Litian Wang

• Vijay, Sudarshan; Wang, Litian; Lyphout, Christophe; Nylen, Per & Markocsan, Nicolaie (2019). Surface characteristics investigation of HVAF sprayed cermet coatings. Applied Surface Science. ISSN 0169-4332. 493, s. 956–962. doi: 10.1016/j.apsusc.2019.07.079.
• Wang, Yan-Feng; Wang, Yue-Sheng & Wang, Litian (2014). Two-dimensional ternary locally resonant phononic crystals with a comblike coating. Journal of Physics D: Applied Physics. ISSN 0022-3727. 47(1:015502). doi: 10.1088/0022-3727/47/1/015502. Vis sammendrag

  Two-dimensional ternary locally resonant phononic crystals can be used for vibration control and noise insulation in the low (even audible) frequency range. They traditionally consist of cylindrical scatterers with uniform coatings in their exterior. An alternative coating profile with a comblike profile is proposed and investigated in this paper. The band structures are calculated using the finite element method. We find that a complete bandgap can be induced at a significantly low frequency, the wavelength of which is more than 20 times the lattice constant. The mechanism for such a change is suggested using an equivalent spring–mass model and analyzing the eigenmodes at the bandgap edges. Numerical results and the results predicted by the spring–mass model are coherent.

• Wang, Litian (2012). Zero-curvature transonic states and one-component surface waves in anisotropic elastic media. Wave motion. ISSN 0165-2125. 49(7), s. 659–666. doi: 10.1016/j.wavemoti.2012.04.002.
• Wang, Litian (2010). Structure of phonon focusing patterns in tetragonal crystals. Journal of the Acoustical Society of America. ISSN 0001-4966. 127(2), s. 746–753. doi: 10.1121/1.3273901. Vis sammendrag

  A set of critical conditions for the characteristic caustic points in the phonon focusing patterns in tetragonal crystals is formulated. A caustic line segment in the focusing pattern is generally associated with either a fold or a cusp on the wave surface. Most of the caustic lines are symmetrical with respect to the principal symmetry plane and can be characterized by the caustic points at the centers of the caustic lines. These characteristic caustic points originated from in?ection/parabolic points with zero in-plane/ex-plane curvature, respectively. By employing the Stroh formalism, the in?ection/parabolic points on the slowness surface are studied in terms of the so-called zero-curvature transonic states. Since these transonic states are related to extraordinary degeneracies in the Stroh eigenvalue equation, the conditions for the degeneracies can be regarded as critical conditions for the characteristic caustic points. These conditions provide an overview of global structure of the phonon focusing patterns in tetragonal crystals. A set of caustic lines in vicinity of s001d plane is also investigated and exempli?ed.

• Wang, Litian (2009). Analytical determination of parabolic points on slowness surface and swallowtail points on wave surface of cubic crystals. Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. ISSN 1364-5021. 465(2104), s. 1231–1247. doi: 10.1098/rspa.2008.0436. Vis sammendrag

  Slowness surface for bulk wave propagation in anisotropic media can be divided into concave, saddle and convex regions by the parabolic lines. When a parabolic line crosses a symmetry plane, it leaves either an inflection point or a parabolic point. Surface normal at these points is associated with cuspidal point and swallowtail point, respectively, on the wave surface and in phonon focusing patterns. By examining the degeneracies in the Stroh eigenvalue equation, we have calculated the cuspidal points in cubic crystals analytically. In this work, the parabolic point and its surface normal are discussed. The main idea is to establish a connection between the parabolic point and the extraordinary transonic state that is related to a degeneracy with a multiplicity of four in the Stroh eigenvalue equation. Such a connection yields a series of simple expressions, which determine the locations of parabolic points and the corresponding swallowtail points. The result is demonstrated using phonon focusing patterns of cubic crystals, and the method also provides a tool for general discussion of the slowness surface geometry.

