• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.851-855
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• 2005

We investigated the unbalanced characteristics of the superconducting fault current limiters (SFCLs) based on YBCO thin films with a single line-to-ground fault. When a single line-to-ground fault occurred, the short circuit current of a fault phase increased about 6 times of transport currents after the fault onset but was effectively limited to the designed current level within 2 ms by the resistance development of the SFCL. The fault currents of the sound phases almost did not change because of their direct grounding system. The unbalanced rates of a fault phase were distributed from 6.4 to 1.4. It was found that the unbalanced rates of currents were noticeably improved within one cycle after the fault onset. We calculated the zero phase currents for a single line-to-ground fault using the balanced component analysis. The positive sequence resistance was reduced remarkably right after the fault onset but eventually approached the balanced positive resistance component prior to the system fault. This means that the system reaches almost the three-phase balanced state in about 60 ms after the fault onset at the three-phase system.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.109-112
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• 2015

The Korean electric railway is growing rapidly such as speed of 300km/h in high speed section and 230km/h in the conventional railway section. But, power supply failure occurs because of loss of contact, defective catenary system and high speed vehicle. Therefore preventive maintenance way based reliability has been applied. Typical example is the facility inspection method using trolley inspection system. But it is required differentiated inspection method to prevent problem such as inspection errors. In this paper, a study on the trolley sliding condition inspection system using monitoring techniques is performed for performance enhancement of inspection system. It proposed the efficient maintenance method through monitoring the deviation and height of contact wire after installing inspection system on the top of train which operates in the metropolitan area. Inspection errors were decreased by virtually monitoring the video of faulty facilities. Also those facilities were identified through the impact sound analysis and tests at the main catenary section.

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.54-62
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• 2006

An experiment about performance characteristics is conducted on a double chamber vane-type rotor. Three different rotors, which have 6, 8 and 9 vanes, are applied to the driver and various lift holes at the rear plate are used to increase the effective vane height. The inner diameter of a double chamber cylinder is ${\phi}27mm$, and the length of the cylinder is 65 mm. The maximum offset length between the rotor outer surface and the cylinder inner surface is 4.5 mm. In this study, specific output torques and powers are measured, and also noise and vibration are measured at the real operating situation. The operating torque on the double chamber is increased to 17% compared to the operating torque obtained at the single chamber which has the same size. The experimental results of noise and vibration show that the operating sound and vibration are directly related to the operating power generated by the double chamber rotor.

• Journal of the Korean Society of Costume
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• v.44
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• pp.19-36
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• 1999

A military uniform has two basic characters. One is functionality for field warfare and the other is decorativeness to express dignity and power to maintain systematic organization. For these purposes, the military uniform is maximizing its effects on functionality and decorativeness on each aspects of material, color, dignity, item, military ornaments and accessories. During wartime, the military uniform improved its functionality and gave much influence on normal clothing at the same time either directly or indirectly. Military look became more diverse. In a mood for the end of century and inflated material civilization, and with nostalgia for the fast, mixed styles of fast, presents and future have come out in variety. In Street Fashion, there are many alternative trends to meet diverse desires of teenagers, and the military look has been steadily favored. The functionality and the decorativeness of military look would have met fashion sense and taste of younger generations pretty well. First, teenagers are active, and the practical materials and functional designs of military style applied to their clothes. Second, they prefer challenging and creative styles, and the decorative elements of military clothing for the colors, patterns, accessories have been applied to they clothing. We may need to understand their culture and emotion more closely and help them enjoy sound and beautiful clothing culture. The military uniform adapted itself to natural and social environments and has been developed and improved, which made that possible.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.559-562
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• 1999

In this paper, we developed on internet based assembly information display system for the blind. The system is consist of hardware and software. The hardware is consist of a voice synthesis device and a tactile display for character information, and the software is consist of internet web browser for the blind and braille program. The tactile-device system consists of a control unit, pin array, pin generator, serial port, and a power supply. The pin exerted by a electromagnetic method, solenoid. The internet web browser separates the character and image from internet web page, and character information in the web page is converted to braille and fed to sound system. Also the image in the web page can be printed developed tactile display. As the results of experiment, the blind could access the internet web site by using this system and understand various internet information.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.527-535
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• 2012

