• 한국정밀공학회지
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• 제18권6호
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• pp.141-147
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• 2001

A heat dissipation technology using flow resonant phenomenon is a kind of new concept in heat transfer area. A vibration exciter is needed to generate an air turbulence which has the natural shedding frequency of a heat system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator. An analytical dynamic model for this mechanical vibration exciter is presented and its validity is verified by the comparison with experimental data. Values of some unko주 system parameters in the analytic model are estimated through the system identification approach. based on this mathematical model, a high bandwidth vibration exciter is designed using feedback control. During the experimental verification phased, it turns out the high frequency modal resonant characteristics of vibrating plate are the major barrier against obtaining a high bandwidth vibration exciter.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.947-951
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• 2007

This paper is concerned with a new concept for the damper without neither a coil spring nor fluid. The new damper concept consists of the permanent magnets and the cylinder of the conducting material. The opposite pole magnets produces the repulsive forces and this is substituted for the coil spring. The relative motion between the magnets and conducting cylinder produces eddy currents thus resulting in the electromagnetic force, which turns out to be the damping force thus and is substituted for a damping fluid. This damper is called the eddy current damper(ECD). The important advantage of the proposed ECD is that it does not require the damping fluid and any external power and is non-contacting and relatively insensitive to temperature. In the present study, the proposed ECD was constructed and experiments were performed to investigate its dynamic characteristics. The experiments shows that the proposed ECD has the excellent damping ability.

• Smart Structures and Systems
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• 제4권5호
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• pp.531-548
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• 2008

Recently, dense sensor instrumentation for structural health monitoring has motivated the need for novel passive wireless sensors that do not require a portable power source, such as batteries. Using a layer-by-layer self-assembly process, nano-structured multifunctional carbon nanotube-based thin film sensors of controlled morphology are fabricated. Through judicious selection of polyelectrolytic constituents, specific sensing transduction mechanisms can be encoded within these homogenous thin films. In this study, the thin films are specifically designed to change electrical properties to strain and pH stimulus. Validation of wireless communications is performed using traditional magnetic coil antennas of various turns for passive RFID (radio frequency identification) applications. Preliminary experimental results shown in this study have identified characteristic frequency and bandwidth changes in tandem with varying strain and pH, respectively. Finally, ongoing research is presented on the use of gold nanocolloids and carbon nanotubes during layer-by-layer assembly to fabricate highly conductive coil antennas for wireless communications.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.291-291
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• 1999

Long 19-filamentary Bi-2223 tapes were prepared using the so called "powder-in-tube" method. In the preparation, two types of precursor powders and two different reduction rates during rolling were used. Also two rolling method, which resulted in different filament geometry, were used. The characteristics of the tapes will be presented. Also A coil was prepared using two 56 m-long 19-filament tape. It was consisted of two double pancake coils. Each pancake, which is separated by FRP spacer, was composed of 98 turns. The experimental results will be presented and compared to the simulation result.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.13-17
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• 2003

In this paper, the design parameters for the magnetic field source at extremely low frequency are proposed. This facility can be used for in vivo experiments with small animals to investigate biological response to the driving magnetic fields. In case that the exposed animals are motionless, the animals may be affected by the directivity of driving field. To avoid this effect, a 2-axis ELF magnetic field driving apparatus was designed, The optimum location and number of turns of each coil were obtained by numerical analysis. Applying these data to the MATLAB code (for computation), the magnetic field distribution was obtained. The calculation result for a well-designed facility showed that the space in which the amplitude of the magnetic field lies within the 95% of the magnetic field distribution was more than 60% of each axis length.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권3호
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• pp.173-178
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• 1999

In this paper, the characteristics of the shielded inductive superconducting fault current limiter(FCL) were simulated and analyzed. After determining parameters fo design for superconducting tube, iron core and primary coil, simple power system composed of shielded inductive FCL was simulated by the numerical analysis. The currents flowing under the fault condition could be limited below 50 A successfully. It was suggested that as the important factors of operational characteristics, the turns of primary coil and size of iron core play a major role for whether the shielded inductive SCFCL operated as inductive type or resistive type FCL.

• 산업기술연구
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• 제20권B호
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• pp.125-130
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• 2000

Heat dissipation technology using flow resonant phenomenon is a kind of new concept in heat transfer area. A vibration exciter is needed to generate air turbulence which has the natural shedding frequency of heat system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator. An analytical dynamic model for this mechanical vibration exciter is presented and its validity is verified by the comparison with experimental data. Values of some unknown system parameters in the analytic model are estimated through the system identification approach. Based on this mathematical model, a high bandwidth vibration phase, it turns out the high modal resonant characteristics of vibrating plate are the major barrier against obtaining a high bandwidth vibration exciter.

• 센서학회지
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• 제20권4호
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• pp.249-253
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• 2011

This paper describes the fabrication and characteristics of vibration-driven electromagnetic energy harvester without spring to use at low frequency like a human body motion. The implemented energy harvester consists of NdFeB magnets, copper coil. The optimization of induced voltage was done by the various widths of coil, number of the turns, size of fixed and moving magnets and thicknesses of the cylinder. The fabricated energy harvester is capable of producing up to 15.0 $V_{pp}$ for basic model and 28.80 $V_{pp}$ for improved model at 5.0 Hz resonance frequency and 0.75 g acceleration level. The basic model and improved model are provided a maximum power of 6.375 mWand 25.831 mW at 1 KHz of load resistance in rectifier circuit.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.58-63
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• 2002

For the experiment the four types of spacer were distinguished by arrangement. The flashover characteristic on each types of spacer was investigated and the flashover phenomena were observed to understand breakdown mechanism in liquid nitrogen($LN_{2}$). The spacer should be placed interior coil as an insulator, a cooling channel and s supporter of structures. The simulated electrode used in the experiment was made from five turns of HTS tape. Experimental results revealed that multi-layer and barrier effects did work well in Air but did not in $LN_{2}$. These result suggested that the flashover in LN2 caused by the bubbles due to partial discharge at micro gap, g. The flashover characteristics decreased to 70% when g is 0.2 mm. The degradation was improved by even treatment on surface of coil electrode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.153-153
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• 2013

Turbomolecular pump (TMP) is widely used to obtain and maintain high vacuum by spinning turbine rotors to migrate gas molecules to the exhaust of the pump. However, performance of the TMP has not been well observed when it is influenced by strong magnetic field. Such study may give useful information about magnetic field tolerance of TMP, development of magnetic shielding technique for key components of TMP, etc. For this purpose, magnetic field induced by a circular current source was firstly designed and investigated. Using spherical coordinates and vector potential, magnetic field throughout the space including axis of rotation was calculated. Due to the rotational symmetry of the circular current source, induced magnetic field is azimuthally symmetric and, thus, is analyzed by radial and polar components of the magnetic fields. In order to enhance the numerical accuracy for the calculation, magnetic field was expressed by complete elliptic integrals of first and second kinds. According to the calculation, when 1 A of DC-current passes through a 1 turned circular wire with 50 cm of diameter, overall magnitude of the inducedmagnetic field was about 0.02 Gauss, which was used to the determination of the current and the number of turns of wires to fabricate the coil for the study on the magnetic field tolerance of TMP.