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Pavalavanni, Pradeep Kumar, Min-Seon Jo, Jae-Eun Kim i Jeong-Yeol Choi. "Numerical Study of Unstable Shock-Induced Combustion with Different Chemical Kinetics and Investigation of the Instability Using Modal Decomposition Technique". Aerospace 10, nr 3 (15.03.2023): 292. http://dx.doi.org/10.3390/aerospace10030292.
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An unstable shock-induced combustion (SIC) case around a hemispherical projectile has been numerically studied which experimentally produced a regular oscillation. Comparison of detailed H2/O2 reaction mechanisms is made for the numerical simulation of SIC with higher-order numerical schemes intended for the use of the code for the hypersonic propulsion and supersonic combustion applications. The simulations show that specific reaction mechanisms are grid-sensitive and produce spurious reactions in the high-temperature region, which trigger artificial instability in the oscillating flow field. The simulations also show that specific reaction mechanisms develop such spurious oscillations only at very fine grid resolutions. The instability mechanism is investigated using the dynamic mode decomposition (DMD) technique and the spatial structure of the decomposed modes are further analyzed. It is found that the instability triggered by the high-temperature reactions strengthens the reflecting compression wave and pushes the shock wave further and disrupts the regularly oscillating mechanism. The spatial coherent structure from the DMD analysis shows the effect of this instability in different regions in the regularly oscillating flow field.
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Fabrikant, A. L. "Harbour oscillations generated by shear flow". Journal of Fluid Mechanics 282 (10.01.1995): 203–17. http://dx.doi.org/10.1017/s0022112095000103.
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A new mechanism that could be responsible for excitation of long-period oscillations in partially enclosed harbours is discussed. This mechanism is based on the interaction between a shear flow and the harbour-basin natural mode and does not suppose any external exciting forces caused by wind waves, tsunami, etc. The growth rate of harbour oscillations is found in terms of a plane-wave reflection coefficient integrated on the wavenumber spectrum of the oscillating outflow field near the harbour entrance. Analytical considerations for simple shear flows (vortex sheet and jet) show that the growth rate changes its sign depending on the ratio of oscillation frequency to flow speed.
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Holstein-Rathlou, N. H., i D. J. Marsh. "A dynamic model of the tubuloglomerular feedback mechanism". American Journal of Physiology-Renal Physiology 258, nr 5 (1.05.1990): F1448—F1459. http://dx.doi.org/10.1152/ajprenal.1990.258.5.f1448.
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We have reported oscillations in proximal tubular pressure and flow and in distal tubular pressure and chloride concentration in halothane-anesthetized Sprague-Dawley rats. These variables oscillated at the same frequency in each animal, approximately 35 mHz, but were out of phase with each other. We suggested that the oscillation arises within the tubuloglomerular feedback (TGF) system. As a test of this hypothesis, we have now developed a dynamic model to determine whether it can simulate the measured frequency and phase relationships with a realistic set of parameters. The model includes a detailed representation of pressure and flow in the tubules based on a reduced version of the Navier-Stokes equations. The NaCl concentration at the macula densa was used as the signal to the TGF mechanism. The tubular NaCl concentration was modeled by a partial differential equation based on conservation of mass. For a realistic set of parameter values the model accurately predicted oscillations with the same frequency and phase relationships among the oscillating variables as was found experimentally. Moreover, tubular NaCl handling significantly influenced the dynamic properties of the TGF system. Thus the model predicted a substantial phase shift of the NaCl concentration relative to the flow oscillation at the macula densa. The results are consistent with the hypothesis that the oscillations are caused by the TGF mechanism. The results further support the notion that the delays and damping caused by the tubule are responsible for the limited high-frequency response of renal autoregulation.
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Ханин, Ю. Н., i Е. Е. Вдовин. "Квантовые осцилляции релаксации фотопроводимости в p-i-n-гетеродиодах GaAs/InAs/AlAs". Физика и техника полупроводников 52, nr 6 (2018): 591. http://dx.doi.org/10.21883/ftp.2018.06.45921.8679.
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AbstractThe photoconductivity and its relaxation characteristics in tunneling p – i – n GaAs/AlAs heterostructures under pulsed illumination is studied. Quantum oscillations in the photoconductivity are detected depending on the bias voltage with the period independent of the light wavelength, as well as an oscillating component of the relaxation curves caused by modulation of the recombination rate at the edge of a triangular quantum well in the undoped i layer, as in the case of photoconductivity oscillations. The common nature of oscillations of the steady-state photoconductivity and relaxation curves under pulsed illumination is directly confirmed by the lack of an oscillating component in both types of dependences of some studied p–i–n heterostructures. Simultaneous suppression of the observed oscillations of dependences of both types as the temperature increases to 80 K also confirms the proposed mechanism of their formation. The dependences of these oscillations on the magnetic field and light flux power are studied. Oscillation-amplitude suppression in a magnetic field of ~2 T perpendicular to the current is caused by the effect of the Lorentz force on the ballistic motion of carriers in the triangular-quantum-well region.
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Manor, Yair, John Rinzel, Idan Segev i Yosef Yarom. "Low-Amplitude Oscillations in the Inferior Olive: A Model Based on Electrical Coupling of Neurons With Heterogeneous Channel Densities". Journal of Neurophysiology 77, nr 5 (1.05.1997): 2736–52. http://dx.doi.org/10.1152/jn.1997.77.5.2736.
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Manor, Yair, John Rinzel, Idan Segev, and Yosef Yarom. Low-amplitude oscillations in the inferior olive: a model based on electrical coupling of neurons with heterogeneous channel densities. J. Neurophysiol. 77: 2736–2752, 1997. The mechanism underlying subthreshold oscillations in inferior olivary cells is not known. To study this question, we developed a single-compartment, two-variable, Hodgkin-Huxley-like model for inferior olive neurons. The model consists of a leakage current and a low-threshold calcium current, whose kinetics were experimentally measured in slices. Depending on the maximal calcium and leak conductances, we found that a neuron model's response to current injection could be of four qualitatively different types: always stable, spontaneously oscillating, oscillating with injection of current, and bistable with injection of current. By the use of phase plane techniques, numerical integration, and bifurcation analysis, we subdivided the two-parameter space of channel densities into four regions corresponding to these behavioral types. We further developed, with the use of such techniques, an empirical rule of thumb that characterizes whether two cells when coupled electrically can generate sustained, synchronized oscillations like those observed in inferior olivary cells in slices, of low amplitude (0.1–10 mV) in the frequency range 4–10 Hz. We found that it is not necessary for either cell to be a spontaneous oscillator to obtain a sustained oscillation. On the other hand, two spontaneous oscillators always form an oscillating network when electrically coupled with any arbitrary coupling conductance. In the case of an oscillating pair of electrically coupled nonidentical cells, the coupling current varies periodically and is nonzero even for very large coupling values. The coupling current acts as an equalizing current to reconcile the differences between the two cells' ionic currents. It transiently depolarizes one cell and/or hyperpolarizes the other cell to obtain the regenerative response(s) required for the synchronized oscillation. We suggest that the subthreshold oscillations observed in the inferior olive can emerge from the electrical coupling between neurons with different channel densities, even if the inferior olive nucleus contains no or just a small proportion of spontaneously oscillating neurons.
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Deineka, Kateryna, i Yuriy Naumenko. "Revealing the mechanism of stability loss of a two-fraction granular flow in a rotating drum". Eastern-European Journal of Enterprise Technologies 4, nr 1 (118) (31.08.2022): 34–46. http://dx.doi.org/10.15587/1729-4061.2022.263097.
