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711 results on '"Zheng, Jiaqi"'

226. Shortest Path Algorithm Through Necessary Nodes with Extra Hard Constraints.

Author

GUO Zhanyu, ZHANG Zhiming, HE Lanshan, ZHENG Jiaqi, ZHAO Shibing, and KANG Qi

Subjects
UNDIRECTED graphs, WEIGHTED graphs, MATHEMATICAL models, ALGORITHMS, SEARCH algorithms, PROBLEM solving, GRAPH algorithms, TABU search algorithm
Abstract

There have been many algorithms for solving the shortest path problems through necessary nodes set, but most of them are insufficient when applied to the circumstances with extra hard constraints. To solve this problem, this paper puts forward a random search algorithm based on depth first search mechanism. The mathematical models are provided by users according to actual situation, and they are abstracted as undirected weighted graphs. Some related variables such as the beginning node, the end node, necessary nodes and extra hard constraints are defined by path planning requirements, and they are saved as adjacency matrix. In the searching process, the feasibility of the path is determined in real time to meet the requirements of extra hard constraints. Finally, the optimal shortest path solution is obtained. Simulation and actual results show that the algorithm effectively avoids the influence of intermediate path under extra hard constraints and generate a shortest path, which means that this algorithm can greatly improve problem solvability. [ABSTRACT FROM AUTHOR]

Published
2022
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232. MiFi: Bounded Update to Optimize Network Performance in Software-Defined Data Centers

Author

Majidi, Akbar, Gao, Xiaofeng, Zhu, Shunjia, Jahanbakhsh, Nazila, Zheng, Jiaqi, and Chen, Guihai

Abstract

A controller needs to solve the multi-commodity flow problem and globally update the network under tight time constraints to maintain optimal network configurations. This centralized optimization in data centers involves many variables and constraints, which has a slow convergence speed and little scalability. In this paper, we propose MiFi, which aims to Minimize Flow cost or intuitively average transmission delay (delay or latency of flows), under reconfiguration budget constraints in data centers. Thus, we formulate this optimization problem as a constrained Markov Decision Process and propose a set of algorithms to solve it in a scalable manner. We first develop a propagation algorithm to identify the flows mostly affected in terms of latency and configuration in the next update. Then, we set a limitation range (the subset of switches requiring network updates) for updating them to improve adaptability and scalability by updating a less number of flows each time to achieve fast operations. Further, based on the Drift-Plus-Penalty method in Lyapunov theory, we propose a heuristic policy without prior information of flow demand and a renewal policy with a performance guarantee to minimize the additive optimality gap. To the best of our knowledge, MiFi is the first paper that studies the range and frequency of flow reconfigurations, which has both theoretical and practical significance in the area. Emulations and numerical simulations, which are much better than the estimated theoretical bound, show that MiFi outperforms the state of the art algorithms in terms of latency by over 45% while making improvements in adaptability and scalability.

Published
2023
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233. Fault diagnosis method for operational inspection of substation relay protection link based on characteristic parameters

Author

Cao, Chengjie, Tian, Fangyuan, He, Darui, Zheng, Jiaqi, and Fan, Yifei

Abstract

Aiming at the problems of low fault location accuracy and large diagnosis error of traditional link fault diagnosis methods, this paper designs a new fault diagnosis method for substation relay protection link operation based on characteristic parameters. Firstly, the equivalent circuit fault characteristic parameters of the link are extracted through the degradation model, and the characteristic parameters such as link rated delay drift, link sampling value and frame loss are determined. Then, the correlation of characteristic parameters is determined according to the clustering core parameters, and the irrelevant characteristic parameters are removed through the error function. Finally, the fault characteristic sequence is determined according to different characteristic parameters in the node, and the fault point location is determined by Min distance to achieve fault diagnosis. The experimental results show that the proposed method can improve the accuracy of link fault location, and the diagnosis effect is good.

Published
2023
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240. Fixed‐time extended state observer‐based trajectory tracking control for autonomous underwater vehicles.

Author

Zheng, Jiaqi, Song, Lei, Liu, Lingya, Yu, Wenbin, Zhu, Shanying, Wang, Yiyin, and Chen, Cailian

Subjects
AUTONOMOUS underwater vehicles, OCEAN waves, PROBLEM solving
Abstract

In this paper, we investigate the trajectory tracking control problem for autonomous underwater vehicles (AUVs) with time‐varying external disturbances of currents and waves in the sea. To solve the problem, a fixed‐time extended state observer (FTESO)‐based tracking controller is proposed. Firstly, by using the extended state observer, the FTESO is proposed for estimating the external disturbances and the velocities of the AUV within the fixed convergence time. Based on the FTESO, the fixed‐time controller is proposed for reducing the tracking errors and improving robustness performance. Theoretical analysis is given, which shows that the unknown external disturbances can be compensated and tracking error can converge to zero within the fixed time. Simulation results show that the proposed FTESO controller not only guarantees the fixed‐time convergence but also reduces the trajectory tracking errors of the AUV. [ABSTRACT FROM AUTHOR]

Published
2022
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245. Evaluation, Treatment, and Outcomes of Patients With Suspected Acute Coronary Syndrome in the Prehospital and Emergency Department: Findings From a Prospective Multicenter Registry in China

Author

Cheng, Kai, primary, Wang, Jiali, additional, Zheng, Wen, additional, Wu, Shuo, additional, Zheng, Jiaqi, additional, Sang, Wentao, additional, Ma, Jingjing, additional, Pang, Jiaojiao, additional, Pan, Chang, additional, Wang, Guangmei, additional, Wu, Yangfeng, additional, Chen, Yuguo, additional, and Xu, Feng, additional

Published
2021
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249. Research on Power Flow and Flexible Control in DC Power System

Author

Li Teng, Wang Qiu, Zheng Jiaqi, Yan Li, Fan Yifei, and Cao Chengjie

Subjects
DC distribution system, business.industry, Computer science, Electrical engineering, Topology reconfiguration, symbols.namesake, Power flow, Electric power system, Jacobian matrix and determinant, symbols, Voltage regulation, MATLAB, business, computer, Excitation, computer.programming_language
Abstract

The DC distribution system has advantages over AC systems on power losses, control complexity, compatibility to DGs (Distributed Sources) and so on. The basic power flow problem in DC system is different from AC system in mathematical domain, bus types and component models. To construct the foundation of DC power system analysis, this paper analyzes the power flow problems in DC distribution system first, including bus types, power flow equations, Jacobian matrix and so on. It is pointed out that voltage regulation in DC power system only needs enough power capacity instead of generator with excitation system like AC system. Then, based on the DC bus voltage regulation property, the power flow path control and virtual topology reconfiguration technologies is proposed. The corresponding equivalent Jacobian matrixes are presented. Those technologies reveal that the DC power system can achieve much higher flexibility in power flow control. At last, simulation verification with MATLAB/SIMULINK is presented.

Published
2019

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