• Title/Summary/Keyword: Continuous Motion Effect

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초음파 비선형 전파특성을 이용한 부분 열화 재료의 평가 (The Evaluation of Partially Degraded Material Using Nonlinear Propagation Characteristics of Ultrasonic Wave)

  • 김경조;장경영;야마와키히사시
    • 대한기계학회논문집A
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    • 제25권2호
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    • pp.214-219
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    • 2001
  • In this paper, the nonlinear behavior of ultrasonic wave in partially degraded material is considered. For this aim, FDM(finite difference method) model for the nonlinear wave equation was developed with the restriction to the 1-D longitudinal wave motion and how the partial degradation in material contributes to the detected nonlinear parameter was analyzed quantitatively. In order to verify the rightness of this simulation method, the relation between the detected nonlinear parameter and the continuous distribution of degradation obtained from simulation was compared with experiment results and the simulation and experiment results showed similar tendency. It can be known from simulation result that the degree of degradation, the range of degradation and the continuous distribution of degradation have strong correlation with the detected nonlinear parameter. As it was possible in these simulations that only special part is assumed as degraded one, the quantitative evaluation of partially degraded material may be obtained by using this method.

Fragility analysis of R/C frame buildings based on different types of hysteretic model

  • Borekci, Muzaffer;Kircil, Murat S.
    • Structural Engineering and Mechanics
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    • 제39권6호
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    • pp.795-812
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    • 2011
  • Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness - strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

Dynamic and static structural displacement measurement using backscattering DC coupled radar

  • Guan, Shanyue;Rice, Jennifer A.;Li, Changzhi;Li, Yiran;Wang, Guochao
    • Smart Structures and Systems
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    • 제16권3호
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    • pp.521-535
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    • 2015
  • Vibration-based monitoring is one approach used to perform structural condition assessment. By measuring structural response, such as displacement, dynamic characteristics of a structure may be estimated. Often, the primary dynamic responses in civil structures are below 5 Hz, making accurate low frequency measurement critical for successful dynamic characterization. In addition, static deflection measurements are useful for structural capacity and load rating assessments. This paper presents a DC coupled continuous wave radar to accurately detect both dynamic and static displacement. This low-cost radar sensor provides displacement measurements within a compact, wireless unit appropriate for a range of structural monitoring applications. The hardware components and operating mechanism of the radar are introduced and a series of laboratory experiments are presented to assess the performance characteristics of the radar. The laboratory and field experiments investigate the effect of factors such as target distance, motion amplitude, and motion frequency on the radar's measurement accuracy. The results demonstrate that the radar is capable of both static and dynamic displacement measurements with sub-millimeter accuracy, making it a promising technology for structural health monitoring.

Characteristics of Motion-blur Free TFT-LCD using Short Persistent CCFL in Blinking Backlight Driving

  • Han, Jeong-Min;Ok, Chul-Ho;Hwang, Jeoung-Yeon;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • 제8권4호
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    • pp.166-169
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    • 2007
  • In applying LCD to TV application, one of the most significant factors to be improved is image sticking on the moving picture. LCD is different from CRT in the sense that it's continuous passive device, which holds images in entire frame period, while impulse type device generate image in very short time. To reduce image sticking problem related to hold type display mode, we made an experiment to drive TN-LCD like CRT. We made articulate images by turn on-off backlight, and we realized the ratio of Back Light on-off time by counting between on time and off time for video signal input during 1 frame (16.7 ms). Conventional CCFL (cold cathode fluorescent lamp) cannot follow fast on-off speed, so we evaluated new fluorescent substances of light source to improve residual light characteristic of CCFL. We realized articulate image generation similar to CRT by CCFL blinking drive and TN-LCD overdriving. As a result, reduced image sticking phenomenon was validated by naked eye and response time measurement.

A novel porosity-based homogenization scheme for propagation of waves in axially-excited FG nanobeams

  • Ebrahimi, Farzad;Dabbagh, Ali
    • Advances in nano research
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    • 제7권6호
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    • pp.379-390
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    • 2019
  • Putting emphasis on the effect of existence of porosity in the functionally graded materials (FGMs) on the dynamic responses of waves scattered in FG nanobeams resulted in implementation of a novel porosity-based homogenization method for FGMs and show its applicability in a wave propagation problem in the presence of axial pre-load for the first time. In the employed porosity-dependent method, the coupling between density and Young's moduli is included to consider for the effective moduli of the FG nanobeam by the means of a more reliable homogenization technique. The beam-type element will be modeled via the classical theory of beams, namely Euler-Bernoulli beam theory. Also, the dynamic form of the principle of virtual work will be extended for such nanobeams to derive the motion equations. Applying the nonlocal constitutive equations of Eringen on the obtained motion equations will be resulted in derivation of the nanobeam's governing equations. Depicted results reveal that the dispersion responses of FG nanobeams will be decreased as the porosity volume fraction is increased which must be noticed by the designers of advanced nanosize devices who are interested in employment of wave dispersion approach in continuous systems for specific goals.

