• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.54.1-54.1
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• 2017

Intrinsic alignments (IA), the coherent alignment of intrinsic galaxy orientations, can be a source of a systematic error of weak lensing surveys. The redshift evolution of IA also contains information about the physics of galaxy formation and evolution. We present the first measurement of IA at high redshift, z~1.4, using the spectroscopic catalog of blue star-forming galaxies of the FastSound redshift survey, with the galaxy shape information from the Canada-Hawaii-France telescope lensing survey. The IA signal is consistent with zero with power-law amplitudes fitted to the projected correlation functions for density-shape and shape-shape correlation components, $A_{\delta+}=-0.0040\pm 0.0754$ and $A_{++}=-0.0159\pm 0.0271$, respectively. These results are consistent with those obtained from blue galaxies at lower redshifts (e.g., $A_{\delta+}=0.0035_{-0.0389}^{+0.0387}$ and $A_{++}=0.0045_{-0.0168}^{+0.0166}$ at z=0.51 from the WiggleZ survey), suggesting no strong redshift evolution of IA. The upper limit of the constrained IA amplitude corresponds to a few percent contamination to the weak-lensing shear power spectrum, resulting in systematic uncertainties on the cosmological parameter estimations by $-0.035<\Delta \sigma_8<0.026$ and $-0.025<\Delta \Omega_{\mathrm m}<0.019$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.501-506
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• 2006

Carbon nanotubes (CNTs) were grown with a microwave plasma enhanced chemical vapor deposition (MPECVD) method, which has been regarded as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the low temperature and the large area growth. MPECVD used methane ($CH_4$) and hydrogen ($H_2$) gas for the growth of CNTs. 10 nm thick Ni catalytic layer were deposited on the Ti coated Si substrate by RF magnetron sputtering method. In this work, the pretreatment was that the Ni catalytic layer in different microwave power (600, 700, and 800 W). After that, CNTs deposited on different pressures (8, 12, 16, and 24 Torr) and grown same microwave power (800 W). SEM (Scanning electron microscopy) images showed Ni catalytic layer diameter and density variations were dependent with their pretreatment conditions. Raman spectroscopy of CNTs shows that $I_D/I_G$ ratios and G-peak positions vary with pretreatment conditions.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.459-465
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• 2017

The goal of this study is to evaluate the effective thermal conductivity and diffusivity of containment walls as heat sinks or passive cooling systems during nuclear power plant (NPP) accidents. Containment walls consist of steel reinforced concrete, steel liners, and tendons, and provide the main thermal resistance of the heat sinks, which varies with the volume fraction and geometric alignment of the rebar and tendons, as well as the temperature and chemical composition. The target geometry for the containment walls of this work is the standard Korean NPP OPR1000. Sample tests and numerical simulations are conducted to verify the correlations for models with different densities of concrete, volume fractions, and alignments of steel. Estimation of the effective thermal conductivity and diffusivity of the containment wall models is proposed. The Maxwell model and modified Rayleigh volume fraction model employed in the present work predict the experiment and finite volume method (FVM) results well. The effective thermal conductivity and diffusivity of the containment walls are summarized as functions of density, temperature, and the volume fraction of steel for the analysis of the NPP accidents.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.481-488
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• 2022

This study proposes compensation methods for the initial position error and torque ripple in vector control of two-phase hybrid stepping motors. Stepping motors have an asymmetrical structure due to misalignment, such as the eccentricity generated by the manufacturing and assembly process. When vector control is applied using the position information measured by an incremental encoder attached to the rotor shaft of such stepping motors, the following problems occur. First, an initial position error occurs during the forced excitation process for the initial rotor position alignment. Second, torque ripple corresponding to the mechanical rotation frequency is generated. In this study, these non-ideal phenomena that occur in vector control of the stepping motor are analyzed, and compensation methods are proposed to eliminate them. The validity of the proposed initial position error and torque ripple compensation methods is verified through experiments on a two-phase hybrid stepping motor drive system.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.6
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• pp.758-765
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• 1986

The design, fabrication and performance of vertical double diffused power MOSFET (VDMOS) were described. On the antimony (Sb) doped (~7x10**17 cm**-3) silicon substrate (N+), epitaxial layer(N-) was grown. The thickness and the resistivity of this layer were 32\ulcorner and about 12\ulcorner-cm, respectively. The P- channel length which was controlled by sequential P-/N+ double diffuison method was about 1~2 \ulcorner, and was processed with the self alignment of 21 \ulcorner width poly silicon. To improve the breakdown voltage with constant on-resistance (Ron) about 1\ulcorner, three P+ guard rings were laid out around main pattern. With chip size of 4800\ulcorner x4840 \ulcorner, the VDMOS has shown breakdown voltage of 410~440V, on-resistance within 1.0~1.2\ulcornerand the current capablity of more than 5A.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.35-40
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• 2024

