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Periodically driven four-dimensional topological insulator with tunable second Chern number

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arXiv 2023年

作者： Liu, Zheng-Rong Chen, Rui Zhou, Bin Department of Physics Hubei University Wuhan430062 China Key Laboratory of Intelligent Sensing System and Security Ministry of Education Hubei University Wuhan430062 China

In recent years, Floquet engineering has attracted considerable attention as a promising approach for tuning topological phase transitions. In this work, we investigate the effects of high-frequency time-periodic driving in a four-dimensional (4D) topological insulator, focusing on topological phase transitions at the off-resonant quasienergy gap. The 4D topological insulator hosts gapless three-dimensional boundary states characterized by the second Chern number C2. We demonstrate that the second Chern number of 4D topological insulators can be modulated by tuning the amplitude of time-periodic driving. This includes transitions from a topological phase with C2 = ±3 to another topological phase with C2 = ±1, or to a topological phase with an even second Chern number C2 = ±2 which is absent in the 4D static system. Finally, the approximation theory in the high-frequency limit further confirms the numerical conclusions. © 2023, CC BY.

关键词： Topology

Multi-Modal Cross-Domain Alignment Network for Video Moment Retrieval

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arXiv 2022年

作者： Fang, Xiang Liu, Daizong Zhou, Pan Hu, Yuchong Hubei Key Laboratory of Distributed System Security Hubei Engineering Research Center on Big Data Security School of Cyber Science and Engineering Huazhong University of Science and Technology Hubei Wuhan430074 China Wangxuan Institute of Computer Technology Peking University No. 128 Zhongguancun North Street Beijing China School of Computer Science and Technology Key Laboratory of Information Storage System Ministry of Education of China Huazhong University of Science and Technology Wuhan430074 China

As an increasingly popular task in multimedia information retrieval, video moment retrieval (VMR) aims to localize the target moment from an untrimmed video according to a given language query. Most previous methods depend heavily on numerous manual annotations (i.e., moment boundaries), which are extremely expensive to acquire in practice. In addition, due to the domain gap between different datasets, directly applying these pre-trained models to an unseen domain leads to a significant performance drop. In this paper, we focus on a novel task: cross-domain VMR, where fully-annotated datasets are available in one domain ("source domain"), but the domain of interest ("target domain") only contains unannotated datasets. As far as we know, we present the first study on cross-domain VMR. To address this new task, we propose a novel Multi-Modal Cross-Domain Alignment (MMCDA) network to transfer the annotation knowledge from the source domain to the target domain. However, due to the domain discrepancy between the source and target domains and the semantic gap between videos and queries, directly applying trained models to the target domain generally leads to a performance drop. To solve this problem, we develop three novel modules: (i) a domain alignment module is designed to align the feature distributions between different domains of each modality;(ii) a cross-modal alignment module aims to map both video and query features into a joint embedding space and to align the feature distributions between different modalities in the target domain;(iii) a specific alignment module tries to obtain the fine-grained similarity between a specific frame and the given query for optimal localization. By jointly training these three modules, our MMCDA can learn domain-invariant and semantic-aligned cross-modal representations. Extensive experiments on three challenging benchmarks (ActivityNet Captions, Charades-STA and TACoS) illustrate that our cross-domain method MMCDA outperforms a

关键词： Alignment

Validating SMT Solvers via Skeleton Enumeration Empowered by Historical Bug-Triggering Inputs

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Validating SMT Solvers via Skeleton Enumeration Empowered by...

