• Title/Summary/Keyword: and resonance

Search Result 10,602, Processing Time 0.032 seconds

Estimation of Dynamic Stress Concentration Factor by Infrared Thermography Stress Analysis (적외선 열화상 응력측정법에 의한 동적 응력집중계수 예측)

  • Choi, Man-Yong;Kang, Ki-Soo;Park, Jeong-Hak;Ahn, Byung-Wook;Kim, Koung-Suk
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.25 no.5
    • /
    • pp.77-81
    • /
    • 2008
  • Structural components subjected to high frequency vibrations, such as those used in vibrating parts of gas turbine engines, are usually required to avoid resonance frequencies. Generally, the operating frequency is designed at more than resonance frequencies. When a vibrating structure starts or stops, the structure has to pass through a resonance frequency, which results in large stress concentration. This paper presents the transient thermoelastic stress analysis of vibrating cantilever beam using infrared thermography and finite element method (FEM). In FEM, stress concentration factor at the 2nd resonance vibration mode is calculated by the mode superposition method of ANSYS. In experiment, stress distributions are investigated with infrared thermography and dynamic stress concentration factor is estimated. Experimental result is agreed with FEM result within 10.6%. The advantage of this technique is a better immunity to contact problem and geometric limitation in stress analysis of small or micro structures.

Estimation of Sensitivity Enhancements of Material-Dependent Localized Surface Plasmon Resonance Sensor Using Nanowire Patterns (금속물질에 따른 나노구조를 이용한 국소 표면 플라즈몬 공명 센서 특성 분석)

  • Ahn, Heesang;Ahn, Dong-Gyu;Song, Yung Min;Kim, Kyujung
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.33 no.5
    • /
    • pp.363-369
    • /
    • 2016
  • We explored localized plasmonic field enhancements using nanowire patterns to improve the sensitivity of a surface plasmon resonance (SPR) sensor. Two different materials, gold and silver, were considered for sample materials. Gold and silver nanowire patterns were fabricated by electron beam lithography for experimental measurements. The wavelength SPR sensor was also designed for these experiments. The material-dependent field enhancements on nanowire patterns were first calculated based on Maxwell's equations. Resonance wavelength shifts were indicated as changes in the refractive index from 1.33 to 1.36. The SPR sensor with silver nanowire patterns showed a much larger resonance wavelength shift than the sensor with gold nanowire patterns, in good agreement with simulation results. These results suggest that silver nanowire patterns are more efficient than gold nanowire patterns, and could be used for sensitivity enhancements in situations where biocompatibility is not a consideration.

Analysis of the THz Resonance Characteristics of H-shaped Metamaterials with Varying Width

  • Ryu, Han-Cheol
    • Current Optics and Photonics
    • /
    • v.5 no.1
    • /
    • pp.66-71
    • /
    • 2021
  • The resonance characteristics of H-shaped metamaterials, whose widths were varied while keeping the height constant, were investigated in the terahertz (THz) frequency range. The H-shaped metamaterials were numerically analyzed in two modes in which the polarization of the incident THz electric field was either parallel or perpendicular to the width of the H-shaped structure. The resonant frequency of the metamaterial changed stably in each mode, even if only the width of the H shape was changed. The resonant frequency of the metamaterial operating in the two modes increases without significant difference regardless of the polarization of the incident electromagnetic wave as the width of the H-shaped metamaterial increases. The electric field distribution and the surface current density induced in the metamaterial in the two modes were numerically analyzed by varying the structure ratio of the metamaterial. The numerical analysis clearly revealed the cause of the change in the resonance characteristics as the width of the H-shaped metamaterial changed. The efficacy of the numerical analysis was verified experimentally using the THz-TDS (time-domain spectroscopy) system. The experimental results are consistent with the simulations, clearly demonstrating the meaningfulness of the numerical analysis of the metamaterial. The analyzed resonance properties of the H-shaped metamaterial in the THz frequency range can be applied for designing THz-tunable metamaterials and improving the sensitivity of THz sensors.

