scholarly journals Algorithmic lattice kirigami: A route to pluripotent materials

2015 ◽  
Vol 112 (24) ◽  
pp. 7449-7453 ◽  
Author(s):  
Daniel M. Sussman ◽  
Yigil Cho ◽  
Toen Castle ◽  
Xingting Gong ◽  
Euiyeon Jung ◽  
...  
Keyword(s):  
Flat Surface ◽  
Inverse Design ◽  
Honeycomb Lattice ◽  
Flat Sheet ◽  
Regular Arrangement ◽  
Stepped Surface ◽  
Design Paradigm ◽  
Complex Target ◽  
General Method

We use a regular arrangement of kirigami elements to demonstrate an inverse design paradigm for folding a flat surface into complex target configurations. We first present a scheme using arrays of disclination defect pairs on the dual to the honeycomb lattice; by arranging these defect pairs properly with respect to each other and choosing an appropriate fold pattern a target stepped surface can be designed. We then present a more general method that specifies a fixed lattice of kirigami cuts to be performed on a flat sheet. This single pluripotent lattice of cuts permits a wide variety of target surfaces to be programmed into the sheet by varying the folding directions.

scholarly journals Phase-to-pattern inverse design paradigm for fast realization of functional metasurfaces via transfer learning

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ruichao Zhu ◽  
Tianshuo Qiu ◽  
Jiafu Wang ◽  
Sai Sui ◽  
Chenglong Hao ◽  
...  
Keyword(s):  
Transfer Learning ◽  
Electromagnetic Waves ◽  
Inverse Method ◽  
Inverse Design ◽  
Learning Network ◽  
Design Paradigm ◽  
Simulation And Experiment ◽  
Meta Atom ◽  
Trained Network ◽  
Input Phase

AbstractMetasurfaces have provided unprecedented freedom for manipulating electromagnetic waves. In metasurface design, massive meta-atoms have to be optimized to produce the desired phase profiles, which is time-consuming and sometimes prohibitive. In this paper, we propose a fast accurate inverse method of designing functional metasurfaces based on transfer learning, which can generate metasurface patterns monolithically from input phase profiles for specific functions. A transfer learning network based on GoogLeNet-Inception-V3 can predict the phases of 28×8 meta-atoms with an accuracy of around 90%. This method is validated via functional metasurface design using the trained network. Metasurface patterns are generated monolithically for achieving two typical functionals, 2D focusing and abnormal reflection. Both simulation and experiment verify the high design accuracy. This method provides an inverse design paradigm for fast functional metasurface design, and can be readily used to establish a meta-atom library with full phase span.

Toward a Universal Roughness Correlation

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Pourya Forooghi ◽  
Alexander Stroh ◽  
Franco Magagnato ◽  
Suad Jakirlić ◽  
Bettina Frohnapfel
Keyword(s):  
Size Distribution ◽  
Skin Friction ◽  
Flat Surface ◽  
Surface Slope ◽  
Uniform Size ◽  
Random Arrangement ◽  
Roughness Elements ◽  
Regular Arrangement ◽  
Data Points ◽  
Probability Density Function Pdf

The effects of several surface parameters on equivalent sand roughness (ks) in fully rough regime are investigated by means of direct numerical simulation (DNS) of flow in channels with different wall geometries at Reτ≅500. The roughness geometry is generated by randomly distributing roughness elements of random size and prescribed shape on a flat surface. The roughness generation approach allows systematic variation of moments of surface height probability density function (PDF), size distribution of roughness peaks, and surface slope. A total number of 38 cases are solved. It is understood that a correlation based on surface height skewness and effective slope (ES) can satisfactorily predict ks normalized with maximum peak-to-valley roughness height within a major part of the studied parameter space. Such a correlation is developed based on the present data points and a number of complementary data points from the literature. It is also shown that the peak size distribution can independently influence the skin friction; at fixed values of rms surface height, skewness, kurtosis, and ES, a surface with uniform size peaks causes higher skin friction compared to one with nonuniform peak sizes. Additionally, it is understood that a roughness generated by regular arrangement of roughness elements may lead to a significantly different skin friction compared to a random arrangement. A staggered and an aligned regular arrangement are examined in this paper and it is observed that the former produces significantly closer results to the corresponding random arrangement.

