Self-oscillations of a two-dimensional shear flow with forcing and dissipation

Science.gov (United States)

López Zazueta, A.; Zavala Sansón, L.

2018-04-01

Two-dimensional shear flows continuously forced in the presence of dissipative effects are studied by means of numerical simulations. In contrast with most previous studies, the forcing is confined in a finite region, so the behavior of the system is characterized by the long-term evolution of the global kinetic energy. We consider regimes with 1 limited to develop only one vortical instability by choosing an appropriate width of the forcing band. The most relevant regime is found for Reλ > 36, in which the energy maintains a regular oscillation around a reference value. The flow configuration is an elliptical vortex tilted with respect to the forcing axis, which oscillates steadily also. Second, the flow is allowed to develop two Kelvin-Helmholtz billows and eventually more complicated structures. The regimes of the one-vortex case are observed again, except for Reλ > 135. At these values, the energy oscillates chaotically as the two vortices merge, form dipolar structures, and split again, with irregular periodicity. The self-oscillations are explained as a result of the alternate competition between forcing and dissipation, which is verified by calculating the budget terms in the energy equation. The relevance of the forcing-vs.-dissipation competition is discussed for more general flow systems.

General Forced Oscillations in a Real Power Grid Integrated with Large Scale Wind Power

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Ping Ju

2016-07-01

Full Text Available According to the monitoring of the wide area measurement system, inter-area oscillations happen more and more frequently in a real power grid of China, which are close to the forced oscillation. Applying the conventional forced oscillation theory, the mechanism of these oscillations cannot be explained well, because the oscillations vary with random amplitude and a narrow frequency band. To explain the mechanism of such oscillations, the general forced oscillation (GFO mechanism is taken into consideration. The GFO is the power system oscillation excited by the random excitations, such as power fluctuations from renewable power generation. Firstly, properties of the oscillations observed in the real power grid are analyzed. Using the GFO mechanism, the observed oscillations seem to be the GFO caused by some random excitation. Then the variation of the wind power measured in this power gird is found to be the random excitation which may cause the GFO phenomenon. Finally, simulations are carried out and the power spectral density of the simulated oscillation is compared to that of the observed oscillation, and they are similar with each other. The observed oscillation is thus explained well using the GFO mechanism and the GFO phenomenon has now been observed for the first time in real power grids.

Bifurcation of forced periodic oscillations for equations with Preisach hysteresis

International Nuclear Information System (INIS)

Krasnosel'skii, A; Rachinskii, D

2005-01-01

We study oscillations in resonant systems under periodic forcing. The systems depend on a scalar parameter and have the form of simple pendulum type equations with ferromagnetic friction represented by the Preisach hysteresis nonlinearity. If for some parameter value the period of free oscillations of the principal linear part of the system coincides with the period of the forcing term, then one may expect the existence of unbounded branches of periodic solutions for nearby parameter values. We present conditions for the existence and nonexistence of such branches and estimates of their number

Forced oscillation of hyperbolic equations with mixed nonlinearities

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Yutaka Shoukaku

2012-04-01

Full Text Available In this paper, we consider the mixed nonlinear hyperbolic equations with forcing term via Riccati inequality. Some sufficient conditions for the oscillation are derived by using Young inequality and integral averaging method.

Effect of static deformation and external forces on the oscillations of levitated droplets

Science.gov (United States)

Suryanarayana, P. V. R.; Bayazitoglu, Y.

1991-01-01

The oscillations of an aspherical droplet subjected to different external forces are considered. For an arbitrary shape deformation, it is shown that the frequency spectrum splits into (2l - 1) peaks for a mode l oscillation, and the splitting of the frequency spectrum is calculated for mode 2, 3, and 4 oscillations. The deformation is then treated as a consequence of a general external force, and the frequency split is obtained in terms of the external force parameters. Droplets levitated by acoustic, electromagnetic, and combined acoustic-electromagnetic forces are considered in particular, and it is shown that the effects of asphericity adequately explain the splitting of the frequency spectrum observed commonly in experiments. The interpretation of spectra with regard to accurate surface tension measurement using the oscillations of levitated droplets is discussed, and the results applied to some previous experimental results. It is shown that the accuracy of surface tension measurements can improve if the asphericity caused by the levitating force, and the resulting frequency split, are taken into account.

Exact solution of a quantum forced time-dependent harmonic oscillator

Science.gov (United States)

Yeon, Kyu Hwang; George, Thomas F.; Um, Chung IN

1992-01-01

The Schrodinger equation is used to exactly evaluate the propagator, wave function, energy expectation values, uncertainty values, and coherent state for a harmonic oscillator with a time dependent frequency and an external driving time dependent force. These quantities represent the solution of the classical equation of motion for the time dependent harmonic oscillator.

Dynamic force microscopy with quartz tuning forks at high oscillation amplitudes

International Nuclear Information System (INIS)

Labardi, M

2007-01-01

Dynamic force microscopy (DFM) with the self-oscillator (SO) method allows reasonably high scanning rates even with high Q-factors of the resonant force sensor, typical of cantilevers in ultra-high vacuum and of quartz tuning forks. However, due to simpler interpretation of force spectroscopy measurements, small oscillation amplitudes (sub-nm level) are generally preferred. In applications like 'apertureless' scanning near-field optical microscopy (SNOM), oscillation amplitudes of the order of 5-10 nm are needed to increase optical sensitivity and to apply standard optical artefact suppression methods. This motivates the study of the behaviour of tuning forks driven at such high amplitudes, as compared to usual air-operated cantilevers. Both constant-excitation-amplitude (CE) and constant-oscillation-amplitude (CA) modes of SO-DFM are analysed, since the CA mode is more convenient for SNOM applications, denoting remarkable differences. In particular, possible instability effects, previously found in CE mode, are not anticipated for CA mode. It is shown how resonance and approach ('isophase') curves in both modes can be conveniently described in terms of the usual 'normalized frequency shift' γ and of a 'normalized gain' η, defined as a measurement of surface dissipation

Spin force and torque in non-relativistic Dirac oscillator on a sphere

Science.gov (United States)

Shikakhwa, M. S.

2018-03-01

The spin force operator on a non-relativistic Dirac oscillator (in the non-relativistic limit the Dirac oscillator is a spin one-half 3D harmonic oscillator with strong spin-orbit interaction) is derived using the Heisenberg equations of motion and is seen to be formally similar to the force by the electromagnetic field on a moving charged particle. When confined to a sphere of radius R, it is shown that the Hamiltonian of this non-relativistic oscillator can be expressed as a mere kinetic energy operator with an anomalous part. As a result, the power by the spin force and torque operators in this case are seen to vanish. The spin force operator on the sphere is calculated explicitly and its torque is shown to be equal to the rate of change of the kinetic orbital angular momentum operator, again with an anomalous part. This, along with the conservation of the total angular momentum, suggests that the spin force exerts a spin-dependent torque on the kinetic orbital angular momentum operator in order to conserve total angular momentum. The presence of an anomalous spin part in the kinetic orbital angular momentum operator gives rise to an oscillatory behavior similar to the Zitterbewegung. It is suggested that the underlying physics that gives rise to the spin force and the Zitterbewegung is one and the same in NRDO and in systems that manifest spin Hall effect.

Characterization of fluid forces exerted on a cylinder array oscillating laterally in axial flow

International Nuclear Information System (INIS)

Divaret, Lise

2014-01-01

This thesis presents an experimental and a numerical study of the fluid forces exerted on a cylinder or a cylinder array oscillating laterally in an axial flow. The parameters of the system are the amplitude, the oscillation frequency, the confinement and the length to diameter ratio of the cylinder. The objective is to determine the fluid damping created by the axial flow, i.e. the dissipative force. The industrial application of this thesis is the determination of the fluid damping of the fuel assemblies in the core of a nuclear power plant during an earthquake. The study focuses on the configurations where the oscillation velocity is small compared to the axial flow velocity. In a first part, we study the case of a cylinder with no confinement oscillating in axial flow. Two methods are used: a dynamical and a quasi-static approach. In dynamics, the damping rate is measured during free oscillations of the cylinder. In the quasi-static approach, the damping coefficient is calculated from the normal force measured on a yawed cylinder. The range of the small ratios between the oscillation and the axial flow velocities corresponds to a range of low yaw angle where the cylinder is in near-axial flow in statics. The case of a yawed cylinder has been studied both experimentally with experiments in a wind tunnel and numerically with CFD calculations. The analyses of the fluid forces shows that for yaw angles smaller than 5 degrees, a linear lift with the yaw angle creates the damping. The origin of the lift force is discussed from pressure and velocity measurements. The results of the quasi-static approach are compared to the results of the dynamical experiments. In a second part, an experimental study is performed on a rigid cylinder array made up of 40 cylinders oscillating in an axial flow. The normal force and the displacement of the cylinder array are measured simultaneously. The added mass and damping coefficient are calculated and their variation with the

Sources of spurious force oscillations from an immersed boundary method for moving-body problems

Science.gov (United States)

Lee, Jongho; Kim, Jungwoo; Choi, Haecheon; Yang, Kyung-Soo

2011-04-01

When a discrete-forcing immersed boundary method is applied to moving-body problems, it produces spurious force oscillations on a solid body. In the present study, we identify two sources of these force oscillations. One source is from the spatial discontinuity in the pressure across the immersed boundary when a grid point located inside a solid body becomes that of fluid with a body motion. The addition of mass source/sink together with momentum forcing proposed by Kim et al. [J. Kim, D. Kim, H. Choi, An immersed-boundary finite volume method for simulations of flow in complex geometries, Journal of Computational Physics 171 (2001) 132-150] reduces the spurious force oscillations by alleviating this pressure discontinuity. The other source is from the temporal discontinuity in the velocity at the grid points where fluid becomes solid with a body motion. The magnitude of velocity discontinuity decreases with decreasing the grid spacing near the immersed boundary. Four moving-body problems are simulated by varying the grid spacing at a fixed computational time step and at a constant CFL number, respectively. It is found that the spurious force oscillations decrease with decreasing the grid spacing and increasing the computational time step size, but they depend more on the grid spacing than on the computational time step size.

Impacts of radiation management techniques on the North Atlantic Oscillation

Science.gov (United States)

Adakudlu, Muralidhar; Helge Otterå, Odd; Tjiputra, Jerry; Muri, Helene; Grini, Alf; Schulz, Michael

2017-04-01

The effectiveness of various climate engineering techniques in limiting the global warming signal to reasonable levels has been the topic of state-of-the-art research on climate change. Using an Earth system model, we show that these techniques have the potential to bring down the high CO2 concentration climate in RCP8.5 to a moderate climate similar to RCP4.5 in terms of global temperature. Nevertheless, their influence on the regional aspects of atmospheric circulation is not clear. The regional circulation patterns in the atmosphere are largely characterized by the natural variability modes, such as the North Atlantic Oscillation (NAO). In this study, we assess the impacts of three radiation managment techniques, namely, Stratospheric Aerosol Injection (SAI), Marine Sky Brightening (MSB) and Cirrus Cloud Thinning (CCT), on the structure and features of the NAO. The results indicate an east-northeastward shift as well as intensification of the NAO spatial pattern in the global warming scenarios of RCP4.5 and RCP8.5, with the signal being most intense in the latter. The climate engineering forcings when applied to the RCP8.5 case tend to reduce the strength of the NAO with little impact on its position. The CCT case appears to have the maximum effect on the NAO signal. The patterns of cloud radiative forcing, expressed as the difference between net radiative forcing at TOA under average conditions and clear sky conditions, reveal a northeastward shift of the radiative heating in the north Atlantic region. This implies a possible link between the changes in the NAO signal and the cloud radiative forcing.

Application of fixed point theory to chaotic attractors of forced oscillators

International Nuclear Information System (INIS)

Stewart, H.B.

1990-11-01

A review of the structure of chaotic attractors of periodically forced second order nonlinear oscillators suggests that the theory of fixed points of transformations gives information about the fundamental topological structure of attractors. First a simple extension of the Levinson index formula is proved. Then numerical evidence is used to formulate plausible conjectures about absorbing regions containing chaotic attractors in forced oscillators. Applying the Levinson formula suggests a fundamental relation between the number of fixed points or periodic points in a section of the chaotic attractor on the one hand, and a topological invariant of an absorbing region on the other hand. (author)

A novel self-sensing technique for tapping-mode atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Ruppert, Michael G.; Moheimani, S. O. Reza [The University of Newcastle, University Drive, Callaghan NSW 2308 (Australia)

2013-12-15

This work proposes a novel self-sensing tapping-mode atomic force microscopy operation utilizing charge measurement. A microcantilever coated with a single piezoelectric layer is simultaneously used for actuation and deflection sensing. The cantilever can be batch fabricated with existing micro electro mechanical system processes. The setup enables the omission of the optical beam deflection technique which is commonly used to measure the cantilever oscillation amplitude. Due to the high amount of capacitive feedthrough in the measured charge signal, a feedforward control technique is employed to increase the dynamic range from less than 1 dB to approximately 35 dB. Experiments show that the conditioned charge signal achieves excellent signal-to-noise ratio and can therefore be used as a feedback signal for atomic force microscopy imaging.

Constraints on spatially oscillating sub-mm forces from the Stanford Optically Levitated Microsphere Experiment data

Science.gov (United States)

Antoniou, I.; Perivolaropoulos, L.

2017-11-01

A recent analysis by one of the authors [L. Perivolaropoulos, Phys. Rev. D 95, 084050 (2017), 10.1103/PhysRevD.95.084050] has indicated the presence of a 2 σ signal of spatially oscillating new force residuals in the torsion balance data of the Washington experiment. We extend that study and analyze the data of the Stanford Optically Levitated Microsphere Experiment (SOLME) [A. D. Rider et al., Phys. Rev. Lett. 117, 101101 (2016), 10.1103/PhysRevLett.117.101101] (kindly provided by A. D. Rider et al.) searching for sub-mm spatially oscillating new force signals. We find a statistically significant oscillating signal for a force residual of the form F (z )=α cos (2/π λ z +c ) where z is the distance between the macroscopic interacting masses (levitated microsphere and cantilever). The best fit parameter values are α =(1.1 ±0.4 )×10-17N , λ =(35.2 ±0.6 ) μ m . Monte Carlo simulation of the SOLME data under the assumption of zero force residuals has indicated that the statistical significance of this signal is at about 2 σ level. The improvement of the χ2 fit compared to the null hypothesis (zero residual force) corresponds to Δ χ2=13.1 . There are indications that this previously unnoticed signal is indeed in the data but is most probably induced by a systematic effect caused by diffraction of non-Gaussian tails of the laser beam. Thus the amplitude of this detected signal can only be useful as an upper bound to the amplitude of new spatially oscillating forces on sub-mm scales. In the context of gravitational origin of the signal emerging from a fundamental modification of the Newtonian potential of the form Veff(r )=-G M/r (1 +αOcos (2/π λ r +θ ))≡VN(r )+Vosc(r ) , we evaluate the source integral of the oscillating macroscopically induced force. If the origin of the SOLME oscillating signal is systematic, the parameter αO is bounded as αOchameleon oscillating potentials etc.).

Diagonal ordering operation technique applied to Morse oscillator

Energy Technology Data Exchange (ETDEWEB)

Popov, Dušan, E-mail: dusan_popov@yahoo.co.uk [Politehnica University Timisoara, Department of Physical Foundations of Engineering, Bd. V. Parvan No. 2, 300223 Timisoara (Romania); Dong, Shi-Hai [CIDETEC, Instituto Politecnico Nacional, Unidad Profesional Adolfo Lopez Mateos, Mexico D.F. 07700 (Mexico); Popov, Miodrag [Politehnica University Timisoara, Department of Steel Structures and Building Mechanics, Traian Lalescu Street, No. 2/A, 300223 Timisoara (Romania)

2015-11-15

We generalize the technique called as the integration within a normally ordered product (IWOP) of operators referring to the creation and annihilation operators of the harmonic oscillator coherent states to a new operatorial approach, i.e. the diagonal ordering operation technique (DOOT) about the calculations connected with the normally ordered product of generalized creation and annihilation operators that generate the generalized hypergeometric coherent states. We apply this technique to the coherent states of the Morse oscillator including the mixed (thermal) state case and get the well-known results achieved by other methods in the corresponding coherent state representation. Also, in the last section we construct the coherent states for the continuous dynamics of the Morse oscillator by using two new methods: the discrete–continuous limit, respectively by solving a finite difference equation. Finally, we construct the coherent states corresponding to the whole Morse spectrum (discrete plus continuous) and demonstrate their properties according the Klauder’s prescriptions.

Diminution of contact angle hysteresis under the influence of an oscillating force.

Science.gov (United States)

Manor, Ofer

2014-06-17

We suggest a simple quantitative model for the diminution of contact angle hysteresis under the influence of an oscillatory force invoked by thermal fluctuations, substrate vibrations, acoustic waves, or oscillating electric fields. Employing force balance rather than the usual description of contact angle hysteresis in terms of Gibbs energy, we highlight that a wetting system, such as a sessile drop or a bubble adhered to a solid substrate, appears at long times to be partially or fully independent of contact angle hysteresis and thus independent of static friction forces, as a result of contact line pinning. We verify this theory by studying several well-known experimental observations such as the approach of an arbitrary contact angle toward the Young contact angle and the apparent decrease (or increase) in an advancing (or a receding) contact angle under the influence of an external oscillating force.

Oscillations in deviating difference equations using an iterative technique

Directory of Open Access Journals (Sweden)

George E Chatzarakis

2017-07-01

Full Text Available Abstract The paper deals with the oscillation of the first-order linear difference equation with deviating argument and nonnegative coefficients. New sufficient oscillation conditions, involving limsup, are given, which essentially improve all known results, based on an iterative technique. We illustrate the results and the improvement over other known oscillation criteria by examples, numerically solved in Matlab.

Oscillating Casimir force between two slabs in a Fermi sea

DEFF Research Database (Denmark)

Li-Wei, Chen; Guo-Zhen, Su; Jin-Can, Chen

2012-01-01

that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude...... of L. In addition, it is found that the amplitude of the Casimir force in a Fermi gas decreases with the increase of the temperature, which also is contrary to the case in a Bose gas, since the bosonic Casimir force increases linearly with the increase of the temperature in the region T

Free oscillation of the Earth

Directory of Open Access Journals (Sweden)

Y. Abedini

2000-06-01

Full Text Available   This work is a study of the Earths free oscillations considering a merge of solid and liquid model. At the turn of 19th century Geophysicists presented the theory of the free oscillations for a self-gravitating, isotropic and compressible sphere. Assuming a steel structure for an Earth size sphere, they predicted a period of oscillation of about 1 hour. About 50 years later, the free oscillations of stars was studied by Cowling and others. They classified the oscillation modes of the stars into acoustic and gravity modes on the basis of their driving forces. These are pressure and buoyancy forces respectively. The earliest measurements for the period of the free oscillations of the Earth was made by Benyove from a study of Kamchathca earthquake. Since then, the Geophysicists have been trying to provide a theoretical basis for these measurements. Recently, the theory concerning oscillations of celestial fluids is extended by Sobouti to include the possible oscillations of the Earthlike bodies. Using the same technique, we study the free oscillations of a spherically symmetric, non-rotating and elastic model for the Earth.   We used the actual data of the Earths interior structure in our numerical calculations. Numerical results show that there exist three distinct oscillation modes namely acoustic, gravity and toroidal modes. These modes are driven by pressure, buoyancy and shear forces respectively. The shear force is due to the elastic properties of the solid part of the Earth. Our numerical results are consistent with the seismic data recorded from earthquake measurements.

On the respiratory mechanics measured by forced oscillation technique in patients with systemic sclerosis.

Directory of Open Access Journals (Sweden)

Ingrid Almeida Miranda

Full Text Available BACKGROUND: Pulmonary complications are the most common cause of death and morbidity in systemic sclerosis (SSc. The forced oscillation technique (FOT offers a simple and detailed approach to investigate the mechanical properties of the respiratory system. We hypothesized that SSc may introduce changes in the resistive and reactive properties of the respiratory system, and that FOT may help the diagnosis of these abnormalities. METHODOLOGY/PRINCIPAL FINDINGS: We tested these hypotheses in controls (n = 30 and patients with abnormalities classified using spirometry (n = 52 and pulmonary volumes (n = 29. Resistive data were interpreted with the zero-intercept resistance (Ri and the slope of the resistance (S as a function of frequency. Reactance changes were evaluated by the mean reactance between 4 and 32 Hz (Xm and the dynamic compliance (Crs,dyn. The mechanical load was evaluated using the absolute value of the impedance in 4 Hz (Z4Hz. A compartmental model was used to obtain central (R and peripheral (Rp resistances, and alveolar compliance (C. The clinical usefulness was evaluated by investigating the area under the receiver operating characteristic curve (AUC. The presence of expiratory flow limitation (EFL was also evaluated. For the groups classified using spirometry, SSc resulted in increased values in Ri, R, Rp and Z4Hz (p0.90. In groups classified by pulmonary volume, SSc resulted in reductions in S, Xm, C and Crs,dyn (p0.80. It was also observed that EFL is not common in patients with SSc. CONCLUSIONS/SIGNIFICANCE: This study provides evidence that the respiratory resistance and reactance are changed in SSc. This analysis provides a useful description that is of particular significance for understanding respiratory pathophysiology and to ease the diagnosis of respiratory abnormalities in these patients.

Correlations between forced oscillation technique parameters and pulmonary densitovolumetry values in patients with acromegaly

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G.B. Camilo

2015-01-01

Full Text Available The aims of this study were to evaluate the forced oscillation technique (FOT and pulmonary densitovolumetry in acromegalic patients and to examine the correlations between these findings. In this cross-sectional study, 29 non-smoking acromegalic patients and 17 paired controls were subjected to the FOT and quantification of lung volume using multidetector computed tomography (Q-MDCT. Compared with the controls, the acromegalic patients had a higher value for resonance frequency [15.3 (10.9-19.7 vs 11.4 (9.05-17.6 Hz, P=0.023] and a lower value for mean reactance [0.32 (0.21-0.64 vs 0.49 (0.34-0.96 cm H2O/L/s2, P=0.005]. In inspiratory Q-MDCT, the acromegalic patients had higher percentages of total lung volume (TLV for nonaerated and poorly aerated areas [0.42% (0.30-0.51% vs 0.25% (0.20-0.32%, P=0.039 and 3.25% (2.48-3.46% vs 1.70% (1.45-2.15%, P=0.001, respectively]. Furthermore, the acromegalic patients had higher values for total lung mass in both inspiratory and expiratory Q-MDCT [821 (635-923 vs 696 (599-769 g, P=0.021 and 844 (650-945 vs 637 (536-736 g, P=0.009, respectively]. In inspiratory Q-MDCT, TLV showed significant correlations with all FOT parameters. The TLV of hyperaerated areas showed significant correlations with intercept resistance (rs=−0.602, P<0.001 and mean resistance (rs=−0.580, P<0.001. These data showed that acromegalic patients have increased amounts of lung tissue as well as nonaerated and poorly aerated areas. Functionally, there was a loss of homogeneity of the respiratory system. Moreover, there were correlations between the structural and functional findings of the respiratory system, consistent with the pathophysiology of the disease.

Three-axial force sensor with capacitive read-out using a differential relaxation oscillator

NARCIS (Netherlands)

Brookhuis, Robert Anton; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.

2013-01-01

A silicon three-axis force sensor is designed and realized to be used for measurement of the interaction force between a human finger and the environment. To detect the force components, a capacitive read-out system using a novel relaxation oscillator has been developed with an output frequency

Oscillation criteria for first-order forced nonlinear difference equations

OpenAIRE

Grace Said R; Agarwal Ravi P; Smith Tim

2006-01-01

Some new criteria for the oscillation of first-order forced nonlinear difference equations of the form Δx(n)+q1(n)xμ(n+1) = q2(n)xλ(n+1)+e(n), where λ, μ are the ratios of positive odd integers 0 <μ < 1 and λ > 1, are established.

Transition to chaos in the damped and forced non-lnear oscillator

International Nuclear Information System (INIS)

Montenegro Joo, J.; Universidad Nacional Mayor de San Marcos, Lima

2009-01-01

A Virtual Lab to study the Transition to Chaos in second order non-linear differential equations has been developed and successfully applied to the search for chaotic behavior in the damped and forced non-linear oscillator. This simulation and visualization software evaluates the equation under investigation at up to one million time-steps, generating in real-time and on the screen, plots like amplitude of oscillation, phase diagram, amplitude oscillation peaks and an animation of an oscillator governed by the problem equation. In this way the investigator not only gets important behavior graphs but he or she also gets a physical visualization of the system under investigation. Visualizing an animation of the system under study is an enormous help because it is not always easy to interpret behavior graphs. (author).

The forced harmonic oscillator with damping and thermal effects

International Nuclear Information System (INIS)

Menezes Franca, H. de; Thomaz, M.T.

1984-01-01

Nonperturbative quantum mechanical solutions of the forced harmonic oscillator with radiation reaction damping are obtained from previous analysis based on Stochastic Electrodynamics. The transition to excited states is shown to be to coherent states which follow the classical trajectory. The quantum Wigner distribution in phase space is constructed. All the results are extended to finite temperatures. (Author) [pt

Técnica de oscilações forçadas na análise da resposta broncodilatadora em voluntários sadios e indivíduos portadores de asma brônquica com resposta positiva Using the forced oscillation technique to evaluate bronchodilator response in healthy volunteers and in asthma patients presenting a verified positive response

Directory of Open Access Journals (Sweden)

Juliana Veiga Cavalcanti

2006-04-01

Full Text Available OBJETIVO: Analisar, através da técnica de oscilações forçadas, pacientes asmáticos com resposta broncodilatadora positiva pelo laudo espirométrico e comparar esses resultados com os obtidos em indivíduos sadios. MÉTODOS: Foram analisados 53 indivíduos não tabagistas, sendo 24 sadios sem história de doença pulmonar e 29 asmáticos com resposta broncodilatadora positiva segundo o laudo espirométrico. Todos foram submetidos à técnica de oscilações forçadas e a espirometria antes e após vinte minutos da administração de salbutamol spray (300 g. Os parâmetros derivados da técnica de oscilações forçadas foram: resistência total, reatância total, resistência extrapolada para o eixo y, coeficiente angular da reta de resistência e complacência dinâmica. Na espirometria, os parâmetros utilizados foram o volume expiratório forçado no primeiro segundo e a capacidade vital forçada. RESULTADOS: No grupo controle, a utilização do broncodilatador produziu alteração significativa na resistência extrapolada para o eixo y (p OBJECTIVE: To use the forced oscillation technique to evaluate asthma patients presenting positive bronchodilator responses (confirmed through spirometry and compare the results with those obtained in healthy individuals. METHODS: The study sample consisted of 53 non-smoking volunteers: 24 healthy subjects with no history of pulmonary disease and 29 asthmatics presenting positive bronchodilator response, as determined through analysis of spirometry findings. All of the subjects were submitted to forced oscillation technique and spirometry immediately before and 20 minutes after the administration of salbutamol spray (300 g. The parameters derived from the forced oscillation technique were total respiratory resistance, total respiratory reactance, resistance extrapolated to the y axis, the slope of resistance, and dynamic compliance. The parameters measured in the spirometry evaluation tests were forced

Experimental Searches for Exotic Short-Range Forces Using Mechanical Oscillators

Science.gov (United States)

Weisman, Evan

Experimental searches for forces beyond gravity and electromagnetism at short range have attracted a great deal of attention over the last decade. In this thesis I describe the test mass development for two new experiments searching for forces below 1 mm. Both modify a previous experiment that used 1 kHz mechanical oscillators as test masses with a stiff conducting shield between them to suppress backgrounds, a promising technique for probing exceptionally small distances at the limit of instrumental thermal noise. To further reduce thermal noise, one experiment will use plated silicon test masses at cryogenic temperatures. The other experiment, which searches for spin-dependent interactions, will apply the spin-polarizable material Dy3Fe5O 12 to the test mass surfaces. This material exhibits orbital compensation of the magnetism associated with its intrinsic electron spin, minimizing magnetic backgrounds. Several plated silicon test mass prototypes were fabricated using photolithography (useful in both experiments), and spin-dependent materials were synthesized with a simple chemical recipe. Both silicon and spin-dependent test masses demonstrate the mechanical and magnetic properties necessary for sensitive experiments. I also describe sensitivity calculations of another proposed spin-dependent experiment, based on a modified search for the electron electric dipole moment, which show unprecedented sensitivity to exotic monopole-dipole forces. Inspired by a finite element model, a study attempting to maximize detector quality factor versus geometry is also presented, with experimental results so far not explained by the model.

Sub-Angstrom oscillation amplitude non-contact atomic force microscopy for lateral force gradient measurement

International Nuclear Information System (INIS)

Atabak, Mehrdad; Unverdi, Ozhan; Ozer, H. Ozguer; Oral, Ahmet

2009-01-01

We report the first results from novel sub-Angstrom oscillation amplitude non-contact atomic force microscopy developed for lateral force gradient measurements. Quantitative lateral force gradients between a tungsten tip and Si(1 1 1)-(7 x 7) surface can be measured using this microscope. Simultaneous lateral force gradient and scanning tunnelling microscope images of single and multi atomic steps are obtained. In our measurement, tunnel current is used as feedback. The lateral stiffness contrast has been observed to be 2.5 N/m at single atomic step, in contrast to 13 N/m at multi atomic step on Si(1 1 1) surface. We also carried out a series of lateral stiffness-distance spectroscopy. We observed lateral stiffness-distance curves exhibit sharp increase in the stiffness as the sample is approached towards the surface. We usually observed positive stiffness and sometimes going into slightly negative region.

Numerical analysis of the immersed boundary method applied to the flow around a forced oscillating cylinder

International Nuclear Information System (INIS)

Pinto, L C; Silvestrini, J H; Schettini, E B C

2011-01-01

In present paper, Navier-Stokes and Continuity equations for incompressible flow around an oscillating cylinder were numerically solved. Sixth order compact difference schemes were used to solve the spatial derivatives, while the time advance was carried out through second order Adams Bashforth accurate scheme. In order to represent the obstacle in the flow, the Immersed Boundary Method was adopted. In this method a force term is added to the Navier-Stokes equations representing the body. The simulations present results regarding the hydrodynamic coefficients and vortex wakes in agreement to experimental and numerical previous works and the physical lock-in phenomenon was identified. Comparing different methods to impose the IBM, it can be concluded that no alterations regarding the vortex shedding mode were observed. The Immersed Boundary Method techniques used here can represent the surface of an oscillating cylinder in the flow.

Exaggerated heart rate oscillations during two meditation techniques.

Science.gov (United States)

Peng, C K; Mietus, J E; Liu, Y; Khalsa, G; Douglas, P S; Benson, H; Goldberger, A L

1999-07-31

We report extremely prominent heart rate oscillations associated with slow breathing during specific traditional forms of Chinese Chi and Kundalini Yoga meditation techniques in healthy young adults. We applied both spectral analysis and a novel analytic technique based on the Hilbert transform to quantify these heart rate dynamics. The amplitude of these oscillations during meditation was significantly greater than in the pre-meditation control state and also in three non-meditation control groups: i) elite athletes during sleep, ii) healthy young adults during metronomic breathing, and iii) healthy young adults during spontaneous nocturnal breathing. This finding, along with the marked variability of the beat-to-beat heart rate dynamics during such profound meditative states, challenges the notion of meditation as only an autonomically quiescent state.

The force analysis for superparamagnetic nanoparticles-based gene delivery in an oscillating magnetic field

Energy Technology Data Exchange (ETDEWEB)

Sun, Jiajia [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an, Shaanxi Province 710049 (China); Shi, Zongqian, E-mail: zqshi@mail.xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an, Shaanxi Province 710049 (China); Jia, Shenli [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an, Shaanxi Province 710049 (China); Zhang, Pengbo [Department of Anesthesiology, Second Affiliated Hospital of Xi’an Jiaotong University School of Medicine, No.157 West 5 Road, Xi’an, Shaanxi Province 710004 (China)

2017-04-01

Due to the peculiar magnetic properties and the ability to function in cell-level biological interaction, superparamagnetic nanoparticles (SMNP) have been being the attractive carrier for gene delivery. The superparamagnetic nanoparticles with surface-bound gene vector can be attracted to the surface of cells by the Kelvin force provided by external magnetic field. In this article, the influence of the oscillating magnetic field on the characteristics of magnetofection is studied in terms of the magnetophoretic velocity. The magnetic field of a cylindrical permanent magnet is calculated by equivalent current source (ECS) method, and the Kelvin force is derived by using the effective moment method. The results show that the static magnetic field accelerates the sedimentation of the particles, and drives the particles inward towards the axis of the magnet. Based on the investigation of the magnetophoretic velocity of the particle under horizontally oscillating magnetic field, an oscillating velocity within the amplitude of the magnet oscillation is observed. Furthermore, simulation results indicate that the oscillating amplitude plays an important role in regulating the active region, where the particles may present oscillating motion. The analysis of the magnetophoretic velocity gives us an insight into the physical mechanism of the magnetofection. It's also helpful to the optimal design of the magnetofection system. - Highlights: • We compare the results of the ECS method and FEA method with the commercial software, Ansys. • We analyze the physic mechanism of the oscillating motion of the particles in the presence of an oscillating magnet. • We discuss the influence of the oscillating amplitude of the magnet on the behavior of the particle.

Rate enhancement in microfabricated chemical reactors under fast forced temperature oscillations

DEFF Research Database (Denmark)

Hansen, Heine Anton; Olsen, Jakob L.; Jensen, Søren

2006-01-01

Oxidation of CO under fast forced temperature oscillations shows increased reaction rate compared to steady state. A maximum increase of 40% is observed relative to steady state. The reaction rate is investigated for varying mean temperature, amplitude and frequency. As function of mean temperatu...

Chaotic synchronization of two complex nonlinear oscillators

International Nuclear Information System (INIS)

Mahmoud, Gamal M.; Mahmoud, Emad E.; Farghaly, Ahmed A.; Aly, Shaban A.

2009-01-01

Synchronization is an important phenomenon commonly observed in nature. It is also often artificially induced because it is desirable for a variety of applications in physics, applied sciences and engineering. In a recent paper [Mahmoud GM, Mohamed AA, Aly SA. Strange attractors and chaos control in periodically forced complex Duffing's oscillators. Physica A 2001;292:193-206], a system of periodically forced complex Duffing's oscillators was introduced and shown to display chaotic behavior and possess strange attractors. Such complex oscillators appear in many problems of physics and engineering, as, for example, nonlinear optics, deep-water wave theory, plasma physics and bimolecular dynamics. Their connection to solutions of the nonlinear Schroedinger equation has also been pointed out. In this paper, we study the remarkable phenomenon of chaotic synchronization on these oscillator systems, using active control and global synchronization techniques. We derive analytical expressions for control functions and show that the dynamics of error evolution is globally stable, by constructing appropriate Lyapunov functions. This means that, for a relatively large set initial conditions, the differences between the drive and response systems vanish exponentially and synchronization is achieved. Numerical results are obtained to test the validity of the analytical expressions and illustrate the efficiency of these techniques for inducing chaos synchronization in our nonlinear oscillators.

The Mechanical of the Small Axisymmetric Oscillations of the Liquid with the Surface Tension Forces in Elastic Tank

Directory of Open Access Journals (Sweden)

D. A. Goncharov

2015-01-01

Full Text Available In this paper we investigate small axisymmetric oscillations of a liquid in an elastic tank. We also take into account the influence of surface tension forces. For this, we turn to the mechanical analogue of the considered mechanical system. To realize the transition to mechanical analogue we use the energy method: postulating the equality of kinetic and potential energy for the investigated mechanical system and the mechanical system analog. Due to this transition we can further investigate the oscillations of a mechanical analogue. As a mechanical analogue, we consider the oscillator in the spring. The mass of the oscillator is calculated as the weight of the fluid to make oscillations. The oscillator spring constant is calculated using the identity of equations, namely, equation of free small oscillations of the oscillator and equation of free small oscillations of the system under investigation: the fluid in the elastic tank. The identity of equations allows us to draw conclusion about the identity of the natural frequencies for the source mechanical system and the system of a mechanical analogue. Next, we take into consideration the action of the surface tension. We record the Laplace condition for excess pressure because of the forces of surface tension. Then we compile the expression for the generalized force, taking into account the phenomenon of the surface tension. Next, we write the equation of oscillations of a mechanical analogue. The surface tension, due to the introduction of the generalized force in the equation for small oscillations of the mechanical analogue will change the natural frequency of the mechanical analogue. The paper presents the appropriate dependencies. The abovementioned allows us to investigate the stability of small motions of fluid in microgravity or low gravity by studying the stability of small motions of mechanical analogue. The latter is especially important due to the design and development of advanced

Effects of the nasal passage on forced oscillation lung function measurements.

Science.gov (United States)

Ngo, Chuong; Krüger, Karl; Vollmer, Thomas; Winter, Stefan; Penzlin, Bernhard; Lehmann, Sylvia; Leonhardt, Steffen; Misgeld, Berno

2017-11-27

The forced oscillation technique (FOT) is a non-invasive pulmonary function test which is based on the measurement of respiratory impedance. Recently, promising results were obtained by the application of FOT on patients with respiratory failure and obstructive sleep apnea (OSA). By using a nasal mask instead of a mouthpiece, the influences of the nasal passage and upper shunt alter the measured mechanical impedance. In this paper, we investigated the effects of the nasal passage and mask on FOT measurements from eight healthy subjects. A method for flow correction has been developed, which contains a pressure-flow characteristics compensation of the undetermined flow leakage at the face-mask interface. Impedance calculation and parameter estimation were performed in the frequency domain using fast Fourier transform (FFT). Average nasal parameters were Rnaw=4.07 cmH2O/l/s for resistance and Lnaw=0.0183 cmH2O/l/s2 for inertance. On average, the nasal resistance corresponds to 65.85% of the total resistance.

Experimental study of oscillating plates in viscous fluids: Qualitative and quantitative analysis of the flow physics and hydrodynamic forces

Science.gov (United States)

Shrestha, Bishwash; Ahsan, Syed N.; Aureli, Matteo

2018-01-01

In this paper, we present a comprehensive experimental study on harmonic oscillations of a submerged rigid plate in a quiescent, incompressible, Newtonian, viscous fluid. The fluid-structure interaction problem is analyzed from both qualitative and quantitative perspectives via a detailed particle image velocimetry (PIV) experimental campaign conducted over a broad range of oscillation frequency and amplitude parameters. Our primary goal is to identify the effect of the oscillation characteristics on the mechanisms of fluid-structure interaction and on the dynamics of vortex shedding and convection and to elucidate the behavior of hydrodynamic forces on the oscillating structure. Towards this goal, we study the flow in terms of qualitative aspects of its pathlines, vortex shedding, and symmetry breaking phenomena and identify distinct hydrodynamic regimes in the vicinity of the oscillating structure. Based on these experimental observations, we produce a novel phase diagram detailing the occurrence of distinct hydrodynamic regimes as a function of relevant governing nondimensional parameters. We further study the hydrodynamic forces associated with each regime using both PIV and direct force measurement via a load cell. Our quantitative results on experimental estimation of hydrodynamic forces show good agreement against predictions from the literature, where numerical and semi-analytical models are available. The findings and observations in this work shed light on the relationship between flow physics, vortex shedding, and convection mechanisms and the hydrodynamic forces acting on a rigid oscillating plate and, as such, have relevance to various engineering applications, including energy harvesting devices, biomimetic robotic system, and micro-mechanical sensors and actuators.

Resolving a puzzle concerning fluctuation theorems for forced harmonic oscillators in non-Markovian heat baths

International Nuclear Information System (INIS)

Chaudhury, Srabanti; Chatterjee, Debarati; Cherayil, Binny J

2008-01-01

A harmonic oscillator that evolves under the action of both a systematic time-dependent force and a random time-correlated force can do work w. This work is a random quantity, and Mai and Dhar have recently shown, using the generalized Langevin equation (GLE) for the oscillator's position x, that it satisfies a fluctuation theorem. In principle, the same result could have been derived from the Fokker–Planck equation (FPE) for the probability density function, P(x,w,t), for the oscillator being at x at time t, having done work w. Although the FPE equivalent to the above GLE is easily constructed and solved, one finds, unexpectedly, that its predictions for the mean and variance of w do not agree with the fluctuation theorem. We show that to resolve this contradiction, it is necessary to construct an FPE that includes the velocity of the oscillator, v, as an additional variable. The FPE for P(x,v,w,t) does indeed yield expressions for the mean and variance of w that agree with the fluctuation theorem

Investigation of a double oscillating-fan cooling device using electromagnetic force

International Nuclear Information System (INIS)

Su, Hsien-Chin; Xu, Han Yang

2016-01-01

Highlights: • The characteristics of a double oscillating-fan cooling device using electromagnetic force was investigated. • The driving current can be either DC PWM or AC within 3–12 V. • The comparison between a double blower pair, the model and a synjet were examined. • A 50 mm ∗ 50 mm ∗ 15 mm model can provide the flow rate of 154.89 l/min while consuming 0.65 W. • The flow rate, sound pressure, power consumption and two thermal tests have been done. - Abstract: This study proposes a double oscillating-fan cooling device using electromagnetic force. The device consists of two oscillating-fans. It requires only one electromagnet and two fan sheets with one magnet on each of them. The electromagnet and fan sheets are situated on a base and arranged accordingly. The electromagnetic force generated by the electromagnet can actuate the fan sheets. The main advantage of the device is its simple structure because there is no bearing and motor in the device. The driving current can be either DC PWM (Pulse width modulation) or AC (Alternating current) within 3–12 V so it is compatible with most electronic devices. The dimensions of the proposed model are 50 mm ∗ 50 mm ∗ 15 mm during operation. Concerning flow rate, sound pressure, power consumption and resonant frequency tests, a comparison between the proposed model and different type of cooling devices has been completed. The result shows that the model can provide cooling ability similar to a rotary fan while consuming 40% of the power of the rotary fan. It shows not only a good cooling ability but also a great potential for structural reliability and design flexibility.

The feasibility of home monitoring of impedance with the forced oscillation technique in chronic obstructive pulmonary disease subjects

International Nuclear Information System (INIS)

Timmins, Sophie C; Diba, Chantale; Thamrin, Cindy; Berend, Norbert; Salome, Cheryl M; King, Gregory G

2013-01-01

Respiratory system resistance (Rrs) and reactance (Xrs) measured by forced oscillation technique (FOT) can be potentially used for home monitoring in COPD. Our aims were to determine the technical acceptability, adherence and variability of unsupervised, home FOT measurements over ten consecutive days. Supervised spirometry and FOT measurements were made on ten clinically stable COPD subjects at their homes at the study initiation. Subjects then self-recorded FOT twice daily for ten consecutive days with data transmitted to the laboratory server via a 3G mobile network. Subjects had a mean (SD) age of 68(8) years, smoking history 38.4(8.7) pack/years, post-bronchodilator FEV1 42.4(12.0)% predicted, FEV1/FVC ratio 0.45(0.10), mean Rrs 121.7(26.1)% predicted and mean Xrs 746.8(330.3)% predicted. The supervised measurements of mean Rrs and mean Xrs were similar to the unsupervised measurements (p = 0.34 and p = 0.92, respectively). 197 of 200 possible measurements were transmitted, all of which were deemed to be technically acceptable. The within-subject standard deviation, Sw, of Rrs-total and Xrs-total were 0.47 and 1.0 cmH 2 O L s –1 , respectively. Subjects who have COPD make reliable, unsupervised FOT measurements at home with a high degree of adherence. The day-to-day variability of FOT measurements was similar to that of supervised laboratory recordings. These results support the conduct of larger, longer-term studies of FOT monitoring in COPD. (paper)

A one-dimensional model of the semiannual oscillation driven by convectively forced gravity waves

Science.gov (United States)

Sassi, Fabrizio; Garcia, Rolando R.

1994-01-01

A one-dimensional model that solves the time-dependent equations for the zonal mean wind and a wave of specified zonal wavenumber has been used to illustrate the ability of gravity waves forced by time-dependent tropospheric heating to produce a semiannual oscillation (SAO) in the middle atmosphere. When the heating has a strong diurnal cycle, as observed over tropical landmasses, gravity waves with zonal wavelengths of a few thousand kilometers and phase velocities in the range +/- 40-50 m/sec are excited efficiently by the maximum vertical projection criterion (vertical wavelength approximately equals 2 x forcing depth). Calculations show that these waves can account for large zonal mean wind accelerations in the middle atmosphere, resulting in realistic stratopause and mesopause oscillations. Calculations of the temporal evolution of a quasi-conserved tracer indicate strong down-welling in the upper stratosphere near the equinoxes, which is associated with the descent of the SAO westerlies. In the upper mesosphere, there is a semiannual oscillation in tracer mixing ratio driven by seasonal variability in eddy mixing, which increases at the solstices and decreases at the equinoxes.

Forced convective boiling of water inside helically coiled tube. Characteristics of oscillation of dryout point

International Nuclear Information System (INIS)

Nagai, Niro; Sugiyama, Kenta; Takeuchi, Masanori; Yoshikawa, Shinji; Yamamoto, Fujio

2006-01-01

The helically coiled tube of heat exchanger is used for the evaporator of prototype fast breeder reactor 'Monju'. This paper aims at the grasp of two-phase flow phenomena of forced convective boiling of water inside helical coiled tube, especially focusing on oscillation phenomena of dryout point. A glass-made helically coiled tube was used to observe the inside water boiling behavior flowing upward, which was heated by high temperature oil outside the tube. This oil was also circulated through a glass made tank to provide the heat source for water evaporation. The criterion for oscillation of dryout point was found to be a function of inlet liquid velocity and hot oil temperature. The observation results suggest the mechanism of dryout point oscillation mainly consists of intensive nucleate boiling near the dryout point and evaporation of thin liquid film flowing along the helical tube. In addition, the oscillation characteristics were experimentally confirmed. As inlet liquid velocity increases, oscillation amplitude also increases but oscillation cycle does not change so much. As hot oil temperature increases, oscillation amplitude and cycle gradually decreases. (author)

Energy Cost of Avoiding Pressure Oscillations in a Discrete Fluid Power Force System

DEFF Research Database (Denmark)

Hansen, Anders Hedegaard; Pedersen, Henrik Clemmensen

2015-01-01

In secondary valve controlled discrete fluid power force systems the valve opening trajectory greatly influences the pressure dynamics in the actuator chambers. For discrete fluid power systems featuring hoses of significant length pressure oscillations due to fast valve switching is well......-known. This paper builds upon theoretical findings on how shaping of the valve opening may reduce the cylinder pressure oscillations. The current paper extents the work by implementing the valve opening characteristics reducing the pressure oscillations on a full scale power take-off test-bench for wave energy...... will present measurements comparing pressure dynamics for two valve opening algorithms. In addition the paper will give a theoretical investigation of the energy loss during valve shifting and finally measurements of average power output from the power take-off system in various sea states are compared...

Feedback control and adaptive synchronization of chaotic forced Bonhoeffer-van der Pol oscillators

Energy Technology Data Exchange (ETDEWEB)

Kontchou, E W Chimi; Fotsin, H B [Laboratoire d' Electronique, Departement de Physique, Faculte des Sciences, Universite de Dschang, B P 67 Dschang (Cameroon); Woafo, P [Laboratory of Modelling and Simulation in Engineering and Biological Physics, Faculty of Science, University of Yaounde I, Box 812, Yaounde (Cameroon)], E-mail: hbfotsin@yahoo.fr

2008-04-15

This paper deals with chaos control and synchronization in forced Bonhoeffer-van der Pol (FBVP) oscillators. The state equations of the model are first established and the stability is analysed. A feedback control strategy for stabilizing the chaotic dynamics on a periodic orbit of the phase space is investigated. Adaptive synchronization of two FBVP oscillators, based on parameter estimation and a nonlinear observer approach, is also investigated. It appears that a particular unknown parameter of the model can be estimated, which gives the possibility of recovering information through chaotic masking. An application in secure communications is presented.

Feedback control and adaptive synchronization of chaotic forced Bonhoeffer-van der Pol oscillators

International Nuclear Information System (INIS)

Kontchou, E W Chimi; Fotsin, H B; Woafo, P

2008-01-01

This paper deals with chaos control and synchronization in forced Bonhoeffer-van der Pol (FBVP) oscillators. The state equations of the model are first established and the stability is analysed. A feedback control strategy for stabilizing the chaotic dynamics on a periodic orbit of the phase space is investigated. Adaptive synchronization of two FBVP oscillators, based on parameter estimation and a nonlinear observer approach, is also investigated. It appears that a particular unknown parameter of the model can be estimated, which gives the possibility of recovering information through chaotic masking. An application in secure communications is presented

Phase-locking regions in a forced model of slow insulin and glucose oscillations

DEFF Research Database (Denmark)

Sturis, Jeppe; Knudsen, Carsten; O'Meara, Niall M.

1995-01-01

We present a detailed numerical investigation of the phase-locking regions in a forced model of slow oscillations in human insulin secretion and blood glucose concentration. The bifurcation structures of period 2pi and 4pi tongues are mapped out and found to be qualitatively identical to those...

