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1دورية أكاديمية
المؤلفون: Milazzo M., Jung G. S., Danti S., Buehler M. J.
المساهمون: Milazzo, M., Jung, G. S., Danti, S., Buehler, M. J.
مصطلحات موضوعية: bioinspiration, biomimicry, collagen, modeling, molecular dynamic, simulation, tissue, wave propagation
الوصف: Collagen is the key protein of connective tissue (i.e., skin, tendons and ligaments, and cartilage, among others), accounting for 25-35% of the whole-body protein content and conferring mechanical stability. This protein is also a fundamental building block of bone because of its excellent mechanical properties together with carbonated hydroxyapatite minerals. Although the mechanical resilience and viscoelasticity have been studied both in vitro and in vivo from the molecular to tissue level, wave propagation properties and energy dissipation have not yet been deeply explored, in spite of being crucial to understanding the vibration dynamics of collagenous structures (e.g., eardrum, cochlear membranes) upon impulsive loads. By using a bottom-up atomistic modeling approach, here we study a collagen peptide under two distinct impulsive displacement loads, including longitudinal and transversal inputs. Using a one-dimensional string model as a model system, we investigate the roles of hydration and load direction on wave propagation along the collagen peptide and the related energy dissipation. We find that wave transmission and energy-dissipation strongly depend on the loading direction. Also, the hydrated collagen peptide can dissipate five times more energy than dehydrated one. Our work suggests a distinct role of collagen in term of wave transmission of different tissues such as tendon and eardrum. This study can step toward understanding the mechanical behavior of collagen upon transient loads, impact loading and fatigue, and designing biomimetic and bioinspired materials to replace specific native tissues such as the tympanic membrane.
العلاقة: info:eu-repo/semantics/altIdentifier/wos/WOS:000519150300006; volume:6; issue:3; firstpage:1367; lastpage:1374; numberofpages:8; journal:ACS BIOMATERIALS SCIENCE & ENGINEERING; info:eu-repo/grantAgreement/EC/H2020/794614; http://hdl.handle.net/11568/1056592Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85081786422
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2دورية أكاديمية
المؤلفون: Milazzo M., Jung G. S., Danti S., Buehler M. J.
المساهمون: Milazzo, M., Jung, G. S., Danti, S., Buehler, M. J.
مصطلحات موضوعية: biocomposite, bone, collagen, molecular dynamic, tissue engineering, wave propagation
الوصف: Collagen is a key structural protein in the human body, which undergoes mineralization during the formation of hard tissues. Earlier studies have described the mechanical behavior of bone at different scales, highlighting material features across hierarchical structures. Here we present a study that aims to understand the mechanical properties of mineralized collagen fibrils upon tensile/compressive transient loads, investigating how the kinetic energy propagates and it is dissipated at the molecular scale, thus filling a gap of knowledge in this area. These specific features are the mechanisms that nature has developed to passively dissipate stress and prevent structural failures. In addition to the mechanical properties of the mineralized fibrils, we observe distinct nanomechanical behaviors for the two regions (i.e., overlap and gap) of the D-period to highlight the effect of the mineralization. We notice decreasing trends for both wave speeds and Young's moduli over input velocity with a marked strengthening effect in the gap region due to the accumulation of the hydroxyapatite. In contrast, the dissipative behavior is not affected by either loading conditions or the mineral percentage, showing a stronger damping effect upon faster inputs compatible to the bone behavior at the macroscale. Our results offer insights into the dissipative behavior of mineralized collagen composites to design and characterize bioinspired composites for replacement devices (e.g., prostheses for sound transmission or conduction) or optimized structures able to bear transient loads, for example, impact, fatigue, in structural applications.
العلاقة: info:eu-repo/semantics/altIdentifier/pmid/32603087; info:eu-repo/semantics/altIdentifier/wos/WOS:000557762800054; volume:14; issue:7; firstpage:8307; lastpage:8316; numberofpages:10; journal:ACS NANO; info:eu-repo/grantAgreement/EC/H2020/794614; http://hdl.handle.net/11568/1056391Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85089710574
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3دورية أكاديمية
المؤلفون: Luschi, L., Iannaccone, G., Pieri, F.
المساهمون: Luschi, L., Iannaccone, G., Pieri, F.
