• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.3
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• pp.259-269
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• 1991

In this paper, power line harmonic noise which is the most serious problem in the secondary power distribution line is eliminated and analyzed using adaptive noise cancellers with two adaptive algorithms, LMS and individual tap LMS(ITLMS) algorithm. To testify the improvement of data transmission characteristics made by the adaptive filter with two adaptive algorithms, BER was measured in DS spread spectrum communication system including the noise canceller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.347-354
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• 2009

In this paper, we propose a new transmit diversity technique for multiple-input multiple-output (MIMO) systems to improve the link level performance of open-loop systems. By cyclically applying a predetermined set of preceding weight vectors, artificially induced fluctuation is created to achieve additional diversity gain in flat fading channels. To design the set of the precoding vectors, we exploit the knowledge on the distribution of near optimum Preceding vectors observed in a beamforming scheme based on the rotation transformations. Simulation results demonstrate that the proposed open-loop diversity scheme with an arbitrary number of transmit antennas achieves a full diversity gain with computational complexity comparable to a single-input single-output (SISO) system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.1
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• pp.12-18
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• 2014

In this paper, a new peak-to-average power ratio (PAPR) reduction method for spatial modulation(SM) is presented. By using the matrix with all non-zero elements to precode the signals before transmitting, the transmit power is scattered over all transmit antennas for achieving the goal of PAPR reduction. If this matrix is also an unitary matrix, the distribution of transmit power over transmit antennas will be uniform and it also could retain the characteristic of avoiding inter channel interference (ICI) due to the orthogonality of unitary matrix. In case of a non-ideal amplifier, the proposed method can produce a considerable improvement that increases with a number of transmit antennas in performance. Furthermore, the new scheme achieves an identical performance with conventional one in the case of ideal amplifier.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.161-162
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• 2008

In this paper we design an irregular low-density parity-check (LDPC) code for a multi-input multi-output (MIMO) system. The considered MIMO system is minimum mean square error soft-interference cancellation (MMSE-SIC) detector. The MMSE-SIC detector and the LDPC decoder exchange soft information and consist a turbo iterative detection and decoding receiver. Extrinsic information transfer (EXIT) charts are used to obtain the edge degree distribution of the irregular LDPC code which is optimized for the input-output transfer chart of the MMSE-SIC detector. It is shown that the performance of the designed LDPC code is much better than that of conventional LDPC code optimized for the AWGN channel.

• International Journal of Human Ecology
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• v.4 no.1
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• pp.1-14
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• 2003

This study examines apparel brand extensions in terms of types and leverage effects. The researchers identified types of apparel brand extensions based on recent data gathered from the Korean apparel market. Three hundred forty eight Korean female subjects in their 20's evaluated three hypothetically extended brands from a major casual brand which actually exists in the Korean market. Major findings of the study follow. First, apparel brands are extended to different product categories by adjusting mostly target profiles as well as product usage, product class, and distribution channel. Secondly, leverage effects, the extent of image transfer from the parent brand to extended brands, are different according to the extension types.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1308-1318
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• 1995

The influence of varying rotation speed of both crystal and crucible was numerically investigated for the Czochralski silicon-crystal growth. Based on a simplified model assuming flatness of free surfrae, the Navier-Stokes Boussinesq equations were employed to identify the flow pattern, temperature distribution as well as the shape of the melt/crystal interface. The present results showed that the interface shape was relatively convex with respect to the melt at lower pulling rate and tended to be concave as the pulling rate increased. In particular, the experimentally observed gull-winged shape of the interface was qualitatively in agreement with the predicted shape. The rotation of crystal alone little affected the growth system. When the rotation speed of the crucible was increased, there occurred inversion of the interface shape from convex to concave pattern. At rapid rotation of the crucible, an interesting channel formation was predictied primarily due to the assumption of laminar flow.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.169-174
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• 2014

This paper proposes a novel beehive-shaped reflector for application to light-emitting diode (LED) transceivers for illumination and bi-directional visible light communication (VLC). By using a diffuse propagation model extended to line-of-sight and direct signals, the distribution of illuminance and the path loss of the transceiver are investigated to evaluate the performance of the beehive-shaped reflector. To verify bi-directional communication, a VLC-based image capture system, comprising a complementary metal-oxide semiconductor (CMOS) image sensor and video processor unit, is demonstrated. Real-time images captured by the CMOS camera are successfully transmitted to the monitoring system via a free-space channel at a rate of 115.2 kbps.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.3
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• pp.164-169
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• 2009

The slip velocity and the temperature jumps for low-speed flow in microchannels are investigated using Langmuir slip boundary condition. This slip boundary condition is suggested to simulate micro flow. The current study analyzes Langmuir slip boundary condition theoretically and it analyzed numerically micro-Couette flow, micro-Poiseuille flow and grooved microchannel flow. First, to prove validity for Langmuir slip condition, an analytical solution for micro-Couette flow is derived from Navier-Stokes equations with Langmuir slip conditions and is compared with DSMC and an analytical solution with Maxwell slip boundary condition. Second, the numerical analysis is performed for micro-Poiseuille flow and grooved microchannel flow. The slip velocity and temperature distribution are compared with results of DSMC or Maxwell slip condition and those are shown in good agreement.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.84-85
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• 2004

Experimental study was conducted to characterize shear-induced lateral migration of $1.0-{\mu}m-diameter$ Brownian particles flowing through a rectangular microchannel which can be used to deliver small amount of liquids, drugs, biological agents and particles in microfluidic devices. Measurements were obtained by using a mercury lamp with a light of 532-nm wavelength, an inverted epi-fluorescence microscope, and a cooled CCD camera to record particle images. Peclet number was used as a parameter to assess the lateral distribution of the particles at a fixed volume fraction of $0.1\%$. It was shown that as Pe increased, particles were moved toward the centerline of the channel, which is in good agreement with previous studies.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.87-90
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• 2003

In this paper, flow characteristics of plasma flow in a micro-tube were investigated experimentally using Micro-PIV. For comparision, the experiments were repeated for DI-water instead of plasma. Both velocity profiles of Plasma and DI-water are well agreed with the theoretical velocity distribution of newtonian fluid. We also carried out generating plasma-in-oil droplet formation at a Y-junction microchannel. In order to clarify the hydrodynamic aspects involved in plasma droplet formation. Rhodamin B were mixed with plasma only for visualization of plasma droplet.