检索结果-内蒙古大学图书馆

Discrete effect on the anti-bounce-back boundary condition of lattice Bhatnagar-Gross-Krook model for convection-diffusion equations

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Wang, Liang Meng, Xuhui Wu, Hao-Chi Wang, Tian-Hu Lu, Gui Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Eduction North China Electric Power University Beijing102206 China School of Energy Power and Mechanical Engineering North China Electric Power University Beijing102206 China Division of Applied Mathematics Brown University ProvidenceRI02912 United States School of Control and Computer Engineering North China Electric Power University Beijing102206 China

The discrete effect on the boundary condition has been a fundamental topic for the lattice Boltzmann method in simulating heat and mass transfer problems. In previous works based on the halfway anti-bounce-back (ABB) boundary condition for convection-diffusion equations (CDEs), it is reported that the discrete effect cannot be commonly removed in the Bhatnagar-Gross-Krook (BGK) model except for a special value of relaxation time. Targeting this point in the present paper, we still proceed within the framework of BGK model for two-dimensional CDEs, and analyze the discrete effect on a non-halfway ABB boundary condition which incorporates the effect of the distance ratio. By analyzing an unidirectional diffusion problem with a parabolic distribution, the theoretical derivations with three different discrete velocity models show that the numerical slip is a combined function of the relaxation time and the distance ratio. Different from previous works, we definitely find that the relaxation time can be freely adjusted by the distance ratio in a proper range to eliminate the numerical slip. Some numerical simulations are carried out to validate the theoretical derivations, and the numerical results for the cases of straight and curved boundaries confirm our theoretical analysis. Finally, it should be noted that the present analysis can be extended from the BGK model to other lattice Boltzmann (LB) collision models for CDEs, which can broaden the parameter range of the relaxation time to approach 0.5. Copyright © 2019, The Authors. All rights reserved.

关键词： Relaxation time

Coordinating vehicle platoons for highway bottleneck decongestion and throughput improvement

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Čičić, Mladen Jin, Li Johansson, Karl Henrik Division of Decision and Control Systems School of Electrical Engineering and Computer Science KTH Royal Institute of Technology Malvinas väg 10 Stockholm10044 Sweden Department of Civil and Urban Engineering C2SMART University Transportation Center New York University Tandon School of Engineering 15 MetroTech Center BrooklynNY11201 USA United States

Truck platooning is a technology that is expected to become widespread in the coming years. Apart from the numerous benefits that it brings, its potential effects on the overall traffic situation needs to be studied further, especially at bottlenecks and ramps. However, assuming we can control the truck platoons from the infrastructure, they can be used as controlled moving bottlenecks, actuating control actions on the rest of the traffic. Thus properly controlled platoons can possibly improve the efficiency and throughput of the whole system. In this paper, we use a multi-class cell transmission model to capture the interaction between truck platoons and background traffic, and propose a corresponding queuing model, which we use for control design. As control inputs, we use platoon speeds, and the number of lanes platoons occupy, and we devise a control strategy for throughput improvement. This control law is applied on a highway section upstream of a bottleneck, with one on- ramp and one off-ramp. By postponing and shaping the inflow to the bottleneck, we are able to keep it in free flow, avoiding traffic breakdown and capacity drop, leading to significant reduction of total time spent of all vehicles. We tested the proposed control in a simulation study and found that by applying, we reduce the median delay of all vehicles by 75:6%. Notably, although they are slowed down while actuating control actions, platoons experience less delay compared to the case without control, since they avoid going through congestion at the bottleneck. Copyright © 2019, The Authors. All rights reserved.

关键词： Queueing theory

A nonlinear impulsive control system with impulse time windows and un-fixed coefficient of impulsive intensity

学校读者我要写书评

暂无评论

A nonlinear impulsive control system with impulse time windo...

International Conference on Informative and Cybernetics for Computational Social Systems (ICCSS)

作者： Yuming Feng Zitao Wang Xiaoyu Liu Wei Zhang Chongqing Engineering Research Center of Internet of Things and Intelligent Control Technology Chongqing Three Gorges University Wanzhou Chongqing China School of Computer Science and Engineering Chongqing Three Gorges University Wanzhou Chongqing China Key Laboratory of Intelligent Information Processing and Control Chongqing Three Gorges University Wanzhou Chongqing China School of Three Gorges Artificial Intelligence Chongqing Three Gorges University Wanzhou Chongqing China

ISBN: (数字)9781728158570

ISBN: (纸本)9781728158587

Based on the fact that there always exists error in the impulsive intensity, which leads to the fact that the coefficient is un-fixed, and in the occurrence of the impulses, we propose a new model, which is called nonlinear impulsive control system with impulse time windows and un-fixed coefficient of impulsive intensity. We find sufficient conditions for ensuring its stability by using Lypunov's method. We choose chaotic Lorenz system and Chua's system as numerical examples to show the effectiveness of the results, by employing such method, the systems are controlled.

