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Vibration Modes (vibration + mode)
Selected AbstractsNonlinear Damping Identification in Precast Prestressed Reinforced Concrete BeamsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2009P. Franchetti Integrated static and dynamic experiments were carried out on three precast PRC beam specimens. The static loading induced different levels of damage to the beams. At each damage level, impulsive loading was applied to the beams and the free vibration response was measured. The dynamic response data were processed using different methods including the multi-input multi-output (MIMO) curve fitting and the Hilbert transform techniques. A strong correlation is observed between the level of concrete damage (cracks) and the amount of nonlinear energy dissipation that can be modeled by means of quadratic damping. The nonlinear damping can be extracted from the free vibration response for each vibration mode. The proposed method is suited for quality control when manufacturing precast PRC members, and can be further extended for in situ detection of damage in concrete structures under ambient vibration. [source] Approximate modal decomposition of inelastic dynamic responses of wall buildingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2004C. Sangarayakul Abstract Two approximate methods for decomposing complicated inelastic dynamic responses of wall buildings into simple modal responses are presented. Both methods are based on the equivalent linear concept, where a non-linear structure is represented by a set of equivalent linear models. One linear model is used for representing only one vibration mode of the non-linear structure, and its equivalent linear parameters are identified from the inelastic response time histories by using a numerical optimizer. Several theoretical relations essential for the modal decomposition are derived under the framework of complex modal analysis. Various numerical examinations have been carried out to check the validity of the proposed modal decomposition methods, and the results are quite satisfactory in all cases. Fluctuating bending moment and shear at any location along the wall height contributed by each individual vibration mode can be obtained. Modal contributions to shear and flexural strength demands, as well as the corresponding modal properties, under various seismic loading conditions can also be identified and examined in detail. Furthermore, the effects of higher vibration modes on seismic demands of wall buildings are investigated by using the modal decomposition methods. Several new insights into the complicated inelastic dynamics of multi-story wall buildings are presented. Copyright © 2004 John Wiley & Sons, Ltd. [source] Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parametersEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2003Chunxiang Li Abstract The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near-zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near-zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM-MTMD1,UM-MTMD3, US-MTMD1,US-MTMD3, UD-MTMD1 and UD-MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near-zero optimum average damping ratio. The structure is represented by the mode-generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near-zero optimum average damping ratio (i.e. the UM-MTMD1,UM-MTMD3, US-MTMD1, US-MTMD2 and UD-MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM-MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM-MTMD3 with the optimum MTMD-1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM-MTMD3 is almost identical to that for the optimum MTMD-1 (without inclusion of the optimum MTMD-1 with the near-zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM-MTMD3 or the optimum MTMD-1 without the near-zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Tetragonal Ba2MgGe2O7 , a novel multifunctional optical crystal with numerous manifestations of nonlinear-laser effects: almost sesqui-octave Stokes and anti-Stokes combs and cascaded ,(3),,(2) lasing with involved second and third harmonic generationLASER PHYSICS LETTERS, Issue 12 2008A.A. Kaminskii Abstract Melilite-type Ba2MgGe2O7 was found to be an attractive, simultaneously ,(2) - and ,(3) -active nonlinear optical crystal. Under one-micron picosecond pumping we observed several manifestations of nonlinear interactions, namely almost sesqui-octave Stokes and anti-Stokes lasing combs, collinear and "Cherenkov"-type SHG, THG, SFG, and cascaded selfconversion ,(3),,(2) generation in the visible and UV range. All recorded lasing components were identified and attributed to a single SRS-promoting vibration mode ,SRS = 771.5 cm,1. A short review of melilite-type compounds is given. