CiteULike: norris's Liu http://www.citeulike.org/user/norris/author/Liu CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/norris/article/2582815 <i>Applied Physics Letters, Vol. 91, No. 20. (2007)</i><br /><br />View this record in Web of Science High refractive-index sonic material based on periodic subwavelength structure Feiyan Cai Fengming Liu Zhaojian He Zhengyou Liu Applied Physics Letters, Vol. 91, No. 20. (2007) 2008-03-24T21:18:59-00:00 Applied Physics Letters 91 20 AIP metamaterial http://www.citeulike.org/user/norris/article/2582813 <i>Physical Review Letters, Vol. 99, No. 9. (2007)</i><br /><br />We report a metamaterial which simultaneously possesses a negative bulk modulus and mass density. This metamaterial is a zinc blende structure consisting of one fcc array of bubble-contained-water spheres (BWSs) and another relatively shifted fcc array of rubber-coated-gold spheres (RGSs) in epoxy matrix. The negative bulk modulus and mass density are simultaneously derived from the coexistent monopolar resonances from the embedded BWSs and dipolar resonances from the embedded RGSs. The Poisson ratio of the metamaterial also turns negative near the resonance frequency. Metamaterial with Simultaneously Negative Bulk Modulus and Mass Density Yiqun Ding Zhengyou Liu Chunyin Qiu Jing Shi doi:10.1103/PhysRevLett.99.093904 Physical Review Letters, Vol. 99, No. 9. (2007) 2008-03-24T21:17:37-00:00 Physical Review Letters 99 9 APS metamaterial http://www.citeulike.org/user/norris/article/2569688 <i>Applied Mathematics and Computation, Vol. 186, No. 1. (1 March 2007), pp. 670-684.</i><br /><br />We simply review symplectic and multi-symplectic algorithms in the paper. These algorithms have many superiorities to general non-symplectic algorithms, such as: they have long time behavior; they can preserve the symplectic geometry structure of the Hamiltonian system exactly; and they can simulate original physical phenomena well. Some commonly used methods to construct symplectic and multi-symplectic schemes are simply surveyed. Numerical examples are also enumerated to illustrate their performances. A survey on symplectic and multi-symplectic algorithms Linghua Kong Ruxun Liu Xiaohong Zheng doi:10.1016/j.amc.2006.08.012 Applied Mathematics and Computation, Vol. 186, No. 1. (1 March 2007), pp. 670-684. 2008-03-21T12:55:17-00:00 Applied Mathematics and Computation 186 1 670 684 numerical http://www.citeulike.org/user/norris/article/2038137 <i>Physical Review B (Condensed Matter and Materials Physics), Vol. 76, No. 13. (2007)</i><br /><br />The static mass density of a composite is simply the volume average of its constituents' densities. The dynamic density of a composite is defined to be the quantity that enters in evaluating the elastic wave velocity at the low-frequency limit. We show through a rigorous derivation that the effective dynamic mass density of an inhomogeneous mixture can differ from its static counterpart when the composite matrix is a fluid or, more generally, when there are relative motions between the matrix and inclusions. Derivation of the dynamic mass density expressions, involving taking the long wavelength limit of the rigorous multiple scattering theory, is detailed for the two-dimensional case. We also extend the effective dynamic mass density expression to finite frequencies where there can be low-frequency resonances. By combining both analytical and numerical approaches, negative or complex dynamic mass density is obtained for composites that contain a sufficient fraction of locally resonant inclusions. Thus, the dynamic mass density of a composite can differ from the static (volume-averaged) value even in the zero frequency limit, although both must be positive in that limit. Negative or complex dynamic mass density can occur at finite frequencies. These two results are shown to be consistent with each other, as well as related by the same underlying physics. As by-products of our rigorous derivation, we also verify some prior known results on the effective elastic moduli of composites. Effective dynamic mass density of composites Jun Mei Zhengyou Liu Weijia Wen Ping Sheng doi:10.1103/PhysRevB.76.134205 Physical Review B (Condensed Matter and Materials Physics), Vol. 76, No. 13. (2007) 2007-12-01T16:32:44-00:00 Physical Review B (Condensed Matter and Materials Physics) 76 13 APS metamaterial http://www.citeulike.org/user/norris/article/1172258 <i>Physical Review B (Condensed Matter and Materials Physics), Vol. 71, No. 1. (2005)</i><br /><br />A simple analytic model is presented to describe the low-frequency effective mass densities of three-component phononic crystals with local resonances. We show that the effective mass densities can turn negative close to the local resonances. Expressions for the effective mass densities are derived for both three-dimensional systems with coated spheres embedded in a host matrix, and two-dimensional systems with coated cylinders embedded in a host matrix. Analytic model of phononic crystals with local resonances Zhengyou Liu CT Chan Ping Sheng doi:10.1103/PhysRevB.71.014103 Physical Review B (Condensed Matter and Materials Physics), Vol. 71, No. 1. (2005) 2007-03-18T22:45:32-00:00 Physical Review B (Condensed Matter and Materials Physics) 71 1 APS phonons http://www.citeulike.org/user/norris/article/975446 <i>Geophysics, Vol. 68, No. 5. (2003), pp. 1731-1743.