소형 곤충형 지상 이동 로봇 주행 메커니즘의 다리 기구 설계 및 분석 (Design and Analysis of Leg Linkage of Small-scale Insect-inspired Ground Mobile Robot)

  • 임소정;이성준;백상민;허석행;유재관;조규진
    • 로봇학회논문지
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    • 제18권3호
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    • pp.285-292
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    • 2023
  • Small-scale ground mobile robots can access confined spaces where people or larger robots are unable. As the scale of the robot decreases, the relative size of the environment increases; therefore, maintaining the mobility of the small-scale robot is required. However, small-scale robots have limitations in using a large number of high-performance actuators, powerful computational devices, and a power source. Insects can effectively navigate various terrains in nature with their legged motion. Discrete contact with the ground and the foot enables creatures to traverse irregular surfaces. Inspired by the leg motion of the insect, researchers have developed small-scale robots and they implemented swing and lifting motions of the leg by designing leg linkages that can be adapted to small-scale robots. In this paper, we propose a leg linkage design for insect-inspired small-scale ground mobile robots. To use minimal actuation and reduce the control complexity, we designed a 1-DOF 3-dimensional leg linkage that can generate a proper leg trajectory using one continuous rotational input. We analyzed the kinematics of the proposed leg linkage to investigate the effect of link parameters on the foot trajectory.

외이전기경혈자극과 경피전기신경자극이 슬관절 전 치환슬 환자의 수술 후 통증조절에 미치는 효과 (The Effects of Auricular Electroacustimulation and Transcutaneous Electrical Nerve Stimulation on Postoperative Pain Control in Total Knee Replacement Patients)

  • 김태열;황태연;허춘복
    • 대한물리치료과학회지
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    • 제1권1호
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    • pp.145-163
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    • 1994
  • This study was done to determine differences in effect of postoperative pain control in patients receiving auricular electroacustimulation vs transcutaneous electrical nerve stimualtion following total knee replacement surgery. Thirty-one cases referred to physical therapy department after treated by total knee replacement surgery by orthopedic surgery department at the Pohang St. Mary's Hospital from January 1993 through June 1994. Of 31 total knee replacement cases, 13 cases were auricular electroacustimulation group, 11 cases were transcutaneous electrical nerve stimulation group, and 7 cases were control group. The results of the study summerized are as follows: Thirty-one total knee replacement cases(male in 12 cases, female in 19 cases), ranging in age from 34 to 61 years(mean${\pm}$SD=49.90 7.56) with diagnoses of degenerative arthritis(20 cases), rheumatoid arthritis(9 cases), and other(2 cases). In auricular electroacustimulation group, there was a significant change of pain intensity, unpleasantness, and active range of motion after treatment(p<0.01). In transcutaneous electrical nerve stimulation group, there was a significant change of pain intensity, unpleasantness, and active range of motion after treatment(p<0.01). In control group, did not show significant pre-posttreatment differences in pain intensity, unpleasantness, active range of motion(p>0.05). The mean change in pain intensity and unpleasantness, active range of motion from pretreatment baseline for the 3 groups. Auricular electroacustimulation group showed the large magnitude of increase in pain intensity and unpleasantness, active range of motion when compared to its own pretreatment cycle. Transcutaneous electrical nerve stimulation group showed small magnitude of increase in pain intensity and unpleasantness, active range of motion when compared to its own pretreatment cycle. No significant changes were observed in control group. Highly significant differences in pain intensity, unpleasantness, and active rage of motion were found using an ANOVA measures between treatment groups and control group(p<0.01). The squares correlation coefficients of pain and function measures pretreatment-posttreatment differences for each group. In treatment group, there was significant correlation between pain scale and function(p<0.001). In control group, there was no correlation between the pain scale and function (p>0.05). The continuous study is needd for many interesting issues of auricular electroacustimulation in new future.

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2차 시스템에 대한 이산시간 외란 관측기의 분석 (Analysis of Discrete-Time Disturbance Observer for Second-Order Systems)

  • 양광진;최영진;정완균
    • 제어로봇시스템학회논문지
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    • 제9권6호
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    • pp.425-434
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    • 2003
  • The disturbance observer(DOB) has been widely used in high speed and high precision motion control applications and the characteristics of DOB have been investigated in depth. Though most of DOB's have been implemented as the discrete-time form in digital devices, we are still short of the researches on discrete-time DOB (DDOB) in spite of rich references on continuous-time DOB. In this paper, we discuss about the disturbance rejection property and measurement noise effect of discrete-time DOB. Especially, we will focus on revealing the role of sampling time in designing the discrete-time DOB and show the validity of analysis through simulations and experiments for optical disk drive systems.

강인 적응성 슬라이딩을 이용한 PMSM 서보드라이브 시스템 제어기 (Robust Adaptive Sliding Mode Controller for PMSM Servo Drives System)

  • 박기광;한병조;김홍필;양해원
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2009년도 제40회 하계학술대회
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    • pp.1640_1641
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    • 2009
  • Dynamic friction and force ripple are the most predominant factors that affect the positioning accuracy of permanent magnet synchronous motor(PMSM) servo drives system, and it is desirable to compensate them in finite time with a continuous control law. In this paper, based on LuGre dynamic friction model, a robust adaptive skidding mode controller is proposed to compensate the nonlinear effect of friction and force ripple. The controller scheme consists of a PD component and a robust adaptive sliding mode controller for estimating the unknown system parameter. Using Lyapunov stability theorem, asymptotic stability analysis and position tracking performance are guaranteed. Simulation results well verify the feasibility and the effectiveness of the proposed scheme for high0precision motion trajectory tracking.

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Cartesian Space Nonlinear PD Control for the Multi-tink Flexible Manipulators

  • Cheong, Joono;Chung, Wankyun;Youm, Youngil
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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    • pp.21-24
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    • 1999
  • There-have been many control strategies for the enact joint position tracking of flexible manipulators, but direct cartesian space tracking control methods an not developed well. In this paper, we propose a PD control method based on the cartesian error in the end point trajectory tracking. the proposed controller is composed of PD control combined with nonlinear saturation term hut has a very simple form. the effect of this term is continuous suppression of vibration which is induced by the coupling of rigid motion. This control works both on the regulation and on the tracking cases. The performance and validity of this control method is shown by simulation examples.

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