Dynamics of Microbeams under Multi-Frequency Excitations
Ibrahim, Alwathiqbellah
2017-01-24
This paper presents an investigation of the dynamics of microbeams under multiple harmonic electrostatic excitation frequencies. First, the response of a cantilever microbeam to two alternating current (AC) source excitation is examined. We show by simulations the response of the microbeam at primary resonance (near the fundamental natural frequency) and at secondary resonances (near half, superharmonic, and twice, subharmonic, the fundamental natural frequency). A multimode Galerkin method combined with the Euler-Bernoulli beam equation, accounting for the nonlinear electrostatic force, has been used to develop a reduced order model. The response of the cantilever microbeam to three AC source excitation is also investigated and shown as a promising technique to enhance the bandwidth of resonators. Finally, an experimental study of a clamped-clamped microbeam is conducted, demonstrating the multi-frequency excitation resonances using two, three, and four AC sources.
Dynamics of Microbeams under Multi-Frequency Excitations
Directory of Open Access Journals (Sweden)
Alwathiqbellah Ibrahim
2017-01-01
Full Text Available This paper presents an investigation of the dynamics of microbeams under multiple harmonic electrostatic excitation frequencies. First, the response of a cantilever microbeam to two alternating current (AC source excitation is examined. We show by simulations the response of the microbeam at primary resonance (near the fundamental natural frequency and at secondary resonances (near half, superharmonic, and twice, subharmonic, the fundamental natural frequency. A multimode Galerkin method combined with the Euler-Bernoulli beam equation, accounting for the nonlinear electrostatic force, has been used to develop a reduced order model. The response of the cantilever microbeam to three AC source excitation is also investigated and shown as a promising technique to enhance the bandwidth of resonators. Finally, an experimental study of a clamped-clamped microbeam is conducted, demonstrating the multi-frequency excitation resonances using two, three, and four AC sources.
Numerical optimization of piezolaminated beams under static and dynamic excitations
Directory of Open Access Journals (Sweden)
Rajan L. Wankhade
2017-06-01
Full Text Available Shape and vibration controls of smart structures in structural applications have gained much attraction due to their ability of actuation and sensing. The response of structure to bending, vibration, and buckling can be controlled by the use of this ability of a piezoelectric material. In the present work, the static and dynamic control of smart piezolaminated beams is presented. The optimal locations of piezoelectric patches are found out and then a detailed analysis is performed using finite element modeling considering the higher order shear deformation theory. In the first part, for an extension mode, the piezolaminated beam with stacking sequence PZT5/Al/PZT5 is considered. The length of the beam is 100 mm, whereas the thickness of an aluminum core is 16 mm and that of the piezo layer is of 1 mm. The PZT actuators are positioned with an identical poling direction along the thickness and are excited by a direct current voltage of 10 V. For the shear mode, the stacking sequence Al/PZT5/Al is adopted. The length of the beam is kept the same as the extension mechanism i.e. 100 mm, whereas the thickness of the aluminum core is 8 mm and that of the piezo layer is of 2 mm. The actuator is excited by a direct current voltage of 20 V. In the second part, the control of the piezolaminated beam with an optimal location of the actuator is investigated under a dynamic excitation. Electromechanical loading is considered in the finite element formulation for the analysis purpose. Results are provided for beams with different boundary conditions and loading for future references. Both the extension and shear actuation mechanisms are employed for the piezolaminated beam. These results may be used to identify the response of a beam under static and dynamic excitations. From the present work, the optimal location of a piezoelectric patch can be easily identified for the corresponding boundary condition of the beam.
Holographic otoscope for nanodisplacement measurements of surfaces under dynamic excitation.
Flores-Moreno, J M; Furlong, Cosme; Rosowski, John J; Harrington, Ellery; Cheng, Jeffrey T; Scarpino, C; Santoyo, F Mendoza
2011-01-01
We describe a novel holographic otoscope system for measuring nanodisplacements of objects subjected to dynamic excitation. Such measurements are necessary to quantify the mechanical deformation of surfaces in mechanics, acoustics, electronics, biology, and many other fields. In particular, we are interested in measuring the sound-induced motion of biological samples, such as an eardrum. Our holographic otoscope system consists of laser illumination delivery (IS), optical head (OH), and image processing computer (IP) systems. The IS delivers the object beam (OB) and the reference beam (RB) to the OH. The backscattered light coming from the object illuminated by the OB interferes with the RB at the camera sensor plane to be digitally recorded as a hologram. The hologram is processed by the IP using the Fresnel numerical reconstruction algorithm, where the focal plane can be selected freely. Our holographic otoscope system is currently deployed in a clinic, and is packaged in a custom design. It is mounted in a mechatronic positioning system to increase its maneuverability degrees to be conveniently positioned in front of the object to be measured. We present representative results highlighting the versatility of our system to measure deformations of complex elastic surfaces in the wavelength scale including a copper foil membrane and postmortem tympanic membrane. SCANNING 33: 342-352, 2011. © 2011 Wiley Periodicals, Inc. Copyright © 2011 Wiley Periodicals, Inc.
Bistable dynamics underlying excitability of ion homeostasis in neuron models.
Directory of Open Access Journals (Sweden)
Niklas Hübel
2014-05-01
Full Text Available When neurons fire action potentials, dissipation of free energy is usually not directly considered, because the change in free energy is often negligible compared to the immense reservoir stored in neural transmembrane ion gradients and the long-term energy requirements are met through chemical energy, i.e., metabolism. However, these gradients can temporarily nearly vanish in neurological diseases, such as migraine and stroke, and in traumatic brain injury from concussions to severe injuries. We study biophysical neuron models based on the Hodgkin-Huxley (HH formalism extended to include time-dependent ion concentrations inside and outside the cell and metabolic energy-driven pumps. We reveal the basic mechanism of a state of free energy-starvation (FES with bifurcation analyses showing that ion dynamics is for a large range of pump rates bistable without contact to an ion bath. This is interpreted as a threshold reduction of a new fundamental mechanism of ionic excitability that causes a long-lasting but transient FES as observed in pathological states. We can in particular conclude that a coupling of extracellular ion concentrations to a large glial-vascular bath can take a role as an inhibitory mechanism crucial in ion homeostasis, while the Na⁺/K⁺ pumps alone are insufficient to recover from FES. Our results provide the missing link between the HH formalism and activator-inhibitor models that have been successfully used for modeling migraine phenotypes, and therefore will allow us to validate the hypothesis that migraine symptoms are explained by disturbed function in ion channel subunits, Na⁺/K⁺ pumps, and other proteins that regulate ion homeostasis.
Hung, Chih-Chang; Yabushita, Atsushi; Kobayashi, Takayoshi; Chen, Pei-Feng; Liang, Keng S
2016-01-01
Ultrafast transient absorption spectroscopy of endothelial NOS oxygenase domain (eNOS-oxy) was performed to study dynamics of ligand or substrate interaction under Soret band excitation. Photo-excitation dissociates imidazole ligand in 4ps. The eNOS-oxy without additive is partially bound with water molecule, thus its photoexcited dynamics also shows ligand dissociation in <800fs. Then it followed by vibrational cooling coupled with charge transfer in 4.8ps, and recombination of ligand to distal side of heme in 12ps. Copyright © 2016 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Wenwen Sui
Full Text Available Abstract Nonlinear dynamic analysis of an axially moving telescopic mechanism for truss structure bridge inspection vehicle under pedestrian excitation is carried out. A biomechanically inspired inverted-pendulum model is utilized to simplify the pedestrian. The nonlinear equations of motion for the beam-pedestrian system are derived using the Hamilton's principle. The equations are transformed into two ordinary differential equations by applying the Galerkin's method at the first two orders. The solutions to the equations are acquired by using the Newmark-β method associated with the Newton-Raphson method. The time-dependent feature of the eigenfunctions for the two beams are taken into consideration in the solutions. Accordingly, the equations of motion for a simplified system, in which the pedestrian is regarded as moving cart, are given. In the numerical examples, dynamic responses of the telescopic mechanism in eight conditions of different beam-telescoping and pedestrian-moving directions are simulated. Comparisons between the vibrations of the beams under pedestrian excitation and corresponding moving cart are carried out to investigate the influence of the pedestrian excitation on the telescopic mechanism. The results show that the displacement of the telescopic mechanism under pedestrian excitation is smaller than that under moving cart especially when the pedestrian approaches the beams end. Additionally, compared with moving cart, the pedestrian excitation can effectively strengthen the vibration when the beam extension is small or when the pedestrian is close to the beams end.
Fang, Fei; Xia, Guanghui; Wang, Jianguo
2018-02-01
The nonlinear dynamics of cantilevered piezoelectric beams is investigated under simultaneous parametric and external excitations. The beam is composed of a substrate and two piezoelectric layers and assumed as an Euler-Bernoulli model with inextensible deformation. A nonlinear distributed parameter model of cantilevered piezoelectric energy harvesters is proposed using the generalized Hamilton's principle. The proposed model includes geometric and inertia nonlinearity, but neglects the material nonlinearity. Using the Galerkin decomposition method and harmonic balance method, analytical expressions of the frequency-response curves are presented when the first bending mode of the beam plays a dominant role. Using these expressions, we investigate the effects of the damping, load resistance, electromechanical coupling, and excitation amplitude on the frequency-response curves. We also study the difference between the nonlinear lumped-parameter and distributed-parameter model for predicting the performance of the energy harvesting system. Only in the case of parametric excitation, we demonstrate that the energy harvesting system has an initiation excitation threshold below which no energy can be harvested. We also illustrate that the damping and load resistance affect the initiation excitation threshold.
Steady-state responses of a belt-drive dynamical system under dual excitations
Ding, Hu
2016-02-01
The stable steady-state periodic responses of a belt-drive system with a one-way clutch are studied. For the first time, the dynamical system is investigated under dual excitations. The system is simultaneously excited by the firing pulsations of the engine and the harmonic motion of the foundation. Nonlinear discrete-continuous equations are derived for coupling the transverse vibration of the belt spans and the rotations of the driving and driven pulleys and the accessory pulley. The nonlinear dynamics is studied under equal and multiple relations between the frequency of the firing pulsations and the frequency of the foundation motion. Furthermore, translating belt spans are modeled as axially moving strings. A set of nonlinear piecewise ordinary differential equations is achieved by using the Galerkin truncation. Under various relations between the excitation frequencies, the time histories of the dynamical system are numerically simulated based on the time discretization method. Furthermore, the stable steady-state periodic response curves are calculated based on the frequency sweep. Moreover, the convergence of the Galerkin truncation is examined. Numerical results demonstrate that the one-way clutch reduces the resonance amplitude of the rotations of the driven pulley and the accessory pulley. On the other hand, numerical examples prove that the resonance areas of the belt spans are decreased by eliminating the torque-transmitting in the opposite direction. With the increasing amplitude of the foundation excitation, the damping effect of the one-way clutch will be reduced. Furthermore, as the amplitude of the firing pulsations of the engine increases, the jumping phenomena in steady-state response curves of the belt-drive system with or without a one-way clutch both occur.
Spin dynamics of an individual Cr atom in a semiconductor quantum dot under optical excitation
Energy Technology Data Exchange (ETDEWEB)
Lafuente-Sampietro, A. [Université Grenoble Alpes, Institut Néel, F-38000 Grenoble (France); CNRS, Institut Néel, F-38000 Grenoble (France); Institute of Materials Science, University of Tsukuba, 305-8573 Tsukuba (Japan); Utsumi, H.; Kuroda, S. [Institute of Materials Science, University of Tsukuba, 305-8573 Tsukuba (Japan); Boukari, H.; Besombes, L., E-mail: lucien.besombes@grenoble.cnrs.fr [Université Grenoble Alpes, Institut Néel, F-38000 Grenoble (France); CNRS, Institut Néel, F-38000 Grenoble (France)
2016-08-01
We studied the spin dynamics of a Cr atom incorporated in a II-VI semiconductor quantum dot using photon correlation techniques. We used recently developed singly Cr-doped CdTe/ZnTe quantum dots to access the spin of an individual magnetic atom. Auto-correlation of the photons emitted by the quantum dot under continuous wave optical excitation reveals fluctuations of the localized spin with a timescale in the 10 ns range. Cross-correlation gives quantitative transfer time between Cr spin states. A calculation of the time dependence of the spin levels population in Cr-doped quantum dots shows that the observed spin dynamics is dominated by the exciton-Cr interaction. These measurements also provide a lower bound in the 20 ns range for the intrinsic Cr spin relaxation time.
Dynamic responses of a riser under combined excitation of internal waves and background currents
Directory of Open Access Journals (Sweden)
Lou Min
2014-09-01
Full Text Available In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-β method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode
Dynamic responses of a riser under combined excitation of internal waves and background currents
Directory of Open Access Journals (Sweden)
Min Lou
2014-09-01
Full Text Available In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-β method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode.
Dynamic responses of a riser under combined excitation of internal waves and background currents
Lou, Min; Yu, Chenglong
2014-09-01
In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-β method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode
Absorption and emission dynamics in concentrated optical ensembles under laser excitation
Smirnov, V. A.; Ermolaeva, G. M.; Shilov, V. B.
2002-06-01
A new theoretical model describing the emission and absorption dynamics in an ensemble of molecules under intense coherent pulsed pumping is developed on the basis of the concepts of cooperative light-induced luminescence (CLIL). The CLIL development is described within the framework of formalism of the system density matrix in the space of photon wave functions. It is shown that the fast growth of CLIL relates to the development of coherent states of the quantum field in the area of efficient cooperative interactions of molecules (coherence volume). A system of equations for the calculation of CLIL energy, population of excited states, and optical absorption of the system in dependence on the laser pump energy density is solved. The theoretical results obtained are in good agreement with the experimental data.
Dynamics of Dirac strings and monopolelike excitations in chiral magnets under a current drive
Lin, Shi-Zeng; Saxena, Avadh
2016-02-01
Skyrmion lines in metallic chiral magnets carry an emergent magnetic field experienced by the conduction electrons. The inflow and outflow of this field across a closed surface is not necessarily equal, thus it allows for the existence of emergent monopoles. One example is a segment of skyrmion line inside a crystal, where a monopole and antimonopole pair is connected by the emergent magnetic flux line. This is a realization of Dirac stringlike excitations. Here we study the dynamics of monopoles in chiral magnets under an electric current. We show that in the process of creation of skyrmion lines, skyrmion line segments are first created via the proliferation of monopoles and antimonopoles. Then these line segments join and span the whole system through the annihilation of monopoles. The skyrmion lines are destroyed via the proliferation of monopoles and antimonopoles at high currents, resulting in a chiral liquid phase. We also propose to create the monopoles in a controlled way by applying an inhomogeneous current to a crystal. Remarkably, an electric field component in the magnetic field direction proportional to the current squared in the low current region is induced by the motion of distorted skyrmion lines, in addition to the Hall and longitudinal voltage. The existence of monopoles can be inferred from transport or imaging measurements.
Holographic otoscope for nano-displacement measurements of surfaces under dynamic excitation
Flores-Moreno, J. M.; Furlong, Cosme; Rosowski, John J.; Harrington, Ellery; Cheng, Jeffrey T.; Scarpino, C.; Santoyo, F. Mendoza
2011-01-01
We describe a novel holographic otoscope system for measuring nano-displacements of objects subjected to dynamic excitation. Such measurements are necessary to quantify the mechanical deformation of surfaces in mechanics, acoustics, electronics, biology and many other fields. In particular, we are interested in measuring the sound-induced motion of biological samples, such as an eardrum. Our holographic otoscope system consists of laser illumination delivery (IS), optical head (OH), and image...
Directory of Open Access Journals (Sweden)
Ming-Hsiang Shih
2014-01-01
Full Text Available The capacity of buildings to resist external excitation is an important factor to consider for the structural design of buildings. When subject to external excitation, a building may suffer a certain degree of damages, and its residual capacity to resist external excitation cannot be evaluated. In this research, dynamic digital image correlation method combined with parameter evaluation available in system identification is used to evaluate the structural capacity to resist external excitation. The results reveal possible building latent safety problems so that timely structural reinforcement or dismantling of the building can be initiated to alleviate further damages. The results of experiments using the proposed method conform to the results obtained using the conventional method, but this method is more convenient and rapid than the latter in the subsequent procedure of data processing. If only the frequency change is used, the damages suffered by the building can be detected, but the damage location is not revealed. The interstory drift mode shape (IDMS based on the characteristic of story drift has higher sensitivity than the approximate story damage index (ADSI method based on modal frequency and vibration type; however, both indices can be used to determine the degree and location of building damages.
Energy Technology Data Exchange (ETDEWEB)
Hao, Y; Lei, J [Beijing Institute of Machinery, Beijing 100085 (China); Zhang, W; Chen, L [College of Mechanical Engineering, Beijing University of Technology, Beijing 100022 (China)], E-mail: bimhao@sohu.com, E-mail: sandyzhang0@yahoo.com
2008-02-15
The present investigation deals with nonlinear oscillation behavior of a simply supported functionally graded rectangular plate in thermal environment with in-plane parametric and transverse external excitations. Material properties are assumed to be temperature-dependent. Based on the Reddy's third-order plate theory and the non-linear strain-displacement relations, the governing equations of motion for the FGM plate are derived by using the Hamilton's principle. The method of multiple scales is utilized to obtain four-dimensional nonlinear averaged equations. Using a numerical method, the averaged equations are analyzed. These results show that under certain conditions the periodic, multi-periodic solutions and chaotic motions of the FGM plates are found.
Hao, Y.; Zhang, W.; Chen, L.; Lei, J.
2008-02-01
The present investigation deals with nonlinear oscillation behavior of a simply supported functionally graded rectangular plate in thermal environment with in-plane parametric and transverse external excitations. Material properties are assumed to be temperature-dependent. Based on the Reddy's third-order plate theory and the non-linear strain-displacement relations, the governing equations of motion for the FGM plate are derived by using the Hamilton's principle. The method of multiple scales is utilized to obtain four-dimensional nonlinear averaged equations. Using a numerical method, the averaged equations are analyzed. These results show that under certain conditions the periodic, multi-periodic solutions and chaotic motions of the FGM plates are found.
Experiments on vibro-impact dynamics of loosely supported tubes under harmonic excitation
International Nuclear Information System (INIS)
Axisa, F.; Izquierdo, P.
1992-01-01
Computational methods have been recently developed by the authors and others to predict the working life or the acceptable vibration limit of tubular structures experiencing fretting-wear caused by impact-sliding interaction with loose supports or adjacent structures. This problem is of practical interest in various nuclear and other industrial components. This paper reports an experimental work intended to validate the numerical techniques used to compute the tube non-linear vibration in presence of impact-sliding interaction. Attention is especially focused on the local and time averaged dynamical parameters governing the rate of fretting-wear. The experiments were carried out on a straight tube excited harmonically by a pair of electromagnetic shakers. The tube motion was limited by a loose support situated at about midspan. On the other hand, numerical simulations of the tests were also performed. Comparison between test and computational data resulted in rather satisfactory agreement, based on the averaged impact forces and the wear work rate. Results are also discussed in terms of detailed time histories of tube displacement and impact forces
Holographic otoscope for nano-displacement measurements of surfaces under dynamic excitation
Flores-Moreno, J. M.; Furlong, Cosme; Rosowski, John J.; Harrington, Ellery; Cheng, Jeffrey T.; Scarpino, C.; Santoyo, F. Mendoza
2011-01-01
Summary We describe a novel holographic otoscope system for measuring nano-displacements of objects subjected to dynamic excitation. Such measurements are necessary to quantify the mechanical deformation of surfaces in mechanics, acoustics, electronics, biology and many other fields. In particular, we are interested in measuring the sound-induced motion of biological samples, such as an eardrum. Our holographic otoscope system consists of laser illumination delivery (IS), optical head (OH), and image processing computer (IP) systems. The IS delivers the object beam (OB) and the reference beam (RB) to the OH. The backscattered light coming from the object illuminated by the OB interferes with the RB at the camera sensor plane to be digitally recorded as a hologram. The hologram is processed by the IP using Fresnel numerical reconstruction algorithm, where the focal plane can be selected freely. Our holographic otoscope system is currently deployed in a clinic, and is packaged in a custom design. It is mounted in a mechatronic positioning system to increase its maneuverability degrees to be conveniently positioned in front of the object to be measured. We present representative results highlighting the versatility of our system to measure deformations of complex elastic surfaces in the wavelength scale including a copper foil membrane and postmortem tympanic membrane (TM). PMID:21898459
Dynamical excitation in fission
International Nuclear Information System (INIS)
Ledergerber, T.; Paltiel, Z.; Fraenkel, Z.; Pauli, H.C.
1976-01-01
The excitation mechanism of the fission process is studied in terms of a model of particles moving in a deformed time-dependent potential. A residual interaction of the pairing type is incoporated by means of the BCS approximation. Only 2-quasi-particle excitations up to some cutoff energy are included. The separation of the total excitation energy into intrinsic and translational parts is made at the scission point. The present calculations for 240 Pu show that, in the framework of this model, most of the available energy at scission is transformed into intrinsic excitation energy. However the convergence of the calculated value for the cutoff energy is unsatisfactory and hence a description in terms of a better model space is needed. The fact that very many channels are involved suggests that a statistical treatment may be useful. (author)
Ramini, Abdallah
2016-01-20
We present experimental investigation of the nonlinear dynamics of a clamped-clamped in-plane MEMS shallow arch when excited by an electrostatic force. We explore the dynamic behaviors of the in-plane motion of the shallow arches via frequency sweeps in the neighborhood of the first resonance frequency. The shallow arch response is video microscopy recorded and analyzed by means of digital imaging. The experimental data show local softening behavior for small DC and AC loads. For high voltages, the experimental investigation reveals interesting dynamics, where the arch exhibits a dynamic snap-Through behavior. These attractive experimental results verify the previously reported complex behavior of in-plane MEMS arches and show promising results to implement these structures for variety of sensing and actuation applications. © Copyright 2015 by ASME.
International Nuclear Information System (INIS)
Muller, Markus
2000-01-01
This work contains an experimental study of the photoluminescence dynamics of cavity polaritons in strong coupling micro-cavities based on II-VI semiconductor compounds. The small exciton size and the strong exciton binding energy in these materials allowed us to study the strong coupling regime between photon and exciton up to high excitation densities, exploring the linear and non-linear emission regimes. Our main experimental techniques are picosecond time-resolved and angular photoluminescence spectroscopy. In the linear regime and for a negative photon-exciton detuning, we observe a suppression of the polariton relaxation by the emission of acoustic phonons leading to a non-equilibrium polariton distribution on the lower branch. This 'bottleneck' effect, which has already been described for polaritons in bulk semiconductors, results from the pronounced photon like character of the polaritons near k(parallel) = 0 in this configuration. At high excitation densities, non-linear relaxation processes, namely final state stimulation of the relaxation and polariton-polariton scattering, bypass this bottleneck giving rise to a very rapid relaxation down to the bottom of the band. We show that this dramatic change in the relaxation dynamics is finally responsible of the super-linear increase of the polariton emission from these states. (author) [fr
Directory of Open Access Journals (Sweden)
Siva Srinivas Kolukula
2013-01-01
Full Text Available When partially filled liquid containers are excited vertically, the plane free-surface of the liquid can be stable or unstable depending on the amplitude and frequency of the external excitation. For some combinations of amplitude and frequency, the free-surface undergoes unbounded motion leading to instability called parametric instability or parametric resonance, and, for few other combinations, the free-surface undergoes bounded stable motion. In parametric resonance, a small initial perturbation on the free-surface can build up unboundedly even for small external excitation, if the excitation acts on the tank for sufficiently long time. In this paper, the stability of the plane free-surface is investigated by numerical simulation. Stability chart for the governing Mathieu equation is plotted analytically using linear equations. Applying fully nonlinear finite element method based on nonlinear potential theory, the response of the plane free-surface is simulated for various cases.
Liquid storage tanks under seismic excitations
International Nuclear Information System (INIS)
Tang, Y.; Aziz Uras, R.; Chang, Y.W.
1993-01-01
A nuclear power plant has to be designed to withstand any earthquakes that may occur at its location. Since a nuclear power plant has many liquid storage tanks, the dynamic response of these tanks under seismic excitations must be properly analyzed in order to design these tanks to survive the earthquakes to which they may be subjected. The dynamic response of liquid-storage tanks subjected to ground excitations has been the subject of numerous studies in the past thirty years. However, most of the studies were focused on the responses of the tanks such that the contained liquid can be considered to be incompressible and inviscid. Thus, the effect of liquid viscosity on the dynamic response of the liquid-tank system is often ignored. This is justified for water-storage tanks because water has a very small viscosity. However, there are cases where the liquid viscosity is not small in comparison with that of water. For such cases the designs of these tanks based on the inviscid assumption become questionable, and the effect of viscosity on the dynamic response needs to be assessed. To the best of our knowledge, due to the complexity of the problem, the effect of viscosity has not been studied satisfactorily to date. Since the governing equations are very complicated if viscosity is included in the analysis, the closed form solutions in most cases are unattainable. Therefore, it is necessary to use a computer code to solve the equations numerically. The computer code used in this study is the finite element code, FLUSTR-ANL (FLUid-STRucture interaction code developed at Argonne National Laboratory). In this study, the tanks are assumed to be rigid and rigidly supported on their bases, and the responses are considered to be linear
Liquid storage tanks under seismic excitations
Energy Technology Data Exchange (ETDEWEB)
Tang, Yu; Uras, R.A.; Chang, Yao W.
1993-08-01
The safety and reliable performance of nuclear power plants is of great concern to both the nuclear community and the general public. A nuclear power plant has to be designed to withstand any earthquakes that may occur at its location. Since a nuclear power plant has many liquid storage tanks, the dynamic response of these tanks under seismic excitations must properly analyzed in order to design these tanks to survive the earthquakes to which they may be subjected. The dynamic response of liquid-storage tanks subjected to ground excitations has been the subject of numerous studies in the past thirty years. However, most of the studies were focused on the responses of the tanks such that the contained liquid can be considered to be incompressible and inviscid. Thus, the effect of liquid viscosity on the dynamic response of the liquid-tank system is often ignored. This is justified for water-storage tanks because water has a very small viscosity. However, there are cases where the liquid viscosity is not small in comparison with that of water. For such cases the designs of these tanks based on the inviscid assumption become questionable, and the effect of viscosity on the dynamic response needs to be assessed. To the best of our knowledge, due to the complexity of the problem, the effect of viscosity has not been studied satisfactorily to date. Since the governing equations are very complicated if viscosity is included in the analysis, the closed form solutions in most cases are unattainable. Therefore, it is necessary to use a computer code to solve the equations-numerically. The computer code used in this study is the finite element code, FLUSTR-ANL(FLUid-STRucture interaction code developed at Argonne National Laboratory) (Chang et al.1988). In this study, the tanks are assumed to be rigid and rigidly supported on their bases, and the responses are considered to be linear.
International Nuclear Information System (INIS)
Maekawa, Akira; Shimizu, Yasutaka; Suzuki, Michiaki; Fujita, Katsuhisa
2007-01-01
The seismic-proof design of a large-scale cylindrical water storage tank has been an important issue for enormous earthquake. For enhancing its reliability, it is necessary to study the vibration behavior of the tank in more detail. This paper describes the results of a vibration test with a 1/10 reduced scale model of a large-scale cylindrical water storage tank, and also refers to the dynamic fluid pressure distribution and its influence on the seismic-proof design. Considering the differences between the experimental values and numerical design ones, it becomes obvious that there is a discrepancy between the positive and the negative pressures of the dynamic fluid pressure and that the dynamic fluid pressure depends on the acceleration magnitude. And it is suggested that such phenomena are caused by oval-type vibrations. They, however, have little effect on the seismic-proof design of the tank in the range of acceleration used in this study. (author)
Excitation energy migration dynamics in upconversion nanomaterials
Tu, L.; Liu, X.; Wu, F.; Zhang, H.
2015-01-01
Recent efforts and progress in unraveling the fundamental mechanism of excitation energy migration dynamics in upconversion nanomaterials are covered in this review, including short-and long-term interactions and other interactions in homogeneous and heterogeneous nanostructures. Comprehension of
Excited-state molecular photoionization dynamics
International Nuclear Information System (INIS)
Pratt, S.T.
1995-01-01
This review presents a survey of work using resonance-enhanced multiphoton ionization and double-resonance techniques to study excited-state photoionization dynamics in molecules. These techniques routinely provide detail and precision that are difficult to achieve in single-photon ionization from the ground state. The review not only emphasizes new aspects of photoionization revealed in the excited-state experiments but also shows how the excited-state techniques can provide textbook illustrations of some fundamental mechanisms in molecular photoionization dynamics. Most of the examples are confined to diatomic molecules. (author)
Dynamics of excitable nodes on random graphs
Indian Academy of Sciences (India)
emergence of different structural features as well as the level of dynamical activity supported on the network. Keywords ... dynamics of discrete excitable nodes and the rules of interaction between them are dis- cussed. ... if there is a connection between nodes i and j, the element Aij of the adjacency matrix A is. 1, else it is 0.
Dynamical analysis of highly excited molecular spectra
Energy Technology Data Exchange (ETDEWEB)
Kellman, M.E. [Univ. of Oregon, Eugene (United States)
1993-12-01
The goal of this program is new methods for analysis of spectra and dynamics of highly excited vibrational states of molecules. In these systems, strong mode coupling and anharmonicity give rise to complicated classical dynamics, and make the simple normal modes analysis unsatisfactory. New methods of spectral analysis, pattern recognition, and assignment are sought using techniques of nonlinear dynamics including bifurcation theory, phase space classification, and quantization of phase space structures. The emphasis is chaotic systems and systems with many degrees of freedom.
Excited nucleon spectrum with two flavors of dynamical fermions
International Nuclear Information System (INIS)
Bulava, John M.; Edward, Robert; Engelson, Eric; Joo, Balint; Lichtl, Adam; Lin, Huey-Wen; Mathur, Nilmani; Morningstar, Colin; Richards, David; Wallace, Stephen
2009-01-01
We compute the spectrum of excited nucleons using the anisotropic Wilson lattice with two flavors of dynamical fermions. Using optimized sets of operators which transform irreducibly under the octahedral group, matrices of correlation functions are computed. We apply the variational method to these matrices to extract excited energy eigenstates. We obtain several states for each irrep and identify the continuum spin for the lowest-lying states, including a J P =5/2 - state.
Seismic load experiments under mean seismic excitation
International Nuclear Information System (INIS)
Steinhilber, H.; Jehlicka, P.; Malcher, L.
1979-01-01
The seismic load experiments carried out within the framework of the HDR safety programme are aimed at enlarging and verifying the know-how with regard to the design of nuclear power plants so as to protect them against the impact of earth-quakes. One of the main objectives is to find out computing methods yielding sufficiently reliable results defining the actual vibrational behaviour of real structures under high seismic excitation. (orig./GL) [de
Liquid storage tanks under vertical excitation
International Nuclear Information System (INIS)
Philippacopoulos, A.J.
1985-01-01
Until recently, the hydrodynamic effects on liquid storage tanks induced by an earthquake excitation were basically treated for the horizontal component of the earthquake. Recent studies, however, showed that the hydrodynamic effects due to the vertical component of an earthquake may be significant. In these studies the tank is assumed to be fixed at the bottom. This paper is concerned with the hydrodynamic behavior of liquid storage tanks induced by vertical earthquake input excitation. First, the fluid-tank system is treated as a fixed-base system and a simple formula is obtained for the coupled fluid-structure natural frequency. Second, additional interaction effects due to the foundation flexibility on the fluid-tank system are investigated. It is concluded that the foundation flexibility may have a significant effect on the hydrodynamic behavior of the liquid storage tanks under a vertical ground shaking
Macroscopic dynamics of thermal nuclear excitations
International Nuclear Information System (INIS)
Bastrukov, S.I.; Deak, F.; Kiss, A.; Seres, Z.
1989-11-01
The concept of kinetic temperature as a local dynamical variable of thermal nuclear collective motion is formulated using long-mean-free-path approach based on the Landau-Vlasov kinetic equation. In the Fermi drop model the thermal fluid dynamics of the spherical nucleus is analyzed. It is shown that in a compressible Fermi liquid the temperature pulses propagate in the form of spherical wave in phase with the acoustic wave. The thermal and compressional excitations are caused by the isotropic harmonic oscillations of the Fermi sphere in momentum space. (author) 25 refs.; 2 figs
Excited state dynamics of DNA bases
Czech Academy of Sciences Publication Activity Database
Kleinermanns, K.; Nachtigallová, Dana; de Vries, M. S.
2013-01-01
Roč. 32, č. 2 (2013), s. 308-342 ISSN 0144-235X R&D Projects: GA ČR GAP208/12/1318 Grant - others:National Science Foundation(US) CHE-0911564; NASA(US) NNX12AG77G; Deutsche Forschungsgemeinschaft(DE) SFB 663; Deutsche Forschungsgemeinschaft(DE) KI 531-29 Institutional support: RVO:61388963 Keywords : DNA bases * nucleobases * excited state * dynamics * computations * gas phase * conical intersections Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.920, year: 2013
Violin bridge mobility analysis under in-plane excitation.
Zhang, Cheng-Zhong; Zhang, Guang-Ming; Ye, Bang-Yan; Liang, Li-Dong
2013-11-08
The vibration of a violin bridge is a dynamic contact vibration with two interfaces: strings-bridge, and bridge feet-top plate. In this paper, the mobility of an isolated bridge under in-plane excitation is explored using finite element modeling based on the contact vibration model. Numerical results show that the dynamic contact stiffness in the two contact interfaces has a great impact on the bridge mobility. A main resonance peak is observed in the frequency range of 2-3 kHz in the frequency response of the isolated bridge when the contact stiffness is smaller than a critical threshold. The main resonance peak frequency is affected by the contact stiffness as well. In order to verify the numerical findings, a novel experimental system is then designed on the basis of a piezoelectric dynamometer for bridge mobility analysis. Experimental results confirm the impact of the dynamic contact stiffness on the bridge mobility.
Violin Bridge Mobility Analysis under In-Plane Excitation
Directory of Open Access Journals (Sweden)
Cheng-Zhong Zhang
2013-11-01
Full Text Available The vibration of a violin bridge is a dynamic contact vibration with two interfaces: strings-bridge, and bridge feet-top plate. In this paper, the mobility of an isolated bridge under in-plane excitation is explored using finite element modeling based on the contact vibration model. Numerical results show that the dynamic contact stiffness in the two contact interfaces has a great impact on the bridge mobility. A main resonance peak is observed in the frequency range of 2–3 kHz in the frequency response of the isolated bridge when the contact stiffness is smaller than a critical threshold. The main resonance peak frequency is affected by the contact stiffness as well. In order to verify the numerical findings, a novel experimental system is then designed on the basis of a piezoelectric dynamometer for bridge mobility analysis. Experimental results confirm the impact of the dynamic contact stiffness on the bridge mobility.
The photodissociation and reaction dynamics of vibrationally excited molecules
Energy Technology Data Exchange (ETDEWEB)
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.
WWER FA modal analysis under vibration force and kinematic excitation
International Nuclear Information System (INIS)
Makarov, V.; Afanasyev, A.; Matvienko, I.; Tutnov, A.; Kiselev, A.; Kiselev, A.; Volkov, S.
2008-01-01
The approach based on mixed application of calculation and experimental methods is assumed for the analysis of WWER FA strength and stability under vibration loads typical as for reactor normal operating conditions so seismic effects. Experimental modal analysis is usually provided in air at 20 deg C, the results are FA modal characteristics: frequencies, shapes, vibration damping factor, transfer functions. Since FA is a non-linear structure, modal analysis is provided at various levels of vibration excitation. The results of experimental modal analysis are initial data for FA calculation modal model, which are used for the analysis of FA vibration strength and stability during the whole service life in the reactor. The results of experimental examination and numerical modelling of WWER-440, WWER-1000, and WWER-1500 FA dynamic characteristics and the analysis of design and operational factors influence on FA dynamic characteristics are presented in the report. This work was organized by JSC TVEL. (authors)
Photodissociation of FONO: an excited state nonadiabatic dynamics study.
Hilal, Allaa R; Hilal, Rifaat
2017-03-01
The photo dissociation of nitrosyl fluorite, FONO, a potential source of atmospheric fluorine, underlies its active role in ozone depletion and other activities in the troposphere. In the present work, the electronic structure of FONO is revisited at high level of ab initio and density functional theory (DFT) theoretical levels. Several different post SCF methods were used to compute excited states, vertical excitation energies and intensities, namely configuration interaction with single excitations (CIS), equation of motion coupled cluster with single and double excitations (EOM-CCSD), and symmetry adopted cluster configuration interaction (SAC-CI) methods. The potential energy functions along two internal coordinates, namely the F-ONO bond and the FONO dihedral angle, have been computed on the ground state relaxed potential energy surface (PES) for the ground, 5A' and 5A″ excited states using the EOM-CCSD method. In the gas phase, the decay of the excited states of FONO was examined closely by calculating the UV photoabsorption cross-section spectrum and by nonadiabatic dynamics simulations. Nonadiabatic dynamics were simulated by sampling 300 trajectories in two spectral windows at 3.0 ± 0.25 and 4.5 ± 0.25 eV using the surface hopping method. Two different photodissociation reaction pathways with two main products, including multifragmentation (FO+NO) and atomic elimination (F) mechanisms were identified. For the cis-isomer, the main photochemical channel is F+NO 2 , representing 67% of all processes. For the trans-isomer, however, the main dissociation pathway is (FO+NO). Graphical Abstract Photodisscociation of nitrosyl fluorite (FONO) seems to underlie its active role in ozone depletion and other activities in the troposphere. The present research revisits the electronic structure of FONO at high level of ab initio and DFT theoretical levels. Cis-trans isomerization and dissociation in the ground and low lying excited states were examined
Thermal response of nanocomposite materials under pulsed laser excitation
International Nuclear Information System (INIS)
Rashidi-Huyeh, Majid; Palpant, Bruno
2004-01-01
The optical properties of nanocomposite materials made of matrix-embedded noble metal nanoparticles strongly depend on thermal effects from different origins. We propose a classical model describing the energy exchanges within the nanoparticles and between the latter and the surrounding dielectric host subsequent to a light pulse absorption. This model, which accounts for the thermal interactions between neighboring particles, allows us to calculate numerically the temperature dynamics of the electrons, metal lattice and matrix as functions of particle size, and metal concentration of the medium, whatever be the pulsed excitation temporal regime. It is illustrated in the case of Au:SiO 2 materials under femtosecond and nanosecond pulse excitation. It is shown that, in the femtosecond regime, the heat transfer to the matrix cannot be neglected beyond a few picosecond delay from which particle size and metal concentration play a significant role in the electron relaxation. In the nanosecond regime, these morphologic parameters influence crucially the material thermal behavior with the possibility of generating a thermal lens effect. The implications in the analysis of experimental results regarding both the electron relaxation dynamics and the nonlinear optical properties are also discussed. Finally, a method to adapt the model to the case of thin nanocomposite film is proposed
Dynamic Testing: Toward a Multiple Exciter Test
2015-04-01
high force in a much smaller footprint. While they lack the bandwidth potential of an electrodynamic exciter, development of dual-stage valves made it...DOF motion. Modern exciter systems and control-system combinations can address a wide range of environmental conditions beyond the classical
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.
Death, dynamics and disorder: Terminating reentry in excitable ...
Indian Academy of Sciences (India)
Death, dynamics and disorder: Terminating reentry in excitable media by dynamically-induced ... ventricular tachycardia, often leading to death. This is typically treated by rapid stimula- tion from ... Note the non-conducting scar tissue (in black) occupying a significant portion of the ventricle. Pacing is usually applied via an ...
Effects of abnormal excitation on the dynamics of spiral waves
Min-Yi, Deng; Xue-Liang, Zhang; Jing-Yu, Dai
2016-01-01
The effect of physiological and pathological abnormal excitation of a myocyte on the spiral waves is investigated based on the cellular automaton model. When the excitability of the medium is high enough, the physiological abnormal excitation causes the spiral wave to meander irregularly and slowly. When the excitability of the medium is low enough, the physiological abnormal excitation leads to a new stable spiral wave. On the other hand, the pathological abnormal excitation destroys the spiral wave and results in the spatiotemporal chaos, which agrees with the clinical conclusion that the early after depolarization is the pro-arrhythmic mechanism of some anti-arrhythmic drugs. The mechanisms underlying these phenomena are analyzed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11365003 and 11165004).
Phasing of independent laser channels under impact SBS excitation
Gordeev, A. A.; Efimkov, V. F.; Zubarev, I. G.; Mikhailov, S. I.
2015-10-01
It is shown experimentally that phasing of independent laser channels under impact SBS excitation calls for a stable difference in arm lengths, as in a classical Michelson interferometer. A scheme with automatic compensation for fluctuations of interferometer arm lengths has been proposed and experimentally implemented. This scheme makes it possible to perform stable phasing of two laser channels under standard laboratory conditions.
Optimal control of peridinin excited-state dynamics
Dietzek, Benjamin; Chábera, Pavel; Hanf, Robert; Tschierlei, Stefanie; Popp, Jürgen; Pascher, Torbjörn; Yartsev, Arkady; Polívka, Tomáš
2010-07-01
Optimal control is applied to study the excited-state relaxation of the carbonyl-carotenoid peridinin in solution. Phase-shaping of the excitation pulses is employed to influence the photoinduced reaction dynamics of peridinin. The outcome of various control experiments using different experimentally imposed fitness parameters is discussed. Furthermore, the effects of pump-wavelength and different solvents on the control efficiency are presented. The data show that excited-state population within either the S 1 or the ICT state can be reduced significantly by applying optimal control, while the efficiency of control decreases upon excitation into the low-energy side of the absorption band. However, we are unable to alter the ratio of S 1 and ICT population or increase the population of either state compared to excitation with a transform-limited pulse. We compare the results to various control mechanisms and argue that characteristic low-wavenumber modes are relevant for the photochemistry of peridinin.
Photodamage of mesotetraphenylporphyrin under one- and two-photon excitation
International Nuclear Information System (INIS)
Wen Yanan; Liu Yuqiang; Yang Zhenling; Yang Yanqiang; Guo Ximing
2010-01-01
Photoinduced damage behavior of mesotetraphenylporphyrin (TPP) under one- and two-photon excitation with femtosecond laser pulses is investigated in the present work. Quenching in the luminescent intensity is observed. Results suggest that laser irradiation on TPP mainly causes two simultaneously occurring photoprocesses: photodamage and formation of a porphine-type photoproduct. The damage rate exhibits a linear dependence on the incident light power in one-photon excitation, whereas in two-photon excitation, the power dependence of the damage rate turns out to be exponential. The photoproduct formed in one- and two-photon excitation is identical. This product, which is observed to possess superior photostability and two-photon absorbing ability compared with the original TPP sensitizer, is likely to be treated as a secondary photosensitizer in the activation process of photodynamic therapy (PDT). This work might be helpful for the drug evaluation in the practical application of PDT.
Reaction dynamics of electronically excited alkali atoms with simpler molecules
International Nuclear Information System (INIS)
Weiss, P.S.; Mestdagh, J.M.; Schmidt, H.; Vernon, M.F.; Covinsky, M.H.; Balko, B.A.; Lee, Y.T.
1985-05-01
The reactions of electronically excited sodium atoms with simple molecules have been studied in crossed molecular beams experiments. Electronically excited Na(3 2 P/sub 3/2/, 4 2 D/sub 5/2/, and 5 2 S/sub 1/2/) were produced by optical pumping using single frequency dye lasers. The effects of the symmetry, and the orientation and alignment of the excited orbital on the chemical reactivity, and detailed information on the reaction dynamics were derived from measurements of the product angular and velocity distributions. 12 refs., 9 figs
Nonlinear Dynamical Analysis for the Cable Excited with Parametric and Forced Excitation
Directory of Open Access Journals (Sweden)
C. Z. Qian
2014-01-01
Full Text Available Considering the deck vibration effect on the cable in cable-stayed bridge, using nonlinear structure dynamics theory, the nonlinear dynamical equation for the stayed cable excited with deck vibration is proposed. Research shows that the vertical vibration of the deck has a combined parametric and forced excitation effect on the cable when the angle of the cable is taken into consideration. Using multiscale method, the 1/2 principle parametric resonance is studied and the bifurcation equation is obtained. Despite the parameters analysis, the bifurcation characters of the dynamical system are studied. At last, by means of numerical method and software MATHMATIC, the effect rules of system parameters to the dynamical behavior of the system are studied, and some useful conclusions are obtained.
Ab Initio molecular dynamics with excited electrons
Alavi, A.; Kohanoff, J.; Parrinello, M.; Frenkel, D.
1994-01-01
A method to do ab initio molecular dynamics suitable for metallic and electronically hot systems is described. It is based on a density functional which is costationary with the finite-temperature functional of Mermin, with state being included with possibly fractional occupation numbers.
Analysis of axial compressive loaded beam under random support excitations
Xiao, Wensheng; Wang, Fengde; Liu, Jian
2017-12-01
An analytical procedure to investigate the response spectrum of a uniform Bernoulli-Euler beam with axial compressive load subjected to random support excitations is implemented based on the Mindlin-Goodman method and the mode superposition method in the frequency domain. The random response spectrum of the simply supported beam subjected to white noise excitation and to Pierson-Moskowitz spectrum excitation is investigated, and the characteristics of the response spectrum are further explored. Moreover, the effect of axial compressive load is studied and a method to determine the axial load is proposed. The research results show that the response spectrum mainly consists of the beam's additional displacement response spectrum when the excitation is white noise; however, the quasi-static displacement response spectrum is the main component when the excitation is the Pierson-Moskowitz spectrum. Under white noise excitation, the amplitude of the power spectral density function decreased as the axial compressive load increased, while the frequency band of the vibration response spectrum increased with the increase of axial compressive load.
Scintillation of sapphire under particle excitation at low temperature
International Nuclear Information System (INIS)
Amare, J; Beltran, B; Cebrian, S; Coron, N; Dambier, G; GarcIa, E; Gomez, H; Irastorza, I G; Leblanc, J; Luzon, G; Marcillac, P de; Martinez, M; Morales, J; Ortiz de Solorzano, A; Pobes, C; Puimedon, J; Redon, T; RodrIguez, A; Ruz, J; Sarsa, M L; Torres, L; Villar, J A
2006-01-01
The scintillation properties of undoped sapphire at very low temperature have been studied in the framework of the ROSEBUD (Rare Objects SEarch with Bolometers UnDerground) Collaboration devoted to dark matter searches. We present an estimation of its light yield under gamma, alpha and neutron excitation
Scintillation of sapphire under particle excitation at low temperature
Energy Technology Data Exchange (ETDEWEB)
Amare, J [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Beltran, B [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Cebrian, S [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Coron, N [Institut d' Astrophysique Spatiale, Bat 121, 91405 Orsay, Paris (France); Dambier, G [Institut d' Astrophysique Spatiale, Bat 121, 91405 Orsay, Paris (France); GarcIa, E; Gomez, H [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Irastorza, I G [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Leblanc, J [Institut d' Astrophysique Spatiale, Bat 121, 91405 Orsay, Paris (France); Luzon, G [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Marcillac, P de [Institut d' Astrophysique Spatiale, Bat 121, 91405 Orsay, Paris (France); Martinez, M [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Morales, J [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Ortiz de Solorzano, A [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Pobes, C [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Puimedon, J [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Redon, T [Institut d' Astrophysique Spatiale, Bat 121, 91405 Orsay, Paris (France); RodrIguez, A [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Ruz, J [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Sarsa, M L [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Torres, L [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain); Villar, J A [Laboratorio de Fisica Nuclear, Universidad de Zaragoza, 50009 Zaragoza (Spain)
2006-05-15
The scintillation properties of undoped sapphire at very low temperature have been studied in the framework of the ROSEBUD (Rare Objects SEarch with Bolometers UnDerground) Collaboration devoted to dark matter searches. We present an estimation of its light yield under gamma, alpha and neutron excitation.
FSI analysis of piping systems under seismic excitation
International Nuclear Information System (INIS)
Uras, R.A.; Ma, D.C.; Chang, Yao W.; Liu, Wing Kam
1991-01-01
A formulation which accounts for fluid-structure interaction of piping system under seismic excitation is presented. The governing equations of the fluid and the structure to model the pipe are stated. Using the finite element method the discretized equations are obtained. A transformation procedure for proper assembly of matrices is introduced. A solution algorithm is described. 9 refs., 2 figs
Generalized Minimum Variance Control for MDOF Structures under Earthquake Excitation
Directory of Open Access Journals (Sweden)
Lakhdar Guenfaf
2016-01-01
Full Text Available Control of a multi-degree-of-freedom structural system under earthquake excitation is investigated in this paper. The control approach based on the Generalized Minimum Variance (GMV algorithm is developed and presented. Our approach is a generalization to multivariable systems of the GMV strategy designed initially for single-input-single-output (SISO systems. Kanai-Tajimi and Clough-Penzien models are used to generate the seismic excitations. Those models are calculated using the specific soil parameters. Simulation tests using a 3DOF structure are performed and show the effectiveness of the control method.
Toward the excited meson spectrum of dynamical QCD
Energy Technology Data Exchange (ETDEWEB)
Dudek, Jozef J.; Edwards, Robert G.; Peardon, Michael J.; Richards, David G.; Thomas, Christopher E.
2010-08-01
We present a detailed description of the extraction of the highly excited isovector meson spectrum on dynamical anisotropic lattices using a new quark-field construction algorithm and a large variational basis of operators. With careful operator construction, the combination of these techniques is used to identify the continuum spin of extracted states reliably, overcoming the reduced rotational symmetry of the cubic lattice. Excited states, states with exotic quantum numbers (0+-, 1-+ and 2+-) and states of high spin are resolved, including, for the first time in a lattice QCD calculation, spin-four states. The determinations of the spectrum of isovector mesons and kaons are performed on dynamical lattices with two volumes and with pion masses down to ~ 400 MeV, with statistical precision typically at or below 1% even for highly excited states.
Phasing of independent laser channels under impact SBS excitation
Energy Technology Data Exchange (ETDEWEB)
Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)
2015-10-31
It is shown experimentally that phasing of independent laser channels under impact SBS excitation calls for a stable difference in arm lengths, as in a classical Michelson interferometer. A scheme with automatic compensation for fluctuations of interferometer arm lengths has been proposed and experimentally implemented. This scheme makes it possible to perform stable phasing of two laser channels under standard laboratory conditions. (control of radiation parameters)
Excited State Structural Dynamics of Carotenoids and Charge Transfer Systems
International Nuclear Information System (INIS)
Van Tassle, Aaron Justin
2006-01-01
This dissertation describes the development and implementation of a visible/near infrared pump/mid-infrared probe apparatus. Chapter 1 describes the background and motivation of investigating optically induced structural dynamics, paying specific attention to solvation and the excitation selection rules of highly symmetric molecules such as carotenoids. Chapter 2 describes the development and construction of the experimental apparatus used throughout the remainder of this dissertation. Chapter 3 will discuss the investigation of DCM, a laser dye with a fluorescence signal resulting from a charge transfer state. By studying the dynamics of DCM and of its methyl deuterated isotopomer (an otherwise identical molecule), we are able to investigate the origins of the charge transfer state and provide evidence that it is of the controversial twisted intramolecular (TICT) type. Chapter 4 introduces the use of two-photon excitation to the S1 state, combined with one-photon excitation to the S2 state of the carotenoid beta-apo-8'-carotenal. These 2 investigations show evidence for the formation of solitons, previously unobserved in molecular systems and found only in conducting polymers Chapter 5 presents an investigation of the excited state dynamics of peridinin, the carotenoid responsible for the light harvesting of dinoflagellates. This investigation allows for a more detailed understanding of the importance of structural dynamics of carotenoids in light harvesting
Excited State Spectra and Dynamics of Phenyl-Substituted Butadienes
DEFF Research Database (Denmark)
Wallace-Williams, Stacie E.; Schwartz, Benjamin J.; Møller, Søren
1994-01-01
A combination of steady-state and dynamic spectral measurements are used to provide new insights into the nature of the excited-state processes of all-trans-1,4-diphenyl-1,3-butadiene and several analogs: 1,4-diphenyl- 1,3-cyclopentadiene, 1,1,4,4-tetraphenylbutadiene, 1,2,3,4-tetraphenyl-1...
Quantum dynamics of vibrational excitations and vibrational charge ...
Indian Academy of Sciences (India)
Administrator
Dedicated to the memory of the late Professor S K Rangarajan. *For correspondence. Quantum dynamics of vibrational excitations and vibrational charge transfer processes in H. +. + O2 collisions at collision energy 23 eV. †. SAIESWARI AMARAN# and SANJAY KUMAR*. Department of Chemistry, Indian Institute of ...
Relaxation dynamics in the excited states of a ketocyanine dye ...
Indian Academy of Sciences (India)
WINTEC
*For correspondence. Relaxation dynamics in the excited states of a ketocyanine dye probed by femtosecond transient absorption spectroscopy. JAHUR A MONDAL, SANDEEP VERMA, HIRENDRA N GHOSH and DIPAK K PALIT*. Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085.
Quantum dynamics of vibrational excitations and vibrational charge ...
Indian Academy of Sciences (India)
Administrator
+ 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 frame- work employing our newly obtained quasi-diabatic potential energy surfaces corresponding to the ground and the first excited ...
Optimal control of peridinin excited-state dynamics
Czech Academy of Sciences Publication Activity Database
Dietzek, B.; Chábera, P.; Hanf, R.; Tschierlei, S.; Popp, J.; Pascher, T.; Yartsev, A.; Polívka, Tomáš
2010-01-01
Roč. 373, 1-2 (2010), s. 129-136 ISSN 0301-0104 Institutional research plan: CEZ:AV0Z50510513 Keywords : peridin * excited-state dynamics * coherent control Subject RIV: BO - Biophysics Impact factor: 2.017, year: 2010
Excited-State Dynamics in Folic Acid and 6-CARBOXYPTERIN upon Uva Excitation
Huang, Huijuan; Vogt, R. Aaron; Crespo-Hernandez, Carlos E.
2013-06-01
The excited-state dynamics of folic acid (FA) and 6-carboxypterin (6CP) are poorly understood and work is needed to uncover the relaxation pathways that ultimately lead to their oxidative damage of DNA. In our approach, broad-band transient absorption spectroscopy was used to monitor the evolution of the excited states in FA and 6CP in basic aqueous solution upon excitation at 350 nm. In addition, quantum-chemical calculations were performed to assist in the interpretation of the experimental results and in the postulation of kinetic mechanisms. The combined experimental and computational results support a kinetic model where excitation of FA results in ultrafast charge separation (τ = 0.6 ps), which decays back to the ground state primarily by charge recombination with a lifetime of 2.2 ps. A small fraction of the charge transfer state undergoes intersystem crossing to populate the lowest-energy triplet state with a lifetime of 200 ps. On the other hand, a large fraction of the initially excited singlet state in 6CP decays by fluorescence emission with a lifetime of 100 ps, while intersystem crossing to the triplet state occurs with a lifetime of 4.4 ns. The potential implications of these results to the oxidative damage of DNA by FA and 6CP will be discussed. Funding from the National Science Foundation is gratefully acknowledged (CHE-1255084).
Modelling hair follicle growth dynamics as an excitable medium.
Directory of Open Access Journals (Sweden)
Philip J Murray
Full Text Available The hair follicle system represents a tractable model for the study of stem cell behaviour in regenerative adult epithelial tissue. However, although there are numerous spatial scales of observation (molecular, cellular, follicle and multi follicle, it is not yet clear what mechanisms underpin the follicle growth cycle. In this study we seek to address this problem by describing how the growth dynamics of a large population of follicles can be treated as a classical excitable medium. Defining caricature interactions at the molecular scale and treating a single follicle as a functional unit, a minimal model is proposed in which the follicle growth cycle is an emergent phenomenon. Expressions are derived, in terms of parameters representing molecular regulation, for the time spent in the different functional phases of the cycle, a formalism that allows the model to be directly compared with a previous cellular automaton model and experimental measurements made at the single follicle scale. A multi follicle model is constructed and numerical simulations are used to demonstrate excellent qualitative agreement with a range of experimental observations. Notably, the excitable medium equations exhibit a wider family of solutions than the previous work and we demonstrate how parameter changes representing altered molecular regulation can explain perturbed patterns in Wnt over-expression and BMP down-regulation mouse models. Further experimental scenarios that could be used to test the fundamental premise of the model are suggested. The key conclusion from our work is that positive and negative regulatory interactions between activators and inhibitors can give rise to a range of experimentally observed phenomena at the follicle and multi follicle spatial scales and, as such, could represent a core mechanism underlying hair follicle growth.
Modelling hair follicle growth dynamics as an excitable medium.
Murray, Philip J; Maini, Philip K; Plikus, Maksim V; Chuong, Cheng-Ming; Baker, Ruth E
2012-01-01
The hair follicle system represents a tractable model for the study of stem cell behaviour in regenerative adult epithelial tissue. However, although there are numerous spatial scales of observation (molecular, cellular, follicle and multi follicle), it is not yet clear what mechanisms underpin the follicle growth cycle. In this study we seek to address this problem by describing how the growth dynamics of a large population of follicles can be treated as a classical excitable medium. Defining caricature interactions at the molecular scale and treating a single follicle as a functional unit, a minimal model is proposed in which the follicle growth cycle is an emergent phenomenon. Expressions are derived, in terms of parameters representing molecular regulation, for the time spent in the different functional phases of the cycle, a formalism that allows the model to be directly compared with a previous cellular automaton model and experimental measurements made at the single follicle scale. A multi follicle model is constructed and numerical simulations are used to demonstrate excellent qualitative agreement with a range of experimental observations. Notably, the excitable medium equations exhibit a wider family of solutions than the previous work and we demonstrate how parameter changes representing altered molecular regulation can explain perturbed patterns in Wnt over-expression and BMP down-regulation mouse models. Further experimental scenarios that could be used to test the fundamental premise of the model are suggested. The key conclusion from our work is that positive and negative regulatory interactions between activators and inhibitors can give rise to a range of experimentally observed phenomena at the follicle and multi follicle spatial scales and, as such, could represent a core mechanism underlying hair follicle growth.
Quaedflieg, Conny W E M; Schwabe, Lars
2018-03-01
Stressful events have a major impact on memory. They modulate memory formation in a time-dependent manner, closely linked to the temporal profile of action of major stress mediators, in particular catecholamines and glucocorticoids. Shortly after stressor onset, rapidly acting catecholamines and fast, non-genomic glucocorticoid actions direct cognitive resources to the processing and consolidation of the ongoing threat. In parallel, control of memory is biased towards rather rigid systems, promoting habitual forms of memory allowing efficient processing under stress, at the expense of "cognitive" systems supporting memory flexibility and specificity. In this review, we discuss the implications of this shift in the balance of multiple memory systems for the dynamics of the memory trace. Specifically, stress appears to hinder the incorporation of contextual details into the memory trace, to impede the integration of new information into existing knowledge structures, to impair the flexible generalisation across past experiences, and to hamper the modification of memories in light of new information. Delayed, genomic glucocorticoid actions might reverse the control of memory, thus restoring homeostasis and "cognitive" control of memory again.
