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Acoustic Power Divider Based on Compressibility-Near-Zero Propagation

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Physical Review Applied 2020年第2期14卷 024057-024057页

作者： Hussein Esfahlani Matthew S. Byrne Andrea Alù Electrical Engineering Institute École Polytechnique Fedérale de Lausanne (EPFL) CH-1015 Lausanne Switzerland Department of Electrical & Computer Engineering The University of Texas at Austin Austin Texas 78712 USA Photonics Initiative Advanced Science Research Center New York New York 10031 USA Kymeta Corporation Redmond Washington 98052 USA Naval Surface Warfare Center Carderock Division West Bethesda Maryland 20817 USA Physics Program Graduate Center New York New York 10016 USA

Materials with properties that can be described by a near-zero index of refraction have received significant attention in the fields of electromagnetics, optics, and acoustics, due to their extraordinary capabilities in wave manipulation. It was recently demonstrated theoretically and experimentally that acoustic waves could manifest near-zero-index propagation based on the effective compressibility of a waveguide channel approaching zero. In turn, this allows tunneling of acoustic waves with nearly infinite wavelength (or equivalently, uniform phase) when the channel cross section is much larger than the feeding lines. Here, we show that these concepts can be leveraged to realize an acoustic power divider and multiplexer offering tunneling of sound to an arbitrary number of output ports, with phase shifts equal to 0° or 180° and robust response to variations in the port position. We present analytical and numerical models describing the properties of this device and study limitations and trade-offs that occur in the presence of losses as the device size is scaled.

关键词： Acoustic metamaterials Acoustic wave phenomena Acoustics

Mixture-of-experts variational autoencoder for clustering and generating from similarity-based representations

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arXiv 2019年

作者： Kopf, Andreas Fortuin, Vincent Somnath, Vignesh Ram Claassen, Manfred Institute of Molecular Systems Biology Department of Biology ETH Zürich Switzerland Biomedical Informatics Group Department of Computer Science ETH Zürich Switzerland Switzerland Life Science Graduate School Zurich PhD Program Systems Biology Switzerland

Clustering high-dimensional data, such as images or biological measurements, is a long-standing problem and has been studied extensively. Recently, Deep Clustering gained popularity due to the non-linearity of neural networks, which allows for flexibility in fitting the specific peculiarities of complex data. Here we introduce the Mixture-of-Experts Similarity Variational Autoencoder (MoE-Sim-VAE), a novel generative clustering model. The model can learn multi-modal distributions of high-dimensional data and use these to generate realistic data with high efficacy and efficiency. MoE-Sim-VAE is based on a Variational Autoencoder (VAE), where the decoder consists of a Mixture-of-Experts (MoE) architecture. This specific architecture allows for various modes of the data to be automatically learned by means of the experts. Additionally, we encourage the latent representation of our model to follow a Gaussian mixture distribution and to accurately represent the similarities between the data points. We assess the performance of our model on synthetic data, the MNIST benchmark data set, and a challenging real-world task of defining cell subpopulations from mass cytometry (CyTOF) measurements on hundreds of different datasets. MoE-Sim-VAE exhibits superior clustering performance on all these tasks in comparison to the baselines and we show that the MoE architecture in the decoder reduces the computational cost of sampling specific data modes with high fidelity. Copyright © 2019, The Authors. All rights reserved.

关键词： Clustering algorithms

Stroke Lesion Detection Using Convolutional Neural Networks

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Stroke Lesion Detection Using Convolutional Neural Networks

2018 International Joint Conference on Neural Networks, IJCNN 2018

作者： Pereira, Danillo Roberto Filho, Pedro P. Rebouças De Rosa, Gustavo Henrique Papa, João Paulo De Albuquerque, Victor Hugo C. Department of Computing São Paulo State University Bauru SP Brazil Federal Institute of Education Science and Technology of Ceará CE Brazil Graduate Program in Applied Informatics University of Fortaleza Fortaleza CE Brazil

ISBN: (纸本)9781509060146

Stroke is an injury that affects the brain tissue, mainly caused by changes in the blood supply to a particular region of the brain. As consequence, some specific functions related to that affected region can be reduced, decreasing the quality of life of the patient. In this work, we deal with the problem of stroke detection in Computed Tomography (CT) images using Convolutional Neural Networks (CNN) optimized by Particle Swarm optimization (PSO). We considered two different kinds of strokes, ischemic and hemorrhagic, as well as making available a public dataset to foster the research related to stroke detection in the human brain. The dataset comprises three different types of images for each case, i.e., the original CT image, one with the segmented cranium and an additional one with the radiological density's map. The results evidenced that CNN's are suitable to deal with stroke detection, obtaining promising results. © 2018 IEEE.

