scholarly journals Design and optimization of a wideband metasurface for utilization in a highly efficient terahertz reflectarray antenna

2021 ◽  
Author(s):  
Raziyeh Sharifi ◽  
Raheleh Basiri ◽  
Ehsan Zareian-Jahromi
Keyword(s):  
Fitness Function ◽  
Phase Variation ◽  
Single Layer ◽  
Horn Antenna ◽  
Mean Value ◽  
Hill Climbing ◽  
Reflected Waves ◽  
Design And Optimization ◽  
Unit Cells ◽  
Magnitude Variation

Abstract In this manuscript, two wideband single layer reflectarray antennas are designed utilizing an optimization-based metasurface in terahertz (THz) regime. It is demanded to design a metasurface with wide phase variation range in a broad frequency region of terahertz band. The proposed metasurface is designed based on Random Hill Climbing optimization algorithm whereas a multiobjective fitness function is defined to consider the desired characteristics. A provided link between Matlab and HFSS softwares is utilized to define and simulate various metasurfaces. The finalized cell has considerable wide phase variation (≥ 600˚) and notable bandwidth of 30.76% (1.1–1.5 THz) whereas the mean value of magnitude variation of reflection coefficient is -0.42dB. Two square and circular metasurfaces are designed based on the optimized cell and illuminated using a THz feeding horn antenna. The angles of incident and reflected waves are considered equal to zero. The simulation results confirm 3-dB gain bandwidths of 20.3% and 20.4% for square and circular reflectors, respectively. Moreover, the considerable efficiencies of 45.67% and 46.27% are achieved for square and circular arrays, consequently. The maximum gain of square array with 361 elements is 25.9dB whereas it is equal to 24.9dB for circular metasurface including 277 unit cells.

Design and optimization of bump (compression surface) for diverterless supersonic inlet

2021 ◽  
pp. 095441002110029
Author(s):  
Irsalan Arif ◽  
Hassan Iftikhar ◽  
Ali Javed
Keyword(s):  
Fitness Function ◽  
Supersonic Jet ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Least Square ◽  
Pressure Recovery ◽  
Design Parameters ◽  
Inlet System ◽  
Design And Optimization ◽  
Supersonic Inlet

In this article design and optimization scheme of a three-dimensional bump surface for a supersonic aircraft is presented. A baseline bump and inlet duct with forward cowl lip is initially modeled in accordance with an existing bump configuration on a supersonic jet aircraft. Various design parameters for bump surface of diverterless supersonic inlet systems are identified, and design space is established using sensitivity analysis to identify the uncertainty associated with each design parameter by the one-factor-at-a-time approach. Subsequently, the designed configurations are selected by performing a three-level design of experiments using the Box–Behnken method and the numerical simulations. Surrogate modeling is carried out by the least square regression method to identify the fitness function, and optimization is performed using genetic algorithm based on pressure recovery as the objective function. The resultant optimized bump configuration demonstrates significant improvement in pressure recovery and flow characteristics as compared to baseline configuration at both supersonic and subsonic flow conditions and at design and off-design conditions. The proposed design and optimization methodology can be applied for optimizing the bump surface design of any diverterless supersonic inlet system for maximizing the intake performance.

scholarly journals Synthesis of heterovalently substituted slab perovskites Sr2–xLnxBIV1–xBxIIIO4 (BIV= Sn, Ti, BIII= Sc, In)

2021 ◽  
pp. 77-83
Author(s):  
Y.A. Titov ◽  
◽  
M.S. Slobodyanik ◽  
V.V. Chumak ◽  
M.V. Tymoshenko ◽  
...  
Keyword(s):  
Layer Structure ◽  
Single Layer ◽  
Continuous Phase ◽  
Phase Region ◽  
Heterovalent Substitution ◽  
Linear Type ◽  
X Ray ◽  
Unit Cells ◽  
Pseudobinary Systems ◽  
New Compounds

The possibility of the heterovalent substitution of A- and B-positions atoms in a single-layer slab perovskite-like structure of strontium titanate and stannate Sr2BIVO4 (BIV= Ti, Sn) by type Sr2–xLnxBIV1–xBxIIIO4 (Ln == La – Tb, BIV= Ti, Sn, BIII= Sc, In) has been established by X-ray powder diffraction methods. The bounda-ries of the heterovalent substitution of A- and B-positions atoms and the crystallographic parameters of the synthesized Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure are determined. The continuous phase area formation with a single-layer structure has been observed in 10 systems: Sr2–xLnxTi1–xScxO4 (Ln = La, Pr, Nd, Sm, Eu), Sr2–xLnxTi1–xInxO4 (Ln = La, Pr), Sr2–xLaxSn1–xScxO4, Sr2–xLnxSn1–xInxO4 (Ln = La, Pr). In-creasing the degree of heterovalent substitution of atoms in these systems leads to a reduction of the sym metry of the crystal lattice of phases from the tetragonal (space group I4/mmm) to the interconnected rhombic one. In the rest of the studied Sr2–xLnxBIV1–xBxIIIO4 systems, the existence of a narrow (x value significantly less than 1) phase region with a single-layer structure based on Sr3BIVO7 is observed. The character of the phase relations in the Sr2–xLnxBIV1–xBxIIIO4 systems (Ln = La – Tb, BIII= Sc, In) (BIV= Sn, Ti) and the linear type of concentra-tion dependences of the parameters of the reduced tetragonal unit cells of Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure indicate that, by their nature, these phases are series of solid solutions in the pseudobinary systems Sr2BIVO4 – SrLnBIIIO4 (BIV= Ti, Sn, BIII = Sc, In). The obtained data can be used to regulate the functional properties of titanates and stannates Sr2BIVO4 and materials based on them, as well as to solve the problem of a purposeful search for new compounds of the type An+1BnO3n+1 with a slab perovskite-like structure.