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Wide-band Raman Stokes and anti-Stokes comb lasing in a BaF2 single crystal under picosecond pumpingLASER PHYSICS LETTERS, Issue 4 2008A.A. Kaminskii Abstract We report on the first observation of stimulated Raman scattering (SRS) in a crystal of cubic BaF2. All registered Stokes and anti-Stokes lasing sidebands in the visible and near-IR (up to the 41st order) are identified to the single ,(3) -promoting vibration mode (,SRS , 238 cm,1) of the crystal. The recorded very broad nonlinear lasing comb (more than one octave spanning) in BaF2 opens the possibility for experiments on femtosecond waveform synthesis and other laser comb applications. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Nonlinear ,(3) -lasing in the tetragonal RbH2PO4 crystalLASER PHYSICS LETTERS, Issue 12 2007A.A. Kaminskii Abstract Raman-induced Stokes and anti-Stokes generation in RbH2PO4 crystal with nanosecond pumping has been observed. All recorded nonlinear-laser wavelengths in the visible and near-IR regions are identified and attributed to the ,(3) -promoting vibration mode of this tetragonal acentric phosphate. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Total reflectance and Raman studies in AlyInxGa1-x-yN epitaxial layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2010A. Margarida Bola Abstract This study comprises a set of AlyInxGa1-x-yN thin films grown on GaN/sapphire substrate by MOVPE, with In content between 2 and 8% and Al between 21 and 38%. The thin films were optically characterized by means of UV-Visible total reflectance and ,-UV-Raman scattering, performed at room temperature. It is shown that the [Al]/[In] ration influences strongly the Reflectance spectra and a good correlation has been found between the reflectance maximum located at higher energy and the band gap predicted by Vegard's law for quaternary alloys. The Raman results indicate that the LO-AlGaN-like vibration mode is the dominated vibration in good agreement with the oscillator strength values obtained theoretically [12] for this alloys. It is shown how the influence of competing effects, such as composition and strain influences the frequency observed for the LO-AlGaN-like mode (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spectroscopic study on structure of horseradish peroxidase in water and dimethyl sulfoxide mixtureBIOPOLYMERS, Issue 2 2002Yasushi Maeda Abstract The structure of horseradish peroxidase (HRP) in phosphate buffered saline (PBS)/dimethyl sulfoxide (DMSO) mixed solvents at different compositions is investigated by IR, electronic absorption, and fluorescence spectroscopies. The fluorescence spectra and the amide I spectra of ferric HRP [HRP(Fe3+)] show that overall structural changes are relatively small up to 60% DMSO. Although the amide I band of HRP(Fe3+) shows a gradual change in the secondary structure and a decrease in the contents of , helices, its fluorescence spectra indicate that the distance between the heme and Trp173 is almost constant. In contrast, the changes in the positions of the Soret bands for resting HRP(Fe3+) and catalytic intermediates (compounds I and II) and the IR spectra at the CO stretching vibration mode of carbonyl ferrous HRP [HRP(Fe2+)-CO] show that the microenvironment in the distal heme pocket is altered, even with low DMSO contents. The large reduction of the catalytic activity of HRP even at low DMSO contents can be attributed to the structural transition in the distal heme pocket. In PBS/DMSO mixtures containing more than 70 vol % DMSO, HRP undergoes large structural changes, including a large loss of the secondary structure and a dissociation of the heme from the apoprotein. The presence of the components of the amide I band that can be assigned to strongly hydrogen bonding amide CO groups at 1616 and 1684 cm,1 suggests that the denatured HRP may aggregate through strong hydrogen bonds. © 2002 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 67: 107,112, 2002 [source] Approximate modal decomposition of inelastic dynamic responses of wall buildingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2004C. Sangarayakul Abstract Two approximate methods for decomposing complicated inelastic dynamic responses of wall buildings into simple modal responses are presented. Both methods are based on the equivalent linear concept, where a non-linear structure is represented by a set of equivalent linear models. One linear model is used for representing only one vibration mode of the non-linear structure, and its equivalent linear parameters are identified from the inelastic response time histories by using a numerical optimizer. Several theoretical relations essential for the modal decomposition are derived under the framework of complex modal analysis. Various