State Parameter Research Articles

Research on a Path Tracking Control Strategy for Autonomous Vehicles Based on State Parameter Identification

With the rapid development of autonomous driving technology, estimating and controlling key vehicle state parameters under complex road conditions have become critical challenges. This study combines Unscented Kalman Filtering (UKF) and Sliding Mode Control (SMC) methods to propose an integrated control model for achieving more efficient control. First, a three-degrees-of-freedom vehicle dynamics model based on the Dugoff tire model is constructed to accurately estimate key vehicle state parameters. Next, UKF is used to estimate road friction coefficients and key vehicle state parameters, and its performance is compared with Extended Kalman Filtering (EKF) under various conditions. The results show the superiority of UKF in identifying road friction coefficients. Based on SMC theory, a sliding surface is designed, and the functional relationship between state variables and control variables is derived to establish the corresponding control model. Joint simulations using Carsim and Simulink under different conditions validate the real-time performance and effectiveness of the designed UKF-SMC integrated control strategy in the presence of external disturbances and system uncertainties. Simulation results indicate that this strategy effectively enhances the overall performance and safety of autonomous vehicles, providing an accurate real-time solution capable of handling complex and variable road conditions. The proposed UKF-SMC integrated control strategy not only proves its theoretical superiority but also demonstrates promising practical applications in simulation experiments. This study provides reliable technical support for the development of autonomous driving technology under complex road conditions.

Shrinkage separation prediction of concrete-filled steel tube arch bridge: A coupling model concerning multiple factors

The shrinkage separation is one of the key factors restricting the development of concrete-filled steel tube (CFST) arch bridge. In this paper, its mechanism and evaluation method concerning multiple factors, including structure, environment, material and construction were investigated. Firstly, the hydration process of in-tube concrete was simulated using the hydration degree as a basic state parameter. Then with the consideration of energy and mass conservation, as well as the moisture and heat transmission effects, the temperature and relative humidity fields, early-age mechanical properties, basic creep, and total deformation of in-tube concrete were further calculated. On the basis, in accordance with the stress criterion and displacement coordination, a multi-field (hydro-thermo-hygro-constraint) coupling model was finally established, taking the ratio of normal stress to bonding strength at the steel-concrete interface as the shrinkage separation risk index. The simulation results obtained from the model were in good agreements with the full-scale CFST model test.

Hawking–Page transition and the dual relations of anti-de Sitter black holes surrounded by dark energy in general dimensions

Recently, a dual relation T 0(n + 1) = T HP (n) between the minimum temperature (T 0(n + 1)) black hole phase and the Hawking–Page transition (T HP (n)) black hole phase in two successive dimensions was introduced by Wei et al (2020 Phys. Rev. D 102 10411); this was reminiscent of the anti-de Sitter/conformal field theory (AdS/CFT) correspondence, as the Hawking–Page transition temperature could be treated as the temperature of the dual physical quantity on the boundary and the latter corresponds to that in the bulk. In this paper, we discuss the Hawking–Page transition and the dual relations in AdS black holes surrounded by dark energy in general dimensions. Our findings reveal the occurrence of the Hawking–Page transition between the thermal AdS radiation and thermodynamically stable large AdS black holes, in both the spacetime surrounded by phantom dark energy and the spacetime surrounded by quintessence dark energy. We discuss the effects of the phantom dark energy and quintessence dark energy on the Hawking–Page transition temperature. For the dual relation in particular, it works well for the case of an AdS black holes surrounded by phantom dark energy. For the case of an AdS black hole surrounded by quintessence dark energy, the dual relation should be modified under an open assumption that the state parameter and the density parameter of the quintessence dark energy depend on the dimensions of the spacetime.

Barrow’s holographic dark energy model in axially symmetric spacetime

The Barrow’s Holographic Dark Energy (BHDE) Model is proposed in an axially symmetric anisotropic spacetime which is employing Hubble horizon as an infrared cutoff (IR cutoff). The transition of the universe from a matter dominated era to a dark energy dominated era is investigated in this model. Furthermore, the Equation of State (EoS) parameter explains how the universe evolves with non-extensive term or Barrow parameter [Formula: see text] for both phase (i) phantom era ([Formula: see text]) and (ii) quintessence era ([Formula: see text]). In order to reconcile the dark energy, the reconstruction of scalar field potential is considered. Some of the physical properties of the model are also described.

