50 results on '"Tao, Xia"'
Search Results
2. A 40nm 2TOPS/W Depth-Completion Neural Network Accelerator SoC With Efficient Depth Engine for Realtime LiDAR Systems
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Miao Sun, Yingjie Cao, Jian Qian, Jie Li, Sifan Zhou, Ziyu Zhao, Yifan Wu, Tao Xia, Yajie Qin, Lei Qiu, Shunli Ma, Patrick Yin Chiang, and Shenglong Zhuo
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Electrical and Electronic Engineering - Published
- 2023
3. Solid-State dToF LiDAR System Using an Eight-Channel Addressable, 20-W/Ch Transmitter, and a 128 × 128 SPAD Receiver With SNR-Based Pixel Binning and Resolution Upscaling
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Shenglong Zhuo, Tao Xia, Lei Zhao, Miao Sun, Yifan Wu, Lei Wang, Hengwei Yu, Jiqing Xu, Jier Wang, Zhihong Lin, Yuan Li, Lei Qiu, Rui Bai, Xuefeng Chen, and Patrick Yin Chiang
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Electrical and Electronic Engineering - Published
- 2023
4. A 200 MHz 14 W Pulsed Optical Illuminator With Laser Driver ASIC and On-Chip DLL-Based Time Interpolator for Indirect Time-of-Flight Applications
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Shenglong Zhuo, Yuwei Wang, Tao Xia, Yifan Wu, Wei Zheng, Miao Sun, Zhihong Lin, and Patrick Yin Chang
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Electrical and Electronic Engineering - Published
- 2023
5. Black-Box Dataset Ownership Verification via Backdoor Watermarking
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Yiming Li, Mingyan Zhu, Xue Yang, Yong Jiang, Tao Wei, and Shu-Tao Xia
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FOS: Computer and information sciences ,Computer Science - Machine Learning ,Computer Science - Cryptography and Security ,Artificial Intelligence (cs.AI) ,Computer Science - Artificial Intelligence ,Computer Networks and Communications ,Computer Vision and Pattern Recognition (cs.CV) ,Computer Science - Computer Vision and Pattern Recognition ,Safety, Risk, Reliability and Quality ,Cryptography and Security (cs.CR) ,Machine Learning (cs.LG) - Abstract
Deep learning, especially deep neural networks (DNNs), has been widely and successfully adopted in many critical applications for its high effectiveness and efficiency. The rapid development of DNNs has benefited from the existence of some high-quality datasets ($e.g.$, ImageNet), which allow researchers and developers to easily verify the performance of their methods. Currently, almost all existing released datasets require that they can only be adopted for academic or educational purposes rather than commercial purposes without permission. However, there is still no good way to ensure that. In this paper, we formulate the protection of released datasets as verifying whether they are adopted for training a (suspicious) third-party model, where defenders can only query the model while having no information about its parameters and training details. Based on this formulation, we propose to embed external patterns via backdoor watermarking for the ownership verification to protect them. Our method contains two main parts, including dataset watermarking and dataset verification. Specifically, we exploit poison-only backdoor attacks ($e.g.$, BadNets) for dataset watermarking and design a hypothesis-test-guided method for dataset verification. We also provide some theoretical analyses of our methods. Experiments on multiple benchmark datasets of different tasks are conducted, which verify the effectiveness of our method. The code for reproducing main experiments is available at \url{https://github.com/THUYimingLi/DVBW}., Comment: This paper is accepted by IEEE TIFS. 15 pages. The preliminary short version of this paper was posted on arXiv (arXiv:2010.05821) and presented in a non-archival NeurIPS Workshop (2020)
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- 2023
6. Portfolio Selection Via Graph-Aware Gaussian Processes With Generalized Gaussian Likelihood
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Naiqi Li, Zhikang Xia, Yiming Li, Ercan E. Kuruoğlu, Yong Jiang, and Shu-Tao Xia
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Artificial Intelligence ,Computer Science Applications - Published
- 2023
7. An 8-A Sub-1ns Pulsed VCSEL Driver IC With Built-In Pulse Monitor and Automatic Peak Current Control for Direct Time-of-Flight Applications
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Tao Xia, Xuefeng Chen, Yifan Wu, Yuwei Wang, Yuan Li, Lei Wang, Liujia Song, Hengwei Yu, Jiqing Xu, Miao Sun, Jier Wang, Lei Zhao, Zhihong Lin, Shenglong Zhuo, and Patrick Yin Chiang
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Electrical and Electronic Engineering - Published
- 2022
8. EBSNN: Extended Byte Segment Neural Network for Network Traffic Classification
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Xiapu Luo, Hai-Tao Zheng, Xi Xiao, Rui Li, Shu-Tao Xia, and Wentao Xiao
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Artificial neural network ,business.industry ,Computer science ,Network packet ,Deep learning ,Intrusion detection system ,computer.software_genre ,Network management ,Traffic classification ,Recurrent neural network ,Header ,Artificial intelligence ,Data mining ,Electrical and Electronic Engineering ,business ,computer - Abstract
Network traffic classification is important to intrusion detection and network management. Most of existing methods are based on machine learning techniques and rely on the features extracted manually from flows or packets. However, with the rapid growth of network applications, it is difficult for these approaches to handle new complex applications. In this paper, we design a novel neural network, the Extended Byte Segment Neural Network (EBSNN), to classify network traffic. EBSNN first divides a packet into header segments and payload segments, which are then fed into encoders composed of the recurrent neural networks with the attention mechanism. Based on the outputs, another encoder learns the high-level representation of the whole packet. In particular, side-channel features are learned from header segments to improve the performance. Finally, the label of the packet is obtained by the softmax function. Furthermore, EBSNN can classify network flows by examining the first few packets. Thorough experiments on the real-world datasets show that EBSNN achieves better performance than the state-of-the-art methods in both the application identification task and the website identification task.
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- 2022
9. Constructions and Weight Distributions of Optimal Locally Repairable Codes
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Jie Hao, Jun Zhang, Shu-Tao Xia, Fang-Wei Fu, and Yixian Yang
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Electrical and Electronic Engineering - Published
- 2022
10. Backdoor Learning: A Survey
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Yiming Li, Yong Jiang, Zhifeng Li, and Shu-Tao Xia
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FOS: Computer and information sciences ,Computer Science - Machine Learning ,Software_OPERATINGSYSTEMS ,Computer Science - Cryptography and Security ,Artificial Intelligence ,Computer Networks and Communications ,Computer Vision and Pattern Recognition (cs.CV) ,Computer Science - Computer Vision and Pattern Recognition ,Cryptography and Security (cs.CR) ,Software ,Machine Learning (cs.LG) ,Computer Science Applications - Abstract
Backdoor attack intends to embed hidden backdoor into deep neural networks (DNNs), so that the attacked models perform well on benign samples, whereas their predictions will be maliciously changed if the hidden backdoor is activated by attacker-specified triggers. This threat could happen when the training process is not fully controlled, such as training on third-party datasets or adopting third-party models, which poses a new and realistic threat. Although backdoor learning is an emerging and rapidly growing research area, its systematic review, however, remains blank. In this paper, we present the first comprehensive survey of this realm. We summarize and categorize existing backdoor attacks and defenses based on their characteristics, and provide a unified framework for analyzing poisoning-based backdoor attacks. Besides, we also analyze the relation between backdoor attacks and relevant fields ($i.e.,$ adversarial attacks and data poisoning), and summarize widely adopted benchmark datasets. Finally, we briefly outline certain future research directions relying upon reviewed works. A curated list of backdoor-related resources is also available at \url{https://github.com/THUYimingLi/backdoor-learning-resources}., 17 pages. A curated list of backdoor learning resources in this paper is presented in the Github Repo (https://github.com/THUYimingLi/backdoor-learning-resources). We will try our best to continuously maintain this Github Repo
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- 2022
11. Single-Phase Three-Level PWM Rectifier Predictive Control With Fixed Switching Frequency Based on Current Convex Optimization
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Xu Zhang, Tao Shi, Qiang Wang, Xiang Wu, Tao Xia, Guojun Tan, and Weifeng Zhang
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Model predictive control ,Optimization problem ,Computer science ,Control theory ,Duty cycle ,Convex optimization ,Electrical and Electronic Engineering ,Extreme point ,PWM rectifier ,Global optimization ,Pulse-width modulation - Abstract
This article proposes a fixed switching frequency predictive control method for neutral point clamped (NPC) single-phase PWM rectifier to achieve global optimization of the current during the entire switching cycle. Through the optimization of the switching sequence, a three-stage switching sequence that can control the midpoint potential balance is obtained. The extreme point, the initial point, and the end point of the current error within the switching period are employed to establish an error matrix, and the error matrix l 2-norm minimality is considered as the optimization objective. This optimization problem is a convex optimization problem, and the optimal duty cycle of the switching sequence can be obtained by solving the convex problem. The optimal duty cycle of each feasible switching sequence is obtained, and then the switching sequence that minimizes the error matrix l 2-norm is selected as the system output among all feasible switching sequences. Finally, the experimental results show that the proposed control scheme has good performance.
