scholarly journals Ultrathin Acoustic Parity-Time Symmetric Metasurface Cloak

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Hao-xiang Li ◽  
María Rosendo-López ◽  
Yi-fan Zhu ◽  
Xu-dong Fan ◽  
Daniel Torrent ◽  
...  
Keyword(s):  
Material Properties ◽  
Material Parameters ◽  
Artificial Material ◽  
Coordinate Grid ◽  
Time Symmetry ◽  
Audible Sound ◽  
Acoustic Media ◽  
Working Frequency

Invisibility or unhearability cloaks have been made possible by using metamaterials enabling light or sound to flow around obstacle without the trace of reflections or shadows. Metamaterials are known for being flexible building units that can mimic a host of unusual and extreme material responses, which are essential when engineering artificial material properties to realize a coordinate transforming cloak. Bending and stretching the coordinate grid in space require stringent material parameters; therefore, small inaccuracies and inevitable material losses become sources for unwanted scattering that are decremental to the desired effect. These obstacles further limit the possibility of achieving a robust concealment of sizeable objects from either radar or sonar detection. By using an elaborate arrangement of gain and lossy acoustic media respecting parity-time symmetry, we built a one-way unhearability cloak able to hide objects seven times larger than the acoustic wavelength. Generally speaking, our approach has no limits in terms of working frequency, shape, or size, specifically though we demonstrate how, in principle, an object of the size of a human can be hidden from audible sound.

Modeling the Inflation Response of C57BL/6 Mouse Sclera

2011 ◽  
Author(s):  
Kristin M. Myers ◽  
Thao D. Nguyen
Keyword(s):  
Material Properties ◽  
Soft Tissues ◽  
Ganglion Cells ◽  
The United States ◽  
Small Rodent ◽  
Tissue Samples ◽  
Tissue Microstructure ◽  
Material Parameters ◽  
Meaningful Material

Small rodent models have become increasingly useful to investigate how the mechanical properties of soft tissues may influence disease development. These animal models allow access to aged, diseased, or genetically-altered tissue samples, and through comparisons with wild-type or normal tissue it can be explored how each of these variables influence tissue function. The challenges to deriving meaningful material parameters for these small tissue samples include designing physiologically-relevant mechanical testing protocols and interpreting the experimental load-displacement data in an appropriate constitutive framework to quantify material parameters. This study was motivated by determining the possible role of scleral material properties in the development of glaucomatous damage to the retinal ganglion cells (RGC). Glaucoma is one of the leading causes of blindness in the United States and in the world with an estimate of 60 million people affected by this year [1]. Through exploring mouse models, the overall goal of our work is to determine the role of scleral material properties and scleral tissue microstructure in the pathogenesis of glaucoma.

scholarly journals Inverse Approach to Evaluate the Tubular Material Parameters Using the Bulging Test

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Yulong Ge ◽  
Xiaoxing Li ◽  
Lihui Lang
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Material Properties ◽  
Hybrid Algorithm ◽  
Material Parameters ◽  
Inverse Approach ◽  
Material Evaluation ◽  
Levenberg Marquardt ◽  
Bulging Test ◽  
Inverse Procedure

Tubular material parameters are required for both part manufactory process planning and finite element simulations. The bulging test is one of the most credible ways to detect the property parameters for tubular material. The inverse approach provides more effective access to the accurate material evaluation than with direct identifications. In this paper, a newly designed set of bulging test tools is introduced. An inverse procedure is adopted to determine the tubular material properties in Krupkowski-Swift constitutive model of material deformation using a hybrid algorithm that combines the differential evolution and Levenberg-Marquardt algorithms. The constitutive model’s parameters obtained from the conventional and inverse methods are compared, and this comparison shows that the inverse approach is able to offer more information with higher reliability and can simplify the test equipment.

scholarly journals Iterative Analysis of Dielectric Constant of Patch Antenna Substrate at UHF Band

2018 ◽  
Vol 7 (2.16) ◽  
pp. 7
Author(s):  
Amish Kumar Jha ◽  
Bharti Gupta Gupta ◽  
Preety D Swami
Keyword(s):  
Dielectric Constant ◽  
Material Properties ◽  
Patch Antenna ◽  
Dielectric Materials ◽  
Substrate Material ◽  
Frequency Range ◽  
Shape Model ◽  
Iterative Analysis ◽  
Working Frequency ◽  
Simulation Results

