bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction for the Rub-Impact Phenomena in Rotor Systems
Authors: Wu Zhiqiang , Chen Yushu 
Published: November 2020

Abstract
By the method (Wu, 2001) developed by authors for singularity analyzing of the bifurcation of the periodic solutions in nonlinear dynamical systems with clearance, the bifurcation patterns of non-impact-rub response and a method for predicting rub-impact are given. It is shown that there are much more types of bifurcation patterns when the clearance constraint is take into account. Given their physical meanings of the parameters in practical rotor systems, the resonant periodic solutions of rotor systems consist of 11 different types of bifurcation patterns among of which the following four types are more likely to appear, (1) patterns without impact and jump, (2) jump patterns without impact, (3) impact pattern without jump and (4) patterns with impact and jump. Based on these results, parameter conditions for rub-impact phenomena are derived. These conditions can give more direct guidance to the design of rotor systems. The method proposed here can be used to predict rub-impact phenomena in more complicated rotor systems.
Nonlinear Dynamic Analysis of Partial Rotor Rub With Experimental Observations
Authors: Choi Yeon-Sun , Bae Chul-Yong 
Published: November 2020

Abstract
Partial rotor rub occurs when an obstacle on the Stator of a rotating machinery disturbs the free whirling motion of a rotor, which is more common than full annular rub for the cases of rubbing in rotating machinery. The nonlinearity due to the intermittent contacts and friction during partial rotor rub makes the phenomenon complex. The several nonlinear phenomena of superharmonics, subharmonics, and jump phenomenon are demonstrated for the partial rub using an experimental apparatus in this study. The forward or backward components in its orbit patterns are calculated using the directional spectrum for the experimental results and are demonstrated by numerical simulations. A piecewise-linear model and a rebound model using the coefficient of restitution are investigated on the basis of experimental observations in order to adopt an analytical model of the contact between the rotor and stator during whirling motion. The contact stiffness, coefficient of restitution, and friction coefficient for the contact during partial rub are calculated from the comparison between the numerical simulation and the experimental results. Also, the numerical simulations for the model of partial rub are done for the various system parameters of clearance, contact stiffness, and friction coefficient in order to find the nonlinear behavior of partial rotor rub.
Computer Aided Analysis of Non-Linear Vibrating Systems
Authors: Rao J. S. , Puri Tarun 
Published: November 2020

Abstract
This paper presents an overview of a computer package to analyze nonlinear vibrations in single degree of freedom systems. This software is designed to aid a new designer and learner of nonlinear vibration principles. It is developed so that it is user friendly and needs very little assistance. It also gives the output in the form of plots so that the user has a quick explanation of the physical phenomenon. In addition the program also gives an animation of the mass to find the way in which it vibrates during the motion.
The software developed considers free and forced vibration of nonlinear systems governed by Duffing, Van der Pol and any general nonlinear system governed by second order differential equation. The solutions are presented graphically in time domain and frequency domain. The graphical representation includes phase plane plots. Chaotic dynamics of Duffing’s oscillator is also included in the software.
Axial Nonlinear Mechanical Vibrations of Large Power Transformer Windings During Short Circuit
Authors: Xu Jian-Xue , Chen Zhen-Mao 
Published: November 2020

Abstract
In this paper, the axial nonlinear vibrations of the transformer winding under steady state operation case and short circuit case are studied in single degree and multi-degree models.
In the case of having ampere-turn balance, the steady state response of the former model is obtained by using multi-scale method and periodic shooting method, analytically and numerically. At the same time, the computing method of Jacobi matrix in the periodic shooting method has been modified, so that the computing CPU time is saved. For multi-degree mechanical model of a single phase transformer windings, the time domain response and relation between the response and various parameters are obtained by Runge-Kutta method.
For ampere-turn unbalance case, an electric-mechanical coupled problem, that the electric force depends the displacement of the winding are foomed, and the nonlinear forced Mathieu equation is established for this problem; and then the nonlinear dynamical response and global dynamical behaviors are analyzed.
Finally, for a 20 MVA single phase three windings transformer, a series of short circuit experiments have been performed and the axial dynamical response force, magnetic field, strain etc. have been measured. The theoretical results well agree with the experimental results.
Research Into the Use of Fractal Geometry for Condition Monitoring of Machinery
Authors: Liu Tianxiong , Hua Hongxing , Chen Zhaoneng , Zhu Jimei 
Published: November 2020

