• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.22-27
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• 2011

This paper presents an efficient technique to reduce PN code acquisition time considerably by adjusting threshold values in direct sequence spread spectrum (DS-SS) systems. The proposed algorithm employs a pre-dump mode prior to a search mode, and the pre-dump mode determines threshold values of both search and verification modes depending on its correlation energy, which can improve not only the rejection performance of false code phases in the search mode but also that in the verification mode. The proposed method can reduce the mean code acquisition time by about 40% without increase of hardware costs compared with the conventional technique.

• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.453-459
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• 2004

TiNi/ Al6061 shape memory alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which under-went pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic Emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/ Al6061 SMA composite.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.123-124
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• 2006

This paper investigates an efficient pre-equalization technique that can be applied on the up-link of a time division duplex (TDD) orthogonal frequency division multiplexing (OFDM) systems. This technique provides the spectral efficiency by omitting the usage of training sequences on the up-link. In this paper, the performance of a variety of pre-equalization techniques is analyzed and simulations are performed by applying power efficient pre-equalization algorithms with phase and amplitude & phase pre-equalization in the Rayleigh fading channel.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.204-210
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• 2004

Most auto-body members fabricated by the sheet metal forming process. During this process the thickness and material properties of the sheet metal are changed with the residual stress and plastic strain. This paper deals with the material properties of the sheet metal at the high strain rate considering the pre-strain effect. Specimens are selected from sheet metals for outer panels and inner members, such as SPCEN, SPRC45E, SPRC35R and EZNCD. The specimens are prepared with the pre-strain of 2, 5 and 10 % by tensile elongation in Instron 5583, which could be equivalent to the plastic strain in sheet metal forming. High speed tensile tests are then carried out with the pre-stained specimens at the strain rate of 1 to 100/sec. The experimental result informs that the material properties are noticeably influenced by the pre-strain when the yield stress of the specimens is moderate as SPCEN, SPRC35R and EZNCD. The result also demonstrates that the ultimate tensile strength as well as the yield stress is increased as the amount of the pre-strain is increased.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.12
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• pp.1119-1125
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• 2010

Most of the sludge pre-treatment methods to improve the anaerobic digestibility of sludge are not practied in the fields with low economical efficiency. The venturi cavitation system (VCS) adopting hydrodynamic cavitation is simple and requires low energy. This research was conducted to investigate the optimum design and operating conditions of the VCS. The experimental results indicated that the optimum number of venturi in series was three, and the suction mode operation of the pump yielded 1.6 times higher pre-treatment efficiency per unit energy consumption than the discharge mode. The combination of venturies with different throat sizes did not affect the pre-treatment efficiency. Also, the parallel installation of the three in series venture unit yielded 30% higher pre-treatment efficiency per unit energy consumption than the single unit. Under parallel conditions, the solubilization efficiency was 5.6 mg ${\Delta}SCOD/g$ TS/kWh, which is higher than the previously reported value.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.9-13
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• 2001

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.9-15
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• 2003

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.24 no.2 s.201
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• pp.45-50
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• 2006

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.6
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• pp.239-244
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• 2005

Nano-sizedporearrayswerepreparedbytheself-organizationprocessesoftheanodicoxidationusingthealuminumplatewith99.999$\%$purity.Sincethealuminumplatehasaroughsurface,thealuminumplateof1mmthicknesswasanodizedafterthepre-treatmentsofpressing,mechanicalpolishing,thermaloxidation,chemicalpolishing,andelectrochemicalpolishing.Thediameterofthenano-sizedporesandthethicknessofbarrierlayercanbecontrolledbyappliedvoltage.Thethicknessofaluminamembranecanalsobecontrolledbytheanodizingcurrent.Thenano-sizedporeswithdiameterof60$\~$120nm,thedistancebetweenthenearestporesof30$\~$60nm,andthethicknessof6$\~$7Wwereobtainedbytheanodicoxidationprocess.Theporewideningprocesswasemployedforobtainingtheone-channelwithflatsurfacebecausetheporesofthealuminamembranepreparedbythefixedvoltagemethodshowsthestructureoftwo-channelwithroughsurface.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.493-498
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• 1999

To extract hydrologic information more easily , the pre-processor for hydrologic model using Geographic Information System was developed . This model was applied to the Balan-reservoir watershed which is located at the southwest of Suwon. For estimation SCS curve number, landuse map and hydrologic soil group map were collected from digital map and reconnaissance soil map respectively. The estimated curve number from the GIS technique was 73.