Hirano, Tsuneo; Nagashima, Umpei; Jensen, Per
2018-04-01
For NCS in the X ˜ 2 Π electronic ground state, three-dimensional potential energy surfaces (3D PESs) have been calculated ab initio at the core-valence, full-valence MR-SDCI+Q/[aug-cc-pCVQZ (N, C, S)] level of theory. The ab initio 3D PESs are employed in second-order-perturbation-theory and DVR3D calculations to obtain various molecular constants and ro-vibrationally averaged structures. The 3D PESs show that the X ˜ 2 Π NCS has its potential minimum at a linear configuration, and hence it is a "linear molecule." The equilibrium structure has re (N-C) = 1.1778 Å, re (C-S) = 1.6335 Å, and ∠e (N-C-S) = 180°. The ro-vibrationally averaged structure, determined as expectation values over DVR3D wavefunctions, has 〈 r (N-C)〉0 = 1.1836 Å, 〈 r (C-S)〉0 = 1.6356 Å, and 〈 ∠ (N-C-S)〉0 = 172.5°. Using these expectation values as the initial guess, a bent r0 structure having an 〈 ∠ (N-C-S)〉0 of 172.2° is deduced from the experimentally reported B0 values for NC32S and NC34S. Our previous prediction that a linear molecule, in any ro-vibrational state including the ro-vibrational ground state, is to be "observed" as being bent on ro-vibrational average, has been confirmed here theoretically through the expectation value for the bond-angle deviation from linearity, 〈 ρ bar 〉 , and experimentally through the interpretation of the experimentally derived rotational-constant values.
Sebastianelli, Francesco; Xu, Minzhong; Bačić, Zlatko
2008-12-01
We report diffusion Monte Carlo (DMC) calculations of the quantum translation-rotation (T-R) dynamics of one to five para-H2 (p-H2) and ortho-D2 (o-D2) molecules inside the large hexakaidecahedral (51264) cage of the structure II clathrate hydrate, which was taken to be rigid. These calculations provide a quantitative description of the size evolution of the ground-state properties, energetics, and the vibrationally averaged geometries, of small (p-H2)n and (o-D2)n clusters, n=1-5, in nanoconfinement. The zero-point energy (ZPE) of the T-R motions rises steeply with the cluster size, reaching 74% of the potential well depth for the caged (p-H2)4. At low temperatures, the rapid increase of the cluster ZPE as a function of n is the main factor that limits the occupancy of the large cage to at most four H2 or D2 molecules, in agreement with experiments. Our DMC results concerning the vibrationally averaged spatial distribution of four D2 molecules, their mean distance from the cage center, the D2-D2 separation, and the specific orientation and localization of the tetrahedral (D2)4 cluster relative to the framework of the large cage, agree very well with the low-temperature neutron diffraction experiments involving the large cage with the quadruple D2 occupancy.
Time average vibration fringe analysis using Hilbert transformation
International Nuclear Information System (INIS)
Kumar, Upputuri Paul; Mohan, Nandigana Krishna; Kothiyal, Mahendra Prasad
2010-01-01
Quantitative phase information from a single interferogram can be obtained using the Hilbert transform (HT). We have applied the HT method for quantitative evaluation of Bessel fringes obtained in time average TV holography. The method requires only one fringe pattern for the extraction of vibration amplitude and reduces the complexity in quantifying the data experienced in the time average reference bias modulation method, which uses multiple fringe frames. The technique is demonstrated for the measurement of out-of-plane vibration amplitude on a small scale specimen using a time average microscopic TV holography system.
Vibrationally averaged dipole moments of methane and benzene isotopologues
Energy Technology Data Exchange (ETDEWEB)
Arapiraca, A. F. C. [Laboratório de Átomos e Moléculas Especiais, Departamento de Física, ICEx, Universidade Federal de Minas Gerais, P. O. Box 702, 30123-970 Belo Horizonte, MG (Brazil); Centro Federal de Educação Tecnológica de Minas Gerais, Coordenação de Ciências, CEFET-MG, Campus I, 30.421-169 Belo Horizonte, MG (Brazil); Mohallem, J. R., E-mail: rachid@fisica.ufmg.br [Laboratório de Átomos e Moléculas Especiais, Departamento de Física, ICEx, Universidade Federal de Minas Gerais, P. O. Box 702, 30123-970 Belo Horizonte, MG (Brazil)
2016-04-14
DFT-B3LYP post-Born-Oppenheimer (finite-nuclear-mass-correction (FNMC)) calculations of vibrationally averaged isotopic dipole moments of methane and benzene, which compare well with experimental values, are reported. For methane, in addition to the principal vibrational contribution to the molecular asymmetry, FNMC accounts for the surprisingly large Born-Oppenheimer error of about 34% to the dipole moments. This unexpected result is explained in terms of concurrent electronic and vibrational contributions. The calculated dipole moment of C{sub 6}H{sub 3}D{sub 3} is about twice as large as the measured dipole moment of C{sub 6}H{sub 5}D. Computational progress is advanced concerning applications to larger systems and the choice of appropriate basis sets. The simpler procedure of performing vibrational averaging on the Born-Oppenheimer level and then adding the FNMC contribution evaluated at the equilibrium distance is shown to be appropriate. Also, the basis set choice is made by heuristic analysis of the physical behavior of the systems, instead of by comparison with experiments.
Structural Stability and Vibration
DEFF Research Database (Denmark)
Wiggers, Sine Leergaard; Pedersen, Pauli
This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....
Structural Stability and Vibration
DEFF Research Database (Denmark)
Wiggers, Sine Leergaard; Pedersen, Pauli
at the University of Southern Denmark, it reports on fundamental formulas and makes uses of graphical representation to promote understanding. Thanks to the emphasis put on analytical methods and numerical results, the book is meant to make students and engineers familiar with all fundamental equations...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....
Improving consensus structure by eliminating averaging artifacts
Directory of Open Access Journals (Sweden)
KC Dukka B
2009-03-01
Full Text Available Abstract Background Common structural biology methods (i.e., NMR and molecular dynamics often produce ensembles of molecular structures. Consequently, averaging of 3D coordinates of molecular structures (proteins and RNA is a frequent approach to obtain a consensus structure that is representative of the ensemble. However, when the structures are averaged, artifacts can result in unrealistic local geometries, including unphysical bond lengths and angles. Results Herein, we describe a method to derive representative structures while limiting the number of artifacts. Our approach is based on a Monte Carlo simulation technique that drives a starting structure (an extended or a 'close-by' structure towards the 'averaged structure' using a harmonic pseudo energy function. To assess the performance of the algorithm, we applied our approach to Cα models of 1364 proteins generated by the TASSER structure prediction algorithm. The average RMSD of the refined model from the native structure for the set becomes worse by a mere 0.08 Å compared to the average RMSD of the averaged structures from the native structure (3.28 Å for refined structures and 3.36 A for the averaged structures. However, the percentage of atoms involved in clashes is greatly reduced (from 63% to 1%; in fact, the majority of the refined proteins had zero clashes. Moreover, a small number (38 of refined structures resulted in lower RMSD to the native protein versus the averaged structure. Finally, compared to PULCHRA 1, our approach produces representative structure of similar RMSD quality, but with much fewer clashes. Conclusion The benchmarking results demonstrate that our approach for removing averaging artifacts can be very beneficial for the structural biology community. Furthermore, the same approach can be applied to almost any problem where averaging of 3D coordinates is performed. Namely, structure averaging is also commonly performed in RNA secondary prediction 2, which
Adaptive techniques for diagnostics of vibrating structures
International Nuclear Information System (INIS)
Skormin, V.A.; Sankar, S.
1983-01-01
An adaptive diagnostic procedure for vibrating structures based on correspondence between current estimates of stiffness matrix and structure status is proposed. Procedure employs adaptive mathematical description of the vibrating structure in frequency domain, statistical techniques for detection and location of changes of structure properties, 'recognition' and prediction of defects. (orig.)
Approximative Krieger-Nelkin orientation averaging and anisotropy of water molecules vibrations
International Nuclear Information System (INIS)
Markovic, M.I.
1974-01-01
Quantum-mechanics approach of water molecules dynamics should be taken into account for precise theoretical calculation of differential scattering cross sections of neutrons. Krieger and Nelkin have proposed an approximate method for averaging orientation of molecules regarding directions of incoming and scattered neutron. This paper shows that this approach can be successfully applied for general shape of water molecule vibration anisotropy
Active and passive vibration control of structures
Spelsberg-Korspeter, Gottfried
2014-01-01
Active and Passive Vibration Control of Structures form an issue of very actual interest in many different fields of engineering, for example in the automotive and aerospace industry, in precision engineering (e.g. in large telescopes), and also in civil engineering. The papers in this volume bring together engineers of different background, and it fill gaps between structural mechanics, vibrations and modern control theory. Also links between the different applications in structural control are shown.
RESEARCH OF BRIDGE STRUCTURE VIBRATION CHARACTERISTICS
Directory of Open Access Journals (Sweden)
V.P. Babak
2005-02-01
Full Text Available Bridge structure test results with using different types of dynamic force have been considered. It has been shown, that the developed technique of registering and processing vibration signals allows obtaining thin spectrum structure. The analysis of its change that is defined by the type of structure loading applied has been carried out. Key parameters of the vibration signals registered have been defined.
Monothiodibenzoylmethane: Structural and vibrational assignments
DEFF Research Database (Denmark)
Hansen, Bjarke Knud Vilster; Gorski, Alexander; Posokhov, Yevgen
2007-01-01
vibrational spectra were compared with theoretical transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT). The results leave no doubt that the stable ground state configuration of TDBM corresponds to the intramolecularly hydrogen bonded enol form (e-CCC), and that the photoproduct corresponds...
Destructive vibration test of a concrete structure
International Nuclear Information System (INIS)
Chen, C.K.; Czarnecki, R.M.; Scholl, R.E.
1977-01-01
Two identical full-scale 4-story reinforced concrete structures were built in 1965-1966 at the Nevada Test Site to investigate their dynamic response behavior to underground nuclear explosions. For eight years following their construction, the structures were the subject of a continuing program of vibration testing, and substantial data has been collected on the elastic response of these structures. In 1974 it was decided to conduct a high-amplitude vibration test that would cause the south structure (free of partitions) to deform beyond its elastic limit and cause major structural damage. Results of the 1974 testing program are summarized
Vibrational Averaging of the Isotropic Hyperfine Coupling Constants for the Methyl Radical
Adam, Ahmad; Jensen, Per; Yachmenev, Andrey; Yurchenko, Sergei N.
2014-06-01
Electronic contributions to molecular properties are often considered as the major factor and usually reported in the literature without ro-vibrational corrections. However, there are many cases where the nuclear motion contributions are significant and even larger than the electronic contribution. In order to obtain accurate theoretical predictions, nuclear motion effects on molecular properties need to be taken into account. The computed isotropic hyperfine coupling constants for the nonvibrating methyl radical CH_3 are far from the experimental values. For CH_3, we have calculated the vibrational-state-dependence of the isotropic hyperfine coupling constant in the electronic ground state. The vibrational wavefunctions used in the averaging procedure were obtained variationally with the TROVE program. Analytical representations for the potential energy surfaces and the hyperfine coupling constant surfaces are obtained in least-squares fitting procedures. Thermal averaging has been carried out for molecules in thermal equilibrium, i.e., with Boltzmann-distributed populations. The calculation methods and the results will be discussed in detail.
Structural Design Optimization On Thermally Induced Vibration
International Nuclear Information System (INIS)
Gu, Yuanxian; Chen, Biaosong; Zhang, Hongwu; Zhao, Guozhong
2002-01-01
The numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in application software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal induced vibration coupled with both linear and nonlinear transient heat conduction is firstly proposed. Based on the finite element method, the structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat conduction. In the thermal analysis model, the nonlinear heat conduction considered is result from the radiation and temperature-dependent materials. The sensitivity analysis of transient linear and nonlinear heat conduction is performed with the precise time integration method. And then, the sensitivity analysis of structural transient dynamics is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration, and there are two adjoint vectors of structure and heat conduction respectively. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. The methods proposed have been implemented in the application software JIFEX of structural design optimization, and numerical examples are given to illustrate the methods and usage of structural design optimization on thermally induced vibration
Identification of Damping from Structural Vibrations
DEFF Research Database (Denmark)
Bajric, Anela
Reliable predictions of the dynamic loads and the lifetime of structures are inﬂuenced by the limited accuracy concerning the level of structural damping. The mechanisms of damping cannot be derived analytically from ﬁrst principles, and in the design of structures the damping is therefore based...... on experience or estimated from measurements. This thesis consists of an extended summary and three papers which focus on enhanced methods for identiﬁcation of damping from random struc-tural vibrations. The developed methods are validated by stochastic simulations, experimental data and full-scale measurements...... which are representative of the vibrations in small and large-scale structures. The ﬁrst part of the thesis presents an automated procedure which is suitable for estimation of the natural frequencies and the modal damping ratios from random response of structures. The method can be incorporated within...
Vibration-based structural health monitoring of harbor caisson structure
Lee, So-Young; Lee, So-Ra; Kim, Jeong-Tae
2011-04-01
This study presents vibration-based structural health monitoring method in foundation-structure interface of harbor caisson structure. In order to achieve the objective, the following approaches are implemented. Firstly, vibration-based response analysis method is selected and structural health monitoring (SHM) technique is designed for harbor caisson structure. Secondly, the performance of designed SHM technique for harbor structure is examined by FE analysis. Finally, the applicability of designed SHM technique for harbor structure is evaluated by dynamic tests on a lab-scaled caisson structure.
Vibration Analysis Of Automotive Structures Using Holographic Interferometry
Brown, G. M.; Wales, R. R.
1983-10-01
Since 1979, Ford Motor Company has been developing holographic interferometry to supplement more conventional test methods to measure vehicle component vibrations. An Apollo PHK-1 Double Pulse Holographic Laser System was employed to visualize a variety of complex vibration modes, primarily on current production and prototype powertrain components. Design improvements to reduce powertrain response to problem excitations have been deter-mined through pulsed laser holography, and have, in several cases, been put into production in Ford vehicles. Whole-field definition of vibration related deflections provide continuity of information missed by accelerometer/modal analysis techniaues. Certain opera-tional problems, common among pulsed ruby holographic lasers, have reauired ongoing hardware and electronics improvements to minimize system downtime. Real-time, time-averaged and stroboscopic C. W. laser holographic techniques are being developed at Ford to complement the double pulse capabilities and provide rapid identification of modal frequencies and nodal lines for analysis of powertrain structures. Methods for mounting and exciting powertrains to minimize rigid body motions are discussed. Work at Ford will continue toward development of C. W. holographic techniques to provide refined test methodology dedicated to noise and vibration diagnostics with particular emphasis on semi-automated methods for quantifying displacement and relative phase using high resolution digitized video and computers. Continued use of refined pulsed and CW laser holographic interferometry for the analysis of complex structure vibrations seems assured.
Vibration-damping structure for reactor building
International Nuclear Information System (INIS)
Kuno, Toshio; Iba, Chikara; Tanaka, Hideki; Kageyama, Mitsuru
1998-01-01
In a damping structure of a reactor building, an inner concrete body and a reactor container are connected by way of a vibration absorbing member. As the vibration absorbing member, springs or dampers are used. The inner concrete body and the reactor container each having weight and inherent frequency different from each other are opposed displaceably by way of the vibration absorbing member thereby enabling to reduce seismic input and reduce shearing force at least at leg portions. Accordingly, seismic loads are reduced to increase the grounding rate of the base thereby enabling to satisfy an allowable value. Therefore, it is not necessary to strengthen the inner concrete body and the reactor container excessively, the amount of reinforcing rods can be reduced, and the amount of a portion of the base buried to the ground can be reduced thereby enabling to constitute the reactor building easily. (N.H.)
Smart paint sensor for monitoring structural vibrations
International Nuclear Information System (INIS)
Al-Saffar, Y; Baz, A; Aldraihem, O
2012-01-01
A class of smart paint sensors is proposed for monitoring the structural vibration of beams. The sensor is manufactured from an epoxy resin which is mixed with carbon black nano-particles to make it electrically conducting and sensitive to mechanical vibrations. A comprehensive theoretical and experimental investigation is presented to understand the underlying phenomena governing the operation of this class of paint sensors and evaluate its performance characteristics. A theoretical model is presented to model the electromechanical behavior of the sensor system using molecular theory. The model is integrated with an amplifier circuit in order to predict the current and voltage developed by the paint sensor when subjected to loading. Furthermore, the sensor/amplifier circuit models are coupled with a finite element model of a base beam to which the sensor is bonded. The resulting multi-field model is utilized to predict the behavior of both the sensor and the beam when subjected to a wide variety of vibration excitations. The predictions of the multi-field finite element model are validated experimentally and the behavior of the sensor is evaluated both in the time and the frequency domains. The performance of the sensor is compared with the performance of conventional strain gages to emphasize its potential and merits. The presented techniques are currently being extended to sensors that can monitor the vibration and structural power flow of two-dimensional structures. (paper)
Flight Control of Biomimetic Air Vehicles Using Vibrational Control and Averaging
Tahmasian, Sevak; Woolsey, Craig A.
2017-08-01
A combination of vibrational inputs and state feedback is applied to control the flight of a biomimetic air vehicle. First, a control strategy is developed for longitudinal flight, using a quasi-steady aerodynamic model and neglecting wing inertial effects. Vertical and forward motion is controlled by modulating the wings' stroke and feather angles, respectively. Stabilizing control parameter values are determined using the time-averaged dynamic model. Simulations of a system resembling a hawkmoth show that the proposed controller can overcome modeling error associated with the wing inertia and small parameter uncertainties when following a prescribed trajectory. After introducing the approach through an application to longitudinal flight, the control strategy is extended to address flight in three-dimensional space.
Structural-Vibration-Response Data Analysis
Smith, W. R.; Hechenlaible, R. N.; Perez, R. C.
1983-01-01
Computer program developed as structural-vibration-response data analysis tool for use in dynamic testing of Space Shuttle. Program provides fast and efficient time-domain least-squares curve-fitting procedure for reducing transient response data to obtain structural model frequencies and dampings from free-decay records. Procedure simultaneously identifies frequencies, damping values, and participation factors for noisy multiple-response records.
Localized structures in vibrated emulsions
Falcón, Claudio; Bruggeman, Jake; Pasquali, Matteo; Deegan, Robert D.
2012-04-01
We report our observations of localized structures in a thin layer of an emulsion subjected to vertical oscillations. We observe persistent holes, which are voids that span the layer depth, and kinks, which are fronts between regions with and without fluid. These structures form in response to a finite amplitude perturbation. Combining experimental and rheological measurements, we argue that the ability of these structures to withstand the hydrostatic pressure of the surrounding fluid is due to convection within their rim. For persistent holes the oscillatory component of the convection generates a normal stress which opposes contraction, while for kinks the steady component of the convection generates a shear stress which opposes the hydrostatic stress of the surrounding fluid.
Vertical structures in vibrated wormlike micellar solutions
Epstein, Tamir; Deegan, Robert
2008-11-01
Vertically vibrated shear thickening particulate suspensions can support a free-standing interfaces oriented parallel to gravity. We find that shear thickening worm-like micellar solutions also support such vertical interfaces. Above a threshold in acceleration, the solution spontaneously accumulates into a labyrinthine pattern characterized by a well-defined vertical edge. The formation of vertical structures is of interest because they are unique to shear-thickening fluids, and they indicate the existence of an unknown stress bearing mechanism.
Occupant traffic estimation through structural vibration sensing
Pan, Shijia; Mirshekari, Mostafa; Zhang, Pei; Noh, Hae Young
2016-04-01
The number of people passing through different indoor areas is useful in various smart structure applications, including occupancy-based building energy/space management, marketing research, security, etc. Existing approaches to estimate occupant traffic include vision-, sound-, and radio-based (mobile) sensing methods, which have placement limitations (e.g., requirement of line-of-sight, quiet environment, carrying a device all the time). Such limitations make these direct sensing approaches difficult to deploy and maintain. An indirect approach using geophones to measure floor vibration induced by footsteps can be utilized. However, the main challenge lies in distinguishing multiple simultaneous walkers by developing features that can effectively represent the number of mixed signals and characterize the selected features under different traffic conditions. This paper presents a method to monitor multiple persons. Once the vibration signals are obtained, features are extracted to describe the overlapping vibration signals induced by multiple footsteps, which are used for occupancy traffic estimation. In particular, we focus on analysis of the efficiency and limitations of the four selected key features when used for estimating various traffic conditions. We characterize these features with signals collected from controlled impulse load tests as well as from multiple people walking through a real-world sensing area. In our experiments, the system achieves the mean estimation error of +/-0.2 people for different occupant traffic conditions (from one to four) using k-nearest neighbor classifier.
Vibrational Based Inspection of Civil Engineering Structures
DEFF Research Database (Denmark)
Rytter, Anders
at the University of Aalborg from 1988 to 1991. Secondly, a research project, In-Field Vibration Based Inspection of Civil Engineering Structures, which has been performed as a pilot project by the Consulting Engineers Rambøll, Hannemann and Højlund in cooperation with the department of Building Technology......The thesis has been written in relation to two different research projects. Firstly, an offshore test programme, Integrated Experimental/Numerical Analysis of the Dynamic behavior of offshore structures, which was performed at the department of Building Technology and Structural Engineering...... and Structural Engineering at the University of Aalborg since the beginning of 1992. Both projects have been supported by the Danish Technical Research Council. Further, the first mentioned project was supported by the Danish Energy Agency. Their financial support is gratefully acknowledged....
Ro-vibrational averaging of the isotropic hyperfine coupling constant for the methyl radical
Energy Technology Data Exchange (ETDEWEB)
Adam, Ahmad Y.; Jensen, Per, E-mail: jensen@uni-wuppertal.de [Fakultät Mathematik und Naturwissenschaften, Physikalische und Theoretische Chemie, Bergische Universität Wuppertal, D-42097 Wuppertal (Germany); Yachmenev, Andrey; Yurchenko, Sergei N. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
2015-12-28
We present the first variational calculation of the isotropic hyperfine coupling constant of the carbon-13 atom in the CH{sub 3} radical for temperatures T = 0, 96, and 300 K. It is based on a newly calculated high level ab initio potential energy surface and hyperfine coupling constant surface of CH{sub 3} in the ground electronic state. The ro-vibrational energy levels, expectation values for the coupling constant, and its temperature dependence were calculated variationally by using the methods implemented in the computer program TROVE. Vibrational energies and vibrational and temperature effects for coupling constant are found to be in very good agreement with the available experimental data. We found, in agreement with previous studies, that the vibrational effects constitute about 44% of the constant’s equilibrium value, originating mainly from the large amplitude out-of-plane bending motion and that the temperature effects play a minor role.
Ro-vibrational averaging of the isotropic hyperfine coupling constant for the methyl radical
Adam, Ahmad Y.; Yachmenev, Andrey; Yurchenko, Sergei N.; Jensen, Per
2015-12-01
We present the first variational calculation of the isotropic hyperfine coupling constant of the carbon-13 atom in the CH3 radical for temperatures T = 0, 96, and 300 K. It is based on a newly calculated high level ab initio potential energy surface and hyperfine coupling constant surface of CH3 in the ground electronic state. The ro-vibrational energy levels, expectation values for the coupling constant, and its temperature dependence were calculated variationally by using the methods implemented in the computer program TROVE. Vibrational energies and vibrational and temperature effects for coupling constant are found to be in very good agreement with the available experimental data. We found, in agreement with previous studies, that the vibrational effects constitute about 44% of the constant's equilibrium value, originating mainly from the large amplitude out-of-plane bending motion and that the temperature effects play a minor role.
Ro-vibrational averaging of the isotropic hyperfine coupling constant for the methyl radical
International Nuclear Information System (INIS)
Adam, Ahmad Y.; Jensen, Per; Yachmenev, Andrey; Yurchenko, Sergei N.
2015-01-01
We present the first variational calculation of the isotropic hyperfine coupling constant of the carbon-13 atom in the CH 3 radical for temperatures T = 0, 96, and 300 K. It is based on a newly calculated high level ab initio potential energy surface and hyperfine coupling constant surface of CH 3 in the ground electronic state. The ro-vibrational energy levels, expectation values for the coupling constant, and its temperature dependence were calculated variationally by using the methods implemented in the computer program TROVE. Vibrational energies and vibrational and temperature effects for coupling constant are found to be in very good agreement with the available experimental data. We found, in agreement with previous studies, that the vibrational effects constitute about 44% of the constant’s equilibrium value, originating mainly from the large amplitude out-of-plane bending motion and that the temperature effects play a minor role
Directory of Open Access Journals (Sweden)
Takashi Yamamoto
2012-07-01
Full Text Available The relationship between the conducting behavior and the degree of charge fluctuation in the β″-type BEDT-TTF salts is reviewed from the standpoints of vibrational spectroscopy and crystal structure. A group of β″-type ET salts demonstrates the best model compounds for achieving the above relationship because the two-dimensional structure is simple and great diversity in conducting behavior is realized under ambient pressure. After describing the requirement for the model compound, the methodology for analyzing the results of the vibrational spectra is presented. Vibrational spectroscopy provides the time-averaged molecular charge, the charge distribution in the two-dimensional layer, and the inter-molecular interactions, etc. The experimental results applied to 2/3-filled and 3/4-filled β″-type ET salts are reported. These experimental results suggest that the conducting property, the difference in the time-averaged molecular charges between the ionic and neutral-like sites, the alternation in the inter-molecular distances and the energy levels in the charge distributions are relevant to one another. The difference in the time-averaged molecular charges, ∆ρ, is a useful criterion for indicating conducting behavior. All superconductors presented in this review are characterized as small but finite ∆ρ.
Takács, Gergely
2012-01-01
Real-time model predictive controller (MPC) implementation in active vibration control (AVC) is often rendered difficult by fast sampling speeds and extensive actuator-deformation asymmetry. If the control of lightly damped mechanical structures is assumed, the region of attraction containing the set of allowable initial conditions requires a large prediction horizon, making the already computationally demanding on-line process even more complex. Model Predictive Vibration Control provides insight into the predictive control of lightly damped vibrating structures by exploring computationally efficient algorithms which are capable of low frequency vibration control with guaranteed stability and constraint feasibility. In addition to a theoretical primer on active vibration damping and model predictive control, Model Predictive Vibration Control provides a guide through the necessary steps in understanding the founding ideas of predictive control applied in AVC such as: · the implementation of ...
Average and local structure of α-CuI by configurational averaging
International Nuclear Information System (INIS)
Mohn, Chris E; Stoelen, Svein
2007-01-01
Configurational Boltzmann averaging together with density functional theory are used to study in detail the average and local structure of the superionic α-CuI. We find that the coppers are spread out with peaks in the atom-density at the tetrahedral sites of the fcc sublattice of iodines. We calculate Cu-Cu, Cu-I and I-I pair radial distribution functions, the distribution of coordination numbers and the distribution of Cu-I-Cu, I-Cu-I and Cu-Cu-Cu bond-angles. The partial pair distribution functions are in good agreement with experimental neutron diffraction-reverse Monte Carlo, extended x-ray absorption fine structure and ab initio molecular dynamics results. In particular, our results confirm the presence of a prominent peak at around 2.7 A in the Cu-Cu pair distribution function as well as a broader, less intense peak at roughly 4.3 A. We find highly flexible bonds and a range of coordination numbers for both iodines and coppers. This structural flexibility is of key importance in order to understand the exceptional conductivity of coppers in α-CuI; the iodines can easily respond to changes in the local environment as the coppers diffuse, and a myriad of different diffusion-pathways is expected due to the large variation in the local motifs
Harrison, Phil; LaVerde, Bruce; Teague, David
2009-01-01
Although applications for Statistical Energy Analysis (SEA) techniques are more widely used in the aerospace industry today, opportunities to anchor the response predictions using measured data from a flight-like launch vehicle structure are still quite valuable. Response and excitation data from a ground acoustic test at the Marshall Space Flight Center permitted the authors to compare and evaluate several modeling techniques available in the SEA module of the commercial code VA One. This paper provides an example of vibration response estimates developed using different modeling approaches to both approximate and bound the response of a flight-like vehicle panel. Since both vibration response and acoustic levels near the panel were available from the ground test, the evaluation provided an opportunity to learn how well the different modeling options can match band-averaged spectra developed from the test data. Additional work was performed to understand the spatial averaging of the measurements across the panel from measured data. Finally an evaluation/comparison of two conversion approaches from the statistical average response results that are output from an SEA analysis to a more useful envelope of response spectra appropriate to specify design and test vibration levels for a new vehicle.
Demoli, Nazif; Vukicevic, Dalibor
2004-10-15
A method of detecting displacements of a surface from its steady-state position to its equilibrium position while it is vibrating has been developed by use of time-average digital holographic interferometry. This method permits extraction of such a hidden deformation by creating two separated systems of interferogram fringes: one corresponding to a time-varying resonantly oscillating optical phase, the other to the stationary phase modification. A mathematical description of the method and illustrative results of experimental verification are presented.
Review of vibration effect during piling installation to adjacent structure
Rahman, Nurul Aishah Abd; Musir, Adhilla Ainun; Dahalan, Nurol Huda; Ghani, Abdul Naser Abdul; Khalil, Muhamad Kasimi Abd
2017-12-01
Basically, many major structures across the world such as towers, high rise building, houses and bridges utilize pile as a support material. The use of pile is important to strengthen the structures. However, this has led to another problem to the nearest surrounding structures resulted from pile driving. As part of a construction work, unavoidable pile driving activity generates a vibration towards the surrounding structures if uncontrolled may cause damage to the adjacent structure. As the current construction works are frequently located in urban areas where the distance between the nearest building structures is not far, vibration may cause damage to nearby structures. Knowing which part of the building that is mostly affected by various vibration patterns from the impact of pile driving is crucial. Thus, it is very important to predict the impact of vibration during piling installation work. This paper reviews the vibrations generated by piling activity toward surrounding structures in terms sources of vibration, impact of piling installation, pile-soil interaction, and factors affecting the vibration impact of building as well as to study the parameters involved in vibration generation during piling works.
MOLECULAR STRUCTURE AND VIBRATIONAL FREQUENCIES OF
Directory of Open Access Journals (Sweden)
Fatih UCUN
2009-02-01
Full Text Available Abstract: The molecular structure, vibrational frequencies and the corresponding assignments of N-aminophthalimide (NAPH in the ground state have been calculated using the Hartree-Fock (HF and density functional methods (B3LYP with 6-31G (d, p basis set. The calculations were utilized in the CS symmetry of NAPH. The obtained vibrational frequencies and optimized geometric parameters (bond lengths and bond angles were seen to be in good agreement with the experimental data. The comparison of the observed and calculated results showed that B3LYP is superior to the scaled HF method. Theoretical infrared intensities and Raman activities were also reported. Key words: N-aminophthalimide; vibrations; IR spectra; Raman spectra; HF; DFT N-AMİNOFİTALOMİD'İN MOLEKÜLER YAPISI VE TİTREŞİM FREKANSLARI Özet: Temel haldeki N-aminofitalamidin (NAPH moleküler yapısı, titreşim frekansları ve uygun mod tanımlamaları, 6-31 G (d, p temel setli Hartree-Fock (HF ve yoğunluk fonksiyonu metodları (B3LYP kullanılarak hesaplandı. Hesaplamalar, NAPH'ın CS simetrisine uyarlandı. Elde edilen titreşim frekansları ve optimize geometrik parametreleri (bağ uzunlukları ve bağ açıları, deneysel değerlerle iyi bir uyum içinde olduğu görüldü. Deneysel ve teorik sonuçların karşılaştırılması, B3LYP'nin HF metodundan daha üstün olduğunu gösterdi. Ayrıca teorik infrared şiddetleri ve Raman aktiviteleri verildi. Anahtar Kelimeler: N-aminofitalamidin; titreşimler; IR spektrumu; Raman Spektrumu; HF; DFT
Nonlinear vibration with control for flexible and adaptive structures
Wagg, David
2015-01-01
This book provides a comprehensive discussion of nonlinear multi-modal structural vibration problems, and shows how vibration suppression can be applied to such systems by considering a sample set of relevant control techniques. It covers the basic principles of nonlinear vibrations that occur in flexible and/or adaptive structures, with an emphasis on engineering analysis and relevant control techniques. Understanding nonlinear vibrations is becoming increasingly important in a range of engineering applications, particularly in the design of flexible structures such as aircraft, satellites, bridges, and sports stadia. There is an increasing trend towards lighter structures, with increased slenderness, often made of new composite materials and requiring some form of deployment and/or active vibration control. There are also applications in the areas of robotics, mechatronics, micro electrical mechanical systems, non-destructive testing and related disciplines such as structural health monitoring. Two broader ...
Molecular structure and vibrational spectroscopy of isoproturon
Vrielynck, L.; Dupuy, N.; Kister, J.; Nowogrocki, G.
2006-05-01
The crystal structure of isoproturon [ N-(4-isopropylphenyl)- N', N'-dimethylurea] has been determined: the compound crystallizes in the space group Pbca with unit cell parameters a=10.186(2) Å, b=11.030(2) Å, c=20.981(4) Å. The structure was solved and refined down to R1=0.0508 and ωR2=0.12470 for 3056 reflections. The crystalline molecular network of this pesticide is stabilized, as for many molecules of the same family, by π-π interactions but especially by a medium-strong N-H⋯C dbnd6 O intermolecular hydrogen bond (2.14 Å). The X-ray parameters were then compared with the results of DFT quantum chemical calculation computed with the GAUSSIAN 94 package. A tentative assignment of the ATR-FT-IR and Raman spectra was proposed supported by vibrational mode calculation and spectroscopic data on benzenic and urea derivatives available in the literature. The presence of a tight band around 3300 cm -1, which can be assigned to the NH bond stretching mode as well as the low frequency position of the amide I band at 1640 cm -1, sensitive to solvent polarity, confirms the existence of a quite strong intermolecular hydrogen bond between neighboring molecules in the crystal of isoproturon.
Directory of Open Access Journals (Sweden)
Sawczuk Wojciech
2017-06-01
Full Text Available Due to their wide range of friction characteristics resulting from the application of different friction materials and good heat dissipation conditions, railway disc brakes have long replaced block brakes in many rail vehicles. A block brake still remains in use, however, in low speed cargo trains. The paper presents the assessment of the braking process through the analysis of vibrations generated by the components of the brake system during braking. It presents a possibility of a wider application of vibroacoustic diagnostics (VA, which aside from the assessment of technical conditions (wear of brake pads also enables the determination of the changes of the average friction coefficient as a function of the braking onset speed. Vibration signals of XYZ were measured and analyzed. The analysis of the results has shown that there is a relation between the values of the point measures and the wear of the brake pads.
Innovation in Active Vibration Control Strategy of Intelligent Structures
Directory of Open Access Journals (Sweden)
A. Moutsopoulou
2014-01-01
Full Text Available Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.
A practical, systematic and structured approach to piping vibration assessment
International Nuclear Information System (INIS)
Sukaih, Naren
2002-01-01
The main aim of this paper is to present a systematic and structured approach to piping vibration assessment and control. Piping vibration assessment is a complex subject, since there are no general analytical methods for dealing with vibration problems. It was noted that most existing vibrating piping systems had poor or degraded support arrangements. This approach therefore focuses mainly on vibration control through assessing and improving the supporting systems. Vibration theory has not been covered in any detail. A simplified procedure is presented for the Integrity custodian to determine when a simple assessment may be carried out and when specialist/consultant services are required. The assessment techniques are based on simplifying assumptions, good rules of thumb and available literature and current practices. A typical case study is used to illustrate the use and the flexibility of the above approach. A standard sheet is proposed to record and document the assessment and recommendations
VIBRATION ANALYSIS OF TURBINE BASED ON FLUID-STRUCTURE COUPLING
Institute of Scientific and Technical Information of China (English)
LIU Demin; LIU Xiaobing
2008-01-01
The vibration of a Francis turbine is analyzed with the additional quality matrix method based on fluid-structure coupling (FSC). Firstly, the vibration frequency and mode of blade and runner in air and water are calculated. Secondly, the influences to runner frequency domain by large flow, small flow and design flow working conditions are compared. Finally the influences to runner modes by centrifugal forces under three rotating speeds of 400 r/min, 500 r/min and 600 r/min are compared. The centrifugal force and small flow working condition have greatly influence on the vibration of small runner. With the increase of centrifugal force, the vibration frequency of the runner is sharply increased. Some order frequencies are even close to the runner natural frequency in the air. Because the low frequency vibration will severely damage the stability of the turbine, low frequency vibration of units should be avoided as soon as possible.
Sumner, Isaiah; Iyengar, Srinivasan S
2007-10-18
We have introduced a computational methodology to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach is based on the recently developed quantum wavepacket ab initio molecular dynamics method that combines quantum wavepacket dynamics with ab initio molecular dynamics. The computational efficiency of the dynamical procedure is drastically improved (by several orders of magnitude) through the utilization of wavelet-based techniques combined with the previously introduced time-dependent deterministic sampling procedure measure to achieve stable, picosecond length, quantum-classical dynamics of electrons and nuclei in clusters. The dynamical information is employed to construct a novel cumulative flux/velocity correlation function, where the wavepacket flux from the quantized particle is combined with classical nuclear velocities to obtain the vibrational density of states. The approach is demonstrated by computing the vibrational density of states of [Cl-H-Cl]-, inclusive of critical quantum nuclear effects, and our results are in good agreement with experiment. A general hierarchical procedure is also provided, based on electronic structure harmonic frequencies, classical ab initio molecular dynamics, computation of nuclear quantum-mechanical eigenstates, and employing quantum wavepacket ab initio dynamics to understand vibrational spectroscopy in hydrogen-bonded clusters that display large degrees of anharmonicities.
Flow-Induced Vibration of Circular Cylindrical Structures
Energy Technology Data Exchange (ETDEWEB)
Chen, Shoei-Sheng [Argonne National Lab. (ANL), Argonne, IL (United States). Components Technology Division
1985-06-01
Flow-induced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. More specifically, the terra covers those cases in which an interaction develops between fluid-dynamic forces and the inertia, damping or elastic forces in the structures. The study of these phenomena draws on three disciplines: (1) structural mechanics, (2) mechanical vibration, and (3) fluid dynamics. The vibration of circular cylinders subject to flow has been known to man since ancient times; the vibration of a wire at its natural frequency in response to vortex shedding was known in ancient Greece as aeolian tones. But systematic studies of the problem were not made until a century ago when Strouhal established the relationship between vortex shedding frequency and flow velocity for a given cylinder diameter. The early research in this area has beer summarized by Zdravkovich (1985) and Goldstein (1965). Flow-induced structural vibration has been experienced in numerous fields, including the aerospace industry, power generation/transmission (turbine blades, heat exchanger tubes, nuclear reactor components), civil engineering (bridges, building, smoke stacks), and undersea technology. The problems have usually been encountered or created accidentally through improper design. In most cases, a structural or mechanical component, designed to meet specific objectives, develops problems when the undesired effects of flow field have not been accounted for in the design. When a flow-induced vibration problem is noted in the design stage, the engineer has different options to eliminate the detrimental vibration. Unfortunately, in many situations, the problems occur after the components are already in operation; the "fix" usually is very costly. Flow-induced vibration comprises complex and diverse phenomena; subcritical vibration of nuclear fuel assemblies, galloping of transmission lines, flutter of pipes conveying fluid, and whirling
Effect of structural design on traffic-induced building vibrations
DEFF Research Database (Denmark)
Persson, Peter; Andersen, Lars Vabbersgaard; Persson, Kent
2017-01-01
Population growth and urbanization results in densified cities, where new buildings are being built closer to existing vibration sources such as road-, tram- and rail traffic. In addition, new transportation systems are constructed closer to existing buildings. Potential disturbing vibrations...... are one issue to consider in planning urban environment and densification of cities. Vibrations can be disturbing for humans but also for sensitive equipment in, for example, hospitals. In determining the risk for disturbing vibrations, the distance between the source and the receiver, the ground...... properties, and type and size of the building are governing factors. In the paper, a study is presented aiming at investigating the influence of various parameters of the building's structural design on vibration levels in the structure caused by ground surface loads, e.g. traffic. Parameters studied...
Structural Characteristics of Rotate Vector Reducer Free Vibration
Directory of Open Access Journals (Sweden)
Chuan Chen
2017-01-01
Full Text Available For RV reducer widely used in robots, vibration significantly affects its performance. A lumped parameter model is developed to investigate free vibration characteristics without and with gyroscopic effects. The dynamic model considers key factors affecting vibration such as involute and cycloid gear mesh stiffness, crankshaft bending stiffness, and bearing stiffness. For both nongyroscopic and gyroscopic systems, free vibrations are examined and compared with each other. Results reveal the specific structure of vibration modes for both systems, which results from symmetry structure of RV reducer. According to vibration of the central components, vibration modes of two systems can be classified into three types, rotational, translational, and planetary component modes. Different from nongyroscopic system, the eigenvalues with gyroscopic effects are complex-valued and speed-dependent. The eigenvalue for a range of carrier speeds is obtained by numerical simulation. Divergence and flutter instability is observed at speeds adjacent to critical speeds. Furthermore, the work studies effects of key factors, which include crankshaft eccentricity and the number of pins, on eigenvalues. Finally, experiment is performed to verify the effectiveness of the dynamic model. The research of this paper is helpful for the analysis on free vibration and dynamic design of RV reducer.
Vibration Antiresonance Design for a Spacecraft Multifunctional Structure
Directory of Open Access Journals (Sweden)
Dong-Xu Li
2017-01-01
Full Text Available Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections between substructures. Especially in this paper, a vibration antiresonance design method is proposed to realize the vibration reduction. The complex zero-point equations of the vibration system are firstly established, and then the vibration antiresonance design for the system is achieved. For solving the difficulties due to viscoelastic characteristics of the connecting parts, we present the determining formulas to obtain the structural parameters, so that the complex zero-point equations can be satisfied. Numerical simulation and ground experiment demonstrate the correctness and effectiveness of the proposed method. This method can solve the structural vibration control problem under the function constraints of load bearing and energy supplying and will expand the performance of spacecraft functional modules.
Approaches for reducing structural vibration of the carbody railway vehicles
Directory of Open Access Journals (Sweden)
Dumitriu Mădălina
2017-01-01
Full Text Available Reducing the weight of the railway vehicles stands as a decisive rule in their design, entailed by higher velocities, the need to consume less energy and lower the manufacturing costs, along with the maximization of the use of loads on the axle. Once complied with this rule, the vehicle flexibility increases and leads to an easy excitation of the structural vibrations in the carbody, with an impact upon the ride comfort in the railway vehicle. For a better ride comfort in lightweight railway vehicles, both vibration isolation approaches and structural damping approaches have been introduced. The paper herein submits a brief review of the main structural damping approaches aiming to reduce the amplitude in the carbody structural vibrations, based on the use of the piezoelectric elements in passive control schemes. The paper outcomes show the potential of the presented methods concerning the reduction of the flexible vibrations in the carbody and the ride comfort improvement.
Structural dynamics and vibration 1995. PD-Volume 70
International Nuclear Information System (INIS)
Ovunc, B.A.; Esat, I.I.; Sabir, A.B.; Karadag, V.
1995-01-01
The themes of this symposium focused on: dynamic responses to temperature cycles and wind excitation; the influence of the hydraulic feedback on stability; structural reliability; vibratory stress relief; fault detection by signal processing; dynamic contact in mechanisms; vibration of thick flexible mechanisms; higher order mechanisms in flexible mechanisms; natural circular frequencies by finite element method; elastic buckling, stability, and vibration of linear and nonlinear structures; buckling of stiffened plates and rings; mixed variable optimization; vibration optimization; and optimization in a constrained space. Separate abstracts were prepared for 20 papers in this book
Bettens, Ryan P A
2003-01-15
Collins' method of interpolating a potential energy surface (PES) from quantum chemical calculations for reactive systems (Jordan, M. J. T.; Thompson, K. C.; Collins, M. A. J. Chem. Phys. 1995, 102, 5647. Thompson, K. C.; Jordan, M. J. T.; Collins, M. A. J. Chem. Phys. 1998, 108, 8302. Bettens, R. P. A.; Collins, M. A. J. Chem. Phys. 1999, 111, 816) has been applied to a bound state problem. The interpolation method has been combined for the first time with quantum diffusion Monte Carlo calculations to obtain an accurate ground state zero-point energy, the vibrationally average rotational constants, and the vibrationally averaged internal coordinates. In particular, the system studied was fluoromethane using a composite method approximating the QCISD(T)/6-311++G(2df,2p) level of theory. The approach adopted in this work (a) is fully automated, (b) is fully ab initio, (c) includes all nine nuclear degrees of freedom, (d) requires no assumption of the functional form of the PES, (e) possesses the full symmetry of the system, (f) does not involve fitting any parameters of any kind, and (g) is generally applicable to any system amenable to quantum chemical calculations and Collins' interpolation method. The calculated zero-point energy agrees to within 0.2% of its current best estimate. A0 and B0 are within 0.9 and 0.3%, respectively, of experiment.
Vibration Antiresonance Design for a Spacecraft Multifunctional Structure
Li, Dong-Xu; Liu, Wang; Hao, Dong
2017-01-01
Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections b...
Input Shaping to Reduce Solar Array Structural Vibrations
Doherty, Michael J.; Tolson, Robert J.
1998-01-01
Structural vibrations induced by actuators can be minimized using input shaping. Input shaping is a feedforward method in which actuator commands are convolved with shaping functions to yield a shaped set of commands. These commands are designed to perform the maneuver while minimizing the residual structural vibration. In this report, input shaping is extended to stepper motor actuators. As a demonstration, an input-shaping technique based on pole-zero cancellation was used to modify the Solar Array Drive Assembly (SADA) actuator commands for the Lewis satellite. A series of impulses were calculated as the ideal SADA output for vibration control. These impulses were then discretized for use by the SADA stepper motor actuator and simulated actuator outputs were used to calculate the structural response. The effectiveness of input shaping is limited by the accuracy of the knowledge of the modal frequencies. Assuming perfect knowledge resulted in significant vibration reduction. Errors of 10% in the modal frequencies caused notably higher levels of vibration. Controller robustness was improved by incorporating additional zeros in the shaping function. The additional zeros did not require increased performance from the actuator. Despite the identification errors, the resulting feedforward controller reduced residual vibrations to the level of the exactly modeled input shaper and well below the baseline cases. These results could be easily applied to many other vibration-sensitive applications involving stepper motor actuators.
Two-phase flow induced parametric vibrations in structural systems
International Nuclear Information System (INIS)
Hara, Fumio
1980-01-01
This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)
International Nuclear Information System (INIS)
Ge, Gen; Li, ZePeng
2016-01-01
A modified stochastic averaging method on single-degree-of-freedom (SDOF) oscillators under white noise excitations with strongly nonlinearity was proposed. Considering the existing approach dealing with strongly nonlinear SDOFs derived by Zhu and Huang [14, 15] is quite time consuming in calculating the drift coefficient and diffusion coefficients and the expressions of them are considerable long, the so-called He's energy balance method was applied to overcome the minor defect of the Zhu and Huang's method. The modified method can offer more concise approximate expressions of the drift and diffusion coefficients without weakening the accuracy of predicting the responses of the systems too much by giving an averaged frequency beforehand. Three examples, a cubic and quadratic nonlinearity coexisting oscillator, a quadratic nonlinear oscillator under external white noise excitations and an externally excited Duffing–Rayleigh oscillator, were given to illustrate the approach we proposed. The three examples were excited by the Gaussian white noise and the Gaussian colored noise separately. The stationary responses of probability density of amplitudes and energy, together with joint probability density of displacement and velocity are studied to verify the presented approach. The reliability of the systems were also investigated to offer further support. Digital simulations were carried out and the output of that are coincide with the theoretical approximations well.
Equilibrium structure and atomic vibrations of Nin clusters
Borisova, Svetlana D.; Rusina, Galina G.
2017-12-01
The equilibrium bond lengths and binding energy, second differences in energy and vibrational frequencies of free clusters Nin (2 ≤ n ≤ 20) were calculated with the use of the interaction potential obtained in the tight-binding approximation (TBA). The results show that the minimum vibration frequency plays a significant role in the evaluation of the dynamic stability of the clusters. A nonmonotonic dependence of the minimum vibration frequency of clusters on their size and the extreme values for the number of atoms in a cluster n = 4, 6, 13, and 19 are demonstrated. This result agrees with the theoretical and experimental data on stable structures of small metallic clusters.
Structure-borne sound structural vibrations and sound radiation at audio frequencies
Cremer, L; Petersson, Björn AT
2005-01-01
Structure-Borne Sound"" is a thorough introduction to structural vibrations with emphasis on audio frequencies and the associated radiation of sound. The book presents in-depth discussions of fundamental principles and basic problems, in order to enable the reader to understand and solve his own problems. It includes chapters dealing with measurement and generation of vibrations and sound, various types of structural wave motion, structural damping and its effects, impedances and vibration responses of the important types of structures, as well as with attenuation of vibrations, and sound radi
Structure of vibrational and rotational nuclei
International Nuclear Information System (INIS)
Otsuka, Takaharu
1980-01-01
The nuclear collective motion is discussed in terms of the Interacting Boson Model (IBM). Results of phenomenological studies by the IBM are presented, and the relation between the IBM and the geometrical models such as the vibration model, the rotor model, etc., is pointed out. A microscopic picture for the IBM is shown, in which bosons are introduced as a tool to describe the motion of nucleon pairs. It is emphasized that the IBM can give a unified understanding of the nuclear collective motion. (author)
Evaluation of blast-induced vibration effects on structures 1
Energy Technology Data Exchange (ETDEWEB)
Lee, Jong Rim; Jeon, Gyu Shick; Lee, Dae Soo; Joo, Kwang Ho; Lee, Woong Keon [Korea Electrotechnology Research Inst., Changwon (Korea, Republic of); Ryu, Chang Ha; Chung, So Keul; Lee, Kyung Won; Shin, Hee Soon; Chun, Sun Woo; Park, Yeon Jun; Synn, Joong Ho; Choi, Byung Hee [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)
1995-12-31
Due to the difficulties of obtaining construction site for new plants, following ones are inevitably being built in the site adjacent to existing power plants. Therefore considerable thought has been recently given to the dynamic loading generated by blasting works near the plants to maintain the safety of structures and facilities in power plants. Our own standard for safety level of blast vibration is not prepared yet, and foreign standards have been generally employed without theoretical and experimental verification. Safety-related structures of power plants and facilities have to be protected against the effects of possible hazards due to blast vibration. Earthquakes have been considered a major dynamic design loading as a requirement of plant design, but the effects of blast-induced vibration are not. In order to ensure the safety, rational safe criterion should be established and blast design should be satisfy it, which requires the development of a model for prediction of vibration level through more systematic measurement and analysis. The main objectives of the study are : to provide background data for establishing the rational safe vibration limits, to develop models for prediction of blast vibration level, to establish safe blast design criterion, and to accumulate techniques for field measurements, data acquisition and analysis (author). 80 refs., 347 figs.
Structural health monitoring with a wireless vibration sensor network
Basten, T.G.H.; Sas, P; Schiphorst, F.B.A.; Jonckheere, S.; Moens, D.
2012-01-01
Advanced maintenance strategies for infrastructure assets such as bridges or off shore wind turbines require actual and reliable information of the maintenance status. Structural health monitoring based on vibration sensing can help in supplying the input needed for structural health monitoring
Flow-induced vibrations of circular cylindrical structures
International Nuclear Information System (INIS)
Chen, S.
1977-06-01
The problems of flow-induced vibrations of circular cylindrical structures are reviewed. First, the general method of analysis and classification of structural responses are presented. Then, the presentation is broken up along the lines with stationary fluid, parallel flow, and cross flow. Finally, design considerations and future research needs are pointed out. 234 references
Average and local structure of selected metal deuterides
Energy Technology Data Exchange (ETDEWEB)
Soerby, Magnus H.
2005-07-01
deuterides at 1 bar D2 and elevated temperatures (373-573 K) is presented in Paper 1. Deuterium atoms occupy chiefly three types of tetrahedral interstitial sites; two coordinated by 4 Zr atoms and one coordinated by 3 Zr and 1 Ni atoms. The site preference is predominantly ruled by sample composition and less by temperature. On the other hand, the spatial deuterium distribution among the preferred sites is strongly temperature dependant as the long-range correlations break down on heating. The sample is fully decomposed into tetragonal ZrD2 and Zr7Ni10 at 873 K. Th2AlD4 was the only metal deuteride with reported D-D separation substantially below 2 Aa (1.79 Aa) prior to the discovery of RENiInD1.33. However, as being the first ternary deuteride ever studied by PND, the original structure solution was based on very low-resolution data. The present reinvestigation (Paper 2) shows that the site preference was correctly determined, but the deuterium atoms are slightly shifted compared to the earlier report, now yielding acceptable interatomic separations. Solely Th4 tetrahedra are occupied in various Th2Al deuterides. Th8Al4D11 (Th2AlD2.75) takes a superstructure with tripled c-axis due to deuterium ordering. Th2AlD2.3 is disordered and the average distance between partly occupied sites appears as just 1.55 Aa in Rietveld refinements. However, short-range order is expected to prevent D-D distances under 2 Aa. Paper 3 present the first Reverse Monte Carlo (RMC) study of a metal deuteride. RMC is used in combination with total neutron scattering to model short-range deuterium correlations in disordered c-VD0.77. A practically complete blocking of interstitial sites closer than 2 Aa from any occupied deuterium site is observed. The short-range correlations resemble those of the fully ordered low temperature phase c-VD0.75 at length scales up to about 3 Aa, i.e. for the first two coordination spheres. Paper 4 concerns RMC modelling of short-range deuterium correlations in ZrCr2D4
Average and local structure of selected metal deuterides
International Nuclear Information System (INIS)
Soerby, Magnus H.
2004-01-01
elevated temperatures (373-573 K) is presented in Paper 1. Deuterium atoms occupy chiefly three types of tetrahedral interstitial sites; two coordinated by 4 Zr atoms and one coordinated by 3 Zr and 1 Ni atoms. The site preference is predominantly ruled by sample composition and less by temperature. On the other hand, the spatial deuterium distribution among the preferred sites is strongly temperature dependant as the long-range correlations break down on heating. The sample is fully decomposed into tetragonal ZrD2 and Zr7Ni10 at 873 K. Th2AlD4 was the only metal deuteride with reported D-D separation substantially below 2 Aa (1.79 Aa) prior to the discovery of RENiInD1.33. However, as being the first ternary deuteride ever studied by PND, the original structure solution was based on very low-resolution data. The present reinvestigation (Paper 2) shows that the site preference was correctly determined, but the deuterium atoms are slightly shifted compared to the earlier report, now yielding acceptable interatomic separations. Solely Th4 tetrahedra are occupied in various Th2Al deuterides. Th8Al4D11 (Th2AlD2.75) takes a superstructure with tripled c-axis due to deuterium ordering. Th2AlD2.3 is disordered and the average distance between partly occupied sites appears as just 1.55 Aa in Rietveld refinements. However, short-range order is expected to prevent D-D distances under 2 Aa. Paper 3 present the first Reverse Monte Carlo (RMC) study of a metal deuteride. RMC is used in combination with total neutron scattering to model short-range deuterium correlations in disordered c-VD0.77. A practically complete blocking of interstitial sites closer than 2 Aa from any occupied deuterium site is observed. The short-range correlations resemble those of the fully ordered low temperature phase c-VD0.75 at length scales up to about 3 Aa, i.e. for the first two coordination spheres. Paper 4 concerns RMC modelling of short-range deuterium correlations in ZrCr2D4 at ambient and low
Active control of noise radiation from vibrating structures
DEFF Research Database (Denmark)
Mørkholt, Jakob
developed, based on the theory of radiation filters for estimating the sound radiation from multimodal vibrations. This model has then been used in simulations of optimal feedback control, with special emphasis of the stability margins of the optimal control scheme. Two different methods of designing...... optimal and robust discrete-time feedback controllers for active vibration control of multimodal structures have been compared. They have been showed to yield controllers with identical frequency response characteristics, even though they employ completely different methods of numerical solutions...... and result in different representations of the controllers. The Internal Model Control structure combined with optimal filtering is suggested as an alternative to state space optimal control techniques for designing robust optimal controllers for audio frequency vibration control of resonant structures....