numerical examinations have been carried out to check the validity of the proposed modal decomposition methods, and the results are quite satisfactory in all cases. Fluctuating bending moment and shear at any location along the wall height contributed by each individual vibration mode can be obtained. Modal contributions to shear and flexural strength demands, as well as the corresponding modal properties, under various seismic loading conditions can also be identified and examined in detail. Furthermore, the effects of higher vibration modes on seismic demands of wall buildings are investigated by using the modal decomposition methods. Several new insights into the complicated inelastic dynamics of multi-story wall buildings are presented. Copyright © 2004 John Wiley & Sons, Ltd. [source] Dynamic performance of twin curved cable-stayed bridgesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2004C. Gentile Abstract The dynamic behaviour of two curved cable-stayed bridges, recently constructed in northern Italy, has been investigated by full-scale testing and theoretical models. Two different excitation techniques were employed in the dynamic tests: traffic-induced ambient vibrations and free vibrations. Since the modal behaviour identified from the two types of test are very well correlated and a greater number of normal modes was detected during ambient vibration tests, the validity of the ambient vibration survey is assessed in view of future monitoring. For both bridges, 11 vibration modes were identified in the frequency range of 0ndash;10Hz, being a one-to-one correspondence between the observed modes of the two bridges. Successively, the information obtained from the field tests was used to validate and improve 3D finite elements so that the dynamic performance of the two systems were assessed and compared based on both the experimental results and the updated theoretical models. Copyright © 2003 John Wiley & Sons, Ltd. [source] Optical, Magnetic and Structural Properties of the Spin-Crossover Complex [Fe(btr)2(NCS)2]·H2O in the Light-Induced and Thermally Quenched Metastable StatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2007Vincent Legrand Abstract [Fe(btr)2(NCS)2]·H2O [btr = 4,4,-bis(1,2,4-triazole)] is thearchetype of highly cooperative and low-dimensional spin-crossover complexes, which exhibit low-spin (LS) to high-spin (HS) light-induced conversion at very low temperature. The structural reorganizations related to the light-induced and thermally induced LS,HS transitions were characterized by single-crystal X-ray diffraction below the relaxation temperature (T = 15 K < TLIESST) and at 130 K within the thermal hysteresis loop. We show that the LIESST and thermal spin transitions lead to the same structural variations, namely an elongation of the Fe,N bonds by 0.18 Å (Fe,NNCS) and 0.20 Å (Fe,Nbtr), on going from LS to HS, together with a reorientation of the NCS group by nearly 13°. The atomic displacement amplitudes, derived from the crystal structures, indicate lattice vibration modes of larger amplitudes and correlatively lower vibration frequencies in the HS state. The deformation of the crystal lattice as a function of temperature and laser excitation was quantitatively analyzed in terms of the HS and LS thermal-expansion (,HS and ,LS) and spin-transition spontaneous-strain (,) tensors. The eigendirections and eigenvalues of the , and , tensors correlate well with the weak and strong interactions in the solid and are responsible for the high cooperativity and low-dimensional behaviour. Magnetic and spectroscopic measurements were performed in all the different spin states and related to the structural findings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] DSC-Ritz method for high-mode frequency analysis of thick shallow shellsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2005C. W. Lim Abstract This paper addresses a challenging problem in computational mechanics,the analysis of thick shallow shells vibrating at high modes. Existing methods encounter significant difficulties for such a problem due to numerical instability. A new numerical approach, DSC-Ritz method, is developed by taking the advantages of both the discrete singular convolution (DSC) wavelet kernels of the Dirichlet type and the Ritz method for the numerical solution of thick shells with all possible combinations of commonly occurred boundary conditions. As wavelets are localized in both frequency and co-ordinate domains, they give rise to numerical schemes with optimal accurate, stability and flexibility. Numerical examples are considered for Mindlin plates and shells with various edge supports. Benchmark solutions are obtained and analyzed in detail. Experimental results validate the convergence, stability, accuracy