Zhao, Bin; Sun, Zhigang; Guo, Hua
2016-10-01
State-to-state differential cross sections (DCSs) are computed quantum mechanically in full dimensionality for the title reaction using a reactant-product decoupling scheme. The DCSs are calculated at three collision energies of 0.25, 0.28, and 0.34 eV, corresponding to the existing experimental results. In good agreement with experiment, the calculated DCSs are dominated by backward scattering, thanks to the direct rebound mechanism, and the DOH product has two quanta of OD stretching vibration in the newly formed OD bond. In addition, the vibrational excitation of the OH reactant is found to result in a very different but predictable vibrational distribution of the DOH product. It is further shown at the state-to-state level that the DCSs of the DOH(vOD, vb, vOH) product state from the OH(v = 1) reactant state resemble the ones of the DOH(vOD, vb, vOH-1) product state from the OH(v = 0) reactant state, thanks to the spectator nature of the OH moiety.
Beecher, L. C.; Williams, F. T.
1970-01-01
Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.
Harun Al Rasid Gazi; Ranjit Biswas
2011-05-01
Fluorescence spectroscopic techniques have been used to study the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in two sets of mixed solvents, (1-propanol + ethyl acetate) and (propylene carbonate + acetonitrile), in the absence and presence of a strong electrolyte, lithium perchlorate. These two sets of mixed solvent systems represent binary solvent mixtures of low and high polarities, respectively. Density, sound velocity and viscosity measurements indicate that these two mixed solvent systems are structurally different. Stronger ion-reactant interaction is evidenced in the mole fraction independence of emission frequencies in electrolyte solutions of low polar binary solvent mixtures. For both these mixtures, the reaction driving force (- ) decreases with increase in mole fraction of the relatively less polar solvent component of the mixture. Interestingly, - increases significantly on addition of electrolyte in low polar mixtures and exhibits mixture composition dependence but, in contrast, - in high polar mixtures does not sense variation in mixture composition in presence of electrolyte. This insensitivity to mixture composition for high polar mixtures is also observed for the measured reaction time constant. In addition, the reaction time constant does not sense the presence of electrolyte in the high polar solvent mixtures. The reaction time constant in low polar mixtures, which becomes faster on addition of electrolyte, lengthens on increasing the mole fraction of the relatively less polar solvent component of the mixture. These observations have been qualitatively explained in terms of the measured solvent reorganization energy and reaction driving force by using expressions from the classical theory of electron transfer reaction.
Effects of reactant rotational excitations on H2 + NH2 → H + NH3 reactivity
Song, Hongwei; Guo, Hua
2014-12-01
Rotational mode specificity of the title reaction is examined using an initial state selected time-dependent wave packet method on an accurate ab initio based global potential energy surface. This penta-atomic reaction presents an ideal system to test several dynamical approximations, which might be useful for future quantum dynamics studies of polyatomic reactions, particularly with rotationally excited reactants. The first approximation involves a seven-dimensional (7D) model in which the two non-reactive N-H bonds are fixed at their equilibrium geometry. The second is the centrifugal sudden (CS) approximation within the 7D model. Finally, the J-shifting (JS) model is tested, again with the fixed N-H bonds. The spectator-bond approximation works very well in the energy range studied, while the centrifugal sudden and J-shifting integral cross sections (ICSs) agree satisfactorily with the coupled-channel counterparts in the low collision energy range, but deviate at the high energies. The calculated integral cross sections indicate that the rotational excitation of H2 somewhat inhibits the reaction while the rotational excitations of NH2 have little effect. These findings are compared with the predictions of the sudden vector projection model. Finally, a simple model is proposed to predict rotational mode specificity using K-averaged reaction probabilities.
Acceleration of the reaction OH + CO → H + CO2 by vibrational excitation of OH.
Kohno, Nanase; Izumi, Mari; Kohguchi, Hiroshi; Yamasaki, Katsuyoshi
2011-05-19
The collision complex formed from a vibrationally excited reactant undergoes redissociation to the reactant, intramolecular vibrational relaxation (randomization of vibrational energy), or chemical reaction to the products. If attractive interaction between the reactants is large, efficient vibrational relaxation in the complex prevents redissociation to the reactants with the initial vibrational energy, and the complex decomposes to the reactants with low vibrational energy or converts to the products. In this paper, we have studied the branching ratios between the intramolecular vibrational relaxation and chemical reaction of an adduct HO(v)-CO formed from OH(X(2)Π(i)) in different vibrational levels v = 0-4 and CO. OH(v = 0-4) generated in a gaseous mixture of O(3)/H(2)/CO/He irradiated at 266 nm was detected with laser-induced fluorescence (LIF) via the A(2)Σ(+)-X(2)Π(i) transition, and H atoms were probed by the two-photon excited LIF technique. From the kinetic analysis of the time-resolved LIF intensities of OH(v) and H, we have found that the intramolecular vibrational relaxation is mainly governed by a single quantum change, HO(v)-CO → HO(v-1)-CO, followed by redissociation to OH(v-1) and CO. With the vibrational quantum number v, chemical process from the adduct to H + CO(2) is accelerated, and vibrational relaxation is decelerated. The countertrend is elucidated by the competition between chemical reaction and vibrational relaxation in the adduct HOCO.
Interception of excited vibrational quantum states by O2 in atmospheric association reactions.
Glowacki, David R; Lockhart, James; Blitz, Mark A; Klippenstein, Stephen J; Pilling, Michael J; Robertson, Struan H; Seakins, Paul W
2012-08-31
Bimolecular reactions in Earth's atmosphere are generally assumed to proceed between reactants whose internal quantum states are fully thermally relaxed. Here, we highlight a dramatic role for vibrationally excited bimolecular reactants in the oxidation of acetylene. The reaction proceeds by preliminary adduct formation between the alkyne and OH radical, with subsequent O(2) addition. Using a detailed theoretical model, we show that the product-branching ratio is determined by the excited vibrational quantum-state distribution of the adduct at the moment it reacts with O(2). Experimentally, we found that under the simulated atmospheric conditions O(2) intercepts ~25% of the excited adducts before their vibrational quantum states have fully relaxed. Analogous interception of excited-state radicals by O(2) is likely common to a range of atmospheric reactions that proceed through peroxy complexes.
Electron impact vibrational excitation of methyl chloride
Sakaamini, Ahmad; Hargreaves, Leigh; Khakoo, Murtadha
2016-05-01
Low energy differential cross sections and excitation functions for vibrational excitation of CH3 Cl are presented for five vibrational features in the electron energy loss spectrum of this molecule. Electron energies range from 1 eV to 15 eV and scattering angles from 10o to 125o. Results will be compared to existing data for CH3 Cl in the literature. Funded by a NSF-AMOP-RUI Grant.
Impact self-excited vibrations of linear motor
Zhuravlev, V. Ph.
2010-08-01
Impact self-exciting vibration modes in a linear motor of a monorail car are studied. Existence and stability conditions of self-exciting vibrations are found. Ways of avoiding the vibrations are discussed.
Barbante, Gregory J; Kebede, Noah; Hindson, Christopher M; Doeven, Egan H; Zammit, Elizabeth M; Hanson, Graeme R; Hogan, Conor F; Francis, Paul S
2014-10-20
We demonstrate a new approach to manipulate the selective emission in mixed electrogenerated chemiluminescence (ECL) systems, where subtle changes in co-reactant properties are exploited to control the relative electron-transfer processes of excitation and quenching. Two closely related tertiary-amine co-reactants, tri-n-propylamine and N,N-diisopropylethylamine, generate remarkably different emission profiles: one provides distinct green and red ECL from [Ir(ppy)3] (ppy=2-phenylpyridinato-C2,N) and a [Ru(bpy)3](2+) (bpy=2,2'-bipyridine) derivative at different applied potentials, whereas the other generates both emissions simultaneously across a wide potential range. These phenomena can be rationalized through the relative exergonicities of electron-transfer quenching of the excited states, in conjunction with the change in concentration of the quenchers over the applied potential range.
Burdzinski, Gotard T; Middleton, Chris T; Gustafson, Terry L; Platz, Matthew S
2006-11-22
Photolysis of phenyl and o-biphenylyl azide (at 270 nm) releases vibrationally excited singlet nitrene which isomerizes to the corresponding hot 1,2-didehydroazepine at a rate competitive with thermal relaxation. Using ultrafast vibrational spectroscopy we observe the formation of vibrationally excited 1,2-4,6-azacycloheptatetraene (1,2-didehydroazepine) in picoseconds following photolysis of phenyl azide in chloroform and o-biphenylyl azide in acetonitrile at ambient temperature.
Tunneling ionization of vibrationally excited nitrogen molecules
Kornev, Aleksei S.; Zon, Boris A.
2015-09-01
Ionization of molecular nitrogen plays an important role in the process of light-filament formation in air. In the present paper we theoretically investigated tunneling ionization of the valence 3 σg and 1 πu shells in a N2 molecule using a strong near-infrared laser field. This research is based on our previously proposed theory of anti-Stokes-enhanced tunneling ionization with quantum accounting for the vibrationally excited states of the molecules [A. S. Kornev and B. A. Zon, Phys. Rev. A 86, 043401 (2012), 10.1103/PhysRevA.86.043401]. We demonstrated that if the N2 molecule is ionized from the ground vibrational state, then the contribution of the 1 πu orbital is 0.5%. In contrast, for vibrationally excited states with a certain angle between the light polarization vector and the molecule axis, both shells can compete and even reverse their contributions due to the anti-Stokes mechanism. The structure constants of molecular orbitals are extracted from numerical solutions to the Hartree-Fock equations. This approach correctly takes into account the exchange interaction. Quantum consideration of vibrational motion results in the occurrence of the critical vibrational state, the tunneling ionization from which has the maximum rate. The numbers of the critical vibrational states are different for different valence shells. In addition, quantum description of vibrations changes the rate of ionization from the ground vibrational state by 20%-40% in comparison with the quasiclassical results.
Influence of the Reactants Rotational Excitation on the H+D2(v=0, j) Reactivity
Aldegunde, J; Jambrina, PG; González-Sanchez, L; Herrero, VJ; Aoiz, FJ
2016-01-01
We have analyzed the influence of the rotational excitation on the H+D2(υ=0, j) reaction through quantum mechanical (QM) and quasiclassical trajectories (QCT) calculations at a wide range of total energies. The agreement between both types of calculations is excellent. We have found that the rotational excitation largely increases the reactivity at large values of the total energy. Such increase cannot be attributed to a stereodynamical effect but to the existence of recrossing trajectories that become reactive as the target molecule gets rotationally excited. At low total energies, however, recrossing is not significant and the reactivity evolution is dominated by changes in the collision energy; the reactivity decreases with the collision energy as it shrinks the acceptance cone. When state-to-state results are considered, rotational excitation leads to cold product’s rovibrational distributions, so that most of the energy is released as recoil energy. PMID:26305719
Vertical Distribution of Vibrationally Excited Hydroxyl
Grygalashvyly, Mykhaylo; Becker, Erich; Sonnemann, Gerd
2016-04-01
Knowledge about the vertical distribution of the vibrationally excited states of hydroxyl (OH*) is important for the interpretation of airglow measurements with respect to dynamical processes in the mesopause region. We derive an approximate analytical expression for the distribution of OH* that highlights the dependence on atomic oxygen and temperature. In addition, we use an advanced numerical model for the formation and relaxation of OH* and investigate the distributions of the different vibrationally exited states of OH*. For the production of OH*, the model includes the reaction of atomic hydrogen with ozone, as well as the reaction of atomic oxygen with hydroperoxy radicals. As loss processes we include 1) deactivation by atomic oxygen, molecular oxygen, and molecular nitrogen, 2) spontaneous emission, and 3) loss due to chemical reaction with atomic oxygen. All these processes take the dependence on the vibrational number into account. The quenching by molecular and atomic oxygen is parameterized by a multi-quantum relaxation scheme. This diagnostic model for OH* has been implemented as part of a chemistry-transport model that is driven by the dynamics simulated with the KMCM (Kühlungsborn Mechanistic general Circulation Model). Numerical results confirm that emission from excited states with higher vibrational number is weaker and emanates from higher altitudes. In addition we find that the OH*-peak altitudes depend significantly on season and latitude. This behavior is mainly controlled by the corresponding variations of atomic oxygen and temperature, as is also confirmed by the aforementioned approximate theory.
Collisional deactivation of highly vibrationally excited pyrazine
Miller, Laurie A.; Barker, John R.
1996-07-01
The collisional deactivation of vibrationally excited pyrazine (C4N2H4) in the electronic ground state by 19 collider gases was studied using the time-resolved infrared fluorescence (IRF) technique. The pyrazine was photoexcited with a 308 nm laser and its vibrational deactivation was monitored following rapid radiationless transitions to produce vibrationally excited molecules in the electronic ground state. The IRF data were analyzed by a simple approximate inversion method, as well as with full collisional master equation simulations. The average energies transferred in deactivating collisions (d) exhibit a near-linear dependence on vibrational energy at lower energies and less dependence at higher energies. The deactivation of ground state pyrazine was found to be similar to that of ground state benzene [J. R. Barker and B. M. Toselli, Int. Rev. Phys. Chem. 12, 305 (1990)], but it is strikingly different from the deactivation of triplet state pyrazine [T. J. Bevilacqua and R. B. Weisman, J. Chem. Phys. 98, 6316 (1993)].
The photodissociation and reaction dynamics of vibrationally excited molecules
Crim, F.F. [Univ. of Wisconsin, Madison (United States)
1993-12-01
This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.
Catalytic synthesis of ammonia using vibrationally excited nitrogen
Henriksen, Niels Engholm; Billing, Gert D.; Hansen, Flemming Yssing
1992-01-01
In a previous study we have considered the catalytic synthesis of ammonia in the presence of vibrationally excited nitrogen. The distribution over vibrational states was assumed to be maintained during the reaction, and it was shown that the yield of ammonia increased considerably compared...... to that from conventional synthesis. In the present study the nitrogen molecules are only excited at the inlet of a plug flow reactor, and the importance of vibrational relaxation is investigated. We show that vibrational excitation can give an enhanced yield of ammonia also in the situation where vibrational...
Vibration analysis of composite laminate plate excited by piezoelectric actuators.
Her, Shiuh-Chuan; Lin, Chi-Sheng
2013-01-01
Piezoelectric materials can be used as actuators for the active vibration control of smart structural systems. In this work, piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. A static analysis based on the piezoelectricity and elasticity is conducted to evaluate the loads induced by the piezoelectric actuators to the host structure. The loads are then employed to develop the vibration response of a simply supported laminate rectangular plate excited by piezoelectric patches subjected to time harmonic voltages. An analytical solution of the vibration response of a simply supported laminate rectangular plate under time harmonic electrical loading is obtained and compared with finite element results to validate the present approach. The effects of location and exciting frequency of piezoelectric actuators on the vibration response of the laminate plate are investigated through a parametric study. Numerical results show that modes can be selectively excited, leading to structural vibration control.
Spectroscopy and reactions of vibrationally excited transient molecules
Dai, H.L. [Univ. of Pennsylvania, Philadelphia (United States)
1993-12-01
Spectroscopy, energy transfer and reactions of vibrationally excited transient molecules are studied through a combination of laser-based excitation techniques and efficient detection of emission from the energized molecules with frequency and time resolution. Specifically, a Time-resolved Fourier Transform Emission Spectroscopy technique has been developed for detecting dispersed laser-induced fluorescence in the IR, visible and UV regions. The structure and spectroscopy of the excited vibrational levels in the electronic ground state, as well as energy relaxation and reactions induced by specific vibronic excitations of a transient molecule can be characterized from time-resolved dispersed fluorescence in the visible and UV region. IR emissions from highly vibrational excited levels, on the other hand, reveal the pathways and rates of collision induced vibrational energy transfer.
Red-light initiated atmospheric reactions of vibrationally excited molecules.
Vaida, V; Donaldson, D J
2014-01-21
We present a brief review of long wavelength, red-light initiated chemistry from excited vibrational levels of the ground electronic state of atmospheric trace species. When sunlight driven electronic state reactions are not effective, photochemical processes occurring by vibrational overtone excitation have been found to be important in reactions of oxidized atmospheric compounds (acids, alcohols and peroxides) prevalent in the Earth's atmosphere. This review focuses on the fundamental energetic, mechanistic and dynamical aspects of unimolecular reactions of vibrationally excited atmospheric species. We will discuss the relevance of these red light initiated reactions to address the discrepancies between atmospheric measurements and results of standard atmospheric models.
Starik, A. M.; Sharipov, A. S.; Titova, N. S.
2010-06-01
A comparative analysis of the kinetic mechanisms that proceed in CO-O2 and syngas-air mixtures when CO molecule vibrations are excited by laser radiation with a wavelength of 4.7 µm and when the laser radiation energy supplied to the gas is spent on heating the mixture is conducted. The efficiencies of both methods of combustion initiation are compared. The simulation shows that the excitation of CO molecule vibrations by laser photons allows significant intensification of the chain processes both in CO-O2(air) and in syngas-air mixtures. This method is much more effective in shortening the induction time and in decreasing the ignition temperature than the method of laser-induced thermal ignition. It was found that in order to ensure the identical delay time it is necessary to add a noticeably higher energy in the case of heating the gas by laser radiation than when exciting the CO molecule vibrations. In addition, a low temperature ignition of the mixture with laser-excited CO molecules makes it possible to raise the efficiency of conversion of the reactant chemical energy to the thermal energy released during combustion compared with the method of heating the mixture by laser radiation.
Segerink, F.B.; Korterik, J.P.; Offerhaus, H.L.
2011-01-01
This article demonstrates a quick and easy way of quantifying the performance of a vibration-isolated platform. We measure the vibration transfer from floor to table using background noise excitation from the floor. As no excitation device is needed, our setup only requires two identical sensors (in
Selective excitation of adsorbate vibrations on dissipative surfaces
2008-01-01
The selective infrared (IR) excitation of molecular vibrations is a powerful tool to control the photoreactivity prior to electronic excitation in the ultraviolet / visible (UV/Vis) light regime ("vibrationally mediated chemistry"). For adsorbates on surfaces it has been theoretically predicted that IR preexcitation will lead to higher UV/Vis photodesorption yields and larger cross sections for other photoreactions. In a recent experiment, IR-mediated desorption of molecular hydrogen from a S...
Vibration energy harvesting from random force and motion excitations
Tang, Xiudong; Zuo, Lei
2012-07-01
A vibration energy harvester is typically composed of a spring-mass system with an electromagnetic or piezoelectric transducer connected in parallel with a spring. This configuration has been well studied and optimized for harmonic vibration sources. Recently, a dual-mass harvester, where two masses are connected in series by the energy transducer and a spring, has been proposed. The dual-mass vibration energy harvester is proved to be able to harvest more power and has a broader bandwidth than the single-mass configuration, when the parameters are optimized and the excitation is harmonic. In fact, some dual-mass vibration energy harvesters, such as regenerative vehicle suspensions and buildings with regenerative tuned mass dampers (TMDs), are subjected to random excitations. This paper is to investigate the dual-mass and single-mass vibration harvesters under random excitations using spectrum integration and the residue theorem. The output powers for these two types of vibration energy harvesters, when subjected to different random excitations, namely force, displacement, velocity and acceleration, are obtained analytically with closed-form expressions. It is also very interesting to find that the output power of the vibration energy harvesters under random excitations depends on only a few parameters in very simple and elegant forms. This paper also draws some important conclusions on regenerative vehicle suspensions and buildings with regenerative TMDs, which can be modeled as dual-mass vibration energy harvesters. It is found that, under white-noise random velocity excitation from road irregularity, the harvesting power from vehicle suspensions is proportional to the tire stiffness and road vertical excitation spectrum only. It is independent of the chassis mass, tire-wheel mass, suspension stiffness and damping coefficient. Under random wind force excitation, the power harvested from buildings with regenerative TMD will depends on the building mass only, not
Excited response of granular ores in vibrating field
无
2001-01-01
The dynamical theory was utilized to probe into the law of the excited response of granular ores generated by the exciting action of exciter and the influence of wave propagation in vibrating field. The exciter with double axes was presented as an example, and the principle of exciter and its mathematical expression of the excitation force were given. The granular ores have viscidity and damping speciality, on the basis of which the motion equation of excited response of ores was established and the approximate expression of mode-displacement by harmonic excitation and the steady effect solution of coordinate response were deduced. Utilizing the step-by-step integration method, the recursion relation matrix of displacement, velocity and acceleration of the excited response of ores were obtained, and the computational flow chart and a computational example were given. The results show that the excited response can change the dynamical character and the flowing characteristic of granular ores.
Reconstruction of Input Excitation Acting on Vibration Isolation System
Pan Zhou
2016-01-01
Full Text Available Vibration isolation systems are widely employed in automotive, marine, aerospace, and other engineering fields. Accurate input forces are of great significance for mechanical design, vibration prediction, and structure modification and optimization. One-stage vibration isolation system including engine, vibration isolators, and flexible supporting structure is modeled theoretically in this paper. Input excitation acting on the vibration isolation system is reconstructed using dynamic responses measured on engine and supporting structure under in-suit condition. The reconstructed forces reveal that dynamic responses on rigid body are likely to provide more accurate estimation results. Moreover, in order to improve the accuracy of excitation reconstructed by dynamic responses on flexible supporting structure, auto/cross-power spectral density function is utilized to reduce measurement noise.
Jans, E.; Frederickson, K.; Yurkovich, M.; Musci, B.; Rich, J. W.; Adamovich, I. V.
2016-08-01
A chemical flow reactor is used to study the vibrational population distribution of CO produced by a reaction between carbon vapor generated in an arc discharge and molecular oxygen. The results demonstrate formation of highly vibrationally excited CO, up to vibrational level v = 14, at low temperatures, T = 400-450 K, with population inversion at v = 4-7, in a collision-dominated environment, 15-20 Torr. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of reaction enthalpy. The results show feasibility of development of a new CO chemical laser using carbon vapor and oxygen as reactants.
H. Bayıroğlu
2012-01-01
Full Text Available Vibrational conveyers with a centrifugal vibration exciter transmit their load based on the jumping method. Common unbalanced-mass driver oscillates the trough. The motion is strictly related to the vibrational parameters. The transition over resonance of a vibratory system, excited by rotating unbalances, is important in terms of the maximum vibrational amplitude produced and the power demand on the drive for the crossover. The mechanical system is driven by the DC motor. In this study, the working ranges of oscillating shaking conveyers with nonideal vibration exciter have been analyzed analytically for superharmonic and subharmonic resonances by the method of multiple scales and numerically. The analytical results obtained in this study agree well with the numerical results.
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.
Modulating unimolecular charge transfer by exciting bridge vibrations.
Lin, Zhiwei; Lawrence, Candace M; Xiao, Dequan; Kireev, Victor V; Skourtis, Spiros S; Sessler, Jonathan L; Beratan, David N; Rubtsov, Igor V
2009-12-23
Ultrafast UV-vibrational spectroscopy was used to investigate how vibrational excitation of the bridge changes photoinduced electron transfer between donor (dimethylaniline) and acceptor (anthracene) moieties bridged by a guanosine-cytidine base pair (GC). The charge-separated (CS) state yield is found to be lowered by high-frequency bridge mode excitation. The effect is linked to a dynamic modulation of the donor-acceptor coupling interaction by weakening of H-bonding and/or by disruption of the bridging base-pair planarity.
Wang, Xi; Yang, Bintang; Yu, Hu; Gao, Yulong
2017-04-01
The impulse excitation of mechanism causes transient vibration. In order to achieve adaptive transient vibration control, a method which can exactly model the response need to be proposed. This paper presents an analytical model to obtain the response of the primary system attached with dynamic vibration absorber (DVA) under impulse excitation. The impulse excitation which can be divided into single-impulse excitation and multi-impulse excitation is simplified as sinusoidal wave to establish the analytical model. To decouple the differential governing equations, a transform matrix is applied to convert the response from the physical coordinate to model coordinate. Therefore, the analytical response in the physical coordinate can be obtained by inverse transformation. The numerical Runge-Kutta method and experimental tests have demonstrated the effectiveness of the analytical model proposed. The wavelet of the response indicates that the transient vibration consists of components with multiple frequencies, and it shows that the modeling results coincide with the experiments. The optimizing simulations based on genetic algorithm and experimental tests demonstrate that the transient vibration of the primary system can be decreased by changing the stiffness of the DVA. The results presented in this paper are the foundations for us to develop the adaptive transient vibration absorber in the future.
Spectroscopic probes of vibrationally excited molecules at chemically significant energies
Rizzo, T.R. [Univ. of Rochester, NY (United States)
1993-12-01
This project involves the application of multiple-resonance spectroscopic techniques for investigating energy transfer and dissociation dynamics of highly vibrationally excited molecules. Two major goals of this work are: (1) to provide information on potential energy surfaces of combustion related molecules at chemically significant energies, and (2) to test theoretical modes of unimolecular dissociation rates critically via quantum-state resolved measurements.
Coherent excitation of vibrational levels using ultra short pulses
De Clercq, LE
2009-07-01
Full Text Available The purpose of this study was to develop a model of the coherent excitation of the first few vibrational modes in the electronic ground state of the molecule. The model will be used in combination with an optimization algorithm to optimize a...
Vibrational motions in rotating nuclei studied by Coulomb excitations
Shimizu, Yoshifumi R. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics
1998-03-01
As is well-known Coulomb excitation is an excellent tool to study the nuclear collective motions. Especially the vibrational excitations in rotating nuclei, which are rather difficult to access by usual heavy-ion fusion reactions, can be investigated in detail. Combined with the famous 8{pi}-Spectrometer, which was one of the best {gamma}-ray detector and had discovered some of superdeformed bands, such Coulomb excitation experiments had been carried out at Chalk River laboratory just before it`s shutdown of physics division. In this meeting some of the experimental data are presented and compared with the results of theoretical investigations. (author)
Electron impact cross sections of vibrationally and electronically excited molecules
Yoon, Jung-Sik, E-mail: jsyoon@nfri.re.kr [Plasma Technology Research Center, National Fusion Research Institute, 814-2, Osikdo-Dong, Gunsan, Jeollabuk-Do, 573-540 (Korea, Republic of); Song, Mi-Young; Kwon, Deuk-Chul; Choi, Heechol [Plasma Technology Research Center, National Fusion Research Institute, 814-2, Osikdo-Dong, Gunsan, Jeollabuk-Do, 573-540 (Korea, Republic of); Kim, Chang-Geun [National Center for Standard Reference Data, Korea Research Institute of Standards and Science, Doryong-Dong, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); Kumar, Vijay [B-82, Aarohi Twin Bungalows, Near Govt. Tubewell, Bopal, Ahmedabad-380058 (India)
2014-10-30
It is well known that the electron impact cross sections for elastic and inelastic processes for the vibrationally and electronically excited molecules are predominantly different than those for molecules in the ground state. Collisions of low energy electrons with excited molecules play an important role in explaining the behavior of gas discharges in laser and plasma physics, in planetary atmospheres, stars, and interstellar medium and in plasmas widely used in the fabrication of microelectronics. This explains as to why there is a need for having validated sets of electron impact cross sections for different processes. This work reviews the subject of electron collisions with vibrationally and electronically excited molecules in a comprehensive way. The survey has been carried out for a few excited molecules such as H{sub 2}, D{sub 2}, T{sub 2}, HD, HT, DT, N{sub 2}, O{sub 2}, and CO{sub 2}. This review includes the discussion on the methods to produce and detect vibrationally and electronically excited molecules. We will take up the cross section data available in the literature for such molecules on electron scattering, dissociation, ionization and attachment processes and will discuss, evaluate and well-validate the same wherever and whenever possible.
Microwave spectroscopy of furfural in vibrationally excited states
Motiyenko, R. A.; Alekseev, E. A.; Dyubko, S. F.
2007-07-01
The results of microwave spectrum investigation of the excited vibrational states of furfural in the frequency range between 49 and 149 GHz are reported. In total 15 excited vibrational states (9 for trans-furfural and 6 for cis-furfural) were assigned and analyzed. Six of the 15 investigated states were assigned for the first time. Accurate values of rigid rotor and quartic centrifugal distortion constants of asymmetric top Hamiltonian have been determined for 13 excited states. Also for some states several sextic and octic level constants were needed in order to fit the data within experimental accuracy. The vt = 3 and vs = 1, va = 1 states of trans-furfural were found to be strongly perturbed and only rotational transitions with low Ka values can be reliably identified in this study.
Vibrationally Excited HCN in the Galactic Center Circumnuclear Disk
Mills, Elisabeth A.; Morris, M. R.; Güsten, R.
2012-05-01
Recent GREAT observations of CO in the Galactic center Circumnuclear Disk (CND) indicate that this structure is transitory, having gas densities on the order of 10^4 to 10^5 cm^-3, much less than those previously determined using high-density tracers such as HCN. We investigate this discrepancy with new HCN data from the APEX telescope in which we detect for the first time vibrationally-excited transitions of HCN in the CND. This suggests that the source of the disagreement in densities inferred from CO and HCN is the assumption that collisional excitation dominates the excitation of both molecules. We find that radiative excitation of HCN is an important contributor in the environment of the CND. We model the radiative excitation using observed rotational lines of HCN and H13CN from J=3-2 to J=8-7 in both the vibrational ground state and the v2=1 excited state. Our results suggest that ignoring radiative pumping from a strong infrared radiation field, such as in the Galactic center or actively star forming galaxies, can lead to overestimates of the density when using HCN and similar molecules.
Reference Excitation Unit for Micro-Vibration Test Facilities
Veal, Dan; Hughes, Ben; Wagner, Mark
2012-07-01
The verification of hardware, in particular with respect to micro-vibration requirements, is challenging for both numerical simulation and experimental methodology. A commonly used test approach is to measure the interface reaction forces, torques, accelerations, velocities or displacements in all six degrees of freedom generated by the unit under test. In Europe, several test facilities exist to measure these generated micro-vibration forces based on dynamometer, pendulum and reverse pendulum principles. All these facilities and test setups need to be validated and calibrated with traceability to recognized international standards to ensure validity of the measurement results. Ideally, inter-facility comparisons would be conducted with identical excitation input signals and identical boundary conditions to increase confidence in the validity of the measurement produced by different facilities. To facilitate this requirement, the National Physical Laboratory (NPL) - the UK’s national measurement institute, is developing a reference vibration excitation unit that will be capable of generating vibrations, linear or angular, of known amplitude and direction traceable to international standards. This activity is funded by the European Space Agency (ESA) in the frame of a Technology Research Study. This paper covers the design of the unit and how the vibrations generated will be traceable to international standards.
Storsional self-excited vibration of rolling mill
唐华平; 严珩志; 钟掘
2002-01-01
The roller's torsional self-excited vibration caused by roller stick-slip,and its influence on strip surface quality have been studied.Based on analysis of roller working surface stick-slip,roller rotation dynamics equations have been established.The nonlinear sliding-frictional resistance has been linearized,and dynamics equations have been solved according to the characteristics of stick and slip between roller and strip.The results show that: 1) with decreasing stick time t 1,torsional vibration wave pattern gradually transforms from serration into sinusoid,and frictional self-excited vibration can cover all frequency components which are lower than that of free vibration;2) stick time t 1 is directly proportional to torque increment Δ MR ,and is inversely proportional to live shaft stiffness K and drive shaft rotational velocity ω ;3) when slip time t 2 is basically steady,the longer the stick time,the larger the energy that system absorbs and discharges.As the slip time is a constant,it easily arouses strip surface shear impact and surface streaks.
Rotary bistable and Parametrically Excited Vibration Energy Harvesting
Kurmann, L.; Jia, Y.; Hoffmann, D.; Manoli, Y.; Woias, P.
2016-11-01
Parametric resonance is a type of nonlinear vibration phenomenon [1], [2] induced from the periodic modulation of at least one of the system parameters and has the potential to exhibit interesting higher order nonlinear behaviour [3]. Parametrically excited vibration energy harvesters have been previously shown to enhance both the power amplitude [4] and the frequency bandwidth [5] when compared to the conventional direct resonant approach. However, to practically activate the more profitable regions of parametric resonance, additional design mechanisms [6], [7] are required to overcome a critical initiation threshold amplitude. One route is to establish an autoparametric system where external direct excitation is internally coupled to parametric excitation [8]. For a coupled two degrees of freedom (DoF) oscillatory system, principal autoparametric resonance can be achieved when the natural frequency of the first DoF f1 is twice that of the second DoF f2 and the external excitation is in the vicinity of f1. This paper looks at combining rotary and translatory motion and use autoparametric resonance phenomena.
Synchronization of Two Asymmetric Exciters in a Vibrating System
Zhaohui Ren
2011-01-01
Full Text Available We investigate synchronization of two asymmetric exciters in a vibrating system. Using the modified average method of small parameters, we deduce the non-dimensional coupling differential equations of the two exciters (NDDETE. By using the condition of existence for the zero solutions of the NDDETE, the condition of implementing synchronization is deduced: the torque of frequency capture is equal to or greater than the difference in the output electromagnetic torque between the two motors. Using the Routh-Hurwitz criterion, we deduce the condition of stability of synchronization that the inertia coupling matrix of the two exciters is positive definite. A numeric result shows that the structural parameters can meet the need of synchronization stability.
Microscale capillary wave turbulence excited by high frequency vibration.
Blamey, Jeremy; Yeo, Leslie Y; Friend, James R
2013-03-19
Low frequency (O(10 Hz-10 kHz)) vibration excitation of capillary waves has been extensively studied for nearly two centuries. Such waves appear at the excitation frequency or at rational multiples of the excitation frequency through nonlinear coupling as a result of the finite displacement of the wave, most often at one-half the excitation frequency in so-called Faraday waves and twice this frequency in superharmonic waves. Less understood, however, are the dynamics of capillary waves driven by high-frequency vibration (>O(100 kHz)) and small interface length scales, an arrangement ideal for a broad variety of applications, from nebulizers for pulmonary drug delivery to complex nanoparticle synthesis. In the few studies conducted to date, a marked departure from the predictions of classical Faraday wave theory has been shown, with the appearance of broadband capillary wave generation from 100 Hz to the excitation frequency and beyond, without a clear explanation. We show that weak wave turbulence is the dominant mechanism in the behavior of the system, as evident from wave height frequency spectra that closely follow the Rayleigh-Jeans spectral response η ≈ ω(-17/12) as a consequence of a period-halving, weakly turbulent cascade that appears within a 1 mm water drop whether driven by thickness-mode or surface acoustic Rayleigh wave excitation. However, such a cascade is one-way, from low to high frequencies. The mechanism of exciting the cascade with high-frequency acoustic waves is an acoustic streaming-driven turbulent jet in the fluid bulk, driving the fundamental capillary wave resonance through the well-known coupling between bulk flow and surface waves. Unlike capillary waves, turbulent acoustic streaming can exhibit subharmonic cascades from high to low frequencies; here it appears from the excitation frequency all the way to the fundamental modes of the capillary wave at some four orders of magnitude in frequency less than the excitation frequency
Lee, J.-H.
1985-01-01
This paper examines the vibrational excitation rate processes expected in the flow field of aeroassisted orbital transfer vehicles (AOTVs). An analysis of the multiple-quantum vibrational excitation processes by electron impact is made to predict the vibrational excitation cross sections, rate coefficients, and relaxation times which control vibrational temperature. The expression for the rate of electron-vibration energy transfer is derived by solving the system of master equations which account for the multiple-level transitions. The vibrational excitation coefficients, which are the prerequisite physical quantities in solving the obtained vibrational equation, are calculated based on the theoretically predicted cross sections. These cross sections are obtained from quantum mechanical calculations, based on the concept that vibrational excitation of molecules by electron impact occurs through formation of an intermediate negative ion state. Finally, the modified Landau-Teller-type rate equation, which is suitable for the numerical calculations for the AOTV flow fields, is suggested.
Molecular Dynamics Simulation of Chain Folding for Polyethylene Subjected to Vibration Excitation
Junfeng Gu
2014-01-01
Full Text Available We propose a molecular dynamics method with vibration excitation, named as VEMD, to investigate the vibration effect on chain folding for polymer molecule. The VEMD method is based on the introduction of periodic force, the amplitude and frequency of which can be adjusted, and the method was applied to the folding simulation of a polyethylene chain. Simulation results show that the vibration excitation significantly affects the folding of the polyethylene, and frequency and amplitude of the vibration excitation play key roles in VEMD. Different frequencies and amplitudes will determine how and to what extent does the vibration excitation affect the folding process of the polyethylene structure.
Dissociative ionization of liquid water induced by vibrational overtone excitation
Natzle, W.C.
1983-03-01
Photochemistry of vibrationally activated ground electronic state liquid water to produce H/sup +/ and OH/sup -/ ions has been initiated by pulsed, single-photon excitation of overtone and combination transitions. Transient conductivity measurements were used to determine quantum yields as a function of photon energy, isotopic composition, and temperature. The equilibrium relaxation rate following perturbation by the vibrationally activated reaction was also measured as a function of temperature reaction and isotopic composition. In H/sub 2/O, the quantum yield at 283 +- 1 K varies from 2 x 10/sup -9/ to 4 x 10/sup -5/ for wave numbers between 7605 and 18140 cm/sup -1/. In D/sub 2/O, the dependence of quantum yield on wavelength has the same qualitative shape as for H/sub 2/O, but is shifted to lower quantum yields. The position of a minimum in the quantum yield versus hydrogen mole fraction curve is consistent with a lower quantum yield for excitation of HOD in D/sub 2/O than for excitation of D/sub 2/O. The ionic recombination distance of 5.8 +- 0.5 A is constant within experimental error with temperature in H/sub 2/O and with isotopic composition at 25 +- 1/sup 0/C.
Copan, Andreas V.; Wiens, Avery E.; Nowara, Ewa M.; Schaefer, Henry F.; Agarwal, Jay, E-mail: jagarwal@uga.edu [Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States)
2015-02-07
Peroxyacetyl radical [CH{sub 3}C(O)O{sub 2}] is among the most abundant peroxy radicals in the atmosphere and is involved in OH-radical recycling along with peroxyacetyl nitrate formation. Herein, the ground (X{sup ~}) and first (A{sup ~}) excited state surfaces of cis and trans peroxyacetyl radical are characterized using high-level ab initio methods. Geometries, anharmonic vibrational frequencies, and adiabatic excitation energies extrapolated to the complete basis-set limit are reported from computations with coupled-cluster theory. Excitation of the trans conformer is found to induce a symmetry-breaking conformational change due to second-order Jahn-Teller interactions with higher-lying excited states. Additional benchmark computations are provided to aid future theoretical work on peroxy radicals.
On the nature of highly vibrationally excited states of Thiophosgene
Keshavamurthy, Srihari
2011-01-01
In this work an analysis of the highly vibrationally excited states of thiophosgene (SCCl$_{2}$) is made in order to gain insights into some of the experimental observations and spectral features. The states analyzed herein lie in a spectrally complex region where strong mode mixings are expected due to the overlap of several strong anharmonic Fermi resonances. Two recent techniques, a semiclassical angle space representation of the eigenstates and the parametric variation of the eigenvalues (level-velocities) are used to identify eigenstate sequences exhibiting common localization characteristics. Preliminary results on the influence of highly excited out-of-plane bending modes on the nature of the eigenstates suggest a possible bifurcation in the system.
Detection of Vibrationally Excited CO in IRC+10216
Patel, Nimesh A; Brünken, Sandra; Menten, Karl M; Thaddeus, Patrick; Wilson, Robert W
2008-01-01
Using the Submillimeter Array we have detected the J=3-2 and 2-1 rotational transitions from within the first vibrationally excited state of CO toward the extreme carbon star IRC+10216 (CW Leo). The emission remains spatially unresolved with an angular resolution of ~2" and, given that the lines originate from energy levels that are ~3100 K above the ground state, almost certainly originates from a much smaller (~10^{14} cm) sized region close to the stellar photosphere. Thermal excitation of the lines requires a gas density of ~10^{9} cm^{-3}, about an order of magnitude higher than the expected gas density based previous infrared observations and models of the inner dust shell of IRC+10216.
On the nature of highly vibrationally excited states of thiophosgene
Srihari Keshavamurthy
2012-01-01
In this work an analysis of the highly vibrationally excited states of thiophosgene (SCCl2) is made in order to gain insights into some of the experimental observations and spectral features. The states analysed here lie in a spectrally complex region where strong mode mixings are expected due to the overlap of several strong anharmonic Fermi resonances. Two recent techniques, a semiclassical angle space representation of the eigenstates and the parametric variation of the eigenvalues (level-velocities) are used to identify eigenstate sequences exhibiting common localization characteristics. Preliminary results on the influence of highly excited out-of-plane bending modes on the nature of the eigenstates suggest a possible bifurcation in the system.
Low-energy electron attachment and detachment in vibrationally excited oxygen
Aleksandrov, N. L.; Anokhin, E. M.
2009-11-01
Three-body electron attachment to O2 molecules and electron detachment from O_{2}^{-} ions have been theoretically studied in vibrationally excited oxygen and O2-containing mixtures. Assuming that electron attachment and detachment proceed via the formation of vibrationally excited temporary O_{2}^{-} ions, the rates of these processes were determined on the basis of the statistical approach for the vibrational transfer and relaxation in collisions between O_{2}^{-} ions and O2 molecules. The calculated attachment and detachment rate constants turned out to agree well with available measurements in unexcited oxygen. This method was extended to calculate attachment and detachment rates in vibrationally excited oxygen. It was shown that the effect of vibrational excitation on electron detachment is profound, whereas attachment of low-energy electrons to vibrationally excited O2 is inefficient. The calculated vibrational distribution of stable O_{2}^{-} ions turned out to be non-equilibrium in an excited gas and the effective vibrational temperature of the ions was much lower than the vibrational temperature of molecules. An analytical method was suggested to determine this distribution and the effective vibrational temperature. The calculated rate constants were used to simulate the formation and decay of an electron-beam-generated plasma in N2 : O2 mixtures at elevated vibrational temperatures. The calculations showed that vibrational excitation of molecules leads to orders of magnitude increase in the plasma density and in the plasma lifetime, in agreement with available observations.
The Microwave Spectroscopy of Aminoacetonitrile in the Vibrational Excited State
Fujita, Chiho; Ozeki, Hiroyuki; Kobayashi, Kaori
2015-06-01
Aminoacetonitrile (NH_2CH_2CN) is a potential precursor of the simplest amino acid, glycine and was detected toward SgrB2(N). It is expected that the strongest transitions will be found in the terahertz region so that we have extended measurements up to 1.3 THz. This study gave an accurate prediction of aminoacetonitrile up to 2 THz which is useful for astronomically search. This molecule has a few low-lying vibrational excited states and the pure rotational transitions in these vibrational excited states are expected to found. We found a series of transitions with intensity of about 30%. Eighty-eight spectral lines including both a-type and b-type transitions were recorded in the frequency region of 400 - 450 GHz, and centrifugal distortion constants up to the sextic term were determined. Perturbation was recognized. We will report the current status of the analysis. A. Belloche, K. M. Menten, C. Comito, H. S. P. Müller, P. Schilke, J. Ott, S. Thorwirth, and C. Hieret, 2008, Astronom. & Astrophys. 482, 179 (2008). Y. Motoki, Y. Tsunoda, H. Ozeki, and K. Kobayashi, Astrophys. J. Suppl. Ser. 209, 23 (2013). B. Bak, E. L. Hansen, F. M. Nicolaisen, and O. F. Nielsen, Can. J. Phys. 53, 2183 (1975).
The Astrophysical Weeds: Rotational Transitions in Excited Vibrational States
Alonso, José L.; Kolesniková, Lucie; Alonso, Elena R.; Mata, Santiago
2017-06-01
The number of unidentified lines in the millimeter and submillimeter wave surveys of the interstellar medium has grown rapidly. The major contributions are due to rotational transitions in excited vibrational states of a relatively few molecules that are called the astrophysical weeds. necessary data to deal with spectral lines from astrophysical weeds species can be obtained from detailed laboratory rotational measurements in the microwave and millimeter wave region. A general procedure is being used at Valladolid combining different time and/or frequency domain spectroscopic tools of varying importance for providing the precise set of spectroscopic constants that could be used to search for this species in the ISM. This is illustrated in the present contribution through its application to several significant examples. Fortman, S. M., Medvedev, I. R., Neese, C.F., & De Lucia, F.C. 2010, ApJ,725, 1682 Rotational Spectra in 29 Vibrationally Excited States of Interstellar Aminoacetonitrile, L. Kolesniková, E. R. Alonso, S. Mata, and J. L. Alonso, The Astrophysical Journal Supplement Series 2017, (in press).
Dynamics of Vibration Machine with Air Flow Excitation and Restrictions on Phase Coordinates
Vība, J; Beresņevičs, V; Štāls, L; Eiduks, M; Kovals, E.; Kruusmaa, M.
2010-01-01
The objective of presented article is to show possibilities of practical use of air or liquid flow in vibration engineering. Dynamics of vibration machine with constant air or liquid flow excitation is considered. In the first part vibration motion of the machine working head under constant air or liquid flow velocity excitation is investigated. The main idea is to find out optimal control law for variation of additional surface area of vibrating object within limits. The criterion of optimiz...
THE ANALYSIS FOR THE AIRFLOW EXCITING-VIBRATION FORCE OF CONTROL STAGE OF STEAM TURBINE
柴山; 张耀明; 马浩; 曲庆文; 赵又群
2001-01-01
Based on the hydrodynamics, the airflow exciting-vibration force of control stage of steam turbine is studied by using the momentum theorem. A formulation for calculating the air exciting-vibration force of the control stage of steam turbine is deduced first by using theoretical analysis method and taking all the design factors of vane and nozzles into consideration. Moreover, the exciting-vibration forces in different load cases are discussed respectively.
2016-03-04
AFRL-AFOSR-VA-TR-2016-0124 Reduced Heat Flux Through Preferential Surface Reactions Leading to Vibrationally and Electronically Excited Product...Reactions Leading to Vibrationally and Electronically Excited Product States 5a. CONTRACT NUMBER FA9550-12-1-0486 5b. GRANT NUMBER 5c. PROGRAM... Leading to Vibrationally and Electronically Excited Product States FINAL TECHNICAL REPORT: Grant #FA9550-12-1-0486 2013 Basic Research Initiative (BRI
Tarana, Michal [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440 (United States); Houfek, Karel; Horacek, Jiri [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University in Prague, V Holesovickach 2, Prague (Czech Republic); Fabrikant, Ilya I. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
2011-11-15
We present a study of dissociative electron attachment and vibrational excitation processes in electron collisions with the CF{sub 3}Cl molecule. The calculations are based on the two-dimensional nuclear dynamics including the C-Cl symmetric stretch coordinate and the CF{sub 3} symmetric deformation (umbrella) coordinate. The complex potential energy surfaces are calculated using the ab initio R-matrix method. The results for dissociative attachment and vibrational excitation of the umbrella mode agree quite well with experiment whereas the cross section for excitation of the C-Cl symmetric stretch vibrations is about a factor-of-three too low in comparison with experimental data.
Laporta, V.; Chakrabarti, K.; Celiberto, R.; Janev, R. K.; Mezei, J. Zs; Niyonzima, S.; Tennyson, J.; Schneider, I. F.
2017-02-01
A theoretical study of resonant vibrational excitation, dissociative recombination and dissociative excitation processes of the beryllium monohydride cation, BeH+, induced by electron impact, is reported. Full sets of ro-vibrationally-resolved cross sections and of the corresponding Maxwellian rate coefficients are presented for the three processes. Particular emphasis is given to the high-energy behaviour. Potential curves of {}2{{{Σ }}}+, {}2{{\\Pi }} and {}2{{Δ }} symmetries and the corresponding resonance widths, obtained from R-matrix calculations, provide the input for calculations which use a local complex-potential model for resonant collisions in each of the three symmetries. Rotational motion of nuclei and isotopic effects are also discussed. The relevant results are compared with those obtained using a multichannel quantum defect theory method. Full results are available from the Phys4Entry database.
Self-excited vibrations in turning : Forces torsor analysis
Bisu, Claudiu-Florinel; K'Nevez, Jean-Yves; Laheurte, Raynald; Cahuc, Olivier; 10.1007/s00170-08-1850-5
2009-01-01
The present work deals with determining the necessary parameters considering a three dimensional model to simulate in a realistic way the turning process on machine tool. This paper is dedicated to the study of the self-excited vibrations incidence on various major mechanics characteristics of the system workpiece / tool / material. The efforts (forces and moments) measurement using a six components dynamometer confirms the tool tip moments existence. The fundamental frequency of 190 Hz proves to be common to the tool tip point displacements, the action application point or at the torque exerted to the tool tip point. The confrontation of the results concerning displacements and efforts shows that the applications points of these elements evolve according to similar ellipses located in quasi identical planes. The large and the small axes of these ellipses are increasing with the feed rate motion values accordingly to the mechanical power injected into the system. Conversely, the respective axes ratios of thes...
Rotational spectra of HCCCN in some excited vibrational states
Yamada, Koichi M. T.; Creswell, R. A.
1986-04-01
The rotational spectra have been measured up to 220 GHz for HCCCN in excited vibrational states up to about 1000 cm -1; the states of ( v4, v5, v6, v7) = (0, 0, 0, 1), (0, 0, 0, 2), (0, 0, 0, 3), (0, 0, 0, 4), (0, 0, 1, 0), (0, 0, 1, 1), (0, 0, 1, 2), (0, 0, 2, 0), (0, 1, 0, 0), (0, 1, 0, 1), (1, 0, 0, 0), and (1, 0, 0, 1). Accurate molecular constants have been determined using an effective Hamiltonian newly proposed by K. M. T. Yamada, F. W. Birss, and M. R. Aliev ( J. Mol. Spectrosc.112, 347-356 (1985). By analyzing the anharmonic resonances, the unperturbed rotational constants for the v4 = 1 and for the v5 = 1 states were obtained as 4537.958(15) and 4550.6218(35) MHz, respectively.
Quantum control of vibrational excitations in a heteronuclear diatomic molecule
Sitansh Sharma; Purshotam Sharma; Harjinder Singh
2007-09-01
Optimal control theory is applied to obtain infrared laser pulses for selective vibrational excitation in a heteronuclear diatomic molecule. The problem of finding the optimized field is phrased as a maximization of a cost functional which depends on the laser field. A time dependent Gaussian factor is introduced in the field prior to evaluation of the cost functional for better field shape. Conjugate gradient method21,24 is used for optimization of constructed cost functional. At each instant of time, the optimal electric field is calculated and used for the subsequent quantum dynamics, within the dipole approximation. The results are obtained using both Morse potential as well as potential energy obtained using ab initio calculations.
Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation
Jiang, Bin; Guo, Hua
2016-03-01
A fully coupled global nine-dimensional potential energy surface for the dissociative chemisorption of CO2 on Ni(100) is constructed from ˜18 000 density functional points. It reveals a complex reaction pathway dominated by two near iso-energetic transition states. The dissociation probabilities obtained by quasi-classical trajectories on the potential energy surface reproduced experimental trends, and indicate that vibrational excitations of CO2 significantly promote the dissociation. Using the sudden vector projection model, the behavior of the reactivity is rationalized by couplings with the reaction coordinate at each transition state. These results offer plausible rationalization for the observed enhancement of CO2 dissociation in non-thermal plasmas by metal surfaces.
Low energy vibrational excitations characteristic of superionic glass
Nakamura, M. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: nakamura.mitsutaka@jaea.go.jp; Iwase, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Arai, M. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kartini, E. [Industrial Material Division, R and D Center for Materials Science and Technology, BATAN, Serpong, Tangerang 15314 (Indonesia); Russina, M. [Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin (Germany); Yokoo, T. [Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba 305-0801 (Japan); Taylor, J.W. [Rutherford Appleton Laboratory, ISIS, Chilton Didcot, Oxon OX11 (United Kingdom)
2006-11-15
The mechanism of high ionic conductivity in superionic glass constitutes an unsolved problem in the field of science. Here we performed inelastic neutron scattering measurements of superionic glass system (AgI){sub x}(Ag{sub 2}S){sub x}(AgPO{sub 3}){sub 1-2x} by using MARI spectrometer at ISIS, and found that the Q-dependence of inelastic intensity in the energy region from 1 to 3meV of superionic phase glass shows an excess intensity above Q=1.8A{sup -1} compared with insulator phase. Similar phenomena were also observed in another superionic glass (AgI){sub 0.5}(AgPO{sub 3}){sub 0.5} by using NEAT spectrometer at HMI with high resolution measurement. These results clearly suggest peculiar low energy vibrational excitations should be universal features of superionic glass.
Experimental investigations on flow induced vibration of an externally excited flexible plate
Purohit, Ashish; Darpe, Ashish K.; Singh, S. P.
2016-06-01
Flow-induced vibration of a harmonically actuated flexible plate in the wake of an upstream bluff body is experimentally investigated. The experiments are performed in an open-ended wind tunnel. A flexible plate trailing a bluff body is under fluid induced excitation due to the flowing fluid. The additional external excitation to the trailing plate is applied using an electro-magnetic exciter. The frequency and amplitude of the external harmonic excitation are selected as variable parameters in the experiments and their effect on the plate vibration and is investigated. To know the nature of acoustic pressure wave generated from the vibrating system, near-field acoustic pressure is also measured. A laser vibrometer, a pressure microphone and a high-speed camera are employed to measure the plate vibration, pressure signal, and instantaneous images of the plate motion respectively. The results obtained indicate that the dynamics of the plate is influenced by both the flow-induced excitation and external harmonic excitation. When frequency of the two excitations is close enough, a large vibration level and a high tonal sound pressure are observed. At higher amplitude of external excitation, the frequency component corresponding to the flow-induced excitation is found to reduce significantly in the frequency spectrum of the vibration signal. It is observed that, for certain range of excitation frequency, the plate vibration first reduces, reaches a minimum value and then increases with increase in the level of external excitation. A fair qualitative agreement of the experimental results with numerical simulation result of the past study has been noted. In addition to the experiments, the role of phase difference between the flow-induced excitation generated from the front obstacle and externally applied harmonic excitation is investigated through numerical simulations. The result obtained reveals that the final steady state vibration of the coupled system is
The multilayer and wide-deck vibrating screen based on the innovative long-span vibration exciter
Zeng, Ming; Xu, Zonglin; Zhang, Jinnan; Zhang, Minghong
2017-09-01
The multilayer and wide-deck innovative single plasmid vibration screen is applicable to the petroleum drilling and the other relevant industries. The structural features and advantages of the components are illustrated, and the innovative long-span vibration exciter together with the steel rope saddle block flexible coupling is emphatically analyzed. Two engineering examples are provided to make the explanation.
Duque, H. V. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Do, T. P. T. [School of Education, Can Tho University, Campus II, 3/2 Street, Xuan Khanh, Ninh Kieu, Can Tho City (Viet Nam); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Konovalov, D. A.; White, R. D. [College of Science, Technology and Engineering, James Cook University, Townsville (Australia); Brunger, M. J., E-mail: michael.brunger@flinders.edu.au, E-mail: darryl.jones@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); Jones, D. B., E-mail: michael.brunger@flinders.edu.au, E-mail: darryl.jones@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia)
2015-03-28
In this paper, we report newly derived integral cross sections (ICSs) for electron impact vibrational excitation of tetrahydrofuran (THF) at intermediate impact energies. These cross sections extend the currently available data from 20 to 50 eV. Further, they indicate that the previously recommended THF ICS set [Garland et al., Phys. Rev. A 88, 062712 (2013)] underestimated the strength of the electron-impact vibrational excitation processes. Thus, that recommended vibrational cross section set is revised to address those deficiencies. Electron swarm transport properties were calculated with the amended vibrational cross section set, to quantify the role of electron-driven vibrational excitation in describing the macroscopic swarm phenomena. Here, significant differences of up to 17% in the transport coefficients were observed between the calculations performed using the original and revised cross section sets for vibrational excitation.
孙卫国; Michael; A.Morrison
1999-01-01
The vibrational excitation differential cross sections （DCS） of low-energy electron-N2 scattering are studied using vibrational close-coupling （VCC） scattering method and quantum scattering potentials which include static, exchange, and polarization contributions based on ab initio calculations. By including the contributions of 11 partial waves （up to l=21）, 15 vibrational states, and 16 molecular symmetries （up to Λ=7）, the converged vibrational excitation （0→2, 0→3, 0→4） DCSs, the scattering resonance, and the vibrational multi-peak structure agree well with experimental results.
Low-energy electron attachment and detachment in vibrationally excited oxygen
Aleksandrov, N L; Anokhin, E M, E-mail: nick_aleksandrov@mail.r, E-mail: nick_aleksandrov@hotmail.co [Moscow Institute of Physics and Technology, Dolgoprudny, 141700 (Russian Federation)
2009-11-21
Three-body electron attachment to O{sub 2} molecules and electron detachment from O{sub 2}{sup -} ions have been theoretically studied in vibrationally excited oxygen and O{sub 2}-containing mixtures. Assuming that electron attachment and detachment proceed via the formation of vibrationally excited temporary O{sub 2}{sup -} ions, the rates of these processes were determined on the basis of the statistical approach for the vibrational transfer and relaxation in collisions between O{sub 2}{sup -} ions and O{sub 2} molecules. The calculated attachment and detachment rate constants turned out to agree well with available measurements in unexcited oxygen. This method was extended to calculate attachment and detachment rates in vibrationally excited oxygen. It was shown that the effect of vibrational excitation on electron detachment is profound, whereas attachment of low-energy electrons to vibrationally excited O{sub 2} is inefficient. The calculated vibrational distribution of stable O{sub 2}{sup -} ions turned out to be non-equilibrium in an excited gas and the effective vibrational temperature of the ions was much lower than the vibrational temperature of molecules. An analytical method was suggested to determine this distribution and the effective vibrational temperature. The calculated rate constants were used to simulate the formation and decay of an electron-beam-generated plasma in N{sub 2} : O{sub 2} mixtures at elevated vibrational temperatures. The calculations showed that vibrational excitation of molecules leads to orders of magnitude increase in the plasma density and in the plasma lifetime, in agreement with available observations.
