Artículos de revistas: "Excitation energy measurement"

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Stamatellou, Antiopi-Malvina y Anestis I. Kalfas. "On the Efficiency of a Piezoelectric Energy Harvester under Combined Aeroelastic and Base Excitation". Micromachines 12, n.º 8 (14 de agosto de 2021): 962. http://dx.doi.org/10.3390/mi12080962.

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A flutter-type, nonlinear piezoelectric energy harvester was tested in various combinations of aerodynamic and harmonic base excitation to study its power output and efficiency. The commercial polyvinylidene fluoride film transducer LDT1-028K was used in 33 excitation mode. The aerodynamic excitation was created by a centrifugal fan and the base excitation by a cone speaker. The excitations were produced by varying independently the mean airflow velocity and the frequency of base vibration. A capacitive load was used to store the harvested energy. A line laser was employed along with long exposure photography and high-speed video, for the visualization of the piezo film’s mode shapes and the measurement of maximum tip deflection. The harvested power was mapped along with the maximum tip deflection of the piezo-film, and a process of optimally combining the two excitation sources for maximum power harvesting is demonstrated. The energy conversion efficiency is defined by means of electrical power output divided by the elastic strain energy rate of change during oscillations. The efficiency was mapped and correlated with resonance conditions and results from other studies. It was observed that the conversion efficiency is related to the phase difference between excitation and response and tends to decrease as the excitation frequency rises.

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2

Ni, Pinghe, Yong Xia, Siu-Seong Law y Songye Zhu. "Structural Damage Detection Using Auto/Cross-Correlation Functions Under Multiple Unknown Excitations". International Journal of Structural Stability and Dynamics 14, n.º 05 (junio de 2014): 1440006. http://dx.doi.org/10.1142/s0219455414400069.

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Traditional structural system identification and damage detection methods use vibration responses under single excitation. This paper presents an auto/cross-correlation function-based method using acceleration responses under multiple ambient white noise or impact excitations. The auto/cross-correlation functions are divided into two parts. One is associated with the structural parameters and the other with the energy of the excitation. These two parts are updated sequentially using a two-stage method. Numerical and experimental studies are conducted to demonstrate the accuracy and robustness of the proposed method. The effects of measurement noise and number of measurement points on the identification results are also studied.

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3

Lövestam, Göran, Mikael Hult, Andreas Fessler, Thierry Gamboni, Joël Gasparro, Wouter Geerts, Ricardo Jaime, Patric Lindahl, Stephan Oberstedt y Hamid Tagziria. "Measurement of neutron excitation functions using wide energy neutron beams". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 580, n.º 3 (octubre de 2007): 1400–1409. http://dx.doi.org/10.1016/j.nima.2007.06.090.

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4

SINGH, B. P., M. G. V. SANKARACHARYULU, M. A. ANSARI, R. PRASAD y H. D. BHARDWAJ. "MEASUREMENT AND ANALYSIS OF EXCITATION FUNCTIONS FOR ALPHA-INDUCED REACTIONS IN BISMUTH". International Journal of Modern Physics E 01, n.º 04 (diciembre de 1992): 823–31. http://dx.doi.org/10.1142/s0218301392000357.

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Excitation functions for 209 Bi (α, 3n), 209 Bi (α, 4n) and 209 Bi (α, 5n) reactions have been measured in the energy range threshold to ≈50 MeV using stacked foil technique. Excitation functions have also been theoretically calculated and as expected, inclusion of pre-equilibrium contribution based on exciton model calculations along with compound nucleus calculations using Hauser–Feshbach formalism reproduces well the measured excitation functions. Interesting trend in the ratio of pre-equilibrium to equilibrium component with projectile energy has been observed.

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5

Omagari, Shun y Martin Vacha. "Toward accurate measurement of the intrinsic quantum yield of lanthanide complexes with back energy transfer". Physical Chemistry Chemical Physics 22, n.º 6 (2020): 3683–90. http://dx.doi.org/10.1039/c9cp06294g.

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6

Nokhbatolfoghahai, A., HM Navazi, Y. Ghobaad y H. Haddadpour. "Experimental measurement of energy density of a vibrating beam". Journal of Vibration and Control 24, n.º 24 (16 de febrero de 2016): 5735–46. http://dx.doi.org/10.1177/1077546316629596.

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This paper presents a method for calculating vibrational energy density from experimental data in a uniform beam. The input excitation is a point random force that induces transverse vibration along the beam. Using finite difference method and four accelerometers, both translational and rotational terms of kinetic and potential energy densities are measured. Also, an energy finite element analysis based computer program is developed. The results of the measurements achieved by developed formulation are compared with those of energy finite element analysis results. It is found that there is a fair agreement between them at relatively lower frequencies. But, in high frequencies, the difference between analytical and experimental results increases which stems from occurrence of errors in calculation of potential energy density. Finally, a comparison between kinetic and potential terms of the energy density is done. It is concluded that an efficient and very simple measurement procedure can be used based on kinetic energy measurement only.

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7

Sipos, Dávid y Dániel Feszty. "Development of a Procedure for the Validation of Statistical Energy Analysis Simulations". Acta Technica Jaurinensis 12, n.º 4 (27 de noviembre de 2019): 335–46. http://dx.doi.org/10.14513/actatechjaur.v12.n4.512.

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This paper describes the development of an NVH measurement procedure that can be used for comparisons to Statistical Energy Analysis (SEA). In SEA, the outputs of the simulation are ensemble averaged quantities for each subsystem, which can be obtained in measurements by averaging some measurement point results. For several reasons, the number of measurement points must be as few as possible, but at the same time, they have to provide a well approximated averaged response of the system. The sufficient number of evaluation points and excitation load cases are determined via Finite Element (FE) simulations. It is shown that in case of a simple, flat plate, 17 randomly chosen evaluation points in at least 3 load cases are enough to properly approximate the SEA results.

