• Title, Summary, Keyword: Resonance

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Breast Magnetic Resonance Image (MRI) Guideline: Breast Imaging Study Group of Korean Society of Magnetic Resonance in Medicine Recommendations

  • Choi, Seon Hyeong;Kang, Bong Joo;Jung, Seung Eun
    • Investigative Magnetic Resonance Imaging
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    • v.22 no.4
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    • pp.205-208
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    • 2018
  • The purpose of this study is to establish an appropriate protocol for breast magnetic resonance imaging (MRI) in the discipline of image quality standards. The intention of the protocol is to increase effectiveness of medical image information exchange involved in construction, activation, and exchange of clinical information for healthcare.

Acoustic resonance by length of acoustic baffle at Finned Tube bank (핀-튜브군에서 배플 길이에 따른 음향공진)

  • 방경보;류제욱
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.98-103
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    • 2003
  • This paper presents phenomena of vibration and noise due to acoustic resonance in tube bank of a HRSG. Acoustic resonance is may arise when the vortex shedding frequency coincides with the acoustic natural frequency. At this tube bank, dominant frequencies of vibration in this system were 43.5, 67.5㎐. The 3$\^$rd/ acoustic natural frequency calculated was 68.5㎐. When the difference of vortex shedding frequency and acoustic natural frequency is within ${\pm}$20%, acoustic resonance could occur. In this system, in order to prevent acoustic resonance, acoustic baffle was installed in the tube bank before operating. But acoustic resonance occurred. So, we evaluate the effect of acoustic mode due to baffle extension length. After investigating, we did revise acoustic baffle to eliminate acoustic resonance effectively.

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Accessory Belly of the Piriformis Muscle as a Cause of Piriformis Syndrome: a Case Report with Magnetic Resonance Imaging and Magnetic Resonance Neurography Imaging Findings

  • Kim, Hae-Jung;Lee, So-Yeon;Park, Hee-Jin;Kim, Kun-Woo;Lee, Young-Tak
    • Investigative Magnetic Resonance Imaging
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    • v.23 no.2
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    • pp.142-147
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    • 2019
  • Piriformis syndrome caused by an accessory belly of the piriformis muscle is very rare. Only a few cases have been reported. Here, we report a case of piriformis syndrome resulting from an extremely rare type of accessory belly of the piriformis muscle originated at the proximal third portion of the main piriformis muscle and attached separately to the greater trochanter inferior to the insertion of the main piriformis muscle. A definitive diagnosis of piriformis syndrome was made based on magnetic resonance imaging and magnetic resonance neurography findings that were consistent with results of nerve conduction study and needle electromyography.

Effects of Calcining Temperature on Planar Coupling Factor and Resonance Charcteristics of BaTiO3 (하소온도가 BaTiO3 세라믹의 Kp와 공진특성에 미치는 영향)

  • 정수태;조상희
    • Journal of the Korean Ceramic Society
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    • v.23 no.6
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    • pp.66-70
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    • 1986
  • The calcining temperature ranging from 900$^{\circ}C$ to 1300$^{\circ}C$ affected on the planar coupling factor and resonance characteristics of BaTiO3 ceramics doped with 0.2 wt% MnO2 have been investigated. Dielectric constant planar coupling factor and anti-resonance frequency of the sample increased with the calcining temperature up to 1,200$^{\circ}C$ and decreased above that temperature but the resonance frequency decreased slightly with the increasing calcining temperature. The planar coupling factor and anti-resonance frequency increased with the sintered density and dielectric constant while the resonance frequency was almost constant. The resonance and anti-resonance frequency increased with the sample temperature.

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Resonance Phenomenon and Its Effects of Laser Texture Disk

  • Choa, Sung-Hoon;Wang, Geng
    • Journal of Mechanical Science and Technology
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    • v.14 no.7
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    • pp.744-751
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    • 2000
  • To achieve lower flying height for high areal recording density, the laser zone texturing of the disk needs to be designed to reduce glide height. One problem of the laser bump design is that the regular laser bump pattern often produces glide resonance phenomenon, which leads to failure of the glide height test. However, it was found in this study that glide resonance is an intrinsic problem of the glide head used and resonance phenomenon depends on the type of the head slider, that is, the natural frequency of the slider body. Therefore, higher glide height or glide failure caused by glide resonance does not lead to head/media interface problem in the real drive operating conditions in which the data head is used. Pseudo-random bump pattern greatly reduces the glide resonance. Smaller bump pitch will also help to reduce the glide resonance. However, as bump spacing becomes smaller, glide height will be increased due to increased air pressure developed around the bumps. Lowering bump height is the most effect way to reduce glide avalanche.

