Classical Dynamics Research Articles

Flight test evaluation of trim tab stabilisation system on a PZL-130 orlik aircraft

Purpose The paper presents the results of the final phase of the project, namely flight tests, aimed at developing a stabilisation system utilizing trim tabs for the PZL-130 Orlik turboprop military trainer aircraft. Design/methodology/approach The proposed flight stabilisation system was developed using modern techniques of model-based design, automatic code generation and software and hardware-in-the-loop testing. The project progressed to the flight testing stage, enabling the assessment of the control system’s quality and its final calibration. Findings Analysis of the results obtained during flight tests confirmed the high quality of the stabilisation system. Specifically, the anticipated accuracy of both longitudinal and lateral channel stabilisation was achieved. Originality/value The proposed flight stabilisation system, utilizing trim tabs, offers several advantages over classic automatic flight systems in terms of weight, energy consumption, structural simplicity and obviates the need for primary control modifications on the aircraft. It was developed using modern techniques of model-based design, automatic code generation and hardware-in-the-loop simulations.

Real-Time CASSCF (Ehrenfest) Modeling of Electron Dynamics in Organic Semiconductors. Dynamics Reaction Paths Driven by Quantum Coherences. Application to a Radical Organic Semiconductor.

We present a strategy for the modeling of charge carrier dynamics in organic semiconductors using conventional quantum chemistry methods, including the analytic gradient for nuclear motion. The theoretical approach uses real-time CASSCF (Ehrenfest) all-electron dynamics coupled to classical nuclear dynamics for the special case of a small number (4-8) of molecular units. The objective is to obtain mechanistic/atomistic insight at the electronic structure level, relating to spin density dynamics, to the effect of crystal structure (e.g., slippage between spin/charge carriers), and to ferromagnetic and antiferromagnetic effects. The initial conditions for our simulations use the equilibrium structures of all the molecular units. At this geometry, a localized hole on one of the units corresponds to a coherent superposition of adiabatic states. We thus generate a dynamics reaction path driven by quantum coherences. Our aim is to inform experiment and to compare with parametrized theoretical models. The methodology is demonstrated for a perfectly π-stacked ethylene model (up to 8 eclipsed molecular units) for both hole transfer and localized exciton transfer. An application for hole transfer is presented for bisdithiazolyl (S,S) and bisdiselenazolyl (Se,Se) radicals for the special case of ferromagnetic coupling. For these examples, the embedded pyridine radical model organic chromophore (up to 6 eclipsed π-stacked molecular units) has been studied on its own as well as the target bisdithiazolyl (S,S) and bisdiselenazolyl (Se,Se) systems. A significant difference between these systems and the ethylene and pyridine stacks is that the (S,S) and (Se,Se) systems exhibit molecular slippage rather than being perfectly eclipsed. This slippage may result from crystal defects or intermolecular vibrations. For the model systems, the electron dynamics is dominated by the initial and final molecular units, irrespective of the length of the chain. The intervening units act as a "superexchange bridge". Our simulations reveal that, in the presence of slippage, charge migration cannot propagate across the entire system; instead, the coherence length is limited to 3 molecular units. The results also suggest that the mechanism of charge transport is different for bisdiselenazolyl (Se,Se) (superexchange-like A -[B]→ C) and bisdithiazolyl (S,S) (direct A → C). An analysis of the spin density suggests that, in the charge carrier dynamics, the additional charge carried by the Se versus S in the "scaffold" is small. Since we use a small number of molecular units, the coupled nuclear dynamics is seen to be complementary to the electron dynamics (i.e., creating a hole causes bond length contraction while filling a hole with an electron lengthens the bond). In all the cases studied, the mechanism of charge mobility is wave-like, rather than hopping, because we use the time dependent Schrödinger equation to propagate the electronic wave function.