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The qualitative nature and quantitative parameters of motion instability of a two-fraction granular filler of a rotating drum were determined. The factors of motion instability and key parameters of the oscillating system were identified and their influence on the self-excitation of pulsed self-oscillations was estimated. Two continuous and one periodic steady-state modes of filler motion were found. Periodic self-oscillations due to the development of instability during the transition from continuous circulation mode to the wall layer mode were revealed. As factors of motion instability, filler dilatancy and damping effect of fine fraction particles on the pulsed interaction of coarse fraction particles were taken. It turned out that the main key parameter of the oscillating system is the drum speed, which determines a change in dilatancy. The increase in instability is realized as a reduction of the bifurcation values of speed and dilatancy. Other key parameters are the content of the fine fraction in the filler κff and the filling degree of the chamber κlf, the growth of which increases the self-oscillating instability. The features of the oscillatory system are the relaxation type, discontinuous nature of self-oscillations and hard self-excitation mode under bistability. The discontinuous character and oscillatory hysteresis increase with decreasing κff and κlf. The limit values of the dynamic motion parameters corresponding to the conditions of self-excitation of self-oscillations in the absence and presence of fine fraction were determined: 0.96–1.11 and 0.218–0.382 for the bifurcation value of relative speed, 0.745–0.855 and 0.24–0.322 for the bifurcation value of dilatancy. The effects found make it possible to substantiate the parameters of the self-oscillating process of processing polygranular materials in drum-type machines.
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Knizhnik, Kalman, Manuel Luna, Karin Muglach, Holly Gilbert, Therese Kucera i Judith Karpen. "Observational Study of Large Amplitude Longitudinal Oscillations in a Solar Filament". Proceedings of the International Astronomical Union 8, S300 (czerwiec 2013): 428–29. http://dx.doi.org/10.1017/s174392131301140x.
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AbstractOn 20 August 2010 an energetic disturbance triggered damped large-amplitude longitudinal (LAL) oscillations in almost an entire filament. In the present work we analyze this periodic motion in the filament to characterize the damping and restoring mechanism of the oscillation. Our method involves placing slits along the axis of the filament at different angles with respect to the spine of the filament, finding the angle at which the oscillation is clearest, and fitting the resulting oscillation pattern to decaying sinusoidal and Bessel functions. These functions represent the equations of motion of a pendulum damped by mass accretion. With this method we determine the period and the decaying time of the oscillation. Our preliminary results support the theory presented by Luna and Karpen (2012) that the restoring force of LAL oscillations is solar gravity in the tubes where the threads oscillate, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Following an earlier paper, we have determined the magnitude and radius of curvature of the dipped magnetic flux tubes hosting a thread along the filament, as well as the mass accretion rate of the filament threads, via the fitted parameters.
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Yeleukulov, Yerlan, Alfiya Atalykova, Algazy Zhauyt, Zhubanyshbay Abdimuratov, Saltanat Yussupova, Assel Alik i Gaukhar Kenzhebayeva. "Mechanical analysis of vibratory conveyor mechanism". MATEC Web of Conferences 226 (2018): 01019. http://dx.doi.org/10.1051/matecconf/201822601019.
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The paper describes some of the basics of kinematics and dynamics of vibratory conveyor drive. Featured are dynamic modes of material that is being transported. Presented are the optimum material handling, and most rational mode. Introducing the empirical dependence transport speed as a function of angle bending conveyor, amplitude of oscillation of the transport container, the oscillation frequency excitation angle at which operates the actuating force and the coefficient mode of operation of the conveyor. Featured are some of the drive vibratory conveyors, and especially the operation of electromagnetic vibratory conveyor. In this paper is studied a vibratory conveyor that is placed on an elastic base. Using the closed contours method it was determined the system that needs to be solved to obtain graphical representation for the generalized coordinates determining the position of the mechanical system elements. The shaking conveyor represents the chase hanged or supported to the fixed section. The chase commits oscillating motions hereupon the cargo which is in the chase, migrates concerning to the chase. The nature of the flow and its parameters are determined by the nature of the oscillating committed by the chase. Justifying the dynamic parameters of the vibratory conveyor and a study of the strain-energy. Installation causes fluctuations fixed tray. Uniformly distributed load on the tray acts in each element of the mechanism. On the basis of the program MSC Adams investigated the strain-energy and kinetic-energy of each link mechanism with results and calculations.
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Cosgrove, R., M. Nicolls, H. Dahlgren, S. Ranjan, E. Sanchez i R. Doe. "Radar detection of a localized 1.4 Hz pulsation in auroral plasma, simultaneous with pulsating optical emissions, during a substorm". Annales Geophysicae 28, nr 10 (29.10.2010): 1961–79. http://dx.doi.org/10.5194/angeo-28-1961-2010.
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Abstract. Many pulsating phenomena are associated with the auroral substorm. It has been considered that some of these phenomena involve kilometer-scale Alfvén waves coupling the magnetosphere and ionosphere. Electric field oscillations at the altitude of the ionosphere are a signature of such wave activity that could distinguish it from other sources of auroral particle precipitation, which may be simply tracers of magnetospheric activity. Therefore, a ground based diagnostic of kilometer-scale oscillating electric fields would be a valuable tool in the study of pulsations and the auroral substorm. In this study we attempt to develop such a tool in the Poker Flat incoherent scatter radar (PFISR). The central result is a statistically significant detection of a 1.4 Hz electric field oscillation associated with a similar oscillating optical emission, during the recovery phase of a substorm. The optical emissions also contain a bright, lower frequency (0.2 Hz) pulsation that does not show up in the radar backscatter. The fact that higher frequency oscillations are detected by the radar, whereas the bright, lower frequency optical pulsation is not detected by the radar, serves to strengthen a theoretical argument that the radar is sensitive to oscillating electric fields, but not to oscillating particle precipitation. Although it is difficult to make conclusions as to the physical mechanism, we do not find evidence for a plane-wave-like Alfvén wave; the detected structure is evident in only two of five adjacent beams. We emphasize that this is a new application for ISR, and that corroborating results are needed.
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Tiberiu Petrescu, Florian Ion, Taher M. Abu-Lebdeh i Antonio Apicella. "Study of an Oscillating Sliding Mechanism". American Journal of Engineering and Applied Sciences 11, nr 2 (1.02.2018): 870–80. http://dx.doi.org/10.3844/ajeassp.2018.870.880.
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Yu, Hao, Wentian Tang, Guanyu Mu, Haocheng Wang, Xiaocong Chang, Huijuan Dong, Liqun Qi, Guangyu Zhang i Tianlong Li. "Micro-/Nanorobots Propelled by Oscillating Magnetic Fields". Micromachines 9, nr 11 (23.10.2018): 540. http://dx.doi.org/10.3390/mi9110540.
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Recent strides in micro- and nanomanufacturing technologies have sparked the development of micro-/nanorobots with enhanced power and functionality. Due to the advantages of on-demand motion control, long lifetime, and great biocompatibility, magnetic propelled micro-/nanorobots have exhibited considerable promise in the fields of drug delivery, biosensing, bioimaging, and environmental remediation. The magnetic fields which provide energy for propulsion can be categorized into rotating and oscillating magnetic fields. In this review, recent developments in oscillating magnetic propelled micro-/nanorobot fabrication techniques (such as electrodeposition, self-assembly, electron beam evaporation, and three-dimensional (3D) direct laser writing) are summarized. The motion mechanism of oscillating magnetic propelled micro-/nanorobots are also discussed, including wagging propulsion, surface walker propulsion, and scallop propulsion. With continuous innovation, micro-/nanorobots can become a promising candidate for future applications in the biomedical field. As a step toward designing and building such micro-/nanorobots, several types of common fabrication techniques are briefly introduced. Then, we focus on three propulsion mechanisms of micro-/nanorobots in oscillation magnetic fields: (1) wagging propulsion; (2) surface walker; and (3) scallop propulsion. Finally, a summary table is provided to compare the abilities of different micro-/nanorobots driven by oscillating magnetic fields.
