bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Pedestal Parameters in Rotor-Bearing-Pedestal Systems Using Known Unbalance
Authors: Feng Ningsheng , Hahn Eric J. 
Published: November 2020

Abstract
This paper details a new technique for identifying the pedestal/foundation vibration parameters, viz. the pedestal or foundation stiffness, damping and mass matrices, of rotor-bearing-pedestal systems. Earlier approaches which relied on a knowledge of the hydrodynamic bearing forces as calculated from Reynolds equation, though promising in theory, proved unsatisfactory in practice. With this new approach on the other hand, at the expense of an additional run to enable the unbalance excitation to be correctly determined and assuming a knowledge of the rotor model, the uncertainties associated with bearing models are bypassed completely. It is shown both numerically and experimentally, that provided corresponding data are sampled at the same speed, good identification of pedestal parameters can be achieved even for pedestals supporting non-linear hydrodynamic bearings.
Theoretical and Experimental Study of the Dynamics of the Tripod-Ball Sliding Joint With Clearance
Authors: Xiaohong Jia , Linhong Ji , Dewen Jin , Jichuan Zhang 
Published: November 2020

Abstract
Clearance is inevitable in the kinematic joints of mechanisms. In this paper the dynamic behavior of a crank-slider mechanism with clearance in its tripod-ball sliding joint is investigated theoretically and experimentally. The mathematical model of this new-type joint is established, and the new concepts of basal system and active system are put forward. Based on the mode-change criterion established in this paper, the consistent equations of motion in full-scale are derived by using Kane method. The experimental rig was set up to measure the effects of the clearance on the dynamic response. Corresponding experimental studies verify the theoretical results satisfactorily. In addition, due to the nonlinear elements in the improved mathematical model of the joint with clearance, the chaotic responses are found in numerical simulation.
Analytical Solution of Forced Vibration of a Column Subjected to Conservative and Nonconservative Forces
Authors: Xu Zhixiang , Seto Kunisato , Tamura Hideyuki 
Published: November 2020

Abstract
This paper presents analytical results of forced transverse vibration of a column with a mass attached at free-end subjected to a tangential follower force and a transverse distributed excitation force, that is a simplified model of some structures in civil and mechanical engineering, e.g., a column of a suspension bridge, a launched rocket in the atmosphere. Because the tangential follower force is nonconservative, it is very difficult to get the analytical solution of the problem by usually-used analysis methods with which the adjoint boundary value problem can not be directly obtained. However, by applying the finite integral transform technique, we directly obtained the adjoint boundary value problem in the analysis process, and successfully obtained the analytical solution of the column’s vibration excited by the transverse distributed force.
Rocking Vibration of Rotating Disk and Spindle Systems With Asymmetric Bearings
Authors: Park Jung Seo , Shen I. Y. , Ku C.-P. Roger 
Published: November 2020

Abstract
This paper studies how bearing asymmetry affects natural frequencies and mode shapes of a rotating disk/spindle system through a numerical simulation and a perturbation analysis. Existing literature has shown that rocking motion of a rotating disk/spindle system with symmetric bearings consists of rigid body rocking of the spindle, one-nodal-diameter modes of each disk, and deformation of spindle bearings. The rocking motion, characterized by (0,1) unbalanced modes, has repeated natural frequencies when the spindle is stationary, because the disk/spindle system is axisymmetric. For a rotating spindle, (0,1) unbalanced modes evolve into forward and backward precession with circular orbits. In this paper, the numerical simulation shows that bearing asymmetry splits a pair of repeated (0,1) unbalanced modes into two modes with distinct frequencies when the spindle is stationary. Moreover, when the rotational speed increases from zero, the (0,1) unbalanced mode with lower frequency evolves into backward precession and the (0,1) unbalanced mode with higher frequency evolves into forward precession. The precession orbits are elliptical because of the bearing asymmetry. Two perturbation schemes are developed to prove the phenomena observed in the numerical simulation. For low rotational speed, a stationary disk/spindle system with symmetric bearings serves as the unperturbed system. Both the bearing asymmetry and gyroscopic effects from rotation form the perturbation. A contraction iteration predicts the effects of bearing asymmetry on natural frequencies and mode shapes. For high rotational speed, a rotating (gyroscopic) disk/spindle system with symmetric bearings serves as the unperturbed system. The bearing asymmetry forms the perturbation. To obtain a perturbation solution, the solvability condition is first derived for the unperturbed gyroscopic system. Lindsted-Poincaré approach then predicts the effects of bearing asymmetry on natural frequencies and mode shapes of the rotating disk/spindle system.
Determination of External Forces: Application to the Calibration of an Electromagnetic Actuator
Authors: Bucher Izhak , Rozenstain Moshe 
Published: November 2020

