• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.6
• /
• pp.217-225
• /
• 1986

This paper describes the Optimal PWM strategy to reduce a pulsating harmonic torque for a variable-speed drive of 3 phase induction motor. This paper suggests the new Optimal control theory which consists of 1) defining a performance index related to the unwanted effects of the voltage harmonics, (i.e., the components of pulsating harmonic torques) 2) achieving its minimization by a suitable choice of the switching patterns. (i.e., of the commutation angles) This PWM strategy is compared with the conventional SPWM strategy by numerical method. It is believed that this proposed strategy can reduce more harmonic components and pulsating harmonic torques than SPWM strategy. Also, We could verify the validety of the numerical method by a result of simulation analysis of a variable speed 3phase induction motor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.1100-1103
• /
• 2004

The paper presents the results of using the fundamental and the low frequency harmonic components of leakage current to study aging of EPDM insulator for contaminated condition by kaolin. The largeer the leakage current during 200ms, the higher harmonic component at 60hz. The harmonic component at 60hz and the odd order harmonics is increase relation without Kaolin Conent. Arcing on the surface was always associated with distortion in the leakage current; hence the low frequency components of the leakage currnent can be used as a means to evaluate the surface degration. Both the fundamental and 3rd & 5th harmonics increase dry-band activity.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.1
• /
• pp.1-10
• /
• 2011

Nonlinear harmonic waves generated at cracked interfaces are investigated both experimentally and theoretically. A compact tension specimen is fabricated and the amplitude of transmitted wave is analyzed as a function of position along the fatigued crack surface. In order to measure as many nonlinear harmonic components as possible a broadband Lithium Niobate ($LiNbO_3$) transducers are employed together with a calibration technique for making absolute amplitude measurements with fluid-coupled receiving transducers. Cracked interfaces are shown to generate high acoustic nonlinearities which are manifested as harmonies in the power spectrum of the received signal. The first subharmonic (f/2) and the second harmonic (2f) waves are found to be dominant nonlinear components for an incident toneburst signal of frequency f. To explain the observed nonlinear behavior a partially closed crack is modeled by planar half interfaces that can account for crack parameters such as crack opening displacement and crack surface conditions. The simulation results show reasonable agreements with the experimental results.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.20 no.3
• /
• pp.434-440
• /
• 2010

In this paper, we define generalized induced linguistic aggregation operator called generalized induced linguistic ordered weighted harmonic mean(GILOWHM) operator. Each object processed by this operator consists of three components, where the first component represents the importance degree or character of the second component, and the second component isused to induce an ordering, through the first component, over the third components which are linguistic variables and then aggregated. It is shown that the induced linguistic ordered weighted harmonic mean(ILOWHM) operator and linguistic ordered weighted harmonic mean(LOWHM) operator are the special cases of the GILOWHM operator. Based on the GILOWHM and LWHM operators, we develop an approach to group decision making with linguistic preference relations. Finally, a numerical example is used to illustrate the applicability of the proposed approach.

• Advances in materials Research
• /
• v.8 no.2
• /
• pp.83-102
• /
• 2019

The present research deals with the time harmonic deformation in transversely isotropic magneto thermoelastic solid with two temperature (2T), rotation and without energy dissipation due to inclined load. Lord-Shulman theory has been formulated for this mathematical model. The entire thermo-elastic medium is rotating with a uniform angular velocity. The Fourier transform techniques have been used to find the solution to the problem. The displacement components, stress components and conductive temperature distribution with the horizontal distance are computed in the transformed domain and further calculated in the physical domain using numerical inversion techniques. The effect of time harmonic source and rotation is depicted graphically on the resulting quantities.

• Coupled systems mechanics
• /
• v.8 no.5
• /
• pp.415-437
• /
• 2019

The present research deals with two-dimensional axisymmetric deformation in transversely isotropic magneto thermoelastic solid with and without energy dissipation, with two temperature and time-harmonic source. The proposed model is helpful for finding the type of relations between mechanical and thermal fields as most of the structural elements of heavy industries are frequently related to mechanical and thermal stresses at a higher temperature. The Hankel transform has been used to find a solution to the problem. The displacement components, stress components, and temperature distribution with the horizontal distance in the physical domain are calculated numerically. The effect of time-harmonic source and two temperature is depicted graphically on the resulting quantities.