Analysis on Response of Dynamic Systems to Pulse Sequences Excitation
Directory of Open Access Journals (Sweden)
Xie Lili
2009-07-01
Full Text Available Near-fault ground motions with long-period pulses can place severe demands on structures near an active fault. These pulse-type ground motions can be represented by pulse sequences with simple shapes. Half-sinusoidal pulse sequences are used to approximate recorded ground motions and dynamic responses of SDOF system under the excitation of these pulse sequences are studied. Four cases are considered: (1 variation in duration of successor sub-pulse; (2 variation in duration of predecessor sub-pulse; (3 variation in amplitude of successor sub-pulse; and (4 variation in amplitude of predecessor sub-pulse. The corresponding acceleration, velocity and displacement response spectra of these pulse sequences are studied. The analysis on SDOF system shows that in some cases the responses are strongly affected by the changes of duration and/or amplitude of the sub-pulse. The study can be useful to understand the influences of sub-pulse in the near-fault pulse-type ground motions.
Classical Dynamics of Excitations of Bose Condensates in Anisotropic Traps
Graham, Robert
This lecture discusses some aspects of the dynamics of the collective and single-particle excitations at zero temperature of Bose-Einstein condensates of alkali-vapors in magnetic traps. We shall discuss those aspects which can be understood by taking the short-wavelength or 'eikonal' limit of the excitations. Trapped Bose-Einstein condensates can be excited experimentally either directly via periodic modulations of the trap potential or by scattering light off the condensate. My discussion here will closely follow some theoretical work published in [1-3] that has recently been done in collaboration with Andras Csordas and Peter Szepfalusy at the Research Institute for solid State Physics and Optics in Budapest, Hungary and with Martin Fliesser at the University of Essen, Germany.
Dynamics of the edge excitations in the FQH effects
International Nuclear Information System (INIS)
Wen, X.G.
1994-01-01
Fractional quantum Hall effects (FQHE) discovered by Tsui, Stormer and Gossard open a new era in theory of strongly correlated system. In the first time the authors have to completely abandon the theories based on the single-body picture and use an intrinsic many-body theory proposed by Laughlin and others to describe the FQHE. Due to the repulsive interaction, the strongly correlated FQH liquid is an incompressible state despite the first Landau level is only partially filled. All the bulk excitations in the FQH states have finite energy gaps. The FQH states and insulators are similar in the sense that both states have finite energy gap and short ranged electron propagators. Because of this similarity, it is puzzling that the FQH systems apparently have very different transport properties than ordinary insulators. Halperin first point out that the integral quantum Hall (IQH) states contain gapless edge excitations. Although the electronic states in the bulk are localized, the electronic states at the edge of the sample are extended. Therefore the nontrivial transport properties of the IQH states come from the gapless edge excitations. Such an edge transport picture has been supported by many experiments. One also found that the edge excitations in the IQH states are described by a chiral 1D Fermi liquid theory. Here, the authors review the dynamical theory of the edge excitations in the FQH effects
Ultrafast excited-state dynamics of 2,5-dimethylpyrrole.
Yang, Dongyuan; Min, Yanjun; Chen, Zhichao; He, Zhigang; Yuan, Kaijun; Dai, Dongxu; Yang, Xueming; Wu, Guorong
2018-04-17
The ultrafast excited-state dynamics of 2,5-dimethylpyrrole following excitation at wavelengths in the range of 265.7-216.7 nm is studied using the time-resolved photoelectron imaging method. It is found that excitation at longer wavelengths (265.7-250.2 nm) results in the population of the S1(1πσ*) state, which decays out of the photoionization window in about 90 fs. At shorter pump wavelengths (242.1-216.7 nm), the assignments are less clear-cut. We tentatively assign the initially photoexcited state(s) to the 1π3p Rydberg state(s) which has lifetimes of 159 ± 20, 125 ± 15, 102 ± 10 and 88 ± 10 fs for the pump wavelengths of 242.1, 238.1, 232.6 and 216.7 nm, respectively. Internal conversion to the S1(1πσ*) state represents at most a minor decay channel. The methyl substitution effects on the decay dynamics of the excited states of pyrrole are also discussed. Methyl substitution on the pyrrole ring seems to enhance the direct internal conversion from the 1π3p Rydberg state to the ground state, while methyl substitution on the N atom has less influence and the internal conversion to the S1(πσ*) state represents a main channel.
Assessment of wind turbine drive-train fatigue loads under torsional excitation
DEFF Research Database (Denmark)
Gallego Calderon, Juan Felipe; Natarajan, Anand
2015-01-01
This paper establishes validated models that can accurately account for the dynamics of the gearbox, along with the external dynamics that excite the system. A drive-train model implementation is presented where the gearbox and generator are coupled to the wind turbine structure in a dynamic...... allows the computation of the bearing and gear-mesh loads. The proposed models are validated by experiments from a 750 kW test-rig. The drive-train model is configured for a 5 MW power capacity and coupled to the corresponding wind turbine and load simulations are carried out under turbulent wind...
Directory of Open Access Journals (Sweden)
Paulo S. Varoto
2006-01-01
Full Text Available Flexible structures are frequently subjected to multiple inputs when in the field environment. The accurate determination of the system dynamic response to multiple inputs depends on how much information is available from the excitation sources that act on the system under study. Detailed information include, but are not restricted to appropriate characterization of the excitation sources in terms of their variation in time and in space for the case of distributed loads. Another important aspect related to the excitation sources is how inputs of different nature contribute to the measured dynamic response. A particular and important driving mechanism that can occur in practical situations is the parametric resonance. Another important input that occurs frequently in practice is related to acoustic pressure distributions that is a distributed type of loading. In this paper, detailed theoretical and experimental investigations on the dynamic response of a flexible cantilever beam carrying a tip mass to simultaneously applied external acoustic and parametric excitation signals have been performed. A mathematical model for transverse nonlinear vibration is obtained by employing Lagrange’s equations where important nonlinear effects such as the beam’s curvature and quadratic viscous damping are accounted for in the equation of motion. The beam is driven by two excitation sources, a sinusoidal motion applied to the beam’s fixed end and parallel to its longitudinal axis and a distributed sinusoidal acoustic load applied orthogonally to the beam’s longitudinal axis. The major goal here is to investigate theoretically as well as experimentally the dynamic behavior of the beam-lumped mass system under the action of these two excitation sources. Results from an extensive experimental work show how these two excitation sources interacts for various testing conditions. These experimental results are validated through numerically simulated results
Dynamic response of parallel resonant circuit with different power excitations
International Nuclear Information System (INIS)
Qi Xin; Xu Zhongxiong; Zhang Jing
2008-01-01
In order to avoid drawing a large reactive power from the alternating current line, the White circuit type resonant network is adopted widely as the structure of the magnet power supply system of the rapid-cycling synchrotron. Reducing the total harmonic distortion (THD)of the magnet current in the parallel resonant network is the key technique for the magnet current tracking accuracy. Based on the dynamic response analysis of a single mesh parallel resonant circuit in the paper, it shows that the continuous power excitation is of great benefit to reducing the magnet current harmonics. The paper also gives a description of our experimental studies on the dynamic response with the pulse and continuous power excitation in a parallel resonant network model. (authors)
Numerical Simulation of Tire Reinforced Sand behind Retaining Wall Under Earthquake Excitation
Directory of Open Access Journals (Sweden)
A. Lazizi
2014-04-01
Full Text Available This paper studies the numerical simulations of retaining walls supporting tire reinforced sand subjected to El Centro earthquake excitation using finite element analysis. For this, four cases are studied: cantilever retaining wall supporting sand under static and dynamical excitation, and cantilever retaining wall supporting waste tire reinforced sand under static and dynamical excitation. Analytical external stability analyses of the selected retaining wall show that, for all four cases, the factors of safety for base sliding and overturning are less than default minimum values. Numerical analyses show that there are no large differences between the case of wall supporting waste tire reinforced sand and the case of wall supporting sand for static loading. Under seismic excitation, the higher value of Von Mises stress for the case of retaining wall supporting waste tire reinforced sand is 3.46 times lower compared to the case of retaining wall supporting sand. The variation of horizontal displacement (U1 and vertical displacement (U2 near the retaining wall, with depth, are also presented.
Dynamics of a Parametrically Excited System with Two Forcing Terms
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Anastasia Sofroniou
2014-09-01
Full Text Available Motivated by the dynamics of a trimaran, an investigation of the dynamic behaviour of a double forcing parametrically excited system is carried out. Initially, we provide an outline of the stability regions, both numerically and analytically, for the undamped linear, extended version of the Mathieu equation. This paper then examines the anticipated form of response of our proposed nonlinear damped double forcing system, where periodic and quasiperiodic routes to chaos are graphically demonstrated and compared with the case of the single vertically-driven pendulum.
Attosecond dynamics of electron correlation in doubly excited atomic states
Energy Technology Data Exchange (ETDEWEB)
Nicolaides, Cleanthes A. [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens (Greece) and Physics Department, National Technical University, Athens (Greece)). E-mail: can@eie.gr] Mercouris, Theodoros; Komninos, Yanis [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens (Greece)]. E-mails: thmerc@eie.gr; ykomn@eie.gr
2002-06-28
We have solved the time-dependent Schroedinger equation describing the simultaneous interaction of the He 1s2s {sup 1}S state with two laser-generated pulses of trapezoidal or Gaussian shape, of duration 86 fs and of frequencies {omega}{sub 1}=1.453 au and {omega}{sub 2}=1.781 au. The system is excited to the energy region of two strongly correlated doubly excited states, chosen for this study according to specific criteria. It is demonstrated quantitatively that, provided one focuses on the dynamics occurring within the attosecond timescale, the corresponding orbital configurations, 2s2p and 2p3d {sup 1}P{sup 0}, exist as nonstationary states, with occupation probabilities that are oscillating as the states decay exponentially into the 1s{epsilon}p continuum, during and after the laser-atom interaction. It follows that it is feasible to probe by attosecond pulses the motion of configurations of electrons as they correlate via the total Hamiltonian. For the particular system studied here, the probe pulses could register the oscillating doubly excited configurations by de-exciting to the He 1s3d {sup 1}D state, which emits at 6680 A. (author). Letter-to-the-editor.
Universal Dynamics of a localized excitation after an interaction quench
Franchini, Fabio; Fabio Franchini Team; Manas Kulkarni Team; Andrey Gromov Team; Andrea Trombettoni Team
We study the time evolution -induced by a quench- of local excitations in one dimension. We focus on interaction quenches: the considered protocol consists in creating a stable localized excitation propagating through the system, and then operating a sudden change of the interaction between the particles. To highlight the effect of the quench, we take the initial excitation to be a soliton. The quench splits the excitation into two packets moving in opposite directions, whose characteristics can be expressed in a universal way. Our treatment, which is hydrodynamic in nature, allows to describe the internal dynamics of these two packets in terms of the different velocities of their components. We confirm our analytical predictions through numerical simulations performed with the Gross-Pitaevskii equation and with the Calogero model (as an example of long range interactions and solvable with a parabolic confinement). Through the Calogero model we also discuss the effect of an external trapping on the protocol. The hydrodynamic approach shows that there is a difference between the bulk velocities of the propagating packets and the velocities of their peaks, accessible through different measurement procedures. H2020 Twinning project No. 692194, \\x98RBIT-WINNING; FP7 Marie Curie PIOF-PHY-276093; CUNY Award award # 68193-00 46; European Project Matterwave.
Dynamics of two-electron excitations in helium
Energy Technology Data Exchange (ETDEWEB)
Caldwell, C.D.; Menzel, A.; Frigo, S.P. [Univ. of Central Florida, Orlando, FL (United States)] [and others
1997-04-01
Excitation of both electrons in helium offers a unique window for studying electron correlation at the most basic level in an atom in which these two electrons and the nucleus form a three-body system. The authors utilized the first light available at the U-8 undulator-SGM monochromator beamline to investigate the dynamic parameters, partial cross sections, differential cross sections, and photoelectron angular distribution parameters ({beta}), with a high resolving power for the photon beam and at the highly differential level afforded by the use of their electron spectrometer. In parallel, they carried out detailed calculations of the relevant properties by a theoretical approach that is based on the hyperspherical close-coupling method. Partial photoionization cross sections {sigma}{sub n}, and photoelectron angular distributions {beta}{sub n} were measured for all possible final ionic states He{sup +}(n) in the region of the double excitations N(K,T){sup A} up to the N=5 threshold. At a photon energy bandpass of 12 meV below the thresholds N=3, 4, and 5, this level of differentiation offers the most critical assessment of the dynamics of the two-electron excitations to date. The experimental data were seen to be very well described by the most advanced theoretical calculations.
Entropy Rate Maps of Complex Excitable Dynamics in Cardiac Monolayers
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Alexander Schlemmer
2015-02-01
Full Text Available The characterization of spatiotemporal complexity remains a challenging task. This holds in particular for the analysis of data from fluorescence imaging (optical mapping, which allows for the measurement of membrane potential and intracellular calcium at high spatial and temporal resolutions and, therefore, allows for an investigation of cardiac dynamics. Dominant frequency maps and the analysis of phase singularities are frequently used for this type of excitable media. These methods address some important aspects of cardiac dynamics; however, they only consider very specific properties of excitable media. To extend the scope of the analysis, we present a measure based on entropy rates for determining spatiotemporal complexity patterns of excitable media. Simulated data generated by the Aliev–Panfilov model and the cubic Barkley model are used to validate this method. Then, we apply it to optical mapping data from monolayers of cardiac cells from chicken embryos and compare our findings with dominant frequency maps and the analysis of phase singularities. The studies indicate that entropy rate maps provide additional information about local complexity, the origins of wave breakup and the development of patterns governing unstable wave propagation.
Periodic responses of a pulley-belt system with one-way clutch under inertia excitation
Ding, Hu
2015-09-01
The stable steady-state periodic response of a two-pulley belt drive system coupled with an accessory by a one-way clutch is presented. For the first time, the pulley-belt system is studied under double excitations. Specifically, the dual excitations consist of harmonic motion of the driving pulley and inertia excitation. The belt spans are modeled as axially moving viscoelastic beams by considering belt bending stiffness. Therefore, integro-partial-differential equations are derived for governing the transverse vibrations of the belt spans. Moreover, the transverse vibrations of the moving belt are coupled with the rotation vibrations of the pulleys by nonlinear dynamic tension. For describing the unidirectional decoupling function of the one-way device, rotation vibrations of the driven pulley and accessory are modeled as coupled piecewise ordinary differential equations. In order to eliminate the influence of the boundary of the belt spans, the non-trivial equilibriums of the pulley-belt system are numerically determined. Furthermore, A nonlinear piecewise discrete-continuous dynamical system is derived by introducing a coordinate transform. Coupled vibrations of the pulley-belt system are investigated via the Galerkin truncation. The natural frequencies of the coupled vibrations are obtained by using the fast Fourier transform. Moreover, frequency-response curves are abstracted from time histories. Therefore, resonance areas of the belt spans, the driven pulley and the accessory are presented. Furthermore, validity of the Galerkin method is examined by comparing with the differential and integral quadrature methods (DQM & IQM). By comparing the results with and without one-way device, significant damping effect of clutch on the dynamic response is discovered. Furthermore, the effects of the intensity of the driving pulley excitation and the inertia excitation are studied. Moreover, numerical results demonstrate that the two excitations interact on the steady
Excited state nucleon spectrum with two flavors of dynamical fermions
International Nuclear Information System (INIS)
Bulava, John M.; Foley, Justin; Morningstar, Colin; Edwards, Robert G.; Joo, Balint; Lin, Huey-Wen; Richards, David G.; Engelson, Eric; Wallace, Stephen J.; Lichtl, Adam; Mathur, Nilmani
2009-01-01
Highly excited states for isospin (1/2) baryons are calculated for the first time using lattice QCD with two flavors of dynamical quarks. Anisotropic lattices are used with two pion masses, m π =416(36) MeV and 578(29) MeV. The lowest four energies are reported in each of the six irreducible representations of the octahedral group at each pion mass. The lattices used have dimensions 24 3 x64, spatial lattice spacing a s ≅0.11 fm, and temporal lattice spacing a t =(1/3)a s . Clear evidence is found for a (5 - /2) state in the pattern of negative-parity excited states. This agrees with the pattern of physical states and spin (5/2) has been realized for the first time on the lattice.
Adaptive Dynamic Surface Control for Generator Excitation Control System
Directory of Open Access Journals (Sweden)
Zhang Xiu-yu
2014-01-01
Full Text Available For the generator excitation control system which is equipped with static var compensator (SVC and unknown parameters, a novel adaptive dynamic surface control scheme is proposed based on neural network and tracking error transformed function with the following features: (1 the transformation of the excitation generator model to the linear systems is omitted; (2 the prespecified performance of the tracking error can be guaranteed by combining with the tracking error transformed function; (3 the computational burden is greatly reduced by estimating the norm of the weighted vector of neural network instead of the weighted vector itself; therefore, it is more suitable for the real time control; and (4 the explosion of complicity problem inherent in the backstepping control can be eliminated. It is proved that the new scheme can make the system semiglobally uniformly ultimately bounded. Simulation results show the effectiveness of this control scheme.
Electronic excited states and relaxation dynamics in polymer heterojunction systems
Ramon, John Glenn Santos
The potential for using conducting polymers as the active material in optoelectronic devices has come to fruition in the past few years. Understanding the fundamental photophysics behind their operations points to the significant role played by the polymer interface in their performance. Current device architectures involve the use of bulk heterojunctions which intimately blend the donor and acceptor polymers to significantly increase not only their interfacial surface area but also the probability of exciton formation within the vicinity of the interface. In this dissertation, we detail the role played by the interface on the behavior and performance of bulk heterojunction systems. First, we explore the relation between the exciton binding energy to the band offset in determining device characteristics. As a general rule, when the exciton binding energy is greater than the band offset, the exciton remains the lowest energy excited state leading to efficient light-emitting properties. On the other hand, if the offset is greater than the binding energy, charge separation becomes favorable leading to better photovoltaic behavior. Here, we use a Wannier function, configuration interaction based approach to examine the essential excited states and predict the vibronic absorption and emission spectra of the PPV/BBL, TFB/F8BT and PFB/F8BT heterojunctions. Our results underscore the role of vibrational relaxation in the formation of charge-transfer states following photoexcitation. In addition, we look at the relaxation dynamics that occur upon photoexcitation. For this, we adopt the Marcus-Hush semiclassical method to account for lattice reorganization in the calculation of the interconversion rates in TFB/F8BT and PFB/F8BT. We find that, while a tightly bound charge-transfer state (exciplex) remains the lowest excited state, a regeneration pathway to the optically active lowest excitonic state in TFB/F8BT is possible via thermal repopulation from the exciplex. Finally
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.
Directory of Open Access Journals (Sweden)
Yuyuan Zhang
2016-11-01
Full Text Available Melamine may have been an important prebiotic information carrier, but its excited-state dynamics, which determine its stability under UV radiation, have never been characterized. The ability of melamine to withstand the strong UV radiation present on the surface of the early Earth is likely to have affected its abundance in the primordial soup. Here, we studied the excited-state dynamics of melamine (a proto-nucleobase and its lysine derivative (a proto-nucleoside using the transient absorption technique with a UV pump, and UV and infrared probe pulses. For melamine, the excited-state population decays by internal conversion with a lifetime of 13 ps without coupling significantly to any photochemical channels. The excited-state lifetime of the lysine derivative is slightly longer (18 ps, but the dominant deactivation pathway is otherwise the same as for melamine. In both cases, the vast majority of excited molecules return to the electronic ground state on the aforementioned time scales, but a minor population is trapped in a long-lived triplet state.
Separating annihilation and excitation energy transfer dynamics in light harvesting systems.
Vengris, Mikas; Larsen, Delmar S; Valkunas, Leonas; Kodis, Gerdenis; Herrero, Christian; Gust, Devens; Moore, Thomas; Moore, Ana; van Grondelle, Rienk
2013-09-26
The dependence of excitation energy transfer kinetics on the electronic state of the acceptor (ground vs excited) has been resolved with a novel multipulse prePump-Pump-Probe spectroscopy. The primary energy transfer and annihilation dynamics in two model light-harvesting systems were explored: an artificially synthesized carotenoid-zinc-phthalocyanine dyad and a naturally occurring light-harvesting peridinin-chlorophyll protein complex from Amphidinium carterae. Both systems use carotenoid as the primary excitation energy donor with porphyrin chromophores as the acceptor molecules. The prePump-Pump-Probe transient signals were analyzed with Monte Carlo modeling to explicitly address the underlying step-by-step kinetics involved in both excitation migration and annihilation processes. Both energy transfer and annihilation dynamics were demonstrated to occur with approximately the same rate in both systems, regardless of the excitation status of the acceptor pigments. The possible reasons for these observations are discussed in the framework of the Förster energy transfer model.
Carrier dynamics in femtosecond-laser-excited bismuth telluride
Wang, J. L.; Guo, L.; Ling, C.; Song, Y. M.; Xu, X. F.; Ni, Z. H.; Chen, Y. F.
2016-04-01
The carrier dynamics of B i2T e3 is studied using the femtosecond pump-probe technique. Three distinct processes, including free carrier absorption, band filling, and electron-hole recombination, are found to contribute to the reflectivity changes. The two-temperature model is used to describe the intraband energy relaxation process of carriers, and the Drude contribution well explains the intensity dependence of the peak values of the nonoscillatory component in the reflectivity signal. The combined effects of free carrier absorption and band filling result in a reflection minimum at about 2 ps after laser excitation. The nonzero background signal increases linearly with the pump fluence, which is attributed to the electron-hole recombination. Finally, our results provide an illustration of investigating the carrier dynamics in semiconductors from the ultrafast reflectivity spectra.
Nonadiabatic excited-state molecular dynamics: On-the-fly limiting of essential excited states
Energy Technology Data Exchange (ETDEWEB)
Nelson, Tammie [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Naumov, Artem [Skolkovo Institute of Science and Technology, Moscow 143026 (Russian Federation); Fernandez-Alberti, Sebastian [Universidad Nacional de Quilmes, Roque Saenz Pea 352, B1876BXD Bernal (Argentina); Tretiak, Sergei, E-mail: serg@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2016-12-20
The simulation of nonadiabatic dynamics in extended molecular systems involving hundreds of atoms and large densities of states is particularly challenging. Nonadiabatic coupling terms (NACTs) represent a significant numerical bottleneck in surface hopping approaches. Rather than using unreliable NACT cutting schemes, here we develop “on-the-fly” state limiting methods to eliminate states that are no longer essential for the non-radiative relaxation dynamics as a trajectory proceeds. We propose a state number criteria and an energy-based state limit. The latter is more physically relevant by requiring a user-imposed energy threshold. For this purpose, we introduce a local kinetic energy gauge by summing contributions from atoms within the spatial localization of the electronic wavefunction to define the energy available for upward hops. The proposed state limiting schemes are implemented within the nonadiabatic excited-state molecular dynamics framework to simulate photoinduced relaxation in poly-phenylene vinylene (PPV) and branched poly-phenylene ethynylene (PPE) oligomers for benchmark evaluation.
Elasto-plastic frame under horizontal and vertical Gaussian excitation
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager; Tarp-Johansen, Niels Jacob; Randrup-Thomsen, S.
1999-01-01
Taking geometric non-linearity into account anoscillator of the form as aportal frame with a rigid traverse and with ideal-elastic ideal-plasticclamped-in columns behaves under horizontalexcitation as an ideal-elastic hardening / softening-plastic oscilator given that the columns carry atension....../compression axial force. Assuming that the horizontal excitationof the traverse is Gaussian white noise, statistics related to the plastic displacement response are determinedby use of simulation based on the Slepian modelprocess method combined with envelope excursion properties. Besidesgiving physical insight...... the method givesgood approximations to results obtained by slow direct simulation of thetotal response. Moreover, the influence of a randomly varying axial column force isinvestigated by direct response simulation. This case corresponds to parametric excitation as generated by the vertical acceleration...
Study on Dynamics of Polygonal Wear of Automotive Tire Caused by Self-Excited Vibration
Directory of Open Access Journals (Sweden)
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.
On the phase-correlation and phase-fluctuation dynamics of a strongly excited Bose gas
Energy Technology Data Exchange (ETDEWEB)
Sakhel, Roger R., E-mail: rogersakhel@yahoo.com [Department of Basic Sciences, Faculty of Information Technology, Isra University, Amman 11622 (Jordan); The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, Trieste 34151 (Italy); Sakhel, Asaad R. [Department of Applied Sciences, Faculty of Engineering Technology, Balqa Applied University, Amman 11134 (Jordan); The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, Trieste 34151 (Italy); Ghassib, Humam B. [Department of Physics, The University of Jordan, Amman 11942 (Jordan)
2015-12-01
The dynamics of a Bose–Einstein condensate (BEC) is explored in the wake of a violent excitation caused by a strong time-dependent deformation of a trapping potential under the action of an intense stirring laser. The system is a two-dimensional BEC confined to a power-law trap with hard-wall boundaries. The stirring agent is a moving red-detuned laser potential. The time-dependent Gross–Pitaevskii equation is solved numerically by the split-step Crank–Nicolson method in real time. The phase correlations and phase fluctuations are examined as functions of time to demonstrate the evolving properties of a strongly-excited BEC. Of special significance is the occurrence of spatial fluctuations while the condensate is being excited. These oscillations arise from stirrer-induced density fluctuations. While the stirrer is inside the trap, a reduction in phase coherence occurs, which is attributed to phase fluctuations.
Nonlinear Resonance Analysis of Slender Portal Frames under Base Excitation
Directory of Open Access Journals (Sweden)
Luis Fernando Paullo Muñoz
2017-01-01
Full Text Available The dynamic nonlinear response and stability of slender structures in the main resonance regions are a topic of importance in structural analysis. In complex problems, the determination of the response in the frequency domain indirectly obtained through analyses in time domain can lead to huge computational effort in large systems. In nonlinear cases, the response in the frequency domain becomes even more cumbersome because of the possibility of multiple solutions for certain forcing frequencies. Those solutions can be stable and unstable, in particular saddle-node bifurcation at the turning points along the resonance curves. In this work, an incremental technique for direct calculation of the nonlinear response in frequency domain of plane frames subjected to base excitation is proposed. The transformation of equations of motion to the frequency domain is made through the harmonic balance method in conjunction with the Galerkin method. The resulting system of nonlinear equations in terms of the modal amplitudes and forcing frequency is solved by the Newton-Raphson method together with an arc-length procedure to obtain the nonlinear resonance curves. Suitable examples are presented, and the influence of the frame geometric parameters and base motion on the nonlinear resonance curves is investigated.
Influence of Road Excitation and Steering Wheel Input on Vehicle System Dynamic Responses
Directory of Open Access Journals (Sweden)
Zhen-Feng Wang
2017-06-01
Full Text Available Considering the importance of increasing driving safety, the study of safety is a popular and critical topic of research in the vehicle industry. Vehicle roll behavior with sudden steering input is a main source of untripped rollover. However, previous research has seldom considered road excitation and its coupled effect on vehicle lateral response when focusing on lateral and vertical dynamics. To address this issue, a novel method was used to evaluate effects of varying road level and steering wheel input on vehicle roll behavior. Then, a 9 degree of freedom (9-DOF full-car roll nonlinear model including vertical and lateral dynamics was developed to study vehicle roll dynamics with or without of road excitation. Based on a 6-DOF half-car roll model and 9-DOF full-car nonlinear model, relationship between three-dimensional (3-D road excitation and various steering wheel inputs on vehicle roll performance was studied. Finally, an E-Class (SUV level car model in CARSIM® was used, as a benchmark, with and without road input conditions. Both half-car and full-car models were analyzed under steering wheel inputs of 5°, 10° and 15°. Simulation results showed that the half-car model considering road input was found to have a maximum accuracy of 65%. Whereas, the full-car model had a minimum accuracy of 85%, which was significantly higher compared to the half-car model under the same scenario.
Directory of Open Access Journals (Sweden)
Yan Deng
2014-10-01
Full Text Available A novel multifrequency excitation (MFE method is proposed to realize rapid and accurate dynamic testing of micromachined gyroscope chips. Compared with the traditional sweep-frequency excitation (SFE method, the computational time for testing one chip under four modes at a 1-Hz frequency resolution and 600-Hz bandwidth was dramatically reduced from 10 min to 6 s. A multifrequency signal with an equal amplitude and initial linear-phase-difference distribution was generated to ensure test repeatability and accuracy. The current test system based on LabVIEW using the SFE method was modified to use the MFE method without any hardware changes. The experimental results verified that the MFE method can be an ideal solution for large-scale dynamic testing of gyroscope chips and gyroscopes.
Multiple spatially localized dynamical states in friction-excited oscillator chains
Papangelo, A.; Hoffmann, N.; Grolet, A.; Stender, M.; Ciavarella, M.
2018-03-01
Friction-induced vibrations are known to affect many engineering applications. Here, we study a chain of friction-excited oscillators with nearest neighbor elastic coupling. The excitation is provided by a moving belt which moves at a certain velocity vd while friction is modelled with an exponentially decaying friction law. It is shown that in a certain range of driving velocities, multiple stable spatially localized solutions exist whose dynamical behavior (i.e. regular or irregular) depends on the number of oscillators involved in the vibration. The classical non-repeatability of friction-induced vibration problems can be interpreted in light of those multiple stable dynamical states. These states are found within a "snaking-like" bifurcation pattern. Contrary to the classical Anderson localization phenomenon, here the underlying linear system is perfectly homogeneous and localization is solely triggered by the friction nonlinearity.
Excited-State Dynamics of Oxyluciferin in Firefly Luciferase
Snellenburg, Joris J.
2016-11-23
The color variations of light emitted by some natural and mutant luciferases are normally attributed to collective factors referred to as microenvironment effects; however, the exact nature of these interactions between the emitting molecule (oxyluciferin) and the active site remains elusive. Although model studies of noncomplexed oxyluciferin and its variants have greatly advanced the understanding of its photochemistry, extrapolation of the conclusions to the real system requires assumptions about the polarity and proticity of the active site. To decipher the intricate excited-state dynamics, global and target analysis is performed here for the first time on the steady-state and time-resolved spectra of firefly oxyluciferin complexed with luciferase from the Japanese firefly (Luciola cruciata). The experimental steady-state and time resolved luminescence spectra of the oxyluciferin/luciferase complex in solution are compared with the broadband time-resolved firefly bioluminescence recorded in vivo. The results demonstrate that de-excitation of the luminophore results in a complex cascade of photoinduced proton transfer processes and can be interpreted by the pH dependence of the emitted light. It is confirmed that proton transfer is the central event in the spectrochemistry of this system for which any assignment of the pH dependent emission to a single chemical species would be an oversimplification.
Effective Micro Grid Stability Under Excitation Limiters in Islanded and Connected Modes
Tashakori, Sajad; Tavakoli, Amir; Mirzaei, Farzad
2017-01-01
International audience; In this paper the authors tried to design a under excitation limiter and a power system stabilizer which can operate without any kind of interaction. The under excitation limiter (UEL) is intended to prevent reduction of generator excitation to a level where the steady state stability limit or the stator core end-region heating limit is exceeded. The power system stabilizer (PSS) uses auxiliary stabilizing signals to control the excitation system so as to improve power...
Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation
Yin, Yudan; Niu, Lin; Zhu, Xiaocui; Zhao, Meiping; Zhang, Zexin; Mann, Stephen; Liang, Dehai
2016-02-01
Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media.
Multi-pulse orbits and chaotic dynamics in motion of parametrically excited viscoelastic moving belt
International Nuclear Information System (INIS)
Zhang Wei; Yao Minghui
2006-01-01
In this paper, the Shilnikov type multi-pulse orbits and chaotic dynamics of parametrically excited viscoelastic moving belt are studied in detail. Using Kelvin-type viscoelastic constitutive law, the equations of motion for viscoelastic moving belt with the external damping and parametric excitation are given. The four-dimensional averaged equation under the case of primary parametric resonance is obtained by directly using the method of multiple scales and Galerkin's approach to the partial differential governing equation of viscoelastic moving belt. From the averaged equations obtained here, the theory of normal form is used to give the explicit expressions of normal form with a double zero and a pair of pure imaginary eigenvalues. Based on normal form, the energy-phrase method is employed to analyze the global bifurcations and chaotic dynamics in parametrically excited viscoelastic moving belt. The global bifurcation analysis indicates that there exist the heteroclinic bifurcations and the Silnikov type multi-pulse homoclinic orbits in the averaged equation. The results obtained above mean the existence of the chaos for the Smale horseshoe sense in parametrically excited viscoelastic moving belt. The chaotic motions of viscoelastic moving belts are also found by using numerical simulation. A new phenomenon on the multi-pulse jumping orbits is observed from three-dimensional phase space
Hydrodynamic response of viscous fluids under seismic excitation
International Nuclear Information System (INIS)
Ma, D.C.
1993-01-01
Hydrodynamic response of liquid-tank systems, such as reactor vessels, spent-fuel pools and liquid storage tanks have been studied extensively in the last decade (Chang et al. 1988; Ma et al. 1991). However, most of the studies are conducted with the assumption of an inviscid fluid. In recent years, the hydrodynamic response of viscous fluids has received increasing attention in high level waste storage tanks containing viscous waste material. This paper presents a numerical study on the hydrodynamic response of viscous fluids in a large 2-D fluid-tank system under seismic excitation. Hydrodynamic responses (i.e. sloshing wave height, fluid pressures, shear stress, etc.) are calculated for a fluid with various viscosities. Four fluid viscosities are considered. They are 1 cp, 120 cp, 1,000 cp and 12,000 cp (1 cp = 1.45 x 10 -7 lb-sec/in 2 ). Note that the liquid sodium of the Liquid-Metal Reactor (LMR) reactor has a viscosity of 1.38 x 10 -5 lb-sec/in 2 (about 95 cp) at an operational temperature of 900 degree F. Section 2 describes the pertinent features of the mathematical model. In Section 3, the fundamental sloshing phenomena of viscous fluid are examined. Sloshing wave height and shear stress for fluid with different viscosities are compared. The conclusions are given in Section 4
Fluorescence study of some xanthine dyes under stepped laser excitation
International Nuclear Information System (INIS)
Chirkova, L.V.; Ketsle, G.A.; Ermagambetov, K.T.
1996-01-01
Paper is devoted to definition of triplet state in molecules of xanthine dyes and study of intramolecular energy circulation. Stepped two-quanta excitation of dyes has been carried out with help of experimental unit. Intensive luminescence activated by excitation of triplet molecules of dyes within triplet-triplet band with wave length of 1060 nm was registered for eosin. Given luminescence spectrally coincides with fast fluorescence. 5 refs., 6 figs
An excitable cortex and memory model successfully predicts new pseudopod dynamics.
Directory of Open Access Journals (Sweden)
Robert M Cooper
Full Text Available Motile eukaryotic cells migrate with directional persistence by alternating left and right turns, even in the absence of external cues. For example, Dictyostelium discoideum cells crawl by extending distinct pseudopods in an alternating right-left pattern. The mechanisms underlying this zig-zag behavior, however, remain unknown. Here we propose a new Excitable Cortex and Memory (EC&M model for understanding the alternating, zig-zag extension of pseudopods. Incorporating elements of previous models, we consider the cell cortex as an excitable system and include global inhibition of new pseudopods while a pseudopod is active. With the novel hypothesis that pseudopod activity makes the local cortex temporarily more excitable--thus creating a memory of previous pseudopod locations--the model reproduces experimentally observed zig-zag behavior. Furthermore, the EC&M model makes four new predictions concerning pseudopod dynamics. To test these predictions we develop an algorithm that detects pseudopods via hierarchical clustering of individual membrane extensions. Data from cell-tracking experiments agrees with all four predictions of the model, revealing that pseudopod placement is a non-Markovian process affected by the dynamics of previous pseudopods. The model is also compatible with known limits of chemotactic sensitivity. In addition to providing a predictive approach to studying eukaryotic cell motion, the EC&M model provides a general framework for future models, and suggests directions for new research regarding the molecular mechanisms underlying directional persistence.
Nonlinear dynamics of a sliding beam on two supports under ...
Indian Academy of Sciences (India)
Abstract. This study deals with the nonlinear dynamics associated with large deformation of a beam sliding on two-knife edge supports under external excitation. The beam is referred to as a Gospodnetic–Frisch-Fay beam, after the researchers who reported its static deformation in closed form. The freedom of the beam to ...
Excited-State Dynamics of Carotenoids Studied by Femtosecond Transient Absorption Spectroscopy
International Nuclear Information System (INIS)
Lee, Ingu; Pang, Yoonsoo; Lee, Sebok
2014-01-01
Carotenoids, natural antenna pigments in photosynthesis share a symmetric backbone of conjugated polyenes. Contrary to the symmetric and almost planar geometries of carotenoids, excited state structure and dynamics of carotenoids are exceedingly complex. In this paper, recent infrared and visible transient absorption measurements and excitation dependent dynamics of 8'-apo-β-caroten-8'-al and 7',7'-dicyano-7'-apo-β-carotene will be reviewed. The recent visible transient absorption measurements of 8'-apo-β-caroten-8'-al in polar and nonpolar solvents will also be introduced to emphasize the complex excited-state dynamics and unsolved problems in the S 2 and S 1 excited states
Sobhy, M. A.
2011-11-07
Single-molecule fluorescence imaging is at the forefront of tools applied to study biomolecular dynamics both in vitro and in vivo. The ability of the single-molecule fluorescence microscope to conduct simultaneous multi-color excitation and detection is a key experimental feature that is under continuous development. In this paper, we describe in detail the design and the construction of a sophisticated and versatile multi-color excitation and emission fluorescence instrument for studying biomolecular dynamics at the single-molecule level. The setup is novel, economical and compact, where two inverted microscopes share a laser combiner module with six individual laser sources that extend from 400 to 640 nm. Nonetheless, each microscope can independently and in a flexible manner select the combinations, sequences, and intensities of the excitation wavelengths. This high flexibility is achieved by the replacement of conventional mechanical shutters with acousto-optic tunable filter (AOTF). The use of AOTF provides major advancement by controlling the intensities, duration, and selection of up to eight different wavelengths with microsecond alternation time in a transparent and easy manner for the end user. To our knowledge this is the first time AOTF is applied to wide-field total internal reflection fluorescence (TIRF) microscopy even though it has been commonly used in multi-wavelength confocal microscopy. The laser outputs from the combiner module are coupled to the microscopes by two sets of four single-mode optic fibers in order to allow for the optimization of the TIRF angle for each wavelength independently. The emission is split into two or four spectral channels to allow for the simultaneous detection of up to four different fluorophores of wide selection and using many possible excitation and photoactivation schemes. We demonstrate the performance of this new setup by conducting two-color alternating excitation single-molecule fluorescence resonance energy
Photoluminescence and excited states dynamics in PbWO4:Pr3+ crystals
Auffray, E; Shalapska, T; Zazubovich, S
2014-01-01
Luminescence and photo-thermally stimulated defects creation processes are studied for a Pr3+-doped PbWO4 crystal at 4.2-400 K under excitation in the band-to-band, exciton, and charge-transfer transitions regions, as well as in the Pr3+-related absorption bands. Emission spectra of Pr3+ centers depend on the excitation energy, indicating the presence of Pr3+ centers of two types. The origin of these centers is discussed. The 2.03-2.06 eV emission, arising from the D-1(2) -> H-3(4) transitions of Pr3+ ions, is found to be effectively excited in a broad intense absorption band peaking at 4.2 K at 3.92 eV. By analogy with some other Pe(3+)-doped compounds, this band is suggested to arise from an electron transfer from an impurity Pr3+ ion to the crystal lattice W6+ or Pb2+ ions. The dynamics of the Pr3+-related excited states is clarified. In the PbWO4:Pr crystal studied, the concentration of single oxygen and lead vacancies as traps for electrons and holes is found to be negligible.
Dynamics of spiral waves in excitable media subjected to external periodic forcing
Schrader, A.; Braune, M.; Engel, H.
1995-07-01
We provide a survey of the behavior of meandering spiral waves in excitable media under periodic modulation of excitability. Model calculations were performed in a modified Oregonator model for the photosensitive Belousov-Zhabotinsky reaction. The spiral's dynamic is followed by its tip motion. We find mode locking if the path curvature period is a rational multiple of the modulation period and resonance response of the spiral's rotation period. A general ordering structure in terms of the Farey tree is observed. The complex motion of the spiral's tip is found to be composed of harmonics of the modulation period. For large forcing amplitudes we observe an overlap of entrainment bands resulting in bi- stable behavior and in the breakup of the spiral at the end of the major entrainment band.
Energy Technology Data Exchange (ETDEWEB)
Tully, John C. [Yale Univ., New Haven, CT (United States)
2017-06-10
Chemical reactions are often facilitated and steered when carried out on solid surfaces, essential for applications such as heterogeneous catalysis, solar energy conversion, corrosion, materials processing, and many others. A critical factor that can determine the rates and pathways of chemical reactions at surfaces is the efficiency and specificity of energy transfer; how fast does energy move around and where does it go? For reactions on insulator surfaces energy transfer generally moves in and out of vibrations of the adsorbed molecule and the underlying substrate. By contrast, on metal surfaces, metallic nanoparticles and semiconductors, another pathway for energy flow opens up, excitation and de-excitation of electrons. This so-called “nonadiabatic” mechanism often dominates the transfer of energy and can directly impact the course of a chemical reaction. Conventional computational methods such as molecular dynamics simulation do not account for this nonadiabatic behavior. The current DOE-BES funded project has focused on developing the underlying theoretical foundation and the computational methodology for the prediction of nonadiabatic chemical reaction dynamics at surfaces. The research has successfully opened up new methodology and new applications for molecular simulation. In particular, over the last three years, the “Electronic Friction” theory, pioneered by the PI, has now been developed into a stable and accurate computational method that is sufficiently practical to allow first principles “on-the-fly” simulation of chemical reaction dynamics at metal surfaces.
Excitation of blade vibration under rotation by synchronous electromagnet
Czech Academy of Sciences Publication Activity Database
Pešek, Luděk; Vaněk, František; Bula, Vítězslav; Cibulka, Jan
2011-01-01
Roč. 18, 3/4 (2011), s. 1-9 ISSN 1802-1484 R&D Projects: GA ČR GA101/09/1166 Institutional research plan: CEZ:AV0Z20760514 Keywords : blade * vibration * excitation * electromagnet Subject RIV: BI - Acoustics
Energy Technology Data Exchange (ETDEWEB)
Bjorgaard, J. A., E-mail: jbjorgaard@lanl.gov [Center for Nonlinear Studies, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Velizhanin, K. A. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Tretiak, S., E-mail: serg@lanl.gov [Center for Integrated Nanotechnologies, Center for Nonlinear Studies, and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2016-04-21
The effects of solvent on molecular processes such as excited state relaxation and photochemical reaction often occurs in a nonequilibrium regime. Dynamic processes such as these can be simulated using excited state molecular dynamics. In this work, we describe methods of simulating nonequilibrium solvent effects in excited state molecular dynamics using linear-response time-dependent density functional theory and apparent surface charge methods. These developments include a propagation method for solvent degrees of freedom and analytical energy gradients for the calculation of forces. Molecular dynamics of acetaldehyde in water or acetonitrile are demonstrated where the solute-solvent system is out of equilibrium due to photoexcitation and emission.
Effect of normal stress under an excitation in poroelastic flat slabs ...
African Journals Online (AJOL)
Effect of normal stress under an excitation in poroelastic flat slabs. BS Rani, T Ramesh, PM Reddy. Abstract. Biot's poroelastic theory is employed to investigate stresses under an excitation in an infinite poroelastic slab of arbitrary thickness. Both for pervious and impervious surfaces, the radial normal stress is obtained, and ...
Resonantly excited exciton dynamics in two-dimensional MoSe2 monolayers
Scarpelli, L.; Masia, F.; Alexeev, E. M.; Withers, F.; Tartakovskii, A. I.; Novoselov, K. S.; Langbein, W.
2017-07-01
We report on the exciton and trion density dynamics in a single layer of MoSe2, resonantly excited and probed using three-pulse four-wave mixing (FWM), at temperatures from 300 K to 77 K. A multiexponential third-order response function for amplitude and phase of the heterodyne-detected FWM signal including four decay processes is used to model the data. We provide a consistent interpretation within the intrinsic band structure, not requiring the inclusion of extrinsic effects. We find an exciton radiative lifetime in the subpicosecond range consistent to what has been recently reported by Jakubczyk et al. [Nano Lett. 16, 5333 (2016), 10.1021/acs.nanolett.6b01060]. After the dominating radiative decay, the remaining exciton density, which has been scattered from the initially excited direct spin-allowed radiative state into dark states of different nature by exciton-phonon scattering or disorder scattering, shows a slower dynamics, covering 10-ps to 10-ns time scales. This includes direct spin-allowed transitions with larger in-plane momentum, as well as indirect and spin-forbidden exciton states. We find that exciton-exciton annihilation is not relevant in the observed dynamics, in variance from previous finding under nonresonant excitation. The trion density at 77 K reveals a decay of the order of 1 ps, similar to what is observed for the exciton. After few tens of picoseconds, the trion dynamics resembles the one of the exciton, indicating that trion ionization occurs on this time scale.
Dynamic performance estimation of stator voltage regulator in rotary exciter system with DC exciter
Directory of Open Access Journals (Sweden)
Stojić Đorđe
2011-01-01
Full Text Available In this paper, procedure for AVR parameter estimation is proposed, based on step responses when synchronous generator in idle run. The exciter system includes AVR, thyristor rectifier and DC exciter. AVR is realized in the form of cascade control structure with two control loops. PID controller in the outer loop represents the primary controller. P controller in the inner loop represents secondary controller which enables the faster field current response time. The aim of procedure is to determine equivalent gain of PID controller and thyristor rectifier. The measurements used in the parameter estimation procedure are taken from fossil power plant 'Kolubara A', aggregate A5.
Multi-stage identification scheme for detecting damage in structures under ambient excitations
International Nuclear Information System (INIS)
Bao, Chunxiao; Li, Zhong-Xian; Hao, Hong
2013-01-01
Structural damage identification methods are critical to the successful application of structural health monitoring (SHM) systems to civil engineering structures. The dynamic response of civil engineering structures is usually characterized by high nonlinearity and non-stationarity. Accordingly, an improved Hilbert–Huang transform (HHT) method which is adaptive, output-only and applicable to system identification of in-service structures under ambient excitations is developed in this study. Based on this method, a multi-stage damage detection scheme including the detection of damage occurrence, damage existence, damage location and the estimation of damage severity is developed. In this scheme, the improved HHT method is used to analyse the structural acceleration response, the obtained instantaneous frequency detects the instant of damage occurrence, the instantaneous phase is sensitive to minor damage and provides reliable damage indication, and the damage indicator developed based on statistical analysis of the Hilbert marginal spectrum detects damage locations. Finally, the response sampled at the detected damage location is continuously analysed to estimate the damage severity. Numerical and experimental studies of frame structures under ambient excitations are performed. The results demonstrate that this scheme accomplishes the above damage detection functions within one flow. It is robust, time efficient, simply implemented and applicable to the real-time SHM of in-service structures. (paper)
An Experimental and Theoretical Investigation of a Micromirror Under Mixed-Frequency Excitation
Ilyas, Saad
2015-01-12
We present an experimental and theoretical investigation of a micromachined mirror under a mixed-frequency signal composed of two harmonic ac sources. The micromirror is made of polyimide as the main structural layer. The experimental and theoretical dynamics are explored via frequency sweeps in the desired neighborhoods. One frequency is fixed while the other frequency is swept through a wide range to study the dynamic responses. To simulate the behavior of the micromirror, it is modeled as a single degree of freedom system, where the parameters of the model are extracted experimentally. A good agreement is reported among the simulation results and the experimental data. These responses are studied under different frequencies and input voltages. The results show interesting dynamics, where the system exhibits primary resonance and combination resonances of additive and subtractive type. The mixed excitation is demonstrated as a way to increase the bandwidth of the resonator near primary resonance, which can be promising for resonant sensing applications in the effort to increase the signal-noise ratio over extended frequency range.
Predissociation and Quenching Dynamics of Electronically Excited Hydroxyl Radicals
National Research Council Canada - National Science Library
Lester, Marsha
2004-01-01
.... Significant progress has been made on three different fronts: (1) simulation of ultraviolet emission data from the Space Shuttle's thruster plume as originating from solar-induced and collision-induced electronic excitation of hydroxyl radicals; (2...
Control of base-excited dynamical systems through piezoelectric energy harvesting absorber
Abdelmoula, H.; Dai, H. L.; Abdelkefi, A.; Wang, L.
2017-09-01
The spring-mass absorber usually offers a good control to dynamical systems under direct base excitations for a specific value of the excitation frequency. As the vibrational energy of a primary dynamical system is transferred to the absorber, it gets dissipated. In this study, this energy is no longer dissipated but converted to available electrical power by designing efficient energy harvesters. A novel design of a piezoelectric beam installed inside an elastically-mounted dynamical system undergoing base excitations is considered. A design is carried out in order to determine the properties and dimensions of the energy harvester with the constraint of simultaneously decreasing the oscillating amplitudes of the primary dynamical system and increasing the harvested power of the energy harvesting absorber. An analytical model for the coupled system is constructed using Euler-Lagrange principle and Galerkin discretization. Different strategies for controlling the primary structure displacement and enhancing the harvested power as functions of the electrical load resistance and thickness of the beam substrate are performed. The linear polynomial approximation of the system’s key parameters as a function of the beam’s substrate thickness is first carried out. Then, the gradient method is applied to determine the adequate values of the electrical load resistance and thickness of the substrate under the constraints of minimizing the amplitudes of the primary structure or maximizing the levels of the harvested power. After that, an iterative strategy is considered in order to simultaneously minimize the amplitudes of the primary structure and maximize the levels of the harvested power as functions of the thickness of the substrate and electrical load resistance. In addition to harmonic excitations, the coupled system subjected to a white noise is explored. Through this analysis, the load resistance and thickness of the substrate of the piezoelectric energy harvester
Dynamics of the excited state intramolecular charge transfer
International Nuclear Information System (INIS)
Joo, T.; Kim, C.H.
2006-01-01
The 6-dodecanoyl-2-dimethylaminonaphtalene (laurdan), a derivative of 6-propanoyl- 2-dimethylaminonaphthalene (prodan), has been used as a fluorescent probe in cell imaging, especially in visualizing the lipid rafts by the generalized polarization (GP) images, where GP=(I 440 -I 490 )/(I 440 +I 490 ) with I being the fluorescence intensity. The fluorescence spectrum of laurdan is sensitive to its dipolar environment due to the intramolecular charge transfer (ICT) process in S 1 state, which results in a dual emission from the locally excited (LE) and the ICT states. The ICT process and the solvation of the ICT state are very sensitive to the dipolar nature of the environment. In this work, the ICT of laurdan in ethanol has been studied by femtosecond time resolved fluorescence (TRF), especially TRF spectra measurement without the conventional spectral reconstruction method. TRF probes the excited states exclusively, a unique advantage over the pump/probe transient absorption technique, although time resolution of the TRF is generally lower than transient absorption and the TRF spectra measurement was possible only though the spectral reconstruction. Over the years, critical advances in TRF technique have been made in our group to achieve <50 fs time resolution with direct full spectra measurement capability. Detailed ICT and the subsequent solvation processes can be visualized unambiguously from the TRF spectra. Fig. 1 shows the TRF spectra of laurdan in ethanol at several time delays. Surprisingly, two bands at 433 and 476 nm are clearly visible in the TRF spectra of laurdan even at T = 0 fs. As time increases, the band at 476 nm shifts to the red while its intensity increases. The band at 433 nm also shifts slightly to the red, but loses intensity as time increases. The intensity of the 476 nm band reaches maximum at around 5 ps, where it is roughly twice as intense as that at 0 fs, and stays constant until lifetime decay is noticeable. The spectra were fit by
Soriano, Diogo C.; Santos, Odair V. dos; Suyama, Ricardo; Fazanaro, Filipe I.; Attux, Romis
2018-03-01
This work has a twofold aim: (a) to analyze an alternative approach for computing the conditional Lyapunov exponent (λcmax) aiming to evaluate the synchronization stability between nonlinear oscillators without solving the classical variational equations for the synchronization error dynamical system. In this first framework, an analytic reference value for λcmax is also provided in the context of Duffing master-slave scenario and precisely evaluated by the proposed numerical approach; (b) to apply this technique to the study of synchronization stability in chaotic Hindmarsh-Rose (HR) neuronal models under uni- and bi-directional resistive coupling and different excitation bias, which also considered the root mean square synchronization error, information theoretic measures and asymmetric transfer entropy in order to offer a better insight of the synchronization phenomenon. In particular, statistical and information theoretical measures were able to capture similarity increase between the neuronal oscillators just after a critical coupling value in accordance to the largest conditional Lyapunov exponent behavior. On the other hand, transfer entropy was able to detect neuronal emitter influence even in a weak coupling condition, i.e. under the increase of conditional Lyapunov exponent and apparently desynchronization tendency. In the performed set of numerical simulations, the synchronization measures were also evaluated for a two-dimensional parameter space defined by the neuronal coupling (emitter to a receiver neuron) and the (receiver) excitation current. Such analysis is repeated for different feedback couplings as well for different (emitter) excitation currents, revealing interesting characteristics of the attained synchronization region and conditions that facilitate the emergence of the synchronous behavior. These results provide a more detailed numerical insight of the underlying behavior of a HR in the excitation and coupling space, being in accordance
DEFF Research Database (Denmark)
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...
Sun, Jiaojiao; Xu, Wei; Lin, Zifei
2018-01-01
In this paper, the reliability of a non-linearly damped friction oscillator under combined additive and multiplicative Gaussian white noise excitations is investigated. The stochastic averaging method, which is usually applied to the research of smooth system, has been extended to the study of the reliability of non-smooth friction system. The results indicate that the reliability of friction system can be improved by Coulomb friction and reduced by random excitations. In particular, the effect of the external random excitation on the reliability is larger than the effect of the parametric random excitation. The validity of the analytical results is verified by the numerical results.
Mössbauer spectroscopy under acoustical excitation: thick target effects
Sadykov, E. K.; Yurichuk, A. A.; Vagizov, F. G.; Mubarakshin, Sh. I.; Valiullin, A. A.
2017-11-01
A new model of Mössbauer absorption (transmission) spectra with an adequate analysis of the possible effects of acoustic excitation in the thick targets is proposed. In particular, the dependence of the line width of acoustical satellites on the degree of phase correlation of the sound oscillations of resonant nuclei in the target is established by calculations and confirmed in experiment. Such a model is stimulated by an increase in the informativeness of the Mössbauer experiments, using thick samples in ultrasound (US) field, and by possible applications of this research technique. The test measurements of Mössbauer absorption spectra on stainless steel are carried out. The fitting of these spectra confirms the relevance of modifications of the model base of Mössbauer processes in US field.
Otobe, T.
2017-12-01
Analytical formulation of subcycle modulation (SCM) of dielectrics including electron excitation is presented. The SCM is sensitive to not only the time-resolved dynamical Franz-Keldysh effect (Tr-DFKE) [T. Otobe et al., Phys. Rev. B 93, 045124 (2016), 10.1103/PhysRevB.93.045124], which is the nonlinear response without the electron excitation, but also the excited electrons. The excited electrons enhance the modulation with even harmonics of pump laser frequency, and generate the odd-harmonics components. The new aspect of SCM is a consequence of (i) the interference between the electrons excited by the pump laser and those excited by the probe-pulse laser and (ii) oscillation of the generated wave packed by the pump laser. When the probe- and pump-pulse polarizations are parallel, the enhancement of the even harmonics and the generation of the odd-harmonics modulation appear. However, if the polarizations are orthogonal, the effect arising from the electron excitations becomes weak. By comparing the parabolic and cosine band models, I found that the electrons under the intense laser field move as quasifree particles.
Peak earthquake response of structures under multi-component excitations
Song, Jianwei; Liang, Zach; Chu, Yi-Lun; Lee, George C.
2007-12-01
Accurate estimation of the peak seismic responses of structures is important in earthquake resistant design. The internal force distributions and the seismic responses of structures are quite complex, since ground motions are multi-directional. One key issue is the uncertainty of the incident angle between the directions of ground motion and the reference axes of the structure. Different assumed seismic incidences can result in different peak values within the scope of design spectrum analysis for a given structure and earthquake ground motion record combination. Using time history analysis to determine the maximum structural responses excited by a given earthquake record requires repetitive calculations to determine the critical incident angle. This paper presents a transformation approach for relatively accurate and rapid determination of the maximum peak responses of a linear structure subjected to three-dimensional excitations within all possible seismic incident angles. The responses can be deformations, internal forces, strains and so on. An irregular building structure model is established using SAP2000 program. Several typical earthquake records and an artificial white noise are applied to the structure model to illustrate the variation of the maximum structural responses for different incident angles. Numerical results show that for many structural parameters, the variation can be greater than 100%. This method can be directly applied to time history analysis of structures using existing computer software to determine the peak responses without carrying out the analyses for all possible incident angles. It can also be used to verify and/or modify aseismic designs by using response spectrum analysis.
Directory of Open Access Journals (Sweden)
Agung Budipriyanto
2014-08-01
Full Text Available Identifying dynamic characteristics of civil engineering structures is still a challenging task. It intends to assess behavior of the structures under time-dependent loads. This paper discusses a methodology suitable for identifying the characteristics of multi-story buildings using only their measured response under earthquake ground excitations. Appropriateness of technique used for structural identification was corroborated through coherence of the structure’s responses. The methodology was applied for identifying the characteristics of 14-story and 20-story office buildings located in a high seismic region. Responses of these two buildings recorded during three different seismic ground motions were investigated. The buildings’ response spectral densities and singular values were computed and utilized to identify their dynamic characteristics, viz. modal frequencies, damping factors, and mode types such as bending or torsion mode. Results of this study were validated through comparisons with the results reported using different structural identification techniques. It indicated that the methodology implemented in this study was capable of identifying the dynamic characteristics of multi-story buildings using responses under seismic ground motions.
Non-adiabatic rotational excitation of dipolar molecule under the ...
Indian Academy of Sciences (India)
NAREX is useful for studies on quantum state resolved collision or reaction dynamics of highly anisotropic state. NAREX can become an important tool for changing and controlling the rotational state distribu- tion of molecules, especially when recent elaborate methods i.e. double-pulse pair28 and shaped pulses29,30.
Beck, Warren F; Bishop, Michael M; Roscioli, Jerome D; Ghosh, Soumen; Frank, Harry A
2015-04-15
A consideration of the excited state potential energy surfaces of carotenoids develops a new hypothesis for the nature of the conformational motions that follow optical preparation of the S2 (1(1)Bu(+)) state. After an initial displacement from the Franck-Condon geometry along bond length alternation coordinates, it is suggested that carotenoids pass over a transition-state barrier leading to twisted conformations. This hypothesis leads to assignments for several dark intermediate states encountered in femtosecond spectroscopic studies. The Sx state is assigned to the structure reached upon the onset of torsional motions near the transition state barrier that divides planar and twisted structures on the S2 state potential energy surface. The X state, detected recently in two-dimensional electronic spectra, corresponds to a twisted structure well past the barrier and approaching the S2 state torsional minimum. Lastly, the S(∗) state is assigned to a low lying S1 state structure with intramolecular charge transfer character (ICT) and a pyramidal conformation. It follows that the bent and twisted structures of carotenoids that are found in photosynthetic light-harvesting proteins yield excited-state structures that favor the development of an ICT character and optimized energy transfer yields to (bacterio)chlorophyll acceptors. Copyright © 2015 Elsevier Inc. All rights reserved.