Phase-locking regions in a forced model of slow insulin and glucose oscillations

DEFF Research Database (Denmark)

Sturis, J.; Knudsen, C.; O'Meara, N.M.

1996-01-01

We present a detailed numerical investigation of the phase-locking regions in a forced model of slow oscillations in human insulin secretion and blood glucose concentration. The bifurcation structures of period 2pi and 4pi tongues are mapped out and found to be qualitatively identical to those...

Amplitude and phase fluctuations of Van der Pol oscillator under external random forcing

Science.gov (United States)

Singh, Aman K.; Yadava, R. D. S.

2018-05-01

The paper presents an analytical study of noise in Van der Pol oscillator output subjected to an external force noise assumed to be characterized by delta function (white noise). The external fluctuations are assumed to be small in comparison to the average response of the noise free system. The autocorrelation function and power spectrum are calculated under the condition of weak nonlinearity. The latter ensures limit cycle oscillations. The total spectral power density is dominated by the contributions from the phase fluctuations. The amplitude fluctuations are at least two orders of magnitude smaller. The analysis is shown to be useful to interpretation microcantilever based biosensing data.

Interval oscillation criteria for second-order forced impulsive delay differential equations with damping term.

Science.gov (United States)

Thandapani, Ethiraju; Kannan, Manju; Pinelas, Sandra

2016-01-01

In this paper, we present some sufficient conditions for the oscillation of all solutions of a second order forced impulsive delay differential equation with damping term. Three factors-impulse, delay and damping that affect the interval qualitative properties of solutions of equations are taken into account together. The results obtained in this paper extend and generalize some of the the known results for forced impulsive differential equations. An example is provided to illustrate the main result.

Evaluation of aerodynamic forces acting on oscillating cantilever beams based on the study of the damped flexural vibration of aluminium test samples

Science.gov (United States)

Egorov, A. G.; Kamalutdinov, A. M.; Nuriev, A. N.

2018-05-01

The paper is devoted to study of the aerodynamic forces acting on flat cantilever beams performing flexural vibrations in a viscous fluid. Original method for the force evaluation is presented based on analysis of experimental measurements of a logarithmic decrement of vibrations and relative variation in frequency of duralumin test specimens. The theoretical core of the method is based on the classical theory of bending beam oscillations and quasi-two dimensional model of interaction between a beam and a gas. Using the proposed method, extensive series of experiments for a wide range of oscillations parameters were carried out. The processing of the experimental data allowed to establish the global influence of the aerodynamic effects on beam oscillations and the local force characteristics of each cross-section of the beam in the form of universal functions of dimensionless amplitude and dimensionless frequency of oscillation. The obtained estimates of the drag and added mass forces showed a good correspondence with the available numerical and experimental data practically in the entire range of the investigated parameters.

Resonance oscillations of nonreciprocal long-range van der Waals forces between atoms in electromagnetic fields

Science.gov (United States)

Sherkunov, Yury

2018-03-01

We study theoretically the van der Waals interaction between two atoms out of equilibrium with an isotropic electromagnetic field. We demonstrate that at large interatomic separations, the van der Waals forces are resonant, spatially oscillating, and nonreciprocal due to resonance absorption and emission of virtual photons. We suggest that the van der Waals forces can be controlled and manipulated by tuning the spectrum of artificially created random light.

Selection of flow-distributed oscillation and Turing patterns by boundary forcing in a linearly growing, oscillating medium.

Science.gov (United States)

Míguez, David G; McGraw, Patrick; Muñuzuri, Alberto P; Menzinger, Michael

2009-08-01

We studied the response of a linearly growing domain of the oscillatory chemical chlorine dioxide-iodide-malonic acid (CDIMA) medium to periodic forcing at its growth boundary. The medium is Hopf-, as well as Turing-unstable and the system is convectively unstable. The results confirm numerical predictions that two distinct modes of pattern can be excited by controlling the driving frequency at the boundary, a flow-distributed-oscillation (FDO) mode of traveling waves at low values of the forcing frequency f , and a mode of stationary Turing patterns at high values of f . The wavelengths and phase velocities of the experimental patterns were compared quantitatively with results from dynamical simulations and with predictions from linear dispersion relations. The results for the FDO waves agreed well with these predictions, and obeyed the kinematic relations expected for phase waves with frequencies selected by the boundary driving frequency. Turing patterns were also generated within the predicted range of forcing frequencies, but these developed into two-dimensional structures which are not fully accounted for by the one-dimensional numerical and analytical models. The Turing patterns excited by boundary forcing persist when the forcing is removed, demonstrating the bistability of the unforced, constant size medium. Dynamical simulations at perturbation frequencies other than those of the experiments showed that in certain ranges of forcing frequency, FDO waves become unstable, breaking up into harmonic waves of different frequency and wavelength and phase velocity.

Quantization and instability of the damped harmonic oscillator subject to a time-dependent force

International Nuclear Information System (INIS)

Majima, H.; Suzuki, A.

2011-01-01

We consider the one-dimensional motion of a particle immersed in a potential field U(x) under the influence of a frictional (dissipative) force linear in velocity (-γx) and a time-dependent external force (K(t)). The dissipative system subject to these forces is discussed by introducing the extended Bateman's system, which is described by the Lagrangian: L=mxy-U(x+1/2 y)+U(x-1/2 y)+(γ)/2 (xy-yx)-xK(t)+yK(t), which leads to the familiar classical equations of motion for the dissipative (open) system. The equation for a variable y is the time-reversed of the x motion. We discuss the extended Bateman dual Lagrangian and Hamiltonian by setting U(x±y/2)=1/2 k(x±y/2) 2 specifically for a dual extended damped-amplified harmonic oscillator subject to the time-dependent external force. We show the method of quantizing such dissipative systems, namely the canonical quantization of the extended Bateman's Hamiltonian H. The Heisenberg equations of motion utilizing the quantized Hamiltonian H surely lead to the equations of motion for the dissipative dynamical quantum systems, which are the quantum analog of the corresponding classical systems. To discuss the stability of the quantum dissipative system due to the influence of an external force K(t) and the dissipative force, we derived a formula for transition amplitudes of the dissipative system with the help of the perturbation analysis. The formula is specifically applied for a damped-amplified harmonic oscillator subject to the impulsive force. This formula is used to study the influence of dissipation such as the instability due to the dissipative force and/or the applied impulsive force. - Highlights: → A method of quantizing dissipative systems is presented. → In order to obtain the method, we apply Bateman's dual system approach. → A formula for a transition amplitude is derived. → We use the formula to study the instability of the dissipative systems.

Forced Rolling Oscillation of a 65 deg-Delta Wing in Transonic Vortex-Breakdown Flow

Science.gov (United States)

Menzies, Margaret A.; Kandil, Osama A.; Kandil, Hamdy A.

1996-01-01

Unsteady, transonic, vortex dominated flow over a 65 deg. sharp-edged, cropped-delta wing of zero thickness undergoing forced rolling oscillations is investigated computationally. The wing angle of attack is 20 deg. and the free stream Mach number and Reynolds number are 0.85 and 3.23 x 10(exp 6), respectively. The initial condition of the flow is characterized by a transverse terminating shock which induces vortex breakdown of the leading edge vortex cores. The computational investigation uses the time accurate solution of the laminar, unsteady, compressible, full Navier-Stokes equations with the implicit, upwind, Roe flux difference splitting, finite-volume scheme. While the maximum roll amplitude is kept constant at 4.0 deg., both Reynolds number and roll frequency are varied covering three cases of forced sinusoidal rolling. First, the Reynolds number is held at 3.23 x 10(exp 6) and the wing is forced to oscillate in roll around the axis of geometric symmetry at a reduced frequency of 2(pi). Second, the Reynolds number is reduced to 0.5 x 10(exp 6) to observe the effects of added viscosity on the vortex breakdown. Third, with the Reynolds number held at 0.5 x 10(exp 6), the roll frequency is reduced to 1(pi) to complete the study.

Open-loop control of quasiperiodic thermoacoustic oscillations

Science.gov (United States)

Guan, Yu; Gupta, Vikrant; Kashinath, Karthik; Li, Larry K. B.

2017-11-01

The open-loop application of periodic acoustic forcing has been shown to be a potentially effective strategy for controlling periodic thermoacoustic oscillations, but its effectiveness on aperiodic thermoacoustic oscillations is less clear. In this experimental study, we apply periodic acoustic forcing to a ducted premixed flame oscillating quasiperiodically at two incommensurate natural frequencies, f1 and f2. We find that (i) above a critical forcing amplitude, the system locks into the forcing by oscillating only at the forcing frequency ff, producing a closed periodic orbit in phase space with no evidence of the original T2 torus attractor; (ii) the critical forcing amplitude required for lock-in decreases as ff approaches either f1 or f2, resulting in characteristic ∨-shaped lock-in boundaries around the two natural modes; and (iii) for a wide range of forcing frequencies, the system's oscillation amplitude can be reduced to less than 20% of that of the unforced system. These findings show that the open-loop application of periodic acoustic forcing can be an effective strategy for controlling aperiodic thermoacoustic oscillations. This work was supported by the Research Grants Council of Hong Kong (Project No. 16235716 and 26202815).

Overall and peripheral lung function assessment by spirometry and forced oscillation technique in relation to asthma diagnosis and control.

Science.gov (United States)

Heijkenskjöld Rentzhog, C; Janson, C; Berglund, L; Borres, M P; Nordvall, L; Alving, K; Malinovschi, A

2017-12-01

Classic spirometry is effort dependent and of limited value in assessing small airways. Peripheral airway involvement, and relation to poor control, in asthma, has been highlighted recently. Forced oscillation technique (FOT) offers an effort-independent assessment of overall and peripheral lung mechanics. We studied the association between lung function variables, obtained either by spirometry or multifrequency (5, 11 and 19 Hz) FOT, and asthma diagnosis and control. Spirometry measures, resistance at 5 (R5) and 19 Hz (R19), reactance at 5 Hz (X5), resonant frequency (f res ), resistance difference between 5-19 Hz (R5-R19) and Asthma Control Test scores were determined in 234 asthmatic and 60 healthy subjects (aged 13-39 years). We used standardized lung function variables in logistic regression analyses, unadjusted and adjusted for age, height, gender and weight. Lower FEV 1 /FVC (OR [95% CI] 0.47 [0.32, 0.69]) and FEF 50 (0.62 [0.46, 0.85]) per standard deviation increase, and higher R5 (3.31 [1.95, 5.62]) and R19 (2.54 [1.65, 3.91]) were associated with asthma diagnosis. Independent predictive effects of FEV 1 /FVC and R5 or R19, respectively, were found for asthma diagnosis. Lower FEV 1 /FVC and altered peripheral FOT measures (X5, f res and R5-R19) were associated with uncontrolled asthma (P-values < .05). Resistance FOT measures were equally informative as spirometry, related to asthma diagnosis, and, furthermore, offered additive information to FEV 1 /FVC, supporting a complementary role for FOT. Asthma control was related to FOT measures of peripheral airways, suggesting a potential use in identifying such involvement. Further studies are needed to determine a clinical value and relevant reference values in children, for the multifrequency FOT measurements. © 2017 John Wiley & Sons Ltd.

Rayleigh-type parametric chemical oscillation

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Shyamolina; Ray, Deb Shankar, E-mail: pcdsr@iacs.res.in [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

2015-09-28

We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

Rayleigh-type parametric chemical oscillation.

Science.gov (United States)

Ghosh, Shyamolina; Ray, Deb Shankar

2015-09-28

We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

Study of the oscillations event of the CNLV-U1 with Wavelets techniques

International Nuclear Information System (INIS)

Amador G, R.; Nunez C, A.; Prieto G, A.; Espinosa P, G.

2004-01-01

Presently work is described and the techniques are applied of the Fourier Transformation in Short Time, the Continuous Transformation of Wavelets and the Multi resolution Analysis for the analysis of the event of oscillations of power in the Nuclear Power station of Laguna Verde Unit 1 happened in January of 1995. In general, the wavelets techniques allows to carry out studies of the different signals generated by a nuclear plant in the plane Time-frequency, Time-scale as well as the decomposition of the signals. The results obtained study presently demonstrate that the frequency of the event of oscillations in the Nuclear Power station of Laguna Verde Unit 1 are approximately 0.52 Hz for the 3 analysis techniques, besides being observed the evolution of the frequency in function of the time. (Author)

FORCED OSCILLATIONS OF SECOND ORDER SUPER-LINEAR DIFFERENTIAL EQUATION WITH IMPULSES

Institute of Scientific and Technical Information of China (English)

无

2012-01-01

At first,by means of Kartsatos technique,we reduce the impulsive differential equation to a second order nonlinear impulsive homogeneous equation.We find some suitable impulse functions such that all the solutions to the equation are oscillatory.Several criteria on the oscillations of solutions are given.At last,we give an example to demonstrate our results.

Electrostatically actuated oscillator of bundle and double-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Kang, Jeong Won; Song, Ki Oh; Hwang, Ho Jung [Chung-Ang University, Seoul (Korea, Republic of); Lee, Jun Ha; Lee, Hoong Joo [Sangmyung University, Chonan (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Yoon, Young Sik; Song, Young Jin [Konyang University, Nonsan (Korea, Republic of)

2006-03-15

Schematics of capacitively driven carbon nanotube (CNT) oscillators were presented and investigated by using classical molecular dynamics simulations. While the capacitive force acting on a CNT oscillator extruded it, the force exerted by the excess van der Waals energy sucked the CNT oscillator into the bundle or outer shell. The CNT oscillator could be oscillated by using both the Coulomb and the van der Waals interactions. The van der Waals force of the bundle-type CNT oscillator was less than the van der Waals force of the double-walled CNT oscillator. Molecular dynamics simulation results showed that double-walled CNT oscillators were better than bundle-type CNT oscillators in the aspects of both energy dissipation and stable operation.

Subharmonic Oscillations and Chaos in Dynamic Atomic Force Microscopy

Science.gov (United States)

Cantrell, John H.; Cantrell, Sean A.

2015-01-01

The increasing use of dynamic atomic force microscopy (d-AFM) for nanoscale materials characterization calls for a deeper understanding of the cantilever dynamics influencing scan stability, predictability, and image quality. Model development is critical to such understanding. Renormalization of the equations governing d- AFM provides a simple interpretation of cantilever dynamics as a single spring and mass system with frequency dependent cantilever stiffness and damping parameters. The renormalized model is sufficiently robust to predict the experimentally observed splitting of the free-space cantilever resonance into multiple resonances upon cantilever-sample contact. Central to the model is the representation of the cantilever sample interaction force as a polynomial expansion with coefficients F(sub ij) (i,j = 0, 1, 2) that account for the effective interaction stiffness parameter, the cantilever-to-sample energy transfer, and the amplitude of cantilever oscillation. Application of the Melnikov method to the model equation is shown to predict a homoclinic bifurcation of the Smale horseshoe type leading to a cascade of period doublings with increasing drive displacement amplitude culminating in chaos and loss of image quality. The threshold value of the drive displacement amplitude necessary to initiate subharmonic generation depends on the acoustic drive frequency, the effective damping coefficient, and the nonlinearity of the cantilever-sample interaction force. For parameter values leading to displacement amplitudes below threshold for homoclinic bifurcation other bifurcation scenarios can occur, some of which lead to chaos.

Effect of structural disorder on quantum oscillations in graphite

Energy Technology Data Exchange (ETDEWEB)

Camargo, B. C., E-mail: b.c-camargo@yahoo.com.br; Kopelevich, Y. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, Unicamp 13083-970, Campinas, São Paulo (Brazil); Usher, A.; Hubbard, S. B. [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

2016-01-18

We have studied the effect of structural disorder on the de Haas van Alphen and Shubnikov de Haas quantum oscillations measured in natural, Kish, and highly oriented pyrolytic graphite samples at temperatures down to 30 mK and at magnetic fields up to 14 T. The measurements were performed on different samples characterized by means of x-ray diffractometry, transmission electron microscopy, and atomic-force microscopy techniques. Our results reveal a correlation between the amplitude of quantum oscillations and the sample surface roughness.

A 65--70 year oscillation in observed surface temperatures

International Nuclear Information System (INIS)

Schlesinger, M.E.; Ramankutty, N.

1994-01-01

There are three possible sources for the 65--70-year ''global'' oscillation: (1) random forcing of the ocean by the atmosphere, such as by white noise; (2) external oscillatory forcing of the climate system, such as by a variation in the solar irradiance; and (3) an internal oscillation of the atmosphere-ocean system. It is unlikely that putative variations in solar irradiance are the source of the oscillation because solar forcing should generate a global response, but the oscillation is not global. It is also unlikely that white-noise forcing is the source of the oscillation because such forcing should generate an oceanwide response, but the oscillation is not panoceanic. Consequently, the most probable cause of the oscillation is an internal oscillation of the atmosphere-ocean system. This conclusion is supported by a growing body of observational evidence and coupled atmosphere/ocean general circulation model simulation results. Comparison of the regional and global-mean temperature changes caused by the oscillation with those induced by GHG + ASA forcing shows that the rapid rise in global-mean temperature between about 1908 and 1946, and the subsequent reversal of this warming until about 1965 were the result of the oscillation. In the North Atlantic and North American regions, the domination of the GHG + ASA-induced warming by the oscillation has obscured and confounded detection of this warming

Oscillation experiments on Cesar and Marius - Experimental devices and measurement techniques

International Nuclear Information System (INIS)

Brunet, Max; Guerange, Jacques; Morier, Francis; Tonolli, Jacky

1969-02-01

An original method of measurement of effective cross sections of fissile materials has been developed by the CEA: a central fuel element of a critical experimental reactor is replaced by a sample containing the material to be studied. The replacement technique is based on oscillating the fuel load of the central channel. Signals are measured which are proportional to reactivity variation and to neutron density disturbance at the vicinity of the central channel, these variation and disturbance being produced by the sample oscillation. Measurements have been performed on experimental reactors (Minerve in Fontenay-aux-Roses, and Cesar and Marius in Cadarache). The authors herein describe the experimental devices and measurement techniques implemented in Marius and Cesar. In a first part, they describe the experimental devices which have been used during the three measurement campaigns (between 1965 and 1967). They report the study of measurement accuracies, and of some problems related to the use of the local detector [fr

Nonlinear response of a forced van der Pol-Duffing oscillator at non-resonant bifurcations of codimension two

International Nuclear Information System (INIS)

Ji, J.C.; Zhang, N.

2009-01-01

Non-resonant bifurcations of codimension two may appear in the controlled van der Pol-Duffing oscillator when two critical time delays corresponding to a double Hopf bifurcation have the same value. With the aid of centre manifold theorem and the method of multiple scales, the non-resonant response and two types of primary resonances of the forced van der Pol-Duffing oscillator at non-resonant bifurcations of codimension two are investigated by studying the possible solutions and their stability of the four-dimensional ordinary differential equations on the centre manifold. It is shown that the non-resonant response of the forced oscillator may exhibit quasi-periodic motions on a two- or three-dimensional (2D or 3D) torus. The primary resonant responses admit single and mixed solutions and may exhibit periodic motions or quasi-periodic motions on a 2D torus. Illustrative examples are presented to interpret the dynamics of the controlled system in terms of two dummy unfolding parameters and exemplify the periodic and quasi-periodic motions. The analytical predictions are found to be in good agreement with the results of numerical integration of the original delay differential equation.

A comparison of force sensing techniques for planetary manipulation

Science.gov (United States)

Helmick, Daniel; Okon, Avi; DiCicco, Matt

2006-01-01

Five techniques for sensing forces with a manipulator are compared analytically and experimentally. The techniques compared are: a six-axis wrist force/torque sensor, joint torque sensors, link strain gauges, motor current sensors, and flexibility modeling. The accuracy and repeatability fo each technique is quantified and compared.

A forced damped oscillation framework for undulatory swimming provides new insights into how propulsion arises in active and passive swimming.

Science.gov (United States)

Bhalla, Amneet Pal Singh; Griffith, Boyce E; Patankar, Neelesh A

2013-01-01

A fundamental issue in locomotion is to understand how muscle forcing produces apparently complex deformation kinematics leading to movement of animals like undulatory swimmers. The question of whether complicated muscle forcing is required to create the observed deformation kinematics is central to the understanding of how animals control movement. In this work, a forced damped oscillation framework is applied to a chain-link model for undulatory swimming to understand how forcing leads to deformation and movement. A unified understanding of swimming, caused by muscle contractions ("active" swimming) or by forces imparted by the surrounding fluid ("passive" swimming), is obtained. We show that the forcing triggers the first few deformation modes of the body, which in turn cause the translational motion. We show that relatively simple forcing patterns can trigger seemingly complex deformation kinematics that lead to movement. For given muscle activation, the forcing frequency relative to the natural frequency of the damped oscillator is important for the emergent deformation characteristics of the body. The proposed approach also leads to a qualitative understanding of optimal deformation kinematics for fast swimming. These results, based on a chain-link model of swimming, are confirmed by fully resolved computational fluid dynamics (CFD) simulations. Prior results from the literature on the optimal value of stiffness for maximum speed are explained.

On complex periodic motions and bifurcations in a periodically forced, damped, hardening Duffing oscillator

International Nuclear Information System (INIS)

Guo, Yu; Luo, Albert C.J.

2015-01-01

In this paper, analytically predicted are complex periodic motions in the periodically forced, damped, hardening Duffing oscillator through discrete implicit maps of the corresponding differential equations. Bifurcation trees of periodic motions to chaos in such a hardening Duffing oscillator are obtained. The stability and bifurcation analysis of periodic motion in the bifurcation trees is carried out by eigenvalue analysis. The solutions of all discrete nodes of periodic motions are computed by the mapping structures of discrete implicit mapping. The frequency-amplitude characteristics of periodic motions are computed that are based on the discrete Fourier series. Thus, the bifurcation trees of periodic motions are also presented through frequency-amplitude curves. Finally, based on the analytical predictions, the initial conditions of periodic motions are selected, and numerical simulations of periodic motions are carried out for comparison of numerical and analytical predictions. The harmonic amplitude spectrums are also given for the approximate analytical expressions of periodic motions, which can also be used for comparison with experimental measurement. This study will give a better understanding of complex periodic motions in the hardening Duffing oscillator.

Imaging of Au nanoparticles deeply buried in polymer matrix by various atomic force microscopy techniques

International Nuclear Information System (INIS)

Kimura, Kuniko; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

2013-01-01

Recently, some papers reported successful imaging of subsurface features using atomic force microscopy (AFM). Some theoretical studies have also been presented, however the imaging mechanisms are not fully understood yet. In the preceeding papers, imaging of deeply buried nanometer-scale features has been successful only if they were buried in a soft matrix. In this paper, subsurface features (Au nanoparticles) buried in a soft polymer matrix were visualized. To elucidate the imaging mechanisms, various AFM techniques; heterodyne force microscopy, ultrasonic atomic force microscopy (UAFM), 2nd-harmonic UAFM and force modulation microscopy (FMM) were employed. The particles buried under 960 nm from the surface were successfully visualized which has never been achieved. The results elucidated that it is important for subsurface imaging to choose a cantilever with a suitable stiffness range for a matrix. In case of using the most suitable cantilever, the nanoparticles were visualized using every technique shown above except for FMM. The experimental results suggest that the subsurface features buried in a soft matrix with a depth of at least 1 µm can affect the local viscoelasticity (mainly viscosity) detected as the variation of the amplitude and phase of the tip oscillation on the surface. This phenomenon presumably makes it possible to visualize such deeply buried nanometer-scale features in a soft matrix. - Highlights: • We visualized subsurface features buried in soft matrix, and investigated its imaging mechanism. • AFM techniques; UAFM, FMM, HFM and 2nd-harmonic UAFM were applied to elucidate the mechanism. • Au nanoparticles buried under 960 nm from surface were visualized, which has never been achieved. • Imaging at contact resonance using a cantilever of suitable stiffness is important. • Subsurface features in a soft matrix affect surface viscoelasticity, which are detected by AFM

Prediction of unsteady separated flows on oscillating airfoils

Science.gov (United States)

Mccroskey, W. J.

1978-01-01

Techniques for calculating high Reynolds number flow around an airfoil undergoing dynamic stall are reviewed. Emphasis is placed on predicting the values of lift, drag, and pitching moments. Methods discussed include: the discrete potential vortex method; thin boundary layer method; strong interaction between inviscid and viscous flows; and solutions to the Navier-Stokes equations. Empirical methods for estimating unsteady airloads on oscillating airfoils are also described. These methods correlate force and moment data from wind tunnel tests to indicate the effects of various parameters, such as airfoil shape, Mach number, amplitude and frequency of sinosoidal oscillations, mean angle, and type of motion.

Feedback control of persistent-current oscillation based on the atomic-clock technique

Science.gov (United States)

Yu, Deshui; Dumke, Rainer

2018-05-01

We propose a scheme of stabilizing the persistent-current Rabi oscillation based on the flux qubit-resonator-atom hybrid structure. The low-Q L C resonator weakly interacts with the flux qubit and maps the persistent-current Rabi oscillation of the flux qubit onto the intraresonator electric field. This oscillating electric field is further coupled to a Rydberg-Rydberg transition of the 87Rb atoms. The Rabi-frequency fluctuation of the flux qubit is deduced from measuring the atomic population via the fluorescence detection and stabilized by feedback controlling the external flux bias. Our numerical simulation indicates that the feedback-control method can efficiently suppress the background fluctuations in the flux qubit, especially in the low-frequency limit. This technique may be extensively applicable to different types of superconducting circuits, paving a way to long-term-coherence superconducting quantum information processing.

Influence of plane bed on the force exerted on a cylinder oscillating in still water

Energy Technology Data Exchange (ETDEWEB)

Naeeni, S.T.O. [Tehran Univ., Dept. of Civil Engineering, Tehran (Iran); Narayanan, R. [Universiti Teknologi Malaysia, Faculty of Civil Engineering, Johor Bahru (Malaysia)

2005-12-01

The wall pressure field on a cylinder oscillating over a plane bed in still water is reported in this paper. Two gaps between the cylinder and the bed were considered. Pressures on the periphery of the cylinder were measured by a transducer and were found to be essentially repeatable from one cycle to the next. The forces determined from the pressure profiles compare well with those measured directly by a force transducer except significantly at Keulegan-Carpenter number of 15.0. The importance of the plane bed when it is stationary or moving with the cylinder is examined. The significance of the roughness of the bed with respect to the oscillatory forces exerted on the cylinder is also assessed. (Author)

Coding of Information in Limit Cycle Oscillators

Science.gov (United States)

Schleimer, Jan-Hendrik; Stemmler, Martin

2009-12-01

Starting from a general description of noisy limit cycle oscillators, we derive from the Fokker-Planck equations the linear response of the instantaneous oscillator frequency to a time-varying external force. We consider the time series of zero crossings of the oscillator’s phase and compute the mutual information between it and the driving force. A direct link is established between the phase response curve summarizing the oscillator dynamics and the ability of a limit cycle oscillator, such as a heart cell or neuron, to encode information in the timing of peaks in the oscillation.

Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age.

Science.gov (United States)

Knudsen, Mads Faurschou; Jacobsen, Bo Holm; Seidenkrantz, Marit-Solveig; Olsen, Jesper

2014-02-25

The Atlantic Multidecadal Oscillation (AMO) represents a significant driver of Northern Hemisphere climate, but the forcing mechanisms pacing the AMO remain poorly understood. Here we use the available proxy records to investigate the influence of solar and volcanic forcing on the AMO over the last ~450 years. The evidence suggests that external forcing played a dominant role in pacing the AMO after termination of the Little Ice Age (LIA; ca. 1400-1800), with an instantaneous impact on mid-latitude sea-surface temperatures that spread across the North Atlantic over the ensuing ~5 years. In contrast, the role of external forcing was more ambiguous during the LIA. Our study further suggests that the Atlantic Meridional Overturning Circulation is important for linking external forcing with North Atlantic sea-surface temperatures, a conjecture that reconciles two opposing theories concerning the origin of the AMO.

A Forced Damped Oscillation Framework for Undulatory Swimming Provides New Insights into How Propulsion Arises in Active and Passive Swimming

Science.gov (United States)

Bhalla, Amneet Pal Singh; Griffith, Boyce E.; Patankar, Neelesh A.

2013-01-01

A fundamental issue in locomotion is to understand how muscle forcing produces apparently complex deformation kinematics leading to movement of animals like undulatory swimmers. The question of whether complicated muscle forcing is required to create the observed deformation kinematics is central to the understanding of how animals control movement. In this work, a forced damped oscillation framework is applied to a chain-link model for undulatory swimming to understand how forcing leads to deformation and movement. A unified understanding of swimming, caused by muscle contractions (“active” swimming) or by forces imparted by the surrounding fluid (“passive” swimming), is obtained. We show that the forcing triggers the first few deformation modes of the body, which in turn cause the translational motion. We show that relatively simple forcing patterns can trigger seemingly complex deformation kinematics that lead to movement. For given muscle activation, the forcing frequency relative to the natural frequency of the damped oscillator is important for the emergent deformation characteristics of the body. The proposed approach also leads to a qualitative understanding of optimal deformation kinematics for fast swimming. These results, based on a chain-link model of swimming, are confirmed by fully resolved computational fluid dynamics (CFD) simulations. Prior results from the literature on the optimal value of stiffness for maximum speed are explained. PMID:23785272

A forced damped oscillation framework for undulatory swimming provides new insights into how propulsion arises in active and passive swimming.

Directory of Open Access Journals (Sweden)

Amneet Pal Singh Bhalla

Full Text Available A fundamental issue in locomotion is to understand how muscle forcing produces apparently complex deformation kinematics leading to movement of animals like undulatory swimmers. The question of whether complicated muscle forcing is required to create the observed deformation kinematics is central to the understanding of how animals control movement. In this work, a forced damped oscillation framework is applied to a chain-link model for undulatory swimming to understand how forcing leads to deformation and movement. A unified understanding of swimming, caused by muscle contractions ("active" swimming or by forces imparted by the surrounding fluid ("passive" swimming, is obtained. We show that the forcing triggers the first few deformation modes of the body, which in turn cause the translational motion. We show that relatively simple forcing patterns can trigger seemingly complex deformation kinematics that lead to movement. For given muscle activation, the forcing frequency relative to the natural frequency of the damped oscillator is important for the emergent deformation characteristics of the body. The proposed approach also leads to a qualitative understanding of optimal deformation kinematics for fast swimming. These results, based on a chain-link model of swimming, are confirmed by fully resolved computational fluid dynamics (CFD simulations. Prior results from the literature on the optimal value of stiffness for maximum speed are explained.

The effect of drive frequency and set point amplitude on tapping forces in atomic force microscopy: simulation and experiment

International Nuclear Information System (INIS)

Legleiter, Justin

2009-01-01

In tapping mode atomic force microscopy (AFM), a sharp probe tip attached to an oscillating cantilever is allowed to intermittently strike a surface. By raster scanning the probe while monitoring the oscillation amplitude of the cantilever via a feedback loop, topographical maps of surfaces with nanoscale resolution can be acquired. While numerous studies have employed numerical simulations to elucidate the time-resolved tapping force between the probe tip and surface, until recent technique developments, specific read-outs from such models could not be experimentally verified. In this study, we explore, via numerical simulation, the impact of imaging parameters, i.e. set point ratio and drive frequency as a function of resonance, on time-varying tip-sample force interactions, which are directly compared to reconstructed tapping forces from real AFM experiments. As the AFM model contains a feedback loop allowing for the simulation of the entire scanning process, we further explore the impact that various tip-sample force have on the entire imaging process.

Nonlinearity induced synchronization enhancement in mechanical oscillators

Science.gov (United States)

Czaplewski, David A.; Lopez, Omar; Guest, Jeffrey R.; Antonio, Dario; Arroyo, Sebastian I.; Zanette, Damian H.

2018-05-08

An autonomous oscillator synchronizes to an external harmonic force only when the forcing frequency lies within a certain interval, known as the synchronization range, around the oscillator's natural frequency. Under ordinary conditions, the width of the synchronization range decreases when the oscillation amplitude grows, which constrains synchronized motion of micro- and nano-mechanical resonators to narrow frequency and amplitude bounds. The present invention shows that nonlinearity in the oscillator can be exploited to manifest a regime where the synchronization range increases with an increasing oscillation amplitude. The present invention shows that nonlinearities in specific configurations of oscillator systems, as described herein, are the key determinants of the effect. The present invention presents a new configuration and operation regime that enhances the synchronization of micro- and nano-mechanical oscillators by capitalizing on their intrinsic nonlinear dynamics.

Extratropical Forcing Triggered the 2015 Madden-Julian Oscillation-El Niño Event.

Science.gov (United States)

Hong, Chi-Cherng; Hsu, Huang-Hsiung; Tseng, Wan-Ling; Lee, Ming-Ying; Chow, Chun-Hoe; Jiang, Li-Chiang

2017-04-24

In this paper, we report the triggering effect of extratropical perturbation on the onset of an atypical Madden-Julian Oscillation (MJO) and onset of the 2015-16 El Niño in March 2015. The MJO exhibited several unique characteristics: the effect of extratropical forcing, atypical genesis location and timing in the equatorial western Pacific, and the extremity of amplitudes in many aspects. The southward-penetrating northerly associated with the extratropical disturbances in the extratropical western North Pacific contributed to triggering the deep convection and westerly wind burst (WWB) and onset of the MJO over the anomalously warm tropical western Pacific in early March. The persisting strong WWB forced downwelling Kelvin wave-like oceanic perturbation that propagated eastward and led to the onset of the 2015-16 El Niño. The proposed novel extratropical forcing mechanism explaining the unique extratropics-MJO-El Niño association, based on both data diagnostics and numerical experiments, warrants further attention for a more detailed understanding of the onset of the MJO and its potential effect on El Niño.

The Influence of the External Signal Modulation Waveform and Frequency on the Performance of a Photonic Forced Oscillator.

Science.gov (United States)

Sánchez-Castro, Noemi; Palomino-Ovando, Martha Alicia; Estrada-Wiese, Denise; Valladares, Nydia Xcaret; Del Río, Jesus Antonio; de la Mora, Maria Beatriz; Doti, Rafael; Faubert, Jocelyn; Lugo, Jesus Eduardo

2018-05-21

Photonic crystals have been an object of interest because of their properties to inhibit certain wavelengths and allow the transmission of others. Using these properties, we designed a photonic structure known as photodyne formed by two porous silicon one-dimensional photonic crystals with an air defect between them. When the photodyne is illuminated with appropriate light, it allows us to generate electromagnetic forces within the structure that can be maximized if the light becomes localized inside the defect region. These electromagnetic forces allow the microcavity to oscillate mechanically. In the experiment, a chopper was driven by a signal generator to modulate the laser light that was used. The driven frequency and the signal modulation waveform (rectangular, sinusoidal or triangular) were changed with the idea to find optimal conditions for the structure to oscillate. The microcavity displacement amplitude, velocity amplitude and Fourier spectrum of the latter and its frequency were measured by means of a vibrometer. The mechanical oscillations are modeled and compared with the experimental results and show good agreement. For external frequency values of 5 Hz and 10 Hz, the best option was a sinusoidal waveform, which gave higher photodyne displacements and velocity amplitudes. Nonetheless, for an external frequency of 15 Hz, the best option was the rectangular waveform.

The Influence of the External Signal Modulation Waveform and Frequency on the Performance of a Photonic Forced Oscillator

Directory of Open Access Journals (Sweden)

Noemi Sánchez-Castro

2018-05-01

Full Text Available Photonic crystals have been an object of interest because of their properties to inhibit certain wavelengths and allow the transmission of others. Using these properties, we designed a photonic structure known as photodyne formed by two porous silicon one-dimensional photonic crystals with an air defect between them. When the photodyne is illuminated with appropriate light, it allows us to generate electromagnetic forces within the structure that can be maximized if the light becomes localized inside the defect region. These electromagnetic forces allow the microcavity to oscillate mechanically. In the experiment, a chopper was driven by a signal generator to modulate the laser light that was used. The driven frequency and the signal modulation waveform (rectangular, sinusoidal or triangular were changed with the idea to find optimal conditions for the structure to oscillate. The microcavity displacement amplitude, velocity amplitude and Fourier spectrum of the latter and its frequency were measured by means of a vibrometer. The mechanical oscillations are modeled and compared with the experimental results and show good agreement. For external frequency values of 5 Hz and 10 Hz, the best option was a sinusoidal waveform, which gave higher photodyne displacements and velocity amplitudes. Nonetheless, for an external frequency of 15 Hz, the best option was the rectangular waveform.

Injection locking of optomechanical oscillators via acoustic waves

Science.gov (United States)

Huang, Ke; Hossein-Zadeh, Mani

2018-04-01

Injection locking is a powerful technique for synchronization of oscillator networks and controlling the phase and frequency of individual oscillators using similar or other types of oscillators. Here, we present the first demonstration of injection locking of a radiation-pressure driven optomechanical oscillator (OMO) via acoustic waves. As opposed to previously reported techniques (based on pump modulation or direct application of a modulated electrostatic force), injection locking of OMO via acoustic waves does not require optical power modulation or physical contact with the OMO and it can easily be implemented on various platforms. Using this approach we have locked the phase and frequency of two distinct modes of a microtoroidal silica OMO to a piezoelectric transducer (PZT). We have characterized the behavior of the injection locked OMO with three acoustic excitation configurations and showed that even without proper acoustic impedance matching the OMO can be locked to the PZT and tuned over 17 kHz with only -30 dBm of RF power fed to the PZT. The high efficiency, simplicity and scalability of the proposed approach paves the road toward a new class of photonic systems that rely on synchronization of several OMOs to a single or multiple RF oscillators with applications in optical communication, metrology and sensing. Beyond its practical applications, injection locking via acoustic waves can be used in fundamental studies in quantum optomechanics where thermal and optical isolation of the OMO are critical.

Determination of alpha-naphthol by an oscillating chemical reaction using the analyte pulse perturbation technique

International Nuclear Information System (INIS)

Yang Wu; Sun Kanjun; Lv Weilian; Bo Lili; He Xiaoyan; Suo Nan; Gao Jinzhang

2005-01-01

An analytical method for the determination of alpha-naphthol (α-NP) is proposed by the sequential perturbation caused by different amounts of alpha-naphthol on the oscillating chemical system involving the Cu(II)-catalyzed oscillating reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium with the aid of continuous-flow stirred tank reactor (CSTR). The method relies on the linear relationship between the changes in the oscillation amplitude of the chemical system and the concentration of alpha-naphthol. The use of the analyte pulse perturbation technique permits sequential determinations in the same oscillating system owing to the expeditiousness with which the steady state is regained after each perturbation. The calibration curve obeys a linear equation very well when the concentration of alpha-naphthol is over the range 0.034-530 umol/L (r = 0.9991). Influences of temperature, injection points, flow rate and reaction variables on the oscillating system are investigated in detail and the possible mechanism of action of alpha-naphthol to the chemical oscillating system is also discussed. The method has been successfully used for the determination of α-naphthol in carbaryl hydrolysates

Oscillation experiments techniques in CEA Minerve experimental reactor

Energy Technology Data Exchange (ETDEWEB)

Antony, M.; Di-Salvo, J.; Pepino, A.; Bosq, J. C.; Bernard, D.; Leconte, P.; Hudelot, J. P.; Lyoussi, A. [CEA CADARACHE, DEN/DER/SPEx, 13108 Saint Paul-lez-Durance (France)

2009-07-01

This paper deals with experiments in the Minerve pool Zero Power Reactor. Minerve is mainly devoted to neutronics studies, in view to improve the calculation routes by reducing the uncertainties of the experimental databases for nuclides arising in plutonium and wastes management. Minerve experimental measurement programs are performed by using the oscillation technique. This experimental technique consists in a periodic insertion and extraction of samples containing the nuclide of interest in a well characterized neutron spectrum. The reactivity variation of the sample is compensated by a calibrated rotary automatic pilot using cadmium sectors. The normal accuracy for measurements of small-worth samples in Minerve by using such a technique is about 3% for absolute reactivity worth, including the uncertainties on the material balance and on the calibration step. Reactivity effects of less than 1.5 cent can be measured. The OSMOSE and the OCEAN programs have been carried out since 2005 and will last until 2011. These programs aim at improving, in different neutron spectra, the absorption cross sections of respectively a majority of the separated heavy nuclides from {sup 232}Th to {sup 245}Cm appearing during the reactor and the fuel cycle physics, and of current and future types of absorbers as Gd, Hf, Er, Dy and Eu. (authors)

Exploring flavor-dependent long-range forces in long-baseline neutrino oscillation experiments

Science.gov (United States)

Chatterjee, Sabya Sachi; Dasgupta, Arnab; Agarwalla, Sanjib Kumar

2015-12-01

The Standard Model gauge group can be extended with minimal matter content by introducing anomaly free U(1) symmetry, such as L e - L μ or L e - L τ . If the neutral gauge boson corresponding to this abelian symmetry is ultra-light, then it will give rise to flavor-dependent long-range leptonic force, which can have significant impact on neutrino oscillations. For an instance, the electrons inside the Sun can generate a flavor-dependent long-range potential at the Earth surface, which can suppress the ν μ → ν e appearance probability in terrestrial experiments. The sign of this potential is opposite for anti-neutrinos, and affects the oscillations of (anti-)neutrinos in different fashion. This feature invokes fake CP-asymmetry like the SM matter effect and can severely affect the leptonic CP-violation searches in long-baseline experiments. In this paper, we study in detail the possible impacts of these long-range flavor-diagonal neutral current interactions due to L e - L μ symmetry, when (anti-)neutrinos travel from Fermilab to Homestake (1300 km) and CERN to Pyhäsalmi (2290 km) in the context of future high-precision superbeam facilities, DUNE and LBNO respectively. If there is no signal of long-range force, DUNE (LBNO) can place stringent constraint on the effective gauge coupling α eμ < 1.9 × 10-53 (7.8 × 10-54) at 90% C.L., which is almost 30 (70) times better than the existing bound from the Super-Kamiokande experiment. We also observe that if α eμ ≥ 2 × 10-52, the CP-violation discovery reach of these future facilities vanishes completely. The mass hierarchy measurement remains robust in DUNE (LBNO) if α eμ < 5 × 10-52 (10-52).

Characteristics of a random force in the phenomenological description of surface oscillations of heated spherical nuclei

International Nuclear Information System (INIS)

Svin'in, I.R.

1987-01-01

A method of calculation of statistical characteristics of a random force is presented. This method is used in the description of oscillations of heated spherical nuclei in the Brownian movement approximation. The mean value and the spectral density of the correlation function are calculated in the noninteracting-particle model. The dependence of the spectral density on the number of nucleons and on the temperature of the nucleus is analyzed

A standing pressure wave hypothesis of oscillating forces generated during a steam line break

International Nuclear Information System (INIS)

Tinoco, H.

2001-01-01

A rapid glance at the figure depicting the net forces acting on the reactor vessel and internals, as obtained through a CFD simulation of a BWR steam line break, reveals an amazing oscillating regularity of these forces which is in glaring contrast to the chaotic behaviour of the steam pressure field in the steam annulus. Assuming that the decompression process excites and maintains standing pressure waves in the annular cylindrical region constituted by the steam annulus, it is possible to reconstruct the net forces acting on the reactor vessel and internals through the contribution of almost only the first dispersive mode. If a Neumann boundary condition is assumed at the section connecting the steam annulus to the steam dome, the frequency predicted is approximately % 5.9 higher than that of the CFD simulations. However, this connecting section allows wave transmission, and a more appropriate boundary condition should be one of the Robin type. Therefore, this section is modelled as an absorbing wall, and the corresponding normal impedance is calculated using the CFD simulations. Week non-linear effects can also be observed in the calculated forces through the presence of the first subharmonic. By the methodology described above, an estimate of the forces acting on the reactor vessel and internals of unit 3 of Forsmark Nuclear Power Plant has been obtained. (author)

Flight Flutter Testing of Rotary Wing Aircraft Using a Control System Oscillation Technique

Science.gov (United States)

Yen, J. G.; Viswanathan, S.; Matthys, C. G.

1976-01-01

A flight flutter testing technique is described in which the rotor controls are oscillated by series actuators to excite the rotor and airframe modes of interest, which are then allowed to decay. The moving block technique is then used to determine the damped frequency and damping variation with rotor speed. The method proved useful for tracking the stability of relatively well damped modes. The results of recently completed flight tests of an experimental soft-in-plane rotor are used to illustrate the technique. Included is a discussion of the application of this technique to investigation of the propeller whirl flutter stability characteristics of the NASA/Army XV-15 VTOL tilt rotor research aircraft.

Injection locking of optomechanical oscillators via acoustic waves.

Science.gov (United States)

Huang, Ke; Hossein-Zadeh, Mani

2018-04-02

Injection locking is an effective technique for synchronization of oscillator networks and controlling the phase and frequency of individual oscillators. As such, exploring new mechanisms for injection locking of emerging oscillators is important for their usage in various systems. Here, we present the first demonstration of injection locking of a radiation pressure driven optomechanical oscillator (OMO) via acoustic waves. As opposed to previously reported techniques (based on pump modulation or direct application of a modulated electrostatic force), injection locking of OMO via acoustic waves does not require optical power modulation or physical contact with the OMO and it can be easily implemented on various platforms to lock different types of OMOs independent of their size and structure. Using this approach we have locked the phase and frequency of two distinct modes of a microtoroidal silica OMO to a piezoelectric transducer (PZT). We have characterized the behavior of the injection locked OMO with three acoustic excitation configurations and showed that even without proper acoustic impedance, matching the OMO can be locked to the PZT and tuned over 17 kHz with only -30 dBm of RF power fed to the PZT. The high efficiency, simplicity, and scalability of the proposed approach paves the road toward a new class of photonic systems that rely on synchronization of several OMOs to a single or multiple RF oscillators with applications in optical communication, metrology, and sensing. Beyond its practical applications, injection locking via acoustic waves can be used in fundamental studies in quantum optomechanics where thermal and optical isolation of the OMO are critical.

Taylor-Couette fluid flow with force oscillation in the inner-cylinder using the immersed boundary method

Energy Technology Data Exchange (ETDEWEB)

Borges, Jonatas Emmanuel; Lourenco, Marcos Antonio de Souza; Padilla, Elie Luis Martinez; Silveira Neto, Aristeu da [Federal University of Uberlandia , MG (Brazil)], e-mails: lourenco@mecanica.ufu.br, epadilla@mecanica.ufu.br, aristeus@mecanica.ufu.br; Leibsohn, Andre Martins [CENPES/Petrobras, Rio de Janeiro, RJ (Brazil)], e-mail: aleibsohn@petrobras.com

2010-07-01

As new challenges arise in the exploration of deep and ultra-deep water oil fields by PETROBRAS more knowledge and research are needed, so that tools could be developed to assist in the critical operations and make things practicable. In the context of the drilling process, the complexity of the fluid flow inside the riser is associated with the nature of the non-Newtonian flow, immersed solid particles, variable eccentricity and the superimposed traveling azimuthal waves on the inflow and outflow boundaries of the Taylor vortices. This work presents the numerical three-dimensional results of the following simplified fluid flows: Taylor-Couette, Taylor-Couette with varying imposed eccentricity and Taylor-Couette with forced oscillation in the inner cylinder. Using the Navier-Stokes equations, a finite volume method discretization with second order accuracy in both time and space was utilized to simulate the Newtonian, single-phase incompressible fluid flow in the three cases. The circular walls of the inner and outer cylinders are represented by the immersed boundary method, with the direct multi-forcing model. The determined results allow to evidence the flow structures in the three cases in a very qualitative way, even so in the presence of the inner cylinder oscillation. (author)

Muscle optimization techniques impact the magnitude of calculated hip joint contact forces

NARCIS (Netherlands)

Wesseling, M.; Derikx, L.C.; de Groote, F.; Bartels, W.; Meyer, C.; Verdonschot, Nicolaas Jacobus Joseph; Jonkers, I.

2015-01-01

In musculoskeletal modelling, several optimization techniques are used to calculate muscle forces, which strongly influence resultant hip contact forces (HCF). The goal of this study was to calculate muscle forces using four different optimization techniques, i.e., two different static optimization

Energy dissipation in fragmented geomaterials associated with impacting oscillators

Science.gov (United States)

Khudyakov, Maxim; Pasternak, Elena; Dyskin, Arcady

2016-04-01

In wave propagation through fragmented geomaterials forced by periodic loadings, the elements (fragments) strike against each other when passing through the neutral position (position with zero mutual rotation), quickly damping the oscillations. Essentially the impacts act as shock absorbers albeit localised at the neutral points. In order to analyse the vibrations of and wave propagation in such structures, a differential equation of a forced harmonic oscillator was investigated, where the each time the system passes through the neutral point the velocity gets reduced by multiplying it with the restitution coefficient which characterise the impact of the fragments. In forced vibrations the impact times depend on both the forced oscillations and the restitution coefficient and form an irregular sequence. Numerical solution of the differential equation was performed using Mathematica software. Along with vibration diagrams, the dependence of the energy dissipation on the ratio of the forcing frequency to the natural frequency was obtained. For small positive values of the restitution coefficient (less than 0.5), the asymmetric oscillations were found, and the phase of the forced vibrations determined the direction of the asymmetry. Also, at some values of the forcing frequencies and the restitution coefficient chaotic behaviour was found.

