bluuebunny/crossref_metadata_2025 huggingface dataset:
Planar Finite Forced Dynamics of a Double Hinged Circular Arch: Theory and Experiments
Authors: Benedettini Francesco
Published: February 2021

The planar dynamics of an elastic circular arch undergoing large displacements under a sinusoidally varying, concentrated, vertical force at its tip is analyzed. First, a revision of theoretical models found in the literature and an analysis on different analytical approximations consistent with different simplifying assumptions is done; then, the analytical results are compared with those of an experimental steel model of a double hinged circular arch. The principal region of instability of the unimodal symmetric solution in which the nonlinear modal coupling excites the antisymmetric component is studied; moreover, inside this principal instability region, subregions of instability of any periodic solution are found and the corresponding increased complexity of the time laws is analyzed by using time series analysis tools.
Multimodal Resonances in Suspended Cables via a Direct Perturbation Approach
Authors: Rega Giuseppe , Lacarbonara Walter , Nayfeh Ali H. , Chin Char-Ming
Published: February 2021

We analyze the nonlinear three–dimensional response of an elastic suspended cable with small sag-to-span ratio to a harmonic excitation. We investigate the case of primary resonance of the first in-plane symmetric mode when it is involved in a one–to–one internal resonance with the first antisymmetric planar and nonplanar modes and a two–to–one internal resonance with the first symmetric nonplanar mode. We apply the method of multiple scales directly to the governing two integro–partial–differential equations and associated boundary conditions with no a priori assumption on the shape of the motion. The result is a system of four coupled nonlinear complex–valued equations describing the modulation of the amplitudes and phases of the four interacting modes. The spatial-temporal corrections to the displacement field at higher orders show that the solution is not separable in space and time. Prelimary comparisons with a companion Galerkin-type discretized model show that the latter must be used with some care in studying finite–amplitude motions of cables.
Near-Resonance Motion of a Rotating System With a Limited Source of Torque
Authors: Petchenev Alex , Bently Donald E. , Goldman Paul
Published: February 2021

The paper describes near-resonance, non-stationary motion of a system consisting of symmetric rotor with constant unbalance and isotropic support. The source of torque (drive) is considered limited, allowing linearization near the resonance.

The system is considered to be in planar motion.

Interaction between the rotor and stator of the system is nonlinear. It provides diverse effects on the rotor motion due to the limited power of the drive. An example of such interaction is the well known Sommerfeld effect, when the system cannot pass a critical speed because all of the power provided by the drive is dissipated by resonance vibration of the rotor supporting system.

Initial differential equations are reduced to a system of equations, mathematically similar to a system describing motion of a pendulum. Further reduction is possible using a specially developed hierarchic technique. An in-depth dynamic analysis makes it possible to apply control to the system, providing higher or lower resonance amplitudes.
Some Aspects of the Analysis of Stick-Slip Vibrations With an Application to Drill Strings
Authors: van de Vrande Bram L. , van Campen Dick H. , de Kraker Bram
Published: February 2021

This paper deals with a systematic procedure to calculate periodic solutions of dynamic systems experiencing dry friction. In this first attempt we limit ourselves to 1 and 2 dof autonomous models where a smooth approximation of the discontinuous friction force is applied. Using the simple shooting method with a numerical integration scheme suitable for stiff differential equations in combination with a path following algorithm, branches of periodic solutions can be followed for a varying design variable. This approach proves to work very well and will be the basis for developing a numerical tool to investigate more complex mdof dynamic systems with stick–slip phenomena.
Stabilization of 1/3-Order Subharmonic Resonance Using an Autoparametric Absorber
Authors: Yabuno Hiroshi , Endo Yasuhiro , Aoshima Nobuharu
Published: February 2021

The paper proposes a stabilization method for 1/3-order subharmonic resonance with an autoparametric vibration absorber. A main system with nonlinear spring stiffness and harmonic excitation, i.e., subjected to a sinusoidally changed magnetic force, is introduced as a model which produces 1/3-order subharmonic resonance. A damped pendulum system, whose natural frequency is in the neighborhood of one-half of the main system, is attached to the main system as an absorber, in order to induce 1:2 internal resonance. The 1/3-order subharmonic resonance which occurs in the case of locked pendulum is avoided due to energy transfer between the main system and the absorber, and due to energy dissipation by the absorber. It is also theoretically shown that a stable nontrivial steady state with respect to the 1/3-order subharmonic frequency component is changed into an unstable one due to the absorber. Experimental results show the validity of the autoparametric vibration absorber for the 1/3-order subharmonic resonance.
An Efficient Definition of Transmissibility for a General Equipment Isolation System
Authors: de Espíndola J. J. , Bavastri C. A.
Published: February 2021

A definition of transmissibility is introduced so that the efficiency of the isolation system is easily assessed. The system to be isolated may, in principle, be of any complexity: an elastic body isolated from an elastic foundation, a rigid body isolated from an elastic or rigid foundation, and so on. The isolators may be of any number and nature, their elastic centre located at any co-ordinates and their angular positions, with respect the isolated system, arbitrary. A numerical example consisting of an aircraft engine mounted with viscoelastic isolators is worked out.
Analysis of Operating Deflection Shapes Based on Subspace Method
Authors: Tsujiuchi Nobutaka , Matsumura Yuichi , Koizumi Takayuki
Published: February 2021

