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Автор: Grafiati
Опубліковано: 7 вересня 2023

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1

YU, Jae-Hyeong, and Chang-Whan Lee. "Study on the Time-Dependent Mechanical Behavior and Springback of Magnesium Alloy Sheet (AZ31B) in Warm Conditions." Materials 14, no. 14 (July 9, 2021): 3856. http://dx.doi.org/10.3390/ma14143856.

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Анотація:
In this study, the time-dependent mechanical behavior of the magnesium alloy sheet (AZ31B) was investigated through the creep and stress relaxation tests with respect to the temperature and pre-strain. The microstructure changes during creep and stress relaxation were investigated. As the tensile deformation increased in the material, twinning and dynamic recrystallization occurred, especially after the plastic instability. As a result, AZ31B showed lower resistance to creep and stress relaxation due to dynamic recrystallization. Additionally, time-dependent springback characteristics in the V- and L-bending processes concerning the holding time and different forming conditions were investigated. We analyzed changes of microstructure at each forming temperature and process. The uniaxial tensile creep test was conducted to compare the microstructures in various pre-strain conditions with those at the secondary creep stage. For the bending process, the change of the microstructure after the forming was compared to that with punch holding maintained for 1000 s after forming. Due to recrystallization, with the holding time in the die set of 60 s, the springback angle decreased by nearly 70%. Increased holding time in the die set resulted in a reduced springback angle.
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2

Sbrescia, Simone, Tom Engels, Evelyne Van Ruymbeke, and Michelle Seitz. "Molecular weight effects on the stress-relaxation behavior of soft thermoplastic elastomer by means of temperature scanning stress relaxation (TSSR)." Journal of Rheology 66, no. 6 (November 1, 2022): 1321–30. http://dx.doi.org/10.1122/8.0000444.

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Анотація:
The mechanical properties of multiblock copolymer thermoplastic elastomers (TPEs) are governed by the interplay of different reversible dynamics [e.g., hard block (HB) association and chain entanglements]. Understanding how these physical processes influence the high-temperature deformation behavior is relevant as many TPEs lose toughness with increasing temperature. Increasing molecular weight (Mw) improves their temperature resistance that is attributed to an increase in network connectivity. Indeed, longer chains are characterized by more HBs per chain and by a longer lifetime of the entanglements in the amorphous phase. Both the associating HB and disentanglement dynamics are temperature and rate dependent. To further understand the interconnected role of Mw, temperature and rate dependencies on the mechanical properties, we perform Temperature Scanning Stress Relaxation (TSSR) tests. The method consists of measuring the stress relaxation of the materials as the temperature monotonically increases, allowing us to probe the stress response as the HBs progressively disassociate due to the increase in temperature. The results show that increasing Mw improves the high-temperature relaxation behavior, allowing the material to retain more stress than its low Mw counterpart as the temperature increases. This distinction does not show itself when performing standard small strain dynamic mechanical thermal analyses. Depending on the deformation experienced before the TSSR is performed, different relaxation behaviors are observed illustrating the importance of the current microstructure in determining the mechanical properties. The TSSR approach is well-suited to benchmark the high-temperature stress-bearing properties of network-based polymers whose morphology and, hence, properties are strongly deformation dependent.
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3

Peng, Fan, Xiumei Zhang, Xiuming Wang, and Hao Chen. "Dynamic permeability in porous media and identification of pore fluids by using borehole Stoneley wave." Journal of Geophysics and Engineering 19, no. 3 (May 24, 2022): 336–45. http://dx.doi.org/10.1093/jge/gxac021.

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Анотація:
Abstract The sound field in porous media is affected by fluid flow governed by dynamic permeability. This macroscopic quantity is frequency dependent and can be connected with a relevant pore-scale estimation called the stochastic dynamic permeability (SDP) model. To further investigate the characteristics of the SDP model with different variables related to Biot relaxation frequency and envisage its potential applications in borehole acoustics, the influence of microstructures from a pore-scale image on dynamic permeability is studied. Then, the characteristics of dynamic permeability and a borehole Stoneley wave with different parameters are explored by sensitivity analysis. According to the influences of pore fluid parameters including density and viscosity, the velocity dispersion and attenuation of Stoneley waves in oil, gas and water-bearing formations are calculated. The results show that the dynamic permeability is affected by the microstructure of pores and the Biot relaxation frequency parameters have a crucial influence on the attenuation of the borehole Stoneley wave. Meanwhile, the attenuation coefficient can be used to identify the type of pore fluids. This is verified by an application to in situ acoustic logging data. The work provides a relatively comprehensive understanding of the features of the SDP dynamic permeability and indicates an approach to identify pore fluid by using a borehole Stoneley wave.
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4

Florêncio, Odila, Paulo Sergio Silva, Rosane Ribeiro, Javier Andres Muñoz Chaves, F. H. Sá, Fábio X. Melo, and Sandra G. Schneider. "Elastic Behavior of the Ti-13Nb-13Zr Alloy Obtained by Anelastic Spectroscopy." Defect and Diffusion Forum 283-286 (March 2009): 84–89. http://dx.doi.org/10.4028/www.scientific.net/ddf.283-286.84.

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Анотація:
Measurements of anelastic relaxation (internal friction and frequency) as a function of temperature were carried out in samples of Ti-13Nb-13Zr using two experimental apparatus: Flexural Vibration of the first tone of samples in Acoustic Elastometer System (Vibran Technology®) operating in a kilohertz bandwidth, and Torsional Vibration of the samples in Kê-type Torsion Pendulum operating in a hertz bandwidth. Experimental spectra of anelastic relaxation were determined in the temperature range from 300 K to 450 K for a heating rate of 1K/min under pressure of 10-5 Torr, in both apparatus. The results show a relaxation structure strongly dependent on the microstructure of the material. The dynamical elastic modulus (E) of Ti-13Nb-13Zr alloy can be determined by flexural vibrations by frequency (f) measurements (f  E1/2). The anelastic relaxation spectrum of Ti-13Nb-13Zr alloy was a function of temperature obtained by torsional vibrations, not revealing the presence of interstitial solutes in solid solution in the temperature range of measurements.
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5

Astafurova, Elena, Anastasiya Fortuna, Evgenii Melnikov, and Sergey Astafurov. "The Effect of Strain Rate on Hydrogen-Assisted Deformation Behavior and Microstructure in AISI 316L Austenitic Stainless Steel." Materials 16, no. 8 (April 9, 2023): 2983. http://dx.doi.org/10.3390/ma16082983.