Performance and mechanism of ‘coagulation co-adsorption’ on simultaneous reduction of turbidity and low-fluoride pollution by a polymer metal-based defluorination and turbidity-removal agent (PMDTA)

ABSTRACT A polymer metal-based defluorination and turbidity-removal agent (PMDTA) was prepared using a poly-Si–Fe coagulant (PSF) and aluminum. Simultaneous reduction of turbidity and fluoride by PMDTA was studied using the ‘coagulation co-adsorption (CcA)’ method for the simulated and real low-fluoride waters, respectively, compared with that by PSF. The surface and bond structures, charged properties, and size of PMDTA and its flocs were explored, and the mechanism of removing turbidity and fluoride was analyzed. The results showed PMDTA decreased fluoride to <1 mg/L (PSF could not), but both decreased turbidity to <0.5 NTU. PMDTA adapted to a wider initial turbidity, humid acid (HA), NaCl, and temperature. PMDTA had similar bond structures to PSF, more complex surface structures than PSF, and higher surface space and adsorption sites than PSF. Filtration had almost no impact on fluoride removal, but gave positive impact on turbidity removal. The removal mechanisms of fluoride and turbidity were different: the former was mainly removed through adsorption on PMDTA-flocs (controlled by their forming conditions) having efficient adsorption properties, and the latter was mainly cleared through a synergistic effect of the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory (classic coagulation mechanism). The efficient fluoride removal by PMDTA can fully utilize the existing facilities in water plants.

Reducing the entry barrier for users and developers of peridynamic high performance computing

AbstractOver the past two decades, Peridynamics (PD) research has exhibited remarkable diversity, with contributions spanning more than 180 journals and involving over 1000 researchers. Despite its broad applicability, a persistent challenge remains—how to foster widespread adoption. In the engineering domain, classical continuum mechanics, predominantly facilitated by the finite element method, enjoys extensive utilization, supported by a plethora of commercial and open‐source software tools. PD simulation tools often find themselves competing with these well‐established counterparts. In research, custom codes tailored for specific applications are frequently created and applied, with little consideration for their future reuse or third‐party utilization. The complexity is further exacerbated in High‐performance computing (HPC) applications, where a deep understanding of solvers, parallel computing, and PD is imperative for a successful software development. Given the constraints of a typical doctoral thesis, large‐scale problems are often left unexplored, and research tends to be confined to simplistic geometries. This paper aims to elucidate various pathways for the seamless integration and utilization of a PD framework. We will showcase examples that illustrate how the barriers for both users and developers can be significantly lowered, ultimately propelling PD simulation tools to a higher standard of maturity in the medium term.

Revenue Maximization Under Unknown Private Values with Nonobligatory Inspection

Rethinking Informational Assumptions in Mechanism Design Mechanism design has proven to be very effective is soliciting buyers’ incentives and finding the optimal way of allocating scares resources. A common assumption in classic mechanism design, however, is that buyers have full information about their values. Motivated by application in e-commerce, Alaei et al. (2024) consider settings without this assumption and finds the optimal selling mechanism for them.

Exploring the Thermodynamic Uncertainty Constant: Insights from a Quasi-Ideal Nano-Gas Model

In previous work, we investigated thermodynamic processes in systems at the mesoscopic level where traditional thermodynamic descriptions (macroscopic or microscopic) may not be fully adequate. The key result is that entropy in such systems does not change continuously, as in macroscopic systems, but rather in discrete steps characterized by the quantization constant β. This quantization reflects the underlying discrete nature of the collision process in low-dimensional systems and the essential role played by thermodynamic fluctuations at this scale. Thermodynamic variables conjugate to the forces, along with Glansdorff–Prigogine’s dissipative variable can be discretized, enabling a mesoscopic-scale formulation of canonical commutation rules (CCRs). In this framework, measurements correspond to determining the eigenvalues of operators associated with key thermodynamic quantities. This work investigates the quantization parameter β in the CCRs using a nano-gas model analyzed through classical statistical physics. Our findings suggest that β is not an unknown fundamental constant. Instead, it emerges as the minimum achievable value derived from optimizing the uncertainty relation within the framework of our model. The expression for β is determined in terms of the ratio χ, which provides a dimensionless number that reflects the relative scales of volume and mass between entities at the Bohr (atomic level) and the molecular scales. This latter parameter quantifies the relative influence of quantum effects versus classical dynamics in a given scattering process.

