Function Of Amplitude Research Articles

Floquet dynamical quantum phase transitions in transverse XY spin chains under periodic kickings

Floquet dynamical quantum phase transitions (DQPTs), which are nonanalytic phenomena recuring periodically in time-periodic driven quantum many-body systems, have been widely studied in recent years. In this article, the Floquet DQPTs in transverse XY spin chains under the modulation of δ-function periodic kickings are investigated. We analytically solve the system, and by considering the eigenstate as well as the ground state as the initial state of the Floquet dynamics, we study the corresponding multiple Floquet DQPTs emerged in the micromotion with different kicking moments. The rate function of return amplitude, the Pancharatnam geometric phase and the dynamical topological order parameter are calculated, which consistently verify the emergence of Floquet DQPTs in the system.

Susceptibility of Microseismic Triggering to Small Sinusoidal Stress Perturbations at the Laboratory Scale

AbstractSmall transient stress perturbations are prone to trigger (micro)seismicity. In the Earth's crust, these stress perturbations can be caused by various sources such as the passage of seismic waves, forcing by tides, or hydrological seasonal loads. A better understanding of the dynamic of earthquake triggering by stress perturbations is essential to improve our understanding of earthquake physics and our consideration of seismic hazard. Here, we study an experimental sandstone‐gouge‐filled fault system undergoing combined far field loading and periodic stress perturbations (of variable amplitude and frequency) at crustal pressure conditions. Microseismicity—in the form of acoustic emissions (AEs)—strains, and stresses, are continuously recorded in order to study the response of microseismicity as a function of loading rate, amplitude, and frequency of a periodic stress perturbation. The observed AE distributions do not follow the predictions of either a Coulomb failure model, taking into account both constant loading and oscillation‐induced strain rates, or a rate and state model. A susceptibility of the system's AE response to the amplitude of the confinement pressure perturbation is estimated, which highlights a linear relation between confinement pressure amplitude and the AE response amplitude, observations which agree with recent higher frequency experimental results on dynamic triggering. The magnitude‐frequency distribution of AEs is also computed. The Gutenberg‐Richter b‐value oscillates with stress oscillations. Our experiments may help complement our understanding of the influence of low inertia stress phenomena on the distribution of seismicity, such as observations of dynamic triggering and seismicity modulation by tides or hydrological loading.

Debris expulsion as a rate determining process in fretting – The effect of slip amplitude on debris expulsion behaviour and rates

In contrast to the well-established understanding of sliding wear, recent work has clearly demonstrated that the instantaneous wear rate in fretting of metals is dependent upon the contact size due to the fact that transport of species in and out of the contact are normally the rate-determining processes (RDPs), the processes being oxygen transport and debris transport respectively.In this work, non-conforming (cylinder-on-flat) contacts were fretted with a range of slip amplitudes between ∼ 5 μm and 80 μm, and the contact size-dependent wear coefficient was determined in each case. It was observed that although a slip amplitude threshold (below which wear does not proceed) may exist, this threshold is below the lowest slip amplitude examined in this work. However, as the slip amplitude was decreased, the number of cycles for wear to be initiated increased; for example, at the lowest slip amplitude examined in this work, measurable wear was not observed after 5 million fretting cycles whilst it was observed after 10 million cycles.The development of wear scar profile as a function of slip amplitude was also examined. It was observed that at a fixed number of cycles, smaller slip amplitudes resulted in W-shaped wear scars whereas larger slip amplitudes resulted in U-shaped scars. It was also observed that at a fixed slip amplitude, the scar shape developed from being U-shaped in the initial stages of fretting to W-shaped as the test proceeded. These changes in scar geometry are interpreted bearing in mind the fact that the scar size is also a function of changes in these parameters due to the non-conforming nature of the contact. Scanning electron microscopy was employed to aid understanding with the observations being interpreted in the framework of debris-ejection as the rate determining process. Reasons for the strong dependence of wear rate on slip amplitude are proposed.

