• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.1
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• pp.42-45
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• 2008

It has been reported that FRP (fiber reinforced plastic) can be recycled by separating into layers instead of crushing into powder. F-fiber obtained from roving layer separated from FRP, has bigger tensile strength than the bundle of glass fibers of which FRP was made (more than 90%). SEM image of F-fiber shows the presence of some resin. Under the proposition of usage of F-fiber in the concrete material, tensile strength is examined after soaking in a basic solution (NaOH+KOH). The reaction mechanism of strength loss may be considered as an attack of hydroxide ion ($OH^-$) on a chemical bond of Si-O-Si of glass fiber. The simulation graph of the strength loss data implies certain reaction mechanism. While in the early stage kinetically controlled reaction results in a fast drop of tensile strength, after 30 days dispersion rate of hydroxide ion plays a major role in strength loss. This result is similar to the one for the AR glass. An extrapolation of the graph would make an assumption about the lift time of F-fiber possible.

• The Journal of the Korea Contents Association
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• v.20 no.9
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• pp.208-223
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• 2020

In the 21st general election held in April 15, 2020, the importance of social media as an election campaigning tool became more prominent when engaged with Corona 19. Therefore, in this study, various studies were conducted to establish SNS strategy as an election campaign tool. This study analyzed the contents of SNS (Facebook, Twitter, YouTube) activities as an election campaign tool to analyze messages on social media messages of candidates Lee Nak-yeon and candidate Hwang Kyo-an of Jongno-gu, Seoul during the 2020 21st National Assembly election. Data collection mainly analyzed posts from each candidate's official account, and the research method used text analysis using the R program. Word cloud, comparative analysis, q-graph analysis, LDA, and STM analysis were used during text analysis. In addition, the analysis result was confirmed to be statistically significant through correlation analysis. As a result of research, candidate Lee Nak-yeon's election includes corona, people, problems, crisis, suffering, and wisdom, which indicates that the crisis caused by corona must be overcome through any means possible. On the other hand, candidate Hwang Kyo-an's election includes Moon Jae-in, the regime, save, the fatherland, the judge, and the economy. And from the perspective of political publicity, candidate Lee Nak-yeon made a lot of acclaims, while candidate Hwang Kyo-an made a lot of attacks, and both themes emphasized the policy rather than the image.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.151-158
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• 2009

To implement the insects' flapping flight for developing flapping MAVs(micro air vehicles), the unsteady flow characteristics of the insects' forward flight is investigated. In this paper, two-dimensional FSI(Fluid-Structure Interaction) simulations are conducted to examine realistic flow features of insects' flapping flight and to examine the flexibility effects of the insect's wing. The unsteady incompressible Navier-Stokes equations with an artificial compressibility method are implemented as the fluid module while the dynamic finite element equations using a direct integration method are employed as the solid module. In order to exchange physical information to each module, the common refinement method is employed as the data transfer method. Also, a simple and efficient dynamic grid deformation technique based on Delaunay graph mapping is used to deform computational grids. Compared to the earlier researches of two-dimensional rigid wing simulations, key physical phenomena and flow patterns such as vortex pairing and vortex staying can still be observed. For example, lift is mainly generated during downstroke motion by high effective angle of attack caused by translation and lagging motion. A large amount of thrust is generated abruptly at the end of upstroke motion. However, the quantitative aspect of flow field is somewhat different. A flexible wing generates more thrust but less lift than a rigid wing. This is because the net force acting on wing surface is split into two directions due to structural flexibility. As a consequence, thrust and propulsive efficiency was enhanced considerably compared to a rigid wing. From these numerical simulations, it is seen that the wing flexibility yields a significant impact on aerodynamic characteristics.