In this paper, we propose the new method to identify the Operating Deflection Shapes (ODSs) from the measurement data of time domain. At first, we present the identification scheme of ODSs based on a state-space model. Then the scheme is extended to identify the ODSs adaptively for the time-varying systems by using the URV Decomposition (URVD). Proposed scheme is able to decompose the deformation of a structure under operating condition into the underlying superposition of well excited frequency components. This paper introduces the algorithm and shows the effectiveness of our proposed scheme applyed for both synthesized and experimental data.
Modified Geometrical Acoustics Phenomena Exhibited by Computations for Hemi-Capped Cylinders in the Mid-Frequency Range
Authors: Ginsberg J. H.
Published: February 2021

The relation between surface pressure and normal velocity on a slender capped cylinder is examined. The data for this study are obtained from the wavenumber-based version of the surface variational principle (SVP), whose representation of the acoustic field is shown to consist of a discretely infinite sum of waves propagating in the circumferential and meridian directions. The circumferential wavenumbers are uncoupled, whereas coupling of the meridional spectra is described by the wet-surface impedance, whose value is obtained within an SVP analysis. Typical mid-frequency range results for this quantity in the case of a hemi-capped cylinder are examined. It is shown that the individual waves are essentially uncoupled, except at wavenumbers close to the pair at which a helical wave traveling along the surface transitions from subsonic to subsonic. The same type of phenomena are shown to occur over broad range of frequencies, even for reasonably short configurations. Interaction between wavenumber pairs, and the need to compute impedance values are the primary new aspects not encountered in ray theory analyses.
On Wavelet-Analyzed Seismic Response of SDOF Systems
Authors: Basu Biswajit , Gupta Vinay K.
Published: February 2021

This paper presents the technique using wavelet analysis to solve the response of a single-degree-of-freedom (SDOF) system subjected to transient excitations such as earthquakes. A brief review of the wavelet transform and its discretization, time-frequency representation of the ground motion and the input-output relation for a SDOF system is presented. A new orthogonal basis function has been used for describing the temporal and frequency characteristics of the input and the response in case of a recorded accelerogram during 1971 San Fernando earthquake. Also, the input-output relation in the wavelet domain has been illustrated through comparison with the time domain simulation results.
Some Recent Advances in Model Updating
Authors: Natke H. Günther , Cottin N. , Oeijeklaus M.
Published: February 2021

Model updating has now become a well-known field of application in engineering. The following is restricted to spatially discretized mathematical models.

First, the classical sensitivity (including sensitivities of the measuring errors) and the selective sensitivity within updating are mentioned. The latter leads to a computational construction of selective excitation force vectors. Reliable estimates can then be obtained.

The solutions of updating methods which result in nonlinear equations with respect to the parameters to be estimated are the global minima of these equations. This problem will be solved by applying interval arithmetic. Additionally, hints are given with regard to an efficient arithmetical procedure by massive parallel computing.

Large-sized problems need the reduction of the model orders. Substructuring and incomplete modal transformations are the methods that are well-known and applied. Some necessary and sufficient conditions are discussed in this context.

Examples will demonstrate the subjects discussed. The outlook mentions more advanced signal processing and identification methods which take non-stationary processes and non-linearly behaving systems into account.
Finite Element Error Localization Using the Error Matrix Method
Authors: Papadopoulos Michael , Garcia Ephrahim
Published: February 2021

A higher order version of the Error Matrix Method is proposed to increase the accuracy in the finite element error localization. The method retains a user specified number of terms from the appropriate binomial expansion. Jacobi’s iterative method is then proposed to solve the set of nonlinear equations. It is hypothesized that keeping the higher order terms will improve the error identification for the same number of coordinate degrees-of-freedom and modes. The method is implemented on a nine degree-of-freedom and an Euler-Bernoulli beam numerical examples. It is shown that while there needs to be a large number of measured coordinates and modes, the magnitude of the errors are more accurately identified.
Optimal Control of Nonlinear Parametrically Excited Beam Vibrations by Spatially Distributed Sensors and Actors
Authors: Kugi Andreas , Schlacher Kurt , Irschik Hans
Published: February 2021

This contribution is focused on a straight composite beam with multiple piezoelectric layers under the action of an axial support motion. In the sense of v. Karman a nonlinear formulation for the axial strain is used and the equations of motion are derived by means of the Hamilton formalism. This system turns out to be a special class of infinite dimensional systems, the so called Hamilton AI-systems with external inputs. In order to suppress the excited vibrations two infinite control laws are proposed. The first one is an infinite PD-feedback law and the second one is based on the nonlinear H∞-design, where an exact solution of the corresponding Hamilton Jacobi Isaacs equation is presented. The necessary quantities for the control laws can be measured by appropriate space-wise shaped sensors and the asymptotic stability of the equilibrium point can be proved.
Characteristics of Enhanced Active Constrained Layer Damping Treatments With Edge Elements: Part II — System Analysis
Authors: Liao W. H. , Wang K. W.
Published: February 2021