Abstract
A method for obtaining an accurate estimate of electromagnetic forces acting upon a vibrating structure is derived in this paper. The method was developed as a means for calibrating an electromagnetic excitation device where the electromagnetic force was sought to be estimated. The unique features of the proposed method are: (a) Compensation of inertial effects; (b) The method relies on indirect measurement of forces and displacements that are fed into an experimentally calibrated dynamical model. The calibration process allows us to precisely estimate distributed inertia and elastic forces and this allows us to model the relationship between the actually applied forces and various measurable physical parameters affected by the external forces. In the case of an electromagnetic device the affected parameters will be air-gap, current and magnetic flux. The lack of information in this case has lead us to a threefold approach where experimental data is combined with an analytical approach together with state-of-the-art measurement-techniques. The necessity to obtain an accurate account of the distribution of inertia in the structure necessitates a precise spatial model that was generated by means of a scanning laser-Doppler sensor. The analytical part involves the implicit estimation of Lagrange multipliers from an extended principal of virtual work.
Passive Vibration Control of the Head Actuator Assembly in Hard Disk Drive
Authors: Xu LiMei , Zeng Sheng , Guo NingQun , Lin Rongming 
Published: November 2020

Abstract
It is known that a quasi-rigid body mode exists in hard disk drives in the frequency range from 3 to 6 kHz and it is caused by the flexibility of the pivot, the mass and structure of the head actuator assembly. The mode hinders performance improvement of servo system in bandwidth. In this paper, a tuned damping device is proposed to suppress this mode. The damping device is to be installed on the arm and hollow space within the voice coil motor on the HDDs. The dynamic characteristics of the head actuator assembly with the tuned damping device are measured in both frequency domain and time domain. It is shown that the tuned damping device can work effectively to suppress the quasi-rigid body vibration of the head actuator assembly and minimize the residual vibration in head positioning.
Internal Resonance of the Jeffcott Rotor With Nonlinear Spring Characteristics
Authors: Ishida Yukio , Inoue Tsuyoshi 
Published: November 2020

Abstract
The Jeffcott rotor is a two-degree-of-freedom linear model with a disk at the midspan of a massless elastic shaft. This model executing lateral whirling motions has been widely used in the linear analyses of rotor vibrations. In the Jeffcott rotor, the natural frequency of a forward whirling mode pf and that of a backward whirling mode pb have the relation of internal resonance pf : pb = 1 : (−1). Recently, many researchers analyzed nonlinear phenomena by using the Jeffcott rotor with nonlinear elements. However, they did not take this internal resonance relationship into account. While, in many cases of the practical rotating machinery, such a relationship holds apprximately due to small gyroscopic moment.
In this paper, nonlinear phenomena in the vicinity of the major critical speed and the rotational speeds of twice and three times the major critical speed are investigated in the Jeffcott rotor and rotor systems with small gyroscopic moment. Especially, the influences of internal resonance on the nonlinear resonances are studied in detail. The following were clarified theoretically and experimentally: (a) the shape of resonance curves becomes far more complex than that of a single resonance, (b) almost-periodic motions occur, (c) these phenomena are influenced remarkably by the asymmetrical nonlinearity and gyroscopic moment, and (d) the internal resonance phenomena are strongly influenced by the degree of the discrepancies among critical speeds. The results teach us the usage of the Jeffcott rotor in nonlinear analyses of rotor systems may induce incrrect results.
Signal Based Methods to Extract A Priori Information for the Identification of Nonlinear Systems
Authors: Bruns Jens-Uwe , Popp Karl 
Published: November 2020