International Conference on Software Engineering (ICSE)

作者： Maolin Sun Yibiao Yang Ming Wen Yongcong Wang Yuming Zhou Hai Jin School of Cyber Science and Engineering Huazhong University of Science and Technology China Hubei Key Laboratory of Distributed System Security Services Computing Technology and System Lab Cluster and Grid Computing Lab Hubei Engineering Research Center on Big Data Security National Engineering Research Center for Big Data Technology and System State Key Laboratory for Novel Software Technology Nanjing University China School of Computer Science and Technology Huazhong University of Science and Technology China

SMT solvers check the satisfiability of logic formulas over first-order theories, which have been utilized in a rich number of critical applications, such as software verification, test case generation, and program synthesis. Bugs hidden in SMT solvers would severely mislead those applications and further cause severe consequences. Therefore, ensuring the reliability and robustness of SMT solvers is of critical importance. Although many approaches have been proposed to test SMT solvers, it is still a challenge to discover bugs effectively. To tackle such a challenge, we conduct an empirical study on the historical bug-triggering formulas in SMT solvers' bug tracking systems. We observe that the historical bug-triggering formulas contain valuable skeletons (i.e., core structures of formulas) as well as associated atomic formulas which can cast significant impacts on formulas' ability in triggering bugs. Therefore, we propose a novel approach that utilizes the skeletons extracted from the historical bug-triggering formulas and enumerates atomic formulas under the guidance of association rules derived from historical formulas. In this study, we realized our approach as a practical fuzzing tool HistFuzz and conducted extensive testing on the well-known SMT solvers Z3 and cvc5. To date, HistFuzz has found 111 confirmed new bugs for Z3 and cvc5, of which 108 have been fixed by the developers. More notably, out of the confirmed bugs, 23 are soundness bugs and invalid model bugs found in the solvers' default mode, which are essential for SMT solvers. In addition, our experiments also demonstrate that HistFuzz outperforms the state-of-the-art SMT solver fuzzers in terms of achieved code coverage and effectiveness.

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Graph Sampling based Fairness-aware Recommendation over Sensitive Attribute Removal

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Graph Sampling based Fairness-aware Recommendation over Sens...

IEEE International Conference on Data Mining (ICDM)

作者： Shenghao Liu Guoyang Wu Xianjun Deng Hongwei Lu Bang Wang Laurence Yang James J. Park Hubei Key Laboratory of Distributed System Security Hubei Engineering Research Center on Big Data Security School of Cyber Science and Engineering Huazhong University of Science and Technology Wuhan China Hubei Key Laboratory of Smart Internet Technology School of Electronic Information and Communications Huazhong University of Science and Technology Wuhan China Department of Computer Science and Engineering Seoul National University of Science and Technology Seoul Korea

Discrimination against different user groups has received growing attention in the recommendation field. To address this problem, existing works typically remove sensitive attributes that may cause discrimination through adversary learning to achieve fair recommendations. However, these approaches leverage all available interactions for learning user representations and overlook the fact that different interactions have varying relevance to users’ sensitive attributes. Ignoring this issue may weaken the effectiveness of adversary learning in removing sensitive attributes. To tackle this challenge, we propose a novel model called GS-FairRec, which distinguishes between user interactions to achieve better removal of sensitive attributes. The model consists of three modules: graph sampling-based representation learning, pseudo-user representation learning, and adversarial learning. Firstly, the graph sampling-based representation learning module removes some irrelevant neighbors from a user-item bipartite graph and employs a graph convolutional network (GCN) to learn user/item representations. Next, items that are relevant to a user’s sensitive information but do not match their preferences are defined as the user’s pseudo-interest items, which are leveraged to learn the pseudo-user representation. In the adversarial learning module, the user’s two kinds of representations are fused for adversarial learning to remove sensitive information. Additionally, we design a new metric to measure the model’s ability to remove sensitive attributes based on how a generated recommendation list discloses the user’s sensitive attributes. Finally, we conduct experiments on two real-world datasets, and our results demonstrate the superiority of our proposed model in fairness tasks.

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A Positive and Negative Crosstalk Suppression Method for High Current Bridge Configuration

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A Positive and Negative Crosstalk Suppression Method for Hig...