This paper presents some important characteristics of enhanced active constrained layer damping (EACL) treatments for vibration controls. Specific interests are on understanding how the edge elements will influence the active action authority, the passive damping ability, and their combined effects in EACL. Analysis results indicate that the edge elements can significantly improve the active action transmissibility of the current active constrained layer damping (ACL) treatment due to the bypass effect. Although the edge elements will slightly reduce the viscoelastic material (VEM) passive damping, the EACL will still have significant damping from the VEM. Combining the overall active and passive actions, the new EACL with sufficiently stiff edge elements not only could achieve better performance with less control effort compared to the current ACL system, but also could outperform the purely active system. With careful analysis, we can map out the required critical edge element stiffness for successful designs. In addition, analysis also shows that the EACL treatment is a more robust design. That is, it could outperform both the purely active and passive systems throughout a much broader design space than the current ACL configuration. With these desirable characteristics, the EACL could be used to realize an overall optimal active-passive hybrid system.
Design of Pendulum Absorbers for Transverse Vibration Attenuation of Rotating Beams
Authors: Wang Yenkai , Shaw Steven W. , Chao Chang-Po
Published: February 2021

This paper considers the placement, sizing and tuning of centrifugal pendulum vibration absorbers for the reduction of transverse vibrations in rotating beams. A simplified model describing the linearized dynamics of a rotating beam with external excitation and attached absorbers is used for the analysis. A design strategy is offered wherein individual absorbers are designed to reduce vibration amplitudes and stress levels caused by troublesome resonances. It is shown that this procedure offers significant reduction in vibratory stresses, even in the case of excitations composed of multiple harmonics.
Self-Excited Vibration Model of Dragonfly’s Wing Based on the Concept of Bionic Design for Small- or Micro-Sized Actuators
Authors: Ishimoto Sagiri , Hashimoto Hiromu
Published: February 2021

This paper describes a self-excited vibration model of dragonfly’s wing based on the concept of bionic design, which is expected as a technological hint to solve the scale effect problems in developing the small- or micro-sized actuators. From a morphological consideration of flight muscle of dragonfly, the nonlinear equation of motion for the wing considering the air drag force due to flapping of wing is formulated. In the model, the dry friction-type and Van der Pol-type driving forces are employed to power the flight muscles and to generate the stable self-excited wing vibration. Two typical Japanese dragonflies, “Anotogaster sieboldii Selys” and “Sympetrum frequens Selys”, are selected as examples, and the self-excited vibration analyses for these dragonfly’s wings are demonstrated. The linearized solutions for the nonlinear equation of motion are compared with the nonlinear solutions, and the vibration system parameters to generate the stable limit cycle of self-excited wing vibration are determined.
Dynamic Instability and Resonances of Geometrically Imperfect Plates
Authors: Ostiguy Germain L. , St-Georges Lyne
Published: February 2021

The parametric resonance and other dynamic instabilities of a rectangular plate with initial geometric imperfections acted upon by parametric excitation have been investigated. The temporal equations of motion describing the non-linear behavior of these plates for large oscillations are solved using a direct integration. Results are compared with those obtained from an approximate analytical method. For a structure with a sufficiently large initial imperfection, the soft-spring nature of parametric resonance is confirmed for small vibration amplitudes, followed by a hard-spring behavior for large vibration amplitudes. However, the temporal response of the imperfect structure displays a predominant inward deflection. This phenomenon increases with an augmentation of the imperfection amplitude. Moreover, some resonances not predicted by analytical methods are observed. Besides the possibility of principal parametric resonance, many internal resonances may be observed during a passage through a single parametric resonance.
Mean-Axis Conditions for Finite Elements Undergoing Large Rotations and Translations
Authors: Sonti Venkata R. , Agrawal Om P.
Published: February 2021

The mean-axis conditions for three types of finite elements that undergo large rotation and translation are derived. The cases include two Lagrangian planar elements (linear triangle and linear rectangle) and a three dimensional rectangular plate element. Each case includes two elements connected at the nodes. Three separate coordinate systems are used in describing the systems. The numerical values of different matrices including the mass matrix are presented for specific cases. It may be seen that the non-linear mass matrix is expressed in terms of a set of time-invariand matrices. The total mass matrix of the body i is obtained by assembling the individual mass matrices of the finite elements of body i.
A Fully Symbolic Model of Multibody Systems Containing Flexible Plates
Authors: Ouatouati A. El , Fisette P. , Johnson D. A.
Published: February 2021

The modelling of flexible elements in mechanical systems has been investigated through several methods issuing from both the field of multi-body dynamics and the area of structural mechanics and vibration theory. Concerning the multibody approach, recursive formulations in relative coordinates have been widely claimed to be most suitable and efficient for a large variety of applications. Such a formalism is developed here for a general multibody system containing flexible plates and in such a way that its full symbolic generation is possible within the ROBOTRAN program (Maes et al. 1989).
On the Use of Virtual Work in a Graph-Theoretic Formulation for Multibody Dynamics
Authors: Shi Pengfei , McPhee John
Published: February 2021