Concentration enhanced red upconversion in nanocrystalline ZrO{sub 2} : Er under IR excitation
Energy Technology Data Exchange (ETDEWEB)
Diaz-Torres, L A [Centro de Investigaciones en Optica A.C., Leon, Gto., C.P. 37000 Mexico (Mexico); Rosa-Cruz, E De la [Centro de Investigaciones en Optica A.C., Leon, Gto., C.P. 37000 Mexico (Mexico); Salas, P [Instituto Mexicano del Petroleo, Cd. de Mexico, D.F. Mexico 07730 (Mexico); Angeles-Chavez, C [Instituto Mexicano del Petroleo, Cd. de Mexico, D.F. Mexico 07730 (Mexico)
2004-09-21
The effects of Er{sup 3+} concentration in ZrO{sub 2} on the red (680 nm) and green (545 nm) upconversion emission from Er{sup 3+} under near infrared radiation (NIR) excitation (at both 1438 and 962 nm) are presented. For the highest Er{sup 3+} concentration used, the red band is almost quenched under VIS (489 nm) excitation, whereas it is enhanced under NIR excitation. Such a difference between photoluminescence and upconversion is explained taking into account the concentration dependent cross-relaxation process ({sup 2}H{sub 11/2} + {sup 4}I{sub 15/2}) {yields} ({sup 4}I{sub 9/2} + {sup 4}I{sub 13/2}). Experimental results suggest that two- and three-photon upconversion processes are taking place under 962 nm and 1438 nm excitation, respectively.
Dynamic performance of slender suspension footbridges under eccentric walking dynamic loads
Huang, Ming-Hui; Thambiratnam, David P.; Perera, Nimal J.
2007-06-01
This paper treats the vibration of slender suspension footbridges caused by eccentrically distributed walking dynamic loads. A suspension footbridge model with reverse profiled cables in both the vertical and horizontal planes was used in this conceptual study, while SAP2000 package is adopted in the numerical analysis. The dynamic behaviour of slender footbridges under walking dynamic loads is simulated by resonant vibration caused by synchronous excitations. It is found that slender suspension footbridges with shallow cable profiles often have coupled vibration modes such as coupled lateral-torsional or coupled torsional-lateral modes. When these coupled vibration modes are excited by walking pedestrians, excessive lateral vibration can be induced. Results also show that the effects of the reverse profiled cables on the dynamic performance in different vibration modes are complex. Reverse profiled cables in the horizontal plane can significantly suppress the lateral vibration in coupled lateral-torsional modes, but slightly increase the lateral vibration in coupled torsional-lateral modes.
Stochastic Averaging of Strongly Nonlinear Oscillators under Poisson White Noise Excitation
Zeng, Y.; Zhu, W. Q.
A stochastic averaging method for single-degree-of-freedom (SDOF) strongly nonlinear oscillators under Poisson white noise excitation is proposed by using the so-called generalized harmonic functions. The stationary averaged generalized Fokker-Planck-Kolmogorov (GFPK) equation is solved by using the classical perturbation method. Then the procedure is applied to estimate the stationary probability density of response of a Duffing-van der Pol oscillator under Poisson white noise excitation. Theoretical results agree well with Monte Carlo simulations.
Non-destructive Testing by Infrared Thermography Under Random Excitation and ARMA Analysis
Bodnar, J. L.; Nicolas, J. L.; Candoré, J. C.; Detalle, V.
2012-11-01
Photothermal thermography is a non-destructive testing (NDT) method, which has many applications in the field of control and characterization of thin materials. This technique is usually implemented under CW or flash excitation. Such excitations are not adapted for control of fragile materials or for multi-frequency analysis. To allow these analyses, in this article, the use of a new control mode is proposed: infrared thermography under random excitation and auto regressive moving average analysis. First, the principle of this NDT method is presented. Then, the method is shown to permit detection, with low energy constraints, of detachments situated in mural paintings.
Seismic Responses of Shot Span Bridge under Three Different Patterns of Earthquake Excitations
International Nuclear Information System (INIS)
Zhou Daochuan; Chen Guorong; Lu Yan
2010-01-01
This paper presents a study of the influence of three different types of seismic input methods on the longitudinal seismic response of a short, three-span, variable cross-section, reinforced concrete bridge. Research progress of the seismic model is introduced briefly. Finite element model is created for the bridge and time history analysis conducted. Three different types of illustrative excitations are considered: 1) the EI-Centro seismic wave is used as uniform excitations at all bridge supports; 2) fixed apparent wave velocity is used for response analysis of traveling wave excitations on the bridge; 3) conforming to a selected coherency model, the multiple seismic excitation time histories considering spatially variable effects are generated. The contrast study of the response analysis result under the three different seismic excitations is conducted and the influence of different seismic input methods is studied. The comparative analysis of the bridge model shows that the uniform ground motion input can not provide conservative seismic demands-in a number of cases it results in lower response than that predicted by multiple seismic excitations. The result of uniform excitation and traveling wave excitation shows very small difference. Consequently, multiple seismic excitations needs to be applied at the bridge supports for response analysis of short span bridge.
Dynamic screening and wake effects on electronic excitation in ion-solid and ion-surface collisions
Energy Technology Data Exchange (ETDEWEB)
Burgdoerfer, J. (Tennessee Univ., Knoxville, TN (United States). Dept. of Physics Oak Ridge National Lab., TN (United States))
1991-01-01
The collective electronic response in a solid effectively alters ionic and atomic potentials giving rise to dynamic screening and to a wake'' of density fluctuations trailing ions as they propagate through the solid. The presence of dynamic screening modifies electronic excitation processes of projectiles in ion-solid collisions as compared to binary ion-atom collisions. We review recent theoretical and experimental studies directed at the search for and identification of signatures of dynamic screening and wake effects. Examples include the formation of excited projectile bound states under channeling conditions, radiative electron capture, the search for wake riding'' electrons in antiproton-solid collisions, and the neutralization of highly charged ions near surfaces. 42 refs., 7 figs.
Excited-State Dynamics of Carotenoids Studied by Femtosecond Transient Absorption Spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Lee, Ingu; Pang, Yoonsoo [Department of Physics and Photon Science, Gwangju (Korea, Republic of); Lee, Sebok [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)
2014-03-15
Carotenoids, natural antenna pigments in photosynthesis share a symmetric backbone of conjugated polyenes. Contrary to the symmetric and almost planar geometries of carotenoids, excited state structure and dynamics of carotenoids are exceedingly complex. In this paper, recent infrared and visible transient absorption measurements and excitation dependent dynamics of 8'-apo-β-caroten-8'-al and 7',7'-dicyano-7'-apo-β-carotene will be reviewed. The recent visible transient absorption measurements of 8'-apo-β-caroten-8'-al in polar and nonpolar solvents will also be introduced to emphasize the complex excited-state dynamics and unsolved problems in the S{sub 2} and S{sub 1} excited states.
Dynamics and quantumness of excitation energy transfer through a complex quantum network
Qin, M.; Shen, H. Z.; Zhao, X. L.; Yi, X. X.
2014-10-01
Understanding the mechanisms of efficient and robust energy transfer in organic systems provides us with insights for the optimal design of artificial systems. In this paper, we explore the dynamics of excitation energy transfer (EET) through a complex quantum network by a toy model consisting of three sites coupled to environments. We study how the coherent evolution and the noise-induced decoherence work together to reach efficient EET and illustrate the role of the phase factor attached to the coupling constant in the EET. By comparing the differences between the Markovian and non-Markovian dynamics, we discuss the effect of environment and the spatial structure of system on the dynamics and the efficiency of EET. A intuitive picture is given to show how the exciton is transferred through the system. Employing the simple model, we show the robustness of EET efficiency under the influence of the environment and elucidate the important role of quantum coherence in EET. We go further to study the quantum feature of the EET dynamics by quantumness and show the importance of quantum coherence from a different perspective. We calculate the energy current in the EET and its quantumness, and results for different system parameters are presented and discussed.
Richaud, Andrea; Penna, Vittorio
2017-07-01
We study the quantum dynamics of the Bose-Hubbard model on a ladder formed by two rings coupled by the tunneling effect. By implementing the Bogoliubov approximation scheme, we prove that, despite the presence of the inter-ring coupling term, the Hamiltonian decouples in many independent sub-Hamiltonians Ĥk associated with momentum-mode pairs ±k . Each sub-Hamiltonian Ĥk is then shown to be part of a specific dynamical algebra. The properties of the latter allow us to perform the diagonalization process, to find the energy spectrum and the conserved quantities of the model, and to derive the time evolution of important physical observables. We then apply this solution scheme to the simplest possible closed ladder, the double trimer. After observing that the excitations of the system are weakly populated vortices, we explore the corresponding dynamics by varying the initial conditions and the model parameters. Finally, we show that the inter-ring tunneling determines a spectral collapse when approaching the border of the dynamical-stability region.
Excited state dynamics and isomerization in ruthenium sulfoxide complexes.
King, Albert W; Wang, Lei; Rack, Jeffrey J
2015-04-21
Molecular photochromic compounds are those that interconvert between two isomeric forms with light. The two isomeric forms display distinct electronic and molecular structures and must not be in equilibrium with one another. These light-activated molecular switch compounds have found wide application in areas of study ranging from chemical biology to materials science, where conversion from one isomeric form to another by light prompts a response in the environment (e.g., protein or polymeric material). Certain ruthenium and osmium polypyridine sulfoxide complexes are photochromic. The mode of action is a phototriggered isomerization of the sulfoxide from S- to O-bonded. The change in ligation drastically alters both the spectroscopic and electrochemical properties of the metal complex. Our laboratory has pioneered the preparation and study of these complexes. In particular, we have applied femtosecond pump-probe spectroscopy to reveal excited state details of the isomerization mechanism. The data from numerous complexes allowed us to predict that the isomerization was nonadiabatic in nature, defined as occurring from a S-bonded triplet excited state (primarily metal-to-ligand charge transfer in character) to an O-bonded singlet ground state potential energy surface. This prediction was corroborated by high-level density functional theory calculations. An intriguing aspect of this reactivity is the coupling of nuclear motion to the electronic wave function and how this coupling affects motions productive for isomerization. In an effort to learn more about this coupling, we designed a project to examine phototriggered isomerization in bis-sulfoxide complexes. The goal of these studies was to determine whether certain complexes could be designed in which a single photon excitation event would prompt two sulfoxide isomerizations. We employed chelating sulfoxides in this study and found that both the nature of the chelate ring and the R group on the sulfoxide affect
Zhao, Yaobing; Huang, Chaohui; Chen, Lincong; Peng, Jian
2018-03-01
The aim of this paper is to investigate temperature effects on the nonlinear vibration behaviors of suspended cables under two-frequency excitation. For this purpose, two combination and simultaneous resonances are chosen and studied in detail. First of all, based on the assumptions of the temperature effects, the partial differential equations of the in-plane and out-of-plane motions with thermal effects under multi-frequency excitations are obtained. The Galerkin method is adopted to discretize the nonlinear dynamic equations, and the single-mode planar discretization is considered. Then, in the absence of the primary and internal resonances, the frequency response equations are obtained by using the multiple scales method. The stability analyses are conducted via investigating the nature of the singular points of equations. After that, temperature effects on nonlinear vibration characteristics of the first symmetric mode are studied. Parametric investigations of temperature effects on corresponding non-dimensional factors and coefficients of linear and nonlinear terms are performed. Numerical results are presented to show the temperature effects via the frequency-response curves and detuning-phase curves of four different sag-to-span ratios. It is found out that effects of temperature variations would lead to significant quantitative and/or qualitative changes of the nonlinear vibration properties, and these effects are closely related to the sag-to-span ratio and the degree of the temperature variation. Specifically, the softening/hardening-type spring behaviors, the response amplitude, the range of the resonance, the intersection and number of branches, the number and phase of the steady-state solutions are all affected by the temperature changes.
Optimum design of a novel pounding tuned mass damper under harmonic excitation
Wang, Wenxi; Hua, Xugang; Wang, Xiuyong; Chen, Zhengqing; Song, Gangbing
2017-05-01
In this paper, a novel pounding tuned mass damper (PTMD) utilizing pounding damping is proposed to reduce structural vibration by increasing the damping ratio of a lightly damped structure. The pounding boundary covered by viscoelastic material is fixed right next to the tuned mass when the spring-mass system is in the equilibrium position. The dynamic properties of the proposed PTMD, including the natural frequency and the equivalent damping ratio, are derived theoretically. Moreover, the numerical simulation method by using an impact force model to study the PTMD is proposed and validated by pounding experiments. To minimize the maximum dynamic magnification factor under harmonic excitations, an optimum design of the PTMD is developed. Finally, the optimal PTMD is implemented to control a lightly damped frame structure. A comparison of experimental and simulated results reveals that the proposed impact force model can accurately model the pounding force. Furthermore, the proposed PTMD is effective to control the vibration in a wide frequency range, as demonstrated experimentally.
Directory of Open Access Journals (Sweden)
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.
International Nuclear Information System (INIS)
Wu, Guorong; Neville, Simon P.; Schalk, Oliver; Sekikawa, Taro; Ashfold, Michael N. R.; Worth, Graham A.; Stolow, Albert
2016-01-01
The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A 2 (πσ ∗ ) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B 1 (π3p y ) Rydberg state, followed by prompt internal conversion to the A 2 (πσ ∗ ) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A 2 (πσ ∗ ) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A 2 (πσ ∗ ) state, facilitating wavepacket motion around the potential barrier in the N–CH 3 dissociation coordinate
Energy Technology Data Exchange (ETDEWEB)
Wu, Guorong [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P. [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Schalk, Oliver [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 106 91 Stockholm (Sweden); Sekikawa, Taro [Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Worth, Graham A. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)
2016-01-07
The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A{sub 2}(πσ{sup ∗}) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B{sub 1}(π3p{sub y}) Rydberg state, followed by prompt internal conversion to the A{sub 2}(πσ{sup ∗}) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A{sub 2}(πσ{sup ∗}) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A{sub 2}(πσ{sup ∗}) state, facilitating wavepacket motion around the potential barrier in the N–CH{sub 3} dissociation coordinate.
Directory of Open Access Journals (Sweden)
Zhi-Wen Zhu
2015-01-01
Full Text Available A kind of high-aspect-ratio shape memory alloy (SMA composite wing is proposed to reduce the wing’s fluttering. The nonlinear dynamic characteristics and optimal control of the SMA composite wings subjected to in-plane stochastic excitation are investigated where the great bending under the flight loads is considered. The stochastic stability of the system is analyzed, and the system’s response is obtained. The conditions of stochastic Hopf bifurcation are determined, and the probability density of the first-passage time is obtained. Finally, the optimal control strategy is proposed. Numerical simulation shows that the stability of the system varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the reliability of the system is improved through optimal control, and the first-passage time is delayed. Finally, the effects of the control strategy are proved by experiments. The results of this paper are helpful for engineering applications of SMA.
DEFF Research Database (Denmark)
Zhou, Qiang; Nielsen, Søren R.K.; Qu, Weilian
2010-01-01
of several factors, which include excitation level and direction as well as damper size, on the dynamic response of the cable is extensively investigated. It is found that the sum of mean square in-plane and out-of-plane displacement is primarily independent of the load direction when the excitation level...... and viscous coefficient of the damper are fixed. Moreover, the peak frequency and half-band width of the spectra of both the in-plane and the out-of-plane displacements are increasing with excitation level when the damper size is constant. It is also observed that, even though the actual optimal damper size......Considering the coupling between the in-plane and out-of-plane vibration, the stochastic response of an inclined shallow cable with linear viscous dampers subjected to Gaussian white noise excitation is investigated in this paper. Selecting the static deflection shape due to a concentrated force...
Electron plasma dynamics during autoresonant excitation of the diocotron mode
Energy Technology Data Exchange (ETDEWEB)
Baker, C. J., E-mail: cbaker@physics.ucsd.edu; Danielson, J. R., E-mail: jrdanielson@ucsd.edu; Hurst, N. C., E-mail: nhurst@physics.ucsd.edu; Surko, C. M., E-mail: csurko@ucsd.edu [Physics Department, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States)
2015-02-15
Chirped-frequency autoresonant excitation of the diocotron mode is used to move electron plasmas confined in a Penning-Malmberg trap across the magnetic field for advanced plasma and antimatter applications. Plasmas of 10{sup 8} electrons, with radii small compared to that of the confining electrodes, can be moved from the magnetic axis to ≥90% of the electrode radius with near unit efficiency and reliable angular positioning. Translations of ≥70% of the wall radius are possible for a wider range of plasma parameters. Details of this process, including phase and displacement oscillations in the plasma response and plasma expansion, are discussed, as well as possible extensions of the technique.
Molecular excitation dynamics and relaxation quantum theory and spectroscopy
Valkunas, Leonas; Mancal, Tomas
2013-01-01
Meeting the need for a work that brings together quantum theory and spectroscopy to convey excitation processes to advanced students and specialists wishing to conduct research and understand the entire field rather than just single aspects.Written by an experienced author and recognized authority in the field, this text covers numerous applications and offers examples taken from different disciplines. As a result, spectroscopists, molecular physicists, physical chemists, and biophysicists will all find this a must-have for their research. Also suitable as supplementary reading in graduate
Tracking excited-state charge and spin dynamics in iron coordination complexes
DEFF Research Database (Denmark)
Zhang, Wenkai; Alonso-Mori, Roberto; Bergmann, Uwe
2014-01-01
to spin state, can elucidate the spin crossover dynamics of [Fe(2,2'-bipyridine)(3)](2+) on photoinduced metal-to-ligand charge transfer excitation. We are able to track the charge and spin dynamics, and establish the critical role of intermediate spin states in the crossover mechanism. We anticipate......Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons(1-4). But a detailed understanding of such non-equilibrium excited-state dynamics and their interplay with structural changes is challenging: a multitude of excited...... states and possible transitions result in phenomena too complex to unravel when faced with the indirect sensitivity of optical spectroscopy to spin dynamics(5) and the flux limitations of ultrafast X-ray sources(6,7). Such a situation exists for archetypal poly-pyridyl iron complexes, such as [Fe(2...
Livingstone, Ruth A; Thompson, James O F; Iljina, Marija; Donaldson, Ross J; Sussman, Benjamin J; Paterson, Martin J; Townsend, Dave
2012-11-14
Time-resolved photoelectron imaging was used to investigate the dynamical evolution of the initially prepared S(1) (ππ*) excited state of phenol (hydroxybenzene), catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), and hydroquinone (1,4-dihydroxybenzene) following excitation at 267 nm. Our analysis was supported by ab initio calculations at the coupled-cluster and CASSCF levels of theory. In all cases, we observe rapid (<1 ps) intramolecular vibrational redistribution on the S(1) potential surface. In catechol, the overall S(1) state lifetime was observed to be 12.1 ps, which is 1-2 orders of magnitude shorter than in the other three molecules studied. This may be attributed to differences in the H atom tunnelling rate under the barrier formed by a conical intersection between the S(1) state and the close lying S(2) (πσ*) state, which is dissociative along the O-H stretching coordinate. Further evidence of this S(1)/S(2) interaction is also seen in the time-dependent anisotropy of the photoelectron angular distributions we have observed. Our data analysis was assisted by a matrix inversion method for processing photoelectron images that is significantly faster than most other previously reported approaches and is extremely quick and easy to implement.
Research on Collapse Process of Cable-Stayed Bridges under Strong Seismic Excitations
Directory of Open Access Journals (Sweden)
Xuewei Wang
2017-01-01
Full Text Available In order to present the collapse process and failure mechanism of long-span cable-stayed bridges under strong seismic excitations, a rail-cum-road steel truss cable-stayed bridge was selected as engineering background, the collapse failure numerical model of the cable-stayed bridge was established based on the explicit dynamic finite element method (FEM, and the whole collapse process of the cable-stayed bridge was analyzed and studied with three different seismic waves acted in the horizontal longitudinal direction, respectively. It can be found from the numerical simulation analysis that the whole collapse failure process and failure modes of the cable-stayed bridge under three different seismic waves are similar. Furthermore, the piers and the main pylons are critical components contributing to the collapse of the cable-stayed bridge structure. However, the cables and the main girder are damaged owing to the failure of piers and main pylons during the whole structure collapse process, so the failure of cable and main girder components is not the main reason for the collapse of cable-stayed bridge. The analysis results can provide theoretical basis for collapse resistance design and the determination of critical damage components of long-span highway and railway cable-stayed bridges in the research of seismic vulnerability analysis.
Energy Technology Data Exchange (ETDEWEB)
Obaid, Rana [Institut für Theoretische Chemie, Universität Wien, Währinger Str. 17, 1090 Wien (Austria); Faculty of Pharmacy, Al-Quds University, Abu Dis, Palestine (Country Unknown); Kinzel, Daniel; Oppel, Markus, E-mail: markus.oppel@univie.ac.at; González, Leticia [Institut für Theoretische Chemie, Universität Wien, Währinger Str. 17, 1090 Wien (Austria)
2014-10-28
Despite the concept of nuclear spin isomers (NSIs) exists since the early days of quantum mechanics, only few approaches have been suggested to separate different NSIs. Here, a method is proposed to discriminate different NSIs of a quinodimethane derivative using its electronic excited state dynamics. After electronic excitation by a laser field with femtosecond time duration, a difference in the behavior of several quantum mechanical operators can be observed. A pump-probe experimental approach for separating these different NSIs is then proposed.
Speckle dynamics under ergodicity breaking
Sdobnov, Anton; Bykov, Alexander; Molodij, Guillaume; Kalchenko, Vyacheslav; Jarvinen, Topias; Popov, Alexey; Kordas, Krisztian; Meglinski, Igor
2018-04-01
Laser speckle contrast imaging (LSCI) is a well-known and versatile approach for the non-invasive visualization of flows and microcirculation localized in turbid scattering media, including biological tissues. In most conventional implementations of LSCI the ergodic regime is typically assumed valid. However, most composite turbid scattering media, especially biological tissues, are non-ergodic, containing a mixture of dynamic and static centers of light scattering. In the current study, we examined the speckle contrast in different dynamic conditions with the aim of assessing limitations in the quantitative interpretation of speckle contrast images. Based on a simple phenomenological approach, we introduced a coefficient of speckle dynamics to quantitatively assess the ratio of the dynamic part of a scattering medium to the static one. The introduced coefficient allows one to distinguish real changes in motion from the mere appearance of static components in the field of view. As examples of systems with static/dynamic transitions, thawing and heating of Intralipid samples were studied by the LSCI approach.
Curchod, Basile F E; Penfold, Thomas J; Rothlisberger, Ursula; Tavernelli, Ivano
2015-07-20
The application of local control theory combined with nonadiabatic ab initio molecular dynamics to study the photoinduced intramolecular proton transfer reaction in 4-hydroxyacridine was investigated. All calculations were performed within the framework of linear-response time-dependent density functional theory. The computed pulses revealed important information about the underlying excited-state nuclear dynamics highlighting the involvement of collective vibrational modes that would normally be neglected in a study performed on model systems constrained to a subset of the full configuration space. This study emphasizes the strengths of local control theory for the design of pulses that can trigger chemical reactions associated with the population of a given molecular excited state. In addition, analysis of the generated pulses can help to shed new light on the photophysics and photochemistry of complex molecular systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Evolutionary dynamics under interactive diversity
Su, Qi; Li, Aming; Wang, Long
2017-10-01
As evidenced by many cases in human societies, individuals often make different behavior decisions in different interactions, and adaptively adjust their behavior in changeable interactive scenarios. However, up to now, how such diverse interactive behavior affects cooperation dynamics has still remained unknown. Here we develop a general framework of interactive diversity, which models individuals’ separated behavior against distinct opponents and their adaptive adjustment in response to opponents’ strategies, to explore the evolution of cooperation. We find that interactive diversity enables individuals to reciprocate every single opponent, and thus sustains large-scale reciprocal interactions. Our work witnesses an impressive boost of cooperation for a notably extensive range of parameters and for all pairwise games. These results are robust against well-mixed and various networked populations, and against degree-normalized and cumulative payoff patterns. From the perspective of network dynamics, distinguished from individuals competing for nodes in most previous work, in this paper, the system evolves in the form of behavior disseminating along edges. We propose a theoretical method based on evolution of edges, which predicts well both the frequency of cooperation and the compact cooperation clusters. Our thorough investigation clarifies the positive role of interactive diversity in resolving social dilemmas and highlights the significance of understanding evolutionary dynamics from the viewpoint of edge dynamics.
Quantum dynamics of vibrational excitations and vibrational charge ...
Indian Academy of Sciences (India)
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 ...
Influence of nuclear dissipation on fission dynamics of the excited ...
Indian Academy of Sciences (India)
A stochastic approach to fission dynamics based on two-dimensional Langevin equations was applied to calculate the anisotropy of the fission fragments angular distribution and average pre-scission neutron multiplicities for the compound nucleus 248Cf formed in the $${16}$O+$^{232}$Th reactions. Postsaddle nuclear ...
Ultrafast electronic dynamics in laser-excited crystalline bismuth
Directory of Open Access Journals (Sweden)
Chekalin S.
2013-03-01
Full Text Available Femtosecond spectroscopy was applied to capture complex dynamics of non equilibrium electrons in bismuth. Data analysis reveals significant wavevector dependence of electron-hole and electron-phonon coupling strength along the Γ-T direction of the Brillouin zone
Beryllium strain under dynamic loading
Directory of Open Access Journals (Sweden)
Pushkov Victor
2015-01-01
Full Text Available There are some data (not much on dynamic characteristics of beryllium that are important, for example, when estimating construction performance at NPP emergencies. A number of data on stress-strain curves, spall strength, shear strength, fracture and structure responses of shock loaded beryllium have obtained in US and Russian laboratories. For today the model description of this complex metal behavior does not have a reasonable agreement with the experimental data, thus a wider spectrum of experimental data is required. This work presents data on dynamic compression-test diagrams of Russian beryllium. Experiments are performed using Hopkinson bar method (SHPB. Strain rates were ε ∼ 103 s−1.
Possible dynamical limitations to excitation energy storage in nuclei
International Nuclear Information System (INIS)
Saint-Laurent, F.; Kyanowski, A.; Ardouin, D.; Delagrange, H.; Doubre, H.; Gregoire, C.; Mittig, W.; Peghaire, A.; Peter, J.; Viyogi, Y.P.; Bizard, G.; Lefebvres, F.; Tamain, B.
1987-01-01
The dependence of the relative populations of particle unbound states on the associated charged particle multiplicity and on the total kinetic energy of the two decay products was investigated for 40 Ar induced reactions on 197 Au at E/A=60 MeV. The measurements indicate that the relative populations exhibit little sensitivity to the violence of the collision and to the time of emission. Implications of these results upon the dynamics of the reaction are discussed
International Nuclear Information System (INIS)
Closser, Kristina D.; Head-Gordon, Martin; Gessner, Oliver
2014-01-01
The dynamics resulting from electronic excitations of helium clusters were explored using ab initio molecular dynamics. The simulations were performed with configuration interaction singles and adiabatic classical dynamics coupled to a state-following algorithm. 100 different configurations of He 7 were excited into the 2s and 2p manifold for a total of 2800 trajectories. While the most common outcome (90%) was complete fragmentation to 6 ground state atoms and 1 excited state atom, 3% of trajectories yielded bound, He 2 * , and <0.5% yielded an excited helium trimer. The nature of the dynamics, kinetic energy release, and connections to experiments are discussed
Qi, Zhongqiang; Au, Francis T. K.
2016-04-01
The vibration mode shapes are often used to identify damage of bridges because the mode shapes are not only important modal properties but also sensitive to damage. However, the key issue is how to conveniently obtain the mode shapes of a bridge in service. Traditional methods invariably require installation of instruments on the bridge for collection of dynamic responses for constructing mode shapes, which are both costly and inconvenient. Therefore a method is developed to construct the mode shapes of simply supported bridges based on Hilbert Transform using only vehicle acceleration response for identification of the location of damage. Firstly, an algorithm is devised to construct the mode shapes by using the dynamic responses extracted from a moving vehicle under impact excitation. Then, based on these intermediate results, the coordinate modal assurance criterion in conjunction with suitable wavelets is used to identify the location of damage. Compared with the traditional methods, the proposed method uses only the information from the moving vehicle. Moreover, additional impact excitation on the vehicle helps to excite the bridge. This helps to improve the accuracy by overcoming the adverse effects of measurement noise and road surface roughness, which leads to high accuracy of damage detection. To verify the feasibility of the proposed method, some numerical studies have been carried out to investigate the effects of measurement noise, road surface roughness and multiple locations of damage on the accuracy of results.
Self-Excited Shock Train Dynamics in a Mach 2 Isolator
Gamba, Mirko; Hunt, Robin; Driscoll, James
2017-11-01
A shock train is the complex system of shock waves that forms in a supersonic ducted flow when the back pressure is raised, and it is typically found in the isolator of air-breathing, high-speed systems. Its formation is due to a balance of the inviscid action of a system of shocks in the core of the flow and the viscous effects at walls. Although the typical description and understanding of shock trains is limited to its steady state behavior, a shock train exhibits significant dynamics, most of which are self-excited, even under nominally constant inflow and outflow conditions. Here we evaluate some of the dynamical properties of a shock train generated in a Mach 2.0 ducted flow. Cross-spectral analysis of pressure and shock position fluctuations are used to identify a complex, frequency dependent system of perturbations that affects the unsteady motion of the shock train. Specifically, we have identified two paths of propagation of perturbations that are associated with two different sources, one associated with the regions of separated flow and one external to the shock train, that affect the steadiness of the shock train, thus partially explaining the observed shock train inherent unsteadiness.
Initial excited-state structural dynamics of 9-methyladenine from UV resonance Raman spectroscopy.
Oladepo, Sulayman A; Loppnow, Glen R
2011-05-19
The photophysics and photochemistry of nucleobases are the factors governing the photostability of DNA and RNA, since they are the UV chromophores in nucleic acids. Because the formation of photoproducts involves structural changes in the excited electronic state, we study here the initial excited-state structural dynamics of 9-methyladenine (9-MeA) by using UV resonance Raman (UVRR) spectroscopy. UV resonance Raman intensities are sensitive to the initial excited-state structural dynamics of molecules. Therefore, information about the initial structural changes in the excited-state of a given molecule can be obtained from its UVRR intensities. The resonance Raman spectra of 9-MeA at wavelengths throughout its 262 nm absorption band were measured, and a self-consistent analysis of the resulting resonance Raman excitation profiles and absorption spectrum was performed using a time-dependent wave packet formalism. We found that the initial structural dynamics of this molecule primarily lie along the N3C4, C4C5, C5C6, C5N7, N7C8, and C8N9 stretching vibrations and CH(3) deformation vibrations. These results are discussed in the context of photochemistry and other deactivation processes. © 2011 American Chemical Society
Population dynamics of excited atoms in non-Markovian environments at zero and finite temperature
International Nuclear Information System (INIS)
Zou Hong-Mei; Fang Mao-Fa
2015-01-01
The population dynamics of a two-atom system, which is in two independent Lorentzian reservoirs or in two independent Ohmic reservoirs respectively, where the reservoirs are at zero temperature or finite temperature, is studied by using the time-convolutionless master-equation method. The influences of the characteristics and temperature of a non-Markovian environment on the population of the excited atoms are analyzed. We find that the population trapping of the excited atoms is related to the characteristics and the temperature of the non-Markovian environment. The results show that, at zero temperature, the two atoms can be effectively trapped in the excited state both in the Lorentzian reservoirs and in the Ohmic reservoirs. At finite temperature, the population of the excited atoms will quickly decay to a nonzero value. (paper)
Casey, Alex; Fenoglio, Gabriel; Detrinidad, Humberto
2017-06-01
Under mechanical excitation, energy is known to localize within an energetic material resulting in `hot spot' formation. While many formation mechanisms have been proposed, additional insight to heat generation mechanisms, the effect of binder/crystal interfaces, and predication capabilities can be gained by quantifying the initiation and growth of the hot spots. Phosphor thermography is a well established temperature sensing technique wherein an object's temperature is obtained by collecting the temperature dependent luminescence of an optically excited phosphor. Herein, the phosphor thermography technique has been applied to Dow Corning Sylgard® 184/octahydro 1,3,5,7 tetranitro 1,3,5,7 tetrazocine (HMX) composite materials under mechanical excitation in order to visualize the evolution of the temperature field, and thus hot spot formation, within the binder. Funded by AFOSR. Supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.
Structural Influence on Excited State Dynamics in Simple Amines
DEFF Research Database (Denmark)
Klein, Liv Bærenholdt
experiments with calculations, provides new insight into the nature of the internal conversion processes that mediate the dynamical evolution between Rydberg states, and how structural variations in simple amine system have a large impact on the non-adiabatic processes. The experimental method of choice...... is femtosecond time-resolved photoelectron velocity map imaging (VMI), which is a newtechnique in the Copenhagen lab. The design, building and implementation of the VMI spectrometer has been a very substantial part of the thesis work. This techniques oers enhanced information content in the form of ecient...... investigated organic species containing N-H bonds, where the ultrafast evolution of the 3s state into valence character iswell-established. Even though the temporal evolution is too fast to be resolved by the experiment, the angle-resolved information still allows for the observation of this process...
International Nuclear Information System (INIS)
Sakko, Arto; Rossi, Tuomas P; Nieminen, Risto M
2014-01-01
The presence of plasmonic material influences the optical properties of nearby molecules in untrivial ways due to the dynamical plasmon-molecule coupling. We combine quantum and classical calculation schemes to study this phenomenon in a hybrid system that consists of a Na 2 molecule located in the gap between two Au/Ag nanoparticles. The molecule is treated quantum-mechanically with time-dependent density-functional theory, and the nanoparticles with quasistatic classical electrodynamics. The nanoparticle dimer has a plasmon resonance in the visible part of the electromagnetic spectrum, and the Na 2 molecule has an electron-hole excitation in the same energy range. Due to the dynamical interaction of the two subsystems the plasmon and the molecular excitations couple, creating a hybridized molecular-plasmon excited state. This state has unique properties that yield e.g. enhanced photoabsorption compared to the freestanding Na 2 molecule. The computational approach used enables decoupling of the mutual plasmon-molecule interaction, and our analysis verifies that it is not legitimate to neglect the backcoupling effect when describing the dynamical interaction between plasmonic material and nearby molecules. Time-resolved analysis shows nearly instantaneous formation of the coupled state, and provides an intuitive picture of the underlying physics. (paper)
International Nuclear Information System (INIS)
Holthaus, M.
1990-04-01
The study of short-time phenomena in strongly interacting quantum systems requires on the theoretical side the development of methods, which are both non-perturbative and 'dynamical', which thus regard the change of outer parameters in the slope of time. For systems with a periodic, fast and a further slow, parametric time dependence both requirements are fulfilled by the Floquet picture of quantum mechanics. This picture, which starts from the adiabatic evolution on effective quasi-energy surfaces, is presented in the first chapter of the present thesis, whereby especially the term of the adiabaticity for periodically time dependent systems is explained. In the second chapter the Floquet theory is applied to the description of microwave experiments with highly excited hydrogen atoms. Here it is shown that the Floquet picture permits to understand a manifold of experimental observations under a unified point of view. Really these microwave experiments offer an ideal possibility for the test of the Floquet picture: On the one hand there is the strength of the outer field of the same order of magnitude as that of the nuclear field, by which the highly excited electron is bound, on the other hand in the experiment an extremely precise control of amplitude, frequency, and pulse shape is possible, so that the conditions for a detailed comparison of theory and experiment are given. The insights, which model calculations yield in the dynamics of highly excited hydrogen atoms in strong alternating fields, allow a prediction of further effects, for which it is to be looked for in new experiments. In the following third chapter some further aspects of these model calculations are discussed, whereby also common properties of the dynamics of excited atoms in microwave fields and that of atoms under the influence of strong laser pulses are discussed. (orig./HSI) [de
International Nuclear Information System (INIS)
Tatchim Bemmo, D.; Siewe Siewe, M.; Tchawoua, C.
2011-01-01
The continuous FitzHugh-Nagumo (FHN for short) model is transformed into modified van der Pol oscillator with asymmetry under external and two-frequency parametric excitations. At the first, the dependence of the solutions on a combined external and two-frequency parametric stimulus forcing is investigated. By using the multiple scale method, ranges of applied current and/or parametric forcing in which nonlinear oscillations are observed are described. Second, when the multiple scale method cannot be used, we numerically prove that in the modified van der Pol oscillator with asymmetry under external and two-frequency parametric excitations, chaos and periodic solution depending on the combination between different frequencies of the model should appear. We also show that the amplitude of the oscillations can be reduced or increased. To do this, we perform the study of the FHN model by choosing a range of parameters exhibiting Hopf bifurcation and two qualitative different regimes in phase portrait. - Highlights: → We model both external and two-frequency parametric excitations in FHN equations. → We examine effects of harmonic forcing on coupled nonlinear oscillator. → Jump and hysteresis phenomena are observed in the dynamical response. → By increasing the constant stimulus we obtain limit cycle. → Some combinations of frequencies produce limit cycle and chaos for other.
Self-modulated dynamics of a relativistic charged particle beam in plasma wake field excitation
Energy Technology Data Exchange (ETDEWEB)
Akhter, T.; Fedele, R. [Dipartimento di Fisica ‘Ettore Pancini’, Università di Napoli Federico II and INFN Sezione di Napoli, Napoli (Italy); Nicola, S. De [CNR-SPIN and INFN Sezione di Napoli, Napoli (Italy); Tanjia, F. [Dipartimento di Fisica ‘Ettore Pancini’, Università di Napoli Federico II and INFN Sezione di Napoli, Napoli (Italy); Jovanović, D. [Institute of Physics, University of Belgrade, Belgrade (Serbia); Mannan, A. [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh)
2016-09-01
The self-modulated dynamics of a relativistic charged particle beam is provided within the context of the theory of plasma wake field excitation. The self-consistent description of the beam dynamics is provided by coupling the Vlasov equation with a Poisson-type equation relating the plasma wake potential to the beam density. An analysis of the beam envelope self-modulation is then carried out and the criteria for the occurrence of the instability are discussed thereby.
Effect of carotenoid structure on excited-state dynamics of carbonyl carotenoids
Czech Academy of Sciences Publication Activity Database
Chábera, P.; Fuciman, M.; Hříbek, P.; Polívka, Tomáš
2009-01-01
Roč. 11, - (2009), s. 8795-8703 ISSN 1463-9076 R&D Projects: GA AV ČR IAA608170604 Institutional research plan: CEZ:AV0Z50510513 Keywords : excited-state dynamics * carbonyl carotenoids * femtosecond spectroscopy Subject RIV: BO - Biophysics Impact factor: 4.116, year: 2009
Lu, Zheng; Huang, Biao; Zhang, Qi; Lu, Xilin
2018-05-01
Eddy-current tuned mass dampers (EC-TMDs) are non-contacting passive control devices and are developed on the basis of conventional tuned mass dampers. They comprise a solid mass, a stiffness element, and a damping element, wherein the damping mechanism originates from eddy currents. By relative motion between a non-magnetic conductive metal and a permanent magnet in a dynamic system, a time-varying magnetic field is induced in the conductor, thereby generating eddy currents. The eddy currents induce a magnetic field with opposite polarity, causing repulsive forces, i.e., damping forces. This technology can overcome the drawbacks of conventional tuned mass dampers, such as limited service life, deterioration of mechanical properties, and undesired additional stiffness. The experimental and analytical study of this system installed on a multi-degree-of-freedom structure is presented in this paper. A series of shaking table tests were conducted on a five-story steel-frame model with/without an EC-TMD to evaluate the effectiveness and performance of the EC-TMD in suppressing the vibration of the model under seismic excitations. The experimental results show that the EC-TMD can effectively reduce the displacement response, acceleration response, interstory drift ratio, and maximum strain of the columns under different earthquake excitations. Moreover, an analytical method was proposed on the basis of electromagnetic and structural dynamic theories. A comparison between the test and simulation results shows that the simulation method can be used to estimate the response of structures with an EC-TMD under earthquake excitations with acceptable accuracy.
Picosecond dynamics of the glutamate receptor in response to agonist-induced vibrational excitation.
Kubo, Minoru; Shiomitsu, Eiji; Odai, Kei; Sugimoto, Tohru; Suzuki, Hideo; Ito, Etsuro
2004-02-01
Conformational changes of proteins are dominated by the excitation and relaxation processes of their vibrational states. To elucidate the mechanism of receptor activation, the conformation dynamics of receptors must be analyzed in response to agonist-induced vibrational excitation. In this study, we chose the bending vibrational mode of the guanidinium group of Arg485 of the glutamate receptor subunit GluR2 based on our previous studies, and we investigated picosecond dynamics of the glutamate receptor caused by the vibrational excitation of Arg485 via molecular dynamics simulations. The vibrational excitation energy in Arg485 in the ligand-binding site initially flowed into Lys730, and then into the J-helix at the subunit interface of the ligand-binding domain. Consequently, the atomic displacement in the subunit interface around an intersubunit hydrogen bond was evoked in about 3 ps. This atomic displacement may perturb the subunit packing of the receptor, triggering receptor activation. Copyright 2003 Wiley-Liss, Inc.
Excited State Structural Dynamics of Carotenoids and ChargeTransfer Systems
Energy Technology Data Exchange (ETDEWEB)
Van Tassle, Aaron Justin [Univ. of California, Berkeley, CA (United States)
2006-01-01
This dissertation describes the development andimplementation of a visible/near infrared pump/mid-infrared probeapparatus. Chapter 1 describes the background and motivation ofinvestigating optically induced structural dynamics, paying specificattention to solvation and the excitation selection rules of highlysymmetric molecules such as carotenoids. Chapter 2 describes thedevelopment and construction of the experimental apparatus usedthroughout the remainder of this dissertation. Chapter 3 will discuss theinvestigation of DCM, a laser dye with a fluorescence signal resultingfrom a charge transfer state. By studying the dynamics of DCM and of itsmethyl deuterated isotopomer (an otherwise identical molecule), we areable to investigate the origins of the charge transfer state and provideevidence that it is of the controversial twisted intramolecular (TICT)type. Chapter 4 introduces the use of two-photon excitation to the S1state, combined with one-photon excitation to the S2 state of thecarotenoid beta-apo-8'-carotenal. These 2 investigations show evidencefor the formation of solitons, previously unobserved in molecular systemsand found only in conducting polymers Chapter 5 presents an investigationof the excited state dynamics of peridinin, the carotenoid responsiblefor the light harvesting of dinoflagellates. This investigation allowsfor a more detailed understanding of the importance of structuraldynamics of carotenoids in light harvesting.
International Nuclear Information System (INIS)
Ye Min; Lu Jing; Zhang Wei; Ding Qian
2005-01-01
The present investigation deals with nonlinear dynamic behavior of a parametrically excited simply supported rectangular symmetric cross-ply laminated composite thin plate for the first time. The governing equation of motion for rectangular symmetric cross-ply laminated composite thin plate is derived by using von Karman equation. The geometric nonlinearity and nonlinear damping are included in the governing equations of motion. The Galerkin approach is used to obtain a two-degree-of-freedom nonlinear system under parametric excitation. The method of multiple scales is utilized to transform the second-order non-autonomous differential equations to the first-order averaged equations. Using numerical method, the averaged equations are analyzed to obtain the steady state bifurcation responses. The analysis of stability for steady state bifurcation responses in laminated composite thin plate is also given. Under certain conditions laminated composite thin plate may have two or multiple steady state bifurcation solutions. Jumping phenomenon occurs in the steady state bifurcation solutions. The chaotic motions of rectangular symmetric cross-ply laminated composite thin plate are also found by using numerical simulation. The results obtained here demonstrate that the periodic, quasi-periodic and chaotic motions coexist for a parametrically excited fore-edge simply supported rectangular symmetric cross-ply laminated composite thin plate under certain conditions
International Nuclear Information System (INIS)
Lutgen, S.; Kaindl, R.A.; Woerner, M.; Elsaesser, T.; Hase, A.; Kuenzel, H.; Gulia, M.; Meglio, D.; Lugli, P.
1996-01-01
The dynamics of electrons in GaInAs/AlInAs quantum wells is studied after excitation from the n=1 to the n=2 conduction subband. Femtosecond pump-probe experiments demonstrate for the first time athermal distributions of n=1 electrons on a surprisingly long time scale of 2ps. Thermalization involves intersubband scattering of excited electrons via optical phonon emission with a time constant of 1ps and intrasubband Coulomb and phonon scattering. Ensemble Monte Carlo simulations show that the slow electron equilibration results from Pauli blocking and screening of carrier-carrier scattering. copyright 1996 The American Physical Society
Thermal Dynamics of Xanthene Dye in Polymer Matrix Excited by Double Pulse Laser Radiation
Samusev, Ilia; Borkunov, Rodion; Tsarkov, Maksim; Konstantinova, Elizaveta; Antipov, Yury; Demin, Maksim; Bryukhanov, Valery
2018-01-01
Double-pulse laser excitation of the eosin and silver nanoparticles embedded into polymer media is known to be a method of electronic-vibrational energy deactivation kinetic process information obtaining and polymer thermal dynamics investigation. We have studied the vibrational relaxation processes in dye molecules (eosin) and nanoparticles in polyvinyl alcohol after two time-shifted laser pulses with fast and delayed fluorescence kinetics study. In order to simulate thermal and photophysical processes caused by double photon excitation, we solved heat transfer and energy deactivation differential equations numerically. The simulation allowed us to obtain the value of heat conductivity coefficient of polymer matrix.
International Nuclear Information System (INIS)
Zhang Li-Sheng; Mi Yuan-Yuan; Gu Wei-Feng; Hu Gang
2014-01-01
All dynamic complex networks have two important aspects, pattern dynamics and network topology. Discovering different types of pattern dynamics and exploring how these dynamics depend on network topologies are tasks of both great theoretical importance and broad practical significance. In this paper we study the oscillatory behaviors of excitable complex networks (ECNs) and find some interesting dynamic behaviors of ECNs in oscillatory probability, the multiplicity of oscillatory attractors, period distribution, and different types of oscillatory patterns (e.g., periodic, quasiperiodic, and chaotic). In these aspects, we further explore strikingly sharp differences among network dynamics induced by different topologies (random or scale-free topologies) and different interaction structures (symmetric or asymmetric couplings). The mechanisms behind these differences are explained physically. (interdisciplinary physics and related areas of science and technology)
Directory of Open Access Journals (Sweden)
Emily K. Stephens
2018-01-01
Full Text Available Serotonin (5-HT selectively excites subpopulations of pyramidal neurons in the neocortex via activation of 5-HT2A (2A receptors coupled to Gq subtype G-protein alpha subunits. Gq-mediated excitatory responses have been attributed primarily to suppression of potassium conductances, including those mediated by KV7 potassium channels (i.e., the M-current, or activation of non-specific cation conductances that underlie calcium-dependent afterdepolarizations (ADPs. However, 2A-dependent excitation of cortical neurons has not been extensively studied, and no consensus exists regarding the underlying ionic effector(s involved. In layer 5 of the mouse medial prefrontal cortex, we tested potential mechanisms of serotonergic excitation in commissural/callosal (COM projection neurons, a subpopulation of pyramidal neurons that exhibits 2A-dependent excitation in response to 5-HT. In baseline conditions, 5-HT enhanced the rate of action potential generation in COM neurons experiencing suprathreshold somatic current injection. This serotonergic excitation was occluded by activation of muscarinic acetylcholine (ACh receptors, confirming that 5-HT acts via the same Gq-signaling cascades engaged by ACh. Like ACh, 5-HT promoted the generation of calcium-dependent ADPs following spike trains. However, calcium was not necessary for serotonergic excitation, as responses to 5-HT were enhanced (by >100%, rather than reduced, by chelation of intracellular calcium with 10 mM BAPTA. This suggests intracellular calcium negatively regulates additional ionic conductances gated by 2A receptors. Removal of extracellular calcium had no effect when intracellular calcium signaling was intact, but suppressed 5-HT response amplitudes, by about 50%, when BAPTA was included in patch pipettes. This suggests that 2A excitation involves activation of a non-specific cation conductance that is both calcium-sensitive and calcium-permeable. M-current suppression was found to be a third
International Nuclear Information System (INIS)
Liu Shuhai; Neiger, Manfred
2003-01-01
In order to quantitatively describe the electrical working principles of dielectric barrier discharges (DBDs), a dynamic electrical model for homogeneous DBDs has been put forward that is composed of a new equivalent circuit for homogeneous DBDs and the equations derived from it. This model is a global and self-consistent model, valid for an arbitrary external excitation voltage. This model reveals instantaneous relations of internal electrical quantities in the gap (gap voltage, internal discharge current and internal power consumption process) to external electrical quantities (external voltage and external total current) and provides the theoretical fundamentals to calculate the temporal development processes of all internal electrical quantities in the discharge gap from the measured external voltage and external total current. The knowledge obtained of dynamic processes of DBDs in the discharge gap explains quantitatively the mechanisms that result in ignition, development and extinction of DBDs and provide physical interpretation of the measured external total current and other phenomena such as memory effect and multiple current pulses in one half period. In this model, several current terms (external total current, external displacement current, external discharge current, internal discharge current and internal displacement current) are introduced to distinguish the different currents involved in DBDs. Moreover, the equations for charge and energy deposition by one discharge and in one half period are derived. Applications of this model to studying a bipolar sine wave excited DBD and a unipolar pulse excited DBD are also included. This model has been proved to be a useful tool to understand DBDs better
Kayal, Surajit; Roy, Khokan; Umapathy, Siva
2018-01-01
Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy. TA measurements on the S1 state reveal step-wise population relaxation from the Franck-Condon (FC) state → relaxed state → twisted state, while the URLS study provides insights on the vibrational dynamics during the course of the reaction. The TA spectral dynamics and vibrational Raman amplitudes within 1 ps reveal vibrational wave packet propagating from the FC state to the relaxed state. Fourier transformation of this oscillation leads to a ˜130 cm-1 low-frequency phenyl torsional mode. Two vibrational marker bands, Cet=Cet stretching (˜1512 cm-1) and Cph=Cph stretching (˜1584 cm-1) modes, appear immediately after photoexcitation in the URLS spectra. The initial red-shift of the Cph=Cph stretching mode with a time constant of ˜400 fs (in butyronitrile) is assigned to the rate of planarization of excited TPE. In addition, the Cet=Cet stretching mode shows initial blue-shift within 1 ps followed by frequency red-shift, suggesting that on the sub-picosecond time scale, structural relaxation is dominated by phenyl torsion rather than the central Cet=Cet twist. Furthermore, the effect of the solvent on the structural dynamics is discussed in the context of ultrafast nuclear dynamics and solute-solvent coupling.
Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction
International Nuclear Information System (INIS)
Li Zhi-Xin; Cao Qing-Jie; Alain, Léger
2016-01-01
We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous (SD) oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography. (paper)
DEFF Research Database (Denmark)
Zhou, Qiang; Nielsen, Søren R.K.; Qu, Weilian
2010-01-01
Considering the coupling between the in-plane and out-of-plane vibration, the stochastic response of an inclined shallow cable with linear viscous dampers subjected to Gaussian white noise excitation is investigated in this paper. Selecting the static deflection shape due to a concentrated force...... at the dampers location and the first sine term as shape functions, a reduced four-degree-of-freedom system of nonlinear stochastic ordinary differential equations are derived to describe dynamic response of the cable. Since only polynomial-type terms are contained, the fourth-order cumulant-neglect closure...... and viscous coefficient of the damper are fixed. Moreover, the peak frequency and half-band width of the spectra of both the in-plane and the out-of-plane displacements are increasing with excitation level when the damper size is constant. It is also observed that, even though the actual optimal damper size...
On a business cycle model with fractional derivative under narrow-band random excitation
International Nuclear Information System (INIS)
Lin, Zifei; Li, Jiaorui; Li, Shuang
2016-01-01
This paper analyzes the dynamics of a business cycle model with fractional derivative of order α (0 < α < 1) subject to narrow-band random excitation, in which fractional derivative describes the memory property of the economic variables. Stochastic dynamical system concepts are integrated into the business cycle model for understanding the economic fluctuation. Firstly, the method of multiple scales is applied to derive the model to obtain the approximate analytical solution. Secondly, the effect of economic policy with fractional derivative on the amplitude of the economic fluctuation and the effect on stationary probability density are studied. The results show macroeconomic regulation and control can lower the stable amplitude of economic fluctuation. While in the process of equilibrium state, the amplitude is magnified. Also, the macroeconomic regulation and control improves the stability of the equilibrium state. Thirdly, how externally stochastic perturbation affects the dynamics of the economy system is investigated.
International Nuclear Information System (INIS)
El Naggar, M.H.
2003-01-01
The planning of foundations for equipment that is sensitive to vibrations requires a thorough dynamic investigation of the proposed location of the foundation with regard to the effect of already existing or additional vibration sources. This paper discusses the analyses performed for a number of foundations supporting vibration-sensitive equipment that has been subjected to ground-transmitted excitations. These analyses considered the dynamic response of the foundations resulting from the normal operation of the supported equipment or the ground-transmitted excitations. In one case, the foundation of the Canadian Light Source, a third generation synchrotron that will be capable of generating electromagnetic radiation used in the study of the atomic and subatomic structure of materials, is examined. Another case involves the vibration analysis of a magnetic resonance imaging unit affected by traffic excitation. In the third case, a power plant facility that is subjected to blast-induced vibration from an adjacent quarry is investigated. The last case involves the response analysis of a compressor foundation affected by the ground-transmitted vibration from another compressor situated on a different foundation within the same facility. To assess the level of seismic excitation at the site due to traffic on an adjacent roadway in the first two cases and to blasting activity in the third case, extensive 'green field' ground vibration-monitoring programs were carried out. The ground accelerations due to traffic and blasting were measured and recorded for three directions simultaneously: a vertical and two orthogonal horizontal directions. The measurements with the most intense ground accelerations taken at the ground surface in the location of the future equipment foundation were selected as the final design acceleration time-history. A Fourier analysis approach was used to predict the response of the foundation to the ground-induced vibrations in the first three cases
Excitation of high energy levels under laser exposure of suspensions of nanoparticles in liquids
International Nuclear Information System (INIS)
Shafeev, G.A.; Simakin, A.V.; Bozon-Verduraz, F.; Robert, M.
2007-01-01
Laser exposure of suspensions of nanoparticles in liquids leads to excitation of high energy levels in both liquid and nanoparticle material. The emission spectrum of the colloidal solution under exposure of a suspension metallic nanoparticles in water to radiation of a Nd:YAG laser of a picosecond range of pulse duration is discussed. Excitation of nuclear energy levels and neutron release is experimentally studied on the model system of transmutation of Hg into Au that occurs under exposure of Hg nanodrops suspended in D 2 O. The proposed mechanism involves: (i) emission of X-ray photons by Hg nanoparticles upon laser exposure, leading to neutron release from D 2 O, (ii) initiation of Hg → Au transmutation by the capture of neutrons. The effect of transmutation is more pronounced using 196 Hg isotope instead of Hg of natural isotope composition. The influence of laser pulse duration on the degree of transmutation (from fs through ns range) is discussed
Excitation of high energy levels under laser exposure of suspensions of nanoparticles in liquids
Shafeev, G. A.; Simakin, A. V.; Bozon-Verduraz, F.; Robert, M.
2007-12-01
Laser exposure of suspensions of nanoparticles in liquids leads to excitation of high energy levels in both liquid and nanoparticle material. The emission spectrum of the colloidal solution under exposure of a suspension metallic nanoparticles in water to radiation of a Nd:YAG laser of a picosecond range of pulse duration is discussed. Excitation of nuclear energy levels and neutron release is experimentally studied on the model system of transmutation of Hg into Au that occurs under exposure of Hg nanodrops suspended in D 2O. The proposed mechanism involves: (i) emission of X-ray photons by Hg nanoparticles upon laser exposure, leading to neutron release from D 2O, (ii) initiation of Hg → Au transmutation by the capture of neutrons. The effect of transmutation is more pronounced using 196Hg isotope instead of Hg of natural isotope composition. The influence of laser pulse duration on the degree of transmutation (from fs through ns range) is discussed.
Stability of Exponential Euler Method for Stochastic Systems under Poisson White Noise Excitations
Li, Longsuo; Zhang, Yu
2014-12-01
The stability of stochastic systems under Poisson white noise excitations which based on the quantum theory is investigated in this paper. In general, the exact solution of the most of the stochastic systems with jumps is not easy to get. So it is very necessary to investigate the numerical solution of equations. On the one hand, exponential Euler method is applied to study stochastic delay differential equations, we can find the sufficient conditions for keeping mean square stability by investigating numerical method of systems. Through the comparison, we get the step-size of this method which is longer than the Euler-Maruyama method. On the other hand, mean square exponential stability of exponential Euler method for semi-linear stochastic delay differential equations under Poisson white noise excitations is confirmed.
Yue, Xiao-Le; Xu, Wei; Zhang, Ying; Wang, Liang
2015-10-01
The piezomagnetoelastic energy harvester system subjected to harmonic and Poisson white noise excitations is studied by using the generalized cell mapping method. The transient and stationary probability density functions (PDFs) of response based on the global viewpoint are obtained by the matrix analysis method. Monte Carlo simulation results verify the accuracy of this method. It can be observed that evolutionary direction of transient and stationary PDFs is in accordance with the unstable manifold for this system, and a stochastic P-bifurcation occurs as the intensity of Poisson white noise increases. This study presents an efficient numerical tool to solve the stochastic response of a three-dimensional dynamical system and provides a new idea to analyze the energy harvester system. Supported by the National Natural Science Foundation of China under Grant Nos. 11302170, 11202160, 11302171, and the Fundamental Research Funds for the Central Universities under Grant No. 3102014JCQ01079
Lamperti, Marco; Maspero, Angelo; Tønnesen, Hanne H; Bondani, Maria; Nardo, Luca
2014-08-28
Cyclovalone is a synthetic curcumin derivative in which the keto-enolic system is replaced by a cyclohexanone ring. This modification of the chemical structure might in principle result in an excited state that is more stable than that of curcumin, which in turn should produce an enhanced phototoxicity. Indeed, although curcumin exhibits photosensitized antibacterial activity, this compound is characterized by very fast excited-state dynamics which limit its efficacy as a photosensitizer. In previous works we showed that the main non-radiative decay pathway of keto-enolic curcuminoids is through excited-state transfer of the enolic proton to the keto-oxygen. Another effective deactivation pathway involves an intermolecular charge transfer mechanism occurring at the phenyl rings, made possible by intramolecular H-bonding between the methoxy and the hydroxyl substituent. In this paper we present UV-Vis and IR absorption spectra data with the aim of elucidating the intramolecular charge distribution of this compound and its solvation patterns in different environments, with particular focus on solute-solvent H-bonding features. Moreover, we discuss steady state and time-resolved fluorescence data that aim at characterizing the excited-state dynamics of cyclovalone, and we compare its decay photophysics to that of curcumin. Finally, because during the characterization procedures we found evidence of very fast photodegradation of cyclovalone, its photostability in four organic solvents was studied by HPLC and the corresponding relative degradation rates were calculated.