Structural and vibrational studies of clean and chemisorbed metal surfaces
International Nuclear Information System (INIS)
Jiang, Qing-Tang.
1992-01-01
Using Medium Energy Ion Scattering, we have studied the structural and vibrational properties of a number of clean and chemisorbed metal surfaces. The work presented in this thesis is mainly of a fundamental nature. However, it is believed that an atomistic understanding of the forces that affect surface structural and vibrational properties can have a beneficial impact on a large number of areas of applied nature. We find that the surface structure of Cu(001) follows the common trend for metal surfaces, where a small oscillatory relaxation exists beginning with a slight contraction in the top layer. In addition, the surface vibrational amplitude is enhanced (as s usually the case) by ∼80%. A detailed analysis of our data shows an unexpected anisotropy of the vibrational amplitude, such that the out-of-plane vibrational amplitude is 30% smaller than the in-plane vibrational amplitude. The unexpected results may imply a large tensile stress on Cu(001). Upon adsorption of 1/4 of a monolayer of S, a p(2 x 2)-S/Cu(001) surface is created. This submonolayer amount of S atoms makes the surface bulk-like, in which the anisotropy of the surface vibrations is removed and the first interlayer contraction is lifted. By comparing our model to earlier contradictory results on this controversial system. We find excellent agreement with a recent LEED study. The presence of 0.1 monolayer of Ca atoms on the Au(113) surface induces a drastic atomic rearrangements, in which half of the top layer Au atoms are missing and a (1 x 2) symmetry results. In addition, the first interlayer spacing of Au(113) is significantly reduced. Our results are discussed in terms of the energy balance between competing surface electronic charge densities
Robust structural design against self-excited vibrations
Spelsberg-Korspeter, Gottfried
2013-01-01
This book studies methods for a robust design of rotors against self-excited vibrations. The occurrence of self-excited vibrations in engineering applications if often unwanted and in many cases difficult to model. Thinking of complex systems such as machines with many components and mechanical contacts, it is important to have guidelines for design so that the functionality is robust against small imperfections. This book discusses the question on how to design a structure such that unwanted self-excited vibrations do not occur. It shows theoretically and practically that the old design rule to avoid multiple eigenvalues points toward the right direction and have optimized structures accordingly. This extends results for the well-known flutter problem in which equations of motion with constant coefficients occur to the case of a linear conservative system with arbitrary time periodic perturbations.
Structure, vibrations, and hydrogen bond parameters of dibenzotetraaza[14]annulene
Gawinkowski, S.; Eilmes, J.; Waluk, J.
2010-07-01
Geometry and vibrational structure of dibenzo[ b, i][1,4,8,11]tetraaza[14]annulene (TAA) have been studied using infrared and Raman spectroscopy combined with quantum-chemical calculations. The assignments were proposed for 106 out of the total of 108 TAA vibrations, based on comparison of the theoretical predictions with the experimental data obtained for the parent molecule and its isotopomer in which the NH protons were replaced by deuterons. Reassignments were suggesteded for the NH stretching and out-of-plane vibrations. The values of the parameters of the intramolecular NH⋯N hydrogen bonds were analysed in comparison with the corresponding data for porphyrin and porphycene, molecules with the same structural motif, a cavity composed of four nitrogen atoms and two inner protons. Both experiment and calculations suggest that the molecule of TAA is not planar and is present in a trans tautomeric form, with the protons located on the opposite nitrogen atoms.
Structural impact response for assessing railway vibration induced on buildings
Kouroussis, Georges; Mouzakis, Harris P.; Vogiatzis, Konstantinos E.
2018-03-01
Over the syears, the rapid growth in railway infrastructure has led to numerous environmental challenges. One such significant issue, particularly in urban areas, is ground-borne vibration. A common source of ground-borne vibration is caused by local defects (e.g. rail joints, switches, turnouts, etc.) that generate large amplitude excitations at isolated locations. Modelling these excitation sources is particularly challenging and requires the use of complex and extensive computational efforts. For some situations, the use of experiments and measured data offers a rapid way to estimate the effect of such defects and to evaluate the railway vibration levels using a scoping approach. In this paper, the problem of railway-induced ground vibrations is presented along with experimental studies to assess the ground vibration and ground borne noise levels, with a particular focus on the structural response of sensitive buildings. The behaviour of particular building foundations is evaluated through experimental data collected in Brussels Region, by presenting the expected frequency responses for various types of buildings, taking into account both the soil-structure interaction and the tramway track response. A second study is dedicated to the Athens metro, where transmissibility functions are used to analyse the effect of various Athenian building face to metro network trough comprehensive measurement campaigns. This allows the verification of appropriate vibration mitigation measures. These benchmark applications based on experimental results have been proved to be efficient to treat a complex problem encountered in practice in urban areas, where the urban rail network interacts with important local defects and where the rise of railway ground vibration problems has clearly been identified.
International Nuclear Information System (INIS)
Trendafilova, I
2011-01-01
Vibration-based structural interrogation and health monitoring is a field which is concerned with the estimation of the current state of a structure or a component from its vibration response with regards to its ability to perform its intended function appropriately. One way to approach this problem is through damage features extracted from the measured structural vibration response. This paper suggests to use a new concept for the purposes of vibration-based health monitoring. The correlation between two signals, an input and an output, measured on the structure is used to develop a damage indicator. The paper investigates the applicability of the signal cross-correlation and a nonlinear alternative, the average mutual information between the two signals, for the purposes of structural health monitoring and damage assessment. The suggested methodology is applied and demonstrated for delamination detection in a composite beam.
Vibration control of active structures an introduction
Preumont, Andre
2002-01-01
This text is an introduction to the dynamics of active structures and to the feedback control of lightly damped flexible structures. The emphasis is placed on basic issues and simple control strategies that work.
Numerical calculation of acoustic radiation from band-vibrating structures via FEM/FAQP method
Directory of Open Access Journals (Sweden)
GAO Honglin
2017-08-01
Full Text Available The Finite Element Method (FEM combined with the Frequency Averaged Quadratic Pressure method (FAQP are used to calculate the acoustic radiation of structures excited in the frequency band. The surface particle velocity of stiffened cylindrical shells under frequency band excitation is calculated using finite element software, the normal vibration velocity is converted from the surface particle velocity to calculate the average energy source (frequency averaged across intensity, frequency averaged across pressure and frequency averaged across velocity, and the FAQP method is used to calculate the average sound pressure level within the bandwidth. The average sound pressure levels are then compared with the bandwidth using finite element and boundary element software, and the results show that FEM combined with FAQP is more suitable for high frequencies and can be used to calculate the average sound pressure level in the 1/3 octave band with good stability, presenting an alternative to applying frequency-by-frequency calculation and the average frequency process. The FEM/FAQP method can be used as a prediction method for calculating acoustic radiation while taking the randomness of vibration at medium and high frequencies into consideration.
Uncertainty Quantification for Monitoring of Civil Structures from Vibration Measurements
Döhler, Michael; Mevel, Laurent
2014-05-01
Health Monitoring of civil structures can be performed by detecting changes in the modal parameters of a structure, or more directly in the measured vibration signals. For a continuous monitoring the excitation of a structure is usually ambient, thus unknown and assumed to be noise. Hence, all estimates from the vibration measurements are realizations of random variables with inherent uncertainty due to (unknown) process and measurement noise and finite data length. In this talk, a strategy for quantifying the uncertainties of modal parameter estimates from a subspace-based system identification approach is presented and the importance of uncertainty quantification in monitoring approaches is shown. Furthermore, a damage detection method is presented, which is based on the direct comparison of the measured vibration signals without estimating modal parameters, while taking the statistical uncertainty in the signals correctly into account. The usefulness of both strategies is illustrated on data from a progressive damage action on a prestressed concrete bridge. References E. Carden and P. Fanning. Vibration based condition monitoring: a review. Structural Health Monitoring, 3(4):355-377, 2004. M. Döhler and L. Mevel. Efficient multi-order uncertainty computation for stochastic subspace identification. Mechanical Systems and Signal Processing, 38(2):346-366, 2013. M. Döhler, L. Mevel, and F. Hille. Subspace-based damage detection under changes in the ambient excitation statistics. Mechanical Systems and Signal Processing, 45(1):207-224, 2014.
Optimal Vibration Control of Civil Engineering Structures
DEFF Research Database (Denmark)
Thesbjerg, Leo
In designing large civil engineering structures, an important consideration is prospective dynamic loadings which may include earthquake ground motion, wind gusts, severe sea states and moving vehicles, rotating and reciprocating machinery and others. successful design of such structures requires...... providing for the safety and integrity of the structure, and in some cases also providing for a measure of comfort for the occupants during such loading which the structure and its occupants must endure. Due to these uncertainties, the civil engineering community has traditionally adopted a very...
Passive and Active Vibration Control of Renewable Energy Structures
DEFF Research Database (Denmark)
Zhang, Zili
The present thesis deals with fundamental researches on passive and active vibration control of renewable energy structures, and provides useful models for practical applications. Effective and robust vibration control methods have been explored for mitigating the lightly damped edgewise blade...... solutions for wave energy point absorbers, in order to maximize the mean absorbed power and to deliver more smooth power to the grid. A novel suboptimal causal control law has been established for controlling the motion of the point absorber, and a new type of point absorber has also been proposed...
Analytical and Experimental Random Vibration of Nonlinear Aeroelastic Structures.
1987-01-28
vibrations. In civil engineenng the mechanical and strength eccentricity in the disks. Parameter variations exist in disk properties of the material vary...support. define the loading and resistance strength of the structure. Figure 10 shows the comparison between theoretical and experi- mental natural... dinamics . Sijthoff- Hilton, H H. and Feigen. M. Minimum weight analysis based on structural Noordhoff Co, Netherlands. reliability. J Aerospace Sc, 27
Directory of Open Access Journals (Sweden)
Wenbin Gu
2015-01-01
Full Text Available As an important parameter in blasting design, charging structure directly influences blasting effect. Due to complex conditions of this blasting and excavating engineering in Jiangsu, China, the authors carried out comparative researches with coupling structure, air-decoupling structure, and water-decoupling structure. After collecting, comparing, and analyzing produced signals on blasting vibration, the authors summarized that when proportional distances are the same, water-decoupling structure can reduce instantaneous energy of blasting vibration more effectively with more average rock fragmentation and less harm of dust. From the perspective of impedance matching, the present paper analyzed influence of charging structure on blasting vibration energy, demonstrating that impedance matching relationship between explosive and rock changes because of different charging structures. Through deducing relationship equation that meets the impedance matching of explosive and rock under different charging structures, the research concludes that when blasting rocks with high impedance, explosive with high impedance can better transmits blasting energy. Besides, when employing decoupling charging, there exists a reasonable decoupling coefficient helping realize impedance matching of explosive and rock.
Statistical techniques for the identification of reactor component structural vibrations
International Nuclear Information System (INIS)
Kemeny, L.G.
1975-01-01
The identification, on-line and in near real-time, of the vibration frequencies, modes and amplitudes of selected key reactor structural components and the visual monitoring of these phenomena by nuclear power plant operating staff will serve to further the safety and control philosophy of nuclear systems and lead to design optimisation. The School of Nuclear Engineering has developed a data acquisition system for vibration detection and identification. The system is interfaced with the HIFAR research reactor of the Australian Atomic Energy Commission. The reactor serves to simulate noise and vibrational phenomena which might be pertinent in power reactor situations. The data acquisition system consists of a small computer interfaced with a digital correlator and a Fourier transform unit. An incremental tape recorder is utilised as a backing store and as a means of communication with other computers. A small analogue computer and an analogue statistical analyzer can be used in the pre and post computational analysis of signals which are received from neutron and gamma detectors, thermocouples, accelerometers, hydrophones and strain gauges. Investigations carried out to date include a study of the role of local and global pressure fields due to turbulence in coolant flow and pump impeller induced perturbations on (a) control absorbers, (B) fuel element and (c) coolant external circuit and core tank structure component vibrations. (Auth.)
Wireless sensor networks for active vibration control in automobile structures
International Nuclear Information System (INIS)
Mieyeville, Fabien; Navarro, David; Du, Wan; Ichchou, Mohamed; Scorletti, Gérard
2012-01-01
Wireless sensor networks (WSNs) are nowadays widely used in monitoring and tracking applications. This paper presents the feasibility of using WSNs in active vibration control strategies. The method employed here involves active-structural acoustic control using piezoelectric sensors distributed on a car structure. This system aims at being merged with a WSN whose head node collects data and processes control laws so as to command piezoelectric actuators wisely placed on the structure. We will study the feasibility of implementing WSNs in active vibration control and introduce a complete design methodology to optimize hardware/software and control law synergy in mechatronic systems. A design space exploration will be conducted so as to identify the best WSN platform and the resulting impact on control. (paper)
Energy Technology Data Exchange (ETDEWEB)
Markovic, M I [Elektrothenicki fakultet, Belgrade (Yugoslavia)
1974-07-01
Quantum-mechanics approach of water molecules dynamics should be taken into account for precise theoretical calculation of differential scattering cross sections of neutrons. Krieger and Nelkin have proposed an approximate method for averaging orientation of molecules regarding directions of incoming and scattered neutron. This paper shows that this approach can be successfully applied for general shape of water molecule vibration anisotropy.
Probabilistic structural damage identification based on vibration data
International Nuclear Information System (INIS)
Hao, H.; Xia, Y.
2001-01-01
Vibration-based methods are being rapidly developed and applied to detect structural damage in civil, mechanical and aerospace engineering communities in the last two decades. But uncertainties existing in the structural model and measured vibration data might lead to unreliable results. This paper will present some recent research results to tackle the above mentioned uncertainty problems. By assuming each of the FE model parameters and measured vibration data as a normally distributed random variable, a probabilistic damage detection procedure is developed based on perturbation method and validated by Monte Carlo simulation technique. With this technique, the damage probability of each structural element can be determined. The method developed has been verified by applying it to identify the damages of laboratory tested structures. It was proven that, as compared to the deterministic damage identification method, the present method can not only reduce the possibility of false identification, but also give the identification results in terms of probability. which is deemed more realistic and practical in detecting possible damages in a structure. It has also been found that the modal data included in damage identification analysis have a great influence on the identification results. With a sensitivity study, an optimal measurement set for damage detection is determined. This set includes the optimal measurement locations and the most appropriate modes that should be used in the damage identification analysis. Numerical results indicated that if the optimal set determined in a pre-analysis is used in the damage detection better results will be achieved. (author)
14th International Conference on Acoustics and Vibration of Mechanical Structures
Marinca, Vasile
2018-01-01
This book is a collection of papers presented at Acoustics and Vibration of Mechanical Structures 2017 – AVMS 2017 – highlighting the current trends and state-of-the-art developments in the field. It covers a broad range of topics, such as noise and vibration control, noise and vibration generation and propagation, the effects of noise and vibration, condition monitoring and vibration testing, modeling, prediction and simulation of noise and vibration, environmental and occupational noise and vibration, noise and vibration attenuators, as well as biomechanics and bioacoustics. The book also presents analytical, numerical and experimental techniques for evaluating linear and non-linear noise and vibration problems (including strong nonlinearity). It is primarily intended for academics, researchers and professionals, as well as PhD students in various fields of the acoustics and vibration of mechanical structures.
Decentralized stabilization of semi-active vibrating structures
Pisarski, Dominik
2018-02-01
A novel method of decentralized structural vibration control is presented. The control is assumed to be realized by a semi-active device. The objective is to stabilize a vibrating system with the optimal rates of decrease of the energy. The controller relies on an easily implemented decentralized switched state-feedback control law. It uses a set of communication channels to exchange the state information between the neighboring subcontrollers. The performance of the designed method is validated by means of numerical experiments performed for a double cantilever system equipped with a set of elastomers with controlled viscoelastic properties. In terms of the assumed objectives, the proposed control strategy significantly outperforms the passive damping cases and is competitive with a standard centralized control. The presented methodology can be applied to a class of bilinear control systems concerned with smart structural elements.
Flow induced vibrational excitation of nuclear reactor structures
International Nuclear Information System (INIS)
Gibert, R.J.
1979-01-01
The pressure fluctuations generated by disturbed flows, encountered in nuclear reactors induce vibrations in the structures. In order to make forecastings for these vibrational levels, it is necessary to know the characteristics of the random pressure fluctuations induced in the walls by the main flow peculiarities of the circuits. This knowledge is essentially provided by experimentation which shows that most of the energy from these fluctuations is in the low frequency area. It is also necessary to determine the transfer functions of the fluid-structure coupled system. Given the frequency range of the excitations, a calculation of the characteristics of the first eigenmodes is generally sufficient. This calculation is carried out by finite element codes, the modal dampings being assessed separately. In this paper, emphasis is placed mainly on the analysis of the sources of excitation due to flow peculiarities. Some examples will also be given of assessments of vibrations in real structures (pipes, reactor internals, etc.) and of comparisons with the experimental results obtained on models or on a site [fr
Vibrating wire apparatus for periodic magnetic structure measurement
International Nuclear Information System (INIS)
Temnykh, A.B.
2003-01-01
Devices with periodic magnetic structures such as wigglers and undulators are often key elements in synchrotron radiation sources. In applications where the coherence of the emitted radiation is important, magnetic field errors distorting the periodicity of the field can significantly reduce the performance of the devices. Thus, the measurement, localization, and correction of the field errors can be a critical issue. This article presents a new method for magnetic field measurements in periodic magnetic structures. The method uses a vibrating taut wire passing through the magnetic structure, and it involves measurements of the amplitudes and phases of the standing waves excited on the wire by the Lorentz force between an AC current in the wire and the surrounding magnetic field. For certain arrangements of the wire, vibrations in the wire will be excited by only non-periodic magnetic field component, i.e., by the error field. By measuring the phase and amplitude of these waves, one can reconstruct the error field distribution and then correct it. The method was tested on a permanent magnet wiggler with 19.8 cm period and a peak field of ∼7000G. It demonstrated ∼0.6G RMS sensitivity, δB rms /B rms ∼1.2x10 -4 and spatial resolution sufficient to identify poles generating the field error. Good agreement was found between field error measurements obtained with the vibrating wire method and with traditional Hall probe field mapping
Structure, vibrational spectrum, and ring puckering barrier of cyclobutane.
Blake, Thomas A; Xantheas, Sotiris S
2006-09-07
We present the results of high level ab initio calculations for the structure, harmonic and anharmonic spectroscopic constants, and ring puckering barrier of cyclobutane (C4H8) in an effort to establish the minimum theoretical requirements needed for their accurate description. We have found that accurate estimates for the barrier between the minimum (D(2d)) and transition state (D(4h)) configurations require both higher levels of electron correlation [MP4, CCSD(T)] and orbital basis sets of quadruple-zeta quality or larger. By performing CCSD(T) calculations with basis sets as large as cc-pV5Z, we were able to obtain, for the first time, a value for the puckering barrier that lies within 10 cm(-1) (or 2%) from experiment, whereas the best previously calculated values were in errors exceeding 40% of experiment. Our best estimate of 498 cm(-1) for the puckering barrier is within 10 cm(-1) of the experimental value proposed originally, but it lies approximately 50 cm(-1) higher than the revisited value, which was obtained more recently using different assumptions regarding the coupling between the various modes. It is therefore suggested that revisiting the analysis of the experimental data might be warranted. Our best computed values (at the CCSD(T)/aug-cc-pVTZ level of theory) for the equilibrium structural parameters of C4H8 are r(C-C) = 1.554 A, r(C-H(alpha)) = 1.093 A, r(C-H(beta)) = 1.091 A, phi(C-C-C) = 88.1 degrees , alpha(H(alpha)-C-H(beta)) = 109.15 degrees , and theta = 29.68 degrees for the puckering angle. We have found that the puckering angle theta is more sensitive to the level of electron correlation than to the size of the basis set for a given method. We furthermore present anharmonic calculations that are based on a second-order perturbative evaluation of rovibrational parameters and their effects on the vibrational spectra and average structure. We have found that the anharmonic calculations predict the experimentally measured fundamental band
Random vibration sensitivity studies of modeling uncertainties in the NIF structures
International Nuclear Information System (INIS)
Swensen, E.A.; Farrar, C.R.; Barron, A.A.; Cornwell, P.
1996-01-01
The National Ignition Facility is a laser fusion project that will provide an above-ground experimental capability for nuclear weapons effects simulation. This facility will achieve fusion ignition utilizing solid-state lasers as the energy driver. The facility will cover an estimated 33,400 m 2 at an average height of 5--6 stories. Within this complex, a number of beam transport structures will be houses that will deliver the laser beams to the target area within a 50 microm ms radius of the target center. The beam transport structures are approximately 23 m long and reach approximately heights of 2--3 stories. Low-level ambient random vibrations are one of the primary concerns currently controlling the design of these structures. Low level ambient vibrations, 10 -10 g 2 /Hz over a frequency range of 1 to 200 Hz, are assumed to be present during all facility operations. Each structure described in this paper will be required to achieve and maintain 0.6 microrad ms laser beam pointing stability for a minimum of 2 hours under these vibration levels. To date, finite element (FE) analysis has been performed on a number of the beam transport structures. Certain assumptions have to be made regarding structural uncertainties in the FE models. These uncertainties consist of damping values for concrete and steel, compliance within bolted and welded joints, and assumptions regarding the phase coherence of ground motion components. In this paper, the influence of these structural uncertainties on the predicted pointing stability of the beam line transport structures as determined by random vibration analysis will be discussed
Full-scale investigation of wind-induced vibrations of mast-arm traffic signal structures.
2014-08-01
Because of their inherent : fl : exibility and low damping ratios, cantilevered mast : - : arm : tra : ffi : c signal structures are suscepti : b : le to : wind : - : induced vibrations. : These vibrations : cause stru : ctural stresses and strains t...
Numerical Analysis of Vibrations of Structures under Moving Inertial Load
Bajer, Czeslaw I
2012-01-01
Moving inertial loads are applied to structures in civil engineering, robotics, and mechanical engineering. Some fundamental books exist, as well as thousands of research papers. Well known is the book by L. Frýba, Vibrations of Solids and Structures Under Moving Loads, which describes almost all problems concerning non-inertial loads. This book presents broad description of numerical tools successfully applied to structural dynamic analysis. Physically we deal with non-conservative systems. The discrete approach formulated with the use of the classical finite element method results in elemental matrices, which can be directly added to global structure matrices. A more general approach is carried out with the space-time finite element method. In such a case, a trajectory of the moving concentrated parameter in space and time can be simply defined. We consider structures described by pure hyperbolic differential equations such as strings and structures described by hyperbolic-parabolic differential equations ...
Vibration tests of a 4-story concrete structure
International Nuclear Information System (INIS)
Chen, C.K.; Czarnecki, R.M.; Scholl, R.E.
1976-01-01
A series of forced vibration tests on a full-scale 4-story reinforced concrete test structure was performed to investigate its dynamic response before, after, and during the time it underwent structural damage. Nondestructive tests were conducted first, exciting four translational modes at force levels within the elastic limit, during which the structure suffered no structural damage. Next, a destructive test excited only the lowest translational mode at high-amplitude destructive levels, during which the structure exhibited inelastic response and suffered major structural damage. Post-destructive tests used force levels similar to the nondestructive tests. The work was in support of the program to develop methods for predicting building response to and damage from underground nuclear explosions
Prediction of Vibration Transmission within Periodic Bar Structures
DEFF Research Database (Denmark)
Domadiya, Parthkumar Gandalal; Andersen, Lars Vabbersgaard; Sorokin, Sergey
2012-01-01
The present analysis focuses on vibration transmission within semi-infinite bar structure. The bar is consisting of two different materials in a periodic manner. A periodic bar model is generated using two various methods: The Finite Element method (FEM) and a Floquet theory approach. A parameter...... study is carried out regarding the influence of the number of periods at various frequencies within a semi-infinite bar, stop bands are illustrated at certain periodic intervals within the structure. The computations are carried out in frequency domain in the range below 500 Hz. Results from both...
Vibrational spectroscopy and structural analysis of complex uranium compounds (review)
International Nuclear Information System (INIS)
Umreiko, D.S.; Nikanovich, M.V.
1985-01-01
The paper reports on the combined application of experimental and theoretical methods of vibrational spectroscopy together with low-temperature luminescence data to determine the characteristic features of the formation and structure of complex systems, not only containing ligands directly coordinated to the CA uranium, but also associated with the extraspherical polyatomic electrically charged particles: organic cations. These include uranyl complexes and heterocyclical amines. Studied here were compounds of tetra-halouranylates with pyridine and its derivates, as well as dipyridyl, quinoline and phenanthroline. Structural schemes are also proposed for other uranyl complexes with protonated heterocyclical amines with a more complicated composition, which correctly reflect their spectroscopic properties
Structure and vibrational properties of oxyhalides of Vanadium
International Nuclear Information System (INIS)
Allaf, A.
2010-01-01
We study the structure and vibrational modes of a wide range of oxyhalides of vanadium (VOX n Y m ; X, Y) = F, Cl, Br, I; n, m = 0-3, n + m≤ 3). The results agree well with experimental results for VOCl 3 and VOF 3 and suggest reassignment of the experimentally observed VOF to VOF 2 . We provide new assignments for various experimental modes, identifying several intermediates (VOBr 2 , VOBr) and mixed structures (e.g., VOCl 2 Br), and discuss formation trends and stabilities.(author)
Vibrations of composite circular shell structures due to transient loads
International Nuclear Information System (INIS)
Schrader, K.-H.; Krutzik, N.; Winkel, G.
1975-01-01
Referring to a container consisting of different shell structures - such as spherical, cylindrical and conical shells - the dynamic behavior of coupled spatial shell structures due to transient loads will be investigated. The spatial structure including the filling of water will be idealized as a three-dimensional model consisting of ring elements. The influence of the water filling on the vibrations will be considered by virtual masses added to the shell structures. In circular direction as well as in meridional direction a consistent mass model has been used. By variation of the virtual masses it will be clarified, how these additional masses influence the vibrational behavior of the composed system. Another aspect which will be investigated is the influence of different stiffnesses of substructures or parts of substructures on the natural frequencies, and on their affiliated eigensystems. Furthermore, the maximum and minimum stresses in the structures caused by transient loads acting on the inner surface of the shells will be explored. Here it seems to be possible to locate an area of maximum strain. Rotational loads as well as nonrotational loads will be considered
A Simple Instrumentation System for Large Structure Vibration Monitoring
Directory of Open Access Journals (Sweden)
Didik R. Santoso
2010-12-01
Full Text Available Traditional instrumentation systems used for monitoring vibration of large-scale infrastructure building such as bridges, railway, and others structural building, generally have a complex design. Makes it simple would be very useful both in terms of low-cost and easy maintenance. This paper describes how to develop the instrumentation system. The system is built based on distributed network, with field bus topology, using single-master multi-slave architecture. Master is a control unit, built based on a PC equipped with RS-485 interface. Slave is a sensing unit; each slave was built by integrating a 3-axis vibration sensor with a microcontroller based data acquisition system. Vibration sensor is designed using the main components of a MEMS accelerometer. While the software is developed for two functions: as a control system hardware and data processing. To verify performance of the developed instrumentation system, several laboratory tests have been performed. The result shows that the system has good performance.
Molecular Origin of the Vibrational Structure of Ice Ih.
Moberg, Daniel R; Straight, Shelby C; Knight, Christopher; Paesani, Francesco
2017-06-15
An unambiguous assignment of the vibrational spectra of ice I h remains a matter of debate. This study demonstrates that an accurate representation of many-body interactions between water molecules, combined with an explicit treatment of nuclear quantum effects through many-body molecular dynamics (MB-MD), leads to a unified interpretation of the vibrational spectra of ice I h in terms of the structure and dynamics of the underlying hydrogen-bond network. All features of the infrared and Raman spectra in the OH stretching region can be unambiguously assigned by taking into account both the symmetry and the delocalized nature of the lattice vibrations as well as the local electrostatic environment experienced by each water molecule within the crystal. The high level of agreement with experiment raises prospects for predictive MB-MD simulations that, complementing analogous measurements, will provide molecular-level insights into fundamental processes taking place in bulk ice and on ice surfaces under different thermodynamic conditions.
Czech Academy of Sciences Publication Activity Database
Paulson, L. O.; Kaminský, Jakub; Anderson, D. T.; Bouř, Petr; Kubelka, J.
2010-01-01
Roč. 6, č. 3 (2010), s. 817-827 ISSN 1549-9618 R&D Projects: GA ČR GA202/07/0732; GA AV ČR IAA400550702 Grant - others:CAREER(US) 0846140; AV ČR(CZ) M200550902 Institutional research plan: CEZ:AV0Z40550506 Keywords : dipole moments * theoretical modelling * vibrational averaging Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.138, year: 2010
Czech Academy of Sciences Publication Activity Database
Dračínský, Martin; Kaminský, Jakub; Bouř, Petr
2009-01-01
Roč. 130, č. 9 (2009), 094106/1-094106/13 ISSN 0021-9606 R&D Projects: GA ČR GA203/06/0420; GA ČR GA202/07/0732; GA AV ČR IAA400550702 Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR * anharmonic forces * vibrational averaging Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.093, year: 2009
Passive Control of Flexible Structures by Confinement of Vibrations
Directory of Open Access Journals (Sweden)
M. Ouled Chtiba
2007-01-01
Full Text Available We propose a two-step strategy for the design of passive controllers for the simultaneous confinement and suppression of vibrations (SCSV in mechanical structures. Once the sensitive and insensitive elements of these structures are identified, the first design step synthesizes an active control law, which is referred to as the reference control law (RCL, for the SCSV. We show that the problem of SCSV can be formulated as an LQR-optimal control problem through which the maximum amplitudes, associated with the control input and the displacements of the sensitive and insensitive parts, can be regulated. In the second design step, a transformation technique that yields an equivalent passive controller is used. Such a technique uses the square root of sum of squares method to approximate an equivalent passive controller while maximizing the effects of springs and dampers characterizing passive elements that are added to the original structure. The viability of the proposed control design is illustrated using a three-DOF mechanical system subject to an excitation. It is assumed that all of the masses are sensitive to the excitation, and thus the vibratory energy must be confined in the added passive elements (insensitive parts. We show that the vibration amplitudes associated with the sensitive masses are attenuated at fast rate at the expense of slowing down the convergence of the passive elements to their steady states. It is also demonstrated that a combination of the RCL and the equivalent passive control strategy leads to similar structural performance.
Harvesting Energy from Vibrations of the Underlying Structure
DEFF Research Database (Denmark)
Han, Bo; Vssilaras, S; Papadias, C.B.
2013-01-01
to the long-term structural health of a building or bridge, but at the same time they can be exploited as a power source to power the wireless sensors that are monitoring this structural health. This paper presents a new energy harvesting method based on a vibration driven electromagnetic harvester. By using......The use of wireless sensors for structural health monitoring offers several advantages such as small size, easy installation and minimal intervention on existing structures. However the most significant concern about such wireless sensors is the lifetime of the system, which depends heavily...... on the type of power supply. No matter how energy efficient the operation of a battery operated sensor is, the energy of the battery will be exhausted at some point. In order to achieve a virtually unlimited lifetime, the sensor node should be able to recharge its battery in an easy way. Energy harvesting...
Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing
Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.
2009-01-01
Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in
Semi-decentralized Strategies in Structural Vibration Control
Directory of Open Access Journals (Sweden)
F. Palacios-Quiñonero
2011-04-01
Full Text Available In this work, the main ideas involved in the design of overlapping and multi-overlapping controllers via the Inclusion Principle are discussed and illustrated in the context of the Structural Vibration Control of tall buildings under seismic excitation. A detailed theoretical background on the Inclusion Principle and the design of overlapping controllers is provided. Overlapping and multi-overlapping LQR controllers are designed for a simplified five-story building model. Numerical simulations are conducted to asses the performance of the proposed semi-decentralized controllers with positive results.
Nonlinear dissipative devices in structural vibration control: A review
Lu, Zheng; Wang, Zixin; Zhou, Ying; Lu, Xilin
2018-06-01
Structural vibration is a common phenomenon existing in various engineering fields such as machinery, aerospace, and civil engineering. It should be noted that the effective suppression of structural vibration is conducive to enhancing machine performance, prolonging the service life of devices, and promoting the safety and comfort of structures. Conventional linear energy dissipative devices (linear dampers) are largely restricted for wider application owing to their low performance under certain conditions, such as the detuning effect of tuned mass dampers subjected to nonstationary excitations and the excessively large forces generated in linear viscous dampers at high velocities. Recently, nonlinear energy dissipative devices (nonlinear dampers) with broadband response and high robustness are being increasingly used in practical engineering. At the present stage, nonlinear dampers can be classified into three groups, namely nonlinear stiffness dampers, nonlinear-stiffness nonlinear-damping dampers, and nonlinear damping dampers. Corresponding to each nonlinear group, three types of nonlinear dampers that are widely utilized in practical engineering are reviewed in this paper: the nonlinear energy sink (NES), particle impact damper (PID), and nonlinear viscous damper (NVD), respectively. The basic concepts, research status, engineering applications, and design approaches of these three types of nonlinear dampers are summarized. A comparison between their advantages and disadvantages in practical engineering applications is also conducted, to provide a reference source for practical applications and new research.
Structural damping results from vibration tests of straight piping sections
International Nuclear Information System (INIS)
Ware, A.G.; Thinnes, G.L.
1984-01-01
EG and G Idaho is assisting the USNRC and the Pressure Vessel Research Committee in supporting a final position on revised damping values for structural analyses of nuclear piping systems. As part of this program, a series of vibrational tests on 76-mm and 203-mm (3-in. amd 8-in.) Schedule 40 carbon steel piping was conducted to determine the changes in structural damping due to various parametric effects. The 10-m (33-ft) straight sections of piping were rigidly supported at the ends. Spring, rod, and constant force hangers, as well as a sway brace and snubbers were included as intermediate supports. Excitation was provided by low-force level hammer inpacts, a hydraulic shaker, and a 445-kN (50-ton) overhead crane. Data was recorded using acceleration, strain, and displacement time histories. This paper presents results from the testing showing the effect of stress level and type of supports on structural damping in piping
Vibration control of a flexible structure with electromagnetic actuators
DEFF Research Database (Denmark)
Gruzman, Maurício; Santos, Ilmar
2016-01-01
This work presents the model of a shear-frame-type structure composed of six flexible beams and three rigid masses. Fixed on the ground, outside the structure, two voltage-controlled electromagnetic actuators are used for vibration control. To model the flexible beams, unidimensional finite...... elements were used. Nonlinear equations for the actuator electromagnetic force, noise in the position sensor, time delays for the control signal update and voltage saturation were also considered in the model. For controlling purposes, a discrete linear quadratic regulator combined with a predictive full......-order discrete linear observer was employed. Results of numerical simulations, where the structure is submitted to an impulsive disturbance force and to a harmonic force, show that the oscillations can be significantly reduced with the use of the electromagnetic actuators....
CSIR Research Space (South Africa)
Heyns, T
2012-10-01
Full Text Available Lw+1 pLw+2 ::: p2Lw ]T . This is repeated until rN=Lw signal segments have been obtained. The signal segments are collected in the matrix Xs, where Xs = [s1 s2 :::srN=Lw ]. Each column in Xs represents a pinion-gear meshing period. 4 A measure... of discrepancy (NLL value) will be computed for each column in Xs. The resulting NLL discrepancy signal will have a much lower sampling rate than the original vibration signal. The lower sampling rate reduces the computational burden of the algorithm, without...
Complete flexural vibration band gaps in membrane-like lattice structures
International Nuclear Information System (INIS)
Yu Dianlong; Liu Yaozong; Qiu Jing; Wang Gang; Zhao Honggang
2006-01-01
The propagation of flexural vibration in the periodical membrane-like lattice structure is studied. The band structure calculated with the plane wave expansion method indicates the existence of complete gaps. The frequency response function of a finite periodic structure is simulated with finite element method. Frequency ranges with vibration attenuation are in good agreement with the gaps found in the band structure. Much larger attenuations are found in the complete gaps comparing to those directional ones. The existence of complete flexural vibration gaps in such a lattice structure provides a new idea for vibration control of thin plates
International Nuclear Information System (INIS)
Uryu, Mitsuru; Shinohara, Takaharu; Terada, Shuji; Yamazaki, Toshihiko; Nakayama, Kazuhiko; Kondo, Toshinari; Hosoya, Hisashi
1997-05-01
When adopting a vibration controlling structure for a nuclear facility building, it is necessary to evaluate a little longer frequency vibration properly. Although various evaluation methods are proposed, there is no finished method. And, to the earthquake itself to investigate, some factors such as effect of surface wave, distant great earthquake, and so on must be considered, and further various evaluations and investigations are required. Here is reported on an evaluation method of the input earthquake vibration for vibration controlling design establishing on adoption of the vibration controlling structure using a vibration control device comprising of laminated rubber and lead damper for the buildings of reprocessing facility in Tokai Works. The input earthquake vibration for vibration controlling design shown in this report is to be adopted for a vibration controlling facility buildings in the Tokai Works. (G.K.)
Control of noise and structural vibration a MATLAB-based approach
Mao, Qibo
2013-01-01
Control of Noise and Structural Vibration presents a MATLAB®-based approach to solving the problems of undesirable noise generation and transmission by structures and of undesirable vibration within structures in response to environmental or operational forces. The fundamentals of acoustics, vibration and coupling between vibrating structures and the sound fields they generate are introduced including a discussion of the finite element method for vibration analysis. Following this, the treatment of sound and vibration control begins, illustrated by example systems such as beams, plates and double plate structures. Sensor and actuator placement is explained as is the idea of modal sensor–actuators. The design of appropriate feedback systems includes consideration of basic stability criteria and robust active structural acoustic control. Single and multi-mode positive position feedback (PPF) control systems are also described in the context of loudspeaker–duct model with non-collocated loudspeaker–microp...
Vibration-based localisation of structural deterioration in frame-like civil engineering structures
DEFF Research Database (Denmark)
Ulriksen, Martin Dalgaard; Damkilde, Lars
2016-01-01
With the existing trend of minimising material use in typical frame-like civil engineering structures, such as buildings, bridges, and offshore platforms, these structures will typically be subjected to substantial wind induced vibrations. Besides being a source of disturbance for the occupants...
[Structure analysis of disease-related proteins using vibrational spectroscopy].
Hiramatsu, Hirotsugu
2014-01-01
Analyses of the structure and properties of identified pathogenic proteins are important for elucidating the molecular basis of diseases and in drug discovery research. Vibrational spectroscopy has advantages over other techniques in terms of sensitivity of detection of structural changes. Spectral analysis, however, is complicated because the spectrum involves a substantial amount of information. This article includes examples of structural analysis of disease-related proteins using vibrational spectroscopy in combination with additional techniques that facilitate data acquisition and analysis. Residue-specific conformation analysis of an amyloid fibril was conducted using IR absorption spectroscopy in combination with (13)C-isotope labeling, linear dichroism measurement, and analysis of amide I band features. We reveal a pH-dependent property of the interacting segment of an amyloidogenic protein, β2-microglobulin, which causes dialysis-related amyloidosis. We also reveal the molecular mechanisms underlying pH-dependent sugar-binding activity of human galectin-1, which is involved in cell adhesion, using spectroscopic techniques including UV resonance Raman spectroscopy. The decreased activity at acidic pH was attributed to a conformational change in the sugar-binding pocket caused by protonation of His52 (pKa 6.3) and the cation-π interaction between Trp68 and the protonated His44 (pKa 5.7). In addition, we show that the peak positions of the Raman bands of the C4=C5 stretching mode at approximately 1600 cm(-1) and the Nπ-C2-Nτ bending mode at approximately 1405 cm(-1) serve as markers of the His side-chain structure. The Raman signal was enhanced 12 fold using a vertical flow apparatus.
Mitigating ground vibration by periodic inclusions and surface structures
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard; Bucinskas, Paulius; Persson, Peter
2016-01-01
Ground vibration from traffic is a source of nuisance in urbanized areas. Trenches and wave barriers can provide mitigation of vibrations, but single barriers need to have a large depth to be effective-especially in the low-frequency range relevant to traffic-induced vibration. Alternatively...
2018-01-01
The structural heterogeneity of water at various interfaces can be revealed by time-resolved sum-frequency generation spectroscopy. The vibrational dynamics of the O–H stretch vibration of interfacial water can reflect structural variations. Specifically, the vibrational lifetime is typically found to increase with increasing frequency of the O–H stretch vibration, which can report on the hydrogen-bonding heterogeneity of water. We compare and contrast vibrational dynamics of water in contact with various surfaces, including vapor, biomolecules, and solid interfaces. The results reveal that variations in the vibrational lifetime with vibrational frequency are very typical, and can frequently be accounted for by the bulk-like heterogeneous response of interfacial water. Specific interfaces exist, however, for which the behavior is less straightforward. These insights into the heterogeneity of interfacial water thus obtained contribute to a better understanding of complex phenomena taking place at aqueous interfaces, such as photocatalytic reactions and protein folding. PMID:29490138
Directory of Open Access Journals (Sweden)
Myung-Hyun Kim
2002-01-01
Full Text Available The integration of actuators and sensors using smart materials enabled various applications including health monitoring and structural vibration control. In this study, a robust control technique is designed and implemented in order to reduce vibration of an active structure. Special attention is given to eliminating the possibility of interaction between the health monitoring system and the control system. Exploiting the disturbance decoupling characteristic of the sliding mode observer, it is demonstrated that the proposed observer can eliminate the possible high frequency excitation from the health monitoring system. At the same time, a damage identification scheme, which tracks the changes of mechanical impedance due to the presence of damage, has been applied to assess the health condition of structures. The main objective of this paper is to examine the potential of combining the two emerging techniques together. Using the collocated piezoelectric sensors/actuators for vibration suppression as well as for health monitoring, this technique enabled to reduce the number of system components, while enhancing the performance of structures. As an initial study, both simulation and experimental investigations were performed for an active beam structure. The results show that this integrated technique can provide substantial vibration reductions, while detecting damage on the structure at the same time.
Nonlinear vibrations analysis of rotating drum-disk coupling structure
Chaofeng, Li; Boqing, Miao; Qiansheng, Tang; Chenyang, Xi; Bangchun, Wen
2018-04-01
A dynamic model of a coupled rotating drum-disk system with elastic support is developed in this paper. By considering the effects of centrifugal and Coriolis forces as well as rotation-induced hoop stress, the governing differential equation of the drum-disk is derived by Donnell's shell theory. The nonlinear amplitude-frequency characteristics of coupled structure are studied. The results indicate that the natural characteristics of the coupling structure are sensitive to the supporting stiffness of the disk, and the sensitive range is affected by rotating speeds. The circumferential wave numbers can affect the characteristics of the drum-disk structure. If the circumferential wave number n = 1 , the vibration response of the drum keeps a stable value under an unbalanced load of the disk, there is no coupling effect if n ≠ 1 . Under the excitation, the nonlinear hardening characteristics of the forward traveling wave are more evident than that of the backward traveling wave. Moreover, because of the coupling effect of the drum and the disk, the supporting stiffness of the disk has certain effect on the nonlinear characteristics of the forward and backward traveling waves. In addition, small length-radius and thickness-radius ratios have a significant effect on the nonlinear characteristics of the coupled structure, which means nonlinear shell theory should be adopted to design rotating drum's parameter for its specific structural parameters.
Structure and vibrational frequencies of gaseous europium dibromide
International Nuclear Information System (INIS)
Giricheva, N.I.; Girichev, S.A.; Shlykov, S.A.; Pelipets, O.V.
2000-01-01
Structure of EuBr 2 molecule is studied in the framework of synchronous electron diffraction and mass-spectrometric experiment at the temperature of 1373(20) K. It is found that the molecule has a nonlinear equilibrium configuration, being characterized by the following effective parameters: r g (Eu - Br) = 2.767 A, r g (Br - Br) = 5.11(5) A, l g (Eu - Br) = 0.109(2) A, l g (Br - Br) = 0.388(5) A, valence angle (Br - Eu - Br) = 135.0(3.5) deg. The electron diffraction data permit ascertaining vibration frequencies ν 1 225(10) cm -1 and ν 2 = 40(4) cm -1 [ru
Variational structure of inverse problems in wave propagation and vibration
Energy Technology Data Exchange (ETDEWEB)
Berryman, J.G.
1995-03-01
Practical algorithms for solving realistic inverse problems may often be viewed as problems in nonlinear programming with the data serving as constraints. Such problems are most easily analyzed when it is possible to segment the solution space into regions that are feasible (satisfying all the known constraints) and infeasible (violating some of the constraints). Then, if the feasible set is convex or at least compact, the solution to the problem will normally lie on the boundary of the feasible set. A nonlinear program may seek the solution by systematically exploring the boundary while satisfying progressively more constraints. Examples of inverse problems in wave propagation (traveltime tomography) and vibration (modal analysis) will be presented to illustrate how the variational structure of these problems may be used to create nonlinear programs using implicit variational constraints.
Epistemic uncertainty propagation in energy flows between structural vibrating systems
Xu, Menghui; Du, Xiaoping; Qiu, Zhiping; Wang, Chong
2016-03-01
A dimension-wise method for predicting fuzzy energy flows between structural vibrating systems coupled by joints with epistemic uncertainties is established. Based on its Legendre polynomial approximation at α=0, both the minimum and maximum point vectors of the energy flow of interest are calculated dimension by dimension within the space spanned by the interval parameters determined by fuzzy those at α=0 and the resulted interval bounds are used to assemble the concerned fuzzy energy flows. Besides the proposed method, vertex method as well as two current methods is also applied. Comparisons among results by different methods are accomplished by two numerical examples and the accuracy of all methods is simultaneously verified by Monte Carlo simulation.
Intelligent failure-proof control system for structural vibration
Energy Technology Data Exchange (ETDEWEB)
Yoshida, Kazuo [Keio Univ., Yokohama (Japan). Faculty of Science and Technology; Oba, Takahiro [Keio Univ., Tokyo (Japan)
2000-11-01
With progress of technology in recent years, gigantism and complication such as high-rise buildings, nuclear reactors and so on have brought about new problems. Particularly, the safety and the reliability for damages in abnormal situations have become more important. Intelligent control systems which can judge whether the situation is normal or abnormal at real time and cope with these situations suitably are demanded. In this study, Cubic Neural Network (CNN) is adopted, which consists of the controllers possessing cubically some levels of information abstracting. In addition to the usual quantitative control, the qualitative control is used for the abnormal situations. And, by selecting a suitable controller, CNN can cope with the abnormal situation. In order to confirm the effectiveness of this system, the structural vibration control problems with sensory failure and elasto-plastic response are dealt with. As a result of simulations, it was demonstrated that CNN can cope with unexpected abnormal situations which are not considered in learning. (author)
Negative derivative feedback for vibration control of flexible structures
International Nuclear Information System (INIS)
Cazzulani, G; Resta, F; Ripamonti, F; Zanzi, R
2012-01-01
In this paper a resonant control technique, called negative derivative feedback (NDF), for structural vibration control is presented. Resonant control is a class of control logics, based on the modal approach, which calculates the control action through a dynamic compensator in order to achieve a damping increase on a certain number of system modes. The NDF compensator is designed to work as a band-pass filter, cutting off the control action far from the natural frequencies associated with the controlled modes and reducing the so-called spillover effect. In the paper the proposed control logic is compared both theoretically and experimentally with the most common state-of-the-art resonant control techniques. (paper)
Intelligent failure-proof control system for structural vibration
International Nuclear Information System (INIS)
Yoshida, Kazuo
2000-01-01
With progress of technology in recent years, gigantism and complication such as high-rise buildings, nuclear reactors and so on have brought about new problems. Particularly, the safety and the reliability for damages in abnormal situations have become more important. Intelligent control systems which can judge whether the situation is normal or abnormal at real time and cope with these situations suitably are demanded. In this study, Cubic Neural Network (CNN) is adopted, which consists of the controllers possessing cubically some levels of information abstracting. In addition to the usual quantitative control, the qualitative control is used for the abnormal situations. And, by selecting a suitable controller, CNN can cope with the abnormal situation. In order to confirm the effectiveness of this system, the structural vibration control problems with sensory failure and elasto-plastic response are dealt with. As a result of simulations, it was demonstrated that CNN can cope with unexpected abnormal situations which are not considered in learning. (author)
Parametric and Non-Parametric Vibration-Based Structural Identification Under Earthquake Excitation
Pentaris, Fragkiskos P.; Fouskitakis, George N.
2014-05-01
The problem of modal identification in civil structures is of crucial importance, and thus has been receiving increasing attention in recent years. Vibration-based methods are quite promising as they are capable of identifying the structure's global characteristics, they are relatively easy to implement and they tend to be time effective and less expensive than most alternatives [1]. This paper focuses on the off-line structural/modal identification of civil (concrete) structures subjected to low-level earthquake excitations, under which, they remain within their linear operating regime. Earthquakes and their details are recorded and provided by the seismological network of Crete [2], which 'monitors' the broad region of south Hellenic arc, an active seismic region which functions as a natural laboratory for earthquake engineering of this kind. A sufficient number of seismic events are analyzed in order to reveal the modal characteristics of the structures under study, that consist of the two concrete buildings of the School of Applied Sciences, Technological Education Institute of Crete, located in Chania, Crete, Hellas. Both buildings are equipped with high-sensitivity and accuracy seismographs - providing acceleration measurements - established at the basement (structure's foundation) presently considered as the ground's acceleration (excitation) and at all levels (ground floor, 1st floor, 2nd floor and terrace). Further details regarding the instrumentation setup and data acquisition may be found in [3]. The present study invokes stochastic, both non-parametric (frequency-based) and parametric methods for structural/modal identification (natural frequencies and/or damping ratios). Non-parametric methods include Welch-based spectrum and Frequency response Function (FrF) estimation, while parametric methods, include AutoRegressive (AR), AutoRegressive with eXogeneous input (ARX) and Autoregressive Moving-Average with eXogeneous input (ARMAX) models[4, 5
The Structural Heat Intercept-Insulation-Vibration Evaluation Rig (SHIVER)
Johnson, W. L.; Zoeckler, J. G.; Best-Ameen, L. M.
2015-01-01
NASA is currently investigating methods to reduce the boil-off rate on large cryogenic upper stages. Two such methods to reduce the total heat load on existing upper stages are vapor cooling of the cryogenic tank support structure and integration of thick multilayer insulation systems to the upper stage of a launch vehicle. Previous efforts have flown a 2-layer MLI blanket and shown an improved thermal performance, and other efforts have ground-tested blankets up to 70 layers thick on tanks with diameters between 2 3 meters. However, thick multilayer insulation installation and testing in both thermal and structural modes has not been completed on a large scale tank. Similarly, multiple vapor cooled shields are common place on science payload helium dewars; however, minimal effort has gone into intercepting heat on large structural surfaces associated with rocket stages. A majority of the vapor cooling effort focuses on metallic cylinders called skirts, which are the most common structural components for launch vehicles. In order to provide test data for comparison with analytical models, a representative test tank is currently being designed to include skirt structural systems with integral vapor cooling. The tank is 4 m in diameter and 6.8 m tall to contain 5000 kg of liquid hydrogen. A multilayer insulation system will be designed to insulate the tank and structure while being installed in a representative manner that can be extended to tanks up to 10 meters in diameter. In order to prove that the insulation system and vapor cooling attachment methods are structurally sound, acoustic testing will also be performed on the system. The test tank with insulation and vapor cooled shield installed will be tested thermally in the B2 test facility at NASAs Plumbrook Station both before and after being vibration tested at Plumbrooks Space Power Facility.
Kim, Heung Soo; Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok
2013-02-06
In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
Directory of Open Access Journals (Sweden)
Seung-Bok Choi
2013-02-01
Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
Vibrational spectroscopy and structural analysis of uranium complexes
Energy Technology Data Exchange (ETDEWEB)
Umrejko, D.S.; Nikanovich, M.V.
1984-12-01
On the basis of experimental and theoretical studies of vibbrational spectra for halides, sulfates, phosphates, uranyl oxalates (and uranium) as well as for more complicated complex systems, reliable spectroscopic criteria have been established for estimation of their structural features by more simple and accessible (than direct) methods. Due to coordination to a central ion of U/sup 6/(U/sup 4/) ligands a geometry variation specific for each method of addition occurs and concomitant redistribution of the force interaction in the mentioned system as well, which directly affects the variation of their frequency characteristics and vibration modes. On this ground stable indications of particular types of coordination for mono- and polyatomic groups (including bridge-type, characteristic of polymetric structures) are pointed out in the IR absorption and Raman spectra. In the investigated structures the predominant effect of coordination on the spectral properties of complexes, as compared with other factors (for example, outer-sphere binding) is established. The presence of water molecules in an interlayer space does not tell essentially on the state of polyatomic ligands with all donor atoms bound with the uranium central atom (particularly, in binary uranyl phosphates). In the presence of free oxygen atoms the H/sub 2/O effect can lead only to some shift of the maxima of separate bands and their additional weak splitting (in uranyl sulfates).
Yang, Yang; Pan, Yayue; Guo, Ping
2017-04-01
Creating orderly periodic micro/nano-structures on metallic surfaces, or structural coloration, for control of surface apparent color and optical reflectivity has been an exciting research topic over the years. The direct applications of structural coloration include color marking, display devices, and invisibility cloak. This paper presents an efficient method to colorize metallic surfaces with periodic micro/nano-gratings using elliptical vibration texturing. When the tool vibration is coupled with a constant cutting velocity, controlled periodic ripples can be generated due to the overlapping tool trajectory. These periodic ripples with a wavelength near visible spectrum can act as micro-gratings to introduce iridescent colors. The proposed technique also provides a flexible method for color marking of metallic surfaces with arbitrary patterns and images by precise control of the spacing distance and orientation of induced micro/nano-ripples. Theoretical analysis and experimental results are given to demonstrate structural coloration of metals by a direct mechanical machining technique.
Harvesting traffic-induced vibrations for structural health monitoring of bridges
International Nuclear Information System (INIS)
Galchev, T V; McCullagh, J; Peterson, R L; Najafi, K
2011-01-01
This paper discusses the development and testing of a renewable energy source for powering wireless sensors used to monitor the structural health of bridges. Traditional power cables or battery replacement are excessively expensive or infeasible in this type of application. An inertial power generator has been developed that can harvest traffic-induced bridge vibrations. Vibrations on bridges have very low acceleration (0.1–0.5 m s −2 ), low frequency (2–30 Hz), and they are non-periodic. A novel parametric frequency-increased generator (PFIG) is developed to address these challenges. The fabricated device can generate a peak power of 57 µW and an average power of 2.3 µW from an input acceleration of 0.54 m s −2 at only 2 Hz. The generator is capable of operating over an unprecedentedly large acceleration (0.54–9.8 m s −2 ) and frequency range (up to 30 Hz) without any modifications or tuning. Its performance was tested along the length of a suspension bridge and it generated 0.5–0.75 µW of average power without manipulation during installation or tuning at each bridge location. A preliminary power conversion system has also been developed
Local and average structure of Mn- and La-substituted BiFeO3
Jiang, Bo; Selbach, Sverre M.
