Deceleration Parameter Research Articles

Modified power law cosmology: theoretical scenarios and observational constraints

Abstract This research paper examines a cosmological model in flat space-time via $f(R,G)$ gravity where $R$ and $G$ are respectively the Ricci scalar and Gauss-Bonnet invariant. Our model assumes that $f(R,G)$ is an exponential function of $G$ combined with a linear combination of $R$. We scrutinize the observational limitations under a power law cosmology that relies on two parameters - $H_0$, the Hubble constant, and $q$, the deceleration parameter, utilizing the 57-point $H(z)$ data, 8-point BAO data, 1048-point Pantheon data, joint data of $H(z)$ + Pantheon, and joint data of $H(z)$ + BAO + Pantheon. The outcomes for $H_0$ and $q$ are realistic within observational ranges. We have also addressed Energy Conditions, $Om(z)$ analysis and cosmographical parameters like Jerk, Lerk and Snap. Our estimate of $H_0$ is remarkably consistent with various recent Planck Collaboration studies that utilize the $\Lambda$CDM model. According to our study, the power law cosmology within the context of $f(R,G)$ gravity provides the most comprehensive explanation for the important aspects of cosmic evolution.

Studying the parameters of acceleration of irregularly shaped solid particles by laminar gas flow in the acceleration channel of the slit section

Studying the parameters of acceleration of irregularly shaped solid particles by laminar gas flow in the acceleration channel of the slit section

Stability of f(Q, B) Gravity via Dynamical System Approach: A Comprehensive Bayesian Statistical Analysis

Abstract In this work, we explore the cosmological stability of f(Q, B) gravity using a dynamical system approach, where Q denotes the nonmetricity scalar and B represents the boundary term. We determine the model parameters of f(Q, B) through Bayesian statistical analysis, employing Markov Chain Monte Carlo techniques. This analysis incorporates numerical solutions and observational data from cosmic chronometers, the extended Pantheon+ data set, and baryonic acoustic oscillation measurements. Our findings reveal a stable critical point within the dynamical system of the model, corresponding to the de Sitter phase, which is consistent with current observations of the Universe dominated by dark energy and undergoing late-time accelerated expansion. Additionally, we utilize center manifold theory to examine the stability of this critical point, providing deeper insights into the behavior of the model. The cosmological implications of f(Q, B) gravity indicate a smooth transition in the deceleration parameters from deceleration to the acceleration phase, underscoring the potential of the model to describe the evolution of the Universe. Our results suggests that the f(Q, B) model presents a viable alternative to the standard ΛCDM model, effectively capturing the observed acceleration of the Universe and offering a robust framework for explaining the dynamics of cosmic expansion.

Study on Slipform Paving of Concrete Containing Alkali-Free Accelerators on Roadway Floor.

Aiming at the problems of collapse, deformation, and displacement in the concrete paving of roadway floors, this paper adopts the way of adding alkali-free accelerators to the concrete on both sides, through mechanical analysis, single factor experiment, orthogonal experiment, and polynomial fitting method, and determines the relevant parameters of concrete and accelerators in the sliding form paving of roadway floor from two aspects of paving material and size. The results show that the FSA-AF alkali-free liquid accelerator is more suitable for roadway floor paving than the J85 powder accelerator. When the FSA-AF accelerator dosage reaches 8%, the decreasing trend of initial setting time curve tends to be flat. The deformation resistance of concrete containing accelerator is positively correlated with the dosage of the accelerator. Concrete side pressure is positively correlated with pavement paving height. The FSA-AF accelerator can reduce the compressive strength of concrete; the compressive strength and retention rate of concrete at all ages are the highest when the dosage of FSA-AF is 7%. A water-cement ratio of 0.4 and a 9% dosage of accelerator are the optimal combination to meet the four evaluation indexes. According to the width estimation formula, the width of the side concrete should be set to 14 cm.