Favorable dynamics of switching and non-switching polarizations in ⟨001⟩pc oriented Sm:PMN-PT crystal

In this investigation, the dynamic behavior of the switching and the non-switching polarization loops has been studied for ⟨001⟩pc oriented PMN-PT and Sm:PMN-PT crystals. A five-pulse triangular wave sequence was employed to measure the switching and non-switching polarization loops separately as a function of amplitude and frequency of the poling field. Dynamic scaling of the switching loops was performed according to the power law <ASW>∝ Eαfβ. The lower negative value of β for Sm:PMN-PT suggests a shorter response time of crystallographic domains for it as compared to that for PMN-PT. The value of exponent α for PMN-PT was found to be higher in the low-field regime where 180° switching dominates the domain reorientation process. For Sm:PMN-PT, on the other hand, the value of α was found to be higher at high fields, which implies a superior ferroelastic domain reorientation. A similar power law scaling was also performed on the non-switching loops, which suggests a faster dynamic response of intrinsic polarization in Sm:PMN-PT as compared to that for PMN-PT. However, the intrinsic polarization in Sm:PMN-PT was found to be less responsive to the increasing field as compared to that for PMN-PT. We believe that the findings of this investigation would add another dimension to the understanding of the mechanism responsible for the high piezoelectric activity in samarium doped PMN-0.28PT crystal and polycrystalline ceramics.

Thermal stability of non-collinear antiferromagnetic Mn3Sn nanodot

D019-Mn3Sn, an antiferromagnet having a non-collinear spin structure in a kagome lattice, has attracted great attention owing to various intriguing properties such as large anomalous Hall effect. Stability of a magnetic state against thermal fluctuation, characterized in general by the thermal stability factor Δ, has been well studied in ferromagnetic systems but not for antiferromagnets. Here, we study Δ of the antiferromagnetic Mn3Sn nanodots as a function of their diameter D. To quantify Δ, we measure the switching probability as a function of the pulse-field amplitude and analyze the results based on a model taking account of two and sixfold magnetic anisotropies in the kagome plane. We observe no significant change in Δ down to D = 300 nm below which it decreases with D. The obtained D dependence is well explained by a single-domain and nucleation-mediated reversal models. These findings provide a basis to understand the thermal fluctuation and reversal mechanism of antiferromagnets for device applications.

Radiation reaction effects in relativistic plasmas: The electrostatic limit.

We study the evolution of electrostatic plasma waves, using the relativistic Vlasov equationextended by the Landau-Lifshitz radiation reaction, accounting for the back-reaction due to the emission of single particle Larmor radiation. In particular, the Langmuir wave damping is calculated as a function of wave number, initial temperature, and initial electric field amplitude. Moreover, the background distribution function loses energy in the process, and we calculate the cooling rate as a function of initial temperature and initial wave amplitude. Finally, we investigate how the relative magnitude of wave damping and background cooling varies with the initial parameters. In particular, it is found that the relative contribution to the energy loss associated with background cooling decreases slowly with the initial wave amplitude.

Controllable unidirectional magnetoresistance in ferromagnetic films with broken symmetry

Spin-related unidirectional magnetoresistance (UMR) exhibits nonreciprocal transport to either charge current or magnetization reversal, providing a potential application for direct electrical readout of in-plane magnetization using simple two-terminal geometry. To achieve such a UMR, it is usually believed that an adjacent heavy metal or other materials with strong spin-orbit coupling (SOC) as the spin polarizer is indispensable, leading to most efforts on multilayer structures rather than single-layer ferromagnetic films. Here, we report the observation of UMR in a single CoPt film by introducing a vertical composition gradient to break the structural inversion symmetry. Moreover, unlike conventional heavy-metal/ferromagnetic-metal bilayer films, the UMR in the CoPt film with a positive Co composition gradient is controllable as a function of current amplitude, which shows the decrease, sign reversal, and then enhancement with the increment of current density. These results reveal two competing UMR mechanisms with opposite signs in electrical current dependency, i.e., bulk Rashba effect induced by composition gradients and anomalous Nernst effect driven by a vertical temperature gradient. Our work provides a promising way to manipulate the UMR in a single ferromagnetic film with the combination of charge-spin conversion and magnetothermal effect.