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8

Chen, Shuming, Dengfeng Wang y Yingfeng Lei. "Automotive Interior Noise Prediction Based on Single Sound Cavity Using Statistical Energy Analysis Method". Noise & Vibration Worldwide 42, n.º 11 (diciembre de 2011): 36–43. http://dx.doi.org/10.1260/0957-4565.42.11.36.

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In order to predict car interior noises at the car design and development stage, the statistical energy analysis (SEA) method was used. All the input parameters – modal density (MD), damping loss factor (DLF) and coupling loss factor (CLF) were calculated with SEA principle. Meanwhile, the sound excitation was calculated with sound power experiment data of internal combustion engine given by the engine manufacturer and sound source radiation formula. Engine mount excitation was also computed through the acceleration at initiative side of the engine mount and the transmissibility. A car virtual prototype was built to calculate a car body suspension receiving excitation from road roughness. A computational fluid dynamics (CFD) model was also built up to analyze the wind excitation on the outside surfaces. The car interior noises were predicted by the SEA model with all of the parameters and excitations. A good agreement was indicated by comparing predicted results with measured ones. The maximum relative error between prediction and measurement results is less than 3%, and the maximum absolute error is less than 2.5 dB (A). The above predicted results satisfy engineering precision requirements and as well as showing that using SEA method to predict car internal noises is feasible. The acoustic sensitivity analysis was made at the end. The car internal noise prediction method presented in the paper can be used at car design and development stage.

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9

Gragston, Mark, Paul Hsu, Anil Patnaik, Zhili Zhang y Sukesh Roy. "Time-Gated Single-Shot Picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS) for Equivalence-Ratio Measurements". Applied Spectroscopy 74, n.º 3 (10 de febrero de 2020): 340–46. http://dx.doi.org/10.1177/0003702819885647.

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Time-gated picosecond laser-induced breakdown spectroscopy (ps-LIBS) for the determination of local equivalence ratios in atmospheric-pressure adiabatic methane–air flames is demonstrated. Traditional LIBS for equivalence-ratio measurements employ nanosecond (ns)-laser pulses, which generate excessive amounts of continuum, reducing measurement accuracy and precision. Shorter pulse durations reduce the continuum emission by limiting avalanche ionization. Furthermore, by contrast the use of femtosecond lasers, plasma emission using picosecond-laser excitation has a high signal-to-noise ratio (S/N), allowing single-shot measurements suitable for equivalence-ratio determination in turbulent reacting flows. We carried out an analysis of the dependence of the plasma emission ratio Hα (656 nm)/NII (568 nm) on laser energy and time-delay for optimization of S/N and minimization of measurement uncertainties in the equivalence ratios. Our finding shows that higher laser energy and shorter time delay reduces measurement uncertainty while maintaining high S/N. In addition to atmospheric-pressure flame studies, we also examine the stability of the ps-LIBS signal in a high-pressure nitrogen cell. The results indicate that the plasma emission and spatial position could be stable, shot-to-shot, at elevated pressure (up to 40 bar) using a lower excitation energy. Our work shows the potential of using ps-duration pulses to improve LIBS-based equivalence-ratio measurements, both in atmospheric and high-pressure combustion environments.

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10

Eck, T., S. J. Walsh y J. L. Horner. "Measurement of Vibrational Energy and Point Mobility of a Beam Subjected to Moment Excitation Using a Finite-Difference Approximation". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 220, n.º 6 (1 de junio de 2006): 795–806. http://dx.doi.org/10.1243/09544062jmes210.

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Moment excitation is often neglected in structural vibration analysis because of difficulties in measuring the applied moment and the resulting wave motion in the structure. Further, it is often assumed that moment-induced vibrational energy is significant only in the high frequency region. However, recent studies have shown that moment excitation should be included in vibrational analysis at all frequencies, when the source location is in close proximity to a structural discontinuity. In this article, a novel method is presented to measure the point mobility and resulting vibrational energy of a beam subjected to moment excitation. The proposed method utilizes a finite-difference approximation to calculate the rotational motion of the beam at the point of excitation. Moment excitation is induced by a specially designed impact rig which applies two equal and opposite forces on two moment arms that are perpendicularly attached to the beam. It is shown that, using the newly developed technique, the measured point mobility follows the trend of the equivalent theoretical structure. The technique also showed good agreement over a wide frequency range between the measured input energy and the measured transmitted flexural wave energy along the beam.

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11

Wense, L. v. d., P. G. Thirolf, D. Kalb y M. Laatiaoui. "Towards a direct transition energy measurement of the lowest nuclear excitation in229Th". Journal of Instrumentation 8, n.º 03 (8 de marzo de 2013): P03005. http://dx.doi.org/10.1088/1748-0221/8/03/p03005.

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12

Fuellekrug, U., M. Boeswald, D. Goege y Y. Govers. "Measurement of FRFs and Modal Identification in Case of Correlated Multi-Point Excitation". Shock and Vibration 15, n.º 3-4 (2008): 435–45. http://dx.doi.org/10.1155/2008/356087.