This paper reports the active vibration control of plates using positive position feedback controller (PPF). The equations of motion of the plate under force and moment pairs were derived and the equations of PPF controllers were formulated. The effect of the parameters - gain and damping ratio - of the PPF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the PPF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies without changing the phase behavior. The increase of the damping ratio of the PPF controller leads to decrease the magnitude of the open loop transfer function and to modify its phase characteristics to be more stable. Two PPF controllers connected in parallel, Each PPF controller is tuned at the $1^{st}$ and $2^{nd}$ modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 2 modes can be obtained.

• Journal of Drive and Control
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• v.14 no.2
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• pp.9-15
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• 2017

The steering systems of all-terrain cranes have been developed with various control strategies for the stability and drivability. To optimally control the input steering angle, an accurate mathematical model that represents the actual crane dynamics is required. The derivation of an accurate mathematical model to optimally control the steering angle, however, is difficult since the steering-control strategy generally varies with the magnitude of the crane's longitudinal velocity, and the postures of the crane's working parts vary while it is being driven. To address this problem, this paper proposes an automatic steering-control algorithm that is based on the MPC (model predictive control) with a disturbance observer for all-terrain cranes. The designed disturbance observer of this study was used to estimate the error between the base steering model and the actual crane. A model predictive controller was used for the computation of the optimal steering angle, along with the use of the base steering model with an estimated uncertainty. Performance evaluations of the designed control algorithms were conducted based on a curved-path scenario in the Matlab/Simulink environment. The performance-evaluation results show a sound reference-path-tracking performance despite the large uncertainties.

• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.107-114
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• 2000

This work is aimed to develop a new type of the Push-Pull ultrasonic transducer that can provide higher sound pressure level and simpler internal structure than conventional types. The driving part of the newly designed transducer is positioned in the middle of the cylinder, and its optimum geometry is determined by using the FEM package, ANSYS. Through FEM model analysis, the effects of all of its geometrical variables such as transducer length, transducer radius, and the edge shape of the end cap have been examined, and the results have led to the optimum geometry. The newly designed transducer has been found to give better performance than that of traditional ones.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.305-310
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• 2001

UBM-coated Si-wafer was fluxlessly soldered with glass substrate in $N_2$ atmosphere using plasma cleaning method. The bulk Sn-37wt.%Pb solder was rolled to the sheet of $100\mu\textrm{m}$ thickness in order to bond a solder disk by fluxless 1st reflow process. The oxide layer on the solder surface was analysed by AES(Auger Electron Spectroscopy). Through rolling, the oxide layer on the solder surface became thin, and it was possible to bond a solder disk on the Si-wafer with fluxless process in $N_2$ gas. The Si-wafer with a solder disk was plasma-cleaned in order to remove oxide layer formed during 1st reflow and soldered to glass by 2nd reflow process without flux in $N_2$ atmosphere. The thickness of oxide layer decreased with increasing plasma power and cleaning time. The optimum plasma cleaning condition for soldering was 500W 12min. The joint was sound and the thicknesses of intermetallic compounds were less than $1\mu\textrm{m}$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.843-848
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• 2011

Planning and construction of railway for high speed trains up to 400 km/h are recently driven in Korea. High speed train is one of the environment-friendly fastest mass transportation means but its noise generated by rolling, traction and aerodynamic mechanism can cause public complaints of residents nearby railways. To cost-effectively prevent the troublesome noise in a railway planning stage, the rational railway noise prediction method considering the characteristics of trains as well as railway structures should be required but it is difficult to find authentic methods for Korean high speed trains such as KTX and KTX-II. In this study, we propose a framework of our own railway noise prediction model emitted by Korean high speed trains over 250 km/h based on the recent research results carried out in EU countries. The model considers railway sound power level using several point sources distributed in heights as well as tracks, whose detail speed- and frequency-dependent emission characteristics of Korean high speed trains should be determined in near future by measurement or numerical analysis. The attenuation during propagation outdoors is calculated by the well-known ISO 9613-2 and auxiliary methods to consider undulated terrain and wind effect.