Moment Of Inertia Research Articles

Dark I-Love-Q

For neutron stars, there exist universal relations insensitive to the equation of states, the so called I-Love-Q relations, which show the connections among the moment of inertia, tidal Love number and quadrupole moment. In this paper, we show that these relations also apply to dark stars, bosonic or fermionic. The relations can be extended to higher ranges of the variables, clarifying the deviations for dark stars in the literature, as those curves all approximate the ones generated by a polytropic equation of state, when taking the low density (pressure) limit. Besides, we find that for equation of states with scaling symmetries, the I-Love-Q curves do not change when adjusting the scaling parameters.

Punitive Inertia: Anti-Blackness and the Policing of Motion

ABSTRACT Theories of the U.S. carceral state often treat anti-Blackness as the disproportionate suffering of Black individuals across a range of measures instead of a distinct form of racial oppression that needs investigation. This article examines how anti-Blackness shapes the formal and informal ways that Black individuals are policed in their everyday lives. Drawing on 23 interviews with adults who identify as Black across the United States, I find that their spatial trajectories are altered by mundane forms of policing that extend beyond the criminal legal system. I offer the term punitive inertia to capture how Black spatial trajectories are policed and resisted. In physics, inertia describes how an object resists a force attempting to change its spatial trajectory. Similarly, punitive inertia describes how policing—underpinned by a history of racial slavery and colonialism—is the force Black individuals resist in attempts to control their own spatial trajectories. I argue that Black bodies are moving through an anti-Black modernity generating incessant moments of punitive inertia that call into question our very notions of Human and the Social as coherent categories. I conclude with a call for scholars to contend with anti-Blackness in further examinations of policing.

Experimental investigation on the reverse mechano-electrical effect of porcine articular cartilage

IntroductionThe electric signals within the cartilage tissue are essential to biological systems and play a significant role in cartilage regeneration. Therefore, this study analyzed and investigated the reverse mechano-electrical effect in porcine articular cartilage and its related influencing factors.MethodsThe deflection of cartilage samples in an electric field was measured to analyze the mechanisms of different factors affecting the reverse mechano-electrical effect in articular cartilage.ResultsThe results showed that the cartilage thickness, water content, and externally applied voltage all impacted the deflection of the cartilage. The reduction in cartilage water content resulted in a decrease in cartilage thickness, following the same influencing mechanism as thickness. On the other hand, an increase in the externally applied voltage led to an increase in the electric field force within the cartilage space, consequently increasing the deflection of the cartilage in the electric field. Additionally, the externally applied voltage also caused a slight temperature rise in the vicinity of the cartilage specimens, and the magnitude of the temperature increase was proportional to the externally applied voltage.DiscussionThe fitting results of the experimental data indicated that cartilage thickness influenced the dielectric constant and moment of inertia of the cartilage in the electric field, thereby affecting the magnitude of the electric field force and deflection of the cartilage. This may provide valuable insights for further investigation into the microscopic mechanisms of cell proliferation, differentiation, and cartilage regeneration induced by electrical stimulation.

The stability of anisotropic compact stars influenced by dark matter under teleparallel gravity: an extended gravitational deformation approach

In our investigation, we pioneer the development of geometrically deformed strange stars within the framework of teleparallel gravity theory through gravitational decoupling via the complete geometric deformation (CGD) technique. The significant finding is the precise solution for deformed strange star (SS) models achieved through the vanishing complexity factor scenario. Further, we introduce the concept of space-time deformation caused by dark matter (DM) content in DM haloes, leading to perturbations in the metric potentials gtt and grr components. Mathematically, this DM-induced deformation is achieved through the CGD method, where the decoupling parameter α governs the extent of DM influence. To validate our findings, we compare our model predictions with observational constraints, including GW190814 (with a mass range of 2.5-2.67M⊙) and neutron stars (NSTRs) such as EXO 1785-248 [mass=1.3-0.2+0.2M⊙], 4U 1608-52 [mass=1.74-0.14+0.14M⊙], and PSR J0952-0607 [mass=2.35-0.17+0.17M⊙]. Our investigation delves into the stability of the model by considering causality conditions, Herrera’s cracking method, the adiabatic index, and the Harrison–Zeldovich–Novikov criterion. We demonstrate that the developed model mimics a wide range of recently observed pulsars. To emphasize its compatibility, we highlight the predicted mass and radius in tabular form by varying both the parameters α and ζ1. Notably, our findings are consistent with the observation of gravitational waves from the first binary merger event. Furthermore, we compare our results with those obtained for a slow-rotating configuration. In addition to this, we discuss the moment of inertia using the Bejger–Haensel approach in this formulation.

