• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.1-7
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• 2006

A reaction mechanism of methane partial oxidation, which consists of thermal and plasma chemistry reaction pathways, has been investigated using with an arc-jet reactor. The reaction zone of the arc-jet reactor is spatially separated into thermal and non-thermal plasma zone. Methane conversion rates, selectivity of $H_2$ and $C_2$ chemicals in each zone are obtained, which reveals clearly different characteristics of reaction pathways depending on the temperature conditions. The conversion rates obtained in thermal plasma zone is higher than those in non-thermal plasma zone. The selectivity, however, obtained in non-thermal plasma zone is significantly higher than those in thermal plasma zone. Further parametric study on $O_2/C$ ratio, arc length and SED shows that the present process is mainly governed by thermal chemistry pathways.

• Journal of the Korean Society of Safety
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• v.23 no.4
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• pp.7-12
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• 2008

This study proposes integrity evaluation method of weld zone in titanium using titanium distance amplitude characteristics curve(TDACC) and ultrasonic signals. For these purposes, the ultrasonic signals for porosity defects of weld zone in titanium are acquired in the type of time series data and echo strength. 4 lines in the DACC indicated damage evaluation standard of weld zone in titanium. The acquired ultrasonic signals agree fairly well with the measured results of reference block and sensitivity block(defect location, bean1 propagation distance, echo strength, etc). The proposed TDACC in this study agree fairy well with the measured results of weld zone in titanium(weld defects as porosity). The proposed TDACC in this study can be used for integrity evaluation of weld zone in titanium.

• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.493-497
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• 2020

Hazardous area classification is designed to prevent chemical plant explosions in advance. Generally, the duration of the explosive atmosphere is used for zone type classification. Herein, IEC code, a quantitative zone type classification methodology, was used to achieve Zone 2 NE, which indicates a practical non-explosion condition. This study analyzed the operating pressure of a vessel handling propane to achieve Zone 2 NE by applying the IEC code via MATLAB. The resulting zone type and hazardous area grades were compared with the results from other design standards, namely API and EI codes. According to the IEC code, the operating pressure of vessels handling propane should be between 101325-116560.59 Pa. In contrast, the zone type classification criteria used by API and EI codes are abstract. Therefore, since these codes could interpret excessively explosive atmospheres, care is required while using them for hazardous area classification design.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.407-409
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• 2011

최근 Smart Phone에서 WiFi Zone의 활용도가 증가되고 있다. WiFi Zone의 무선 인터넷은 무선이 가지고 있는 취약점을 그대로 가지고 있기 때문에 보안에 대한 취약점이 존재하고 침해사고에 대비한 연구가 필요하다. 본 논문에서는 WiFi Zone에서 암호가 설정된 무선 AP의 패킷을 수집하여 분석하고, 해당 무선 AP의 access 암호를 알아낸다. 암호분석과 WiFi Zone의 취약점을 분석하여 War Driving 기술을 사용하여 무선 인터넷의 취약점을 분석하고, 무선 AP에 대한 공격과 ARP Spoofing 공격을 하여 해당 무선 AP를 마비시키거나 위장 무선 AP를 설정하여 정보를 취득 하였다. 본 논문 연구를 통하여 Smart Phone과 무선 네트워크 보안성을 강화하는 연구 자료로 사용할 것이다.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.221-227
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• 2008

The proposed zone-based self-organized clustering broadcasts neighbor information to only a zone with the same ID. Besides, the zone-based self-organized clustering with unique IDs can communicate securely even if the state transition of nodes in zone-based self-organized clustering is threatened by corrupted nodes. For this security, the Byzantine agreement protocol with proactive asynchronous verifiable secret sharing (AVSS) is considered. As a result of simulation, an efficiency and a security of the proposed clustering are better than those of a traditional clustering. Therefore, this paper describes a new and extended self-organized clustering that securely seeks to minimize the interference in mobile ad hoc networks (MANETs).