Abstract
A new method of condition monitoring is proposed. Wavelet transform and fractal geometry are the means. A variety of condition monitoring techniques are currently in use for diagnosis of machinery faults. However, little research into the detection of fractal characteristics in processing signals has been done. This paper establishes wavelet transformation based on the noise signal for analysis of the correlation dimension of the typical working condition. Correlation dimension of the decomposing coefficient of wavelet transformation is calculated to identify the working condition. A field experiment shows the correlation dimension of similar working conditions has similar values while different working conditions show distinct characteristics. The correlation dimensions of the typical working condition of a pump plotted here have a different domain. The experimental results and correlation graph confirmed the proposed method’s feasibility and validity.
Visco-Elastic Systems Under Narrow-Band Excitation
Authors: Xu Wei , Rong Haiwu , Fang Tong 
Published: November 2020

Abstract
The study of the response of nonlinear systems to narrow-band random excitation is importance. For example, the excitation of secondary system would be a narrow-band random process if the primary system could be modeled as a single -degree-of-freedom system with light damping subject to borad-band excitation. In the theory of nonlinear random vibration, most results obtained so far are attributed to the response of nonlinear oscillators to borad-band random excitation. In comparison, results on the effect of narrow-band excitation on non-linear oscillators are quite limited. Furthermore, some results in this area are disputable.
For linear viscoelastic systems under both additive and multiplicative borad-band excitation excitations, Ariaratnam studied the stochastic stability of the system by using the method of stochastic averaging. Cai, Lin and Xu determined the condition for asymptotic sample stability of the system by using an improved stochastic averging procedure. In this paper, the response of visco-elastic systems to combined deterministic harmonic and random excitation is investigated. The method of harmonic balance and the method of stochastic averaging are used to determine the response of the system. Theoretical analyses and numerical simulations show that when the intensity of the random excitation increase, the steady state solution may change form a limit cycle to a diffused limit cycle. Under some conditions the system may have two steady state solutions and jumps may exist.
The Analysis of Nonlinear Random Vibration of Vehicles
Authors: Miao Jingliang , Liu Haixiang 
Published: November 2020

Abstract
In Engineering, Vehicles in motion which undergo some random excitation given by the surroundings, may result in violent vibrations. The calculated results indicate that:
1) the softening nonlinear spring isolator usually is effective.
2) In the vibration system, sometimes, added more damping meterial can not effectively isolate the vibration of vehicles. But choosing the reasonable forms of nonlinear structures just is a effective isolating method.
The Nonlinear Vibration of a Vehicle and Passenger System
Authors: Yu Ke , Luo Albert C. J. , He Yuancheng 
Published: November 2020

Abstract
The vibration of passengers in a vehicle traveling on a rough pavement surface is investigated. The nonlinear equations of motion for a vehicle and passenger system with impacts are derived, and the corresponding equilibrium and stability are investigated. The dynamic responses for the vehicle and passenger system with and without impacts are simulated numerically. This investigation shows that the strong torsional spring is required in order to reduce the vibration amplitudes of passengers and to avoid impacts between the vehicle and passenger.
The Effect of Nonlinear Stiffness on the Maximum Response of the Shock-Isolating System Under Shock Action
Authors: Weng Xue-Tao , Zhu Shi-Jian , Qian Wei-Jian , He Lin 
Published: November 2020

