• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.691-700
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• 2003

어디서나 접속할 수 있는 인터넷의 광역성과 최근 들어 인터넷을 통한 전자상거래의 급진전, 네트웍을 통한 다양한 형태의 원격 접속 확대 등으로 이제 많은 기업들이 통신비가 상대적으로 저렴하면 서도 기밀성이 보장되는 인터넷을 기반으로 하는 Internet Protocol Virtual Private Network(IP VPN) 도입을 서두르고 있다 VPN은 공중망 인프라를 공유하여 구축된 가상 사설망을 의미한다. IP VPN으로 기업은 본사와 지사를 연결하는 Intranet, 협력사와 연결되는 Extranet 그리고 최근 들어 급증하고 있는 이동 근무자와 재택 근무자를 회사에 안전하게 연결시킬 수 있는 원격 접속 등을 경제적으로 구축할 수 있다. 또한 광케이블과 동축케이블이 혼합된 Hybrid Fiber & Coaxial(HFC)망이 초고속인터넷, 디지털방송, 주문형비디오(VOD) 등의 멀티미디어 서비스를 수용하기에 가장 좋은 방안으로 최근 각광을 받고 있다. HFC망은 기존의 CATV망을 기반으로 하므로 신규 투자비가 적게 들면서도 다양한 형태의 고속 데이터 통신이 가능하다. 이에 본 논문에서는 HFC망에서의 IP VPN의 성능을 전송 프로토콜과 암호화 알고리즘을 달리 하면서 어떤 요소가 성능에 얼마나 영향을 주는지와 요소간 상호작용이 어떻게 일어나는지, 또한 어떤 조합으로 VPN 통신을 할 때 가장 좋은 성능을 보이는지를 비교 분석한다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.284-285
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• 2007

In this paper, we present the effect on a novel transmission line filter response by the etch hole position on the suspended ground and the residue on the resonator under ground plane. We defined the etch hole offset as the distance from the sidewall of the suspended ground to the nearest side of the etch holes. We simulated new filter responses to reflect the real value of the changed etch hole offset caused by characteristics of negative photoresist. Return loss is distorted by the residue on the center conductor remained after sacrificial layer removing. By comparison of simulation and measurements, we concluded the residue on the resonator distorted the RF response worse than etch hole offset variation did.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.135-140
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• 2006

The stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition has been studied experimentally. The objectives are to explain the phenomenon of a liftoff height decreasing as increasing fuel velocity and to reveal the mechanisms of flame stability Hydrogen was varied from 100 to 300 m/s and a coaxial air was fixed at 16 m/s with a coflow air less than 0.1 m/s. The technique of PIV and OH PLIF was used simultaneously with CCD and ICCD cameras. It was found that the liftoff height of the jet decreased with an increased fuel jet exit velocity. The leading edge at the flame base was moving along the stoichiometric line. Finally we confirmed that the stabilization of lifted hydrogen diffusion flames is related with a turbulent intensity, which means combustion is occurred where the local flow velocity is equal to the turbulent flame propagation velocity.

• Journal of the Korean Society of Visualization
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• v.6 no.1
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• pp.59-65
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• 2008

Distribution of spray was measured. Optical Line Patternator (OLP) was used to measure the planar distribution of the spray from a swirl-coaxial type injector. Ambient pressure was varied and injection pressure was fixed in experiment. As ambient pressure increased, spray distribution was changed from hallow cone to solid cone shape, and spray angle was decreased. Limitation in measuring dense spray was found at high ambient pressure condition.

• Bulletin of the Korean Chemical Society
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• v.21 no.4
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• pp.405-411
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• 2000

Electrochemical and spectroelectrochemical studies of cobalt-Schiff (Co-SB) base complexes, Co(salen) [N-N'-bis(salicylaldehyde)-ethylenediimino cobalt(II)] and Co(salophen) [N-N'-bis(salicylaldehyde)-1,2-pheny-lenediimino cobalt(II)], have been c arried out to test them as oxygen reduction catalysts. Both compounds were found to form an adduct with oxygen and exhibit catalytic activities for oxygen reduction. Comparison of spec-tra obtained from electrooxidized complexes with those from Co-SB complexes equilibrated with oxygen in-dicates that the latter are consistent with the postulated complex formed with oxygen occupying the coaxial ligand position, namely, Co(III)-SB·O2 - .The catalysis of oxygen reduction is thus achieved by reducing Co(III) in the oxygen-Co-SB adduct, releasing the oxygen reduction product, e.g., O2 - ., from the Co(II)-SB complex.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.229-234
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• 2004

The objective of the present study is to conduct model combustion tests for double swirl coaxial injectors to identify their combustion stability characteristics. Gaseous oxygen and mixture of methane and propane have been used as simulant propellants. Two model chambers tuned to the If acoustic resonance mode of a full-scale thrust chamber were manufactured to be used as a combustion cylinder. The main idea of the experiment is that the mixing mechanism is considered as a dominant factor significantly affecting combustion instability in a full-scale thrust chamber. Self-excited dynamic pressure values in a model chamber show different combustion stability zones with respect to a recess number. Upon test results, couplings between combustion conditions and the IT acoustic resonance mode become strengthened with the increase of a recess length.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.326-330
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• 2011

Development and validation of performance analysis model for dual combustion ramjet engines has been performed. A typical performance model for hypersonic intake flow and supersonic mixing and combustion was demonstrated; Taylor-Maccoll equation for coaxial intakes and a quasi-one dimensional reacting flow analysis with CEA chemical equilibrium for supersonic combustion. The results, thermodynamic data of intake and supersonic combustor were validated with CFD numerical results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.69-72
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• 2011

Hot-firing tests were performed on the third sub-scale gas generator for development of a 75 ton-class liquid rocket engine. This paper deals with the analysis results of low-frequency combustion instabilities that were encountered during combustion tests of the gas generator. The low-frequency pressure fluctuations seem to be related to chamber pressure and pressure drops through oxidizer/fuel injectors.

• Smart Structures and Systems
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• v.7 no.4
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• pp.319-328
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• 2011

In this study, the measurements of the dielectric constants of soil at 900 MHz and 1 GHz were made to relate those properties to the moisture content of the soil. This study's intention was to use the relationship between the dielectric constant and the moisture content to develop a landslide prediction system. By monitoring the change of the moisture content within the soil using ground penetrating radar (GPR) systems in the field, the possibility of a landslide is expected to be detected. To establish a database for the dielectric constants and the moisture content, the measurements of soil samples were made using both an open-ended dielectric coaxial probe and the GPR. Based on the measurement results, correlations between the GPR and reflector for each frequency at 900 MHz and 1 GHz were found for the dielectric constants and the moisture content. Finally, the mechanism of the measurement device to be implemented in the field is suggested.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.65-69
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• 1989

Mather type dense plasma focus device was develooped for the feasibili쇼 study in its application to the x-ray lithography. To etermine the electrical characteristics,the temporal begavior of the discharge current and the voltage was measured by using the Rogowski coil and the high voltage probe respectively. The results are 9 $\mu\textrm{s}$ of the period, 18m$\Omega$ of resistance and 0.16$\mu$Η of inductance. The average current sheath velocity was measured by the light signal emitted at the moving plasma sheath. The light signal was detected through two fiber bundles. When the applied voltage was 13 kV and the initial jpressure of argon was 21.8 Pa, the best plasma focus was occurred. The x-ray emission characteristics from the plasma focus was determined by the x-ray pictures taken by pinhole camera. It is focus that the plasma was focused at 1.4 cm distant position above the center electrode and its diameter was about 1.0 m.