• International Journal of Aeronautical and Space Sciences
• /
• v.17 no.4
• /
• pp.518-525
• /
• 2016

This paper presents the characteristics of non-fundamental multi-mode combustion instability and the effects of high-harmonic components on the Rayleigh criterion. Phenomenological observations of multi-harmonic-mode dynamic pressure waves regarding the intensity of harmonic components and the source of wave distortion have been explained by introducing examples of second- and third-order harmonics at various amplitudes. The amplitude and order of the harmonic components distorted the wave shapes, including the peak and the amplitude, of the dynamic pressure and heat release, and consequently the temporal Rayleigh index and its integrals. A cause-and-effect analysis was used to identify the root causes of the phase delay and the amplification of the Rayleigh index. From this analysis, the skewness of the dynamic pressure turned out to be a major source in determining whether multi-mode instability is driving or damping, as well as in optimizing the combustor design, such as the mixing length and the combustor length, to avoid unstable regions. The results can be used to minimize errors in predicting combustion instability in cases of high multi-mode combustion instability. In the future, the amount of research and the number of applications will increase because new fuels, such as fast-burning syngases, are prone to generating multi-mode instabilities.

• The Journal of the Society of Korean Medicine Diagnostics
• /
• v.11 no.2
• /
• pp.1-12
• /
• 2007

Objectives: The aim of the present investigation was to determine whether the finger photoplethysmographic waveform of a healthy young man will become analogous to those of healthy old men when the photoplethysmographic harmonic components in the young man decrease. Methods and Results: The finger photoplethysgmoraphy was measured in 21 old men over the age of 60 years and a young men. We acquired the representative pulse waveform of old man by averaging the finger photoplethysmographic waveforms measured in the old men. after the photoplethysmographic harmonic components in the young man were diminished with notch filtering, we compared the representative pulse waveform of old man and the pulse waveforms of which the harmonic components decreased in the young man. The finger photoplethysmographic waveform of the young man became analogous to those of the old men as the photoplethysmographic harmonic components in the young man were diminished with notch filtering. Conclusions: Decrease of the second harmonic component may be a precondition of typical age-related change of the pulse waveform.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.3
• /
• pp.319-327
• /
• 2011

An iterative technique based on orthogonal filters and frequency tracking is proposed to estimate harmonic components in power systems. The technique uses frequency interpolation to estimate fundamental frequency and harmonics when the nominal frequency of the signal is a non-integer value. Due to the number of computations involved during the generation of filter coefficients, an offline computation is suggested. Beneficial features of the proposed technique include fixed sampling rate and fixed data window size. The performance of the proposed technique is examined by simulating different power system operating conditions and evaluating the data from these simulations. A technique based on Fast Fourier Transform is also used to estimate the harmonic components for all the simulated signals. These estimates are compared with those obtained from the proposed technique. Results show that the proposed technique can converge to the accurate fundamental frequency and therefore, provide accurate harmonic components even when the fundamental frequency is not equal to the nominal frequency.

• The Journal of Korean Medicine
• /
• v.29 no.2
• /
• pp.60-70
• /
• 2008

Objectives: The aim of the present investigation was to determine whether the finger photoplethysmography (PPG) of the young will become analogous to those of the old when the PPG harmonic components in the young decrease. Methods: The PPG was measured in 46 old men (21 males and 25 females) over the age of 60 years and 10 young men (5 males and 5 females). We acquired the representative pulse waveform of old men by averaging the PPG waveforms measured in the old men. after the PPG harmonic components in the young men were diminished with notch filtering, we compared the representative pulse waveform of old men and those of the young men. Results: The PPG waveform of the young males became analogous to the representative pulse waveform of the old as the PPG harmonic components in the young were diminished with notch filtering. Especially after the second harmonic component in the young was diminished with notch filtering, increase of the Pearson's correlation coefficient was prominent. On the other hand, the Pearson's correlation coefficient between the PPG waveforms of the young females and that of the old deceased after the second harmonic component diminished in the young. Conclusions: Decrease of the second harmonic component may be a precondition of typical age-related change of the pulse waveform in the healthy male.