• Title/Summary/Keyword: structures of task

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Development of a full-scale magnetorheological damper model for open-loop cable vibration control

  • Zhang, Ru;Ni, Yi-Qing;Duan, Yuanfeng;Ko, Jan-Ming
    • Smart Structures and Systems
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    • v.23 no.6
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    • pp.553-564
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    • 2019
  • Modeling of magnetorheological (MR) dampers for cable vibration control to facilitate the design of even more effective and economical systems is still a challenging task. In this study, a parameter-adaptive three-element model is first established for a full-scale MR damper based on laboratory tests. The parameters of the model are represented by a set of empirical formulae in terms of displacement amplitude, voltage input, and excitation frequency. The model is then incorporated into the governing equation of cable-damper system for investigation of open-loop vibration control of stay cables in a cable-stayed bridge. The concept of optimal voltage/current input achieving the maximum damping for the system is put forward and verified. Multi-mode suboptimal and Single-mode optimal open-loop control method is then developed. Important conclusions are drawn on application issues and unique characteristics of open-loop cable vibration control using MR dampers.

Design of a TMD solution to mitigate wind-induced local vibrations in an existing timber footbridge

  • Bortoluzzi, Daniele;Casciati, Sara;Elia, Lorenzo;Faravelli, Lucia
    • Smart Structures and Systems
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    • v.16 no.3
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    • pp.459-478
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    • 2015
  • The design of a passive control solution based on tuned mass dampers (TMD's) requires the estimation of the actual masses involved in the undesired vibration. This task may result not so straightforward as expected when the vibration resides in subsets of different structural components. This occurs, for instance, when the goal is to damp out vibrations on stays. The theoretical aspects are first discussed and a design process is formulated. For sake of exemplification, a multiple TMD's configurations is eventually conceived for an existing timber footbridge located in the municipality of Trasaghis (North-Eastern Italy). The bridge span is 83 m and the deck width is 3.82 m.

Using nanotechnology for improving the mechanical behavior of spherical impactor in sport problem via complex networks

  • Bo Jin Cheng;Peng Cheng;Lijun Wang
    • Steel and Composite Structures
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    • v.49 no.1
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    • pp.31-45
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    • 2023
  • The network theory studies interconnection between discrete objects to find about the behavior of a collection of objects. Also, nanomaterials are a collection of discrete atoms interconnected together to perform a specific task of mechanical or/and electrical type. Therefore, it is reasonable to use the network theory in the study of behavior of super-molecule in sport nano-scale. In the current study, we aim to examine vibrational behavior of spherical nanostructured composite with different geometrical and materials properties. In this regard, a specific shear deformation displacement theory, classical elasticity theory and analytical solution to find the natural frequency of the spherical nano-composite sport structure equipment. The analytical results are validated by comparison to finite element (FE). Further, a detail comprehensive results of frequency variations are presented in terms of different parameters. It is revealed that the current methodology provides accurate results in comparison to FE results. On the other hand, different geometrical and weight fraction have influential role in determining frequency of the structure.

NONLINEAR FREE SURFACE CONDITION DUE TO SECOND ORDER DIFFRACTION BY A PAIR OF CYLINDERS

  • BHATTA DAMBARU D.
    • Journal of applied mathematics & informatics
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    • v.18 no.1_2
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    • pp.171-182
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    • 2005
  • An analysis of the non-homogeneous term involved in the free surface condition for second order wave diffraction on a pair of cylinders is presented. In the computations of the nonlinear loads on offshore structures, the most challenging task is the computation of the free surface integral. The main contribution to this integrand is due to the non-homogeneous term present in the free surface condition for second order scattered potential. In this paper, the free surface condition for the second order scattered potential is derived. Under the assumption of large spacing between the two cylinders, waves scattered by one cylinder may be replaced in the vicinity of the other cylinder by equivalent plane waves together with non-planner correction terms. Then solving a complex matrix equation, the first order scattered potential is derived and since the free surface term for second order scattered potential can be expressed in terms of the first order potentials, the free surface term can be obtained using the knowledge of first order potentials only.

Optimal Design of Fault-Tolerant Spatial Manipulators (고장에 견디는 공간형 매니퓰레이터의 최적설계)

  • 이병주;김동구;김희국
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1994.10a
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    • pp.605-610
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    • 1994
  • Optimal design of fault-tolerant, spatial type maniplators is treated in this paper. Design objective is to guarantte three degree-of-freedom translational motions in the task space, upon failure of one arbitrary joint of 4 degree-of -freedom manipulators. Realizing the nonfault-tolerant characteristics of current, wrist-type industrial manipulators, several 4 degree-of-freedom redundant structures with one joint redundancy are suggested as the fault-tolerant spatial -type manipulators. Fault-tolerant charactersitics are investigated basedon the analysis of the self-motion and the null-space elements, of a redundant manipulator. Finally, in order to maximize the fault-tolerant capability,optimal design is performed for a spatial-type manipulator with respect to the global isotropic index, and the performance enhancement of the optimized case is shown by simulation.