The Tucson-Melbourne Three-Body Force in a Translationally-Invariant Harmonic Oscillator Basis

Science.gov (United States)

Marsden, David; Navratil, Petr; Barrett, Bruce

2000-09-01

A translationally-invariant three-body basis set has been employed in shell model calculations on ^3H and ^3He including the Tucson-Melbourne form of the real nuclear three-body force. The basis consists of harmonic oscillators in Jacobi coordinates, explicitly avoiding the centre of mass drift problem in the calculations. The derivation of the three-body matrix elements and the results of large basis effective interaction shell model calculations will be presented. J. L. Friar, B. F. Gibson, G. L. Payne and S. A. Coon; Few Body Systems 5, 13 (1988) P. Navratil, G.P. Kamuntavicius and B.R. Barrett; Phys. Rev. C. 61, 044001 (2000)

NOx Emission Reduction by Oscillating Combustion

Energy Technology Data Exchange (ETDEWEB)

None

2005-09-01

This project focuses on a new technology that reduces NOx emissions while increasing furnace efficiency for both air- and oxygen-fired furnaces. Oscillating combustion is a retrofit technology that involves the forced oscillation of the fuel flow rate to a furnace. These oscillations create successive, fuel-rich and fuel-lean zones within the furnace.

Electromagnetically actuated micromanipulator using an acoustically oscillating bubble

International Nuclear Information System (INIS)

Kwon, J O; Yang, J S; Lee, S J; Rhee, K; Chung, S K

2011-01-01

A novel non-invasive micromanipulation technique has been developed where a microrobot swimming in an aqueous medium manipulates micro-objects, through electromagnetic actuation using an acoustically oscillating bubble attached to the microrobot as a grasping tool. This micromanipulation concept was experimentally verified; an investigation of electromagnetic actuation and acoustic excitation was also performed. Two-dimensional propulsion of a magnetic piece was demonstrated through electromagnetic actuation, using three pairs of electric coils surrounding the water chamber, and confirming that the propulsion speed of the magnetic piece was linearly proportional to the applied current intensity. Micro-object manipulation was separately demonstrated using an air bubble with glass beads (80 µm diameter) and a steel ball (800 µm diameter) in an aqueous medium. Upon acoustic excitation of the bubble by a piezo-actuator around its resonant frequency, the generated radiation force attracted and captured the neighboring glass beads and steel ball. The grasping force was indirectly measured by exposing the glass beads captured by the oscillating bubble to a stream generated by an auto-syringe pump in a mini-channel. By measuring the maximum speed of the streaming flow when the glass beads detached from the oscillating bubble and flowed downstream, the grasping force was calculated as 50 nN, based on Stokes' drag approximation. Finally, a fish egg was successfully manipulated with the integration of electromagnetic actuation and acoustic excitation, using a mini-robot consisting of a millimeter-sized magnetic piece with a bubble attached to its bottom. This novel micromanipulation may be an efficient tool for both micro device assembly and single-cell manipulation.

Electromagnetically actuated micromanipulator using an acoustically oscillating bubble

Science.gov (United States)

Kwon, J. O.; Yang, J. S.; Lee, S. J.; Rhee, K.; Chung, S. K.

2011-11-01

A novel non-invasive micromanipulation technique has been developed where a microrobot swimming in an aqueous medium manipulates micro-objects, through electromagnetic actuation using an acoustically oscillating bubble attached to the microrobot as a grasping tool. This micromanipulation concept was experimentally verified; an investigation of electromagnetic actuation and acoustic excitation was also performed. Two-dimensional propulsion of a magnetic piece was demonstrated through electromagnetic actuation, using three pairs of electric coils surrounding the water chamber, and confirming that the propulsion speed of the magnetic piece was linearly proportional to the applied current intensity. Micro-object manipulation was separately demonstrated using an air bubble with glass beads (80 µm diameter) and a steel ball (800 µm diameter) in an aqueous medium. Upon acoustic excitation of the bubble by a piezo-actuator around its resonant frequency, the generated radiation force attracted and captured the neighboring glass beads and steel ball. The grasping force was indirectly measured by exposing the glass beads captured by the oscillating bubble to a stream generated by an auto-syringe pump in a mini-channel. By measuring the maximum speed of the streaming flow when the glass beads detached from the oscillating bubble and flowed downstream, the grasping force was calculated as 50 nN, based on Stokes' drag approximation. Finally, a fish egg was successfully manipulated with the integration of electromagnetic actuation and acoustic excitation, using a mini-robot consisting of a millimeter-sized magnetic piece with a bubble attached to its bottom. This novel micromanipulation may be an efficient tool for both micro device assembly and single-cell manipulation.

Non-linear oscillations of fluid in a container

NARCIS (Netherlands)

Verhagen, J.H.G.; van Wijngaarden, L.

1965-01-01

This paper is concerned with forced oscillations of fluid in a rectangular container. From the linearized approximation of the equations governing these oscillations, resonance frequencies are obtained for which the amplitude of the oscillations becomes infinite. Observation shows that under these

Frequency-dependent transient response of an oscillating electrically actuated droplet

International Nuclear Information System (INIS)

Dash, S; Kumari, N; Garimella, S V

2012-01-01

The transient response of a millimeter-sized sessile droplet under electrical actuation is experimentally investigated. Under dc actuation, the droplet spreading rate increases as the applied voltage is increased due to the higher electrical forces induced. At sufficiently high dc voltages, competition between the electrical actuation force, droplet inertia, the retarding surface tension force and contact line friction leads to droplet oscillation. The timescale for the droplet to attain its maximum wetted diameter during step actuation is analyzed. Systematic experiments are conducted over a frequency range of 5–200 Hz and actuation voltages of 40–80 V rms to determine the dependence of droplet oscillation on these parameters. The response of the droplet to different actuation frequencies and voltages is determined in terms of its contact angle and contact radius variation. The frequency of the driving force (equal to twice the frequency of the applied electrical signal) determines the mode of oscillation of the droplet which, together with its resonance characteristics, governs whether the droplet contact angle and contact radius vary in phase or out of phase with each other. In addition to the primary frequency response at the electrical forcing frequency, the droplet oscillation exhibits sub-harmonic oscillation at half of the forcing frequency that is attributed to the parametric nature of the electrical force acting on the triple contact line of the droplet. (paper)

Persistent fluctuations in synchronization rate in globally coupled oscillators with periodic external forcing

Science.gov (United States)

Atsumi, Yu; Nakao, Hiroya

2012-05-01

A system of phase oscillators with repulsive global coupling and periodic external forcing undergoing asynchronous rotation is considered. The synchronization rate of the system can exhibit persistent fluctuations depending on parameters and initial phase distributions, and the amplitude of the fluctuations scales with the system size for uniformly random initial phase distributions. Using the Watanabe-Strogatz transformation that reduces the original system to low-dimensional macroscopic equations, we show that the fluctuations are collective dynamics of the system corresponding to low-dimensional trajectories of the reduced equations. It is argued that the amplitude of the fluctuations is determined by the inhomogeneity of the initial phase distribution, resulting in system-size scaling for the random case.

Automated force controller for amplitude modulation atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Miyagi, Atsushi, E-mail: atsushi.miyagi@inserm.fr, E-mail: simon.scheuring@inserm.fr; Scheuring, Simon, E-mail: atsushi.miyagi@inserm.fr, E-mail: simon.scheuring@inserm.fr [U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 Avenue de Luminy, 13009 Marseille (France)

2016-05-15

Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed.

Experimental study on flow past a rotationally oscillating cylinder

Science.gov (United States)

Gao, Yang-yang; Yin, Chang-shan; Yang, Kang; Zhao, Xi-zeng; Tan, Soon Keat

2017-08-01

A series of experiments was carried out to study the flow behaviour behind a rotationally oscillating cylinder at a low Reynolds number (Re=300) placed in a recirculation water channel. A stepper motor was used to rotate the cylinder clockwise- and- counterclockwise about its longitudinal axis at selected frequencies. The particle image velocimetry (PIV) technique was used to capture the flow field behind a rotationally oscillating cylinder. Instantaneous and timeaveraged flow fields such as the vorticity contours, streamline topologies and velocity distributions were analyzed. The effects of four rotation angle and frequency ratios F r ( F r= f n/ f v, the ratio of the forcing frequency f n to the natural vortex shedding frequency f v) on the wake in the lee of a rotationally oscillating cylinder were also examined. The significant wake modification was observed when the cylinder undergoes clockwise-and-counterclockwise motion with amplitude of π, especially in the range of 0.6≤ F r≤1.0.

Innovative hybrid pile oscillator technique in the Minerve reactor: open loop vs. closed loop

Science.gov (United States)

Geslot, Benoit; Gruel, Adrien; Bréaud, Stéphane; Leconte, Pierre; Blaise, Patrick

2018-01-01

Pile oscillator techniques are powerful methods to measure small reactivity worth of isotopes of interest for nuclear data improvement. This kind of experiments has long been implemented in the Mineve experimental reactor, operated by CEA Cadarache. A hybrid technique, mixing reactivity worth estimation and measurement of small changes around test samples is presented here. It was made possible after the development of high sensitivity miniature fission chambers introduced next to the irradiation channel. A test campaign, called MAESTRO-SL, took place in 2015. Its objective was to assess the feasibility of the hybrid method and investigate the possibility to separate mixed neutron effects, such as fission/capture or scattering/capture. Experimental results are presented and discussed in this paper, which focus on comparing two measurements setups, one using a power control system (closed loop) and another one where the power is free to drift (open loop). First, it is demonstrated that open loop is equivalent to closed loop. Uncertainty management and methods reproducibility are discussed. Second, results show that measuring the flux depression around oscillated samples provides valuable information regarding partial neutron cross sections. The technique is found to be very sensitive to the capture cross section at the expense of scattering, making it very useful to measure small capture effects of highly scattering samples.

Nonlinear state-space modelling of the kinematics of an oscillating circular cylinder in a fluid flow

Science.gov (United States)

Decuyper, J.; De Troyer, T.; Runacres, M. C.; Tiels, K.; Schoukens, J.

2018-01-01

The flow-induced vibration of bluff bodies is an important problem of many marine, civil, or mechanical engineers. In the design phase of such structures, it is vital to obtain good predictions of the fluid forces acting on the structure. Current methods rely on computational fluid dynamic simulations (CFD), with a too high computational cost to be effectively used in the design phase or for control applications. Alternative methods use heuristic mathematical models of the fluid forces, but these lack the accuracy (they often assume the system to be linear) or flexibility to be useful over a wide operating range. In this work we show that it is possible to build an accurate, flexible and low-computational-cost mathematical model using nonlinear system identification techniques. This model is data driven: it is trained over a user-defined region of interest using data obtained from experiments or simulations, or both. Here we use a Van der Pol oscillator as well as CFD simulations of an oscillating circular cylinder to generate the training data. Then a discrete-time polynomial nonlinear state-space model is fit to the data. This model relates the oscillation of the cylinder to the force that the fluid exerts on the cylinder. The model is finally validated over a wide range of oscillation frequencies and amplitudes, both inside and outside the so-called lock-in region. We show that forces simulated by the model are in good agreement with the data obtained from CFD.

Study of Belousov—Zhabotinsky oscillators in water—acetonitrile medium employing EMF and EPR techniques with o-vanillin, p-vanillin and adrenaline as substrates

Science.gov (United States)

Lalitha, P. V.; Ramaswamy, R.; Ramakrishnan, Geetha; Rao, P. Sambasiva

1994-12-01

The oscillatory behaviour of three substrates, ortho-vanillin, para-vanillin and adrenaline, in mixed media (water plus 20% acetonitrile) has been investigated using EPR and EMF techniques. All these substrates exhibit two types of oscillation involving Br 2/Br - and Mn(III)/Mn(II) redox couples. From the oscillatory characteristics (total time, number of oscillations and time per oscillation) obtained by employing these techniques, the reactivities of the vanillins have been correlated. The Field—Koros—Noyes mechanism, suggested for catalysed systems in pure aqueous medium, is established to be applicable even in mixed media.

Flextime: A Modified Work Force Scheduling Technique for Selected Headquarters Air Force Logistics Command Organizations.

Science.gov (United States)

Kimzey, Reed T.; Prince, Samuel M. O.

The thesis discusses the advantages and disadvantages of one work force scheduling technique--flextime. The authors were interested in determining if a flextime schedule could be put into effect in a governmental organization such as Headquarters Air Force Logistics Command (AFLC). The study objectives were to determine the feasibility,…

Capillary forces in tapping mode atomic force microscopy

NARCIS (Netherlands)

Zitzler, L.; Herminghaus, S.; Mugele, Friedrich Gunther

2002-01-01

We investigated the influence of the relative humidity on amplitude and phase of the cantilever oscillation while operating an atomic force microscope (AFM) in the tapping mode. If the free oscillation amplitude A0 exceeds a certain critical amplitude Ac, the amplitude- and phase-distance curves

Photoinduced force microscopy: A technique for hyperspectral nanochemical mapping

Science.gov (United States)

Murdick, Ryan A.; Morrison, William; Nowak, Derek; Albrecht, Thomas R.; Jahng, Junghoon; Park, Sung

2017-08-01

Advances in nanotechnology have intensified the need for tools that can characterize newly synthesized nanomaterials. A variety of techniques has recently been shown which combines atomic force microscopy (AFM) with optical illumination including tip-enhanced Raman spectroscopy (TERS), scattering-type scanning near-field optical microscopy (sSNOM), and photothermal induced resonance microscopy (PTIR). To varying degrees, these existing techniques enable optical spectroscopy with the nanoscale spatial resolution inherent to AFM, thereby providing nanochemical interrogation of a specimen. Here we discuss photoinduced force microscopy (PiFM), a recently developed technique for nanoscale optical spectroscopy that exploits image forces acting between an AFM tip and sample to detect wavelength-dependent polarization within the sample to generate absorption spectra. This approach enables ∼10 nm spatial resolution with spectra that show correlation with macroscopic optical absorption spectra. Unlike other techniques, PiFM achieves this high resolution with virtually no constraints on sample or substrate properties. The applicability of PiFM to a variety of archetypal systems is reported here, highlighting the potential of PiFM as a useful tool for a wide variety of industrial and academic investigations, including semiconducting nanoparticles, nanocellulose, block copolymers, and low dimensional systems, as well as chemical and morphological mixing at interfaces.

Periodic synchronization and chimera in conformist and contrarian oscillators

Science.gov (United States)

Hong, Hyunsuk

2014-06-01

We consider a system of phase oscillators that couple with both attractive and repulsive interaction under a pinning force and explore collective behavior of the system. The oscillators can be divided into two subpopulations of "conformist" oscillators with attractive interaction and "contrarian" ones with repulsive interaction. We find that the interplay between the pinning force and the opposite relationship of the conformist and contrarian oscillators induce peculiar dynamic states: periodic synchronization, breathing chimera, and fully pinned state depending on the fraction of the conformists. Using the Watanabe-Strogatz transformation, we reduce the dynamics into a low-dimensional one and find that the above dynamic states are generated from the reduced dynamics.

Harmonic oscillations, chaos and synchronization in systems consisting of Van der Pol oscillator coupled to a linear oscillator

International Nuclear Information System (INIS)

Woafo, P.

1999-12-01

This paper deals with the dynamics of a model describing systems consisting of the classical Van der Pol oscillator coupled gyroscopically to a linear oscillator. Both the forced and autonomous cases are considered. Harmonic response is investigated along with its stability boundaries. Condition for quenching phenomena in the autonomous case is derived. Neimark bifurcation is observed and it is found that our model shows period doubling and period-m sudden transitions to chaos. Synchronization of two and more systems in their chaotic regime is presented. (author)

Vibrations of a molecule in an external force field.

Science.gov (United States)

Okabayashi, Norio; Peronio, Angelo; Paulsson, Magnus; Arai, Toyoko; Giessibl, Franz J

2018-05-01

The oscillation frequencies of a molecule on a surface are determined by the mass distribution in the molecule and the restoring forces that occur when the molecule bends. The restoring force originates from the atomic-scale interaction within the molecule and with the surface, which plays an essential role in the dynamics and reactivity of the molecule. In 1998, a combination of scanning tunneling microscopy with inelastic tunneling spectroscopy revealed the vibrational frequencies of single molecules adsorbed on a surface. However, the probe tip itself exerts forces on the molecule, changing its oscillation frequencies. Here, we combine atomic force microscopy with inelastic tunneling spectroscopy and measure the influence of the forces exerted by the tip on the lateral vibrational modes of a carbon monoxide molecule on a copper surface. Comparing the experimental data to a mechanical model of the vibrating molecule shows that the bonds within the molecule and with the surface are weakened by the proximity of the tip. This combination of techniques can be applied to analyze complex molecular vibrations and the mechanics of forming and loosening chemical bonds, as well as to study the mechanics of bond breaking in chemical reactions and atomic manipulation.

Observed linkages between the northern annular mode/North Atlantic Oscillation, cloud incidence, and cloud radiative forcing

Science.gov (United States)

Li, Ying; Thompson, David W. J.; Huang, Yi; Zhang, Minghong

2014-03-01

The signature of the northern annular mode/North Atlantic Oscillation (NAM/NAO) in the vertical and horizontal distribution of tropospheric cloudiness is investigated in CloudSat and CALIPSO data from June 2006 to April 2011. During the Northern Hemisphere winter, the positive polarity of the NAM/NAO is marked by increases in zonally averaged cloud incidence north of ~60°N, decreases between ~25 and 50°N, and increases in the subtropics. The tripolar-like anomalies in cloud incidence associated with the NAM/NAO are largest over the North Atlantic Ocean basin/Middle East and are physically consistent with the NAM/NAO-related anomalies in vertical motion. Importantly, the NAM/NAO-related anomalies in tropospheric cloud incidence lead to significant top of atmosphere cloud radiative forcing anomalies that are comparable in amplitude to those associated with the NAM/NAO-related temperature anomalies. The results provide observational evidence that the most prominent pattern of Northern Hemisphere climate variability is significantly linked to variations in cloud radiative forcing. Implications for two-way feedback between extratropical dynamics and cloud radiative forcing are discussed.

Innovative hybrid pile oscillator technique in the Minerve reactor: open loop vs. closed loop

Directory of Open Access Journals (Sweden)

Geslot Benoit

2018-01-01

Full Text Available Pile oscillator techniques are powerful methods to measure small reactivity worth of isotopes of interest for nuclear data improvement. This kind of experiments has long been implemented in the Mineve experimental reactor, operated by CEA Cadarache. A hybrid technique, mixing reactivity worth estimation and measurement of small changes around test samples is presented here. It was made possible after the development of high sensitivity miniature fission chambers introduced next to the irradiation channel. A test campaign, called MAESTRO-SL, took place in 2015. Its objective was to assess the feasibility of the hybrid method and investigate the possibility to separate mixed neutron effects, such as fission/capture or scattering/capture. Experimental results are presented and discussed in this paper, which focus on comparing two measurements setups, one using a power control system (closed loop and another one where the power is free to drift (open loop. First, it is demonstrated that open loop is equivalent to closed loop. Uncertainty management and methods reproducibility are discussed. Second, results show that measuring the flux depression around oscillated samples provides valuable information regarding partial neutron cross sections. The technique is found to be very sensitive to the capture cross section at the expense of scattering, making it very useful to measure small capture effects of highly scattering samples.

Analyzing endosonic root canal file oscillations: an in vitro evaluation.

Science.gov (United States)

Lea, Simon C; Walmsley, A Damien; Lumley, Philip J

2010-05-01

Passive ultrasonic irrigation may be used to improve bacterial reduction within the root canal. The technique relies on a small file being driven to oscillate freely within the canal and activating an irrigant solution through biophysical forces such as microstreaming. There is limited information regarding a file's oscillation patterns when operated while surrounded by fluid as is the case within a canal root. Files of different sizes (#10 and #30, 27 mm and 31 mm) were connected to an ultrasound generator via a 120 degrees file holder. Files were immersed in a water bath, and a laser vibrometer set up with measurement lines superimposed over the files. The laser vibrometer was scanned over the oscillating files. Measurements were repeated 10 times for each file/power setting used. File mode shapes are comprised of a series of nodes/antinodes, with thinner, longer files producing more antinodes. The maximum vibration occurred at the free end of the file. Increasing generator power had no significant effect on this maximum amplitude (p > 0.20). Maximum displacement amplitudes were 17 to 22 microm (#10 file, 27 mm), 15 to 21 microm (#10 file, 31 mm), 6 to 9 microm (#30 file, 27 mm), and 5 to 7 microm (#30, 31 mm) for all power settings. Antinodes occurring along the remaining file length were significantly larger at generator power 1 than at powers 2 through 5 (p generator powers, energy delivered to the file is dissipated in unwanted vibration resulting in reduced vibration displacement amplitudes. This may reduce the occurrence of the biophysical forces necessary to maximize the technique's effectiveness. Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effect of fatigue on force production and force application technique during repeated sprints.

Science.gov (United States)

Morin, Jean-Benoit; Samozino, Pierre; Edouard, Pascal; Tomazin, Katja

2011-10-13

We investigated the changes in the technical ability of force application/orientation against the ground vs. the physical capability of total force production after a multiple-set repeated sprints series. Twelve male physical education students familiar with sprint running performed four sets of five 6-s sprints (24s of passive rest between sprints, 3min between sets). Sprints were performed from a standing start on an instrumented treadmill, allowing the computation of vertical (F(V)), net horizontal (F(H)) and total (F(Tot)) ground reaction forces for each step. Furthermore, the ratio of forces was calculated as RF=F(H)F(Tot)(-1), and the index of force application technique (D(RF)) representing the decrement in RF with increase in speed was computed as the slope of the linear RF-speed relationship. Changes between pre- (first two sprints) and post-fatigue (last two sprints) were tested using paired t-tests. Performance decreased significantly (e.g. top speed decreased by 15.7±5.4%; Pmultiple-set repeated sprint series, both the total force production capability and the technical ability to apply force effectively against the ground are altered, the latter to a larger extent than the former. Copyright © 2011 Elsevier Ltd. All rights reserved.

Mitigation of Power System Oscillation Caused by Wind Power Fluctuation

DEFF Research Database (Denmark)

Su, Chi; Hu, Weihao; Chen, Zhe

2013-01-01

oscillation mitigation controllers are proposed and compared. A model of direct-drive-full-convertor-based wind farm connected to the IEEE 10-machine 39-bus system is adopted as the test system. The calculations and simulations are conducted in DIgSILENT PowerFactory 14.0. Results are presented to show......Wind power is increasingly integrated in modern power grids, which brings new challenges to the power system operation. Wind power is fluctuating because of the uncertain nature of wind, whereas wind shear and tower shadow effects also cause periodic fluctuations. These may lead to serious forced...... oscillation when the frequencies of the periodic fluctuations are close to the natural oscillation frequencies of the connected power system. By using modal analysis and time-domain simulations, this study studies the forced oscillation caused by the wind shear and tower shadow effects. Three forced...

Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

KAUST Repository

Ge, Xiaoqing

2010-12-01

Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

KAUST Repository

Ge, Xiaoqing; Arcak, Murat; Salama, Khaled N.

2010-01-01

Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

Lorentz force actuation of a heated atomic force microscope cantilever.

Science.gov (United States)

Lee, Byeonghee; Prater, Craig B; King, William P

2012-02-10

We report Lorentz force-induced actuation of a silicon microcantilever having an integrated resistive heater. Oscillating current through the cantilever interacts with the magnetic field around a NdFeB permanent magnet and induces a Lorentz force that deflects the cantilever. The same current induces cantilever heating. With AC currents as low as 0.2 mA, the cantilever can be oscillated as much as 80 nm at resonance with a DC temperature rise of less than 5 °C. By comparison, the AC temperature variation leads to a thermomechanical oscillation that is about 1000 times smaller than the Lorentz deflection at the cantilever resonance. The cantilever position in the nonuniform magnetic field affects the Lorentz force-induced deflection, with the magnetic field parallel to the cantilever having the largest effect on cantilever actuation. We demonstrate how the cantilever actuation can be used for imaging, and for measuring the local material softening temperature by sensing the contact resonance shift.

Reducing pressure oscillations in discrete fluid power systems

DEFF Research Database (Denmark)

Hansen, Anders Hedegaard; Pedersen, Henrik Clemmensen

2016-01-01

Discrete fluid power systems featuring transmission lines inherently include pressure oscillations. Experimental verification of a discrete fluid power power take off system for wave energy converters has shown the cylinder pressure to oscillate as force shifts are performed. This article investi...... investigates how cylinder pressure oscillations may be reduced by shaping the valve opening trajectory without the need for closed loop pressure feedback. Furthermore the energy costs of reducing pressure oscillations are investigated....

Principal oscillation patterns

International Nuclear Information System (INIS)

Storch, H. von; Buerger, G.; Storch, J.S. von

1993-01-01

The Principal Oscillation Pattern (POP) analysis is a technique which is used to simultaneously infer the characteristic patterns and time scales of a vector time series. The POPs may be seen as the normal modes of a linearized system whose system matrix is estimated from data. The concept of POP analysis is reviewed. Examples are used to illustrate the potential of the POP technique. The best defined POPs of tropospheric day-to-day variability coincide with the most unstable modes derived from linearized theory. POPs can be derived even from a space-time subset of data. POPs are successful in identifying two independent modes with similar time scales in the same data set. The POP method can also produce forecasts which may potentially be used as a reference for other forecast models. The conventional POP analysis technique has been generalized in various ways. In the cyclostationary POP analysis, the estimated system matrix is allowed to vary deterministically with an externally forced cycle. In the complex POP analysis not only the state of the system but also its ''momentum'' is modeled. Associated correlation patterns are a useful tool to describe the appearance of a signal previously identified by a POP analysis in other parameters. (orig.)

Effect of waveforms of inspired gas tension on the respiratory oscillations of carotid body discharge.

Science.gov (United States)

Kumar, P; Nye, P C; Torrance, R W

1991-07-01

The responses of carotid body chemoreceptor discharge to repeated ramps (20- to 60-s forcing cycle durations) of inspired gas tensions were studied in spontaneously breathing and in artificially ventilated pentobarbitone-anesthetized cats. In all animals the mean intensity of chemoreceptor discharge followed the frequency of the forcing cycle, and superimposed on this were oscillations at the frequency of ventilation (breath-by-breath oscillations). The amplitude of the breath-by-breath oscillations in discharge was often large, and it waxed and waned with the forcing cycle. It was greatest when the mean level of discharge was falling and smallest near the peak of mean discharge. No qualitative differences were observed between PO2-alone forcing in constant normocapnia and PCO2-alone forcing in constant hypoxia. The variation in the amplitudes of breath-by-breath oscillations was shown to be due primarily to variations in the amplitudes of the downslope component of the discharge oscillation. Variations in the upslope component of individual oscillations were small. The factors responsible for the breath-by-breath oscillations are discussed, and it is concluded that the shape of the waveform of arterial gas tensions that stimulate the peripheral chemoreceptors departs markedly from that of a line joining end-tidal gas tensions. This causes breath-by-breath oscillations of discharge to be very large after an "off" stimulus. Reflex studies involving the forcing of respiratory gases should therefore include consideration of these effects.

An Energy Balanced Double Oscillator Model for Vortex-Induced Vibrations

DEFF Research Database (Denmark)

Krenk, S.; Nielsen, Søren R. K.

A model consisting of two couple oscillators is developed for the representation of vortex-induced oscillations of structural elements. The mutual forcing terms are different from previous models and based on exact transfer of energy from the fluid to the structural oscillator. This leads...

The effect of the descent technique and truck cabin layout on the landing impact forces.

Science.gov (United States)

Patenaude, S; Marchand, D; Samperi, S; Bélanger, M

2001-12-01

The majority of injuries to truckers are caused by falls during the descent from the cab of the truck. Several studies have shown that the techniques used to descend from the truck and the layout of the truck's cabin are the principal cause of injury. The goal of the present study was to measure the effects of the descent techniques used by the trucker and the layout of the truck's cabin on the impact forces absorbed by the lower limbs and the back. Kinematic data, obtained with the aid of a video camera, were combined with the force platform data to allow for calculation of the lower limb and L5-S1 torques as well as L5-S1 compressive forces. The trucker descended from two different conventional tractor cabin layouts. Each trucker descended from cabin using either "facing the truck" (FT) or "back to the truck" (BT) techniques. The results demonstrate that the BT technique produces greater ground impact forces than the FT technique, particularly when the truck does not have a handrail. The BT technique also causes an increase in the compressive forces exerted on the back. In conclusion, the use of the FT technique along with the aids (i.e., handrails and all the steps) help lower the landing impact forces as well as the lumbosacral compressive forces.

Energy dissipation in multifrequency atomic force microscopy

Directory of Open Access Journals (Sweden)

Valentina Pukhova

2014-04-01

Full Text Available The instantaneous displacement, velocity and acceleration of a cantilever tip impacting onto a graphite surface are reconstructed. The total dissipated energy and the dissipated energy per cycle of each excited flexural mode during the tip interaction is retrieved. The tip dynamics evolution is studied by wavelet analysis techniques that have general relevance for multi-mode atomic force microscopy, in a regime where few cantilever oscillation cycles characterize the tip–sample interaction.

Cubication of conservative nonlinear oscillators

International Nuclear Information System (INIS)

Belendez, Augusto; Alvarez, Mariela L; Fernandez, Elena; Pascual, Inmaculada

2009-01-01

A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.

Improving tapping mode atomic force microscopy with piezoelectric cantilevers

International Nuclear Information System (INIS)

Rogers, B.; Manning, L.; Sulchek, T.; Adams, J.D.

2004-01-01

This article summarizes improvements to the speed, simplicity and versatility of tapping mode atomic force microscopy (AFM). Improvements are enabled by a piezoelectric microcantilever with a sharp silicon tip and a thin, low-stress zinc oxide (ZnO) film to both actuate and sense deflection. First, we demonstrate self-sensing tapping mode without laser detection. Similar previous work has been limited by unoptimized probe tips, cantilever thicknesses, and stress in the piezoelectric films. Tests indicate self-sensing amplitude resolution is as good or better than optical detection, with double the sensitivity, using the same type of cantilever. Second, we demonstrate self-oscillating tapping mode AFM. The cantilever's integrated piezoelectric film serves as the frequency-determining component of an oscillator circuit. The circuit oscillates the cantilever near its resonant frequency by applying positive feedback to the film. We present images and force-distance curves using both self-sensing and self-oscillating techniques. Finally, high-speed tapping mode imaging in liquid, where electric components of the cantilever require insulation, is demonstrated. Three cantilever coating schemes are tested. The insulated microactuator is used to simultaneously vibrate and actuate the cantilever over topographical features. Preliminary images in water and saline are presented, including one taken at 75.5 μm/s - a threefold improvement in bandwidth versus conventional piezotube actuators

Body-force-driven multiplicity and stability of combined free and forced convection in rotating curved ducts: Coriolis force

Science.gov (United States)

Yang, T.; Wang, L.

A numerical study is made on the fully developed bifurcation structure and stability of forced convection in a rotating curved duct of square cross-section. Solution structure is determined as variation of a parameter that indicates the effect of rotation (Coriolis-force-driven multiplicity). Three solutions for the flows in a stationary curved duct obtained in the work of Yang and Wang [1] are used as initial solutions of continuation calculations to unfold the solution branches. Twenty-one solution branches are found comparing with five obtained by Selmi and Nandakumar [2]. Dynamic responses of the multiple solutions to finite random disturbances are examined by the direct transient computation. Results show that characteristics of physically realizable fully developed flows changes significantly with variation of effect of rotation. Fourteen sub-ranges are identified according to characteristics of physically realizable solutions. As rotation effect changes, possible physically realizable fully-developed flows can be stable steady 2-cell state, stable multi-cell state, temporal periodic oscillation between symmetric/asymmetric 2-cell/4-cell flows, temporal oscillation with intermittency, temporal chaotic oscillation and temporal oscillation with pseudo intermittency. Among these possible physically realizable fully developed flows, stable multi-cell state and stable steady 2-cell state exist as dual stable. And oscillation with pseudo intermittency is a new phenomenon. In addition to the temporal oscillation with intermittency, sudden shift from stationary stable solution to temporal chaotic oscillation is identified to be another way of onset of chaos.

Vertical vibration and shape oscillation of acoustically levitated water drops

International Nuclear Information System (INIS)

Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

2014-01-01

We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

Vertical vibration and shape oscillation of acoustically levitated water drops

Energy Technology Data Exchange (ETDEWEB)

Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

2014-09-08

We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

Ground reaction forces produced by two different hockey skating arm swing techniques.

Science.gov (United States)

Hayward-Ellis, Julie; Alexander, Marion J L; Glazebrook, Cheryl M; Leiter, Jeff

2017-10-01

The arm swing in hockey skating can have a positive effect on the forces produced by each skate, and the resulting velocity from each push off. The main purpose of this study was to measure the differences in ground reaction forces (GRFs) produced from an anteroposterior versus a mediolateral style hockey skating arm swing. Twenty-four elite-level female hockey players performed each technique while standing on a ground-mounted force platform, and all trials were filmed using two video cameras. Force data was assessed for peak scaled GRFs in the frontal and sagittal planes, and resultant GRF magnitude and direction. Upper limb kinematics were assessed from the video using Dartfish video analysis software, confirming that the subjects successfully performed two distinct arm swing techniques. The mediolateral arm swing used a mean of 18.38° of glenohumeral flexion/extension and 183.68° of glenohumeral abduction/adduction while the anteroposterior technique used 214.17° and 28.97° respectively. The results of this study confirmed that the mediolateral arm swing produced 37% greater frontal plane and 33% less sagittal plane GRFs than the anteroposterior arm swing. The magnitudes of the resultant GRFs were not significantly different between the two techniques; however, the mediolateral technique produced a resultant GRF with a significantly larger angle from the direction of travel (44.44°) as compared to the anteroposterior technique (31.60°). The results of this study suggest that the direction of GRFs produced by the mediolateral arm swing more closely mimic the direction of lower limb propulsion during the skating stride.

Stability diagram for the forced Kuramoto model.

Science.gov (United States)

Childs, Lauren M; Strogatz, Steven H

2008-12-01

We analyze the periodically forced Kuramoto model. This system consists of an infinite population of phase oscillators with random intrinsic frequencies, global sinusoidal coupling, and external sinusoidal forcing. It represents an idealization of many phenomena in physics, chemistry, and biology in which mutual synchronization competes with forced synchronization. In other words, the oscillators in the population try to synchronize with one another while also trying to lock onto an external drive. Previous work on the forced Kuramoto model uncovered two main types of attractors, called forced entrainment and mutual entrainment, but the details of the bifurcations between them were unclear. Here we present a complete bifurcation analysis of the model for a special case in which the infinite-dimensional dynamics collapse to a two-dimensional system. Exact results are obtained for the locations of Hopf, saddle-node, and Takens-Bogdanov bifurcations. The resulting stability diagram bears a striking resemblance to that for the weakly nonlinear forced van der Pol oscillator.

Singular perturbation techniques in the gravitational self-force problem

International Nuclear Information System (INIS)

Pound, Adam

2010-01-01

Much of the progress in the gravitational self-force problem has involved the use of singular perturbation techniques. Yet the formalism underlying these techniques is not widely known. I remedy this situation by explicating the foundations and geometrical structure of singular perturbation theory in general relativity. Within that context, I sketch precise formulations of the methods used in the self-force problem: dual expansions (including matched asymptotic expansions), for which I identify precise matching conditions, one of which is a weak condition arising only when multiple coordinate systems are used; multiscale expansions, for which I provide a covariant formulation; and a self-consistent expansion with a fixed worldline, for which I provide a precise statement of the exact problem and its approximation. I then present a detailed analysis of matched asymptotic expansions as they have been utilized in calculating the self-force. Typically, the method has relied on a weak matching condition, which I show cannot determine a unique equation of motion. I formulate a refined condition that is sufficient to determine such an equation. However, I conclude that the method yields significantly weaker results than do alternative methods.

On the motion of non-linear oscillators with a fractional-order restoring force and time variable parameters

International Nuclear Information System (INIS)

Kovacic, Ivana

2009-01-01

An analytical approach to determine the approximate solution for the periodic motion of non-conservative oscillators with a fractional-order restoring force and slowly varying parameters is presented. The solution has the form of the first-order differential equation for the amplitude and phase of motion. The method used is based on the combination of the Krylov-Bogoliubov method with Hamilton's variational principle with the uncommutative rule for the variation of velocity. The conservative systems with slowly varying parameters are also considered. The corresponding adiabatic invariant is obtained. Two examples are given to illustrate derived theoretical results.

The influence of cricket fast bowlers' front leg technique on peak ground reaction forces.

Science.gov (United States)

Worthington, Peter; King, Mark; Ranson, Craig

2013-01-01

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries.

Taking a peek at Bloch oscillations

Science.gov (United States)

Morsch, Oliver

2016-11-01

Bloch oscillations arise when matter waves inside a periodic potential, such as a crystal lattice, are accelerated by a constant force. Keßler et al (2016 New J. Phys. 18 102001) have now experimentally tested a method that allows one to observe those oscillations continuously, without a destructive measurement on the matter wave. Their approach could help to make cold atom-based accelerometers and gravimeters more precise.

Higher-Order Approximations of Motion of a Nonlinear Oscillator Using the Parameter Expansion Technique

Science.gov (United States)

Ganji, S. S.; Domairry, G.; Davodi, A. G.; Babazadeh, H.; Seyedalizadeh Ganji, S. H.

The main objective of this paper is to apply the parameter expansion technique (a modified Lindstedt-Poincaré method) to calculate the first, second, and third-order approximations of motion of a nonlinear oscillator arising in rigid rod rocking back. The dynamics and frequency of motion of this nonlinear mechanical system are analyzed. A meticulous attention is carried out to the study of the introduced nonlinearity effects on the amplitudes of the oscillatory states and on the bifurcation structures. We examine the synchronization and the frequency of systems using both the strong and special method. Numerical simulations and computer's answers confirm and complement the results obtained by the analytical approach. The approach proposes a choice to overcome the difficulty of computing the periodic behavior of the oscillation problems in engineering. The solutions of this method are compared with the exact ones in order to validate the approach, and assess the accuracy of the solutions. In particular, APL-PM works well for the whole range of oscillation amplitudes and excellent agreement of the approximate frequency with the exact one has been demonstrated. The approximate period derived here is accurate and close to the exact solution. This method has a distinguished feature which makes it simple to use, and also it agrees with the exact solutions for various parameters.

Selective particle trapping using an oscillating microbubble.

Science.gov (United States)

Rogers, Priscilla; Neild, Adrian

2011-11-07

The ability to isolate and sort analytes within complex microfluidic volumes is essential to the success of lab-on-a-chip (LOC) devices. In this study, acoustically-excited oscillating bubbles are used to selectively trap particles, with the selectivity being a function of both particle size and density. The operating principle is based on the interplay between the strong microstreaming-induced drag force and the attractive secondary Bjerknes force. Depending upon the size of the bubble, and thus its resonant frequency, it is possible to cause one force to dominate over the other, resulting in either particle attraction or repulsion. A theoretical analysis reveals the extent of the contribution of each force for a given particle size; in close agreement with experimental findings. Density-based trapping is also demonstrated, highlighting that denser particles experience a larger secondary Bjerknes force resulting in their attraction. This study showcases the excellent applicability and versatility of using oscillating bubbles as a trapping and sorting mechanism within LOC devices. This journal is © The Royal Society of Chemistry 2011

Stable And Oscillating Acoustic Levitation

Science.gov (United States)

Barmatz, Martin B.; Garrett, Steven L.

1988-01-01

Sample stability or instability determined by levitating frequency. Degree of oscillation of acoustically levitated object along axis of levitation chamber controlled by varying frequency of acoustic driver for axis above or below frequency of corresponding chamber resonance. Stabilization/oscillation technique applied in normal Earth gravity, or in absence of gravity to bring object quickly to rest at nominal levitation position or make object oscillate in desired range about that position.

The chimera state in colloidal phase oscillators with hydrodynamic interaction

Science.gov (United States)

Hamilton, Evelyn; Bruot, Nicolas; Cicuta, Pietro

2017-12-01

The chimera state is the incongruous situation where coherent and incoherent populations coexist in sets of identical oscillators. Using driven non-linear oscillators interacting purely through hydrodynamic forces at low Reynolds number, previously studied as a simple model of motile cilia supporting waves, we find concurrent incoherent and synchronised subsets in small arrays. The chimeras seen in simulation display a "breathing" aspect, reminiscent of uniformly interacting phase oscillators. In contrast to other systems where chimera has been observed, this system has a well-defined interaction metric, and we know that the emergent dynamics inherit the symmetry of the underlying Oseen tensor eigenmodes. The chimera state can thus be connected to a superposition of eigenstates, whilst considering the mean interaction strength within and across subsystems allows us to make a connection to more generic (and abstract) chimeras in populations of Kuramoto phase oscillators. From this work, we expect the chimera state to emerge in experimental observations of oscillators coupled through hydrodynamic forces.

Force scanning: a rapid, high-resolution approach for spatial mechanical property mapping

International Nuclear Information System (INIS)

Darling, E M

2011-01-01

Atomic force microscopy (AFM) can be used to co-localize mechanical properties and topographical features through property mapping techniques. The most common approach for testing biological materials at the microscale and nanoscale is force mapping, which involves taking individual force curves at discrete sites across a region of interest. The limitations of force mapping include long testing times and low resolution. While newer AFM methodologies, like modulated scanning and torsional oscillation, circumvent this problem, their adoption for biological materials has been limited. This could be due to their need for specialized software algorithms and/or hardware. The objective of this study is to develop a novel force scanning technique using AFM to rapidly capture high-resolution topographical images of soft biological materials while simultaneously quantifying their mechanical properties. Force scanning is a straightforward methodology applicable to a wide range of materials and testing environments, requiring no special modification to standard AFMs. Essentially, if a contact-mode image can be acquired, then force scanning can be used to produce a spatial modulus map. The current study first validates this technique using agarose gels, comparing results to ones achieved by the standard force mapping approach. Biologically relevant demonstrations are then presented for high-resolution modulus mapping of individual cells, cell-cell interfaces, and articular cartilage tissue.

Assessment of Effective Prestressed Force of Nuclear Containment Building using SI Technique

Energy Technology Data Exchange (ETDEWEB)

Lee, H. P.; Jang, J. B.; Hwang, K. M.; Song, Y. C. [Korea Electric Power Research Institute, Daejeon (Korea, Republic of)

2010-10-15

Bonded tendons have been used in reactor buildings of heavy water reactors and the light water reactors of some nuclear power plants operating in Korea. The assessment of prestressed forces on those bonded tendons is becoming an important issue in assuring their continuous operation beyond their design life. In order to assess the effective prestressed force on the bonded tendon, indirect assessment techniques have been applying to the test beams which were manufactured on construction time. Therefore, this research mainly forced to establish the assessment methodology to measure directly the effective prestressed force on the bonded tendon of containment buildings using System Identification (SI) technique. To accomplish this purpose, simple SI method was proposed and adapted three dimensional finite element analysis of the 1:4 scale prestressed concrete containment vessel (PCCV) tested by Sandia National Laboratory in 2000

All-Atom Polarizable Force Field for DNA Based on the Classical Drude Oscillator Model

Science.gov (United States)

Savelyev, Alexey; MacKerell, Alexander D.

2014-01-01

Presented is a first generation atomistic force field for DNA in which electronic polarization is modeled based on the classical Drude oscillator formalism. The DNA model is based on parameters for small molecules representative of nucleic acids, including alkanes, ethers, dimethylphosphate, and the nucleic acid bases and empirical adjustment of key dihedral parameters associated with the phosphodiester backbone, glycosidic linkages and sugar moiety of DNA. Our optimization strategy is based on achieving a compromise between satisfying the properties of the underlying model compounds in the gas phase targeting QM data and reproducing a number of experimental properties of DNA duplexes in the condensed phase. The resulting Drude force field yields stable DNA duplexes on the 100 ns time scale and satisfactorily reproduces (1) the equilibrium between A and B forms of DNA and (2) transitions between the BI and BII sub-states of B form DNA. Consistency with the gas phase QM data for the model compounds is significantly better for the Drude model as compared to the CHARMM36 additive force field, which is suggested to be due to the improved response of the model to changes in the environment associated with the explicit inclusion of polarizability. Analysis of dipole moments associated with the nucleic acid bases shows the Drude model to have significantly larger values than those present in CHARMM36, with the dipoles of individual bases undergoing significant variations during the MD simulations. Additionally, the dipole moment of water was observed to be perturbed in the grooves of DNA. PMID:24752978

Periodic Forcing of a 555-IC Based Electronic Oscillator in the Strong Coupling Limit

Science.gov (United States)

Santillán, Moisés

We designed and developed a master-slave electronic oscillatory system (based on the 555-timer IC working in the astable mode), and investigated its dynamic behavior regarding synchronization. For that purpose, we measured the rotation numbers corresponding to the phase-locking rhythms achieved in a large set of values of the normalized forcing frequency (NFF) and of the coupling strength between the master and the slave oscillators. In particular, we were interested in the system behavior in the strong-coupling limit, because such problem has not been extensively studied from an experimental perspective. Our results indicate that, in such a limit, a degenerate codimension-2 bifurcation point at NFF = 2 exists, in which all the phase-locking regions converge. These findings were corroborated by means of a mathematical model developed to that end, as well as by ad hoc further experiments.

Critical heat flux of forced convection boiling in an oscilating acceleration field. Pt. 1

International Nuclear Information System (INIS)

Otsuji, T.; Kurosawa, A.

1982-01-01

The influence of periodically varying acceleration on critical heat flux (CHF) of Freon-113 flowing upward in a uniformly heated vertical annular channel has been studied experimentally. The freon loop was oscillated vertically to determine the ratio of CHF in the oscillating acceleration field to the corresponding stationary value. The amplitude of inlet flow oscillation induced by variation of acceleration, which causes early CHF, is proportional to the acceleration amplitude. The dependence of inlet flow rate on the oscillating acceleration decreases with increasing inlet subcooling, and no oscillation of inlet flow is observed in the case of negative exit quality (subcooled boiling). Nevertheless the degradation of CHF is more remarkable in the low quality region. This result suggests the necessity to introduce an other mechanism of early CHF than flow oscillation. (orig.)

Quantum enhanced feedback cooling of a mechanical oscillator using nonclassical light.

Science.gov (United States)

Schäfermeier, Clemens; Kerdoncuff, Hugo; Hoff, Ulrich B; Fu, Hao; Huck, Alexander; Bilek, Jan; Harris, Glen I; Bowen, Warwick P; Gehring, Tobias; Andersen, Ulrik L

2016-11-29

Laser cooling is a fundamental technique used in primary atomic frequency standards, quantum computers, quantum condensed matter physics and tests of fundamental physics, among other areas. It has been known since the early 1990s that laser cooling can, in principle, be improved by using squeezed light as an electromagnetic reservoir; while quantum feedback control using a squeezed light probe is also predicted to allow improved cooling. Here we show the implementation of quantum feedback control of a micro-mechanical oscillator using squeezed probe light. This allows quantum-enhanced feedback cooling with a measurement rate greater than it is possible with classical light, and a consequent reduction in the final oscillator temperature. Our results have significance for future applications in areas ranging from quantum information networks, to quantum-enhanced force and displacement measurements and fundamental tests of macroscopic quantum mechanics.

Nonlinear oscillations

CERN Document Server

Nayfeh, Ali Hasan

1995-01-01

Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim

Nonlinear analysis of ring oscillator circuits

KAUST Repository

Ge, Xiaoqing

2010-06-01

Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

Nonlinear analysis of ring oscillator circuits

KAUST Repository

Ge, Xiaoqing; Arcak, Murat; Salama, Khaled N.

2010-01-01

Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

SPECIALTY OF ROTOR’S DRIVE MECHANISM OSCILLATIONS

Directory of Open Access Journals (Sweden)

V. S. Loveikin

2016-02-01

Full Text Available Purpose. Scientific work is devoted to study the influence of dynamic coefficients of bearings segment (coefficients of resistance and recirculating power on stability and subharmonics self-oscillating components of the rotor vibration in unstable region of rotational speeds. Methodology. The study is based on the methods: the theory of vibrations of mechanical systems with lumped parameters; Lagrange functions; linear algebra. Findings. The researchers made: a justification of the discrete two-mass model of an unbalanced rotor, which takes into account the influence of rotation on dynamic coefficients; b analysis and improvement of methods for engineering analysis of stability and parameter subharmonic self-oscillations in the unstable range of frequencies of rotation of the rotor; c installation and classification of the main rotor causes of vibrations constructive or those arising in the manufacture, assembly and operation of the machine, and on the other hand, rotary systems specific for non-conservative forces, that lead under certain conditions to the self-oscillation; d determination (identification the characteristics/differences of rotor vibration, which lies in the fact that in most cases they are associated with the transverse vibrations of the rotors, while torsional or longitudinal oscillations play the incomparably smaller role, and therefore the last in this study were rejected; eit is shown that the characteristic feature of the functioning of rotor systems of modern machines and units have no direct relationship with the level of vibration with amount of power that is transmitted through them or produced engine. Originality. In this paper the authors first considered the nonlinear response bearing lubrication layer, namely the coefficients of resistance and circulating forces that determine the dynamic coefficient of segment bearings. Practical value. The engineering calculations subharmonic stability and self-oscillations of

Oscillations of spherical fullerenes interacting with graphene sheet

Energy Technology Data Exchange (ETDEWEB)

Ghavanloo, Esmaeal, E-mail: ghavanloo@shirazu.ac.ir; Fazelzadeh, S. Ahmad

2017-01-01

In the present study, the oscillations of spherical fullerenes in the vicinity of a fully constrained graphene sheet are investigated. Using the continuous approximation and Lennard-Jones potential, the van der Waals (vdW) potential energy and interaction forces are obtained. The equation of motion is derived and directly solved based on the actual force distribution between the fullerene molecules and the graphene sheet. Numerical results are obtained and shown that the oscillation is sensitive to the size of the fullerene as well as the distance between the center of the fullerene and the graphene sheet.

