Increase In Oscillation Period Research Articles

Low-frequency regular pulse and intermittent oscillation in a mid-infrared interband cascade laser with optoelectronic feedback.

In this work, we experimentally investigate the nonlinear dynamics of a mid-infrared interband cascade laser (ICL) subject to optoelectronic feedback (OEF) through inspecting the time series and power spectrum of the laser output. The results show that, within the range of feedback strength limited by the experiment condition, the ICL sequentially presents stable state, continuously periodical oscillation (CPO), low-frequency regular pulse (LF-RP) and intermittent oscillation state with the increase of feedback strength. For the LF-RP state, the peak-to-peak value and the oscillation period increase with the increase of feedback strength. For the intermittent oscillation state, the time series is composed of the laminar region and burst region appeared alternately, and the average value and standard deviation for the duration of burst region gradually decrease with the increase of feedback strength.

Forced vibrations of high-rise buildings

Studies were conducted to analyze the behavior of a high-rise structure on various kinematic effects, taking into account the real geometry, dissipative and nonlinear properties of the structure material. A generalized approach was developed for the dynamic calculation of high-rise structures, and the frequency response characteristics at various points of the structure were built. It was found that nonlinear properties are manifested when the impact can cause significant strain in the structure. This applies not only to the magnitude of the impact intensity, but also to its frequency content. If a non-linearly elastic strain of the material is manifested in the structure, then this leads to a decrease in the amplitudes of points displacements and to an increase in oscillation period compared to a linearly elastic structure under similar kinematic effects.

Drag reduction in turbulent flow along a cylinder by circumferential oscillating Lorentz force

Direct numerical simulations are performed to study the drag reduction effect in turbulent flow along a cylinder by the circumferential oscillating Lorentz force at the Reynolds number Reτ = 272 based on the reference friction velocity and the thickness of the boundary layer. The maximum drag reduction rate obtained in the present work is 42.6%. The intensity, penetration thickness, distribution (idealized or realistic), and oscillation period of the Lorentz force are all crucial in determining the drag reduction rate. As the Lorentz force is intensified or its penetration thickness and oscillation period increase, the wall friction drag will prominently decrease as long as the circumferential flow is stable. The Stokes layer, introduced by the circumferential oscillating Lorentz force, effectively manipulated the near-wall coherent structures, leading to the decrease of the wall friction drag. However, the occurrence of the force-induced vortices in the near-wall region can also lead to significant drag increase by enhancing the radial momentum transportation due to centrifugal instability. By estimating the energy consumption rate, it is clear that the extra power to implement the Lorentz force is far more than the power saved due to drag reduction, which is the result of the low conductivity of the fluid media. Taking the coupling between the electromagnetic field and the flow field into consideration, the wall friction drag is nearly zero and the turbulence intensity in the near-wall region is very low when the induced Lorentz force is high. But the induced Lorentz drag is greatly increased and the turbulence fluctuations are enhanced in the outer region.

Temperature effect on qubit in RbCl quantum rod

We change the ellipsoidal boundary in a quantum rod (QR) into a spherical one by a coordinate transformation, and then study the influences of the ellipsoid aspect ratio and polaron radius on the probability density (PD) and oscillation period (OP) of an electron with the variational method of Pekar type (VMPT). By employing the quantum statistics theory (QST), we investigate the temperature effects on the PD and the OP. Numerical results denote that the electron probability density and the oscillation period increase (decay) with raising temperature in lower (higher) temperature regime. The electron probability density increases (decreases) with increasing ellipsoid aspect ratio when the temperature is in lower (higher) regime. The electron probability density decays (enhances) with increasing polaron radius when the temperature is in lower (higher) temperature regime. The oscillation period is an increasing function of the ellipsoid aspect ratio, whereas it is a decreasing one of the polaron radius.

Modeling Follicle Cell Length Oscillations During Tissue Elongation in Drosophila Egg Chamber

Periodic processes are an indispensable part of biological phenomena. Circadian rhythms, heart rhythms, neuronal oscillations, cell cycle, and cytoskeletal structures such as the axonemes of cilia are all examples of systems exhibiting oscillatory dynamics. The underlying mechanisms of several such processes can be explained by understanding the origins of these oscillations and characterizing them. One particular example is the follicle cell basal surface area oscillations observed in Drosophila egg chamber during oogenesis. It has been suggested that these oscillations restrict the egg chamber width, and thus help in elongation of the tissue. In this work, we attempt to model these oscillations in follicle cell length using a mechano-chemical model. Our model predicts an increase in oscillation period, upon removal of the basement membrane, which has been observed experimentally upon collagenase treatment of the egg chamber. The model also predicts an inverse relationship of maximum contractile force and oscillation period.