Two-photon vibrational excitation of air by long-wave infrared laser pulses
Palastro, J P; Johnson, L A; Hafizi, B; Wahlstrand, J K; Milchberg, H M
2016-01-01
Ultrashort long-wave infrared (LWIR) laser pulses can resonantly excite vibrations in N2 and O2 through a two-photon transition. The absorptive, vibrational component of the ultrafast optical nonlinearity grows in time, starting smaller than, but quickly surpassing, the electronic, rotational, and vibrational refractive components. The growth of the vibrational component results in a novel mechanism of 3rd harmonic generation, providing an additional two-photon excitation channel, fundamental + 3rd harmonic. The original and emergent two-photon excitations drive the resonance exactly out of phase, causing spatial decay of the absorptive, vibrational nonlinearity. This nearly eliminates two-photon vibrational absorption. Here we present simulations and analytical calculations demonstrating how these processes modify the ultrafast optical nonlinearity in air. The results reveal nonlinear optical phenomena unique to the LWIR regime of ultrashort pulse propagation in atmosphere.
Resonant vibrational excitation of ethylene molecules in laser-assisted diamond deposition
Fan, L. S.; Zhou, Y. S.; Wang, M. X.; Gao, Y.; Liu, L.; Silvain, J. F.; Lu, Y. F.
2014-07-01
The influence of resonant vibrational excitation of ethylene molecules in combustion chemical vapor deposition of diamond was investigated. Resonant vibrational excitation of the CH2-wagging mode (a type c fundamental band, υ7, at 949.3 cm-1) in ethylene molecules was achieved by using a wavelength-tunable CO2 laser with a matching wavelength at 10.532 µm. By comparing to laser irradiation at off-resonance wavelengths, an on-resonance vibrational excitation is more efficient in energy coupling, increasing flame temperatures, accelerating the combustion reactions, and promoting diamond deposition. An enhanced rate of 5.7 was achieved in terms of the diamond growth rate with an improved diamond quality index at a high flame temperature under a resonant excitation of the CH2-wagging mode. This study demonstrates that a resonant vibrational excitation is an effective route for coupling energy into the gas phase reactions and promoting the diamond synthesis process.
Amplitude control of the track-induced self-excited vibration for a maglev system.
Zhou, Danfeng; Li, Jie; Zhang, Kun
2014-09-01
The Electromagnet Suspension (EMS) maglev train uses controlled electromagnetic forces to achieve suspension, and self-excited vibration may occur due to the flexibility of the track. In this article, the harmonic balance method is applied to investigate the amplitude of the self-excited vibration, and it is found that the amplitude of the vibration depends on the voltage of the power supplier. Based on this observation, a vibration amplitude control method, which controls the amplitude of the vibration by adjusting the voltage of the power supplier, is proposed to attenuate the vibration. A PI controller is designed to control the amplitude of the vibration at a given level. The effectiveness of this method shows a good prospect for its application to commercial maglev systems.
Airflow energy harvesters of metal-based PZT thin films by self-excited vibration
Suwa, E.; Tsujiura, Y.; Kurokawa, F.; Hida, H.; Kanno, I.
2014-11-01
We developed self-excited vibration energy harvesters of Pb(Zr,Ti)O3 (PZT) thin films using airflow. To enhance the self-excited vibration, we used 30-μm-thick stainless steel (SS304) foils as base cantilevers on which PZT thin films were deposited by rf-magnetron sputtering. To compensate for the initial bending of PZT/SS304 unimorph cantilever due to the thermal stress, we deposited counter PZT thin films on the back of the SS304 cantilever. We evaluated power-generation performance and vibration mode of the energy harvester in the airflow. When the angle of attack (AOA) was 20° to 30°, large vibration was generated at wind speeds over 8 m/s. By FFT analysis, we confirmed that stable self-excited vibration was generated. At the AOA of 30°, the output power reached 19 μW at wind speeds of 12 m/s.
Off-resonant vibrational excitation: Orientational dependence and spatial control of photofragments
Machholm, Mette; Henriksen, Niels Engholm
2000-01-01
-dependent response to the IR fields is due to the anharmonicity of the potential. A subsequent ultraviolet laser pulse in resonance at the outer turning point of the vibrational motion can then dissociate the oscillating molecules, all with the same orientation, leading to spatial control of the photofragment......Off-resonant and resonant vibrational excitation with short intense infrared (IR) laser pulses creates localized oscillating wave packets, but differs by the efficiency of the excitation and surprisingly by the orientational dependence. Orientational selectivity of the vibrational excitation...... of randomly oriented heteronuclear diatomic molecules can be obtained under simultaneous irradiation by a resonant and an off-resonant intense IR laser pulse: Molecules with one initial orientation will be vibrationally excited, while those with the opposite orientation will be at rest. The orientation...
Kobayashi, K.; Sakai, Y.; Sasaki, M.; Kakimoto, S.; Takano, S.
2013-10-01
The spectral lines of methyl formate in the second torsional excited state were identified in Orion KL for the first time as well as the ground and the first torsional excited state. This identification was made it possible by the recent laboratory microwave spectroscopic study. It was found that the vibrational temperature is twice as large as the rotational temperature. The difference may be attributed to the collision with H2 and/or far infrared pumping.
Lan, C. B.; Qin, W. Y. [Department of Engineering Mechanics, Northwestern Polytechnical University, Xi' an 710072 (China)
2014-09-15
This letter investigates the energy harvesting from the horizontal coherent resonance of a vertical cantilever beam subjected to the vertical base excitation. The potential energy of the system has two symmetric potential wells. So, under vertical excitation, the system can jump between two potential wells, which will lead to the large vibration in horizontal direction. Two piezoelectric patches are pasted to harvest the energy. From experiment, it is found that the vertical excitation can make the beam turn to be bistable. The system can transform vertical vibration into horizontal vibration of low frequency when excited by harmonic motion. The horizontal coherence resonance can be observed when excited by a vertical white noise. The corresponding output voltages of piezoelectric films reach high values.
Vibration-assisted resonance in photosynthetic excitation energy transfer
Irish, E K; Lovett, B W
2013-01-01
Coherent quantum energy transfer, as observed in photosynthetic pigment-protein complexes, is inhibited by energetic disorder. While this difficulty can be overcome to some extent by the addition of environmental noise, it has recently has begun to be appreciated that discrete intra- and/or intermolecular vibrational modes may play an important role in quantum dynamics. We present a microscopic mechanism by which intramolecular vibrational modes create resonant energy transfer pathways, enhancing the efficiency of both coherent and dephasing-assisted transfer. The principles of this vibration-assisted resonance are illustrated in a simple model based on one energy-transfer branch of the well-characterised Fenna-Matthews-Olson complex. Despite its simplicity, this model captures the interplay between strong electronic coupling that produces delocalised exciton states and resonance-enhanced weak coupling to local vibrational modes. Analytical and numerical results show that intramolecular vibrations can enhance...
Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule
Laporta, V; Celiberto, R
2016-01-01
Vibrational-excitation cross sections of ground electronic state of carbon dioxide molecule by electron-impact through the CO2-(2\\Pi) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume decoupling between normal modes and employ the local complex potential model for the treatment of the nuclear dynamics, usually adopted for the electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and comparison with data present in the literature is discussed.
Current Density Distribution on the Perimeter of Waveguide Exciter Cylindrical Vibrator Conductor
Zakharia, Yosyp
2010-01-01
On ground of electrodynamic analysis the surface current distribution nonuniformity on the perimeter of waveguide-exciter cylindrical conductor is found. Considerable influence of current distribution nonuniformity on exciter input reactance is established. It is also showed, that the current distribution on the vibrator perimeter, for conductor radius no greater then 0,07 of waveguide cross section breadth, approximately uniform is.
Vibrational excitation in O2and Cl2inductively-coupled plasmas and DC discharges
Booth, Jean-Paul; Marinov, Daniil; Foucher, Mickael; Annusova, Adriana; Guerra, Vasco
2016-09-01
Low-energy electrons can interact with molecules via resonances to cause vibrational excitation with large cross-sections. Such processes can absorb significant energy from the plasma electrons, affecting the electron energy distribution and potentially (via vibration-translation (VT) energy transfer) causing substantial gas heating. The presence of vibrationally excited molecules may significant increase the rates of collisional processes, including electron dissociative attachment and electron impact dissociation into neutral atoms. However, the cross-sections of these processes are often poorly known since they are extremely difficult to measure directly, and reliable theoretical calculations are only now appearing for simple diatomic molecules. We have measured the vibrational distributions in discharges in pure O2 and pure Cl2, using high-sensitivity ultra-broadband ultraviolet absorption spectroscopy. In O2 plasmas significant vibrational excitation is observed, up to v'' =18, with a tail temperature of around 8000K. In Cl2 excitation is only observed up to v'' =3, and the distribution appears to be in local equilibrium with the gas translational temperature (up to 1500K). We are developing a detailed self-consistent 0D global model of these systems including vibrational excitation. Work performed in the LABEX Plas@par project, with financial state aid (ANR-11-IDEX-0004-02 and ANR-13-BS09-0019).
Saturation influence of control voltage on maglev stationary self-excited vibration
李金辉; 李杰; 余佩
2016-01-01
This work addresses the saturation influence of control voltage on the occurring of self-excited vibration of maglev vehicle-bridge interaction system, which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, the interaction model of vehicle-bridge system is developed. Based on the interaction model, the relationship between the control voltage and vibration frequency is solved. Then, the variation of the effective direct component and fundamental harmonic are discussed. Furthermore, from the perspective of energy transmission between the levitation system and bridge, the principle underlying the self-excited vibration is explored, and the influence on the stability is discussed. Finally, in terms of the variation of the characteristic roots, the influence is analyzed further and some conclusions are obtained. This study provides a theoretical guidance for mastering the self-excited vibration problems.
Capitelli, Mario [Dipartimento di Chimica, Universitá di Bari, Via Orabona 4, 70125 Bari (Italy); CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Colonna, Gianpiero; D' Ammando, Giuliano; Laricchiuta, Annarita [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Laporta, Vincenzo [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)
2013-10-15
Electron energy distribution functions have been calculated by a self-consistent model which couples the electron Boltzmann equation with vibrationally and electronically excited state kinetics and plasma chemistry. Moderate pressure nitrogen gas discharges in the E/N range from 30 to 60 Townsend are investigated comparing an electron-impact cross section set considering transitions starting from all the vibrational states, with reduced models, taking into account only collisions involving the ground vibrational level. The results, while confirming the important role of second kind collisions in affecting the eedf, show a large dependence of the eedf on the set of inelastic processes involving vibrationally and electronically excited molecules, pointing out the need of using a cross section database including processes linking excited states in non-equilibrium plasma discharge models.
Production of vibrationally excited hydrogen molecules by atom recombination on Cu and W materials.
Markelj, Sabina; Čadež, Iztok
2011-03-28
We have measured vibrational population of H(2) and D(2) molecules produced by atom (H or D) recombination on tungsten and copper material. The vibrational spectroscopy, based on the properties of dissociative electron attachment to hydrogen molecule, was used. The vibrationally excited molecules were produced by atom recombination in a cell where the studied sample is exposed to hydrogen atoms, from hot tungsten filament. Vibrational populations were obtained for the studied materials, which can be well described by the Boltzmann distribution, with specific vibrational temperatures for each material. The experimentally obtained vibrational populations for copper approximately agree with the theoretical predictions, whereas the experimentally obtained vibrational temperature for tungsten is higher and thus showing a considerable overpopulation of highly excited vibrational states than predicted. We propose that the origin of this higher excitation is related to the existence of high hydrogen surface coverage on tungsten, where hydrogen is occupying binding sites with different desorption energies. In order to obtain an insight into the recombination mechanism with more than one binding site per unit cell, a Monte Carlo simulation was performed, where it was assumed that the main production of molecules proceeds through the hot-atom recombination with an adsorbed atom. The results show that the recombination proceeds mainly through the weak binding sites, once they are occupied.
Slow Intramolecular Vibrational Relaxation Leads to Long-Lived Excited-State Wavepackets.
Rafiq, Shahnawaz; Scholes, Gregory D
2016-09-01
Broadband optical pump and compressed white light continuum probe were used to measure the transient excited-state absorption, ground-state bleach, and stimulated emission signals of cresyl violet solution in methanol. Amplitude oscillations caused by wavepacket motion in the ground and excited electronic states were analyzed. It was found that vibrational coherences in the excited state persist for more than the experimental waiting time window of 6 ps, and the strongest mode had a dephasing time constant of 2.4 ps. We hypothesize the dephasing of the wavepacket in the excited state is predominantly caused by intramolecular vibrational relaxation (IVR). Slow IVR indicates weak mode-mode coupling and therefore weak anharmonicity of the potential of this vibration. Thus, the initially prepared vibrational wavepacket in the excited state is not significantly perturbed by nonadiabatic coupling to other electronic states, and hence the diabatic and adiabatic representations of the system are essentially identical within the Born-Oppenheimer approximation. The wavepacket therefore evolves with time in an almost harmonic potential, slowly dephased by IVR and the pure vibrational decoherence. The consistency in the position of node (phase change in the wavepacket) in the excited-state absorption and stimulated emission signals without undergoing any frequency shift until the wavepacket is completely dephased conforms to the absence of any reactive internal conversion.
A symmetry adapted approach to vibrational excitations in atomic clusters
Frank, A I; Bijker, R; Lemus, R; Pérez-Bernal, F
1998-01-01
An algebraic method especially suited to describe strongly anharmonic vibrational spectra in molecules may be an appropriate framework to study vibrational spectra of Na$^+_n$ clusters, where nearly flat potential energy surfaces and the appearance of close lying isomers have been reported. As an illustration we describe the model and apply it to the Be$_4$, H$_3^+$, Be$_3$ and Na$_3^+$ clusters.
Vibrations of a delivery car excited by railway track crossing
Litak, Grzegorz [Department of Applied Mechanics, Lublin University of Technology, Nadbystrzycka 36, PL-20-618 Lublin (Poland); Dipartimento di Architettura, Costruzioni e Strutture, Universita Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona (Italy)], E-mail: g.litak@pollub.pl; Borowiec, Marek [Department of Applied Mechanics, Lublin University of Technology, Nadbystrzycka 36, PL-20-618 Lublin (Poland); Hunicz, Jacek; Koszalka, Grzegorz; Niewczas, Andrzej [Department of Combustion Engines and Transport, Lublin University of Technology, Nadbystrzycka 36, PL-20-618 Lublin (Poland)
2009-10-15
Vertical vibrations of a delivery car passing through railway tracks have been investigated in this paper. The application of recurrence plots allows to examine short time series of acceleration non-stationary courses. Recurrence quantification analysis and square deviations estimated in small windows have been used to monitor car vibrations and transient behaviour. Measuring acceleration on the 'sprung' and 'unsprung' masses of a vehicle has enabled also to test the quality of a car suspension.
Huo Rui; Shi Yin
2005-01-01
In view of difficulties concerned with direct measurement of excitations inside source equipments and their significant influence on vibration isolation effectiveness, a dynamical model, for vibration isolation of a rigid machine with six-degree-of-freedom mounted on a flexible foundation through multiple mounts, is analyzed, in which the complicated and multiple disturbances inside the machine are described as an equivalent excitation spectrum. And a method for the estimation of the equivalent excitation spectrum according to system dynamic responses is discussed for the quantitative prediction of isolation effectiveness.Both theoretical analysis and experimental results are demonstrated. Further work shows the quantitative prediction of transmitted power flow in a flexible vibration isolation experiment system using the proposed equivalent excitation spectrum method, by comparison with its testing results.
Arghya Nandi; Sumanta Neogy; Sankha Bhaduri
2011-02-01
This work presents performance analysis of a Lorentz force based noncontact vibration exciter by mounting a couple of permanent magnets on a piezoelectric stack. A conductor is attached to the structure to be excited and is placed midway between unlike poles of a couple of permanent magnets. The permanent magnets are placed on a piezoelectric stack. This stack, because of its nano-positioning capabilities, can impart an accurate and adjustable harmonic vibratory motion to the couple of permanent magnets. The piezoelectric stack, because of its high stiffness remains uncoupled with the dynamics of the structure. Due to the relative motion between the magnets and the conductor, Lorentz force is generated within the conductor. This Lorentz force is responsible for vibration of the structure in a plane parallel to the pole faces of the magnets. This keeps the magnetic field almost independent of the vibration of the structure and the chance of the structure hitting the magnet during large vibration is totally eliminated. If the amplitude of displacement of the stack is kept constant, the non-contact excitation force in this exciter remains proportional to the excitation frequency. Though use of this exciter eliminates mass (apart from that of the conductor attached to the structure) and stiffness coupling, a known damping term gets added to that of the excited structure.
Roles of the Excitation in Harvesting Energy from Vibrations.
Zhang, Hui; Ma, Tianwei
2015-01-01
The study investigated the role of excitation in energy harvesting applications. While the energy ultimately comes from the excitation, it was shown that the excitation may not always behave as a source. When the device characteristics do not perfectly match the excitation, the excitation alternately behaves as a source and a sink. The extent to which the excitation behaves as a sink determines the energy harvesting efficiency. Such contradictory roles were shown to be dictated by a generalized phase defined as the instantaneous phase angle between the velocity of the device and the excitation. An inductive prototype device with a diamagnetically levitated seismic mass was proposed to take advantage of the well established phase changing mechanism of vibro-impact to achieve a broader device bandwidth. Results suggest that the vibro-impact can generate an instantaneous, significant phase shift in response velocity that switches the role of the excitation. If introduced properly outside the resonance zone it could dramatically increase the energy harvesting efficiency.
Roles of the Excitation in Harvesting Energy from Vibrations.
Hui Zhang
Full Text Available The study investigated the role of excitation in energy harvesting applications. While the energy ultimately comes from the excitation, it was shown that the excitation may not always behave as a source. When the device characteristics do not perfectly match the excitation, the excitation alternately behaves as a source and a sink. The extent to which the excitation behaves as a sink determines the energy harvesting efficiency. Such contradictory roles were shown to be dictated by a generalized phase defined as the instantaneous phase angle between the velocity of the device and the excitation. An inductive prototype device with a diamagnetically levitated seismic mass was proposed to take advantage of the well established phase changing mechanism of vibro-impact to achieve a broader device bandwidth. Results suggest that the vibro-impact can generate an instantaneous, significant phase shift in response velocity that switches the role of the excitation. If introduced properly outside the resonance zone it could dramatically increase the energy harvesting efficiency.
Jans, Elijah R.; Eckert, Zakari; Frederickson, Kraig; Rich, Bill; Adamovich, Igor V.
2017-06-01
Measurements of the vibrational distribution function of carbon monoxide produced via a reaction between carbon vapor and molecular oxygen has shown a total population inversion on vibrational levels 4-7. Carbon vapor, produced using an arc discharge to sublimate graphite, is mixed with an argon oxygen flow. The excited carbon monoxide is vibrationally populated up to level v=14, at low temperatures, T=400-450 K, in a collision-dominated environment, 15-20 Torr, with total population inversions between v=4-7. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of the reaction enthalpy. Kinetic modeling of the flow reactor, including state specific vibrational processes, was performed to infer the vibrational distribution of the products of the reaction. The results show viability of developing of a new chemical CO laser from the reaction of carbon vapor and oxygen.
Godtliebsen, Ian H; Christiansen, Ove
2015-10-07
It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde.
Manipulation of molecular vibrational motions via pure rotational excitations
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
The coupling between different molecular degrees of freedom plays a decisive role in many quantum phenomena, including electron transfer and energy redistribution. Here, we demonstrate a quantum-mechanical time-dependent simulation to explore how a vibrational motion in a molecule can be affected...
HUANG Xiao-Jiang; XIN Yu; ZHANG Jie; NING Zhao-Yuan
2009-01-01
By using optical emission spectroscopy (OES), N2 and N+2 vibrational temperatures in capacitively coupled plasma discharges with different exciting frequencies are investigated. The vibrational temperatures are acquired by comparing the measured and calculated spectra of selected transitions with a least-square procedure. It is found that 512 and N+2 vibrational temperatures almost increase linearly with increasing exciting frequency up to 23 MHz, then increase slowly or even decrease. The pressure corresponding to the maximum point of N2 vibrational temperature decreases with the increasing exciting frequency. These experimental phenomena are attributed to the increasing electron density, whereas the electron temperature decreases with exciting frequency rising.
Vacuum-Induced Coherence in Ultracold Photoassociative Ro-Vibrational Excitations
Das, Sumanta; Deb, Bimalendu
2011-01-01
We show that coherence between two excited ro-vibrational states belonging to the same molecular electronic configuration arises quite naturally due to their interaction with electromagnetic vacuum. For initial preparation of a molecule in the desired ro-vibrational states, we propose to employ the method of ultracold photoassociation. Spontaneous decay of the excited molecule then gives rise to vacuum induced coherence between the excited ro-vibrational states. We demonstrate theoretically an interesting interplay of effects due to vacuum induced coherence and photoassociation. We apply our theory to photoassociation of bosonic Ytterbium (^{174}Yb) atoms which appear to be a promising system for exploring such interplay. The effects discussed here can be important for controlling decoherence and dissipation in molecular systems.
The Analysis of Vibration Due to Magnetic Exciting Force in the Brushless DC Motor
Han, Ki Jin [LG Innotek (Korea); Cho, Han Sam; Jung, Hyun Kyo [Seoul National University, Seoul (Korea)
2001-01-01
In this paper, the general research on the analysis of the vibration due to magnetic exciting force in the small brushless DC(BLDC) motor, which is used in the Digital Versatile Disk(DVD) ROM driving system, is performed. The first part of the study is the analysis of the magnetic exciting force in the air gap region. As a verification of the exciting force by numerical analysis, the magnetic exciting force distribution in the airgap region is computed by using Reluctance Network Method(RNM). In addition, thr effect of the eccentricity on the magnetic exciting force is discussed. The other part of the research is the structural analysis if the rotor structure of thr BLDC motor. The natural mode analysis of thr rotor structure is performed, and the vibration response due to magnetic exciting force is found. As a result of the procedures, the basic estimation of the effect of the magnetic exciting force on the vibration of BLDC motor is suggested. (author). 14 refs., 10 figs., 1 tab.
Study on Dynamics of Polygonal Wear of Automotive Tire Caused by Self-Excited Vibration
Shuguang Zuo
2014-01-01
Full Text Available Considering the underlying reason of tire polygonal wear, a unified mechanical tire model is developed to analyze the different vibration properties between the driving wheel and follower wheel. And the LuGre dynamic friction model is applied to determine the frictional forces between the wheel with a slip angel and the road. Through the stability analysis with Lyapunov theory, it is found that tread self-excited vibration is periodic oscillation caused by Hopf bifurcation. The analysis of the lateral vibration of driving wheel shows that the tread vibration system loses its stability and self-excited vibration occurs when the wheel is rolling at a high speed, is over-loaded, is having a large toe-in angle, or is under a low tire pressure. On this basis, the dynamic behaviors of the driving and follower wheels are distinguished with different slip rates by the numerical simulation. Compared with the dynamic behaviors of the follower wheel under the same condition, the self-excited vibration occurs on the driving wheel with more limited parameter scope, lower oscillation energy, and lower occurrence, which explains why the polygonal wear is less likely to occur on the driving wheel.
The Nonlinear Behavior of Vibrational Conveyers with Single-Mass Crank-and-Rod Exciters
G. Füsun Alışverişçi
2012-01-01
Full Text Available The single-mass, crank-and-rod exciters vibrational conveyers have a trough supported on elastic stands which are rigidly fastened to the trough and a supporting frame. The trough is oscillated by a common crank drive. This vibration causes the load to move forward and upward. The moving loads jump periodically and move forward with relatively small vibration. The movement is strictly related to vibrational parameters. This is applicable in laboratory conditions in the industry which accommodate a few grams of loads, up to those that accommodate tons of loading capacity. In this study I explore the transitional behavior across resonance, during the starting of a single degree of freedom vibratory system excited by crank-and-rod. A loaded vibratory conveyor is more safe to start than an empty one. Vibrational conveyers with cubic nonlinear spring and ideal vibration exciter have been analyzed analytically for primary and secondary resonance by the Method of Multiple Scales, and numerically. The approximate analytical results obtained in this study have been compared with the numerical results and have been found to be well matched.
Vibrationally excited CS: A new probe of conditions in young protostellar systems
Walker, Christopher K.; Maloney, Philip R.; Serabyn, E.
1994-01-01
We present the first detection of vibrationally excited C(32)S J = 10-9 and J = 7-6 emission toward a young stellar object (YSO). Toward IRAS 16293-2422, the vibrationally excited C(32)S emission is redshifted approximately 3.9 km/s from the systemic velocity of the core. The emission must arise in warm (T greater than or approximately equal 1000 K), dense (n greater than or approximately equal to 10(exp 11)-10(exp 12) per cc) gas. The most plausible origin for the emission appears to be self-gravitating instabilities in a protostellar accretion disk, which produce waves and shocks.
Do, T. P. T. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); School of Education, Can Tho University, Campus II, 3/2 Street, Xuan Khanh, Ninh Kieu, Can Tho City (Viet Nam); Duque, H. V. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Konovalov, D. A.; White, R. D. [College of Science, Technology and Engineering, James Cook University, Townsville (Australia); Brunger, M. J., E-mail: michael.brunger@flinders.edu.au, E-mail: darryl.jones@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); Jones, D. B., E-mail: michael.brunger@flinders.edu.au, E-mail: darryl.jones@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia)
2015-03-28
We report differential cross sections (DCSs) for electron-impact vibrational-excitation of tetrahydrofuran, at intermediate incident electron energies (15-50 eV) and over the 10°-90° scattered electron angular range. These measurements extend the available DCS data for vibrational excitation for this species, which have previously been obtained at lower incident electron energies (≤20 eV). Where possible, our data are compared to the earlier measurements in the overlapping energy ranges. Here, quite good agreement was generally observed where the measurements overlapped.
Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation
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.
Chu, P.M.Y.
1991-10-01
The vibrational to translational (V{yields}T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V{yields}T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH{sub 3} production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.
Chu, Pamela Mei-Ying [Univ. of California, Berkeley, CA (United States)
1991-10-01
The vibrational to translational (V→T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V→T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH_{3} production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.
Exploring the vibrational fingerprint of the electronic excitation energy via molecular dynamics
Deyne, Andy Van Yperen-De; Pauwels, Ewald; Ghysels, An; Waroquier, Michel; Van Speybroeck, Veronique; Hemelsoet, Karen, E-mail: karen.hemelsoet@ugent.be [Center for Molecular Modeling (CMM), Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium); De Meyer, Thierry [Center for Molecular Modeling (CMM), Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium); Department of Textiles, Ghent University, Technologiepark 907, 9052 Zwijnaarde (Belgium); De Clerck, Karen [Department of Textiles, Ghent University, Technologiepark 907, 9052 Zwijnaarde (Belgium)
2014-04-07
A Fourier-based method is presented to relate changes of the molecular structure during a molecular dynamics simulation with fluctuations in the electronic excitation energy. The method implies sampling of the ground state potential energy surface. Subsequently, the power spectrum of the velocities is compared with the power spectrum of the excitation energy computed using time-dependent density functional theory. Peaks in both spectra are compared, and motions exhibiting a linear or quadratic behavior can be distinguished. The quadratically active motions are mainly responsible for the changes in the excitation energy and hence cause shifts between the dynamic and static values of the spectral property. Moreover, information about the potential energy surface of various excited states can be obtained. The procedure is illustrated with three case studies. The first electronic excitation is explored in detail and dominant vibrational motions responsible for changes in the excitation energy are identified for ethylene, biphenyl, and hexamethylbenzene. The proposed method is also extended to other low-energy excitations. Finally, the vibrational fingerprint of the excitation energy of a more complex molecule, in particular the azo dye ethyl orange in a water environment, is analyzed.
Itikawa, Yukikazu [Institute of Space and Astronautical Science, Sagamihara, Kanagawa (Japan)
2001-04-01
A list of papers reporting cross sections for electron-impact excitations of rotational and vibrational states of molecules is presented. The list includes both the theoretical and the experimental papers published in 1980-2000. An index by molecular species is provided at the end of the bibliography. (author)
Hansen, Flemming Yssing; Taub, H.
1987-01-01
The collective vibrational excitations of two different crystalline monolayer phases of ethane (C2H6) adsorbed on the graphite (0001) surface have been investigated theoretically and experimentally. The monolayer phases studied are the commensurate 7/8 ×4 structure in which the ethane molecules lie...
Intermediate energy electron impact excitation of composite vibrational modes in phenol
Neves, R. F. C. [School of Chemical and Physical Sciences, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001 (Australia); Instituto Federal do Sul de Minas Gerais, Campus Poços de Caldas, Minas Gerais (Brazil); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, Minas Gerais (Brazil); Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001 (Australia); Lopes, M. C. A.; Nixon, K. L. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, Minas Gerais (Brazil); Oliveira, E. M. de; Lima, M. A. P. [Instituto de Física ‘Gleb Wataghin,’ Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Costa, R. F. da [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580 Santo André, São Paulo (Brazil); Varella, M. T. do N. [Instituto de Física, Universidade de São Paulo, C.P. 66318, 05315-970 São Paulo (Brazil); Bettega, M. H. F. [Departamento de Física, Universidade Federal do Paraná, C.P. 19044, 81531-990 Curitiba, Paraná (Brazil); Silva, G. B. da [Universidade Federal de Mato Grosso, Barra do Garças, Mato Grosso (Brazil); Brunger, M. J., E-mail: Michael.Brunger@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2015-05-21
We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C{sub 6}H{sub 5}OH). The measurements were carried out at incident electron energies in the range 15–40 eV and for scattered-electron angles in the range 10–90°. The energy resolution of those measurements was typically ∼80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C{sub 6}H{sub 5}OH molecule by electron impact.
The repopulation of electronic states upon vibrational excitation of niobium carbide clusters
Chernyy, V.; Logemann, R.; Bakker, J. M.; Kirilyuk, A.
2016-07-01
We study the infrared (IR) resonant heating of neutral niobium carbide clusters probed through ultraviolet photoionization spectroscopy. The IR excitation not only changes the photoionization spectra for the photon energies above the ionization threshold, but also modulates ion yield for energies significantly below it. An attempt to describe the experimental spectra using either Fowler's theory or thermally populated vibrational states was not successful. However, the data can be fully modeled by vibrationally and rotationally broadened discrete electronic levels obtained from Density Functional Theory (DFT) calculations. The application of this method to spectra with different IR pulse energies not only yields information about the excited electronic states in the vicinity of the HOMO level, populated by manipulation of the vibrational coordinates of a cluster, but also can serve as an extra indicator for the cluster isomeric structure and corresponding DFT-calculated electronic levels.
Phase-absorption method for studying vibrational relaxation during laser excitation of molecules
Kuntsevich, V.F.; Pisarchik, A.N.; Churakov, V.V.
1987-11-01
The authors investigate the potential of the phase-absorption method for investigating vibrational de-excitation of a laser molecular gas for the case when modulation in the vibrational state populations is done by an infrared laser pulse and the determination of the unknown value is based on measuring the phase difference between the periodic oscillations of the intensities of the excitation radiation and the probing radiation. The gas studied is carbon dioxide. The advantages of using optical rather than electrical pumping for the determination are cited. The method was also assessed for its effectiveness in studying the vibrational relaxation of carbon dioxide comprised of carbon 12/oxygen 18 and carbon 13/oxygen 16 isotopes.
The repopulation of electronic states upon vibrational excitation of niobium carbide clusters.
Chernyy, V; Logemann, R; Bakker, J M; Kirilyuk, A
2016-07-14
We study the infrared (IR) resonant heating of neutral niobium carbide clusters probed through ultraviolet photoionization spectroscopy. The IR excitation not only changes the photoionization spectra for the photon energies above the ionization threshold, but also modulates ion yield for energies significantly below it. An attempt to describe the experimental spectra using either Fowler's theory or thermally populated vibrational states was not successful. However, the data can be fully modeled by vibrationally and rotationally broadened discrete electronic levels obtained from Density Functional Theory (DFT) calculations. The application of this method to spectra with different IR pulse energies not only yields information about the excited electronic states in the vicinity of the HOMO level, populated by manipulation of the vibrational coordinates of a cluster, but also can serve as an extra indicator for the cluster isomeric structure and corresponding DFT-calculated electronic levels.
Laboratory spectroscopic study and astronomical detection of vibrationally excited n-propyl cyanide
Müller, Holger S. P.; Walters, Adam; Wehres, Nadine; Belloche, Arnaud; Wilkins, Olivia H.; Liu, Delong; Vicente, Rémi; Garrod, Robin T.; Menten, Karl M.; Lewen, Frank; Schlemmer, Stephan
2016-11-01
Context. We performed a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1. We determined line intensities of n-propyl cyanide in the ground vibrational states of its gauche and anti conformers toward the hot molecular core Sagittarius B2(N2) which suggest that we should also be able to detect transitions pertaining to excited vibrational states. Aims: We wanted to determine spectroscopic parameters of low-lying vibrational states of both conformers of n-propyl cyanide to search for them in our ALMA data. Methods: We recorded laboratory rotational spectra of n-propyl cyanide in two spectral windows between 36 and 127 GHz. We searched for emission lines produced by these states in the ALMA spectrum of Sagittarius B2(N2). We modeled their emission and the emission of the ground vibrational states assuming local thermodynamic equilibrium (LTE). Results: We have made extensive assignments of a- and b-type transitions of the four lowest vibrational states of the gauche conformer which reach J and Ka quantum numbers of 65 and 20, respectively. We assigned mostly a-type transitions for the anti conformer with J and Ka quantum numbers up to 48 and 24, respectively. Rotational and Fermi perturbations between two anti states allowed us to determine their energy difference. The resulting spectroscopic parameters enabled us to identify transitions of all four vibrational states of each conformer in our ALMA data. The emission features of all states, including the ground vibrational state, are well-reproduced with the same LTE modeling parameters, which gives us confidence in the reliability of the identifications, even for the states with only one clearly detected line. Conclusions: Emission features pertaining to the highest excited vibrational states of n-propyl cyanide reported in this work have been identified just
Active Vibration Control of a Nonlinear Beam with Self- and External Excitations
J. Warminski
2013-01-01
Full Text Available An application of the nonlinear saturation control (NSC algorithm for a self-excited strongly nonlinear beam structure driven by an external force is presented in the paper. The mathematical model accounts for an Euler-Bernoulli beam with nonlinear curvature, reduced to first mode oscillations. It is assumed that the beam vibrates in the presence of a harmonic excitation close to the first natural frequency of the beam, and additionally the beam is self-excited by fluid flow, which is modelled by a nonlinear Rayleigh term for self-excitation. The self- and externally excited vibrations have been reduced by the application of an active, saturation-based controller. The approximate analytical solutions for a full structure have been found by the multiple time scales method, up to the first-order approximation. The analytical solutions have been compared with numerical results obtained from direct integration of the ordinary differential equations of motion. Finally, the influence of a negative damping term and the controller's parameters for effective vibrations suppression are presented.
Asymptotic Method and Numerical Analysis for Self-Excited Vibration in Rolling Mill with Clearance
Hongguang Li
2001-01-01
Full Text Available In this paper, a dynamic model is proposed for analysis of nonlinear vibrations of rolling mills with fixed and time-varying clearances. Self-excited vibrations of the system that is basically involved with piece-wise nonlinearity and discontinuities are investigated via asymptotic method. It is shown by numerical results obtained for the nonlinear system with a time-varying clearance that different forms of nonlinear vibrations appear to be periodic, quasi-periodic and chaotic. Influence of the system parameters on the nonlinear vibration behaviors is examined by applying the Poincare sections, the bifurcation diagram and the largest Lyapunov exponent. New phenomena are observed in nonlinear motions of the rolling mill mechanism and are of significant importance for design of this type of mechanical systems.
João C. O. Marra
2016-01-01
Full Text Available Vibratory phenomena have always surrounded human life. The need for more knowledge and domain of such phenomena increases more and more, especially in the modern society where the human-machine integration becomes closer day after day. In that context, this work deals with the development and practical implementation of a hybrid (passive-active/adaptive vibration control system over a metallic beam excited by a broadband signal and under variable temperature, between 5 and 35°C. Since temperature variations affect directly and considerably the performance of the passive control system, composed of a viscoelastic dynamic vibration neutralizer (also called a viscoelastic dynamic vibration absorber, the associative strategy of using an active-adaptive vibration control system (based on a feedforward approach with the use of the FXLMS algorithm working together with the passive one has shown to be a good option to compensate the neutralizer loss of performance and generally maintain the extended overall level of vibration control. As an additional gain, the association of both vibration control systems (passive and active-adaptive has improved the attenuation of vibration levels. Some key steps matured over years of research on this experimental setup are presented in this paper.
Pradhan, G. B.; Juanes-Marcos, J. C.; Balakrishnan, N., E-mail: naduvala@unlv.nevada.edu [Department of Chemistry, University of Nevada Las Vegas, Las Vegas, Nevada 89154 (United States); Kendrick, Brian K. [Theoretical Division (T-1, MS B221), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2013-11-21
Quantum scattering calculations are reported for state-to-state vibrational relaxation and reactive scattering in O + OH(v = 2 − 3, j = 0) collisions on the electronically adiabatic ground state {sup 2}A′′ potential energy surface of the HO{sub 2} molecule. The time-independent Schrödinger equation in hyperspherical coordinates is solved to determine energy dependent probabilities and cross sections over collision energies ranging from ultracold to 0.35 eV and for total angular momentum quantum number J = 0. A J-shifting approximation is then used to compute initial state selected reactive rate coefficients in the temperature range T = 1 − 400 K. Results are found to be in reasonable agreement with available quasiclassical trajectory calculations. Results indicate that rate coefficients for O{sub 2} formation increase with increasing the OH vibrational level except at low and ultralow temperatures where OH(v = 0) exhibits a slightly different trend. It is found that vibrational relaxation of OH in v = 2 and v = 3 vibrational levels is dominated by a multi-quantum process.
The Microwave Spectroscopy of Aminoacetonitrile in the Vibrational Excited States 2
Fujita, Chiho; Higurashi, Haruka; Ozeki, Hiroyuki; Kobayashi, Kaori
2016-06-01
Aminoacetonitrile (NH_2CH_2CN) is a potential precursor of the simplest amino acid, glycine in the interstellar space and was detected toward SgrB2(N). We have extended measurements up to 1.3 THz so that the strongest transitions that may be found in the terahertz region should be covered. Aminoacetonitrile has a few low-lying vibrational excited states and indeed the pure rotational transitions in these vibrational excited states were found. The pure rotational transitions in six vibrational excited states in the 80-180 GHz range have been assigned and centrifugal distortion constants up to the sextic terms were determined. Based on spectral intensities and the vibrational information from Bak et al., They were assigned to the 3 low-lying fundamentals, 1 overtone and 2 combination bands. In the submillimeter wavelength region, perturbations were recognized and some of the lines were off by more than a few MHz. At this moment, these perturbed transitions are not included in our analysis. A. Belloche, K. M. Menten, C. Comito, H. S. P. Müller, P. Schilke, J. Ott, S. Thorwirth, and C. Hieret, 2008, Astronom. & Astrophys. 482, 179 (2008). Y. Motoki, Y. Tsunoda, H. Ozeki, and K. Kobayashi, Astrophys. J. Suppl. Ser. 209, 23 (2013). B. Bak, E. L. Hansen, F. M. Nicolaisen, and O. F. Nielsen, Can. J. Phys. 53, 2183 (1975) C. Fujita, H. Ozeki, and K. Kobayashi, 70th International Symposium on Molecular Spectroscopy (2015), MH14.
Xue-Liang Zhang; Bang-Chun Wen; Chun-Yu Zhao
2012-01-01
In this paper,the synchronization problem of three homodromy coupled exciters in a non-resonant vibrating system of plane motion is studied.By introducing the average method of modified small parameters,we deduced dimensionless coupling equation of three exciters,which converted the problem of synchronization into that of the existence and stability of zero solutions for the average differential equations of the small parameters.Based on the dimensionless coupling torques and characteristics of the corresponding limited functions,the synchronization criterion for three exciters was derived as the absolute value of dimensionless residual torque difference between arbitrary two motors being less than the maximum of their dimensionless coupling torques.The stability criterion of its synchronous state lies in the double-condition that the inertia coupling matrix is positive definite and all its elements are positive as well.The synchronization determinants are the coefficients of synchronization ability,also called as the general dynamical symmetry coefficients.The double-equilibrium state of the vibrating system is manifested by numeric method,and the numeric and simulation results derived thereof indicate the indispensable and crucial role the structural parameters of the vibrating system play in the stability criterion of synchronous operation.Besides,by adjusting its structural parameters,the elliptical motion of the vibrating system successfully met the requirements in engineering applications.
Brunger, Michael J.; Ratnavelu, Kuru; Buckman, Stephen J.; Jones, Darryl B.; Muñoz, Antonio; Blanco, Francisco; García, Gustavo
2016-03-01
We report on our results of a study into the sensitivity of charged-particle (electron) track simulations in liquid pyrimidine, to the vibrational cross sections and vibrational energy loss distribution function employed in those simulations. We achieve this by repeating the earlier investigation of Fuss et al. [J. Appl. Phys. 117, 214701 (2015)], but now incorporating more accurate data for the vibrational integral cross sections and the energy loss distribution function that have recently become available. We find that while changes in absorbed dose or particle range are quite minor, due to the energy transferred via vibrational excitations being low in comparison to that for other processes such as ionisation, at the very end of the tracks, where non-ionizing interactions dominate, the significantly large numbers of vibrational excitation processes increases the electrons' ability to induce other effects (e.g. sample heating, bond breaking and radical formation) that might cause damage. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.
Lifetime-vibrational interference effects in resonantly excited x-ray emission spectra of CO
Skytt, P.; Glans, P.; Gunnelin, K. [Uppsala Univ. (Sweden)] [and others
1997-04-01
The parity selection rule for resonant X-ray emission as demonstrated for O{sub 2} and N{sub 2} can be seen as an effect of interference between coherently excited degenerate localized core states. One system where the core state degeneracy is not exact but somewhat lifted was previously studied at ALS, namely the resonant X-ray emission of amino-substituted benzene (aniline). It was shown that the X-ray fluorescence spectrum resulting from excitation of the C1s at the site of the {open_quotes}aminocarbon{close_quotes} could be described in a picture separating the excitation and the emission processes, whereas the spectrum corresponding to the quasi-degenerate carbons could not. Thus, in this case it was necessary to take interference effects between the quasi-degenerate intermediate core excited states into account in order to obtain agreement between calculations and experiment. The different vibrational levels of core excited states in molecules have energy splittings which are of the same order of magnitude as the natural lifetime broadening of core excitations in the soft X-ray range. Therefore, lifetime-vibrational interference effects are likely to appear and influence the band shapes in resonant X-ray emission spectra. Lifetime-vibrational interference has been studied in non-resonant X-ray emission, and in Auger spectra. In this report the authors discuss results of selectively excited soft X-ray fluorescence spectra of molecules, where they focus on lifetime-interference effects appearing in the band shapes.
Resonances in nonlinear structure vibrations under multifrequency excitations
El-Bassiouny, A F [Faculty of Science, Mathematics Department, Benha University, Benha 1358 (Egypt); El-Latif, G M Abd [Faculty of Science, Mathematics Department, Sohag University, Sohag (Egypt)
2006-10-15
The response of a single-degree-of-freedom system with quadratic, cubic and quartic nonlinearities subjected to a sinusoidal excitation that involves multiple frequencies is considered. The method of multiple scales is used to construct a first order uniform expansion yielding two first-order nonlinear ordinary differential equations that are derived for the evolution of the amplitude and phase. These oscillations involve a subharmonic oscillation of order one-fourth and superharmonic oscillation of order two. Steady state responses and their stability are computed for selected values of the system parameters. The effects of these (quadratic, cubic, and quartic) nonlinearities on these oscillations are specifically investigated. With this study, it has been verified that the qualitative effects of these nonlinearities are different. Regions of hardening (softening) behaviour of the system exist for the case of subharmonic resonance. The response curve is not affected by decreasing the damping factor for the case of superharmonic resonance. It is shown that the response curve contracts or expands as the parameters vary. The multivalued region increases or decreases when some parameters vary.
A Magnetic Suspension and Excitation System for Spin Vibration Testing of Turbomachinery Blades
Johnson, Dexter; Brown, Gerald V.; Mehmed, Oral
1998-01-01
The Dynamic Spin Rig (DSR) is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. A heteropolar radial active magnetic bearing was integrated into the DSR to provide non-contact magnetic suspension and mechanical excitation of the rotor to induce turbomachinery blade vibrations. The magnetic bearing replaces one of the two existing conventional radial ball bearings. Prior operation of the DSR used two voice-coil type linear electromagnetic shakers which provided axial excitation of the rotor. The new magnetic suspension and excitation system has provided enhanced testing capabilities. Tests were performed at high rotational speeds for longer duration and higher vibration amplitudes. Some characteristics of the system include magnetic bearing stiffness values up to 60,000 lb./in., closed loop control bandwidth around 500 Hz, and multi-directional radial excitation of the rotor. This paper reports on the implementation and operation of this system and presents some test results using this system.
Dynamical potential approach to dissociation of H-C bond in HCO highly excited vibration
Fang Chao; Wu Guo-Zhen
2009-01-01
The highly excited vibrational levels of HCO in the electronic ground state, X1A', are employed to determine the coefficients of an algebraic Hamiltonian, by which the dynamical potential is derived and shown to be very useful for interpreting thc intramolecular vibrational relaxation (IVR) which operates via the HCO bending motion. The IVR inhibits the dissociation of H atom and enhances the stochastic degree of dynamical character. This approach is from a global viewpoint on a series of levels classified by the polyad number which is a constant of motion in a certain dynamical domain. In this way, the seemingly complicated level structure shows very regular picture, dynamically.
Li, Yanbin; Mulani, Sameer B.; Kapania, Rakesh K.; Fei, Qingguo; Wu, Shaoqing
2017-07-01
An algorithm that integrates Karhunen-Loeve expansion (KLE) and the finite element method (FEM) is proposed to perform non-stationary random vibration analysis of structures under excitations, represented by multiple random processes that are correlated in both time and spatial domains. In KLE, the auto-covariance functions of random excitations are discretized using orthogonal basis functions. The KLE for multiple correlated random excitations relies on expansions in terms of correlated sets of random variables reflecting the cross-covariance of the random processes. During the response calculations, the eigenfunctions of KLE used to represent excitations are applied as forcing functions to the structure. The proposed algorithm is applied to a 2DOF system, a 2D cantilever beam and a 3D aircraft wing under both stationary and non-stationary correlated random excitations. Two methods are adopted to obtain the structural responses: a) the modal method and b) the direct method. Both the methods provide the statistics of the dynamic response with sufficient accuracy. The structural responses under the same type of correlated random excitations are bounded by the response obtained by perfectly correlated and uncorrelated random excitations. The structural response increases with a decrease in the correlation length and with an increase in the correlation magnitude. The proposed methodology can be applied for the analysis of any complex structure under any type of random excitation.
Zhang, Qicheng; Lan, Yu; Lu, Wei; Wang, Shuai
2017-05-01
Active piezoelectric materials are applied to one-dimensional phononic crystals, for the control of longitudinal vibration propagation both in active and passive modes. Based on the electromechanical coupling between the acoustical vibration and electric field, the electromechanical equivalent method is taken to theoretically predict the transmission spectrum of the longitudinal vibration. It is shown that the phononic rod can suppress the vibration efficiently at the frequencies of interest, by actively optimizing the motions of piezoelectric elements. In an illustrated phononic rod of 11.2cm long, active tunable isolations of more than 20dB at low frequencies (500Hz-14kHz) are generated by controlling the excitation voltages of piezoelectric elements. Meanwhile, passive fixed isolation at high frequencies (14k-63kHz) are presented by its periodicity characteristics. Finite element simulations and vibration experiments on the rod demonstrate the effectiveness of the approach in terms of its vibration isolation capabilities and tunable characteristics. This phononic rod can be manufactured easily and provides numerous potential applications in designing isolation mounts and platforms.
Qicheng Zhang
2017-05-01
Full Text Available Active piezoelectric materials are applied to one-dimensional phononic crystals, for the control of longitudinal vibration propagation both in active and passive modes. Based on the electromechanical coupling between the acoustical vibration and electric field, the electromechanical equivalent method is taken to theoretically predict the transmission spectrum of the longitudinal vibration. It is shown that the phononic rod can suppress the vibration efficiently at the frequencies of interest, by actively optimizing the motions of piezoelectric elements. In an illustrated phononic rod of 11.2cm long, active tunable isolations of more than 20dB at low frequencies (500Hz-14kHz are generated by controlling the excitation voltages of piezoelectric elements. Meanwhile, passive fixed isolation at high frequencies (14k-63kHz are presented by its periodicity characteristics. Finite element simulations and vibration experiments on the rod demonstrate the effectiveness of the approach in terms of its vibration isolation capabilities and tunable characteristics. This phononic rod can be manufactured easily and provides numerous potential applications in designing isolation mounts and platforms.
Robie, Daniel C.; Jusinski, Leonard E.; Bischel, William K.
1990-02-01
We report the first detection by optical means of highly vibrationally excited H2 X1Σ+g(vx=6-11). Vibrationally excited H2 was generated using a recently discovered hot-wire effect in H2 gas, and was detected in 40 bands with 2+1 resonantly enhanced multiphoton ionization via the EF state (vEF=0-14). Rotational temperatures are in the range 200-650 K, well below that required for thermal excitation of the observed vibrational levels.
Portnov, Alexander; Epshtein, Michael; Bar, Ilana
2017-06-01
Nonadiabatic processes, dominated by dynamic passage of reactive fluxes through conical intersections (CIs) are considered to be appealing means for manipulating reaction paths. One approach that is considered to be effective in controlling the course of dissociation processes is the selective excitation of vibrational modes containing a considerable component of motion. Here, we have chosen to study the predissociation of the model test molecule, methylamine and its deuterated isotopologues, excited to well-characterized quantum states on the first excited electronic state, S_{1}, by following the N-H(D) bond fission dynamics through sensitive H(D) photofragment probing. The branching ratios between slow and fast H(D) photofragments, the internal energies of their counter radical photofragments and the anisotropy parameters for fast H photofragments, confirm correlated anomalies for predissociation initiated from specific rovibronic states, reflecting the existence of a dynamic resonance in each molecule. This resonance strongly depends on the energy of the initially excited rovibronic states, the evolving vibrational mode on the repulsive S_{1} part during N-H(D) bond elongation, and the manipulated passage through the CI that leads to radicals excited with C-N-H(D) bending and preferential perpendicular bond breaking, relative to the photolyzing laser polarization, in molecules containing the NH_{2} group. The indicated resonance plays an important role in the bifurcation dynamics at the CI and can be foreseen to exist in other photoinitiated processes and to control their outcome.
Dissociative recombination and vibrational excitation of BF+ in low energy electron collisions
Mezei, J. Zs; Colboc, F.; Pop, N.; Ilie, S.; Chakrabarti, K.; Niyonzima, S.; Lepers, M.; Bultel, A.; Dulieu, O.; Motapon, O.; Tennyson, J.; Hassouni, K.; Schneider, I. F.
2016-10-01
The latest molecular data—potential energy curves and Rydberg-valence interactions—characterising the super-excited electronic states of BF are reviewed in order to provide the input for the study of their fragmentation dynamics. Starting from this input, the main paths and mechanisms of BF+ dissociative recombination and vibrational excitation are analysed. Their cross sections are computed for the first time using a method based on the multichannel quantum defect theory (MQDT), and Maxwellian rate-coefficients are calculated and displayed in ready-to-be-used format for low temperature plasma kinetics simulations.
Excitation of vibrational quanta in furfural by intermediate-energy electrons
Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Neves, R. F. C. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Instituto Federal do Sul de Minas Gerais, Campus Poços de Caldas, Minas Gerais (Brazil); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, MG (Brazil); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, MG (Brazil); Costa, R. F. da [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, Campinas, 13083-859 São Paulo (Brazil); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, 09210-580 São Paulo (Brazil); Varella, M. T. do N. [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, São Paulo (Brazil); Bettega, M. H. F. [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); Lima, M. A. P. [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, Campinas, 13083-859 São Paulo (Brazil); García, G. [Instituto de Física Fundamental, CSIC, Serrano 113-bis, 28006 Madrid (Spain); and others
2015-12-14
We report cross sections for electron-impact excitation of vibrational quanta in furfural, at intermediate incident electron energies (20, 30, and 40 eV). The present differential cross sections are measured over the scattered electron angular range 10°–90°, with corresponding integral cross sections subsequently being determined. Furfural is a viable plant-derived alternative to petrochemicals, being produced via low-temperature plasma treatment of biomass. Current yields, however, need to be significantly improved, possibly through modelling, with the present cross sections being an important component of such simulations. To the best of our knowledge, there are no other cross sections for vibrational excitation of furfural available in the literature, so the present data are valuable for this important molecule.
Kolli, Avinash; Scholes, Gregory D; Olaya-Castro, Alexandra
2012-01-01
The importance of fast vibrations in enhancing and controlling energy transfer and conversion in biomolecules is an issue of current debate. In this article we show that coupling between localised high-frequency vibrations and electronic degrees of freedom is fundamental for efficient excitation transport in photosynthetic light-harvesting systems with high degree of disorder. We consider the cryptophyte antennae protein phycoerythrin 545 and discuss how the balance between electronic interactions and coupling to fast vibronic modes supports the biological function of these antennae by generating a non-cascaded transport that leads to a rapid, directed and wider spatial distribution of excitation energy across the complex. Furthermore, we illustrate signatures of vibronic influence in the beating of excitonic coherences and show that mechanisms supporting coherent evolution of excitons also assist coupling to selected modes that enhance energy transfer to preferential sites in the complex. We therefore argue ...
Excitation of vibrational quanta in furfural by intermediate-energy electrons
Jones, D. B.; Neves, R. F. C.; Lopes, M. C. A.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Lima, M. A. P.; García, G.; Blanco, F.; Brunger, M. J.
2015-12-01
We report cross sections for electron-impact excitation of vibrational quanta in furfural, at intermediate incident electron energies (20, 30, and 40 eV). The present differential cross sections are measured over the scattered electron angular range 10°-90°, with corresponding integral cross sections subsequently being determined. Furfural is a viable plant-derived alternative to petrochemicals, being produced via low-temperature plasma treatment of biomass. Current yields, however, need to be significantly improved, possibly through modelling, with the present cross sections being an important component of such simulations. To the best of our knowledge, there are no other cross sections for vibrational excitation of furfural available in the literature, so the present data are valuable for this important molecule.
Shape vibrations and quasiparticle excitations in the lowest 0+ excited state of the Erbium isotopes
Chen, Fang-Qi
2016-01-01
The ground and first excited 0+ states of the {156-172}Er isotopes are analyzed in the framework of the generator coordinate method. The shape parameter beta is used to generate wave functions with different deformations which together with the two-quasiparticle states built on them provide a set of states. An angular momentum and particle number projection of the latter spawn the basis states of the generator coordinate method. With this ansatz and using the separable pairing plus quadrupole interaction we obtain a good agreement with the experimental spectra and E2 transition rates up to moderate spin values. The structure of the wave functions suggests that the first excited 0+ states in the soft Er isotopes are dominated by shape fluctuations, while in the well deformed Er isotopes the two-quasiparticle states are more relevant. In between both degrees of freedom are necessary .
Control Application of Piezoelectric Materials to Aeroelastic Self-Excited Vibrations
Mohammad Amin Rashidifar
2014-01-01
Full Text Available A method for application of piezoelectric materials to aeroelasticity of turbomachinery blades is presented. The governing differential equations of an overhung beam are established. The induced voltage in attached piezoelectric sensors due to the strain of the beam is calculated. In aeroelastic self-excited vibrations, the aerodynamic generalized force of a specified mode can be described as a linear function of the generalized coordinate and its derivatives. This simplifies the closed loop system designed for vibration control of the corresponding structure. On the other hand, there is an industrial interest in measurement of displacement, velocity, acceleration, or a contribution of them for machinery condition monitoring. Considering this criterion in quadratic optimal control systems, a special style of performance index is configured. Utilizing the current relations in an aeroelastic case with proper attachment of piezoelectric elements can provide higher margin of instability and lead to lower vibration magnitude.
Cross Sections and Rate Coefficients for Vibrational Excitation of HeH+ Molecule by Electron Impact
Mehdi Ayouz
2016-12-01
Full Text Available Cross sections and thermally-averaged rate coefficients for vibration (de-excitation of HeH + by an electron impact are computed using a theoretical approach that combines the multi-channel quantum defect theory and the UK R-matrix code. Fitting formulas with a few numerical parameters are derived for the obtained rate coefficients. The interval of applicability of the formulas is from 40 to 10,000 K.
Bartels, Nils; Krüger, Bastian C; Auerbach, Daniel J; Wodtke, Alec M; Schäfer, Tim
2014-12-08
The loss or gain of vibrational energy in collisions of an NO molecule with the surface of a gold single crystal proceeds by electron transfer. With the advent of new optical pumping and orientation methods, we can now control all molecular degrees of freedom important to this electron-transfer-mediated process, providing the most detailed look yet into the inner workings of an electron-transfer reaction and showing how to control its outcome. We find the probability of electron transfer increases with increasing translational and vibrational energy as well as with proper orientation of the reactant. However, as the vibrational energy increases, translational excitation becomes unimportant and proper orientation becomes less critical. One can understand the interplay of all three control parameters from simple model potentials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Detection of vibrationally excited methyl formate in W51 e2
Demyk, K.; Wlodarczak, G.; Carvajal, M.
