Manipulation of negative-index collimation beam using band-gap guidance

2018 ◽  
Vol 82 (1) ◽  
pp. 10401
Author(s):  
Fengfu Shen ◽  
Ge Zhu ◽  
Qing Shi ◽  
Zengtao Lv
Keyword(s):  
Integrated Circuits ◽  
Band Gap ◽  
Acoustic Waves ◽  
Resonant Mode ◽  
Negative Index ◽  
First Order ◽  
Directional Emission ◽  
Source Distance ◽  
Potential Applications ◽  
Sonic Crystal

We manipulate the source distance, emission position and number of negative-index collimation beam in a two-dimensional hybrid sonic crystal by using band-gap waveguide to control the flow of acoustic waves from a point source. The desired beam manipulations can be achieved at many different frequencies by suitably selecting the first order resonant mode of two crystal components and the waveguide structures. These results have potential applications in acoustic mutifunctional directional emission and acoustic integrated circuits. The proposed approach is also applicable for the similar manipulations of other types of acoustic collimation beams.

Numerical Studies on Band-Gap Structures and Resonant-Mode Wave-Guides of Typical Sonic Crystals Made of Rigid Cylinders in Fluid by Means of Elastic FDTD Method

2005 ◽  
Author(s):  
Toyokatsu Miyashita
Keyword(s):  
Band Gap ◽  
Fdtd Method ◽  
Transmission Band ◽  
Resonant Mode ◽  
Mode Wave ◽  
Periodic Arrays ◽  
Sonic Crystal ◽  
Wave Guides ◽  
Periodic Repetition ◽  
Fdtd Methods

We have investigated band-gap structures of three typical sonic/phononic crystals, namely periodic arrays of methacrylic resin cylinders in air, aluminum cylinders in air, and steel cylinders in water, by two different FDTD methods; one method is a sonic one that deals with only longitudinal waves, and the other is an elastic one that includes also shear waves. We show that both FDTD methods give almost the same band-gap structures for the former two crystals. Namely, the band-gaps by the sonic FDTD method lie at higher frequency only by 0.01 ~ 0.02 in the normalized frequency than those by the elastic one. The theoretical band-gap structures agree well with the experimental ones. In contrast, it is shown that the third crystal should be analyzed by the elastic FDTD method. Resonant-mode wave-guides are made by a periodic repetition of single-defects along a line in a sonic crystal of rigid cylinders in air. The obtained resonant and well-guided transmission band lies inside the full band-gap of the original bulk crystal. A combination of such wave-guides with a line-defect wave-guide is shown to have desirable characteristics for filtered wave-guides and wave-couplers.

Light-Driven Acoustic Band Gap Based on Metal Nanospheres

2009 ◽  
Vol 74 ◽  
pp. 17-20 ◽  
Author(s):  
Jiu Hui Wu ◽  
Boris Luk’yanchuk ◽  
Hua Ling Chen ◽  
Ai Qun Liu
Keyword(s):  
Band Gap ◽  
Acoustic Waves ◽  
Van Der Waals ◽  
Low Frequency ◽  
Optical Force ◽  
Potential Applications ◽  
Incident Laser Intensity ◽  
Metal Materials ◽  
Optical Distribution ◽  
Gap Width

In this paper, light-driven acoustic band gap is presented by considering two metal nanospheres illuminated simultaneously by laser and acoustic waves. The interaction between the photonics and phonons is investigated through optical distribution force, van der Waals distribution force, and acoustic pressure upon these nanospheres. Based on the optical force and van der Waals force, the acoustic form functions for the metal nanoaggregates with different optical intensity are calculated, and the light-driven acoustics band gap at low frequency band has been found. It is shown that the band gap width can be widened with increasing the incident laser intensity, or by using proper metal materials and background media. This could provide potential applications in optical nanoswitches and acoustical filters.

Using the secondary electrons (SE) of SEM with NIST‘s MONSEL-II program to obtain improved linewidth measurements and slope angles of line edges on a MMIC GaAs device

1996 ◽  
Vol 54 ◽  
pp. 944-945
Author(s):  
Richard G. Sartore
Keyword(s):  
Integrated Circuits ◽  
Plasma Etching ◽  
Microwave Integrated Circuits ◽  
Monolithic Microwave Integrated Circuits ◽  
Thick Gold ◽  
Gaas Devices ◽  
Source Distance ◽  
Margin Of Error ◽  
Dimensional Measurements ◽  
Barrier Metal