Directory of Open Access Journals (Sweden)
Marco Lamperti
2014-08-01
Full Text Available Cyclovalone is a synthetic curcumin derivative in which the keto-enolic system is replaced by a cyclohexanone ring. This modification of the chemical structure might in principle result in an excited state that is more stable than that of curcumin, which in turn should produce an enhanced phototoxicity. Indeed, although curcumin exhibits photosensitized antibacterial activity, this compound is characterized by very fast excited-state dynamics which limit its efficacy as a photosensitizer. In previous works we showed that the main non-radiative decay pathway of keto-enolic curcuminoids is through excited-state transfer of the enolic proton to the keto-oxygen. Another effective deactivation pathway involves an intermolecular charge transfer mechanism occurring at the phenyl rings, made possible by intramolecular H-bonding between the methoxy and the hydroxyl substituent. In this paper we present UV-Vis and IR absorption spectra data with the aim of elucidating the intramolecular charge distribution of this compound and its solvation patterns in different environments, with particular focus on solute-solvent H-bonding features. Moreover, we discuss steady state and time-resolved fluorescence data that aim at characterizing the excited-state dynamics of cyclovalone, and we compare its decay photophysics to that of curcumin. Finally, because during the characterization procedures we found evidence of very fast photodegradation of cyclovalone, its photostability in four organic solvents was studied by HPLC and the corresponding relative degradation rates were calculated.
Strength of concrete structures under dynamic loading
Kumpyak, O. G.; Galyautdinov, Z. R.; Kokorin, D. N.
2016-01-01
The use of elastic supports is one the efficient methods of decreasing the dynamic loading. The paper describes the influence of elastic supports on the stress-strain state of steel concrete structures exposed to one-time dynamic loading resulting in failure. Oblique bending beams on elastic supports and their elastic, elastoplastic, and elastoplastic consolidation behavior are considered in this paper. For numerical calculations the developed computer program is used based on the finite element method. Research findings prove high efficiency of elastic supports under dynamic loading conditions. The most effective behavior of elastic supports is demonstrated at the elastoplastic stage. A good agreement is observed between the theoretical and experimental results.
Two-step excitation and blue fluorescence under continuous-wave pumping in Nd:YLF
Fan, T. Y.; Byer, Robert L.
1986-01-01
Near-UV and blue fluorescence from the 4D3/2 and 4D5/2 manifolds in Nd:YLF has been observed at room temperature under CW pumping by a rhodamine 590 dye laser. Excitation to these manifolds is attributed to two-step excitation involving excited-state absorption from the 4F3/2 metastable level. A similar phenomenon has also been observed in Nd:YAG and Nd:glass. The effective excited-state absorption cross section is measured to be (2 + or - 1) x 10 to the -20th sq cm at 587.4 nm in the pi polarization, and the peak effective stimulated emission cross section is measured to be 5 x 10 to the -20th sq cm at 411.7 nm, also in the pi polarization. Estimated laser threshold at 411.7 nm for two-step pumping at 587.4 nm is 70 mW.
Influence of Road Excitation and Steering Wheel Input on Vehicle System Dynamic Responses
Zhen-Feng Wang; Ming-Ming Dong; Liang Gu; Jagat-Jyoti Rath; Ye-Chen Qin; Bin Bai
2017-01-01
Considering the importance of increasing driving safety, the study of safety is a popular and critical topic of research in the vehicle industry. Vehicle roll behavior with sudden steering input is a main source of untripped rollover. However, previous research has seldom considered road excitation and its coupled effect on vehicle lateral response when focusing on lateral and vertical dynamics. To address this issue, a novel method was used to evaluate effects of varying road level and steer...
Dynamic control of a bistable wing under aerodynamic loading
International Nuclear Information System (INIS)
Bilgen, Onur; Arrieta, Andres F; Friswell, Michael I; Hagedorn, Peter
2013-01-01
The aerodynamic evaluation of a dynamic control technique applied to a bistable unsymmetrical cross-ply composite plate with surface bonded piezoelectric actuators is presented. The plate is clamped on one end to form a low-aspect-ratio wing. A previously proposed dynamic control method, utilizing bending resonance in different stable equilibrium positions, is used to induce snap-through between the two equilibrium states. Compared to quasi-static actuation, driving the bistable plate near resonance using surface bonded piezoelectric materials requires, theoretically, a lower peak excitation voltage to achieve snap-through. First, a set of extensive wind tunnel experiments are conducted on the passive bistable wing to understand the change in the dynamic behavior under various aerodynamic conditions. The passive wing demonstrated sufficient bending stiffness to sustain its shape under aerodynamic loading while preserving the desired bistable behavior. Next, by the use of the resonant control technique, the plate is turned into an effectively monostable structure, or alternatively, both stable equilibrium positions can be reached actively from the other stable equilibrium. Dynamic forward and reverse snap-through is demonstrated in the wind tunnel which shows both the effectiveness of the piezoelectric actuation as well as the load carrying capability of both states of the bistable wing. (paper)
Multicolor tunable yellow-red emission in Eu/Er:LiNbO3 under ultraviolet and blue excitation
Zhang, Zhengyu; Tang, Xunze; Qian, Yannan; Zhang, Haiyan; Wang, Wenguang; Wang, Rui
2017-12-01
The ability to manipulate the multicolor luminescence will greatly enhance the scope of their applications, ranging from infrared solar cells to volumetric multiplexed bioimaging. Tuning from yellow to red emission was successfully achieved in Eu/Er:LiNbO3 under ultraviolet (UV) and blue excitation. The excitation spectra of Eu/Er:LiNbO3 monitored at 590 nm/618 nm/626 nm were studied. The CIE 1931 color coordinates showed that the emissions fell within the yellow and red region, respectively, under 376 nm and 397 nm excitation. The color coordinates shifted from yellow toward red region upon diode laser excitation of 476 nm.
Excitation of plane Lamb wave in plate-like structures under applied surface loading
Zhou, Kai; Xu, Xinsheng; Zhao, Zhen; Yang, Zhengyan; Zhou, Zhenhuan; Wu, Zhanjun
2018-02-01
Lamb waves play an important role in structure health monitoring (SHM) systems. The excitation of Lamb waves has been discussed for a long time with absorbing results. However, little effort has been made towards the precise characterization of Lamb wave excitation by various transducer models with mathematical foundation. In this paper, the excitation of plane Lamb waves with plane strain assumption in isotropic plate structures under applied surface loading is solved with the Hamiltonian system. The response of the Lamb modes excited by applied loading is expressed analytically. The effect of applied loading is divided into the product of two parts as the effect of direction and the effect of distribution, which can be changed by selecting different types of transducer and the corresponding transducer configurations. The direction of loading determines the corresponding displacement of each mode. The effect of applied loading on the in-plane and normal directions depends on the in-plane and normal displacements at the surface respectively. The effect of the surface loading distribution on the Lamb mode amplitudes is mainly reflected by amplitude versus frequency or wavenumber. The frequencies at which the maxima and minima of the S0 or A0 mode response occur depend on the distribution of surface loading. The numerical results of simulations conducted on an infinite aluminum plate verify the theoretical prediction of not only the direction but also the distribution of applied loading. A pure S0 or A0 mode can be excited by selecting the appropriate direction and distribution at the corresponding frequency.
Spectroscopy and mid-IR lasing of Cr2+ ions in ZnSe/ZnS crystals under visible excitation
Peppers, J.; Konak, T.; Martyshkin, D. V.; Fedorov, V. V.; Mirov, S. B.
2014-02-01
Recent efforts have demonstrated efficient Cr2+ :II-VI chalcogenide (e.g. ZnSe, ZnS) broadly tunable (1.9-3.3μm) lasers under direct intra-shell Cr2+ optical excitation. We report on the spectroscopic study of Cr2++:ZnSe/ZnS under visible excitation into the charge transfer band of Cr2+ ions. Polycrystalline samples prepared by thermal diffusion method were studied. Middle-infrared (mid-IR) photo-luminescence (PL) of Cr2+ ions was compared under continuous wave (CW) direct 1532nm (5T2→5E) excitation and under 532nm excitation into charge transfer band. The quantum yield of Cr:ZnSe mid-IR luminescence under CW green excitation was estimated as close to 100% at room temperature. To estimate Cr excitation rate via charge transfer band under short pulse excitation, mid-IR PL kinetic measurements were performed with the use of 532nm picosecond and nanosecond pumping. Mid-IR PL kinetics of Cr:ZnSe under pulsed green excitation exhibit a relatively slow growth reaching a peak at ~5-10μs for nanosecond and picosecond excitations, respectively, while PL kinetics in Cr:ZnS reveal shorter measured rise time (<1μs) limited by the response time of the detector. This rise of the PL intensity under 532nm pulsed excitation implies that 5E population continues to grow after the excitation pulse due to slow relaxation processes from higher-lying excited levels of Cr2+ to the upper laser level 5E. At the same time for nanosecond excitation the excited level is pumped at a rate faster than it is depleted and, hence, it is reasonable to expect that the population of the 5E level could be inverted. For laser experiments we used 5ns radiation from BBO based optical parametric oscillator tunable over 450-700nm. Cr:ZnSe lasing at 2.5μm induced by 2+→1+→2+ ionization transitions of chromium under visible excitation was achieved.
Optimal Portfolios Under Dynamic Shortfall Constraints | Akume ...
African Journals Online (AJOL)
industry standard with regulatory authorities enforcing its use in risk measurement and management. Despite its widespread acceptance, VaR is not coherent. Tail Conditional Expectation (TCE), on the other hand, for an underlying continuous distribution, is a coherent risk measures. Our focus in this paper is the dynamic ...
Optimal Portfolios Under Dynamic Shortfall Constraints
African Journals Online (AJOL)
industry standard with regulatory authorities enforcing its use in risk measure- ment and management. Despite its widespread acceptance, VaR is not coherent. Tail Conditional Expectation (TCE), on the other hand, for an underlying con- tinuous distribution, is a coherent risk measures. Our focus in this paper is the dynamic ...
Energy Technology Data Exchange (ETDEWEB)
Wu, Guorong [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P.; Worth, Graham A., E-mail: g.a.worth@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Schalk, Oliver [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm (Sweden); Sekikawa, Taro [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada)
2015-02-21
The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole’s electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A{sub 2}(πσ{sup ∗}) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A{sub 1}(ππ{sup ∗}) and B{sub 2}(ππ{sup ∗}) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole’s electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B{sub 1}(πσ{sup ∗}) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B{sub 1}(πσ{sup ∗}) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A{sub 2}(πσ{sup ∗}) state.
Luminescence of the SrCl2:Pr crystals under high-energy excitation
International Nuclear Information System (INIS)
Antonyak, O.T.; Voloshinovskii, A.S.; Vistovskyy, V.V.; Stryganyuk, G.B.; Kregel, O.P.
2014-01-01
The present research was carried out in order to elucidate the mechanisms of energy transfer from the crystal lattice to Pr 3+ ions in SrCl 2 . The luminescence excitation and emission spectra as well as luminescence kinetics of the SrCl 2 :Pr single crystals containing 0.2 mol% Pr were investigated at 300 and 10 K using the vacuum ultraviolet (VUV) synchrotron radiation. The X-ray excited luminescence spectra of the SrCl 2 :Pr (C Pr =0.2 and 0.5 mol%) and SrCl 2 :Pr, K (C Pr =1.5 mol%; C K =1.5 mol%) crystals were studied at 294 and 80 K. Under optical excitation of the samples in the Pr 3+ absorption bands, there were observed five fast ultraviolet emissions assigned to the 4f 1 5d→4f 2 transitions, and two long-wave bands corresponding to the f–f transitions. Furthermore, the intrinsic emission bands of SrCl 2 were observed at 10 K. The X-ray excited luminescence spectrum of the SrCl 2 :Pr crystal containing 0.2 mol% Pr, besides intrinsic emission band near 400 nm, has got a long-wave band at about 490 nm of the Pr 3+ centers. There were not observed any emission bands of the Pr 3+ centers corresponding to the 4f 1 5d–4f 2 transitions in the X-ray excited luminescence spectrum of the SrCl 2 :Pr crystal. The possible mechanisms of energy transfer from the SrCl 2 matrix to the Pr 3+ centers are discussed. -- Highlights: • Spectral-luminescent properties of SrCl 2 :Pr have been investigated. • The identification of emission 4f–4f and 5d–4f bands of Pr 3+ ions was performed. • Adding of potassium prevents clustering of the Pr 3+ centers in the SrCl 2 :Pr, K crystals. • Under X-ray excitation at 80–300 K only Pr 3+ 4f–4f and intrinsic emission is observed
Rüfenacht, M.; Tsujino, S.; Sakaki, H.
1998-06-01
Recently, it was shown that an electron-hole radiative recombination is induced by a mid-infrared light exciting an intersubband transition in a charge transfer double quantum well (CTDQW). This recombination was attributed to an upstream transfer of electrons from an electron-rich well to a hole-rich well. In this study, we investigated the electrical response of a CTDQW under intersubband optical excitation, and found that a positive photocurrent, opposite in sign and proportional to the applied electric field, accompanies the intersubband-transition-induced luminescence (ITIL) signal. A negative photocurrent component was also observed and attributed to heating processes. This work brings a further evidence of the ITIL process and shows that an important proportion of the carriers are consumed by the transfer of electrons.
Spirals in a reaction-diffusion system: Dependence of wave dynamics on excitability
Mahanta, Dhriti; Das, Nirmali Prabha; Dutta, Sumana
2018-02-01
A detailed study of the effects of excitability of the Belousov-Zhabotinsky (BZ) reaction on spiral wave properties has been carried out. Using the Oregonator model, we explore the various regimes of wave activity, from sustained oscillations to wave damping, as the system undergoes a Hopf bifurcation, that is achieved by varying the excitability parameter, ɛ . We also discover a short range of parameter values where random oscillations are observed. With an increase in the value of ɛ , the frequency of the wave decreases exponentially, as the dimension of the spiral core expands. These numerical results are confirmed by carrying out experiments in thin layers of the BZ system, where the excitability is changed by varying the concentrations of the reactant species. Effect of reactant concentrations on wave properties like time period and wavelength are also explored in detail. Drifting and meandering spirals are found in the parameter space under investigation, with the excitability affecting the tip trajectory in a way predicted by the numerical studies. This study acts as a quantitative evidence of the relationship between the excitability parameter, ɛ , and the substrate concentrations.
Wlodarczyk, Lucyna M; Dinc, Emine; Croce, Roberta; Dekker, Jan P
2016-06-01
The efficient use of excitation energy in photosynthetic membranes is achieved by a dense network of pigment-protein complexes. These complexes fulfill specific functions and interact dynamically with each other in response to rapidly changing environmental conditions. Here, we studied how in the intact cells of Chlamydomonas reinhardtii (C.r.) the lack of the photosystem I (PSI) core or the photosystem II (PSII) core affects these interactions. To that end the mutants F15 and M18 (both PSI-deficient) and FUD7 (PSII-deficient) were incubated under conditions known to promote state transitions in wild-type. The intact cells were then instantly frozen to 77K and the full-spectrum time-resolved fluorescence emission of the cells was measured by means of streak camera. In the PSI-deficient mutants excitation energy transfer (EET) towards light-harvesting complexes of PSI (Lhca) occurs in less than 0.5 ns, and fluorescence from Lhca decays in 3.1 ns. Decreased trapping by PSII and increased fluorescence of Lhca upon state 1 (S1)→state 2 (S2) transition appears in the F15 and less in the M18 mutant. In the PSII-deficient mutant FUD7, quenched (0.5 ns) and unquenched (2 ns) light-harvesting complexes of PSII (LHCII) are present in both states, with the quenched form more abundant in S2 than in S1. Moreover, EET of 0.4 ns from the remaining LHCII to PSI increases upon S1→S2 transition. We relate the excitation energy kinetics observed in F15, M18 and FUD7 to the remodeling of the photosynthetic apparatus in these mutants under S1 and S2 conditions. Copyright © 2016 Elsevier B.V. All rights reserved.
Ultrafast Excited-State Dynamics of Cytosine Aza-Derivative and Analogues.
Zhou, Zhongneng; Zhou, Xueyao; Wang, Xueli; Jiang, Bin; Li, Yongle; Chen, Jinquan; Xu, Jianhua
2017-04-13
Excited state dynamics of 5-azacytosine (5-AC), 2,4-diamino-1,3,5-triazine (2,4-DT), and 2-amino-1,3,5-triazine (2-AT) were comprehensively investigated by steady state absorption, fluorescence, and femtosecond transient absorption measurements. Time-dependent density functional theory (TDDFT) calculations were performed to help assign the absorption bands and understand the excited state decay mechanisms. The experimental results of excited singlet state dynamics for 5-AC, 2,4-DT, and 2-AT with femtosecond time resolution were reported for the first time. Two distinct decay pathways, with ∼1 ps and tens of picosecond lifetimes, were observed in 5-AC. Only one decay pathway with 17 ps lifetime was observed in 2,4-DT while an emissive state was found in 2-AT. TDDFT calculations suggest that 5-AC has a dark nπ* (S 1 ) state below the first allowed ππ* (S 2 ) state, which leads to the ultrafast decay of the ππ* state. In 2,4-DT, there is no dark nπ* state below the bright ππ* (S 1 ) state and the 17 ps lifetime is assigned to the relaxation from the ππ* (S 1 ) state to ground state. Two dark nπ* states (S 1 and S 2 ) were found in 2-AT, which exhibits much more complex excited state dynamics compared with the other two. Photoluminescence in 2-AT has been confirmed to be fluorescence emission from its bright ππ* (S 3 ) state. Our results strongly suggest that electronic structures are very sensitive to the substitution on the triazine ring and that the photophysical properties of nucleic acid analogues depend highly on their molecular structures.
Energy Technology Data Exchange (ETDEWEB)
Nelson, Tammie Renee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tretiak, Sergei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-01-06
Understanding and controlling excited state dynamics lies at the heart of all our efforts to design photoactive materials with desired functionality. This tailor-design approach has become the standard for many technological applications (e.g., solar energy harvesting) including the design of organic conjugated electronic materials with applications in photovoltaic and light-emitting devices. Over the years, our team has developed efficient LANL-based codes to model the relevant photophysical processes following photoexcitation (spatial energy transfer, excitation localization/delocalization, and/or charge separation). The developed approach allows the non-radiative relaxation to be followed on up to ~10 ps timescales for large realistic molecules (hundreds of atoms in size) in the realistic solvent dielectric environment. The Collective Electronic Oscillator (CEO) code is used to compute electronic excited states, and the Non-adiabatic Excited State Molecular Dynamics (NA-ESMD) code is used to follow the non-adiabatic dynamics on multiple coupled Born-Oppenheimer potential energy surfaces. Our preliminary NA-ESMD simulations have revealed key photoinduced mechanisms controlling competing interactions and relaxation pathways in complex materials, including organic conjugated polymer materials, and have provided a detailed understanding of photochemical products and intermediates and the internal conversion process during the initiation of energetic materials. This project will be using LANL-based CEO and NA-ESMD codes to model nonradiative relaxation in organic and energetic materials. The NA-ESMD and CEO codes belong to a class of electronic structure/quantum chemistry codes that require large memory, “long-queue-few-core” distribution of resources in order to make useful progress. The NA-ESMD simulations are trivially parallelizable requiring ~300 processors for up to one week runtime to reach a meaningful restart point.
Liao, Bolin; Najafi, Ebrahim; Li, Heng; Minnich, Austin J.; Zewail, Ahmed H.
2017-09-01
Charge carrier dynamics in amorphous semiconductors has been a topic of intense research that has been propelled by modern applications in thin-film solar cells, transistors and optical sensors. Charge transport in these materials differs fundamentally from that in crystalline semiconductors owing to the lack of long-range order and high defect density. Despite the existence of well-established experimental techniques such as photoconductivity time-of-flight and ultrafast optical measurements, many aspects of the dynamics of photo-excited charge carriers in amorphous semiconductors remain poorly understood. Here, we demonstrate direct imaging of carrier dynamics in space and time after photo-excitation in hydrogenated amorphous silicon (a-Si:H) by scanning ultrafast electron microscopy (SUEM). We observe an unexpected regime of fast diffusion immediately after photoexcitation, together with spontaneous electron-hole separation and charge trapping induced by the atomic disorder. Our findings demonstrate the rich dynamics of hot carrier transport in amorphous semiconductors that can be revealed by direct imaging based on SUEM.
Lattice dynamics of solid xenon under pressure.
Dewhurst, J K; Ahuja, R; Li, S; Johansson, B
2002-02-18
We use density-functional perturbation theory to obtain the phonon spectrum of fcc xenon under pressure. Thermodynamic properties obtained within the quasiharmonic approximation are in fair to good agreement with experiment at zero pressure. The transition pressure from the fcc to hcp phase is predicted to occur at 5 GPa. The fcc structure is found to be dynamically stable up to a pressure of 100 GPa, beyond which the phonon modes at the X and L symmetry points soften. We attribute the observed sluggish kinetics of the fcc-hcp transition to the small energy difference between the phases as well as to the high dynamical stability of the fcc phase.
Shahab, S.; Erturk, A.
2014-04-01
Low-power electronic systems are used in various underwater applications ranging from naval sensor networks to ecological monitoring for sustainability. In this work, underwater base excitation of cantilevers made of Macro-Fiber Composite (MFC) piezoelectric structures is explored experimentally and theoretically to harvest energy for such wireless electronic components toward enabling self-powered underwater systems. Bimorph cantilevers made of MFCs with different length-to-width ratios and same thickness are tested in air and under water to characterize the change in natural frequency and damping with a focus on the fundamental bending mode. The real and imaginary parts of hydrodynamic frequency response functions are identified and corrected based on this set of experiments. An electrohydroelastic model is developed and experimentally validated for predicting the power delivered to an electrical load as well as the shunted underwater vibration response under base excitation. Variations of the electrical power output with excitation frequency and load resistance are obtained for different length-to-width ratios. Underwater power density results are reported and compared with their in-air counterparts. Specifically a nonlinear dependence of the power density to the cantilever width is reported for energy harvesting from underwater base excitation.
Combustion and stabilization characteristics of a branched flame under Helmholtz-type excitations
Energy Technology Data Exchange (ETDEWEB)
Yei-Chin, Chao; Hung-Wei, Hsu; Guan-Bang, Chen; Zhao-Hway, Tseng [National Cheng Kung Univ., Tainan (Taiwan). Inst. of Aeronaut. and Astronaut.
2002-02-01
The combustion and pollution characteristics of the newly rediscovered ''branched flame'' are experimentally investigated using a Helmholtz-type excitation. Under specific excitation conditions, high-amplitude Helmholtz excitation induces side jet ejection, which leads to a branched flame. Intense combustion and enhanced heat transfer due to strong oscillation of the flame and hot gases of the branched flame increase the heating effectiveness and fuel saving. Strong velocity oscillation results in accumulation of jet fluid ahead of the ring structure for generation of the side jet. In the side-jet evolution, the strong entrainment of the ring vortex in the initial stages followed by the early growth of the streamwise vortical structures greatly shortens the route to mixing transition of fuel and air in the upstream region of the flame. This enhanced premixing process of the side jet leading to high F probability, which is defined as the probability of the presence of a premixture of fuel and air with concentration within the flammability limits, and low strain rate has significant implications for the stabilization of the branched flame. NOx emission indices for the branched flames can be 30% higher and CO emission indices 50% lower than the unexcited case. (orig.)
Hole dynamics in canted antiferromagnets: Coexistence of many-body and free-like excitations
Hamad, I. J.; Manuel, L. O.; Martinez, G.; Trumper, A. E.
2006-09-01
We have analyzed the dynamics of a single hole doped in a canted antiferromagnet using the t-J model. Within the self-consistent Born approximation we have found that the hole propagates at two different energy scales along the antiferromagnetic and the ferromagnetic components of the canted order, respectively. While the many body quasiparticle excitation has its origin in the coherent coupling of the hole with the magnon excitations of the antiferromagnetic component, the ferromagnetic component gives rise to a free-like hole motion at higher energies. We have found a nontrivial behavior of the hole spectral function with the canting angle θ . In particular, in the strong coupling regime, the quasiparticle weight strongly depends on the momenta, vanishing inside the magnetic Brillouin zone for θ≳60° .
Dynamics of the helium atom close to the full fragmentation threshold: Ionization excitation
International Nuclear Information System (INIS)
Bouri, C.; Selles, P.; Malegat, L.; Teuler, J.M.; Njock, M. Kwato; Kazansky, A.K.
2005-01-01
The hyperspherical R-matrix method with semiclassical outgoing waves, designed to provide accurate double-ionization cross sections, is extended to allow for the computation of ionization-excitation data of comparable quality. Accordingly, it appears now as a complete method for treating the correlated dynamics of two-electron atoms, in particular above their full fragmentation threshold. Cross sections σ n and asymmetry parameters β n are obtained for single photoionization of helium with excitation of the residual ion up to as high a level as n=50 at 0.1 eV above the double-ionization threshold. These data are extrapolated to infinite values of n in order to check widespread assumptions regarding this limit. Our data are found consistent with the assumed n -3 dependence of the partial ionization cross sections. However, the β ∞ =-0.636 obtained still lies far from the -1 value expected at the double-ionization threshold
On the dynamics of excited atoms in time dependent electromagnetic fields
Energy Technology Data Exchange (ETDEWEB)
Foerre, Morten
2004-06-01
This thesis is composed of seven scientific publications written in the period 2001-2004. The focus has been set on Rydberg atoms of hydrogen and lithium in relatively weak electromagnetic fields. Such atoms have been studied extensively during many years, both experimentally and theoretically, They are relatively easy to handle in the laboratory. Their willingness to react to conventional field sources and their long lifetimes, are two reasons for this. Much new insight into fundamental quantum mechanics has been extracted from such studies. By exciting a non-hydrogenic ground state atom or molecule into a highly excited state, many properties of atomic hydrogen are adopted. In many cases the dynamics of such systems can be accurately described by the hydrogenic theory, or alternatively by some slightly modified version like quantum defect theory. In such theories the Rydberg electron(s) of the non-hydrogenic Rydberg system is treated like it is confined in a modified Coulomb potential, which arises from the non-hydrogenic core. defined by the non-excited electrons and the nucleus. The more heavily bound core electrons are less influenced from external perturbations than the excited electrons, giving rise to the so-called frozen-core approximation. where the total effect of the core electrons is put into a modified Coulomb potential. A major part of this thesis has been allocated to the study of core effects in highly excited states of lithium. In collaboration with time experimental group of Erik Horsdal-Pedersen at Aarhus University, we have considered several hydrogenic and non-hydrogenic aspects of such states, when exposed to weak slowly varying electromagnetic fields. The dynamics was restricted to one principal shell (intrashell). Two general features were observed, either the hydrogenic theory applied or alternatively, in case of massive deviation, the dynamics was accurately described by quantum defect theory, clearly demonstrating the usefulness of such
Brennan Ashwood; Steffen Jockusch; Carlos E. Crespo-Hernández
2017-01-01
6-Thioguanine, an immunosuppressant and anticancer prodrug, has been shown to induce DNA damage and cell death following exposure to UVA radiation. Its metabolite, 6-thioguanosine, plays a major role in the prodrug’s overall photoreactivity. However, 6-thioguanine itself has proven to be cytotoxic following UVA irradiation, warranting further investigation into its excited-state dynamics. In this contribution, the excited-state dynamics and photochemical properties of 6-thioguanine are studie...
DEFF Research Database (Denmark)
Roland, Per E.; Bonde, Lars H.; Forsberg, Lars E.
2017-01-01
-time dynamics of excitation and inhibition simultaneously in dendrites and axons over four visual areas of ferrets exposed to visual scenes with stationary and moving objects. The visual stimuli broke the tight balance between excitation and inhibition such that the network exhibited longer episodes of net...... over the whole network to a flow on a low-(3)-dimensional manifold within 80 ms. In contrast to the pure temporal dynamics, the low dimensional flow evolved to distinguish the simple visual scenes....
Light yield of undoped sapphire at low temperature under particle excitation
International Nuclear Information System (INIS)
Amare, J.; Beltran, B.; Cebrian, S.; Garcia, E.; Gomez, H.; Irastorza, I.G.; Luzon, G.; Martinez, M.; Morales, J.; Ortiz de Solorzano, A.; Pobes, C.; Puimedon, J.; Rodriguez, A.; Ruz, J.; Sarsa, M.L.; Torres, L.; Villar, J.A.; Coron, N.; Dambier, G.; Leblanc, J.
2005-01-01
In this letter, we report on the performance of scintillating sapphire bolometers developed in the framework of the ROSEBUD (Rare Objects Search with Bolometers UnDerground) Collaboration devoted to dark matter searches. The simultaneous measurement of heat and light allows the discrimination of the type of particle increasing the sensitivity for these searches. A heat versus light negative correlation for gamma events has been observed. Its interpretation, in a simple framework, allows the estimation of the light yield of undoped sapphire at a temperature of about 20 mK under gamma, alpha, and neutron excitation
Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation
Directory of Open Access Journals (Sweden)
Shi-Jian Zhu
2014-01-01
Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.
Agueny, Hicham; Makhoute, Abdelkader; Dubois, Alain
2017-06-01
We theoretically investigate quantum virtual path interference caused by the dynamic Stark effect in bound-bound electronic transitions. The effect is studied in an intermediate resonant region and in connection with the energetic electron impact excitation of a helium atom embedded in a weak low-frequency laser field. The process under investigation is dealt with via a Born-Floquet approach. Numerical calculations show a resonant feature in laser-assisted cross sections. The latter is found to be sensitive to the intensity of the laser field dressing. We show that this feature is a signature of quantum beats which result from the coherent mixture of different quantum virtual pathways, and that excitation may follow in order to end up with a common final channel. This mixture arises from the dynamic Stark effect, which produces a set of avoided crossings in laser-dressed states. The effect allows one to coherently control quantum virtual path interference by varying the intensity of the laser field dressing. Our findings suggest that the combination of an energetic electron and a weak laser field is a useful tool for the coherent control of nonadiabatic transitions in an intermediate resonant region.
Gas Bubble Dynamics under Mechanical Vibrations
Mohagheghian, Shahrouz; Elbing, Brian
2017-11-01
The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.
Luminescence of Er3+ doped double lead halide crystals under X-ray, UV, VIS and IR excitation
Serazetdinov, A. R.; Smirnov, A. A.; Pustovarov, V. A.; Isaenko, L. I.
2017-09-01
Er3+ doped double lead halide crystals incorporate a number of properties making them interesting for practical use in light conducting materials. X-ray excited luminescence (XRL) spectra, photoluminescence (PL) spectra in region of 1.5-3.5 eV, photoluminescence excitation (PLE) spectra (2.75-5 eV) and anti-stokes luminescence (ASL) spectra were measured at room temperature in KPb2Cl5 (KPC) and RbPb2Br5 (RPB) matrices doped with Er3+ (1%) ions and in KPC doped with Er3++ Yb3+ ions(1:3 ratio concentration). Intraconfigurational f→f transitions are observed in Er3+ ions in most of the cases. The concrete spectrum form is strongly dependent on the excitation energy. Under 980 nm excitation upper Er3+ levels are excited, showing upconversional processes. In case of 313 nm (UV) and 365 nm (VIS) excitation self trapped exciton luminescence was detected in RPB crystal. Additional Yb3+ doping ions strongly increase quantum yield under 980 nm excitation and this doping cause insignificant influence on quantum yield under VIS or UV excitation.
DEFF Research Database (Denmark)
Turchinovich, Dmitry; Monozon, B. S.; Jepsen, Peter Uhd
2006-01-01
In this work we describe the ultrafast excitation kinetics of biased quantum well, arising from the optically induced dynamical screening of a bias electric field. The initial bia electric field inside the quantum well is screened by the optically excited polarized electron-hole pairs. This leads...... to a dynamical modification of the properties of the system within an excitation pulse duration. We calculate the excitation kinetics of a biased quantum well and the dependency of resulting electronic and optical properties on the excitation pulse fluence, quantum well width,and initial bias field strength. Our...... wells are in good agreement with our experimental observations [Turchinovich et al., Phys. Rev. B 68, 241307(R) (2003)], as well as in perfect compliance with qualitative considerations. ©2006 American Institute of Physics...
Joseph, Saju
2017-10-02
We characterize the dynamic nature of the lowest excited state in a pentacene/C60 complex on the femtosecond time scale, via a combination of ab initio molecular dynamics and time-dependent density functional theory. We analyze the correlations between the molecular vibrations of the complex and the oscillations in the electron-transfer character of its lowest excited state, which point to vibration-induced coherences between the (pentacene-based) local-excitation (LE) state and the complex charge-transfer (CT) state. We discuss the implications of our results on this model system for the exciton-dissociation process in organic solar cells.
Study of the IPR-R1 dynamics by means of reactivity pseudo-aleatory excitations
International Nuclear Information System (INIS)
Roedel, G.
1983-01-01
Aiming to demonstrate the feasibility of using the reactor noise neutronic analysis tecniques a dynamic model was developed for the IPR-R1 reactor at CDTN. This model allows reactivity feedback, due to the variations of fuel and coolant temperature. The system was excited by the variations of reactivity modulated by a pseudo aleatory binary sequence and its answer was measured by means of the fluctuactions dround the stationary power. The model developed and the technique used was tested, and the values of the system parameters obtained from the adjustment of the theoretical and experimental transfer function were compared to another, obtained from independent process. (E.G.) [pt
Phasing of Stokes radiation under shock excitation of stimulated Brillouin scattering
Energy Technology Data Exchange (ETDEWEB)
Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)
2011-11-30
Interaction of counterpropagating waves in Brillouin-active media has been analysed by numerical computation. The dynamics of the development of acoustic waves is described using a secondorder equation. It is shown that in the case of counterpropagating waves with sufficiently steep leading pulse edges ({tau}{sub f} {<=} 3T{sub 2}, where T{sub 2} is the acoustic phonon lifetime), SBS begins from the level of acoustic waves induced by shock excitation in the bulk of the active medium rather than from the spontaneous noise level. This mechanism determines the phase of the output Stokes wave, which is generated in the backward direction to the wave with the highest input intensity, irrespective of the ratio of counterpropagating-wave frequencies.
Jagannathan, S
1999-01-01
The local structure of CMAC neural networks (NN) result in better and faster controllers for nonlinear dynamical systems. A CMAC neural network-based discrete-time controller which linearizes the unknown multiinput and multioutput (MIMO) nonlinear system through feedback is presented. Control action is defined in order to achieve tracking performance for this unknown nonlinear system. An efficient and localized weight addressing scheme for the CMAC NN's is described using an appropriate choice of the B-spline receptive field functions that form a basis. A uniform ultimate boundedness of the closed-loop system is given in the sense of Lyapunov using the persistency of excitation (PE) condition. Simulation results are shown to demonstrate the theoretical conclusions.
Impact-Based Electromagnetic Energy Harvester with High Output Voltage under Low-Level Excitations
Directory of Open Access Journals (Sweden)
Qian Luo
2017-11-01
Full Text Available To expand the applications of vibrational energy harvesters (VEHs as power sources of wireless sensor nodes, it is of significance to improve the scavenging efficiency for the broadband, low-frequency, and low-level vibrational energy. The output voltages of electromagnetic vibrational energy harvesters (EMVEHs are usually low, which complicates the power management circuit by an indispensable voltage boosting element. To this end, an impact-based non-resonant EMVEH mainly composed of an outer frame and an inner frame on rollers is proposed. Numerical simulations based on a mathematical model of the harvester are conducted to analyze the effects of structural parameters on the output performance. Under base excitation of 0.1 and 0.3 (where g is the gravitational acceleration, 1 g = 9.8 m · s − 2 , the experimental maximum root mean square voltages of a harvester prototype across a resistor of 11 kΩ are as high as 7.6 and 16.5 V at 6.0 and 8.5 Hz, respectively, with the maximum output powers of 5.3 and 24.8 mW, or the power densities of 54.6 and 256 μW cm−3. By using a management circuit without a voltage boosting element, a wireless sensor node driven by the prototype can measure and transmit the temperature and humidity every 20 s under base excitation of 0.1 g at 5.4 Hz.
Chen, Z.; To, C. W. S.
2005-10-01
The extended stochastic central difference (ESCD) method is proposed as a viable alternative for computing linear responses of discretized multi-degrees-of-freedom (mdof) systems under narrow band stationary and nonstationary random disturbances. The method provides a means of controlling the center frequencies and bandwidths of narrow band stationary and nonstationary random excitation processes. It is suitable for larger-scale random response analysis of complicated structures idealized by the finite element method. Its additional important feature is that application of normal mode or complex normal mode analysis or direct numerical integration algorithms such as the fourth-order Runge-Kutta scheme is not required. Examples, including one of flow-induced vibration of a pipe containing a moving fluid are included to demonstrate: (1) the capability of the proposed method and difference between responses of discretized systems under narrow band and wide band random excitations, and (2) its accuracy and efficiency by way of comparison to the Monte Carlo simulation data. Generalization of the ESCD method for computation of responses of nonlinear mdof systems is presented in a companion paper.
Excitation of high energy levels under laser exposure of suspensions of nanoparticles in liquids
Energy Technology Data Exchange (ETDEWEB)
Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute, 38, Vavilov Street, 119991 Moscow (Russian Federation)], E-mail: shafeev@kapella.gpi.ru; Simakin, A.V. [Wave Research Center of A.M. Prokhorov General Physics Institute, 38, Vavilov Street, 119991 Moscow (Russian Federation); Bozon-Verduraz, F. [ITODYS, UMR CNRS 7086, Universite Paris 7-Denis Diderot, 2, place Jussieu, 75251 Paris cedex 05 (France); Robert, M. [Laboratoire d' Electrochimie Moleculaire, UMR CNRS 7591, Universite Paris 7 Denis Diderot, 2, place Jussieu, 75251 Paris cedex 05 (France)
2007-12-15
Laser exposure of suspensions of nanoparticles in liquids leads to excitation of high energy levels in both liquid and nanoparticle material. The emission spectrum of the colloidal solution under exposure of a suspension metallic nanoparticles in water to radiation of a Nd:YAG laser of a picosecond range of pulse duration is discussed. Excitation of nuclear energy levels and neutron release is experimentally studied on the model system of transmutation of Hg into Au that occurs under exposure of Hg nanodrops suspended in D{sub 2}O. The proposed mechanism involves: (i) emission of X-ray photons by Hg nanoparticles upon laser exposure, leading to neutron release from D{sub 2}O, (ii) initiation of Hg {yields} Au transmutation by the capture of neutrons. The effect of transmutation is more pronounced using {sup 196}Hg isotope instead of Hg of natural isotope composition. The influence of laser pulse duration on the degree of transmutation (from fs through ns range) is discussed.
International Nuclear Information System (INIS)
Yuan Wujie; Luo Xiaoshu; Jiang Pinqun
2007-01-01
In this paper, we propose a new model of weighted small-world biological neural networks based on biophysical Hodgkin-Huxley neurons with side-restrain mechanism. Then we study excitement properties of the model under alternating current (AC) stimulation. The study shows that the excitement properties in the networks are preferably consistent with the behavior properties of a brain nervous system under different AC stimuli, such as refractory period and the brain neural excitement response induced by different intensities of noise and coupling. The results of the study have reference worthiness for the brain nerve electrophysiology and epistemological science.
Directory of Open Access Journals (Sweden)
Brennan Ashwood
2017-02-01
Full Text Available 6-Thioguanine, an immunosuppressant and anticancer prodrug, has been shown to induce DNA damage and cell death following exposure to UVA radiation. Its metabolite, 6-thioguanosine, plays a major role in the prodrug’s overall photoreactivity. However, 6-thioguanine itself has proven to be cytotoxic following UVA irradiation, warranting further investigation into its excited-state dynamics. In this contribution, the excited-state dynamics and photochemical properties of 6-thioguanine are studied in aqueous solution following UVA excitation at 345 nm in order to provide mechanistic insight regarding its photochemical reactivity and to scrutinize whether N9-glycosylation modulates its phototoxicity in solution. The experimental results are complemented with time-dependent density functional calculations that include solvent dielectric effects by means of a reaction-field solvation model. UVA excitation results in the initial population of the S2(ππ* state, which is followed by ultrafast internal conversion to the S1(nπ* state and then intersystem crossing to the triplet manifold within 560 ± 60 fs. A small fraction (ca. 25% of the population that reaches the S1(nπ* state repopulates the ground state. The T1(ππ* state decays to the ground state in 1.4 ± 0.2 μs under N2-purged conditions, using a 0.2 mM concentration of 6-thioguanine, or it can sensitize singlet oxygen in 0.21 ± 0.02 and 0.23 ± 0.02 yields in air- and O2-saturated solution, respectively. This demonstrates the efficacy of 6-thioguanine to act as a Type II photosensitizer. N9-glycosylation increases the rate of intersystem crossing from the singlet to triplet manifold, as well as from the T1(ππ* state to the ground state, which lead to a ca. 40% decrease in the singlet oxygen yield under air-saturated conditions. Enhanced vibronic coupling between the singlet and triplet manifolds due to a higher density of vibrational states is proposed to be responsible for the observed
Chen, Maomao; Zhou, Yuan; Su, Han; Zhang, Dong; Luo, Jianwen
2017-04-01
Imaging of the pharmacokinetic parameters in dynamic fluorescence molecular tomography (DFMT) can provide three-dimensional metabolic information for biological studies and drug development. However, owing to the ill-posed nature of the FMT inverse problem, the relatively low quality of the parametric images makes it difficult to investigate the different metabolic processes of the fluorescent targets with small distances. An excitation-resolved multispectral DFMT method is proposed; it is based on the fact that the fluorescent targets with different concentrations show different variations in the excitation spectral domain and can be considered independent signal sources. With an independent component analysis method, the spatial locations of different fluorescent targets can be decomposed, and the fluorescent yields of the targets at different time points can be recovered. Therefore, the metabolic process of each component can be independently investigated. Simulations and phantom experiments are carried out to evaluate the performance of the proposed method. The results demonstrated that the proposed excitation-resolved multispectral method can effectively improve the reconstruction accuracy of the parametric images in DFMT.
Tresser, Shachar; Dolev, Amit; Bucher, Izhak
2018-02-01
High-speed machinery is often designed to pass several "critical speeds", where vibration levels can be very high. To reduce vibrations, rotors usually undergo a mass balancing process, where the machine is rotated at its full speed range, during which the dynamic response near critical speeds can be measured. High sensitivity, which is required for a successful balancing process, is achieved near the critical speeds, where a single deflection mode shape becomes dominant, and is excited by the projection of the imbalance on it. The requirement to rotate the machine at high speeds is an obstacle in many cases, where it is impossible to perform measurements at high speeds, due to harsh conditions such as high temperatures and inaccessibility (e.g., jet engines). This paper proposes a novel balancing method of flexible rotors, which does not require the machine to be rotated at high speeds. With this method, the rotor is spun at low speeds, while subjecting it to a set of externally controlled forces. The external forces comprise a set of tuned, response dependent, parametric excitations, and nonlinear stiffness terms. The parametric excitation can isolate any desired mode, while keeping the response directly linked to the imbalance. A software controlled nonlinear stiffness term limits the response, hence preventing the rotor to become unstable. These forces warrant sufficient sensitivity required to detect the projection of the imbalance on any desired mode without rotating the machine at high speeds. Analytical, numerical and experimental results are shown to validate and demonstrate the method.
Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction
Zhi-Xin, Li; Qing-Jie, Cao; Léger, Alain
2016-01-01
We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous (SD) oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography. Project supported by the National Natural Science Foundation of China (Grant Nos. 11372082 and 11572096) and the National Basic Research Program of China (Grant No. 2015CB057405).
DEFF Research Database (Denmark)
Eriksen, Janus J.; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin
2012-01-01
picture leading to the PE-Random-Phase Approximation (PE-RPA) and bridge the expressions to a Second-Order Polarization Propagator Approximation (SOPPA) frame such that dynamic reaction field contributions are included at the RPA level in addition to the static response described at the SOPPA level...... but with HF induced dipole moments. We conduct calculations on para-nitro-aniline and para-nitro-phenolate using said model in addition to dynamic PE-RPA and PE-CAM-B3LYP. We compare the results to recently published PE-CCSD data and demonstrate how the cost effective SOPPA based model successfully recovers...... a great portion of the inherent PE-RPA error when the observable is the solvatochromic shift. We furthermore demonstrate that whenever the change in density resulting from the ground state-excited state electronic transition in the solute is not associated with a significant change in the electric field...
Total dynamic response of a PSS vehicle negotiating asymmetric road excitations
Zhu, Jian Jun; Khajepour, Amir; Esmailzadeh, Ebrahim
2012-12-01
A planar suspension system (PSS) is a novel automobile suspension system in which an individual spring-damper strut is implemented in both the vertical and longitudinal directions, respectively. The wheels in a vehicle with such a suspension system can move back and forth relative to the chassis. When a PSS vehicle experiences asymmetric road excitations, the relative longitudinal motion of wheels with respect to the chassis in two sides of the same axle are not identical, and thus the two wheels at one axle will not be aligned in the same axis. The total dynamic responses, including those of the bounce, pitch and the roll of the PSS vehicle, to the asymmetric road excitation may exhibit different characteristics from those of a conventional vehicle. This paper presents an investigation into the comprehensive dynamic behaviour of a vehicle with the PSS, in such a road condition, on both the straight and curved roads. The study was carried out using an 18 DOF full-car model incorporating a radial-spring tyre-ground contact model and a 2D tyre-ground dynamic friction model. Results demonstrate that the total dynamic behaviour of a PSS vehicle is generally comparable with that of the conventional vehicle, while PSS exhibits significant improvement in absorbing the impact forces along the longitudinal direction when compared to the conventional suspension system. The PSS vehicle is found to be more stable than the conventional vehicle in terms of the directional performance against the disturbance of the road potholes on a straight line manoeuvre, while exhibiting a very similar handling performance on a curved line.
Machine learning for quantum dynamics: deep learning of excitation energy transfer properties.
Häse, Florian; Kreisbeck, Christoph; Aspuru-Guzik, Alán
2017-12-01
Understanding the relationship between the structure of light-harvesting systems and their excitation energy transfer properties is of fundamental importance in many applications including the development of next generation photovoltaics. Natural light harvesting in photosynthesis shows remarkable excitation energy transfer properties, which suggests that pigment-protein complexes could serve as blueprints for the design of nature inspired devices. Mechanistic insights into energy transport dynamics can be gained by leveraging numerically involved propagation schemes such as the hierarchical equations of motion (HEOM). Solving these equations, however, is computationally costly due to the adverse scaling with the number of pigments. Therefore virtual high-throughput screening, which has become a powerful tool in material discovery, is less readily applicable for the search of novel excitonic devices. We propose the use of artificial neural networks to bypass the computational limitations of established techniques for exploring the structure-dynamics relation in excitonic systems. Once trained, our neural networks reduce computational costs by several orders of magnitudes. Our predicted transfer times and transfer efficiencies exhibit similar or even higher accuracies than frequently used approximate methods such as secular Redfield theory.
Excited-state dynamics of size-dependent colloidal TiO{sub 2}-Au nanocomposites
Energy Technology Data Exchange (ETDEWEB)
Karam, Tony E.; Khoury, Rami A.; Haber, Louis H., E-mail: lhaber@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)
2016-03-28
The ultrafast excited-state dynamics of size-dependent TiO{sub 2}-Au nanocomposites synthesized by reducing gold nanoclusters to the surface of colloidal TiO{sub 2} nanoparticles are studied using pump-probe transient absorption spectroscopy with 400 nm excitation pulses. The results show that the relaxation processes of the plasmon depletion band, which are described by electron-phonon and phonon-phonon scattering lifetimes, are independent of the gold nanocluster shell size surrounding the TiO{sub 2} nanoparticle core. The dynamics corresponding to interfacial electron transfer between the gold nanoclusters and the TiO{sub 2} bandgap are observed to spectrally overlap with the gold interband transition signal, and the electron transfer lifetimes are shown to significantly decrease as the nanocluster shell size increases. Additionally, size-dependent periodic oscillations are observed and are attributed to acoustic phonons of a porous shell composed of aggregated gold nanoclusters around the TiO{sub 2} core, with frequencies that decrease and damping times that remain constant as the nanocluster shell size increases. These results are important for the development of improved catalytic nanomaterial applications.
Directory of Open Access Journals (Sweden)
Minodora Maria PASĂRE
2010-10-01
Full Text Available In these paper, starting from the relations for the displacements and spinning the transversal section of a bar with thin walls of sections opened expressed by the corresponding influence functions and introducing the components of the exterior forces distributed and the moments of the exterior forces distributed due to the inertia forces, the exciting axial forces together with the following effect of these and of the reaction forces of the elastic environment for leaning it may reach to the system of the equations of parametric vibrations under the form of three integral equation These equations may serve for the study of vibrations of the bars, to study the static stability and to study the dynamic stability
Dynamics of Nonlinear Excitation of the High-Order Mode in a Single-Mode Step-Index Optical Fiber
Burdin, V.; Bourdine, A.
2018-04-01
This work is concerned with approximate model of higher-order mode nonlinear excitation in a singlemode silica optical fiber. We present some results of simulation for step-index optical fiber under femtosecond optical pulse launching, which confirm ability of relatively stable higher-order mode excitation in such singlemode optical fiber over sufficiently narrow range of launched optical power variation.
Complex networks under dynamic repair model
Chaoqi, Fu; Ying, Wang; Kun, Zhao; Yangjun, Gao
2018-01-01
Invulnerability is not the only factor of importance when considering complex networks' security. It is also critical to have an effective and reasonable repair strategy. Existing research on network repair is confined to the static model. The dynamic model makes better use of the redundant capacity of repaired nodes and repairs the damaged network more efficiently than the static model; however, the dynamic repair model is complex and polytropic. In this paper, we construct a dynamic repair model and systematically describe the energy-transfer relationships between nodes in the repair process of the failure network. Nodes are divided into three types, corresponding to three structures. We find that the strong coupling structure is responsible for secondary failure of the repaired nodes and propose an algorithm that can select the most suitable targets (nodes or links) to repair the failure network with minimal cost. Two types of repair strategies are identified, with different effects under the two energy-transfer rules. The research results enable a more flexible approach to network repair.
Fundamental Dynamical Modes Underlying Human Brain Synchronization
Directory of Open Access Journals (Sweden)
Catalina Alvarado-Rojas
2012-01-01
Full Text Available Little is known about the long-term dynamics of widely interacting cortical and subcortical networks during the wake-sleep cycle. Using large-scale intracranial recordings of epileptic patients during seizure-free periods, we investigated local- and long-range synchronization between multiple brain regions over several days. For such high-dimensional data, summary information is required for understanding and modelling the underlying dynamics. Here, we suggest that a compact yet useful representation is given by a state space based on the first principal components. Using this representation, we report, with a remarkable similarity across the patients with different locations of electrode placement, that the seemingly complex patterns of brain synchrony during the wake-sleep cycle can be represented by a small number of characteristic dynamic modes. In this space, transitions between behavioral states occur through specific trajectories from one mode to another. These findings suggest that, at a coarse level of temporal resolution, the different brain states are correlated with several dominant synchrony patterns which are successively activated across wake-sleep states.
Babaev, A. A.; Pivovarov, Yu L.
2010-04-01
Resonant coherent excitation (RCE) of relativistic hydrogen-like ions is investigated by computer simulations methods. The suggested theoretical model is applied to the simulations of recent experiments on RCE of 390 MeV/u Ar17+ ions under (220) planar channeling in a Si crystal performed by T.Azuma et al at HIMAC (Tokyo). Theoretical results are in a good agreement with these experimental data and clearly show the appearance of the doublet structure of RCE peaks. The simulations are also extended to greater ion energies in order to predict the new RCE features at the future accelerator facility FAIR OSI and as an example, RCE of II GeV/u U91+ ions is considered in detail.
Excited-state vibronic wave-packet dynamics in H2 probed by XUV transient four-wave mixing
Cao, Wei; Warrick, Erika R.; Fidler, Ashley; Leone, Stephen R.; Neumark, Daniel M.
2018-02-01
The complex behavior of a molecular wave packet initiated by an extreme ultraviolet (XUV) pulse is investigated with noncollinear wave mixing spectroscopy. A broadband XUV pulse spanning 12-16 eV launches a wave packet in H2 comprising a coherent superposition of multiple electronic and vibrational levels. The molecular wave packet evolves freely until a delayed few-cycle optical laser pulse arrives to induce nonlinear signals in the XUV via four-wave mixing (FWM). The angularly resolved FWM signals encode rich energy exchange processes between the optical laser field and the XUV-excited molecule. The noncollinear geometry enables spatial separation of ladder and V- or Λ-type transitions induced by the optical field. Ladder transitions, in which the energy exchange with the optical field is around 3 eV, appear off axis from the incident XUV beam. Each vibrationally revolved FWM line probes a different part of the wave packet in energy, serving as a promising tool for energetic tomography of molecular wave packets. V- or Λ-type transitions, in which the energy exchange is well under 1 eV, result in on-axis nonlinear signals. The first-order versus third-order interference of the on-axis signal serves as a mapping tool of the energy flow pathways. Intra- and interelectronic potential energy curve transitions are decisively identified. The current study opens possibilities for accessing complete dynamic information in XUV-excited complex systems.
International Nuclear Information System (INIS)
Park, Young-Min; Kim, Kwang-Joon
2011-01-01
Piezoelectric exciters have been receiving greater attention recently as a vibration source for tactile feedback in devices with touch screens, such as a mobile phones, in place of DC motors due to lower energy consumption and smaller volume. Their insufficient excitation level, however, still remains a problem. In this paper, dynamic modeling and design improvement of a piezoelectric exciter are presented. The excitation performance is defined as the acceleration response at the center of a touch screen per electric power and to be maximized around 250 Hz where the index finger is most sensitive. The piezoelectric exciter consists of a z-shaped metal beam, a piezoelectric layer on the long horizontal segment and an adhesive layer between the short horizontal segment and the touch screen. Assuming that the piezoelectric exciter is attached onto a rigid ground due to its low mechanical impedance compared with that of the touch screen, the piezoelectric exciter is dynamically modeled by applying Hamilton's principle, where the adhesive layer is treated as a distributed stiffness. The touch screen is modeled approximately as a simply supported beam such that it may have the same fundamental natural frequency and bending stiffness as the screen based on measurements. The performance improvement is focused on the change of five geometric parameters of the piezoelectric exciter: length of the long horizontal segment, thickness of the piezoelectric layer, thickness of the elastic metal layer, width of the beams and tip mass. The procedure to improve the performance of the piezoelectric exciter via dynamic modeling is presented together with experimental results on a prototype. Effectiveness of the design modification and limitations in practice are further discussed as well
Park, Young-Min; Kim, Kwang-Joon
2011-05-01
Piezoelectric exciters have been receiving greater attention recently as a vibration source for tactile feedback in devices with touch screens, such as a mobile phones, in place of DC motors due to lower energy consumption and smaller volume. Their insufficient excitation level, however, still remains a problem. In this paper, dynamic modeling and design improvement of a piezoelectric exciter are presented. The excitation performance is defined as the acceleration response at the center of a touch screen per electric power and to be maximized around 250 Hz where the index finger is most sensitive. The piezoelectric exciter consists of a z-shaped metal beam, a piezoelectric layer on the long horizontal segment and an adhesive layer between the short horizontal segment and the touch screen. Assuming that the piezoelectric exciter is attached onto a rigid ground due to its low mechanical impedance compared with that of the touch screen, the piezoelectric exciter is dynamically modeled by applying Hamilton's principle, where the adhesive layer is treated as a distributed stiffness. The touch screen is modeled approximately as a simply supported beam such that it may have the same fundamental natural frequency and bending stiffness as the screen based on measurements. The performance improvement is focused on the change of five geometric parameters of the piezoelectric exciter: length of the long horizontal segment, thickness of the piezoelectric layer, thickness of the elastic metal layer, width of the beams and tip mass. The procedure to improve the performance of the piezoelectric exciter via dynamic modeling is presented together with experimental results on a prototype. Effectiveness of the design modification and limitations in practice are further discussed as well.
Djomo Mbong, T. L. M.; Siewe Siewe, M.; Tchawoua, C.
2018-01-01
In this study, the effect of a controllable parametric excitation on both linear and nonlinear vibrational resonances on the dynamic of a buckled beam excited by a combination of uncontrollable low- and high-frequency periodic forces are investigated. First of all, the beam dynamic is assumed to be constrained by two periodic and independent ambient solicitations, such as wind and earthquake. An axial load of the beam represented by a periodic and parametric excitation is used to control the vibrational resonance phenomenon, induced by the presence of the two external excitations. Approximate analytical expressions for the linear response and the high-frequency force amplitude at which linear vibrational resonance occurs are obtained. An analytical expression of the amplitude of the nonlinear response at the superharmonic equal to the double of the low-frequency, is obtained. For all these expressions, we show the effect of the parametric excitation. We compare all the obtained results with the ones of the case where, the parametric force is absent. It is shown that, the presence of the parametric excitation permit the suppression of both linear and nonlinear vibrational resonances. Moreover, the vibration amplitudes of the buckled beam are significantly reduced, around certain threshold values for the amplitude and the frequency of the parametric excitation.
Dynamical anisotropic response of black phosphorus under magnetic field
Liu, Xuefeng; Lu, Wei; Zhou, Xiaoying; Zhou, Yang; Zhang, Chenglong; Lai, Jiawei; Ge, Shaofeng; Sekhar, M. Chandra; Jia, Shuang; Chang, Kai; Sun, Dong
2018-04-01
Black phosphorus (BP) has emerged as a promising material candidate for next generation electronic and optoelectronic devices due to its high mobility, tunable band gap and highly anisotropic properties. In this work, polarization resolved ultrafast mid-infrared transient reflection spectroscopy measurements are performed to study the dynamical anisotropic optical properties of BP under magnetic fields up to 9 T. The relaxation dynamics of photoexcited carrier is found to be insensitive to the applied magnetic field due to the broadening of the Landau levels and large effective mass of carriers. While the anisotropic optical response of BP decreases with increasing magnetic field, its enhancement due to the excitation of hot carriers is similar to that without magnetic field. These experimental results can be well interpreted by the magneto-optical conductivity of the Landau levels of BP thin film, based on an effective k · p Hamiltonian and linear response theory. These findings suggest attractive possibilities of multi-dimensional control of anisotropic response (AR) of BP with light, electric and magnetic field, which further introduces BP to the fantastic magnetic field sensitive applications.