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The modal identification of large and dynamically complex structures often requires a multi-point excitation. Sine sweep excitation runs are applied when it is necessary to concentrate more energy on each line of the frequency spectrum. The conventional estimation of FRFs from multi-point excitation requires uncorrelated excitation signals. In case of multi-point (correlated) sine sweep excitation, several sweep runs with altered excitation force patterns have to be performed to estimate the FRFs. An alternative way, which offers several advantages, is to process each sine sweep run separately. The paper first describes the conventional method for FRF estimation in case of multi-point excitation, followed by two alternative methods applicable in case of correlated excitation signals. Both methods generate a virtual single-point excitation from a single run with multi-point excitation. In the first method, an arbitrary structural point is defined as a virtual driving point. This approach requires a correction of the modal masses obtained from modal analysis. The second method utilizes the equality of complex power to generate virtual FRFs along with a single virtual driving point. The computation of FRFs and the modal identification using virtual single-point excitation are explained. It is shown that the correct set of modal parameters can be identified. The application of the methods is elucidated by an illustrative analytical example. It could be shown that the separate evaluation of symmetric and anti-symmetric multi-point excitation runs yield obviously better and more reliable results compared to the conventional method. In addition, the modal analysis of the separate symmetric and anti-symmetric excitation runs is easier, since the stabilization diagrams are easier to interpret. The described methods were successfully applied during the Ground Vibration Tests on Airbus A380 and delivered excellent results. The methods are highly advantageous and may thus be established as a new standard procedure for testing aerospace structures.

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13

Hasselbach, F. y A. Schäfer. "Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions". Proceedings, annual meeting, Electron Microscopy Society of America 48, n.º 2 (12 de agosto de 1990): 110–11. http://dx.doi.org/10.1017/s0424820100134144.

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Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

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14

Masuda, Takahiko, Tsukasa Watanabe, Kjeld Beeks, Hiroyuki Fujimoto, Takahiro Hiraki, Hiroyuki Kaino, Shinji Kitao et al. "Absolute X-ray energy measurement using a high-accuracy angle encoder". Journal of Synchrotron Radiation 28, n.º 1 (1 de enero de 2021): 111–19. http://dx.doi.org/10.1107/s1600577520014526.

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This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.

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15

Ambrożkiewicz, Bartłomiej, Grzegorz Litak y Piotr Wolszczak. "Modelling of Electromagnetic Energy Harvester with Rotational Pendulum Using Mechanical Vibrations to Scavenge Electrical Energy". Applied Sciences 10, n.º 2 (17 de enero de 2020): 671. http://dx.doi.org/10.3390/app10020671.

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A concept of non-linear electromagnetic system with the rotational magnetic pendulum for energy harvesting from mechanical vibrations was presented. The system was stimulated by vertical excitation coming from a shaker. The main assumption of the system was the montage of additional regulated stationary magnets inside coils creating double potential well, and the system was made with a 3D printing technique in order to avoid a magnetic coupling with the housing. In validation process of the system, modelling of electromagnetic effects in different configurations of magnets positions was performed with the application of a finite element method (FEM) obtaining the value of magnetic force acting on the pendulum. A laboratory measurement circuit was built and an experiment was carried out. The voltage and power outputs were measured for different excitations in range of system operational frequencies found experimentally. The experimental results of the physical system with electrical circuit and numerical estimations of the magnetic field of a stationary magnet’s configuration were used to derive a mathematical model. The equation of motion for the rotational pendulum was used to prove the broadband frequency effect.

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16

Raanan, Dekel, Liqing Ren, Dan Oron y Yaron Silberberg. "Impulsive Raman spectroscopy via precision measurement of frequency shift with low energy excitation". Optics Letters 43, n.º 3 (23 de enero de 2018): 470. http://dx.doi.org/10.1364/ol.43.000470.

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17

Шпеник, О. Б., А. И. Булгакова, А. Н. Завилопуло, Н. М. Эрдевди y Ю. А. Бандурин. "Возбуждение молекул валина электронным ударом в газовой фазе". Письма в журнал технической физики 47, n.º 14 (2021): 30. http://dx.doi.org/10.21883/pjtf.2021.14.51184.18810.

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The measurement procedure and the results obtained by optical spectroscopy upon excitation of valine molecules in the gas phase by slow electrons are described. The emission spectra of the molecules under study in the range of 200-520 nm with excitation by electrons in the energy range of 0-90 eV, as well as the optical functions of the excitation of the most intense spectral lines (bands) of radiation are presented.

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18

McDade, I. C., E. J. Llewellyn y B. H. Solheim. "A rocket measurement of O(1S) and emissions in a pulsating aurora". Canadian Journal of Physics 63, n.º 7 (1 de julio de 1985): 983–87. http://dx.doi.org/10.1139/p85-161.

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Rocket measurements of the O(1S–1D) 557.7-nm and [Formula: see text] (0–0) 391.4-nm emission profiles for the steady component of an international brightness coefficient 1+ aurora, which exhibited irregular pulsations, are presented. The [Formula: see text] volume emission profile is found to be in good agreement with theoretical profiles calculated from the primary-electron energy spectra recorded near apogee on the same flight. The O(1S) emission is found to increase with altitude relative to the [Formula: see text] emission between 100 and 130 km, and possible mechanisms for the excitation of O(1S) are examined. It is found that either energy transfer from [Formula: see text] or the reaction of N+ with O2 can explain most of the observed O(1S) emission, but the possibility of a different excitation mechanism cannot be ruled out.

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19

UROIĆ, MILIVOJ, DURO MILJANIĆ, SAŠA BLAGUS, MLADEN BOGOVAC, NATKO SKUKAN, NEVEN SOIĆ, MARIJA MAJER et al. "T = 1 ISOSPIN EXCITATION SPECTRUM IN 10B". International Journal of Modern Physics E 17, n.º 10 (noviembre de 2008): 2345–48. http://dx.doi.org/10.1142/s0218301308011586.

