• Journal of Communications and Networks
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• v.17 no.3
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• pp.265-266
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• 2015

In a recent paper [1], the authors investigated the maximum stable throughput region of a network composed of a rechargeable primary user and a secondary user plugged to a reliable power supply. The authors studied the cases of an infinite and a finite energy queue at the primary transmitter. However, the results of the finite case are incorrect. We show that under the proposed energy queue model (a decoupled M/D/1 queueing system with Bernoulli arrivals and the consumption of one energy packet per time slot), the energy queue capacity does not affect the stability region of the network.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2668-2670
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• 2002

The generators of a small size below 100Kw are often used as power suppliers for emergency only in most domestic telecommunication companies. Serious twisted waves occur due to the inflow of harmonies from the generator into a S-type rectifier. And the increasing by stages of load upon the rectifier end up a stoppage of power supply during the serious hunting, which makes it difficult to supply power securely on the other part as well as that of communications. In case of long time of power failure the generators of a small size will be essential because the battery for emergency has a limit in capacity. Therefore it is necessary to solve the problems concerning the generators. This study is focused on the identifying and solving the problem including use of SCR elements connected to the generators.

• Korean System Dynamics Review
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• v.9 no.1
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• pp.125-141
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• 2008

It is very difficult to predict future demand/supply, price for resources with acceptable accuracy using regression analysis. We try to use system dynamics to forecast the demand/supply and price for nickel. Nickel is very expensive mineral resource used for stainless production or other industrial production like battery, alloy making. Recent nickel price trend showed non-linear pattern and we anticipated the system dynamic method will catch this non-linear pattern better than the regression analysis. Our model has been calibrated for the past 6 year quarterly data (2002-2007) and tested for next 5 year quarterly data(2008-2012). The results were acceptable and showed higher accuracy than the results obtained from the regression analysis. And we ran the simulations for scenarios made by possible future changes in demand or supply related variables. This simulations implied some meaningful price change patterns.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1543-1546
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• 1994

Ignitabilility of explosive gas mixture by spark of dry cell in case of short circuit by accident was studied for the purpose of evaluation of intrinsically safe characteristics of dry cell that manufactured in Korea. IEC type spark test apparatus, $21{\pm}2$ Vol% of hydrogen - air mixture, and dry cell that produced in Korea was used for the experiment. The result of this research could be used for design, manufacturing, and using the intrinsically safe electrical apparatus.

• International journal of advanced smart convergence
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• v.7 no.3
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• pp.101-109
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• 2018

In this paper, we propose an adaptive filtering scheme of connection requests for the defense of malicious energy consumption attacks against wireless computing devices with limited energy budget. The energy consumption attack tries to consume the battery energy of a wireless device with repeated connection requests and shut down the wireless device by exhausting its energy budget. The proposed scheme blocks a connection request of the energy consumption attack in the middle, if the same connection request is repeated and its request result is failed continuously. In order to avoid the blocking of innocuous mistakes of normal users, the scheme gives another chance to allow connection request after a fixed blocking time. The scheme changes the blocking time adaptively by comparing the message arriving ate during non-blocking period and that during blocking period. Evaluation shows that the proposed defense scheme saves up to 94% energy consumption compared to the non-defense case.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.61-63
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• 2005

Utility interactive photovoltaic systems is one of the most premising applications of photovoltaic systems. These systems are employed in applications where utility service is already available. In this case, there is no need for battery storage because utility power may be used to supplement photovoltaic systems when the load exceeds available PV generation. The load receives electricity from both the photovoltaic array and the utility inter-tied. In this paper, Principle and operating characteristic of Utility Interconnected Photovoltaic System is presented. For the purpose of optimal utility Inter-tied photovoltaic system design and installation. It is that demonstrate throughout the installed 3 PV system respectively, 3kW utility interconnected residential system.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.139-144
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• 2003

This study was aimed to establish failure management plan of the rubber-tired AGT light rail vehicle for its safety case, which was developed according to the Korean standardized specifications for the light rail vehicle. Vehicular 9 failure modes anticipated during the system operation were considered, which are single malfunction of redundant equipment, malfunction of train radio, public address and air compressor, battery, main circuit NFB trip, on-board ATO control device malfunction, on-board ATP control device malfunction, fail of brake release, flat tire, train emergency door open.

• Journal of Korean Institute of Industrial Engineers
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• v.13 no.1
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• pp.11-24
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• 1987

Automatic Guided Vehicle Systems feature battery powered driverless vehicles with programming capabilities for path selection and positoning. Vehicles serve the machines in shop, following a guide path system installed on the shop floor. The basic problem in the system is to determine a fixed set of vehicle routes of minimal total distance(time) while keeping capacity and distance(time) constraints. In this paper, a heuristic algorithm is presented for scheduling the automatic guided vehicles. The algorithm routes the machines based on their distances and polor coordinate angles, taking into account the structural feature of the system. Computational experiments are performed on several test problems in order to evaluate the proposed algorithm. Finally, a framework for dealing with the case where supplies from the machines are probabilistic is described.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.87-89
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• 2004

정밀화와 더불어 고품질화 되고 있는 사출성형 산업에서 CAE기술(Computer Aided Engineering)은 성형 시행오차를 줄여 원가를 절감하고, 생산성을 향상시킬 수 있는 최적의 대안이라 할 수 있다. 본 연구는 이러한 CAE 기술을 활용하여 현장에서 사출성형하기 힘든, 두께 0.3mm인 소형 RC비행기 Battery Case제품을 대상으로 유동해석을 통해 최적 Gate와 유동기구의 설계 조건을 도출하고 구현하고자 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.339-342
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• 2000

Polypyrrole(PPy) nanotubules were formed within template pores by chemical synthesis using $FeCl_3$ as an oxidant. The oxidation peak of PPy nanotubules in the cyclic voltammogram was observed at about 2.8V and 3.3V vs. $Li/Li^+$, while in the case of PPy film, that was observed at about 3.0V. It suggests that the electron hopping on the main chain of PPy nanotubules was improved. When the PPy nanotubules was used to a cathode of lithium secondary battery, we obtained discharge capacity as much as 27 mAh/g, and initial coulomb efficiency by 90%. We expect that the capacity can be improved by further study.