Non Linear Dynamics Research Papers (original) (raw)

2025, physica status solidi (a)

Renucci 1 ) (a), T. Amand (a), X. Marie (a), P. Sellenart (b), J. Bloch (b), and B. Sermage (b)

2025, Computers & Structures

Geometric and material dispersions of bladed disks imply some mistuning effects, which result in both the loss of cyclic symmetry properties and a vibratory response amplification in areas of high modal density. These conditions complicate the prediction of vibratory behavior, causing high modal density and extreme sensitivity to mistuning. A non-intrusive spectral stochastic method has been developed to predict the vibratory behavior of a mistuned stator vane. To apply this method to an industrial model, a Karhunen-Loève expansion and a double modal synthesis method have been combined with the stochastic method. The complete method was first tested on a simple academic model and then on an industrial stator vane sector.

2025

For narrow band vibration control applications, the alternating stop band characteristics of periodic structures have been widely used. The objective of the present work is to extend this idea for broadband excitations. We seek to synthesize a torsional periodic structure having the largest fraction of the frequencies falling in the attenuation bands of the structure. The unit cell of such a periodic structure is comprised of two distinct regions having different inertial and stiffness properties. Guidelines are derived for suitable selection of inertial and stiffness properties of the two regions in the unit cell, such that the maximal frequency region corresponds to attenuation bands of the periodic structure. It is found that higher the impedance mismatch between the neighbouring regions of the unit cell leads to maximal attenuating frequencies. It is found that more than 98% of the frequencies are blocked in the extreme case. For torsional excitations, it is shown that large, fi...

2025, Mechatronics

We present design, fabrication, and characterization of a mechanically coupled MEMS H resonator capable of performing simultaneous mechanical amplification and filtering in air. The device comprises of two doubly clamped polyimide microbeams joined through the middle by a coupling beam of the same size. The resonator is fabricated via a multi-layer surface micromachining process. A special fabrication process and device design is employed to enable operation in air and to achieve mechanical amplification of the output response. Moreover, mixed-frequency excitation is used to demonstrate a tunable wide band filter for low frequency applications. It is demonstrated that through the multi-source harmonic excitation and the operation in air, an improved bandpass filter with flat response and minimal ripples can be achieved.

2025, IEEE Transactions on Instrumentation and Measurement

2025, Electroencephalography and Clinical Neurophysiology

A multi-channel switched-capacitor 6-pole filter for significantly reducing the EMG artifact present during seizures recorded by long-term monitoring procedures has been implemented for routine use. This permits repeated replay of the seizures with different filter settings. All of the channels can be simultaneously dialed to any cut-off frequency (3 dB down) between 8 Hz and 70 Hz and the event replayed for filtering and write-out onto any standard EEG machine. The advantage of the 6-pole switched-capacitor filter is that it does not require a complex design with high precision RC components. The cut-off frequency is determined by the frequency of a simple clock that is used to select the same cut-off point for all 16 channels. By changing the clock frequency, the operator moves the cut-off point linearly. The dramatic improvement obtained by off-line digital filtering that was recently reported indicates that more efficient filtering of EMG contaminated seizures is diagnostically significant in selected cases. This approach is limited by the availability and expense of not only the computer's hardware but also the dedicated software. Specially designed 4-pole analog filters are less expensive than digital filtering, but are difficult to design even at specific frequencies and do not allow for a range of frequencies. The switched-capacitor 6-pole filters have all the advantages of the above but are even more efficient in reducing EMG artifact. They also do not have any of the above disadvantages and cost only a few dollars per channel.

2025, International Journal of Non-Linear Mechanics

The non-linear free and forced vibrations of simply supported thin circular cylindrical shells are investigated using Lagrange's equations and an improved transverse displacement expansion. The purpose of this approach was to provide engineers and designers with an easy method for determining the shell non-linear mode shapes, with their corresponding amplitude dependent non-linear frequencies. The Donnell non-linear shell theory has been used and the flexural deformations at large vibration amplitudes have been taken into account. The transverse displacement expansion has been made using two terms including both the driven and the axisymmetric modes, and satisfying the simply supported boundary conditions. The non-linear dynamic variational problem obtained by applying Lagrange's equations was then transformed into a static case by adopting the harmonic balance method. Minimisation of the energy functional with respect to the basic function contribution coefficients has led to a simple non-linear multi-modal equation, the solution of which gives in the case of a single mode assumption an expression for the non-linear frequencies which is much simpler than that derived from the non-linear partial differential equation obtained previously by several authors. Quantitative results based on the present approach have been computed and compared with experimental data. The good agreement found was very satisfactory, in comparison with previous old and recent theoretical approaches, based on sophisticated numerical methods, such as the finite element method (FEM), the method of normal forms (MNF), and analytical methods, such as the perturbation method.