Reynolds number effect on the Lagrangian evolution of hairpin vortices in turbulent channel flow

The evolution and generation of hairpins are studied in a Lagrangian perspective in turbulent channel flows. Direct numerical simulation database of turbulent channel flow at friction Reynolds numbers R e τ = 590, 390, and 180 is employed to perform tracking and interpolation algorithms of fluid particles on hairpins. These particles are carefully selected using a vortex line identification technique developed to extract the hairpin's core line. Interesting results are observed regarding the Reynolds number impact on the evolution and regeneration of hairpins. As the Reynolds number increases, the head and the vortical tongues are compressed and aligned in the main flow direction and the hairpin structures tend to orient more horizontally. The deformation shape of hairpins using the strain state parameter, which is correlated with the dissipation rate, is analysed using the probability density function. Most phenomena related to the generation of secondary hairpins, including the existence of vortical tongues, occur in the range 35 ≲ y + ≲ 50 . The results reveal that the Lagrangian perspective is a proper technique to address the extension of vortical tongues, generation of the secondary hairpin, and stretch of hairpin legs.

Motion frequency exploration based force separator for surgical robots interacting with a beating heart

Robotics-assisted beating heart surgery holds significant potential for application as it can reduce the risks of infection. A crucial requirement in beating heart surgery is the real-time and accurate feedback of the interaction forces between the end-effector and cardiac tissues. The primary challenge is developing a sensorless scheme to separate the beating motion-coupled force (MCF) from the robot dynamic state-coupled force (SCF). Acquiring the accurate beating frequency before surgery is often challenging, which limits the use of conventional force observers. To address these difficulties, this article proposes an online force separation scheme. Specifically, we establish a robot-cardiac tissue coupled model that considers robot dynamics, force generation mechanisms, and heart motion characteristics. Based on this, we design a motion frequency exploration-based force separator (MSEFS), utilizing an online expectation–maximization procedure for the joint estimation of the motion state and frequency parameter. Simulation results demonstrate that the proposed scheme surpasses existing force estimation schemes in performance due to its capability for motion frequency exploration.

Optimization of the MSMGWB models used to predict remote infrared signals of jet engine in various spectral intervals

Further improvements are reported for an optimization method that was used in previous work to determine the best combination of Gauss quadrature schemes and wavenumber subinterval division results for the multi-scale multi-group wide-band k-distribution (MSMGWB) model, which is used in calculation of remote infrared signals of hot combustion gases from hydrocarbon fuels and gray walls in the 3–5 µm spectral interval. In addition, the application range of the MSMGWB model was extended to the 8–14 µm, 7.7–9.7 µm, 3.7–4.8 µm, and 2–2.5 µm spectral intervals. Compared with previous works, the new optimization procedure considered a broader range of thermodynamic state parameter combinations of the combustion gas and the atmosphere. The optimization effect was evaluated further via prediction of remote sensing thermal images in various spectral intervals for solid structures and hot jet of an aero-engine’s supersonic exhaust system. Furthermore, an optimized MSMGWB model that considers the spectral response characteristics of infrared detectors has been established and evaluated.

Equivalent state parameter dependency on gradation properties of medium sand-fines mixtures

Multiple studies confirm that determining the liquefaction resistance of sand-silt mixtures is more intricate compared to pure sand. Furthermore, it has been observed that the global void ratio fails to accurately predict the behavior of silty sand soils due to the fines particles, which can occupy voids between sand grains without significantly contributing to resisting external forces. To address this, a new parameter called equivalent void ratio (e*) has been proposed to better forecast the response of medium sand-fines mixtures. To investigate this further, a series of compression triaxial tests were conducted on mixtures comprising medium sand with low plastic fines. These mixtures were prepared in the laboratory with an initial relative density and subjected to varying confining pressures. The test results were utilized to assess the undrained shear strength of medium sand-silt mixtures based on the equivalent void ratio (e*) and to establish the equivalent granular steady-state line, which serves as a reference for calculating the equivalent state parameter (ψ*). Analysis of the obtained data suggests a correlation between the equivalent void ratio (e*) and the equivalent state parameter (ψ*) with the grading characteristics (such as D10, D50, Cu, D10R, D50R, and CUR) of the medium silty sand.

