• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.79.2-79.2
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• 2011

플라이 휠 에너지 저장장치(Flywheel Energy Storage System: FESS)는 전기 에너지를 회전 운동 에너지로 저장하였다가 필요시 회전 운동에너지를 전기 에너지로 변환하여 재사용 가능한 에너지 저장장치 이다. 최근 전력 변환 기술의 발전으로 인하여 플라이휠 에너지 저장 장치의 에너지 입출력 속도가 빨라지고 대용량의 에너지를 저장할 수 있게 되었다. 본 논문에서는 이러한 플라이휠 에너지 저장 장치의 전력 입출력 특성을 이용하여 전력 시스템에서 발생하는 저주파 진동(Low frequency oscillation)을 억제하는 방안을 제시 하여 안정도를 향상 시키고자 하였다. 전력 시스템은 발전조건, 전송조건, 부하조건에 따라 동작 조건이 지속적으로 변하고 있다. 이러한 동작 환경 변화는 전력 시스템에 대한 수학적인 표현과 실제 전력계통간의 차이가 발생하기 때문에 정확한 제어 목적을 달성하기가 힘들다. 따라서 본 논문에서는 제어기 설계 단계에서 전력 계통의 불확실성을 고려할 수 있는 $H_{\infty}$ 제어 기법을 이용하여 플라이휠 에너지 저장장치를 위한 강인 제어기를 설계 하였다. 제안한 플라이휠 에너지 저장장치의 강인 제어기의 유용성을 입증하기 위하여 1기 무한대 모선에 적용한 결과를 비선형 시뮬레이션을 통하여 다양한 외란이 발생한 경우에 외란 억제 성능과 강인성에 대하여 고찰 하였으며, 제안한 방식이 기존의 전력계통 안정화 장치(Power system stabilizer: PSS) 보다 효율적이며 전력계통의 안정도 향상에 크게 기여함을 보이고자 하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.12
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• pp.1220-1226
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• 2012

This paper proposes a novel type of tactile device utilizing magnetorheological(MR) fluid which can be applicable for haptic master of minimally invasive surgery(MIS) robotic system. The salient feature of the controllability of rheological properties by the intensity of the magnetic field(or current) makes this potential candidate of the tactile device. As a first step, an appropriate size of the tactile device is designed and manufactured via magnetic analysis. Secondly, in order to determine proper input magnetic field the repulsive forces of the real body parts such as hand and neck are measured. Subsequently, the repulsive forces of the tactile device are measured by dividing 5 areas. The final step of this work is to obtain desired force in real implementation. Thus, in order to demonstrate this goal a neuro-fuzzy logic is applied to get the desired repulsive force and the error between the desired and actual force is evaluated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.8
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• pp.636-645
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• 2012

The performance of various type plate exchangers with different chevron angle, dimple size and arrangement was analysed by using Ansys v13.0. Heat transfer performance, pressure drop and flow patten of plate heat exchanger were investigated according to mass flow ratio investigated and compared. As a result, the $60^{\circ}$-chevron type plate heat exchanger showed the highest heat transfer performance but pressure drop was relatively high. The efficiency of $45^{\circ}$-chevron type plate heat exchanger showed the best performance in considering of heat transfer performance and pressure drop simultaneously. Among dimple type plate heat exchangers, the highest heat transfer performance was shown in a dim_zigzag type plate heat exchanger but pressure drop was very high. Besides, the dim_upsize plate heat exchanger showed very low pressure drop.

• The Korean Journal of Ceramics
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• v.7 no.2
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• pp.58-62
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• 2001

The relationship between the addition of Sb$_2$O$_3$ and the color difference by solarization in photosensitive glasses was investigated. Glasses containing CeO$_2$ and Sb$_2$O$_3$ simultaneously and glasses with only CeO$_2$ were changed reddish and yellowish respectively after exposing to ultra violet ray. Color difference between compositions was represented by dominant wavelength and purity. Since, in glasses containing CeO$_2$ and Sb$_2$O$_3$ simultaneously, Sb$_2$O$_3$ as reduction agent affected Ce$^3+$ ions to increase in glass and more Ce$^4+$ ions were induced than in glasses with only CeO$_2$ during UV irradiation, more electrons released by photo-ionization, which were color centers, were trapped by Ce$^4+$. In conclusion, the introduction of Sb$_2$O$_3$ to photosensitive glasses with CeO$_2$ resulted in the change of color center concentration in glasses and prevented the solarization of photosensitive glasses with CeO$_2$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.511-517
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• 2003

An experiment is conducted to investigate the effect of air and water mass flow rates on cooling characteristics of mist impinging jet on a flat plate. The air mass flow rate ranges from 0.0 to 3.0 g/s, and water mass flow rates from 5.0 to 20.0 g/s. An air-atomizing nozzle is used fur the purpose of controlling air and water mass flow rates. The test section is designed distinctively from previous works to obtain local heat transfer coefficient distributions. Heat transfer characteristics of the mist impinging jet are explained with the aid of flow visualization. Surface temperature and heat transfer coefficient distributions become more uniform as air mass flow rate increases. The water flow rate provides substantial contribution to enhancement of cooling performance. On the other hand, The air mass flow rate weakly influences the averaged heat transfer rate when the water mass flow rate is low, but the averaged heat transfer rate Increases remarkably with the air mass flow rate in case of the high water mass flow rate.