This paper presents an investigation of effect of substrate material properties on the performance of antenna. The simulations are tested for 30 different dielectric materials on the basic RPA antenna model as well as on the most common U shape model using CST Microwave Studio. Two designs are proposed. On the basis of simulation results it has been concluded that for the first design the best material is which has a dielectric constant of 2.7 (𝜀r = 2.7) with bandwidth improvements of around 69.33% to 88.6% as compared to the most frequently used materials at present. For the second design the best result is obtained for the material that has dielectric constant in the range 2.0 to 2.7.  For a material having dielectric constant of 2.1 (𝜀r = 2.1) bandwidth improvement of around 11.74% with respect to RT Duroid was observed. For the second design, radiations from all other materials were not available in the working frequency range of 1GHz to 6GHz.  

Non-Linear Contact Analysis of an API Line Pipe Coupling

2009 ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Patrick De Baets ◽  
Wim De Waele
Keyword(s):  
Material Properties ◽  
Element Model ◽  
Test Results ◽  
Line Pipe ◽  
Bending Fatigue ◽  
Material Parameters ◽  
Four Point Bending ◽  
Pipe Coupling ◽  
Contact Behaviour ◽  
The Finite Element Model

In this study, the finite element model of an API Line Pipe threaded pipe connection is presented. The non-linearities in material properties and contact behaviour are discussed. A series of modifications of the standard connection are simulated to gain a better understanding in the influence of geometrical and material parameters on the connection’s performance. Finally, test results obtained from a four-point bending fatigue experiment are presented and compared with numerical simulations.

Characterization of Electromagnetic Properties of MID Materials for High Frequency Applications up to 67 GHz

2014 ◽  
Vol 1038 ◽  
pp. 63-68 ◽  
Author(s):  
Quang Huy Dao ◽  
Aline Friedrich ◽  
Bernd Geck
Keyword(s):  
Radio Frequency ◽  
Material Properties ◽  
High Frequency ◽  
Coplanar Waveguide ◽  
Electromagnetic Properties ◽  
Research Project ◽  
Material Parameters ◽  
Important Material ◽  
Rf Performance

This paper presents results of the research project: "Characterization of the radio frequency (RF) properties of LDS-MID" where RF parameters of laser direct structureable (LDS) molded interconnect device (MID) materials were investigated. First of all the most important material parameters influencing the RF performance of a device are introduced. In the next section the broadband characterization of the metallization and material properties using a coplanar waveguide (CPW) is described. For a selected LDS material the conduction losses due to different metallization compositions are discussed in detail.

Effects of Freeze-Thaw Cycling on Material Properties of Cancellous Cervine Bone as Characterized by Nanoindentation

2013 ◽  
Author(s):  
Alexander K. Landauer ◽  
Philip A. Yuya ◽  
Laurel Kuxhaus
Keyword(s):  
Material Properties ◽  
Applied Load ◽  
Dynamic Testing ◽  
Small Scale ◽  
Phase Lag ◽  
Static Force ◽  
Cross Sectional ◽  
Freeze Thaw ◽  
Material Parameters ◽  
Storage And Loss Moduli

Cancellous bone is an important load-bearing component of whole bone, and due to the plate-and-rod nature of trabeculae, small-scale testing is required to measure material parameters for use in modern analytic techniques such as finite element modeling [1, 2]. These material properties are measurable via nanoindentation techniques. During nanoindentation, the indenter tip is forced into the surface of the material while the applied load and tip displacement are monitored. Using these data, along with the tip’s cross-sectional area, mechanical properties are determined. Dynamic testing quantifies viscoelastic response and can obtain material response parameters such as storage and loss moduli. During dynamic testing, a low magnitude sinusoidal force is superimposed on a constant static force. The displacement response is measured at the same frequency as the applied oscillating force, and the resulting phase lag is related to material damping [3].

An inverse approach to the characterisation of material parameters of piezoelectric discs with triple-ring-electrodes

2019 ◽  
Vol 86 (2) ◽  
pp. 59-65
Author(s):  
Nadine Feldmann ◽  
Benjamin Jurgelucks ◽  
Leander Claes ◽  
Veronika Schulze ◽  
Bernd Henning ◽  
...  
Keyword(s):  
Material Properties ◽  
Measurement Procedure ◽  
Material Parameters ◽  
Inverse Approach ◽  
Precise Knowledge ◽  
Simulation Based Design ◽  
Simulation Based ◽  
Set Up ◽  
Optimisation Procedure ◽  
Single Set

AbstractFor its usage in simulation-based design processes a precise knowledge of the employed material properties is inevitable. In the case of piezoelectric ceramics, the provided material parameters often suffer from large uncertainties and even inconsistencies since the standardised measurement procedure needs several specimens to determine a single set of material parameters. In contrast, the presented measurement set-up allows to calculate material parameters using one unique disc-shaped specimen with an optimised electrode topology. Using an inverse problem approach, fitting material parameters can be found using an optimisation procedure.

