Effects Of Radiation Damping Research Articles

Considering Effects of Infinite Foundation Radiation Damping on The Dynamic Response of Nuclear Island Structure

The effective simulation of influence of infinite foundation radiation damping is a key technical problem for implement seismic response analysis of nuclear island. Basd on Super FLUSH software as a platform, the vicous boundary is imposed on the boundary of the ground to dissipate the energy and the effect of infinite foundation radiation damping is considered. By taking calculation model of a practical engineering as the object of study and the contrast with rigid foundation, conducting a research on the impact of foundation radiation damping for seismic response of nuclear island structure. In addition, by comparing the influence of different elastic modulus of foundation on the radiation damping is also studied and the findings suggest that influence of the radiation damping is obvious. The calculation results show that the influence of radiation damping is obvious under the condition of soft foundation. The model shows good accuracy and computational efficiency. The results have some reference values for similar projects.

Real-time hybrid simulation of full-scale tuned liquid column dampers to control multi-order modal responses of structures

This paper aims to demonstrate the real performance of tuned liquid column dampers (TLCDs) in controlling seismic response of multi-degree-of-freedom (MDOF) structures based on the advantages of real-time hybrid simulation (RTHS). An RTHS framework is developed to carry out full-scale experiments of TLCD-structure-foundation system, and the application of multiple TLCDs to control single-order and multi-order modal responses of a nine-story benchmark building is investigated, respectively, as an example. Moreover, the effect of soil–structure interaction (SSI) on TLCD performance is examined, in which the finite and semi-infinite soil flexible foundations are simulated through a finite element model with 1160 DOFs embedding fixed and artificial boundaries, respectively. Results show that MTLCD is more effective than a single TLCD in suppressing structural responses; and the former is suggested to be used to control multi-order modal responses because of the uncertainty of the frequency content of earthquake excitations. The SSI effect significantly reduces TLCD performance, and the semi-infinite foundation may eliminate the control effect of TLCD due to the radiation damping effect. The parameters of the TLCD device should be regulated according to the characteristics of SSI-structure system when the SSI effect is unneglectable.

Radiative rates and electron-impact excitation for then≤ 6 fine-structure levels in H-like ions with 13 ≤Z≤ 42

Context. Many observed emission lines from space missions are due to highly charged H-like ions. An analysis of the lines provides information on the temperature, density, and chemical composition of plasmas. A wide range of atomic parameters, such as energy levels, radiative rates, and excitation rate coefficients are needed to achieve this goal.Aims. In this paper we report on calculations for energy levels, radiative rates, collision strengths, and effective collision strengths for transitions among the 36 lowest levels of the n ≤ 6 configurations of highly charged H-like ions with 13 ≤ Z ≤ 42.Methods. The widely used Flexible Atomic Code (FAC) is adopted for the calculation. Energy levels and radiative rates are calculated within the relativistic configuration-interaction method. Employing relativistic distorted-wave approximation, direct excitation collision strengths are calculated at eleven scattered electron energies E ′ f = 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1.0, and 2.5, where E ′ f is in units of Z 2 rydbergs. Collision strengths at higher energies are estimated by interpolation/extrapolation using relativistic Bethe form. Resonance contributions through the relevant He-like doubly excited n ′l ′n ′′l ′′ configurations with n ′ ≤ 7 and n ′′ ≤ 75 are explicitly taken into account using the independent-process isolated-resonance approximation. Radiation damping effects are taken into account.Results. We present the radiative rates, oscillator strengths, and line strengths for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), magnetic quadrupole (M2), electric octupole (E3), and magnetic octupole (M3) transitions. Assuming a Maxwellian electron velocity distribution, we report effective collision strengths over a wide temperature range between 2 × 103 × Z 2 and 2 × 106 × Z 2 K. We believe that the present results are the most extensive and definitive atomic dataset to date for highly charged H-like ions.