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Анотація:
The influence of strain rate in the interval of (10−5–10−3) 1/s on room temperature tensile behavior, dislocation arrangement, deformation mechanisms, and fracture of austenitic stainless steel AISI 316L electrochemically charged with hydrogen was investigated. Independently on strain rate, hydrogen charging provides the increase in the yield strength of the specimens due to a solid solution hardening of austenite, but it slightly influences deformation behavior and strain hardening of the steel. Simultaneously, hydrogen charging assists surface embrittlement of the specimens during straining and reduces an elongation to failure, which both are strain rate-dependent parameters. Hydrogen embrittlement index decreases with increase in strain rate, which testifies the importance of hydrogen transport with dislocations during plastic deformation. The stress–relaxation tests directly confirm the hydrogen-enhanced increase in the dislocation dynamics at low strain rates. The interaction of the hydrogen atoms with dislocations and hydrogen-associated plastic flow are discussed.
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6

Muhlestein, Michael B., and Michael R. Haberman. "A micromechanical approach for homogenization of elastic metamaterials with dynamic microstructure." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2192 (August 2016): 20160438. http://dx.doi.org/10.1098/rspa.2016.0438.

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Анотація:
An approximate homogenization technique is presented for generally anisotropic elastic metamaterials consisting of an elastic host material containing randomly distributed heterogeneities displaying frequency-dependent material properties. The dynamic response may arise from relaxation processes such as viscoelasticity or from dynamic microstructure. A Green's function approach is used to model elastic inhomogeneities embedded within a uniform elastic matrix as force sources that are excited by a time-varying, spatially uniform displacement field. Assuming dynamic subwavelength inhomogeneities only interact through their volume-averaged fields implies the macroscopic stress and momentum density fields are functions of both the microscopic strain and velocity fields, and may be related to the macroscopic strain and velocity fields through localization tensors. The macroscopic and microscopic fields are combined to yield a homogenization scheme that predicts the local effective stiffness, density and coupling tensors for an effective Willis-type constitutive equation. It is shown that when internal degrees of freedom of the inhomogeneities are present, Willis-type coupling becomes necessary on the macroscale. To demonstrate the utility of the homogenization technique, the effective properties of an isotropic elastic matrix material containing isotropic and anisotropic spherical inhomogeneities, isotropic spheroidal inhomogeneities and isotropic dynamic spherical inhomogeneities are presented and discussed.
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7

Brechtl, Jamieson, Zhong Wang, Xie Xie, Jun-Wei Qiao, and Peter K. Liaw. "Relation Between the Defect Interactions and the Serration Dynamics in a Zr-Based Bulk Metallic Glass." Applied Sciences 10, no. 11 (June 4, 2020): 3892. http://dx.doi.org/10.3390/app10113892.

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Анотація:
For this study, the effects of thermal annealing and compressive strain rate on the complexity of the serration behavior in a Zr-based bulk metallic glass (BMG) was investigated. Here, as-cast and thermally-annealed (300 °C, 1 week) Zr52.5Cu17.9Ni14.6Al10Ti5 BMG underwent room-temperature compression tests in the unconstrained condition at strain rates of 2 × 10−5 s−1 and 2 × 10−4 s−1. The complexity of the serrated flow was determined, using the refined composite multiscale entropy technique. Nanoindentation testing and X-ray diffraction characterization were performed to assess the changes in the microstructure and mechanical properties of the BMG that occurred during annealing. The results indicated that the BMG did not crystallize during annealing in the prescribed heating condition. Nanoindentation tests revealed that annealing led to a significant increase in the depth-dependent nanoindentation hardness and Young’s modulus, which were attributed to the structural relaxation in the glass. Furthermore, both annealing and an increased strain rate resulted in a marked enhancement in the complexity of the serrated flow during compression. It was concluded that the increase in the sample entropy with increasing strain rate is related to an increase in the number of defect interactions during the serrated flow.
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8

Yin, Lihong, Harold Bien, and Emilia Entcheva. "Scaffold topography alters intracellular calcium dynamics in cultured cardiomyocyte networks." American Journal of Physiology-Heart and Circulatory Physiology 287, no. 3 (September 2004): H1276—H1285. http://dx.doi.org/10.1152/ajpheart.01120.2003.

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Анотація:
Structural and functional changes ensue in cardiac cell networks when cells are guided by three-dimensional scaffold topography. We report enhanced synchronous pacemaking activity in association with slow diastolic rise in intracellular Ca2+ concentration ([Ca2+]i) in cell networks grown on microgrooved scaffolds. Topography-driven changes in cardiac electromechanics were characterized by the frequency dependence of [Ca2+]i in syncytial structures formed of ventricular myocytes cultured on microgrooved elastic scaffolds (G). Cells were electrically paced at 0.5–5 Hz, and [Ca2+]i was determined using microscale ratiometric (fura 2) fluorescence. Compared with flat (F) controls, the G networks exhibited elevated diastolic [Ca2+]i at higher frequencies, increased systolic [Ca2+]i across the entire frequency range, and steeper restitution of Ca2+ transient half-width ( n = 15 and 7 for G and F, respectively, P < 0.02). Significant differences in the frequency response of force-related parameters were also found, e.g., overall larger total area under the Ca2+ transients and faster adaptation of relaxation time to pacing rate ( P < 0.02). Altered [Ca2+]i dynamics were paralleled by higher occurrence of spontaneous Ca2+ release and increased sarcoplasmic reticulum load ( P < 0.02), indirectly assessed by caffeine-triggered release. Electromechanical instabilities, i.e., Ca2+ and voltage alternans, were more often observed in G samples. Taken together, these findings 1) represent some of the first functional electromechanical data for this in vitro system and 2) demonstrate direct influence of the microstructure on cardiac function and susceptibility to arrhythmias via Ca2+-dependent mechanisms. Overall, our results substantiate the idea of guiding cellular phenotype by cellular microenvironment, e.g., scaffold design in the context of tissue engineering.
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9

Dierdorf, Jens, Johannes Lohmar, and Gerhard Hirt. "Investigation on Hardening and Softening Behavior of Steel after Rapid Strain Rate Changes." Key Engineering Materials 716 (October 2016): 121–28. http://dx.doi.org/10.4028/www.scientific.net/kem.716.121.