2017-06-01
The local and average structure of solid solutions of the multiferroic perovskite BiFeO3 is investigated by synchrotron X-ray diffraction (XRD) and electron density functional theory (DFT) calculations. The average experimental structure is determined by Rietveld refinement and the local structure by total scattering data analyzed in real space with the pair distribution function (PDF) method. With equal concentrations of La on the Bi site or Mn on the Fe site, La causes larger structural distortions than Mn. Structural models based on DFT relaxed geometry give an improved fit to experimental PDFs compared to models constrained by the space group symmetry. Berry phase calculations predict a higher ferroelectric polarization than the experimental literature values, reflecting that structural disorder is not captured in either average structure space group models or DFT calculations with artificial long range order imposed by periodic boundary conditions. Only by including point defects in a supercell, here Bi vacancies, can DFT calculations reproduce the literature results on the structure and ferroelectric polarization of Mn-substituted BiFeO3. The combination of local and average structure sensitive experimental methods with DFT calculations is useful for illuminating the structure-property-composition relationships in complex functional oxides with local structural distortions.
Tao, Yunwen; Zou, Wenli; Cremer, Dieter; Kraka, Elfi
2018-03-05
Using catastrophe theory and the concept of a mutation path, an algorithm is developed that leads to the direct correlation of the normal vibrational modes of two structurally related molecules. The mutation path is defined by weighted incremental changes in mass and geometry of the molecules in question, which are successively applied to mutate a molecule into a structurally related molecule and thus continuously converting their normal vibrational spectra from one into the other. Correlation diagrams are generated that accurately relate the normal vibrational modes to each other by utilizing mode-mode overlap criteria and resolving allowed and avoided crossings of vibrational eigenstates. The limitations of normal mode correlation, however, foster the correlation of local vibrational modes, which offer a novel vibrational measure of similarity. It will be shown how this will open new avenues for chemical studies. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Flow induced vibrations of the CLIC X-Band accelerating structures
Charles, Tessa; Boland, Mark; Riddone, Germana; Samoshkin, Alexandre
2011-01-01
Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure’s motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualization and wavelet ana...
Wang, Yuxi; Niu, Shengkai; Hu, Yuantai
2017-06-01
The paper proposes a new piezoelectric smart structure with the integrated passive/active vibration-reduction performances, which is made of a series of periodic structural units. Every structural unit is made of two layers, one is an array of piezoelectric bimorphs (PBs) and one is an array of metal beams (MBs), both are connected as a whole by a metal plate. Analyses show that such a periodic smart structure possesses two aspects of vibration-reduction performance: one comes from its phonon crystal characteristics which can isolate those vibrations with the driving frequency inside the band gap(s). The other one comes from the electromechanical conversion of bent PBs, which is actively aimed at those vibrations with the driving frequency outside the band gap(s). By adjusting external inductance, the equivalent circuit of the proposed structure can be forced into parallel resonance such that most of the vibration energy is converted into electrical energy for dissipation by a resistance. Thus, an external circuit under the parallel resonance state is equivalent to a strong damping to the interrelated vibrating structure, which is just the action mechanism of the active vibration reduction performance of the proposed smart structure.
Influence of Structural Periodicity on Vibration Transmission in a Multi-Storey Wooden Building
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard
2013-01-01
Noise is a nuisance to people, and buildings should therefore be designed to prevent propagation of sound and vibration in the audible frequency range as well as the range of frequencies relevant to whole-body vibrations of humans. In heavy structures made of concrete and masonry, a source...
Nondestructive structural evaluation of wood floor systems with a vibration technique.
Xiping Wang; Robert J. Ross; Lawrence Andrew Soltis
2002-01-01
The objective of this study was to determine if transverse vibration methods could be used to effectively assess the structural integrity of wood floors as component systems. A total of 10 wood floor systems, including 3 laboratory-built floor sections and 7 in-place floors in historic buildings, were tested. A forced vibration method was applied to the floor systems...
Structural determination of some uranyl compounds by vibrational spectroscopy
International Nuclear Information System (INIS)
Rodriguez S, A.; Martinez Q, E.
1990-07-01
The vibrational spectra of different uranyl compounds has been studied and of it spectral information has been used the fundamental asymmetric vibrational frequency, to determine the length and constant bond force U=O by means of the combination of the concept of absorbed energy and the mathematical expression of Badger modified by Jones. It is intended a factor that simplifies the mathematical treatment and the results are compared with the values obtained for other methods. (Author)
An adjoint method of sensitivity analysis for residual vibrations of structures subject to impacts
Yan, Kun; Cheng, Gengdong
2018-03-01
For structures subject to impact loads, the residual vibration reduction is more and more important as the machines become faster and lighter. An efficient sensitivity analysis of residual vibration with respect to structural or operational parameters is indispensable for using a gradient based optimization algorithm, which reduces the residual vibration in either active or passive way. In this paper, an integrated quadratic performance index is used as the measure of the residual vibration, since it globally measures the residual vibration response and its calculation can be simplified greatly with Lyapunov equation. Several sensitivity analysis approaches for performance index were developed based on the assumption that the initial excitations of residual vibration were given and independent of structural design. Since the resulting excitations by the impact load often depend on structural design, this paper aims to propose a new efficient sensitivity analysis method for residual vibration of structures subject to impacts to consider the dependence. The new method is developed by combining two existing methods and using adjoint variable approach. Three numerical examples are carried out and demonstrate the accuracy of the proposed method. The numerical results show that the dependence of initial excitations on structural design variables may strongly affects the accuracy of sensitivities.
Chen, Wenyuan
2018-03-01
The modal parameters such as natural frequency and vibration mode of the frame structure of the layer stiffness sensitivity is inconsistent. This article focuses on the theoretical derivation of the frequency and mode of the frame structure layer stiffness of the first-order sensitivity. The numerical examples show that the frame structure of layer stiffness higher than with the first order sensitivity vibration frequency.
Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation
Directory of Open Access Journals (Sweden)
Shi-Jian Zhu
2014-01-01
Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.
Local and average structure of Mn- and La-substituted BiFeO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Jiang, Bo; Selbach, Sverre M., E-mail: selbach@ntnu.no
2017-06-15
The local and average structure of solid solutions of the multiferroic perovskite BiFeO{sub 3} is investigated by synchrotron X-ray diffraction (XRD) and electron density functional theory (DFT) calculations. The average experimental structure is determined by Rietveld refinement and the local structure by total scattering data analyzed in real space with the pair distribution function (PDF) method. With equal concentrations of La on the Bi site or Mn on the Fe site, La causes larger structural distortions than Mn. Structural models based on DFT relaxed geometry give an improved fit to experimental PDFs compared to models constrained by the space group symmetry. Berry phase calculations predict a higher ferroelectric polarization than the experimental literature values, reflecting that structural disorder is not captured in either average structure space group models or DFT calculations with artificial long range order imposed by periodic boundary conditions. Only by including point defects in a supercell, here Bi vacancies, can DFT calculations reproduce the literature results on the structure and ferroelectric polarization of Mn-substituted BiFeO{sub 3}. The combination of local and average structure sensitive experimental methods with DFT calculations is useful for illuminating the structure-property-composition relationships in complex functional oxides with local structural distortions. - Graphical abstract: The experimental and simulated partial pair distribution functions (PDF) for BiFeO{sub 3}, BiFe{sub 0.875}Mn{sub 0.125}O{sub 3}, BiFe{sub 0.75}Mn{sub 0.25}O{sub 3} and Bi{sub 0.9}La{sub 0.1}FeO{sub 3}.
A primal sub-gradient method for structured classification with the averaged sum loss
Directory of Open Access Journals (Sweden)
Mančev Dejan
2014-12-01
Full Text Available We present a primal sub-gradient method for structured SVM optimization defined with the averaged sum of hinge losses inside each example. Compared with the mini-batch version of the Pegasos algorithm for the structured case, which deals with a single structure from each of multiple examples, our algorithm considers multiple structures from a single example in one update. This approach should increase the amount of information learned from the example. We show that the proposed version with the averaged sum loss has at least the same guarantees in terms of the prediction loss as the stochastic version. Experiments are conducted on two sequence labeling problems, shallow parsing and part-of-speech tagging, and also include a comparison with other popular sequential structured learning algorithms.
Control of 2D Flexible Structures by Confinement of Vibrations and Regulation of Their Energy Flow
Directory of Open Access Journals (Sweden)
Fakhreddine Landolsi
2009-01-01
Full Text Available In this paper, we investigate the control of 2D flexible structures by vibration confinement and the regulation of their energy flow along prespecified spatial paths. A discretized-model-based feedback strategy, aiming at confining and suppressing simultaneously the vibration, is proposed. It is assumed that the structure consists of parts that are sensitive to vibrations. The control design introduces a new pseudo-modal matrix derived from the computed eigenvectors of the discretized model. Simulations are presented to show the efficacy of the proposed control law. A parametric study is carried out to examine the effects of the different control parameters on the simultaneous confinement and suppression of vibrations. In addition, we conducted a set of simulations to investigate the flow control of vibrational energy during the confinement-suppression process. We found that the energy flow can be regulated via a set of control parameters for different confinement configurations.
Identification, detection, and validation of vibrating structures: a signal processing approach
International Nuclear Information System (INIS)
Candy, J.V.; Lager, D.L.
1979-01-01
This report discusses the application of modern signal processing techniques to characterize parameters governing the vibrational response of a structure. Simulated response data is used to explore the feasibility of applying these techniques to various structural problems. On-line estimator/indentifiers are used to estimate structural parameters, validate designed structures, and detect structural failure when used with a detector
Directory of Open Access Journals (Sweden)
Buhl Stefan
2016-01-01
Full Text Available Cycle-to-Cycle Variations (CCV in IC engines is a well-known phenomenon and the definition and quantification is well-established for global quantities such as the mean pressure. On the other hand, the definition of CCV for local quantities, e.g. the velocity or the mixture distribution, is less straightforward. This paper proposes a new method to identify and calculate cyclic variations of the flow field in IC engines emphasizing the different contributions from large-scale energetic (coherent structures, identified by a combination of Proper Orthogonal Decomposition (POD and conditional averaging, and small-scale fluctuations. Suitable subsets required for the conditional averaging are derived from combinations of the the POD coefficients of the second and third mode. Within each subset, the velocity is averaged and these averages are compared to the ensemble-averaged velocity field, which is based on all cycles. The resulting difference of the subset-average and the global-average is identified as a cyclic fluctuation of the coherent structures. Then, within each subset, remaining fluctuations are obtained from the difference between the instantaneous fields and the corresponding subset average. The proposed methodology is tested for two data sets obtained from scale resolving engine simulations. For the first test case, the numerical database consists of 208 independent samples of a simplified engine geometry. For the second case, 120 cycles for the well-established Transparent Combustion Chamber (TCC benchmark engine are considered. For both applications, the suitability of the method to identify the two contributions to CCV is discussed and the results are directly linked to the observed flow field structures.
Influence of vibration on structure rheological properties of a highly concentrated suspension
Ouriev Uriev, Boris N.; Uriev, Naum B.
2005-08-01
The influence of mechanical vibration on the flow properties of a highly concentrated multiphase food system is explored in this work. An experimental set-up was designed and adapted to a conventional rotational rheometer with precise rheological characterization capability. A number of calibration tests were performed prior to fundamental experiments with a highly concentrated chocolate suspension. Also, the prediction of wall slippage in shear flow under vibration was evaluated. Analysis of the boundary conditions shows that no side effects such as wall slippage or the Taylor effect were present during the shear experiment under vibration. It was found that superposition of mechanical vibration and shear flow radically decreases the shear viscosity. Comparison between reference shear viscosities at specified shear rates and those measured under vibration shows considerable differences in flow properties. Conversion of the behaviour of the concentrated suspension from strongly shear-thinning to Newtonian flow is reported. Also, the appearance of vibration-induced dilatancy as a new phenomenon is described. It is suggested to relate such phenomena to the non-equilibrium between structure formation and disintegration under vibration and hydrodynamic forces of shear flow. The influence of vibration on structure formation can be well observed during measurement of the yield value of the chocolate suspension under vibration. Comparison with reference data shows how sensitive the structure of the concentrated suspension is to vibration in general. The effects and observations revealed provide a solid basis for further fundamental investigations of structure formation regularities in the flow of any highly concentrated system. The results also show the technological potential for non-conventional treatment of concentrated, multiphase systems.
Directory of Open Access Journals (Sweden)
Dmitrii A. Oshmarin
2016-09-01
Full Text Available In technical applications it takes place the problem of vibration damping in certain regions of the structure, at the location of optical sensors for instance, at any external dynamic excitations with no mass increase and no changes in spectral portrait. In order to solve these problems it is widespread the use of special damping devices: piezoelectric elements connected to external electric circuits and attached to the structure. It became possible due to piezoelectric effect, which provides transformation of part of energy of vibrations into electric one, which is dissipated in external electric circuit. So that by using appropriate electric circuits one may dissipate internal energy and therefore reduce structural vibrations in definite frequency range. As a rule, external circuit of single branch, which shunts single piezoelectric element, allows vibration damping on one certain frequency. Due to the fact, that practical applications usually include requirements of damping of several modes by one and the same technical devices, the problem of multimodal vibration damping in smart-structures is rather acute. The objective of this paper is the study of possibility of vibration damping on several modes by using single external series RL-circuit, connected to electrodes of single piezoelectric element on the basis of solution of problems on natural and forced steady-state vibrations of electroelastic systems with external electric circuits.
Directory of Open Access Journals (Sweden)
Mohammad Rastgaar
2009-01-01
Full Text Available This paper provides a state-of-the-art review of eigenstructure assignment methods for vibration cancellation. Eigenstructure assignment techniques have been widely used during the past three decades for vibration suppression in structures, especially in large space structures. These methods work similar to mode localization in which global vibrations are managed such that they remain localized within the structure. Such localization would help reducing vibrations more effectively than other methods of vibration cancellation, by virtue of confining the vibrations close to the source of disturbance. The common objective of different methods of eigenstructure assignment is to provide controller design freedom beyond pole placement, and define appropriate shapes for the eigenvectors of the systems. These methods; however, offer a large and complex design space of options that can often overwhelm the control designer. Recent developments in orthogonal eigenstructure control offers a significant simplification of the design task while allowing some experience-based design freedom. The majority of the papers from the past three decades in structural vibration cancellation using eigenstructure assignment methods are reviewed, along with recent studies that introduce new developments in eigenstructure assignment techniques.
Kaloni, Thaneshwor P.
2013-01-01
This thesis covers the structural, electronic, magnetic, and vibrational properties of graphene and silicene. In Chapter I, we will start with an introduction to graphene and silicene. In Chapter II, we will briefly discuss about the methodology (i
National Research Council Canada - National Science Library
Wang, Kon-Well
2006-01-01
The objective of this research is to advance the state of the art of vibration control of mistuned periodic structures utilizing the electromechanical coupling and damping characteristics of piezoelectric networking...
National Research Council Canada - National Science Library
Wang, Kon-Well
2002-01-01
The overall goal of this DURIP project is to acquire major facilities that are critical in the development of a comprehensive experimental testbed for advancing the technology of low vibration periodic structures (e.g...
Low frequency torsional vibration gaps in the shaft with locally resonant structures
International Nuclear Information System (INIS)
Yu Dianlong; Liu Yaozong; Wang Gang; Cai Li; Qiu Jing
2006-01-01
The propagation of torsional wave in the shaft with periodically attached local resonators is studied with the transfer matrix theory and the finite element method. The analytical dispersion relation and the complex band structure of such a structure is presented for the first time, which indicates the existence of low frequency gaps. The effect of shaft material on the vibration attenuation in band gap is investigated. The frequency response function of the shaft with finite periodic locally resonant oscillators is simulated with finite element method, which shows large vibration attenuation in the frequency range of the gap as expected. The low frequency torsional gap in shafts provides a new idea for vibration control
Modal Vibration Control in Periodic Time-Varying Structures with Focus on Rotor Blade Systems
DEFF Research Database (Denmark)
Christensen, Rene Hardam; Santos, Ilmar
2004-01-01
of active modal controllers. The main aim is to reduce vibrations in periodic time-varying structures. Special emphasis is given to vibration control of coupled bladed rotor systems. A state feedback modal control law is developed based on modal analysis in periodic time-varying structures. The first step...... in the procedure is a transformation of the model into a time-invariant modal form by applying the modal matrices, which are also periodic time-variant. Due to coupled rotor and blade motions complex vibration modes occur in the modal transformed state space model. This implies that the modal transformed model...
VIBRATION OF FRAME BUILDING STRUCTURES CAUSED BY UNDERGROUND TRAINS
Directory of Open Access Journals (Sweden)
P. V. Аliavdin
2011-01-01
Full Text Available The paper contains investigations on element vibration of a real residential 9-storeyed reinforced-concrete frame building induced by train movement in the shallow subway. A design model for a problem on propagation of bending waves within the limits of the typical fragment of a skeleton is presented in the paper. The steady state vibrations of a column and reinforced-concrete slab induced by an excited force which is equivalent to the impact of the subway trains have been investigated in the paper. The problem has been solved numerically on the basis of the ANSYS FEA program. Numerical results have been compared with an approximate analytical solution and data on full-scale experiment. A prediction technique for vibration propagation in the designed buildings is offered in the paper.
X-ray refractive index: A tool to determine the average composition in multilayer structures
International Nuclear Information System (INIS)
Miceli, P.F.; Neumann, D.A.; Zabel, H.
1986-01-01
We present a novel and simple method to determine the average composition of multilayers and superlattices by measuring the x-ray refractive index. Since these modulated structures exhibit Bragg reflections at small angles, by using a triple axis x-ray spectrometer we have accurately determined the peak shifts due to refraction in GaAs/Al/sub x/Ga/sub 1-x/As and Nb/Ta superlattices. Knowledge of the refractive index provides the average fractional composition of the periodic structure since the refractive index is a superposition of the refractive indices of the atomic constituents. We also present a critical discussion of the method and compare the values of the average fractional composition obtained in this manner to the values obtained from the lattice parameter change in the GaAs/Al/sub x/Ga/sub 1-x/As superlattices due to the Al
International Nuclear Information System (INIS)
Mello, J.D.B. de; Arruda, A.C.F. de
1980-01-01
This study concerns the effect of mechanical vibration applied simultaneously with inoculation (0,05% Nb) on the solidification structure of aluminium, with a view to refining the grain size. The results shows that the method used is an efficient way to control the final structure of the aluminium. The best results were found for low values of the frequencies of vibration and for the small amplitudes. (Author) [pt
Category structure determines the relative attractiveness of global versus local averages.
Vogel, Tobias; Carr, Evan W; Davis, Tyler; Winkielman, Piotr
2018-02-01
Stimuli that capture the central tendency of presented exemplars are often preferred-a phenomenon also known as the classic beauty-in-averageness effect . However, recent studies have shown that this effect can reverse under certain conditions. We propose that a key variable for such ugliness-in-averageness effects is the category structure of the presented exemplars. When exemplars cluster into multiple subcategories, the global average should no longer reflect the underlying stimulus distributions, and will thereby become unattractive. In contrast, the subcategory averages (i.e., local averages) should better reflect the stimulus distributions, and become more attractive. In 3 studies, we presented participants with dot patterns belonging to 2 different subcategories. Importantly, across studies, we also manipulated the distinctiveness of the subcategories. We found that participants preferred the local averages over the global average when they first learned to classify the patterns into 2 different subcategories in a contrastive categorization paradigm (Experiment 1). Moreover, participants still preferred local averages when first classifying patterns into a single category (Experiment 2) or when not classifying patterns at all during incidental learning (Experiment 3), as long as the subcategories were sufficiently distinct. Finally, as a proof-of-concept, we mapped our empirical results onto predictions generated by a well-known computational model of category learning (the Generalized Context Model [GCM]). Overall, our findings emphasize the key role of categorization for understanding the nature of preferences, including any effects that emerge from stimulus averaging. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
Low Frequency Vibration approach to asess the Performance of wood structural Systems
Xiping Wang; Robert J. Ross; Michael O. Hunt
2004-01-01
The primary means of inspecting buildings and other structures is to evaluate each structure member individually. This is a time consuming process that is expensive, particularly if sheathing or other covering materials must be removed to access the structural members. This paper presents an effort to use a low frequency vibration method for assessing the structural...
The vibrational structure of dibenzo-p-dioxin
DEFF Research Database (Denmark)
Eriksen, Troels Kongsgaard; Hansen, Bjarke Knud Vilster; Spanget-Larsen, Jens
2008-01-01
by the results of a harmonic analysis based on B3LYP/cc-pVTZ density functional theory (DFT). The combined experimental and theoretical results led to proposal of a nearly complete assignment of the fundamental vibrational transitions of DD, involving reassignment of several transitions. The results...
Resonant vibrations and acoustic radiation of rotating spherical structures.
CSIR Research Space (South Africa)
Shatalov, M
2006-07-01
Full Text Available involved into rotation (precession) with respect to the inertial space with scale factors depending on nature of elastic modes and their numbers. Corresponding scales factors or Bryan’s factors of the vibrating mode’s precession are calculated depending...
Flow-induced vibration of circular cylindrical structures
International Nuclear Information System (INIS)
Chen, S.S.
1985-06-01
This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs
Vibrations in a Multi-Storey Lightweight Building Structure
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard; Kirkegaard, Poul Henning
2013-01-01
This paper provides a quantification of the changes in vibration level that can be expected in a lightweight multi-storey wooden building due to reduced connection stiffness or added nonstructural mass. Firstly, the impact of changes in the floor-to-wall connections is examined. Secondly, a study...
Active vibration control of smart hull structure using piezoelectric composite actuators
International Nuclear Information System (INIS)
Sohn, Jung Woo; Choi, Seung-Bok; Lee, Chul-Hee
2009-01-01
In this paper, active vibration control performance of the smart hull structure with macro-fiber composite (MFC) is evaluated. MFC is an advanced piezoelectric composite which has great flexibility and increased actuating performance compared to a monolithic piezoelectric ceramic patch. The governing equations of motion of the hull structure with MFC actuators are derived based on the classical Donnell–Mushtari shell theory. The actuating model for the interaction between hull structure and MFC is included in the governing equations. Subsequently, modal characteristics are investigated and compared with the results obtained from experiment. The governing equations of the vibration control system are then established and expressed in the state space form. A linear quadratic Gaussian (LQG) control algorithm is designed in order to effectively and actively control the imposed vibration. The controller is experimentally realized and vibration control performances are evaluated
Fang, Yuanyuan; Zuo, Yanyan; Xia, Zhaowang
2018-03-01
The noise level is getting higher with the development of high-power marine power plant. Mechanical noise is one of the most obvious noise sources which not only affect equipment reliability, riding comfort and working environment, but also enlarge underwater noise. The periodic truss type device which is commonly applied in fields of aerospace and architectural is introduced to floating raft construction in ship. Four different raft frame structure are designed in the paper. The vibration transmissibility is taken as an evaluation index to measure vibration isolation effect. A design scheme with the best vibration isolation effect is found by numerical method. Plate type and the optimized periodic truss type raft frame structure are processed to experimental verify vibration isolation effect of the structure of the periodic raft. The experimental results demonstrate that the same quality of the periodic truss floating raft has better isolation effect than that of the plate type floating raft.
Energy Technology Data Exchange (ETDEWEB)
Boda, Łukasz, E-mail: lboda@chemia.uj.edu.pl; Boczar, Marek; Gług, Maciej; Wójcik, Marek J. [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków (Poland)
2015-11-28
Interaction energies, molecular structure and vibrational frequencies of the binary complex formed between H(D)Cl and dimethyl ether have been obtained using quantum-chemical methods. Equilibrium and vibrationally averaged structures, harmonic and anharmonic wavenumbers of the complex and its deuterated isotopomer were calculated using harmonic and anharmonic second-order perturbation theory procedures with Density Functional Theory B3LYP and B2PLYP-D and ab initio Møller-Plesset second-order methods, and a 6-311++G(3d,3p) basis set. A phenomenological model describing anharmonic-type vibrational couplings within hydrogen bonds was developed to explain the unique broadening and fine structure, as well as the isotope effect of the Cl–H and Cl–D stretching IR absorption bands in the gaseous complexes with dimethyl ether, as an effect of hydrogen bond formation. Simulations of the rovibrational structure of the Cl–H and Cl–D stretching bands were performed and the results were compared with experimental spectra.
Coupled thermal, structural and vibrational analysis of a hypersonic engine for flight test
Energy Technology Data Exchange (ETDEWEB)
Sook-Ying, Ho [Defence Science and Technology Organisation, SA (Australia); Paull, A. [Queensland Univ., Dept. of Mechanical Engineering (Australia)
2006-07-15
This paper describes a relatively simple and quick method for implementing aerodynamic heating models into a finite element code for non-linear transient thermal-structural and thermal-structural-vibrational analyses of a Mach 10 generic HyShot scram-jet engine. The thermal-structural-vibrational response of the engine was studied for the descent trajectory from 60 to 26 km. Aerodynamic heating fluxes, as a function of spatial position and time for varying trajectory points, were implemented in the transient heat analysis. Additionally, the combined effect of varying dynamic pressure and thermal loads with altitude was considered. This aero-thermal-structural analysis capability was used to assess the temperature distribution, engine geometry distortion and yielding of the structural material due to aerodynamic heating during the descent trajectory, and for optimising the wall thickness, nose radius of leading edge, etc. of the engine intake. A structural vibration analysis was also performed following the aero-thermal-structural analysis to determine the changes in natural frequencies of the structural vibration modes that occur at the various temperatures associated with the descent trajectory. This analysis provides a unique and relatively simple design strategy for predicting and mitigating the thermal-structural-vibrational response of hypersonic engines. (authors)
DEFF Research Database (Denmark)
Friis, Lars; Ohlrich, Mogens
2008-01-01
Many complicated systems of practical interest consist basically of a well-defined outer shell-like master structure and a complicated internal structure with uncertain dynamic properties. Using the "fuzzy structure theory" for predicting audible frequency vibration, the internal structure......-dimensional continuous boundary. Additionally, a simple method for determining the so-called equivalent coupling factor is presented. The validity of this method is demonstrated by numerical simulations of the vibration response of a master plate structure with fuzzy attachments. It is revealed that the method performs...
Qin, Yechen; He, Chenchen; Shao, Xinxin; Du, Haiping; Xiang, Changle; Dong, Mingming
2018-04-01
This paper presents a new approach for vibration mitigation based on a dynamic vibration absorbing structure (DVAS) for electric vehicles (EVs) that use in-wheel switched reluctance motors (SRMs). The proposed approach aims to alleviate the negative effects of vibration caused by the unbalanced electromagnetic force (UMEF) that arises from road excitations. The analytical model of SRMs is first formulated using Fourier series, and then a model of the coupled longitudinal-vertical dynamics is developed taking into consideration the external excitations consisting of the aerodynamic drag force and road unevenness. In addition, numerical simulations for a conventional SRM-suspension system and two novel DVASs are carried out for varying road levels specified by ISO standards and vehicle velocities. The results of the comparison reveal that a 35% improvement in ride comfort, 30% improvement of road handling, and 68% improvement in air gap between rotor and stator can be achieved by adopting the novel DVAS compared to the conventional SRM-suspension system. Finally, multi-body simulation (MBS) is performed using LMS Motion to validate the feasibility of the proposed DVAS. Analysis of the results shows that the proposed method can augment the effective application of SRMs in EVs.
Energy Technology Data Exchange (ETDEWEB)
Yadav, Anand [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Department of Physics, MEDICAPS Institute of Science and Technology, Pithampur 453331 (India); Rajpoot, Rambabu; Dar, M. A.; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com, E-mail: anand.212@gmail.com [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India)
2016-05-23
Transition metal Cu{sup 2+} doped Mg-Zn ferrite [Mg{sub 0.5}Zn{sub 0.5-x}Cu{sub x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 0.5)] were prepared by sol gel auto combustion (SGAC) method to probe the structural, vibrational and electrical properties. X-ray diffraction (XRD) pattern reveals a single-phase cubic spinel structure without the presence of any secondary phase corresponding to other structure. The average particle size of the parent Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} is found to be ~29.8 nm and is found to increase with Cu{sup 2+} doping. Progressive reduction in lattice parameter of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} has been observed due to difference in ionic radii of cations with improved Cu doping. Spinel cubic structure is further confirmed by Raman spectroscopy. Small shift in Raman modes towards higher wave number has been observed in doped Mg-Zn ferrites. The permittivity and dielectric loss decreases at lower doping and increases at higher order doping of Cu{sup 2+}.
Effect of nonlinearity of connecting dampers on vibration control of connected building structures
Directory of Open Access Journals (Sweden)
Masatoshi eKasagi
2016-01-01
Full Text Available The connection of two building structures with dampers is one of effective vibration control systems. In this vibration control system, both buildings have to possess different vibration properties in order to provide a higher vibration reduction performance. In addition to such condition of different vibration properties of both buildings, the connecting dampers also play an important role in the vibration control mechanism. In this paper, the effect of nonlinearity of connecting dampers on the vibration control of connected building structures is investigated in detail. A high-damping rubber damper and an oil damper with and without relief mechanism are treated. It is shown that, while the high-damping rubber damper is effective in a rather small deformation level, the linear oil damper is effective in a relatively large deformation level. It is further shown that, while the oil dampers reduce the response in the same phase as the case without dampers, the high-damping rubber dampers change the phase. The merit is that the high-damping rubber can reduce the damper deformation and keep the sufficient space between both buildings. This can mitigate the risk of building pounding.
Vibration-based monitoring for performance evaluation of flexible civil structures in Japan
FUJINO, Yozo
2018-01-01
The vibration-based monitoring of flexible civil structures and performance evaluation from this monitoring are reviewed, with an emphasis on research and practice in Japan and the author’s experiences. Some new findings and unexpected vibrations from the monitoring of real bridges and buildings are reported to emphasize the importance of monitoring. Future developments and applications of vibration-based monitoring to civil infrastructure management are also described. Many examples are taken from the author’s past 30 years’ experience of research on bridge dynamics. PMID:29434082
Fluid induced structural vibrations in steam generators and heat exchangers
International Nuclear Information System (INIS)
Catton, I.; Adinolfi, P.; Alquaddoomi, O.
2003-01-01
Fluid-elastic instability (FEI) in tube bundle heat exchangers was studied experimentally. The motion of an array of 15 stainless steel vibrating tubes (Φ 25.4mm) in water cross-flow, suspended using stainless steel piano wire has been recorded with a CCD camera. The individual motion and relative motion of the tubes are reported and can be used for computational model validation. The relative displacement of the tubes allows identification of the most potentially damaging patterns of tube bundle vibration. A critical reduced velocity may be determined by specification of an allowable limit on tube motion amplitude. Measurements were made for various tube array configurations, tube natural frequencies and flow conditions. (author)
Crystal structure and vibrational spectra of melaminium arsenate
Anbalagan, G.; Marchewka, M. K.; Pawlus, K.; Kanagathara, N.
2015-01-01
The crystals of the new melaminium arsenate (MAS) [C3H7N6+ṡH2AsO4-] were obtained by the slow evaporation of an aqueous solution at room temperature. Single crystal X-ray diffraction analysis reveals that the crystal belongs to triclinic system with centro symmetric space group P-1. The crystals are built up from single protonated melaminium residues and single dissociated arsenate H2AsO4- anions. The protonated melaminium ring is almost planar. A combination of ionic and donor-acceptor hydrogen-bond interactions linking together the melaminium and arsenate residues forms a three-dimensional network. Vibrational spectroscopic analysis is reported on the basis of FT-IR and FT-Raman spectra recorded at room temperature. Hydrogen bonded network present in the crystal gives notable vibrational effect. DSC has also been performed for the crystal shows no phase transition in the studied temperature range (113-293 K).
Vibration insensitive interferometry
Millerd, James; Brock, Neal; Hayes, John; Kimbrough, Brad; North-Morris, Michael; Wyant, James C.
2017-11-01
The largest limitation of phase-shifting interferometry for optical testing is the sensitivity to the environment, both vibration and air turbulence. An interferometer using temporal phase-shifting is very sensitive to vibration because the various phase shifted frames of interferometric data are taken at different times and vibration causes the phase shifts between the data frames to be different from what is desired. Vibration effects can be reduced by taking all the phase shifted frames simultaneously and turbulence effects can be reduced by averaging many measurements. There are several techniques for simultaneously obtaining several phase-shifted interferograms and this paper will discuss two such techniques: 1) Simultaneous phase-shifting interferometry on a single detector array (PhaseCam) and 2) Micropolarizer phase-shifting array. The application of these techniques for the testing of large optical components, measurement of vibrational modes, the phasing of segmented optical components, and the measurement of deformations of large diffuse structures is described.
Vibration test on KMRR reactor structure and primary cooling system piping
Energy Technology Data Exchange (ETDEWEB)
Chung, Seung Hoh; Kim, Tae Ryong; Park, Jin Hoh; Park, Jin Suk; Ryoo, Jung Soo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1994-10-01
Most equipments, piping systems and reactor structures in nuclear power plants are subjected to flow induced vibration due to high temperature and high pressure coolant flowing inside or outside of the equipments, systems and structures. Because the flow induced vibration sometimes causes significant damage to reactor structures and piping systems, it is important and necessary to evaluate the vibration effect on them and to prove their structural integrity. Korea Multipurpose Research Reactor (KMRR) being constructed by KAERI is 30 MWt pool type research reactor. Since its main structures and piping systems were designed and manufactured in accordance with the standards and guidelines for commercial nuclear power plant, it was decided to evaluate their vibratory response in accordance with the standards and guidelines for commercial NPP. The objective of this vibration test is the assessment of vibration levels of KMRR reactor structure and primary cooling piping system for their structural integrity under the steady-state or transient operating condition. 38 figs, 14 tabs, 2 refs. (Author).
Vibration test on KMRR reactor structure and primary cooling system piping
International Nuclear Information System (INIS)
Chung, Seung Hoh; Kim, Tae Ryong; Park, Jin Hoh; Park, Jin Suk; Ryoo, Jung Soo
1994-10-01
Most equipments, piping systems and reactor structures in nuclear power plants are subjected to flow induced vibration due to high temperature and high pressure coolant flowing inside or outside of the equipments, systems and structures. Because the flow induced vibration sometimes causes significant damage to reactor structures and piping systems, it is important and necessary to evaluate the vibration effect on them and to prove their structural integrity. Korea Multipurpose Research Reactor (KMRR) being constructed by KAERI is 30 MWt pool type research reactor. Since its main structures and piping systems were designed and manufactured in accordance with the standards and guidelines for commercial nuclear power plant, it was decided to evaluate their vibratory response in accordance with the standards and guidelines for commercial NPP. The objective of this vibration test is the assessment of vibration levels of KMRR reactor structure and primary cooling piping system for their structural integrity under the steady-state or transient operating condition. 38 figs, 14 tabs, 2 refs. (Author)
Synthesis of vibration control and health monitoring of building structures under unknown excitation
International Nuclear Information System (INIS)
He, Jia; Huang, Qin; Xu, You-Lin
2014-01-01
The vibration control and health monitoring of building structures have been actively investigated in recent years but often treated separately according to the primary objective pursued. In this study, a time-domain integrated vibration control and health monitoring approach is proposed based on the extended Kalman filter (EKF) for identifying the physical parameters of the controlled building structures without the knowledge of the external excitation. The physical parameters and state vectors of the building structure are then estimated and used for the determination of the control force for the purpose of the vibration attenuation. The interaction between the health monitoring and vibration control is revealed and assessed. The feasibility and reliability of the proposed approach is numerically demonstrated via a five-story shear building structure equipped with magneto-rheological (MR) dampers. Two types of excitations are considered: (1) the EI-Centro ground excitation underneath of the building and (2) a swept-frequency excitation applied on the top floor of the building. Results show that the structural parameters as well as the unknown dynamic loadings could be identified accurately; and, at the same time, the structural vibration is significantly reduced in the building structure. (paper)
Loendersloot, Richard; Ooijevaar, T.H.; Warnet, Laurent; Akkerman, Remko; de Boer, Andries; Meguid, S.A.; Gomes, J.F.S.
2009-01-01
The feasibility of a vibration based damage identification method is investigated. The Modal Strain Energy method is applied to a T–beam structure. The dynamic response of an intact structure and a damaged, delaminated structure is analysed employing a commercially available Finite Element package.
Preventive measures against vibration of FBR reactor vessel cooling structure
International Nuclear Information System (INIS)
Eguchi, Yuzuru; Tanaka, Nobukazu
1989-01-01
The present paper describes the fundamental feature of the fluid-elastic vibration of flexible overflow weir, as observed in the French demonstration fast breeder reactor, Super Phenix-1. In the experimental study, the instability criterion of the fluid-elastic vibration was studied by using a simple experimental apparatus of a rectangular tank separated by a flexible weir. A spring-mass model was developed to clarify the mechanism of the instability. The instability condition was analytically derived from the equations of the spring-mass model. The equations of the spring-mass model was also computationally integrated in time to simulate the temporal evolution of the fluid-elastic vibration. The comparison between the experimental and theoretical results indicates that the present theoretical model is capable of predicting most of the physical tendencies observed in the experiment. The present study revealed that the lag time of waterfall at the weir is the most influential parameter among other hydro-elastic parameters. (author)
Testing and diagnosis of the cause of increased vibration of the fan plant's support structure
Directory of Open Access Journals (Sweden)
Varju Đerđ
2015-01-01
Full Text Available This paper presents a procedure of determining the causes of increased vibration of a fan plant and its support structure in the PUC 'Subotička toplana'. Excessive vibrations were observed following the installation of the frequency converter, thus a methodological approach of testing-analysis-diagnosis has been applied. Based on the definition of the causes of this problem, the paper also suggests possible repair procedures.
A broadband frequency-tunable dynamic absorber for the vibration control of structures
International Nuclear Information System (INIS)
Komatsuzaki, T; Inoue, T; Terashima, O
2016-01-01
A passive-type dynamic vibration absorber (DVA) is basically a mass-spring system that suppresses the vibration of a structure at a particular frequency. Since the natural frequency of the DVA is usually tuned to a frequency of particular excitation, the DVA is especially effective when the excitation frequency is close to the natural frequency of the structure. Fixing the physical properties of the DVA limits the application to a narrowband, harmonically excited vibration problem. A frequency-tunable DVA that can modulate its stiffness provides adaptability to the vibration control device against non-stationary disturbances. In this paper, we suggest a broadband frequency-tunable DVA whose natural frequency can be extended by 300% to the nominal value using the magnetorheological elastomers (MREs). The frequency adjustability of the proposed absorber is first shown. The real-time vibration control performance of the frequency-tunable absorber for an acoustically excited plate having multiple resonant peaks is then evaluated. Investigations show that the vibration of the structure can be effectively reduced with an improved performance by the DVA in comparison to the conventional passive- type absorber. (paper)
Zhang, Yulong; Wang, Tianyang; Zhang, Ai; Peng, Zhuoteng; Luo, Dan; Chen, Rui; Wang, Fei
2016-12-01
In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s 2 at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.
Pan, Chu-Dong; Yu, Ling; Liu, Huan-Lin
2017-08-01
Traffic-induced moving force identification (MFI) is a typical inverse problem in the field of bridge structural health monitoring. Lots of regularization-based methods have been proposed for MFI. However, the MFI accuracy obtained from the existing methods is low when the moving forces enter into and exit a bridge deck due to low sensitivity of structural responses to the forces at these zones. To overcome this shortcoming, a novel moving average Tikhonov regularization method is proposed for MFI by combining with the moving average concepts. Firstly, the bridge-vehicle interaction moving force is assumed as a discrete finite signal with stable average value (DFS-SAV). Secondly, the reasonable signal feature of DFS-SAV is quantified and introduced for improving the penalty function (∣∣x∣∣2 2) defined in the classical Tikhonov regularization. Then, a feasible two-step strategy is proposed for selecting regularization parameter and balance coefficient defined in the improved penalty function. Finally, both numerical simulations on a simply-supported beam and laboratory experiments on a hollow tube beam are performed for assessing the accuracy and the feasibility of the proposed method. The illustrated results show that the moving forces can be accurately identified with a strong robustness. Some related issues, such as selection of moving window length, effect of different penalty functions, and effect of different car speeds, are discussed as well.
Young, Ken (Inventor); Hindle, Timothy (Inventor); Barber, Tim Daniel (Inventor)
2016-01-01
Mounting systems for structural members, fastening assemblies thereof, and vibration isolation systems including the same are provided. Mounting systems comprise a pair of mounting brackets, each clamped against a fastening assembly forming a mounting assembly. Fastening assemblies comprise a spherical rod end comprising a spherical member having a through opening and an integrally threaded shaft, first and second seating members on opposite sides of the spherical member and each having a through opening that is substantially coaxial with the spherical member through opening, and a partially threaded fastener that threadably engages each mounting bracket forming the mounting assembly. Structural members have axial end portions, each releasably coupled to a mounting bracket by the integrally threaded shaft. Axial end portions are threaded in opposite directions for permitting structural member rotation to adjust a length thereof to a substantially zero strain position. Structural members may be vibration isolator struts in vibration isolation systems.
Vulnerability Assessment for a Complex Structure Using Vibration Response Induced by Impact Load
International Nuclear Information System (INIS)
Park, Jeongwon; Park, Junhong; Koo, Man Hoi
2014-01-01
This work presents a vulnerability assessment procedure for a complex structure using vibration characteristics. The structural behavior of a three-dimensional framed structure subjected to impact forces was predicted using the spectral element method. The Timoshenko beam function was applied to simulate the impact wave propagations induced by a high-velocity projectile at relatively high frequencies. The interactions at the joints were analyzed for both flexural and longitudinal wave propagations. Simulations of the impact energy transfer through the entire structure were performed using the transient displacement and acceleration responses obtained from the frequency analysis. The kill probabilities of the crucial components for an operating system were calculated as a function of the predicted acceleration amplitudes according to the acceptable vibration levels. Following the proposed vulnerability assessment procedure, the vulnerable positions of a three-dimensional combat vehicle with high possibilities of damage generation of components by impact loading were identified from the estimated vibration responses
Vibrational spectra of solid solution series with ordered perovskite structure
Blasse, G.
I.R. and Raman spectra are reported for the following three systems: Ba2CaMo1−xTexO6, Ba2−xSrxMgWO6 and Ba2Ca1−xMgxWO6. In the first series the internal vibrations of the M6+O6 octahedra do not influence each other. The intensity of ν1 (MoO6) is five times that of ν1 (TeO6). In the second system
Vibration analysis of thin-wall structures containing piezoactive layers
International Nuclear Information System (INIS)
Guz, I A; Kashtalyan, M; Zhuk, Y A
2010-01-01
A coupled dynamic problem of electro-mechanics for a layered beam is formulated based on the Kirchhoff-Love hypotheses. In the case of harmonic loading, a simplified formulation is given using the single frequency approximation and the concept of complex moduli. As an example, the problem of forced vibration of a three-layer sandwich beam (aluminium alloy core covered with piezoelectric layers) with hinged ends is solved in order to investigate the accuracy and applicability of the approximate monoharmonic approach. Different aspects of the beam response to the mechanical and electric excitation are studied.
The ABRAVIBE toolbox for teaching vibration analysis and structural dynamics
DEFF Research Database (Denmark)
Brandt, A.
2013-01-01
, a MATLAB toolbox (the ABRAVIBE toolbox) has been developed as an accompanying toolbox for the recent book "Noise and Vibration Analysis" by the author. This free, open software, published under GNU Public License, can be used with GNU Octave, if an entirely free software platform is wanted, with a few...... functional limitations. The toolbox includes functionality for simulation of mechanical models as well as advanced analysis such as time series analysis, spectral analysis, frequency response and correlation function estimation, modal parameter extraction, and rotating machinery analysis (order tracking...
Dual resonant structure for energy harvesting from random vibration sources at low frequency
Directory of Open Access Journals (Sweden)
Shanshan Li
2016-01-01
Full Text Available We introduce a design with dual resonant structure which can harvest energy from random vibration sources at low frequency range. The dual resonant structure consists of two spring-mass subsystems with different frequency responses, which exhibit strong coupling and broad bandwidth when the two masses collide with each other. Experiments with piezoelectric elements show that the energy harvesting device with dual resonant structure can generate higher power output than the sum of the two separate devices from random vibration sources.
DEFF Research Database (Denmark)
Pawlowski, F; Jorgensen, P; Olsen, Jeppe
2002-01-01
A detailed study is carried out of the accuracy of molecular equilibrium geometries obtained from least-squares fits involving experimental rotational constants B(0) and sums of ab initio vibration-rotation interaction constants alpha(r)(B). The vibration-rotation interaction constants have been...... calculated for 18 single-configuration dominated molecules containing hydrogen and first-row atoms at various standard levels of ab initio theory. Comparisons with the experimental data and tests for the internal consistency of the calculations show that the equilibrium structures generated using Hartree......-Fock vibration-rotation interaction constants have an accuracy similar to that obtained by a direct minimization of the CCSD(T) energy. The most accurate vibration-rotation interaction constants are those calculated at the CCSD(T)/cc-pVQZ level. The equilibrium bond distances determined from these interaction...
Arjunan, V; Devi, L; Subbalakshmi, R; Rani, T; Mohan, S
2014-09-15
The stable geometry of 2-hydroxy-4-methoxyacetophenone is optimised by DFT/B3LYP method with 6-311++G(∗∗) and cc-pVTZ basis sets. The structural parameters, thermodynamic properties and vibrational frequencies of the optimised geometry have been determined. The effects of substituents (hydroxyl, methoxy and acetyl groups) on the benzene ring vibrational frequencies are analysed. The vibrational frequencies of the fundamental modes of 2-hydroxy-4-methoxyacetophenone have been precisely assigned and analysed and the theoretical results are compared with the experimental vibrations. 1H and 13C NMR isotropic chemical shifts are calculated and assignments made are compared with the experimental values. The energies of important MO's, the total electron density and electrostatic potential of the compound are determined. Various reactivity and selectivity descriptors such as chemical hardness, chemical potential, softness, electrophilicity, nucleophilicity and the appropriate local quantities are calculated. Copyright © 2014 Elsevier B.V. All rights reserved.
Conformational Stability, Structural Parameters And Vibrational Assignments of Allantoin
International Nuclear Information System (INIS)
Haman, S.
2008-01-01
Allantoin 2,5-Dioxo-4-imidazolinyl) urea , the diureide of glyoxylic acid, is a crystallisable oxidation product of uric acid found in allantoic and amniotic fluids, in fetal urine and in many plants. It is a healing, moisturizing, soothing and anti-irritating, keratolytic and non-toxic agent useful in dermatological, cosmetic and veterinary preparation. The optimized geometries and energies of the low-energy conformers of allantoin have been calculated using density functional theory (Daft) method. The calculations were performed with Beck's nonlocal three-parameter hybrid functional in combination with the Lee, Yang, and Parr correlation functional (By-play) using the 6-311++G(d,p) basis set. We calculated the infrared frequencies and intensities of the most stable conformers in order to assist in the assignment of the vibrational bands in the experimental spectrum. The B3LYP/6-311+G(d,p) harmonic force constants were scaled by applying the scaled quantum mechanical force field (SQM) technique. The calculated vibrational spectra were interpreted and band assignments were reported
Transverse Resonant Vibration of Non-Bearing Structures Caused by Wind
Jendzelovsky, Norbert; Antal, Roland
2017-10-01
Nowadays, there are increasing use of very thin, subtle and light structures in the field of building constructions. We can find such a structures as part of roofs or design facades. By using these lamellas like, non-bearing structures as a part of architectural design of buildings, it is necessary to consider wind effects on these structures. Subtle structures of this type are prone to vibration in the transverse direction of the wind flow. The fact that the vibration occurs depends on wind parameters (wind velocity, direction of an air flow) and it also depends on the properties of lamella (shape, length, mass, natural frequency, support type). The principal idea of this article is to show susceptibility of lamellae-like structures to transverse resonant vibration caused by the phenomenon called Von Karman effect. Comparison of susceptibility to transverse resonance vibration was analysed on the different shapes of lamellas loaded by different wind speed. Analysis was based on usage of empirically derived equations. Von Karman effect arise from wind flow past an object. Turbulence in the form of vortices are formed at the object and shed into the flowing stream intermittently. The potential problem is that this turbulence can induce vibrations into the lamella itself. In terms of this vibration problem, two frequencies are interesting. Von Karman shedding frequency is the frequency at which the vortices are formed and shed at the object. The vortex-shedding frequency increases with the velocity of the wind flow and decreases with the size of the object. Natural frequency of the object depends on the construction of the lamella itself. Parameters of lamella as a shape, mass, length, elasticity modulus of material and support types are directly involved in the calculation of natural frequency. Worst case scenario in the term of transverse resonant vibration occurs when the natural frequency of lamella is equal to the vortex-shedding frequency. In this case
Brian K. Brashaw; Robert Vatalaro; Xiping Wang; Kevin Sarvela; James P. Wacker
2008-01-01
Approximately 4,000 vehicle bridges in the State of Minnesota contain structural timber members. Recent research at the University of Minnesota Duluth Natural Resources Research Institute (UMD NRRI) has been conducted on vibration testing of timber bridges as a means of developing rapid in-place testing techniques for assessing the structural health of bridges. The...
Phononic band gaps and vibrations in one- and two-dimensional mass-spring structures
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard
2003-01-01
The vibrational response of finite periodic lattice structures subjected to periodic loading is investigated. Special attention is devoted to the response in frequency ranges with gaps in the band structure for the corresponding infinite periodic lattice. The effects of boundaries, viscous dampin...
The validation of an aerospace structure through the sine vibration analysis
Directory of Open Access Journals (Sweden)
Cristina-Diana BRATU
2018-06-01
Full Text Available Sinusoidal vibrations represent an ideal case. Technically, it is quite hard to generate pure sinusoidal vibrations without containing other spectral components, called harmonics. Sinusoidal vibrations can appear on propeller, propulsion and turbofan aircraft as well as on helicopters and aerospace structures. They can occur during different phases of flight (take-off, ascent, cruise, landing, etc.. The aim of this article is to present how a structure can be validated by using the mathematical formulas or a FEM software such as PATRAN-NASTRAN (and the equations behind it. As an application, an aerospace structure such as thruster brackets will be analyzed. A sinusoidal signal of 1g was applied on the attachment points and the response was read from the center of gravity of the thrusters.
Pan, Shijia; Mirshekari, Mostafa; Fagert, Jonathon; Ramirez, Ceferino Gabriel; Chung, Albert Jin; Hu, Chih Chi; Shen, John Paul; Zhang, Pei; Noh, Hae Young
2018-02-01
Many human activities induce excitations on ambient structures with various objects, causing the structures to vibrate. Accurate vibration excitation source detection and characterization enable human activity information inference, hence allowing human activity monitoring for various smart building applications. By utilizing structural vibrations, we can achieve sparse and non-intrusive sensing, unlike pressure- and vision-based methods. Many approaches have been presented on vibration-based source characterization, and they often either focus on one excitation type or have limited performance due to the dispersion and attenuation effects of the structures. In this paper, we present our method to characterize two main types of excitations induced by human activities (impulse and slip-pulse) on multiple structures. By understanding the physical properties of waves and their propagation, the system can achieve accurate excitation tracking on different structures without large-scale labeled training data. Specifically, our algorithm takes properties of surface waves generated by impulse and of body waves generated by slip-pulse into account to handle the dispersion and attenuation effects when different types of excitations happen on various structures. We then evaluate the algorithm through multiple scenarios. Our method achieves up to a six times improvement in impulse localization accuracy and a three times improvement in slip-pulse trajectory length estimation compared to existing methods that do not take wave properties into account.
Active Vibration Control of a Monopile Offshore Structure
DEFF Research Database (Denmark)
Nielsen, Søren R. K.; Kirkegaard, Poul Henning; Thesbjerg, L.
1996-01-01
coefficient should be obtained in order to have a relatively small excitation on the cylinder. The drag coefficient can be controlled if the separation points of the boundary layers can be controlled. It is proposed to control the separation points by blowing compressed air out of the holes in the cylinder....... If the natura1 separation points of the boundary layers are rejected by blowing air out of the holes the drag coefficient will increase while it will decrease if it is possible to attach the boundary layer. The results from the experimental test have shown that it is possible to increase the drag coefficient...... with a factor 1.5-2 by blowing air out of the holes in a cylinder vibrating in a stationary water flow....
Platis, Andreas; Martinez, Daniel; Bange, Jens
2014-05-01
Turbulent structure parameters of temperature and humidity can be derived from scintillometer measurements along horizontal paths of several 100 m to several 10 km. These parameters can be very useful to estimate the vertical turbulent heat fluxes at the surface (applying MOST). However, there are many assumptions required by this method which can be checked using in situ data, e.g. 1) Were CT2 and CQ2 correctly derived from the initial CN2 scintillometer data (structure parameter of density fluctuations or refraction index, respectively)? 2) What is the influence of the surround hetereogeneous surface regarding its footprint and the weighted averaging effect of the scintillometer method 3) Does MOST provide the correct turbulent fluxes from scintillometer data. To check these issues, in situ data from low-level flight measurements are well suited, since research aircraft cover horizontal distances in very short time (Taylor's hypothesis of a frozen turbulence structure can be applyed very likely). From airborne-measured time series the spatial series are calculated and then their structure functions that finally provide the structure parameters. The influence of the heterogeneous surface can be controlled by the definition of certain moving-average window sizes. A very useful instrument for this task are UAVs since they can fly very low and maintain altitude very precisely. However, the data base of such unmanned operations is still quite thin. So in this contribution we want to present turbulence data obtained with the Helipod, a turbulence probe hanging below a manned helicopter. The structure parameters of temperature and moisture, CT2 and CQ2, in the lower convective boundary layer were derived from data measured using the Helipod in 2003. The measurements were carried out during the LITFASS03 campaign over a heterogeneous land surface around the boundary-layer field site of the Lindenberg Meteorological Observatory-Richard-Aßmann-Observatory (MOL) of the
A wireless vibrating wire sensor node for continuous structural health monitoring
International Nuclear Information System (INIS)
Lee, H M; Park, H S; Kim, J M; Sho, K
2010-01-01
Vibrating wire sensors (VWS) are generally used for strain measurements of structures in buildings and civil infrastructures. In this paper, a wireless vibrating wire sensor node is developed which can measure resonance frequencies from vibrating wire sensors and can remotely communicate the frequencies by wireless. The wireless sensor node consists of a sensor module, which excites the vibrating wire and reads the resonance frequencies, a wireless communication module, which transmits the wire's resonance frequencies to the user or administrator, and a processor that controls the two modules. The wireless sensor node has the following characteristics: it has multiple channels to enable measurement of multiple vibrating wire sensors (up to four) using a single sensor node; it has a power-saving feature that enables operation for up to one year; and lastly, the wireless unit uses the 424 MHz UHF (ultra-high frequency) band with good diffraction that has an effect on minimizing the influence of impediments such as structural or nonstructural elements. The wireless sensor node is tested in terms of its measurement precision and its wireless communication performance. As a result, it is confirmed that the node enables the long-term structural health monitoring of buildings and infrastructures
Fluid-structure coupling between a vibrating cylinder and a narrow annular flow
International Nuclear Information System (INIS)
Perotin, L.
1994-01-01
This paper presents an analytical investigation of the fluidelastic coupling between an axial annular flow and a flexible vibrating axisymmetrical structure. The model presented is suited to single-phase, incompressible, viscous fluids and to annular flows of variable cross-section, axially symmetrical when the structure is motionless.An experimental validation of this model is presented at the end of the paper: the results obtained with the numerical model are compared with experimental data for an oscillating cylinder free to vibrate under the effect of a variable-cross-section annular flow. ((orig.))