Distortions in Classical Mechanics as a Consequence of Euclidean Geometry Utilization

We live on a huge sphere. When the sum of interior angles in a triangle is greater than [Formula: see text] and each point has a different local vertical, we must use spherical geometry. Euclidean and non-Euclidean geometries are non-equivalent systems, with their own premises and completely different foundations. The use of any logic and tool from orthogonal into non-orthogonal realities (and vice versa), leads to big errors. Newtonian concepts are treated as absolutes in classical mechanics. Content analysis shows that even recent physics publications have inadmissible distortions in the description of natural phenomena in the domain of classical mechanics, inherited through the utilization of the Euclidean model. The whole objective reality has been presented using the tools of Euclidean geometry. When we use the tools of spherical geometry to examine the same phenomena, we get very different findings. The Law of conservation of energy appears as the most efficient tool for the evaluation of these significantly different findings. It confirms the validity of the new discoveries presented in this paper and gives legitimacy to the whole project! Classical mechanics becomes more consistent with the conservation laws of Physics, and the subject’s coherence is lifted to a significantly higher level.

General Three-Body Problem in Conformal-Euclidean Space: New Properties of a Low-Dimensional Dynamical System

Despite the huge number of studies of the three-body problem in physics and mathematics, the study of this problem remains relevant due to both its wide practical application and taking into account its fundamental importance for the theory of dynamical systems. In addition, one often has to answer the cognitive question: is irreversibility fundamental for the description of the classical world? To answer this question, we considered a reference classical dynamical system, the general three-body problem, formulating it in conformal Euclidean space and rigorously proving its equivalence to the Newtonian three-body problem. It has been proven that a curved configuration space with a local coordinate system reveals new hidden symmetries of the internal motion of a dynamical system, which makes it possible to reduce the problem to a sixth-order system instead of the eighth order. An important consequence of the developed representation is that the chronologizing parameter of the motion of a system of bodies, which we call internal time, differs significantly from ordinary time in its properties. In particular, it more accurately describes the irreversible nature of multichannel scattering in a three-body system and other chaotic properties of a dynamical system. The paper derives an equation describing the evolution of the flow of geodesic trajectories, with the help of which the entropy of the system is constructed. New criteria for assessing the complexity of a low-dimensional dynamical system and the dimension of stochastic fractal structures arising in three-dimensional space are obtained. An effective mathematical algorithm is developed for the numerical simulation of the general three-body problem, which is traditionally a difficult-to-solve system of stiff ordinary differential equations.

The Concept of Weight as Reflecting the Epistemological Changes in Physics

AbstractThe goal of this study was to elicit and juxtapose the account of the concept of weight in history vis a vis physics education. The results reveal the problem of consistency in the currently employed teaching materials. The weight concept is very old and remains ubiquitous in science. Its history reflects the maturation of scientific methodology. The latter implied three periods of its development: old, classical, and modern. The “old” weight designated heaviness, or gravity, of bodies and the quantity of matter, both measured through weighing by balance. The “old” weight served as the basis for trade and technology. “Old” weight split in the scientific revolution of the seventeenth century into mass and gravitational force that explained the weight of massive objects—weight was identified with gravitational force. The third period followed the scientific revolution of the twentieth century. Classical Mechanics adopted the equivalence principle and included the accelerated observers. This implied redefinition of weight by the operational definition as the result of weighing. Thus, weight was distinguished from the gravitational force. All three periods reflect the change of physics methodology. In education, physics textbooks are currently divided between the contradictory accounts of the second and third periods of weight history. The weight concept is often confused by students who show numerous related misconceptions. Facing this complexity, we argue for using weight teaching as a tool for promoting the modern perspective of knowledge construction in physics, its epistemology, that is, revealing the nature of science, the need for a reliable operational definition alongside a theoretical one, to the students. The teaching in accordance with the discipline-culture paradigm emphasizes the discursive nature of science, reveals the conceptual dialogue, and suggests its presentation in science/physics classes.