2025, International Journal of Mechanical Sciences

Friction induced vibrations are a major concern in a wide variety of mechanical systems. This is especially the case in aircraft braking systems where the problem of unstable vibrations in disk brakes has been studied by a number of researchers. Solving potential vibration problems requires experimental and theoretical approaches. A nonlinear model for the analysis of mode aircraft brake whirl is presented and developed based on experimental observations. The non-linear contact between the rotors and the stators, and mechanisms between components of the brake system are considered. Stability is analyzed by determining the eigenvalues of the Jacobian matrix of the linearized system at the equilibrium point. Linear stability theory is applied in order to determine the effect of system parameters on stability.

2025, Computers & Structures

Stability analysis and non-linear behaviour of structural systems using the complex non-linear modal analysis (CNLMA)

2025, Journal of Sound and Vibration

In this paper, a non-linear strategy, based on the centre m anifold, the rational approxim ants and the alternating frequency/time domain method has been developed, in order to study the non-linear dynamical behaviour of a system in the neighbourhood of a critical steady state equilibrium point. The stability analysis and the non-linear dynam ics of a com plex braking system with a non-linear rotor/stator contact are presented. Moreover, one of the m ost im portant steps of this paper is the determination of the nonlinear behaviour and the limit cycle amplitudes of this complex system. In order to conduct this study, the dynam ic response is evaluated by using applying the centre m anifold, the rational approximants and the alternating frequency/tim e dom ain m ethod, that perm it to obtain rapidly and efficiently the non-linear behaviour of the system . The dynam ic response obtained by applying this m ethod is com pared with that evaluated through num erical integration.

2025, Engineering Reports

This article examines the (2 + 1)-dimensional variable coefficient KdV-type equation that arises in oceanography. Oceanography is the science of studying the oceans. It is an earth science that addresses many different subjects, such as the dynamics of ecosystems, ocean currents, waves, and geophysical fluid dynamics. Fluid dynamics is a nonlinear science that studies the flow of liquids and gases in physics, physical chemistry, and engineering. The assistance of the Hirota bilinear method secures different forms of multiple solitons and M-lump waves, such as one-, two-, and three-soliton, by using different functions of variable coefficients. Moreover, the long-wave technique is under consideration when analyzing hybrid solutions, namely mixed soliton-lump, two-soliton-lump, and soliton-two-lump solutions. The results of this exploration exhibit the physical characteristics of solutions and collision-related aspects within the variety of nonlinear systems. The physical significance of the extracted solutions is meticulously analyzed by presenting a variety of profiles that display the behavior of the solutions for specific parameter values. Our results indicate their potential use in future endeavors to discover unique and assorted solutions for nonlinear evolution equations encountered in engineering and mathematical physics. The reported results in this study are the first of their kind to be reported in the literature. These results may be helpful in explaining the physical behavior of various nonlinear physical models. 1 | Introduction Mathematical modeling of complex time-varying processes requires examining several types of nonlinear partial differential equations. Since the mid-1800 s, experts have tried distilling complicated physical phenomena into nonlinear partial differential equations. Special modeling simulates many nonlinear aspects, including quantum mechanics, fluid mechanics, nonlinear optics, neural networks, and solid-state physics, to name a

2025, Acta Pharmaceutica

Non-linear free energy transducers with a variable slip are more suitable for controlling metabolism and are more efficient than linear transducers in storing free energy.

2025, non-milleplateaux.de

Articulates a theoretical framework of recursive systems, conceptual drift, and ontological instability. It reconfigures discrete operations—algorithmic synthesis, geological perception, simulation kernels, and fragmented memory—into a saturated matrix of co-implicated modulations. Grounded in recursive pataphysics, posthumanist cognition, and semiotic liquidity, the text proposes a radical departure from linear epistemologies. Meaning, memory, and subjectivity dissolve into performative recursion, governed by the indeterminate logic of the Phantom Operator. The drift becomes not an aberration but a generative principle of systemhood.