Abstract
The identification of nonlinear dynamical systems still is a non-trivial procedure. Signal based methods that retrieve basic information about the system prior to detailed identification can provide valuable assistance in this task. In the paper the detection and characterization of nonlinearities as well as the estimation of the system order are discussed. Regarding the first topic, a new method is presented that is based on the Method of Internal Harmonics Cross-Correlation by Dimentberg and Sokolov but provides additional information about the nature of the nonlinearity and uses nonlinear instead of linear correlation. Concerning the second topic, a method is presented that, in contrast to most existing methods for nonlinear systems, incorporates a random input signal to promote the excitation of all system states. Both methods are illustrated with numerical examples.
Nonlinear and Chaotic Snap-Through Response of Buckled Plates Under Sinusoidal Base Excitation
Authors: Ng C. F. , Poon W. Y. , Lee Y. Y. 
Published: November 2020

Abstract
A simple dynamic model of a general buckled plate using a single mode model is used to present the typical trend of nonlinear behavior. The nonlinear dynamic buckling of curved plate acted upon by a sinusoidal excitation and its effects on the overall dynamic response can be easily interpreted using the single-mode formula. The important non-linear dynamic characteristics of curved plates are found to be the transition from softening spring effects to hardening spring effects through the intermediate region of chaotic motion. The chaotic motion is an intermittent motion with large amplitude between the two static buckled positions of the plate. The theoretical predictions are in agreement with the experimental results. The experience from the studies can also be used to improve the testing and monitoring techniques for noise transmission and nonlinear vibration of curved plate under acoustic or airflow load.
Improved Estimations of Unstable Periodic Orbits Extracted From Chaotic Sets
Authors: Al-Zamel Z. , Feeny B. F. 
Published: November 2020

Abstract
Unstable periodic orbits of the saddle type are often extracted from chaotic sets. We use the recurrence method of extracting segments of the chaotic data to approximate the true unstable periodic orbit. Then nearby trajectories are then examined to obtain the dynamics local to the extracted orbit, in terms of an affine map. The affine map is then used to estimate the true orbit. Accuracy is evaluated in examples including well known maps and the Duffing oscillator.
Symmetry-Breaking and Chaos in Oscillatory Neural Networks
Authors: Chen Yonghong , Xu Jianxue , Fang Tong 
Published: November 2020

Abstract
Complex dynamical behavior of neural networks may lead to new methodology of information processing. In this paper the dynamics of a neural network designed by the normal form for Hopf bifurcation is studied. The secondary Hopf bifurcation of the network is discussed and a two-torus is observed. Examining the phase-locking motions on the two-torus, we present the conditions of symmetry-breaking occurring in the system. If the ratio of the two frequencies of the codimension two Hopf bifurcation is represented by an irreducible fraction, then the symmetry-breaking will occur when either the numerator or the denominator of the fraction is an even number. Chaotic attractors may be created with the sigmoid nonlinearities added to the right hand side of the normal form equations. The phase trajectory and the second order Poincaré maps of the chaotic attractor are given. The chaotic attractor looks like a butterfly on some of the second order Poincaré maps. This is a marvelous example for chaos to mimic nature.
Delayed Position-Feedback Controller for the Reduction of Payload Pendulations of Rotary Cranes
Authors: Nayfeh Ali H. , Masoud Ziyad N. 
Published: November 2020