Directory of Open Access Journals (Sweden)
Zihao Liu
2016-01-01
Full Text Available Torsional vibration of shafts is a very important problem in engineering, in particular in ship engines and aeroengines. Due to their high levels of integration and complexity, it is hard to get their accurate structural data or accurate modal data. This lack of data is unhelpful to vibration control in the form of structural modifications. Besides, many parts in shaft systems are not allowed to be modified such as rotary inertia of a pump or an engine, which is designed for achieving certain functions. This paper presents a strategy for torsional vibration control of shaft systems in the form of structural modifications based on receptances, which does not need analytical or modal models of the systems under investigation. It only needs the torsional receptances of the system, which can be obtained by testing simple auxiliary structure attached to relevant locations of the shaft system and using the finite element model (FEM of the simple structure. An optimization problem is constructed to determine the required structural modifications, based on the actual requirements of modal frequencies and mode shapes. A numerical experiment is set up and the influence of several system parameters is analysed. Several scenarios of constraints in practice are considered. The numerical simulation results demonstrate the effectiveness of this method and its feasibility in solving torsional vibration problems in practice.
Cartmell, Matthew P.
2016-09-01
The Editor wishes to make the reader aware that the paper "A new method for predicting nonlinear structural vibrations induced by ground impact loading" by Jun Liu, Yu Zhang, Bin Yun, Journal of Sound and Vibration, 331 (2012) 2129-2140, did not contain a direct citation of the fundamental and original work in this field by Dr. Mark Svinkin. The Editor regrets that this omission was not noted at the time that the above paper was accepted and published.
The structure of filled skutterudites and the local vibration behavior of the filling atom
Energy Technology Data Exchange (ETDEWEB)
Zhou, Xiaojuan [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Dongguan Institute of Neutron Science, Dongguan 523808 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zong, Peng-an [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Chen, Xihong [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Tao, Juzhou, E-mail: taoj@ihep.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Dongguan Institute of Neutron Science, Dongguan 523808 (China); Lin, He, E-mail: linhe@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201204 (China)
2017-02-15
Both of atomic pair distribution function (PDF) and extended x-ray absorption fine structure (EXAFS) experiments have been carried out on unfilled and Yb-filled skutterudites Yb{sub x}Co{sub 4}Sb{sub 12} (x=0, 0.15, 0.2 and 0.25) samples. The structure refinements on PDF data confirm the large amplitude vibration of Yb atom and the dependence of Yb vibration amplitude on the filling content. Temperature dependent EXAFS experiment on filled skutterudites have been carried out at Yb L{sub Ⅲ}-edge in order to explore the local vibration behavior of filled atom. EXAFS experiments show that the Einstein temperature of the filled atom is very low (70.9 K) which agrees with the rattling behavior.
International Nuclear Information System (INIS)
Czachor, A.
1979-01-01
The configuration-averaged displacement-displacement Green's function, derived in the locator-based approximation accounting for average transfer of information on local coupling and mass, has been applied to study the force-and-mass-disorder induced modifications of phonon dispersion relations in substitutional alloys of cubic structures. In this approach the translational invariance condition is obeyed whereas damping is neglected. The force-disorder was found to lead to additional splitting of phonon curves besides that due to mass-disorder, even in the small impurity-concentration case; at larger concentrations the number of splits (frequency gaps) should be still greater. The use of a quasi-locator in the Green's function derivation allows one to partly reconcile the present results with those of the average t-matrix approximation. The experimentally observed splitting in the [100]T phonon dispersion curve for Al-Ag alloys has been interpreted in terms of the above theory and of a quasi-mass of heavy impurity atoms. (Author)
DEFF Research Database (Denmark)
Kawchuk, Gregory N; Hartvigsen, Jan; Edgecombe, Tiffany
2016-01-01
Structural health monitoring (SHM) is an engineering technique used to identify mechanical abnormalities not readily apparent through other means. Recently, SHM has been adapted for use in biological systems, but its invasive nature limits its clinical application. As such, the purpose of this pr......Structural health monitoring (SHM) is an engineering technique used to identify mechanical abnormalities not readily apparent through other means. Recently, SHM has been adapted for use in biological systems, but its invasive nature limits its clinical application. As such, the purpose...... of this project was to determine if a non-invasive form of SHM could identify structural alterations in the spines of living human subjects. Lumbar spines of 10 twin pairs were visualized by magnetic resonance imaging then assessed by a blinded radiologist to determine whether twin pairs were structurally...... concordant or discordant. Vibration was then applied to each subject's spine and the resulting response recorded from sensors overlying lumbar spinous processes. The peak frequency, area under the curve and the root mean square were computed from the frequency response function of each sensor. Statistical...
Wire rope isolators for vibration isolation of equipment and structures – A review
International Nuclear Information System (INIS)
Balaji, P S; Rahman, M E; Lau, H H; Moussa, Leblouba
2015-01-01
Vibrations and shocks are studied using various techniques and analyzed to predict their detrimental effect on the equipment and structures. In cases, where the effects of vibration become unacceptable, it may cause structural damage and affect the operation of the equipment. Hence, adding a discrete system to isolate the vibration from source becomes necessary. The Wire Rope Isolator (WRI) can be used to effectively isolate the system from disturbing vibrations. The WRI is a type of passive isolator that exhibits nonlinear behavior. It consists of stranded wire rope held between two metal retainer bars and the metal wire rope is made up of individual wire strands that are in frictional contact with each other, hence, it is a kind of friction-type isolator. This paper compiles the research work on wire rope isolators. This paper presents the research work under two categories, namely monotonic and cyclic loading behaviors of WRI. The review also discusses the different terminologies associated with vibration isolation system and highlights the comparison between various isolation systems. (paper)
Vibration modeling of structural fuzzy with continuous boundary
DEFF Research Database (Denmark)
Friis, Lars; Ohlrich, Mogens
2008-01-01
a multitude of different sprung masses each strongly resisting any motion of the main structure (master) at their base antiresonance. The “theory of structural fuzzy” is intended for modeling such high damping. In the present article the theory of fuzzy structures is briefly outlined and a method of modeling...
Restoration solution of increased vibrations of the fan plant's support structure
Directory of Open Access Journals (Sweden)
Varju Đerđ
2016-01-01
Full Text Available This paper presents a restoration solution of increased vibration of the fan plant's support structure. Based on vibrodiagnostic tests and dynamic analysis, a technical solution of the problem is given with additional steel bracing. There is particular emphasis on the diagnosis and forming of a dynamic model.
Experimental vibration analysis for a 3D scaled model of a three-floor steel structure
Directory of Open Access Journals (Sweden)
Ernesto F. Castillo
Full Text Available In this paper we present an experimental study of a three dimensional physical model of a three-floor structure subjected to forced vibrations by imposing displacements in its support. The aim of this work is to analyze the behavior of the building when a dynamic vibration absorber (DVA is acting. An analytic simplified analysis and a numerical study are developed to obtain the natural frequencies of the structure. Experiments are carried out in a vibrating table. The frequency range to be experimentally analyzed is determined by the first natural frequency of the structure for which the DVA damping effects are verified. The equipment capabilities, i.e. the frequencies, amplitudes and admissible load, limit the analyses. Nevertheless, satisfactory results are obtained for the study of the first mode of vibration. The effect of different amplitudes of the imposed support motion is also analyzed. In addition, the damping effect of the DVA device is evaluated upon varying its mass and its location in the structure. The characteristic curves in the frequency domain are obtained computing the Fast Fourier Transformation (FFT of the acceleration history registered with piezoelectric accelerometers at different checkpoints for the cases analyzed.
The study of crystal structures and vibrational spectra of inorganicsalts of 2,4-diaminopyrimidine
Czech Academy of Sciences Publication Activity Database
Matulková, I.; Mathauserová, J.; Císařová, I.; Němec, I.; Fábry, Jan
2016-01-01
Roč. 1103, Jan (2016), s. 82-93 ISSN 0022-2860 R&D Projects: GA ČR GA14-05506S Institutional support: RVO:68378271 Keywords : salts of 2,4-diaminopyrimidine * single crystal X-ray structural analysis * vibrational spectra Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.753, year: 2016
Structural, vibrational, elastic and topological properties of PaN under pressure
DEFF Research Database (Denmark)
Modak, P.; K. Verma, Ashok; Svane, A.
2013-01-01
Electronic, structural, vibrational and elastic properties of PaN have been studied both at ambient and high pressures, using first principles methods with several commonly used parameterizations of the exchange-correlation energy. The generalized gradient approximation (GGA) reproduces the groun...
International Nuclear Information System (INIS)
Li Hui; Ou Jinping
2008-01-01
A number of researchers have been focused on structural vibration control in the past three decades over the world and fruit achievements have been made. This paper introduces the recent advances in structural vibration control including passive, active and semiactive control in mainland China. Additionally, the co-author extends the structural vibration control to failure mode control. The research on the failure mode control is also involved in this paper. For passive control, this paper introduces full scale tests of buckling-restrained braces conducted to investigate the performance of the dampers and the second-editor of the Code of Seismic Design for Buildings. For active control, this paper introduces the HMD system for wind-induced vibration control of the Guangzhou TV tower. For semiactive control, the smart damping devices, algorithms for semi-active control, design methods and applications of semi-active control for structures are introduced in this paper. The failure mode control for bridges is also introduced
Vibration monitoring of the mechanical behavior of the internal structures of PWR reactors
International Nuclear Information System (INIS)
Assedo, R.; Carre, J.C.; Sol, J.C.
1979-01-01
The internal structures of pressurized water reactors are the seat of vibrations induced by fluctuations in primary fluid flow. A knowledge of these phenomena is indispensable in order to ensure that the structures are in proper mechanical order. It can also be used for operational monitoring. This paper describes all the methods developed and the results already achieved in this domain. The first part deals with tests on mockup associated with the calculation models which afforded a good knowledge of the vibrational characteristics of the internal structures, as well as the measurements made during hot tests of certain reactors which made it possible to qualify these models on real structures. The second part describes the means of detection (neutron noise, external accelerometers) as well as the processing methods used in the follow-up. A few typical results obtained on site are then presented. Finally, the general principles of operational monitoring of the mechanical behavior of the internal structures are described [fr
Passive Vibration Control of Existing Structures by Gravity-Loaded Cables
Alvis, E.; Tsang, H. H.; Hashemi, M. J.
2017-06-01
Structures with high concentration of mass at or close to the top such as highway bridge piers are vulnerable in earthquakes or accidents. In this paper, a simple and convenient retrofit strategy is proposed for minimizing vibrations and damages, extending service life and preventing collapse of existing structures. The proposed system comprises of tension-only cables secured to the sides of the structure through gravity anchor blocks that are free to move in vertical shafts. The system is installed in such a way that the cables do not induce unnecessary stress on the main structure when there is no lateral motion or vibration. The effectiveness of controlling global structural responses is investigated for tension-only bilinear-elastic behaviour of cables. Results of a realistic case study for a reinforced concrete bridge pier show that response reduction is remarkably well under seismic excitation.
Vibration test of spherical shell structure and replacing method into mathematical model
International Nuclear Information System (INIS)
Takayanagi, M.; Suzuki, S.; Okamura, T.; Haas, E.E.; Krutzik, N.J.
1989-01-01
To verify the beam-type and oval-type vibratory characteristics of a spherical shell structure, two test specimens were made and vibration tests were carried out. Results of these tests are compared with results of detailed analyses using 3-D FEM and 2-D axisymmetric FEM models. The analytical results of overall vibratory characteristics are in good agreement with the test results, has been found that the effect of the attached mass should be considered in evaluating local vibration. The replacing method into equivalent beam model is proposed
Effect of Space Vehicle Structure Vibration on Control Moment Gyroscope Dynamics
Dobrinskaya, Tatiana
2008-01-01
Control Moment Gyroscopes (CMGs) are used for non-propulsive attitude control of satellites and space stations, including the International Space Station (ISS). CMGs could be essential for future long duration space missions due to the fact that they help to save propellant. CMGs were successfully tested on the ground for many years, and have been successfully used on satellites. However, operations have shown that the CMG service life on the ISS is significantly shorter than predicted. Since the dynamic environment of the ISS differs greatly from the nominal environment of satellites, it was important to analyze how operations specific to the station (dockings and undockings, huge solar array motion, crew exercising, robotic operations, etc) can affect the CMG performance. This task became even more important since the first CMG failure onboard the ISS. The CMG failure resulted in the limitation of the attitude control capabilities, more propellant consumption, and additional operational issues. Therefore, the goal of this work was to find out how the vibrations of a space vehicle structure, caused by a variety of onboard operations, can affect the CMG dynamics and performance. The equations of CMG motion were derived and analyzed for the case when the gyro foundation can vibrate in any direction. The analysis was performed for unbalanced CMG gimbals to match the CMG configuration on ISS. The analysis showed that vehicle structure vibrations can amplify and significantly change the CMG motion if the gyro gimbals are unbalanced in flight. The resonance frequencies were found. It was shown that the resonance effect depends on the magnitude of gimbal imbalance, on the direction of a structure vibration, and on gimbal bearing friction. Computer modeling results of CMG dynamics affected by the external vibration are presented. The results can explain some of the CMG vibration telemetry observed on ISS. This work shows that balancing the CMG gimbals decreases the effect
Energy-averaged neutron cross sections of fast-reactor structural materials
International Nuclear Information System (INIS)
Smith, A.; McKnight, R.; Smith, D.
1978-02-01
The status of energy-averaged cross sections of fast-reactor structural materials is outlined with emphasis on U.S. data programs in the neutron-energy range 1-10 MeV. Areas of outstanding accomplishment and significant uncertainty are noted with recommendations for future efforts. Attention is primarily given to the main constituents of stainless steel (e.g., Fe, Ni, and Cr) and, secondarily, to alternate structural materials (e.g., V, Ti, Nb, Mo, Zr). Generally, the mass regions of interest are A approximately 50 to 60 and A approximately 90 to 100. Neutron total and elastic-scattering cross sections are discussed with the implication on the non-elastic-cross sections. Cross sections governing discrete-inelastic-neutron-energy transfers are examined in detail. Cross sections for the reactions (n;p), (n;n',p), (n;α), (n;n',α) and (n;2n') are reviewed in the context of fast-reactor performance and/or diagnostics. The primary orientation of the discussion is experimental with some additional attention to the applications of theory, the problems of evaluation and the data sensitivity of representative fast-reactor systems
Reconstruction of 3D structures of MET antibodies from electron microscopy 2D class averages.
Directory of Open Access Journals (Sweden)
Qi Chen
Full Text Available Dynamics of three MET antibody constructs (IgG1, IgG2, and IgG4 and the IgG4-MET antigen complex was investigated by creating their atomic models with an integrative experimental and computational approach. In particular, we used two-dimensional (2D Electron Microscopy (EM images, image class averaging, homology modeling, Rapidly exploring Random Tree (RRT structure sampling, and fitting of models to images, to find the relative orientations of antibody domains that are consistent with the EM images. We revealed that the conformational preferences of the constructs depend on the extent of the hinge flexibility. We also quantified how the MET antigen impacts on the conformational dynamics of IgG4. These observations allow to create testable hypothesis to investigate MET biology. Our protocol may also help describe structural diversity of other antigen systems at approximately 5 Å precision, as quantified by Root-Mean-Square Deviation (RMSD among good-scoring models.
Directory of Open Access Journals (Sweden)
Douglas Domingues Bueno
2008-01-01
Full Text Available This paper deals with the study of algorithms for robust active vibration control in flexible structures considering uncertainties in system parameters. It became an area of enormous interest, mainly due to the countless demands of optimal performance in mechanical systems as aircraft, aerospace, and automotive structures. An important and difficult problem for designing active vibration control is to get a representative dynamic model. Generally, this model can be obtained using finite element method (FEM or an identification method using experimental data. Actuators and sensors may affect the dynamics properties of the structure, for instance, electromechanical coupling of piezoelectric material must be considered in FEM formulation for flexible and lightly damping structure. The nonlinearities and uncertainties involved in these structures make it a difficult task, mainly for complex structures as spatial truss structures. On the other hand, by using an identification method, it is possible to obtain the dynamic model represented through a state space realization considering this coupling. This paper proposes an experimental methodology for vibration control in a 3D truss structure using PZT wafer stacks and a robust control algorithm solved by linear matrix inequalities.
Formation and vibrational structure of Si nano-clusters in ZnO matrix
Energy Technology Data Exchange (ETDEWEB)
Garcia-Serrano, J. [Universidad Autonoma del Estado de Hidalgo, Hidalgo (Mexico); Pal, U. [Universidad Autonoma de Puebla, Puebla (Mexico); Koshizaki, N.; Sasaki, T. [National Institute of Materials and Chemical Research, Ibaraki (Japan)
2001-02-01
We have studied the formation and vibrational structure of Si nano-clusters in ZnO matrix prepared by radio-frequency (r.f.) co-sputtering, and characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) spectroscopy techniques. The composite films of Si/ZnO were grown o quartz substrates by co-sputtering of Si and ZnO targets. TEM images show a homogeneous distribution of clusters in the matrix with average size varied from 3.7 nm to 34 nm depending on the temperature of annealing. IR absorption measurements revealed the bands correspond to the modes of vibrations of Si{sub 3} in its triangular geometrical structure. By analysing the IR absorption and XPS spectra we found that the nano-clusters consist of a Si{sub 3} core and a SiO{sub x} cap layer. With the increase of annealing temperature, the vibrational states of Si changed from the triplet {sup 3}B1(C2{sub v}) and {sup 3}A'{sub 2}(D{sub 3h}) states to its singlet ground state {sup 1}A{sub 1}(C2{sub v}) and the oxidation state of Si in SiO{sub x} increased. The evolution of the local atomic structure of the Si nano-clusters with the variation of Si content in the film and with the variation of the temperature of annealing are discussed. [Spanish] Se estudia la formacion y estructura vibracional de nano-cumulos de Si en matriz de ZnO preparados por la tecnica de radio-frecuencia (r.f.) co-sputtering, y caracterizados por Microscopia Electronica de Transmision (TEM), Espectroscopia Fotoelectronica de rayos X (XPS) y Espectroscopia de Infrarrojo (IR). Las peliculas compositas de Si/ZnO fueron crecidas sobre sustratos de cuarzo mediante el co-sputtering de blancos de Si y ZnO. Las imagenes de TEM mostraron una distribucion homogenea de cumulos en la matriz con un tamano promedio de 3.7 nm a 34 nm dependiendo de la temperatura de tratamiento. Las mediciones de IR relevaron las bandas correspondientes a los modos de vibracion de Si{sub 3} en su estructura
Uncertainty and Variation of Vibration in Lightweight Structures
DEFF Research Database (Denmark)
Dickow, Kristoffer Ahrens
2012-01-01
Multi-family dwellings and ofﬁces build from lightweight materials are becoming a cost efﬁcient and environmentally friendly alternative to traditional heavy structures.......Multi-family dwellings and ofﬁces build from lightweight materials are becoming a cost efﬁcient and environmentally friendly alternative to traditional heavy structures....
Ab initio and DFT studies of the structure and vibrational spectra of anhydrous caffeine
Srivastava, Santosh K.; Singh, Vipin B.
2013-11-01
Vibrational spectra and molecular structure of anhydrous caffeine have been systematically investigated by second order Moller-Plesset (MP2) perturbation theory and density functional theory (DFT) calculations. Vibrational assignments have been made and many previous ambiguous assignments in IR and Raman spectra are amended. The calculated DFT frequencies and intensities at B3LYP/6-311++G(2d,2p) level, were found to be in better agreement with the experimental values. It was found that DFT with B3LYP functional predicts harmonic vibrational wave numbers more close to experimentally observed value when it was performed on MP2 optimized geometry rather than DFT geometry. The calculated TD-DFT vertical excitation electronic energies of the valence excited states of anhydrous caffeine are found to be in consonance to the experimental absorption peaks.
International Nuclear Information System (INIS)
Preumont, A.; Shilab, S.; Cornaggia, L.; Reale, M.; Labbe, P.; Noe, H.
1992-01-01
This benchmark exercise is the continuation of the state-of-the-art review (EUR 11369 EN) which concluded that the random vibration approach could be an effective tool in seismic analysis of nuclear power plants, with potential advantages on time history and response spectrum techniques. As compared to the latter, the random vibration method provides an accurate treatment of multisupport excitations, non classical damping as well as the combination of high-frequency modal components. With respect to the former, the random vibration method offers direct information on statistical variability (probability distribution) and cheaper computations. The disadvantages of the random vibration method are that it is based on stationary results, and requires a power spectral density input instead of a response spectrum. A benchmark exercise to compare the three methods from the various aspects mentioned above, on one or several simple structures has been made. The following aspects have been covered with the simplest possible models: (i) statistical variability, (ii) multisupport excitation, (iii) non-classical damping. The random vibration method is therefore concluded to be a reliable method of analysis. Its use is recommended, particularly for preliminary design, owing to its computational advantage on multiple time history analysis
Vibronic-structure tracking: A shortcut for vibrationally resolved UV/Vis-spectra calculations
Energy Technology Data Exchange (ETDEWEB)
Barton, Dennis; König, Carolin; Neugebauer, Johannes, E-mail: j.neugebauer@uni-muenster.de [Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster (Germany)
2014-10-28
The vibrational coarse structure and the band shapes of electronic absorption spectra are often dominated by just a few molecular vibrations. By contrast, the simulation of the vibronic structure even in the simplest theoretical models usually requires the calculation of the entire set of normal modes of vibration. Here, we exploit the idea of the mode-tracking protocol [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] in order to directly target and selectively calculate those normal modes which have the largest effect on the vibronic band shape for a certain electronic excitation. This is achieved by defining a criterion for the importance of a normal mode to the vibrational progressions in the absorption band within the so-called “independent mode, displaced harmonic oscillator” (IMDHO) model. We use this approach for a vibronic-structure investigation for several small test molecules as well as for a comparison of the vibronic absorption spectra of a truncated chlorophyll a model and the full chlorophyll a molecule. We show that the method allows to go beyond the often-used strategy to simulate absorption spectra based on broadened vertical excitation peaks with just a minimum of computational effort, which in case of chlorophyll a corresponds to about 10% of the cost for a full simulation within the IMDHO approach.
A new electromagnetic shunt damping treatment and vibration control of beam structures
International Nuclear Information System (INIS)
Niu Hongpan; Zhang Xinong; Xie Shilin; Wang Pengpeng
2009-01-01
In this paper a new class of shunted electromagnetic damping treatment is proposed: a non-contact electromagnetic shunt damper (NC-EMSD). The NC-EMSD consists of an electromagnet attached to a host structure, a permanent magnet attached to the fixed boundary and an electrical impedance connected to the terminals of the electromagnet. The electromagnet and the shunt impedance constitute a closed circuit. When the structure vibrates, an induced electromotive force will be produced and results in the electromagnetic force as damping force, which can suppress the vibration of the structure. The model of NC-EMSD is built up based on the equivalent current method. The governing equations of the beam with NC-EMSD are established using Hamilton's principle. The capacitor-matching-inductance (CMI) method and the negative resistive capacitor-matching-inductance (NR-CMI) method are proposed, respectively. Then the vibration control of a cantilever beam with NC-EMSD is simulated and measured by CMI and NR-CMI control methods, respectively. The results show that both the CMI and NR-CMI can attenuate the vibration effectively, and the NR-CMI provides much better control performance than that by CMI. It is indicated as well from the studies that the decrease of either the gap between the magnet pair or the resistance of the shunt impedance contributes to the improvement of control performance
Directory of Open Access Journals (Sweden)
Elham Ghandi
2016-09-01
Full Text Available The free vibration of frame structures has been usually studied in literature without considering the effect of axial loads. In this paper, the continuous system method is employed to investigate this effect on the free flexural and torsional vibration of two and three dimensional symmetric frames. In the continuous system method, in approximate analysis of buildings, commonly, the structure is replaced by an equivalent beam which matches the dominant characteristics of the structure. Accordingly, the natural frequencies of the symmetric frame structures are obtained through solving the governing differential equation of the equivalent beam whose stiffness and mass are supposed to be uniformly distributed along the length. The corresponding axial load applied to the replaced beam is calculated based on the total weight and the number of stories of the building. A numerical example is presented to show the simplicity and efficiency of the proposed solution.
Modelling, structural, thermal, optical and vibrational studies of a ...
Indian Academy of Sciences (India)
chemical density functional theory (DFT) calculation. ... Recently, much attention has been devoted to the large family of organic–inorganic metal halides due to their partic- ular structural features and physical properties. ... Integration.
International Nuclear Information System (INIS)
Perotin, L.; Granger, S.
1997-01-01
In order to improve the prediction of wear problems due to flow-induced vibration in PWR components, an inverse method for identifying a distributed random excitation acting on a dynamical system has been developed at EDF. This method, whose applications go far beyond the flow-induced vibration field, has been implemented into the MEIDEE software. This method is presented. (author)
Huo, Linsheng; Qu, Chunxu; Li, Hongnan
2014-01-01
Passive liquid dampers have been used to effectively reduce the dynamic response of civil infrastructures subjected to earthquakes or strong winds. The design of liquid dampers for structural vibration control involves the determination of the optimal parameters. This paper presents an optimal design methodology for tuned liquid column dampers (TLCDs) based on the H∞ control theory. A practical structure, Dalian Xinghai Financial Business Building, is used to illustrate the feasibility of the...
Vibrational structures in electron-CO2 scattering below the 2Πu shape resonance
International Nuclear Information System (INIS)
Allan, Michael
2002-01-01
Structures of vibrational origin were discovered in vibrationally inelastic electron-CO 2 cross sections in the energy range 0.4-0.9 eV, well below the 2 Π u shape resonance. They appear in the excitation of higher vibrational levels, in particular the highest members of the Fermi polyads of the type (n, 2m, 0) with n+m=2-4. The lowest two structures, at 0.445 and 0.525 eV, are narrow; higher-lying structures are broader and boomerang-like. The structures are absent when the antisymmetric stretch is co-excited. The structures are interpreted in terms of a wavepacket of the nuclei reflected from a potential surface of the CO 2 - anion in a bent and stretched geometry. A state emerging from the virtual state upon bending and stretching and the state resulting from bending the 2 Π u shape resonance are discussed as possibly being responsible for the structures. (author). Letter-to-the-editor
Fluid-structure finite-element vibrational analysis
Feng, G. C.; Kiefling, L.
1974-01-01
A fluid finite element has been developed for a quasi-compressible fluid. Both kinetic and potential energy are expressed as functions of nodal displacements. Thus, the formulation is similar to that used for structural elements, with the only differences being that the fluid can possess gravitational potential, and the constitutive equations for fluid contain no shear coefficients. Using this approach, structural and fluid elements can be used interchangeably in existing efficient sparse-matrix structural computer programs such as SPAR. The theoretical development of the element formulations and the relationships of the local and global coordinates are shown. Solutions of fluid slosh, liquid compressibility, and coupled fluid-shell oscillation problems which were completed using a temporary digital computer program are shown. The frequency correlation of the solutions with classical theory is excellent.
Temperature dependent structural and vibrational properties of liquid indium
Patel, A. B.; Bhatt, N. K.
2018-05-01
The influence of the temperature effect on both the structure factor and the phonon dispersion relation of liquid indium have been investigated by means of pseudopotential theory. The Percus-Yevick Hard Sphere reference system is applied to describe the structural calculation. The effective electron-ion interaction is explained by using modified empty core potential due to Hasegawa et al. along with a local field correction function due to Ichimaru-Utsumi (IU). The temperature dependence of pair potential needed at higher temperatures was achieved by multiplying the damping factor exp(- π/kBT2k F r ) in the pair potential. Very close agreement of static structure factor, particularly, at elevated temperatures confirms the validity of the local potential. A positive dispersion is found in low-q region and the correct trend of phonon dispersion branches like the experimental; shows all broad features of collective excitations in liquid metals.
Energy Technology Data Exchange (ETDEWEB)
Dimitrievska, Mirjana; White, James L.; Zhou, Wei; Stavila, Vitalie; Klebanoff, Leonard E.; Udovic, Terrence J.
2016-01-01
The structure-dependent vibrational properties of different Mg(BH4)2 polymorphs (..alpha.., ..beta.., ..gamma.., and ..delta.. phases) were investigated with a combination of neutron vibrational spectroscopy (NVS) measurements and density functional theory (DFT) calculations, with emphasis placed on the effects of the local structure and orientation of the BH4- anions. DFT simulations closely match the neutron vibrational spectra. The main bands in the low-energy region (20-80 meV) are associated with the BH4- librational modes. The features in the intermediate energy region (80-120 meV) are attributed to overtones and combination bands arising from the lower-energy modes. The features in the high-energy region (120-200 meV) correspond to the BH4- symmetric and asymmetric bending vibrations, of which four peaks located at 140, 142, 160, and 172 meV are especially intense. There are noticeable intensity distribution variations in the vibrational bands for different polymorphs. This is explained by the differences in the spatial distribution of BH4- anions within various structures. An example of the possible identification of products after the hydrogenation of MgB2, using NVS measurements, is presented. These results provide fundamental insights of benefit to researchers currently studying these promising hydrogen-storage materials.
Effect of curvature on structures and vibrations of zigzag carbon ...
Indian Academy of Sciences (India)
Wintec
tronic structures, full phonon dispersions and thermal properties of zigzag single wall carbon nanotubes. (SWCNTs) are presented. ... estimate thermal expansion coefficient of nanotubes within a quasiharmonic approximation and identify the modes that ... the linear scaling mode, we used an option of explicit. *Author for ...
Molecular and vibrational structure of 2,2'-dihydroxybenzophenone
DEFF Research Database (Denmark)
Birklund Andersen, Kristine; Langgård, M.; Spanget-Larsen, Jens
1999-01-01
2,2'-dihydroxybenzophenone (DHBP) contains similar bifold intramolecular H-bonding as the psoriatic drug anthralin, but because of steric interference the phenolic rings are twisted in a propeller-like manner, resulting in a molecular structure of C2 symmetry. In contrast to the case of C2v...
Molecular and vibrational structure of 2,2'-dihydroxybenzophenone
DEFF Research Database (Denmark)
Birklund Andersen, Kristine; Langgård, M.; Spanget-Larsen, Jens
1999-01-01
2,2'-dihydroxybenzophenone (DHBP) contains similar bifold intramolecular H-bonding as the psoriatic drug anthralin, but because of steric interference the phenolic rings are twisted in a propeller-like manner, resulting in a molecular structure of C2 symmetry. In contrast to the case of C2v anthr...
Sakellariou, J. S.; Fassois, S. D.
2006-11-01
A stochastic output error (OE) vibration-based methodology for damage detection and assessment (localization and quantification) in structures under earthquake excitation is introduced. The methodology is intended for assessing the state of a structure following potential damage occurrence by exploiting vibration signal measurements produced by low-level earthquake excitations. It is based upon (a) stochastic OE model identification, (b) statistical hypothesis testing procedures for damage detection, and (c) a geometric method (GM) for damage assessment. The methodology's advantages include the effective use of the non-stationary and limited duration earthquake excitation, the handling of stochastic uncertainties, the tackling of the damage localization and quantification subproblems, the use of "small" size, simple and partial (in both the spatial and frequency bandwidth senses) identified OE-type models, and the use of a minimal number of measured vibration signals. Its feasibility and effectiveness are assessed via Monte Carlo experiments employing a simple simulation model of a 6 storey building. It is demonstrated that damage levels of 5% and 20% reduction in a storey's stiffness characteristics may be properly detected and assessed using noise-corrupted vibration signals.
Probabilistic analysis of wind-induced vibration mitigation of structures by fluid viscous dampers
Chen, Jianbing; Zeng, Xiaoshu; Peng, Yongbo
2017-11-01
The high-rise buildings usually suffer from excessively large wind-induced vibrations, and thus vibration control systems might be necessary. Fluid viscous dampers (FVDs) with nonlinear power law against velocity are widely employed. With the transition of design method from traditional frequency domain approaches to more refined direct time domain approaches, the difficulty of time integration of these systems occurs sometimes. In the present paper, firstly the underlying reason of the difficulty is revealed by identifying that the equations of motion of high-rise buildings installed with FVDs are sometimes stiff differential equations. Thus, an approach effective for stiff differential systems, i.e., the backward difference formula (BDF), is then introduced, and verified to be effective for the equation of motion of wind-induced vibration controlled systems. Comparative studies are performed among some methods, including the Newmark method, KR-alpha method, energy-based linearization method and the statistical linearization method. Based on the above results, a 20-story steel frame structure is taken as a practical example. Particularly, the randomness of structural parameters and of wind loading input is emphasized. The extreme values of the responses are examined, showing the effectiveness of the proposed approach, and also necessitating the refined probabilistic analysis in the design of wind-induced vibration mitigation systems.
International Nuclear Information System (INIS)
Jiang, Jian-ping; Li, Dong-xu
2010-01-01
The decentralized robust vibration control with collocated piezoelectric actuator and strain sensor pairs is considered in this paper for spacecraft solar panel structures. Each actuator is driven individually by the output of the corresponding sensor so that only local feedback control is implemented, with each actuator, sensor and controller operating independently. Firstly, an optimal placement method for the location of the collocated piezoelectric actuator and strain gauge sensor pairs is developed based on the degree of observability and controllability indices for solar panel structures. Secondly, a decentralized robust H ∞ controller is designed to suppress the vibration induced by external disturbance. Finally, a numerical comparison between centralized and decentralized control systems is performed in order to investigate their effectiveness to suppress vibration of the smart solar panel. The simulation results show that the vibration can be significantly suppressed with permitted actuator voltages by the controllers. The decentralized control system almost has the same disturbance attenuation level as the centralized control system with a bit higher control voltages. More importantly, the decentralized controller composed of four three-order systems is a better practical implementation than a high-order centralized controller is
Directory of Open Access Journals (Sweden)
Adrien Oth
2012-01-01
Full Text Available Major threats to bridges primarily consist of the aging of the structural elements, earthquake-induced shaking and standing waves generated by windstorms. The necessity of information on the state of health of structures in real-time, allowing for timely warnings in the case of damaging events, requires structural health monitoring (SHM systems that allow the risks of these threats to be mitigated. Here we present the results of a short-duration experiment carried out with low-cost wireless instruments for monitoring the vibration characteristics and dynamic properties of a strategic civil infrastructure, the Adolphe Bridge in Luxembourg City. The Adolphe Bridge is a masonry arch construction dating from 1903 and will undergo major renovation works in the upcoming years. Our experiment shows that a network of these wireless sensing units is well suited to monitor the vibration characteristics of such a historical arch bridge and hence represents a low-cost and efficient solution for SHM.
Energy Technology Data Exchange (ETDEWEB)
Jurado, J. F.; Londono C, A.; Jurado L, F. F.; Romero S, J. D., E-mail: jfjurado@unal.edu.co [Universidad Nacional de Colombia, Laboratorio de Propiedades Termicas Dielectricas de Compositos, A. A. 127, Manizales (Colombia)
2014-07-01
The synthesis of Zn O by reaction in solid state from two precursor salts (zinc acetate and zinc sulfate), presented significant differences concerning morphology, structure, vibrational order and optical gap. As well as covering in the size of the compounds, a homogeneous distribution of nanoparticles of 21±3 nm and micro stars of 1.03±0.19 μm respectively. The Zn O showed a structural phase with a vibrational state of the hexagonal type (wurtzite). The variation in the morphology due to the precursor is attributed to the disorder within of lattice, which contributes to vibrational changes and is correlated to the degrees of freedom of molecules. Measurements of UV-Vis of nanoparticles displayed a band gap (E{sub g}) lower than the one reported for the bulk material. The structural characterization of the compounds was carried out by using a X-ray Bruker D8 Advance diffractometer. The vibrational order was assessed throughout micro-Raman with a monochromatic radiation source of 473 nm). (Author)
Complex modes and frequencies in damped structural vibrations
DEFF Research Database (Denmark)
Krenk, Steen
2004-01-01
It is demonstrated that the state space formulation of the equation of motion of damped structural elements like cables and beams leads to a symmetric eigenvalue problem if the stiffness and damping operators are self-adjoint, and that this is typically the case in the absence of gyroscopic forces....... The corresponding theory of complex modal analysis of continuous systems is developed and illustrated in relation to optimal damping and impulse response of cables and beams with discrete dampers....
International Nuclear Information System (INIS)
Lee, D.E.
1988-06-01
The vibrational behaviour of the generator support structure at Koeberg nuclear power station at frequencies primarily in the region of 80 Hz to 110 Hz was examined. The effect of soil-structure interaction and the change in stiffness of the foundation soil was investigated. Vibration tests were performed on the generator support structure and the results were compared with a theoretical finite element analysis of the structure. By varying the soil-cement foundation stiffness it was possible to demonstrate the change in dynamic behaviour of the structure in the higher frequency band 80 Hz to 110 Hz. Comment has been made on the design code DIN 4024 in view of the findings of this thesis. It was concluded that the empirical rules regarding the inclusion of the foundation in an analysis specified by the code do not cover all cases and greater cognisance of the effect of the foundation stiffness on the vibration behaviour of such machine foundations is necessary. Obvious machine frequencies higher than the operational frequencies should be analysed where it is considered necessary. 24 refs., 25 tabs., 83 figs
International Nuclear Information System (INIS)
Ayikoglu, A.
2008-01-01
The molecular structure, vibrational frequencies and corresponding vibrational assignments of tetrafluoro isophthalonitrile (TFPN) in the ground state have been calculated using the Hartree-Fock (HF) and density functional methods (B3LYP) with 6-311++G (d, p) basis set. The calculations were utilized in the CS symmetry of TFPN. The obtained vibrational frequencies and optimized geometric parameters (bond lengths and bond angles) were seen to be in good agreement with the experimental data. The comparison of the observed and calculated results showed that the B3LYP method is superior to the HF method for both the vibrational frequencies and geometric parameters
Forced vibration and wave propagation in mono-coupled periodic structures
DEFF Research Database (Denmark)
Ohlrich, Mogens
1986-01-01
This paper describes the wave propagation and vibration characteristics of mono-coupled structures which are of spatially periodic nature. The receptance approach to periodic structure theory is applied to study undamped periodic systems with composite structural elements; particular emphasis...... and a general `closed form' solution is found for the forced harmonic response at element junctions. This `junction-receptance' is used to determine-discrete junction mode shapes of a finite system. Finally, the forced response of a finite structure with an internal obstruction is derived as a natural extension...... of the determination of the junction-receptance. The influence of such a disorder is illustrated by a simple example...
Dimitrić Marković, Jasmina M; Marković, Zoran S; Milenković, Dejan; Jeremić, Svetlana
2011-12-01
This paper addresses experimental and theoretical research in fisetin (2-(3,4-dihydroxyphenyl)-3,7-dihydroxychromen-4-one) structure by means of experimental IR and Raman spectroscopies and mechanistic calculations. Density Functional Theory calculations, with M05-2X functional and the 6-311+G (2df, p) basis set implemented in the Gaussian 09 package, are performed with the aim to support molecular structure, vibrational bands' positions and their intensities. Potential energy distribution (PED) values and the description of the largest vibrational contributions to the normal modes are calculated. The most intense bands appear in the 1650-1500 cm(-1) wavenumber region. This region involves a combination of the CO, C2C3 and C-C stretching vibrational modes. Most of the bands in the 1500-1000 cm(-1) range involve C-C stretching, O-C stretching and in-plane C-C-H, C-O-H, C-C-O and C-C-C bending vibrations of the rings. The region below 1000 cm(-1) is characteristic to the combination of in plane C-C-C-H, H-C-C-H, C-C-C-C, C-C-O-C and out of plane O-C-C-C, C-C-O-C, C-C-C-C torsional modes. The Raman spectra of baicalein and quercetin were used for qualitative comparison with fisetin spectrum and verification of band assignments. The applied detailed vibrational spectral analysis and the assignments of the bands, proposed on the basis of fundamentals, reproduced the experimental results with high degree of accuracy. Copyright © 2011 Elsevier B.V. All rights reserved.
Dimitrić Marković, Jasmina M.; Marković, Zoran S.; Milenković, Dejan; Jeremić, Svetlana
2011-12-01
This paper addresses experimental and theoretical research in fisetin (2-(3,4-dihydroxyphenyl)-3,7-dihydroxychromen-4-one) structure by means of experimental IR and Raman spectroscopies and mechanistic calculations. Density Functional Theory calculations, with M05-2X functional and the 6-311+G (2df, p) basis set implemented in the Gaussian 09 package, are performed with the aim to support molecular structure, vibrational bands' positions and their intensities. Potential energy distribution (PED) values and the description of the largest vibrational contributions to the normal modes are calculated. The most intense bands appear in the 1650-1500 cm -1 wavenumber region. This region involves a combination of the C dbnd O, C2 dbnd C3 and C-C stretching vibrational modes. Most of the bands in the 1500-1000 cm -1 range involve C-C stretching, O-C stretching and in-plane C-C-H, C-O-H, C-C-O and C-C-C bending vibrations of the rings. The region below 1000 cm -1 is characteristic to the combination of in plane C-C-C-H, H-C-C-H, C-C-C-C, C-C-O-C and out of plane O-C-C-C, C-C-O-C, C-C-C-C torsional modes. The Raman spectra of baicalein and quercetin were used for qualitative comparison with fisetin spectrum and verification of band assignments. The applied detailed vibrational spectral analysis and the assignments of the bands, proposed on the basis of fundamentals, reproduced the experimental results with high degree of accuracy.
Application of the random vibration approach in the seismic analysis of LMFBR structures
International Nuclear Information System (INIS)
Preumont, A.
1988-01-01
The first part discusses the general topic of the spectral analysis of linear multi-degree-of-freedom structure subjected to a stationary random field. Particular attention is given to structures with non-classical damping and hereditary characteristics. The method is implemented in the computer programme RANDOM. Next, the same concepts are applied to multi-supported structures subjected to a stationary seismic excitation. The method is implemented in the computer programme SEISME. Two related problems are dealt with in the next two chapters: (i) the relation between the input of the random vibration analysis and the traditional ground motion specification for seismic analysis (the Design Response Spectra) and (ii) the application of random vibration techniques to the direct generation of floor response spectra. Finally the problem of extracting information from costly time history analyses is addressed. This study has mainly been concerned with the methodology and the development of appropriate softwares. Some qualitative conclusions have been drawn regarding the expected benefit of the approach. They have been judged promising enough to motivate a benchmark exercise. Specifically, the random vibration approach will be compared to the current approximate methods (response spectrum) and time-history analyses (considered as representative of the true response) for a set of typical structures. The hope is that some of the flaws of the current approximate methods can be removed
An Equivalent Circuit of Longitudinal Vibration for a Piezoelectric Structure with Losses.
Yuan, Tao; Li, Chaodong; Fan, Pingqing
2018-03-22
Equivalent circuits of piezoelectric structures such as bimorphs and unimorphs conventionally focus on the bending vibration modes. However, the longitudinal vibration modes are rarely considered even though they also play a remarkable role in piezoelectric devices. Losses, especially elastic loss in the metal substrate, are also generally neglected, which leads to discrepancies compared with experiments. In this paper, a novel equivalent circuit with four kinds of losses is proposed for a beamlike piezoelectric structure under the longitudinal vibration mode. This structure consists of a slender beam as the metal substrate, and a piezoelectric patch which covers a partial length of the beam. In this approach, first, complex numbers are used to deal with four kinds of losses-elastic loss in the metal substrate, and piezoelectric, dielectric, and elastic losses in the piezoelectric patch. Next in this approach, based on Mason's model, a new equivalent circuit is developed. Using MATLAB, impedance curves of this structure are simulated by the equivalent circuit method. Experiments are conducted and good agreements are revealed between experiments and equivalent circuit results. It is indicated that the introduction of four losses in an equivalent circuit can increase the result accuracy considerably.
GaAs nanocrystals: Structure and vibrational properties
International Nuclear Information System (INIS)
Nayak, J.; Sahu, S.N.; Nozaki, S.
2006-01-01
GaAs nanocrystals were grown on indium tin oxide substrate by an electrodeposition technique. Atomic force microscopic measurement indicates an increase in the size of the nanocrystal with decrease in the electrolysis current density accompanied by the change in the shape of the crystallite. Transmission electron microscopic measurements identify the crystallite sizes to be in the range of 10-15 nm and the crystal structure to be orthorhombic. On account of the quantum size effect, the first optical transition was blue shifted with respect to the band gap of the bulk GaAs and the excitonic peak appeared prominent. A localized phonon mode ascribed to certain point defect occurred in the room temperature micro-Raman spectrum
Structural characterization of chiral molecules using vibrational circular dichroism spectroscopy
DEFF Research Database (Denmark)
Lassen, Peter Rygaard
2006-01-01
comparison of experimental and calculated spectra. Theoretical structures of the sample molecules were constructed and optimized using molecular mechanical force fields followed by the quantum mechanical method density functional theory (DFT). Calculations of IR absorption and VCD spectra were then carried...... out using the same DFT methods. Here, VCD has the advantage over CD that time-independent DFT calculations are sufficient. During the course of this project, the above methodology has been applied to a range of molecules. Some of them (nyasol, curcuphenol dimers and ginkgolide) are purely organic...... or as flexible as the curcuphenol dimer with 11 variable dihedral angles. This illustrates the capabilities of the method, which are primarily limited by the duration of DFT calculations. In the case of metal complexes, they have only recently become within reach of DFT, which opens new possibilities...
On the dimension of complex responses in nonlinear structural vibrations
Wiebe, R.; Spottswood, S. M.
2016-07-01
The ability to accurately model engineering systems under extreme dynamic loads would prove a major breakthrough in many aspects of aerospace, mechanical, and civil engineering. Extreme loads frequently induce both nonlinearities and coupling which increase the complexity of the response and the computational cost of finite element models. Dimension reduction has recently gained traction and promises the ability to distill dynamic responses down to a minimal dimension without sacrificing accuracy. In this context, the dimensionality of a response is related to the number of modes needed in a reduced order model to accurately simulate the response. Thus, an important step is characterizing the dimensionality of complex nonlinear responses of structures. In this work, the dimensionality of the nonlinear response of a post-buckled beam is investigated. Significant detail is dedicated to carefully introducing the experiment, the verification of a finite element model, and the dimensionality estimation algorithm as it is hoped that this system may help serve as a benchmark test case. It is shown that with minor modifications, the method of false nearest neighbors can quantitatively distinguish between the response dimension of various snap-through, non-snap-through, random, and deterministic loads. The state-space dimension of the nonlinear system in question increased from 2-to-10 as the system response moved from simple, low-level harmonic to chaotic snap-through. Beyond the problem studied herein, the techniques developed will serve as a prescriptive guide in developing fast and accurate dimensionally reduced models of nonlinear systems, and eventually as a tool for adaptive dimension-reduction in numerical modeling. The results are especially relevant in the aerospace industry for the design of thin structures such as beams, panels, and shells, which are all capable of spatio-temporally complex dynamic responses that are difficult and computationally expensive to
DEFF Research Database (Denmark)
Liang, Shanshan; Crovetto, Andrea; Peng, Zhuoteng
2016-01-01
and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity......This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision...
DEFF Research Database (Denmark)
Bucinskas, Paulius; Andersen, Lars Vabbersgaard; Persson, Kent
2016-01-01
Construction of high speed railway lines has been an increasing trend in recent years. Countries like Denmark and Sweden plan to expand and upgrade their railways to accommodate high-speed traffic. To benefit from the full potential of the reduced commuting times, these lines must pass through...... densely populated urban areas with the collateral effect of increased noise and vibrations levels. This paper aims to quantify the vibrations levels in the area surrounding an elevated railway line built as a multi-span bridge structure. The proposed model employs finite-element analysis to model......-space. The paper analyses the effects of structure-soil-structure interaction on the dynamic behaviour of the surrounding soil surface. The effects of different soil stratification and material properties as well as different train speeds are assessed. Finally, the drawbacks of simplifying the numerical model...
Structural vibration control of micro/macro-manipulator using feedforward and feedback approaches
International Nuclear Information System (INIS)
Lew, J.Y.; Cannon, D.W.; Magee, D.P.; Book, W.J.
1995-09-01
Pacific Northwest Laboratory (PDL) researchers investigated the combined use of two control approaches to minimize micro/macro-manipulator structural vibration: (1) modified input shaping and (2) inertial force active damping control. Modified input shaping (MIS) is used as a feedforward controller to modify reference input by canceling the vibratory motion. Inertial force active damping (IFAD) is applied as a feedback controller to increase the system damping and robustness to unexpected disturbances. Researchers implemented both control schemes in the PNL micro/macro flexible-link manipulator testbed collaborating with Georgia Institute of Technology. The experiments successfully demonstrated the effectiveness of two control approaches in reducing structural vibration. Based on the results of the experiments, the combined use of two controllers is recommended for a micro/macro manipulator to achieve the fastest response to commands while canceling disturbances from unexpected forces
Ab-initio study of structural, vibrational and optical properties of solid oxidizers
Energy Technology Data Exchange (ETDEWEB)
Yedukondalu, N.; Vaitheeswaran, G., E-mail: gvsp@uohyd.ernet.in
2016-09-15
We report the structural, elastic and vibrational properties of five ionic-molecular solid oxidizers MNO{sub 3} (M = Li, Na, K) and MClO{sub 3} (M = Na, K). By treating long range electron-correlation effects, dispersion corrected method leads to more accurate predictions of structural properties and phase stability of KNO{sub 3} polymorphs. The obtained elastic moduli show soft nature of these materials and are consistent with Ultrasonic Pulse Echo measurements. We made a complete assignment of vibrational modes which are in good accord with available experimental results. From calculated IR and Raman spectra, it is found that the vibrational frequencies show a red-shift from Li → Na → K (Na → K) and N → Cl for nitrates (chlorates) due to increase in mass of metal and non-metal atoms, respectively. The calculated electronic structure using recently developed Tran-Blaha modified Becke-Johnson potential show that the materials are wide band gap insulators with predominant ionic bonding between M{sup +} (metal) and NO{sub 3}{sup −}/ClO{sub 3}{sup −} ions and covalent bonding (N−O and Cl−O) within nitrate and chlorate anionic group. From the calculated optical spectra, we observe that electric-dipole transitions are due to nitrate/chlorate group below 20 eV and cationic transitions occur above 20 eV. The calculated reflectivity spectra are consistent with the available experimental measurements. - Highlights: • Ground state properties with inclusion of dispersion correction method. • Elastic constants and mechanical properties. • Vibrational spectra and their complete assignment. • Raman and IR spectra. • Electronic structure and optical properties using TB-mBJ potential.
Estimating the Effects of Damping Treatments on the Vibration of Complex Structures
2012-09-26
26 4.3 Literature review 26 4.3.1 CLD Theory 26 4.3.2 Temperature Profiling 28 4.4 Constrained Layer Damping Analysis 29 4.5 Results 35...Coordinate systems and length scales are noted. Constraining layer, viscoelastic layer and base layer pertain to the nomenclature used through CLD ...for vibrational damping 4.1 Introduction Constrained layer damping ( CLD ) treatment systems are widely used in complex structures to dissipate
Reichard, Karl M.; Lindner, Douglas K.; Claus, Richard O.
1991-01-01
Modal domain optical fiber sensors have recently been employed in the implementation of system identification algorithms and the closed-loop control of vibrations in flexible structures. The mathematical model of the modal domain optical fiber sensor used in these applications, however, only accounted for the effects of strain in the direction of the fiber's longitudinal axis. In this paper, we extend this model to include the effects of arbitrary stress. Using this sensor model, we characterize the sensor's sensitivity and dynamic range.
Solution of quadratic matrix equations for free vibration analysis of structures.
Gupta, K. K.
1973-01-01
An efficient digital computer procedure and the related numerical algorithm are presented herein for the solution of quadratic matrix equations associated with free vibration analysis of structures. Such a procedure enables accurate and economical analysis of natural frequencies and associated modes of discretized structures. The numerically stable algorithm is based on the Sturm sequence method, which fully exploits the banded form of associated stiffness and mass matrices. The related computer program written in FORTRAN V for the JPL UNIVAC 1108 computer proves to be substantially more accurate and economical than other existing procedures of such analysis. Numerical examples are presented for two structures - a cantilever beam and a semicircular arch.
Arjunan, V.; Kalaivani, M.; Marchewka, M. K.; Mohan, S.
2013-08-01
The crystal structure investigations of melamine with phosphorous acid, namely melaminium dihydrogenphosphite monohydrate (C3N6H7·H2PO3·H2O) have been investigated by means of single crystal X-ray diffraction method. The title compound crystallizes in monoclinic crystal system, and the space group is P21/c with a = 10.069 Å, b = 21.592 Å, c = 12.409 Å and Z = 12. The vibrational assignments and analysis of melaminium dihydrogen phosphite monohydrate have also been performed by FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical simulations were performed with DFT (B3LYP) method using 6-31G**, cc-pVTZ, and 6-311++G** basis sets to determine the energy, structural, thermodynamic parameters and vibrational frequencies of melaminium dihydrogen phosphite monohydrate. The hydrogen atom from phosphorous acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak Osbnd H···O and Nsbnd H···O hydrogen bonds shows notable vibrational effects.
Kubicki, James D; Paul, Kristian W; Kabalan, Lara; Zhu, Qing; Mrozik, Michael K; Aryanpour, Masoud; Pierre-Louis, Andro-Marc; Strongin, Daniel R
2012-10-16
Periodic plane-wave density functional theory (DFT) and molecular cluster hybrid molecular orbital-DFT (MO-DFT) calculations were performed on models of phosphate surface complexes on the (100), (010), (001), (101), and (210) surfaces of α-FeOOH (goethite). Binding energies of monodentate and bidentate HPO(4)(2-) surface complexes were compared to H(2)PO(4)(-) outer-sphere complexes. Both the average potential energies from DFT molecular dynamics (DFT-MD) simulations and energy minimizations were used to estimate adsorption energies for each configuration. Molecular clusters were extracted from the energy-minimized structures of the periodic systems and subjected to energy reminimization and frequency analysis with MO-DFT. The modeled P-O and P---Fe distances were consistent with EXAFS data for the arsenate oxyanion that is an analog of phosphate, and the interatomic distances predicted by the clusters were similar to those of the periodic models. Calculated vibrational frequencies from these clusters were then correlated with observed infrared bands. Configurations that resulted in favorable adsorption energies were also found to produce theoretical vibrational frequencies that correlated well with experiment. The relative stability of monodentate versus bidentate configurations was a function of the goethite surface under consideration. Overall, our results show that phosphate adsorption onto goethite occurs as a variety of surface complexes depending on the habit of the mineral (i.e., surfaces present) and solution pH. Previous IR spectroscopic studies may have been difficult to interpret because the observed spectra averaged the structural properties of three or more configurations on any given sample with multiple surfaces.
Niessen, Katherine; Xu, Mengyang; Snell, Edward; Markelz, Andrea
Long-range intramolecular vibrations may enable efficient access to functionally important conformations. We examine how these motions change with inhibitor binding and mutation using terahertz anisotropic absorption and molecular modeling. The measured anisotropic absorption dramatically changes with 3NAG inhibitor binding for wild type (WT) free chicken egg white lysozyme (CEWL). We examine the evolution of internal motions with binding using normal mode analysis to calculate an ensemble averaged vibrational density of states (VDOS) and isotropic and anisotropic absorptions for both WT and a two residue (R14 and H15) deletion mutant which has a 1.4 higher activity rate. While the VDOS and isotropic response are largely unchanged with inhibitor binding, the anisotropic response changes dramatically with binding. However, for the mutant the calculated unbound anisotropic absorption more closely resembles its bound spectrum, and it has increased calculated mean squared fluctuations in regions overlapping those in its bound state. These results indicate that the mutant's enhanced activity may be due to a shift in the direction of vibrations toward those of the bound state, increasing the sampling rate of the bound conformation.
On the analytical modeling of the nonlinear vibrations of pretensioned space structures
Housner, J. M.; Belvin, W. K.