Thermodynamic features of AdS black holes within the rastall gravity and perfect fluid matter framework

In this study, we analyzed the impact of a perfect fluid on the phase transition of Anti-de Sitter (AdS) black holes within the Rastall gravitational background. Compared to similar studies in the literature, the findings of this work are highlighted by the determination of analytical expressions for critical points for charged and Kerr-Newman AdS black holes using approximated formulas for the horizon radius. An accurate analysis of these new analytical expressions allowed us to discover a new viable condition that relates the Rastall parameter κ λ to the equation of state parameter ω, expressed as: κλ=ω1+ω . Thanks to this new condition, we were able to reproduce all the analytical expressions of critical points calculated within the framework of Einsteinâs general relativity for two cases: a charged AdS black hole and a rotating AdS black hole. These findings suggest that Rastall gravity, considering this new condition, could serve as an alternative theory of gravitation to general relativity. The approximate expression of the horizon radius also enabled the exploration of the distinctiveness of fractional-order phase transitions in these AdS black holes. Furthermore, we calculated the critical exponents, offering insights into the behavior of crucial thermodynamic quantities near the inflection point. Examining how a perfect fluid influences phase transition reveals various critical behaviors, demonstrating that the variation in the phase transition depends on the intensity of the perfect fluid. Notably, this variation is portrayed by a linearly increasing trajectory with the escalation of this intensity.

Restoring cosmological concordance with axion-like early dark energy and dark matter characterized by a constant equation of state?

The Hubble tension persists as a challenge in cosmology. Even early dark energy (EDE) models, initially considered the most promising for alleviating the Hubble tension, fall short of addressing the issue without exacerbating other tensions, such as the S 8 tension. Considering that a negative dark matter (DM) equation of state (EoS) parameter is conducive to reduce the value of the σ 8 parameter, we extend the axion-like EDE model in this paper by replacing the cold dark matter (CDM) with DM characterized by a constant EoS w dm (referred to as WDM hereafter). We then impose constraints on this axion-like EDE extension model, along with three other models: the axion-like EDE model, ΛWDM, and ΛCDM. These constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background, baryon acoustic oscillations, and the Pantheon compilation, as well as a prior on H 0 (i.e. H 0 = 73.04 ± 1.04, based on the latest local measurement by Riess et al) and a Gaussianized prior on S 8 (i.e. S 8 = 0.766 ± 0.017, determined through the joint analysis of KID1000+BOSS+2dLenS). We find that although the new model maintains the ability to alleviate the Hubble tension to ∼1.4σ, it still exacerbates the S 8 tension to a level similar to that of the axion-like EDE model.

A novel framework for deriving water retention behavior of multimodal unsaturated soils based on pore size distribution data

AbstractThe soil water retention curve (SWRC) strongly influences the hydro-mechanical properties of unsaturated soils. It plays a decisive role in geotechnical and geo-environmental applications in the vadose zone. This paper advances a novel framework to derive the water retention behavior of multimodal deformable soils based on the pore size distribution (PSD) measurements. The multiple effects of suction on the soil pore structure and total volume during SWRC tests are considered. The complete picture of soil microstructure is quantitatively described by the void ratio (for the pore volume) and a newly defined microstructural state parameter (for pore size distribution) from a probabilistic multimodal PSD model. Assuming a reversible microstructure evolution, a unique PSD surface for wetting and drying links the SWRC and PSD curves in the pore radius-suction-probability space. A closed-form water retention expression is obtained, facilitating the model's implementation in particle applications. The model is validated using the water retention data of four different soil types, showing a strong consistency between the measurement and the reproduced curve. The proposed method provides new insights into the pore structure evolution, the water retention behavior and the relationship between them for multimodal deformable soils.

Quantum nonlocality phenomena in scalar and Dirac fields near a Schwarzschild black hole

In this work, we explore the impact of the Hawking effect on quantum nonlocality, specifically the maximum violation of the Bell-CHSH inequality, for both scalar and Dirac fields within Schwarzschild spacetime. We reveal the nuanced behavior of the Bell-CHSH inequality as the Hawking temperature (HT) varies. For scalar fields, we observe distinct degradation patterns in the Bell-CHSH inequality, influenced by the state parameter α and its normalized counterpart 1−α2 . In contrast, Dirac fields exhibit two distinct degradation trajectories, each converging to different nonzero minimum values as HT approaches infinity T→∞ , however, this does not apply to the maximally entangled state. Remarkably, the maximum violation of Bell-CHSH inequality becomes zero for scalar fields at infinite HT, while it stabilizes at a finite nonzero value for Dirac fields. Additionally, the quantum nonlocality robustness of the Dirac fields is stronger than that of the scalar fields. Therefore, this study enhances our understanding of the dynamic characteristics of nonlocality within scalar and Dirac fields near a Schwarzschild black hole.