Anisotropic Cosmic Expansion Inspired by Some Novel Holographic Dark Energy Models in f(Q)$f(Q)$ Theory

AbstractThe present work discusses the topic of cosmic evolution in an intriguing framework of theory of gravity (with as a non‐metricity (NM) scalar which controls the gravitational interaction) by using some recently proposed holographic dark energy (HDE) models. To achieve this goal, the dynamical equations for locally rotationally symmetric (LRS) Bianchi type‐I (BI) geometry are formulated with matter contents as a mixture of dust and anisotropic fluids. By assuming that the time‐redshift relation follows a Lambert function, the cosmological model is constructed by using Rényi HDE (RHDE), Sharma–Mittal HDE (SMHDE) and Generalized HDE (GHDE) as separate cases where Hubble horizon is taken as an infrared (IR) cutoff. Cosmological characteristics of these models are then examined through graphs of energy densities, skewness parameter , deceleration, and EoS parameters. The evolution of the EoS parameter is also studied, i.e., to discuss the dynamical characteristics of constructed DE models and assess the stability of models via the squared speed of sound parameter. It is found that the plane shows the freezing region for RHDE and GHDE models while the thawing region for the SMHDE case. Also, it is concluded that all constructed models exhibit cosmologically viable and stable behavior.

Non-Parametric Reconstruction of Cosmological Observables Using Gaussian Processes Regression

The current accelerated expansion of the Universe remains one of the most intriguing topics in modern cosmology, driving the search for innovative statistical techniques. Recent advancements in machine learning have significantly enhanced its application across various scientific fields, including physics, and particularly cosmology, where data analysis plays a crucial role in problem-solving. In this work, a non-parametric regression method with Gaussian processes is presented along with several applications to reconstruct some cosmological observables, such as the deceleration parameter and the dark energy equation of state, in order to contribute some information that helps to clarify the behavior of the Universe. It was found that the results are consistent with λCDM and the predicted value of the Hubble parameter at redshift zero is H0=68.798±6.340(1σ)kms−1Mpc−1.

Effects of Newtonian Heating on MHD Jeffrey Hybrid Nanofluid Flow via Porous Medium

In recent years, hybrid nanoparticles have gained significant attention for their ability to enhance thermal conductivity in various fluid systems, making them effective heat transport catalysts. Despite advancements in thermal fluid technology, a gap remains in understanding how hybrid nanoparticles interact within non-Newtonian Jeffrey fluid systems, particularly under complex boundary conditions like Newtonian heating. The present study aims to shed light on the effect of hybrid nanoparticles (alumina and copper) incorporated into a Jeffrey fluid model on flow and heat transport, considering them as heat transport catalyst and subject to Newtonian heating to optimize thermal efficiency. An exponentially accelerated plate is used to induce the fluid flow, taking into account the effects of porosity, MHD, and thermal radiation. The examined fluid exhibits an unsteady one-dimensional flow, formulated by deriving partial differential equations, which are subsequently transformed into ordinary differential equations using suitable non-dimensional variables and the Laplace transformation. This research distinguishes itself by presenting a novel mathematical model for MHD Jeffrey hybrid nanofluid, accounting for porosity and Newtonian heating effects. The inverse of Laplace is used to generate the exact solutions for velocity and temperature profiles, which is not explored in existing literature. Graphical representations are generated using Mathcad, depicting the velocity and temperature distributions. A comparison with prior study from the literature demonstrates strong agreement between our findings and theirs. The findings indicate that the velocity and temperature profiles of the hybrid nanofluid are higher with Newtonian heating than without it. Additionally, an increase in the Grashof number, radiation, acceleration, and porosity parameters also leads to an enhanced velocity profile.

Stability Analysis in Cosmological Models Using Perturbative Methods in f(R,T) Theory

This study examines the stability of cosmological models through perturbation theory, focusing on different formulations of the deceleration parameter (DP). By analysing the eigenvalues of perturbations, we identify key insights into the models’ long-term dynamics and stability. The results reveal the presence of stable and marginally stable modes, indicating how perturbations evolve and dissipate over cosmic time. These findings provide a deeper understanding of cosmic evolution, the formation of large-scale structures, and the behaviour of perturbations, offering significant contributions to cosmological research and theoretical modelling of the Universe.

