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Three-Dimensional Acoustic Double-Zero-Index Medium with a Fourfold Degenerate Dirac-like Point

Physical Review Letters 2020年第7期124卷 074501-074501页

作者： Changqing Xu Guancong Ma Ze-Guo Chen Jie Luo Jinjie Shi Yun Lai Ying Wu Division of Computer Electrical and Mathematical Science and Engineering King Abdullah University of Science and Technology (KAUST) Thuwal 23955-6900 Saudi Arabia Department of Physics Hong Kong Baptist University Kowloon Tong Hong Kong School of Physical Science and Technology Soochow University Suzhou 215006 China MOE Key Laboratory of Modern Acoustics National Laboratory of Solid State Microstructures School of Physics and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

We report the first realization of a three-dimensional (3D) acoustic double-zero-index medium (DZIM) made of a cubic lattice of metal rods. While the past decade has seen several realizations of 2D DZIM, achieving such a medium in 3D has remained an elusive challenge. Here, we show how a fourfold degenerate point with conical dispersion can be induced at the Brillouin zone center, such that the material becomes a 3D DZIM with the effective mass density and compressibility simultaneously acquiring near-zero values. To demonstrate the functionalities of this new medium, we have fabricated an acoustic waveguide of 3D DZIM in form of a “periscope” with two 90° turns and observed tunneling of a normally incident planar wave through the waveguide yielding undistorted planar wave front at the waveguide exit. Our findings establish a practical route to realize 3D DZIM as an effective acoustic “void space” that offers unprecedented control over acoustic wave propagation.

关键词： Photonic crystals Acoustic metamaterials

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Physics-based iterative reconstruction for dual source and flying focal spot computed tomography

arXiv

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arXiv 2020年

作者： Wang, Xiao MacDougall, Robert D. Chen, Peng Bouman, Charles A. Warfield, Simon K. Department of Radiology Boston Children's Hospital Harvard Medical School BostonMA02115 United States National Institute of Advanced Industrial Science and Technology Japan RIKEN Center for Computational Science Japan School of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States

Purpose: For single source helical Computed Tomography (CT), both Filtered-Back Projection (FBP) and statistical iterative reconstruction have been investigated. However for dual source CT with flying focal spot (DS-FFS CT), statistical iterative reconstruction that accurately models the scanner geometry and acquisition physics remains unknown to researchers. Therefore, our purpose is to present a novel physics-based iterative reconstruction method for DS-FFS CT and assess its image quality. Methods: Our algorithm uses precise physics models to reconstruct from the native cone-beam geometry and interleaved dual source helical trajectory of a DS-FFS CT. To do so, we construct a noise physics model to represent data acquisition noise and a prior image model to represent image noise and texture. In addition, we design forward system models to compute the locations of deflected focal spots, the dimension and sensitivity of voxels and detector units, as well as the length of intersection between X-rays and voxels. The forward system models further represent the coordinated movement between the dual sources by computing their X-ray coverage gaps and overlaps at an arbitrary helical pitch. With the above models, we reconstruct images by using an advanced Consensus Equilibrium (CE) numerical method to compute the maximum a posteriori estimate to a joint optimization problem that simultaneously fits all models. Results: We compared our reconstruction with Siemens ADMIRE, which is the clinical standard hybrid iterative reconstruction (IR) method for DS-FFS CT, in terms of spatial resolution, noise profile and image artifacts through both phantoms and clinical scan datasets. Experiments show that our reconstruction has a higher spatial resolution, with a Task-Based Modulation Transfer Function (MTFtask) consistently higher than the clinical standard hybrid IR. In addition, our reconstruction shows a reduced magnitude of image undersampling artifacts than the clinical standard.

关键词： computerized tomography

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Challenges in partially-automated roadway feature mapping using mobile laser scanning and vehicle trajectory data

arXiv

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arXiv 2019年

作者： Billah, Mohammad Rahman, Farzana S. Maskooki, Arash Todd, Michael Barth, Matthew Farrell, Jay A. Department of Electrical and Computer Engineering University of California Riverside92521 United States Center for Environmental Research & Technology University of California Riverside92521 United States Faculty of Electrical and Computer Engineering University of California Riverside92521 United States

Connected vehicle and driver’s assistance applications are greatly facilitated by Enhanced Digital Maps (EDMs) that represent roadway features (e.g., lane edges or centerlines, stop bars). Due to the large number of signalized intersections and miles of roadway, manual development of EDMs on a global basis is not feasible. Mobile Terrestrial Laser Scanning (MTLS) is the preferred data acquisition method to provide data for automated EDM development. Such systems provide an MTLS trajectory and a point cloud for the roadway environment. The challenge is to automatically convert these data into an EDM. This article presents a new processing and feature extraction method, experimental demonstration providing SAE-J2735 map messages for eleven example intersections, and a discussion of the results that points out remaining challenges and suggests directions for future research. Copyright © 2019, The Authors. All rights reserved.