Study on Smart Cooling Technology by Acoustic Streaming Generated by Ultrasonic Vibration Using 3D PIV (3차원 PIV를 활용한 초음파 진동에 의해 발생된 음향 유동을 이용한 스마트 냉각법 연구)

  • Lee, Dong-Ryul;Loh, Byoung-Gook;Kwon, Ki-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.20 no.11
    • /
    • pp.1078-1088
    • /
    • 2010
  • In order to analyze the quantitative characteristics of acoustic streaming, experimental setup of 3-D stereoscopic PIV(particle imaging velocimetry) was designed and quantitative ultrasonic flow fields in the gap between the ultrasonic vibrator and heat source were measured. Utilizing acoustic streaming induced by ultrasonic vibration, surface temperature drop of cooling object was also measured. The study on smart cooling method by acoustic streaming induced by ultrasonic vibration was performed due to the empirical relations of flow pattern, average flow velocity, different gaps, and enhancement on cooling rates in the gap. Average velocity fields and maximum acoustic streaming velocity in the open gap between the stationary cylindrical heat source and ultrasonic vibrator were experimentally measured at no vibration, resonance, and non-resonance. It was clearly observed that the enhancement of cooling rates existed owing to the acoustic air flow in the gap at resonance and non-resonance induced by ultrasonic vibration. The ultrasonic wave propagating into air in the gap creates steady-state secondary eddy called acoustic streaming which enhances heat transfer from the heat source to encompassing air. The intensity of the acoustic streaming induced by ultrasonic vibration experimentally depended upon the gap between the heat source and ultrasonic vibrator. The ultrasonic vibration at resonance caused the increase of the acoustic streaming velocity and convective heat transfer augmentation when the flow fields by 3D stereoscopic PIV and temperature drop of the heat source were measured experimentally. The acoustic streaming velocity of air enhancement on cooling rates in the gap is maximal when the gap agrees with the multiples of half wavelength of the ultrasonic wave, which is specifically 12 mm.

Cerebrospinal fluid flow in normal beagle dogs analyzed using magnetic resonance imaging

  • Cho, Hyunju;Kim, Yejin;Hong, Saebyel;Choi, Hojung
    • Journal of Veterinary Science
    • /
    • v.22 no.1
    • /
    • pp.2.1-2.10
    • /
    • 2021
  • Background: Diseases related to cerebrospinal fluid flow, such as hydrocephalus, syringomyelia, and Chiari malformation, are often found in small dogs. Although studies in human medicine have revealed a correlation with cerebrospinal fluid flow in these diseases by magnetic resonance imaging, there is little information and no standard data for normal dogs. Objectives: The purpose of this study was to obtain cerebrospinal fluid flow velocity data from the cerebral aqueduct and subarachnoid space at the foramen magnum in healthy beagle dogs. Methods: Six healthy beagle dogs were used in this experimental study. The dogs underwent phase-contrast and time-spatial labeling inversion pulse magnetic resonance imaging. Flow rate variations in the cerebrospinal fluid were observed using sagittal time-spatial labeling inversion pulse images. The pattern and velocity of cerebrospinal fluid flow were assessed using phase-contrast magnetic resonance imaging within the subarachnoid space at the foramen magnum level and the cerebral aqueduct. Results: In the ventral aspect of the subarachnoid space and cerebral aqueduct, the cerebrospinal fluid was characterized by a bidirectional flow throughout the cardiac cycle. The mean ± SD peak velocities through the ventral and dorsal aspects of the subarachnoid space and the cerebral aqueduct were 1.39 ± 0.13, 0.32 ± 0.12, and 0.76 ± 0.43 cm/s, respectively. Conclusions: Noninvasive visualization of cerebrospinal fluid flow movement with magnetic resonance imaging was feasible, and a reference dataset of cerebrospinal fluid flow peak velocities was obtained through the cervical subarachnoid space and cerebral aqueduct in healthy dogs.