Propagation of Lamb waves in an elastic layer with irregular surfaces

In this article, we investigate the problem of Lamb wave propagation in a layer composed of homogeneous, isotropic material with irregular free surfaces. It is assumed that the irregular free surfaces vary slowly in the direction of wave propagation. By employing an asymptotic perturbation method, a unique asymptotic solution for the amplitude function of Lamb waves is obtained. The dispersion relation is expressed as a function of phase velocity of waves, wave number and the direction of wave propagation. We examine the effect of irregularities of the boundary surfaces on the propagation of waves under the assumption that free surfaces have periodic properties.

Arrhenius Fatigue Life Modeling for Lead-Free Solder Joints in Accelerated Combined Fatigue and Creep Tests at Different Operating Temperatures

Frequent failures in interconnected materials in microelectronic packages play a vital role in determining the reliability of electronic devices. Differences in the thermal expansion coefficients of the solder joint, printed circuit board (PCB), and electronic package are a major source of applied stress on solder joints. Due to health concerns and governmental regulations associated with using leaded solder alloys, SAC solder alloys are commonly used as an alternative to Pb-alloys because of their outstanding solderability and reliability. The shear fatigue creep accelerated test at different load levels (16 MPa, 20 MPa, and 24 MPa) was implemented in this study by using a universal micro-testing machine to investigate solder joint reliability. The creep effects were demonstrated by employing 60 seconds of dwell time for each alternating stress value and comparing its impact on solder joint reliability with the fatigue test results. The accelerated test was applied to SAC305 (96.5% Sn, 3% Ag, 0.5% Cu) solder joints with OSP surface finish at different testing temperatures (25°C, 60°C, and 100°C). Seven replicates were considered as a sample size for the reliability analysis. A two-parameter Weibull distribution was employed as the dominant distribution to describe the fatigue behavior at each condition. The characteristic life and shape parameters at each condition were extracted from the obtained Weibull models. The stress–life equation was used to estimate the reliability performance of the solder joints against fluctuations in stress amplitude at differing testing temperatures. The inelastic work per cycle and plastic strain were calculated from the acquired hysteresis loop under each condition. Coffin–Manson and Morrow energy models illustrate the relationships between fatigue life versus plastic strain and inelastic work, respectively. The effects of the oscillated testing temperature on the stress–life model, Morrow energy model, and Coffin–Manson model were elaborated using the Arrhenius equation. The results indicated a severe degradation of fatigue life with increased testing temperature. Raising the stress amplitude had a less significant impact on fatigue life reduction than increasing the testing temperature. The reliability prediction models, as a function of the fatigue properties and testing temperature, were derived from the Arrhenius, Coffin–Manson, and Morrow energy models. The acquired prediction equations produced acceptable goodness-of-fit values. Finally, a general reliability model with a 99% adequacy value (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) was constructed as a function of testing temperature and stress amplitude.

Electronic states of a disordered two-dimensional quasiperiodic tiling: From critical states to Anderson localization

We consider critical eigenstates in a two dimensional quasicrystal and their evolution as a function of disorder. By exact diagonalization of finite size systems we show that the evolution of properties of a typical wave-function is non-monotonic. That is, disorder leads to states delocalizing, until a certain crossover disorder strength is attained, after which they start to localize. Although this non-monotonic behavior is only present in finite-size systems and vanishes in the thermodynamic limit, the crossover disorder strength decreases logarithmically slowly with system size, and is quite large even for very large approximants. The non-monotonic evolution of spatial properties of eigenstates can be observed in the anomalous dimensions of the wave-function amplitudes, in their multifractal spectra, and in their dynamical properties. We compute the two-point correlation functions of wave-function amplitudes and show that these follow power laws in distance and energy, consistent with the idea that wave-functions retain their multifractal structure on a scale which depends on disorder strength. Dynamical properties are studied as a function of disorder. We find that the diffusion exponents do not reflect the non-monotonic wave-function evolution. Instead, they are essentially independent of disorder until disorder increases beyond the crossover value, after which they decrease rapidly, until the strong localization regime is reached. The differences between our results and earlier studies on geometrically disordered ``phason-flip'' models lead us to propose that the two models are in different universality classes. We conclude by discussing some implications of our results for transport and a proposal for a Mott hopping mechanism between power law localized wave-functions, in moderately disordered quasicrystals.

