68 results for qubit oscillator frequency
Contributors: Rego Costa, Artur, Débarre, Florence, Chevin, Luis-Miguel
frequency-dependent selection caused by competitive interactions mediated...frequency of chaos at each simulation time point for different values ...oscillating optimum for d = 70....oscillations of an optimal phenotype interacts with the internal dynamics...oscillations. In contrast, weak forcing can increase the probability of...oscillating optimum for d = 40. ... Among the factors that may reduce the predictability of evolution, chaos, characterized by a strong dependence on initial conditions, has received much less attention than randomness due to genetic drift or environmental stochasticity. It was recently shown that chaos in phenotypic evolution arises commonly under frequency-dependent selection caused by competitive interactions mediated by many traits. This result has been used to argue that chaos should often make evolutionary dynamics unpredictable. However, populations also evolve largely in response to external changing environments, and such environmental forcing is likely to influence the outcome of evolution in systems prone to chaos. We investigate how a changing environment causing oscillations of an optimal phenotype interacts with the internal dynamics of an eco-evolutionary system that would be chaotic in a constant environment. We show that strong environmental forcing can improve the predictability of evolution, by reducing the probability of chaos arising, and by dampening the magnitude of chaotic oscillations. In contrast, weak forcing can increase the probability of chaos, but it also causes evolutionary trajectories to track the environment more closely. Overall, our results indicate that, although chaos may occur in evolution, it does not necessarily undermine its predictability.
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Contributors: Farzad Rafieian, François Girardin, Zhaoheng Liu, Marc Thomas, Bruce Hazel
frequency clearly indicates the impacting nature of the process and captures...oscillations. (For interpretation of the references to color in this figure...high-frequency repeating impacts in robotic grinding (detailed views)....frequency in single-pass grinding (overview). (For interpretation of the...frequency...frequency in Test (3) at 4500rpm. (For interpretation of the references...high-frequency impacts that mainly last for only a small fraction of the ... In a robotic machining process, a light-weight cutter or grinder is usually held by an articulated robot arm. Material removal is achieved by the rotating cutting tool while the robot end effector ensures that the tool follows a programmed trajectory in order to work on complex curved surfaces or to access hard-to-reach areas. One typical application of such process is maintenance and repair work on hydropower equipment. This paper presents an experimental study of the dynamic characteristics of material removal in robotic grinding, which is unlike conventional grinding due to the lower structural stiffness of the tool-holder robot. The objective of the study is to explore the cyclic nature of this mechanical operation to provide the basis for future development of better process control strategies. Grinding tasks that minimize the number of iterations to converge to the target surface can be better planned based on a good understanding and modeling of the cyclic material removal mechanism. A single degree of freedom dynamic analysis of the process suggests that material removal is performed through high-frequency impacts that mainly last for only a small fraction of the grinding disk rotation period. To detect these discrete cutting events in practice, a grinder is equipped with a rotary encoder. The encoder's signal is acquired through the angular sampling technique. A running cyclic synchronous average is applied to the speed signal to remove its non-cyclic events. The measured instantaneous rotational frequency clearly indicates the impacting nature of the process and captures the transient response excited by these cyclic impacts. The technique also locates the angular positions of cutting impacts in revolution cycles. It is thus possible to draw conclusions about the cyclic nature of dynamic changes in impact-cutting behavior when grinding with a flexible robot. The dynamics of the impacting regime and transient responses to impact-cutting excitations captured synchronously using the angular sampling technique provide feedback that can be used to regulate the material removal process. The experimental results also make it possible to correlate the energy required to remove a chip of metal through impacting with the measured drop in angular speed during grinding.
Contributors: Schanz, Ansgar, Hocke, Klemens, Kämpfer, Niklaus
oscillations is challenging. However, dynamical responses to short-term...oscillations. Two simulations were conducted with short-term solar forcing...oscillation comes along with other periods of the extra-long period wave ... The Whole Atmosphere Community Climate Model was used to investigate the influences of solar fluctuations on zonal wind oscillations. Two simulations were conducted with short-term solar forcing (<35 days) on and off. We found that a 27-day wave is an inherent feature of the atmosphere when the short-term solar forcing is inactive. This internal 27-day oscillation comes along with other periods of the extra-long period wave band (20–40 days) and cannot be linked to the Sun’s rotation period. When the short-term solar variability is part of the forcing, including the solar 27-day periodicity, it affects a wide range of the spectrum of zonal wind. At mid-latitudes, a 10-day wave emerges by the short-term solar forcing, which suggests that indirect and nonlinear interactions are involved. Solar short-term variability seems to generate atmospheric perturbations that interact with modes of the internal wave spectrum or the background mean flow. A robust and clear solar interpretation of these wind oscillations is challenging. However, dynamical responses to short-term solar variability exist and need further investigation.
