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Now showing items 1 - 13 of 13

  • Theoretical study of two-dimensional phononic crystals with viscoelasticity based on fractional derivative models

    Liu, Yaozong   Yu, Dianlong   Zhao, Honggang   Wen, Jihong   Wen, Xisen  

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  • [ASME ASME 2005 International Mechanical Engineering Congress and Exposition - Orlando, Florida, USA (November 5 – 11, 2005)] Noise Control and Acoustics - A Heuristic Model for Estimating the Lowest Gap of Locally Resonant Phononic Crystals

    Liu, Yaozong   Shao, Lihui   Wang, Gang   Yu, Dianlong  

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  • Absorptive properties of three-dimensional phononic crystal

    Zhao, Honggang   Liu, Yaozong   Yu, Dianlong   Wang, Gang   Wen, Jihong   Wen, Xisen  

    We consider the absorptive properties of three-dimensional phononic crystal (PC) composed of steel spheres arranged in viscoelastic rubber. The mode conversions during the Mie scattering of a single steel sphere in unbounded rubber are analyzed in detail. Then the multiple scattering (MS) and absorption effects induced by the simple cubic lattice and the viscosity of the rubber are investigated by the MS method. The results show that the shear and viscoelastic properties of the rubber are crucial, and the destructive interface induced by MS below each Bloch frequency enhances the absorption. Finally, the acoustic properties of finite PC slabs variation with the filling fraction and the incident angle are discussed for a variety of cases. The results show that the PC can be used as underwater anechoic material. (c) 2007 Published by Elsevier Ltd.
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  • Dynamics of the Bogie of Maglev Train with Distributed Magnetic Forces

    Liu, Yaozong   Deng, Wenxi   Gong, Pu  

    A dynamic model of the bogie of maglev train with distributed magnetic forces and four identical levitating controllers is formulated. The vertical, pitching, and rolling degree of freedom of the electromagnet modules and their coupling are considered. The frequency responses of the bogie to track irregularity are investigated with numerical simulation. The results tell us that there are resonances related to the first electromagnetic suspension whose frequencies are determined by the control parameters. A comparative analysis has been carried out between the models with distributed or concentrated magnetic forces. The comparison indicates that simplifying the distributed magnetic force to concentrated one degenerates the dynamic behavior of the maglev bogie, especially resulting in overestimated resonances of the first electromagnetic suspension of maglev trains. The results also indicate that those resonances only occur on specific wavelengths of irregularity that relate to the length of the electromagnets.
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  • DPRF: A Differential Privacy Protection Random Forest

    Hou, Jun   Li, Qianmu   Meng, Shunmei   Ni, Zhen   Chen, Yini   Liu, Yaozong  

    Providing privacy protection for classification algorithms has become a research hotspot in current data mining. In this paper, differential privacy is applied to the random forest classification algorithm, and a random forest algorithm based on differential privacy is proposed to protect the privacy information in the data classification process. Firstly, differential privacy provides privacy protection by adding perturbation noise, which leads to a decrease in the classification accuracy of random forest algorithms. In order to reduce the impact of differential privacy protection on the accuracy of random forest classification, a hybrid decision tree algorithm is proposed. For the construction of a single decision tree in a random forest, the information gain ratio in the ID3 algorithm and the information gain ratio in the C4.5 are combined to generate a new attribute metric IG_GR to improve the classification accuracy of a single decision tree. Secondly, a new privacy budget allocation strategy is proposed. For nodes of different depths in the decision tree, the privacy budget is allocated to its counting query and attribute query by weight, which is used to balance the signalto-noise ratio of differential privacy technology to nodes of different depths in the decision tree. At the same time, the hybrid decision tree algorithm is applied to the construction of random forest, which balances the privacy and classification accuracy of the random forest algorithm based on differential privacy. Finally, this paper conducted experiments on UCI's Adult and Mushroom datasets. The results show that compared with the traditional decision tree algorithm, the algorithm proposed in this paper has better classification accuracy; and the DPRF can provide effective privacy protection under the premise of ensuring high classification performance. The work of this paper achieves a balance between privacy and classification accuracy, and has practical application value.
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  • Dynamics and sound attenuation in viscoelastic polymer containing hollow glass microspheres

