• Journal of Power System Engineering
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• v.12 no.1
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• pp.58-65
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• 2008

A method to test thin-walled tubes by guided ultrasonic wave is reported. The principle is that applicate two types of axially symmetric ultrasonic tube modes and "longitudinal" modes with particle displacement, which is coupled in axial and radial directions for transverse failures and torsional modes, oscillating in the circumferential direction only, for longitudinal failures. Both types of modes propagate along the tube in the axial direction. Therefore, a pulse-echo technique is possible. The pulses are excited and received at one end of the tube without contact electro-dynamic transducers. As soon as the tubes is put into a transducer coil at one end, the test of the whole tube can be accomplished in a few milliseconds. It is not necessary to rotate and transport the tubes during the test.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.259-264
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• 2007

In this paper, to analyze the initial valued non-homogeneous elastic half space by the scaled boundary analysis, the infinite element approach was introduced. The free surface of the initial valued non-homogeneous elastic half space was mode1ed as a circumferential direction of boundary scaled boundary coordinate. The infinite element was used to represent the infinite length of the free surface. The initial value of material property(elastic modulus) was considered by the combination of the position of the sealing center and the power function of the radial direction. By use of the mapping type infinite element, the consistent e1ements formulation could be available. The performance and the feasibility of proposed approach are examined by two numerical examples.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.118-125
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• 2008

Single walled carbon nanotubes (SWCNTs) can be modified to produce a new concept of hybrid materials by introducing atoms or molecules inside their cylindrical empty space. Such an endohedral doping of the SWCNTs is expected to decisively alter their electronic transport and mechanical properties, In this study, we purified SWCNTs by three-step purification processes and formed the peapod structure by introducing $C_{60}$ fullerenes inside the SWCNTs. $C_{60}$ molecules were observed to be regularly arranged by transmission electron microscopy. In Raman spectra, the radial breathing mode (RBM) rather than the other modes was significantly affected by the endohedral injection of $C_{60}$. The RBM intensity was more greatly reduced in the large-diameter SWCNTs than the small-diameter ones, Raman spectroscopy is expected to be a key technique for analyzing $C_{60}$-encapsulated SWCNTs.

• Structural Engineering and Mechanics
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• v.29 no.5
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• pp.581-597
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• 2008

In this paper, the double displacement coupled statics and dynamics of the electromechanical integrated electrostatic harmonic drive are developed. The linearization of the nonlinear dynamic equations is completed. Based on natural frequency and mode function, the double displacement coupled forced response of the drive system to voltage excitation are obtained. Changes of the forced response along with the system parameters are investigated. The voltage excitation can cause the radial and tangent coupled forced responses of the flexible ring. The flexible ring radius, ring thickness and clearance between the ring and stator have obvious influences on the double displacement coupled forced responses.

• Journal of Magnetics
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• v.22 no.1
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• pp.78-84
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• 2017

This paper investigates the influence of mechanical energy storage on the interior permanent magnet synchronous machine (IPMSM) when it is operated in the generating mode. An IPMSM with six-poles and nine-slots employing concentrated coil winding type is considered as the analysis model, and a surface-mounted permanent magnet synchronous motor directly connected to a heavy wheel is applied as the mechanical energy storage system by using the moment of inertia. Based on the constructed experimental set-up with manufactured machines and power converters, the generated electrical energy is converted into the mechanical energy, and the electromagnetic filed characteristics of IPMSM are subsequently investigated by applying the measured phase current of IPMSM based on finite element method. Compared to the characteristics in a no-load condition, it is confirmed that the magnetic behavior, radial force, and power loss characteristics are highly influenced by the harmonics of the phase current due to the mechanical energy storage system.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2179-2186
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• 2005

The lubrication modes of line contact between the vane and the camring in an oil hydraulic vane pump have been investigated. First, variations of the radial acting force of a vane were calculated from previously measured results of the dynamic internal pressure in four chambers surrounding a vane. Next, distinctions of the lubrication modes were made using Hooke's chart, which represents an improvement over Johnson's chart. Finally, the influence of boundary conditions in the lubrication region on fluid film lubrication was examined by calculating film pressure distributions. The results show that the lubrication modes of the vane tip are a rigid-variable viscosity region. This region discharges pressure higher than 7 MPa, and exerts a great influence on oil film pressure in the large arc section due to the Piezo-viscous effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.325-332
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• 2004

Tire vibration modes are known to play a key role in vehicle ride and comfort characteristics. Inputs to the tire such as impacts, rough road surface, tire nonuniformities, and tread patterns can potentially excite tire vibration. In this study, experimental modal analysis on the tire with ground contact are performed by impacting the tire in the radial direction at the center of contact patch. To investigate which modes of tire influence the vibration of wheel and axle when the tire is in contact with ground, the vibration characteristics such as frequency response functions, natural frequencies and their mode shapes from tire to wheel/axle are examined.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.40-44
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• 2005

Catalytic performance of Co catalysts supported on MgO for the formation of multiwall carbon nanotubes (MWCNTs) Having 40-60 nm in diameter has been investigated through acetylene decomposition at $600^{\circ}C$. Scanning electron microscopy measurements show that the nanotubes are chain and coiled structures whereas x-ray diffraction patterns indicate the formation of MWCNTs with Co nanoparticles. In addition Raman spectra confirms the format ion of MWCNTs due to presence of characteristic radial breathing mode along with D and G bands.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.94-99
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• 1999

It is the hybrid structure of HMM and neural network(NN) that shows high recognition rate in speech recognition algorithms. And it is a method which has majorities of statistical model and neural network model respectively. In this study, we propose a new style of the hybrid structure of semi-continuous HMM(SCHMM) and radial basis function(RBF), which re-estimates weighting coefficients probability affecting observation probability after Baum-Welch estimation. The proposed method takes account of the similarity of basis Auction of RBF's hidden layer and SCHMM's probability density functions so as to discriminate speech signals sensibly through the learned and estimated weighting coefficients of RBF. As simulation results show that the recognition rates of the hybrid structure SCHMM/RBF are higher than those of SCHMM in unlearned speakers' recognition experiment, the proposed method has been proved to be one which has more sensible property in recognition than SCHMM.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.54-60
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• 2008

The atomization characteristics of the dual air supplying twin-fluid nozzle were investigated experimentally using PIV and PDA systems. The two-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air and the main nozzle to produce the spray. The main nozzle has the swirl tip with four equally spaced tangential slots, which give the injecting fluid an angular momentum. The angle of the swirl tip varied with 0$^{\circ}$ 30$^{\circ}$, 60$^{\circ}$ and 90$^{\circ}$, and the ratios of carrier air to assist air and ALR(total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the mean velocity, turbulent intensity and SMD distributions of the sprays were measured using PDA system. As the results, the mean axial velocity at the spray centerline decrease with the increase of the swirl angle. The turbulent intensities of the axial and radial velocity were increased with the increase of the swirl angle. The mean SMD (Sauter mean diameter) of the radial direction along the axial distance shows the lowest value at the swirl angle of 60$^{\circ}$.