• Journal of Acupuncture Research
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• v.21 no.2
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• pp.183-203
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• 2004

Objective : Tension-type headache is the most common headache. The objective of this study is to find the clinical manifestation of tension-type headache and correlation with autonomic bioelectric response. Methods : This observation was carried out on 60 patients with tension-type headache. We used headache questionnaire and the Autonomic Bioelectric Response recoder(ABR-2000) for this study. Results : 1. Distribution of sex & age : male : female=5 : 7, 50s&60s group (28.3%) 2. Duration of onset : over 5years(50%), over one years(83.4%) 3. Causes of illness : stress(58.3%), severe fatigue(53.5%), tension(33.3%) 4. Time of attack : irregular(56.7%), day time(16.7%) 5. Pattern of pain: heavy(31 people), stiffness of occipital region (27 people) tightening around the head(25 people) 6. Curve : 40%, 56.7%, 35.0% SL(Slope low) at peak 1, 2, 3/ SH&SI not found 7. Regulation : 16.7% RR(Regulation reverse) at peak 1, 25% RH(Regulation high) at peak 2, 15% RR(Regulation reverse) at peak 3 8. Graph : Activity-60.0%, 70.0%, 63.3% lowered reaction(L, LR, L!) at peak 1, 2, 3 Reactivity-83.3%, 95.0%, 93.3% lowered reaction at peak 1, 2, 3 Conclusion : We find tension-type headache has remarkable relativeness with autonomic bioelectric response.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.152-155
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• 2018

Over the past years, Link Flooding Attacks (LFAs) have been introduced as new network threats. LFAs are indirect DDoS attacks that selectively flood intermediate core links, while legacy DDoS attacks directly targets end points. Flooding bandwidth in the core links results in that a wide target area is affected by the attack. In the traditional network, mitigating LFAs is a challenge since an attacker can easily construct a link map that contains entire network topology via traceroute. Security researchers have proposed many solutions, however, they focused on reactive countermeasures that respond to LFAs when attacks occurred. We argue that this reactive approach is limited in that core links are already exposed to an attacker. In this paper, we present SDHoneyNet that prelocates vulnerable links by computing static and dynamic property on Software-defined Networks (SDN). SDHoneyNet deploys Honey Topology, which is obfuscated topology, on the nearby links. Using this approach, core links can be hidden from attacker's sight, which leads to effectively building proactive method for mitigating LFAs.

• Journal of Digital Convergence
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• v.17 no.8
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• pp.105-113
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• 2019

The purpose of this study is to analyze cyber security risk modeling of critical infrastructure, draw out limitations and improvement measures. This paper analyzed cyber security risk modeling of national critical infrastructure like as electricity sector, nuclear power plant, SCADA. This paper analyzed the 26 precedent research cases of risk modeling in electricity sector, nuclear power plant, SCADA. The latest Critical Infrastructure is digitalized and has a windows operating system. Critical Infrastructure should be operated at all times, it is not possible to patch a vulnerability even though find vulnerability. This paper suggest the advanced cyber security modeling characteristic during the life cycle of the critical infrastructure and can be prevented.

• Journal of Acupuncture Research
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• v.21 no.3
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• pp.215-229
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• 2004

Objective : We had a clinical report in headache but didn't in migraine. We have planned this study in order to get the basic data of migraine in oriental medicine. Methods : The patient of 36 in migraine checked sex, age, onset, family history, severity of pain, influences of life, induced cause, clinical pain characteristics, associated symptom, treatment style, and prescription, frequency, using period of analgesics by a questionnaire and differentiated syndromes in migraine and evaluated autonomic bioelectric response recorder(ABR-2000). Results : There are 23.4% in prevalence rate of migraine. The ratio of sex is M:F=1:17. The age of an attack is the highest in thirties. The patient are the most in forties. The mean duration of illness is $12.0{\pm}9.9$ years. 83.4% had a family history. 61.1% had a moderate grade in severity of pain. 77.8% selected fatigue in induced cause of migraine. 69.4% had tingling sense, nausea and vomiting in the associated symptoms. 91.7% used analgesics for treatment and 51.5% of them used analgesics voluntarily. 61.9% of them take analgesics less than once in a week. 33.6% had the phlegm syncope headache in differentiation of syndrome. In ABR-2000 results, item of graph showed low tendency mostly. Conclusions : We expected that this report of clinical progress, differentiation of syndromes and ABR-2000 results in migraine would be used basic data by oriental medicine to treat migraine.