• 한국통신학회논문지
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• 제35권1B호
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• pp.8-19
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• 2010

본 논문에서는 DDoS (Distributed Denial of Service) 공격에 따른 비정상적인 트래픽의 범람(flood)을 방지하고 합법적인 트래픽 전송을 보장하기 위하여 NCP (Network Control Platform) 기반의 DDoS 공격 대응 기법을 제안한다. 또한 이를 위하여 NCP와 SR (Source Router), VR (Victim Router)의 기능 모듈을 정의하고 high-flow 감지를 위한 임계값 및 공격 패킷 폐기율 결정식을 제안한다. 제안한 기법에서 NCP는 SR과 VR로부터 수집된 high-flow정보와 큐 정보를 기반으로 DDoS 공격 여부를 판단하고 이에 따라 패킷 폐기율을 결정한다. SR과 VR은 NCP에 의하여 결정된 패킷 폐기율에 따라 해당 플로우에 속하는 패킷을 폐기시킨다. 성능 평가를 위하여 OPNET 환경에서 시뮬레이션을 수행하고 SR, VR의 큐 크기, 공격 트래픽의 전송량 관점에서 비교 분석한다.

• International Journal of Aerospace System Engineering
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• 제9권2호
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• pp.1-9
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• 2022

The NEA release mechanism is used to provide restraint and release functions with low shock for critical deployment operations on solar arrays after launch. The GK3 solar array consists of 2 wings and 6 hold down points per panel. The NEA SSD9103S1 is a part of the GK3 solar array hold-down and release mechanism. Each NEA unit is equipped with two Z-diodes which provide power to a NEA unit connected in series after actuation of the fuse wire. This paper presents the hot firing test results of a quadrature NEA SSD9103S1 configuration. One output powers a maximum of 4 NEA SSD9103S1 units simultaneously. The necessary actuation pulse duration has been determined to meet margin requirement for thermal energy of minimum 4. Actuation thermal energy difference is about 6.6% between each half of two fired serial NEAs. Thermal energy margin at worst case is minimum 5.9 in case of an actuation pulse duration of 500 ms. Two series Zener impedance depend on current applied has been characterized by an additional actuation after all fuse wires are open circuit. Total number of actuation commands to the GK3 NEA unit reduce drastically from 24 in case of single NEA configuration down to 8 in case of parallel and quadrature NEA configurations. It can be accommodated by the existing HP2U Pyro design without any impact.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.259-275
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• 2018

In mechanical analysis of spacecraft structures situations appear where static and dynamic loads must be considered simultaneously. This could be necessary either by load definition or preloaded structures. The superposition of these environments has an impact on the load and stress distribution of the analysed structures. However, this superposition cannot be done by adding both load contributions directly. As an example, to compute equivalent Von Mises stresses, the phase information must be taken into account in the stress tensor superposition. Finite Element based frequency response solvers do not allow the calculation of superposed static and dynamic responses. A manual combination of loads in a post-processing task is required. In this paper, procedures for static and harmonic loads superposition are presented and supported by analytical and finite element-based examples. The aim of the paper is to provide evidence of the risks of using different superposition techniques. Real application examples such as preloaded mechanism structures and propulsion system tubing assemblies are provided. This study has been performed by the Structural Engineering department of Airbus Defence and Space GmbH Friedrichshafen.

• The Korean Journal of Ecology
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• 제20권5호
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• pp.315-321
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• 1997

Peroxidase activities and isozyme patte군 of the pine needles (Pinus densiflora) were examined and compared in the coastal regions of Anmyum-Do(Choongnam, Taean-Gun) and inland regions of Shinchang-Myun(Choongnam, Asan-City). The pine needle peroxidase from Anmyum-Do showed approximately three times higher specfic activity than Shinchang pine needle peroxidase. The pine needle extracts of Anmyun-Do and Shinchang contained three anionic isoperoxidases, named A1, A2 and A3, when subjected to starch gel electrophoresis at pH 7.0. Cjationic isoperoxidases could not be found in both extracts., However, there existed unique isoperoxidase An only from the extracts of Anmyun-Do pine needles under the salinary environment. Moreover, the specific activities of catalase and glucose-6-phosphate dehydrogenase from Anmyun-Do, known for the inducible enzymes under the stress condition, were about 1.8 times higher than those of Shinchang pine needles. However, the specific activities of other enzymes did not show great differences between the two regions. Considering the above results of the higher specific activity of peroxidase and the unique expression of isoperoxidase An, pine needle peroxidase might involve in the defence mechanism against the salinary stress of Anmyun-Do.

• 대한의생명과학회지
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• 제8권3호
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• pp.155-159
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• 2002

To evaluate the physiological significance of xanthine oxidase (XO) in rat skin, the activity of XO (type O) in skin was compared with that of small intestine or liver. Concomitantly, XO activities in some partial portions (scalp, leg, dorsal and ventral part) of skin were determined and then compared with each partial portion. XO activity of skin was lower than that of small intestine and rather higher than that of liver. Furthermore, the activity of XO in skin, after clipping of hairs and then in 5 days, was more increased than that of rat which was clipped before having been sacrificed. As for activities of free radical scavenging system (GPx, GST, SOD), skin is lower than liver and small intestine. Although it is hewn that the oxygen free radical generated by XO system lead to injurious effect on the cell, the XO activity of ventral part which is to be less exposed to xenobiotics and biological agents was the lowest among those of ventral, dorsal, leg and scalp parts in skin. In conclusion, it may be hypothesized that XO system in skin act on defence mechanism.

