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We have investigated the role of the radiation damping term (RDT) on repeated earthquake ruptures by modeling the faulting process through a single one-dimensional analog fault system governed by different constitutive laws. The RDT expresses the energy lost by the seismic waves. The RDT is inherently accounted for in more elaborated, fully dynamic models of extended fault, whereas it is neglected in one-dimensional fault models. In this study, we adopt various formulations of the laboratory-derived rate-dependent and state-dependent friction constitutive laws: the Dieterich-Ruina law, the Ruina-Dieterich law and the Chester and Higgs law. Our numerical results clearly indicate that the RDT significantly affects the system dynamics. More specifically, the more the RDT is effective, the more frequent the slip failures are (with a cycle-time reduction of ca. 30%). We also show that inclusion of the RDT tends to promote smaller but more frequent earthquake instabilities, irrespective of the choice of the governing law. Our data shed light on the limitations implied by the conventional formulation of the equation of motion for the spring system, in which the energy radiation is ignored.

It is well known that a direct Lagrangian description of radiation damping is still missing. In this paper a specific approach to this problem is used, which is different from the standard way to treat the radiation damping problem. An [ABSTRACT FROM AUTHOR]

Based on a Chinese national high arch dam located in a meizoseismal region, a nonlinear numerical analysis model of the damage and failure process of a dam-foundation system is established by employing a 3-D deformable distinct element code (3DEC) and its re-development functions. The proposed analysis model considers the dam-foundation-reservoir coupling effect, influence of nonlinear contact in the opening and closing of the dam seam surface and abutment rock joints during strong earthquakes, and radiation damping of far field energy dissipation according to the actual workability state of an arch dam. A safety assessment method and safety evaluation criteria is developed to better understand the arch dam system disaster process from local damage to ultimate failure. The dynamic characteristics, disaster mechanism, limit bearing capacity and the entire failure process of a high arch dam under a strong earthquake are then analyzed. Further, the seismic safety of the arch dam is evaluated according to the proposed evaluation criteria and safety assessment method. As a result, some useful conclusions are obtained for some aspects of the disaster mechanism and failure process of an arch dam. The analysis method and conclusions may be useful in engineering practice. [ABSTRACT FROM AUTHOR]

The influence of the gravitational radiation damping on the evolution of the orbital elements of compact binary stars is examined by using the method of perturbation. The perturbation equations with the true anomaly as an independent variable are given. This effect results in both the secular and periodic variation of the semi-major axis, the eccentricity, the mean longitude at the epoch and the mean longitude. However, the longitude of periastron exhibits no secular variation, but only periodic variation. The effect of secular variation of the orbit would lead to collapse of the system of binary stars. The deduced formulae are applied to the calculation of secular variation of the orbital elements for three compact binary stars: PSR19 13 + 16, PSR J0737-3039 and M33X-7. The results obtained are discussed. [ABSTRACT FROM AUTHOR]

Abstract: After a brief description of the main characteristics that define Soil Dynamics and its engineering applications, the role of Simplified Methods is discussed. Despite the current wide availability of powerful computer simulations, it is concluded that Simplified Methods will continue to play an important role in Soil Dynamics as they do in the rest of Geotechnical Engineering. Simplified Methods allow the engineer to conduct calculations by hand or with a minimum computational effort, including parametric variations. In the process, the engineer has the possibility to develop a feel for the physical meaning and relative importance of the various factors, with more personal control of calculations and decisions including use of engineering judgment as needed. A list of simplified procedures proposed by the author is provided, covering systems that range from the free field and earth dams to shallow and deep foundations, subjected to excitations that include both seismic shaking and machine vibrations. Basic understanding of the basic theory and simplifications behind the simplified procedure can be very helpful to engineers, including Dynamics and Wave Propagation concepts. Some of this understanding is developed in the paper, with focus on shallow machine foundations and other dynamic soil–structure interaction applications. The Lecture concentrates on shallow machine foundations on a half-space subjected to dynamic loads in any of the six degrees of freedom of the foundation, and the Simplified Methods that have been proposed over the years to characterize the corresponding equivalent soil springs and dashpots. This includes both frequency-dependent and frequency-independent springs and dashpots. It started with the circular surface foundation which was studied over much of the 20th Century, until the breakthroughs by Lysmer and others in 1966–1971, and continued with the cases of surface and embedded foundations of arbitrary shape that culminated in the two summary publications by Gazetas in 1990 and 1991. The development of these simplified equivalent springs and dashpots for both surface and embedded foundations of arbitrary shape is discussed in some detail, including the contribution of the author in the early part of the process. [Copyright &y& Elsevier]