Chaos of the Relativistic Forced van der Pol Oscillator

International Nuclear Information System (INIS)

Ashkenazya, Y.; Gorma, C; Horwitz, L. P.

1998-01-01

A manifestly relativistically covariant form of the van der Pol oscillator in 1 + 1 dimensions is studied. We show that the driven relativistic equations, for which z and t are coupled, relax very quickly to a pair of identical decoupled equations, due to a rapid vanishing of the angular momentum (the boost in 1 + 1 dimensions). A similar effect occurs in the damped driven covariant Duffing oscillator previously treated. This effect is an example of entrainment, or synchronization (phase locking) , of coupled chaotic systems. The Lyapunov exponents are calculated using the very efficient method of Habib and Ryne. We show a Poincare map that demonstrates this effect and maintains remarkable stability in spite of the inevitable accumulation of computer error in the chaotic region. For our choice of parameters, the positive Lyapunov exponent is about 0.242 almost independently of the integration method

A Wearable Gait Phase Detection System Based on Force Myography Techniques

Directory of Open Access Journals (Sweden)

Xianta Jiang

2018-04-01

Full Text Available (1 Background: Quantitative evaluation of gait parameters can provide useful information for constructing individuals’ gait profile, diagnosing gait abnormalities, and better planning of rehabilitation schemes to restore normal gait pattern. Objective determination of gait phases in a gait cycle is a key requirement in gait analysis applications; (2 Methods: In this study, the feasibility of using a force myography-based technique for a wearable gait phase detection system is explored. In this regard, a force myography band is developed and tested with nine participants walking on a treadmill. The collected force myography data are first examined sample-by-sample and classified into four phases using Linear Discriminant Analysis. The gait phase events are then detected from these classified samples using a set of supervisory rules; (3 Results: The results show that the force myography band can correctly detect more than 99.9% of gait phases with zero insertions and only four deletions over 12,965 gait phase segments. The average temporal error of gait phase detection is 55.2 ms, which translates into 2.1% error with respect to the corresponding labelled stride duration; (4 Conclusions: This proof-of-concept study demonstrates the feasibility of force myography techniques as viable solutions in developing wearable gait phase detection systems.

Control of Oscillating Foil for Propulsion of Biorobotic Autonomous Underwater Vehicle (AUV

Directory of Open Access Journals (Sweden)

S. N. Singh

2005-01-01

Full Text Available The paper treats the question of control of a laterally and rotationally oscillating hydrofoil for the propulsion of biologically inspired robotic (biorobotic autonomous underwater vehicles (BAUVs. Sinusoidal oscillations of foils produce maneuvering and propulsive forces. The design is based on the internal model principle. Two springs are used to transmit forces from the actuators to the foil. Oscillating fins produce periodic forces, which can be used for fish-like propulsion and control of autonomous underwater vehicles (AUVs. The equations of motion of the foil include hydrodynamic lift and moment based on linear, unsteady, aerodynamic theory. A control law is derived for the lateral and rotational sinusoidal oscillation of the foil. In the closed-loop system, the lateral displacement and the rotational angle of the foil asymptotically follow sinusoidal trajectories of distinct frequencies and amplitudes independently. Simulation results are presented to show the trajectory tracking performance of the foil for different freestream velocities and sinusoidal command trajectories.

Electrogravitational stability of oscillating streaming fluid cylinder

International Nuclear Information System (INIS)

Hasan, Alfaisal A.

2011-01-01

The electrogravitational instability of on oscillating streaming fluid cylinder under the action of the selfgravitating, capillary and electrodynamic forces has been discussed. The model is governed by the Mathieu second order integro-differential equation. Some limiting cases are recovering from the present general one. The capillary force is destabilizing in a small axisymmetric domain 0< x<1 and stabilizing otherwise. In the absence of electric fields, we found that the model is unstable in a small domain while it is selfgravitating stable in all other domains. The presence of the electric field led to the presence of a great number of stable waves. The electric field has a strong stabilizing influence on the selfgravitating instability of the model. The capillary force has a strong destabilizing influence on the selfgravitating instability of the model. Generally, the uniform stream supports the unstable waves, while the oscillating streaming has stability tendency.

Thermonuclear burst oscillations: where firestorms meet fundamental physics.

CERN Multimedia

CERN. Geneva

2017-01-01

Neutron stars offer a unique environment in which to develop and test theories of the strong force. Densities in neutron star cores can reach up to ten times the density of a normal atomic nucleus, and the stabilising effect of gravitational confinement permits long-timescale weak interactions. This generates matter that is neutron-rich, and opens up the possibility of stable states of strange matter, something that can only exist in neutron stars. Strong force physics is encoded in the Equation of State (EOS), the pressure-density relation, which links to macroscopic observables such as mass M and radius R via the stellar structure equations. By measuring and inverting the M-R relation we can recover the EOS and diagnose the underlying dense matter physics. One very promising technique for simultaneous measurement of M and R exploits hotspots (burst oscillations) that form on the neutron star surface when material accreted from a companion star undergoes a thermonuclear explosion (a Type I X-ray burst). As ...

A simulation technique for 3D MR-guided acoustic radiation force imaging

International Nuclear Information System (INIS)

Payne, Allison; Bever, Josh de; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.

2015-01-01

Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison

Dissipative and electrostatic force spectroscopy of indium arsenide quantum dots by non-contact atomic force microscopy

Science.gov (United States)

Stomp, Romain-Pierre

This thesis is devoted to the studies of self-assembled InAs quantum dots (QD) by low-temperature Atomic Force Microscopy (AFM) in frequency modulation mode. Several spectroscopic methods are developed to investigate single electron charging from a two-dimensional electron gas (2DEG) to an individual InAs QD. Furthermore, a new technique to measure the absolute tip-sample capacitance is also demonstrated. The main observables are the electrostatic force between the metal-coated AFM tip and sample as well as the sample-induced energy dissipation, and therefore no tunneling current has to be collected at the AFM tip. Measurements were performed by recording simultaneously the shift in the resonant frequency and the Q-factor degradation of the oscillating cantilever either as a function of tip-sample voltage or distance. The signature of single electron charging was detected as an abrupt change in the frequency shift as well as corresponding peaks in the dissipation. The main experimental features in the force agree well with the semi-classical theory of Coulomb blockade by considering the free energy of the system. The observed dissipation peaks can be understood as a back-action effect on the oscillating cantilever beam due to the fluctuation in time of electrons tunneling back and forth between the 2DEG and the QD. It was also possible to extract the absolute value of the tip-sample capacitance, as a consequence of the spectroscopic analysis of the electrostic force as a function of tip-sample distance for different values of the applied voltage. At the same time, the contact potential difference and the residual non-capacitive force could also be determined as a function of tip-sample distance.

Towards nano-physiology of insects with atomic force microscopy.

Science.gov (United States)

Dokukin, M E; Guz, N V; Sokolov, I

2011-02-01

Little study of insects with modern nanotechnology tools has been done so far. Here we use one of such tool, atomic force microscopy (AFM) to study surface oscillations of the ladybird beetles (Hippodamia convergens) measured in different parts of the insect at picometer level. This allows us to record a much broader spectral range of possible surface vibrations (up to several kHz) than the previously studied oscillations due to breathing, heartbeat cycles, coelopulses, etc. (up to 5-10Hz). Here we demonstrate three different ways with which one can identify the origins of the observed peaks - by physical positioning the probe near a specific organ, and by using biological or chemical stimuli. We report on identification of high frequency peaks associated with H. convergens heart, spiracular closer muscles, and oscillations associated with muscles activated while drinking. The method, being a relatively non-invasive technique providing a new type of information, may be useful in developing "nanophysiology" of insects. Copyright © 2010 Elsevier Ltd. All rights reserved.

Reducing Fatigue Loading Due to Pressure Shift in Discrete Fluid Power Force Systems

DEFF Research Database (Denmark)

Hansen, Anders Hedegaard; Pedersen, Henrik Clemmensen

2016-01-01

power force system. The current paper investigates the correlation between pressure oscillations in the cylinder chambers and valve flow in the manifold. Furthermore, the correlation between the pressure shifting time and the pressure overshoot is investigated. The study therefore focus on how to shape......Discrete Fluid Power Force Systems is one of the topologies gaining focus in the pursuit of lowering energy losses in fluid power transmission systems. The cylinder based Fluid Power Force System considered in this article is constructed with a multi-chamber cylinder, a number of constant pressure...... oscillations in the cylinder chamber, especially for systems with long connections between the cylinder and the valve manifold. Hose pressure oscillations will induce oscillations in the produced piston force. Hence, pressure oscillations may increase the fatigue loading on systems employing a discrete fluid...

Optimum design of A fluidic micro-oscillator

International Nuclear Information System (INIS)

Noh, Yoojeong; Youn, Sungkie; Kim, Moonuhn

2002-01-01

A fluidic micro-oscillator is used to control a linear tool as generating an oscillating fluid jet at its two output ports. The linear tool is a linear actuator that transforms the fluidic energy into mechanical energy via a double acting piston placed in linear actuator housing. Together the two devices form a dynamic microsystem that can be used in medical application. In this paper, we intend to optimize the geometry of the fluidic micro-oscillator. A basic oscillator design is varied in terms of supply nozzle geometry, length of the feedback channels, wall angle, control port width and etc. It was found that characteristics parameters such as frequency, volume flow and output pressure depends strongly on above mentioned design parameters. According to above the observations, we can determine an object function and design variables. Since we eventually have to maximize force to drive and steer a cutting tool, the output pressure difference is chosen as an object function and nozzle width, feedback channel, control port width, distance between splitter and nozzle can be chosen as the design variables. As a result of such design optimization, we can obtain the maximum force. At this time we maximize the output pressure difference using shape optimization

Effect of various periodic forces on Duffing oscillator

Indian Academy of Sciences (India)

ω respectively. However, the Fourier series of all the forces except the force sin ωt considered in our study have various frequencies. The frequencies present in the forces and in the periodic solution confined to the left well alone corresponding to the amplitude f = 0.2 are studied by constructing the Fourier series. 352.

Axion forces, gravity experiments and T violation

International Nuclear Information System (INIS)

Moody, J.E.

1984-01-01

A variety of light, weakly-coupled bosons have recently been suggested. Among them is the axion. This thesis considers the possibility of detecting axions or other light bosons via the macroscopic forces they mediate. The motivation for the axion is reviewed along with a detailed calculation of its mass and couplings. The microphysical basis of macroscopic forces is described and the three distinct axion force laws are thereby obtained. Of particular interest is the unique P and T violating monopole-dipole force. The magnitudes and ranges of axion forces are compared with the existing experimental limits. The possibilities for searching for (monopole) 2 , spin-spin and monopole-dipole forces are evaluated. Monopole-dipole experiments seem promising because the sensitive high-Q techniques of gravity wave research are applicable. Ultimate sensitivity, as limited by thermal noise, is evaluated for crystal oscillators and levitated systems. The very interesting problem of quantum uncertainty in weak force measurement is considered along with a way of getting around it called back action evasion. This is followed by a presentation of signal to noise analysis which folds together amplifier noise, quantum uncertainty, and Langevin noise

Acoustic forcing of a liquid drop

Science.gov (United States)

Lyell, M. J.

1992-01-01

The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

Cervical spine mobilisation forces applied by physiotherapy students.

Science.gov (United States)

Snodgrass, Suzanne J; Rivett, Darren A; Robertson, Val J; Stojanovski, Elizabeth

2010-06-01

Postero-anterior (PA) mobilisation is commonly used in cervical spine treatment and included in physiotherapy curricula. The manual forces that students apply while learning cervical mobilisation are not known. Quantifying these forces informs the development of strategies for learning to apply cervical mobilisation effectively and safely. This study describes the mechanical properties of cervical PA mobilisation techniques applied by students, and investigates factors associated with force application. Physiotherapy students (n=120) mobilised one of 32 asymptomatic subjects. Students applied Grades I to IV central and unilateral PA mobilisation to C2 and C7 of one asymptomatic subject. Manual forces were measured in three directions using an instrumented treatment table. Spinal stiffness of mobilised subjects was measured at C2 and C7 using a device that applied a standard oscillating force while measuring this force and its concurrent displacement. Analysis of variance was used to determine differences between techniques and grades, intraclass correlation coefficients (ICC) were used to calculate the inter- and intrastudent repeatability of forces, and linear regression was used to determine the associations between applied forces and characteristics of students and mobilised subjects. Mobilisation forces increased from Grades I to IV (highest mean peak force, Grade IV C7 central PA technique: 63.7N). Interstudent reliability was poor [ICC(2,1)=0.23, 95% confidence interval (CI) 0.14 to 0.43], but intrastudent repeatability of forces was somewhat better (0.83, 95% CI 0.81 to 0.86). Higher applied force was associated with greater C7 stiffness, increased frequency of thumb pain, male gender of the student or mobilised subject, and a student being earlier in their learning process. Lower forces were associated with greater C2 stiffness. This study describes the cervical mobilisation forces applied by students, and the characteristics of the student and mobilised

Polarizable Force Field for DNA Based on the Classical Drude Oscillator: I. Refinement Using Quantum Mechanical Base Stacking and Conformational Energetics.

Science.gov (United States)

Lemkul, Justin A; MacKerell, Alexander D

2017-05-09

Empirical force fields seek to relate the configuration of a set of atoms to its energy, thus yielding the forces governing its dynamics, using classical physics rather than more expensive quantum mechanical calculations that are computationally intractable for large systems. Most force fields used to simulate biomolecular systems use fixed atomic partial charges, neglecting the influence of electronic polarization, instead making use of a mean-field approximation that may not be transferable across environments. Recent hardware and software developments make polarizable simulations feasible, and to this end, polarizable force fields represent the next generation of molecular dynamics simulation technology. In this work, we describe the refinement of a polarizable force field for DNA based on the classical Drude oscillator model by targeting quantum mechanical interaction energies and conformational energy profiles of model compounds necessary to build a complete DNA force field. The parametrization strategy employed in the present work seeks to correct weak base stacking in A- and B-DNA and the unwinding of Z-DNA observed in the previous version of the force field, called Drude-2013. Refinement of base nonbonded terms and reparametrization of dihedral terms in the glycosidic linkage, deoxyribofuranose rings, and important backbone torsions resulted in improved agreement with quantum mechanical potential energy surfaces. Notably, we expand on previous efforts by explicitly including Z-DNA conformational energetics in the refinement.

Integrability and symmetries for the Helmholtz oscillator with friction

International Nuclear Information System (INIS)

Almendral, Juan A; Sanjuan, Miguel A F

2003-01-01

This paper deals with the Helmholtz oscillator, which is a simple nonlinear oscillator whose equation presents a quadratic nonlinearity and the possibility of escape. When a periodic external force is introduced, the width of the stochastic layer, which is a region around the separatrix where orbits may exhibit transient chaos, is calculated. In the absence of friction and external force, it is well known that analytical solutions exist since it is completely integrable. When only friction is included, there is no analytical solution for all parameter values. However, by means of the Lie theory for differential equations we find a relation between parameters for which the oscillator is integrable. This is related to the fact that the system possesses a symmetry group and the corresponding symmetries are computed. Finally, the analytical explicit solutions are shown and related to the basins of attraction

Remark on the role of the driving force in BWR instability

International Nuclear Information System (INIS)

Dykin, V.; Pazsit, I.

2009-01-01

Simple models of BWR instability, used e.g. in understanding the role of the various oscillation modes in the overall stability of the plant, assume that each oscillation mode can be described by a second order system (a damped harmonic oscillator) driven by a white noise driving force. Change of the decay ratio (DR) of the observed signal is, as a rule, associated with the changing of the parameters of the damped oscillator, mainly its damping coefficient, and is interpreted in terms of the change of the stability of the system. However, conceptually, one cannot exclude cases when the change of the response of a driven damped oscillator is due to the change of the properties of the driving force. In this work we investigate the effect of a non-white driving force on the behaviour of the system. A question of interest is how changes of the spectrum of the driving force influence the observed autocorrelation function (ACF) of the resulting signal. Hence we calculate the response of a damped harmonic oscillator driven by a non-white driving force, corresponding to the reactivity effect of propagating density fluctuations in two-phase flow. It is shown how in some special cases such a driving force, when interpreting the neutron noise as if induced by a white noise driving source, can lead to an erroneous conclusion regarding the stability of the system. It is also concluded that in the practically interesting cases the effect of the coloured driving force, arising from propagating density fluctuations, is negligible.

Experimental identification of the behaviour of and lateral forces from freely-walking pedestrians on laterally oscillating structures in a virtual reality environment.

Science.gov (United States)

Bocian, Mateusz; Macdonald, John H G; Burn, Jeremy F; Redmill, David

2015-12-15

Modelling pedestrian loading on lively structures such as bridges remains a challenge. This is because pedestrians have the capacity to interact with vibrating structures which can lead to amplification of the structural response. Current design guidelines are often inaccurate and limiting as they do not sufficiently acknowledge this effect. This originates in scarcity of data on pedestrian behaviour on vibrating ground and uncertainty as to the accuracy of results from previous experimental campaigns aiming to quantify pedestrian behaviour in this case. To this end, this paper presents a novel experimental setup developed to evaluate pedestrian actions on laterally oscillating ground in the laboratory environment while avoiding the implications of artificiality and allowing for unconstrained gait. A biologically-inspired approach was adopted in its development, relying on appreciation of operational complexities of biological systems, in particular their adaptability and control requirements. In determination of pedestrian forces to the structure consideration was given to signal processing issues which have been neglected in past studies. The results from tests conducted on the setup are related to results from previous experimental investigations and outputs of the inverted pendulum pedestrian model for walking on laterally oscillating ground, which is capable of generating self-excited forces.

A technique for monitoring fast tuner piezoactuator preload forces for superconducting rf cavities

International Nuclear Information System (INIS)

Pischalnikov, Y.; Branlard, J.; Carcagno, R.; Chase, B.; Edwards, H.; Orris, D.; Makulski, A.; McGee, M.; Nehring, R.; Poloubotko, V.; Sylvester, C.; Fermilab

2007-01-01

The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities [1]. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant static force (preload) on the piezo actuator in the range of 10 to 50% of its specified blocking force. Determining the preload force during cool-down, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. The design and testing of piezo actuator preload sensor technology is discussed. Results from measurements of preload sensors installed on the tuner of the Capture Cavity II (CCII)[2] tested at FNAL are presented. These results include measurements during cool-down, warmup, and cavity tuning along with dynamic Lorentz force compensation

A technique for monitoring fast tuner piezoactuator preload forces for superconducting rf cavities

Energy Technology Data Exchange (ETDEWEB)

Pischalnikov, Y.; Branlard, J.; Carcagno, R.; Chase, B.; Edwards, H.; Orris, D.; Makulski, A.; McGee, M.; Nehring, R.; Poloubotko, V.; Sylvester, C.; /Fermilab

2007-06-01

The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities [1]. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant static force (preload) on the piezo actuator in the range of 10 to 50% of its specified blocking force. Determining the preload force during cool-down, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. The design and testing of piezo actuator preload sensor technology is discussed. Results from measurements of preload sensors installed on the tuner of the Capture Cavity II (CCII)[2] tested at FNAL are presented. These results include measurements during cool-down, warmup, and cavity tuning along with dynamic Lorentz force compensation.

Calculation of a steam generating tube stressed state under temperature oscillations in burnout zone

International Nuclear Information System (INIS)

Vorob'ev, V.A.; Loshchinin, V.M.; Remizov, O.V.

1982-01-01

The technique for evaluating the steam generating tube stressed state under the wall temperature oscillations in the burnout zone is described. The technique is based on analytical solutions for transfer functions connecting the amplitude of surface temperature oscillation with the amplitude and frequency of heat transfer coefficient oscillation and amplitude of thermoelastic stress oscillation with that of temperature oscillation. The results of calculations according to considered technique are compared with that of the problem numerical solution. The conclusion is made that the technique under consideration may be applied for evaluation of steam generator evaporating tube lifetime [ru

Theory of a quantum anharmonic oscillator

International Nuclear Information System (INIS)

Carusotto, S.

1988-01-01

The time evolution of a quantum single-quartic anharmonic oscillator is considered. The study is carried on in operational form by use of the raising and lowering operators of the oscillator. The equation of motion is solved by application of a new integration method based on iteration techniques, and the rigorous solutions that describe the time development of the displacement and momentum operators of the oscillator are obtained. These operators are presented as a Laplace transform and a subsequent inverse Laplace transform of suitable functionals. Finally, the results are employed to describe the time evolution of a quasiclassical anharmonic oscillator

Mapping Electrostatic Forces Using Higher Harmonics Tapping Mode Atomic Force Microscopy in Liquid

NARCIS (Netherlands)

van Noort, S.J.T.; Willemsen, O.H.; van der Werf, Kees; de Grooth, B.G.; Greve, Jan

1999-01-01

A simple model of a damped, harmonic oscillator is used to describe the motion of an atomic force microscope cantilever tapping in fluid. By use of experimentally obtained parameters, excellent agreement is found between theory and experimental results. From the model we estimate that the force

VARIABILITY OF FORCED OSCILLATION (SIEMENS SIREGNOST FD-5) MEASUREMENTS OF TOTAL RESPIRATORY RESISTANCE IN PATIENTS AND HEALTHY-SUBJECTS

NARCIS (Netherlands)

GIMENO, F; VANDERWEELE, LT; KOETER, GH; DEMONCHY, JGR; VANALTENA, R

The reproducibility of total respiratory resistance (R(rs)) measured with a simplified forced oscillatory method (Siemens Siregnost FD 5) was measured and compared with that of slow inspiratory vital capacity (IVC) and forced expiratory volume in one second (FEV1). The former technique has the

Rate control and quality assurance during rhythmic force tracking.

Science.gov (United States)

Huang, Cheng-Ya; Su, Jyong-Huei; Hwang, Ing-Shiou

2014-02-01

Movement characteristics can be coded in the single neurons or in the summed activity of neural populations. However, whether neural oscillations are conditional to the frequency demand and task quality of rhythmic force regulation is still unclear. This study was undertaken to investigate EEG dynamics and behavior correlates during force-tracking at different target rates. Fourteen healthy volunteers conducted load-varying isometric abduction of the index finger by coupling the force output to sinusoidal targets at 0.5 Hz, 1.0 Hz, and 2.0 Hz. Our results showed that frequency demand significantly affected EEG delta oscillation (1-4 Hz) in the C3, CP3, CPz, and CP4 electrodes, with the greatest delta power and lowest delta peak around 1.5 Hz for slower tracking at 0.5 Hz. Those who had superior tracking congruency also manifested enhanced alpha oscillation (8-12 Hz). Alpha rhythms of the skilled performers during slow tracking spread through the whole target cycle, except for the phase of direction changes. However, the alpha rhythms centered at the mid phase of a target cycle with increasing target rate. In conclusion, our findings clearly suggest two advanced roles of cortical oscillation in rhythmic force regulation. Rate-dependent delta oscillation involves a paradigm shift in force control under different time scales. Phasic organization of alpha rhythms during rhythmic force tracking is related to behavioral success underlying the selective use of bimodal controls (feedback and feedforward processes) and the timing of attentional focus on the target's peak velocity. Copyright © 2013 Elsevier B.V. All rights reserved.

Counting Unfolding Events in Stretched Helices with Induced Oscillation by Optical Tweezers

Science.gov (United States)

Bacabac, Rommel Gaud; Otadoy, Roland

Correlation measures based on embedded probe fluctuations, single or paired, are now widely used for characterizing the viscoelastic properties of biological samples. However, more robust applications using this technique are still lacking. Considering that the study of living matter routinely demonstrates new and complex phenomena, mathematical and experimental tools for analysis have to catch up in order to arrive at newer insights. Therefore, we derive ways of probing non-equilibrium events in helical biopolymers provided by stretching beyond thermal forces. We generalize, for the first time, calculations for winding turn probabilities to account for unfolding events in single fibrous biopolymers and globular proteins under tensile stretching using twin optical traps. The approach is based on approximating the ensuing probe fluctuations as originating from a damped harmonic oscillator under oscillatory forcing.

Phase-locking phenomena and excitation of damped and driven nonlinear oscillators

DEFF Research Database (Denmark)

Shagalov, A.G.; Juul Rasmussen, Jens; Naulin, Volker

2009-01-01

Resonant phase-locking phenomena ('autoresonance') in the van der Pol Duffing oscillator forced by a small amplitude periodic driving with slowly varying frequency have been studied. We show that autoresonance occurs for oscillators with sufficiently small damping, when the system may have bi-stable...

Nonlinear dynamics of a magnetically driven Duffing-type spring–magnet oscillator in the static magnetic field of a coil

International Nuclear Information System (INIS)

Donoso, Guillermo; Ladera, Celso L

2012-01-01

We study the nonlinear oscillations of a forced and weakly dissipative spring–magnet system moving in the magnetic fields of two fixed coaxial, hollow induction coils. As the first coil is excited with a dc current, both a linear and a cubic magnet-position dependent force appear on the magnet–spring system. The second coil, located below the first, excited with an ac current, provides the oscillating magnetic driving force on the system. From the magnet–coil interactions, we obtain, analytically, the nonlinear motion equation of the system, found to be a forced and damped cubic Duffing oscillator moving in a quartic potential. The relative strengths of the coefficients of the motion equation can be easily set by varying the coils’ dc and ac currents. We demonstrate, theoretically and experimentally, the nonlinear behaviour of this oscillator, including its oscillation modes and nonlinear resonances, the fold-over effect, the hysteresis and amplitude jumps, and its chaotic behaviour. It is an oscillating system suitable for teaching an advanced experiment in nonlinear dynamics both at senior undergraduate and graduate levels. (paper)

An alternating voltage battery with two salt-water oscillators

Science.gov (United States)

Cervellati, Rinaldo; Soldà, Roberto

2001-05-01

We built a simple alternating voltage battery that periodically reverses value and sign of its electromotive force (emf). This battery consists of two coupled concentration salt-water oscillators that are phase shifted by initially extracting some drops of salt solution from one of the two oscillators. Although the actual frequency (period: ˜30 s) and emf (˜±55 mV) is low, our battery is suitable to demonstrate a practical application of oscillating systems in the physical, chemical, or biological laboratory for undergraduates. Interpretation of the phenomenon is given.

Quantitative comparison of two independent lateral force calibration techniques for the atomic force microscope

International Nuclear Information System (INIS)

Barkley, Sarice S.; Cannara, Rachel J.; Deng Zhao; Gates, Richard S.; Reitsma, Mark G.

2012-01-01

Two independent lateral-force calibration methods for the atomic force microscope (AFM)--the hammerhead (HH) technique and the diamagnetic lateral force calibrator (D-LFC)--are systematically compared and found to agree to within 5% or less, but with precision limited to about 15%, using four different tee-shaped HH reference probes. The limitations of each method, both of which offer independent yet feasible paths toward traceable accuracy, are discussed and investigated. We find that stiff cantilevers may produce inconsistent D-LFC values through the application of excessively high normal loads. In addition, D-LFC results vary when the method is implemented using different modes of AFM feedback control, constant height and constant force modes, where the latter is more consistent with the HH method and closer to typical experimental conditions. Specifically, for the D-LFC apparatus used here, calibration in constant height mode introduced errors up to 14 %. In constant force mode using a relatively stiff cantilever, we observed an ≅ 4 % systematic error per μN of applied load for loads ≤ 1 μN. The issue of excessive load typically emerges for cantilevers whose flexural spring constant is large compared with the normal spring constant of the D-LFC setup (such that relatively small cantilever flexural displacements produce relatively large loads). Overall, the HH method carries a larger uncertainty, which is dominated by uncertainty in measurement of the flexural spring constant of the HH cantilever as well as in the effective length dimension of the cantilever probe. The D-LFC method relies on fewer parameters and thus has fewer uncertainties associated with it. We thus show that it is the preferred method of the two, as long as care is taken to perform the calibration in constant force mode with low applied loads.

The charged bubble oscillator: Dynamics and thresholds

Indian Academy of Sciences (India)

The nonlinear, forced oscillations of a bubble in a fluid due to an external pressure field are studied theoretically. ... for the system, delineating different dynamics. Keywords. ..... (c) Power spectral density of the charged and uncharged bub-.

Force coordination in static manipulation tasks performed using standard and non-standard grasping techniques.

Science.gov (United States)

de Freitas, Paulo B; Jaric, Slobodan

2009-04-01

We evaluated coordination of the hand grip force (GF; normal component of the force acting at the hand-object contact area) and load force (LF; the tangential component) in a variety of grasping techniques and two LF directions. Thirteen participants exerted a continuous sinusoidal LF pattern against externally fixed handles applying both standard (i.e., using either the tips of the digits or the palms; the precision and palm grasps, respectively) and non-standard grasping techniques (using wrists and the dorsal finger areas; the wrist and fist grasp). We hypothesized (1) that the non-standard grasping techniques would provide deteriorated indices of force coordination when compared with the standard ones, and (2) that the nervous system would be able to adjust GF to the differences in friction coefficients of various skin areas used for grasping. However, most of the indices of force coordination remained similar across the tested grasping techniques, while the GF adjustments for the differences in friction coefficients (highest in the palm and the lowest in the fist and wrist grasp) provided inconclusive results. As hypothesized, GF relative to the skin friction was lowest in the precision grasp, but highest in the palm grasp. Therefore, we conclude that (1) the elaborate coordination of GF and LF consistently seen across the standard grasping techniques could be generalized to the non-standard ones, while (2) the ability to adjust GF using the same grasping technique to the differences in friction of various objects cannot be fully generalized to the GF adjustment when different grasps (i.e., hand segments) are used to manipulate the same object. Due to the importance of the studied phenomena for understanding both the functional and neural control aspects of manipulation, future studies should extend the current research to the transient and dynamic tasks, as well as to the general role of friction in our mechanical interactions with the environment.

NOx Emission Reduction by Oscillating Combustion

Energy Technology Data Exchange (ETDEWEB)

John C. Wagner

2004-03-31

High-temperature, natural gas-fired furnaces, especially those fired with preheated air, produce large quantities of NO{sub x} per ton of material processed. Regulations on emissions from industrial furnaces are becoming increasingly more stringent. In addition, competition is forcing operators to make their furnaces more productive and/or efficient. Switching from preheated air to industrial oxygen can increase efficiency and reduce NO{sub x}, but oxygen is significantly more costly than air and may not be compatible with the material being heated. What was needed, and what was developed during this project, is a technology that reduces NO{sub x} emissions while increasing furnace efficiency for both air- and oxy-fired furnaces. Oscillating combustion is a retrofit technology that involves the forced oscillation of the fuel flow rate to a furnace. These oscillations create successive, fuel-rich and fuel-lean zones within the furnace. Heat transfer from the flame to the load increases due to the more luminous fuel-rich zones, a longer overall flame length, and the breakup of the thermal boundary layer. The increased heat transfer shortens heat up times, thereby increasing furnace productivity, and reduces the heat going up the stack, thereby increasing efficiency. The fuel-rich and fuel-lean zones also produce substantially less NO{sub x} than firing at a constant excess air level. The longer flames and higher heat transfer rate reduces overall peak flame temperature and thus reduces additional NO{sub x} formation from the eventual mixing of the zones and burnout of combustibles from the rich zones. This project involved the development of hardware to implement oscillating combustion on an industrial scale, the laboratory testing of oscillating combustion on various types of industrial burners, and the field testing of oscillating combustion on several types of industrial furnace. Before laboratory testing began, a market study was conducted, based on the

NOx Emission Reduction by Oscillating combustion

Energy Technology Data Exchange (ETDEWEB)

Institute of Gas Technology

2004-01-30

High-temperature, natural gas-fired furnaces, especially those fired with preheated air, produce large quantities of NO{sub x} per ton of material processed. Regulations on emissions from industrial furnaces are becoming increasingly more stringent. In addition, competition is forcing operators to make their furnaces more productive and/or efficient. Switching from preheated air to industrial oxygen can increase efficiency and reduce NO{sub x}, but oxygen is significantly more costly than air and may not be compatible with the material being heated. What was needed, and what was developed during this project, is a technology that reduces NO{sub x} emissions while increasing furnace efficiency for both air- and oxy-fired furnaces. Oscillating combustion is a retrofit technology that involves the forced oscillation of the fuel flow rate to a furnace. These oscillations create successive, fuel-rich and fuel-lean zones within the furnace. Heat transfer from the flame to the load increases due to the more luminous fuel-rich zones, a longer overall flame length, and the breakup of the thermal boundary layer. The increased heat transfer shortens heat up times, thereby increasing furnace productivity, and reduces the heat going up the stack, thereby increasing efficiency. The fuel-rich and fuel-lean zones also produce substantially less NO{sub x} than firing at a constant excess air level. The longer flames and higher heat transfer rate reduces overall peak flame temperature and thus reduces additional NO{sub x} formation from the eventual mixing of the zones and burnout of combustibles from the rich zones. This project involved the development of hardware to implement oscillating combustion on an industrial scale, the laboratory testing of oscillating combustion on various types of industrial burners, and the field testing of oscillating combustion on several types of industrial furnace. Before laboratory testing began, a market study was conducted, based on the

The macroscopic harmonic oscillator and quantum measurements

International Nuclear Information System (INIS)

Hayward, R.W.

1982-01-01

A quantum mechanical description of a one-dimensional macroscopic harmonic oscillator interacting with its environment is given. Quasi-coherent states are introduced to serve as convenient basis states for application of a density matrix formalism to characterize the system. Attention is given to the pertinent quantum limits to the precision of measurement of physical observables that may provide some information on the nature of a weak classical force interacting with the oscillator. A number of ''quantum nondemolition'' schemes proposed by various authors are discussed. (Auth.)

Resonant difference-frequency atomic force ultrasonic microscope

Science.gov (United States)

Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

2010-01-01

A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

Forced synchronization and asynchronous quenching in a thermo-acoustic system

Science.gov (United States)

Mondal, Sirshendu; Pawar, Samadhan A.; Sujith, Raman

2017-11-01

Forced synchronization, which has been extensively studied in theory and experiments, occurs through two different mechanisms known as phase locking and asynchronous quenching. The latter indicates the suppression of oscillation amplitude. In most practical combustion systems such as gas turbine engines, the main concern is high amplitude pressure oscillations, known as thermo-acoustic instability. Thermo-acoustic instability is undesirable and needs to be suppressed because of its damaging consequences to an engine. In the present study, a systematic experimental investigation of forced synchronization is performed in a prototypical thermo-acoustic system, a Rijke tube, in its limit cycle operation. Further, we show a qualitatively similar behavior using a reduced order model. In the phase locking region, the simultaneous occurrence of synchronization and resonant amplification leads to high amplitude pressure oscillations. However, a reduction in the amplitude of natural oscillations by about 78% of the unforced amplitude is observed when the forcing frequency is far lower than the natural frequency. This shows the possibility of suppression of the oscillation amplitude through asynchronous quenching in thermo-acoustic systems.

Part 2: Dynamics of magnetic oscillator

International Nuclear Information System (INIS)

Anon.

1987-01-01

This is an experimental study of a forced symmetric oscillator containing a saturable inductor with magnetic hysteresis. It displays a Hopf bifurcation to quasiperiodicity, entrainment horns, and chaos. The bifurcations and hysteresis occurring near points of resonance (particularly ''strong resonance'') are studied in detail and it is shown how the observed behavior can be understood using Arnold's theory. Much of the behavior relating to the entrainment horns is explored: period doubling and symmetry breaking bifurcations; homoclinic bifurcations; and crises and other bifurcations taking place at the horn boundaries. Important features of the behavior related to symmetry properties of the oscillator are studied and explained through the concept of a half-cycle map. The system is shown to exhibit a Hopf bifurcation from a phase-locked state to periodic ''islands,'' similar to those found in Hamiltonian systems. An initialization technique is used to observe the manifolds of saddle orbits and other hidden structure. An unusual differential equation model is developed which is irreversible and generates a noninvertible Poincare map of the plane. Noninvertibility of this planar map has important effects on the behavior observed. The Poincare map may also be approximated through experimental measurements, resulting in a planar map with parameter dependence. This model gives good correspondence with the system in a region of the parameter space. 31 refs., 36 figs., 1 tab

Inertial Oscillations and the Galilean Transformation

Science.gov (United States)

Korotaev, G. K.

2018-03-01

This paper presents a general solution of shallow-water equations on the f-plane. The solution describes the generation of inertial oscillations by wind-pulse forcing over the background of currents arbitrarily changing in time and space in a homogeneous fluid. It is shown that the existence of such a complete solution of shallow-water equations on the f-plane is related to their invariance with respect to the generalized Galilean transformations. Examples of velocity hodographs of inertial oscillations developing over the background of a narrow jet are presented which explain the diversity in their forms.

New Oscillation Criteria for Second-Order Forced Quasilinear Functional Differential Equations

Directory of Open Access Journals (Sweden)

Mervan Pašić

2013-01-01

or delay-advanced types. The nonlinear terms are of superlinear or supersublinear (mixed types. Consequences and examples are shown to illustrate the novelty and simplicity of our oscillation criteria.

Separation control with fluidic oscillators in water

Science.gov (United States)

Schmidt, H.-J.; Woszidlo, R.; Nayeri, C. N.; Paschereit, C. O.

2017-08-01

The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet's exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.

Neutrino oscillation: status and outlooks

International Nuclear Information System (INIS)

Nedelec, P.

1994-01-01

Whether the neutrinos are massive or not is one of the most puzzling question of physics today. If they are massive, they can contribute significantly to the Dark Matter of the Universe. An other consequence of a non-zero mass of neutrinos is that they might oscillate from one flavor to another. This oscillation process is by now the only way to detect a neutrino with a mass in the few eV range. Several neutrino experiments are currently looking for such an oscillation, in different modes, using different techniques. An overview of the experimental situation for neutrino experiments at accelerators is given. (author). 9 refs., 5 figs., 5 tabs

Control, synchronization, and enhanced reliability of aperiodic oscillations in the Mercury Beating Heart system

Science.gov (United States)

Kumar, Pawan; Parmananda, P.

2018-04-01

Experiments involving the Mercury Beating Heart (MBH) oscillator, exhibiting irregular (aperiodic) dynamics, are performed. In the first set of experiments, control over irregular dynamics of the MBH oscillator was obtained via a superimposed periodic voltage signal. These irregular (aperiodic) dynamics were recovered once the control was switched off. Subsequently, two MBH oscillators were coupled to attain synchronization of their aperiodic oscillations. Finally, two uncoupled MBH oscillators were subjected, repeatedly, to a common stochastic forcing, resulting in an enhancement of their mutual phase correlation.

Molecular dynamics simulation of square graphene-nanoflake oscillator on graphene nanoribbon.

Science.gov (United States)

Kang, Jeong Won; Lee, Kang Whan

2014-12-01

Graphene nanoflakes (GNFs) have been of interest for a building block in order to develop electromechanical devices on a nanometer scale. Here, we present the oscillation motions of a square GNF oscillator on graphene nanoribbon (GNR) in the retracting-motions by performing classical molecular dynamics simulations. The simulation results showed that the GNF oscillators can be considered as a building block for nanoelectromechanical systems such as carbon-nanotube (CNT) oscillators. The oscillation dynamics of the GNF oscillator were similar to those of the CNT oscillators. When the square GNF had an initial velocity as impulse dynamics, its oscillation motions on the GNR were achieved from its self-retracting van der Waals force. For low initial velocity, its translational motions were dominant in its motions rather than its rotational motions. The kinetic energy damping ratio rapidly decreased as initial velocity increased and the kinetic energy for the translational motion of the GNF oscillator rapidly transferred into that for its rotational motion. The oscillation frequency of the GNF oscillator was dependent on its initial velocity.

Finger Forces in Clarinet Playing

Directory of Open Access Journals (Sweden)

Alex Hofmann

2016-08-01

Full Text Available Clarinettists close and open multiple tone holes to alter the pitch of the tones. Their fingering technique must be fast, precise, and coordinated with the tongue articulation. In this empirical study, finger force profiles and tongue techniques of clarinet students (N = 17 and professional clarinettists (N = 6 were investigated under controlled performance conditions. First, in an expressive-performance task, eight selected excerpts from the first Weber Concerto were performed. These excerpts were chosen to fit in a 2 x 2 x 2 design (register: low--high; tempo: slow--fast, dynamics: soft--loud. There was an additional condition controlled by the experimenter, which determined the expression levels (low--high of the performers. Second, a technical-exercise task, an isochronous 23-tone melody was designed that required different effectors to produce the sequence (finger-only, tongue-only, combined tongue-finger actions. The melody was performed in three tempo conditions (slow, medium, fast in a synchronization-continuation paradigm. Participants played on a sensor-equipped Viennese clarinet, which tracked finger forces and reed oscillations simultaneously. From the data, average finger force (Fmean and peak force (Fmax were calculated. The overall finger forces were low (Fmean = 1.17 N, Fmax = 3.05 N compared to those on other musical instruments (e.g. guitar. Participants applied the largest finger forces during the high expression level performance conditions (Fmean = 1.21 N.For the technical exercise task, timing and articulation information were extracted from the reed signal. Here, the timing precision of the fingers deteriorated the timing precision of the tongue for combined tongue-finger actions, especially for faster tempi. Although individual finger force profiles were overlapping, the group of professional players applied less finger force overall (Fmean = 0.54 N. Such sensor instruments provide useful insights into player

Experimental study on inter-particle acoustic forces.

Science.gov (United States)

Garcia-Sabaté, Anna; Castro, Angélica; Hoyos, Mauricio; González-Cinca, Ricard

2014-03-01

A method for the experimental measurement of inter-particle forces (secondary Bjerknes force) generated by the action of an acoustic field in a resonator micro-channel is presented. The acoustic radiation force created by an ultrasonic standing wave moves suspended particles towards the pressure nodes and the acoustic pressure induces particle volume oscillations. Once particles are in the levitation plane, transverse and secondary Bjerknes forces become important. Experiments were carried out in a resonator filled with a suspension composed of water and latex particles of different size (5-15 μm) at different concentrations. Ultrasound was generated by means of a 2.5 MHz nominal frequency transducer. For the first time the acoustic force generated by oscillating particles acting on other particles has been measured, and the critical interaction distance in various cases has been determined. Inter-particle forces on the order of 10(-14) N have been measured by using this method.

Nonlinear (Anharmonic Casimir Oscillator

Directory of Open Access Journals (Sweden)

Habibollah Razmi

2011-01-01

Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.

Servo-controlled pneumatic pressure oscillator for respiratory impedance measurements and high-frequency ventilation.

Science.gov (United States)

Kaczka, David W; Lutchen, Kenneth R

2004-04-01

The ability to provide forced oscillatory excitation of the respiratory system can be useful in mechanical impedance measurements as well as high frequency ventilation (HFV). Experimental systems currently used for generating forced oscillations are limited in their ability to provide high amplitude flows or maintain the respiratory system at a constant mean pressure during excitation. This paper presents the design and implementation of a pneumatic pressure oscillator based on a proportional solenoid valve. The device is capable of providing forced oscillatory excitations to the respiratory system over a bandwidth suitable for mechanical impedance measurements and HVF. It delivers high amplitude flows (> 1.4 l/s) and utilizes a servo-control mechanism to maintain a load at a fixed mean pressure during simultaneous oscillation. Under open-loop conditions, the device exhibited a static hysteresis of approximately 7%, while its dynamic magnitude and phase responses were flat out to 10 Hz. Broad-band measurement of total harmonic distortion was approximately 19%. Under closed-loop conditions, the oscillator was able to maintain a mechanical test load at both positive and negative mean pressures during oscillatory excitations from 0.1 to 10.0 Hz. Impedance of the test load agreed closely with theoretical predictions. We conclude that this servo-controlled oscillator can be a useful tool for respiratory impedance measurements as well as HFV.

Oscillations and NMDA Receptors: Their Interplay Create Memories

Directory of Open Access Journals (Sweden)

Chris Cadonic

2014-06-01

Full Text Available Oscillatory activity is inherent in many types of normal cellular function. Importantly, oscillations contribute to cellular network activity and cellular decision making, which are driving forces for cognition. Theta oscillations have been correlated with learning and memory encoding and gamma oscillations have been associated with attention and working memory. NMDA receptors are also implicated in oscillatory activity and contribute to normal function and in disease-related pathology. The interplay between oscillatory activity and NMDA receptors are intellectually curious and a fascinating dimension of inquiry. In this review we introduce some of the essential mathematical characteristics of oscillatory activity in order to provide a platform for additional discussion on recent studies concerning oscillations involving neuronal firing and NMDA receptor activity, and the effect of these dynamic mechanisms on cognitive processing in health and disease.

Invariant manifolds and the parameterization method in coupled energy harvesting piezoelectric oscillators

DEFF Research Database (Denmark)

Granados, Albert

2017-01-01

Energy harvesting systems based on oscillators aim to capture energy from mechanical oscillations and convert it into electrical energy. Widely extended are those based on piezoelectric materials, whose dynamics are Hamiltonian submitted to different sources of dissipation: damping and coupling...... in Hamiltonian systems and hence could be very useful in energy harvesting applications. This article is a first step towards this goal. We consider two piezoelectric beams submitted to a small forcing and coupled through an electric circuit. By considering the coupling, damping and forcing as perturbations, we...

Apparent CPT violation in neutrino oscillation experiments

International Nuclear Information System (INIS)

Engelhardt, Netta; Nelson, Ann E.; Walsh, Jonathan R.

2010-01-01

We consider searching for light sterile fermions and new forces by using long baseline oscillations of neutrinos and antineutrinos. A new light sterile state and/or a new force can lead to apparent CPT violation in muon neutrino and antineutrino oscillations. As an example, we present an economical model of neutrino masses containing a sterile neutrino. The potential from the standard model weak neutral current gives rise to a difference between the disappearance probabilities of neutrinos and antineutrinos, when mixing with a light sterile neutrino is considered. The addition of a B-L interaction adds coherently to the neutrino current potential and increases the difference between neutrino and antineutrino disappearance. We find that this model can improve the fit to the results of MINOS for both neutrinos and antineutrinos, without any CPT violation, and that the regions of parameter space which improve the fit are within experimental constraints.

Parameter study of global and cluster synchronization in arrays of dry friction oscillators

Energy Technology Data Exchange (ETDEWEB)

Marszal, Michał, E-mail: michal.marszal@p.lodz.pl; Stefański, Andrzej

2017-04-18

Highlights: • Synchronization properties in arrays of coupled dry friction oscillators are investigated. • Master stability function in form of two-oscillator probe is used for predicting synchronization thresholds. • Two network topologies are checked: open and closed nearest neighbor coupling. • Regions of complete and cluster synchronization are found in parameter space. - Abstract: We investigate synchronization thresholds in arrays of identical classic stick-slip dry friction oscillators connected in a nearest neighbor fashion in closed and open ring network. Friction force is modeled by smoothened Stribeck model. Arrays of different length are checked in two parameter space (i.e., coupling coefficient vs. excitation frequency) for complete synchronization as well as cluster synchronization. Synchronization thresholds obtained by brute force numerical integration are compared with possible synchronization regions using the concept called master stability function in the form of two-oscillator reference probe. The results show existence of both complete synchronization and cluster synchronization regions in the investigated systems and confirm that two-oscillator probe can be applied for prediction of synchronization thresholds in systems with stick-slip phenomenon.

Martial arts fall techniques decrease the impact forces at the hip during sideways falling.

NARCIS (Netherlands)

Groen, B.E.; Weerdesteijn, V.G.M.; Duysens, J.E.J.

