• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.172-176
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• 2000

Solid solutions of Ti$_{0.5}$Zr$_{0.5}$B$_2$were successfully synthesized and densified simultaneously from elemental reactants by the use of a field-activated, pressure-assisted synthesis method. The method involves the application of an electric current and mechanical pressure across reactant compacts to achieve combustion synthesis. Dense solid solutions with relative densities of up to 99% were produced and characterized by XRD, SEM, and EPMA methods. With a maximum measured temperature of 145$0^{\circ}C$ under a load of 86 MPa for 30 min, the desired dense solid solution wad synthesized.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.7
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• pp.720-725
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• 2010

In AGPS method, user position can be obtained even in the shadow region by improving signal sensitivity. A hybrid long integration scheme employing both coherent and non-coherent integration method is commonly used in AGPS receivers. Because coherent loss increases as residual frequency become large, residual frequency should be minimized to maximize coherent integration gain. This paper presents performance analysis of residual frequency estimator using FFT in fine-time assistance AGPS method. Considering the hardware complexity and the estimation accuracy, optimal length of FFT is proposed for GPS L1 C/A signal. Signal sensitivity for estimating the residual frequency is also analysed. By field experimental results, it is found that the residual frequency can be successfully estimated using 1 second snap-shot data when GPS signal strength is larger than -150 dBm and its RMS error is 3Hz.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.37-44
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• 2000

High velocity, gas-assisted liquid drop trajectories were investigated under well-controlled experimental conditions at elevated gas densities and room temperature. A monodisperse stream of drops which are generated by a vibrating-orifice drop generator were injected into a transverse high velocity gas stream. The gas density and air jet velocity were adjusted independently to keep the Weber numbers constant. The Weber numbers studied were 72, 148, 270, 532. The range of experimental conditions included studied the three drop breakup regimes previously referred as bag, stretching/thinning and catastrophic breakup regimes. High-magnification photography and conventional spray field photographs were taken to study the microscopic breakup mechanisms and the drop trajectories in high velocity gas flow fields, respectively. The parent drop trajectories were affected by the gas density and the gas jet velocities and do not show similarity with respect to the either Weber or the Reynolds number, as expected.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.564-564
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• 2012

Graphene has been emerged as a fascinating material for future nanoelectronic applications due to its extraordinally electronic properties. However, their zero-bandgap semimetallic nature is a major problem for applications in high performance field-effect transistors (FETs). Graphene nanoribbons (GNRs) with narrow widths (${\geq}10nm$) exhibit semiconducting behavior, which can be used to overcome this problem. In previous reports, GNRs were produced by several approaches, such as electron beam lithography patterning, chemically derived GNRs, longitudinal unzipping of carbon nanotubes, and inorganic nanowire template. Using these methods, however, the width distribution of GNRs was a quiet broad and substantial defects were inevitably occurred. Here, we report a novel approach for fabricating width-tailored GNRs by focused ion beam-assisted chemical vapor deposition (FIB-CVD). Width-tailored phenanthrene ($C_{14}H_{10}$) templates for direct growth of GNRs were prepared on $SiO_2$/Si substrate by FIB-CVD. The GNRs on the templates were synthesized at $900-1,050^{\circ}C$ with introducing $CH_4$ $(20sccm)/H_2$ (10 sccm) mixture gas for 10-300 min. Structural characterizations of the GNRs were carried out using Raman spectroscopy, scanning electron microscopy, and atomic force microscopy.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.90-95
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• 2008

We studied the effect of thermal annealing and hydrofluoric (HF) acid treatment on the field emission properties of carbon nanotube field emitter arrays (CNT-FEAs) grown with the resist-assisted patterning (RAP) process. After thermal and HF treatment, it was observed that the electron emission properties were remarkably improved. The enhanced electron emission was also found to depend strongly on the sequence of the treatments; the electronemission current density is 656 $mA/cm^2$ with the process of thermal treatment prior to HF treatment while the current density is reduced by 426 $mA/cm^2$ with the reversal processes. This is due to the increased crystalline structure by thermal annealing and then strong fluorine bond was formed by HF treatment.

• Korean Journal of Breeding Science
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• v.41 no.4
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• pp.456-462
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• 2009

Bacterial pustule (BP), caused by Xanthomonas axonopodis pv. glycines, is prevalent disease in major soybean production areas. BP can reduce seed yield as well as seed quality. To identify the genomic region associated with the resistance to BP, QTL analysis was conducted using $F_{10}$ RIL (recombinant inbred lines) population, Keunolkong${\times}$Shinpaldalkong. Four QTLs for BP disease were identified on the linkage group B2, D2, I and K in field accounts for 36.4% of the phenotypic variation. Especially, QTL at near of Satt135 on LG D2 was identified in green house experiment explaining 20.9% of the phenotypic variation was found to be a major QTL conferring BP. One of these QTLs, Satt135 on the LG D2, was also identified in green house experiment. In both field and green house condition, the position of major QTL for BP was detected between Satt135 and Satt397 on the LG D2. The major QTL for BP may be used for minimizing soybean BP through effective marker-assisted selection (MAS).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.211-211
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• 2012

