Eccentric Mass Research Articles

Follow-up Timing of 12 Pulsars Discovered in Commensal Radio Astronomy FAST Survey

We present phase-connected timing ephemerides, polarization pulse profiles, and Faraday rotation measurements of 12 pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST Survey. The observational data for each pulsar span at least 1 yr. Among them, PSR J1840+2843 shows subpulse drifting, and five pulsars are detected to exhibit pulse nulling phenomena. PSR J0640−0139 and PSR J2031−1254 are isolated millisecond pulsars (MSPs) with stable spin-down rates ( Ṗ ) of 4.8981(6) × 10−20 s s−1 and 6.01(2) × 10−21 s s−1, respectively. Additionally, one pulsar (PSR J1602−0611) is in a neutron star−white dwarf (WD) binary system with an 18.23-day orbit and a companion of ≤0.65 M ⊙. PSR J1602−0611 has a spin period, companion mass, and orbital eccentricity that are consistent with the theoretical expectations for MSP−helium WD (He WD) systems. Therefore, we believe that it might be an MSP−He WD binary system. The locations of PSR J1751−0542 and PSR J1840+2843 on the P−Ṗ diagram are beyond the traditional death line. This indicates that FAST has discovered some low- Ė pulsars, contributing new samples for testing pulsar radiation theories. We estimated the distances of these 12 pulsars based on NE2001 and YMW16 electron density models, and our work enhances the data set for investigating the electron density model of the Galaxy.

Analysis of vibration characteristics of ship propeller spindle

In order to obtain the vibration response characteristics of the propeller spindle system effectively and accurately, and provide the basis for the subsequent fault diagnosis, the modal simulation and test of the spindle model were carried out. With the propeller set as eccentric mass, the amplitude and torsion angle of the spindle model were simulated under the condition of excited vibration and unexcited vibration respectively, and the frequency response of bending and torsion under the coupled condition was obtained. The newmark-β method was used to solve the transient response of the bent-torsional coupling model. The results shows that when the propeller spindle system undergoes rotation at a specific frequency and experiences bending vibration excitation force, the latter will induce torsional vibration response. Moreover, the amplitude of the torsional vibration response varies with changes in the frequency of the bending vibration excitation force.

A vibroacoustic model for low-frequency sound transmission loss in circular membranes with added strip mass

Noise control strategies involve physical barriers in the transmission path. Conventional barriers conform to the mass law which states an inverse relation between sound transmission, barrier mass, and incident frequency. Practical scenarios for low-frequency noise attenuation require prohibitively thick barriers making them infeasible. Mass-loaded membranes exhibit marked differences in their dynamic nature from that of bare membranes as they do not necessarily conform to the mass law. Being thin, compact, and lightweight makes them geometrically ideal for most applications. The paper presents an analytical model based on the Newtonian approach for the vibroacoustic behavior of a pre-stretched elastic circular membrane with rigidly attached strip mass under normal incidence. The point collocation approach distributes the effect of the strip mass on the membrane as a collection of discretized concentrated loads along the interfacial boundary resulting in a summation that is easier to solve. The peak and dip frequencies of sound transmission are determined for circular membranes with eccentric and central strip mass. The present study evaluates strip mass-loaded membranes' capability to attenuate noise at low frequencies as an unconventional physical barrier.

Gravitational waves for eccentric extreme mass ratio inspirals of self-dual spacetime

In this paper, we calculate the frequencies of geodesic orbits in self-dual spacetime on the equatorial plane and obtain the leading-order effects of loop quantum parameters P on the energy flux and angular momentum flux in eccentric extreme mass ratio inspirals. The gravitational waveform under different eccentricity is carried out by improved “analytic-kludge” method. We calculate the waveform mismatches for the LISA detector and the measurement error on loop quantum parameters. The constraint capability on P will be improved by a factor of 3 to 10, compared to the weak field experiments in the solar system.