• Wang, Litian (2008). Caustic and anticaustic points in the phonon focusing patterns of cubic crystals. Journal of the Acoustical Society of America. ISSN 0001-4966. 123(6), s. 4140–4146. Vis sammendrag

  Slowness surface for bulk wave propagation in anisotropic media can be divided into concave, saddle and convex regions by the parabolic lines. When a parabolic line crosses a symmetry plane, it leaves either an inflectional point or a parabolic point. Surface normals at these points are associated with cuspidal point and swallowtail point, respectively, on wave surface and in phonon focusing patterns. By examining degeneracies in Stroh eigenvalue equation, we have calculated the cuspidal points in cubic crystals analytically. In this work, the parabolic point and its surface normal are discussed. The main idea is to establish a connection between the parabolic point and the extraordinary transonic state which is related to a degeneracy with multiplicity of four in the Stroh eigenvalue equation. Such a connection yields a series of simple expressions which determine the locations of parabolic points and corresponding swallowtail points. The result is demonstrated using phonon focusing patterns of cubic crystals, and the method also provides a tool for general discussion of the slowness surface geometry.

• Wang, Litian (2008). Extraordinary degeneracy and space of degeneracy in transversely isotropic elastic media. Wave motion. ISSN 0165-2125. 45(3), s. 264–277. Vis sammendrag

  A large variety of degeneracy exist in both static and dynamic regimes in anisotropic elastic media. Extraordinary degeneracies occur mostly in the static regime and they are of great importance in understanding the existence of the so-called space of degeneracy in the dynamic regime. This paper deals with the interconnection between degeneracies in the static and dynamic regimes. Both the modified Lekhnitskii formalism and the Stroh formalism are employed in exploring the degeneracies in the transversely isotropic media. It is demonstrated that the space of degeneracy can be regarded as an extension of the static degeneracy, and the development of the static extraordinary degeneracy into the dynamic regime is via a number of spaces of degeneracy of various types. The static degeneracy can also span a space of degeneracy.

• Wang, Litian & Ryne, Kent (2007). Existence of extraordinary zero-curvature slowness curve in anisotropic elastic media. Journal of the Acoustical Society of America. ISSN 0001-4966. 122(4), s. 1873–1875. Vis sammendrag

  Acoustic wave propagation in elastic media is characterized by the slowness surface. The slowness surface consists of three sheets associated with three modes of wave propagation and the two outer sheets can have zero-curvature locally. It is shown that the outmost sheet can admit extraordinary zero-curvature and the slowness curve can appear as a straight line locally. Using the perturbation method, the conditions for the extraordinary zero-curvature are derived analytically without violating the thermodynamic condition for elastic media. The results can be applied to crystals with higher symmetry and to the study of phonon focusing and surface waves.

• Wang, Litian (2004). Space of degeneracy in the Stroh eigensystem and surface waves in transversely isotropic elastic media. Wave motion. ISSN 0165-2125. 40(2), s. 173–190. Vis sammendrag

  Surface waves in anisotropic elastic media can be described by the linear combination of eigenvectors of the Stroh fundamental matrix N. The matrix N can admit two types of degeneracies: semisimple and nonsemisimple. The present study is toshow that inthe transversely isotropic media the degeneracies can span a two-dimensional space for either type of the degeneracies. Relationship between the spaces of degeneracy and the surface waves is discussed and analytical results for thesurface wave solutions admitting generalized eigenvectors ispresented with examples for the ß-configuration in the transversely isotropic elastic media

• Lothe, Jens & Wang, Litian (1997). Self-orthogonal sextic formalism for simple reflection and mode conversion at the free surface of an anisotropic elastic half-space. ?. 453(nr 1960), s. 897–911. Vis sammendrag

  Simple reflection and mode conversion of acoustic waves at a free sur face of a semiinfinite anisotropic elastic medium are investigated us ing the Stroh sextic formalism. By introducing new sets of self-ortho gonal wavefunctions in the self-orthogonal sextic formalism, we estab lish a series of linear dependence relations which enable us to analy se various kinds of simple reflection and mode conversion under a uni fied theoretical framemork. It is shown that the properties of simple reflection and mode conversion can be described in terms of th ree i ndependent constants.

