A General Visco-Hyperelastic Model for Dielectric Elastomers and Its Efficient Simulation Based on Complex Frequency Representation

2015 ◽  
Vol 07 (01) ◽  
pp. 1550011 ◽  
Author(s):  
Yongquan Wang ◽  
Hualing Chen ◽  
Yanjie Wang ◽  
Dichen Li
Keyword(s):  
Electromechanical Coupling ◽  
Dielectric Elastomers ◽  
Complex Frequency ◽  
Energy Potential ◽  
Mechanical Deformations ◽  
Convolution Integral Equation ◽  
Frequency Representation ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Hyperelastic Model

A general visco-hyperelastic model for dielectric elastomers (DE) is presented in this paper, derived from the Quasi-Linear Viscoelastic (QLV) framework. To gain a physical insight into the time-dependent constitutive relation and solve it efficiently, a complex frequency representation of the convolution integral equation, with the legible form of block-scheme, is specifically constructed, in which the viscoelastic stress is interpreted considering the instantaneous response (depicted by Yeoh strain energy potential) as a signal filtered by a linear system (superposition of characteristic modes of the time relaxation function, i.e., Prony series). By incorporating the effects of electrostatic pressure, the model is further extended to the electromechanical coupling state, which can be expediently implemented by the general software, MATLAB/Simulink. Comparisons of the theoretical predictions from the proposed model with the experimental results previously reported (for VHB elastomers) show good agreements over a wide range of stretch rates (from 10-4 to ~ 1 s-1), whether the membrane is only subjected to large mechanical deformations, or undergoes electric loads simultaneously.

QCD at Fixed Order: Processes

2018 ◽  
Author(s):  
John Campbell ◽  
Joey Huston ◽  
Frank Krauss
Keyword(s):  
Hadron Collider ◽  
Detailed Comparison ◽  
Theoretical Description ◽  
Higgs Bosons ◽  
Final States ◽  
Collider Physics ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Fixed Order ◽  
The Subject

At the core of any theoretical description of hadron collider physics is a fixed-order perturbative treatment of a hard scattering process. This chapter is devoted to a survey of fixed-order predictions for a wide range of Standard Model processes. These range from high cross-section processes such as jet production to much more elusive reactions, such as the production of Higgs bosons. Process by process, these sections illustrate how the techniques developed in Chapter 3 are applied to more complex final states and provide a summary of the fixed-order state-of-the-art. In each case, key theoretical predictions and ideas are identified that will be the subject of a detailed comparison with data in Chapters 8 and 9.

SIMULATION OF AN AXISYMMETRIC RISING BUBBLE BY A MULTIPLE RELAXATION TIME LATTICE BOLTZMANN METHOD

2009 ◽  
Vol 23 (24) ◽  
pp. 4907-4932 ◽  
Author(s):  
ABBAS FAKHARI ◽  
MOHAMMAD HASSAN RAHIMIAN
Keyword(s):  
Free Surface ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Rise Velocity ◽  
Rising Bubble ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Multiple Relaxation Time ◽  
Bubble Rising ◽  
Boltzmann Method

In this paper, the lattice Boltzmann method is employed to simulate buoyancy-driven motion of a single bubble. First, an axisymmetric bubble motion under buoyancy force in an enclosed duct is investigated for some range of Eötvös number and a wide range of Archimedes and Morton numbers. Numerical results are compared with experimental data and theoretical predictions, and satisfactory agreement is shown. It is seen that increase of Eötvös or Archimedes number increases the rate of deformation of the bubble. At a high enough Archimedes value and low Morton numbers breakup of the bubble is observed. Then, a bubble rising and finally bursting at a free surface is simulated. It is seen that at higher Archimedes numbers the rise velocity of the bubble is greater and the center of the free interface rises further. On the other hand, at high Eötvös values the bubble deforms more and becomes more stretched in the radial direction, which in turn results in lower rise velocity and, hence, lower elevations for the center of the free surface.

scholarly journals Impact of Transformer Turns Ratio on the Power Losses and Efficiency of the Wide Range Isolated Buck–Boost Converter for Photovoltaic Applications

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5645
Author(s):  
Hamed Mashinchi Maheri ◽  
Dmitri Vinnikov ◽  
Andrii Chub ◽  
Vadim Sidorov ◽  
Elizaveta Liivik
Keyword(s):  
High Efficiency ◽  
Input Voltage ◽  
Power Losses ◽  
Efficient Operation ◽  
Wide Range ◽  
Photovoltaic Applications ◽  
Theoretical Predictions ◽  
Converter Topology ◽  
Isolation Transformer ◽  
The Impact