In this paper, graph-theoretic and virtual work methods are combined in a new formulation of the equations of motion for rigid and flexible multibody systems. In addition to extending the theory for existing graph-theoretic approaches, this new formulation offers two distinct improvements. First, the set of differential-algebraic dynamic equations are smaller in number than those obtained using conventional formulations. Secondly, the equations of motion for rigid and flexible multibody systems can be generated using a consistent graph-theoretic approach, thereby leading to an efficient and modular computer implementation.
Recursive Dynamics and Adaptive Control for Animating Articulated Figures
Authors: Kokkevis Evangelos , Metaxas Dimitris
Published: February 2021

We present a dynamic system for the guided animation of articulated figures. Based on an efficient forward dynamics simulator, we introduce a robust feedback control scheme and a fast two-stage collision response algorithm. A user of our system provides kinematic trajectories for selected degrees of freedom (DOFs) of the figure. The output motion is fully generated using forward dynamics. The specified motion trajectories are the input to a control system which computes the forces and torques that should be exerted to achieve the desired motion. The dynamic controllers, designed based on the Model Reference Adaptive Control paradigm, continuously self-adjust for optimal performance in trajectory following. Moreover, the user is given a handle on the type and speed of reaction of the figure’s controlled DOFs to sudden changes in their desired motion. The overall goal of our system is to provide a platform for generating and studying realistic, user controlled motion at interactive rates. We require minimal user involvement in specifying non-intuitive parameters.
Small Vibrations Superimposed on Non-Linear Rigid Body Motion
Authors: Schwab A. L. , Meijaard J. P.
Published: February 2021

In the case of small elastic deformations in a flexible multi-body system, the periodic motion of the system can be modelled as a superposition of a small linear vibration and a non-linear rigid body motion. For the small deformations this analysis results in a set of linear differential equations with periodic coefficients. These equations give more insight in the vibration phenomena and are computationally more efficient than a direct non-linear analysis by numeric integration. The realization of the method in a program for flexible multibody systems is discussed which requires, besides the determination of the periodic rigid motion, the determination of the linearized equations of motion. The periodic solutions for the linear equations are determined with a harmonic balance method, while transient solutions are obtained by averaging. The stability of the periodic solution is considered. The method is applied to a pendulum with a circular motion of its support point and a slider-crank mechanism with flexible connecting rod. A comparison is made with previous non-linear results.
A Study on the Simulation of Flexible Link Mechanics Based on FEM
Authors: Honke Koichi , Inoue Yoshio , Hirooka Eiko , Sugano Naoki
Published: February 2021

The dynamics analysis of link structure, including elastic vibrations, is presented. The two nodes element including large displacement is developed. This element is based on the theory of finite rotation, and includes geometric stiffness. The stiffness matrix and the inertia matrix are obtained from the FEM model by the theory of Guyan’s reduction including large displacement motion. In this paper, we explain the theory of this element and show some examples of analysis.
A Theoretical and Experimental Study of the Vibratory Behavior of a High-Precision Optical Positioning Table
Authors: Basdogan Ipek , Royston Thomas J. , Barraza Juan , Shu Deming , Kuzay Tuncer M.
Published: February 2021

At the Advanced Photon Source (APS), a state-of-the-art synchrotron radiation facility at Argonne National Laboratory (ANL), high-precision optical positioning systems are needed to conduct a wide range of experiments utilizing the high-brilliance x-ray beam. The high-precision, multi-dimensional positioning capability required for these positioning systems may be compromised by vibratory motion. The vibratory dynamics of the complex kinematic joints and components that comprise these multibody structures are not easily described by simple theoretical models. A combined experimental and theoretical approach has been developed to predict the dynamic properties of the individual components and joints and of the assembled multibody system. A prototypical optical table has been analyzed as an example case.
Controlling a Dynamic System With Open and Closed Loops: Application to Ladder Climbing
Authors: Lo Janzen , Metaxas Dimitris , Badler Norman I.
Published: February 2021

We develop a method for animating systems with open and closed loops and in particular ladder climbing for virtual world applications. Ladder climbing requires the modeling of dynamic open and closed-loop chains. We model the stance phase and the associated closed-loop dynamics, through the use of the Lagrange multiplier method which results in a system of differential algebraic equations (DAE). We use the Lagrange method for the dynamic formulation of the swing phase. The input to the algorithm is a given forward velocity, step length, step frequency and a chosen gait. The algorithm then determines the initial and final positions for each phase of ladder climbing. We use the Newton-Ralphson method to find the vector of joint torques that drives the dynamic system from the initial position to the final position. We use the Baumgarte stabilization method to achieve stability of the numerical integration. We present a series of real-time animations involving ladder climbing.
Fatigue Life Predictions by Coupling Finite Element and Multibody Systems Calculations
Authors: Dietz Stefan , Netter Helmuth , Sachau Delf
Published: February 2021