Cosmology in non-coincident gauge formulation of f(Q,C) gravity theory

This paper is an investigation of dark energy cosmological models in non-coincident gauge formulation of non-metricity gravity with boundary term. We have considered an arbitrary function [Formula: see text], where [Formula: see text] is the non-metricity scalar, [Formula: see text] is the boundary term derived by [Formula: see text], and [Formula: see text] are the model parameters, to obtain the modified field equations from action. We have parameterized the Hubble function as [Formula: see text] with [Formula: see text] are arbitrary constants and [Formula: see text] is the scale-factor depending upon cosmic time. We have compared this Hubble function with [Formula: see text] datasets and obtained best fit values of model parameters using likelihood analysis. Using these best fit values of model parameters, we have done our result analysis and discussion with cosmological parameters viz effective equation of state parameter, energy density, energy conditions, deceleration parameter, om diagnostic analysis and age of the universe. We have found a transit phase universe model with effective EoS parameter [Formula: see text] over redshift [Formula: see text].

Cosmographic analysis of the dynamics of universe in higher dimensional compactified space with Tachyonic field

In this work, the considered model is contained in higher dimensional compactified space in the form of M4 × M6, where M6 is compact inner space. Since, for a higher dimensional cosmological model, Tachyon matter is an automatic and fantastic choice, we have supposed that the scalar field is driven by Tachyon together with the higher dimensional cosmological constant [Formula: see text]. Our observation is that the theory provides a good solution for the cosmological scale factor of the present universe. Here, it is important that the forms of the tachyonic field ϕ and potential V are simple trigonometric hyperbolic functions. We study the cosmographical parameters like equation of state parameter, statefinder parameters, jerk, snap, and lerk parameters. The graphical representations of cosmological parameters show the overall evolution of the universe under a tachyonic field in a higher dimensional model. The classical stability of the model due to small perturbations both for dark energy and metric are examined by the study of the square speed of sound and by the linear perturbation method. We also analyzed the model in ω−ω′ and r− s cosmological plane.

The role of vectors in reheating

We explore various aspects concerning the role of vector bosons during the reheating process. Generally, reheating occurs during the period of oscillations of the inflaton condensate and the evolution of the radiation bath depends on the inflaton equation of state. For oscillations about a quadratic minimum, the equation of state parameter, w = p/ρ = 0, and the evolution of the temperature, T(a) with respect to the scale factor is independent of the spin of the inflaton decay products. However, for cases when w > 0, there is a dependence on the spin, and here we consider the evolution when the inflaton decays or scatters to vector bosons. We also investigate the gravitational production of vector bosons as potential dark matter candidates. Gravitational production predominantly occurs through the longitudinal mode. We compare these results to the gravitational production of scalars.

Insights on Granda–Oliveros holographic dark energy: possibility of negative dark energy at z≳2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z\\gtrsim 2$$\\end{document}

In holographic dark energy (HDE) models, infrared cut-offs with derivatives of the Hubble parameter, such as the Granda–Oliveros cut-off, offer a coherent explanation for late-time acceleration while ensuring causal consistency. We show that such HDE will inevitably mimic the dominant energy forms unless we forcefully calibrate the free parameters. This feature reveals the dependency between the model’s ability to explain the late-time acceleration and the integration constant, highlighting that one cannot arbitrarily set this constant to zero. We see that the origins of HDE and the Friedmann equations from the first law of horizon thermodynamics offer a natural explanation for this behaviour. Thus, the holographic principle naturally extends to all energy components, diverging from the prevalent notion in HDE models. The model also allows dark energy to transit from an early negative energy to a present positive value, with a singular dark energy equation of state parameter, which can relax the tension in the BAO Lyman-α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} observations. Furthermore, we present observational constraints utilizing Pantheon+,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+,$$\\end{document} OHD, CMB Shift parameter, QSO and BAO data, indicating the presence of early negative energy as an unavoidable consequence. Upon using the SH0ES prior, we see that the model accounts for the Hubble parameter at the cost of affecting the matter density while simultaneously relaxing the tensions in BAO Lyman-α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} observations and the age estimations. This study also underscores notable features stemming from the comprehensive utilization of the covariance matrix within cosmic chronometers, BAO and CMB distance prior and clarifies the implications of negative dark energy density derived from the high redshift Pantheon+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} sample. Additionally, we provide a brief overview of the theoretical framework surrounding linear perturbation within the wGOHDE model.