• 대한한방종양학회지
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• 제5권1호
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• pp.137-150
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• 1999

Macrophage play a major role in host defence against infection and tumor development and this activity is regulated through the production of several mediators. In particular, the production of NO by macrophages mediates killing or growth inhibition of tumor cells, bacteria, fungi and parasites. However, over-expression of iNOS by various stimuli, resulting in over-production of NO, contributes to the pathogenesis of septic shock and some inflammator and auto-immune disease. Therefore, it would be valuable to develop potent and selective inhibitors of for potential therapeutic use. Thus the agent that supprees the expression of iNOS mRNA or enzyme protein will be usefull for the prevention of various diseases. We are intersted in identifying selective inhibitiors of iNOS which might be useful intreating inflammatory human diseases. In summary, we have demenstrated that scopoletin, isolated from Seman Armenicae and Radix Trichosanthis the production of NO induced by $IFN-\gammer$ plus LPS in RAW 264.7 macrophages, The mechanism for the inhibition of NO production was due to suppression of the expression of iNOS mRNA or enzyme protein.

• 한국정보과학회논문지:정보통신
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• 제31권5호
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• pp.438-449
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• 2004

조직이 운영하는 네트워크의 규모가 방대해지고, 인터넷 사용이 활성화되면서 보안의 중요성도 함께 증가하였다. 그러나 최근 보안의 핵심으로 부각되고 있는 침입탐지 시스템들은 인터넷상의 공격들에 대한 적절한 분석이나 효율적인 대응책을 제공해 주기보다는, 대량의 침입탐지 정보를 생성시켜 관리자의 부담을 가중시키고 있다. 본 논문에서는 침입탐지 시스템이 생성하는 대량의 침입탐지 정보들간에 존재하는 연관성을 분석하여 대응에 필요한 고 수준의 정보를 실시간으로 생성해 냄으로써 관리 및 분석의 효율성을 증진시키고, 나아가서는 분산 서비스 거부 공격(DDoS) 같은 대규모의 공격까지도 조기에 탐지해 낼 수 있는 능력을 갖춘 침입탐지 정보 분석 시스템을 제안한다. 그리고 제안된 시스템의 성능 분석을 위해 각 모듈의 처리 효율을 측정하고 알려진 공격 시나리오 기반의 시험 평가를 실시한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권9호
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• pp.3377-3395
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• 2015

Recently, several approaches to share road conditions and/or digital contents through VANETs have been proposed, and such approaches have generally considered the radial distance from the information source as well as the TTL to provision an ephemeral, geographically-limited information sharing service. However, they implement general MANETs and have not been tailored to the constrained movement of vehicles on roads that are mostly linear. In this paper, we propose a novel application-level mechanism that can be used to share road conditions, including accidents, detours and congestion, through a VANET. We assign probabilities to roads around each of the intersections in the neighborhood road network. We then use the graph representation of the road network to build a spanning tree of roads with the information source as the root node. Nodes below the root represent junctions, and the edges represent inter-connecting road segments. Messages propagate along the branches of the tree, and as the information propagates down the branches, the probability of replication decreases. The information is replicated until a threshold probability has been reached, and our method also ensures that messages are not delivered to irrelevant vehicles, independently of their proximity to the source. We evaluated the success rate and performance of this approach using NS-3 simulations, and we used IDM car following and MOBIL lane change models to provide realistic modeling of the vehicle mobility.

• 한국항공우주학회지
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• 제48권8호
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• pp.581-588
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• 2020

고전압 기폭관의 노화 특성에 관하여 연구하였다. 노화 특성 관측을 위해 먼저 고전압 기폭관의 주요 구성품을 분류하고, 고장 메커니즘을 정의하였다. 위력과 감도 측면에서 노화 특성을 정의하였으며, HFC (Heat Flow Calorimetry)를 통해 계산된 활성화 에너지와 아레니우스 이론을 기반으로 가속노화시험 계획을 수립하였다. 노화된 시료를 이용하여 민감도 시험인 Neyer Test와 위력시험인 Dent Test를 통하여 성능 변화를 관측하였다. 민감도 시험을 통해 구한 반폭점에서 노화 경향을 관찰하였으나 관련 규격을 고려하면 충분히 긴 수명을 가지고 있는 것으로 분석되었다.

• 한국수산과학회지
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• 제30권6호
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• pp.1033-1043
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• 1997

In order to understand the generation mechanism of the Ulleung Eddy, we carried out a series of numerical experiments using the nonlinear 11/2 - layer model allowing the inflow of the Tsushima Current. According to our numerical results, the Ulleung Eddy was generated due to the inflow variations of the Tsushima Current. Its inflow through the Korea Strait was deflected to the east due to the Coriolis force and the nonlinear self advection. Thus, an anticyclonic motion was formed at the north of the Korea Strait. The inflow became a coastal boundary current, and finally flowed out model ocean through the eastern exit. When the speed of inflow decreased slowly, the eddy- like motion at the north of the Korea Strait changed into an enclosed anticyclonic eddy of about 200 km in diameter. The Ulleung Eddy became circular shape due to the nonlinear self advection, then changed into elliptical shape in meridional direction because of the blocking effect of the western boundary.