Component Modal Synthesis Methods Based on Hybrid Models, Part II: Numerical Tests and Experimental Identification of Hybrid Models

A double modal synthesis method in which compatibility conditions at substructure interfaces are ensured by the introduction of loaded modes is presented in this study. These loaded modes, which are obtained by introducing mass loading or stiffness loading along the boundaries, are used to define generalized boundary coordinates. Thus the hybrid models presented in the first part of this study are developed so that they can be derived from test data as results of independent modal identifications. Unlike in classical modal synthesis methods, in this double modal synthesis method, it is not necessary to clamp the interfaces, which is always difficult to carry out during vibration tests. By introducing loaded modes, generalized boundary coordinates which represent boundary deformability in the frequency range under study can be defined.

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Component Modal Synthesis Methods Based on Hybrid Models, Part I: Theory of Hybrid Models and Modal Truncation Methods

Journal of Applied Mechanics ◽

10.1115/1.2901383 ◽

1994 ◽

Vol 61 (1) ◽

pp. 100-108 ◽

Cited By ~ 22

Author(s):

L. Jezequel ◽

H. D. Seito

Keyword(s):

Synthesis Method ◽

Integral Operators ◽

Hybrid Models ◽

Force Distribution ◽

Synthesis Methods ◽

Displacement Distribution ◽

New Methods ◽

Modal Synthesis ◽

Intermediate Problem ◽

Modal Truncation

The assembly of structures along continuous boundaries poses great difficulties for expressing generalized boundary coordinates in modal synthesis, especially in the context of experiments. In order to solve such problems, a hybrid modal synthesis method is proposed in this study. This approach is based on the intermediate problem theory of Weinstein and brings out the duality between the formulation in displacement and the formulation in force. Generalized boundary coordinates are defined by introducing static deformations resulting from force distribution or displacement distribution along the boundaries depending on which formulation is to be used. By introducing integral operators associated with intermediate problems, two new methods of modal truncation can be proposed.

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A Combination of Modal Synthesis and Subspace Iteration for an Efficient Algorithm for Modal Analysis within a FE-Code

Shock and Vibration ◽

10.1155/2003/147898 ◽

2003 ◽

Vol 10 (1) ◽

pp. 27-35 ◽

Cited By ~ 1

Author(s):

M.W. Zehn

Keyword(s):

Eigenvalue Problem ◽

Modal Analysis ◽

Efficient Algorithm ◽

Degrees Of Freedom ◽

Synthesis Method ◽

Problem Solver ◽

Synthesis Methods ◽

Combined Method ◽

Subspace Iteration ◽

Modal Synthesis

Various well-known modal synthesis methods exist in the literature, which are all based upon certain assumptions for the relation of generalised modal co-ordinates with internal modal co-ordinates. If employed in a dynamical FE substructure/superelement technique the generalised modal co-ordinates are represented by the master degrees of freedom (DOF) of the master nodes of the substructure. To conduct FE modal analysis the modal synthesis method can be integrated to reduce the number of necessary master nodes or to ease the process of defining additional master points within the structure. The paper presents such a combined method, which can be integrated very efficiently and seamless into a special subspace eigenvalue problem solver with no need to alter the FE system matrices within the FE code. Accordingly, the merits of using the new algorithm are the easy implementation into a FE code, the less effort to carry out modal synthesis, and the versatility in dealing with superelements. The paper presents examples to illustrate the proper work of the algorithm proposed.

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Torsional Vibration Analysis of Complicated Multi-Branched Shafting Systems by Modal Synthesis Method

Journal of Vibration and Acoustics ◽

10.1115/1.1569949 ◽

2003 ◽

Vol 125 (3) ◽

pp. 317-323 ◽

Cited By ~ 5

Author(s):

Chun-Ping Zou ◽

Duan-Shi Chen ◽

Hong-Xing Hua

Keyword(s):

