• Advances in materials Research
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• v.4 no.4
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• pp.215-226
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• 2015

Experiment on roughness and micro pit defects of SUS 430 ferrite stainless steel was investigated in laboratory. The relation between roughness and glossiness with reduction in height, roll surface roughness, emulsion parameters was analyzed. The surface morphology of micro pit defects was observed by SEM, and the effects of micro pit defects on rolling reduction, roll surface roughness, emulsion parameters, lubrication oil in deformation zone and work roll diameter were discussed. With the increasing of reduction ratio strip surface roughness Ra(s), Rp(s) and Rv(s) were decreasing along rolling and width direction, the drop value in rolling direction was faster than that in width direction. The roughness and glossiness were obtained under emulsion concentration 3% and 6%, temperature $55^{\circ}C$ and $63^{\circ}C$, roll surface roughness $Ra(r)=0.5{\mu}m$, $Ra(r)=0.7{\mu}m$ and $Ra(r)=1.0{\mu}m$. The glossiness was declined rapidly when the micro defects ratio was above 23%. With the pass number increasing, the micro pit defects were reduced, uneven peak was decreased and gently along rolling direction. The micro pit defects were increased with the roll surface roughness increase. The defects ratio was declined with larger gradient at pass number 1 to 3, but gentle slope at pass number 4 to 5. When work roll diameter was small, bite angle was increasing, lubrication oil in micro pit of deformation zone was decreased, micro defects were decreased, and glossiness value on the surface of strip was increased.

• Journal of Environmental Policy
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• v.14 no.3
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• pp.3-19
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• 2015

In this paper, we reviewed the method of replacing the number of registered vehicles with the number of trips to more realistically calculate vehicle emissions. Using the Korea Transport Data Base (KTDB) in replacing the number of registered vehicles with adjusted number of registered vehicle by specific vehicle type in the metropolitan area, the results by region showed that Seoul had the widest rate of error and that, among vehicles, trucks had the widest rate of error. Also, the absolute value of deviation of registered vehicles and adjusted number of registered vehicle influenced by the calculation of the quantity of vehicle emissions showed that out of the metropolitan regional government all trucks showed the widest deviation. The results of calculating the quantity of vehicle emissions showed an average of 9% difference between the emissions based on the number of registered vehicles and the emissions based on adjusted number of registered vehicle.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.835-842
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• 2014

Cutback control in a grid code is one of the functions of a wind power plant (WPP) that is required to support the system protection and frequency stability. When a cutback control command signal is delivered to the WPP from the system operator, the output of a WPP should be decreased to 20% of the rated power within 5 s. In this paper, we propose a dedicated cutback control algorithm of a WPP based on the ratio of the command power to the available power. If a cutback control signal is delivered, the algorithm determines the pitch angle for the cutback control and starts the pitch angle control. The proposed algorithm keeps the rotor speed at the speed before the start of the cutback control to quickly recover the previous output prior to the cutback control. The performance of the algorithm was validated for a 100 MW aggregated WPP based on a permanent magnet synchronous generator under various wind conditions using an EMTP-RV simulator. The results clearly shows that the proposed algorithm not only successfully reduces the output to the command power within 5 s by minimizing the fluctuation of the pitch angle, but also rapidly recovers to the output level before the cutback control.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.827-834
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• 2014

In order to meet the low voltage ride-through requirement in a grid code, a wind power plant (WPP) has to stay connected to a grid, supporting the voltage recovery for a grid fault. To do this, a plant-level controller as well as a wind generator (WG) controller is essential. The dynamic response of a WPP should be analyzed in order to design a plant-level controller. The dynamic response of a WPP for a grid fault is the collective response of all WGs, which depends on the wind speed approaching the WG. Thus, the dynamic response of a WPP should be analyzed by taking the wake effect into consideration, because different wind speeds at WGs will result in different responses of the WPP. This paper analyzes the response of a doubly fed induction generator (DFIG)-based offshore WPP with a grid fault taking into account the wake effect. To obtain the approaching wind speed of a WG in a WPP, we considered the cumulative impact of multiple shadowing and the effect of the wind direction. The voltage, reactive power, and active power at the point of common coupling of a 100 MW DFIG-based offshore WPP were analyzed during and after a grid fault under various wind and fault conditions using an EMTP-RV simulator. The results clearly demonstrate that not considering the wake effect leads to significantly different results, particularly for the reactive power and active power, which could potentially lead to incorrect conclusions and / or control schemes for a WPP.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.49-54
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• 2015