2025, Geophysical Journal International

The temperature of a 10-point vertical profile at the rock-atmosphere interface has been monitored since 2000 September in an underground vault at Aburatsubo, Japan, where resistivity variations have been reported in association with earthquakes. The non-ventilated vault is characterized by an annual temperature variation of about 1.2 • C peak to peak, compatible with thermal diffusion in the surrounding tuff rock, and by a long-term temperature increase of about 0.1 • C per year, possibly due to a local or global climate change. Owing to a careful relative calibration of the 10 thermistors used in this experiment, these data establish that the ceiling temperature is higher than the floor temperature by 0.04 to 0.28 • C. Transient temperature variations are observed in association with human presence or with typhoons, with a characteristic spatial pattern revealing structural heterogeneity. Variations with periods ranging from 1 day to 1 week, with an amplitude two time larger and a phase advance on the floor with respect to the ceiling, are observed from November to May. Variations with periods larger than 1 week, with an amplitude two times smaller and a phase lag on the floor with respect to the ceiling, are observed from June to October. These cycles are linked to the sign of the seasonal heat flux. We propose an interpretation in which heat transfer in the cavity is dominated by diffusion of water vapour from June to October (heat flux downwards, summer regime) and by convective water transport from November to May (heat flux upwards, winter regime). The water flow inferred from this model can be used to predict the water saturation of the rock as a function of time. Because of a permanent radiative heat flux from top to bottom, the upward water flow in the winter regime is larger than the downward water flow in the summer regime, resulting in a slow depletion of water from the rock below the cavity. This unbalanced water flow could contribute to an observed steady secular increase of rock resistivity, and possibly also to the long-term temperature increase of 0.1 • C per year. It is important to understand these processes in the context of underground geophysical observatories, underground waste storage and contaminant transport, as well as for the preservation of cultural items such as cave paintings.

2025, 2009 2nd International Symposium on Resillient Control Systems

This paper explores the overlaps between the Control community's work on System IdentiÀcation (SysID) and the Physics, Mathematics, Chaos, and Complexity communities' work on phase-space reconstruction via time-delay embedding. There are numerous overlaps between the goals of each community. Nevertheless, the Controls community can gain new insight as well as some new very powerful tools for SysID from the latest developments within the Physics, Mathematics, Chaos, and Complexity communities. These insights are gained via the work on phase-space reconstruction of non-linear dynamics. New methods for discovering non-linear differential based equations that evolved from embedding operations can shed new light on hybrid-systems theory, Nyquest-Shannon's Theories, and network based control theory. This paper strives to guide the Controls community towards a closer inspection of the tools and additional insights being developed within the Physics, Mathematics, Chaos, and Complexity communities for discovery of system dynamics, the Àrst step in control system development. The paper introduces the concepts of phase-space reconstruction via time-delay embedding (made famous by Whitney, Takens, and Sauer's Thoreoms), intergrate-and-Àre embedding, and non-linear differential equation discovery based on Perona's method.

2025

The static response of an electrostatic micro-catilever beam has been obtained by using Galerkin's method. To make the system bi-stable, a controller has been added and the static response profile is presented using a multi-mode model for the beam. The number of mode shapes leading to convergence has been studied. The softening effect of adding more mode shapes has been investigated along with the effect of changing the system parameters on the static response. Decreasing the controller gain has been found to widen the voltage range of the bi-stability region and increasing the sensor amplification factor is shown to push the upper equilibrium point away from pull-in. Properly choosing these parameters can adjust the range of voltage for bi-stability. By doing a linearization about the stable fixed points, we also found the two natural frequencies for each stable equilibrium point. Finally, we have found the dynamic response of the bistable system using one-and three-mode-model...

2025, Chemical Engineering Science

Methods for identifying flow regime transitions in a trickle bed with structured packing based on the response of conductimetric probes are proposed. Time series of conductance measurements, obtained with an array of eight probes flushed to the reactor wall, are analyzed using tools borrowed from the theory of non-linear dynamics and symbolic dynamics. For the same range of gas and liquid velocities, the local hydrodynamics is inspected within a channel of the structured packing in a non-intrusive manner with a set of conductimetric probes imprinted on one of the corrugated plastic sheets that conforms a packing element. The local hydrodynamics within the channel is explored to interpret the trends of characteristic numbers calculated from the time series measured at the wall. The gas-liquid pattern shows a slugging behavior within the channel that is reflected in the analysis of the flushed probes response.

