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arXiv 2024年

作者： Wang, Haozhe Shao, Xiaodan Zheng, Beixiong Shi, Xiaoming Zhang, Rui School of Science and Engineering The Chinese University of Hong Kong Guangdong Shenzhen518172 China Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada School of Microelectronics South China University of Technology Guangzhou511442 China School of Science and Engineering Shenzhen Research Institute of Big Data The Chinese University of Hong Kong Guangdong Shenzhen518172 China Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

Six-dimensional movable antenna (6DMA) is a promising solution for enhancing wireless network capacity through the adjustment of both three-dimensional (3D) positions and 3D rotations of distributed antenna surfaces. Previous works mainly consider 6DMA surfaces composed of active antenna elements, thus termed as active 6DMA. In this letter, we propose a new passive 6DMA system consisting of distributed passive intelligent reflecting surfaces (IRSs) that can be adjusted in terms of 3D position and 3D rotation. Specifically, we study a passive 6DMA-aided multiuser uplink system and aim to maximize the users’ achievable sum rate by jointly optimizing the 3D positions, 3D rotations, and reflection coefficients of all passive 6DMA surfaces, as well as the receive beamforming matrix at the base station (BS). To solve this challenging non-convex optimization problem, we propose an alternating optimization (AO) algorithm that decomposes it into three subproblems and solves them alternately in an iterative manner. Numerical results are presented to investigate the performance of the proposed passive 6DMA system under different configurations and demonstrate its superior performance over the traditional fixed-IRS counterpart for both directive and isotropic radiation patterns of passive reflecting elements. Copyright © 2024, The Authors. All rights reserved.

关键词： Convex optimization

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Fast impression painting using multi-color fused deposition modeling with a diamond hotend

Fast impression painting using multi-color fused deposition ...

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2022 ASPE and euspen Summer Topical Meeting on Advancing Precision in Additive Manufacturing

作者： Tonello, Riccardo Abedini, Fereshteh Pedersen, David Bue Frisvad, Jeppe Revall Department of Computer Science Technical University of Denmark Building 324 R. Petersens PL Kgs. Lyngby2800 Denmark Department of Mechanical Engineering Technical University of Denmark Building 427A Produktionstorvet Kgs. Lyngby2800 Denmark Department of Science and Technology Linkoping University Kopparhammaren 2 Campus Norrkoping KO2038 Sweden

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6DMA-Aided Cell-Free Massive MIMO Communication

arXiv

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arXiv 2024年

作者： Shi, Xiaoming Shao, Xiaodan Zheng, Beixiong Zhang, Rui School of Science and Engineering The Chinese University of Hong Kong Guangdong Shenzhen518172 China Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada School of Microelectronics South China University of Technology Guangzhou511442 China School of Science and Engineering Shenzhen Research Institute of Big Data The Chinese University of Hong Kong Guangdong Shenzhen518172 China The Department of Electrical and Computer Engineering National University of Singapore 117583 Singapore

—In this letter, we propose a six-dimensional movable antenna (6DMA)-aided cell-free massive multiple-input multiple-output (MIMO) system to fully exploit its macro spatial diversity, where a set of distributed access points (APs), each equipped with multiple 6DMA surfaces, cooperatively serve all users in a given area. Connected to a central processing unit (CPU) via fronthaul links, 6DMA-APs can optimize their combining vectors for decoding the users’ information based on either local channel state information (CSI) or global CSI shared among them. We aim to maximize the average achievable sum-rate via jointly optimizing the rotation angles of all 6DMA surfaces at all APs, based on the users’ spatial distribution. Since the formulated problem is non-convex and highly non-linear, we propose a Bayesian optimization-based algorithm to solve it efficiently. Simulation results show that, by enhancing signal power and mitigating interference through reduced channel cross-correlation among users, 6DMA-APs with optimized rotations can significantly improve the average sum-rate, as compared to the conventional cell-free network with fixed-position antennas and that with only a single centralized AP with optimally rotated 6DMAs, especially when the user distribution is more spatially diverse. Copyright © 2024, The Authors. All rights reserved.