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Анотація:
The design of industrial hot metal forming processes nowadays is mostly carried out using commercial Finite Element (FE) software codes. For precise FE simulations, reliable material properties are a crucial factor. In bulk metal forming, the most important material property is the materials flow stress, which determines the form filling and the necessary forming forces. At elevated temperatures, the flow stress of steels is determined by strain hardening, dynamic recovery and partly by dynamic recrystallization, which is dependent on strain rate and temperature. To simulate hot forming processes, which are often characterized by rapidly changing strain rates and temperatures, the flow stress is typically derived from flow curves, determined at arbitrary constant temperatures and strain rates only via linear interpolation. Hence, the materials instant reaction and relaxation behavior caused by rapid strain rate changes is not captured during simulation. To investigate the relevance of the relaxation behavior for FE simulations, trails with abrupt strain rate change are laid out and the effect on the material flow stress is analyzed in this paper. Additionally, the microstructure evolution due to the strain rate change is investigated. For this purpose, cylinder compression tests of an industrial case hardening steel are conducted at elevated temperatures and different strain rates. To analyze the influence of rapid strain rate changes, changes by one power of ten are performed at a strain of 0.3. As a reference, flow curves of the same material are determined at the initial and final constant strain rate. To investigate the microstructure evolution, compression samples are quenched at different stages, before and after the strain rate change. The results show that the flow curves after the strain rate change tend to approximate the flow curves measured for the final strain rate. However, directly after the strain rate change significant differences between the assumed instant flow stress and the real material behavior can be observed. Furthermore, it can be shown that the state of dynamic recrystallization at the time of the strain rate change influences the material response and relaxation behavior resulting in different slopes of the investigated flow curves after the strain rate change.
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10

Parnell, William J., and Riccardo De Pascalis. "Soft metamaterials with dynamic viscoelastic functionality tuned by pre-deformation." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2144 (March 18, 2019): 20180072. http://dx.doi.org/10.1098/rsta.2018.0072.

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Анотація:
The small amplitude dynamic response of materials can be tuned by employing inhomogeneous materials capable of large deformation. However, soft materials generally exhibit viscoelastic behaviour, i.e. loss and frequency-dependent effective properties. This is the case for inhomogeneous materials even in the homogenization limit when propagating wavelengths are much longer than phase lengthscales, since soft materials can possess long relaxation times. These media, possessing rich frequency-dependent behaviour over a wide range of low frequencies, can be termed metamaterials in modern terminology. The sub-class that are periodic are frequently termed soft phononic crystals although their strong dynamic behaviour usually depends on wavelengths being of the same order as the microstructure. In this paper we describe how the effective loss and storage moduli associated with longitudinal waves in thin inhomogeneous rods are tuned by pre-stress. Phases are assumed to be quasi-linearly viscoelastic, thus exhibiting time-deformation separability in their constitutive response. We illustrate however that the effective incremental response of the inhomogeneous medium does not exhibit time-deformation separability. For a range of nonlinear materials it is shown that there is strong coupling between the frequency of the small amplitude longitudinal wave and initial large deformation. This article is part of the theme issue ‘Rivlin's legacy in continuum mechanics and applied mathematics’.
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11

Terentjev, E. M., A. Hotta, S. M. Clarke, and M. Warner. "Liquid crystalline elastomers: dynamics and relaxation of microstructure." Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 361, no. 1805 (February 28, 2003): 653–64. http://dx.doi.org/10.1098/rsta.2002.1155.

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12

Karam, Tony E., Noureen Siraj, Isiah M. Warner, and Louis H. Haber. "Anomalous Size-Dependent Excited-State Relaxation Dynamics of NanoGUMBOS." Journal of Physical Chemistry C 119, no. 50 (December 7, 2015): 28206–13. http://dx.doi.org/10.1021/acs.jpcc.5b09729.

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13

Clayton, Andrew H. A. "Spectral Relaxation Imaging Microscopy II: Complex Dynamics." International Journal of Molecular Sciences 24, no. 15 (July 31, 2023): 12271. http://dx.doi.org/10.3390/ijms241512271.

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Анотація:
The dynamics of condensed matter can be measured by the time-dependent Stokes shift of a suitable fluorescent probe. The time-dependent spectral correlation function is typically described by one or more spectral relaxation correlation times, which, in liquid solvents, characterize the timescales of the dipolar relaxation processes around the excited-state probe. The phasor plot provides a powerful approach to represent and analyze time and frequency-domain data acquired as images, thus providing a spatial map of spectral dynamics in a complex structure such as a living cell. Measurements of the phase and modulation at two emission wavelength channels were shown to be sufficient to extract a single excited-state lifetime and a single spectral relaxation correlation time, supplying estimates of the mean rate of excited-state depopulation and the mean rate of spectral shift. In the present contribution, two more issues were addressed. First, the provision of analytic formulae allowing extraction of the initial generalized polarization and the relaxed generalized polarization, which characterize the fluorescence spectrum of the unrelaxed state and the fully relaxed state. Second, improved methods of model discrimination and model parameter extraction for more complex spectral relaxation phenomena. The analysis workflow was illustrated with examples from the literature.
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14

Salvi, Nicola, Anton Abyzov, and Martin Blackledge. "Solvent-dependent segmental dynamics in intrinsically disordered proteins." Science Advances 5, no. 6 (June 2019): eaax2348. http://dx.doi.org/10.1126/sciadv.aax2348.