Stepped Fe(100) and V/Fe(100) Magnetism

1991 ◽  
Vol 231 ◽  
Author(s):  
A. Vega ◽  
A. Rubio ◽  
L.C. Balbas ◽  
J. Dorantes-Davila ◽  
C. Demangeat ◽  
...  
Keyword(s):  
Transition Metal ◽  
Flat Surface ◽  
Magnetic Moments ◽  
Tight Binding ◽  
Step Length ◽  
Real Space ◽  
External Edge ◽  
Transition Metal Surface ◽  
Self Consistent ◽  
Stepped Surface

AbstractWe have investigated the magnetic arrangment of 3d transition-metal stepped surface by using a self-consistent real-space tight-binding method. As expected, the presence of steps modifies locally the properties of a transition-metal surface. We emphasized the influence of atomic environment. We found for the (100)-Fe surface, an enhancement of the magnetic moments of the external edge of this step as compared to the flat surface. The results are not very sensitives to the step length. More striking is the case of the (100)-V stepped surface where atoms at the external edge display a large magnetic moment.

Multi-class, multi-functional design of photonic topological insulators by rational symmetry-indicators engineering

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jiachen Luo ◽  
Zongliang Du ◽  
Yilin Guo ◽  
Chang Liu ◽  
Weisheng Zhang ◽  
...  
Keyword(s):  
Time Reversal ◽  
Three Dimensional ◽  
Higher Order ◽  
Band Gaps ◽  
Inverse Design ◽  
Functional Design ◽  
Rational Engineering ◽  
Design Paradigm ◽  
Point Groups ◽  
Topological Crystalline Insulators

Abstract An explicit topology optimization-based design paradigm is proposed for the design of photonic topological crystalline insulators (TCIs). To strictly guarantee the topological property, rational engineering of symmetry-indicators is carried out by mathematical programming, which simultaneously maximizes the width of nontrivial topological band gaps and achieves the desired quantized bulk polarization. Our approach is successfully applied to design photonic TCIs with time-reversal symmetry in two-dimensional point groups, higher-order magnetic TCIs, and higher-order photonic TCIs. This methodology paves the way for inverse design of optimized photonic/phononic, multiphysics, and multifunctional three-dimensional TCIs.

scholarly journals Multivalued Inverse Design: Multiple Surface Geometries from One Flat Sheet

2021 ◽  
Vol 127 (12) ◽  
Author(s):  
Itay Griniasty ◽  
Cyrus Mostajeran ◽  
Itai Cohen
Keyword(s):  
Inverse Design ◽  
Flat Sheet

Inverse Design of 2D Airfoils using Conditional Generative Models and Surrogate Log-Likelihoods

2021 ◽  
pp. 1-22
Author(s):  
Qiuyi Chen ◽  
Jun Wang ◽  
Phillip Pope ◽  
Wei (Wayne) Chen ◽  
Mark Fuge
Keyword(s):  
Optimal Transport ◽  
Generative Models ◽  
Inverse Design ◽  
Optimal Designs ◽  
Design Problems ◽  
Airfoil Optimization ◽  
Optimal Value ◽  
Design Paradigm ◽  
Low Dimensional ◽  
2D Airfoil

Abstract This paper shows how to use conditional generative models in 2D airfoil optimization to probabilistically predict good initialization points within the vicinity of the optima given the input boundary conditions, thus warm starting and accelerating further optimization. We accommodate the possibility of multiple optimal designs corresponding to the same input boundary condition and take this inversion ambiguity into account when designing our prediction framework. To this end, we first employ the conditional formulation of our previous work BezierGAN---Conditional BezierGAN (CBGAN)---as a baseline, then introduce its sibling conditional entropic BezierGAN (CEBGAN), which is based on optimal transport regularized with entropy. Compared with CBGAN, CEBGAN overcomes mode collapse plaguing conventional GANs, improves the average lift-drag (C_l/C_d) efficiency of airfoil predictions from 80.8% of the optimal value to 95.8%, and meanwhile accelerates the training process by 30.7%. Furthermore, we investigate the unique ability of CEBGAN to produce a log-likelihood lower bound that may help select generated samples of higher performance (e.g., aerodynamic performance). In addition, we provide insights into the performance differences between these two models with low-dimensional toy problems and visualizations. These results and the probabilistic formulation of this inverse problem justify the extension of our GAN-based inverse design paradigm to other inverse design problems or broader inverse problems.