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Wandel, Sebastian, Arne Bartschat, Jakob Glodowski, Norbert Bader i Gerhard Poll. "Wear Development in Oscillating Rolling Element Bearings". Lubricants 11, nr 3 (7.03.2023): 117. http://dx.doi.org/10.3390/lubricants11030117.
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Rotor blade bearings enable rotor blades to pivot about their longitudinal axis and thus control the power output and reduce the loads acting on the wind turbine. Over a design period of 20 years, rolling bearings are exposed to frequent oscillation movements with amplitude ratios of x/2b > 1, especially due to new control concepts such as Individual Pitch Control, which can lead to wear and a reduction in service life. The objective of this paper was to identify the dominant wear mechanisms and their consequences for the operation of oscillating bearings. Oscillating experiments with an increasing number of cycles on the angular contact ball bearings of two different sizes (types 7208 and 7220) show that the damage initiation starts with adhesive and corrosive wear mechanisms, which result in a sharp increase in the torque as well as the wear volume on the bearing raceway. As the number of cycles increases, an abrasive mechanism occurs, resulting in a lower slope of the wear curve and a smoothing of the resulting wear depressions. The wear and torque curves were evaluated and classified using an energy-wear approach according to Fouvry.
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Perianez-Rodriguez, Juan, Marcos Rodriguez, Marco Marconi, Estefano Bustillo-Avendaño, Guy Wachsman, Alvaro Sanchez-Corrionero, Hugues De Gernier i in. "An auxin-regulable oscillatory circuit drives the root clock in Arabidopsis". Science Advances 7, nr 1 (styczeń 2021): eabd4722. http://dx.doi.org/10.1126/sciadv.abd4722.
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In Arabidopsis, the root clock regulates the spacing of lateral organs along the primary root through oscillating gene expression. The core molecular mechanism that drives the root clock periodicity and how it is modified by exogenous cues such as auxin and gravity remain unknown. We identified the key elements of the oscillator (AUXIN RESPONSE FACTOR 7, its auxin-sensitive inhibitor IAA18/POTENT, and auxin) that form a negative regulatory loop circuit in the oscillation zone. Through multilevel computer modeling fitted to experimental data, we explain how gene expression oscillations coordinate with cell division and growth to create the periodic pattern of organ spacing. Furthermore, gravistimulation experiments based on the model predictions show that external auxin stimuli can lead to entrainment of the root clock. Our work demonstrates the mechanism underlying a robust biological clock and how it can respond to external stimuli.
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Chen, Weixing, Xiangdun Meng, Ye Li i Feng Gao. "Type synthesis of parallel mechanisms capturing wave energy". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, nr 19-20 (30.07.2019): 6689–97. http://dx.doi.org/10.1177/0954406219866466.
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Wave energy is clean, renewable, and abundant, awaiting exploitation. A wide range of wave energy converters have been proposed so far. Oscillating body systems are an important class of wave energy converters. Many mechanisms have been invented to absorb the random wave energy. Nowadays, there is a lack of method to design the mechanism for oscillating body systems to extract the wave energy. Parallel mechanism has the advantages of high stiffness and high load, which are suitable for design of the mechanism for wave energy converters. In this paper, a procedural method based on the generalized function ( G F) sets theory is proposed to design parallel mechanisms to capture wave energy. Using this method, numerous parallel mechanisms have been obtained, which provides the foundation of the development of wave energy converters.
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Li, Yan-Hom, i Shao-Chun Chen. "Propulsion Mechanism of Flexible Microbead Swimmers in the Low Reynolds Number Regime". Micromachines 11, nr 12 (15.12.2020): 1107. http://dx.doi.org/10.3390/mi11121107.
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A propulsion mechanism for a flexible microswimmer constructed from superparamagnetic microbeads with different diameters and subjected to an oscillating field was studied experimentally and theoretically herein. Various types of artificial swimmers with different bending patterns were fabricated to determine the flexibility and an effective waveform for a planar beating flagellum. Waveform evolutions for various swimmer configurations were studied to determine the flexible mechanism of the swimmers. A one-armed microswimmer can propel itself only if the friction of its wavelike body is anisotropic. A swimmer with a larger head and a stronger magnetic dipole moment with a flexible tail allows the bending wave to propagate from the head toward the tail to generate forward thrust. The oscillating head and tail do not simultaneously generate positive thrust all the time within a period of oscillation. To increase the propulsion for a bending swimmer, this study proposes a novel configuration for a microbead swimmer that ensures better swimming efficiency. The ratio of the oscillation amplitude of the head to the length of the swimmer (from 0.26 to 0.28) produces a faster swimmer. On the other hand, the swimmer is propelled more effectively if the ratio of the oscillation amplitude of the tail to the length of the swimmer is from 0.29 to 0.33. This study determined the optimal configuration for a flexible microbead swimmer that generates the greatest propulsion in a low Reynolds number environment.
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Botros, K. K., G. H. Dunn i J. A. Hrycyk. "Riser-Relief Valve Dynamic Interactions (Extension to a Previous Model)". Journal of Pressure Vessel Technology 120, nr 2 (1.05.1998): 207–12. http://dx.doi.org/10.1115/1.2842242.
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Further investigation of the dynamic stability behavior of a typical pilot-operated relief valve is reported. The present study is an extension to Botros et al. (1997) model, which includes mapping of the oscillating frequencies and amplitudes with riser dimensionless length L/D; inclusion of the effects of a wedge-O-ring seal in the model; detailed analyses of the field tests revealing unknown values for model parameters. These model refinements resulted in a better agreement between simulation results and field measurements. Analysis of piston oscillation frequencies and amplitudes indicates that the piston oscillation frequency mirrors the riser’s one-quarter-wave resonance frequency for lower values of L/D. At L/D = 20 and higher, two modes of oscillations started to emerge with two distinct frequencies. Maximum oscillation amplitudes occurred at L/D corresponding to one-quarter wave. Wedge-O-ring seal mechanism helps in suppressing piston oscillations; but it must be used in conjunction with a proper lubricant, otherwise the piston may jam partway during the upward stroke.
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Barrabino, Albert, Torleif Holt, Bård Bjørkvik i Erik Lindeberg. "First Approach to Measure Interfacial Rheology at High-Pressure Conditions by the Oscillating Drop Technique". Colloids and Interfaces 5, nr 2 (13.04.2021): 23. http://dx.doi.org/10.3390/colloids5020023.
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An oscillating drop rheometer capable of operating under conditions of high pressure and high temperature has been built. The oscillating drop mechanism was able to support pressures as high as 1300 bar and successfully performed oscillations at constant pressure. Apparent elastic and viscous complex moduli were measured for a system of CO2 and synthetic seawater containing 100 ppm of a linear alkyl ethoxylate surfactant for different pressures and temperatures. The moduli had strong dependencies on both pressure and temperature. At temperatures of 40 and 80 °C, the apparent elastic modulus passed through a maximum for pressures between 100 and 300 bar. The harmonic distortion of the oscillations was calculated for all measurements, and it was found that drop oscillations below ca. 2.6 µL caused distortions above 10% due to a mechanical backlash of the motor.