关键词： Convolution

Temperature study of Rydberg exciton optical properties in Cu2O

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Physical Review B 2021年第20期103卷 205203-205203页

作者： Dongyeon Daniel Kang Aaron Gross HeeBong Yang Yusuke Morita Kyung Soo Choi Kosuke Yoshioka Na Young Kim Institute for Quantum Computing University of Waterloo 200 University Ave. West Waterloo Ontario Canada N2L 3G1 Department of Electrical and Computer Engineering University of Waterloo 200 University Ave. West Waterloo Ontario Canada N2L 3G1 Department of Physics Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan Department of Physics and Astronomy University of Waterloo 200 University Ave. West Waterloo Ontario Canada N2L 3G1 Perimeter Institute for Theoretical Physics 31 Caroline St. N Waterloo Ontario Canada N2L 2Y5 Photon Science Center School of Engineering The University of Tokyo 2-11-16 Yayoi Bunkyo-ku Tokyo 113-8656 Japan Department of Chemistry University of Waterloo 200 University Ave. West Waterloo Ontario Canada N2L 3G1

Rydberg excitons in Cu2O can be an emergent platform for solid-state quantum information processing by utilizing the exaggerated properties of high-lying excited states within the material. To develop practical quantum systems, high-temperature operation is desirable. Here, we study the temperature dependence of the yellow and green Rydberg exciton resonances in a thin Cu2O crystal via broad-band phonon-assisted absorption spectra between 4 K and 100 K. At 4 K, we can identify the principal quantum number n=11 yellow and n=4 green Rydberg exciton states, beyond which we are limited by the spectral resolution of standard absorption techniques. Above liquid nitrogen boiling temperature (∼80K), the n=6 yellow and n=4 green Rydberg exciton states are readily captured and higher-temperature yellow Rydberg exciton optical properties still exhibit the standard scaling laws seen at low temperatures. This promising result lays the groundwork for a new route to build a high-temperature Rydberg quantum information processing architecture with solid-state Cu2O.

关键词： Excitons Rydberg atoms & molecules Semiconductors Optical spectroscopy Photoluminescence

Energy-Efficiency Exploration of Memory Hierarchy using NVMs for HEVC Motion Estimation

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Energy-Efficiency Exploration of Memory Hierarchy using NVMs...

IEEE International Conference on Electronics, Circuits and Systems

作者： Wagner Penny Jones Goebel Douglas Correa Anderson Martins Gabriel Nazar Luciano Agostini Daniel Palomino Marcelo Porto Bruno Zatt Sul-rio-grandense Federal Institute Pelotas Brazil Computer Science Graduate Program Video Technology Research Group Federal University of Pelotas Pelotas Brazil Institute of Informatics Federal University of Rio Grande do Sul Porto Alegre Brazil

Efficient video coding techniques applied by modern video encoders - e.g. the High Efficiency Video Coding (HEVC) - enable the handling and sharing of digital videos content. The applied complex data-intensive algorithms, as the Motion Estimation (ME), pose severe constraints in terms of memory communication and energy consumption, especially for battery-powered devices. Thus, an evaluation using efficient memory hierarchies, exploring multiple cache configurations and the use of non-volatile memories (NVMs) as main memory, was performed. Our evaluation considered TZS algorithm, encoding FHD videos, under 32 different cache configurations, combined with three main memory technologies: DRAM, STTRAM, and ReRAM. The best cache configurations were selected in terms of lowest total energy consumption, moreover, different energy savings were achieved using non-volatile memories as main memory, varying from 33.4% to 57.6%, for STTRAM and ReRAM, respectively, with ReRAM presenting the best energy results and reducing the optimal cache size.

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Enhanced meta-displays using advanced phase-change materials

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arXiv 2021年

作者： Hemmatyar, Omid Abdollahramezani, Sajjad Zeimpekis, Ioannis Lepeshov, Sergey Krasnok, Alex Khan, Asir Intisar Neilson, Kathryn M. Teichrib, Christian Brown, Tyler Pop, Eric Hewak, Daniel W. Wuttig, Matthias Alù, Andrea Muskens, Otto L. Adibi, Ali School of Electrical and Computer Engineering Georgia Institute of Technology 778 Atlantic Drive NW AtlantaGA30332-0250 United States Zepler Institute Faculty of Engineering and Physical Sciences University of Southampton SouthamptonSO17 1BJ United Kingdom ITMO University St. Petersburg197101 Russia Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Department of Electrical Engineering Department of Materials Science and Engineering Precourt Institute for Energy Stanford University StanfordCA94305 United States Physikalisches Institut IA RWTH Aachen Sommerfeldstrasse 14 Aachen52074 Germany Physics Program Graduate Center City University of New York New YorkNY10016 United States Physics and Astronomy Faculty of Engineering and Physical Sciences University of Southampton SouthamptonSO17 1BJ United Kingdom