1983-01-01
Pretensioned structures are receiving considerable attention as candidate large space structures. A typical example is a hoop-column antenna. The large number of preloaded members requires efficient analytical methods for concept validation and design. Validation through analyses is especially important since ground testing may be limited due to gravity effects and structural size. The present investigation has the objective to present an examination of the analytical modeling of pretensioned members undergoing nonlinear vibrations. Two approximate nonlinear analysis are developed to model general structural arrangements which include beam-columns and pretensioned cables attached to a common nucleus, such as may occur at a joint of a pretensioned structure. Attention is given to structures undergoing nonlinear steady-state oscillations due to sinusoidal excitation forces. Three analyses, linear, quasi-linear, and nonlinear are conducted and applied to study the response of a relatively simple cable stiffened structure.
Directory of Open Access Journals (Sweden)
Shijia Pan
2017-05-01
Full Text Available This paper presents a collaboratively adaptive vibration monitoring system that captures high-fidelity structural vibration signals induced by pedestrians. These signals can be used for various human activities’ monitoring by inferring information about the impact sources, such as pedestrian footsteps, door opening and closing, and dragging objects. Such applications often require high-fidelity (high resolution and low distortion signals. Traditionally, expensive high resolution and high dynamic range sensors are adopted to ensure sufficient resolution. However, for sensing systems that use low-cost sensing devices, the resolution and dynamic range are often limited; hence this type of sensing methods is not well explored ubiquitously. We propose a low-cost sensing system that utilizes (1 a heuristic model of the investigating excitations and (2 shared information through networked devices to adapt hardware configurations and obtain high-fidelity structural vibration signals. To further explain the system, we use indoor pedestrian footstep sensing through ambient structural vibration as an example to demonstrate the system performance. We evaluate the application with three metrics that measure the signal quality from different aspects: the sufficient resolution rate to present signal resolution improvement without clipping, the clipping rate to measure the distortion of the footstep signal, and the signal magnitude to quantify the detailed resolution of the detected footstep signal. In experiments conducted in a school building, our system demonstrated up to 2× increase on the sufficient resolution rate and 2× less error rate when used to locate the pedestrians as they walk along the hallway, compared to a fixed sensing setting.
Sun, Zhiyuan; Guo, Bing; Rao, Zhimin; Zhao, Qingliang
2014-08-01
In consideration of the excellent property of SiC, the ground micro-structured surface quality is hard to meet the requirement - consequently the ultrasonic vibration assisted polishing (UVAP) of micro-structures of molds is proposed in this paper. Through the orthogonal experiment, the parameters of UVAP of micro-structures were optimized. The experimental results show that, abrasive polishing process, the effect of the workpiece feed rate on the surface roughness (Ra), groove tip radius (R) and material removal rate (MRR) of micro-structures is significant. While, the UVAP, the most significant effect factor for Ra, R and MRR is the ultrasonic amplitude of the ultrasonic vibration. In addition, within the scope of the polishing process parameters selected by preliminary experiments, ultrasonic amplitude of 2.5μm, polishing force of 0.5N, workpiece feed rate of 5 mm·min-1, polishing wheel rotational speed of 50rpm, polishing time of 35min, abrasive size of 100nm and the polishing liquid concentration of 15% is the best technology of UVAP of micro-structures. Under the optimal parameters, the ground traces on the micro-structured surface were removed efficiently and the integrity of the edges of the micro-structure after grinding was maintained efficiently.
Energy Technology Data Exchange (ETDEWEB)
Walker, William C. [ORNL
2018-02-01
This report presents a methodology for deriving the equations which can be used for calculating the radially-averaged effective impact area for a theoretical aircraft crash into a structure. Conventionally, a maximum effective impact area has been used in calculating the probability of an aircraft crash into a structure. Whereas the maximum effective impact area is specific to a single direction of flight, the radially-averaged effective impact area takes into consideration the real life random nature of the direction of flight with respect to a structure. Since the radially-averaged effective impact area is less than the maximum effective impact area, the resulting calculated probability of an aircraft crash into a structure is reduced.
International Nuclear Information System (INIS)
Cinar, M.
2008-01-01
In the present study, the structural properties of N,N,4-Tri chlorobenzenesulfonamide have been studied extensively using Density Functional Theory (DFT) employing B3LYP exchange correlation. The geometry of the molecule was fully optimized, vibrational spectrum was calculated and fundamental vibrations were assigned based on the scaled theoretical wavenumbers. The 1 H and 13 C nuclear magnetic resonance (NMR) chemical shifts of the compound were calculated using the Gauge-Invariant Atomic Orbital (GIAO) method. To investigate the basis set effects, calculations were performed at the 6-31G(d,p), 6-311G(d,p), 6-31++G(d,p) and 6-311++G(d,p) levels. Finally, geometric parameters, vibrational bands and isotropic chemical shifts were compared with available experimental data of compound. The fully optimized geometry of the molecule was found to be consistent with the X-ray crystal structure. The observed and calculated frequencies and chemical shifts were found to be in very good agreement. The computed results appear that the basis set has slight effect on the molecular geometry of N,N,4-Tri chlorobenzenesulfonamide
Ab initio structural and vibrational properties of GaAs diamondoids and nanocrystals
Directory of Open Access Journals (Sweden)
Mudar Ahmed Abdulsattar
2014-12-01
Full Text Available Gallium arsenide diamondoids structural and vibrational properties are investigated using density functional theory at the PBE/6-31(d level and basis including polarization functions. Variation of energy gap as these diamondoids increase in size is seen to follow confinement theory for diamondoids having nearly equiaxed dimensions. Density of energy states transforms from nearly single levels to band structure as we reach larger diamondoids. Bonds of surface hydrogen with As atoms are relatively localized and shorter than that bonded to Ga atoms. Ga-As bonds have a distribution range of values due to surface reconstruction and effect of bonding to hydrogen atoms. Experimental bulk Ga-As bond length (2.45 Å is within this distribution range. Tetrahedral and dihedral angles approach values of bulk as we go to higher diamondoids. Optical-phonon energy of larger diamondoids stabilizes at 0.037 eV (297 cm-1 compared to experimental 0.035 eV (285.2 cm-1. Ga-As force constant reaches 1.7 mDyne/Å which is comparable to Ga-Ge force constant (1.74 mDyne/Å. Hydrogen related vibrations are nearly constant and serve as a fingerprint of GaAs diamondoids while Ga-As vibrations vary with size of diamondoids.
Magnetically tuned mass dampers for optimal vibration damping of large structures
International Nuclear Information System (INIS)
Bourquin, Frederic; Siegert, Dominique; Caruso, Giovanni; Peigney, Michael
2014-01-01
This paper deals with the theoretical and experimental analysis of magnetically tuned mass dampers, applied to the vibration damping of large structures of civil engineering interest. Two devices are analysed, for which both the frequency tuning ratio and the damping coefficient can be easily and finely calibrated. They are applied for the damping of the vibrations along two natural modes of a mock-up of a bridge under construction. An original analysis, based on the Maxwell receding image method, is developed for estimating the drag force arising inside the damping devices. It also takes into account self-inductance effects, yielding a complex nonlinear dependence of the drag force on the velocity. The analysis highlights the range of velocities for which the drag force can be assumed of viscous type, and shows its dependence on the involved geometrical parameters of the dampers. The model outcomes are then compared to the corresponding experimental calibration curves. A dynamic model of the controlled structure equipped with the two damping devices is presented, and used for the development of original optimization expressions and for determining the corresponding maximum achievable damping. Finally, several experimental results are presented, concerning both the free and harmonically forced vibration damping of the bridge mock-up, and compared to the corresponding theoretical predictions. The experimental results reveal that the maximum theoretical damping performance can be achieved, when both the tuning frequencies and damping coefficients of each device are finely calibrated according to the optimization expressions. (paper)
Vibration technique for non-destructive testing of carbon fiber reinforced plastic structures
International Nuclear Information System (INIS)
Miller, W.G.
1982-01-01
For nondestructive testing of structures of KFK (carbon fiber reinforced plastics) Adams and a group at the English University of Bristol, Department of Mechanical Engineering have developed a vibrational testing method. It is based on the fact that the decreasing self-oscillations of a structure can be measured in connection with a dynamical analysis at only one particular location of that structure. This way a damage can be localized and be quantized rawly. The mathematical model is simple and for every tested structure only one analysis is needed. Many kinds of damages in structures can be determined and reproduced especially in structures that represent typical cases of application of KFK in air and aerospace industry. (orig.) [de
Influence of structural parameters of deep groove ball bearings on vibration
Yu, Guangwei; Wu, Rui; Xia, Wei
2018-04-01
Taking 6201 bearing as the research object, a dynamic model of 4 degrees of freedom is established to solve the vibration characteristics such as the displacement, velocity and acceleration of deep groove ball bearings by MATLAB and Runge-Kutta method. By calculating the theoretical value of the frequency of the rolling element passing through the outer ring and the simulation value of the model, it can be known that the theoretical calculation value and the simulation value have good consistency. By the experiments, the measured values and simulation values are consistent. Using the mathematical model, the effect of structural parameters on vibration is obtained. The method in the paper is testified to be feasible and the results can be used as references for the design, manufacturing and testing of deep groove ball bearings.
Ladetto, María F.; Márquez, María B.; Brandán, Silvia A.
2014-10-01
In this work, we have presented a structural and vibrational study on the properties in gas and aqueous solution phases of oxcarbazepine, a polymorphic anticonvulsant substance, combining the available IR and Raman spectra with Density Functional Theory (DFT) calculations. Two stable C1 and C2 forms for the title molecule were theoretically determined by using the hybrid B3LYP/6-31G* method. The integral equation formalism variant polarised continuum model (IEFPCM) was employed to study the solvent effects by means of the self-consistent reaction field (SCRF) method. The vibrational spectra for the two forms of oxcarbazepine were completely assigned together with two dimeric species also observed in the solid phase. The presences of the two C1 and C2 forms together with the two dimeric species are supported by the IR and Raman bands between 1424 and 125 cm-1. Here, the properties for both forms of oxcarbazepine are compared and discussed.
Surface energy effect on free vibration of nano-sized piezoelectric double-shell structures
Fang, Xue-Qian; Zhu, Chang-Song; Liu, Jin-Xi; Liu, Xiang-Lin
2018-01-01
Combining Goldenveizer-Novozhilov shell theory, thin plate theory and electro-elastic surface theory, the size-dependent vibration of nano-sized piezoelectric double-shell structures under simply supported boundary condition is presented, and the surface energy effect on the natural frequencies is discussed. The displacement components of the cylindrical nano-shells and annular nano-plates are expanded as the superposition of standard Fourier series based on Hamilton's principle. The total stresses with consideration of surface energy effect are derived, and the total energy function is obtained by using Rayleigh-Ritz energy method. The free vibration equation is solved, and the natural frequency is analyzed. In numerical examples, it is found that the surface elastic constant, piezoelectric constant and surface residual stress show different effects on the natural frequencies. The effect of surface piezoelectric constant is the maximum. The effect of dimensions of the double-shell under different surface material properties is also examined.
Kiefer, Johannes; Wagenfeld, Sabine; Kerlé, Daniela
2018-01-01
Alkyl alcohols are widely used in academia, industry, and our everyday lives, e.g. as cleaning agents and solvents. Vibrational spectroscopy is commonly used to identify and quantify these compounds, but also to study their structure and behavior. However, a comprehensive investigation and comparison of all normal alkanols that are liquid at room temperature has not been performed, surprisingly. This study aims at bridging this gap with a combined experimental and computational effort. For this purpose, the alkyl alcohols from methanol to undecan-1-ol have been analyzed using infrared and Raman spectroscopy. A detailed assignment of the individual peaks is presented and the influence of the alkyl chain length on the hydrogen bonding network is discussed. A 2D vibrational mapping allows a straightforward visualization of the effects. The conclusions drawn from the experimental data are backed up with results from Monte Carlo simulations using the simulation package Cassandra.
Cuisset, Arnaud; Drumel, Marie-Aline Martin; Hindle, Francis; Mouret, Gaël; Sadovskií, Dmitrií A.
2013-10-01
We report on the successful extended analysis of the high-frequency (200-700 GHz) part of the gas phase (sub)mm-wave spectra of dimethylsulfoxide (DMSO). The spectrum was recorded at 100 kHz resolution using a solid state subTHz spectrometer. The five lowest energy fundamental vibrational states of DMSO with frequencies below 400 cm-1 were observed as sidebands along with the main 0←0 band. Neglecting the internal rotation of methyls, our rotational Hamiltonian reproduced the spectrum to the subMHz accuracy. We have found that the asymmetric bending state ν23 is the only low frequency fundamental vibrational state with the "anomalous" rotational structure uncovered in Cuisset et al. [1]. dmsomw 2013-09-04 15:03
Computer codes for the calculation of vibrations in machines and structures
International Nuclear Information System (INIS)
1989-01-01
After an introductory paper on the typical requirements to be met by vibration calculations, the first two sections of the conference papers present universal as well as specific finite-element codes tailored to solve individual problems. The calculation of dynamic processes increasingly now in addition to the finite elements applies the method of multi-component systems which takes into account rigid bodies or partial structures and linking and joining elements. This method, too, is explained referring to universal computer codes and to special versions. In mechanical engineering, rotary vibrations are a major problem, and under this topic, conference papers exclusively deal with codes that also take into account special effects such as electromechanical coupling, non-linearities in clutches, etc. (orig./HP) [de
El-Mansy, M. A. M.
2017-08-01
Structural and vibrational spectroscopic studies were performed on indigo carmine (IC) isomers using FT-IR spectral analysis along with DFT/B3LYP method utilizing Gaussian 09 software. GaussView 5 program has been employed to perform a detailed interpretation of vibrational spectra. Simulation of infrared spectra has led to an excellent overall agreement with the observed spectral patterns. Mulliken population analyses on atomic charges, MEP, HOMO-LUMO, NLO, first order hyperpolarizability and thermodynamic properties have been examined by (DFT/B3LYP) method with the SDD basis set level. Density of state spectra (DOS) were calculated using GaussSum 3 at the same level of theory. Molecular modeling approved that DOS Spectra are the most significant tools for differentiating between two IC isomers so far. Moreover, The IC isomers (cis-isomer) have shown an extended applicability for manufacturing both NLO and photovoltaic devices such as solar cells.
International Nuclear Information System (INIS)
Jiang, Jian-ping; Li, Dong-xu
2010-01-01
This paper is devoted to the study of the decentralized guaranteed cost static output feedback vibration control for piezoelectric smart structures. A smart panel with collocated piezoelectric actuators and velocity sensors is modeled using a finite element method, and then the size of the model is reduced in the state space using the modal Hankel singular value. The necessary and sufficient conditions of decentralized guaranteed cost static output feedback control for the reduced system have been presented. The decentralized and centralized static output feedback matrices can be obtained from solving two linear matrix inequalities. A comparison between centralized control and decentralized control is performed in order to investigate their effectiveness in suppressing vibration of a smart panel. Numerical results show that when the system is subjected to initial displacement or white noise disturbance, the decentralized and centralized controls are both very effective and the control results are very close
Ji, Pengfei; Zhang, Yuwen; Yang, Mo
2016-01-01
The structural, dynamic, and vibrational properties during the heat transfer process in Si/Ge superlattices, are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) ar...
A simplified method for random vibration analysis of structures with random parameters
International Nuclear Information System (INIS)
Ghienne, Martin; Blanzé, Claude
2016-01-01
Piezoelectric patches with adapted electrical circuits or viscoelastic dissipative materials are two solutions particularly adapted to reduce vibration of light structures. To accurately design these solutions, it is necessary to describe precisely the dynamical behaviour of the structure. It may quickly become computationally intensive to describe robustly this behaviour for a structure with nonlinear phenomena, such as contact or friction for bolted structures, and uncertain variations of its parameters. The aim of this work is to propose a non-intrusive reduced stochastic method to characterize robustly the vibrational response of a structure with random parameters. Our goal is to characterize the eigenspace of linear systems with dynamic properties considered as random variables. This method is based on a separation of random aspects from deterministic aspects and allows us to estimate the first central moments of each random eigenfrequency with a single deterministic finite elements computation. The method is applied to a frame with several Young's moduli modeled as random variables. This example could be expanded to a bolted structure including piezoelectric devices. The method needs to be enhanced when random eigenvalues are closely spaced. An indicator with no additional computational cost is proposed to characterize the ’’proximity” of two random eigenvalues. (paper)
Vibration-based damage detection of structural joints in presence of uncertainty
Directory of Open Access Journals (Sweden)
Al-Bugharbee Hussein
2018-01-01
Full Text Available Early damage detection of structure’s joints is essential in order to ensure the integrity of structures. Vibration-based methods are the most popular way of diagnosing damage in machinery joints. Any technique that is used for such a purpose requires dealing with the variability inherent to the system due to manufacturing tolerances, environmental conditions or aging. The level of variability in vibrational response can be very high for mass-produced complex structures that possess a large number of components. In this study, a simple and efficient time frequency method is proposed for detection of damage in connecting joints. The method suggests using singular spectrum analysis for building a reference space from the signals measured on a healthy structure and then compares all other signals to that reference space in order to detect the presence of faults. A model of two plates connected by a series of mounts is used to examine the effectiveness of the method where the uncertainty in the mount properties is taken into account to model the variability in the built-up structure. The motivation behind the simplified model is to identify the faulty mounts in trim-structure joints of an automotive vehicle where a large number of simple plastic clips are used to connect the trims to the vehicle structure.
Abdeljaber, Osama; Avci, Onur; Kiranyaz, Serkan; Gabbouj, Moncef; Inman, Daniel J.
2017-02-01
Structural health monitoring (SHM) and vibration-based structural damage detection have been a continuous interest for civil, mechanical and aerospace engineers over the decades. Early and meticulous damage detection has always been one of the principal objectives of SHM applications. The performance of a classical damage detection system predominantly depends on the choice of the features and the classifier. While the fixed and hand-crafted features may either be a sub-optimal choice for a particular structure or fail to achieve the same level of performance on another structure, they usually require a large computation power which may hinder their usage for real-time structural damage detection. This paper presents a novel, fast and accurate structural damage detection system using 1D Convolutional Neural Networks (CNNs) that has an inherent adaptive design to fuse both feature extraction and classification blocks into a single and compact learning body. The proposed method performs vibration-based damage detection and localization of the damage in real-time. The advantage of this approach is its ability to extract optimal damage-sensitive features automatically from the raw acceleration signals. Large-scale experiments conducted on a grandstand simulator revealed an outstanding performance and verified the computational efficiency of the proposed real-time damage detection method.
International Nuclear Information System (INIS)
Combescure, A.
1983-05-01
The buckling of shells subjected to seismic type of loads is not very well known. To study this type of phenomenon, theoretical and experimental investigations on structures consisting of two shells separed by a thin fluid layer , and submitted to a seismic type of load have been performed. The objectives of these investigations are the following: study coupling between buckling modes vibrations modes and buckling, and the effects of this coupling on the level of pressure; study of the appearance on such structures of dynamic instabilities processes; qualification of computer codes of the CEASEMT system; and, qualification or criticism of the methodology used in the design based on a ''static equivalent'' idea
Bruner, Anne M.; Belvin, W. Keith; Horta, Lucas G.; Juang, Jer-Nan
1991-01-01
The development of control of large flexible structures technology must include practical demonstrations to aid in the understanding and characterization of controlled structures in space. To support this effort, a testbed facility has been developed to study practical implementation of new control technologies under realistic conditions. The paper discusses the design of a second order, acceleration feedback controller which acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated sensor/actuator pairs in the absence of sensor/actuator dynamics and computational time delay. Experimental results in the presence of these factors are presented and discussed. The robustness of this design under model uncertainty is demonstrated.
Eulerian frequency analysis of structural vibrations from high-speed video
International Nuclear Information System (INIS)
Venanzoni, Andrea; De Ryck, Laurent; Cuenca, Jacques
2016-01-01
An approach for the analysis of the frequency content of structural vibrations from high-speed video recordings is proposed. The techniques and tools proposed rely on an Eulerian approach, that is, using the time history of pixels independently to analyse structural motion, as opposed to Lagrangian approaches, where the motion of the structure is tracked in time. The starting point is an existing Eulerian motion magnification method, which consists in decomposing the video frames into a set of spatial scales through a so-called Laplacian pyramid [1]. Each scale — or level — can be amplified independently to reconstruct a magnified motion of the observed structure. The approach proposed here provides two analysis tools or pre-amplification steps. The first tool provides a representation of the global frequency content of a video per pyramid level. This may be further enhanced by applying an angular filter in the spatial frequency domain to each frame of the video before the Laplacian pyramid decomposition, which allows for the identification of the frequency content of the structural vibrations in a particular direction of space. This proposed tool complements the existing Eulerian magnification method by amplifying selectively the levels containing relevant motion information with respect to their frequency content. This magnifies the displacement while limiting the noise contribution. The second tool is a holographic representation of the frequency content of a vibrating structure, yielding a map of the predominant frequency components across the structure. In contrast to the global frequency content representation of the video, this tool provides a local analysis of the periodic gray scale intensity changes of the frame in order to identify the vibrating parts of the structure and their main frequencies. Validation cases are provided and the advantages and limits of the approaches are discussed. The first validation case consists of the frequency content
Oshmarin, D.; Sevodina, N.; Iurlov, M.; Iurlova, N.
2017-06-01
In this paper, with the aim of providing passive control of structure vibrations a new approach has been proposed for selecting optimal parameters of external electric shunt circuits connected to piezoelectric elements located on the surface of the structure. The approach is based on the mathematical formulation of the natural vibration problem. The results of solution of this problem are the complex eigenfrequencies, the real part of which represents the vibration frequency and the imaginary part corresponds to the damping ratio, characterizing the rate of damping. A criterion of search for optimal parameters of the external passive shunt circuits, which can provide the system with desired dissipative properties, has been derived based on the analysis of responses of the real and imaginary parts of different complex eigenfrequencies to changes in the values of the parameters of the electric circuit. The efficiency of this approach has been verified in the context of natural vibration problem of rigidly clamped plate and semi-cylindrical shell, which is solved for series-connected and parallel -connected external resonance (consisting of resistive and inductive elements) R-L circuits. It has been shown that at lower (more energy-intensive) frequencies, a series-connected external circuit has the advantage of providing lower values of the circuit parameters, which renders it more attractive in terms of practical applications.
Kamarudin, A. F.; Mokhatar, S. N.; Zainal Abidin, M. H.; Daud, M. E.; Rosli, M. S.; Ibrahim, A.; Ibrahim, Z.; Noh, M. S. Md
2018-04-01
Monitoring of structural health from initial stage of building construction to its serviceability is an ideal practise to assess for any structural defects or damages. Structural integrity could be intruded by natural destruction or structural deterioration, and worse if without remedy action on monitoring, building re-assessment or maintenance is taken. In this study the application of ambient vibration (AV) testing is utilized to evaluate the health of eighth stories medium rise reinforced concrete building in Universiti Tun Hussein Onn Malaysia (UTHM), based comparison made between the predominant frequency, fo, determined in year 2012 and 2017. For determination of fo, popular method of Fourier Amplitude Spectra (FAS) was used to transform the ambient vibration time series by using 1 Hz tri-axial seismometer sensors and City SharkII data recorder. From the results, it shows the first mode frequencies from FAS curves indicate at 2.04 Hz in 2012 and 1.97 Hz in 2017 with only 3.14% of frequency reduction. However, steady state frequencies shown at the second and third modes frequencies of 2.42 Hz and 3.31 Hz by both years. Two translation mode shapes were found at the first and second mode frequencies in the North-South (NS-parallel to building transverse axis) and East-West (EsW-parallel to building longitudinal axis) components, and the torsional mode shape shows as the third mode frequency in both years. No excessive deformation amplitude was found at any selective floors based on comparison made between three mode shapes produced, that could bring to potential feature of structural deterioration. Low percentages of natural frequency disparity within five years of duration interval shown by the first mode frequencies under ambient vibration technique was considered in good health state, according to previous researchers recommendation at acceptable percentages below 5 to 10% over the years.
Madsen, Niels Kristian; Godtliebsen, Ian H.; Losilla, Sergio A.; Christiansen, Ove
2018-01-01
A new implementation of vibrational coupled-cluster (VCC) theory is presented, where all amplitude tensors are represented in the canonical polyadic (CP) format. The CP-VCC algorithm solves the non-linear VCC equations without ever constructing the amplitudes or error vectors in full dimension but still formally includes the full parameter space of the VCC[n] model in question resulting in the same vibrational energies as the conventional method. In a previous publication, we have described the non-linear-equation solver for CP-VCC calculations. In this work, we discuss the general algorithm for evaluating VCC error vectors in CP format including the rank-reduction methods used during the summation of the many terms in the VCC amplitude equations. Benchmark calculations for studying the computational scaling and memory usage of the CP-VCC algorithm are performed on a set of molecules including thiadiazole and an array of polycyclic aromatic hydrocarbons. The results show that the reduced scaling and memory requirements of the CP-VCC algorithm allows for performing high-order VCC calculations on systems with up to 66 vibrational modes (anthracene), which indeed are not possible using the conventional VCC method. This paves the way for obtaining highly accurate vibrational spectra and properties of larger molecules.
Average structure of the upper earth mantle and crust between Albuquerque and the Nevada Test Site
International Nuclear Information System (INIS)
Garbin, H.D.
1979-08-01
Models of Earth structures were constructed by inverting seismic data obtained from nuclear events with a 1600-m-long laser strain meter. With these models the general structure of the earth's upper mantle and crust between Albuquerque and the Nevada Test Site was determined. 3 figures, 3 tables
Keiderling, Timothy A
2017-12-01
Isotope labeling has a long history in chemistry as a tool for probing structure, offering enhanced sensitivity, or enabling site selection with a wide range of spectroscopic tools. Chirality sensitive methods such as electronic circular dichroism are global structural tools and have intrinsically low resolution. Consequently, they are generally insensitive to modifications to enhance site selectivity. The use of isotope labeling to modify vibrational spectra with unique resolvable frequency shifts can provide useful site-specific sensitivity, and these methods have been recently more widely expanded in biopolymer studies. While the spectral shifts resulting from changes in isotopic mass can provide resolution of modes from specific parts of the molecule and can allow detection of local change in structure with perturbation, these shifts alone do not directly indicate structure or chirality. With vibrational circular dichroism (VCD), the shifted bands and their resultant sign patterns can be used to indicate local conformations in labeled biopolymers, particularly if multiple labels are used and if their coupling is theoretically modeled. This mini-review discusses selected examples of the use of labeling specific amides in peptides to develop local structural insight with VCD spectra. © 2017 Wiley Periodicals, Inc.
Hussan, Mosaruf; Sharmin, Faria; Kim, Dookie
2017-08-01
The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.
Directory of Open Access Journals (Sweden)
Lezin Seba MINSILI
2013-11-01
Full Text Available The purpose of this research paper was to assess and predict the effect of vibrations induced by an underground railway on nearby-existing buildings prior to the construction of projected new railway lines of the National Railway Master Plan of Cameroon and after upgrading of the railway conceded to CAMRAIL linking the two most densely populated cities of Cameroon: Douala and Yaoundé. With the source-transmitter-receiver mathematical model as the train-soil-structure interaction model, taking into account sub-model parameters such as type of the train-railway system, typical geotechnical conditions of the ground and the sensitivity of the nearby buildings, the analysis is carried out over the entire system using the dynamic finite element method in the time domain. This subdivision of the model is a powerful tool that allows to consider different alternatives of sub-models with different characteristics, and thus to determine any critical excessive vibration impact. Based on semi-empirical analytical results obtained from presented models, the present work assesses and predicts characteristics of traffic-induced vibrations as a function of time duration, intensity and vehicle speed, as well as their influence on buildings at different levels.
Amalanathan, M.; Jasmine, G. Femina; Roy, S. Dawn Dharma
2017-08-01
The molecular structure, vibrational spectra and polarizabilities of Ethyl 4-Dimethylaminobenzoate (EDAB) was investigated by density functional theory employing Becke's three parameter hybrid exchange functional with Lee-Yang-Parr (B3LYP) co-relational functional involving 6-311++G(d,p) basis set and compared with some other levels. A detailed interpretation of the IR and Raman spectra of EDBA have been reported and analyzed. Complete vibrational assignments of the vibrational modes have been done on the basis of the potential energy distribution (TED) using VEDA software. The molecular electrostatic potential mapped onto total density surface has been obtained. A study on the electronic properties, such as absorption wavelength, and frontier molecular orbitals energy, was performed using DFT approach. The stability of the molecule arising from hyper conjugative interactions and accompanying charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The natural and Mulliken charge also calculated and compared with different level of calculation. The dipole moment, polarizability and first, second order hyperpolarizabilities of the title molecule were calculated and compared with the experimental values. The energy gap between frontier orbitals has been used along with electric moments and first order hyperpolarizability, to understand the non linear optical (NLO) activity of the molecule. The NLO activity of molecule was confirmed by SHG analysis.
Çırak, Çağrı; Demir, Selçuk; Ucun, Fatih; Çubuk, Osman
2011-08-01
Experimental and theoretical vibrational spectra of β-2-aminopyridinium dihydrogenphosphate (β-2APDP) have been investigated. The FT-IR spectrum of β-2APDP was recorded in the region 4000-400 cm -1. The optimized molecular structure and theoretical vibrational frequencies of β-2APDP have been investigated using ab initio Hartree-Fock (HF) and density functional B3LYP method with 6-311++G(d,p) basis set. The optimized geometric parameters (bond lengths and bond angles) and theoretical frequencies have been compared with the corresponding experimental data and it is found that they agree well with each other. All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. Furthermore, the used scale factors were obtained from the ratio of the frequency values of the strongest peaks in the experimental and theoretical IR spectra. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies.
Tanak, H.; Pawlus, K.; Marchewka, M. K.
2016-10-01
Melaminium N-acetylglycinate dihydrate, an organic material has been synthesized and characterized by X-ray diffraction, FT-IR, and FT-Raman spectroscopies for the protiated and deuteriated crystals. The title complex crystallizes in the triclinic system, and the space group is P-1 with a = 5.642(1) Å, b = 7.773(2) Å, c = 15.775(3) Å, α = 77.28(1)°, β = 84.00(1)°, γ = 73.43(1)° and Z = 2. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional method (B3LYP) with the 6-311++G(d,p) basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. The intermolecular hydrogen bonding interactions of the title compound have been investigated using the natural bonding orbital analysis. It reveals that the O-H···O, N-H···N and N-H···O intermolecular interactions significantly influence crystal packing of this molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, thermodynamic properties, frontier orbitals and chemical reactivity descriptors were also performed at 6-311++G(d,p) level of theory.
Macia, Didac; Pujol, Jesus; Blanco-Hinojo, Laura; Martínez-Vilavella, Gerard; Martín-Santos, Rocío; Deus, Joan
2018-04-24
There is ample evidence from basic research in neuroscience of the importance of local cortico-cortical networks. Millimetric resolution is achievable with current functional MRI (fMRI) scanners and sequences, and consequently a number of "local" activity similarity measures have been defined to describe patterns of segregation and integration at this spatial scale. We have introduced the use of Iso-Distant local Average Correlation (IDAC), easily defined as the average fMRI temporal correlation of a given voxel with other voxels placed at increasingly separated iso-distant intervals, to characterize the curve of local fMRI signal similarities. IDAC curves can be statistically compared using parametric multivariate statistics. Furthermore, by using RGB color-coding to display jointly IDAC values belonging to three different distance lags, IDAC curves can also be displayed as multi-distance IDAC maps. We applied IDAC analysis to a sample of 41 subjects scanned under two different conditions, a resting state and an auditory-visual continuous stimulation. Multi-distance IDAC mapping was able to discriminate between gross anatomo-functional cortical areas and, moreover, was sensitive to modulation between the two brain conditions in areas known to activate and de-activate during audio-visual tasks. Unlike previous fMRI local similarity measures already in use, our approach draws special attention to the continuous smooth pattern of local functional connectivity.
Consensus positive position feedback control for vibration attenuation of smart structures
Omidi, Ehsan; Nima Mahmoodi, S.
2015-04-01
This paper presents a new network-based approach for active vibration control in smart structures. In this approach, a network with known topology connects collocated actuator/sensor elements of the smart structure to one another. Each of these actuators/sensors, i.e., agent or node, is enhanced by a separate multi-mode positive position feedback (PPF) controller. The decentralized PPF controlled agents collaborate with each other in the designed network, under a certain consensus dynamics. The consensus constraint forces neighboring agents to cooperate with each other such that the disagreement between the time-domain actuation of the agents is driven to zero. The controller output of each agent is calculated using state-space variables; hence, optimal state estimators are designed first for the proposed observer-based consensus PPF control. The consensus controller is numerically investigated for a flexible smart structure, i.e., a thin aluminum beam that is clamped at its both ends. Results demonstrate that the consensus law successfully imposes synchronization between the independently controlled agents, as the disagreements between the decentralized PPF controller variables converge to zero in a short time. The new consensus PPF controller brings extra robustness to vibration suppression in smart structures, where malfunctions of an agent can be compensated for by referencing the neighboring agents’ performance. This is demonstrated in the results by comparing the new controller with former centralized PPF approach.
Average Structure Evolution of δ-phase Pu-Ga Alloys
Energy Technology Data Exchange (ETDEWEB)
Smith, Alice Iulia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Page, Katharine L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Gourdon, Olivier [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Siewenie, Joan E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Richmond, Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Saleh, Tarik A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramos, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Schwartz, Daniel S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-03-30
[Full Text] Plutonium metal is a highly unusual element, exhibiting six allotropes at ambient pressure, from room temperature to its melting point. Many phases of plutonium metal are unstable with temperature, pressure, chemical additions, and time. This strongly affects structure and properties, and becomes of high importance, particularly when considering effects on structural integrity over long time periods. The fcc δ-phase deserves additional attention, not only in the context of understanding the electronic structure of Pu, but also as one of the few high-symmetry actinide phases that can be stabilized down to ambient pressure and room temperature by alloying it with trivalent elements. We will present results on recent work on aging of Pu-2at.%Ga and Pu-7at.%Ga alloys
Qing, Xinlin (Inventor); Beard, Shawn J. (Inventor); Li, Irene (Inventor)
2013-01-01
Sensors affixed to various such structures, where the sensors can withstand, remain affixed, and operate while undergoing both cryogenic temperatures and high vibrations. In particular, piezoelectric single crystal transducers are utilized, and these sensors are coupled to the structure via a low temperature, heat cured epoxy. This allows the transducers to monitor the structure while the engine is operating, even despite the harsh operating conditions. Aspects of the invention thus allow for real time monitoring and analysis of structures that operate in conditions that previously did not permit such analysis. A further aspect of the invention relates to use of piezoelectric single crystal transducers. In particular, use of such transducers allows the same elements to be used as both sensors and actuators.
Field control in a standing wave structure at high average beam power
International Nuclear Information System (INIS)
McKeown, J.; Fraser, J.S.; McMichael, G.E.
1976-01-01
A 100% duty factor electron beam has been accelerated through a graded-β side-coupled standing wave structure operating in π/2 mode. Three non-interacting control loops are necessary to provide the accelerating field amplitude and phase and to control structure resonance. The principal disturbances have been identified and measured over the beam current range of 0 to 20 mA. Design details are presented of control loops which regulate the accelerating field amplitude to +-0.3% and its phase to +-0.5 deg for 50% beam loading. (author)
Koroleva, L. A.; Tyulin, V. I.; Matveev, V. K.; Pentin, Yu. A.
2012-04-01
The assignments of absorption bands of the vibrational structure of the UV spectrum are compared with the assignments of bands obtained by the CRDS method in a supersonic jet from the time of laser radiation damping for the trans isomer of acrolein in the excited ( S 1) electronic state. The ν00 trans = 25861 cm-1 values and fundamental frequencies, including torsional vibration frequency, obtained by the two methods were found to coincide in the excited electronic state ( S 1) for this isomer. The assignments of several absorption bands of the vibrational structure of the spectrum obtained by the CRDS method were changed. Changes in the assignment of (0-v') transition bands of the torsional vibration of the trans isomer in the Deslandres table from the ν00 trans trans origin allowed the table to be extended to high quantum numbers v'. The torsional vibration frequencies up to v' = 5 were found to be close to the frequencies found by analyzing the vibrational structure of the UV spectrum and calculated quantum-mechanically. The coincidence of the barrier to internal rotation (the cis-trans transition) in the one-dimensional model with that calculated quantum-mechanically using the two-dimensional model corresponds to a planar structure of the acrolein molecule in the excited ( S 1) electronic state.
Directory of Open Access Journals (Sweden)
Yu Han
2017-01-01
Full Text Available We report the development of a new analytical model similar to the Reynolds-averaged Navier-Stokes equations to determine the distribution of streamwise velocity by considering the bursting phenomenon. It is found that, in two-dimensional (2D flows, the underlying mechanism of the wake law in 2D uniform flow is actually a result of up/down events. A special experiment was conducted to examine the newly derived analytical model, and good agreement is achieved between the experimental data in the inner region and the model’s prediction. The obtained experimental data were also used to examine the DML-Law (dip-modified-log-law, MLW-Law (modified-log-wake law, and CML-Law (Cole’s wake law, and the agreement is not very satisfactory in the outer region.
The impact of intermediate structure on the average fission cross sections
International Nuclear Information System (INIS)
Bouland, O.; Lynn, J.E.; Talou, P.
2014-01-01
This paper discusses two common approximations used to calculate average fission cross sections over the compound energy range: the disregard of the W II factor and the Porter-Thomas hypothesis made on the double barrier fission width distribution. By reference to a Monte Carlo-type calculation of formal R-matrix fission widths, this work estimates an overall error ranging from 12% to 20% on the fission cross section in the case of the 239 Pu fissile isotope in the energy domain from 1 to 100 keV with very significant impact on the competing capture cross section. This work is part of a recent and very comprehensive formal R-matrix study over the Pu isotope series and is able to give some hints for significant accuracy improvements in the treatment of the fission channel. (authors)
Kawchuk, Gregory N; Hartvigsen, Jan; Edgecombe, Tiffany; Prasad, Narasimha; van Dieen, Jaap H
2016-03-11
Structural health monitoring (SHM) is an engineering technique used to identify mechanical abnormalities not readily apparent through other means. Recently, SHM has been adapted for use in biological systems, but its invasive nature limits its clinical application. As such, the purpose of this project was to determine if a non-invasive form of SHM could identify structural alterations in the spines of living human subjects. Lumbar spines of 10 twin pairs were visualized by magnetic resonance imaging then assessed by a blinded radiologist to determine whether twin pairs were structurally concordant or discordant. Vibration was then applied to each subject's spine and the resulting response recorded from sensors overlying lumbar spinous processes. The peak frequency, area under the curve and the root mean square were computed from the frequency response function of each sensor. Statistical analysis demonstrated that in twins whose structural appearance was discordant, peak frequency was significantly different between twin pairs while in concordant twins, no outcomes were significantly different. From these results, we conclude that structural changes within the spine can alter its vibration response. As such, further investigation of SHM to identify spinal abnormalities in larger human populations is warranted.
Measurement of average continuous-time structure of a bond and ...
African Journals Online (AJOL)
The expected continuous-time structure of a bond and bond's interest rate risk in an investment settings was studied. We determined the expected number of years an investor or manager will wait until the stock comes to maturity. The expected principal amount to be paid back per stock at time 't' was determined, while ...
Vibration based structural assessment of the rehabilitation intervention in r.c. segmental bridge
Franchetti Paolo; Frizzarin Michele; Leonardi Andrea; Zeni Fabio
2015-01-01
A vibration based structural assessment campaign was carried out on a r.c. segmental bridge in North East Italy. The bridge has a cantilever static scheme, fixed at the top of the piers and with a hinge at the centre of the span. The particular configuration of the hinge consists in a couple of steel elements, each one composed by a tongue and groove joint. Since the year 1960, the hinge was subjected to consumption and degradation, that caused a malfunctioning of the device. An intervention ...
Uncertainty modeling in vibration, control and fuzzy analysis of structural systems
Halder, Achintya; Ayyub, Bilal M
1997-01-01
This book gives an overview of the current state of uncertainty modeling in vibration, control, and fuzzy analysis of structural and mechanical systems. It is a coherent compendium written by leading experts and offers the reader a sampling of exciting research areas in several fast-growing branches in this field. Uncertainty modeling and analysis are becoming an integral part of system definition and modeling in many fields. The book consists of ten chapters that report the work of researchers, scientists and engineers on theoretical developments and diversified applications in engineering sy
Vibrational behavior of adaptive aircraft wing structures modelled as composite thin-walled beams
Song, O.; Librescu, L.; Rogers, C. A.
1992-01-01
The vibrational behavior of cantilevered aircraft wings modeled as thin-walled beams and incorporating piezoelectric effects is studied. Based on the converse piezoelectric effect, the system of piezoelectric actuators conveniently located on the wing yield the control of its associated vertical and lateral bending eigenfrequencies. The possibility revealed by this study enabling one to increase adaptively the eigenfrequencies of thin-walled cantilevered beams could play a significant role in the control of the dynamic response and flutter of wing and rotor blade structures.
R.W. Strachan (Rodney); H.K. van Dijk (Herman)
2008-01-01
textabstractA Bayesian model averaging procedure is presented that makes use of a finite mixture of many model structures within the class of vector autoregressive (VAR) processes. It is applied to two empirical issues. First, stability of the Great Ratios in U.S. macro-economic time series is
Giacomazzi, Luigi; Umari, P; Pasquarello, Alfredo
2005-08-12
We analyze the principal vibrational spectra of vitreous GeO(2) and derive therefrom structural properties referring to length scales beyond the basic tetrahedral unit. We generate a model structure that yields a neutron structure factor in accord with experiment. The inelastic-neutron, the infrared, and the Raman spectra, calculated within a density-functional approach, also agree with respective experimental spectra. The accord for the Raman spectrum supports a Ge-O-Ge angle distribution centered at 135 degrees. The Raman feature X(2) is found to result from vibrations in three-membered rings, and therefore constitutes a distinctive characteristic of the medium-range structure.
Cox, T. H.; Gilyard, G. B.
1986-01-01
The drones for aerodynamic and structural testing (DAST) project was designed to control flutter actively at high subsonic speeds. Accurate knowledge of the structural model was critical for the successful design of the control system. A ground vibration test was conducted on the DAST vehicle to determine the structural model characteristics. This report presents and discusses the vibration and test equipment, the test setup and procedures, and the antisymmetric and symmetric mode shape results. The modal characteristics were subsequently used to update the structural model employed in the control law design process.
DEFF Research Database (Denmark)
Stokbro, Kurt
1999-01-01
We report a first principles study of the structure and the vibrational properties of the Si(100)-H(2 x 1) surface in an electric field. The calculated vibrational parameters are used to model the vibrational modes in the presence of the electric field corresponding to a realistic scanning...
International Nuclear Information System (INIS)
Julien, C.M.; Camacho-Lopez, M.A.
2004-01-01
Lithiated spinel manganese oxides with various amounts of lithium have been prepared through solid-state reaction and electrochemical intercalation and deintercalation. Local structure of the samples are studied using Raman scattering and Fourier transform infrared spectroscopy. We report vibrational spectra of lithiated manganese oxides Li x Mn 2 O 4 as a function of lithium concentration in the range 0.1≤x≤2.0. Raman and Fourier transform infrared (FTIR) spectral results indicated multiple-phase reactions when the lithium content is modified in the spinel lattice. Lattice dynamics of lithiated spinel manganese oxides have been interpreted using either a classical factor-group analysis or a local environment model. The structural modifications have been studied on the basis of vibrations of LiO 4 tetrahedral and MnO 6 octahedral units when Li/Mn≤0.5, and LiO 4 , LiO 6 , and MnO 6 structural units when Li/Mn>0.5
Kaloni, Thaneshwor P.
2013-11-01
This thesis covers the structural, electronic, magnetic, and vibrational properties of graphene and silicene. In Chapter I, we will start with an introduction to graphene and silicene. In Chapter II, we will briefly discuss about the methodology (i. e. density functional theory)In Chapter III, we will introduce band gap opening in graphene either by introducing defects/doping or by creating superlattices with h-BN substrate. In Chapter IV, we will focus on the structural and electronic properties of K and Ge-intercalated graphene on SiC(0001). In addition, the enhancement of the superconducting transition temperature in Li-decorated graphene supported by h-BN substrate will be discussed. In Chapter V, we will discuss the vibrational properties of free-standing silicene. In addition, superlattices of silicene with h-BN as well as the phase transition in silicene by applying an external electric field will be discussed. The electronic and magnetic properties transition metal decorated silicene will be discussed, in particular the realization of the quantum anomalous Hall effect will be addressed. Furthermore, the structural, electronic, and magnetic properties of Mn decorated silicene supported by h-BN substrate will be discussed. The conclusion is included in Chapters VI. Finally, we will end with references and a list of publications for this thesis.
About a sequential method for non destructive testing of structures by mechanical vibrations
International Nuclear Information System (INIS)
Suarez Antola, R.
2001-01-01
The presence and growth of cracks voids or fields of pores under applied forces or environmental actions can produce a meaningful lowering in the proper frequencies of normal modes of mechanical vibration in structures.A quite general expression for the square of modes proper frequency as a functional of displacement field,density field and elastic moduli fields is used as a starting point.The effect of defects on frequency are modeled as equivalent changes in density and elastic moduli fields,introducing the concept of region of influence of each defect.An approximate expression is obtained which relates the relative lowering in the square of modes proper frequency with position,size,shape and orientation of defects in mode displacement field.Some simple examples of structural elements with cracks or fields of pores are considered.the connection with linear elastic fracture mechanics is briefly exemplified.A sequential method is proposed for non-destructive testing of structures using mechanical vibrations combined with properly chosen local nondestructive testing methods
Design of lightweight magnesium car body structure under crash and vibration constraints
Directory of Open Access Journals (Sweden)
Morteza Kiani
2014-06-01
Full Text Available Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality. In this paper, material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight. Through finite element simulations, full frontal, offset frontal, and side crashes of a full car model are evaluated for peak acceleration, intrusion distance, and the internal energy absorbed by the structural parts. In addition, the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints. The wall thicknesses of twenty-two parts are considered as the design variables. Latin Hypercube Sampling is used to sample the design space, while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies. A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints. Using Sequential Quadratic Programming, the design optimization problem is solved with the results verified by finite element simulations. The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.
Bykov, A. A.; Matveenko, B. P.; Serovaev, G. S.; Shardakov, I. N.; Shestakov, A. P.
2015-03-01
The contemporary construction industry is based on the use of reinforced concrete structures, but emergency situations resulting in fracture can arise in their exploitation. In a majority of cases, reinforced concrete fracture is realized as the process of crack formation and development. As a rule, the appearance of the first cracks does not lead to the complete loss of the carrying capacity but is a fracture precursor. One method for ensuring the safe operation of building structures is based on crack initiation monitoring. A vibration method for the monitoring of reinforced concrete structures is justified in this paper. An example of a reinforced concrete beam is used to consider all stages related to the analysis of the behavior of natural frequencies in the development of a crack-shaped defect and the use of the obtained numerical results for the vibration test method. The efficiency of the method is illustrated by the results of modeling of the physical part of the method related to the analysis of the natural frequency evolution as a response to the impact action in the crack development process.
Huopana, J
2010-01-01
The CLIC (Compact LInear Collider) is being studied at CERN as a potential multi-TeV e+e- collider [1]. The manufacturing and assembly tolerances for the required RF-components are important for the final efficiency and for the operation of CLIC. The proper function of an accelerating structure is very sensitive to errors in shape and location of the accelerating cavity. This causes considerable issues in the field of mechanical design and manufacturing. Currently the design of the accelerating structures is a disk design. Alternatively it is possible to create the accelerating assembly from quadrants, which favour the mass manufacturing. The functional shape inside of the accelerating structure remains the same and a single assembly uses less parts. The alignment of these quadrants has been previously made kinematic by using steel pins or spheres to align the pieces together. This method proved to be a quite tedious and time consuming method of assembly. To limit the number of different error sources, a meth...
Price, Malcolm J; Welton, Nicky J; Briggs, Andrew H; Ades, A E
2011-01-01
Standard approaches to estimation of Markov models with data from randomized controlled trials tend either to make a judgment about which transition(s) treatments act on, or they assume that treatment has a separate effect on every transition. An alternative is to fit a series of models that assume that treatment acts on specific transitions. Investigators can then choose among alternative models using goodness-of-fit statistics. However, structural uncertainty about any chosen parameterization will remain and this may have implications for the resulting decision and the need for further research. We describe a Bayesian approach to model estimation, and model selection. Structural uncertainty about which parameterization to use is accounted for using model averaging and we developed a formula for calculating the expected value of perfect information (EVPI) in averaged models. Marginal posterior distributions are generated for each of the cost-effectiveness parameters using Markov Chain Monte Carlo simulation in WinBUGS, or Monte-Carlo simulation in Excel (Microsoft Corp., Redmond, WA). We illustrate the approach with an example of treatments for asthma using aggregate-level data from a connected network of four treatments compared in three pair-wise randomized controlled trials. The standard errors of incremental net benefit using structured models is reduced by up to eight- or ninefold compared to the unstructured models, and the expected loss attaching to decision uncertainty by factors of several hundreds. Model averaging had considerable influence on the EVPI. Alternative structural assumptions can alter the treatment decision and have an overwhelming effect on model uncertainty and expected value of information. Structural uncertainty can be accounted for by model averaging, and the EVPI can be calculated for averaged models. Copyright © 2011 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights
Structural, electronic and vibrational properties of lanthanide monophosphide at high pressure
Energy Technology Data Exchange (ETDEWEB)
Panchal, J. M., E-mail: amitjignesh@yahoo.co.in [Government Engineering College, Gandhinagar382028, Gujarat (India); Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat (India); Joshi, Mitesh [Government Polytechnic for Girls, Athwagate, Surat395001, Gujarat (India); Gajjar, P. N., E-mail: pngajjar@rediffmail.com [Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat (India)
2016-05-06
A first-principles plane wave self-consistent method with the ultra-soft-pseudopotential scheme in the framework of the density functional theory (DFT) is performed to study structural, electronic and vibrational properties of LaP for Rock-salt (NaCl/Bl) and Cesium-chloride (CsCl/B2) phases. The instability of Rock-salt (NaCl/Bl) phases around the transition is discussed. Conclusions based on electronic energy band structure, density of state, phonon dispersion and phonon density of states in both phases are outlined. The calculated results are consistence and confirm the successful applicability of quasi-harmonic phonon theory for structural instability studies for the alloys.
Structural, electronic and vibrational properties of lanthanide monophosphide at high pressure
International Nuclear Information System (INIS)
Panchal, J. M.; Joshi, Mitesh; Gajjar, P. N.
2016-01-01
A first-principles plane wave self-consistent method with the ultra-soft-pseudopotential scheme in the framework of the density functional theory (DFT) is performed to study structural, electronic and vibrational properties of LaP for Rock-salt (NaCl/Bl) and Cesium-chloride (CsCl/B2) phases. The instability of Rock-salt (NaCl/Bl) phases around the transition is discussed. Conclusions based on electronic energy band structure, density of state, phonon dispersion and phonon density of states in both phases are outlined. The calculated results are consistence and confirm the successful applicability of quasi-harmonic phonon theory for structural instability studies for the alloys.
Experimental results of active control on a large structure to suppress vibration
Dunn, H. J.
1991-01-01
Three design methods, Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR), H-infinity, and mu-synthesis, are used to obtain compensators for suppressing the vibrations of a 10-bay vertical truss structure, a component typical of what may be used to build a large space structure. For the design process the plant dynamic characteristics of the structure were determined experimentally using an identification method. The resulting compensators were implemented on a digital computer and tested for their ability to suppress the first bending mode response of the 10-bay vertical truss. Time histories of the measured motion are presented, and modal damping obtained during the experiments are compared with analytical predictions. The advantages and disadvantages of using the various design methods are discussed.
Vibrational dynamics and band structure of methyl-terminated Ge(111)
International Nuclear Information System (INIS)
th Street, Chicago, Illinois 60637 (United States))" data-affiliation=" (The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637 (United States))" >Hund, Zachary M.; th Street, Chicago, Illinois 60637 (United States))" data-affiliation=" (The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637 (United States))" >Nihill, Kevin J.; th Street, Chicago, Illinois 60637 (United States))" data-affiliation=" (The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637 (United States))" >Sibener, S. J.; Campi, Davide; Bernasconi, M.; Wong, Keith T.; Lewis, Nathan S.; Benedek, G.
2015-01-01
A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge(111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge(111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD 3 -Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH 3 -Ge(111) and CH 3 -Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers
Vibrational dynamics and band structure of methyl-terminated Ge(111)
Energy Technology Data Exchange (ETDEWEB)
Hund, Zachary M.; Nihill, Kevin J.; Sibener, S. J., E-mail: s-sibener@uchicago.edu [The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57" t" h Street, Chicago, Illinois 60637 (United States); Campi, Davide; Bernasconi, M. [Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy); Wong, Keith T.; Lewis, Nathan S. [Division of Chemistry and Chemical Engineering, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 210 Noyes Laboratory, 127-72, Pasadena, California 91125 (United States); Benedek, G. [Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy); Donostia International Physics Center (DIPC), Universidad del País Vasco (EHU), 20018 Donostia/San Sebastian (Spain)
2015-09-28
A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge(111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge(111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD{sub 3}-Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH{sub 3}-Ge(111) and CH{sub 3}-Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers.
Vibration Control of Structures using Vibro-Impact Nonlinear Energy Sinks
Directory of Open Access Journals (Sweden)
M. Ahmadi
2016-09-01
Full Text Available Using Vibro-Impact Nonlinear Energy Sinks (VI NESs is one of the novel strategies to control structural vibrations and mitigate their seismic response. In this system, a mass is tuned on the structure floor, so that it has a specific distance from an inelastic constraint connected to the floor mass. In case of structure stimulation, the displaced VI NES mass collides with the inelastic constraint and upon impacts, energy is dissipated. In the present work, VI NES is studied when its parameters, including clearance and stiffness ratio, are simultaneously optimized. Harmony search as a recent meta-heuristic algorithm is efficiently specialized and utilized for the aforementioned continuous optimization problem. The optimized attached VI NES is thus shown to be capable of interacting with the primary structure over a wide range of frequencies. The resulting controlled response is then investigated, in a variety of low and medium rise steel moment frames, via nonlinear dynamic time history analyses. Capability of the VI NES to dissipate siesmic input energy of earthquakes and their capabilitiy in reducing response of srtructures effectively, through vibro-impacts between the energy sink’s mass and the floor mass, is discussed by extracting several performance indices and the corresponding Fourier spectra. Results of the numerical simulations done on some structural model examples reveal that the optimized VI NES has caused successive redistribution of energy from low-frequency high-amplitude vibration modes to high-frequency low-amplitude modes, bringing about the desired attenuation of the structural responses.
International Nuclear Information System (INIS)
Berger, E.; Tinic, S.