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- 2021
12. Construction of MDS Euclidean Self-Dual Codes via Two Subsets
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Fang-Wei Fu, Shu-Tao Xia, and Weijun Fang
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FOS: Computer and information sciences ,Discrete mathematics ,Lemma (mathematics) ,Intersection (set theory) ,Computer Science - Information Theory ,Information Theory (cs.IT) ,Multiplicative function ,94B05 ,Disjoint sets ,Library and Information Sciences ,Computer Science Applications ,Finite field ,Euclidean geometry ,Coset ,Symmetric difference ,Information Systems ,Mathematics - Abstract
The parameters of a $q$ -ary MDS Euclidean self-dual codes are completely determined by its length and the construction of MDS Euclidean self-dual codes with new length has been widely investigated in recent years. In this paper, we give a further study on the construction of MDS Euclidean self-dual codes via generalized Reed-Solomon (GRS) codes and their extended codes. The main idea of our construction is to choose suitable evaluation points such that the corresponding (extended) GRS codes are Euclidean self-dual. Firstly, we consider the evaluation set consists of two disjoint subsets, one of which is based on the trace function, the other one is a union of a subspace and its cosets. Then four new families of MDS Euclidean self-dual codes are constructed. Secondly, we give a simple but useful lemma to ensure that the symmetric difference of two intersecting subsets of finite fields can be taken as the desired evaluation set. Based on this lemma, we generalize our first construction and provide two new families of MDS Euclidean self-dual codes. Finally, by using two multiplicative subgroups and their cosets which have nonempty intersection, we present three generic constructions of MDS Euclidean self-dual codes with flexible parameters. Several new families of MDS Euclidean self-dual codes are explicitly constructed.
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- 2021
13. Improved Bounds and Singleton-Optimal Constructions of Locally Repairable Codes With Minimum Distance 5 and 6
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Fang-Wei Fu, Weijun Fang, Shu-Tao Xia, Jie Hao, and Bin Chen
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Discrete mathematics ,Singleton ,Locality ,020206 networking & telecommunications ,Incidence matrix ,02 engineering and technology ,Coding theory ,Library and Information Sciences ,Upper and lower bounds ,Computer Science Applications ,0202 electrical engineering, electronic engineering, information engineering ,Projective plane ,Erasure code ,Information Systems ,Coding (social sciences) ,Mathematics - Abstract
Repair locality has been an important metric in a distributed storage system (DSS). Erasure codes with small locality are more popular in a DSS, which means fewer available nodes participating in the repair process of failed nodes. Locally repairable codes (LRCs) as a new coding scheme have given more rise to the system performance and attracted a lot of interest in the theoretical research in coding theory. The particular concern among the research problems is the bounds and optimal constructions of LRCs. The problem of optimal constructions of LRCs includes the most important case of Singleton-optimal LRCs whose minimum distance achieves the Singleton-like bound, which is the core consideration in this paper. In this work, we first of all derive an improved and general upper bound on the code length of Singleton-optimal LRCs with minimum distance $d=5, 6$ , some known constructions are shown to exactly achieve our new bound, which verifies its tightness. For locality $r=2$ and distance $d=6$ , we construct three new Singleton-optimal LRCs whose code length $n=3(q+1)$ , $n=3(q+\sqrt {q}+1)$ and $n=3(2q-4)$ , respectively. Moreover, we obtain a complete characterization for Singleton-optimal LRCs with $r=2$ and $d=6$ . Such characterization has established an important connection between the existence of Singleton-optimal LRCs and that of a special subset of lines of finite projective plane $PG(2, q)$ , thus provides a methodology for constructing LRCs with longer length based on any advance on finite projective plane $PG(2, q)$ . In the end, we employ the well-known line-point incidence matrix and Johnson bounds for constant weight codes to derive tighter upper bounds on the code length. These new bounds further help us to prove that some of the previous Singleton-optimal constructions or their extensions achieve the longest possible code length for $q=3, 4, 5, 7$ . It’s worth noting that all of our Singleton-optimal constructions possess small locality $r=2$ , which are attractive in a DSS.
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- 2021
14. Optimized Switching Finite Control Set Model Predictive Control of NPC Single-Phase Three-Level Rectifiers
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Tao Xia, Xiang Wu, Guojun Tan, Xu Zhang, and Qiang Wang
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Model predictive control ,Modulation ,Computer science ,Control theory ,020208 electrical & electronic engineering ,0202 electrical engineering, electronic engineering, information engineering ,Torque ,02 engineering and technology ,Electrical and Electronic Engineering ,Invariant (mathematics) ,PWM rectifier ,Pulse-width modulation ,Power (physics) - Abstract
A new model predictive control scheme, optimized switching finite control set model predictive control, is studied in this article for neutral-point-clamped (NPC) single-phase three-level pulsewidth modulation (PWM) rectifiers. To ensure the actual stability of the power converter, the ac-side current error of single-phase PWM rectifier and the neutral point voltage of the converter are both converged to the bounded invariant set, and the adjustment of system performance is thus realized by setting the bounded invariant set. Based on the NPC single-phase three-level PWM rectifier model, the ac-side current, the neutral point voltage, and the current error in the future time can be predicted in advance. The above objectives are achieved by optimizing the selection of switch combinations. The advantage of the proposed method is that it can reduce the average switching frequency of the converter when the ac-side current error and the neutral point voltage of the converter are controlled within a certain range, which makes it suitable for the application of high-power single-phase PWM rectifier.
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- 2020
15. A Dual Attention Neural Network for Airborne LiDAR Point Cloud Semantic Segmentation
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Zhang, Ka, primary, Ye, Longjie, additional, Xiao, Wen, additional, Sheng, Yehua, additional, Zhang, Shan, additional, Tao, Xia, additional, and Zhou, Yaqin, additional
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- 2022
- Full Text
- View/download PDF
16. A Scalable, High-Performance, and Fault-Tolerant Network Architecture for Distributed Machine Learning
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Jianping Wu, Dan Li, Shuai Wang, Shu-Tao Xia, Songtao Wang, Yanshu Wang, Jinkun Geng, and Yang Cheng
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Ethernet ,Network architecture ,Computer Networks and Communications ,Computer science ,business.industry ,Testbed ,Local area network ,020206 networking & telecommunications ,Fault tolerance ,02 engineering and technology ,Machine learning ,computer.software_genre ,Synchronization ,Computer Science Applications ,Server ,Scalability ,0202 electrical engineering, electronic engineering, information engineering ,Network performance ,Artificial intelligence ,Electrical and Electronic Engineering ,business ,Fat tree ,computer ,Software - Abstract
In large-scale distributed machine learning (DML), the network performance between machines significantly impacts the speed of iterative training. In this paper we propose BML , a scalable, high-performance and fault-tolerant DML network architecture on top of Ethernet and commodity devices. BML builds on BCube topology, and runs a fully-distributed gradient synchronization algorithm. Compared to a Fat-Tree network with the same size, a BML network is expected to take much less time for gradient synchronization, for both low theoretical synchronization time and its benefit to RDMA transport. With server/link failures, the performance of BML degrades in a graceful way. Experiments of MNIST and VGG-19 benchmarks on a testbed with 9 dual-GPU servers show that, BML reduces the job completion time of DML training by up to 56.4% compared with Fat-Tree running state-of-the-art gradient synchronization algorithm.
