working on lithium-air battery. These batteries could significantly increase the range of electric vehicles due to their high energy density, which could theoretically be equal to the energy density of gasoline. Li-air batteries are potentially viable ultra-high energy density chemical power sources, which could potentially offer specific energies up to 3000 $Whkg^{-1}$ being rechargeable. This paper provides a review on Lithium air battery as alternate energy resource for the future.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.347-350
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• 2002

Transposed scan is an innovation that paves the road to ultra-slim CRTs with deflection angles up to 135$^{\circ}C$ We discuss the integration of video transposition with the other video processing functions in the television set. An in-place transposition algorithm which minimizes the amount of frame memory is proposed as a low-cost solution for transposed scan conversion. The difference in visual perception of transposed scan and normal scan depends on the frame rate and the line density of the video format. We found that for high frame rates and high line densities, no difference was perceived for both scan modes.

• Journal of Powder Materials
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• v.10 no.3
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• pp.181-185
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• 2003

Resistance sintering under ultra-high pressure if developed to fabricate W-Cu composite containing 5 to 80v/o copper. The consolidation was carried out under pressure of 6 to 8 GPa and input power of 18 to 23 kW for 50 seconds. The densification effect and microstructure of these W-Cu composites are investigated. The effect of W particle size on ,sintering density was also studied. The micro hardness was measured to evaluate the sintering effect.