Molded Circucit Breaker(MCCB) is a most widely used device to protect loads from the over-current in low power level distribution system. When the MCCB interrupts the over-current, the arc discharge occurred between fixed contact and moving contact to create hot gas. By the Lorentz force due to arc current, the occurred arc is bent to the grids. The grids extend and cool and divide it for arc extinguish. In the majority cases, the MCCB protects loads by interrupting the over-current successfully but in some cases the re-ignition is occurred by hot-gas created during process of interruption. The re-ignition arises when the recovery voltage(RV) is more higher than the recovery strength between contacts and it leads to interruption fault. Therefore to find out the dielectric recovery characteristics of protecting device has a great importance for preventing interruption fault. In this paper, we studies measurement method of the dielectric recovery characteristics considering inherent attribute of the MCCB. To measure the dielectric recovery characteristic of MCCB, we makes an experiment circuit for applying the over-current and the randomly recovery voltage. The measurement methode to find out the dielectric recovery voltage of the MCCB was established and the result was based on experiment results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1334-1339
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• 2016

In a power grid that has a high wind power penetration, the fast voltage support of a wind power plant (WPP) during the grid fault is required to stabilize the grid voltage. This paper proposes a voltage control scheme of a doubly-fed induction generator (DFIG)-based WPP that can promptly support the voltage of the point of common coupling (PCC) of a WPP during the grid fault. In the proposed scheme, the WPP and DFIG controllers operate in a voltage control mode. The DFIG controller employs two control loops: a maximum voltage dip-dependent reactive current injection loop and a reactive power to voltage loop. The former injects the reactive power in proportion to the maximum voltage dip; the latter injects the reactive power in proportion to the available reactive power capability of a DFIG. The former improves the performance of the conventional voltage control scheme, which uses the latter only, by increasing the reactive power as a function of the maximum voltage dip. The performance of the proposed scheme was investigated for a 100-MW WPP consisting of 20 units of a 5-MW DFIG under various grid fault scenarios using an EMTP-RV simulator. The simulation results indicate that the proposed scheme promptly supports the PCC voltage during the fault under various fault conditions by increasing the reactive current with the maximum voltage dip.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1326-1333
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• 2016

It is important to clear the fault and prevent resulting in damage to power system. Although the frequency of generator internal fault is relatively low, it can lead to incalculable damage to power system as well as generator. Especially, loss of field on generator can cause the generator to lose synchronism for a short time if it is not removed promptly. Therefore, it is needed to conduct research on loss of field relay for detecting or clearing the loss of field. However, the setting of the relay may vary in generator operator or engineer, and the relay is not coordinated well with other elements associated with loss of field. In this paper, we address specifically the coordination of positive offset mho loss of field relay which is one of the protection schemes for loss of field. Computer simulations are performed by using ElectroMagnetic Transients Program-Restructured Version (EMTP-RV) based on actual data.

• Journal of Chest Surgery
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• v.18 no.4
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• pp.635-642
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• 1985