Effects of radiation damping for biomolecular NMR experiments in solution: a hemisphere concept for water suppression.

Abundant solvent nuclear spins, such as water protons in aqueous solution, cause radiation damping in NMR experiments. It is important to know how the effect of radiation damping appears in high-resolution protein NMR because macromolecular studies always require very high magnetic field strengths with a highly sensitive NMR probe that can easily cause radiation damping. Here, we show the behavior of water magnetization after a pulsed-field gradient (PFG) using nutation experiments at 900 MHz with a cryogenic probe: when water magnetization is located in the upper hemisphere (having +Z component, parallel to the external magnetic field), dephasing of the magnetization by a PFG effectively suppresses residual water magnetization in the transverse plane. In contrast, when magnetization is located in the lower hemisphere (having -Z component), the small residual transverse component remaining after a PFG is still sufficient to induce radiation damping. Based on this observation, we designed 1H-15N HSQC experiments in which water magnetization is maintained in the upper hemisphere, but not necessarily along Z, and compared them with the conventional experiments, in which water magnetization is inverted during the t1 period. The result demonstrates moderate gain of signal-to-noise ratio, 0-28%. Designing the experiments such that water magnetization is maintained in the upper hemisphere allows shorter pulses to be used compared to the complete water flip-back and, thereby, is useful as a building block of protein NMR pulse programs in solution.

Internal Referencing for ¹³C Position-Specific Isotope Analysis Measured by NMR Spectrometry.

The intramolecular (13)C composition of a molecule retains evidence relevant to its (bio)synthetic history and can provide valuable information in numerous fields ranging from biochemistry to environmental sciences. Isotope ratio monitoring by (13)C NMR spectrometry (irm-(13)C NMR) is a generic method that offers the potential to conduct (13)C position-specific isotope analysis with a precision better than 1‰. Until now, determining absolute values also required measurement of the global (or bulk) (13)C composition (δ(13)Cg) by mass spectrometry. In a radical new approach, it is shown that an internal isotopic chemical reference for irm-(13)C NMR can be used instead. The strategy uses (1)H NMR to quantify both the number of moles of the reference and of the studied compound present in the NMR tube. Thus, the sample preparation protocol is greatly simplified, bypassing the previous requirement for precise purity and mass determination. The key to accurate results is suppressing the effect of radiation damping in (1)H NMR which produces signal distortion and alters quantification. The methodology, applied to vanillin with dimethylsulfone as an internal standard, has an equivalent accuracy (<1‰) to that of the conventional approach. Hence, it was possible to clearly identify vanillin from different origins based on the (13)C isotopic profiles.

Influence of construction interfaces on dynamic characteristics of roller compacted concrete dams

To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams (RCCDs), mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary (VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam. However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes, combination quality of the RCC layers should be significantly ensured.

Radiation damping of an arbitrarily shaped bubble

Large encapsulated bubbles have recently been used for abating low-frequency anthropogenic underwater noise [J. Acoust. Soc. Am. 135, 1700–1708 (2014)]. The use of encapsulation allows for the possibility of bubbles that are significantly nonspherical in their equilibrium state. Strasberg [J. Acoust. Soc. Am. 25, 536–537 (1953)] investigated the resonance frequency of an ideal bubble with arbitrary shape and found that the dependence of resonance frequency on the shape of the bubble reduced to a well-known problem in electrostatics. The present work extends that analysis to include the effects of radiation damping on the oscillation of a bubble, and does so by including a loss term due to Ilinskii and Zabolotskaya [J. Acoust. Soc. Am. 92, 2837–2841 (1992)] in the volume-frame dynamical equation for the bubble. An expression is given for the amplitude of the acoustic field scattered from the bubble, and it is shown that radiation damping scales as resonance frequency cubed for arbitrarily shaped bubbles having the same volume. Comparisons are made with previous work on scattering from spherical and prolate spheroidal bubbles, and various new bubble shapes are considered. [Work supported by AdBm Technologies, the ARL:UT McKinney Fellowship in Acoustics and ONR.]

