• Transactions on Electrical and Electronic Materials
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• v.9 no.6
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• pp.265-272
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• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2366-2371
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• 2007

Spray combustion characteristics of a conducting fuel electrospray have been studied for clean combustion technology. The multiplexing system which can retain the characteristics of the cone-jet mode is inevitable for the electrospray application. Charged micro droplets can be obtained in almost uniform size during operating the electrospray in the cone-jet mode. This experiment device set up the multiplexed grooved nozzle system with the extractor. Using the grooved nozzle, the stable cone-jet mode can be achieved at the each groove in the grooved mode. This electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray. In case of the single grooved nozzle electrospray, the diffusion flames are occurred at each jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion.

• Transactions of Materials Processing
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• v.21 no.7
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• pp.447-452
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• 2012

This paper is concerned with forming of Al-Zn-Mg-Sc aluminum alloy bolts, focusing on the effects of heat treatment and age-hardening on the formability and ductile damage evolution. Both experimental and finite element studies were performed. From the experiments, it is observed that the heat treatment or the normalization of Al-Zn-Mg-Sc aluminum alloy increases its formability dramatically resulting in successful bolt forming, while the effects of age-hardening at room temperature on the stress-strain relationship and formability are not very critical. Deformation characteristics such as distribution of effective stress and strain, material flow, and ductile damage evolution during bolt forming are examined using a commercial finite element package, Deform-2D. It should be noted that the extrusion load predicted by the finite element method matches well the experiment results. The finite element predictions on the deformation characteristics support the experimental observations such as fracture of bolt head flange, material flow, and distribution of hardness.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.6
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• pp.345-351
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• 2012

In traditional target-based data deduplication system, all of the files should be chunked and compared for reducing duplicated data blocks. One of the critical problem of this system arises as the number of files are increasing. The system suffers from computational delay for calculating hash value and processing metadata for handling each file. To overcome this problem, in this paper, we propose a novel data deduplication system using logical partition of storage system. The system applies data deduplication scheme to each logical partition not each file. Experiment result shows that the proposed system is more efficient compared with traditional deduplication scheme where the logical partition is full of files by 50% in terms of deduplication capacity and processing time.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.144.1-144.1
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• 2015

The triggered vacuum switch(TVS) is a one of the important component in consisiting high power control systems(HPCS). The operating condition is depended on material, geometry, operating power and so on. Our research is focused on the effects of thses basic properties and ptimized condition, because these are critical conditons in understanding the TVS operation. Our experiment is accomplished with a copper electrode and a tungsten trigger pin after being assembled into a vacuum chamber. The operating voltage in our system is more than dozens of kV at the 5kV trigger pulse. Our goal is up to 300kJ, therefore the currents should be more optimized in additional experiments,

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.21-24
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• 2003

In hot forming process of the backward end-bulkhead of a pressure hull, the blank diameter and the tool clearance are the critical factors which influence wrinkling defect, forming load and shape completeness of the product. Two F.E.A softwares with the elasto-plastic material model and rigid plastic model were utilized to predict the occurrence of wrinkling defect. Tool clearance was determined by considering the increase of blank thickness, die strength and the stretching effect. Heat treatment condition after the hot forming to recover the original properties of the material was estabilished by specimen-based heat treating experiment.

• Environmental Engineering Research
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• v.13 no.2
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• pp.98-104
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• 2008

In this study, chromate and cetylperidinium chloride (CPC) removal from artificial wastewater was monitored by using micellar enhanced ultrafiltration (MEUF) and activated carbon fibre (ACF) adsorption hybrid processes. For the efficient chromate removal, molar concentration of the CPC should be five times that of chromate and it should be at least one critical micelle concentration (CMC). The MEUF was found to be effective in the chromate removal while ACF in the CPC adsorption to produce chromate and CPC free effluents. The chromate and CPC removal was 99.8% from MEUF-ACF process. Effluent chromate concentration was exponentially correlated with molar ratio of CPC to chromate and pH.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
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• 2002.05a
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• pp.37-44
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• 2002

In order to review the failure rate of PC monitor under normal environmental conditions, we experimented for various levels of each factors, e.g Power on/off, DPM mode, using voltage, Incoming Surge, Torque strength etc. According to the results of experiment and SN ratios we investigated that the causes of the failure for the horizontal output TR of monitor are Mode change, dispersion of Torque and $h_{FE}$ and these are critical effect. For the new reliability test we suggested that strengthened part tests In IQC branch, Torque change controls in the TR specification are necessary.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2032-2038
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• 2009

The amount of phenol and NaOH for the colorimetric determination of ammonia in Korean standard methods (KSM) is found to be highly excessive compared to the standard methods of several other countries. The absorbance of indophenol formed by the Berthelot reaction for ammonia analysis was measured under the various reaction conditions classified in experiment groups 1, 2, 3, 4 and KSM and American standards methods (ASM), and the relationships between the absorbance of indophenol and concentration of ammonia were compared. The amount of phenol can be reduced to 10 g (current 25 g in KSM) and NaOH can be reduced to 1.76 g (current 11 g in KSM) for the preparation of 200 mL phenate solution, and the absorbance sensitivity increased. The concentration of the phenol and NaOH correlatively affect the pH of the solution, which is a critical variable in achieving the maximum sensitivity and rapid and stable color development.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.681-683
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• 2004

This paper describes the control of a geared DC motor having a backlash for implementation of a humanoid robot using disturbance observer. Critical problem of the humanoid robot is caused by the nonlinearity such as a backlash. To meet this problem, a control method using disturbance observer has been proposed. The disturbance observer is designed to estimate the effects of nonlinearities in the system, to make the nonlinear system behave linearly. To design the low-pass filter in the disturbance observer, cut-off frequency of the output should be found. The goal of this paper is the implementation of the proposed system, compensating the backlash effect. To accomplish the goat, PD control and disturbance observer are employed to the system with no load and full load. As a result, system stability can be guaranteed by compensating the effect of backlash. In addition, real experiment shows the proposed control methodology will satisfy the stable working of a humanoid type in the future.