and reliability of the proposed approach. In particular, with a reasonable number of grid points, the new DSC-Ritz method is capable of producing highly accurate numerical results for high-mode vibration frequencies, which are hitherto unavailable to engineers. Moreover, the capability of predicting high modes endows us the privilege to reveal a discrepancy between natural higher-order vibration modes of a Mindlin plate and those calculated via an analytical relationship linking Kirchhoff and Mindlin plates. Copyright © 2004 John Wiley & Sons, Ltd. [source] Theory of chemical bonds in metalloenzymes III: Full geometry optimization and vibration analysis of ferredoxin-type [2Fe,2S] clusterINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2007Mitsuo Shoji Abstract The nature of chemical bonds in a ferredoxin-type [2Fe,2S] cluster has been investigated on the basis of natural orbitals and several bond indices developed in Parts I and II of this study. The broken-symmetry hybrid density functional theory (BS-HDFT) with spin projection approach has been applied to elucidate the natural orbitals and occupation numbers for a model compound [Fe2S2(SCH3)4] (1), which is used to calculate the indices. The molecular structure, vibration frequencies, electronic structures, and magnetic properties in both oxidized and reduced forms of 1 have been calculated and compared with the experimental values. The optimized molecular structures after approximate spin projection have been in good agreement with experimental data. The structure changes upon one-electron reduction have been slight (<0.1 Å) and only limited around one side of the Fe atom. Raman and infrared (IR) spectra have been calculated, and their vibration modes have been assigned using the bridging 34S isotope substitution. Their magnetic properties have been examined in terms of spin Hamiltonians that contain exchange interactions and double exchange interactions. The BS-HDFT methods have provided the magnetic parameters; i.e., effective exchange integral (J) values and valence delocalization (B) values, which agree with the experimental results. It is found that large charge transfer (CT) from the bridging sulfur to the iron atoms has led to the strong antiferromagnetic interactions between iron atoms. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Analysis of Phase Coexistence in Fe2O3 -Doped 0.2PZN,0.8PZT Ferroelectric Ceramics by Raman Scattering SpectraJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Man-Kang Zhu In this work, we suggested a method to evaluate quantitatively the effect of doping oxide on the phase coexistence of PbZr1,xTixO3 (PZT)-based ceramics through the analysis of the Raman scattering spectra. Theoretically, the degenerated T3u mode in the cubic phase of PZT will transform as A1(3) and E(4) modes in the tetragonal phase or as rhombohedral (R) modes in the rhombohedral phase below the Curie temperature, which set up the theoretical base to study the phase coexistence in ferroelectric materials. Through separation by fitting of the Raman bands, the shifts and intensities of different Raman vibration modes were determined. A calculation equation representing the phase coexistence was put forward based on the theoretical analysis of the degenerated T3u modes. The results showed that a turning point appears at the Fe2O3 addition of 0.3%. The variation in the electrical properties of the Fe2O3 -doped Pb(Zn1/3Nb2/3)O3 (PZN),PZT ceramics also affirmed the turning point of the phase evolution as the addition of Fe2O3. [source] Potassium and ammonium hydrogen phthalates KHC6H4(COO)2 and (NH4)HC6H4(COO)2 , new organic crystals for Raman laser converters with large frequency shiftLASER PHYSICS LETTERS, Issue 7 2009A.A. Kaminskii Abstract Raman-induced many-phonons Stokes and anti-Stokes generation in a orthorhombic crystals KHC6H4(COO)2 and (NH4)HC6H4(COO)2 under picosecond pumping has been observed. All recorded nonlinear lasing lines in the visible and near-IR regions are identified and attributed to the ,(3) -promoting vibration modes of these orthorhombic phthalates. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Trigonal Na3Li(MoO4)2·6H2O , a new many-phonon SRS molybdate crystal offering numerous nonlinear-laser interactions: several cascaded lasing (,(3),,(2)) effects and more than sesqui-octave Stokes and anti-Stokes comb generation under one-micron picosecond pumpingLASER PHYSICS LETTERS, Issue 5 2009A.A. Kaminskii Abstract Trigonal Na3Li(MoO4)2·6H2O was found to be an attractive, simultaneously ,(2) - and ,(3) -active nonlinear optical crystal. We investigated its basic optical properties and observed several nonlinear effects, namely many-phonon SRS, almost twooctave Stokes and anti-Stokes lasing combs, SHG, THG, and efficient cascaded (,(3),,(2))-generation, as well as SRS arising from nonlinear interaction of two different ,(3) -active vibrations. All recorded nonlinear-lasing components were identified and attributed to SRS-promoting vibration modes. A short review of nonlinear-laser molybdates is given. