Wave Shape Transformers Based on Transformation Medium Slabs

2013 ◽  
Vol 712-715 ◽  
pp. 1811-1815
Author(s):  
You Gang Ke ◽  
Fu Gui Yang ◽  
Liang Qiao
Keyword(s):  
Numerical Simulations ◽  
Gaussian Beam ◽  
Coordinate Transformations ◽  
Wave Shape ◽  
Transformation Medium ◽  
Theoretical Design ◽  
Planar Wave ◽  
Constitutive Parameters ◽  
Wave Shapes ◽  
Beam Collimation

We propose wave shape transformers using slab transformation media which can transform planar wave shapes to convex or concave ones. By finite embedded coordinate transformations, a transformation is established from a parabola to a plane and the constitutive parameters of slabs are obtained. Numerical simulations are given to validate the performance of the theoretical design. Using such transformers, Gaussian beam collimation and focusing can be realized.

Design of a Wave Shifter with the Exit Direction Controllable Based on Coordinate Transformation Theory

2013 ◽  
Vol 798-799 ◽  
pp. 590-593
Author(s):  
Wen Yan Yan ◽  
You Gang Ke
Keyword(s):  
Numerical Simulations ◽  
Coordinate Transformation ◽  
Longitudinal Axis ◽  
The Other ◽  
Wave Direction ◽  
Transformation Theory ◽  
Transformation Medium ◽  
Theoretical Design ◽  
Constitutive Parameters

We propose a wave shifter with the exit wave direction controllable by using a transformation-medium slab. The coordinate transformation takes two steps. One is along the longitudinal axis to realize shift and the other is on the transversal axis to adjust the exit directon. By using coordinate transformation theory, the constitutive parameters of the slab are obtained. Numerical simulations are further given to validate the performance of the theoretical design.

scholarly journals Numerical Simulations of Clay Tiles Compression

2012 ◽  
Vol 504-506 ◽  
pp. 1403-1408 ◽  
Author(s):  
Jérémie Vignes ◽  
Fabrice Schmidt ◽  
Gilles Dusserre ◽  
Olivier de Almeida ◽  
Jean Frédéric Dalmasso
Keyword(s):  
Numerical Model ◽  
Tensile Stress ◽  
Numerical Simulations ◽  
Compression Tests ◽  
Rheological Study ◽  
Constitutive Parameters ◽  
Actual Geometry ◽  
Clay Tiles ◽  
Force Displacement ◽  
Tribological Parameters

During the pressing step, the clay tiles undergo stresses which result in the appearance of defects. A rheological study, based on free compression tests, allowed to confirm the Elasto-visco-plastic behaviour of the clay. The different constitutive parameters were estimated by fitting the force-displacement experimental curves using the optimisation algorithm (ES Metamodel) implanted in the commercial software Forge 2009®. The influence of the tribological parameters was studied using squeezing numerical simulations of a full tile. The numerical model was validated with experimental squeezing test of technological specimen with a tile lug. Then, we have compared experimental force with the numerical one and deduced that the clay/tool interface is not perfectly sliding. A friction Tresca’s law was used to model the clay/tool interface. Numerical results showed that the actual geometry of tile lug didn’t allow to form correctly the tile. Several areas undergo tensile stress, air traps ,... A new geometry of tile lug was proposed in order to limit this phenomenon. Using a simplified defect criteria (Latham and Cockroft), the numerical model allowed to locate the areas where there is a risk of crack.

Numerical Simulations of Fractional Fourier Transform of Hypergeometric-Gaussian Beam

2013 ◽  
Vol 765-767 ◽  
pp. 780-784 ◽  
Author(s):  
Zhen Feng Yang ◽  
Wen Dan Miao ◽  
Zhen Jun Yang ◽  
Shu Min Zhang
Keyword(s):  
Fourier Transform ◽  
Numerical Simulations ◽  
Gaussian Beam ◽  
Intensity Distribution ◽  
Fractional Fourier Transform ◽  
Focal Length ◽  
Beam Width ◽  
Laser Beams ◽  
New Type ◽  
Lens Focal Length

The fractional Fourier transform (FRFT) of a new type of laser beams called the hypergeometric-Gaussian beam (HyGGB) is investigated in detail. The analytical expression for the FRFT of a HyGGB is derived. The properties of a HyGGB in the FRFT plane with different parameters are illustrated. The results show that the intensity distribution of a HyGGB in the FRFT plane strongly depends on the fractional order, the lens focal length and the initial beam width.

