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Spacetime modulation in floating thin elastic plates

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Physical Review B 2021年第1期104卷 014308-014308页

作者： Mohamed Farhat Sebastien Guenneau Pai-Yen Chen Ying Wu Computer Electrical and Mathematical Science and Engineering (CEMSE) Division King Abdullah University of Science and Technology (KAUST) Thuwal 23955-6900 Saudi Arabia UMI 2004 Abraham de Moivre-CNRS Imperial College London London SW7 2AZ United Kingdom Department of Electrical and Computer Engineering University of Illinois at Chicago Chicago Illinois 60607 USA

We consider the propagation of flexural-gravity waves in thin elastic plates floating atop nonviscous fluids, e.g., seawater, which are governed by a partial differential equation with Laplacian and tri-Laplacian terms. We investigate the effect of time modulation as well as spacetime modulation on thin floating elastic plates and show the peculiarity of the phenomena of the k-band gap and the rotated k-band gap in the context of flexural-gravity waves. This makes possible floating plates with nonreciprocal features and behaving as elastodynamic analogs of luminal electromagnetic metamaterials, with exotic applications in enhanced control of ocean waves, such as filtering devices, unidirectional acoustic propagation, and isolation effects and energy harvesting in maritime engineering.

关键词： Band gap Elastic deformation Phonons Metamaterials

Dynamic SDN-based radio access network slicing with deep reinforcement learning for URLLC and eMBB services

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arXiv 2022年

作者： Filali, Abderrahime Mlika, Zoubeir Cherkaoui, Soumaya Kobbane, Abdellatif INTERLAB Research Laboratory Faculty of Engineering Department of Electrical and Computer Science Engineering Université de Sherbrooke SherbrookeQCJ1K 2R1 Canada UM5R ENSIAS BP 713 Rabat Morocco

Radio access network (RAN) slicing is a key technology that enables 5G network to support heterogeneous requirements of generic services, namely ultra-reliable low-latency communication (URLLC) and enhanced mobile broadband (eMBB). In this paper, we propose a two time-scales RAN slicing mechanism to optimize the performance of URLLC and eMBB services. In a large time-scale, an SDN controller allocates radio resources to gNodeBs according to the requirements of the eMBB and URLLC services. In a short time-scale, each gNodeB allocates its available resources to its end-users and requests, if needed, additional resources from adjacent gNodeBs. We formulate this problem as a non-linear binary program and prove its NPhardness. Next, for each time-scale, we model the problem as a Markov decision process (MDP), where the large-time scale is modeled as a single agent MDP whereas the shorter time-scale is modeled as a multi-agent MDP. We leverage the exponentialweight algorithm for exploration and exploitation (EXP3) to solve the single-agent MDP of the large time-scale MDP and the multi-agent deep Q-learning (DQL) algorithm to solve the multi-agent MDP of the short time-scale resource allocation. Extensive simulations show that our approach is efficient under different network parameters configuration and it outperforms recent benchmark solutions. © 2022, CC BY.

关键词： Deep learning

A Non-Resonant Partially Reflecting Surface Antenna With a Phase-Correcting Surface for Gain Enhancement

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TechRxiv

TechRxiv 2022年

作者： Ge, Yuehe Ren, Xiaolei Chen, Zhizhang David Zhang, Hai The College of Information Science and Engineering Huaqiao University Fujian Xiamen361021 China The College of Physics and Information Engineering Fuzhou University Fuzhou350108 China The Department of Electrical and Computer Engineering Dalhousie University HalifaxNSB3H 4R2 Canada

Partially-reflecting surface (PRS) resonant antennas have attracted significant attention for the past two decades. However, their radiation performance is still not as good as expected. This paper proposes a non-resonant PRS antenna that does not require the conventional resonant condition that limits design flexibility and gain performance. It consists of a PRS, a ground, a small feed, and a transparent phase-correcting surface (PCS) placed above the PRS for phase compensation. The ray-tracing method is used to analyze the proposed non-resonant PRS antenna, and numerical simulations are conducted to verify its effectiveness. Three prototypes are fabricated and tested, and the measured results show a better gain performance than the conventional PRS antennas that require the resonant condition. © , CC BY.

