• Journal of Medicine and Life Science
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• 제17권1호
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• pp.25-28
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• 2020

The prevalence of pulmonary pargonimiasis in Korea has been steadily decreasing due to develop of the public health, and there have been few clinical cases of paragonimiasis infections, especially in pneumothorax. A 22-year-old man referred to emergency department for dyspnea and chest pain. The right lung was totally collapsed on a chest X-ray. We emergently performed a closed thoracostomy with a 28-Fr chest tube. However, the air leak from the chest tube persisted for three days after the closed thoracostomy. A chest computed tomography showed multiple subpleural consolidative nodular lesions and mixed ground-glass attenuation nodules. We potentially suspected a secondary pneumothorax resulting from pulmonary paragonimiasis infection because the patient was a Chinese man who was working at a Korean restaurant. We decided to perform a medical treatment instead of pulmonary wedge resections. The air leak was discontinued three days after the prescription of praziquantel. The patient was discharged nine days after the admission. We suggest that anti-parasitic drugs are very effective in the secondary pneumothorax resulting from paragonimiasis.

• 태양에너지
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• 제20권3호
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• pp.11-19
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• 2000

In this study, the basic data which were required for development of LHSS(latent heat storage system) were experimentally obtained. Experiments were carried out under the following conditions. The initial temperatures of P.C.M. which were used by parameter is $5^{\circ}C,\;9^{\circ}C$ and $14^{\circ}C$. The conditions of working fluid are $-6^{\circ}C,\;-4^{\circ}C$, and $65{\ell}$/min.. The pure water of which the freezing point is $0^{\circ}C$ was filled in the system, and the Ethylene glycol(brine) was circulated through the 10 vertical tubes as a secondary fluid in order to cool the P.C.M. down. The inlet temperature of the secondary fluid and the initial temperature of the water were varied to investigate the effects of the important design parameters. The phenomenons of temperature conversion of P.C.M. were appeared for the conductive heat transfer and free convective heat transfer by buoyancy force in this storage unit system. In order to find the effective water circulation path, we obtained P.CM. temperature distributions of 5 parts in the storage tank during freezing process.

• Structural Engineering and Mechanics
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• 제35권5호
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• pp.555-570
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• 2010

Shallow fixed arches have a nonlinear primary equilibrium path with limit points and an unstable postbuckling equilibrium path, and they may also have bifurcation points at which equilibrium bifurcates from the nonlinear primary path to an unstable secondary equilibrium path. When a shallow fixed arch is subjected to a central step load, the load imparts kinetic energy to the arch and causes the arch to oscillate. When the load is sufficiently large, the oscillation of the arch may reach its unstable equilibrium path and the arch experiences an escaping-motion type of dynamic buckling. Nonlinear dynamic buckling of a two degree-of-freedom arch model is used to establish energy criteria for dynamic buckling of the conservative systems that have unstable primary and/or secondary equilibrium paths and then the energy criteria are applied to the dynamic buckling analysis of shallow fixed arches. The energy approach allows the dynamic buckling load to be determined without needing to solve the equations of motion.

• 대한수학교육학회지:학교수학
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• 제18권3호
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• pp.711-731
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• 2016

본 연구에서는 중등 수학 예비교사가 교과서의 수학 과제(Mathematical task)를 어떻게 변형하는지 그리고 그 과정에서 예비교사들이 어떤 학습 기회를 가지는지 조사하였다. 이를 위하여 교과서의 미분계수 단원에서 과제를 선정하고 5명의 예비교사를 대상으로 과제 변형 활동을 실시하여 분석한 결과, 다음과 같은 결론을 얻을 수 있었다. 첫째, 과제는 인지적 노력 수준을 유지하거나 높이는 방향으로 이루어졌으며 이러한 경향은 예비교사들이 미분계수의 개념적 이해를 추구하는 가운데 나타났다. 둘째, 과제 변형 활동은 예비교사들에게 다양한 학습기회를 제공하였다. 예비교사들은 교육과정과 교과서의 의도를 파악하기 위해 노력하였고, 학생의 반응을 예측하는 것의 중요성을 알게 되었으며, 협업과 반성적 사고의 기회를 가졌다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3081-3099
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• 2012

We propose a new multipath-based reliable routing protocol on MANETs, Multipath-based Reliable routing protocol with Fast-Recovery of failures (MRFR). For reliable message transmission, MRFR tries to find the most reliable path between a source and a destination considering the end-to-end packet reception reliability of the routes. The established path consists of a primary path that is used to transmit messages, and the secondary paths that are used to recover the path when detecting failures on the primary path. After establishing the path, the source transmits messages through the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to locally recover the route failure, the proposed protocol can handle the dynamic topological change of the MANETs efficiently. The simulation result using the QualNet simulator shows that the MRFR protocol performs better than other protocols in terms of the end-to-end message delivery ratio and fault-tolerance capability.