1988-01-01
The Beznau Nuclear Power Plant is located in northern Switzerland. The plant is owned and operated by the Nordostschweizerische Kraftwerke AG (NOK) in Baden, Switzerland. It is a twin unit plant (2 x 350 MWe) which was designed in the early 1960's and placed into commercial operation between 1969 and 1971. In connection with a major backfit project, which will improve the safety of the plant against external events, the free-standing boric water tanks had to be relocated and were replaced by two boric water tanks in a new building (the so called BOTA-building). It enabled to plan and perform full scale vibration tests.The scope of experimental investigation was to determine the eigenfrequencies and damping values for fundamental soil-structure interaction. The vibration tests allowed identification of the important modes of the soil-structure system in the range 3 to 15 Hz. The excitation was strung enough to generate accelerations in the structure comparable to those of a small earthquake. From the comparisons of computed and measured results it is concluded that the rocking frequency can be reasonably well predicted by either Finite Element or Lumped Parameter models with springs simulating the soil-foundation stiffness, provided in the case of the latter the embedment is taken into account. The prediction of the amplitude of structural response appears to be more difficult, as shown by the differences in the mode shapes. In the frequency range 8 to 10 Hz the agreement between computed and test results was less satisfactory. The actual structural behaviour turned out to be more complex than expected and needs further investigation with the aid of more refined models for the soil-structure system
Energy Technology Data Exchange (ETDEWEB)
Berger, E [Basler and Hofmann AG, Consulting Engineers, Zurich (Switzerland); Tinic, S [Nordostschweizerische Kraftwerke AG, Baden (Switzerland)
1988-07-01
The Beznau Nuclear Power Plant is located in northern Switzerland. The plant is owned and operated by the Nordostschweizerische Kraftwerke AG (NOK) in Baden, Switzerland. It is a twin unit plant (2 x 350 MWe) which was designed in the early 1960's and placed into commercial operation between 1969 and 1971. In connection with a major backfit project, which will improve the safety of the plant against external events, the free-standing boric water tanks had to be relocated and were replaced by two boric water tanks in a new building (the so called BOTA-building). It enabled to plan and perform full scale vibration tests.The scope of experimental investigation was to determine the eigenfrequencies and damping values for fundamental soil-structure interaction. The vibration tests allowed identification of the important modes of the soil-structure system in the range 3 to 15 Hz. The excitation was strung enough to generate accelerations in the structure comparable to those of a small earthquake. From the comparisons of computed and measured results it is concluded that the rocking frequency can be reasonably well predicted by either Finite Element or Lumped Parameter models with springs simulating the soil-foundation stiffness, provided in the case of the latter the embedment is taken into account. The prediction of the amplitude of structural response appears to be more difficult, as shown by the differences in the mode shapes. In the frequency range 8 to 10 Hz the agreement between computed and test results was less satisfactory. The actual structural behaviour turned out to be more complex than expected and needs further investigation with the aid of more refined models for the soil-structure system.
International Nuclear Information System (INIS)
Aspelund, O.
In the nuclear structure part, the foundations of Faessler and Greiner's rotation-vibration coupling theory are reviewed, whereafter an alternative derivation of Faessler and Greiner's Hamiltonian is presented. A non-spherical quadrupole phonon number N is defined and used in the matrix elements reported for odd-even/even-odd nuclei. These matrix elements are shown to evince oblate-prolate effects that can be exploited for assessing the signs of quadrupole deformations. In the nuclear reaction part, the wave functions emerging from the structure part are applied in a complete and consistent description of elastic and inelastic particle scattering, one-nucleon transfer, and particle/γ-ray angular correlations. The intentions are to demonstrate that anomolous angular distributions and 1=2 j-effects observed in one-nucleon transfer are interrelated phenomena, that can be satisfactorily explained in terms of the elementary vibrational excitation modes inherent in Faessler and Greiner's theory. The latter is regarded as a non-spherical approach to the theory of the quadrupole component of the nuclear potential energy surface. (Auth.)
Directory of Open Access Journals (Sweden)
Jeffrey D. Poston
2017-11-01
Full Text Available Counting the number of occupants in building areas over time—occupancy tracking—provides valuable information for responding to emergencies, optimizing thermal conditions or managing personnel. This capability is distinct from tracking individual building occupants as they move within a building, has lower complexity than conventional tracking algorithms require, and avoids privacy concerns that tracking individuals may pose. The approach proposed here is a novel combination of data analytics applied to measurements from a building’s structural dynamics sensors (e.g., accelerometers or geophones. Specifically, measurements of footstep-generated structural waves provide evidence of occupancy in a building area. These footstep vibrations can be distinguished from other vibrations, and, once identified, the footsteps can be located. These locations, in turn, form the starting point of estimating occupancy in an area. In order to provide a meaningful occupancy count, however, it is first necessary to associate discrete footsteps with individuals. The proposed framework incorporates a tractable algorithm for this association task. The proposed algorithms operate online, updating occupancy count over time as new footsteps are detected. Experiments with measurements from a public building illustrate the operation of the proposed framework. This approach offers an advantage over others based on conventional technologies by avoiding the cost of a separate sensor system devoted to occupancy tracking.
Arjunan, V.; Raj, Arushma; Santhanam, R.; Marchewka, M. K.; Mohan, S.
2013-02-01
Extensive vibrational investigations of 2-amino-4-methoxybenzothiazole have been carried out with FTIR and FT-Raman spectral techniques. The electronic structure of the molecule has been analysed by UV-Visible and NMR spectroscopies. The DFT studies were carried out with B3LYP and HF methods utilising 6-31G(d,p), 6-311++G(d,p) and cc-pVDZ basis sets to determine the structural, thermodynamical, vibrational, electronic characteristics of the compound and also to understand the electronic and steric influence of the methoxy amino groups on the skeletal frequencies. The mixing of the fundamental modes was determined with the help of total energy distribution (TED). The energies of the frontier molecular orbitals have also been determined. The kinetic and thermodynamic stability and chemical hardness of the molecule have been determined. Complete NBO analysis was also carried out to find out the intramolecular electronic interactions and their stabilisation energy. 1H and 13C NMR chemical shifts and the electronic transitions of the molecule are also discussed.
Arjunan, V; Raj, Arushma; Santhanam, R; Marchewka, M K; Mohan, S
2013-02-01
Extensive vibrational investigations of 2-amino-4-methoxybenzothiazole have been carried out with FTIR and FT-Raman spectral techniques. The electronic structure of the molecule has been analysed by UV-Visible and NMR spectroscopies. The DFT studies were carried out with B3LYP and HF methods utilising 6-31G(d,p), 6-311++G(d,p) and cc-pVDZ basis sets to determine the structural, thermodynamical, vibrational, electronic characteristics of the compound and also to understand the electronic and steric influence of the methoxy amino groups on the skeletal frequencies. The mixing of the fundamental modes was determined with the help of total energy distribution (TED). The energies of the frontier molecular orbitals have also been determined. The kinetic and thermodynamic stability and chemical hardness of the molecule have been determined. Complete NBO analysis was also carried out to find out the intramolecular electronic interactions and their stabilisation energy. (1)H and (13)C NMR chemical shifts and the electronic transitions of the molecule are also discussed. Copyright © 2012 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Arkadiusz Mróz
2015-01-01
Full Text Available A numerical study is presented, which tailors so-called prestress accumulation-release (PAR strategy to mitigate free vibrations of frame structures. First, the concept of proposed semiactive technique is outlined and possible applications are specified. In the second part of the work a parametric study is discussed, which illustrates the potential of the method for mitigation of free vibrations induced by impact or other initial load scenarios. Special attention is given to the energy balance including all relevant contributions to the total energy of the considered dissipative system. The proposed technique shows a very high potential in mitigation of free vibrations, exceeding 99% of the reference amplitude after 5 cycles of vibration.
International Nuclear Information System (INIS)
Opdahl, Aric; Koffas, Telly S; Amitay-Sadovsky, Ella; Kim, Joonyeong; Somorjai, Gabor A
2004-01-01
Sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM) have been used to study polymer surface structure and surface mechanical behaviour, specifically to study the relationships between the surface properties of polymers and their bulk compositions and the environment to which the polymer is exposed. The combination of SFG surface vibrational spectroscopy and AFM has been used to study surface segregation behaviour of polyolefin blends at the polymer/air and polymer/solid interfaces. SFG surface vibrational spectroscopy and AFM experiments have also been performed to characterize the properties of polymer/liquid and polymer/polymer interfaces, focusing on hydrogel materials. A method was developed to study the surface properties of hydrogel contact lens materials at various hydration conditions. Finally, the effect of mechanical stretching on the surface composition and surface mechanical behaviour of phase-separated polyurethanes, used in biomedical implant devices, has been studied by both SFG surface vibrational spectroscopy and AFM. (topical review)
TLP Structural Health Monitoring Based on Vibration Signal of Energy Harvesting System
Directory of Open Access Journals (Sweden)
Vahid Jahangiri
Full Text Available Abstract Structural Health Monitoring (SHM of Tension Leg Platform (TLP is very crucial for preventing catastrophic and sudden collapse of the structures. One of the methods of monitoring these structures is implementing SHM sensors. Supplying energy for these sensors for a long period is a challenging problem. So, one of the new methods of supplying energy for SHM, is usage of mechanical energy. In this method, the piezoelectric material is employed to convert the mechanical energy which is resulted from vibration of structure, to electrical energy. The advantage of this method is based on not implementing the battery charging system. Therefore, in this paper, after modeling TLP structure, energy supplying of these sensors with piezoelectric converters is studied. Furthermore, fault diagnosis of these structures in the presence of different uncertainties is proposed by the features of voltage signal, produced from piezoelectric patches and fuzzy classification method. Results show that this method can diagnose faults of the structure with an acceptable success rate.
U.S. Department of Health & Human Services — A list of a variety of averages for each state or territory as well as the national average, including each quality measure, staffing, fine amount and number of...
Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure
Directory of Open Access Journals (Sweden)
Pengwei Li
2015-04-01
Full Text Available As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.
Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure
Energy Technology Data Exchange (ETDEWEB)
Li, Pengwei, E-mail: lipengwei@tyut.edu.cn; Wang, Yanfen; Luo, Cuixian; Li, Gang; Hu, Jie; Zhang, Wendong [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Liu, Ying [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China); Liu, Wei [Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China)
2015-04-15
As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams) show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.
An Efficient Modal Control Strategy for the Active Vibration Control of a Truss Structure
Directory of Open Access Journals (Sweden)
Ricardo Carvalhal
2007-01-01
Full Text Available In this paper an efficient modal control strategy is described for the active vibration control of a truss structure. In this approach, a feedback force is applied to each mode to be controlled according to a weighting factor that is determined by assessing how much each mode is excited by the primary source. The strategy is effective provided that the primary source is at a fixed position on the structure, and that the source is stationary in the statistical sense. To test the effectiveness of the control strategy it is compared with an alternative, established approach namely, Independent Modal Space Control (IMSC. Numerical simulations show that with the new strategy it is possible to significantly reduce the control effort required, with a minimal reduction in control performance.
Numerical solution of quadratic matrix equations for free vibration analysis of structures
Gupta, K. K.
1975-01-01
This paper is concerned with the efficient and accurate solution of the eigenvalue problem represented by quadratic matrix equations. Such matrix forms are obtained in connection with the free vibration analysis of structures, discretized by finite 'dynamic' elements, resulting in frequency-dependent stiffness and inertia matrices. The paper presents a new numerical solution procedure of the quadratic matrix equations, based on a combined Sturm sequence and inverse iteration technique enabling economical and accurate determination of a few required eigenvalues and associated vectors. An alternative procedure based on a simultaneous iteration procedure is also described when only the first few modes are the usual requirement. The employment of finite dynamic elements in conjunction with the presently developed eigenvalue routines results in a most significant economy in the dynamic analysis of structures.
Directory of Open Access Journals (Sweden)
Marius STAN
2013-05-01
Full Text Available Vibration analysis applications in operation is one of the diagnostic methods ofoperation of the facility. Analysis of these types of failures indicated the existence of specificfeatures prints and related equipment vibration spectra. Modeling and identification of theseparticular aspects in the spectrum of vibration machines help to control the operation of oilfacilities built safely.
Marius STAN
2013-01-01
Vibration analysis applications in operation is one of the diagnostic methods ofoperation of the facility. Analysis of these types of failures indicated the existence of specificfeatures prints and related equipment vibration spectra. Modeling and identification of theseparticular aspects in the spectrum of vibration machines help to control the operation of oilfacilities built safely.
International Nuclear Information System (INIS)
Kessentini, A.; Belhouchet, M.; Suñol, J.J.; Abid, Y.; Mhiri, T.
2014-01-01
The crystals of the family of alkylammonuim tetrachloridocuprate (II), (C 5 H 7 N 2 ) 2 CuCl 4 H 2 O, have been grown, structurally characterized and their vibrational as well as optical properties been studied. A preliminary single crystal X-ray diffraction structural analysis has revealed that the title compound belongs to the monoclinic system with space group C2/c. Its unit cell dimensions are: a=8.454 (2) Å, b=14.279 (2) Å, c=14.363 (3) Å, β=95.813 (4)°, with Z=4 and its crystal structure was determined and refined down to R 1 =0.029 and wR 2 =0.080. The crystal lattice is composed of discrete [CuCl 4 ] 2− tetrahedra surrounded by 4-aminopyridinium cations and water molecules which are interconnected by means of hydrogen bonding contacts [N–H…Cl, O–H…Cl and N–H…O]. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The optimized molecular structure and the vibrational spectra were calculated by the density functional theory (DFT) method using the B3LYP function. The organic–inorganic hybrid crystal thin film can be easily prepared by spin-coating method from the ethanol solution of the (C 5 H 7 N 2 ) 2 CuCl 4 H 2 O perovskite and it showed characteristic absorptions of CuCl-based layered perovskite centered at 288 and 400 nm, as well as the photoluminescence peak at around 443 nm. The unaided-eye-detectable blue luminescence emission comes from the excitonic transition in the CuCl 4 anions. - Highlights: • A new hybrid compound (C 5 H 7 N 2 ) 2 CuCl 4 H 2 O was synthesized. • Vibrational properties were studied by IR and Raman spectroscopy and examined theoretically using the DFT/B3LYP/LanL2DZ level of theory. • The UV–vis spectrum shows two absorption peaks at 288 and at 400 nm. • This compound show a strong blue emission at 443 nm
Energy Technology Data Exchange (ETDEWEB)
Kessentini, A., E-mail: kessentiniabir@gmail.com [Laboratoire Physico-Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Belhouchet, M. [Laboratoire Physico-Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Suñol, J.J. [Departamento De Fisica, Universita de Girona, Compus Montilivi, Girona 17071 (Spain); Abid, Y. [Laboratoire de Physique appliquée, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Mhiri, T. [Laboratoire Physico-Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia)
2014-05-01
The crystals of the family of alkylammonuim tetrachloridocuprate (II), (C{sub 5}H{sub 7}N{sub 2}){sub 2}CuCl{sub 4}H{sub 2}O, have been grown, structurally characterized and their vibrational as well as optical properties been studied. A preliminary single crystal X-ray diffraction structural analysis has revealed that the title compound belongs to the monoclinic system with space group C2/c. Its unit cell dimensions are: a=8.454 (2) Å, b=14.279 (2) Å, c=14.363 (3) Å, β=95.813 (4)°, with Z=4 and its crystal structure was determined and refined down to R{sub 1}=0.029 and wR{sub 2}=0.080. The crystal lattice is composed of discrete [CuCl{sub 4}]{sup 2−} tetrahedra surrounded by 4-aminopyridinium cations and water molecules which are interconnected by means of hydrogen bonding contacts [N–H…Cl, O–H…Cl and N–H…O]. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The optimized molecular structure and the vibrational spectra were calculated by the density functional theory (DFT) method using the B3LYP function. The organic–inorganic hybrid crystal thin film can be easily prepared by spin-coating method from the ethanol solution of the (C{sub 5}H{sub 7}N{sub 2}){sub 2}CuCl{sub 4}H{sub 2}O perovskite and it showed characteristic absorptions of CuCl-based layered perovskite centered at 288 and 400 nm, as well as the photoluminescence peak at around 443 nm. The unaided-eye-detectable blue luminescence emission comes from the excitonic transition in the CuCl{sub 4} anions. - Highlights: • A new hybrid compound (C{sub 5}H{sub 7}N{sub 2}){sub 2}CuCl{sub 4}H{sub 2}O was synthesized. • Vibrational properties were studied by IR and Raman spectroscopy and examined theoretically using the DFT/B3LYP/LanL2DZ level of theory. • The UV–vis spectrum shows two absorption peaks at 288 and at 400 nm. • This compound show a strong blue emission at 443 nm.
International Nuclear Information System (INIS)
Granger, S.; Perotin, L.
1997-01-01
Maintaining the PWR components under reliable operating conditions requires a complex design to prevent various damaging processes, including fatigue and wear problems due to flow-induced vibration. In many practical situations, it is difficult, if not impossible, to perform direct measurements or calculations of the external forces acting on vibrating structures. Instead, vibrational responses can often be conveniently measured. This paper presents an inverse method for estimating a distributed random excitation from the measurement of the structural response at a number of discrete points. This paper is devoted to the presentation of the theoretical development. The force identification method is based on a modal model for the structure and a spatial orthonormal decomposition of the excitation field. The estimation of the Fourier coefficients of this orthonormal expansion is presented. As this problem turns out to be ill-posed, a regularization process is introduced. The minimization problem associated to this process is then formulated and its solutions is developed. (author)
Carr, J. K.; Buchanan, L. E.; Schmidt, J. R.; Zanni, M. T.; Skinner, J. L.
2013-01-01
Urea/water is an archetypical “biological” mixture, and is especially well known for its relevance to protein thermodynamics, as urea acts as a protein denaturant at high concentration. This behavior has given rise to an extended debate concerning urea’s influence on water structure. Based on a variety of methods and of definitions of water structure, urea has been variously described as a structure-breaker, a structure-maker, or as remarkably neutral towards water. Because of its sensitivity to microscopic structure and dynamics, vibrational spectroscopy can help resolve these debates. We report experimental and theoretical spectroscopic results for the OD stretch of HOD/H2O/urea mixtures (linear IR, 2DIR, and pump-probe anisotropy decay) and for the CO stretch of urea-D4/D2O mixtures (linear IR only). Theoretical results are obtained using existing approaches for water, and a modification of a frequency map developed for acetamide. All absorption spectra are remarkably insensitive to urea concentration, consistent with the idea that urea only very weakly perturbs water structure. Both this work and experiments by Rezus and Bakker, however, show that water’s rotational dynamics are slowed down by urea. Analysis of the simulations casts doubt on the suggestion that urea immobilizes particular doubly hydrogen bonded water molecules. PMID:23841646
Ye, Shuji; Wei, Feng; Li, Hongchun; Tian, Kangzhen; Luo, Yi
2013-01-01
In situ and real-time characterization of molecular structures and orientation of proteins at interfaces is essential to understand the nature of interfacial protein interaction. Such work will undoubtedly provide important clues to control biointerface in a desired manner. Sum frequency generation vibrational spectroscopy (SFG-VS) has been demonstrated to be a powerful technique to study the interfacial structures and interactions at the molecular level. This paper first systematically introduced the methods for the calculation of the Raman polarizability tensor, infrared transition dipole moment, and SFG molecular hyperpolarizability tensor elements of proteins/peptides with the secondary structures of α-helix, 310-helix, antiparallel β-sheet, and parallel β-sheet, as well as the methodology to determine the orientation of interfacial protein secondary structures using SFG amide I spectra. After that, recent progresses on the determination of protein structure and orientation at different interfaces by SFG-VS were then reviewed, which provides a molecular-level understanding of the structures and interactions of interfacial proteins, specially understanding the nature of driving force behind such interactions. Although this review has focused on analysis of amide I spectra, it will be expected to offer a basic idea for the spectral analysis of amide III SFG signals and other complicated molecular systems such as RNA and DNA. Copyright © 2013 Elsevier Inc. All rights reserved.
Analysis of an NPP Structure subjected to Vibrations Induced from Airplane Crashes
International Nuclear Information System (INIS)
Noh, Sang Hoon; Kim, Yong Soo; Kim, Chong Hak
2009-01-01
After the terrorists' attacks with civilian airplanes on September 11, 2001, special attention has been paid to the potential for an airplane crash into a Nuclear Power Plant (NPP) as a man-made hazard. An airplane crash (APC) into an NPP has the potential to damage the roofs and walls of these structures, as well as other systems and components such as pipelines, electric motors, power supplies, power cables of electricity transmission that are important for safety. Therefore, an evaluation of the structural response to an APC is important for the safety of NPPs to be confirmed. A structural integrity analysis was carried out focusing on the vibration effects of an APC on an NPP structure. The NPP structure under consideration has been conceptually redesigned based on APR1400 to have double containments for the purpose of a feasibility study to meet European requirements. The finite element method was used for the structural analysis of the NPP, and the computer code ABAQUS was employed for this analysis
Energy Technology Data Exchange (ETDEWEB)
Sharpes, Nathan; Kumar, Prashant [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Abdelkefi, Abdessattar; Abdelmoula, Hichem [Department of Mechanical and Aerospace Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Adler, Jan [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Institute of Dynamics and Vibration Research (IDS), Leibniz Universität, Hannover 30167 (Germany); Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)
2016-07-18
Mode shapes in the design of mechanical energy harvesters, as a means of performance increase, have been largely overlooked. Currently, the vast majority of energy harvester designs employ some variation of a single-degree-of-freedom cantilever, and the mode shapes of such beams are well known. This is especially true for the first bending mode, which is almost exclusively the chosen vibration mode for energy harvesting. Two-dimensional beam shapes (those which curve, meander, spiral, etc., in a plane) have recently gained research interest, as they offer freedom to modify the vibration characteristics of the harvester beam for achieving higher power density. In this study, the second bending mode shape of the “Elephant” two-dimensional beam shape is examined, and its interaction with the first bending mode is evaluated. A combinatory mode shape created by using mass loading structural modification to lower the second bending modal frequency was found to interact with the first bending mode. This is possible since the first two bending modes do not share common areas of displacement. The combined mode shape is shown to produce the most power of any of the considered mode shapes.
Analysis of the phenomena associated with structural damage using real time vibration analysis
International Nuclear Information System (INIS)
Garcia Peyrano, O; Cismondi, L; Damiani, H; Torres, E
2004-01-01
It is of interest to have analytical methodologies available for the dynamic behavior of large mechanical structures like those in thermal cycle systems of nuclear power plants or in transport systems during the experimental stage prior to their construction, as happens in aeronautics, where prototypes are tested in experimental banks on a scale of 1 to 1. The same does not occur with systems for the generation of electrical energy such as a nuclear power plant or in ships, competition automobiles, railway systems, etc. Not because of the technical impossibility but because of the high costs involved. This work aims to implement a technology based on the analysis of the vibrations to obtain a profile of the modal dynamic response and its influence on the critical components of the mechanisms with the particularity of detecting the preventive location of the component that may suffer a potential damage. The Vibrations Analysis Laboratory has resolved different cases in the Embalse Nuclear Plant, in the Atucha Nuclear Plant, in the Heavy Water Industrial Plant, in the automobile industry and in other industrial areas (CW)
Application of smart structure concepts to vibration suppression of a cryocooler coldfinger
International Nuclear Information System (INIS)
Glaser, R.J.; Kuo, Chinpo, Garba, J.A.
1993-01-01
A flight experiment demonstrating vibration suppression using smart structure technology is being flown on a small British satellite in late 1993. Piezo actuators are used to suppress motion of the tip of a cryocooler coldfinger in three dimensions. Two actuation methods are being demonstrated: low voltage piezo translators and applique ceramics. The applique ceramics stretch the coldfinger to cancel the tip motion and is discussed in detail in a companion paper. Commercially available piezo translators displace the entire cryocooler to cancel the motion of the tip of the coldfinger as measured by three eddy current transducers. Two types of control systems are being demonstrated: a real time analog control system using position feedback, and a digital feed forward controller that updates it's waveform every second or so. The flight experiment is a technology demonstration. The coldfinger is not being used to cool an operational sensor. Instead, the cooler vibration experiment will demonstrate that this class of hardware can be flown successfully. This includes qualification of the piezos for launch, and for the space environment; the design and qualification of low-power flight piezo drivers; and design and implementation of the control systems
Tanak, Hasan; Marchewka, Mariusz K.; Drozd, Marek
2013-03-01
The experimental and theoretical vibrational spectra of Bis(melaminium) terephthalate dihydrate were studied. The Fourier transform infrared (FT-IR) spectra of the Bis(melaminium) terephthalate dihydrate and its deuterated analogue were recorded in the solid phase. The molecular geometry and vibrational frequencies of Bis(melaminium) terephthalate dihydrate in the ground state have been calculated by using the density functional method (B3LYP) with 6-31++G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains the weak hydrogen bonds of Nsbnd H⋯O, Nsbnd H⋯N and Osbnd H⋯O types, and those bonds are calculated with DFT method. In addition, molecular electrostatic potential, frontier molecular orbitals and natural bond orbital analysis of the title compound were investigated by theoretical calculations. The lack of the second harmonic generation (SHG) confirms the presence of macroscopic center of inversion.
Harne, Ryan L
2012-07-01
Conversion of ambient vibrational energy into electric power has been the impetus of much modern research. The traditional analysis has focused on absolute electrical power output from the harvesting devices and efficiency defined as the convertibility of an infinite resource of vibration excitation into power. This perspective has limited extensibility when applying resonant harvesters to host resonant structures when the inertial influence of the harvester is more significant. Instead, this work pursues a fundamental understanding of the coupled dynamics of a main mass-spring-damper system to which an electromagnetic or piezoelectric mass-spring-damper is attached. The governing equations are derived, a metric of efficiency is presented, and analysis is undertaken. It is found that electromagnetic energy harvesting efficiency and maximum power output is limited by the strength of the coupling such that no split system resonances are induced for a given mass ratio. For piezoelectric harvesters, only the coupling strength and certain design requirements dictate maximum power and efficiency achievable. Since the harvesting circuitry must "follow" the split resonances as the piezoelectric harvesters become more massive, the optimum design of piezoelectric harvesters appears to be more involved than for electromagnetic devices.
Yuan, Yongliang; Song, Xueguan; Sun, Wei; Wang, Xiaobang
2018-05-01
The dynamic performance of a belt drive system is composed of many factors, such as the efficiency, the vibration, and the optimal parameters. The conventional design only considers the basic performance of the belt drive system, while ignoring its overall performance. To address all these challenges, the study on vibration characteristics and optimization strategies could be a feasible way. This paper proposes a new optimization strategy and takes a belt drive design optimization as a case study based on the multidisciplinary design optimization (MDO). The MDO of the belt drive system is established and the corresponding sub-systems are analyzed. The multidisciplinary optimization is performed by using an improved genetic algorithm. Based on the optimal results obtained from the MDO, the three-dimension (3D) model of the belt drive system is established for dynamics simulation by virtual prototyping. From the comparison of the results with respect to different velocities and loads, the MDO method can effectively reduce the transverse vibration amplitude. The law of the vibration displacement, the vibration frequency, and the influence of velocities on the transverse vibrations has been obtained. Results show that the MDO method is of great help to obtain the optimal structural parameters. Furthermore, the kinematics principle of the belt drive has been obtained. The belt drive design case indicates that the proposed method in this paper can also be used to solve other engineering optimization problems efficiently.
Directory of Open Access Journals (Sweden)
Jiménez-Alonso, J. F.
2014-12-01
Full Text Available Although the scientific community had knowledge of the human induced vibration problems in structures since the end of the 19th century, it was not until the occurrence of the vibration phenomenon happened in the Millennium Bridge (London, 2000 that the importance of the problem revealed and a higher level of attention devoted. Despite the large advances achieved in the determination of the human-structure interaction force, one of the main deficiencies of the existing models is the exclusion of the effect of changes in the footbridge dynamic properties due to the presence of pedestrians. In this paper, the formulation of a human-structure interaction model, addresses these limitations, is carried out and its reliability is verified from previously published experimental results.Aunque la comunidad científica tenía conocimiento de los problemas vibratorios inducidos por peatones en estructuras desde finales del siglo xix, no fue hasta la ocurrencia de los eventos vibratorios acontecidos en la pasarela del Milenio (Londres, 2000, cuando la importancia del problema se puso de manifiesto y se le comenzó a dedicar un mayor nivel de atención. A pesar de los grandes avances alcanzados en la caracterización de la fuerza de interacción peatón-estructura una de las principales deficiencias de los modelos existentes es la exclusión del cambio en las propiedades dinámicas de la pasarela por la presencia de peatones. En este artículo, se presenta la formulación de un modelo de interacción peatón-estructura que intenta dar respuesta a dichas limitaciones, y su validación a partir de resultados experimentales previamente publicados por otros autores.
Spálovská, Dita; Králík, František; Kohout, Michal; Jurásek, Bronislav; Habartová, Lucie; Kuchař, Martin; Setnička, Vladimír
2018-05-01
Recently, there has been a worldwide substantial increase in the consumption of new psychoactive substances (NPS), compounds that mimic the structure of illicit drugs, such as amphetamines or ecstasy. The producers try to avoid the law by a slight modification of illicit structures, thereby developing dozens of temporarily legal NPS every year. The current trends in the detection and monitoring of such substances demand a fast and reliable analysis. Molecular spectroscopy represents a highly effective tool for the identification of NPS and chiroptical methods can provide further information on their 3D structure, which is the key for the determination of their biological activity. We present the first systematic study of NPS, specifically butylone, combining chiroptical and vibrational spectroscopies with ab initio calculations. According to density functional theory calculations, 6 stable lowest energy conformers of butylone were found and their molecular structure was described. For each conformer, the relative abundance based on the Boltzmann distribution was estimated, their population weighted spectra predicted and compared to the experimental results. Very good agreement between the experimental and the simulated spectra was achieved, which allowed not only the assignment of the absolute configuration, but also a precise description of the molecular structure. © 2018 Wiley Periodicals, Inc.
Analysis of Parameters Assessment on Laminated Rubber-Metal Spring for Structural Vibration
International Nuclear Information System (INIS)
Salim, M.A.; Putra, A.; Mansor, M.R.; Musthafah, M.T.; Akop, M.Z.; Abdullah, M.A.
2016-01-01
This paper presents the analysis of parameter assessment on laminated rubber-metal spring (LR-MS) for vibrating structure. Three parameters were selected for the assessment which are mass, Young's modulus and radius. Natural rubber materials has been used to develop the LR-MS model. Three analyses were later conducted based on the selected parameters to the LR-MS performance which are natural frequency, location of the internal resonance frequency and transmissibility of internal resonance. Results of the analysis performed were plotted in frequency domain function graph. Transmissibility of laminated rubber-metal spring (LR-MS) is changed by changing the value of the parameter. This occurrence was referred to the theory from open literature then final conclusion has been make which are these parameters have a potential to give an effects and trends for LR-MS transmissibility. (paper)
Energy Technology Data Exchange (ETDEWEB)
Proskuryakov, K.N.; Yang Shan Afshar, E.; Polyakov, N.I. [Nuclear Power Plant Department of Moscow Power Engineering Institute Technical Univ., Moscow (Russian Federation)
2007-07-01
The experimental data that have been obtained from the measurements of noise signals in primary circuit of NPP with reactor of WWER-1000 are presented. The causes of resonant interaction between Eigen-Frequencies of Oscillations of the Coolant Pressure (EFOCP) and structure vibrations are discussed. An application-oriented approach to the problem of identification of abnormal phenomena of thermal-hydraulic parameters is proposed. Logarithmic Decrement {delta} is determined. The bigger damping ratio {zeta} provides bigger {delta} and correspondingly smaller values of Q-factor and amplitude X(t)max. All experimental units intended for NPP severe accident investigation must satisfy to the NPP Q-factor criterion of similarity. (authors)
International Nuclear Information System (INIS)
Proskuryakov, K.N.; Yang Shan Afshar, E.; Polyakov, N.I.
2007-01-01
The experimental data that have been obtained from the measurements of noise signals in primary circuit of NPP with reactor of WWER-1000 are presented. The causes of resonant interaction between Eigen-Frequencies of Oscillations of the Coolant Pressure (EFOCP) and structure vibrations are discussed. An application-oriented approach to the problem of identification of abnormal phenomena of thermal-hydraulic parameters is proposed. Logarithmic Decrement δ is determined. The bigger damping ratio ζ provides bigger δ and correspondingly smaller values of Q-factor and amplitude X(t)max. All experimental units intended for NPP severe accident investigation must satisfy to the NPP Q-factor criterion of similarity. (authors)
Marchewka, M. K.; Pietraszko, A.
2008-02-01
The piperazinium bis(4-hydroxybenzenesulphonate) crystallizes from water solution at room temperature in P2 1/ c space group of monoclinic system. The crystals are built up of doubly protonated piperazinium cations and ionized 4-hydroxybenzenesulphonate anions that interact through weak hydrogen bonds of O-H⋯O and N-H⋯O type. Mutual orientation of anions is determined by non-conventional hydrogen bonds of C-H⋯π type. Room temperature powder FT IR and FT Raman measurements were carried out. The vibrational spectra are in full agreement with the structure obtained from X-ray crystallography. The big single crystals of the title salt can be grown.
Arjunan, V; Thillai Govindaraja, S; Jayapraksh, A; Mohan, S
2013-04-15
Quantum chemical calculations of energy, structural parameters and vibrational wavenumbers of 4-bromoisoquinoline (4BIQ) were carried out by using B3LYP method using 6-311++G(**), cc-pVTZ and LANL2DZ basis sets. The optimised geometrical parameters obtained by DFT calculations are in good agreement with electron diffraction data. Interpretations of the experimental FTIR and FT-Raman spectra have been reported with the aid of the theoretical wavenumbers. The differences between the observed and scaled wavenumber values of most of the fundamentals are very small. The thermodynamic parameters have also been computed. Electronic properties of the molecule were discussed through the molecular electrostatic potential surface, HOMO-LUMO energy gap and NBO analysis. To provide precise assignments of (1)H and (13)CNMR spectra, isotropic shielding and chemical shifts were calculated with the Gauge-Invariant Atomic Orbital (GIAO) method. Copyright © 2013 Elsevier B.V. All rights reserved.
Arjunan, V; Devi, L; Remya, P; Mohan, S
2013-09-01
The FTIR and FT-Raman spectra of 3,4-dimethoxybenzonitrile (34DMBN) have been analysed. Quantum chemical studies were performed with B3LYP method using 6-311++G(d,p), 6-31G(d,p) and cc-pVTZ basis sets. The electron donating effect of -OCH3 and electron withdrawing effect of -C≡N groups on the ring parameters were thoroughly analysed. The structural parameters, energies, thermodynamic properties, vibrational frequencies and the NBO charges of 34DMBN were determined. The (1)H and (13)C chemical shifts with respect to TMS were investigated and also calculated theoretically using the gauge independent atomic orbital method and compared with the experimental data. The delocalisation energy of different types of bonding interactions was investigated. Copyright © 2013 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Cho Dae Seung
2015-04-01
Full Text Available Thin and thick plates, plates with holes, stiffened panels and stiffened panels with holes are primary structural members in almost all fields of engineering: civil, mechanical, aerospace, naval, ocean etc. In this paper, a simple and efficient procedure for the free vibration analysis of such elements is presented. It is based on the assumed mode method and can handle different plate thickness, various shapes and sizes of holes, different framing sizes and types as well as different combinations of boundary conditions. Natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange’s equations. Mindlin theory is applied for a plate and Timoshenko beam theory for stiffeners. The applicability of the method in the design procedure is illustrated with several numerical examples obtained by the in-house developed code VAPS. Very good agreement with standard commercial finite element software is achieved.
Ngamkhanong, Chayut; Kaewunruen, Sakdirat
2018-06-15
At present, railway infrastructure experiences harsh environments and aggressive loading conditions from increased traffic and load demands. Ground borne vibration has become one of these environmental challenges. Overhead line equipment (OHLE) provides electric power to the train and is, for one or two tracks, normally supported by cantilever masts. A cantilever mast, which is made of H-section steel, is slender and has a poor dynamic behaviour by nature. It can be seen from the literature that ground borne vibrations cause annoyance to people in surrounding areas especially in buildings. Nonetheless, mast structures, which are located nearest and alongside the railway track, have not been fully studied in terms of their dynamic behaviour. This paper presents the effects of ground borne vibrations generated by high speed trains on cantilever masts and contact wire located alongside railway tracks. Ground borne vibration velocities at various train speeds, from 100 km/h to 300 km/h, are considered based on the consideration of semi-empirical models for predicting low frequency vibration on ground. A three-dimensional mast structure with varying soil stiffness is made using a finite element model. The displacement measured is located at the end of cantilever mast which is the position of contact wire. The construction tolerance of contact stagger is used as an allowable movement of contact wire in transverse direction. The results show that the effect of vibration velocity from train on the transverse direction of mast structure is greater than that on the longitudinal direction. Moreover, the results obtained indicate that the ground bourn vibrations caused by high speed train are not strong enough to cause damage to the contact wire. The outcome of this study will help engineers improve the design standard of cantilever mast considering the effect of ground borne vibration as preliminary parameter for construction tolerances. Copyright © 2018 Elsevier B
Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures
Vlahopoulos, Nickolas; Schiller, Noah H.
2011-01-01
The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.
International Nuclear Information System (INIS)
Widjaja, Joko; Samali, Bijan; Li, Jianchun
2007-01-01
This paper presents a study of controllable real-time frequency shift using a fluid pin damper, so called 'smart pin', mounted at a beam-column connection. Unlike the stationary frequency shifter, the pin can increase or decrease the rotational stiffness of the connection, leading to an actively adjustable structural frequency due to real-time responses of polarised magneto-rheological (MR) fluid, whose rheological properties can change in milliseconds. The feedback to the pin damper governs the structural frequency changes. To demonstrate this concept, a single storey plane steel frame model with one hinge and one 'smart pin' damper, mounted at each beam-column connection and subjected to two scaled earthquake excitations, namely El-Centro 1940 and Northridge 1994, which respectively represent near- and farfield excitations, was tested using the shake table at the University of Technology, Sydney (UTS) structures laboratory, for 'proof-of-concept' investigation. Further, the dynamic performance of the model using a proposed switching strategy with a displacement threshold as an indicator for alternately supplied current level (flip-flop) was examined, assuming the earthquake records were known. The results showed some potential use of this control technique for structural vibration mitigation, however, further study to optimize the performance of the switching strategy is still required
Damage Detection in Bridge Structure Using Vibration Data under Random Travelling Vehicle Loads
International Nuclear Information System (INIS)
Loh, C H; Hung, T Y; Chen, S F; Hsu, W T
2015-01-01
Due to the random nature of the road excitation and the inherent uncertainties in bridge-vehicle system, damage identification of bridge structure through continuous monitoring under operating situation become a challenge problem. Methods for system identification and damage detection of a continuous two-span concrete bridge structure in time domain is presented using interaction forces from random moving vehicles as excitation. The signals recorded in different locations of the instrumented bridge are mixed with signals from different internal and external (road roughness) vibration sources. The damage structure is also modelled as the stiffness reduction in one of the beam element. For the purpose of system identification and damage detection three different output-only modal analysis techniques are proposed: The covariance-driven stochastic subspace identification (SSI-COV), the blind source separation algorithms (called Second Order Blind Identification) and the multivariate AR model. The advantages and disadvantages of the three algorithms are discussed. Finally, the null-space damage index, subspace damage indices and mode shape slope change are used to detect and locate the damage. The proposed approaches has been tested in simulation and proved to be effective for structural health monitoring. (paper)
Robinson, J C; Luft, H S
1985-12-01
A variety of recent proposals rely heavily on market forces as a means of controlling hospital cost inflation. Sceptics argue, however, that increased competition might lead to cost-increasing acquisitions of specialized clinical services and other forms of non-price competition as means of attracting physicians and patients. Using data from hospitals in 1972 we analyzed the impact of market structure on average hospital costs, measured in terms of both cost per patient and cost per patient day. Under the retrospective reimbursement system in place at the time, hospitals in more competitive environments exhibited significantly higher costs of production than did those in less competitive environments.
International Nuclear Information System (INIS)
McCallen, D.
1997-01-01
Alignment requirements for the National Ignition Facility (NIF) optical components will require a number of support structures which minimize the system displacements and deformations. The stringent design requirements for this facility will result in a system in which vibrations due to ambient environmental loads (e.g. foundation motion due to typical traffic loads, microseisms or nearby equipment) will have a significant, and perhaps predominant, influence on the design of the supporting structures. When considering the total deformations and displacements of the structural systems, the contribution of the foundation to the overall system flexibility must be addressed. Classical fixed-base structural analyses, which are predicated on an assumption of an infinitely rigid foundation system, neglect the influence of foundation flexibility and for the vibration regime in which the NIF structures reside, may result in significant underestimation of the system ambient vibration displacements. In the work described herein, parametric studies were performed in order to understand the potential contributions of soil-structure- interaction (SSI) to optical system displacements. Time domain finite element analyses were employed to quantify the effect of wave scattering by the mat foundation and the effects of inertial SSI due to the rocking of the massive shear wall support structures. A simplified procedure is recommended for accounting for SSI effects in the design of the special equipment structures. The simplified approach consists of applying a scale factor to displacements obtained from fixed base analyses to approximately account for the effects of soil-structure interaction and variable support input motion
Fang, C.M.; Wijs, G.A. de
2004-01-01
The phonon spectrum Of C3N4 with defect zincblende-type structure (deltaC(3)N(4)) was calculated by density functional theory (DFT) techniques. The results permit an assessment of important mechanical and thermodynamical properties such as the bulk modulus, lattice specific heat, vibration energy,
Directory of Open Access Journals (Sweden)
Reem Yassine
2016-12-01
Full Text Available The frequency response function is a quantitative measure used in structural analysis and engineering design; hence, it is targeted for accuracy. For a large structure, a high number of substructures, also called cells, must be considered, which will lead to a high amount of computational time. In this paper, the recursive method, a finite element method, is used for computing the frequency response function, independent of the number of cells with much lesser time costs. The fundamental principle is eliminating the internal degrees of freedom that are at the interface between a cell and its succeeding one. The method is applied solely for free (no load nodes. Based on the boundary and interior degrees of freedom, the global dynamic stiffness matrix is computed by means of products and inverses resulting with a dimension the same as that for one cell. The recursive method is demonstrated on periodic structures (cranes and buildings under harmonic vibrations. The method yielded a satisfying time decrease with a maximum time ratio of 1 18 and a percentage difference of 19%, in comparison with the conventional finite element method. Close values were attained at low and very high frequencies; the analysis is supported for two types of materials (steel and plastic. The method maintained its efficiency with a high number of forces, excluding the case when all of the nodes are under loads.
Directory of Open Access Journals (Sweden)
Nicola Caterino
2018-01-01
Full Text Available Sky-hook damping is one of the most promising techniques for feedback control of structural vibrations. It is based on the idea of connecting the structure to an ideal fixed point of the space through passive dissipative devices. Herein the benefit of semiactive (SA sky-hook (SH damping is investigated for seismic protection of a two-storey steel frame via shaking table tests. This kind of SA control is achieved implementing a continuous monitoring of selected structural response parameters and using variable dampers. The damping properties of the latter are changed in real-time so as to make the force provided by the damper match the desired SH damping force as closely as possible. To this aim, two prototype magnetorheological dampers have been installed at the first level of the frame and remotely driven by a SH controller. The effectiveness of the control strategy is measured as response to reduction in terms of floor accelerations and interstory drift in respect to the uncontrolled configuration. Two different calibrations of the SH controller have been tested. The experimental results are deeply discussed in order to identify the optimal one and understand the motivations of its better performance.
International Nuclear Information System (INIS)
Takeda, Nobukazu; Kakudate, Satoshi; Shibanuma, Kiyoshi
2005-01-01
The vibration experiments of the support structures with flexible plates for the ITER major components such as toroidal field coil (TF coil) and vacuum vessel (VV) were performed using small-sized flexible plates aiming to obtain its basic mechanical characteristics such as dependence of the stiffness on the loading angle. The experimental results obtained by the hammering and frequency sweep tests were agreed each other, so that the experimental method is found to be reliable. In addition, the experimental results were compared with the analytical ones in order to estimate an adequate analytical model for ITER support structure with flexible plates. As a result, the bolt connection of the flexible plates on the base plate strongly affected on the stiffness of the flexible plates. After studies of modeling the bolts, it is found that the analytical results modeling the bolts with finite stiffness only in the axial direction and infinite stiffness in the other directions agree well with the experimental ones. Using this adequate model, the stiffness of the support structure with flexible plates for the ITER major components can be calculated precisely in order to estimate the dynamic behaviors such as eigen modes and amplitude of deformation of the major components of the ITER tokamak device. (author)
International Nuclear Information System (INIS)
Chrien, R.E.
1986-10-01
The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs
International Nuclear Information System (INIS)
Sohn, Jung Woo; Choi, Seung-Bok
2014-01-01
In the present work, the modal characteristics and vibration control performance of a cylindrical structure in air and water are experimentally investigated, and the results are presented in time and frequency domains. In order to achieve this goal, an end-capped cylindrical shell structure is considered as a host structure, and MFC (macro fiber composite) actuators, which are flexible, are bonded on the surface of the structure. After manufacturing a cylindrical shell structure with aluminum, a modal test is carried out, and the natural frequencies of the proposed structure are obtained and analyzed. To verify the modal test results, a finite element analysis is also performed, and the results are compared with the modal test results. By using the experimentally obtained modal characteristics, a state space control model is established. An optimal controller is then designed in order to control the unwanted vibration and is experimentally realized. It has been shown that the structural vibration can be effectively decreased with the optimal control methodology in both air and water environmental conditions. (technical note)
International Nuclear Information System (INIS)
Comert, H.
2010-01-01
The molecular geometry and vibrational frequencies of The 5-Aminolevulinic acid's hexyl ester (ALA-H) in the ground state have been calculated using Hartree-Fock (HF) and Density functional method (B3LYP) with 6-31++G(d) basis set. The calculated vibrational spectra and geometric parameters of title compound were compered with experimental ones.
Lehnert, Nicolai; Galinato, Mary Grace I; Paulat, Florian; Richter-Addo, George B; Sturhahn, Wolfgang; Xu, Nan; Zhao, Jiyong
2010-05-03
This study presents Nuclear Resonance Vibrational Spectroscopy (NRVS) data on the five-coordinate (5C) ferrous heme-nitrosyl complex [Fe(OEP)(NO)] (1, OEP(2-) = octaethylporphyrinato dianion) and the corresponding (15)N(18)O labeled complex. The obtained spectra identify two isotope sensitive features at 522 and 388 cm(-1), which shift to 508 and 381 cm(-1), respectively, upon isotope labeling. These features are assigned to the Fe-NO stretch nu(Fe-NO) and the in-plane Fe-N-O bending mode delta(ip)(Fe-N-O), the latter has been unambiguously assigned for the first time for 1. The obtained NRVS data were simulated using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Since complex 1 can potentially exist in 12 different conformations involving the FeNO and peripheral ethyl orientations, extended density functional theory (DFT) calculations and QCC-NCA simulations were performed to determine how these conformations affect the NRVS properties of [Fe(OEP)NO]. These results show that the properties and force constants of the FeNO unit are hardly affected by the conformational changes involving the ethyl substituents. On the other hand, the NRVS-active porphyrin-based vibrations around 340-360, 300-320, and 250-270 cm(-1) are sensitive to the conformational changes. The spectroscopic changes observed in these regions are due to selective mechanical couplings of one component of E(u)-type (in ideal D(4h) symmetry) porphyrin-based vibrations with the in-plane Fe-N-O bending mode. This leads to the observed variations in Fe(OEP) core mode energies and NRVS intensities without affecting the properties of the FeNO unit. The QCC-NCA simulated NRVS spectra of 1 show excellent agreement with experiment, and indicate that conformer F is likely present in the samples of this complex investigated here. The observed porphyrin-based vibrations in the NRVS spectra of 1 are also assigned based on the QCC-NCA results. The obtained force constants of the Fe-NO and N
Indian Academy of Sciences (India)
We make music by causing strings, membranes, or air columns to vibrate. Engineers design safe structures by control- ling vibrations. I will describe to you a very simple vibrating system and the mathematics needed to analyse it. The ideas were born in the work of Joseph-Louis Lagrange (1736–1813), and I begin by quot-.
Vibration based structural assessment of the rehabilitation intervention in r.c. segmental bridge
Directory of Open Access Journals (Sweden)
Franchetti Paolo
2015-01-01
Full Text Available A vibration based structural assessment campaign was carried out on a r.c. segmental bridge in North East Italy. The bridge has a cantilever static scheme, fixed at the top of the piers and with a hinge at the centre of the span. The particular configuration of the hinge consists in a couple of steel elements, each one composed by a tongue and groove joint. Since the year 1960, the hinge was subjected to consumption and degradation, that caused a malfunctioning of the device. An intervention of rehabilitation of the bridge led to a reinforcement of the existing hinges with the coupling of new metallic devices: new tongue and groove hinges were applied, that by one side allow the horizontal displacements and rotation, by the other side strongly reduce the relative vertical displacements of the two parts of the bridge. A dynamic test campaign was set up in order to assess the effectiveness of the intervention. The principal dynamic parameters were calculated and analysed with respect to the intervention that was realized. The tests clearly showed the effectiveness of the intervention, and helped the designer to have a better understanding of the structural behaviour of the bridge.
Semi-active control for vibration mitigation of structural systems incorporating uncertainties
International Nuclear Information System (INIS)
Miah, Mohammad S; Chatzi, Eleni N; Weber, Felix
2015-01-01
This study introduces a novel semi-active control scheme, where the linear-quadratic regulator (LQR) is combined with an unscented Kalman filter (UKF) observer, for the real-time mitigation of structural vibration. Due to a number of factors, such as environmental effects and ageing processes, the controlled system may be characterized by uncertainties. The UKF, which comprises a nonlinear observer, is employed herein for devising an adaptive semi-active control scheme capable of tackling such a challenge. This is achieved through the real-time realization of joint state and parameter estimation during the structural control process via the proposed LQR-UKF approach. The behavior of the introduced scheme is exemplified through two numerical applications. The efficacy of the devised methodology is firstly compared against the standard LQR-KF approach in a linear benchmark application where the system model is assumed known a priori, and secondly, the method is validated on a joint state and parameter estimation problem where the system model is assumed uncertain, formulated as nonlinear, and updated in real-time. (paper)
Intermittency and emergence of coherent structures in wave turbulence of a vibrating plate
Mordant, Nicolas; Miquel, Benjamin
2017-10-01
We report numerical investigations of wave turbulence in a vibrating plate. The possibility to implement advanced measurement techniques and long-time numerical simulations makes this system extremely valuable for wave turbulence studies. The purely 2D character of dynamics of the elastic plate makes it much simpler to handle compared to much more complex 3D physical systems that are typical of geo- and astrophysical issues (ocean surface or internal waves, magnetized plasmas or strongly rotating and/or stratified flows). When the forcing is small the observed wave turbulence is consistent with the predictions of the weak turbulent theory. Here we focus on the case of stronger forcing for which coherent structures can be observed. These structures look similar to the folds and D-cones that are commonly observed for strongly deformed static thin elastic sheets (crumpled paper) except that they evolve dynamically in our forced system. We describe their evolution and show that their emergence is associated with statistical intermittency (lack of self similarity) of strongly nonlinear wave turbulence. This behavior is reminiscent of intermittency in Navier-Stokes turbulence. Experimental data show hints of the weak to strong turbulence transition. However, due to technical limitations and dissipation, the strong nonlinear regime remains out of reach of experiments and therefore has been explored numerically.
An interferometric radar sensor for monitoring the vibrations of structures at short ranges
Directory of Open Access Journals (Sweden)
Luzi Guido
2018-01-01
Full Text Available The Real-Aperture-Radar (RAR interferometry technique consolidated in the last decade as an operational tool for the monitoring of large civil engineering structures as bridges, towers, and buildings. In literature, experimental campaigns collected through a well-known commercial equipment have been widely documented, while the cases where different types of sensors have been tested are a few. On the bases of some experimental tests, a new sensor working at high frequency, providing some improved performances, is here discussed. The core of the proposed system is an off-the-shelf, linear frequency modulated continuous wave device. The development of this apparatus is aimed at achieving a proof-of-concept, tackling operative aspects related to the development of a low cost and reliable system. The capability to detect the natural frequencies of a lightpole has been verified; comparing the results of the proposed sensor with those ones obtained through a commercial system based on the same technique, a more detailed description of the vibrating structure has been achieved. The results of this investigation confirmed that the development of sensors working at higher frequencies, although deserving deeper studies, is very promising and could open new applications demanding higher spatial resolutions at close ranges.
Molecular structure, vibrational, HOMO-LUMO, MEP and NBO analysis of hafnium selenite
Yankova, Rumyana; Genieva, Svetlana; Dimitrova, Ginka
2017-08-01
In hydrothermal condition hafnium selenite with estimated chemical composition Hf(SeO3)2·n(H2O) was obtained and characterized by powder X-Ray diffraction, IR spectroscopy and thermogravimetrical analysis. The composition of the obtained crystalline phase was established as dihydrate of tetraaqua complex of the hafnium selenite [Hf(SeO3)2(H2O)4]·2H2O. The results of the thermogravimetrical analysis are shown that the two hydrated water molecules are released in the temperature interval 80-110°C, while the four coordinated water molecules - at 210-300°C. By DFT method, with Becke's three parameter exchange-functional combined with gradient-corrected correlation functional of Lee, Yang and Parr and 6-31G(d), 6-311 + G(d,p) basis sets and LANL2DZ for Hf atom were calculated the molecular structure, vibrational frequencies and thermodynamic properties of the structure. The UV-Vis spectra and electronic properties are presented. The energy and oscillator strength calculated by time-dependent density functional theory corresponds well with the experimental ones. Molecular electrostatic potential (MEP) was performed. Mulliken population analysis on atomic charges was also calculated. The stability and intramolecular interactions are interpreted by NBO analysis.
Ohto, Tatsuhiko; Hunger, Johannes; Backus, Ellen H G; Mizukami, Wataru; Bonn, Mischa; Nagata, Yuki
2017-03-08
The osmolyte molecule trimethylamine-N-oxide (TMAO) stabilizes the structure of proteins. As functional proteins are generally found in aqueous solutions, an important aspect of this stabilization is the interaction of TMAO with water. Here, we review, using vibrational spectroscopy and molecular dynamics simulations, recent studies on the structure and dynamics of TMAO with its surrounding water molecules. This article ends with an outlook on the open questions on TMAO-protein and TMAO-urea interactions in aqueous environments.
Agostoni, S.; Cheli, F.; Leo, E.; Pezzola, M.
2012-08-01
Motor vehicle ride comfort is mainly affected by reciprocating engine inertia unbalances. These forces are transmitted to the driver through the main frame, the engine mounts, and the auxiliary sub systems—all components with which he physically comes into contact. On-road traction vehicle engines are mainly characterized by transient exercise. Thus, an excitation frequency range from 800 RPM (≈15 Hz for stationary vehicles) up to 15,000 RPM (≈250 Hz as a cut off condition) occurs. Several structural resonances are induced by the unbalancing forces spectrum, thus exposing the driver to amplified vibrations. The aim of this research is to reduce driver vibration exposure, by acting on the modal response of structures with which the driver comes into contact. An experimental methodology, capable of identifying local vibration modes was developed. The application of this methodology on a reference vehicle allows us to detect if/when/how the above mentioned resonances are excited. Numerical models were used to study structural modifications. In this article, a handlebar equipped with an innovative multi reciprocating tuned mass damper was optimized. All structural modifications were designed, developed and installed on a vehicle. Modal investigations were then performed in order to predict modification efficiency. Furthermore, functional solution efficiency was verified during sweep tests performed on a target vehicle, by means of a roller bench capable of replicating on-road loads. Three main investigation zones of the vehicle were detected and monitored using accelerometers: (1) engine mounts, to characterize vibration emissions; (2) bindings connecting the engine to the frame, in order to detect vibration transfer paths, with particular attention being paid to local dynamic amplifications due to compliances and (3) the terminal components with which the driver comes into contact.
IDENTIFICATION OF MODAL PARAMETERS OF VIBRATING STRUCTURES WITH UNKNOWN ORSTOCHASTIC EXCITATION
Amaro Baldeón, Roberto; Gardel Kurka, Paulo
2014-01-01
The Vector Autoregressive Moving Average (VARMA) Model is used to identify dynamical characteristics of a structural system in the presence of noise. In order to estimate the parameters of the VARMA Model, the Spliid’s fast algorithm is used. To determine the modal parameters the companion matrix is built with the autoregressive part of the VARMA Model. The performance of this method here discussed is presented by means of simulations, using three degrees of freedom mass-dampingstiffness vibr...