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Isobaric analogues of three states in 10 Be forming a rotational band with high moment of inertia are expected in 10 B and 10 C . This article reports a measurement of excitation spectrum in 10 B obtained through 11 B (3 He ,α)10 B reaction. A T = 1 state is found on 11.3 MeV excitation energy. It is a possible candidate for the 4+ state of the analogue rotation band.

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20

Armbruster, B., I. Blair, B. A. Bodmann, N. E. Booth, G. Drexlin, V. Eberhard, J. A. Edgington et al. "Measurement of the weak neutral current excitation at Eνμ=29.8 MeV". Physics Letters B 423, n.º 1-2 (marzo de 1998): 15–20. http://dx.doi.org/10.1016/s0370-2693(98)00087-2.

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21

Singh, Varinderjit, B. R. Behera, Maninder Kaur, A. Jhingan, Rupinder Kaur, P. Sugathan, Davinder Siwal et al. "Measurement of fission excitation function for 19F + 194, 196, 198Pt reactions". Journal of Physics G: Nuclear and Particle Physics 48, n.º 7 (21 de mayo de 2021): 075104. http://dx.doi.org/10.1088/1361-6471/abe8cd.

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22

Qiao, Baijie, Tong Zhao, Xuefeng Chen y Jinxin Liu. "The assessment of active vibration isolation performance of rotating machinery using power flow and vibrational energy: Experimental investigation". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, n.º 2 (10 de febrero de 2015): 159–73. http://dx.doi.org/10.1177/0954406215572434.

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The aim of vibration isolation for rotating machinery is to reduce the energy from the vibration source through transfer paths into the receiver structure. However, the direct measurement of energy characteristics that have been thoroughly researched in theory and numerical simulation is always difficult to implement. In this paper, power flow combined with vibrational energy is applied to assess the performance of active vibration isolation of rotating machinery. The indirect measurement methods associated with both power flow and vibrational energy are proposed and a link between them is established. As the first step in experimental investigation, a simple test rig is performed to verify the proposed measurement methods. The power flow into the foundation is calculated by the proposed time averaged, fundamental frequency and second harmonic frequency methods; the vibrational energy of the foundation is estimated by the driving impedance and mobility methods. The second step is to build another experimental rig for imitating the rotating machinery with active vibration isolation. Under multiple excitations, the power flow from the unbalanced rotor excitation through each actuator into the foundation is calculated by the proposed fundamental frequency method; the vibrational energy is calculated by the proposed mobility matrix method. Finally, comparison of assessing the performance of active vibration isolation between using acceleration and force and using the two energy characteristics are carried out.

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23

Wang, Zhe, Ximing Cui, Haiming Pu y Yihua Kang. "Influence of surface roughness on energy change of excitation process in EMAT thickness measurement". International Journal of Applied Electromagnetics and Mechanics 59, n.º 4 (21 de marzo de 2019): 1479–86. http://dx.doi.org/10.3233/jae-171121.

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24

He, Da Wei, Yan Ning Shi, Tao Hou y Dan Zhou. "Luminescence Properties of M₂MgSi₂O₇: Re (M = Ba, Sr, Ca) (Re = Eu²⁺, Ce³⁺, Tb³⁺)". Key Engineering Materials 336-338 (abril de 2007): 622–24. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.622.

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A series of phosphors of M2MgSi2O7: Eu2+ (M=Ba,Sr,Ca) have been synthesized and studied. The excitation spectra measurement showed that the phosphors had absorption in long UV light, the excitation spectra of the phosphors consisted of two broad bands: one in the range from 280nm to 330 nm and the other from 360nm to 420 nm. The main excitation band centered at around 395nm was belong to 4f→5d transitions of Eu2+. Analysis of the spectra of Ce3+ and Tb3+ co-doped phosphor showed that energy transfer from Ce3+ to Tb3+ in Ba2MgSi2O7 under UV excitation was efficient.

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25

McCaig, Lori, Zhan Shi, Teresa Holbrook Woodrum, Stephen Brewer y Richard Sacks. "Sampling, Excitation, and Ionization Characteristics of a Planar Magnetron Glow-Discharge Device". Applied Spectroscopy 46, n.º 12 (diciembre de 1992): 1762–68. http://dx.doi.org/10.1366/0003702924123593.

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Measurements of mass loss during sputtering, atomic emission intensities, and ionization characteristics are described for a coaxial magnetron glow-discharge device. By the use of the magnetic field from a coaxial magnet pair placed behind the cathode, stable plasma operation is achieved for all pressures from 0.0004 Torr (0.05 Pa) to over 2.5 Torr (330 Pa). Mass loss measurement values from pellets of Al, Cu, brass, Zn, and Au located in the region of greatest sputtering show much larger values at pressures which are lower than those usually used with glow-discharge excitation and ionization sources. Emission line ratio measurements at the lower pressures indicate that populations of low-energy electronic states are greater than equilibrium values. This observation suggests that the plasma is dominated by ionization processes rather than by recombination processes. Emission line ratio and mass spectrometric measurements also indicate that ionization is increased at the lower pressures.

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26

Cheng, S. C., Y. Y. Wang y V. P. Dravid. "The measurements of the elastic-inelastic multiple scattering electron intensity in EELS". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 de agosto de 1995): 300–301. http://dx.doi.org/10.1017/s0424820100137872.