Lower Extremity Electromyography During Submaximal Squats with Varying Moments of Inertia

INTRODUCTION: Spaceflight impairs muscle size, strength, recruitment, and aerobic capacity. Flywheel-based inertial training (FIT) has been used as a countermeasure to preserve muscle strength and size. The objective of this study was to determine how submaximal FIT squats with varying moments of inertia (MOI) affects lower extremity muscle recruitment. METHODS: Subjects (7 men, 7 women) completed FIT squats with various MOI: 0.000, 0.005, 0.010, 0.015, and 0.020 kg · m−2 (stages 1–5, respectively) at a pace of 50 squats/min for 3 min each. Electromyography (EMG) of the vastus lateralis, gluteus maximus (GM), biceps femoris, and soleus (SOL) were measured and normalized to maximal effort. Data were analyzed by repeated measures analysis of variance. RESULTS: Peak EMG amplitude [effect size (ES): 0.75–1.43] and integrated EMG activity (ES: 0.73–1.24) for all muscles increased linearly across MOI. Mean eccentric EMG amplitude was greater than concentric for the vastus lateralis (19–63% greater; ES: 1.58). A significant phase × MOI interaction was noted for the GM and SOL (ES: 1.27 and 2.08, respectively) where greater MOI preferentially increased eccentric EMG amplitude. DISCUSSION: Increasing MOI increases EMG amplitude of hip extensors, knee extensors, and plantarflexors during submaximal FIT squats in the concentric and eccentric phases. At higher MOI, EMG amplitude is preferentially increased in GM and SOL, especially in the eccentric phase. Submaximal FIT squats can be performed for up to 3 min continuously with active concentric and eccentric phases. This training modality may concomitantly preserve muscle and cardiorespiratory fitness during unloading but this remains to be tested. Mitchinson CJ, Caruso J, Best S, Bollinger L. Lower extremity electromyography during submaximal squats with varying moments of inertia. Aerosp Med Hum Perform. 2025; 96(2):93–100.

Jointed tails enhance control of three-dimensional body rotation.

Tails used as inertial appendages induce body rotations of animals and robots-a phenomenon that is governed largely by the ratio of the body and tail moments of inertia. However, vertebrate tails have more degrees of freedom (e.g. number of joints and rotational axes) than most current theoretical models and robotic tails. To understand how morphology affects inertial appendage function, we developed an optimization-based approach that finds the maximally effective tail trajectory and measures error from a target trajectory. For tails of equal total length and mass, increasing the number of equal-length joints increased the complexity of maximally effective tail motions. When we optimized the relative lengths of tail bones while keeping the total tail length, mass and number of joints the same, this optimization-based approach found that the lengths matched the pattern found in the tail bones of mammals specialized for inertial manoeuvring. In both experiments, adding joints enhanced the performance of the inertial appendage, but with diminishing returns, largely due to the total control effort constraint. This optimization-based simulation can compare the maximum performance of diverse inertial appendages that dynamically vary in a moment of inertia in three-dimensional space, predict inertial capabilities from skeletal data and inform the design of robotic inertial appendages.

Performance analysis of a micro pneumatic turbine using actual driving conditions simulation

Currently, nearly all literature discussing the performance of a micro pneumatic turbine using computational fluid dynamics (CFD) adopts either single reference frame simulation (SRFS) or multiple reference frame simulation (MRFS), with previously specified inlet pressure, outlet pressure and rotation speed. The overly constrained boundary conditions prevent the simulations from obtaining the turbine performance accurately under actual driving conditions, leading to calculation errors. This article proposes actual driving conditions simulation (ADCS) to predict the performance of a micro pneumatic turbine. In this approach, the inlet and outlet pressures are specified, while the turbine inertia moment is set according to the physical model of the turbine. SST k-ω turbulence model and dynamic grid technology are used to compute intricately time-varying flow parameters for obtaining the performance of the turbine. The results of SRFS, MRFS, ADCS and theory calculation (TC) demonstrate that the torque of a micro pneumatic turbine increases with an increase in supply pressure. The average torque calculated by ADCS is closer to that of TC compared with SRFS and MRFS. Moreover, the relative error of rotation speed between ADCS and experiments ranges from 2% to 10.9%, which is lower than that of between TC and experiments at the same working conditions.