2025, Environmental Modelling & Software

Our study aims to estimate confounded effects of nutrients and grazing zooplankton (Crustacea) on phytoplankton groupsdspecifically on nitrogen-fixing Cyanobacteriadin the shallow, mesotrophic Lake Pyha ¨ja ¨rvi in the northern hemisphere (Finland, northern Europe, lat. 60 54 0 e 61 06 0 , long. 22 09 0 e22 22 0 ). Phytoplankton is modelled with a non-linear dynamic model which describes the succession of three dominant algae groups (Diatomophyceae, Chrysophyceae, nitrogen-fixing Cyanobacteria) and minor groups summed together as a function of total phosphorus, total nitrogen, temperature, global irradiance and crustacean zooplankton grazing. The model is fitted using 8 years of in situ observations and adaptive Markov chain Monte Carlo (MCMC) methods for estimation of model parameters. The approach offers a way to deal with noisy data and a large number of weakly identifiable parameters in a model. From our posterior simulations we calculate the lower limit for zooplankton carbon mass concentration (45 mgC L À1 ) and the upper limit for total phosphorus concentration (16 mg L À1 ) that satisfy with 0.95 probability our predefined water quality criteria (Cyanobacteria concentration during late summer period does not exceed the value 0.86 mg L À1 ). Within the observational range total phosphorus has marginal effect on Cyanobacteria compared to the zooplankton grazing effect, which is temperature-dependent. Extensive fishing efforts are needed to attain the criteria.

2025

Concrete gravity dam (140 m high) of proposed Tanahu Hydroelectric project (140 MW), Nepal has been modelled in SAP2000 for this study. The entire modelling is based on US-Army Engineering Manuals. Near-field earthquake effect is studied and compared with the far field counterpart. Linear and Nonlinear time-history analysis are used to assess earthquake performance of non-overflow gravity dam section. The results of linear time history analysis are compared with the EM 1110-2-6051 and EM 1110-2-6053 performance acceptance criteria for gravity dams. This study indicated that the dam would suffer significant cracking along the base for all the fifteen selected near-field earthquake record and should be assessed on the basis of nonlinear time-history analysis. This study also concluded that near-field earthquake with higher PGV may affect more than that having more PGA but lower PGV. At the other hand, response for far-field earthquake response indicates that the dam will not suffer pr...

2025, arXiv (Cornell University)

We studied correlations between different nodes in small electronic networks with active links operating as jitter generators. Unexpectedly, we found that under certain conditions signals from the most remote nodes in the networks correlate stronger than signals from all of the other coupled nodes. The phenomenon resembles selective remote correlation between electrons in Cooper's pairs or entangled particles.

2025

Magnetic Reconnection has long been recognized as the dominant mechanism responsible for solar flare energy release. However, standard models fail to adequately account for the timing, intensity, and spatial structure observed in flare events. This study introduces Magnetic Breakdown as the incipient physical mechanism underlying Magnetic Reconnection, framed through a conservation of energy analysis between interacting magnetic flux tubes. By modeling field lines as mechanical photon-based chains in Photony Theory, we show that the breakdown of these structures initiates energy release preceding reconnection. Observational support is provided through early-phase flare data and analytical treatment of chain fragmentation energetics.

2025, International Journal of Non-Linear Mechanics

In this paper the nonlinear dynamics of circular cylindrical shells under axial static (compressive) and periodic resonant loads have been experimentally investigated, the goal is to study the dynamic scenario and to analyze nonlinear regimes. A special test rig has been developed for the experiment in order to apply a static axial load combined with a dynamic axial load. The setup allows for investigating the linear behavior under static preload by means of the usual modal testing techniques; moreover, it allows for analyzing the nonlinear response which occurs when the dynamic axial load is periodic and gives rise to complex resonances. The complex dynamics, arising when a periodic axial load excites the asymmetric (shell like) modes, are analyzed by means of amplitude frequency diagrams, waterfall spectrum diagrams, bifurcation diagrams of Poincaré maps; a deep analysis of time histories, spectra, phase portraits and Poincaré maps completes the study of the complex dynamic scenario.

2025, Applied Surface Science

This paper is a theoretical and a numerical investigation of the stability of a tip±cantilever system used in noncontact atomic force microscopy (NC-AFM) when it oscillates close to a surface. No additional dissipative force is considered. The theoretical approach is based on a variational method exploiting a coarse grained operation that gives the temporal dependence of the nonlinear-coupled equations of motion in amplitude and phase of the oscillator. Stability criterions for the resonance peak are deduced and predict a stable behavior of the oscillator in the vicinity of the resonance. The numerical approach is based on the results obtained with a virtual NC-AFM developed by our group. The effect of the size of the stable domain in phase is investigated. These results are in particularly good agreement with the theoretical predictions. Also they show the in¯uence of the phase shifter in the feedback loop and the way it can affect the damping signal.

2025

We test for the presence of low-dimensional chaotic structure in the Stock Exchange of Thailand (SET) Index. While we find strong evidence of nonlinear dependencies, the evidence is not consistent with chaos. Our test results indicate that ARCH-type processes generally explain the nonlinearities in the data. We also show that employing seasonally adjusted index series contributes to obtaining robust results via some of the existing tests for chaotic structure.