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Анотація:
Protein and water dynamics have a synergistic relationship, which is particularly important for intrinsically disordered proteins (IDPs), although the details of this coupling remain poorly understood. Here, we combine temperature-dependent molecular dynamics simulations using different water models with extensive nuclear magnetic resonance (NMR) relaxation to examine the importance of distinct modes of solvent and solute motion for the accurate reproduction of site-specific dynamics in IDPs. We find that water dynamics play a key role in motional processes internal to “segments” of IDPs, stretches of primary sequence that share dynamic properties and behave as discrete dynamic units. We identify a relationship between the time scales of intrasegment dynamics and the lifetime of hydrogen bonds in bulk water. Correct description of these motions is essential for accurate reproduction of protein relaxation. Our findings open important perspectives for understanding the role of hydration water on the behavior and function of IDPs in solution.
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15

Kundu, S. K., S. Choe, K. Sasaki, R. Kita, N. Shinyashiki, and S. Yagihara. "Relaxation dynamics of liposomes in an aqueous solution." Physical Chemistry Chemical Physics 17, no. 28 (2015): 18449–55. http://dx.doi.org/10.1039/c5cp01334h.

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Анотація:
The gel–liquid crystal phase transition has been studied by the temperature and frequency dependent dielectric relaxation behavior of liposomes in an aqueous solution (40 g L−1 DPPC–water mixture).
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16

YANG, ZHENYU, and YA-PU ZHAO. "SIZE-DEPENDENT ELASTIC PROPERTIES OF Ni NANOFILMS BY MOLECULAR DYNAMICS SIMULATION." Surface Review and Letters 14, no. 04 (August 2007): 661–65. http://dx.doi.org/10.1142/s0218625x07010032.

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Анотація:
Size-dependent elastic properties of Ni nanofilms are investigated by molecular dynamics (MD) simulations with embedded atom method (EAM). The surface effects are considered by calculating the surface relaxation, surface energy, and surface stress. The Young's modulus and yield stress are obtained as functions of thickness and crystallographic orientation. It is shown that the surface relaxation has important effects on the the elastic properties at nanoscale. When the surface relaxation is outward, the Young's modulus decreases with the film thickness decreasing, and vice versa. The results also show that the yield stresses of the films increase with the films becoming thinner. With the thickness of the nanofilms decreasing, the surface effects on the elastic properties become dominant.
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17

Madsen, D., C. L. Thomsen, J. Thøgersen, and S. R. Keiding. "Temperature dependent relaxation and recombination dynamics of the hydrated electron." Journal of Chemical Physics 113, no. 3 (July 15, 2000): 1126–34. http://dx.doi.org/10.1063/1.481891.

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18

Lu, Dong-Xiao, Ying-Hui Wang, Fang-Fei Li, Xiao-Li Huang, Ling-Yun Pan, Yuan-Bo Gong, Bo Han, Qiang Zhou, and Tian Cui. "Pressure-Dependent Relaxation Dynamics of Excitons in Conjugated Polymer Film." Journal of Physical Chemistry C 119, no. 23 (May 26, 2015): 13194–99. http://dx.doi.org/10.1021/acs.jpcc.5b04441.

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19

Zheng, Guang Ping, Z. Han, and Y. Z. Liu. "The Microstructural, Mechanical and Electro-Mechanical Properties of Graphene Aerogel-PVDF Nanoporous Composites." Journal of Nano Research 29 (December 2014): 1–6. http://dx.doi.org/10.4028/www.scientific.net/jnanor.29.1.

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Анотація:
Graphene aerogel-poly (vinylidene fluoride) (GA-PVDF) nanoporous composites with different concentrations of PVDF are fabricated. Scanning electron microscopy reveals that PVDF films with a typical thickness below 100 nm are coated at the graphene sheets in the nanoporous composites. The GA-PVDF composites show excellent compressibility, ductility and mechanical strength, as well as better sensitivity of stress-dependent electrical resistance compared with those of GAs. The improved mechanical and electro-mechanical behaviours of nanoporous composites are ascribed to the PVDF which possesses piezoelectricity. The structural properties of the graphene-PVDF nanosized hybrid scaffolds are analyzed by dynamical mechanical relaxation. The results demonstrate that the nanoporous composites could be used as high-performance sensors, actuators and kinetic energy harvesters.
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20

Chizhik, V. I., A. V. Egorov, A. V. Komolkin, and A. A. Vorontsova. "Microstructure and dynamics of electrolyte solutions containing polyatomic ions by NMR relaxation and molecular dynamics simulation." Journal of Molecular Liquids 98-99 (May 2002): 173–82. http://dx.doi.org/10.1016/s0167-7322(01)00306-3.

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21

Brooksby, Craig, Oleg V. Prezhdo, and Philip J. Reid. "Molecular dynamics study of the weakly solvent dependent relaxation dynamics following chlorine dioxide photoexcitation." Journal of Chemical Physics 119, no. 17 (November 2003): 9111–20. http://dx.doi.org/10.1063/1.1614203.

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22

Asmussen, Jakob D., Rupert Michiels, Katrin Dulitz, Aaron Ngai, Ulrich Bangert, Manuel Barranco, Marcel Binz, et al. "Unravelling the full relaxation dynamics of superexcited helium nanodroplets." Physical Chemistry Chemical Physics 23, no. 28 (2021): 15138–49. http://dx.doi.org/10.1039/d1cp01041g.

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The relaxation dynamics of superexcited superfluid He nanodroplets is thoroughly investigated by means of extreme-ultraviolet (XUV) femtosecond electron and ion spectroscopy complemented by time-dependent density functional theory (TDDFT).
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23

Stepanyuk, V. S., A. Szasz, A. A. Katsnelson, O. S. Trushin, H. Müller, and H. Kirchmayr. "Microstructure and its relaxation in FeB amorphous system simulated by moleculular dynamics." Journal of Non-Crystalline Solids 159, no. 1-2 (June 1993): 80–87. http://dx.doi.org/10.1016/0022-3093(93)91284-a.

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24

Dvorsek, D., V. V. Kabanov, J. Demsar, J. Karpinski, S. M. Kazakov, and D. Mihailovic. "Femtosecond Pump-Probe Polarization Dependent Investigation of Relaxation Dynamics in YBa2Cu4O8." Journal of Superconductivity 17, no. 1 (February 2004): 89–92. http://dx.doi.org/10.1023/b:josc.0000011847.78265.4a.