Time-dependent propulsion of fully inertial active stochastic particles: Theory and simulations.

Up to now, studies on fully inertial (adding mass and moment of inertia) active Brownian particles (IABPs) have only considered a constant propulsion force. This work overcomes this by studying IABPs but with a time-dependent propulsion and analytically characterizes this system by finding its mean-square displacement and effective diffusion for any periodic time-dependent propulsion speed. To exemplify the periodic general expressions, three particular self-propulsion signals are addressed, expressly, a cosine, a square-wave, and a zig-zag propulsion force. Langevin dynamics simulations are also employed to validate the analytical findings. &#xD.

Feedback linearization-based model reference adaptive control for multirotor UAVs under uncertainties from fuel and payload

This paper proposes a feedback linearization-based model reference adaptive control (FL-MRAC) scheme to handle a multirotor unmanned aerial vehicle (UAV) equipped with a gasoline-battery-type hybrid system under uncertainties. The gasoline-battery-type hybrid propulsion systems are increasingly used to increase operational time. This multirotor system suffers from uncertainties that may originate from offcentered payloads, or fuel consumption during flight. These uncertainties can change model parameters such as mass, moment of inertia, and center of gravity. Therefore, a new control strategy is applied using feedback linearization as a baseline design augmented with a model reference adaptive control strategy on a multirotor UAV. To formulate the structure of uncertainties, the mathematical model of the multirotor UAV with fuel and payload is constructed considering the effect of the mass change rate and the off-diagonal inertia tensor. FL-MRAC improves the performance of attitude and altitude tracking using the closed-loop reference model under model parameter uncertainties and time-varying nature. To guarantee stability, the uniform ultimate boundedness of the closed-loop system is proved considering the time-varying parameters. Numerical simulations are performed using the root-mean-square error and the fast Fourier transform. In Case 1, FL-MRAC with a closed reference model exhibits a more accurate tracking performance and transient response than FL-MRAC with an open reference model under the uncertainties of time-varying parameter uncertainties. In Case 2, the proposed method of tracking performance demonstrates an improved attitude and altitude tracking performance compared to sliding mode control and nonlinear disturbance observer under time-varying parameter uncertainties and external disturbances due to fuel sloshing effect.

Methodology for developing models to estimate vehicle instantaneous energy consumption based on hub-type dyno test data

This paper describes a methodology to develop simple energy consumption models of road vehicles exploiting transient experimental datasets obtained from a vehicle/powertrain four-dyno testbed available at the Center for Automotive Research and Sustainable mobility (CARS@POLITO) of Politecnico di Torino. These models, based on a locally weighted linear regression method, can serve as a simpler alternative to more conventional methods based, for example, on engine maps obtained by steady-state characterization at engine testbeds, and combined with powertrain subsystem models. The present methodology was applied to a conventional diesel-powered vehicle. Three different modeling approaches are proposed: vehicle-based (VB), engine-based (EB) and engine-based modified (EB*). The VB approach is the simplest, being able to estimate the vehicle fuel consumption by only using, as inputs, wheel torque and speed, while the EB and EB* approaches enhance modeling accuracy by using engine speed and torque, as inputs, along with transmission-related parameters and/or by considering the moments of inertia of the powertrain rotating parts. The manuscript describes, in full, the process used to develop these models, providing significant guidance for researchers who may want to replicate the procedure with their own experimental data. These energy consumption models can be useful tools for the development and assessment of eco-driving or ADAS functions or for energy consumption comparison between different vehicles that were not tested on the same driving cycle. They can also support the estimation of the total energy consumption of vehicles along different traffic conditions or routes, based on a limited number of experiments and low computational effort.