关键词： Impulsive control system impulse time windows impulsive intensity stability control systems Impulsiveness Pulses Time windows

Edge-Enhanced Dual Discriminator Generative Adversarial Network for Fast MRI with Parallel Imaging Using Multi-view Information

学校读者我要写书评

暂无评论

arXiv 2021年

作者： Huang, Jiahao Ding, Weiping Lv, Jun Yang, Jingwen Dong, Hao Del Ser, Javier Xia, Jun Ren, Tiaojuan Wong, Stephen T. Yang, Guang College of Information Science and Technology Zhejiang Shuren University Hangzhou310015 China National Heart and Lung Institute Imperial College London London United Kingdom School of Information Science and Technology Nantong University Nantong226019 China School of Computer and Control Engineering Yantai University Yantai264005 China Department of Prosthodontics Peking University School Hospital of Stomatology Beijing China Center on Frontiers of Computing Studies Peking University Beijing China Derio48160 Spain Bilbao48013 Spain Department of Radiology Shenzhen Second People’s Hospital The First Affiliated Hospital of Shenzhen University Health Science Center Shenzhen China Systems Medicine and Bioengineering Department Houston Methodist Cancer Center HoustonTX77030 United States Department of Radiology Houston Methodist Hospital Weill Cornell Medicine HoustonTX77030 United States Cardiovascular Research Centre Royal Brompton Hospital London United Kingdom

In clinical medicine, magnetic resonance imaging (MRI) is one of the most important tools for diagnosis, triage, prognosis, and treatment planning. However, MRI suffers from an inherent slow data acquisition process because data is collected sequentially in k-space. In recent years, most MRI reconstruction methods proposed in the literature focus on holistic image reconstruction rather than enhancing the edge information. This work steps aside this general trend by elaborating on the enhancement of edge information. Specifically, we introduce a novel parallel imaging coupled dual discriminator generative adversarial network (PIDD-GAN) for fast multi-channel MRI reconstruction by incorporating multi-view information. The dual discriminator design aims to improve the edge information in MRI reconstruction. One discriminator is used for holistic image reconstruction, whereas the other one is responsible for enhancing edge information. An improved U-Net with local and global residual learning is proposed for the generator. Frequency channel attention blocks (FCA Blocks) are embedded in the generator for incorporating attention mechanisms. Content loss is introduced to train the generator for better reconstruction quality. We performed comprehensive experiments on Calgary-Campinas public brain MR dataset and compared our method with state-of-the-art MRI reconstruction methods. Ablation studies of residual learning were conducted on the MICCAI13 dataset to validate the proposed modules. Results show that our PIDD-GAN provides high-quality reconstructed MR images, with well-preserved edge information. The time of single-image reconstruction is below 5ms, which meets the demand of faster processing. © 2021, CC BY-NC-ND.

关键词： Generative adversarial networks

A network monitoring game with heterogeneous component criticality levels

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Milošević, Jezdimir Dahan, Mathieu Amin, Saurabh Sandberg, Henrik Division of Decision and Control Systems School of Electrical Engineering and Computer Science KTH Royal Institute of Technology Stockholm Sweden Center for Computational Engineering Massachusetts Institute of Technology CambridgeMA United States Department of Civil and Environmental Engineering Institute for Data Systems and Society Massachusetts Institute of Technology Cambridge United States

We consider an attacker-operator game for monitoring a large-scale network that is comprised on components that differ in their criticality levels. In this zero-sum game, the operator seeks to position a limited number of sensors to monitor the network against an attacker who strategically targets a network component. The operator (resp. attacker) seeks to minimize (resp. maximize) the network loss. To study the properties of mixed-strategy Nash Equilibria of this game, we first study two simple instances: (i) When component sets monitored by individual sensor locations are mutually disjoint;(ii) When only a single sensor is positioned, but with possibly overlapping monitoring component sets. Our analysis reveals new insights on how criticality levels impact the players equilibrium strategies. Next, we extend a previously known approach to obtain an approximate Nash equilibrium for the general case of the game. This approach uses solutions to minimum set cover and maximum set packing problems to construct an approximate Nash equilibrium. Finally, we implement a column generation procedure to improve this solution and numerically evaluate the performance of our approach. Copyright © 2019, The Authors. All rights reserved.

关键词： Criticality (nuclear fission)

An Improved Event-triggered H∞ Filtering for Nonlinear Systems

学校读者我要写书评

暂无评论

An Improved Event-triggered H∞ Filtering for Nonlinear Syst...

