• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.114-118
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• 2016

In this paper, we present the advanced open collector circuit, interface circuit between aerospace electronics. Satellite is composed of a number of electronics, which were provided from various manufacturers. Each company manufactured its own electronics for satellite using its heritage and requirements for their electronics. Therefore each electronics may use different internal supplies. It make a problem between electronics because the supply is different from other electronics, such as the increasing of power dissipation because of the static current and the mismatch of interface voltage, the offset. Proposed circuit can reduce the static current and rising time, and also decrease the useless power dissipation caused by the static current for open collector circuit

• Journal of Biosystems Engineering
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• v.10 no.1
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• pp.54-68
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• 1985

It is desirable to collect the solar thermal energy at relatively high temperature in order to minimize the size of thermal storage system and to enlarge the scope of solar thermal energy utilization. So far the concentrating solar collector has been developed to collect solar thermal energy at relatively high temperature, but it has some difficulties in maintaining the volumetric body of solar collector for long term utilization. On the other hand, the flat-plate solar collector has been developed to collect the solar thermal energy at low temperature, and it has advantages in maintaining the system for long term utilization, since it's thickness is thin and not volumetric. In this study, to develop a solar collector that has both advantages of collecting solar thermal energy at high temperature and fixing conveniently the collector system for long term period, a cylindrical parabolic concentrating solar collector was designed, which has two rows of parabolic reflectors and thin thickness such as the flat-plate solar collector, maintaining the optical form of concentrating solar collector. The characteristics of the concentrating parabolic solar collector newly designed was analysed and the results are summarized as follows; 1. The temperature of the air enclosed in solar collector was all the same as $50^{\circ}C$ in both cases of the open and closed loop, and when the heat transfer fluid was not circulated in tubular absorber, the maximum surface temperature of the absorber was $118-120^{\circ}C$, this results suggested that the heat transfer fluid could be heated up to $118^{\circ}C$. 2. In case of longitudinal installation of the solar collector, the temperature difference of heat transfer fluid between inlet and outlet was $4^{\circ}-6^{\circ}C$ at the flow rate of $110-130{\ell}/hr$, and the collected solar energy per unit area of collector was $300-465W/m^2$. 3. The collected solar energy per unit area for 7 hours was 1960 Kcal/$m^2$ for the open loop and 220 Kcal/$m^2$ for the closed loop. Therefore it is necessary to combine the open and closed loop of solar collectors to improve the thermal efficiency of solar collector. 4. The thermal efficiency of the solar collector (C.P.C.S.C.) was proportional to the density of solar radiation, indicating the maximum thermal efficiency ${\eta}_{max}=58%$ with longitudinal installation and ${\eta}_{max}=45%$ with lateral installation. 5. The thermal efficiency of the solar collector (C.P.C.S.C.) was increased in accordance with the increase of flow rate of heat transfer fluid, presenting the flow rate of $110{\ell}/hr$ was the value of turning point of the increasing rate of the collector efficiency, therefore the flow rate of $110{\ell}/hr$ was considered as optimum value for the test of the solar collector (C.P.C.S.C.) performance when the heat transfer fluid is a liquid. 6. In both cases of longitudinal and lateral installation of the solar collector (C.P.C.S.C.), the thermal efficiency was decreased linearly with an increase in the value of the term ($T_m-T_a$)/Ic and the increasing rate of the thermal efficiency was not effected by the installation method of solar collector.

• Journal of Bio-Environment Control
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• v.5 no.1
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• pp.57-64
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• 1996

To use effectively the solar energy in greenhouse heating, a high performance solar collector should be developed. And then the size of the solar collector and thermal storage tank should be determined through the calculation of heating load. The solar collector must be set in the optimum tilt angle and direction to take daily solar radiation maximally, and the flow rate of heat transfer fluid through the solar collector should be kept in the optimum range. In this research, the performance tests of a capillary tube solar collector were performed to determine the optimum water flow rate and the results summarized as follows. 1. The regressive equations for efficiency estimations of the capillary tube solar collector in the open loop were modeled in the water flow rate of 700-l,000 $\ell$/hr. 2. The optimum water flow rate of the solar collector was estimated by the second order polynomial regression and the maximum efficiency was 80% at the water flow rate of 850 $\ell$/hr. 3. The solar thermal storage system consisted of a capillary tube solar collector and a water storage tank was tested at the water flow rate of 850 $\ell$/hr in the closed loop, and obtained the solar thermal storage efficiency of 55.2%. 4. As the capillary tube solar collector engaged in this experiment was made of non-corrosive polyolefin tubes, its weight was as light as 1/30 of the flat plate solar collector made of copper tubes. Therefore it was considered to be suitable for the greenhouse heating system.

• Journal of Korea Multimedia Society
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• v.17 no.8
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• pp.988-994
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• 2014

Software Defined Network (SDN) is a new technology in computer network area which enables user to centralize control plane. The security issue is important in computer network to protect system from attackers. SYN flooding attack is one of Distributed Denial of Service attack methods which are popular to degrade availability of targeted service on Internet. There are many methods to protect system from attackers, i.e. firewall and IDS. Even though firewall is designed to protect network system, but it cannot mitigate DDoS attack well because it is not designed to do so. To improve performance of DDOS mitigation we utilize another mechanism by using SDN technology such as OpenFlow and sFlow. The methodology of sFlow to detect attacker is by capturing and sum cumulative traffic from each agent to send to sFlow collector to analyze. When sFlow collector detect some traffics as attacker, OpenFlow controller will modify the rule in OpenFlow table to mitigate attacks by blocking attack traffic. Hence, by combining sum cumulative traffic use sFlow and blocking traffic use OpenFlow we can detect and mitigate SYN flooding attack quickly and cheaply.