A General Method for Spectrometer Design in the Scoff Approximation

1976 ◽  
Vol 34 ◽  
pp. 538-539
Author(s):  
J. R. Fields
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Energy Analysis ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Chemical Identification ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
General Method

The energy analysis of electrons scattered by a specimen in a scanning transmission electron microscope can improve contrast as well as aid in chemical identification. In so far as energy analysis is useful, one would like to be able to design a spectrometer which is tailored to his particular needs. In our own case, we require a spectrometer which will accept a parallel incident beam and which will focus the electrons in both the median and perpendicular planes. In addition, since we intend to follow the spectrometer by a detector array rather than a single energy selecting slit, we need as great a dispersion as possible. Therefore, we would like to follow our spectrometer by a magnifying lens. Consequently, the line along which electrons of varying energy are dispersed must be normal to the direction of the central ray at the spectrometer exit.

Electron-Channelling Patterns: Principles and Techniques

1976 ◽  
Vol 34 ◽  
pp. 400-401
Author(s):  
David C. Joy
Keyword(s):  
Crystal Structure ◽  
Electron Flux ◽  
Lattice Structure ◽  
Incident Beam ◽  
Bloch Wave ◽  
Crystalline Solid ◽  
Angle Of Incidence ◽  
Electron Channelling ◽  
Regular Arrangement ◽  
Backscattered Signals

In a crystalline solid the regular arrangement of the lattice structure influences the interaction of the incident beam with the specimen, leading to changes in both the transmitted and backscattered signals when the angle of incidence of the beam to the specimen is changed. For the simplest case the electron flux inside the specimen can be visualized as the sum of two, standing wave distributions of electrons (Fig. 1). Bloch wave 1 is concentrated mainly between the atom rows and so only interacts weakly with them. It is therefore transmitted well and backscattered weakly. Bloch wave 2 is concentrated on the line of atom centers and is therefore transmitted poorly and backscattered strongly. The ratio of the excitation of wave 1 to wave 2 varies with the angle between the incident beam and the crystal structure.

Phase behavior of cationic and anionic surfactants at low concentrations

1992 ◽  
Vol 50 (1) ◽  
pp. 694-695
Author(s):  
E. Naranjo
Keyword(s):  
Phase Behavior ◽  
Structural Characterization ◽  
Dynamic Systems ◽  
Anionic Surfactants ◽  
Intermolecular Forces ◽  
Stable Form ◽  
Surfactant Mixtures ◽  
Low Concentrations ◽  
Cationic And Anionic Surfactants ◽  
General Method

Equilibrium vesicles, those which are the stable form of aggregation and form spontaneously on mixing surfactant with water, have never been demonstrated in single component bilayers and only rarely in lipid or surfactant mixtures. Designing a simple and general method for producing spontaneous and stable vesicles depends on a better understanding of the thermodynamics of aggregation, the interplay of intermolecular forces in surfactants, and an efficient way of doing structural characterization in dynamic systems.

Scanned tip measurement of deep vertical facets on a flat surface: Measuring roughness on gaas laser waveguide mirrors

1993 ◽  
Vol 51 ◽  
pp. 532-533
Author(s):  
Chang Shen ◽  
Phil Fraundorf ◽  
Robert W. Harrick
Keyword(s):  
Integrated Circuits ◽  
Flat Surface ◽  
Scanning Force Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Optoelectronic Integrated Circuits ◽  
Laser Waveguide ◽  
Scanning Force ◽  
Gaas Laser

Monolithic integration of optoelectronic integrated circuits (OEIC) requires high quantity etched laser facets which prevent the developing of more-highly-integrated OEIC's. The causes of facet roughness are not well understood, and improvement of facet quality is hampered by the difficulty in measuring the surface roughness. There are several approaches to examining facet roughness qualitatively, such as scanning force microscopy (SFM), scanning tunneling microscopy (STM) and scanning electron microscopy (SEM). The challenge here is to allow more straightforward monitoring of deep vertical etched facets, without the need to cleave out test samples. In this presentation, we show air based STM and SFM images of vertical dry-etched laser facets, and discuss the image acquisition and roughness measurement processes. Our technique does not require precision cleaving. We use a traditional tip instead of the T shape tip used elsewhere to preventing “shower curtain” profiling of the sidewall. We tilt the sample about 30 to 50 degrees to avoid the curtain effect.

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