In the evaluation of GaAs devices from the MMIC (Monolithic Microwave Integrated Circuits) program for Army applications, there was a requirement to obtain accurate linewidth measurements on the nominal 0.5 micrometer gate lengths used to fabricate these devices. Preliminary measurements indicated a significant variation (typically 10 % to 30% but could be more) in the critical dimensional measurements of the gate length, gate to source distance and gate to drain distance. Passivation introduced a margin of error, which was removed by plasma etching. Additionally, the high aspect ratio (4-5) of the thick gold (Au) conductors also introduced measurement difficulties. The final measurements were performed after the thick gold conductor was removed and only the barrier metal remained, which was approximately 250 nanometer thick platinum on GaAs substrate. The thickness was measured using the penetration voltage method. Linescan of the secondary electron signal as it scans across the gate is shown in Figure 1.

scholarly journals Efficient Graph Collaborative Filtering via Contrastive Learning

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4666
Author(s):  
Zhiqiang Pan ◽  
Honghui Chen
Keyword(s):  
Collaborative Filtering ◽  
State Of The Art ◽  
Representation Learning ◽  
First Order ◽  
Satisfactory Performance ◽  
Potential Applications ◽  
Benchmark Datasets ◽  
Bayesian Personalized Ranking ◽  
Graph Neural Networks ◽  
Training Efficiency

Collaborative filtering (CF) aims to make recommendations for users by detecting user’s preference from the historical user–item interactions. Existing graph neural networks (GNN) based methods achieve satisfactory performance by exploiting the high-order connectivity between users and items, however they suffer from the poor training efficiency problem and easily introduce bias for information propagation. Moreover, the widely applied Bayesian personalized ranking (BPR) loss is insufficient to provide supervision signals for training due to the extremely sparse observed interactions. To deal with the above issues, we propose the Efficient Graph Collaborative Filtering (EGCF) method. Specifically, EGCF adopts merely one-layer graph convolution to model the collaborative signal for users and items from the first-order neighbors in the user–item interactions. Moreover, we introduce contrastive learning to enhance the representation learning of users and items by deriving the self-supervisions, which is jointly trained with the supervised learning. Extensive experiments are conducted on two benchmark datasets, i.e., Yelp2018 and Amazon-book, and the experimental results demonstrate that EGCF can achieve the state-of-the-art performance in terms of Recall and normalized discounted cumulative gain (NDCG), especially on ranking the target items at right positions. In addition, EGCF shows obvious advantages in the training efficiency compared with the competitive baselines, making it practicable for potential applications.

scholarly journals Visualization of Surface Acoustic Waves in Thin Liquid Films

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
R. W. Rambach ◽  
J. Taiber ◽  
C. M. L. Scheck ◽  
C. Meyer ◽  
J. Reboud ◽  
...  
Keyword(s):  
Liquid Film ◽  
Acoustic Waves ◽  
Low Cost ◽  
Thin Liquid Film ◽  
Surface Acoustic Waves ◽  
Liquid Films ◽  
Theoretical Description ◽  
Propagation Path ◽  
Microfluidic Channels ◽  
Potential Applications

Abstract We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfluidic channels. It also enables low-cost characterisation of IDT designs thereby allowing the determination of anisotropy and orientation of the piezoelectric substrate without the requirement for sophisticated and expensive equipment. Here, we show that the optical visibility of the sound path critically depends on the physical properties of the liquid film and identify heptane and methanol as most contrast rich solvents for visualization of SAW. We also provide a detailed theoretical description of this effect.

A DoD Perspective on Left Handed Negative Index Materials and Potential Applications

2006 ◽  
Vol 919 ◽  
Author(s):  
Valerie Browning ◽  
Minas H Tanielian ◽  
Richard W. Ziolkowski ◽  
Nader Engheta ◽  
David R. Smith
Keyword(s):  
Composite Structures ◽  
Beam Steering ◽  
Electromagnetic Response ◽  
Electromagnetic Spectrum ◽  
Negative Index ◽  
Negative Index Materials ◽  
Left Handed ◽  
Potential Applications ◽  
Novel Approaches ◽  
Electromagnetic Transport

AbstractIn the quest for ever smaller, lighter weight, and conformal components and devices for radar and communication applications, researchers in the RF community have increasingly turned to artificially engineered, composite structures (or “metamaterials”) in order to exploit the extraordinary electromagnetic response these materials offer. One particularly promising class of metamaterials that has recently received a great deal of attention are “left-handed” or negative index materials. Because these metamaterials exhibit the unique ability to bend and focus light in ways no other conventional materials can, they hold great potential for enabling a number of innovative lens and antenna structures for a broad range of commercial and DoD relevant applications. Exploring the possible implementation of negative index materials for such applications will require significant enhancements in the properties of existing Negative Index Materials (NIM) (bandwidth, loss, operational frequency, etc.), as well as improved understanding of the physics of their electromagnetic transport properties. For this reason the Defense Advanced Research Project Agency (DARPA) has initiated a program that seeks to further develop and demonstrate NIM for future DoD missions including, but not limited to, the following: 1) lightweight, compact lenses with improved optics; 2) sub wavelength/high resolution imaging across the electromagnetic spectrum; 3) novel approaches to beam steering for radar, RF, and/or optical communications; and 4) novel approaches for integrating optics with semiconductor electronics. A brief overview of the salient properties of NIM will be presented as well as a general discussion of a few of their potential applications.