Spectroscopy of eclipsing compact hierarchical triples

Context. Eclipsing compact hierarchical triples (CHTs) are systems in which a tertiary star orbits an eclipsing binary (EB) in an orbit of fewer than 1000 days. In a CHT, all three stars exist in a space that is less than 5 AU in radius. A low-mass CHT is an interesting case through which we can understand the formation of multiple stars and planets at such small scales. Aims. In this study, we combine spectroscopy and photometry to estimate the orbital, stellar, and atmospheric parameters of stars in a sample of CHTs. Using the complete set of parameters, we aim to constrain the metallicity and age of the systems. Methods. We used time-series spectroscopy to obtain radial velocities (RVs) and disentangled spectra. Using RV modelling, EB light curve modelling, and spectral analysis, we estimated the metallicities and temperatures. Using isochrone fitting, we constrained the ages of the system. We then combined observations of masses, outer eccentricities (e2), orbital periods, and age estimates of the systems from the literature. We compared the distributions of e2, and the tertiary mass ratio, q3 = M3/(M1 + M2), for three different metallicity ranges and two age ranges. Results. We have estimated the masses, radii, temperatures, metallicities, and ages of 12 stars in four CHTs. The CHT CD-32 6459 shows signs of von Zeipel-Lidov-Kozai oscillations, while CD-62 1257 can evolve to form a triple common envelope. The rest of the CHTs are old and have an M-dwarf tertiary. We find that the q3 distribution for CHTs with sub-solar metallicity has a uniform distribution but the systems with solar and above-solar metallicity peak between 0.5 and 1. When dividing them according to their ages, we find the q3 of old systems to be around 0.5. The eccentricity, e2, favours a value of around 0.3 irrespective of metallicity or age. The distributions of q3 and e2 resemble the distributions of the mass ratio and eccentricity of close field binaries.

Precession of a rotor with a different number of discrete radial elastic damping supports

A design model of a rotary system in the form of a cantilevered flexible shaft with a massive unbalanced disk at the free end is considered. In the plane of rotation of the disk, point elastically damped supports are discretely located with a clearance, stabilizing the vibrations of the rotor in the supercritical zone. With the help of the introduced precession indicator, the type and direction of the precession of the rotor during interaction with the supports is analyzed. The influence of a different number of supports on the evolution of the rotor precession in the supercritical zone after the Poincare-Andronov-Hopf bifurcation is investigated. The effect of the clearance and eccentricity of the disk mass at the contact of the disk with the supports on the precession of the rotor is analyzed.

3D coupled vibrations of asymmetric nano-particle mass sensors: Two-phase integral nonlocal strain gradient model and MD simulation

Since it is possible for the nano-particle to have any asymmetric shape and may attach to every position of the resonator-based mass sensors, any type of mass eccentricity and subsequently coupled vibrations are possible. So, in the present work, the 3D coupled axial-torsional-flexural vibrations of the mass nano-sensors are investigated considering both in-plane and out-of-plane bending as well as axial and torsional vibrations. In addition, the integral form of the two-phase local/nonlocal strain gradient (LNSG), as the consistent type of the common nonlocal strain gradient (NSG) elasticity theory, is employed for the first time to consider the size effects in the mass nano-sensors. A quasi-3D coupled FE model is constructed with no shear-locking within the complicated environment of the integral LNSG. The impacts of the LNSG elasticity and diverse types of possible coupling in changing the vibrational behavior of the mass nano-sensor are scrutinized and their crucial role in modeling of the nano-sensors is indicated. Furthermore, molecular dynamic (MD) simulations are implemented to identify and analyze the coupled vibrations of a mass nano-sensor consisting of a fixed-free carbon nanotube. Comparison between the MD results with those of the present coupled FE model reveals that considering the coupling effects reduces the modeling error, especially in the cases in which the coupling influences intensify. The present work can help to provide more accurate models of mechanical resonance-based nanosensors to detect nanoparticles with different shapes, larger sizes, and high mass ratios, which can lead to achieving sensors with higher sensitivity.