Abstract: A simplified discrete system in the form of a simple oscillator is developed to simulate the dynamic behavior of a structure founded through footings or piles on compliant ground, under harmonic excitation. Exact analytical expressions for the fundamental natural period and the corresponding damping coefficients of the above system are derived, as function of geometry and the frequency-dependent foundation impedances. In an effort to quantify the coupling between swaying and rocking oscillations in embedded foundations such as piles, the reference system is translated from the footing–soil interface to the depth where the resultant soil reaction is applied, to ensure a diagonal impedance matrix. The resulting eccentricity is a measure of the coupling effect between the two oscillation modes. The amounts of radiation damping generated from a single pile and a surface footing are evaluated. In order to compare the damping of a structure on a surface footing and a pile, the notion of static and geometric equivalence is introduced. It is shown that a pile may generate significantly higher radiation damping than an equivalent footing, thus acting as an elementary protective system against seismic action. [Copyright &y& Elsevier]

The fundamental features of nonlinear dynamical systems are investigated in the context of vibration-based energy harvesting. A generalized, global, multi-frequency resonance condition is shown to exist in nonlinear systems where the energy harvesting efficiency has been maximized. Results show that damping and modulation of the excitation play critical roles in facilitating the frequency match required for resonance by tuning the frequencies of the system and modifying the frequency content of the excitation. [ABSTRACT FROM AUTHOR]

Highlights: [•] GRAPE used to optimize relaxation selective pulses (RSP) at T 2 = and T 1 = αT 2. [•] RSP optimized with respect to field inhomogeneity and saturation profile. [•] Adiabatic HS1 and time-optimal pulse inputs were found to work best for GRAPE. [•] Similarity between relaxation and radiation damping derived for soliton pulse. [•] Expressions for time-optimal saturation pulses are presented. [Copyright &y& Elsevier]

Based on the methods of variable separation and matching eigenfunction expansions for velocity potential, analytical solutions are developed for a water wave radiation problem by a submerged vertical cylinder in finite water depth. They are validated by comparison with results from the higher order boundary element method and convergent examinations on the number of expansion models. Numerical analysis is carried out to investigate the influence submerged depth, cylinder length, and water depth on added mass and radiation damping. When the submerged depth is large, the added mass approaches a stable value, and radiation damping tends to zero. At high frequency range, the heave and pitch of the added mass of the submerged cylinder is about twice that of the floating cylinder. The influence of cylinder length for hydrodynamic coefficients is quite complex and shows the various properties at different frequency ranges. Added mass can be increased with the decrease of water depth, whereas the effect of water depth on radiation damping is quite small. [ABSTRACT FROM AUTHOR]

By using three-dimensional particle-in-cell simulations with synchrotron radiation damping incorporated, dynamics of ultra-intense laser driven mass-limited foils is presented. When a circularly polarized laser pulse with a peak intensity of ~1022 W/cm2 irradiates a mass-limited nanofoil, electrons are pushed forward collectively and a strong charge separation field forms which acts as a "light sail" and accelerates the protons. When the laser wing parts overtake the foil from the foil boundaries, electrons do a betatron-like oscillation around the center proton bunch. Under some conditions, betatron-like resonance takes place, resulting in energetic circulating electrons. Finally, bright femto-second x rays are emitted in a small cone. It is also shown that the radiation damping does not alter the foil dynamics radically at considered laser intensities. The effects of the transverse foil size and laser polarization on x-ray emission and foil dynamics are also discussed. [ABSTRACT FROM AUTHOR]

Purpose The goal of this study is to develop novel MR contrast by frequency lock-in technique. Methods An electronic feedback device that can control the frequency and bandwidth of the feedback RF field is presented. In this study, the effects of lock-in suppressed imaging are discussed both theoretically and experimentally. Results Two important imaging experiments were performed. The first experiment used magnetizations with the same central frequency but different frequency distributions and was compared with MR images obtained with T2 contrast agents. Lock-in suppressed images showed an improvement in contrast relative to the conventional imaging method. The second experiment used magnetizations with small shifts in frequency and a broad frequency distribution. This is helpful for differentiating between small structural variations in biological tissues. The contrast achieved in in vivo tumor imaging using the lock-in suppressed technique provide higher spatial resolutions and discriminate the regimes of necrosis and activation consistent with pathologic results. Conclusion Lock-in suppressed imaging introduces a conceptually new approach to MRI. Heightened sensitivity to underlying susceptibility variations and their relative contribution to total magnetization may thus be achieved to yield new and enhanced contrast. Magn Reson Med 71:1676-1681, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In superfluid He-B externally pumped quantized spin-wave excitations or magnons spontaneously form a Bose-Einstein condensate in a 3-dimensional trap created with the order-parameter texture and a shallow minimum in the polarizing field. The condensation is manifested by coherent precession of the magnetization with a common frequency in a large volume. The trap shape is controlled by the profile of the applied magnetic field and by the condensate itself via the spin-orbit interaction. The trapping potential can be experimentally determined with the spectroscopy of the magnon levels in the trap. We have measured the decay of the ground state condensates after switching off the pumping in the temperature range (0.14÷0.2) T. Two contributions to the relaxation are identified: (1) spin diffusion with the diffusion coefficient proportional to the density of thermal quasiparticles and (2) the approximately temperature-independent radiation damping caused by the losses in the NMR pick-up circuit. The measured dependence of the relaxation on the shape of the trapping potential is in a good agreement with our calculations based on the magnetic field profile and the magnon-modified texture. Our values for the spin diffusion coefficient at low temperatures agree with the theoretical prediction and earlier measurements at temperatures above 0.5 T. [ABSTRACT FROM AUTHOR]