Strong Coupling of aGd3+Multilevel Spin System to an On-Chip Superconducting Resonator

We report the realization of a strong coupling between a Gd$^{3+}$ spin ensemble hosted in a scheelite (CaWO$_4$) single crystal and the resonant mode of a coplanar stripline superconducting cavity leading to a large separation of spin-photon states of 146 MHz. The interaction is well described by the Dicke model and the crystal-field Hamiltonian of the multilevel spin system. We observe a change of the crystal-field parameters due to the presence of photons in the cavity that generates a significant perturbation of the crystal ground state. Using finite-element calculations, we numerically estimate the cavity sensing volume as well as the average spin-photon coupling strength of $g_0\approx$ 620 Hz. Lastly, the dynamics of the spin-cavity states are explored via pulsed measurements by recording the cavity ring-down signal as a function of pulse length and amplitude. The results indicate a potential method to initialize this multilevel system in its ground state via an active cooling process.

Reliability modeling of the fatigue life of lead-free solder joints at different testing temperatures and load levels using the Arrhenius model

Reliability of the microelectronic interconnection materials for electronic packages has a significant impact on the fatigue properties of the electronic assemblies. This is due to the correlation between solder joints reliability and the most frequent failure modes seen in electronic devices. Due to their superior mechanical and fatigue properties, SAC alloys have supplanted Pb-solder alloys as one of the most commonly used solder materials used as interconnection joints on electronic packages. The main aim of this study is to develop a prediction model of the fatigue life of the solder joints as a function of the experimental conditions. Using a customized experimental setup, an accelerated fatigue shear test is applied to examine the fatigue life of the individual SAC305 solder joints at actual setting conditions. OSP surface finish and solder mask defined are used in the studied test vehicle. The fatigue test includes three levels of stress amplitude and four levels of testing temperature. A two-parameter Weibull distribution is used for the reliability analysis for the fatigue life of the solder joints. A stress–strain curve is plotted for each cycle to construct the hysteresis loop at each cyclic load and testing temperature. The acquired hysteresis loop is used to estimate the inelastic work per cycle and plastic strain. The Morrow energy and Coffin Manson models are employed to describe the effects of the fatigue properties on the fatigue life of the solder joints. The Arrhenius model is implemented to illustrate the evolutions in the stress life, Morrow, and Coffin Manson equations at various testing temperatures. The fatigue life of SAC305 solder joints is then predicted using a general reliability model as a function of the stress amplitude and testing temperature.

One-component delocalized nonlinear vibrational modes of square lattices

All possible one-component delocalized nonlinear vibrational modes (DNVMs) in a square lattice are analyzed. DNVMs are obtained taking into account exclusively the symmetry of a square lattice, and therefore, they exist regardless of the type of interactions between particles. In this work, the interactions of the nearest and next nearest neighbors are described by the $$\beta $$ -FPUT potential. For each DNVM, frequency, kinetic and potential energies are described as functions of amplitude. The mechanical stresses caused by DNVMs and the effect of DNVMs on the stiffness constants of the lattice are presented. DNVMs with higher vibration frequencies have a stronger effect on the mechanical properties of the lattice. Examples of analytical analysis of DNVMs are given. It is found that two of the sixteen one-component DNVMs can have frequencies above the phonon band in the entire range of their amplitudes. It is shown that these DNVMs can be used to construct discrete breathers by applying localizing functions. The modulational instability of these two DNVMs leads to the formation of chaotic DBs. The presented results contribute to a better understanding of the nonlinear dynamics of a square lattice by analyzing the properties of a class of delocalized exact solutions and demonstrating their connection with discrete breathers.

Large amplitude oscillatory shear study of a colloidal gel near the critical state.