Electric dipole versus full interaction in the dynamics of laser excitation of Rydberg wavepackets
Energy Technology Data Exchange (ETDEWEB)
Mercouris, Theodoros; Komninos, Yannis [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens (Greece)]. E-mails: thmerc@eie.gr; ykomn@eie.gr; Nicolaides, Cleanthes A. [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens (GR) and Physics Department, National Technical University, Athens (Greece)]. E-mail: can@eie.gr
2002-03-28
We solve the time-dependent Schroedinger equation (TDSE) that describes the resonant excitation of the hydrogen 1s state to Rydberg states and wavepackets using the electric dipole approximation (EDA) in the length form as well as the full electric interaction of the multipolar Hamiltonian. The time-dependent wavefunctions are expanded in a hydrogenic basis and the TDSE is transformed into a system of coupled integro-differential equations. The truncation of this expansion is done systematically and judiciously within a scheme which we call the multimanifold intrashell approximation, according to which the intershell matrix elements are ignored. The ensuing drastic reduction in the size of the overall calculation allows an economic and meaningful solution of the problem when the multipolar interaction to all orders is taken into account. Three categories of calculations were carried out, all involving many hydrogenic n-manifolds, without and with intrashell couplings. A series of computations dealt with resonant excitation of manifolds up to n{sub res}=85. The first two categories of calculations involved the EDA and multimanifold expansions without and with intrashell matrix elements. The third category involved the full multipolar interaction and multimanifold expansions with intrashell matrix elements. The reported time-dependent survival probabilities revealed that, even for the weak field used (8.75x10{sup 7} W cm{sup -2}), as the level of the resonant excitation rises beyond n{>=}10, the EDA fails to describe the correct dynamics of such processes. The results herein provide quantitative information and demonstrate beyond doubt the limitations and inaccuracies of the EDA when the field-atom coupling involves extended wavefunctions, such as the high-lying Rydberg states. (author)
Directory of Open Access Journals (Sweden)
Mohamed E. A. Farrag
2014-01-01
Full Text Available Incentives, such as the Feed-in-tariff are expected to lead to continuous increase in the deployment of Small Scale Embedded Generation (SSEG in the distribution network. Self-Excited Induction Generators (SEIG represent a significant segment of potential SSEG. The quality of SEIG output voltage magnitude and frequency is investigated in this paper to support the SEIG operation for different network operating conditions. The dynamic behaviour of the SEIG resulting from disconnection, reconnection from/to the grid and potential operation in islanding mode is studied in detail. The local load and reactive power supply are the key factors that determine the SEIG performance, as they have significant influence on the voltage and frequency change after disconnection from the grid. Hence, the aim of this work is to identify the optimum combination of the reactive power supply (essential for self excitation of the SEIG and the active load (essential for balancing power generation and demand. This is required in order to support the SEIG operation after disconnection from the grid, during islanding and reconnection to the grid. The results show that the generator voltage and speed (frequency can be controlled and maintained within the statuary limits. This will enable safe disconnection and reconnection of the SEIG from/to the grid and makes it easier to operate in islanding mode.
Dynamic Balance of Excitation and Inhibition in Human and Monkey Neocortex
Dehghani, Nima; Peyrache, Adrien; Telenczuk, Bartosz; Le van Quyen, Michel; Halgren, Eric; Cash, Sydney S.; Hatsopoulos, Nicholas G.; Destexhe, Alain
2016-03-01
Balance of excitation and inhibition is a fundamental feature of in vivo network activity and is important for its computations. However, its presence in the neocortex of higher mammals is not well established. We investigated the dynamics of excitation and inhibition using dense multielectrode recordings in humans and monkeys. We found that in all states of the wake-sleep cycle, excitatory and inhibitory ensembles are well balanced, and co-fluctuate with slight instantaneous deviations from perfect balance, mostly in slow-wave sleep. Remarkably, these correlated fluctuations are seen for many different temporal scales. The similarity of these computational features with a network model of self-generated balanced states suggests that such balanced activity is essentially generated by recurrent activity in the local network and is not due to external inputs. Finally, we find that this balance breaks down during seizures, where the temporal correlation of excitatory and inhibitory populations is disrupted. These results show that balanced activity is a feature of normal brain activity, and break down of the balance could be an important factor to define pathological states.
Godfrey, T. J.; Yu, Hui; Ullrich, Susanne
2014-07-01
The studies herein investigate the involvement of the low-lying 1La and 1Lb states with 1ππ* character and the 1πσ* state in the deactivation process of indole following photoexcitation at 201 nm. Three gas-phase, pump-probe spectroscopic techniques are employed: (1) Time-resolved photoelectron spectroscopy (TR-PES), (2) hydrogen atom (H-atom) time-resolved kinetic energy release (TR-KER), and (3) time-resolved ion yield (TR-IY). Each technique provides complementary information specific to the photophysical processes in the indole molecule. In conjunction, a thorough examination of the electronically excited states in the relaxation process, with particular focus on the involvement of the 1πσ* state, is afforded. Through an extensive analysis of the TR-PES data presented here, it is deduced that the initial excitation of the 1Bb state decays to the 1La state on a timescale beyond the resolution of the current experimental setup. Relaxation proceeds on the 1La state with an ultrafast decay constant (IY experiments, both specifically probing 1πσ* dynamics, exhibit similar decay constants, further validating these observations.
Nonlinear dynamics of a support-excited flexible rotor with hydrodynamic journal bearings
Dakel, Mzaki; Baguet, Sébastien; Dufour, Régis
2014-05-01
The major purpose of this study is to predict the dynamic behavior of an on-board rotor mounted on hydrodynamic journal bearings in the presence of rigid support movements, the target application being turbochargers of vehicles or rotating machines subject to seismic excitation. The proposed on-board rotor model is based on Timoshenko beam finite elements. The dynamic modeling takes into account the geometric asymmetry of shaft and/or rigid disk as well as the six deterministic translations and rotations of the rotor rigid support. Depending on the type of analysis used for the bearing, the fluid film forces computed with the Reynolds equation are linear/nonlinear. Thus the application of Lagrange's equations yields the linear/nonlinear equations of motion of the rotating rotor in bending with respect to the moving rigid support which represents a non-inertial frame of reference. These equations are solved using the implicit Newmark time-step integration scheme. Due to the geometric asymmetry of the rotor and to the rotational motions of the support, the equations of motion include time-varying parametric terms which can lead to lateral dynamic instability. The influence of sinusoidal rotational or translational motions of the support, the accuracy of the linear 8-coefficient bearing model and the interest of the nonlinear model for a hydrodynamic journal bearing are examined and discussed by means of stability charts, orbits of the rotor, time history responses, fast Fourier transforms, bifurcation diagrams as well as Poincaré maps.
Neural dynamics underlying emotional transmissions between individuals.
Golland, Yulia; Levit-Binnun, Nava; Hendler, Talma; Lerner, Yulia
2017-08-01
Emotional experiences are frequently shaped by the emotional responses of co-present others. Research has shown that people constantly monitor and adapt to the incoming social-emotional signals, even without face-to-face interaction. And yet, the neural processes underlying such emotional transmissions have not been directly studied. Here, we investigated how the human brain processes emotional cues which arrive from another, co-attending individual. We presented continuous emotional feedback to participants who viewed a movie in the scanner. Participants in the social group (but not in the control group) believed that the feedback was coming from another person who was co-viewing the same movie. We found that social-emotional feedback significantly affected the neural dynamics both in the core affect and in the medial pre-frontal regions. Specifically, the response time-courses in those regions exhibited increased similarity across recipients and increased neural alignment with the timeline of the feedback in the social compared with control group. Taken in conjunction with previous research, this study suggests that emotional cues from others shape the neural dynamics across the whole neural continuum of emotional processing in the brain. Moreover, it demonstrates that interpersonal neural alignment can serve as a neural mechanism through which affective information is conveyed between individuals. © The Author (2017). Published by Oxford University Press.
Reliability of dynamic systems under limited information.
Energy Technology Data Exchange (ETDEWEB)
Field, Richard V., Jr. (.,; .); Grigoriu, Mircea
2006-09-01
A method is developed for reliability analysis of dynamic systems under limited information. The available information includes one or more samples of the system output; any known information on features of the output can be used if available. The method is based on the theory of non-Gaussian translation processes and is shown to be particularly suitable for problems of practical interest. For illustration, we apply the proposed method to a series of simple example problems and compare with results given by traditional statistical estimators in order to establish the accuracy of the method. It is demonstrated that the method delivers accurate results for the case of linear and nonlinear dynamic systems, and can be applied to analyze experimental data and/or mathematical model outputs. Two complex applications of direct interest to Sandia are also considered. First, we apply the proposed method to assess design reliability of a MEMS inertial switch. Second, we consider re-entry body (RB) component vibration response during normal re-entry, where the objective is to estimate the time-dependent probability of component failure. This last application is directly relevant to re-entry random vibration analysis at Sandia, and may provide insights on test-based and/or model-based qualification of weapon components for random vibration environments.
Dynamic and steady state current response to light excitation of multilayered organic photodiodes
Zaus, E. S.; Tedde, S.; Fürst, J.; Henseler, D.; Döhler, G. H.
2007-02-01
Measurements of current transients are used to gain insight into the mechanism of charge transport and extraction of photodiodes based on bulk heterojunction blends of poly-3-hexyl-thiophene and [6,6]-phenyl C61 butyric acid methyl ester. It is shown that the implementation of an appropriate hole conducting layer leads to a reduction of the dark current in the reverse direction. It is observed that the dynamic response to light excitation is strongly influenced by the thickness of the hole conducting layer, the light intensity, and the applied bias. Charge accumulation at the interface is assumed to result in the characteristic shape of the transients. The shape of the switch-off transient can be understood qualitatively by an equivalent circuit diagram.
Vibrational dynamics of aniline (N2)1 clusters in their first excited singlet state
Hineman, M. F.; Kim, S. K.; Bernstein, E. R.; Kelley, D. F.
1992-04-01
The first excited singlet state S1 vibrational dynamics of aniline(N2)1 clusters are studied and compared to previous results on aniline(CH4)1 and aniline(Ar)1. Intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) rates fall between the two extremes of the CH4 (fast IVR, slow VP) and Ar (slow IVR, fast VP) cluster results as is predicted by a serial IVR/VP model using Fermi's golden rule to describe IVR processes and a restricted Rice-Ramsperger-Kassel-Marcus (RRKM) theory to describe unimolecular VP rates. The density of states is the most important factor determining the rates. Two product states, 00 and 10b1, of bare aniline and one intermediate state ˜(00) in the overall IVR/VP process are observed and time resolved measurements are obtained for the 000 and ˜(000) transitions. The results are modeled with the serial mechanism described above.
Dynamic polarization by coulomb excitation in the closed formalism for heavy ion scattering
International Nuclear Information System (INIS)
Frahn, W.E.; Hill, T.F.
1978-01-01
We present a closed-form treatment of the effects of dynamic polarization by Coulomb excitation on the elastic scattering of deformed heavy ions. We assume that this interaction can be represented by an absorptive polarization potential. The relatively long range of this potential entails a relatively slow variation of the associated reflection function in l-space. This feature leads to a simple generalization of the closed formula derived previously for the elastic scattering amplitude of spherical heavy nuclei. We use both the polarization potential of Love et al. and the recent improved potential of Baltz et al. to derive explicit expressions for the associated reflection functions in a Coulomb-distorted eikonal approximation. As an example we analyze the elastic scattering of 90-MeV 18 O ions by 184 W and show that both results give a quantitative description of the data. (orig.) [de
International Nuclear Information System (INIS)
Thenint, Th.
2011-01-01
The steam generator is a heat exchanger and participates to the nuclear safety. Energy is transferred from the primary to the secondary fluid through many U-tubes maintained vertically by support plates. A sludge deposit tends to modify the boundary conditions and the secondary fluid flow. A fluid-elastic instability can then occur and lead to quick tube ruin. This thesis seeks a better understanding of the effect of contact nonlinearity on the dynamics of a tube in-air intermittently impacting the support plates and its consequences in regards with instability. The use of discretized contact conditions with circular obstacles distributed over the thickness of the plates and the use of enriched reduction bases allow quick and relevant nonlinear numerical simulations. These simulations are well correlated with experimental measurements and valid even with strong nonlinearity or negative modal damping. The evolution of power spectral densities (PSD) with growing excitation amplitude is analyzed: padding of the anti-resonances, peak shift and spread. It is then shown that an apparent stiffness associated with a permanent bilateral contact is pertinent to describe these transitions. In the case of an unstable linear system, one demonstrates that the nonlinearity keeps the responses bounded or stabilised, thus paving the way for future work with real or simulated fluid flows. (author)
Luminescence of CsPbBr3 films under high-power excitation
高橋, 一彰; 斎藤, 忠昭; 近藤, 新一; 浅田, 拡志
2004-01-01
Highly excited photoluminescence of CsPbBr3 has been measured for thin films prepared by crystallization from the amorphous phase into microcrystalline/ polycrystalline states. With the increase of excitation intensity, there occurs jumping of the dominant emission band from a free-exciton band to a new band originating from exciton-exciton inelastic collision. Stimulated emission is observed for the new band at very low threshold excitation intensities of the order of 10kW/cm2.
Saikiran, V.; Bazylewski, P.; Sameera, I.; Bhatia, Ravi; Pathak, A. P.; Prasad, V.; Chang, G. S.
2018-05-01
Multi-wall carbon nanotubes (MWCNT) filled with Fe nanorods were shown to have contracted and deformed under heavy ion irradiation. In this study, 120 MeV Ag and 80 MeV Ni ion irradiation was performed to study the deformation and defects induced in iron filled MWCNT under heavy ion irradiation. The structural modifications induced due to electronic excitation by ion irradiation were investigated employing high-resolution transmission electron microscopy, micro-Raman scattering experiments, and synchrotron-based X-ray absorption and emission spectroscopy. We understand that the ion irradiation causes modifications in the Fe nanorods which result in compressions and expansions of the nanotubes, and in turn leads to the buckling of MWCNT. The G band of the Raman spectra shifts slightly towards higher wavenumber and the shoulder G‧ band enhances with the increase of ion irradiation fluence, where the buckling wavelength depends on the radius 'r' of the nanotubes as exp[(r)0.5]. The intensity ratio of the D to G Raman modes initially decreases at the lowest fluence, and then it increases with the increase in ion fluence. The electron diffraction pattern and the high resolution images clearly show the presence of ion induced defects on the walls of the tube and encapsulated iron nanorods.
The stochastic network dynamics underlying perceptual discrimination
Directory of Open Access Journals (Sweden)
Genis Prat-Ortega
2015-04-01
Full Text Available The brain is able to interpret streams of high-dimensional ambiguous information and yield coherent percepts. The mechanisms governing sensory integration have been extensively characterized using time-varying visual stimuli (Britten et al. 1996; Roitman and Shadlen 2002, but some of the basic principles regarding the network dynamics underlying this process remain largely unknown. We captured the basic features of a neural integrator using three canonical one-dimensional models: (1 the Drift Diffusion Model (DDM, (2 the Perfect Integrator (PI which is a particular case of the DDM where the bounds are set to infinity and (3 the double-well potential (DW which captures the dynamics of the attractor networks (Wang 2002; Roxin and Ledberg 2008. Although these models has been widely studied (Bogacz et al. 2006; Roxin and Ledberg 2008; Gold and Shadlen 2002, it has been difficult to experimentally discriminate among them because most of the observables measured are only quantitatively different among these models (e.g. psychometric curves. Here we aim to find experimentally measurable quantities that can yield qualitatively different behaviors depending on the nature of the underlying network dynamics. We examined the categorization dynamics of these models in response to fluctuating stimuli of different duration (T. On each time step, stimuli are drawn from a Gaussian distribution N(μ, σ and the two stimulus categories are defined by μ > 0 and μ < 0. Psychometric curves can therefore be obtained by quantifying the probability of the integrator to yield one category versus μ . We find however that varying σ can reveal more clearly the differences among the different integrators. In the small σ regime, both the DW and the DDM perform transient integration and exhibit a decaying stimulus reverse correlation kernel revealing a primacy effect (Nienborg and Cumming 2009; Wimmer et al. 2015 . In the large σ regime, the integration in the DDM
Quantum dynamics of solid Ne upon photo-excitation of a NO impurity: A Gaussian wave packet approach
Energy Technology Data Exchange (ETDEWEB)
Unn-Toc, W.; Meier, C.; Halberstadt, N. [Laboratoire Collisions Agregats et Reactivite, IRSAMC, UMR CNRS 5589, Universite Paul Sabatier, 31062 Toulouse (France); Uranga-Pina, Ll. [Laboratoire Collisions Agregats et Reactivite, IRSAMC, UMR CNRS 5589, Universite Paul Sabatier, 31062 Toulouse (France); Facultad de Fisica, Universidad de la Habana, San Lazaro y L, Vedado, 10400 La Habana (Cuba); Rubayo-Soneira, J. [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), Ave. Salvador Allende y Luaces, Habana 10600, AP 6163 La Habana (Cuba)
2012-08-07
A high-dimensional quantum wave packet approach based on Gaussian wave packets in Cartesian coordinates is presented. In this method, the high-dimensional wave packet is expressed as a product of time-dependent complex Gaussian functions, which describe the motion of individual atoms. It is applied to the ultrafast geometrical rearrangement dynamics of NO doped cryogenic Ne matrices after femtosecond laser pulse excitation. The static deformation of the solid due to the impurity as well as the dynamical response after femtosecond excitation are analyzed and compared to reduced dimensionality studies. The advantages and limitations of this method are analyzed in the perspective of future applications to other quantum solids.
Energy Technology Data Exchange (ETDEWEB)
Laras, A
1999-07-01
The reactor building of a nuclear power plant must ensure its protection and tightness functions in the most unfavorable conditions of operation, like during an earthquake. The method currently used for the seismic calculation of buildings consists in the determination of the maximum probable response for each of the Eigen-modes of the structure. The aim of this study is to develop a non-linear calculation model for the estimation of the response of reinforced concrete structures. The structure under study is a beam embedded in its base and having a 2 tons load on its top. The structure is excited by a seismic or pulsed signal. In a first step, the global behavioural model of reinforced concrete is determined using the concrete and steel armatures behaviour laws. Then, a computer code is developed for the calculation of the seismic excitation of the beam. The beam is assimilated to a non-linear oscillator. A damaging parameter has been introduced in the model to take into account the damping observed experimentally. Finally, the excitation signal is analyzed in order to determine the parameter responsible for the significant increase of the structure response. (J.S.)
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
Responses of first-order dynamical systems to Matérn, Cauchy, and Dagum excitations
Shen, Lihua; Ostoja-Starzewski, Martin; Porcu, Emilio
2015-01-01
International audience; The responses of dynamical systems under random forcings is a well-understood area of research. The main tool in this area, as it has evolved over a century, falls under the heading of stochastic differential equations. Most works in the literature are related to random forcings with a known parametric spectral density. This paper considers a new framework: the Cauchy and Dagum covariance functions indexing the random forcings, do not have a closed form for the associa...
Directory of Open Access Journals (Sweden)
Y. X. Hao
2010-01-01
Full Text Available The nonlinear dynamic response of functionally graded rectangular plates under combined transverse and in-plane excitations is investigated under the conditions of 1 : 1, 1 : 2 and 1 : 3 internal resonance. The material properties are assumed to be temperature-dependent and vary along the thickness direction. The thermal effect due to one-dimensional temperature gradient is included in the analysis. The governing equations of motion for FGM rectangular plates are derived by using Reddy's third-order plate theory and Hamilton's principle. Galerkin's approach is utilized to reduce the governing differential equations to a two-degree-of-freedom nonlinear system including quadratic and cubic nonlinear terms, which are then solved numerically by using 4th-order Runge-Kutta algorithm. The effects of in-plane excitations on the internal resonance relationship and nonlinear dynamic response of FGM plates are studied.
Wildfires in the Lab: Simple Experiment and Models for the Exploration of Excitable Dynamics
Punckt, Christian; Bodega, Pablo S.; Kaira, Prabha; Rotermund, Harm H.
2015-01-01
Wildfires lead to the loss of life and property in many parts of the world. Understanding their dangers and, more particularly, the underlying dynamics which lead to fires of catastrophic scale contributes to better awareness as well as prevention and firefighting capabilities within the affected areas. In order to enable a basic understanding of…
Magnetic order dynamics in optically excited multiferroic TbMn O3
Johnson, J. A.; Kubacka, T.; Hoffmann, M. C.; Vicario, C.; de Jong, S.; Beaud, P.; Grübel, S.; Huang, S.-W.; Huber, L.; Windsor, Y. W.; Bothschafter, E. M.; Rettig, L.; Ramakrishnan, M.; Alberca, A.; Patthey, L.; Chuang, Y.-D.; Turner, J. J.; Dakovski, G. L.; Lee, W.-S.; Minitti, M. P.; Schlotter, W.; Moore, R. G.; Hauri, C. P.; Koohpayeh, S. M.; Scagnoli, V.; Ingold, G.; Johnson, S. L.; Staub, U.
2015-11-01
We performed ultrafast time-resolved near-infrared pump, resonant soft x-ray diffraction probe measurements to investigate the coupling between the photoexcited electronic system and the spin cycloid magnetic order in multiferroic TbMn O3 at low temperatures. We observe melting of the long range antiferromagnetic order at low excitation fluences with a decay time constant of 22.3 ±1.1 ps , which is much slower than the ˜1 ps melting times previously observed in other systems. To explain the data, we propose a simple model of the melting process where the pump laser pulse directly excites the electronic system, which then leads to an increase in the effective temperature of the spin system via a slower relaxation mechanism. Despite this apparent increase in the effective spin temperature, we do not observe changes in the wave vector q of the antiferromagnetic spin order that would typically correlate with an increase in temperature under equilibrium conditions. We suggest that this behavior results from the extremely low magnon group velocity that hinders a change in the spin-spiral wave vector on these time scales.
Directory of Open Access Journals (Sweden)
Xue-wen Chen
2018-01-01
Full Text Available A fuzzy increment controller is designed aimed at the vibration system of automobile active suspension with seven degrees of freedom (DOF. For decreasing vibration, an active control force is acquired by created Proportion-Integration-Differentiation (PID controller. The controller’s parameters are adjusted by a fuzzy increment controller with self-modifying parameters functions, which adopts the deviation and its rate of change of the body’s vertical vibration velocity and the desired value in the position of the front and rear suspension as the input variables based on 49 fuzzy control rules. Adopting Simulink, the fuzzy increment controller is validated under different road excitation, such as the white noise input with four-wheel correlation in time-domain, the sinusoidal input, and the pulse input of C-grade road surface. The simulation results show that the proposed controller can reduce obviously the vehicle vibration compared to other independent control types in performance indexes, such as, the root mean square value of the body’s vertical vibration acceleration, pitching, and rolling angular acceleration.
Ultrafast emission from colloidal nanocrystals under pulsed X-ray excitation
Turtos, R.M.; Polovitsyn, A.; Christodoulou, S.; Salomoni, M.; Auffray, E.; Moreels, I.; Lecoq, P.; Grim, J.Q.
2016-01-01
Fast timing has emerged as a critical requirement for radiation detection in medical and high energy physics, motivating the search for scintillator materials with high light yield and fast time response. However, light emission rates from conventional scintillation mechanisms fundamentally limit the achievable time resolution, which is presently at least one order of magnitude slower than required for next-generation detectors. One solution to this challenge is to generate an intense prompt signal in response to ionizing radiation. In this paper, we present colloidal semiconductor nanocrystals (NCs) as promising prompt photon sources. We investigate two classes of NCs: two-dimensional CdSe nanoplatelets (NPLs) and spherical CdSe/CdS core/giant shell quantum dots (GS QDs). We demonstrate that the emission rates of these NCs under pulsed X-ray excitation are much faster than traditional mechanisms in bulk scintillators, i.e. 5d-4f transitions. CdSe NPLs have a sub-100 ps effective decay time of 77 ps and CdSe/...
Leyva, Verónica; Corral, Inés; Feixas, Ferran; Migani, Annapaola; Blancafort, Lluís; González-Vázquez, Jesús; González, Leticia
2011-08-28
Ab initio surface-hopping dynamics calculations have been performed to simulate the intramolecular excited state hydrogen transfer dynamics of ortho-nitrobenzaldehyde (o-NBA) in the gas phase from the electronic S(1) excited state. Upon UV excitation, the hydrogen is transferred from the aldehyde substituent to the nitro group, generating o-nitrosobenzoic acid through a ketene intermediate. The semiclassical propagations show that the deactivation from the S(1) is ultrafast, in agreement with the experimental measurements, which detect the ketene in less than 400 fs. The trajectories show that the deactivation mechanism involves two different conical intersections. The first one, a planar configuration with the hydrogen partially transferred, is responsible for the branching between the formation of a biradical intermediate and the regeneration of the starting material. The conversion of the biradical to the ketene corresponds to the passage through a second intersection region in which the ketene group is formed.
Effect of vibrational excitation on the dynamics of ion-molecule reactions
International Nuclear Information System (INIS)
Anderson, S.L.
1981-11-01
A new experimental technique for the study of vibrational effects on ion-molecule reaction cross sections is described. Vibrational and collision energy dependent cross sections are presented for proton and H atom transfer, charge transfer and collision induced dissociation reactions in various isotopic H 2 + + H 2 systems. Charge and proton transfer cross sections are presented for the reactions of H 2 + and D 2 + with Ar, N 2 , CO, and O 2 . All the reactions are shown to be highly influenced by avoided crossings between the ground and first excited potential energy surfaces. Because of the nature of the crossings, vibrational motion of the systems can cause both adiabatic and non-adiabatic behavior of the system. This makes the vibrational dependences of the various cross sections a very sensitive probe of the dynamics of the collisions particularly, their behavior in the region of the crossings. Evidence is seen for charge transfer between reagents as they approach each other, transition to and in some cases reactions on excited potential energy surfaces, competition between different channels, and strong coupling of proton and charge transfer channels which occurs only for two of the systems studied (H 2 + + Ar, N 2 ). Oscillatory structure is observed in the collision energy dependence of the endoergic H 2 + (v = 0) + Ar charge transfer reaction for the first time, and a simple model which is commonly used for atom-atom charge transfer is used to fit the peaks. Finally a simple model is used to assess the importance of energy resonance and Franck-Condon effects on molecular charge transfer
Neural Population Dynamics Underlying Motor Learning Transfer.
Vyas, Saurabh; Even-Chen, Nir; Stavisky, Sergey D; Ryu, Stephen I; Nuyujukian, Paul; Shenoy, Krishna V
2018-03-07
Covert motor learning can sometimes transfer to overt behavior. We investigated the neural mechanism underlying transfer by constructing a two-context paradigm. Subjects performed cursor movements either overtly using arm movements, or covertly via a brain-machine interface that moves the cursor based on motor cortical activity (in lieu of arm movement). These tasks helped evaluate whether and how cortical changes resulting from "covert rehearsal" affect overt performance. We found that covert learning indeed transfers to overt performance and is accompanied by systematic population-level changes in motor preparatory activity. Current models of motor cortical function ascribe motor preparation to achieving initial conditions favorable for subsequent movement-period neural dynamics. We found that covert and overt contexts share these initial conditions, and covert rehearsal manipulates them in a manner that persists across context changes, thus facilitating overt motor learning. This transfer learning mechanism might provide new insights into other covert processes like mental rehearsal. Copyright © 2018 Elsevier Inc. All rights reserved.
Far above bandgap photonics: attosecond dynamics of highly excited electrons in materials
Chen, Cong; Tao, Zhensheng; Carr, Adra; Szilvási, Tibor; Keller, Mark; Mavrikakis, Manos; Murnane, Margaret M.; Kapteyn, Henry C.
2017-05-01
Tabletop-scale coherent EUV generated through high-harmonic generation (HHG) produces light in the form of an attosecond pulse train that uniquely combines characteristics of good energy resolution (≍100-300meV) with sub-fs time resolution. This makes HHG an ideal source for studying the fastest dynamics in materials. Furthermore, using angle-resolved photoemission spectroscopy (ARPES), it is possible to extract detailed information about electron dynamics over the entire Brillouin zone. In recently published work, we combined HHG with ARPES to identify a sub-femtosecond excited-state lifetime for the first time. Photoemission occurs as a three-step process: 1) An electron is photoexcited from the valence band to far above the Fermi energy; 2) it transports to the surface, and 3) it overcomes the work function and exits. If the electron is promoted into a highlyexcited unoccupied band in the material (as opposed to a free-electron-like state), we observe the electron emission lifetime to increase in a measurable way—the Ni band 22 eV above the Fermi level has a lifetime of 212+/-30 attoseconds. Furthermore, by comparing photoemission from Cu and Ni, we reveal the influence of attosecond-timescale electron screening vs scattering by the electrons near the fermi surface. This work for the first time demonstrates the relevance of attosecond spectroscopy to the study of intrinsic properties and band structure in materials, as opposed to the strong-field induced dynamics studied extensively to-date.
Semi-analytical approach to modelling the dynamic behaviour of soil excited by embedded foundations
DEFF Research Database (Denmark)
Bucinskas, Paulius; Andersen, Lars Vabbersgaard
2017-01-01
The underlying soil has a significant effect on the dynamic behaviour of structures. The paper proposes a semi-analytical approach based on a Green’s function solution in frequency–wavenumber domain. The procedure allows calculating the dynamic stiffness for points on the soil surface as well...... as for points inside the soil body. Different cases of soil stratification can be considered, with soil layers with different properties overlying a half-space of soil or bedrock. In this paper, the soil is coupled with piles and surface foundations. The effects of different foundation modelling configurations...
Evidence of dynamical dipole excitation in the fusion-evaporation of the 40Ca+152Sm heavy system
Parascandolo, C.; Pierroutsakou, D.; Alba, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Agodi, C.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; Inglima, G.; La Commara, M.; Martin, B.; Mazzocchi, C.; Mazzocco, M.; Rizzo, C.; Romoli, M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifirò, A.; Trimarchi, M.
2016-04-01
The excitation of the dynamical dipole mode along the fusion path was investigated for the first time in the formation of a heavy compound nucleus in the A ˜190 mass region. The compound nucleus was formed at identical conditions of excitation energy and spin from two entrance channels: the charge-asymmetric 40Ca+152Sm and the nearly charge-symmetric 48Ca+144Sm at Elab=11 and 10.1 MeV/nucleon, respectively. High-energy γ rays and light charged particles were measured in coincidence with evaporation residues by means of the MEDEA multidetector array (Laboratori Nazionali del Sud, Italy) coupled to four parallel plate avalanche counters. The charged particle multiplicity spectra and angular distributions were used to pin down the average excitation energy, the average mass, and the average charge of the compound nucleus. The γ -ray multiplicity spectrum and angular distribution related to the nearly charge-symmetric channel were employed to obtain new data on the giant dipole resonance in the compound nucleus. The dynamical dipole mode excitation in the charge-asymmetric channel was evidenced, in a model-independent way, by comparing the γ -ray multiplicity spectra and angular distributions of the two entrance channels with each other. Calculations of the dynamical dipole mode in the 40Ca+152Sm channel, based on a collective bremsstrahlung analysis of the reaction dynamics, are presented. Possible interesting implications in the superheavy-element quest are discussed.
Czech Academy of Sciences Publication Activity Database
Chábera, P.; Fuciman, M.; Naqvi, K.R.; Polívka, Tomáš
2010-01-01
Roč. 373, 1-2 (2010), s. 56-64 ISSN 0301-0104 Institutional research plan: CEZ:AV0Z50510513 Keywords : hydrophilic carotenoids * excited-state dynamics * charge-transfer state Subject RIV: BO - Biophysics Impact factor: 2.017, year: 2010
Czech Academy of Sciences Publication Activity Database
Polívka, Tomáš; Kaligotla, S.; Chábera, P.; Frank, H.A.
2011-01-01
Roč. 13, č. 22 (2011), s. 1463-9076 ISSN 1463-9076 Institutional research plan: CEZ:AV0Z50510513 Keywords : carotenoid * retinal * excited-state dynamics * charge-transfer state Subject RIV: BO - Biophysics Impact factor: 3.573, year: 2011
Rury, Aaron S; Wiley, Theodore E; Sension, Roseanne J
2015-03-17
Porphyrins and the related chlorins and corrins contain a cyclic tetrapyrrole with the ability to coordinate an active metal center and to perform a variety of functions exploiting the oxidation state, reactivity, and axial ligation of the metal center. These compounds are used in optically activated applications ranging from light harvesting and energy conversion to medical therapeutics and photodynamic therapy to molecular electronics, spintronics, optoelectronic thin films, and optomagnetics. Cobalt containing corrin rings extend the range of applications through photolytic cleavage of a unique axial carbon-cobalt bond, permitting spatiotemporal control of drug delivery. The photochemistry and photophysics of cyclic tetrapyrroles are controlled by electronic relaxation dynamics including internal conversion and intersystem crossing. Typically the electronic excitation cascades through ring centered ππ* states, ligand to metal charge transfer (LMCT) states, metal to ligand charge transfer (MLCT) states, and metal centered states. Ultrafast transient absorption spectroscopy provides a powerful tool for the investigation of the electronic state dynamics in metal containing tetrapyrroles. The UV-visible spectrum is sensitive to the oxidation state, electronic configuration, spin state, and axial ligation of the central metal atom. Ultrashort broadband white light probes spanning the range from 270 to 800 nm, combined with tunable excitation pulses, permit the detailed unravelling of the time scales involved in the electronic energy cascade. State-of-the-art theoretical calculations provide additional insight required for precise assignment of the states. In this Account, we focus on recent ultrafast transient absorption studies of ferric porphyrins and corrin containing cob(III)alamins elucidating the electronic states responsible for ultrafast energy cascades, excited state dynamics, and the resulting photoreactivity or photostability of these compounds. Iron
Mixed quantum-classical dynamics of an amide-I vibrational excitation in a protein α -helix
Freedman, Holly; Martel, Paulo; Cruzeiro, Leonor
2010-11-01
Adenosine triphosphate (ATP) is known to be the main energy currency of the living cell, and is used as a coenzyme to generate energy for many cellular processes through hydrolysis to adenosine diphosphate (ADP), although the mechanism of energy transfer is not well understood. It has been proposed that following hydrolysis of the ATP cofactor bound to a protein, up to two quanta of amide-I vibrational energy are excited and utilized to bring about important structural changes in the protein. To study whether, and how, amide-I vibrational excitations are capable of leading to protein structural changes, we have added components arising from quantum-mechanical amide-I vibrational excitations to the total energy and force terms within a molecular-dynamics simulation. This model is applied to helical deca-alanine as a test case to investigate how its dynamics differs in the presence or absence of an amide-I excitation. We find that the presence of an amide-I excitation can bias the structure toward a more helical state.
Effects of ligand substitution on the excited state dynamics of the Ru(dcbpy)(CO) 2I 2 complex
Lehtovuori, Viivi; Kallioinen, Jani; Myllyperkiö, Pasi; Haukka, Matti; Korppi-Tommola, Jouko
2003-11-01
Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [ trans-I-Ru(dcbpy)(CO) 2I 2] (dcbpy= 4,4 '-dicarboxy-2,2 '-bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [ cis-I-Ru(dcbpy)(CO)(Sol)I 2] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K indicate interligand charge transfer from mixed Ru-I states to empty dcbpy orbitals. For the photoproduct, no such transfer was observed. In both complexes recovery from the lowest energy excited triplet state to the ground state occurs via two channels: radiative relaxation and a parallel barrier controlled non-radiative relaxation. The barrier is much higher in the reactant (about 850 cm -1) than in the product. A combination of DFT and ZINDO/CI calculations was used to estimate excited singlet and triplet spectra of the reactant and the product molecules. Calculated singlet-triplet difference spectra qualitatively match the observed transient spectra 500 fs after excitation supporting the idea that observed excited state relaxation occurs from the triplet states in both complexes.
Effects of ligand substitution on the excited state dynamics of the Ru(dcbpy)(CO)2I2 complex
International Nuclear Information System (INIS)
Lehtovuori, Viivi; Kallioinen, Jani; Myllyperkioe, Pasi; Haukka, Matti; Korppi-Tommola, Jouko
2003-01-01
Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [trans-I-Ru(dcbpy)(CO) 2 I 2 ] (dcbpy4,4 ' -dicarboxy-2,2 ' -bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [cis-I-Ru(dcbpy)(CO)(Sol)I 2 ] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K indicate interligand charge transfer from mixed Ru-I states to empty dcbpy orbitals. For the photoproduct, no such transfer was observed. In both complexes recovery from the lowest energy excited triplet state to the ground state occurs via two channels: radiative relaxation and a parallel barrier controlled non-radiative relaxation. The barrier is much higher in the reactant (about 850 cm -1 ) than in the product. A combination of DFT and ZINDO/CI calculations was used to estimate excited singlet and triplet spectra of the reactant and the product molecules. Calculated singlet-triplet difference spectra qualitatively match the observed transient spectra 500 fs after excitation supporting the idea that observed excited state relaxation occurs from the triplet states in both complexes
Electron-Ion Dynamics in Semiconductors with Defects under Ion Irradiation
Lee, Cheng-Wei; Schleife, André
Long-term stability is challenging for semiconductor devices under ion radiation such as solar panels in outer space. Exposure to ion radiation induces formation of defects that ultimately reduce solar cell efficiency. It is well-known in the literature that high-energy ion radiation transfers energy to the materials mostly via electronic excitation which is traditionally hard to model. Previously, we demonstrated that Ehrenfest molecular dynamics based on time-dependent density functional theory correctly describes electronic stopping of semiconductors. To better understand the effect of excited electrons on evolution of defects during ion irradiation, we further investigate the time-evolution of occupation number and found that it is correlated to long-term ion dynamics after passage of proton. Furthermore, we found that the presence of excited electrons significantly reduces the atomic diffusion barrier, indicating this effect is essential for the analysis of defect formation and ion dynamics under ion radiation conditions. An award of computer time was provided by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program.
Fusion-fission dynamics at high excitation energies studied by neutron emission
Zank, W. P.; Hilscher, D.; Ingold, G.; Jahnke, U.; Lehmann, M.; Rossner, H.
1986-02-01
Neutron emission in coincidence with fusion-fission events and evaporation residues was measured in the heavy-ion reactions 141+(316 MeV) 40Ar and 175Lu+(192 MeV) 12C. Both reactions are leading to similar composite systems and excitation energies as the previously investigated reaction 165Ho+ 20Ne. In order to determine the lifetimes of the composite systems prior to scission and to study entrance channel and angular-momentum effects, the results for all three systems are compared. From measured cross sections of fission and evaporation residues, the angular momentum intervals leading to fission are deduced to be 50-109 ħ and 49-62 ħ for Pr+Ar and Lu+C, respectively. The corresponding prescission neutron multiplicities are deduced to be Mnpresc=3.6+/-0.6 and 6.3+/-0.8, whereas the respective postscission multiplicities are Mnpost=4.4+/-0.4 and 3.6+/-0.6. For the system 175Lu+ 12C it is found that 0.5+/-0.2 preequilibrium neutrons are emitted. In contrast to the evaporative neutrons, a strong anisotropy anPE=2.2+/-0.6 relative to the reaction plane defined by one fission fragment and the beam direction is observed. From the prescission neutron multiplicities, the evaporation time of the system prior to scission is deduced using the statistical model to ~=(3-12)×10-20 s. Nucleus deformation effects and neutron emission from not fully accelerated fission fragments are taken into account. The unexpected long prescission lifetimes can be explained as long transition times to the scission point caused by a large two-body viscosity. Under this assumption the viscosity parameter of the highly excited nuclei has been determined in a first approximation to μ~=0.1 TP. The results might be understood also assuming a mixture of a two-body and one-body friction.
Bloksgaard, Maria; Brewer, Jonathan; Bagatolli, Luis A
2013-12-18
This mini-review reports on applications of particular multiphoton excitation microscopy-based methodologies employed in our laboratory to study skin. These approaches allow in-depth optical sectioning of the tissue, providing spatially resolved information on specific fluorescence probes' parameters. Specifically, by applying these methods, spatially resolved maps of water dipolar relaxation (generalized polarization function using the 6-lauroyl-2-(N,N-dimethylamino)naphthale probe), activity of protons (fluorescence lifetime imaging using a proton sensitive fluorescence probe--2,7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein) and diffusion coefficients of distinct fluorescence probes (raster imaging correlation spectroscopy) can be obtained from different regions of the tissue. Comparative studies of different tissue strata, but also between equivalent regions of normal and abnormal excised skin, including applications of fluctuation correlation spectroscopy on transdermal penetration of liposomes are presented and discussed. The data from the different studies reported reveal the intrinsic heterogeneity of skin and also prove these strategies to be powerful noninvasive tools to explore structural and dynamical aspects of the tissue. Copyright © 2013 Elsevier B.V. All rights reserved.
Hossain, Jahangir; Mahmud, Apel; Roy, Naruttam K.; Pota, Hemanshu R.
2013-10-01
In stressed power systems with large induction machine component, there exist undamped electromechanical modes and unstable monotonic voltage modes. This article proposes a sequential design of an excitation controller and a power system stabiliser (PSS) to stabilise the system. The operating region, with induction machines in stressed power systems, is often not captured using a linearisation around an operating point, and to alleviate this situation a robust controller is designed which guarantees stable operation in a large region of operation. A minimax linear quadratic Gaussian design is used for the design of the supplementary control to automatic voltage regulators, and a classical PSS structure is used to damp electromechanical oscillations. The novelty of this work is in proposing a method to capture the unmodelled nonlinear dynamics as uncertainty in the design of the robust controller. Tight bounds on the uncertainty are obtained using this method which enables high-performance controllers. An IEEE benchmark test system has been used to demonstrate the performance of the designed controller.
Khenfouch, M.; Bajjou, O.; Baïtoul, M.; Mongwaketsi, N.; Maaza, M.; Wery Venturini, J.
2015-04-01
Few layers of reduced graphene oxide (FRGO) were functionalized with porphyrins self assembled nanostructure. These new hybrid nanocomposites were investigated using Transmission Electron Microscopy (TEM), UV-visible, Raman scattering, Fourier transform infrared (FT-IR) and photoluminescence. The structural and morphological results show strong interactions between these hybrids components. Moreover, steady state photoluminescence (PL) of both porphyrin nanorods (PN) and (PN)/FRGO composite show clearly the PL quenching confirming a charge transfer from porphyrin molecules to graphene sheets. In addition, the relaxation kinetics of the PN and (PN)/FRGO were studied by means of time resolved photoluminescence (TR-PL) and the excitation density in the sample was of 1017 cm3/pulse. The major change of the carrier dynamics in porphyrin nanorods after their interaction with FRGO was in the increase in the fast time constants, which found to be slower at 650 nm, τ1 = 196 ps and τ2 = 1171 ps. This has been explained by the change in their energy band gap due to the role of FRGO as doping related to the size of the nanometer-scale sp2 clusters, which leads to a slower interband carrier recombination.
Devi, Anita; De, Arijit K.
2017-08-01
Experimental evidence indicates that high-repetition-rate ultrafast pulsed excitation is more efficient in optical trapping of dielectric nanoparticles as compared with continuous-wave excitation at the same average power. The physics behind the different nature of force under these two excitation conditions remained deceptive until quite recently when it was theoretically explained, in the dipole limit, as a combined effect of (1) repetitive instantaneous momentum transfer and (2) optical Kerr nonlinearity. The role of optical Kerr effect was theoretically studied for larger dielectric spherical particles, in the ray optics limit, also. However, a theoretical underpinning is yet to be established as to whether the effect of optical nonlinearity is omnipresent across different particle sizes, which we investigate here. Using localized approximation of generalized Lorenz-Mie theory, we theoretically analyze the nature of force (and potential) and provide a detailed comparative discussion between this generalized scattering formulation with dipole scattering formulation for dielectric nanoparticles.
International Nuclear Information System (INIS)
Maheshwari, B.K.; Truman, K.Z.; El Naggar, M.H.; Gould, P.L.
2004-01-01
The effects of material nonlinearity of soil and separation at the soil-pile interface on the dynamic behaviour of a single pile and pile groups are investigated. An advanced plasticity-based soil model, hierarchical single surface (HiSS), is incorporated in the finite element formulation. To simulate radiation effects, proper boundary conditions are used. The model and algorithm are verified with analytical results that are available for elastic and elastoplastic soil models. Analyses are performed for seismic excitation and for the load applied on the pile cap. For seismic analysis, both harmonic and transient excitations are considered. For loading on the pile cap, dynamic stiffness of the soil-pile system is derived and the effect of nonlinearity is investigated. The effects of spacing between piles are investigated, and it was found that the effect of soil nonlinearity on the seismic response is very much dependent on the frequency of excitation. For the loading on a pile cap, the nonlinearity increases the response for most of the frequencies of excitation while decreasing the dynamic stiffness of the soil-pile system. (author)
Çelik, Kayhan; Kurt, Erol; Uzun, Yunus
2017-07-01
In the present study, experimental and theoretical explorations on the buckling features of a wind energy harvester have been performed. The harvester consists of a piezoelectric layer, which has a certain stiffness and voltage conversion rate. A blade rotates on a shaft carrying a magnet and sweeps the tip of the layer causing a serial buckling effect resulting in energy generation. Since the modeling of the buckling under a magnetic strength includes nonlinear terms over displacements, one requires a detailed study on the characteristics of buckling phenomena. It has been proven that the piezoelectric beam having the magnet at its tip can produce regular and chaotic dynamics for different frequencies (i.e. the rotation speed). In addition, there exist a number of quasi-periodic regions on the parameter space. The overall result indicates that the large area of complicated dynamics requires a detailed study in order to stabilize the position and velocity of the layer tip, thereby a much stabilized energy conversion from mechanical to electrical can be obtained. The present survey on the dynamics of the harvester is a new study and is considered as a two-parameter diagram [i.e. the wind speed (frequency) and magnetic strength]. Mainly, single-, double-, triple- and quadruple-type phase space portraits have been observed and the ripples on the maximal and minimal values of the beam velocity have been observed for certain rotation speeds. These results can be used in order to stabilize the harvester in terms of the reduction of total harmonic distortion in the generated waveform.
Persistent luminescence upconversion for Er{sub 2}O{sub 3} under 975 nm excitation in vacuum
Energy Technology Data Exchange (ETDEWEB)
Wang, Jiwei [Faculty of Physics, Liaoning University, Shenyang 110036 (China); Hao, Jian Hua [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR (Hong Kong); Tanner, Peter A. [Department of Science and Environmental Studies, The Hong Kong Institute of Education, Tai Po, Hong Kong SAR (Hong Kong)
2015-08-15
The 975 nm excited emission of Er{sub 2}O{sub 3} in the infrared (IR) and visible spectral regions at powers below the threshold for broadband white light generation has been investigated. In this regime the log(emission intensity) vs log(power) plots for emission at 660 nm and 1540 nm exhibit slopes for the sample in air (vacuum) of ~1 (~5) and ~1 (~2), respectively and the excitation mechanisms are discussed. The build-up of the emission is on the timescale of seconds and the excitation and decay transients have been recorded and analyzed for various excitation powers. The decay of the IR and visible emission each follow biexponential processes on a second timescale. The duration and kinetics of the emission decay are characteristic of persistent luminescence. - Highlights: • Infrared and red emission of Er{sub 2}O{sub 3} under 975 nm excitation. • Power dependence of emission. • Fitting of decay and rise transients. • Features characteristic of persistent luminescence.
Behavior of Brittle Materials Under Dynamic Loading
National Research Council Canada - National Science Library
Kanel, G
2000-01-01
Dynamic loading of brittle materials is related to many applications, including explosive excavation of rocks, design of ceramic armor, meteor impact on spacecraft windows, particle damage to turbine blades, etc...
Kwac, Kijeong; Geva, Eitan
2012-03-08
We present a mixed quantum-classical molecular dynamics study of the hydrogen-bonding structure and dynamics of a vibrationally excited hydroxyl stretch in methanol/carbon-tetrachloride mixtures. The adiabatic Hamiltonian of the quantum-mechanical hydroxyl is diagonalized on-the-fly to obtain the ground and first-excited adiabatic energy levels and wave functions which depend parametrically on the instantaneous configuration of the classical degrees of freedom. The dynamics of the classical degrees of freedom are determined by Hellmann-Feynman forces obtained by taking the expectation value of the force with respect to the ground or excited vibrational wave functions. Polarizable force fields are used which were previously shown to reproduce the experimental infrared absorption spectrum rather well, for different isotopomers and over a wide composition range [Kwac, K.; Geva, E. J. Phys. Chem. B 2011, 115, 9184]. We show that the agreement of the absorption spectra with experiment can be further improved by accounting for the dependence of the dipole moment derivatives on the configuration of the classical degrees of freedom. We find that the propensity of a methanol molecule to form hydrogen bonds increases upon photoexcitation of its hydroxyl stretch, thereby leading to a sizable red-shift of the corresponding emission spectrum relative to the absorption spectrum. Treating the relaxation from the first excited to the ground state as a nonadiabatic process, and calculating its rate within the framework of Fermi's golden rule and the harmonic-Schofield quantum correction factor, we were able to predict a lifetime which is of the same order of magnitude as the experimental value. The experimental dependence of the lifetime on the transition frequency is also reproduced. Nonlinear mapping relations between the hydroxyl transition frequency and bond length in the excited state and the electric field along the hydroxyl bond axis are established. These mapping relations
Dyba, Marcus; Hell, Stefan W
2003-09-01
Saturated stimulated-emission depletion (STED) of a fluorescent marker has been shown to break the diffraction barrier in far-field fluorescence microscopy and to facilitate spatial resolution down to a few tens of nanometers. Here we investigate the photostability of a fluorophore that, in this concept, is repeatedly excited and depleted by synchronized laser pulses. Our study of bacteria labeled with RH-414, a membrane marker, reveals that increasing the duration of the STED pulse from approximately 10 to 160 ps fundamentally improves the photostability of the dye. At the same time the STED efficiency is maintained. The observed photobleaching of RH-414 is due primarily to multiphoton absorption from its ground state. One can counteract photobleaching by employing STED pulses that range from 150 ps to approximately half of the lifetime of the excited state. The results also have implications for multiphoton excitation microscopy.
Stochastic stability of mechanical systems under renewal jump process parametric excitation
DEFF Research Database (Denmark)
Iwankiewicz, R.; Nielsen, Søren R.K.; Larsen, Jesper Winther
2005-01-01
independent, negative exponential distributed variables; hence, the arrival process may be termed as a generalized Erlang renewal process. The excitation process is governed by the stochastic equation driven by two independent Poisson processes, with different parameters. If the response in a single mode...... is investigated, the problem is governed in the state space by two stochastic equations, because the stochastic equation for the excitation process is autonomic. However due to the parametric nature of the excitation, the nonlinear term appears at the right-hand sides of the equations. The equations become linear...... of the stochastic equation governing the natural logarithm of the hyperspherical amplitude process and using the modification of the method wherein the time averaging of the pertinent expressions is replaced by ensemble averaging. It is found that the direct simulation is more suitable and that the asymptotic mean...
Study on the Business Cycle Model with Fractional-Order Time Delay under Random Excitation
Directory of Open Access Journals (Sweden)
Zifei Lin
2017-07-01
Full Text Available Time delay of economic policy and memory property in a real economy system is omnipresent and inevitable. In this paper, a business cycle model with fractional-order time delay which describes the delay and memory property of economic control is investigated. Stochastic averaging method is applied to obtain the approximate analytical solution. Numerical simulations are done to verify the method. The effects of the fractional order, time delay, economic control and random excitation on the amplitude of the economy system are investigated. The results show that time delay, fractional order and intensity of random excitation can all magnify the amplitude and increase the volatility of the economy system.
Oscar, Breland G; Liu, Weimin; Zhao, Yongxin; Tang, Longteng; Wang, Yanli; Campbell, Robert E; Fang, Chong
2014-07-15
Fluorescent proteins (FPs) have played a pivotal role in bioimaging and advancing biomedicine. The versatile fluorescence from engineered, genetically encodable FP variants greatly enhances cellular imaging capabilities, which are dictated by excited-state structural dynamics of the embedded chromophore inside the protein pocket. Visualization of the molecular choreography of the photoexcited chromophore requires a spectroscopic technique capable of resolving atomic motions on the intrinsic timescale of femtosecond to picosecond. We use femtosecond stimulated Raman spectroscopy to study the excited-state conformational dynamics of a recently developed FP-calmodulin biosensor, GEM-GECO1, for calcium ion (Ca(2+)) sensing. This study reveals that, in the absence of Ca(2+), the dominant skeletal motion is a ∼ 170 cm(-1) phenol-ring in-plane rocking that facilitates excited-state proton transfer (ESPT) with a time constant of ∼ 30 ps (6 times slower than wild-type GFP) to reach the green fluorescent state. The functional relevance of the motion is corroborated by molecular dynamics simulations. Upon Ca(2+) binding, this in-plane rocking motion diminishes, and blue emission from a trapped photoexcited neutral chromophore dominates because ESPT is inhibited. Fluorescence properties of site-specific protein mutants lend further support to functional roles of key residues including proline 377 in modulating the H-bonding network and fluorescence outcome. These crucial structural dynamics insights will aid rational design in bioengineering to generate versatile, robust, and more sensitive optical sensors to detect Ca(2+) in physiologically relevant environments.
Dynamics of social balance under temporal interaction
Nishi, Ryosuke; Masuda, Naoki
2014-08-01
Real social contacts are often intermittent such that a link between a pair of nodes in a social network is only temporarily used. The effects of such temporal networks on social dynamics have been investigated for several phenomenological models such as epidemic spreading, linear diffusion processes, and nonlinear oscillations. Here, we numerically investigate nonlinear social balance dynamics in such a situation. Social balance is a classical psychological theory, which dictates that a triad is balanced if the three agents are mutual friends or if the two of them are the friends of each other and hostile to the other agent. We show that the social balance dynamics is slowed down on the temporal complete graph as compared to the corresponding static complete graph.
Evolution of entanglement under echo dynamics
International Nuclear Information System (INIS)
Prosen, Tomaz; Znidaric, Marko; Seligman, Thomas H.
2003-01-01
Echo dynamics and fidelity are often used to discuss stability in quantum-information processing and quantum chaos. Yet fidelity yields no information about entanglement, the characteristic property of quantum mechanics. We study the evolution of entanglement in echo dynamics. We find qualitatively different behavior between integrable and chaotic systems on one hand and between random and coherent initial states for integrable systems on the other. For the latter the evolution of entanglement is given by a classical time scale. Analytic results are illustrated numerically in a Jaynes-Cummings model
Kirschner, Matthew S; Hannah, Daniel C; Diroll, Benjamin T; Zhang, Xiaoyi; Wagner, Michael J; Hayes, Dugan; Chang, Angela Y; Rowland, Clare E; Lethiec, Clotilde M; Schatz, George C; Chen, Lin X; Schaller, Richard D
2017-09-13
Ultrafast optical pump, X-ray diffraction probe experiments were performed on CdSe nanocrystal (NC) colloidal dispersions as functions of particle size, polytype, and pump fluence. Bragg peak shifts related to heating and peak amplitude reduction associated with lattice disordering are observed. For smaller NCs, melting initiates upon absorption of as few as ∼15 electron-hole pair excitations per NC on average (0.89 excitations/nm 3 for a 1.5 nm radius) with roughly the same excitation density inducing melting for all examined NCs. Diffraction intensity recovery kinetics, attributable to recrystallization, occur over hundreds of picoseconds with slower recoveries for larger particles. Zincblende and wurtzite NCs revert to initial structures following intense photoexcitation suggesting melting occurs primarily at the surface, as supported by simulations. Electronic structure calculations relate significant band gap narrowing with decreased crystallinity. These findings reflect the need to consider the physical stability of nanomaterials and related electronic impacts in high intensity excitation applications such as lasing and solid-state lighting.
Blades Forced Vibration Under Aero-Elastic Excitation Modeled by Van der Pol
Czech Academy of Sciences Publication Activity Database
Půst, Ladislav; Pešek, Luděk
2017-01-01
Roč. 27, č. 11 (2017), č. článku 1750166. ISSN 0218-1274 R&D Projects: GA ČR GA16-04546S Institutional support: RVO:61388998 Keywords : ade vibration * aero-elastic force * self-excitation * van der Pol Subject RIV: BI - Acoustics OBOR OECD: Applied mechanics Impact factor: 1.329, year: 2016
Dynamically loaded beam failure under corroded conditions
Veerman, R.P.; Koenders, E.A.B.
2014-01-01
De-icing salts, used on roads in heavy winters, may enter reinforced concrete (RC) structures via its capillary pore system or via cracks, initiating reinforcement corrosion and reducing its remaining service-life. Vehicles passing real bridges exert a dynamic impact action that might activate a
Material properties under intensive dynamic loading
Cherne, Frank J; Zhernokletov, Mikhail V; Glushak, B L; Zocher, Marvin A
2007-01-01
Understanding the physical and thermomechanical response of materials subjected to intensive dynamic loading is a challenge of great significance in engineering today. This volume assumes the task of gathering both experimental and diagnostic methods in one place, since not much information has been previously disseminated in the scientific literature.
Stochastic Online Learning in Dynamic Networks under Unknown Models
2016-08-02
Stochastic Online Learning in Dynamic Networks under Unknown Models This research aims to develop fundamental theories and practical algorithms for...12211 Research Triangle Park, NC 27709-2211 Online learning , multi-armed bandit, dynamic networks REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S... Online Learning in Dynamic Networks under Unknown Models Report Title This research aims to develop fundamental theories and practical algorithms for
Nonlinear Dynamics of Carbon Nanotubes Under Large Electrostatic Force
Xu, Tiantian
2015-06-01
Because of the inherent nonlinearities involving the behavior of CNTs when excited by electrostatic forces, modeling and simulating their behavior is challenging. The complicated form of the electrostatic force describing the interaction of their cylindrical shape, forming upper electrodes, to lower electrodes poises serious computational challenges. This presents an obstacle against applying and using several nonlinear dynamics tools typically used to analyze the behavior of complicated nonlinear systems undergoing large motion, such as shooting, continuation, and integrity analysis techniques. This works presents an attempt to resolve this issue. We present an investigation of the nonlinear dynamics of carbon nanotubes when actuated by large electrostatic forces. We study expanding the complicated form of the electrostatic force into enough number of terms of the Taylor series. Then, we utilize this form along with an Euler-Bernoulli beam model to study for the first time the dynamic behavior of CNTs when excited by large electrostatic force. The geometric nonlinearity and the nonlinear electrostatic force are considered. An efficient reduced-order model (ROM) based on the Galerkin method is developed and utilized to simulate the static and dynamic responses of the CNTs. Several results are generated demonstrating softening and hardening behavior of the CNTs near their primary and secondary resonances. The effects of the DC and AC voltage loads on the behavior have been studied. The impacts of the initial slack level and CNT diameter are also demonstrated.
NONLINEAR DYNAMICS OF CARBON NANOTUBES UNDER LARGE ELECTROSTATIC FORCE
Xu, Tiantian
2015-06-01
Because of the inherent nonlinearities involving the behavior of CNTs when excited by electrostatic forces, modeling and simulating their behavior is challenging. The complicated form of the electrostatic force describing the interaction of their cylindrical shape, forming upper electrodes, to lower electrodes poises serious computational challenges. This presents an obstacle against applying and using several nonlinear dynamics tools typically used to analyze the behavior of complicated nonlinear systems undergoing large motion, such as shooting, continuation, and integrity analysis techniques. This works presents an attempt to resolve this issue. We present an investigation of the nonlinear dynamics of carbon nanotubes when actuated by large electrostatic forces. We study expanding the complicated form of the electrostatic force into enough number of terms of the Taylor series. Then, we utilize this form along with an Euler-Bernoulli beam model to study for the first time the dynamic behavior of CNTs when excited by large electrostatic force. The geometric nonlinearity and the nonlinear electrostatic force are considered. An efficient reduced-order model (ROM) based on the Galerkin method is developed and utilized to simulate the static and dynamic responses of the CNTs. Several results are generated demonstrating softening and hardening behavior of the CNTs near their primary and secondary resonances. The effects of the DC and AC voltage loads on the behavior have been studied. The impacts of the initial slack level and CNT diameter are also demonstrated.
Dynamics of Hyperbranched Polymers under Confinement
Androulaki, Krystallenia; Chrissopoulou, Kiriaki; Anastasiadis, Spiros H.; Prevosto, Daniele; Labardi, Massimiliano
2015-03-01
The effect of severe confinement on the dynamics of three different generations of hyperbranched polyesters (Boltorns) is investigated by Dielectric Spectroscopy. The polymers are intercalated within the galleries of natural Na+-MMT, thus, forming 1nm polymer films confined between solid walls. The Tg's of the polymers determined by DSC show a clear dependence on the generation whereas the transition is completely suppressed when all the polymer chains are intercalated. The dynamic investigation of the bulk polymers reveals two sub-Tg processes, with similar behavior for the three polymers with the segmental relaxation observed above the Tg of each. For the nanocomposites, where all polymers are severely confined, the dynamics show significant differences compared to that of the bulk polymers. The sub-Tg processes are similar for the three generations but significantly faster and with weaker temperature dependence than those in the bulk. The segmental process appears at temperatures below the bulk polymer Tg, it exhibits an Arrhenius temperature dependence and shows differences for the three generations. A slow process that appears at higher temperatures is due to interfacial polarization. Co-financed by the EU and Greek funds through the Operational Program ``Education and Lifelong Learning'' of the NSRF-Research Funding Program: THALES-Investing in knowledge society through the Eur. Social Fund (MIS 377278) and COST Action MP0902-COINAPO.