• Journal of Environmental Science International
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• v.12 no.2
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• pp.101-109
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• 2003

Yangdong village is located at Kangdong-myun, Kyungju, Kyungsangbuk-do, Korea. There are two major families, the Sons of Wallsung beginned from Son, So(1433∼1484) and the Lees of Yeohkang the descendant of Lee, Unjeok. They are lived together under check and help for 500 years. The village located on the hill of Ankang plain. There are Homyung mountain and Sonaiu peak in front of it and Solchang mountain on the back. 47 shaped ridges form Blue dragon to the east, and White tiger to the west. Ahnrockchon flows from north Joined Hyungsan river and flows into Youngilman. Therefore the village is located at mountain on it's back and along with stream. Buildings are deployed on the valley between hills, it is not easily detected, but it give it's atmosphere of mountain village. Village location and space composition combined with natural environment, folk belief, feng-shui, and social system of confucianism. Blended buildings affected between ruling and ruled classes or among different families shown environmental design accomplishing united cultural space. The prospect of Yangdong village, a mountain village, expressed two sides of visible scenery of open inside and invisible from outside. Observation point such as head family house, pavilion, and village school are deployed at the point taking bird's-eye view, which striving mental stability.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.12-14
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• 2005

Inductively Coupled Plasma Chemical Vapor Deposition(ICP-CVD)를 이용하여 공정온도 $150^{\circ}C$에서 Nanocrystalline silicon (nc-Si) 박막을 증착하였다. 실험에서 헬륨(He)가스, 수소($H_2$)가스 그리고 헬륨(He)과 수소($H_2$)의 혼합가스로 희석한 사일렌($SiH_4$)을 반응가스로 이용하였다. 이 혼합가스는 3sccm의 사일렌($SiH_4$)에 헬륨(He)과 수소($H_2$)의 주입율을 20sccm에서부터 60sccm까지 변화시켜 조건을 달리하여 사용했다. 증착한 Nc-Si 박막을 X-ray diffraction (XRD)으로 분석하여 각각의 조건에 대한 Nc-Si 박막의 속성을 연구하였다. 헬륨(He) 또는 수소($H_2$) 혼합가스의 주입율이 커지면서 <111>과 <222>의 최고점(peak)이 더 높아졌으며 결정화 되지 않고 비결정질로 남아 있는 성장층(incubation layer)이 얇아졌다. 이 결과는 nc-Si를 증착할 때 사용한 수소($H_2$) 플라즈마와 헬륨(He) 플라즈마의 효과로 설명할 수 있다. 실험을 통해 ICP-CVD로 증착한 nc-Si 박막을 박막 전계효과트랜지스터 (TFT)에서 우수한 특성의 전자수송층(active layer)으로 사용할 수 있는 것을 확인하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.573-576
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• 2012

We have analyzed the induction effects by separation distance between the power feeding station and the telecommunication cables. To do this we measured the induced voltage in 11 sections(10km) between Jangseong and Imgok at Jeon-nam province using telecommunication cable installed nearby KTX's feeder line. Sub-section has about 1km length of telecommunication cable. And we used normalization method in installed length of telecommunication cables and mutual inductance to analysis the induction effects more rationally.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.215-218
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• 2011

VoIP(Voice over Internet Protocol) 서비스는 기존의 음성전화 서비스(Public Switched Telephone Network, PSTN)와 달리 IP 프로토콜을 이용한 저렴한 통신비용 등의 장점이 있는 음성통신 기술로써, 기존의 아날로그 음성전화 서비스를 대신하는 서비스이며, 새로운 인터넷 융합서비스로 많은 사용자가 이용하고 있다. 하지만 VoIP 서비스가 인터넷망을 이용함으로 IP Spoofing, DoS (Denial of Server) / DDoS(Distributed Denial of Service), 등의 여러 가지 보안의 문제점을 가지고 있다. VoIP 서비스에서 DDoS 공격은 Proxy 서버 등에 대량의 공격 메시지를 보냄으로써 서버의 자원을 고갈시켜 정상적인 서비스를 하지 못하게 한다. DoS, DDoS 공격 중 Invite Flooding 공격은 1분에 수천 개의 Invite 메시지를 보내 회선의 자원을 고갈시키는 공격이다. 특히 IP/Port 위조하여 공격 경우 공격 패킷 탐지하기 어려우므로 차단할 수 없다. 따라서 본 논문에서는 VoIP의 DoS/DDoS 중 하나인 Invite Flooding 공격 시 SIP Proxy Server에서 메시지 분산시키는 방법과 MAC Address와 사용자 번호 등 IP 이외의 고정적인 사용자 정보를 확인하여 공격을 탐지하고, 공격 Agent에 감염된 Phone을 공격차단서비스로 보내 복구시키는 방법을 제안한다.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.52-62
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• 1990

Cationic polycarbonate type polyurethane was prepared from the quaternization reaction of N-methyldiethanolamine(MDEA) in urethane backbone which was obtained from the reaction of polycarbonate polyol, MDI and MDEA(chain exetender). Tensile strength and modulus of the cationic urethane resins were increased sharply with increasing the ionic content in urethane backbone. But hydrolysis resistance was decreased with increasing ionic contents. The selectivity of the cationic polycabonate urethane membrane for water/ethanol separation by pervaporation was about 20. The carrier mediated transport mechanism was considered the most probable separation mechanism for these membranes.