Structural colors generated due to light scattering from static all-dielectric metasurfaces have successfully enabled high-resolution, high-saturation, and wide-gamut color printing applications. Despite recent advances, most demonstrations of these structure-dependent colors lack post-fabrication tunability. This hinders their applicability for front-end dynamic display technologies. Phase-change materials (PCMs), with significant contrast of their optical properties between their amorphous and crystalline states, have demonstrated promising potentials in reconfigurable nanophotonics. Herein, we leverage tunable all-dielectric reflective metasurfaces made of newly emerged classes of low-loss optical PCMs, i.e., antimony trisulphide (Sb2S3) and antimony triselenide (Sb2Se3), with superb characteristics to realize switchable, high-saturation, high-efficiency and high-resolution dynamic meta-pixels. Exploiting polarization-sensitive building blocks, the presented meta-pixel can generate two different colors when illuminated by either one of two orthogonally polarized incident beams. Such degrees of freedom (i.e., material phase and polarization state) enable a single reconfigurable metasurface with fixed geometrical parameters to generate four distinct wide-gamut colors. We experimentally demonstrate, for the first time, an electrically-driven micro-scale display through the integration of phase-change metasurfaces with an on-chip heater formed by transparent conductive oxide. Our experimental findings enable a versatile platform suitable for a wide range of applications, including tunable full-color printing, enhanced dynamic displays, information encryption, and anti-counterfeiting. © 2021, CC BY.

关键词： Light scattering

Percutaneous Coronary Intervention With a Drug-Eluting Stent Versus Coronary Artery Bypass Grafting in Patients Receiving Dialysis: A National Study From Taiwan

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Kidney medicine 2024年第2期6卷 100768页

作者： Szu-Yu Pan Ju-Yeh Yang Nai-Chi Teng Yun-Yi Chen Shi-Heng Wang Chien-Lin Lee Kang-Lung Chen Yen-Ling Chiu Shih-Ping Hsu Yu-Sen Peng Yung-Ming Chen Shuei-Liong Lin Likwang Chen Department of Integrated Diagnostics and Therapeutics National Taiwan University Hospital Taipei Taiwan. Division of Nephrology Department of Internal Medicine National Taiwan University Hospital Taipei Taiwan. Division of Nephrology Department of Internal Medicine Far Eastern Memorial Hospital New Taipei City Taiwan. Institute of Health Policy and Management College of Public Health National Taiwan University Taipei Taiwan. Institute of Population Health Sciences National Health Research Institutes Zhunan Taiwan. Department of Research Shin-Kong Wu Ho-Su Memorial Hospital Taipei Taiwan. Institute of Hospital and Health Care Administration National Yang Ming Chiao Tung University Taipei Taiwan. National Center for Geriatrics and Welfare Research National Health Research Institutes Yunlin Taiwan. Department of Cardiology Far Eastern Memorial Hospital New Taipei City Taiwan. Department of Cardiovascular Surgery Far Eastern Memorial Hospital New Taipei City Taiwan. Graduate Program in Biomedical Informatics Department of Computer Science and Engineering College of Informatics Yuan Ze University Taoyuan Taiwan. Graduate Institute of Clinical Medicine National Taiwan University College of Medicine Taipei Taiwan. Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan.

Rationale & Objective:We aimed to study the comparative effectiveness of percutaneous coronary intervention with drug-eluting stent and coronary artery bypass grafting in patients receiving dialysis. Study Design:This was a retrospective observational cohort study. Setting & Participants:This population-based study identified patients receiving dialysis hospitalized for coronary revascularization between January 1, 2009 and December 31, 2015, in the Taiwan National Health Insurance Research Database. Exposures:Patients received percutaneous coronary intervention with drug-eluting stent versus coronary artery bypass grafting. Outcomes:The study outcomes were all-cause mortality, in-hospital mortality, and repeat revascularization. Analytical Approach:Propensity scores were used to match patients. Cox proportional hazards models and logistic regression models were constructed to examine associations between revascularization strategies and mortality. Interval Cox models were fitted to estimate time-varying hazards during different periods. Results:A total of 1,840 propensity score-matched patients receiving dialysis were analyzed. Coronary artery bypass grafting was associated with higher in-hospital mortality (coronary artery bypass grafting vs percutaneous coronary intervention with drug-eluting stent; crude mortality rate 12.5% vs 3.3%; adjusted OR, 5.22; 95% CI, 3.42-7.97; < 0.001) and longer hospitalization duration (median [IQR], 20 [14-30] days vs 3 [2-8] days; < 0.001). After discharge, repeat revascularization, acute coronary syndrome, and repeat hospitalization all occurred more frequently in the percutaneous coronary intervention with drug-eluting stent group. Importantly, with a median follow-up of 2.8 years, coronary artery bypass grafting was significantly associated with a higher risk of all-cause overall mortality (adjusted HR, 1.19; 95% CI, 1.05-1.35; = 0.006) in the multivariable Cox proportional hazard model. Sensitivity and subgroup analyses yie