Influences of temperature and coulomb bound potential on the properties of quantum rod qubit

We study the eigenenergies and the eigenfunctions of the ground and the first excited states of an electron strongly coupled to LO-phonon in a quantum rod (QR) with a hydrogen-like impurity at the center by using variational method of Pekar type. This QR system may be used as a two-level quantum qubit. When the electron is in the superposition state of the ground and the first excited states, we obtained the time evolution of the electron probability density oscillating in the QR with a certain period. We then investigate the effects of the temperature and the hydrogen-like impurity on the time evolution of the electron probability density and the oscillation period. It is found that the electron probability density and the oscillation period increase (decrease) with increasing temperature in lower (higher) temperature regime. The electron probability density and the oscillation period decrease (increase) with increasing electron–phonon coupling strength when the temperature is lower (higher). Whereas they increase (decrease) with increasing Coulomb bound potential when the temperature is lower (higher).

DUAL TRIGGER OF TRANSVERSE OSCILLATIONS IN A PROMINENCE BY EUV FAST AND SLOW CORONAL WAVES:SDO/AIA ANDSTEREO/EUVI OBSERVATIONS

We analyze flare-associated transverse oscillations in a quiescent solar prominence on 2010 September 8–9. Both the flaring active region and the prominence were located near the west limb, with a favorable configuration and viewing angle. The full-disk extreme ultraviolet (EUV) images of the Sun obtained with high spatial and temporal resolution by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory show flare-associated lateral oscillations of the prominence sheet. The STEREO-A spacecraft, 815 ahead of the Sun–Earth line, provides an on-disk view of the flare-associated coronal disturbances. We derive the temporal profile of the lateral displacement of the prominence sheet by using the image cross-correlation technique. The displacement curve was de-trended and the residual oscillatory pattern was derived. We fit these oscillations with a damped cosine function with a variable period and find that the period is increasing. The initial oscillation period (P0) is ∼28.2 minutes and the damping time (τD) ∼ 44 minutes. We confirm the presence of fast and slow EUV wave components. Using STEREO-A observations, we derive a propagation speed of ∼250 km s−1 for the slow EUV wave by applying the time-slice technique to the running difference images. We propose that the prominence oscillations are excited by the fast EUV wave while the increase in oscillation period of the prominence is an apparent effect, related to a phase change due to the slow EUV wave acting as a secondary trigger. We discuss implications of the dual trigger effect for coronal prominence seismology and scaling law studies of damping mechanisms.

The effect of temperature and magnetic field on a quantum rod qubit

The Hamiltonian of a quantum rod (QR) with an ellipsoidal boundary is given after a coordinate transformation, which changes the ellipsoidal boundary into a spherical one. We obtain the eigenenergies and eigenfunctions of the ground and the first excited states of an electron, which is strongly coupled to the LO-phonon in a QR under an applied magnetic field by using the Pekar variational method. This system in QR may be employed as a two-level qubit. When the electron is in the superposition state of the ground and the first-excited states, we study the time evolution of the electron probability density. The relations of the probability density of electron on the temperature and the relations of the period of oscillation on the temperature and the cyclotron frequency of magnetic field are taken into consideration. The results show that the probability density of the electron oscillates in the QR with a oscillation period. It is found that the electron probability density and the oscillation period increase (decrease) with increasing temperature in lower (higher) temperature regime. The electron probability density increases (decreases) with increasing cyclotron frequency when the temperature is lower (higher). The oscillation period decreases with the increase of the cyclotron frequency.

The Effects of Temperature and Electric Field on a Quantum Rod Qubit

The Hamiltonian of a quantum rod (QR) with an ellipsoidal boundary is given after a coordinate transformation, which changes the ellipsoidal boundary into a spherical one. We then study the eigenenergies and the eigenfunctions of the ground and the first excited states of an electron strongly coupled to LO-phonon under an applied electric field by using variational method of Pekar type. This QR system may be used as a two-level quantum qubit. When the electron is in the superposition state of the ground and the first excited states, we obtained the time evolution of the electron probability density oscillating in the QR with a certain period. We then investigate the effects of the temperature and the electric field on the time evolution of the electron probability density and the oscillation period. It is found that the electron probability density and the oscillation period increase (decrease) with increasing temperature in lower (higher) temperature regime. The electron probability density decreases (increases) with increasing electric field when the temperature is lower (higher). The oscillation period decreases with the increase of the electric field along the ρ x direction.

Quantum Transition of Two-Level System in a Parabolic Quantum Dot

The time evolution of the quantum mechanical state of an electron is calculated by using variational method of Pekar type on the condition of electric-LO phonon strong coupling in a parabolic quantum dot. We obtained the eigen energies of the ground state and the first-excited state, the eigen functions of the ground state and the first-excited state this system in a quantum dot may be employed as a two-level quantum system-qubit. The supposition electron is in system’s ground state in the initial time, the electron transit from the ground state to the excited state in presence of an electric field F along the x axis. The results indicate that the electron transition probability and the oscillation period increase with decreasing the electron-LO-phonon coupling constant, increasing the electric field and the confinement length.