The dynamic loads and accelerations acting on a railway bogie are predicted by multibody simulation. The bogie frame is considered as an elastic body of the MBS-model, in which elastic displacements are represented by eigen and staticmodes. Stresses are calculated for the most stressed locations of a bogie in the MBS-postprocessor. Based on these a fatigue life prediction is carried out.
Monitoring Fault Condition During Manufacturing Using the Karhunen-Loève Transform
Authors: Turner Irem Y. , Wood Kristin L. , Busch-Vishniac Ilene J.
Published: February 2021

Monitoring the condition of parts and machine components is a crucial task in ensuring fault-free manufacturing. In this work, we propose an alternative condition monitoring technique, with great potential in extracting and isolating individual fault patterns from manufacturing signals. We propose that the Karhunen-Loève transform provides the ability to decompose measured signals into decorrelated fault patterns, in the form of fundamental eigenvectors. These fundamental eigenvectors can then be monitored by means of coefficient vectors, which indicate any changes in the fault patterns. The technique can provide accurate fault information, whether the manufacturing signals are deterministic, stochastic, stationary, or nonstationary.

This paper presents the fundamentals of the proposed technique and its extension to condition monitoring. The outputs of the Karhunen-Loève transform are studied to interpret their physical significance. Then, a subset of general manufacturing signals is used to understand the mathematical foundations of the technique. Extensions to general functions are investigated by means of numerical simulations. The technique proposed in this paper has great potential in providing a robust condition monitoring tool.
Multivariable Feedback Relevant System Identification of a Wafer Stepper System
Authors: de Callafon Raymond A. , Van den Hof Paul M. J.
Published: February 2021

This paper discusses the approximate and feedback relevant parametric identification of a positioning mechanism present in a wafer stepper. The positioning mechanism in a wafer stepper is used in chip manufacturing processes for accurate positioning of the silicon wafer on which the chips are to be produced. The accurate positioning requires a robust and high performance feedback controller that enables a fast through put of silicon wafers. A set of multivariable finite dimensional linear time invariant discrete time models will be estimated, that is suitable for model-based robust control design of the positioning mechanism.
Frequency and Time Signal Analysis in Source Identification of Vibration and Noise in Cylindrical Cam Mechanisms
Authors: Ge Song Lin , Nerli Giovanni , Pierini Marco
Published: February 2021

It is vitally important to identify sources from which unwanted noise and vibration are emitted before further research work can commence on the design optimization of the cylindrical cam mechanism. Acoustic microphone and vibration accelerometer measurement systems were used to analyze the system characteristics in both the time and frequency domains. We have succeeded in identifying the sources of noise and vibration and distinguishing the signals between the regions of the groove junctions and the groove inversions in terms of the relative values of their instantaneous powers. Some of the problems encountered were impossible to resolve using only frequency analysis techniques due to the characteristics of the rectilinear reciprocating motions of the cam mechanism follower. The results obtained from the cam analyzed show that the structure of the groove inversion has a greater influence on the noise levels emitted from the mechanism than the structure of the groove junction. The emitted noise level from the former is generally twice that emitted from the latter.
Identification of System and Periodic Disturbances
Authors: Phan Minh Q. , Goodzeit Neil E. , Juang Jer-Nan
Published: February 2021

This paper addresses the problem of system identification in the presence of unknown periodic disturbances. Available for identification is a set of excitation input and the disturbance-corrupted response. This paper shows that the excitation-to-output system dynamics can still be identified successfully with disturbance-corrupted data in a manner analogous to the case when there is no disturbance present. This input-output domain derivation is in agreement with a similar result previously derived in the state-space domain. Criteria to distinguish the disturbances from system dynamics are discussed. A detailed analysis of experimental data obtained from a structural acoustic test setup is used to support the theoretical results.
On Frequency-Domain System Identification
Authors: Blades Eric L. , Craig Roy R.
Published: February 2021

Over the past three decades vibration tests have frequently been conducted on structures and machines for the purpose of validating (updating) finite element models. Such testing is usually referred to as experimental modal analysis. The results of the vibration test are generally presented as a modal model consisting of natural frequencies, mode shapes, and modal damping factors, and the algorithms most frequently used to reduce the test data to modal-model form are time-domain algorithms. Alternatively, direct-parameter system identification may be performed, in which case the direct-parameter model consists of system mass, damping, and stiffness matrices. This paper discusses several features of a new frequency-domain direct-parameter system identification algorithm. Simulations based on a 52-DOF “payload simulator” are used to illustrate the performance of this algorithm.
Mass Transfer Influence on the Rollover Threshold for a Vehicle With Nonlinear Suspension
Authors: Gonzalez Oscar M. , Jauregui Juan C.
Published: February 2021

A dynamic model for a two-axle vehicle equipped with different types of suspensions is presented in this paper. The model is formulated considering the roll and pitch moments acting on the vehicle’s body and the roll moments on each of the axles during cornering.

The pitch-roll model is preferred to a single-roll plane model in order to analyze the mass transfer caused by the vertical displacements of each axle. These displacements usually have a negative effect in the rollover threshold of the vehicle. The model is solved numerically in the time domain for a steady state cornering in order to obtain the rollover threshold of the vehicle and for a sinusoidal steering input.