Torsional Vibration ◽

Vibration Analysis ◽

Synthesis Method ◽

Synthesis Methods ◽

Elastic Coupling ◽

Improved Method ◽

Modal Synthesis ◽

Rigid Connection ◽

Flexible Connections ◽

Fixed Interface

The torsional vibration calculations of the complicated multi-branched system with rigid connection and flexible connections made up of elastic-coupling parts are very difficult to perform using conventional methods. In this paper, a modal synthesis method of torsional vibration analysis for the system is proposed. This approach is an improved method of Hurty’s fixed-interface and Hou’s free-interface modal synthesis methods. Because of the introduction of flexible substructure, the improved modal synthesis method can effectively treat the complicated system in which there exists a rigid connection and a flexible connection that is formed by an elastic-coupling part. When the calculation is performed, the complicated multi-branched system is divided into several substructures that are analyzed by FEM (finite element method) except the special elastic-coupling part that is defined as flexible substructure and treated individually. The efficiency of modal synthesis is improved by choosing suitable number of lower-frequency modes in modal synthesis. As an example of an application of this method, the analysis of torsional vibration of a cam-type engine shafting system is carried out both numerically and experimentally. The results show that the above kind of multi-branched shafting system can be analyzed effectively by the proposed method.

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Structural Dynamics Optimization Based on a Hybrid Inverse Synthesis Method Using a Quadratic Approximation

Journal of Vibration and Acoustics ◽

10.1115/1.1688759 ◽

2004 ◽

Vol 126 (2) ◽

pp. 253-259 ◽

Cited By ~ 2

Author(s):

Alain Schorderet ◽

Thomas Gmu¨r

Keyword(s):

Structural Dynamics ◽

Shape Factor ◽

Synthesis Method ◽

Synthesis Methods ◽

The Novel ◽

Synthesis Algorithm ◽

Numerical Examples ◽

Dynamic Constraints ◽

Modal Synthesis ◽

Synthesis Approach

This paper lies within the framework of the so-called redesign problem of structures subjected to dynamic constraints. A hybrid synthesis algorithm is developed, combining the truncated modal basis of the initial system and the spatial or material co-ordinates of an added component, which is modelled with shell-type finite elements parameterized with respect to a shape factor. Based upon a quadratic inverse formulation, the proposed technique shows several advantages in comparison to other synthesis methods, such as a refined sensitivity strategy, a powerful modal synthesis approach and a simplified optimization phase. Numerical examples are provided illustrating the capabilities of the novel procedure.

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Study for Efficient Simulation of a Full Vehicle System in Mid Frequency Range Using Modal Synthesis Method

10.4271/2005-08-0590 ◽

2005 ◽

Cited By ~ 1

Author(s):

Hiromichi Ebisawa ◽

Yutaka Nagao ◽

Keiichiro Tsutsui ◽

Kenji Yamazaki

Keyword(s):

Synthesis Method ◽

Frequency Range ◽

Efficient Simulation ◽

Full Vehicle ◽

Vehicle System ◽

Modal Synthesis

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Interrelations of Synthesis Method, Polyethylene Glycol Coating, Physico-Chemical Characteristics, and Antimicrobial Activity of Silver Nanoparticles

Nanomaterials ◽

10.3390/nano10122475 ◽

2020 ◽

Vol 10 (12) ◽

pp. 2475

Author(s):

Amirah Shafilla Mohamad Kasim ◽

Arbakariya Bin Ariff ◽

Rosfarizan Mohamad ◽

Fadzlie Wong Faizal Wong

Keyword(s):

Antimicrobial Activity ◽

Silver Nanoparticles ◽

Polyethylene Glycol ◽

Pathogenic Bacteria ◽

Synthesis Method ◽

Chemical Characteristics ◽

Synthesis Methods ◽

Uniform Size ◽

Transmission Electron Microscopy Analysis ◽

Physico Chemical

Silver nanoparticles (AgNPs) have been found to have extensive biomedical and biological applications. They can be synthesised using chemical and biological methods, and coated by polymer to enhance their stability. Hence, the changes in the physico-chemical characteristics of AgNPs must be scrutinised due to their importance for biological activity. The UV-Visible absorption spectra of polyethylene glycol (PEG) -coated AgNPs displayed a distinctive narrow peak compared to uncoated AgNPs. In addition, High-Resolution Transmission Electron Microscopy analysis revealed that the shapes of all AgNPs, were predominantly spherical, triangular, and rod-shaped. Fourier-Transform Infrared Spectroscopy analysis further confirmed the role of PEG molecules in the reduction and stabilisation of the AgNPs. Moreover, dynamic light scattering analysis also revealed that the polydispersity index values of PEG-coated AgNPs were lower than the uncoated AgNPs, implying a more uniform size distribution. Furthermore, the uncoated and PEG-coated biologically synthesised AgNPs demonstrated antagonisms activities towards tested pathogenic bacteria, whereas no antagonism activity was detected for the chemically synthesised AgNPs. Overall, generalisation on the interrelations of synthesis methods, PEG coating, characteristics, and antimicrobial activity of AgNPs were established in this study.

