bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chaos of Nonlinear Vibratory System With Single Well Potential
Authors: Zhang Wei 
Published: March 2021

Abstract
In this paper we study chaotic dynamics of nonlinear vibratory system under combined parametric and forcing excitations with single well potential. Especially we focus on chaos of a centrifugal pendulum vibration absorber. The centrifugal pendulum vibration absorber is an efficient device that is used to reduce torsional vibration in crank shaft of internal combustion engine. Because reduced dynamical model of the centrifugal pendulum vibration absorber is a nonlinear system, there is very rich dynamical behavior in this system. We use Meknikov’s method and numerical method to study chaotic dynamics of the centrifugal pendulum vibration absorber and discuss the route from bifurcations of T2 torus to chaotic motion.
Experimental Correlation of Dynamic Finite Element Models
Authors: Martin Raymond E. , O’Brien David M. 
Published: March 2021

Abstract
Finite element models used in the dynamic analysis of structures benefit from correlation with experimental data at each step in the analytical development. The steps Aircraft Landing Systems has followed in obtaining both modal and operational data for the validation of aircraft wheel, brake, and strut FEA models are discussed in this paper. These steps include the creation of a valid experimental modal model for major components in the structure, correlation of the modal results to tie FE model results, testing of sub-assemblies, and collecting data from dynamometer tests of the system and their correlation to the assembled FE model of the system. Various procedures are described which have been developed and adapted by Aircraft Landing Systems and which enable practical correlation to frequencies as high as 2000 Hz. The application of the procedures are demonstrated with examples from recent testing.
Optimal Windows for the Time-Frequency Analysis of Arbitrary Swept Frequency Signals
Authors: Mooney James A. , Soom Andres 
Published: March 2021

Abstract
In noise and vibration analysis, as well as in many other engineering applications, it may be necessary to extract or analyze signals with time-varying frequency components. Examples include start-up and shut-down of rotating machinery, transient structural vibrations, vehicle passing noise, and speech analysis. Both Short-Time Fourier Transforms (STFT), representing a set of non-causal filters of constant bandwidth, and Wavelet Transforms, representing a set of non-causal filters of constant Q or constant percent bandwidth, have been used for such Joint Time Frequency Analysis (JTFA). In the present work, an arbitrary swept frequency signal is approximated locally, in time, by a linearized frequency sweep. We show that an optimal time window can be identified which, at a given frequency, is inversely proportional to the square root of the instantaneous rate of change of frequency. We find that the constant bandwidth of the STFT and the constant-Q of the Wavelet transform represent extreme cases which are each optimal for certain types of signals. In between the two extremes there lies a continuous range of variation of the effective bandwidth with frequency. Many important types of signals require analysis window variation in this range between STFT and Wavelet analysis. The paper concludes with some simple rules for optimizing the variation of the analysis window with frequency for various types of signals.
A Coupling of FEM-BEM for Elastic Structure in a Transient Acoustic Field
Authors: Filipe M. , Ha-Duong T. 
Published: March 2021

Abstract
We propose in this paper a space-time variational formulation for the scattering problem of transient acoustic waves in a fluid medium with a submerged elastic object. The problem is first reduced to a coupling problem between partial differential equations and boundary integral equations and an energy formula given in terms of the unknowns of this coupling problem. The variational formulation follows then. A space-time finite element method based on this formulation gives rise to a time-stepping scheme with both volume and surface spatial elements as variables.
Studies of Acoustic Characteristics and Their Comparison With Vibration Ones
Authors: Ekimov Alexander E. 
Published: March 2021

Abstract
The present paper gives the methods, schemes and results of experiments based on direct and reciprocal methods of measurements. The use of the reciprocity method made it possible to solve the problem of determining the acoustic characteristics of the distributed system model where vibroactive sources are represented in the form of passive models. It has been shown that the normalized transfer coefficient characterizing a link between force and acoustic fields has the same value both for the model and in nature (in case of their full similarity) that can be used:
- to improve the methods of designing and technological manufacturing of models based on the comparison of normalized transfer coefficients obtained for full-scale and physical models;
- to forecast the acoustic radiation of some vibroactive mechanisms using the assigned force characteristics and normalized transfer coefficients obtained for a model with the modelling scale taken into account.
Resonance Low Frequency Sound Source With Extended Frequency Band
Authors: Donskoy Dimitri M. , Nazalewicz Jan 
Published: March 2021

