• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.138-142
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• 2005

In this paper, a method to eliminate the polarization dependent properties of fiber-to-planar waveguide couplers using a thin half-waveplate is proposed and demonstrated. The operation principle of the device is explained and the fabrication technology is presented. It is experimentally shown that the resonance wavelengths of the device are independent of the polarization state of input light.

• Proceedings of the Korea Society for Simulation Conference
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• 2005.05a
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• pp.57-63
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• 2005

The purpose of this paper is to analyze transport ability of AGV(Automated Guided Vehicle) and SHC(SHuttle Carrier). The main difference between two types of transport vehicles is that AGV depends on container crane or transfer crane to do loading/unloading container, but SHC is very independent to it. Therefore, the transport ability of SHC is expected to be higher than AGV, So, in this paper, we established simulation model to evaluate two types of transport vehicles and analyzed the results. Simulation model was established to automated container terminal with perpendicular yard layout, and applied closed loop operation of transport vehicle between apron and stacking yard. In the result, SHC showed very superior than AGV aspect of container crane productivity and vehicle fleets,

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.844-849
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• 2006

The electric facilities for subway stations require reliable and safe electricity in spite of their load increases rapidly. Nevertheless, Korea Electrical Safety Corporation reports that the accidents of independent electric facilities increased greatly from 4,632 cases in 1998 to 6,024 in 1999 and 6,776 cases in 2000, while the ratio of the accidents related with transformers grew gradually. As it is, it is deemed very important to minimize the spreading effects of the electric system accidents and thereby, enhance reliability of the electric supply as well as its safety. According to the fact that the electric facilities for subway stations are important for the public safety and conveniences, it should be careful to set their capacity instead of simply applying the general capacity standard to them, and thereby, improve their economy as well as prevent their accidents. With such a basic conception in mind, this study is aimed at analyzing the characteristics of the electric load in the subway stations and thereupon, suggesting some guidelines for setting of the electric facility capacity for subway stations in terms of optimal operation and safety.

• Journal of the military operations research society of Korea
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• v.23 no.1
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• pp.100-114
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• 1997

The network for proving information exchange function in distributed system is interconnected among other networks which are in the state of independent construction and operation. However, due to various network protocols and distributed applications, Problems occurred in the area of network interconnectivity and interoperability of distributed applications in internetworking which should provide a good interoperability. This paper proposed an improved method for finding route which has the highest interworkability between end-systems using the interrelationship of network protocol. An algorithm and method of constructing a virtual network which is suitable for required distributed application are also proposed in this research.

• Journal of the Korean Data and Information Science Society
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• v.25 no.3
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• pp.623-632
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• 2014

We shall consider the estimation for the parameter and the right tail probability in a general exponential distribution. We also shall consider the estimation of the reliability P(X < Y ) and the skewness trends of the density function of the ratio X=(X+Y) for two independent general exponential variables each having different shape parameters and known scale parameter. We then shall consider the estimation of the failure rate average and the hazard function for a general exponential variable having the density function with the unknown shape and known scale parameters, and for a bivariate density induced by the general exponential density.

• Journal of Power Electronics
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• v.4 no.4
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• pp.246-255
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• 2004

Ac-dc PWM single-stage converters that integrate the PFC and dc-dc conversion functions in a single switching converter have been proposed to try to minimize the cost and complexity associated with implementing two separate and independent switch-mode converters. In this paper, two simple ac-dc single-stage PWM full-bridge converters are considered - one current-fed, the other voltage-fed. The operation of both converters is explained and their properties are noted. Experimental results obtained from simple lab prototypes of both converters are presented, then compared and discussed.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.226-228
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• 2007

SRM drive systems are designed to meet operating standards such as low cost, constant torque independent of rotor position, a desired operating speed range, high efficiency, and high performance. In applications using small motors, low cost and high performance with self-starting capabilities are highly desired. This paper discusses a novel two phase SRM (TPSRM) that has high performance characteristics with self-starting capability, low manufacturing cost with a two phase inverter and simple magnetic structure, and high efficiency. The principle of operation, analysis, and simulation for design are presented. The machine design is verified using finite element analysis (FEA) software. Analysis and simulation results are given to validate the TPSRM design.

• Journal of Power Electronics
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• v.12 no.5
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• pp.739-747
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• 2012

This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.

• Transactions of the Society of Information Storage Systems
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• v.6 no.2
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• pp.41-46
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• 2010

Recently, Flash Memory Drives are one of the best media to support portable and desktop computers' storage devices. Their features include non-volatility, low power consumption, and fast access time for read operations, which are sufficient to present flash memories as major database storage components for desktop and server computers. However, we need to improve traditional storage management schemes based on HDD(Hard Disk Drive) and RAID(Redundant Array of Independent Disks) due to the relatively slow or freezing characteristics of write operations of SSDs, as compared to fast read operations. In order to achieve this goal, we propose a new storage management scheme called Hetero-Mirroring based on traditional HDD mirroring scheme. Hetero-Mirroring-based storage management improves RAID-1 operation performance by balancing write-workloads and delaying write operations to avoid SSD freezing.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.4 no.1
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• pp.7-24
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• 1996

A methodology has been developed for predicting aircraft reliability incorporating both C.C.F.s(Common-Cause Failures), and phased missions. Failure behaviour of an aircraft, or it's systems are predicted. Both independent failures, and C.C.F.s, are modelled by the Markov process, and simulated using Monte Carlo sampling with the robust variance reduction method. Prediction of safety and reliability is made through discrete-event simulation of aircraft operations. A case study is described for investigating the safety and reliability of the propulsion system of two-, three- and four-engined aircraft. This is particularly important for the design of ETOPS(Extended Range of Two-Engined Aircraft Operations) and results are presented for the cases with, and without the effect of C.C.F.s.