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207 results on '"Zhu, ZhenYuan"'

2. On the Optimal Lower and Upper Complexity Bounds for a Class of Composite Optimization Problems

Author

Zhu, Zhenyuan, Chen, Fan, Zhang, Junyu, and Wen, Zaiwen

Subjects
Mathematics - Optimization and Control, 90C25, 90C26, 90C46, 90C60
Abstract

We study the optimal lower and upper complexity bounds for finding approximate solutions to the composite problem $\min_x\ f(x)+h(Ax-b)$, where $f$ is smooth and $h$ is convex. Given access to the proximal operator of $h$, for strongly convex, convex, and nonconvex $f$, we design efficient first order algorithms with complexities $\tilde{O}\left(\kappa_A\sqrt{\kappa_f}\log\left(1/{\epsilon}\right)\right)$, $\tilde{O}\left(\kappa_A\sqrt{L_f}D/\sqrt{\epsilon}\right)$, and $\tilde{O}\left(\kappa_A L_f\Delta/\epsilon^2\right)$, respectively. Here, $\kappa_A$ is the condition number of the matrix $A$ in the composition, $L_f$ is the smoothness constant of $f$, and $\kappa_f$ is the condition number of $f$ in the strongly convex case. $D$ is the initial point distance and $\Delta$ is the initial function value gap. Tight lower complexity bounds for the three cases are also derived and they match the upper bounds up to logarithmic factors, thereby demonstrating the optimality of both the upper and lower bounds proposed in this paper.

Published
2023

3. A Unified Primal-Dual Algorithm Framework for Inequality Constrained Problems

Author

Zhu, Zhenyuan, Chen, Fan, Zhang, Junyu, and Wen, Zaiwen

Subjects
Mathematics - Optimization and Control, 90C25, 90C46, 90C47, 90C60
Abstract

In this paper, we propose a unified primal-dual algorithm framework based on the augmented Lagrangian function for composite convex problems with conic inequality constraints. The new framework is highly versatile. First, it not only covers many existing algorithms such as PDHG, Chambolle-Pock (CP), GDA, OGDA and linearized ALM, but also guides us to design a new efficient algorithm called Simi-OGDA (SOGDA). Second, it enables us to study the role of the augmented penalty term in the convergence analysis. Interestingly, a properly selected penalty not only improves the numerical performance of the above methods, but also theoretically enables the convergence of algorithms like PDHG and SOGDA. Under properly designed step sizes and penalty term, our unified framework preserves the $\mathcal{O}(1/N)$ ergodic convergence while not requiring any prior knowledge about the magnitude of the optimal Lagrangian multiplier. Linear convergence rate for affine equality constrained problem is also obtained given appropriate conditions. Finally, numerical experiments on linear programming, $\ell_1$ minimization problem, and multi-block basis pursuit problem demonstrate the efficiency of our methods.

Published
2022

24. Extraction of Underwater Acoustic Signals across Sea–Air Media Using Butterworth Filtering.

Author

Cui, Tengyuan, Cao, Xiaolong, Yang, Yiguang, Tan, Qi, Du, Yuchen, Zhang, Tongchang, Yuan, Jiaqi, Zhu, Zhenyuan, and Yao, Jianquan

Subjects
FREQUENCY shift keying, OCEAN waves, WATER waves, SIGNAL-to-noise ratio, WIRELESS communications
Abstract

Direct wireless communication through sea–air media is essential for constructing an integrated communication network that spans space, air, land, and sea. The amplitude of acoustically induced micromotion surface waves is much smaller than the noise interference in complex sea states, making the accurate extraction of these signals from the raw signals detected by an FMCW millimeter-wave radar a major challenge. In this paper, Butterworth filtering is used to extract underwater acoustic signals from the surface waves detected by radar. The physical processes of the channel were simulated theoretically and verified experimentally. The results demonstrate a fitting coefficient of 0.99 between the radar-detected water surface waves and the simulation outcomes, enabling the effective elimination of noise interference and the extraction of acoustically induced micromotion signals in environments with a signal-to-noise ratio (SNR) of −20 dB to −10 dB. Experiments modifying frequency and linear frequency modulation have verified that the usable frequency range for underwater acoustic signals is at least 400 Hz, meeting the frequency requirements of Binary Frequency Shift Keying (2FSK) modulation encoding methods. This research confirms the accuracy of the simulation results and the feasibility of filtering and extracting underwater acoustic signals, providing a theoretical basis and an experimental foundation for building cross-media communication links. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Control strategy of parallel three-phase four-leg inverter under unbalanced conditions

Author

Zhu Zhenyuan, Cao Yilong, Jiang Youhua, and Huang Guanhua

Subjects
unbalanced three-phase load, three-phase four-leg inverter, deadbeat control, repetitive control, Electronics, TK7800-8360
Abstract

A compound control strategy is proposed in order to solve the low control accuracy and poor anti-disturbance of deadbeat control. In this method, the repetitive control is embedded into the deadbeat control to improve the robustness of the control system and the variation of inductance parameters. According to the mathematical model of three-phase four-leg inverter, the deadbeat control algorithm applied to the current loop is deduced and modified, then the repetitive control algorithm is added. Finally, the strategy is simulated and verified by experiments to verify the effectiveness of the strategy.

Published
2019
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40. An Entailment-Based Question Answering System over Semantic Web Data

Author

Ou, Shiyan, Zhu, Zhenyuan, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Xing, Chunxiao, editor, Crestani, Fabio, editor, and Rauber, Andreas, editor

Published
2011
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44. Effects of Chitosan-Based Ca2+ on Softening and Browning of Custard Apple Fruit During Postharvest Storage.

Author

Li, Chenchen, Su, Xueru, Chen, Lisha, and Zhu, Zhenyuan

Subjects
ANNONA, FOURIER transform infrared spectroscopy, POLYPHENOL oxidase, CALCIUM chloride, COMPOSITE coating
Abstract

Calcium treatment can reduce fruit softening and browning and enhance postharvest fruit quality. Chitosan (CS) had a certain viscosity. Therefore, in this study, calcium chloride (CaCl2) was used as a calcium source and CS was used as a carrier to study the interaction of Ca2+ and CS of the film coating through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). At the same time, the softening and browning process of custard apple fruit was investigated by single and composite coating with 1% CS and 2% CaCl2. The results showed that Ca2+ and CS produced physical and chemical cross-linking, and CS-CaCl2 could maintain total calcium content in coated custard apple. Compared with other treatments, CS-CaCl2 had the best postharvest effect on custard apple, which could reduce the weight loss rate of custard apple; maintain the firmness, color, moisture and cell wall material content of custard apple; and inhibit the rise and degradation of water-soluble pectin (WSP). At the same time, it could also improve the activity of superoxide dismutase (SOD) and inhibit malondialdehyde (MDA), polyphenol oxidase (PPO), and cellulase (CX) activity. This study provides a theoretical basis for improving the shelf life of custard apple. [ABSTRACT FROM AUTHOR]

Published
2023
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