    Zhao, Honggang   Liu, Yaozong   Wen, Jihong   Yu, Dianlong   Wen, Xisen  

    The practical design of composite material suggests that there is a need for an improved quantitative understanding of the interaction between acoustic waves and microspheres. The multiple scattering method is used to investigate the sound attenuation of the viscoelastic polymer containing hollow glass microspheres. Then the dynamics of the hollow glass microspheres is investigated by reference to the elements of the scattering matrices. It shows that the dilatational vibration of the microsphere plays a key role in the sound attenuation within the viscoelastic polymer composite at the quasistatic region. The thinner glass shell undergoes more severe dilatational vibration and induces more attenuation in the polymer composite. (c) 2007 American Institute of Physics.
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  • Tri-component phononic crystals for underwater anechoic coatings

    Zhao, Honggang   Liu, Yaozong   Wen, Jihong   Yu, Dianlong   Wen, Xisen  

    Localized resonance in phononic crystal, composed of three-dimensional arrays of composite units, has been discovered recently. The composite unit is a high-density sphere coated by soft silicon rubber. In this Letter, the absorptive properties induced by the localized resonance are systemically investigated. The mode conversions during the Mie scattering of a single coated lead sphere in unbounded epoxy are analyzed by referring the elements of the scattering matrix. Then the anechoic properties of a slab containing a plane of such composite scatterers are investigated with the multiple- scattering method by accounting the effects of the multiple scattering and the viscous dissipation. The results show that the longitudinal to transverse mode conversion nearby the locally resonant region is an effective way to enhance the anechoic performance of the finite slab of phononic crystal. Then, the influences of the viscoelasticity of the silicon rubber and the coating thickness on the acoustic properties of the finite slab are investigated for anechoic optimization. Finally, we synthetically consider the destructive scattering in the finite slab of phononic crystal and the backing, and design an anechoic slab composed of bi-layer coated spheres. The results show that the most of the incident energy is absorbed at the desired frequency band. (c) 2007 Elsevier B.V. All rights reserved.
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  • Reliable control design for composite-driven scheme based on delay networked T-S fuzzy system

    Aslam, Muhammad Shamrooz   Dai, Xisheng   Hou, Jun   Li, Qianmu   Ullah, Rizwan   Ni, Zhen   Liu, Yaozong  

    This paper is focused on reliable controller design for a composite-driven scheme of networked control systems via Takagi-Sugeno fuzzy model with probabilistic actuator fault under time-varying delay. The proposed scheme is distinguished from the other schemes as mentioned in this paper. Aims of this article are to solve the control problem by considering the H-infinity, dissipative, and L-2-L-infinity constraints in a unified way. Firstly, to improve the efficient utilization of bandwidth, the adaptive composite-driven scheme is introduced. In such a scenario, the channel transmission mechanism can be adjusted between adaptive event-triggered generator scheme and time-driven scheme. In this study, the threshold is dependent on a new adaptive law, which can be obtained online rather than a predefined constant. With a constant threshold, it is difficult to get the variation of the system. Secondly, a novel fuzzy Lyapunov-Krasovskii functional is constructed to design the fuzzy controller, and delay-dependent conditions for stability and performance analysis of the control system are obtained. Then, LMI-based conditions for the existence of the desired fuzzy controller are presented. Finally, an inverted pendulum that is controlled through the channel is provided to illustrate the effectiveness of the proposed method.
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  • Adaptive Event-Triggered Mixed H-infinity and Passivity-Based Filter Design for Nonlinearar T-S Fuzzy Markovian Switching Systems With Time-Varying Delays

    Aslam, Muhammad Shamrooz   Rajput, Ahmed Raza   Li, Qianmu   Liu, Yaozong   Niazi, Shahab Ahmad  