In this paper, the design, implementation, and analysis of a device capable of transmitting and receiving millimeter-wave signals and performing channel sounding measurements in atmospheric conditions at distances of up to approximately 10km outdoors are presented. The device is expected to be instrumental in studying the propagation characteristics of millimeter-wave frequencies. Utilizing data such as received power levels and power delay profiles (PDPs), comparisons with predicted values using path loss, K-factor, and other propagation models are facilitated. The mobile transceiver unit, integrated onto a vehicle platform, allows for flexible adjustment of transmitter and receiver positions, while synchronization issues with distance are mitigated using a rubidium atomic clock. Furthermore, automatic boresight alignment using scanning techniques is employed to locate the main sector of the antenna.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.186-186
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• 2009

Most liquid crystal display modes, including the twisted nematic (TN) $mode^1$, the in-plane switching (IPS) $mode^2$, the fringe field switching (FFS) $mode^3$, and the vertically aligned (VA) $mode^4$ are based on either a horizontal or a vertical alignment. However, for some applications, such as no-bias-bend (NBB) pi cell or bistable bend-splay display, an intermediate pretilt angle is essential$^5$. NBB pi cells have been a focus of interest because of their fast response time; however, the reliable control of the intermediate pretilt angle of liquid crystals that is required for the fabrication of NBB pi cells is challenging. The controllable pre-tilt angle of liquid crystals was investigated using a blend of horizontal and vertical polyimide prepared by a rubbing method. Various pretilt angles in the range from 0^{\circ}$ to 90^{\circ}$ were achieved as a function of the vertical polyimide content. We observed uniform liquid crystal alignment on the rubbing-treated blended polyimide layer. A NBB pi cell with an intermediate pretilt angle of 47.8^{\circ}$ was manufactured. This cell had no initial bias voltage and a low threshold voltage, which indicates that it has low power consumption. In addition, the response time of the NBB pi cell was rapid.

• The Korean Journal of Applied Statistics
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• v.31 no.5
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• pp.599-610
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• 2018

The method of Mack and Skillings (Technometrics, 23, 171-177, 1981) is a nonparametric multiple comparison method in a randomized block design with replications. This method is likely to result in loss of information because each block is ranked using the average of observations instead of repeated observations. In this paper, we proposed a new nonparametric multiple comparison method in the randomized block model with replications using an alignment method proposed by Hodges and Lehmann (The Annals of Mathematical Statistics, 33, 482-497, 1962) that extend the joint placement method proposed by Chung and Kim (Communications for Statistical Applications and Methods, 14, 551-560, 2007). In addition, Monte Carlo simulation compared the family wise error rate and power with the parametric method and the nonparametric method.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.1
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• pp.51-56
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• 1981

A new I2L process for a high performance I2L structure is proposed. The modifiedstructure consists of a heavily doped extrinsic base and lowly doped intrinsic base where the collector regions are self-alignment with the intrinsic base regions. The proposed process untilizes spin-on sources as the diffusion sources and the self-alignment of collectors is achieved by using the hardened spin-on source as a diffusion mask. Test devices including a 13-stage ring oscillator have been fabricated by the proposed process on n/n+ silicon wafers with 6.5$\mu$m epitaxial layer. The maximum upward current gain of npn transistors is 8 for a three collector I2L cell. The speed-power product and minimum propagation delay for a one collector structure are 3.5 pJ and 50 ns, respectively.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.111-120
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• 2000

Recently, metal oxide films such as MgO or ZrO$_2$ have been studied as buffer layers to fabricate the superconductor with preferred orientation and as diffusion barriers to prevent the reaction between superconductor and metal substrate. In this research, we focused fabrication and characterization of MgO and ZrO$_2$ films on textured metal substrates. We fabricated MgO and ZrO$_2$ films on the Ni metal sheets by sol-gel dipping method. The microstrcures of the films were investigated by SEM and AES analyses. The films were coated with different cycles and dryed at 400$^{\circ}$C and 500$^{\circ}$C . The final films were heat-treated at 700$^{\circ}$C, 800$^{\circ}$C, and 1000$^{\circ}$C, in air atmosphere. We investigated the alignment of MgO and ZrO$_2$ films on Ni metal sheets by XRD and pole figure. The grain growth of metal oxide films was improved by the increase of the drying temperature and annealing temperature. The grain growth was increased with the annealing temperature. The alignment of metal oxide films depended on the thickness.