Power Electronics and Application Symposium (PEAS), IEEE International

作者： Wenqiang Lin Shangzhi Pan Jinwu Gong Zisen Lin Hui Zou Xiaoming Zha Hubei Key Laboratory of Power Equipment & System Security for Integrated Energy School of Electrical Engineering and Automation Wuhan University Wuhan China

The wide band-gap (WBG) devices have received widespread attention due to their excellent characteristics like low on-resistance, fast switching speed and better thermal conductivity. However, the crosstalk problem restricts the performance of high-speed WBG transistors in bridge-leg converters. What's more, in high current converters, the crosstalk problem will become more severe. To overcome the crosstalk problem in high current converters and fulfill the WBG devices' high-speed potentials, a simple positive and negative crosstalk mitigation method is presented in this article. This method does not require extra auxiliary controlled switches and extra control strategies, and can mitigate the positive and negative crosstalk spikes. What's more, it is simple implementation, and can be easily integrated with the conventional voltage source gate drivers. The effectiveness of the presented crosstalk suppression method is proved by the simulated and experimental outcomes.

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A Novel SVPWM Strategy With Model Prediction Torque Control of Six-Phase Open-Winding PMSM Considering the Nonsinusoidal Back-EMF

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A Novel SVPWM Strategy With Model Prediction Torque Control ...

Electrical Engineering (CIYCEE), IEEE China International Youth Conference on

作者： Chen Sun Yuhang Peng Jinwu Gong Shangzhi Pan Xiaoming Zha Hubei Key Laboratory of Power Equipment & System Security for Integrated Energy School of Electrical Engineering and Automation Wuhan University Wuhan China

ISBN: (数字)9798331530174

ISBN: (纸本)9798331530181

Compared with ordinary three-phase motor, multiphase open-winding motor has higher DC voltage utilization and output power, so it is well-suited for high-power drive applications. However, there are few researches on multiphase open-winding motors at present, in which model predictive current control(MPCC) is the main focus. However, in the applications requiring high dynamic response speed such as marine propulsion, The model predictive torque control(MPTC) is more suitable for application scenario, and the influence of non-sinusoidal back-electromotive force(EMF) on multiphase open-winding motor control system is rarely considered. Therefore, this article takes the six-phase open-winding permanent magnet synchronous motor(SOW-PMSM) as the research object and establishes a complete control system of the multiphase open winding motor. Firstly, the paper analyzes the harmonic generation mechanism of the motor and derives the effects of non-sinusoidal back-EMF and inverter dead time on the motor. It then establishes a mathematical model of the SOW-PMSM that takes into account harmonic in permanent magnet(PM) flux linkage and based on this mathematical model, the reference voltage required by Space Vector Pulse Width Modulation (SVPWM) is obtained by using the deadbeat torque control. In addition, a new SVPWM strategy is proposed by using the abundant voltage vectors of the six H-bridge inverters. By using multiple effective vectors, the motor can achieve a high DC voltage utilization while the harmonic plane vector synthesis is zero. Finally, the rationality of the proposed algorithm is verified by simulation.

关键词： Space vector pulse width modulation Torque Simulation Torque control Predictive models Motors Harmonic analysis Vectors Mathematical models Permanent magnets

d-DSE: Distinct Dynamic Searchable Encryption Resisting Volume Leakage in Encrypted Databases

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arXiv 2024年

作者： Liu, Dongli Wang, Wei Xu, Peng Yang, Laurence T. Luo, Bo Liang, Kaitai Huazhong University of Science and Technology China Hubei Key Laboratory of Distributed System Security School of Cyber Science and Engineering China JinYinHu Laboratory China State Key Laboratory of Cryptology China St. Francis Xavier University The University of Kansas United States Delft University of Technology Netherlands