关键词： Energy gap

MANTRA: A Graph-based Unified Information Aggregation Foundation for Enhancing Cybersecurity Management in Critical Infrastructures

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MANTRA: A Graph-based Unified Information Aggregation Founda...

Open Identity Summit 2023

作者： Fuxen, Philipp Hackenberg, Rudolf Heinl, Michael P. Ross, Mirko Roßnagel, Heiko Schunck, Christian H. Yahalom, Raphael OTH Regensburg Faculty Computer Science and Mathematics Seybothstr. 2 Regensburg93053 Germany Fraunhofer Institute for Applied and Integrated Security AISEC Department Product Protection and Industrial Security Lichtenbergstr. 11 near Munich Garching85748 Germany asvin GmbH Schulze-Delitzsch-Str. 16 Stuttgart70565 Germany Fraunhofer Institute for Industrial Engineering IAO Group Identity Management Nobelstr. 12 Stuttgart70569 Germany Massachusetts Institute of Technology MIT Sloan School of Management 100 Main Street CambridgeMA02142 United States

ISBN: (纸本)9783885797296

The digitization of almost all sectors of life and the quickly growing complexity of interrelationships between actors in this digital world leads to a dramatically increasing attack surface regarding both direct and also indirect attacks over the supply chain. These supply chain attacks can have different characters, e.g., vulnerabilities and backdoors in hardware and software, illegitimate access by compromised service providers, or trust relationships to suppliers and customers exploited in the course of business email compromise. To address this challenge and create visibility along these supply chains, threat-related data needs to be rapidly exchanged and correlated over organizational borders. The publicly funded project MANTRA is meant to create a secure and resilient framework for real-time exchange of cyberattack patterns and automated, contextualized risk management. The novel graph-based approach provides benefits for automation regarding cybersecurity management, especially when it comes to prioritization of measures for risk reduction and during active defense against cyberattacks. In this paper, we outline MANTRA’s scope, objectives, envisioned scientific approach, and challenges. © 2023 Gesellschaft fur Informatik (GI). All rights reserved.

关键词： Critical infrastructures

Audio-visual transformer based crowd counting

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arXiv 2021年

作者： Sajid, Usman Chen, Xiangyu Sajid, Hasan Kim, Taejoon Wang, Guanghui Electrical Engineering and Computer Science University of Kansas LawrenceKS66045 United States School of Mechanical and Manufacturing Engineering NUST Islamabad Pakistan Department of Computer Science Ryerson University TorontoONM5B 2K3 Canada

Crowd estimation is a very challenging problem. The most recent study tries to exploit auditory information to aid the visual models, however, the performance is limited due to the lack of an effective approach for feature extraction and integration. The paper proposes a new audiovisual multi-task network to address the critical challenges in crowd counting by effectively utilizing both visual and audio inputs for better modalities association and productive feature extraction. The proposed network introduces the notion of auxiliary and explicit image patch-importance ranking (PIR) and patch-wise crowd estimate (PCE) information to produce a third (run-time) modality. These modalities (audio, visual, run-time) undergo a transformer-inspired cross-modality co-attention mechanism to finally output the crowd estimate. To acquire rich visual features, we propose a multi-branch structure with transformer-style fusion in-between. Extensive experimental evaluations show that the proposed scheme outperforms the state-of-the-art networks under all evaluation settings with up to 33.8% improvement. We also analyze and compare the vision-only variant of our network and empirically demonstrate its superiority over previous approaches. © 2021, CC BY.