2007-01-01

Falls to the side and those with impact on the hip are risky for hip fractures in the elderly. A previous study has indicated that martial arts (MA) fall techniques can reduce hip impact force, but the underlying mechanism is unknown. Furthermore, the high impact forces at the hand used to break the

Nonequilibrium forces between atoms and dielectrics mediated by a quantum field

International Nuclear Information System (INIS)

Behunin, Ryan O.; Hu, Bei-Lok

2011-01-01

In this paper we give a first principles microphysics derivation of the nonequilibrium forces between an atom, treated as a three-dimensional harmonic oscillator, and a bulk dielectric medium modeled as a continuous lattice of oscillators coupled to a reservoir. We assume no direct interaction between the atom and the medium but there exist mutual influences transmitted via a common electromagnetic field. By employing concepts and techniques of open quantum systems we introduce coarse-graining to the physical variables--the medium, the quantum field, and the atom's internal degrees of freedom, in that order--to extract their averaged effects from the lowest tier progressively to the top tier. The first tier of coarse-graining provides the averaged effect of the medium upon the field, quantified by a complex permittivity (in the frequency domain) describing the response of the dielectric to the field in addition to its back action on the field through a stochastic forcing term. The last tier of coarse-graining over the atom's internal degrees of freedom results in an equation of motion for the atom's center of mass from which we can derive the force on the atom. Our nonequilibrium formulation provides a fully dynamical description of the atom's motion including back-action effects from all other relevant variables concerned. In the long-time limit we recover the known results for the atom-dielectric force when the combined system is in equilibrium or in a nonequilibrium stationary state.

Modified Legendre Wavelets Technique for Fractional Oscillation Equations

OpenAIRE

Mohyud-Din, Syed; Iqbal, Muhammad; Hassan, Saleh

2015-01-01

Physical Phenomena’s located around us are primarily nonlinear in nature and their solutions are of highest significance for scientists and engineers. In order to have a better representation of these physical models, fractional calculus is used. Fractional order oscillation equations are included among these nonlinear phenomena’s. To tackle with the nonlinearity arising, in these phenomena’s we recommend a new method. In the proposed method, Picard’s iteration is used to convert the nonlinea...

Experimental investigation on the thermal performance of a closed oscillating heat pipe in thermal management

Science.gov (United States)

Rao, Zhonghao; Wang, Qingchao; Zhao, Jiateng; Huang, Congliang

2017-10-01

To investigate the thermal performance of the closed oscillating heat pipe (OHP) as a passive heat transfer device in thermal management system, the gravitation force, surface tension, cooling section position and inclination angle were discussed with applied heating power ranging from 5 to 65 W. The deionized water was chosen as the working fluid and liquid-filling ratio was 50 ± 5%. The operation of the OHP mainly depends on the phase change of the working fluid. The working fluid within the OHP was constantly evaporated and cooled. The results show that the movement of the working fluid was similar to the forced damped mechanical vibration, it has to overcome the capillary resistance force and the stable oscillation should be that the OHP could successful startup. The oscillation frequency slowed and oscillation amplitude decreased when the inclination angle of the OHP increased. However, the thermal resistance increased. With the increment of the heating power, the average temperature of the evaporation and condensation section would be close. If the heating power was further increased, dry-out phenomenon within the OHP would appeared. With the decrement of the L, the start-up heating power also decreased and stable oscillation would be formed.

Vorticity confinement technique for drag prediction

Science.gov (United States)

Povitsky, Alex; Snyder, Troy

2011-11-01

This work couples wake-integral drag prediction and vorticity confinement technique (VC) for the improved prediction of drag from CFD simulations. Induced drag computations of a thin wing are shown to be more accurate than the more widespread method of surface pressure integration when compared to theoretical lifting-line value. Furthermore, the VC method improves trailing vortex preservation and counteracts the shift from induced drag to numerical entropy drag with increasing distance of Trefftz plane downstream of the wing. Accurate induced drag prediction via the surface integration of pressure barring a sufficiently refined surface grid and increased computation time. Furthermore, the alternative wake-integral technique for drag prediction suffers from numerical dissipation. VC is shown to control the numerical dissipation with very modest computational overhead. The 2-D research code is used to test specific formulations of the VC body force terms and illustrate the computational efficiency of the method compared to a ``brute force'' reduction in spatial step size. For the 3-D wing simulation, ANSYS FLUENT is employed with the VC body force terms added to the solver with user-defined functions (UDFs). VC is successfully implemented to highly unsteady flows typical for Micro Air Vehicles (MAV) producing oscillative drag force either by natural vortex shedding at high angles of attack or by flapping wing motion.

On the measurement of a weak classical force coupled to a harmonic oscillator: experimental progress

International Nuclear Information System (INIS)

Bocko, M.F.; Onofrio, R.

1996-01-01

Several high-precision physics experiments are approaching a level of sensitivity at which the intrinsic quantum nature of the experimental apparatus is the dominant source of fluctuations limiting the sensitivity of the measurements. This quantum limit is embodied by the Heisenberg uncertainty principle, which prohibits arbitrarily precise simultaneous measurements of two conjugate observables of a system but allows one-time measurements of a single observable with any precision. The dynamical evolution of a system immediately following a measurement limits the class of observables that may be measured repeatedly with arbitrary precision, with the influence of the measurement apparatus on the system being confined strictly to the conjugate observables. Observables having this feature, and the corresponding measurements performed on them, have been named quantum nondemolition or back-action evasion observables. In a previous review (Caves et al., 1980, Rev. Mod. Phys. 52, 341) a quantum-mechanical analysis of quantum nondemolition measurements of a harmonic oscillator was presented. The present review summarizes the experimental progress on quantum nondemolition measurements and the classical models developed to describe and guide the development of practical implementations of quantum nondemolition measurements. The relationship between the classical and quantum theoretical models is also reviewed. The concept of quantum nondemolition and back-action evasion measurements originated in the context of measurements on a macroscopic mechanical harmonic oscillator, though these techniques may be useful in other experimental contexts as well, as is discussed in the last part of this review. copyright 1996 The American Physical Society

An oscillating dynamic model of collective cells in a monolayer

Science.gov (United States)

Lin, Shao-Zhen; Xue, Shi-Lei; Li, Bo; Feng, Xi-Qiao

2018-03-01

Periodic oscillations of collective cells occur in the morphogenesis and organogenesis of various tissues and organs. In this paper, an oscillating cytodynamic model is presented by integrating the chemomechanical interplay between the RhoA effector signaling pathway and cell deformation. We show that both an isolated cell and a cell aggregate can undergo spontaneous oscillations as a result of Hopf bifurcation, upon which the system evolves into a limit cycle of chemomechanical oscillations. The dynamic characteristics are tailored by the mechanical properties of cells (e.g., elasticity, contractility, and intercellular tension) and the chemical reactions involved in the RhoA effector signaling pathway. External forces are found to modulate the oscillation intensity of collective cells in the monolayer and to polarize their oscillations along the direction of external tension. The proposed cytodynamic model can recapitulate the prominent features of cell oscillations observed in a variety of experiments, including both isolated cells (e.g., spreading mouse embryonic fibroblasts, migrating amoeboid cells, and suspending 3T3 fibroblasts) and multicellular systems (e.g., Drosophila embryogenesis and oogenesis).

Linear drag law for high-Reynolds-number flow past an oscillating body

Science.gov (United States)

Agre, Natalie; Childress, Stephen; Zhang, Jun; Ristroph, Leif

2016-07-01

An object immersed in a fast flow typically experiences fluid forces that increase with the square of speed. Here we explore how this high-Reynolds-number force-speed relationship is affected by unsteady motions of a body. Experiments on disks that are driven to oscillate while progressing through air reveal two distinct regimes: a conventional quadratic relationship for slow oscillations and an anomalous scaling for fast flapping in which the time-averaged drag increases linearly with flow speed. In the linear regime, flow visualization shows that a pair of counterrotating vortices is shed with each oscillation and a model that views a train of such dipoles as a momentum jet reproduces the linearity. We also show that appropriate scaling variables collapse the experimental data from both regimes and for different oscillatory motions into a single drag-speed relationship. These results could provide insight into the aerodynamic resistance incurred by oscillating wings in flight and they suggest that vibrations can be an effective means to actively control the drag on an object.

Magnetic force microscopy: advanced technique for the observation of magnetic domains

International Nuclear Information System (INIS)

Asenjo, A.; Garcia, J. M.; Vazquez, M.

2001-01-01

An overview on the Magnetic Force Microscopy, MFM, as an advanced technique to observe magnetic domains and walls is displayed. Basic concepts are first introduced on the domain structure formation as well as on other techniques to observe magnetic domains. Afterwards, the MFM instrumentation is described making also an emphasis in micro magnetic consideration to interpret the images. Finally, a set of selected advanced magnetic materials with different domain structures is chosen to show the wide possibilities of this techniques to characterise the surface magnetic behaviour. The domain structure of materials as commercial magnetic recording media, thin films and multilayers, amorphous micro tubes, nanocrystalline ribbons, perovskites or magnetic nano wires is shown. (Author) 16 refs

Introduction to Classical and Quantum Harmonic Oscillators

International Nuclear Information System (INIS)

Latal, H

1997-01-01

As the title aptly states, this book deals with harmonic oscillators of various kinds, from classical mechanical and electrical oscillations up to quantum oscillations. It is written in a lively language, and occasional interspersed anecdotes make the reading of an otherwise mathematically oriented text quite a pleasure. Although the author claims to have written an 'elementary introduction', it is certainly necessary to have a good deal of previous knowledge in physics (mechanics, electrodynamics, quantum theory), electrical engineering and, of course, mathematics in order to follow the general line of his arguments. The book begins with a thorough treatment of classical oscillators (free, damped, forced) that is followed by an elaboration on Fourier analysis. Lagrange and Hamilton formalisms are then introduced before the problem of coupled oscillations is attacked. A chapter on statistical perspectives leads over to the final discussion of quantum oscillations. With the book comes a diskette containing a number of worksheets (Microsoft Excel) that can be used by the reader for instant visualization to get a better qualitative and quantitative understanding of the material. To the reviewer it seems difficult to pinpoint exactly the range of prospective readership of the book. It can certainly not be intended as a textbook for students, but rather as a reference book for teachers of physics or researchers, who want to look up one or other aspect of harmonic oscillations, for which purpose the diskette represents a very valuable tool. (book review)

Study of the oscillations event of the CNLV-U1 with Wavelets techniques; Estudio del evento de oscilaciones de la CNLV-U1 con tecnicas de wavelets

Energy Technology Data Exchange (ETDEWEB)

Amador G, R.; Nunez C, A. [CNSNS, Dr. Barragan 779, 03020 Mexico D.F. (Mexico)]. E-mail: ragarcia@cnsns.gob.mx; Prieto G, A.; Espinosa P, G. [UAM-I, 09340 Mexico D.F. (Mexico)

2004-07-01

Presently work is described and the techniques are applied of the Fourier Transformation in Short Time, the Continuous Transformation of Wavelets and the Multi resolution Analysis for the analysis of the event of oscillations of power in the Nuclear Power station of Laguna Verde Unit 1 happened in January of 1995. In general, the wavelets techniques allows to carry out studies of the different signals generated by a nuclear plant in the plane Time-frequency, Time-scale as well as the decomposition of the signals. The results obtained study presently demonstrate that the frequency of the event of oscillations in the Nuclear Power station of Laguna Verde Unit 1 are approximately 0.52 Hz for the 3 analysis techniques, besides being observed the evolution of the frequency in function of the time. (Author)

Near-field Light Scattering Techniques for Measuring Nanoparticle-Surface Interaction Energies and Forces.

Science.gov (United States)

Schein, Perry; Ashcroft, Colby K; O'Dell, Dakota; Adam, Ian S; DiPaolo, Brian; Sabharwal, Manit; Shi, Ce; Hart, Robert; Earhart, Christopher; Erickson, David

2015-08-15

Nanoparticles are quickly becoming commonplace in many commercial and industrial products, ranging from cosmetics to pharmaceuticals to medical diagnostics. Predicting the stability of the engineered nanoparticles within these products a priori remains an important and difficult challenge. Here we describe our techniques for measuring the mechanical interactions between nanoparticles and surfaces using near-field light scattering. Particle-surface interfacial forces are measured by optically "pushing" a particle against a reference surface and observing its motion using scattered near-field light. Unlike atomic force microscopy, this technique is not limited by thermal noise, but instead takes advantage of it. The integrated waveguide and microfluidic architecture allow for high-throughput measurements of about 1000 particles per hour. We characterize the reproducibility of and experimental uncertainty in the measurements made using the NanoTweezer surface instrument. We report surface interaction studies on gold nanoparticles with 50 nm diameters, smaller than previously reported in the literature using similar techniques.

Comparison of heaving buoy and oscillating flap wave energy converters

Science.gov (United States)

Abu Bakar, Mohd Aftar; Green, David A.; Metcalfe, Andrew V.; Najafian, G.

2013-04-01

Waves offer an attractive source of renewable energy, with relatively low environmental impact, for communities reasonably close to the sea. Two types of simple wave energy converters (WEC), the heaving buoy WEC and the oscillating flap WEC, are studied. Both WECs are considered as simple energy converters because they can be modelled, to a first approximation, as single degree of freedom linear dynamic systems. In this study, we estimate the response of both WECs to typical wave inputs; wave height for the buoy and corresponding wave surge for the flap, using spectral methods. A nonlinear model of the oscillating flap WEC that includes the drag force, modelled by the Morison equation is also considered. The response to a surge input is estimated by discrete time simulation (DTS), using central difference approximations to derivatives. This is compared with the response of the linear model obtained by DTS and also validated using the spectral method. Bendat's nonlinear system identification (BNLSI) technique was used to analyze the nonlinear dynamic system since the spectral analysis was only suitable for linear dynamic system. The effects of including the nonlinear term are quantified.

Hypothesis-driven methods to augment human cognition by optimizing cortical oscillations

Directory of Open Access Journals (Sweden)

Jörn M. Horschig

2014-06-01

Full Text Available Cortical oscillations have been shown to represent fundamental functions of a working brain, e.g. communication, stimulus binding, error monitoring, and inhibition, and are directly linked to behavior. Recent studies intervening with these oscillations have demonstrated effective modulation of both the oscillations and behavior. In this review, we collect evidence in favor of how hypothesis-driven methods can be used to augment cognition by optimizing cortical oscillations. We elaborate their potential usefulness for three target groups: healthy elderly, patients with attention deficit/hyperactivity disorder, and healthy young adults. We discuss the relevance of neuronal oscillations in each group and show how each of them can benefit from the manipulation of functionally-related oscillations. Further, we describe methods for manipulation of neuronal oscillations including direct brain stimulation as well as indirect task alterations. We also discuss practical considerations about the proposed techniques. In conclusion, we propose that insights from neuroscience should guide techniques to augment human cognition, which in turn can provide a better understanding of how the human brain works.

Collapse and revival in inter-band oscillations of a two-band Bose-Hubbard model

Energy Technology Data Exchange (ETDEWEB)

Ploetz, Patrick; Wimberger, Sandro [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, 69120 Heidelberg (Germany); Madronero, Javier, E-mail: ploetz@thphys.uni-heidelberg.d [Physik Department, Technische Universitaet Muenchen, James-Franck-Str. 1, 85748 Garching (Germany)

2010-04-28

We study the effect of a many-body interaction on inter-band oscillations in a two-band Bose-Hubbard model with an external Stark force. Weak and strong inter-band oscillations are observed, where the latter arise from a resonant coupling of the bands. These oscillations collapse and revive due to a weak two-body interaction between the atoms. Effective models for oscillations in and out of resonance are introduced that provide predictions for the system's behaviour, particularly for the time scales for the collapse and revival of the resonant inter-band oscillations. (fast track communication)

Experimental Study and Mathematical Modeling of Self-Sustained Kinetic Oscillations in Catalytic Oxidation of Methane over Nickel.

Science.gov (United States)

Lashina, Elena A; Kaichev, Vasily V; Saraev, Andrey A; Vinokurov, Zakhar S; Chumakova, Nataliya A; Chumakov, Gennadii A; Bukhtiyarov, Valerii I

2017-09-21

The self-sustained kinetic oscillations in the oxidation of CH 4 over Ni foil have been studied at atmospheric pressure using an X-ray diffraction technique and mass spectrometry. It has been shown that the regular oscillations appear under oxygen-deficient conditions; CO, CO 2 , H 2 , and H 2 O are detected as the products. According to in situ X-ray diffraction measurements, nickel periodically oxidizes to NiO initiating the reaction-rate oscillations. To describe the oscillations, we have proposed a five-stage mechanism of the partial oxidation of methane over Ni and a corresponding three-variable kinetic model. The mechanism considers catalytic methane decomposition, dissociative adsorption of oxygen, transformation of chemisorbed oxygen to surface nickel oxide, and reaction of adsorbed carbon and oxygen species to form CO. Analysis of the kinetic model indicates that the competition of two processes, i.e., the oxidation and the carbonization of the catalyst surface, is the driving force of the self-sustained oscillations in the oxidation of methane. We have compared this mechanism with the detailed 18-stage mechanism described previously by Lashina et al. (Kinetics and Catalysis 2012, 53, 374-383). It has been shown that both kinetic mechanisms coupled with a continuous stirred-tank reactor model describe well the oscillatory behavior in the oxidation of methane under non-isothermal conditions.

Three-dimensional analysis of nonlinear plasma oscillation

International Nuclear Information System (INIS)

Miano, G.

1990-01-01

In an underdense plasma a large-amplitude plasma oscillation may be produced by the beating of two external and colinear electromagnetic waves with a frequency difference approximately equal to the plasma frequency - plasma beat wave (PBW) resonant mechanism. The plasma oscillations are driven by the ponderomotive force arising from the beating of the two imposed electromagnetic waves. In this paper two pump electromagnetic waves with arbitrary transverse profiles have been considered. The plasma is described by using the three dimensinal weakly relativistic fluid equations. The nonlinear plasma oscillation dynamics is studied by using the eulerian description, the averaging and the multiple time scale methods. Unlike the linear theory a strong cross field coupling between longitudinal ans transverse electric field components of the plasma oscillation comes out, resulting in a nonlinear phase change and energy transfer between the two components. Unlike the one-dimensional nonlinear theory, the nonlinear frequency shift is caused by relativistic effects as well as by convective effects and electromagnetic field generated from the three dimensional plasma oscillation. The large amplitude plasma oscillation dynamics produced by a bunched relativistic electron beam with arbitrary transverse profile - plasma wave field (PWF) - or by a high power single frequency short electromagnetic pulse with arbitrary transverse profile - electromagnetic plasma wake field (EPWF) - may be described by means of the present theory. (orig.)

The perturbation theory model of a spherical oscillator in electric field and the vibrational stark effect in polyatomic molecular species

Science.gov (United States)

Petreska, Irina; Ivanovski, Gjorgji; Pejov, Ljupčo

2007-04-01

The effect of external electrostatic fields on the spherical oscillator energy states was studied using stationary perturbation theory. Besides the spherical oscillator with ideal symmetry, also a variety of the deformed systems were considered in which the deformations may be induced by the external fields, but also by the short-range crystal lattice forces. The perturbation theory analysis was carried out using the field-dependent basis functions. Predicted spectral appearances and band splittings due to the deformations and external field influences were shown to be helpful in interpreting the experimental spectra of molecular oscillator possessing subsets of mutually orthogonal triply degenerate normal modes (such as, e.g. tetrahedral species). To verify the results of the perturbation theory treatments, as well as to provide a further illustration of the usefulness of the employed technique, a numerical HF/aug-cc-pVTZ study of the vibrational states of methane molecule in external electrostatic field was performed.

Parametric Resonance in a Time-Dependent Harmonic Oscillator

Directory of Open Access Journals (Sweden)

P. N. Nesterov

2013-01-01

Full Text Available In this paper, we study the phenomenon of appearance of new resonances in a timedependent harmonic oscillator under an oscillatory decreasing force. The studied equation belongs to the class of adiabatic oscillators and arises in connection with the spectral problem for the one-dimensional Schr¨odinger equation with Wigner–von Neumann type potential. We use a specially developed method for asymptotic integration of linear systems of differential equations with oscillatory decreasing coefficients. This method uses the ideas of the averaging method to simplify the initial system. Then we apply Levinson’s fundamental theorem to get the asymptotics for its solutions. Finally, we analyze the features of a parametric resonance phenomenon. The resonant frequencies of perturbation are found and the pointwise type of the parametric resonance phenomenon is established. In conclusion, we construct an example of a time-dependent harmonic oscillator (adiabatic oscillator in which the parametric resonances, mentioned in the paper, may occur.

Fracture force analysis at the interface of Pd and SrTiO3

International Nuclear Information System (INIS)

Nazarpour, S.; Zamani, C.; Cirera, A.

2009-01-01

The objective of this work is to develop an experimental indentation based method to determine the fracture force at the interface of Pd thin films and SrTiO 3 perovskite substrate. This paper reports on the results obtained for indentation into Pd thin films which were deposited in various thicknesses from 20 nm to 200 nm under vacuum and 300 deg. C substrate temperature by an electron beam physical vapor deposition. Initially, the relation between grain size, elastic module and hardness was considered as a function of film thickness. Thereafter, in developing new method, oscillating indentation was performed with different applied forces and oscillating times in order to measure the critical fracture force in each thickness. The effect of oscillating time on plastically deformed regions surrounding an indentation was schematically explained in conjunction with variation of oscillating time to determine the interfacial properties of the Pd thin film. Furthermore, the accuracy of the critical fracture force was ensured by applied force versus piling up height plot. The method is validated experimentally for the soft thin films over the hard substrate. However, further study would be essential to measure the film adhesion by means of fracture force at the interface

Ponderomotive Forces in Cosmos

Science.gov (United States)

Lundin, R.; Guglielmi, A.

2006-12-01

This review is devoted to ponderomotive forces and their importance for the acceleration of charged particles by electromagnetic waves in space plasmas. Ponderomotive forces constitute time-averaged nonlinear forces acting on a media in the presence of oscillating electromagnetic fields. Ponderomotive forces represent a useful analytical tool to describe plasma acceleration. Oscillating electromagnetic fields are also related with dissipative processes, such as heating of particles. Dissipative processes are, however, left outside these discussions. The focus will be entirely on the (conservative) ponderomotive forces acting in space plasmas. The review consists of seven sections. In Section 1, we explain the rational for using the auxiliary ponderomotive forces instead of the fundamental Lorentz force for the study of particle motions in oscillating fields. In Section 2, we present the Abraham, Miller, Lundin-Hultqvist and Barlow ponderomotive forces, and the Bolotovsky-Serov ponderomotive drift. The hydrodynamic, quasi-hydrodynamic, and ‘`test-particle’' approaches are used for the study of ponderomotive wave-particle interaction. The problems of self-consistency and regularization are discussed in Section 3. The model of static balance of forces (Section 4) exemplifies the interplay between thermal, gravitational and ponderomotive forces, but it also introduces a set of useful definitions, dimensionless parameters, etc. We analyze the Alfvén and ion cyclotron waves in static limit with emphasis on the specific distinction between traveling and standing waves. Particular attention has been given to the impact of traveling Alfvén waves on the steady state anabatic wind that blows over the polar regions (Section~5). We demonstrate the existence of a wave-induced cold anabatic wind. We also show that, at a critical point, the ponderomotive acceleration of the wind is a factor of 3 greater than the thermal acceleration. Section 6 demonstrates various

Nonlinear oscillations of the FitzHugh-Nagumo equations under combined external and two-frequency parametric excitations

International Nuclear Information System (INIS)

Tatchim Bemmo, D.; Siewe Siewe, M.; Tchawoua, C.

2011-01-01

The continuous FitzHugh-Nagumo (FHN for short) model is transformed into modified van der Pol oscillator with asymmetry under external and two-frequency parametric excitations. At the first, the dependence of the solutions on a combined external and two-frequency parametric stimulus forcing is investigated. By using the multiple scale method, ranges of applied current and/or parametric forcing in which nonlinear oscillations are observed are described. Second, when the multiple scale method cannot be used, we numerically prove that in the modified van der Pol oscillator with asymmetry under external and two-frequency parametric excitations, chaos and periodic solution depending on the combination between different frequencies of the model should appear. We also show that the amplitude of the oscillations can be reduced or increased. To do this, we perform the study of the FHN model by choosing a range of parameters exhibiting Hopf bifurcation and two qualitative different regimes in phase portrait. - Highlights: → We model both external and two-frequency parametric excitations in FHN equations. → We examine effects of harmonic forcing on coupled nonlinear oscillator. → Jump and hysteresis phenomena are observed in the dynamical response. → By increasing the constant stimulus we obtain limit cycle. → Some combinations of frequencies produce limit cycle and chaos for other.

Torsional resonance mode magnetic force microscopy: enabling higher lateral resolution magnetic imaging without topography-related effects

International Nuclear Information System (INIS)

Kaidatzis, A; García-Martín, J M

2013-01-01

We present experimental work that reveals the benefits of performing magnetic force microscopy measurements employing the torsional resonance mode of cantilever oscillation. This approach provides two clear advantages: the ability of performing magnetic imaging without topography-related interference and the significant lateral resolution improvement (approximately 15%). We believe that this work demonstrates a significant improvement to a versatile magnetic imaging technique widely used in academia and in industry. (paper)

The Solar and Southern Oscillation Components in the Satellite Altimetry Data

DEFF Research Database (Denmark)

Howard, Daniel; Shaviv, Nir J.; Svensmark, Henrik

2015-01-01

altimetry data can be explained as the combined effect of both the solar forcing and the El Niño-Southern Oscillation (ENSO). The phase of the solar component can be used to derive the different steric and eustatic contributions. We find that the peak to peak radiative forcing associated with the solar...

Hydroelastic Oscillations of a Circular Plate, Resting on Winkler Foundation

Science.gov (United States)

Kondratov, D. V.; Mogilevich, L. I.; Popov, V. S.; Popova, A. A.

2018-01-01

The forced hydroelastic oscillations of a circular plate resting on elastic foundation are investigated. The oscillations are caused by a stamp vibration under interaction with a plate through a thin layer of viscous incompressible liquid. The axis-symmetric problem for the regime of the steady-state harmonic oscillations is considered. On the basis of hydroelasticity problem solution the laws of plate deflection and pressure in the liquid are found. The functions of the amplitudes deflection distribution and liquid pressure along the plate are constructed. The presented mathematical model provides for investigating viscous liquid layer interaction dynamics with a circular plate resting on an elastic foundation. The above-mentioned model makes it possible to define the plate oscillations resonance frequencies and the corresponding amplitudes of deflection and liquid pressure, as well.

Distribution of radiation lifetime and oscillator strengths in atomic and ion spectra

Energy Technology Data Exchange (ETDEWEB)

Shabanova, L.N.; Gruzdev, P.F.; Verolajnen, Ya.F. (Leningradskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Fizicheskij Inst.)

1984-04-01

Analysis of present experimental and theoretical data on determination of radiation life time and forces of oscillators for disclosing general regularities inherent in radiation constants inside the atom, homologous atoms inside subgroups of atoms and ions of isoelectronic subsequences is conducted. Another purpose is to chose most reliable values of constants and to obtain extrapolation formulae for their determination on the base of the corresponding statistical processing data and revealed regularities. A hydrogen atom, isoelectronic series NaI-Ni18, isoelectronic series Ne, He, ZnI, CdI are considered. Systematics of radiation life time depending on the basic quantum number is presented. The force of oscillators f is considered on the example of an atomic system with one valent electron outside the locked shell - Li, Na, K, Rb, Cs. Distribution of force density of the oscillator df/dE is considered, here continuous spectrum near the threshold of ionization is regarded simultaneously with discrete spectrum. An interpolation formula for the number f for high members of atom series (n>=10) of alkaline metals is presented. Values of coefficients included in this formula are tabulated.

Suppressing nonlinear resonances in an impact oscillator using SMAs

International Nuclear Information System (INIS)

Sitnikova, Elena; Pavlovskaia, Ekaterina; Ing, James; Wiercigroch, Marian

2012-01-01

In this paper, we study the resonant responses of an impact oscillator with a one sided SMA motion constraint operating in the pseudoelastic regime. The effectiveness of the SMA restraint in suppressing nonlinear resonances of the impact oscillator is assessed by comparing the dynamic responses of the impact oscillator with SMA and elastic restraints. It is shown that the hysteretic behaviour of the SMA restraint provides an overall vibration reduction in the resonant frequency ranges. Due to the softening behaviour of the SMA element, the resonant frequencies for the SMA oscillator were found to be lower than for the oscillator with an elastic restraint. At each resonance, a single periodic response for the oscillator with the elastic restraint corresponds to two co-existing periodic responses of the SMA oscillator. While at the first resonance peak the emergence of one of the co-existing responses is associated with the hardening effect of the SMA restraint when the pseudoelastic force varies over a complete transformation cycle, at higher frequency resonances incomplete phase transformations in the SMA were detected for both responses. The experimental study undertaken verified the response-modification effects predicted by the numerical analysis conducted under the isothermal approximation. The experimental results showed a good quantitative correspondence with the mathematical modelling. (paper)

Dependence of oscillational instabilities on the amplitude of the acoustic wave in single-axis levitators

DEFF Research Database (Denmark)

Orozco-Santillán, Arturo; Ruiz-Boullosa, Ricardo; Cutanda Henríquez, Vicente

2007-01-01

It is well known that acoustic waves exert forces on a boundary with which they interact; these forces can be so intense that they can compensate for the weight of small objects up to a few grams. In this way, it is possible to maintain solid or liquid samples levitating in a fluid, avoiding...... the use of containers, which may be undesirable for certain applications. Moreover, small samples can be manipulated by means of acoustic waves. In this paper, we report a study on the oscillational instabilities that can appear on a levitated solid sphere in single-axis acoustic devices. A theory...... proportional to the oscillation frequency of the levitated sample. We also present experimental results that show that the oscillational instabilities can be reduced if the amplitude of the acoustic wave is increased; as a result, stable conditions can be obtained where the oscillations of the sphere...

Derivation of Oscillators from Biquadratic Band Pass Filters Using Circuit Transformations

Directory of Open Access Journals (Sweden)

Hung-Yu Wang

2014-09-01

Full Text Available Network transformations are the techniques to obtain new functional schemes from available circuits. They are systematic methodologies, since each transformation technique can be applied to many circuits to obtain the desired functions or characteristics. A convenient network transformation method, exploiting different circuit transformations, for deriving linear sinusoidal oscillators from biquadratic band pass filters is proposed. This method with generality can be applied to any band pass filter. The oscillation frequency of the new obtained oscillator is identical to the center frequency of the original band pass filter, and the useful properties of the selected band pass filter can be retained. Two examples are illustrated to confirm the feasibility of the proposed approach. The workability of the obtained oscillators is verified with PSPICE simulations.

Asymmetric Collision of Concepts: Why Eigenstates Alone are Not Enough for Neutrino Flavor Oscillations

OpenAIRE

Williams, John Michael

2000-01-01

The symmetry of the problem of the apparent deficit in upward-going atmospheric muon neutrinos reveals two possible, nonexclusive kinds of solution: Nonlinearity in distance or nonlinearity in angle of observation. Nonlinearity in distance leads to the most popular theory for the atmospheric problem, neutrino flavor oscillations. If the observed deficit is caused by oscillations and not, say, flavor-changing or other weak-force scattering, neutrinos must be massive. But, if flavor oscillation...

Observation of a new plasma regime with stationary electron temperature oscillations on Tore Supra

International Nuclear Information System (INIS)

Artaud, J.F.; Giruzzi, G.; Imbeaux, F.; Segui, J.L.; Garbet, X.

2003-01-01

This document is a copy of the slides presented on the 9. joint US-European Transport Task Force meeting. The first part is devoted to the experimental observations of a new tokamak plasma regime with stationary electron temperature oscillations. The oscillations appear on ECE spontaneously, sometimes associated with a transition to the LHEP regime. The second part presents an interpretation of these oscillations by analogy with a predator-prey system. (A.L.B.)

Studies of hydromagnetic waves and oscillations in plasmas

International Nuclear Information System (INIS)

Sawley, M.L.

1980-10-01

Small amplitude magnetoacoustic oscillations in a partially ionized, non-uniform, current carrying plasma column of finite beta are considered. The linearized magnetohydrodynamic equations are used to develop a theory describing both free and forced magnetoacoustic oscillations. The results of numerical calculations are given for the specific case of diffuse pinch equilibrium configurations. In an experimental study the amplitude of the oscillating axial magnetic flux is determined for several frequencies in the vicinity of the first magnetoacoustic resonance. Accurate determination of the plasma density profile is shown to be possible. Finite-amplitude effects on the propagation of axisymmetric hydromagnetic waves are examined. A nonlinear theory is developed which describes the second-order perturbation that accompanies the primary wave. The influence of Hall currents and the presence of neutral atoms on the second-order fields is treated. In an investigation on the propagation of torsional waves the observed second-order fields are shown to exhibit good quantitative agreement with theoretical calculations for moderate primary wave amplitudes. The re-ionization of the plasma by a torsional wave is investigated. A theoretical description is given of the nonlinear excitation of magnetoacoustic oscillations by means of an oscillating axial current

Computing with networks of nonlinear mechanical oscillators.

Directory of Open Access Journals (Sweden)

Jean C Coulombe

Full Text Available As it is getting increasingly difficult to achieve gains in the density and power efficiency of microelectronic computing devices because of lithographic techniques reaching fundamental physical limits, new approaches are required to maximize the benefits of distributed sensors, micro-robots or smart materials. Biologically-inspired devices, such as artificial neural networks, can process information with a high level of parallelism to efficiently solve difficult problems, even when implemented using conventional microelectronic technologies. We describe a mechanical device, which operates in a manner similar to artificial neural networks, to solve efficiently two difficult benchmark problems (computing the parity of a bit stream, and classifying spoken words. The device consists in a network of masses coupled by linear springs and attached to a substrate by non-linear springs, thus forming a network of anharmonic oscillators. As the masses can directly couple to forces applied on the device, this approach combines sensing and computing functions in a single power-efficient device with compact dimensions.

Acoustic loading effects on oscillating rod bundles

International Nuclear Information System (INIS)

Lin, W.H.

1980-01-01

An analytical study of the interaction between an infinite acoustic medium and a cluster of circular rods is described. The acoustic field due to oscillating rods and the acoustic loading on the rods are first solved in a closed form. The acoustic loading is then used as a forcing function for rod responses, and the acousto-elastic couplings are solved simultaneously. Numerical examples are presented for several cases to illustrate the effects of various system parameters on the acoustic reaction force coefficients. The effect of the acoustic loading on the coupled eigenfrequencies are discussed

A memristor-based third-order oscillator: beyond oscillation

KAUST Repository

Talukdar, Abdul Hafiz Ibne

2012-10-06

This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

A memristor-based third-order oscillator: beyond oscillation

KAUST Repository

Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

2012-01-01

This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

Non-linear neutron star oscillations viewed as deviations from an equilibrium state

International Nuclear Information System (INIS)

Sperhake, U

2002-01-01

A numerical technique is presented which facilitates the evolution of non-linear neutron star oscillations with a high accuracy essentially independent of the oscillation amplitude. We apply this technique to radial neutron star oscillations in a Lagrangian formulation and demonstrate the superior performance of the new scheme compared with 'conventional' techniques. The key feature of our approach is to describe the evolution in terms of deviations from an equilibrium configuration. In contrast to standard perturbation analysis we keep all higher order terms in the evolution equations and thus obtain a fully non-linear description. The advantage of our scheme lies in the elimination of background terms from the equations and the associated numerical errors. The improvements thus achieved will be particularly significant in the study of mildly non-linear effects where the amplitude of the dynamic signal is small compared with the equilibrium values but large enough to warrant non-linear effects. We apply the new technique to the study of non-linear coupling of Eigenmodes and non-linear effects in the oscillations of marginally stable neutron stars. We find non-linear effects in low amplitude oscillations to be particularly pronounced in the range of modes with vanishing frequency which typically mark the onset of instability. (author)

Changes in myosin S1 orientation and force induced by a temperature increase.

Science.gov (United States)

Griffiths, Peter J; Bagni, Maria A; Colombini, Barbara; Amenitsch, Heinz; Bernstorff, Sigrid; Ashley, Christopher C; Cecchi, Giovanni; Ameritsch, Heinz

2002-04-16

Force generation in myosin-based motile systems is thought to result from an angular displacement of the myosin subfragment 1 (S1) tail domain with respect to the actin filament axis. In muscle, raised temperature increases the force generated by S1, implying a greater change in tail domain angular displacement. We used time-resolved x-ray diffraction to investigate the structural corollary of this force increase by measuring M3 meridional reflection intensity during sinusoidal length oscillations. This technique allows definition of S1 orientation with respect to the myofilament axis. M3 intensity changes were approximately sinusoid at low temperatures but became increasingly distorted as temperature was elevated, with the formation of a double intensity peak at maximum shortening. This increased distortion could be accounted for by assuming a shift in orientation of the tail domain of actin-bound S1 toward the orientation at which M3 intensity is maximal, which is consistent with a tail domain rotation model of force generation in which the tail approaches a more perpendicular projection from the thin filament axis at higher temperatures. In power stroke simulations, the angle between S1 tail mean position during oscillations and the position at maximum intensity decreased by 4.7 degrees, corresponding to a mean tail displacement toward the perpendicular of 0.73 nm for a temperature-induced force increase of 0.28 P(0) from 4 to 22 degrees C. Our findings suggest that at least 62% of crossbridge compliance is associated with the tail domain.

Use of an oscillation technique to measure effective cross-sections of fissionable samples in critical assemblies

International Nuclear Information System (INIS)

Tretiakoff, O.; Vidal, R.; Carre, J.C.; Robin, M.

1964-01-01

The authors describe the technique used to measure the effective absorption and neutron-yield cross-sections of a fissionable sample. These two values are determined by analysing the signals due to the variation in reactivity (over-all signal) and the local perturbation in the flux (local signal) produced by the oscillating sample. These signals are standardized by means of a set of samples containing quantities of fissionable material ( 235 U) and an absorber, boron, which are well known. The measurements are made for different neutron spectra characterized by lattice parameters which constitute the central zone within which the sample moves. This technique is used to study the effective cross-sections of uranium-plutonium alloys for different heavy-water and graphite lattices in the MINERVE and MARIUS critical assemblies. The same experiments are carried out on fuel samples of different irradiations in order to determine the evolution of effective cross-sections as a function of the spectrum and the irradiations. (authors) [fr

A hybrid firefly algorithm and pattern search technique for SSSC based power oscillation damping controller design

Directory of Open Access Journals (Sweden)

Srikanta Mahapatra

2014-12-01

Full Text Available In this paper, a novel hybrid Firefly Algorithm and Pattern Search (h-FAPS technique is proposed for a Static Synchronous Series Compensator (SSSC-based power oscillation damping controller design. The proposed h-FAPS technique takes the advantage of global search capability of FA and local search facility of PS. In order to tackle the drawback of using the remote signal that may impact reliability of the controller, a modified signal equivalent to the remote speed deviation signal is constructed from the local measurements. The performances of the proposed controllers are evaluated in SMIB and multi-machine power system subjected to various transient disturbances. To show the effectiveness and robustness of the proposed design approach, simulation results are presented and compared with some recently published approaches such as Differential Evolution (DE and Particle Swarm Optimization (PSO. It is observed that the proposed approach yield superior damping performance compared to some recently reported approaches.

Technique to measure contact angle of micro/nanodroplets using atomic force microscopy

International Nuclear Information System (INIS)

Jung, Yong Chae; Bhushan, Bharat

2008-01-01

Contact angle is the primary parameter that characterizes wetting; however, the measurement techniques have been limited to droplets with a diameter as low as about 50 μm. The authors developed an atomic force microscopy-based technique to measure the contact angle of micro- and nanodroplets deposited using a modified nanoscale dispensing tip. The obtained contact angle results were compared with those of a macrodroplet (2.1 mm diameter). It was found that the contact angle on various surfaces decreases with decreasing the droplet size

Western tropical Pacific multidecadal variability forced by the Atlantic multidecadal oscillation

Science.gov (United States)

Kucharski, F.; Sun, C.; Li, J.; Jin, F. F.; Kang, I. S.; Ding, R.

2017-12-01

Observational analysis suggests that the western tropical Pacific (WTP) sea surface temperature (SST) shows predominant variability over multidecadal time scales, which is unlikely to be explained by the Interdecadal Pacific Oscillation. Here we show that this variability is largely explained by the remote Atlantic multidecadal oscillation (AMO). A suite of Atlantic Pacemaker experiments successfully reproduces the WTP multidecadal variability and the AMO-WTP SST connection. The AMO warm SST anomaly generates an atmospheric teleconnection to the North Pacific, which weakens the Aleutian low and subtropical North Pacific westerlies. The wind changes induce a subtropical North Pacific SST warming through wind-evaporation-SST effect, and in response to this warming, the surface winds converge towards the subtropical North Pacific from the tropics, leading to anomalous cyclonic circulation and low pressure over the WTP region. The warm SST anomaly further develops due to the SST-sea level pressure-cloud-longwave radiation positive feedback. Our findings suggest that the Atlantic Ocean acts as a key pacemaker for the western Pacific decadal climate variability.

Torsional tapping atomic force microscopy for molecular resolution imaging of soft matter

Science.gov (United States)

Hobbs, Jamie; Mullin, Nic

2012-02-01

Despite considerable advances in image resolution on challenging, soft systems, a method for obtaining molecular resolution on `real' samples with significant surface roughness has remained elusive. Here we will show that a relatively new technique, torsional tapping AFM (TTAFM), is capable of imaging with resolution down to 3.7 Angrstrom on the surface of `bulk' polymer films [1]. In TTAFM T-shaped cantilevers are driven into torsional oscillation. As the tip is offset from the rotation axis this provides a tapping motion. Due to the high frequency and Q of the oscillation and relatively small increase in spring constant, improved cantilever dynamics and force sensitivity are obtained. As the tip offset from the torsional axis is relatively small (typically 25 microns), the optical lever sensitivity is considerably improved compared to flexural oscillation. Combined these give a reduction in noise floor by a factor of 12 just by changing the cantilever geometry. The ensuing low noise allows the use of ultra-sharp `whisker' tips with minimal blunting. As the cantilevers remain soft in the flexural axis, the force when imaging with error is also reduced, further protecting the tip. We will show that this combination allows routine imaging of the molecular structure of semicrystalline polymer films, including chain folds, loose loops and tie-chains in polyethylene, and the helical conformation of polypropylene within the crystal, using a standard, commercial AFM. [4pt] [1] N Mullin, JK Hobbs, PRL 107, 197801 (2011)

Oscillating shells: A model for a variable cosmic object

OpenAIRE

Nunez, Dario

1997-01-01

A model for a possible variable cosmic object is presented. The model consists of a massive shell surrounding a compact object. The gravitational and self-gravitational forces tend to collapse the shell, but the internal tangential stresses oppose the collapse. The combined action of the two types of forces is studied and several cases are presented. In particular, we investigate the spherically symmetric case in which the shell oscillates radially around a central compact object.

Oscillating field current drive for reversed field pinch discharges

International Nuclear Information System (INIS)

Schoenberg, K.F.; Gribble, R.F.; Baker, D.A.

1984-06-01

Oscillating Field Current Drive (OFCD), also known as F-THETA pumping, is a steady-state current-drive technique proposed for the Reversed Field Pinch (RFP). Unlike other current-drive techniques, which employ high-technology, invasive, and power intensive schemes using radio frequency or neutral particle injection, F-THETA pumping entails driving the toroidal and poloidal magnetic field circuits with low-frequency (audio) oscillating voltage sources. Current drive by this technique is a consequence of the strong nonlinear plasma coupling in the RFP. Because of its low frequency and efficient plasma coupling, F-THETA pumping shows excellent promise as a reactor-relevant current-drive technique. A conceptual and computational study of this concept, including its experimental and reactor relevance, is explored in this paper

On Interactions of Oscillation Modes for a Weakly Non-Linear Undamped Elastic Beam with AN External Force

Science.gov (United States)

BOERTJENS, G. J.; VAN HORSSEN, W. T.

2000-08-01

In this paper an initial-boundary value problem for the vertical displacement of a weakly non-linear elastic beam with an harmonic excitation in the horizontal direction at the ends of the beam is studied. The initial-boundary value problem can be regarded as a simple model describing oscillations of flexible structures like suspension bridges or iced overhead transmission lines. Using a two-time-scales perturbation method an approximation of the solution of the initial-boundary value problem is constructed. Interactions between different oscillation modes of the beam are studied. It is shown that for certain external excitations, depending on the phase of an oscillation mode, the amplitude of specific oscillation modes changes.

Cancellation of the centrifugal space-charge force

International Nuclear Information System (INIS)

Lee, E.P.

1990-01-01

The transverse dynamics of high-energy electrons confined in curved geometry are examined, including the effects of space-charge-induced fields. Attention is restricted to the centrifugal-space-charge force, which is the result of noncancellation of beam-induced transverse electric and magnetic fields in the curved geometry. This force is shown to be nearly cancelled in the evaluation of the horizontal tune and chromaticity by another, often overlooked term in the equation of motion. The additional term is the consequence of oscillations of the kinetic energy, which accompany betatron oscillations in the beam-induced electric potential. In curved geometry this term is of first order in the amplitude of the radial oscillation. A highly simplified system model is employed so that physical effects appear in as clear a form as possible. We assume azimuthal and median plane symmetry, static fields, and ultrarelativistic particle velocity (1/γ 2 ->0). (author) 9 refs

Flow over an inline oscillating circular cylinder in the wake of a stationary circular cylinder

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yang; Zhu, Keqiang, E-mail: zhukeqiang@nbu.edu.cn [Faculty of Maritime and Transportation, Ningbo University, Ningbo 315211 (China)

2017-02-15

Flow interference between an upstream stationary cylinder and an inline oscillating cylinder is studied with the lattice Boltzmann method. With a fixed Reynolds number Re  = 100 and pitch ratio L / D  = 4, the effects of oscillation amplitude A / D  = [0.25, 1] and frequency f {sub e}/ f {sub s} = [0.5, 2] are investigated. The wake response state is categorized into lock-in and non-lock-in. The lock-in zone in the bifurcation diagram of amplitude versus frequency is discontinuous. Response states of upstream and downstream wakes are similar under the conditions of small amplitude or low frequency. However, with large oscillating parameters, the two wakes are prone to be in different states as the flow field becomes irregular. Two distinct flow regimes have been identified, i.e., single-cylinder and two-cylinder shedding regimes. The presence of single-cylinder shedding regime is attributed to the low shedding frequency of the downstream cylinder at large amplitude. Hydrodynamic forces of the oscillating tandem system are discussed. The results reveal that forces on the two cylinders behave differently and that the absence of vortices in the gap flow significantly reduces the forces exerting on the tandem system. (paper)

Machine learning techniques for gait biometric recognition using the ground reaction force

CERN Document Server

Mason, James Eric; Woungang, Isaac

2016-01-01

This book focuses on how machine learning techniques can be used to analyze and make use of one particular category of behavioral biometrics known as the gait biometric. A comprehensive Ground Reaction Force (GRF)-based Gait Biometrics Recognition framework is proposed and validated by experiments. In addition, an in-depth analysis of existing recognition techniques that are best suited for performing footstep GRF-based person recognition is also proposed, as well as a comparison of feature extractors, normalizers, and classifiers configurations that were never directly compared with one another in any previous GRF recognition research. Finally, a detailed theoretical overview of many existing machine learning techniques is presented, leading to a proposal of two novel data processing techniques developed specifically for the purpose of gait biometric recognition using GRF. This book · introduces novel machine-learning-based temporal normalization techniques · bridges research gaps concerning the effect of ...

Self-similar oscillations of the Extrap pinch

International Nuclear Information System (INIS)

Tendler, M.

1987-11-01

The method of the dynamic stabilization is invoked to explain the enhanced stability of a Z-pinch in EXTRAP configuration. The oscillatory motion is assumed to be forced on EXTRAP due to self-similar oscillations of a Z-pinch. Using a scaling for the net energy loss with plasma density and temperature typical for divertor configurations, a new analytic, self-similar solution of the fluid equations is presented. Strongly unharmonic oscillations of the plasma parameters in the pinch arise. These results are used in a discussion on the stability of EXTRAP, considered as a system with a time dependent internal magnetic field. The effect of the dynamic stabilization is considered by taking estimates. (author)

Discrete oscillator design linear, nonlinear, transient, and noise domains

CERN Document Server

Rhea, Randall W

2014-01-01

Oscillators are an essential part of all spread spectrum, RF, and wireless systems, and today's engineers in the field need to have a firm grasp on how they are designed. Presenting an easy-to-understand, unified view of the subject, this authoritative resource covers the practical design of high-frequency oscillators with lumped, distributed, dielectric and piezoelectric resonators. Including numerous examples, the book details important linear, nonlinear harmonic balance, transient and noise analysis techniques. Moreover, the book shows you how to apply these techniques to a wide range of os

Oscillation of nested fullerenes (carbon onions) in carbon nanotubes

International Nuclear Information System (INIS)

Thamwattana, Ngamta; Hill, James M.