Correlations and signaling in the Schrödinger–Newton model

Abstract The Schrödinger–Newton (SN) model is a semi-classical theory in which, in addition to mutual attraction, massive quantum particles interact with their own gravitational fields. While there are many studies on the phenomenology of single particles, correlation dynamics in multipartite systems is largely unexplored. Here, we show that the SN interactions preserve the product form of the initial state of a many-body system, yet on average agreeing with classical mechanics of continuous mass distributions. This leads to a simple test of the model, based on verifying bipartite gravitational evolution towards non-product states. We show using standard quantum mechanics that, with currently accessible single-particle parameters, two masses released from harmonic traps get correlated well before any observable entanglement is accumulated. Therefore, the SN model can be tested with setups aimed at observation of gravitational entanglement with significantly relaxed requirements on coherence time. We also present a mixed-state extension of the model that avoids superluminal signaling.

Proposal of a quantum version of active particles via a nonunitary quantum walk.

The main aim of the present paper is to define an active particle in a quantum framework as a minimal model of quantum active matter and investigate the differences and similarities of quantum and classical active matter. Although the field of active matter has been expanding, most research has been conducted on classical systems. Here, we propose a truly deterministic quantum active-particle model with a nonunitary quantum walk as the minimal model of quantum active matter. We aim to reproduce results obtained previously with classical active Brownian particles; that is, a Brownian particle, with finite energy take-up, becomes active and climbs up a potential wall. We realize such a system with nonunitary quantum walks. We introduce new internal states, the ground state and the excited state , and a new nonunitary operator N(g) for an asymmetric transition between and . The non-Hermiticity parameter promotes the transition to the excited state; hence, the particle takes up energy from the environment. For our quantum active particle, we successfully observe that the movement of the quantum walker becomes more active in a nontrivial manner as we increase the non-Hermiticity parameter , which is similar to the classical active Brownian particle. We also observe three unique features of quantum walks, namely, ballistic propagation of peaks in one dimension, the walker staying on the constant energy plane in two dimensions, and oscillations originating from the resonant transition between the ground state and the excited state both in one and two dimensions.

Effective potential approach to study hydrodynamics and particle dynamics in Kerr geometry

In this paper, we derive the exact form of effective potential in Kerr geometry from the general relativistic radial momentum equation. The effective potential accurately mimics the general relativistic features, over the entire range of the spin parameter [Formula: see text]. We obtain the exact expression of the rate of dragging of inertial frames that can be used to study the relativistic precession of twisted accretion disks that are formed when the disk outskirts are tilted relative to the equatorial plane of the black hole. We then present an effective potential that provides a simplistic approach to study particle dynamics using physical concepts analogous to the Newtonian physics. We compare the equatorial as well as off-equatorial particle trajectories obtained using our potential with the general relativistic solutions. We find that our approach can capture the salient features of Kerr geometry and is applicable to studies of accretion processes around Kerr black holes.

Bosonic Mpemba effect with non-classical states of light

The Mpemba effect (ME) refers to the surprising observation where, under certain conditions, a far-from-equilibrium state can relax toward equilibrium faster than a state closer to equilibrium. A paradigmatic example is provided by the curious fact that hot water can sometimes freeze faster than cold water. The ME has intrigued scientists for a long time and has been predicted and observed in a variety of classical and quantum systems. Recently, the search for Mpemba-like effects of purely quantum nature has raised a major interest. Here, we predict the emergence of ME in the quantum optics context exploiting non-classical states of light. By analyzing the decay dynamics of photon fields in a leaky optical resonator or waveguide, it is demonstrated that bosonic ME emerges in the context of the quantum nature of light. In particular, the relaxation dynamics are strongly influenced by the photon statistics of the initially trapped light field. The ME is observed when comparing the decay dynamics of classical light fields (coherent states) with certain non-classical states, such as Fock states, squeezed states, and Schrödinger cat states.