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- 2020
17. All-Pass-Filter-Based PLL for Single-Phase Grid-Connected Converters Under Distorted Grid Conditions
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Tao Xia, Xu Zhang, Guojun Tan, and Yezhao Liu
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General Computer Science ,Computer science ,020209 energy ,020208 electrical & electronic engineering ,General Engineering ,dc offset ,02 engineering and technology ,Converters ,Grid ,phase-locked loop (PLL) ,All-pass-filter (APF) ,Phase-locked loop ,harmonic ,Control theory ,Filter (video) ,Harmonics ,0202 electrical engineering, electronic engineering, information engineering ,Harmonic ,General Materials Science ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,lcsh:TK1-9971 ,All-pass filter ,DC bias - Abstract
All-pass-filter-based single-phase phase-locked loop (APF-PLL) is a widely used grid synchronization method in grid-connected power converters. However, the performance of APF-PLL degrades under distorted grid conditions and the estimated phase and frequency will contain low-frequency oscillation terms, which is not conducive to practical application. To deal with this problem, this paper proposes two advanced APF-PLLs, which have good ability to suppress harmonics and dc offset interference without sacrificing the dynamic response of the system. In the first one, a band-pass filter (BPF) is used as the prefilter of APF-PLL to process the input voltage signal, and in the second one, the APF-PLL input signal is processed by using a harmonic decoupling network (HDN) and multiple prefilters. In addition, their parameter design procedure is also described in detail and is easy to follow. The experimental results presented in this paper finally verify the superiority and effectiveness of the two proposed methods.
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- 2020
18. Optimal Locally Repairable Codes for Parallel Reading
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Shu-Tao Xia, Kenneth W. Shum, Jie Hao, and Deyin Li
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Common code ,Discrete mathematics ,General Computer Science ,Singleton-like bound ,Reading (computer) ,Minimum distance ,General Engineering ,Upper and lower bounds ,erasure codes ,optimal LRCs ,Symbol (programming) ,Distributed data store ,Field size ,General Materials Science ,Node (circuits) ,Locally repairable codes ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,lcsh:TK1-9971 ,Mathematics - Abstract
Locally repairable codes (LRCs) have important applications in distributed storage systems. In this paper, we study q-ary [n, k, d] LRCs with (r, t, δ)-information-locality, where each of the i-th (1 ≤ i ≤ k) information symbol is contained in t punctured subcodes with length ≤ r + δ - 1, minimum distance δ, and the i-th information symbol is the unique common code symbol of these t subcodes, furthermore, each subcode contains exactly δ - 1 parity symbols. Firstly, an upper bound on the minimum distance of such q-ary LRCs with (r, t, δ)-information-locality is given. Then, we propose a general construction framework of q-ary optimal LRCs with (r, t, δ)-information-locality and minimum distanced = t(δ-1)+1, where the required field size is just q ≥ r+δ-2. The proposed optimal LRCs can always repair a failed information node locally in case of at most tδ - 1 node failures. Moreover, multiple repair subcodes can support parallel readings of data, thus make the proposed codes attractive for distributed storage systems with hot data.
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- 2020
19. A Fully Integrated 25 Gb/s Low-Noise TIA+CDR Optical Receiver Designed in 40-nm-CMOS
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Jianxu Ma, Shang Hu, Patrick Chiang, Nan Qi, Juncheng Wang, Quan Pan, Yajie Qin, Xin Wang, Rui Bai, Yuanxi Zhang, Yaxin Cai, Xuefeng Chen, and Tao Xia
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Transimpedance amplifier ,Physics ,business.industry ,020208 electrical & electronic engineering ,020206 networking & telecommunications ,02 engineering and technology ,Optical modulation amplitude ,Capacitance ,Phase detector ,Photodiode ,law.invention ,CMOS ,law ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,Automatic gain control ,Electrical and Electronic Engineering ,business ,Negative impedance converter - Abstract
A fully integrated 25 Gb/s low-noise optical receiver is presented which integrates transimpedance amplifier (TIA), continuous-time linear equalizer (CTLE), high-gain and high-bandwidth limiting amplifier (LA), and clock and data recovery (CDR) circuit into a single die. The TIA employs an inverter-based pseudo-differential TIA scheme with input series-inductor peaking, cross-coupled negative Gm pair and negative capacitance to improve the bandwidth, and noise performance, while a MOSFET corner compensation (MCC) circuit compensates for CMOS corner variations. A gain control (GC) scheme is proposed which solves the group delay issue caused by TIA input impedance variations from small input to overload current. Finally, a 2x-oversampling CDR using a bang-bang phase detector is included. The receiver is fabricated in 40-nm CMOS process, and the 850 nm VCSEL-based full-link measurement results show that the optical receiver achieves 44 $\mu \text{A}_{\mathrm {pp}}$ (RSSI Current = 43 $\mu \text{A}$ , ER = 4.94 dB) optical modulation amplitude (OMA) sensitivity (BER
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- 2019
20. Expander Recovery Performance of Bipartite Graphs With Girth Greater Than 4
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Shu-Tao Xia, Weiyu Li, Weizhi Lu, and Wei Zhang
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Random graph ,Computer Networks and Communications ,Iterative method ,020208 electrical & electronic engineering ,Binary number ,020206 networking & telecommunications ,Basis pursuit ,02 engineering and technology ,Combinatorics ,Signal Processing ,Data_FILES ,0202 electrical engineering, electronic engineering, information engineering ,Bipartite graph ,Graph (abstract data type) ,Logical matrix ,Information Systems ,Sparse matrix ,Mathematics - Abstract
Expander recovery is an iterative algorithm designed to recover sparse signals measured with binary matrices with linear complexity. In the paper, we study the expander recovery performance of the bipartite graph with girth greater than 4, which can be associated with a binary matrix with column correlations equal to either 0 or 1. For such a graph, expander recovery is proved to achieve the same performance as the traditional basis pursuit recovery, as the signal is dissociated. Compared to random graphs widely used for expander recovery, the graph we study tends to present better empirical performance. Furthermore, its special structure enables reducing the iteration number of expander recovery from $O(n\log k)$ times to exactly $k$ times in serial recovery, and from $\mathcal {O}(\log k)$ times to exactly one time in parallel recovery.
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- 2019
21. Constructions of Optimal $(r,\delta)$ Locally Repairable Codes via Constacyclic Codes
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Bin Chen, Weijun Fang, Fang-Wei Fu, and Shu-Tao Xia
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Delta ,05 social sciences ,Minimum distance ,050801 communication & media studies ,020206 networking & telecommunications ,02 engineering and technology ,Coding theory ,Upper and lower bounds ,Combinatorics ,0508 media and communications ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Completeness (statistics) ,Decoding methods ,Mathematics - Abstract
Locally repairable codes (LRCs) are introduced in distributed storage systems due to their low repair overhead. An LRC is called optimal if its minimum distance attains the Singleton-like upper bound. Chen et al. (2018) recently studied the constructions of optimal $(r, \delta)$ -LRCs with length $n \mid (q+1)$ and $(r+\delta -1) \mid n$ , where many classes of optimal cyclic constructions were obtained. In this paper, by employing constacyclic MDS codes, we construct seven classes of optimal $(r, \delta)$ -LRCs with new parameters. After adding these new optimal LRCs via constacyclic codes, we have completely obtained all optimal $(r, \delta)$ -LRCs with length $n \mid (q+1)$ and $(r+\delta -1) \mid n$ for all possible parameters for the completeness in the coding theory. It is worth noting that the optimal constacyclic LRCs with new parameters provide more alternatives to cyclic LRCs in the practical demands of distributed storage systems, where specific values of $n$ , $k$ , $r$ , and $\delta $ are required. Moreover, constacyclic LRCs also possess the encoding and decoding efficiency as cyclic LRCs.
