bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimum Design of Sandwich Panels With Piezoelectric and Shape Memory Alloy Actuators
Authors: Birman Victor , Simonyan Arthur 
Published: March 2021

Abstract
The problems of optimum distribution of stiffener-actuators manufactured from piezoelectric or shape memory alloy materials and bonded to or embedded within the facings of a sandwich plate are considered. The sandwich plate consists of thin composite or isotropic facings and a thick shear deformable core. The amplitude of forced vibrations of the plate is reduced using symmetric couples of piezoelectric actuators subjected to out-of-phase dynamic voltages. Shape memory alloy stiffener-actuators are used to reduce bending deformations. In the latter case, a desirable effect is achieved by activating the stiffeners on one side of the middle surface. Optimum design is considered based on the requirement of minimal transverse static or dynamic deflections subject to a constraint on the volume of the material of the actuators. The variables employed in the process of optimization are the ratios of the cross sectional areas of the stiffener-actuators in each direction to their respective spacings. It is shown, that, dependent on the load, materials, and geometry, optimization can significantly reduce deflections, i.e. enhance the strength, of sandwich plates.
Elasto-Plastic Analysis of Anisotropic Plates and Shells With Moderate Thickness by FEM
Authors: Zhong W. F. , Huang Y. Y. 
Published: March 2021

Abstract
A numerical analysis of anisotropic plates and shells with moderate thickness is dealt with in this paper by using elasto-plastic finite element method. The Huber-Mises yield surface extended by Hill and the nine-node Heterosis element are introduced into the present model. In order to increase the computational accuracy and the speed of convergence an improving arc-length iteration method for solving nonlinear increment finite element equations is presented. Numerical examples are given and compared with available solutions. It is shown that the proposed method is more efficient than existing finite element method.
The Efficacy of the Momentum Balance Method in Transverse Impact Problems
Authors: Yigit Ahmet S. , Christoforou Andreas P. 
Published: March 2021

Abstract
An elastic-plastic contact law that incorporates local permanent deformation in the contact zone has been used to investigate the efficacy of the momentum balance method in transverse impact problems. The momentum balance solution is compared to the numerical solution of the same equations using the contact law. It is shown that the momentum balance method gives very good results for the post impact behavior of both the impacter and the beam. In certain cases, it is also shown to yield satisfactory results for the dynamic behavior during contact. It is demonstrated that the momentum balance method with an appropriate coefficient of restitution obtained from the contact law, is physically the same as using the contact law itself, with the difference that the local deformation is neglected.
Split Vibration Modes in Acoustically-Coupled Disk Stacks
Authors: Tseng Jung-Ge , Wickert Jonathan 
Published: March 2021

Abstract
Vibration of an array of stacked annular plates, in which adjacent plates couple weakly through an acoustic layer, is investigated through experimental and theoretical methods. Such acoustic coupling manifests itself through split natural frequencies, beating in the time responses of adjacent or separated plates, and system-level modes in which plates in the array vibrate in- or out-of-phase at closely-spaced frequencies. Laboratory measurements, including a technique in which the frequency response function of all in-phase modes but no out-of-phase modes, or visa versa, is measured, demonstrate the contribution of coupling to the natural frequency spectrum, and identify the combinations of design parameters for which it is important. For the lower modes of primary interest here, the natural frequencies of the out-of-phase system modes decrease as the air layer becomes thinner, while those of the in-phase mode remain sensibly constant at the in vacuo values. A vibration model comprising N classical thin plates that couple through the three-dimensional acoustic fields established in the annular cavities between plates is developed, and its results are compared with measurements of the natural frequencies and mode shapes.
Green’s Function Synthesis for Layered Distributed Parameter Systems
Authors: Lueschen Gerhard G. G. , Bergman Lawrence. A. 
Published: March 2021