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25

Sarkar, Rupa, Ajay Kumar Shaw, S. Shankara Narayanan, Carsten Rothe, Susanne Hintschich, Andy Monkman, and Samir Kumar Pal. "Size and shape-dependent electron–hole relaxation dynamics in CdS nanocrystals." Optical Materials 29, no. 11 (July 2007): 1310–20. http://dx.doi.org/10.1016/j.optmat.2006.06.006.

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26

Mohamed, Mona B., Clemens Burda, and Mostafa A. El-Sayed. "Shape Dependent Ultrafast Relaxation Dynamics of CdSe Nanocrystals: Nanorods vs Nanodots." Nano Letters 1, no. 11 (November 2001): 589–93. http://dx.doi.org/10.1021/nl0155835.

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27

Plokker, M. P., and E. van der Kolk. "Temperature dependent relaxation dynamics of luminescent NaX:Tm2+ (X=Cl, Br, I)." Journal of Luminescence 216 (December 2019): 116694. http://dx.doi.org/10.1016/j.jlumin.2019.116694.

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28

Qiu, Yun-Hang, Fan Nan, Ya-Fang Zhang, Jia-Hong Wang, Guan-Yang He, Li Zhou, and Qu-Quan Wang. "Size-dependent plasmon relaxation dynamics and saturable absorption in gold nanorods." Journal of Physics D: Applied Physics 49, no. 18 (April 8, 2016): 185107. http://dx.doi.org/10.1088/0022-3727/49/18/185107.

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29

Zhao, Chen, and Du. "Evolution of Dielectric Behavior of Regenerated Cellulose Film during Isothermal Dehydration Monitored in Real Time via Dielectric Spectroscopy." Polymers 11, no. 11 (October 24, 2019): 1749. http://dx.doi.org/10.3390/polym11111749.

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Анотація:
The dielectric relaxation behavior of a regenerated cellulose (RC) film during isothermal dehydration was monitored in real time via dielectric spectroscopy, in order to investigate on one hand the influence of water on its dynamics and the variation of microstructure and phase composition during dehydration on the other. The progression of water loss is clearly revealed by the evolution of the dielectric relaxation behavior with drying time, which suggests two distinctly different drying stages separated by a striking transition period. The dielectric relaxation behavior at the first drying stage is found overwhelmingly dominated by ionic motion, and that at the second stage is basically a result of molecular dynamics. The mechanisms of these relaxations are proposed, through which the influence of water on the dynamics of the RC film and the variation of the microstructure and phase composition of the film at different hydration state are discussed in detail. An interesting finding is that highly ordered but noncrystalline arrangement of cellulose molecules exists, but it can be formed only when the film is in specific hydration state. This study demonstrates that dielectric spectroscopy is an effective tool in real-time monitoring kinetic process.
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30

Czerwinski, Artur. "Entanglement Dynamics Governed by Time-Dependent Quantum Generators." Axioms 11, no. 11 (October 25, 2022): 589. http://dx.doi.org/10.3390/axioms11110589.

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In the article, we investigate entanglement dynamics defined by time-dependent linear generators. We consider multilevel quantum systems coupled to an environment that induces decoherence and dissipation, such that the relaxation rates depend on time. By applying the condition of partial commutativity, one can precisely describe the dynamics of selected subsystems. More specifically, we investigate the dynamics of entangled states. The concurrence is used to quantify the amount of two-qubit entanglement in the time domain. The framework appears to be an efficient tool for investigating quantum evolution of entangled states driven by time-local generators. In particular, non-Markovian effects can be included to observe the restoration of entanglement in time.
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31

Kober, Jan, Alena Kruisova, and Marco Scalerandi. "Elastic Slow Dynamics in Polycrystalline Metal Alloys." Applied Sciences 11, no. 18 (September 16, 2021): 8631. http://dx.doi.org/10.3390/app11188631.

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Elastic slow dynamics, consisting in a reversible softening of materials when an external strain is applied, was experimentally observed in polycrystalline metals and presents analogies with the same phenomenon more widely observed in consolidated granular media. Since the effect is extremely small in metals, precise experimental techniques are needed. Reliable measurement of relative velocity variations of the order of 10−7 is crucial to perform the analysis. In addition, the grain structure and the nature of grain boundaries in metals is very different from that in rocks or concrete. Therefore, linking relaxation elastic effects to the microstructure is needed to understand the physical origin of slow dynamics in metals. Here, interpreting the relaxation phenomenon as a multirelaxation process, we show that it is sensitive to the spatial scale at the microstructural level, up to the point of allowing the identification of the existence of features at different spatial scales, particularly distinguishing damage from microstructural inhomogeneities.
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32

Halle, Bertil, Per-Ola Quist, and István Furó. "Microstructure and dynamics in lyotropic liquid crystals. Principles and applications of nuclear spin relaxation." Liquid Crystals 14, no. 1 (January 1993): 227–63. http://dx.doi.org/10.1080/02678299308027314.

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33

Pradhan, Soumen, Martando Rath, Adrian David, Deepak Kumar, Wilfrid Prellier, and M. S. Ramachandra Rao. "Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K0.5Na0.5NbO3 Ferroelectric Thin Films." ACS Applied Materials & Interfaces 13, no. 30 (July 26, 2021): 36407–15. http://dx.doi.org/10.1021/acsami.1c05699.

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34

Chandra, Amalendu, and Biman Bagchi. "Breakdown of Onsager’s conjecture on distance dependent polarization relaxation in solvation dynamics." Journal of Chemical Physics 91, no. 4 (August 15, 1989): 2594–98. http://dx.doi.org/10.1063/1.457020.

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35

Hong, Tao, Zhengming Tang, and Huacheng Zhu. "Anomalous dielectric relaxation with linear reaction dynamics in space-dependent force fields." Journal of Chemical Physics 145, no. 24 (December 28, 2016): 244105. http://dx.doi.org/10.1063/1.4972863.

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36

Ichida, Masao, Satoshi Sakoda, Yumie Kiyohara, Singo Saito, Yasumitsu Miyata, Hiromichi Kataura, Ken-ichi Mizuno, and Hiroaki Ando. "Diameter-dependent relaxation dynamics of 1D excitons in single-walled carbon nanotubes." Journal of Luminescence 128, no. 5-6 (May 2008): 952–55. http://dx.doi.org/10.1016/j.jlumin.2007.11.037.