Impact of Tolman–Kuchowicz potentials on Gauss–Bonnet gravity and isotropic stellar structures

In this manuscript, we study the behavior of charged isotropic compact stellar objects within the framework of modified f(G) theory of gravity by considering the Tolman–Kuchowicz spacetime. We use some matching condition of spherically symmetric space–time with Bardeen’s model as an exterior geometry and examine the physical behavior of stellar structures. In the current analysis, we discuss the energy conditions to check the viability of our model. Many physical aspects have been examined, such as energy density, pressure evolution, equation of state parameter, and causality condition. Furthermore, an equilibrium condition can be visualized through the modified Tolman–Oppenheimer–Volkov equation. Further, we study mass–radius function, compactness and redshift function, which are some essential features of charged compact star model. It is worthwhile to mention here for the current study that our stellar structure in the background of Bardeen’s model is more viable and stable.

An information field theory approach to Bayesian state and parameter estimation in dynamical systems

Dynamical system state estimation and parameter calibration problems are ubiquitous across science and engineering. Bayesian approaches to the problem are the gold standard as they allow for the quantification of uncertainties and enable the seamless fusion of different experimental modalities. When the dynamics are discrete and stochastic, one may employ powerful techniques such as Kalman, particle, or variational filters. Practitioners commonly apply these methods to continuous-time, deterministic dynamical systems after discretizing the dynamics and introducing fictitious transition probabilities. However, approaches based on time-discretization suffer from the curse of dimensionality since the number of random variables grows linearly with the number of time-steps. Furthermore, the introduction of fictitious transition probabilities is an unsatisfactory solution because it increases the number of model parameters and may lead to inference bias. To address these drawbacks, the objective of this paper is to develop a scalable Bayesian approach to state and parameter estimation suitable for continuous-time, deterministic dynamical systems. Our methodology builds upon information field theory. Specifically, we parameterize the dynamical system state path using a linear basis. Then, we construct a physics-informed prior probability measure for the coefficients of the linear basis such that functions that satisfy the physics are more likely. This prior allows us to quantify model form errors. We connect the system's response to observations through a probabilistic model of the measurement process. The joint posterior over the system responses and all parameters is given by Bayes' rule. To approximate the intractable posterior, we develop a stochastic variational inference algorithm. In summary, the developed methodology offers a powerful framework for Bayesian estimation in dynamical systems.

Analysis of cosmic evolution admitting Garcia-Salcedo ghost and generalized ghost dark energy models

This study aims to explore the Garcia-Salcedo ghost dark energy and generalized ghost dark energy models in the context of f(R,T2) theory, where R is the Ricci scalar and T2 is the self-contraction of stress–energy tensor. We investigate the non-interacting case only corresponding to flat Friedmann–Robertson–Walker universe. We reconstruct the corresponding f(R,T2) gravity models using the considered dark energy models by taking two particular models of this gravity. The stability analysis is performed for all the cases. The behavior of the equation of state parameter is also checked. It is found that some of the reconstructed f(R,T2) models successfully describe both the phantom and quintessence epochs of the universe, which support the current cosmic accelerated expansion. This exploration reveals the intricate connections between dark energy models and modified gravitational theory, providing significant understanding into the dynamics of the cosmos on a large scale.

Cosmology of Barrow holographic QCD ghost dark energy and a look into the thermodynamics

The present study endeavours to study the cosmology of QCD ghost dark energy based on Barrow holographic fluid, a particular example of Nojiri-Odintsov holographic dark energy (2006, General Relativity and Gravitation, 38, 1285–1304); (2017, The European Physical Journal C, 77, 1–8). The Hubble parameter is reconstructed and according the equation of state parameter is reconstructed for the Barrow holographic QCD ghost dark energy. It is observed that the effective equation of state parameter has a transition from quintessence to phantom and for the current universe the equation of state parameter is very close to −1. The deceleration parameter is computed based on the reconstructed Hubble parameter and it is observed that the model can have a transition from decelerated to accelerated universe. The statefinder trajectories are plotted and an interpolation between dust and ΛCDM phases is observed. Finally, the thermodynamics is studied considering apparent horizon as the enveloping horizon of the Universe.