• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.54-59
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• 1996

As the current shape of SRM is of pulse type and changed by the motor parameters and drive conditions, the influences on the drive efficiency by control method are more than other types of motors. In this paper, a proper excitation condition to drive a SRM with high efficiency is proposed and tested. It is derived from the conditions that the phase current of a SRM is to be flat-topped at various drive. The saturation effect of magnetic circuit is accounted for more accurate analysis. Experimental tests are executed to verify the proposed excitation method. This drive system is easy to commutate and also advantageous in reducing torque ripple. (author). 6 refs., 10 figs., 1 tab.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.1-4
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• 2001

SRM(Switched Reluctance Motor) uses reluctance torque by pulse excitation control. SRM drives are much studied in electrical vehicles and industrial application due to the simple, robust mechanical structure and high speed characteristics. For the high performance control of SRM, it is necessary to synchronize the stator phase excitation with the rotor position. This paper proposes a new encoder for high performance excitation control of SRM. The proposed encoder has complex structures of incremental and absolute encoder. An each phase inductance profile can be synchronized with 4-bit absolute position signal and incremental pulses are used for speed detection. Low cost and simple manufacturing of SRM encoder is possible.

• Structural Engineering and Mechanics
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• v.34 no.6
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• pp.755-778
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• 2010

Near-fault ground motion with directivity or fling effects is significantly influenced by the rupture mechanism and substantially different from ordinary records. This class of ground motion has large amplitude and long period, exhibits unusual response spectra shapes, possesses high PGV/PGA and PGD/PGA ratios and is best characterized in the velocity and the displacement time-histories. Such ground motion is also characterized by its energy being contained in a single or very few pulses, thus capable of causing severe damage to the structures. This paper investigates the characteristics of near-fault pulse-like ground motions and their implications on the structural responses using new proposed measures, such as, the effective frequency range, the energy rate (in time and frequency domains) and the damage indices. The paper develops also simple mathematical expressions for modeling this class of ground motion and the associated structural responses, thus eliminating numerical integration of the equations of motion. An optimization technique is also developed by using energy concepts and damage indices for modeling this class of ground motion for inelastic structures at sites having limited earthquake data.

• Journal of Magnetics
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• v.20 no.3
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• pp.312-316
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• 2015

Unlike conventional Eddy Current Test (ECT), Pulsed Eddy Current (PEC) uses a multiple-frequency current pulse through the excitation coil. In the present study, the detection of subsurface cracks using a specially designed probe that allows the detection of a deeper crack with a relatively small current density has been attempted using the PEC technique. The tested sample is a piece of 304 stainless steel (SS304) with a thickness of 30mm. Small electrical discharge machining (EDM) notches were put in the test sample at different depths from the surface to simulate the subsurface cracks in a pipe. The designed PEC probe consists of an excitation coil and a Hall sensor and can detect a subsurface crack as narrow and shallow as 0.2 mm wide and 2 mm deep. The maximum distance between the probe and the defect is 28 mm. The peak amplitude of the detected pulse is used to evaluate the cracks under the sample surface. In time domain analysis, the greater the crack depth the greater the peak amplitude of the detected pulse. The experimental results indicated that the proposed system has the potential to detect the subsurface cracks in stainless steel plates.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.3
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• pp.131-137
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• 2000

2 phase 8 pole HB-type(flat-type) Linear Pulse Motor can be used as the high precision position actuator because of its many advantages (simple control circuit, high stiffness characteristics, etc). Also, using the microstep drive, its noise and vibration can be reduced considerably and positional resolution may be increased further. But, $20^{\circ}$tapered tooth shape to reduce the normal force have an much effect on the static thrust force characteristics. And, because of hybrid-type LPM, interaction between the permanent magnet and the excitation current have an effect on the various characteristics of LPM. Hence, in this paper, the effect of tooth shape on static thrust force characteristics was analyzed using the air gap permeance by finite element method. For analyzing the effect of unbalance between the m.m.f of permanent magnet and the m.m.f of excitation current, unbalanced m.m.f coefficient $\sigma$ were introduced with the permenace matrix and switching matrix.