Abstract
This paper discusses the affection of elastic element’s nonlinear dynamic stiffness, shock stiffness and damping on the maximum response of the shock-isolating system through calculating and comparing the maximum displacement and acceleration of the shock-isolating system under distinct prerequisites. The result shows that under the same shock action, a shock-isolating system with desired nonlinear dynamic stiffness, shock stiffness and damping has better shock-isolating performance than the system with linear ones.
Prospect of Applying Controlling Chaotic Vibration in the Waterborne-Noise Confrontation
Authors: Jiang Rong-Jun , Zhu Shi-Jian , He Lin , Qian Wei-Jian 
Published: November 2020

Abstract
This paper taking the Duffing system with nonlinear soft stiffness as an example, discusses the possibility of applying the chaotic phenomenon to get a broadband frequency output for a single frequency input. Thereby proves the application value of controlling chaos in the waterborne-noise confrontation.
Amplitude Nonlinear Normal Modes of Piecewise Linear Systems
Authors: Jiang Dongying , Soumier Vincent , Pierre Christophe , Shaw Steven W. 
Published: November 2020

Abstract
A numerical method for constructing nonlinear normal modes for piecewise linear autonomous systems is presented. Based on the concept of invariant manifolds, a Galerkin based approach is applied here to obtain nonlinear normal modes numerically. The accuracy of the constructed nonlinear modes is checked by the comparison of the motion on the invariant manifold to the exact solution, in both time and frequency domains. It is found that the Galerkin based construction approach can represent the invariant manifold accurately over strong nonlinearity regions. Several interesting dynamic characteristics of the nonlinear modal motion are found and compared to those of linear modes. The stability of the nonlinear normal modes of a two-degree of freedom system is investigated using characteristic multipliers and Poincaré maps, and a flip bifurcation is found for both nonlinear modes.
Analysis of Periodic Frictional Contact in Finite Elements Problems
Authors: Nacivet Samuel , Pierre Christophe , Thouverez Fabrice , Jezequel Louis 
Published: November 2020

Abstract
This paper considers the dynamics of structural systems modeled using the finite element method and subject to dry friction damping, using Coulomb’s law for the friction force model. A new frequency-time domain method, the Dynamic Lagrangian mixed Frequency-Time method (DLFT), is developed to calculate the steady-state forced response. The dynamic Lagrangians formulation introduced herein, when used in conjunction with a nonlinear solver in the frequency domain, is better suited to handling dry friction nonlinearities than the traditional augmented Lagrangians method. Namely, the use of dynamic Lagrangians allows one to solve for the nonlinear forces between two finite element nodes of the structure without using artifacts such as a spring. Hence the finite element model does not have to be degraded at the contact interface. Furthermore, a new reduction of the nonlinear system is proposed to decrease the required computation time. Finally, a set of numerical examples is presented for a beam in contact with a flexible dry friction element connected to ground, for frictional constraints that feature two-dimensional relative motion, and for a large-scale structural system with many friction dampers.
Newtonian and Variational Formulations of the Vibrations of Plates With Active Constrained Layer Damping
Authors: Park Chul H. , Baz A. 
Published: November 2020

Abstract
This paper presents Newtonian and variational formulations of the dynamics of plates treated fully with Active Constrained Layer Damping (ACLD). The developed equations of the plate/ACLD system provide analytical models for predicting the dynamic of laminated plates subjected to passive and active vibration damping controls. Numerical solutions of the analytical models are presented for simply-supported plates in order to study the performance of the plate/ACLD system for different control strategies. The developed models present invaluable means for designing and predicting the performance of the smart laminated plates that can be used in many critical engineering applications.
A Model to Evaluate the Aerodynamic Energy Requirements of Active Materials in Morphing Wings
Authors: Pettit Gregory W. , Robertshaw Harry H. , Gern Frank H. , Inman Daniel J. 
Published: November 2020