Origin of excitation underlying locomotion in the spinal circuit of zebrafish
Eklöf-Ljunggren, Emma; Haupt, Sabine; Ausborn, Jessica; Dehnisch, Ivar; Uhlén, Per; Higashijima, Shin-ichi; El Manira, Abdeljabbar
2012-01-01
Neural circuits in the spinal cord transform instructive signals from the brain into well-coordinated locomotor movements by virtue of rhythm-generating components. Although evidence suggests that excitatory interneurons are the essence of locomotor rhythm generation, their molecular identity and the assessment of their necessity have remained unclear. Here we show, using larval zebrafish, that V2a interneurons represent an intrinsic source of excitation necessary for the normal expression of the locomotor rhythm. Acute and selective ablation of these interneurons increases the threshold of induction of swimming activity, decreases the burst frequency, and alters the coordination of the rostro–caudal propagation of activity. Thus, our results argue that V2a interneurons represent a source of excitation that endows the spinal circuit with the capacity to generate locomotion. PMID:22431619
Effective properties of mechanical systems under high-frequency excitation at multiple frequencies
DEFF Research Database (Denmark)
Thomsen, Jon Juel
2008-01-01
Effects of strong high-frequency excitation at multiple frequencies (multi-HFE) are analyzed for a class of generally nonlinear systems. The effects are illustrated for a simple pendulum system with a vibrating support, and for a parametrically excited flexible beam. For the latter, theoretical...... contribution of slowly oscillating stiffness appears. This may cause strong parametric resonance at conditions that might not appear obvious, i.e. when the difference in two HFE frequencies is near twice an effective system natural frequency, which due to the HFE itself is shifted away from the natural......-HFE with non-close frequencies. The general results may be used to investigate or utilize general effects, or as a shortcut to calculate effective properties for specific systems, or to calculate averaged equations of motion that may be much faster to simulate numerically....
Quantifying uncertainties of a Soil-Foundation Structure-Interaction System under Seismic Excitation
Energy Technology Data Exchange (ETDEWEB)
Tong, C
2008-04-07
We applied a spectrum of uncertainty quantification (UQ) techniques to the study of a two-dimensional soil-foundation-structure-interaction (2DSFSI) system (obtained from Professor Conte at UCSD) subjected to earthquake excitation. In the process we varied 19 uncertain parameters describing material properties of the structure and the soil. We present in detail the results for the different stages of our UQ analyses.
Marchetto, Christophe; Maxit, Laurent; Robin, Olivier; Berry, Alain
2017-06-01
This paper aims at developing an experimental method to characterize the vibroacoustic response of a panel to a diffuse acoustic field (DAF) excitation with a different laboratory setup than those used in standards (i.e., coupled rooms). The proposed methodology is based on a theoretical model of the DAF and on the measurement of the panel's sensitivity functions, which characterize its vibroacoustic response to wall plane waves. These functions can be estimated experimentally using variations of the reciprocity principle, which are described in the present paper. These principles can either be applied for characterizing the structural response by exciting the panel with a normal force at the point of interest or for characterizing the acoustic response (radiated pressure, acoustic intensity) by exciting the panel with a monopole and a dipole source. For both applications, the validity of the proposed approach is numerically and experimentally verified on a test case composed of a baffled simply supported plate. An implementation for estimating the sound transmission loss of the plate is finally proposed. The results are discussed and compared with measurements performed in a coupled anechoic-reverberant room facility following standards.
Optical excitations of transition-metal oxides under the orbital multiplicity effects
International Nuclear Information System (INIS)
Lee, J S; Kim, M W; Noh, T W
2005-01-01
We investigated optical excitations of transition-metal (TM) oxides with metal oxygen octahedra taking account of the orbital multiplicity effects. We predicted excitation energies of intersite d-d transitions and p-d transitions of TM oxides. We compared the evaluated excitation energies with reported experimental data, and found that they are in good agreement with each other. Moreover, we could demonstrate possible answers for a few long-standing problems of the low-frequency spectral features in some early 3d TM oxides: (i) the broad and multi-peak structures of the d-d transitions (ii) the low values (around 2 eV) of the d-d transition energies for some t 2g 1 and t 2g 2 systems, and (iii) the lack of the d-d transition below 4.0 eV region for LaCrO 3 , one of the t 2g 3 systems. These indicate that our approach considering the orbital multiplicity effects could provide good explanations of intriguing features in the optical spectra of some early TM oxides. In addition, we showed that optical spectroscopy can be useful as a powerful tool to investigate spin and/or orbital correlations in the TM ions. Finally, we discussed the implications of the orbital multiplicity in the Zannen-Sawatzky-Allen scheme, which has been used successfully to classify correlated electron systems
Directory of Open Access Journals (Sweden)
Yu Tong
2016-02-01
Full Text Available Photoacoustic Doppler (PAD power spectra showing an evident Doppler shift represent the major characteristics of the continuous wave-excited or burst wave-excited versions of PAD flow measurements. In this paper, the flow angle dependences of the PAD power spectra are investigated using an experiment setup that was established based on intensity-modulated continuous wave laser excitation. The setup has an overall configuration that is similar to a previously reported configuration, but is more sophisticated in that it accurately aligns the laser illumination with the ultrasound detection process, and in that it picks up the correct sample position. In the analysis of the power spectra data, we find that the background power spectra can be extracted by combining the output signals from the two channels of the lock-in amplifier, which is very useful for identification of the PAD power spectra. The power spectra are presented and analyzed in opposite flow directions, at different flow speeds, and at different flow angles. The power spectra at a 90° flow angle show the unique properties of symmetrical shapes due to PAD broadening. For the other flow angles, the smoothed power spectra clearly show a flow angle cosine relationship.
Subspace-based damage detection under changes in the ambient excitation statistics
Döhler, Michael; Mevel, Laurent; Hille, Falk
2014-03-01
In the last ten years, monitoring the integrity of the civil infrastructure has been an active research topic, including in connected areas as automatic control. It is common practice to perform damage detection by detecting changes in the modal parameters between a reference state and the current (possibly damaged) state from measured vibration data. Subspace methods enjoy some popularity in structural engineering, where large model orders have to be considered. In the context of detecting changes in the structural properties and the modal parameters linked to them, a subspace-based fault detection residual has been recently proposed and applied successfully, where the estimation of the modal parameters in the possibly damaged state is avoided. However, most works assume that the unmeasured ambient excitation properties during measurements of the structure in the reference and possibly damaged condition stay constant, which is hardly satisfied by any application. This paper addresses the problem of robustness of such fault detection methods. It is explained why current algorithms from literature fail when the excitation covariance changes and how they can be modified. Then, an efficient and fast subspace-based damage detection test is derived that is robust to changes in the excitation covariance but also to numerical instabilities that can arise easily in the computations. Three numerical applications show the efficiency of the new approach to better detect and separate different levels of damage even using a relatively low sample length.
The dynamic regulation of cortical excitability is altered in episodic ataxia type 2
DEFF Research Database (Denmark)
Helmich, Rick C; Siebner, Hartwig R; Giffin, Nicola
2010-01-01
Episodic ataxia type 2 and familial hemiplegic migraine are two rare hereditary disorders that are linked to dysfunctional ion channels and are characterized clinically by paroxysmal neurological symptoms. Impaired regulation of cerebral excitability is thought to play a role in the occurrence......-pulse transcranial magnetic stimulation at an interstimulus interval of 2 and 10 ms to assess intracortical inhibition and facilitation, respectively. The time course of burst-induced excitability changes differed between groups. Healthy controls showed a short-lived increase in excitability that was only present 50...... ms after the burst. In contrast, patients with episodic ataxia type 2 showed an abnormally prolonged increase in corticospinal excitability that was still present 250 ms after the transcranial magnetic stimulation burst. Furthermore, while controls showed a decrease in intracortical facilitation...
Energy Technology Data Exchange (ETDEWEB)
Laursen, S.L.
1990-01-01
Investigations of chemical reactions on electronically excited reaction surfaces are presented. The role of excited-surface multiplicity is of particular interest, as are chemical reactivity and energy transfer in systems in which photochemistry is initiated through a metal atom sensitizer.'' Two approaches are employed: A heavy-atom matrix affords access to forbidden triplet reaction surfaces, eliminating the need for a potentially reactive sensitizer. Later, the role of the metal atom in the photosensitization process is examined directly.
International Nuclear Information System (INIS)
Laursen, S.L.
1990-01-01
Investigations of chemical reactions on electronically excited reaction surfaces are presented. The role of excited-surface multiplicity is of particular interest, as are chemical reactivity and energy transfer in systems in which photochemistry is initiated through a metal atom ''sensitizer.'' Two approaches are employed: A heavy-atom matrix affords access to forbidden triplet reaction surfaces, eliminating the need for a potentially reactive sensitizer. Later, the role of the metal atom in the photosensitization process is examined directly
Energy Technology Data Exchange (ETDEWEB)
Blancafort, Lluis [Institut de Quimica Computacional, Department de Quimica, Universitat de Girona, Campus de Montilivi, 17071 Girona (Spain); Gatti, Fabien [CTMM, Institut Charles Gerhardt Montpellier (UMR 5253), CC 1501, Universite Montpellier 2, 34095 Montpellier Cedex 05 (France); Meyer, Hans-Dieter [Theoretische Chemie, Ruprecht-Karls-Universitaet, Im Neuenheimer Feld 229, 69120 Heidelberg (Germany)
2011-10-07
The double bond photoisomerization of fulvene has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method. Fulvene is a test case to develop optical control strategies based on the knowledge of the excited state decay mechanism. The decay takes place on a time scale of several hundred femtoseconds, and the potential energy surface is centered around a conical intersection seam between the ground and excited state. The competition between unreactive decay and photoisomerization depends on the region of the seam accessed during the decay. The dynamics are carried out on a four-dimensional model surface, parametrized from complete active space self-consistent field calculations, that captures the main features of the seam (energy and locus of the seam and associated branching space vectors). Wave packet propagations initiated by single laser pulses of 5-25 fs duration and 1.85-4 eV excitation energy show the principal characteristics of the first 150 fs of the photodynamics. Initially, the excitation energy is transferred to a bond stretching mode that leads the wave packet to the seam, inducing the regeneration of the reactant. The photoisomerization starts after the vibrational energy has flowed from the bond stretching to the torsional mode. In our propagations, intramolecular energy redistribution (IVR) is accelerated for higher excess energies along the bond stretch mode. Thus, the competition between unreactive decay and isomerization depends on the rate of IVR between the bond stretch and torsion coordinates, which in turn depends on the excitation energy. These results set the ground for the development of future optical control strategies.
International Nuclear Information System (INIS)
Blancafort, Lluis; Gatti, Fabien; Meyer, Hans-Dieter
2011-01-01
The double bond photoisomerization of fulvene has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method. Fulvene is a test case to develop optical control strategies based on the knowledge of the excited state decay mechanism. The decay takes place on a time scale of several hundred femtoseconds, and the potential energy surface is centered around a conical intersection seam between the ground and excited state. The competition between unreactive decay and photoisomerization depends on the region of the seam accessed during the decay. The dynamics are carried out on a four-dimensional model surface, parametrized from complete active space self-consistent field calculations, that captures the main features of the seam (energy and locus of the seam and associated branching space vectors). Wave packet propagations initiated by single laser pulses of 5-25 fs duration and 1.85-4 eV excitation energy show the principal characteristics of the first 150 fs of the photodynamics. Initially, the excitation energy is transferred to a bond stretching mode that leads the wave packet to the seam, inducing the regeneration of the reactant. The photoisomerization starts after the vibrational energy has flowed from the bond stretching to the torsional mode. In our propagations, intramolecular energy redistribution (IVR) is accelerated for higher excess energies along the bond stretch mode. Thus, the competition between unreactive decay and isomerization depends on the rate of IVR between the bond stretch and torsion coordinates, which in turn depends on the excitation energy. These results set the ground for the development of future optical control strategies.
Reschke, S.; Wang, Zhe; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.
2017-10-01
We report on THz time-domain spectroscopy on multiferroic GeV4S8 , which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8 , this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.
Observation and quantification of the quantum dynamics of a strong-field excited multi-level system.
Liu, Zuoye; Wang, Quanjun; Ding, Jingjie; Cavaletto, Stefano M; Pfeifer, Thomas; Hu, Bitao
2017-01-04
The quantum dynamics of a V-type three-level system, whose two resonances are first excited by a weak probe pulse and subsequently modified by another strong one, is studied. The quantum dynamics of the multi-level system is closely related to the absorption spectrum of the transmitted probe pulse and its modification manifests itself as a modulation of the absorption line shape. Applying the dipole-control model, the modulation induced by the second strong pulse to the system's dynamics is quantified by eight intensity-dependent parameters, describing the self and inter-state contributions. The present study opens the route to control the quantum dynamics of multi-level systems and to quantify the quantum-control process.
International Nuclear Information System (INIS)
Fabeni, P.; Krasnikov, A.; Kaerner, T.; Laguta, V.V.; Nikl, M.; Pazzi, G.P.; Zazubovich, S.
2009-01-01
Time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 150-300 K for the green emission of PbWO 4 :Mo crystals. It was found that the slow (μs-ms) decay component observed under excitation in the defect-related absorption region (around 3.8-3.9 eV) arises from the G(II) emission which appears at the tunneling recombination of optically created electron and hole centers. The study of the emission decay kinetics at different temperatures and excitation intensities allowed concluding that both the monomolecular and the bimolecular tunneling recombination process can be stimulated in the mentioned energy range. The monomolecular process takes place in the isolated spatially correlated pairs of electron and hole centers produced without release of electrons into the conduction band. The bimolecular process takes place in the pairs of randomly distributed centers created at the trapping of free electrons from the conduction band. The formation of electron centers under irradiation in the defect-related absorption region was investigated by the electron spin resonance (ESR) and thermally stimulated luminescence (TSL) methods. The possibility of various photo-thermally stimulated defects creation processes, which take place with and without release of free electrons into the conduction band, was confirmed.
International Nuclear Information System (INIS)
Anderson, C.R.
2000-01-01
We present neutron inelastic scattering measurements of the low energy excitations of superfluid 4 He. Measurements on three types of superfluid system have been taken: Bulk superfluid, superfluid in the presence of static disorder ( 4 He confined in porous glasses) and superfluid in the presence of dynamic disorder (dilute 3 He- 4 He mixtures). For the bulk liquid, we find that the temperature dependence of the roton may be described well by the generally accepted BPZ theory [Bedell 1984], over the temperature region 0.4-1.8 K. However we also find our results to be in agreement with the high-resolution measurements of Andersen et al who reported a deviation from the BPZ theory at temperatures below 1 K [Andersen 1996]. We find that the energy of the maxon does surpass that of two times the roton energy at elevated pressure. This result cannot be explained simply from a theoretical point of view and we offer an explanation in terms of a hybridisation between the single particle excitation and the two-roton continuum. A high-resolution study of the roton when the superfluid is confined in porous aerogel glass shows the excitation to remain sharp down to temperatures of 0.07 K. This result contradicts the results of previous studies [Gibbs 1997, Plantevin 1998] who found that the roton exhibited an anomalous linewidth at low temperatures. We present the first successful neutron scattering measurements of the superfluid confined in porous Vycor and xerogel glasses. We observe a sharp excitation with a dispersion almost identical to that of the phonon-roton excitation of the bulk liquid. We also observe extra scattering at energies below that of the bulk-like excitation. This scattering has been attributed to two-dimensional layer excitations previously only observed in neutron scattering studies of thin films of the superfluid adsorbed onto various forms of graphite substrate. High resolution studies of S(Q,ω) of a 1% mixture of 3 He in superfluid 4 He reveals no
Rahmani, O.; Shokrnia, M.; Golmohammadi, H.; Hosseini, S. A. H.
2018-02-01
Transverse forced vibration of a single-walled carbon nanotube (SWCNT) under excitation of a moving harmonic load has been analyzed based on modified nonlocal elasticity theory. In the parametric study, influences of nonlocal parameter, velocity of the moving load, excitation frequency, order of derivative and their interactive effects on forced deflection of the nanotube have been investigated in details. Numerical amounts of the dimensionless static deflection of the SWCNT have been calculated and compared with those of existing papers and an excellent agreement has been achieved. The results show that the variation of N affects the dynamic deflection and natural frequency of SWCNTs, significantly. Also by amplification of the excitation frequency, differences between the amounts of dynamic deflection become smaller for various values of N . Furthermore, decreasing the frequency ratio causes a reduction of the maximum deflection and increasing the frequency ratio causes an increase of the maximum deflection for values of load velocity which are greater than a specified value.
Dynamic investigation of a locomotive with effect of gear transmissions under tractive conditions
Chen, Zaigang; Zhai, Wanming; Wang, Kaiyun
2017-11-01
Locomotive is used to drag trailers to move or supply the braking forces to slow the running speed of a train. The electromagnetic torque of the motor is always transmitted by the gear transmission system to the wheelset for generation of the tractive or braking forces at the wheel-rail contact interface. Consequently, gear transmission system is significant for power delivery of a locomotive. This paper develops a comprehensive locomotive-track vertical-longitudinal coupled dynamics model with dynamic effect of gear transmissions. This dynamics model enables considering the coupling interactions between the gear transmission motion, the vertical and the longitudinal motions of the vehicle, and the vertical vibration of the track structure. In this study, some complicated dynamic excitations, such as the gear time-varying mesh stiffness, nonlinear gear tooth backlash, the nonlinear wheel-rail normal contact force and creep force, and the rail vertical geometrical irregularity, are considered. Then, the dynamic responses of the locomotive under the tractive conditions are demonstrated by numerical simulations based on the established dynamics model and by experimental test. The developed dynamics model is validated by the good agreement between the experimental and the theoretical results. The calculated results reveal that the gear transmission system has strong dynamic interactions with the wheel-rail contact interface including both the vertical and the longitudinal motions, and it has negligible effect on the vibrations of the bogie frame and carbody.
Food-web dynamics under climate change
DEFF Research Database (Denmark)
Zhang, L.; Takahashi, M.; Hartvig, Martin
2017-01-01
Climate change affects ecological communities through its impact on the physiological performance of individuals. However, the population dynamic of species well inside their thermal niche is also determined by competitors, prey and predators, in addition to being influenced by temperature changes....... We use a trait-based food-web model to examine how the interplay between the direct physiological effects from temperature and the indirect effects due to changing interactions between populations shapes the ecological consequences of climate change for populations and for entire communities. Our...... climatically well-adapted species may be brought to extinction by the changed food-web topology. Our results highlight that the impact of climate change on specific populations is largely unpredictable, and apparently well-adapted species may be severely impacted...
Food-web dynamics under climate change
DEFF Research Database (Denmark)
Zhang, L.; Takahashi, M.; Hartvig, Martin
2017-01-01
. We use a trait-based food-web model to examine how the interplay between the direct physiological effects from temperature and the indirect effects due to changing interactions between populations shapes the ecological consequences of climate change for populations and for entire communities. Our......Climate change affects ecological communities through its impact on the physiological performance of individuals. However, the population dynamic of species well inside their thermal niche is also determined by competitors, prey and predators, in addition to being influenced by temperature changes...... climatically well-adapted species may be brought to extinction by the changed food-web topology. Our results highlight that the impact of climate change on specific populations is largely unpredictable, and apparently well-adapted species may be severely impacted...
Quantum Entanglement Growth under Random Unitary Dynamics
Directory of Open Access Journals (Sweden)
Adam Nahum
2017-07-01
Full Text Available Characterizing how entanglement grows with time in a many-body system, for example, after a quantum quench, is a key problem in nonequilibrium quantum physics. We study this problem for the case of random unitary dynamics, representing either Hamiltonian evolution with time-dependent noise or evolution by a random quantum circuit. Our results reveal a universal structure behind noisy entanglement growth, and also provide simple new heuristics for the “entanglement tsunami” in Hamiltonian systems without noise. In 1D, we show that noise causes the entanglement entropy across a cut to grow according to the celebrated Kardar-Parisi-Zhang (KPZ equation. The mean entanglement grows linearly in time, while fluctuations grow like (time^{1/3} and are spatially correlated over a distance ∝(time^{2/3}. We derive KPZ universal behavior in three complementary ways, by mapping random entanglement growth to (i a stochastic model of a growing surface, (ii a “minimal cut” picture, reminiscent of the Ryu-Takayanagi formula in holography, and (iii a hydrodynamic problem involving the dynamical spreading of operators. We demonstrate KPZ universality in 1D numerically using simulations of random unitary circuits. Importantly, the leading-order time dependence of the entropy is deterministic even in the presence of noise, allowing us to propose a simple coarse grained minimal cut picture for the entanglement growth of generic Hamiltonians, even without noise, in arbitrary dimensionality. We clarify the meaning of the “velocity” of entanglement growth in the 1D entanglement tsunami. We show that in higher dimensions, noisy entanglement evolution maps to the well-studied problem of pinning of a membrane or domain wall by disorder.
Energy Technology Data Exchange (ETDEWEB)
Penillard, A., E-mail: anne.penillard@espci.fr; Tripon-Canseliet, C.; Maksimovic, I.; Géron, E. [Laboratoire de Physique et d' Etude des Matériaux, Ecole Supérieure de Physique et de Chimie Industrielle de la ville de Paris, UMR8213, 10 rue Vauquelin 75231 Paris Cedex 05 (France); Rosticher, M. [Laboratoire Pierre Aigrain, Département de Physique de l' Ecole Normale Supérieure, 24 rue Lhomond 75231 Paris Cedex 05 (France); Liu, Z. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)
2016-01-14
We present a microwave photoconductive switch based on exfoliated black phosphorus and strongly responding to a 1.55 μm optical excitation. According to its number of atomic layers, exfoliated black phosphorus presents unique properties for optoelectronic applications, like a tunable direct bandgap from 0.3 eV to 2 eV, strong mobilities, and strong conductivities. The switch shows a maximum ON/OFF ratio of 17 dB at 1 GHz, and 2.2 dB at 20 GHz under 1.55-μm laser excitation at 50 mW, never achieved with bidimensional materials.
Larionov, A V; Hvam, J; Soerensen, K
2002-01-01
The time evolution and kinetics of the photoluminescence (PL) spectra of the interwall excitons under the pulse resonant excitation of the interwall excitons are studied in the GaAs/AlGaAs binary quantum well. It is established, that the collective exciton phase originates with the time delay relative to the exciting pulse (several nanoseconds), which is conditioned by the density and temperature relaxation to the equilibrium values.The origination of the collective phase of the interwall excitons is accompanied by the strong narrowing of the corresponding photoluminescence line, the superlinear growth of its intensity and large time of change in the degree of the circular polarization.The collective exciton phase originates at the temperatures < 6 K and the interwall excitons densities 3 x 10 sup 1 sup 0 cm sup - sup 2
Energy Technology Data Exchange (ETDEWEB)
Bryk, Taras [Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Street, UA-79011 Lviv (Ukraine); Lviv Polytechnic National University, 12 S. Bandera Street, UA-79013 Lviv (Ukraine); Ruocco, G. [Dipartimento di Fisica, Universita di Roma La Sapienza, 5 Piazzale Aldo Moro, I-00185 Roma (Italy); Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia, 295 Viale Regina Elena, I-00161 Roma (Italy); Scopigno, T. [Dipartimento di Fisica, Universita di Roma La Sapienza, 5 Piazzale Aldo Moro, I-00185 Roma (Italy); IPCF-CNR, c/o Universita di Roma La Sapienza, 5 Piazzale Aldo Moro, I-00185 Roma (Italy); Seitsonen, Ari P. [Département de Chimie, Université de Zurich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Département de Chimie, École Normale Supérieure, 24 rue Lhomond, F-75005 Paris (France)
2015-09-14
Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagation of harmonic displacements of atoms around stable local energy minima. The viscoelasticity of liquids, reflected in transition from the adiabatic to elastic high-frequency speed of sound and in absence of the long-wavelength transverse excitations, results in dispersions of longitudinal (L) and transverse (T) collective excitations essentially different from the typical phonon ones. Practically, nothing is known about the effect of high pressure on the dispersion of collective excitations in liquids, which causes strong changes in liquid structure. Here dispersions of L and T collective excitations in liquid Li in the range of pressures up to 186 GPa were studied by ab initio simulations. Two methodologies for dispersion calculations were used: direct estimation from the peak positions of the L/T current spectral functions and simulation-based calculations of wavenumber-dependent collective eigenmodes. It is found that at ambient pressure, the longitudinal and transverse dynamics are well separated, while at high pressures, the transverse current spectral functions, density of vibrational states, and dispersions of collective excitations yield evidence of two types of propagating modes that contribute strongly to transverse dynamics. Emergence of the unusually high-frequency transverse modes gives evidence of the breakdown of a regular viscoelastic theory of transverse dynamics, which is based on coupling of a single transverse propagating mode with shear relaxation. The explanation of the observed high-frequency shift above the viscoelastic value is given by the presence of another branch of collective excitations. With the pressure increasing, coupling between the two types of collective excitations is rationalized within a proposed extended viscoelastic model of transverse dynamics.
Response of a Shape Memory Alloy Beam Model under Narrow Band Noise Excitation
Directory of Open Access Journals (Sweden)
Gen Ge
2014-01-01
Full Text Available To describe the hysteretic nonlinear characteristic of the strain-stress relation of shape memory alloy (SMA, a Van-der-Pol hysteretic cycle is applied to simulate the hysteretic loops. Then, the model of a simply supported SMA beam subject to transverse narrow band noise excitation with nonlinear damping was proposed. The deterministic and the stochastic responses are studied, respectively, applying the multiple scale method. The stability of the steady state responses is analyzed by Floquet theory and the moment method. The numerical simulation results quite agree with the theoretical analysis.
Stochastic dynamical model of a growing citation network based on a self-exciting point process.
Golosovsky, Michael; Solomon, Sorin
2012-08-31
We put under experimental scrutiny the preferential attachment model that is commonly accepted as a generating mechanism of the scale-free complex networks. To this end we chose a citation network of physics papers and traced the citation history of 40,195 papers published in one year. Contrary to common belief, we find that the citation dynamics of the individual papers follows the superlinear preferential attachment, with the exponent α=1.25-1.3. Moreover, we show that the citation process cannot be described as a memoryless Markov chain since there is a substantial correlation between the present and recent citation rates of a paper. Based on our findings we construct a stochastic growth model of the citation network, perform numerical simulations based on this model and achieve an excellent agreement with the measured citation distributions.
Dynamics of anisotropic particles under waves
Dibenedetto, Michelle; Ouellette, Nicholas; Koseff, Jeffrey
2017-11-01
We present results on anisotropic particles in wavy flows in order to gain insight into the transport and mixing of microplastic particles in the near-shore environment. From theory and numerical simulations, we find that the rate of alignment of the particles is not constant and depends strongly on their initial orientation; thus, variations in initial particle orientation result in dispersion of anisotropic-particle plumes. We find that this dispersion is a function of the particle's eccentricity and the ratio of the settling and wave time scales. Experiments in which non-spherical particles of various shapes are released under surface gravity waves were also performed. Our main goal is to explore the effects of particle shape under various wave scenarios. We vary the aspect ratio of the particle in our experiments while holding other variables constant. Our results demonstrate that particle shape can be important when predicting transport.
Dynamic Stability of a Circular Pre-Stressed Elastic Orthotropic Plate Subjected to Shock Excitation
Directory of Open Access Journals (Sweden)
Yuriy A. Rossikhin
2006-01-01
Full Text Available The problem on low-velocity impact of an elastic body upon a pre-stressed circular orthotropic plate possessing cylindrical anisotropy is considered. The dynamic behavior of the plate is described by equations taking the rotary inertia and transverse shear deformations into account. Longitudinal compressing forces are uniformly distributed along the plate’s median plane. Contact interaction is modeled by a linear spring, and a force arising in it is the linear approximation of Herts’z contact force. During the shock interaction of the impactor with the plate, the waves which are the surfaces of strong discontinuity are generated in the plate and begin to propagate. Behind the fronts of these waves, the solution is constructed in terms of ray series, which coefficients are the different order discontinuities in partial time-derivatives of the desired functions, and a variable is the time elapsed after the wave arrival at the plate’s point under consideration. The ray series coefficients are determined from recurrent equations within accuracy of arbitrary constants, which are then determined from the conditions of dynamic contact interaction of the impactor with the target. The found arbitrary constants allow one to construct the solution both within and out of the contact region. The analysis of the solution obtained enables one to find out the new effect and to make the inference that under a certain critical magnitude of the compression force the orthotropic plate goes over into the critical state, what is characterized by ‘locking’ the shear wave within the contact region, resulting in plate damage within this zone as soon as the compression force exceeds its critical value.
Neural dynamics underlying emotional transmissions between individuals
Golland, Yulia; Levit-Binnun, Nava; Hendler, Talma; Lerner, Yulia
2017-01-01
Abstract Emotional experiences are frequently shaped by the emotional responses of co-present others. Research has shown that people constantly monitor and adapt to the incoming social–emotional signals, even without face-to-face interaction. And yet, the neural processes underlying such emotional transmissions have not been directly studied. Here, we investigated how the human brain processes emotional cues which arrive from another, co-attending individual. We presented continuous emotional...
International Nuclear Information System (INIS)
Chu, P.M.Y.
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
Energy Technology Data Exchange (ETDEWEB)
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.
Energy Technology Data Exchange (ETDEWEB)
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.
Xing, Jing Tang; Sun, Zhe; Zhou, Sulian; Tan, Mingyi
2017-04-01
An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by: (1) the natural modes and frequencies of the vehicle; (2) the vehicle rolling and pitching motions; (3) different road excitations on four wheels; (4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guidelines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.
Dynamics of excited state proton transfer in nitro substituted 10-hydroxybenzo[h] quinolines
DEFF Research Database (Denmark)
Marciniak, H.; Hristova, S.; Deneva, V.
2017-01-01
The ground state tautomerism and excited state intramolecular proton transfer (ESIPT) of 10-hydroxybenzo[h]quinoline (HBQ) and its nitro derivatives, 7-nitrobenzo[h]quinolin-10-ol (2) and 7,9-dinitrobenzo[h]quinolin-10-ol (3), have been studied in acetonitrile using steady state as well as time...... occurs with a time constant of 0.89 ps and 0.68 ps, respectively. In both cases a mixture of the enol and proton transfer forms is optically excited. The enol form exhibits then the ESIPT and subsequently both fractions take the same relaxation path. We propose that in 2 and 3 the ESIPT path exhibits...... a potential energy barrier resulting in an incoherent rate governed process while in HBQ the ESIPT proceeds as a ballistic wavepacket motion along a path without significant barriers. The theoretical calculations (M06-2X/TZVP) confirm the existence of a barrier in the ground and excited states as result...
International Nuclear Information System (INIS)
Zhu, Zhi-Wen; Zhang, Qing-Xin; Xu, Jia
2014-01-01
A kind of shape memory alloy (SMA) hysteretic nonlinear model was developed, and the nonlinear dynamics and bifurcation characteristics of the SMA thin film subjected to in-plane stochastic excitation were investigated. Van der Pol difference item was introduced to describe the hysteretic phenomena of the SMA strain–stress curves, and the nonlinear dynamic model of the SMA thin film subjected to in-plane stochastic excitation was developed. The conditions of global stochastic stability of the system were determined in singular boundary theory, and the probability density function of the system response was obtained. Finally, the conditions of stochastic Hopf bifurcation were analyzed. The results of theoretical analysis and numerical simulation indicate that self-excited vibration is induced by the hysteretic nonlinear characteristics of SMA, and stochastic Hopf bifurcation appears when the bifurcation parameter was changed; there are two limit cycles in the stationary probability density of the dynamic response of the system in some cases, which means that there are two vibration amplitudes whose probabilities are both very high, and jumping phenomena between the two vibration amplitudes appear with the change in conditions. The results obtained in this current paper are helpful for the application of the SMA thin film in stochastic vibration fields. - Highlights: • Hysteretic nonlinear model of shape memory alloy was developed. • Van der Pol item was introduced to interpret hysteretic strain–stress curves. • Nonlinear dynamic characteristics of the shape memory alloy film were analyzed. • Jumping phenomena were observed in the change of the parameters
Directory of Open Access Journals (Sweden)
T. Frigge
2018-03-01
Full Text Available The photoinduced structural dynamics of the atomic wire system on the Si(111-In surface has been studied by ultrafast electron diffraction in reflection geometry. Upon intense fs-laser excitation, this system can be driven in around 1 ps from the insulating (8×2 reconstructed low temperature phase to a metastable metallic (4×1 reconstructed high temperature phase. Subsequent to the structural transition, the surface heats up on a 6 times slower timescale as determined from a transient Debye-Waller analysis of the diffraction spots. From a comparison with the structural response of the high temperature (4×1 phase, we conclude that electron-phonon coupling is responsible for the slow energy transfer from the excited electron system to the lattice. The significant difference in timescales is evidence that the photoinduced structural transition is non-thermally driven.
Ramini, Abdallah
2015-12-11
We present an experimental investigation for the nonlinear dynamic behaviors of clamped–clamped in-plane MEMS shallow arches when excited by harmonic electrostatic forces. Frequency sweeps are conducted to study the dynamic behaviors in the neighborhoods of the first and third resonance frequencies as well as the super-harmonic resonances. Experimental results show local softening behavior of small oscillations around the first resonance frequency and hardening behavior at the third resonance frequency for small dc and ac loads. Interesting dynamic snap-through cross-well motions are observed experimentally at high voltages for the first time in the micro-scale world. In addition to the dynamic snap-through motion, the MEMS arch exhibits large oscillations of a continuous band of snap-through motion between the super-harmonic resonance regime and the first primary resonance regime. This continuous band is unprecedented experimentally in the micro/macro world, and is promising for a variety of sensing, actuation and communications applications.
Directory of Open Access Journals (Sweden)
Dae-Seung Cho
2010-06-01
Full Text Available The structural intensity analysis, which calculates the magnitude and direction of vibrational energy flow from vibratory velocity and internal force at any point of a structure, can give information on dominant transmission paths, positions of sources and sinks of vibration energy. This paper presents a numerical simulation system for structural intensity analysis and visualization to apply for ship structures based on the finite element method. The system consists of a general purpose finite element analysis program MSC/Nastran, its pre- and post-processors and an in-house program module to calculate structural intensity using the model data and its forced vibration analysis results. Using the system, the structural intensity analysis for a 4,100 TEU container carrier is carried out to visualize structural intensity fields on the global ship structure and to investigate dominant energy flow paths from harmonic excitation sources to superstructure at resonant hull girder and superstructure modes.
Field quality in the twin aperture D2 dipoles for LHC under asymmetric excitation
Jain, A; Willen, E
1999-01-01
Twin aperture D2 magnets are one of the several types of dipoles to be built by BNL for the interaction regions of LHC. To minimize the number of dipole correctors required in the interaction regions, D2 will also be used as part of the steering system. Consequently, the operating fields in the two apertures may differ by up to ~10at 7 TeV operation and ~33at injection in order to compensate for the strengths of the correctors that would otherwise be required. Such asymmetric excitation of the two apertures may induce undesirable field harmonics. The saturation behavior of various harmonics is studied using POISSON and OPERA-2D. It is shown that the changes in harmonics resulting from the anticipated asymmetry are within tolerable limits. (2 refs).
Terahertz signatures of the exciton formation dynamics in non-resonantly excited semiconductors
Kira, M.; Hoyer, W.; Koch, S. W.
2004-03-01
A microscopic theory for the induced terahertz (THz) absorption of semiconductors is applied to study the time-dependent system response after non-resonant optical excitation. The formation of excitonic populations from an interacting electron-hole plasma is analyzed and the characteristic THz signatures are computed. Good qualitative agreement with recent experiments is obtained.
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available The excited state structural relaxation of 4 -dimethylaminobenzenes with various para-acceptor substituents having double-band emission, local excited (LE and charge transfer (CT, has been investigated. Fluorescence measurements at different temperatures and in different solvents have confirmed the existence of viscosity-dependent, temperature, and polarity-activated relaxation. The kinetics analysis has shown that the radiative deactivation rate constants of the individual LE and CT states differ by 7 – 112 -fold. The dipole moment changes at the excitation for CT states are significantly larger than those for LE states. The spectral-kinetics behavior of compounds studied agrees with the models A→ A ∗ → B ∗ or A→ A ∗ ↔ B ∗ , where A ∗ is the local excited planar and B ∗ is the relaxed twisted state of the molecule. The rate constants of the twisted state formation have been calculated in the temperature range 293 – 77 K. The activation energies of forward process for compounds studied have been estimated.
Dynamic Response of Non-Linear Inelsatic Systems to Poisson-Driven Stochastic Excitations
DEFF Research Database (Denmark)
Nielsen, Søren R. K.; Iwankiewicz, R.
A single-degree-of-freedom inelastic system subject to a stochastic excitation in form of a Poisson-distributed train of impulses is considered. The state variables of the system form a non-diffusive, Poisson-driven Markov process. Two approximate analytical techniques are developed: modification...
Energy Technology Data Exchange (ETDEWEB)
Zych, Aleksander, E-mail: a.k.zych@uu.nl [CMI, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 1, 3508TA Utrecht (Netherlands); Leferink op Reinink, Anke; Eerden, Koen van der; Mello Donega, Celso de; Meijerink, Andries [CMI, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 1, 3508TA Utrecht (Netherlands)
2011-03-31
Research highlights: > Fast d-f luminescence from Ce{sup 3+} and Pr{sup 3+} doped SrCl{sub 2} and BaCl{sub 2} has been observed. > Radiative lifetime of 26 ns for Ce{sup 3+} and 13 ns for Pr{sup 3+}d-f emission in SrCl{sub 2} has been measured. > Radiative lifetime of 19 ns for Ce{sup 3+} and 10 ns for Pr{sup 3+}d-f emission in BaCl{sub 2} has been measured. - Abstract: The photoluminescence and radioluminescence of Ce{sup 3+}, Pr{sup 3+} and Nd{sup 3+} in SrCl{sub 2} and BaCl{sub 2} are reported and discussed in relation to application as a (fast) scintillator material. The Ce{sup 3+} doped materials exhibit the typical fast cerium d-f emission (358, 382 nm in SrCl{sub 2} and 350, 375 nm in BaCl{sub 2}) both under synchrotron and ionizing radiation excitations. A weak afterglow is observed. For Pr{sup 3+} a very fast d-f emission is observed in SrCl{sub 2} (250, 263, 300 and 328 nm, {tau} = 13 ns) and BaCl{sub 2} (260, 288 and 315 nm, {tau} = 10 ns), but only under direct f-d excitation. No d-f luminescence is observed for Pr{sup 3+} under X-ray excitation. The absence of d-f emission is explained by the energy of the host lattice emission which is too low for energy transfer to the high energy fd states of Pr{sup 3+} (230 nm in SrCl{sub 2} and 235 nm in BaCl{sub 2}). The neodymium doped chlorides do not show d-f luminescence.
Stochastic population dynamics under resource constraints
Energy Technology Data Exchange (ETDEWEB)
Gavane, Ajinkya S., E-mail: ajinkyagavane@gmail.com; Nigam, Rahul, E-mail: rahul.nigam@hyderabad.bits-pilani.ac.in [BITS Pilani Hyderabad Campus, Shameerpet, Hyd - 500078 (India)
2016-06-02
This paper investigates the population growth of a certain species in which every generation reproduces thrice over a period of predefined time, under certain constraints of resources needed for survival of population. We study the survival period of a species by randomizing the reproduction probabilities within a window at same predefined ages and the resources are being produced by the working force of the population at a variable rate. This randomness in the reproduction rate makes the population growth stochastic in nature and one cannot predict the exact form of evolution. Hence we study the growth by running simulations for such a population and taking an ensemble averaged over 500 to 5000 such simulations as per the need. While the population reproduces in a stochastic manner, we have implemented a constraint on the amount of resources available for the population. This is important to make the simulations more realistic. The rate of resource production then is tuned to find the rate which suits the survival of the species. We also compute the mean life time of the species corresponding to different resource production rate. Study for these outcomes in the parameter space defined by the reproduction probabilities and rate of resource production is carried out.
Stochastic population dynamics under resource constraints
International Nuclear Information System (INIS)
Gavane, Ajinkya S.; Nigam, Rahul
2016-01-01
This paper investigates the population growth of a certain species in which every generation reproduces thrice over a period of predefined time, under certain constraints of resources needed for survival of population. We study the survival period of a species by randomizing the reproduction probabilities within a window at same predefined ages and the resources are being produced by the working force of the population at a variable rate. This randomness in the reproduction rate makes the population growth stochastic in nature and one cannot predict the exact form of evolution. Hence we study the growth by running simulations for such a population and taking an ensemble averaged over 500 to 5000 such simulations as per the need. While the population reproduces in a stochastic manner, we have implemented a constraint on the amount of resources available for the population. This is important to make the simulations more realistic. The rate of resource production then is tuned to find the rate which suits the survival of the species. We also compute the mean life time of the species corresponding to different resource production rate. Study for these outcomes in the parameter space defined by the reproduction probabilities and rate of resource production is carried out.
International Nuclear Information System (INIS)
Ouyang, Bing; Xue, Jia-Dan; Zheng, Xuming; Fang, Wei-Hai
2014-01-01
The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S 2 (A′), S 6 (A′), and S 7 (A′) excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S 2 (A′), S 6 (A′), and S 7 (A′) excited states were very different. The conical intersection point CI(S 2 /S 1 ) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S 2 (A′) state: the radiative S 2,min → S 0 transition and the nonradiative S 2 → S 1 internal conversion via CI(S 2 /S 1 ). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S 1 /T 1 ) in the excited state decay dynamics of PITC is evaluated
Energy Technology Data Exchange (ETDEWEB)
Raman, R N; Pivetti, C D; Rubenchik, A M; Matthews, D L; Troppmann, C; Demos, S G
2008-12-12
The use of reduced nicotinamide adenine dinucleotide (NADH) fluorescence to gain metabolic information on kidneys in response to an alteration in oxygen availability has previously been experimentally demonstrated, but signal quantification has not to date been addressed. In this work the relative contribution to rat kidney autofluorescence of the capsule vs. cortex under ultraviolet excitation is determined from experimental results obtained using autofluorescence microscopy and a suitable mathematical model. The results allow for a quantitative assessment of the relative contribution of the signal originating in the metabolically active cortex as a function of capsule thickness for different wavelengths.
Directory of Open Access Journals (Sweden)
Z. W. Zhu
2014-03-01
Full Text Available The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.
International Nuclear Information System (INIS)
Chiba, T.; Mieda, T.; Jitu, K.
1993-01-01
The dynamic characteristics of the co-axial cylinder subjected to the seismic loading was studied. This paper presents the analytical and the experimental results of the modal parameters of the fluid filled co-axial cylinders in the horizontal and the vertical excitations. Also, the effects of the annular space and the input level on the dynamic response of the cylinder are discussed. It is of interest to note that as the annular space becomes smaller, the dynamic response of the vertical direction increases. The nonlinear dynamic response is observed in the coupled excitation of the horizontal and the vertical directions at a narrow annular space
Li, Li; Hu, Feng; Chang, Yu-Qiang; Zhou, Yan; Wang, Peng; Zhang, Jian-Ping
2015-07-01
Siphonaxanthin and siphonein are two keto-carotenoids. Upon anthracene-sensitizing, triplet excitation dynamics of these two carotenoids were studied in n-hexane and in methanol, respectively, by ns flash photolysis spectroscopy. In n-hexane, bleaching of the ground state absorption (GSB) and the excitation triplet (3Car*) absorption were observed. In methanol, upon the decay of the 3Car*, the cation dehydrodimer of carotenoid, #[Car]2+, generated by the same rate, while an additional GSB generated synchronously, a polar solvent assisted and anthracene-sensitized mechanism was addressed based on the discussion. The environment-sensitive triplet excitation dynamics imply their potential role in photo-protection in vivo.
Effect of normal stress under an excitation in poroelastic flat slabs
African Journals Online (AJOL)
user
Math.,1957, pp.465-481. M.Tajuddin, and G. Narayan Reddy, Effect of boundaries on the dynamic interaction of a liquid filled porous layer and a supporting continuum, Sadhana, Vol. 30, part 4, 2005, pp.527-535. M.Tajuddin and S.A. Shah, Circumferential waves of infinite poroelastic cylinders, Trans. ASME, J. Appl. Mech., ...
TDDFT investigation of excitation of water tetramer under femtosecond laser pulse irradiation
Wang, Zhiping; Xu, Xuefen; Zhang, Fengshou; Qian, Chaoyi
2018-04-01
We study the static properties of water tetramer in ground state, the optical absorption spectra and ultrafast nonadiabatic dynamical response of water tetramer to short and intense laser pulses with different intensities by a real-space, real-time implementation of time-dependent density functional theory coupled to molecular dynamics (TDDFT-MD) nonadiabatically. The calculated results are in good agreement with available values in literature. Four typical irradiated scenarios of water tetramer in laser field, which are “normal vibration,” “break and reorganization,” “fragmentation and new formation” and “pure fragmentation”, are explored by discussing the ionization, the bond lengths of OH bonds and hydrogen bonds and the kinetic energy of ions. The dynamic simulation shows that the reaction channel of water tetramer can really be controlled by choosing appropriate laser parameters referring to the optical absorption spectra and hydrogen ions play an important role in the reaction channel. Furthermore, it is found that the laser intensity affects the kinetic energy of ejected protons more than that of the remaining fragments and all dynamic processes are somehow directly related to the velocity of departing protons.
2010-11-01
NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army Research Laboratory ATTN: RDRL-SEE-M 2800 Powder Mill Road Adelphi, MD 20783...Acknowledgment We thank Anand Sampath for the material growth. We also thank Yang Wang for useful discussions and numerical work in the earlier stages...piezoelectric interaction 1/2 s0 2 ij PE qVu2ρεεq ξeqeq q)k(k,M ijl,l , (10) where el,ij is the third rank tensor of the
Bailey, Joseph; Long, Nicholas; Hunze, Arvid
2017-09-28
This work investigates an eddy current-based non-destructive testing (NDT) method to characterize corrosion of pipes under thermal insulation, one of the leading failure mechanisms for insulated pipe infrastructure. Artificial defects were machined into the pipe surface to simulate the effect of corrosion wall loss. We show that by using a giant magnetoresistance (GMR) sensor array and a high current (300 A), single sinusoidal low frequency (5-200 Hz) pipe-encircling excitation scheme it is possible to quantify wall loss defects without removing the insulation or weather shield. An analysis of the magnetic field distribution and induced currents was undertaken using the finite element method (FEM) and analytical calculations. Simple algorithms to remove spurious measured field variations not associated with defects were developed and applied. The influence of an aluminium weather shield with discontinuities and dents was ascertained and found to be small for excitation frequency values below 40 Hz. The signal dependence on the defect dimensions was analysed in detail. The excitation frequency at which the maximum field amplitude change occurred increased linearly with the depth of the defect by about 3 Hz/mm defect depth. The change in magnetic field amplitude due to defects for sensors aligned in the azimuthal and radial directions were measured and found to be linearly dependent on the defect volume between 4400-30,800 mm³ with 1.2 × 10 -3 -1.6 × 10 -3 µT/mm³. The results show that our approach is well suited for measuring wall loss defects similar to the defects from corrosion under insulation.
International Nuclear Information System (INIS)
Fina, A.
1990-04-01
Some of the physico-chemical properties of organic solids like conductivity or permeation can be improved by irradiation. The aim of this work is to characterize modifications induced in poly (vinylidene fluoride) films (PVDF) by charged particles (ions and electrons), with electronic stopping power, for doses ranging from zero to twenty G-Grays. Influence of dose, density of electronic excitations, and flux (in particles per square centimeter), and the nature of defects induced by the beam, were studied with two methods: X-ray Photoelectron Spectroscopy (or XPS) for surface analysis, and electron Spin Resonance (or ESR) to probe the bulk of the film. Three ranges of doses are revealed in view of experimental results. At lower doses, PVDF undergoes deshydrofluorination induced by desorption; it is a low modifications regime. For intermediate range doses, conjugated carbon backbones of polyene compounds are produced. At higher doses, intermolecular interactions between the resulting fragments give a crosslinked network. For the upper limit of doses used, bond breaking results in a non reversible degradation of PVDF. In this last situation, direct atomic displacement of target atoms, is not negligible [fr
Dynamic Excitation of Monopiles by Steep and Breaking Waves: Experimental and Numerical Study
DEFF Research Database (Denmark)
Bredmose, Henrik; Slabiak, Peter; Sahlberg-Nielsen, Lasse
2013-01-01
An experiment with a flexible pile subjected to steep and breaking irregular waves has been conducted. The pile was constructed to represent a monopile wind turbine at scale 1:80. Two point masses were mounted on the pile to achieve the right scaled values for the first and second natural frequency....... Emphasis is given to the observed impulsive excitation of the natural modes by steep and breaking waves. Additionally, springing and ringing-type continuous forcing of the first natural mode is seen for the moderately steep waves. The experiments were carried out at three depths and with two wave climates...... wave kinematics, combined with a finite element model with Morison-based forcing. A good overall reproduction of the wave field and structural response is achieved for two selected episodes. For some of the waves, however, the numerical response magnitude does not match the observed excitations...
International Nuclear Information System (INIS)
Yue Xiao-Le; Xu Wei; Zhang Ying; Wang Liang
2015-01-01
The piezomagnetoelastic energy harvester system subjected to harmonic and Poisson white noise excitations is studied by using the generalized cell mapping method. The transient and stationary probability density functions (PDFs) of response based on the global viewpoint are obtained by the matrix analysis method. Monte Carlo simulation results verify the accuracy of this method. It can be observed that evolutionary direction of transient and stationary PDFs is in accordance with the unstable manifold for this system, and a stochastic P-bifurcation occurs as the intensity of Poisson white noise increases. This study presents an efficient numerical tool to solve the stochastic response of a three-dimensional dynamical system and provides a new idea to analyze the energy harvester system. (paper)
Honório, Leonardo M; Costa, Exuperry Barros; Oliveira, Edimar J; Fernandes, Daniel de Almeida; Moreira, Antonio Paulo G M
2018-04-13
This work presents a novel methodology for Sub-Optimal Excitation Signal Generation and Optimal Parameter Estimation of constrained nonlinear systems. It is proposed that the evaluation of each signal must also account for the difference between real and estimated system parameters. However, this metric is not directly obtained once the real parameter values are not known. The alternative presented here is to adopt the hypothesis that, if a system can be approximated by a white box model, this model can be used as a benchmark to indicate the impact of a signal over the parametric estimation. In this way, the proposed method uses a dual layer optimization methodology: (i) Inner Level; For a given excitation signal a nonlinear optimization method searches for the optimal set of parameters that minimizes the error between the outputs of the optimized and benchmark models. (ii) At the outer level, a metaheuristic optimization method is responsible for constructing the best excitation signal, considering the fitness coming from the inner level, the quadratic difference between its parameters and the cost related to the time and space required to execute the experiment. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.
Dynamic Stability of Euler Beams under Axial Unsteady Wind Force
Directory of Open Access Journals (Sweden)
You-Qin Huang
2014-01-01
Full Text Available Dynamic instability of beams in complex structures caused by unsteady wind load has occurred more frequently. However, studies on the parametric resonance of beams are generally limited to harmonic loads, while arbitrary dynamic load is rarely involved. The critical frequency equation for simply supported Euler beams with uniform section under arbitrary axial dynamic forces is firstly derived in this paper based on the Mathieu-Hill equation. Dynamic instability regions with high precision are then calculated by a presented eigenvalue method. Further, the dynamically unstable state of beams under the wind force with any mean or fluctuating component is determined by load normalization, and the wind-induced parametric resonant response is computed by the Runge-Kutta approach. Finally, a measured wind load time-history is input into the dynamic system to indicate that the proposed methods are effective. This study presents a new method to determine the wind-induced dynamic stability of Euler beams. The beam would become dynamically unstable provided that the parametric point, denoting the relation between load properties and structural frequency, is located in the instability region, no matter whether the wind load component is large or not.
Production and stability of radiation-induced defects in MgAl2O4 under electronic excitation
International Nuclear Information System (INIS)
Yasuda, K.; Yamamoto, T.; Seki, S.; Shiiyama, K.; Matsumura, S.
2008-01-01
This paper investigates the formation process of radiation-induced defects in magnesium aluminate spinel and their stability using transmission electron microscopy, with emphasis on the effects of electronic excitation. Small interstitial-type dislocation loops disappeared under electron-induced electronic excitation. The elimination rate of the loops was found to be one order higher than for α-alumina. The disappearance of dislocation loops by a dissociation mechanism into isolated interstitials is discussed through analysis of the growth-and-shrink process of the loops. HARECXS analysis on cross section specimens irradiated with 350 MeV Au ions has shown the progress of cation disordering along ion tracks to be a function of electronic stopping power, (dE/dx) e . Cations were found to exchange their sites toward a random configuration. Such disordering appears from (dE/dx) e = 10 keV/nm, and increases in size with increasing (dE/dx) e to reach nearly 10 nm in diameter at 30 keV/nm, under an assumption of a fully disordered configuration
Directory of Open Access Journals (Sweden)
Wang Hongjin
2014-01-01
Full Text Available Two improved analytical methods of calculations for natural frequencies and mode shapes of a uniform cantilever beam carrying a tip-mass under base excitation are presented based on forced vibration theory and the method of separation of variables, respectively. The cantilever model is simplified in detail by replacing the tip-mass with an equivalent inertial force and inertial moment acting at the free end of the cantilever based on D’Alembert’s principle. The concentrated equivalent inertial force and inertial moment are further represented as distributed loads using Dirac Delta Function. In this case, some typical natural frequencies and mode shapes of the cantilever model are calculated by the improved and unimproved analytical methods. The comparing results show that, after improvement, these two methods are in extremely good agreement with each other even the offset distance between the gravity center of the tip-mass and the attachment point is large. As further verification, the transient and steady displacement responses of the cantilever system under a sine base excitation are presented in which two improved methods are separately utilized. Finally, an experimental cantilever system is fabricated and the theoretical displacement responses are validated by the experimental measurements successfully.
SEDIGISM: Structure, excitation, and dynamics of the inner Galactic interstellar medium
Schuller, F.; Csengeri, T.; Urquhart, J. S.; Duarte-Cabral, A.; Barnes, P. J.; Giannetti, A.; Hernandez, A. K.; Leurini, S.; Mattern, M.; Medina, S.-N. X.; Agurto, C.; Azagra, F.; Anderson, L. D.; Beltrán, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Dobbs, C. L.; Dumke, M.; Finger, R.; Ginsburg, A.; Gonzalez, E.; Henning, T.; Kauffmann, J.; Mac-Auliffe, F.; Menten, K. M.; Montenegro-Montes, F. M.; Moore, T. J. T.; Muller, E.; Parra, R.; Perez-Beaupuits, J.-P.; Pettitt, A.; Russeil, D.; Sánchez-Monge, Á.; Schilke, P.; Schisano, E.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.; Wang, K.; Wienen, M.; Wyrowski, F.; Zavagno, A.
2017-05-01
data in the (1-0) transition of CO isotopologues from the ThrUMMS survey, we are able to compute a 3D realization of the excitation temperature and optical depth in the interstellar medium. Ultimately, this survey will provide a detailed, global view of the inner Galactic interstellar medium at an unprecedented angular resolution of 30''. This publication is based on data acquired with the Atacama Pathfinder EXperiment (APEX) under programmes 092.F-9315(A) and 193.C-0584(A). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.Full Table 5 and Table A.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A124
Directory of Open Access Journals (Sweden)
Thomas eGrüter
2015-05-01
Full Text Available Psychosis is accompanied by severe attentional deficits, and impairments in associational-memory processing and sensory information processing that are ascribed to dysfunctions in prefrontal and hippocampal function. Disruptions of glutamatergic signalling may underlie these alterations: Antagonism of the N-methyl-D-aspartate receptor (NMDAR results in similar molecular, cellular, cognitive and behavioural changes in rodents and/or humans as those that occur in psychosis, raising the question as to whether changes in glutamatergic transmission may be intrinsic to the pathophysiology of the disease. In an animal model of psychosis that comprises treatment with the irreversible NMDAR-antagonist, MK801, we explored the cellular mechanisms that may underlie hippocampal dysfunction in psychosis. MK801-treatment resulted in a profound loss of hippocampal LTP that was evident 4 weeks after treatment. Whereas neuronal expression of the immediate early gene, Arc, was enhanced in the hippocampus by spatial learning in controls, MK801-treated animals failed to show activity-dependent increases in Arc expression. By contrast, a significant increase in basal Arc expression in the absence of learning was evident compared to controls. Paired-pulse facilitation was increased at the 40 ms interval indicating that NMDAR and/or fast GABAergic-mediated neurotransmission was disrupted. In line with this, MK801-treatment resulted in a significant decrease in GABA(A, and increase in GABA(B-receptor-expression in PFC, along with a significant increase of GABA(B- and NMDAR-GluN2B expression in the dentate gyrus. NMDAR-GluN1 or GluN2A subunit expression was unchanged. These data suggest that in psychosis, deficits in hippocampus-dependent memory may be caused by a loss of hippocampal LTP that arises through enhanced hippocampal neuronal excitability, altered GluN2B and GABA receptor expression and an uncoupling of the hippocampus-prefrontal cortex circuitry.
Effect of CH stretching excitation on the reaction dynamics of F + CHD{sub 3} → DF + CHD{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Yang, Jiayue; Zhang, Dong; Chen, Zhen; Jiang, Bo [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian, Liaoning 116023 (China); Blauert, Florian [Dynamics at Surfaces, Faculty of Chemistry, Georg-August-Universität Göttingen, 37077 Göttingen (Germany); Dai, Dongxu; Wu, Guorong, E-mail: wugr@dicp.ac.cn, E-mail: xmyang@dicp.ac.cn; Zhang, Donghui; Yang, Xueming, E-mail: wugr@dicp.ac.cn, E-mail: xmyang@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)
2015-07-28
The vibrationally excited reaction of F + CHD{sub 3}(ν{sub 1} = 1) → DF + CHD{sub 2} at a collision energy of 9.0 kcal/mol is investigated using the crossed-beams and time-sliced velocity map imaging techniques. Detailed and quantitative information of the CH stretching excitation effects on the reactivity and dynamics of the title reaction is extracted with the help of an accurate determination of the fraction of the excited CHD{sub 3} reagent in the crossed-beam region. It is found that all vibrational states of the CHD{sub 2} products observed in the ground-state reaction, which mainly involve the excitation of the umbrella mode of the CHD{sub 2} products, are severely suppressed by the CH stretching excitation. However, there are four additional vibrational states of the CHD{sub 2} products appearing in the excited-state reaction which are not presented in the ground-state reaction. These vibrational states either have the CH stretching excitation retained or involve one quantum excitation in the CH stretching and the excitation of the umbrella mode. Including all observed vibrational states, the overall cross section of the excited-state reaction is estimated to be 66.6% of that of the ground-state one. Experimental results also show that when the energy of CH stretching excitation is released during the reaction, it is deposited almost exclusively as the rovibrational energy of the DF products, with little portion in the translational degree of freedom. For vibrational states of the CHD{sub 2} products observed in both ground- and excited-state reactions, the CH stretching excitation greatly suppresses the forward scattered products, causing a noticeable change in the product angular distributions.
