• Title/Summary/Keyword: Displacement

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CHANCE OF JOINT SPACE ACCORDING TO ANTERIOR DISC DISPLACEMENT OF TMJ (악관절원판의 전방변위에 따른 관절간극의 변화)

  • Bae Jung-Soo;Kim Joon-Bae;Kim Hyung-Soon
    • The Journal of Korean Academy of Prosthodontics
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    • v.39 no.4
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    • pp.410-416
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    • 2001
  • Objective: Disc displacement may affect the joint space narrowing between condylar head and glenoid fossa. This study was designed to evaluate the correlation between the joint space change and the severity of anterior disc displacement. Materials and Methods: Two hundreds temporomandibular joints MR images of TMD patients(170 joints) and asymptomatic volunteers(30 joints) were evaluated for this purpose. Anterior disc displacement was divided into 3 stages(normal, little to mild, and moderate to severe displacement) based on sagittal images, then joint spaces were measured at medial, central and lateral parts of condyle head on coronal MR images, respectively The joint spaces of 3 groups divided according to the severity of anterior disc displacement were compared. Results: The reduction of joint space was related to the severity of the anterior disc displacement at lateral, medial side and especially at center Conclusion: The temporomandibular joint space was affected by the severity of the anterior disc displacement.

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Pose-graph optimized displacement estimation for structural displacement monitoring

  • Lee, Donghwa;Jeon, Haemin;Myung, Hyun
    • Smart Structures and Systems
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    • v.14 no.5
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    • pp.943-960
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    • 2014
  • A visually servoed paired structured light system (ViSP) was recently proposed as a novel estimation method of the 6-DOF (Degree-Of-Freedom) relative displacement in civil structures. In order to apply the ViSP to massive structures, multiple ViSP modules should be installed in a cascaded manner. In this configuration, the estimation errors are propagated through the ViSP modules. In order to resolve this problem, a displacement estimation error back-propagation (DEEP) method was proposed. However, the DEEP method has some disadvantages: the displacement range of each ViSP module must be constrained and displacement errors are corrected sequentially, and thus the entire estimation errors are not considered concurrently. To address this problem, a pose-graph optimized displacement estimation (PODE) method is proposed in this paper. The PODE method is based on a graph-based optimization technique that considers entire errors at the same time. Moreover, this method does not require any constraints on the movement of the ViSP modules. Simulations and experiments are conducted to validate the performance of the proposed method. The results show that the PODE method reduces the propagation errors in comparison with a previous work.

The MIN-N family of pure-displacement, triangular, Mindlin plate elements

  • Liu, Y. Jane;Riggs, H.R.
    • Structural Engineering and Mechanics
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    • v.19 no.3
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    • pp.297-320
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    • 2005
  • In recent years the pure displacement formulation for plate elements has not been as popular as other formulations. We revisit the pure displacement formulation for shear-deformable plate elements and propose a family of N-node, displacement-compatible, fully-integrated, pure-displacement, triangular, Mindlin plate elements, MIN-N. The development has been motivated by the relative simplicity of the pure displacement formulation and by the success of the existing 3-node plate element, MIN3. The formulation of MIN3 is generalized to obtain the MIN-N family, which possesses complete, fully compatible kinematic fields, in which the interpolation functions for transverse displacement are one degree higher than those for rotations. General element-level formulas for the thin-limit Kirchhoff constraints are developed. The 6-node, 18 degree-of-freedom element MIN6, with cubic displacement and quadratic rotations, is implemented and tested extensively. Numerical results show that MIN6 exhibits good performance for both static and dynamic analyses in the linear, elastic regime. The results illustrate that the fully-integrated MIN6 element has excellent performance in the thin limit, even for coarse meshes, and that it does not require shear relaxation.