Abstract
In this work, we show that in rotary cranes, it is possible to reduce payload pendulations significantly by controlling the translational and rotational degrees of freedom of the crane. Such a control can be achieved with the heavy equipment that is already part of the crane so that retrofitting existing cranes with such a controller would require a small effort. Moreover, the control is superimposed on the commands of the operator transparently. The successful control strategy is based on delayed-position feedback of the payload motion in-plane and out-of-plane of the crane. Its effectiveness is demonstrated with a fully nonlinear three-dimensional computer simulation and with an experiment on a scaled model of a rotary crane. The results demonstrate that the pendulations can be significantly reduced, and therefore the operations rate can be greatly increased. The effectiveness of the controller is demonstrated for both rotary and gantry modes of operation of the crane.
Stochastic Car Vibrations With Strong Nonlinearities
Authors: Wedig Walter V. , von Wagner Utz 
Published: November 2020

Abstract
High dimensional probability density functions of nonlinear dynamical systems are calculated by solutions of Fokker-Planck equations. First approximations are derived via the solutions of the associated linear system and the analytical results of the expected values. These first approximations are utilized as weighting functions for the construction of generalized orthogonal polynomials. The Fokker-Planck equation is expanded into these polynomials and solved by a Galerkin method.
As an example, a simple model of a quarter car with nonlinear damping subjected to white or coloured noise excitation is considered. The damping characteristic is piecewisely linear and highly non-symmetrical. The excitation is generated by the roughness of the road surface on which the car is driving with constant velocity. The main result is a non-vanishing mean value of the vertical car vibrations. Monte-Carlo simulations and analytical results are applied for comparison and tests.
Dynamic Analysis of Unsymmetrical Flexible Rotor-Bearing Foundation System Under an Unsteady Oil-Film Force
Authors: Liu Zhansheng , Huang Senlin , Su Jiexian , Huang Wenhu 
Published: November 2020

Abstract
Based on an unsymmetrical rotor model, the dynamic analysis of an unsymmetrical flexible rotor-bearing-foundation system supported by short journal bearing is presented, considering anisotropy of foundation stiffness and asymmetry of rotor stiffness. A more reasonable nonlinear unsteady oil-film force model, which is determined only by three functions, is adopted in the paper and the explicit analytical formula of oil-film force for short journal bearing is used. Using the Runge-Kutta method, the influence of parameters on the unsymmetrical flexible rotor-bearing-foundation system is investigated. Numerical results show that instability of system may be improved by decreasing the asymmetry of rotor stiffness and increasing the stiffness of foundation.
Fault Tolerant Control of Magnetic Bearings
Authors: Na Uhn Joo , Provenza Andrew , Palazzolo Alan B. , Choi Benjamin , Montague Gerald , Kascak Albert 
Published: November 2020

Abstract
This paper provides a new algorithm and test verification for implementing fault-tolerant operation of magnetically suspended, flexible shaft, rotating machinery. The currents to the magnetic bearing are redistributed in a manner so that the bearing actuator preserves the same linearized magnetic forces after some of its coils experience failure. The algorithm that searches a database for the appropriate failure compensation matrix utilizes a Boolean description of the failure state to quickly locate and download its target. The test results are shown to have good agreement with the system simulation results presented.
Non-Smooth Variational Problems in Mechanics
Authors: Bajkowski Jerzy , Grzesikiewicz Wiesław , Oslński Zbigniew 
Published: November 2020

Abstract
We consider a variational problem in which the minimized functional is convex but non-differentiable. In the static case, the variational problem serves to describe the mechanical system’s equilibrium position. In the rheological case it is employed to determine the velocities, and in the dynamical case it can be used to determine the accelerations of the body.
Theory, Experiments and Numerical Simulations of Instantaneous Collisions of Solids
Authors: Dimnet Eric 
Published: November 2020