Toplogy Design and Optimization of Nonlinear Metamaterials

2012 ◽  
Author(s):  
Kevin L. Manktelow ◽  
Michael J. Leamy ◽  
Massimo Ruzzene
Keyword(s):  
Frequency Shift ◽  
Phononic Crystal ◽  
Pattern Search ◽  
Nonlinear Frequency ◽  
Design And Optimization ◽  
Mass Distributions ◽  
Impedance Contrast ◽  
Lumped Parameter ◽  
Unit Cells ◽  
Complete Bandgap

We consider topology optimization of lumped and continuous nonlinear metamaterial systems. Structures that consist of alternating layers of material with high impedance contrast are a simple example of a continuous phononic crystal that may exhibit nonlinearity. Analysis of this system, subject to prescribed constraints, shows that optimal design for a bilayered system consists of a thin nonlinear layer. Optimal, in this context, refers to a design which maximizes the frequency shift (and thus bandgap shift) at the edge of the first Brillouin Zone for the acoustic branch. Computer simulations of this system validate the predicted dispersion behavior. Optimization of two-dimensional arrays is presented using lumped-parameter models with nonlinear spring elements. Pattern-search algorithms identify topology (discrete mass distributions) that produce large increases in complete bandgap width. The analytical expression used in calculating nonlinear frequency shifts reveals that the largest contributions to the frequency shift are primarily produced from the resonant components of the system. Optimizing continuous multidimensional unit cells using a commercial finite-element code is briefly addressed.

Design and Optimization of a New 1–18 GHz Double Ridged Guide Horn Antenna

2007 ◽  
Vol 21 (4) ◽  
pp. 501-516 ◽  
Author(s):  
M. Abbas-Azimi ◽  
F. Arazm ◽  
J. Rashed-Mohassel ◽  
R. Faraji-Dana
Keyword(s):  
Horn Antenna ◽  
Design And Optimization

Gradient Enhanced Surrogate Models Based on Adjoint CFD Methods for the Design of a Counter Rotating Turbofan

2012 ◽  
Author(s):  
Jan Backhaus ◽  
Marcel Aulich ◽  
Christian Frey ◽  
Timea Lengyel ◽  
Christian Voß
Keyword(s):  
Fitness Function ◽  
Computational Cost ◽  
Surrogate Models ◽  
Training Data ◽  
Design And Optimization ◽  
Additional Information ◽  
Gradient Based ◽  
Reference Design ◽  
Objective Function Values ◽  
The Impact

This paper studies the use of adjoint CFD solvers in combination with surrogate modelling in order to reduce the computational cost of the optimization of complex 3D turbomachinery components. The method is applied to a previously optimized counter rotating turbofan, with a shape parameterized by 104 CAD parameters. Through random changes on the reference design, a small number of design variations are created to serve as training samples for the surrogate models. A steady RANS solver and its discrete adjoint are then used to calculate objective function values and their corresponding sensitivities. Kriging and neural networks are used to build surrogate models from the training data. To study the impact of the additional information provided by the adjoint solver, each model is trained with and without the sensitivity information. The accuracy of the different surrogate model predictions is assessed by comparison against CFD calculations. The results show a considerable improvement of the fitness function approximation when the sensitivity information is taken into account. Through a gradient based optimization on one of the surrogate models, a design with higher isentropic efficiency at the aerodynamic design point is created. This application demonstrates that the improved surrogate models can be used for design and optimization.

Biomimetic Micropore of Bearing Human Bone in the Design and Optimization Based on Finite Element Analysis and Simulation

2010 ◽  
Vol 37-38 ◽  
pp. 230-233
Author(s):  
Li Jun Yang ◽  
Xi Nan Dang ◽  
Li Li Wang ◽  
Lian Zhou
Keyword(s):  
Unit Cell ◽  
Human Bone ◽  
Boolean Operation ◽  
Artificial Bone ◽  
Element Analysis ◽  
Tissue Properties ◽  
Design And Optimization ◽  
Unit Cells ◽  
Average Modulus ◽  
Cylindrical Holes

Modeling, design and fabrication of tissue scaffolds with intricate architecture, porosity and pore size for desired tissue properties presents a challenge in tissue engineering. Based on comparison and analysis of the two kinds of existing unit cells, the new micropore unit cell with a sphere hole in the middle and three cylindrical holes in the edge was gained. The negative model of bearing human bone was designed according to the new unit cell. Boolean Operation to the negative mode and entity contour profile, then the interconnected scaffold of artificial bone with certain porosity and gradient micropore was obtained. The results of simulation show that the average modulus of the model is 8.5Gpa, and the porosity is from 25.8% to 42.7%. It can meet the mechanical and biomimetic requests of bearing human artificial bone.

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