• Title/Summary/Keyword: Dynamic Measuring

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Static and Repeat Loads Model Test on Soft Clay Layer due to the Geotextile Reinforcement (토목섬유로 보강된 연약지반의 정.동적 모형실험)

  • Kim, Young-Su;Kwon, Sung-Mok;Kim, Yeun-Wook;Kim, Hyoung-Jun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.232-239
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    • 2005
  • Recently geosynthetics that can be constructed on soft ground have been used for reinforcement and separation in various ways. Through laboratory model tests and numerical analysis, in this study, estimated the suitability of cable elements and appropriate input factors considering loading effect in modeling of geosynthetics. First, in laboratory model tests, geosynthetics were constructed on the clay, and covered with the thickness, 7.5cm of sand mat. And then static and dynamic model tests were performed measuring loading, settlement, ground lateral displacement, and displacements of geosynthetics, but, for cyclic loading, bearing capacity increased linearly with stiff slop because cyclic loading with constant cyclic pressure compacted the ground. Numerical analysis were performed with FLAC 4.0 2D using Mohr-Coulomb and Modified Cam-Clay models, and they compared with the results of model tests. Cable elements of FLAC in modeling geosynthetics couldn't consider the characteristics of geosynthetics that increase shear strength between geosynthetics and clay according to the loading increase. Therefore, in this study, appropriate equation that can consider loading effects in Cable elements was proposed by Case Study.

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A Study on the Algorithm for Detection of Partial Discharge in GIS Using the Wavelet Transform

  • J.S. Kang;S.M. Yeo;Kim, C.H.;R.K. Aggarwal
    • KIEE International Transactions on Power Engineering
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    • v.3A no.4
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    • pp.214-221
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    • 2003
  • In view of the fact that gas insulated switchgear (GIS) is an important piece of equipment in a substation, it is highly desirable to continuously monitor the state of equipment by measuring the partial discharge (PD) activity in a GIS, as PD is a symptom of an insulation weakness/breakdown. However, since the PD signal is relatively weak and the external noise makes detection of the PD signal difficult, it therefore requires careful attention in its detection. In this paper, the algorithm for detection of PD in the GIS using the wavelet transform (WT) is proposed. The WT provides a direct quantitative measure of the spectral content and dynamic spectrum in the time-frequency domain. The most appropriate mother wavelet for this application is the Daubechies 4 (db4) wavelet. 'db4', the most commonly applied mother wavelet in the power quality analysis, is very well suited to detecting high frequency signals of very short duration, such as those associated with the PD phenomenon. The proposed algorithm is based on utilizing the absolute sum value of coefficients, which are a combination of D1 (Detail 1) and D2 (Detail 2) in multiresolution signal decomposition (MSD) based on WT after noise elimination and normalization.

Observation of Morphology, Surface potential and Optical Transmission Images in the Thin Film Using SPM (SPM을 이용한 박막의 모폴로지, 표면전위와 광투과이미지 관찰)

  • Shin, Hoon-Kyu;Kwon, Young-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.05b
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    • pp.327-330
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    • 2000
  • The scanning Maxwell-stress microscopy (SMM) is a dynamic noncontact electric force microscopy that allows simultaneous access to the electrical properties of molecular system such as surface potential, surface charge, dielectric constant and conductivity along with the topography. The Scanning near-field optical / atomic force microscopy (SNOAM) is a new tool for surface imaging which was introduced as one application of the atomic force microscope (AFM). Operated with non-contact forces between the optical fiber and sample as well as equipped with the piezoscanners, the instrument reports on surface topology without damaging or modifying the surface for measuring of optical characteristic in the films. We report our recent results of its application to nanoscopic study of domain structures and electrical functionality in organic thin films by SMM. Furthermore, we have illustrated the SNOAM image in obtaining the merocyanine dye films as well as the optical image.