Contributors: Cliff Orori Mosiori
frequencies just like those under seismic wave interactions and this work...oscillations are expected to behave in cylinder carrying a suspended mass...oscillator in a cylindrical acoustic medium that allow such waves to be...Oscillations ... Free vibrating motion can take place in an acoustic media. This motion can be steady hence have constant periodic variations or unsteady and thus experience light damping or heavy damping. We give a modeled analysis of unsteady periodic motion of an oscillator in a cylindrical acoustic medium that allow such waves to be transmitted through them. This has been approached by calculating variation within the proposed boundary functions and boundary potentials. Limitations for these calculations have been done depending on the time, and how free oscillations are expected to behave in cylinder carrying a suspended mass. This work investigated motion by constructions that interact with their environment with the acoustic media. Since the dynamics considered here were very complex, modeling the system with one grade of free motion and applying different types of constructions whether ground, underground, cylindrical, spherical constructions and containers was considered. This work borrowed heavily on the modeling of seismic and blast waves as modeled with rigid inclusions containing elastically fastened mass interacting continuous solid medium. This study joined motion of any continuous medium with other discrete systems. The results displayed measurement systems for wave processes having interference at their eigen- frequencies just like those under seismic wave interactions and this work considered the result as similar to those in discrete systems.
Contributors: Uzundag Murat, Silvotti Roberto, Baran Andrzej, Vuckovic Maja, Ostensen Roy, Reed Mike
frequencies. K2 dataset had revealed that HD 4539 is a hybrid pulsator...frequency region (>2000 µHz) consists of only 9 pressure p - modes. We...low-frequency region (<2000 µHz) includes at least 144 independent g - ... We analysed one of the brightest pulsating subdwarf B star, HD 4539 (=EPIC 220641886). The star was observed by the Kepler Spacecraft during K2 mission at Campaign 8. The full K2 data set spans ∼ 80 days, and from this we extract 153 signicant pulsation frequencies. K2 dataset had revealed that HD 4539 is a hybrid pulsator sdB giving it a rich asteroseismic potential. The amplitude spectrum of the star displays a rich content of gravity (g) - modes. The low-frequency region (2000 µHz) consists of only 9 pressure p - modes. We used asymptotic period spacing to identify the modal degree of the majority of the modes, ranging from l = 1 to l = 12, apart from l = 3 and l = 11 modes, that are not seen. For the rst time in a subdwarf B pulsator, the identication of the modes seems quite robust up to l = 6.
Physiological cyclic hydrostatic pressure induces osteogenic lineage commitment of human bone marrow stem cells: a systematic study
Contributors: Stavenschi, Elena, Corrigan, Michele A., Johnson, Gillian P., Riffault, Mathieu, Hoey, David A.
frequency and cultured statically for an additional 1–2 weeks. Pressure-induced...frequency regimes (2 Hz). Interestingly, long-term mechanical stimulation...frequency-dependent manner, that is gene specific. COX2 expression elicited...frequencies of 0.5 Hz, 1 Hz and 2 Hz for 1 h, 2 h and 4 h of stimulation...frequency elicited a magnitude-dependent release of ATP; however, all ... Background: Physical loading is necessary to maintain bone tissue integrity. Loading-induced fluid shear is recognised as one of the most potent bone micromechanical cues and has been shown to direct stem cell osteogenesis. However, the effect of pressure transients, which drive fluid flow, on human bone marrow stem cell (hBMSC) osteogenesis is undetermined. Therefore, the objective of the study is to employ a systematic analysis of cyclic hydrostatic pressure (CHP) parameters predicted to occur in vivo on early hBMSC osteogenic responses and late-stage osteogenic lineage commitment.Methods: hBMSC were exposed to CHP of 10 kPa, 100 kPa and 300 kPa magnitudes at frequencies of 0.5 Hz, 1 Hz and 2 Hz for 1 h, 2 h and 4 h of stimulation, and the effect on early osteogenic gene expression of COX2, RUNX2 and OPN was determined. Moreover, to decipher whether CHP can induce stem cell lineage commitment, hBMSCs were stimulated for 4 days for 2 h/day using 10 kPa, 100 kPa and 300 kPa pressures at 2 Hz frequency and cultured statically for an additional 1–2 weeks. Pressure-induced osteogenesis was quantified based on ATP release, collagen synthesis and mineral deposition.Results: CHP elicited a positive, but variable, early osteogenic response in hBMSCs in a magnitude- and frequency-dependent manner, that is gene specific. COX2 expression elicited magnitude-dependent effects which were not present for RUNX2 or OPN mRNA expression. However, the most robust pro-osteogenic response was found at the highest magnitude (300 kPa) and frequency regimes (2 Hz). Interestingly, long-term mechanical stimulation utilising 2 Hz frequency elicited a magnitude-dependent release of ATP; however, all magnitudes promoted similar levels of collagen synthesis and significant mineral deposition, demonstrating that lineage commitment is magnitude independent. This therefore demonstrates that physiological levels of pressures, as low as 10 kPa, within the bone can drive hBMSC osteogenic lineage commitment.Conclusion: Overall, these findings demonstrate an important role for cyclic hydrostatic pressure in hBMSCs and bone mechanobiology, which should be considered when studying pressure-driven fluid shear effects in hBMSCs mechanobiology. Moreover, these findings may have clinical implication in terms of bioreactor-based bone tissue engineering strategies.