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Reconstruction of Neural Circuits Using Serial Block-Face Scanning Electron Microscopy

  • Kim, Gyu Hyun;Lee, Sang-Hoon;Lee, Kea Joo
    • Applied Microscopy
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    • v.46 no.2
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    • pp.100-104
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    • 2016
  • Electron microscopy is currently the only available technique with a spatial resolution sufficient to identify fine neuronal processes and synaptic structures in densely packed neuropil. For large-scale volume reconstruction of neuronal connectivity, serial block-face scanning electron microscopy allows us to acquire thousands of serial images in an automated fashion and reconstruct neural circuits faster by reducing the alignment task. Here we introduce the whole reconstruction procedure of synaptic network in the rat hippocampal CA1 area and discuss technical issues to be resolved for improving image quality and segmentation. Compared to the serial section transmission electron microscopy, serial block-face scanning electron microscopy produced much reliable three-dimensional data sets and accelerated reconstruction by reducing the need of alignment and distortion adjustment. This approach will generate invaluable information on organizational features of our connectomes as well as diverse neurological disorders caused by synaptic impairments.

Study on tensile performance change by recycled materials of TPO sheet applied to rooftop and artificial ground Rootproofings (옥상 및 인공지반 방근공사에 적용되는 TPO시트의 재생 소재 적용에 따른 인장성능 변화 연구)

  • Kim, Sun-Do;Kim, Jin-Sung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2018.05a
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    • pp.103-104
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    • 2018
  • Recently, in addition to greening of roof and artificial soil, Rootproofing to prevent damage to the waterproof layer and structures by roots is recognized as an important task. Therefore, various related products and construction methods have been developed and applied in the field. However, in the case of synthetic polymer-based sheets most commonly used in domestic construction sites, Most are produced using 100% new materials that are not suitable for green trends such as resource conservation and environmental protection. Therefore, in this study, we developed TPO sheet using recycled material, which is a technology that can secure eco-friendliness by utilizing recycled resources. As a result of the evaluation of tensile performance of the TPO sheet according to the recycled material content, The tensile strength of the specimens with the recycled content of 50 ~ 70% was the highest, The elongation rate of the specimen with the recycled content of 30 ~ 40% was the best.

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Seam Puckering Behavior of Breathable Waterproof Fabrics with Various Finishing Methods (가공방법에 따른 투습방수직물의 심 퍼커링 거동)

  • Jeong, Won-Young;Han, Won-Hee;An, Seung-Kook
    • Proceedings of the Korean Fiber Society Conference
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    • 2003.04a
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    • pp.402-403
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    • 2003
  • Garment manufacture represents the final stage of processing a finished fabric. The main task of the garment manufacturer is to produce shell structures out of flat fabrics to match the shape of the human body, and the most acceptable means of joining textile materials for apparel use is by sewing. On the sewing process, the bottom layer is pushed forward by the feed-dog, but the presser foot tends to retard the passage of the top layer. Since the friction between the layers is low, is possible that the components will move out of phase and pucker. (omitted)

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Identification of 18 flutter derivatives by covariance driven stochastic subspace method

  • Mishra, Shambhu Sharan;Kumar, Krishen;Krishna, Prem
    • Wind and Structures
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    • v.9 no.2
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    • pp.159-178
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    • 2006
  • For the slender and flexible cable supported bridges, identification of all the flutter derivatives for the vertical, lateral and torsional motions is essential for its stability investigation. In all, eighteen flutter derivatives may have to be considered, the identification of which using a three degree-of-freedom elastic suspension system has been a challenging task. In this paper, a system identification technique, known as covariance-driven stochastic subspace identification (COV-SSI) technique, has been utilized to extract the flutter derivatives for a typical bridge deck. This method identifies the stochastic state-space model from the covariances of the output-only (stochastic) data. All the eighteen flutter derivatives have been simultaneously extracted from the output response data obtained from wind tunnel test on a 3-DOF elastically suspended bridge deck section-model. Simplicity in model suspension and measurements of only output responses are additional motivating factors for adopting COV-SSI technique. The identified discrete values of flutter derivatives have been approximated by rational functions.

Definition of Digital Twin Models for Prediction of Future Performance of Bridges (교량의 장기성능 예측을 위한 디지털 트윈모델 정의)

  • Shim, Chang-Su;Jeon, Chi Ho;Kang, Hwi Rang;Dang, Ngoc Son;Lon, Sokanya
    • Journal of KIBIM
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    • v.8 no.4
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    • pp.13-22
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    • 2018
  • Future performance prediction of bridges is challenging task for structural engineers. Well-organized information from design, construction and operation stages is essential for the assessment of structures. Digital twin model is a new concept to realize more reliable data platform for management of infrastructures. Damage history including degradation of material, cracking, corrosion, etc. needs to be accumulated in the digital model. The digital model is linked to the analysis model for the assessment of structural performance considering changed mechanical properties of structural components. In this paper, initial definition digital twin model of a PSC-I girder bridge is proposed.