Spray Chemical Vapor Deposition of CuInS2 Thin Films for Application in Solar Cell Devices

1997 ◽  
Vol 495 ◽  
Author(s):  
Jennifer A. Hollingsworth ◽  
William E. Buhro ◽  
Aloysius F. Hepp ◽  
Philip P. Jenkins ◽  
Mark A. Stan
Keyword(s):  
Thin Films ◽  
Chemical Vapor Deposition ◽  
Band Gap ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Fused Silica ◽  
Direct Band Gap ◽  
Cuins2 Thin Films ◽  
Potential Applications ◽  
Direct Band

ABSTRACTChalcopyrite CuInS2 is a direct band gap semiconductor (1.5 eV) that has potential applications in photovoltaic thin film and photoelectrochemical devices. We have successfully employed spray chemical vapor deposition using the previously known, single-source, metalorganic precursor, (Ph3P)2CuIn(SEt)4, to deposit CuInS2 thin films. Stoichiometric, polycrystalline films were deposited onto fused silica over a range of temperatures (300–400 °C). Morphology was observed to vary with temperature: spheroidal features were obtained at lower temperatures and angular features at 400 °C. At even higher temperatures (500 °C), a Cu-deficient phase, CuIn5S8, was obtained as a single phase. The CuInS2 films were determined to have a direct band gap of ca. 1.4 eV.

High Temperature Silicon Carbide CMOS Integrated Circuits

2011 ◽  
Vol 679-680 ◽  
pp. 726-729 ◽  
Author(s):  
David T. Clark ◽  
Ewan P. Ramsay ◽  
A.E. Murphy ◽  
Dave A. Smith ◽  
Robin. F. Thompson ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Integrated Circuits ◽  
Band Gap ◽  
High Temperatures ◽  
Wide Band ◽  
Cmos Technology ◽  
Cmos Integrated Circuits ◽  
Wide Band Gap ◽  
Circuit Performance

The wide band-gap of Silicon Carbide (SiC) makes it a material suitable for high temperature integrated circuits [1], potentially operating up to and beyond 450°C. This paper describes the development of a 15V SiC CMOS technology developed to operate at high temperatures, n and p-channel transistor and preliminary circuit performance over temperature achieved in this technology.

Propagation of acoustic waves in the woodpile sonic crystal with a defect

2012 ◽  
Vol 73 (4) ◽  
pp. 312-322 ◽  
Author(s):  
Liang-Yu Wu ◽  
Lien-Wen Chen
Keyword(s):  
Acoustic Waves ◽  
Sonic Crystal

Planarization of Deep Structures Using Self-Leveling Materials

2012 ◽  
Vol 2012 (1) ◽  
pp. 000079-000083
Author(s):  
Dongshun Bai ◽  
Michelle Fowler ◽  
Curtis Planje ◽  
Xie Shao
Keyword(s):  
Integrated Circuits ◽  
Microelectromechanical Systems ◽  
Flat Panel Displays ◽  
New Materials ◽  
Flat Panel ◽  
Light Emitting ◽  
Good Thermal Stability ◽  
Device Integration ◽  
Potential Applications ◽  
Processing Steps

To achieve device integration that will allow the manufacture of smaller, more functional, and more efficient microelectronics, the industry increasingly requires materials to fill and planarize devices with deep structures. Brewer Science has developed several new self-leveling materials to address these planarization needs. These newly developed materials are designed to be either temporary materials that can be removed after their use in processing steps or permanent materials that can stay in a device for its lifetime. These new materials can be applied easily by means of a spin-coating process. They are unique because they can fill and planarize high-aspect-ratio trenches and vias hundreds of microns deep. Some of the materials are photosensitive and can be patterned using photolithography. All of the photosensitive materials in this paper can be developed with industry-accepted solvents and some with an aqueous TMAH solution. Because of their good thermal stability, high transparency, and excellent planarization properties, these materials have potential applications for microelectromechanical systems (MEMS), 3-D integrated circuits, light-emitting diodes (LEDs), semiconductors, flat-panel displays, and related microelectronic and optoelectronic devices. This paper will discuss the properties of these new materials and will present the filling and leveling results obtained in several applications.

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