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- 2019
22. A $4\times25$ Gb/s Optical Transmitter Using Low-Cost 10 Gb/s VCSELs in 40-nm CMOS
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Rui Bai, Jianxu Ma, Tao Xia, Lei Wang, Yi Peng, Juncheng Wang, Nan Qi, Xin Wang, Patrick Chiang, Yuanxi Zhang, Xuefeng Chen, and Shang Hu
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Physics ,Optical transmitter ,business.industry ,Bandwidth (signal processing) ,Dissipation ,Laser ,Temperature measurement ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Vertical-cavity surface-emitting laser ,law.invention ,CMOS ,law ,Optoelectronics ,Electrical and Electronic Engineering ,business - Abstract
This letter presents a $4\times 25$ Gb/s optical transmitter in 40-nm CMOS. Low-cost vertical cavity surface-emitting lasers (VCSELs) with 10-GHz bandwidth (BW) are employed, which are then overdriven to 25 Gb/s by the proposed pre-emphasized quad-channel driver. Digitally assisted asymmetric-pulsed equalization technique is proposed to overcome the VCSEL modulation non-linearity and maximize the eye-diagram margin against the 100-GbE standard mask. The measurement results show >30% eye-mask margin and error-free (BER $ ) optical transmission for each 25-Gb/s channel, resulting in 280-mW power dissipation per channel under 1.2–/3.3-V dual supply.
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- 2019
23. Polar Transformed Subdomain Modeling for Double-Stator Permanent Magnet Linear Synchronous Machine
- Author
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Zhanchuan Wu, Guo Rong, Tao Xia, Yong Kong, Haitao Yu, and Xiaomei Liu
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010302 applied physics ,Laplace transform ,Stator ,020208 electrical & electronic engineering ,Mathematical analysis ,02 engineering and technology ,Permeance ,Function (mathematics) ,Counter-electromotive force ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Cartesian coordinate system ,Electrical and Electronic Engineering ,Polar coordinate system ,Synchronous motor ,Mathematics - Abstract
This paper presents a developed 2-D analytical subdomain model for design and analysis of the double-stator permanent magnet linear synchronous machine (DS-PMLSM) to account for both the primary and secondary end effects. First, considering the time constraint, polar transformed method is adopted to establish the 2-D subdomain analytical model, the DS-PMLSM is deformed into a ring-segment PMLSM, and the analytical model is calculated in polar coordinates instead of Cartesian coordinates. Then, the subdomain method is adopted to analyze the analytical model by solving Laplace’s equation and Poisson’s equation, and 2-D relative permeance function is used to consider the slot effect. The flux density and back electromotive force are calculated based on the developed analytical model. Finally, the analytical results are verified by the finite-element method and experiment. The results show that the proposed analytical model can accurately predict the electromagnetic performance, which is useful for the initial design of the DS-PMLSM.
- Published
- 2018
24. A Novel Consistent Random Forest Framework: Bernoulli Random Forests
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Jia Wu, Qingtao Tang, Xingquan Zhu, Yisen Wang, and Shu-Tao Xia
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Artificial neural network ,Computer Networks and Communications ,Contrast (statistics) ,02 engineering and technology ,computer.software_genre ,01 natural sciences ,Ensemble learning ,Computer Science Applications ,Random forest ,010104 statistics & probability ,Bernoulli's principle ,Tree (data structure) ,Artificial Intelligence ,Consistency (statistics) ,0202 electrical engineering, electronic engineering, information engineering ,Feature (machine learning) ,Artificial Intelligence & Image Processing ,020201 artificial intelligence & image processing ,Data mining ,0101 mathematics ,computer ,Algorithm ,Software ,Mathematics - Abstract
© 2012 IEEE. Random forests (RFs) are recognized as one type of ensemble learning method and are effective for the most classification and regression tasks. Despite their impressive empirical performance, the theory of RFs has yet been fully proved. Several theoretically guaranteed RF variants have been presented, but their poor practical performance has been criticized. In this paper, a novel RF framework is proposed, named Bernoulli RFs (BRFs), with the aim of solving the RF dilemma between theoretical consistency and empirical performance. BRF uses two independent Bernoulli distributions to simplify the tree construction, in contrast to the RFs proposed by Breiman. The two Bernoulli distributions are separately used to control the splitting feature and splitting point selection processes of tree construction. Consequently, theoretical consistency is ensured in BRF, i.e., the convergence of learning performance to optimum will be guaranteed when infinite data are given. Importantly, our proposed BRF is consistent for both classification and regression. The best empirical performance is achieved by BRF when it is compared with state-of-the-art theoretical/consistent RFs. This advance in RF research toward closing the gap between theory and practice is verified by the theoretical and experimental studies in this paper.
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- 2018
25. Research on the Field-Modulated Tubular Linear Generator With Quasi-Halbach Magnetization for Ocean Wave Energy Conversion
- Author
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Xiaomei Liu, Tao Xia, Guo Rong, and Haitao Yu
- Subjects
010302 applied physics ,Physics ,Field (physics) ,020209 energy ,Acoustics ,02 engineering and technology ,Superconducting magnet ,Permanent magnet synchronous generator ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Magnetization ,Linear congruential generator ,0103 physical sciences ,Wind wave ,0202 electrical engineering, electronic engineering, information engineering ,Energy transformation ,Electrical and Electronic Engineering - Abstract
A field-modulated tubular linear generator (FMTLG) with quasi-Halbach magnetization is proposed for ocean wave energy conversion. The FMTLG, which is equipped with field-modulated technology and quasi-Halbach arrays, can overcome the disadvantages of heavy weight and inefficiency caused by low-speed ocean waves to some extent. To design and optimize the FMTLG in a short time, the open-circuit magnetic field distribution is established with an analytical method. Results of a finite-element method show that the back EMF of the FMTLG is 43% higher than that of a tubular linear permanent magnet generator (TLPMG) with quasi-Halbach magnetization. A novel assistant tooth of the FMTLG makes the cogging force eight times smaller than that generated by the TLPMG. Finally, a prototype is manufactured to verify the simulation results by experiments.
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- 2018
26. A Simplified Subdomain Analytical Model for the Design and Analysis of a Tubular Linear Permanent Magnet Oscillation Generator
- Author
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Zhenchuan Shi, Xiaomei Liu, Tao Xia, Weibo Zhong, Guo Rong, and Haitao Yu
- Subjects
T-LPMOG ,General Computer Science ,Coordinate system ,Boundary (topology) ,magnetic field ,02 engineering and technology ,01 natural sciences ,Coordinate transformation method ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,slot effect ,Cylindrical coordinate system ,010302 applied physics ,Physics ,Laplace transform ,020208 electrical & electronic engineering ,Mathematical analysis ,General Engineering ,Magnetic flux ,Finite element method ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,subdomain model ,Polar coordinate system ,Poisson's equation ,lcsh:TK1-9971 ,end effect - Abstract
We present a simplified 2-D analytical subdomain model to predict the open-circuit magnetic field of a tubular linear permanent magnet oscillation generator (T-LPMOG) to account for its primary and secondary end effects. At present, the magnetic field calculations of the T-LPMOG are typically analyzed in cylindrical coordinates, and the end effect is neglected accordingly to apply the periodic boundary. In this paper, a simplified 2-D analytical subdomain model in polar coordinates is proposed to consider the end effect. First, a coordinate transformation method is adopted to establish the 2-D subdomain analytical model, the cylindrical coordinates are converted into polar coordinates, and the T-LPMOG is analyzed under this new coordinate system. Next, the subdomain method is used to analyze the analytical model by solving Laplace's equation and the Poisson equation. Based on the simplified analytical model, the flux density and back-electromotive force are obtained. The analytical results are verified using the finite element analysis (FEA) method, and the computational times compared with the FEA method are provided. Finally, a T-LPMOG prototype is manufactured and tested, and the results show that the proposed analytical model can be useful in the initial design and optimization of the T-LPMOG.