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Fang, Zifan, Jiajia Wang, Fei Xiong i Xueyuan Xie. "Research on the dynamic characteristics of the acquisition mechanism of the oscillating flapping wing wave energy power generation device based on the bond graph". Journal of Physics: Conference Series 2125, nr 1 (1.11.2021): 012050. http://dx.doi.org/10.1088/1742-6596/2125/1/012050.
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Abstract Taking the acquisition mechanism of the oscillating flapping-wing wave energy power generation device as the research object, the design of the acquisition mechanism, the bond graph model of the acquisition mechanism and the dynamic characteristics are studied. According to the working principle of the acquisition mechanism of the oscillating flapping wing wave energy power generation device, the bond graph model and the state space equation of the acquisition mechanism are established. Based on the bond graph theory, the AMESim software is used for simulation analysis to verify the correctness of the bond graph model of the acquisition mechanism. The research results show that the designed oscillating flapping wing wave energy generation device acquisition mechanism responds quickly and stably, and the bond graph model basically matches the real system. The research process provides an effective reference for the development of the acquisition mechanism of the oscillating flapping wing wave energy power generation device.
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Loveikin, Viacheslav, Yurii Romasevich, Liubov Shymko, Yurii Loveikin i Kostiantyn Pochka. "The dynamic analysis of the joint trolley movement and hoisting mechanism in the tower crane". Strength of Materials and Theory of Structures, nr 108 (30.05.2022): 267–82. http://dx.doi.org/10.32347/2410-2547.2022.108.267-282.
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The task of this paper is to research the simultaneous use of trolley and hoisting mechanism by the tower crane with a beam jib. To conduct research, a dynamic model of joint movement of mechanisms has been developed, which takes into account the main movement of drive mechanisms and oscillating movement of the load on a flexible suspension and links of mechanisms with elastic properties. A mathematical model of the motion of mechanisms is constructed on the basis of a dynamic model with the help of Lagrange equations of the second kind. For a specific jib system of the tower crane, dynamic calculations were performed using the developed mathematical model. According to the results of the calculations, a dynamic analysis of the joint movement of trolley and hoisting mechanism was carried out. The analysis revealed significant dynamic and energy overloads of mechanisms during transients (start, braking) and the presence of high-frequency oscillations in the links with elastic properties and low-frequency oscillations of the load on a flexible suspension.
To reduce the overload of crane mechanisms in the areas of transients and eliminate oscillations during steady traffic, it is recommended to optimize traffic modes and develop drive control systems to implement the desired traffic modes.
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Ricco, Pierre, Claudio Ottonelli, Yosuke Hasegawa i Maurizio Quadrio. "Changes in turbulent dissipation in a channel flow with oscillating walls". Journal of Fluid Mechanics 700 (25.04.2012): 77–104. http://dx.doi.org/10.1017/jfm.2012.97.
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AbstractHarmonic oscillations of the walls of a turbulent plane channel flow are studied by direct numerical simulations to improve our understanding of the physical mechanism for skin-friction drag reduction. The simulations are carried out at constant pressure gradient in order to define an unambiguous inner scaling: in this case, drag reduction manifests itself as an increase of mass flow rate. Energy and enstrophy balances, carried out to emphasize the role of the oscillating spanwise shear layer, show that the viscous dissipation of the mean flow and of the turbulent fluctuations increase with the mass flow rate, and the relative importance of the latter decreases. We then focus on the turbulent enstrophy: through an analysis of the temporal evolution from the beginning of the wall motion, the dominant, oscillation-related term in the turbulent enstrophy is shown to cause the turbulent dissipation to be enhanced in absolute terms, before the slow drift towards the new quasi-equilibrium condition. This mechanism is found to be responsible for the increase in mass flow rate. We finally show that the time-average volume integral of the dominant term is linearly related to the drag reduction.
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Yamaguchi, Shun, Shigeru Mitsui, Lily Yan, Kazuhiro Yagita, Shigeru Miyake i Hitoshi Okamura. "Role of DBP in the Circadian Oscillatory Mechanism". Molecular and Cellular Biology 20, nr 13 (1.07.2000): 4773–81. http://dx.doi.org/10.1128/mcb.20.13.4773-4781.2000.
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ABSTRACT Transcript levels of DBP, a member of the PAR leucine zipper transcription factor family, exhibit a robust rhythm in suprachiasmatic nuclei, the mammalian circadian center. Here we report that DBP is able to activate the promoter of a putative clock oscillating gene,mPer1, by directly binding to the mPer1promoter. The mPer1 promoter is cooperatively activated by DBP and CLOCK-BMAL1. On the other hand, dbp transcription is activated by CLOCK-BMAL1 through E-boxes and inhibited by the mPER and mCRY proteins, as is the case for mPer1. Thus, a clock-controlled dbp gene may play an important role in central clock oscillation.
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Hattori, Yuji, i Ryu Komatsu. "Mechanism of aeroacoustic sound generation and reduction in a flow past oscillating and fixed cylinders". Journal of Fluid Mechanics 832 (26.10.2017): 241–68. http://dx.doi.org/10.1017/jfm.2017.668.
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The aeroacoustic sound generated in a flow past two cylinders, one of which is oscillating and the other is fixed, is studied by direct numerical simulation. This problem involves key ingredients of the aeroacoustic noise generated from wind turbines, helicopters, axial flow fans and other turbomachinery: flow, a moving body and a fixed body. The corrected volume penalization method is successfully applied to resolve the sound pressure of aeroacoustic waves as a solution of the compressible Navier–Stokes equations. The sound pressure was shown to be in good agreement with the prediction by the Ffowcs Williams–Hawkings aeroacoustic analogy, which takes account of the cylinder motion, confirming the accuracy of the corrected volume penalization method. Prior to the case of two cylinders, sound generation in flow past a single oscillating cylinder is considered. The fluid motion can be either periodic or non-periodic depending on the frequency and the amplitude of cylinder oscillation. The acoustic power is significantly reduced when the fluid motion locks in to a frequency lower than the natural frequency of vortex shedding from a fixed cylinder. When a fixed cylinder is added, the acoustic power depends strongly on the distance between the cylinders, since that determines whether synchronization occurs and the phase difference between the three forces: the lift forces exerted on the two cylinders and the inertial force due to volume displacement effect of the oscillating cylinder. In particular, significant sound reduction is observed when the fixed cylinder is placed upstream and the frequency of the cylinder oscillation is set to the frequency for which the acoustic power is minimized in the single-cylinder case.
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NAGAI, Minoru, Isao TERUYA, Kazuhiro UECHI i Toshinobu MIYAZATO. "Study on an Oscillating Wing Propulsion Mechanism." Transactions of the Japan Society of Mechanical Engineers Series B 62, nr 593 (1996): 200–206. http://dx.doi.org/10.1299/kikaib.62.200.
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LiWang, Andy. "The oscillating mechanism of a circadian clock". Biophysical Journal 122, nr 3 (luty 2023): 46a. http://dx.doi.org/10.1016/j.bpj.2022.11.461.
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Lu, Yang, Jian Lai, Junping Pang, Xin Li, Chen Zhang i Ming Gao. "Microstructure and Fracture Behaviors of Oscillating Laser Welded 5A06 Aluminum Alloy Lock Butt Joint". Applied Sciences 13, nr 6 (7.03.2023): 3381. http://dx.doi.org/10.3390/app13063381.