关键词： Feature extraction

A Unified Joint Optimization of Training Sequences and Transceivers Based on Matrix-Monotonic Optimization

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arXiv 2022年

作者： Xing, Chengwen Yu, Tao Song, Jinpeng Zheng, Zhong Zhao, Lian Hanzo, Lajos School of Information and Electronics Beijing Institute of Technology Beijing100081 China School of Cyberspace Science and Technology Beijing Institute of technology Beijing100081 China The Department of Electrical Computer and Biomedical Engineering Ryerson University TorontoONM5B 2K3 Canada The Department of Electronics and Computer Science University of Southampton SouthamptonSO17 1BJ United Kingdom

Channel estimation and data transmission constitute the most fundamental functional modules of multiple-input multiple-output (MIMO) communication systems. The underlying key tasks corresponding to these modules are training sequence optimization and transceiver optimization. Hence, we jointly optimize the linear transmit precoder and the training sequence of MIMO systems using the metrics of their effective mutual information (MI), effective mean squared error (MSE), effective weighted MI, effective weighted MSE, as well as their effective generic Schur-convex and Schur-concave functions. Both statistical channel state information (CSI) and estimated CSI are considered at the transmitter in the joint optimization. A unified framework termed as joint matrix-monotonic optimization is proposed. Based on this, the optimal precoder matrix and training matrix structures can be derived for both CSI scenarios. Then, based on the optimal matrix structures, our linear transceivers and their training sequences can be jointly optimized. Compared to state-of-the-art benchmark algorithms, the proposed algorithms visualize the bold explicit relationships between the attainable system performance of our linear transceivers conceived and their training sequences, leading to implementation ready recipes. Finally, several numerical results are provided, which corroborate our theoretical results and demonstrate the compelling benefits of our proposed pilot-aided MIMO solutions. Copyright © 2022, The Authors. All rights reserved.

关键词： Matrix algebra

Electronic structure and surface band bending of Sn-doped β−Ga2O3 thin films studied by x-ray photoemission spectroscopy and ab initio calculations

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Physical Review B 2024年第11期110卷 115120页

作者： Jiaye Zhang Zhenni Yang Siliang Kuang Ziqi Zhang Shenglong Wei Joe Willis Tien-Lin Lee Piero Mazzolini Oliver Bierwagen Shanquan Chen Zuhuang Chen Duanyang Chen Hongji Qi David Scanlon Kelvin H. L. Zhang State Key Laboratory of Physical Chemistry of Solid Surfaces College of Chemistry and Chemical Engineering Hangzhou Institute of Optics and Fine Mechanics Hangzhou 311421 People's Republic of China Department of Chemistry Harwell Science and Innovation Campus Didcot OX11 0DE United Kingdom Department of Mathematical Physical and Computer Sciences Leibniz-Institut im Forschungsverbund Berlin e.V. Hausvogteiplatz 5-7 10117 Berlin Germany School of Materials Science and Engineering Key Laboratory of Materials for High Power Laser and Research Center of Laser Crystal School of Chemistry The University of Birmingham Edgbaston Birmingham B15 2TT United Kingdom

The bulk and surface electronic structures of Sn-doped β−Ga2O3 thin films have been studied by soft and hard x-ray photoemission spectroscopy (soft PES at 1486.6 eV and HAXPES at 5920 eV). The experimental spectra are compared with density functional theory calculated density of states in the valence band and conduction band. Excellent agreement was found between experimental spectra and calculated density of states by taking into account the photoionization cross section of different orbitals involved in the valence and conduction bands. The electronic states derived from Ga 4s character are selectively enhanced by HAXPES. This allows us to infer that the states at the conduction band and bottom of the valence band contain pronounced Ga 4s character. The occupation of the lower conduction band in degenerately Sn-doped Ga2O3 is clearly observed by HAXPES, which allows for direct measurement of Burstein-Moss shift and band-gap renormalization as a function of Sn doping. A comparison of the valence band spectra of Sn-doped Ga2O3 films with Si-doped samples suggests that Sn doping has different effects on the electronic structure than Si doping. An in-gap electronic state is observed for Sn-doped Ga2O3, which is attributed to self-compensating Sn2+ related defects. Furthermore, a larger band-gap renormalization is found in Sn-doped samples, because the Sn 5s dopant orbital mixes strongly with the host Ga 4s derived conduction band. Finally, a comparison of the valence band and core-level spectra excited with soft and hard x rays allows us to identify an upward band bending at the surface region of Sn-doped Ga2O3 films.