2008-01-01

Nested spherical fullerenes, which are sometimes referred to as carbon onions, of I h symmetries which have N(n) carbon atoms in the nth shell given by N(n) = 60n 2 are studied in this paper. The continuum approximation together with the Lennard-Jones potential is utilized to determine the resultant potential energy. High frequency nanoscale oscillators or gigahertz oscillators created from fullerenes and both single- and multi-walled carbon nanotubes have attracted much attention for a number of proposed applications, such as ultra-fast optical filters and ultra-sensitive nano-antennae that might impact on the development of computing and signalling nano-devices. Further, it is only at the nanoscale where such gigahertz frequencies can be achieved. This paper focuses on the interaction of nested fullerenes and the mechanics of such molecules oscillating in carbon nanotubes. Here we investigate such issues as the acceptance condition for nested fullerenes into carbon nanotubes, the total force and energy of the nested fullerenes, and the velocity and gigahertz frequency of the oscillating molecule. In particular, optimum nanotube radii are determined for which nested fullerenes oscillate at maximum velocity and frequency, which will be of considerable benefit for the design of future nano-oscillating devices

Adaptive elimination of synchronization in coupled oscillator

Science.gov (United States)

Zhou, Shijie; Ji, Peng; Zhou, Qing; Feng, Jianfeng; Kurths, Jürgen; Lin, Wei

2017-08-01

We present here an adaptive control scheme with a feedback delay to achieve elimination of synchronization in a large population of coupled and synchronized oscillators. We validate the feasibility of this scheme not only in the coupled Kuramoto’s oscillators with a unimodal or bimodal distribution of natural frequency, but also in two representative models of neuronal networks, namely, the FitzHugh-Nagumo spiking oscillators and the Hindmarsh-Rose bursting oscillators. More significantly, we analytically illustrate the feasibility of the proposed scheme with a feedback delay and reveal how the exact topological form of the bimodal natural frequency distribution influences the scheme performance. We anticipate that our developed scheme will deepen the understanding and refinement of those controllers, e.g. techniques of deep brain stimulation, which have been implemented in remedying some synchronization-induced mental disorders including Parkinson disease and epilepsy.

Adaptive elimination of synchronization in coupled oscillator

International Nuclear Information System (INIS)

Zhou, Shijie; Lin, Wei; Ji, Peng; Feng, Jianfeng; Zhou, Qing; Kurths, Jürgen

2017-01-01

We present here an adaptive control scheme with a feedback delay to achieve elimination of synchronization in a large population of coupled and synchronized oscillators. We validate the feasibility of this scheme not only in the coupled Kuramoto’s oscillators with a unimodal or bimodal distribution of natural frequency, but also in two representative models of neuronal networks, namely, the FitzHugh–Nagumo spiking oscillators and the Hindmarsh–Rose bursting oscillators. More significantly, we analytically illustrate the feasibility of the proposed scheme with a feedback delay and reveal how the exact topological form of the bimodal natural frequency distribution influences the scheme performance. We anticipate that our developed scheme will deepen the understanding and refinement of those controllers, e.g. techniques of deep brain stimulation, which have been implemented in remedying some synchronization-induced mental disorders including Parkinson disease and epilepsy. (paper)

Fluid-structure coupling for an oscillating hydrofoil

Science.gov (United States)

Münch, C.; Ausoni, P.; Braun, O.; Farhat, M.; Avellan, F.

2010-08-01

Fluid-structure investigations in hydraulic machines using coupled simulations are particularly time-consuming. In this study, an alternative method is presented that linearizes the hydrodynamic load of a rigid, oscillating hydrofoil. The hydrofoil, which is surrounded by incompressible, turbulent flow, is modeled with forced and free pitching motions, where the mean incidence angle is 0° with a maximum angle amplitude of 2°. Unsteady simulations of the flow, performed with ANSYS CFX, are presented and validated with experiments which were carried out in the EPFL High-Speed Cavitation Tunnel. First, forced motion is investigated for reduced frequencies ranging from 0.02 to 100. The hydrodynamic load is modeled as a simple combination of inertia, damping and stiffness effects. As expected, the potential flow analysis showed the added moment of inertia is constant, while the fluid damping and the fluid stiffness coefficients depend on the reduced frequency of the oscillation motion. Behavioral patterns were observed and two cases were identified depending on if vortices did or did not develop in the hydrofoil wake. Using the coefficients identified in the forced motion case, the time history of the profile incidence is then predicted analytically for the free motion case and excellent agreement is found for the results from coupled fluid-structure simulations. The model is validated and may be extended to more complex cases, such as blade grids in hydraulic machinery.

A Possible Mechanism for Driving Oscillations in Hot Giant Planets

Energy Technology Data Exchange (ETDEWEB)

Dederick, Ethan; Jackiewicz, Jason, E-mail: dederiej@nmsu.edu, E-mail: jasonj@nmsu.edu [New Mexico State University, Las Cruces, NM (United States)

2017-03-10

The κ -mechanism has been successful in explaining the origin of observed oscillations of many types of “classical” pulsating variable stars. Here we examine quantitatively if that same process is prominent enough to excite the potential global oscillations within Jupiter, whose energy flux is powered by gravitational collapse rather than nuclear fusion. Additionally, we examine whether external radiative forcing, i.e., starlight, could be a driver for global oscillations in hot Jupiters orbiting various main-sequence stars at defined orbital semimajor axes. Using planetary models generated by the Modules for Experiments in Stellar Astrophysics and nonadiabatic oscillation calculations, we confirm that Jovian oscillations cannot be driven via the κ -mechanism. However, we do show that, in hot Jupiters, oscillations can likely be excited via the suppression of radiative cooling due to external radiation given a large enough stellar flux and the absence of a significant oscillatory damping zone within the planet. This trend does not seem to be dependent on the planetary mass. In future observations, we can thus expect that such planets may be pulsating, thereby giving greater insight into the internal structure of these bodies.

A Possible Mechanism for Driving Oscillations in Hot Giant Planets

International Nuclear Information System (INIS)

Dederick, Ethan; Jackiewicz, Jason

2017-01-01

The κ -mechanism has been successful in explaining the origin of observed oscillations of many types of “classical” pulsating variable stars. Here we examine quantitatively if that same process is prominent enough to excite the potential global oscillations within Jupiter, whose energy flux is powered by gravitational collapse rather than nuclear fusion. Additionally, we examine whether external radiative forcing, i.e., starlight, could be a driver for global oscillations in hot Jupiters orbiting various main-sequence stars at defined orbital semimajor axes. Using planetary models generated by the Modules for Experiments in Stellar Astrophysics and nonadiabatic oscillation calculations, we confirm that Jovian oscillations cannot be driven via the κ -mechanism. However, we do show that, in hot Jupiters, oscillations can likely be excited via the suppression of radiative cooling due to external radiation given a large enough stellar flux and the absence of a significant oscillatory damping zone within the planet. This trend does not seem to be dependent on the planetary mass. In future observations, we can thus expect that such planets may be pulsating, thereby giving greater insight into the internal structure of these bodies.

Magnetic molecule on a microcantilever: quantum magnetomechanical oscillations.

Science.gov (United States)

Jaafar, Reem; Chudnovsky, E M

2009-06-05

We study the quantum dynamics of a system consisting of a magnetic molecule placed on a microcantilever. The amplitude and frequencies of the coupled magnetomechanical oscillations are computed. Parameter-free theory shows that the existing experimental techniques permit observation of the driven coupled oscillations of the spin and the cantilever, as well as of the splitting of the mechanical modes of the cantilever caused by spin tunneling.

Conventional and anomalous quantum Rabi oscillations in graphene

International Nuclear Information System (INIS)

Khan, Enamullah; Kumar, Vipin; Kumar, Upendra; Setlur, Girish S.

2014-01-01

We study the non linear response of graphene in presence of quantum field in two different regimes. Far from resonance, using our new technique asymptotic rotating wave approximation (ARWA), we obtained that the matter field interaction leads to the slow oscillations like conventional Rabi oscillations observed in conventional semiconductors using well known rotating wave approximation (RWA). The Rabi frequency obtained in both the regimes

Pure odd-order oscillators with constant excitation

Science.gov (United States)

Cveticanin, L.

2011-02-01

In this paper the excited vibrations of a truly nonlinear oscillator are analyzed. The excitation is assumed to be constant and the nonlinearity is pure (without a linear term). The mathematical model is a second-order nonhomogeneous differential equation with strong nonlinear term. Using the first integral, the exact value of period of vibration i.e., angular frequency of oscillator described with a pure nonlinear differential equation with constant excitation is analytically obtained. The closed form solution has the form of gamma function. The period of vibration depends on the value of excitation and of the order and coefficient of the nonlinear term. For the case of pure odd-order-oscillators the approximate solution of differential equation is obtained in the form of trigonometric function. The solution is based on the exact value of period of vibration. For the case when additional small perturbation of the pure oscillator acts, the so called 'Cveticanin's averaging method' for a truly nonlinear oscillator is applied. Two special cases are considered: one, when the additional term is a function of distance, and the second, when damping acts. To prove the correctness of the method the obtained results are compared with those for the linear oscillator. Example of pure cubic oscillator with constant excitation and linear damping is widely discussed. Comparing the analytically obtained results with exact numerical ones it is concluded that they are in a good agreement. The investigations reported in the paper are of special interest for those who are dealing with the problem of vibration reduction in the oscillator with constant excitation and pure nonlinear restoring force the examples of which can be found in various scientific and engineering systems. For example, such mechanical systems are seats in vehicles, supports for machines, cutting machines with periodical motion of the cutting tools, presses, etc. The examples can be find in electronics

Three-dimensional vortex-induced vibrations of supported pipes conveying fluid based on wake oscillator models

Science.gov (United States)

Wang, L.; Jiang, T. L.; Dai, H. L.; Ni, Q.

2018-05-01

The present study develops a new three-dimensional nonlinear model for investigating vortex-induced vibrations (VIV) of flexible pipes conveying internal fluid flow. The unsteady hydrodynamic forces associated with the wake dynamics are modeled by two distributed van der Pol wake oscillators. In particular, the nonlinear partial differential equations of motion of the pipe and the wake are derived, taking into account the coupling between the structure and the fluid. The nonlinear equations of motion for the coupled system are then discretized by means of the Galerkin technique, resulting in a high-dimensional reduced-order model of the system. It is shown that the natural frequencies for in-plane and out-of-plane motions of the pipe may be different at high internal flow velocities beyond the threshold of buckling instability. The orientation angle of the postbuckling configuration is time-varying due to the disturbance of hydrodynamic forces, thus yielding sometimes unexpected results. For a buckled pipe with relatively low cross-flow velocity, interestingly, examining the nonlinear dynamics of the pipe indicates that the combined effects of the cross-flow-induced resonance of the in-plane first mode and the internal-flow-induced buckling on the IL and CF oscillation amplitudes may be significant. For higher cross-flow velocities, however, the effect of internal fluid flow on the nonlinear VIV responses of the pipe is not pronounced.

CLIMATE CHANGE: LONG-TERM TRENDS AND SHORT-TERM OSCILLATIONS

Institute of Scientific and Technical Information of China (English)

GAO Xin-quan; ZHANG Xin; QIAN Wei-hong

2006-01-01

Identifying the Northern Hemisphere (NH) temperature reconstruction and instrumental data for the past 1000 years shows that climate change in the last millennium includes long-term trends and various oscillations. Two long-term trends and the quasi-70-year oscillation were detected in the global temperature series for the last 140 years and the NH millennium series. One important feature was emphasized that temperature decreases slowly but it increases rapidly based on the analysis of different series. Benefits can be obtained of climate change from understanding various long-term trends and oscillations. Millennial temperature proxies from the natural climate system and time series of nonlinear model system are used in understanding the natural climate change and recognizing potential benefits by using the method of wavelet transform analysis. The results from numerical modeling show that major oscillations contained in numerical solutions on the interdecadal timescale are consistent with that of natural proxies. It seems that these oscillations in the climate change are not directly linked with the solar radiation as an external forcing. This investigation may conclude that the climate variability at the interdecadal timescale strongly depends on the internal nonlinear effects in the climate system.

Experimental studies of neutrino oscillations

CERN Document Server

Kajita, Takaaki

2016-01-01

The 2015 Nobel Prize in physics has been awarded to Takaaki Kajita and Arthur McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass". Takaaki Kajita of Tokyo University is a Japanese physicist, known for neutrino experiments at the Kamiokande and its successor, Super-Kamiokande. This volume of collected works of Kajita on neutrino oscillations provides a good glimpse into as well as a record of the rise and the role of Asian research in the frontiers of neutrino physics. Japan is now a major force in the study of the 3 families of neutrinos. Much remains to be done to clarify the Dirac vs. Majorana nature of the neutrino, and the cosmological implications of the neutrino. The collected works of Kajita and his Super-Kamiokande group will leave an indelible foot-print in the history of big and better science.

Deterministic and stochastic control of chimera states in delayed feedback oscillator

Energy Technology Data Exchange (ETDEWEB)

Semenov, V. [Department of Physics, Saratov State University, Astrakhanskaya Str. 83, 410012 Saratov (Russian Federation); Zakharova, A.; Schöll, E. [Institut für Theoretische Physik, TU Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Maistrenko, Y. [Institute of Mathematics and Center for Medical and Biotechnical Research, NAS of Ukraine, Tereschenkivska Str. 3, 01601 Kyiv (Ukraine)

2016-06-08

Chimera states, characterized by the coexistence of regular and chaotic dynamics, are found in a nonlinear oscillator model with negative time-delayed feedback. The control of these chimera states by external periodic forcing is demonstrated by numerical simulations. Both deterministic and stochastic external periodic forcing are considered. It is shown that multi-cluster chimeras can be achieved by adjusting the external forcing frequency to appropriate resonance conditions. The constructive role of noise in the formation of a chimera states is shown.

Forces on particles in microstreaming flows

Science.gov (United States)

Hilgenfeldt, Sascha; Rallabandi, Bhargav; Thameem, Raqeeb

2015-11-01

In various microfluidic applications, vortical steady streaming from ultrasonically driven microbubbles is used in concert with a pressure-driven channel flow to manipulate objects. While a quantitative theory of this boundary-induced streaming is available, little work has been devoted to a fundamental understanding of the forces exerted on microparticles in boundary streaming flows, even though the differential action of such forces is central to applications like size-sensitive sorting. Contrary to other microfluidic sorting devices, the forces in bubble microstreaming act over millisecond times and micron length scales, without the need for accumulated deflections over long distances. Accordingly, we develop a theory of hydrodynamic forces on the fast time scale of bubble oscillation using the lubrication approximation, showing for the first time how particle displacements are rectified near moving boundaries over multiple oscillations in parallel with the generation of the steady streaming flow. The dependence of particle migration on particle size and the flow parameters is compared with experimental data. The theory is applicable to boundary streaming phenomena in general and demonstrates how particles can be sorted very quickly and without compromising device throughput. We acknowledge support by the National Science Foundation under grant number CBET-1236141.

Motion of a damped oscillating sphere as a function of the medium viscosity

International Nuclear Information System (INIS)

Mendoza-Arenas, J J; Perico, E L D; Fajardo, F

2010-01-01

In this paper, an experimental setup for undergraduate courses to study the damped harmonic motion of a sphere inside a fluid as a function of the medium viscosity is presented. To observe the dependence of the oscillation of the sphere on the medium viscosity, different concentrations of glycerin in water were used. The sphere is suspended on the end of a spring and its displacement is indirectly obtained using a force sensor. To describe the sphere motion, a drag force different from that given by Stokes' law is used. Our experimental results fit satisfactorily when semiempirical coefficients are introduced in the model. The frequency and relaxation time of the sphere oscillations diminish as the concentration of glycerin increases. Boundary effects due to the fluid container size are studied. We found that when the container size decreases the oscillations decay more rapidly due to a greater resistance to the motion of the sphere.

Noise-Induced Synchronization among Sub-RF CMOS Analog Oscillators for Skew-Free Clock Distribution

Science.gov (United States)

Utagawa, Akira; Asai, Tetsuya; Hirose, Tetsuya; Amemiya, Yoshihito

We present on-chip oscillator arrays synchronized by random noises, aiming at skew-free clock distribution on synchronous digital systems. Nakao et al. recently reported that independent neural oscillators can be synchronized by applying temporal random impulses to the oscillators [1], [2]. We regard neural oscillators as independent clock sources on LSIs; i. e., clock sources are distributed on LSIs, and they are forced to synchronize through the use of random noises. We designed neuron-based clock generators operating at sub-RF region (CMOS implementation with 0.25-μm CMOS parameters. Through circuit simulations, we demonstrate that i) the clock generators are certainly synchronized by pseudo-random noises and ii) clock generators exhibited phase-locked oscillations even if they had small device mismatches.

Impedance-Based Cable Force Monitoring in Tendon-Anchorage Using Portable PZT-Interface Technique

Directory of Open Access Journals (Sweden)

Thanh-Canh Huynh

2014-01-01

Full Text Available In this paper, a portable PZT interface for tension force monitoring in the cable-anchorage subsystem is developed. Firstly, the theoretical background of the impedance-based method is presented. A few damage evaluation approaches are outlined to quantify the variation of impedance signatures. Secondly, a portable PZT interface is designed to monitor impedance signatures from the cable-anchorage subsystem. One degree-of-freedom analytical model of the PZT interface is established to explain how to represent the loss of cable force from the change in the electromechanical impedance of the PZT interface as well as reducing the sensitive frequency band by implementing the interface device. Finally, the applicability of the proposed PZT-interface technique is experimentally evaluated for cable force-loss monitoring in a lab-scaled test structure.

Circuit oscillations in odor perception and memory.

Science.gov (United States)

Kay, Leslie M

2014-01-01

Olfactory system neural oscillations as seen in the local field potential have been studied for many decades. Recent research has shown that there is a functional role for the most studied gamma oscillations (40-100Hz in rats and mice, and 20Hz in insects), without which fine odor discrimination is poor. When these oscillations are increased artificially, fine discrimination is increased, and when rats learn difficult and highly overlapping odor discriminations, gamma is increased in power. Because of the depth of study on this oscillation, it is possible to point to specific changes in neural firing patterns as represented by the increase in gamma oscillation amplitude. However, we know far less about the mechanisms governing beta oscillations (15-30Hz in rats and mice), which are best associated with associative learning of responses to odor stimuli. These oscillations engage every part of the olfactory system that has so far been tested, plus the hippocampus, and the beta oscillation frequency band is the one that is most reliably coherent with other regions during odor processing. Respiratory oscillations overlapping with the theta frequency band (2-12Hz) are associated with odor sniffing and normal breathing in rats. They also show coupling in some circumstances between olfactory areas and rare coupling between the hippocampus and olfactory bulb. The latter occur in specific learning conditions in which coherence strength is negatively or positively correlated with performance, depending on the task. There is still much to learn about the role of neural oscillations in learning and memory, but techniques that have been brought to bear on gamma oscillations (current source density, computational modeling, slice physiology, behavioral studies) should deliver much needed knowledge of these events. © 2014 Elsevier B.V. All rights reserved.

Principle and performance of the transverse oscillation vector velocity technique in medical ultrasound

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt; Pihl, Michael Johannes; Udesen, Jesper

2010-01-01

Medical ultrasound systems measure the blood velocity by tracking the blood cells motion along the ultrasound field. The is done by pulsing in the same direction a number of times and then find e.q. the shift in phase between consecutive pulses. Properly normalized this is directly proportional...... a double oscillating field. A special estimator is then used for finding both the axial and lateral velocity component, so that both magnitude and phase can be calculated. The method for generating double oscillating ultrasound fields and the special estimator are described and its performance revealed...

Numerical simulation on quantum turbulence created by an oscillating object

Energy Technology Data Exchange (ETDEWEB)

Fujiyama, S; Tsubota, M [Department of Physics, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka City, Osaka (Japan)], E-mail: fujiyama@sci.osaka-cu.ac.jp

2009-02-01

We have conducted a numerical simulation of vortex dynamics in superfluid {sup 4}He in the presence of an oscillating sphere. The experiment on a vibrating wire that measured the transition from laminar to turbulent flow is modelled in our simulations. The simulation exhibits the details of vortex growth by the oscillating sphere. Our result also shows that a more realistic modelling may change the destiny of the vortex rings detached from the sphere. We have evaluated the force driven by the sphere in the simulation and have confirmed the onset of the quantum turbulence.

Free Fall and Harmonic Oscillations: Analyzing Trampoline Jumps

Science.gov (United States)

Pendrill, Ann-Marie; Eager, David

2015-01-01

Trampolines can be found in many gardens and also in some playgrounds. They offer an easily accessible vertical motion that includes free fall. In this work, the motion on a trampoline is modelled by assuming a linear relation between force and deflection, giving harmonic oscillations for small amplitudes. An expression for the cycle-time is…

Waves and oscillations in plasma crystals

International Nuclear Information System (INIS)

Piel, A; Homann, A; Klindworth, M; Melzer, A; Zafiu, C; Nosenko, V; Goree, J

2003-01-01

An overview of the properties of plasma crystals and clusters is given with emphasis on oscillations of particles in the plasma trap, instabilities associated with the solid-liquid phase transition and the propagation of waves. It is demonstrated how laser manipulation can be used to stimulate particle motion and waves. From characteristic resonance frequencies and from wave dispersion the particle charge and shielding length parameters, which determine the interparticle forces, can be quantitatively measured

Texture-induced modulations of friction force: the fingerprint effect.

Science.gov (United States)

Wandersman, E; Candelier, R; Debrégeas, G; Prevost, A

2011-10-14

Modulations of the friction force in dry solid friction are usually attributed to macroscopic stick-slip instabilities. Here we show that a distinct, quasistatic mechanism can also lead to nearly periodic force oscillations during sliding contact between an elastomer patterned with parallel grooves, and abraded glass slides. The dominant oscillation frequency is set by the ratio between the sliding velocity and the grooves period. A model is derived which quantitatively captures the dependence of the force modulations amplitude with the normal load, the grooves period, and the slides roughness characteristics. The model's main ingredient is the nonlinearity of the friction law. Since such nonlinearity is ubiquitous for soft solids, this "fingerprint effect" should be relevant to a large class of frictional configurations and have important consequences in human digital touch.

Damping of Crank–Nicolson error oscillations

DEFF Research Database (Denmark)

Britz, Dieter; Østerby, Ole; Strutwolf, J.

2003-01-01

The Crank–Nicolson (CN) simulation method has an oscillatory response to sharp initial transients. The technique is convenient but the oscillations make it less popular. Several ways of damping the oscillations in two types of electrochemical computations are investigated. For a simple one......-dimensional system with an initial singularity, subdivision of the first time interval into a number of equal subintervals (the Pearson method) works rather well, and so does division with exponentially increasing subintervals, where however an optimum expansion parameter must be found. This method can...... be computationally more expensive with some systems. The simple device of starting with one backward implicit (BI, or Laasonen) step does damp the oscillations, but not always sufficiently. For electrochemical microdisk simulations which are two-dimensional in space and using CN, the use of a first BI step is much...

The effect of loss of immunity on noise-induced sustained oscillations in epidemics.

Science.gov (United States)

Chaffee, J; Kuske, R

2011-11-01

The effect of loss of immunity on sustained population oscillations about an endemic equilibrium is studied via a multiple scales analysis of a SIRS model. The analysis captures the key elements supporting the nearly regular oscillations of the infected and susceptible populations, namely, the interaction of the deterministic and stochastic dynamics together with the separation of time scales of the damping and the period of these oscillations. The derivation of a nonlinear stochastic amplitude equation describing the envelope of the oscillations yields two criteria providing explicit parameter ranges where they can be observed. These conditions are similar to those found for other applications in the context of coherence resonance, in which noise drives nearly regular oscillations in a system that is quiescent without noise. In this context the criteria indicate how loss of immunity and other factors can lead to a significant increase in the parameter range for prevalence of the sustained oscillations, without any external driving forces. Comparison of the power spectral densities of the full model and the approximation confirms that the multiple scales analysis captures nonlinear features of the oscillations.

The fractional oscillator process with two indices

International Nuclear Information System (INIS)

Lim, S C; Teo, L P

2009-01-01

We introduce a new fractional oscillator process which can be obtained as a solution of a stochastic differential equation with two fractional orders. Basic properties such as fractal dimension and short-range dependence of the process are studied by considering the asymptotic properties of its covariance function. By considering the fractional oscillator process as the velocity of a diffusion process, we derive the corresponding diffusion constant, fluctuation-dissipation relation and mean-square displacement. The fractional oscillator process can also be regarded as a one-dimensional fractional Euclidean Klein-Gordon field, which can be obtained by applying the Parisi-Wu stochastic quantization method to a nonlocal Euclidean action. The Casimir energy associated with the fractional field at positive temperature is calculated by using the zeta function regularization technique

Spatial xenon oscillation control with expert systems

International Nuclear Information System (INIS)

Alten, S.; Danofsky, R.A.

1993-01-01

Spatial power oscillations were attributed to the xenon transients in a reactor core in 1958 by Randall and St. John. These transients are usually initiated by a local reactivity insertion and lead to divergent axial flux oscillations in the core at constant power. Several heuristic manual control strategies and automatic control methods were developed to damp the xenon oscillations at constant power operations. However, after the load-follow operation of the reactors became a necessity of life, a need for better control strategies arose. Even though various advanced control strategies were applied to solve the xenon oscillation control problem for the load-follow operation, the complexity of the system created difficulties in modeling. The strong nonlinearity of the problem requires highly sophisticated analytical approaches that are quite inept for numerical solutions. On the other hand, the complexity of a system and heuristic nature of the solutions are the basic reasons for using artificial intelligence techniques such as expert systems

HYDRODYNAMICS OF OSCILLATING WING ON THE PITCH ANGLE

Directory of Open Access Journals (Sweden)

Vitalii Korobov

2017-07-01

Full Text Available Purpose: research of the hydrodynamic characteristics of a wing in a nonstationary stream. Methods: The experimental studies of the hydrodynamic load acting on the wing of 1.5 elongation, wich harmonically oscillated respect to the transversal axis in the frequency range of 0.2-2.5 Hz. The flow speed in the hydrodynamic tunnel ranged of 0.2-1.5 m/s. Results: The instantaneous values of the coefficients of lift and drag / thrust on the pitch angle at unsteady flow depends on the Strouhal number.Discussion: with increasing oscillation frequency coefficients of hydrodynamic force components significantly higher than the data for the stationary blowing out of the wing.

Narrow linewidth pulsed optical parametric oscillator

Indian Academy of Sciences (India)

Tunable narrow linewidth radiation by optical parametric oscillation has many applications, particularly in spectroscopic investigation. In this paper, different techniques such as injection seeding, use of spectral selecting element like grating, grating and etalon in combination, grazing angle of incidence, entangled cavity ...

Ratchet baryogenesis and an analogy with the forced pendulum

Science.gov (United States)

Bamba, Kazuharu; Barrie, Neil D.; Sugamoto, Akio; Takeuchi, Tatsu; Yamashita, Kimiko

2018-06-01

A new scenario of baryogenesis via the ratchet mechanism is proposed based on an analogy with the forced pendulum. The oscillation of the inflaton field during the reheating epoch after inflation plays the role of the driving force, while the phase 𝜃 of a scalar baryon field (a complex scalar field with baryon number) plays the role of the angle of the pendulum. When the inflaton is coupled to the scalar baryon, the behavior of the phase 𝜃 can be analogous to that of the angle of the forced pendulum. If the oscillation of the driving force is adjusted to the pendulum’s motion, a directed rotation of the pendulum is obtained with a nonvanishing value of 𝜃˙, which models successful baryogenesis since 𝜃˙ is proportional to the baryon number density. Similar ratchet models which lead to directed motion have been used in the study of molecular motors in biology. There, the driving force is supplied by chemical reactions, while in our scenario this role is played by the inflaton during the reheating epoch.

A non-orthogonal harmonic-oscillator basis for three-body problems

International Nuclear Information System (INIS)

Agrello, D.A.; Aguilera-Navarro, V.C.; Chacon, E.

1979-01-01

A set of harmonic-oscillator states suitable for the representation of the wave function of the bound states of a system of three identical particles, is presented. As an illustration of the possibilities of the states defined in this paper, they are applied in a variational determination of the lowest symmetric S state of 12 C, in the model of three structureless α particles interacting through the Coulomb force plus a phenomenological two-body force. (author) [pt

Transient and Steady-State Responses of an Asymmetric Nonlinear Oscillator

Directory of Open Access Journals (Sweden)

Alex Elías-Zúñiga

2013-01-01

oscillator that describes the motion of a damped, forced system supported symmetrically by simple shear springs on a smooth inclined bearing surface. We also use the percentage overshoot value to study the influence of damping and nonlinearity on the transient and steady-state oscillatory amplitudes.

Analytical solution of strongly nonlinear Duffing oscillators

OpenAIRE

El-Naggar, A.M.; Ismail, G.M.

2016-01-01

In this paper, a new perturbation technique is employed to solve strongly nonlinear Duffing oscillators, in which a new parameter α=α(ε)α=α(ε) is defined such that the value of α is always small regardless of the magnitude of the original parameter εε. Therefore, the strongly nonlinear Duffing oscillators with large parameter ε are transformed into a small parameter system with respect to αα. Approximate solution obtained by the present method is compared with the solution of energy balance m...

Quantum oscillators in the canonical coherent states

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, R. de Lima [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Lima, A.F. de; Ferreira, K. de Araujo [Paraiba Univ., Campina Grande, PB (Brazil). Dept. de Fisica; Vaidya, A.N. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Fisica

2001-11-01

The main characteristics of the quantum oscillator coherent states including the two-particle Calogero interaction are investigated. We show that these Calogero coherent states are the eigenstates of the second-order differential annihilation operator which is deduced via Wigner-Heisenberg algebraic technique and correspond exactly to the pure uncharged-bosonic states. They posses the important properties of non-orthogonality and completeness. The minimum uncertainty relation for the Wigner oscillator coherent states are investigated. New sets of even and odd coherent states are point out. (author)

Tuning the synchronization of a network of weakly coupled self-oscillating gels via capacitors

Science.gov (United States)

Fang, Yan; Yashin, Victor V.; Dickerson, Samuel J.; Balazs, Anna C.

2018-05-01

We consider a network of coupled oscillating units, where each unit comprises a self-oscillating polymer gel undergoing the Belousov-Zhabotinsky (BZ) reaction and an overlaying piezoelectric (PZ) cantilever. Through chemo-mechano-electrical coupling, the oscillations of the networked BZ-PZ units achieve in-phase or anti-phase synchronization, enabling, for example, the storage of information within the system. Herein, we develop numerical and computational models to show that the introduction of capacitors into the BZ-PZ system enhances the dynamical behavior of the oscillating network by yielding additional stable synchronization modes. We specifically show that the capacitors lead to a redistribution of charge in the system and alteration of the force that the PZ cantilevers apply to the underlying gel. Hence, the capacitors modify the strength of the coupling between the oscillators in the network. We utilize a linear stability analysis to determine the phase behavior of BZ-PZ networks encompassing different capacitances, force polarities, and number of units and then verify our findings with numerical simulations. Thus, through analytical calculations and numerical simulations, we determine the impact of the capacitors on the existence of the synchronization modes, their stability, and the rate of synchronization within these complex dynamical systems. The findings from our study can be used to design robotic materials that harness the materials' intrinsic, responsive properties to perform such functions as sensing, actuation, and information storage.

Enhancement of multitasking performance and neural oscillations by transcranial alternating current stimulation

NARCIS (Netherlands)

Hsu, W.Y.; Zanto, T.P.; van Schouwenburg, M.R.; Gazzaley, A.

2017-01-01

Multitasking is associated with the generation of stimulus-locked theta (4–7 Hz) oscillations arising from prefrontal cortex (PFC). Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that influences endogenous brain oscillations. Here, we investigate

Avoidance of transmission line pressure oscillations in discrete hydraulic systems – by shaping of valve opening characteristics

DEFF Research Database (Denmark)

Hansen, Anders Hedegaard; Pedersen, Henrik C.; Bech, Michael Møller

2015-01-01

The architecture of multi pressure line discrete fluid power force systems imposes rapid pressure shifts in the actuator volumes. These fast shifts between pressure levels often introduce pressure oscillations in the actuator chamber and connecting pipes. The topic of this paper is to perform...... pressure shifts by changing the connection between various fixed pressure lines without introducing significant pressure oscillation. As a case study a discrete force system is utilised is a Power Take Off(PTO) system of a wave energy converter. Four pressure shifting algorithms are proposed...

A low cost, printed microwave based level sensor with integrated oscillator readout circuitry

KAUST Repository

Karimi, Muhammad Akram

2017-10-24

This paper presents an extremely low cost, tube conformable, printed T-resonator based microwave level sensor, whose resonance frequency shifts by changing the level of fluids inside the tube. Printed T-resonator forms the frequency selective element of the tunable oscillator. Unlike typical band-pass resonators, T-resonator has a band-notch characteristics because of which it has been integrated with an unstable amplifying unit having negative resistance in the desired frequency range. Magnitude and phase of input reflection coefficient of the transistor has been optimized over the desired frequency range. Phase flattening technique has been introduced to maximize the frequency shift of the oscillator. With the help of this technique, we were able to enhance the percentage tuning of the oscillator manifolds which resulted into a level sensor with higher sensitivity. The interface level of fluids (oil and water in our case) causes a relative change in oscillation frequency by more than 50% compared to maximum frequency shift of 8% reported earlier with dielectric tunable oscillators.

Phase-space treatment of the driven quantum harmonic oscillator

Indian Academy of Sciences (India)

A recent phase-space formulation of quantum mechanics in terms of the Glauber coherent states is applied to study the interaction of a one-dimensional harmonic oscillator with an arbitrary time-dependent force. Wave functions of the simultaneous values of position q and momentum p are deduced, which in turn give the ...

Correlation to predict heat transfer of an oscillating loop heat pipe consisting of three interconnected columns

International Nuclear Information System (INIS)

Arslan, Goekhan; Ozdemir, Mustafa

2008-01-01

In this paper, heat transfer in an oscillating loop heat pipe is investigated experimentally. The oscillation of the liquid columns at the evaporator and condenser sections of the heat pipe are driven by gravitational force and the phase lag between evaporation and condensation because the dimensions of the heat pipe are large enough to neglect the effect of capillary forces. The overall heat transfer coefficient based on the temperature difference between the evaporator and condenser surfaces is introduced by a correlation function of dimensionless numbers such as kinetic Reynolds number, c p ΔT/h fg and the geometric parameters

Unified Power Flow Controller Placement to Improve Damping of Power Oscillations

OpenAIRE

M. Salehi; A. A. Motie Birjandi; F. Namdari

2015-01-01

Weak damping of low frequency oscillations is a frequent phenomenon in electrical power systems. These frequencies can be damped by power system stabilizers. Unified power flow controller (UPFC), as one of the most important FACTS devices, can be applied to increase the damping of power system oscillations and the more effect of this controller on increasing the damping of oscillations depends on its proper placement in power systems. In this paper, a technique based on controllability is pro...

PERFORMANCE IMPROVEMENT OF A CHEMICAL REACTOR BY NONLINEAR NATURAL OSCILLATIONS

NARCIS (Netherlands)

RAY, AK

1995-01-01

The dynamic behaviour of two coupled continuous stirred tank reactors in sequence is studied when the first reactor is being operated under limit cycle regimes producing self-sustained natural oscillations. The periodic output from the first reactor is then used as a forced input into the second

Parametric spatiotemporal oscillation in reaction-diffusion systems.

Science.gov (United States)

Ghosh, Shyamolina; Ray, Deb Shankar

2016-03-01

We consider a reaction-diffusion system in a homogeneous stable steady state. On perturbation by a time-dependent sinusoidal forcing of a suitable scaling parameter the system exhibits parametric spatiotemporal instability beyond a critical threshold frequency. We have formulated a general scheme to calculate the threshold condition for oscillation and the range of unstable spatial modes lying within a V-shaped region reminiscent of Arnold's tongue. Full numerical simulations show that depending on the specificity of nonlinearity of the models, the instability may result in time-periodic stationary patterns in the form of standing clusters or spatially localized breathing patterns with characteristic wavelengths. Our theoretical analysis of the parametric oscillation in reaction-diffusion system is corroborated by full numerical simulation of two well-known chemical dynamical models: chlorite-iodine-malonic acid and Briggs-Rauscher reactions.

Electroacoustic oscillations in the LEP SC. cavities

CERN Document Server

Boussard, Daniel; Tückmantel, Joachim

1996-01-01

The LEP superconducting cavities have been plagued by electroacoustic oscillations. Tests have been done to eliminate these by a special feed-back loop in the tuning circuit as well as a feed-forward path, but they could only be eliminated safely up to the design field by running the cavities close to tune neglecting beam-loading compensation. This technique proved successful during the first LEP2 test run at 70 GeV. The mechanism and essential parameters driving these oscillations have been analysed as well as the corresponding stronger loading of the power coupler.

Regular and chaotic behaviors of plasma oscillations modeled by a modified Duffing equation

International Nuclear Information System (INIS)

Enjieu Kadji, H.G.; Chabi Orou, J.B.; Woafo, P.; Abdus Salam International Centre for Theoretical Physics, Trieste

2005-07-01

The regular and chaotic behavior of plasma oscillations governed by a modified Duffing equation is studied. The plasma oscillations are described by a nonlinear differential equation of the form x + w 0 2 x + βx 2 + αx 3 = 0 which is similar to a Duffing equation. By focusing on the quadratic term, which is mainly the term modifying the Duffing equation, the harmonic balance method and the fourth order Runge-Kutta algorithm are used to derive regular and chaotic motions respectively. A strong chaotic behavior exhibited by the system in that event when the system is subjected to an external periodic forcing oscillation is reported as β varies. (author)

Noncommuting limits of oscillator wave functions

International Nuclear Information System (INIS)

Daboul, J.; Pogosyan, G. S.; Wolf, K. B.

2007-01-01

Quantum harmonic oscillators with spring constants k > 0 plus constant forces f exhibit rescaled and displaced Hermite-Gaussian wave functions, and discrete, lower bound spectra. We examine their limits when (k, f) → (0, 0) along two different paths. When f → 0 and then k → 0, the contraction is standard: the system becomes free with a double continuous, positive spectrum, and the wave functions limit to plane waves of definite parity. On the other hand, when k → 0 first, the contraction path passes through the free-fall system, with a continuous, nondegenerate, unbounded spectrum and displaced Airy wave functions, while parity is lost. The subsequent f → 0 limit of the nonstandard path shows the dc hysteresis phenomenon of noncommuting contractions: the lost parity reappears as an infinitely oscillating superposition of the two limiting solutions that are related by the symmetry

Estimating bridge stiffness using a forced-vibration technique for timber bridge health monitoring

Science.gov (United States)

James P. Wacker; Xiping Wang; Brian Brashaw; Robert J. Ross

2006-01-01

This paper describes an effort to refine a global dynamic testing technique for evaluating the overall stiffness of timber bridge superstructures. A forced vibration method was used to measure the frequency response of several simple-span, sawn timber beam (with plank deck) bridges located in St. Louis County, Minnesota. Static load deflections were also measured to...

Quenching oscillating behaviors in fractional coupled Stuart-Landau oscillators

Science.gov (United States)

Sun, Zhongkui; Xiao, Rui; Yang, Xiaoli; Xu, Wei

2018-03-01

Oscillation quenching has been widely studied during the past several decades in fields ranging from natural sciences to engineering, but investigations have so far been restricted to oscillators with an integer-order derivative. Here, we report the first study of amplitude death (AD) in fractional coupled Stuart-Landau oscillators with partial and/or complete conjugate couplings to explore oscillation quenching patterns and dynamics. It has been found that the fractional-order derivative impacts the AD state crucially. The area of the AD state increases along with the decrease of the fractional-order derivative. Furthermore, by introducing and adjusting a limiting feedback factor in coupling links, the AD state can be well tamed in fractional coupled oscillators. Hence, it provides one an effective approach to analyze and control the oscillating behaviors in fractional coupled oscillators.

Bifurcations and Crises in a Shape Memory Oscillator

Directory of Open Access Journals (Sweden)

Luciano G. Machado

2004-01-01

Full Text Available The remarkable properties of shape memory alloys have been motivating the interest in applications in different areas varying from biomedical to aerospace hardware. The dynamical response of systems composed by shape memory actuators presents nonlinear characteristics and a very rich behavior, showing periodic, quasi-periodic and chaotic responses. This contribution analyses some aspects related to bifurcation phenomenon in a shape memory oscillator where the restitution force is described by a polynomial constitutive model. The term bifurcation is used to describe qualitative changes that occur in the orbit structure of a system, as a consequence of parameter changes, being related to chaos. Numerical simulations show that the response of the shape memory oscillator presents period doubling cascades, direct and reverse, and crises.

Enthalpy of sublimation as measured using a silicon oscillator

Science.gov (United States)

Shakeel, Hamza; Pomeroy, J. M.

In this study, we report the enthalpy of sublimation of common gases (nitrogen, oxygen, argon, carbon dioxide, neon, krypton, xenon, and water vapor) using a large area silicon oscillator with a sub-ng (~0.027 ng/cm2) mass sensitivity. The double paddle oscillator design enables high frequency stability (17 ppb) at cryogenic temperatures and provides a consistent technique for enthalpy measurements. The enthalpies of sublimation are derived from the rate of mass loss during programmed thermal desorption and are detected as a change in the resonance frequency of the self-tracking oscillator. These measured enthalpy values show excellent agreement with the accepted literature values.

Lepton Flavorful Fifth Force and Depth-Dependent Neutrino Matter Interactions

Energy Technology Data Exchange (ETDEWEB)

Wise, Mark B. [Caltech; Zhang, Yue [Northwestern U.

2018-03-01

We consider a fifth force to be an interaction that couples to matter with a strength that grows with the number of atoms. In addition to competing with the strength of gravity a fifth force can give rise to violations of the equivalence principle. Current long range constraints on the strength and range of fifth forces are very impressive. Amongst possible fifth forces are those that couple to lepton flavorful charges $L_e-L_{\\mu}$ or $L_e-L_{\\tau}$. They have the property that their range and strength are also constrained by neutrino interactions with matter. In this brief note we review the existing constraints on the allowed parameter space in gauged $U(1)_{L_e-L_{\\mu}, L_{\\tau}}$. We find two regions where neutrino oscillation experiments are at the frontier of probing such a new force. In particular, there is an allowed range of parameter space where neutrino matter interactions relevant for long baseline oscillation experiments depend on the depth of the neutrino beam below the surface of the earth.

Transverse acoustic forcing of a round hydrodynamically self-excited jet

Science.gov (United States)

Kushwaha, Abhijit Kumar; Mazur, Marek; Worth, Nicholas; Dawson, James; Li, Larry K. B.

2017-11-01

Hydrodynamically self-excited jets can readily synchronize with longitudinal acoustic forcing, but their response to transverse acoustic forcing is less clear. In this experimental study, we apply transverse acoustic forcing to an axisymmetric low-density jet at frequencies around its natural global frequency. We place the jet in a rectangular box containing two loudspeakers, one at each end, producing nominally one-dimensional standing pressure waves. By traversing the jet across this box, we subject it to a range of acoustic modes, from purely longitudinal (streamwise) modes at the pressure anti-node to purely transverse (cross-stream) modes at the pressure node. Using time-resolved Background-Oriented Schlieren (BOS) imaging and hot-wire anemometry, we characterize the jet response for different forcing frequencies, amplitudes and mode shapes, providing new insight into the way transverse acoustic oscillations interact with axisymmetric hydrodynamic oscillations. This work was supported by the Research Grants Council of Hong Kong (Project No. 16235716 and 26202815).

The origin of star-shaped oscillations of Leidenfrost drops

Science.gov (United States)

Ma, Xiaolei; Burton, Justin C.

We experimentally investigate the oscillations of Leidenfrost drops of water, liquid nitrogen, ethanol, methanol, acetone and isopropyl alcohol. The drops levitate on a cushion of evaporated vapor over a hot, curved surface which keeps the drops stationary. We observe star-shaped modes along the periphery of the drop, with mode numbers n = 2 to 13. The number of observed modes is sensitive to the properties of the liquid. The pressure oscillation frequency in the vapor layer under the drop is approximately twice that of the drop frequency, which is consistent with a parametric forcing mechanism. However, the Rayleigh and thermal Marangoni numbers are of order 10,000, indicating that convection should play a dominating role as well. Surprisingly, we find that the wavelength and frequency of the oscillations only depend on the thickness of the liquid, which is twice the capillary length, and do not depend on the mode number, substrate temperature, or the substrate curvature. This robust behavior suggests that the wavelength for the oscillations is set by thermal convection inside the drop, and is less dependent on the flow in the vapor layer under the drop

Atomic Force Microscopy Techniques for Nanomechanical Characterization: A Polymeric Case Study

Science.gov (United States)

Reggente, Melania; Rossi, Marco; Angeloni, Livia; Tamburri, Emanuela; Lucci, Massimiliano; Davoli, Ivan; Terranova, Maria Letizia; Passeri, Daniele

2015-04-01

Atomic force microscopy (AFM) is a versatile tool to perform mechanical characterization of surface samples at the nanoscale. In this work, we review two of such methods, namely contact resonance AFM (CR-AFM) and torsional harmonics AFM (TH-AFM). First, such techniques are illustrated and their applicability on materials with elastic moduli in different ranges are discussed, together with their main advantages and limitations. Then, a case study is presented in which we report the mechanical characterization using both CR-AFM and TH-AFM of polyaniline and polyaniniline doped with nanodiamond particles tablets prepared by a pressing process. We determined the indentation modulus values of their surfaces, which were found in fairly good agreement, thus demonstrating the accuracy of the techniques. Finally, the determined surface elastic moduli have been compared with the bulk ones measured through standard indentation testing.

Decadal variability of drought conditions over the southern part of Europe based on Principal Oscillation Pattern Analysis

Science.gov (United States)

Ionita-Scholz, Monica; Tallaksen, Lena M.; Scholz, Patrick

2017-04-01

This study introduces a novel method of estimating the decay time, mean period and forcing statistics of drought conditions over large spatial domains, demonstrated here for southern part of Europe (10°E - 40°E, 35°N - 50°N). It uses a two-dimensional stochastically forced damped linear oscillator model with the model parameters estimated from a Principal Oscillation Pattern (POP) analysis and associated observed power spectra. POP is a diagnostic technique that aims to derive the space-time characteristics of a data set objectively. This analysis is performed on an extended observational time series of 114 years (1902 - 2015) of the Standardized Precipitation Evapotranspiration Index for an accumulation period of 12 months (SPEI12), based on the Climate Research Unit (CRU TS v. 3.24) data set. The POP analysis reveals four exceptionally stable modes of variability, which together explain more than 62% of the total explained variance. The most stable POP mode, which explains 16.3% of the total explained variance, is characterized by a period of oscillation of 14 years and a decay time of 31 years. The real part of POP1 is characterized by a monopole-like structure with the highest loadings over Portugal, western part of Spain and Turkey. The second stable mode, which explains 15.9% of the total explained variance, is characterized by a period of oscillation of 20 years and a decay time of 26.4 years. The spatial structure of the real part of POP2 has a dipole-like structure with the highest positive loadings over France, southern Germany and Romania and negative loadings over southern part of Spain. The third POP mode, in terms of stability, explains 14.0% of the total variance and is characterized by a period of oscillation of 33 years and a decay time of 43.5 years. The real part of POP3 is characterized by negative loadings over the eastern part of Europe and positive loadings over Turkey. The fourth stable POP mode, explaining 15.5% of the total variance

Oscillators and Eigenvalues

DEFF Research Database (Denmark)

Lindberg, Erik

1997-01-01

In order to obtain insight in the nature of nonlinear oscillators the eigenvalues of the linearized Jacobian of the differential equations describing the oscillator are found and displayed as functions of time. A number of oscillators are studied including Dewey's oscillator (piecewise linear wit...... with negative resistance), Kennedy's Colpitts-oscillator (with and without chaos) and a new 4'th order oscillator with hyper-chaos....

An Introduction to Waves and Oscillations in the Sun

CERN Document Server

Narayanan, A Satya

2013-01-01

Astrophysicists and others studying the Sun will find this expansive coverage of what we know about waves and oscillations in our nearest star an informative introduction to a hot contemporary topic. After a section summarizing the Sun's physical characteristics, the volume moves on to explore the basics of electrodynamics, which in turn facilitate a discussion of magnetohydrodynamics (MHD). The material also details the often complex nature of waves and oscillations in uniform and non-uniform media, before categorizing the observational signatures of oscillations and exploring the instabilities in fluid, dealing with a range of known forms. Lastly, a section on helioseismology explores our growing familiarity with the internal structure of the Sun. This book is a unified portal to a thorough grounding in solar waves that includes a wealth of explanatory vignettes demystifying concepts such as flux tubes, current-free and force-free magnetic fields, the prominences, and the relationship between the vorticity ...

Solar and stellar oscillations

International Nuclear Information System (INIS)

Fossat, E.

1981-01-01

We try to explain in simple words what a stellar oscillation is, what kind of restoring forces and excitation mechanisms can be responsible for its occurence, what kind of questions the theoretician asks to the observer and what kind of tools the latter is using to look for the answers. A selected review of the most striking results obtained in the last few years in solar seismology and the present status of their consequences on solar models is presented. A brief discussion on the expected extension towards stellar seismology will end the paper. A selected bibliography on theory as well as observations and recent papers is also included. (orig.)