• 한국전기전자재료학회논문지
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• 제32권4호
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• pp.341-348
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• 2019

This paper reports the microstructure and electrochemical properties of Si-Al-Fe ternary amorphous alloys prepared by rapid solidification as an anode for lithium secondary batteries. The microstructure was analyzed using XRD and HR-TEM with EDS mapping. In accordance with DSC analysis, annealing was performed to crystallize the active nano-Si in the amorphous alloy. Thus, nano-Si forms (~80 nm) embedded in the matrix alloy, such as $Fe_2Al_3Si_3$, $FeSi_2$, and $Fe_{0.42}Si_{2.67}$, were successfully synthesized. The electrode based on the Si-Al-Fe ternary alloy delivered an initial discharge capacity of approximately $700mAh^{g-1}$, and exhibited a high Coulombic efficiency of 99.0~99.6% from the $2^{nd}$ to $70^{th}$ cycles.

• 한국항공우주학회지
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• 제47권1호
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• pp.1-8
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• 2019

비례제어밸브를 이용한 초음속 추력편향제어의 특성을 관찰하기 위한 실험적 연구가 진행되었다. 노즐 압력비에 따라 세 가지 서로 다른 추력편향 제어특성이 나타나고, 밸브작동에 따른 강한 이력현상이 관찰되었다. 아울러 이차챔버의 압력이 추력편향에 영향을 주는 주요 인자 중의 하나임이 확인되었다. 이에 이력현상을 회피하고 밸브제어에 따른 안정된 추력편향을 구현하기 위하여 이차챔버의 압력계수를 이용한 제어 알고리즘이 적용되었다. 그 결과 비례제어밸브를 통하여 최대 추력편향각 $20^{\circ}$ 범위에서 안정적인 추력편향제어가 구현 가능함이 확인되었다.

• Journal of Platform Technology
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• 제9권1호
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• pp.3-14
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• 2021

Cognitive Radio network (CR) is a promising paradigm that helps the unlicensed user (Secondary User) to analyse the spectrum and coordinate the spectrum access to support the creation of common control channel (CCC). The cooperation of secondary users and broadcasting between them is done through transmitting messages in CCC. In case, if the control channels may get jammed and it may directly degrade the network's performance and under such scenario jammers will devastate the control channels. Hopping sequences may be one of the predominant approaches and it may be used to fight against this problem to confront jammer. The jamming attack can be alleviated using one of the game modelling approach and in this proposed scheme stochastic games has been analysed with more single users to provide the flexible control channels against intrusive attacks by mentioning the states of each player, strategies ,actions and players reward. The proposed work uses a modern player action and better strategic view on game theoretic modelling is stochastic game theory has been taken in to consideration and applied to prevent the jamming attack in CR network. The selection of decision is based on Q learning approach to mitigate the jamming nodes using the optimal MDP decision process

• Corrosion Science and Technology
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• 제21권4호
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• pp.250-257
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• 2022

Transition metal sulfide materials have emerged as a new anode material for Li secondary batteries owing to their high capacity and rate capability facilitated by fast Li-ion transport through the layered structure. Among these materials, niobium disulfide (NbS₂) has attracted much attention with its high electrical conductivity and high theoretical capacity (683 mAh g^-1). In this study, we propose a facile synthesis of Fe_xNbS₂/C composite via simple ball milling and heat treatment. The starting materials of FeS and Nb were reacted in the first milling step and transformed into an Fe-Nb-S composite. In the second milling step, activated carbon was incorporated and the sulfide was crystallized into Fe_xNbS₂ by heat treatment. The prepared materials were characterized by X-ray diffraction, electron spectroscopies, and X-ray photoelectron spectroscopy. The electrochemical test results reveal that the synthesized Fe_xNbS₂/C composite electrode demonstrates a high reversible capacity of more than 600 mAh g^-1, stable cycling stability, and excellent rate performance for Li-ion battery anodes.

• Journal of Forest and Environmental Science
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• 제26권3호
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• pp.161-170
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• 2010

A study was conducted for indentifying the floral biodiversity of woody species by calculating four diversity indices using data collected from 4 stands of different age groups and disturbance regimes in two areas of Madhupur tract. Results showed that highest species diversity in the old growth secondary coppice forest (>60 years) under moderate anthropogenic disturbances of Madhupur National Park area (delete (D=0.74, H'=3.36) followed by old growth secondary forest stands (>40 years) under moderate disturbances at Bhawal National Park area (D=0.65, H'=2.81). Plant species diversity of the young enrichment plantations (<20 years and <15 years) under high anthropogenic disturbances in both the areas are much low (D=0.54 and H'=2.16 and D=0.52 and H'=1.92 respectively), which indicate high anthropogenic disturbances coupled with introduction of invasive exotics that are rival for endemic species are detrimental for conservation of biological diversity of tropical moist deciduous forests of Madhupur tract in Bangladesh.