2008-10-01
Context: Hot cores in molecular clouds, such as Orion KL, Sgr B2, W51 e1/e2, are characterized by the presence of molecules at sufficiently high temperatures to populate their low-frequency vibrationally excited states significantly. Complex organic molecules, such as methyl formate, ethyl cyanide or dimethyl ether, are characterized by a dense spectrum both in the ground state and in the excited states and lines from vibrationally excited states certainly participate to the spectral confusion. Aims: Following a laboratory study of the first torsional excited mode of methyl formate, we search for methyl formate, HCOOCH3, in its first torsionally excited state (\\upsilon_t=1) in the molecular cloud W51 e2. Methods: We performed observations of the molecular cloud W51 e2 in different spectral regions at 1.3, 2, and 3 mm with the IRAM 30 m single dish antenna. Results: Methyl formate in its first torsionally excited state (\\upsilon_t=1 at 131 cm-1) is detected for the first time toward W51 e2. We detect 82 transitions among which 46 are unblended with other species. For a total of 16 A-E pairs in the observed spectrum, 9 are unblended; these 9 pairs are all detected. All transitions from excited methyl formate within the observed spectral range are detected and no strong lines are missing. The column density of the excited state is comparable to that of the ground state. For a source size of 7´´, we find that {T_rot} = 104 ± 14 K and N = 9.4+4.0-2.8 × 1016 cm-2 for the excited state and {T_rot} = 176 ± 24 K and N = 1.7+.2-.2 × 1017 cm-2 for the ground state. Lines from ethyl cyanide in its two first excited states (\\upsilon_t=1, torsion mode at 212 cm-1) and (\\upsilon_b=1, CCN in-plane bending mode at 206 cm-1) are also present in the observed spectrum. Blending problems prevent a precise estimate of its abundance, although as for methyl formate, it should be comparable to the value derived for the ground state for which we find {T_rot} = 103 ± 9 K and N = 3
The separation of vibrational coherence from ground- and excited-electronic states in P3HT film
Song, Yin
2015-06-07
© 2015 AIP Publishing LLC. Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S (λ 1, T∼ 2, λ 3)) along the population time (T∼ 2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S (λ 1, ν∼ 2, λ 3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ ν∼ 2) in the rephasing beating map and at negative frequency (- ν∼ 2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.
In-plane Auto-Parametric Vibration of Inclined Cables under Random Transverse Excitation
WANG Bo; ZHANG Hai-long; XU Feng; GUO Cui-cui
2008-01-01
In-plane auto-parametric stochastic vibration of inclined cables subjected to Gaussian white noise in transverse bridge orientation is investigated. Based on Newton's laws of motion and Galerkin's modal truncation principle, the influences of geometry nonlinearity induced by sag and large displacement of cables and the initial equilibrium state are taken into account. Meanwhile, the three-dimensional non-linear differential equations of inclined cables for coupling vibration are deduced, equivalent stochastic linearization method is applied to derive the 1A-dimensional first-order nonlinear differential equations of state vectors, and the Runge-Kutta integration method is utilized to obtain the root mean square (RMS) response. Results show that when the transverse random excitation imposed on the stayed cable exceeds a critical value, the in-plane transverse vibration of the cable are excited due to the auto-parametric nonlinear coupling, and the critical value of random excitation increases with the damping ratio. In this motion, the cable response possesses non-stationary characteristics, even though the loading keeps stationary.
Maglev self-excited vibration suppression with a virtual sky-hooked damper
李金辉; 李杰; 周丹峰; 王连春
2016-01-01
This work addresses the problem of self-excited vibration, which degrades the stability of the levitation control, decreases the ride comfort, and restricts the construction cost of maglev system. Firstly, a minimum model containing a flexible bridge and a single levitation unit is presented. Based on the simplified model, the principle underlying the self-excited vibration is explored. After investigations about the energy transmission between the levitation system and bridge, it is concluded that the increment of modal damping can dissipate the accumulated energy by the bridge and the self-excited vibration may be avoided. To enlarge the equivalent modal damping of bridge, the sky-hooked damper is adopted. Furthermore, to avoid the hardware addition of real sky-hooked damper, considering the fact that the electromagnet itself is an excellent actuator that is capable of providing sufficiently fast and large force acting on the bridge to emulate the influence of the real sky-hooked damper, the technique of the virtual sky-hooked damper is proposed. The principle underlying the virtual sky-hooked damper by electromagnet is explored and the vertical velocity of bridge is estimated. Finally, numerical and experimental results illustrating the stability improvement of the vehicle-bridge interaction system are provided.
Spectroscopic Study and Astronomical Detection of Vibrationally Excited n-PROPYL Cyanide
Müller, Holger S. P.; Wehres, Nadine; Wilkins, Olivia H.; Lewen, Frank; Schlemmer, Stephan; Walters, Adam; Vicente, Rémi; Liu, Delong; Garrod, Robin T.; Belloche, Arnaud; Menten, Karl M.
2016-06-01
We have obtained ALMA data of Sagittarius (Sgr for short) B2(N) between 84.0 and 114.4 GHz in its Early Science Cycles 0 and 1. We have focused our analyses on the northern, secondary hot molecular core Sgr B2(N2) because of the smaller line widths. The survey led to the first detection of a branched alkyl compound, iso-propyl cyanide, i-C_3H_7CN, in space besides the ˜2.5 times more abundant straight chain isomer n-propyl cyanide, a molecule which we had detected in our IRAM 30 m survey. We suspected to be able to detect n-propyl cyanide in vibrationally excited states in our ALMA data. We have recorded laboratory rotational spectra of this molecule in three large frequency regions and identified several excited vibrational states. The analyses of these spectra have focused on the 36 to 70 GHz and 89 to 127 GHz regions and on the four lowest excited vibrational states of both the lower lying gauche- and the slightly higher lying anti-conformer for which rotational constants had been published. We will present results of our laboratory spectroscopic investigations and will report on the detection of these states toward Sgr B2(N2). A. Belloche et al., Science 345 (2014) 1584. A. Belloche et al., A&A 499 (2009) 215. E. Hirota, J. Chem. Phys. 37 (1962) 2918.
Analysis on pseudo excitation of random vibration for structure of time flight counter
Wu, Qiong; Li, Dapeng
2015-03-01
Traditional computing method is inefficient for getting key dynamical parameters of complicated structure. Pseudo Excitation Method(PEM) is an effective method for calculation of random vibration. Due to complicated and coupling random vibration in rocket or shuttle launching, the new staging white noise mathematical model is deduced according to the practical launch environment. This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter(ToFC). The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level. Considering stiffness of fixture structure, the random vibration experiments are conducted in three directions to compare with the revised PEM. The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained. The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results. The maximum error is within 9%. The reasons of errors are analyzed to improve reliability of calculation. This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.
Analysison Pseudo Excitation of Random Vibration for Structure of Time Flight Counter
WU Qiong; LI Dapeng
2015-01-01
Traditional computing method is inefficient for getting key dynamical parameters of complicated structure. Pseudo Excitation Method(PEM) is an effective method for calculation of random vibration. Due to complicated and coupling random vibration in rocket or shuttle launching, the new staging white noise mathematical model is deduced according to the practical launch environment. This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter(ToFC). The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level. Considering stiffness of fixture structure, the random vibration experiments are conducted in three directions to compare with the revised PEM. The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained. The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results. The maximum error is within 9%. The reasons of errors are analyzed to improve reliability of calculation. This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.
Piezoelectric Wind Energy Harvesting from Self-Excited Vibration of Square Cylinder
Junlei Wang
2016-01-01
Full Text Available Self-excited vibration of a square cylinder has been considered as an effective way in harvesting piezoelectric wind energy. In present work, both of the vortex-induced vibration and unstable galloping phenomenon process are investigated in a reduced velocity (Ur=U/ωn·D range of 4≤Ur≤20 with load resistance ranging in 100 Ω≤R≤1 MΩ. The vortex-induced vibration covers presynchronization, synchronization, and postsynchronization branches. An aeroelectromechanical model is given to describe the coupling of the dynamic equation of the fluid-structure interaction and the equation of Gauss law. The effects of load resistance are investigated in both the open-circuit and close-circuit system by a linear analysis, which covers the parameters of the transverse displacement, aerodynamic force, output voltage, and harvested power utilized to measure the efficiency of the system. The highest level of the transverse displacement and the maximum value of harvested power of synchronization branch during the vortex-induced vibration and galloping are obtained. The results show that the large-amplitude galloping at high wind speeds can generate energy. Additionally, energy can be harvested by utilization of the lock-in phenomenon of vortex-induced vibration under low wind speed.
Laporta, V. [Istituto di Metodologie Inorganiche e dei Plasmi, CNR, Bari, Italy and Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Celiberto, R. [Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica, Politecnico di Bari, Italy and Istituto di Metodologie Inorganiche e dei Plasmi, CNR, Bari (Italy); Tennyson, J. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)
2014-12-09
Rate coefficients for dissociative electron attachment and electron-impact dissociation processes, involving vibrationally excited molecular oxygen, are presented. Analytical fits of the calculated numerical data, useful in the applications, are also provided.
Forces exciting generation roll at rotor vibrations when rotor-to-stator rubbing
Shatokhin, V. F.
2017-07-01
The consequences of emergencies of turbosets for different application are revealed, the cause of forced shutdown and even catastrophic destructions of which many researchers consider the rotor-to-stator rubbing and development—to a greater or lesser extent—of the phenomena of the rotor generation roll over the stator. The synchronous or asynchronous generation roll is determined by the rotor precession direction, coinciding or not coinciding with the self-rotation direction of the rotor. Asynchronous generation roll is the most dangerous form of the rotor-stator contact interaction with the vibrations with rubbing. The basic equations of rotor vibrations are presented: symmetric rotor fixed on two supports and that fixed on several supports after abrupt imbalance with and without rotor coming in contact with a flexible stator. The vibration process is considered as the rotor motion in a backlash with subsequent contact with the stator, loss of contact, or development of generation roll. The latter essentially depends on the properties of the "rotor-support-stator" dynamic system. The stator stiffness characteristic is specified in "force-deformation" coordinates that make it possible to take into account damping in the supports and power loss in the stator. The diagram of elastic-damping device was presented, which makes it possible to ensure a certain level of power loss at the stator displacements. The exciting forces promoting development of self-exciting vibrations of the rotor in the form of asynchronous generation roll were compared with the exciting forces of oil film of sliding bearings and forces of aerodynamic excitation in the turbine flow path and sealings. For the rotor systems of high and medium pressure of a 300 MW capacity turboset, the simulation results of the process of development of asynchronous generation roll at the vibrations with rubbing were revealed, and the basic characteristics of development of generation roll in a span between
Xie, Z. Q.; Zhou, Y. S.; He, X. N.; Gao, Y.; Park, J. B.; Guillemet, T.; Lu, Y. F.
2011-03-01
Fast growth of diamond crystals in open air was achieved by laser-assisted combustion synthesis through vibrational excitation of precursor molecules. A wavelength-tunable CO2 laser (spectrum range from 9.2 to 10.9 μm) was used for the vibrational excitation in synthesis of diamond crystals. A pre-mixed C2H4/C2H2/O2 gas mixture was used as precursors. Through resonant excitation of the CH2-wagging mode of ethylene (C2H4) molecules using the CO2 laser tuned at 10.532 Μm, high-quality diamond crystals were grown on silicon substrates with a high growth rate of ~139 μm/hr. Diamond crystals with a length up to 5 mm and a diameter of 1 mm were grown in 36 hours. Sharp Raman peaks at 1332 cm-1 with full width at half maximum (FWHM) values around 4.5 cm-1 and distinct X-ray diffraction spectra demonstrated the high quality of the diamond crystals. The effects of the resonant excitation of precursor molecules by the CO2 laser were investigated using optical emission spectroscopy.
Mitchell, Deborah G; Johnson, Alan M; Johnson, Jeremy A; Judd, Kortney A; Kim, Kilyoung; Mayhew, Maurine; Powell, Amber L; Sevy, Eric T
2008-02-14
Relaxation of highly vibrationally excited 1,2-, 1,3-, and 1,4-difluorobenzne (DFB) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot DFB (E' approximately 41,000 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Collisions between hot DFB isomers and CO2 result in large amounts of rotational and translational energy transfer from the hot donors to the bath. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these states. The amount of translational energy gained by CO2 during collisions was determined using Doppler spectroscopy to measure the width of the absorption line for each transition. The energy transfer probability distribution function, P(E,E'), for the large DeltaE tail was obtained by resorting the state-indexed energy transfer probabilities as a function of DeltaE. P(E,E') was fit to a biexponential function to determine the average energy transferred in a single DFB/CO2 collision and fit parameters describing the shape of P(E,E'). P(E,E') fit parameters for DFB/CO2 and the previously studied C6F6/CO2 system are compared to various donor molecular properties. A model based on Fermi's Golden Rule indicates that the shape of P(E,E') is primarily determined by the low-frequency out-of-plane donor vibrational modes. A fractional mode population analysis is performed, which suggests that for energy transfer from DFB and C6F6 to CO2 the two key donor vibrational modes from which energy leaks out of the donor into the bath are nu11 and nu16. These "gateway" modes are some of the same modes determined to be the most efficient energy transfer modes by quantum scattering studies of benzene/He collisions.
Propagation of vibration caused by electrical excitation in the normal human heart.
Kanai, Hiroshi
2009-06-01
The ability to noninvasively detect regional dynamic myocardial damage related to action potentials and mechanical properties affected by heart disease is of great clinical importance. Though there are invaluable clinical tools for diagnosis of a broad range of cardiac conditions, such myocardial properties cannot be evaluated. We have previously shown that pulsive vibration occurs on the myocardium after electrical stimulation of an isolated heart. In this study, using a novel technique for ultrasonic measurement of the myocardial motion, we detected pulsive vibrations spontaneously caused by electrical excitation and by valve closure. Using a sparse sector scan, the vibrations were measured almost simultaneously at about 10,000 points set in the heart wall at a high temporal resolution. The consecutive spatial distributions of the phase of the vibrations revealed wave propagation along the wall in healthy subjects for the first time in vivo. At around the time of the Q-wave of the electrocardiogram, the propagation started from the interventricular septum and extended to both the base and apical sides of the heart with a speed of 1 m/s, which corresponds to the propagation of electrical excitation from the Purkinje fiber-myocyte junction in the interventricular septum. Other vibrations then propagated from the base at several m/s, although some of them had dispersion properties. These are shear waves caused by the mitral-valve closure, corresponding to the first heart sound. These phenomena have potential for detection of regional myocardial tissue damage related to propagation of the action potentials and regional myocardial viscoelasticity.
2008-01-01
The vibration tests of Laoshan bicycle gymnasium for the Olympic Games are performed under multi-support excitations in order to verify the effectiveness of multi-support time history method. The excitation sources come from the impact forces acting on the ring beam of the reticulated structure, on the basis of which the records of motions of each excited point and corresponding structural vibration responses are all collected. The theoretical analytical model of the structure is further established and the structural dynamic responses are obtained subjected to the same excitation case via multi-support time history method. The calculation results are generally in agreement with those of the test in both time domain and frequency domain, which verify the effectiveness of multi-support time history method. The vibration test can also provide references for long-span structures under multi-support excitations.
Wang, Dunyou; Stallcop, James R.; Dateo, Christopher E.; Schwenke, David W.; Huo, Winifred M.
2004-01-01
A three-dimensional time-dependent quantum dynamics approach using a recently developed ab initio potential energy surface is applied to study ro-vibrational excitation in N+N2 exchange scattering for collision energies in the range 2.1- 3.2 eV. State-to-state integral exchange cross sections are examined to determine the distribution of excited rotational states of N(sub 2). The results demonstrate that highly-excited rotational states are produced by exchange scattering and furthermore, that the maximum value of (Delta)j increases rapidly with increasing collision energies. Integral exchange cross sections and exchange rate constants for excitation to the lower (upsilon = 0-3) vibrational energy levels are presented as a function of the collision energy. Excited-vibrational-state distributions for temperatures at 2,000 K and 10,000 K are included.
Nonlinear Analysis of Cable Vibration of a Multispan Cable-Stayed Bridge under Transverse Excitation
Kun Lin
2014-01-01
Full Text Available The nonlinear vibrations of cable in a multispan cable-stayed bridge subjected to transverse excitation are investigated. The MECS (multielements cable system model, where multielements per cable stay are used, is built up and used to analyze the model properties of the multispan cable-stayed bridges. Then, a simplified two-degrees-of-freedom (2-DOFs model, where the tower or the deck is reduced to a beam, is proposed to analyze the nonlinear dynamic behaviors of the beam and cable. The results of MECS model analysis show that the main tower in the multispan cable-stayed bridge is prone to the transverse vibration, and the local vibration of cables only has a little impact on the frequency values of the global modes. The results of simplified model analysis show that the energy can be transformed between the modes of the beam and cable when the nature frequencies of them are very close. On the other hand, with the transverse excitation changing, the cable can exhibit richer quasi-periodic or chaotic motions due to the nonlinear terms caused by the coupled mode between the beam and cable.
Lateral Vibrations of a Cable-Stayed Bridge under Crowd Excitation
Lijun Ouyang
2015-01-01
Full Text Available A cable-stayed bridge model under crowd excitation is established in this paper by considering the geometric nonlinear property of the cables. Lateral vibrations of the model are investigated by employing the center manifold theory, and the first-order approximation solution of the periodic vibration of the bridge is derived by using the energy method. Numerical simulations are carried out to verify the validity of our analytical expressions. Our research shows that the existence of the cables can reduce the amplitude and frequency of the bridge, especially for the large amplitude case. This might explain why measured data of a cable-stayed bridge (T-bridge in Japan vibrating under crowd excitation are much less than the theoretical results reported in previous studies in which the cable-stayed bridge is viewed as a single-degree-of-freedom system. Our analysis results suggest that the structure types of footbridges should not be easily ignored in the study of pedestrian-footbridge interaction.
Effects of repeated Achilles tendon vibration on triceps surae stiffness and reflex excitability.
Lapole, Thomas; Pérot, Chantal
2011-02-01
Clinical studies frequently report an increase in stiffness and a loss of range of motion at joints placed in disuse or immobilization. This is notably the case for subjects maintained in bed for a long period, whilst their joints are not affected. Recently we documented on healthy subjects the benefit in terms of force and activation capacities of the triceps surae offered by vibrations applied to the Achilles tendon. Knowing that stiffness changes may contribute to force changes, the aim of the present study was to investigate the effects of tendon vibration on the triceps surae stiffness of healthy subjects. The vibration program consisted in 14 days of 1h daily Achilles tendon vibration applied at rest. Nineteen healthy students were involved in this study. Before and at the end of the vibration program, musculo-tendinous stiffness in active conditions was determined by use of a quick-release test. Passive stiffness was also analyzed by a flexibility test: passive torque-angle relationships were established from maximal plantar-flexion to maximal dorsiflexion. Passive stiffness indexes at 10°, 15° and 20° dorsiflexion were defined as the slope of the relationships at the corresponding angle. Tendinous reflex, influenced by stiffness values, was also investigated as well as the H reflex to obtain an index of the central reflex excitability. After the program, musculo-tendinous stiffness was significantly decreased (p=.01). At the same time, maximal passive dorsiflexion was increased (p=.005) and passive stiffness indexes at 10°, 15° and 20° dorsiflexion decreased (ptriceps surae parameters are diminished after the vibration program, it could be beneficial to immobilized persons as hypo-activity is known to increase muscular stiffness.
Daly, A. M.; Bermudez, C.; Alonso, J. L. [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Area de Quimica-Fisica, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada del CSIC, Universidad de Valladolid, E-47005 Valladolid (Spain); Lopez, A.; Tercero, B.; Cernicharo, J. [Department of Astrophysics, CAB, INTA-CSIC, Crta Torrejon, E-28850 Torrejon de Ardoz, Madrid (Spain); Pearson, J. C. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Padadena, CA 91109 (United States); Marcelino, N., E-mail: adammichael.daly@uva.es, E-mail: cbermu@qf.uva.es, E-mail: jlalonso@qf.uva.es, E-mail: lopezja@cab.inta-csic.es, E-mail: terceromb@cab.inta-csic.es, E-mail: jcernicharo@cab.inta-csic.es, E-mail: John.C.Pearson@jpl.nasa.gov, E-mail: nmarceli@nrao.edu [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
2013-05-01
Ethyl cyanide, CH{sub 3}CH{sub 2}CN, is an important interstellar molecule with a very dense rotational-vibrational spectrum. On the basis of new laboratory data in the range of 17-605 GHz and ab initio calculations, two new vibrational states, {nu}{sub 12} and {nu}{sub 20}, have been detected in molecular clouds of Orion. Laboratory data consist of Stark spectroscopy (17-110 GHz) and frequency-modulated spectrometers (GEM laboratory in Valladolid: 17-170, 270-360 GHz; Toyama: 26-200 GHz; Emory: 200-240 GHz; Ohio State: 258-368 GHz; and JPL: 270-318, 395-605 GHz). More than 700 distinct lines of each species were measured in J up to 71 and in K{sub a} up to 25. The states were fitted with Watson's S-reduction Hamiltonian. The two new states have been identified in the interstellar medium toward the Orion Nebula (Orion KL). The ground state, the isotopologues of CH{sub 3}CH{sub 2}CN, and the vibrationally excited states have been fitted to obtain column densities and to derive vibrational temperatures. All together, ethyl cyanide is responsible for more than 2000 lines in the observed frequency range of 80-280 GHz.
Laboratory spectroscopic study and astronomical detection of vibrationally excited n-propyl cyanide
Müller, Holger S P; Wehres, Nadine; Belloche, Arnaud; Wilkins, Olivia H; Liu, Delong; Vicente, Rémi; Garrod, Robin T; Menten, Karl M; Lewen, Frank; Schlemmer, Stephan
2016-01-01
We performed a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius~B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1. We determined line intensities of n-propyl cyanide in the ground vibrational states of its gauche and anti conformers toward the hot molecular core Sagittarius B2(N2) which suggest that we should also be able to detect transitions pertaining to excited vibrational states. We wanted to determine spectroscopic parameters of low-lying vibrational states of both conformers of n-propyl cyanide to search for them in our ALMA data. We recorded laboratory rotational spectra of n-propyl cyanide in two spectral windows between 36 and 127 GHz. We searched for emission lines produced by these states in the ALMA spectrum of Sagittarius B2(N2). We modeled their emission and the emission of the ground vibrational states assuming local thermodynamic equilibrium (LTE). We have made extensive assignment...
Linear stability of the Couette flow of a vibrationally excited gas. 2. viscous problem
Grigor'ev, Yu. N.; Ershov, I. V.
2016-03-01
Based on the linear theory, stability of viscous disturbances in a supersonic plane Couette flow of a vibrationally excited gas described by a system of linearized equations of two-temperature gas dynamics including shear and bulk viscosity is studied. It is demonstrated that two sets are identified in the spectrum of the problem of stability of plane waves, similar to the case of a perfect gas. One set consists of viscous acoustic modes, which asymptotically converge to even and odd inviscid acoustic modes at high Reynolds numbers. The eigenvalues from the other set have no asymptotic relationship with the inviscid problem and are characterized by large damping decrements. Two most unstable viscous acoustic modes (I and II) are identified; the limits of these modes were considered previously in the inviscid approximation. It is shown that there are domains in the space of parameters for both modes, where the presence of viscosity induces appreciable destabilization of the flow. Moreover, the growth rates of disturbances are appreciably greater than the corresponding values for the inviscid flow, while thermal excitation in the entire considered range of parameters increases the stability of the viscous flow. For a vibrationally excited gas, the critical Reynolds number as a function of the thermal nonequilibrium degree is found to be greater by 12% than for a perfect gas.
Jan Freundlich
2013-01-01
Full Text Available The paper presents vibration analysis of a simply supported beam with a fractional order viscoelastic material model. The Bernoulli-Euler beam model is considered. The beam is excited by the supports movement. The Riemann – Liouville fractional derivative of order 0 α ⩽ 1 is applied. In the first stage, the steady-state vibrations of the beam are analyzed and therefore the Riemann – Liouville fractional derivative with lower terminal at −∞ is assumed. This assumption simplifies solution of the fractional differential equations and enables us to directly obtain amplitude-frequency characteristics of the examined system. The characteristics are obtained for various values of fractional derivative of order α and values of the Voigt material model parameters. The studies show that the selection of appropriate damping coefficients and fractional derivative order of damping model enables us to fit more accurately dynamic characteristic of the beam in comparison with using integer order derivative damping model.
Three-dimensional quantum calculations on the ground and excited state vibrations of ethylene
Groenenboom, Gerrit Cornelis
Three dimensional potential energy surfaces of the ground and excited states of ethylene were calculated at the MRCEPA (Multi Reference Coupled Electronic Pair Approximation) level. The modes included are the torsion, the CC stretch, and the symmetric scissors. Full vibrational calculations were performed using the Lanczos/grid method. The avoided crossing between the V and the R state was dealt with in a diabetic model. The ground state results agree within 3 up to the highest vibrational level known experimentally. The origin and the maximum of the V back arrow N band are calculated at 5.68 and 7.82 eV, respectively, approximately 0.2 eV above the somewhat ambiguous experimental values. This work considerably diminishes the existing gap of approximately 0.5 eV between theory and experiment.
Takayanagi, Toshiyuki; Suzuki, Kento; Yoshida, Takahiko; Kita, Yukiumi; Tachikawa, Masanori
2017-05-01
We present computational results of vibrationally enhanced positron annihilation in the e+ + HCN/DCN collisions within a local complex potential model. Vibrationally elastic and inelastic cross sections and effective annihilation rates were calculated by solving a time-dependent complex-potential Schrödinger equation under the ab initio potential energy surface for the positron attached HCN molecule, [HCN; e+], with multi-component configuration interaction level (Kita and Tachikawa, 2014). We discuss the effect of vibrational excitation on the positron affinities from the obtained vibrational resonance features.
A force torsor analysis for a turning process in the presence of self-excited vibrations
Ispas, Constantin; Bisu, Claudiu-Florinel; Gérard, Alain
2009-01-01
A testing device in turning including, in particular, a six-component dynamometer, is used to measure the complete torque of the cutting actions, in a case of self-excited vibrations. For the tests, the used tool was a noncoated carbide tool (TNMA 160412) without chip breaker. The cutting material is a chrome molybdenum alloy type (ASI 4140). The cylindrical test tubes have a diameter of 120 mm and a length of 30 mm. For the first time, we present an analysis of forces and moments for different depths of cut and different feed rates.
Nonlinear Analysis of Cable Vibration of a Multispan Cable-Stayed Bridge under Transverse Excitation
Kun Lin; Dujian Zou; Minghai Wei
2014-01-01
The nonlinear vibrations of cable in a multispan cable-stayed bridge subjected to transverse excitation are investigated. The MECS (multielements cable system) model, where multielements per cable stay are used, is built up and used to analyze the model properties of the multispan cable-stayed bridges. Then, a simplified two-degrees-of-freedom (2-DOFs) model, where the tower or the deck is reduced to a beam, is proposed to analyze the nonlinear dynamic behaviors of the beam and cable. The res...
冯东太; 丁世良; 王美山
2003-01-01
The highly excited vibrational states of asymmetric linear tetratomic molecules are studied in the framework of Lie algebra. By using symmetric group U1(4) U2(4) U3(4), we construct the Hamiltonian that includes not only Casimir operators but also Majorana operators M12,M13 and M23, which are useful for getting potential energy surface and force constants in Lie algebra method. By Lie algebra treatment, we obtain the eigenvalues of the Hamiltonian, and make the concrete calculation for molecule C2HF.
Significance of the Formal Quantum Number in the Highly Excited Vibration of the DCN Molecule
郑敦胜; 吴国祯
2002-01-01
For the eigenstates of the highly excited vibration of the simple molecule DCN with two stretching modes, a classical approach in a multi-dimensional coset phase space is employed to show that the formal quantum numbers are related to regular or 1east "irregular" trajectories, with zero or least Lyapunov exponents, and are always located in the inner regions of the phase space. This property reflects that they are the approximate constants of motion. It is also demonstrated that formal quantum numbers correspond to the significant phase space density.
Bassan, M; Cavallari, G; Coccia, E; D'Antonio, S; Fafone, V; Foggetta, L G; Ligi, C; Marini, A; Mazzitelli, G; Modestino, G; Pizzella, G; Quintieri, L; Ronga, F; Valente, P; Vinko, S M
2011-01-01
We report new measurements of the acoustic excitation of an Al5056 superconductive bar when hit by an electron beam, in a previously unexplored temperature range, down to 0.35 K. These data, analyzed together with previous results of the RAP experiment obtained for T > 0.54 K, show a vibrational response enhanced by a factor 4.9 with respect to that measured in the normal state. This enhancement explains the anomalous large signals due to cosmic rays previously detected in the NAUTILUS gravitational wave detector.
杨忠志; 李慎敏; 唐敖庆
1995-01-01
By using the quasiclassical trajectory method,changes of normal and local mode vibrationalexcitation energies with time are investigated for XH4 （X=C,Si,Ge） molecules.The results demonstrate thatin a CH4 molecule the coupling between C—H stretching vibration and H—C—H bending vibration is relative-ly large so that the energy transfer is fast;while in SiH4 or GeH4 molecules this coupling is relativelysmall and thus an obvious energy relaxation is observed.This implies that there exists approximate local modevibrations for certain vibrational excitation states.
Duque, H V; Chiari, L; Jones, D B; Pettifer, Z; da Silva, G B; Limão-Vieira, P; Blanco, F; García, G; White, R D; Lopes, M C A; Brunger, M J
2014-06-01
Differential and integral cross section measurements, for incident electron energies in the 20-50 eV range, are reported for excitation of several composite vibrational modes in α-tetrahydrofurfuryl alcohol (THFA). Optimisation and frequency calculations, using GAUSSIAN 09 at the B3LYP/aug-cc-pVDZ level, were also undertaken for the two most abundant conformers of THFA, with results being reported for their respective mode classifications and excitation energies. Those calculations assisted us in the experimental assignments of the composite features observed in our measured energy loss spectra. There are, to the best of our knowledge, no other experimental or theoretical data currently available in the literature against which we can compare the present results.
Bainbridge, A. R.; Harrington, J.; Kirrander, A.; Cacho, C.; Springate, E.; Bryan, W. A.; Minns, R. S.
2015-10-01
Femtosecond vacuum ultraviolet pulses from a monochromated high harmonic generation source excite vibrational wavepackets in the {B}1{{{Σ }}}{{g}}+ state of D2. The wavepacket motion is measured through strong field ionization into bound and dissociative ion states yielding {{{D}}}2+ and D+ products. The time dependence of the {{{D}}}2+ and D+ ion signals provides a sensitive fingerprint of the quantum nuclear wavepacket, due to the different ionization rates for the two channels. The experiments are modelled with excitation and ionization processes included explicitly, with the results of the model showing a very good agreement with the experimental observations. The experiment demonstrates the level of detail attainable when studying ultrafast quantum nuclear dynamics using high harmonic sources.
Neves, R. F. C. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Instituto Federal do Sul de Minas Gerais, Campus Poços de Caldas, Minas Gerais (Brazil); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Blanco, F. [Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, 28040 Madrid (Spain); García, G. [Instituto de Física Fundamental, CSIC, Serrano 113-bis, 28006 Madrid (Spain); Ratnavelu, K. [Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); Brunger, M. J., E-mail: Michael.Brunger@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2015-05-21
We report on measurements of integral cross sections (ICSs) for electron impact excitation of a series of composite vibrational modes and electronic-states in phenol, where the energy range of those experiments was 15–250 eV. There are currently no other results against which we can directly compare those measured data. We also report results from our independent atom model with screened additivity rule correction computations, namely, for the inelastic ICS (all discrete electronic states and neutral dissociation) and the total ionisation ICS. In addition, for the relevant dipole-allowed excited electronic states, we also report f-scaled Born-level and energy-corrected and f-scaled Born-level (BEf-scaled) ICS. Where possible, our measured and calculated ICSs are compared against one another with the general level of accord between them being satisfactory to within the measurement uncertainties.
Damage detection in composite structures using vibration response under stochastic excitation
Yang, Zhichun; Wang, Le; Wang, Hui; Ding, Yan; Dang, Xiaojuan
2009-09-01
The investigations in damage detection methods based on vibration response are reviewed according to two categories, i.e. model-based damage detection method (MBDDM) and non-model-based damage detection method (NMBDDM). Then a new concept of inner product vector (IPV) is introduced using the cross correlation function of the measured vibration responses of the structure, and the corresponding damage detection method is proposed based on this vector. It is theoretically proved that the elements in IPV of a structure is the inner product of the time domain vibration responses of corresponding measurement points, and this vector can be directly calculated using the measured time domain vibration responses. Under white noise excitation the IPV of a structure is a weighted summation of mode shapes of the structure, and the weighted factors of the summation only depend on modal parameters of the structure. The effect of measurement noise on IPV is also considered, and the effect can be eliminated by the definition of IPV and an interpolation technique. The difference of IPVs between the intact and damaged structure is adopted as the damage index, and damage location is determined by the abrupt change in the difference of IPV. In order to distinguish the abrupt change caused by structural damage and measurement noise, two thresholds are proposed to classify the damaged and intact structures. Numerical simulation results of damage detection of single-location and multi-location delamination in a composite laminate beam demonstrate the effectiveness and veracity of the proposed method, even though measurement noise is considered in the vibration responses.
Le, Thanh Danh; Ahn, Kyoung Kwan
2011-12-01
This paper designs and fabricates a vibration isolation model for improving vibration isolation effectiveness of the vehicle seat under low excitation frequencies. The feature of the proposed system is to use two symmetric negative stiffness structures (NSS) in parallel to a positive stiffness structure. Here, theoretical analysis of the proposed system is clearly presented. Then, the design procedure is derived so that the resonance peak of frequency-response curve drifts to the left, the load support capacity of the system is maintained, the total size of the system is reduced for easy practical application and especially, the bending of the frequency-response curve is minimized. Next the dynamic equation of the proposed system is set up. Then, the harmonic balance (HB) method is employed to seek the characteristic of the motion transmissibility of the proposed system at the steady state for each of the excitation frequency. From this characteristic, the curves of the motion transmission are predicted according to the various values of the configurative parameters of the system. Then, the time responses to the sinusoidal, multi frequency and random excitations are also investigated by simulation and experiment. In addition, the isolation performance comparison between the system with NSS and system without NSS is realized. The simulation results reveal that the proposed system has larger frequency region of isolation than that of the system without NSS. The experimental results confirm also that with a random excitation mainly spreading from 0.1 to 10 Hz, the isolation performance of the system with NSS is greatly improved, where the RMS values of the mass displacement may be reduced to 67.2%, whereas the isolation performance of the system without NSS is bad. Besides, the stability of the steady-state response is also studied. Finally, some conclusions are given.
A novel torsional exciter for modal vibration testing of large rotating machinery
Sihler, Christof
2006-10-01
A novel exciter for applying a dynamic torsional force to a rotating structure is presented in this paper. It has been developed at IPP in order to perform vibration tests with shaft assemblies of large flywheel generators (synchronous machines). The electromagnetic exciter (shaker) needs no fixture to the rotating shaft because the torque is applied by means of the stator winding of an electrical machine. Therefore, the exciter can most easily be applied in cases where a three-phase electrical machine (a motor or generator) is part of the shaft assembly. The oscillating power for the shaker is generated in a separate current-controlled DC circuit with an inductor acting as a buffer storage of magnetic energy. An AC component with adjustable frequency is superimposed on the inductor current in order to generate pulsating torques acting on the rotating shaft with the desired waveform and frequency. Since this torsional exciter does not require an external power source, can easily be installed (without contact to the rotating structure) and provides dynamic torsional forces which are sufficient for multi-megawatt applications, it is best suited for on-site tests of large rotating machinery.
Excited superdeformed Kπ=0+ rotational bands in /β-vibrational fission resonances of 240Pu
Hunyadi, M.; Gassmann, D.; Krasznahorkay, A.; Habs, D.; Thirolf, P. G.; Csatlós, M.; Eisermann, Y.; Faestermann, T.; Graw, G.; Gulyás, J.; Hertenberger, R.; Maier, H. J.; Máté, Z.; Metz, A.; Chromik, M. J.
2001-04-01
The intermediate structure of fission resonances of 240Pu was observed with an experimental energy resolution of 7 keV in the excitation energy region of E*=3.8-5.6 MeV using the 239Pu(d,pf)240Pu reaction. Two-vibrational resonance groups centered at E*=4.6 MeV and 5.1 MeV, and attributed to the excitation of three and four /β-phonons, were resolved into individual substates, which could be assigned to the low-spin members of Kπ=0+ superdeformed (SD) rotational bands. In the region of the lower E*=4.6 MeV resonance individual moments of inertia of six well separated bands could be extracted for the first time with values of Θ/ℏ2 around 157 MeV-1, close to that of the ground state band in the second well. From the level density of these Kπ=0+ band heads the excitation energy of the SD ground state was determined to (/2.25+/-0.20) MeV, in agreement with earlier estimates from excitation functions.
Equalization equations in reactant resolution
Jacek Korchowiec
2005-09-01
The chemical system can be analyzed in different resolutions. The assumed resolution imposes a given partitioning of the system in physical or functional space. The most frequently explored are global, reactant, atoms-in-molecule, orbital, and local resolutions. In this paper we have considered reactant resolution, i.e., the mutually polarized reactants before the charge-transfer among them. We have demonstrated that a certain type of generalized sensitivity, the system responses to the population variables, is equalized throughout the space up to the infinite order in the perturbation expansion.
Xueqian, Chen; Zhanpeng, Shen; Qinshu, He; Qiang, Du; Xin'en, Liu
2016-09-01
Rubber isolators are widely used in engineering structures, which often exhibit some nonlinearity and uncertainty properties subjected to different environment exciting. In order to study the nonlinear characteristic and uncertainty of a rubber isolator system, the sin-sweep vibration tests with different base exciting level are carried out firstly. Then a single freedom degree mass-spring-damper model is introduced to simplify the rubber isolator system. In the theory model, the spring and the damper are represented by polynomial functions of the relative displacement. The coefficients in the functions are identified by the test data, while the uncertainties of the coefficients are quantified by the principal components analysis (PCA) and Monte Carlo (MC) simulations. The major resonant frequencies and the damping ratios of the isolation system are calculated according to the theory model, the amplitude-frequency nonlinear characteristics are simulated by Runge-Kutta numerical method. The simulation results agree well with the experimental results, which indicate that the nonlinear model and the uncertainty quantifying results are feasible to predict the vibration characteristic and uncertainty of the isolation systems.
Single- and multi-phonon excitations of $\\gamma$ vibration in rotating odd-$A$ nuclei
Matsuzaki, Masayuki
2014-01-01
Collective motions in quantum many-body systems are described as bosonic excitations. Multi-phonon excitations in atomic nuclei, however, were observed very rarely. In particular, the first two-phonon \\gamma vibration (2\\gamma) in odd-A nuclei was reported in 2006 and only a few have been known. Two theoretical calculations for the data on Nb103 were done, one of which was done by the present author within a limited model space. Quite recently, conspicuously enhanced B(E2) feeding the 2\\gamma were observed in Nb105 and conjectured that their mother states are candidates of 3\\gamma. In the present work, the model space is enlarged up to 4\\gamma states. The purposes are two-folds: One is to see how the description in the previous work is improved, and the other is to look into the existence of 3\\gamma states, and when they exist, study their collectivity through calculating interband B(E2). The particle-vibration coupling model based on the cranking model and the random-phase approximation is used to calculate ...
Possible interaction between thermal electrons and vibrationally excited N2 in the lower E-region
C. Z. Cheng
2011-03-01
Full Text Available As one of the tasks to find the energy source(s of thermal electrons, which elevate(s electron temperature higher than neutral temperature in the lower ionosphere E-region, energy distribution function of thermal electron was measured with a sounding rocket at the heights of 93–131 km by the applying second harmonic method. The energy distribution function showed a clear hump at the energy of ~0.4 eV. In order to find the reason of the hump, we conducted laboratory experiment. We studied difference of the energy distribution functions of electrons in thermal energy range, which were measured with and without EUV radiation to plasma of N2/Ar and N2/O2 gas mixture respectively. For N2/Ar gas mixture plasma, the hump is not clearly identified in the energy distribution of thermal electrons. On the other hand for N2/O2 gas mixture, which contains vibrationally excited N2, a clear hump is found when irradiated by EUV. The laboratory experiment seems to suggest that the hump is produced as a result of interaction between vibrationally excited N2 and thermal electrons, and this interaction is the most probable heating source for the electrons of thermal energy range in the lower E-region. It is also suggested that energy distribution of the electrons in high energy part may not be Maxwellian, and DC probe measures the electrons which are non Maxwellian, and therefore "electron temperature" is calculated higher.
Intermediate energy cross sections for electron-impact vibrational-excitation of pyrimidine
Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Ellis-Gibbings, L.; García, G. [Instituto de Física Fundamental, CSIC, Serrano 113-bis, 28006 Madrid (Spain); Nixon, K. L. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); School of Biology, Chemistry and Forensic Science, University of Wolverhampton, Wolverhampton WV1 1LY (United Kingdom); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Brunger, M. J., E-mail: Michael.Brunger@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2015-09-07
We report differential cross sections (DCSs) and integral cross sections (ICSs) for electron-impact vibrational-excitation of pyrimidine, at incident electron energies in the range 15–50 eV. The scattered electron angular range for the DCS measurements was 15°–90°. The measurements at the DCS-level are the first to be reported for vibrational-excitation in pyrimidine via electron impact, while for the ICS we extend the results from the only previous condensed-phase study [P. L. Levesque, M. Michaud, and L. Sanche, J. Chem. Phys. 122, 094701 (2005)], for electron energies ⩽12 eV, to higher energies. Interestingly, the trend in the magnitude of the lower energy condensed-phase ICSs is much smaller when compared to the corresponding gas phase results. As there is no evidence for the existence of any shape-resonances, in the available pyrimidine total cross sections [Baek et al., Phys. Rev. A 88, 032702 (2013); Fuss et al., ibid. 88, 042702 (2013)], between 10 and 20 eV, this mismatch in absolute magnitude between the condensed-phase and gas-phase ICSs might be indicative for collective-behaviour effects in the condensed-phase results.
Trajectory study of supercollision relaxation in highly vibrationally excited pyrazine and CO2.
Li, Ziman; Sansom, Rebecca; Bonella, Sara; Coker, David F; Mullin, Amy S
2005-09-01
Classical trajectory calculations were performed to simulate state-resolved energy transfer experiments of highly vibrationally excited pyrazine (E(vib) = 37,900 cm(-1)) and CO(2), which were conducted using a high-resolution transient infrared absorption spectrometer. The goal here is to use classical trajectories to simulate the supercollision energy transfer pathway wherein large amounts of energy are transferred in single collisions in order to compare with experimental results. In the trajectory calculations, Newton's laws of motion are used for the molecular motion, isolated molecules are treated as collections of harmonic oscillators, and intermolecular potentials are formed by pairwise Lennard-Jones potentials. The calculations qualitatively reproduce the observed energy partitioning in the scattered CO(2) molecules and show that the relative partitioning between bath rotation and translation is dependent on the moment of inertia of the bath molecule. The simulations show that the low-frequency modes of the vibrationally excited pyrazine contribute most to the strong collisions. The majority of collisions lead to small DeltaE values and primarily involve single encounters between the energy donor and acceptor. The large DeltaE exchanges result from both single impulsive encounters and chattering collisions that involve multiple encounters.
Marinov, Daniil; Guerra, Vasco; Guaitella, Olivier; Booth, Jean-Paul; Rousseau, Antoine
2013-10-01
A combined experimental and modeling investigation of the ozone kinetics in the afterglow of pulsed direct current discharges in oxygen is carried out. The discharge is generated in a cylindrical silica tube of radius 1 cm, with short pulse durations between 0.5 and 2 ms, pressures in the range 1-5 Torr and discharge currents ˜40-120 mA. Time-resolved absolute concentrations of ground-state atoms and ozone molecules were measured simultaneously in situ, by two-photon absorption laser-induced fluorescence and ultraviolet absorption, respectively. The experiments were complemented by a self-consistent model developed to interpret the results and, in particular, to evaluate the roles of vibrationally excited ozone and of ozone formation on surfaces. It is found that vibrationally excited ozone, O_3^{*} , plays an important role in the ozone kinetics, leading to a decrease in the ozone concentration and an increase in its formation time. In turn, the kinetics of O_3^{*} is strongly coupled with those of atomic oxygen and O2(a 1Δg) metastables. Ozone formation at the wall does not contribute significantly to the total ozone production under the present conditions. Upper limits for the effective heterogeneous recombination probability of O atoms into ozone are established.
Piezoelectric Shunt Vibration Damping of F-15 Panel under High Acoustic Excitation
Wu, Shu-Yau; Turner, Travis L.; Rizzi, Stephen A.
2000-01-01
At last year's SPIE symposium, we reported results of an experiment on structural vibration damping of an F-15 underbelly panel using piezoelectric shunting with five bonded PZT transducers. The panel vibration was induced with an acoustic speaker at an overall sound pressure level (OASPL) of about 90 dB. Amplitude reductions of 13.45 and 10.72 dB were achieved for the first and second modes, respectively, using single- and multiple-mode shunting. It is the purpose of this investigation to extend the passive piezoelectric shunt-damping technique to control structural vibration induced at higher acoustic excitation levels, and to examine the controllability and survivability of the bonded PZT transducers at these high levels. The shunting experiment was performed with the Thermal Acoustic Fatigue Apparatus (TAFA) at the NASA Langley Research Center using the same F-15 underbelly panel. The TAFA is a progressive wave tube facility. The panel was mounted in one wall of the TAFA test section using a specially designed mounting fixture such that the panel was subjected to grazing-incidence acoustic excitation. Five PZT transducers were used with two shunt circuits designed to control the first and second modes of the structure between 200 and 400 Hz. We first determined the values of the shunt inductance and resistance at an OASPL of 130 dB. These values were maintained while we gradually increased the OASPL from 130 to 154 dB in 6-dB steps. During each increment, the frequency response function between accelerometers on the panel and the acoustic excitation measured by microphones, before and after shunting, were recorded. Good response reduction was observed up to the 148dB level. The experiment was stopped at 154 dB due to wire breakage from vibration at a transducer wire joint. The PZT transducers, however, were still bonded well on the panel and survived at this high dB level. We also observed shifting of the frequency peaks toward lower frequency when the OASPL
Global Dynamic Characteristic of Nonlinear Torsional Vibration System under Harmonically Excitation
SHI Peiming; LIU Bin; HOU Dongxiao
2009-01-01
Torsional vibration generally causes serious instability and damage problems in many rotating machinery parts. The global dynamic characteristic of nonlinear torsional vibration system with nonlinear rigidity and nonlinear friction force is investigated. On the basis of the generalized dissipation Lagrange's equation, the dynamics equation of nonlinear torsional vibration system is deduced. The bifurcation and chaotic motion in the system subjected to an external harmonic excitation is studied by theoretical analysis and numerical simulation. The stability of unperturbed system is analyzed by using the stability theory of equilibrium positions of Hamiltonian systems. The criterion of existence of chaos phenomena under a periodic perturbation is given by means of Melnikov's method. It is shown that the existence of homoclinic and heteroclinic orbits in the unperturbed system implies chaos arising from breaking of homoclinic or heteroclinic orbits under perturbation. The validity of the result is checked numerically. Periodic doubling bifurcation route to chaos, quasi-periodic route to chaos, intermittency route to chaos are found to occur due to the amplitude varying in some range. The evolution of system dynamic responses is demonstrated in detail by Poincare maps and bifurcation diagrams when the system undergoes a sequence of periodic doubling or quasi-periodic bifurcations to chaos. The conclusion can provide reference for deeply researching the dynamic behavior of mechanical drive systems.
Excitation of the lowest CO2 vibrational states by electrons in hypersonic boundary layers
Armenise, I.
2017-07-01
The state-to-state vibrational kinetics of a CO2/O2/CO/C/O/e- mixture in a hypersonic boundary layer under conditions compatible with the Mars re-entry is studied. The model adopted treats three CO2 modes (the two degenerated bending modes are approximated as a unique one) as not independent ones. Vibrational-translational transitions in the bending mode, inter-mode exchanges within CO2 molecule and between molecules of different chemical species as well as dissociation-recombination reactions are considered. Attention is paid to the electron-CO2 collisions that cause transitions from the ground vibrational state, CO2(0,0,0), to the first excited ones, CO2(1,0,0), CO2(0,1,0) and CO2(0,0,1). The corresponding processes rate coefficients are obtained starting from the electron energy distribution function, calculated either as an equilibrium Boltzmann distribution at the local temperature or by solving the Boltzmann equation. Results obtained either neglecting or including in the kinetic scheme the electron-CO2 collisions are compared and explained by analysing the rate coefficients of the electron-CO2 collisions.
He, Xiping; Yao, Jing; Zhang, Haidao; Liu, Doudou; Li, Jiaxing
2015-04-01
The flexural vibration characteristics of a rectangular plate in stripe mode, driven at its center by a different longitudinal vibration ultrasonic transducer (LVUT) with different excitation area are investigated. The variation in the nodal lines and corresponding resonant frequency of the rectangular plate under different excitation area are calculated by using finite element method (FEM). The results show that the resonant frequency increases with the excitation area of the LVUT increasing, and the nodal lines bend obviously when the radius r of excitation area is greater than a certain value. The experimental tests are carried out by the aid of Polytec PSV-400 Scanning laser Vibrometer, and the results agree well those of numerically calculated. It indicates that the larger excitation area of longitudinal transducer may affect the ultrasonic field radiated by the rectangular plate.
Vibrational relaxation of hydrogen fluoride by HF dimers in a laser excited nozzle beam
Knuth, E.L.; Rubahn, H.; Toennies, J.P.; Wanner, J.
1986-09-01
An HF nozzle beam and a cw HF laser beam in a coaxial and antiparallel arrangement facilitated exciting HF molecules vibrationally in v-italic = 1,J-italic up to the saturation limit. A beam consisting exclusively of monomeric HF was generated by heating the beam source to 600 K and was confirmed using a mass spectrometer. Energy-flux measurements made using a bolometer indicate that the vibrational energy distribution initiated by the laser is conserved, confirming that V--T energy transfer to monomers is slow. The maximum measured flux of HF(v-italic = 1,J-italic) molecules was 1.5 x 10/sup 17/ molecules s/sup -1/ sr/sup -1/ at 670 mbar stagnation pressure. Beams consisting of a mixture of monomeric and polymeric HF were generated using appropriate combinations of source temperature and pressure. In the presence of dimers, the excited monomers relax rapidly by a fast V--V transfer and subsequent predissociation of the metastable dimers. The loss of beam energy due to energy transport by the departing dimer fragments was detected bolometrically. The laser-induced depletion of dimers was determined over a wide source pressure range at T-italic/sub 0/ = 300 K using a mass spectrometer. From a kinetic model of these dimer-depletion data, the product of cross section and transfer probability for V--V energy transfer from HF (v-italic = 1) monomers to dimers was deduced to be 14 A-circle/sup 2/. The terminal-dimer-concentration equation for HF nozzle beams was refined. An analysis of the energy fluxes measured by the bolometer with no laser excitation of the beam revealed that, for an HF nozzle beam, the flow from the source to the detector is, in general, nonisenthalpic due to the onset of dimerization. Mach-number focusing enriches the dimer mole fractions detected by the bolometer.
Chamon, L.C., E-mail: luiz.chamon@dfn.if.usp.b [Departamento de Fisica Nuclear, Instituto de Fisica da Universidade de Sao Paulo, Caixa Postal 66318, 05315-970, Sao Paulo, SP (Brazil); Carlson, B.V. [Departamento de Fisica, Instituto Tecnologico de Aeronautica, Centro Tecnico Aeroespacial, Sao Jose dos Campos, SP (Brazil)
2010-11-30
We present a large-scale systematics of charge densities, excitation energies and deformation parameters for hundreds of heavy nuclei. The systematics is based on a generalized rotation-vibration model for the quadrupole and octupole modes and takes into account second-order contributions of the deformations as well as the effects of finite diffuseness values for the nuclear densities. We compare our results with the predictions of classical surface vibrations in the hydrodynamical approximation.
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
Ro-vibrational excitation of an organic molecule (HCN) in protoplanetary disks
Bruderer, Simon; van Dishoeck, Ewine F
2014-01-01
(Abridged) Organic molecules are important constituents of protoplanetary disks. Their ro-vibrational lines observed in the near- and mid-infrared are commonly detected toward T Tauri disks. These lines are the only way to probe the chemistry in the inner few au where terrestrial planets form. To understand this chemistry, accurate molecular abundances have to be determined. This is complicated by excitation effects. Most analyses so far have made the assumption of local thermal equilibrium (LTE). Starting from estimates for the collisional rate coefficients of HCN, non-LTE slab models of the HCN emission were calculated to study the importance of different excitation mechanisms. Using a new radiative transfer model, the HCN emission from a full two-dimensional disk was then modeled to study the effect of the non-LTE excitation, together with the line formation. We ran models tailored to the T Tauri disk AS 205 (N) where HCN lines in both the 3 {\\mu}m and 14 {\\mu}m bands have been observed by VLT-CRIRES and t...
López, A; Kisiel, Z; Daly, A M; Bermúdez, C; Calcutt, H; Marcelino, N; Viti, S; Drouin, B J; Medvedev, I R; Neese, C F; Pszczółkowski, L; Alonso, J L; Cernicharo, J
2014-01-01
New laboratory data of CH$_2$CHCN (vinyl cyanide) in its ground and vibrationally excited states at the microwave to THz domain allow searching for these excited state transitions in the Orion-KL line survey. Frequency-modulated spectrometers combined into a single broadband 50-1900 GHz spectrum provided measurements of CH$_2$CHCN covering a spectral range of 18-1893 GHz, whose assignments was confirmed by Stark modulation spectra in the 18-40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of CH$_2$CHCN species detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The total column density of CH$_2$CHCN in the ground state is (3.0$\\pm$0.9)x10$^{15}$ cm$^{-2}$. We report on the first interstellar ...
Yan-Lei Zhang
2016-01-01
Full Text Available Nonlinear vibration of a fluid-conveying pipe subjected to a transverse external harmonic excitation is investigated in the case with two-to-one internal resonance. The excitation amplitude is in the same magnitude of the transverse displacement. The fluid in the pipes flows in the speed larger than the critical speed so that the straight configuration becomes an unstable equilibrium and two curved configurations bifurcate as stable equilibriums. The motion measured from each of curved equilibrium configurations is governed by a nonlinear integro-partial-differential equation with variable coefficients. The Galerkin method is employed to discretize the governing equation into a gyroscopic system consisting of a set of coupled nonlinear ordinary differential equations. The method of multiple scales is applied to analyze approximately the gyroscopic system. A set of first-order ordinary differential equations governing the modulations of the amplitude and the phase are derived via the method. In the supercritical regime, the subharmonic, superharmonic, and combination resonances are examined in the presence of the 2 : 1 internal resonance. The steady-state responses and their stabilities are determined. The various jump phenomena in the amplitude-frequency response curves are demonstrated. The effects of the viscosity, the excitation amplitude, the nonlinearity, and the flow speed are observed. The analytical results are supported by the numerical integration.
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.
Multi-modal vibration amplitudes of taut inclined cables due to direct and/or parametric excitation
Macdonald, J. H. G.
2016-02-01
Cables are often prone to potentially damaging large amplitude vibrations. The dynamic excitation may be from external loading or motion of the cable ends, the latter including direct excitation, normally from components of end motion transverse to the cable, and parametric excitation induced by axial components of end motion causing dynamic tension variations. Geometric nonlinearity can be important, causing stiffening behaviour and nonlinear modal coupling. Previous analyses of the vibrations, often neglecting sag, have generally dealt with direct and parametric excitation separately or have reverted to numerical solutions of the responses. Here a nonlinear cable model is adopted, applicable to taut cables such as on cable-stayed bridges, that allows for cable inclination, small sag (such that the vibration modes are similar to those of a taut string), multiple modes in both planes and end motion and/or external forcing close to any natural frequency. Based on the method of scaling and averaging it is found that, for sinusoidal inputs and positive damping, non-zero steady state responses can only occur in the modes in each plane with natural frequencies close to the excitation frequency and those with natural frequencies close to half this frequency. Analytical solutions, in the form of non-dimensional polynomial equations, are derived for the steady state vibration amplitudes in up to three modes simultaneously: the directly excited mode, the corresponding nonlinearly coupled mode in the orthogonal plane and a parametrically excited mode with half the natural frequency. The stability of the solutions is also identified. The outputs of the equations are consistent with previous results, where available. Example results from the analytical solutions are presented for a typical inclined bridge cable subject to vertical excitation of the lower end, and they are validated by numerical integration of the equations of motion and against some previous experimental
Self-Excited Vibrations in Turning: Efforts Torsor and Average Friction Coefficient Analysis
Gérard, Alain; Zapciu, Miron
2009-01-01
An experimental device in turning including, in particular, a six-component dynamometer is exploited to measure the complete torque of cutting forces in a case of self-excited vibrations. For the tests, the tool used is type TNMA 16 04 12 carbide not covered (nuance carbide-SUMITIMO ELECTRIC), without chip breeze. The machined material is an alloy of chrome molybdenum type 42 CrMo24. The test-tubes are cylindrical with a diameter of 120 mm and a length of 30 mm. The effort of analysis relates to the moments. In particular, to the tool tip point, when feed rate increases the friction coefficient of swivelling is increasing while that of bearing is decreasing. Innovative remarks on the evolution of the average friction coefficient for various depths of cut and feed rate are presented
O Faolain, Eoghan; Hunter, Mary B.; Byrne, Joe M.; Kelehan, Peter; Byrne, Hugh J.; Lyng, Fiona M.
2005-06-01
The application of vibrational spectroscopy to disease diagnosis is a relatively new, rapidly evolving scientific field. Techniques such as Raman and infrared spectroscopy have shown great promise in this regard over the past number of years. This study directly compared Raman spectroscopy and synchrotron infrared (SR-IR) spectroscopy on parallel cervical cancer samples. Both frozen and dewaxed formalin fixed paraffin preserved tissue sections were examined. Both tissue types produced good quality Raman and SR-IR spectra, although the lesser processed, frozen tissue sections displayed the most detailed spectra. Spectroscopy was shown capable of discriminating between different cell types in normal cervical tissue. Spectra recorded from invasive carcinoma showed a marked difference from those recorded from normal cervical epithelial cells. Spectral differences identified with the onset of carcinogenesis include increased nucleic acid contributions and decreased glycogen levels. These investigations pave the way for an enlarged study into this exciting new diagnostic field.
Fast and slow dynamics in a nonlinear elastic bar excited by longitudinal vibrations
Favrie, Nicolas; Payan, Cédric
2014-01-01
Heterogeneous materials, such as rocks and concrete, have a complex dynamics including hysteresis, nonlinear elasticity and viscoelasticity. It is very sensitive to microstructural changes and damage. The goal of this paper is to propose a physical model describing the longitudinal vibrations of this class of material, and to develop a numerical strategy for solving the evolution equations. The theory relies on the coupling between two processes with radically-different time scales: a fast process at the frequency of the excitation, governed by nonlinear elasticity and viscoelasticity; a slow process, governed by the evolution of defects. The evolution equations are written as a nonlinear hyperbolic system with relaxation. A time-domain numerical scheme is developed, based on a splitting strategy. The numerical simulations show qualitative agreement with the features observed experimentally by Dynamic Acousto-Elastic Testing.