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Oscillating laser welding is potential to improve the quality of aluminum alloy joints, but has been seldom addressed on lock butt joint. In this paper, the effects of beam oscillation frequencies (f) on the properties of laser-welded 5A06 aluminum alloy lock butt joints were investigated, especially those at the lock step. In the microstructure, the columnar grain zone (CGZ) near the fusion line narrowed, the porosity was reduced, and the angle between lock step and fusion line increased with the increase of f. Correspondingly, the fracture changed from equiaxed grain zone to heat affected zone (HAZ), and the fracture angle between lock step and crack propagation line from 90° to 45°. The maximum ultimate tensile strength and elongation of oscillating weld reached 308 MPa and 18.2%, respectively, 36.3% and 203.3% higher than non-oscillating weld. The fracture behaviors indicated that the crack always initiated at the lock step, and then preferably propagated to the pores, followed closely by the weaker CGZ, and then the stronger HAZ when CGZ was narrowed enough. Notably, when the pore size was small (<0.39 mm) and located below the lock step, the pore was not on the crack propagation path. The crack tended to propagate towards the weaker CGZ. Finally, the fracture mechanism was discussed. The results clarify the fracture mechanism of oscillating laser-welded lock butt joints and contribute to the development of oscillating laser welding.
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Mrákavová, Marta, i Ľudovít Treindl. "Oscillation system of Belousov-Zhabotinskii type in presence of Cl- ions". Collection of Czechoslovak Chemical Communications 51, nr 12 (1986): 2693–701. http://dx.doi.org/10.1135/cccc19862693.
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A modified Belousov-Zhabotinskii oscillation system involving ethyl ester of 3-oxobutanoic acid and Fe(phen)32+ - Fe(phen)33+ as redox catalyst is remarkable in that it shows an oxygen-induced excitability. The oscillating state, involving 4-5 oscillations in the absorbancy of Fe(phen)32+ ions, comes soon to its end but can be restored by shaking the reaction system, thus incresing the transport of oxygen from the air. This phenomenon is not influenced by Cl- ions in a low concentration, but if this is equal to 10-3 mol dm-3 or higher, no oscillations are observed, the increase of the concentration of Fe(phen)32+ ions is autocatalytic in character and can be reproduced several times by shaking or stirring the solution. These phenomena are discussed in terms of a probable reaction mechanism.
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Bi, Shusheng, Hongwei Ma, Yueri Cai, Chuanmeng Niu i Yuliang Wang. "Dynamic modeling of a flexible oscillating pectoral fin for robotic fish". Industrial Robot: An International Journal 41, nr 5 (12.08.2014): 421–28. http://dx.doi.org/10.1108/ir-04-2014-0330.
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Purpose – The paper aims to present a dynamic model of flexible oscillating pectoral fin for further study on its propulsion mechanism. Design/methodology/approach – The chordwise and spanwise motions of cow-nosed ray’s pectoral fin are first analyzed based on the mechanism of active/passive flexible deformation. The kinematic model of oscillating pectoral fin is established by introducing the flexible deformation. Then, the dynamic model of the oscillating pectoral fin is developed based on the quasi-steady blade element theory. A series of hydrodynamic experiments on the oscillating pectoral fin are carried out to investigate the influences of motion parameters on the propulsion performance of the oscillating pectoral fin. Findings – The experimental results are consistent with that obtained through analytical calculation within a certain range, which indicates that the developed dynamic model in this paper is applicable to describe the dynamic characteristics of the oscillating pectoral fin approximately. The experimental results show that the average thrust of an oscillating pectoral fin increases with the increasing oscillating amplitude and frequency. However, the relationship between the average thrust and the oscillating frequency is nonlinear. Moreover, the experimental results show that there is an optimal phase difference at which the oscillating pectoral fin achieves the maximum average thrust. Originality/value – The developed dynamic model provides the theoretical basis for further research on propulsion mechanism of oscillating pectoral fins. It can also be used in the design of the bionic pectoral fins.
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Schopf, Paul S., i Robert J. Burgman. "A Simple Mechanism for ENSO Residuals and Asymmetry". Journal of Climate 19, nr 13 (1.07.2006): 3167–79. http://dx.doi.org/10.1175/jcli3765.1.
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Abstract A simple mechanism is offered that accounts for a change in the long-term (decadal scale) mean of ocean temperatures as the El Niño–Southern Oscillation (ENSO) amplitude changes. It is intended as an illustration of a kinematic effect of oscillating a nonlinear temperature profile with finite-amplitude excursions that will cause the Eulerian time mean temperature to rise (fall) where the curvature of the temperature is positive (negative) as the amplitude of the oscillations increases. This mechanism is found to be able to mimic observed changes in the mean sea surface temperatures in the Pacific between the 1920s, 1960s, and 1990s due to the changing ENSO amplitude. The effects alter both the calculated mean surface temperatures and the time mean temperatures at depth. It also results in a skewness of the temperature distribution that shares many properties with the observed SST. In this model, the time-local gradients of temperature never change if referenced to a single isotherm (i.e., the Lagrangian description is one of DT/Dt = 0). This implies that changes in the amplitude of ENSO will have no influence on the stability of the underlying system, and that the simple Eulerian decadal mean temperature structure has no predictive value. This is in direct contrast to recent work that ascribes a change in ENSO statistics as due to a change in the background state.
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Jiang, Shao Dong, Ran Shi, An Ping Qiu i Yan Su. "Micro Leverage Modeling, Simulation and Optimization for Micromechanical Silicon Oscillating Accelerometer". Advanced Materials Research 189-193 (luty 2011): 4130–34. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.4130.
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The proof mass of micromechanical silicon oscillating accelerometer is small in size and light in weight, which badly restricts the improvement of accelerometer sensitivity. So a method of using micro leverage mechanisms to amplify the inertia force is widely accepted. There are restraints existing in the input and output beam end of the leverage mechanism, and the whole structure is flexible body. Therefore the Card Theorem is adopted to deduce the theoretical formula of the leverage amplification factor. The finite element analysis (FEA) is conducted to verify the theoretical formula. Then optimize the leverage mechanics with the complex optimal method to get the reasonable design parameters of the leverage mechanism. Finally, another simulation is conducted to test the optimized result.
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Liu, Guo Dong, i Xi Jing Zhu. "Study on Ultrasonic Cavitation Mechanism of Honing". Advanced Materials Research 189-193 (luty 2011): 4149–53. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.4149.
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Ultrasonic cavitation is an extremely complex physical phenomenon. It displays a series of nonlinear dynamics as the bubbles oscillating, growth, shrinkage and even collapse. For ultrasonic honing, it causes the device to generate chatter and noise because of the cavitation effect, and even generates denudation on the workpiece surface. In this paper, it describes the cavitation mechanism in ultrasonic honing, and analysises the acoustic pressure of the formation of cavitation from the numerical, furthermore it experimentally demonstrated. It also analyzes the nonlinear oscillation of cavitation bubbles for the impact on the ultrasonic honing chatter. Through studying on ultrasonic cavitation mechanism of honing, it provided a theoretical basis to solution the problem of the ultrasonic honing chatter and improves the level of precision and ultra precision machining.
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Chen, C. K., L. Wang, J. T. Yang i L. T. Chen. "Experimental and Computational Analysis of Periodic Flow Structure in Oscillatory Gas Flow Meters". Journal of Mechanics 22, nr 2 (czerwiec 2006): 137–44. http://dx.doi.org/10.1017/s1727719100004433.