• Architectural research
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• v.18 no.2
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• pp.75-82
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• 2016

To secure the anticorrosive performance of structures in the oceanic environment it is necessary to select appropriate finishing materials and thickness of cover. However, airborne chloride deposition varies depending on the collector used, and it is difficult to select appropriate finishing materials. For this reason, an eight-directional collector is proposed in this study through reviewing the differences between existing airborne chloride collectors and the new one. To analyze airborne chloride deposition according to the direction from which it flows and verify the performance of the collector proposed in this study, airborne chlorides were deposited on the collector for one year at five different locations in an oceanic environment. From the experiment, it was verified that in terms of direction, there were differences in airborne chloride deposition of up to more than 1.5 times. Based on these research findings, the anti-corrosive method applied can be different for each side of a building's structure, and this is believed to serve as an effective and systemic chloride resistance design.

• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.5
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• pp.1-6
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• 1977

When the input of synchronizer which is used for the purpose of synchronizing the master clock of computer with the interrupt system, a sort of random variable device, is gated with asynchronous intersection of the fall time of the master clock and the risetime oi the interrupt request, synchronizer is drived in Metastable region. This paper is presented circuit analysis of Metastable phenomena and analysis for transient process from metastable point to stable state, and also realities the collect logic with Inverter and open collector methods with a view to improving logic failure caused by the mishappen phenomena.

• KIEAE Journal
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• v.3 no.3
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• pp.19-25
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• 2003

The Address No.0 of Eco-friendly Architecture offers unique experience for those who visit the place to envisage the future architecture where nature, human and building exist in harmony. It is open to the general public including the students of elementary and secondary schools. This house has been built to provide opportunities for the general public to experience eco-friendly architecture. It's floor area is 42 pyung($140m^2$) and the overall site has the area of 180 pyung($600m^2$). The following illustrates some of its prominent features : ${\bullet}$ Remodeling of a traditional Korean residence ${\bullet}$ Application of passive solar systems ${\bullet}$ Use of clerestory windows and daylighting systems(washroom and machine room) ${\bullet}$ Operation of solar water heaters with flat plate collectors ${\bullet}$ Construction of Biotop(small ecological world) ${\bullet}$ Water circulation for Biotop by photovoltaic(150W) and wind power(400W) generation ${\bullet}$ Outdoor hot water supplied by all-glass evacuated solar tubes. Through this Address No.0 of Eco-friendly Architeture conclusions are as followings. 1. The array of tubes in collector has the best nice in that the number of tube is nine and the tilt angle is the latitude $+20^{\circ}$. 2. The thermal performance of the all-glass solar vacuum collector was excellent than of the flate-plate solar collector. 3. The adaption of new small wind power systems to buildings were proved to produce a profit if it is considered the expense of environment improvement and the wind speed increasing according to rise of building hight.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.26-30
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• 2013

The purpose of this study is to find risk factors by analyzing the operation principle of a photo coupler (P/C) used to remove the noise of electronic devices and establish a base for the performance improvement of developed products. It was found from the P/C circuit analysis of normal products that they were equipped with an electrolytic condenser of $0.1{\mu}F$ to smooth system signals. Due to the epoxy resin packing the external part of the P/C, this study experienced a limit to visually examine the damage to it. It could be seen from the analysis of electric characteristics of the P/C that the forward voltage ($V_f$) and reverse current ($I_r$) were 1.3 V and 10 uA, respectively. In addition, it is required that the breakdown voltage (VCE) between the collector (C) and emitter (E) be maintained at less than 35 V. The and of the damaged product #1 were comparatively good. However, the measurement of was 100.0 uA. From this, it is thought that a short circuit occurred to the internal circuit. Moreover, from the fact that the of the damaged product #2 was open circuit and the measurement of was 0.0 uA, it is thought that the collector and emitter was separated or insulation resistance was significantly high. Furthermore, from the fact that the of the damaged product #3 was open circuit and the measurement of was 0.0 uA, it is thought that the space between the collector (C) and emitter (E) failed to meet the design standard or that they were separated. Therefore, it is thought that fabricating the P/C by increasing the reverse current 10 mA to 50 mA will prevent its malfunction.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.56-64
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• 2004

A numerical study have been performed on a cavity with one heat source by the open ratio and tilt angle. The goal of this study is to get the information for designing a solar collector absorber. semi-conductor equipment and block heater and so on. The parameters for this study is the various open ratio. and tilt angle of the cavity and Rayleigh numbers The finite volume method with SIMPLE computational algorithm are used and calculated the heat transfer in the cavity. As a result, the heat trans(or was promoted by increase of Rayliegh numbers and open ratios But, the heat transfer was not promted at lower wall of cavity because the flow pattern are very small at lower space in the cavity(Or=0.1) As the Rayleigh number is increased the mean nusselt numbers are increased at inside wall.

• Solar Energy
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• v.12 no.1
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• pp.95-102
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• 1992

A small scale solar collector system composed of a Fresnel lens of $0.5m^2$ area as a solar concentrator and a compact fluidized-bed solar receiver was developed. Performance and temperature distribution in the fluidized bed receiver were measured using SiC for particles and air for working fluid. The maximum gas temperature was attained up to 1250K at this moment. In this study, energy efficiency achieved by the present experiment was high for the small scale solar collector system and compact receiver.