Abstract
Dynamic Green’s functions for a class of layered distributed parameter systems are derived using a new method. The resulting system Green’s function, which is comprised of the elemental Green’s function of each of the substructures, defines the dynamics of the fully coupled system. Green’s functions for sandwiched beams with both identical and different layer properties are derived. The result retains the accuracy of the constituent elemental Green’s functions. The application of the method to other layered structures is immediate as long as the elemental Green’s functions of the substructures are known.
Effects of the Electromagnetic Forces on Vibrational Behavior of the Laminated Mechanical Structure of Stator Cores
Authors: Ozturk Cuneyt 
Published: March 2021

Abstract
Stator laminations can have mutual excitation sources depending to the inertial forces that can excite the mechanical resonances and radial components of the electromagnetic forces that vary with the magnetic flux changes and the magnetostrictive forces.
Magnetostrictive forces can appear depending to the material properties of the plates and have mechanical and magnetic causes Mechanical properties of the lamination plates can be determined both in numerical and experimental methods.
Magnetostrictive effects of the laminations have significant contribution to the audible noise of electric motors. The combined effects of radial components of electromagnetic forces and magnetostrictive deformation can cause further amplification problems of noise.
This study investigates the effects of magnetostrictive forces on the laminated mechanical structure of stator core by referring to the changes of the plate materials depending to applicable heat treatments, magnetic properties and silicon alloying that were all considered as factors to modify the effects of magnetostriction.
Analysis of the Equations of Linear Controlled Structures
Authors: Ma F. , Lee W. C. 
Published: March 2021

Abstract
The coefficients of the equation of a linear controlled structure are arbitrary matrices lacking the usual properties of symmetry and definiteness. Classical modal analysis is extended in this paper so as to apply to structures with nonsymmetric coefficients. The extension utilizes equivalence transformations and does not require conversion of the equations of motion to first-order forms. Compared with the state-space approach, the generalized modal analysis can offer substantial reduction in computational effort and ample physical insight.
An Operator-Adjoint Approach to Electrical Impedance Tomography
Authors: Wade J. G. 
Published: March 2021

Abstract
Electrical impedance tomography (EIT) is a nondestructive imaging technique whereby spatial variations in the electrical conductivity of a medium can be determined from measurements of the electric current and potential on the boundary of the medium. The EIT problem is naturally viewed as a distributed parameter inverse problem, and in this paper it is formulated as a least-squares minimization problem for the unknown conductivity function. The main focus is on a mathematical and numerical “adjoint” approach whereby the the derivatives of least-squares function may be computed efficiently when the number of degrees of freedom in the conductivity is large. Numerical examples are provided.
On the Local Regularization of Inverse Problems of Volterra Type
Authors: Lamm Patricia K. 
Published: March 2021

Abstract
We consider a local regularization method for the solution of first-kind Volterra integral equations with convolution kernel. The local regularization is based on a splitting of the original Volterra operator into “local” and “global” parts, and a use of Tikhonov regularization to stabilize the inversion of the local operator only. The regularization parameters for the local procedure include the standard Tikhonov parameter, as well as a parameter that represents the length of the local regularization interval. We present a convergence theory for the infinite-dimensional regularization problem and show that the regularized solutions converge to the true solution as the regularization parameters go to zero (in a prescribed way). In addition, we show how numerical implementation of the ideas of local regularization can lead to the notion of “sequential Tikhonov regularization” for Volterra problems; this approach has been shown in (Lamm and Eldén, 1995) to be just as effective as Tikhonov regularization, but to be much more efficient computationally.
Parameter Estimation for an Imperfectly Clamped Plate: Numerical Examples
Authors: Banks H. T. , Smith R. C. , Wang Yun 
Published: March 2021

Abstract
The problems associated with maintaining truly fixed (zero displacement and slope) or simple (zero displacement and moment) boundary conditions in applications involving vibrating structures have led to the development of models which admit slight rotation and displacement at the boundaries. In this paper, numerical examples demonstrating the dynamics of a model for a circular plate with imperfectly clamped boundary conditions are presented. The latitude gained when using the model for estimating parameters through fit-to-data techniques is also demonstrated. Through these examples, the manner in which the model accounts for the physical manifestation of imperfectly clamped edges is illustrated, and issues regarding the use of the model in physical experiments are defined.
A Numerical Algorithm for Determining a Coefficient in an Elliptic Equation
Authors: Lowe Bruce D. , Rundell William 
Published: March 2021

