• Journal of the Korean Magnetic Resonance Society
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• v.13 no.1
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• pp.35-55
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• 2009

The two correlation times previously obtained in our coupled $^{13}C$ relaxation measurement for the methyl group in 2,6-dichlorotoluene may be used as a criterion for evaluating the reorientation dynamics of an internal rotor. We numerically tested an extended diffusion model and the Smoluchowski diffusion equation to see how the rotational inertial effect and jump character contribute to the internal correlation time ratio of the internal rotor. We also analytically solved the general jump model with three different rate constants in a sixfold symmetric potential barrier. By assuming that the internal rotation of the methyl group in 2,6-dichlorotoluene can be described in terms of jumps among sixfold harmonic potential wells, we can conclude that the jump model satisfactorily reproduce the experimental data and the rate for sixfold jump is at least 1.53 times as great as that of a threefold jump.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.223-228
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• 2001

The thermoacoustic refrigerator has not only considerable possibility but also commercial usability, because it has high reliability, lower vibration, no moving part, and can easily be constructed. In this study, The thermoacoustic refrigerator were constructed. The apparatus is capable of driving closed systems containing He or air at mean pressures ranging from 1-9.3 bar, at frequencies ranging from 100-1000Hz. The resonance characteristics of the thermoacoustic refrigerator were investigated for better performance, The resonance tube is 340.5mm in length. In case of using air as a coolant. Freezing frequency is 174Hz, In case of using He as a coolant Freezing frequency is 625Hz. Using He, The cold-part temperature of the heat exchanger fell to $-23.7^{\circ}C$ after 120 minutes in 70W.

• The Korean Journal of Rheology
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• v.5 no.1
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• pp.65-75
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• 1993

PP에 PE를 용융혼합하여 방사불안정성을 줄일수 있는 방사조건에 대한 연구를 수 행하였다. 연신공명에 대한 주파수 분석결과 harmonic overtone이 나타나고 연식공명의 주 기가 체류시간에 비례함을 밝혔다. PP에 PE를 혼합시킴으로써 연신공명을 줄일수 있었으나 PE가 연속상이 되는 PE함유량에서는 임계연신비보다 낮은 연신비에서 사절이 발생하였다. 또한 낮은 방사온도에서는 melt fracture 현상이 연신공명을 쉽게 일어나게 하는 용인으로 작용하여 PP/PE 혼합물의 방사 안정성을 저해하였다, 토출량이 같을 때 방사구 지름은 연 신공명의 Dmax/Dmax 값에 영향을 미치지 않았고 방사길이가 짧으면 임계연신비가 증가하였 다. 방사구 L/D가 클때에는 방사구 L/D가 연신공명에 영향을 미치지 않았으나 방사구 L/D 가 짧을 때에는 임계연신비가 크게 저하되었다.

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.1-4
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• 2010

We investigated a linear carbon nanotube motor serving as the key building block for nano-scale motion control by using molecular dynamics simulations. This linear nano-motor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.65-70
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• 2001

An investigation into asymmetric vibrations of a clamped circular place under a harmonic excitation is made. We examine a primary resonance. in which the frequency of excitation is near the natural frequency of an asymmetric mode of the plate. We found not only a response haying the form of standing wave but also one having the form of traveling wave, which was not observed by Sridhar, Mook and ${Nayfeh}^{(1)}$

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.337-345
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• 1997

An analysis is presented for the response of a beam constrained by a nonlinear spring to a harmonic excitation. The system is governed by a linear partial differential equation with a nonlinear boundary condition. The method of multiple scales is used to reduce the nonlinear boundary value problem to a system of autonomous ordinary differential equations of the amplitudes and phases. The case of the third-order subharmonic resonance is considered in this study. The autonomous system is used to determine the steady-state responses and their stability.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.184-184
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• 2012

Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering the range of MCR, however, the range is un-measurable. To resolve the measurement issue, this study shows the measuring method and the estimating method of whiling vibration by using resonance frequency of sub harmonic.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.12
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• pp.587-591
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• 2001

This paper describes the general and efficient design method of an axial and a radial shim coils to correct field impurities of various harmonic orders in the imaging volume of Magnetic Resonance Imaging magnet. Shim coils are optimized by BCLSF subroutine of IMSL, which is the well-known commercial package for optimization, aiming at maximizing the magnitude of the desired field component as well as minimizing other field components. In order to evaluate their effect, the developed method was applied to the MRI magnet constructed in KERI.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1235-1237
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• 2003

For small capacity rectifier circuits as these for consumer electronics and appli capacitor input type rectifier circuits are gen used. Consequently. various harmonics gen within the power system become a serious pro Various studies of this effect have been pres previously. However. most of these employ swit devices, such as FETs and the like. The absen switching devices makes systems more toleran over -load, and brings low radio noise benefits propose a power factor correction scheme using resonant in commercial frequency without swit devices. In this method. It makes a sinusoidal by widening conduction period using the cu resonance in commercial frequency. Hence, harmonic characteristics can be significantly imp where the lower order harmonics. such as the and seventh orders are much reduced. The resu confirmed by the theoretical and experm implementations.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.545-562
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• 2023

In this work, superharmonic and subharmonic resonance of rotating stiffened FGM truncated conical shells exposed to harmonic excitation in a thermal environment is investigated. Utilizing classical shell theory considering Coriolis acceleration and the centrifugal force, the governing equations are extracted. Non-linear model is formulated employing the von Kármán non-linear relations. In this study, to model the stiffener effects the smeared stiffened technique is utilized. The non-linear partial differential equations are discretized into non-linear ordinary differential equations by applying Galerkin's method. The method of multiple scales is utilized to examine the non-linear superharmonic and subharmonic resonances behavior of the conical shells. In this regard, the effects of the rotating speed of the shell on the frequency response plot are investigated. Also, the effects of different semi-vertex angles, force amplitude, volume-fraction index, and temperature variations on the frequency-response graph are examined for different rotating speeds of the stiffened FGM truncated conical shells.