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$^{19}F$ MR Imaging of 5-FU Metabolism in Mice

  • Chaejoon Cheong;Lee, Seung-C.;Jae-G. Seo;Kim, Sung W.;Lee, Chulhyun;Kim, Chul S.;Taegyun Yang
    • Journal of the Korean Magnetic Resonance Society
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    • v.5 no.2
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    • pp.110-117
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    • 2001
  • $^{19}$ F imaging of mice was carried out. For $^{19}$ F imaging, 5-flouro-uracil (5-FU) was injected into a mouse and in vivo detection of the catabolism of 5-FU to a-fluoro-P-alanine (FBAL) was carried out. The chemical shift selective (CHESS) imaging technique was employed. The 19F spectra and images give temporal and spatial information of the metabolism for 5-FU in mice.

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A Study on the Analysis of Damping Loads to Prevent Harmonic Resonance (고조파 공진 억제를 위한 완충부하 투입량 분석에 관한 연구)

  • Lim, Chan-Ho;Lee, Kyeong-Seob;Yu, Won-Kun;Lee, Heung-Jae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.2
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    • pp.262-266
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    • 2010
  • During the restoration process of primary restorative transmission system, the over voltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. This over voltage is caused by harmonic resonance and can be prevented by damping loads that are connected before restoration process of primary restorative transmission system. But it is very difficult to predict the occurrence possibility of the harmonic resonance previously. This paper analyzes the relationship between the harmonic resonance and the amount of damping loads to prevent the harmonic resonance. This paper calculates the minimum amount of damping loads to prevent harmonic resonance while changing the length of primary restorative transmission line. And this paper confirmed that the amount of damping loads is not proportional to length of transmission line. The result of this paper will be used as important experiment data to predict the occurrence possibility of harmonic resonance previously.

FEM acoustic modal analysis due to location of acoustic baffles to avoid acoustic resonance in the tube bank of boiler for power plant (보일러 튜브군의 음향공진 회피를 위한 음향배플의 위치에 따른 FEM 음향모드해석)

  • Ahn, Sung-Jong;Ju, Young-Ho;Kim, Cheol-Hong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.150-154
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    • 2012
  • A flow induced mechanical vibration and acoustic resonance should be considered at design stage because they are mainly occurred in the tube bank of boiler. Acoustic resonance is occurred when the vortex shedding frequency of tube bank coincides with the acoustic natural frequency of the cavity. Effective solution to avoid acoustic resonance is installing acoustic baffles in the tube banks parallelly inside of the flow cavity. Thus, location and number of acoustic baffles should be exactly calculated to eliminate the acoustic resonance. This paper presents case study of acoustic resonance due to inappropriate number and location of acoustic baffles. Measured frequency and mode in the study is verified by FEM acoustic modal analysis. The number and location of acoustic baffles to avoid acoustic resonance are calculated by using FEM acoustic modal analysis.

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Experimental study on moonpool resonance of offshore floating structure

  • Yang, Seung-Ho;Kwon, Sun-Hong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.5 no.2
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    • pp.313-323
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    • 2013
  • Offshore floating structures have so-called moonpool in the centre area for the purpose of drilling, installation of subsea structures, recovery of Remotely-Operated Vehicle (ROV) and divers. However, this vertical opening has an effect on the operating performance of floating offshore structure in the vicinity of moonpool resonance frequency; piston mode and sloshing mode. Experimental study based on model test was carried out. Moonpool resonance of floating offshore structure on fixed condition and motion free condition were investigated. And, the effect of cofferdam which is representative inner structure inside moonpool was examined. Model test results showed that Molin's theoretical formula can predict moonpool resonance on fixed condition quite accurately. However, motion free condition has higher resonance frequency when it is compared with that of motion fixed. The installation of cofferdam moves resonance frequency to higher region and also generates secondary resonance at lower frequency. Furthermore, it was found that cofferdam was the cause of generating waves in the longitudinal direction when the vessel was in beam sea.