关键词： Convex optimization

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LCPFormer: Towards Effective 3D Point Cloud Analysis via Local Context Propagation in Transformers

arXiv

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arXiv 2022年

作者： Huang, Zhuoxu Zhao, Zhiyou Li, Banghuai Han, Jungong The Department of Computer Science Aberystwyth University AberystwythSY23 3DB United Kingdom Co. Ltd China The Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai200240 China The School of Electronics Engineering and Computer Science Peking University Beijing100871 China The Department of Computer Science University of Sheffield SheffieldS10 2TN United Kingdom

Transformer with its underlying attention mechanism and the ability to capture long-range dependencies makes it become a natural choice for unordered point cloud data. However, local regions separated from the general sampling architecture corrupt the structural information of the instances, and the inherent relationships between adjacent local regions lack exploration. In other words, the transformer only focuses on the long-range dependence, while local structural information is still crucial in a transformer-based 3D point cloud model. To enable transformers to incorporate local structural information, we proposed a straightforward solution based on the natural structure of the point clouds to exploit the message passing between neighboring local regions, thus making their representations more comprehensive and discriminative. Concretely, the proposed module, named Local Context Propagation (LCP), is inserted between two transformer layers. It takes advantage of the overlapping points of adjacent local regions (statistically shown to be prevalent) as intermediaries, then re-weighs the features of these shared points from different local regions before passing them to the next layers. Finally, we design a flexible LCPFormer architecture equipped with the LCP module, which is applicable to several different tasks. Experimental results demonstrate that our proposed LCPFormer outperforms various transformer-based methods in benchmarks including 3D shape classification and dense prediction tasks such as 3D object detection and semantic segmentation. Code will be released for reproduction. Copyright © 2022, The Authors. All rights reserved.

关键词： Object detection

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Enhancing Power Grid Stability: Design and Integration of a Fast Bus Tripping System in Protection Relays

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IEEE Transactions on Consumer Electronics 2024年

作者： Ghiasi, Mohammad Wang, Zhanle Mehrandezh, Mehran Alhelou, Hassan Haes Ghadimi, Noradin University of Regina Faculty of Engineering and Applied Science ReginaSKS4S 0A2 Canada School of Engineering CambridgeMA United States Monash University Department of Electrical and Computer System Engineering Australia Islamic Azad University Young Researchers and Elite Club Ardabil Branch Ardabil Iran

This article introduces a novel method for efficiently and promptly operating protection relays within a power system, with a specific emphasis on adaptive overcurrent (OC) protection in a power grid. The approach utilizes SEL751 and SEL751A relays that communicate through the IEC-61850 GOOSE protocol, establishing connections using intelligent electronic devices (IED) at several locations in the system. The power system, consisting of transformers, bus bars, and feeders, employs protection relays to identify OC faults based on time and current parameters. Relay configurations are tested in a case study at the Omicron Lab involving a 138/25kV substation. The test encompasses various fault scenarios on the low-voltage (LV) and high-voltage (HV) sides, incorporating different current values and fault times, utilizing the chosen time-overcurrent U3 (very inverse) curve. The proposed approach exhibits the ability to promptly remove faults in transformers and substations at both the HV and the LV levels. Furthermore, the experimental results closely match the theoretical calculations, validating the effectiveness of the proposed approach in the protection of AC grids. Additionally, built-in cybersecurity measures in SEL relays ensure secure and reliable operation, mitigating the risks of cyber-related relay failures. © 1975-2011 IEEE.

关键词： Relay protection

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Mean Aggregator is More Robust than Robust Aggregators under Label Poisoning Attacks on Distributed Heterogeneous Data

arXiv

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arXiv 2024年

作者： Peng, Jie Li, Weiyu Vlaski, Stefan Ling, Qing School of Computer Science and Engineering Sun Yat-Sen University Guangdong Guangzhou510006 China School of Engineering and Applied Science Harvard University CambridgeMA02138 United States Department of Electrical and Electronic Engineering Imperial College London LondonSW7 2BT United Kingdom