- Published
- 2018
27. Binary Matrices for Compressed Sensing
- Author
-
Weizhi Lu, Tao Dai, and Shu-Tao Xia
- Subjects
Ideal (set theory) ,Degree (graph theory) ,Mathematical analysis ,Binary number ,020206 networking & telecommunications ,02 engineering and technology ,Upper and lower bounds ,Combinatorics ,Compressed sensing ,Signal Processing ,0202 electrical engineering, electronic engineering, information engineering ,Coherence (signal processing) ,020201 artificial intelligence & image processing ,Logical matrix ,Electrical and Electronic Engineering ,Sparse matrix ,Mathematics - Abstract
For an $m\times n$ binary matrix with $d$ nonzero elements per column, it is interesting to identify the minimal column degree $d$ that corresponds to the best recovery performance. Consider this problem is hard to be addressed with currently known performance parameters, we propose a new performance parameter, the average of nonzero correlations between normalized columns. The parameter is proved to perform better than the known coherence parameter, namely the maximum correlation between normalized columns, when used to estimate the performance of binary matrices with high compression ratios $n/m$ and low column degrees $d$ . By optimizing the proposed parameter, we derive an ideal column degree $d=\lceil \sqrt{m}\rceil$ , around which the best recovery performance is expected to be obtained. This is verified by simulations. Given the ideal number $d$ of nonzero elements in each column, we further determine their specific distribution by minimizing the coherence with a greedy method. The resulting binary matrices achieve comparable or even better recovery performance than random binary matrices.
- Published
- 2018
28. Research on a PM Slotless Linear Generator Based on Magnet Field Analysis Model for Wave Energy Conversion
- Author
-
Minqiang Hu, Tao Xia, Jing Zhang, Lei Huang, and Haitao Yu
- Subjects
010302 applied physics ,Physics ,Acoustics ,01 natural sciences ,Finite element method ,Magnetic flux ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Generator (circuit theory) ,Nuclear magnetic resonance ,Electromagnetic coil ,Linear congruential generator ,Magnet ,0103 physical sciences ,Energy transformation ,Electrical and Electronic Engineering - Abstract
In this paper, a permanent magnet (PM) slotless tubular linear generator based on magnet field analysis model is presented for wave energy conversion. To improve air flux density and efficiency of the generator, two improved Halbach PM Arrays (T-PM structure and claw-PM structure) applied in the slotless linear generator is proposed and compared with Halbach PM Arrays. Combined with axisymmetric dimensional finite-element method (FEM), no-load electromagnetic performance is analyzed. Finally, due to test and analysis model results of prototype concordant with the FEM results, the generator model and the analysis method are correct.
- Published
- 2017
29. Design and Analysis of a Field-Modulated Tubular Linear Permanent Magnet Generator for Direct-Drive Wave Energy Conversion
- Author
-
Haitao Yu, Lei Huang, Minqiang Hu, Tao Xia, Xiaomei Liu, and Chen Zhongxian
- Subjects
010302 applied physics ,Electromagnetic field ,Physics ,Field (physics) ,020208 electrical & electronic engineering ,02 engineering and technology ,Mechanics ,Permanent magnet synchronous generator ,Optical field ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Classical mechanics ,Linear congruential generator ,0103 physical sciences ,Wind wave ,0202 electrical engineering, electronic engineering, information engineering ,Energy transformation ,Electrical and Electronic Engineering - Abstract
A two-body buoys power generation system using the field-modulated tubular linear permanent magnet generator (FM-TLPMG) is proposed for direct-drive wave energy conversion in this paper. The traditional linear generator has disadvantages of large weight and low-power density caused by the slow speed of ocean wave. The FM-TLPMG can overcome these disadvantages in some extent through accelerating the speed of the traveling magnetic field. In order to design a suitable FM-TLPMG for the direct-drive wave energy conversion in a short time, ocean wave theory is applied to analyze hydrodynamic problems of the two-body buoys and calculate the operating velocity of FM-TLPMG in the sea. A 2-D analytical model for FM-TLPMG design is presented to obtain the electromagnetic field distribution by solving the Laplace and Poisson equations for each region. The analytical result has been compared with the finite-element analysis and shows its validation for the design.
- Published
- 2017
30. Constructions of Optimal Binary Locally Repairable Codes With Multiple Repair Groups
- Author
-
Jie Hao and Shu-Tao Xia
- Subjects
Block code ,Discrete mathematics ,Concatenated error correction code ,Reed–Muller code ,020206 networking & telecommunications ,020207 software engineering ,Data_CODINGANDINFORMATIONTHEORY ,02 engineering and technology ,Linear code ,Expander code ,Computer Science Applications ,Combinatorics ,Group code ,Modeling and Simulation ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Low-density parity-check code ,Hamming code ,Mathematics - Abstract
In distributed storage systems, locally repairable codes (LRCs) have attracted lots of interest recently. If a code symbol can be repaired respectively by $t$ disjoint groups of other symbols, each of which has size at most $r$ , we say that the code symbol has $(r,t) $ -locality. LDPC codes are linear block codes defined by low-density parity-check matrices. A regular $(\tau,\rho)$ -LDPC code has the parity-check matrix with uniform column weight $\tau$ and uniform row weight $\rho$ . In this letter, we employ regular LDPC codes to construct optimal binary LRCs with $(r,t) $ -locality for information symbols. After proposing construction frameworks, three detailed constructions of binary LRCs with information locality are obtained, all of which have a single parity symbol in each repair group. All our codes attain the distance bounds of LRCs when each repair group contains a single parity symbol and thus are optimal. For storage systems with hot data, the proposed binary LRCs seem promising for system implementations since the encoding, repairing, parallel reading, and data reconstruction can be performed by simple XOR operations.
- Published
- 2016
31. End-to-end coding for TCP
- Author
-
Yisen Wang, Lian Wang, Fengyuan Ren, Shu-Tao Xia, Yong Cui, and Xin Wang
- Subjects
TCP acceleration ,Computer Networks and Communications ,Computer science ,business.industry ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,TCP tuning ,020206 networking & telecommunications ,02 engineering and technology ,H-TCP ,TCP global synchronization ,TCP Friendly Rate Control ,TCP Westwood plus ,Hardware and Architecture ,0202 electrical engineering, electronic engineering, information engineering ,Zeta-TCP ,020201 artificial intelligence & image processing ,business ,BIC TCP ,Software ,Information Systems ,Computer network - Abstract
Although widely used, TCP has many limitations in meeting the throughput and latency requirements of applications in wireless networks, high-speed data center networks, and heterogeneous multi-path networks. Instead of relying purely on retransmission upon packet loss, coding has potential to improve the performance of TCP by ensuring better transmission reliability. Coding has been verified to work well at the link layer but has not been fully studied at the transport layer. There are many advantages but also challenges in exploiting coding at the transport layer. In this article, we focus on how to leverage end-to-end coding in TCP. We reveal the problems TCP faces and the opportunities coding can bring to improve TCP performance. We further analyze the challenges faced when applying the coding techniques to TCP and present the current applications of coding in TCP.
- Published
- 2016
32. Image Dimming Perceptual Model Based Pixel Compensation and Backlight Adjustment
- Author
-
Rong Li, Tao Xia, Jiazhong Chen, Bingpeng Ma, and Hua Cao
- Subjects
Visual perception ,Pixel ,business.industry ,Computer science ,Image quality ,media_common.quotation_subject ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Function (mathematics) ,Backlight ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Compensation (engineering) ,Image (mathematics) ,Quality (business) ,Computer vision ,Artificial intelligence ,Electrical and Electronic Engineering ,business ,media_common - Abstract
In this paper, an image dimming perceptual model is proposed as the foundation of image compensation and quality evaluation. Specifically, under this model an ideal compensation function is derived out and objective quality metrics SSIM and PSNR are adopted to evaluate the compensation performance. A practical compensation function is obtained by modifying the ideal compensation function under the consideration both of visual perception and objective quality. By using the SSIM and PSNR metrics, the relationship between image mean values, backlight levels, and image quality is further investigated. Base on this a novel scheme of backlight level adaptive adjustment is presented. Numerous experimental results verify the effectiveness of the model and demonstrate the advantages of the compensation and backlight level adaptive adjustment techniques.