Abstract
We consider the question of recovering coefficients such as q or k from the equation −∇.(k∇uj) + q(x)uj = fj(x) in a domain Ω ⊂ Rn where uj(x) is subject to Dirichlet boundary conditions. The non-homogeneous source terms {fj(x)}j=1∞ form a basis for L2(Ω). We will prove that a unique determination is possible from data measurements consisting of the average flux leaving a fixed subset of the boundary of the region for each input source. The particular aplication we have in mind is the recovery of interior parameters in heat conduction problems given that we can only make measurements on the boundary, but are able to generate a sequence of internal heat sources. An algorithm that allows efficient numerical reconstruction of the coefficients from finite data will be given.
An Optimization Based Approach to Flow Matching for Burger’s Equation With a Forcing Term
Authors: Herdman Terry L. , Kang Kyehong 
Published: March 2021

Abstract
We consider the use of a numerical optimization technique to solve an inverse problem for Burger’s equation with a periodic forcing term. The solution depends on the initial data profile. The goal is to obtain an optimal continuous linear initial profile which generates the fixed target solution using a numerical optimization technique. Because Burger’s equation is time dependent, the cost function measures the difference between the target and the computed solution at a fixed final time. The optimization algorithm utilizes BFGS updates without computing Hessians and a line search is applied as a globalization. Burger’s equation is solved by a generalized Lax-Friedrichs scheme. This problem is motivated by flow matching problems in optimal design of nozzles and 1-dimensional ducts (see [1]).
On the Inverse Multiplicative Eigenvalue Problem With an Engineering Application
Authors: Sivan Dmitri D. , Ram Yitshak M. 
Published: March 2021

Abstract
The problem of determining the masses of a mass-spring system is an inverse multiplicative eigenvalue problem. Generally, the solutions of this problem are not yet fully characterised. Since all known methods of solution follow an iterative approach, the possibility of developing a closed-form algorithm is examined. Although such method is found for the two and three degree-of-freedom systems, it appears to be impractical for higher order systems. Two well known existing algorithms are then examined numerically. Both converge locally at a quadratic rate. However, for practical applications, a globally converging algorithm may be more effective. In this paper a new, linearly converging algorithm is advised. The three methods are then tested on some selected numerical examples, and their performances compared.
New Approaches for Identifying Structural Models
Authors: Cogan Scott , Lallement Gérard , Sanseigne Laetitia 
Published: March 2021

Abstract
The present synthesis highlights the recent developments in the research work at the R.C.A.M.L. concerning the difficulties encountered at various stages of the correcting process of linear elastodynamics finite element models and some of the solutions suggested to reduce them : optimizing test preparation, combining the principle of selective sensitivity with the concept of pseudo-tests, utilizing additional information coming from base excitations, quantifying the quality of the updated model for applications such as structural modifications or dynamic sub-structuring.
Application of a FRF Based Model Updating Technique for the Validation of Finite Element Models of Components of the Automotive Industry
Authors: Lammens Stefan , Brughmans Marc , Leuridan Jan , Heylen Ward , Sas Paul 
Published: March 2021

Abstract
This paper presents two applications of the RADSER model updating technique (Lammens et al. (1995) and Larsson (1992)). The RADSER technique updates finite element model parameters by solution of a linearised set of equations that optimise the Reduced Analytical Dynamic Stiffness matrix based on Experimental Receptances.
The first application deals with the identification of the dynamic characteristics of rubber mounts.
The second application validates a coarse finite element model of a subframe of a Volvo 480.
Selective Sensitivity for Model Updating With Modal Data
Authors: Gola Muzio M. , Somà Aurelio 
Published: March 2021