关键词： Laser applications

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Resting-state dynamic functional network connectivity predicts cognition in 37,784 participants of UK Biobank

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Alzheimer's & Dementia 2023年第S3期19卷

作者： Mohammad S.E. Sendi Elaheh Zendehrouh Robyn L Miller David H Salat Vince D Calhoun School of Electrical and Computer Engineering (ECE) at the Georgia Institute of Technology Atlanta GA USA Tri-Institutional Georgia State University/Georgia Institute of Technology/Emory University Center for Translational Research in Neuroimaging and Data Science Atlanta GA USA Wallace H. Coulter Department of Biomedical Engineering at Emory University and Georgia Tech Atlanta GA USA Georgia State University Atlanta GA USA Neuroimaging Research for Veterans Center VA Boston Healthcare System Jamaica Plain MA USA Massachusetts General Hospital Charlestown MA USA Harvard Medical School Boston MA USA Athinoula A. Martinos Center for Biomedical Imaging Charlestown MA USA

Background Age-related cognitive decline after 65 is a well-known phenomenon, but little is known about how brain functional changes are related to cognitive decline. To this end, previous studies explored the link between functional network connectivity (FNC) estimated from resting-state functional MRI (rs-fMRI) and cognitive scores in healthy adults. FNC is often assumed to be static over time. However, this assumption runs contrary to the dynamic nature of brain FNC, and dynamic FNC (dFNC) has been recently introduced to overcome this limitation. The current study investigated the relationship between dFNC estimated from 36,263 individuals from UK Biobank and cognition. Method We used the resting-state fMRI (duration: 5min) data of 37,784 (20,157 females) adults’ brains, demographic information (age:64.06± 7.51), and cognitive scores from the UK Biobank in which the cognitive scores include fluid intelligence (FI), reaction time (RT), and pairs matching (Pairs). We adapted group independent component analysis to extract 53 data-driven components for the whole brain using a fully automated approach (Fig.1: Step1). Next, we used the sliding window and Pearson correlation to estimate the dFNC among 53 components (Fig.1: Step2). We used k-means clustering to put dFNCs of all individuals into three separated states and calculated individual state vectors (Fig.1: Step3). Then, we estimated 32 dFNC features based on three estimated states and state vectors (Fig.1: Step4). Finally, we trained a two-fold cross-validation support vector regression to predict the cognitive scores (Fig.1: Step5). Result The estimated dFNC feature predicted FI score with high accuracy (the correlation between measure and predicted score is R = 0.043, p = 6.6e −17 , Fig.2A), mean time to correctly identify match in RT task (R = 0.065, p = 1.9 −34 , Fig.2B), and time to complete Pairs task (R = 0.049, p = 1.3e −20 , Fig.2C). Conclusion Here we explored the link between dFNC features and cogniti

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Improved SVM for High Gain Tri-state CSI to Reduce DC Side Inductor Current Ripple

Improved SVM for High Gain Tri-state CSI to Reduce DC Side I...

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International Conference on Power Electronics (ICPE)

作者： Chufeng Li Liuchen Chang Meiqin Mao Research Center for Photovoltaic System Engineering Hefei University of Technology Hefei China Department of Electrical and Computer Engineering University of New Brunswick Fredericton New Brunswick Canada

ISBN: (纸本)9781728116129

Extending our previous work proposing a high gain tri-state current source inverter (CSI), in this paper, an improved space vector modulation (SVM) method is proposed in order to reduce the DC side inductor current ripple. By the proposed SVM method, the active state time is divided into four equal segments and the shoot-through state time is divided into six equal segments and inserted into the four equal active state segments, respectively. Theoretically, the maximum ripple can be obtained to 1/3 of that compared with the traditional SVM mode. The proposed improved SVM method is compared with the traditional SVM method. Simulation and experimental results verify the effectiveness of the proposed strategy.