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The Electron energy loss function in the low energy range is determined by collective excitation of valence electrons and charge carriers, i.e. plasmons, as well as interband and intraband excitations. The explicit dependence of the cross-section on the momentum transfer q allows the observation of nonvertical interband transition and a measurement of the dispersion of plasmon excitations. The drawback of the momentum resolved electron spectroscopy is the multiple scattering, which often obscure the single scattering events. Under relatively small scattering angles, both strong elasticinelastic multiple (E-I-M) scattering and elastic scattering events compared to the inelastic scattering have been reported. In order to find out in what momentum range the E-I-M scattering intensity can be ignored in the momentum resolved electron spectroscopy, we have measured the angular dependency of the intensities of the E-I-M scattering electrons Ie+in. The intensities of the elastic scattering electrons Ie as well as of the inelastic scattering electrons Iin were also measured and are presented in this paper together. A simple relationship between Ie and Ie+in is found.

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Chakravarty, N., P. K. Sarkar, Maitreyee Nandy y Sudip Ghosh. "Excitation function measurement and reaction mechanism analysis for alpha-induced reactions on". Journal of Physics G: Nuclear and Particle Physics 24, n.º 1 (1 de enero de 1998): 151–66. http://dx.doi.org/10.1088/0954-3899/24/1/019.

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28

Kaur, Sukhdeep y Einar Halvorsen. "Parameter sensitivity of an in-plane gap closing electrostatic energy harvester with end-stop impacts". Journal of Intelligent Material Systems and Structures 28, n.º 12 (24 de enero de 2017): 1640–50. http://dx.doi.org/10.1177/1045389x16679287.

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Conventionally modeled as spring–damper system, the end-stops in vibration energy harvesters set a limit to the displacement of the proof mass at sufficiently high excitation levels. In some studies, it is seen that the end-stop parameters needed adjustment to fit the simulations to the measurements at particular operating condition. In this article, the discrepancy between the simulation and measurement results on varying the operating condition is investigated in detail. A check on sensitivity of an electrostatic in-plane gap closing energy harvester to the parameters end-stop stiffness, end-stop damping, and end-stop position at various biases and excitation levels is performed. The simulations at 3-V bias and root mean square (RMS) acceleration amplitude 0.6 g show a remarkable variation of 30 Hz in up-sweep jump-down frequency on varying end-stop position by 0.12 µm. The simulation results also show a significant increase in sensitivity of up-sweep jump-down frequency to end-stop damping on increasing excitation level at fixed bias. The article also discusses the sensitivity in jump frequencies to perturbations in the excitation signal due to the presence of noise, where the jump-down frequency becomes smaller as the noise level increases. The trajectories studied at 8-V bias and RMS acceleration amplitude 0.6 g with different end-stop parameters show a strong influence of the end-stop model parameters on the motion of the proof mass. A lumped model of the device is fitted to the measurements for a whole range of operating conditions with one fixed set of model parameter, where asymmetric end-stop positions and their effect on the device behavior are shown to be crucial. The results presented in this article show that in order to reproduce and analyze the measured behavior of the harvester over a range of operating conditions, very fine details in the model are significant.

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Cao, Y., D. G. Mazzone, D. Meyers, J. P. Hill, X. Liu, S. Wall y M. P. M. Dean. "Ultrafast dynamics of spin and orbital correlations in quantum materials: an energy- and momentum-resolved perspective". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, n.º 2145 (abril de 2019): 20170480. http://dx.doi.org/10.1098/rsta.2017.0480.

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Many remarkable properties of quantum materials emerge from states with intricate coupling between the charge, spin and orbital degrees of freedom. Ultrafast photo-excitation of these materials holds great promise for understanding and controlling the properties of these states. Here, we introduce time-resolved resonant inelastic X-ray scattering (tr-RIXS) as a means of measuring the charge, spin and orbital excitations out of equilibrium. These excitations encode the correlations and interactions that determine the detailed properties of the states generated. After outlining the basic principles and instrumentations of tr-RIXS, we review our first observations of transient antiferromagnetic correlations in quasi two dimensions in a photo-excited Mott insulator and present possible future routes of this fast-developing technique. The increasing number of X-ray free electron laser facilities not only enables tackling long-standing fundamental scientific problems, but also promises to unleash novel inelastic X-ray scattering spectroscopies. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

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30

Man, Michael K. L., Julien Madéo, Chakradhar Sahoo, Kaichen Xie, Marshall Campbell, Vivek Pareek, Arka Karmakar et al. "Experimental measurement of the intrinsic excitonic wave function". Science Advances 7, n.º 17 (abril de 2021): eabg0192. http://dx.doi.org/10.1126/sciadv.abg0192.

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An exciton, a two-body composite quasiparticle formed of an electron and hole, is a fundamental optical excitation in condensed matter systems. Since its discovery nearly a century ago, a measurement of the excitonic wave function has remained beyond experimental reach. Here, we directly image the excitonic wave function in reciprocal space by measuring the momentum distribution of electrons photoemitted from excitons in monolayer tungsten diselenide. By transforming to real space, we obtain a visual of the distribution of the electron around the hole in an exciton. Further, by also resolving the energy coordinate, we confirm the elusive theoretical prediction that the photoemitted electron exhibits an inverted energy-momentum dispersion relationship reflecting the valence band where the partner hole remains, rather than that of conduction band states of the electron.

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31

Wang, Y. Y., V. P. Dravid y F. C. Zhang. "Symmetry of molecular wavefunction in BaBiO3 determined by q-resolved EELS". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 de agosto de 1995): 298–99. http://dx.doi.org/10.1017/s0424820100137860.

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Momentum-transfer (q) resolved electron energy loss spectroscopy is a unique technique to investigate the symmetry of electronic excitations in materials. Under small momentum-transfer conditions, the dielectric function derived from electron energy loss spectrum (EELS) is comparable to the dielectric function obtained by optical measurement. However, relatively large momentum-transfer conditions, which optical spectroscopy cannot achieve, can be met with high energy electrons and such q-resolved EELS data can provide dynamic information of the excitations as well as possible location of optically forbidden transitions.According to the Born approximation, the differential cross section of inelastic scattering can be written as:(1)where Ψo and Ψf are the initial- and final-state wave functions with energies as Eo and Ef, respectively, q is the momentum transfer. If rc is the effective radius of the excitation, then for q<1/rc, one can write:(2)For small q, the second term dominates the integral, permitting dipole-allowed transitions. For large q, the third term, which contains monopole and quadrupole transitions, increases in strength relative to the dipole transitions.

