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Science China(Information Sciences) 2014年第4期57卷 30-41页

作者： ZHAI GuoWei TIAN Lin ZHOU YiQing SHI JingLin Wireless Technology research center Institute of Computing Technology Chinese Academy of Science Key Laboratory of Mobile computing and Pervasive Device University of Chinese Academy of Sciences

To reduce construction cost and energy consumption of cellular networks,the centralized radio access cellular network infrastructure with a Super BS(CSBS)architecture has been *** CSBS architecture has the advantage that the centralized processing resource can be flexibly ***,the problem of low processing resource efficiency caused by load discrepancy of base stations still exists and the processing resource allocation methods for physical layer processing are not suitable for protocol *** this article,a framework for protocol processing resource management is designed and a load diversity based processing resource allocation(LDA)algorithm is proposed,which employs dynamic programming with the consideration of load ***,to support large mumber of BSs,a suboptimal algorithm hybrid load diversity based processing resource allocation(H-LDA)is also *** results show that LDA and H-LDA algorithm significantly outperforms the conventional methods,respectively,by more than 60%and 55%in the processing resource efficiency and the performance gap grows with the increasing BS number.

关键词： processing resource load diversity virtual base station protocol processing server dynamic programming

Transceiver designs with matrix-version water-filling architecture under mixed power constraints

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Science China(Information Sciences) 2016年第10期59卷 169-180页

作者： Chengwen XING Zesong FEI Yiqing ZHOU Zhengang PAN Hualei WANG School of Information and Electronics Beijing Institute of Technology Wireless Communication research center Institute of Computing TechnologyChinese Academy of Sciences China Mobile research Institute

In this paper, we investigate the multiple-input multiple-output(MIMO) transceiver design under an interesting power model named mixed power constraints. In the considered power model, several antenna subsets are constrained by sum power constraints while the other antennas are subject to per-antenna power constraints. This kind of transceiver designs includes both the transceiver designs under sum power constraint and per-antenna power constraint as its special cases. This kind of designs is of critical importance for distributed antenna systems(DASs) with heterogeneous remote radio heads(RRHs) such as cloud radio access networks(C-RANs). In our work, we try to solve the optimization problem in an analytical way instead of using some famous software packages e.g., CVX or Se Du Mi. In our work, to strike tradeoffs between performance and complexity, both iterative and non-iterative solutions are proposed. Interestingly the non-iterative solution can be interpreted as a matrix-version water-filling solution extended from the well-known and extensively studied vector version. Finally, simulation results demonstrate the accuracy of our theoretical results.

关键词： convex optimization MIMO matrix-version water-filling transceiver designs mix power constraints

Neural recovery machine for Chinese dropped pronoun

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Frontiers of Computer Science 2019年第5期13卷 1023-1033页

作者： Weinan ZHANG Ting LIU Qingyu YIN Yu ZHANG research center for Social computing and Information Retrieval School of Computer Science and Technology Harbin Institute of TechnologyHarbin 150001China

Dropped pronouns (DPs) are ubiquitous in pro-drop languages like Chinese, Japanese etc. Previous work mainly focused on painstakingly exploring the empirical features for DPs recovery. In this paper, we propose a neural recovery machine (NRM) to model and recover DPs in Chinese to avoid the non-trivial feature engineering process. The experimental results show that the proposed NRM significantly outperforms the state-of-the-art approaches on two heterogeneous datasets. Further experimental results of Chinese zero pronoun (ZP) resolution show that the performance of ZP resolution can also be improved by recovering the ZPs to DPs.

关键词： neural network Chinese dropped pronoun re-covery Chinese zero pronoun resolution

A Non-Forced-Write Atomic Commit Protocol for Cluster File Systems

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Journal of Computer Science & Technology 2014年第2期29卷 303-315页

作者：邵冰清张军伟郑彩平张浩刘振军许鲁 Data Storage and Management Technology research center Institute of Computing TechnologyChinese Academy of Sciences University of Chinese Academy of Sciences

Distributed metadata consistency is one of the critical issues of metadata clusters in distributed file systems. Existing methods to maintain metadata consistency generally need several log forced write operations. Since synchronous disk IO is very inefficient, the average response time of metadata operations is greatly increased. In this paper, an asynchronous atomic commit protocol （ACP） named Dual-Log （DL） is presented. It does not need any log forced write operations. Optimizing for distributed metadata operations involving only two metadata servers, DL mutually records the redo log in counterpart metadata servers by transferring through the low latency network. A crashed metadata server can redo the metadata operation with the redundant redo log. Since the latency of the network is much lower than the latency of disk IO, DL can improve the performance of distributed metadata service significantly. The prototype of DL is implemented based on local journal. The performance is tested by comparing with two widely used protocols, EP and S2PC-MP, and the results show that the average response time of distributed metadata operations is reduced by about 40%-60%, and the recovery time is only I second under 10 thousands uncompleted distributed metadata operations.