Generalized ghost pilgrim dark energy fractal cosmology with observational constraint

Abstract In this work, we explore dark energy models, mainly ghost, generalized ghost, and generalized ghost pilgrim dark energy models within the framework of fractal cosmology. To obtain solutions for the field equations, we employed a parameterization of the deceleration parameter, as proposed by R. K. Tiwari. By utilizing Markov Chain Monte Carlo (MCMC) analysis, we impose constraints on the free parameters of the derived solutions. The analysis is based on observational datasets, including 57 data points from the Observational Hubble Data (OHD) and, 1048 points from the $Pantheon$ Supernovae sample. This approach allows us to assess the viability of the dark energy models in describing the current cosmic expansion. According to the effective equation-of-state parameter, the model maintains itself in the quintessence era and ultimately switches into the Einstein-de Sitter model. Furthermore, we investigate the statefinder, jerk, snap, and lerk parameters. The energy conditions of each model satisfy the weak and null energy conditions but violate the strong energy condition. We find that the Om(z) curves for the data samples exhibit a consistently negative slope throughout the entire range.

Unveiling Differences in Seismic Response: Comparative Study of Equivalent Linear and Nonlinear Analyses in the Central Coastal Region of Bengkulu, Indonesia

Seismic response analysis is a key aspect in earthquake geotechnical engineering, as it provides important insights into the behavior of soils when exposedtoseismic forces. This research compares equivalent linear and non-linear models in the central coastal region of Bengkulu, which is known for its complex geology and high seismicity. By evaluating the accuracy and reliability of each model in predicting ground motion amplification,this research aims to provide useful recommendations for seismic design. The research method uses one-dimensional equivalent linear and nonlinear propagation modeling, namely Pressure Dependent Hyperbolic (PDH). The analysis resulted in the parameters of Peak Ground Acceleration (PGA), time history acceleration, spectral response acceleration, and amplification factor. The equivalent linear method consistently produced higher values for peak ground acceleration (PGA), spectral response acceleration, time history acceleration, and amplification factor compared to the nonlinear method. The analysis results show that the equivalent linear PGA values are in the range of 0.32g to 0.63g, while the nonlinear values range from 0.20g to 0.52g. The resulting spectral responses are averaged over the design spectrum within 0.2 s to 0.9 s, which can affect low- to high-ceilinged buildings. The equivalent linear amplification factor has a range of 1.59 to 1.91, while the nonlinear has a range of 0.80 to 1.59. Both methods have their advantages, with the nonlinear approach offering greater accuracy for large seismic events, while the equivalent linear model remains useful for preliminary analysis. Hopefully, these findings will improve the understanding of ground response in coastal areas and provide valuable data for improving infrastructure resilience in earthquake-prone areas around the world.

Flat Friedmann-Lemaitre-Robertson-Walker Cosmological Model with Time-Dependent Cosmological Constant in Brans-Dicke Theory of Gravity

Recently, there has been much interest in investigating outstanding problems of cosmology with modified theories of gravity. The Brans-Dicke theory of gravity is one such theory developed by Brans and Dicke absorbing Mach’s principle into the General Theory of Relativity. In Brans-Dicke theory, gravity couples with a time-dependent scalar field ϕ through a coupling parameter ω. This theory reduces to the General Theory of Relativity if the scalar field ϕ is constant and the coupling parameter ω →∞. In this paper, we consider a flat Friedmann-Lemaıtre-Robertson-Walker (FLRW) universe with a time-dependent cosmological constant in Brans-Dicke theory of gravity. Exact solutions of the field equations are obtained by using a power law relation between the scale factor and the Brans-Dicke scalar field ϕ and by taking the Hubble parameter H to be a hyperbolic function of the cosmic time t. We study the cosmological dynamics of our model by graphically representing some important cosmological parameters such as the deceleration parameter, energy density parameter, equation of state parameter, jerk parameter, snap parameter, lerk parameter etc. The statefinder diagnostic pair of the model is also obtained and the validity of the four energy conditions, viz. the Strong energy condition (SEC), Weak energy condition (WEC), Dominant energy condition (DEC) and Null energy condition (NEC), is examined. We find that the universe corresponding to our model is expanding throughout its evolution and exhibits late time cosmic acceleration, which is in agreement with the current observational data.