2025, Energy Economics

We test for the presence of low-dimensional chaotic structure in crude oil, heating oil, and unleaded gasoline futures prices from the early 1980s. Evidence on chaos will have important implications for regulators and short-term trading strategies. While we find strong evidence of non-linear dependencies, the evidence is not consistent with chaos. Our test results indicate that ARCH-type processes, with controls for seasonal variation in prices, generally explain the non-linearities in the data. We also demonstrate that employing seasonally adjusted price series contributes to obtaining robust results via the existing tests for chaotic structure. Maximum likelihood methodologies, that are robust to the non-linear dynamics, lend support for Samuelson's hypothesis on contract-maturity effects in futures price-changes. However, the tests for chaos are not found to be sensitive to the maturity effects in the futures contracts. The results are robust to controls for the oil shocks of 1986 and 1991.

2025, International Journal of …

2025, Agricultural Economics

We conduct tests for the presence of low-dimensional chaotic structure in the futures prices of four important agricultural commodities. Though there is strong evidence of non-linear dependence, the evidence suggests that there is no long-lasting chaotic structure. The dimension estimates for the commodity futures series are generally much higher than would be for low dimension chaotic series. Our test results indicate that autoregressive conditional heteroskedasticity (ARCH)-type processes, with controls for seasonality and contract-maturity effects, explain much of the non-linearity in the data. We make a case that employing seasonally adjusted price series is important in obtaining robust results via some of the existing tests for chaotic structure. Finally, maximum likelihood methodologies, that are robust to the non-linear dynamics, lend strong support to the Samuelson hypothesis of maturity effects in futures price changes.

2025

One of the main challenges in the European fusion roadmap is to design a heat and power exhaust system able to withstand the large loads expected in the divertor of a DEMO fusion power plant. Therefore, in parallel with the programme to optimise the operation with a conventional divertor based on detached conditions to be tested on the ITER device currently under construction in Cadarache, a specific project has been launched to investigate alternative power exhaust solutions for DEMO, aimed at the definition and the design of a Divertor Tokamak Test facility. This tokamak should be capable of hosting scaled experiments integrating most of the possible aspects of the DEMO power and particle exhaust. DTT should retain the possibility to test different divertor magnetic configurations, liquid metal divertor targets, and other possible solutions for the power exhaust problem. The DTT design proposal refers to a set of parameters selected so as to have edge conditions as close as possib...

2025, 2010 10th IEEE-RAS International Conference on Humanoid Robots

2025, Control Engineering Practice

In this paper static-state feedback laws are considered which address the problem of output stabilization of non-linear dynamic control systems without drift. It is shown that as long as a dynamic-state control law exists which input-output decouples a given system, it is possible to construct a static-state control which stabilizes the systerffs output. The design procedure sheds light on the inherent difficulties in designing internally stable control laws for non-linear systems. To demonstrate the theory, it is applied to the task of designing an output stabilizing feedback for a simple model of a mobile robot.

2025, Northeast Journal of Complex Systems

Literature on educational reforms is rich of cases where changes have been attempted, without however to attain success. Likewise the Greek education system had experienced a lot of reforms, most of which have failed to make the intended changes and they attenuated shortly after their implementation or they ceased at the stage of legislative planning. On the other hand, the traditional research have failed to develop a coherent theoretical perspective and provide satisfactory interpretations of the perpetually unsuccessful reforms. This paper is part of wider project which attempts to address the above issue following the Complex Dynamical Systems (CDS) perspective, that is, by fostering the CDS epistemological assumptions and applying nonlinear methodological approaches. This endeavor focuses on teachers' readiness for change and explores the dimensions of the resistance to change related to the values, attitudes, dysfunction beliefs and planed behaviors of teachers. Given that the project is still ongoing, here, only the outline of the research design and the strategy followed are discussed along with some preliminary findings. At a first stage, the investigation implemented focus-group settings to reveal clues of those dimensions. The recorded data were analyzed via orbital decomposition analysis (ODA), a method designed for categorical time series and discourse analysis. Some of the crucial dimensions of resistance-to-change were subsequently measured via a survey instrument and were used to predict teachers' position with linear and nonlinear models. Statistical analysis showed that the cusp catastrophe model was superior to the linear alternatives and revealed discontinuities in teachers' positions, while certain variables proved to be bifurcation factors. The implications of these findings are discussed, while methodological aspects of ODA and catastrophe theory modeling are briefly presented. The present work sets a framework for the application of complexity theory and nonlinear dynamics in organizational theory of educational change.