Constructing stellar solutions with spherical symmetry through quadratic anisotropy in f(Q) gravity

This article examines anisotropic models to characterize compact stars (CSs) in the context of modified f(Q) gravity theory. To achieve this, we employ the linear functional form f(Q)=αQ+β. A physically meaningful metric potential grr is considered, and a quadratic form of anisotropy is utilized to solve the Einstein field equations in closed form. This class of solutions is then applied to characterize observed pulsars from various perspectives. In the scope of f(Q) gravity, we address the Darmois–Israel junction requirements to guarantee a smooth matching of the inner metric with the external metric (Schwarzschild (Anti-) de Sitter solution) at the boundary hypersurface. By applying these junction conditions, we determine the model parameters involved in the solutions. Additionally, this study evaluates the physical viability and dynamical stability of the solution for different values of the f(Q)-parameter α within the compact star (CS). The mass–radius relationships associated with observational constraints are analyzed for several compact stars, including Vela X-1, PSR J1614-2230, and PSR J0952-0607. The investigation indicates that the estimated radius of the compact object PSR J0952-0607, with mass 2.35±0.17M⊙, is around 15.79-0.09+0.05 km for a particular parameter value of α=2.0, and the moment of inertia for the de Sitter space is determined as 4.31×1045gcm2. The I-M curve shows greater sensitivity to the stiffness of the equation of state than the M-R curve, reinforcing our conclusion about the I-M framework’s responsiveness. Finally, we predicted the corresponding radii and moments of inertia for various values of α based on the M-R and M-I curves.

Davydov–Chaban Hamiltonian with deformation-dependent mass term for the sextic potential

This paper presents analytical expressions for spectra and wave functions derived from a Davydov–Chaban Hamiltonian, which models the collective motion of nonaxial nuclei within a sextic potential and incorporates the Deformation-Dependent Mass (DDM) formalism. The resulting solution, termed the Sextic and DDM Approach ([Formula: see text]-SDDMA), is attained through the combined application of Quasi-Exact Solvability (QES) and a Quantum Perturbation Method (QPM). Spectra and [Formula: see text] transition rates are provided for a selection of 15 nuclei: [Formula: see text]Xe, [Formula: see text]Pt and [Formula: see text]Pd, demonstrating a notable agreement with experimental data. Notably, the DDM parameter plays a crucial role in representing, for the first time, the [Formula: see text] band levels [Formula: see text] and [Formula: see text] as well as the higher levels within the natural ordering, resolving a previously identified anomaly present in all models related to the Davydov–Chaban Hamiltonian. Additionally, we explore the impact of DDM on the staggering effect of the [Formula: see text] band, moments of inertia, and shape phase transition, focusing on the prominent isotopic chains of Xe, Pt and Nd where some of the best candidates are obtained. Moreover, the DDM effect is found to facilitate the emergence of the backbending phenomenon in select nuclei in contrast with other models.

Reducing undesirable effects of revolute joint clearances on the dynamic performance of spatial parallel mechanism

To mitigate the adverse effects of joint clearances on the dynamic performance of mechanisms, it is essential to investigate the dynamic optimization design of spatial parallel mechanisms with clearances. Currently, there are many studies on the dynamic characteristics of mechanisms with clearances, but there are few studies on dynamic optimization design of mechanisms with clearances, especially on the optimization design of parallel mechanisms with clearances. Therefore, the dynamic optimization design of 3-RRPaR (R stands for revolute joint, Pa stands for quadrilateral structure) parallel mechanism with dry friction clearance of revolute joints is studied. The dynamic model of the parallel mechanism with revolute joint clearance is derived. On these grounds, the dynamic response of the end actuator, the contact collision force at the clearance joint, and their weighted combination are defined as objective functions, respectively. The mass and moment of inertia of the end actuator are taken as optimization variables. A mathematical model for the dynamic optimization design of the parallel mechanism considering dry friction clearances is developed, and the optimal mass and moment of inertia of the end actuator are obtained by G-MSRS method. This study comparatively analyzes the dynamic characteristics of parallel mechanisms with clearances before and after optimization. The results indicate that dynamic optimization significantly enhances the dynamic characteristics of the mechanism. This study lays a theoretical foundation for dynamic optimization design of parallel mechanisms with clearances.