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AbstractThe oscillatory characteristics and dynamic structure of periodic flow in an oscillatory gas flow meter were studied experimentally and numerically. The flow oscillations were triggered by the Coanda effect and an universal correlation between Strouhal number and Reynolds number, Str = 1.09 × 10−3 for ReHD >800, was deduced based on spectral analysis of the pressure fluctuations in the flow channel. Numerical simulation indicated that the evolution of the flow patterns was classified into stages of induction and sustainable periodic oscillation. The transformation between the two stages was noticeably affected by the design of the feedback channels. The results further revealed that the development of the main vortex in the oscillating chamber and the small vortices at the entrance of the feedback channels concurrently modulate the mechanism of oscillation. The small vortices located at both entrances of the feedback channels play the role of a pair of modulating valves, which alternatively switch on and off the bypass flow through each feedback channel, thus reinforcing the periodic oscillation.
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Han, Hongfang, i Qinsheng Bi. "Bursting Oscillations as well as the Mechanism in a Filippov System with Parametric and External Excitations". International Journal of Bifurcation and Chaos 30, nr 12 (30.09.2020): 2050168. http://dx.doi.org/10.1142/s0218127420501680.
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The main purpose of this paper is to explore the bursting oscillations as well as the mechanism of a parametric and external excitation Filippov type system (PEEFS), in which different types of bursting oscillations such as fold/nonsmooth fold (NSF)/fold/NSF, fold/NSF/fold and fold/fold bursting oscillations can be observed. By employing the overlap of the transformed phase portrait and the equilibrium branches of the generalized autonomous system, the mechanisms of the bursting oscillations are investigated. Our results show that the fold bifurcation and the boundary equilibrium bifurcation (BEB) can cause the transitions between the quiescent states and repetitive spiking states. The oscillating frequencies of the spiking states can be approximated theoretically by their occurring mechanisms, which agree well with the numerical simulations. Furthermore, some nonsmooth evolutions are investigated by employing differential inclusions theory, which reveals that the positional relationship between the points of the trajectory interacting with the nonsmooth boundary and the related sliding boundary of the nonsmooth system may affect the nonsmooth evolutions.
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Yao, Cheng, Yuxue Pu, Zhongming Wang i Yongxin Gao. "Mitigating Forced Shock-Wave Oscillation with Two-Dimensional Wavy Surface". Aerospace 9, nr 12 (26.11.2022): 756. http://dx.doi.org/10.3390/aerospace9120756.
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Oscillating flow is one challenge for wide-Mach-number-range flight with supersonic/hype-rsonic vehicles. Aiming to mitigate the large-amplitude forced shock-wave oscillation, a 2D wavy surface has been implemented onto the flat-bottomed wall of the Sajben diffuser under downstream pressure disturbance. The oscillating SBLI in the diffuser is captured using the finite volume method with the second-order implicit dual-time-stepping method. Impacts of the wavy surface on the forced shock-wave oscillation are numerically investigated. It is found that increasing the wavy surface’s depth benefits mitigation of the shock-wave oscillation amplitudes on the walls under the given conditions, but that decreasing the wavy surface’s length may increase or decrease the oscillation amplitudes, depending on the specific value. The mitigating mechanism is interpreted from two viewpoints, i.e., the shock-wave stability and the work performed by a moving shock-wave. The transient second shock-wave temporally appears in the flow field and can be explained by the post-shock expansion.
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Wang, Liming. "Effects of initial conditions and coupling competition modes on behaviors of coupled non-identical fractional-order bistable oscillators". Canadian Journal of Physics 94, nr 11 (listopad 2016): 1158–66. http://dx.doi.org/10.1139/cjp-2016-0086.
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The effects of the initial conditions and the coupling competition modes on the dynamic behaviors of coupled non-identical fractional-order bistable oscillators are investigated intensively and the various phenomena are explored. The coupled system can be controlled to form chaos synchronization, chaos anti-phase synchronization, amplitude death, oscillation death, etc., by setting the initial conditions or selecting the coupling competition modes. Depending on whether the arbitrary initial conditions can let two coupled oscillators stop oscillating, the dynamic behaviors of the coupled system are further classified into three types, that is, both of oscillators stop oscillating, only one oscillator stops oscillating, and none of oscillators stop oscillating. Based on the principle of Monte Carlo method, the percentages of three types of dynamic behaviors are calculated for the different coupling competition modes and the dynamic behaviors of the coupled system are characterized from the perspective of statistics. Moreover, the mechanism behind the various phenomena is explained in detail by the concept of boundary layer and the optimum coupling competition modes are found.
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Qiu, Ke, Feng Luo, Dong Fang Zhao, Zhong Lei Li i Jin Peng Sun. "Study of New Atomization Mechanism for Manufacturing Metal Powder". Advanced Materials Research 562-564 (sierpień 2012): 502–5. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.502.
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The paper introduces a new atomization mechanism combining the centrifugal, the oscillating and the impact breakage atomization as a trinity, breaking through the traditional single atomization model. The atomization mechanism here makes full use of the comprehensive effects of the centrifugal atomization, the oscillating atomization and the impact breakage atomization, synthesizing the superiorities of the three as an organic and powerfully efficient whole, and making their mutual reactions stronger step by step. The impact breakage atomization is a new auxiliary mechanism among the three, which can improve the atomizing process of droplets considerably after the centrifugal and the oscillating atomization, producing much better an atomizing result. It is very convenient, simple and direct to fulfill the three-in-one. This atomization mechanism can achieve the goal of even atomization and much tinier droplets and be energy-efficient with low cost as well. Therefore it is a highly practical and useful method.
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Dai, Z. G. "Gravitational waves from post-merger radially oscillating millisecond pulsars". Astronomy & Astrophysics 622 (luty 2019): A194. http://dx.doi.org/10.1051/0004-6361/201834552.
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Observations of short-duration gamma-ray bursts and their afterglows show that a good fraction (perhaps ≳50%) of binary neutron star mergers lead to strongly magnetized, rapidly rotating pulsars (including millisecond magnetars), no matter whether the pulsar remnants are short- or long-lived. Such compact objects are very likely to have significant radial oscillations and high interior temperatures, as indicated in recent numerical simulations. In this paper, we have investigated rotation-induced gravitational radiation from possibly existing, radially oscillating pulsars after binary neutron star mergers, and find that this mechanism can efficiently damp the radial oscillations. The resulting gravitational waves (GWs) could have a non-negligible contribution to the high-frequency spectrum. We provide an order-of-magnitude estimate of the event rate and suggest that such GW events would be detectable with the advanced LIGO/Virgo or next-generation detectors. Our discussion can also be applied to newborn, radially oscillating, millisecond pulsars formed through the other astrophysical processes.
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Raballand, Thierry. "Stirling Engine and oil-free compressors". E3S Web of Conferences 313 (2021): 04005. http://dx.doi.org/10.1051/e3sconf/202131304005.
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Refering to figure 1 [Fig.1], an oscillating « flipper » piston (1) and its associated chamber (2) are maintained without reciprocal contact. No oil is required because there is no contact and so no friction. An oscillating shaft (22) maintains the oscillating « flipper »piston (1). Around shaft (22), a twisting seal (8) allows for absolute sealing. This characteristic is important for Stirling engines and oil-free compressors. Referring to figure 4 [Fig.4], the two oscillating « flipper » pistons on the left belong to a Stirling-Franchot engine, more particularly to a Stirling-Franchot engine with two oscillating « flipper » pistons and so with two quadric crank mechanisms. The oscillating « flipper » piston on the right belongs to an oil-free compressor. The Stirling engine shaft (11), which is in alternative rotation, directly powers the oil-free compressor shaft (22). This prevents the use of a third quadric crank mechanism from shaft (33) to shaft (22). A Stirling engine connected to an oilfree compressor is useful when the fluid is precious or dangerous. A French patent was taken out on Februar 1st, 2020.