Abstract
A new concept of a low-frequency (&lt; 1000-Hz) underwater sound source has been proposed and tested (Donskoy and Blue, 1994). The present work is a further development of the source. A full scale reaction force driver to power the source was developed, built, and tested. In order to extend frequency band of the source, a double resonance approach (resonating reaction mass and resonating radiation piston) was employed. This approach allows for a significant extension (up to 400%) of the frequency band without an increase in a vibromotive force.
The driver consists of a brushless servomotor, a brushless resolver for feedback, a Digital Signal Processor (DSP) based servo amplifier, and an interface with a PC. Vibromotive force is created with an eccentric weight mounted to a resonating mechanical structure. The driver can generate up to 8.000 lbs force, it has a programmable frequency control in the range up to 117 Hz, high power output (3.3 kW), compact size, low weight, and relatively low cost.
Acoustic Shape Optimization Using Parametric Finite Elements
Authors: Huff John E. , Bernhard Robert J. 
Published: March 2021

Abstract
A procedure for shape optimization of acoustic enclosures using parametric finite elements is presented. Use of this method facilitates both design sensitivity calculations and the automation of the optimization process. The parametric finite elements can also be used to achieve a reduction of the computational cost of finding the optimal solution for a design problem. The method is verified using a model of a one dimensional, driven acoustic duct. The optimization technique is then applied to a sample problem of the reduction of the sound pressure level inside a two dimensional model of an automobile interior. The optimization is done for both a single frequency and a frequency band. The novel aspects of the use of parametrically defined finite elements and the merits of the method are discussed.
Structural Acoustic Design
Authors: Nicolas Jean , Atalla Noureddine , Foin Olivier , Berry Alain 
Published: March 2021

Abstract
Nowadays, acoustic quietening of manufactured products is gaining importance. Due to cost, severe weight and operational constraints, classical noise control techniques, although still usable, are becoming less attractive. Nowadays, engineers follow essentially two major approaches (i) reduce noise by passive means, design modifications of structures and systems (ii) reduce noise by active sound and vibration control. This paper is devoted to the structural acoustic design approach for which there are either some simple rules of thumb either huge numerical codes. The main objective of this paper is to bridge the gap between these two extremes.
For the vibration response, the approach is based on a variational method. The basic structure is a plate with several degrees of complexity: added local or distributed masses, added local or distributed stiffeners, added stiffeners, added damping and constrained layer damping, force and moment type of excitations. The general trend has been to model an equivalent plate with two objectives in mind: (i) numerical calculations may be performed on a P.C., (ii) results are as close as possible to the exact solution.
For the acoustic radiation, a novel approach has been used based on Berry’s idea (Berry, 1994) to develop the Green function in terms of a Taylor expansion. Analytical impedance functions may then be calculated for various aspect ratios and then extracted directly from files which allow considerable atime gains over any other rigorous approaches.
The A.D.N.R. (Acoustic Design Noise Reduction) code has been validated through several experimental steps and agreement is revealed to be quite good. Not only is A.D.N.R. precise, but it also covers a wide frequency range (low, medium and high frequencies) which is really an advantage.
The output data are diversified and among them we may cite: modal shape, operating deflection shape, quadratic velocity, radiation factor and overall sound power.
In practice, A.D.N.R. revealed itself to be a great tool at the pre-design stage, when clear and quick trends are needed.
Substructuring: Definition of the Analytical Dynamic Model of a Complex System During its Design Stage
Authors: Llorca Fabrice , Gerard Alain , Hennequin Denis , Brenot Dominique 
Published: March 2021

Abstract
A structure is often an assembly of several components coupled by various joints such as bolted or riveted joints. Component mode synthesis methods are very practical tools to define a dynamic model. But, several points have to be examined and improved in order to give a complet representation of the modal behaviour of the whole structure.
For example, rotational degrees of freedom on connecting points between adjacent substructures should be estimated to give a better representation of the multidirectional connecting forces. These informations may be evaluated through a method based on both interpolation and spatial derivation of the experimental translational displacements of the components.
Unlike many other structural elements, the dynamic properties of a connection are very difficult to evaluate. So, we propose a method of determining joint stiffness characteristics. We consider only the conservative problem so the damping properties of the different components of the considered assembly are not taken into account. The joint characteristics are extracted comparing experimental modal data base and component mode synthesis simulation. The updating procedure is based on a nonlinear iterative least-square method. Results are presented concerning a particular assemblie of rectangular plates. Structural modification is applied for one component. We show that the joint properties stay the same if the connecting interface is not modified. The close correlation between predicted and experimental results demonstrate that this method is well adaptated to the study of structural modifications.
A Comparative Study on the Monitoring and Diagnostics of Machinery Gear Systems
Authors: El-Karmalawy Moataz , Ganesan R. , Sankar T. S. 
Published: March 2021