第30届中国控制与决策会议

作者： Zhongda Lu Guangtao Ran Fengbin Zhang Fengxia Xu School of Computer and Control Engineering Qiqihar University College of Computer Science and Technology Harbin University of Science and Technology

This paper addresses event-triggered ∞H filtering for nonlinear Networked control Systems with time-delay. A new event-triggered scheme is proposed to determine the state transmission only when satisfying trigger conditions. Considering the effects of the event-triggered scheme and network-induced, the fuzzy filtering error system is built based on T-S fuzzy model. An augmented Lyapunov function is constructed with integral items, and the Writinger inequality is first utilized to analysis and design ∞H filtering error system to derived a less conservative stability criterion. An illustrative example is presented to demonstrate the merit of the proposed event-triggered scheme and the effectiveness of the proposed method.

关键词： Event-triggered ∞H filtering Networked control Systems Writinger inequality

Mean-field transmission power control in dense networks part II - Social welfare evaluation

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Wu, Yuchi Wu, Junfeng Huang, Minyi Shi, Ling Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Hong Kong College of Control Science and Engineering Zhejiang University Hangzhou310027 China School of Mathematics and Statistics Carleton University OttawaONK1S 5B6 Canada

We consider uplink power control in wireless communication when massive users compete over the channel resources. In Part I [1], we have formulated massive transmission power control contest in a mean-field game framework. In this part, our goal is to investigate whether the power-domain non-orthogonal multiple access (NOMA) protocol can regulate the non-cooperative channel access behaviors, i.e., steering the competition among the noncooperative users in a direction with improved efficiency and fairness. It is compared with the CDMA protocol, which drives each user to fiercely compete against the population, hence the efficiency of channel usage is sacrificed. The existence and uniqueness of an equilibrium strategy under CDMA and NOMA have already been characterized in Part I. In this paper, we adopt the social welfare of the population as the performance metric, which is defined as the expectation of utility over the distribution of different types of channel users. It is shown that under the corresponding equilibrium strategies, NOMA outperforms CDMA in the social welfare achieved, which is illustrated through simulation with different unit price for power consumption. Moreover, it can be observed from numerical results that NOMA can improve the fairness of the achieved data rates among different users. Copyright © 2019, The Authors. All rights reserved.

关键词： 5G mobile communication systems

Cooperative Caching Strategy Based on Cache Cost for Information-Centric Networking

学校读者我要写书评

暂无评论

Dongbei Daxue Xuebao/Journal of Northeastern University 2018年第2期39卷 166-171页

作者： Cai, Ling Wang, Jin-Kuan Wang, Xing-Wei Han, Lai-Quan School of Control Engineering Northeastern University at Qinhuangdao Qinhuangdao066004 China School of Information Science & Engineering Northeastern University Shenyang110819 China School of Software Northeastern University Shenyang110169 China School of Computer and Communication Engineering Northeastern University at Qinhuangdao Qinhuangdao066004 China

In-network caching is one of the core issues in information-centric networking (ICN) which will directly restrict the data dissemination performance of the network. Considering the cache cost contains not only the path cost raised by accessing a cache node on the path but also the replacement cost of old information, a path and node cost based cooperative caching strategy (PNC3S) is proposed. The PNC3S considers the path cost and replacement cost comprehensively, and whether information matches a node or not depends on the total cost. Then the optimization algorithm is introduced into the proposed strategy to make caching decision. The simulation experiments demonstrate that the proposed PNC3S, compared with CEE (cache everything everywhere) and LCD (leave copy down), improves such performance as cached information ratio, server load ratio, average link utilization ratio and hop reduction ratio. © 2018, Editorial Department of Journal of Northeastern University. All right reserved.

关键词： Optimization

Mean-Field transmission power control in dense networks: Part I - Characterization of the equilibrium strategy

学校读者我要写书评

暂无评论

arXiv 2019年

We consider uplink power control in wireless communication when massive users compete over the channel resources. The CDMA protocol, as a supporting technology of 3G networks accommodating signal from different sources over the code domain, represents the orthogonal multiple access techniques. With the development of 5G wireless networks, non-orthogonal multiple access (NOMA) is introduced to improve the efficiency of channel allocation. Our goal is to investigate whether the power-domain NOMA protocol can introduce a natural fair principle when the users interact with each other in a non-cooperative manner. It is compared with the CDMA protocol, where the fierce competition among users jeopardizes the efficiency of channel usage. The whole work is split into two parts. In this paper, (i.e., Part I), we conduct analysis with a mean-field game (MFG) model, and show the existence and uniqueness of an equilibrium strategy. To determine whether NOMA is a more efficient communication protocol for uplink communication, the social welfare comparison is conducted in Part II [1]. Copyright © 2019, The Authors. All rights reserved.

关键词： 5G mobile communication systems