Image-based structural dynamic displacement measurement using different multi-object tracking algorithms

  • Ye, X.W.;Dong, C.Z.;Liu, T.
    • Smart Structures and Systems
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    • v.17 no.6
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    • pp.935-956
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    • 2016
  • With the help of advanced image acquisition and processing technology, the vision-based measurement methods have been broadly applied to implement the structural monitoring and condition identification of civil engineering structures. Many noncontact approaches enabled by different digital image processing algorithms are developed to overcome the problems in conventional structural dynamic displacement measurement. This paper presents three kinds of image processing algorithms for structural dynamic displacement measurement, i.e., the grayscale pattern matching (GPM) algorithm, the color pattern matching (CPM) algorithm, and the mean shift tracking (MST) algorithm. A vision-based system programmed with the three image processing algorithms is developed for multi-point structural dynamic displacement measurement. The dynamic displacement time histories of multiple vision points are simultaneously measured by the vision-based system and the magnetostrictive displacement sensor (MDS) during the laboratory shaking table tests of a three-story steel frame model. The comparative analysis results indicate that the developed vision-based system exhibits excellent performance in structural dynamic displacement measurement by use of the three different image processing algorithms. The field application experiments are also carried out on an arch bridge for the measurement of displacement influence lines during the loading tests to validate the effectiveness of the vision-based system.

Dynamic displacement estimation by fusing biased high-sampling rate acceleration and low-sampling rate displacement measurements using two-stage Kalman estimator

  • Kim, Kiyoung;Choi, Jaemook;Koo, Gunhee;Sohn, Hoon
    • Smart Structures and Systems
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    • v.17 no.4
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    • pp.647-667
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    • 2016
  • In this paper, dynamic displacement is estimated with high accuracy by blending high-sampling rate acceleration data with low-sampling rate displacement measurement using a two-stage Kalman estimator. In Stage 1, the two-stage Kalman estimator first approximates dynamic displacement. Then, the estimator in Stage 2 estimates a bias with high accuracy and refines the displacement estimate from Stage 1. In the previous Kalman filter based displacement techniques, the estimation accuracy can deteriorate due to (1) the discontinuities produced when the estimate is adjusted by displacement measurement and (2) slow convergence at the beginning of estimation. To resolve these drawbacks, the previous techniques adopt smoothing techniques, which involve additional future measurements in the estimation. However, the smoothing techniques require more computational time and resources and hamper real-time estimation. The proposed technique addresses the drawbacks of the previous techniques without smoothing. The performance of the proposed technique is verified under various dynamic loading, sampling rate and noise level conditions via a series of numerical simulations and experiments. Its performance is also compared with those of the existing Kalman filter based techniques.

An integrated visual-inertial technique for structural displacement and velocity measurement

  • Chang, C.C.;Xiao, X.H.
    • Smart Structures and Systems
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    • v.6 no.9
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    • pp.1025-1039
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    • 2010
  • Measuring displacement response for civil structures is very important for assessing their performance, safety and integrity. Recently, video-based techniques that utilize low-cost high-resolution digital cameras have been developed for such an application. These techniques however have relatively low sampling frequency and the results are usually contaminated with noises. In this study, an integrated visual-inertial measurement method that combines a monocular videogrammetric displacement measurement technique and a collocated accelerometer is proposed for displacement and velocity measurement of civil engineering structures. The monocular videogrammetric technique extracts three-dimensional translation and rotation of a planar target from an image sequence recorded by one camera. The obtained displacement is then fused with acceleration measured from a collocated accelerometer using a multi-rate Kalman filter with smoothing technique. This data fusion not only can improve the accuracy and the frequency bandwidth of displacement measurement but also provide estimate for velocity. The proposed measurement technique is illustrated by a shake table test and a pedestrian bridge test. Results show that the fusion of displacement and acceleration can mitigate their respective limitations and produce more accurate displacement and velocity responses with a broader frequency bandwidth.

