• Journal of KIISE:Information Networking
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• v.31 no.4
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• pp.405-413
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• 2004

Design an efficient and secure electronic payment system is important for M-Commerce. In this paper, we propose an efficient Micro-Payment Protocol that allows multiple transactions using ID-based public key cryptosystem. Current PayWord system requires to generate certificate of the vendor for each transaction. In this paper, we use a session key instead of certificate key generated by Weil Pairing which use an Elliptic Curve Cryptosystem over finite field $F_q$ for transactions Therefore, it is more secure in Known key attacks as well as Man-in-the-middle attacks.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.7
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• pp.331-338
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• 2002

An inverter-fed induction is driven by a harmonic voltage source so that it is necessary to be analysed by time-stepping F.E.M. But it takes so long time that disadvantageous to design. This paper presents a simple analysis method for inverter-fed induction motor using FEM and harmonic equivalent circuit. First, the rotor bar resistance and the leakage reactance are determinated by FEA for 1 slot region in rotor to consider the skin effect and the saturation. Secondly, the characteristic of the motor is analyzed by the harmonic equivalent circuits consisting of the obtained parameters from the FEA. This method is carried out to analyze an induction motor driven by the sinusoidal voltage and the inverter. The results are verified by comparing with those of the time-step F.E.A and the experiment.

• Journal of the Korean Solar Energy Society
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• v.23 no.2
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• pp.71-79
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• 2003

The goal of this paper is to measure and compare the performance of solar heat pump for refrigerants. To accomplish the goal, solar heat pump with aluminum roll bond type evaporator and indoor heat exchanged(condenser) was built. The test results showed that the COP and heating capacity of HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) were higher than those of HCFC-22$(CHClF_2)$. A study proved that best conditions to use heating system that is about $40m^2$ and $80m^2$. The COP range of the whole system was from 4 to 6 according to the solar collector's area variation. Hydrochlo-rofluorocarbon HCFC-22$(CHClF_2)$ is included in the compound to be controlled. HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) is the most suitable replacement HCFC-22$(CHClF_2)$ in solar heat pump application. The solar heat pump system was designed to show the best efficiency that the room temperature make $18\sim20^{\circ}C$ and $23\sim25^{\circ}C$ in Seoul during the fall season.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.453-461
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• 1999

In this paper, we have studied on the effects of annular and quadrupole illuminations by changing their conditions for enhancing the pattern resolution and depth of focus (OaF) in the optical lithography system using KrF Eximer laser 0.248$\mu$m and 0.65 NA. As a result, it is revealed that each illumination condition to optimize the resolution and the OaF for the mask containing the assistance pattern is different under the annular illumination. And in case of quadrupole illumination, we could ascertain that the resolution and the OaF would be enhanced through changing the arrangement of each pole from the conventional X type (45 degrees) to some proper type according to the main pattern direction. ction.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.1
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• pp.40-51
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• 2009

A paired many-to-many k-disjoint path cover (paired k-DPC) of a graph G is a set of k disjoint paths joining k distinct source-sink pairs in which each vertex of G is covered by a path. In this paper, we investigate disjoint path covers in recursive circulants G($cd^m$,d) with $d{\geq}3$ and tori, and show that provided the number of faulty elements (vertices and/or edges) is f or less, every nonbipartite recursive circulant and torus of degree $\delta$ has a paired k-DPC for any f and $k{\geq}1$ with $f+2k{\leq}{\delta}-1$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.198-202
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• 2005

Gas generator is the equipment to produce high enthalpy gas used to generate sufficient power to operate turbine and pump system for propellant feeding in liquid rocket engine. Since the limit in operating temperature is imposed due to turbine blade, the gas generator has to be operated at the temperature far below stoichiometric maintaining fuel rich combustion. In this research, fundamental study was performed to understand the non-equilibrium combustion process with in-house code and CFD-ACE as well.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.150-152
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• 2022

F2C(Fog-to-Cloud) 환경에서 클라우드와 포그는 긴밀하게 협업하여, 동적으로 작용하며 서비스를 제공할 수 있어야 한다. 이에 본 논문에서는 기존 클라우드/서버 컴퓨팅에서 클라우드 서버 중심의 단방향 서비스 이미지 배포대신에 레지스트리를 이용하여 클라우드, 포그, 그리고 에지까지 서비스 이미지를 배포 가능하게 하여, 동적인 서비스 상호운용이 가능한 시스템을 제안하였다. 또한, 클라우드, 포그에 레지스트리 이미지를 설치하고, 서비스 이미지 등록을 통해 서비스 배포, 실행되는 시스템을 구현하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.713-715
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• 2012

본 논문은 24GHz 차량 추돌 예방 레이더 시스템-온-칩을 위한 입력 임피던스, 전압이득 및 잡음지수를 자동으로 측정할 수 있는 새로운 형태의 고주파 자체 내부검사(BIST, Built-In Self-Test) 회로를 제안한다. 이러한 BIST 회로는 TSMC $0.13{\mu}m$ 혼성신호/고주파 CMOS 공정 ($f_T/f_{MAX}$=140/120GHz)으로 설계되어 있다. 알고리즘은 LabVIEW로 구현되어 있다. BIST 알고리즘은 입력 임피던스 정합과 출력 직류 전압 측정원리를 이용한다. 본 논문에서 제안하는 방법은 자동으로 쉽게 고주파 회로의 성능변수를 측정할 수 있기 때문에 시스템-온-칩의 저가 성능 검사의 대안이 될 것으로 기대한다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.5
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• pp.75-82
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• 1985

The fuel pump system is developed with the Model Reference Adaptive Control (M.R.A.C.) algorithm based on the Weight Least Square (W.L.S.) algorithm for the parameter Identification and the one step ahead dead-beat control with the reference model. The value of some parameters as the sampling period 7, the weighting coefficient L, and the State Variable Filter (5.V,F.) coefficient f which a(fects the system performance are selected through computer simulation. For the variation of the plante dynamics rspecially due to the change of the fuel viscosity with the ambient temperature condition, the adaptability of the control system is studied in the case of regulation and tracking.

• Membrane Journal
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• v.16 no.1
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• pp.31-38
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• 2006

The ceramic microfiltration system with periodic $N_2$-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal filtration time interval for HC04 membrane with $0.4{\mu}m$ pore size was lower value of 4 min than 16 min for HC10 with $1.0{\mu}m$ pore size at fixed back-flushing time 40 sec, trans-membrane pressure $1.0kg_f/cm^2$ and back-flushing pressure $5.0kg_f/cm^2$. From the results of TMP effect at fixed filtration time interval and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate at the highest TMP for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multi channels ceramic membranes, and the treated water could be reused in paper process.