Dynamic hierarchical intrusion detection system for internet of vehicle on edge computing platform

AbstractIn recent days, the Internet of Vehicles (IoV) and its network of connected automobiles have revealed several new security risks. Classical intrusion detection systems face challenges in identifying intrusions due to the growing number of vehicles, the dynamic nature of IoV, and limited resources. A hierarchical clustering method allows dividing the IoV network into clusters. The elements that determine the outcome are the geographical proximity and the traffic density. It is called the Dynamic Hierarchical Intrusion Detection Framework (DHIDF) for the IoV. To protect infrastructure and passengers, an IoV‐specific DHIDF using edge computing has been proposed. Because of this, anomaly detection and localised assessment of danger will become less required. The application of DHIDF on a large scale inside the ecosystem of IoV is not entirely out of the question. The term encompasses several subfields, including intelligent transportation networks (ITNs), smart city infrastructure, fleet management, transportation, and autonomous vehicle systems. The efficacy of DHIDF is assessed through simulations that replicate current and potential future threats, including those related to the Internet of Things. Analysis of key performance parameters, including response time, detection accuracy, asset utilization, and scalability, has been conducted to assess the system's feasibility and durability.

Cavity induced modulation of intramolecular vibrational energy flow pathways.

Recent experiments in polariton chemistry indicate that reaction rates can be significantly enhanced or suppressed inside an optical cavity. One possible explanation for the rate modulation involves the cavity mode altering the intramolecular vibrational energy redistribution (IVR) pathways by coupling to specific molecular vibrations in the vibrational strong coupling (VSC) regime. However, the mechanism for such a cavity-mediated modulation of IVR is yet to be understood. In a recent study, Ahn et al. [Science 380, 1165 (2023)] observed that the rate of alcoholysis of phenyl isocyanate (PHI) is considerably suppressed when the cavity mode is tuned to be resonant with the isocyanate (NCO) stretching mode of PHI. Here, we analyze the quantum and classical IVR dynamics of a model effective Hamiltonian for PHI involving the high-frequency NCO-stretch mode and two of the key low-frequency phenyl ring modes. We compute various indicators of the extent of IVR in the cavity-molecule system and show that tuning the cavity frequency to the NCO-stretching mode strongly perturbs the cavity-free IVR pathways. Subsequent IVR dynamics involving the cavity and the molecular anharmonic resonances lead to efficient scrambling of an initial NCO-stretching overtone state over the molecular quantum number space. We also show that the hybrid light-matter states of the effective Hamiltonian undergo a localization-delocalization transition in the VSC regime.

Centrifugal Compressor Surge in Innovative Heat Pump: Fluid Dynamic and Vibrational Analysis

Abstract In the current energy scenario, it is necessary to reduce fossil fuel consumption to achieve the far-sighted and stringent decarbonization goals. To date, heat is mainly produced through fossil fuels. Alternatively, electrically driven heat pumps can exploit renewable power to recover environmental and waste heat, offering energy efficient and environmentally friendly heating and cooling for applications ranging from domestic and commercial buildings to process industries. For this reason, they are expected to play a primary role in complementing or displacing natural gas boilers in the residential and industrial sectors in the near future. Centrifugal compressors are already used as prime movers of the working fluid in heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low noise. However, they are subject to instabilities such as surge and stall like any other dynamic compressor and these phenomena develop quite differently than in classic open-loop systems such as gas turbines. In fact, such peculiarity is mainly due to the closed-loop configuration with real gases in two-phase conditions, occurring in typical heat pump cycles. In addition, heat exchangers also contribute to make these phenomena different from what is commonly studied. Compressor surge in closed-loop heat pump systems has received lower attention than other applications by the engineering community, lacking dedicated experimental characterization, and clear exposition of the phenomenon. The aim of this paper is to experimentally investigate the behavior of a centrifugal compressor installed into an innovative close loop heat pump system under stable and unstable conditions from both vibrational and fluid-dynamic points of view. The impact of the main process parameters on the evolution of the instability is shown, highlighting how surge cycles change by varying system operating conditions. The energy contents of surge cycles and pressure fluctuations are highlighted, using data postprocessing techniques such as fast Fourier transform and phase locked average. The vibro-acoustic analysis enrich the comprehension of the phenomena. The experimental results shown in this paper can be a basis for the future development of validated mathematical models of closed-loop heat pumps systems equipped with dynamic compressors operating under stable and unstable operating conditions.