Mechanics-based algorithms to determine the current state of a bridge using quasi-static loading and strain measurement

2018 ◽  
Vol 18 (5-6) ◽  
pp. 1874-1888 ◽  
Author(s):  
Pandi Pitchai ◽  
U Saravanan ◽  
Rupen Goswami
Keyword(s):  
Boundary Conditions ◽  
Young’S Modulus ◽  
Material Properties ◽  
High Performance ◽  
High Performance Concrete ◽  
Young's Modulus ◽  
Moving Load ◽  
Material Parameters ◽  
Current State ◽  
Slow Moving

Knowing the current state of a bridge is of interest for a variety of reasons. Some parameters that determine the current state of a bridge are the material properties and boundary conditions. Using strain measurements obtained from a slow-moving vehicle on a bridge, the boundary condition and material properties are determined through a mechanistic-based approach. Observing that the sign of the curvature would change at locations near the support when a load passes over a bridge with end rotational restraints, a methodology for determining the boundary conditions is proposed and validated. The linear elastic properties of the material that the bridge is made up of is determined from the strain measured at locations where the stress is independent of the material property. In this procedure, the structure is analyzed assuming some material properties and the stress at the measured point is determined. Then, the material parameters in the isotropic Hooke’s law are determined so that the stress estimated from the experimentally determined strains agrees with that obtained from the analysis with arbitrarily assumed material parameters. A prestressed high-performance concrete pi-shaped girder tested under a three-axle slow-moving load with strains measured at different locations is used to bring out the efficacy and appropriateness of the proposed methodologies. The mean value of Young’s modulus of the prestressed concrete bridge agrees well with the experimentally determined Young’s modulus.

Preliminary Experimental Study of SMA Knitted Actuation Architectures

Aerospace ◽  
2006 ◽  
Author(s):  
Julianna Evans ◽  
Diann Brei ◽  
Jonathan Luntz
Keyword(s):  
Experimental Study ◽  
Smart Materials ◽  
Material Properties ◽  
Geometric Parameters ◽  
Design Parameters ◽  
Static Force ◽  
Vast Array ◽  
Material Parameters ◽  
Wide Range ◽  
And Control

Nature builds an immense set of materials exhibiting a wide range of behaviors using only a small number of basic compounds. The range of materials comes about through architecture, giving functional structure to the basic materials. Analogously, a new genre of actuators can be derived from existing smart materials through architecture. This paper presents a preliminary experimental study of knitted actuation architectures that yield high strains (up to 73%) with moderate forces (tens of Newtons or more) from basic contracting smart material fibers. By different combinations of the two primary knit loops – purl and knit – a variety of behaviors can be achieved including contraction, rolling, spirals, accordions, arching, and any combination of these across the fabric. This paper catalogs several basic knit stitches and their actuated form: garter, stockinette, seed, rib and I-cord. These knitted architectures provide performance tailorability (force, strain, stiffness, and motion) by manipulation of key design parameters such as the material properties of the wire, the geometric parameters (wire diameter, loop size, and gauge), and architectural parameters (stitch type and orientation). This is demonstrated via a quasi-static force-deflection experimental study with several shape memory alloy garter prototypes with varying geometric parameters. While the basic architecture of a knit is simple, it affords a vast array of architectural combinations and control of geometrical and material parameters that generate a myriad of gross motion capabilities beyond that of current day actuation strategies.

Evaluation of influence of interphase material parameters on effective material properties of three phase composites

2008 ◽  
Vol 68 (3-4) ◽  
pp. 684-691 ◽  
Author(s):  
Sreedhar Kari ◽  
Harald Berger ◽  
Ulrich Gabbert ◽  
Raul Guinovart-Dıaz ◽  
Julian Bravo-Castillero ◽  
...  
Keyword(s):  
Material Properties ◽  
Material Parameters ◽  
Three Phase ◽  
Effective Material Properties
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