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32

SOKHAN, D., D. WATTS, D. BRANFORD y F. KLEIN. "A NEW MEASUREMENT OF BEAM ASYMMETRY IN PION PHOTOPRODUCTION FROM THE NEUTRON USING CLAS". International Journal of Modern Physics A 24, n.º 02n03 (30 de enero de 2009): 497–500. http://dx.doi.org/10.1142/s0217751x09043936.

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We present a preliminary analysis of the photon beam asymmetry observable (Σ) from the photoproduction reaction channel γn → π-p. This new data was obtained using the near-4π CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 - 2.3 GeV. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle.

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33

Watanabe, Kazuya y Yoshiyasu Matsumoto. "Nuclear Wavepacket Dynamics of Alkali Adsorbates on Metal Surfaces Studied by Time-Resolved Second Harmonic Generation". Physics Research International 2012 (11 de abril de 2012): 1–8. http://dx.doi.org/10.1155/2012/172987.

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This paper reviews recent efforts to understand the dynamics of coherent surface vibrations of alkali atoms adsorbed on metal surfaces. Time-resolved second harmonic generation is used for the coherent excitation and detection of the nuclear wavepacket dynamics of the surface modes. The principles of the measurement and the experimental details are described. The main focus is on coverage and excitation photon energy dependences of the coherent phonon dynamics for Na-, K-, and Cs-covered Cu(111). The excitation mechanism of the coherent phonon has been revealed by the ultrafast time-domain technique and theoretical modelings.

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34

TAKAYAMA, YASUHIRO, HIDEO OHTSUBO, MOTOKI SHINODA, KENJI OBU, CHOL LEE, HIDETSUGU SHIOZAWA, HIROYOSHI ISHII, TSUNEAKI MIYAHARA y JUN OKAMOTO. "MAGNETIC CIRCULAR DICHROISM OF 4d–4f RESONANT X-RAY EMISSION FOR GADOLINIUM AND TERBIUM". Surface Review and Letters 09, n.º 02 (abril de 2002): 837–41. http://dx.doi.org/10.1142/s0218625x02003020.

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We have measured the magnetic circular dichroism (MCD) of X-ray emission spectra (XES) for gadolinium and terbium in the 4d–4f resonant excitation region. Clear MCD signals in the XES were observed and they dramatically changed as the excitation energy changed. Especially, an extremely large MCD signal appeared with the 8D resonant excitation for gadolinium. Comparison between the MCD for XES and total photoelectron yield (TEY) shows that the XES are very insensitive to the surface state. As a result, the measurement of XES was proved to be a superior technique for estimating the genuine magnetic moment in the bulk.

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35

Rocchini, M., K. Hadyńska-Klȩk, A. Nannini, J. J. Valiente-Dobón, A. Goasduff, D. Testov, P. R. John et al. "First measurement with a new setup for low-energy Coulomb excitation studies at INFN LNL". Physica Scripta 92, n.º 7 (7 de junio de 2017): 074001. http://dx.doi.org/10.1088/1402-4896/aa7162.

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36

Delaunay, F. y F. M. Nunes. "On the measurement of B(E2, 0+1 → 2+1) using intermediate-energy Coulomb excitation". Journal of Physics G: Nuclear and Particle Physics 34, n.º 10 (12 de septiembre de 2007): 2207–13. http://dx.doi.org/10.1088/0954-3899/34/10/010.

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37

Verhoef, A. J., A. V. Mitrofanov, X. T. Nguyen, M. Krikunova, S. Fritzsche, N. M. Kabachnik, M. Drescher y A. Baltuška. "Time-and-energy-resolved measurement of Auger cascades following Kr 3d excitation by attosecond pulses". New Journal of Physics 13, n.º 11 (3 de noviembre de 2011): 113003. http://dx.doi.org/10.1088/1367-2630/13/11/113003.

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38

Arai, Masatoshi y Jens-Erik Jørgensen. "Low energy excitation measurement on epoxy resin: The possibility of fracton and phonon-assisted migration". Physics Letters A 133, n.º 1-2 (octubre de 1988): 70–74. http://dx.doi.org/10.1016/0375-9601(88)90739-6.

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39

AGARWAL, AVINASH, I. A. RIZVI, RAKESH KUMAR, B. K. YOGI y A. K. CHAUBEY. "MEASUREMENT AND ANALYSIS OF EXCITATION FUNCTIONS AND FORWARD RECOIL RANGE DISTRIBUTIONS IN 12C + 59Co SYSTEM". International Journal of Modern Physics E 17, n.º 02 (febrero de 2008): 393–406. http://dx.doi.org/10.1142/s0218301308007009.

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With the motivation of studying complete and incomplete fusion reactions in a 12 C +59 Co projectile target system, the excitation functions for ( C , p3n ), ( C , 2p2n ), ( C , αn ), ( C , α2n ), ( C , αp3n ) and ( C , 2α2n ) reactions have been measured up to 80 MeV. The well-known activation technique followed by offline high purity Ge γ-ray spectroscopy was used. The measured experimental values were compared with the statistical model calculations by using the ALICE-91 and CASCADE codes. For the calculations obtained by CASCADE, the variation of parameter Fθ, which is the ratio of actual moment of inertia to the rigid body value have also been studied. Considerable enhancement of the measured excitation functions compared to theoretical predictions for some channels clearly indicates the presence of incomplete fusion with complete fusion in the present projectile energy range. The measurements of forward recoil range distribution of evaporation residues at 80 MeV projectile energy confirm these observations.