FLRW cosmological model in f(R,T) gravity

In this paper, the Friedmann-Lemaitre-Robertson-Walker cosmological models with a perfect fluid in the f(R,T) theory of gravity are re-discussed. There are several ways to generate solutions. One way is to assume a barotropic equation of state. The other is to use a deceleration parameter that varies linearly with time. An existing solution in the literature is reviewed, where solutions are obtained by assuming, in addition to a barotropic equation of state, a linear varying deceleration parameter. It is pointed out such an assumption leads to an over-determination of the solution. Hence, the feasibility of the solutions is a necessary condition to be satisfied. Only one of the assumptions of an equation of state or of a linearly varying deceleration parameter is sufficient to generate solutions. The proper solutions are given and discussed.

A032: Archery Consistency Assessment by Using Inertial Measurement Unit (IMU)

Background/Purpose: Nowadays, the primary methods for evaluating archery techniques, especially the consistency, include force plates, motion capture systems, etc. However, these methods are characterized by their high cost, slow feedback, and lack of portability. Therefore, this study attempted to evaluate the consistency of archery techniques by using Inertial Measurement Unit (IMU) and to verify its feasibility. Method: Six Chinese national archery team archers (3 men, 3 women, elite) participated in the 50m-target field test by using 5 IMUs (Xsens-DOT, Netherlands; 60Hz) and 8-lens Qualisys Motion Capture Equipment (Qualisys-OQUS-700, Sweden; 200Hz). Phases were divided based on Qualisys data, and the Coefficient of Multiple Correlation (CMC) was used to verify the feasibility of inertial sensor in archery. DTW-distance, which was calculated by Dynamic Time Warping (DTW) algorithm, was used to evaluate the consistency of archery. One-way ANOVA was used to compare the DTW-distance in different body parts. The paired T-test was used to compare the DTW-distance between ten-ring groups and non-ten-ring groups. The significance level was set at 0.05. Results: In the comparison of acceleration parameters obtained by Xsens-DOT and Qualisys, it was found that most CMC values were greater than 0.75 (with high similarity), indicating that the acceleration curves obtained by the two systems had high similarity. Moreover, DTW-distance was used to evaluate movement consistency, and it was found that the consistency of lumbar was better than other parts (P < 0.05). Additionally, there was no statistical significance in the movement consistency between the ten-ring group and non-ten-ring group of Chinese top archers (P > 0.05). Conclusion: Compared with motion capture system, IMU and motion capture system have high similarity in acquiring acceleration parameters, which can be used for technical feedback of archery daily training. Additionally, the DTW-distance of lumbar acceleration parameters in the aiming phase can be used as a feedback index for archery techniques. Future research can follow up with larger sample sizes and examine the IMUs' prolonged validity and feasibility in archery.

Modeling and Simulation Method of Coordinated Manipulator Based on Robotic Toolbox and ADAMS

Abstract The coordinator was an important component of the automatic ammunition loading system of large-caliber artillery. In this paper, kinematics and dynamics of a coordination manipulator with five degrees of freedom were carried out. The forward and inverse kinematics analysis and motion trajectory planning of the simplified coordination manipulator under different firing angles were carried out with Robotic Toolbox to obtain the motion parameters of angular displacement, angular velocity and angular acceleration at each driving joint of the manipulator. Using the motion parameters obtained from the trajectory planning, the inverse dynamics of the manipulator was analyzed by ADAMS, and the driving torque curves of each joint were calculated, which provided a reference for the subsequent prototype development and simulation control of the manipulator.