مصطلحات موضوعية: Sound, Acoustic wave propagation, Band gap, Wave mechanics, Acoustic waves
الوصف: The acoustic attenuation inside the bandgaps is, together with the bandgap width, a fundamental design parameter for phononic-crystal-based systems. We discuss approximate expressions for the maximum attenuation inside the bandgaps of one-dimensional longitudinal phononic crystals and its dependence on the acoustic contrast and the fractional bandwidth. We provide different approximations at small and large fractional bandwidths, computed from the trace of the transmission matrix of the crystal elementary cell. We show that, for relatively small gaps, the attenuation is roughly proportional to the fractional bandwidth, in analogy with the flexural case. For larger gaps, a large attenuation can be obtained only for high (and possibly impractical) acoustic contrasts. Approximate expressions are validated through comparison with FEM results. We also derive asymptotic upper limits for the bandgap borders and show that high contrasts do not necessarily lead to wide bandgaps, a fact connected to geometrical phase inversion for the acoustic wave in the crystal. We finally compare the attenuation of flexural and longitudinal waves at a fixed fractional bandwidth and derive regions of optimum attenuation for the two propagation modes.
وصف الملف: STAMPA
العلاقة: info:eu-repo/semantics/altIdentifier/wos/WOS:000417494300017; volume:122; issue:21; numberofpages:7; journal:JOURNAL OF APPLIED PHYSICS; http://hdl.handle.net/11568/890589Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85037728598; http://scitation.aip.org/content/aip/journal/japTest
الإتاحة: https://doi.org/10.1063/1.5001900Test
http://hdl.handle.net/11568/890589Test
http://scitation.aip.org/content/aip/journal/japTest -
4دورية أكاديمية
المؤلفون: Antonio A. D'Amico, Andrea de Jesus Torres, Luca Sanguinetti, Moe Win
المساهمون: D'Amico, Antonio A., DE JESUS TORRES, Andrea, Sanguinetti, Luca, Win, Moe
مصطلحات موضوعية: Estimation, Computational modeling, Analytical model, Antenna array, Standard, Location awarene, Electromagnetic, Cramer-Rao bound, wave propagation theory, source localization, planar electromagnetic surface, holographic positioning
الوصف: Multiple antennas arrays combined with high carrier frequencies play a key role in wireless networks for communications but also for localization and sensing applications. To understand the fundamental limits of electromagnetically large antenna arrays for localization, this paper combines wave propagation theory with estimation theory, and computes the Cramer-Rao Bound (CRB) for the estimation of the source position on the basis of the three Cartesian components of the electric field, observed over a rectangular surface area. The problem is referred to as holographic positioning and it intrinsically depends on the radiation angular pattern of the transmitting source, which is typically ignored in standard signal processing models. We assume that the source is a Hertzian dipole, and address the holographic positioning problem in both cases, that is, with and without a priori knowledge of its orientation. To simplify the analysis and gain further insights, we also consider the case in which the dipole is located on the line perpendicular to the surface center. Numerical and asymptotic results are given to quantify the CRBs, and to quantify the effect of various system parameters on the ultimate estimation accuracy. It turns out that square surfaces with side comparable to the distance are needed to guarantee a centimeter-level accuracy in the mmWave bands. Moreover, we show that the CRBs with and without a priori knowledge of the source dipole orientation are numerically the same. The provided CRBs are also used to benchmark different maximum-likelihood estimators (MLEs) derived on the basis of a discrete representation of different models of the electric field. The analysis shows that, if the standard models are used (neglecting the radiation angular pattern), the MLE accuracy is far from the CRB. On the other hand, it approaches the CRB when the more detailed electromagnetic model is considered.
العلاقة: info:eu-repo/semantics/altIdentifier/wos/WOS:000912703900001; volume:70; firstpage:5518; lastpage:5532; numberofpages:15; journal:IEEE TRANSACTIONS ON SIGNAL PROCESSING; https://hdl.handle.net/11568/1186170Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85142860596
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5دورية أكاديمية
المؤلفون: Bulanov SV, Esirkepov TZh, Kando M, Koga JK, Pirozhkov AS, Nakamura T, Bulanov SS, Schroeder CB, Esarey E, CALIFANO, FRANCESCO, PEGORARO, FRANCESCO
المساهمون: Bulanov, Sv, Esirkepov, Tzh, Kando, M, Koga, Jk, Pirozhkov, A, Nakamura, T, Bulanov, S, Schroeder, Cb, Esarey, E, Califano, Francesco, Pegoraro, Francesco
مصطلحات موضوعية: Plasma properties and parameters, Plasma waves, Electromagnetism, Turbulent flows, Wave mechanics, Electronic shell, Wave propagation, Partial differential equations, Plasma flows, Laser plasma interactions
الوصف: In thermal plasma, the structure of the density singularity formed in a relativistically large amplitude plasma wave close to the wavebreaking limit leads to a refraction coefficient with discontinuous spatial derivatives. This results in a non-exponentially small above-barrier reflection of an electromagnetic wave interacting with the nonlinear plasma wave.
