Covariance regression for operational modal analysis

2021 ◽  
pp. 107754632199014
Author(s):  
Zhong-Rong Lu ◽  
Dahao Yang ◽  
Linchong Huang ◽  
Li Wang
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Test Case ◽  
Harmonic Load ◽  
Numerical Examples ◽  
Regression Procedure ◽  
Matrix Coefficients ◽  
Regression Approach ◽  
The Matrix ◽  
The One

This article proposes a covariance regression procedure for operational modal analysis. The whole work is mainly twofold. On the one hand, two identities on the covariance are presented and they reveal that the covariance at different times is linearly dependent through both scalar and matrix coefficients. On the other hand, based on the two identities, the scalar covariance regression approach and the matrix covariance regression approach are naturally invoked. In proceeding so, the scalar or matrix coefficients are first acquired through covariance regression, and then, the modal parameters are simply extracted from the coefficients. Numerical examples and a field test case are studied to see the effectiveness of the proposed covariance regression procedure, and the ability to deal with harmonic load, large damping, and closely spaced modes is clearly verified.

scholarly journals Experimental vs Operational Modal Analysis: A Flyover Test Case

2015 ◽  
pp. 365-377
Author(s):  
Giorgio Busca ◽  
Alessio Datteo ◽  
Murathan Paksoy ◽  
Chiara Pozzuoli ◽  
Carlo Segato ◽  
...  
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Test Case

Operational modal parameter identification with correlated colored noise excitation

2021 ◽  
pp. 107754632110113
Author(s):  
Xiangyu Lu ◽  
Huaihai Chen ◽  
Xudong He
Keyword(s):  
Modal Analysis ◽  
Cantilever Beam ◽  
Colored Noise ◽  
Matrix Theory ◽  
Vibration Signal ◽  
Operational Modal Analysis ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Analysis Algorithm ◽  
The Matrix

Operational modal analysis refers to the modal analysis of a structure in its operating state. The advantage of operational modal analysis is that only the output vibration signal of a system is used. The classical operational modal analysis algorithm is based on the white noise excitation assumption, and it is considered that there is no correlation between the excitations; several identification methods have been developed in time and frequency domains. But excitations are not completely independent with each other and not pure white. In this article, the matrix theory is used to prove that the operational modal analysis algorithm can still be used to identify modal parameters when the excitation is correlated. In the simulation, five kinds of colored noise excitations are applied to the cantilever beam with correlated excitations, which shows that the idea proposed in this article is rational. In the experiment, the foundation excitation of colored noise is added to the cantilever beam, which can be regarded as applying several related excitations. It also shows the rationality of this idea.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

Response and Operational Modal Analysis from Wind Tunnel Test of the EOLO Flexible Aircraft

2021 ◽  
Author(s):  
David F. Castillo Zuñiga ◽  
Alain Giacobini Souza ◽  
Roberto G. da Silva ◽  
Luiz Carlos Sandoval Góes
Keyword(s):  
Wind Tunnel ◽  
Modal Analysis ◽  
Wind Tunnel Test ◽  
Operational Modal Analysis ◽  
Flexible Aircraft

scholarly journals Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1602
Author(s):  
Ángel Molina-Viedma ◽  
Elías López-Alba ◽  
Luis Felipe-Sesé ◽  
Francisco Díaz
Keyword(s):  
Modal Analysis ◽  
Energy Absorption ◽  
High Speed ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Image Correlation ◽  
Composite Panel ◽  
Impact Excitation ◽  
Full Field ◽  
The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

scholarly journals Operational modal analysis for characterization of mechanical and thermal–hydraulic fluctuations in simulated neutron noise

2021 ◽  
Vol 373 ◽  
pp. 111017
Author(s):  
Luis Alejandro Torres Delgado ◽  
Vasudha Verma ◽  
Cristina Montalvo ◽  
Abdelhamid Dokhane ◽  
Agustín García-Berrocal
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Neutron Noise

scholarly journals Divergent ⇒ complex amplitudes in two dimensional string theory

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Ashoke Sen
Keyword(s):  
Scattering Amplitudes ◽  
String Theory ◽  
Matrix Model ◽  
Two Dimensional ◽  
Full Matrix ◽  
Instanton Contribution ◽  
The Matrix ◽  
Theory Result ◽  
The One ◽  
Remarkable Agreement

Abstract In a recent paper, Balthazar, Rodriguez and Yin found remarkable agreement between the one instanton contribution to the scattering amplitudes of two dimensional string theory and those in the matrix model to the first subleading order. The comparison was carried out numerically by analytically continuing the external energies to imaginary values, since for real energies the string theory result diverges. We use insights from string field theory to give finite expressions for the string theory amplitudes for real energies. We also show analytically that the imaginary parts of the string theory amplitudes computed this way reproduce the full matrix model results for general scattering amplitudes involving multiple closed strings.

Operational modal analysis of a self-supporting antenna mast

2021 ◽  
Vol 209 ◽  
pp. 104490
Author(s):  
K. Luis García ◽  
K. Maes ◽  
V. Elena Parnás ◽  
G. Lombaert
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis

scholarly journals Exenatide Microspheres for Monthly Controlled-Release Aided by Magnesium Hydroxide

Pharmaceutics ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 816
Author(s):  
Yuxuan Ge ◽  
Zhenhua Hu ◽  
Jili Chen ◽  
Yujie Qin ◽  
Fei Wu ◽  
...  
Keyword(s):  
Controlled Release ◽  
Dosage Form ◽  
Continuous Phase ◽  
Plga Microspheres ◽  
Receptor Agonists ◽  
Monkey Model ◽  
The Matrix ◽  
Glass Membrane ◽  
The One ◽  
Long Acting

GLP-1 receptor agonists are a class of diabetes medicines offering self-regulating glycemic efficacy and may best be administrated in long-acting forms. Among GLP-1 receptor agonists, exenatide is the one requiring the least dose so that controlled-release poly(d, l-lactic-co-glycolic acid) (PLGA) microspheres may best achieve this purpose. Based on this consideration, the present study extended the injection interval of exenatide microspheres from one week of the current dosage form to four weeks by simply blending Mg(OH)2 powder within the matrix of PLGA microspheres. Mg(OH)2 served as the diffusion channel creator in the earlier stage of the controlled-release period and the decelerator of the self-catalyzed degradation of PLGA (by the formed lactic and glycolic acids) in the later stage due to its pH-responsive solubility. As a result, exenatide gradually diffused from the microspheres through Mg(OH)2-created diffusion channels before degradation of the PLGA matrix, followed by a mild release due to Mg(OH)2-buffered degradation of the polymer skeleton. In addition, an extruding–settling process comprising squeezing the PLGA solution through a porous glass membrane and sedimentation-aided solidification of the PLGA droplets was used to prepare the microspheres to ensure narrow size distribution and 95% encapsulation efficiency in an aqueous continuous phase. A pharmacokinetic study using rhesus monkey model confirmed the above formulation design by showing a steady blood concentration profile of exenatide with reduced CMAX and dosage form index. Mg·(OH)2

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