Robustness to malicious attacks is of paramount importance for distributed learning. Existing works usually consider the classical Byzantine attacks model, which assumes that some workers can send arbitrarily malicious messages to the server and disturb the aggregation steps of the distributed learning process. To defend against such worst-case Byzantine attacks, various robust aggregators have been proposed. They are proven to be effective and much superior to the often-used mean aggregator. In this paper, however, we demonstrate that the robust aggregators are too conservative for a class of weak but practical malicious attacks, as known as label poisoning attacks, where the sample labels of some workers are poisoned. Surprisingly, we are able to show that the mean aggregator is more robust than the state-of-the-art robust aggregators in theory, given that the distributed data are sufficiently heterogeneous. In fact, the learning error of the mean aggregator is proven to be order-optimal in this case. Experimental results corroborate our theoretical findings, showing the superiority of the mean aggregator under label poisoning attacks. Copyright © 2024, The Authors. All rights reserved.

关键词： Adversarial machine learning

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Breaking the Interference and Fading Gridlock in Backscatter Communications: State-of-the-Art, Design Challenges, and Future Directions

arXiv

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arXiv 2023年

作者： Gu, Bowen Li, Dong Din, Haiyang Wang, Gongpu Tellambura, Chintha School of Computer Science and Engineering Macau University of Science and Technology Avenida Wai Long Taipa999078 China College of Information and Communication National University of Defense Technology Wuhan430019 China School of Computer and Information Technology Beijing Jiaotong University Beijing100044 China Department of Electrical and Computer Engineering University of Alberta EdmontonABT6G 2R3 Canada

As the Internet of Things (IoT) advances by leaps and bounds, a multitude of devices are becoming interconnected, marking the onset of an era where all things are connected. While this growth opens up opportunities for novel products and applications, it also leads to increased energy demand and battery reliance for IoT devices, creating a significant bottleneck that hinders sustainable progress. At this juncture, backscatter communication (BackCom), as a low-power and passive communication method, emerges as one of the promising solutions to this energy impasse by reducing the manufacturing costs and energy consumption of IoT devices. However, BackCom systems face challenges such as complex interference environments, including direct link interference (DLI) and mutual interference (MI) between tags, which can severely disrupt the efficiency of BackCom networks. Moreover, double-path fading is another major issue that leads to the degraded system performance. To fully unleash the potential of BackComs, the purpose of this paper is to furnish a comprehensive review of existing solutions with a focus on combatting these specific interference challenges and overcoming dual-path fading, offering an insightful analysis and comparison of various strategies for effectively mitigating these issues. Specifically, we begin by introducing the preliminaries for the BackCom, including its history, operating mechanisms, main architectures, etc, providing a foundational understanding of the field. Then, we delve into fundamental issues related to BackCom systems, such as solutions for the DLI, the MI, and the double-path fading. This paper thoroughly provides state-of-the-art advances for each case, particularly highlighting how the latest innovations in theoretical approaches and system design can strategically address these challenges. Finally, we explore emerging trends and challenges in BackComs by forecasting potential technological advancements and providing insights and gui

关键词： Internet of things

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Performance of Existing Methods in Baselining Demand Response From Commercial Building HVAC Fans

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Journal of engineering for Sustainable Buildings and Cities 2021年第2期2卷 021002页

作者： Lei, Shunbo Mathieu, Johanna L. Jain, Rishee K. Department of Electrical Engineering and Computer Science University of Michigan–Ann Arbor 4305 EECS 1301 Beal Avenue Ann Arbor 48109 MI United States Department of Electrical Engineering and Computer Science University of Michigan–Ann Arbor 4116 EECS 1301 Beal Avenue Ann Arbor 48109 MI United States Department of Civil and Environmental Engineering Stanford University 269B Y2E2 473 Via Ortega Stanford 94305 CA United States