On the O2(a1Δ) quenching by vibrationally excited ozone
Azyazov, V. N.; Mikheyev, P. A.; Heaven, M. C.
2010-09-01
The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen (O2(a)) in electric discharge. It is important to understand the mechanisms by which O2(a) is quenched in these devices. To gain understanding of this mechanisms quenching of O2(a) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a) quenching were followed by observing the 1268 nm fluorescence of the O2 a --> X transition. Fast quenching of O2(a) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.
Asymptotic theory of neutral stability curve of the Couette flow of vibrationally excited gas
Grigor'ev, Yu N.; Ershov, I. V.
2016-06-01
The asymptotic theory of neutral stability curve of the supersonic plane Couette flow of vibrationally excited gas is constructed. The system of two-temperature viscous gas dynamics equations was used as original mathematical model. Spectral problem for an eighth order linear system of ordinary differential equations was obtained from the system within framework of classical theory of linear stability. Transformations of the spectral problem universal for all shear flows were carried along the classical Dunn — Lin scheme. As a result the problem was reduced to secular algebraic equation with a characteristic division on “inviscid” and “viscous” parts which was solved numerically. The calculated neutral stability curves coincide in limits of 10% with corresponding results of direct numerical solution of original spectral problem.
Panchenko, Yurii N.
2013-06-01
The shifts of the molecular vibrational frequencies when going from the ground electronic state to the lowest excited electronic states pose some problems for the mutual co-assignment of the calculated vibrational frequencies in the different excited states. The trans-{C_2 O_2 F_2} shift of the frequency of the symmetrical ν(C=O) stretching vibration between the S_0 and T_1 is 373 wn. The feasibility of mutual co-assignments of the vibrational frequencies in these electronic states has been demonstrated for trans-{C_2 O_2 F_2}. Matrices analogous to the Duschinsky matrix were used to juxtapose the a_g vibrational frequencies of this molecule calculated at the CASPT2/cc-pVTZ level in the ground S_0 and excited triplet T_1 and singlet S_1 electronic states. The analog of the Duschinsky matrix D was obtained for this molecule using the equation D = (L_{I})^{-1} L_{II} where L_{I} and L_{II} are the matrices of the vibrational modes (normalized atomic displacements) obtained by solving the vibrational problems for the S_0 and T_1 electronic states, respectively. Choosing the dominant elements in columns of the D matrix and permuting these columns to arrange these elements along the diagonal of the transformed matrix D^* makes it possible to establish the correct mutual co-assignments of the calculated a_g vibrational frequencies of the trans-{C_2 O_2 F_2} molecule in the S_0 and T_1 electronic states. The analogous procedure was performed for the trans-{C_2 O_2 F_2} molecule in the T_1 and S_1 excited electronic states. The recent reassignments of the νb{2} and νb{3} calculated vibrational frequencies in the trans-{C_2 O_2 F_2} molecule in the ground state were also obtained for the triplet T_1 and singlet S_1 excited electronic states. The approach set forth in this text makes it possible to juxtapose the calculated vibrational frequencies of the same molecule in the different electronic states and to refine the assignments of these frequencies. This is essential
Dasch, C.J.
1978-09-01
Single rovibrational states of HCl(v=2), HBr(v=2), DCl(v=2), and CO(v=2) were excited with a pulsed optical parametric oscillator (OPO). Total vibrational relaxation rates near - resonance quenchers were measured at 295/sup 0/K using time resolved infrared fluorescence. These rates are attributed primarily to V - V energy transfer, and they generally conform to a simple energy gap law. A small deviation was found for the CO(v) + DCl(v') relaxation rates. Upper limits for the self relaxation by V - R,T of HCl(v=2) and HBr(v=2) and for the two quantum exchange between HCl and HBr were determined. The HF dimer was detected at 295/sup 0/K and 30 torr HF pressure with an optoacoustic spectrometer using the OPO. Pulsed and chopped, resonant and non-resonant spectrophones are analyzed in detail. From experiments and first order perturbation theory, these V - V exchange rates appear to behave as a first order perturbation in the vibrational coordinates. The rotational dynamics are known to be complicated however, and the coupled rotational - vibrational dynamics were investigated theoreticaly in infinite order by the Dillon and Stephenson and the first Magnus approximations. Large ..delta..J transitions appear to be important, but these calculations differ by orders of magnitude on specific rovibrational transition rates. Integration of the time dependent semiclassical equations by a modified Gordon method and a rotationally distorted wave approximation are discussed as methods which would treat the rotational motion more accurately. 225 references.
Parametric vibrations of a restrained beam with an end mass under displacement excitation
Gürgöze, M.
1986-07-01
This paper is concerned with the stability and the steady state response of the main parametric resonance vibrations of a simply supported vertical beam. The beam carries a concentrated mass and is restrained at one end and subjected to a periodic axial displacement excitation at the other end. This system can be looked upon as a dynamic model of the vibrations of an engine valve mechanism. Non-linear terms arising from moderately large curvatures, longitudinal inertia of the beam elements and concentrated mass are included in the equation of motion. By using the one mode approximation and applying Galerkin's method, the governing partial differential equation is reduced to a non-linear ordinary differential equation with a periodic coefficient. The boundaries of the main parametric instability region of the linearized equation are obtained. The harmonic balance method is applied to solve the equation and an analytical expression for the dynamic response in the vicinity of the main parametric resonance is derived. The effects of various parameters on the boundaries of the instability region and the dynamic response are investigated.
Nonlinear TeraHertz Coherent Excitation of Vibrational Modes of Liquids
Allodi, Marco A; Blake, Geoffrey A
2015-01-01
We report the first coherent excitation of intramolecular vibrational modes via the nonlinear interaction of a TeraHertz (THz) light field with molecular liquids. A TeraHertz-TeraHertz-Raman pulse sequence prepares the coherences with a broadband, high-energy, (sub)picosecond TeraHertz pulse, that are then measured in a TeraHertz Kerr effect spectrometer via phase-sensitive, heterodyne detection with an optical pulse. The spectrometer reported here has broader TeraHertz frequency coverage and an increased sensitivity relative to previously reported TeraHertz Kerr effect experiments. Vibrational coherences are observed in liquid diiodomethane at 3.66 THz (122 cm$^{-1}$), and in carbon tetrachloride at 6.50 THz (217 cm$^{-1}$), in exact agreement with literature values of those intramolecular modes. This work opens the door to 2D spectroscopies, nonlinear in TeraHertz field, that can study the dynamics of condensed-phase molecular systems, as well as coherent control at TeraHertz frequencies.
An Experimental Validated Control Strategy of Maglev Vehicle-Bridge Self-Excited Vibration
Lianchun Wang
2017-01-01
Full Text Available This study discusses an experimentally validated control strategy of maglev vehicle-bridge vibration, which degrades the stability of the suspension control, deteriorates the ride comfort, and limits the cost of the magnetic levitation system. First, a comparison between the current-loop and magnetic flux feedback is carried out and a minimum model including flexible bridge and electromagnetic levitation system is proposed. Then, advantages and disadvantages of the traditional feedback architecture with the displacement feedback of electromagnet yE and bridge yB in pairs are explored. The results indicate that removing the feedback of the bridge’s displacement yB from the pairs (yE − yB measured by the eddy-current sensor is beneficial for the passivity of the levitation system and the control of the self-excited vibration. In this situation, the signal acquisition of the electromagnet’s displacement yE is discussed for the engineering application. Finally, to validate the effectiveness of the aforementioned control strategy, numerical validations are carried out and the experimental data are provided and analyzed.
Mitigation of electron attachment to oxygen in high pressure air plasmas by vibrational excitation
Frederickson, K.; Lee, W.; Palm, P.; Adamovich, I. V.; Rich, J. W.; Lempert, W. R.
2007-05-01
A series of time resolved microwave attenuation measurements are performed of the electron number density of an electron beam generated, CO laser excited nonequilibrium O2/N2 plasma. Resonant absorption of infrared radiation from the CO laser produces the nonequilibrium state, in which the heavy species vibrational modes are disproportionately excited, compared to the rotational and translational modes (Tvib≈2000-3000K vs TR /T≈300K). It is shown that this results in an increase in the plasma free electron lifetime by two orders of magnitude compared to the unexcited cold gas, an effect which is ascribed to complete mitigation of rapid three-body electron attachment to molecular oxygen. A series of heavy species filtered pure rotational Raman scattering measurements are also presented, which exhibit minimal temperature change (+50K), indicating that the observed lifetime increase cannot be due to heavy-species thermal effects. Finally, computational modeling results infer an increase in the rate of O2- detachment by four to five orders of magnitude, compared to the equilibrium value.
Asymptotic theory of neutral stability of the Couette flow of a vibrationally excited gas
Grigor'ev, Yu. N.; Ershov, I. V.
2017-01-01
An asymptotic theory of the neutral stability curve for a supersonic plane Couette flow of a vibrationally excited gas is developed. The initial mathematical model consists of equations of two-temperature viscous gas dynamics, which are used to derive a spectral problem for a linear system of eighth-order ordinary differential equations within the framework of the classical linear stability theory. Unified transformations of the system for all shear flows are performed in accordance with the classical Lin scheme. The problem is reduced to an algebraic secular equation with separation into the "inviscid" and "viscous" parts, which is solved numerically. It is shown that the thus-calculated neutral stability curves agree well with the previously obtained results of the direct numerical solution of the original spectral problem. In particular, the critical Reynolds number increases with excitation enhancement, and the neutral stability curve is shifted toward the domain of higher wave numbers. This is also confirmed by means of solving an asymptotic equation for the critical Reynolds number at the Mach number M ≤ 4.
Dehdashti-Jahromi, M.; Farrokhpour, H.
2017-02-01
Ionization and excitation energies, IR and Raman spectra of sulfur hexafluoride (SF6), located inside helium (He) nanoclusters with different sizes (SF6@Hen; n = 20, 40, 60), were calculated. The effect of the cluster size on the spectroscopic properties of the SF6 was investigated and found that the Hen-SF6 interaction in the He clusters with large number of atoms is small so that the ionization and absorption energies of SF6 are not affected while for small He nanoclusters the Hen-SF6 interaction is more important. The effect of Hen-SF6 interaction and deformation of the fragments on the photoelectron and absorption spectra of SF6@Hen were separated theoretically and discussed in details. It was deduced that the effect of the cluster size on the IR and Raman vibrational frequencies of the SF6 is negligible for the cluster size range considered in this work. Density functional theory (DFT) employing M06-2X functional and 6-31 + G(df) basis set were used for optimizing the structures of SF6@Hen. Symmetry adapted cluster-configuration interaction (SAC-CI) methodology, with the same basis set, were used to calculate the ionization and excitation energies of the SF6@Hen structures. Using the calculated ionization and absorption energies and their intensities, the photoelectron and absorption spectra of the considered SF6@Hen structures were simulated and compared with the experiment.
Decay Rate Measurement of the First Vibrationally Excited State of MgH+ in a Cryogenic Paul Trap
Versolato, O.O.; Schwarz, M.; Hansen, A.K.
2013-01-01
We present a method to measure the decay rate of the first excited vibrational state of polar molecular ions that are part of a Coulomb crystal in a cryogenic linear Paul trap. Specifically, we have monitored the decay of the |ν=1,J=1⟩X towards the |ν=0,J=0⟩X level in MgH+ by saturated laser...
Jinhui Li
2015-01-01
Full Text Available This paper addresses the self-excited vibration problems of maglev vehicle-bridge interaction system which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, two levitation models with different complexity are developed, and the comparison of the energy curves associated with the two models is carried out. We conclude that the interaction model with a single levitation control unit is sufficient for the study of the self-excited vibration. Then, the principle underlying the self-excited vibration is explored from the standpoint of work acting on the bridge done by the levitation system. Furthermore, the influences of the parameters, including the modal frequency and modal damping of bridge, the gain of the controller, the sprung mass, and the unsprung mass, on the stability of the interaction system are carried out. The study provides a theoretical guidance for solving the self-excited vibration problems of the vehicle-bridge interaction systems.
Hortobagyi, T.; Rider, P.; DeVita, P.
2014-01-01
We examined the effects of whole-body mechanical vibration (WBV) on indices of motoneuronal excitability at rest and during muscle contraction in healthy humans. Real and sham WBV at 30Hz had no effect on reflexes measured during muscle contraction. Real WBV at 30 and 50Hz depressed the H-reflex app
Kozolupenko, V.P.; Kuntsevich, B.F.; Maliuta, D.D.; Mezhevov, V.S.; Strel' tsov, A.P. (Institut Atomnoi Energii, Moscow (USSR))
1989-03-01
The dependence of the nonresonant part of the refractive index on vibrational molecular excitation is shown to be one of the possible mechanisms responsible for the chirping of the radiation frequency of pulsed single-frequency CO{sub 2} lasers. A heterodyning method was used to record the radiation frequency variation with two receivers utilizing HgCdTe. 12 refs.
Spectroscopic determination of ground and excited state vibrational potential energy surfaces
Laane, Jaan
Far-infrared spectra, mid-infrared combination band spectra, Raman spectra, and dispersed fluorescence spectra of non-rigid molecules can be used to determine the energies of many of the quantum states of conformationally important vibrations such as out-of-plane ring modes, internal rotations, and molecular inversions in their ground electronic states. Similarly, the fluorescence excitation spectra of jet-cooled molecules, together with electronic absorption spectra, provide the information for determining the vibronic energy levels of electronic excited states. One- or two-dimensional potential energy functions, which govern the conformational changes along the vibrational coordinates, can be determined from these types of data for selected molecules. From these functions the molecular structures, the relative energies between different conformations, the barriers to molecular interconversions, and the forces responsible for the structures can be ascertained. This review describes the experimental and theoretical methodology for carrying out the potential energy determinations and presents a summary of work that has been carried out for both electronic ground and excited states. The results for the out-of-plane ring motions of four-, five-, and six-membered rings will be presented, and results for several molecules with unusual properties will be cited. Potential energy functions for the carbonyl wagging and ring modes for several cyclic ketones in their S1(n,pi*) states will also be discussed. Potential energy surfaces for the three internal rotations, including the one governing the photoisomerization process, will be examined for trans-stilbene in both its S0 and S1(pi,pi*) states. For the bicyclic molecules in the indan family, the two-dimensional potential energy surfaces for the highly interacting ring-puckering and ring-flapping motions in both the S0 and S1(pi,pi*) states have also been determined using all of the spectroscopic methods mentioned above
Self-excited multi-scale skin vibrations probed by optical tracking micro-motions of tracers on arms
Chen, Wei-Chia; Chen, Hsiang-Ying; Chen, Yu-Sheng; Tian, Yong; I, Lin
2017-07-01
The self-excited multi-scale mechanical vibrations, their sources and their mutual coupling of different regions on the forearms of supine subjects, are experimentally investigated, using a simple noncontact method, optical video microscopy, which provides 1 μm and 25 ms spatiotemporal resolutions. It is found that, in proximal regions far from the radial artery, the vibrations are the global vibrations of the entire forearm excited by remote sources, propagating through the trunk and the limb. The spectrum is mainly composed of peaks of very low frequency motion (down to 0.05 Hz), low frequency respiration modes, and heartbeat induced modes (about 1 Hz and its harmonics), standing out of the spectrum floor exhibiting power law decay. The nonlinear mode-mode coupling leads to the cascaded modulations of higher frequency modes by lower frequency modes. The nearly identical waveforms without detectable phase delays for a pair of signals along or transverse to the meridian of regions far away from the artery rule out the detectable contribution from the propagation of Qi, some kind of collective excitation which more efficiently propagates along meridians, according to the Chinese medicine theory. Around the radial artery, in addition to the global vibration, the local vibration spectrum shows very slow breathing type vibration around 0.05 Hz, and the artery pulsation induced fundamental and higher harmonics with descending intensities up to the fifth harmonics, standing out of a flat spectrum floor. All the artery pulsation modes are also modulated by respiration and the very slow vibration.
Amano, T.
2011-05-01
Rotational transitions of DNC have been observed in the submillimeter-wave region in an extended negative glow discharge in a gas mixture of CD 4 and N 2. The dissociative recombination reaction of DCND + with electrons is thought to be a dominant channel to produce DNC in highly excited vibrational states. The vibrational temperature for the ν3 vibrational mode is found to be about 4000 K, and the rotational lines in levels up to (0 0 8) are observed. The rotational and centrifugal distortion constants are determined for these states along with those for the (1 0 0) state. The measurement accuracy is high enough to determine some higher order vibration-rotation interaction constants.
Trivikram, T. Madhu; Niu, M. L.; Wcisło, P.; Ubachs, W.; Salumbides, E. J.
2016-12-01
Accurate EF^1Σ^+_g{-}X^1Σ^+_g transition energies in molecular hydrogen were determined for transitions originating from levels with highly excited vibrational quantum number, v = 11, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H_2^*, produced via the photodissociation of H2S, yielding transition frequencies with accuracies of 45 MHz or 0.0015 cm-1. An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing 7pπ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known EF level energies, the level energies of X( v = 11, J = 1, 3-5) states are derived with accuracies of typically 0.002 cm-1. These experimental values are in excellent agreement with and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.
Microwave Spectral Taxonomy and Astronomical Searches for Vibrationally-Excited C_2S and C_3S
McGuire, Brett A.; Martin-Drumel, Marie-Aline; Stanton, John F.; McCarthy, Michael C.
2016-06-01
C_2S and C_3S are common interstellar species, and have relatively simple reaction chemistries. For these reasons, they frequently serve as probes of chemical evolution and physical conditions in rich astronomical sources. Because their rotational lines are often conspicuous there, detection of C_2S and C_3S in vibrationally-excited states might provide additional insight into formation pathways and excitation conditions. However, knowledge of the vibrational satellite transitions of both species is incomplete. Here, we report laboratory measurements of rotational spectra of vibrationally-excited C_2S and C_3S obtained from two microwave spectral taxonomy studies, in which CS_2 alone or in combination with a hydrocarbon precursor (acetylene or diacetylene), were produced using an electrical discharge. For C_3S, these studies, in combination with high-level quantum chemical calculations, greatly extend previous microwave measurements, while for C_2S, satellite transitions from several vibrational states have been observed for the first time. On the basis of precise laboratory rest frequencies, renewed searches for these transitions can be undertaken with confidence in publicly-available astronomical line surveys.
Koppers, G.A.A.
1996-11-01
Ozone is `the` most important trace gas in the middle atmosphere. Despite the large efforts that have been made to calculate its concentration in the middle atmosphere there is long standing discrepancy between in-situ and remote sensing measurements on one hand and model results on the other. The latter tend to be about 30% too low in the upper stratosphere and mesosphere. One of the photolysis products of ozone itself, O2({upsilon}) - an oxygen molecule with extra vibrational energy, has been suggested as an intermediate in a reaction sequence that possibly could represent the missing ozone source. A key point in model calculations that estimate the magnitude of the proposed extra ozone source is the fractional population distribution of O2({upsilon}) after ozone photodissociation. Recent statistical calculations supply the vibrational distribution of O2({upsilon}) as a function of the wavelength at which ozone is dissociated. Based on these results a 2D chemical model that includes O2({upsilon}) chemistry has been used to investigate the importance of this mechanism. The extra ozone production by this mechanism has been compared for several other vibrational distributions taken from literature, different collisional deactivation rates of the excited oxygen fragments, and including a reaction between high vibrational excited oxygen with ground state oxygen producing two odd oxygen molecules. Our results indicate that regardless of whether the high vibrational reaction is included, alternatively the deactivation rates are decreased or not, the vibrational excited oxygen mechanism can not simultaneously match the absolute amount of the difference between the model results and SAGE II data and the height distribution of this difference. 23 refs, 17 figs, 2 tabs
Sub- and Super-Synchronous Self-Excited Vibrations of a Columnar Rotor Due to Axial Clearance Flow
Nishimura, H.; Horiguchi, H.; Suzuki, T.; Sugiyama, K.; Tsujimoto, Y.
2016-11-01
Sub- and super-synchronous self-excited vibrations due to axial clearance flows were observed in a columnar rotor with an upstream seal in experiments. A smaller clearance on the downstream seal had a larger effect of stabilizing the rotor. In computations, it was found that the rotordynamic fluid force tangential to the whirling orbit, which is caused as a response to the vibrations (whirling motions), destabilizes the rotor in the case of the upstream seal and stabilizes the rotor in the case of the downstream seal. It was clarified in the 1-D flow model that the tangential rotordynamic fluid force is mainly caused by an inertia of the clearance flow.
M.M.Kamel; W.A.A.El-Ganaini; Y.S.Hamed
2009-01-01
Ultrasonic machining (USM) is of particular interest for the machining of non-conductive, brittle mate-rials such as engineering ceramics, In this paper, a multi-tool technique is used in USM to reduce the vibration in the tool holder and have reasonable amplitude for the tools. This can be done via dynamic absorbers. The coupling of four non-linear oscillators of the tool holder and tools representing ultrasonic cutting process are investigated. This leads to a four-degree-of-freedom system subjected to multi-external and multi-parametric excitation forces. The aim of this work is to control the tool holder behavior at simultaneous pri-mary, sub-harmonic and internal resonance condition. Mul-tiple scale perturbation method is used to obtain the solution up to the second order approximations. The different reso-nance cases are reported and studied numerically. The stabil-ity of the system is investigated by using both phase-plane and frequency response techniques. The effects of the differ-ent parameters of the tools on the system behavior are studied numerically. Comparison with the available published work is reported.
Millimetre-wave spectroscopy of HC{sub 4}Cl in ground and excited vibrational states
Bizzocchi, Luca [Dipartimento di Chimica ' G. Ciamician' , Universita di Bologna, via F. Selmi 2, 40126 Bologna (Italy)], E-mail: luca.bizzocchi@unibo.it; Degli Esposti, Claudio [Dipartimento di Chimica ' G. Ciamician' , Universita di Bologna, via F. Selmi 2, 40126 Bologna (Italy)], E-mail: claudio.degliesposti@unibo.it
2008-05-04
The semi-stable HC{sub 4}Cl molecule has been detected in the pyrolysis products of propyne and carbon tetrachloride mixtures. The rotational spectrum of the most abundant isotopologue HC{sub 4}{sup 35}Cl has been investigated in the millimetre- and sub-millimetre-wave regions for the ground and 12 vibrationally excited states which approximately lie below 630 cm{sup -1}, namely ({nu}{sub 5}{nu}{sub 6}{nu}{sub 7}{nu}{sub 8}{nu}{sub 9})=(10000), (01000), (00100), (00010), (00001), (00020), (00002), (00003), (00004), (00101), (00011) and (00012). Transitions up to J=151 <- 150 were measured for the ground state, allowing for a precise evaluation of the quartic and sextic centrifugal distortion constants D and H. The l-type resonances between the different sublevels of the bending states and the anharmonic resonance which couples the states {nu}{sub 5}=1, {nu}{sub 8}=2 and {nu}{sub 9}=4 have been taken into account in the analysis of the spectra, which yielded precise determinations of the x{sub L(99)}, x{sub L(88)}, x{sub L(89)} and x{sub L(79)} anharmonicity constants and of the {phi}{sub 588} normal coordinate cubic force constant. Extensive measurements have also been performed for the HC{sub 4}{sup 37}Cl isotopologue.
Asymptotic modal analysis of a rectangular acoustic cavity excited by wall vibration
Peretti, Linda F.; Dowell, Earl H.
1992-01-01
Asymptotic modal analysis, a method that has recently been developed for structural dynamical systems, has been applied to a rectangular acoustic cavity. The cavity had a flexible vibrating portion on one wall, and the other five walls were rigid. Banded white noise was transmitted through the flexible portion (plate) only. Both the location along the wall and the size of the plate were varied. The mean square pressure levels of the cavity interior were computed as a ratio of the result obtained from classical modal analysis to that obtained from asymptotic modal analysis for the various plate configurations. In general, this ratio converged to 1.0 as the number of responding modes increased. Intensification effects were found due to both the excitation location and the response location. The asymptotic modal analysis method was both efficient and accurate in solving the given problem. The method has advantages over the traditional methods that are used for solving dynamics problems with a large number of responding modes.
Silva, M.; Jongma, R.; Field, R. W.; Wodtke, A. M.
2001-01-01
We review stimulated emission pumping as used to study molecular dynamics. The review presents unimolecular as well as scattering studies. Topics include intramolecular vibrational redistribution, unimolecular isomerization and dissociation, van der Waals clusters, rotational energy transfer, vibrat
ANALYSIS OF VIBRATORY PROTECTION SYSTEM VIBRATION DURING HARMONIC AND POLYHARMONIC EXCITATIONS
T. N. Mikulik
2011-01-01
Full Text Available The paper considers a mathematical model of local «driver-seat» system and an algorithm for vibratory loading formation at external actions. Results of the investigations on the system vibration according to minimum vibration acceleration depending on transfer force factor acting on the seat and a vibration isolation factor are presented in the paper.
Interaction of electronic excitations of Tm3+ ions with acoustic vibrations in KTm(MoO4)2
Kamenskyi, D.; Poperezhai, S.; Gogoi, P.; Engelkamp, H.; Maan, J. C.; Wosnitza, J.; Kut'ko, V.
2014-01-01
Electron paramagnetic resonance spectra of KTm(MoO4)2 were measured as a function of magnetic field between 3 and 11.5 cm-1 at T =2 K. We found that in addition to the absorption line caused by the electronic excitation of Tm3+ ions, the spectra contain sidebands. Far-infrared transmission measured with polarized light from 10 to 75 cm-1 revealed vibration modes at 16.7 and 25.7 cm-1 for polarizations Eω∥a and Eω∥c, respectively. We show that sidebands in the spectra of paramagnetic resonance result from a parametric resonance between the electronic excitations of the Tm3+ ions and the acoustic vibrations of the crystal lattice.
Excited-state structure, vibrations, and nonradiative relaxation of jet-cooled 5-fluorocytosine.
Lobsiger, Simon; Trachsel, Maria A; Den, Takuya; Leutwyler, Samuel
2014-03-20
The S0 → S1 vibronic spectrum and S1 state nonradiative relaxation of jet-cooled keto-amino 5-fluorocytosine (5FCyt) are investigated by two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm(–1) resolution. The 0(0)(0) rotational band contour is polarized in-plane, implying that the electronic transition is (1)ππ*. The electronic transition dipole moment orientation and the changes of rotational constants agree closely with the SCS-CC2 calculated values for the (1)ππ* (S1) transition of 5FCyt. The spectral region from 0 to 300 cm(–1) is dominated by overtone and combination bands of the out-of-plane ν1′ (boat), ν2′ (butterfly), and ν3′ (HN–C6H twist) vibrations, implying that the pyrimidinone frame is distorted out-of-plane by the (1)ππ* excitation, in agreement with SCS-CC2 calculations. The number of vibronic bands rises strongly around +350 cm(–1); this is attributed to the (1)ππ* state barrier to planarity that corresponds to the central maximum of the double-minimum out-of-plane vibrational potentials along the ν1′, ν2′, and ν3′ coordinates, which gives rise to a high density of vibronic excitations. At +1200 cm(–1), rapid nonradiative relaxation (k(nr) ≥ 10(12) s(–1)) sets in, which we interpret as the height of the (1)ππ* state barrier in front of the lowest S1/S0 conical intersection. This barrier in 5FCyt is 3 times higher than that in cytosine. The lifetimes of the ν′ = 0, 2ν1′, 2ν2′, 2ν1′ + 2ν2′, 4ν2′, and 2ν1′ + 4ν2′ levels are determined from Lorentzian widths fitted to the rotational band contours and are τ ≥ 75 ps for ν′ = 0, decreasing to τ ≥ 55 ps at the 2ν1′ + 4ν2′ level at +234 cm(–1). These gas-phase lifetimes are twice those of S1 state cytosine and 10–100 times those of the other canonical nucleobases in the gas phase. On the other hand, the 5FCyt gas-phase lifetime is close to the 73 ps lifetime in room-temperature solvents. This lack of
Trachsel, Maria A.; Wiedmer, Timo; Blaser, Susan; Frey, Hans-Martin; Li, Quansong; Ruiz-Barragan, Sergi; Blancafort, Lluís; Leutwyler, Samuel
2016-10-01
We have investigated the S0 → S1 UV vibronic spectrum and time-resolved S1 state dynamics of jet-cooled amino-keto 1-methylcytosine (1MCyt) using two-color resonant two-photon ionization, UV/UV holeburning and depletion spectroscopies, as well as nanosecond and picosecond time-resolved pump/delayed ionization measurements. The experimental study is complemented with spin-component-scaled second-order coupled-cluster and multistate complete active space second order perturbation ab initio calculations. Above the weak electronic origin of 1MCyt at 31 852 cm-1 about 20 intense vibronic bands are observed. These are interpreted as methyl group torsional transitions coupled to out-of-plane ring vibrations, in agreement with the methyl group rotation and out-of-plane distortions upon 1ππ∗ excitation predicted by the calculations. The methyl torsion and ν1 ' (butterfly) vibrations are strongly coupled, in the S1 state. The S0 → S1 vibronic spectrum breaks off at a vibrational excess energy Eexc ˜ 500 cm-1, indicating that a barrier in front of the ethylene-type S1⇝S0 conical intersection is exceeded, which is calculated to lie at Eexc = 366 cm-1. The S1⇝S0 internal conversion rate constant increases from kIC = 2 ṡ 109 s-1 near the S1(v = 0) level to 1 ṡ 1011 s-1 at Eexc = 516 cm-1. The 1ππ∗ state of 1MCyt also relaxes into the lower-lying triplet T1 (3ππ∗) state by intersystem crossing (ISC); the calculated spin-orbit coupling (SOC) value is 2.4 cm-1. The ISC rate constant is 10-100 times lower than kIC; it increases from kISC = 2 ṡ 108 s-1 near S1(v = 0) to kISC = 2 ṡ 109 s-1 at Eexc = 516 cm-1. The T1 state energy is determined from the onset of the time-delayed photoionization efficiency curve as 25 600 ± 500 cm-1. The T2 (3nπ∗) state lies >1500 cm-1 above S1(v = 0), so S1⇝T2 ISC cannot occur, despite the large SOC parameter of 10.6 cm-1. An upper limit to the adiabatic ionization energy of 1MCyt is determined as 8.41 ± 0.02 e
Michaels, Chris Arthur
The relaxation of highly vibrationally excited donor molecules, C4H4N2 and C6F6, (E vib ~ 5 eV), by collisions with a bath of CO2 is investigated using high resolution, infrared transient absorption spectroscopy. The vibrationally hot donor molecules are formed by 248 nm excimer laser pumping, followed by rapid radiationless decay to the ground electronic state. This technique yields the nascent bath quantum state distributions following a single donor/bath collision. Absolute energy transfer rates are measured along with the partitioning of energy among the bath degrees of freedom. These measurements provide insight into the nature of the intermolecular forces mediating the energy transfer and allow the construction of energy transfer distribution functions, P(E,E') for these systems. Pyrazine/CO2 collisions which result in the excitation of bath vibrational modes, including the anti- symmetric stretch (0001), the Fermi-mixed symmetric stretch/bending overtone (1000 r1 and 1000 r2) and the unmixed bending overtone (0220), are studied. The vibrational energy transfer is accompanied by very little rotational and translational excitation and displays the characteristic strong, inverse temperature dependence (probability of transfer increases with decreasing temperature) expected of energy transfer mediated by a long range attractive interaction. Collisions between highly vibrationally excited C6F6 and CO2, which result in significant excitation of the bath rotational and translational degrees of freedom, are examined. This type of energy transfer is mediated by the short range repulsive region of the C6F6/CO2 intermolecular potential. A gap law model is used to fit the weak temperature dependence of these scattering processes in an effort to quantify the energy transfer magnitudes. A prescription for mapping bath quantum state resolved energy transfer rate constants onto an energy transfer probability distribution function, P(E,E') is described in detail. Analysis of
Excitation of the low lying vibrational levels of H2O by O(3P) as measured on Spacelab 2
Meyerott, R. E.; Swenson, G. R.; Schweitzer, E. L.; Koch, D. G.
1994-01-01
The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(3P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (101) level at an O(3P) velocity of approximately 7.75 km/s. Contributions to the radiation in the 1.7-3.0 micron band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 micron and the nighttime data for the 1.7-3.0 micron sensors are consistent with being explained by collision excitation of H2O by O(3P), (2) diurnal variations of 4.5-9.5 micron intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests greater than 60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 micron intensity data suggests that O(+) may likely be instrumental in producing excited H2O(+) through charge exchange.
Laporta, V; Wadehra, J M
2012-01-01
Electron-impact vi->vf vibrational excitations cross sections, involving rovibrationally excited N_{2}(v_{i}, J) and NO(v_{i}, J) molecules (fixed J), are calculated for collisions occurring through the nitrogen resonant electronic state N_{2}^{-} (X ^{2}\\Pi_{g}), and the three resonant states of nitric oxide NO^{-}(^{3}\\Sigma^{-},^{1} \\Delta,^{1} \\Sigma^{+}). Complete sets of cross sections have been obtained for all possible transitions involving 68 vibrational levels of N2(X ^{1}\\Sigma^{+}_{g}) and 55 levels of NO(X ^{2}\\Pi), for the incident electron energy between 0.1 and 10 eV. In order to study the rotational motion in the resonant processes, cross sections have been also computed for rotationally elastic transitions characterized by the rotational quantum number J running from 0 through 150. The calculations are performed within the framework of the local complex potential model, by using potentials energies and widths optimized in order to reproduce the experimental cross sections available in litera...
Enhancement of channel wall vibration due to acoustic excitation of an internal bubbly flow
Zhang, M.M.; Katz, J.; Prosperetti, A.
2010-01-01
The effect of an internal turbulent bubbly flow on vibrations of a channel wall is investigated experimentally and theoretically. Our objective is to determine the spectrum and attenuation rate of sound propagating through a bubbly liquid flow in a channel, and connect these features with the vibrat
Saieswari Amaran; Sanjay Kumar
2009-09-01
Quantum mechanical study of vibrational state-resolved differential cross sections and transition probabilities for both the elastic/inelastic and the charge transfer processes have been carried out in the H+ + O2 collisions at the experimental collision energy of 23 eV. The quantum dynamics has been performed within the vibrational close-coupling rotational infinite-order sudden approximation framework employing our newly obtained quasi-diabatic potential energy surfaces corresponding to the ground and the first excited electronic states which have been computed using ab initio procedures and Dunning’s correlation consistent-polarized valence triple zeta basis set at the multireference configuration interaction level of accuracy. The present theoretical results for elastic/inelastic processes provide an overall agreement with the available state-selected experimental data, whereas the results for the charge transfer channel show some variance in comparison with those of experiments and are similar to the earlier theoretical results obtained using model effective potential based on projected valence bond method and using semi-empirical diatomics-in-molecules potential. The possible reason for discrepancies and the likely ways to improve the results are discussed in terms of the inclusion of higher excited electronic states into the dynamics calculation.
Colonna, Gianpiero; Celiberto, Roberto; Capitelli, Mario; Tennyson, Jonathan
2015-01-01
The formation of the electron energy distribution function in nanosecond atmospheric nitrogen discharges is investigated by means of self-consistent solution of the chemical kinetics and the Boltzmann equation for free electrons. The post-discharge phase is followed to few microseconds. The model is formulated in order to investigate the role of the cross section set, focusing on the vibrational-excitation by electron-impact through resonant channel. Four different cross section sets are considered, one based on internally consistent vibrational-excitation calculations which extend to the whole vibrational ladder, and the others obtained by applying commonly used scaling-laws.
Trivikram, T Madhu; Wcisło, P; Ubachs, W; Salumbides, E J
2016-01-01
Accurate $EF{}^1\\Sigma^+_g-X{}^1\\Sigma^+_g$ transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, $v=11$, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H$_2^*$, produced via the photodissociation of H$_2$S, yielding transition frequencies with accuracies of $45$ MHz or $0.0015$ cm$^{-1}$. An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing $7p\\pi$ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known $EF$ level energies, the level energies of $X(v=11, J=1,3-5)$ states are derived with accuracies of typically 0.002 cm$^{-1}$. These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.
Vibration serviceability of footbridges under human-induced excitation: a literature review
Živanović, S.; Pavic, A.; Reynolds, P.
2005-01-01
Increasing strength of new structural materials and longer spans of new footbridges, accompanied with aesthetic requirements for greater slenderness, are resulting in more lively footbridge structures. In the past few years this issue attracted great public attention. The excessive lateral sway motion caused by crowd walking across the infamous Millennium Bridge in London is the prime example of the vibration serviceability problem of footbridges. In principle, consideration of footbridge vibration serviceability requires a characterisation of the vibration source, path and receiver. This paper is the most comprehensive review published to date of about 200 references which deal with these three key issues. The literature survey identified humans as the most important source of vibration for footbridges. However, modelling of the crowd-induced dynamic force is not clearly defined yet, despite some serious attempts to tackle this issue in the last few years. The vibration path is the mass, damping and stiffness of the footbridge. Of these, damping is the most uncertain but extremely important parameter as the resonant behaviour tends to govern vibration serviceability of footbridges. A typical receiver of footbridge vibrations is a pedestrian who is quite often the source of vibrations as well. Many scales for rating the human perception of vibrations have been found in the published literature. However, few are applicable to footbridges because a receiver is not stationary but is actually moving across the vibrating structure. During footbridge vibration, especially under crowd load, it seems that some form of human-structure interaction occurs. The problem of influence of walking people on footbridge vibration properties, such as the natural frequency and damping is not well understood, let alone quantified. Finally, there is not a single national or international design guidance which covers all aspects of the problem comprehensively and some form of their
Wang, Aixing; Fang, Chao; Liu, Yibao
2016-08-22
The dynamic potentials of highly excited vibrational states of deuterated phosphaethyne (DCP) in the D-C and C-P stretching coordinates with anharmonicity and Fermi coupling are studied in this article and the results show that the D-C-P bending vibration mode has weak effects on D-C and C-P stretching modes under different Polyad numbers (P number). Furthermore, the dynamic potentials and the corresponding phase space trajectories of DCP are given, as an example, in the case of P = 30. In the end, a comparative study between deuterated phosphaethyne (DCP) and phosphaethyne (HCP) with dynamic potential is done, and it is elucidated that the uncoupled mode makes the original horizontal reversed symmetry breaking between the dynamic potential of HCP ( q 3 ) and DCP ( q 1 ), but has little effect on the vertical reversed symmetry, between the dynamic potential of HCP ( q 2 ) and DCP ( q 3 ).
Yanhua Wang; Min Peng; Jianying Tong; Yuliang Wang
2015-08-01
Quasi-classical trajectory (QCT) calculations of H+HBr → H2 + Br reaction have been performed on a recently proposed ab initio potential energy surface. The reaction probability and integral cross section are found to be in fairly good agreement with the available quantum mechanical (QM) results on this surface. The behavior of reactivity is well consistent with properties of exothermic reaction. Once the energy of vibrational excited HBr is larger than the barrier height, the integral cross sections for the reaction diverge at very low collision energies close to the threshold, similarly to capture reaction. In addition, differential cross sections show that scattering of the product H2 shift from backward to forward directions as the collision energy and vibrational quantum number increase. All the theoretical findings are reasonably explained by the properties of the surface, as well as reactive mechanisms.
Hazra, Milan
2016-01-01
Valuable dynamical and structural information about neat liquid DMSO at ambient conditions can be obtained through study of low frequency vibrations in the far infrared (FIR), that is, terahertz regime. For DMSO, collective excitations as well as single molecule stretches and bends have been measured by different kinds of experiments such as OHD-RIKES and terahertz spectroscopy. In the present work we investigate the intermolecular vibrational spectrum of DMSO through three different computational techniques namely (i) the far-infra red spectrum obtained through Fourier transform of total dipole moment auto time correlation function, (ii) from Fourier transform of the translational and angular velocity time autocorrelation functions and a (iii) quenched normal mode analysis of the parent liquid at 300K. The three spectrum, although exhibit differences among each other, reveal similar features which are in good, semi-quantitative, agreement with experimental results. Study of participation ratio of the density...
Effects of gap size and excitation frequency on the vibrational behavior and wear rate of fuel rods
Hu, Zupan [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Thouless, M.D., E-mail: thouless@umich.edu [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Lu, Wei, E-mail: weilu@umich.edu [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)
2016-11-15
Graphical abstract: A wear map shows wear rate as a function of the grid-to-rod gap size and the frequency of the excitation force. The critical gap size, which is associated with the maximum wear rate, lies within the harmonic regime. In the no wear region the amplitude of the rod vibration is smaller than the gap size so that no impact between the rod and plate can happen. The curve of the resonant frequency of the system appears to overlap with the peaks in the contour. - Highlights: • A 3D finite-element based approach to study grid-to-rod fretting. • Two important factors: grid-to-rod gap size and frequency of the excitation force. • Rod vibration shows three regimes: harmonic, period-doubling and chaotic. • A critical gap size is associated with the maximum wear rate. • A wear map shows wear rate as a function of the gap size and excitation frequency. - Abstract: Grid-to-rod fretting (GTRF) wear is a major cause of fuel leaks. Understanding its mechanism is crucial for improving the reliability of nuclear reactors. In this paper we present a three-dimensional, finite-element based approach, which reveals how the wear rate depends on the size of the gap between the grid and the fuel rod, and on the frequency of the excitation force. We show that these two factors affect the dynamic vibration of the rod, which leads to three different regimes: harmonic, period-doubling and chaotic. The wear rate in the harmonic regime is significantly larger than that in the other two regimes, and reaches a maximum when the excitation frequency is close to the resonant frequency of the system, which is dependent on the gap size. We introduce the concept of a critical gap size that gives the maximum wear rate, and we identify the properties and values of this critical gap size. A wear map is developed as a result of a large number of parametric studies. This map shows quantitatively the wear rate as a function of the gap size and excitation frequency, and will be a
ZENG Yang-Yang; FENG Hao; SUN Wei-Guo; WANG Bin
2009-01-01
A theoretical investigation on the differential cross section (DCS) from low-energy electron scattering of high-lying vibrational excited 112 molecules is reported. The body-frame vibrational close-coupling (BFVCC) approach is used to solve the scattering equations. Quantum scattering potentials include static, exchange, and polarization contributions based on ab initio calculations. By including the contributions of 9 partial waves (Ne=9), 18 Morse vibrational states (Nv = 18), and 16 molecular symmetries (A=0, 1,..., 7), the calculated DCSs have good agreement with available experimental measurements and theoretical studies, and show that high angular momenta and good vibrational wavefunctions are necessary to better describe the scattering physics of electron-molecule vibrational excitation collisions.
Xue-Liang Zhang
2013-01-01
Full Text Available In this paper we give some theoretical analyses and experimental results on synchronization of the two non-identical exciters. Using the average method of modified small parameters, the dimensionless coupling equation of the two exciters is deduced. The synchronization criterion for the two exciters is derived as the torque of frequency capture being equal to or greater than the absolute value of difference between the residual electromagnetic torques of the two motors. The stability criterion of synchronous state is verified to satisfy the Routh-Hurwitz criterion. The regions of implementing synchronization and that of stability of phase difference for the two exciters are manifested by numeric method. Synchronization of the two exciters stems from the coupling dynamic characteristic of the vibrating system having selecting motion, especially, under the condition that the parameters of system are complete symmetry, the torque of frequency capture stemming from the circular motion of the rigid frame drives the phase difference to approach PI and carry out the swing of the rigid frame; that from the swing of the rigid frame forces the phase difference to near zero and achieve the circular motion of the rigid frame. In the steady state, the motion of rigid frame will be one of three types: pure swing, pure circular motion, swing and circular motion coexistence. The numeric and experiment results derived thereof show that the two exciters can operate synchronously as long as the structural parameters of system satisfy the criterion of stability in the regions of frequency capture. In engineering, the distance between the centroid of the rigid frame and the rotational centre of exciter should be as far as possible. Only in this way, can the elliptical motion of system required in engineering be realized.
Golgir, Hossein Rabiee; Zhou, Yun Shen; Li, Dawei; Keramatnejad, Kamran; Xiong, Wei; Wang, Mengmeng; Jiang, Li Jia; Huang, Xi; Jiang, Lan; Silvain, Jean Francois; Lu, Yong Feng
2016-09-01
The influence of exciting ammonia (NH3) molecular vibration in the growth of gallium nitride (GaN) was investigated by using an infrared laser-assisted metal organic chemical vapor deposition method. A wavelength tunable CO2 laser was used to selectively excite the individual vibrational modes. Resonantly exciting the NH-wagging mode (v2) of NH3 molecules at 9.219 μm led to a GaN growth rate of 84 μm/h, which is much higher than the reported results. The difference between the resonantly excited and conventional thermally populated vibrational states was studied via resonant and nonresonant vibrational excitations of NH3 molecules. Resonant excitation of various vibrational modes was achieved at 9.219, 10.35, and 10.719 μm, respectively. Nonresonant excitation was conducted at 9.201 and 10.591 μm, similar to conventional thermal heating. Compared to nonresonant excitation, resonant excitation noticeably promotes the GaN growth rate and crystalline quality. The full width at half maximum value of the XRD rocking curves of the GaN (0002) and GaN (10-12) diffraction peaks decreased at resonant depositions and reached its minimum value of 45 and 53 arcmin, respectively, at the laser wavelength of 9.219 μm. According to the optical emission spectroscopic studies, resonantly exciting the NH3 v2 mode leads to NH3 decomposition at room temperature, reduces the formation of the TMGa:NH3 adduct, promotes the supply of active species in GaN formation, and, therefore, results in the increased GaN growth rate.
Lewis, NHC; Gruenke, NL; Oliver, TAA; Ballottari, M; Bassi, R; Fleming, GR
2016-10-05
Light-harvesting complex II (LHCII) serves a central role in light harvesting for oxygenic photosynthesis and is arguably the most important photosynthetic antenna complex. In this article, we present two-dimensional electronic–vibrational (2DEV) spectra of LHCII isolated from spinach, demonstrating the possibility of using this technique to track the transfer of electronic excitation energy between specific pigments within the complex. We assign the spectral bands via comparison with the 2DEV spectra of the isolated chromophores, chlorophyll a and b, and present evidence that excitation energy between the pigments of the complex are observed in these spectra. Lastly, we analyze the essential components of the 2DEV spectra using singular value decomposition, which makes it possible to reveal the relaxation pathways within this complex.
Wang, Haitao; Xing, J. T.; Price, W. G.; Li, Weiji
2008-10-01
A mathematical model is developed to control aircraft vibrations caused by runway excitation using an active landing gear system. Equations are derived to describe the integrated aircraft-active system. The nonlinear characteristics of the system are modelled and it is actively controlled using a Proportional Integral Derivative (PID) strategy. The performance of this system and its corresponding passive system are compared using numerical simulations. It is demonstrated that the impact loads and the vertical displacement of the aircraft's centre of gravity caused by landing and runway excitations are greatly reduced using the active system, which result in improvements to the performance of the landing gear system, benefits the aircraft's fatigue life, taxiing performance, crew/passenger comfort and reduces requirements on the unevenness of runways.
Wang, Yi-Ze; Wang, Yue-Sheng; Ke, Liao-Liang
2016-09-01
In the present work, the nonlinear vibration of a carbon nanotube which is subjected to the external parametric excitation is studied. By the nonlocal continuum theory and nonlinear von Kármán beam theory, the governing equation of the carbon nanotube is derived with the consideration of the large deformation. The principle parametric resonance of the nanotube is discussed and the approximation explicit solution is presented by the multiple scale method. Numerical calculations are performed. It can be observed that when the mode number is 1, the stable region can be significantly changed by the parametric excitation, length-to-diameter ratio and matrix stiffness. This phenomenon becomes different to appear if the mode number increases. Moreover, the small scale effects have great influences on the positive bifurcation point for the short carbon nanotube, and the nonlocal continuum theory can present the proper model.
Dallinger, R.F.; Farquharson, S.; Woodruff, W.H.; Rodgers, M.A.J.
1981-12-16
Resonance Raman and electronic absorption spectra are reported for the S/sub 0/ and T/sub 1/ states of the carotenoids ..beta..-carotene, zeaxanthin, echinenone, canthaxanthin, dihydroxylycopene, astaxanthin, decapreno(C/sub 50/)-..beta..-carotene, ..beta..-apo-8'-carotenal, and ethyl ..beta..-apo-8'-carotenoate. The results reveal qualitatively similar ground-state spectra and similar frequency shifts in all observed resonance Raman modes between S/sub 0/ and T/sub 1/, regardless of carotenoid structure. Examinations of the relationship of the putative C--C and C==C frequencies in S/sub 0/ and T/sub 1/ reveals anomalous shifts to lower frequency in the ''single-bond'' mode upon electronic excitation. These shifts may be due to molecular distortions in the excited state which force changes in molecular motions comprising the observed modes. However, another possibility requiring no distortion is that the interaction (off-diagonal) force constants connecting the C--C and C==C modes change sign upon electronic excitation. This latter phenomenon may provide a unitary explanation for the ''anomalous'' frequency shifts in the C--C and C==C modes, both in the T/sub 1/ states of carotenoids and in the S/sub 1/ states of simpler polyenes, without postulating large, unpredicted structural changes upon excitation or general errors in existing vibrational or theoretical analyses. Resonance Raman and absorbance studies with 35-ps time resolution suggest that S/sub 1/ lifetime (of the /sup 1/B/sub u/ and/or the /sup 1/A/sub g/* states) of ..beta..-carotene in benzene is less than 1 ps.
Femtosecond Twisting and Coherent Vibrational Motion in the Excited State of Tetraphenylethylene
Lenderink, E; Duppen, K.; Wiersma, D. A.
1995-01-01
The initial dynamics after excitation to the S-1 state of tetraphenylethylene is studied using femtosecond pump-probe spectroscopy. From the rapid spectral changes during the first few hundred femtoseconds, we conclude that a fast ethylenic twisting motion occurs in the excited state within this tim
Effective system properties and spectral density in random vibration with parametric excitation
Krenk, Steen; Lin, Y. K.; Rüdinger, Finn
2002-01-01
The characteristic frequency and bandwidth of the random response to parametric excitation may be influenced by the excitation process. It is demonstrated that the effrective stiffness and damping properties can be expressed as conditional mean values for given displacement and energy levels...
Pumping of Vibrational Excitations in the Coulomb-Blockade Regime in a Suspended Carbon Nanotube
Hüttel, A.K.; Witkamp, B.; Leijnse, M.; Wegewijs, M.R.; Van der Zant, H.S.J.
2009-01-01
Low-temperature transport spectroscopy measurements on a suspended few-hole carbon nanotube quantum dot are presented, showing a gate-dependent harmonic excitation spectrum which, strikingly, occurs in the Coulomb-blockade regime. The quantized excitation energy corresponds to the scale expected for
Vibrational excitations of proteins and their hydration water in the far-infrared range
Paciaroni, A., E-mail: alessandro.paciaroni@fisica.unipg.it [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy); Conti Nibali, V. [Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum (Germany); Orecchini, A. [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy); Institut Laue Langevin, 6 rue J. Horowitz, F-38042 Grenoble (France); Petrillo, C. [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy); Haertlein, M.; Moulin, M. [Institut Laue Langevin, 6 rue J. Horowitz, F-38042 Grenoble (France); Tarek, M. [UMR Structure et Réactivité des Systèmes Moléculaires Complexes, Nancy-University, CNRS (France); D’Angelo, G. [Dipartimento di Fisica, Universita’ degli Studi di Messina, Viale F. Stagno d’Alcontres 31, I-98166 Messina (Italy); Sacchetti, F. [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy)
2013-10-16
Highlights: • We characterize the vibrations of proteins and hydration water in far-infrared range. • Isotopic contrast is used to highlight protein or water component. • MD simulations help understanding vibrational bands. • The inelastic behavior of proteins is quite independent on the solvent. • Protein hydration water vibrational behavior is similar to amorphous ice. - Abstract: Incoherent neutron scattering has been used to single out the vibrational contribution from maltose binding protein (MBP) and its hydration water in the energy range 1 meV–80 meV. The vibrational density of states from both protein and hydration water have been investigated by measuring respectively dry and D{sub 2}O-hydrated isotopically natural MBP and dry and H{sub 2}O-hydrated perdeuterated MBP. Molecular dynamics simulations done on the same system allow us to attribute the protein inelastic features. The inelastic behavior of the biomolecule seems to be largely independent on the presence of solvent. Conversely, protein hydration water exhibits remarkable differences with respect to hexagonal ice in the whole spectral range, with clear similarities to amorphous phases of ice.
Khouri, T.; Vlemmings, W. H. T.; Ramstedt, S.; Lombaert, R.; Maercker, M.; De Beck, E.
2016-11-01
We report the serendipitous detection with ALMA of the vibrationally-excited pure-rotational CO transition $v=1, J=3-2$ towards five asymptotic giant branch (AGB) stars, $o$ Cet, R Aqr, R Scl, W Aql, and $\\pi^1$ Gru. The observed lines are formed in the poorly-understood region located between the stellar surface and the region where the wind starts, the so-called warm molecular layer. We successfully reproduce the observed lines profiles using a simple model. We constrain the extents, densities, and kinematics of the region where the lines are produced. R Aqr and R Scl show inverse P-Cygni line profiles which indicate infall of material onto the stars. The line profiles of $o$ Cet and R Scl show variability. The serendipitous detection towards these five sources shows that vibrationally-excited rotational lines can be observed towards a large number of nearby AGB stars using ALMA. This opens a new possibility for the study of the innermost regions of AGB circumstellar envelopes.
Khouri, T; Ramstedt, S; Lombaert, R; Maercker, M; De Beck, E
2016-01-01
We report the serendipitous detection with ALMA of the vibrationally-excited pure-rotational CO transition $v=1, J=3-2$ towards five asymptotic giant branch (AGB) stars, $o$ Cet, R Aqr, R Scl, W Aql, and $\\pi^1$ Gru. The observed lines are formed in the poorly-understood region located between the stellar surface and the region where the wind starts, the so-called warm molecular layer. We successfully reproduce the observed lines profiles using a simple model. We constrain the extents, densities, and kinematics of the region where the lines are produced. R Aqr and R Scl show inverse P-Cygni line profiles which indicate infall of material onto the stars. The line profiles of $o$ Cet and R Scl show variability. The serendipitous detection towards these five sources shows that vibrationally-excited rotational lines can be observed towards a large number of nearby AGB stars using ALMA. This opens a new possibility for the study of the innermost regions of AGB circumstellar envelopes.
Remick, Kevin; Dane Quinn, D.; Michael McFarland, D.; Bergman, Lawrence; Vakakis, Alexander
2016-05-01
The authors investigate a vibration-based energy harvesting system utilizing essential (nonlinearizable) nonlinearities and electromagnetic coupling elements. The system consists of a grounded, weakly damped linear oscillator (primary system) subjected to a single impulsive load. This primary system is coupled to a lightweight, damped oscillating attachment (denoted as nonlinear energy sink, NES) via a neodymium magnet and an inductance coil, and a piano wire, which generates an essential geometric cubic stiffness nonlinearity. Under impulsive input, the transient damped dynamics of this system exhibit transient resonance captures (TRCs) causing intentional large-amplitude and high-frequency instabilities in the response of the NES. These TRCs result in strong energy transfer from the directly excited primary system to the light-weight attachment. The energy is harvested by the electromagnetic elements in the coupling and, in the present case, dissipated in a resistive element in the electrical circuit. The primary goal of this work is to numerically, analytically, and experimentally demonstrate the efficacy of employing this type of intentional high-frequency dynamic instability to achieve enhanced vibration energy harvesting under impulsive excitation.
Observations of earth eigen vibrations possibly excited by low frequency gravity waves
Tuman, V. S.
1971-01-01
A cryogenic gravity meter made of two parts, a magnetic suspension unit and a detection module, was used to monitor earth eigen vibrations. The magnetic field and field gradient are generated by energizing a set of superconducting coils made of niobium-zirconium alloy wire. The detection module is a double Josephson junction magnetometer. The output is printed on a chart recorder and later digitized using a computer; a Fourier transformation is performed on the accumulated data. The measurements of eigen vibrations are summarized in tabular and graphical representations.
DETERMINING THE RESPONSE IN CASE OF VIBRATIONS OF STRAIGHT BARS WITH RANDOM EXCITATIONS
Monica BALDEA
2012-05-01
Full Text Available By applying the finite element calculus to the study of bar vibrations, one obtains a system of linear diferential equations. One carries out the determination of the response to random stimulations by calculating the statistical terms as a function of the statistical terms of the stimulation
Dodge, W. G.
1968-01-01
Computer program determines the forced vibration in three dimensional space of a multiple degree of freedom beam type structural system. Provision is made for the longitudinal axis of the analytical model to change orientation at any point along its length. This program is used by industries in which structural design dynamic analyses are performed.
