• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.138-145
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• 1999

Surface hardening of AC4C aluminium alloy with TiC powders was obtained by plasma transferred are (PTA) method, Bead appearance, microstrucutre and wear behavior were characterized in relation to the torch current, powder feed rate and wear condition. The width and the depth of bead were mainly increased with increasing torch current. The comparison of wear behavior between AC4C alloy and PTA treated AC4C alloy showed the remarkable enhancement of wear resistance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.11
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• pp.541-545
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• 2002

This paper proposes the new narrow erase method to erase wall charges formed in an AC plasma display panel (PDP) cell. In the proposed method, pulse timing of switch at the sustain period is adjusted for inducing, a weak discharge. Then, after the narrow erase, the voltage of the X electrode is set to differ from that of the Y electrode. For the proposed method, the measured maximum address voltage margin was 38.3V at Y_Rest voltage of 100V and sustain voltage of 180${\sim}$185V. However, for the conventional method, in which the X and Y electrodes are set to be of equal voltage after the narrow erase, the measured maximum address voltage margin was 31.3V at Y_Rest voltage of 150V and sustain voltage of 180V. This result shows that the measured maximum voltage margin for the proposed method is about 7V(22%) higher than that for the conventional method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.119-123
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• 2011

We have investigated the luminous efficiency of various cell resolution and structure from 50" FHD to 50" QFHD Plasma Display. The suggested test panels have two different cell array types which are the delta and matrix cell array type. The results showed that, in the case of the suggested QFHDs, the firing and sustain voltage were increased and voltage margin was decreased. These results are caused by the reduced wall voltage and increased charged particle loss, at the side wall. The luminance of the suggested QFHDs was lower from 20% to 40% than that of the suggested FHDs and the power consumption was higher from 42% to 83% than that of the suggested FHDs. In conclusion, the maximum luminous efficiency of the suggested QFHD(D110) has reached about 38%, compared with suggested FHDs($\fallingdotseq$ 2.7 lm/W).

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1093-1102
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• 1994

PWM converters employing GTO's are proposed to be used for the currently planned Korean High-Speed Train system. In this paper, operating methods and harmonic spectrums are investigated for the PWM modulated voltage controlled GTO AC/DC converter used in the High-Speed Train System. It is shown that harmonic components can be controlled by varying carrier frequency in PWM modulation schemes. Then the input power-factor control scheme is suggested and analyzed. It is found that the power-factor can be varied by controlling the converter input voltage and phase angles between the input supply voltage and the converter input voltage. Finally, simulation programs are developed and converter systems are implemented.

• Clean Technology
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• v.26 no.2
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• pp.137-144
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• 2020

Metal-impregnated activated carbons were prepared via ultrasonic-assisted impregnation method for regeneration and low ammonia concentration. Magnesium and copper were selected as metals, while chloride (Cl^-) and nitrate (NO₃^-) precursors were used to impregnate the surface of activated carbon. The physical and chemical properties of the prepared adsorbents were characterized by TGA, BET, and NH₃-TPD. The ammonia breakthrough test was carried out using a fixed bed and flowing ammonia gas (1000 mg L^-1 NH₃, balanced N₂) at 100 mL min^-1, under conditions of temperature swing adsorption (TSA) and pressure swing adsorption (PSA, 0.3, 0.5, 0.7, 0.9 Mpa). The adsorption and desorption performance of ammonia were in the order of AC-Mg(Cl) > AC-Cu(Cl) > AC-Mg(N) > AC-Cu(N) > AC through NH₃-TPD and TSA and PSA processes. AC-Mg(Cl) using MgCl₂ showed the average adsorption amount of 2.138 mmol/g at TSA process. Also, AC-Mg(Cl) showed the highest initial adsorption amount of 3.848 mmol/g at PSA 0.9 Mpa. When metal impregnated the surface of the activated carbon, it was confirmed that not only physical adsorption, but also chemical adsorption increased, making enhancement in adsorption and desorption performances possible. Also, the prepared adsorbents showed stable adsorption and desorption performances despite repeated processes, confirming their applicability in the TSA and PSA processes.

• Smart Structures and Systems
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• v.7 no.1
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• pp.27-40
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• 2011

Geopolymer concrete is finding a growing number of niche applications in the field of civil engineering due to its high compressive strength and strength gain rate, retainage of structural properties in elevated temperature environments, chemical stability in highly acidic conditions and environmental benefits. Combining the above mentioned characteristics with induced electrical conductivity, could enable geopolymer cement to serve as a smart and sustainable cementitious material suitable for health monitoring of civil structures. Carbon fibers were added to fresh geopolymer and OPC (ordinary Portland cement) mixes to enhance their electrical conductivities. AC-impedance spectroscopy analysis was performed on the specimens with fiber fraction ranging from 0.008 to 0.8 with respect to the weight of cementitious binder, to measure their electrical resistivity values and to determine the maximum beneficial fiber content required to attain electrical percolation. Experimental observations suggest that CFR-geopolymer cement exhibits superior performance to CFR-OPC in terms of conducting electrical current.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1081-1083
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• 1993

A superconducting multistranded cable is used to realize high current capacity for AC use. The critical current value of the cable to be less than the simple summation of individual critical current value of each strand. The causes for such a degradation of the critical current value have not been revealed. This paper investigates the current distribution in multistrands before and after their quenching by using $7{\times}7$-strand superconducting cable.