Radius-Dependent Inhibition and Activation of Chemical Oscillations in Small Droplets

The oscillatory dynamics in droplets of the ferroin-catalyzed Belousov-Zhabotinsky solution is investigated. Due to a diffusive influx of molecular oxygen from a surrounding hydrophobic phase, droplets experience an increase in oscillation period with decreasing drop radius. If the radius is smaller than approximately 1.5 mm, no oscillations are observed. The phase of oscillations showed a radial dependence that gives rise to nontransient phase waves propagating from the center outward. In the absence of oxygen, the period decreases slightly with decreasing drop radii. A simple geometrical analysis qualitatively explains the main experimental observations. The analysis stems from an approach that relates the efficiency of inhibition to the surfaceto-volume ratio of droplets.

Equatorial oscillations maintained by gravity waves as described with the Doppler Spread Parameterization: I. Numerical experiments

Gravity Waves (GW) as described with the Doppler Spread Parameterization (DSP) of Hines have been shown to produce significant Quasi-biennial and Semi-annual oscillations (QBO and SAO) in the zonal circulation at equatorial latitudes. To elucidate the process involved, we discuss computer experiments performed without the external, seasonal variations in solar differential heating, and the conclusions are summarized here. (1) As reported earlier, two kinds of oscillations are then generated spontaneously: one at lower altitudes in the stratosphere which has a long period approaching that of the QBO, the other one at higher altitudes in the mesosphere which has a shorter period close to that of the SAO. The amplitudes of these oscillations are weaker, however, than those generated with seasonal heating. (2) When the time independent solar heating is turned off, the oscillations continue but with significantly reduced period in the mesosphere where the vertical winds driven by solar differential heating produce Doppler shifting. The associated temperature variations are then small, consistent with the one dimensional prototype calculations discussed by Lindzen and Holton. (3) When the GW momentum source is turned off above 40 km to suppress the short-period oscillation, the long-period oscillation below continues with enhanced amplitude and period. When the source is turned off below 35 km, the amplitude of the short-period oscillation increases at higher altitudes, indicative of increased acceleration. (4) The wind oscillations change systematically and dramatically with changing eddy diffusivity/viscosity ( K ). The amplitudes and periods of both short- and long-period oscillations decrease (increase) with increasing (decreasing) K , and above a certain value of viscosity, both oscillations completely cease. Lowering K thus helps in generating a larger and longer period QBO at lower altitudes, but can be detrimental to the SAO when the natural oscillation period increase significantly above six months. (5) Under oscillation conditions, the height variations in the GW vertical wave numbers reveal a staircase pattern reflecting the intermittence characteristic of the wave interaction. It reveals the nonlinearity of the GW interaction to be of third (odd) order, which has the distinctive property that it can feed and maintain the fundamental harmonic of the oscillation—considered a prerequisite for sustaining the oscillations without external time dependent source. In the companion paper, an analytical model of the equatorial oscillation is presented which describes some of the trends reported here.

Increase in Period of Oscillatory Coupling in Cu by Doping with Ni

ABSTRACTThe origin of oscillatory interlayer coupling via Cu is explored in sputtered Co/Cu Multilayers by varying the hole concentration in the copper layers by doping with elements of different valence. Detailed studies were carried out for a series of Cu-Ni alloys. The oscillation period of pure Cu is observed to increase monotonically with increasing Ni concentration and is almost doubled for 40 atomic % Ni. The increase in oscillation period can be accounted for by considering changes in the topology of (he Fermi surface of the alloy resulting from the change in band Tilling.

Relation of unsaturated fatty acid composition of rat liver mitochondria to oscillation period, spin label motion, permeability and oxidative phosphorylation

An investigation was made of the influence of mitochondrial unsaturated fatty acid composition on the following mitochondrial parameters: oscillation period, spin label motion (ESR), permeability, and oxidative phosphorylation. Liver mitochondria from rats fed diets deficient in or supplemented with essential fatty acids showed approximately the same total number of unsaturated fatty acids but changed unsaturation levels. Electron microscopy showed that the morphology of the inner membrane compartment was unchanged. Two differences were correlated with unsaturated fatty acid composition: (1) a slower frequency (or time period) of the oscillatory state of energy-dependent ion transport and (2) a reduction in the motional freedom of each of three spin labels (12NS, 5N10 and 7N14). The increase in oscillation period could arise from a number of rate-limiting processes, including permeability of mitochondria to various anions, cations, and substrate metabolites. However, when the permeability of mitochondria to such substances was tested, no changes were observed in passive or active uptake of these substances or in the efficiency of oxidative phosphorylation under steady-state conditions. Thus, the two parameters, oscillation period and freedom of spin label motion, which are dependent upon large domains of the mitochondrial membranes, are significantly influenced by the change in unsaturated fatty acid composition in essential fatty acid-depleted mitochondria, even though processes such as permeability of ionic materials and oxidative phosphorylation were not measurably affected by these changes in unsaturated fatty acid composition.