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A Review of Studies Comparing of Surface Electromyography Values between the Low-back Pain Group and Healthy Controls (요통환자군과 정상대조군 사이의 표면근전도값 비교에 관한 연구문헌 고찰)

  • Yoo, Duk-Joo;Cho, Jae-Heung;Chung, Seok-Hee
    • Journal of Korean Medicine Rehabilitation
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    • v.23 no.4
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    • pp.83-93
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    • 2013
  • Objectives To present reviews of studies comparing surface-electromyography (SEMG) values between low back pain group and control group. Methods We searched 8 databases including KoreaMed, Google, KISS (Korean studies Information Service System), RISS (Research Information Sharing Service), OASIS (Oriental medicine Advanced Searching Integrated System), Pubmed, Ovid-MEDLINE and EMBASE. After searching, we conducted study selection by using inclusion and exclusion criteria and quality-assessment. We reviewed the selected studies concerning about the subject's measuring position, findings, sensitivities and specificities. Results 27 Studies were searched and reviewed. In static surface electromyography, more muscle activities observed in low back pain subjects than in controls. In dynamic surface electromyography, the low back pain subjects showed more muscle activites during flexion, while the control group showed more muscle activities during extension. Faster muscle fatigue observed in isometric muscle analysis. Conclusions Surface electromyography values will be able to be objective marker for evaluating low back pain. Further research is needed to determine additional unified protocol such as the type of SEMG and its directions.

Design of Irrigation Pumping System Controller for Operational Instrument of Articulation (관절경 수술을 위한 관주(灌注)시스 (Irrigation Pumping System) 제어기의 개발)

  • 김민수;이순걸
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1294-1297
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    • 2003
  • With the development of medical field, many kinds of operations have been performed on human articulation. Arthroscopic surgery, which has Irrigation Pumping System for security of operator vision and washing spaces of operation, has been used for more merits than others. In this paper, it is presented that the research on a reliable control algorithm of the pumping system instrument for arthroscopic surgery. Before clinical operation, the flexible artificial articulation model is used for realizing the model the most same as human's and the algorithm has been exploited for it. This system is considered of the following; limited sensing point, dynamic effect by compliance, time delay by fluid flow and so on. The system is composed with a pressure controller, a regulator for keeping air pressure, an airtight tank that can have distilled water packs, artificial articulation and a measuring system, and has controlled by the feedback of pressure sensor on the artificial articulation. Also the system has applied to Smith Predictor for time delay and the parameter estimation method for the most suitable system with both the experiment data and modeling. In this paper, the pressure error that is between an air pressure tank and an artificial articulation was measured so that the system could be presumed and then the controller had developed for performing State-Feedback. Finally, the controller with a real microprocessor has realized. The confidence of system can be proved by applying this control algorithm to an artificial articulation experiment material.

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Optimum Cam Profile Design and Experimental Verification on an OHC Type Cam-valve System (OHC형 캠-밸브 기구의 최적 캠 형상설계 및 실험적 검증)

  • 김성훈;김원경;박윤식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.11
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    • pp.2049-2058
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    • 1992
  • In this work, a 6 degree of freedom lumped mass model is constructed for an OHC-type cam valve train analysis, and the model is verified experimentally. Using the verified model, an optimum cam profile is designed to minimize the maximum contact force between cam and follower under the constraints such as cam lift and cam event angle. The designed cam was carefully machined and tested experimentally. As operating the designed cam shaft on the test rig, the valve motion was precisely measured with laser displacement meter and the contact force was indirectly monitored by measuring strain at a certain point of the finger follower. Judging from the model simulation and experiment results, the maximum contact force can be reduced as much as more than 16.7 percent under maintaining the original valve flow area by adopting the optimum cam profile.

Integrated Monitoring System of Maglev Guideway based on FBG Sensing System (FBG 센서 기반의 자기부상열차 통합 모니터링 시스템)

  • Chung, Won-Seok;Kang, Dong-Hoon;Yeo, In-Ho;Lee, Jun-S.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.761-765
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    • 2008
  • This study presents an effective methodology on integrated monitoring system for a maglev guideway using WDM-based FBG sensors. The measuring quantities include both local and global quantities of the guideway response, such as stains, curvatures, and vertical deflections. The strains are directly measured from multiplexed FBG sensors at various locations of the test bridge followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the Bernoulli beam theory and regression analysis. Frequency contents obtained from the proposed method are compared with those from a conventional accelerometer. Verification tests were conducted on the newly-developed Korean Maglev test track. It has been shown that good agreement between the measured deflection and the estimated deflection is achieved. The difference between the two peak displacements was only 3.5% in maximum and the correlations between data from two sensing systems are overall very good. This confirms that the proposed technique is capable of tracing the dynamic behavior of the maglev guideway with an acceptable accuracy. Furthermore, it is expected that the proposed scheme provides an effective tool for monitoring the behavior of the maglev guideway structures without electro magnetic interference.