International Nuclear Information System (INIS)
Naitoh, Masanori; Uchida, Shunsuke; Koshizuka, Seiichi; Ninokata, Hisashi; Anahara, Naoki; Dosaki, Koji; Katono, Kenichi; Akiyama, Minoru; Saitoh, Hiroaki
2007-01-01
Problems in major components and structural materials in nuclear power plants have often been caused by flow induced vibration, corrosion and their overlapping effects. In order to establish safe and reliable plant operation, it is necessary to predict future problems for structural materials based on combined analyses of flow dynamics and corrosion and to mitigate them before they become serious issues for plant operation. An innovative method for flow induced vibration of structures in two phase flow by combined analyses of three dimensional flow dynamics and structures is to be introduced. (author)
Chróścielewski, Jacek; Schmidt, Rüdiger; Eremeyev, Victor A.
2018-05-01
This paper addresses modeling and finite element analysis of the transient large-amplitude vibration response of thin rod-type structures (e.g., plane curved beams, arches, ring shells) and its control by integrated piezoelectric layers. A geometrically nonlinear finite beam element for the analysis of piezolaminated structures is developed that is based on the Bernoulli hypothesis and the assumptions of small strains and finite rotations of the normal. The finite element model can be applied to static, stability, and transient analysis of smart structures consisting of a master structure and integrated piezoelectric actuator layers or patches attached to the upper and lower surfaces. Two problems are studied extensively: (i) FE analyses of a clamped semicircular ring shell that has been used as a benchmark problem for linear vibration control in several recent papers are critically reviewed and extended to account for the effects of structural nonlinearity and (ii) a smart circular arch subjected to a hydrostatic pressure load is investigated statically and dynamically in order to study the shift of bifurcation and limit points, eigenfrequencies, and eigenvectors, as well as vibration control for loading conditions which may lead to dynamic loss of stability.
International Nuclear Information System (INIS)
Sert, Y.
2008-01-01
The optimised molecular structure, vibrational frequencies and corresponding vibrational assignments of 2-, 3- and 4- nitro anilines have been calculated using the Hartree-Fock (HF) and density functional methods (B3LYP) with 6-311++G (d, p) basis set. The calculations were adapted to the C S symmetries of all the molecules. The calculated vibrational frequencies and geometric parameters (bond lengths and bond angles) were seen to be in good agreement with the experimental data. The comparison of the experimental and theoretical results showed that the HF method is superior to the B3LYP method for both the vibrational frequencies and geometric parameters
International Nuclear Information System (INIS)
Uvan Catton; Dhir, Vijay K.; Deepanjan Mitra; Omar Alquaddoomi; Pierangelo Adinolfi
2004-01-01
Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers
Hiremath, Sudhir M.; Hiremath, C. S.; Khemalapure, S. S.; Patil, N. R.
2018-05-01
This paper reports the experimental and theoretical study on the structure and vibrations of 2-Methylphenyl boronic acid (2MPBA). The different spectroscopic techniques such as FT-IR (4000-400 cm-1) and FT-Raman (4000-50 cm-1) of the title molecule in the solid phase were recorded. The geometry of the molecule was fully optimized using density functional theory (DFT) (B3LYP) with 6-311++G(d, p) basis set calculations. The vibrational wavenumbers were also corrected with scale factor to take better results for the calculated data. Vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes obtained from VEDA 4 program. The calculated wavenumbers showed the best agreement with the experimental results. Whereas, it is observed that, the theoretical frequencies are more than the experimental one for O-H stretching vibration modes of the title molecule.
Phase and gain control policies for robust active vibration control of flexible structures
International Nuclear Information System (INIS)
Zhang, K; Ichchou, M N; Scorletti, G; Mieyeville, F
2013-01-01
The interest of this paper is to develop a general and systematic robust control methodology for active vibration control of flexible structures. For this purpose, first phase and gain control policies are proposed to impose qualitative frequency-dependent requirements on the controller to consider a complete set of control objectives. Then the proposed control methodology is developed by employing phase and gain control policies in the dynamic output feedback H ∞ control: according to the set of control objectives, phase and gain control policies incorporate necessary weighting functions and determine them in a rational and systematic way; on the other hand, with the appropriate weighting functions efficient H ∞ control algorithms can automatically realize phase and gain control policies and generate a satisfactory H ∞ controller. The proposed control methodology can be used for both SISO and MIMO systems with collocated or non-collocated sensors and actuators. In this paper, it is validated on a non-collocated piezoelectric cantilever beam. Both numerical simulations and experimental results demonstrate the effectiveness of the proposed control methodology. (paper)
Operational feedback on internal structure vibration in 54 French PWRs during 300 fuel cycles
International Nuclear Information System (INIS)
Trenty, A.
1995-01-01
EDF has acquired extensive feedback on vibration of reactor vessel internals by analysing ex-core neutron noise on its 54 pressurized water reactors during the course of over 300 fuel cycles. This feedback has been built up by processing more than 3,000 vibratory signatures acquired since the startup of its reactors. These signatures are now centralized for the whole of France in the ''SINBAD'' data base. Signature processing has enabled: distinguishing between mechanical phenomena and signature variation linked to unit operation: in particular, the impact on signature level of unit operating parameters such as initial fuel enrichment and burn-up rate was assessed; among the purely mechanical phenomena, pointing up slight changes in position of vessel internals and the first signs of structural wear; relaxation (in the hold-down spring and fuel rod assemblies) and wear on surfaces of contact between internals and reactor vessel were detected; lastly and most importantly, automatic recognition of the various types of vibratory behavior of internals. It was consequently possible to draw up user requirement specifications for automated monitoring of internals, which should soon be integrated in PSAD, a system which groups several reactor monitoring functions. (author)
International Nuclear Information System (INIS)
Monteseguro, V.; Rodríguez-Hernández, P.; Muñoz, A.
2015-01-01
The structural, elastic, and vibrational properties of yttrium aluminum garnet Y 3 Al 5 O 12 are studied under high pressure by ab initio calculations in the framework of the density functional theory. The calculated ground state properties are in good agreement with the available experimental data. Pressure dependences of bond length and bulk moduli of the constituent polyhedra are reported. The evolution of the elastic constants and the major elastic properties, Young and shear modulus, Poisson's ratios, and Zener anisotropy ratio, are described. The mechanical stability is analyzed, on the light of “Born generalized stability criteria,” showing that the garnet is mechanically unstable above 116 GPa. Symmetries, frequencies, and pressure coefficients of the Raman-active modes are discussed on the basis of the calculated total and partial phonon density of states, which reflect the dynamical contribution of each atom. The relations between the phonon modes of Y 3 Al 5 O 12 and the internal and external molecular modes of the different polyhedra are discussed. Infrared-active modes, as well as the silent modes, and their pressure dependence are also investigated. No dynamical instabilities were found below 116 GPa
Role of Fe doping on structural and vibrational properties of ZnO nanostructures
Energy Technology Data Exchange (ETDEWEB)
Pandiyarajan, T.; Udayabhaskar, R.; Karthikeyan, B. [National Institute of Technology, Department of Physics, Tiruchirappalli (India)
2012-05-15
In this report, Raman and Fourier Transform Infrared (FTIR) measurements were carried out to study the phonon modes of pure and Fe doped ZnO nanoparticles. The nanoparticles were prepared by sol-gel technique at room temperature. The X-ray diffraction measurements reveal that the nanoparticles are in hexagonal wurtzite structure and doping makes the shrinkage of the lattice parameters, whereas there is no alteration in the unit cell. Raman measurements show both E{sub 2}{sup low} and E{sub 2}{sup High} optical phonon mode is shifted towards lower wave number with Fe incorporation and explained on the basis of force constant variation, stress measurements, respectively. In addition, Fe related local vibrational modes (LVM) were observed for higher concentration of Fe doping. FTIR spectra reveal a band at 444 cm{sup -1} which is specific to E{sub 1} (TO) mode; a red-shift of this mode in Fe doped samples and some surface phonon modes were observed. Furthermore, the observation of additional IR modes, which is considered to have an origin related to Fe dopant in the ZnO nanostructures, is also reported. These additional mode features can be regarded as an indicator for the incorporation of Fe ions into the lattice position of the ZnO nanostructures. (orig.)
Self-consistent average-atom scheme for electronic structure of hot and dense plasmas of mixture
International Nuclear Information System (INIS)
Yuan Jianmin
2002-01-01
An average-atom model is proposed to treat the electronic structures of hot and dense plasmas of mixture. It is assumed that the electron density consists of two parts. The first one is a uniform distribution with a constant value, which is equal to the electron density at the boundaries between the atoms. The second one is the total electron density minus the first constant distribution. The volume of each kind of atom is proportional to the sum of the charges of the second electron part and of the nucleus within each atomic sphere. By this way, one can make sure that electrical neutrality is satisfied within each atomic sphere. Because the integration of the electron charge within each atom needs the size of that atom in advance, the calculation is carried out in a usual self-consistent way. The occupation numbers of electron on the orbitals of each kind of atom are determined by the Fermi-Dirac distribution with the same chemical potential for all kinds of atoms. The wave functions and the orbital energies are calculated with the Dirac-Slater equations. As examples, the electronic structures of the mixture of Au and Cd, water (H 2 O), and CO 2 at a few temperatures and densities are presented
Self-consistent average-atom scheme for electronic structure of hot and dense plasmas of mixture.
Yuan, Jianmin
2002-10-01
An average-atom model is proposed to treat the electronic structures of hot and dense plasmas of mixture. It is assumed that the electron density consists of two parts. The first one is a uniform distribution with a constant value, which is equal to the electron density at the boundaries between the atoms. The second one is the total electron density minus the first constant distribution. The volume of each kind of atom is proportional to the sum of the charges of the second electron part and of the nucleus within each atomic sphere. By this way, one can make sure that electrical neutrality is satisfied within each atomic sphere. Because the integration of the electron charge within each atom needs the size of that atom in advance, the calculation is carried out in a usual self-consistent way. The occupation numbers of electron on the orbitals of each kind of atom are determined by the Fermi-Dirac distribution with the same chemical potential for all kinds of atoms. The wave functions and the orbital energies are calculated with the Dirac-Slater equations. As examples, the electronic structures of the mixture of Au and Cd, water (H2O), and CO2 at a few temperatures and densities are presented.
Local and average structures of 0.7Pb(Mg1/3Nb2/3)O3 - 0.3PbZrO3
International Nuclear Information System (INIS)
Krishna, P.S.R.; Shinde, A.B.; Narasimhan, S.L.; Tiwari, V.S.; Singh, G.
2005-01-01
The local and average structure of 0.7Pb(Mg 1/3 Nb 2/3 )O 3 - 0.3PbZrO 3 (PMN-PZ) was studied by neutron diffraction. The Rietveld refinement was carried out to determine the average, long-range crystallographic structure, while the pair density function (PDF) analysis was used in studying the local atomic structure. The local atomic structure determined by the PDF analysis, was found to be significantly different from the average crystallographic structure determined by the Rietveld analysis. These results show that the conflict between the local structural preference and the average structure is not limited to relax or ferroelectric oxides, but may be widely prevalent in mixed-ion ferroelectrics. (author)
Advances in nonlinear vibration analysis of structures. Part-I. Beams
Indian Academy of Sciences (India)
Unknown
element analysis of nonlinear beams under static and dynamic loads. ... linearization, substitution of inplane boundary conditions at element level rather .... Modelling the nonlinear vibration problems using finite elements, albeit with a couple.
Karakaya, Mustafa; Kürekçi, Mehmet; Eskiyurt, Buse; Sert, Yusuf; Çırak, Çağrı
2015-01-01
In present study, the experimental and theoretical harmonic vibrational frequencies of gliclazide molecule have been investigated. The experimental FT-IR (400-4000 cm-1) and Laser-Raman spectra (100-4000 cm-1) of the molecule in the solid phase were recorded. Theoretical vibrational frequencies and geometric parameters (bond lengths and bond angles) have been calculated using ab initio Hartree Fock (HF), density functional theory (B3LYP hybrid function) methods with 6-311++G(d,p) and 6-31G(d,p) basis sets by Gaussian 09W program. The assignments of the vibrational frequencies were performed by potential energy distribution (PED) analysis by using VEDA 4 program. Theoretical optimized geometric parameters and vibrational frequencies have been compared with the corresponding experimental data, and they have been shown to be in a good agreement with each other. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies have been found.
International Nuclear Information System (INIS)
Goekce, H.; Bahceli, S.
2010-01-01
FT-IR and Raman spectra of CTAB [C 1 6H 3 3N(CH 3 ) 3 ] + Br - have been experimentally recorded in the region 550-4000 cm - 1 and 400-3100 cm - 1, respectively. The molecular geometry and vibrational frequencies of CTAB in the ground state have been calculated by using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with the 6-31+G(d,p) basis set. The obtained optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies were in very good agreement with the experimental data. The comparisons of the observed fundamental vibrational frequencies and calculated results for the fundamental vibrational frequencies of CTAB shows that the scaled B3LYP method is superior compared to the scaled HF method.
A new online secondary path modeling method for adaptive active structure vibration control
International Nuclear Information System (INIS)
Pu, Yuxue; Zhang, Fang; Jiang, Jinhui
2014-01-01
This paper proposes a new variable step size FXLMS algorithm with an auxiliary noise power scheduling strategy for online secondary path modeling. The step size for the secondary path modeling filter and the gain of auxiliary noise are varied in accordance with the parameters available directly. The proposed method has a low computational complexity. Computer simulations show that an active vibration control system with the proposed method gives much better vibration attenuation and modeling accuracy at a faster convergence rate than existing methods. National Instruments’ CompactRIO is used as an embedded processor to control simply supported beam vibration. Experimental results indicate that the vibration of the beam has been effectively attenuated. (papers)
Park, Junhong; Palumbo, Daniel L.
2004-01-01
The use of shunted piezoelectric patches in reducing vibration and sound radiation of structures has several advantages over passive viscoelastic elements, e.g., lower weight with increased controllability. The performance of the piezoelectric patches depends on the shunting electronics that are designed to dissipate vibration energy through a resistive element. In past efforts most of the proposed tuning methods were based on modal properties of the structure. In these cases, the tuning applies only to one mode of interest and maximum tuning is limited to invariant points when based on den Hartog's invariant points concept. In this study, a design method based on the wave propagation approach is proposed. Optimal tuning is investigated depending on the dynamic and geometric properties that include effects from boundary conditions and position of the shunted piezoelectric patch relative to the structure. Active filters are proposed as shunting electronics to implement the tuning criteria. The developed tuning methods resulted in superior capabilities in minimizing structural vibration and noise radiation compared to other tuning methods. The tuned circuits are relatively insensitive to changes in modal properties and boundary conditions, and can applied to frequency ranges in which multiple modes have effects.
Energy Dissipation from Vibrating Floor Slabs due to Human-Structure Interaction
Directory of Open Access Journals (Sweden)
James M.W. Brownjohn
2001-01-01
Full Text Available Lightweight pre-cast flooring systems using post-tensioning to increase strength but not stiffness are increasingly popular, and vibration serviceability problems tend to govern design of such floors where human occupants are increasingly concerned with vibrations. At the same time as inducing response, stationary human observers can also participate in the response as mitigating influence and it is clear that a human behaves as a highly effective damper, even when seated.
Arjunan, V.; Thirunarayanan, S.; Marchewka, M. K.; Mohan, S.
2017-10-01
The new hydrogen bonded molecular complex 1,2,4-triazolium hydrogenselenate (THS) is prepared by the reaction of 1H-1,2,4-triazole and selenic acid. This complex is stabilised by N-H⋯O and C-H⋯O hydrogen bonding and electrostatic attractive forces between 1H and 1,2,4-triazolium cations and hydrogen selenate anions. The XRD studies revealed that intermolecular proton transfer occur from selenic acid to 1H-1,2,4-triazole molecule, results in the formation of 1,2,4-triazolium hydrogenselenate which contains 1,2,4-triazolium cations and hydrogenselenate anions. The molecular structure of THS crystal has also been optimised by using Density Functional Theory (DFT) using B3LYP/cc-pVTZ and B3LYP/6-311++G** methods in order to find the whole characteristics of the molecular complex. The theoretical structural parameters such as bond length, bond angle and dihedral angle determined by DFT methods are well agreed with the XRD parameters. The atomic charges and thermodynamic properties are also calculated and analysed. The energies of frontier molecular orbitals HOMO, LUMO, HOMO-1, LUMO+1 and LUMO-HUMO energy gap are calculated to understand the kinetic stability and chemical reactivity of the molecular complex. The natural bond orbital analysis (NBO) has been performed in order to study the intramolecular bonding interactions and delocalisation of electrons. These intra molecular charge transfer may induce biological activities such as antimicrobials, antiinflammatory, antifungal etc. The complete vibrational assignments of THS have been performed by using FT-IR and FT-Raman spectra.
Li{sub 4}Ba[BN{sub 2}]{sub 2} - structure and vibrational spectra
Energy Technology Data Exchange (ETDEWEB)
Seidel, Stefan; Rodewald, Ute C.; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Somer, Mehmet; Kiraz, Kamil [Chemistry Department, Koc University, Sariyer-Istanbul (Turkey)
2017-12-13
The nitridoborate Li{sub 4}Ba[BN{sub 2}]{sub 2} was synthesized from a 4:1 molar ratio of Li{sub 3}[BN]{sub 2} and Ba{sub 3}[BN{sub 2}]{sub 2} in an arc-welded niobium ampoule at a maximum annealing temperature of 1173 K. The structure was refined from single-crystal X-ray diffractometer data: new type, P1, a = 533.9(2), b = 585.0(3), c = 860.6(4) pm, α = 80.72(3), β = 73.84(6), γ = 89.87(4) , wR{sub 2} = 0.1196, 1429 F{sup 2} values, 50 variables. The Li{sub 4}Ba[BN{sub 2}]{sub 2} structure contains two crystallographically independent [BN{sub 2}]{sup 3-} units with 134 pm B-N distance, which are slightly bent: 178 for N2-B1-N1 and 175 for N4-B2-N3. Due to the high lithium content both [BN{sub 2}]{sup 3-} units have a strongly distorted coordination by 8Li{sup +} + 3Ba{sup 2+}. The four crystallographically independent lithium cations show distorted tetrahedral coordination by [BN{sub 2}]{sup 3-} units with Li-N distances ranging from 195 to 247 pm. IR and Raman spectra show the typical vibrations of the [BN{sub 2}] unit along with a well-resolved splitting of the ν({sup 10}B) and ν({sup 11}B) frequencies. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Rai, Man Mohan
2018-05-01
The near wake of a flat plate is investigated via direct numerical simulations. Many earlier experimental investigations have used thin plates with sharp trailing edges and turbulent boundary layers to create the wake. This results in large θ/DTE values (θ is the boundary layer momentum thickness toward the end of the plate and DTE is the trailing edge thickness). In the present study, the emphasis is on relatively thick plates with circular trailing edges (CTEs) resulting in θ/D values less than one (D is the plate thickness and the diameter of the CTE) and vigorous vortex shedding. The Reynolds numbers based on the plate length and D are 1.255 × 106 and 10 000, respectively. Two cases are computed: one with turbulent boundary layers on both the upper and lower surfaces of the plate (statistically the same, symmetric wake, Case TT) and the other with turbulent and laminar boundary layers on the upper and lower surfaces, respectively (asymmetric case, Case TL). The data and understanding obtained are of considerable engineering interest, particularly in turbomachinery where the pressure side of an airfoil can remain laminar or transitional because of a favorable pressure gradient and the suction side is turbulent. Shed-vortex structure and phase-averaged velocity statistics obtained in the two cases are compared here. The upper negative shed vortices in Case TL (turbulent separating boundary layer) are weaker than the lower positive ones (laminar separating boundary layer) at inception (a factor of 1.27 weaker in terms of peak phase-averaged spanwise vorticity at the first appearance of a peak). The upper vortices weaken rapidly as they travel downstream. A second feature of interest in Case TL is a considerable increase in the peak phase-averaged, streamwise normal intensity (random component) with increasing streamwise distance (x/D) that occurs near the positive vortex cores. This behavior is observed for a few diameters in the near wake. This is counter to
Petrenko, Taras; Rauhut, Guntram
2017-03-01
Vibrational configuration interaction theory is a common method for calculating vibrational levels and associated IR and Raman spectra of small and medium-sized molecules. When combined with appropriate configuration selection procedures, the method allows the treatment of configuration spaces with up to 1010 configurations. In general, this approach pursues the construction of the eigenstates with significant contributions of physically relevant configurations. The corresponding eigenfunctions are evaluated in the subspace of selected configurations. However, it can easily reach the dimension which is not tractable for conventional eigenvalue solvers. Although Davidson and Lanczos methods are the methods of choice for calculating exterior eigenvalues, they usually fall into stagnation when applied to interior states. The latter are commonly treated by the Jacobi-Davidson method. This approach in conjunction with matrix factorization for solving the correction equation (CE) is prohibitive for larger problems, and it has limited efficiency if the solution of the CE is based on Krylov's subspace algorithms. We propose an iterative subspace method that targets the eigenvectors with significant contributions to a given reference vector and is based on the optimality condition for the residual norm corresponding to the error in the solution vector. The subspace extraction and expansion are modified according to these principles which allow very efficient calculation of interior vibrational states with a strong multireference character in different vibrational structure problems. The convergence behavior of the method and its performance in comparison with the aforementioned algorithms are investigated in a set of benchmark calculations.
Energy Technology Data Exchange (ETDEWEB)
Lee, Ju Chul; Park, Sang Hu; Min, June Kee; Ha, Man Yeong; Shin, Bo Sung [Pusan National University, Busan (Korea, Republic of); Cho, Jong Rae [Korea Maritime University, Busan (Korea, Republic of)
2016-05-15
Heat transfer enhancement is an important issue in energy systems. To improve the efficiency of a cooling channel used inside injection molds, turbine blades, and high-temperature devices, channels with various shapes, such as wavy, elliptical, and twisted, have been studied. A cooling channel with a partially wavy inner structure has shown outstanding cooling performance despite a small increase in friction factor. However, generating a partially wavy inner structure inside a channel through conventional machining processes is not easy. To address this problem, we developed a new process called Perpendicular vibration-induced electrical discharge machining (PV-EDM). A specific electrode and one- and random-directional vibrating devices controlled by a pneumatic load were designed for the PV-EDM process. Experimental results showed that local shaping on the inner wall of a channel is possible, which confirmed the possibility of application of this process to actual industrial problems.
Energy Technology Data Exchange (ETDEWEB)
Ji, Pengfei; Zhang, Yuwen, E-mail: zhangyu@missouri.edu [Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Yang, Mo [College of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093 (China)
2013-12-21
The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.
International Nuclear Information System (INIS)
Ji, Pengfei; Zhang, Yuwen; Yang, Mo
2013-01-01
The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective
Ji, Pengfei; Zhang, Yuwen; Yang, Mo
2013-12-01
The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.
International Nuclear Information System (INIS)
McCrea, Keith R.
2001-01-01
In the results discussed above, it is clear that Sum Frequency Generation (SFG) is a unique tool that allows the detection of vibrational spectra of adsorbed molecules present on single crystal surfaces under catalytic reaction conditions. Not only is it possible to detect active surface intermediates, it is also possible to detect spectator species which are not responsible for the measured turnover rates. By correlating high-pressure SFG spectra under reaction conditions and gas chromatography (GC) kinetic data, it is possible to determine which species are important under reaction intermediates. Because of the flexibility of this technique for studying surface intermediates, it is possible to determine how the structures of single crystal surfaces affect the observed rates of catalytic reactions. As an example of a structure insensitive reaction, ethylene hydrogenation was explored on both Pt(111) and Pt(100). The rates were determined to be essentially the same. It was observed that both ethylidyne and di-(sigma) bonded ethylene were present on the surface under reaction conditions on both crystals, although in different concentrations. This result shows that these two species are not responsible for the measured turnover rate, as it would be expected that one of the two crystals would be more active than the other, since the concentration of the surface intermediate would be different on the two crystals. The most likely active intermediates are weakly adsorbed molecules such as(pi)-bonded ethylene and ethyl. These species are not easily detected because their concentration lies at the detection limit of SFG. The SFG spectra and GC data essentially show that ethylene hydrogenation is structure insensitive for Pt(111) and Pt(100). SFG has proven to be a unique and excellent technique for studying adsorbed species on single crystal surfaces under high-pressure catalytic reactions. Coupled with kinetic data obtained from gas chromatography measurements, it can
International Nuclear Information System (INIS)
Uryu, Mitsuru; Terada, Shuji; Shinohara, Takaharu; Yamazaki, Toshihiko; Nakayama, Kazuhiko; Kondo, Toshinari; Hosoya, Hisashi
1997-10-01
The Tokai reprocessing facility buildings are constituted by a lower foundation, vibration controlling layers, and upper structure. At the vibration controlling layer, a laminated rubber aiming support of the building load and extension of the eigenfrequency and a damper aiming absorption of earthquake energy are provided. Of course, the facility buildings are directly supported at the arenaceous shale (Taga Layer) of the Miocene in the Neogene confirmed to the stablest ground, as well the buildings with high vibration resistant importance in Japan. This report shows that when the vibration controlling structure is adopted for the reprocessing facility buildings where such high vibration resistance is required, reduction of input acceleration for equipments and pipings can be achieved and the earthquake resistant safety can also be maintained with sufficient tolerance and reliability. (G.K.)
Directory of Open Access Journals (Sweden)
Stephen M Talai
2016-12-01
Full Text Available This article pertains to the prediction of structural vibration frequencies from frictional temperature evolution through numerical simulation. To achieve this, a finite element analysis was carried on AISI 304 steel cantilever beam-like structures coupled with a lacing wire using the commercial software ABAQUS/CAE. The coupled temperature–displacement transient analysis simulated the frictional thermal generation. Furthermore, an experimental analysis was carried out with infrared cameras capturing the interfacial thermal images while the beams were subjected to forced excitation, thus validating the finite element analysis results. The analysed vibration frequencies using a MATLAB fast Fourier transform algorithm confirmed the validity of its prediction from the frictional temperature time domain waveform. This finding has a great significance to the mechanical and aerospace engineering communities for the effective structural health monitoring of dynamic structures online using infrared thermography, thus reducing the downtime and maintenance cost, leading to increased efficiency.
Liu, Jinxin; Chen, Xuefeng; Gao, Jiawei; Zhang, Xingwu
2016-12-01
Air vehicles, space vehicles and underwater vehicles, the cabins of which can be viewed as variable section cylindrical structures, have multiple rotational vibration sources (e.g., engines, propellers, compressors and motors), making the spectrum of noise multiple-harmonic. The suppression of such noise has been a focus of interests in the field of active vibration control (AVC). In this paper, a multiple-source multiple-harmonic (MSMH) active vibration suppression algorithm with feed-forward structure is proposed based on reference amplitude rectification and conjugate gradient method (CGM). An AVC simulation scheme called finite element model in-loop simulation (FEMILS) is also proposed for rapid algorithm verification. Numerical studies of AVC are conducted on a variable section cylindrical structure based on the proposed MSMH algorithm and FEMILS scheme. It can be seen from the numerical studies that: (1) the proposed MSMH algorithm can individually suppress each component of the multiple-harmonic noise with an unified and improved convergence rate; (2) the FEMILS scheme is convenient and straightforward for multiple-source simulations with an acceptable loop time. Moreover, the simulations have similar procedure to real-life control and can be easily extended to physical model platform.
Sangeetha, V.; Govindarajan, M.; Kanagathara, N.; Marchewka, M. K.; Gunasekaran, S.; Anbalagan, G.
Melaminium bis(trifluoroacetate) trihydrate (MTFA), an organic material has been synthesized and single crystals of MTFA have been grown by the slow solvent evaporation method at room temperature. X-ray powder diffraction analysis confirms that MTFA crystal belongs to the monoclinic system with space group P2/c. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional theory (DFT) B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets. The X-ray diffraction data have been compared with the data of optimized molecular structure. The theoretical results show that the crystal structure can be reproduced by optimized geometry and the vibrational frequencies show good agreement with the experimental values. The nuclear magnetic resonance (NMR) chemical shift of the molecule has been calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. HOMO-LUMO, and other related molecular and electronic properties are calculated. The Mulliken and NBO charges have also been calculated and interpreted.
Exploring of PST-TBPM in Monitoring Dynamic Deformation of Steel Structure in Vibration
Chen, Mingzhi; Zhao, Yongqian; Hai, Hua; Yu, Chengxin; Zhang, Guojian
2018-01-01
In order to monitor the dynamic deformation of steel structure in the real-time, digital photography is used in this paper. Firstly, the grid method is used correct the distortion of digital camera. Then the digital cameras are used to capture the initial and experimental images of steel structure to obtain its relative deformation. PST-TBPM (photographing scale transformation-time baseline parallax method) is used to eliminate the parallax error and convert the pixel change value of deformation points into the actual displacement value. In order to visualize the deformation trend of steel structure, the deformation curves are drawn based on the deformation value of deformation points. Results show that the average absolute accuracy and relative accuracy of PST-TBPM are 0.28mm and 1.1‰, respectively. Digital photography used in this study can meet accuracy requirements of steel structure deformation monitoring. It also can warn the safety of steel structure and provide data support for managers’ safety decisions based on the deformation curves on site.
Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih
2013-09-01
In the present work, the experimental and theoretical vibrational spectra of 4-chlorobenzothioamide were investigated. The FT-IR (400-4000 cm-1) and μ-Raman spectra (100-4000 cm-1) of 4-chlorobenzothioamide in the solid phase were recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared and Raman intensities of the title molecule in the ground state were calculated using ab initio Hartree-Fock and density functional theory (B3LYP) methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and the theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 4-chlorobenzothioamide was also simulated to evaluate the effect of intermolecular hydrogen bonding on the vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while the in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H⋯S hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.
Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih
2014-06-01
In the present work, the experimental and theoretical vibrational spectra of 5-hydroxymethyluracil were investigated. The FT-IR (4000-400 cm-1) spectrum of the molecule in the solid phase was recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared intensities of the title molecule in the ground state were calculated using density functional B3LYP and M06-2X methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data, and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 5-hydroxymethyluracil molecule was also simulated to evaluate the effect of intermolecular hydrogen bonding on its vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while its in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H⋯O hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.
Yang, Li-Farn; Mikulas, Martin M., Jr.; Park, K. C.; Su, Renjeng
1993-01-01
This paper presents a moment-gyro control approach to the maneuver and vibration suppression of a flexible truss arm undergoing a constant slewing motion. The overall slewing motion is triggered by a feedforward input, and a companion feedback controller is employed to augment the feedforward input and subsequently to control vibrations. The feedforward input for the given motion requirement is determined from the combined CMG (Control Momentum Gyro) devices and the desired rigid-body motion. The rigid-body dynamic model has enabled us to identify the attendant CMG momentum saturation constraints. The task for vibration control is carried out in two stages; first in the search of a suitable CMG placement along the beam span for various slewing maneuvers, and subsequently in the development of Liapunov-based control algorithms for CMG spin-stabilization. Both analytical and numerical results are presented to show the effectiveness of the present approach.
Microscopic structure of high-spin vibrational states in superdeformed A=190 nuclei
Energy Technology Data Exchange (ETDEWEB)
Nakatsukasa, Takashi [Chalk River Labs., Ontario (Canada); Matsuyanagi, Kenichi [Kyoto Univ. (Japan); Mizutori, Shoujirou [Oak Ridge National Lab., TN (United States)] [and others
1996-12-31
Microscopic RPA calculations based on the cranked shell model are performed to investigate the quadrupole and octupole correlations for excited superdeformed (SD) bands in even-even A=190 nuclei. The K = 2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. The Coriolis coupling at finite frequency produces different effects depending on the neutron and proton number of nucleus. The calculations also indicate that some collective excitations may produce moments of inertia almost identical to those of the yrast SD band. An interpretation of the observed excited bands invoking the octupole vibrations is proposed, which suggests those octupole vibrations may be prevalent in even-even SD A=190 nuclei.
Tekin, Nalan; Pir, Hacer; Sagdinc, Seda
2012-12-01
The effects of 15 solvents on the C=O stretching vibrational frequency of flurbiprofen (FBF) were determined to investigate solvent-solute interactions. Solvent effects on the geometry and C=O stretching vibrational frequency, ν(C=O), of FBF were studied theoretically at the DFT/B3LYP and HF level in combination with the polarizable continuum model and experimentally using attenuated total reflection infrared spectroscopy (ATR-IR). The calculated C=O stretching frequencies in the liquid phase are in agreement with experimental values. Moreover, the wavenumbers of ν(C=O) of FBF in different solvents have been obtained and correlated with the Kirkwood-Bauer-Magat equation (KBM), the solvent acceptor numbers (ANs), and the linear solvation energy relationships (LSERs). The solvent-induced stretching vibrational frequency shifts displayed a better correlation with the LSERs than with the ANs and KBM.
International Nuclear Information System (INIS)
Kurt, M.
2005-01-01
The molecular geometry and vibrational frequencies of 6-methylquinoline(6MQ) and 8-methylquinolines(8MQ) in the ground state have been calculated by using the Hartree-Fock and density functional methods (B3LYP and BLYP) with 6-31G (d) as the basis set. The optimized geometric bond lengths obtained by using B3LYP and bond angles obtained by BLYP were given corresponding experimental values of similar molecule. Comparison of the observed fundamental vibrational frequencies of these molecules and calculated results by density functional B3LYP, BLYP and Hartree-Fock methods indicates that B3LYP is superior to the scaled Hartree- Fock and BLYP approach for molecular vibrational problems
Dumitriu, M.
2017-08-01
The paper approaches the issue of reduction in the vertical bending vibrations of the railway vehicle carbody and the ride comfort enhancement at high velocities, starting from the prospect of isolating the vibrations by the best possible selection of the passive suspension damping in the vehicle. To this purpose, the examination falls on the influence of the vertical suspension damping upon the vibrations regime of the vehicle at the bending resonance frequency and upon the ride comfort. The results of the numerical simulations regarding the frequency response of the carbody acceleration and the comfort index will be therefore used. A value of the secondary suspension damping can be thus identified that will provide the best ride comfort performance. Similarly, the ride comfort can be increased by raising the primary suspension damping ratio.
International Nuclear Information System (INIS)
Daraji, A H; Hale, J M
2012-01-01
The optimal placement of sensors and actuators in active vibration control is limited by the number of candidates in the search space. The search space of a small structure discretized to one hundred elements for optimising the location of ten actuators gives 1.73 × 10 13 possible solutions, one of which is the global optimum. In this work, a new quarter and half chromosome technique based on symmetry is developed, by which the search space for optimisation of sensor/actuator locations in active vibration control of flexible structures may be greatly reduced. The technique is applied to the optimisation for eight and ten actuators located on a 500×500mm square plate, in which the search space is reduced by up to 99.99%. This technique helps for updating genetic algorithm program by updating natural frequencies and mode shapes in each generation to find the global optimal solution in a greatly reduced number of generations. An isotropic plate with piezoelectric sensor/actuator pairs bonded to its surface was investigated using the finite element method and Hamilton's principle based on first order shear deformation theory. The placement and feedback gain of ten and eight sensor/actuator pairs was optimised for a cantilever and clamped-clamped plate to attenuate the first six modes of vibration, using minimization of linear quadratic index as an objective function.
Martens, William L.; Woszczyk, Wieslaw
2005-09-01
For multimodal display systems in which realistic reproduction of impact events is desired, presenting structure-borne vibration along with multichannel audio recordings has been observed to create a greater sense of immersion in a virtual acoustic environment. Furthermore, there is an increased proportion of reports that the impact event took place within the observer's local area (this is termed ``presence with'' the event, in contrast to ``presence in'' the environment in which the event occurred). While holding the audio reproduction constant, varying the intermodal arrival time and level of mechanically displayed, synthetic whole-body vibration revealed a number of other subjective attributes that depend upon multimodal interaction in the perception of a representative impact event. For example, when the structure-borne component of the displayed impact event arrived 10 to 20 ms later than the airborne component, the intermodal delay was not only tolerated, but gave rise to an increase in the proportion of reports that the impact event had greater power. These results have enabled the refinement of a multimodal simulation in which the manipulation of synthetic whole-body vibration can be used to control perceptual attributes of impact events heard within an acoustic environment reproduced via a multichannel loudspeaker array.
Tanak, H.; Pawlus, K.; Marchewka, M. K.; Pietraszko, A.
2014-01-01
In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of the potential nonlinear optical (NLO) material anilinium trichloroacetate. The FT-IR and FT-Raman spectra of the compound have been recorded together between 4000-80 cm-1 and 3600-80 cm-1 regions, respectively. The compound crystallizes in the noncentrosymmetric space group of monoclinic system. The optimized molecular structure, vibrational wavenumbers, IR intensities and Raman activities have been calculated by using density functional method (B3LYP) with 6-311++G(d,p) as higher basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. DSC measurements on powder samples do not indicate clearly on the occurrence of phase transitions in the temperature 113-293 K. The Kurtz and Perry powder reflection technique appeared to be very effective in studies of second-order nonlinear optical properties of the molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, frontier orbitals and thermodynamic properties were also performed at 6-311++G(d,p) level of theory. For title crystal the SHG efficiency was estimated by Kurtz-Perry method to be deff = 0.70 deff (KDP).
MACS, Lattice Vibrations Structure Factors for Thermal Neutron Scattering in Moderators
International Nuclear Information System (INIS)
McMurry, H.L.; Suitt, W.J.; Worlton, T.G.; Martin, R.M.
1974-01-01
1 - Description of problem or function: This package of seven related codes is basically aimed at giving maximum capability for calculating slow-neutron scattering by moderators. MACS-C computes crystal vibrations when the potential energy is a sum of parts arising from short-range forces and long-range Coulomb interactions. It also obtains Jacobian matrices for determining adjustments in force constants and ionic charge which can lead to improved agreement with data. Structure factors for neutron inelastic scattering can also be calculated. MACS-J computes the dynamical matrix for the harmonic oscillations of a crystal, its eigenvalues and eigenvectors, the corresponding structure factors for coherent single-phonon scattering of neutrons, and Jacobian matrices for use in adjusting force constants to fit calculated to observed dispersion curves. REVISED-D calculates valance coordinates in terms of mass adjusted atom displacements, together with coordinates which define rigid group rotations. REVISED-MVFC constructs force constant matrices for use in valance force potential functions which are used in other programs dealing with molecular and crystal vibrations. ADJUSTER is a force adjuster program to obtain a least squares fit to observed frequencies of molecules and crystals. DIPOLE-SUM calculates dipole sums for an arbitrary crystal. MODEL-PI calculates crystal vibrations when the potential energy is a sum of short-range and long- or intermediate-range terms in the dipole coordinate approximation. It also obtains Jacobian matrices for use in adjusting input parameters. 2 - Method of solution: In MACS-C, ADJUSTER, and REVISED-D, matrix manipulations are applied to matrices which describe physical conditions. In MACS-J, first-order difference equations are substituted for partial differential equations for Jacobian elements. In MVFC the user employs a set of criteria for defining different types of interactions to prepare by hand the input to the program. For
International Nuclear Information System (INIS)
Akeju, T.A.I.; Kelly, D.W.; Zienkiewicz, O.C.; Kanaka Raju, K.
1981-01-01
The eigenvalue equations governing the free vibration of axisymmetric solids are derived by means of a semi-analytical finite element scheme. In particular we investigated the use of an 8-node solid element in structures which exhibit a 'shell-like' behaviour. Bathe-Wilson subspace iteration algorithm is employed for the solution of the equations. The element is shown to give good results for beam and shell vibration problems. It is also utilised to solve a complex solid in the form of an internal component of a modern jet engine. This particular application is of considerable practical importance as the dynamics of such components form a dominant design constraint. (orig./HP)
Zentgraf, Florian; Stephan, Michael; Berrocal, Edouard; Albert, Barbara; Böhm, Benjamin; Dreizler, Andreas
2017-07-01
Structured laser illumination planar imaging (SLIPI) is combined with gas phase thermometry measurements using thermographic phosphor (TGP) particles. The technique is applied to a heated jet surrounded by a coflow which is operated at ambient temperature. The respective air flows are seeded with a powder of BaMgAl10O17:Eu2+ (BAM) which is used as temperature-sensitive gas phase tracer. Upon pulsed excitation in the ultraviolet spectral range, the temperature is extracted based on the two-color ratio method combined with SLIPI. The main advantage of applying the SLIPI approach to phosphor thermometry is the reduction of particle-to-particle multiple light scattering and diffuse wall reflections, yielding a more robust calibration procedure as well as improving the measurement accuracy, precision, and sensitivity. For demonstration, this paper focuses on sample-averaged measurements of temperature fields in a jet-in-coflow configuration. Using the conventional approach, which in contrast to SLIPI is based on imaging with an unmodulated laser light sheet, we show that for the present setup typically 40% of the recorded signal is affected by the contribution of multiply scattered photons. At locations close to walls even up to 75% of the apparent signal is due to diffuse reflection and wall luminescence of BAM sticking at the surface. Those contributions lead to erroneous temperature fields. Using SLIPI, an unbiased two-color ratio field is recovered allowing for two-dimensional mean temperature reconstructions which exhibit a more realistic physical behavior. This is in contrast to results deduced by the conventional approach. Furthermore, using the SLIPI approach it is shown that the temperature sensitivity is enhanced by a factor of up to 2 at 270 °C. Finally, an outlook towards instantaneous SLIPI phosphorescence thermometry is provided.
Vibration of hydraulic machinery
Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong
2013-01-01
Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...
Nguyen, Theanh; Chan, Tommy H. T.; Thambiratnam, David P.; King, Les
2015-12-01
In the structural health monitoring (SHM) field, long-term continuous vibration-based monitoring is becoming increasingly popular as this could keep track of the health status of structures during their service lives. However, implementing such a system is not always feasible due to on-going conflicts between budget constraints and the need of sophisticated systems to monitor real-world structures under their demanding in-service conditions. To address this problem, this paper presents a comprehensive development of a cost-effective and flexible vibration DAQ system for long-term continuous SHM of a newly constructed institutional complex with a special focus on the main building. First, selections of sensor type and sensor positions are scrutinized to overcome adversities such as low-frequency and low-level vibration measurements. In order to economically tackle the sparse measurement problem, a cost-optimized Ethernet-based peripheral DAQ model is first adopted to form the system skeleton. A combination of a high-resolution timing coordination method based on the TCP/IP command communication medium and a periodic system resynchronization strategy is then proposed to synchronize data from multiple distributed DAQ units. The results of both experimental evaluations and experimental-numerical verifications show that the proposed DAQ system in general and the data synchronization solution in particular work well and they can provide a promising cost-effective and flexible alternative for use in real-world SHM projects. Finally, the paper demonstrates simple but effective ways to make use of the developed monitoring system for long-term continuous structural health evaluation as well as to use the instrumented building herein as a multi-purpose benchmark structure for studying not only practical SHM problems but also synchronization related issues.
Fatigue damage from random vibration pulse process of tubular structural elements subject to wind
DEFF Research Database (Denmark)
Christensen, Claus F.; Ditlevsen, Ove Dalager
1997-01-01
In a wide range of the Reynolds number an elastically suspended circular cylinder surrounded by a homogeneous wind velocity field will generate vortex shedding of a frequency that by and large is proportional to the far field wind velocity. However, if the cylinder is free to vibrate, resonance w...
Numerical methods for analysis of structure and ground vibration from moving loads
DEFF Research Database (Denmark)
Andersen, L.; Nielsen, S.R.K.; Krenk, Steen
2007-01-01
An overview of the main theoretical aspects of finite-element and boundary-element modelling of the response to moving loads is given. The moving loads represent sources of noise and vibration generated by moving vehicles, and the analysis describes the propagation of the disturbances generated i...
Xiping Wang; James P. Wacker; Robert J. Ross; Brian K. Brashaw; Robert Vatalaro
2005-01-01
This paper describes an effort to develop a global dynamic testing technique for evaluating the overall stiffness of timber bridge superstructures. A forced vibration method was used to measure the natural frequency of single-span timber bridges in the laboratory and field. An analytical model based on simple beam theory was proposed to represent the relationship...
Fonda, James; Rao, Vittal S.; Sana, Sridhar
2001-08-01
This paper provides an account of a student research project conducted under the sponsoring of the National Science Foundation (NSF) program on Research Experience for Undergraduates (REU) in Mechatronics and Smart Strictures in the summer of 2000. The objective of the research is to design and test a stand-alone controller for a vibration isolation/suppression system. The design specification for the control system is to suppress the vibrations induced by the external disturbances by at least fiver times and hence to achieve vibration isolation. Piezo-electric sensors and actuators are utilized for suppression of unwanted vibrations. Various steps such as modeling of the system, controller design, simulation, closed-loop testing using d- Space rapid prototyping system, and analog control implementation are discussed in the paper. Procedures for data collection, the trade-offs carried out in the design, and analog controller implementation issues are also presented in the paper. The performances of various controllers are compared. The experiences of an undergraduate student are summarized in the conclusion of the paper.
International Nuclear Information System (INIS)
Saedtler, E.
1981-01-01
The method for controlling the vibrating behaviour of primary circuit components or for a general systems control is a combination of methods of the statistic systems theory, optimum filter theory, statistic decision theory and of the pattern recognition method. It is appropriate for automatic control of complex systems and stochastic events. (DG) [de
Morishita, Tetsuya
2009-05-21
We report a first-principles study of the structural, electronic, and dynamical properties of high-density amorphous (HDA) silicon, which was found to be formed by pressurizing low-density amorphous (LDA) silicon (a normal amorphous Si) [T. Morishita, Phys. Rev. Lett. 93, 055503 (2004); P. F. McMillan, M. Wilson, D. Daisenberger, and D. Machon, Nature Mater. 4, 680 (2005)]. Striking structural differences between HDA and LDA are revealed. The LDA structure holds a tetrahedral network, while the HDA structure contains a highly distorted tetrahedral network. The fifth neighboring atom in HDA tends to be located at an interstitial position of a distorted tetrahedron composed of the first four neighboring atoms. Consequently, the coordination number of HDA is calculated to be approximately 5 unlike that of LDA. The electronic density of state (EDOS) shows that HDA is metallic, which is consistent with a recent experimental measurement of the electronic resistance of HDA Si. We find from local EDOS that highly distorted tetrahedral configurations enhance the metallic nature of HDA. The vibrational density of state (VDOS) also reflects the structural differences between HDA and LDA. Some of the characteristic vibrational modes of LDA are dematerialized in HDA, indicating the degradation of covalent bonds. The overall profile of the VDOS for HDA is found to be an intermediate between that for LDA and liquid Si under pressure (high-density liquid Si).
Improving the shear wave velocity structure beneath Bucharest (Romania) using ambient vibrations
Manea, Elena Florinela; Michel, Clotaire; Poggi, Valerio; Fäh, Donat; Radulian, Mircea; Balan, Florin Stefan
2016-11-01
Large earthquakes from the intermediate-depth Vrancea seismic zone are known to produce in Bucharest ground motion characterized by predominant long periods. This phenomenon has been interpreted as the combined effect of both seismic source properties and site response of the large sedimentary basin. The thickness of the unconsolidated Quaternary deposits beneath the city is more than 200 m, the total depth of sediments is more than 1000 m. Complex basin geometry and the low seismic wave velocities of the sediments are primarily responsible for the large amplification and long duration experienced during earthquakes. For a better understanding of the geological structure under Bucharest, a number of investigations using non-invasive methods have been carried out. With the goal to analyse and extract the polarization and dispersion characteristics of the surface waves, ambient vibrations and low-magnitude earthquakes have been investigated using single station and array techniques. Love and Rayleigh dispersion curves (including higher modes), Rayleigh waves ellipticity and SH-wave fundamental frequency of resonance (f0SH) have been inverted simultaneously to estimate the shear wave velocity structure under Bucharest down to a depth of about 8 km. Information from existing borehole logs was used as prior to reduce the non-uniqueness of the inversion and to constrain the shallow part of the velocity model (array (the URS experiment) installed by the National Institute for Earth Physics and by the Karlsruhe Institute of Technology during 10 months in the period 2003-2004. The array consisted of 32 three-component seismological stations, deployed in the urban area of Bucharest and adjacent zones. The large size of the array and the broad-band nature of the available sensors gave us the possibility to characterize the surface wave dispersion at very low frequencies (0.05-1 Hz) using frequency-wavenumber techniques. This is essential to explore and resolve the deeper
David, Ingrid; Sánchez, Juan-Pablo; Piles, Miriam
2018-05-10
Indirect genetic effects (IGE) are important components of various traits in several species. Although the intensity of social interactions between partners likely vary over time, very few genetic studies have investigated how IGE vary over time for traits under selection in livestock species. To overcome this issue, our aim was: (1) to analyze longitudinal records of average daily gain (ADG) in rabbits subjected to a 5-week period of feed restriction using a structured antedependence (SAD) model that includes IGE and (2) to evaluate, by simulation, the response to selection when IGE are present and genetic evaluation is based on a SAD model that includes IGE or not. The direct genetic variance for ADG (g/d) increased from week 1 to 3 [from 8.03 to 13.47 (g/d) 2 ] and then decreased [6.20 (g/d) 2 at week 5], while the indirect genetic variance decreased from week 1 to 4 [from 0.43 to 0.22 (g/d) 2 ]. The correlation between the direct genetic effects of different weeks was moderate to high (ranging from 0.46 to 0.86) and tended to decrease with time interval between measurements. The same trend was observed for IGE for weeks 2 to 5 (correlations ranging from 0.62 to 0.91). Estimates of the correlation between IGE of week 1 and IGE of the other weeks did not follow the same pattern and correlations were lower. Estimates of correlations between direct and indirect effects were negative at all times. After seven generations of simulated selection, the increase in ADG from selection on EBV from a SAD model that included IGE was higher (~ 30%) than when those effects were omitted. Indirect genetic effects are larger just after mixing animals at weaning than later in the fattening period, probably because of the establishment of social hierarchy that is generally observed at that time. Accounting for IGE in the selection criterion maximizes genetic progress.
Directory of Open Access Journals (Sweden)
Wei Jing
2016-01-01
Full Text Available In order to study the vibration problem of liquid-solid coupling of rectangular liquid-storage structure with horizontal elastic baffle, ignoring the influence of surface gravity wave, two different velocity potential functions corresponding to the liquid above and below the elastic baffle are assumed; based on the theory of mathematical equation and energy method, the formulas of basic frequency of liquid-solid coupling vibration system are derived, the baffle joined to the tank wall with 3 kinds of boundary conditions, namely, four edges simply supported, two opposite edges clamped and two opposite edges simply supported, and four edges clamped; the influence rules of baffle length-width ratio, the ratio of baffle height to liquid level, baffle elastic modulus, baffle density, baffle thickness, and liquid density on the coupling vibration performance are studied. The results show that the frequency of the clamped boundary is minimum; the influences of baffle length-width ratio and relative height on the basic frequency are much greater than that of the other system parameters; the relation between baffle length-width ratio and the frequency is exponential, while baffle relative height has a parabola relation with the frequency; the larger the baffle length-width ratio, the closer the baffle to the liquid level; the coupling frequency will be reduced more obviously.
Jha, Omkant; Yadav, T K; Yadav, R A
2018-01-15
Structural and vibrational studies for the most stable conformer of dopamine {4-(2-Aminoethyl) benzene-1, 2-diol} have been carried out at the DFT/B3LYP/6-311++G** level using the Gaussian 09 software. The IR and Raman spectra have been recorded and analyzed in light of the computed vibrational parameters using the DFT and the PEDs computed with the help of the GAR2PED software. Some of the fundamentals have considerably changed frequencies in going from benzene to dopamine. Except the rocking and wagging modes of the NH 2 group the other four modes are pure group modes. The rocking and wagging modes of the NH 2 group show mixing with the other modes. The two OH stretching vibrations are highly localized modes. The Kekule phenyl ring stretching mode is found to remain almost unchanged. The HOMO-LUMO study suggests the existence of charge transfer within the molecule and the energy gap supports the pharmacological active property of the dopamine molecule. The NBO analysis has been carried out to understand the proper and improper hydrogen bonding. Copyright © 2017. Published by Elsevier B.V.
Energy Technology Data Exchange (ETDEWEB)
Versteijlen, W.G; Metrikine, A.; Hoving, J.S.; Smidt, E.H.; De Vries, W.E. [Department Hydraulic Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology TUD, Delft (Netherlands)
2012-01-15
In today's cutting costs environment in the offshore wind industry, significant achievements can be made with a better assessment of dynamic soil-pile interaction. Of the main damping mechanisms active at an OWT (offshore wind turbine), least is known about soil damping. The values for this contribution used in the industry today - mostly calculated analogously to a study performed in 1980 - are expected to be on the low side. More research on the topic is recommended. Presence of more damping than currently assumed, would signify that the (often) design driving fatigue damage accumulation is lower than assumed. This would justify designing more light-weight structures using less construction steel, or allowing for longer (insured) OWT lifetimes then the now applied 20 years. Both these measures significantly decrease costs of offshore wind. This paper evaluates measured signals of twelve 'rotorstop' - test on an OWT at Dong Energy owned - Burbo Banks windfarm. The vibration decay was measured with an accelerometer and strain gauges along the tower. A simplistic analytical model has been developed enabling analyses of the measured signals. Two main modal shapes were identified with similar shape, but deviating amplitudes in the soil profile. The large difference in damping that exists between the vibrations of these modes is attributed to the difference in influence that the soil can have on these vibrations. The found effect of soil on the damping of this particular OWT is significantly larger than the order of magnitude used in the industry today.
Arjunan, V; Jayaprakash, A; Carthigayan, K; Periandy, S; Mohan, S
2013-05-01
Experimental and theoretical quantum chemical studies were carried out on 4-hydroxybenzohydrazide (4HBH) and 4-aminobenzohydrazide (4ABH) using FTIR and FT-Raman spectral data. The structural characteristics and vibrational spectroscopic analysis were carried performed by quantum chemical methods with the hybrid exchange-correlation functional B3LYP using 6-31G(**), 6-311++G(**) and aug-cc-pVDZ basis sets. The most stable conformer of the title compounds have been determined from the analysis of potential energy surface. The stable molecular geometries, electronic and thermodynamic parameters, IR intensities, harmonic vibrational frequencies, depolarisation ratio and Raman intensities have been computed. Molecular electrostatic potential and frontier molecular orbitals were constructed to understand the electronic properties. The potential energy distributions (PEDs) were calculated to explain the mixing of fundamental modes. The theoretical geometrical parameters and the fundamental frequencies were compared with the experimental. The interactions of hydroxy and amino group substitutions on the characteristic vibrations of the ring and hydrazide group have been analysed. Copyright © 2013 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
John E. Lavery
2012-10-01
Full Text Available We present evidence that one can calculate generically combinatorially expensive Lp and lp averages, 0 < p < 1, in polynomial time by restricting the data to come from a wide class of statistical distributions. Our approach differs from the approaches in the previous literature, which are based on a priori sparsity requirements or on accepting a local minimum as a replacement for a global minimum. The functionals by which Lp averages are calculated are not convex but are radially monotonic and the functionals by which lp averages are calculated are nearly so, which are the keys to solvability in polynomial time. Analytical results for symmetric, radially monotonic univariate distributions are presented. An algorithm for univariate lp averaging is presented. Computational results for a Gaussian distribution, a class of symmetric heavy-tailed distributions and a class of asymmetric heavy-tailed distributions are presented. Many phenomena in human-based areas are increasingly known to be represented by data that have large numbers of outliers and belong to very heavy-tailed distributions. When tails of distributions are so heavy that even medians (L1 and l1 averages do not exist, one needs to consider using lp minimization principles with 0 < p < 1.