Go big or spin fast? Biomechanical deterministic models for snowboard freestyle tricks performed on a trampoline

ABSTRACT In snowboard freestyle, rotation is the key indicator of trick difficulty, encouraging riders to perform tricks with more rotation. In many cases, snowboarders learn and practice tricks using training tools such as trampolins and/or landingbags before they transfer this tricks on-snow. It has not yet been scientifically investigated which movement parameters are primarily responsible for the acquisistion of increasingly difficult cork tricks. Hence, the aim of this study was to investigate the influence of each theoretically defined performance parameter on the amount of rotation using deterministic models for halfpipe and kicker tricks, separated for the direction of rotation, performed on a trampoline with a bounce board. Kinematic motion tracking was used to determine biomechanical performance parameters of 157 corks performed by 15 riders, and random intercept models were used to develop deterministic models. The results show that regardless of the discipline and direction of rotation, angular velocity, take-off velocity and the moment of inertia are key performance indicators to increase the amount of rotation. The coefficient of determination showed a high goodness-of-fit and the standardized estimate was highly significant for all investigated performance parameters. These results are important for coaches and riders to teach and learn new skills.

A method introducing deteriorating bond at the interfaces and declining load transfer at the joints in the existing design methods for concrete pavements

Most of the concrete highways of the Belgian road system have a structure composed of a CRCP surface layer, a thin intermediate asphalt bond layer and a lean concrete base layer on one or more granular sub bases. They are designed as an equivalent composite rigid layer on an elastic granular sub grade. The equivalent Young’s modulus of the composite layer is assumed to be equal to the modulus of the concrete surface layer, the thickness is assumed to be equal to the sum of the thickness of the three layers; the equivalent moment of inertia and the equivalent stiffness depend on the values of the thickness and the moduli of each layer and the bond conditions between the layers. Several investigations regularly performed on pavements currently thirty years old have shown a systemic deterioration of the bond between the surface layers and of the load transfer at the cracks of the CRCP or at the joints of concrete slabs. In this paper we present a mathematical model that permits the computation of the influence of this systemic deterioration on the lifetime of the pavements.

Surface Morphology and Remaining Geometric Parameters of Corroded Members on Bailey Truss

Abstract Bailey truss has been widely used in temporary constructional structures of bridges, and is reusable. In the service duration, Bailey truss is commonly exposed to corrosion threats due to the failure of anti-corrosion coatings, resulting in corrosion damage on members which induces degradation of its structural behavior. This paper presents an investigation on the corrosion damage of a Bailey truss which had been in service for eight years in the Northeast China. A total of 18 member segments were obtained from the chords, diagonals, and verticals of the Bailey truss, and were scanned by a 3D laser scanner after clearing the paint and rust. Then reverse modeling was performed based on the 3D coordinates of the specimen surfaces. The surface topography was discussed for different members on the basis of the separated roughness component, the residual thickness was analyzed for plates, and the residual cross-sectional area and moment of inertia about axes of the members were calculated and discussed. Coupon tests were carried out on corroded specimens from chords, diagonals, and verticals to quantitatively analyze the degradation of corroded Bailey truss. It was found that the corrosion damage on flanges was more severe than that on webs, in terms of the surface roughness and thickness loss. The corrosion status can be influenced by the microstructures and serving location. Upon the true values of the remaining cross-sections, it was concluded that the chords, diagonals, and verticals of the Bailey truss all exhibited the largest loss ratio in moment of inertia about y axis and the smallest loss ratio in cross-sectional area. The vertical member had the largest dispersion of average nominal loss rates, especially for moment of inertia about y axis, whose maximum and minimum values differed by 157.1%. A practical method for estimating the residual cross-sectional area and moment of inertia was validated. In addition, the engineering mechanical parameters (the elastic modulus, yield strength, ultimate strength, and the elongation after fracture) of each member basically show linear degradation. The mechanical parameters of diagonal web are most affected by corrosion. There is 10% thickness loss in chord web with up to 27% loss bearing capability in 8 years, and the factor of safety with respect to a reference parameter is lowered.

Analytic four-body limaçon choreography

The trajectories and interaction forces of four bodies with equal masses are analytically described. The bodies follow a choreographic motion in a trisectrix limax periodic orbit without collisions. The curve is similar to a numerical curve of a folded figure of eight. The center of mass is fixed at the origin. The moment of inertia, the non-zero angular momentum as well as the kinetic and potential energies of the system are constant. The interaction forces are not Newtonian but linear attractive and repulsive forces along the lines joining the bodies. To the best of our knowledge, this is the first analytical solution to a four-body choreography in a curve other than the circle.