The formulation includes non-linear terms due to the weight transfer between the axles and the suspension behavior for the non-linear spring rate case.

Results are analyzed and compared with those obtained from quasi-static.
Characterization and Identification of Damping and Nonlinear Systems Parameters With Bispectral Analysis
Authors: Nayfeh A. H. , Hajj M. R. , Fung J. , Fahey S. O’F.
Published: February 2021

We propose a consistent methodology whereby perturbation techniques, complex Fourier amplitudes, and higher-order statistics can be combined to characterize and quantify the damping and parameters of nonlinear systems. The methodology is used to characterize and quantify the damping and parameters of the first mode of a three-beam two-mass frame. The frame is excited harmonically near twice the natural frequency of its first mode. The generalized coordinate of this mode is modeled with a second-order nonlinear equation with quadratic and cubic geometric nonlinearities, a cubic inertia nonlinearity, linear and quadratic damping, and parametric and external excitation terms. The method of multiple scales is used to obtain a second-order approximate solution of this equation. This solution shows how the response amplitude and frequency content and phase difference between that of the excitation and response depend on the damping, nonlinear system parameters, and excitation amplitude and frequency. Measurements of the response amplitude, “phase difference” obtained from the bispectrum, and complex Fourier amplitudes at the excitation frequency and its one-half, under different excitation levels are then used to determine the damping and nonlinear parameters.
Novel Speed and Position Estimation in Field-Oriented Control of Induction Machine Drive System
Authors: Khater Faeka M. H. , Abu-Elsebah Mohamed I. , Ahmed Farouk I.
Published: February 2021

This paper describes a novel technique which has been proposed to simplify field orientation control system. This technique depends on zero crossing detection of different waveform of stator fluxes using the comparator reference signal which control the inverter transistors. By using this technique it is available to update the position θ and current components in the rotational reference frame up to twelve times per cycle. As a result, the transformation from two phase stationary reference frame (SRF) to two phase rotating synchronously reference frame (RRF), has been canceled which leads to less consumption time in software. Thus control algorithm requires less time to be implemented via software for position detection and speed estimation.
A simple method for moving source depth estimation applied to the SWellEx96 data
Authors: Zhang Jianguo , Yang T. C. , Zheng Guangying
Published: February 2021

Existing methods for source localization in an ocean waveguide generally require simultaneous range and depth estimation as they are intrinsically coupled in the acoustic field. Using beam intensities averaged over ranges longer than the mode cycle distances, it is shown that the range-averaged vertical beam distribution is insensitive to the source range and sensitive to the source depth. An incoherent matched beam processing method is presented and applied to the SWellEx96 moving source data to estimate source depth based on the 127 and 130 Hz signals with good results.
Daily Myofibrillar Protein Synthesis Rates in Response to Low- and High-Frequency Resistance Exercise Training in Healthy, Young Men
Authors: Shad Brandon J. , Thompson Janice L. , Mckendry James , Holwerda Andrew M. , Elhassan Yasir S. , Breen Leigh , van Loon Luc J.C. , Wallis Gareth A.
Published: February 2021

The impact of resistance exercise frequency on muscle protein synthesis rates remains unknown. The aim of this study was to compare daily myofibrillar protein synthesis rates over a 7-day period of low-frequency (LF) versus high-frequency (HF) resistance exercise training. Nine young men (21 ± 2 years) completed a 7-day period of habitual physical activity (BASAL). This was followed by a 7-day exercise period of volume-matched, LF (10 × 10 repetitions at 70% one-repetition maximum, once per week) or HF (2 × 10 repetitions at ∼70% one-repetition maximum, five times per week) resistance exercise training. The participants had one leg randomly allocated to LF and the other to HF. Skeletal muscle biopsies and daily saliva samples were collected to determine myofibrillar protein synthesis rates using 2H2O, with intracellular signaling determined using Western blotting. The myofibrillar protein synthesis rates did not differ between the LF (1.46 ± 0.26%/day) and HF (1.48 ± 0.33%/day) conditions over the 7-day exercise training period (p > .05). There were no significant differences between the LF and HF conditions over the first 2 days (1.45 ± 0.41%/day vs. 1.25 ± 0.46%/day) or last 5 days (1.47 ± 0.30%/day vs. 1.50 ± 0.41%/day) of the exercise training period (p > .05). Daily myofibrillar protein synthesis rates were not different from BASAL at any time point during LF or HF (p > .05). The phosphorylation status and total protein content of selected proteins implicated in skeletal muscle ribosomal biogenesis were not different between conditions (p > .05). Under the conditions of the present study, resistance exercise training frequency did not modulate daily myofibrillar protein synthesis rates in young men.
Linezolid Resistance Genes in Enterococci Isolated from Sediment and Zooplankton in Two Italian Coastal Areas
Authors: Fioriti Simona , Coccitto Sonia Nina , Cedraro Nicholas , Simoni Serena , Morroni Gianluca , Brenciani Andrea , Mangiaterra Gianmarco , Vignaroli Carla , Vezzulli Luigi , Biavasco Francesca , Giovanetti Eleonora
Published: February 2021