Abstract
The efficiency and suitability of on-line vibration measurements as a diagnostic signal for condition monitoring and diagnostics of gear systems, are investigated. To this end, representation of a gear system as a single-degree-of-freedom dynamic system is considered. Mathematical models of faults or malfunctions of the gear system for use in the above dynamic system as its system and excitation parameters are synthesized. Further, the sensitivities of vibration signal parameters including time-domain, frequency domain and statistical parameters, to various different faults or malfunctions are identified and explained. Based on this information, the rational basis of using on-line vibration signal parameters as the diagnostic indices of a gear system is established. Experimental results are obtained from real-life gear testers that have different types of faults or malfunctions. On-line vibration signals obtained from these gears tests are analyzed for time-domain, frequency domain, quefrency domain, statistical and time series model parameters. The efficiency and performance levels of each of these indices in diagnosing a particular type of fault are demonstrated. Reliable signal parameters corresponding to various types of faults or malfunctions in the gear system, that serve as best indications of damage development, are identified from the test results. Theoretical predictions and experimental observations of various types of gear system failures are compared in order to establish the confidence levels about the on-line vibration signal parameters.
Identification of Frequency Response Functions and Modal Data From Base Excitation Tests Using Measured Interface Forces
Authors: Schedlinski Carsten , Link Michael 
Published: March 2021

Abstract
Base excitation testing is used in industry in order to qualify mechanical systems with respect to specified base acceleration levels. This type of excitation only allows to identify eigenfrequencies, mode shapes and modal damping values of the fixed/free system. Modal masses, mass participation factors and effective masses of the fixed/free system as well as the modal data of the free/free system cannot be identified because the excitation forces are unknown.
This paper introduces an approach to identify these modal data as well. For this purpose the reaction forces at the table/structure interface have to be measured also. Furthermore, the verification of the theory using a laboratory test structure will be presented.
Active Vibration Quenching Using Inverse Dynamics
Authors: Trautt Thomas A. , Bayo Eduardo 
Published: March 2021

Abstract
An inverse dynamics algorithm is derived for active vibration quenching of structures. The algorithm uses frequency domain technicques to compute an input function needed to produce a desired response at a particular degree of freedom. The desired response is a transition from the initial vibrating condition to a non-vibrating condition. The algorithm can also be used to modify the input function to correct for system disturbances while the input function is already being applied to the system.
The algorithm is demostrated in a simulation of a simply supported beam controlled by a torque actuator at one end of the beam. The finite element method is used to discretize the equations of motion of the beam.
Vibration Control of Moving Flexible Structure by Repetitive Control
Authors: Mitsuta Shinji , Tsuji Hideki , Itoh Hiroyuki , Ogasawara Yasushi , Seto Kazuto 
Published: March 2021

Abstract
The purpose of this study is to move a flexible structure, such as conveyance equipment that moves periodically, quickly and accurately by controlling its vibration. In order to reduce the vibration of a flexible structure actively, a hydraulic actuator is arranged on the motion transmission path between a drive system and a flexible structure. Generally, it is possible to obtain good effects for reducing a residual vibration by using feedback control. However, the vibration displacement in motion is mainly forced vibration which is caused by motion acceleration, so it is difficult to reduce the vibration displacement by using feedback control. Thus, by considering that the flexible structure is driven periodically, we use the repetitive control method to reduce the vibration displacement in motion. In this study, the repetitive control method with the step response, which does not need model identification, is shown. Furthermore, the validity of this method is examined by simulation and experiment.
The Treatment of Systematic Errors in Model Updating
Authors: Friswell Michael I. , Mottershead John E. , Zhang Youhe 
Published: March 2021

Abstract
In the standard methods, accurate parameter estimates in finite element model updating rely on the model being fully converged in the frequency range of interest. In this paper a method is presented for the estimation of natural frequency discretisation errors in finite element models. The discretisation error is added to the measured data and is shown to reduce the bias in the resulting parameters estimates. The method is demonstrated using a bar and a beam example.
IMA genome - F14
Authors: van der Nest Magriet A. , Chávez Renato , De Vos Lieschen , Duong Tuan A. , Gil-Durán Carlos , Ferreira Maria Alves , Lane Frances A. , Levicán Gloria , Santana Quentin C. , Steenkamp Emma T. , Suzuki Hiroyuki , Tello Mario , Rakoma Jostina R. , Vaca Inmaculada , Valdés Natalia , Wilken P. Markus , Wingfield Michael J. , Wingfield Brenda D. 
Published: March 2021