关键词： atomic commit protocol cluster file system distributed metadata operation consistency Dual-Log

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A CONTROL ALGORITHM FOR RAPID MOVEMENTS NEAR THE RADIUS COMPENSATION SINGULARITY IN FIVE-AXIS END MILLING

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Journal of Systems Science & Complexity 2013年第5期26卷 718-734页

作者： WANG Feng LIN Hu ZHENG Liaomo LIU Feng YANG Lei GENG Cong Graduate University of Chinese Academy of Sciences National Engineering research center for High-End CNC Shenyang Institute of Computing TechnologyChinese Academy of Sciences National Engineering research center For High-End CNC Shenyang Institute of Computing TechnologyChinese Academy of Sciences University of Science and Technology of China

When the five-axis CNC system executes the 3D cutter radius compensation function,the angle between two adjacent radius compensation vectors might become very large and the linear axes would move too fast if the tool orientation vector is close to the surface *** reason that results in this phenomenon is analyzed based on building the transmission relationship between the cutter contact point and the cutter location *** taking the square-end tool as an example,an optimization algorithm to control the undesired movements is *** the singular area where sudden change exists,the number of interpolation cycles is determined by the cutter feedrate,the limit speeds of machine axes and the maximum allowable angle between radius compensation vectors of adjacent NC *** radius compensation vector of each interpolation cycle is obtained by a kind of vector rotation *** maintaining the perpendicularity between the radius compensation vector and the tool orientation vector,the rapid movements of the linear axes are eliminated.A trial-cut experiment is performed to verify the correctness and the effectiveness of the proposed algorithm.

关键词： Five-axis machining motion control singularity 3D radius compensation.

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Towards trustworthy blockchain systems in the era of “Internet of value”: development, challenges, and future trends

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Science China(Information Sciences) 2022年第5期65卷 250-260页

作者： Hai JIN Jiang XIAO National Engineering research center for Big Data Technology and System Services Computing Technology and System Lab Cluster and Grid Computing Lab School of Computer Science and TechnologyHuazhong University of Science and Technology

Since the advent of cryptocurrencies such as Bitcoin, blockchain, as their underlying technologies,has drawn a massive amount of attention from both academia and the industry. This ever-evolving technology inherits the “genes” of distributed systems, offering significant advantages of immutability, transparency,auditability, and tamper-resistance. These benefits help blockchain re-establish public confidence, and hold the significant promise of reliable information sharing and value transfer. Therefore, blockchain has become the foundation of crucial strategic deployments in countries across the world, and the fundamental basis for building the next generation Web 3.0 — “Internet of value”. In this article, we will start with unraveling the essential ingredients of blockchain technology, and showing the characteristics of each of these ingredients in the context of distributed systems. We will then present the core technical challenges that need to be addressed prior to unleashing its full potential, including its performance, scalability, and cross-chain interoperability. Finally, we will introduce the recent developments of blockchain systems, and discuss the future trends of the blockchain ecosystem.

关键词： blockchain distributed systems internet of value challenges development

HMvisor: dynamic hybrid memory management for virtual machines

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Science China(Information Sciences) 2021年第9期64卷 74-89页

作者： Dang YANG Haikun LIU Hai JIN Yu ZHANG National Engineering research center for Big Data Technology and System Services Computing Technology and System Lab Cluster and Grid Computing LabSchool of Computer Science and Technology Huazhong University of Science and Technology

Emerging non-volatile memory(NVM) technologies promise high density, low cost and dynamic random access memory(DRAM)-like performance, at the expense of limited write endurance and high write energy consumption. It is more practical to use NVM combining with the traditional DRAM. However, the hybrid memory management such as page migration becomes more challenging in a virtualization environment because virtual machines(VMs) are unaware of the memory heterogeneity. In this paper, we propose HMvisor, a hypervisor and VM coordinated hybrid memory management mechanism to better utilize DRAM and NVM resources. HMvisor exposes the memory heterogeneity to VMs by mapping virtual NUMA nodes to different physical NUMA nodes. We propose a lightweight and efficient page migration mechanism by decoupling page hotness tracking from page migration. HMvisor performs those operations in the hypervisor and VMs separately, without disrupting the execution of VMs. We also propose a memory resource trading policy to adjust the capacity of DRAM and NVM for each VM, with the monetary cost unchanged. We implement our prototype system based on QEMU/KVM and evaluate it with several benchmarks. Experimental results show that HMvisor can reduce 50% of write traffic to NVM with less than 5% performance overhead. Moreover, the hybrid memory adjustment scheme in HMvisor can significantly improve application performance by up to 30×.