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37

Song, K. S., and R. T. Williams. "Temperature-dependent self-trapped exciton relaxation in alkali halides: molecular dynamics study." physica status solidi (b) 243, no. 14 (November 2006): 3782–94. http://dx.doi.org/10.1002/pssb.200672156.

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38

Flory, W. C., and G. J. Blanchard. "Excitation Energy-Dependent Transient Spectral Relaxation of Coumarin 153." Applied Spectroscopy 52, no. 1 (January 1998): 82–90. http://dx.doi.org/10.1366/0003702981942366.

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We report on the excitation energy-dependent transient spectral response of the polar dye molecule coumarin 153 (C153) in selected solvents. We find that the blue edge of the spontaneous emission spectrum of C153 contains several spectral features and that the relative contribution of these features to the overall response varies with the identity of the solvent and the excitation wavelength. The central result of these data is that the transient spectral response of C153 depends sensitively on the excitation wavelength and that the spectral evolution behavior of this molecule is therefore not related in a simple manner to solvent reorganization dynamics.
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39

Martínez Narváez, Carina D. V., Thomas Mazur, and Vivek Sharma. "Dynamics and extensional rheology of polymer–surfactant association complexes." Soft Matter 17, no. 25 (2021): 6116–26. http://dx.doi.org/10.1039/d1sm00335f.

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We find the aqueous PEO–SDS mixtures show a significantly weaker concentration-dependent variation in the extensional relaxation time, filament lifespan, and extensional viscosity values than anticipated by the shear viscosity vs. concentration plots.
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40

Gao, Hongyu. "History-Dependent Stress Relaxation of Liquids under High-Confinement: A Molecular Dynamics Study." Lubricants 10, no. 2 (January 19, 2022): 15. http://dx.doi.org/10.3390/lubricants10020015.

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When liquids are confined into a nanometer-scale slit, the induced layering-like film structure allows the liquid to sustain non-isotropic stresses and thus be load-bearing. Such anisotropic characteristics of liquid under confinement arise naturally from the liquids’ wavenumber dependent compressibility, which does not need solidification to take place as a prerequisite. In other words, liquids under confinement can still retain fluidity with molecules being (sub-)diffusive. However, the extensively prolonged structural relaxation times can cause hysteresis of stress relaxation of confined molecules in response to the motions of confining walls and thereby rendering the quasi-static stress tensors history-dependent. In this work, by means of molecular dynamics, stress tensors of a highly confined key base-oil component, i.e., 1-decene trimer, are calculated after its relaxation from being compressed and decompressed. A maximum of 77.1 MPa normal stress discrepancy has been detected within a triple-layer boundary film. Analyses with respect to molecular morphology indicate that among the effects (e.g., confinement, molecular structure, and film density) that can potentially affect confined stresses, the ordering status of the confined molecules plays a predominant role.
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41

Johnson, A. R., A. Tessler, and M. Dambach. "Dynamics of Thick Viscoelastic Beams." Journal of Engineering Materials and Technology 119, no. 3 (July 1, 1997): 273–78. http://dx.doi.org/10.1115/1.2812256.

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A viscoelastic higher-order thick beam finite element formulation is extended to include elastodynamic deformations. The material constitutive law is a special differential form of the Maxwell solid, which employs viscous strains as internal variables to determine the viscous stresses. The total time-dependent stress is the superposition of its elastic and viscous components. In the constitutive model, the elastic strains and the conjugate viscous strains are coupled through a system of first-order ordinary differential equations. The use of the internal strain variables allows for a convenient finite element formulation. The elastodynamic equations of motion are derived from the virtual work principle. Computational examples are carried out for a thick orthotropic cantilevered beam. Relaxation, creep, relaxation followed by free damped vibrations, and damping related modal interactions are discussed.
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42

Ghosh, Goutam, Bikash Jana, Sumanta Sain, Arnab Ghosh, and Amitava Patra. "Influence of shape on the carrier relaxation dynamics of CsPbBr3 perovskite nanocrystals." Physical Chemistry Chemical Physics 21, no. 35 (2019): 19318–26. http://dx.doi.org/10.1039/c9cp03386f.

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43

Roth, Benedikt, Wolfgang Wildner, and Dietmar Drummer. "Dynamic Compression Induced Solidification." Polymers 12, no. 2 (February 22, 2020): 488. http://dx.doi.org/10.3390/polym12020488.

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This study presents a method for the determination of the dynamic pressure-dependent solidification of polycarbonate (PC) during flow using high pressure capillary rheometer (HPC) measurements. In addition, the pressure-dependent solidification was determined by isothermal pressure-volume-temperature (pvT) measurements under static conditions without shear. Independent of the compression velocity, a linear increase of the solidification pressure with temperature could be determined. Furthermore, the results indicate that the relaxation time at a constant temperature and compression rate can increase to such an extent that the material can no longer follow within the time scale specified by the compression rate. Consequently, the flow through the capillary stops at a specific pressure, with higher compression rates resulting in lower solidification pressures. Consequently, in regard to HPC measurements, it could be shown that the evaluation of the pressure via a pressure hole can lead to measurement errors in the limit range. Since the filling process in injection molding usually takes place under such transient conditions, the results are likely to be relevant for modelling the flow processes of thin-walled and microstructures with high aspect ratios.
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44

Dey, Amrita, Simone Strohmair, Fei He, Quinten A. Akkerman, and Jochen Feldmann. "Fast electron and slow hole spin relaxation in CsPbI3 nanocrystals." Applied Physics Letters 121, no. 20 (November 14, 2022): 201106. http://dx.doi.org/10.1063/5.0103102.