Ren, Ling
2015-07-15
The prospects for minimally invasive surgery, spatial imaging with mass spectrometry and rapid high throughput biodiagnosis require new means of tissue incision and biomolecule extraction with conserved molecular structure. Towards this aim, a laser ablation process is utilized in this dissertation, which is capable of performing precise tissue incision with minimal collateral damage and extracting intact biological entities with conserved biological functions. The method is based on the recently developed Picosecond Infrared Laser (PIRL) designed to excite selectively the water vibrational modes under the condition of ultrafast Desorption by Impulsive Vibrational Excitation (DIVE). The basic concept is that the selectively excited water molecules act as propellant to ablate whole biological complexes into the plume, faster than any thermal deleterious effect or fragmentation that would mask molecular identities.The PIRL ablation under DIVE condition is applied for the first time to six types of ocular tissues, rendering precise and minimally invasive incisions in a well-controlled and reproducible way. An eminent demonstration is the contact-free and applanation-free corneal trephination with the PIRL. Mass spectrometry and other analytical techniques show that great abundance of proteins with various molecular weights are extracted from the tissue by the PIRL ablation, and that fragmentation or other chemical alternation does not occur to the proteins in the ablation plume. With various microscope imaging and biochemical analysis methods, nano-scale single protein molecules, viruses and cells in the ablation plume are found to be morphologically and functionally identical to their corresponding controls. The PIRL ablation provides a new means to push the frontiers of laser surgery in ophthalmology and can be applied to resolve chemical activities in situ and in vivo. The most important finding is the conserved nature of the extracted biological entities
Ehlers, Florian; Scholz, Mirko; Schimpfhauser, Jens; Bienert, Jürgen; Oum, Kawon; Lenzer, Thomas
2015-04-28
In recent work, we demonstrated that the S* signal of β-carotene observed in transient pump-supercontinuum probe absorption experiments agrees well with the independently measured steady-state difference absorption spectrum of vibrationally hot ground state molecules S0* in solution, recorded at elevated temperatures (Oum et al., Phys. Chem. Chem. Phys., 2010, 12, 8832). Here, we extend our support for this "vibrationally hot ground state model" of S* by experiments for the three terminally aldehyde-substituted carotenes β-apo-12'-carotenal, β-apo-4'-carotenal and 3',4'-didehydro-β,ψ-caroten-16'-al ("torularhodinaldehyde") which were investigated by ultrafast pump-supercontinuum probe spectroscopy in the range 350-770 nm. The apocarotenals feature an increasing conjugation length, resulting in a systematically shorter S1 lifetime of 192, 4.9 and 1.2 ps, respectively, in the solvent n-hexane. Consequently, for torularhodinaldehyde a large population of highly vibrationally excited molecules in the ground electronic state is quickly generated by internal conversion (IC) from S1 already within the first picosecond of relaxation. As a result, a clear S* signal is visible which exhibits the same spectral characteristics as in the aforementioned study of β-carotene: a pronounced S0 → S2 red-edge absorption and a "finger-type" structure in the S0 → S2 bleach region. The cooling process is described in a simplified way by assuming an initially formed vibrationally very hot species S0** which subsequently decays with a time constant of 3.4 ps to form a still hot S0* species which relaxes with a time constant of 10.5 ps to form S0 molecules at 298 K. β-Apo-4'-carotenal behaves in a quite similar way. Here, a single vibrationally hot S0* species is sufficient in the kinetic modeling procedure. S0* relaxes with a time constant of 12.1 ps to form cold S0. Finally, no S0* features are visible for β-apo-12'-carotenal. In that case, the S1 → S0 IC process is expected
Kiani, Keivan
2017-08-01
Until now various aspects of vibrations of single-walled carbon nanotubes (SWCNTs) have been explored; however, their dynamics and possible instabilities because of the excitation of matrix have not been addressed methodically. By considering a harmonic transverse excitation, the explicit expressions of elastic fields are obtained based on the nonlocal Rayleigh, Timoshenko, and higher-order beam models. The roles of the nonlocality, slenderness ratio, amplitude and frequency of matrix excitation and interactional behavior of the embedded nanotube on the dynamic transverse displacements of SWCNTs are comprehensively displayed. The capabilities of the Rayleigh model as well as the Timoshenko model in capturing the deflection of the nanostructure based on the higher-order beam theory are also explained in some detail. The nonlocal elastodynamic fields of the nanostructure in the resonance state as well as the critical values of lateral and rotational stiffness of the matrix are also introduced and the influences of crucial factors on such parameters are explained and discussed carefully.
Mukuta, Tatsuhiko; Fukazawa, Naoto; Murata, Kei; Inagaki, Akiko; Akita, Munetaka; Tanaka, Sei'ichi; Koshihara, Shin-ya; Onda, Ken
2014-03-03
This work involved a detailed investigation into the infrared vibrational spectra of ruthenium polypyridyl complexes, specifically heteroleptic [Ru(bpy)2(bpm)](2+) (bpy = 2,2'-bipyridine and bpm = 2,2'-bipyrimidine) and homoleptic [Ru(bpy)3](2+), in the excited triplet state. Transient spectra were acquired 500 ps after photoexcitation, corresponding to the vibrational ground state of the excited triplet state, using time-resolved infrared spectroscopy. We assigned the observed bands to specific ligands in [Ru(bpy)2(bpm)](2+) based on the results of deuterium substitution and identified the corresponding normal vibrational modes using quantum-chemical calculations. Through this process, the more complex vibrational bands of [Ru(bpy)3](2+) were assigned to normal vibrational modes. The results are in good agreement with the model in which excited electrons are localized on a single ligand. We also found that the vibrational bands of both complexes associated with the ligands on which electrons are little localized appear at approximately 1317 and 1608 cm(-1). These assignments should allow the study of the reaction dynamics of various photofunctional systems including ruthenium polypyridyl complexes.
Kofsky, I. L.; Barrett, J. L.
1985-01-01
Laboratory experiments in which recombined CO, CO2, D2O, OH, N2, H2, and O2 molecules desorb from surfaces in excited internal and translational states are briefly reviewed. Unequilibrated distributions predominate from the principally catalytic metal substrates so far investigated. Mean kinetic energies have been observed up to approx. 3x, and in some cases less than, wall-thermal; the velocity distributions generally vary with emission angle, with non-Lambertian particle fluxes. The excitation state populations are found to depend on surface impurities, in an as yet unexplained way.
Takigami, Tadao; Tomioka, Takahiro
Bending vibration characteristics of railway vehicles have been investigated in general under excitation tests, in which a carbody was directly excited by a shaker. It is however very difficult with their results to evaluate the ride quality of passengers under conditions that the vehicle runs on a certain track. The authors are therefore developing an evaluation system for vertical vibration of railway vehicles. This system consists of an excitation system equipped with linear actuators, the elastic supporting device installed between wheels and rails, and analytical techniques to estimate the power spectral density (PSD) and the ride quality level (LT) which feature the ride quality. In this paper, we describe the excitation tests performed using an actual commuter car and the estimated PSD and LT are compared with what substantially measured under the running conditions.
Müller, H S P; Pearson, J C; Ordu, M H; Wehres, N; Lewen, F
2016-01-01
Methyl cyanide is an important trace molecule in space, especially in star-forming regions where it is one of the more common molecules used to derive kinetic temperatures. We want to obtain accurate spectroscopic parameters of minor isotopologs of methyl cyanide in their lowest excited v8 = 1 vibrational states to support astronomical observations, in particular, with interferometers such as ALMA. The laboratory rotational spectrum of methyl cyanide in natural isotopic composition has been recorded from the millimeter to the terahertz regions. Transitions with good signal-to-noise ratios could be identified for the three isotopic species CH3(13)CN, (13)CH3CN, and CH3C(15)N up to about 1.2 THz (J" <= 66). Accurate spectroscopic parameters were obtained for all three species. The present data were already instrumental in identifying v8 = 1 lines of methyl cyanide with one (13)C in IRAM 30 m and ALMA data toward Sagittarius B2(N).
Golibrzuch, Kai; Kandratsenka, Alexander; Rahinov, Igor; Cooper, Russell; Auerbach, Daniel J; Wodtke, Alec M; Bartels, Christof
2013-08-15
We measured absolute probabilities for vibrational excitation of NO(v = 0) molecules in collisions with a Au(111) surface at an incidence energy of translation of 0.4 eV and surface temperatures between 300 and 1100 K. In addition to previously reported excitation to v = 1 and v = 2, we observed excitation to v = 3. The excitation probabilities exhibit an Arrhenius dependence on surface temperature, indicating that the dominant excitation mechanism is nonadiabatic coupling to electron-hole pairs. The experimental data are analyzed in terms of a recently introduced kinetic model, which was extended to include four vibrational states. We describe a subpopulation decomposition of the kinetic model, which allows us to examine vibrational population transfer pathways. The analysis indicates that sequential pathways (v = 0 → 1 → 2 and v = 0 → 1 → 2 → 3) alone cannot adequately describe production of v = 2 or 3. In addition, we performed first-principles molecular dynamics calculations that incorporate electronically nonadiabatic dynamics via an independent electron surface hopping (IESH) algorithm, which requires as input an ab initio potential energy hypersurface (PES) and nonadiabatic coupling matrix elements, both obtained from density functional theory (DFT). While the IESH-based simulations reproduce the v = 1 data well, they slightly underestimate the excitation probabilities for v = 2, and they significantly underestimate those for v = 3. Furthermore, this implementation of IESH appears to overestimate the importance of sequential energy transfer pathways. We make several suggestions concerning ways to improve this IESH-based model.
Kim, Kilyoung; Johnson, Alan M; Powell, Amber L; Mitchell, Deborah G; Sevy, Eric T
2014-12-21
Collisional energy transfer between vibrational ground state CO2 and highly vibrationally excited monofluorobenzene (MFB) was studied using narrow bandwidth (0.0003 cm(-1)) IR diode laser absorption spectroscopy. Highly vibrationally excited MFB with E' = ∼41,000 cm(-1) was prepared by 248 nm UV excitation followed by rapid radiationless internal conversion to the electronic ground state (S1→S0*). The amount of vibrational energy transferred from hot MFB into rotations and translations of CO2 via collisions was measured by probing the scattered CO2 using the IR diode laser. The absolute state specific energy transfer rate constants and scattering probabilities for single collisions between hot MFB and CO2 were measured and used to determine the energy transfer probability distribution function, P(E,E'), in the large ΔE region. P(E,E') was then fit to a bi-exponential function and extrapolated to the low ΔE region. P(E,E') and the biexponential fit data were used to determine the partitioning between weak and strong collisions as well as investigate molecular properties responsible for large collisional energy transfer events. Fermi's Golden rule was used to model the shape of P(E,E') and identify which donor vibrational motions are primarily responsible for energy transfer. In general, the results suggest that low-frequency MFB vibrational modes are primarily responsible for strong collisions, and govern the shape and magnitude of P(E,E'). Where deviations from this general trend occur, vibrational modes with large negative anharmonicity constants are more efficient energy gateways than modes with similar frequency, while vibrational modes with large positive anharmonicity constants are less efficient at energy transfer than modes of similar frequency.
G.M. Golenkov
2015-12-01
Full Text Available Purpose. The research of the influence of value and direction of current on the equivalent spring magnetic force based on coaxial-linear motor (CLM – MS. Methodology. We carried out investigation of the equivalent harshness of magnetic spring with determination of electromechanical propulsion performance characteristics by the methods of computer modeling and experimental research of physical model of CLM – MS. The modeling of magnetic spring of CLM – MS is carried out by the finite-element method. The challenge is met as an axisymmetric challenge in cylindrical co-ordinates in magnetostatic approach. The experimental investigattion of the propulsion performance characteristics of magnetic spring is carried out on the test bench. Results. After the computer modeling and the experimental investigation of the electromechanical propulsion performance characteristics of magnetic spring the expressions of equivalent stiffness coefficient depending on the current in winding are obtained. The results of computer modeling are confirmed experimentally. Originality. The determination of equivalent stiffness coefficient of magnetic spring of vibration exciter based on coaxial-linear motor. Practical value. The obtained determination of equivalent stiffness coefficient of magnetic spring may be used in process of designing of vibration machines with devices for change of natural oscillation frequency.
Demin ZHAO; Jianlin LIU; C Q WU
2015-01-01
The parametric excited vibration of a pipe under thermal loading may occur because the fluid is often transported heatedly. The effects of thermal loading on the pipe stability and local bifurcations have rarely been studied. The stability and the local bifurcations of the lateral parametric resonance of the pipe induced by the pulsating fluid velocity and the thermal loading are studied. A mathematical model for a simply supported pipe is developed according to the Hamilton principle. Two partial differential equations describing the lateral and longitudinal vibration are obtained. The singularity theory is utilized to analyze the stability and the bifurcation of the system solutions. The transition sets and the bifurcation diagrams are obtained both in the unfolding parameter space and the physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The frequency response and the relationship between the critical thermal rate and the pulsating fluid velocity are obtained. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and the stability and local bifurcation analyses. It also confirms the existence of the chaos. The presented work can provide valuable information for the design of the pipeline and the controllers to prevent the structural instability.
Laporta, V; Tennyson, J
2016-01-01
Resonant vibrational-excitation cross sections and rate constants for electron scattering by molecular oxygen are presented. Transitions between all 42 vibrational levels of O$_2(\\textrm{X}\\ ^3\\Sigma_g^- $) are considered. Molecular rotations are parameterized by the rotational quantum number $J$ which is considered in the range 1 to 151. The lowest four resonant states of O$_2^-$, $^2\\Pi_g$, $^2\\Pi_u$, $^4\\Sigma_u^-$ and $^2\\Sigma_u^-$, are taken into account. The calculations are performed using the fixed-nuclei R-matrix approach to determine the resonance positions and widths, and the boomerang model to characterize the nuclei motion. Two energy regions below and above 4~eV are investigated: the first one is characterized by sharp structures in the cross section, and the second by a broad resonance peaked at 10~eV. The computed cross sections are compared with theoretical and experimental results available in literature for both the energy regions, and are made available for use by modelers. The effect of ...
Nonlinear Vibration Analysis for a Jeffcott Rotor with Seal and Air-Film Bearing Excitations
Yuefang Wang
2010-01-01
Full Text Available The nonlinear coupling vibration and bifurcation of a high-speed centrifugal compressor with a labyrinth seal and two air-film journal bearings are presented in this paper. The rotary shaft and disk are modeled as a rigid Jeffcott rotor. Muszynska's model is used to express the seal force with multiple parameters. For air-film journal bearings, the model proposed by Zhang et al. is adopted to express unsteady bearing forces. The Runge-Kutta method is used to numerically determine the vibration responses of the disk center and the bearings. Bifurcation diagrams for transverse motion of the rotor are presented with parameters of rotation speed and pressure drop of the seal. Multiple subharmonic, periodic, and quasiperiodic motions are presented with two seal-pressure drops. The bifurcation characteristics show inherent interactions between forces of the air-film bearings and the seal, presenting more complicated rotor dynamics than the one with either of the forces alone. Bifurcation diagrams are obtained with parameters of pressure drop and seal length determined for the sake of operation safety.
Weber, F.
2014-09-01
The semi-active vibration absorber (SVA) based on controlled semi-active damper is formulated to realize the behaviour of the passive undamped vibration absorber tuned to the actual harmonic disturbing frequency. It is shown that the controlled stiffness force, which is emulated by the semi-active damper to realize the precise real-time frequency tuning of the SVA, is unpreventably combined with the generation of undesirable damping in the semi-active damper whereby the SVA does not behave as targeted. The semi-active stiffness force is therefore optimized for minimum primary structure response. The results point out that the optimal semi-active stiffness force reduces the undesirable energy dissipation in the SVA at the expenses of slight imprecise frequency tuning. Based on these findings, a real-time applicable suboptimal SVA is formulated that also takes the relative motion constraint of real mass dampers into account. The results demonstrate that the performance of the suboptimal SVA is closer to that of the active solution than that of the passive mass damper.
Radi, P.P.; Tulej, M.; Knopp, G.; Beaud, P.; Gerber, T.
2004-03-01
Stimulated emission pumping by applying two-color resonant four-wave mixing is used to measure rotationally resolved spectra of the HCO (0,0,0) B {sup 2}A' - (0,3,1) X {sup 2}A' transition. The formyl radical is produced by photodissociation of formaldehyde at 31710.8 cm{sup -1} under thermalized conditions in a low pressure cell. In contrast to the highly congested one-color spectrum of HCO at room temperature, the doubleresonance method yields well isolated transitions which are assigned unambiguously due to intermediate level labeling. 89 rotational transitions have been assigned and yield accurate rotational constants for the vibrationally excited (0,3,1) band of the electronic ground state X {sup 2}A' of HCO. The determined rotational constant A = 25.84{+-}0.01 cm-1 is considerably higher than that for the vibrationless ground state and reflects the structural change due to excitation of the bending mode of the formyl radical. (author)
Kobayashi Takayoshi.
2013-03-01
Full Text Available Time-resolved transient absorption spectroscopy for water solution of cytosine with sub-10fs deep ultraviolet laser pulse is reported. Ultrafast electronic excited state dynamics and coherent molecular vibrational dynamics are simultaneously observed and their relaxation mechanisms are discussed.
Bhavesh K Shandilya; Manabendra Sarma; Satrajit Adhikari; Manoj K Mishra
2012-01-01
Vibrational excitation cross-sections $\\sigma_{v_{f}\\leftarrow v_{i}}(E)$ in resonant e-F2 and HCl scattering are calculated from transition matrix elements $T_{v_{f}\\leftarrow v_{i}}(E)$ obtained using Fourier transform of the cross correlation function 〈$_{v_{f}}$ () | $_{v_{i}}$ (, ) 〉. where $_{v_{i}}$ (, ) ≈ $e^{i \\hbar H_{AB^-}(R)t}$ $_{v_{i}}$ (). Time evolution under the influence of the resonance anionic Hamiltonian H$_{AB^{-}}$ (AB=F2/HCl) is effected using Lanczos reduction technique followed by fast Fourier transform and the target (AB) vibrational eigenfunctions $_{v_{i}}$ () and $_{v_{f}}$ () are calculated using Fourier grid Hamiltonian method applied to potential energy (PE) curve of the neutral target. The resulting vibrational excitation cross-sections provide reasonable agreement with experimental and other theoretical results.
Chunyu Zhao
2009-01-01
Full Text Available The paper focuses on the quantitative analysis of the coupling dynamic characteristics of two non-identical exciters in a non-resonant vibrating system. The load torque of each motor consists of three items, including the torque of sine effect of phase angles, that of coupling sine effect and that of coupling cosine effect. The torque of frequency capture results from the torque of coupling cosine effect, which is equal to the product of the coupling kinetic energy, the coefficient of coupling cosine effect, and the sine of phase difference of two exciters. The motions of the system excited by two exciters in the same direction make phase difference close to π and that in opposite directions makes phase difference close to 0. Numerical results show that synchronous operation is stable when the dimensionless relative moments of inertia of two exciters are greater than zero and four times of their product is greater than the square of their coefficient of coupling cosine effect. The stability of the synchronous operation is only dependent on the structural parameters of the system, such as the mass ratios of two exciters to the vibrating system, and the ratio of the distance between an exciter and the centroid of the system to the equivalent radius of the system about its centroid.
Jinghui Peng
2014-07-01
Full Text Available The resonance of the armature assembly is the main problem leading to the fatigue of the spring pipe in a torque motor of hydraulic servo valves, which can cause the failure of servo valves. To predict the vibration characteristics of the armature assembly, this paper focuses on the mathematical modeling of the vibration characteristics of armature assembly in a hydraulic servo valve and the identification of parameters in the models. To build models more accurately, the effect of the magnetic spring is taken into account. Vibration modal analysis is performed to obtain the mode shapes and natural frequencies, which are necessary to implement the identification of damping ratios in the mathematical models. Based on the mathematical models for the vibration characteristics, the harmonic responses of the armature assembly are analyzed using the finite element method and measured under electromagnetic excitations. The simulation results agree well with the experimental studies.
Teramoto, Yoshiyuki; Ono, Ryo
2014-08-01
Vibrationally excited N2(v = 1, 2) in an atmospheric-pressure air pulsed corona discharge was measured using coherent anti-Stokes Raman scattering (CARS). In a dry air discharge, the vibrational temperature determined from the ratio N2(v = 2)/N2(v = 0), Tv2, was approximately 500 K higher than that determined from N2(v = 1)/N2(v = 0), Tv1, immediately after the discharge pulse. Both vibrational temperatures reached equilibrium within 100 μs after the discharge pulse by the vibration-to-vibration (V-V) process of N2-N2. The translational temperature was also measured using CARS. The rise in the translational temperature due to vibration-to-translation (V-T) energy transfer was not observed for a postdischarge time of 5 μs-1 ms in the dry-air discharge. However, when the air was humidified, a significant V-T energy transfer was observed. It was due to an extremely rapid V-T process of H2O-H2O following the V-V process of N2-H2O. Measurements showed that the humidification of the ambient air accelerated the decrease in the N2 vibrational temperature and increased the translational temperature. N2(v) was generated mostly in the secondary streamer, not in the primary one, according to estimation from the measured N2(v) density.
Aalto, S; Gonzalez-Alfonso, E; Muller, S; Sakamoto, K; Fuller, G A; Garcia-Burillo, S; van der Werf, P; Neri, R; Spaans, M; Combes, F; Viti, S; Muehle, S; Armus, L; Evans, A; Sturm, E; Cernicharo, J; Henkel, C; Greve, T R
2015-01-01
We present high resolution (0."4) IRAM PdBI and ALMA mm and submm observations of the (Ultra) Luminous Infrared Galaxies ((U)LIRGs) IRAS17208-0014, Arp220, IC860 and Zw049.057 that reveal intense line emission from vibrationally excited (v2=1) J=3-2 and 4-3 HCN. The emission is emerging from buried, compact (r5e13 Lsun/kpc2. These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, v2=1, lines of HCN are excited by intense 14 micron mid-infrared emission and are excellent probes of the dynamics, masses and physical conditions of (U)LIRG nuclei when H2 column densities exceed 1e24 cm-2. It is clear that these lines open up a new interesting avenue to gain access to the most obscured AGNs and starbursts. Vibrationally excited HCN acts as a proxy for the absorbed mid-infrared emission from the embedded nuclei, which allows for reconstruction of the intrinsic, hotter dust SED. In contrast, the ground vibrational state (v=0), J=3-2 and 4-3 ro...
Goudreau, E. S.; Tokaryk, Dennis W.; Ross, Stephen Cary; Billinghurst, Brant E.
2016-06-01
Despite being an important prototype molecule for intramolecular proton tunnelling, the far-IR spectrum of the internally hydrogen-bonded species malonaldehyde (C_3O_2H_4) is not yet well understood. In the talk I gave at the ISMS meeting in 2015 I discussed the high-resolution spectra we obtained at the Canadian Light Source synchrotron in Saskatoon, Saskatchewan. These spectra include a number of fundamental vibrational bands in the 100-2000 cm-1 region. In our efforts to analyze these bands we have noticed that our ground state combination differences show a large drift (up to an order of magnitude larger than our experimental error) away from those calculated using constants established by Baba et al., particularly in regions of high J (above 30) and low Ka (below 5). An examination of the previous microwave and far-IR studies reveals that this region of J-Ka space was not represented in the lines that Baba et al. used to generate the values for their fitting parameters. By including our own measurements in the fitting, we were able to improve the characterization of the ground state so that it is now consistent with all of the existing data. This characterization now covers a much larger range of J-Ka space and has enabled us to make significant progress in analyzing our far-IR synchrotron spectra. These include an excited vibrational state at 241 cm-1 as well as several states split by the tunnelling effect at higher wavenumber. T. Baba, T. Tanaka, I. Morino, K. M. T. Yamada, K. Tanaka. Detection of the tunneling-rotation transitions of malonaldehyde in the submillimeter-wave region. J. Chem. Phys., 110. 4131-4133 (1999) P. Turner, S. L. Baughcum, S. L. Coy, Z. Smith. Microwave Spectroscopic Study of Malonaldehyde. 4. Vibration-Rotation Interaction in Parent Species. J. Am. Chem. Soc., 106. 2265-2267 (1984) D. W. Firth, K. Beyer, M. A. Dvorak, S. W. Reeve, A. Grushow, K. R. Leopold. Tunable far-infrared spectroscopy of malonaldehyde. J. Chem. Phys., 94. 1812
Fenglan Wang
2013-06-01
Full Text Available The self-excited vibration of blooming mill is a kind of torsional vibration, which occurs only when the rolling machine slips under appropriate conditions. Once in place, this may cause the larger peak pressure of each component in the main drive system; reduce the service life of the components, cause components′ damage directly. A large number of studies have shown that, at present there are not effective methods for diagnosis, monitoring of slipping and take proper measures in time to stop slipping so as to avoid the occurrence of malignant accidents. In this paper, author set out from another angle, take the main drive system of rolling mill as an example, to study stability of self-excited vibration. The conditions of the stable vibration are gained. By combining with the actual working conditions of blooming mill, author has put forward some effective measures to meet the stable conditions in order to make the blooming mill work in the stable state. Practice research has proved that the effective measures can contribute to reduce structural damage directly caused by the torsional vibration when “slipping” phenomenon occurred and to extend the service life of the components.
Mohammed, Omar F.
2014-05-01
We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S 2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S 1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S2) and 1,10-quinone (S1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S2 and S1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S2/S1 relaxation to either the ground or triplet state. © 2014 American Chemical Society.
Rezaee, Mousa; Jahangiri, Reza
2015-05-01
In this study, in the presence of supersonic aerodynamic loading, the nonlinear and chaotic vibrations and stability of a simply supported Functionally Graded Piezoelectric (FGP) rectangular plate with bonded piezoelectric layer have been investigated. It is assumed that the plate is simultaneously exposed to the effects of harmonic uniaxial in-plane force and transverse piezoelectric excitations and aerodynamic loading. It is considered that the potential distribution varies linearly through the piezoelectric layer thickness, and the aerodynamic load is modeled by the first order piston theory. The von-Karman nonlinear strain-displacement relations are used to consider the geometrical nonlinearity. Based on the Classical Plate Theory (CPT) and applying the Hamilton's principle, the nonlinear coupled partial differential equations of motion are derived. The Galerkin's procedure is used to reduce the equations of motion to nonlinear ordinary differential Mathieu equations. The validity of the formulation for analyzing the Limit Cycle Oscillation (LCO), aero-elastic stability boundaries is accomplished by comparing the results with those of the literature, and the convergence study of the FGP plate is performed. By applying the Multiple Scales Method, the case of 1:2 internal resonance and primary parametric resonance are taken into account and the corresponding averaged equations are derived and analyzed numerically. The results are provided to investigate the effects of the forcing/piezoelectric detuning parameter, amplitude of forcing/piezoelectric excitation and dynamic pressure, on the nonlinear dynamics and chaotic behavior of the FGP plate. It is revealed that under the certain conditions, due to the existence of bi-stable region of non-trivial solutions, system shows the hysteretic behavior. Moreover, in absence of airflow, it is observed that variation of control parameters leads to the multi periodic and chaotic motions.
Imanishi, Masatoshi; Izumi, Takuma
2016-01-01
We present the results of ALMA Cycle 2 observations of the ultraluminous infrared galaxy, IRAS 20551-4250, at HCN/HCO+/HNC J=3-2 lines at both vibrational-ground (v=0) and vibrationally excited (v2=1) levels. This galaxy contains a luminous buried active galactic nucleus (AGN), in addition to starburst activity, and our ALMA Cycle 0 data revealed a tentatively detected vibrationally excited HCN v2=1f J=4-3 emission line. In our ALMA Cycle 2 data, the HCN/HCO+/HNC J=3-2 emission lines at v=0 are clearly detected. The HCN and HNC v2=1f J=3-2 emission lines are also detected, but the HCO+ v2=1f J=3-2 emission line is not. Given the high-energy level of v2=1 and the resulting difficulty of collisional excitation, we compared these results with those of the calculation of infrared radiative pumping, using the available infrared 5-35 micron spectrum. We found that all of the observational results were reproduced, if the HCN abundance was significantly higher than that of HCO+ and HNC. The flux ratio and excitation ...
Compact mixed-reactant fuel cells
Priestnall, Michael A.; Kotzeva, Vega P.; Fish, Deborah J.; Nilsson, Eva M.
The compact mixed-reactant (CMR) fuel cell is an important new "platform" approach to the design and operation of all types of fuel cell stacks. Amongst several other advantages, CMR has the potential to reduce polymer electrolyte membrane (PEM) stack component costs by around a third and to raise volumetric power densities by an order of magnitude. Mixed-reactant fuel cells, in which the fuel and oxidant within a cell are allowed to mix, rely upon the selectivity of anode and cathode electrocatalysts to separate the electrochemical oxidation of fuel and reduction of oxidant. A comprehensive review of the 50-year history of mixed-reactant literature has demonstrated that such systems can perform as well as and, in some circumstances, much better than conventional fuel cells. The significant innovation that Generics has introduced to this field is to combine the concept of mixed-reactant fuel cells with that of a fully porous membrane electrode assembly (MEA) structure. Passing a fuel-oxidant mixture through a stack of porous cells allows the conventional bipolar flow-field plates required in many fuel cell designs to be eliminated. In a conventional PEM stack, for example, the bipolar carbon flow-field plates may block up to half of the active cell area and account for up to 90% of the volume of the stack and of the order of one-third of the materials costs. In addition to all the advantages of mixed-reactant systems, the "flow-through" mode, embodied in Generics' CMR approach, significantly enhances mass-transport of reactants to the electrodes and can reduce reactant pressure drops across the stack. Redesigning fuel cells to operate in a CMR mode with selective electrodes offers the attractive prospect of much reduced stack costs and significantly higher stack power densities for all types of fuel cell. Initial modeling and proof of principle experiments using an alkaline system have confirmed the validity of the CMR approach and the potential for substantial
Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon
Tinck, Stefan; Bogaerts, Annemie
2016-06-01
In this work, the role of vibrationally excited HBr (HBr(vib)) is computationally investigated for a HBr/He inductively coupled plasma applied for Si etching. It is found that at least 50% of all dissociations of HBr occur through HBr(vib). This additional dissociation pathway through HBr(vib) makes the plasma significantly more atomic. It also results in a slightly higher electron temperature (i.e. about 0.2 eV higher compared to simulation results where HBr(vib) is not included), as well as a higher gas temperature (i.e. about 50 K higher than without including HBr(vib)), due to the enhanced Franck-Condon heating through HBr(vib) dissociation, at the conditions investigated. Most importantly, the calculated etch rate with HBr(vib) included in the model is a factor 3 higher than in the case without HBr(vib), due to the higher fluxes of etching species (i.e. H and Br), while the chemical composition of the wafer surface shows no significant difference. Our calculations clearly show the importance of including HBr(vib) for accurate modeling of HBr-containing plasmas.
Hortobágyi, T; Rider, P; DeVita, P
2014-12-01
We examined the effects of whole-body mechanical vibration (WBV) on indices of motoneuronal excitability at rest and during muscle contraction in healthy humans. Real and sham WBV at 30 Hz had no effect on reflexes measured during muscle contraction. Real WBV at 30 and 50 Hz depressed the H-reflex ∼45%. These depressions diminished across the five inter-bout rest intervals. The depression converted to 27% and 7% facilitation over the 15-min long recovery period following real WBV at 30 and 50 Hz, respectively. The depression, measured during the inter-bout rest, correlated r = 0.48 (P = 0.007) with the subsequent facilitation, measured during the follow-up. The depression produced by sham vs real WBV was significant but less (23%), recovered faster, and the facilitation was absent in the 15-min long follow-up period. WBV produced time-varying depression followed by facilitation of the H-reflex at rest. A lack of change in volitional wave suggests that WBV did not affect the efferent neural drive.
Harne, R. L.; Zhang, Chunlin; Li, Bing; Wang, K. W.
2016-07-01
Impulsive energies are abundant throughout the natural and built environments, for instance as stimulated by wind gusts, foot-steps, or vehicle-road interactions. In the interest of maximizing the sustainability of society's technological developments, one idea is to capture these high-amplitude and abrupt energies and convert them into usable electrical power such as for sensors which otherwise rely on less sustainable power supplies. In this spirit, the considerable sensitivity to impulse-type events previously uncovered for bistable oscillators has motivated recent experimental and numerical studies on the power generation performance of bistable vibration energy harvesters. To lead to an effective and efficient predictive tool and design guide, this research develops a new analytical approach to estimate the electroelastic response and power generation of a bistable energy harvester when excited by an impulse. Comparison with values determined by direct simulation of the governing equations shows that the analytically predicted net converted energies are very accurate for a wide range of impulse strengths. Extensive experimental investigations are undertaken to validate the analytical approach and it is seen that the predicted estimates of the impulsive energy conversion are in excellent agreement with the measurements, and the detailed structural dynamics are correctly reproduced. As a result, the analytical approach represents a significant leap forward in the understanding of how to effectively leverage bistable structures as energy harvesting devices and introduces new means to elucidate the transient and far-from-equilibrium dynamics of nonlinear systems more generally.
Müller, Holger S. P.; Drouin, Brian J.; Pearson, John C.; Ordu, Matthias H.; Wehres, Nadine; Lewen, Frank
2016-02-01
Context. Methyl cyanide is an important trace molecule in space, especially in star-forming regions where it is one of the more common molecules used to derive kinetic temperatures. Aims: We want to obtain accurate spectroscopic parameters of minor isotopologs of methyl cyanide in their lowest excited ν8 = 1 vibrational states to support astronomical observations, in particular, with interferometers such as ALMA. Methods: The laboratory rotational spectrum of methyl cyanide in natural isotopic composition has been recorded from the millimeter to the terahertz regions. Results: Transitions with good signal-to-noise ratios could be identified for the three isotopic species CH313CN, 13CH3CN, and CH3C15N up to about 1.2 THz (J'' ≤ 66). Accurate spectroscopic parameters were obtained for all three species. Conclusions: The present data were already instrumental in identifying ν8 = 1 lines of methyl cyanide with one 13C in IRAM 30 m and ALMA data toward Sagittarius B2(N).
鄢国森; 先晖; 谢代前
1997-01-01
A 285-pomt multi-reference configuration-interaction involving single and double excitations ( MRS DCI) potential energy surface for the electronic ground state of L12H is determined by using 6-311G (2df,2pd)basis set.A Simons-Parr-Finlan polynomial expansion is used to fit the discrete surface with a x2 of 4.64×106 The equn librium geometry occurs at Rc=0.172 nm and,LiHL1=94.10°.The dissociation energy for reaction I2H(2A)→L12(1∑g)+H(2S) is 243.910 kJ/mol,and that for reaction L12H(2A’)→HL1(1∑) + L1(2S) is 106.445 kl/mol The inversion barrier height is 50.388 kj/mol.The vibrational energy levels are calculated using the discrete variable representation (DVR) method.
Sharma, Sitansh; Sharma, Purshotam; Singh, Harjinder; Balint-Kurti, Gabriel G
2009-06-01
Time dependent quantum dynamics and optimal control theory are used for selective vibrational excitation of the N6-H (amino N-H) bond in free adenine and in the adenine-thymine (A-T) base pair. For the N6-H bond in free adenine we have used a one dimensional model while for the hydrogen bond, N6-H(A)...O4(T), present in the A-T base pair, a two mathematical dimensional model is employed. The conjugate gradient method is used for the optimization of the field dependent cost functional. Optimal laser fields are obtained for selective population transfer in both the model systems, which give virtually 100% excitation probability to preselected vibrational levels. The effect of the optimized laser field on the other hydrogen bond, N1(A)...H-N3(T), present in A-T base pair is also investigated.
R. O. Manuilova
2006-11-01
Full Text Available The traditional kinetics of electronically excited products of O3 and O2 photolysis is supplemented with the processes of the energy transfer between electronically-vibrationally excited levels O2(a1Δg, v and O2(b1Σ+g, v, excited atomic oxygen O(1D, and the O2 molecules in the ground electronic state O2(X3Σg−, v. In contrast to the previous models of kinetics of O2(a1Δg and O2 (b1Σ+g, our model takes into consideration the following basic facts: first, photolysis of O3 and O2 and the processes of energy exchange between the metastable products of photolysis involve generation of oxygen molecules on highly excited vibrational levels in all considered electronic states – b1Σ+g, a1Δg and X3Σg−; second, the absorption of solar radiation not only leads to populating the electronic states on vibrational levels with vibrational quantum number v equal to 0 – O2(b1Σ+g, v=0 (at 762 nm and O2(a1Δg, v=0 (at 1.27 µm, but also leads to populating the excited electronic–vibrational states O2(b1Σ+g, v=1 and O2(b1Σ+g, v=2 (at 689 nm and 629 nm. The proposed model allows one to calculate not only the vertical profiles of the O2(a1Δg, v=0 and O2(b1Σg, v=0 concentrations, but also the profiles of [O2(a1Δg, v≤5], [O2 (b1Σ+g , v=1, 2] and O2(X3Σg−, v=1–35. In the altitude range 60–125 km, consideration of the electronic-vibrational kinetics significantly changes the calculated concentrations of the metastable oxygen molecules and reduces the discrepancy between the altitude profiles of ozone concentrations retrieved from the 762-nm and 1.27-µm emissions measured simultaneously.
李永庆; 张永嘉; 赵金峰; 赵美玉; 丁勇
2015-01-01
Vector correlations of the reaction N(2D)+H2(X1Σ+g )→NH(a1∆)+H(2S) are studied based on a recent DMBE-SEC PES for the first excited state of NH2 [J. Phys. Chem. A 114 9644 (2010)] by using a quasi-classical trajectory method. The effects of collision energy and the reagent initial vibrational excitation on cross section and product polarization are investigated for v=0–5 and j=0 states in a wide collision energy range (10–50 kcal/mol). The integral cross section could be increased by H2 vibration excitation remarkably based on the DMBE-SEC PES. The different phenomena of differential cross sections with different collision energies and reagent vibration excitations are explained. Particularly, the NH molecules are scattered mainly in the backward hemisphere at low vibration quantum number and evolve from backward to forward direction with increasing vibration quantum number, which could be explained by the fact that the vibrational excitation enlarges the H–H distance in the entrance channel, thus enhancing the probability of collision between N atom and H atom. A further study on product polarization demonstrates that the collision energy and vibrational excitation of the reagent remarkably influence the distributions of P(θr ), P(φr ), and P(θr ,φr ).
Yufei Liu
2015-01-01
Full Text Available This paper investigates the dynamic of a flexible robotic manipulator (FRM which consists of rigid driving base, flexible links, and flexible joints. With considering the motion fluctuations caused by the coupling effect, such as the motor parameters and mechanism inertias, as harmonic disturbances, the system investigated in this paper remains a parametrically excited system. An elastic restraint model of the FRM with elastic joints (FRMEJ is proposed, which considers the elastic properties of the connecting joints between the flexible arm and the driving base, as well as the harmonic disturbances aroused by the electromechanical coupling effect. As a consequence, the FRMEJ accordingly remains a flexible multibody system which conveys the effects of rigid-flexible couple and electromechanical couple. The Lagrangian function and Hamilton’s principle are used to establish the dynamic model of the FRMEJ. Based on the dynamic model proposed, the vibration power flow is introduced to show the vibration energy distribution. Numerical simulations are conducted to investigate the effect of the joint elasticities and the disturbance excitations, and the influences of the structure parameters and motion parameters on the vibration power flow are studied. The results obtained in this paper contribute to the structure design, motion optimization, and vibration control of FRMs.
Ray, Sara E.; Vissers, Gé W. M.; McCoy, Anne B.
2009-06-01
Hydrogen-transfer reactions are probed through vibrational excitation of the HCl bond in the pre-reactive F\\cdotsHCl complex. Such open-shell species provide a challenge for quantum dynamical calculations due to the need to take into account multiple potential energy surfaces to accurately describe the system.A three-dimensional, fully-coupled potential energy surface has been constructed based on electronic energies calculated at the multireference configuration interaction+Davidson correction (MRCI+Q) level of theory with an aug-cc-pVnZ (n=2,3,4) basis. Spin orbit calculations have also been included. Here we present the results of time-dependent quantum wave packet calculations on the asymmetric hydrogen-transfer reaction of F(^2P) + HCl. In these calculations, the reaction is initiated by vibrationally exciting the HCl stretching motion in the pre-reactive F\\cdotsHCl complex. The wave packet is propagated on the coupled potential energy surfaces. Product state distributions were calculated for reactions initiated in the first three vibrationally excited states of HCl, v=1-3. M. P. Deskevich, M. Y. Hayes, K. Takahashi, R. T. Skodje, and D. J. Nesbitt J. Chem. Phys. 124 (22) 224303 (2006) M. P. Deskevich and D. J. Nesbitt private communication(2007)
Chunyu Zhao
2009-01-01
Full Text Available In this paper an analytical approach is proposed to study the feature of frequency capture of two non-identical coupled exciters in a non-resonant vibrating system. The electromagnetic torque of an induction motor in the quasi-steady-state operation is derived. With the introduction of two perturbation small parameters to average angular velocity of two exciters and their phase difference, we deduce the Equation of Frequency Capture by averaging two motion equations of two exciters over their average period. It converts the synchronization problem of two exciters into that of existence and stability of zero solution for the Equation of Frequency Capture. The conditions of implementing frequency capture and that of stabilizing synchronous operation of two motors have been derived. The concept of torque of frequency capture is proposed to physically explain the peculiarity of self-synchronization of the two exciters. An interesting conclusion is reached that the moments of inertia of the two exciters in the Equation of Frequency Capture reduce and there is a coupling moment of inertia between the two exciters. The reduction of moments of inertia and the coupling moment of inertia have an effect on the stability of synchronous operation.
关大任; 赵显; 邓从豪; John Z.H.Zhang
1997-01-01
Three-dimensional quantum mechanical calculations for vibrational predissociation of HeI2(B) van der Waals molecules are presented using the time-dependent wave packet technique within the golden rule approxima tion.The total and partial decay widths,lifetimes,rates and their dependence on initial vibrational states were obtained for HeI2 at low initial vibrational excited levels.Our calculations show that the calculated tota decay widths,lifetimes and rates agree well with those extrapolated from experimental data available The predicted total decay widths as a function of initial vibrational states exhibit highly nonlinear behavior.The very short propagation time (less.than 1 ps) required in the golden rule wave packet calculation is determined by the duration time of the final state inter-action between the fragments on the vibrationally deexcited adiabatic potential surface.The final state interaction between the fragments is shown to play an important role in determining the final rotational distri
The excited triplet (T{sub 1}) state structure and vibrational properties of 2,2'-bipyridine
Lapouge, C.; Buntinx, G. [Laboratoire de Spectrochimie Infrarouge et Raman, UMR 8516 de l' Universite et du CNRS, Centre d' Etudes et de Recherches Lasers et Applications (FR 2416 du CNRS), Bat. C5, Universite des Sciences et Technologies de Lille, 59655 Villeneuve d' Ascq (France); Poizat, O. [Laboratoire de Spectrochimie Infrarouge et Raman, UMR 8516 de l' Universite et du CNRS, Centre d' Etudes et de Recherches Lasers et Applications (FR 2416 du CNRS), Bat. C5, Universite des Sciences et Technologies de Lille, 59655 Villeneuve d' Ascq (France)], E-mail: olivier.poizat@univ-lille1.fr
2008-06-02
The geometry of the lowest lying excited triplet state (T{sub 1}) of 2,2'-bipyridine (22BPY) was optimized by using the time-dependent density functional theory (TD-DFT) with the B3LYP functional and the SVP basis set. The T{sub 1} state is of {sup 3}B{sub u} symmetry and results from a nearly one-electron {pi}{pi}* transition from the 3b{sub g} HOMO to the 4a{sub u} LUMO. Its geometry is trans-planar and essentially characterized by a reinforcement of the interring CC bond and a quinoidal distortion of the rings. This calculated triplet structure is firmly validated by an unequivocal agreement, for four 22BPY isotopomers, between the derived theoretical vibrational frequencies and previously reported experimental time-resolved resonance Raman (TR3) spectra. Moreover, vertical transitions to the 10 lowest energy triplet states T{sub n} were calculated and the corresponding T{sub 1} state resonance Raman intensities estimated, in the short-time dynamics approximation of the Franck-Condon scattering mechanism, from the gradient of the T{sub n} potential surfaces at the T{sub 1} geometry along the totally symmetric modes. Excellent agreement with the experimental resonance Raman intensities was observed for a 4a{sub u} (LUMO) {yields} 5b{sub g} (LUMO + 3) T{sub 1} {yields} T{sub n} transition. This analysis provides a further support of the TD-DFT optimized T{sub 1} state structure of 22BPY.
Biggs, Jason D
2009-01-01
The preceding paper describes a strategy for externally influencing the course of short-time electronic excitation transfer (EET) in molecular dimers and observing the process by nonlinear wave-packet interferometry (nl-WPI). Within a sample of isotropically oriented dimers having a specified internal geometry, a vibrational mode internal to the acceptor chromophore can be preferentially driven by electronically nonresonant impulsive stimulated Raman (or resonant infrared) excitation with a short polarized control pulse. A subsequent electronically resonant polarized pump then preferentially excites the donor, and EET ensues. Here we test both the control strategy and its spectroscopic investigation-with some sacrifice of amplitude-level detail-by calculating the pump-probe difference signal. That signal is the limiting case of the control-influenced nl-WPI signal in which the two pulses in the pump pulse-pair coincide, as do the two pulses in the probe pulse-pair. We present calculated pump-probe difference ...
Wang, Aixing; Fang, Chao; Liu, Yibao
2017-01-07
In this article the dynamic features of the highly excited vibrational states of the hypochlorous acid (HOCl) non-integrable system are studied using the dynamic potential and Lyapunov exponent approaches. On the condition that the 3:1 resonance between the H-O stretching and H-O-Cl bending modes accompany the 2:1 Fermi resonance between the O-Cl stretching and H-O-Cl bending modes, it is found that the dynamic potentials of the highly excited vibrational states vary regularly with different Polyad numbers (P numbers). As the P number increases, the dynamic potentials of the H-O stretching mode remain the same, but those of the H-O-Cl bending mode gradually become complex. In order to investigate the chaotic and stable features of the highly excited vibrational states of the HOCl non-integrable system, the Lyapunov exponents of different energy levels lying in the dynamic potentials of the H-O-Cl bending mode (P = 4 and 5) are calculated. It is shown that the Lyapunov exponents of the energy levels staying in the junction of Morse potential and inverse Morse potential are relative large, which indicates the degrees of chaos for these energy levels is relatively high, but the stabilities of the corresponding states are good. These results could be interpreted as the intramolecular vibrational relaxation (IVR) acting strongly via the HOCl bending motion and causing energy transfers among different modes. Based on the previous studies, these conclusions seem to be generally valid to some extent for non-integrable triatomic molecules.
推进器激励船舶振动辐射声计算方法%Calculational method for radiating sound excited by vibration of ship propeller
谢基榕; 徐利刚; 沈顺根; 吴有生
2011-01-01
Based on Timoshenko beam model, the calculation model of coupling vibration of propeller, shaft and ship hull is established in this paper, and the sound pressure derived by hull vibration is calculated with monopole or dipole model. Difference between the sound derived by hull vibration induced propeller excitation directly acting on hull and that acting on shaft is also analyzed, and therefore the effect of shaft on propeller excitation transmission to hull is demonstrated.%文章在铁木辛柯梁的基础上,建立螺旋桨、轴系及船体耦合振动的数学物理模型,采用声极子模型计算各船体截面振动引起的辐射声压.计算分析了激励力直接作用到船体和经螺旋桨、轴系激励船体振动产生声辐射的差别,指出轴系振动对螺旋桨激励力激起船体振动并产生声辐射有着关键的影响作用.
Self-excited vibration analysis for wheel/rail lateral contact system%轮轨横向接触系统的自激振动分析
王振; 陈照波; 焦映厚; 刘旺中
2011-01-01
To study the influence of self-excited vibration on the curve squeal noise in the wheel/rail contact,the dynamical equation for 1-DOF wheel/rail lateral contact system is derived.A new friction coefficient model based on De Beer model is adopted to calculate the friction force in the wheel/rail contact surface.The influence of kinetic and static friction coefficients as well as the lateral creepage on the stability of self-excited vibration system is investigated.The calculation results show that wheel＇s inherent modes will be excited by the unstable self-excited vibration.If the structural damping of wheel/rail contact system is larger than the equivalent damping of the friction force,or the value of lateral creepage is less than 0.0024,the self-excited vibration system will be stable,and thus the curve squeal noise can be restrained.%为了研究轮轨接触过程中发生的自激振动现象对轮轨曲线啸叫噪声的影响,建立了轮轨横向接触系统的单自由度动力学方程,采用基于De Beer模型的改进的新型摩擦系数模型计算了轮轨接触面上的摩擦力变化,用相平面法分析了动、静摩擦系数以及横向蠕滑率对该自激振动系统的稳定性影响.计算结果表明：不稳定的轮轨自激振动会激发车轮的若干模态产生啸叫噪声;轮轨接触系统的结构阻尼大于因摩擦力变化而引起的等效阻尼,轮轨间横向蠕滑率小于0.002 4可以使该系统保持稳定,抑制啸叫噪声.
Salvi, Jonathan; Giaralis, Agathoklis
2016-09-01
A novel dynamic vibration absorber (DVA) configuration is introduced for simultaneous vibration suppression and energy harvesting from oscillations typically exhibited by large-scale low-frequency engineering structures and structural components. The proposed configuration, termed energy harvesting-enabled tuned mass-damper-inerter (EH-TMDI) comprises a mass grounded via an in-series electromagnetic motor (energy harvester)-inerter layout, and attached to the primary structure through linear spring and damper in parallel connection. The governing equations of motion are derived and solved in the frequency domain, for the case of harmonically-excited primary structures, here modelled as damped single-degree- of-freedom (SDOF) systems. Comprehensive parametric analyses proved that by varying the mass amplification property of the grounded inerter, and by adjusting the stiffness and the damping coefficients using simple optimum tuning formulae, enhanced vibration suppression (in terms of primary structure peak displacement) and energy harvesting (in terms of relative velocity at the terminals of the energy harvester) may be achieved concurrently and at nearresonance frequencies, for a fixed attached mass. Hence, the proposed EH-TMDI allows for relaxing the trade-off between vibration control and energy harvesting purposes, and renders a dual-objective optimisation a practically-feasible, reliable task.
Tullia Gallina Toschi
2014-02-01
Full Text Available The mechanical vibrations characterized by a frequency lower than 200 Hz could promote the cells breakage and improve the oil extraction process by avoiding, at the same time, the negative effects on the commercial qualitative parameters due to the use of the heating during malaxation. Vibration tests were conducted by means of an electrodynamic shaker in order to find the optimal frequency levels of excitation, able to put in a resonant condition the olive paste. Sinusoidal accelerations at constant acceleration (120 m/s2, in a range between 5 and 200 Hz were explored. The 50 Hz and 80 Hz frequencies were able to put in resonant condition the olive paste. In the vibrated samples at 50 Hz (15 min of treatment, the maximum increment of the extraction efficiency (about 53% in comparison with the control, was observed. Further studies could be conducted in order to assess the synergic effect of the mechanical vibrations and the malaxation on the oil extraction efficiency, with the aim of reducing the time of the whole phase and avoiding changes in the oil quality traits.
Caballero, J.F.; Wittig, C.
1981-08-15
The IR multiple photon excitation and dissociation of C2H5F and 1,1-C2H4F2 has been studied by monitoring vibrational fluorescence in the region 2000-4000 cm following excitation with the focused output from a CO2 TEA laser. 21 references, 2 figures.
Reshetova, A. I.; Poplavskaya, T. V.
2016-10-01
The problem of disturbances evolution in a hypersonic viscous shock layer on a flat plate is considered. Numerical simulation was performed by solving 2D Navier-Stokes equations using the ANSYS Fluent software package within the model of thermally perfect gas. The change of vibrational energy was simulated by the Landau-Teller equation, in which the finite time of vibrational relaxation of CO2 molecules was taken into account. The quantitative data on the effect of vibrational relaxation of CO2 molecules on the evolution of acoustic disturbances in the shock layer on a plate is obtained.
Shen Guang-Xian; Linghu Rong-Feng; Wang Rong-Kai; Yang Xiang-Dong
2007-01-01
In this paper, close-coupling method was applied to the He-H2(D2,T2) system, and the first vibrational excitation differences of these partial wave cross sections, this paper have obtained the change rules of the partial wave cross sections with increases of quantum number, and with change of reduced mass of system. Based on the calculation,influence on the partial wave cross sections brought by the variations in the reduced mass of systems and in the relative kinetic energy of incident atoms is discussed.
Paulson, Leif O; Kaminský, Jakub; Anderson, David T; Bouř, Petr; Kubelka, Jan
2010-03-01
Recent experimental studies of trans-formic acid (FA) in solid para-hydrogen (pH2) highlighted the importance of vibrationally averaged dipole moments for the interpretation of the high-resolution infrared (IR) spectra, in particular for the C═O stretch (ν3) mode. In this report, dipole moments for the ν3 ground (v = 0) and excited (v = 1, 2, 3, and 4) anharmonic vibrational states in trans-FA are investigated using two different approaches: a single mode approximation, where the vibrational states are obtained from the solution of the one-dimensional Schrödinger equation for the harmonic normal coordinate, and a limited vibrational configuration interaction (VCI) approximation. Density functional theory (B3LYP, BPW91) and correlated ab initio (MP2 and CCSD(T)) electronic methods were employed with a number of double- and triple-ζ and correlation consistent basis sets. Both single mode and VCI approaches show comparable agreement with experimental data, which is more dependent on the level of theory used. In particular, the BPW91/cc-pVDZ level appears to perform remarkably well. Effects of solvation of FA in solid state Ar and pH2 matrices were simulated at the BPW91/cc-pVDZ level using a conductor-like polarized continuum model (CPCM). The Ar and pH2 solid-state matrices cause quite a substantial increase in the FA dipole moments. Compared to gas-phase calculations, the CPCM model for pH2 better reproduces the experimental FA spectral shifts caused by interaction with traces of ortho-hydrogen (oH2) species in solid pH2. The validity of the single mode approach is tested against the multidimensional VCI results, suggesting that the isolated (noninteracting) mode approximation is valid up to the third vibrationally excited state (v = 3). Finally, the contribution of the ground anharmonic vibrational states of the remaining modes to the resulting ν3 single mode dipole moments is examined and discussed.
Collisional Energy Transfer between Highly Vibrationally Excited CsH(X1∑+,v=15-22)and H2
ZHU Dong-Hui; ZHANG Bin; SHEN Yi-Fan; DAI Kang
2011-01-01
@@ oms are prepared in the 6D state by two-photon absorption.CsH(X1∑+,v"=0)is generated from the Cs(6D)+H2 reaction.By overtone excitation with a pulsed dye laser,highly vibrational states v">15 of CsH in its ground electronic state are obtained.A diode laser is used to probe either the prepared vibrational state or the collisionally populated states.The decay signal of the time-resolved fluorescence from the A1∑+(v')→X1∑+(v")transition is monitored.Based on the Stern-Volmer equation,the total rate coefficients for v"=15-22 are yielded.The time evolution and relative intensities of three related states,v",v"-1 and v"-2,made by the initially prepared v"state of CsH are measured.Rate coefficients of single-and double-quantum relaxation are obtained.These results show that single-quantum relaxation accounts for ≥50%of the total relaxation out of states v"=17-20.Multiquantum relaxation(△v≥2)makes major contribution(≥62%)to the vibrational relaxation at v"=21 and 22.A simple explanation is given.%The Cs atoms are prepared in the 6D state by two-photon absorption. CsH(X1E+ ,v" =0) is generated from the Cs(6D)+H2 reaction. By overtone excitation with a pulsed dye laser, highly vibrational states v" > 15 ofCsH in its ground electronic state are obtained. A diode laser is used to probe either the prepared vibrational state or the collisionally populated states. The decay signal of the time-resolved fluorescence from the A1E+(v') -* X1S+(v") transition is monitored. Based on the Stern- Volmer equation, the total rate coefficients for v"=15-22 are yielded. The time evolution and relative intensities of three related states, v", v" - 1 and v" - 2, made by the initially prepared v" state of CsH are measured. Rate coefficients of single- and double-quantum relaxation are obtained. These results show that single-quantum relaxation accounts for >50% of the total relaxation out of states v"=17-20. Multiquantum relaxation (Av >2) makes major contribution (>62%) to
Aalto, S; Muller, S; Winters, J M; Gonzalez-Alfonso, E; van der Werf, P; Henkel, C; Costagliola, F; Neri, R
2014-01-01
We obtained high resolution (0."25 to 0."90) observations of HCN and HCO+ J=3-2 of the ultraluminous QSO galaxy Mrk231 with the IRAM Plateau de Bure Interferometer. We find luminous HCN and HCO+ 3-2 emission in the main disk and we detect compact (r350 pc) line wings are found for HCN 3-2 with velocities +-750 km/s. Line ratios indicate that the emission is emerging in dense gas n=1e4 - 5e5 cm-3 of elevated HCN abundance X(HCN)=1e-8 to 1e-6. High X(HCN) also allows for the emission to originate in gas of more moderate density. We tentatively detect nuclear emission from the reactive ion HOC+ with HCO+/HOC+=10-20. The HCN v2=1f line emission is consistent with the notion of a hot, dusty, warped inner disk of Mrk231 where the v2=1f line is excited by bright mid-IR 14 micron continuum. We estimate the vibrational temperature T_vib to 200-400 K. We propose that 50% of the main HCN emission may have its excitation affected by the radiation field through IR pumping of the vibrational ground state. The HCN emission ...
Smith, Andrew; LaVerde, Bruce; Jones, Douglas; Towner, Robert; Waldon, James; Hunt, Ron
2013-01-01
Producing fluid structural interaction estimates of panel vibration from an applied pressure field excitation are quite dependent on the spatial correlation of the pressure field. There is a danger of either over estimating a low frequency response or under predicting broad band panel response in the more modally dense bands if the pressure field spatial correlation is not accounted for adequately. It is a useful practice to simulate the spatial correlation of the applied pressure field over a 2d surface using a matrix of small patch area regions on a finite element model (FEM). Use of a fitted function for the spatial correlation between patch centers can result in an error if the choice of patch density is not fine enough to represent the more continuous spatial correlation function throughout the intended frequency range of interest. Several patch density assumptions to approximate the fitted spatial correlation function are first evaluated using both qualitative and quantitative illustrations. The actual response of a typical vehicle panel system FEM is then examined in a convergence study where the patch density assumptions are varied over the same model. The convergence study results illustrate the impacts possible from a poor choice of patch density on the analytical response estimate. The fitted correlation function used in this study represents a diffuse acoustic field (DAF) excitation of the panel to produce vibration response.
Wei Zhang
2017-05-01
Full Text Available As a key component of hydraulic control systems, hydraulic servovalves influence their performance significantly. Unpredictable self-excited noise inside hydraulic servovalves may cause instability and even failure. Being functional, with higher saturation magnetization and increased viscosity when exposed to a magnetic field, magnetic fluids (MFs have been widely used in dampers, sealing, and biomedical treatment. In this paper, magnetic fluids are applied in the torque motor of a hydraulic servovalve to exert damping and resistance for vibration and noise suppression. Construction of the torque motor armature with magnetic fluids is introduced and the forces due to magnetic fluids on the torque motor armature are studied. Based on a bi-viscosity-constituted relationship, a mathematical model of the damping force from magnetic fluids is built when magnetic fluids are filled in the working gaps of the torque motor. Measurements of the properties of an Fe3O4 composite magnetic fluid are carried out to calculate the parameters of this mathematical model and to investigate the influence of magnetic fluids on the vibration characteristics of the armature assembly. The simulated and tested harmonic responses of the armature with and without magnetic fluids show the good suppression effects of magnetic fluids on the self-excited noise inside the servovalve.