وصف الملف: STAMPA
العلاقة: info:eu-repo/semantics/altIdentifier/wos/WOS:000312033700045; volume:19; issue:11; firstpage:113103-1; lastpage:113103-7; numberofpages:7; journal:PHYSICS OF PLASMAS; http://hdl.handle.net/11568/203439Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84870627168
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6دورية أكاديمية
المؤلفون: Simonelli, A, IGEL, HEINER, Wassermann, J, Belfi, J, Di Virgilio, A, Beverini, N, De Luca, G, Saccorotti, G
المساهمون: Simonelli, A, Igel, Heiner, Wassermann, J, Belfi, J, Di virgilio, A, Beverini, N, De luca, G, Saccorotti, G
الوصف: We present the analysis of rotational and translational ground motions from earthquakes recorded during October-November 2016, in association with the Central Italy seismic sequence. We use co-located measurements of the vertical ground rotation rate from a large ring laser gyroscope and the three components of ground velocity from a broad-band seismometer. Both instruments are positioned in a deep underground environment, within the Gran Sasso National Laboratories of the Istituto Nazionale di Fisica Nucleare. We collected dozens of events spanning the 3.5-5.9 magnitude range and epicentral distances between 30 and 70 km. This data set constitutes an unprecedented observation of the vertical rotational motions associated with an intense seismic sequence at local distance. Under the plane-wave approximation we process the data set in order to get an experimental estimation of the events backazimuth. Peak values of rotation rate (PRR) and horizontal acceleration (PGA) are markedly correlated, according to a scaling constant which is consistent with previous measurements from different earthquake sequences. We used a prediction model in use for Italy to calculate the expected PGA at the recording site, obtaining consequently predictions for PRR. Within the modelling uncertainties, predicted rotations are consistent with the observed ones, suggesting the possibility of establishing specific attenuation models for ground rotations, like the scaling of peak velocity and peak acceleration in empirical ground-motion prediction relationships. In a second step, after identifying the direction of the incoming wavefield, we extract phase-velocity data using the spectral ratio of the translational and rotational components. This analysis is performed over time windows associated with the P-coda, S-coda and Lg phase. Results are consistent with independent estimates of shear wave velocities in the shallow crust of the Central Apennines.
وصف الملف: STAMPA
العلاقة: info:eu-repo/semantics/altIdentifier/wos/WOS:000448235200048; volume:214; issue:1; firstpage:705; lastpage:715; numberofpages:11; journal:GEOPHYSICAL JOURNAL INTERNATIONAL; http://hdl.handle.net/11568/949798Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85047832501; https://academic.oup.com/gji/article/214/1/705/4993544Test
الإتاحة: https://doi.org/10.1093/gji/ggy186Test
http://hdl.handle.net/11568/949798Test
https://academic.oup.com/gji/article/214/1/705/4993544Test -
7دورية أكاديمية
المؤلفون: VENUTELLI, MAURIZIO
المساهمون: Venutelli, Maurizio
مصطلحات موضوعية: Finite difference schemes, Compact formulations, Optimization, Dispersion errors, Wave propagation
الوصف: Two optimized fourth-order compact centered finite difference schemes are presented in this paper. By minimizing, over a range of the wave numbers domain, the variations of the phase speed with the wave number, an optimization least-squares problem is formulated. Hence, solving a linear algebraic system, obtained by incorporating the relations between the coefficients for the fourth-order three-parameter family schemes, the corresponding well-resolved wave number domains, and the related optimized coefficients, for two levels of accuracy, are analytically evaluated. Several dispersion comparisons, including the asymptotic behavior between the proposed and other existing optimized pentadiagonal fourth-order schemes, are presented and discussed. The schemes applicable directly on the interior nodes, are associated with a set of fourth-order boundary closure expressions. By adopting a fourth-order six-stage optimized Runge Kutta algorithm for time marching, the stability bounds, the global errors, and the computational efficiency, for the fully discrete schemes, are examined. The performances of the presented schemes, are tested on benchmark problems that involve both the one-dimensional linear convection, and the one-dimensional nonlinear shallow water equations. Finally, the one-dimensional schemes are extended to two dimensions and, using the two dimensional shallow water equations, classical applications are presented. The results allow us to propose, as the ideal candidate for simulating wave propagation problems, the scheme which corresponds to the strict level of accuracy with the maximum resolution over a narrow wave number space.