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Spin-dependent properties of lead halide perovskites (LHPs) have recently gained significant attention paving their way toward spin-optoelectronic applications. However, separate measurements of the electron and hole spin relaxation rates are so far missing in LHPs. The knowledge of the electron and hole spin relaxation timescales is necessary to understand the spin-dependent properties of LHPs. Here, we report on the spin polarization dynamics in CsPbI3 nanocrystals (NCs). We employ polarization dependent ultrafast differential transmission spectroscopy (DTS) at room temperature to study the spin polarization dynamics in this system. In the case of pure CsPbI3 NCs, it is not possible to measure separately electron and hole spin relaxation rates from the polarization dependent DTS. Here, we introduce the soluble fullerene derivative PC60BM as an electron acceptor along with CsPbI3 to create an imbalance between the photoexcited electrons and holes in the NCs and, thus, affecting their spin-dependent carrier distribution. CsPbI3:PC60BM blend sample shows a distinct difference in the spin dependent kinetics of the DTS spectra as compared to the NCs-only sample. With the help of a kinetic model for the spin-dependent charge carrier distributions, we separately determine the electron and hole spin relaxation times in CsPbI3 NCs. We find that the room temperature hole spin lifetime ( τh ∼ 5 ps) is ∼13 times longer than the electron spin lifetime ( τe ∼ 0.4 ps). We ascribe the fast electron spin relaxation to the presence of strong spin–orbit coupling in the conduction band, which is ineffective for holes in the s-type valence band.
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45

Liu, Weidong, and Liangchi Zhang. "Mechanisms of the Complex Thermo-Mechanical Behavior of Polymer Glass Across a Wide Range of Temperature Variations." Polymers 10, no. 10 (October 16, 2018): 1153. http://dx.doi.org/10.3390/polym10101153.

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This paper aims to explore the mechanisms of the complex thermo-mechanical behavior of polymer glass across a wide range of temperature variations. To this end, the free vibration frequency spectrum of simply supported poly(methyl methacrylate) (PMMA) beams was thoroughly investigated with the aid of the impulse excitation technique. It was found that the amplitude ratio of the multiple peaks in the frequency spectrum is a strongly dependent on temperature, and that the peaks correspond to the multiple vibrational modes of the molecular network of PMMA. At a low temperature, the vibration is dominated by the overall microstructure of PMMA. With increasing the temperature, however, the contribution of the sub-microstructures is retarded by β relaxation. Above 80 °C, the vibration is fully dominated by the microstructure after relaxation. The relaxation time at the transition temperature is of the same order of the vibration period, confirming the contribution of β relaxation. These findings provide a precise method for establishing reliable physical-based constitutive models of polymer glass.
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46

TEWARI, S. P., and JYOTI SOOD. "COLLECTIVE DYNAMICS OF LIQUID Al." Modern Physics Letters B 18, no. 16 (July 10, 2004): 811–16. http://dx.doi.org/10.1142/s0217984904007293.

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The recently suggested modified microscopic theory of liquids has been used successfully to explain the collective dynamics of liquid Al near its melting point. Considering the frequency-dependent self-diffusion coefficient occurring in the intermediate self-correlation function, which is inextricably linked with the collective dynamics of the system, the observed variation in dynamical structure factor of Al can be quantitatively reproduced for wave vector range 0.42 Å-1 to 1.38 Å-1 taking into account single relaxation time.
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47

SCHLOTTER, W. F., C. CIONCA, S. S. PARUCHURI, J. B. CUNNINGHAM, E. DUFRESNE, S. B. DIERKER, D. ARMS, R. CLARKE, J. M. GINDER, and M. E. NICHOLS. "THE DYNAMICS OF MAGNETORHEOLOGICAL ELASTOMERS STUDIED BY SYNCHROTRON RADIATION SPECKLE ANALYSIS." International Journal of Modern Physics B 16, no. 17n18 (July 20, 2002): 2426–32. http://dx.doi.org/10.1142/s0217979202012463.

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We introduce a new technique for probing the microscopic relaxation of magneto-viscoelastic materials consisting of magnetic particles embedded in a natural rubber matrix. Transversely coherent x-rays from a high brilliance synchrotron source are scattered by the magnetic particles, forming a speckle pattern at low scattering angles. The time dependence of this pattern is recorded with a CCD area detector while the sample is cyclically perturbed by a reversal of the magnetic field direction. The corresponding time-resolved scattering pattern probes both the dynamics of the particles and the relaxation of the matrix in which they are embedded. X-ray photon correlation spectroscopy (XPCS) reveals characteristic time scales for this relaxation by applying the intensity auto-correlation function to the time dependent speckle pattern. For low angle scattering, the wave vector dependence of the relaxation rate exhibits power law length scaling.
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48

Quan, Li Na, Yoonjae Park, Peijun Guo, Mengyu Gao, Jianbo Jin, Jianmei Huang, Jason K. Copper, et al. "Vibrational relaxation dynamics in layered perovskite quantum wells." Proceedings of the National Academy of Sciences 118, no. 25 (June 15, 2021): e2104425118. http://dx.doi.org/10.1073/pnas.2104425118.

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Organic–inorganic layered perovskites, or Ruddlesden–Popper perovskites, are two-dimensional quantum wells with layers of lead-halide octahedra stacked between organic ligand barriers. The combination of their dielectric confinement and ionic sublattice results in excitonic excitations with substantial binding energies that are strongly coupled to the surrounding soft, polar lattice. However, the ligand environment in layered perovskites can significantly alter their optical properties due to the complex dynamic disorder of the soft perovskite lattice. Here, we infer dynamic disorder through phonon dephasing lifetimes initiated by resonant impulsive stimulated Raman photoexcitation followed by transient absorption probing for a variety of ligand substitutions. We demonstrate that vibrational relaxation in layered perovskite formed from flexible alkyl-amines as organic barriers is fast and relatively independent of the lattice temperature. Relaxation in layered perovskites spaced by aromatic amines is slower, although still fast relative to bulk inorganic lead bromide lattices, with a rate that is temperature dependent. Using molecular dynamics simulations, we explain the fast rates of relaxation by quantifying the large anharmonic coupling of the optical modes with the ligand layers and rationalize the temperature independence due to their amorphous packing. This work provides a molecular and time-domain depiction of the relaxation of nascent optical excitations and opens opportunities to understand how they couple to the complex layered perovskite lattice, elucidating design principles for optoelectronic devices.
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49

Onanko, Yurii Anatoliyovich, Dmytro Volodymyrovych Charnyi, Anatoliy Petrovich Onanko, Eugene Michaylovich Matseliuk, Oksana Petrivna Dmytrenko, Mukola Polikarpovich Kulish, Tatiana Mukolaivna Pinchuk-Rugal, Petro Petrovich Ilyin, and Anna Andriivna Kuzmych. "Internal Friction and Mechanical Spectroscopy of SiO2/Si, Nanocomposites of Multiwalled Carbon Nanotubes and Polyamide, Polyethylene, Polyvinyl Chloride, Expanded Polystyrene." ECS Meeting Abstracts MA2022-02, no. 64 (October 9, 2022): 2365. http://dx.doi.org/10.1149/ma2022-02642365mtgabs.