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Stimulated Raman scattering and cascaded nonlinear laser (,(3) , ,(2)) effects in tetragonal non-centrosymmetric Li2B4O7 single crystalsLASER PHYSICS LETTERS, Issue 11 2006A. A. Kaminskii Abstract Multiple stimulated Raman scattering (SRS) and cascaded nonlinear ,(3) , ,(2) generation in tetragonal non-centrosymmetric Li2B4O7 crystal were observed under picosecond Nd3+:Y3Al5O12 laser excitation. All registered Stokes and anti-Stokes lasing components in the visible and near-IR were identified and attributed to the SRS-promoting vibration modes of the studied crystal. We classify the Li2B4O7 crystals as a promising media for up- and down-Raman laser-frequency converters. In the work a brief review of nonlinear-laser properties of SRSactive borate crystals is given. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Observation of nonlinear lasing ,(3) -effects in highly transparent nanocrystalline Y2O3 and Y3Al5O12 ceramicsLASER PHYSICS LETTERS, Issue 1 2004A.A. Kaminskii Abstract Multi-wavelength nonlinear parametric ,(3) -effects were observed in highly transparent Y2O3 and Y3Al5O12 nanocrystalline ceramics under picosecond pumping at 300 K. All recorded Stokes and anti-Stokes components in the visible and near IR were identified and attributed to the stimulated Raman scattering active vibration modes of these novel optical and laser-host crystalline materials. For both materials, the steadystate first-Stokes Raman gain coefficient was estimated at a wavelength of around 1 ,m. (© 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source] Symmetry of electron states and optical transitions in GaN/AlN hexagonal quantum dotsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2004P. Tronc Abstract The exact symmetry of hexagonal quantum dots (QDs) made of materials with the wurtzite structure such as GaN/AlN QDs for example, is described by the C3v point group and does not depend on the existence of a wetting layer. We have determined the possible exact symmetries of electron states and vibration modes in the dots and derived the optical selection rules. The vibration modes involved in the Frölich interaction are totally symmetric with respect to the C3v group and can induce transitions only between states with the same symmetry. The not totally symmetric modes provide other channels for lowering the energy of excited carriers and excitons by connecting states with symmetries different one from another. The rapid decay of created polarons, due to the short lifetime of vibration modes, releases the carriers and excitons into ground levels. In the envelope function approximation (EFA), the symmetry of the dots is represented by the C6v point group. Interband transitions are allowed only between states whose envelope functions have the same symmetry. EFA artificially increases the number of dark exciton symmetries. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] An active fiber sensor for mirror vibration metrology in astronomical interferometersASTRONOMISCHE NACHRICHTEN, Issue 5 2009S. Minardi Abstract We present a fiber sensor based on an active integrated component which could be effectively used to measure the longitudinal vibration modes of telescope mirrors in an interferometric array. We demonstrate the possibility to measure vibrations with frequencies up to ,100 Hz with a precision better than 10 nm (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Comparative Study of the Structural, Electronic, and Vibrational Properties of NH3BH3 and LiNH2BH3: Theory and ExperimentCHEMPHYSCHEM, Issue 11 2009Seung Mi Lee Dr. Abstract Herein, we systematically investigate the structural, electronic, and vibrational properties of ammonia borane (NH3BH3, AB) and lithium amidoborane (LiNH2BH3, LAB) through both density functional calculations and experiments. AB and LAB samples are generated and their vibrational spectra are obtained by using Fourier transformed infrared spectroscopy (FTIR). The measured vibrational spectra are in good agreement with the calculated ones. Our calculations show that the Li-related vibration modes are primarily found in the low-frequency region (<1000 cm,1), and that the intermolecular interactions significantly influence the vibrational spectra. Electronic structure calculations provide insights into the differences between the binding natures of AB and LAB and their influence on the vibrational properties of these compounds. [source] | ||||||||||||||||