关键词： hypervisor virtual machine non-volatile memory hybrid memory management

Influence of Methane-Hydrogen Mixture Characteristics on Compressor Vibrations

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Fluid Dynamics & Materials Processing 2024年第5期20卷 1031-1043页

作者： Vladimir Ya.Modorskii Ivan E.Cherepanov High Performance computing center Perm National Research Polytechnic UniversityPerm614990Russia

A transition to clean hydrogen energy will not be possible until the issues related to its production, transportation,storage, etc., are adequately resolved. Currently, however, it is possible to use methane-hydrogen *** gas can be transported using a pipeline system with the required pressure being maintained by gascompression stations. This method, however, is affected by some problems too. Compressors emergency stopscan be induced by vibrations because in some cases, mechanical methods are not able to reduce the vibrationamplitude. As an example, it is known that a gas-dynamic flow effect in labyrinth seals can lead to increasedvibrations. This paper presents the numerical simulation of rotor oscillations taking into account a gas-dynamicload. The influence of a transported mixture on the oscillatory process is investigated. Mixtures consisting ofmethane and hydrogen in various proportions and an air mixture are considered. The results are discussed forvarious operating pressures and include the rotor motion trajectories and oscillation frequency spectra obtainednumerically. It is shown that the gas mixture composition has a significant effect on the oscillations and theiroccurrence. Hydrogen as a working fluid reduces the vibration amplitude. Operating a compressor with hydrogenleads to a decrease in the resonant frequency, bringing it closer to the operating one. However, the operatingpressure at which maximum oscillations are observed depends slightly on the gas mixture composition.

关键词： Seal stabilities vibration FSI CFD multiphase flows hydrogen

Recent advances in deep learning based sentiment analysis

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Science China(Technological Sciences) 2020年第10期63卷 1947-1970页

作者： YUAN JianHua WU Yang LU Xin ZHAO YanYan QIN Bing LIU Ting research center for Social computing and Information Retrieval Harbin Institute of TechnologyHarbin 150001China Pengcheng Lab Shenzhen 518066China

Sentiment analysis is one of the most popular research areas in natural language *** is extremely useful in many applications,such as social media monitoring and *** application of deep learning based methods has dramatically changed the research strategies and improved the performance of many traditional sentiment analysis tasks,such as sentiment classification and aspect based sentiment ***,it also pushed the boundary of various sentiment analysis task,including sentiment classification of different text granularities and in different application scenarios,implicit sentiment analysis,multimodal sentiment analysis and generation of sentiment-bearing *** this paper,we give a brief introduction to the recent advance of the deep learning-based methods in these sentiment analysis tasks,including summarizing the approaches and analyzing the *** survey can be well suited for the researchers studying in this field as well as the researchers entering the field.

关键词： coarse-grained fine-grained implicit multi-modal generation

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Filling the gap: thermal properties and device applications of graphene

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Science China(Information Sciences) 2021年第4期64卷 103-119页

作者： Rui WU Rui-Zhi ZHU Shi-Hui ZHAO Gang ZHANG He TIAN Tian-Ling REN Institute of Microelectronics and Beijing National research center for Information Science and Technology (BNRist) Tsinghua University Institute of High Performance computing A*STAR

With the miniaturization and integration of electronic devices, the heat dissipation problems caused by higher power density are getting more serious, limiting the development of integrated circuits industry. Graphene, as a representative of two-dimensional materials, has attracted extensive attention for its excellent thermal properties. Ever since it has been discovered, researches have been carried out and achievements have been made both theoretically and practically. Here, we review the established theories and simulation system for 2D heat conduction, different measurement methods for thermal conductivity and graphene’s device applications. We propose two gaps between different scales and between theoretical prediction and practical effect. Owing to the higher heat dissipation requirements and the endless pursuit of better thermal performance, it is challenging but critical to continue studying and further understand the thermal properties of graphene. Challenges and opportunities are both emphasized. It is hoped that the diversification and progress in morphology and manufacturing technology can bring new development and that graphene can eventually be widely used and make huge changes to micoelectronic industry.

关键词： graphene thermal properties device application thermal conductivity 2D material