A system undergoing sol-gel transition passes through a unique point, known as the critical gel state, where it forms the weakest space spanning percolated network. We investigate the nonlinear viscoelastic behavior of a colloidal dispersion at the critical gel state using large amplitude oscillatory shear rheology. The colloidal gel at the critical point is subjected to oscillatory shear flow with increasing strain amplitude at different frequencies. We observe that the first harmonic of the elastic and viscous moduli exhibits a monotonic decrease as the material undergoes a linear to nonlinear transition. We analyze the stress waveform across this transition and obtain the nonlinear moduli and viscosity as a function of frequency and strain amplitude. The analysis of the nonlinear moduli and viscosities suggests intracycle strain stiffening and intracycle shear thinning in the colloidal dispersion. Based on the insights obtained from the nonlinear analysis, we propose a potential scenario of the microstructural changes occurring in the nonlinear region. We also develop an integral model using the time-strain separable Kaye-Bernstein-Kearsley-Zapas constitutive equation with a power-law relaxation modulus and damping function obtained from experiments. The proposed model with a slight adjustment of the damping function inferred using a spectral method, compares well with experimental data at all frequencies.

The roles of Kerr nonlinearity in a bosonic quantum neural network

The emerging technology of quantum neural networks (QNNs) offers a quantum advantage over classical artificial neural networks (ANNs) in terms of speed or efficiency of information processing tasks. It is well established that nonlinear mapping between input and output is an indispensable feature of classical ANNs, while in a QNN the roles of nonlinearity are not yet fully understood. As one tends to think of QNNs as physical systems, it is natural to think of nonlinear mapping originating from a physical nonlinearity of the system, such as Kerr nonlinearity. Here we investigate the effect of Kerr nonlinearity on a bosonic QNN in the context of both classical (simulating an XOR gate) and quantum (generating Schrödinger cat states) tasks. Aside offering a mechanism of nonlinear input-output mapping, Kerr nonlinearity reduces the effect of noise or losses, which are particularly important to consider in the quantum setting. We note that nonlinear mapping may also be introduced through a nonlinear input-output encoding rather than a physical nonlinearity: for example, an output intensity is already a nonlinear function of input amplitude. While in such cases Kerr nonlinearity is not strictly necessary, it still increases the performance in the face of noise or losses.

Annealing Effects of Multidirectional Oscillatory Shear in Model Glass Formers

We study the effects of cyclic, athermal quasi-static shear on a model glass-forming system in three dimensions. We utilize the three available orthogonal shear planes, namely $XY, YZ \text{ and } XZ$ to better explore the energy landscape. Using measurements of the stroboscopic $(\gamma = 0)$ energy, we study the effects of using an orthogonal shear direction to perturb unidirectional steady-states. We find that that each sequence of the unidirectional protocol leads to compaction with the universal, $\Delta E \sim N^{-1}$ behavior as a function of the number of cycles, $N$. Additionally we find that cyclic shear utilizing multiple shear planes presents hierarchical compaction, producing progressively lower steady state energies compared to a protocol involving unidirectional cyclic shear alone. Furthermore, with the periodicity of the stroboscopic energy as reference, we show that it is possible to achieve steady state limit-cycles of tunable periodicities using different combinations of the three orthogonal strain directions. We find that such protocols exhibit better annealing as compared to protocols with steady states created using unidirectional shear. Importantly, we find a non-trivial trend in the annealing energy and the period of the steady-state limit-cycle, with an aperiodic protocol appearing to produce the most well annealed states. Finally, we compare the phase diagram of the average steady state energy $\langle E_{\text{S.S.}} \rangle$, as a function of the shearing amplitude $\gamma_{\max}$, using unidirectional and multidirectional protocols, and find that the universal features are preserved.

Electroretinograms from Crayfish Compound Eyes Evokedby Mid-infrared Irradiation:Spectral Sensitivity Measurements of the Fast and Late Reactions

Free-electron lasers at Kyoto University and Nihon University were used as mid-infrared (IR) irradiation stimuli for crayfish compound eyes, and two corneal reactions were detected as the amplitude function of electroretinograms and were identified as a fast reaction and a late reaction. This fast reaction is a new discovery. The spectralsensitivities of the two corneal reactions were measured with an electrophysiological technique at eight selectedmid-IR wavelengths in 2 µm steps ranging from 4 to 18 µm. The wavelength at which maximum sensitivity wasreached was 12–14 µm for the fast reaction and 10–12 µm for the late reaction. In addition, adaptation (attenuationand restoration) of the late reaction to repeated mid-IR stimuli was observed.