وصف الملف: STAMPA
العلاقة: volume:87; firstpage:53; lastpage:73; numberofpages:21; journal:APPLIED NUMERICAL MATHEMATICS; http://hdl.handle.net/11568/649863Test
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8دورية أكاديمية
المساهمون: Faganello, Matteo, Califano, Francesco, Pegoraro, Francesco, A., Retino'
مصطلحات موضوعية: Magnetic reconnection, Magnetohydrodynamic and fluid equation, Nonlinear phenomena: wave, wave propagation
الوصف: Observational signatures of Kelvin-Helmholtz (K-H) vortices and of double midlatitude reconnection are highlighted in satellite data of the THEMIS mission. It is shown that the plasma fluid quantities at the low-latitude flank of the Earth’s magnetosphere are compatible with K-H vortices, as described by three-dimensional simulations. At the same time it is shown that the particle fluxes are compatible with the presence of magnetic-field lines, embedded in the K-H vortices, that close on Earth but are connected to the solar wind at low latitude. These field lines are generated during the K-H evolution by magnetic reconnection proceeding spontaneously in both hemispheres at mid-latitudes, allowing the solar-wind plasma to enter the Earth’s magnetosphere directly
وصف الملف: STAMPA
العلاقة: info:eu-repo/semantics/altIdentifier/wos/WOS:000340760500035; volume:107; issue:19001; firstpage:19001-p1; lastpage:19001-p6; numberofpages:6; journal:EUROPHYSICS LETTERS; http://hdl.handle.net/11568/649067Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84904200080
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9مؤتمر
المؤلفون: Martini E., Monorchio A.
المساهمون: Martini, E., Monorchio, A.
مصطلحات موضوعية: Finite element time domain method, Numerical dispersion, Wave propagation
الوصف: Numerical dispersion relations in finite element time-domain methods are analytically derived for different mesh structures and basis functions. It is shown that, for certain combinations of mesh structure and basis functions, there is a particular choice of the discrete time step which minimizes the dispersion error. Some numerical results are presented to validate the theoretical analysis.
وصف الملف: ELETTRONICO
العلاقة: info:eu-repo/semantics/altIdentifier/isbn/978 0 86341 842 6; ispartofbook:IET Seminar Digest; 2nd European Conference on Antennas and Propagation, EuCAP 2007; volume:2007; issue:11961; firstpage:674; lastpage:674; numberofpages:1; http://hdl.handle.net/11568/1038624Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-70349758556
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10كتاب
المؤلفون: Bousbia Salah A., D’Auria F.
المساهمون: Bousbia Salah, A., D’Auria, F.
مصطلحات موضوعية: Peach Bottom, BWR TT, Turbine Trip, Condenser valve opening time, role of SRV, steam line pressure wave propagation
الوصف: A research activity started at the end of 80’s was substantiated within the context of the participation of the TMI-1 (Three Mile –Unit 1) Benchmark in 1998. A coupled thermal-hydraulic neutron physics code was developed. This was used for the Boiling Water Reactor (BWR) Turbine Trip (TT) experiment planned and executed in the Peach Bottom Nuclear Power Plant (NPP) in the USA. The test was originated by the quick closing of the turbine inlet valve, followed by the quick opening of the condenser bypass line and, in the core region, by the arrival of a pressure wave. The pressure wave cause void collapse and increase of fission core power for a factor 5 in a few seconds after the turbine trip. The overall scenario was successfully reproduced by the coupled Relap5/Parcs code. This document discusses the results of additional accident scenarios in the ‘now-qualified’ Peach Bottom NPP scenario. The analysis demonstrated, among the other things, the role and the importance of SRV (Steam Relief Valves) opening in preventing code damage.
وصف الملف: STAMPA
العلاقة: ispartofseries:DIMNP NT; volume:NT 500(03); firstpage:1; lastpage:33; numberofpages:33; http://hdl.handle.net/11568/904973Test