Smart control application in the oscillations using FACTS (STATCOM and SVC

Directory of Open Access Journals (Sweden)

Alfonso James Alzate Gomez

2017-07-01

Full Text Available Context: Reducing the oscillations of the electrical power systems is an important task in order to maintain their stability. This paper presents a methodology for adjusting the parameters of a fuzzy oscillations controller with a Static Var Compensator (SVC and a Static Synchronous Compensator (STATCOM. Methodology: The methodology consists of tuning a fuzzy controller to dampen oscillations in an electrical power system, with different optimization techniques such as: Genetic Algorithms (GA, Particle Swarm Optimization (PSO, and Chaotic Optimization Algorithm (COA. Results: The voltage and speed oscillations of a system composed of a synchronous machine connected to an infinite bus bar (SMIB are obtained through simulations. There is data before and after connecting a SVC and a STATCOM, installed independently and in different operating conditions. The results obtained show that using a technique for adjusting parameters in the fuzzy controller is better than the adjustment of trial and error. Conclusion: With the obtained results, it is possible to verify the effectiveness of the fuzzy controller using Flexible AC Transmissions Systems (FACTS.

Avaliação de mecânica ventilatória por oscilações forçadas: fundamentos e aplicações clínicas Analysis of the ventilatory mechanics by forced oscillations technique: main concepts and clinical applications

Directory of Open Access Journals (Sweden)

PEDRO LOPES DE MELO

2000-08-01

Full Text Available Requerendo apenas cooperação passiva e fornecendo novos parâmetros para análise da mecânica ventilatória, a técnica de oscilações forçadas (TOF apresenta características complementares aos métodos clássicos de avaliação pulmonar. Neste trabalho, inicialmente é apresentada uma revisão dos princípios da técnica juntamente com uma discussão sobre suas vantagens e atuais limitações. A performance da técnica é comparada com a dos métodos clássicos na detecção de afecções respiratórias. As principais aplicações clínicas reportadas anteriormente na literatura, incluindo a avaliação da mecânica ventilatória infantil, estudos em neonatos, monitorização de pacientes sob ventilação mecânica, medicina ocupacional e avaliação de distúrbios no sono, são revisadas e discutidas. Com base na revisão efetuada e nos resultados obtidos em estudos efetuados em laboratório, os autores concluem que a TOF pode contribuir para um exame mais detalhado, assim como para facilitar a realização de testes de função pulmonar em condições nas quais as técnicas tradicionais não são adequadas.Requesting passive cooperation from the patient and supplying new parameters for the analysis of the ventilatory mechanics, the forced oscillations technique (FOT has complementary characteristics to the classical methods of lung evaluation. In this work, a review of the principles of this technique is initially presented together with a discussion about its advantages and present limitations. The performance of the technique is compared to classical methods in the detection of breathing disorders. The main clinical applications reported previously in the literature, including the evaluation of the ventilatory mechanics in children, studies in neonates, monitoring of patients under mechanical ventilation, occupational medicine, and evaluation of respiratory sleep disturbances are reviewed and discussed. Based on this review and on the

THE EFFECTS OF MAGNETIC-FIELD GEOMETRY ON LONGITUDINAL OSCILLATIONS OF SOLAR PROMINENCES

International Nuclear Information System (INIS)

Luna, M.; Díaz, A. J.; Karpen, J.

2012-01-01

We investigate the influence of the geometry of the solar filament magnetic structure on the large-amplitude longitudinal oscillations. A representative filament flux tube is modeled as composed of a cool thread centered in a dipped part with hot coronal regions on either side. We have found the normal modes of the system and establish that the observed longitudinal oscillations are well described with the fundamental mode. For small and intermediate curvature radii and moderate to large density contrast between the prominence and the corona, the main restoring force is the solar gravity. In this full wave description of the oscillation a simple expression for the oscillation frequencies is derived in which the pressure-driven term introduces a small correction. We have also found that the normal modes are almost independent of the geometry of the hot regions of the tube. We conclude that observed large-amplitude longitudinal oscillations are driven by the projected gravity along the flux tubes and are strongly influenced by the curvature of the dips of the magnetic field in which the threads reside.

North-south asymmetry of ultra-low-frequency oscillations of Earth's electromagnetic field

Science.gov (United States)

Guglielmi, Anatol; Klain, Boris; Potapov, Alexander

2017-12-01

In the paper, we present the result of an experimental study of north-south asymmetry of ultralow-frequency electromagnetic oscillations IPCL. This study is based on observations made at Mirny Observatory (Antarctica). IPCLs are excited in the dayside sector of the auroral oval in the range 3-10 min periods and represent one of the most powerful types of oscillations of Earth's magnetosphere. These oscillations were discovered in the 1970s during IPhE AS USSR polar expeditions organized by Prof. V.A. Troitskaya. We have shown that IPCL activity in Mirny depends on the inclination (north-south asymmetry) of interplanetary magnetic field (IMF) lines to the plane of the geomagnetic equator before the front of the magnetosphere. The result suggests a controlling exposure of IMF on the magnetospheric oscillations and gives rise to the hypothesis that IPCLs are forced oscillations of a nonlinear dynamical system whose major structural elements are dayside polar cusps. The paper is dedicated to the memory of Professor V.A. Troitskaya (1917-2010).

Modal analysis of temperature feedback in oscillations induced by xenon

International Nuclear Information System (INIS)

Passos, E.M. dos.

1976-01-01

The flux oscillations induced by Xenon distribution in homogeneous thermal reactors are studied treating the space dependence through the modal expansion technique and the stability limits against power oscillations and spatial oscillations are determined. The effect of the feedbacks due to Xenon and temperature coefficient on the linear stability of the free system is investigated employing several number of terms in the transient expansion, considering the various sizes of the reactor. The heat transfer model considered includes one term due to cooling proportional to the temperature. A PWR model reactor is utilized for numerical calculations. It is found that a slightly higher temperature feedback coefficient is necessary for stability against power oscillations when larger number of terms in the transient modal expansion is maintained. (author)

Resonance oscillations of the Soufrière Hills Volcano (Montserrat, W.I.) magmatic system induced by forced magma flow from the reservoir into the upper plumbing dike

Science.gov (United States)

Chen, Chin-Wu; Huang, Hsin-Fu; Hautmann, Stefanie; Sacks, I. Selwyn; Linde, Alan T.; Taira, Taka'aki

2018-01-01

Short-period deformation cycles are a common phenomenon at active volcanoes and are often attributed to the instability of magma flow in the upper plumbing system caused by fluctuations in magma viscosity related to cooling, degassing, and crystallization. Here we present 20-min periodic oscillations in ground deformation based on high-precision continuous borehole strain data that were associated with the 2003 massive dome-collapse at the Soufrière Hills Volcano, Montserrat (West Indies). These high-frequency oscillations lasted 80 min and were preceded by a 4-hour episode of rapid expansion of the shallow magma reservoir. Strain amplitude ratios indicate that the deformational changes were generated by pressure variations in the shallow magma reservoir and - with reversed polarity - the adjacent plumbing dike. The unusually short period of the oscillations cannot be explained with thermally induced variations in magma properties. We investigate the underlying mechanism of the oscillations via a numerical model of forced magma flow through a reservoir-dike system accounting for time-dependent dilation/contraction of the dike due to a viscous response in the surrounding host rock. Our results suggest that the cyclic pressure variations are modulated by the dynamical interplay between rapid expansion of the magma chamber and the incapacity of the narrow dike to take up fast enough the magma volumes supplied by the reservoir. Our results allow us to place first order constraints on the viscosity of crustal host rocks and consequently its fractional melt content. Hence, we present for the first time crustal-scale in situ measurements of rheological properties of mush zones surrounding magmatic systems.

Measurement of Long Baseline Neutrino Oscillations and Improvements from Deep Learning

Energy Technology Data Exchange (ETDEWEB)

Psihas, Fernanda [Indiana U.

2018-01-01

NOvA is a long-baseline neutrino oscillation experiment which measures the oscillation of muon neutrinos from the NuMI beam at Fermilab after they travel through the Earth for 810 km. In this dissertation I describe the operations and monitoring of the detectors which make it possible to record over 98% of the delivered neutrino beam. I also present reconstruction and identification techniques using deep convolutional neural networks (CNNs), which are applicable to multiple analyses. Lastly, I detail the oscillation analyses in the $\

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

Science.gov (United States)

Neuman, Keir C.; Nagy, Attila

2012-01-01

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

The Use of Atomic Force Microscopy as a Technique for the Identification of Cancerous Cells

International Nuclear Information System (INIS)

Lekka, M.

2007-11-01

The monograph presents the use of atomic force microscopy (AFM) as a tool for the identification of cancerous cells by studies of the expression of different types of molecules directly on the surface of living cells. The full quantitative description (that is not accessible by other techniques) performed for a given type of molecular interactions has been obtained by using the following quantities: an unbinding force, probability, rupture length and the effective spring constant taking into account the stiffness of a single complex. All, these parameters were extracted from AFM measurements The analysis of the interaction forces performed by AFM allows the quantitative determination of: i) the static properties of a single molecular complex where its strength of interaction and stiffness of the studied complex can be obtained, ii) dynamic properties, on the basis of which the kinetic properties of the unbinding process can be delivered, and iii) properties of adhesion clusters, where the interrelation between single complexes can be characterized, in particular the mechanism of the unbinding can be obtained. The presented characterization of the interaction force between single molecules demonstrates that atomic force microscopy can be used as exceptional technique to study the expression of molecules on a cell surface. Such measurements are not limited to a typical interactions occurring between single molecules but also it is possible to study the interactions between parts of molecules. The results presented in this monograph point to a novel approach to identify cancer-related changes in a quantitative way what can be used for describing and confirming the pathological state of a single cell. (author)

Modeling Friction Performance of Drill String Torsional Oscillation Using Dynamic Friction Model

Directory of Open Access Journals (Sweden)

Xingming Wang

2017-01-01

Full Text Available Drill string torsional and longitudinal oscillation can significantly reduce axial drag in horizontal drilling. An improved theoretical model for the analysis of the frictional force was proposed based on microscopic contact deformation theory and a bristle model. The established model, an improved dynamic friction model established for drill strings in a wellbore, was used to determine the relationship of friction force changes and the drill string torsional vibration. The model results were in good agreement with the experimental data, verifying the accuracy of the established model. The analysis of the influence of drilling mud properties indicated that there is an approximately linear relationship between the axial friction force and dynamic shear and viscosity. The influence of drill string torsional oscillation on the axial friction force is discussed. The results indicated that the drill string transverse velocity is a prerequisite for reducing axial friction. In addition, low amplitude of torsional vibration speed can significantly reduce axial friction. Then, increasing the amplitude of transverse vibration speed, the effect of axial reduction is not significant. In addition, by involving general field drilling parameters, this model can accurately describe the friction behavior and quantitatively predict the frictional resistance in horizontal drilling.

On the non-linear dynamics of potential relaxation oscillations in bounded plasmas

International Nuclear Information System (INIS)

Krssak, M.; Skalny, J.D.; Gyergyek, T.; Cercek, M.

2007-01-01

Plasma in a 1-dimensional diode is studied theoretically and the computer simulations are used for verification of the theoretical model. When collector in the diode is biased positively, a double-layer is created in the system and consequently, we are able to observe oscillations of the potential, density and other plasma parameters. When external periodic forcing is applied, spectra of these oscillations are changed and effects of synchronisation and periodic pulling can be observed. Both of these effects are of non-linear nature and a good explanation is found using the analogy with Van der Pol oscillators. Following [1] and [2] approximate analytical solutions are found and then compared with computer simulations obtained using a 1-dimensional particle-in-cell code XPDP1. (author)

Analogies between oscillation and rotation of bodies induced or influenced by vortex shedding

Science.gov (United States)

Lugt, H. J.

Vortex-induced or vortex-influenced rotation and oscillation of bodies in a parallel flow are discussed. A steady flow occurs if the body axis is parallel to the flow or if the axis of rotation is perpendicular to the flow. Flows around an oscillating body are quasi-steady only if the Strougal number is much smaller than unity. The connection between rotation and oscillation is demonstrated in terms of the autorotation of a Lanchester propeller, and conditions for stable autorotation are defined. The Riabouchinsky curve is shown to be typical of forces and torques on bodies with vortical wakes, including situations with fixed body axes perpendicular to the flow. A differential equation is formulated for rotational and oscillating bodies that shed vortices by extending the pendulum equation to include vortical effects expressed as a fifth-order polynomial.

Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

Science.gov (United States)

Cantrell, John H., Jr.; Cantrell, Sean A.

2008-01-01

A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

Quantitative analysis of tip-sample interaction in non-contact scanning force spectroscopy

International Nuclear Information System (INIS)

Palacios-Lidon, Elisa; Colchero, Jaime

2006-01-01

Quantitative characterization of tip-sample interaction in scanning force microscopy is fundamental for optimum image acquisition as well as data interpretation. In this work we discuss how to characterize the electrostatic and van der Waals contribution to tip-sample interaction in non-contact scanning force microscopy precisely. The spectroscopic technique presented is based on the simultaneous measurement of cantilever deflection, oscillation amplitude and frequency shift as a function of tip-sample voltage and tip-sample distance as well as on advanced data processing. Data are acquired at a fixed lateral position as interaction images, with the bias voltage as fast scan, and tip-sample distance as slow scan. Due to the quadratic dependence of the electrostatic interaction with tip-sample voltage the van der Waals force can be separated from the electrostatic force. Using appropriate data processing, the van der Waals interaction, the capacitance and the contact potential can be determined as a function of tip-sample distance. The measurement of resonance frequency shift yields very high signal to noise ratio and the absolute calibration of the measured quantities, while the acquisition of cantilever deflection allows the determination of the tip-sample distance

Effect of alternate-vortex on flow-induced in-line oscillation

International Nuclear Information System (INIS)

Kondo, Masaya; Anoda, Yoshinari

1999-01-01

Experiments were performed to study the in-line oscillations of a flexible cylinder in a water crossflow to estimate the effects of alternate-vortex. The measured oscillations were analyzed using the Gabor wavelet function to define the temporal phase relation between the in-line displacement and the vortex-induced force. The analysis shows that 1) the stability region located between two excited regions is generated by alternate vortex effect, 2) the phase relation, which was changed as the crossflow velocity increased, can be classified into three categories, 3) though the contribution of the alternate vortex at the excited region was positive, the contribution at the stability region was negative. (author)

Atomic force microscopy as nano-stethoscope to study living organisms, insects

Science.gov (United States)

Sokolov, Igor; Dokukin, Maxim; Guz, Nataliia

2012-02-01

Atomic force microscopy (AFM) is a known method to study various surfaces. Here we report on the use of AFM to study surface oscillations (coming from the work of internal organs) of living organisms, like insects. As an example, ladybird beetles (Hippodamia convergens) measured in different parts of the insect at picometer level. This allows us to record a much broader spectral range of possible surface vibrations (up to several kHz) than the previously studied oscillations due to breathing, heartbeat cycles, coelopulses, etc. (up to 5 -10 Hz). The used here AFM method allows collecting signal from the area as small as ˜100nm2 (0.0001μm2) with an example of noise level of (2±0.2)x10-3 nm r.m.s. at the range of frequencies >50Hz (potentially, up to a MHz). Application of this method to humans is discussed. The method, being a relatively non-invasive technique providing a new type of information, may be useful in developing of what could be called ``nanophysiology.''

Dynamic electrostatic force microscopy technique for the study of electrical properties with improved spatial resolution

International Nuclear Information System (INIS)

Maragliano, C; Heskes, D; Stefancich, M; Chiesa, M; Souier, T

2013-01-01

The need to resolve the electrical properties of confined structures (CNTs, quantum dots, nanorods, etc) is becoming increasingly important in the field of electronic and optoelectronic devices. Here we propose an approach based on amplitude modulated electrostatic force microscopy to obtain measurements at small tip–sample distances, where highly nonlinear forces are present. We discuss how this improves the lateral resolution of the technique and allows probing of the electrical and surface properties. The complete force field at different tip biases is employed to derive the local work function difference. Then, by appropriately biasing the tip–sample system, short-range forces are reconstructed. The short-range component is then separated from the generic tip–sample force in order to recover the pure electrostatic contribution. This data can be employed to derive the tip–sample capacitance curve and the sample dielectric constant. After presenting a theoretical model that justifies the need for probing the electrical properties of the sample in the vicinity of the surface, the methodology is presented in detail and verified experimentally. (paper)

Modeling the Aerodynamic Lift Produced by Oscillating Airfoils at Low Reynolds Number

OpenAIRE

Khalid, Muhammad Saif Ullah; Akhtar, Imran

2014-01-01

For present study, setting Strouhal Number (St) as control parameter, numerical simulations for flow past oscillating NACA-0012 airfoil at 1,000 Reynolds Numbers (Re) are performed. Temporal profiles of unsteady forces; lift and thrust, and their spectral analysis clearly indicate the solution to be a period-1 attractor for low Strouhal numbers. This study reveals that aerodynamic forces produced by plunging airfoil are independent of initial kinematic conditions of airfoil that proves the ex...

The two-capacitor problem revisited: a mechanical harmonic oscillator model approach

International Nuclear Information System (INIS)

Lee, Keeyung

2009-01-01

The well-known two-capacitor problem, in which exactly half the stored energy disappears when a charged capacitor is connected to an identical capacitor, is discussed based on the mechanical harmonic oscillator model approach. In the mechanical harmonic oscillator model, it is shown first that exactly half the work done by a constant applied force is dissipated irrespective of the form of dissipation mechanism when the system comes to a new equilibrium after a constant force is abruptly applied. This model is then applied to the energy loss mechanism in the capacitor charging problem or the two-capacitor problem. This approach allows a simple explanation of the energy dissipation mechanism in these problems and shows that the dissipated energy should always be exactly half the supplied energy whether that is caused by the Joule heat or by the radiation. This paper, which provides a simple treatment of the energy dissipation mechanism in the two-capacitor problem, is suitable for all undergraduate levels

Weak wide-band signal detection method based on small-scale periodic state of Duffing oscillator

Science.gov (United States)

Hou, Jian; Yan, Xiao-peng; Li, Ping; Hao, Xin-hong

2018-03-01

The conventional Duffing oscillator weak signal detection method, which is based on a strong reference signal, has inherent deficiencies. To address these issues, the characteristics of the Duffing oscillatorʼs phase trajectory in a small-scale periodic state are analyzed by introducing the theory of stopping oscillation system. Based on this approach, a novel Duffing oscillator weak wide-band signal detection method is proposed. In this novel method, the reference signal is discarded, and the to-be-detected signal is directly used as a driving force. By calculating the cosine function of a phase space angle, a single Duffing oscillator can be used for weak wide-band signal detection instead of an array of uncoupled Duffing oscillators. Simulation results indicate that, compared with the conventional Duffing oscillator detection method, this approach performs better in frequency detection intervals, and reduces the signal-to-noise ratio detection threshold, while improving the real-time performance of the system. Project supported by the National Natural Science Foundation of China (Grant No. 61673066).

Entraining the topology and the dynamics of a network of phase oscillators

Science.gov (United States)

Sendiña-Nadal, I.; Leyva, I.; Buldú, J. M.; Almendral, J. A.; Boccaletti, S.

2009-04-01

We show that the topology and dynamics of a network of unsynchronized Kuramoto oscillators can be simultaneously controlled by means of a forcing mechanism which yields a phase locking of the oscillators to that of an external pacemaker in connection with the reshaping of the network’s degree distribution. The entrainment mechanism is based on the addition, at regular time intervals, of unidirectional links from oscillators that follow the dynamics of a pacemaker to oscillators in the pristine graph whose phases hold a prescribed phase relationship. Such a dynamically based rule in the attachment process leads to the emergence of a power-law shape in the final degree distribution of the graph whenever the network is entrained to the dynamics of the pacemaker. We show that the arousal of a scale-free distribution in connection with the success of the entrainment process is a robust feature, characterizing different networks’ initial configurations and parameters.

Oscillating microbubbles for selective particle sorting in acoustic microfluidic devices

Science.gov (United States)

Rogers, Priscilla; Xu, Lin; Neild, Adrian

2012-05-01

In this study, acoustic waves were used to excite a microbubble for selective particle trapping and sorting. Excitation of the bubble at its volume resonance, as necessary to drive strong fluid microstreaming, resulted in the particles being either selectively attracted to the bubble or continuing to follow the local microstreamlines. The operating principle exploited two acoustic phenomena acting on the particle suspension: the drag force arising from the acoustic microstreaming and the secondary Bjerknes force, i.e. the attractive radiation force produced between an oscillating bubble and a non-buoyant particle. It was also found that standing wave fields within the fluid chamber could be used to globally align bubbles and particles for local particle sorting by the bubble.

Thalamocortical Oscillations in the Sleeping and Aroused Brain

Science.gov (United States)

Steriade, Mircea; McCormick, David A.; Sejnowski, Terrence J.

1993-10-01

Sleep is characterized by synchronized events in billions of synaptically coupled neurons in thalamocortical systems. The activation of a series of neuromodulatory transmitter systems during awakening blocks low-frequency oscillations, induces fast rhythms, and allows the brain to recover full responsiveness. Analysis of cortical and thalamic networks at many levels, from molecules to single neurons to large neuronal assemblies, with a variety of techniques, ranging from intracellular recordings in vivo and in vitro to computer simulations, is beginning to yield insights into the mechanisms of the generation, modulation, and function of brain oscillations.

Tracking the Atlantic Multidecadal Oscillation through the last 8,000 years

DEFF Research Database (Denmark)

Knudsen, Mads Faurschou; Seidenkrantz, Marit-Solveig; Jacobsen, B. H.

2011-01-01

Understanding the internal ocean variability and its influence on climate is imperative for society. A key aspect concerns the enigmatic Atlantic Multidecadal Oscillation (AMO), a feature defined by a 60- to 90-year variability in North Atlantic sea-surface temperatures. The nature and origin...... of the AMO is uncertain, and it remains unknown whether it represents a persistent periodic driver in the climate system, or merely a transient feature. Here, we show that distinct, ~55- to 70-year oscillations characterized the North Atlantic ocean-atmosphere variability over the past 8,000 years. We test...... and reject the hypothesis that this climate oscillation was directly forced by periodic changes in solar activity. We therefore conjecture that a quasi-persistent ~55- to 70-year AMO, linked to internal ocean-atmosphere variability, existed during large parts of the Holocene. Our analyses further suggest...

Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction

Science.gov (United States)

Pasini, Antonello; Triacca, Umberto; Attanasio, Alessandro

2017-08-01

The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean-atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001-2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere-ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean.

Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators

KAUST Repository

Talukdar, Abdul Hafiz Ibne

2012-07-28

Traditionally, the necessary and sufficient condition for any system to be oscillating is that its poles are located on the imaginary (jω) axis. In this paper, for the first time, we have shown that systems can oscillate with time-domain oscillating poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating resistance and triangular shape of FFT are also demonstrated with mathematical reasoning and simulation results to support the unusual and surprising characteristics. © 2009 IEEE.

Force sensing based on coherent quantum noise cancellation in a hybrid optomechanical cavity with squeezed-vacuum injection

Science.gov (United States)

Motazedifard, Ali; Bemani, F.; Naderi, M. H.; Roknizadeh, R.; Vitali, D.

2016-07-01

We propose and analyse a feasible experimental scheme for a quantum force sensor based on the elimination of backaction noise through coherent quantum noise cancellation (CQNC) in a hybrid atom-cavity optomechanical setup assisted with squeezed vacuum injection. The force detector, which allows for a continuous, broadband detection of weak forces well below the standard quantum limit (SQL), is formed by a single optical cavity simultaneously coupled to a mechanical oscillator and to an ensemble of ultracold atoms. The latter acts as a negative-mass oscillator so that atomic noise exactly cancels the backaction noise from the mechanical oscillator due to destructive quantum interference. Squeezed vacuum injection enforces this cancellation and allows sub-SQL sensitivity to be reached in a very wide frequency band, and at much lower input laser powers.

Force sensing based on coherent quantum noise cancellation in a hybrid optomechanical cavity with squeezed-vacuum injection

International Nuclear Information System (INIS)

Motazedifard, Ali; Bemani, F; Naderi, M H; Roknizadeh, R; Vitali, D

2016-01-01

We propose and analyse a feasible experimental scheme for a quantum force sensor based on the elimination of backaction noise through coherent quantum noise cancellation (CQNC) in a hybrid atom-cavity optomechanical setup assisted with squeezed vacuum injection. The force detector, which allows for a continuous, broadband detection of weak forces well below the standard quantum limit (SQL), is formed by a single optical cavity simultaneously coupled to a mechanical oscillator and to an ensemble of ultracold atoms. The latter acts as a negative-mass oscillator so that atomic noise exactly cancels the backaction noise from the mechanical oscillator due to destructive quantum interference. Squeezed vacuum injection enforces this cancellation and allows sub-SQL sensitivity to be reached in a very wide frequency band, and at much lower input laser powers. (paper)

Displacement of organelles in plant gravireceptor cells by vibrational forces and ultrasound.

Science.gov (United States)

Kuznetsov, O.; Nechitailo, G.; Kuznetsov, A.

Plant gravity perception can be studied by displacing statoliths inside receptor cells by forces other than gravity. Due to mechanical heterogeneity of statocytes various ponderomotive forces can be used for this purpose. In a plant subjected to non- symmetric vibrations statoliths experience inertial force proportional to the difference between their density and that of cytoplasm and to the instantaneous acceleration of the cell. This force causes cyclic motion of statoliths relative to cytoplasm and, depending on the profile of oscillations, can result in a net displacement of them (due to complex rheology of the cell interior), similar to sedimentation. This can be described as "vibrational" ponderomotive force acting on the statoliths. Vertically growing Arabidopsis seedlings, subjected to horizontal, sawtooth shaped oscillations (250 Hz, 1.5 mm amplitude), showed 17+/-2o root curvature toward and shoot curvature of 11+/-3o against the stronger acceleration. When the polarity of the oscillations was reversed, the direction of curvature of shoots and roots was also reversed. Control experiments with starchless mutants (TC7) produced no net curvature, which indicates that dense starch-filled amyloplasts are needed for the effect. These control experiments also eliminate touch-induced reactions or other side-effects as the cause of the curvature. Linum roots curved 25+/-7o . Ceratodon protonemata subjected to the same oscillations have shown displacement of plastids and curvature consistent with the pattern observed during graviresponse: positively gravitropic wwr mutant curved in the direction of the plastid displacement, WT curved in the opposite direction. Acoustic ponderomotive forces, originating from transfer of a sonic beam momentum to the medium due to sound scattering and attenuation in a mechanically heterogeneous system, also can displace statoliths. Vertical flax seedlings curved away from the ultrasonic source (800 kHz, 0.1 W/cm2 ) presumably as a

Synchronization and desynchronization in a network of locally coupled Wilson-Cowan oscillators.

Science.gov (United States)

Campbell, S; Wang, D

1996-01-01

A network of Wilson-Cowan (WC) oscillators is constructed, and its emergent properties of synchronization and desynchronization are investigated by both computer simulation and formal analysis. The network is a 2D matrix, where each oscillator is coupled only to its neighbors. We show analytically that a chain of locally coupled oscillators (the piecewise linear approximation to the WC oscillator) synchronizes, and we present a technique to rapidly entrain finite numbers of oscillators. The coupling strengths change on a fast time scale based on a Hebbian rule. A global separator is introduced which receives input from and sends feedback to each oscillator in the matrix. The global separator is used to desynchronize different oscillator groups. Unlike many other models, the properties of this network emerge from local connections that preserve spatial relationships among components and are critical for encoding Gestalt principles of feature grouping. The ability to synchronize and desynchronize oscillator groups within this network offers a promising approach for pattern segmentation and figure/ground segregation based on oscillatory correlation.

Rayleigh-Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries

Science.gov (United States)

Titarchuk, Lev

2002-01-01

Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the

Nature's Autonomous Oscillators

Science.gov (United States)

Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.

2012-01-01

Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.

The effect of nonlinear forces on coherently oscillating space-charge-dominated beams

International Nuclear Information System (INIS)

Celata, C.M.

1987-03-01

A particle-in-cell computer simulation code has been used to study the transverse dynamics of nonrelativistic misaligned space-charge-dominated coasting beams in an alternating gradient focusing channel. In the presence of nonlinear forces due to dodecapole or octupole imperfections of the focusing fields or to image forces, the transverse rms emittance grows in a beat pattern. Analysis indicates that this emittance dilution is due to the driving of coherent modes of the beam near their resonant frequencies by the nonlinear force. The effects of the dodecapole and images forces can be made to effectively cancel for some boundary conditions, but the mechanism is not understood at this time

Time-Dependent Simulation of Free-Electron Laser Amplifiers and Oscillators

CERN Document Server

Freund, H

2005-01-01

Time-dependent FEL simulations use a variety of techniques. Most simulations use a slowly varying envelope approximation (SVEA). One such technique assumes that the envelope varies only in z combined with a field representation as an ensemble of discrete harmonics, which is equivalent to a time-dependent simulation [1] but is computationally prohibitive. A second technique uses an SVEA in both in z and t [2]. The particles and fields are advanced in z using the same process as in steady-state simulations and then the time derivative describing slippage is applied. This is used in wiggler-averaged codes such as GINGER [3] and GENESIS [4]. We describe the inclusion of this technique in the non-wiggler-averaged code MEDUSA [5], which is applied to amplifiers and oscillators. MEDUSA differs from GINGER and GENESIS also in the way the field is treated. GINGER and GENESIS use a field solver and must explicitly propagate the field outside the wiggler oscillators. This is computationally intensive. MEDUSA uses a Gaus...

Oscillating heat pipes

CERN Document Server

Ma, Hongbin

2015-01-01

This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation,  theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary  factors affecting oscillating motions and heat transfer,  neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes.  The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, gradua...

Heteroclinic Bifurcation Behaviors of a Duffing Oscillator with Delayed Feedback

Directory of Open Access Journals (Sweden)

Shao-Fang Wen

2018-01-01

Full Text Available The heteroclinic bifurcation and chaos of a Duffing oscillator with forcing excitation under both delayed displacement feedback and delayed velocity feedback are studied by Melnikov method. The Melnikov function is analytically established to detect the necessary conditions for generating chaos. Through the analysis of the analytical necessary conditions, we find that the influences of the delayed displacement feedback and delayed velocity feedback are separable. Then the influences of the displacement and velocity feedback parameters on heteroclinic bifurcation and threshold value of chaotic motion are investigated individually. In order to verify the correctness of the analytical conditions, the Duffing oscillator is also investigated by numerical iterative method. The bifurcation curves and the largest Lyapunov exponents are provided and compared. From the analysis of the numerical simulation results, it could be found that two types of period-doubling bifurcations occur in the Duffing oscillator, so that there are two paths leading to the chaos in this oscillator. The typical dynamical responses, including time histories, phase portraits, and Poincare maps, are all carried out to verify the conclusions. The results reveal some new phenomena, which is useful to design or control this kind of system.

Optimal oscillation-center transformations

International Nuclear Information System (INIS)

Dewar, R.L.

1984-08-01

A variational principle is proposed for defining that canonical transformation, continuously connected with the identity transformation, which minimizes the residual, coordinate-dependent part of the new Hamiltonian. The principle is based on minimization of the mean-square generalized force. The transformation reduces to the action-angle transformation in that part of the phase space of an integrable system where the orbit topology is that of the unperturbed system, or on primary KAM surfaces. General arguments in favor of this definition are given, based on Galilean invariance, decay of the Fourier spectrum, and its ability to include external fields or inhomogeneous systems. The optimal oscillation-center transformation for the physical pendulum, or particle in a sinusoidal potential, is constructed

Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators

KAUST Repository

Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

2012-01-01

poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating

Airway Clearance Techniques (ACTs)

Medline Plus

Full Text Available ... Cycle of Breathing Technique Airway Clearance Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing ... Facebook Twitter Email More Related Content Medications Autogenic Drainage Positive Expiratory Pressure High-Frequency Chest Wall Oscillation ( ...

Estimation of single plane unbalance parameters of a rotor-bearing system using Kalman filtering based force estimation technique

Science.gov (United States)

Shrivastava, Akash; Mohanty, A. R.

2018-03-01

This paper proposes a model-based method to estimate single plane unbalance parameters (amplitude and phase angle) in a rotor using Kalman filter and recursive least square based input force estimation technique. Kalman filter based input force estimation technique requires state-space model and response measurements. A modified system equivalent reduction expansion process (SEREP) technique is employed to obtain a reduced-order model of the rotor system so that limited response measurements can be used. The method is demonstrated using numerical simulations on a rotor-disk-bearing system. Results are presented for different measurement sets including displacement, velocity, and rotational response. Effects of measurement noise level, filter parameters (process noise covariance and forgetting factor), and modeling error are also presented and it is observed that the unbalance parameter estimation is robust with respect to measurement noise.

One dimension harmonic oscillator

International Nuclear Information System (INIS)

Cohen-Tannoudji, Claude; Diu, Bernard; Laloe, Franck.

1977-01-01

The importance of harmonic oscillator in classical and quantum physics, eigenvalues and eigenstates of hamiltonian operator are discussed. In complement are presented: study of some physical examples of harmonic oscillators; study of stationnary states in the /x> representation; Hermite polynomials; resolution of eigenvalue equation of harmonic oscillator by polynomial method; isotope harmonic oscillator with three dimensions; charged harmonic oscillator in uniform electric field; quasi classical coherent states of harmonic oscillator; eigenmodes of vibration of two coupled harmonic oscillators; vibration modus of a continuous physical system (application to radiation: photons); vibration modus of indefinite linear chain of coupled harmonic oscillators (phonons); one-dimensional harmonic oscillator in thermodynamic equilibrium at temperature T [fr

A review of recent studies on the mechanisms and analysis methods of sub-synchronous oscillation in wind farms

Science.gov (United States)

Wang, Chenggen; Zhou, Qian; Gao, Shuning; Luo, Jia; Diao, Junchao; Zhao, Haoran; Bu, Jing

2018-04-01

This paper reviews the recent studies of Sub-Synchronous Oscillation(SSO) in wind farms. Mechanisms and analysis methods are the main concerns of this article. A classification method including new types of oscillation occurred between wind farms and HVDC systems and oscillation caused by Permanent Magnet Synchronous Generators(PMSG) is proposed. Characteristics of oscillation analysis techniques are summarized.

Reactor oscillator - I - III, Part I; Reaktorski oscilator - I-III, I Deo

Energy Technology Data Exchange (ETDEWEB)

Lolic, B [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

1961-12-15

Project 'Reactor oscillator' covers the following activities: designing reactor oscillators for reactors RA and RB with detailed engineering drawings; constructing and mounting of the oscillator; designing and constructing the appropriate electronic equipment for the oscillator; measurements at the RA and RB reactors needed for completing the oscillator construction.

Self-synchronization of populations of nonlinear oscillators in the thermodynamic limit

International Nuclear Information System (INIS)

Bonilla, L.L.; Casado, J.M.; Morillo, M.

1987-01-01

A population of identical nonlinear oscillators, subject to random forces and coupled via a mean-field interaction, is studied in the thermodynamic limit. The model presents a nonequilibrium phase transition from a stationary to a time-periodic probability density. Below the transition line, the population of oscillators is in a quiescent state with order parameter equal to zero. Above the transition line, there is a state of collective rhythmicity characterized by a time-periodic behavior of the order parameter and all moments of the probability distribution. The information entropy of the ensemble is a constant both below and above the critical line. Analytical and numerical analyses of the model are provided

Controlled vesicle deformation and lysis by single oscillating bubbles

Science.gov (United States)

Marmottant, Philippe; Hilgenfeldt, Sascha

2003-05-01

The ability of collapsing (cavitating) bubbles to focus and concentrate energy, forces and stresses is at the root of phenomena such as cavitation damage, sonochemistry or sonoluminescence. In a biomedical context, ultrasound-driven microbubbles have been used to enhance contrast in ultrasonic images. The observation of bubble-enhanced sonoporation-acoustically induced rupture of membranes-has also opened up intriguing possibilities for the therapeutic application of sonoporation as an alternative to cell-wall permeation techniques such as electroporation and particle guns. However, these pioneering experiments have not been able to pinpoint the mechanism by which the violently collapsing bubble opens pores or larger holes in membranes. Here we present an experiment in which gentle (linear) bubble oscillations are sufficient to achieve rupture of lipid membranes. In this regime, the bubble dynamics and the ensuing sonoporation can be accurately controlled. The use of microbubbles as focusing agents makes acoustics on the micrometre scale (microacoustics) a viable tool, with possible applications in cell manipulation and cell-wall permeation as well as in microfluidic devices.

Analysis of Oscillations in a Cableway: Wind Load Effects

Directory of Open Access Journals (Sweden)

Jan Gustincic

2013-06-01

Full Text Available The purpose of this paper is to develop and investigate a non-linear model for analysing the reaction of a self-detachable cabin monocable ropeway exposed to a sudden deceleration and wind forces. The First and Second Newton's Law and Differential Equations are the basic tools for building the model. Furthermore a few basic considerations have been made about the air “dragging and lifting" forces that induce oscillations and vibrations in mechanical systems alike. All the numerical data used for the simulation was taken from a ropeway in the skiing site of Ravascletto-Zoncolan in the North- East of Italy.

An improved visualization-based force-measurement technique for short-duration hypersonic facilities

Energy Technology Data Exchange (ETDEWEB)

Laurence, Stuart J.; Karl, Sebastian [Institute of Aerodynamics and Flow Technology, Spacecraft Section, German Aerospace Center (DLR), Goettingen (Germany)

2010-06-15

This article is concerned with describing and exploring the limitations of an improved version of a recently proposed visualization-based technique for the measurement of forces and moments in short-duration hypersonic wind tunnels. The technique is based on tracking the motion of a free-flying body over a sequence of high-speed visualizations; while this idea is not new in itself, the use of high-speed digital cinematography combined with a highly accurate least-squares tracking algorithm allows improved results over what have been previously possible with such techniques. The technique precision is estimated through the analysis of artificially constructed and experimental test images, and the resulting error in acceleration measurements is characterized. For wind-tunnel scale models, position measurements to within a few microns are shown to be readily attainable. Image data from two previous experimental studies in the T5 hypervelocity shock tunnel are then reanalyzed with the improved technique: the uncertainty in the mean drag acceleration is shown to be reduced to the order of the flow unsteadiness, 2-3%, and time-resolved acceleration measurements are also shown to be possible. The response time of the technique for the configurations studied is estimated to be {proportional_to}0.5 ms. Comparisons with computations using the DLR TAU code also yield agreement to within the overall experimental uncertainty. Measurement of the pitching moment for blunt geometries still appears challenging, however. (orig.)

The capillary adhesion technique: a versatile method for determining the liquid adhesion force and sample stiffness

Directory of Open Access Journals (Sweden)

Daniel Gandyra

2015-01-01

Full Text Available We report a novel, practical technique for the concerted, simultaneous determination of both the adhesion force of a small structure or structural unit (e.g., an individual filament, hair, micromechanical component or microsensor to a liquid and its elastic properties. The method involves the creation and development of a liquid meniscus upon touching a liquid surface with the structure, and the subsequent disruption of this liquid meniscus upon removal. The evaluation of the meniscus shape immediately before snap-off of the meniscus allows the quantitative determination of the liquid adhesion force. Concurrently, by measuring and evaluating the deformation of the structure under investigation, its elastic properties can be determined. The sensitivity of the method is remarkably high, practically limited by the resolution of the camera capturing the process. Adhesion forces down to 10 µN and spring constants up to 2 N/m were measured. Three exemplary applications of this method are demonstrated: (1 determination of the water adhesion force and the elasticity of individual hairs (trichomes of the floating fern Salvinia molesta. (2 The investigation of human head hairs both with and without functional surface coatings (a topic of high relevance in the field of hair cosmetics was performed. The method also resulted in the measurement of an elastic modulus (Young’s modulus for individual hairs of 3.0 × 105 N/cm2, which is within the typical range known for human hair. (3 Finally, the accuracy and validity of the capillary adhesion technique was proven by examining calibrated atomic force microscopy cantilevers, reproducing the spring constants calibrated using other methods.

Cutting force response in milling of Inconel: analysis by wavelet and Hilbert-Huang Transforms

Directory of Open Access Journals (Sweden)

Grzegorz Litak

Full Text Available We study the milling process of Inconel. By continuously increasing the cutting depth we follow the system response and appearance of oscillations of larger amplitude. The cutting force amplitude and frequency analysis has been done by means of wavelets and Hilbert-Huang transform. We report that in our system the force oscillations are closely related to the rotational motion of the tool and advocate for a regenerative mechanism of chatter vibrations. To identify vibrations amplitudes occurrence in time scale we apply wavelet and Hilbert-Huang transforms.

Calcium oscillations in wounded fibroblast monolayers are spatially regulated through substrate mechanics

Science.gov (United States)

Lembong, Josephine; Sabass, Benedikt; Stone, Howard A.

2017-08-01

The maintenance of tissue integrity is essential for the life of multicellular organisms. Healing of a skin wound is a paradigm for how various cell types localize and repair tissue perturbations in an orchestrated fashion. To investigate biophysical mechanisms associated with wound localization, we focus on a model system consisting of a fibroblast monolayer on an elastic substrate. We find that the creation of an edge in the monolayer causes cytosolic calcium oscillations throughout the monolayer. The oscillation frequency increases with cell density, which shows that wound-induced calcium oscillations occur collectively. Inhibition of myosin II reduces the number of oscillating cells, demonstrating a coupling between actomyosin activity and calcium response. The spatial distribution of oscillating cells depends on the stiffness of the substrate. For soft substrates with a Young’s modulus E ~ 360 Pa, oscillations occur on average within 0.2 mm distance from the wound edge. Increasing substrate stiffness leads to an average localization of oscillations away from the edge (up to ~0.6 mm). In addition, we use traction force microscopy to determine stresses between cells and substrate. We find that an increase of substrate rigidity leads to a higher traction magnitude. For E    ~8 kPa, traction magnitude is on average almost uniform beneath the monolayer. Thus, the spatial occurrence of calcium oscillations correlates with the cell-substrate traction. Overall, the experiments with fibroblasts demonstrate a collective, chemomechanical localization mechanism at the edge of a wound with a potential physiological role.

Oscillator monitor

International Nuclear Information System (INIS)

McNeill, G.A.

1981-01-01

Present high-speed data acquisition systems in nuclear diagnostics use high-frequency oscillators to provide timing references for signals recorded on fast, traveling-wave oscilloscopes. An oscillator's sinusoidal wave shape is superimposed on the recorded signal with each cycle representing a fixed time increment. During data analysis the sinusoid is stripped from the signal, leaving a clean signal shape with known timing. Since all signal/time relationships are totally dependant upon working oscillators, these critical devices must have remote verification of proper operation. This manual presents the newly-developed oscillator monitor which will provide the required verification

Robust Weak Chimeras in Oscillator Networks with Delayed Linear and Quadratic Interactions

Science.gov (United States)

Bick, Christian; Sebek, Michael; Kiss, István Z.

2017-10-01

We present an approach to generate chimera dynamics (localized frequency synchrony) in oscillator networks with two populations of (at least) two elements using a general method based on a delayed interaction with linear and quadratic terms. The coupling design yields robust chimeras through a phase-model-based design of the delay and the ratio of linear and quadratic components of the interactions. We demonstrate the method in the Brusselator model and experiments with electrochemical oscillators. The technique opens the way to directly bridge chimera dynamics in phase models and real-world oscillator networks.

Self-organization and oscillation of negatively charged dust particles in a 2-dimensional dusty plasma

Energy Technology Data Exchange (ETDEWEB)

Song, Y.L. [College of Science, China Agricultural University, Beijing 100083 (China); Huang, F., E-mail: huangfeng@cau.edu.cn [College of Science, China Agricultural University, Beijing 100083 (China); Chen, Z.Y., E-mail: chenzy@mail.buct.edu.cn [Department of Physics, Beijing University of Chemical Technology, Beijing 100029 (China); State Key Laboratory of Laser Propulsion & Application, Beijing 101416 (China); Liu, Y.H. [School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025 (China); Yu, M.Y. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Institute for Theoretical Physics I, Ruhr University, D-44801 Bochum (Germany)

2016-02-22

Negatively charged dust particles immersed in 2-dimensional dusty plasma system are investigated by molecular dynamics simulations. The effects of the confinement potential and attraction interaction potential on dust particle self-organization are studied in detail and two typical dust particle distributions are obtained when the system reaches equilibrium. The average radial velocity (ARV), average radial force (ARF) and radial mean square displacement are employed to analyze the dust particles' dynamics. Both ARVs and ARFs exhibit oscillation behaviors when the simulation system reaches equilibrium state. The relationships between the oscillation and confinement potential and attraction potential are studied in this paper. The simulation results are qualitatively similar to experimental results. - Highlights: • Self-organization and oscillation of a 2-dimensional dusty plasma is investigated. • Effect of the confinement potential on dust self-organization and oscillation is given. • Effect of the attraction potential on dust self-organization and oscillation is studied.

Self-organization and oscillation of negatively charged dust particles in a 2-dimensional dusty plasma

International Nuclear Information System (INIS)

Song, Y.L.; Huang, F.; Chen, Z.Y.; Liu, Y.H.; Yu, M.Y.

2016-01-01

Negatively charged dust particles immersed in 2-dimensional dusty plasma system are investigated by molecular dynamics simulations. The effects of the confinement potential and attraction interaction potential on dust particle self-organization are studied in detail and two typical dust particle distributions are obtained when the system reaches equilibrium. The average radial velocity (ARV), average radial force (ARF) and radial mean square displacement are employed to analyze the dust particles' dynamics. Both ARVs and ARFs exhibit oscillation behaviors when the simulation system reaches equilibrium state. The relationships between the oscillation and confinement potential and attraction potential are studied in this paper. The simulation results are qualitatively similar to experimental results. - Highlights: • Self-organization and oscillation of a 2-dimensional dusty plasma is investigated. • Effect of the confinement potential on dust self-organization and oscillation is given. • Effect of the attraction potential on dust self-organization and oscillation is studied.

One-dimensional multiple-well oscillators: A time-dependent

Indian Academy of Sciences (India)

... quantum mechanical multiple-well oscillators. An imaginary-time evolution technique, coupled with the minimization of energy expectation value to reach a global minimum, subject to orthogonality constraint (for excited states) has been employed. Pseudodegeneracy in symmetric, deep multiple-well potentials, probability ...

Tapping mode atomic force microscopy in liquid

NARCIS (Netherlands)

Putman, Constant A.J.; Putman, C.A.J.; van der Werf, Kees; de Grooth, B.G.; van Hulst, N.F.; Greve, Jan

1994-01-01

We show that standard silicon nitride cantilevers can be used for tapping mode atomic force microscopy (AFM) in air, provided that the energy of the oscillating cantilever is sufficiently high to overcome the adhesion of the water layer. The same cantilevers are successfully used for tapping mode

Power oscillation damping controller

DEFF Research Database (Denmark)

2012-01-01

A power oscillation damping controller is provided for a power generation device such as a wind turbine device. The power oscillation damping controller receives an oscillation indicating signal indicative of a power oscillation in an electricity network and provides an oscillation damping control...

Optogenetically evoked gamma oscillations are disturbed by cocaine administration

Directory of Open Access Journals (Sweden)

Jonathan E Dilgen

2013-11-01

Full Text Available Drugs of abuse have enormous societal impact by degrading the cognitive abilities, emotional state and social behavior of addicted individuals. Among other events involved in the addiction cycle, the study of a single exposure to cocaine, and the contribution of the effects of that event to the continuous and further use of drugs of abuse are fundamental. Gamma oscillations are thought to be important neural correlates of cognitive processing in the prefrontal cortex (PFC which include decision making, set shifting and working memory. It follows that cocaine exposure might modulate gamma oscillations, which could result in reduced cognitive ability. Parvalbumin-positive fast-spiking interneurons play an orchestrating role in gamma oscillation induction and it has been shown recently that gamma oscillations can be induced in an anesthetized animal using optogenetic techniques. We use a knock-in mouse model together with optogenetics and in vivo electrophysiology to study the effects of acute cocaine on PFC gamma oscillation as a step toward understanding the cortical changes that may underlie continuous use of stimulants. Our results show that acute cocaine administration increases entrainment of the gamma oscillation to the optogentically induced driving frequency. Our results also suggest that this modulation of gamma oscillations is driven trough activation of DAD1 receptors. The acute cocaine-mediated changes in mPFC may underlie the enhancement of attention and awareness commonly reported by cocaine users and may contribute to the further use and abuse of psychostimulants.