关键词： Inductors Switches Support vector machines Inverters Modulation Topology Switching frequency

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Multi-Parameter Performance Modeling Based on Machine Learning with Basic Block Features

Multi-Parameter Performance Modeling Based on Machine Learni...

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IEEE International Conference on Big Data and Cloud Computing (BdCloud)

作者： Meng Hao Weizhe Zhang Yiming Wang Dong Li Wen Xia Hao Wang Chen Lou School of Computer Science and Technology Harbin Institute of Technology China Cyberspace Security Research Center Peng Cheng Laboratory Shenzhen China Department of Electrical Engineering and Computer Science University of California Merced Department of Computer Science Norwegian University of Science and Technology Norway

ISBN: (数字)9781728143286

ISBN: (纸本)9781728143293

Considering the increasing complexity and scale of HPC architecture and software, the performance modeling of parallel applications on large-scale HPC platforms has become increasingly important. It plays an important role in many areas, such as performance analysis, job management, and resource estimation. In this work, we propose a multi-parameter performance modeling and prediction framework called MPerfPred, which utilizes basic block frequencies as features and uses machine learning algorithms to automatically construct multi-parameter performance models with high generalization ability. To reduce the prediction overhead, we propose some feature-filtering strategies to reduce the number of features in the training stage and build a serial program called BBF collector for each target application to quickly collect feature values in the prediction stage. We demonstrate the use of MPerfPred on the TianHe-2 supercomputer with six parallel applications. Results show that MPerfPred with SVR achieves better prediction than other input parameter-based modeling methods. The average prediction error and average standard deviation of prediction errors of MPerfPred are 8.42% and 6.09%, respectively. In the prediction stage, the average prediction overhead of MPerfPred is less than 0.13% of the total execution time.

关键词： Training Predictive models Machine learning algorithms Machine learning Instruments Data models Prediction algorithms

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Breakdown of the weak coupling limit in quantum annealing

arXiv

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arXiv 2021年

作者： Bando, Yuki Yip, Ka-Wa Chen, Huo Lidar, Daniel A. Nishimori, Hidetoshi Institute of Innovative Research Tokyo Institute of Technology Kanagawa Yokohama226-8503 Japan Center for Quantum Information Science & Technology University of Southern California Los AngelesCA90089 United States Department of Physics & Astronomy University of Southern California Los AngelesCA90089 United States Department of Electrical & Computer Engineering University of Southern California Los AngelesCA90089 United States Department of Chemistry University of Southern California Los AngelesCA90089 United States International Research Frontiers Initiative Tokyo Institute of Technology Kanagawa Yokohama226-8503 Japan Graduate School of Information Sciences Tohoku University Miyagi Sendai980-8579 Japan Saitama Wako351-0198 Japan

Reverse annealing is a variant of quantum annealing, in which the system is prepared in a classical state, reverse-annealed to an inversion point, and then forward-annealed. We report on reverse annealing experiments using the D-Wave 2000Q device, with a focus on the p = 2 p-spin problem, which undergoes a second order quantum phase transition with a gap that closes polynomially in the number of spins. We concentrate on the total and partial success probabilities, the latter being the probabilities of finding each of two degenerate ground states of all spins up or all spins down, the former being their sum. The empirical partial success probabilities exhibit a strong asymmetry between the two degenerate ground states, depending on the initial state of the reverse anneal. To explain these results, we perform open-system simulations using master equations in the limits of weak and strong coupling to the bath. The former, known as the adiabatic master equation (AME), with decoherence in the instantaneous energy eigenbasis, predicts perfect symmetry between the two degenerate ground states, thus failing to agree with the experiment. In contrast, the latter, known as the polaron transformed Redfield equation (PTRE), is in close agreement with experiment. Thus our results present a challenge to the sufficiency of the weak system-bath coupling limit in describing the dynamics of current experimental quantum annealers, at least for reverse annealing on timescales of a μsec or longer. © 2021, CC BY.