High-order mode Laguerre–Gaussian beam transformation using a 127-actuator deformable mirror: numerical simulations

2011 ◽  
Vol 104 (3) ◽  
pp. 725-733 ◽  
Author(s):  
L. Dong ◽  
P. Yang ◽  
B. Xu ◽  
X. Lei ◽  
Y. Ning ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Gaussian Beam ◽  
High Order Mode ◽  
High Order ◽  
Deformable Mirror ◽  
Order Mode

Experiments and Numerical Simulations on Thin Metallic Plates Subjected to an Explosion

2000 ◽  
Vol 123 (2) ◽  
pp. 203-209 ◽  
Author(s):  
Krzysztof Woznica ◽  
Olivier Pennetier ◽  
Je´ro^me Renard
Keyword(s):  
Numerical Simulations ◽  
High Strain ◽  
Explicit Scheme ◽  
Experimental Setup ◽  
Strain Rates ◽  
Metallic Structure ◽  
Aluminum Alloy 5754 ◽  
Specific Loading ◽  
Simulation Based ◽  
Constitutive Parameters

Submitted to a sudden and a transient loading, a metallic structure quickly evolves toward viscoplastic behavior, including high strain rates. After generalities about the specific loading and the description of the experimental setup, a numerical simulation based on the F.E.M. using an explicit scheme is presented. Three different constitutive laws are discussed: the Perzyna, the Bodner-Partom, and that of Chaboche. The identification of constitutive parameters is made using unidirectional tests on the studied material (aluminum alloy 5754). A comparison between numerical simulations and experiments shows that the method is relevant.

scholarly journals An Improved Passivity-based Control of Electrostatic MEMS Device

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 688 ◽  
Author(s):  
Mutaz Ryalat ◽  
Hazem Salim Damiri ◽  
Hisham ElMoaqet ◽  
Imad AlRabadi
Keyword(s):  
Numerical Simulations ◽  
Controller Design ◽  
Damping Ratio ◽  
Coordinate Transformations ◽  
Parallel Plates ◽  
Microelectromechanical System ◽  
Electrostatic Mems ◽  
Mems Device ◽  
Passivity Based Control ◽  
Improved Performance

It is commonly known that the performance of an electrostatic microelectromechanical system (MEMS) device is limited to a specific range of the full gap distance due to the inherited “pull-in instability” phenomenon. In this work, we design a controller to extend the stabilization range of an electrostatic MEMS device and to enhance its performance. The interconnection and damping assignment-passivity based control (IDA-PBC) method is used and the controller design involves coordinate transformations and a coupling between the mechanical and electrical subsystems of the device. The method deploys a design of a speed observer to estimate the speed, which cannot be directly measured by sensors. The effectiveness of the dynamical controller is verified via numerical simulations; it is evident by the extended travel range of the parallel plates as well as the improved performance of the plates, even with a naturally lighter damping ratio.

scholarly journals Nonsimilar Normal Mode Vibrations of Nonlinear Systems Having Two Degrees of Freedom

1964 ◽  
Vol 31 (2) ◽  
pp. 283-290 ◽  
Author(s):  
R. M. Rosenberg ◽  
J. K. Kuo
Keyword(s):  
Experimental Study ◽  
Nonlinear System ◽  
Nonlinear Systems ◽  
Normal Mode ◽  
Degrees Of Freedom ◽  
Normal Modes ◽  
Wave Shape ◽  
Time Histories ◽  
Mode Vibration ◽  
Wave Shapes

When a nonlinear system having several masses vibrates in normal modes, the time histories of the motion of these masses are, in general, different in wave shape (although in certain special nonlinear systems they differ at most in amplitude, but not in shape). When the wave shapes differ, the normal mode vibration is called nonsimilar. In this paper, nonsimilar normal mode vibrations are analyzed with respect to wave shape and stability. The systems considered are those lying close to systems having similar normal mode vibrations. An example is worked out in detail, and a comparison with an experimental study is reported.

