scholarly journals Efficient Numerical Analysis of a Periodic Structure of Multistate Unit Cells

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Ladislau Matekovits ◽  
Karu P. Esselle ◽  
Mirko Bercigli ◽  
Rodolfo Guidi
Keyword(s):  
Computational Complexity ◽  
Numerical Analysis ◽  
Single Unit ◽  
Microstrip Line ◽  
Periodic Structures ◽  
Unit Cell ◽  
Active Structure ◽  
Unit Cells ◽  
Synthetic Function

Application of the synthetic function expansion (SFX) algorithm to the analysis of active 1- and 2D periodic structures is presented. The single unit cell consisting of a microstrip line loaded by patches positioned below the line is turned into an active structure by inserting a pair of 2 switches to the two ends of each patch; the states of the pair of switches are changed contemporaneously. Variation of the states of the switches modifies the current distribution on the structure. The tunable multistate unit cell is arranged in 24-, 120-, and 9 × 24 element configurations and numerically analyzed. The computational complexity required for the characterization of the large number of possible configurations is lightened by the use of the proposed numerical method.

Design of Three-Dimensional, Triply Periodic Unit Cell Scaffold Structures for Additive Manufacturing

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Mazher Iqbal Mohammed ◽  
Ian Gibson
Keyword(s):  
Additive Manufacturing ◽  
Periodic Structures ◽  
Three Dimensional ◽  
Unit Cell ◽  
Final Size ◽  
Fused Filament Fabrication ◽  
Cell Structures ◽  
Triply Periodic ◽  
Unit Cells ◽  
Scaffold Structure

Highly organized, porous architectures leverage the true potential of additive manufacturing (AM) as they can simply not be manufactured by any other means. However, their mainstream usage is being hindered by the traditional methodologies of design which are heavily mathematically orientated and do not allow ease of controlling geometrical attributes. In this study, we aim to address these limitations through a more design-driven approach and demonstrate how complex mathematical surfaces, such as triply periodic structures, can be used to generate unit cells and be applied to design scaffold structures in both regular and irregular volumes in addition to hybrid formats. We examine the conversion of several triply periodic mathematical surfaces into unit cell structures and use these to design scaffolds, which are subsequently manufactured using fused filament fabrication (FFF) additive manufacturing. We present techniques to convert these functions from a two-dimensional surface to three-dimensional (3D) unit cell, fine tune the porosity and surface area, and examine the nuances behind conversion into a scaffold structure suitable for 3D printing. It was found that there are constraints in the final size of unit cell that can be suitably translated through a wider structure while still allowing for repeatable printing, which ultimately restricts the attainable porosities and smallest printed feature size. We found this limit to be approximately three times the stated precision of the 3D printer used this study. Ultimately, this work provides guidance to designers/engineers creating porous structures, and findings could be useful in applications such as tissue engineering and product light-weighting.

An Antagonistic Flexural Unit Cell for Design of Shape Morphing Structures

Aerospace ◽  
2004 ◽  
Author(s):  
Aarash Y. N. Sofla ◽  
Dana M. Elzey ◽  
Haydn N. G. Wadley
Keyword(s):  
Shape Memory ◽  
Unit Cell ◽  
External Energy ◽  
Full Characterization ◽  
Shape Morphing ◽  
Cyclic Operation ◽  
Unit Cells ◽  
External Forces ◽  
Reversed Cyclic

An antagonistic flexural unit cell (AFC) concept for the design and fabrication of novel 2-D and 3-D lightweight shape morphing structures is introduced. A fully reversible flexural shape changing cell utilizing opposing one-way shape memory alloy (SMA) actuators is shown to require no spring-like bias elements. The SMA actuating elements are arranged such that the actuation (contraction) of one of them stretches the other one in the cell, preparing it to be actuated later to reverse a flexural displacement. This antagonistic operation allows fully reversed cyclic operation. The focus of this paper is an assessment of performance at the single cell level. The cell logically provides four possible configurations in different stages of its cycle. Two of them are of particular interest because they provide two different fixed shapes for the cell that can be maintained without the continuous supply of external energy. The final deformations of the cell and equilibrium stresses in the SMA elements depend on the amount of stored shape memory strain in each element, external forces and cell geometry. A model is developed, which allows a full characterization of the AFC. The model is used to study NiTi SMA-based AFCs and the results are therefore directly applicable to the design of shape morphing structures using such unit cells.