Clinical Study of Acute and Chronic Pain by the Application of Magnetic Resonance Analyser $I_{TM}$ (자기공명분석기를 이용한 통증관리)

  • Park, Wook;Jin, Hee-Cheol;Cho, Myun-Hyun;Yoon, Suk-Jun;Lee, Jin-Seung;Lee, Jeong-Seok;Choi, Surk-Hwan;Kim, Sung-Yell
    • The Korean Journal of Pain
    • /
    • v.6 no.2
    • /
    • pp.192-198
    • /
    • 1993
  • In 1984, a magnetic resonance spectrometer(magnetic resonance analyser, MRA $I_{TM}$) was developed by Sigrid Lipsett and Ronald J. Weinstock in the USA, Biomedical applications of the spectrometer have been examined by Dr. Hoang Van Duc(pathologist, USC), and Nakamura, et al(Japan). From their theoretical views, the biophysical functions of this machine are to analyse and synthesize a healthy tissue and organ resonance pattern, and to detect and correct an abnormal tissue and organ resonance pattern. All of the above functions are based on Quantum physics. The healthy tissue and organ resonance patterns are predetermined as standard magnetic resonance patterns by digitizing values based on peak resonance emissions(response levels or high pitched echo-sounds amplified via human body). In clinical practice, a counter or neutralizing resonance pattern calculated by the spectrometer can correct a phase-shifted resonance pattern(response levels or low pitched echo-sounds) of a diseased tissue and organ. By administering the counter resonance pattern into the site of pain and trigger point, it is possible to readjust the phase-shifted resonance pattern and then to alleviate pain through regulation of the neurotransmitter function of the nervous system. For assessing clinical effectiveness of pain relief with MRA $I_{TM}$ this study was designed to estimate pain intensity by the patient's subjective verbal rating scale(VRS such as graded to no pain, mild, moderate and severe) before application of it, to evaluate an amount of pain relief as applied the spectrometer by the patients subjective pain relief scale(visual analogue scale, VAS, 0~100%), and then to observe a continuation of pain relief following its application for managing acute and chronic pain in the 102 patients during an 8 months period beginning March, 1993. An application time of the spectrometer ranged from 15 to 30 minutes daily in each patient at or near the site of pain and trigger point when the patient wanted to be treated. The subjects consisted of 54 males and 48 females, with the age distribution between 23~40 years in 29 cases, 41~60 years in 48 cases and 61~76 years in 25 cases respectively(Table 1). The kinds of diagnosis and the main site of pain, the duration of pain before the application, and the frequency of it's application were recorded on the Table 2, 3 and 4. A distinction between acute and chronic pain was defined according to both of the pain intervals lasting within and over 3 months. The results of application of the spectrometer were noted as follows; In 51 cases of acute pain before the application, the pain intensities were rated mild in 10 cases, moderate in 15 cases and severe in 26 cases. The amounts of pain relief were noted as between 30~50% in 9 cases, 51~70% in 13 cases and 71~95% in 29 cases. The continuation of pain relief appeared between 6~24 hours in two cases, 2~5 days in 10 cases, 6~14 days in 4 cases, 15 days in one case, and completely relived of pain in 34 cases(Table 5~7). In 51 cases of chronic pain before the application, the pain intensities were rated mild in 12 cases, moderate in l8 cases and severe in 21 cases. The amounts of pain relief were noted as between 0~50% in 10 cases, 51~70% in 27 cases and 71~90% in 14 cases. The continuation of pain relief appeared to have no effect in two cases. The level of effective duration was between 6~12 hours in two cases, 2~5 days in 11 cases, 6~14 days in 14 cases, 15~60 days in 9 cases and in 13 cases the patient was completely relieved of pain(Table 5~7). There were no complications in the patients except a mild reddening and tingling sensation of skin while applying the spectrometer. Total amounts of pain relief in all of the subjects were accounted as poor and fair in 19(18.6%) cases, good in 40(39.2%) cases and excellent in 43(42.2%) cases. The clinical effectiveness of MRA $I_{TM}$ showed variable distributions from no improvements to complete relief of pain by the patient's assessment. In conclusion, we suggest that MRA $I_{TM}$ may be successful in immediate and continued pain relief but still requires several treatments for continued relief and may be gradually effective in pain relief while being applied repeatedly.