Abstract
A computational model is presented which predicts the force, stroke, and energy needed to overcome aerodynamic loads encountered by morphing wings during aircraft maneuvers. This low-cost model generates wing section shapes needed to follow a desired flight path, computes the resulting aerodynamic forces using a unique combination of conformal mapping and the vortex panel method, computes the longitudinal motion of the simulated aircraft, and closes the loop with a zero-error control law. The aerodynamic force prediction method has been verified against two more expensive codes. This overall model will be used to predict the performance of morphing wings and the requirements for the active material actuators in the wings.
Development and Implementation of Adaptive Order Analysis in the Application of Multiaxial Systems
Authors: Pan Min-chun , Chen Jeng-xing 
Published: November 2020

Abstract
This study investigates the varying-order analysis based on mechanism, and realizes it in dynamic signal processing of rotary machinery. Firstly, the synthetic signatures consisting of fixed-order, varying-order components and resonance-related ones as well are designed to validate the developed computation schemes. Secondly, this work takes an electrical scooter as a test bench, which some experiments have been conducted on. The noise and vibration signatures are measured and processed to characterize different spectral components and identify their sources. Some of the annoying ones belong to fixed order (e.g., gear whine noise), varying order (e.g., CVT-belt noise) and structure resonance (e.g., the structure-borne noise originated from the CVT housing). Therefore, the concerned noise/vibration can subsequently be coped with via machine component modification.
Nonlinear Analysis of Rotor Systems Including a Bearing Clearance by the Multiple Shooting Method
Authors: Demailly David , Thouverez Fabrice , Jézéquel Louis , Bonini Jérôme 
Published: November 2020

Abstract
In this paper the Multiple Shooting Method is briefly exposed. This method is then applied to a simplified model of a rotor/stator system including a bearing with clearance under static and unbalance forces. With bearing having a small amount of clearance, it is pointed out that the orbits are no longer circular at certain frequencies as for linear systems. If the clearance is large, the frequency response curve can be divided into three zones: a non-contact zone, a zone with one or several gains and looses of contact per period and a full contact zone. For both cases we emphasize on the evolution of the orbits while passing through transition zones.
Dynamic Polytope Function and Control Modeling
Authors: Wang Du , Guo Zhongyang , Hagiwara Ichiro 
Published: November 2020

Abstract
This study is motivated from the investigation of vehicle suspension system with changeable damping and variant stiffness parameters. Such suspension system can be modeled as a dynamic polytope based on the mapping of affinely changed parameters. According to the polytopic dynamics decomposition, knowledge of linear time invariant system can be applied to each polytope vertex and the time variant system is solved by the polytope convex synthesis method. For time variant vehicle suspension system, the different model structures for control purposes are formulated. A quarter-car is taken as the example for demonstration in observer design and nonlinear control design.
Stressors and support system among parents of neonates hospitalised with systemic infections: qualitative study in South India
Authors: Murthy Shruti , Guddattu Vasudeva , Lewis Leslie , Nair Narayanapillai Sreekumaran , Haisma Hinke , Bailey Ajay 
Published: November 2020

ObjectiveTo explore stressors and support system for families with a neonate admitted with a systemic infection.DesignQualitative study using in-depth interviews (IDIs), based on principles of grounded theory.SettingA busy level III neonatal unit of a tertiary care teaching hospital in coastal Karnataka, India, between May 2018 and January 2019.ParticipantsParents and accompanying attendants of neonates admitted to the neonatal unit with one or more systemic infections.MethodsUsing purposive sampling, semi-structured IDIs were audio recorded, transcribed verbatim and a thematic analysis was performed.ResultsThirty-eight participants were interviewed, lasting between 30 and 59 min. Babies’ hospitalisation with sepsis was an unprecedented, sudden and overwhelming event. Stressors related to uncertainties due to the information gap inherent to the nature of illness, cultural rituals, financial constraints, barriers to bonding and others. Parents reported experiencing insomnia, gastric disturbances and fatigue. Support (emotional and/or financial) was sought from families and friends, peers, staff and religion. Availability and preference of emotional support system differed for mothers and fathers. In our context, families, peers and religion were of particular importance for reinforcing the available support system. Participant responses were shaped by clinical, cultural, financial, religious and health service contexts.ConclusionDesigning a family-centred care in our context needs consideration of stressors that extend beyond the immediate neonatal intensive care unit environment and interactions. Understanding the influence of the nature of illness, financial, familial and cultural contexts helps identify the families who are particularly vulnerable to stress.
ATF4 activation promotes hepatic mitochondrial dysfunction by repressing NRF1–TFAM signalling in alcoholic steatohepatitis
Authors: Hao Liuyi , Zhong Wei , Dong Haibo , Guo Wei , Sun Xinguo , Zhang Wenliang , Yue Ruichao , Li Tianjiao , Griffiths Alexandra , Ahmadi Ali Reza , Sun Zhaoli , Song Zhenyuan , Zhou Zhanxiang 
Published: November 2020