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Abstract: In this work after X-ray irradiation outcomes of the evaluation of dynamic characteristics interstitial atoms Sij, vacancy V and O-complexes was applied for account of a condition of an annealing with the purpose of deriving specific structural defects in SiO2/Si wafer-plate. The nondestructive method, which is allow to determine from internal friction difference ΔQ-1/Q-1 0 of elastic vibrations structure defects density Nd and the depth of broken layer hb, is offered for SiO2/Si wafer-plates. 1. Introduction Defect annealing leads to a change in the shape of the internal friction (IF) temperature spectrum Q-1(T) [1]. IF method allows to set the spectrum of structural defects on the analysis of positions of maximums IF, on duration of relaxation time τ and on their deposit in attenuation of elastic vibrations [2]. A non-destructive method for the technological control of the structure defects by measuring internal friction (IF) and elastic modulus E after laser radiation was developed. 2. Experimental procedure Ultrasonic (US) pulse-phase method using USMV-LETI, modernized USMV-KNU and computerized “KERN-4” with frequencies f║ ≈ 1 MHz and f┴ ≈ 0,7 MHz, US invariant-polarization method for determining the effective acoustic μil and elastic constants Cijkl were used [3,4]. The measured velocity error was equal to ΔV/V = 0,5÷1,5%. The study of influence of structure defects on damping of vibrations in Si/SiO2 wafer-plates by the diameter of D = 100÷60 mm and by the thickness of hSiO2 ≈ 600 nm, hSi ≈ 470 000 nm, allows to estimate the degree of perfection of crystalline structure Metallography optical supervision of microstructure by means of the microscope ”LOMO MVT”, atomic-force microscopy (AFM) were used. 3. Results and discussion The quasi-longitudinal US velocity V║[001] = 5870 m/s, elastic modulus E001 = ρV║[001] 2 = 80,28 GPa for SiO2/Si from the oscillogram were determined. Temperature dependence of internal friction Q-1(T) in SiO2/Si wafer-plate p-type, doped with B, KDB-7.5(100) diameter D ≈ 76∙10-3 m, thickness hSi ≈ 460∙103 nm with SiO2 layer thickness hSiO2 ≈ 100 nm after X-ray irradiation with dose Dγ ≈ 102 Gy is showed. 4. Conclusions 1. The growth of internal friction maximum height QM -1 testifies the growth of the structural defects concentration n, and the broadening of internal friction maximum ΔQM -1 here represents the relaxation process of structural defects new types in SiO2/Si wafer-plate. 2. It was found that as the result of the structural defect annealing IF background Q0 -1 significantly decreases during measuring of IF temperature dependence Q-1(T), which indicates the improvement of SiO2/Si crystal structure. 3. The elastic modulus Е, the shear modulus G, Poisson coefficient μ, IF Q-1 are dependent from SiO2/Si wafer-plate anisotropy. 4. The value of IF background Q-1 0 after temperature T, mechanical treatments describes the changes of the elastic stress σi fields in SiO2/Si wafer-plate. 5. The study of vibrations of disk wafer-plate Si/SiO2 at different harmonic frequencies f0, f2 made it possible to develop the technique for determining the structural defects density nD for semiconductor wafers-substrates. 6. The relationship between IF Q-1 value, the logarithmic decrement of ultrasound damping δ and the dislocations density nD was established for disk-shaped semiconductor wafers-substrates. Acknowledgements This work has been supported by Ministry of Education and Science of Ukraine: Grant of the Ministry of Education and Science of Ukraine for perspective development of a scientific direction "Mathematical sciences and natural sciences" at Taras Shevchenko National University of Kyiv. References [1] Golovin I. S. 2012 Internal friction and mechanical spectroscopy of metal materials (Moscow: Publishing company MISIS). [2] Shpak A. P., Kunickiy Y. A. and Karbovskiy V. L. 2001 Cluster and nano structural materials (Kyiv: Academy periodicals). [3] Onanko A. P., Kuryliuk V. V., Onanko Y. A. et al. 2020 Peculiarity of elastic and inelastic properties of radiation cross-linked hydrogels. J. Nano- Electron. Phys. 12, № 4, 04026(5). DOI: https://doi.org/10.21272/jnep.12(4).04026. [4] Onanko A. P., Kuryliuk V. V., Onanko Y. A. et al. 2021 Features of inelastic and elastic characteristics of Si and SiO2/Si structures. J. Nano- Electron. Phys. 13, № 5, 05017(5). DOI: https://doi.org/10.21272/jnep.13(5).05017. Figure 1
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50

Iomin, Alexander. "Floquet Theory of Classical Relaxation in Time-Dependent Field." Mathematics 11, no. 13 (June 24, 2023): 2832. http://dx.doi.org/10.3390/math11132832.

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Анотація:
The anomalous transport of particles in the presence of a time-dependent field is considered in the framework of a comb model. This turbulent-like dynamics consists of inhomogeneous time-dependent advection along the x-backbone and Brownian motion along the y-side branches. This geometrically constrained transport leads to anomalous diffusion along the backbone, which is described by a fractional diffusion equation with time-dependent coefficients. The time periodic process leads to localization of the transport and a particular form of relaxation. The analytical approach is considered in the framework of the Floquet theory, which is developed for the fractional diffusion equation with periodic in time coefficients. This physical situation is considered in detail and analytical expressions for both the probability density function and the mean squared displacement are obtained. The new analytical approach is developed in the framework of the fractional Floquet theory that makes it possible to investigate a new class of anomalous diffusion in the presence of time periodic fields.
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