Non-linear tidal dynamics are investigated in a network that consists of a semi-enclosed main channel and a secondary channel at an arbitrary position. The water motion, governed by the one-dimensional shallow water equations, is forced by an incoming tidal wave. Solutions are obtained with the method of characteristics. The overall aim is to quantify and understand the spatial structure of different tidal harmonics (the principal tide and its non-linear overtides) and of tidal asymmetry for both the vertical and the horizontal tide in the main channel for different locations of the secondary channel. This is of practical interest in the context of possible construction of secondary channels to reduce tidal range in estuaries. Moreover, tidal asymmetry is an important factor in driving net sediment transport. Analysis of the different tidal harmonics shows that their characteristics are similar to those obtained with an earlier linear model. In particular, amplitudes of the harmonics are reduced landward of the secondary channel if the latter is positioned less than a quarter wavelength of the respective tidal wave away from the landward boundary. Thus, the distortions of the tide due to the presence of the secondary channel are generated locally and afterwards propagate through the network. Tidal asymmetry is quantified by examining tidal range, flood-to-ebb ratio and the duration of the falling tide and the duration between maximum flood and maximum ebb. A spatial non-uniform reduction in tidal range is observed that shows very localised increase and decrease depending on the position of the secondary channel. The changes in the velocity characteristics induce changes in net sediment transport. It turns out that the direction of the peak current, derived from the flood-to-ebb ratio, is not sensitive to the position of the secondary channel, whereas the duration between flood and ebb can change from more to less than half the tidal cycle. However, the changes in the velocity asymmetries are confined to a small region. [ABSTRACT FROM AUTHOR]

Context. Rapidly damped transverse oscillations of coronal loop systems are often observed. Aims. We aim to study analytically the resonantly damped oscillations of a system of two not necessarily identical coronal loops and their dependence on the equilibrium parameters, improving on and extending the results for two identical coronal loops. Methods. The linearised magnetohydrodynamic equations for a cold plasma were solved in the long-wavelength limit and for thin boundary layers in bicylindrical coordinates. We investigated the effects of the density contrast between the two loops, the thickness of their inhomogeneous layers, and the separation distance between them. The complex spectrum was also studied. Results. We obtained more general expressions for the linear damping rate of the transverse oscillations in a system of two coronal loops. The results can be reduced to expressions found previously for the special cases of one vanishing loop or two identical loops. The interaction between the loops results in a stronger damping of the high-frequency eigenoscillation in comparison with that of the low-frequency eigenoscillation. By decreasing the distance between loops, the efficiency of resonant damping is reduced. [ABSTRACT FROM AUTHOR]

ABSTRACT The tuning and matching conditions of rf circuits, as well as the properties of the transmission lines connecting these to the preamplifier, have direct consequences for NMR probe sensitivity and as for the optimum delivery of rf power to the sample. In addition, tuning/matching conditions influence radiation damping effects, which manifest themselves as fast signal flip-back and line broadening effects, and can lead to concentration-dependent frequency shifts. Previous studies have also shown that the appearance of spin-noise and absorbed circuit noise signals heavily depended on tuning settings. Consequently, all these phenomena are linked together. The mutual connections and interdependences of these effects are highlighted and reviewed here. © 2014 The Authors Concepts in Magnetic Resonance, Part B: Magnetic Resonance Engineering Published by Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 44B: 1-11, 2014 [ABSTRACT FROM AUTHOR]

Highlights: [•] An application of the time dependent variation of parameters to NMR problems. [•] Analytical radiation damping dynamics in an inhomogeneous magnetic field. [•] A radiation damping suppression pulse sequence is analyzed and another proposed. [•] The approach is general and can be applied to any time dependent problem. [ABSTRACT FROM AUTHOR]

