• Title/Summary/Keyword: Phase displacement

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Enhanced Strain Imaging Using Quality Measure

  • Jeong, Mok-Kun;Kwon, Sung-Jae
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.3E
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    • pp.84-94
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    • 2008
  • Displacement estimation is a crucial step in ultrasonic strain imaging. The displacement between a pre- and postcompression signal in the current data window is estimated by first shifting the postcompression signal by the displacement obtained in the previous data window to reduce their decorrelation and then determining the remaining part of the displacement through autocorrelation and conversion of phase difference into time delay. However, since strain image quality tends to vary with the amount of compression applied, we propose two new methods for enhancing strain image quality, i.e., displacement normalization and adaptive persistence. Both in vitro and in vivo experiments are carried out to acquire ultrasound data and produce strain images in real time under the application of quasi static compression. The experimental results demonstrate that the methods are quite effective in improving strain image quality and thus can be applied to implementing an ultrasound elasticity imaging system that operates in real time.

Application of Phase-shifting Method using fourier Transform to Measurement of In-plane Displacement by Speckle Interferometry

  • Kim, Myung-Soo;Baek, Tae-Hyun;Morimoto, Yoshiharu;Fujigaki, Motoharu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.3
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    • pp.171-177
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    • 2005
  • Phase-shifting method using Fourier transform (PSM/FT) has been applied to measurement of in-plane displacement of a specimen. Thirty-two interference fringe patterns each of which has different phase of ${\pi}/16$ radian have been gathered from a specimen with in-plane displacement. Low-pass filtering by 2-D Fourier transform is used to suppress spatial noise of the fringe patterns. ${\alpha}-directional$ Fourier transform for PSM/FT is performed by use of the low-pass filtered 32 fringe patterns. Two kinds of specimens are used for experiment. One is a rectangular steel plate and the other one is a rectangular steel plate containing a circular hole at the center. In-plane displacement of each specimen is measured by PSM/FT, and calculated by finite element method (ANSYS) for comparison. The results are quite comparable, so that PSM/FT can be applied to measurement of in-plane displacement.

A Study on the Phase Bandwidth Frequency of a Directional Control Valve Based on the Hydraulic Line Pressure (배관 압력을 이용한 방향제어밸브 위상각 대역폭 주파수 측정에 관한 연구)

  • Kim, Sungdong;Lee, Jung-eun;Shin, Daeyoung
    • Journal of Drive and Control
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    • v.15 no.4
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    • pp.1-10
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    • 2018
  • Spool displacement of a direction control valve is the standard signal to measure the bandwidth frequency of the direction control valve. When the spool displacement signal is not available, it is suggested in this study to use the metering hydraulic line as an alternative way to measure - 90 degree phase bandwidth frequency of the hydraulic direction control valve. Dynamics of the hydraulic line is composed of inertia, capacitance, and friction effects. The effect of oil inertia is dominant in common hydraulic line dynamics and the line dynamics is close to a derivative action in a range of high frequency; such as a range of bandwidth frequency of common directional control valves. Phase difference between spool displacement and line load pressure is nearly constant as a valve close to 90 degree. If phase difference is compensated from the phase between valve input and pressure, compensated phase may be almost same as the phase of spool displacement that is a standard signal to measure phase bandwidth frequency of the directional control valve. A series of experiments were conducted to examine the possibility of using line pressure in to measure phase bandwidth frequency of a directional control valve. Phase bandwidth frequency could be measured with relatively high precision based on metering hydraulic line technique and it reveals consistent results even when valve input, oil temperature, and supply pressure change.

An Investigation about Dynamic Behavior of Three Point Bending Specimen

  • Cho, Jae-Ung;Han, Moon-Sik
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.4
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    • pp.149-157
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    • 2000
  • Computer simulations of the mechanical behavior of a three point bend specimen with a quarter notch under impact load are performed. The case with a load application point at the side is considered. An elastic-plastic von Mises material model is chosen. Three phases such as impact bouncing and bending phases are found to be identified during the period from the moment of impact to the estimated time for crack initiation. It is clearly shown that no plastic deformation near the crack tip is appeared at the impact phase. However it is confirmed that the plastic zone near the crack tip emerges in the second phase and the plastic hinge has been formed in the third phase. Gap opening displacement crack tip opening displacement and strain rate are compared with rate dependent material(visco-plastic material). The stability during various dynamic load can be seen by using the simulation of this study.