关键词： Doping effects Electronic structure Surface states Doped semiconductors Thin films Wide band gap systems Ab initio calculations Density functional calculations Laser ablation Photoemission spectroscopy

Purcell enhanced optical refrigeration

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arXiv 2024年

作者： Ju, Peng Püschel, Stefan Shen, Kunhong Jin, Yuanbin Tanaka, Hiroki Li, Tongcang Department of Physics and Astronomy Purdue University West LafayetteIN47907 United States Max-Born-Str. 2 Berlin12489 Germany Elmore Family School of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States Birck Nanotechnology Center Purdue University West LafayetteIN47907 United States Purdue Quantum Science and Engineering Institute Purdue University West LafayetteIN47907 United States

Optical refrigeration of solids with anti-Stokes fluorescence has been widely explored as a vibration-free cryogenic cooling technology. A minimum temperature of 87 K has been demonstrated with rare-earth ion doped crystals using optical refrigeration. However, the depletion of the upper-lying energy levels in the ground state manifold hinders further cooling to below liquid nitrogen (LN2) temperatures, confining its applications. In this work, we introduce a Purcell enhanced optical refrigeration method to circumvent this limitation. This approach enhances the emission of high energy photons by coupling to a nearby nanocavity, blue shifting the mean emission wavelength. Such Purcell enhanced emission facilitates cooling starting from a lower energy level in the ground state manifold, which exhibits a higher occupation below LN2 temperatures. Using our experimentally measured optical coefficients, our theoretical analysis predicts a minimum achievable temperature of 38 K for a Yb3+:YLiF4 nanocrystal near a cavity under realistic conditions. The proposed method is applicable to other rare-earth ion doped materials and semiconductors, and will have applications in creating superconducting and other quantum devices with solid-state cooling. Copyright © 2024, The Authors. All rights reserved.

关键词： Ground state

Advanced biomedical imaging for identifying blood cell type: Integrating segmentation, feature extraction, and GraphSAGE model

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Biomedical engineering Advances 2025年 9卷

作者： Nur Mohammad Fahad Mohaimenul Azam Khan Raiaan Arefin Ittesafun Abian Ripon Kumar Debnath Sidratul Montaha Mirjam Jonkman Sami Azam Department of Computer Science and Engineering United International University Dhaka 1212 Bangladesh Faculty of Science and Technology Charles Darwin University Casuarina NT 0909 Australia Department of Computer Science University of Calgary Calgary AB T2N 1N4 Canada

Background The analysis of blood, including red blood cells (RBC) and different types of white blood cells (WBCs) plays a major role in the diagnosis of certain diseases. Automated segmentation of blood cells and their components can assist clinicians in effectively making diagnoses; however, it is quite challenging Objective: This study proposes a computerized approach to assessing the significance of biomedical imaging. It presents a framework for segmenting blood cells as well as their nuclei from the histopathological images of multiple datasets. Additionally, a custom algorithm is developed for blood cell counting. Methods This study introduces two automated methods for WBC analysis, including image segmentation to distinguish between WBCs and RBCs, the nuclei of the WBC, and classifying WBC types using clinically important features. An effective segmentation approach with image preprocessing algorithms is developed for automatic counting of WBCs and RBCs. An improved GraphSAGE model is constructed to classify blood cells. Clinically relevant features are extracted from segmented WBCs and nuclei for a final dataset. Feature ranking analysis identifies optimal features and reduces dimensionality, aiding graph dataset construction based on data similarity. Results Our proposed model achieved an accuracy of 96.67 %. A comparative analysis with benchmark models is done to assess the effectiveness of the model. The explainability of the model is addressed to enhance the transparency of the diagnostic system and provide insight into the decision-making process. Conclusion Leveraging the automated, simultaneous segmentation of blood cells and exploring their relationships for effective classification substantially helps to improve the reliability and applicability of this diagnostic system and aid clinicians.

关键词： Biomedical imaging Blood cell Segmentation Graph representation GraphSAGE model