    This paper discusses the problem of mixed H-infinity and passivity-based filter design for non-linear T-S Fuzzy Markovian Switching Systems (F-MSSs) with time-varying delays, under the adaptive event-triggered scheme. At first, an adaptive event-triggered scheme (AET-S) is put forward, that adjusts the communication threshold level, in an adaptive manner, in order to mitigate the effect of the communication burden. Second, the filter design problem is solved with the communication delays in terms of linear matrix inequalities (LMIs), by considering a novel Fuzzy-Markovian Lyapunov-Krasovskii functional (FMLKF) containing mode-dependent integral terms such that the resulting filtering error system is stable with the desired H-infinity performance. Finally, a tunnel diode example in elaborated to show the effectiveness of our proposed method.
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  • Metamodel for 2D magnet-rail relationship based on stepwise regression

    Zeng, Shuo   Liu, Yaozong   Li, Jun  

    Almost all existing analytical formulae describing the magnet-rail relationship for maglev trains have been derived with the assumption that magnetic media operate within the linear zone of the B-H curve and, therefore, over-predict the levitation and guidance forces when the magnetic media are in their saturation states. In such cases, finite element simulations are commonly used to obtain an accurate solution of the electromagnetic force, but this process is time-consuming. In this study, metamodels suitable for saturated magnetic media are constructed based on the methods of uniform design and stepwise regression, and their performance is assessed in terms of data fitting and prediction accuracy.
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  • Design guidelines for flexural wave attenuation of slender beams with local resonators

    Liu, Yaozong   Yu, Dianlong   Li, Li   Zhao, Honggang   Wen, Jihong   Wen, Xisen  

    The complex band structures and attenuation spectra of flexural waves in slender beams with periodically mounted local resonators are investigated with transfer matrix method. It is noteworthy that the frequency range and attenuation coefficient of the locally resonant gap become larger in complex band structures if larger resonators were used. But given the total add-on mass of resonators, the attenuation spectra of finite beams with large but few resonators do not demonstrate such phenomena because the attenuation needs several periods to establish. So with the view of application, a large number of small local resonators widely spread along the beam are preferred given the total add-on mass to the beam. (c) 2006 Elsevier B.V. All rights reserved.
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  • The directional propagation characteristics of elastic wave in two-dimensional thin plate phononic crystals

    Wen, Jihong   Yu, Dianlong   Wang, Gang   Zhao, Honggang   Liu, Yaozong   Wen, Xisen  

    The directional propagation characteristics of elastic wave during pass bands in two-dimensional thin plate phononic crystals are analyzed by using the lumped-mass method to yield the phase constant surface. The directions and regions of wave propagation in phononic crystals for certain frequencies during pass bands are predicted with the iso-frequency contour lines of the phase constant surface, which are then validated with the harmonic responses of a finite two-dimensional thin plate phononic crystals with 16 x 16 unit cells. These results are useful for controlling the wave propagation in the pass bands of phononic crystals. (C) 2006 Elsevier B.V. All rights reserved.
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  • Theoretical study of two-dimensional phononic crystals with viscoelasticity based on fractional derivative models

    Liu, Yaozong   Yu, Dianlong   Zhao, Honggang   Wen, Jihong   Wen, Xisen  

    Wave propagation in two-dimensional phononic crystals (PCs) with viscoelasticity is investigated using a finite-difference-time-domain (FDTD) method. The viscoelasticity is evaluated using the Kelvin-Voigt model with fractional derivatives (FDs) so that both the dispersion and dissipation are considered. Numerical approximation of FDs is integrated into the FDTD scheme to simulate wave propagation in such PCs. All the constituent materials are treated as isotropic and homogeneous. The gaps are substantially displaced and widened and the attenuation is noticeably enhanced due to the dispersion and dissipation of host material and the complicated multiple scattering between scatterers. These results indicate that the viscoelasticity of the damping host has significant influence on wave propagation in PCs and should be considered.
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