Analysis and Decoupling Study of the Coupling Effects on Projectile Acceleration Parameters

Abstract Internal ballistic parameter testing is crucial for evaluating artillery performance and design, with projectile acceleration being a core parameter. During the firing process, projectile acceleration parameters can easily be coupled with the projectile’s modal effects and the transverse effects of triaxial accelerometers, leading to inaccurate measurements. Therefore, this paper innovatively proposes a data decoupling method to improve the accuracy of acceleration measurements. Firstly, the internal ballistic firing mechanism and the transverse effects of triaxial accelerometers are analyzed. Secondly, a simulation analysis of the projectile modal is conducted, combined with the projectile’s motion state within the barrel, to determine the modal orders and frequencies under axial stretching and compression vibration modes. Thirdly, shock tests are performed on triaxial accelerometers using a shock table to establish the relationships between triaxial acceleration signals. Finally, the projectile modal, Empirical Mode Decomposition (EMD), and the transverse effects of triaxial accelerometers are combined to decouple the acceleration signals. A comparison between the decoupled acceleration signals and theoretical data shows that the error is reduced from 8.1% to 3.2%, significantly improving the accuracy of the acceleration signals.

Effectiveness of photobiomodulation with low-level lasers on the acceleration of orthodontic tooth movement: an umbrella review.

Photobiomodulation (PBM) with low-level laser therapy (LLLT) is a non-invasive method for accelerating orthodontic tooth movement (OTM). Several systematic reviews (SRs) have assessed the effectiveness of LLLT on OTM acceleration. However, the interpretations and analysis of the findings of these SRs are inconclusive and inconsistent due to the substantial heterogeneity of their results, mainly due to the wide variety of parameters employed in the primary studies. This umbrella review (UR) aims to (i) Evaluate and summarize the findings of SRs evaluating the effect of LLLT on OTM acceleration. (ii) Suggest an evidence-based protocol with the most predictable application LLLT parameters for OTM acceleration. Medline (PubMed), Web of Science, and Scopus were searched from inception to December 2023. AMSTAR-2 and ROBIS were used to evaluate methodological quality and risk of bias respectively. Six SRs met the inclusion criteria. All the SRs suggest that PBM with LLLT tends to be effective in accelerating OTM. However, the high heterogeneity of SRs hinders a precise evaluation of the LLLT's effect on OTM acceleration. The parameters most associated with OTM acceleration are LLLT frequency: At least twice a month, irradiation points: 4-10 points, irradiation time per point: 3-50 s, output power: 20-150 mW, energy density: 5.3 J/cm2 and wavelength range:780-810 nm. The risk of bias assessment identified that 50% of the included SR had a risk of bias ranging from uncertain to high. Similarly, three SRs obtained a "Critically low-quality" assessment. Although, all the SRs included in this UR suggest that LLLT may accelerate OTM in comparison to control groups. The primary goal of future studies examining the influence of LLLT on the acceleration of OTM should be to create standardised protocols for the use of LLLT, allowing the development of more predictable therapies. The research protocol was registered on the Prospero CRD42024497420.

Cosmic thermodynamics of interacting scenario of EBEC dark matter and holographic dark energy

The current article is base on the concept of interacting dark matter in the framework of Extended Bose–Einstein condensate dark matter with the holographic dark energy model. In the scenario of dark energy and different cases of the dark matter interaction term, we discuss the behavior of the cosmological parameters, thermodynamics and thermal equilibrium conditions. To investigate the accelerated expansion or decelerated phase of the universe, we consider the observational values from literature of all parameters and graphically examine the different phases of the cosmological parameters which are deceleration, equation of state, jerk and snap parameters. We also graphically discuss the stability condition of the generalized second law of thermodynamics and thermal equilibrium condition by utilizing the observational values. We conclude that for all cases the deceleration parameter represents the accelerated behavior and for all cases the universe is stable for generalized second law of thermodynamics and for two cases the thermal equilibrium condition is stable and for third case it shows the partial stability.