In this paper, the impact of transformer turns ratio on the performance of the quasi-Z-source galvanically isolated DC-DC converters is studied. Embedded buck–boost functionality enables these converters to regulate the input voltage and load in a wide range, which makes them suitable for such demanding application as photovoltaic microconverters. The isolation transformer here plays a central role as its turns ratio defines the point of transition between the boost and buck modes and overall capability of the converter to regulate the input voltage in a wide range at high efficiency. The studied quasi-Z-source galvanically isolated DC-DC converter is benchmarked in terms of power loss of components and weighted power conversion efficiency for three different turns ratios of isolation transformer to achieve the best and optimized turns ratio lead to the efficient operation. Operation in a wide range of input voltage at high efficiency is the main criterion for assessing the effect of turns ratio on the efficiency of the converter. The proposed loss model and theoretical predictions of the efficiency were validated with the help of a 300 W experimental prototype of the photovoltaic microconverter based on the quasi-Z-source galvanically isolated DC-DC converter topology.

scholarly journals The optically bright post-AGB population of the LMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 415-420
Author(s):  
Els van Aarle ◽  
Hans van Winckel ◽  
Tom Lloyd Evans ◽  
Peter R. Wood
Keyword(s):  
Selection Process ◽  
Shell Morphology ◽  
High Spectral Resolution ◽  
Agb Stars ◽  
Limited Sample ◽  
Fundamental Properties ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Circumstellar Shell ◽  
Important Structure

AbstractThe detected variety in chemistry and circumstellar shell morphology of the limited sample of Galactic post-AGB stars is so large, that there is no consensus yet on how individual objects are linked by evolutionary channels. The evaluation is complicated by the fact that the distances and hence luminosities of these objects are poorly known. In this contribution we report on our project to overcome this problem by focusing on a significant sample of post-AGB stars with known distances: those in the LMC. Via cross-correlation of the infrared SAGE-SPITZER catalogue with optical catalogues we selected a sample of 322 LMC post-AGB candidates based on their position in the various colour-colour diagrams. We determined the fundamental properties of 82 of them, using low resolution optical spectra that we obtained at Siding Spring and SAAO. We selected a subsample to be studied at high spectral resolution in order to obtain accurate abundances of a wide range of species. This will allow us to connect the theoretical predictions with the obtained surface chemistry at a given luminosity and metallicity. By this, we want to constrain important structure parameters of the evolutionary models. Preliminary results of the selection process are presented.

A dynamic visco-hyperelastic model of dielectric elastomers and their energy dissipation characteristics

2013 ◽  
Vol 112 (2) ◽  
pp. 339-347 ◽  
Author(s):  
Yongquan Wang ◽  
Huanhuan Xue ◽  
Hualing Chen ◽  
Junhua Qiang
Keyword(s):  
Energy Dissipation ◽  
Dielectric Elastomers ◽  
Hyperelastic Model

scholarly journals Mapping intrinsic electromechanical responses at the nanoscale via sequential excitation scanning probe microscopy empowered by deep data

2018 ◽  
Vol 6 (1) ◽  
pp. 55-63 ◽  
Author(s):  
Boyuan Huang ◽  
Ehsan Nasr Esfahani ◽  
Jiangyu Li
Keyword(s):  
Scanning Probe Microscopy ◽  
Data Analytics ◽  
Electromechanical Coupling ◽  
Principal Component ◽  
Scientific Data ◽  
Scanning Probe ◽  
Physical Analysis ◽  
Brute Force ◽  
Probe Microscopy ◽  
Wide Range

Abstract Ever-increasing hardware capabilities and computation powers have enabled acquisition and analysis of big scientific data at the nanoscale routine, though much of the data acquired often turn out to be redundant, noisy and/or irrelevant to the problems of interest, and it remains nontrivial to draw clear mechanistic insights from pure data analytics. In this work, we use scanning probe microscopy (SPM) as an example to demonstrate deep data methodology for nanosciences, transitioning from brute-force analytics such as data mining, correlation analysis and unsupervised classification to informed and/or targeted causative data analytics built on sound physical understanding. Three key ingredients of such deep data analytics are presented. A sequential excitation scanning probe microscopy (SE-SPM) technique is first developed to acquire high-quality, efficient and physically relevant data, which can be easily implemented on any standard atomic force microscope (AFM). Brute-force physical analysis is then carried out using a simple harmonic oscillator (SHO) model, enabling us to derive intrinsic electromechanical coupling of interest. Finally, principal component analysis (PCA) is carried out, which not only speeds up the analysis by four orders of magnitude, but also allows a clear physical interpretation of its modes in combination with SHO analysis. A rough piezoelectric material has been probed using such a strategy, enabling us to map its intrinsic electromechanical properties at the nanoscale with high fidelity, where conventional methods fail. The SE in combination with deep data methodology can be easily adapted for other SPM techniques to probe a wide range of functional phenomena at the nanoscale.