2025, Systems & Control Letters

This paper concerns the control design of a PID controlled gimbals suspension gyro, whose parameters are determined by using bifurcation theory. The non-linear mathematical model of the gyro is deduced by using the nutation theory of gyroscopes. Considering a PID controller with constrained integral action, it is shown that depending on different values of the maximum allowed integral action a Poincaré-Andronov-Hopf bifurcation may appear. The analysis of the stability or instability of this bifurcation, from the first Lyapunov value, gives a procedure to adjust the parameters of the PID controller. The developed control methodology is evaluated through numerical simulations.

2025

This work investigates the inverse problem of identifying a time-dependent source term in a time-fractional semi-linear degenerate parabolic equation using integral measurement data. We establish the unique solvability of the inverse problem within a suitable functional framework. The proof methodology is based on the Rothe method, where the variational formulation is discretized in time, and a priori estimates for discrete solutions are derived. These estimates are then utilized to demonstrate the convergence of Rothe approximations to a unique weak solution. Additionally, we develop a numerical scheme based on the L 1-Galerkin finite element method, combined with iterative refinement, to reconstruct the unknown source term. The numerical performance of the proposed method is validated through a series of computational experiments, demonstrating its stability and robustness against noisy data.

2025

Complex dynamical systems existing in an unobservable multidimensional space can be successfully represented via an artificial vector space, created from the single output variable of such a dynamical system. Visual Recurrence Analysis (VRA) method enables visualisation of the single time series in such a space. This paper uses VRA method and Hurst exponents as the means of estimating, describing and qualifying some of the properties of several financial time series. Weak evidence of chaos in daily returns is indicated.

2025, Journal of Statistical Theory and Applications

The purpose of this paper is to provide a valid Edgeworth expansion for the parametric bootstrap t-statistic of a linear regression process whose error terms are stationary, Gaussian, and strongly dependent time series. Under some sets of conditions on the spectral density function and the parametric values, an Edgeworth expansion of the bootstrap t-statistic of arbitrarily large order of the process is proved to have an error of o(n 1-s/2 ) where s is a positive integer. The result is similar to the Edgeworth expansion obtained by Andrews and Lieberman [2002], which was established for the parametric bootstrap t-statistic of the plug-in maximum likelihood (PML) estimators of stationary, Gaussian, and strongly dependent processes, but without the linear regression component.

2025

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2025

L'objet de ce travail etait etudier l'influence des collisions electron-electron sur la dynamique electronique et ionique d'un agregat de sodium lors d'une excitation laser femtoseconde. Dans ce but, nous avons utilise une approche semi-classique qui substitue a la fonction d'onde a N corps quantique representant les electrons de valence de l'agregat, une fonction de distribution dans l'espace des phases. L'avantage formel d'une representation semi-classique est qu'elle permet d'inclure facilement, via les equations cinetiques, le terme de collision d'Uhling-Uhlenbeck (UU), pour aller au-dela du champ moyen. L'evolution en temps de la fonction de distribution est ainsi regie par l'equation de Vlasov-Uhling-Uhlenbeck (VUU), qui est resolue numeriquement, a l'aide de la methode des particules test.

2025

2025, IT Analysis and Training Ltd

We are proposing a comprehensive observational campaign involving deep, multi-epoch mid-infrared and optical imaging of two intriguing candidates located at approximately right ascension 2h30m and declination 0°, which correspond to the hypothesized location of a distant massive exoplanet, commonly referred to as Planet Nine. Additionally, these observations will investigate the possibility of a captured or co-formed satellite body, potentially a moon associated with the planet. Utilizing archival data from the Wide-field Infrared Survey Explorer (WISE) in the W4 band alongside the 2024 SkyView datasets, our preliminary analysis through a method of archival subtraction has revealed the presence of two faint, slow-moving cold objects in the vicinity. These objects exhibit apparent motions consistent with a separation ranging from approximately 0.2 to 0.6 arcseconds per year, suggesting their intriguing dynamical relationship. To firmly establish the existence and properties of these candidates, it is essential to conduct repeated imaging sessions at high sensitivity to enhance our detection capabilities. The overarching goals of this project include accurately characterizing the proper motion of these potential bodies, confirming the dynamics of a binary system, and constraining their mass and thermal characteristics through detailed infrared observations. This thorough analysis will enhance our understanding of these elusive objects and their potential connections to the broader framework of our solar system's architecture.