• Lothe, Jens & Wang, Litian (1995). Self-orthogonal sextic formalism for anisotropic elastic media-spaces of simple reflection and 2-component surface-waves. Wave motion. ISSN 0165-2125. 21(nr 2), s. 163–181.
• Wang, Litian & Lothe, Jens (1995). Dislocation instability in anisotropic elastic cubic media. ?. 71(nr 2), s. 359–387.
• Wang, Litian (1995). Determination of the ray surface and recovery of elastic-constants of anisotropic elastic media - a direct and inverse approach. ?. 7(nr 20), s. 3863–3880.

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• Nilsen, Rino; Mouland, Anders; Wang, Yan-Feng; Wu, Hong; Wang, Yue-Sheng & Wang, Litian (2015). A phononic construction material.
• Wang, Litian (2014). Lydløse materialer.
• Wang, Litian (2013). «Lydløse materialer» inn i fremtidens skip? [Internett]. Plastforum.no. Vis sammendrag

  Støy og vibrasjon om bord i fartøyer er et problem og har gjennom tidene avstedkommet mye irritasjon og ubehag. Høgskolen i Østfold har i tre års tid drevet et FoU-prosjekt omkring fononiske komposittmaterialer. Nå ses resultatene og i oktober tas det stilling til om tiden er moden for kommersialisering.

• Wang, Litian (2013). Vil dempe motorbråk med plastkompositt. [Avis]. Teknisk ukeblad. Vis sammendrag

  Forsker mener plastkompositt kan fjerne så godt som all støy fra maskinrommet i båter.

• Wang, Litian (2013). Jakter på lydløst materiale. [Internett]. Forskning.no. Vis sammendrag

  Materialer som fanger opp all støy fra maskinrommet i båten er målet for forskere fra Østfold og Kina. Men bruksområdene kan bli flere.

• Wang, Yanfeng; Wang, Yue-Sheng & Wang, Litian (2013). Two-Dimensional Square Phononic Crystal and Phononic Crystal Slabs with Cross-Like holes.
• Wang, Yanfeng; Wang, Yue-Sheng & Wang, Litian (2013). Complex Band Structures of Two-Dimensional Viscoelastic Phononic Crystals Obtained by using Finite Element Method.
• Wang, Yanfeng; Wang, Yue-Sheng & Wang, Litian (2012). Two- and three- dimensional holey phononic crystals with unit cells of resonators.
• Wang, Yanfeng; Wang, Yue-Sheng & Wang, Litian (2012). Complete bandgaps in three-dimensional holey phononic crystals with Helmholtz resonators.
• Wang, Litian (2012). Plastmkerne. [Avis]. Fredriksstad Blad.
• Wang, Litian (2011). Utvikling av lydløse materialer. [Radio]. NRK Radio - Østfold.
• Wang, Litian (2011). Funksjonelle materialer.
• Wang, Litian (2011). Utvikling av lydløse materialer. Vis sammendrag

  Presentasjon på et FoU prosjekt i Avdeling for ingeniørfag, Høgskolen i Østfold.

• Wang, Litian (2011). Hovedprosjektet - Lydløse materialer.
• Wang, Litian (2011). Design and Optimization of Phononic Materials with Application to Soundshield Technology.
• Wang, Litian (2011). Funksjonelle materialer - Phononiske krystaller.
• Wang, Litian (2011). Lydløse materialer - En funksjonelle materialer til lydstyring/-demping.
• Wang, Litian (2011). Phononic material and its application as soundshield.
• Wang, Litian (2010). Design and optimization of phononic materials with application to soundshield technology Funksjonelle,fononiske materialer til bl.a. relevant lydstyring/-demping.
• Wang, Litian (2009). Stroh formalism and its applications to wave propagations in anisotropic media. Vis sammendrag