System dynamics of manpower planning strategies under various demand scenarios
Directory of Open Access Journals (Sweden)
Michael Mutingi
2012-09-01
Full Text Available The development of human resources recruitment and training strategies in a dynamic environment poses a challenge to many policy makers in various organisations. The goal of every human resource manager is to recruit, train and deploy the right personnel at the right place and at the right time in order to meet organizational requirements. We develop a system dynamics simulation model that captures the dynamic behaviour of a typical corporate manpower system. Three major strategies are indentified and simulated under different manpower demand scenarios. Based on a set of performance indices, the impact of the strategies is simulated under assumed demand scenarios including steady increasing, fluctuating, and s-shaped demand. Useful managerial insights are derived from the study. The model is a decision support tool for developing reliable dynamic manpower policies in terms of recruitment, training capacity, available skills, and attrition. This approach can assist organizations to design effective manpower strategies.
Wind-excited vibrations - Solution by passive dynamic vibration absorbers of different types
Czech Academy of Sciences Publication Activity Database
Fischer, Ondřej
2007-01-01
Roč. 95, 9-11 (2007), s. 1028-1039 ISSN 0167-6105. [EACWE 4. Praha, 11.07.2005-15.07.2005] R&D Projects: GA AV ČR(CZ) IAA200710505; GA AV ČR(CZ) IAA2071401; GA ČR(CZ) GA103/06/0099 Institutional research plan: CEZ:AV0Z20710524 Keywords : wind-excited vibrations * slender structures * vibration absorption Subject RIV: JM - Building Engineering Impact factor: 0.959, year: 2007
Cho, Dae Won; Kim, Yong Hee; Yoon, Minjoong; Jeoung, Sae Chae; Kim, Dongho
1994-08-01
The picosecond time-resolved fluorescence and transient absorption behavior of piroxicam at room temperature are reported. The keto tautomer in the excited singlet state ( 1K*) formed via the fast intramolecular proton transfer (≈ 20 ps) is observed. The short-lived (7.5 ns) triplet state of keto tauomer ( 3K*) is generated from 1K * in toluene whereas it is hardly observed in ethanol. Consequently, rapid reverse proton transfer takes place from 3K * to the enol triplet state ( 3E *.
Dynamics of excited instantons in the system of forced Gursey nonlinear differential equations
Aydogmus, F.
2015-02-01
The Gursey model is a 4D conformally invariant pure fermionic model with a nonlinear spinor self-coupled term. Gursey proposed his model as a possible basis for a unitary description of elementary particles following the "Heisenberg dream." In this paper, we consider the system of Gursey nonlinear differential equations (GNDEs) formed by using the Heisenberg ansatz. We use it to understand how the behavior of spinor-type Gursey instantons can be affected by excitations. For this, the regular and chaotic numerical solutions of forced GNDEs are investigated by constructing their Poincaré sections in phase space. A hierarchical cluster analysis method for investigating the forced GNDEs is also presented.
Formation Dynamics of Excited Components in ArF Excimer Laser Discharge
古橋, 秀夫; 内田, 悦行
1993-01-01
Time-resolved density measurements of excited components in a discharge pumped ArF excimer laser were performed using laser absorption probing with a cw dye laser pumped by a Ar^+ laser. The dependence of the He^* 2p^3P densities on the gas parameters were measured. The relationships between laser output power and the number densities of He^* are discussed. The relationships between the laser output power and the formation rate of Ar^+ ions by Penning ionization with He^* atoms are also discu...
The influence of the excitation pulse length on ultrafast magnetization dynamics in nickel
Directory of Open Access Journals (Sweden)
A. Fognini
2015-03-01
Full Text Available The laser-induced demagnetization of a ferromagnet is caused by the temperature of the electron gas as well as the lattice temperature. For long excitation pulses, the two reservoirs are in thermal equilibrium. In contrast to a picosecond laser pulse, a femtosecond pulse causes a non-equilibrium between the electron gas and the lattice. By pump pulse length dependent optical measurements, we find that the magnetodynamics in Ni caused by a picosecond laser pulse can be reconstructed from the response to a femtosecond pulse. The mechanism responsible for demagnetization on the picosecond time scale is therefore contained in the femtosecond demagnetization experiment.
Böttcher, J.; Jahn, M.; Tatzko, S.
2017-12-01
Pseudoelastic shape memory alloys exhibit a stress-induced phase transformation which leads to high strains during deformation of the material. The stress-strain characteristic during this thermomechanical process is hysteretic and results in the conversion of mechanical energy into thermal energy. This energy conversion allows for the use of shape memory alloys in vibration reduction. For the application of shape memory alloys as vibration damping devices a dynamic modeling of the material behavior is necessary. In this context experimentally determined material parameters which accurately represent the material behavior are essential for a reliable material model. Subject of this publication is the declaration of suitable material parameters for pseudoelastic shape memory alloys and the methodology of their identification from experimental investigations. The used test rig was specifically designed for the characterization of pseudoelastic shape memory alloys.
Energy Technology Data Exchange (ETDEWEB)
Lin, Guan-Bo; Schubert, E. Fred; Cho, Jaehee; Park, Jun Hyuk; Kim, Jong Kyu
2015-08-19
The efficiency of Ga0.87In0.13N/GaN single and multiple quantum well (QW) light-emitting diodes is investigated under photoluminescence (PL) and electroluminescence (EL) excitation. By measuring the laser spot area (knife-edge method) and the absorbance of the GaInN QW (transmittance/reflectance measurements), the PL excitation density can be converted to an equivalent EL excitation density. The EL efficiency droop-onset occurs at an excitation density of 2.08 × 1026 cm–3 s–1 (J = 10 A/cm2), whereas no PL efficiency droop is found for excitation densities as high as 3.11 × 1027 cm–3 s–1 (J = 149 A/cm2). Considering Shockley–Read–Hall, radiative, and Auger recombination and including carrier leakage shows that the EL efficiency droop is consistent with a reduction of injection efficiency.
Photodissociation dynamics of Ar2(+) and Ar3(+) excited by 527 nm photons.
Lepère, V; Picard, Y J; Barat, M; Fayeton, J A; Lucas, B; Béroff, K
2009-05-21
The photofragmentation dynamics of Ar(2)(+) and Ar(3)(+) clusters has been investigated at a 527 nm wavelength (2.35 eV) using a setup that allows simultaneous detection of the ionic and neutral fragments in a coincidence experiment. Measurement of positions and times of flight enables in principle a complete description of the fragmentation dynamics. The photofragmentation dynamics of Ar(3)(+) clusters is similar to that of Ar(2)(+) with, in addition, the ejection of a third fragment that can be neutral or ionized via a resonant electron capture. This is attributed to the triangular geometry of the Ar(3)(+) ion.
Directory of Open Access Journals (Sweden)
M.R. Mofakhami
2008-01-01
Full Text Available In this paper sound transmission through the multilayered viscoelastic air filled cylinders subjected to the incident acoustic wave is studied using the technique of separation of variables on the basis of linear three dimensional theory of elasticity. The effect of interior acoustic medium on the mode maps (frequency vs geometry and noise reduction is investigated. The effects of internal absorption and external moving medium on noise reduction are also evaluated. The dynamic viscoelastic properties of the structure are rigorously taken into account with a power law technique that models the viscoelastic damping of the cylinder. A parametric study is also performed for the two layered infinite cylinders to obtain the effect of viscoelastic layer characteristics such as thickness, material type and frequency dependency of viscoelastic properties on the noise reduction. It is shown that using constant and frequency dependent viscoelastic material with high loss factor leads to the uniform noise reduction in the frequency domain. It is also shown that the noise reduction obtained for constant viscoelastic material property is subjected to some errors in the low frequency range with respect to those obtained for the frequency dependent viscoelastic material.
Investigation of a bistable dual-stage vibration isolator under harmonic excitation
International Nuclear Information System (INIS)
Yang, Kai; Huang, Hai; Harne, R L; Wang, K W
2014-01-01
This study explores the steady-state performance of a dual-stage vibration isolator, which is configured by a bistable oscillator and a linear oscillator. The potential force of the bistable stage comprises negative linear and positive cubic nonlinear stiffnesses such that the two restoring force contributions may counterbalance to minimize dynamic force transmission. By applying a first-order harmonic balance, it is predicted that the bistable dual-stage isolator may significantly outperform an equivalent pure linear dual-stage isolator. This conclusion is verified through a series of numerical investigations. Following a parametric study, design guidelines are detailed to achieve performance improvements. Then, the ‘valley’ response, which is the special phenomenon of the bistable dual-stage isolator due to the counterbalance of the negative linear and positive nonlinear potential forces, is revealed and quantitatively explained. Numerical studies demonstrate the role of initial conditions, and it is shown that the likelihood of beneficial single periodic valley and intra-well responses for isolation purposes can be increased by greater bistable stage damping. Finally, a bistable dual-stage isolator prototype is developed and tested, and the numerical and experimental results verify the theoretical predictions. (paper)
Propagation of Computer Virus under Human Intervention: A Dynamical Model
Chenquan Gan; Xiaofan Yang; Wanping Liu; Qingyi Zhu; Xulong Zhang
2012-01-01
This paper examines the propagation behavior of computer virus under human intervention. A dynamical model describing the spread of computer virus, under which a susceptible computer can become recovered directly and an infected computer can become susceptible directly, is proposed. Through a qualitative analysis of this model, it is found that the virus-free equilibrium is globally asymptotically stable when the basic reproduction number R0≤1, whereas the viral equilibrium is globally asympt...
Modeling electroluminescence in insulating polymers under ac stress: effect of excitation waveform
Energy Technology Data Exchange (ETDEWEB)
Baudoin, F; Le Roy, S; Teyssedre, G; Laurent, C [University of Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse cedex 9 (France); Mills, D H; Lewin, P L, E-mail: fulbert.baudoin@laplace.univ-tlse.fr [University of Southampton, The Tony Davies High Voltage Laboratory (United Kingdom)
2011-04-27
A charge transport model allowing the description of electroluminescence in polyethylene films under ac stress is proposed. The fluid model incorporates bipolar charge injection/extraction, transport and recombination. The physics is based on hopping mobility of electronic carriers between traps with an exponential distribution in which trap filling controls the mobility. The computation mesh is very tight close to the electrodes, of the order of 0.4 nm, allowing mapping of the density of positive and negative carriers during sinusoidal, triangular and square 50 Hz voltage waveforms. Experiment and simulation fit nicely and the time dependence of the electroluminescence intensity is accounted for by the charge behaviour. Light emission scales with the injection current. It is shown that space charge affects a layer 10 nm away from the electrode where the mobility is increased as compared with the bulk mobility due to the high density of charge. The approach is very encouraging and opens the way to model space charge under time-varying voltages.
Vibration and acoustic noise emitted by dry-type air-core reactors under PWM voltage excitation
Li, Jingsong; Wang, Shanming; Hong, Jianfeng; Yang, Zhanlu; Jiang, Shengqian; Xia, Shichong
2018-05-01
According to coupling way between the magnetic field and the structural order, structure mode is discussed by engaging finite element (FE) method and both natural frequency and modal shape for a dry-type air-core reactor (DAR) are obtained in this paper. On the basis of harmonic response analysis, electromagnetic force under PWM (Pulse Width Modulation) voltage excitation is mapped with the structure mesh, the vibration spectrum is gained and the consequences represents that the whole structure vibration predominates in the radial direction, with less axial vibration. Referring to the test standard of reactor noise, the rules of emitted noise of the DAR are measured and analyzed at chosen switching frequency matches the sample resonant frequency and the methods of active vibration and noise reduction are put forward. Finally, the low acoustic noise emission of a prototype DAR is verified by measurement.
Pramodini, S.; Poornesh, P.
2014-11-01
We report thermally induced third-order nonlinearity and optical limiting behaviour of Indigo Carmine dye. z-Scan technique was used to determine the sign and magnitude of absorptive and refractive nonlinearities. Continuous wave (CW) He-Ne laser operating at 633 nm was used as source of excitation. In open aperture z-scan experiments, samples exhibited reverse saturable absorption (RSA) process. For closed aperture z-scan experiments, samples revealed self-defocusing property. The presence of donor and acceptor groups in the structure increases the conjugation length and in turn increases the optical nonlinearity. Induced self-diffraction rings pattern was recorded for the samples and it is attributed to refractive index change and thermal lensing. Also, optical limiting and clamping studies were carried out for various input power. Optical clamping of about ~1 mW was observed. This endorses that the dye under investigation is a positive candidate for opto-electronic and photonic applications.
High-efficient, bicolor-emitting GdVO4:Dy3+ phosphor under near ultraviolet excitation
International Nuclear Information System (INIS)
Lu, Jinjin; Zhou, Jia; Jia, Huayu; Tian, Yue
2015-01-01
Bicolor emitting GdVO 4 :Dy 3+ phosphor with short columniation-shape was prepared via a simple co-precipitation process. The optimal doping concentration for obtaining maximal luminescent intensity was confirmed to be 0.3 mol% and the electric dipole–dipole interaction is responsible for concentration quenching of Dy 3+ emission in GdVO 4 phosphor. In order to evaluate the luminescent performance of as-prepared phosphor, the luminescent efficiency and color coordinates were studied. The results show that luminescent efficiency of this phosphor is very high under near UV excitation and twice times higher than commercial Y 2 O 2 S:Eu 3+ phosphor. In addition, the color coordinates for optimal Dy 3+ concentration are (0.339, 0.379), which are close to equal energy point. Therefore, the GdVO 4 :Dy 3+ phosphor may have potential application for solid state lighting.
Dynamics of excited instantons in the system of forced Gursey nonlinear differential equations
International Nuclear Information System (INIS)
Aydogmus, F.
2015-01-01
The Gursey model is a 4D conformally invariant pure fermionic model with a nonlinear spinor self-coupled term. Gursey proposed his model as a possible basis for a unitary description of elementary particles following the “Heisenberg dream.” In this paper, we consider the system of Gursey nonlinear differential equations (GNDEs) formed by using the Heisenberg ansatz. We use it to understand how the behavior of spinor-type Gursey instantons can be affected by excitations. For this, the regular and chaotic numerical solutions of forced GNDEs are investigated by constructing their Poincaré sections in phase space. A hierarchical cluster analysis method for investigating the forced GNDEs is also presented
Dynamics of Deformable Active Particles under External Flow Field
Tarama, Mitsusuke
2017-10-01
In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.
Excited-State Dynamics in 6-THIOGUANOSINE from Femtosecond to Microsecond Time Scale
Guo, Cao; Reichardt, Christian; Crespo-Hernández, Carlos E.
2011-06-01
6-thioguanine is a widely used pro-drug in which the oxygen atom in the carbonyl group of guanine is replaced by a sulfur atom. Previous studies have shown that patients treated with 6-thioguanine can metabolize and incorporate it in DNA as 6-thioguanosine (6tGuo). These patients show a high incidence of skin cancer when they are exposed to extended periods of sunlight irradiation. In this work, the photodynamics of 6tGuo is investigated by broad band time resolved transient spectroscopy. Similar to previously studied 4-thiothymidine, our results show that excitation of 6tGuo with UVA light at 340 nm results in efficient and ultrafast intersystem crossing to the triplet manifold (τ = 0.31±0.05 ps) and a high triplet quantum yield (φ = 0.8±0.2). The triplet state has a lifetime of 720±10 ns in N2-saturated vs. 460±10 ns in air-saturated aqueous solution. In addition, a minor picosecond deactivation channel (80±15 ps) is observed, which is tentatively assigned to internal conversion from the lowest-energy excited singlet state to the ground state. Quantum chemical calculations support the proposed kinetic model. Based on the high triplet quantum yield measured, it is proposed that the phototoxicity of 6tGuo is due to its ability to photosensitized singlet oxygen, which can result in oxidative damage to DNA. P. O'Donovan, C. M. Perrett, X. Zhang, B. Montaner, Y.-Z. Xu, C. A. Harwood, J. M. McGregor, S. L. Walker, F. Hanaoka, P. Karran, Science 309, 1871 (2005). C. Reichardt, C. Guo, C. E. Crespo-Hernández, J. Phys. Chem. B. in press (2011). C. Reichardt, C. E. Crespo-Hernández, J. Phys. Chem. Lett. 1, 2239 (2010) C. Reichardt, C. E. Crespo-Hernández, Chem. Comm. 46, 5963 (2010).
Wideband impedance measurements of DC motors under dynamic load conditions
Diouf, F.; Buesink, Frederik Johannes Karel; Leferink, Frank Bernardus Johannes; Duval, Fabrice; Bensetti, Mohamed
2013-01-01
One of the principal conducted EMI(electromagnetic interferences) sources of low voltage DC (direct current) motors is the commutation occurring during rotation. In this paper the small-signal impedance of low voltage DC motors under different functioning modes, including the dynamic one is studied
GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma
Lécz, Zs.; Konoplev, I. V.; Seryi, A.; Andreev, A.
2016-10-01
This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration.
Femtosecond quantum fluid dynamics of helium atom under an intense laser field
International Nuclear Information System (INIS)
Dey, B.K.
1998-01-01
A comprehensive, nonperturbative, time-dependent quantum mechanical (TDQM) approach is proposed for studying the dynamics of a helium atom under an intense, ultrashort (femtoseconds) laser pulse. The method combines quantum fluid dynamics (QFD) and density functional theory. It solves a single generalized nonlinear Schroedinger equation of motion (EOM), involving time and three space variables, which is obtained from two QFD equations, namely, a continuity equation and an Euler-type equation. A highly accurate finite difference scheme along with a stability analysis is presented for numerically solving the EOM. Starting from the ground-state Hartree-Fock density for He at t = 0, the EOM yields the time-dependent (TD) electron density, effective potential surface, difference density, difference effective potential, ground-state probability, left-angle r right-angle, magnetic susceptibility, polarizability, flux, etc. By a Fourier transformation of the TD dipole moment along the linearly polarized-field direction, the power and rate spectra for photoemission are calculated. eleven mechanistic routes for photoemission are identified, which include high harmonic generation as well as many other spectral transitions involving ionized, singly excited, doubly excited (autoionizing), and continuum He states, based on the evolution of the system up to a particular time. Intimate connections between photoionization and photoemission are clearly observed through computer visualizations. Apart from being consistent with current experimental and theoretical results, the present results offer certain predictions on spectral transitions which are open to experimental verification
Chen, Guanying; Ohulchanskyy, Tymish Y.; Kachynski, Aliaksandr; Ågren, Hans; Prasad, Paras N.
2012-01-01
We report intense upconversion photoluminescence (PL) in colloidal LiYF4:Er3+ nanocrystals under excitation with telecom-wavelength at 1490 nm. The intensities of two- and three-photon anti-Stokes upconversion PL bands are higher than or comparable to that of the Stokes emission under excitation with low power density in the range of 5–120 W/cm2. The quantum yield of the upconversion PL was measured to be as high as ~1.2±0.1%, which is almost 4 times higher than the highest upconversion PL quantum yield reported up to date for lanthanide-doped nanocrystals in 100 nm sized hexagonal NaYF4:Yb3+20%, Er3+2% using excitation at ~980 nm. Power dependence study revealed that the intensities of all PL bands have linear dependence on the excitation power density, which was explained by saturation effects in the intermediate energy states. PMID:21557587
Soil Moisture Dynamics under Corn, Soybean, and Perennial Kura Clover
Ochsner, T.; Venterea, R. T.
2009-12-01
Rising global food and energy consumption call for increased agricultural production, whereas rising concerns for environmental quality call for farming systems with more favorable environmental impacts. Improved understanding and management of plant-soil water interactions are central to meeting these twin challenges. The objective of this research was to compare the temporal dynamics of soil moisture under contrasting cropping systems suited for the Midwestern region of the United States. Precipitation, infiltration, drainage, evapotranspiration, soil water storage, and freeze/thaw processes were measured hourly for three years in field plots of continuous corn (Zea mays L.), corn/soybean [Glycine max (L.) Merr.] rotation, and perennial kura clover (Trifolium ambiguum M. Bieb.) in southeastern Minnesota. The evapotranspiration from the perennial clover most closely followed the temporal dynamics of precipitation, resulting in deep drainage which was reduced up to 50% relative to the annual crops. Soil moisture utilization also continued later into the fall under the clover than under the annual crops. In the annual cropping systems, crop sequence influenced the soil moisture dynamics. Soybean following corn and continuous corn exhibited evapotranspiration which was 80 mm less than and deep drainage which was 80 mm greater than that of corn following soybean. These differences occurred primarily during the spring and were associated with differences in early season plant growth between the systems. In the summer, soil moisture depletion was up to 30 mm greater under corn than soybean. Crop residue also played an important role in the soil moisture dynamics. Higher amounts of residue were associated with reduced soil freezing. This presentation will highlight key aspects of the soil moisture dynamics for these contrasting cropping systems across temporal scales ranging from hours to years. The links between soil moisture dynamics, crop yields, and nutrient leaching
Schmitt, Hans-Christian; Flock, Marco; Welz, Eileen; Engels, Bernd; Schneider, Heidi; Radius, Udo; Fischer, Ingo
2017-03-02
We describe an investigation of the excited-state dynamics of isolated 1,3-di-tert-butyl-imidazoline-2-ylidene (tBu 2 Im, C 11 H 20 N 2 , m/z=180), an Arduengo-type carbene, by time- and frequency-resolved photoionization using a picosecond laser system. The energies of several singlet and triplet excited states were calculated by time-dependent density functional theory (TD-DFT). The S 1 state of the carbene deactivates on a 100 ps time scale possibly by intersystem crossing. In the experiments we observed an additional signal at m/z=196, that was assigned to the oxidation product 1,3-di-tert-butyl-imidazolone, tBu 2 ImO. It shows a well-resolved resonance-enhanced multiphoton ionization (REMPI) spectrum with an origin located at 36951 cm -1 . Several low-lying vibrational bands could be assigned, with a lifetime that depends strongly on the excitation energy. At the origin the lifetime is longer than 3 ns, but drops to 49 ps at higher excess energies. To confirm formation of the imidazolone we also performed experiments on benzimidazolone (BzImO) for comparison. Apart from a redshift for BzImO the spectra of the two compounds are very similar. The TD-DFT values display a very good agreement with the experimental data. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
A variational approach to Bogoliubov excitations and dynamics of dipolar Bose–Einstein condensates
International Nuclear Information System (INIS)
Kreibich, Manuel; Main, Jörg; Wunner, Günter
2013-01-01
We investigate the stability properties and the dynamics of Bose–Einstein condensates with axial symmetry, especially with dipolar long-range interaction, using both simulations on grids and variational calculations. We present an extended variational ansatz which is applicable for axial symmetry and show that this ansatz can reproduce the lowest eigenfrequencies of the Bogoliubov spectrum, and also the corresponding eigenfunctions. Our variational ansatz is capable of describing the roton instability of pancake-shaped dipolar condensates for arbitrary angular momenta. After investigating the linear regime we apply the ansatz to determine the dynamics and show how the angular collapse is correctly described within the variational framework. (paper)
MgB_{2} nonlinear properties investigated under localized high rf magnetic field excitation
Directory of Open Access Journals (Sweden)
Tamin Tai
2012-12-01
Full Text Available The high transition temperature and low surface resistance of MgB_{2} attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB_{2} at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the π band, the nonlinear response of MgB_{2} at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB_{2}, as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615 (2011ITASE91051-822310.1109/TASC.2010.2096531]. MgB_{2} films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.
Comparative performance of passive devices for piping system under seismic excitation
Energy Technology Data Exchange (ETDEWEB)
Kumar, Praveen, E-mail: pra_veen74@rediffmail.com [Bhabha Atomic Research Centre, Trombay, Mumbai, 400085 (India); Jangid, R.S. [Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 (India); Reddy, G.R. [Bhabha Atomic Research Centre, Trombay, Mumbai, 400085 (India)
2016-03-15
Highlights: • Correlated the analytical results obtained from the proposed analytical procedures with experimental results in the case of XPD. • Substantial reduction of the seismic response of piping system with passive devices is observed. • Significant increase in the modal damping of the piping system is noted. • There exist an optimum parameters of the passive devices. • Good amount of energy dissipation is observed by using passive devices. - Abstract: Among several passive control devices, X-plate damper, viscous damper, visco-elastic damper, tuned mass damper and multiple tuned mass dampers are popular and used to mitigate the seismic response in the 3-D piping system. In the present paper detailed studies are made to see the effectiveness of the dampers when used in 3-D piping system subjected to artificial earthquake with increasing amplitudes. The analytical results obtained using Wen's model are compared with the corresponding experimental results available which indicated a good match with the proposed analytical procedure for the X-plate dampers. It is observed that there is significant reduction in the seismic response of interest like relative displacement, acceleration and the support reaction of the piping system with passive devices. In general, the passive devices under particular optimum parameters such as stiffness and damping are very effective and practically implementable for the seismic response mitigation, vibration control and seismic requalification of piping system.
Alsulami, Qana
2015-06-25
Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.
Tanaka, Kazunori; Iida, Satoko; Takaichi, Shinichi; Mimuro, Mamoru; Murakami, Akio; Akimoto, Seiji
2016-12-01
Photosynthetic light-harvesting complexes, found in aquatic photosynthetic organisms, contain a variety of carotenoids and chlorophylls. Most of the photosynthetic dinoflagellates possess two types of light-harvesting antenna complexes: peridinin (Peri)-chlorophyll (Chl) a/c-protein, as an intrinsic thylakoid membrane complex protein (iPCP), and water-soluble Peri-Chl a-protein, as an extrinsic membrane protein (sPCP) on the inner surface of the thylakoid. Peri is a unique carotenoid that has eight C=C bonds and one C=O bond, which results in a characteristic absorption band in the green wavelength region. In the present study, excitation relaxation dynamics of Peri in solution and excitation energy transfer processes of sPCP and the thylakoid membranes, prepared from the photosynthetic dinoflagellate, Symbiodinium sp., are investigated by ultrafast time-resolved fluorescence spectroscopy. We found that Peri-to-Chl a energy transfer occurs via the Peri S 1 state with a time constant of 1.5 ps or 400 fs in sPCP or iPCP, respectively, and that Chl c-to-Chl a energy transfer occurs in the time regions of 350-400 fs and 1.8-2.6 ps.
Fracture characterisation of float glass under static and dynamic loading
Directory of Open Access Journals (Sweden)
A. Nyounguè
2016-12-01
Full Text Available This paper presents the study of float glass fracture under static and dynamic loading, with the use of experimental and numerical fracture mechanics methods. It has been shown that the value of notch fracture toughness under static loading depends neither on the kind of test nor on specimen geometry. This makes it possible to replace the three-points-bending specimens with the Brazilian discs which are, under certain test conditions, simpler and convenient to study. For both types of specimens, an analysis of the fracture strength, the notch stress intensity factor and fragmentation of specimens was carried out.
Energy Technology Data Exchange (ETDEWEB)
Praveen Kumar, E-mail: praveen@barc.gov.in [Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Jangid, R.S. [Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Reddy, G.R. [Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)
2013-05-15
Highlights: ► Piping system with semi-active variable stiffness damper is investigated under different seismic excitations. ► Switching control law and modified switching control law are adopted. ► There exist an optimum parameters of the SAVSD. ► Substantial reduction of the seismic response of piping system with SAVSD is observed. ► Good amount of energy dissipation is observed. -- Abstract: Seismic loads on piping system due to earthquakes can cause excessive vibrations, which can lead to serious instability resulting in damage or complete failure. In this paper, semi-active variable stiffness dampers (SAVSDs) have been studied to mitigate seismic response and vibration control of piping system used in the process industries, fossil and fissile fuel power plant. The SAVSD changes its stiffness depending upon the piping response and accordingly adds the control forces in the piping system. A study is conducted on the performance of SAVSD due to variation in device stiffness ratios in the switching control law and modified switching control law, which plays an important role in the present control algorithm of the damper. The effectiveness of the SAVSD in terms of reduction in the responses, namely, displacements, accelerations and base shear of the piping system is investigated by comparing uncontrolled responses under four different artificial earthquake motions with increasing amplitudes. The analytical results demonstrate that the SAVSDs under particular optimum parameters are very effective and practically implementable for the seismic response mitigation, vibration control and seismic requalification of piping systems.
Non-adiabatic dynamics of pyrrole: Dependence of deactivation mechanisms on the excitation energy
Czech Academy of Sciences Publication Activity Database
Barbatti, M.; Pittner, Jiří; Pederzoli, Marek; Werner, U.; Mitrić, R.; Bonačić-Koutecký, V.; Lischka, H.
2010-01-01
Roč. 375, č. 1 (2010), s. 26-34 ISSN 0301-0104 R&D Projects: GA AV ČR IAA400400810 Institutional research plan: CEZ:AV0Z40400503 Keywords : non-adiabatic dynamics * ultrafast phenomena * pyrrole Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.017, year: 2010
Temporal dynamics of motor cortex excitability during perception of natural emotional scenes
Borgomaneri, Sara; Gazzola, Valeria; Avenanti, Alessio
2014-01-01
Although it is widely assumed that emotions prime the body for action, the effects of visual perception of natural emotional scenes on the temporal dynamics of the human motor system have scarcely been investigated. Here, we used single-pulse transcranial magnetic stimulation (TMS) to assess motor
Effect of Isomerization on Excited-State Dynamics of Carotenoid Fucoxanthin
Czech Academy of Sciences Publication Activity Database
Kuznetsova, V.; Chábera, P.; Litvín, Radek; Polívka, Tomáš; Fuciman, M.
2017-01-01
Roč. 121, č. 17 (2017), s. 4438-4447 ISSN 1520-6106 Institutional support: RVO:60077344 Keywords : charge-transfer state * light-harvesting complex * pump-probe spectroscopy * ultrafast dynamics Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 3.177, year: 2016
Dynamic response of sliced rigid bodies subjected to harmonic base excitations
International Nuclear Information System (INIS)
Manos, G.C.; Demosthenous, M.
1993-01-01
The dynamic response of sliced rigid-block type bodies is investigated by subjecting a number of specimens to a variety of horizontal sinusoidal base motions as they are reproduced by the Earthquake Simulator of Aristotle University. The sliced specimens are either square prisms, cylinders or truncate cones and are assumed to represent models of prototype structures 20 times larger. (author)
Numerical studies of the membrane fluorescent dyes dynamics in ground and excited states
Czech Academy of Sciences Publication Activity Database
Barucha-Kraszewska, Justyna; Kraszewski, S.; Jurkiewicz, Piotr; Ramseyer, Ch.; Hof, Martin
2010-01-01
Roč. 1798, č. 9 (2010), s. 1724-1734 ISSN 0005-2736 R&D Projects: GA MŠk(CZ) LC06063; GA ČR GA203/08/0114 Institutional research plan: CEZ:AV0Z40400503 Keywords : molecular dynamics * fluorescent probe * membrane Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.647, year: 2010
International Nuclear Information System (INIS)
Singh, D.; Linda, Sneha Bharti; Giri, Pankaj K.; Singh, Smita Shree; Kumar, Harish; Afzal Ansari, M.; Ali, Rahbar; Rashid, M.H.; Guin, R.; Das, S.K.
2015-01-01
In the present work, an attempt has been made to address some important aspects of CF and ICF dynamics for the system 20 Ne + 59 Co in the projectile energy range ≈ 62–150 MeV by using recoil catcher activation technique with the following off-line γ-ray spectroscopy. Excitation Functions (EFs) for the following reactions: 59 Co(Ne, α p4n) 70 Ga, 59 Co(Ne, 3αp3n) 63 Zn, 59 Co (Ne, 3αp4n) 62 Zn and 59 Co (Ne, 4α3n) 60 Cu have been measured. No precursor decay contribution has been observed for these measured evaporation residues. The measured values of total fusion cross-sections of the above evaporation residues have been compared with the theoretical total complete fusion cross sections calculated by code PACE-2, which do not take into account ICF contribution
Excited-state dissociation dynamics of phenol studied by a new time-resolved technique
Lin, Yen-Cheng; Lee, Chin; Lee, Shih-Huang; Lee, Yin-Yu; Lee, Yuan T.; Tseng, Chien-Ming; Ni, Chi-Kung
2018-02-01
Phenol is an important model molecule for the theoretical and experimental investigation of dissociation in the multistate potential energy surfaces. Recent theoretical calculations [X. Xu et al., J. Am. Chem. Soc. 136, 16378 (2014)] suggest that the phenoxyl radical produced in both the X and A states from the O-H bond fission in phenol can contribute substantially to the slow component of photofragment translational energy distribution. However, current experimental techniques struggle to separate the contributions from different dissociation pathways. A new type of time-resolved pump-probe experiment is described that enables the selection of the products generated from a specific time window after molecules are excited by a pump laser pulse and can quantitatively characterize the translational energy distribution and branching ratio of each dissociation pathway. This method modifies conventional photofragment translational spectroscopy by reducing the acceptance angles of the detection region and changing the interaction region of the pump laser beam and the molecular beam along the molecular beam axis. The translational energy distributions and branching ratios of the phenoxyl radicals produced in the X, A, and B states from the photodissociation of phenol at 213 and 193 nm are reported. Unlike other techniques, this method has no interference from the undissociated hot molecules. It can ultimately become a standard pump-probe technique for the study of large molecule photodissociation in multistates.
A modeling study of dynamic characteristic analysis of isolated structure for seismic exciting tests
International Nuclear Information System (INIS)
Lee, Jae Han; Koo, G. H.; Yoo, Bong
1998-04-01
The fundamental frequency of the isolated superstructure for seismic exciting tests was calculated by 16 Hz with a initial modal analysis model. but the actual modal test resulted in 5 Hz. This large difference was resulted from some uncertainties in analysis modeling of several connection parts between column and upper beam, cross bars of each face of the isolated superstructure. When the stiffness of cross-bars are larger than certain level in all the analyses, the joint stiffness between main slab and columns does not effect to the fundamental frequency. So the fundamental frequency of the isolated superstructure was governed by the cross-bar's stiffness. In actual tests the first and second frequencies show a little difference regardless of the cross section characteristics (inertia moments) of four columns because the joint stiffness between column and main slab is less than 10 8 1b f in/radian. The mounting device of each column to main slab, and the bolting device of each column to upper beam are fabricated with lower stiffness compared to design value. The bolting of cross-bars and the fitness of bolt-hole to bolt were loosed during the modal tests. In the future the tight connecting and the precise assembling of isolated superstructure are required to reduce the difference of the fundamental frequencies obtained from the modal analysis and actual test. (author). 4 refs
Collective modes: Dynamical dipole excitation in dissipative heavy-ion reactions
Pierroutsakou, D.; Parascandolo, C.; Silvestri, R.; Agodi, C.; Alba, R.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Del Zoppo, A.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; Inglima, G.; La Commara, M.; Maiolino, C.; Martin, B.; Mazzocco, M.; Mazzocchi, C.; Molini, P.; Rizzo, C.; Romoli, M.; Sandoli, M.; Santonocito, D.; Signorini, C.; Soramel, F.; Trifirò, A.; Trimarchi, M.
2012-02-01
The existence of the dynamical dipole mode in the 192Pb composite system was investigated, through the study of its prompt γ decay, employing the 40Ca+152Sm and 48Ca+144Sm reactions at Elab=11 and 10.1 MeV/nucleon, respectively. The γ-rays and light charged particles were detected in coincidence with evaporation residues and fission fragments. First results of this experiment show that the dynamical dipole mode survives in collisions involving heavier mass reaction partners than those studied previously. As a fast cooling mechanism on the fusion path, the prompt dipole γ radiation could be of interest for the synthesis of super-heavy elements through "hot" fusion reactions. Furthermore, by using radioactive beams and the prompt γ radiation as a probe we could get information on the symmetry energy at sub-saturation densities.
Dynamic stability of a vertically excited non-linear continuous system
Czech Academy of Sciences Publication Activity Database
Náprstek, Jiří; Fischer, Cyril
2015-01-01
Roč. 155, July (2015), s. 106-114 ISSN 0045-7949 R&D Projects: GA ČR(CZ) GA15-01035S Institutional support: RVO:68378297 Keywords : non-linear systems * auto-parametric systems * semi-trivial solution * dynamic stability * system recovery * post- critical response Subject RIV: JM - Building Engineering Impact factor: 2.425, year: 2015 http://www.sciencedirect.com/science/article/pii/S0045794915000024
Energy Technology Data Exchange (ETDEWEB)
Butkus, Vytautas; Gelzinis, Andrius; Valkunas, Leonas [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania); Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius (Lithuania); Augulis, Ramūnas [Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius (Lithuania); Gall, Andrew; Robert, Bruno [Institut de Biologie et Technologies de Saclay, Bât 532, Commissariat à l’Energie Atomique Saclay, 91191 Gif sur Yvette (France); Büchel, Claudia [Institut für Molekulare Biowissenschaften, Universität Frankfurt, Max-von-Laue-Straße 9, Frankfurt (Germany); Zigmantas, Donatas [Department of Chemical Physics, Lund University, P.O. Box 124, 22100 Lund (Sweden); Abramavicius, Darius, E-mail: darius.abramavicius@ff.vu.lt [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania)
2015-06-07
Energy transfer processes and coherent phenomena in the fucoxanthin–chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of Q{sub y} transitions of chlorophylls a and c. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) a and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the Q{sub y} transition of Chl c revealed previously not identified, mutually non-interacting chlorophyll c states participating in femtosecond or picosecond energy transfer to the Chl a molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the vibrations-assisted coherent energy transfer between Chl c and Chl a and the overall spatial arrangement of chlorophyll molecules.
Excited state dynamics in nanoscale materials: time-domain ab initio studies
Prezhdo, Oleg
Photo-induced processes at interfaces are key to photovoltaic and photo-catalytic applications. They require understanding of dynamical response of novel materials on atomic and nanometer scales. Our non-adiabatic molecular dynamics techniques, implemented within time-dependent density functional theory, allow us to model such non-equilibrium response in real time. The talk will focus on photo-initiated charge and energy transfer in several classes of nanoscale materials. Examples include semiconductor surfaces sensitized with organic molecules, water, semiconductor quantum dots, graphene and perovskites, carbon nanotube bundles, mixtures of C60 with inorganic particles, etc. Photo-induced charge separation and recombination across such interfaces creates many challenges due to stark differences between molecular and periodic, and organic and inorganic systems. Our simulations provide a unifying description of quantum dynamics on nanoscale, characterize the rates and branching ratios of competing processes, resolve debated issues, and generate theoretical guidelines for development of novel systems for solar energy harvesting, electronics and other applications.
Coggan, Jay S.; Ocker, Gabriel K.; Sejnowski, Terrence J.; Prescott, Steven A.
2011-10-01
Neurons rely on action potentials, or spikes, to relay information. Pathological changes in spike generation likely contribute to certain enigmatic features of neurological disease, like paroxysmal attacks of pain and muscle spasm. Paroxysmal symptoms are characterized by abrupt onset and short duration, and are associated with abnormal spiking although the exact pathophysiology remains unclear. To help decipher the biophysical basis for 'paroxysmal' spiking, we replicated afterdischarge (i.e. continued spiking after a brief stimulus) in a minimal conductance-based axon model. We then applied nonlinear dynamical analysis to explain the dynamical basis for initiation and termination of afterdischarge. A perturbation could abruptly switch the system between two (quasi-)stable attractor states: rest and repetitive spiking. This bistability was a consequence of slow positive feedback mediated by persistent inward current. Initiation of afterdischarge was explained by activation of the persistent inward current forcing the system to cross a saddle point that separates the basins of attraction associated with each attractor. Termination of afterdischarge was explained by the attractor associated with repetitive spiking being destroyed. This occurred when ultra-slow negative feedback, such as intracellular sodium accumulation, caused the saddle point and stable limit cycle to collide; in that regard, the active attractor is not truly stable when the slowest dynamics are taken into account. The model also explains other features of paroxysmal symptoms, including temporal summation and refractoriness.
Thermomechanical behavior of EUV pellicle under dynamic exposure conditions
Goldfarb, Dario L.; Bloomfield, Max O.; Colburn, Matthew
2016-03-01
The utilization of EUV pellicles as protective layers for EUV masks requires the use of refractory materials that can tolerate large temperature excursions due to the non-negligible absorption of EUV radiation during exposure. Additionally, the mechanical stress induced on the EUV pellicle by the thermal load is dependent on the thermal expansion of the material which can be responsible for transient wrinkling. In this study, an ultrathin (20 nm), free-standing membrane based on silicon nitride is utilized as a learning vehicle to understand the material requirements of EUV pellicles under dynamic exposure conditions that are typical of commercial EUV scanners. First, the nanoscale radiative properties (emissivity) and thermo-mechanical failure temperature of the dielectric film under vacuum conditions are experimentally investigated utilizing a pulsed ArF (193 nm) probing laser. The silicon nitride membrane is found to be marginally compatible with an equivalent 80W EUV source power under steady state illumination conditions. Next, the thermal behavior of the EUV pellicle under dynamic exposure conditions is simulated using a finite element solver. The transient temperature profile and stress distribution across the membrane under stationary state conditions are extracted for an equivalent 60W EUV power source and the pellicle wrinkling due to heating and consequent impact on CD uniformity is estimated. The present work provides a generalized methodology to anticipate the thermal response of a EUV pellicle under realistic exposure conditions.
Energy Technology Data Exchange (ETDEWEB)
Xiao, Pan [LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); Kang, Zhitao; Summers, Christopher J. [Phosphor Technology Center of Excellence, Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, Georgia 30332-0826 (United States); Bansihev, Alexandr A.; Christensen, James M.; Dlott, Dana D. [School of Chemical Sciences and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Breidenich, Jennifer; Scripka, David A.; Thadhani, Naresh N. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Zhou, Min, E-mail: min.zhou@gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States)
2016-01-04
Laser-driven shock compression experiments and corresponding finite element method simulations are carried out to investigate the blueshift in the optical emission spectra under continuous laser excitation of a dilute composite consisting of 0.15% CdTe quantum dots by weight embedded in polyvinyl alcohol polymer. This material is a potential candidate for use as internal stress sensors. The analyses focus on the time histories of the wavelength blue-shift for shock loading with pressures up to 7.3 GPa. The combined measurements and calculations allow a relation between the wavelength blueshift and pressure for the loading conditions to be extracted. It is found that the blueshift first increases with pressure to a maximum and subsequently decreases with pressure. This trend is different from the monotonic increase of blueshift with pressure observed under conditions of quasistatic hydrostatic compression. Additionally, the blueshift in the shock experiments is much smaller than that in hydrostatic experiments at the same pressure levels. The differences in responses are attributed to the different stress states achieved in the shock and hydrostatic experiments and the time dependence of the mechanical response of the polymer in the composite. The findings offer a potential guide for the design and development of materials for internal stress sensors for shock conditions.
Xu, Xuhui; Zhang, Wenfei; Jin, Limin; Qiu, Jianbei; Yu, Siu Fung
2015-10-21
We report the observation of random lasing from Eu(3+) doped borate glass ceramic films embedded with Ag nanoparticles through three-photon absorption at room temperature. Under 1179 nm ultrashort femtosecond pulse excitation, discrete sharp peaks with linewidth ∼0.4 nm emerge randomly from a broad emission band with peak wavelength at ∼612 nm. In addition, the number of sharp peaks increases with the increase of excitation power. We also show that the emission spectrum varies with different observation angles and the corresponding lasing threshold is dependent on the excitation area. Hence, we verify unambiguously that the Eu(3+) doped borate glass ceramic film supports random lasing action via three-photon absorption excitation. In addition, Ag nanoparticles, which act as light scatterers, allow the formation of random microcavities inside the bulk film.
Wang, Jun; Huang, Jing; Du, Likai; Lan, Zhenggang
2015-07-09
The photoinduced intramolecular excited-state energy-transfer (EET) process in conjugated polymers has received a great deal of research interest because of its important role in the light harvesting and energy transport of organic photovoltaic materials in photoelectric devices. In this work, the silylene-bridged biphenyl and stilbene (SBS) system was chosen as a simplified model system to obtain physical insight into the photoinduced intramolecular energy transfer between the different building units of the SBS copolymer. In the SBS system, the vinylbiphenyl and vinylstilbene moieties serve as the donor (D) unit and the acceptor (A) unit, respectively. The ultrafast excited-state dynamics of the SBS system was investigated from the point of view of nonadiabatic dynamics with the surface-hopping method at the TDDFT level. The first two excited states (S1 and S2) are characterized by local excitations at the acceptor (vinylstilbene) and donor (vinylbiphenyl) units, respectively. Ultrafast S2-S1 decay is responsible for the intramolecular D-A excitonic energy transfer. The geometric distortion of the D moiety play an essential role in this EET process, whereas the A moiety remains unchanged during the nonadiabatic dynamics simulation. The present work provides a direct dynamical approach to understand the ultrafast intramolecular energy-transfer dynamics in SBS copolymers and other similar organic photovoltaic copolymers.
Armengol, Pau; Gelabert, Ricard; Moreno, Miquel; Lluch, José M
2015-02-12
Green fluorescent protein variant S65T/H148D has been reported to host a photocycle involving the photoinduced proton transfer reaction between the chromophore and residue Asp148 under 50 fs and without a measurable kinetic isotope effect, and experimental evidence is suggestive of the existence of a highly delocalized proton between these residues. The blinding speed at which this biological system undergoes proton transfer has been ascribed to the extreme increase of acidity of the GFP chromophore in the electronic excited state where proton transfer takes place. This work strives to present a coherent, complete, and balanced description of the dynamics of this specific variant of GFP in which it will be shown that this increase of acidity is insufficient to explain the behavior observed. This study tracks the behavior of this photosystem to the delicate interplay between structure and dynamics shown in the presence of solvent. In this way, it has been found that the dynamics of this protein intertwines its structure with the intervening solvent to give rise to effectively degenerate situations in what concerns the reactants and products of the proton transfer reaction in ground and, most importantly, photoexcited state, in terms of potential energy profiles associated with the proton migration. Under these conditions, proton transfer can occur in accordance with the experimental data available. This set of characteristics is possibly common to a host of other proton transfer based fluorescent proteins, and helps promoting GFP S65T/H148D to a case of archetypal significance. Thus, our results can be useful to understand the way many fluorescent proteins work and, more generally, the molecular basis for proton transfer reactions in proteins.
Jaris, M.; Yahagi, Y.; Mahato, B. K.; Dhuey, S.; Cabrini, S.; Nikitin, V.; Stout, J.; Hawkins, A. R.; Schmidt, H.
2016-11-01
We report the all-optical observation of intrinsic spin dynamics and extraction of magnetic material parameters from arrays of sub-100 nm spin-transfer torque magnetic random access memory (STT-MRAM) devices with a CoFeB/MgO interface. To this end, the interference of surface acoustic waves with time-resolved magneto-optic signals via magneto-elastic coupling was suppressed using a dielectric coating. The efficacy of this method is demonstrated experimentally and via modeling on a nickel nanomagnet array. The magnetization dynamics for both coated nickel and STT-MRAM arrays shows a restored field-dependent Kittel mode from which the effective damping can be extracted. We observe an increased low-field damping due to extrinsic contributions from magnetic inhomogeneities and variations in the nanomagnet shape, while the intrinsic Gilbert damping remains unaffected by patterning. The data are in excellent agreement with a local resonance model and have direct implications for the design of STT-MRAM devices as well as other nanoscale spintronic technologies.
Dynamic Pricing Competition with Strategic Customers Under Vertical Product Differentiation
Qian Liu; Dan Zhang
2013-01-01
We consider dynamic pricing competition between two firms offering vertically differentiated products to strategic customers who are intertemporal utility maximizers. We show that price skimming arises as the unique pure-strategy Markov perfect equilibrium in the game under a simple condition. Our results highlight the asymmetric effect of strategic customer behavior on quality-differentiated firms. Even though the profit of either firm decreases as customers become more strategic, the low-qu...
Dynamics and stability of electron plasma vortices under external strain
Hurst, N. C.; Danielson, J. R.; Dubin, D. H. E.; Surko, C. M.
2017-10-01
The behavior of an initially axisymmetric 2D ideal vortex under an externally imposed strain flow is studied experimentally. The experiments are carried out using pure electron plasmas confined in a Penning-Malmberg trap; here, the dynamics of the plasma density transverse to the field are directly analogous to the dynamics of vorticity in a 2D ideal fluid. An external strain flow is applied using boundary conditions in a way that is consistent with 2D fluid dynamics. Primarily, elliptical distortions of the vortex core are studied, including dynamical orbits, equilibria, and stability properties. In the case of a quasi-flat vorticity profile, the results are in good agreement with a simple theory of a piecewise elliptical vorticity distribution. For smooth vorticity profiles, deviations from this theory are discussed. Results for time-dependent strain and tests of adiabatic behavior will also be discussed. These experiments may be relevant to many types of quasi-2D fluid behavior, including the dynamics of geophysical fluids, other types of strongly magnetized plasma, and various astrophysical scenarios. This work supported by NSF Grant PHY-1414570 and DOE Grants DE-SC0002451 and DE-SC0016532.
Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu
2015-11-03
Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications.
International Nuclear Information System (INIS)
Geiger, L.C.
1985-01-01
This dissertation is a collection of four projects in theoretical chemical dynamics. In the first two projects collisional excitation in H + CO was studied using the quasiclassical trajectory method and the quantum infinite order sudden approximation (QIOS). Integral cross sections calculated using these methods were found to agree well with experimental and classical IOS results. The trajectory study was also used to examine the effects of potential energy surface features on the dynamics. Two surfaces were examined: a fitted surface based on ab initio points and a global ab initio surface. Next, the quasiclassical trajectory method was used to obtain cross sections and rate constants for O + H 2 → OH + H and analogous deuterium isotope reactions. The results using the Johnson and Winter surface agreed well with those of transition state theory (TST) and experiment, except for O + HD → OH + D. TST rate constants were calculated using an ab initio surface. These results were in poor agreement with calculations using the Johnson and Winter surface. A theory of action-angle variables for coupled oscillator systems was developed in the fourth project
Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu
2015-01-01
Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications. PMID:26525841
A novel test rig to investigate under-platform damper dynamics
Botto, Daniele; Umer, Muhammad
2018-02-01
In the field of turbomachinery, vibration amplitude is often reduced by dissipating the kinetic energy of the blades with devices that utilize dry friction. Under-platform dampers, for example, are often placed in the underside of two consecutive turbine blades. Dampers are kept in contact with the under-platform of the respective blades by means of the centrifugal force. If the damper is well designed, vibration of blades instigate a relative motion between the under-platform and the damper. A friction force, that is a non-conservative force, arises in the contact and partly dissipates the vibration energy. Several contact models are available in the literature to simulate the contact between the damper and the under-platform. However, the actual dynamics of the blade-damper interaction have not fully understood yet. Several test rigs have been previously developed to experimentally investigate the performance of under-platform dampers. The majority of these experimental setups aim to evaluate the overall damper efficiency in terms of reduction in response amplitude of the blade for a given exciting force that simulates the aerodynamic loads. Unfortunately, the experimental data acquired on the blade dynamics do not provide enough information to understand the damper dynamics. Therefore, the uncertainty on the damper behavior remains a big issue. In this work, a novel experimental test rig has been developed to extensively investigate the damper dynamic behavior. A single replaceable blade is clamped in the rig with a specific clamping device. With this device the blade root is pressed against a groove machined in the test rig. The pushing force is controllable and measurable, to better simulate the actual centrifugal load acting on the blade. Two dampers, one on each side of the blade, are in contact with the blade under-platforms and with platforms on force measuring supports. These supports have been specifically designed to measure the contact forces on the
Excited-State Dynamics of Isolated and Microsolvated Cinnamate-Based UV-B Sunscreens
Tan, E.M.M.; Hilbers, M.; Buma, W.J.
2014-01-01
Sunscreens are aimed at providing protection from solar UV radiation. However, the same mechanism that underlies this protection (absorption of UV radiation) is also responsible for their light-induced adverse effects. Here, high-resolution spectroscopic methods are applied to one of the most
Dynamics of a prey-predator system under Poisson white noise excitation
Pan, Shan-Shan; Zhu, Wei-Qiu
2014-10-01
The classical Lotka-Volterra (LV) model is a well-known mathematical model for prey-predator ecosystems. In the present paper, the pulse-type version of stochastic LV model, in which the effect of a random natural environment has been modeled as Poisson white noise, is investigated by using the stochastic averaging method. The averaged generalized Itô stochastic differential equation and Fokker-Planck-Kolmogorov (FPK) equation are derived for prey-predator ecosystem driven by Poisson white noise. Approximate stationary solution for the averaged generalized FPK equation is obtained by using the perturbation method. The effect of prey self-competition parameter ɛ2 s on ecosystem behavior is evaluated. The analytical result is confirmed by corresponding Monte Carlo (MC) simulation.
Impact of Ada in the Flight Dynamics Division: Excitement and frustration
Bailey, John; Waligora, Sharon; Stark, Mike
1993-01-01
In 1985, NASA Goddard's Flight Dynamics Division (FDD) began investigating how the Ada language might apply to their software development projects. Although they began cautiously using Ada on only a few pilot projects, they expected that, if the Ada pilots showed promising results, they would fully transition their entire development organization from FORTRAN to Ada within 10 years. However, nearly 9 years later, the FDD still produces 80 percent of its software in FORTRAN, despite positive results on Ada projects. This paper reports preliminary results of an ongoing study, commissioned by the FDD, to quantify the impact of Ada in the FDD, to determine why Ada has not flourished, and to recommend future directions regarding Ada. Project trends in both languages are examined as are external factors and cultural issues that affected the infusion of this technology. This paper is the first public report on the Ada assessment study, which will conclude with a comprehensive final report in mid 1994.
Modal analysis and dynamic stresses for acoustically excited Shuttle insulation tiles
Ojalvo, I. U.; Ogilvie, P. I.
1976-01-01
The thermal protection system of the Space Shuttle consists of thousands of separate insulation tiles, of varying thicknesses, bonded to the orbiter's surface through a soft strain-isolation pad which is bonded, in turn, to the vehicle's stiffened metallic skin. A modal procedure for obtaining the acoustically induced RMS stress in these comparatively thick tiles is described. The modes employed are generated by a previously developed iterative procedure which converges rapidly for the combined system of tiles and primary structure considered. Each tile is idealized by several hundred three-dimensional finite elements and all tiles on a given panel interact dynamically. Acoustic response results from the present analyses are presented. Comparisons with other analytical results and measured modal data for a typical Shuttle panel, both with and without tiles, are made, and the agreement is good.
Dynamical study of triangle excitation with N(e,e'π) reaction
International Nuclear Information System (INIS)
The authors report on the results from their investigation of pion electroproduction based on the dynamical model developed in the SL Model. The essential point of SL model is to have a consistent description of the πN scattering and γN → πN transition. This is important in extracting the γN → Δ form factors since it was found that the nonresonant mechanisms and the final πN interaction can account for about 40% of the M1 strength at Q 2 = 0. The details have been discussed and the talk given by T. Sato in this conference. Here they only present their results for the γN → Δ form factors
Park, Hyo Seon; Oh, Byung Kwan
2018-03-01
This paper presents a new approach for the damage detection of building structures under ambient excitation based on the inherent modal characteristics. In this study, without the extraction of modal parameters widely utilized in the previous studies on damage detection, a new index called the modal participation ratio (MPR), which is a representative value of the modal response extracted from dynamic responses measured in ambient vibration tests, is proposed to evaluate the change of the system of a structure according to the reduction of the story stiffness. The relationship between the MPR, representing a modal contribution for a specific mode and degree of freedom in buildings, and the story stiffness damage factor (SSDF), representing the extent of reduction in the story stiffness, is analyzed in various damage scenarios. From the analyses with three examples, several rules for the damage localization of building structures are found based on the characteristics of the MPR variation for the first mode subject to change in the SSDF. In addition, a damage severity function, derived from the relationship between the MPR for the first mode in the lowest story and the SSDF, is constructed to identify the severity of story stiffness reduction. Furthermore, the locations and severities of multiple damages are identified via the superposition of the presented damage severity functions. The presented method was applied to detect damage in a three-dimensional reinforced concrete (RC) structure.
Luminescent properties of (Y,Gd)BO3:Bi3+,RE3+ (RE=Eu, Tb) phosphor under VUV/UV excitation
International Nuclear Information System (INIS)
Zeng Xiaoqing; Im, Seoung-Jae; Jang, Sang-Hun; Kim, Young-Mo; Park, Hyoung-Bin; Son, Seung-Hyun; Hatanaka, Hidekazu; Kim, Gi-Young; Kim, Seul-Gi
2006-01-01
Bi 3+ - and RE 3+ -co-doped (Y,Gd)BO 3 phosphors were prepared and their luminescent properties under vacuum ultraviolet (VUV)/UV excitation were investigated. Strong red emission for (Y,Gd)BO 3 :Bi 3+ ,Eu 3+ and strong green emission for (Y,Gd)BO 3 :Bi 3+ ,Tb 3+ are observed under VUV excitation from 147 to 200 nm with a much broader excitation region than that of single Eu 3+ -doped or Tb 3+ -doped (Y,Gd)BO 3 phosphor. Strong emissions are also observed under UV excitation around 265 nm where as nearly no luminescence is observed for single Eu 3+ -doped or Tb 3+ -doped (Y,Gd)BO 3 . The luminescence enhancement of Bi 3+ - and RE 3+ -co-doped (Y,Gd)BO 3 phosphors is due to energy transfer from Bi 3+ ion to Eu 3+ or Tb 3+ ion not only in the VUV region but also in the UV region. Besides, host sensitization competition between Bi 3+ and Eu 3+ or Tb 3+ is also observed. The investigated phosphors may be preferable for devices with a VUV light 147-200 nm as an excitation source such as PDP or mercury-free fluorescent lamp
Nonlinear friction dynamics on polymer surface under accelerated movement
Directory of Open Access Journals (Sweden)
Yuuki Aita
2017-04-01
Full Text Available Nonlinear phenomena on the soft material surface are one of the most exciting topics of chemical physics. However, only a few reports exist on the friction phenomena under accelerated movement, because friction between two solid surfaces is considered a linear phenomenon in many cases. We aim to investigate how nonlinear accelerated motion affects friction on solid surfaces. In the present study, we evaluate the frictional forces between two polytetrafluoroethylene (PTFE resins using an advanced friction evaluation system. On PTFE surfaces, the normalized delay time δ, which is the time lag in the response of the friction force to the accelerated movement, is observed in the pre-sliding friction process. Under high-velocity conditions, kinetic friction increases with velocity. Based on these experimental results, we propose a two-phase nonlinear model including a pre-sliding process (from the beginning of sliding of a contact probe to the establishment of static friction and a kinetic friction process. The present model consists of several factors including velocity, acceleration, stiffness, viscosity, and vertical force. The findings reflecting the viscoelastic properties of soft material is useful for various fields such as in the fabrication of clothes, cosmetics, automotive materials, and virtual reality systems as well as for understanding friction phenomena on soft material surfaces.
Managheb, S. A. M.; Ziaei-Rad, S.; Tikani, R.