The effect of blade turning angle on rotation improvement of a small horizontal axis wind turbine

Optimization of wind turbine aerodynamic performances implies solving the problem in the domains such as airfoil selection, blade rotation angle, chord optimization, number of blades, appropriate tip speed ratio, etc. The current paper studies the effect of blade rotation angle [Formula: see text] on power coefficient [Formula: see text], torque [Formula: see text] and mechanical power [Formula: see text] in a small horizontal axis wind turbine ( HAWT). The analysis involves two models of blades ( V and) of the airfoil class SD 7003. The first part of the paper employs numerical analysis, that is, Ansys CFX and Ansys Fluent software packages, to define wind turbine characteristics. The obtained results indicate that as the rotation angle [Formula: see text] increases the [Formula: see text] increases within an appropriate range of tip speed ratio [Formula: see text] change. The second part describes experimental investigation conducted on considered HAWT to define the values of [Formula: see text] and [Formula: see text] for studied blade rotation angles and comparison with the values obtained from Ansys. Existing differences in values are a consequence of the design of the HAWT, that is, the influence of the mass moment of inertia of the rotor and generator as well as the placement of the generator. Experimental setup and methodology allow for investigating the effect of different blade models, rotor and generator structure on wind turbine torque and mechanical power output characteristic.

Design Process for Scaled Model Wind Turbines Using Field Measurements

Abstract This paper presents a method for designing wind turbine-scaled models based on field data. The scaling process requires careful consideration of the system's physical laws and similarity criteria. Scaling methods depend on the prototype's operating conditions (full-size wind turbine) and the experimental conditions (scaled model dimensions and wind tunnel capabilities). The data from a field turbine are the input for creating a scaled model and testing it in a wind tunnel. There are few field data available. The task is not straightforward since most operating conditions must be satisfied, and the similarity criteria could result in different scaled models and wind tunnel conditions. The drawback of the scaling models is their inability to reproduce all the operating conditions. The method presented here considers most of the recommended similarities, including the dynamic modeling of the system and two additional similarities, one related to the blade's natural frequencies and the other to the rotor's moment of inertia. The additional similarities allow the designers to define the blade's mass and stiffness. The final scaled-model design was obtained by modifying the blade profile to reproduce similar power, pitch momentum, and trust coefficients, keeping the same twist angle as the prototype. Since the possible profiles are too large, the best approximation was obtained by comparing the coefficient curves of different blade profiles with the prototype's curves. The curves were calculated using the blade element momentum (BEM) method. It was found that the scaled model has an entirely different design.

Relationship of skeletal muscle mass, length of sports experience, and sexual maturity with bone density and geometry in adolescent athletes.

To identify the relationship between length of sports experience, muscle mass, and sexual maturity with bone mineral density (BMD) and geometry in adolescent basketball and track and field athletes. The study included adolescent (11-18 years) athletes, of both sexes, who practiced basketball (n = 26) or track and field (n = 24). Skeletal muscle mass was measured by bioelectrical impedance analysis. Data on sports training and sexual maturity were collected through a questionnaire. Total body, lumbar, femoral, and forearm BMD were determined by dual-energy X-ray absorptiometry. Femoral scans were used to generate bone geometry measurements (femur strength index, cross-sectional area, cross-sectional moment of inertia, section modulus, and buckling ratio). Bone outcomes were compared between modalities by the Mann-Whitney U-test or Student's t-test and by analysis of covariance with adjustment for sports experience, sexual maturity, and skeletal muscle mass. In the crude analysis, the basketball group had higher mean values for height, body weight, muscle mass, femoral neck BMD, cross-sectional area, and cross-sectional moment of inertia. In the covariate-adjusted analysis, the track and field group had higher total-body-less-head (0.995 vs. 1.035, p = 0.043), lumbar (1.012 vs. 1.107, p = 0.005), and radial (0.734 vs. 0.800, p = 0.005) BMD. Muscle mass was the main covariate influencing bone parameters, followed by sexual maturity. Skeletal muscle mass was the main determinant of bone outcomes in adolescent athletes, followed by sexual maturity, underscoring the importance of considering these variables when assessing bone health in this population.