• Journal of the Korean Society for Railway
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• v.10 no.4
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• pp.444-450
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• 2007

The bi-modal tram guided by the magnetic guidance system has two car-bodies and three axles. Each axle of the vehicle has an independent suspension to lower the floor of the car and improve ride quality. The turning radius of the vehicle may increase as a consequence of the long wheel base. Therefore, the vehicle is equipped with the All-Wheel-Steering(AWS) system for safe driving on a curved road. Front and rear axles should be steered in opposite directions, which means a negative mode, to minimize the turning radius. On the other hand, they also should be steered in the same direction, which means a positive mode, for the stopping mode. Moreover, only the front axle is steered for stability of the vehicle upon high-speed driving. In summary, steering angles and directions of the each axle should be changed according to the driving environment and steering mode. This paper proposes an appropriate AWS control algorithm for stable driving of the bi-modal tram. Furthermore, a multi-body model of the vehicle is simulated to verify the suitability of the algorithm. This model can also analyze the different dynamic characteristics between 2WS and AWS.

• International Journal of Railway
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• v.6 no.4
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• pp.160-168
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• 2013

A spiral lattice girder-reinforced Bi-block sleeper which has enhanced durability against increasingly growing impact force and vibration by wheel load and improved structural performance while train runs at 350km/h high speed is hereby proposed. The section of a spiral lattice girder has stable and superior structural performance thanks to its confinement effect. To compare and analyze the structural performance of spiral lattice girder-reinforced bi-block sleeper, strain and stress distribution were evaluated after applying same load condition as existing triangular lattice girder-reinforced biblock sleeper, and to compare the structural performance of triangular lattice girder and spiral lattice girder, structural analysis of lattice girder was performed separately. As a result, a spiral lattice girder proved to have had superior structural characteristics to bi-block sleeper, and furthermore as a result of evaluating the fastener interface and constructibility with shape-improved lattice girder, no interference with existing railroad structure was found and in terms of cost efficiency, a spiral lattice girder appeared to be superior to existing lattice girder.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.1-5
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• 2019

We investigated the effect of Fe₃O₄ addition on the critical temperature of (Bi, Pb)-2223 polycrystalline samples. Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ + x wt. % Fe₃O₄ (x = 0.0, 0.2, 0.4, 0.6, and 0.8) samples were prepared by using a solid-state reaction method. The analysis of X-ray diffraction data indicates that as Fe₃O₄ is added, dominant phase of the sample changes from Bi-2223 to Bi-2212 with an increasing Bi-2201 phase. The transition temperature of the samples drastically decreased with the Fe₃O₄ addition. The resistance data of samples with x = 0.2 and 0.4 showed a double transition indicating a coexistence of Bi-2223 and Bi-2212 phase while the samples with x = 0.6 and 0.8 showed a single transition with a semiconducting behavior. This phase transition may originate from changes in local structure of the Bi-2223 system by Fe₃O₄ addition. Analysis of the pair distribution function of the Cu-O pair in the CuO₂ plane calculated from extended X-ray absorption fine structure data revealed that the oxygen coordination of copper ion changes from CuO₄ planar type (x = 0.0 - 0.4) to CuO₅ pyramidal type (x = 0.6, 0.8). The correlated Debye-Waller factor, providing information on the atomic disorder within the CuO₂ plane, shows an inverse relation to the coordination number. These results indicate that addition of Fe₃O₄ changes the oxygen distribution around Cu in the CuO₂ plane, causing a phase transition from Bi-2223 to more stable Bi-2212/Bi-2201 phases.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.270-270
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• 2013

We have investigated the self-assembled structures of glutaric acid (HOOC-(CH2)3-COOH) on the Cu(110) surface as a function of coverage using Scanning Tunneling Microscopy (STM). At low coverage, glutaric acid molecules diffuse freely on Cu(110) surface at room temperature, thus they can't form ordered structures at this coverage. However, when we scanned the same area several times, novel structures have been created during scanning due to the field-induced self-assembly. Also, the induced structures are quite stable during continuous scanning process. At 0.25 ML, glutaric acid adsorbs as a bi-glutarate (-OOC(CH2)3-COO-) after annealing to 450 K producing a racemic conglomerate of coexisting mirror domains. Although the molecule is achiral, it forms chiral domains on the surface from adsorption-induced asymmetrization. At 0.5 ML coverage, zigzag structure is observed, and still gltutaric acid adsorbs as a bidentate configuration. This bi-glutarate structure is stable until 650. Finally, at 1ML, glutaric acid adsorbs as a mono-glutarate at room temperature forming close packed structures.