Yan, Guiyun; Chen, Fuquan; Wu, Yingxiong
2016-01-01
Different from previous researches which mostly focused on linear response control of seismically excited high-rise buildings, this study aims to control nonlinear seismic response of high-rise buildings. To this end, a semi-active control strategy, in which H∞ control algorithm is used and magneto-rheological dampers are employed for an actuator, is presented to suppress the nonlinear vibration. In this strategy, a modified Kalman-Bucy observer which is suitable for the proposed semi-active strategy is developed to obtain the state vector from the measured semi-active control force and acceleration feedback, taking into account of the effects of nonlinearity, disturbance and uncertainty of controlled system parameters by the observed nonlinear accelerations. Then, the proposed semi-active H∞ control strategy is applied to the ASCE 20-story benchmark building when subjected to earthquake excitation and compared with the other control approaches by some control criteria. It is indicated that the proposed semi-active H∞ control strategy provides much better control performances by comparison with the semi-active MPC and Clipped-LQG control approaches, and can reduce nonlinear seismic response and minimize the damage in the buildings. Besides, it enhances the reliability of the control performance when compared with the active control strategy. Thus, the proposed semi-active H∞ control strategy is suitable for suppressing the nonlinear vibration of high-rise buildings.
Imanishi, Masatoshi
2013-01-01
We present results from our ALMA Cycle 0 observations, at the frequencies around the HCN, HCO+, and HNC J=4-3 transition lines, of the luminous infrared galaxy IRAS 20551-4250 at z=0.043, which is known to host an energetically important obscured AGN. In addition to the targeted HCN, HCO+, and HNC J=4-3 emission lines, two additional strong emission lines are seen, which we attribute to H2S and CH3CN(+CCH). The HCN-to-HCO+ J=4-3 flux ratio (~0.7) is higher than in the other starburst-dominated galaxy (~0.2) observed in our ALMA Cycle 0 program. We tentatively (~5 sigma) detected the vibrationally excited (v2=1) HCN J=4-3 (l=1f) emission line, which is important for testing an infrared radiative pumping scenario for HCN. This is the second detection of this molecular transition in external galaxies. The most likely reason for this detection is not only the high flux of this emission line, but also the small molecular line widths observed in this galaxy, suggesting that vibrational excitation of HCN may be rela...
徐万海; 杜杰; 余建星; 李敬成
2011-01-01
A wake oscillator model is presented for the stream-wise vortex-induced vibration of a circular cylinder in the second excitation region. The near wake dynamics related to the fluctuating nature of alternate vortex shedding is modeled based on the classical van der Pol equation. An appropriate approach used in cross-Sow VIV is developed to estimate the model empirical parameters. The comparison between our calculations and experiments is carried out to validate the proposed model. It is found that the present model results agree fairly well with the experimental data.%A wake oscillator model is presented for the stream-wise vortex-induced vibration of a circular cylinder in the second excitation region.The near wake dynamics related to the fluctuating nature of alternate vortex shedding is modeled based on the classical van der Pol equation.An appropriate approach used in cross-flow VIV is developed to estimate the nodel empirical parameters.The comparison between our calculations and experiments is carried out to validate the proposed model.It is found that the present model results agree fairly well with the experimental data.
De Clercq, L
2010-09-01
Full Text Available molecules for which spectroscopic data for the vibrational modes are available in literature. A density matrix approach was followed. The time evolution of the density matrix is given by the Von Neumann equation [1] , , 1 ( )a l b lN i t i tab lb al... of the individual vibrational levels, and Iab the matrix elements of the interaction Hamiltonian [2] which include the detailed time dependence of the shaped femtosecond pulse. 2. Simulation results A transform limited 150 femtosecond laser pulse with a...
Sarma, Manabendra; Adhikari, S; Mishra, Manoj K
2007-01-28
Vibrational excitation (nu(f), where psi(nu(i))(R,t) approximately =e(-iH(A(2))-(R)t/h phi(nu(i))(R) with time evolution under the influence of the resonance anionic Hamiltonian H(A(2) (-))(A(2) (-)=N(2)(-)/H(2) (-)) implemented using Lanczos and fast Fourier transforms. The target (A(2)) vibrational eigenfunctions phi(nu(i))(R) and phi(nu(f))(R) are calculated using Fourier grid Hamiltonian method applied to potential energy (PE) curves of the neutral target. Application of this simple systematization to calculate vibrational structure in e-N(2) and e-H(2) scattering cross-sections provides mechanistic insights into features underlying presence/absence of structure in e-N(2) and e-H(2) scattering cross-sections. The results obtained with approximate PE curves are in reasonable agreement with experimental/calculated cross-section profiles, and cross correlation functions provide a simple demarcation between the boomerang and impulse models.
Lombardi, Andrea; Faginas-Lago, Noelia; Pacifici, Leonardo; Costantini, Alessandro
2013-11-14
We present extended applications of an established theoretical and computational machinery suitable for the study of the dynamics of CO2+CO2 collisions, focusing on vibrational energy exchange, considered over a wide range of energies and rotational temperatures. Calculations are based on quasi-classical trajectories on a potential energy function (a critical component of dynamics simulations), tailored to accurately describe the intermolecular interactions, modeled by the recently proposed bond-bond semiempirical formulation that allows the colliding molecules to be stretchable, rather than frozen at their equilibrium geometry. In a previous work, the same potential energy surface has been used to show that modifications in the geometry (and in physical properties such as polarizability and charge distribution) of the colliding partners affect the intermolecular interaction and determine the features of the energy exchange, to a large extent driven by long-range forces. As initial partitioning of the energy among the molecular degrees of freedom, we consider the excitation of the vibrational bending mode, assuming an initial rotational distribution and a rotational temperature. The role of the vibrational angular momentum is also carefully assessed. Results are obtained by portable implementations of this approach in a Grid-computing framework and on high performance platforms. Cross sections are basic ingredients to obtain rate constants of use in advanced state-to-state kinetic models, under equilibrium or nonequilibrium conditions, and this approach is suitable for gas dynamics applications to plasmas and modeling of hypersonic flows.
Reich, Daniel M
2013-01-01
Laser cooling of molecules employing broadband optical pumping involves a timescale separation between laser excitation and spontaneous emission. Here, we optimize the optical pumping step using shaped laser pulses. We derive two optimization functionals to drive population into those excited state levels that have the largest spontaneous emission rates to the target state. We show that, when using optimal control, laser cooling of molecules works even if the Franck-Condon map governing the transitions is preferential to heating rather than cooling. Our optimization functional is also applicable to the laser cooling of other degrees of freedom provided the cooling cycle consists of coherent excitation and dissipative deexcitation steps whose timescales are separated.
2016-06-03
IR and UV-visible ranges. The absorption spectrum corresponding to excitation states of As-H2O complexes consisting of relatively small numbers of...complexes consisting of relatively small numbers of water molecules using DFT and TD- DFT. Calculation of excited state resonance structure using DFT and TD...absorption spectra. A significant aspect of using DFT and TD-DFT for the calculation of absorption spectra is that it adopts the perspective of computational
1984-04-01
Fr other sets of excitation cross sections for H2 , see: M. G. Hi-ips and A. E. S. Green, J. Apdl. Phys. 46, 4718 (1975); P. Micheal and R. Winkler...Phys. 58, 4599 (1973); K. P. Lynch, T. C. Schwab, and J. V. Micheal , Int. J. Chem. Kinetics 8, 651 (1976). 51 i% %.€. - . . . ..-.-. ..-.-. " . .V...G. Ferguson and A. W. Read, Trans. Faraday Soc. 61 1559 (1965). 52 % *.~ *-.~:. -7_ 7o . .. ... ... .. .. .4 49. J. E. Land, J. Appl. Phys. 49, 5716
Leiweke, Robert John
2004-09-01
A new trans-rotational temperature diagnostic with ±50K accuracy has been developed for use in nonequilibrium, low temperature, monatomic gases seeded with carbon monoxide (CO). The scheme utilizes single- photon laser induced fluorescence (LIF) of CO under vibrationally-excited conditions in which single-photon transitions from the CO X1Σ + ground electronic state to upper electronic A1Π or D'1Σ+ states become accessible to a tunable, narrowband ArF excimer laser at 193 nm. Two vibrationally excited environments in which the chemistry is well understood were used as a testbed; an optically-pumped 3% CO/Ar plasma at 100 torr and a 4% CO/He d.c. glow discharge at 8 torr. The LIF saturation limit was experimentally investigated and diagnostic advantages of either regime discussed. For the optically-pumped CO/Ar plasma, a spatially-averaged LIF temperature of 536 ± 103 K (2σ) was obtained from rotationally resolved X 1Σ+ (v' = 20) → D '1Σ+ (v' = 2) LIF excitation spectra. Temperature measurements pumping the X 1Σ+ (v' = 7) → A 1Π (v' = 1) 4th Positive (528 ± 51 K) were also found to compare well with line-of-sight Fourier Transform-InfraRed (FT-IR) emission measurements (536 ± 10 K). Spatially averaged FT- IR spectroscopy of the CO 1st overtone was used to verify that an adequate vibrational population (˜0.1%) existed within the positive column of the CO/He d.c. glow discharge. The A-X (7,1) transition was pumped and subsequent (8,1) emission at 200.8 nm collected. The resulting rotational spectral peaks were assigned and a subset used to determine a spatially averaged rotational temperature of 432 ± 44 K on the discharge centerline. This was found to be in good agreement with FT-IR spectroscopy measurements (395 ± 10 K). As a prelude to Planar-LIF (PLIF) temperature measurements, vibrationally-resolved emission from laser excitation of various rotational lines within the A-X and D'-X bands were used to investigate spectral interferences. This
Kryvohuz, M; Marcus, R A
2010-06-14
A theory that describes the non-RRKM (non-Rice-Ramsperger-Kassel-Marcus) effects in the lifetime statistics of activated ozone molecules is derived. The non-RRKM effects are shown to originate due to the diffusive energy exchange between vibrational and rotational degrees of freedom in ozone molecule. The lifetime statistics is found to be intramolecular diffusion controlled at long times. The theoretical results are in good agreement with the direct MD simulations of lifetime statistics.
de Clercq, L
2010-09-01
Full Text Available of a Vibrational Level Within the Electronic Ground State of a Polyatomic Molecule with Ultra Short Pulses Ludwig de Clercq1,2, Lourens Botha1,2, Hermann Uys1, Anton Du Plessis1,2, Erich Rohwer2 1CSIR National Laser Centre, PO BOX 395, Pretoria... al lbl d i I e I e dt ? , )? ? ? ? ?=?= ??h (1) where, , .a b a b? ? ?= ? , (2) ?ab gives the elements of the density matrix, ?a the frequencies...
Hauer, B [Institut fuer Festkoerperforschung, Forschungszentrum Juelich, D-52425 Juelich (Germany); Hempelmann, R [Physikalische Chemie, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); Udovic, T J [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Rush, J J [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Kockelmann, W [Mineralogisches Institut der Universitaet Bonn, Aussenstelle Juelich, D-52425 Juelich (Germany); Schaefer, W [Mineralogisches Institut der Universitaet Bonn, Aussenstelle Juelich, D-52425 Juelich (Germany); Jansen, E [Mineralogisches Institut der Universitaet Bonn, Aussenstelle Juelich, D-52425 Juelich (Germany); Richter, D [Institut fuer Festkoerperforschung, Forschungszentrum Juelich, D-52425 Juelich (Germany)
2004-07-28
Neutron vibrational spectroscopy and neutron diffraction have been used to study the optical hydrogen vibrations in and the structure of ordered niobium hydrides NbH{sub x} and deuterides NbD{sub x} in the concentration range 0.73
Selectivity and mixed reactant fuel cells
Riess, Ilan
2015-01-01
Mixed reactant fuel cells (MR-FCs), are aimed at using a uniform mixture of fuel and oxygen applied to both the anode and the cathode. This allows redesign of fuel cells with a significantly simpler construction, having potentially a higher power density, better fuel utilization and be less expensive. The challenge in realizing MR-FCs is finding selective electrodes that can enhance oxygen reduction at the cathode, fuel oxidation at the anode while inhibiting the chemical reaction between the fuel and oxygen in the gas mixture. This task is in particular challenging in solid oxide fuel cells (SOFCs), as they operate at elevated temperatures, where many reactions are easily activated and selectivity is difficult to achieve. As a result no true MR-FC of the SOFC type were reported while some were found for low temperature fuel cells (FCs). The so-called single-chamber-SOFC are not true MR-FCs as they do not contain two selective electrodes, as required. We shall discuss potential ways to search for and develop selective anodes and cathodes for SOFC type MR-FCs. We first consider material properties which should contribute to that goal. This refers to electronic properties of the bulk, band banding under adsorbed specie, point defects in the bulk and on the surface. We then proceed to show how cell design, in particular electrode structure, can contribute to selectivity. Finally operation conditions are considered and it is shown that they also can contribute to selectivity. The operation condition considered are gas mixture composition, gas mixture residence time in the hot zone, hence gas flow rate, current density and temperature. The topics discussed hold for all FC types but are crucial for the SOFC type because of the difficulty to achieve selectivity at elevated temperatures. It is suggested that a concerted effort taking advantage of all those options should allow development of a true SOFC type MR-FC.
无
2009-01-01
Due to the highly sensitive electrochemiluminescence (ECL), tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+) is often used in the field of bioarrays with the help of co-reactants. However, the generally used co-reactant, tripropylamine (TPA), is toxic, corrosive and volatile. Therefore, the search for safe, sensitive and economical co-reactants is critical. Herein, three aminocarboxylic acids, ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and 2-hydroxyethylethylene diaminetriacetic acid (HEDTA), have been investigated as potential co-reactants for promoting Ru(bpy)32+ ECL behaviour. A possible ECL mechanism is also presented. The experimental results suggested that the co-reactants have a different ECL behaviour compared to TPA, such as different pH- and surfactant-responses. The detection limits of Ru(bpy)32+ using NTA, EDTA and HEDTA as co-reactants are 1, 60 and 680 fmol·L-1, respectively. The results indicate that NTA has a much higher efficiency than TPA to excite Ru(bpy)3 2+ ECL under their own optimal conditions. NTA could be widely used in many fields because it is less toxic, corrosive and volatile than TPA. Moreover, using Ru(bpy)3 2+ ECL, a sensitive method for the detection of aminocarboxylic acids is also developed. An improvement of four orders of magnitude in detection limits is obtained for EDTA compared to the known Ru(bpy) 3 2+ chemiluminescent methods.
Zhao Juan; Luo Yi
2011-01-01
Based on an extended London-Eyring-Polanyi-Sato(LEPS)potential energy surface(PES), the Ba+HF reaction has been studied by the quasi-classical trajectory(QCT)method. The reaction integral cross section as a function of collision energy for the Ba+HF→ BaF+H reaction is presented and the influence of isotope substitution on the differential cross sections(DCSs)and alignments of the product's rotational angular momentum have also been studied.The results suggest that the integral cross sections increase with increasing collision energy, and the vibrational excitation of the reagent has great influence on the DCS. In addition, the product's rotational polarization is very strong as a result of heavy-heavy-light(HHL)mass combination, and the distinct effect of isotope substitution on the stereodynamics is also revealed.
Kim, Kilyoung; Johnson, Alan M.; Powell, Amber L.; Mitchell, Deborah G.; Sevy, Eric T., E-mail: esevy@byu.edu [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States)
2014-12-21
Collisional energy transfer between vibrational ground state CO{sub 2} and highly vibrationally excited monofluorobenzene (MFB) was studied using narrow bandwidth (0.0003 cm{sup −1}) IR diode laser absorption spectroscopy. Highly vibrationally excited MFB with E′ = ∼41 000 cm{sup −1} was prepared by 248 nm UV excitation followed by rapid radiationless internal conversion to the electronic ground state (S{sub 1}→S{sub 0}*). The amount of vibrational energy transferred from hot MFB into rotations and translations of CO{sub 2} via collisions was measured by probing the scattered CO{sub 2} using the IR diode laser. The absolute state specific energy transfer rate constants and scattering probabilities for single collisions between hot MFB and CO{sub 2} were measured and used to determine the energy transfer probability distribution function, P(E,E′), in the large ΔE region. P(E,E′) was then fit to a bi-exponential function and extrapolated to the low ΔE region. P(E,E′) and the biexponential fit data were used to determine the partitioning between weak and strong collisions as well as investigate molecular properties responsible for large collisional energy transfer events. Fermi's Golden rule was used to model the shape of P(E,E′) and identify which donor vibrational motions are primarily responsible for energy transfer. In general, the results suggest that low-frequency MFB vibrational modes are primarily responsible for strong collisions, and govern the shape and magnitude of P(E,E′). Where deviations from this general trend occur, vibrational modes with large negative anharmonicity constants are more efficient energy gateways than modes with similar frequency, while vibrational modes with large positive anharmonicity constants are less efficient at energy transfer than modes of similar frequency.
Faye, M.; Boudon, V.; Loëte, M.; Roy, P.; Manceron, L.
2017-03-01
Sulfur hexafluoride is an important prototypal molecule for modeling highly excited vibrational energy flow and multi quanta absorption processes in hexafluoride molecules of technological importance. It is also a strong greenhouse gas of anthropogenic origin. This heavy species, however, features many hot bands at room temperature (at which only 30% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6=1 vibrational state. Using a cryogenic long path cell with variable optical path length and temperatures regulated between 120 and 163 K, coupled to Synchrotron Radiation and a high resolution interferometer, Doppler-limited spectra of the 2ν1 +ν3 , ν1 +ν2 +ν3 , ν1 +ν3 , ν2 +ν3 , 3ν3, ν2 + 3ν3 and ν1 + 3ν3 from 2000 to 4000 cm-1 near-infrared region has been recorded. Low temperature was used to limit the presence of hot bands. The spectrum has been analyzed thanks to the XTDS software package. Combining with previously observed weak difference bands in the far infrared region involving the v1, v2, v3=1 states, we are thus able to use the tensorial model to build a global fit of spectroscopic parameters for v1=1,2, v2=1, v3=1,2,3. The model constitutes a consistent set of molecular parameters and enable spectral rovibrational simulation for all multi-quanta transitions involving v1, v2 and v3 up to v1-3 = 3 . Tests simulation on rovibrational transitions not yet rovibrationally assigned are presented and compared to new experimental data.
2014-07-22
behavior of these species is then compared with that of very similar model systems in order to enable the synthesis of new materials that will be...systems in order to enable the synthesis of new materials that will be energetic by design. This must be the first step in the determination of the unique...1,2,4- triazole -1,1’-diol, respectively), following electronic state excitation, is investigated both experimentally and theoretically. Different from
Rehman, N U; Naveed, M A; Zakaullah, M [Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Khan, F U [Department of Physics, Gomal University D.I. Khan (Pakistan)
2008-05-01
Optical emission spectroscopy is used to investigate the effect of neon mixing on the excitation and vibrational temperatures of the second positive system in nitrogen plasma generated by a 13.56 MHz RF generator. The excitation temperature is determined from Ne I line intensities, using Boltzmann's plot. The overpopulation of the levels of the N{sub 2} (C {sup 3}{pi}{sub u}, {nu}') states with neon mixing are monitored by measuring the emission intensities of the second positive system of nitrogen molecules. The vibrational temperature is calculated for the sequence {delta}{nu} = -2, with the assumption that it follows Boltzmann's distribution. But due to overpopulation of levels, e.g. 1, 4, a linearization process was employed for such distributions allowing us to calculate the vibrational temperature of the N{sub 2} (C {sup 3}{pi}{sub u}, {nu}') state. It is found that the excitation temperature as well as the vibrational temperature of the second positive system can be raised significantly by mixing neon with nitrogen plasma. It is also found that the vibrational temperature increases with power and pressure up to 0.5 mbar.
Van Duzor, Matthew; Mbaiwa, Foster; Lasinski, Joshua; Dao, Diep; Holtgrewe, Nicholas; Mabbs, Richard
2011-05-14
Cl(-)·CH(3)I cluster anion photoelectron images are recorded over a range of detachment wavelengths in the immediate post threshold region. The photoelectron spectral features fall into two categories. A number of weak, photon energy dependent transitions are observed and attributed to atomic anion fragmentation products. Several more intense, higher electron binding energy transitions result from single photon cluster anion detachment. Comparison with I(-)·CH(3)I suggests that the detachment process is more complicated for Cl(-)·CH(3)I. The single photon transition spacing is consistent with CH(3)I ν(3) mode excitation, but the two distinct vibronic bands of I(-)·CH(3)I detachment are not easily distinguished in the Cl(-)·CH(3)I spectra. Similarly, while the spectral intensities for both cluster anions show non-Franck Condon behavior, the level of vibrational excitation appears greater for Cl(-)·CH(3)I detachment. These observations are discussed in terms of low lying electronic states of CH(3)I along the C-I coordinate, and the influence of the CH(3)I moiety on the neutral halogen atom states.
Van Duzor, Matthew; Mbaiwa, Foster; Lasinski, Joshua; Dao, Diep; Holtgrewe, Nicholas; Mabbs, Richard
2011-05-01
Cl-.CH3I cluster anion photoelectron images are recorded over a range of detachment wavelengths in the immediate post threshold region. The photoelectron spectral features fall into two categories. A number of weak, photon energy dependent transitions are observed and attributed to atomic anion fragmentation products. Several more intense, higher electron binding energy transitions result from single photon cluster anion detachment. Comparison with I-.CH3I suggests that the detachment process is more complicated for Cl-.CH3I. The single photon transition spacing is consistent with CH3I ν3 mode excitation, but the two distinct vibronic bands of I-.CH3I detachment are not easily distinguished in the Cl-.CH3I spectra. Similarly, while the spectral intensities for both cluster anions show non-Franck Condon behavior, the level of vibrational excitation appears greater for Cl-.CH3I detachment. These observations are discussed in terms of low lying electronic states of CH3I along the C-I coordinate, and the influence of the CH3I moiety on the neutral halogen atom states.
Pietanza, L. D.; Colonna, G.; D'Ammando, G.; Capitelli, M.
2017-01-01
A time-dependent self-consistent model based on the coupling of the Boltzmann equation for the electron energy distribution function (EEDF) with the non-equilibrium vibrational kinetics of the asymmetric mode, as well as a simplified global model, have been implemented for a pure CO2 plasma. The simplified time-dependent global model takes into account dissociation and ionization as well as the reverse of these processes. It also takes into account the excitation/de-excitation of an electronic excited state at 10.5 eV. The model has been applied to describe the discharge and post-discharge conditions typically met in an atmospheric-pressure dielectric barrier discharge (DBD) and in a moderate-pressure microwave discharge. The reported results show the strong coupling between the excited state and the electron energy distribution kinetics due to superelastic (vibrational and electronic) collisions. Moreover, the dissociation rate from a pure vibrational mechanism can become competitive with the corresponding rate from the direct electron impact mechanism at high values of vibrational temperature.
Ercoli, L.; La Malfa, S. [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Bahia Blanca (Argentina). Inst. de Mecanica Aplicada]|[Universidad Tecnologica Nacional (Argentina). Grupo Analisis de Sistemas Mecanicos
1995-07-01
This study presents experimental dynamic analysis of two big vertical pumps induced to vibrate due to the excitation of natural frequencies of the structural systems: pump-mounting. It is demonstrated that a proper diagnostic of the working condition avoids unecessary and time-consuming equipment stops, with the consequent saving in the production costs. (author)
Diskin, Glenn S.; Lempert, Walter R.; Miles, Richard B.
1996-01-01
The vibrational relaxation of ground-state molecular oxygen (O2, X(sup 3)Sigma(sup -)(sub g)) has been observed, following stimulated Raman excitation to the first excited vibrational level (v=1). Time delayed laser-induced fluorescence probing of the ro-vibrational population distribution was used to examine the temporal relaxation behavior. In the presence of water vapor, the relaxation process is rapid, and is dominated by near-resonant vibrational energy exchange between the v=1 level of O2 and the n2 bending mode of H2O. In the absence of H2O, reequilibration proceeds via homogeneous vibrational energy transfer, in which a collision between two v=1 O2 molecules leaves one molecule in the v=2 state and the other in the v=0 state. Subsequent collisions between molecules in v=1 and v>1 result in continued transfer of population up the vibrational ladder. The implications of these results for the RELIEF flow tagging technique are discussed.
Wierschem, Nicholas E.; Hubbard, Sean A.; Luo, Jie; Fahnestock, Larry A.; Spencer, Billie F.; McFarland, D. Michael; Quinn, D. Dane; Vakakis, Alexander F.; Bergman, Lawrence A.
2017-02-01
Limiting peak stresses and strains in a structure subjected to high-energy, short-duration transient loadings, such as blasts, is a challenging problem, largely due to the well-known insensitivity of the first few cycles of the structural response to damping. Linear isolation, while a potential solution, requires a very low fundamental natural frequency to be effective, resulting in large nearly-rigid body displacement of the structure, while linear vibration absorbers have little or no effect on the early-time response where relative motions, and thus stresses and strains, are at their highest levels. The problem has become increasingly important in recent years with the expectation of blast-resistance as a design requirement in new construction. In this paper, the problem is examined experimentally and computationally in the context of offset-blast loading applied to a custom-built nine story steel frame structure. A fully-passive response mitigation system consisting of six lightweight, essentially nonlinear vibration absorbers (termed nonlinear energy sinks - NESs) is optimized and deployed on the upper two floors of this structure. Two NESs have vibro-impact nonlinearities and the other four possess smooth but essentially nonlinear stiffnesses. Results of the computational and experimental study demonstrate the efficacy of the proposed passive nonlinear mitigation system to rapidly and efficiently attenuate the global structural response, even at early time (i.e., starting at the first response cycle), thus minimizing the peak demand on the structure. This is achieved by nonlinear redistribution of the blast energy within the modal space through low-to-high energy scattering due to the action of the NESs. The experimental results validate the theoretical predictions.
Near Critical Catalyst Reactant Branching Processes with Controlled Immigration
Budhiraja, Amarjit
2012-01-01
Near critical catalyst-reactant branching processes with controlled immigration are studied. The reactant population evolves according to a branching process whose branching rate is proportional to the total mass of the catalyst. The bulk catalyst evolution is that of a classical continuous time branching process; in addition there is a specific form of immigration. Immigration takes place exactly when the catalyst population falls below a certain threshold, in which case the population is instantaneously replenished to the threshold. Such models are motivated by problems in chemical kinetics where one wants to keep the level of a catalyst above a certain threshold in order to maintain a desired level of reaction activity. A diffusion limit theorem for the scaled processes is presented, in which the catalyst limit is described through a reflected diffusion, while the reactant limit is a diffusion with coefficients that are functions of both the reactant and the catalyst. Stochastic averaging principles under ...
Mousavi, Seyed Amin; Zahrai, Seyed Mehdi; Bargi, Khosrow
2012-12-01
In this study, the effectiveness of a tuned liquid column-gas damper, TLCGD, on the suppression of seismicinduced vibrations of steel jacket platforms is evaluated. TLCGD is an interesting choice in the case of jacket platforms because it is possible to use the structural elements as the horizontal column of the TLCGD. The objective here is to find the optimum geometric parameters, namely orientation and configuration of vertical columns, length ratio, and area ratio of the TLCGD, considering nonlinear damping of the TLCGD and water-structure interaction between the jacket platform and sea water. The effects of different characteristics of ground motion such as PGA and frequency content on the optimum geometry are also investigated and it is observed that these features have some influence on the optimum area ratio. Finally it is observed that pulse arrangement of ground acceleration is one of the most important parameters affecting the efficiency of a TLCGD. In other words, it is found that the TLCGD's capability to reduce the RMS responses depends only on the frequency content of the ground acceleration, but its capability to reduce the maximum responses depends on both the frequency content and the pulse arrangement of the ground acceleration.
Zakharenko, Olena; Motiyenko, R. A.; Aviles Moreno, Juan-Ramon; Huet, T. R.
2016-06-01
Methacrolein and methyl vinyl ketone are the two major oxidation products of isoprene emitted in the troposphere. New spectroscopic information is provided with the aim to allow unambiguous identification of these molecules, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. Comprehensive sets of molecular parameters have been obtained. The torsion-rotation-vibration effects will be discussed in detail. From the atmospheric application point of view the results provide precise ground state molecular constants essential as a foundation (by using the Ground State Combination Differences method) for the analysis of high resolution spectrum, recorded from 600 to 1600 wn. The infrared range can be then refitted using appropriate Hamiltonian parameters. The present work is funded by the French ANR through the PIA under contract ANR-11-LABX-0005-01 (Labex CaPPA), by the Regional Council Nord-Pas de Calais and by the European Funds for Regional Economic Development (FEDER).
Peretti, L. F.; Dowell, E. H.
1992-01-01
An experiment was performed on a rigid wall rectangular acoustic cavity driven by a flexible plate mounted in a quarter of one end wall and excited by white noise. The experiment was designed so that the assumptions of Asymptotic Modal Analysis (AMA) were satisfied for certain bandwidths and center frequencies. Measurements of sound pressure levels at points along the boundaries and incrementally into tbe interior were taken. These were compared with the theoretical results predicted with AMA, and found to be in good agreement, particularly for moderate (1/3 octave) bandwidths and sufficiently high center frequencies. Sound pressure level measurements were also taken well into the cavity interior at various points along the 5 totally rigid walls. The AMA theory, including boundary intensification effects, was shown to be accurate provided the assumption of large number of acoustic modes is satisfied, and variables such as power spectra of the wall acceleration, frequency, and damping are slowly varying in the frequency of bandwidth.
Peretti, L. F.; Dowell, E. H.
1992-10-01
An experiment was performed on a rigid wall rectangular acoustic cavity driven by a flexible plate mounted in a quarter of one end wall and excited by white noise. The experiment was designed so that the assumptions of Asymptotic Modal Analysis (AMA) were satisfied for certain bandwidths and center frequencies. Measurements of sound pressure levels at points along the boundaries and incrementally into tbe interior were taken. These were compared with the theoretical results predicted with AMA, and found to be in good agreement, particularly for moderate (1/3 octave) bandwidths and sufficiently high center frequencies. Sound pressure level measurements were also taken well into the cavity interior at various points along the 5 totally rigid walls. The AMA theory, including boundary intensification effects, was shown to be accurate provided the assumption of large number of acoustic modes is satisfied, and variables such as power spectra of the wall acceleration, frequency, and damping are slowly varying in the frequency of bandwidth.
Chang, K. Y.; Kao, G. C.
1974-01-01
Simplified methods are described to estimate the test criteria of primary structures at component attachment points subjected to broadband random acoustic excitations. The current method utilizes a constant smeared component mass attenuation factor across the frequency range of interest. The developed method indicates that the attenuation factor is based on a frequency dependent ratio of the mechanical impedances of both the component and primary structures. The procedures used to predict the structural responses are considered as the present state-of-the-art and provide satisfactory prediction results. Example problems are used to illustrate the application procedures of the two methods and to compare the significant difference. It was found that the lower test criteria obtained by the impedance ratio method is due to the results of considering the effects of component/primary structure interaction.
Pearson, J. C.; Pickett, Herbert M.; Sastry, K. V. L. N.
2000-01-01
C2H5CN (Propionitrile or ethyl cyanide) is a well known interstellar species abundantly observed in hot cores during the onset of star formation. The onset of star formation generally results in elevated temperature, which thermally populates may low lying vibrational states such as the 206/cm in-plane bend and the 212/cm first excited torsional state in C2H5CN. Unfortunately, these two states are strongly coupled through a complex series of torsion-vibration-rotation interactions, which dominate the spectrum. In order to understand the details of these interactions and develop models capable of predicting unmeasured transitions for astronomical observations in C2H5CN and similar molecules, several thousand rotational transitions in the lowest excited in-plane bend and first excited torsional state have been recorded, assigned and analyzed. The analysis reveals very strong a- and b-type Coriolis interactions and a number of other smaller interactions and has a number of important implications for other C3V torsion-rotation-vibration systems. The relative importance and the physical origins of the coupling among the rotational, vibrational and torsional motions will be presented along with a full spectroscopic analysis and supporting astronomical observations.
Bermúdez-Montaña, M.; Lemus, R.
2017-01-01
The vibrational spectroscopic description of the ozone molecule 16O3 in its electronic ground state X1A1 is presented in the framework of a simple local model, where Morse potentials are associated with both stretching and bending modes. The Hamiltonian is written in terms of internal coordinates considering the local mode character of the ozone molecule. Later on an algebraic representation in terms of Morse ladder operators is introduced through a linear approximation in the expansion of the coordinates and momenta. Three polyads are considered in our study: P11 =ν1 +ν3 +ν2 , P21 = 2 (ν1 +ν3) +ν2 , and P32 = 3 (ν1 +ν3) + 2ν2 , as suggested by resonances derived from the fundamentals as well as from previous variational analysis. The best description is provided by the P11 polyad scheme, yielding an rms deviation of 1.85 cm-1 for a fit involving 121 energy levels. Considering the other two polyads the description is less accurate: rms = 2.78 cm-1 for polyad P21 and rms = 2.63 cm-1 for polyad P32 , considering 99 and 100 energy levels, respectively. These fits represent the best descriptions in the framework of an algebraic approach. In addition, since our algebraic model keeps the connection with configuration space, the force constants derived from the three fits have been estimated. We have found that all the available experimental energies may be assigned at least to one of the three fits. As the energy increases the eigenstates obtained from different polyad schemes differ. This fact paves the way to establish a polyad breaking approach as a next step to improve the description.
Idini, A.; Potel, G.; Barranco, F.; Vigezzi, E.; Broglia, R. A.
2015-09-01
A complete characterization of the structure of nuclei can be obtained by combining information arising from inelastic scattering, Coulomb excitation, and γ -decay, together with one- and two-particle transfer reactions. In this way it is possible to probe both the single-particle and collective components of the nuclear many-body wave function resulting from the coupling of these modes and, as a result, diagonalizing the low-energy Hamiltonian. We address the question of how accurately such a description can account for experimental observations in the case of superfluid nuclei. Our treatment goes beyond the traditional approach, in which these properties are calculated separately, and most often for systems near closed shells, based on perturbative approximations (weak coupling). It is concluded that renormalizing empirically and on equal footing bare single-particle and collective motion of open-shell nuclei in terms of self-energy (mass) and vertex corrections (screening), as well as particle-hole and pairing interactions through particle-vibration coupling (PVC), leads to a detailed, quantitative account of the data, constraining the possible values of the k mass, of the 1S0 bare N N interaction, and of the PVC strengths within a rather narrow window.
Toebaert, D.; Desoppere, E. [Univ. of Gent (Belgium). Dept. of Applied Physics; Muys, P. [Radius Engineering NV, Gent (Belgium)
1995-10-01
Results of measurements of longitudinally-averaged vibrational and rotational temperatures of CO{sub 2} for different radial positions in the active medium of a fast-axial-flow, dc-excited CO{sub 2} laser are reported. The diagnostic technique which was implemented is high resolution absorption spectroscopy of the laser plasma, using a tunable diode laser (TDL). Two different gas inlet sections for the CO{sub 2} laser were tested: one with a single anode pin in front of a relatively large inlet nozzle, as still commonly used in industrial high-power lasers, and another with multiple anodes symmetrically spaced around the perimeter of the discharge tube, each in front of a small diameter inlet nozzle. It is shown that the latter design is capable of creating an essentially flat profile regarding rotational temperature T{sub R} and combined bending mode (T{sub 2}) and symmetric stretch mode (T{sub 1} {approx} T{sub 2}) temperature, while the asymmetric stretch temperature T{sub 3} exhibits a small central maximum. This type of gain pattern is considered to be beneficial for mode quality. The former, mostly used gas inlet design, fails to provide an adequate gain profile (i.e., flat or centered and symmetrical). The combination of the information provided by the spectroscopic technique and a previously developed theoretical model can prove to be a real design aid for developing compact, high-power, gaussian mode CO{sub 2} lasers for materials processing applications.
Ludwig Kohaupt
2015-12-01
Full Text Available For a linear stochastic vibration model in state-space form, $ \\dot{x}(t = A x(t+b(t, \\, x(0=x_0, $ with system matrix A and white noise excitation $ b(t $, under certain conditions, the solution $ x(t $ is a random vector that can be completely described by its mean vector, $ m_x(t:=m_{x(t} $, and its covariance matrix, $ P_x(t:=P_{x(t} $. If matrix $ A $ is asymptotically stable, then $ m_x(t \\rightarrow 0 \\, (t \\rightarrow \\infty $ and $ P_x(t \\rightarrow P \\, (t \\rightarrow \\infty $, where $ P $ is a positive (semi-definite matrix. As the main new points, in this paper, we derive two-sided bounds on $ \\Vert m_x(t\\Vert _2 $ and $ \\Vert P_x(t- P\\Vert _2 $ as well as formulas for the right norm derivatives $ D_+^k \\Vert P_x(t- P\\Vert _2, \\, k=0,1,2 $, and apply these results to the computation of the best constants in the two-sided bounds. The obtained results are of special interest to applied mathematicians and engineers.
Leng, Jiaming; Yan, Xiaojun; Zhang, Xiaoyong; Qi, Mingjing; Liu, Zhiwei; Huang, Dawei
2017-10-01
Most Nitinol-alloy-based biomedical devices are usually manufactured from straight drawn microwires or microbeams. Fatigue due to cyclic bending is interpreted as the primary failure mechanism in these devices. However, the bending fatigue performance of a Nitinol microwire is rarely studied because of the lack of test devices. Therefore, we firstly establish a bending fatigue test device based on the self-excited vibration principle. Then, we further improve and experimentally verify the device in three aspects to enlarge the strain amplitude: electrode distance optimization, electrode placement angle optimization and local stiffness enhancement. Based on these improvements, the strain amplitude is increased to 6%, successfully meeting the requirements of Nitinol microwire bending fatigue tests. Using the improved test device, a group of superelastic Nitinol (55.8% Ni-44.2% Ti) microwires with a diameter of 50.8 μm are tested. The test results show that the fatigue strain limit for the chosen life (1 × 106 cycles) is around 1.9%, and the inflexion appears at a strain amplitude of 2.3%. SEM observation shows the typical features of low-cycle and high-cycle fatigue on the fracture surfaces.
Chen, G. X.; Zhou, Z. R.; Ouyang, H.; Jin, X. S.; Zhu, M. H.; Liu, Q. Y.
2010-10-01
The present work proposes friction coupling at the wheel-rail interface as the mechanism for formation of rail corrugation. Stability of a wheelset-track system is studied using the finite element complex eigenvalue method. Two models for a wheelset-track system on a tight curved track and on a straight track are established. In these two models, motion of the wheelset is coupled with that of the rail by friction. Creep force at the interface is assumed to become saturated and approximately equal to friction force, which is equal to the normal contact force multiplied by dynamic coefficient of friction. The rail is supported by vertical and lateral springs and dampers at the positions of sleepers. Numerical results show that there is a strong propensity of self-excited vibration of the wheelset-track system when the friction coefficient is larger than 0.21. Some unstable frequencies fall in the range 60-1200 Hz, which correspond to frequencies of rail corrugation. Parameter sensitivity analysis shows that the dynamic coefficient of friction, spring stiffness and damping of the sleeper supports all have important influences on the rail corrugation formation. Bringing the friction coefficient below a certain level can suppress or eliminate rail corrugation.
陈美霞; 和卫平; 邱昌林; 陈清坤
2011-01-01
With single or double ring-stiffened cylindrical shells taken as an object, the model experiment was carried out to study the influence of the internal medium on the shell vibration and sound radiation, and the vibration and sound radiation of single/double cylindrical shells under different excitation were compared. The result shows that when the interior of cylindrical shells are full of air, the coupling between acoustic cavity and structure has little influence on the shell vibration and internal acoustic field; when shells are excited by force excitation, the sound radiation is related to structural vibration mode, and when shells are excited by sound excitation, the sound radiation is related to structural vibration mode and cavity mode; the outer shell of double cylindrical shells has a shielding effect to the vibration and sound radiation of cylindrical shells.%以单、双层环肋圆柱壳为对象,通过模型试验分析圆柱壳内部介质与壳体的耦合对壳体声振性能的影响,进而对比分析力激励与声激励下,壳体振动与声辐射的关系以及单、双壳的声振性能.结果表明:当圆柱壳内部介质为空气时,声激励作用下声腔模态与结构模态耦合与否对壳体振动以及内部声场的影响很小;当壳体受力激励作用时,外场声辐射与壳体结构模态有关,当壳体受声激励作用时,外场声辐射与壳体结构模态、声腔模态有关;双壳的外壳对力激励和声激励时的振动与声辐射均起到屏蔽作用.
Raman Kumar Singh; Manabendra Sarma; Ankit Jain; Satrajit Adhikari; Manoj K Mishra
2007-09-01
Results from application of a new implementation of the time-dependent wave packet (TDWP) approach to the calculation of vibrational excitation cross-sections in resonant e-CO scattering are presented to examine its applicability in the treatment of e-molecule resonances. The results show that the SCF level local complex potential (LCP) in conjunction with the TDWP approach can reproduce experimental features quite satisfactorily.
PMR polyimide composites for aerospace applications. [Polymerization of Monomer Reactants
Serafini, T. T.
1984-01-01
A novel class of addition-type polyimides has been developed in response to the need for high temperature polymers with improved processability. The new plastic materials are known as PMR (for in situ polymerization of monomer reactants) polyimides. The highly processable PMR polyimides have made it possible to realize much of the potential of high temperature resistant polymers. Monomer reactant combinations for several PMR polyimides have been identified. The present investigation is concerned with a review of the current status of PMR polyimides. Attention is given to details of PMR polyimide chemistry, the processing of composites and their properties, and aerospace applications of PMR-15 polyimide composites.
Reactant-Product Quantum Coherence in Electron Transfer Reactions
Kominis, I K
2012-01-01
We investigate the physical meaning of quantum superposition states between reactants and products in electron transfer reactions. We show that such superpositions are strongly suppressed and to leading orders of perturbation theory do not pertain in electron transfer reactions. This is because of the intermediate manifold of states separating the reactants from the products. We provide an intuitive description of these considerations with Feynman diagrams. We also discuss the relation of such quantum coherences to understanding the fundamental quantum dynamics of spin-selective radical-ion-pair reactions.
刹车系统的摩擦自激振动和控制%FRICTION-INDUCED SELF-EXCITED VIBRATION AND CONTROL OF A BRAKE SYSTEM
贾尚帅; 丁千
2012-01-01
The non-linear dynamics and control of friction-induced vibration in a brake system are investigated. Adopting the LuGre friction model, the dynamical equations of a 2-DOF disc brake system are derived by considering the friction force between the disc and the pad. The critical speed of Hopf bifurcation of the equilibrium is obtained through stability analysis. The design method based on differential geometry and linear quadratic optimal control for SISO nonlinear system controller is used to reduce the chatter phenomena during deceleration-type braking by postponing the critical speed of Hopf bifurcation. At last, the influences of the controller and the system parameters are analyzed. The simulation result shows that the method based on differential geometry and linear quadratic optimal is effective to control the self-excited vibration.%研究刹车系统的摩擦自激振动和控制问题。采用LuGre模型计算摩擦力，建立了两自由度盘式刹车系统的动力学模型。通过平衡点的稳定性分析，给出Hopf分岔失稳的临界速度。应用基于微分几何法和线性二次型最优控制相结合的方法，设计单输入单输出的非线性系统控制器，以便通过推迟系统的分岔临界速度，减少减速型刹车过程中的摩擦颤振，避免刹车啸叫。最后分析了控制器和系统参数对控制效果的影响。仿真表明，该控制器能有效的抑制刹车系统中的摩擦自激振动。
YIN XueBo; SHA BeiBei; HE XiWen
2009-01-01
Due to the highly sensitive electrochemiluminescence (ECL),tris(2,2'-bipyridyl) ruthenium(Ⅱ) (Ru(bpy)32+)is often used in the field of bioarrays with the help of co-reactants.However,the generally used co-reactant,tripropylamine (TPA),is toxic,corrosive and volatile.Therefore,the search for safe,sensitive and economical co-reactants is critical.Herein,three aminocarboxylic acids,ethylenediaminetetraacetic acid (EDTA),nitrilotriacetic acid (NTA),and 2-hydroxyethylethylene diaminetriacetic acid (HEDTA),have been investigated as potential co-reactants for promoting Ru(bpy)32+ ECL behaviour.A possible ECL mechanism is also presented.The experimental results suggested that the co-reactants have a different ECL behaviour compared to TPA,such as different pH-and surfactant-responses.The detection limits of Ru(bpy)32+ using NTA,EDTA and HEDTA as co-reactants are 1,60 and 680 fmoI.L1,respectively.The results indicate that NTA has a much higher efficiency than TPA to excite Ru(bpy)32+ ECL under their own optimal conditions.NTA could be widely used in many fields because it is less toxic,corrosive and volatile than TPA.Moreover,using Ru(bpy)32+ ECL,a sensitive method for the detection of aminocarboxylic acids is also developed.An improvement of four orders of magnitude in detection limits is obtained for EDTA compared to the known Ru(bpy)32+ chemiluminescent methods.
Stanis, Ronald J.; Lambert, Timothy N.
2016-12-06
An apparatus of an aspect includes a fuel cell catalyst layer. The fuel cell catalyst layer is operable to catalyze a reaction involving a fuel reactant. A fuel cell gas diffusion layer is coupled with the fuel cell catalyst layer. The fuel cell gas diffusion layer includes a porous electrically conductive material. The porous electrically conductive material is operable to allow the fuel reactant to transfer through the fuel cell gas diffusion layer to reach the fuel cell catalyst layer. The porous electrically conductive material is also operable to conduct electrons associated with the reaction through the fuel cell gas diffusion layer. An electrically conductive polymer material is coupled with the fuel cell gas diffusion layer. The electrically conductive polymer material is operable to limit transfer of the fuel reactant to the fuel cell catalyst layer.
Stanis, Ronald J.; Lambert, Timothy N.
2016-12-06
An apparatus of an aspect includes a fuel cell catalyst layer. The fuel cell catalyst layer is operable to catalyze a reaction involving a fuel reactant. A fuel cell gas diffusion layer is coupled with the fuel cell catalyst layer. The fuel cell gas diffusion layer includes a porous electrically conductive material. The porous electrically conductive material is operable to allow the fuel reactant to transfer through the fuel cell gas diffusion layer to reach the fuel cell catalyst layer. The porous electrically conductive material is also operable to conduct electrons associated with the reaction through the fuel cell gas diffusion layer. An electrically conductive polymer material is coupled with the fuel cell gas diffusion layer. The electrically conductive polymer material is operable to limit transfer of the fuel reactant to the fuel cell catalyst layer.
Koopman, R.P.
1977-06-30
A series of experiments was performed in which gamma-ray spectra were measured, using a Ge(Li) detector, for incident 7 to 26-MeV protons on the even-even vibrational nuclei /sup 56/Fe, /sup 62/Ni, /sup 64/Zn, /sup 108/Pd, /sup 110/Cd, /sup 114/Cd, /sup 116/Cd, /sup 116/Sn, /sup 120/Sn, and /sup 206/Pb, and for incident 14-MeV neutrons on natural Fe, Ni, Zn, Cd, Sn, and Pb. These measurements yielded gamma-ray cross sections from which it was inferred that almost all of the gamma cascades from (p,p') and (n,n') reactions passed down through the first 2/sup +/ levels. Consequently, the strength of the 2/sup +/ ..-->.. 0/sup +/ gamma transitions were found to be an indirect measure of the (p,p') or (n,n') cross sections. Several types of nuclear model calculations were performed and compared with experimental results. These calculations included coupled-channel calculations to reproduce the direct, collective excitation of the low-lying levels, and statistical plus pre-equilibrium model calculations to reproduce the (p,p') and the (n,n') cross sections for comparison with the 2/sup +/ ..-->.. 0/sup +/ gamma measurements. The agreement between calculation and experiment was generally good except at high energies, where pre-equilibrium processes dominate (i.e. around 26-MeV). Here discrepancies between calculations from the two different pre-equilibrium models and between the data and the calculations were found. Significant isospin mixing of T/sub greater than/ into T/sub less than/ states was necessary in order to have the calculations match the data for the (p,p') reactions, up to about 18-MeV.
Koopman, R.P.
1977-06-30
A series of experiments was performed in which gamma-ray spectra were measured, using a Ge(Li) detector, for incident 7 to 26-MeV protons on the even-even vibrational nuclei /sup 56/Fe, /sup 62/Ni, /sup 64/Zn, /sup 108/Pd, /sup 110/Cd, /sup 114/Cd, /sup 116/Cd, /sup 116/Sn, /sup 120/Sn, and /sup 206/Pb, and for incident 14-MeV neutrons on natural Fe, Ni, Zn, Cd, Sn, and Pb. These measurements yielded gamma-ray cross sections from which it was inferred that almost all of the gamma cascades from (p,p') and (n,n') reactions passed down through the first 2/sup +/ levels. Consequently, the strength of the 2/sup +/ ..-->.. 0/sup +/ gamma transitions were found to be an indirect measure of the (p,p') or (n,n') cross sections. Several types of nuclear model calculations were performed and compared with experimental results. These calculations included coupled-channel calculations to reproduce the direct, collective excitation of the low-lying levels, and statistical plus pre-equilibrium model calculations to reproduce the (p,p') and the (n,n') cross sections for comparison with the 2/sup +/ ..-->.. 0/sup +/ gamma measurements. The agreement between calculation and experiment was generally good except at high energies, where pre-equilibrium processes dominate (i.e. around 26-MeV). Here discrepancies between calculations from the two different pre-equilibrium models and between the data and the calculations were found. Significant isospin mixing of T/sub greater than/ into T/sub less than/ states was necessary in order to have the calculations match the data for the (p,p') reactions, up to about 18-MeV.
A Fixed Bed Barrier Reactor with Separate Feed of Reactants
Neomagus, H.W.J.P.; Saracco, G.; Versteeg, G.F.
2001-01-01
A new type of gas-solid reactor was developed and characterised in the series of reactor configurations with separate feed of reactants studied by our group. The novelty in the proposed design lies in the use of a fixed bed of small catalytic particles instead of a porous catalytic membrane. The maj
A Fixed Bed Barrier Reactor with Separate Feed of Reactants
Neomagus, H.W.J.P.; Saracco, G.; Versteeg, G.F.
2001-01-01
A new type of gas-solid reactor was developed and characterised in the series of reactor configurations with separate feed of reactants studied by our group. The novelty in the proposed design lies in the use of a fixed bed of small catalytic particles instead of a porous catalytic membrane. The maj
张长友; 朱昌明; 林忠钦
2004-01-01
This paper discusses a simple way to suppress the parametrically excited lateral vibration of a mass-loaded string. Supposing that the mass at the lower end of the string is subjected to a vertical harmonic excitation and neglecting the higher order vibration modes, the equation of motion for the mass-loaded string can be represented by a Mathieus equation with cubic nonlinearity. According to the theory of the Mathieus equation, in the mass-loaded string system, when the vertical vibration frequency of the mass approaches twice the natural frequency of the string lateral vibration, once the vertical vibration amplitude of the mass exceeds a critical value, the parametric resonance will occur in the string. To avoid the parametric resonance, a vibration absorber, composed of a thin beam and two mass blocks attached at both sides of the beam symmetrically, is proposed to install with the mass to reduce its vertical vibration, and ultimately suppress the lateral vibration of the string. Such a suppression strategy is finally validated by experiments.%论述了一种抑制载重绳索参数激励横向振动的简便方法. 假设绳索底端的质量受到一个垂直简谐激励并忽略载重绳索高阶振型的影响, 载重绳索的运动方程可以用一个带有立方非线性项的Mathieu方程来描述. 根据Mathieu方程的有关理论, 在载重绳索系统中, 当索端质量垂直振动的频率接近绳索横向振动固有频率2倍时, 一旦索端质量垂直振动的幅度超过某个临界数值时, 绳索将产生参数共振. 为了避免这种现象, 建议在索端质量上加装一个减振器以削减索端质量的垂直振动, 进而抑制绳索的横向振动. 实验验证了该减振方案的有效性.
谢建军; 吴晓
2012-01-01
研究碳纤维材料矩形单层索网在基础位移激励下的非线性振动问题,是索网抗震防震设计的基础.在考虑温度变化的基础上,建立了碳纤维矩形索网在基础位移激励下的非线性振动方程,采用Galerkin原理及KBM法求得了碳纤维材料矩形单层索网非线性振动的近似解.在把碳纤维索网与钢丝索网比较的基础上,讨论分析了温度、位移激励、振幅、阻尼等因素对矩形单层索网非线性振动的影响,得到了碳纤维索网振动特性优于钢丝索网振动特性的结论.%It was studied that the nonlinear vibration of rectangular cable net using carbon fiber cables under foundation displacement excitation,and it is the base of earthquake prevention design of cable net. Meanwhile its nonlinear vibration equation was presented on the basis of considering temperature changing. And the approximate solution of nonlinear vibration of rectangular cable mesh was given used Galerkin principle and KBM method. Then something that affects its nonlinear vibration, such as the amount of temperature changing, foundation displacement excitation, amplitude as well as damping was discussed with the comparison between steel cable and carbon fiber cable. At last the conclusions was got that the vibration characteristics of cable net using carbon fiber cables is superior to cable net using steel.
刘少斌
2011-01-01
研究碳纤维材料索桁架在主体结构位移激励下的非线性振动问题,是空间索结构抗震防震设计的基础.在考虑温度变化的基础上,建立碳纤维索桁架在主体结构位移激励下的非线性振动方程,采用Galerkin原理及Krylov-Bogo1iulov-Mitropolsky法求得碳纤维材料索桁架非线性振动的近似解.在将碳纤维索网与钢丝索网比较的基础上,讨论分析温度、位移激励、振幅、阻尼等因素对索桁架非线性振动的影响,得到碳纤维索桁架振动特性优于钢丝索桁架振动特性的结论.%It was studied that the nonlinear vibration of cable truss using carbon fiber cables under main structure displacement excitation, and it is the base of earthquake prevention design of cable net.Meanwhile its nonlinear vibration equation was presented on the basis of considering temperature changing.And the approximate solution of nonlinear vibration of cable truss was given used Galerkin principle and Krylov-Bogoliulov-Mitropolsky method.Then something that affects its nonlinear vibration, such as the amount of temperature changing, main structure displacement excitation, amplitude as well as damping was discussed with the comparison between steel cable and carbon fiber cable.At last the conclusions was got that the vibration characteristics of cable net using carbon fiber cables is superior to cable net using steel.
Kis, Z.; Janszky, J.; Vinogradov, An. V.; Kobayashi, T.
1996-01-01
The optical Schroedinger cat states are simple realizations of quantum states having nonclassical features. It is shown that vibrational analogues of such states can be realized in an experiment of double pulse excitation of vibrionic transitions. To track the evolution of the vibrational wave packet we derive a non-unitary time evolution operator so that calculations are made in a quasi Heisenberg picture.
陈程; 李友荣
2015-01-01
In order to research the mechanism of self-excited vibration in rolling process of F2 rolling mill production in a hot strip mill set and to eliminate the self-excited vibration of rolling mill,the main drive system of the rolling mill was simplified into two single degree of freedom systems with equal natural frequency,and the nonlinear dynamical equations of a twist vibration model of the main drive system were established.The progressive method was used to solve the nonlinear dynamical equations.The results of simulation analysis draw the following conclusions:due to the unstable rolling lubrication, the friction in rolling deformation zone declines and causes the negative damping phenomenon,resulting in the self-excited vibration of the mill.Through the field test and theoretical analysis,it is found:reasonable changes of the dynamic viscosity of rolling lubricating liquid and rolling speed can avoid the appearance of negative damping and eliminate the self-excited vibration of the mill.%为研究热连轧机组 F2轧机轧制过程中自激振动产生机理及如何消除轧机自激振动，将轧机主传动系统简化为两固有频率相同的单自由度系统建立扭振模型的非线性动力学方程。用渐进法求解非线性动力学方程。结合仿真分析表明，由于轧制变形区轧制润滑不稳定，使变形区摩擦系数下降出现负阻尼现象导致轧机产生自激振动；合理改变轧制润滑液的动力粘度及轧制速度，可避免轧制系统内产生负阻尼。
卢小锐; 马俊达; 王晖; 王洋
2016-01-01
动力总成激励引起的低频结构噪声对驾驶室内振动噪声影响较大，应在车辆开发前期进行控制。文章讲述了某车型开发前期，通过试验与仿真相结合的手段，控制动力总成激励对驾驶室内振动噪声影响的过程。通过仿真计算预测存在风险的结构并进行优化，满足整车 NVH 目标要求，减少后期实车验证阶段的工作。%Lowfrequency noise and vibration caused by excitation of powertrain have significant influence on interior noise and vibration, it should be controlled in the early stage. This paper represents that in the early stage of a vehicle development, using the way of experiment and simulation to control the influence of vibration and noise of vehicle based on excitation of powertrain, through the simulation to predict risks and optimize structure, to meet the NVH target of vehicle and reduce the work of real vehicle validation.
GAUTAM MANJEET SINGH
2016-05-01
Limitations of the static Woods–Saxon potential and the applicability of the energy dependent Woods–Saxon potential (EDWSP) model within the framework of one-dimensional Wong formula to explore the sub-barrier fusion data are highlighted. The inelastic surface excitations of the fusing nuclei are found to be dominating in the enhancement of sub-barrier fusion excitation function data and the effects of such dominant vibrational states are exploited through the coupled channel calculations obtained by using the code CCFULL. It is worth mentioning here that the influence of multiphonon vibrational states of the reactants can be simulated by introducing the energy dependence in the nucleus–nucleus potential.
分子高激发振动态的经典非线性性质%The classical nonlinear properties of molecular highly excited vibration
吴国祯
2011-01-01
The concepts of classical nonlinear dynamics are employed to interpret the spectroscopic properties of the molecular highly excited vibration. These concepts include the Morse oscillator, the pendulum dynamics, chaos and the overlapping of resonances leading to chaos. The relations of resonance, constant of motion and the basic dynamical unit to the pendulum dynamics are stressed. An algebraic Hamiltonian in the coset space is employed for the dynamical analysis from which the dynamical potential can be easily obtained. The dynamical potential is closely related to the classical fixed points in which the quantized levels are embedded in various quantal environments.Localized modes are easily identified in various systems which share similar dynamical potentials. The dissociation of DCO radical is finally interpreted by these concepts from the classical nonlinear dynamics.%该文阐述如何运用经典非线性力学的概念,来理解分子高激发振动态的谱学性质.内容包括:莫尔斯振子,单摆的动力学和共振的关系,力学体系的构成单元是单摆,一个共振对应于一个守恒量,混沌,共振的重叠导致混沌的产生等.我们的出发点是运用二次量子化算子构成的代数哈密顿量,经由海森伯对应而得到的陪集空间上的动力学体系.从此哈密顿量,可以得到动力学势.而动力学势和经典的不动点关系密切,并且量子态就处在由动力学势所包围,分成的几个量子环境中.从动力学势,可以依据它的对称性,方便推得局域模式的存在,最后我们利用这些非线性力学的概念,来分析DCO分子高激发振动态的解离问题.