Effective Heterogeneous Data Fusion procedure via Kalman filtering

  • Ravizza, Gabriele;Ferrari, Rosalba;Rizzi, Egidio;Chatzi, Eleni N.
    • Smart Structures and Systems
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    • v.22 no.5
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    • pp.631-641
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    • 2018
  • This paper outlines a computational procedure for the effective merging of diverse sensor measurements, displacement and acceleration signals in particular, in order to successfully monitor and simulate the current health condition of civil structures under dynamic loadings. In particular, it investigates a Kalman Filter implementation for the Heterogeneous Data Fusion of displacement and acceleration response signals of a structural system toward dynamic identification purposes. The procedure is perspectively aimed at enhancing extensive remote displacement measurements (commonly affected by high noise), by possibly integrating them with a few standard acceleration measurements (considered instead as noise-free or corrupted by slight noise only). Within the data fusion analysis, a Kalman Filter algorithm is implemented and its effectiveness in improving noise-corrupted displacement measurements is investigated. The performance of the filter is assessed based on the RMS error between the original (noise-free, numerically-determined) displacement signal and the Kalman Filter displacement estimate, and on the structural modal parameters (natural frequencies) that can be extracted from displacement signals, refined through the combined use of displacement and acceleration recordings, through inverse analysis algorithms for output-only modal dynamics identification, based on displacements.

Changes in Selected Electrolyte Concentrations in Dairy Cowe with Abomasal Displacement (제사위전위증유우에 있어서 몇가지 혈청전해질 농도에 관한 조사연구)

  • Lee Sa-Kyun;Cheong Chang-Kook
    • Journal of Veterinary Clinics
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    • v.2 no.1
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    • pp.143-150
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    • 1985
  • The concentrations of serum calcium, inorganic phosphorus, sodium and potassium from 24 cows with left displacement of abomasum and 21 cows with right displacement of abomasum on pre and postoperation were determined. 1. The preoperative levels of serum calcium in left and right displacement of abomasum were below normal and returned to normal levels postoperatively. 2. The preoperative levels of serum inorganic phosphorus in left and right displacement of abomasum showed slight increase preoperatively and consistent slight rise postoperatively. 3. The preoperative levels of serum sodium in left and right displacement of abomasum were slightly below normal and maintained low levels postoperatively. 4. The preoperative levels of serum patassium in left and right displacement of abomasum were low normal limit and increased to upper normal limit postoperatively.

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Temperature-Compensative Displacement Sensor based on a Pair of Fiber Bragg Gratings Attached to a Metal Band

  • Kim, Kwang Taek;Kim, Dong Geun
    • Journal of Sensor Science and Technology
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    • v.27 no.2
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    • pp.82-85
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    • 2018
  • This paper proposes a new temperature-compensative displacement sensor with a pair of fiber Bragg gratings (FBG) attached to the inner and outer surfaces of an elastic metal band. The sensor can be also used as a temperature sensor with high sensitivity. The FBG pair shifted Bragg wavelengths in the same direction according to changes in the temperature. However, because the pressure of the metal band shifted a pair of Bragg wavelengths in the opposite direction, the displacement sensor could compensate for the effect of the temperature change in the proposed FBG pair. Results of the experiments showed that the two FBG displacement sensors responded linearly and symmetrically with respect to the displacement, and the displacement could be obtained using the difference between the two Bragg wavelengths.

Measurement of Static and Dynamic Displacement by Image Processing and Study for Prediction Method of Velocity and Acceleration (영상처리를 이용한 정적·동적 변위 계측과 속도·가속도 추산방식 연구)

  • Heo, Seok;Lee, Bum-Ho;Jang, Il-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.2
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    • pp.112-119
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    • 2011
  • This paper is concerned with the measurement of static and dynamic displacement by image processing(IP) and study for prediction method of velocity and acceleration. To measure the displacement visually, the measurement system consists of a telephoto zoom camera, CCD(charge coupled device) image device and a computer. The specific target on the white board is used to calculate the displacement of the structure. The captured image is then converted into a pixel-based data and then analyzed numerically. The limitation of the system depends on the image capturing speed and the pixel-size of image. In this paper, we developed for the displacement measurement using the image processing method. The proposed method enables us to measure the vibration displacement, velocity and acceleration directly without any contact. The current resolution for the displacement measurement can be seen from the results.