• Economic and Environmental Geology
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• v.32 no.5
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• pp.519-535
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• 1999

Precambrian metasedimetay rocks in the Sunchang Shear Zone (so-called Seologri and Yongamsan Formation) consist of black slate, phylite, mica schistm quartzite and rarely calc schist. The metamorphic rocks in the area have undergone at least three stages of metamorphism, which are two prograde (M1 and M2) and one contact metamorphism (M3). The metamorphism which made the most prevailing mineral assemblages in the area, is M2 stage metamorphism. The metamorphic grade of M2 methamorphism in metapelites increases from the Chlorite zone through Biotituzone, Garnet zone to Staurolite zone. The M1 stage metamorphism is recognized by kyanite and sillimanite pressure type regional metamorphism. The M3 stage methamorphism is represented in the contact boundary, which area is the chlorite zone and biotite zone near the Sunchang foliated granite and the namwon granite. The M3 stage methamorphism is characterized by andalusite bearing mineral assemblages. The peak temperature condition of M2 metamorphism estimated from coexising garnet and biotite (Kretz, 1990) is 518~598$^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.4
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• pp.233-239
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• 1992

A study of the precipitation process of Al-Li binary alloy at low ageing temperature has been carried by electrical resistivity measurement. Two types of G.P.zones were formed during ageing at low temperature. G.P. (1) zone and G.P. (2) zone have been formed primarily at ageing temperature below $60^{\circ}C$ and at ageing temperature range of $80^{\circ}C$ to $100^{\circ}C$, respectively. Therefore the precipitation process of Al-Li binary alloy was as follows; G.P.(1) zone ${\rightarrow}$ G.P.(2) zone ${\rightarrow}{\delta}^{\prime}{\rightarrow}{\delta}$ G.P. (1) zone might be affected by excess vacancies, but G.P. (2) zone might be affected by secondary defects. clusters and Li-vacancy pairs. The activation energy for formation of G.P. (2) zone is 0.87eV. It is lower than that of Al-Cu alloy.

• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.28-32
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• 2011

This research was carried out to examine the ultrasonic properties of $Phyllostachys$ $bambusoids$ Sieb et Zucc depending on three directions for providing the fundamental properties of the Korea traditional flute, Daekeum. The ultrasonic properties of $Phyllostachys$ $bambusoids$ Sieb. et Zucc were found to be different from those of wood, because of the distinctive anatomical structure of bamboo tissue. The ultrasonic velocity of peripheral zone showed higher values of all three directions. The ratio of longitudinal velocities to perpendicular velocities showed 1.16 at peripheral zone, 1.70 at central zone, 1.38 at inner zone respectively. The ratio of radial velocities to tangential velocities were measured as 1.286 at peripheral zone, 1.325 at central zone, 0.829 at inner zone respectively.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.331-338
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• 2005

The grain structure, dislocation density and second phase particles in various regions including the stir zone(SZ), thermo-mechanically affected zone(TMAZ), and heat affected zone(HAZ) of a friction stir weld 6.35mm thick aluminum 7075-T651 alloy were investigated and compared with the base metal. The microstruectures of nugget zone were compared according to tool rotation speeds and tool transition speeds. The hardness profiles of nugget zone were increased, while decreasing rotation speed and increasing welding speed. The optimal microstructure was gained at the low rotation speed 800rpm and th high welding speed 124mm/min. The nugget microstructures of fracture surface, transgranular dimple and quasicleavage type were showed different fracture type with the HAZ, shear fracture type.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.161-167
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• 2004

Zone 3 of the distance relay is used to provide the remote back-up protection in case of the failure of the primary protection. However, the risk lot mal-operations under stressed conditions such as heavy loading, voltage and transient instability is usually high. Zone 3 is used in combination with the derivatives of the voltage, and current, etc to prevent mal-operations. Sometimes, the impedance characteristics that restrict the tripping area of relay are used to avoid the mal-operations due to load encroachment. This paper presents a novel Zone 3 scheme based on combining the steady-state components (i.e. 60Hz) and the transient components (TCs) using a state diagram that visualizes the sequence of studies that emanate from the sequence of events. The simulation results show that the novel zone 3 distance relay elements using the proposed method operates correctly for the various events.