Combustion flame-plasma hybrid reactor systems, and chemical reactant sources
Kong, Peter C
2013-11-26
Combustion flame-plasma hybrid reactor systems, chemical reactant sources, and related methods are disclosed. In one embodiment, a combustion flame-plasma hybrid reactor system comprising a reaction chamber, a combustion torch positioned to direct a flame into the reaction chamber, and one or more reactant feed assemblies configured to electrically energize at least one electrically conductive solid reactant structure to form a plasma and feed each electrically conductive solid reactant structure into the plasma to form at least one product is disclosed. In an additional embodiment, a chemical reactant source for a combustion flame-plasma hybrid reactor comprising an elongated electrically conductive reactant structure consisting essentially of at least one chemical reactant is disclosed. In further embodiments, methods of forming a chemical reactant source and methods of chemically converting at least one reactant into at least one product are disclosed.
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...
高菊; 陈美霞
2011-01-01
The noise generated by the propeller is the major contribution to the total noise of naval vessel.This paper uses a finite truncated conical shell to simulate the stem of submarine and analyzes the sound and vibration of a truncated conical shell under excitation of dipole source and force, Moreover, a discussion on the position of excitation is presented.The acquired conclusions show that the sound and vibration caused by the exciting force are larger than those by the dipole source.When the dipole source is at the center of shell's section, the sound and vibration of the shell are smaller than those at asymmetrical place.%螺旋桨噪声是舰船辐射噪声的主要组成部分,采用有限长截顶锥形壳模拟潜艇艉部,根据螺旋桨噪声产生机理,对比分析了集中力激励与偶极子源激励下锥形壳产生的辐射噪声,并讨论了激励作用位置对壳体振动与辐射噪声的影响.结论显示力激励作用引起的壳体的振动与声辐射要大于偶极子源作用下的情况:当激励施加在锥形壳体截面的中心位置时,壳体在低频时的振动与声辐射要小于激励施加在截面非对称位置处的情况.
Chen, G X; Cui, X L; Qian, W J
2016-01-01
A finite element vibration model of a multiple wheel–rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks...
G. X. Chen X. L. Cui W. J. Qian
2016-01-01
A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks...
张军伟; 陈伟; 周忆; 周海; 王时龙; 景峰; 张小民
2011-01-01
Ambient vibration is the main factor that has the influence on the structure stability of inertial confinement fusion (ICF) solid state laser driver.The stability of optical elements was analyzed by the method of pseudo excitation and the weight formulations of all kinds of vibration were obtained.Muti-channel micro vibration measurement equipment was used to analyze the ambient vibration of Shengguang- Ⅲ technical integrate line (SG- Ⅲ TIL), getting the weight coefficients of HVAC (high ventilation air condition) vibration, vacuum set vibration and broadband ambient vibration as 0.457 ,0.281, and 0.162, respectively.The weight coefficients were different from NIF, which is important for the designing optimization and improving the vibration control level of TIL and the more largescale ICF driver.%环境振动是影响ICF固体激光驱动器光学元件结构稳定性的主要因素.环境振动包括:宽带环境振动、局部振动等.不同类型振动的大小对光学兀件设计、环境保障设施建造有直接的影响.采用虚拟激励法对环境振动对光学元件稳定性的影响进行了分析,得到了各类激励源的环境权重公式,采用多通道微振动测试仪器对神光-Ⅲ原型装置的振动载荷进行了分析,并根据其大小对其权重进行了确定.原型装置暖通空调振动、真空机组振动、宽带环境振动的权重系数分别为0.457、0.281、0.162,该系数与NIF装置环境载荷权重有较大差别,该权重系数对明确中国ICF装置环境振动特征,改进ICF装置的没计,提升现有装置环境振动控制水平具有一定的指导作用.
陈明; 王斌; 张胜业
2008-01-01
设计了一个接近实际情况的多舱段复杂壳体模型,安装小型机械设备,分别进行了单台设备激励与多台设备同时激励的水下复杂壳体振动与声辐射试验;试验结果表明,多源激励下水中复杂壳体的结构响应、辐射声场近似为单源激励下结构响应、辐射声场的非相干叠加.然后从结构声辐射理论上推导了激励源与结构响应、辐射声场之间的传递关系,并以两个源激励为例分析了非相干叠加引起的误差,从而解释了多源激励下结构响应、辐射声场近似为单源激励下结构响应、辐射声场非相干叠加的合理性.这些研究表明,非相干叠加方法可推广应用于水下复杂壳体在多源激励情况下的振动与声场计算,对指导工程设计具有重要价值.%A design of complex multiple compartment shell model with some small mechanical fa-cilities, which is used to simulate real ships, is introduced in this paper. The underwater vibration and acoustic radiation experiments with single and multiple excitations are implemented and related research work is also provided.Results show that the response of complex structure and sound pres-sure which are caused by multiple excitations can be approximately analysed by the approach of in-coherent superposition of individual excitation.The transitive relation between the vibro-acoustic characteristics of the submerged complex structure with multiple excitations and that with individual excitation are deduced analytically. The error of incoherent superposition is also estimated by an ex-ample of with two excitation so as to validate this approximation.It is indicated that the incoherent superposition approach can be applied to investigate the vibration and sound radiation of more complex multiple compartment shell structures with multiple excitations and it is especially useful for both qualitative and quantitative evaluation at design stages of practical structures.
张彬; 朱冬辉; 戴康; 沈异凡
2012-01-01
Rb-H2 mixture was irradiated with pulses of 696.4 nm radiation from a OPO laser, populating 6D state by two-photon absorption. The vibrational levels of RbH(X1∑+,v"=0~2) generated in the reaction of Rb(6D) with H2. Vibrational-state-specific total-removal relaxation rate coefficients, kv(M), for RbH(X1∑+,v"=15~22) by M=H2 and N2 were investigated in a pump and probe configuration. By the overtone pumping with a cw diode laser, highly vibrational states v =15~22 of RbH in its ground electronic state were obtained. Another diode laser was used to probe the prepared vibrational state. The decay signal of laser induced time-resolved fluorescence from A1∑+ (v')→X1∑+(v") transition was monitored. Based on the Stern-Volmer e-quation, the total relaxation rate coefficient kv ( H2) were yielded. A plot of kv ( H2 + N2) vsai mole fraction H2) yields a line with a slope of kv(H2)-kv(N2) and an intercept of kv(N2). The values of kv(H2) obtained from the slope of the fitted lines compare well with determined values of the kv(H2) from the Sern-Volmer plots. At v"<18, the rate coefficients kv(M) increases linearly with vibrational quantum number. This linear region is dominated by single quantum relaxation (Ai/=1) collisional propensity rules. The region (v"≥18) where the dependence is much stronger than linear shows significant contribution from multiquantum (△μ≥2) relaxation or resonant vibration-vibration energy transfer between highly vibrationally excited RbH and H2 or N2. For RbH(v")+N2(0), we measured the time-profile of v"=16 after preparation of v" = 21. A clear bimodal distribution was observed. The first peak is due to resonant vibration-vibration energy transfer; RbH(v"=21) + N2(0)→RbH(v"=16) + N2(l). The much broader second peak, at longer time delays, is due to sequential single-quantum relaxation. Although the second process results in a distribution that is much more spread out in time, the peak height is in the same order of magnitude
崔旭利; 陈怀海; 贺旭东; 姜双燕
2012-01-01
频响函数估计是多输入多输出随机振动试验控制算法中的必要环节.在振动环境试验中,通常不采集振动台的实际激励信号,而用实测的响应信号和计算机内存中的激励信号来进行系统频响函数估计.由于计算机内存中的激励信号与实际振动台上的激励信号之间在相位上存在着差异,从而导致实测的响应信号和计算机内存中的激励信号不同步.这给系统频响函数的估计带来了较大困难.为此,根据线性系统中激励和响应之间的关系,结合随机减量法,提出了一种二次相关法用于系统频响函数的估计,用该方法进行频响函数估计只需要采集响应信号.在三轴振动台上进行了对比试验,结果验证了所提出的二次相关法的正确性.%The estimation of frequency response functions ( FRFs) is unavoidable in MIMO ( multiple input and multiple output) random vibration test control. The actual excitation signals on the shaker tables are always not sampled during the vibration test. So, the FRFs are usually estimated by the response signals acturally measured and the excitation signals stored in the computer memory. Because there is a phase lag between the signal in the memory and the actual signal on the shaker table, the response signal is not synchronous with the memory excitation signal, which makes difficulty to estimat FRFs. Based on the relationship between the excitation and response in linear system and utilizing the random decrement technique, a dual correlation method ( DCM) was presented to estimate FRFs without measuring the actual driving force signals. A comparison test between DCM and the conventional method which needs to sample the excitation and response signals simultaneously was accomplished on a 3-axis vibration table. The result shows the correctness of the presented DCM.
武星宇; 纪刚; 周其斗; 黄振卫
2016-01-01
潜艇的艇体结构是潜艇螺旋桨激振力向外辐射噪声的重要通道，而轴系是螺旋桨激振力传递到艇体的必经之路，因此有必要研究潜艇轴系向艇体传递的激振力对潜艇艇体振动和辐射声功率的影响。为此，分别针对螺旋桨轴向激振力、螺旋桨侧向激振力和螺旋桨垂向激振力工况，使用模式分析的方法，将轴系对艇体的作用力分解为互不相关的力传递模式的叠加。建立潜艇结构有限元模型，采用结构有限元耦合流体边界元的附加质量附加阻尼算法，分析单阶力传递模式作用于艇体时艇体的振动和声辐射特性。所做的研究可为分析螺旋桨激振力作用下的艇体振动和声辐射提供一种新的方法。%The hull system is an important path for radiating propeller noise. Propeller excitation must be transmitted by the thrust to the hull system. As such,the study of the relations between force transmission and the vibration and sound power of submarines is very important. To this end,this paper aims at propel⁃ler excitation force,lateral excitation force and vertical excitation force. The transmission modes of the force loaded by the thrust system are analyzed,and the combined fluid-structure interaction,vibration and sound power of the finite element model of the submarine are analyzed. This provides a new method for analyzing the vibration and radiation of submarines under propeller excitation force.
Addition-type polyimides from solutions of monomeric reactants
Delvigs, P.; Serafini, T. T.; Lightsey, G. R.
1972-01-01
The monomeric reactants approach was used to fabricate addition-type polyimide/graphite fiber composites with improved mechanical properties and thermal stability characteristics over those of composites derived from addition-type amide acid prepolymers. A screening study of 24 different monomer combinations was performed. The results of a more extensive investigation of a selected number of monomer combinations showed that the combination providing the best thermomechanical properties was 5-norbornene-2,3-dicarboxylic acid monomethyl ester/4,4'-methylenedianiline/3,3'4,4'-benzophenone tetracarboxylic acid dimethyl ester at a molar ratio of 2/3.09/2.09.
Jose, Linta; Seth, Michael; Ziegler, Tom
2012-02-23
We have applied time dependent density functional theory to study excited state structures of the tetroxo d(0) transition metal complexes MnO(4)(-), TcO(4)(-), RuO(4), and OsO(4). The excited state geometry optimization was based on a newly implemented scheme [Seth et al. Theor. Chem. Acc. 2011, 129, 331]. The first excited state has a C(3v) geometry for all investigated complexes and is due to a "charge transfer" transition from the oxygen based HOMO to the metal based LUMO. The second excited state can uniformly be characterized by "charge transfer" from the oxygen HOMO-1 to the metal LUMO with a D(2d) geometry for TcO(4)(-), RuO(4), and OsO(4) and two C(2v) geometries for MnO(4)(-). It is finally found that the third excited state of MnO(4)(-) representing the HOMO to metal based LUMO+1 orbital transition has a D(2d) geometry. On the basis of the calculated excited state structures and vibrational modes, the Franck-Condon method was used to simulate the vibronic structure of the absorption spectra for the tetroxo d(0) transition metal complexes. The Franck-Condon scheme seems to reproduce the salient features of the experimental spectra as well as the simulated vibronic structure for MnO(4)(-) generated from an alternative scheme [Neugebauer J. J. Phys. Chem. A 2005, 109, 1168] that does not apply the Franck-Condon approximation.
时培明; 李纪召; 刘彬; 韩东颖
2012-01-01
Considering the effects caused by the coexisting of two different periodic parametric excitations in rotating machinery driving system, the dynamical equation of a nonlinear torsional vibration system was established based on Lagrange equation. The model contains quasi-periodic parametrically excited stiffness and friction damping. The amplitude-frequency characteristic equation and bifurcation response equation were obtained by solving the torsional vibration system using multi-scale method. On this basis, the periodic bursting of the nonlinear torsional vibration system was studied when large difference gap exists between the frequencies of the two periodic parametrical excitations. The influences of fast-varying parametrical excitation and slow-varying parametrical excitation on the periodic bursting of the torsional vibration system were analyzed. The parameter regions of periodic bursting were obtained with the help of numerical simulation. The mutual transition between quiescent state and spiking state of the system occurs in this region. When the amplitude of the fast-varying excitation reduces, the area of spiking state extends and the time of bursting prolongs. The bursting type and trajectory of the system can be changed by regulating the amplitude of slow-varying parametric excitation.%摘要:考虑旋转机械中两种频率不同的周期参数激励同时存在对其传动系统的影响,基于拉格朗日方程,建立一类含准周期参激刚度和摩擦阻尼的非线性扭振系统的动力学方程.运用多尺度法对该扭振系统进行求解,得到系统在1/2亚谐波主参数共振下的幅频特性方程和分岔响应方程.在此基础上,研究了当两种周期参激的频率相差较大时非线性扭振系统的周期簇发现象,分析了快变参激和慢变参激对扭振系统的周期簇发的影响.通过数值仿真,给出了产生周期簇发的参数取值区域.在该区域内系统发生静息态与激发态的相互转
Quantum state specific reactant preparation in a molecular beam by rapid adiabatic passage
Chadwick, Helen, E-mail: helen.chadwick@epfl.ch; Hundt, P. Morten; Reijzen, Maarten E. van; Yoder, Bruce L.; Beck, Rainer D. [Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland)
2014-01-21
Highly efficient preparation of molecules in a specific rovibrationally excited state for gas/surface reactivity measurements is achieved in a molecular beam using tunable infrared (IR) radiation from a single mode continuous wave optical parametric oscillator (cw-OPO). We demonstrate that with appropriate focusing of the IR radiation, molecules in the molecular beam crossing the fixed frequency IR field experience a Doppler tuning that can be adjusted to achieve complete population inversion of a two-level system by rapid adiabatic passage (RAP). A room temperature pyroelectric detector is used to monitor the excited fraction in the molecular beam and the population inversion is detected and quantified using IR bleaching by a second IR-OPO. The second OPO is also used for complete population transfer to an overtone or combination vibration via double resonance excitation using two spatially separated RAP processes.
Communication: Creation of molecular vibrational motions via the rotation-vibration coupling
Shu, Chuan-Cun [Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Kongens Lyngby (Denmark); School of Engineering and Information Technology, University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Henriksen, Niels E., E-mail: neh@kemi.dtu.dk [Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Kongens Lyngby (Denmark)
2015-06-14
Building on recent advances in the rotational excitation of molecules, we show how the effect of rotation-vibration coupling can be switched on in a controlled manner and how this coupling unfolds in real time after a pure rotational excitation. We present the first examination of the vibrational motions which can be induced via the rotation-vibration coupling after a pulsed rotational excitation. A time-dependent quantum wave packet calculation for the HF molecule shows how a slow (compared to the vibrational period) rotational excitation leads to a smooth increase in the average bond length whereas a fast rotational excitation leads to a non-stationary vibrational motion. As a result, under field-free postpulse conditions, either a stretched stationary bond or a vibrating bond can be created due to the coupling between the rotational and vibrational degrees of freedom. The latter corresponds to a laser-induced breakdown of the adiabatic approximation for rotation-vibration coupling.
胡亚冰; 苏华昌; 张鹏飞
2015-01-01
A typical simple structure is designed in this paper. The uniaxial and triaxial vibration examinations of the typical structure are done on triaxial vibration examination system, and the fatigue damages of the structure under uniaxial and triaxial excitation are compared. This research gives a train of thoughts to choose more suitable vibration examination fashion.%设计一种典型标准试验件，对该标准件在单轴与三轴随机振动环境下的响应进行理论仿真，并在三轴振动试验系统上开展试验研究。基于试验响应数据，对试件三轴与单轴顺序加载所造成的相对疲劳损伤进行对比分析，为航天产品振动试验方式的选取提供参考。
Park, G Barratt; Baraban, Joshua H; Field, Robert W
2014-10-07
A full-dimensional Franck-Condon calculation has been applied to the Ã (1)Au-X̃ 1Σg+ transition in acetylene in the harmonic normal mode basis. Details of the calculation are discussed in Part I of this series. To our knowledge, this is the first full-dimensional Franck-Condon calculation on a tetra-atomic molecule undergoing a linear-to-bent geometry change. In the current work, the vibrational intensity factors for levels involving excitation in ungerade vibrational modes are evaluated. Because the Franck-Condon integral accumulates away from the linear geometry, we have been able to treat the out-of-plane component of trans bend (ν4('')) in the linear X̃ state in the rotational part of the problem, restoring the χ Euler angle and the a-axis Eckart conditions. A consequence of the Eckart conditions is that the out-of-plane component of ν4('') does not participate in the vibrational overlap integral. This affects the structure of the coordinate transformation and the symmetry of the vibrational wavefunctions used in the overlap integral, and results in propensity rules involving the bending modes of the X̃ state that were not previously understood. We explain the origin of some of the unexpected propensities observed in IR-UV laser-induced fluorescence spectra, and we calculate emission intensities from bending levels of the Ã state into bending levels of the X̃ state, using normal bending mode and local bending mode basis sets. Our calculations also reveal Franck-Condon propensities for the Cartesian components of the cis bend (ν5('')), and we predict that the best Ã-state vibrational levels for populating X̃-state levels with large amplitude bending motion localized in a single C-H bond (the acetylene↔vinylidene isomerization coordinate) involve a high degree of excitation in ν6(') (cis-bend). Mode ν4(') (torsion) populates levels with large amplitude counter-rotational motion of the two hydrogen atoms.
Calculating fusion neutron energy spectra from arbitrary reactant distributions
Eriksson, J.; Conroy, S.; Andersson Sundén, E.; Hellesen, C.
2016-02-01
The Directional Relativistic Spectrum Simulator (DRESS) code can perform Monte-Carlo calculations of reaction product spectra from arbitrary reactant distributions, using fully relativistic kinematics. The code is set up to calculate energy spectra from neutrons and alpha particles produced in the D(d, n)3He and T(d, n)4He fusion reactions, but any two-body reaction can be simulated by including the corresponding cross section. The code has been thoroughly tested. The kinematics calculations have been benchmarked against the kinematics module of the ROOT Data Analysis Framework. Calculated neutron energy spectra have been validated against tabulated fusion reactivities and against an exact analytical expression for the thermonuclear fusion neutron spectrum, with good agreement. The DRESS code will be used as the core of a detailed synthetic diagnostic framework for neutron measurements at the JET and MAST tokamaks.
崔亚辉; 张俊杰; 徐福海; 毕春海; 温武斌; 陈荣轩
2012-01-01
Hie vibration of a certain 300MW steam turbine was effected by the opening order and size of control valve obviously,the vibration characteristics and the steam force which originated from control valve were analyzed,and the results showed that the vibration of unit could not be decreased or eliminated by increasing the load of journal, the load of journal could be adjusted by steam force which originated from the opening order of control valve. On the contrary, it increased the vibration of unit. The reason was that the radial position of rotor which located in casing had changed, and then the clearance of overcross section was changed. The offset of rotor was decreased by applying reasonable opening order and size of control valve, although the eccentricity and load of journal were decreased, the vibration was decreased obviously. Therefore,there are several methods to inhibit steam-excited vibration,the contradiction may occur when some methods are implemented on site. Firstly,it need to analyze the main factor which arouses steam-excited vibration,the satisfactory effect can be gained by applying key management.%某台300MW汽轮机的振动明显受到调门开启顺序和开度大小的影响,通过对机组的振动特征以及调门产生的汽流力进行分析、研究发现:采用调整阀门的开启顺序产生汽流力来提高轴承载荷并不能减小或消除该机组的振动,反而增大了机组的振动；原因是转子在汽缸中的径向位置发生了变化,改变了通流部分的间隙；通过采取合理的调门开启顺序和开度减小转子在汽缸中的偏移,虽然轴承偏心率减小、轴承载荷下降,但是振动水平明显降低了.由此可知,抑制汽流激振的方法有若干种,有些方法在现场实施起来可能会出现矛盾,此时首先需分析引起汽流激振的主要因素,然后采取能解决问题的关键措施,才能取得满意的效果.
An ASAP treatment of vibrationally excited S2O: The ν3 mode and the ν3 + ν2 - ν2 hot band
Thorwirth, S.; Martin-Drumel, M. A.; Endres, C. P.; Salomon, T.; Zingsheim, O.; van Wijngaarden, J.; Pirali, O.; Gruet, S.; Lewen, F.; Schlemmer, S.; McCarthy, M. C.
2016-01-01
The fundamental S-S stretching mode ν3 of disulfur monoxide, S2O, located at 679 cm-1, has been investigated using Fourier-transform far-infrared spectroscopy at the SOLEIL synchrotron facility. A spectroscopic analysis has been performed using an Automated Spectral Assignment Procedure (ASAP) which permits accurate determination of more than 2000 energy levels from ν3. In addition, the ν3 + ν2 - ν2 hot band was observed for the first time and some 500 corresponding energy levels were assigned. The high-resolution synchrotron study was complemented with pure rotational spectra of S2O in the (v1, v2, v3) = (0, 0, 1) vibrational state observed in the frequency range from 250 to 280 GHz using a long-path absorption cell. From these combined measurements, extensive molecular parameter sets have been determined and precise band centers have been derived for both vibrational bands.
Communication: creation of molecular vibrational motions via the rotation-vibration coupling
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
Building on recent advances in the rotational excitation of molecules, we show how the effect of rotation-vibration coupling can be switched on in a controlled manner and how this coupling unfolds in real time after a pure rotational excitation. We present the first examination of the vibrational...... motions which can be induced via the rotation-vibration coupling after a pulsed rotational excitation. A time-dependent quantum wave packet calculation for the HF molecule shows how a slow (compared to the vibrational period) rotational excitation leads to a smooth increase in the average bond length...... whereas a fast rotational excitation leads to a non-stationary vibrational motion. As a result, under field-free postpulse conditions, either a stretched stationary bond or a vibrating bond can be created due to the coupling between the rotational and vibrational degrees of freedom. The latter corresponds...
Vibration control in accelerators
Montag, C.
2011-01-01
In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.
Soft X-Ray Photochemistry of Condensed Mixed Reactants: Thin Film Growth and Ion Desorption
Moore, Jerry Franklin, Jr.
A novel process for the growth of thin film dielectric materials is presented. By condensing a mixture of reactive compounds onto a surface that is cooled under vacuum, a mixed molecular layer is formed. This layer can then be exposed to soft x-ray radiation to form a refractory thin film of dielectric material. By using either trimethylaluminum (TMA), silane, or tetramethylsilane (TMS) alone or in combination with water or ammonia, it was possible to grow oxide, nitride and carbide films. The growth of these films was generally seen to stop after 30A, and extended exposure to soft x -rays led to decomposition of the films into a more elemental state. The self-limiting growth at 30A was not observed for unmixed systems such as when aluminum carbide was grown from a TMA layer. The explanation for this is that the self-limiting growth is due to excitation of the reaction by substrate electrons, while there are enough electrons generated in the carbide to perpetuate growth indefinitely. Additionally, unlimited growth was observed for TMA and water mixtures excited by ultraviolet radiation (4.6eV). This effect is due to direct photon absorption in the layer that leads to reaction and film growth. Decomposition of the films was observed at extended exposures. It is likely that core excitation is the main cause of this phenomenon. A model that accounts for this decomposition, the relative absorption density of the substrate and the growing film, and the mean free path of the electrons in the film, is presented. The model demonstrates that a limited thickness can be expected when the cross section for film decomposition is significant and the film absorption density is relatively low. Observations of the desorbed ions from the condensed mixtures show that core excitation can lead directly to subsequent reactions. For example, OH^+ was formed from an initial excitation of O _2. The utility of stimulated desorption as a energy dependent probe of these condensed mixed
Stoller, R J
1976-08-01
Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.
Excited states rotational effects on the behavior of excited molecules
Lim, Edward C
2013-01-01
Excited States, Volume 7 is a collection of papers that discusses the excited states of molecules. The first paper reviews the rotational involvement in intra-molecular in vibrational redistribution. This paper analyzes the vibrational Hamiltonian as to its efficacy in detecting the manifestations of intra-molecular state-mixing in time-resolved and time-averaged spectroscopic measurements. The next paper examines the temporal behavior of intra-molecular vibration-rotation energy transfer (IVRET) and the effects of IVRET on collision, reaction, and the decomposition processes. This paper also
Greve, Christian; Preketes, Nicholas K.; Fidder, Henk; Costard, Rene; Koeppe, Benjamin; Heisler, Ismael A.; Mukamel, Shaul; Temps, Friedrich; Nibbering, Erik T. J.; Elsaesser, Thomas
2013-01-01
We explore the N-H stretching vibrations of adenosine-thymidine base pairs in chloroform solution with linear and nonlinear infrared spectroscopy. Based on estimates from NMR measurements and ab initio calculations, we conclude that adenosine and thymidine form hydrogen bonded base pairs in Watson-Crick, reverse Watson-Crick, Hoogsteen and reverse Hoogsteen configurations with similar probability. Steady-state concentration- and temperature dependent linear FT-IR studies, including H/D exchange experiments, reveal that these hydrogen-bonded base pairs have complex N-H/N-D stretching spectra with a multitude of spectral components. Nonlinear 2D-IR spectroscopic results, together with IR-pump-IR-probe measurements, as also corroborated by ab initio calculations, reveal that the number of N-H stretching transitions is larger than the total number of N-H stretching modes. This is explained by couplings to other modes, such as an underdamped low-frequency hydrogen-bond mode, and a Fermi resonance with NH2 bending overtone levels of the adenosine amino-group. Our results demonstrate that modeling based on local N-H stretching vibrations only is not sufficient and call for further refinement of the description of the N-H stretching manifolds of nucleic acid base pairs of adenosine and thymidine, incorporating a multitude of couplings with fingerprint and low-frequency modes. PMID:23234439
Lim, Edward C
2013-01-01
Excited States, Volume 4 is a collection of papers that deals with the excited states of molecular activity. One paper investigates the resonance Raman spectroscopy as the key to vibrational-electronic coupling. This paper reviews the basic theory of Raman scattering; it also explains the derivation of the Raman spectra, excitation profiles, and depolarization ratios for simple resonance systems. Another paper reviews the magnetic properties of triplet states, including the zero-field resonance techniques, the high-field experiments, and the spin Hamiltonian. This paper focuses on the magnetic
Very high frequency plasma reactant for atomic layer deposition
Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo; Kim, Tae Hyung; Yeom, Geun Young; Kim, Kangsik; Lee, Zonghoon; Jung, Hanearl; Lee, Chang Wan; Kim, Hyungjun; Lee, Han-Bo-Ram
2016-11-01
Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al2O3 were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al2O3 shows superior physical and electrical properties over RF PE-ALD Al2O3, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al2O3 on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.
Lasowicz, Natalia; Jankowski, Robert
2015-03-01
Lighter and slender structural members of a typical grandstand leads to a significant reduction in the frequencies, that is why such structures are more easily induced to vibrations. The aim of the present paper is to show the results of the experimental tests and the numerical analyses focused on the behaviour of a part of a typical temporary steel grandstand under dynamic loads. The peak values of accelerations of a steel scaffolding grandstand under human-induced excitation have been determined and compared with the limit values concerning the perception of vibrations by people. The results of the study indicate that the human-induced excitation may induce structural vibrations which substantially exceed the allowable limits. Coraz bardziej powszechne staje się stosowanie trybun stalowych podczas różnego rodzaju koncertów i imprez sportowych, podczas których konstrukcje te są narażone na oddziaływania dynamiczne wywołane przez przebywających na nich ludzi. Lekkie i smukłe elementy, z jakich wykonane są trybuny stalowe przyczyniają się do niskich wartości częstotliwości drgań własnych konstrukcji, przez co łatwiej wzbudzić je do drgań. W niniejszym artykule przedstawiono wyniki badań eksperymentalnych i analiz numerycznych dotyczące zachowania się przykładowej tymczasowej trybuny stalowej poddanej oddziaływaniom dynamicznym wywołanym przez ludzi. Podczas eksperymentalnych badań polowych, analizowany fragment konstrukcji wzbudzano do drgań poprzez poziome wychylenie górnej części konstrukcji celem wyznaczenia wartości dominującej częstotliwości drgań własnych. Z kolei, przeprowadzone analizy numeryczne obejmowały analizę modalną oraz analizę dynamiczną trybuny stalowej obciążonej tłumem skaczących widzów. Maksymalne wartości przyspieszeń konstrukcji poddanej dynamicznym oddziaływaniom ludzi porównano z wartościami granicznymi określonymi w literaturze. Na tej podstawie przeanalizowano wpływ drgań konstrukcji
何康康; 张洪; 史富增
2012-01-01
基于以混沌激振器为激励设备的八边形冲击压路机压实轮的工作状态,建立＂机架-压实轮-土壤＂的四自由度动力学模型,对压实轮系统的动态特性进行了研究。发现其相轨图在一定区域内缠绕、重叠、不重复,poincare图分布在一定区域内,不重叠并具有一定结构,其最大Lyapounov指数λmax=0.0317.仿真结果从定性和定量两方面表明,八边形工作轮系统的运动是混沌的,混沌激振同样适用于冲击压实。仿真结果对混沌激振在冲击压路机中的应用及混沌冲击压路机的设计及研究有参考价值。%Based on the working state of octagonal compaction roller wheel with device,4-DOF dynamics model of rack-compaction wheel-soil was built and the chaotic vibration exciter as exciting dynamic performances of compac- tion wheel system were studied. The simulation illustrated that the phase diagram was track-winding, overlapping and non-repetitive in a certain area, the poincare fingure was distributed in certain aera without overlop and with a certain structure. Its maximum Lypounov index λmax is 0.0317. The results indicate both qualitatively and quantitatively that the system of octagonal compaction roller is chaotic and chaotic vibration is also adaptable to impact compaction. The simulation results could provide reference value for the application of chaotic excitation in impact roller and the design of chaotic impact roller.
Juan Zhang; Shunle Dong
2013-07-01
To investigate the effects of reagent vibrational and rotational states on the stereodynamical properties of the N(4S) + H2(, )→NH + H reaction and its reverse reaction of H(2S) + NH(, )→N(4S) + H2, we reported a detailed quasiclassical trajectory study using the 4A" double many-body expansion potential energy surface and at the collision energy of 35 kcal/mol. The density distribution of (r) as a function of the angle between and ', and that of (r) as a function of the dihedral angle between the plane containing -' and the plane containing '- ', the normal differential cross-sections as well as the averaged product rotational alignment parameter 〈 2('.) 〉 are calculated and reported. Comparison between the two reactions has showed that the degrees of alignment and orientation of products related to reagent rovibrational state have marked differences for the two reactive systems.
钟艳春; 杨庆俊; 包钢
2011-01-01
The nonlinear dynamics characteristic of pneumatic vibration isolation system with a multi-frequency excitation was studied with the method of nonlinear dynamics. First, relative load curve of an air spring under a certain initial pressure was obtained by test, and based on the test data, a cube polynomial equation was obtained by means of nonlinear polynomial curve fitting according to the equilibrium heights of the air spring. Then, the nonlinear model of pneumatic vibration isolation system with a multi-frequency excitation was built and nonlinear dynamics equation was obtained according to nonlinear restoring force of the air spring. Next, the method of multiple scales was used to solve the nonlinear dynamics equation. Finally, combination resonance of pneumatic vibration isolation system with a multi-frequency excitation was analyzed and influences of the nonlinear parameter to the system were discussed. The results show that when combination frequencies are near the linearized natural frequency, combination resonance becomes strong. Cube nonlinear parameter directly influences nonlinear characteristic of the system, the greater the excitation amplitude, the more obvious of the nonlinear characteristic.%运用非线性动力学的方法研究气动隔振系统在多个频率激励下的非线性动力学特性.通过试验的方法得到空气弹簧在一定初始压力下的相对载荷曲线,以空气弹簧工作高度为自变量,用三次多项式对该曲线进行非线性拟合,得到弹簧非线性恢复力与工作高度的三次多项式表达式.建立气动隔振系统在3个激励频率下的非线性模型,根据弹簧的非线性恢复力,得到系统的非线性动力学方程.运用多尺度法对该非线性动力学方程进行求解,分析3个频率共同作用下的组合共振,讨论各非线性参数对系统的影响.研究结果表明:当组合频率接近系统线性化固有频率时,系统具有很强的组合共振;三次非线性
Very high frequency plasma reactant for atomic layer deposition
Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Tae Hyung; Yeom, Geun Young [Department of Advanced Materials Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Kangsik; Lee, Zonghoon [School Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919 (Korea, Republic of); Jung, Hanearl; Lee, Chang Wan [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyungjun, E-mail: hyungjun@yonsei.ac.kr [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Han-Bo-Ram, E-mail: hbrlee@inu.ac.kr [Department of Materials Science and Engineering, Incheon National University, 406-840 Incheon (Korea, Republic of)
2016-11-30
Highlights: • Fundamental research plasma process for thin film deposition is presented. • VHF plasma source for PE-ALD Al{sub 2}O{sub 3} was employed to reduce plasma damage. • The use of VHF plasma improved all of the film qualities and growth characteristics. - Abstract: Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al{sub 2}O{sub 3} were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al{sub 2}O{sub 3} shows superior physical and electrical properties over RF PE-ALD Al{sub 2}O{sub 3}, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al{sub 2}O{sub 3} on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.
Zakharenko, O.; Motiyenko, R. A.; Aviles Moreno, J.-R.; Huet, T. R., E-mail: Therese.Huet@univ-lille1.fr [Laboratoire de Physique des Lasers, Atomes et Molécules, UMR8523 CNRS – Université Lille 1, Bâtiment P5, F- 59655 Villeneuve d’Ascq Cedex (France); Jabri, A. [Laboratoire Inter-universitaire des Systèmes Atmosphériques, CNRS - Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex (France); Institute for Physical Chemistry, RWTH Aachen University, Aachen (Germany); Kleiner, I. [Laboratoire Inter-universitaire des Systèmes Atmosphériques, CNRS - Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex (France)
2016-01-14
Methacrolein is a major oxidation product of isoprene emitted in the troposphere. New spectroscopy information is provided with the aim to allow unambiguous identification of this complex molecule, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. For the most stable s-trans conformer of atmospheric interest, the torsional and rotational structures have been characterized for the ground state, the first excited methyl torsional state (ν{sub 27}), and the first excited skeletal torsional state (ν{sub 26}). The inverse sequence of A and E tunneling sub-states as well as anomalous A-E splittings observed for the rotational lines of v{sub 26} = 1 state clearly indicates a coupling between methyl torsion and skeletal torsion. A comprehensive set of molecular parameters has been obtained. The far infrared spectrum of Durig et al. [Spectrochim. Acta, Part A 42, 89–103 (1986)] was reproduced, and a Fermi interaction between ν{sub 25} and 2ν{sub 27} was evidenced.
Dynamic Testing: Toward a Multiple Exciter Test
2015-04-01
55 Defense AT&L: March–April 2015 Dynamic Testing Toward a Multiple Exciter Test Michael T. Hale n William A. Barber Hale is an electronics...has taken decades of advancements in vibration control and exciter technology. Below are a short historical path of the evolution of the discipline...toward multiple exciter /multiple degree-of-freedom (MDOF) testing, an example of an MDOF vibration system and a discussion of benefits of the
Vibration enhanced quantum transport
Semião, F L; Milburn, G J
2009-01-01
In this paper, we study the role of a collective vibrational motion in the phenomenon of electronic energy transfer (EET) between chromophores with different electronic transition frequencies. Previous experimental work on EET in conjugated polymer samples has suggested that the common structural framework of the macromolecule introduce correlations in the energy gap fluctuations which cause coherent EET. We present a simple model describing the coupling between the chromophores and a common vibrational mode, and find that vibration can indeed lead to an enhancement in the transport of excitations across the quantum network. Furthermore, in our model phase information is partially retained in the transfer process from a donor to an acceptor, as experimentally demonstrated in the conjugated polymer system. Consequently, this mechanism of vibration enhanced quantum transport might find applications in quantum information transfer of qubit states or entanglement.
Computer analysis of railcar vibrations
Vlaminck, R. R.
1975-01-01
Computer models and techniques for calculating railcar vibrations are discussed along with criteria for vehicle ride optimization. The effect on vibration of car body structural dynamics, suspension system parameters, vehicle geometry, and wheel and rail excitation are presented. Ride quality vibration data collected on the state-of-the-art car and standard light rail vehicle is compared to computer predictions. The results show that computer analysis of the vehicle can be performed for relatively low cost in short periods of time. The analysis permits optimization of the design as it progresses and minimizes the possibility of excessive vibration on production vehicles.
Vendrell, Oriol; Brill, Michael; Gatti, Fabien; Lauvergnat, David; Meyer, Hans-Dieter
2009-06-21
Quantum dynamical calculations are reported for the zero point energy, several low-lying vibrational states, and the infrared spectrum of the H(5)O(2)(+) cation. The calculations are performed by the multiconfiguration time-dependent Hartree (MCTDH) method. A new vector parametrization based on a mixed Jacobi-valence description of the system is presented. With this parametrization the potential energy surface coupling is reduced with respect to a full Jacobi description, providing a better convergence of the n-mode representation of the potential. However, new coupling terms appear in the kinetic energy operator. These terms are derived and discussed. A mode-combination scheme based on six combined coordinates is used, and the representation of the 15-dimensional potential in terms of a six-combined mode cluster expansion including up to some 7-dimensional grids is discussed. A statistical analysis of the accuracy of the n-mode representation of the potential at all orders is performed. Benchmark, fully converged results are reported for the zero point energy, which lie within the statistical uncertainty of the reference diffusion Monte Carlo result for this system. Some low-lying vibrationally excited eigenstates are computed by block improved relaxation, illustrating the applicability of the approach to large systems. Benchmark calculations of the linear infrared spectrum are provided, and convergence with increasing size of the time-dependent basis and as a function of the order of the n-mode representation is studied. The calculations presented here make use of recent developments in the parallel version of the MCTDH code, which are briefly discussed. We also show that the infrared spectrum can be computed, to a very good approximation, within D(2d) symmetry, instead of the G(16) symmetry used before, in which the complete rotation of one water molecule with respect to the other is allowed, thus simplifying the dynamical problem.
覃方芳; 党育
2011-01-01
The measured vertical velocity and acceleration exceed the normal requirements when multi-storey factory floor subjected to machine excitation. This paper used several TMDs (tuned mass dampers) hanging in specific location to reduce floor vertical vibration with the construction and operation requirements in considering. The analysis model was established by SAP2000 software, including designed multi-vertical-TMD and o-riginal structure. The response was analyzed and compared between the additional-TMD-structure floor and o-riginal one. Numerical simulation results show that vibration-reduction effects of the TMD designed in this paper are remarkable, and reduction-ratio is up to 70%.%多层工业厂房楼板在机器扰力下,实测发现楼板竖向速度和加速度超过结构正常使用要求.考虑到施工和使用要求,本文用多个TMD(调谐质量阻尼器)悬挂在楼板特定位置,以减少楼板竖向振动.通过理论推导,设计了多TMD体系的参数,并用SAP2000建立楼板与TMD的振动模型,得到附加TMD后楼板的响应,并与不加TMD的楼板振动响应比较.结果表明,本文设计的TMD可有效减小楼板在机器扰力下的竖向振动响应,减振比达到70％以上.
张琪昌; 费杰; 冯晶晶
2012-01-01
为深入研究薄壁圆柱壳在流体脉动激励下的运动特性,应用Donnell简化壳理论,考虑阻尼、结构非线性和附加质量的影响,建立了薄壁圆柱壳在流体脉动激励下的非线性振动方程.基于Galerkin方法将偏微分方程转化为方便求解的常微分方程,利用多尺度法求解了系统主共振的一次近似解,得到了系统稳态响应的转迁集与分岔图,并通过奇异性分析,得到了系统工作稳定性和可靠性的结构参数区域.对薄壁圆柱壳在流体作用下的振动特性进行了数值模拟和实验研究,考察了阻尼系数、脉动频率、液体深度等对系统动力学特性的影响.研究表明,考虑阻尼、结构非线性和附加质量的非线性振动方程更能体现薄壁圆柱壳在流体脉动激励下完整的动力学特性,同时系统中存在多种分岔行为.%In order to further research the characteristics of thin cylindrical shell excited by pulsating flow, considering the influences of damping, geometric nonlinearity and added mass, a nonlinear vibration equation under pulsating flow excitation was established by using Donnell's shallow-shell theory. The partial differential equation was transformed into an ordinary differential equation by using Galerkin method. By means of the method of multiple scales, the first approximate solution of the primary resonance of the system was acquired. The transition variety and bifurcation diagram in the unfolding parametric plane were given, the singularity and stability of the system were analysed and the stable regions of structural parameters were achieved. Experiments and numerical simulations were accomplished to study the impact of system parameters, such as the damping the pulsating frequency, the depth of liquid, etc. . The results show that the nonlinear vibration equation presented in the paper is better to reflect the dynamic characteristics, and various bifurcation behaviors existing in the system are
配气机构激励力对柴油机振动特性影响研究%Study on Effect of Valve Train' s Exciting Force to Vibration of Diesel Engine
陆传荣; 马炳杰; 王志刚
2012-01-01
Based on multi-body system dynamics and FEM, the dynamic simulation of the mobile parts in diesel engine, including crank and connecting rod mechanism, valve train and gear transmission system were carried out, thus the dynamics characteristic data, such as cam bearing force and valve seat reaction force, as well as rocking arm exciting force, etc. were obtained from the model. The finite element anal- ysis model of diesel engine was built and the effect of valve train exciting force to vibration characteristics of the whole diesel engine and its main parts was studied. The results showed that the vibration of diesel engine was affected by valve train, when under 1000Hz, the influence tended to be bigger, and the influence is small when the frequency is above 1000Hz; valve train made greater influence on valve chamber cover, cylinder head and uooer engine body than oil sump and nether engine body.%基于多体动力学和有限元方法，对柴油机运动件，包括曲柄连杆机构、配气机构以及齿轮传动系统进行了仿真分析，得到配气机构的凸轮轴承力、气门落座力和摇臂激励力等激励力。建立某柴油机结构有限元模型，研究了配气机构激励力对柴油机整机及主要部件振动特性的影响。结果表明：配气机构激励力对柴油机整机总频段振动有一定影响，其中对1000Hz以下频段影响较大，而1000Hz以上频段影响不大；对气门室罩、气缸盖和机体上侧振动影响比较大，对机体下侧和油底壳影响相对较小。
赵学; 王介修; 勾志硕; 贾艳敏
2014-01-01
By the actual test and theoretical analysis for vibration of the skew box girder bridge under human-induced excitation,the determina-tion of dynamic characteristic and the dynamic reaction under the effect of moving pedestrian,actual working state of the bridge under moving load have been studied,with safe bearing capacity and use condition of the whole structure determined.%通过对三跨预应力连续斜箱梁桥在人群荷载作用下的振动问题进行实桥测试和理论分析，测定其动态特性及在跑动的人群荷载作用下的动态响应，了解了该桥在动荷载作用下的实际工作状态，从而判断该桥整体结构的安全承载能力和使用条件。
发动机激励下客车车身怠速振动仿真研究%Simulation of vehicle body vibration in case of excitation by engine idle speed
袁爽; 杨啟梁; 胡溧; 龚海清
2015-01-01
M ulti‐body dynamics and finite element method w ere used to analyze dynamic response of vehicle body under excitation of engine .Dynamic model of the whole vehicle was established by Mo‐tionView ,and finite element model for the bus body was designed by HyperMesh .The dynamic load caused by engine excitation on powertrain mounting system was solved by MotionSolve .By applying three dimensional dynamic load on the mounting system in the finite element model ,dynamic respon‐ses on the feature points of bus body were quantitatively solved by RADIOSS .In case of excitation by engine idle speed ,the simulation and practical testing root‐mean‐square values of the vibration accel‐eration on the specific location of bus body were compared . The results show that the simulation method combining multi‐body dynamics with finite element analysis is feasible .%以某国产客车为研究对象，综合运用多体动力学和有限元分析法来研究发动机激励下车身的动态响应。在多体动力学软件MotionView中建立整车的动力学模型，在有限元软件 HyperMesh中建立车身有限元模型，用MotionSolve求解发动机激励引起的动力总成悬置系统的动载荷，将悬置系统的三向动载荷施加到有限元模型上，用RADIOSS定量求解出车身特征点的动态响应。以发动机怠速工况为例，将车身特征点振动加速度均方根值的仿真计算结果与实车测试结果进行对比分析，验证仿真方法的正确性。结果表明，将多体动力学仿真和有限元仿真有机结合起来研究发动机怠速激励下客车车身的动态响应是行之有效的。
Complex nonlinear behaviour of a fixed bed reactor with reactant recycle
Recke, Bodil; Jørgensen, Sten Bay
1999-01-01
The fixed bed reactor with reactant recycle investigated in this paper can exhibit periodic solutions. These solutions bifurcate from the steady state in a Hopf bifurcation. The Hopf bifurcation encountered at the lowest value of the inlet concentration turns the steady state unstable and marks......,that the dynamic behaviour of a fixed bed reactor with reactant recycle is much more complex than previously reported....
Reactant ion chemistry for detection of TNT, RDX, and PETN using an ion mobility spectrometer
Klassen, S.E.; Rodacy, P.; Silva, R.
1997-09-01
This report describes the responses of three energetic materials (TNT, RDX, and PETN) to varying reactant ion chemistries and IMS cell temperatures. The following reactant ion chemistries were evaluated; air-dry; air-wet; methylene chloride-dry; methylene chloride-wet; methylene bromide-dry; nitrogen dioxide-wet; sulfur dioxide-wet. The temperature was varied between 160 - 220{degrees}C.
Sloot, H.J.; Versteeg, G.F.; Swaaij, W.P.M. van
1990-01-01
A novel type of membrane reactor with separated feeding of the reactants is presented for chemical processes normally requiring strict stoichiometric feed rates of premixed reactants. The reactants are fed in the reactor to the different sides of a porous membrane which is impregnated with a catalys
Sloot, H.J.; Versteeg, G.F.; Swaaij, W.P.M. van
1990-01-01
A novel type of membrane reactor with separated feeding of the reactants is presented for chemical processes normally requiring strict stoichiometric feed rates of premixed reactants. The reactants are fed in the reactor to the different sides of a porous membrane which is impregnated with a
Monte Carlo simulations for a Lotka-type model with reactant surface diffusion and interactions.
Zvejnieks, G; Kuzovkov, V N
2001-05-01
The standard Lotka-type model, which was introduced for the first time by Mai et al. [J. Phys. A 30, 4171 (1997)] for a simplified description of autocatalytic surface reactions, is generalized here for a case of mobile and energetically interacting reactants. The mathematical formalism is proposed for determining the dependence of transition rates on the interaction energy (and temperature) for the general mathematical model, and the Lotka-type model, in particular. By means of Monte Carlo computer simulations, we have studied the impact of diffusion (with and without energetic interactions between reactants) on oscillatory properties of the A+B-->2B reaction. The diffusion leads to a desynchronization of oscillations and a subsequent decrease of oscillation amplitude. The energetic interaction between reactants has a dual effect depending on the type of mobile reactants. In the limiting case of mobile reactants B the repulsion results in a decrease of amplitudes. However, these amplitudes increase if reactants A are mobile and repulse each other. A simplified interpretation of the obtained results is given.
叶文强; 薛春霞
2014-01-01
以压电陶瓷-金属-压电陶瓷对称层合结构为研究对象，基于能量法得到了等截面压电层合对称悬臂梁在横向激振电压下的强迫振动微分方程。用ANSYS软件对建立的相关有限元模型进行模态分析、谐响应分析及瞬态动力学分析，仿真结果与理论值基本吻合，验证了理论的正确性。进一步分析了阻尼对横向位移响应的影响，讨论了速度、加速度随时间的变化规律，分析了压电悬臂梁的最大应力出现位置及最大应力值随时间的关系。所得结论可为压电振子的设计和分析提供必要理论参考。%Taking the piezoelectric ceramic-metal-piezoelectric ceramic symmetric laminated structure as research object,the forced vibration differential equation of a piezoelectric laminated symmetrical cantilever beam under transverse excitation voltage was built based on the energy method.A finite element model was established,and the modal,harmonic response and transient dynamic response of the beam were analyzed by using ANSYS software.The simulation results agree well with the theoretical values,which verifies the validity of the theory.Furthermore,the influence of damping on the transverse displacement response was analyzed,and the variations of velocity and acceleration with time were discussed. The location of the maximum stress of the piezoelectric cantilever beam and the characteristics of the maximum stress with time were analyzed.The conclusion can provide necessary theoretical reference for the design and analysis of piezoelectric vibrators.
The mechanisms of Excited states in enzymes
Petersen, Frederic Nicolas Rønne; Bohr, Henrik
2010-01-01
Enzyme catalysis is studied on the basis of excited state processes, which are of electronic, vibrational and thermal nature. The ways of achieving the excited state, such as photo-absorption and ligand binding, are discussed and exemplified by various cases of enzymes.......Enzyme catalysis is studied on the basis of excited state processes, which are of electronic, vibrational and thermal nature. The ways of achieving the excited state, such as photo-absorption and ligand binding, are discussed and exemplified by various cases of enzymes....
The mechanisms of Excited states in enzymes
Petersen, Frederic Nicolas Rønne; Bohr, Henrik
2010-01-01
Enzyme catalysis is studied on the basis of excited state processes, which are of electronic, vibrational and thermal nature. The ways of achieving the excited state, such as photo-absorption and ligand binding, are discussed and exemplified by various cases of enzymes.......Enzyme catalysis is studied on the basis of excited state processes, which are of electronic, vibrational and thermal nature. The ways of achieving the excited state, such as photo-absorption and ligand binding, are discussed and exemplified by various cases of enzymes....
Nonlinear vibration absorption for a flexible arm via a virtual vibration absorber
Bian, Yushu; Gao, Zhihui
2017-07-01
A semi-active vibration absorption method is put forward to attenuate nonlinear vibration of a flexible arm based on the internal resonance. To maintain the 2:1 internal resonance condition and the desirable damping characteristic, a virtual vibration absorber is suggested. It is mathematically equivalent to a vibration absorber but its frequency and damping coefficients can be readily adjusted by simple control algorithms, thereby replacing those hard-to-implement mechanical designs. Through theoretical analyses and numerical simulations, it is proven that the internal resonance can be successfully established for the flexible arm, and the vibrational energy of flexible arm can be transferred to and dissipated by the virtual vibration absorber. Finally, experimental results are presented to validate the theoretical predictions. Since the proposed method absorbs rather than suppresses vibrational energy of the primary system, it is more convenient to reduce strong vibration than conventional active vibration suppression methods based on smart material actuators with limited energy output. Furthermore, since it aims to establish an internal vibrational energy transfer channel from the primary system to the vibration absorber rather than directly respond to external excitations, it is especially applicable for attenuating nonlinear vibration excited by unpredictable excitations.
Faultage behavior of wet granular materials under vibrational excitation%探讨振动激励下湿颗粒物质中的断层行为
母应坤; 孔维姝; 胡林; 王影
2014-01-01
研究了竖直振动激励下湿颗粒物质中的一种断层行为，实验表明断层块的运动具有周期性，其周期是激振周期的整数倍，倍率强烈地依赖于约化加速度Г，随着Г的加大，倍率阶梯式增加。采用蹦球模型对其进行了动力学分析，其数值解结果对于倍率为三倍和四倍的周期运动对应的Г值与实验结果吻合较好，对于倍率为两倍的周期运动对应的Г值比实验值小，最后定性地解释了偏小的原因。%The faultage behavior of wet granular materials under vertical vibration excitation was studied.An experiment shows the motion of the faultage block is of periodicity,with the period of an integral multiple of the driving period.The ratio n (the period of faultage block divided by the driving period ) is dependent on the normalized acceleration Гintensively,and it increases stepwisely with the increase ofГ.A dynamic analysis was given based on the bouncing ball model.Comparing the numerical results and the experimental data,it concludes that the valueГin the case of n=2 or n =3 coincides well with the experimental value,but the value Гin the case of n =2 is smaller than the experimental value,and the reason was explained qualitatively.
Water Induced Vibration in the NSRRC
Wang, Duan J; Tsai, Zong-Da; Wang, Jeremy
2005-01-01
Water flow related vibrations were found on the spectrum of electron beam position monitor in the NSRRC. They were associated with the vibrations of quadrupole magnets. One major vibration source was from a pump in the cooling water system. Most amount of vibration coupled through water pipe and water flow and propagated to the magnets. A small water flow station was set up to study the effect about coupling, propagating and excitation. Some damping schemes tested in the ring to improve the vibration are also included..
Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY
2012-03-13
The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.
Vibrational Autodetachment in Nitroalkane Anions
Adams, Christopher L.; Weber, J. Mathias
2010-06-01
Nitroalkanes have electron affinities ge 1370 cm-1, well below the excitation energies for CH stretching modes, with the excess charge localized on the nitro group. Upon absorption of an IR photon in a CH stretching vibrational mode, the absorbed energy is redistributed in the molecule. If enough energy is transferred to the NO2 stretching/wagging modes, the excess electron residing on the nitro group is emitted. Vibrational autodetachment (VAD) spectra encode information regarding intramolecular vibrational relaxation (IVR) processes leading up to electron emission. We present VAD photoelectron spectroscopy of polyatomic molecular anions and discuss how a VAD photoelectron spectrum can be modeled.
Pedersen, Lars
2007-01-01
A flooring-system, e.g. a floor in a building, is excited dynamically when a person walks across the floor, and resonant excitation might bring structural vibrations to unacceptable levels. Stationary (non-moving) crowds of people might be present on the same floor and they will sense the floor vibrations, but they will also interact dynamically with the floor in a passive sense, thus altering the dynamic system excited to vibration by the walking person. Consequently, the vibration level of ...
The origins of vibration theory
Dimarogonas, A. D.
1990-07-01
The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.
Zhang, Binbin; Song, Jinliang; Liu, Huizhen; Han, Buxing; Jiang, Tao; Fan, Honglei; Zhang, Zhaofu; Wu, Tianbin
2012-12-01
Exploration of new and effective routes to conduct organic reactions in water using the special properties of water/organics is of great importance. In this work, we performed the disproportionation of various aromatic alcohols in water and in different organic solvents. It was demonstrated that the disproportionation reactions of the alcohols were accelerated more effectively in water than organic-solvent-based or solvent-free reactions. A series of control experiments were conducted to study the mechanism of the accelerated reaction rate in water. It was shown that the reactants could emulsify the reactant/water systems at the reaction conditions owing to their amphiphilic nature. The regularly orientated reactant molecules at the water/reactant droplet interface improved the contact probability of the reactive groups and the Pd nanocatalysts, which is one of the main reasons for the enhanced reaction rate in water. Controlling the self-emulsification of amphiphilic reactant/water systems has great application potential for optimizing the rate and/or selectivity of many organic reactions.
Using Fast Vibrations to Quench Friction-induced Oscillations
Thomsen, Jon Juel
1999-01-01
-frequency excitation. It appears that high-frequency excitation can effectively cancel the negative slope in the friction-velocity relationship, and may thus prevent self-excited oscillations. To accomplish this it is sufficient that the (nondimensional) product of excitation amplitude and frequency exceeds the veloc...... change under the action of fast vibrations....
Moellenbeck, Simone
2011-04-11
In the present work ultra fast time resolved electron diffraction (TR-RHEED) at various adsorbate systems on silicon (Si) substrates was performed. Using the Debye-Waller-effect, the vibrational amplitude of the excited adsorbate atoms can be directly observed in the experiments as a function of time. For a coverage of 4/3 monolayers Lead (Pb) on Si(1 1 1) forms a ({radical}(3) x {radical}(3))-reconstruction. The transient intensity evolution of the diffraction spots is recorded in a TR-RHEED-experiment. After excitation with a fs-laser pulse the intensity decreases due to the Debye-Waller-effect. The temporal behavior of the de-excitation process can be described with two exponential functions: a short time constant of 100 ps and a long one of 2800 ps. The two time constants can be assigned to two different phonon modes of the Pb-adsorbate. The huge difference between the two time constants and thus difference in the coupling to the substrate is explained by the bonding geometry in the structural model. To confirm this possible explanation, further TR-RHEED-experiments for the ({radical}(7) x {radical}(3))-reconstruction of Pb on Si(1 1 1) were performed. The ({radical}(7) x {radical}(3))-reconstruction with a coverage of 1.2 monolayers shows comparable structural elements. The transient intensity evolution can be described with the identical two time constants. In addition, first experiments on the {beta} ({radical}(3) x {radical}(3))-phase of Pb/Si(1 1 1) are presented. This {beta} ({radical}(3) x {radical}(3))-reconstruction, with a coverage of 1/3 monolayers of Pb, shows a phase transition to a (3 x 3)-reconstruction, which was observed in the experiments. Further investigated adsorbate systems are: ({radical}(3) x {radical}(3))Ag/Si(1 1 1), ({radical}(3) x {radical}(3))In/Si(1 1 1), ({radical}(31) x {radical}(31))In/Si(1 1 1), and ({radical}(3) x {radical}(3))Bi/Si(1 1 1). In the second part of the present work the structural dynamics of strongly driven
Influence of vibration in the reactive scattering of D + MuH: the effect of dynamical bonding.