Abstract
In the present work a criterion for the minimum measured data set (modes and degree of freedom) required for a successful updating is established in the case of the inverse sensitivity method. The finite element model is used as a tool for the pre-analysis in order to plan the modal experiments, the selection of modes and degree of freedom to put into play in the updating procedure are obtained though the evaluation covariance matrix of the estimated parameters.
A two stage procedure is proposed, in the first part of the work the modal sensitivity problem is reviewed in order to illustrate a systematic procedure capable of enucleating the set of modes that effectively contributes to the updating procedure. Then the procedure is extended to the determination of the minimum number of degrees of freedom to be measured in relation to a desired upper limit for the standard deviation of the structural parameters which are to be updated.
Simple frame structures with different parameter locations are used as examples, the convergence on two parameters maps is used as demonstration of the powerful of the selection procedure to predict the chances of the successful updating.
Mode Shape Expansion Techniques for Model Error Localization and Damage Detection
Authors: Levine-West Marie B. , Milman Mark H. 
Published: March 2021

Abstract
Several methods for mode shape expansion are investigated. The most popular methods use the dynamic equations of motions to obtain direct solutions, or use orthogonal projections. Both approaches can also be formulated as constrained optimization problems. To account for uncertainties in the measurements and in the prediction, a new expansion technique based on least squares minimization with quadratic inequality constraints (LSQI) is proposed. Each modal expansion technique is evaluated with experimental data obtained on the Micro-Precision Interferometer testbed, using both the pre-test and updated analytical models. The robustness of these methods is verified with respect to measurement noise and model error. It is shown that the proposed LSQI method has the best performance and can reliably predict mode shapes, and can be used to locate damage elements, even in very adverse situations. A new LSQI algorithm is also proposed which significantly decreases the solution time.
Model Updating of Evolutionary Structures
Authors: Levine-West Marie B. , Melody James W. 
Published: March 2021

Abstract
A methodology is proposed for dynamic testing, modal identification and model correlation of structures which are assembled in an evolutionary manner. The methodology prescribes initial testing of the base structure without any attached components. As components are added onto the base structure, additional tests are performed. Three testing options are proposed, all of which enable to update the physical parameters of the components only using a Bayesian Estimation Technique (BET). Improvements to former BET implementations have been made, all of which contribute to higher fidelity models and more efficient computational times. These improvements include an optimal modal expansion technique, an error localization technique based on element modal strain energy errors, a model reduction option with component mode synthesis, and a line search algorithm to accelerate convergence. The proposed methodology has been successfully tested on an actual evolutionary structure, and significant improvement from the updated pre-test model are demonstrated.
The Dynamic Effects of Robotic Grasping Considering Flexible Joints
Authors: Kövecses J. , Fenton R. G. , Cleghorn W. L. 
Published: March 2021

Abstract
In this paper the dynamics of an important and frequently used robotic working process is investigated. The robot manipulator approaches, suddenly grasps and lifts a three dimensional object which is travelling on a conveyor. The spatial robot manipulator has two rigid links, rigid rotors and flexible joints. In order to model the joint flexibility, one-degree of freedom torsional springs have been used. The effects of continuous and discontinuous constraint equations are analysed. Simulation results are presented.
Stroboscope Phase Shifting Shearography for Automated Vibration Measurement
Authors: Chen Frank , Griffen Christopher T. , Hung Yau Y. 
Published: March 2021

Abstract
A new method for measurement and visualization of structural dynamic vibration characteristics is presented. Using digital shearography as an imaging tool combined with a stroboscopic phase shifting technique for quantitative fringe pattern interpretation, the fullfield modeshape amplitude and phase distribution is calculated. Theory together with experimental verification is discussed.
High Speed Digital Holography for Measuring Time-Dependent Displacement and Vibrations
Authors: Hung Y. Y. , Griffen C. T. 
Published: March 2021