• Applied Microscopy
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• v.47 no.3
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• pp.110-120
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• 2017

Non-isothermal thermogravimetry (TG) measurements on melt-quenched $Bi_xSe_{100-x}$ specimens (x=0, 2.5, 7.5 at%) were made at a heating rate ${\beta}=10^{\circ}C/min$ in the range $T=35^{\circ}C{\sim}950^{\circ}C$. The as-measured TG curves confirm that $Bi_xSe_{100-x}$ samples were thermally stable with minor loss at $T{\leq}400^{\circ}C$ and mass loss starts to decrease up to $600^{\circ}C$, beyond which trivial mass loss was observed. These TG curves were used to estimate molar (Se/Bi)-ratios of $Bi_xSe_{100-x}$ samples, which were not in accordance with initial composition. Shaping features of conversion curves ${\alpha}(T)-T$ of $Bi_xSe_{100-x}$ samples combined with a reliable flow chart were used to reduce kinetic mechanisms that would have caused their thermal mass loss to few nth-order reaction models of the form $f[{\alpha}(T)]{\propto}[1-{\alpha}(T)]^n$ (n=1/2, 2/3, and 1). The constructed ${\alpha}(T)-T$ and $(d{\alpha}(T)/dT)-T$ curves were analyzed using Coats-Redfern (CR) and Achar-Brindley-Sharp (ABS) kinetic formulas on basis of these model functions, but the linearity of attained plots were good in a limited ${\alpha}(T)-region$. The applicability of CR and ABS methods, with model function of kinetic reaction mechanism R0 (n=0), was notable as they gave best linear fits over much broader ${\alpha}(T)-range$.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.144-151
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• 2008

The bi-modal vehicle is composed of two car-bodies and three axles. Each axle of the vehicle has an independent suspension and all wheels are steerable. Since the bi-modal vehicle has longer wheelbase than most urban buses, the All-Wheel-Steering(AWS) system is adapted for to ensure safe driving and proper turning radius on a curved road. This paper proposes an AWS control algorithm for stable driving of bi-modal vehicle. Steering angles and directions of each axle of bi-modal vehicle changed according to the driving environment and steering modes. In the case that front and rear axles should be steered in opposite directions is a negative mode, and the other case that the axles should be steered in the same direction is a positive mode. For example, in the positive mode, front and real axles are steered in the same direction, while in the negative mode, they are steered in the opposite direction. A multibody model of the vehicle is used to verify the performance of the steering algorithm and simulation results of 2WS are compared with those of AWS under the same condition.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.178-183
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• 2016

Ferroelectric relaxor ceramics with $BaTiO_3-NaNbO_3-Bi(Mg_{1/2}Ti_{1/2})O_3$ ternary compositions (BT-NN-BMT) have been prepared by sol-gel powder synthesis and consequent bulk ceramic processing. Through the modified chemical approach, fine and single-phase complex perovskite compositions were successfully obtained. Temperature and frequency dependent dielectric properties indicated typical relaxor characteristics of the BT-NN-BMT compositions. The ferroelectric-paraelectric phase transition became diffusive when NN and BMT were added to form BT based solid solutions. BMT additions to the BT-NN solid solutions affected the high temperature dielectric properties, which might be attributable to the compositional inhomogeneity of the complex perovskite and resulting weak dielectric coupling of the Bi-containing polar nanoregions (PNRs). The temperature stability of the dielectric properties was good enough to satisfy the X9R specification. The quasi-linear P-E response and the temperature- stable dielectric properties imply the high potential of this ceramic compound for use in high temperature capacitors.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.99-108
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• 2007

The bi-modal tram guided by the magnetic guidance system has two car-bodies and three axles. Each axle of the vehicle has an independent suspension to lower the floor of the car and improve ride quality. The turning radius of the vehicle may increase as a consequence of the long wheel base. Therefore, the vehicle is equipped with the All-Wheel-Steering(AWS) system for safe driving on a curved road. Front and rear axles should be steered in opposite directions, which means a negative mode, to minimize the turning radius. On the other hand, they also should be steered in the same direction, which means a positive mode, for the stopping mode. Moreover, only the front axle is steered for stability of the vehicle upon high-speed driving. In summary, steering angles and directions of the each axle should be changed according to the driving environment and steering mode. This paper proposes an appropriate AWS control algorithm for stable driving of the bi-modal tram. Furthermore, a multi-body model of the vehicle is simulated to verify the suitability of the algorithm. This model can also analyze the different dynamic characteristics between 2WS and AWS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.369-372
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• 2004

The characteristics of antimony implants are relatively well-known. Antimony has lower diffusion coefficient, shorter implantation range, and smaller scattering as compared with conventional dopants such as phosphorous and arsenic. It has been commonly used in the doping of buried layer in Bi-CMOS process. In this paper, characteristics and appropriate condition of monitoring in antimony implant beam tuning using $Sb_2O_3$ were investigated to get a reliable process. TW(Thema Wave) and Rs(Sheet Resistance) test were carried out to set up condition of monitoring for stable operation through the periodic inspection of instruction condition. The monitoring was progressed at the point that the slant of Rs varied significantly to investigate the variation of instruction accurately.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.406-411
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• 2002

Ni-Zn ferrite is required to have predominant and stable characteristics in the range of high frequency for the power line communication, so that microstructures and magnetic properties such as power loss and initial permeability in $Ni_{0.8}Zn_{0.2}Fe_2O_4$ were investigated in terms of variable $Bi_2O_3,CaO$ and $V_2O_5$ contents. $Bi_2O_3$ and $V_2O_5$ liquid phase created during sintering process promoted sintering and grain growth but much of the closed pore existed in the grains. The grain size of the specimens with $V_2O_5$ of over 0.5 wt% decreased as the result of "pinning effect"and the resonance frequency increased with CaO of 0.3we%. The high initial permeability of 81.52%, resonance frequency of 17.05 MHz and low power loss of 17,858 kW/$\textrm{m}^3$ were obtained from the samples with $Bi_2O_3$ of 0.5, CaO of 0.3, and $V_2O_5$ of 0.7 wt%.