Quantum control of nuclear magnetic resonance spin systems

With the development of quantum information science, the active manipulation of quantum systems is becoming an important research frontier. To build realistic quantum information processors, one of the challenges is to implement arbitrary desired operations with high precision on quantum systems. A large number of quantum control methods and relevant numerical techniques have been put forward in recent years, such as quantum optimal control and quantum feedback control. Nuclear magnetic resonance (NMR) spin systems offer an excellent testbed to develop benchmark tools and techniques for controlling quantum systems. In this review paper, we briefly introduce some of the basic control ideas developed for NMR systems in recent years. We first explain, for the liquid spin systems, the physics of various couplings and the causes of relaxation effects. These mechanisms govern the system dynamics, and thus are crucial for constructing rigorous and efficient control models. We also identify three types of available control means: 1) raido-frequency fields as coherent controls; 2) phase cycling, gradient fields and relaxation effects as non-unitary controls; 3) radiation damping effect as feedback control mechanism. Then, we elucidate some important control tasks, which may arise from the conventional NMR spectroscopy (e.g., pulse design and polarization transfer) or from quantum information science (e.g., algorithmic cooling and pseudo-pure state preparation). In the last part, we review some of the most important control methods that are applicable to NMR control tasks. For systems with a relatively small number of spins, it is possible to use analytic optimal control theory to realize the target unitary operations. However, for larger systems, numerical methods are necessary. The gradient ascent pulse engineering algorithm and pulse compiler techniques are the most successful techniques for implementing complicated quantum networks currently. There are some interesting topics of utilizing radiation damping and relaxation effects to achieve more powerful controls. Finally, we give an outline of the possible future work.

Radiative damping and synchronization in a graphene-based terahertz emitter

We investigate the collective electron dynamics in a recently proposed graphene-based terahertz emitter under the influence of the radiative damping effect, which is included self-consistently in a molecular dynamics approach. We show that under appropriate conditions synchronization of the dynamics of single electrons takes place, leading to a rise of the oscillating component of the charge current. The synchronization time depends dramatically on the applied dc electric field and electron scattering rate and is roughly inversely proportional to the radiative damping rate that is determined by the carrier concentration and the geometrical parameters of the device. The emission spectra in the synchronized state, determined by the oscillating current component, are analyzed. The effective generation of higher harmonics for large values of the radiative damping strength is demonstrated.

Comparison of end-of-drive and restrike signal matching analysis for a real case using continuum numerical modelling

The main objective of this paper is introducing a so-called continuum numerical model to overcome some of the limitations of the mass–spring–dashpot systems. Two continuum numerical schemes including a finite difference method (FDM) and a finite element method (FEM) are utilized. Unlike the previous continuum numerical models, the adopted models follow a signal matching procedure similar to lumped models. A real driven pile that has been carefully monitored is considered for model verification and validation, for which the dynamic and static test results, soil profile and soil characteristics are available. Among the major advantages of the model are considerations of soil inertia and/or radiation damping effects. A signal matching procedure is followed by changing the strength and deformation parameters of the soil and interface between pile–soil, both at the “End-Of-Drive” (EOD) and “Beginning of Restrike” (BOR). The results indicate a substantial increase in the soil strength parameters of the pile–shaft interface and the soil modulus below the pile tip at restrike. It is found that the effect of radiation damping significantly changes the pile–soil stiffness during pile hammering. The comparisons between FDM and FEM predictions show very good agreements. Two sets of parameters involved in signal matching are introduced for EOD and BOR signal matching analyses, to compare the variations during the soil setup process. The parameters are also compared against the in situ soil parameters acquired from soil investigation data.

Dependence of NMR noise line shapes on tuning, matching, and transmission line properties.

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.