scholarly journals The Stability of Incremental Analysis Update

2018 ◽  
Vol 146 (10) ◽  
pp. 3259-3275 ◽  
Author(s):  
Lawrence L. Takacs ◽  
Max J. Suárez ◽  
Ricardo Todling
Keyword(s):  
Digital Filter ◽  
General Circulation ◽  
Circulation Model ◽  
Stability Diagram ◽  
Recent Attempt ◽  
Complex Frequency ◽  
Incremental Analysis ◽  
Wide Range ◽  
The Stability ◽  
Background Fields

Abstract A recent attempt to downscale the 50-km MERRA-2 analyses to 7 km revealed an instability associated with the incremental analysis update (IAU) procedure that has thus far gone unnoticed. A theoretical study based on a simple damped harmonic oscillator with complex frequency provides the framework to diagnose the problem and suggests means to avoid it. Three possible approaches to avoid the instability are to (i) choose an “ideal” ratio of the lengths of the predictor and corrector steps of IAU based on a theoretical stability diagram, (ii) time average the background fields used to construct the IAU tendencies with given frequency, or (iii) apply a digital filter modulation to the IAU tendencies. All these are shown to control the instability for a wide range of resolutions when doing up- or downscaling, experiments with the NASA GMAO atmospheric general circulation model. Furthermore, it is found that combining IAU with the ensemble recentering step typical of hybrid ensemble–variational approaches also results in an instability based on the same mechanisms in the members of the ensemble. An example of such occurrence arises in an experiment performed with the GMAO 12.8-km hybrid 4D-EnVar system. Modulation of the ensemble IAU tendencies with a digital filter is shown to avoid the instability. In addition, the stability of certain 4D incremental analysis update (4DIAU) implementations is analyzed and a suggestion is made to improve its results, though a complete study of this subject is postponed to a follow-up work.

Analyze the Transient Response of a Control Systems

2013 ◽  
Vol 706-708 ◽  
pp. 639-643
Author(s):  
Wei Yan ◽  
Yong Chun Yang ◽  
Xu Feng Guo
Keyword(s):  
Control Systems ◽  
Transfer Functions ◽  
System Model ◽  
Complex Frequency ◽  
Frequency Representation ◽  
Time Domain Response ◽  
Poles And Zeros ◽  
System Analyst ◽  
And Control ◽  
Relationship Of

It is important for the control system analyst to understand the complete relationship of the complex-frequency representation of a linear system, the poles and zeros of its transfer function, and its time-domain response to step and other inputs. In such areas as signal processing and control, many of the analysis and designed collations are done in the complex-frequency plane, where a system model is represented in terms of the poles and zeros of its transfer functions.

On the Theory and Practice of Multifactor Portfolios

2019 ◽  
Keyword(s):  
Considerable Effect ◽  
Theory And Practice ◽  
Single Factor ◽  
Information Ratio ◽  
Multiple Exposures ◽  
Investment Choice ◽  
Number Of Factors ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Relative Factor

Investors interested in factor investing often seek exposure to several factors, not just one or two. The decision on how to implement multiple exposures may have a considerable effect on performance. In this article, the author considers the investment choice between a set of single-factor subportfolios and a single integrated portfolio. He defines factor exposures in a way that precisely relates relative factor exposures to the number and correlation of factors and predicts analytically consequent changes in risk and return. Theoretically, integrated portfolios increasingly outperform segregated portfolios when the number of factors is large and average correlation is low. He tests his predictions by generating over 1,000 matched pairs of historical portfolios using a wide range of factor definitions. This contrasts with the existing literature, which typically focuses on a handful of portfolios using particular versions of factors. The empirical results strongly support the theoretical predictions. In practical terms, an integrated portfolio of four orthogonal factors generates twice the factor exposure of the corresponding set of single-factor portfolios, twice the outperformance, and a 40% higher information ratio.

A Chambered Porous Damper for Rotor Vibration Control: Part I—Concept Development

1993 ◽  
Vol 115 (2) ◽  
pp. 360-365 ◽  
Author(s):  
J. Tecza ◽  
J. Walton
Keyword(s):  
Concept Development ◽  
Squeeze Film ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
High Eccentricity ◽  
Wide Range ◽  
Squeeze Film Dampers ◽  
Theoretical Predictions ◽  
Damper Design ◽  
Control Part

In this paper a novel, high-load chambered porous damper design, supporting analysis, and experimental results are presented. It was demonstrated that significant damping can be generated from the viscous discharge losses of capillary tubes arranged in chambered segments with large radial clearances and that the resulting damping is predictable and fairly constant with speed and eccentricity ratio. This design avoids the nonlinearities associated with high-eccentricity operation of conventional squeeze film dampers. Controlled orbit tests with a porous chambered configuration were completed and favorably compared with theoretical predictions. The ability to accommodate high steady-state and transient imbalance conditions makes this damper well suited to a wide range of rotating machinery, including aircraft gas turbine engines.

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