关键词： Coronary artery bypass grafting coronary revascularization dialysis drug-eluting stent end-stage kidney disease mortality percutaneous coronary intervention survival

Magnetic Control of Soft Chiral Phonons in PbTe

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arXiv 2021年

作者： Baydin, Andrey Hernandez, Felix G.G. Rodriguez-Vega, Martin Okazaki, Anderson K. Tay, Fuyang Timothy Noe, G. Katayama, Ikufumi Takeda, Jun Nojiri, Hiroyuki Rappl, Paulo H.O. Abramof, Eduardo Fiete, Gregory A. Kono, Junichiro Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Smalley-Curl Institute Rice University HoustonTX77005 United States Instituto de Física Universidade de São Paulo SP São Paulo05508-090 Brazil Theoretical Division Los Alamos National Laboratory Los AlamosNM87545 United States Laboratório Associado de Sensores e Materiais Instituto Nacional de Pesquisas Espaciais SP São José dos Campos12201-970 Brazil Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama240-8501 Japan Institute for Materials Research Tohoku University Sendai980-8577 Japan Department of Physics Northeastern University BostonMA02115 United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Material Science and NanoEngineering Rice University HoustonTX77005 United States

PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this phonon via polarization-dependent terahertz spectroscopy. We observed softening of this mode with decreasing temperature, indicative of incipient ferroelectricity, which we explain through a model including strong anharmonicity with a quartic displacement term. In magnetic fields up to 25 T, the phonon mode splits into two modes with opposite handedness, exhibiting circular dichroism. Their frequencies display Zeeman splitting together with an overall diamagnetic shift with increasing magnetic field. Using a group-theoretical approach, we demonstrate that these observations are the result of magnetic field-induced morphic changes in the crystal symmetries through the Lorentz force exerted on the lattice ions. Thus, our study reveals a novel process of controlling phonon properties in a soft ionic lattice by a strong magnetic field. Copyright © 2021, The Authors. All rights reserved.

关键词： Magnetic fields

Semi-supervised self-growing generative adversarial networks for image recognition

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arXiv 2019年

作者： Wang, Haoqian Xu, Zhiwei Xu, Jun An, Wangpeng Zhang, Lei Dai, Qionghai Graduate School at Shenzhen Tsinghua University Shenzhen Institute of Future Media Technology Shenzhen518055 China Media Computing Lab College of Computer Science Nankai University Tianjin China TNLIST Department of Automation Tsinghua University Beijing100084 China Department of Computing Hong Kong Polytechnic University Hong Kong

Image recognition is an important topic in computer vision and image processing, and has been mainly addressed by supervised deep learning methods, which need a large set of labeled images to achieve promising performance. However, in most cases, labeled data are expensive or even impossible to obtain, while unlabeled data are readily available from numerous free on-line resources and have been exploited to improve the performance of deep neural networks. To better exploit the power of unlabeled data for image recognition, in this paper, we propose a semi-supervised and generative approach, namely the semi-supervised self-growing generative adversarial network (SGGAN). Label inference is a key step for the success of semisupervised learning approaches. There are two main problems in label inference: how to measure the confidence of the unlabeled data and how to generalize the classifier. We address these two problems via the generative framework and a novel convolutionblock- transformation technique, respectively. To stabilize and speed up the training process of SGGAN, we employ the metric Maximum Mean Discrepancy as the feature matching objective function and achieve larger gain than the standard semisupervised GANs (SSGANs), narrowing the gap to the supervised methods. Experiments on several benchmark datasets show the effectiveness of the proposed SGGAN on image recognition and facial attribute recognition tasks. By using the training data with only 4% labeled facial attributes, the SGGAN approach can achieve comparable accuracy with leading supervised deep learning methods with all labeled facial attributes. Copyright © 2019, The Authors. All rights reserved.

关键词： Generative adversarial networks