• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.1
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• pp.19-24
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• 2003

Design and test results of a VRAG(Vacuum Rotary Arc Gap) switch were presented. To control the damage of electrodes caused by the vacuum arc, Lorentz's force by the radial magnetic field between spiral electrodes was used to rotate the vacuum uc. VRAG switch electrodes were made of the material of CuCr and OFHC. Gap distance between two spiral type electrodes for the rotation of the arc discharge is 8, 10, 12mm. In the cathode, one trigger electrode was inserted into each spiral wing. Normal operation of the VRAG switch was confirmed with 10.6[$mutextrm{s}$]of trigger delay and 2~3[$mutextrm{s}$] of the jitter time. The speed of the vacuum arc was measured to be 0.6 ~ 1[km/s] by a motion analyzer.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.17 no.4
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• pp.85-93
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• 2009

Bird strike is big issue in aviation. Because a bird strike causes not only an aircraft damage but also a fatality, aviation societies are gearing up to prevent a bird strike. However, the accidents is not going down yet. Annal average of bird strikes in Korea is 1.15 accidents per ten thousand of flight, which is lower than the other country, for example 1.84 accidents in France and 2.38 accidents in Switzerland, 1.15 accidents. In the U.S.A, there are 89,727 accidents for the 19 year(1990-2008). Also flight delay is total 637,692 hours. The cost is total 350,258 billion dollar and 18,435 billion dollar per year. In related with those data's, this research is about the current and legal status of the bird strike. Also it will be useful to establish aviation safety policy and manage the bird strike.

• Natural Product Sciences
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• v.8 no.4
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• pp.144-146
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• 2002

Rhapontica uniflora, Platycodon grandiflorum and Solanum tuberosum extracts affected the recovery of radiation-induced damage at all tested doses $(15.6,\;31.3,\;62.5\;and\;125\;{\mu}g/ml)$. The survival rate of pretreatment with extracts was increased by 2 times more than its compared with untreated cells. All tested extracts protected the growh-delay of normal cells and haematological parameters from their radiation-induced fall. In tested extracts, Solanum tuberosum was significantly superior to Platycodon grandiflorum and Rhapontica uniflora in radio-protection activity.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3334-3341
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• 2023

We studied the irradiation effects of fast neutron generated by a 30 MeV cyclotron on the electrical and switching characteristics of NPT-IGBT devices. Fast neutron fluence ranges from 2.7 × 10⁹ to 1.82 × 10¹³ n/cm². Electrical characteristics of the IGBT device such as I-V, forward voltage drop and additionally switching characteristics of turn-on and -off were measured. As the neutron fluence increased, the device's threshold voltage decreased, the forward voltage drop increased significantly, and the turn-on and turn-off time became faster. In particular, the delay time of turn-on switching was improved by about 35% to a maximum of about 39.68 ns, and that of turn-off switching was also reduced by about 40%-84.89 ns, showing a faster switching.

• Korean Journal of Radiology
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• v.20 no.6
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• pp.894-908
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• 2019

Kidney transplantation is the treatment of choice for patients with end-stage renal disease, as it extends survival and increases quality of life in these patients. However, chronic allograft injury continues to be a major problem, and leads to eventual graft loss. Early detection of allograft injury is essential for guiding appropriate intervention to delay or prevent irreversible damage. Several advanced MRI techniques can offer some important information regarding functional changes such as perfusion, diffusion, structural complexity, as well as oxygenation and fibrosis. This review highlights the potential of multiparametric MRI for noninvasive and comprehensive assessment of renal allograft injury.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.12 no.2
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• pp.85-93
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• 2012

Purpose: Developmental delay is caused by very diverse etiologic diseases. Most chronic disorders has some influence on development. Chronic or acute disorders of CNS are main etiologic diseases of developmental delay. Up to now, over 60 diseases are included in organic acidopathies and most of them causes acute or chronic recurrent CNS damage and developmental delay. We have done this study to find out the importance of organic acidopathies causing developmental delay in Korean childhood and adolescent patients. Method: Retrograde analysis for 738 patients with developmental delay whose clinical informations are available and have done urine organic acid analysis for 5 years period, between Jan. 1st 2007 to Dec. 31th 2011. Statistical analysis was done with Student's t test using SPSS. Result: Out of 738 patients, 340 patients (46.1%) showed abnormalities on urine organic acid analysis. The most frequent disease was mitochondrial respiratory chain disorders (MRCD) (253, 34.3%), followed by ketolytic defects(39, 5.3%), 3-hydroxyisobutyric aciduria (26, 3.5%), glutaric aciduria type II (8, 1.1%), pyruvate dehydrogenase deficiency (3, 0.4%), 3-methylglutaric aciduria (2, 0.3%), glutaric aciduria type I (2, 0.3%), ethylmalonic aciduria (1, 0.15%), methylmalonic aciduria (1, 0.15%), HMG-CoA lyase deficiency (1, 0.15%), 3-methylcrotonylglycinuria (1, 0.15%), fatty acid oxidation disorders(1, 0.15%) and FAOD (1, 0.15%). Conclusion: Mitochondrial disorders are most frequent etiologic disease on all age group, followed by ketolytic defects and various organic acidopathies. The number and diversities of organic acidopathies emphasize meticulous evaluation of basic routine laboratory examinations and organic acid analysis with initial sample on every developmental patient.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.5
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• pp.671-683
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• 2018