Dynamics of cosmological phase crossover during Bose–Einstein condensation of dark matter in Tsallis cosmology

During the cosmic evolution process, as the temperature of a cosmological boson gas falls below a certain threshold, a Bose–Einstein condensation process can occur at various points throughout the cosmic history of the Universe. In this model, dark matter, conceptualized as a non-relativistic, Newtonian gravitational condensate is governed by the Gross–Pitaevskii–Poisson system. In our present study, we investigate the Bose–Einstein condensation process of bosonic DM by treating it as an approximate first-order phase transition within a modified cosmological framework, known as Tsallis cosmology. We examine the evolution of relevant physical quantities characterizing the evolution dynamics of the Universe, including energy density, temperature, redshift, scale factor, Hubble parameter, and dimensionless deceleration parameter before, during, and following the Bose–Einstein condensation phase transition takes place. Additionally, we especially investigate the specific era of the evolution of the Universe characterized by a mixture of normal and condensate phases of dark matter. We analyze the behavior of temporal evolution of an important time-dependent parameter, called the condensate dark matter fraction throughout the condensation process and find the time duration of condensation of dark matter in the Tsallis cosmological model. We see that the presence of Bose–Einstein condensate dark matter in the framework of Tsallis-modified cosmology significantly alters the cosmological evolution of the Universe as compared to the standard model of cosmology. We also find for a typical value of Tsallis non-extensive parameter β=0.35, the model could explain an accelerated Universe without invoking any additional energy component and solve the age problem of our Universe.

Cosmic analysis through dark energy models in fractal universe with non-linear interaction term

This study investigates the cosmological effects of different dark energy models within a fractal universe framework, including a non-nonlinear coupling between dark components. We examine well-known dark energy models, including generalized ghost and power-law entropy corrected, using the Hubble horizon as the infrared boundary. Well-known cosmological parameters are also analyzed to explain the current scenario of the universe. Hence, to find the universe’s expansion rate, we evaluate the Hubble parameter (H), the deceleration parameter (q) to investigate its acceleration or deceleration, the equation of state parameter ωΛ to check the nature of dark energy and Vs2 to study the stability of cosmic evolution. The behavior of ωΛ−ωΛ′ plane is also investigate as it is a valuable tool in cosmology for tracking the evolutionary behavior of dark energy and understanding its dynamic properties over time. Our analysis reveals that the Hubble parameter ranges from 74.5−1.5+1.5 and the generalized ghost dark energy model to 77−3+3 for the power-law entropy corrected model. Both models demonstrate the phase transition of the universe from deceleration to acceleration phase and ωΛ→−1, indicating a cosmological constant-like behavior. Stability of the models is assessed using the squared speed of sound parameter, confirming stability across all cases. Furthermore, the results for the ωΛ−ωΛ′ plane are consistent with Planck 2018 for both models.

The effects of horizontal deceleration training on sprint and countermovement jump neuromuscular performance qualities

ABSTRACT This study examined the effect of 6-week training to improve horizontal deceleration ability on sprint acceleration and countermovement jump (CMJ) neuromuscular performance (NMP) parameters. Twenty male soccer players were divided into the training (TRA), and the control (CON) group. Pre-and post-training players performed an acceleration-deceleration ability test (ADA) and a jump on a vertical axis dual force plate. ADA deceleration parameters were analysed using Kinovea Software. Distance-to-stop (DTS), time-to-stop (TTS), 20 m sprint time (t 20 m), CMJ parameters were measured at pre-post-training. The largest improvement was determined in the TRA in the t 20 m (effect size = 0.88). Despite the increase in the weight of the TRA, t 20 m was shortened by 5.62% in TRA and 1.91% in CON. Deceleration ability was evaluated with CMJ eccentric parameters. While the percentage change of eccentric peak force differed between the groups, eccentric peak power (11.84 vs. 14.57 W·kg–1, ds: 0.72) and velocity (0.91 vs. 1.05 m.s–1, ds: 0.70) increased. Accordingly, it was determined that the improvement in CMJ eccentric and concentric peak velocity was due to speed-based power output. The training improved the maximum horizontal deceleration ability and confirmed that concentric peak velocity, as well as CMJ eccentric parameters, is an important NMP determinant of horizontal deceleration ability.