Abstract
We describe the collision of a point with a fixed plane and the simultaneous collisions of a collection of rigid bodies following the theory of collisions by M. Frémond. We then give some existence and uniqueness results for simultaneous collisions of a collection of rigid bodies, and we show some numerical simulations of the evolutions of collections of solids during which such collisions happen. We also modelize instantaneous collisions of deformable bodies. Then, considering the impact of a hammer with a deformable bar, we show the agreement between measurements and our modeling.
Rapid implementation of Microsoft Teams in response to COVID-19: one acute healthcare organisation’s experience
Authors: Mehta Jay , Yates Timothy , Smith Penelope , Henderson Daisy , Winteringham Glenn , Burns Aine 
Published: November 2020

BackgroundCOVID-19 presented significant challenges to healthcare organisations, which needed to rapidly remodel their services but were unable to allow staff to meet face to face to minimise infection risk. During this communication predicament, National Health Service (NHS) Digital announced the provision of Microsoft Teams, a digital communication and collaboration tool, which was implemented at Royal Free London NHS Foundation Trust within 2 weeks.MethodGiven the need to deploy at scale, rapidly and with minimal resource, an agile decentralised innovation management approach was used, empowering staff to be local implementors.ResultsResulting use cases were highly original and varied, ranging from a COVID-19 Education Programme to coordination of oxygen demand. Analytics showed rapid and persistent adoption, surpassing 500 daily active users within 11 days. Usage continues to increase, consistent with a direct network effect.ConclusionThese findings suggest a high demand for this format of communication and high willingness to adopt it. Further qualitative research into staff perceptions would be valuable to confirm this, and to assess the user experience.Overall, this has been a radical approach to digital implementation in healthcare, and has so far proved effective in delivering a cost minimal, rapid communication tool at scale in the midst of a global pandemic.
Modification of diet, exercise and lifestyle (MODEL) study: a randomised controlled trial protocol
Authors: Radavelli-Bagatini Simone , Bondonno Catherine P , Sim Marc , Blekkenhorst Lauren C , Anokye Reindolf , Connolly Emma , Bondonno Nicola P , Schousboe John T , Woodman Richard J , Zhu Kun , Szulc Pawel , Jackson Ben , Dimmock James , Schlaich Markus P , Cox Kay L , Kiel Douglas P , Lim Wai H , Stanley Mandy , Devine Amanda , Thompson Peter L , Gianoudis Jenny , De Ross Belinda , Daly Robin M , Lewis Joshua R , Hodgson Jonathan M 
Published: November 2020

IntroductionMost cardiovascular disease (CVD)-related events could be prevented or substantially delayed with improved diet and lifestyle. Providing information on structural vascular disease may improve CVD risk factor management, but its impact on lifestyle change remains unclear. This study aims to determine whether providing visualisation and pictorial representation of structural vascular disease (abdominal aortic calcification (AAC)) can result in healthful diet and lifestyle change.Methods and analysisThis study, including men and women aged 60–80 years, is a 12-week, two-arm, multisite randomised controlled trial. At baseline, all participants will have AAC assessed from a lateral spine image captured using a bone densitometer. Participants will then be randomised to receive their AAC results at baseline (intervention group) or a usual care control group that will receive their results at 12 weeks. All participants will receive information about routinely assessed CVD risk factors and standardised (video) diet and lifestyle advice with three simple goals: (1) increase fruit and vegetable (FV) intake by at least one serve per day, (2) improve other aspects of the diet and (3) reduce sitting time and increase physical activity. Clinical assessments will be performed at baseline and 12 weeks.OutcomesThe primary outcome is a change in serum carotenoid concentrations as an objective measure of FV intake. The study design, procedures and treatment of data will adhere to Standard Protocol Items for Randomized Trials guidelines.Ethics and disseminationEthics approval for this study has been granted by the Edith Cowan University and the Deakin University Human Research Ethics Committees (Project Numbers: 20513 HODGSON and 2019-220, respectively). Results of this study will be published in peer-reviewed academic journals and presented in scientific meetings and conferences. Information regarding consent, confidentiality, access to data, ancillary and post-trial care and dissemination policy has been disclosed in the participant information form.Trial registration numberAustralian New Zealand Clinical Trial Registry (ACTRN12618001087246).