- Published
- 2015
33. Nonlocal Pixel Selection for Multisurface Fitting-Based Super-Resolution
- Author
-
Fei Zhou, Qingmin Liao, and Shu-Tao Xia
- Subjects
Sequence ,Similarity (geometry) ,Pixel ,business.industry ,Small number ,Frame (networking) ,Image (mathematics) ,Media Technology ,Computer vision ,Artificial intelligence ,Electrical and Electronic Engineering ,business ,Image resolution ,Algorithm ,Selection (genetic algorithm) ,Mathematics - Abstract
In this paper, we address a super-resolution (SR) problem that constructs a high-resolution (HR) frame/image from a short sequence of low-resolution (LR) frames/images. It is well known that SR is a difficult problem, especially when the number of LR inputs is small. In particular, our previous work involving multisurface fitting-based SR exhibits relatively poor performance in the above case. To cope with this problem, we take advantage of nonlocal pixels to fit local surfaces. The pixels from nonlocal spatial–temporal positions are selected and weighted based on patch similarity and outlier removal. With this method, the fitted surfaces become more elaborate so that more details can be retrieved in SR results. Experiments demonstrate that the proposed method is very effective in producing HR frames through a small number of LR inputs when compared with some state-of-the-art methods.
- Published
- 2014
34. Improved Analysis for Subspace Pursuit Algorithm in Terms of Restricted Isometry Constant
- Author
-
Shu-Tao Xia, Chaobing Song, and Xin-Ji Liu
- Subjects
Compressed sensing ,Applied Mathematics ,Signal Processing ,Subspace pursuit ,Convergence (routing) ,Key (cryptography) ,Context (language use) ,Electrical and Electronic Engineering ,Isometry (Riemannian geometry) ,Constant (mathematics) ,Algorithm ,Mathematics ,Restricted isometry property - Abstract
In the context of compressed sensing (CS), subspace pursuit (SP) is an important iterative greedy recovery algorithm which could reduce the recovery complexity greatly comparing with l 1 -minimization. Restricted isometry property (RIP) and restricted isometry constant (RIC) of measurement matrices which ensure the convergence of iterative algorithms play key roles for the guarantee of successful reconstructions. In this letter, we show that for the s-sparse recovery, the RIC is enlarged to for SP, which improves the known results significantly. The proposed result also applies to almost sparse signals and corrupted measurements.
- Published
- 2014
35. Sparse Signal Recovery by <formula formulatype='inline'> <tex Notation='TeX'>${\ell_q}$</tex></formula> Minimization Under Restricted Isometry Property
- Author
-
Shu-Tao Xia and Chaobing Song
- Subjects
Physics ,Applied Mathematics ,Order (ring theory) ,Context (language use) ,Restricted isometry property ,Combinatorics ,Statistics::Machine Learning ,Compressed sensing ,Signal recovery ,Signal Processing ,Isometry ,Minification ,Electrical and Electronic Engineering ,Constant (mathematics) - Abstract
In the context of compressed sensing, the nonconvex ${\ell_q}$ minimization with $0 has been studied in recent years. In this letter, by generalizing the sharp bound for ${\ell_1}$ minimization of Cai and Zhang, we show that the condition ${\delta_{({s^q} + 1)k}} in terms of restricted isometry constant (RIC) can guarantee the exact recovery of $k$ -sparse signals in the noiseless case and the stable recovery of approximately $k$ -sparse signals in the noisy case by ${\ell_q}$ minimization. This result is more general than the sharp bound for ${\ell_1}$ minimization when the order of RIC is greater than $2k$ and illustrates the fact that a better approximation to ${\ell_0}$ minimization is provided by ${\ell_q}$ minimization than that provided by ${\ell_1}$ minimization.
- Published
- 2014
36. Application of wide area measurement systems to islanding detection of bulk power systems
- Author
-
Zhenzhi Lin, Kevin Tomsovic, Yanzhu Ye, Yilu Liu, Tao Xia, Terry Bilke, Ye Zhang, Fushuan Wen, and Lang Chen
- Subjects
Engineering ,business.industry ,Real-time computing ,Phasor ,Energy Engineering and Power Technology ,Frequency deviation ,Phasor measurement unit ,Power (physics) ,Electric power system ,Islanding ,Voltage source ,Electrical and Electronic Engineering ,business ,FNET - Abstract
A fast islanding detection tool can help power dispatchers monitor and control power system operations. Frequency monitoring network (FNET) is a low cost and quickly deployable wide-area phasor measurement system at the distribution system level. The frequency disturbance recorder (FDR) in FNET is actually a single-phase phasor measurement unit (PMU) installed at ordinary 120 V outlets in the sense that it measures the voltage phase angle, amplitude, and frequency from a single-phase voltage source. Based on the data collected by the FDRs deployed in the North American power grid, two islanding detection methods, the frequency difference method and the change of angle difference method, are proposed. The nine real cases recorded, including islanding cases, generation trip cases, load shedding cases and oscillation cases, are presented to verify the proposed methods of islanding detection. Sensitivity analysis on the thresholds of the frequency deviation and angle deviation is done based on the real measurement data for obtaining the insensitive interval of two thresholds. The results show that the proposed methods can correctly detect power system islanding, and will not be falsely triggered by generation trips, load shedding and system oscillations.
- Published
- 2013
37. Stopping Set Distributions of Some Reed–Muller Codes
- Author
-
Shu-Tao Xia, Fang-Wei Fu, and Yong Jiang
- Subjects
Discrete mathematics ,Code (set theory) ,Reed–Muller code ,Data_CODINGANDINFORMATIONTHEORY ,Library and Information Sciences ,Linear code ,Computer Science Applications ,Dual code ,Combinatorics ,Puncturing ,Matrix (mathematics) ,Hamming code ,Decoding methods ,Information Systems ,Mathematics - Abstract
Stopping sets and stopping set distribution of a linear code are used to determine the performance of this code under iterative decoding over a binary erasure channel (BEC). Let C be a binary [n,k] linear code with parity-check matrix H, where the rows of H may be dependent. A stopping set S of C with parity-check matrix H is a subset of column indices of H such that the restriction of H to S does not contain a row of weight one. The stopping set distribution {Ti(H)}i=0n enumerates the number of stopping sets with size i of C with parity-check matrix H. Note that stopping sets and stopping set distribution are related to the parity-check matrix H of C. Let H* be the parity-check matrix of C which is formed by all the nonzero codewords of its dual code C⊥. A parity-check matrix H is called BEC-optimal if Ti(H)=Ti(H*), i=0,1,..., n and H has the smallest number of rows. In this paper, we study stopping sets, stopping set distributions and BEC-optimal parity-check matrices of binary linear codes. Using finite geometry in combinatorics, we obtain BEC-optimal parity-check matrices and then determine the stopping set distributions for the Simplex codes, the Hamming codes, the first order Reed-Muller codes, and the extended Hamming codes, which are some Reed-Muller codes or their shortening or puncturing versions.
- Published
- 2011
38. Wide-Area Frequency Monitoring Network (FNET) Architecture and Applications
- Author
-
Richard W. Conners, Jason Bank, Penn Markham, J. Burgett, Zhongyu Wu, Yingchen Zhang, Lang Chen, Yanzhu Ye, Yilu Liu, Tao Xia, Zhiyong Yuan, and Lei Wang
- Subjects
Engineering ,General Computer Science ,Situation awareness ,Event (computing) ,business.industry ,Real-time computing ,Control engineering ,Phasor measurement unit ,Units of measurement ,Electric power system ,Smart grid ,Server ,business ,FNET - Abstract
Recent developments in smart grid technology have spawned interest in the use of phasor measurement units to help create a reliable power system transmission and distribution infrastructure. Wide-area monitoring systems (WAMSs) utilizing synchrophasor measurements can help with understanding, forecasting, or even controlling the status of power grid stability in real-time. A power system frequency monitoring network (FNET) was first proposed in 2001 and was established in 2004. As a pioneering WAMS, it serves the entire North American power grid through advanced situational awareness techniques, such as real-time event alerts, accurate event location estimation, animated event visualization, and post event analysis. Several papers published in the past several years discussed the FNET structure and its functionality. This paper presents some of the latest implementations of FNET's applications, which add significant capacities to this system for observing power system problems.