scholarly journals Method to Remove Tilt-to-Length Coupling Caused by Interference of Flat-Top Beam and Gaussian Beam

2019 ◽  
Vol 9 (19) ◽  
pp. 4112 ◽  
Author(s):  
Ya Zhao ◽  
Zhi Wang ◽  
Yupeng Li ◽  
Chao Fang ◽  
Heshan Liu ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Numerical Simulations ◽  
Gaussian Beam ◽  
Laser Interferometer ◽  
Physical Models ◽  
Space Antenna ◽  
Coupling Noise ◽  
Laser Interferometer Space Antenna ◽  
Flat Top Beam ◽  
Special Case

We discuss the tilt-to-length (TTL) coupling noise caused by interference between a flat-top beam and a Gaussian beam. Several physical models are presented to research the effects of non-diffracted and diffracted beams on TTL noise. A special case that can remove TTL coupling noise is discovered and is verified via both theoretical analysis and numerical simulations. The proposed case could provide desirable suggestions for the construction of high-precision interferometers such as the Laser Interferometer Space Antenna (LISA), Taiji program, or other interferometry systems.

scholarly journals Non-closed acoustic cloaking devices enabled by sequential-step linear coordinate transformations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zahra Basiri ◽  
Mohammad Hosein Fakheri ◽  
Ali Abdolali ◽  
Chen Shen
Keyword(s):  
Material Properties ◽  
Free Space ◽  
Incident Radiation ◽  
Coordinate Transformations ◽  
Physical Realization ◽  
Homogeneous Materials ◽  
Meta Atom ◽  
Constitutive Parameters ◽  
Arbitrary Objects ◽  
The Physical Realization

AbstractHitherto acoustic cloaking devices, which conceal objects externally, depend on objects' characteristics. Despite previous works, we design cloaking devices placed adjacent to an arbitrary object and make it invisible without the need to make it enclosed. Applying sequential linear coordinate transformations leads to a non-closed acoustic cloak with homogeneous materials, creating an open invisible region. Firstly, we propose to design a non-closed carpet cloak to conceal objects on a reflecting plane. Numerical simulations verify the cloaking effect, which is completely independent of the geometry and material properties of the hidden object. Moreover, we extend this idea to achieve a directional acoustic cloak with homogeneous materials that can render arbitrary objects in free space invisible to incident radiation. To demonstrate the feasibility of the realization, a non-resonant meta-atom is utilized which dramatically facilitated the physical realization of our design. Due to the simple acoustic constitutive parameters of the presented structures, this work paves the way toward realization of non-closed acoustic devices, which could find applications in airborne sound manipulation and underwater demands.

UNCERTAINTY ANALYSIS OF A ONE-DIMENSIONAL CONSTITUTIVE MODEL FOR SHAPE MEMORY ALLOY THERMOMECHANICAL DESCRIPTION

2014 ◽  
Vol 06 (06) ◽  
pp. 1450067 ◽  
Author(s):  
SERGIO A. OLIVEIRA ◽  
MARCELO A. SAVI ◽  
ILMAR F. SANTOS
Keyword(s):  
Experimental Data ◽  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Uncertainty Analysis ◽  
Numerical Simulations ◽  
Shape Memory ◽  
Tensile Tests ◽  
One Dimensional ◽  
Uncertainty Range ◽  
Constitutive Parameters

The use of shape memory alloys (SMAs) in engineering applications has increased the interest of the accuracy analysis of their thermomechanical description. This work presents an uncertainty analysis related to experimental tensile tests conducted with shape memory alloy wires. Experimental data are compared with numerical simulations obtained from a constitutive model with internal constraints employed to describe the thermomechanical behavior of SMAs. The idea is to evaluate if the numerical simulations are within the uncertainty range of the experimental data. Parametric analysis is also developed showing the most sensitive constitutive parameters that contribute to the uncertainty. This analysis provides the contribution of each parameter establishing the accuracy of the constitutive equations.

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