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40

Xu, Zhao-Dong, Shu Li y Xin Zeng. "Distributed Strain Damage Identification Technique for Long-Span Bridges Under Ambient Excitation". International Journal of Structural Stability and Dynamics 18, n.º 11 (22 de octubre de 2018): 1850133. http://dx.doi.org/10.1142/s021945541850133x.

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Distributed strain measurement, such as long-gauge fiber bragger grating (FBG) techniques, has developed rapidly in the field of structural health monitoring. However, strategies of corresponding damage identification still need to be enhanced. The damage identification technique based on distributed strain measurement is proposed identifying the structural damage under ambient excitation. Damage indices, like the distributed strain energy difference (DSED) and the relative distributed strain energy (RDSE), are derived from the power spectral density of the frequency response function of distributed strain response and further employed by detecting damages in the structure. A numerical analysis is performed on a long-span cable-stayed bridge with several assumed damage scenarios at various degrees in the girder. Damage localization capability and robustness of the proposed damage indices are discussed. In addition, damage quantification utilizing the proposed indices is conducted. The results indicate that the proposed technique can accurately identify the locations and extent of the damage under ambient vibration excitation.

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41

Oravcová, Monika, Peter Palček, Mária Chalupová y Milan Uhríčik. "Temperature dependent measurement of internal damping of austenitic stainless steels". MATEC Web of Conferences 157 (2018): 07008. http://dx.doi.org/10.1051/matecconf/201815707008.

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This article is aimed on the analysis of the internal damping changes of austenitic stainless steels AISI 304, AISI 316L and AISI 316Ti depending from temperature. In experimental measurements only resonance method was used which is based on continuous excitation of oscillations of the specimens and the whole apparatus vibrates at the frequency near to the resonance. Microplastic processes and dissipation of energy within the metals are evaluated and investigated by internal damping measurements. Damping capacity of materials is closely tied to the presence of defects including second phase particles and voids. By measuring the energy dissipation in the material, we can determine the elastic characteristics, Youngs modulus, the level of stress relaxation and many other.

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42

Pella, P. A. y C. G. Soares. "Secondary Target X-ray Excitation for In Vivo Measurement of Lead in Bone". Advances in X-ray Analysis 34 (1990): 293–98. http://dx.doi.org/10.1154/s0376030800014580.

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Environmental lead exposure continues to be a health hazard, especially to young children, and is a serious problem In the U.S. Since lead is stored in the skeleton, measurement of lead in bone (e.g. finger or tibia) can serve as an Indicator of lifetime exposure. Energy-dispersive x-ray fluorescence (XRF) currently seems to be the method of choice for non-Invasive testing, and is expected to be further developed for screening purposes.

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43

SAITO, SHINGO y TOHRU SUEMOTO. "SPATIAL AND MOMENTUM DIFFUSION OF ENERGETIC HOLES IN InAs BY TWO COLOR PUMP-PROBE METHOD". International Journal of Modern Physics B 15, n.º 28n30 (10 de diciembre de 2001): 3932–35. http://dx.doi.org/10.1142/s0217979201009037.

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Time-resolved electronic Raman scattering of a direct-gap semiconductor, InAs was measured by pump-probe method. We used fundamental pulses and second harmonic pulses of mode-locked Ti:S laser as excitation sources, and fundamental pulses as the probe beam. The time-resolved Raman intensities corresponding to the transition from heavy hole band to light hole band showed different features depending on the excitation energy. In case of the fundamental beam excitation, Raman intensity decreased monotonously. On the contrary, Raman intensity under the second harmonic excitation showed a maximum at a few picosecond after excitation. From the analysis, the temperature of photo-excited hole changed from 5300K to 1300K in 2psec and from 1300K to RT within 4 psec under the second harmonics excitation. It has been shown that the time-resolved Raman scattering measurement is a useful tool to investigate dynamics of the energetic carriers.

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44

Meissner, Axel, Jens ø. Duus y Ole Winneche Sørensen. "Spin-State-Selective Excitation. Application for E.COSY-Type Measurement ofJHHCoupling Constants". Journal of Magnetic Resonance 128, n.º 1 (septiembre de 1997): 92–97. http://dx.doi.org/10.1006/jmre.1997.1213.

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45

Grochowalski, Jacek Michał y Tomasz Chady. "Pulsed Multifrequency Excitation and Spectrogram Eddy Current Testing (PMFES-ECT) for Nondestructive Evaluation of Conducting Materials". Materials 14, n.º 18 (15 de septiembre de 2021): 5311. http://dx.doi.org/10.3390/ma14185311.

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This paper presents a new method for nondestructive testing—a pulsed multifrequency excitation and spectrogram eddy current testing (PMFES-ECT), which is an extension of the multifrequency excitation and spectrogram eddy current testing. The new method uses excitation in the form of pulses repeated at a specified time, containing several periods of a waveform consisting of the sum of sinusoids with a selected frequency, amplitude and phase. This solution allows the maintenance of the advantages of multifrequency excitation and, at the same time, generates high energy pulses similar to those used in pulse eddy current testing (PECT). The effectiveness of the new method was confirmed by numerical simulations and the measurement of thin Inconel plates, consisting of notches manufactured by the electric-discharge method.

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46

Lundberg, Karl-Ola. "An Alternative Method for Measurement of Airborne Sound Insulation". Building Acoustics 8, n.º 1 (marzo de 2001): 57–74. http://dx.doi.org/10.1260/1351010011501731.