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A Theoretical Study for the Thermal Diffusivity Measurement of Solid Material using Photothermal Displacement Method (광열변위법을 이용한 재료의 열확산계수 측정에 대한 이론적 연구)

  • Jeon, Pil-Soo;Lee, Eun-Ho;Lee, Kwang-Jai;Yoo, Jai-Suk;Kim, Ki-Hyun
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.132-137
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    • 2000
  • A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in solid materials. The influence of parameters - radius and modulation frequency of pump beam and thickness of material - on the phase lag was studied. The phase decreases up to a certain position, then starts to increase and does have an asymptotic value. The position, where phase has the minimum value, is a function of thermal diffusion length thickness of sample, and radius of pump beam. A new method based on minimum phase lag is described to determine the thermal diffusivity of solid material.

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Thermal diffusivity measurements of opaque solid using the phase lag of photothermal displacement. (광열변위의 위상차를 이용한 불투명 고체의 열확산계수 측정)

  • Lee, Eun-Ho;Lee, Kwang-Jai;Jeon, Pil-Soo;Yoo, Jai-Suk
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.138-143
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    • 2000
  • A new method of measuring the thermal diffusivity of solid material at room temperature with photothermal displacement method is proposed. The influence of the parameters on phase lag was studied. From the minimum position of phase of measured deflection with respect to the pump beam the thermal diffusivity of the materials can be obtained. The minimum position of phase is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying new method are in good agreement with the literature values.

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The Relationship between the Plantar Center of Pressure Displacement and Dynamic Balance Measures in Hemiplegic Gait (편마비 보행 시 족저압력중심의 이동특성과 동적균형능력의 상관관계 연구)

  • Park, Ji-Won;Nam, Ki-Seok;Back, Mi-Youn
    • Physical Therapy Korea
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    • v.12 no.1
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    • pp.11-21
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    • 2005
  • The purpose of this study was to investigate how COP displacement of a hemiplegic foot in stance phase during gait is related to clinical balance measures and the recovery stage in hemiplegic stroke patients. Twenty-eight functionally ambulant hemiplegic patients who had suffered from strokes and thirty age-matched healthy subjects participated in this study. COP parameters were calculated. Clinical balance was measured using the Functional Reach Test (FRT) and Timed Up and Go Test (TUGT). The recovery stage, proprioception, and clonus of the ankles or lower extremities were also measured for physical impairment status. The COPx max-displacement in the medial-lateral side of the stroke patients was significantly longer than that of the normal group (p=.038). The COPy max-displacement in the anterior-posterior side of the stroke patients was significantly shorter than that of normal group (p<.001). Significant differences in the COPx and COPy displacement asymmetry index were found between the two groups (p<.01). The FRT was correlated with the COPx displacement (r=.552) and COPy displacement (r=.765). The TUGT was correlated with the COPy displacement (r=-.588) only. The recovery stage of the lower extremities was correlated with COPy displacement (r=.438). The results of the study indicate that the characteristic of COP displacement in hemiplegic feet in stance phase during gait is related to balance ability and recovery in stroke patients. COP parameters acquired by the mapping of foot pressure in stance phase during gait will provide additional useful clinical information. This information can be used by clinicians to assess objectively the pathologic gait with other diseases and to evaluate the therapeutic effects on gait in stroke patients.

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The Kinematical Analysis of Straddle Jump to Push up Motion on Sports Aerobics (스포츠 에어로빅스 Straddle Jump to Push up 동작의 운동학적 분석)