- Published
- 2010
39. Single-Phase Phase Angle Measurements in Electric Power Systems
- Author
-
Yilu Liu and Tao Xia
- Subjects
Engineering ,business.industry ,Computation ,System of measurement ,Phase angle ,Phasor ,Energy Engineering and Power Technology ,Electric power system ,Power system simulation ,Control theory ,Goniometer ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
Computation of phase angles using the discrete Fourier transform (DFT) algorithm has been proven to be sufficiently accurate in a variety of power system applications when the input signal is three-phase voltage and the voltage frequency is near the nominal value. However, the performance of the DFT algorithm in time of the singe-phase voltage input with a large frequency excursion so far has not been well explored, much less documented. This paper briefly discusses the importance of the synchronized phase angle measurement in power systems, and brings up the necessity of research on single-phase measurement systems. The performance of the DFT algorithm in power system phase angle measurements is thoroughly analyzed. Corresponding rectifying methods, including quasi-positive-sequence DFT and offset compensation, are proposed and examined by relevant numerical simulations and necessary laboratory tests. The results of the simulations and tests show a perfect match between the derived equations and the phase angle data, and thus verify the effectiveness of the proposed algorithm, which is believed to be able to greatly improve the performance of DFT in the aspect of phase angle calculation when severe power system upsets with remarkable frequency excursions are present.
- Published
- 2010
40. Minimum Pseudoweight and Minimum Pseudocodewords of LDPC Codes
- Author
-
Shu-Tao Xia and Fang-Wei Fu
- Subjects
Discrete mathematics ,Code word ,Minimum weight ,Girth (graph theory) ,Library and Information Sciences ,Upper and lower bounds ,Computer Science Applications ,Combinatorics ,Low-density parity-check code ,Tanner graph ,Error detection and correction ,Decoding methods ,Computer Science::Information Theory ,Information Systems ,Mathematics - Abstract
In this correspondence, we study the minimum pseudoweight and minimum pseudocodewords of low-density parity-check (LDPC) codes under linear programming (LP) decoding. First, we show that the lower bound of Kelley, Sridhara, Xu, and Rosenthal on the pseudoweight of a nonzero pseudocodeword of an LDPC code whose Tanner graph has girth greater than is tight if and only if this pseudocodeword is a real multiple of a codeword. Then, the lower bound of Kashyap and Vardy on the stopping distance of an LDPC code is proved to be also a lower bound on the pseudoweight of a nonzero pseudocodeword of an LDPC code whose Tanner graph has girth , and this lower bound is tight if and only if this pseudocodeword is a real multiple of a codeword. Using these results we further obtain that for some LDPC codes, there are no other minimum pseudocodewords except the real multiples of minimum weight codewords. This means that the LP decoding for these LDPC codes is asymptotically optimal in the sense that the ratio of the probabilities of decoding errors of LP decoding and maximum-likelihood decoding approaches as the signal-to-noise ratio (SNR) tends to infinity. Finally, some LDPC codes are listed to illustrate these results.
- Published
- 2008
41. Subjective and Objective Comparison of Advanced Motion Compensation Methods for Blocking Artifact Reduction in a 3-D Wavelet Coding System
- Author
-
Tao Xia, Zuowei Shen, Wen-Liang Hwang, and Cho-Chun Cheng
- Subjects
Motion compensation ,business.industry ,Wavelet transform ,Blocking (statistics) ,Peak signal-to-noise ratio ,Wavelet ,Motion estimation ,Media Technology ,Computer vision ,Artificial intelligence ,Electrical and Electronic Engineering ,business ,Block (data storage) ,Mathematics ,Interpolation - Abstract
We compare, both objectively and subjectively, the performance of various advanced motion compensation methods, including overlapped block motion compensation (OBMC) and control grid interpolation (CGI), in a 3-D wavelet-based coding system. The motion vectors of the methods are obtained by using a sequence of 1-D dynamic programming algorithms that minimizes the cost function. Our experiment results indicate that an OBMC sequence usually has a higher peak signal-to-noise ratio (PSNR) than other methods, while a CGI sequence usually contains the fewest blocking artifacts. We provide a simple framework that combines the OBMC and CGI sequences. The proposed hybrid method removes more than 50% of the blocking artifacts of an OBMC sequence, while simultaneously maintaining a high PSNR performance
- Published
- 2006
42. A Lower Bound on the Probability of Undetected Error for Binary Constant Weight Codes
- Author
-
San Ling, Shu-Tao Xia, and Fang-Wei Fu
- Subjects
Discrete mathematics ,Conjecture ,Error floor ,Binary number ,Library and Information Sciences ,Upper and lower bounds ,Computer Science Applications ,Combinatorics ,Steiner system ,Exponent ,Binary code ,Constant-weight code ,Error detection and correction ,Constant (mathematics) ,Information Systems ,Mathematics - Abstract
In this correspondence, we study the probability of undetected error for binary constant weight codes. First, we derive a new lower bound on the probability of undetected error for binary constant weight codes. Next, we show that this bound is tight if and only if the binary constant weight codes are generated from certain t-designs in combinatorial design theory. This means that these binary constant weight codes generated from certain t-designs are uniformly optimal for error detection. Along the way, we determine the distance distributions of such binary constant weight codes. In particular, it is shown that binary constant weight codes generated from Steiner systems are uniformly optimal for error detection. Thus, we prove a conjecture of Xia, Fu, Jiang, and Ling. Furthermore, the distance distribution of a binary constant weight code generated from a Steiner system is determined. Finally, we study the exponent of the probability of undetected error for binary constant weight codes. We derive some bounds on the exponent of the probability of undetected error for binary constant weight codes. These bounds enable us to extend the region in which the exponent of the probability of undetected error is exactly determined
- Published
- 2006
43. Restoring warped document images through 3D shape modeling
- Author
-
Tao Xia, Zheng Zhang, Chew Lim Tan, and Li Zhang
- Subjects
Computer science ,Information Storage and Retrieval ,Image processing ,Documentation ,computer.software_genre ,Sensitivity and Specificity ,Pattern Recognition, Automated ,Imaging, Three-Dimensional ,Artificial Intelligence ,Image Interpretation, Computer-Assisted ,Computer Graphics ,Computer Simulation ,Point (geometry) ,Computer vision ,Image warping ,Image restoration ,Electronic Data Processing ,business.industry ,Applied Mathematics ,Distortion (optics) ,Reproducibility of Results ,Optical character recognition ,Models, Theoretical ,Albedo ,Image Enhancement ,Photometric stereo ,Computational Theory and Mathematics ,Computer Vision and Pattern Recognition ,Artificial intelligence ,Shading ,Artifacts ,Geometric modeling ,business ,computer ,Algorithms ,Software - Abstract
Scanning a document page from a thick bound volume often results in two kinds of distortions in the scanned image, i.e., shade along the "spine" of the book and warping in the shade area. In this paper, we propose an efficient restoration method based on the discovery of the 3D shape of a book surface from the shading information in a scanned document image. From a technical point of view, this shape from shading (SFS) problem in real-world environments is characterized by 1) a proximal and moving light source, 2) Lambertian reflection, 3) nonuniform albedo distribution, and 4) document skew. Taking all these factors into account, we first build practical models (consisting of a 3D geometric model and a 3D optical model) for the practical scanning conditions to reconstruct the 3D shape of the book surface. We next restore the scanned document image using this shape based on deshading and dewarping models. Finally, we evaluate the restoration results by comparing our estimated surface shape with the real shape as well as the OCR performance on original and restored document images. The results show that the geometric and photometric distortions are mostly removed and the OCR results are improved markedly.