  The Stroh formalism is a powerful method for solving problems on elastostatics and elastodynamics. This talk covers the following topics in wave propagation in anisotropic media: (a) Brief introduction to the Stroh formalism (b) Application to surface waves (c) Application to interfacial surface waves (d) Application to waves in plates (e) Application to phonon focusing

• Wang, Litian (2009). Dislocation instability in anisotropic media. Vis sammendrag

  Static configuration of dislocations in elastic anisotropic media is dependent on elastic energy of the dislocations. A dislocation segment can be ustable along certain directions and moves/relaxes into a new configuration because of line-tension of the dislocation. The unstable directions are determined mainly on the elastic energy, and a scheme is developed to calculate the energy and line tension so that the stable or favorable directions can be identified.

• Wang, Litian (2008). General analytical scheme for determining the characteristic caustic points in phonon focusing patterns of cubic crystals. Vis sammendrag

  Phonon focusing patterns are dependent on the existence of concave/saddle regions and acoustic axes in the slowness surface. The main feature of the focusing patterns in cubic crystals can be characterized by the cuspidal and swallowtail points in the symmetry planes. By applying the Stroh formalism, these points are investigated in relation to degeneracies in the Stroh eigenvalue equation. Explicit expressions for these points are derived.

• Wang, Litian (2004). Space of extraordinary degeneracy in the Stroh formalism and the generalized surface wave in transversely isotropic elastic media. Vis sammendrag

  The Stroh fundamental matrix N(v) for elastodynamic systems generally admits both semisimple and nonsemisimple degeneracies. Extraordinary nonsemisimple degeneracy with multiplicity of three can occur in the transversely isotropic elastic media, and spans a one-dimensional space. Generalized eigenvectors for the extraordinary nonsemisimple degenerate N(v) are constructed analytically as a chain, and criteria for the existence of the so-called generalized surface wave solution arederived explicitly for the ß-configuration in the transversely isotropic elastic media.

• Wang, Litian (1999). Bi-characteristic surfaces for the Christoffel equation and reciprocity for wave propagation in anisotropic systems. Vis sammendrag

  The present presentation deals with the topics related to (a) partial different equations and b) mathematicalphysics. We will present and a analytical reformulation of bicharacteristic surfaces for the Christoffel equation and an inverse scheme for determination of elements of the anisotropic elastic stiffness tensor. We will also introduce a socalled self-orthogonal formalism related to the Christoffel equation in a set of self-orthogonal vectors which are normalized and transformed in such a way that the reciprocity for wave propagation in anisotropic media can be expressed

• Wang, Litian; Hemelrijck, Danny van & Anastassopoulos, Athanassios (1998). Inverse scheme for determination of elastic constants of anisotropic media. Vis sammendrag

  The acoustic ray surface for anisotropic media is usually determined parametrically from the slowness surface. This poses a difficulty in recoverin elastic constant directly from group velocity measurement. By applying the Stroh formalism for elastodynamics, a direct scheme i s developed by analyzing the degeneracy in the Stroh eigenvalue equat ion in the vicinity of symmetry directions or pure mode directions. A n inverse scheme is also established which enable us to recover all t he elastic constants of anositropic media from group velocities along symmetry directions.

• Wang, Litian (2001). Innføring i ORACLE og SQL Kompendium for 3ID30 - Datamodellering og Databaser. Høgskolen i Innlandet. Vis sammendrag

  Kompendium består av fire deler: (a) Innføring i Oracle SQL*Plus, (b) Innføring i SQL, (c) Innføring i PL/SQL Programmering og (d) Innføring i Database administrasjon. The book consists of four parts: (a) Introduction to Oracle SQL*Plus, (b) Introduction to SQL, (c) Introduction to PL/SQL Programing og (d) Introduction to Database administration.

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