Linezolid is one of the few antimicrobials available to treat severe infections due to drug-resistant Gram-positive bacteria; therefore, the emergence of linezolid-resistant enterococci carrying transferable resistance determinants is of great concern for public health. Linezolid resistance genes (
cfr
,
optrA
, and
poxtA
), often plasmid located, can be transmitted via horizontal gene transfer and have the potential to spread globally.
Interferon Regulatory Factor 3 Supports the Establishment of Chronic Gammaherpesvirus Infection in a Route- and Dose-Dependent Manner
Authors: Johnson K. E. , Sylvester P. A. , Jondle C. N. , Aurubin C. A. , Tarakanova V. L.
Published: February 2021

Interferon regulatory factor 3 (IRF-3) is a critical component of the innate immune response, in part due to its transactivation of beta interferon (IFN-β) expression. Similar to that observed in all acute virus infections examined to date, IRF-3 suppresses lytic viral replication during acute gammaherpesvirus infection.
Opioids and the developing brain: time to rethink perinatal care for infants of opioid-dependent mothers
Authors: Boardman James P , Mactier Helen , Devlin Lori A
Published: February 2021

Illicit use of opioids is a global health crisis with major implications for women and children. Strategies for managing opioid use disorder (OUD) in pregnancy have been tested over the past 40 years, but studies have focused on maternal and pregnancy outcomes, with less attention given to long-term follow-up of exposed children. Here, we provide a narrative review of recent advances in the assessment and management of neonatal opioid withdrawal syndrome (NOWS), and we summarise evidence from multiple domains—neuroimaging, electrophysiology, visual development and function, neurodevelopment, behaviour, cognition and education—which suggests that prenatal opioid exposure modifies child development. Further studies are required to determine the optimal management of pregnant women with OUD and babies with NOWS. We identify knowledge gaps and suggest that future study designs should evaluate childhood outcomes, including infant brain development and long-term neurocognitive and visual function.
Clinically isolated descending thoracic aortitis in a healthy older woman: a diagnostic challenge
Authors: Hoffman Max Amos , Ekladious Adel
Published: February 2021

A woman travelling to Australia in her early 70s presents to a regional emergency department with chest pain and associated shortness of breath. Her medical history was that of seasonal affective disorder treated with citalopram, and an allergy to ibuprofen. Subsequent CT imaging revealed aortic wall thickening and associated periaortic fluid, and a moderate pleural effusion. This was successfully treated with oral prednisolone, responding within 1 day. Further blood tests revealed a high CD4/CD8 T-cell ratio, which can be seen in autoimmune disease, sarcoidosis and haematological malignancies. Without evidence for other autoimmune processes, the patient was given a provisional diagnosis of descending thoracic aortitis secondary to sarcoidosis, prescribed a weaning regimen of prednisolone, and asked to seek further investigation and management in her home country. This is a case with several learning points; rare disease can cause common presentations/reports, and sometimes empirical therapy is the only therapy.
Musculoskeletal ultrasound using superb microvascular imaging documents treatment response to biosimilar infliximab in rheumatoid arthritis
Authors: Santos Julian Alejandro , Tee Cherica Afurong , Galsim Romelito Jose Galvan , Tee Michael Lucas
Published: February 2021

A 60-year-old woman with rheumatoid arthritis consulted for acute flare. She had elevated disease activity score 28 - erythrocyte sedimentation rate (DAS 28-ESR) of 6.88 and clinical disease activity index (CDAI) of 32. Her 12-joint ultrasound revealed widespread joint effusion. Synovial vascularity scores measured through superb microvascular imaging (SMI) and power Doppler were universally increased. We documented her treatment response 2 weeks after she received a single dose of biosimilar infliximab using clinical and sonographic data. Her DAS 28-ESR and CDAI scores decreased to 4.21 and 7.0, respectively. Reduction in synovial vascularity scores was demonstrated using SMI. While there was near total resolution in joint effusion and tenosynovitis, SMI was able to demonstrate synovial vascularity in joints with no clinical swelling nor tenderness. Musculoskeletal ultrasound and superb microvascular imaging are useful adjuncts in evaluating synovitis in rheumatoid arthritis and documenting treatment response through documentation of synovial vascularity, effusion and tenosynovitis.
Challenges in the diagnosis and management ofGranulicatella elegansendocarditis in a 9-year-old child
Authors: Holloway Victoria , Jacob George , Hayes Nicholas
Published: February 2021