AbstractDraft genomes of Penicillium roqueforti, Fusarium sororula, Chalaropsis populi, and Chrysoporthe puriensis are presented. Penicillium roqueforti is a model fungus for genetics, physiological and metabolic studies, as well as for biotechnological applications. Fusarium sororula and Chrysoporthe puriensis are important tree pathogens, and Chalaropsis populi is a soil-borne root-pathogen. The genome sequences presented here thus contribute towards a better understanding of both the pathogenicity and biotechnological potential of these species.
Experimental melt inclusion homogenization in a hydrothermal diamond-anvil cell: Comparison with homogenization at one atmosphere
Authors: Li Shenghu , Li Jiankang , Chou I-Ming 
Published: March 2021

Abstract
Melt inclusion (MI) homogenization experiments are essential for determining the pressure-volume-temperature-composition (P-V-T-X) parameters of magma systems. The hydrothermal diamond-anvil cell (HDAC) is currently the only equipment that can exert external pressure on MIs while allowing in situ observation of MI phase changes during heating. The HDAC’s pressure potentially prevents the MI diffusion that, under heating at one atmosphere, produces artificially elevated measurements of phase transition temperatures. It is important to compare the phase transition temperatures measured using HDAC at elevated external pressure with those obtained using conventional equipment at one atmosphere. Such a comparison not only helps assess the reliability of HDAC phase transition temperatures but also helps determine phase transition temperatures that are naturally occurring in MI during the natural history of cooling.
In this study, we homogenized MIs hosted in quartz from the granitic porphyry in the Yixingzhai Au deposit, China, using HDAC at an elevated pressure of ~(140–230) MPa. We compared our experimental results with published data measured using a Linkam TS1500 stage at one atmosphere. The experiments show that the initial melting temperature (TIniM), total melting temperature (TTotM), and total homogenization temperature (ThTot) of the MIs are 695 ± 20, 780 ± 15, and 833 ± 17 °C, respectively. These phase transition temperatures are as much as 374 °C lower than the corresponding values measured at one atmosphere using the Linkam stage. Moreover, the temperatures measured using HDAC agree with actual values estimated using the linear extrapolation method based on correlations of MI size with phase transition temperatures measured using the Linkam stage. Based on the experimental HDAC results, we estimate that MIs in the Yixingzhai Au deposit were trapped at ~140 Ma and contained ~2 wt% H2O. These values are consistent with previously estimated emplacement pressures and H2O contents of granitic magmas in granitic porphyry-type Cu-Au deposits. Our results demonstrate that MI-homogenization experiments using HDAC at suitably elevated pressures can yield reliable naturally occurring phase transition temperatures in MI during the melt cooling process.
Use of a Telemedicine Risk Assessment Tool to Predict the Risk of Hospitalization of 496 Outpatients With COVID-19: Retrospective Analysis
Authors: O'Keefe James B , Tong Elizabeth J , Taylor Jr Thomas H , O’Keefe Ghazala A Datoo , Tong David C 
Published: March 2021

Background
Risk assessment of patients with acute COVID-19 in a telemedicine context is not well described. In settings of large numbers of patients, a risk assessment tool may guide resource allocation not only for patient care but also for maximum health care and public health benefit.

Objective
The goal of this study was to determine whether a COVID-19 telemedicine risk assessment tool accurately predicts hospitalizations.

Methods
We conducted a retrospective study of a COVID-19 telemedicine home monitoring program serving health care workers and the community in Atlanta, Georgia, with enrollment from March 24 to May 26, 2020; the final call range was from March 27 to June 19, 2020. All patients were assessed by medical providers using an institutional COVID-19 risk assessment tool designating patients as Tier 1 (low risk for hospitalization), Tier 2 (intermediate risk for hospitalization), or Tier 3 (high risk for hospitalization). Patients were followed with regular telephone calls to an endpoint of improvement or hospitalization. Using survival analysis by Cox regression with days to hospitalization as the metric, we analyzed the performance of the risk tiers and explored individual patient factors associated with risk of hospitalization.

Results
Providers using the risk assessment rubric assigned 496 outpatients to tiers: Tier 1, 237 out of 496 (47.8%); Tier 2, 185 out of 496 (37.3%); and Tier 3, 74 out of 496 (14.9%). Subsequent hospitalizations numbered 3 out of 237 (1.3%) for Tier 1, 15 out of 185 (8.1%) for Tier 2, and 17 out of 74 (23%) for Tier 3. From a Cox regression model with age of 60 years or older, gender, and reported obesity as covariates, the adjusted hazard ratios for hospitalization using Tier 1 as reference were 3.74 (95% CI 1.06-13.27; P=.04) for Tier 2 and 10.87 (95% CI 3.09-38.27; P<.001) for Tier 3.

Conclusions
A telemedicine risk assessment tool prospectively applied to an outpatient population with COVID-19 identified populations with low, intermediate, and high risk of hospitalization.