Shaking table test of TLD/TLCD vibration control for offshore wind turbine support structure

In this research, a scale-model with a similarity-ratio of 1:15 is specifically designed for shaking table test based on a 6.45MW OWT (Offshore wind turbine). The scale-model is equipped with a TLD (Tuned liquid damper) at the top and a TLCD (Tuned liquid column damper) at 2/3 of its height. Various external excitations with distinct spectral characteristics are applied to analyze the vibration characteristics of the OWT and the damping performance of the TLD/TLCD. The results indicate that the dynamic characteristics satisfy the similarity-ratio between the prototype-model and scale-model. The acceleration response of the OWT is significantly influenced by the external excitation spectrum, whereas the displacement response is primarily governed by the model 1st-order natural-frequency. With the mass eccentricity applied at the tower top and bidirectional excitation input, torsional deformation occurs in the tower, resulting in a ‘beat vibration’ phenomenon. Upon the incorporation of TLD/TLCD, the vibration response attenuation-ratio can reach up to 70 % under harmonic excitation, up to 25 % under seismic excitation and up to 50 % under equivalent base acceleration. After the implementation of vibration attenuation, there is a significant reduction in the time-domain response, and the rate of reduction is accelerated. In the frequency-domain response, the spectral peak at the natural-frequency disappears.

Seal dynamics of supercritical carbon dioxide turbine with the uncertain rotor nonlinear motion

The actual rotor motion and seal dynamics are nonlinear and uncertain. The uncertain effects include the seal flow and the rotor system parameters. While the influence of system parameters makes it more difficult to accurately predict the seal dynamics. A rotor nonlinear whirling model was established to achieve the synchronous solution of rotor motion and seal simulation. The coupling effect between rotor system parameters and seal aerodynamic performance was adopted. The actual seal dynamics for SCO2 turbine were obtained and evaluated by the numerical finite difference method. In the rotor nonlinear whirling model, the rotor has the uncertain continuous free motion. The influence of the system main parameters, such as elastic recovery stiffness and unbalanced mass force, on seal dynamics is revealed. And the dynamic coefficients beyond the artificial specific disturbance frequency are shown. The results show that the rotor nonlinear whirling can better predict the seal dynamics. The rotation speed, elastic recovery stiffness and unbalanced mass eccentricity have different significant effects on seal dynamics.

Toward Automated Structural Design for Controlled Vibration Characteristics Using Topology Optimization and Computer Vision in Space Missions

This study explores the integration of computer vision with topology optimization for additive manufacturing, with a focus on maximizing eigenfrequency in a design domain. Utilizing custom-developed photogrammetry software, high-resolution images are processed to generate detailed 3D models, which are subsequently converted to STL files with precision. Adaptive meshing in COMSOL 5.3 Multiphysics, controlled through a MATLAB 2023 API, ensures optimal mesh resolution. Prioritizing resource conservation in extraterrestrial environments, the original volume is reduced by 50% while preserving structural integrity. The design domain undergoes rigorous topology optimization in MATLAB, supported by COMSOL’s advanced FEM simulation. The optimized design exhibits a 57% performance improvement and a 50% weight reduction, maintaining the desired vibration characteristics, validating the efficacy of the modifications. Moreover, the case with an eccentric mass shows a significant 64% increase in eigenfrequency.