关键词： Ground state

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Photonic waveguide to free-space Gaussian beam extreme mode converter

引用

Light(Science & Applications) 2018年第1期7卷 346-358页

作者： Sangsik Kim Daron A.Westly Brian J.Roxworthy Qing Li Alexander Yulaev Kartik Srinivasan Vladimir A.Aksyuk Center for Nanoscale Science and Technology National Institute of Standards and TechnologyGaithersburgMD 20899USA Maryland Nanocenter University of MarylandCollege ParkMD 20742USA Department of Electrical and Computer Engineering Texas Tech UniversityLubbockTX 79409USA

Integration of photonic chips with millimeter-scale atomic,micromechanical,chemical,and biological systems can advance science and enable new miniaturized hybrid devices and *** interaction via small evanescent volumes restricts performance in applications such as gas spectroscopy,and a general ability to photonically access optical fields in large free-space volumes is ***,conventional inverse tapers and grating couplers do not directly scale to create wide,high-quality collimated beams for low-loss diffraction-free propagation over many millimeters in free space,necessitating additional bulky collimating optics and expensive ***,we develop an extreme mode converter,which is a compact planar photonic structure that efficiently couples a 300 nm×250 nm silicon nitride high-index single-mode waveguide to a well-collimated near surface-normal Gaussian beam with an≈160μm waist,which corresponds to an increase in the modal area by a factor of>*** beam quality is thoroughly characterized,and propagation over 4mm in free space and coupling back into a single-mode photonic waveguide with low loss via a separate identical mode converter is *** achieve low phase error over a beam area that is>100×larger than that of a typical grating coupler,our approach separates the two-dimensional mode expansion into two sequential separately optimized stages,which create a fully expanded and well-collimated Gaussian slab mode before out-coupling it into free *** at 780 nm for integration with chip-scale atomic vapor cell cavities,our design can be adapted for visible,telecommunication,or other *** technique can be expanded to more arbitrary phase and intensity control of both large-diameter,free-space optical beams and wide photonic slab modes.

关键词： waveguide millimeter mode

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Recent advances in intelligent automated fruit harvesting robots

Open Agriculture Journal

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Open Agriculture Journal 2019年第1期13卷 101-106页

作者： Hua, Yanbin Zhang, Nairu Yuan, Xin Quan, Lichun Yang, Jiangang Nagasaka, Ken Zhou, Xin-Gen Fruit Industry Service Center of Fufeng County Fufeng Shaanxi 722299 China Department of Electrical Engineering and Computer Science Tokyo University of Agriculture and Technology 2-24-16 Nakamachi Koganei-shi 184-8588 Tokyo Japan Texas A&M AgriLife Research Center Texas A&M University System 1509 Aggie Drive Beaumont 77713 TX United States

Robotic harvesting offers a solution to reducing labor costs, optimizing harvest scheduling, enabling selective harvesting, and increasing operation efficiency. These attributes allow the users of robotic harvesters to maximize production efficiency and profits. This article reviews automated fruit harvesting systems of sweet pepper, tomato, apple and kiwifruit as an example to demonstrate the recent advances in intelligent automatic harvesting robots in horticulture. ©2019 Yanbin Hua et al. © 2019, Bentham Science Publishers. All rights reserved.

关键词： Automated fruit harvesting robot Efficiency Horticulture Intelligent Kiwifruit Selective harvesting

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Constructions of Partial MDS Codes over Small Fields

Constructions of Partial MDS Codes over Small Fields

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作者： Gabrys, Ryan Yaakobi, Eitan Blaum, Mario Siegel, Paul H. Spawar Systems Center San Diego San DiegoCA92115 United States Department of Computer Science Technion - Israel Institute of Technology Haifa32000 Israel IBM Research Division Almaden Research Center San JoseCA95120 United States Department of Electrical and Computer Engineering University of California at San Diego San DiegoCA92093 United States Center for Memory and Recording Research University of California at San Diego San DiegoCA92093 United States

Partial MDS (PMDS) codes are a class of erasure-correcting array codes that combine local correction of the rows with global correction of the array. An m× n array code is called an (rs) PMDS code if each row belongs to an [n, n-r, r+1] MDS code and the code can correct erasure patterns consisting of r erasures in each row together with s more erasures anywhere in the array. While a recent construction by Calis and Koyluoglu generates (r;s) PMDS codes for all r and s, its field size is exponentially large. In this paper, a family of PMDS codes with field size O\left (max m, nr+ss}\right) is presented for the case where r= O(1), s= O(1). © 1963-2012 IEEE.

关键词： Codes (symbols)

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