2025, arXiv (Cornell University)

In this paper we analyze the cycle-to-cycle variations of maximum pressure pmax and peak pressure angle αpmax in a four-cylinder spark ignition engine. We examine the experimental time series of pmax and αpmax for three different spark advance angles. Using standard statistical techniques such as return maps and histograms we show that depending on the spark advance angle, there are significant differences in the fluctuations of pmax and αpmax. We also calculate the multiscale entropy of the various time series to estimate the effect of randomness in these fluctuations. Finally, we explain how the information on both pmax and αpmax can be used to develop optimal strategies for controlling the combustion process and improving engine performance.

2025, Journal of Theoretical Biology

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2025, arXiv: Astrophysics

In this paper we present a new local Lagrangian approximation to the gravitational dynamics of cold matter. We describe the dynamics of a Lagrangian fluid element through only one quantity, the deformation tensor. We show that this tensor is clearly suited to the study of gravitational dynamics and, moreover, that knowing its evolution is enough to completely describe a fluid element. Our approximate dynamics treat exactly the conservation of mass, of the velocity divergence and of the shear and is exact in the case of planar, cylindrical and spherical collapses. It also reproduces very accurately the evolution of all dynamical quantities for a very wide class of initial conditions as illustrated by a detailed comparison with the homogeneous ellipsoid model. Beside, we highlight, for the first time, the important dynamical role played by the Newtonian counterpart of the magnetic part of the Weyl tensor.

2025, Applied Mathematics

In this article, we present asymptotic solutions of fourth order critically oscillatory undamped nonlinear systems in which the four eigenvalues are pairwise equal and imaginary. In this regard, the modified Krylov-Bogoliubov-Mitropolskii (KBM) method is used, which is considered to be a well-suited method for investigating the transient behaviour of oscillating systems, to obtain the solutions of fourth order critically oscillatory nonlinear systems. This paper suggests that the solutions obtained by the modified KBM method are quite well consonant with those obtained by the numerical method using Mathematica.

2025, Computers & Chemical Engineering

In many chemical engineering process control applications, one frequently encounters differential-algebraic optimization problems. Such optimal control problems are difficult to solve, in general, because of the presence of singular arcs for systems whose Hamiltonian is linear with respect to the control variable. We propose the use of absolute error penalty functions (AEPF) in handling constrained optimal control problems in chemical engineering by posing the problem as a nonsmooth dynamic optimization problem. We show that Iterative dynamic programming (JDP) is a very useful technique for solving constrained dynamic optimization problems without unduly increasing the dimension of the system or the computational burden. A move suppression criterion has been incorporated into the IDP algorithm in order to penalize excessive control moves. To show the efficacy of the method, an analytical (exact) solution of a simple problem is obtained using least squares control theory and compared with results obtained using IDP. Results obtained for other seemingly difficult optimal control problems in chemical engineering compare very favourably with those reported in the optimization and optimal control literature.

2025

Superradiance and nonlinear evolution of a FEL pulse in a single-pass FEL were experimentally demonstrated at the National Synchrotron Light Source (NSLS) Source Development Laboratory (SDL). The experiment was performed using a 1.5 ps high-brightness electron beam and a 100fs Ti:Sapphire seed laser. The seed laser and electron beam interact in the 10 meter long NISUS undulator with a period of 3.89 cm. The FEL spectrum, energy and pulse length along the undulator were measured. FEL saturation was observed, and gain of more the 200 (relative to seed laser) was measured. Both FEL spectrum widening and pulse length shortening were observed; FEL pulses as short as 65 fs FWHM were measured. The superrandiance and nonlinear evolution were also simulated using the numerical code GENESIS1.3 yielding good agreement with the experimental results.

2025, Journal of Magnetism and Magnetic Materials

This study treats with the influence of a symmetry-breaking transversal magnetic field on the nonlinear dynamics of ferrofluidic Taylor-Couette flow -flow confined between two concentric independently rotating cylinders. We detected alternating 'flip' solutions which are flow states featuring typical characteristics of slow-fast-dynamics in dynamical systems. The flip corresponds to a temporal change in the axial wavenumber and we find them to appear either as pure 2-fold axisymmetric (due to the symmetry-breaking nature of the applied transversal magnetic field) or involving non-axisymmetric, helical modes in its interim solution. The latter ones show features of typical ribbon solutions. In any case the flip solutions have a preferential first axial wavenumber which corresponds to the more stable state (slow dynamics) and second axial wavenumber, corresponding to the short appearing more unstable state (fast dynamics). However, in both cases the flip time grows exponential with increasing the magnetic field strength before the flip solutions, living on 2-tori invariant manifolds, cease to exist, with lifetime going to infinity. Further we show that ferrofluidic flow turbulence differ from the classical, ordinary (usually at high Reynolds number) turbulence. The applied magnetic field hinders the free motion of ferrofluid partials and therefore smoothen typical turbulent quantities and features so that speaking of mildly chaotic dynamics seems to be a more appropriate expression for the observed motion.

