• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.206-210
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• 1998

A study on dynamic characteristics of rotating disks in magneto optical disk drives is presented. Natural frequencies of rotating disks are investigated experimentally and numerically. The frequency response and critical speeds of the ASMO disk are discussed. The characteristics of airflow around the disk and their effects on disk vibrations are also investigated. It is found that the numerical calculation of the natural frequencies of rotating disks agrees well with the experimental results. The airflow around the disk in the cartridge affects the characteristics of the disk vibrations to reduce the modal frequencies of the disk. The experiment shows that negative vertical offsets of the disk in the cartridge possibly increase the vibration amplitudes. As being influenced by the geometry of the cartridge, the rotation of the disk causes an asymmetric airflow in the presence of window.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.426-430
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• 2000

This study is about the human sensibility measurement method. Researches on human sensibility measurement have been performed in many aspects. However, due to the subtlety and intricacy of human sensibility, it has been difficult to exactly measure human sensibility.At present, Semantic Differential(SD) method is most widely used to quantify human sensibility. In SD method, complicate human sensibility is represented on a scale with equal interval or equal ratio. However, this method has a critical problem in that human sensibility cannot be expressed with equal interval or equal ratio.In order to complement SD method and represent human sensibilities appropriately, we proposed an alternative method using the chroma-scale with saturation that had not equal interval or ratio. In experiment, proposed method shown that subjects understood a new scale easily and they could express their sensibilities on a new scale without any limitation. As a result, the chroma-scale can be used not only for measuring consumer's preference but also for evaluating or selecting sensibility words.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1788-1794
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• 2011

The mold transformer is a complex and critical component of DC substations in Metro system. In this paper, a cost effective and intelligent condition monitoring system for mold transformers in DC substations was developed. This paper also provides an overview of the management program using PD (partial discharge) data on mold transformers. Prior to application of the proposed system to Metro DC substations, experiments were performed at the metro line substation located in Seoul and presented case studies for the use of the intelligent condition monitoring system for mold transformer in DC substations. The experiment results indicated that the developing system can be need in helping mange the risk of unexpected failure of mold type transformers.

• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.298-309
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• 1990

A mathematical model was developed to simulate sideways overturning of agricultural tractor-trailer systems. Sideways overturn of a tractor-trailer system was described by oscillatory motions of the tractor with respect to the first and second tipping axes, and of the trailer with respect to the drawbar hitch point when either the tractor or trailer rides over an obstacle on slopes. By a computer simulation, critical slope angles of the ground on which the tractor-trailer system is likely to sideways overturn were evaluated under the given operational conditions. Validity of the proposed mathematical model was proved by comparing the results of computer simulation and experiment with a model tractor-trailer system. A close agreement was observed between the two results.

• Journal of Korea Multimedia Society
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• v.16 no.6
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• pp.735-745
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• 2013

The emergence of Web 2.0 technologies, such as blogs and wiki, enable even naive users to easily create and share content on the Web using freely available content sharing tools. Wide availability of almost free data and promiscuous sharing of content through social networking platforms created a content borrowing phenomenon, where the same content appears (in many cases in the form of extensive quotations) in different outlets. An immediate side effect of this phenomenon is that identifying which content is re-used by whom is becoming a critical tool in social network analysis, including expert identification and analysis of information flow. Internet-scale reuse detection, however, poses extremely challenging scalability issues: considering the large size of user created data on the web, it is essential that the techniques developed for content-reuse detection should be fast and scalable. Thus, in this paper, we propose a $qSign_{lsh}$ algorithm, a mechanism for identifying multi-sentence content reuse among documents by efficiently combining sentence-level evidences. The experiment results show that $qSign_{lsh}$ significantly improves the reuse detection speed and provides high recall.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.198-204
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• 2012

3-Phase voltage sag compensator protects a critical load from grid sags. The paper presents an algorithm and design of 3-phase voltage compensator. Compensator algorithm consists of a 3-phase voltage sag detection, thyrister commutation method and inverter output voltage control. The compensator satisfies SEMI F47 standard and 10kW 3-phase voltage sag compensator prototype is assembled. Validity of the proposed compensator is verified by simulation and experiment.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2843-2845
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• 2005

This paper deals with the design of real-time embedded system using RTOS (real-time operating system) and SOPC (system on a programmable chip). It is, in general, known that RTOS has the problem of time delay caused by the multiple tasks and task management approach. Since the increase in time delay in real-time embedded system makes the overall system have the poor performance or the critical behavior of instability and unreliability, the method employed RTOS and SOPC is proposed to attack the above problems. The proposed system is implemented on the RC-motor controller and is verified by real experiment.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.145-148
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• 2001

Bi-2223/Ag HTS tapes fabricated by PIT process are used to make the power transmission cable, motor, fault current limiter, transformer etc. But some problems are still remained as like bubbling, sausaging to got the high Jc. In this study. we carried out the experiment to prevent bubbling in the HTS tape. The bubbling mainly occurred when HTS tape was heat-treating. Therefore, additional vacuum annealing at 400 ~ $600^{\circ}C$and slowly ramp-up sintering method were used to decrease the bubbling. slowly ramp-up sintering was more effective to decrease the bubbling than the vacuum annealing, but Jc was also decreased after heat treatment. Optimum ramp-up sintering schedule was searched to get the high critical current and prevent bubbling at same time.

• Progress in Superconductivity and Cryogenics
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• v.7 no.4
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• pp.20-23
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• 2005

The Resistive Type High Temperature Superconducting Fault Current Limiter (SFCL) has been developed in many countries. Until now, materials of the resistive SFCL were Bi2212 bulk and YBCO thin film. Although YBCO coated conductor (CC) has many advantages such as high n-value and critical current for applying resistive SFCL, the resistive SFCL using CC doesn't have developed yet. The bifilar winding type SFCL was manufactured and tested rated on 30V/80A. In normal state, the SFCL using pancake type bifilar winding had very low impedance. When a fault occurred, the SFCL limited the fault current efficiently. Through these results of experiment, large-scale SFCL using CC should be developed in the future.

• Progress in Superconductivity and Cryogenics
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• v.5 no.2
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• pp.66-70
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• 2003

Transient magnetic diffusion process in a melt-cast Bi2Sr2CaCu20X(Bi-2212) tube was studied by experimental and numerical analyses. The transient diffusion partial differential equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical state model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper. This experiment measure the magnetic flux density in the supercondutor after supply direct-current of Bi-2212 rounded by copper coil. This study was discussed of valid of a previous numerical solution which is compared by the penetrate time and the magnetic flux density difference of between the present results and the numerical solution.