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A method for determination of the transmission coefficient from Complex Modulation Transfer Functions CMTF:s based on measured impulse-responses is shown. In the method a separate measurement of the equivalent sound absorption area is not needed in contrast to in the standardised measurement. By averaging over a number of estimates of the impulse-response the influence of background noise can be reduced substantially, implying that low-power sources can be used. A model for the power balance in the receiving room with time-varying power is considered. In the model the quotient of the receiving room intensity and the source room intensity has one pole, which is proportional to the equivalent sound absorption area in the receiving room, and a gain, proportional to the transmission coefficient. In the physical system the power can be time-varied by letting the system excitation signal consist of random noise modulated with a deterministic time-varying function. However, since the ensemble average of the squared response is proportional to the squared impulse-response convolved with the squared modulating function, random excitation is avoided and replaced by impulse-response measurements. The quotient of intensities in the model is in the physical system a quotient of CMTF:s. Experiments are carried out in an airborne sound insulation laboratory. For comparison, standardised measurements are also carried out. It is found that the presented method gives as result comparatively small transmission coefficients, though the relative differences are small. By refining the power balance model by introducing an energy propagation time delay, and selecting an appropriate delay, the differences were diminished.

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47

Agarwal, Avinash, I. A. Rizvi y A. K. Chaubey. "Non-equilibrium emission of neutrons in α-particle induced reactions with holmium". Canadian Journal of Physics 86, n.º 3 (1 de marzo de 2008): 495–500. http://dx.doi.org/10.1139/p07-133.

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The stacked-foil activation technique followed by off line high-purity Ge γ-ray spectroscopy was used for the measurement of the excitation functions for energies up to 50 MeV for the 165Ho(α, 2n) 167Tm, 165Ho(α, 3n) 166Tm, and 165Ho(α, 4n) 165Tm reactions. The measured excitation functions were compared with theoretical predications considering equilibrium as well as pre-equilibrium reaction mechanisms according to the geometry-dependent hybrid (GDH) model of Blann using computer code ALICE-91. The high-energy parts of the excitation functions are due to the pre-equilibrium reaction mechanism, while the low-energy parts are mediated by compound-nucleus decay. It was found that the compound-nucleus-decay mechanism alone is unable to explain the experimental trend of our data. The pre-equilibrium fraction was also calculated. PACS Nos.: 22.55.–e, 27.60.+j

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48

Yu, D. H., P. A. Hayes, J. F. Williams y J. E. Furst. "Polarised Electron Study of Angular Momentum Coupling in the Neon 3p States". Australian Journal of Physics 50, n.º 3 (1997): 639. http://dx.doi.org/10.1071/p96106.

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The excitation of the 2p5 3p[]3 and 2p5 3p′[½]1 states in the neon 3p manifold by transversally polarised electrons is studied in the electron energy region near threshold and beyond. The spin-orbit and exchange interactions during the excitation are explored by the measurement of integrated Stokes parameters P2 and P3 for the decay radiation from these states. Experimental evidence is given for the breakdown of LS coupling for the neon 3p (J = 1) state and the important role of spin–orbit and exchange interactions of the atomic electrons for the excitation of the state. Negative ion resonances strongly influence the polarisations of the decay radiations.

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49

Ahn, C. C. y O. L. Krivanek. "Excited State Lifetime Measurement By EEL-CL Coincidence". Proceedings, annual meeting, Electron Microscopy Society of America 43 (agosto de 1985): 406–7. http://dx.doi.org/10.1017/s0424820100118904.

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The lifetime of an excited state can be measured by detecting both the excitation (by EELS) and the de-excitation (by catho- doluminescence), and measuring the delay between the two events. We have adapted this technique for the measurement of lifetimes in an electron microscope.The experimental set-up is shown in Fig. 1. The arrival time and the energy loss of single electrons is monitored by the EELS (Gatan 607), and the arrival time and wavelength of single photons is monitored by the CL spectrometer. Pulses corresponding to the two events are fed to a time-to-amplitude converter (TAC), which outputs a variable height pulse proportional to the delay between the events. If no second (stop) pulse is detected within a preset time interval, the TAC recognizes a “false start”, does not output anything, and starts looking for a “start” pulse again. Since the count rate in the CL channel was typically 10 to 100 times weaker than in the EEL channel, we minimized the false starts by using the CL signal as the start pulse and the EEL signal, suitably delayed, as the stop pulse. This yields a “reversed time” spectrum, but minimizes the dead time of the electronics.

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50

Kreckel, Holger, Annemieke Petrignani, Oldřich Novotný, Kyle Crabtree, Henrik Buhr, Benjamin J. McCall y Andreas Wolf. "Storage ring measurements of the dissociative recombination of H 3 +". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, n.º 1978 (13 de noviembre de 2012): 5088–100. http://dx.doi.org/10.1098/rsta.2012.0019.

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The dissociative recombination (DR) of is a key process in interstellar chemistry. More than 30 experimental studies of the DR process have been published in the literature. The DR rate coefficient results obtained from these measurements, however, have not always been consistent. The outcome seems to depend on the experimental method, on the exact measurement procedure and sometimes even on the interpretation of the experimental data. In the past two decades, heavy-ion storage rings have become the working horse for DR measurements, as they provide a direct measurement of the DR products. Furthermore, storage ring measurements yield energy-resolved rate coefficients with unprecedented resolution that allow for detailed comparison with theory. DR results from different storage ring facilities have shown a remarkable consistency throughout the years and they provide additional information on break-up dynamics and internal excitation. In this study, we will review the storage ring DR measurements that have been carried out for .

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