Abstract
This paper presents a novel technique allowing time-dependent displacement of an object to be studied by continuously digitizing the speckle images using a high speed image acquisition system. Instead of generating fringe patterns, the displacement versus time for any point of interest can be studied. Therefore, the technique is equivalent to “many” massless and noncontact displacement sensors, which is particularly useful for vibration measurement.
apoA2 correlates to gestational age with decreased apolipoproteins A2, C1, C3 and E in gestational diabetes
Authors: Ramanjaneya Manjunath , Butler Alexandra E , Bashir Mohammed , Bettahi Ilham , Moin Abu Saleh Md , Ahmed Lina , Elrayess Mohamed A , Hunt Steven C , Atkin Stephen L , Abou-Samra Abdul Badi 
Published: March 2021

IntroductionPregnant women with gestational diabetes mellitus (GDM) are at risk of adverse outcomes, including gestational hypertension, pre-eclampsia, and preterm delivery. This study was undertaken to determine if apolipoprotein (apo) levels differed between pregnant women with and without GDM and if they were associated with adverse pregnancy outcome.Research design and methodsPregnant women (46 women with GDM and 26 women without diabetes (ND)) in their second trimester were enrolled in the study. Plasma apos were measured and correlated to demographic, biochemical, and pregnancy outcome data.ResultsapoA2, apoC1, apoC3 and apoE were lower in women with GDM compared with control women (p=0.0019, p=0.0031, p=0.0002 and p=0.015, respectively). apoA1, apoB, apoD, apoH, and apoJ levels did not differ between control women and women with GDM. Pearson bivariate analysis revealed significant correlations between gestational age at delivery and apoA2 for women with GDM and control women, and between apoA2 and apoC3 concentrations and C reactive protein (CRP) as a measure of inflammation for the whole group.ConclusionsApoproteins apoA2, apoC1, apoC3 and apoE are decreased in women with GDM and may have a role in inflammation, as apoA2 and C3 correlated with CRP. The fact that apoA2 correlated with gestational age at delivery in both control women and women with GDM raises the hypothesis that apoA2 may be used as a biomarker of premature delivery, and this warrants further investigation.
Implantable cardiac defibrillator events in patients with arrhythmogenic right ventricular cardiomyopathy
Authors: Woźniak Olgierd , Borowiec Karolina , Konka Marek , Cicha-Mikołajczyk Alicja , Przybylski Andrzej , Szumowski Łukasz , Hoffman Piotr , Poślednik Krzysztof , Biernacka Elżbieta Katarzyna 
Published: March 2021

ObjectiveArrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with a risk of sudden cardiac death. Optimal risk stratification is still under debate. The main purpose of this long-term, single-centre observation was to analyse predictors of appropriate and inappropriate implantable cardioverter-defibrillator (ICD) interventions in the population of patients with ARVC with a high risk of life-threatening arrhythmias.MethodsThe study comprised 65 adult patients (median age 40 years, 48 men) with a definite diagnosis of ARVC who received ICD over a time span of 20 years in primary (40%) or secondary (60%) prevention of sudden cardiac death. The study endpoints were first appropriate and inappropriate ICD interventions (shock or antitachycardia pacing) after device implantation.ResultsDuring a median follow-up of 7.75 years after ICD implantation, nine patients died and six individuals underwent heart transplantation. Appropriate ICD interventions occurred in 43 patients (66.2%) and inappropriate ICD interventions in 18 patients (27.7%). Multivariable analysis using cause-specific hazard model identified three predictors of appropriate ICD interventions: right ventricle dysfunction (cause-specific HR 2.85, 95% CI 1.56 to 5.21, p<0.001), age <40 years at ICD implantation (cause-specific HR 2.37, 95% CI 1.13 to 4.94, p=0.022) and a history of sustained ventricular tachycardia (cause-specific HR 2.55, 95% CI 1.16 to 5.63, p=0.020). Predictors of inappropriate ICD therapy were not found. Complications related to ICD implantation occurred in 12 patients.ConclusionsRight ventricle dysfunction, age <40 years and a history of sustained ventricular tachycardia were predictors of appropriate ICD interventions in patients with ARVC. The results may be used to improve risk stratification before ICD implantation.