Dynamic Searchable Encryption (DSE) has emerged as a solution to efficiently handle and protect large-scale data storage in encrypted databases (EDBs). Volume leakage poses a significant threat, as it enables adversaries to reconstruct search queries and potentially compromise the security and privacy of data. Padding strategies are common countermeasures for the leakage, but they significantly increase storage and communication costs. In this work, we develop a new perspective to handle volume leakage. We start with distinct search and further explore a new concept called distinct DSE (d-DSE). We also define new security notions, in particular Distinct with Volume-Hiding security, as well as forward and backward privacy, for the new concept. Based on d-DSE, we construct the d-DSE designed EDB with related constructions for distinct keyword (d-KW-dDSE), keyword (KW-dDSE), and join queries (JOIN-dDSE) and update queries in encrypted databases. We instantiate a concrete scheme BF-SRE, employing Symmetric Revocable Encryption. We conduct extensive experiments on real-world datasets, such as Crime, Wikipedia, and Enron, for performance evaluation. The results demonstrate that our scheme is practical in data search and with comparable computational performance to the SOTA DSE scheme (MITRA*, AURA) and padding strategies (SEAL, ShieldDB). Furthermore, our proposal sharply reduces the communication cost as compared to padding strategies, with roughly 6.36 to 53.14x advantage for search queries. Copyright © 2024, The Authors. All rights reserved.

关键词： Cryptography

Hypotheses Tree Building for One-Shot Temporal Sentence Localization

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arXiv 2023年

作者： Liu, Daizong Fang, Xiang Zhou, Pan Di, Xing Lu, Weining Cheng, Yu Hubei Key Laboratory of Distributed System Security Hubei Engineering Research Center on Big Data Security School of Cyber Science and Engineering Huazhong University of Science and Technology China Peking University China Nanyang Technological University Singapore ProtagoLabs Inc United States Tsinghua University China Microsoft Research United States

Given an untrimmed video, temporal sentence localization (TSL) aims to localize a specific segment according to a given sentence query. Though respectable works have made decent achievements in this task, they severely rely on dense video frame annotations, which require a tremendous amount of human effort to collect. In this paper, we target another more practical and challenging setting: one-shot temporal sentence localization (one-shot TSL), which learns to retrieve the query information among the entire video with only one annotated frame. Particularly, we propose an effective and novel tree-structure baseline for one-shot TSL, called Multiple Hypotheses Segment Tree (MHST), to capture the query-aware discriminative frame-wise information under the insufficient annotations. Each video frame is taken as the leaf-node, and the adjacent frames sharing the same visual-linguistic semantics will be merged into the upper non-leaf node for tree building. At last, each root node is an individual segment hypothesis containing the consecutive frames of its leaf-nodes. During the tree construction, we also introduce a pruning strategy to eliminate the interference of query-irrelevant nodes. With our designed self-supervised loss functions, our MHST is able to generate high-quality segment hypotheses for ranking and selection with the query. Experiments on two challenging datasets demonstrate that MHST achieves competitive performance compared to existing methods. Copyright © 2023, The Authors. All rights reserved.

关键词： Semantics

Active Power Regulation Control of Grid-Tied system for Transient Stability Enhancement 12

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Active Power Regulation Control of Grid-Tied System for Tran...

12th International Conference on Renewable Power Generation, RPG 2023

作者： Ling, Yangjian Huang, Meng Fu, Xikun Zha, Xiaoming Zhang, Hongying Deng, Jun Hubei Key Laboratory of Power Equipment & System Security for Integrated Energy School of Electrical Engineering and Automation Wuhan University Wuhan China China Electric Power Research Institute Nanjing China Power Research Institute of State Grid Shaanxi Electric Power Company Limited Xi'an China

With the high penetration of renewable energy sources, the grid stiffness goes weak. When the fault occurs, the system trends to be unstable in the weak grid. To enhance the transient stability of the system, it is vital to design the new control. Therefore, the paper builds the state-space model of the system with considering the DC voltage loop. The influence of the short-circuit ratio on the system is analysed. An active power regulation control is proposed to enhance the transient stability of the system. The control can regulate the active power with frequency feedback. The state-space model of the system with the proposed control is built. The impact of parameters on the system stability is analysed. The proposed control makes the system operate in the weaker grid and improve the transient stability of the system under fault. Finally, the simulation and experiment results validate the effectiveness of the proposed control. © The Institution of Engineering & Technology 2023.

关键词： Transients