- Published
- 2006
44. The Probability of Undetected Error for Binary Constant-Weight Codes
- Author
-
Yong Jiang, San Ling, Shu-Tao Xia, and Fang-Wei Fu
- Subjects
Block code ,Discrete mathematics ,Linear programming ,Binary number ,Library and Information Sciences ,Linear code ,Computer Science Applications ,Combinatorics ,Steiner system ,Combinatorial design ,Binary code ,Error detection and correction ,Information Systems ,Mathematics - Abstract
In this correspondence, we study the probability of undetected error for binary constant-weight codes. First, we derive a new formula on the probability of undetected error for binary constant-weight codes. Second, using this new formula and linear programming, we give two new lower bounds on the probability of undetected error for binary constant-weight codes. These two new lower bounds improve on previously known lower bounds in certain cases. Furthermore, we show that these two lower bounds are tight if and only if the binary constant-weight codes are generated from certain t-designs in combinatorial design theory. This means that these binary constant-weight codes generated from certain t-designs are uniformly optimal for error detection. Along the way, we determine the distance distributions of such binary constant-weight codes. Finally, several examples are given to illustrate the results obtained in this correspondence.
- Published
- 2005
45. Reconstruction Guarantee Analysis of Basis Pursuit for Binary Measurement Matrices in Compressed Sensing
- Author
-
Shu-Tao Xia, Xin-Ji Liu, and Fang-Wei Fu
- Subjects
Discrete mathematics ,Binary number ,020206 networking & telecommunications ,Basis pursuit ,02 engineering and technology ,Girth (graph theory) ,Sparse approximation ,Library and Information Sciences ,Computer Science Applications ,Combinatorics ,Matrix (mathematics) ,Tree (descriptive set theory) ,Compressed sensing ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Low-density parity-check code ,Information Systems ,Mathematics - Abstract
Recently, binary 0-1 measurement matrices, especially those from coding theory, were introduced to compressed sensing. Dimakis et al. found that the linear programming (LP) decoding of LDPC codes is very similar to the LP reconstruction of compressed sensing, and they further showed that the sparse binary parity-check matrices of good LDPC codes can be used as provably good measurement matrices for compressed sensing under basis pursuit (BP). Moreover, Khajehnejad et al. made use of girth to certify the good performances of sparse binary measurement matrices. In this paper, we examine the performance of binary measurement matrices with uniform column weight and arbitrary girth under BP. For a fixed measurement matrix, we first introduce a performance indicator $w^{BP}_{min}$ called minimum BP weight , and show that any $k$ -sparse signals could be exactly recovered by BP if and only if $k\le (w^{BP}_{min}-1)/2$ . Then, lower bounds of $w^{BP}_{min}$ are studied. Borrowing ideas from the tree bound for the LDPC codes, we obtain several explicit lower bounds of $w_{BP}^{min}$ , which improve on the previous results in some cases. These lower bounds also imply explicit $\ell _{1}/\ell _{1}$ , $\ell _{2}/\ell _{1}$ and $\ell _\infty /\ell _{1}$ sparse approximation guarantees, and further confirm that large girth has positive impacts on the performance of binary measurement matrices under BP.
- Published
- 2017
46. Optimal multifilter banks: design, related symmetric extension transform, and application to image compression
- Author
-
Qingtang Jiang and Tao Xia
- Subjects
Discrete wavelet transform ,Mathematical optimization ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Wavelet transform ,Data_CODINGANDINFORMATIONTHEORY ,Wavelet packet decomposition ,Orthogonal wavelet ,Wavelet ,Signal Processing ,Electrical and Electronic Engineering ,Algorithm ,Biorthogonal wavelet ,Image compression ,Data compression ,Mathematics - Abstract
The design of optimal multifilter banks and optimum time-frequency resolution multiwavelets with different objective functions is discussed. The symmetric extension transform related to multifilter banks with symmetric properties is presented. It is shown that such a symmetric extension transform is nonexpensive. More optimal multifilter banks for image compression are constructed, and some of them are used in image compression. Experiments show that optimal multifilter banks have better performances in image compression than Daubechies' orthogonal wavelet filters and Daubechies' least asymmetric wavelet filters, and for some images, they even have better performances than the scalar (9,7)-tap biorthogonal wavelet filters. Experiments also show that the symmetric extension transform provided in this paper improves the rate-distortion performance compared with the periodic extension transform.
- Published
- 1999
47. Binary constant-weight codes for error detection
- Author
-
Fang-Wei Fu and Shu-Tao Xia
- Subjects
Block code ,Gray code ,Discrete mathematics ,Concatenated error correction code ,Turbo code ,Library and Information Sciences ,Low-density parity-check code ,Linear code ,Binary symmetric channel ,Expander code ,Computer Science Applications ,Information Systems ,Mathematics - Abstract
The undetected error probability of binary constant weight codes on a binary symmetric channel is studied in this correspondence. First, we present a necessary condition for the binary constant weight codes to be proper for error detection. Then, by using the necessary condition, we study the error detection capability of binary optimum constant weight codes.
- Published
- 1998
48. On the stopping distance of finite geometry ldpc codes
- Author
-
Shu-Tao Xia and Fang-Wei Fu
- Subjects
Discrete mathematics ,Block code ,Concatenated error correction code ,Coding theory ,Linear code ,Expander code ,Computer Science Applications ,Combinatorics ,Modeling and Simulation ,Turbo code ,Electrical and Electronic Engineering ,Low-density parity-check code ,Tanner graph ,Mathematics - Abstract
In this letter, the stopping sets and stopping distance of finite geometry LDPC (FG-LDPC) codes are studied. It is known that FG-LDPC codes are majority-logic decodable and a lower bound on the minimum distance can be thus obtained. It is shown in this letter that this lower bound on the minimum distance of FG-LDPC codes is also a lower bound on the stopping distance of FG-LDPC codes, which implies that FG-LDPC codes have considerably large stopping distance. This may explain in one respect why some FG-LDPC codes perform well with iterative decoding in spite of having many cycles of length 4 in their Tanner graphs.
- Published
- 2006
49. On the minimum pseudo-codewords of LDPC codes
- Author
-
Shu-Tao Xia and Fang-Wei Fu
- Subjects
Discrete mathematics ,Block code ,Concatenated error correction code ,TheoryofComputation_GENERAL ,Data_CODINGANDINFORMATIONTHEORY ,Serial concatenated convolutional codes ,Coding theory ,Upper and lower bounds ,Computer Science Applications ,Combinatorics ,Modeling and Simulation ,Projective plane ,Hardware_ARITHMETICANDLOGICSTRUCTURES ,Electrical and Electronic Engineering ,Low-density parity-check code ,Decoding methods ,Computer Science::Information Theory ,Mathematics - Abstract
In this letter, we study the minimum pseudo-codewords of low-density parity-check (LDPC) codes under linear programming (LP) decoding. We show that a lower bound of Chaichanavong and Siegel on the pseudo-weight of a pseudo-codeword is tight if and only if this pseudo-codeword is a real multiple of a codeword. Using this result we further show that for some LDPC codes, e.g., Euclidean plane and projective plane LDPC codes, there are no other minimum pseudo-codewords except the real multiples of minimum codewords.
- Published
- 2006
50. The undetected error probability threshold of m-out-of-n codes
- Author
-
Shu-Tao Xia, Fang-Wei Fu, and Torleiv Kløve
- Subjects
Combinatorics ,Error analysis ,Probability of error ,Statistics ,Library and Information Sciences ,Omega ,Computer Science Applications ,Information Systems ,Mathematics - Abstract
The well-known m-out-of-n code /spl Omega//sub n//sup m/ consists of all binary vectors of length n and weight m. It is known that it is good for error detection (in the technical sense, that is, the probability of undetected error P/sub ud/(/spl Omega//sub n//sup m/,p)/spl les/P/sub ud/(/spl Omega//sub n//sup m/,1/2) for all p, 0/spl les/p/spl les/1/2) only for a few small values of m and n. It is therefore of interest to determine (bounds for) the threshold in general, that is, find the range of bit-error probabilities p for which P/sub ud/ (/spl Omega//sub n//sup m/,p)/spl les/P/sub ud/ (/spl Omega//sub n//sup m/,1/2). In this article such bounds are given.
- Published
- 2000
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