• Journal of the Korean Magnetic Resonance Society
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• v.26 no.4
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• pp.51-58
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• 2022

The baseline flattened NMR spectrum has been achieved by several methodologies including pulse manipulation with a series of phase cycling. The background signal inherent in the probe is also main source of baseline distortion both in solution and solid NMR. The simple direct polarization with 90° pulse flipping the magnetization from the z-axis onto the receiver coil requires the strong rf pulse enough to encompass the wide frequency range to excite the resonance of interest nuclei. Albeit the perfect polarization 90° pulse, the signal from the unwanted magnetic fields such as background signal can not be completely suppressed by suitable phase cycling. Moreover, slowly baseline wiggling signal from the low 𝛾 nuclei is not easy to eliminate with multiple pulse manipulation. So there is still need to contrive the new scheme for that purpose in an adroit manner. In this article new triple pulse excitation schemes for TIP and modified DEPTH pulse sequence are analytically examined in terms of arbitrary phase and flip angle of pulse. The suitable phase cycling for these pulse trains is necessary for the good sensitivity and resolution of the spectrum. It is observed that the ¹³C sensitivity TIP experiment is almost equal to the CP/MAS with modified DEPTH sequence, both of which are applicable to both solid and solution state NMR.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.471-474
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• 1997

Several selective excitation pulses are used in MRI. Because of the nonlinearity of the Block equation, the pulse problem is nonlinear generally. Recently, Shinnar & Le Roux have proposed a direct solution of this problem. In this paper, we introduce the SLR algorithm and design pulses using SLR algorithm. This SLR pulse produces a specified slice profile. For example, we demonstrate the sinc function pulse with piece wise constant duration ${\Delta}t$. Further, we will design $\pi/2$ pulse and slice profile.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.188-192
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• 1996

It is shown that the inversion of the undamped Bloch equation for an amplitude-modulated broadband π/2 pulse can be precisely treated as an inverse scattering problem for a Schrodinger equation on the positive semiaxis. The pulse envelope is closely related to the central potential and asymptotically the wave function takes the form of a regular solution of the radial Schrodinger equation for s-wave scattering. An integral equation, which allows the calculation of the pulse amplitude (the potential) from the phase shift of the asymptotic solution, is derived. An exact analytical inversion of the integral equation shows that the detuning-independent π/2 pulse amplitude is given by a delta function. The equation also provides a means to calculate numerically approximate π/2 pulses for broadband excitation.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.325-331
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• 1992

By using the general theoretical framework proposed recently for treating the fluorescence quenching kinetics, we investigate the effect of light pulse intensity on the decay of fluorescence which follows excitation of fluorophors by the light pulse of very short but finite duration. It is seen that conventional theory breaks down when the exciting light pulse has a pulse width comparable to the fluorescent lifetime and its intensity is very high. We also find that even when the light intensity is not too high, conventional theory may fail in either of the following cases: (i) when the quencher concentration is high, (ii) when there is an attractive potential of mean force between the fluorophor and quencher, or (iii) when the energy transfer from the fluorophor to the quencher may also occur at a distance, e.g., via dipole-dipole interaction. The validity of the predictions of the present theory may thus be tested by fluorescence quenching experiments performed under such situations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.27-34
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• 2005

We analyze in detail axially symmetric theoretical study for the photothermal pulsed radiometry of a cylindrical model. The theoretical solutions describe the transient infrared radiation from the sample heated by short-duration pulsed heating. In the conventional transmission radiometry technique, the excitation source and the detector are on opposite sides of the sample, otherwise in the new single ended radiometry technique, the excitation source and the detector are on same sides of the sample. The analytical solution described for photothermal radiometry in this study would not need to cut or polish samples to measure the thermal diffusivity. Therefore the radial area and axial thickness of samples are not limited. The effects of excitation pulse duration and the area of heat source are discussed.