Hydroxyl-Proton Hydrogen Bonding in the Heparin Oligosaccharide Arixtra in Aqueous Solution

Heparin is best known for its anticoagulant activity, which is mediated by the binding of a specific pentasaccharide sequence to the protease inhibitor antithrombin-III (AT-III). Although heparin oligosaccharides are thought to be flexible in aqueous solution, the recent discovery of a hydrogen bond between the sulfamate (NHSO3(-)) proton and the adjacent 3-O-sulfo group of the 3,6-O-sulfated N-sulfoglucosamine residue of the Arixtra (fondaparinux sodium) pentasaccharide demonstrates that definable elements of local structure are accessed. Molecular dynamics simulations of Arixtra suggest the presence of additional hydrogen bonds involving the C3-OH groups of the glucuronic acid and 2-O-sulfo-iduronic acid residues. NMR measurements of temperature coefficients, chemical shift differences, and solvent exchange rate constants provide experimental confirmation of these hydrogen bonds. We note that the extraction of rate constants from cross-peak buildup curves in 2D exchange spectroscopy is complicated by the presence of radiation damping in aqueous solution. A straightforward model is presented that explicitly takes into account the effects of radiation damping on the water proton relaxation and is sufficiently robust to provide an accurate measure of the proton exchange rate between the analyte hydroxyl protons and water.

Radiation Damping in a Non-Abelian Strongly-Coupled Gauge Theory

We study a 'composite' or 'dressed' quark in strongly-coupled = 4 super-Yang-Mills (SYM), making use of the AdS/CFT correspondence. We show that the standard string dynamics nicely captures the physics of the quark and its surrounding non-Abelian field configuration, making it possible to derive a relativistic equation of motion that incorporates the effects of radiation damping. From this equation one can deduce a non-standard dispersion relation for the composite quark, as well as a Lorentz covariant formula for its rate of radiation.

Linking the Recurrence Time of Earthquakes to Source Parameters: A Dream or a Real Possibility?

By using a single-degree-of-freedom spring-slider analog fault model, we generate a synthetic catalog of nearly 500 different seismic sequences. We explore the parameter space by assuming different values of constitutive parameters and tectonic environment. We also consider three different versions of the rate-dependent and state-dependent friction laws [the Dieterich-Ruina (DR), the Ruina-Dieterich (RD) and the Chester-Higgs (CH) models], and different approximations of the behavior of the friction at high sliding speeds, as well as the radiation damping effects. Our results indicate that for all the considered models, the recurrence time (T cycle) exhibits an inverse proportionality on the loading rate; a linear, positive dependence on the effective normal stress; and a linear, negative dependence on the characteristic distance controlling the state variable evolution. These results confirm and generalize previous studies. Remarkably, we found here that the coefficients of proportionality strongly depend on the adopted friction model, on the high speed behavior and on the reference set of parameters. Notably, we also found that the positive proportionality between T cycle and the difference b – a, confirmed for DR and RD laws, does not hold in general for the CH law. Overall, we conclude that even in the simplest (and idealized) case of characteristic earthquakes considered here, in which the limiting cycle is reached by the system, and even in the framework of a very simplified fault model, the possibility to a priori predict, through an universal analytical relation, the inter-event time of an impending earthquake still remains only a dream. On the other hand, a numerical prediction of T cycle would require the exact knowledge of the rheological model (and its parameters at all times over the entire life of the fault) and the actual state of the fault, which indeed are often unknown.

Analytical approximations to inhomogeneously broadened, radiation damped free precession and echo signals

The Dirac–Frenkel–Maclachlan (DFM) variation of parameters approach to approximately solving the time dependent Schrödinger equation is used to generate free precession and echo signals from the Bloch equations corrected for the effects of radiation damping and inhomogeneous broadening. Following a brief description of how the DFM method can be applied to the non-linear Bloch equations, two figures of merit designed to evaluate how a DFM optimized approximation compares with the exact solution is provided. This framework is used to optimize and evaluate the performance of six trial functions describing inhomogeneously broadened, radiation damped free precession and echo signals. The trial functions are then used to analyze the resolution enhancement and signal attenuation produced by pulse sequences that suppress radiation damping.

