• International Journal of Naval Architecture and Ocean Engineering
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• 제3권3호
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• pp.201-207
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• 2011

In this paper, we focused on computing the higher-harmonic components of the transmitted wave passing over a submerged circular cylinder to show that it is causing a horizontal negative drift force. As numerical models, a circular cylinder held fixed under free surface in deep water is adopted. As the submergence of a circular cylinder decreases and the incident wavelength becomes longer, the higher-harmonic components of the transmitted wave starts to increase. An increase of the higher-harmonic components of the transmitted wave makes the horizontal drift force be negative. It is also found that the higher-harmonic amplitudes averaged over the transmitted wave region become larger with the increase of wave steepness and wavelength as well as the decrease of submergence depth.

• Journal of Magnetics
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• 제1권2호
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• pp.90-93
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• 1996

For the design of high efficiency electric machines, analysis of higher harmonic frequency components of the magnetic induction is necessary. We have measured ac magnetic properties of non-oriented silicon steel under harmonic frequencies ranging from $3^rd$ (180 Hz) to $9^th$(540 Hz) and harmonic amplitude components from 10% to 50% of the total amplitude ($B_max$=1.5T). From the experiment, it is found that, if the magnetic induction waveform has above $9^th$ harmonic frequency components of the magnetic induction, the core losses only depended on the harmonic amplitude component, but if harmonic frequency becomes lower than 9th harmonic frequency, the core losses depend on the phase angle and the harmonic amplitude, and phase angle should be considered in the design of electric machine.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.725-730
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• 2012

In this paper, flow noise characteristics of Savonius-type vertical-axis wind turbines are numerically investigated using hybrid CAA techniques. High frequency harmonics as well as BPF components are identified in the predicted noise spectra from a Savonius wind turbine. As the BPF components belong to infrasound, the higher harmonic components affects human response dominantly. Further analysis is performed to investigate the reason causing the higher frequency harmonic noise by changing operational conditions of a Savonius wind turbine. Based on this result, it is revealed that the frequency of higher harmonic components is determined by the radius of blades and angular velocity of Savonius wind turbine.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1100-1103
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• 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.

• 비파괴검사학회지
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• 제31권1호
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• pp.1-10
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• 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.

• Coupled systems mechanics
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• 제8권5호
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• pp.415-437
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.581-586
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• 2014

In general vibration test considers both harmonic vibration and random vibration, When developing the vehicle component. But the effect of harmonic vibration is larger in the parts around the vehicle engine, sole testing the harmonic vibration is considered. In this study, the fatigue damage of the linear system fixed around the engine is analyzed when the effect of random vibration is higher, harsher than the normal road surface condition. In condition the vehicle speed and the engine RPM are similar, the higher the harshness of the road surface condition is, the larger the fatigue damage level is. Therefore both random vibration and harmonic vibration must be considered in vibration test of components around the engine. Proposing the sine on random(SOR) vibration test that can exam considering both of vibrations, harmonic and random.

• Structural Monitoring and Maintenance
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• 제1권3호
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• pp.309-322
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• 2014

Detection of fatigue cracks at an early stage of their development is important in structural health monitoring. The breathing of cracks in a structure generates higher harmonic components of the exciting frequency in the frequency spectrum. Previously, the residual operational deflection shape (R-ODS) method was successfully applied to beams with a single crack. The method is based on the ODSs at the exciting frequency and its higher harmonic components which consider both amplitude and phase information of responses to map the deflection pattern of structures. Although the R-ODS method shows the location of a single crack clearly, its identification for the location of multiple cracks in a structure is not always obvious. Therefore, an improvement to the R-ODS method is presented here to make the identification process distinct for the beams with multiple cracks. Numerical and experimental examples are utilised to investigate the effectiveness of the improved method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.144-146
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• 2018

In order to meet the harmonics standards such as IEEE 519 and P1547 the output quality of a grid connected inverter should satisfy a certain level of Total Harmonic Distortion (THD) value. However, the output quality of an inverter gets degraded due to the grid voltage harmonics, the dead time effects and the nonlinearity of the switches, which all contributes to a higher THD value of the output. In order to meet the required THD value for the inverter output under the distorted grid condition the use of harmonic controller is essential. In this paper a novel feedforward harmonic compensation method is proposed in order to effectively eliminate the low order harmonics in the inverter current to the grid. In the proposed method, unlike the conventional harmonic control methods, the hamonic components are directly compensated by the feedforward terms generated by the PR controller with the grid current in the stationary frame. The proposed method is simple in implementation but powerful in eliminating the harmonics from the output. The effectiveness of proposed method is verified through the PSIM simulation and the experiments with a 5kW single phase grid connected inverter.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권4호
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• pp.330-343
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• 2016

This paper presents results of an experimental investigation of vortex-induced vibration (VIV) of a flexibly mounted and rigid cylinder with two-degrees-of-freedom with respect to varying ratio of in-line natural frequency to cross-flow natural frequency, $f^*$, at a fixed low mass ratio. Combined in-line and cross-flow motion was observed in a sub-critical Reynolds number range. Three-dimensional displacement meter and tension meter were used to measure dynamic responses of the model. To validate the results and the experiment system, x and y response amplitudes and ratio of oscillation frequency to cross-flow natural frequency were compared with other experimental results. It has been found that the higher harmonics, such as third and more vibration components, can occur on a certain part of steel catenary riser under a condition of dual resonance mode. In the present work, however, due to the limitation of a size of circulating water channel, the whole test of a whole configuration of the riser at an adequate scale for VIV phenomenon was not able to be conducted. Instead, we have modeled a rigid cylinder and assumed that the cylinder is a part of steel catenary riser where the higher harmonic motions could occur. Through the experiment, we have found that even though the cylinder was assumed to be rigid, the occurrence of the higher harmonic motions was observed in a small reduced velocity ($V_r$) range, where the influence of the in-line response is relatively large. The transition of the vortex shedding mode from one to another was examined by using time history of x and y directional displacement over all experimental cases. We also observed the influence of in-line restoring force power spectral density with $f^*$.