2018-05-01
The coupling between polarization and strain gradients is called flexoelectricity. This phenomenon exists in all dielectrics with any symmetry. In this paper, energy harvesting from a Timoshenko beam is studied by considering the flexoelectric and strain gradient effects. General governing equations and related boundary conditions are derived using Hamilton's principle. The flexoelectric effects are defined by gradients of normal and shear strains which lead to a more general model. The developed model also covers the classical Timoshenko beam theory by ignoring the flexoelectric effect. Based on the developed model, flexoelectricity effect on dielectric beams and energy harvesting from cantilever beam under harmonic base excitation is investigated. A parametric study was conducted to evaluate the effects of flexoelectric coefficients, strain gradient constants, base acceleration and the attaching tip mass on the energy harvested from a cantilever Timoshenko beam. Results show that the flexoelectricity has a significant effect on the energy harvester performance, especially in submicron and nano scales. In addition, this effect makes the beam to behave softer than before and also it changes the harvester first resonance frequency. The present study provides guidance for flexoelectric nano-beam analysis and a method to evaluate the performance of energy harvester in nano-dielectric devices.
Chen, Yong; Chen, Guohua; Liu, Xiangyu; Yuan, Changlai; Zhou, Changrong
2017-11-01
Tm3+/Dy3+ co-doped phosphate glasses for white light-emitting diodes were synthesized by a conventional melting-quenching method. A spectroscopic research based on optical, photoluminescence spectrum and decay time curves in Tm3+/Dy3+ co-doped phosphate glasses was carried out. The color of luminescence could be tuned by altering the concentrations of Tm3+ ions. Under UV light excitation, the CIE chromaticity coordinates (0.3471, 0.3374) and color correlate temperature (CCT = 4866.21 K) close to the standard white-light illumination (0.333, 0.333 and CCT = 5454.12 K) could be achieved in 0.4 Tm3+/0.6 Dy3+ (mol %) co-doped glass sample. The decrease of the Dy3+ emission decay time in existence of Tm3+ ascertained that non-radiative energy transfer from Dy3+ to Tm3+ occurred. Moreover, the research of energy transfers between Dy3+ and Tm3+ based on the Inokuti-Hirayama model revealed that an electric quadrupole-quadrupole interaction might be the predominant mechanism participated in the energy transfer. This finding suggests that the as-prepared Tm3+/Dy3+ co-doped phosphate glasses may be promising candidate for white LEDs and other display devices.
Luminescent properties under X-ray excitation of Ba(1-x)PbxWO4 disordered solid solution
Bakiz, B.; Hallaoui, A.; Taoufyq, A.; Benlhachemi, A.; Guinneton, F.; Villain, S.; Ezahri, M.; Valmalette, J.-C.; Arab, M.; Gavarri, J.-R.
2018-02-01
A series of polycrystalline barium-lead tungstate Ba1-xPbxWO4 with 0 ≤ x ≤ 1 was synthesized using a classical solid-state method with thermal treatment at 1000 °C. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Raman (FT-Raman) spectroscopy. X-ray diffraction profile analyses were performed using Rietveld method. These materials crystallized in the scheelite tetragonal structure and behaved as quasi ideal solid solution. Raman spectroscopy confirmed the formation of the solid solution. Structural distortions were evidenced in X-ray diffraction profiles and in vibration Raman spectra. The scanning electron microscopy experiments showed large and rounded irregular grains. Luminescence experiments were performed under X-ray excitation. The luminescence emission profiles have been interpreted in terms of four Gaussian components, with a major contribution of blue emission. The integrated intensity of luminescence reached a maximum value in the composition range x = 0.3-0.6, in relation with distortions of crystal lattice.
MAVRI, J; BERENDSEN, HJC
1995-01-01
The methodology for treatment of proton transfer processes by density matrix evolution (DME) with inclusion of many excited states is presented. The DME method (Berendsen, H. J. C.; Mavri, J. J. Phys. Chem. 1993, 97, 13464) that simulates the dynamics of quantum systems embedded in a classical
Optical techniques for probing the excited state dynamics of quantum dot solids
International Nuclear Information System (INIS)
Moroz, P.; Kholmicheva, N.; Razgoniaeva, N.; Burchfield, D.; Sharma, N.; Acharya, A.; Zamkov, M.
2016-01-01
Highlights: • Optical techniques represent a powerful tool for probing exciton diffusion in QD solids. • Exciton dissociation in QD solids is caused by charge tunneling to traps and other dots. • Exciton and free-carrier lifetimes are given by fast and slow components of PL decay. • Surface PL offers valuable information on the type and density of traps in QD solids. - Abstract: Quantum dot (QD) solids represent an important class of functional materials that holds strong promise for future applications in technology. Their optoelectronic properties are determined by energy diffusion processes, which character can often be inferred from the temporal and spectral analysis of the film’s photoluminescence (PL). Here, optical techniques based on PL lifetime, bulk quenching, and temperature-dependent PL will be discussed. These techniques complement the electrical conductivity measurements by mapping the flow of optically induced excitons through undepleted, contact-free films with an unprecedented temporal and spatial resolution. By correlating the QD solid morphology with the ensuing photoluminescence (PL) dynamics, these methods allow estimating important transport characteristics, including exciton and charge carrier diffusion lengths, the rate of interparticle energy transfer, carrier mobility, and the exciton diffusivity. The review will cover most popular PL-based strategies and summarize the key experimental findings resulting from these works.
Fission dynamics of excited nuclei within the liquid-drop model
Radionov, S V; Kolomietz, V M; Magner, A G
2002-01-01
The temperature T sub s sub c sub i sub s at the scission point and the saddle-to-scission time tau sub s sub c sub i sub s for the fission of heated nuclei is evaluated. The classical Lagrange-like equations of motion within the liquid-drop model are used. The nuclear surface is parametrized by the two-parametric family of the Lawrence shapes. Conservative forces are defined through the free energy of the nucleus at finite temperatures. The friction tensor derived from the Navier-Stokes momentum flux tensor taking into account the boundary conditions on the nuclear surface is used. The scission line is determined from the instability condition of the nuclear shape with respect to the variations of the neck radius. The numerical solution of the dynamical equations is performed for the nucleus sup 2 sup 3 sup 6 U. The viscosity coefficient mu was obtained from the comparison of the experimental data for the kinetic energy for the fission fragments with the computed one. A significant deviation of mu, obtained ...
Stochastic Dynamics of a Time-Delayed Ecosystem Driven by Poisson White Noise Excitation
Directory of Open Access Journals (Sweden)
Wantao Jia
2018-02-01
Full Text Available We investigate the stochastic dynamics of a prey-predator type ecosystem with time delay and the discrete random environmental fluctuations. In this model, the delay effect is represented by a time delay parameter and the effect of the environmental randomness is modeled as Poisson white noise. The stochastic averaging method and the perturbation method are applied to calculate the approximate stationary probability density functions for both predator and prey populations. The influences of system parameters and the Poisson white noises are investigated in detail based on the approximate stationary probability density functions. It is found that, increasing time delay parameter as well as the mean arrival rate and the variance of the amplitude of the Poisson white noise will enhance the fluctuations of the prey and predator population. While the larger value of self-competition parameter will reduce the fluctuation of the system. Furthermore, the results from Monte Carlo simulation are also obtained to show the effectiveness of the results from averaging method.
Detection of Damage in a Lattice Mast Excited by Wind by Dynamic Measurements
DEFF Research Database (Denmark)
Pedersen, Lars; Brincker, Rune
2007-01-01
under ambient loading conditions. The paper presents the instrumentation and considerations regarding layout of instrumentation and strategies for acquisition and processing of data. Damage in the mast is provoked using a hacksaw and the cross sectional area of one the diagonals of the mast (one located...... are identified. By studying the recorded variations it seems reasonable to conclude that by implementing a vibration monitoring system on the mast it would be possible to reliably detect a damage corresponding to less than a 50% loss of cross sectional area of the diagonal. This would allow for issue...
Dynamic response of multiple nanobeam system under a moving nanoparticle
Directory of Open Access Journals (Sweden)
Shahrokh Hosseini Hashemi
2018-03-01
Full Text Available In this article, nonlocal continuum based model of multiple nanobeam system (MNBS under a moving nanoparticle is investigated using Eringen’s nonlocal theory. Beam layers are assumed to be coupled by winkler elastic medium and the nonlocal Euler-Bernoulli beam theory is used to model each layer of beam. The Hamilton’s principle, Eigen function technique and the Laplace transform method are employed to solve the governing equations. Analytical solutions of the transverse displacements for MNBs with simply supported boundary condition are presented for double layered and three layered MNBSs. For higher number of layers, the governing set of equations is solved numerically and the results are presented. This study shows that small-scale parameter has a significant effect on dynamic response of MNBS under a moving nanoparticle. Sensitivity of dynamical deflection to variation of nonlocal parameter, stiffness of Winkler elastic medium and number of nanobeams are presented in nondimensional form for each layer. Keywords: Dynamic response, Analytical solution, Moving particle, Nanobeam, Multi-layered nanobeam
Effect of support conditions on structural response under dynamic loading
International Nuclear Information System (INIS)
Akram, T.; Memon, S.A.
2008-01-01
In design practice, dynamic structural analysis is carried out with base of structure considered as fixed; this means that foundation is placed on rock like soil material. While conducting this type of analyses the role of foundation and soil behaviour is totally neglected. The actions in members and loads transferred at foundation level obtained in this manner do not depict the true structural behaviour. FEM (Finite Element Methods) analysis where both superstructure and foundation soil are coupled together is quite complicated and expensive for design environments. A simplified model is required to depict dynamic response of structures with foundations based on flexible soils. The primary purpose of this research is to compare the superstructure dynamic responses of structural systems with fixed base to that of simple soil model base. The selected simple soil model is to be suitable for use in a design environment to give more realistic results. For this purpose building models are idealized with various heights and structural systems in both 2D (Two Dimensional) and 3D (Three Dimensional) space. These models are then provided with visco-elastic supports representing three soil bearing capacities and the analysis results are compared to that of fixed supports models. The results indicate that fixed support system underestimates natural time period of the structures. Dynamic behavior and force response of visco-elastic support is different from fixed support model. Fixed support models result in over designed base columns and under designed beams. (author)
Predicting Dynamic Response of Structures under Earthquake Loads Using Logical Analysis of Data
Directory of Open Access Journals (Sweden)
Ayman Abd-Elhamed
2018-04-01
Full Text Available In this paper, logical analysis of data (LAD is used to predict the seismic response of building structures employing the captured dynamic responses. In order to prepare the data, computational simulations using a single degree of freedom (SDOF building model under different ground motion records are carried out. The selected excitation records are real and of different peak ground accelerations (PGA. The sensitivity of the seismic response in terms of displacements of floors to the variation in earthquake characteristics, such as soil class, characteristic period, and time step of records, peak ground displacement, and peak ground velocity, have also been considered. The dynamic equation of motion describing the building model and the applied earthquake load are presented and solved incrementally using the Runge-Kutta method. LAD then finds the characteristic patterns which lead to forecast the seismic response of building structures. The accuracy of LAD is compared to that of an artificial neural network (ANN, since the latter is the most known machine learning technique. Based on the conducted study, the proposed LAD model has been proven to be an efficient technique to learn, simulate, and blindly predict the dynamic response behaviour of building structures subjected to earthquake loads.
Interaction-based transition from passivity to excitability
Petrov, V. S.; Osipov, G. V.
2014-09-01
In this paper we study the process of transition from passive to excitable behavior due to interaction between nonlinear dynamical systems. We show that under certain conditions a passive unit may demonstrate qualitatively new excitable dynamics. We study the properties of an excitable medium constructed on the basis of the proposed transition. The effects are demonstrated with the realistic Luo-Rudy model. Application to the cardiac dynamics and functioning is discussed. The qualitative analytic and numerical description is also given for the phenomenological FitzHugh-Nagumo system.
Display of high dynamic range images under varying viewing conditions
Borer, Tim
2017-09-01
Recent demonstrations of high dynamic range (HDR) television have shown that superb images are possible. With the emergence of an HDR television production standard (ITU-R Recommendation BT.2100) last year, HDR television production is poised to take off. However research to date has focused principally on HDR image display only under "dark" viewing conditions. HDR television will need to be displayed at varying brightness and under varying illumination (for example to view sport in daytime or on mobile devices). We know, from common practice with conventional TV, that the rendering intent (gamma) should change under brighter conditions, although this is poorly quantified. For HDR the need to render images under varying conditions is all the more acute. This paper seeks to explore the issues surrounding image display under varying conditions. It also describes how visual adaptation is affected by display brightness, surround illumination, screen size and viewing distance. Existing experimental results are presented and extended to try to quantify these effects. Using the experimental results it is described how HDR images may be displayed so that they are perceptually equivalent under different viewing conditions. A new interpretation of the experimental results is reported, yielding a new, luminance invariant model for the appropriate display "gamma". In this way the consistency of HDR image reproduction should be improved, thereby better maintaining "creative intent" in television.
Strong-field dissociation dynamics of NO2+: A multiphoton electronic or vibrational excitation?
Jochim, Bethany; Zohrabi, M.; Ablikim, U.; Gaire, B.; Anis, F.; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.; Wells, E.; Uhlíková, T.
2013-05-01
We utilize a 3-D momentum imaging technique to study laser-induced dissociation of a metastable NO2+ beam into N++ O+. Using an estimated initial vibrational population, measured kinetic energy release and angular distribution spectra, and time-dependent Schrödinger equation calculations, we identify the most likely dissociation pathways. While lower intensity pulses (process underlying this highly-aligned feature is a multiphoton permanent dipole transition solely within the electronic ground state, leading to its continuum. Supported by the DOE Chemical Sciences, Geosciences, and Biosciences Division, Office of Science. BJ also by NSF (PHY-0851599) and DOE SCGF (DE-AC05-06OR23100), BJ and EW by NSF (PHY-0969687), and TU by GACR and MetaCentrum.
Modeling the Underlying Dynamics of the Spread of Crime
McMillon, David; Simon, Carl P.; Morenoff, Jeffrey
2014-01-01
The spread of crime is a complex, dynamic process that calls for a systems level approach. Here, we build and analyze a series of dynamical systems models of the spread of crime, imprisonment and recidivism, using only abstract transition parameters. To find the general patterns among these parameters—patterns that are independent of the underlying particulars—we compute analytic expressions for the equilibria and for the tipping points between high-crime and low-crime equilibria in these models. We use these expressions to examine, in particular, the effects of longer prison terms and of increased incarceration rates on the prevalence of crime, with a follow-up analysis on the effects of a Three-Strike Policy. PMID:24694545
Numerical solution of dynamic equilibrium models under Poisson uncertainty
DEFF Research Database (Denmark)
Posch, Olaf; Trimborn, Timo
2013-01-01
We propose a simple and powerful numerical algorithm to compute the transition process in continuous-time dynamic equilibrium models with rare events. In this paper we transform the dynamic system of stochastic differential equations into a system of functional differential equations...... of the retarded type. We apply the Waveform Relaxation algorithm, i.e., we provide a guess of the policy function and solve the resulting system of (deterministic) ordinary differential equations by standard techniques. For parametric restrictions, analytical solutions to the stochastic growth model and a novel...... solution to Lucas' endogenous growth model under Poisson uncertainty are used to compute the exact numerical error. We show how (potential) catastrophic events such as rare natural disasters substantially affect the economic decisions of households....
DYNAMIC HYBRIDS UNDER SOLVENCY II: RISK ANALYSIS AND MODIFICATION POSSIBILITIES
Directory of Open Access Journals (Sweden)
Christian Maier
2017-06-01
Full Text Available In this study, we investigate the new and standardized European system of supervisory called Solvency II. In essence, asymmetric distribution of information between policyholder and insurer triggered this new regulation which aims at better protecting policyholders. Its three-pillar model is about to challenge both, insurers as well as policyholders. The first pillar includes quantitative aspects, the second pillar contains qualitative aspects and the third pillar comprises market transparency and reporting obligations. Underwriting risks, the default risk of a bank and market risks can be identified for the dynamic hybrid. Solvency II covers all these risks in the first pillar and insurers shall deposit sufficient risk-bearing capital. In our analysis, we first identify the dynamic hybrid specific risks under the Solvency II regime und then develop product modifications to reduce this risk.
Aerobic storage under dynamic conditions in activated sludge processes
DEFF Research Database (Denmark)
Majone, M.; Dircks, K.
1999-01-01
In activated sludge processes, several plant configurations (like plug-flow configuration of the aeration tanks, systems with selectors, contact-stabilization processes or SBR processes) impose a concentration gradient of the carbon sources to the biomass. As a consequence, the biomass grows under...... mechanisms can also contribute to substrate removal, depending on the microbial composition and the previous "history" of the biomass. In this paper the type and the extent of this dynamic response is discussed by review of experimental studies on pure cultures, mixed cultures and activated sludges...... and with main reference to its relevance on population dynamics in the activated sludge. Possible conceptual approaches to storage modelling are also presented, including both structured and unstructured modelling. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved....
Biologically Driven Differences in Decomposition Dynamics Under Changing Ecosystems (Invited)
Grandy, S.
2010-12-01
Predicting the effects of environmental changes on soil organic matter dynamics remains difficult. Here I explore the possibility that differences in decomposition and soil organic matter dynamics are due in part to links between litter decomposition processes, changes in litter chemistry, and variation in decomposer communities. I explored these relationships under three types of ecosystem changes: 1) N enrichment of forest ecosystems; 2) elevated atmospheric carbon dioxide concentrations in forest ecosystems; and 3) agricultural land-use intensification. My overarching hypothesis was that litter mass loss and litter chemistry would vary under different environmental conditions, and those differences would correlate with ecosystem-specific variations in decomposer community structure and function. In three separate field experiments, I found strong evidence that decomposer communities influenced the chemistry of decomposing litter. In a related laboratory study I found that the presence of the oribatid mite Scheloribates moestus Banks (Acari: Oribatida) can substantially change litter decomposition dynamics and the molecular chemistry of decomposing litter. Most current conceptual models estimate changes in litter chemistry over the course of decomposition from initial litter chemistry and the extent of mass loss. These models suggest consistent and predictable changes in the chemical structure of organic matter during decomposition and do not explicitly consider the potential effects of variations in decomposer community structure on decomposition. In contrast, my results show that differences in decomposer communities lead to changes in litter chemistry during decomposition. Accurately predicting management effects on litter chemistry. and thus also soil organic matter dynamics, through time may require accounting for the degree to which variations in decomposer community composition influence organic matter chemistry.
Cracks dynamics under tensional stress - a DEM approach
Debski, Wojciech; Klejment, Piotr; Kosmala, Alicja; Foltyn, Natalia; Szpindler, Maciej
2017-04-01
Breaking and fragmentation of solid materials is an extremely complex process involving scales ranging from an atomic scale (breaking inter-atomic bounds) up to thousands of kilometers in case of catastrophic earthquakes (in energy scale it ranges from single eV up to 1024 J). Such a large scale span of breaking processes opens lot of questions like, for example, scaling of breaking processes, existence of factors controlling final size of broken area, existence of precursors, dynamics of fragmentation, to name a few. The classical approach to study breaking process at seismological scales, i.e., physical processes in earthquake foci, is essentially based on two factors: seismic data (mostly) and the continuum mechanics (including the linear fracture mechanics). Such approach has been gratefully successful in developing kinematic (first) and dynamic (recently) models of seismic rupture and explaining many of earthquake features observed all around the globe. However, such approach will sooner or latter face a limitation due to a limited information content of seismic data and inherit limitations of the fracture mechanics principles. A way of avoiding this expected limitation is turning an attention towards a well established in physics method of computational simulations - a powerful branch of contemporary physics. In this presentation we discuss preliminary results of analysis of fracturing dynamics under external tensional forces using the Discrete Element Method approach. We demonstrate that even under a very simplified tensional conditions, the fragmentation dynamics is a very complex process, including multi-fracturing, spontaneous fracture generation and healing, etc. We also emphasis a role of material heterogeneity on the fragmentation process.
Wu, Baogan; Zang, Rubo
1993-03-01
Calculation and comparative study of the chlorophyll fluorescence ratio F685/F735 in brown alage ( Laminaria japonica, Underia pinnatifida and Padina crassa) excited by blue and green light showed that the fluorescence ratios were higher when the algae were excited by blue light (440 nm), but reduced obviously under green light (540 nm) excitation. The values also reduced under dehydration but could recover during rehydration if the stress was not serious. The variation of the fluorescence ratio under dehydration was mainly because changes in fluorescence emission at 735 nm were always sharper than those at 685 nm. The ratio was sensitive to stress and has potential as a stress indicator in phycological research. Measurement of the fluorescence excitation spectra showed that the only peak at 540 nm changed apparently during dehydration. It meant that the function of the Ch1 a/Fucoxanthin protein complex for energy transfer was easily inhibited by water stress. However, no variation of the ratio was found in green alga Ulva pertusa under dehydration. So it seemed to be something special for brown algae. The mechanism of this phenomenon is still unclear but may be related to the photosynthetic pigments and structural characteristics of brown algae.
Semenova, L. E.
2018-04-01
The hyper-Raman scattering of light by LO-phonons under two-photon excitation near resonance with the An=2 exciton level in the wurtzite semiconductors A2B6 was theoretically investigated, taking into account the influence of the complex structure of the top valence band.
Energy Technology Data Exchange (ETDEWEB)
Lehtovuori, Viivi; Kallioinen, Jani; Myllyperkioe, Pasi; Haukka, Matti; Korppi-Tommola, Jouko
2003-11-15
Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [trans-I-Ru(dcbpy)(CO){sub 2}I{sub 2}] (dcbpy4,4{sup '}-dicarboxy-2,2{sup '}-bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [cis-I-Ru(dcbpy)(CO)(Sol)I{sub 2}] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K indicate interligand charge transfer from mixed Ru-I states to empty dcbpy orbitals. For the photoproduct, no such transfer was observed. In both complexes recovery from the lowest energy excited triplet state to the ground state occurs via two channels: radiative relaxation and a parallel barrier controlled non-radiative relaxation. The barrier is much higher in the reactant (about 850 cm{sup -1}) than in the product. A combination of DFT and ZINDO/CI calculations was used to estimate excited singlet and triplet spectra of the reactant and the product molecules. Calculated singlet-triplet difference spectra qualitatively match the observed transient spectra 500 fs after excitation supporting the idea that observed excited state relaxation occurs from the triplet states in both complexes.
The tank's dynamic response under nuclear explosion blast wave
International Nuclear Information System (INIS)
Xu Mei; Wang Lianghou; Li Xiaotian; Yu Suyuan; Zhang Zhengming; Wan Li
2005-01-01
To weapons and equipment, blast wave is the primary destructive factor. In this paper, taken the real model-59 tank as an example, we try to transform the damage estimation problem into computing a fluid structure interaction problem with finite element method. The response of tank under nuclear explosion blast wave is computed with the general-coupling algorithm. Also, the dynamical interaction of blast wave and tank is reflected in real time. The deformation of each part of the tank is worked out and the result corresponds to the real-measured data. (authors)
International Nuclear Information System (INIS)
Brodmann, R.; Zimmerer, G.; Hamburg Univ.; Hahn, U.
1976-02-01
The fluorescence of Xe at a pressure of 10 Torr has been excited by monochromatic light in the wavelength region from 1,040 A to 1,500 A. Besides the well known first and second continuum additional emission bands appear at 1,192 A and 1,300 A. They are ascribed to an atomic transition 5d(3/2) 1 → 1 S 0 and a molecular transition O + sub(u)(6s'(1/2) + 1 S 0 ) → O + sub(g)( 1 S 0 + 1 S 0 ). The excitation spectra of the first and second continuum yield high fluorescence efficiency if higher Rydberg states are excited. Excitation of the first resonance line of Xe results in a low fluorescence intensity. Obviously the formation of highly excited molecules Xe** and intramolecular relaxation play an important role for the population of the vibrationally relaxed excited states (O + sub(u), 1sub(u)) of the Xe* 2 molecule. (orig.) [de
DEFF Research Database (Denmark)
Roland, Per E.
2017-01-01
In the cerebral cortex, membrane currents, i.e., action potentials and other membrane currents, express many forms of space-time dynamics. In the spontaneous asynchronous irregular state, their space-time dynamics are local non-propagating fluctuations and sparse spiking appearing at unpredictable...... positions. After transition to active spiking states, larger structured zones with active spiking neurons appear, propagating through the cortical network, driving it into various forms of widespread excitation, and engaging the network from microscopic scales to whole cortical areas. At each engaged...... cortical site, the amount of excitation in the network, after a delay, becomes matched by an equal amount of space-time fine-tuned inhibition that might be instrumental in driving the dynamics toward perception and action....
International Nuclear Information System (INIS)
Perez Polo, Manuel F.; Perez Molina, Manuel; Gil Chica, Javier
2009-01-01
This paper explores chaotic behaviour and control of micro-electro-mechanical systems (MEMS), which consist of thousands of small read/write probe tips that access gigabytes of data stored in a non-volatile magnetic surface. The model of the system is formed by two masses connected by a nonlinear spring and a viscous damping. The paper shows that, by means of an adequate feedback law, the masses can behave as two coupled Duffing's oscillators, which may reach chaotic behaviour when harmonic forces are applied. The chaotic motion is destroyed by applying the following control strategies: (i) static output feedback control law with constant forces and (ii) geometric nonlinear control. The aim is to drive the masses to a set point even with harmonic base excitation, by using chaotic dynamics and nonlinear control. The paper shows that it is possible to obtain a positioning time around a few ms with sub-nanometre accuracy, velocities, accelerations and forces, as it appears in the design of present MEMS devices. Numerical simulations are used to verify the mathematical discussions.
Zaouris, Dimitris; Kartakoullis, Andreas; Glodic, Pavle; Samartzis, Peter C; Rafn Hróðmarsson, Helgi; Kvaran, Ágúst
2015-04-28
Photoexcitation dynamics of the E((1)Σ(+)) (v' = 0) Rydberg state and the V((1)Σ(+)) (v') ion-pair vibrational states of HBr are investigated by velocity map imaging (VMI). H(+) photoions, produced through a number of vibrational and rotational levels of the two states were imaged and kinetic energy release (KER) and angular distributions were extracted from the data. In agreement with previous work, we found the photodissociation channels forming H*(n = 2) + Br((2)P3/2)/Br*((2)P1/2) to be dominant. Autoionization pathways leading to H(+) + Br((2)P3/2)/Br*((2)P1/2) via either HBr(+)((2)Π3/2) or HBr(+)*((2)Π1/2) formation were also present. The analysis of KER and angular distributions and comparison with rotationally and mass resolved resonance enhanced multiphoton ionization (REMPI) spectra revealed the excitation transition mechanisms and characteristics of states involved as well as the involvement of the E-V state interactions and their v' and J' dependence.
Energy Technology Data Exchange (ETDEWEB)
Perez Polo, Manuel F. [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Escuela Politecnica Superior, Campus de San Vicente, 03071 Alicante (Spain)], E-mail: manolo@dfists.ua.es; Perez Molina, Manuel [Facultad de Ciencias Matematicas, Universidad Nacional de Educacion a Distancia. UNED, C/Boyero 12-1A, Alicante 03007 (Spain)], E-mail: ma_perez_m@hotmail.com; Gil Chica, Javier [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Escuela Politecnica Superior, Campus de San Vicente, 03071 Alicante (Spain)], E-mail: gil@dfists.ua.es
2009-02-15
This paper explores chaotic behaviour and control of micro-electro-mechanical systems (MEMS), which consist of thousands of small read/write probe tips that access gigabytes of data stored in a non-volatile magnetic surface. The model of the system is formed by two masses connected by a nonlinear spring and a viscous damping. The paper shows that, by means of an adequate feedback law, the masses can behave as two coupled Duffing's oscillators, which may reach chaotic behaviour when harmonic forces are applied. The chaotic motion is destroyed by applying the following control strategies: (i) static output feedback control law with constant forces and (ii) geometric nonlinear control. The aim is to drive the masses to a set point even with harmonic base excitation, by using chaotic dynamics and nonlinear control. The paper shows that it is possible to obtain a positioning time around a few ms with sub-nanometre accuracy, velocities, accelerations and forces, as it appears in the design of present MEMS devices. Numerical simulations are used to verify the mathematical discussions.
Cupellini, Lorenzo; Giannini, Samuele; Mennucci, Benedetta
2017-12-20
Photoinduced electron transfer (ET), hole transfer (HT), charge recombination (CR) and energy transfer (EET) are fundamental mechanisms, which occur in both natural and artificial light harvesting systems. Here, we present a computational strategy which determines ET, HT, CR and EET rates in a consistent way and merges them in a kinetic model to reproduce the net excited state dynamics. The effects of the solvent are included in all steps of the calculations making the present strategy a useful tool for a rational design of charge and energy transfer processes in complex systems. An application to covalently linked zinc and free-base porphyrin-naphthalenediimide dyads is presented. For each of the two systems, ultrafast optical spectroscopy experiments have shown a specific photophysics with different processes taking place simultaneously. The model reveals that such a diversity is mainly due to the different relative stability of the charge-separated state, while the electronic couplings for charge and energy transfer processes are quite similar in the two dyads.
Kalyvas, N.; Valais, I.; David, S.; Michail, Ch.; Fountos, G.; Liaparinos, P.; Kandarakis, I.
2014-05-01
Single crystal scintilators are used in various radiation detectors applications. The efficiency of the crystal can be determined by the Detector Optical Gain (DOG) defined as the ratio of the emitted optical photon flux over the incident radiation photons flux. A parameter affecting DOG is the intrinsic conversion efficiency ( n C ) giving the percentage of the X-ray photon power converted to optical photon power. n C is considered a constant value for X-ray energies in the order of keV although a non-proportional behavior has been reported. In this work an analytical model, has been utilized to single crystals scintillators GSO:Ce, LSO:Ce and LYSO:Ce to examine whether the intrinsic conversion efficiency shows non proportional behavior under X-ray excitation. DOG was theoretically calculated as a function of the incident X-ray spectrum, the X-ray absorption efficiency, the energy of the produced optical photons and the light transmission efficiency. The theoretical DOG values were compared with experimental data obtained by irradiating the crystals with X-rays at tube voltages from 50 to 140 kV and by measuring the light energy flux emitted from the irradiated screen. An initial value for n C (calculated from literature data) was assumed for the X-ray tube voltage of 50 kV. For higher X-ray tube voltages the optical photon propagation phenomena was assumed constant and any deviations between experimental and theoretical data were associated with changes in the intrinsic conversion efficiency. The experimental errors were below 7% for each experimental setup. The behavior of n C values for LSO:Ce and LYSO:Ce were found very similar, i.e., ranging with values from 0.089 at 50 kV to 0.015 at 140 kV, while for GSO:Ce, n C demonstrated a peak at 80 kV.
Dynamics of spins in semiconductor quantum wells under drift
International Nuclear Information System (INIS)
Idrish Miah, M.
2009-01-01
The dynamics of spins in semiconductor quantum wells under applied electric bias has been investigated by photoluminescence (PL) spectroscopy. The bias-dependent polarization of PL (P PL ) was measured at different temperatures. The P PL was found to decay with an enhancement of increasing the strength of the negative bias, with an exception occurred for a low value of the negative bias. The P PL was also found to depend on the temperature. The P PL in the presence of a transverse magnetic field was also studied. The results showed that P PL in the magnetic field oscillates under an applied bias, demonstrating that the dephasing of electron spin occurs during the drift transport in semiconductor quantum wells.
Dynamics of spins in semiconductor quantum wells under drift
Energy Technology Data Exchange (ETDEWEB)
Idrish Miah, M., E-mail: m.miah@griffith.edu.a [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)
2009-09-15
The dynamics of spins in semiconductor quantum wells under applied electric bias has been investigated by photoluminescence (PL) spectroscopy. The bias-dependent polarization of PL (P{sub PL}) was measured at different temperatures. The P{sub PL} was found to decay with an enhancement of increasing the strength of the negative bias, with an exception occurred for a low value of the negative bias. The P{sub PL} was also found to depend on the temperature. The P{sub PL} in the presence of a transverse magnetic field was also studied. The results showed that P{sub PL} in the magnetic field oscillates under an applied bias, demonstrating that the dephasing of electron spin occurs during the drift transport in semiconductor quantum wells.
Interaction Between Ecohydrologic Dynamics and Microtopographic Variability Under Climate Change
Le, Phong V. V.; Kumar, Praveen
2017-10-01
Vegetation acclimation resulting from elevated atmospheric CO2 concentration, along with response to increased temperature and altered rainfall pattern, is expected to result in emergent behavior in ecologic and hydrologic functions. We hypothesize that microtopographic variability, which are landscape features typically of the length scale of the order of meters, such as topographic depressions, will play an important role in determining this dynamics by altering the persistence and variability of moisture. To investigate these emergent ecohydrologic dynamics, we develop a modeling framework, Dhara, which explicitly incorporates the control of microtopographic variability on vegetation, moisture, and energy dynamics. The intensive computational demand from such a modeling framework that allows coupling of multilayer modeling of the soil-vegetation continuum with 3-D surface-subsurface flow processes is addressed using hybrid CPU-GPU parallel computing framework. The study is performed for different climate change scenarios for an intensively managed agricultural landscape in central Illinois, USA, which is dominated by row-crop agriculture, primarily soybean (Glycine max) and maize (Zea mays). We show that rising CO2 concentration will decrease evapotranspiration, thus increasing soil moisture and surface water ponding in topographic depressions. However, increased atmospheric demand from higher air temperature overcomes this conservative behavior resulting in a net increase of evapotranspiration, leading to reduction in both soil moisture storage and persistence of ponding. These results shed light on the linkage between vegetation acclimation under climate change and microtopography variability controls on ecohydrologic processes.
Cone Algorithm of Spinning Vehicles under Dynamic Coning Environment
Directory of Open Access Journals (Sweden)
Shuang-biao Zhang
2015-01-01
Full Text Available Due to the fact that attitude error of vehicles has an intense trend of divergence when vehicles undergo worsening coning environment, in this paper, the model of dynamic coning environment is derived firstly. Then, through investigation of the effect on Euler attitude algorithm for the equivalency of traditional attitude algorithm, it is found that attitude error is actually the roll angle error including drifting error and oscillating error, which is induced directly by dynamic coning environment and further affects the pitch angle and yaw angle through transferring. Based on definition of the cone frame and cone attitude, a cone algorithm is proposed by rotation relationship to calculate cone attitude, and the relationship between cone attitude and Euler attitude of spinning vehicle is established. Through numerical simulations with different conditions of dynamic coning environment, it is shown that the induced error of Euler attitude fluctuates by the variation of precession and nutation, especially by that of nutation, and the oscillating frequency of roll angle error is twice that of pitch angle error and yaw angle error. In addition, the rotation angle is more competent to describe the spinning process of vehicles under coning environment than Euler angle gamma, and the real pitch angle and yaw angle are calculated finally.
HAWT dynamic stall response asymmetries under yawed flow conditions
Energy Technology Data Exchange (ETDEWEB)
Schreck, S.; Robinson, M.; Hand, M.; Simms, D.
2000-02-28
Horizontal axis wind turbines can experience significant time varying aerodynamic loads, potentially causing adverse effects on structures, mechanical components, and power production. As designers attempt lighter and more flexible wind energy machines, greater accuracy and robustness will become even more critical in future aerodynamics models. Aerodynamics modeling advances, in turn, will rely on more thorough comprehension of the three-dimensional, unsteady, vortical flows that dominate wind turbine blade aerodynamics under high load conditions. To experimentally characterize these flows, turbine blade surface pressures were acquired at multiple span locations via the NREL Phase IV Unsteady Aerodynamics Experiment. Surface pressures and associated normal force histories were used to characterize dynamic stall vortex kinematics and normal force amplification. Dynamic stall vortices and normal force amplification were confirmed to occur in response to angle of attack excursions above the static stall threshold. Stall vortices occupied approximately one-half of the blade span and persisted for nearly one-fourth of the blade rotation cycle. Stall vortex convection varied along the blade, resulting in dramatic deformation of the vortex. Presence and deformation of the dynamic stall vortex produced corresponding amplification of normal forces. Analyses revealed consistent alterations to vortex kinematics in response to changes in reduced frequency, span location, and yaw error. Finally, vortex structures and kinematics not previously documented for wind turbine blades were isolated.
Multi-level opinion dynamics under bounded confidence.
Kou, Gang; Zhao, Yiyi; Peng, Yi; Shi, Yong
2012-01-01
Opinion dynamics focuses on the opinion evolution in a social community. Recently, some models of continuous opinion dynamics under bounded confidence were proposed by Deffuant and Krause, et al. In the literature, agents were generally assumed to have a homogeneous confidence level. This paper proposes an extended model for a group of agents with heterogeneous confidence levels. First, a social differentiation theory is introduced and a social group is divided into opinion subgroups with distinct confidence levels. Second, a multi-level heterogeneous opinion formation model is formulated under the framework of bounded confidence. Finally, computer simulations are conducted to study the collective opinion evolution, focusing on three key factors: the fractions of heterogeneous agents, the initial opinions, and the group size. The simulation results demonstrate that the number of final opinions depends on the fraction of close-minded agents when the group size and the initial opinions are fixed; the final opinions converge more easily when the initial opinions are closer; and the number of final opinions can be approximately modeled by a linear increasing function of the group size and the increasing rate is the fraction of close-minded agents.
Incremental Dynamic Analysis of Koyna Dam under Repeated Ground Motions
Zainab Nik Azizan, Nik; Majid, Taksiah A.; Nazri, Fadzli Mohamed; Maity, Damodar; Abdullah, Junaidah
2018-03-01
This paper discovers the incremental dynamic analysis (IDA) of concrete gravity dam under single and repeated earthquake loadings to identify the limit state of the dam. Seven ground motions with horizontal and vertical direction as seismic input considered in the nonlinear dynamic analysis based on the real repeated earthquake in the worldwide. All the ground motions convert to respond spectrum and scaled according to the developed elastic respond spectrum in order to match the characteristic of the ground motion to the soil type. The scaled was depends on the fundamental period, T1 of the dam. The Koyna dam has been selected as a case study for the purpose of the analysis by assuming that no sliding and rigid foundation, has been estimated. IDA curves for Koyna dam developed for single and repeated ground motions and the performance level of the dam identifies. The IDA curve of repeated ground motion shown stiffer rather than single ground motion. The ultimate state displacement for a single event is 45.59mm and decreased to 39.33mm under repeated events which are decreased about 14%. This showed that the performance level of the dam based on seismic loadings depend on ground motion pattern.
Dynamics of Under Ice Boundary Layers Below Floating Ice Shelves
Shaw, W. J.; Stanton, T. P.
2016-02-01
Pine Island Glacier (PIG), a major outlet stream of the Western Antarctic Ice Sheet, has dramatically thinned and accelerated in recent decades. It is believed that a weakening of the floating portion of the glacier, known as the ice shelf, due to increased ocean thermal forcing is a primary cause of the observed increasing discharge of PIG. In order to better understand the controls on the exchange of heat between the PIG shelf and the underlying ocean cavity, a numerical model, MITgcm, has been configured to study the dynamics of the sloping, meltwater-forced, buoyant boundary layer below the ice shelf A 2-D approximation allows for high vertical resolution that resolves well the under shelf ocean boundary layer. We are particularly interested in the dynamical balance between buoyancy along the sloping ice shelf base, drag, and entrainment/detrainment and the associated feedback of basal melting of the ice shelf. Numerical results will be compared to in-situ observations obtained through a field campaign in 2013.
Eslamizadeh, H.
2017-02-01
Evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity for the excited compound nuclei {}168{{Y}}{{b}}, {}172{{Y}}{{b}}, {}178{{W}} and {}227{{P}}{{a}} produced in fusion reactions have been calculated in the framework of the modified statistical model and multidimensional dynamical model. In the dynamical calculations, the dynamics of fission of excited nuclei has been studied by solving three- and four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis, K, were considered in the four-dimensional dynamical model. A non-constant dissipation coefficient of K, {γ }k, was applied in the four-dimensional dynamical calculations. A comparison of the results of the three- and four-dimensional dynamical models with the experimental data showed that the results of the four-dimensional dynamical model for the evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity are in better agreement with the experimental data. It was also shown that the modified statistical model can reproduce the above-mentioned experimental data by choosing appropriate values of the temperature coefficient of the effective potential, λ , and the scaling factor of the fission-barrier height, {r}s.
Excitation Methods for Bridge Structures
Energy Technology Data Exchange (ETDEWEB)
Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.
1999-02-08
This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.
Energy Technology Data Exchange (ETDEWEB)
Queiroz, Thiago B. de, E-mail: thiago.branquinho-de-queiroz@uni-bayreuth.de; Kümmel, Stephan [Theoretical Physics IV, University of Bayreuth, D-95440 Bayreuth (Germany)
2014-08-28
Charge transfer excitations play a prominent role in the fields of molecular electronics and light harvesting. At the same time they have developed a reputation for being hard to predict with time-dependent density functional theory, which is the otherwise predominant method for calculating molecular structure and excitations. Recently, it has been demonstrated that range-separated hybrid functionals, in particular with an “optimally tuned” range separation parameter, describe charge-transfer excitations reliably for different molecules. Many of these studies focused on molecules in vacuum. Here we investigate the influence of solvation on the electronic excitations of thiophene oligomers, i.e., paradigm low gap systems. We take into account bulk solvation using a continuum solvation model and geometrical distortions from molecular dynamics. From our study, three main findings emerge. First, geometrical distortions increase absorption energies by about 0.5 eV for the longer thiophene oligomers. Second, combining optimal tuning of the range separation parameter with a continuum solvation method is not straightforward and has to be approached with great care. Third, optimally tuned range-separated hybrids without a short-range exchange component tend to inherit undesirable characteristics of semi-local functionals: with increasing system size the range separation parameter takes a smaller value, leading to a functional of effectively more semi-local nature and thus not accurately capturing, e.g., the saturation of the optical gap with increasing system size.
International Nuclear Information System (INIS)
Queiroz, Thiago B. de; Kümmel, Stephan
2014-01-01
Charge transfer excitations play a prominent role in the fields of molecular electronics and light harvesting. At the same time they have developed a reputation for being hard to predict with time-dependent density functional theory, which is the otherwise predominant method for calculating molecular structure and excitations. Recently, it has been demonstrated that range-separated hybrid functionals, in particular with an “optimally tuned” range separation parameter, describe charge-transfer excitations reliably for different molecules. Many of these studies focused on molecules in vacuum. Here we investigate the influence of solvation on the electronic excitations of thiophene oligomers, i.e., paradigm low gap systems. We take into account bulk solvation using a continuum solvation model and geometrical distortions from molecular dynamics. From our study, three main findings emerge. First, geometrical distortions increase absorption energies by about 0.5 eV for the longer thiophene oligomers. Second, combining optimal tuning of the range separation parameter with a continuum solvation method is not straightforward and has to be approached with great care. Third, optimally tuned range-separated hybrids without a short-range exchange component tend to inherit undesirable characteristics of semi-local functionals: with increasing system size the range separation parameter takes a smaller value, leading to a functional of effectively more semi-local nature and thus not accurately capturing, e.g., the saturation of the optical gap with increasing system size
Cheng, Yung-Chang; Lin, Deng-Huei; Jiang, Cho-Pei; Lee, Shyh-Yuan
2015-01-01
The main aim of this article was to introduce the application of a uniform design for experimental methods to drop the micromotion of a novel ITI dental implant model under the dynamic loads. Combining the characteristics of the traditional ITI and Nano-Tite implants, a new implant with concave holes has been constructed. Compared to the traditional ITI dental implant model, the micromotion of the new dental implant model was significantly reduced by explicit dynamic finite element analysis. From uniform design of experiments, the dynamic finite element analysis method was applied to caluculated the maximum micromotion of the full model. Finally, the chief design in all the experiment simulations which cause the minimum micromotion is picked as the advanced model of the design. Related to the original design, which was associated with a micromotion of 45.11 μm, the micromotion of the improved version was 31.37 μm, for an improvement rate of 30.5%.
Van Zandwijk, Jan Peter; Bobbert, Maarten F.; Baan, Guus C.; Huijing, Peter A.
1996-01-01
In models of the excitation of muscles it is often assumed that excitation during a tetanic contraction can be obtained by the linear summation of responses to individual stimuli from which the active state of the muscle is calculated. The purpose of this study was to investigate whether such a
Directory of Open Access Journals (Sweden)
Endah Wahyuni
2012-05-01
Full Text Available The paper presents the dynamic behavior of a Submerged Floating Tunnel (SFT in the Seribu Archipelago crossing under seismic loadings by using the different cable configurations. The SFT is a tubular structure submerged in the water at a fixed depth, which features several advantages from the structural and environmental impact points of view. In particular, the structural system is suited for waterway crossings in seismicity zones. Its interaction with the water provides additional damping and inertia to the system. To evaluate the SFT structural response of seismic loadings, a response spectrum analyses were carried out, in which the ground multi-support excitation is considered. The investigation of the different cable system configurations were also carried out. Both static and dynamic analyses were carried to find the optimal configuration of the structural system. Although the paper has had a definitive conclusion yet, the results gave useful indications of responses of Submerged Floating Tunnels subjected to earthquake. The SFT with two cable diagonals perpendicular with SFT’s body (called Model C shows the optimal structural configuration compared with others.
High-frequency dynamics of the glass former dibutylphthalate under pressure
International Nuclear Information System (INIS)
Mermet, A.; Krisch, M.; Duval, E.; Polian, A.
2002-01-01
The high-frequency dynamics of a fragile molecular glass former (dibutylphthalate) was studied through inelastic x-ray scattering (IXS), as a function of pressure and temperature. The mesoscopic structural arrest associated with the glass transition process was tracked by following upon cooling the inelastic excitations at fixed Q points in the dispersion curves, at ambient pressure and 2 kbar. The application of pressure to this system induces an offset between the macroscopic glass transition temperature T g and the mesoscopic glass transition temperature, as determined from IXS. The concomitant fragility decrease of dibutylphthalate under pressure unveils that the stronger the glass former is, the more its mesoscopic dynamics differ from the macroscopic regime. This trend is interpreted as the signature of a nanoscopic inhomogeneous elastic network. Further aspects of this system are obtained when studying the temperature dependence of its nonergodicity factor f Q (T). The chemical specificity of the molecule is suggested to be responsible for the nonobservation of a critical temperature T c in dibutylphthalate up to ∼300 K
Nakano, Masaru; Kumagai, Hiroyuki; Kumazawa, Mineo; Yamaoka, Koshun; Chouet, Bernard A.
1998-05-01
We present a method to quantify the source excitation function and characteristic frequencies of long-period volcanic events. The method is based on an inhomogeneous autoregressive (AR) model of a linear dynamic system, in which the excitation is assumed to be a time-localized function applied at the beginning of the event. The tail of an exponentially decaying harmonic waveform is used to determine the characteristic complex frequencies of the event by the Sompi method. The excitation function is then derived by operating an AR filter constructed from the characteristic frequencies to the entire seismogram of the event, including the inhomogeneous part of the signal. We apply this method to three long-period events at Kusatsu-Shirane Volcano, central Japan, whose waveforms display simple decaying monochromatic oscillations except for the beginning of the events. We recover time-localized excitation functions lasting roughly 1 s at the start of each event and find that the estimated functions are very similar to each other at all the stations of the seismic network for each event. The phases of the characteristic oscillations referred to the estimated excitation function fall within a narrow range for almost all the stations. These results strongly suggest that the excitation and mode of oscillation are both dominated by volumetric change components. Each excitation function starts with a pronounced dilatation consistent with a sudden deflation of the volumetric source which may be interpreted in terms of a choked-flow transport mechanism. The frequency and Q of the characteristic oscillation both display a temporal evolution from event to event. Assuming a crack filled with bubbly water as seismic source for these events, we apply the Van Wijngaarden-Papanicolaou model to estimate the acoustic properties of the bubbly liquid and find that the observed changes in the frequencies and Q are consistently explained by a temporal change in the radii of the bubbles
Eslamizadeh, H.
2016-02-01
A stochastic approach based on one- and two-dimensional Langevin equations is applied to calculate the pre-scission neutron multiplicity, fission probability, anisotropy of fission fragment angular distribution, fission cross section and the evaporation cross section for the compound nuclei 188Pt, 227Pa and 251Es in an intermediate range of excitation energies. The chaos weighted wall and window friction formula are used in the Langevin equations. The elongation parameter, c, is used as the first dimension and projection of the total spin of the compound nucleus onto the symmetry axis, K, considered as the second dimension in Langevin dynamical calculations. A constant dissipation coefficient of K, γK = 0.077(MeV zs)-1/2, is used in two-dimensional calculations to reproduce the above mentioned experimental data. Comparison of the theoretical results of the pre-scission neutron multiplicity, fission probability, fission cross section and the evaporation cross section with the experimental data shows that the results of two-dimensional calculations are in better agreement with the experimental data. Furthermore, it is shown that the two-dimensional Langevin equations together with a dissipation coefficient of K, γK = 0.077(MeV zs)-1/2, can satisfactorily reproduce the anisotropy of fission fragment angular distribution for the heavy compound nucleus 251Es. However, a larger value of γK = 0.250(MeV zs)-1/2 is needed to reproduce the anisotropy of fission fragment angular distribution for the lighter compound nucleus 227Pa.
A technique for measuring dynamic friction coefficient under impact loading.
Lin, Y L; Qin, J G; Chen, R; Zhao, P D; Lu, F Y
2014-09-01
We develop a novel setup based on the split Hopkinson pressure bar technique to test the dynamic friction coefficient under impact loading. In the setup, the major improvement is that the end of the incident bar near the specimen is wedge-shaped, which results in a combined compressive and shear loading applied to the specimen. In fact, the shear loading is caused by the interfacial friction between specimen and bars. Therefore, when the two loading force histories are measured, the friction coefficient histories can be calculated without any assumptions and theoretical derivations. The geometry of the friction pairs is simple, and can be either cuboid or cylindrical. Regarding the measurements, two quartz transducers are used to directly record the force histories, and an optical apparatus is designed to test the interfacial slip movement. By using the setup, the dynamic friction coefficient of PTFE/aluminum 7075 friction pairs was tested. The time resolved dynamic friction coefficient and slip movement histories were achieved. The results show that the friction coefficient changes during the loading process, the average data of the relatively stable flat plateau section of the friction coefficient curves is 0.137, the maximum normal pressure is 52 MPa, the maximum relative slip velocity is 1.5 m/s, and the acceleration is 8400 m(2)/s. Furthermore, the friction test was simulated using an explicit FEM code LS-DYNA. The simulation results showed that the constant pressure and slip velocity can both be obtained with a wide flat plateau incident pulse. For some special friction pairs, normal pressure up to a few hundred MPa, interfacial slip velocities up to 10 m/s, and slip movement up to centimeter-level can be expected.
Strength of coffee beans under static and dynamic loading
Directory of Open Access Journals (Sweden)
Šárka Nedomová
2013-01-01
Full Text Available Paper deals with experimental research on the crushing of coffee beans of different kinds under quasi-static and dynamic compression. The process of the crushing is described in details. It has been shown that there is variability in the crushing strength values. A relation between crushing strength and the coffee grain shape is also studied. Roasted Arabica coffee (Coffea arabica beans were used for analyses. Arabica coffees were produced in different countries. All Arabica samples were submitted to a light roast. The detail analysis of the experimental data shows that there is no significant relation between parameters describing the fracture behaviour of the grains and grain geometry. These parameters are also independent on the grain weight. Compression of the coffee grains leads to their crushing. The fracture force is different for the different kinds of the coffee. The same is fact valid also for the strain at the fracture and for the energy absorbed during the grain crushing. Dynamic loading leads to the increase in the fracture force of coffee grains in comparison with the quasi static loading.
Prototypes for the dynamics underlying precipitation and temperature extremes
Neelin, J. David
Projecting changes in precipitation and temperature extreme events can be aided by a deeper understanding of the dynamics underlying such variations. For precipitation, this is closely connected to the interaction of fast, small-scale motions with variability of large-scale climate. Simple prototype models from the physics and applied math literature can point to analysis methods, connections among related quantities, and hypotheses for the dynamics, especially when the prototype models can be derived from climate-model equations. An overview will be provided including recent work with a number of collaborators. For distributions of precipitation-related variables, prototypes including Fokker-Planck solutions and first-passage problems for variations across an onset threshold yield insights into the form of present-day observed distributions and predictions for the form of the global warming change to evaluate in climate models. In distributions of water vapor and temperature, the widespread occurrence of non-Gaussian tails is likely explained in part by prototypes for tracer advection across a maintained gradient. The shape of these tails can have substantial implications for regional changes in probabilities of precipitation and temperature extremes with large-scale warming. Supported in part by the National Science Foundation.
Planar dynamics of large-deformation rods under moving loads
Zhao, X. W.; van der Heijden, G. H. M.
2018-01-01
We formulate the problem of a slender structure (a rod) undergoing large deformation under the action of a moving mass or load motivated by inspection robots crawling along bridge cables or high-voltage power lines. The rod is described by means of geometrically exact Cosserat theory which allows for arbitrary planar flexural, extensional and shear deformations. The equations of motion are discretised using the generalised-α method. The formulation is shown to handle the discontinuities of the problem well. Application of the method to a cable and an arch problem reveals interesting nonlinear phenomena. For the cable problem we find that large deformations have a resonance detuning effect on cable dynamics. The problem also offers a compelling illustration of the Timoshenko paradox. For the arch problem we find a stabilising (delay) effect on the in-plane collapse of the arch, with failure suppressed entirely at sufficiently high speed.
Dynamic malware containment under an epidemic model with alert
Zhang, Tianrui; Yang, Lu-Xing; Yang, Xiaofan; Wu, Yingbo; Tang, Yuan Yan
2017-03-01
Alerting at the early stage of malware invasion turns out to be an important complement to malware detection and elimination. This paper addresses the issue of how to dynamically contain the prevalence of malware at a lower cost, provided alerting is feasible. A controlled epidemic model with alert is established, and an optimal control problem based on the epidemic model is formulated. The optimality system for the optimal control problem is derived. The structure of an optimal control for the proposed optimal control problem is characterized under some conditions. Numerical examples show that the cost-efficiency of an optimal control strategy can be enhanced by adjusting the upper and lower bounds on admissible controls.
Dynamic Group Diffie-Hellman Key Exchange under standard assumptions
International Nuclear Information System (INIS)
Bresson, Emmanuel; Chevassut, Olivier; Pointcheval, David
2002-01-01
Authenticated Diffie-Hellman key exchange allows two principals communicating over a public network, and each holding public-private keys, to agree on a shared secret value. In this paper we study the natural extension of this cryptographic problem to a group of principals. We begin from existing formal security models and refine them to incorporate major missing details (e.g., strong-corruption and concurrent sessions). Within this model we define the execution of a protocol for authenticated dynamic group Diffie-Hellman and show that it is provably secure under the decisional Diffie-Hellman assumption. Our security result holds in the standard model and thus provides better security guarantees than previously published results in the random oracle model
van Swaaij, G. A.; Bystrov, K.; Borodin, D.; Kirschner, A.; van der Vegt, L. B.; van Rooij, G. J.; De Temmerman, G.; W. J. Goedheer,
2012-01-01
For understanding carbon erosion and redeposition in nuclear fusion devices, it is important to understand the transport and chemical break-up of hydrocarbon molecules in edge plasmas, often diagnosed by emission of the CH A(2)Delta-X-2 Pi Gero band around 430 nm. The CH A-level can be excited
Sustainable infrastructure system modeling under uncertainties and dynamics
Huang, Yongxi
Infrastructure systems support human activities in transportation, communication, water use, and energy supply. The dissertation research focuses on critical transportation infrastructure and renewable energy infrastructure systems. The goal of the research efforts is to improve the sustainability of the infrastructure systems, with an emphasis on economic viability, system reliability and robustness, and environmental impacts. The research efforts in critical transportation infrastructure concern the development of strategic robust resource allocation strategies in an uncertain decision-making environment, considering both uncertain service availability and accessibility. The study explores the performances of different modeling approaches (i.e., deterministic, stochastic programming, and robust optimization) to reflect various risk preferences. The models are evaluated in a case study of Singapore and results demonstrate that stochastic modeling methods in general offers more robust allocation strategies compared to deterministic approaches in achieving high coverage to critical infrastructures under risks. This general modeling framework can be applied to other emergency service applications, such as, locating medical emergency services. The development of renewable energy infrastructure system development aims to answer the following key research questions: (1) is the renewable energy an economically viable solution? (2) what are the energy distribution and infrastructure system requirements to support such energy supply systems in hedging against potential risks? (3) how does the energy system adapt the dynamics from evolving technology and societal needs in the transition into a renewable energy based society? The study of Renewable Energy System Planning with Risk Management incorporates risk management into its strategic planning of the supply chains. The physical design and operational management are integrated as a whole in seeking mitigations against the
Directory of Open Access Journals (Sweden)
Amir R. Askari
2014-01-01
Full Text Available The influence of the Casimir excitation on dynamic pull-in instability of a nanoelectromechanical beam under ramp-input voltage is studied. The ramp-input actuation has applications in frequency sweeping of RF-N/MEMS. The presented model is nonlinear due to the inherent nonlinearity of electrostatics and the Casimir excitations as well as the geometric nonlinearity of midplane stretching. A Galerkin based reduced order modeling is utilized. It is found that the calculated dynamic pull-in ramp input voltage leads to dynamic pull-in step input voltage by increasing the slope of voltage-time diagram. This fact is utilized to verify the results of present study.
Producing coherent excitations in pumped Mott antiferromagnetic insulators
Wang, Yao; Claassen, Martin; Moritz, B.; Devereaux, T. P.
2017-12-01
Nonequilibrium dynamics in correlated materials has attracted attention due to the possibility of characterizing, tuning, and creating complex ordered states. To understand the photoinduced microscopic dynamics, especially the linkage under realistic pump conditions between transient states and remnant elementary excitations, we performed nonperturbative simulations of various time-resolved spectroscopies. We used the Mott antiferromagnetic insulator as a model platform. The transient dynamics of multiparticle excitations can be attributed to the interplay between Floquet virtual states and a modification of the density of states, in which interactions induce a spectral weight transfer. Using an autocorrelation of the time-dependent spectral function, we show that resonance of the virtual states with the upper Hubbard band in the Mott insulator provides the route towards manipulating the electronic distribution and modifying charge and spin excitations. Our results link transient dynamics to the nature of many-body excitations and provide an opportunity to design nonequilibrium states of matter via tuned laser pulses.
Thermographic measurement of thermal bridges in buildings under dynamic behavior
Ferrarini, G.; Bison, P.; Bortolin, A.; Cadelano, G.; De Carli, M.
2016-05-01
The accurate knowledge of the thermal performance could reduce significantly the impact of buildings on global energy consumption. Infrared thermography is widely recognized as one of the key technologies for building surveys, thanks to its ability to acquire at a glance thermal images of the building envelope. However, a spot measurement could be misleading when the building is under dynamic thermal conditions. In this case data should be acquired for hours or days, depending on the thermal properties of the walls. Long term thermographic monitoring are possible but imply strong challenges from a practical standpoint. This work investigates the possibilities and limitations of spot thermographic surveys coupled with contact probes, that are able to acquire continuously the thermal signal for days, to investigate the thermal bridges of a building. The goal is the estimation of the reliability and accuracy of the measurement under realistic environmental conditions. Firstly, numerical simulations are performed to determine the reference value of an experimental case. Then a long term thermographic survey is performed and integrated with the contact probe measurement, assessing the feasibility of the method.