Double outlet left ventricle [DOLV] is a rare cardiac anomaly in which both great arteries arise entirely, or predominantly above the morphologically left ventricle. About 100 cases of DOLV have been reported in the literatures by 1984. We have experienced eight cases of DOLV at Seoul National University Hospital during the period from October 1981 to July 1905. Ages of the patients were ranged from 12 months to 24 years old, and chief complaints on admission were frequent URI and DOE in 5 cases and cyanosis in other 3 cases. In all eight patients, Cardiac catheterization and cineangiography were performed but pre-operative diagnoses were incorrect except one case [VSD in 2 cases, DORV in 2cases, c-TGA in 2 cases and TOF in one case] We have performed total corrective surgery in seven patients. In case I, patch closure of VSD aligning aorta and pulmonary artery with LV, ligation of proximal pulmonary artery and the use of external valved conduit from RV to PA have been employed. In other 6 cases, intraventricular repair using boomerang shaped Dacron patch with correction of associated anomalies were employed. In remaining one patient who had coexistent PDA and coarctation of aorta, we have performed coarctoplasty and PDA ligation initially and the patient is waiting for subsequent total corrective procedure. In seven patients whom we have performed total corrective surgery, there is one hospital mortality due to right heart failure and one complication of complete heart block necessitating permanent pacemaker implantation. All survivors are doing well in follow up period of 9 months to 4 years. To our knowledge, this is the first report of surgical experiences for DOLV in the Korean literature.

• Journal of Chest Surgery
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• v.27 no.6
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• pp.435-443
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• 1994

Surgical procedures to relieve congenital right ventricular outflow tract[RVOT] obstruction of heart were performed on 125 patients from September 1985 to August 1992. There were 65 males and 60 females. Ages ranged from 7 months to 33 years with a mean age of 8 years. All the patients were divided into three main groups[I, II, III] depending on the presence or absence of cyanosis and combined anomalies. The patient were classified into two groups; A and B according to the outcome after surgical repair. Group A included the patients who had a good postoperative outcome with or without mild complications such as wound disruption, or hydrothorax. Group B included the patients who had a poor outcome including hospital death and significant postoperative complications such as heart failure, low output syndrome, respiratory failure, hepatic failure and others. And the results were summarized as follows. 1. There were no significant differences in age, body surface area and aortic dimension among the group I, II, and III, but there were significant differences among groups in pulmonary arterial dimension, ACT[aortic cross clamping time], TBT [total bypass time], preoperative and postoperative ratio of systolic pressure of right and left ventricles [pre PRV/RV and post PRV/LV], and the size of Hegar dilator which passed through the RVOT postoperatively [p<0.05]. 2. In the group A and B, there were significant differences in pulmonary arterial dimension [group A:1.6$\pm$0.5 cm, group B:1.9$\pm$0.6 cm], ACT [group A:102.3$\pm$ 46.0 minute, group B:76.1$\pm$46.1 minute], TBT [group A:133.9$\pm$56.6 minute, group B:94.9$\pm$51.9 minute], pre PRV/LV [group A:1.06$\pm$0.24, group B:0.8$\pm$0.32], post PRV/LV [group A:0.58$\pm$0.18, group B:0.43$\pm$0.16].It has been concluded that postoperative prognosis of RVOT obstruction was influenced by pulmonary arterial dimension, ACT, TBT, severity of RVOT obstruction [pre PRV/LV] and post PRV/LV.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.2
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• pp.217-223
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• 2004

A cathepsin L-like cysteine protease, v-cath, encoded by the baculovirus has been shown to playa role in host liquefaction. We have identified a v-cath gene in the silkworm virus, Bombyx mori nuclear polyhedrosis virus (BmNPV) K1 strain. The 969 bp v-cath has an open reading frame of 323 amino acids. A putative cleavage site and catalytic sites were conserved in BmNPV-K1 v-cath. The predicted three-dimensional structure of BmNPV-K1 v-cath revealed that the overall fold of BmNPV-K1 v-cath is similar to that of other proteases of the papain family. The deduced amino acid sequence of BmNPV-K1 v-cath showed 98% and 97% protein sequence identity to BmNPV T3 strain and to Autographa californica nuclear polyhedrosis virus, respectively. The BmNPV-K1 v-cath differed at 4 amino acid positions from BmNPV T3. The v-cath gene in BmNPV-K1 genome is located on the EcoRV 6 kb and XhoI 9 kb fragments. Northern hybridization analysis of BmNPV K1 v-cath gene revealed that it is expressed late in infection.