The electrical loss of the photo-generated carriers is dominated by the recombination at the metal- semiconductor interface. In order to enhance the performance of the solar cells, many studies have been performed on the surface treatment with passivation layer like SiN, SiO2, Al2O3, and a-Si:H. In this work, Al2O3 thin films were investigated to reduce recombination at surface. The Al2O3 thin films have two advantages, such as good passivation properties and back surface field (BSF) effect at rear surface. It is usually deposited by atomic layer deposition (ALD) technique. However, ALD process is a very expensive process and it has rather low deposition rate. In this study, the ICP-assisted reactive magnetron sputtering method was used to deposit Al2O3 thin films. For optimization of the properties of the Al2O3 thin film, various fabrication conditions were controlled, such as ICP RF power, substrate bias voltage and deposition temperature, and argon to oxygen ratio. Chemical states and atomic concentration ratio were analyzed by x-ray photoelectron spectroscopy (XPS). In order to investigate the electrical properties, Al/(Al2O3 or SiO2,/Al2O3)/Si (MIS) devices were fabricated and characterized using the C-V measurement technique (HP 4284A). The detailed characteristics of the Al2O3 passivation thin films manufactured by ICP-assisted reactive magnetron sputtering technique will be shown and discussed.

• Journal of Magnetics
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• v.20 no.4
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• pp.336-341
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• 2015

MnBi alloys were fabricated by arc melting and annealing at 573 K. The heat treatment enhanced the content of the low-temperature phase (LTP) of MnBi up to 83 wt%. The Bi-excess assisted LTP MnBi alloys were used in the hybridization with the Nd-Fe-B commercial Magnequench ribbons to form the hybrid magnets (100-x)NdFeB/xMnBi, x = 20, 30, 40, 50, and 80 wt%. The as-milled powder mixtures of Nd-Fe-B and MnBi were aligned in a magnetic field of 18 kOe and warm-compacted to anisotropic and dense bulk magnets at 573 K by 2,000 psi for 10 min. The magnetic ordering of two hard phase components strengthened by the exchange coupling enhanced the Curie temperature ($T_c$) of the magnet in comparison to that of the powder mixture sample. The prepared hybrid magnets were highly anisotropic with the ratio $M_r/M_s$ > 0.8. The exchange coupling was high, and the coercivity $_iH_c$ of the magnets was ~11-13 kOe. The maximum value of the energy product $(BH)_{max}$ was 8.4 MGOe for the magnet with x = 30%. The preparation of MnBi alloys and hybrid magnets are discussed in details.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.430-430
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• 2012

The surface recombination velocity of the silicon solar cell could be reduced by passivation with insulating layers such as $SiO_2$, SiNx, $Al_2O_3$, a-Si. Especially, the aluminium oxide has advantages over other materials at rear surface, because negative fixed charge via Al vacancy has an additional back surface field effect (BSF). It can increase the lifetime of the hole carrier in p-type silicon. The aluminium oxide thin film layer is usually deposited by atomic layer deposition (ALD) technique, which is expensive and has low deposition rate. In this study, ICP-assisted reactive magnetron sputtering technique was adopted to overcome drawbacks of ALD technique. In addition, it has been known that by annealing aluminium oxide layer in nitrogen atmosphere, the negative fixed charge effect could be further improved. By using ICP-assisted reactive magnetron sputtering technique, oxygen to nitrogen ratio could be precisely controlled. Fabricated aluminium oxy-nitride (AlON) layer on silicon wafers were analyzed by x-ray photoelectron spectroscopy (XPS) to investigate the atomic concentration ratio and chemical states. The electrical properties of Al/($Al_2O_3$ or $SiO_2/Al_2O_3$)/Si (MIS) devices were characterized by the C-V measurement technique using HP 4284A. The detailed characteristics of the AlON passivation layer will be shown and discussed.

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.593-600
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• 2021

Herein, a series of g-C₃N₄ modified Bi₂MoO₆ nanocomposites using Bi₂MoO₆ and melamine as original materials are fabricated via sintering process. For presynthesis of Bi₂MoO₆ an ultrasonic-assisted hydrothermal technique is researched. The structure and composition of the nanocomposites are characterized by Raman spectroscopy, X-ray diffraction (XRD), and high-resolution field emission scanning electron microscopy (SEM). The improved photoelectrochemical properties are studied by photocurrent density, EIS, and amperometric i-t curve analysis. It is found that the structure of Bi₂MoO₆ nanoparticles remains intact, with good dispersion status. The as-prepared g-C₃N₄/Bi₂MoO₆ nanocomposites (BMC 5-9) are selected and investigated by SEM analysis, which inhibits special morphology consisting of Bi₂MoO₆ nanoparticles and some g-C₃N₄ nanosheets. The introduction of small sized g-C₃N₄ nanosheets in sample BMC 9 is effective to improve the charge separation and transfer efficiency, resulting in enhancing of the photoelectric behavior of Bi₂MoO₆. The improved photoelectronic behavior of g-C₃N₄/Bi₂MoO₆ may be attributed to enhanced charge separation efficiency, photocurrent stability, and fast electron transport pathways for some energy applications.