Investigation of a mutual interaction force at different pressure amplitudes in sulfuric acid

International Nuclear Information System (INIS)

Rezaee, Nastaran; Sadighi-Bonabi, Rasoul; Mirheydari, Mona; Ebrahimi, Homa

2011-01-01

This paper investigates the secondary Bjerknes force for two oscillating bubbles in various pressure amplitudes in a concentration of 95% sulfuric acid. The equilibrium radii of the bubbles are assumed to be smaller than 10 μm at a frequency of 37 kHz in various strong driving acoustical fields around 2.0 bars (1 bar=10 5 Pa). The secondary Bjerknes force is investigated in uncoupled and coupled states between the bubbles, with regard to the quasi-adiabatic model for the bubble interior. It finds that the value of the secondary Bjerknes force depends on the driven pressure of sulfuric acid and its amount would be increased by liquid pressure amplitude enhancement. The results show that the repulsion area of the interaction force would be increased by increasing the driven pressure because of nonlinear oscillation of bubbles. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Noise-sustained and controlled synchronization of stirred excitable media by external forcing

International Nuclear Information System (INIS)

Zhou Changsong; Kurths, Juergen

2005-01-01

Most of the previous studies on constructive effects of noise in spatially extended systems have focused on static media, e.g., of the reaction-diffusion type. Because many active chemical or biological processes occur in a fluid environment with mixing, we investigate here the interplay among noise, excitability, mixing and external forcing in excitable media advected by a chaotic flow, in a two-dimensional FitzHugh-Nagumo model described by a set of reaction-advection-diffusion equations. In the absence of external forcing, noise may generate sustained coherent oscillations of the media in a range of noise intensities and stirring rates. We find that these noise-sustained oscillations can be synchronized by external periodic signals much smaller than the threshold. Analysis of the locking regions in the parameter space of the signal period, stirring rate and noise intensity reveals that the mechanism underlying the synchronization behaviour is a matching between the time scales of the forcing signal and the noise-sustained oscillations. The results demonstrate that, in the presence of a suitable level of noise, the stirred excitable media act as self-sustained oscillatory systems and become much easier to be entrained by weak external forcing. Our results may be verified in experiments and are useful to understand the synchronization of population dynamics of oceanic ecological systems by annual cycles

Noise-sustained and controlled synchronization of stirred excitable media by external forcing

Energy Technology Data Exchange (ETDEWEB)

Zhou Changsong; Kurths, Juergen [Institute of Physics, University of Potsdam, PF 601553, 14415 Potsdam (Germany)

2005-01-01

Most of the previous studies on constructive effects of noise in spatially extended systems have focused on static media, e.g., of the reaction-diffusion type. Because many active chemical or biological processes occur in a fluid environment with mixing, we investigate here the interplay among noise, excitability, mixing and external forcing in excitable media advected by a chaotic flow, in a two-dimensional FitzHugh-Nagumo model described by a set of reaction-advection-diffusion equations. In the absence of external forcing, noise may generate sustained coherent oscillations of the media in a range of noise intensities and stirring rates. We find that these noise-sustained oscillations can be synchronized by external periodic signals much smaller than the threshold. Analysis of the locking regions in the parameter space of the signal period, stirring rate and noise intensity reveals that the mechanism underlying the synchronization behaviour is a matching between the time scales of the forcing signal and the noise-sustained oscillations. The results demonstrate that, in the presence of a suitable level of noise, the stirred excitable media act as self-sustained oscillatory systems and become much easier to be entrained by weak external forcing. Our results may be verified in experiments and are useful to understand the synchronization of population dynamics of oceanic ecological systems by annual cycles.

Observation of helium flow induced beam orbit oscillations at RHIC

International Nuclear Information System (INIS)

Montag, C.; Bonati, R.; Brennan, J.M.; Butler, J.; Cameron, P.; Ganetis, G.; He, P.; Hirzel, W.; Jia, L.X.; Koello, P.; Louie, W.; McIntyre, G.; Nicoletti, A.; Rank, J.; Roser, T.; Satogata, T.; Schmalzle, J.; Sidi-Yekhlef, A.; Sondericker, J.; Tallerico, T.

2006-01-01

Horizontal beam orbit jitter at frequencies around 10 Hz has been observed at RHIC for several years. The distinct frequencies of this jitter have been found at superconducting low-beta quadrupole triplet magnets around the ring, where they coincide with mechanical vibration modes of the cold masses. Recently, we have identified liquid helium flow as the driving force of these oscillations

Nonstandard conserved Hamiltonian structures in dissipative/damped systems: Nonlinear generalizations of damped harmonic oscillator

International Nuclear Information System (INIS)

Pradeep, R. Gladwin; Chandrasekar, V. K.; Senthilvelan, M.; Lakshmanan, M.

2009-01-01

In this paper we point out the existence of a remarkable nonlocal transformation between the damped harmonic oscillator and a modified Emden-type nonlinear oscillator equation with linear forcing, xe+αxx+βx 3 +γx=0, which preserves the form of the time independent integral, conservative Hamiltonian, and the equation of motion. Generalizing this transformation we prove the existence of nonstandard conservative Hamiltonian structure for a general class of damped nonlinear oscillators including Lienard-type systems. Further, using the above Hamiltonian structure for a specific example, namely, the generalized modified Emden equation xe+αx q x+βx 2q+1 =0, where α, β, and q are arbitrary parameters, the general solution is obtained through appropriate canonical transformations. We also present the conservative Hamiltonian structure of the damped Mathews-Lakshmanan oscillator equation. The associated Lagrangian description for all the above systems is also briefly discussed.

An Apparatus to Demonstrate Linear and Nonlinear Oscillations of a Pendulum

Science.gov (United States)

Mayer, V. V.; Varaksina, E. I.

2016-01-01

A physical pendulum with a magnetic load is proposed for comparison of linear and nonlinear oscillations. The magnetic load is repelled by permanent magnets which are disposed symmetrically relative to the load. It is established that positions of the pendulum and the magnets determine the dependence of restoring force on displacement of the load.…

Modal analysis of inter-area oscillations using the theory of normal modes

Energy Technology Data Exchange (ETDEWEB)

Betancourt, R.J. [School of Electromechanical Engineering, University of Colima, Manzanillo, Col. 28860 (Mexico); Barocio, E. [CUCEI, University of Guadalajara, Guadalajara, Jal. 44480 (Mexico); Messina, A.R. [Graduate Program in Electrical Engineering, Cinvestav, Guadalajara, Jal. 45015 (Mexico); Martinez, I. [State Autonomous University of Mexico, Toluca, Edo. Mex. 50110 (Mexico)

2009-04-15

Based on the notion of normal modes in mechanical systems, a method is proposed for the analysis and characterization of oscillatory processes in power systems. The method is based on the property of invariance of modal subspaces and can be used to represent complex power system modal behavior by a set of decoupled, two-degree-of-freedom nonlinear oscillator equations. Using techniques from nonlinear mechanics, a new approach is outlined, for determining the normal modes (NMs) of motion of a general n-degree-of-freedom nonlinear system. Equations relating the normal modes and the physical velocities and displacements are developed from the linearized system model and numerical issues associated with the application of the technique are discussed. In addition to qualitative insight, this method can be utilized in the study of nonlinear behavior and bifurcation analyses. The application of these procedures is illustrated on a planning model of the Mexican interconnected system using a quadratic nonlinear model. Specifically, the use of normal mode analysis as a basis for identifying modal parameters, including natural frequencies and damping ratios of general, linear systems with n degrees of freedom is discussed. Comparisons to conventional linear analysis techniques demonstrate the ability of the proposed technique to extract the different oscillation modes embedded in the oscillation. (author)

A Fabrication Technique for Nano-gap Electrodes by Atomic Force Microscopy Nano lithography

International Nuclear Information System (INIS)

Jalal Rouhi; Shahrom Mahmud; Hutagalung, S.D.; Kakooei, S.

2011-01-01

A simple technique is introduced for fabrication of nano-gap electrodes by using nano-oxidation atomic force microscopy (AFM) lithography with a Cr/ Pt coated silicon tip. AFM local anodic oxidation was performed on silicon-on-insulator (SOI) surfaces by optimization of desired conditions to control process in contact mode. Silicon electrodes with gaps of sub 31 nm were fabricated by nano-oxidation method. This technique which is simple, controllable, inexpensive and fast is capable of fabricating nano-gap structures. The current-voltage measurements (I-V) of the electrodes demonstrated very good insulating characteristics. The results show that silicon electrodes have a great potential for fabrication of single molecule transistors (SMT), single electron transistors (SET) and the other nano electronic devices. (author)

Flow around an oscillating cylinder: computational issues

Energy Technology Data Exchange (ETDEWEB)

Jiang, Fengjian; Gallardo, José P; Pettersen, Bjørnar [Department of Marine Technology, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); Andersson, Helge I, E-mail: fengjian.jiang@ntnu.no [Department of Energy and Process Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway)

2017-10-15

We consider different computational issues related to the three-dimensionalities of the flow around an oscillating circular cylinder. The full time-dependent Navier–Stokes equations are directly solved in a moving reference frame by introducing a forcing term. The choice of quantitative validation criteria is discussed and discrepancies of previously published results are addressed. The development of Honji vortices shows that short simulation times may lead to incorrect quasi-stable vortex patterns. The viscous decay of already established Honji vortices is also examined. (paper)

Power system low frequency oscillation monitoring and analysis based on multi-signal online identification

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

The advance in the wide-area measurement system (WAMS) is driving the power system to the trend of wide-area monitoring and control.The Prony method is usually used for low frequency oscillation online identification.However,the identified amplitude and phase information is not sufficiently used.In this paper,the amplitude is adopted to detect the occurrence of the oscillation and to obtain the mode observability of the sites.The phase is adopted to identify the oscillation generator grouping and to obtain the mode shapes.The time varying characteristics of low frequency oscillations are studied.The behaviors and the characters of low frequency oscillations are displayed by dynamic visual techniques.Demonstrations on the "11.9" low frequency oscillation of the Guizhou Power Grid substantiate the feasibility and the validation of the proposed methods.

Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact.

Science.gov (United States)

Sylos-Labini, Francesca; d'Avella, Andrea; Lacquaniti, Francesco; Ivanenko, Yury

2018-01-01

Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free) arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating) arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries ("quadrupedal" arm-leg coordination) during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and coordinate steps during

Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact

Directory of Open Access Journals (Sweden)

Francesca Sylos-Labini

2018-03-01

Full Text Available Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries (“quadrupedal” arm-leg coordination during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and

Oscillators - a simple introduction

DEFF Research Database (Denmark)

Lindberg, Erik

2013-01-01

Oscillators are kernel components of electrical and electronic circuits. Discussion of history, mechanisms and design based on Barkhausens observation. Discussion of a Wien Bridge oscillator based on the question: Why does this circuit oscillate ?......Oscillators are kernel components of electrical and electronic circuits. Discussion of history, mechanisms and design based on Barkhausens observation. Discussion of a Wien Bridge oscillator based on the question: Why does this circuit oscillate ?...

The natural oscillation of two types of ENSO events based on analyses of CMIP5 model control runs

Science.gov (United States)

Xu, Kang; Su, Jingzhi; Zhu, Congwen

2014-07-01

The eastern- and central-Pacific El Niño-Southern Oscillation (EP- and CP-ENSO) have been found to be dominant in the tropical Pacific Ocean, and are characterized by interannual and decadal oscillation, respectively. In the present study, we defined the EP- and CP-ENSO modes by singular value decomposition (SVD) between SST and sea level pressure (SLP) anomalous fields. We evaluated the natural features of these two types of ENSO modes as simulated by the pre-industrial control runs of 20 models involved in phase five of the Coupled Model Intercomparison Project (CMIP5). The results suggested that all the models show good skill in simulating the SST and SLP anomaly dipolar structures for the EP-ENSO mode, but only 12 exhibit good performance in simulating the tripolar CP-ENSO modes. Wavelet analysis suggested that the ensemble principal components in these 12 models exhibit an interannual and multi-decadal oscillation related to the EP- and CP-ENSO, respectively. Since there are no changes in external forcing in the pre-industrial control runs, such a result implies that the decadal oscillation of CP-ENSO is possibly a result of natural climate variability rather than external forcing.

Multiphase patterns in periodically forced oscillatory systems

International Nuclear Information System (INIS)

Elphick, C.; Hagberg, A.; Meron, E.

1999-01-01

Periodic forcing of an oscillatory system produces frequency locking bands within which the system frequency is rationally related to the forcing frequency. We study extended oscillatory systems that respond to uniform periodic forcing at one quarter of the forcing frequency (the 4:1 resonance). These systems possess four coexisting stable states, corresponding to uniform oscillations with successive phase shifts of π/2. Using an amplitude equation approach near a Hopf bifurcation to uniform oscillations, we study front solutions connecting different phase states. These solutions divide into two groups: π fronts separating states with a phase shift of π and π/2 fronts separating states with a phase shift of π/2. We find a type of front instability where a stationary π front 'decomposes' into a pair of traveling π/2 fronts as the forcing strength is decreased. The instability is degenerate for an amplitude equation with cubic nonlinearities. At the instability point a continuous family of pair solutions exists, consisting of π/2 fronts separated by distances ranging from zero to infinity. Quintic nonlinearities lift the degeneracy at the instability point but do not change the basic nature of the instability. We conjecture the existence of similar instabilities in higher 2n:1 resonances (n=3,4,hor-ellipsis) where stationary π fronts decompose into n traveling π/n fronts. The instabilities designate transitions from stationary two-phase patterns to traveling 2n-phase patterns. As an example, we demonstrate with a numerical solution the collapse of a four-phase spiral wave into a stationary two-phase pattern as the forcing strength within the 4:1 resonance is increased. copyright 1999 The American Physical Society

Upper Incisor Changes Due to Modifying the Point of Application of Forces during Space Closure in MBT Technique

Directory of Open Access Journals (Sweden)

H. Ravanmehr

2004-06-01

Full Text Available Statement of Problem: A recent technique (MBT has been introduced for easy and efficient orthodontic treatment by means of straight wire fixed appliances. Although this technique has many advantages, in space closure stage causes up righting problem in upper incisors, which should be adjusted by applying additional torque in anterior region.Purpose: The purpose of this clinical trial was to determine whether there is a significant difference in final incisor inclination (torque of two groups one treated with MBT technique and the other by changing the point of application of the closing force (in anterior region.Materials and Methods: Twelve patients (8 girls, 4 boys with Cl I malocclusion and crowding, whom were candidate for first premolars extraction, were selected.For space closure, 6 anterior teeth (canine to canine in upper and lower jaws ligated and the applied force was from the hooks on canines to hooks on the first molars.After space closure the results compared with the results of a previous study which treatment plan was according to original MBT technique (anterior hooks soldered to arch wire. Forces applied randomly among quadrants by NiTi coil spring (American Orthodontics Co. or active tie backs with elastic modules (Dentaurum Co.Results: The results showed a statistically significant difference between final torques of two techniques (P=0.0001. Also, the rate of space closure with NiTi coils was significantly greater than active tie back (P=0.0001.Conclusion: Anchorage loss in two groups compared and the results indicated significantly lower anchorage loss in NiTi coil spring group (P=0.035.

New force replica exchange method and protein folding pathways probed by force-clamp technique.

Science.gov (United States)

Kouza, Maksim; Hu, Chin-Kun; Li, Mai Suan

2008-01-28

We have developed a new extended replica exchange method to study thermodynamics of a system in the presence of external force. Our idea is based on the exchange between different force replicas to accelerate the equilibrium process. This new approach was applied to obtain the force-temperature phase diagram and other thermodynamical quantities of the three-domain ubiquitin. Using the C(alpha)-Go model and the Langevin dynamics, we have shown that the refolding pathways of single ubiquitin depend on which terminus is fixed. If the N end is fixed then the folding pathways are different compared to the case when both termini are free, but fixing the C terminal does not change them. Surprisingly, we have found that the anchoring terminal does not affect the pathways of individual secondary structures of three-domain ubiquitin, indicating the important role of the multidomain construction. Therefore, force-clamp experiments, in which one end of a protein is kept fixed, can probe the refolding pathways of a single free-end ubiquitin if one uses either the polyubiquitin or a single domain with the C terminus anchored. However, it is shown that anchoring one end does not affect refolding pathways of the titin domain I27, and the force-clamp spectroscopy is always capable to predict folding sequencing of this protein. We have obtained the reasonable estimate for unfolding barrier of ubiquitin, using the microscopic theory for the dependence of unfolding time on the external force. The linkage between residue Lys48 and the C terminal of ubiquitin is found to have the dramatic effect on the location of the transition state along the end-to-end distance reaction coordinate, but the multidomain construction leaves the transition state almost unchanged. We have found that the maximum force in the force-extension profile from constant velocity force pulling simulations depends on temperature nonlinearly. However, for some narrow temperature interval this dependence becomes

Using qubits to reveal quantum signatures of an oscillator

Science.gov (United States)

Agarwal, Shantanu

In this thesis, we seek to study the qubit-oscillator system with the aim to identify and quantify inherent quantum features of the oscillator. We show that the quantum signatures of the oscillator get imprinted on the dynamics of the joint system. The two key features which we explore are the quantized energy spectrum of the oscillator and the non-classicality of the oscillator's wave function. To investigate the consequences of the oscillator's discrete energy spectrum, we consider the qubit to be coupled to the oscillator through the Rabi Hamiltonian. Recent developments in fabrication technology have opened up the possibility to explore parameter regimes which were conventionally inaccessible. Motivated by these advancements, we investigate in this thesis a parameter space where the qubit frequency is much smaller than the oscillator frequency and the Rabi frequency is allowed to be an appreciable fraction of the bare frequency of the oscillator. We use the adiabatic approximation to understand the dynamics in this quasi-degenerate qubit regime. By deriving a dressed master equation, we systematically investigate the effects of the environment on the system dynamics. We develop a spectroscopic technique, using which one can probe the steady state response of the driven and damped system. The spectroscopic signal clearly reveals the quantized nature of the oscillator's energy spectrum. We extend the adiabatic approximation, earlier developed only for the single qubit case, to a scenario where multiple qubits interact with the oscillator. Using the extended adiabatic approximation, we study the collapse and revival of multi-qubit observables. We develop analytic expressions for the revival signals which are in good agreement with the numerically evaluated results. Within the quantum restriction imposed by Heisenberg's uncertainty principle, the uncertainty in the position and momentum of an oscillator is minimum and shared equally when the oscillator is prepared

Symmetry-breaking analysis for the general Helmholtz-Duffing oscillator

International Nuclear Information System (INIS)

Cao Hongjun; Seoane, Jesus M.; Sanjuan, Miguel A.F.

2007-01-01

The symmetry breaking phenomenon for a general Helmholtz-Duffing oscillator as a function of a symmetric parameter in the nonlinear force is investigated. Different values of this parameter convert the general oscillator into either the Helmholtz or the Duffing oscillator. Due to the variation of the symmetric parameter, the phase space patterns of the unperturbed Helmholtz-Duffing oscillator will cause a huge difference between the left-hand homoclinic orbit and the right-hand one. In particular, the area of the left-hand homoclinic orbits is a strictly monotonously decreasing function, while the area of the right-hand homoclinic orbit varies only in a very small range. There exist distinct local supercritical and subcritical saddle-node bifurcations at two different centers. The left-hand and the right-hand existing regions of the harmonic solutions of the Helmholtz-Duffing oscillator created by the left-hand and the right-hand saddle-node bifurcation curves will lead to different transition in the amplitude-frequency plane. There exists also a critical frequency which has the effect that the left-hand homoclinic bifurcation value is equal to the right-hand homoclinic bifurcation value. And, if the amplitude coefficient of the Helmholtz-Duffing oscillator is used as the control parameter, and it is larger than the same left-hand and right-hand homoclinic bifurcation, then the global stability of the system will be destroyed at a lowest cost. Besides this critical frequency, the left-hand and the right-hand homoclinic bifurcations are not only unequal, but also their effects for the system's stability are different. Among them, the effect resulting from the small homoclinic bifurcation for the system's stability is local and negligible, while the effect from the large homoclinic bifurcation is global but this is accomplished at a quite larger cost

Thermal decomposition of hydrotalcite-like compounds studied by a novel tapered element oscillating microbalance (TEOM)

International Nuclear Information System (INIS)

Perez-Ramirez, Javier; Abello, Sonia

2006-01-01

For the first time, we report on the application of a tapered element oscillating microbalance (TEOM) as a novel technique to investigate the thermal decomposition of hydrotalcite-like compounds (HTlcs) in air. Experiments were performed in the temperature range of 323-973 K with Mg-Al, Ni-Al, and Co-Al-HTlcs. The TEOM technique measures mass changes based on inertial forces, presenting important advantages over conventional thermogravimetric analyzers, such as the very rapid time response and the well-defined flow pattern. In general terms, excellent agreement between TEOM, TGA, and DTA techniques during HTlc decomposition was obtained. Interestingly, transition temperatures in the TEOM were lower than in TGA and DTA, particularly for removal of interlayer water but also for dehydroxylation of the brucite-like layers and decarbonation. This was attributed to the flow-through operation in the tapered element of the TEOM as compared to the recognized gas stagnancy and bypass in sample crucibles of conventional thermogravimetric analyzers. Our results conclude that the TEOM technique is suitable for temperature-programmed studies. However, due to its operation principle, blank runs are required in contrast to the more automatic operation in commercial thermogravimetric units. Besides, a careful sample loading and packing in the micro-reactor is essential for reproducible results

Anharmonic 1D actuator model including electrostatic and Casimir forces with fractional damping perturbed by an external force

Science.gov (United States)

Mansoori Kermani, Maryam; Dehestani, Maryam

2018-06-01

We modeled a one-dimensional actuator including the Casimir and electrostatic forces perturbed by an external force with fractional damping. The movable electrode was assumed to oscillate by an anharmonic elastic force originated from Murrell-Mottram or Lippincott potential. The nonlinear equations have been solved via the Adomian decomposition method. The behavior of the displacement of the electrode from equilibrium position, its velocity and acceleration were described versus time. Also, the changes of the displacement have been investigated according to the frequency of the external force and the voltage of the electrostatic force. The convergence of the Adomian method and the effect of the orders of expansion on the displacement versus time, frequency, and voltage were discussed. The pull-in parameter was obtained and compared with the other models in the literature. This parameter was described versus the equilibrium position and anharmonicity constant.

Anharmonic 1D actuator model including electrostatic and Casimir forces with fractional damping perturbed by an external force

Science.gov (United States)

Mansoori Kermani, Maryam; Dehestani, Maryam

2018-03-01

We modeled a one-dimensional actuator including the Casimir and electrostatic forces perturbed by an external force with fractional damping. The movable electrode was assumed to oscillate by an anharmonic elastic force originated from Murrell-Mottram or Lippincott potential. The nonlinear equations have been solved via the Adomian decomposition method. The behavior of the displacement of the electrode from equilibrium position, its velocity and acceleration were described versus time. Also, the changes of the displacement have been investigated according to the frequency of the external force and the voltage of the electrostatic force. The convergence of the Adomian method and the effect of the orders of expansion on the displacement versus time, frequency, and voltage were discussed. The pull-in parameter was obtained and compared with the other models in the literature. This parameter was described versus the equilibrium position and anharmonicity constant.

Restoration of oscillation in network of oscillators in presence of direct and indirect interactions

Energy Technology Data Exchange (ETDEWEB)

Majhi, Soumen; Bera, Bidesh K. [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India); Bhowmick, Sourav K. [Department of Electronics, Asutosh College, Kolkata-700026 (India); Ghosh, Dibakar, E-mail: diba.ghosh@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India)

2016-10-23

The suppression of oscillations in coupled systems may lead to several unwanted situations, which requires a suitable treatment to overcome the suppression. In this paper, we show that the environmental coupling in the presence of direct interaction, which can suppress oscillation even in a network of identical oscillators, can be modified by introducing a feedback factor in the coupling scheme in order to restore the oscillation. We inspect how the introduction of the feedback factor helps to resurrect oscillation from various kinds of death states. We numerically verify the resurrection of oscillations for two paradigmatic limit cycle systems, namely Landau–Stuart and Van der Pol oscillators and also in generic chaotic Lorenz oscillator. We also study the effect of parameter mismatch in the process of restoring oscillation for coupled oscillators. - Highlights: • Amplitude death is observed using direct and indirect coupling. • Revival of oscillation using feedback parameter is discussed. • Restoration of oscillation is observed in limit cycle and chaotic systems.

Equivalent Representation Form of Oscillators with Elastic and Damping Nonlinear Terms

Directory of Open Access Journals (Sweden)

Alex Elías-Zúñiga

2013-01-01

Full Text Available In this work we consider the nonlinear equivalent representation form of oscillators that exhibit nonlinearities in both the elastic and the damping terms. The nonlinear damping effects are considered to be described by fractional power velocity terms which provide better predictions of the dissipative effects observed in some physical systems. It is shown that their effects on the system dynamics response are equivalent to a shift in the coefficient of the linear damping term of a Duffing oscillator. Then, its numerical integration predictions, based on its equivalent representation form given by the well-known forced, damped Duffing equation, are compared to the numerical integration values of its original equations of motion. The applicability of the proposed procedure is evaluated by studying the dynamics response of four nonlinear oscillators that arise in some engineering applications such as nanoresonators, microresonators, human wrist movements, structural engineering design, and chain dynamics of polymeric materials at high extensibility, among others.

An Investigation of an Irradiated Fuel Pin by Measurement of the Production of Fast Neutrons in a Thermal Column and by Pile Oscillation Technique

International Nuclear Information System (INIS)

Gustavsson, Veine

1968-05-01

A fuel pin irradiated to about 3400 MWd/tU from the Halden reactor has been investigated by a measurement of the production of fast neutrons in a thermal column and by pile oscillator technique in the central channel of the reactor R1. Calibration was made by using samples with different U 235 enrichments. The thermal column experiment gives the quantity ave(νΣ f ) (average in the thermal column spectrum) for the Halden sample. Σ f is the macroscopic fission cross section and ν is the number of fast neutrons produced per fission. The result of the oscillator measurements is a value of ave(Σ a ) - w ave(Σ f ) (average in the central channel spectrum) for the irradiated sample, w is the importance of a fast neutron relative to a thermal one and ave(Σ a ) is the macroscopic absorption cross section. The results from both the experiments have been compared with values calculated by the REBUS code and the agreement was good

Exact diagonalization of the D-dimensional spatially confined quantum harmonic oscillator

Directory of Open Access Journals (Sweden)

Kunle Adegoke

2016-01-01

Full Text Available In the existing literature various numerical techniques have been developed to quantize the confined harmonic oscillator in higher dimensions. In obtaining the energy eigenvalues, such methods often involve indirect approaches such as searching for the roots of hypergeometric functions or numerically solving a differential equation. In this paper, however, we derive an explicit matrix representation for the Hamiltonian of a confined quantum harmonic oscillator in higher dimensions, thus facilitating direct diagonalization.

Power system low frequency oscillation mode estimation using wide area measurement systems

Directory of Open Access Journals (Sweden)

Papia Ray

2017-04-01

Full Text Available Oscillations in power systems are triggered by a wide variety of events. The system damps most of the oscillations, but a few undamped oscillations may remain which may lead to system collapse. Therefore low frequency oscillations inspection is necessary in the context of recent power system operation and control. Ringdown portion of the signal provides rich information of the low frequency oscillatory modes which has been taken into analysis. This paper provides a practical case study in which seven signal processing based techniques i.e. Prony Analysis (PA, Fast Fourier Transform (FFT, S-Transform (ST, Wigner-Ville Distribution (WVD, Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT, Hilbert-Huang Transform (HHT and Matrix Pencil Method (MPM were presented for estimating the low frequency modes in a given ringdown signal. Preprocessing of the signal is done by detrending. The application of the signal processing techniques is illustrated using actual wide area measurement systems (WAMS data collected from four different Phasor Measurement Unit (PMU i.e. Dadri, Vindyachal, Kanpur and Moga which are located near the recent disturbance event at the Northern Grid of India. Simulation results show that the seven signal processing technique (FFT, PA, ST, WVD, ESPRIT, HHT and MPM estimates two common oscillatory frequency modes (0.2, 0.5 from the raw signal. Thus, these seven techniques provide satisfactory performance in determining small frequency modes of the signal without losing its valuable property. Also a comparative study of the seven signal processing techniques has been carried out in order to find the best one. It was found that FFT and ESPRIT gives exact frequency modes as compared to other techniques, so they are recommended for estimation of low frequency modes. Further investigations were also carried out to estimate low frequency oscillatory mode with another case study of Eastern Interconnect Phasor Project

David Shoenberg and the beauty of quantum oscillations

Science.gov (United States)

Pudalov, V. M.

2011-01-01

The quantum oscillation effect was discovered in Leiden in 1930, by W. J. de Haas and P. M. van Alphen when measuring magnetization, and by L. W. Shubnikov and de Haas when measuring magnetoresistance. Studying single crystals of bismuth, they observed oscillatory variations in the magnetization and magnetoresistance with magnetic field. Shoenberg, whose first research in Cambridge had been on bismuth, found that much stronger oscillations are observed when a bismuth sample is cooled to liquid helium temperature rather than liquid hydrogen, which had been used by de Haas. In 1938 Shoenberg went from Cambridge to Moscow to study these oscillations at Kapitza's Institute where liquid helium was available at that time. In 1947, J. Marcus observed similar oscillations in zinc and that persuaded Schoenberg to return to this research. After that, the dHvA effect became one of his main research topics. In particular, he developed techniques for quantitative measurement of this effect in many metals. A theoretical explanation of quantum oscillations was given by L. Onsager in 1952, and an analytical quantitative theory by I. M. Lifshitz and A. M. Kosevich in 1955. These theoretical advances seemed to provide a comprehensive description of the effect. Since then, quantum oscillations have been widely used as a tool for measuring Fermi surface extremal cross-sections and all-angle electron scattering times. In his pioneering experiments of the 1960's, Shoenberg revealed the richness and deep essence of the quantum oscillation effect and showed how the beauty of the effect is disclosed under nonlinear conditions imposed by interactions in the system under study. It was quite surprising that "magnetic interaction" conditions could cause the apparently weak quantum oscillation effect to have such strong consequences as breaking the sample into magnetic (now called "Shoenberg") domains and forming an inhomogeneous magnetic state. With his contributions to the field of quantum

David Schoenberg and the beauty of quantum oscillations

International Nuclear Information System (INIS)

Pudalov, V.M.

2012-01-01

The quantum oscillation effect was discovered in Leiden, in 1930, by W.J. de Haas and P.M. van Alphen in magnetization measurement, and by L.W. Shubnikov and de Haas - in magnetoresistance. Studying single crystals of bismuth, they observed oscillatory variations of magnetization and magnetoresistance with magnetic field. Shoenberg, whose first research in Cambridge had been on bismuth, found that much stronger oscillations are observed when a bismuth sample is cooled to liquid helium rather than to liquid hydrogen, which had been used by de Haas. In 1938 Shoenberg came from Cambridge to Moscow to study these oscillations at Kapitza Institute where liquid helium was available at that time. In 1947, J. Marcus observed similar oscillations in zinc, that persuaded Shoenberg to return to this research, and, since then, the dHvA effect had been one of his main research topic. In particular, he developed techniques for quantitative measurements of the effect in many metals. Theoretical explanation of quantum oscillations was given by L. Onsager in 1952, and the analytical quantitative theory by I.M. Lifshitz and A.M. Kosevich in 1955. These theoretical advancements seemed to provide a comprehensive description of the effect. Since then, quantum oscillations were commonly considered as a tool for measuring Fermi surface extremal cross-sections and all-angle electron scattering times. However, in his pioneering experiments in 1960s, Shoenberg revealed the richness and deep essence of the quantum oscillation effect and showed how the beauty of the effect is disclosed under nonlinear conditions imposed by interactions in the system under study. It was quite unexpected, that under 'magnetic interaction' conditions, the apparently weak effect of quantum oscillations may lead to such strong consequences as breaking the sample into magnetic (now called 'Shoenberg') domains and the formation of an inhomogeneous magnetic state. Owing to his contribution to the field of quantum

Short-range fundamental forces

International Nuclear Information System (INIS)

Antoniadis, I.; Baessler, S.; Buchner, M.; Fedorov, V.V.; Hoedl, S.; Nesvizhevsky, V.V.; Pignol, G.; Protasov, K.V.; Lambrecht, A.; Reynaud, S.; Sobolev, Y.

2010-01-01

We consider theoretical motivations to search for extra short-range fundamental forces as well as experiments constraining their parameters. The forces could be of two types: 1) spin-independent forces; 2) spin-dependent axion-like forces. Different experimental techniques are sensitive in respective ranges of characteristic distances. The techniques include measurements of gravity at short distances, searches for extra interactions on top of the Casimir force, precision atomic and neutron experiments. We focus on neutron constraints, thus the range of characteristic distances considered here corresponds to the range accessible for neutron experiments

The Pacific Ventilated Thermocline and its Influence on the Pacific Decadal Oscillation and Global Warming

Science.gov (United States)

Kuntz, L.; Schrag, D. P.

2017-12-01

Over the past century, global surface temperatures have warmed episodically despite relatively steady increases in radiative forcing. Coincident with these transitions, we identify changes in the structure of the ventilated thermocline in the Pacific as well as changes in the intensity of the equatorial undercurrent. We propose a new mechanism for the Pacific Decadal Oscillation that involves oscillations in the strength of the equatorial undercurrent and may explain multi-decadal variability of global temperatures. We suggest that the oscillation results in a greater or lesser volume of cold water reaching the eastern Pacific, which ultimately leads to a change in the heat flux out of this critical region. By varying the heat flux in the tropical Pacific in model simulations, we reproduce a stepwise pattern of warming that resembles the historical climate record without additional variability in forcing. In addition, the trajectory of the changes in thermocline structure that we now observe in the Pacific looks like it will arrive at the equator in the middle of the next decade, suggesting that the current period of reduced warming (aka "hiatus") will persist through the mid-2020s.

Study of aerosol sample interaction with dc plasma in the presence of oscillating magnetic field

International Nuclear Information System (INIS)

Stoiljkovic, M.M.; Pavlovic, M.S.; Savovic, J.; Kuzmanovic, M.; Marinkovic, M.

2005-01-01

Oscillating magnetic field was used to study the efficiency of the aerosol sample introduction into the dc plasma. At atmospheric plasmas, the effect of magnetic field is reduced to Lorentz forces on the current carrying plasma, which produces motion of the plasma. The motion velocity of dc plasma caused by oscillating magnetic field was correlated to spectral emission enhancement of analytes introduced as aerosols. Emission enhancement is the consequence of the reduced barrier to introduction of analyte species and aerosol particles into the hot plasma region. Two hypotheses described in the literature for the origin of the barrier are considered: (i) barrier induced by temperature field is based upon the thermophoretic forces on the aerosol particles when their radius is comparable to the molecular free path in the surrounding gas and (ii) barrier induced by radial electric field, recently described, that originates from gradients of charged particles in radial direction. Correlation between ionization energy of the analyte atoms with experimental emission enhancement obtained by the use of oscillating magnetic field indicates that mechanism (ii) based upon the radial electric field is predominant. The ultimate emission enhancement and possible analytical advantage is discussed

Oscillations of void lattices

International Nuclear Information System (INIS)

Akhiezer, A.I.; Davydov, L.N.; Spol'nik, Z.A.

1976-01-01

Oscillations of a nonideal crystal are studied, in which macroscopic defects (pores) form a hyperlattice. It is shown that alongside with acoustic and optical phonons (relative to the hyperlattice), in such a crystal oscillations of the third type are possible which are a hydridization of sound oscillations of atoms and surface oscillations of a pore. Oscillation spectra of all three types were obtained

Interfacial force measurements using atomic force microscopy

NARCIS (Netherlands)

Chu, L.

2018-01-01

Atomic Force Microscopy (AFM) can not only image the topography of surfaces at atomic resolution, but can also measure accurately the different interaction forces, like repulsive, adhesive and lateral existing between an AFM tip and the sample surface. Based on AFM, various extended techniques have

Remarks to the local power oscillation phenomenon at BWRs

International Nuclear Information System (INIS)

Lange, Carsten; Hennig, Dieter; Hurtado, Antonio

2011-01-01

In the framework of BWR stability analysis, local neutron-flux oscillation events have attracted the attention of a number of researchers. In 1996, an unusual instability event occurred at Forsmark-1 in which superimposed on the classical, spatial mode oscillations, there were relatively large-amplitude, highly localised oscillations. Subsequent time-series analysis of the local power range monitor (LPRM) signals resulted in a space-dependent decay ratio, an inexplicable result. Furthermore, noise analysis-based localization techniques pointed towards the existence of two strong 'perturbation sources' in the two halves of the core, one of them coinciding with the radial position of an unseated bundle. In the scope of a theoretical work, the possibility of a space-dependent decay ratio was discussed but not comprehensively understood. Motivated by these findings the effect of local neutron-flux oscillations on the BWR stability behaviour is discussed and one possible interpretation is proposed which is able to explain the space dependent decay ratio and the long term oscillation pattern as well. The effect of the local neutron flux oscillating sources on the space and time dependent neutron field is described by a rigorous application of the mode expansion approach. The consequences to signal analysis are then discussed. It will be pointed out in the paper that when a BWR system is stable regarding power oscillations but driven by local neutron-flux oscillating sources, the decay ratio is on the one hand not space-dependent and on the other hand it does not indicate the real BWR stability behaviour. The RAM-ROM method is applied to the Forsmark case M2 and an operational point (KKB-B8) of NPP Brunsbüttel, where a local neutron-flux oscillation is superimposed on an unstable global power oscillation. The results of the bifurcation analysis, using BIFDD, and of the numerical integration are presented for KKB-B8 and Forsmark M2. (author)

Measuring background by the DIN-1M spectrometer using the oscillating absorbing screen method

International Nuclear Information System (INIS)

Glazkov, Yu.Yu.; Liforov, V.G.; Novikov, A.G.; Parfenov, V.A.; Semenov, V.A.

1982-01-01

Technique for measuring background by a double pulse slow neutron spectrometer is described. To measure the background on oscillating absorbing screen (OAS) periodically overlapping primary neutron beam at the input of a mechanical interrupter was used. During the overlapping monochromatic neutrons conditioned the effect are removed out of the beam and general background conditions are not practically applied. Screen oscillation permits to realize the condition of simultaneous measurement of effect and background neutrons. The optimal period of oscillations amounts to approximately 3 min. Analysis of neutron spectra scattered with different materials and corresponding background curves measured by means of the OAS technique shows that the share of monochromatic neutrons passing through the screen constitutes less than 1% of elastic peak and relative decrease of the total background level doesn't exceed 1.5-2%

Stimulus-dependent modulation of spontaneous low-frequency oscillations in the rat visual cortex.

Science.gov (United States)

Huang, Liangming; Liu, Yadong; Gui, Jianjun; Li, Ming; Hu, Dewen

2014-08-06

Research on spontaneous low-frequency oscillations is important to reveal underlying regulatory mechanisms in the brain. The mechanism for the stimulus modulation of low-frequency oscillations is not known. Here, we used the intrinsic optical imaging technique to examine stimulus-modulated low-frequency oscillation signals in the rat visual cortex. The stimulation was presented monocularly as a flashing light with different frequencies and intensities. The phases of low-frequency oscillations in different regions tended to be synchronized and the rhythms typically accelerated within a 30-s period after stimulation. These phenomena were confined to visual stimuli with specific flashing frequencies (12.5-17.5 Hz) and intensities (5-10 mA). The acceleration and synchronization induced by the flashing frequency were more marked than those induced by the intensity. These results show that spontaneous low-frequency oscillations can be modulated by parameter-dependent flashing lights and indicate the potential utility of the visual stimulus paradigm in exploring the origin and function of low-frequency oscillations.

Oscillations of disks

CERN Document Server

Kato, Shoji

2016-01-01

This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...

Self-oscillation in spin torque oscillator stabilized by field-like torque

International Nuclear Information System (INIS)

Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Imamura, Hiroshi

2014-01-01

The effect of the field-like torque on the self-oscillation of the magnetization in spin torque oscillator with a perpendicularly magnetized free layer was studied theoretically. A stable self-oscillation at zero field is excited for negative β while the magnetization dynamics stops for β = 0 or β > 0, where β is the ratio between the spin torque and the field-like torque. The reason why only the negative β induces the self-oscillation was explained from the view point of the energy balance between the spin torque and the damping. The oscillation power and frequency for various β were also studied by numerical simulation

The influence of "C-factor" and light activation technique on polymerization contraction forces of resin composite

Directory of Open Access Journals (Sweden)

Sérgio Kiyoshi Ishikiriama

2012-12-01

Full Text Available OBJECTIVES: This study evaluated the influence of the cavity configuration factor ("C-Factor" and light activation technique on polymerization contraction forces of a Bis-GMA-based composite resin (Charisma, Heraeus Kulzer. MATERIAL AND METHODS: Three different pairs of steel moving bases were connected to a universal testing machine (emic DL 500: groups A and B - 2x2 mm (CF=0.33, groups C and D - 3x2 mm (CF=0.66, groups e and F - 6x2 mm (CF=1.5. After adjustment of the height between the pair of bases so that the resin had a volume of 12 mm³ in all groups, the material was inserted and polymerized by two different methods: pulse delay (100 mW/cm² for 5 s, 40 s interval, 600 mW/cm² for 20 s and continuous pulse (600 mW/cm² for 20 s. Each configuration was light cured with both techniques. Tensions generated during polymerization were recorded by 120 s. The values were expressed in curves (Force(N x Time(s and averages compared by statistical analysis (ANOVA and Tukey's test, p<0.05. RESULTS: For the 2x2 and 3x2 bases, with a reduced C-Factor, significant differences were found between the light curing methods. For 6x2 base, with high C-Factor, the light curing method did not influence the contraction forces of the composite resin. CONCLUSIONS: Pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced C-Factor is present.

Electrical characterization of grain boundaries of CZTS thin films using conductive atomic force microscopy techniques

Energy Technology Data Exchange (ETDEWEB)

Muhunthan, N.; Singh, Om Pal [Compound Semiconductor Solar Cell, Physics of Energy Harvesting Division, New Delhi 110012 (India); Toutam, Vijaykumar, E-mail: toutamvk@nplindia.org [Quantum Phenomena and Applications Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Singh, V.N., E-mail: singhvn@nplindia.org [Compound Semiconductor Solar Cell, Physics of Energy Harvesting Division, New Delhi 110012 (India)

2015-10-15

Graphical abstract: Experimental setup for conducting AFM (C-AFM). - Highlights: • Cu{sub 2}ZnSnS{sub 4} (CZTS) thin film was grown by reactive co-sputtering. • The electronic properties were probed using conducting atomic force microscope, scanning Kelvin probe microscopy and scanning capacitance microscopy. • C-AFM current flow mainly through grain boundaries rather than grain interiors. • SKPM indicated higher potential along the GBs compared to grain interiors. • The SCM explains that charge separation takes place at the interface of grain and grain boundary. - Abstract: Electrical characterization of grain boundaries (GB) of Cu-deficient CZTS (Copper Zinc Tin Sulfide) thin films was done using atomic force microscopic (AFM) techniques like Conductive atomic force microscopy (CAFM), Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM). Absorbance spectroscopy was done for optical band gap calculations and Raman, XRD and EDS for structural and compositional characterization. Hall measurements were done for estimation of carrier mobility. CAFM and KPFM measurements showed that the currents flow mainly through grain boundaries (GB) rather than grain interiors. SCM results showed that charge separation mainly occurs at the interface of grain and grain boundaries and not all along the grain boundaries.

Competition of elastic and adhesive properties of carbon nanotubes anchored to atomic force microscopy tips

International Nuclear Information System (INIS)

Bernard, Charlotte; Marsaudon, Sophie; Boisgard, Rodolphe; Aime, Jean-Pierre

2008-01-01

In this paper we address the mechanical properties of carbon nanotubes anchored to atomic force microscopy (AFM) tips in a detailed analysis of experimental results and exhaustive description of a simple model. We show that volume elastic and surface adhesive forces both contribute to the dynamical AFM experimental signals. Their respective weights depend on the nanotube properties and on an experimental parameter: the oscillation amplitude. To quantify the elastic and adhesive contributions, a simple analytical model is used. It enables analytical expressions of the resonance frequency shift and dissipation that can be measured in the atomic force microscopy dynamical frequency modulation mode. It includes the nanotube adhesive contribution to the frequency shift. Experimental data for single-wall and multi-wall carbon nanotubes compare well to the model predictions for different oscillation amplitudes. Three parameters can be extracted: the distance necessary to unstick the nanotube from the surface and two spring constants corresponding to tube compression and to the elastic force required to overcome the adhesion force

Exact solutions for oscillators with quadratic damping and mixed-parity nonlinearity

International Nuclear Information System (INIS)

Lai, S K; Chow, K W

2012-01-01

Exact vibration modes of a nonlinear oscillator, which contains both quadratic friction and a mixed-parity restoring force, are derived analytically. Two families of exact solutions are obtained in terms of rational expressions for classical Jacobi elliptic functions. The present solutions allow the investigation of the dynamical behaviour of the system in response to changes in physical parameters that concern nonlinearity. The physical significance of the signs (i.e. attractive or repulsive nature) of the linear, quadratic and cubic restoring forces is discussed. A qualitative analysis is also conducted to provide valuable physical insight into the nature of the system. (paper)

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study.

Directory of Open Access Journals (Sweden)

Ilka Meinert

Full Text Available Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill on oscillations at the Achilles tendon.Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running.Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01 with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition.Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs.

Application of a modified rational harmonic balance method for a class of strongly nonlinear oscillators

International Nuclear Information System (INIS)

Belendez, A.; Gimeno, E.; Alvarez, M.L.; Mendez, D.I.; Hernandez, A.

2008-01-01

An analytical approximate technique for conservative nonlinear oscillators is proposed. This method is a modification of the rational harmonic balance method in which analytical approximate solutions have rational form. This approach gives us the frequency of the motion as a function of the amplitude of oscillation. We find that this method works very well for the whole range of parameters, and excellent agreement of the approximate frequencies with the exact one has been demonstrated and discussed. The most significant features of this method are its simplicity and its excellent accuracy for the whole range of oscillation amplitude values and the results reveal that this technique is very effective and convenient for solving conservative truly nonlinear oscillatory systems with complex nonlinearities

Effects of phase lag on the information rate of a bistable Duffing oscillator

International Nuclear Information System (INIS)

Perkins, Edmon; Balachandran, Balakumar

2015-01-01

To utilize noise for systems, which are transmitting or receiving information, the information rate is a necessary metric to consider. The phase lag, which is the difference between the sender (applied forcing) and receiver (the oscillator) phases, has a significant effect on the information rate. However, this phase lag is a nonlinear function of the noise level. Here, the effects of phase lag on the information rate for a Duffing oscillator are examined and comparative discussions are made with phase lag from linear response theory. The phase lag is shown to be an important variable in calculating the information rate. - Highlights: • Simulations and Fokker–Planck analysis for Duffing oscillator response are performed. • The phase lag is found to be a nonlinear function of the noise level. • The phase lag is shown to be important for calculating the information rate metric

Effects of phase lag on the information rate of a bistable Duffing oscillator

Energy Technology Data Exchange (ETDEWEB)

Perkins, Edmon, E-mail: edmon@umd.edu; Balachandran, Balakumar, E-mail: balab@umd.edu

2015-02-06

To utilize noise for systems, which are transmitting or receiving information, the information rate is a necessary metric to consider. The phase lag, which is the difference between the sender (applied forcing) and receiver (the oscillator) phases, has a significant effect on the information rate. However, this phase lag is a nonlinear function of the noise level. Here, the effects of phase lag on the information rate for a Duffing oscillator are examined and comparative discussions are made with phase lag from linear response theory. The phase lag is shown to be an important variable in calculating the information rate. - Highlights: • Simulations and Fokker–Planck analysis for Duffing oscillator response are performed. • The phase lag is found to be a nonlinear function of the noise level. • The phase lag is shown to be important for calculating the information rate metric.

Characteristics of low-frequency oscillation intensity of airsea turbulent heat fluxes over the northwest Pacific

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

Based on the daily turbulent heat fluxes and related meteorological variables datasets (1985-2006) from Objectively Analyzed air-sea Fluxes (OAFlux) Project of Woods Hole Oceanographic Institution (WHOI), characteristics of low-frequency oscillation intensity of air-sea turbulent heat fluxes over the northwest Pacific are analyzed by linear perturbation method and correlation analysis. It can be concluded that: 1) the distribution of low-frequency oscillation intensity of latent heat flux (LHF) over the northwest Pacific is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea humidity gradient (Δq′) as well as mean air-sea humidity gradient ( Δ q), while the distribution of low-frequency oscillation intensity of sensible heat flux (SHF) is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea temperature gradient (ΔT′). 2) The low-frequency oscillation of turbulent heat fluxes over the northwest Pacific is the strongest in winter and the weakest in summer. And the seasonal transition of low-frequency oscillation intensity of LHF is jointly influenced by those of low-frequency oscillation intensity of Δq′, low-frequency oscillation intensity of anomalous wind speed (U′), Δ q and mean wind speed (U ), while the seasonal transition of low-frequency oscillation intensity of SHF is mainly influenced by those of low-frequency oscillation intensity of ΔT′ and U . 3) Over the tropical west Pacific and sea areas north of 20°N, the low-frequency oscillation of LHF (SHF) is mainly influenced by atmospheric variables qa′ (Ta′) and U′, indicating an oceanic response to overlying atmospheric forcing. In contrast, over the tropical eastern and central Pacific south of 20°N, qs′ (Ts′) also greatly influences the low-frequency oscillation of LHF (SHF).

Oscillation of a class of fractional differential equations with damping term.

Science.gov (United States)

Qin, Huizeng; Zheng, Bin