Miniaturized on-chip optical differentiator based on 2F-structured metasurfaces.

Analog optical computing based on Fourier optics has attracted ever-growing attention, offering unprecedented low power consumption and high parallelism computation at the speed of light. Typically, classical optical 4F systems have been widely employed as one of the most common approaches for analog optical computing. However, most existing schemes replicate the original architecture relying on two Fourier transforms and one spatial-frequency filtering, resulting in bulky size and complex structure. Here, we propose a novel, to the best of our knowledge, on-chip 2F structure that achieves ultra-miniaturized optical analog computing. Taking advantage of the exceptional design flexibility of metasurfaces, we reduce the optical path length through a combination of phase compensation and complex amplitude modulation, thereby significantly simplifying the system structure without sacrificing accuracy compared to the traditional 4F system. As a proof-of-concept demonstration, we design and fabricate an on-chip optical differentiator on a silicon-on-insulator platform, achieving 84.01% and 79.81% differentiation accuracy in simulation and experiment, respectively.

Morse Predecomposition of an Invariant Set

Motivated by the study of recurrent orbits and dynamics within a Morse set of a Morse decomposition we introduce the concept of Morse predecomposition of an isolated invariant set within the setting of both combinatorial and classical dynamical systems. While Morse decomposition summarizes solely the gradient part of a dynamical system, the developed generalization extends to the recurrent component as well. In particular, a chain recurrent set, which is indecomposable in terms of Morse decomposition, can be represented more finely in the Morse predecomposition framework. This generalization is achieved by forgoing the poset structure inherent to Morse decomposition and relaxing the notion of connection between Morse sets (elements of Morse decomposition) in favor of what we term ’links’. We prove that a Morse decomposition is a special case of Morse predecomposition indexed by a poset. Additionally, we show how a Morse predecomposition may be condensed back to retrieve a Morse decomposition.

Lissajous dynamics of a quantum particle in a tilted two-dimensional discrete lattice

The quantum dynamics of a single particle in a discrete two-dimensional tilted lattice is analyzed from the perspective of the classical-quantum correspondence. Utilizing the fact that tilting the lattice results in oscillatory dynamics, we show how the parameters of the lattice and the initial state of the particle can be tuned so that during evolution the probability distribution does not change its shape, while its center follows the trajectory known in classical mechanics as Lissajous curves.

Full Forward Kinematics of Lower-Mobility Planar Parallel Continuum Robots

In rigid lower-mobility parallel manipulators the motion of the end-effector is partially constrained due to a combination of passive kinematic pairs and rigid components. Translational mechanisms, such as the Delta manipulator, are the most common ones among this type of mechanisms. When flexible elements are introduced, as in Parallel Continuum Manipulators, the constraint is no longer rigid, and new challenges arise in performing certain motions depending on the degree of compliance. Mobility analysis shifts from being purely a geometric issue to one that heavily relies on force distribution within the mechanism. Simply converting classical lower-mobility rigid parallel mechanisms into Parallel Continuum Mechanisms may yield unexpected outcomes. This work, making use of a planar parallel continuum Delta manipulator, on the one hand, presents two different approaches to solve the Forward Kinematics of planar continuum manipulators, and, on the other hand, explores some challenges and issues in assessing the resultant workspace for different design alternatives of this kind of flexible manipulators.