Ramesh, Gaddam; Reddy, Byru Venkatram
2018-05-01
In this investigation, the monomeric structure is determined for picolinic and isonicotinic acids based on geometry optimization for one of the four possible conformers and intramolecular hydrogen bond of Osbnd H⋯O using density functional theory (DFT) employing B3LYP functional supplemented with 6-311++G(d,p) basis set. Using this optimized monomeric form, the dimer structure is determined based on minimum energy and length of hydrogen bonds obtained for two possible dimeric forms yielded due to head-to-tail intermolecular Osbnd H⋯N hydrogen bond (dimer 1) linkage and tail-to -tail intermolecular Osbnd H⋯O hydrogen bond (dimer 2) linkage between pyridine ring and carboxyl group. The structure parameters obtained for monomer and dimer forms are in good agreement with the experimental literature values. The vibrational assignments have been made unambiguously for all the vibrations from FTIR and FT-Raman spectra based on the potential energy distribution (PED) and eigen vectors obtained in DFT and inverse vibrational problem (IVP) computations. The rms error between the observed and scaled frequencies is 7.7 and 9.4 cm-1 for PIA and INA, respectively. A 74-element modified valence force field is derived by Wilson's GF matrix method using 58 experimental frequencies of the two molecules in overlay least-squares technique. The average error between observed and computed frequencies by this method is calculated to be 10.39 cm-1. The results of both DFT and IVP computations yielded good agreement between observed and calculated frequencies. The NLO behaviour using hyperpolarizability values; and HOMO and LUMO energies; of the two molecules are investigated by DFT. Charge density distribution and site of chemical reactivity of the molecules are studied by molecular electrostatic surface potential (MESP). Stability of the molecules arising from hyper conjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO
International Nuclear Information System (INIS)
Catton, Ivan; Dhir, Vijay K.; Alquaddoomi, O.S.; Mitra, Deepanjan; Adinolfi, Pierangelo
2004-01-01
OAK-B135 Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers. In the nuclear industry, steam generators are often affected by this problem. However, flow-induced vibration is not limited to nuclear power plants, but to any type of heat exchanger used in many industrial applications such as chemical processing, refrigeration and air conditioning. Specifically, shell and tube type heat exchangers experience flow-induced vibration due to the high velocity flow over the tube banks. Flow-induced vibration in these heat exchangers leads to equipment breakdown and hence expensive repair and process shutdown. The goal of this research is to provide accurate measurements that can help modelers to validate their models using the measured experimental parameters and thereby develop better design criteria for avoiding fluid-elastic instability in heat exchangers. The research is divided between two primary experimental efforts, the first conducted using water alone (single phase) and the second using a mixture of air or steam and water as the working fluid (two phase). The outline of this report is as follows: After the introduction to fluid-elastic instability, the experimental apparatus constructed to conduct the experiments is described in Chapter 2 along with the measurement procedures. Chapter 3 presents results obtained on the tube array and the flow loop, as well as techniques used in data processing. The project performance is described and evaluated in Chapter 4 followed by
Structure of two-phase air-water flows. Study of average void fraction and flow patterns
International Nuclear Information System (INIS)
Roumy, R.
1969-01-01
This report deals with experimental work on a two phase air-water mixture in vertical tubes of different diameters. The average void fraction was measured in a 2 metre long test section by means of quick-closing valves. Using resistive probes and photographic techniques, we have determined the flow patterns and developed diagrams to indicate the boundaries between the various patterns: independent bubbles, agglomerated bubbles, slugs, semi-annular, annular. In the case of bubble flow and slug flow, it is shown that the relationship between the average void fraction and the superficial velocities of the phases is given by: V sg = f( ) * g(V sl ). The function g(V sl ) for the case of independent bubbles has been found to be: g(V sl ) = V sl + 20. For semi-annular and annular flow conditions; it appears that the average void fraction depends, to a first approximation only on the ratio V sg /V sl . (author) [fr
FEATURES OF WELDED TITANIUM STRUCTURE ELEMENT DESTRUCTION (RIBBED PANELS UNDER VIBRATION LOADS
Directory of Open Access Journals (Sweden)
Mr. Pavel V. Bakhmatov
2016-12-01
Full Text Available The article presents data on the experimental studies results of welded ribbed panel vibration load of the BT-20 titanium alloy. It was established that in the areas of attachment, there is elevated dynamic alternating stress, which in combination with the "hard" of the sample holder creates favorable conditions for the emergence and development of fatigue cracks, and stress concentrators greatly reduce the time before the formation of the hearth destruction. An exception in these zones of superficial defects do not affect the nature and kinetics of destruction. Construction of titanium alloys made in the application of gas-laser cutting blanks for optimal regimes in the technical environment of nitrogen and subsequent heat treatment on vibration reliability is not inferior to design, made by traditional technology.
Zyubin, A.; Konstantinova, E.; Slezhkin, V.; Matveeva, K.; Samusev, I.; Bryukhanov, V.
2017-12-01
In this paper we perform results of conformational analysis of septic human serum albumin (HSA) carried out by Raman spectroscopy (RS), infrared (IR) spectroscopy and fluorescent spectroscopy. The main vibrational groups were identified and analyzed for septic HSA and its health control. Comparison between Raman and IR results were done. Fluorescent spectral changes of Trp-214 group were analyzed. Application of Raman, IR spectroscopy, fluorescent spectroscopy for conformational changes study of HSA during pathology were shown.
International Nuclear Information System (INIS)
Gunyasu, Kenzo; Hiramoto, Tsuneyuki; Tanimoto, Mitsumori; Osano, Minetada
2002-01-01
We describe a new method for solving large-scale system of linear equations resulting from discretization of ordinary differential equation and partial differential equation directly. This new method effectively reduces the memory capacity requirements and computing time problems for analyses using finite difference method and finite element method. In this paper we have tried to solve one-million linear equations directly for the case that initial displacement and boundary displacement are known about the finite difference scheme of second order inhomogeneous differential equation for vibration of a 10 story structure. Excellent results were got. (author)
International Nuclear Information System (INIS)
Krylov, V.I.; Sorokin, S.V.
1998-01-01
The dynamics of a Euler-Bernoulli beam with a time-and-space dependent bending stiffness is studied. The , problem is considered in connection with the application of noise control using smart structures. It is shown that a control for the vibrations of the beam can be achieved by varying the bending stiffness. The technique of direct separation of fast and slow motion coupled with a Green's function method is used to analyze the dynamics of the beam with high-frequency modulation of the stiffness
International Nuclear Information System (INIS)
Bunkin, A.F.; Maltsev, D.V.; Surskii, K.O.; Shapiro, Y.G.; Chernov, V.G.
1988-01-01
A method is proposed for decomposing into components by computer the partially resolved polarization CARS spectra of the ν OH Raman band of stretching vibrations of liquid water under various experimental conditions. The spectroscopic parameters of the ν OH band of the components at water temperatures of 5 degree C and 20 degree C are given. It is shown that single-mode-continuum models and mixed models of the structure of liquid water (in the 5--60 degree C range) contradict the results of experiments on polarization CARS
International Nuclear Information System (INIS)
Gloth, Gerrit
2009-01-01
Monitoring and diagnostic systems are of main importance for a safe and efficient operation of nuclear power plants. The author describes new developments with respect to vibration monitoring with a functional extension in the time domain for den secondary circuit, the development of a local system for the surveillance of rotating machines, the structure-borne sound monitoring with improvement of event analysis, esp. the loose part locating, leakage monitoring with a complete system for humidity measurement, and the development of a common platform for all monitoring and diagnostic systems, that allows an efficient access for comparison and cross references.
International Nuclear Information System (INIS)
Debrus, S.; Marchewka, M.K.; Baran, J.; Drozd, M.; Czopnik, R.; Pietraszko, A.; Ratajczak, H.
2005-01-01
The first X-ray diffraction and vibrational spectroscopic analysis of a novel complex between L-lysine and L-tartaric acid is reported. The structure was solved in two temperatures (320 and 260 K) showing incommensurate phase between them. Room-temperature powder infrared and Raman measurements for the L-lysine-L-tartaric acid molecular complex (1:1) were carried out. DSC measurements on powder samples indicate two phase transitions points at about 295, 300 and 293, 300 K, for heating and cooling, respectively, with noticeable temperature interval between them. Second harmonic generation efficiency d eff =0.35 d eff (KDP)
Directory of Open Access Journals (Sweden)
Wan-You Li
2014-01-01
Full Text Available A novel hybrid method, which simultaneously possesses the efficiency of Fourier spectral method (FSM and the applicability of the finite element method (FEM, is presented for the vibration analysis of structures with elastic boundary conditions. The FSM, as one type of analytical approaches with excellent convergence and accuracy, is mainly limited to problems with relatively regular geometry. The purpose of the current study is to extend the FSM to problems with irregular geometry via the FEM and attempt to take full advantage of the FSM and the conventional FEM for structural vibration problems. The computational domain of general shape is divided into several subdomains firstly, some of which are represented by the FSM while the rest by the FEM. Then, fictitious springs are introduced for connecting these subdomains. Sufficient details are given to describe the development of such a hybrid method. Numerical examples of a one-dimensional Euler-Bernoulli beam and a two-dimensional rectangular plate show that the present method has good accuracy and efficiency. Further, one irregular-shaped plate which consists of one rectangular plate and one semi-circular plate also demonstrates the capability of the present method applied to irregular structures.
Luzi, Guido; Crosetto, Michele; Fernández, Enric
2017-03-24
The potential of a coherent microwave sensor to monitor the vibration characteristics of civil structures has been investigated in the past decade, and successful case studies have been published by different research teams. This remote sensing technique is based on the interferometric processing of real aperture radar acquisitions. Its capability to estimate, simultaneously and remotely, the displacement of different parts of the investigated structures, with high accuracy and repeatability, is its main advantage with respect to conventional sensors. A considerable amount of literature on this technique is available, including various case studies aimed at testing the ambient vibration of bridges, buildings, and towers. In the last years, this technique has been used in Spain for civil structures monitoring. In this paper, three examples of such case studies are described: the monitoring of the suspended bridge crossing the Ebro River at Amposta, the communications tower of Collserola in Barcelona, and an urban building located in Vilafranca del Penedès, a small town close to Barcelona. This paper summarizes the main outcomes of these case studies, underlining the advantages and limitations of the sensors currently available, and concluding with the possible improvements expected from the next generation of sensors.
Brambilla, Luigi
2014-10-14
© 2014 American Chemical Society. In this work, we report a comparative analysis of the infrared and Raman spectra of octa(3-hexylthiophene) (3HT)8, trideca(3-hexylthiophene) (3HT)13, and poly(3-hexylthiophene) P3HT recorded in various phases, namely, amorphous, semicrystalline, polycrystalline and single crystal. We have based our analysis on the spectra of the (3HT)8 single crystal (whose structure has been determined by selected area electron diffraction) taken as reference and on the results of DFT calculations and molecular vibrational dynamics. New and precise spectroscopic markers of the molecular structures show the existence of three phases, namely: hairy (phase 1), ordered (phase 2), and disordered/amorphous (phase 3). Conceptually, the identified markers can be used for the molecular structure analysis of other similar systems.
Energy Technology Data Exchange (ETDEWEB)
Coban, Cansu [Balikesir Univ. (Turkey). Dept. of Physics
2017-07-01
The pressure dependent behaviour of the structural, electronic, mechanical, vibrational, and thermodynamic properties of Pd{sub 2}TiX (X=Ga, In) Heusler alloys was investigated by ab initio calculations. The lattice constant, the bulk modulus and its first pressure derivative, the electronic band structure and the density of states (DOS), mechanical properties such as elastic constants, anisotropy factor, Young's modulus, etc., the phonon dispersion curves and phonon DOS, entropy, heat capacity, and free energy were obtained under pressure. It was determined that the calculated lattice parameters are in good agreement with the literature, the elastic constants obey the stability criterion, and the phonon dispersion curves have no negative frequency which shows that the compounds are stable. The band structures at 0, 50, and 70 GPa showed valence instability at the L point which explains the superconductivity in Pd{sub 2}TiX (X=Ga, In).
Ge, Aimin; Matsusaki, Michiya; Qiao, Lin; Akashi, Mitsuru; Ye, Shen
2016-04-26
Sum frequency generation (SFG) vibrational spectroscopy was employed to investigate the surface structures of polyelectrolyte multilayers (PEMs) constructed by sequentially alternating adsorption of poly(diallyldimethylammonium chloride) (PDDA) and poly(styrenesulfonate) (PSS). It was found that the surface structures and surface charge density of the as-deposited PEMs of PDDA/PSS significantly depend on the concentration of sodium chloride (NaCl) present in the polyelectrolyte solutions. Furthermore, it was found that the surface structure of the as-deposited PEMs is in a metastable state and will reach the equilibrium state by diffusion of the polyelectrolyte chain after an aging process, resulting in a polyelectrolyte mixture on the PEM surfaces.
Arjunan, V.; Kalaivani, M.; Marchewka, M. K.; Mohan, S.
2013-04-01
The structural investigations of the molecular complex of melamine with maleic acid, namely melaminium maleate monohydrate have been carried out by quantum chemical methods in addition to FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical studies were performed with DFT (B3LYP) method using 6-31G**, cc-pVDZ and 6-311++G** basis sets to determine the energy, structural and thermodynamic parameters of melaminium maleate monohydrate. The hydrogen atom from maleic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak Osbnd H⋯O and Nsbnd H⋯O hydrogen bonds shows notable vibrational effects.
Arjunan, V; Kalaivani, M; Marchewka, M K; Mohan, S
2013-04-15
The structural investigations of the molecular complex of melamine with maleic acid, namely melaminium maleate monohydrate have been carried out by quantum chemical methods in addition to FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical studies were performed with DFT (B3LYP) method using 6-31G(**), cc-pVDZ and 6-311++G(**) basis sets to determine the energy, structural and thermodynamic parameters of melaminium maleate monohydrate. The hydrogen atom from maleic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak OH···O and NH···O hydrogen bonds shows notable vibrational effects. Copyright © 2013 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Pincu, Madeleine [Univ. of California, Irvine, CA (United States); Gerber, Robert Benny [Univ. of California, Irvine, CA (United States). Dept. of Chemistry
2013-07-17
This work was undertaken with the main objective to investigate basic reactions that take place in relatively simple saccharides (mono-saccharides and cellobiose - the building block of cellulose) , in isolation and in cluster with few water molecules or with (gas-phase) clusters of few waters and ionic compounds (salt, isolated ions like H^{+} or OH^{-}). Within the context of this work, different potentials were investigated; among them, were the PM3 semi empirical potential, DFT/BLYP and a new hybrid potential constructed from MP2 for the harmonic part and from adjusted Hartree-Fock anharmonic interactions (VSCF-PT2). These potentials were evaluated by comparison with experimental data from published sources and from several collaborating groups. The findings show excellent agreement between experiments and predictions with the hybrid VSCF-PT2 potential and very good agreement with predictions obtained from dynamics with dispersion corrected DFT/BLYP potential. Investigation of hydration of cellobiose, was another topic of interest. Guided by a hydration motif demonstrated by our experimental collaborators (team of Prof J.P. Simons), we demonstrated large energetic and structural differences between the two species of cellobiose: cis and trans. The later, which is dominant in solid and liquid phases, is higher in energy in the gas-phase and compared to pure water, it does not disturb as much the network of H bonds. In contrast, the cis species exhibits asymmetric hydration in cluster with up to 25 waters, indicating that it has surfactant properties. Another highlight of this research effort was the successful first time spectrometric and spectroscopic study of a gas-phase protonated sugar derivative (alpha-D-Galactopyranoside) and its interpretation by Ab Initio molecular dynamics (AIMD) simulations. The findings demonstrate the formation of a motif in which a proton bridges between two Oxygen atoms (belonging to OH groups) at the sugar; The
International Nuclear Information System (INIS)
Zhong, Jianfeng; Zhong, Shuncong; Zhang, Qiukun; Lu, Huancai; Zhuang, Yizhou; Fu, Xinbin
2017-01-01
A non-projection fringe vision measurement system suitable for vibration monitoring was proposed by using the concept of a 2D optical coherence vibration tomography (2D-OCVT) technique. An artificial quasi-interferogram fringe pattern (QIFP), similar to the interferogram of the 2D-OCVT system, was pasted onto the surface of a vibrating structure as a sensor. Image sequences of the QIFP were captured by a high-speed CMOS camera that worked as a detector. It was possible to obtain both the in-plane and out-of-plane vibration simultaneously. The in-plane vibration was obtained by tracking the center of the imaged QIFP using an image cross-correlation method, whilst the out-of-plane vibration was obtained from the changes in period density of the imaged QIFP. The influence of the noise sources from the CMOS image sensor, together with the effect of the imaging distance, the period density of the QIFP and also the key parameters of the fringe density enhanced by the spectrum correction method on the accuracy of the displacement measurement, were investigated by numerical simulations and experiments. Compared with the results from a conventional accelerometer-based measurement system, the proposed method was demonstrated to be an effective and accurate technique for measuring structural vibration without introducing any extra mass from the accelerometer. The significant advantages of this method include its simple installation and real-time dynamic response measurement capability, making the measurement system ideal for the low- and high-frequency vibration monitoring of engineering structures. (paper)
Energy Technology Data Exchange (ETDEWEB)
Petkov, Valeri [Central Michigan University, Mt. Pleasant, MI (United States); Prasai, Binay [Central Michigan University, Mt. Pleasant, MI (United States); Shastri, Sarvjit [Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division; Park, Hyun-Uk [Sungkyunkwan University, Suwon (Korea). Department of Chemistry; Kwon, Young-Uk [Sungkyunkwan University, Suwon (Korea). Department of Chemistry; Skumryev, Vassil [Institucio Catalana de Recerca i Estudis Avançats (ICREA), Barcelona (Spain); Universitat Autònoma de Barcelona (Spain). Department of Physics
2017-09-12
Practical applications require the production and usage of metallic nanocrystals (NCs) in large ensembles. Besides, due to their cluster-bulk solid duality, metallic NCs exhibit a large degree of structural diversity. This poses the question as to what atomic-scale basis is to be used when the structure–function relationship for metallic NCs is to be quantified precisely. In this paper, we address the question by studying bi-functional Fe core-Pt skin type NCs optimized for practical applications. In particular, the cluster-like Fe core and skin-like Pt surface of the NCs exhibit superparamagnetic properties and a superb catalytic activity for the oxygen reduction reaction, respectively. We determine the atomic-scale structure of the NCs by non-traditional resonant high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Using the experimental structure data we explain the observed magnetic and catalytic behavior of the NCs in a quantitative manner. Lastly, we demonstrate that NC ensemble-averaged 3D positions of atoms obtained by advanced X-ray scattering techniques are a very proper basis for not only establishing but also quantifying the structure–function relationship for the increasingly complex metallic NCs explored for practical applications.
Hansson, J E; Eklund, L; Kihlberg, S; Ostergren, C E
1987-03-01
The main objective of the study was to find efficient hand tools which caused only minor vibration loading. Vibration measurements were carried out under standardised working conditions. The time during which car body repairers in seven companies were exposed to vibration was determined. Chisel hammers, impact wrenches, sanders and saws were the types of tools which generated the highest vibration accelerations. The average daily exposure at the different garages ranged from 22 to 70 min. The risk of vibration injury is currently rated as high. The difference between the highest and lowest levels of vibration was considerable in most tool categories. Therefore the choice of tool has a major impact on the magnitude of vibration exposure. The importance of choosing the right tools and working methods is discussed and a counselling service on vibration is proposed.
Local vibrations and lift performance of low Reynolds number airfoil
Directory of Open Access Journals (Sweden)
TariqAmin Khan
2017-06-01
Full Text Available The 2D incompressible Navier-Stokes equations are solved based on the finite volume method and dynamic mesh technique is used to carry out partial fluid structure interaction. The local flexible structure (hereinafter termed as flexible structure vibrates in a single mode located on the upper surface of the airfoil. The Influence of vibration frequency and amplitude are examined and the corresponding fluid flow characteristics are investigated which add complexity to the inherent problem in unsteady flow. The study is conducted for flow over NACA0012 airfoil at 600≤Re≤3000 at a low angle of attack. Vibration of flexible structure induces a secondary vortex which modifies the pressure distribution and lift performance of the airfoil. At some moderate vibration amplitude, frequency synchronization or lock-in phenomenon occurs when the vibration frequency is close to the characteristic frequency of rigid airfoil. Evolution and shedding of vortices corresponding to the deformation of flexible structure depends on the Reynolds number. In the case of Re≤1000, the deformation of flexible structure is considered in-phase with the vortex shedding i.e., increasing maximum lift is linked with the positive deformation of flexible structure. At Re=1500 a phase shift of about 1/π exists while they are out-of-phase at Re>1500. Moreover, the oscillation amplitude of lift coefficient increases with increasing vibration amplitude for Re≤1500 while it decreases with increasing vibration amplitude for Re>1500. As a result of frequency lock-in, the average lift coefficient is increased with increasing vibration amplitude for all investigated Reynolds numbers (Re. The maximum increase in the average lift coefficient is 19.72% within the range of investigated parameters.
International Nuclear Information System (INIS)
Ji, Hongli; Qiu, Jinhao; Xia, Pinqi; Inman, Daniel
2012-01-01
Modal coupling is an important issue in the analysis and control of structural systems with multi-degrees of freedom (MDOF). In this paper, modal coupling induced by energy conversion in the structural control of an MDOF system using a synchronized switch damping method is investigated theoretically and validated numerically. In the analysis, it is supposed that the voltage on the piezoelectric actuator is switched at the displacement extrema of a given mode. Two types of coupling in energy conversion are considered. The first is whether the switching action based on one mode induces energy conversion of the other modes. The second is whether the vibration of one mode affects the energy conversion of the other modes. The results indicate that the modal coupling in energy conversion is very complicated. In most cases the switching action based on one mode does induce energy conversion of another mode, but the efficiency depends on the frequency ratio of the two modes. The vibration of one mode affects the energy conversion of another mode only when the frequency ratio of the two modes takes some special values. Discussions are also given on the potential application of the theoretical results in the design of an energy harvesting device. (paper)
International Nuclear Information System (INIS)
Razi, Pejman; Esmaeel, Ramadan A; Taheri, Farid
2011-01-01
This paper presents the application of a novel vibration-based technique for detecting fatigue cracks in structures. The method utilizes the empirical mode decomposition method (EMD) to establish an effective energy-based damage index. To investigate the feasibility of the method, fatigue cracks of different sizes were introduced in an aluminum beam subjected to a cyclic load under a three-point bending configuration. The vibration signals corresponding to the healthy and the damaged states of the beam were acquired via piezoceramic sensors. The signals were then processed by the proposed methodology to obtain the damage indices. In addition, for the sake of comparison, the frequency and damping analysis were performed on the test specimen. The results of this study concluded with two major observations. Firstly, the method was highly successful in not only predicting the presence of the fatigue crack, but also in quantifying its progression. Secondly, the proposed energy-based damage index was proved to be superior to the frequency-based methods in terms of sensitivity to the damage detection and quantification. As a result, this technique could be regarded as an efficient non-destructive tool, since it is simple, cost-effective and does not rely on analytical modeling of structures. In addition, the capability of the finite element method (FEM) in mimicking the experiments, and hence for consideration as an effective tool for conducting future parametric studies, was also investigated
International Nuclear Information System (INIS)
Ten, G.N.; Kadrov, D.M.; Baranov, V.I.
2014-01-01
Structure and vibrational spectra of the zwitter-ionic forms of glycine and alanine in water solution and solid state have been calculated in the B3LYP/6-311++G(d,p) approximation. The environment influence has been taken into account by two methods: the self-consistent reaction field (SCRF) method and one of modeling the glycine and alanine complexes with molecules of water. The structure, energy and spectral properties have been determined which allow establishing an influence of the hydrophobic radical on the glycine and alanine ability to form the hydrogen bonds. It is shown by comparison with experiment that for the calculation of vibrational (IR and Raman) spectra of the zwitter-ionic forms of glycine and alanine in the condensed states they must be surrounded with three molecules of water, one of which is located between the N + H 3 and COO - ionic groups. The value of energy necessary to form the Ala complexes with water compared to Gly ones is 56.47 and 12.55 kcal/mol higher in the case of the complex formation with 1and 3 molecules of water, respectively, located between bipolar groups. (authors)
Vibrations versus collisions and the iterative structure of two-body dynamics
International Nuclear Information System (INIS)
Pfitzner, A.; Cassing, W.; Peter, A.
1993-11-01
The two-body correlation function is decomposed into two channel correlation functions for the pp- and the ph-channel. The associated coupled equations describe the evolution in the respective channels as well as their mixing. Integration of the ph-channel in terms of vibrational RPA-states yields a closed equation for the correlations in the pp-channel comprising phonon-particle coupling and a memory term. In the stationary limit the equation for a generalised effective interaction is derived which iterates both the G-matrix (ladders) and the polarisation matrix (loops), thus accounting nonperturbatively for the mixing of ladders and loops. (orig.)
DEFF Research Database (Denmark)
Lassen, Peter Rygaard
2005-01-01
The absolute configuration of the norlignan (+)-nyasol was determined to be S by comparison of the experimental vibrational circular dichroism data with first-principle calculations taking into account the eight lowest energy conformations. The established absolute configuration of (+)-nyasol...... enables establishment of the absolute configuration of (-)-hinokiresinol, which is concluded to be S. A total synthesis and resolution of hinokiresinol has been performed to resolve the conflicting reports of the coupling constant of the vinylic protons of the disubstituted double bond in this molecule...
International Nuclear Information System (INIS)
Pribytkov, G.A.; Chzhan Khajfen; Yuj Baokhaj; Khu Zoangchi
2003-01-01
Effects of a vibration grinding treatment of TiC-Ni and TiC-Ni-Cr titanium carbide-metal powder composition on the size of X-ray coherent scattering zones as well as the melt and crystallization temperatures under liquid-phase sintering have been investigated. Hardness and strength of composites sintered from the blends grinded for 4 h and more are found to be decreased that is explained by high porosity due to oxygen contamination of powder blends during a dry grinding treatment [ru
International Nuclear Information System (INIS)
Fritzen, M.R.; Fritzen, T.A.
1994-01-01
Anytime that blasting operations will be conducted near existing inhabited structures, vibration damage claims are a major concern of the blasting contractor. It has been the authors' experience that even when vibration and airblast levels generated from a blast are well below accepted damage thresholds, damage claims can still arise. The single greatest source of damage claims is the element of surprise associated with not knowing that blasting operations are being conducted nearby. The second greatest source of damage claims arise form the inability to produce accurate and detailed records of all blasting activity which provides evidence that vibration and air blast levels from each blast had been taken by seismic recording equipment. Using a two part plan consisting of extensive public relations followed by a detailed and accurate monitoring and recording of blasting operations has resulted in no substantiated claims of damage since its' incorporation. The authors experience shows that by using this two part process when conducting blasting operations near inhabited structures, unsubstantiated blast vibration damage claims may be significantly reduced
Energy Technology Data Exchange (ETDEWEB)
Fritzen, M.R.; Fritzen, T.A. [Blasting Technology, Inc., Maui, HI (United States)
1994-12-31
Anytime that blasting operations will be conducted near existing inhabited structures, vibration damage claims are a major concern of the blasting contractor. It has been the authors` experience that even when vibration and airblast levels generated from a blast are well below accepted damage thresholds, damage claims can still arise. The single greatest source of damage claims is the element of surprise associated with not knowing that blasting operations are being conducted nearby. The second greatest source of damage claims arise form the inability to produce accurate and detailed records of all blasting activity which provides evidence that vibration and air blast levels from each blast had been taken by seismic recording equipment. Using a two part plan consisting of extensive public relations followed by a detailed and accurate monitoring and recording of blasting operations has resulted in no substantiated claims of damage since its` incorporation. The authors experience shows that by using this two part process when conducting blasting operations near inhabited structures, unsubstantiated blast vibration damage claims may be significantly reduced.
Treyssède, Fabien
2018-01-01
Understanding thermal effects on the vibration of local (cable-dominant) modes in multi-cable structures is a complicated task. The main difficulty lies in the modification by temperature change of cable tensions, which are then undetermined. This paper applies a finite element procedure to investigate the effects of thermal loads on the linear dynamics of prestressed self-weighted multi-cable structures. Provided that boundary conditions are carefully handled, the discretization of cables with nonlinear curved beam elements can properly represent the thermoelastic behavior of cables as well as their linearized dynamics. A three-step procedure that aims to replace applied pretension forces with displacement continuity conditions is used. Despite an increase in the computational cost related to beam rotational degrees of freedom, such an approach has several advantages. Nonlinear beam finite elements are usually available in commercial codes. The overall method follows a thermoelastic geometrically non-linear analysis and hereby includes the main sources of non-linearities in multi-cable structures. The effects of cable bending stiffness, which can be significant, are also naturally accounted for. The accuracy of the numerical approach is assessed thanks to an analytical model for the vibration of a single inclined cable under temperature change. Then, the effects of thermal loads are investigated for two cable bridges, highlighting how natural frequencies can be affected by temperature. Although counterintuitive, a reverse relative change of natural frequency may occur for certain local modes. This phenomenon can be explained by two distinct mechanisms, one related to the physics intrinsic to cables and the other related to the thermal deflection of the superstructure. Numerical results show that cables cannot be isolated from the rest of the structure and the importance of modeling the whole structure for a quantitative analysis of temperature effects on the
Ucun, Fatih; Sağlam, Adnan; Güçlü, Vesile
2007-06-01
The molecular structures, vibrational frequencies and corresponding vibrational assignments of xanthine and its methyl derivatives (caffeine and theobromine) have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-31G(d, p) basis set level. The calculations were utilized to the CS symmetries of the molecules. The obtained vibrational frequencies and optimised geometric parameters (bond lengths and bond angles) were seen to be well agreement with the experimental data. The used scale factors which have been obtained the ratio of the frequency values of the strongest peaks in the calculated and experimental spectra seem to cause the gained vibrations well corresponding to the experimental ones. Theoretical infrared intensities and Raman activities are also reported.
Ertürk, Esra; Gürel, Tanju
2018-05-01
We present an ab initio study of structural, elastic and vibrational properties of transition-metal disilicides NbSi2 and TaSi2. The calculations have been carried out within the density-functional theory and linear-response formalism using norm-conserving pseudopotentials and a plane-wave basis. The calculated lattice parameters, bulk moduli, and elastic constants agree well with previous theoretical and experimental results. The calculated phonon frequencies at the Brillouin zone center are in good agreement with the reported Raman spectra and provide reference values for the future infrared and neutron phonon measurements. Phonon dispersion relations, mode Grüneisen parameters, and total and partial phonon density of states are also discussed. Mode Grüneisen parameters of NbSi2 and TaSi2 at Brillouin zone center show similar trends and all values are found to be positive. From phonon dispersion relations and phonon density of states, we have found a gap around 200 cm-1 for TaSi2, where the frequencies below this gap mainly belong to Ta vibrations and frequencies above the gap is mainly related with Si vibrations. In the case of NbSi2, there is no such gap and both Nb and Si atoms contribute to the phonon density of states in an energy range of 150-270 cm-1.
Energy Technology Data Exchange (ETDEWEB)
Asath, R. Mohamed; Premkumar, S.; Mathavan, T.; Benial, A. Milton Franklin, E-mail: miltonfranklin@yahoo.com [Department of Physics, N.M.S.S.V.N College, Madurai-625019, Tamilnadu (India); Rekha, T. N. [PG & Research Department of Physics, Lady Doak College, Madurai 625002, Tamilnadu (India); Jawahar, A. [Department of Chemistry, N.M.S.S.V.N College, Madurai-625019, Tamilnadu (India)
2016-05-23
The conformational analysis was carried out for 6-aminonicotinamide (ANA) using potential energy surface scan method and the most stable optimized conformer was predicted. The theoretical vibrational frequencies were calculated for the optimized geometry using DFT/B3LYP cc-pVQZ basis set by Gaussian 09 Program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using VEDA 4.0 program. The Mulliken atomic charge values were calculated. In the Frontier molecular orbitals analysis, the molecular reactivity, kinetic stability, intermolecular charge transfer studies and the related molecular properties were calculated. The ultraviolet-visible spectrum was simulated for both in the gas phase and liquid phase (ethanol) and the π to π* electronic transition was predicted. The nonlinear optical (NLO) activity was studied by means of the first order hyperpolarizability value, which was 8.61 times greater than the urea and the natural bond orbital analysis was also performed to confirm the NLO activity of the molecule. Hence, the ANA molecule is a promising candidate for the NLO materials.
Asath, R. Mohamed; Premkumar, S.; Rekha, T. N.; Jawahar, A.; Mathavan, T.; Benial, A. Milton Franklin
2016-05-01
The conformational analysis was carried out for 6-aminonicotinamide (ANA) using potential energy surface scan method and the most stable optimized conformer was predicted. The theoretical vibrational frequencies were calculated for the optimized geometry using DFT/B3LYP cc-pVQZ basis set by Gaussian 09 Program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using VEDA 4.0 program. The Mulliken atomic charge values were calculated. In the Frontier molecular orbitals analysis, the molecular reactivity, kinetic stability, intermolecular charge transfer studies and the related molecular properties were calculated. The ultraviolet-visible spectrum was simulated for both in the gas phase and liquid phase (ethanol) and the л to л* electronic transition was predicted. The nonlinear optical (NLO) activity was studied by means of the first order hyperpolarizability value, which was 8.61 times greater than the urea and the natural bond orbital analysis was also performed to confirm the NLO activity of the molecule. Hence, the ANA molecule is a promising candidate for the NLO materials.
Sivaprakash, S.; Prakash, S.; Mohan, S.; Jose, Sujin P.
2017-12-01
Quantum chemical calculations of energy and geometrical parameters of 1-aminoisoquinoline [1-AIQ] were carried out by using DFT/B3LYP method using 6-311G (d,p), 6-311G++(d,p) and cc-pVTZ basis sets. The vibrational wavenumbers were computed for the energetically most stable, optimized geometry. The vibrational assignments were performed on the basis of potential energy distribution (PED) using VEDA program. The NBO analysis was done to investigate the intra molecular charge transfer of the molecule. The frontier molecular orbital (FMO) analysis was carried out and the chemical reactivity descriptors of the molecule were studied. The Mulliken charge analysis, molecular electrostatic potential (MEP), HOMO-LUMO energy gap and the related properties were also investigated at B3LYP level. The absorption spectrum of the molecule was studied from UV-Visible analysis by using time-dependent density functional theory (TD-DFT). Fourier Transform Infrared spectrum (FT-IR) and Raman spectrum of 1-AIQ compound were analyzed and recorded in the range 4000-400 cm-1 and 3500-100 cm-1 respectively. The experimentally determined wavenumbers were compared with those calculated theoretically and they complement each other.
Malfunction tests and vibration analysis of P.W.R. internal structures
International Nuclear Information System (INIS)
Puyal, C.; Carre, J.C.; Epstein, A.
1987-01-01
To diagnose changes liable to occur in the vibration behavior of internals, it is important to understand the influence of changes in the mechanical properties of elements on the output signals obtained from neutron chambers placed out of core and accelerometers fixed to the reactor vessel. To do this, the effects of changes liable to occur in the hold-down springs and the flexures were simulated on the SAFRAN loop, using a representative hydroelastic mock-up. The results obtained experimentally on SAFRAN for different characteristics of the hold-down spring, which lies between the upper part of the core barrel and the vessel head, have been published. In this paper, we propose to present the results of the investigation of the fracture of one or more flexures which connect the cylindrical thermal shield to the core barrel. This work is in two parts: a) Computation based on a hydroelastic model using the substructuration computer program TRISTANA of the CASTEM system. b) Tests simulating flexure fracture: 1 - in air, for an understanding of the mechanisms involved; 2 - on the SAFRAN loop with a representative flow in order to estimate the strains liable to exist on the vibration signatures recorded on displacement transducers and accelerometers. Good agreement was observed between the computation results with the theoretical model employed and those obtained experimentally [fr
Arjunan, V.; Anitha, R.; Marchewka, M. K.; Mohan, S.; Yang, Haifeng
2015-01-01
The Fourier transform infrared (FTIR) and FT-Raman spectra of cis-2-methoxycinnamic acid have been measured in the range 4000-400 and 4000-100 cm-1, respectively. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FTIR and FT-Raman data. The geometry was optimised without any symmetry constrains using the DFT/B3LYP method utilising 6-311++G∗∗ and cc-pVTZ basis sets. The thermodynamic stability and chemical reactivity descriptors of the molecule have been determined. The exact environment of C and H of the molecule has been analysed by NMR spectroscopies through 1H and 13C NMR chemical shifts of the molecule. The energies of the frontier molecular orbitals have also been determined. Complete NBO analysis was also carried out to find out the intramolecular electronic interactions and their stabilisation energy. The vibrational frequencies which were determined experimentally are compared with those obtained theoretically from density functional theory (DFT) gradient calculations employing the B3LYP/6-311++G∗∗ and cc-pVTZ methods.
Yang, Yongchao; Dorn, Charles; Mancini, Tyler; Talken, Zachary; Nagarajaiah, Satish; Kenyon, Garrett; Farrar, Charles; Mascareñas, David
2017-03-01
Enhancing the spatial and temporal resolution of vibration measurements and modal analysis could significantly benefit dynamic modelling, analysis, and health monitoring of structures. For example, spatially high-density mode shapes are critical for accurate vibration-based damage localization. In experimental or operational modal analysis, higher (frequency) modes, which may be outside the frequency range of the measurement, contain local structural features that can improve damage localization as well as the construction and updating of the modal-based dynamic model of the structure. In general, the resolution of vibration measurements can be increased by enhanced hardware. Traditional vibration measurement sensors such as accelerometers have high-frequency sampling capacity; however, they are discrete point-wise sensors only providing sparse, low spatial sensing resolution measurements, while dense deployment to achieve high spatial resolution is expensive and results in the mass-loading effect and modification of structure's surface. Non-contact measurement methods such as scanning laser vibrometers provide high spatial and temporal resolution sensing capacity; however, they make measurements sequentially that requires considerable acquisition time. As an alternative non-contact method, digital video cameras are relatively low-cost, agile, and provide high spatial resolution, simultaneous, measurements. Combined with vision based algorithms (e.g., image correlation or template matching, optical flow, etc.), video camera based measurements have been successfully used for experimental and operational vibration measurement and subsequent modal analysis. However, the sampling frequency of most affordable digital cameras is limited to 30-60 Hz, while high-speed cameras for higher frequency vibration measurements are extremely costly. This work develops a computational algorithm capable of performing vibration measurement at a uniform sampling frequency lower than
Arjunan, V; Rani, T; Santhanam, R; Mohan, S
2012-10-01
The FT-IR and FT-Raman spectra of H bond inner conformer of 2,3-epoxypropanol have been recorded in the regions 3700-400 and 3700-100 cm(-1), respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The normal coordinate analysis was carried out to confirm the precision of the assignments. The structure of the conformers H bond inner and H bond outer1 were optimised and the structural characteristics were determined by density functional theory (DFT) using B3LYP and MP2 methods with 6-31G** and 6-311++G** basis sets. The vibrational frequencies were calculated in all these methods and were compared with the experimental frequencies which yield good agreement between observed and calculated frequencies. The electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. Copyright © 2012 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Stef Iulian Ioan
2013-05-01
Full Text Available In the upper basin of the Sebes Valley, the oldest storage lakes have been temporary artificial lakes, called haituri in Romanian. They were created within the forest exploitation areas. Inside the dams of those retention lakes, which dams are made of a wooden skeleton, filled with soil and stones, there have been weirs for the quick discharge of the water, having the purpose of creating some flood trends, capable of carrying over the logs, downstream the lake. At present, some of those temporary artificial lakes are used as trout farms, while others are damaged, or operate as basins for the sedimentation of the alluvial deposits. The difference of level between the springs of the Sebes and the Mures Rivers generates a convertible hydroelectric potential, having an average power exceeding 60,000 kW" />
International Nuclear Information System (INIS)
Tovar, Miguel A.
2012-01-01
Socioeconomic and behavioural variables that influence the household’s adoption of energy efficiency measures such as cavity and loft insulation and upgrades to the boiler are identified, contrary to previous literature. By extending Brechling and Smith’s (1994) and Hassett and Metcalf's (1995) models, it is shown that the application of the Energy Act 2011, which contains provisions on the Green Deal, the new Energy Company Obligation (ECO) and the private rented sector, needs to follow a tailored strategy to reach the low adoption households identified by my model. Moreover, for the current adopters of the analysed measures, average monetary and environmental adoption benefits are estimated based on Parti and Parti’s (1980) demand model. These estimates are smaller than their expected values showing an important energy efficiency gap in the sector. Particularly low cost measures can bring important savings that can help to meet the ''pay as you save'' rule (i.e., the Golden rule) of the new regulation. My model also shows that a poor state of dwelling repair can reduce the adoption benefits increasing the need of subsidies that will be financed through consumer’s energy bills. However, this can increase the number of households in fuel poverty. - Highlights: ► Analysis of socioeconomic and behavioural factors that can affect the Green Deal uptake. ► The Energy Company Obligation (ECO) needs to follow a tailored strategy. ► Average adoption benefits of cavity and loft insulation and upgrades to the boiler are estimated. ► There is an important energy efficiency gap in the UK domestic sector. ► A poor state of dwelling repair could bring financial pressure to the ECO program.
International Nuclear Information System (INIS)
Yadav, P. S.; Pandey, D. K.; Agrawal, S.; Agrawal, B. K.
2010-01-01
An ab initio study of the stability, structural, electronic. and optical properties has been performed for 46 zinc sulfide nanoclusters Zn x S y (x + y = n = 2 to 5). Five out of them are seen to be unstable as their vibrational frequencies are found to be imaginary. A B3LYP-DFT/6-311G(3df) method is employed to optimize the geometries and a TDDFT method is used for the study of the optical properties. The binding energies (BE), HOMO-LUMO gaps and the bond lengths have been obtained for all the clusters. For the ZnS 2 , ZnS 3 , and ZnS 4 nanoclusters, our stable structures are seen to be different from those obtained earlier by using the effective core potentials. We have also considered the zero point energy (ZPE) corrections ignored by the earlier workers. For a fixed value of n, we designate the most stable structure the one, which has maximum final binding energy per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), charges on the atoms, dipole moments, optical properties, vibrational frequencies, infrared intensities, relative infrared intensities, and Raman scattering activities have been investigated for the most stable structures. The nanoclusters containing large number of S atoms for each n is found to be most stable. The HOMO-LUMO gap decreases from n = 2-3 and then increases above n = 3. The IP and EA both fluctuate with the cluster size n. The optical absorption is quite weak in visible region but strong in the ultraviolet region in most of the nanoclusters except a few. The optical absorption spectrum or electron energy loss spectrum (EELS) is unique for every nanocluster and may be used to characterize a specific nanocluster. The growth of most stable nanoclusters may be possible in the experiments.
Jedidi, Abdesslem
2015-11-13
Vibrational fingerprints of small PtnP2n (n = 1–5) clusters were computed from their low-lying structures located from a global exploration of their DFT potential energy surfaces with the GSAM code. Five DFT methods were assessed from the CCSD(T) wavenumbers of PtP2 species and CCSD relative energies of Pt2P4 structures. The eight first PtnP2n isomers found are reported. The vibrational computations reveal (i) the absence of clear signatures made by overtone or combination bands due to very weak mechanical and electrical anharmonicities and (ii) some significant and recurrent vibrational fingerprints in correlation with the different PP bonding situations in the PtnP2n structures.
Jedidi, Abdesslem; Li, Rui; Fornasiero, Paolo; Cavallo, Luigi; Carbonniere, Philippe
2015-01-01
Vibrational fingerprints of small PtnP2n (n = 1–5) clusters were computed from their low-lying structures located from a global exploration of their DFT potential energy surfaces with the GSAM code. Five DFT methods were assessed from the CCSD(T) wavenumbers of PtP2 species and CCSD relative energies of Pt2P4 structures. The eight first PtnP2n isomers found are reported. The vibrational computations reveal (i) the absence of clear signatures made by overtone or combination bands due to very weak mechanical and electrical anharmonicities and (ii) some significant and recurrent vibrational fingerprints in correlation with the different PP bonding situations in the PtnP2n structures.
Comparison of Interpolation Methods as Applied to Time Synchronous Averaging
National Research Council Canada - National Science Library
Decker, Harry
1999-01-01
Several interpolation techniques were investigated to determine their effect on time synchronous averaging of gear vibration signals and also the effects on standard health monitoring diagnostic parameters...
Cole, Milton W; Crespi, Vincent H; Dresselhaus, Mildred S; Dresselhaus, Gene; Fischer, John E; Gutierrez, Humberto R; Kojima, K; Mahan, Gerald D; Rao, Apparao M; Sofo, Jorge O; Tachibana, M; Wako, K; Xiong, Qihua
2010-08-25
This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C(60) and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature
International Nuclear Information System (INIS)
Cole, Milton W; Crespi, Vincent H; Dresselhaus, Mildred S; Dresselhaus, Gene; Fischer, John E; Gutierrez, Humberto R; Kojima, K; Wako, K; Mahan, Gerald D; Rao, Apparao M; Sofo, Jorge O; Tachibana, M; Xiong Qihua
2010-01-01
This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C 60 and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature
Fielicke, André; von Helden, Gert; Meijer, Gerard; Pedersen, David B; Simard, Benoit; Rayner, David M
2005-06-15
We report on the interaction of carbon monoxide with cationic gold clusters in the gas phase. Successive adsorption of CO molecules on the Au(n)(+) clusters proceeds until a cluster size specific saturation coverage is reached. Structural information for the bare gold clusters is obtained by comparing the saturation stoichiometry with the number of available equivalent sites presented by candidate structures of Au(n)(+). Our findings are in agreement with the planar structures of the Au(n)(+) cluster cations with n < or = 7 that are suggested by ion mobility experiments [Gilb, S.; Weis, P.; Furche, F.; Ahlrichs, R.; Kappes, M. M. J. Chem. Phys. 2001, 116, 4094]. By inference we also establish the structure of the saturated Au(n)(CO)(m)(+) complexes. In certain cases we find evidence suggesting that successive adsorption of CO can distort the metal cluster framework. In addition, the vibrational spectra of the Au(n)(CO)(m)(+) complexes in both the CO stretching region and in the region of the Au-C stretch and the Au-C-O bend are measured using infrared photodepletion spectroscopy. The spectra further aid in the structure determination of Au(n)(+), provide information on the structure of the Au(n)(+)-CO complexes, and can be compared with spectra of CO adsorbates on deposited clusters or surfaces.
Energy Technology Data Exchange (ETDEWEB)
Ahn, Chang Kee; Shim, Joo Sup [Shinwa Technology Information, Seoul (Korea)
2001-04-01
The objective of this study is to deduce the dynamic correlation between the fuel assembly and the reactor structure. Dynamic characteristics analyses for reactor structure related with vibration of HANARO fuel assembly have been performed For the dynamic characteristic analysis, the in-air models of the round and hexagonal flow tubes, 18-element and 36-element fuel assemblies, and reactor structure were developed. By calculating the hydrodynamic mass and distributing it on the in-air models, the in-water models of the flow tubes, the fuel assemblies, and the reactor structure were developed. Then, modal analyses for developed in-air and in-water models have been performed. Especially, two 18-element fuel assemblies and three 36-element fuel assemblies were included in the in-water reactor models. For the verification of the modal analysis results, the natural frequencies and the mode shapes of the fuel assembly were compared with those obtained from the experiment. Finally the analysis results of the reactor structure were compared with them performed by AECL Based on the reactor model without PCS piping, the in-water reactor model including the fuel assemblies was developed, and its modal analysis was performed. The analysis results demonstrate that there are no resonance between the fuel assembly and the reactor structures. 26 refs., 419 figs., 85 tabs. (Author)
Lesar, Douglas E.
1992-01-01
The performance of the NASTRAN CQUAD4 membrane and plate element in the analysis of undamped natural vibration modes of thin fiber reinforced composite plates was evaluated. The element provides natural frequency estimates that are comparable in accuracy to alternative formulations, and, in most cases, deviate by less than 10 percent from experimentally measured frequencies. The predictions lie within roughly equal accuracy bounds for the two material types treated (GFRP and CFRP), and for the ply layups considered (unidirectional, cross-ply, and angle-ply). Effective elastic lamina moduli had to be adjusted for fiber volume fraction to attain this level of frequency. The lumped mass option provides more accurate frequencies than the consistent mass option. This evaluation concerned only plates with L/t ratios on the order of 100 to 150. Since the CQUAD4 utilizes first-order corrections for transverse laminate shear stiffness, the element should provide useful frequency estimates for plate-like structures with lower L/t. For plates with L/t below 20, consideration should be given to idealizing with 3-D solid elements. Based on the observation that natural frequencies and mode shapes are predicted with acceptable engineering accuracy, it is concluded that CQUAD4 should be a useful and accurate element for transient shock and steady state vibration analysis of naval ship
Prashanth, J.; Reddy, Byru Venkatram
2018-03-01
The Fourier transform infrared (FTIR) spectra of organic compounds 4-fluoro-2-azido-1-phenylethanone (FAP), 4-chloro-2-azido-1-phenylethanone (CAP) and 4-bromo-2-azido-1-phenylethanone (BAP) have been recorded in the region 4000-400 cm-1. The optimized molecular structure for global minimum energy of the titled molecules is determined by evaluating torsional potentials as a function of rotation angle about free rotation bonds among the substituent groups subjecting them to DFT employing B3LYP functional with 6-311++G (d,p) basis set. The vibrational frequencies along with infrared intensities are computed by SQM procedure. The rms error between observed and calculated frequencies is found to be 9.27, 8.17 and 7.95 cm-1 for FAP, CAP and BAP, respectively which shows good agreement between experimental and scaled values of calculated frequencies obtained by DFT. The vibrational assignments of all the fundamental bands of each molecule are made unambiguously using PED and eigen vectors obtained in the computations. The computed values of dipole moment, polarizability and hyperpolarizability indicate that the titled molecules exhibit NLO behaviour and hence may be considered for potential applicants for the development of NLO materials. HOMO and LUMO energies evaluated in the study demonstrate chemical stability of the molecules. NBO analysis is made to study the stability of the molecules arising from hyper conjugative interactions and charge delocalization. The molecular electrostatic surface potential (MESP) and thermodynamic parameters are also evaluated.
Thirunarayanan, S.; Arjunan, V.; Marchewka, M. K.; Mohan, S.
2017-04-01
The hydrogen bonded molecular complex bis(1-hydroxy-2-methylpropan-2-aminium)selenate (C8H24N2O6Se) has been prepared by the reaction of 2-amino-2-methyl propanol and selenic acid. The X-ray diffraction analysis revealed that the intermolecular proton transfer from selenic acid (SeO4H2) to 2-amino-2-methylpropanol results in the formation of bis(1-hydroxy-2-methylpropan-2-aminium)selenate (HMPAS) salt and the fragments are connected through H-bonding and ion pairing. The N-H⋯O and O-H⋯O interactions between 2-amino-2-methylpropanol and selenic acid determine the supramolecular arrangement in three-dimensional space. The salt crystallises in the space group P121/n1 of monoclinic system. The complete vibrational assignments of HMPAS have been performed by FTIR and FT-Raman spectroscopy. The experimental data are correlated with the structural properties namely the energy, thermodynamic parameters, atomic charges, hybridization concepts and vibrational frequencies determined by quantum chemical studies performed with B3LYP method using 6-311++G*, 6-31+G* and 6-31G** basis sets.
DEFF Research Database (Denmark)
Stein, George Juraj; Darula, Radoslav; Sorokin, Sergey
2012-01-01
A theoretical analysis of an electromagnetic vibration controller is presented. The analyzed device consists of a pot-type iron core with a coil and a permanent magnet as a source of constant magnetic flux. The magnetic circuit is closed by a yoke, excited by an external harmonic mechanical force....... The so generated magnetic flux variation induces alternating voltage in the electric circuit, which is dissipated in a shunt resistor. The induced current driven through the coil generates magnetic force, which damps the excitation force and changes the damped natural frequency of the oscillatory system....... Due to the hysteretic effects in the magnetic material the internal losses influence the overall system’s performance. A mathematical model of the force balance in the oscillatory system is derived in a simplified, linearised form. The electric as well as mechanical system is modelled using lumped...
Directory of Open Access Journals (Sweden)
Alejandra Londono-Calderon
2014-01-01
Full Text Available The sintering of different ZnO nanostructures by the thermal decomposition of zinc acetate is reported. Morphological changes from nanorods to nanoparticles are exhibited with the increase of the decomposition temperature from 300 to 500°C. The material showed a loss in the crystalline order with the increase in the temperature, which is correlated to the loss of oxygen due to the low heating rate used. Nanoparticles have a greater vibrational freedom than nanorods which is demonstrated in the rise of the main Raman mode E 2(high during the transformation. The energy band gap of the nanostructured material is lower than the ZnO bulk material and decreases with the rise in the temperature.
Similarity analysis and prediction for data of structural acoustic and vibration
International Nuclear Information System (INIS)
Mei Liquan; Ding Xuemei; Zhang Shujuan
2010-01-01
Support vector machine (SVM) is a learning machine based on statistical learning theory, which can get a model having good generalization. It can solve 'learning more' when dealing with small size. It can also avoid 'dimensional disaster' when solving nonlinear problems. This paper works on the parameters optimization for support vector regression machine (SVRM) and its applications. Solution path algorithm can save much CPU time when it is employed to optimize the regularization parameter of SVRM. Simulated annealing algorithm has good ability of finding global optimal solution. An improved solution path algorithm and simulated annealing algorithm are combined to optimize parameters of SVRM in the regression analysis of the acoustic and vibration data for complex practical problems. The numerical results show the model has good predictive capability. (authors)
International Nuclear Information System (INIS)
Li Wei-Yin; Chen Fu-Yi
2014-01-01
We investigate the effects of shape and single-atom doping on the structural, optical absorption, Raman, and vibrational properties of Ag 13 , Ag 12 Cu 1 , Cu 13 , and Cu 12 Ag 1 clusters by using the (time-dependent) density functional theory. The results show that the most stable structures are cuboctahedron (COh) for Ag 13 and icosahedron (Ih) for Cu 13 , Ag 12 Cu 1core , and Cu 12 Ag 1sur . In the visible—near infrared optical absorption, the transitions consist of the interband and the intraband transitions. Moreover, red shifts are observed as follows: 1) clusters change from Ag 12 Cu 1core to Ag 13 to Ag 12 Cu 1sur with the same motifs, 2) the shapes of pure Ag 13 and Ag 12 Cu 1core clusters change from COh to Ih to decahedron (Dh), 3) the shape of Ag 12 Cu 1sur clusters changes from Ih to COh to Dh, and 4) the shapes of pure Cu 13 and Cu 12 Ag 1 clusters change from Ih to Dh to COh. All of the Raman and vibrational spectra exhibit many significant vibrational modes related to the shapes and the compositions of the clusters. The ranges of vibrational spectra of Ag 13 , Ag 12 Cu 1 or Cu 13 , and Cu 12 Ag 1 clusters become narrower and the vibrational intensities increase as the shape of the clusters changes from Ih to Dh to COh. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
International Nuclear Information System (INIS)
Tang, H.T.; Nakamura, N.
1995-01-01
A 1/4-scale cylindrical reactor containment model was constructed in Hualien, Taiwan for foil-structure interaction (SSI) effect evaluation and SSI analysis procedure verification. Forced vibration tests were executed before backfill (FVT-1) and after backfill (FVT-2) to characterize soil-structure system characteristics under low excitations. A number of organizations participated in the pre-test blind prediction and post-test correlation analyses of the forced vibration test using various industry familiar methods. In the current study, correlation analyses were performed using a three-dimensional flexible volume substructuring method. The results are reported and soil property sensitivities are evaluated in the paper. (J.P.N.)