• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.1
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• pp.81-87
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• 2020

Recently, the network configuration is being rapidly changed to enable easy and free network service configuration based on SDN/NFV. Despite the many advantages and applications of SDN, many security issues such as Distributed Denial of Service (DDoS) attacks are being constantly raised as research issues. In particular, the effectiveness of DDoS attacks is much faster, SDN is causing more and more fatal damage. In this paper, we propose an entropy-based technique to detect and mitigate DDoS attacks in SDN, and prove it through experiments. The proposed scheme is designed to mitigate these attacks by detecting DDoS attacks on single and multiple victim systems and using time - specific techniques. We confirmed the effectiveness of the proposed scheme to reduce packet loss rate by 20(19.86)% while generating 3.21% network congestion.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.100-106
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• 2013

In this paper, in order to analyze lightning impulse response characteristics in combined installations of SPDs and RCDs, surge protection coordination between SPDs and RCDs are experimentally investigated by using the combination wave generator. Six different types of single-phase residual current operated circuit-breakers with integral overcurrent protection for household and similar uses(RCBOs) being present on the domestic market are tested according to KS C IEC 61009-1 standard. As a result, when a class I SPD is located on the source side of an RCBO, all kinds of specimens are able to provide the proper coordination between the SPD and RCBOs without nuisance tripping, unintended operation or damage due to test impulse currents. However, in the case that the class II SPD is located on the load side of RCBOs, a lot of L-N mode injected currents is split into the RCBO, and a few RCBOs are damaged. Coordination between SPDs and RCDs is not valid and a role of SPDs is of no use. When combining SPDs with RCDs, it is necessary to select SPDs and RCDs in consideration of the protection voltage level of metal oxide varistor embedded in RCDs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.131-139
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• 2012

The lateral reinforcements of concrete such as hoops and spiral bars are known to confine concrete to compensate the strength loss due to fire by reducing explosive spalling and improving the capacity of ductility. In this context, a study was conducted to investigate the residual mechanical properties of confined and unconfined concrete($f_{ck}$=60MPa) after a single thermal cycle at 300, 600, $800^{\circ}C$. The main parameters required to establish the stress-strain relationship are the peak stress, the elastic modulus, and the strain at peak stress. The knowledge of the residual mechanical properties of concrete is necessary whenever the thermally damaged structure is required to bear a significant share of the loads, even after a severe thermal accident. Based on the results obtained in this study, the residual stress of confined concrete under thermal damage is higher according to the level of confinement and the larger strain made it to have better ductility. The decreasing ratio of elastic modulus from the relationship of stress and strain was also smaller than that of unconfined concrete.

• Archives of Plastic Surgery
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• v.37 no.4
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• pp.421-426
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• 2010

Purpose: Patients with serious burns are prone to chondritis due to lack of soft tissue in the auricle, which can cause severe defects in the auricular morphology. In addition, skin damage occurs frequently in the vicinity of post-burn wounds, presenting difficulties in reconstruction surgery. An auricular reconstruction has functional and cosmetic significance. The aim of this study is to develop appropriate reconstruction methods for auricular defects. Methods: Thirty seven patients, who were treated for auricular defects from 2005 to 2009, were enrolled in this study. A local flap, multiple regional flaps and cartilage framework with or without a temporal fascial flap were applied in reconstruction surgery according to the location of the auricular defect. Results: The age of the subjects ranged from 11 to 56. Some subjects had defects that cover more than half of the helical rim with most exhibiting post-burn scars in the vicinity, for whom a multiple regional flap was used. A single use of a tubed flap was sufficient for subjects with defects that covered less than half of the helical rim. A regional flap was also used for reconstruction in subjects with defects covering both the helical rim and antehelix. Conclusion: Achieving satisfactory results from the skin flaps and skin grafts for post-burn auricular defects in both functional and cosmetic aspects is a difficult task. Therefore, selecting an appropriate surgical method through proper diagnosis of the auricular defect and the state of the available skin in the vicinity is essential.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.20-25
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• 2012

New Zealand suffers from regular floods, these being the most common source of insurance claims for damage from natural hazard events in the country. This paper describes the origin and distribution of the largest floods in New Zealand, and describes the systems used to monitor and predict floods. In New Zealand, broad-scale heavy rainfall (and flooding), is the result of warm moist air flowing out from the tropics into the mid-latitudes. There is no monsoon in New Zealand. The terrain has a substantial influence on the distribution of rainfall, with the largest annual totals occurring near the South Island's Southern Alps, the highest mountains in the country. The orographic effect here is extreme, with 3km of elevation gained over a 20km distance from the coast. Across New Zealand, short duration high intensity rainfall from thunderstorms also causes flooding in urban areas and small catchments. Forecasts of severe weather are provided by the New Zealand MetService, a Government owned company. MetService uses global weather models and a number of limited-area weather models to provide warnings and data streams of predicted rainfall to local Councils. Flood monitoring, prediction and warning are carried out by 16 local Councils. All Councils collect their own rainfall and river flow data, and a variety of prediction methods are utilized. These range from experienced staff making intuitive decisions based on previous effects of heavy rain, to hydrological models linked to outputs from MetService weather prediction models. No operational hydrological models are linked to weather radar in New Zealand. Councils provide warnings to Civil Defence Emergency Management, and also directly to farmers and other occupiers of flood prone areas. Warnings are distributed by email, text message and automated voice systems. A nation-wide hydrological model is also operated by NIWA, a Government-owned research institute. It is linked to a single high resolution weather model which runs on a super computer. The NIWA model does not provide public forecasts. The rivers with the greatest flood flows are shown, and these are ranked in terms of peak specific discharge. It can be seen that of the largest floods occur on the West Coast of the South Island, and the greatest flows per unit area are also found in this location.