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Miall, Christopher. "The Storage of Time Intervals Using Oscillating Neurons". Neural Computation 1, nr 3 (wrzesień 1989): 359–71. http://dx.doi.org/10.1162/neco.1989.1.3.359.
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A mechanism to store and recall time intervals ranging from hundreds of milliseconds to tens of seconds is described. The principle is based on beat frequencies between oscillating elements; any small group of oscillators codes specifically for an interval equal to the lowest common multiple of their oscillation periods. This mechanism could be realized in the nervous system by an output neuron, excited by a group of pacemaker neurons, and able to select via a Hebbian rule a subgroup of pacemaker cells to encode any given interval, or small number of intervals (for example, a pattern of pulses). Recall could be achieved by resetting the pacemaker cells and setting a threshold for activation of the output unit. A simulation is described and the main features of such an encoding scheme are discussed.
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Bathellier, Brice, Alan Carleton i Wulfram Gerstner. "Gamma Oscillations in a Nonlinear Regime: A Minimal Model Approach Using Heterogeneous Integrate-and-Fire Networks". Neural Computation 20, nr 12 (grudzień 2008): 2973–3002. http://dx.doi.org/10.1162/neco.2008.11-07-636.
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Fast oscillations and in particular gamma-band oscillation (20–80 Hz) are commonly observed during brain function and are at the center of several neural processing theories. In many cases, mathematical analysis of fast oscillations in neural networks has been focused on the transition between irregular and oscillatory firing viewed as an instability of the asynchronous activity. But in fact, brain slice experiments as well as detailed simulations of biological neural networks have produced a large corpus of results concerning the properties of fully developed oscillations that are far from this transition point. We propose here a mathematical approach to deal with nonlinear oscillations in a network of heterogeneous or noisy integrate-and-fire neurons connected by strong inhibition. This approach involves limited mathematical complexity and gives a good sense of the oscillation mechanism, making it an interesting tool to understand fast rhythmic activity in simulated or biological neural networks. A surprising result of our approach is that under some conditions, a change of the strength of inhibition only weakly influences the period of the oscillation. This is in contrast to standard theoretical and experimental models of interneuron network gamma oscillations (ING), where frequency tightly depends on inhibition strength, but it is similar to observations made in some in vitro preparations in the hippocampus and the olfactory bulb and in some detailed network models. This result is explained by the phenomenon of suppression that is known to occur in strongly coupled oscillating inhibitory networks but had not yet been related to the behavior of oscillation frequency.
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Taylor, Annette F. "Mechanism and Phenomenology of an Oscillating Chemical Reaction". Progress in Reaction Kinetics and Mechanism 27, nr 4 (grudzień 2002): 247–326. http://dx.doi.org/10.3184/007967402103165414.
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Chemical reactions, which are far from equilibrium, are capable of displaying oscillations in species concentrations and hence in colour, electrode potential, pH and/or temperature. The oscillations arise from the interplay between positive and negative kinetic feedback. Mechanisms for such reactions are presented, along with the rich phenomenology that these systems exhibit, from complex oscillations and chemical waves, to stationary concentration patterns. This review will focus on the Belousov-Zhabotinksy reaction but reference to other reactions will be made where appropriate.
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SUZUKI, Ryota, i Yoshihisa UCHIDA. "Characterization of oscillating mower mechanism for mower robot". Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) 2017 (2017): 1A1—D04. http://dx.doi.org/10.1299/jsmermd.2017.1a1-d04.
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NAKASHIMA, Masahiro, i Tsutomu NOZAKI. "Characteristics of Dust Remover Applying Flow Oscillating Mechanism." Transactions of the Japan Society of Mechanical Engineers Series B 63, nr 612 (1997): 2745–51. http://dx.doi.org/10.1299/kikaib.63.2745.
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Nakariakov, Valery M., i Dmitrii Y. Kolotkov. "Magnetohydrodynamic Waves in the Solar Corona". Annual Review of Astronomy and Astrophysics 58, nr 1 (18.08.2020): 441–81. http://dx.doi.org/10.1146/annurev-astro-032320-042940.
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The corona of the Sun is a unique environment in which magnetohydrodynamic (MHD) waves, one of the fundamental processes of plasma astrophysics, are open to a direct study. There is striking progress in both observational and theoretical research of MHD wave processes in the corona, with the main recent achievements summarized as follows: ▪ Both periods and wavelengths of the principal MHD modes of coronal plasma structures, such as kink, slow and sausage modes, are confidently resolved. ▪ Scalings of various parameters of detected waves and waveguiding plasma structures allow for the validation of theoretical models. In particular, kink oscillation period scales linearly with the length of the oscillating coronal loop, clearly indicating that they are eigenmodes of the loop. Damping of decaying kink and standing slow oscillations depends on the oscillation amplitudes, demonstrating the importance of nonlinear damping. ▪ The dominant excitation mechanism for decaying kink oscillations is associated with magnetized plasma eruptions. Propagating slow waves are caused by the leakage of chromospheric oscillations. Fast wave trains could be formed by waveguide dispersion. ▪ The knowledge gained in the study of coronal MHD waves provides ground for seismological probing of coronal plasma parameters, such as the Alfvén speed, the magnetic field and its topology, stratification, temperature, fine structuring, polytropic index, and transport coefficients.
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Hu, Gang, Qin Wang, Min Meng, Ming Ying Lu, Fu Sheng Zhao i Lin Hu. "Kinetic Determination of Paracetamol using a Novel Belousov-Zhabotinskii Oscillating System Catalyzed by a Tetraazamacrocyclic Complex". E-Journal of Chemistry 9, nr 3 (2012): 1412–21. http://dx.doi.org/10.1155/2012/626982.
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A new analytical method for determination of paracetamol is proposed. This method is based on a novel B-Z oscillating system, which involves a Tetraazamacrocyclic Complex [CuL](ClO4)2as catalyst and malic acid as the substrate. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. By perturbation mount of paracetamol on the B-Z system, there is a linear relationship between the changes in the oscillation amplitude and the logarithm of paracetamol concentration in the range 5×10-7to 2×10-4M, with a correlation coefficient of 0.99743. The effects of influential variables, such as the concentration of reaction components, temperature and on the determinations were studied. The probable mechanism involving the perturbation of paracetamol on the oscillating chemical system was also discussed.
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Zhang, Hai Long, Ning Zhang, Fu Hong Min i En Rong Wang. "Analysis on Chaotic Vibrations of the Magneto-Rheological Suspension System". Applied Mechanics and Materials 826 (luty 2016): 28–34. http://dx.doi.org/10.4028/www.scientific.net/amm.826.28.
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The magneto-rheological(MR) suspension system has been established, by employing the modified Bouc-wen force-velocity (F-v) model of magneto-rheological damper(MRD). The possibility of chaotic motions in MR suspension is discovered by employing nonlinear systems stability theory. With the bifurcation diagram and corresponding Lyapunov exponent spectrum diagrams detected through numerical calculation, we can observe the complex dynamical behaviors and oscillating mechanism of alternating periodic oscillations, quasi-periodic oscillations and chaotic oscillations with different profiles of road excitation, as well as the dynamical evolution to chaos by period-doubling bifurcations, saddle-node bifurcations and reverse period-doubling bifurcations.