A 9-year-old child, with a background of repaired pulmonary atresia and Ebstein’s anomaly, presented with fever, night sweats and lethargy. Blood cultures grewGranulicatella elegans, a nutritionally variantStreptococcusand known cause of infective endocarditis (IE). Echocardiogram revealed no clear vegetation, but increased stenosis of the right ventricle to pulmonary artery conduit. The child was successfully managed with high-dose benzylpenicillin, completing 2 weeks in the hospital, and was discharged to complete the ﬁnal 4 weeks of therapy with ceftriaxone in the community, as per European Society of Cardiology guidance. IE caused by anyGranulicatellaspecies is rare, with infection due toG. elegansrarer still. It is a Gram-positive bacteria that presents a diagnostic challenge due to non-speciﬁc symptoms at presentation and diﬃculty in growing the organism on culture medium. We present a case ofG. elegansendocarditis in a young child, which illustrates the challenges in managing this condition and the importance of considering atypical organism endocarditis in children presenting with fever of unknown origin, in particular those with a background of congenital cardiac disease. We review the literature onGranulicatellaendocarditis, and brieﬂy discuss the challenges of managing this condition in a child with an autism spectrum disorder and learning diﬃculties.
Rebubbling and graft failure in Descemet membrane endothelial keratoplasty: a prospective Dutch registry study
Authors: Dunker Suryan , Winkens Bjorn , van den Biggelaar Frank , Nuijts Rudy , Kruit Pieter Jan , Dickman Mor
Published: February 2021

Aims

To identify risk factors for rebubbling, and early graft failure after Descemet membrane endothelial keratoplasty (DMEK).

Methods

In this prospective registry study, all consecutive DMEK procedures registered in the Netherlands Organ Transplant Registry were assessed (n=752). Univariable and multivariable analysis was performed using logistic regression. The effect of rebubbling on endothelial cell density was analysed using a linear mixed model.

Results

144 of 752 (19%) eyes underwent rebubbling. Rebubbling was successful in 101 eyes (70%). In eyes that underwent rebubbling, the graft failure rate was significantly higher than eyes that did not undergo rebubbling (30% vs 9%, respectively; OR: 4.28, 95% CI 2.72 to 6.73, p<0.001). In multivariable analysis, independent risk factors for rebubbling were surgical complication (OR: 2.28, 95% CI 1.20 to 4.33, p=0.012) and older recipient age (OR: 1.04 (per increase of 1 year), 95% CI 1.01 to 1.07, p=0.003). Risk factors for developing graft failure within 3 months were transplant before 2016 (OR: 3.32, 95% CI 1.87 to 5.90, p<0.001), and surgical complication (OR: 2.93, 95% CI 1.42 to 6.04, p=0.004). Throughout the study period, rebubbling and early graft failure were inversely related. Eyes that underwent rebubbling showed significantly lower endothelial cell densities at 3, 6 and 12 months compared with eyes that did not undergo rebubbling (all p<0.001).

Conclusions

This Dutch registry study identified independent risk factors for DMEK graft detachment leading to rebubbling, namely recipient age and surgical complication, and early graft failure, namely transplantation before 2016 and surgical complication. Rebubbling was associated with significantly higher endothelial cell loss in the first year after surgery.
Evidence-based interventions to reduce mortality among preterm and low-birthweight neonates in low-income and middle-income countries: a systematic review and meta-analysis
Authors: Kleinhout Mirjam Y , Stevens Merel M , Osman Kwabena Aqyapong , Adu-Bonsaffoh Kwame , Groenendaal Floris , Biza Zepro Nejimu , Rijken Marcus J , Browne Joyce L
Published: February 2021

Background

Preterm birth is the leading cause of under-five-mortality worldwide, with the highest burden in low-income and middle-income countries (LMICs). The aim of this study was to synthesise evidence-based interventions for preterm and low birthweight (LBW) neonates in LMICs, their associated neonatal mortality rate (NMR), and barriers and facilitators to their implementation. This study updates all existing evidence on this topic and reviews evidence on interventions that have not been previously considered in current WHO recommendations.

Methods

Six electronic databases were searched until 3 March 2020 for randomised controlled trials reporting NMR of preterm and/or LBW newborns following any intervention in LMICs. Risk ratios for mortality outcomes were pooled where appropriate using a random effects model (PROSPERO registration number: CRD42019139267).

Results

1236 studies were identified, of which 49 were narratively synthesised and 9 contributed to the meta-analysis. The studies included 39 interventions in 21 countries with 46 993 participants. High-quality evidence suggested significant reduction of NMR following antenatal corticosteroids (Pakistan risk ratio (RR) 0.89; 95% CI 0.80 to 0.99|Guatemala 0.74; 0.68 to 0.81), single cord (0.65; 0.50 to 0.86) and skin cleansing with chlorhexidine (0.72; 0.55 to 0.95), early BCG vaccine (0.64; 0.48 to 0.86; I20%), community kangaroo mother care (OR 0.73; 0.55 to 0.97; I20%) and home-based newborn care (preterm 0.25; 0.14 to 0.48|LBW 0.42; 0.27 to 0.65). No effects on perinatal (essential newborn care 1.02; 0.91 to 1.14|neonatal resuscitation 0.95; 0.84 to 1.07) or 7-day NMR (essential newborn care 1.03; 0.83 to 1.27|neonatal resuscitation 0.92; 0.77 to 1.09) were observed after training birth attendants.

Conclusion

The findings of this study encourage the implementation of additional, evidence-based interventions in the current (WHO) guidelines and to be selective in usage of antenatal corticosteroids, to reduce mortality among preterm and LBW neonates in LMICs. Given the global commitment to end all preventable neonatal deaths by 2030, continuous evaluation and improvement of the current guidelines should be a priority on the agenda.