Contributors: Smith, Robert W., van Sluijs, Bob, Fleck, Christian
oscillations. In this work we present a generalised in silico evolutionary...oscillators, and by performing multi-objective optimisation to find a ...oscillators and feed-forward loops that are optimal at balancing different...oscillators for experimental construction.Conclusions: In this work we ... Background: Evolution has led to the development of biological networks that are shaped by environmental signals. Elucidating, understanding and then reconstructing important network motifs is one of the principal aims of Systems & Synthetic Biology. Consequently, previous research has focused on finding optimal network structures and reaction rates that respond to pulses or produce stable oscillations. In this work we present a generalised in silico evolutionary algorithm that simultaneously finds network structures and reaction rates (genotypes) that can satisfy multiple defined objectives (phenotypes).Results: The key step to our approach is to translate a schema/binary-based description of biological networks into systems of ordinary differential equations (ODEs). The ODEs can then be solved numerically to provide dynamic information about an evolved networks functionality. Initially we benchmark algorithm performance by finding optimal networks that can recapitulate concentration time-series data and perform parameter optimisation on oscillatory dynamics of the Repressilator. We go on to show the utility of our algorithm by finding new designs for robust synthetic oscillators, and by performing multi-objective optimisation to find a set of oscillators and feed-forward loops that are optimal at balancing different system properties. In sum, our results not only confirm and build on previous observations but we also provide new designs of synthetic oscillators for experimental construction.Conclusions: In this work we have presented and tested an evolutionary algorithm that can design a biological network to produce desired output. Given that previous designs of synthetic networks have been limited to subregions of network- and parameter-space, the use of our evolutionary optimisation algorithm will enable Synthetic Biologists to construct new systems with the potential to display a wider range of complex responses.
Contributors: Ashwin, Peter, Coombes, Stephen, Nicks, Rachel
oscillator theory have had a profound impact on the neuroscience community...oscillator perspective to provide a practical framework for further successful...oscillator...oscillator network ... The tools of weakly coupled phase oscillator theory have had a profound impact on the neuroscience community, providing insight into a variety of network behaviours ranging from central pattern generation to synchronisation, as well as predicting novel network states such as chimeras. However, there are many instances where this theory is expected to break down, say in the presence of strong coupling, or must be carefully interpreted, as in the presence of stochastic forcing. There are also surprises in the dynamical complexity of the attractors that can robustly appear—for example, heteroclinic network attractors. In this review we present a set of mathematical tools that are suitable for addressing the dynamics of oscillatory neural networks, broadening from a standard phase oscillator perspective to provide a practical framework for further successful applications of mathematics to understanding network dynamics in neuroscience.
Contributors: Gancarski, Pawel, Gonzalez Salcedo, Alvaro, Green, Richard, Heisselmann, Hendrik, Moriarty, Patrick, Munduate, Xabier, Pires, Oscar
oscillation ... A selection of four different unsteady aerodynamic experiments have been done to prepare a database which will serve for the analysis, investigation and tool validation of airfoil unsteady behavior of wind turbine blades. The four experiments and selected data are: University of Glasgow dynamic stall experiments: NACA0015 and NACA0030 airfoils tested at sinusoidal type motion of the pitch. NREL OSU experiments: LS(1)0417MOD, NACA4415 and S809 airfoils tested at sinusoidal type motion of the pitch. CENER unsteady airfoil pitching and flapping tests at DTU: NACA643-418 airfoil tested at sinusoidal type motion of the pitch, the flap and combined pitch and flap. ForWind airfoil tests under tailored inflow turbulence: DU00W212 airfoil with laminar flow, open grid condition and one sinusoidal dynamic grid condition.
Contributors: Shibahashi, Hiromoto, Murphy, Simon J.
frequency and the amplitude of this modulation allow the true peaks to ... We propose a photometric technique for future space missions that overcomes the problem of Nyquist aliases. These aliases result from typically long cadences of observation imposed by telemetry constraints. The proposed method is to introduce a periodic modulation to the sampling rate. Suitable combinations of the frequency and the amplitude of this modulation allow the true peaks to be distinguished from the aliases. We provide an analytical proof of the validity of this method and some demonstrations with simulated data. We also propose to divide a long cadence into two unequal parts, aiming at reproducing the intrinsic amplitude spectrum of stars without a severe smearing effect due to long exposures. The two exposures can be summed to recover the photon statistics if the user is interested in doing so. Based on these proposals, a specific recommendation for the PLATO mission is made to maximise its capability of photometry for asteroseismology, without serious interference with its other scientific missions.