ObjectiveMitochondrial dysfunction plays a dominant role in the pathogenesis of alcoholic liver disease (ALD); however, the underlying mechanisms remain to be fully understood. We previously found that hepatic activating transcription factor 4 (ATF4) activation was associated with mitochondrial dysfunction in ALD. This study aimed to investigate the function and mechanism of ATF4 in alcohol-induced hepatic mitochondrial dysfunction.DesignATF4 activation was detected in the livers of patients with severe alcoholic hepatitis (AH). The role of ATF4 and mitochondrial transcription factor A (TFAM) in alcohol-induced liver damage was determined in hepatocyte-specific ATF4 knockout mice and liver-specific TFAM overexpression mice, respectively.ResultsHepatic PERK-eIF2α-ATF4 ER stress signalling was upregulated in patients with AH. Hepatocyte-specific ablation of ATF4 in mice ameliorated alcohol-induced steatohepatitis. ATF4 ablation also attenuated alcohol-impaired mitochondrial biogenesis and respiratory function along with the restoration of TFAM. Cell studies confirmed that TFAM expression was negatively regulated by ATF4. TFAM silencing in hepatoma cells abrogated the protective effects of ATF4 knockdown on ethanol-mediated mitochondrial dysfunction and cell death. Moreover, hepatocyte-specific TFAM overexpression in mice attenuated alcohol-induced mitochondrial dysfunction and liver damage. Mechanistic studies revealed that ATF4 repressed the transcription activity of nuclear respiratory factor 1 (NRF1), a key regulator of TFAM, through binding to its promoter region. Clinical relevance among ATF4 activation, NRF1–TFAM pathway disruption and mitochondrial dysfunction was validated in the livers of patients with AH.ConclusionThis study demonstrates that hepatic ATF4 plays a pathological role in alcohol-induced mitochondrial dysfunction and liver injury by disrupting the NRF1–TFAM pathway.
Pilot training and surgical education: flying towards a brighter future
Authors: Ahmed Hanad , Scott Alexander 
Published: November 2020

ABSTRACTAimHuman factors, surgery and aviation are intimately tied together by the common threads of error, risk and interpersonal relationships. A plethora of research abounds in all disciplines individually. The lessons learnt in one domain however are not unique and can be shared between all to promote best practice, further research and a greater understanding at a fundamental level.MethodsA structured, thematic, literature review was performed. PubMed, EMBASE and Ovid MEDLINE databases were interrogated directly. The Health Foundation, National Health Service and Department of Health online databases were used through querying intrinsic search functions.ResultsWith expanding use of technologies such as checklists, there is a gap left to better address and understand the nuances and roles of stress, communication and emotion on both learning and clinical practice. These can be prominent in the high-pressure environments shared between aviation and surgery.ConclusionsThe authors explore lessons learnt from aviation, the human factors applicable to both and how they can be extrapolated to improve patient safety outcomes and promote the use of the ‘Software, Hardware, Environment, Liveware’ tool to aid practice.