• The Korean Journal of Food And Nutrition
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• v.30 no.4
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• pp.673-680
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• 2017

Fludarabine, a chain terminating anti-cancer drug, is a purine analogue that causes DNA strand breaks in normal cells. In this study, we determined if A. melanocarpa and Korean red ginseng extract mixture reduce cytotoxicity of fludarabine. Treatment of HaCaT cells with $10{\mu}M$ of fludarabine for 24 hours decreased cell viability and increased DNA strand breaks. Treatment of A. melanocarpa and Korean red ginseng extract mixture for 24 hours increased cell viability as compared with single extract treatment. The protective effect of these extracts on cell activity increased in a concentration-dependent manner. DNA strand breaks induced by fludarabine decreased as concentration of extract mixture increased. p-H2AX level, a marker of DNA strand breakage, decreased depending on the concentration of extract mixture. The effect of mixed extract of A. melanocarpa and Korean red ginseng on DNA damage is due to the anti-oxidative effect of A. melanocarpa and signal transmission through glucocorticoid receptor upon binding of saponin of Korean red ginseng.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.63-69
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• 2003

In this study seismic design procedure for buckling-restrained braced frame systems was proposed using hysteretic energy spectrum and accumulated ductility spectrum constructed from single degree of freedom systems. The hysteretic energy spectra and accumulated ductility spectra corresponding to target ductility ratio were constructed first. The cross-sectional area of braces required to meet a given target displacement was obtained by equating the hysteretic energy demand to the accumulated plastic energy dissipated by braces. Twenty earthquake records were utilized to construct the spectra and to verify the validity of the design procedure. According to analysis results of three- and eight-story buckling-restrained braced frame structures designed using the proposed method, the mean values for the top story displacement correspond well with the given performance target displacements. Also, the inter-story drifts turned out to be relatively uniform over the structure height, which is desirable because uniform inter-story drifts indicate uniform damage distribution. Therefore if was concluded that the proposed energy-based method could be a reliable alternative to conventional strength-based design procedure for structures with buckling-restrained braces.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.2
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• pp.138-143
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• 1993

In this study the onion juice (2%) in diet fed rats simultaneously ingested lead acetate 100mg/ kg (OP group) showed more increased weight gain than single lead treated rats (P group). The OP group had also improved in the hemoglobin contents and biochemical analyzed values of blood including GPT, blood urea nitrogen and alkaline phosphatase, which were elevated in case of P group rats. The Pb content in the rats liver of OP group was lower than in the rats liver of P group. In the histopathological findings of liver cell OP group rats did not show any signs of liver damage as observed in P group rats that had degenerated hepatocytes, followed sinusoidal dilatation, perivascular hemorrhage and some necrosis of hepatic cells accompanied by increased Kuffer cell bearing dark brown pigment. In conclusion 2% onion juice diet in rat have somewhat antidotic effects on the lead intoxicated rats.

• Journal of Yeungnam Medical Science
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• v.23 no.1
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• pp.19-25
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• 2006

Background: There is limited data on comparisons between the effect of histidin-etryptophan-ketoglutarate (HTK) solution and cold blood cardioplegic (CBC) solution in pediatric cardiac surgery. The purpose of this study was to compare the myocardial protective effect of HTK solution and CBC solution in patients undergoing pediatric cardiac surgery. Materials and Methods: We selected 49 patients with ventricular septal defect and atrial septal defect. HTK solution was used in 21 patients and CBC solution was used in 28 patents. HTK solution was given as a single dose, whereas CBC solution was used in the usual multi-dose method. The incidence of EKG change and concentration of Troponin T and CK-MB were compared for the evaluation of myocardial damage. Results: There were no significant differences in the incidence of ST, T segment change by EKG and serial cardiac enzyme levels between two groups. Conclusion: These results suggested that the myocardial protective effect of HTK solution was similar to CBC solution in simple pediatric cardiac surgery.

• Bulletin of the Korean Chemical Society
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• v.8 no.2
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• pp.69-72
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• 1987

The structures of dehydrated $Ag_9Cs_3$-A treated with hydrogen gas at three different temperatures have been determined by single-crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at 23(1) $^{\circ}C$. All crystals were ion exchanged in flowing streams of aqueous $AgNO_3$/$CsNO_3$ with a mole ratio 1:3.0 to achieve the desired crystal composition. The structures treated with hydrogen at $23^{\circ}C(a=12.288(1)\;{\AA})\;and\;310^{\circ}C(a=12.291(2)\;{\AA})$ refined to the final error indices R1 = 0.091 and R2 = 0.079, and 0.065 and 0.073, respectively, using the 216 and 227 reflections, respectively, for which I >3${\sigma}$(I). In both of these structures, eight $Ag^+$ ions are found nearly at 6-ring centers, and three $Cs^+$ ions lie at the centers of the 8-rings at sites of $D_{4h}$ symmetry. One $Ag^{\circ}atom$, presumably formed from the reduction of a $Ag^+$ ion by an oxide ion of a residual water molecule or of the zeolite framework during the dehydration process, is retained within the zeolite, perhaps in a cluster. In these two structures hydrogen gas could not enter the zeolite to reduce the $Ag^+$ ions because the large $Cs^+$ ions blocked all the 8-windows. However, hydrogen could slowly diffuse into the zeolite and was able to reach and to reduce about half of the $Ag^+$ ions in the structure only at high temperature ($470^{\circ}C$). The silver atoms produced migrated out of the zeolite framework, and the protons generated led to substantial crystal damage.