3D Pattern Synthesis of Time-Modulated Conformal Arrays with a Multiobjective Optimization Approach

This paper addresses the synthesis of the three-dimensional (3D) radiation patterns of the time-modulated conformal arrays. Due to the nature of periodic time modulation, harmonic radiation patterns are generated at the multiples of the modulation frequency in time-modulated arrays. Thus, the optimization goal of the time-modulated conformal array includes the optimization of the sidelobe level at the operating frequency and the sideband levels (SBLs) at the harmonic frequency, and the design can be regarded as a multiobjective problem. The multiobjective particle swarm optimization (MOPSO) is applied to optimize the switch-on instants and pulse durations of the time-modulated conformal array. To significantly reduce the optimization variables, the modified Bernstein polynomial is employed in the synthesis process. Furthermore, dual polarized patch antenna is designed as radiator to achieve low cross-polarization level during the beam scanning. A 12 × 13 (156)-element conical conformal microstrip array is simulated to demonstrate the proposed synthesis mechanism, and good results reveal the promising ability of the proposed algorithm in solving the synthesis of the time-modulated conformal arrays problem.

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Conformal Array Pattern Synthesis Using a Hybrid WARP/2LB-MOPSO Algorithm

International Journal of Antennas and Propagation ◽

10.1155/2012/202906 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 6

Author(s):

Roghieh Karimzadeh Baee ◽

Keyvan Forooraghi ◽

Somayyeh Chamaani

Keyword(s):

Degrees Of Freedom ◽

Mutual Coupling ◽

Side Lobe ◽

Penalty Functions ◽

Main Beam ◽

Side Lobe Level ◽

Initial Population ◽

Pattern Synthesis ◽

Conformal Array ◽

Multiobjective Particle Swarm Optimization

This paper addresses conformal array synthesis as a constrained multiobjective optimization problem. Simultaneous reduction of side lobe level (SLL) and cross-polarization (XPL) level is aimed with a constraint on main beam direction. A hybrid of weighted alternating reverse projection (WARP) and two local best multiobjective particle swarm optimization (2LB-MOPSO) is proposed to optimize the pattern. First, the WARP method finds a moderate and feasible solution. Second, 2LB-MOPSO begins with an initial population including the solution of WARP and penalty functions for constraint handling. Involving WARP result in the initial population of 2LB-MOPSO leads to higher convergence rate, avoiding local extermum traps and less sensitivity to penalty functions. Compared to WARP method which stagnates rapidly, the proposed hybrid method gives better SLL and XPL after adequate iterations. In addition, as 2LB-MOPSO offers a set of optimum solutions (Pareto front) instead of a single solution, this method provides more degrees of freedom in selection of proper practical arrays. Finally, to examine the mutual coupling consideration in array design, the same procedure was applied ignoring the mutual coupling between elements. The results show that the SLL and XPL strongly depend on mutual coupling.

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Phased-only pattern synthesis for sunflower and conformal arrays with shaped radiation patterns

2018 35th National Radio Science Conference (NRSC) ◽

10.1109/nrsc.2018.8354356 ◽

2018 ◽

Author(s):

D. M. Azzam ◽

H. A. Malhat ◽

S. H. Zainud-Deen

Keyword(s):

Radiation Patterns ◽

Pattern Synthesis ◽

Conformal Arrays

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Characterization of a monolayer graphitic structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100171535 ◽

1994 ◽

Vol 52 ◽

pp. 760-761

Author(s):

X. Lin ◽

X. K. Wang ◽

V. P. Dravid ◽

J. B. Ketterson ◽

R. P. H. Chang

Keyword(s):

Three Dimensional ◽

Single Layer ◽

Synthesis Process ◽

Graphitic Structure ◽

Positive Gaussian Curvature ◽

Graphitic Sheet ◽

Structural And Electronic Properties ◽

New Material ◽

Hexagonal Network

For small curvatures of a graphitic sheet, carbon atoms can maintain their preferred sp2 bonding while allowing the sheet to have various three-dimensional geometries, which may have exotic structural and electronic properties. In addition the fivefold rings will lead to a positive Gaussian curvature in the hexagonal network, and the sevenfold rings cause a negative one. By combining these sevenfold and fivefold rings with sixfold rings, it is possible to construct complicated carbon sp2 networks. Because it is much easier to introduce pentagons and heptagons into the single-layer hexagonal network than into the multilayer network, the complicated morphologies would be more common in the single-layer graphite structures. In this contribution, we report the observation and characterization of a new material of monolayer graphitic structure by electron diffraction, HREM, EELS.The synthesis process used in this study is reported early. We utilized a composite anode of graphite and copper for arc evaporation in helium.

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Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

npj Computational Materials ◽

10.1038/s41524-020-00461-w ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Wei Luo ◽

Yuma Nakamura ◽

Jinseon Park ◽

Mina Yoon

Keyword(s):

Tight Binding ◽

Three Dimensional ◽

Interlayer Coupling ◽

First Principles Calculation ◽

Optimization Approach ◽

Binding Model ◽

Nodal Lines ◽

Weyl Semimetal ◽

Topological Quantum ◽

First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

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Robot Path Planning and Obstacle Avoidance: A Design Optimization Approach

15th Design Automation Conference: Volume 2 — Design Optimization ◽

10.1115/detc1989-0087 ◽

1989 ◽

Author(s):

E. Sandgren ◽

S. Venkataraman

Keyword(s):

Path Planning ◽

Design Optimization ◽

Dynamic Programming Algorithm ◽

Three Dimensional ◽

Programming Algorithm ◽

Optimization Approach ◽

Robot Arm ◽

Robot Path Planning ◽

Real Time Control ◽

Robot Path

Abstract A design optimization approach to robot path planning in a two dimensional workplace is presented. Obstacles are represented as a series of rectangular regions and collision detection is performed by an operation similar to clipping in computer graphics. The feasible design space is approximated by a discrete set of robot arm and gripper positions. Control is applied directly through the angular motion of each link. Feasible positions which are located between the initial and final robot link positions are grouped into stages. A dynamic programming algorithm is applied to locate the best state within each stage which minimizes the overall path length. An example is presented involving a three link planar manipulator. Extensions to three dimensional robot path planning and real time control in a dynamically changing workplace are discussed.

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Use of reciprocity theorem for obtaining Rayleigh wave radiation patterns

Bulletin of the Seismological Society of America ◽

10.1785/bssa0560040925 ◽

1966 ◽

Vol 56 (4) ◽

pp. 925-936 ◽

Cited By ~ 1

Author(s):

I. N. Gupta

Keyword(s):

Rayleigh Wave ◽

Rayleigh Waves ◽

Three Dimensional ◽

Reciprocity Theorem ◽

Point Sources ◽

Dimensional Case ◽

Wave Radiation ◽

Radiation Patterns ◽

Homogeneous Half Space ◽

Double Couple

abstract The reciprocity theorem is used to obtain Rayleigh wave radiation patterns from sources on the surface of or within an elastic semi-infinite medium. Nine elementary line sources first considered are: horizontal and vertical forces, horizontal and vertical double forces without moment, horizontal and vertical single couples, center of dilatation (two dimensional case), center of rotation, and double couple without moment. The results are extended to the three dimensional case of similar point sources in a homogeneous half space. Haskell's results for the radiation patterns of Rayleigh waves from a fault of arbitrary dip and direction of motion are reproduced in a much simpler manner. Numerical results on the effect of the depth of these sources on the Rayleigh wave amplitudes are shown for a solid having Poisson's ratio of 0.25.

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