• Title/Summary/Keyword: spot excitation

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A Measurement of Size of the Open Crack using Ultrasound Thermography (초음파 서모그라피를 이용한 개방 균열의 크기 측정)

  • Cho, Jai-Wan;Seo, Yong-Chil;Jung, Seung-Ho;Jung, Hyun-Kyu;Kim, Seung-Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.13 no.3
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    • pp.218-223
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    • 2007
  • The dissipation of high-power ultrasonic energy at the faces of the defect causes an increase in temperature. It is resulted from localized selective heating in the vicinity of cracks because of the friction effect. In this paper the measurement of size and direction of crack using UET(Ultrasound Excitation Thermography) is described. The ultrasonic pulse energy is injected into the sample in one side. The hot spot, which is a small area around the crack tip and heated up highly, is observed. The hot spot, which is estimated as the starting point of the crack, is seen in the nearest position from the ultrasonic excitation point. Another ultrasonic pulse energy is injected into the sample in the opposite side. The hot spot, the ending point of the crack, is seen in the closest distance from the injection point also. From the calculation of the coordinates of both the first hot spot and the second hot spot observed, the size and slope of the crack is estimated. In the experiment of STS fatigue crack specimen(thickness 14mm), the size and the direction of the crack was measured.

AE Source Location in Planar Defects using Spot Excitation (Spot 가진을 이용한 평면결함의 음향방출 위치표정)

  • Rhee Zhang-Kyu;Park Sung-Oan;Woo Chang-Ki
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.5
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    • pp.87-95
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    • 2004
  • From the results of AE(Acoustic Emission) source location occurred by the spot exciting as suggested in this research, it has been confirmed that AE technique is quite fruitful in figuring out the location of the occurrence, form, size and direction of the defects. As the results of examining the distribution of event for the angle of crack $\alpha$ to Xs and Ys, as the increases from $0^{\circ}$ ~ $90^{\circ}$, gradually changes its width from the axis Xs to the axis Ys. So event appears approximately similar in its size at the angle of crack $\alpha$=$45^{\circ}$, yet opposite when $\alpha$ is lager. It is believed that this is a phenomenon where its crack legnth $\alpha$, assumed as a planar defect, is to be prcjected toward the direction with a larger size. Thus, it is expected that the application of the experimental method suggested in this study would make it possible to identify the location of the defect in the material in the nondestructive way.

Application of Accelerated Vibration Testing to Spot-welding Specimen (점용접 표준시편에 대한 가속내구시험법의 적용)

  • 김관주;조성신;정진성
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.209-213
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    • 2003
  • It is advantage of accelerated vibration testing to compress service exposures to operating vibration into a reduced laboratory test by increasing the amplitude or frequency of the applied input excitations. This paper proposes an accelerated test method to estimate the high-cycle fatigue life under random excitation. The method consists of conducting a test with amplified input excitation and extrapolating linearly the lift in the accelerated condition into the real lift in field condition. The extrapolation is carried out applying the high-cycle irregular excitation fatigue theory including the rainflow counting, Miner’s damage accumulation rule, and Goodman’s mean stress correction. As a verification, those estimated lift is compared with that acquired by experiment f3r the simple case of spot welding specimen with good agreement. This testing procedure will provide an useful scheme that can reduce testing period associated with developing time schedule of new product.

Excitation Frequency Characteristics of a Conductive Fabric Sensor Using the Bio-impedance for Estimating Knee Joint Movements (슬관절 운동 평가를 위한 생체 임피던스 측정용 전도성 섬유 센서의 여기 주파수별 특성 평가)

  • Lee, Byung-Woo;Lee, Chung-Keun;Kim, Jin-Kwon;Jeong, Wan-Jin;Lee, Myoung-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.7
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    • pp.1427-1433
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    • 2011
  • This study describes a conductive fabric sensor and determines an optimum excitation frequency of the sensor to evaluate knee joint movements. Subjects were composed of 15 males (age: $30.7{\pm}5.3$) with no known problems with their knee joints. The upper side of subjects' lower limbs was divided into two areas and the lower side of subjects' lower limbs was divided into three areas. The sensors were attached to 1 for 3 spot from a hip joint and to 3 for 4 spot from a knee joint which are the optimum conductive fabric sensor configuration to evaluate knee joint movements. As a result, the optimum excitation frequency for evaluating knee joint movements using conductive fabric sensors was 25 kHz. Average and standard deviation of bio-impedance changes from 15 subjects were $92.1{\pm}137.2{\Omega}$ at 25 kHz. The difference of bio-impedance changes between 25 kHz and 50 kHz was statistically significant (p<0.05) and the difference of bio-impedance changes between 25 kHz and 100 kHz was also statistically significant (p<0.001). These results showed that conductive fabric sensors are more sensitive to measure bio-impedance for evaluating knee joint movements as an excitation frequency decreases.