  • PDF

$H_{\infty}$ Control of Two-Mass System with Resonance Ratio Control (공진비제어를 갖는 2관성계의 $H_{\infty}$ 제어)

  • Kim, Jin-Soo;Kim, Seoung-Beom;Kim, Hyun-Jung;Kim, Young-Seok
    • Proceedings of the KIEE Conference
    • /
    • 1996.07a
    • /
    • pp.504-506
    • /
    • 1996
  • In the industrial motor drive systems, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of this system. The resonance ratio control is proposed for suppressing the torsional vibration. In this paper, first, the optimal resonance ratio is sellected and the controller to the resonance ratio controlled outward plant is designed based on $H_{\infty}$ control theory. Secondly, the two-degree-of-freedom controller, which includes the above $H_{\infty}$ controller, is designed in order to improve the tracking characteristics for the commanded speed. The control performances are examined by the computer simulations and it is clarified that the proposed speed control system is useful for two-mass system.

  • PDF

Seeding Metastasis of Chromophobe Renal Cell Carcinoma after Robot-Assisted Laparoscopic Partial Nephrectomy

  • Lee, Kanghun;Choi, Moon Hyung
    • Investigative Magnetic Resonance Imaging
    • /
    • v.21 no.2
    • /
    • pp.119-124
    • /
    • 2017
  • Chromophobe renal cell carcinoma (RCC) is an uncommon subtype of RCC having a better prognosis than clear cell RCC. Although there are several reports of seeding metastasis of RCC after biopsy, seeding metastasis of chromophobe RCC after surgical resection has seldom been reported. Here, we describe a case of multiple seeding metastases in the abdomen and pelvis 78 months after robot-assisted laparoscopic partial nephrectomy, without prior history of biopsy for chromophobe RCC in the right kidney. As magnetic resonance imaging (MRI) of the pelvic mass showed a similar appearance to the primary renal mass and displayed separate margins with the rectum and prostate gland, we were able to make a diagnosis before pathologic confirmation.

Physical Principles of Magnetic Resonance Imaging in Animal (동물에서 자기 공명 영상 진단의 물리적 원리)

  • 김종규
    • Journal of Veterinary Clinics
    • /
    • v.16 no.1
    • /
    • pp.75-79
    • /
    • 1999
  • Magnetic resonance imaging (MRI) is an imaging technique used to produce high quality images of the inside of the animal body. MRI is based on the principles of nuclear magnetic resonance (NMR) and started out as a tomographic imaging technique, that is it produced an image of the NMR signal in a thin slice through the animal body. The animal body is primarily fat and water, Fat and water have many hydrogen atoms. Hydrogen nuclei have an NMR signal. For these reasons magnetic resonance imaging primarily images the NMR signal from the hydrogen nuclei. Hydrogen protons, within the body align with the magnetic field. By applying short radio frequency (RF) pulses to a specific anatomical slice, the protons in the slice absorb energy at this resonant frequency causing them to spin perpendicular to the magnetic field. As the protons relax back into alignment with the magnetic field, a signal is received by an RF coil that acts as an antennae. This signal is processed by a computer to produce diagnostic images of the anatomical area of interest.

  • PDF

An Experimental Investigation on Noise Reduction Performance of the Absorption and the Resonance Type Duct Silencers (흡음형과 공명형 덕트 소음기의 소음저감 성능에 관한 실험적 고찰)

  • Lee, Young-Sup;Chung, Kwang-Seop;Lee, Dong-Hoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.22 no.12
    • /
    • pp.897-901
    • /
    • 2010
  • A silencer has been widely used for the purpose of suppressing the noises propagated from duct of air conditioning system. The absorption type silencer is usually applied to reduce the noise with high frequency bandwidth. On the order hand, the resonance type silencer is applied to reduce the noise with low-middle frequency bandwidth. The insertion loss of silencer is measured in the reverberation room. The cut-off frequency of reverberation room is 100 Hz. The insertion loss of absorption type silencer is more larger than that for resonance type silencer regardless of changing the flow velocity.