  • Kim, Cha-Nam
    • Korean Journal of Applied Biomechanics
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    • v.12 no.2
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    • pp.77-90
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    • 2002
  • This study serves the purpose of understanding about correct jump and landing motion through Kinematical Analysis of Straddle Jump to Push up Motion at target by four elite sports aerobics athletes have more than four years career. And further more that make good assistance for coaches effective guidance through an offer basic data and correct diagnosis, evaluate of motions. It was picture-taked by two-video camera for Straddle Jump to Push up Motions. Camera speeds are 60 frame/sec. There are Kinematical Variation elements for analysis, the displacement of COG, each angle displacement left/right of shoulder-joint, each angle displacement left/right of knee-joint and each speed left/right of tip of the toes. Every each person accomplished severaly 3 times and we have acquired this conclusion. The conclusions were as follows; 1. Each situation for displacement of COG showed low height of COG by phase 1, 4, 5(79.05${\pm}9.07,\;46.41{\pm}3.65,\;18.66{\pm}0.54cm$) and It showed high height of COG by phase 2, 3($120.80{\pm}6.13,\;148.12{\pm}9.19cm$). 2. Each displacement left, right of shoulder-joint flexion by phase 1($91.07{\pm}8.30,\;90.77{\pm}5.72$deg/sec)and It showed maximal extension angles by phase 2($102.48{\pm}10.00,\;102.39{\pm}10.51$deg/sec). in part of phase 3, left of shoulder-joint angle($94.43{\pm}4.12$deg/sec) showed flexion phase 1, the other right shoulder-joint angle(88.38${\pm}$4.98deg/sec) showed more a little lower than phase 1, in last phase that showed most low by phase 4($70.58{\pm}13.72,\;54.24{\pm}11.58$deg/sec). 3. Each displacement left, right of hip joint showed maximal extent conditions by phase 2, 3($160.35{\pm}22.68,\;1534.77{\pm}5.40$deg/sec, $150.04{\pm}12.79,\;145.54{\pm}13.00$deg/sec) beside, ankle-joint showed minimal angle by phase 1, 4($93.59{\pm}18.92,\;85.37{\pm}13.23$deg/sec, $66.60{\pm}15.77,\;80.60{\pm}16.57$deg/sec). 4. Each displacement left, right of hip joint showed maximal extent conditions by phase 2($157.15{\pm}9.13,\;163.52{\pm}8.18$deg/sec), and right of hip joint showed minimal angle by phase 3($110.87{\pm}13.81,\;77.53{\pm}8.95$deg/sec) It showed alike condition of low angle by phase 1, 4($91.04{\pm}2.31,\;96.26{\pm}2.20$deg/sec). 5. Each displacement left, right of knee-joint showed maximal extent conditions by phase 1, 3, 4($173.46{\pm}2.95,\;171.51{\pm}5.44$deg/sec, $172.24{\pm}4.49,\;171.26{\pm}0.65$deg/sec, $162.78{\pm}2.13,\;164.10{\pm}5.97$deg/sec) but It showed flexion only left of knee-joint by phase 2($164.45{\pm}7.51,\;159.38{\pm}3.48$deg/sec). 6. Each speed left, right of the tip of the toes showed most fastest when someone jumped with lift up leges by phase 1, 2($321.32{\pm}67.91,\;316.90{\pm}41.97$cm/sec, $410.06{\pm}153.06,\;399.77{\pm}189.34$cm/sec), It showed more less speed than phase 1,2 by phase 3($169.74{\pm}67.17,\;150.00{\pm}63.80$cm/sec) and It showed most slow speed than phase 1,2,3 by phase 4($87.22{\pm}34.90,\;85.72{\pm}52.23$cm/sec).

A study on the movement of Liquid DMPE and DLPE monolayer on a water subphase by Maxwell Displacement Currents (변위전류에 의한 DMPE, DLPE 지질막의 수면상 거동 연구)

  • ;;;;M. Iwamoto
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.11a
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    • pp.191-194
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    • 1996
  • Maxwell displacement current clearly shows the onset of a first order phase transition from gaseous to gaseous-fluid phase, and polar ordering of liquid molecules in the solid phase coexisting with fluid. For further monolayer compression in the fluid/solid phase transition, the condensation of domains was suggested.

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Simultaneous measurement of in-plane and out-of-plane displacement using holographic interferometry (홀로그래피 간섭계를 이용한 횡변위와 종변위의 동시 측정)

  • 김달우;임부빈
    • Korean Journal of Optics and Photonics
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    • v.8 no.4
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    • pp.267-276
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    • 1997
  • We set up a four-wave holographic interferometer using a symmetric dual-beam illumination which is to measure in-plane and out-of-plane displacement simultaneously. In order to acquire the displacement phase map we applied the phase-shifting method and removed the noise of the phase map with least-squares fitting. In this approach the access to information relative to both the difference and sum of phases existing in the two arms of four-wave holographic interferometer was allowed. As a result, in-plane and out-of-plane displacement was measured to the accuracy of λ/40 and λ/100, respectively at λ=632.8nm

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