Harmonic current filtering and resonance damping have become important concerns in the operation and control of the islanded microgrids. To address these challenges, this paper proposes a control method for the inverter-interfaced distributed generation (DG) units to autonomously share the harmonic currents and resonance damping burdens. The approach employs a load compensator based on the decomposition of output current, in addition to the outer droop-based power controller and the inner voltage and current controllers. The load compensator consists of a virtual-fundamental-impedance loop for the enhanced reactive power sharing and a variable-harmonic-impedance loop which allows to counteract the harmonic voltage drops across the grid-side inductance of the DG inverter and also to dampen out harmonic resonance propagation in the microgrid. Finally, the laboratory tests on a three-phase islanded microgrid setup are carried out to validate the performance of the proposed control scheme. [ABSTRACT FROM AUTHOR]

We explore the electrodynamic coupling between a plane wave and an infinite two-dimensional periodic lattice of magnetoelectric point scatterers, deriving a semianalytical theory with consistent treatment of radiation damping, retardation, and energy conservation. We apply the theory to arrays of split ring resonators and provide a quantitative comparison of measured and calculated transmission spectra at normal incidence as a function of lattice density, showing excellent agreement. We further show angle-dependent transmission calculations for circularly polarized light and compare with the angle-dependent response of a single split ring resonator, revealing the importance of cross coupling between electric dipoles and magnetic dipoles for quantifying the pseudochiral response under oblique incidence of split ring lattices. [ABSTRACT FROM AUTHOR]

Abstract: We study the Cauchy problem for damped wave equations with a fractional damping in . We derive more sharp decay estimates of the total energy based on the energy method in the Fourier space combined with the Haraux–Komornik inequality. Especially, in the case when the rate of decay of the total energy becomes almost optimal. The method in this paper can be applied to other equations and in particular it seems to be quite effective in the case of frictional dissipation, i.e., when . [Copyright &y& Elsevier]

We present some applications of geometric optimal control theory to control problems in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI). Using the Pontryagin Maximum Principle (PMP), the optimal trajectories are found as solutions of a pseudo-Hamiltonian system. This computation can be completed by second-order optimality conditions based on the concept of conjugate points. After a brief physical introduction to NMR, this approach is applied to analyze two relevant optimal control issues in NMR and MRI: the control of a spin 1/2 particle in presence of radiation damping effect and the maximization of the contrast in MRI. The theoretical analysis is completed by numerical computations. This work has been made possible by the central and essential role of B. Bonnard, who has been at the heart of this project since 2009. [ABSTRACT FROM AUTHOR]

The entropy exchange between a tow-level atom and a single-mode radiation field is studies in a damped system. The results show that there is an entropy exchange phenomenon between atom and field. Especially, it is prove that there is a condition for entropy exchange between atom and damped field. [ABSTRACT FROM AUTHOR]

The history of renormalization is reviewed with a critical eye, starting with Lorentz's theory of radiation damping, through perturbative QED with Dyson, Gell-Mann and Low, and others, to Wilson's formulation and Polchinski's functional equation, and applications to "triviality," and dark energy in cosmology. [ABSTRACT FROM AUTHOR]

The laser line-width required in PSK homodyne communication systems with Dither phase-locked loop receivers are exactly evaluated. It is shown that second-order phase-locked loops require at least 0.2pW of signal power per every Hz of laser line-width (this number refers to the system with the detector responsivity 0.94 A/W, damping ratio 0.707, and the phase error standard deviation 10°). This signal power is used for phase locking, and is, therefore lost from the data receiver. This study for the first time shows the imperfect-phase-recovery-induced power penalty as a function of laser line-width. It can be estimated from the theoretical result that an optimal dither phase locked-loop receiver requires the laser line-width as Δυ ≤3.14×10−5 × R b, where R b is the system bit rate. This number refers to the system with power penalty of 1dB at BER=10−10. [ABSTRACT FROM AUTHOR]

Interaction of a moving body with a compressible fluid is considered in light of electrodynamic analogies. For a sphere-shaped body, the “relativistic” correction to the added mass and radiation damping force is calculated. Motion with small velocities, as well as the case of near-sonic motion, is considered. For comparison with the 3-D case, the 1-D problem of the motion of a barge in a canal is solved, with the nontrivial dispersion of the surface gravity waves taken into account. The question of a stationary solution is discussed, taking into account dispersion and nonlinearity. [ABSTRACT FROM AUTHOR]

Using a microscopic model and the Green's function technique we have studied the phonon properties of ion doped single- and bilayer graphene. There are differences in the behavior of the energy and damping of the G and 2D modes in a p- and n-doped single-layer graphene. A microscopic explanation is proposed. The influence of the electron-phonon interaction is discussed. We report also phonon energy and damping renormalization in bi-layer graphene as a function of doping. The results are in qualitative agreement with the experimental data. [ABSTRACT FROM AUTHOR]