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Sol-Gel Synthesis of the Double Perovskite Sr2FeMoO6 by Microwave Technique

Materials ◽

10.3390/ma14143876 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3876

Author(s):

Jesús Valdés ◽

Daniel Reséndiz ◽

Ángeles Cuán ◽

Rufino Nava ◽

Bertha Aguilar ◽

...

Keyword(s):

Particle Size ◽

Hydrothermal Synthesis ◽

Microwave Radiation ◽

Structural Characteristics ◽

Sol Gel ◽

Synthesis Method ◽

Double Perovskite ◽

Synthesis Methods ◽

X Ray ◽

Sol Gel Synthesis

The effect of microwave radiation on the hydrothermal synthesis of the double perovskite Sr2FeMoO6 has been studied based on a comparison of the particle size and structural characteristics of products from both methods. A temperature, pressure, and pH condition screening was performed, and the most representative results of these are herein presented and discussed. Radiation of microwaves in the hydrothermal synthesis method led to a decrease in crystallite size, which is an effect from the reaction temperature. The particle size ranged from 378 to 318 nm when pH was 4.5 and pressure was kept under 40 bars. According to X-ray diffraction (XRD) results coupled with the size-strain plot method, the product obtained by both synthesis methods (with and without microwave radiation) have similar crystal purity. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques showed that the morphology and the distribution of metal ions are uniform. The Curie temperature obtained by thermogravimetric analysis indicates that, in the presence of microwaves, the value was higher with respect to traditional synthesis from 335 K to 342.5 K. Consequently, microwave radiation enhances the diffusion and nucleation process of ionic precursors during the synthesis, which promotes a uniform heating in the reaction mixture leading to a reduction in the particle size, but keeping good crystallinity of the double perovskite. Precursor phases and the final purity of the Sr2FeMoO6 powder can be controlled via hydrothermal microwave heating on the first stages of the Sol-Gel method.

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Microwave-Assisted vs. Conventional Hydrothermal Synthesis of MoS2 Nanosheets: Application towards Hydrogen Evolution Reaction

Crystals ◽

10.3390/cryst10111040 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1040 ◽

Cited By ~ 1

Author(s):

Getachew Solomon ◽

Raffaello Mazzaro ◽

Vittorio Morandi ◽

Isabella Concina ◽

Alberto Vomiero

Keyword(s):

Hydrothermal Synthesis ◽

Hydrothermal Method ◽

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Current Density ◽

Crystal Morphology ◽

Synthesis Method ◽

Synthesis Methods ◽

Mos2 Nanosheets ◽

Microwave Assisted

Molybdenum sulfide (MoS2) has emerged as a promising catalyst for hydrogen evolution applications. The synthesis method mainly employed is a conventional hydrothermal method. This method requires a longer time compared to other methods such as microwave synthesis methods. There is a lack of comparison of the two synthesis methods in terms of crystal morphology and its electrochemical activities. In this work, MoS2 nanosheets are synthesized using both hydrothermal (HT-MoS2) and advanced microwave methods (MW-MoS2), their crystal morphology, and catalytical efficiency towards hydrogen evolution reaction (HER) were compared. MoS2 nanosheet is obtained using microwave-assisted synthesis in a very short time (30 min) compared to the 24 h hydrothermal synthesis method. Both methods produce thin and aggregated nanosheets. However, the nanosheets synthesized by the microwave method have a less crumpled structure and smoother edges compared to the hydrothermal method. The as-prepared nanosheets are tested and used as a catalyst for hydrogen evolution results in nearly similar electrocatalytic performance. Experimental results showed that: HT-MoS2 displays a current density of 10 mA/cm2 at overpotential (−280 mV) compared to MW-MoS2 which requires −320 mV to produce a similar current density, suggesting that the HT-MoS2 more active towards hydrogen evolutions reaction.

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