2025, Seminars in Cancer Biology

Cancer is a highly complex disease due to the disruption of tissue architecture. Thus, tissues, and not individual cells, are the proper level of observation for the study of carcinogenesis. This paradigm shift from a reductionist approach to a systems biology approach is long overdue. Indeed, cell phenotypes are emergent modes arising through collective non-linear interactions among different cellular and microenvironmental components, generally described by "phase space diagrams", where stable states (attractors) are embedded into a landscape model. Within this framework, cell states and cell transitions are generally conceived as mainly specified by generegulatory networks. However, the system s dynamics is not reducible to the integrated functioning of the genome-proteome network alone; the epithelia-stroma interacting system must be taken into consideration in order to give a more comprehensive picture. Given that cell shape represents the spatial geometric configuration acquired as a result of the integrated set of cellular and environmental cues, we posit that fractal-shape parameters represent "omics descriptors of the epithelium-stroma system. Within this framework, function appears to follow form, and not the other way around.

2025, arXiv: Soft Condensed Matter

This work deals with a mesoscopic and deterministic theory for the collective dynamics of Water Coherence Domains, and it represents a continuation of a previous work published in Plos ONE this https URL This approach qualitatively reproduces some features of the experimental phenomenology, and it could sustain an evolutionary theory based on layered synchronization processes. Its relevance for the description of the processes behind the emergence of life is discussed.

2025, Technical science and innovation

The article deals with the problems of numerical modeling of nonlinear physical processes of the stress-strain state of structural elements. An elastoplastic medium of a homogeneous solid material is investigated. The results of computational experiments on the study of the process of physically nonlinear deformation of isotropic elements of three-dimensional structures with a system of one- and double-periodic spherical cavities under uniaxial compression are presented. The influence and mutual influence of stress concentrators in the form of spherical cavities, vertically located two cavities and a horizontally located system of two cavities on the deformation of the structure are investigated. Numerical algorithms have been developed for solving the problems of physically nonlinear deformation of structures made of structural materials, which make it possible to effectively use the capabilities of computer technology. The optimal parameters of computational experiments on the con...

2025

To elucidate the time course of sympathovagal balance and its relationship to left ventricular function in heart failure, we serially evaluated left ventricular contractility and relaxation and autonomic tone in 11 conscious dogs with tachycardiainduced heart failure. We determined a dynamic map of sympathetic and parasympathetic modulation by power spectral analysis of heart rate variability. The left ventricular peak ϩdP/dt substantially fell from 3,364 Ϯ 338 to 1,959 Ϯ 318 mmHg/s (P Ͻ 0.05) on the third day and declined gradually to 1,783 Ϯ 312 mmHg/s at 2 wk of rapid ventricular pacing. In contrast, the time constant of left ventricular pressure decay and end-diastolic pressure increased gradually from 25 Ϯ 4 to 47 Ϯ 5 ms (P Ͻ 0.05) and from 10 Ϯ 2 to 21 Ϯ 3 mmHg (P Ͻ 0.05), respectively, at 2 wk of pacing. The high-frequency component (0.15-1.0 Hz), a marker of parasympathetic modulation, decreased from 1,928 Ϯ 1,914 to 62 Ϯ 68 ϫ 10 3 ms 2 (P Ͻ 0.05) on the third day and further to 9 Ϯ 12 ϫ 10 3 ms 2 (P Ͻ 0.05) at 2 wk. Similar to the time course of left ventricular diastolic dysfunction, plasma norepinephrine levels and the ratio of low (0.05-to 0.15-Hz)-to highfrequency component increased progressively from 135 Ϯ 50 to 532 Ϯ 186 pg/ml (P Ͻ 0.05) and from 0.06 Ϯ 0.06 to 1.12 Ϯ 1.01 (P Ͻ 0.05), respectively, at 2 wk of pacing. These cardiac and autonomic dysfunctions recovered gradually toward the normal values at 2 wk after cessation of pacing. Thus a parallel decline in left ventricular contractility with parasympathetic influence and a parallel progression in left ventricular diastolic dysfunction with sympathoexcitation suggest a close relationship between cardiac dysfunction and autonomic dysregulation during development of heart failure.