• Clinics in Shoulder and Elbow
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• v.22 no.2
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• pp.93-99
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• 2019

Background: Modified Phemister operation has been widely used for the treatment of acute acromioclavicular (AC) joint dislocation. Additionally, the use of suture anchor for coracoclavicular (CC) fixation has been reported to provide CC stability. This study was conducted to evaluate the clinical and radiological results of a modified Phemister operation with CC ligament augmentation using suture anchor for acute AC joint dislocation. Methods: Seventy-four patients underwent the modified Phemister operation with CC ligament augmentation using suture anchor for acute AC joint dislocation and were followed-up for an average of 12.3 months. The visual analogue scale (VAS), range of motion, Constant score, and Korean shoulder scoring system (KSS) were used for clinical assessment. Acromioclavicular interval (ACI), coracoclavicular distance (CCD), and acromioclavicular distance (ACD) were obtained to evaluate the radiological assessments. Results: At the last follow-up, the mean VAS Score was 1.7 points, the mean joint range of the forward flexion was $164.6^{\circ}$, external rotation at the side was $61.2^{\circ}$ and internal rotation to the posterior was a level of T12. The mean Constant score and the mean KSS was 82.7 points and 84.2 points, respectively. At the mean ACI, CCD, and ACD, significant differences were found preoperatively and at the last follow-up. When the ACI, CCD, and ACD were compared with the contralateral unaffected shoulder at the last follow-up, the affected shoulders had significantly higher values. Conclusions: The modified Phemister operation with CC ligament augmentation using suture anchor is clinically and radiologically effective at acute AC joint dislocation.

• Korean Journal of Veterinary Research
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• v.24 no.1
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• pp.91-98
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• 1984

A total of 466 foremilk from dairy farms in Chonnam district was examined for the subclinical mastitis over a period of one year, using a method of the electrical conductivities(EC); absolute conductivity(AC) and differential conductivity(DC) and quarter difference value(QD), in relation to the California mastitis test(CMT) and the direct somatic cell count(DSCC). The compatibility and efficiency rating between the EC values and the other screening tests was conducted. Obtained results are summarized as follows. 1. A linear relationship was found between the EC values and the CMT scores and direct somatic cell counts and it was found that electrical conductivity measurements were comparable with other screening tests for diagnosing animals with mastitis. 2. Compatibilities between the EC and CMT were 70.4% in AC, 74.6% in DC and 70.7% in QD, and that of the EC and DSCC were 53.0% in AC, 63.1% in DC and 53.2% in QD. On the other hand, relative efficiency ratings of Postle's equation between EC and CMT were 37.3% in AC, 26.5% in DC and 13.6% in QD, and that of the EC and DSCC were 33.1% in AC, 20.2% in DC and 11.9% in QD. 3. In the foremilk samples collected from damaged quarters determined by EC, the false positive rate wart higher than the false negative rate, and consequently tests of EC produced lower compatibility or efficiency rating scores. These tendencies suggested that any factors other than the mastitic condition influencing the EC values might be existed.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.4
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• pp.438-443
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• 2007

This study was done to investigate perchlorate contamination in Nakdong river. The perchlorate was detected in Nakdong river and ranged from ND to $82.1{\mu}g/L$. The highest concentration was observed in Wheguan. The perchlorate concentration was decreased with the down stream of Nakdong river. Three different virgin activated carbons made of each coal(Calgon), coconut(Samchully) and wood(Picabiol) based activated carbon(AC) were tested for an adsorption performance of perchlorate in a continuous adsorption column. Breakthrough behavior was investigated that the breakthrough points of coal, coconut and wood based AC as 2,300 bed volumn(BV), 719 BV and 288 BV respectively. Adsorption capacity(X/M) of real, coconut and wood based AC was observed. The experimental results of adsorption capacity showed that coal based AC was highest$(768.2{\mu}g/g)$, coconut based AC was intermediate$(299{\mu}g/g)$ and wood based AC was lowest$(99.2{\mu}g/g)$. Moreover, carbon usage rates(CURs) for coal, coconut and wood based AC had been shown as 0.71 g/day, 2.16 g/day and 3.45 g/day respectively. The constant characteristic of the system, k of coal, coconut and wood based ACs were found to be 307.2, 102.5 and 94.2, respectively.