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Structural damage detection by principle component analysis of long-gauge dynamic strains

  • Xia, Q.;Tian, Y.D.;Zhu, X.W.;Xu, D.W.;Zhang, J.
    • Structural Engineering and Mechanics
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    • v.54 no.2
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    • pp.379-392
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    • 2015
  • A number of acceleration-based damage detection methods have been developed but they have not been widely applied in engineering practices because the acceleration response is insensitive to minor damage of civil structures. In this article, a damage detection approach using the long-gauge strain sensing technology and the principle component analysis technology is proposed. The Long gauge FBG sensor has its special merit for damage detection by measuring the averaged strain over a long-gauge length, and it can be connected each other to make a distributed sensor network for monitoring the large-scale civil infrastructure. A new damage index is defined by performing the principle component analyses of the long-gauge strains measured from the intact and damaged structures respectively. Advantages of the long gauge sensing and the principle component analysis technologies guarantee the effectiveness for structural damage localization. Examples of a simple supported beam and a steel stringer bridge have been investigated to illustrate the successful applications of the proposed method for structural damage detection.

Analysis of thermal and damage effects over structural modal parameters

  • Ortiz Morales, Fabricio A.;Cury, Alexandre A.
    • Structural Engineering and Mechanics
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    • v.65 no.1
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    • pp.43-51
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    • 2018
  • Structural modal parameters i.e. natural frequencies, damping ratios and mode shapes are dynamic features obtained either by measuring the vibration responses of a structure or by means of finite elements models. Over the past two decades, modal parameters have been used to detect damage in structures by observing its variations over time. However, such variations can also be caused by environmental factors such as humidity, wind and, more importantly, temperature. In so doing, the use of modal parameters as damage indicators can be seriously compromised if these effects are not properly tackled. Many researchers around the world have found numerous methods to mitigate the influence of such environmental factors from modal parameters and many advanced damage indicators have been developed and proposed to improve the reliability of structural health monitoring. In this paper, several vibration tests are performed on a simply supported steel beam subjected to different damage scenarios and temperature conditions, aiming to describe the variation in modal parameters due to temperature changes. Moreover, four statistical methodologies are proposed to identify damage. Results show a slightly linear decrease in the modal parameters due to temperature increase, although it is not possible to establish an empirical equation to describe this tendency.

Study on the Chemical Treatment of Silica for SBR Reinforcement (화학처리(化學處理) Silica의 SBR에 대한 보강효과(補强效果)에 관(關)한 연구(硏究))

  • Park, Gun-Rok;Yoo, Chong-Sun;Choi, Sei-Young
    • Elastomers and Composites
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    • v.29 no.1
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    • pp.18-29
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    • 1994
  • The purpose of this study is to investigate reinforced effect between silica treated by coupling agents and rubber matrix under the configuration chemical bonds, and the effect of silica particles coated by organic polymers using aluminum chloride as the catalyst. In vulcanization characteristies were tested by Curastometer. The M-series vulcanizates were reached to the fastest optimum cure $time(t_{90})$ and R-series vulcanizates with the same formula had the shorted optimum cure times. Tensile characteristics measuring with a tensile tester revealed that the M-series vulcanizate was the best in the physical properties, such as tensile strength. In 100% modulus, however, the S-series vulcanizates appeared to be better than the other vulcanizates. Also, hardness showed the following order : S-series>R-series>M-series with the order of elongation R-series>M-series>S-series. In SEM test, shapes of chemical treated silicas were observed. The dispersion of filler in the SBR composite appeard uniformly. In RDS test for the dynamic characteristics, G' indicates that S-3 shows the highest value with the next order M-3>R-3, and the order of damping values are as followe: M-3>M-3>R-3.

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