Long-term evolution of binary orbits induced by circumbinary disks

Circumbinary disks are found in a variety of astrophysical scenarios, spanning binary star formation to accreting supermassive black hole binaries. Depending on the characteristics of the system, the interaction with a circumbinary disk can either damp or excite the binary’s eccentricity and can also widen or shrink the orbit. To predict the outcome of the long-term disk-binary interaction, we present a new formalism based on the results of recent suites of hydrodynamic simulations, which resolve the complex geometry of the gas in the vicinity of the binary and fully account for the gravitational and accretion forces. We released a python package, spindler, that implements our model. We show that – under the assumed thin disk model with a fixed thickness and viscosity prescription – accretion onto the binary depletes the disk mass before inducing a significant change in the orbital separation or the mass ratio, unless the mass reservoir feeding the disk is comparable to the mass of the binary. This finding implies that, in most scenarios, an interaction with a circumbinary disk is not an efficient mechanism to shrink the orbit of the binary. However, the interaction can excite the eccentricity up to an equilibrium value, and induce a statistical correlation between the mass ratio and eccentricity, as long as the mass of the disk is at least a few percent of the mass of the binary. We consider the applicability of our model to a variety of astrophysical scenarios: during star formation, in evolved stellar binaries, triples, and in supermassive black hole binaries. We discuss the theoretical and observational implications of our predictions.

Nonlinear dynamic analysis of high-speed precision grinding considering multi-effect coupling

The aerostatic spindle is widely used in the field of precision grinding because of its excellent machining stability and machining accuracy. The spindle is jointly affected by multiple excitation effects in the high-speed grinding process. In order to study the dynamic characteristics of the aerostatic spindle under high-speed precision machining, it is necessary to analyse the nonlinear response of the aerostatic spindle with multi-physical field coupling. In this paper, the nonlinear dynamic model of the aerostatic spindle system under multi-effect coupling is established by considering three aspects: fluid-structure coupling, mass eccentricity excitation coupling, and vibration-grinding force coupling. Firstly, the instantaneous nonlinear air film force excitation is calculated by the derivation of the dynamic air film thickness model with multi-degree-of-freedom vibration responses coupling. The mass eccentricity excitation considering dynamic deflection angle is derived through the eccentric-load relationship. Afterwards, the dynamic precision grinding force model under the full surface of the tool is established based on judging the material removal mode, which considers the grain-workpiece interaction relationship under the influence of the nonlinear vibration. Finally, the accuracy and effectiveness of the coupled model is verified by high-speed precision grinding experiments, and the nonlinear dynamic behaviour under different operating parameters is analysed.

A Prediction Model of Two-Sided Unbalance in the Multi-Stage Assembled Rotor of an Aero Engine

In rotating machinery with a multi-stage assembled rotor, such as is found in aero engines, any unbalance present will undergo unknown changes at each stage when rotating the assembly phases of the rotor. Repeated disassembly and adjustments are often required to meet the rotor’s residual unbalance specifications. Therefore, developing a prediction model of this two-sided unbalance for a multi-stage assembled rotor is crucial for improving the first-time assembly pass rate and assembly efficiency. In this paper, we propose a prediction model of the two-sided unbalance seen in the multi-stage assembled rotor of an aero engine. Firstly, a method was proposed to unify the mass feature parameters of each stage’s rotor into a geometric measurement coordinate system, achieving the synchronous transmission of geometric and mass feature parameters during the assembly process of the multi-stage rotor. Building upon this, a linear parameter equation of the actual rotation axis of the multi-stage rotor was established. Based on this axis, the mass eccentricity errors of the rotor were calculated at each stage, further enabling the accurate prediction of two-sided unbalance and its action phase in a multi-stage rotor. The experimental results indicate that the maximum prediction errors of the two-sided unbalance and its action phase for a four-stage rotor are 9.6% and 2.5%, respectively, when using this model, which is a reduction of 53.0% and 38.1% compared to the existing model.

Tidal heating as a discriminator for horizons in equatorial eccentric extreme mass ratio inspirals