Residual entropy and magnetocaloric effect in a diluted sawtooth spin model of hole-doped CuO chains.

Ground-state and magnetocaloric properties of a site-diluted sawtooth magnetic chain in the presence of an external magnetic field are exactly investigated by using the transfer-matrix method. The model captures the main magnetic interactions along CuO chains present in some hole-doped cuprates. The ground-state diagram is exhibited and analytical expressions for the residual entropy within each ground state and along the transition lines are derived. We explicitly discuss the role of the underlying pairing correlations and the entropy maximization principle. The isothermal entropy change is determined as a function of interaction parameters, doping concentration, and magnetic-field amplitude. Normal and inverse magnetocaloric effects are reported. Adiabatic demagnetization curves are discussed in connection with configurational and spin contributions to the residual entropy.

Simulation Analysis of a Single-Phase AC Circuit with a Nonlinear Load

The IEEE 1459 standard states that: “There is a need to quantify correctly the distortions caused by the nonlinear and parametric loads …” The paper undertakes this problem. The article includes an analysis of selected steady-state properties of a single-phase AC circuit containing a series connection of a resistance, an inductance, and a nonlinear element described by a signum function. The circuit is supplied from a sinusoidal voltage source. The mathematical model of this circuit is described using dimensionless variables. Based on the harmonic balance, a description of the circuit for the fundamental harmonic and the circuit for the remaining harmonics was separated. On the basis of the relationship between the current and voltage waveforms, the solution for all harmonics, the harmonic content coefficients, and the elements of the equivalent scheme of the nonlinear load, were estimated symbolically. Based on the circuit equations, a circuit model and measurement systems were developed in Simulink, as well as a program that controls these models in MATLAB and determines the characteristics of the circuit model. The paper presents selected circuit characteristics as a function of load voltage amplitude and circuit resistance. The conclusions drawn from these studies have practical significance.

Assessing the Heat Generation and Self-Heating Mechanism of Superparamagnetic Fe3O4 Nanoparticles for Magnetic Hyperthermia Application: The Effects of Concentration, Frequency, and Magnetic Field.

Magnetite nanoparticles (MNPs) exhibit favorable heating responses under magnetic excitation, which makes them particularly suited for various hyperthermia applications. Herein, we report the detailed self-heating mechanisms of MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology. The as-prepared MNPs were fully characterized using various spectroscopic techniques including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). MNPs exhibited stable 15 nm quasi-spherical small-sized particles, pure crystalline cubic Fe3O4 phases, high saturation magnetizations (Ms = ~40 emu·g-1), and superparamagnetic behavior. In response to alternating magnetic fields (AMFs), these MNPs displayed excellent self-heating efficiencies with distinctive heating responses, even when minimal doses of MNPs were used. Heating efficacies and specific absorption rate (SAR) values as functions of concentration, frequency, and amplitude were systematically investigated. Remarkably, within only a few minutes, MNPs (2.5 mg/mL) showed a rapid dissipation of heat energy, giving a maximum intrinsic loss power (ILP) of 4.29 nHm2/kg and a SAR of 261 W/g. Hyperthermia temperatures were rapidly reached in as early as 3 min and could rise up to 80 °C. In addition, Rietveld refinement, Langevin, and linear response theory (LRT) models were studied to further assess the magnetic and heating mechanisms. The LRT model was used to determine the Néel relaxation time (τR = 5.41 × 10-7 s), which was compared to the Brownian relation time value (τB = 11 × 10-7 s), showing that both mechanisms are responsible for heat dissipated by the MNPs. Finally, the cytotoxicity assay was conducted on aqueous dispersions of MNPs, indicating their biocompatibility and low toxicity. Our results strongly suggest that the as-prepared Fe3O4 MNPs are promising vehicles for potential magnetically triggered biomedical hyperthermia applications.