scholarly journals Characteristic Mode Analysis of Unit Cells of Metal-Only Infinite Arrays

2019 ◽  
Vol 8 (2) ◽  
pp. 134-142 ◽  
Author(s):  
Y. Haykir ◽  
O. A. Civi
Keyword(s):  
Periodic Structures ◽  
Unit Cell ◽  
Mode Analysis ◽  
Radiation Characteristics ◽  
Characteristic Mode ◽  
Unit Cell Size ◽  
Characteristic Modes ◽  
Unit Cells ◽  
Physical Insight ◽  
Cost Efficient

Characteristic mode analysis of metal only unit cells of periodic structures is performed using Method of Moments based formulation. Ewald’s transformation is incorporated for a fast and cost efficient solution and the advantages over spatial Green’s function are discussed. The influence of the unit cell size on the characteristic modes is demonstrated. Various metal-only reflectarray elements are compared and their radiation characteristics are interpreted using the theory of characteristic modes. It is shown that characteristic modes of the unit cell can help us to understand the radiation and scattering behavior of the unit cell and this physical insight can be used in periodic array unit cell design.

scholarly journals STEADY STATE FINITE ELEMENT ANALYSIS OF A SINGLE STACK COLD PLATE WITH HEAT LOSSES

2017 ◽  
Vol 19 (1) ◽  
pp. 77-90 ◽  
Author(s):  
G. A. Quadir ◽  
Shiao Lin Bell ◽  
K. N. Seetharamu ◽  
A. Y. Hassan
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Single Unit ◽  
Heat Losses ◽  
Unit Cell ◽  
Bottom Surface ◽  
Cold Plate ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Unit Cells

Steady state analysis of a single stack cold plate used for the cooling of electronic components is carried out using the finite element method. The present methodology takes into account the heat losses from the top and bottom surfaces of the stack. In addition dimensionless parameters are used in the analysis. The analysis is divided into two parts: a single unit cell analysis and the analysis of the assembly of several unit cells. The results from the present analysis of a single unit cell for single stack cold plate without heat losses compare well with those available in the literature. The analyses of the assembly of unit cells with heat losses from the top and bottom surface of the stack show that the single unit cell can be considered to be the representative of the stacks only when there are no heat losses.

scholarly journals Experimental Characterization of 2 × 2 Electronically Reconfigurable 1 Bit Unit Cells for a Beamforming Transmitarray at X Band

2021 ◽  
Vol 21 (2) ◽  
pp. 153-160
Author(s):  
Biswarup Rana ◽  
In-Gon Lee ◽  
Ic-Pyo Hong
Keyword(s):  
Phase Shifter ◽  
Unit Cell ◽  
Experimental Characterization ◽  
Waveguide Transition ◽  
Transmitted Waves ◽  
X Band ◽  
Unit Cells ◽  
New Type ◽  
Good Agreement

This paper proposes a reconfigurable unit cell for a transmitarray operating at the X band. The unit cell consists of an active patch, a passive patch, and a phase shifter. The active patch has two PIN diodes that change the phase of 180° of the transmitted waves. The passive and active patches both have circular slots to enhance the bandwidth of the transmitted wave. We also propose a new type of experimental characterization technique to measure the performance of the unit cells at the X band without fabricating the entire transmitarray. Instead of a 1 unit cell as described in the literature, we propose 2 × 2 unit cells to measure the performance of unit cells using the X band waveguide. The waveguide consists of a WR-90 section and a rectangular to square waveguide transition section that can be fit to our proposed structure. A good agreement between simulated and measured results was found.

Homogenization and Parameter Retrieval

2018 ◽  
pp. 124-140
Keyword(s):  
Single Unit ◽  
Periodic Structures ◽  
Propagation Direction ◽  
Negative Permittivity ◽  
Asymmetric Unit ◽  
S Parameter ◽  
Effective Media ◽  
Permittivity And Permeability ◽  
Unit Cells ◽  
Parameter Retrieval

This chapter describes the metamaterials based on periodic structures inhabiting theoretically a distinctive place among effective media and photonic crystals. The S-parameter retrieval procedures that have been exploited recently to describe metamaterials have been made known to be effective for metamaterials having asymmetric unit cells. The single unit cell of a conventional symmetric (in the propagation direction) metamaterial arrangement is illustrated, and it produces negative permittivity and permeability.