Tidal heating in a binary black hole system is driven by the absorption of energy and angular momentum by the black hole’s horizon. Previous works have shown that this phenomenon becomes particularly significant during the late stages of an extreme mass ratio inspiral (EMRI) into a rapidly spinning massive black hole, a key focus for future low-frequency gravitational-wave observations by (for instance) the Laser Interferometer Space Antenna mission. Past analyses have largely focused on quasicircular inspiral geometry, with some of the most detailed studies looking at equatorial cases. Though useful for illustrating the physical principles, this limit is not very realistic astrophysically, since the population of EMRI events is expected to arise from compact objects scattered onto relativistic orbits in galactic centers through many-body events. In this work, we extend those results by studying the importance of tidal heating in equatorial EMRIs with generic eccentricities. Our results suggest that accurate modeling of tidal heating is crucial to prevent significant dephasing and systematic errors in EMRI parameter estimation. We examine a phenomenological model for EMRIs around exotic compact objects by parametrizing deviations from the black hole (BH) picture in terms of the fraction of radiation absorbed compared to the BH case. Based on a mismatch calculation, we find that reflectivities as small as |R|2∼O(10−5) are distinguishable from the BH case, irrespective of the value of the eccentricity. We stress, however, that this finding should be corroborated by future parameter estimation studies. Published by the American Physical Society 2024

Dynamics of the regenerative turning chatter with little mass eccentricity

The little mass eccentricity of the workpiece is taken into account when we develop a single-degree-of-freedom regenerative turning chatter dynamic model. This study provides a numerical and analytical analysis of regenerative turning chatter, with a focus on the little mass eccentricity of the workpiece. By using a numerical approach, it is examined how a little mass eccentricity affects the turning chatter bifurcation features in various initial states. It primarily concentrates on applying the multiple scale method to analyze the impact of little mass eccentricity and workpiece angular velocity on the primary resonance of turning chatter. According to the research presented in this paper, mass eccentricity cannot be disregarded throughout the turning process.

Coupled wind-induced response of inter-story isolated eccentric tall buildings with friction-pendulum bearings

The isolation technology is widely used to protect structures against strong earthquake. For the inter-story isolated tall building located in strong wind-prone area, the soft isolation layer prolongs the structural period, which can make the wind effects significant. This study presents an analytical framework for assessing three-dimensional coupled wind-induced response of inter-story isolated eccentric tall buildings employing friction-pendulum bearings. The framework utilizes a biaxial Bouc-Wen hysteresis model and a velocity-dependent friction coefficient to describe the coupled frictional forces at each bearing. To enhance the computational efficiency, a simplified model with reduced degrees of freedom is proposed to represent the building. This study investigates eighty combinations of stiffness and mass eccentricities of lower and upper structures relative to isolation layer to analyze their impact on building acceleration. A spherical and two aspheric sliding surfaces of the bearing are examined to understand their effects on building response. The findings suggest that the stiffness eccentricity of either lower or upper building solely affects its own response without influencing other part of the structure. Conversely, the mass eccentricity of upper building induces significant mode coupling, resulting in noticeable impact on the accelerations of both upper and lower buildings. Moreover, the acceleration of the story conner farther from the mass eccentric position experiences significantly amplification. The proposed aspherical bearing demonstrates the capability to substantially reduce the bearing displacement, although with a limited increase in other building responses not exceeding 20 %.

A hot-Jupiter progenitor on a super-eccentric retrograde orbit.

Giant exoplanets orbiting close to their host stars are unlikely to have formed in their present configurations1. These 'hotJupiter' planets are instead thought to have migrated inward from beyond the ice line and several viable migration channels have been proposed, including eccentricity excitation through angular-momentum exchange with a third body followed by tidally driven orbital circularization2,3. The discovery of the extremely eccentric (e = 0.93) giant exoplanet HD 80606 b (ref. 4) provided observational evidence that hot Jupiters may have formed through this high-eccentricity tidal-migration pathway5. However, no similar hot-Jupiter progenitors have been found and simulations predict that one factor affecting the efficacy of this mechanism is exoplanet mass, as low-mass planets are more likely to be tidally disrupted during periastron passage6-8. Here we present spectroscopic and photometric observations of TIC 241249530 b, a high-mass, transiting warm Jupiter with an extreme orbital eccentricity of e = 0.94. The orbit of TIC 241249530 b is consistent with a history of eccentricity oscillations and a future tidal circularization trajectory. Our analysis of the mass and eccentricity distributions of the transiting-warm-Jupiter population further reveals a correlation between high mass and high eccentricity.