The flood damage caused by heavy rains in urban watershed is increasing, and, as evidenced by many previous studies, urban flooding usually exceeds the water capacity of drainage networks. The flood on the area which considerably urbanized and densely populated cause serious social and economic damage. To solve this problem, deterministic and probabilistic studies have been conducted for the prediction flooding in urban areas. However, it is insufficient to obtain lead times and to derive the prediction results for the flood volume in a short period of time. In this study, IDNN, TDNN and NARX were compared for real-time flood prediction based on urban runoff analysis to present the optimal real-time urban flood prediction technique. As a result of the flood prediction with rainfall event of 2010 and 2011 in Gangnam area, the Nash efficiency coefficient of the input delay artificial neural network, the time delay neural network and nonlinear autoregressive network with exogenous inputs are 0.86, 0.92, 0.99 and 0.53, 0.41, 0.98 respectively. Comparing with the result of the error analysis on the predicted result, it is revealed that the use of nonlinear autoregressive network with exogenous inputs must be appropriate for the establishment of urban flood response system in the future.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.1
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• pp.9-17
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• 2003

Typhoon RUSA, which caused serious damage was passed over in Korea peninsula during 30 August to 1 September, 2002. We estimated tropospheric wet delay using GPS data and meteorological data during this period. Integrated Water Vapor(IWV) gives the total amount of water vapor from tropospheric wet delay and Precipitable Water Vapor(PWV) is calculated the IWV scaled by the density of water. We obtained GPS PWV at 13th GPS permanent stations(Seoul, Wonju. Seosan, Sangju, Junju, Cheongju, Taegu, Wuljin, Jinju, Daejeon, Mokpo, Sokcho, Jeju). We retrieve GPS data hourly and use Gipsy-Oasis II software and we compare PWV and precipitation. GPS observed PWV time series demonstrate that PWV is, in general, high before and during the occurrence of the typhoon RUSA, and low after the typhoon RUSA. GPS PWV peak time at each station is related to the progress of a typhoon RUSA. We got very near result as we compare GMS Satellite image with tomograph using GPS PWV and we could present practical use possibility by numerical model for weather forecast.

• The Journal of Pediatrics of Korean Medicine
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• v.24 no.2
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• pp.1-12
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• 2010

Objectives Taking detailed patient history helps earlier diagnosis and treatment of developmental disability. In this study we analyzed the clinical questionnaire to find out the clinical characteristics of those with five-retardation, five-limpness, or five-stiffness. Methods The data was collected from 484 children under the age of six who have visited H oriental medicine clinic for developmental delay. The clinical questionnaire was filled out by their parents and the data was analyzed statistically. Results 436 children showed symptoms of five-retardation, 90 children suffered from five-stiffness, 54 children showed five-limpness and 7 children suffered from five-stiffness and five-limpness complex. Generally, boys had higher chance to show disease symptoms than the girls (2.32:1) and 40 children (8.26%) reported family history of developmental disability. Cerebral palsy ranks the most common familial disease, followed by developmental delay, mental retardation, autistic disorder and language disorder. Among the children we have studied, 285 children (63.19%) showed delayed unassisted walk while 192 children (42.57%) had language disorder. Also, 138 children (28.51%) had both walk and language disorders. The children in this study also showed delayed toilet training and half of them had little stranger anxiety when they were infants. It was also found that 120 children (24.79%) experienced epilepsy. This study reaffirmed that low birth weight, premature birth, and suffocation are major risks causing neurological damage. Conclusions They had history which including family history, problems at birth, epilepsy, face recognition, muscle tone disorder, delayed walking without assistance, language ability, and toilet training.

• Journal of the Korean Professional Engineers Association
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• v.23 no.2
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• pp.81-93
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• 1990

The blasting to construct subways in Seoul, Korea. have often increased complaints of ground vibration. In order to prevent the damage to structures, it was necessary to predict the level of blasting induced vibration and to determine the maximum charge weight per delay within a allowable vibration level. A total of 109 blasts were recorded at ten sites. Blast-to-structure distances ranged from 8 to 84.2 meter, where charge weight varied from 0,1125 to 7.85 kg per delay. The data from blast were studied to determine the effect of explosives type on the vibration constants(k). Vibration constants were also analyzed in terms of compressive strength of rock and blasting patterns.