Commercial buildings generally have large thermal inertia and thus can provide services to power grids (e.g., demand response (DR)) by modulating their heating, ventilation, and air conditioning (HVAC) systems. Shifting consumption on timescales of minutes to an hour can be accomplished through temperature setpoint adjustments that affect HVAC fan consumption. Estimating the counterfactual baseline power consumption of HVAC fans is challenging but is critical for assessing the capacity and participation of DR from HVAC fans in grid-interactive efficient buildings (GEBs). DR baseline methods have been developed for whole-building power profiles. This study evaluates those methods on total HVAC fan power profiles, which have different characteristics than whole-building power profiles. Specifically, we assess averaging methods (e.g., Y-day average, HighXofY, and MidXofY, with and without additive adjustments), which are the most commonly used in practice, and a least squares-based linear interpolation method recently developed for baselining HVAC fan power. We use empirical submetering data from HVAC fans in three University of Michigan buildings in our assessment. We find that the linear interpolation method has a low bias and by far the highest accuracy, indicating that it is potentially the most effective existing baseline method for quantifying the effects of short-term load shifting of HVAC fans. Overall, our results provide new insights on the applicability of existing DR baseline methods to baselining fan power and enable the more widespread contribution of GEBs to DR and other grid services. Copyright © 2021 by ASME.

关键词： air conditioning baseline methods commercial buildings demand response fan power grid-interactive efficient buildings HVAC systems interactive buildings load shifting renewable smart grid

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GBSense: A GHz-Bandwidth Compressed Spectrum Sensing System

arXiv

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arXiv 2024年

作者： Song, Zihang Zhang, Xingjian Chen, Zhe Tafazolli, Rahim Gao, Yue the Department of Engineering King’s College London Strand LondonWC2R 2LS United Kingdom Shenzhen China the School of Computer Science Fudan University Shanghai200433 China University of Surrey Guildford United Kingdom

This paper presents GBSense, an innovative compressed spectrum sensing system designed for GHz-bandwidth signals in dynamic spectrum access (DSA) applications. GBSense introduces an efficient approach to periodic nonuniform sampling, capturing wideband signals using significantly lower sampling rates compared to traditional Nyquist sampling. By integrating time-interleaved analog-to-digital conversion, GBSense overcomes the hardware complexity typically associated with traditional multicoset sampling, providing precise, real-time adjustable sampling patterns without the need for analog delay circuits. The system’s ability to process signals with a 2 GHz radio frequency bandwidth using only a 400 MHz average sampling rate enables more efficient spectrum monitoring and access in wideband cognitive radios. Lab tests demonstrate 100% accurate spectrum detection when the spectrum occupancy is below 100 MHz and over 80% accuracy for occupancy up to 200 MHz. Additionally, an integrated system utilizing a low-power Raspberry Pi processor achieves a low processing latency of around 30 ms per frame, demonstrating the system’s potential for real-time applications in cognitive radio networks, 5G, and future 6G infrastructures. © 2024, CC BY-NC-ND.

关键词： Cognitive radio

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Research on the design of progressive addition lenses with adjustable meridional curvature

Optics Continuum

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Optics Continuum 2025年第6期4卷 1279-1293页

作者： Tao Jin Jiang Liu Qi Hang Zhou Zhong Xu Yuan School of Optical-Electrical and Computer Engineering University of Shanghai for Science and Technology Shanghai 200093 China Jiangsu Mingyue Optical Glasses Co. Ltd. Jiangsu 212300 China Department of General Surgery Anhui No. 2 Provincial People's Hospital Hefei 230041 Anhui China

The distribution of meridian optical power is critical for controlling the far, near, and channel zones in progressive addition lenses (PALs), whether using direct or indirect design methods. Traditional power distribution functions, represented by linear functions, trigonometric functions, or higher-order polynomials, fail to effectively control the rate of change of optical power, limiting the flexibility in designing individualized PALs. To address this issue, we employ a high-order Bezier function to describe the desired meridian optical power distribution. By adjusting the control points of the Bezier curve, the rate of change in optical power can be flexibly controlled, enabling personalized management of optical power and astigmatism distribution in PALs. Two distinct PAL designs were developed for different application scenarios using this method. A comparison of computational simulations, facial analysis, and profile measurements indicates that the designed PALs meet wearable requirements, exhibiting lower astigmatism extremes and a broader area of optical power stabilization. These results demonstrate the high versatility of the Bezier curve, offering meridian flexibility and adjustability to effectively control the design's key areas, including the position and size of the distance vision, near vision, and channel zones.

关键词： Astigmatism computer simulation Lens design Optical properties Refractive index Spherical aberration

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