Seismic Analysis of an Intake Tunnel of Different Tunnellining Programs for a Nuclear Power Plant

Developing an analysis program and simulating the radiation damping effect in the infinite foundation and inputs ground motion rationally. The static and dynamic analysis of an intake tunnel for a nuclear power plant is performed with ANSYS based on some 2-D finite element models considering of structure-foundation interaction by Time-History Analysis. Aiming at different programs of two linings in tunnel, the stress and internal force distribution of the tunnel , the wall rocks and the lining is researched and analyzed, and the diagram of stress and internal force is drawn. The regularity obtained can provide the basis for the seismic response analysis and design of tunnels.

Biomolecular ligands screening using radiation damping difference WaterLOGSY spectroscopy

Water-ligand observed via gradient spectroscopy (WaterLOGSY) is a widely used nuclear magnetic resonance method for ligand screening. The crucial procedure for the effectiveness of WaterLOGSY is selective excitation of the water resonance. The selective excitation is conventionally achieved by using long selective pulse, which causes partial saturation of the water magnetization leading to reduction of sensitivity, in addition to time consuming and error prone. Therefore, many improvements have been made to enhance the sensitivity and robustness of the method. Here we propose an alternative selective excitation scheme for WaterLOGSY by utilizing radiation damping effect. The pulse scheme starts simply with a hard inversion pulse, instead of selective pulse or pulse train, followed by a pulse field gradient to control the radiation damping effect. The rest parts of the pulse scheme are similar to conventional WaterLOGSY. When the gradient pulse is applied immediately after the inversion pulse, the radiation damping effect is suppressed, and all of the magnetization is inversed. When the gradient pulse and the inversion pulse are about 10-20ms apart, the radiation damping effect remains active and drives the water magnetization toward +z-axis, resulting in selective non-inversion of the water magnetization. By taking the differences of the spectra obtained under these two conditions, one should get the result of WaterLOGSY. The method is demonstrated to be simple, robust and sensitive for ligand screening.

Time-optimal control of spin-1/2 particles with dissipative and generalized radiation-damping effects

We analyze the time-optimal control of spin-1/2 particles with bounded field amplitudes in the presence of dissipative and radiation damping effects. Using tools of geometric optimal control theory, we determine different optimal syntheses for specific values of the system parameters. We show the nontrivial role of the effective radiation damping effect on the optimal control law.

Radiation damping optical enhancement in cold atoms

The typically tiny effect of radiation damping on a moving body can be amplified to a favorable extent by exploiting the sharp reflectivity slope at one edge of an optically induced stop-band in atoms loaded into an optical lattice. In this paper, this phenomenon is demonstrated for the periodically trapped and coherently driven cold 87Rb atoms, where radiation damping might be much larger than that anticipated in previous proposals and become comparable with radiation pressure. Such an enhancement could be observed even at speeds of only a few meters per second with less than 1.0% absorption, making radiation damping experimentally accessible. Subjecting an ensemble of cold rubidium atoms to a particular combination of optical beams should enable the study of ‘radiation damping’, a typically minuscule velocity-dependent effect that a light source exerts on a moving body. This is the finding of a theoretical study performed by Jin-Hui Wu at Jilin University, China, in cooperation with researchers from the university of Exeter (UK), the Lens Laboratory and Scuola Normale Superiore (IT). Their proposal is based on exploiting reflections at the boundary between allowed and forbidden frequency bands in the photonic crystal made by periodically distributed cold atoms. This approach should provide a way of amplifying radiation damping to a level suitable for experimental study, making it useful for manipulating cold atoms and potentially other material systems.

超强激光-等离子体相互作用过程中的辐射阻尼效应

超强激光-等离子体相互作用过程中的辐射阻尼效应