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Braun, H. A., M. T. Huber, M. Dewald, K. Schäfer i K. Voigt. "Computer Simulations of Neuronal Signal Transduction: The Role of Nonlinear Dynamics and Noise". International Journal of Bifurcation and Chaos 08, nr 05 (maj 1998): 881–89. http://dx.doi.org/10.1142/s0218127498000681.
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Nonlinear ionic interactions at the nerve cell membrane can account for oscillating membrane potentials and the generation of periodic neuronal impulse activity. In combination with noise, external modulation of the endogenous oscillations allows for continuous transitions between a variety of impulse patterns. Such "noisy oscillators" afford, thereby, an important mechanism of neuronal encoding as is demonstrated here with experimental data from peripheral cold receptors and corresponding computer simulations.
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Dolmetsch, R. E., i R. S. Lewis. "Signaling between intracellular Ca2+ stores and depletion-activated Ca2+ channels generates [Ca2+]i oscillations in T lymphocytes." Journal of General Physiology 103, nr 3 (1.03.1994): 365–88. http://dx.doi.org/10.1085/jgp.103.3.365.
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Stimulation through the antigen receptor (TCR) of T lymphocytes triggers cytosolic calcium ([Ca2+]i) oscillations that are critically dependent on Ca2+ entry across the plasma membrane. We have investigated the roles of Ca2+ influx and depletion of intracellular Ca2+ stores in the oscillation mechanism, using single-cell Ca2+ imaging techniques and agents that deplete the stores. Thapsigargin (TG; 5-25 nM), cyclopiazonic acid (CPA; 5-20 microM), and tert-butylhydroquinone (tBHQ; 80-200 microM), inhibitors of endoplasmic reticulum Ca(2+)-ATPases, as well as the Ca2+ ionophore ionomycin (5-40 nM), elicit [Ca2+]i oscillations in human T cells. The oscillation frequency is approximately 5 mHz (for ATPase inhibitors) to approximately 10 mHz (for ionomycin) at 22-24 degrees C. The [Ca2+]i oscillations resemble those evoked by TCR ligation in terms of their shape, amplitude, and an absolute dependence on Ca2+ influx. Ca(2+)-ATPase inhibitors and ionomycin induce oscillations only within a narrow range of drug concentrations that are expected to cause partial depletion of intracellular stores. Ca(2+)-induced Ca2+ release does not appear to be significantly involved, as rapid removal of extracellular Ca2+ elicits the same rate of [Ca2+]i decline during the rising and falling phases of the oscillation cycle. Both transmembrane Ca2+ influx and the content of ionomycin-releasable Ca2+ pools fluctuate in oscillating cells. From these data, we propose a model in which [Ca2+]i oscillations in T cells result from the interaction between intracellular Ca2+ stores and depletion-activated Ca2+ channels in the plasma membrane.
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Pogrebnyak, V. G., i І. V. Perkun. "The Peculiarities of Oil Displacement in the Process of Oscillating Injection of Polymer Solution into the Bed with Layered Heterogeneity". Prospecting and Development of Oil and Gas Fields, nr 3(72) (30.09.2019): 42–50. http://dx.doi.org/10.31471/1993-9973-2019-3(72)-42-50.
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The authors study the filtration flow of polyethylene oxide (PEO) water solutions of molecular weights 4∙106 and 6∙106 within the concentration range from 0 to 0.05% when exposed to an oscillating hydrodynamic field. Photographs characterizing the displacement of oil (with a viscosity of 10 to 50 mPa. s) with PEO water solutions from model porous formations with layered heterogeneity have been obtained. They have made it possible to specify the effectiveness of different oil displacement modes. It is shown that pumping a polymer solution into porous heterogeneous strata, while exposing it to oscillating hydrodynamic field, proved to yield a higher oil displacement ratio, as compared with a stationary oil displacement mode. The authors find out the conditions providing the positive influence on elastic deformations effects in the process of enhanced oil recovery by using polymer solutions. If elastic deformations take place, the filtration flow of polymer solutions should be carried out in the oscillating mode, whereas the frequency of the oscillating effect on the filtration flow should correspond to the dissipative function maximum. The stated results of the polymer solution flow research, under model conditions of a porous bed, have confirmed the nonlinearity mechanism of the polymer solutions filtration flow. In essence, the molecular and macromolecular non-linearity mechanism of the polymer solutions filtration flow means that in a porous medium under the influence of quasi-regular longitudinal velocity gradients, there arise self-sustained oscillations of reversible macromolecular deployment; the deployed macromolecules, in turn, influence the structure of the filtration flow, both on the molecular and macromolecular levels. Deformation oscillations of macromolecules and dissolubility of dynamic macromolecular structures formed under the influence of tensile currents result in the energy dissipation increase and the filtration flow nonlinearity. The nonlinearity of polymer solutions filtration flow ensures the alignment of the frontal advance of the polymer solutions within a porous bed with a layered heterogeneity and, consequently, higher oil displacement efficiency.
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Karube, Shu, Yuki Uemura, Takuji Kousaka i Naohiko Inaba. "Revealing the mechanism causing stepwise maximum bounce height changes in a bouncing ball system". AIP Advances 12, nr 6 (1.06.2022): 065022. http://dx.doi.org/10.1063/5.0083804.
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The bouncing ball system is a simple mechanical collision system that has been extensively studied for several decades. It is a fundamental problem in impact dynamics. We studied a traditional bouncing ball system numerically and experimentally and discovered novel bifurcation structures where the maximum height of the bouncing ball with respect to the stationary state increases stepwise nonsmoothly when we increase the frequency of the oscillating table continuously even though the bouncing ball is in chaotic states [Karube et al., Chaos 30, 103111 (2020)]. We attempt to reveal the trick causing the stepwise changes of the maximum heights of the bouncing ball. We focus on the time interval for the ball to take off and land on the oscillating table at which the ball takes the maximum height. Let this time interval be denoted by t-interval. In addition, let the oscillation frequency of the table be denoted by f. The stepwise increases in the maximum heights of the bouncing ball in the stationary states occur when the multiplication of the t-interval and f coincides with integer values. This is the mechanism causing the nonsmooth maximum heights. Furthermore, results that are qualitatively consistent with the numerical ones are verified in the actual bouncing ball system using table tennis ball equipment.
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Luo, Feng, i Ke Qiu. "A Research on the Trinity Mechanism of Atomization Based on Centrifugation Oscillation and Impact Breakage". Key Engineering Materials 467-469 (luty 2011): 589–92. http://dx.doi.org/10.4028/www.scientific.net/kem.467-469.589.
Pełny tekst źródłaStreszczenie:
The paper advances a new atomization mechanism combining the centrifugal, the oscillating and the impact breakage atomization as a trinity, breaking through the traditionally single atomization model. The atomization mechanism raised here makes full use of the comprehensive effects of the centrifugal atomization, the oscillating atomization and the impact breakage atomization, synthesizing the superiorities of the three as an organic and powerfully efficient whole, and making their mutual reactions stronger step by step. Among the three, the impact breakage atomization is a new auxiliary mechanism, which can considerably improve the droplet’s atomizing process after the centrifugal and the oscillating atomization, producing much better an atomizing result. It is very convenient, simple and direct to fulfill “the-three-in-one”. This atomization mechanism not only can achieve the goal of even atomization and much tinier droplets, but can be energy-efficient with low cost and less labor intensity as well. Therefore it is a highly practical and useful method.