A Hybrid Approach on Metamaterial-Loaded Fractal Antenna Design

2020 ◽  
Vol 35 (9) ◽  
pp. 1022-1029
Author(s):  
Dudla Prabhakar ◽  
C. Rajendra Babu ◽  
V. Adinarayana ◽  
V. Prasad
Keyword(s):  
Microstrip Line ◽  
Ring Resonator ◽  
Structural Parameters ◽  
Hybrid Approach ◽  
Split Ring Resonator ◽  
Unit Cell ◽  
Dual Band ◽  
Fractal Antenna ◽  
Split Ring ◽  
Unit Cells

The paper provides the interoperable hybrid Grasshopper–Grey Wolf optimization (GHGWO) of the Square Split-Ring Resonator (SRR) metamaterial unit cell. This paper discusses the complex phase strategies of the electric and magnetic interplay of the charged microstrip line of the split ring resonator (SRR). Optimized unit of metamaterial cells for their bandwidth enhancement is packed into a new square fractal antenna. In the interim period of dual band efficiency, a new design is introduced for a microstrip line-feeding square fractal antenna with a faulty ground composition. In the second stage, a quasi-static SRR model is being used to streamline its structural parameters in an effort to reinforce the bandwidth so that optimized composition resonates at the required intensity area. In the GHGWO hybrid algorithm, SRR unit cell size limitations should be optimized and the convergence actions of the algorithm improved. Certain evolutions termed modified hybrid BF-PSO classical BFO, chaos PSO and IWO are being tested for efficiency of the Hybrid GHGWO algorithm. In the final stage, optimized SRR unit cells are stacked into a square fractal antenna that provides bandwidth output suited to wireless usages with upper and lower band. The prototype square fractal antenna without and with SRR unit cells is efficiently evaluated by trial results.

Design of Disordered Periodic Structures for Mode Localization

2017 ◽  
Author(s):  
Gabriele Cazzulani ◽  
Emanuele Riva ◽  
Edoardo Belloni ◽  
Francesco Braghin
Keyword(s):  
Wave Propagation ◽  
Periodic Structures ◽  
Unit Cell ◽  
Band Gaps ◽  
Mode Shapes ◽  
Mode Localization ◽  
Geometrical Properties ◽  
Unit Cells ◽  
The Mean ◽  
Propagation Properties

Periodic structures are the repetition of unit cells in space, that provide a filtering behavior for wave propagation. In particular, it is possible to tailor the geometrical, physical and elastic properties of the unit cells, in order to attenuate certain frequency bands, called band-gaps or stop-bands. Having each element characterized with the same parameters, the filtering behavior of the system can be described through the wave propagation properties of the unit cell. This is technologically impossible to obtain, therefore the Lyapunov factor is used, in order to define the mean attenuation of a quasi-periodic structure. Tailoring Gaussian unit cell properties potentially allows to extend the stop-bands width in the frequency domain. A drawback is that some unexpected resonance peaks may lie in the neighborhood of the extended regions. However, the correspondent mode-shapes are localized in a particular region of the structure, and they partially decrease the global attenuating behavior. In this paper, the aperiodicity introduced in the otherwise perfect repetition is investigated, providing an explanation for the mode-localization problem and for the stop-bands extension. Then, the proposed approach is applied to a passive quasi-periodic beam, characterized from a localized peak within a designed band-gap. The geometrical properties of its aperiodic parts are changed in order to deterministically move the localization peak in the frequency response. Numerical and experimental results are compared.

scholarly journals CHARACTERIZATION OF SURFACE OF THE (010) FACE OF BORAX CRYSTALS USING EX SITU ATOMIC FORCE MICROSCOPY (AFM):

2010 ◽  
Vol 5 (3) ◽  
pp. 274-277
Author(s):  
Suharso Suharso
Keyword(s):  
Atomic Force Microscopy ◽  
Unit Cell ◽  
Surface Topology ◽  
Ex Situ ◽  
Layered Compounds ◽  
Force Microscopy ◽  
Atomic Force ◽  
Unit Cells

The surface topology of borax crystals grown at a relative supersaturation of 0.21 has been investigated using ex situ atomic force microscopy (AFM). It was found that the cleavage of borax crystals along the (010) face planes has features of the cleavage of layered compounds, exhibiting cleavage steps of low heights. The step heights of the cleavage of the (010) face of borax crystal are from one unit cell to three unit cells of this face.   Keywords: AFM, cleavage, borax.

Sign in / Sign up

Export Citation Format

Share Document