• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.202-207
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• 2006

The aeroacoustic noise from intake head of a vacuum cleaner is caused by complicated transient pressure fluctuation and it greatly affects the overall SPL of the vacuum cleaner. In this study, we intended to decrease the overall SPL by reducing the aeroacoustic noise from intake head. In the first the place, we analyzed the aeroacoustic noise from the unsteady fluid analysis of intake head. And then, we grasped the dominant frequency band from the aeroacoustic noise by comparing the spectrum distributions between examinations and analyses. Also, we systematically investigated the aeroacoustic noise sources from each part composing the intake head. Consequently, we redesigned each part of the dominant noise sources and suggested the modified intake head, resulting in the reduction ortho overall SPL by 3.6dB(A).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.369-374
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• 2002

This paper presents theoretical analysis of the NRRO(non-repeatable run-out) for a ball bearing with geometric imperfection. The 3DOF dynamic analysis of a ball bearing using the Newton-Raphson method is performed to calculate the displacement of shaft center. Frequency and magnitude characteristics of radial and axial vibrations are investigated. The ball form errors of the ball, the inner race, and the outer race in a HDD spindle ball bearing are precisely measured. NRRO of a ball bearing is analyzed by using the measured waviness data. It is concluded that dominant components of radial vibrations are ${\Large}f_c\;and\;2{\Larg}f_b{\pm}{\Large}f_c$, and dominant component of axial vibrations is $2{\Large}f_b$. These are generated by the size error and the second waviness of the balls.

• Ocean Systems Engineering
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• v.6 no.3
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• pp.233-244
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• 2016

Tension Leg Platform (TLP) is a floating structure that consists of four columns with large diameter. The diffraction theory is used to calculate the wave force of floating structures with large dimensions (TLP). In this study, the diffraction and Froude-Krylov wave forces of TLP for surge, sway and heave motions and wave force moment for roll, pitch degrees of freedom in different wave periods and three wave approach angles have been investigated. From the numerical results, it can be concluded that the wave force for different wave approach angle is different. There are some humps and hollows in the curve of wave forces and moment in different wave periods (different wavelengths). When wave incidents with angle 0 degree, the moment of diffraction force for pitch in high wave periods (low frequencies) is dominant. The diffraction force for heave in low wave periods (high wave frequencies) is dominant. The phase difference between Froude-Krylov and diffraction forces is important to obtain total wave force.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.930-938
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• 2004

This paper presents the noise source identification of a car A/V system. There are two different kinds of noise sources noise generated by loading mechanism and rattle noise by externally forced vibration. A dynamometer has been made to produce stationary inertia to the loading mechanism of A/V system. Sound pressure spectra and sound intensity were measured by operating the dynamometer setup as various motor speeds, and the results were analyzed. A dominant rattle noise source about A/V system's components has been found by multi-dimensional spectral analysis. Residual spectrum method was applied for eliminating coherence between the vibration sources. In result, the dominant rattle noise source was identified by partial coherent output spectrum of individual vibration component.

• Explosives and Blasting
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• v.27 no.2
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• pp.42-47
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• 2009

Ground vibrations caused by pile driving or explosive blasting can affect the stability of power line tower and its foundation. Because the characteristics of ground vibrations generally depend on the distances from the blast, the ground vibrations should be controlled by taking the distance into account. In this study, ground vibration levels were measured at the foundation of a power line tower and on ground surface adjacent to the tower. The relationships between the dominant frequencies of the ground vibrations that were measured at both locations were comparatively investigated.

• Animal cells and systems
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• v.7 no.2
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• pp.119-122
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• 2003

In order to determine whether foals of move dominant mothers were harassed less by mares than those of lower-ranked mothers, harassment of foals was studied in a herd of Jeju ponies (Equus caballus) consisting of 73 mares, their 53 foals, and one stallion. Mares Harassed the foals on 71 occasions between March to September,1998. The frequency of harassment tended to decrease as foals aged, but the relationship was not significant (P = 0.079). Foals were harassed when sleeping (n = 14), grazing (n = 19), moving (n = 8), approaching a mare in the vicinity (n = 13), or play-fighting with the foal of the harassing mare (n = 17). Mares harassed foals of younger, more subordinate mares than those of older, more dominant mares (P < 0.001). We conclude that early social experience of foals is associated with the dominance rank of its mother.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.1-5
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• 2019

In this study, optimum locations for a loop-type ground radiation antenna are evaluated for C-shaped ground planes of two different sizes. To achieve good radiation performance, the antenna needs to be located such that it couples with the dominant current mode of the ground plane. Antenna locations are proposed using the characteristic mode analysis of the ground planes. The measured bandwidths of the antennas at the proposed locations have more than twice the bandwidths of the cases in which the antennas are coupled with non-dominant modes. The operating frequency of the antennas is 2.45 GHz.

• Journal of Veterinary Clinics
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• v.13 no.2
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• pp.163-170
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• 1996

This study was performed to analyse the common calls of poddle spectrographically : bark, growl, howl, snore, yelp and whine. The sonograms of 6 common calls were shown their own specific features. There were significant differences among each types of common callsin the parceter of minimun frequency of call (MIFC), maximun frequency of call (MAFC), duration of call (DC), interval between call (IBC), dominant frequency (DF), F1 formant, F2 formant and F3 formant (P<0.01). It was considered that it was possible to record the main common calls dogs by sonograms and it sould be applied to objective basic data for understanding the psychological stats of dogs, the social relationship among them and the relationship sith human being.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.6
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• pp.582-590
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• 2020

This paper presents the results of new error analysis on the veering of marine target with the concept of frequency of occurrence, and shows how to apply the midcourse guidance errors of anti-ship missile. The veering error would be a dominant factor in the midcourse guidance errors with flight time increase. This study suggests the reasonable application method of the veering error based on the characteristics of abnormal error, and describes the tailoring method including trade-off between the midcourse guidance range of veering target and the value of frequency of occurrence on veering error.

• Journal of KSNVE
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• v.9 no.4
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• pp.761-768
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• 1999

This paper presents an NVH test of Automotive power steering system performed at a half-car Test-rig. The test was done for neutral and full turn(or relief) conditions in steering wheel at a fixed rpm first, then followed by the same conditions for the rpm run-up. The sound intensity measurement verified the results from the frequency and order analysis, especially about the identification of major noise sources and their dominant frequencies. The results from thie study can be utilized in the system noise tuning when a new steering component is installed. In particular, the noise and vibration reduction at the relief condition will be accomplished through the knowledge obtained from this study and from the on-going research on the hose tuning techniques usign silencers and tuning cable inserted in the pressure hose.