Identification and trimming of the eccentric mass in shell resonators

This paper presents a novel method to identify and suppress the undesired spurious mode caused by the 1st and 3rd harmonics of eccentric mass defects in shell resonators. This approach eliminates the need for pre-trimming of frequency split, simplifying the identification and trimming process, with the advantages of high efficiency and minimal structural damage. Firstly, the influence of the mass defects on the dynamics of resonators is analyzed using the mass ring model. The shear force caused by the 1st and 3rd harmonics of the eccentric mass, as well as the axial force caused by the 2nd harmonic, result in forced bending vibration and axial vibration of resonators. These two types of vibrations are superimposed as spurious modes with the operating mode. The bending vibration caused by eccentric mass is decoupled from the mixed vibration signal by analyzing the dynamic characteristics. An analytic scheme is proposed to identify the 1st and 3rd harmonics without eliminating frequency split. To validate the proposed scheme, the identification and trimming process for eccentric mass is simulated by the finite element method based on the geometric model with preset first four harmonics. Finally, experimental identification and trimming of the eccentric mass for the hemispherical resonator are performed based on the laser Doppler vibrometer and ion beam etching process. After multiple iterations, the 1st and 3rd harmonics are reduced by 87.2% and 49.8%, and the quality factors of the operating modes increase by 26.7% and 40.7%, respectively, demonstrating the effectiveness of the proposed method.

Dynamic investigation of the electromechanical coupling system in a permanent magnet direct-drive locomotive under rotor eccentricity faults

In the traction system of a direct-drive locomotive, the gearbox design is eliminated, enabling the direct transmission of output torque from the traction motor to the wheelset. Due to this unique structure, rotor eccentricity, which is a common fault in traction motors, can have a direct impact on the dynamic performance of key components such as the motor, bogie, and wheelset in locomotives. In order to investigate the dynamic response of the direct drive locomotive under rotor eccentricity faults, a comprehensive electromechanical coupling model that considers the dynamic motion of the rotor is established in this paper. The coupling effect between the mechanical system and the electrical system, as well as the dynamic forces induced by rotor eccentricity, are taken into account in the model. The simulation results reveal that ripple torque has an obvious effect on rotor dynamics behaviour, while rotor air-gap eccentricity and mass eccentricity exhibit varying degrees of influence on the dynamic performance of the vehicle system. Furthermore, the influence laws of rotor eccentric distance on the vibration responses of critical locomotive components are revealed. These findings provide valuable theoretical guidance for the operational maintenance and fault diagnosis of traction motors in direct-drive locomotives.

Transverse vibration analysis and active disturbance rejection decoupling control of rain erosion whirling arm

The transverse vibration caused by the mass eccentricity of the whirling arm and the unbalanced magnetic pull of the motor rotor is a critical factor that affects the stability and safety of the rain erosion whirling arm. To investigate the transverse vibration characteristics of the rain erosion whirling arm during operation, a four-degree-of-freedom transverse vibration model of the rotor-rain erosion whirling arm is established using the lumped mass method. The differential equation of motion of the rotor-rain erosion whirling arm, considering the influence of mass eccentricity and unbalanced magnetic pull, is then established based on the Lagrange equation. This equation is numerically solved using the Runge-Kutta algorithm to investigate the axis trajectory and amplitude distribution of the rotor-rain erosion whirling arm. To reduce the fatigue damage caused by vibration, the active disturbance rejection decoupling control method is employed. Furthermore, the parameters of the extended state observer are adjusted using pole assignment and bandwidth. The simulation results reveal that the vibration amplitude of the rotating blade can be reduced to within 0.2 mm, referring to the BSS7393 test standard. Additionally, experimental research is conducted to compare the vibration of the rain erosion whirling arm before and after implementing the active disturbance rejection decoupling control. The results demonstrate that the active disturbance rejection decoupling control method effectively suppresses the vibration of the rain erosion whirling arm, illustrating its feasibility and effectiveness for system vibration control.