Sáez-Rábanos, V; Verdasco, J E; Aoiz, F J; Herrero, V J
2016-05-21
The dynamics of the D + MuH(v = 1) reaction has been investigated using time-independent quantum mechanical calculations. The total reaction cross sections and rate coefficients have been calculated for the two exit channels of the reaction leading, respectively, to DMu + H and DH + Mu. Over the 100-1000 K temperature range investigated the rate coefficients for the DMu + H channel are of the order of 10(-10) cm(3) s(-1) and those for the DH + Mu channel vary between 1 × 10(-12) and 8 × 10(-11) cm(3) s(-1). These results point to a virtually barrierless reaction for the DMu + H channel and to the presence of a comparatively small barrier for the DH + Mu channel and are consistent with the profiles of their respective collinear vibrationally adiabatic potentials (VAPs). The effective barrier in the VAP of the DH + Mu channel is located in the reactant valley and, consequently, translation is found to be more efficient than vibration for the promotion of the reaction over a large energy interval in the post threshold region. Below this barrier, the DH + Mu channel can be accessible through an indirect mechanism implying crossing from the DMu + H pathway. The most salient feature found in the present study is revealed in the total reaction cross section for the DMu + H channel, which shows a sharp resonance caused by the presence of a deep well in the vibrationally adiabatic potential. This well has a dynamical origin, reminiscent of that found recently in the vibrationally bonded BrMuBr complex [Fleming, et al., Angew. Chem., Int. Ed., 2014, 53, 1], and is due to the stabilizing effect of the light Mu atom oscillating between the heavier H and D isotopes and to the bond softening associated with vibrational excitation of MuH.
Damping of roll vibrations of vehicle suspension
Le, K. C.; Pieper, A.
2014-04-01
Small forced vibrations of an axle model of independent suspensions having four degrees of freedom are studied. The exact analytical solution of the generalised Lagrange equation enables one to produce 3D plots of the normalised amplitudes of forced vibrations versus frequency and excitation ratio or phase difference of the road inputs. The analysis of these plots exhibits some deficiency in damping of roll vibrations of conventional vehicle suspensions. The possibilities of improvement are discussed.
Electron impact on vibrationally cold {{HF}}^{+}
Cristian Stroe, Marius; Fifirig, Magda
2016-12-01
The dissociative recombination and vibrational excitation processes induced by electron impact on vibrationally cold {{HF}}+ are investigated in the framework of the multichannel quantum defect theory for electron energies below 1 eV. The thermal rate coefficients for the electron temperature range from 10 to 5000 K are reported.
Enhanced bactericidal action of acidified sodium chlorite caused by the saturation of reactants.
Kim, N H; Park, T H; Rhee, M S
2014-06-01
Factors affecting the antibacterial action of acidified sodium chlorite (ASC), a widely used disinfectant, have not been determined. This study investigated the significant factors suggesting efficient production method to maximize bactericidal action of ASC. The effects of (i) preparation procedures (total three methods); (ii) initial concentrations of reactants: sodium chlorite (SC) and citric acid (CTA) (up to maximum solubility of each reactant) and (iii) final pH values (3·0 and 2·5) to the bactericidal action of ASC were investigated with a fixed final concentration of SC (10 ppm) using various foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aureus). The antimicrobial compounds produced and the bactericidal effects depended on the preparation procedure and the initial concentrations of the reactants. The ASC prepared by premixing highly concentrated reactants (in particular > 40%) followed by dilution (dilution after reaction, DAR) was more effective in inactivating foodborne pathogens, and it produced higher antimicrobial compound (Cl(2) and ClO(2)) yields than the other procedures. A 5-min treatment with ASC, produced using the other procedures, resulted in a reduction of < 3·5 log CFU ml(-1) (Gram positive = 0·18-0·78; Gram negative = 0·03-3·49 log CFU ml(-1)), whereas ASC produced with the DAR procedure using the saturated reactants completely inactivated all of the test pathogens within 5 min without recovery (initial concentration = 6·94-7·08 log CFU ml(-1)). The ASC production with the DAR procedure using the saturated reactants maximizes both the antimicrobial compound yields and bactericidal effects of the ASC solutions. This study will contribute to increase the efficiency of ASC treatments for disinfections reducing the effective SC concentrations for industrial use. © 2014 The Society for Applied Microbiology.
Nonlinear dynamic response of stay cables under axial harmonic excitation
Xu XIE; He ZHAN; Zhi-cheng ZHANG
2008-01-01
This paper proposes a new numerical simulation method for analyzing the parametric vibration of stay cables based on the theory of nonlinear dynamic response of structures under the asynchronous support excitation.The effects of important parameters related to parametric vibration of cables,I.e., characteristics of structure,excitation frequency,excitation amplitude,damping effect of the air and the viscous damping coefficient of the cables,were investigated by using the proposed method for the cables with significant length difference as examples.The analysis results show that nonlinear finite element method is a powerful technique in analyzing the parametric vibration of cables,the behavior of parametric vibration of the two cables with different Irvine parameters has similar properties,the amplitudes of parametric vibration of cables are related to the frequency and amplitude of harmonic support excitations and the effect of distributed viscous damping on parametric vibration of the cables is very small.
Song, Hongwei; Li, Jun; Jiang, Bin; Yang, Minghui; Lu, Yunpeng; Guo, Hua
2014-02-01
The dynamics of the hydrogen abstraction reaction between methane and hydroxyl radical is investigated using an initial state selected time-dependent wave packet method within a six-dimensional model. The ab initio calibrated global potential energy surface of Espinosa-García and Corchado was used. Integral cross sections from several low-lying rotational states of both reactants have been obtained using the centrifugal sudden and J-shifting approximations. On the empirical potential energy surface, the rotational excitation of methane has little effect on the reaction cross section, but excited rotational states of OH inhibit the reactivity slightly. These results are rationalized with the newly proposed sudden vector projection model.
Role of inlet reactant mixedness on the thermodynamic performance of a rotating detonation engine
Nordeen, C. A.; Schwer, D.; Schauer, F.; Hoke, J.; Barber, T.; Cetegen, B. M.
2016-07-01
Rotating detonation engines have the potential to achieve the high propulsive efficiencies of detonation cycles in a simple and effective annular geometry. A two-dimensional Euler simulation is modified to include mixing factors to simulate the imperfect mixing of injected reactant streams. Contrary to expectations, mixing is shown to have a minimal impact on performance. Oblique detonation waves are shown to increase local stream thermal efficiency, which compensates for other losses in the flow stream. The degree of reactant mixing is, however, a factor in controlling the stability and existence of rotating detonations.
CINE: Comet INfrared Excitation
de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.
2017-08-01
CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.
Nicolas, Maxime
2016-01-01
Engineering school; This course is designed for students of Polytech Marseille, engineering school. It covers first the physics of vibration of the harmonic oscillator with damping and forcing, coupled oscillators. After a presentation of the wave equation, the vibration of strings, beams and membranes are studied.
Evidence of Ultrafast Charge Transfer Driven by Coherent Lattice Vibrations.
Rury, Aaron S; Sorenson, Shayne A; Dawlaty, Jahan M
2017-01-05
We report evidence that intermolecular vibrations coherently drive charge transfer between the sites of a material on ultrafast time scales. Following a nonresonant stimulated Raman pump pulse that excites the organic material quinhydrone, we observe the initial appearance of oscillations due to intermolecular lattice vibrations and then the delayed appearance of a higher-frequency oscillation that we assign to a totally symmetric intramolecular vibration. We use the coherent dynamics of the transient reflectivity signal to propose that coherence transfer drives excitation of this intramolecular vibration. Furthermore, we conclude that the dynamical frequency shift of the intramolecular vibration reports the formation of a quasi-stable charge-separated state on ultrafast time scales. We calculate model dynamics using the extended Hubbard Hamiltonian to explain coherence transfer due to vibrationally driven charge transfer. These results demonstrate that the coherent excitation of low-frequency vibrations can drive charge transfer in the solid state and control material properties.
Random torsional vibration in automobile transmissions
无
2003-01-01
The action of a road profile to the torsional vibrations in automobile transmissions is studied. The model to calculate the random torsional vibrations in the transmissions is proposed and the values of the model parameters are determined by both computation and experiment. Furthermore, the dynamic characteristics and the responses of automobile transmissions to the random excitation of road profile are calculated. The results of road experiment demonstrate that the theoretic analyses and the calculation are correct, which imply that the low frequency torsional vibrations in automobile transmissions are caused by the random excitation of a road profile.
Solid oxide fuel cell systems with hot zones having improved reactant distribution
Poshusta, Joseph C.; Booten, Charles W.; Martin, Jerry L.
2016-05-17
A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.
The catalytic combustion of natural gas in a membrane reactor with separate feed of reactants
Neomagus, H.W.J.P.; Saracco, G.; Wessel, H.F.W.; Versteeg, G.F.
2000-01-01
This paper provides an experimental and modelling analysis of the performance of a membrane reactor with separate feed of reactants for the combustion of methane. In this reactor concept methane and air streams are fed at opposite sides of a Pt/γ-Al2O3-activated porous membrane which hosts their
The catalytic combustion of natural gas in a membrane reactor with separate feed of reactants
Neomagus, H.W.J.P.; Saracco, G.; Wessel, H.F.W.; Versteeg, G.F.
2000-01-01
This paper provides an experimental and modelling analysis of the performance of a membrane reactor with separate feed of reactants for the combustion of methane. In this reactor concept methane and air streams are fed at opposite sides of a Pt/γ-Al2O3-activated porous membrane which hosts their rea
Ilinich, O.M.; Cuperus, F.P.; Gemert, van R.W.; Gribov, E.N.; Nosova, L.V.
2000-01-01
The series of mono- and bi-metallic catalysts with Pd and/or Cu supported over γ-Al 2O 3 was investigated with respect to reduction of nitrate and nitrite ions in water by hydrogen. Pronounced limitations of catalytic performance due to intraporous diffusion of the reactants were observed in the rea
Isolation of a lipopolysaccharide-binding acute phase reactant from rabbit serum.
Tobias, P S; Soldau, K; Ulevitch, R J
1986-09-01
This report describes the purification of an acute phase reactant from acute phase rabbit serum, which endows normal serum with the properties of acute phase serum, insofar as LPS is concerned. The acute phase reactant is referred to as LPS-binding protein, or LBP. LBP was purified approximately 2,000-fold by chromatography of acute phase serum on Bio-Rex 70 and Mono-Q resins. The resulting preparation consisted of two glycoproteins having molecular weights of 60,500 and 58,000; the two were obtained in a variable ratio, usually near 10:1, respectively. After separation by SDS-PAGE, the N-terminal 36 amino acid sequences of the two proteins were identical. From the N-terminal sequence, as well as other properties of LBP, LBP appears to be unrelated to any known acute phase reactants. The direct interaction of LPS and LBP was inferred from two types of evidence: first, immunoprecipitation of [3H]LPS from APRS by anti-LBP sera; and second, by the 125I-labeling of LBP when APRS-containing 125I-labeled 2-(p-azidosalicylamido)ethyl 1,3'-dithiopropionyl-LPS was photolysed. The data presented here support the concept that the 60-kD glycoprotein we have termed LBP is a newly recognized acute phase reactant that may modulate the biochemical and biologic properties of LPS in vivo.
共反应剂TPPD的制备%Synthesis of a nevol co-reactant TPPD
冉红; 梁艳霞; 刘娟娟; 肖丹
2012-01-01
本实验合成了一种共反应剂N,N,N’,N’-4-丙基-戊二胺(TPPD),它的分子中含有两个叔氨基,与传统的共反应剂三丙胺(TPA)相比增加了一个氮的活性位点.并且分子中的碳碳长链使得TPPD的疏水性增加,因此能与钌配合物[Ru(bpy)3] [4-(Clph)4B]2同时固定到ITO电极上,减少了ECL过程中的共反应剂的消耗.%In this work,a new organic-soluble co-reactant N,N,N',N'-tetrakis(propyl)-pentanediamine(TPPD) was synthesized. It contains two tertiary amines. Compared with the traditional co-reactant, such as tripropylamine (TPA) it has two nitrogen active sites. The new co-reactant is very hydrophobic and thus could be co-immobilized with tris(2,2'-bipyridine)ruthenium(II)ditetrakis (4-chlorophenyl)borate[Ru(bpy)3] [4-(Clph)4B]2 on an indium tin oxide(ITO) electrode. So the consumption of co-reactant is greatly reduced in the electrochemiluminescent(ECL) process.
Ilinich, O.M.; Cuperus, F.P.; Gemert, van R.W.; Gribov, E.N.; Nosova, L.V.
2000-01-01
The series of mono- and bi-metallic catalysts with Pd and/or Cu supported over γ-Al 2O 3 was investigated with respect to reduction of nitrate and nitrite ions in water by hydrogen. Pronounced limitations of catalytic performance due to intraporous diffusion of the reactants were observed in the
The catalytic combustion of natural gas in a membrane reactor with separate feed of reactants
Neomagus, H.W.J.P.; Saracco, G.; Wessel, H.F.W.; Versteeg, G.F.
2000-01-01
This paper provides an experimental and modelling analysis of the performance of a membrane reactor with separate feed of reactants for the combustion of methane. In this reactor concept methane and air streams are fed at opposite sides of a Pt/γ-Al2O3-activated porous membrane which hosts their rea
Laserlike Vibrational Instability in Rectifying Molecular Conductors
Lu, Jing Tao; Hedegård, Per; Brandbyge, Mads
2011-01-01
We study the damping of molecular vibrations due to electron-hole pair excitations in donor-acceptor (D-A) type molecular rectifiers. At finite voltage additional nonequilibrium electron-hole pair excitations involving both electrodes become possible, and contribute to the stimulated emission and...
Mcpeak, W. L.
1975-01-01
A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.
Wideband MEMS Resonator Using Multifrequency Excitation
Jaber, Nizar
2016-03-09
We demonstrate the excitation of combination resonances of additive and subtractive types and their exploitations to realize a large bandwidth micro-machined resonator of large amplitude even at higher harmonic modes of vibrations. The investigation is conducted on a Microelectromechanical systems (MEMS) clamped-clamped microbeam fabricated using polyimide as a structural layer coated with nickel from top and chromium and gold layers from bottom. The microbeam is excited by a two-source harmonic excitation, where the first frequency source is swept around the targeted resonance (first or third mode of vibration) while the second source frequency is kept fixed. We report for the first time a large bandwidth and large amplitude response near the higher order modes of vibration. Also, we show that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled.
Novel Adsorbent-Reactants for Treatment of Ash and Scrubber Pond Effluents
Bill Batchelor; Dong Suk Han; Eun Jung Kim
2010-01-31
The overall goal of this project was to evaluate the ability of novel adsorbent/reactants to remove specific toxic target chemicals from ash and scrubber pond effluents while producing stable residuals for ultimate disposal. The target chemicals studied were arsenic (As(III) and As(V)), mercury (Hg(II)) and selenium (Se(IV) and Se(VI)). The adsorbent/reactants that were evaluated are iron sulfide (FeS) and pyrite (FeS{sub 2}). Procedures for measuring concentrations of target compounds and characterizing the surfaces of adsorbent-reactants were developed. Effects of contact time, pH (7, 8, 9, 10) and sulfate concentration (0, 1, 10 mM) on removal of all target compounds on both adsorbent-reactants were determined. Stability tests were conducted to evaluate the extent to which target compounds were released from the adsorbent-reactants when pH changed. Surface characterization was conducted with x-ray photoelectron spectroscopy (XPS) to identify reactions occurring on the surface between the target compounds and surface iron and sulfur. Results indicated that target compounds could be removed by FeS{sub 2} and FeS and that removal was affected by time, pH and surface reactions. Stability of residuals was generally good and appeared to be affected by the extent of surface reactions. Synthesized pyrite and mackinawite appear to have the required characteristics for removing the target compounds from wastewaters from ash ponds and scrubber ponds and producing stable residuals.
Laser induced structural vibration
Koss, L. L.; Tobin, R. C.
1983-01-01
A technique is described for exciting structural vibration by using a focussed laser beam to vaporize material from a target attached to the structure. The rapid ejection of material results in an impulsive reaction to the target which is transmitted to the structure. The method has been studied with a Nd: glass laser, operated in the long pulse mode, in combination with a bismuth target attached in turn to a ballistic pendulum and cantilever beam. The specific mechanical energy was found to be proportional to the laser pulse energy raised to a power in the range 2.5-2.9. The highest efficiency of energy transfer achieved for the first vibrational mode of the cantilever was about 2 millipercent for the maximum laser pulse energy used, 1.5 J, the signal to noise ratio then being about 40 dB.
Multidimensional Time-Resolved Spectroscopy of Vibrational Coherence in Biopolyenes
Buckup, Tiago; Motzkus, Marcus
2014-04-01
Multidimensional femtosecond time-resolved vibrational coherence spectroscopy allows one to investigate the evolution of vibrational coherence in electronic excited states. Methods such as pump-degenerate four-wave mixing and pump-impulsive vibrational spectroscopy combine an initial ultrashort laser pulse with a nonlinear probing sequence to reinduce vibrational coherence exclusively in the excited states. By carefully exploiting specific electronic resonances, one can detect vibrational coherence from 0 cm-1 to over 2,000 cm-1 and map its evolution. This review focuses on the observation and mapping of high-frequency vibrational coherence for all-trans biological polyenes such as Î²-carotene, lycopene, retinal, and retinal Schiff base. We discuss the role of molecular symmetry in vibrational coherence activity in the S1 electronic state and the interplay of coupling between electronic states and vibrational coherence.
Multidimensional time-resolved spectroscopy of vibrational coherence in biopolyenes.
Buckup, Tiago; Motzkus, Marcus
2014-01-01
Multidimensional femtosecond time-resolved vibrational coherence spectroscopy allows one to investigate the evolution of vibrational coherence in electronic excited states. Methods such as pump-degenerate four-wave mixing and pump-impulsive vibrational spectroscopy combine an initial ultrashort laser pulse with a nonlinear probing sequence to reinduce vibrational coherence exclusively in the excited states. By carefully exploiting specific electronic resonances, one can detect vibrational coherence from 0 cm(-1) to over 2,000 cm(-1) and map its evolution. This review focuses on the observation and mapping of high-frequency vibrational coherence for all-trans biological polyenes such as β-carotene, lycopene, retinal, and retinal Schiff base. We discuss the role of molecular symmetry in vibrational coherence activity in the S1 electronic state and the interplay of coupling between electronic states and vibrational coherence.
Srinivasa Rao Karumuri; Joydeep Choudhury; Nirmal Kumar Sarkar; Ramendu Bhattacharjee
2010-01-01
Using Lie algebraic techniques and simpler expressions of the matrix elements of Majorana and Casimir operators given by us, we obtain an effective Hamiltonian operator which conveniently describes stretching vibrations of biomolecules. For a copper tetramesityl porphyrin molecule, the higher excited vibrational levels are calculated by applying the (2) algebraic approach.
Theoretical studies of excited state 1,3 dipolar cycloadditions
Belluccci, Michael A.
The 1,3 dipolar photocycloaddition reaction between 3-hydroxy-4',5,7-trimethoxyflavone (3-HTMF) and methyl cinnamate is investigated in this work. Since its inception in 2004 [JACS, 124, 13260 (2004)], this reaction remains at the forefront in the synthetic design of the rocaglamide natural products. The reaction is multi-faceted in that it involves multiple excited states and is contingent upon excited state intramolecular proton transfer (ESIPT) in 3-HTMF. Given the complexity of the reaction, there remain many questions regarding the underlying mechanism. Consequently, throughout this work we investigate the mechanism of the reaction along with a number of other properties that directly influence it. To investigate the photocycloaddition reaction, we began by studying the effects of different solvent environments on the ESIPT reaction in 3-hydroxyflavone since this underlying reaction is sensitive to the solvent environment and directly influences the cycloaddition. To study the ESIPT reaction, we developed a parallel multi-level genetic program to fit accurate empirical valence bond (EVB) potentials to ab initio data. We found that simulations with our EVB potentials accurately reproduced experimentally determined reaction rates, fluorescence spectra, and vibrational frequency spectra in all solvents. Furthermore, we found that the ultrafast ESIPT process results from a combination of ballistic transfer and intramolecular vibrational redistribution. To investigate the cycloaddition reaction mechanism, we utilized the string method to obtain minimum energy paths on the ab initio potential. These calculations demonstrated that the reaction can proceed through formation of an exciplex in the S1 state, followed by a non-adiabatic transition to the ground state. In addition, we investigated the enantioselective catalysis of the reaction using alpha,alpha,alpha',alpha'-tetraaryl-1,3-dioxolan-4,5-dimethanol alcohol (TADDOL). We found that TADDOL lowered the energy
Panesar, Lucy
2007-01-01
Good Vibrations was a market research exercise conducted by Felicity (my alter-ego) and assistants to help develop marketing and packaging for an electro-therapeutic device (vibrator) used to treat hysteria and other female stress related disorders. It was a live art work commissioned by The Live Art Development Agency for East End Collaborations on 6th May 2007 and the South London Gallery for Bonkersfest on 2nd June 2007.
Application Of Holographic Interferometry To Practical Vibration Study
Murata, M.; Kuroda, M.
1983-10-01
This paper describes a brief summary of applications of holographic interferometry to practical vibration study in Nagasaki Technical Institute of MHI. The applications of vibration mode measurement are concerned with steam turbine blades, compressor impeller, internal combustion engine, car body and car brake disk. The techniques of holography contained herein are (1) the time average method giving contour fringes of vibration amplitude,(2)the phase modulation method providing information on the relative phases of vibration, and(3)the double pulse method that offers the possibility of visualizing the vibration pattern of internal combustion engine in operating condition,and the transient vibration pattern of an object excited by impact force.
Gupta, Amita; Singh, Ranvir; Ahmad, Amir; Kumar, Mahesh
2003-10-01
Today, vibration sensors with low and medium sensitivities are in great demand. Their applications include robotics, navigation, machine vibration monitoring, isolation of precision equipment & activation of safety systems e.g. airbags in automobiles. Vibration sensors have been developed at SSPL, using silicon micromachining to sense vibrations in a system in the 30 - 200 Hz frequency band. The sensing element in the silicon vibration sensor is a seismic mass suspended by thin silicon hinges mounted on a metallized glass plate forming a parallel plate capacitor. The movement of the seismic mass along the vertical axis is monitored to sense vibrations. This is obtained by measuring the change in capacitance. The movable plate of the parallel plate capacitor is formed by a block connected to a surrounding frame by four cantilever beams located on sides or corners of the seismic mass. This element is fabricated by silicon micromachining. Several sensors in the chip sizes 1.6 cm x 1.6 cm, 1 cm x 1 cm and 0.7 cm x 0.7 cm have been fabricated. Work done on these sensors, techniques used in processing and silicon to glass bonding are presented in the paper. Performance evaluation of these sensors is also discussed.
Vorotilin, V. P.
2017-01-01
A generalization of the theory of chemical transformation processes under turbulent mixing of reactants and arbitrary values of the rate of molecular reactions is presented that was previously developed for the variant of an instantaneous reaction [13]. The use of the features of instantaneous reactions when considering the general case, namely, the introduction of the concept of effective reaction for the reactant volumes and writing a closing conservation equation for these volumes, became possible due to the partition of the whole amount of reactants into "active" and "passive" classes; the reactants of the first class are not mixed and react by the mechanism of instantaneous reactions, while the reactants of the second class approach each other only through molecular diffusion, and therefore their contribution to the reaction process can be neglected. The physical mechanism of reaction for the limit regime of an ideal mixing reactor (IMR) is revealed and described. Although formally the reaction rate in this regime depends on the concentration of passive fractions of the reactants, according to the theory presented, the true (hidden) mechanism of the reaction is associated only with the reaction of the active fractions of the reactants with vanishingly small concentration in the volume of the reactor. It is shown that the rate constant of fast chemical reactions can be evaluated when the mixing intensity of reactants is much less than that needed to reach the mixing conditions in an IMR.
Neomagus, H.W.J.P.; van Swaaij, Willibrordus Petrus Maria; Versteeg, Geert
1998-01-01
The oxidation of H2S is studied in a membrane reactor with separate feed of reactants. As a novelty in the concept of separate introduction of the reactants, a sintered stainless steel membrane is used, because this type of material is easy to integrate into the reactor, and the catalytic properties
The catalytic oxidation of H2S in a stainless steel membrane reactor with separate feed of reactants
Neomagus, H.W.J.P.; Swaaij, W.P.M. van; Versteeg, G.F.
1998-01-01
The oxidation of H2S is studied in a membrane reactor with separate feed of reactants. As a novelty in the concept of separate introduction of the reactants, a sintered stainless steel membrane is used, because this type of material is easy to integrate into the reactor, and the catalytic properties
A study of reactant interfaces in Ni+Al particle systems during shock wave propagation
Austin, Ryan A.; McDowell, David L.; Horie, Yasuyuki; Benson, David J.
2007-06-01
Macro-scale responses of energetic materials during shock compression are influenced strongly by thermo-mechano-chemical processes occurring at the level of the microstructure. For example, it is believed that the propagation of chemical reactions in reactive particle systems is intimately linked to conditions at reactant interfaces such as surface temperature, phase changes, defect density, and mass mixing due to inelastic deformation. To provide explicit resolution of such interfacial conditions, numerical models are constructed. The finite element method is used to numerically solve the differential equations that govern the coupled thermomechanical response of micron-size particle mixtures of Ni and Al during shock wave propagation (interface chemistry is not yet modeled). The size and temperature distributions of contiguous reactant contact surfaces are quantified for a range of shock strengths. A parametric study of mixture attributes is undertaken to assess the sensitivity of the aforementioned distributions to variations of the microstructure.
Dongbing Li; Ajay K. Ray; Madhumita B. Ray; Jesse Zhu
2012-01-01
Rotational asymmetric distribution of reactant (ozone) concentration and its evolution along with the gas-solid reactive flow were studied in a 76 mm i.d.,10.2 m high circulating fluidized bed (CFB) riser reactor.The superficial gas velocity ranged from 3 to 5 m/s and the solids circulation rates were 50 and 100kg/(m2 s).Experimental results show that the asymmetry of reactant distribution can extend to a height close to the length of flow developing zone of the CFB riser reactor and then disappears.Based on the hydrodynamics of the gas and solid phases in the solids entrance region,this asymmetry can be attributed to the effect of the solids entrance structure.
Gommes, Cédric J; Basiura, Monika; Goderis, Bart; Pirard, Jean-Paul; Blacher, Silvia
2006-04-20
The microstructure of hybrid silica xerogels synthesized by the base-catalyzed polymerization of tetraethoxysilane (TEOS) in ethanol in the presence of 3-aminopropyltriethoxysilane (AES) and of 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) as co-reactants, and dried in subcritical conditions, is analyzed. A thorough structural characterization of the samples is performed combining nitrogen adsorption, small-angle X-ray scattering (SAXS), and transmission electron microscopy coupled with digital image analysis. The use of these methods shows that, for both co-reactants, the xerogels are made of macropores supported by filaments, with each filament being formed of smaller structures. The quantitative impact of the additive on each structural level is assessed. The data are compared with a previous time-resolved SAXS study conducted during the formation of the gels (J. Phys. Chem. B 2004, 108, 8983-8991). The results are analyzed in the framework of a double phase separation model.
Acute-phase reactants in periodontal disease: current concepts and future implications.
Archana, Vilasan; Ambili, Ranjith; Nisha, Krishnavilasam Jayakumary; Seba, Abraham; Preeja, Chandran
2015-05-01
Periodontal disease has been linked to adverse cardiovascular events by unknown mechanisms. C-reactive protein is a systemic marker released during the acute phase of an inflammatory response and is a prognostic marker for cardiovascular disease, with elevated serum levels being reported during periodontal disease. Studies also reported elevated levels of various other acute-phase reactants in periodontal disease. It has been reported extensively in the literature that treatment of periodontal infections can significantly lower serum levels of C-reactive protein. Therefore, an understanding of the relationship between acute-phase response and the progression of periodontal disease and other systemic health complications would have a profound effect on the periodontal treatment strategies. In view of this fact, the present review highlights an overview of acute-phase reactants and their role in periodontal disease. © 2014 Wiley Publishing Asia Pty Ltd.
A mixed-reactants solid-polymer-electrolyte direct methanol fuel cell
Scott, K.; Shukla, A. K.; Jackson, C. L.; Meuleman, W. R. A.
Mixed-reactants solid-polymer-electrolyte direct methanol fuel cells (SPE-DMFCs) with a PtRu/C anode and a methanol-tolerant oxygen-reduction cathode catalyst have been assembled and have been subjected to galvanostatic polarisation studies. The oxygen-reduction cathode was either of the FeTMPP/C, CoTMPP/C, FeCoTMPP/C and RuSe/C. It was found that the SPE-DMFC with the RuSe/C cathode yielded the best performance. It has been possible to achieve power densities of approximately 50 and 20 mW/cm 2 while operating a mixed-reactants SPE-DMFC at 90 °C with oxygen and air fed cathodes, respectively. Interestingly, these SPE-DMFCs exhibit no parasitic oxidation of methanol with oxygen.
A continuous flow microfluidic calorimeter: 3-D numerical modeling with aqueous reactants
Sen, Mehmet A.; Kowalski, Gregory J.; Fiering, Jason; Larson, Dale
2015-01-01
A computational analysis of the reacting flow field, species diffusion and heat transfer processes with thermal boundary layer effects in a microchannel reactor with a coflow configuration was performed. Two parallel adjacent streams of aqueous reactants flow along a wide, shallow, enclosed channel in contact with a substrate, which is affixed to a temperature controlled plate. The Fluent computational fluid dynamics package solved the Navier–Stokes, mass transport and energy equations. The e...
Vibrational Quantum Decoherence in Liquid Water.
Joutsuka, Tatsuya; Thompson, Ward H; Laage, Damien
2016-02-18
Traditional descriptions of vibrational energy transfer consider a quantum oscillator interacting with a classical environment. However, a major limitation of this simplified description is the neglect of quantum decoherence induced by the different interactions between two distinct quantum states and their environment, which can strongly affect the predicted energy-transfer rate and vibrational spectra. Here, we use quantum-classical molecular dynamics simulations to determine the vibrational quantum decoherence time for an OH stretch vibration in liquid heavy water. We show that coherence is lost on a sub-100 fs time scale due to the different responses of the first shell neighbors to the ground and excited OH vibrational states. This ultrafast decoherence induces a strong homogeneous contribution to the linear infrared spectrum and suggests that resonant vibrational energy transfer in H2O may be more incoherent than previously thought.
Wet in situ transesterification of microalgae using ethyl acetate as a co-solvent and reactant.
Park, Jeongseok; Kim, Bora; Chang, Yong Keun; Lee, Jae W
2017-04-01
This study addresses wet in situ transesterification of microalgae for the production of biodiesel by introducing ethyl acetate as both reactant and co-solvent. Ethyl acetate and acid catalyst are mixed with wet microalgae in one pot and the mixture is heated for simultaneous lipid extraction and transesterification. As a single reactant and co-solvent, ethyl acetate can provide higher FAEE yield and more saccharification of carbohydrates than the case of binary ethanol and chloroform as a reactant and a co-solvent. The optimal yield was 97.8wt% at 114°C and 4.06M catalyst with 6.67mlEtOAC/g dried algae based on experimental results and response surface methodology (RSM). This wet in situ transesterification of microalgae using ethyl acetate doesn't require an additional co-solvent and it also promises more economic benefit as combining extraction and transesterification in a single process. Copyright © 2017 Elsevier Ltd. All rights reserved.
Yang, Chuqiao; Yakovlev, Vadim V
2013-01-01
Microwave-assisted chemical reactions have become very popular in preparative chemistry due to many advantages such as accelerated reaction rate, higher chemical yield and lower energy use. In dedicated equipment, however, the microwave units operate as "black boxes" keeping the role of the thermal effects in microwave-assisted chemical processes somewhat obscure. To address this issue, in this paper, we propose a simple mathematical model for computing microwave-induced temperature in a three-media cylindrical structure representing a core element of a typical microwave reactor with the reactant assumed to be stirred by convection flows. The model determines the average temperature of the reactant for the known absorbed microwave power and heating time. To illustrate its functionality, the model is used to compute time-temperature characteristics of water, ethanol, and methanol heated in the batch reactor MiniFlow 200SS. The curve calculated for water appears to be in an excellent agreement with an experiment. This confirms the hypothesis on temperature homogenization in liquid reactants in batch reactors due to convection and suggests that modeling can be helpful in clarifying and quantifying the details of microwave-assisted chemical processes.
ZHOU,Zheng-Yu(周正宇); CHENG,Xue-Li(程学礼); GUO,Li(郭丽)
2002-01-01
On the basis of the computed results got by the Gaussian 94 package at B3LYP/6-311 + +G * * level, the reaction mechanism of CH3O radical with CO has been investigated thoroughly via the vibrational model analysis. And the relationships among the reactants, eight transition states, four intermediates and various products involved this multichannel reaction are elucidated. The vibrational mode analysis shows that the reaction mechanism is reliable.
Ultrafast vibrations of gold nanorings
Kelf, T; Tanaka, Y; Matsuda, O;
2011-01-01
elucidate the corresponding mode shapes and find that the substrate plays an important role in determining the mode damping. This study demonstrates the need for a plasmonic nano-optics approach to understand the optical excitation and detection mechanisms for the vibrations of plasmonic nanostructures.......We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...
Lim, Edward C
1974-01-01
Excited States, Volume I reviews radiationless transitions, phosphorescence microwave double resonance through optical spectra in molecular solids, dipole moments in excited states, luminescence of polar molecules, and the problem of interstate interaction in aromatic carbonyl compounds. The book discusses the molecular electronic radiationless transitions; the double resonance techniques and the relaxation mechanisms involving the lowest triplet state of aromatic compounds; as well as the optical spectra and relaxation in molecular solids. The text also describes dipole moments and polarizab
Schnee, Josefine; Gaigneaux, Eric M.
2017-02-01
Characterizing catalysts under working conditions is crucial to understand and to optimize their behavior and performance. However, when Raman spectroscopy is used, attention has to be paid to laser-induced artefacts. While laser irradiation is often claimed to lead to a temperature gradient between the integral catalyst bed and the sampling point, neither the circumstances when such effect appears, nor if it systematically occurs or not, are really explored in details. The present paper shows that the sensitivity of a catalyst to laser-induced heating largely depends on the gas composition under which the analysis is done, in particular that it depends whether the catalyst has adsorbed reactant molecules or not. These aspects are here addressed via the Raman in situ exploration of H3PW12O40. This heteropolyacid is a widely used acid catalyst due to its very high Brönsted acidity, approaching the superacid region. In particular, we have investigated the impact of laser irradiation in the Raman monitoring of solid H3PW12O40 at work under a flow of methanol in nitrogen at 50 °C. When 1 single spectrum of H3PW12O40 was measured after 3 h of exposure to methanol, the characteristic Csbnd H vibration bands of adsorbed methanol appeared. However, when spectra were measured continuously throughout the experiment, the same Csbnd H vibration bands were observed only during the first hour, then they disappeared and the characteristic bands of polyaromatic molecules appeared. Under continuous laser irradiation, adsorbed methanol was thus converted into polyaromatic coke as resulting from a laser-induced heating. However, the spectra collected under pure nitrogen show that the laser does not heat the catalyst in the absence of methanol. UV-Vis revealed the reason of the laser-induced heating in the presence of methanol, and the subsequent formation of coke. Actually the catalyst gets reduced by the adsorbed methanol, what darkens the catalyst bed. Such a darkening renders
Parametric Vibration and Vibration Reduction of Cables in Cable-stayed Space Latticed Structure
BAO Yan; ZHOU Dai; LIU Jie
2008-01-01
Mechanical model and vibration equation of a cable in cable-stayed sparse latticed structure (CSLS) under external axial excitation were founded. Determination of the mass lumps and natural frequencies supplied by the space latticed structure (SLS) was analyzed. Multiple scales method (MSM) was introduced to analyze the characteristics of cable's parametric vibration, and the precise time-integration method (PTIM) was used to solve vibration equation. The vibration behavior of a cable is closely relative to the frequency ratio of the cable and SLS. The cable's parametric vibration caused by the external axial excitation easily occurs if the frequency ratio of the cable and SLS is in a certain range, and the cable's vibration amplitude varies greatly even if the initial disturbance supplied by SLS changes a little. Furthermore, the mechanical model and vibration equation of the composite cable system consisting of main cables and assistant cables were studied. The parametric analysis such as the pre-tension level and arrangement of the assistant cables was carried out. Due to the assistant cables, the single-cable vibration mode can be transferred to the global vibration mode, and the stiffness and damping of the cable system are enhanced. The natural frequencies of the composite cable system with the curve line arrangement of assistant cables are higher than those with the straight-line arrangement and the former is more effective than the latter on the cable's vibration suppression.
Vibrational-state-selected ion--molecule reaction cross sections at thermal energies
Pijkeren, D. van; Boltjes, E.; Eck, J. van; Niehaus, A.
1984-01-01
A method designed to measure relative ion—molecule reaction rates at thermal collision energies for selected reactant ion vibrational states is described. Relative reaction rates are determined for the three endothermic reactions: H2+ (υ)(He,H)HeH+, H2+ (υ)(Ne,H)NeH+, D2+(υ)(Ne, D)NeD+, and for the
Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen
2012-01-01
In this paper we describe a field study conducted with a wearable vibration belt where we test to determine the vibration intensity sensitivity ranges on a large diverse group of participants with evenly distributed ages and...... lab studies in that we found a decreased detection rate in busy environments. Here we test with a much larger sample and age range, and contribute with the first vibration sensitivity testing outside the lab in an urban public...
Force transmissibility and vibration power flow behaviour of inerter-based vibration isolators
Yang, Jian
2016-09-01
This paper investigates the dynamics and performance of inerter-based vibration isolators. Force / displacement transmissibility and vibration power flow are obtained to evaluate the isolation performance. Both force and motion excitations are considered. It is demonstrated that the use of inerters can enhance vibration isolation performance by enlarging the frequency band of effective vibration isolation. It is found that adding inerters can introduce anti-resonances in the frequency-response curves and in the curves of the force and displacement transmissibility such that vibration transmission can be suppressed at interested excitation frequencies. It is found that the introduction of inerters enhances inertial coupling and thus have a large influence on the dynamic behaviour at high frequencies. It is shown that force and displacement transmissibility increases with the excitation frequency and tends to an asymptotic value as the excitation frequency increases. In the high-frequency range, it was shown that adding inerters can result in a lower level of input power. These findings provide a better understanding of the effects of introducing inerters to vibration isolation and demonstrate the performance benefits of inerter-based vibration isolators.
Ground test for vibration control demonstrator
Meyer, C.; Prodigue, J.; Broux, G.; Cantinaud, O.; Poussot-Vassal, C.
2016-09-01
In the objective of maximizing comfort in Falcon jets, Dassault Aviation is developing an innovative vibration control technology. Vibrations of the structure are measured at several locations and sent to a dedicated high performance vibration control computer. Control laws are implemented in this computer to analyse the vibrations in real time, and then elaborate orders sent to the existing control surfaces to counteract vibrations. After detailing the technology principles, this paper focuses on the vibration control ground demonstration that was performed by Dassault Aviation in May 2015 on Falcon 7X business jet. The goal of this test was to attenuate vibrations resulting from fixed forced excitation delivered by shakers. The ground test demonstrated the capability to implement an efficient closed-loop vibration control with a significant vibration level reduction and validated the vibration control law design methodology. This successful ground test was a prerequisite before the flight test demonstration that is now being prepared. This study has been partly supported by the JTI CleanSky SFWA-ITD.
Adaptive Piezoelectric Absorber for Active Vibration Control
Sven Herold
2016-02-01
Full Text Available Passive vibration control solutions are often limited to working reliably at one design point. Especially applied to lightweight structures, which tend to have unwanted vibration, active vibration control approaches can outperform passive solutions. To generate dynamic forces in a narrow frequency band, passive single-degree-of-freedom oscillators are frequently used as vibration absorbers and neutralizers. In order to respond to changes in system properties and/or the frequency of excitation forces, in this work, adaptive vibration compensation by a tunable piezoelectric vibration absorber is investigated. A special design containing piezoelectric stack actuators is used to cover a large tuning range for the natural frequency of the adaptive vibration absorber, while also the utilization as an active dynamic inertial mass actuator for active control concepts is possible, which can help to implement a broadband vibration control system. An analytical model is set up to derive general design rules for the system. An absorber prototype is set up and validated experimentally for both use cases of an adaptive vibration absorber and inertial mass actuator. Finally, the adaptive vibration control system is installed and tested with a basic truss structure in the laboratory, using both the possibility to adjust the properties of the absorber and active control.
Magnetically levitated autoparametric broadband vibration energy harvesting
Kurmann, L.; Jia, Y.; Manoli, Y.; Woias, P.
2016-11-01
Some of the lingering challenges within the current paradigm of vibration energy harvesting (VEH) involve narrow operational frequency range and the inevitable non-resonant response from broadband noise excitations. Such VEHs are only suitable for limited applications with fixed sinusoidal vibration, and fail to capture a large spectrum of the real world vibration. Various arraying designs, frequency tuning schemes and nonlinear vibratory approaches have only yielded modest enhancements. To fundamentally address this, the paper proposes and explores the potentials in using highly nonlinear magnetic spring force to activate an autoparametric oscillator, in order to realize an inherently broadband resonant system. Analytical and numerical modelling illustrate that high spring nonlinearity derived from magnetic levitation helps to promote the 2:1 internal frequency matching required to activate parametric resonance. At the right internal parameters, the resulting system can intrinsically exhibit semi-resonant response regardless of the bandwidth of the input vibration, including broadband white noise excitation.
Umesh P. Agarwal; Rajai Atalla
2010-01-01
Vibrational spectroscopy is an important tool in modern chemistry. In the past two decades, thanks to significant improvements in instrumentation and the development of new interpretive tools, it has become increasingly important for studies of lignin. This chapter presents the three important instrumental methods-Raman spectroscopy, infrared (IR) spectroscopy, and...
2009-01-01
Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.
Few Issues Related to an Electrodynamic Exciter Control
Čala, M.
2015-01-01
There are multiple problems to solve when controlling an electromagnetic exciter for vibrations generation. Main challenge is to straighten a frequency response of an exciter which is normally not uniform due to resonances resulting from the mechanical construction of an exciter, specimen to test, or mounting fixture. This paper describes number of aspects to consider, which arose during implementation of the control system for small electrodynamic exciter on the Department of Control and Ins...
Vibration-enhanced quantum transport
2009-01-01
In this paper, we study the role of collective vibrational motion in the phenomenon of electronic energy transfer (EET) along a chain of coupled electronic dipoles with varying excitation frequencies. Previous experimental work on EET in conjugated polymer samples suggested that the common structural framework of the macromolecule introduces correlations in the energy gap fluctuations that cause coherent EET. Inspired by these results, we present a simple model in which a driven nanomechanica...
Human comfort in relation to sinusoidal vibration
Jones, B.; Rao, B. K. N.
1975-01-01
An investigation was made to assess the overall subjective comfort levels to sinusoidal excitations over the range 1 to 19 Hz using a two axis electrohydraulic vibration simulator. Exposure durations of 16 minutes, 25 minutes, 1 hour, and 2.5 hours have been considered. Subjects were not exposed over such durations, but were instructed to estimate the overall comfort levels preferred had they been constantly subjected to vibration over such durations.
Sorokin, Vladislav
2014-01-01
In the classical papers (see, e.g. P.L. Kapitsa, Pendulum with vibrating axis of suspension. Usp. Fiz. Nauk 44 1 (1954) 7-20 (in Russian)) motion of pendulum with vibrating suspension axis was considered in the case when frequency of external loading is much higher than the natural frequency...... of the pendulum in the absence of this loading. The present paper is concerned with the analysis of inverted pendulums motion at unconventional values of parameters. Case when frequency of external loading and the natural frequency of the pendulum in the absence of this loading are of the same order is studied...... in the stability domain. It is revealed that in the considered range of parameters not only the effective stiffness of the system changes due to the external loading, but also its effective mass. Applicability of the proposed approach for solving non-linear equations without small parameter is demonstrated...
魏达; 贾杰; 褚若帆; 孔高强; 张义卓
2015-01-01
以钢结构箱形梁过街天桥为例，通过实测数据建立人行荷载模拟，分析行人的舒适度指标，采取阻尼片振动控制措施并分析了减振效果，对今后的过街天桥建设有参考借鉴意义。%Based on the steel box girder pedestrian,the people’s load simulation is established through the measured data,comfortable index is analyzed in this paper. Simultaneously,vibration control measures of the damping is presented and vibration effect is analyzed. These will be the basis of the future construction of the pedestrian bridges.
Performance of a Piezoelectric Energy Harvester under Vibrations Taken from a Helicopter
Zhu, Dibin; Beeby, Steve; Tudor, John; Grabham, Neil; White, Neil; Harris, Nick
2011-01-01
This paper compares performance of a piezoelectric vibration energy harvester, in terms of output power, under different types of vibration. The most common method used to characterize a vibration energy harvester is to excite the energy harvester under a sinusoidal vibration of its resonant frequency and measure the voltage across certain electrical loads. However, in practical applications, the vibration spectrum usually contains multiple peaks at different frequencies. In this research, a ...
Gahn, R. F.; Hagedorn, N. H.; Ling, J. S.
Experimental studies in a 14.5 sq cm single cell system using mixed reactant solutions at 65 C are described. Systems were tested under isothermal conditions i.e., reactants and the cell were at the same temperature. Charging and discharging performance were evaluted by measuring watt-hour and coulombic efficiencies, voltage-current relationships, hydrogen evolution and membrane resistivity. Watt-hour efficiencies ranged from 86% at 43 ma/sq cm to 75% at 129 ma/sq cm with corresponding coulombic efficiencies of 92% and 97%, respectively. Hydrogen evolution was less than 1% of the charge coulombic capacity during charge-discharge cycling. Bismuth and bismuth-lead catalyzed chromium electrodes maintained reversible performance and low hydrogen evolution under normal and adverse cycling conditions. Reblending of the anode and cathode solutions was successfully demonstrated to compensate for osmotic volume changes. Improved performance was obtained with mixed reactant systems in comparison to the unmixed reactant systems.
Localized Surface Plasmons in Vibrating Graphene Nanodisks
Wang, Weihua; Li, Bo-Hong; Stassen, Erik
2016-01-01
in graphene disks have the additional benefit to be highly tunable via electrical stimulation. Mechanical vibrations create structural deformations in ways where the excitation of localized surface plasmons can be strongly modulated. We show that the spectral shift in such a scenario is determined...... by a complex interplay between the symmetry and shape of the modal vibrations and the plasmonic mode pattern. Tuning confined modes of light in graphene via acoustic excitations, paves new avenues in shaping the sensitivity of plasmonic detectors, and in the enhancement of the interaction with optical emitters...
Simulation applied to working frequency selection in large-scale vibrating screen's design
PENG Chen-yu; SU Rong-hua
2011-01-01
The working frequency selection of the ZK30525 vibrating screen was studied using ANSYS.Integrating the dynamic performance simulation analysis of the vibrating screen structure,the variation laws of beams' vibration displacements changing with different exciting frequencies were researched.These beams include six beams,with one discharging beam and one in-material beam.Results indicate that vibration displacements in the middle of these beams increase with the augmentation of exciting frequency.When exciting frequency exceeds a certain value,there exists a flat change region for vibration displacement.According to vibrator characteristics,the vibrating screen's working frequency should be selected in the flat change region,and be far away from modal frequencies.The study provides theoretical guidance for the reasonable working frequency selection of the large-scale vibrating screen.
Gear Noise and Vibration : A Literature Survey
Åkerblom, Mats
2001-01-01
This paper is a survey of the literature on gear noise and vibration. It is divided into three parts, “Transmission error”, “Dynamic models” and “Noise and vibration measurement”. Transmission error (TE) is considered to be an important excitation mechanism for gear noise and vibration. The definition of transmission error is “The difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate”. Dynamic models of the system...
High Energy Vibration for Gas Piping
Lee, Gary Y. H.; Chan, K. B.; Lee, Aylwin Y. S.; Jia, ShengXiang
2017-07-01
In September 2016, a gas compressor in offshore Sarawak has its rotor changed out. Prior to this change-out, pipe vibration study was carried-out by the project team to evaluate any potential high energy pipe vibration problems at the compressor’s existing relief valve downstream pipes due to process condition changes after rotor change out. This paper covers high frequency acoustic excitation (HFAE) vibration also known as acoustic induced vibration (AIV) study and discusses detailed methodologies as a companion to the Energy Institute Guidelines for the avoidance of vibration induced fatigue failure, which is a common industry practice to assess and mitigate for AIV induced fatigue failure. Such detailed theoretical studies can help to minimize or totally avoid physical pipe modification, leading to reduce offshore plant shutdown days to plant shutdowns only being required to accommodate gas compressor upgrades, reducing cost without compromising process safety.
Fendell, Francis; Rungaldier, Harald
1999-01-01
An experimental apparatus for the examination of a planar, virtually strain-rate-free diffusion flame in microgravity has been designed and fabricated. Such a diffusion flame is characterized by relatively large spatial scale and high symmetry (to facilitate probing), and by relatively long fluid-residence time (to facilitate investigation of rates associated with sooting phenomena). Within the squat rectangular apparatus, with impervious, noncatalytic isothermal walls of stainless steel, a thin metallic splitter plate subdivides the contents into half-volumes. One half-volume initially contains fuel vapor diluted with an inert gas, and the other, oxidizer diluted with another inert gas-so that the two domains have equal pressure, density, and temperature. As the separator is removed, by translation in its own plane, through a tightly fitting slit in one side wall, a line ignitor in the opposite side wall initiates a triple-flame propagation across the narrow layer of combustible mixture formed near midheight in the chamber. The planar diffusion flame so emplaced is quickly disrupted in earth gravity. In microgravity, the planar flame persists, and travels ultimately into the half-volume containing the stoichiometrically deficient reactant; the flame eventually becomes extinguished owing to reactant depletion and heat loss to the walls.
Kritzenberger, J.; Wokaun, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)
1997-06-01
Oxidation of CO over palladium/zirconia catalyst obtained from an amorphous Pd{sub 25}Zr{sub 75} precursor was investigated by time resolved FTIR spectroscopy. Sine wave shaped modulation of the reactant concentration, i.e. variation of CO or O{sub 2} partial pressure, was used to induce variations of the IR signals of product (CO{sub 2}) and unconverted reactant (CO), which were detected in a multi-pass absorption cell. The phase shift {phi} between external perturbation and variation of the CO{sub 2} signal was examined in dependence on temperature (100{sup o}C{<=}T{<=}350{sup o}C) and modulation frequency (1.39x10{sup -4}Hz{<=}{omega}{<=}6.67x10{sup -2}Hz). From the phase shift values, a simple Eley-Rideal mechanism is excluded, and the rate limiting step of the Langmuir-Hinshelwood mechanism for the CO oxidation may be identified. Adsorption and possible surface movement of CO to the actual reaction site determine the rate of the CO oxidation on the palladium/zirconia catalyst used in our study. The introduction of an external perturbation is a first step towards the application of two-dimensional infrared spectroscopy to heterogeneous catalyzed reactions. (author) 3 figs., 4 refs.
Quantum Calculation of Dipole Excitation in Fusion Reaction
2000-01-01
The excitation of the giant dipole resonance by fusion is studied with N/Z asymmetry in the entrance channel. the TDHF solution exhibits a strong dipole vibration which can be associated with a giant vibration along the main axis of a fluctuating prolate shape. The consequences on the gamma-ray emission from hot compound nuclei are discussed.
Zhong, Jianfeng; Zhong, Shuncong; Zhang, Qiukun
2016-10-01
A high-speed camera-based two-dimensional optical coherence vibration tomography (2DOCVT) system with a subnanometre displacement resolution was developed and employed for low-frequency vibration measurement and modal analysis. Experimental results demonstrated the ability of low-frequency absolute displacement measurement of structural line vibrations without scanning. Three-dimensional (3D) surface displacement of a vibrating structure could also be obtained using the developed 2DOCVT by scanning the structure. The scanning 2DOCVT system acted like a 3D optical coherence vibration tomography system. The developed 2DOCVT system could capture structural modal parameters without vibration excitation input information, and therefore, it is a response-only method. The 2DOCVT could be recommended in the application of low-frequency vibration measurement and modal analysis of beam and plate structures, especially when the vibration amplitude is at nanometre or micrometre scale.
Interfacial instabilities in vibrated fluids
Porter, Jeff; Laverón-Simavilla, Ana; Tinao Perez-Miravete, Ignacio; Fernandez Fraile, Jose Javier
2016-07-01
Vibrations induce a range of different interfacial phenomena in fluid systems depending on the frequency and orientation of the forcing. With gravity, (large) interfaces are approximately flat and there is a qualitative difference between vertical and horizontal forcing. Sufficient vertical forcing produces subharmonic standing waves (Faraday waves) that extend over the whole interface. Horizontal forcing can excite both localized and extended interfacial phenomena. The vibrating solid boundaries act as wavemakers to excite traveling waves (or sloshing modes at low frequencies) but they also drive evanescent bulk modes whose oscillatory pressure gradient can parametrically excite subharmonic surface waves like cross-waves. Depending on the magnitude of the damping and the aspect ratio of the container, these locally generated surfaces waves may interact in the interior resulting in temporal modulation and other complex dynamics. In the case where the interface separates two fluids of different density in, for example, a rectangular container, the mass transfer due to vertical motion near the endwalls requires a counterflow in the interior region that can lead to a Kelvin-Helmholtz type instability and a ``frozen wave" pattern. In microgravity, the dominance of surface forces favors non-flat equilibrium configurations and the distinction between vertical and horizontal applied forcing can be lost. Hysteresis and multiplicity of solutions are more common, especially in non-wetting systems where disconnected (partial) volumes of fluid can be established. Furthermore, the vibrational field contributes a dynamic pressure term that competes with surface tension to select the (time averaged) shape of the surface. These new (quasi-static) surface configurations, known as vibroequilibria, can differ substantially from the hydrostatic state. There is a tendency for the interface to orient perpendicular to the vibrational axis and, in some cases, a bulge or cavity is induced
Mukhopadhyay, N.C.
1986-01-01
The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)
Semiactive variable stiffness control for parametric vibration of cables
Li Hui; Chen Wenli; Ou Jinping
2006-01-01
In this paper, a semiactive variable stiffness (SVS) device is used to decrease cable oscillations caused by parametric excitation, and the equation of motion of the parametric vibration of the cable with this SVS device is presented.The ON/OFF control algorithm is used to operate the SVS control device. The vibration response of the cable with the SVS device is numerically studied for a variety of additional stiffness combinations in both the frequency and time domains and for both parametric and classical resonance vibration conditions. The numerical studies further consider the cable sag effect.From the numerical results, it is shown that the SVS device effectively suppresses the cable resonance vibration response, and as the stiffness of the device increases, the device achieves greater suppression of vibration. Moreover, it was shown that the SVS device increases the critical axial displacement of the excitation under cable parametric vibration conditions.
Vibration Control Induced by Ice of a Jacket Platform
郑宏宇; 姜大宁; 唐友刚; 周满红
2003-01-01
Based on the self-excited vibration theory of ice, the vibration control technology of jacket platform is studied in this paper. The magnetorheological suspensions (MR) unit is chosen as the damper, the control objective function for vibration excited by ice is determined by instantaneous optimal control (IOC) method, and genetic algorithm (GA) is used to select the optimal control force. For the jacket platform of 40 m in height and a 3-floor deck, the vibration responses induced by ice have been calculated before and after control considering the different thickness and speed of ice. It is shown that the control method presented in this paper can reduce the vibration response by 30%, and it is feasible to adopt MR absorber and GA in the control of vibration induced by ice.
覃文源; 张志谊; 华宏星
2013-01-01
The load state of stern bearing of the propulsion shafting system is affected by the alignment between propeller and shafting. Unreasonable design or poor installation of the shafting system can result in poor lubrication of the rubber bearing, which can cause the stick-slip motion between the shaft and the bearing, and abnormal bending and torsional vibration of the shafting system. In this paper, the bending and torsional coupled vibration induced by the friction between the stern bearing and the propulsion shaft was analyzed theoretically based on a simplified propulsion-shafting system. The characteristics of friction induced shaft vibration and noise were revealed.%推进轴系的艉轴承负荷受螺旋桨、轴系对中等因素影响，不合理设计或安装可能导致轴承润滑不良，使轴颈与橡胶轴承间容易存在“粘着-滑动”状态，进而导致轴系的弯曲、扭转振动异常。通过简化的推进轴系模型，从机理上分析轴系在艉部橡胶轴承摩擦力作用下的弯-扭耦合振动特性及其主要影响因素，为识别轴系异常振动和噪声提供参考。
刘新英; 王立志
2012-01-01
基于Ramachandran B等人制作的3 A′′势能面[Ramachandran B et al 2003J.Chem.Phys.1199590],运用准经典轨线方法,计算了反应物不同振动激发态时,反应O（3P）＋HCl（υ=0,1,2,j=0）→OH＋Cl的P（θr）,P（φr）与极化微分反应截面（2π/σ）（dσ00/dωt）、（2π/σ）（dσ22＋/dωt）.结果表明,反应物HCl振动激发对反应的k-j′两矢量相关和k-k′-j′三矢量相关分布都产生了较大影响.%Quasi-classical trajectory（QCT） calculations have been carried out to study the effect of reagent vibrational excitation on the stereo-dynamics of the O（3P） ＋ HCl（v=0,1,2,3,j=0） → OH ＋ Cl reaction on the 3A＇＇ potential energy surface [constructed by Ramachandran B et al [Ramachandran B et al 2003 J.Chem.Phys.119 9590].The distributions of P（θr） and P（φr）,generalized polarization-dependent differential cross-sections（PDDCSs）（2π/σ）（dσ00/dωt）、（2π/σ）（dσ22＋/dωt）describing the k-j′ correlation and the k-k′-j′ correlation respectively,have been calculated.The results indicate the reagent＇s vibrational excitation has a considerable influence on the distribution of k-j′ correlation and the k-k′-j′ correlation.