</i><br /><br />A new 3D cylindrical perfectly matched layer (PML) formulation is developed for elastic wave propagation in a pressurized borehole surrounded by a triaxially stressed solid formation. The linear elastic formation is altered by overburden and tectonic stresses that cause significant changes in the wave propagation characteristics in a borehole. The 3D cylindrical problem with both radial and azimuthal heterogeneities is suitable for numerical solutions of the wave equations by finite-difference time-domain (FDTD) and pseudospectral time-domain (PSTD) methods. Compared to the previous 2.5D formulation with other absorbing boundary conditions, this 3D cylindrical PML formulation allows modeling of a borehole-conformal, full 3D description of borehole elastic waves in a stress-induced heterogeneous formation. We have developed an FDTD method using this PML as an absorbing boundary condition. In addition to the ability to solve full 3D problems, this method is found to be advantageous over the previously reported 2.5D finite-difference formulation because a borehole can now be adequately simulated with fewer grid points. Results from the new FDTD technique confirm the principle of superposition of the influence of various stress components on both the borehole monopole and dipole dispersions. In addition, we confirm that the increase in shear-wave velocity caused by a uniaxial stress applied in the propagation direction is the same as that applied parallel to the radial polarization direction. A 3D cylindrical PML/FDTD method for elastic waves in fluid-filled pressurized boreholes in triaxially stressed formations Qing Liu Bikash Sinha doi:10.1190/1.1620646 Geophysics, Vol. 68, No. 5. (2003), pp. 1731-1743. 2006-12-05T16:39:52-00:00 Geophysics 68 5 1731 1743 SEG elasticity numerical http://www.citeulike.org/user/norris/article/920817 <i>(13 November 2001)</i><br /><br /><P>This book presents a set of high-performance, analytical-numerical methods for elastic wave analysis of anisotropic layered structures. A number of advanced techniques are discussed, including the strip element method and methods that combine the finite element method and the Fourier transform approaches. Methods for solving inverse problems using elastic waves are also presented. Relevant to a diverse audience of students in science and engineering disciplines, structural, mechanical , and civil engineers, electronic packaging specialists, biomedical engineers, and thin film researchers in data storage areas, this will prove itself an indispensable reference for those engaged in the use of laminates, and in handling NDE problems</P> Elastic Waves in Anisotropic Laminates GR Liu ZC Xi (13 November 2001) 2006-10-31T21:45:29-00:00 CRC anisotropy http://www.citeulike.org/user/norris/article/805289 <i>Physical Review Letters, Vol. 70, No. 18. (3 May 1993), 2750.</i><br /><br />The structure of β-cristobalite has been studied though a first-principles total-energy minimization in the local-density approximation using a CarâParrinello-type algorithm combined with the Vanderbilt ultrasoft pseudopotential scheme. It was found that the hypothetical ordered structure proposed by Wright and Leadbetter is favored and the resulting structural parameters agree very well with experiment. Also; correlated relaxation of Si and O atoms toward α-cristobalite positions in the vicinity of domain boundaries is indicated. First-principles studies on structural properties of beta -cristobalite Feng Liu Stephen Garofalini RD King-Smith David Vanderbilt doi:10.1103/PhysRevLett.70.2750 Physical Review Letters, Vol. 70, No. 18. (3 May 1993), 2750. 2006-08-18T13:27:33-00:00 Physical Review Letters 70 18 2750 American Physical Society cristobalite http://www.citeulike.org/user/norris/article/699273 <i>Applied Physics Letters, Vol. 86, No. 18. (2005)</i><br /><br />The temperature dependence (15–320  K) of the acoustic dissipation was studied for some lower vibrational modes of a suspended silicon plate 1.5  µm thick. Our oscillator was exposed to the laboratory environment prior to measurement, laser annealed while in a cryogenic vacuum, and remeasured. We find a dissipation peak at 160  K, similar to results by others, and a second dissipation peak near 30  K. Annealing reduced the dissipation at 160  K by as much as a factor of 10, and gave quality factors as high as 1.4×106 at 470  kHz and our lowest temperature. Our data support the idea that the 160  K peak is related to adsorbates, and show this mechanism is important at room temperature. Post-anneal room-temperature dissipation appears to be limited by thermoelastic loss for certain modes. Effects of annealing and temperature on acoustic dissipation in a micromechanical silicon oscillator Hans Haucke Xiao Liu JF Vignola BH Houston MH Marcus JW Baldwin doi:10.1063/1.1921354 Applied Physics Letters, Vol. 86, No. 18. (2005) 2006-06-17T15:00:50-00:00 Applied Physics Letters 86 18 AIP damping plates thermoelasticity http://www.citeulike.org/user/norris/article/699191 <i>Journal of Applied Physics, Vol. 97, No. 2. (2005)</i><br /><br />The room-temperature quality factors of silicon micromechanical oscillators have been investigated by scanning laser vibrometry. One of the flexural modes has very little attachment loss to its environment, which enables us to study internal loss mechanisms. After several consecutive annealing steps up to 800  °C, the quality factor Q has increased from 8×104 to 6.0×105. However, the Q decays to 1.4×105 over six months in air. We conclude that near-surface lattice defects caused by reactive-ion etching and surface adsorbates are the main source of internal loss while surface adsorbates are responsible for the time dependence. We also discuss the thermoelastic limit in terms of Zener's theory and flexural modal components of thin plates with vibratory volume change, and compare it with our results. A loss mechanism study of a very high Q silicon micromechanical oscillator Xiao Liu JF Vignola HJ Simpson BR Lemon BH Houston DM Photiadis doi:10.1063/1.1819980 Journal of Applied Physics, Vol. 97, No. 2. (2005) 2006-06-17T14:41:37-00:00 Journal of Applied Physics 97 2 AIP damping plates thermoelasticity