A Study of Frictional Contact Vibration Influence on Hot Spot in Automotive Disk Brake (디스크 브레이크에서 접촉 마찰 진동이 열섬에 미치는 영향 연구)

  • Cho, Ho-Joon;Kim, Myoung-Gu;Cho, Chong-Du
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.154-161
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    • 2007
  • Hot spot phenomenon that occurs, during judder vibration, is locally concentrated heat due to friction between brake disk and pad. It is important to understand the reason behind hot spot phenomenon, for reduction of judder vibration. In this experimental study, experiments were performed in accordance with rotation speed of brake disk, pressure of master cylinder and pad length for achieving different aspects of hot spot phenomenon. Temperature distribution of hot spot was obtained by using the infrared camera. As the hot spot occurred, vibration was measured and frequency analysis was performed. Finite element analysis of thermal deformation of disk was performed by using temperature distribution that was achieved by experimental results. And mode shapes of disk was analyzed by finite element analysis and compared with experimental results. It was observed that the excitation frequency band of frictional contact and frictional force mainly affects the hot spot phenomenon.

AE Source Location Techniques in Planar Defects (음향방출에 의한 평면결함의 위치표정 기술)

  • 우창기;이장규;박성완;김봉각;윤종의;인승현
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2002.04a
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    • pp.369-375
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    • 2002
  • The results of source location in terms of AE signal occurred by the spot exciting as suggested in this research, it has been confirmed that AE technique is quite fruitful in figuring out the location of the occurrence, form, size and direction of the defects. Thus, it is expected that the application of the experimental method suggested in this study would make it possible to identify, in the nondestructive way, the location of the defect in the material.

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Design, Manufacture and Characteristic Experiment of a Superconducting power Supply with Superconducting Excitation Coil (초전도여자기를 이용한 초전도전원장치의 설계.제작 및 특성해석)

  • Chu, Yong;Kim, Ho-Min;Yoon, Yong-Soo;Ko, Tae-Kuk;Han, Tae-Su
    • Progress in Superconductivity and Cryogenics
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    • v.2 no.1
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    • pp.14-18
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    • 2000
  • This paper describes a series of experiments to investigate the operational characteristics of a superconducting power supply with superconducting excitation coil. In this experiment, the superconducting excitation coil is introduced to control the pole-flex in the air gap of the machine. The operating current of the superconducting powder supply is designed to have the value of 300 [A] for the rotational speed of 600 rpm. Sensors installed on the Nb sheet yield the information on the spatial and temporal behaviors of the magnetic field in spot and on the characteristics of the superconducting power supply.

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Image Processing by a Diffusion Neural Network (확산뉴런망을 이용한 영상처리)

  • Kwon, Yool;Nam, Ki-Gon;Yoon, Tae-Hoon;Kim, Jae-Chang
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.30B no.1
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    • pp.90-98
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    • 1993
  • A Gaussian is formed by diffusing a spot excitation. In this paper, a diffusion neural network model is derived from the diffusion equation. And it is shown that a difference of two Gaussians(DOG) may have the same shape as a Laplacian of Gaussian(LOG), A neural network model executing a DOG convolution by diffusing an external excitation is proposed. By this model intensity changes of image may be detected. This model may be implemented economically because each neuron has only four fixed-valued synapes.

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3-D Magnetostatic Finite Element Simulation of a Low-Tc Superconducting Power Supply with Respect to the Excitation Current (여자전류에 따른 저온초전도전원장치의 3차원 정자계 유한요소 시뮬레이션)

  • Bae, Deok-Gwon;Kim, Ho-Min;Lee, Chan-Ju;Yun, Yeong-Su;Lee, Sang-Jin
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.7
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    • pp.364-369
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    • 2002
  • In this paper, 3-D magnetostatic finite element simulation of a rotux type Low-Tc superconducing (LTS) superconducting power supply, finite element method, cryogenic system, superconducting foil by generated magnetic flux from the rotating pole. The magnetic flux density on the superconducting foil caused by two exciters is therefore sufficiently greater than its critical magnetic flux density and it is an essential point in LTS power supply design. To establish the sufficient flux path of this machine, ferromagnetic materials is used in this power supply. When ferromagnetic materials is used at extremely low temperature, its characteristic of magnetization differs to that at room temperature. For this reason, special consideration is needed in the magnetic analysis of cryogenic systems. When the excitation current is 10A, the normal spot appears on superconducting foil. The results of this analysis are calculated and compared with the experimental results. The linkage flux due to the excitation current of 10, 20, 30, 40 and 50A are respectively $1.30{\times}10-4$, $2.67{\times}10-4$, $5.08{\times}10-4$ and $6.15{\times}10-4Wb$.

Excitation Processes of the CH4 Aurorae of Jupiter and Saturn

  • Kim, Sang Joon
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.1
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    • pp.72.1-72.1
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    • 2018
  • Recently, an analysis of 3-micron spectra of CH4 line emission from our Gemini/GNIRS observations of Jupiter's polar regions yielded an unexpected result: The homopause (~1 microbar pressure level) located directly above the long-lasting 8-micron CH4 north-polar hot spot (Great 8-micron Hot Spot: GHS) is cool compared with the temperatures of nearby auroral regions (Kim et al. 2017). Most of the 8-micron emission of the GHS originates from CH4 at the ~1 mbar level (i.e., deeper in the stratosphere, where cooling time is several years), much longer than at the altitude of the homopause. We propose a mechanism to explain the temperature difference: locally-fixed and transient, but energetic auroral particles, which can penetrate to the 1 mbar level and deposit energy there creating and maintaining the GHS. For Saturn, thus far we have not detected distinctive 8-micron nor 3-micron CH4 hot spots in the polar regions. We will present a possible implication for this difference between Jupiter and Saturn.

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