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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

Middleware for Wireless Sensor Networks:A Survey

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Journal of Computer Science & Technology 2008年第3期23卷 305-326页

作者：王苗苗曹建农李京 Sajal K.Dasi Department of Computer Science The University of Science and Technology of China Internets and mobile computing Lab Department of ComputingThe Hong Kong Polytechnic University Department of Computer Science and Engineering The University of Texas at Arlington

Wireless Sensor Networks （WSNs） have found more and more applications in a variety of pervasive computing environments. However, how to support the development, maintenance, deployment and execution of applications over WSNs remains to be a nontrivial and challenging task, mainly because of the gap between the high level requirements from pervasive computing applications and the underlying operation of WSNs. Middleware for WSN can help bridge the gap and remove impediments. In recent years, research has been carried out on WSN middleware from different aspects and for different purposes. In this paper, we provide a comprehensive review of the existing work on WSN middleware, seeking for a better understanding of the current issues and future directions in this field. We propose a reference framework to analyze the functionalities of WSN middleware in terms of the system abstractions and the services provided. We review the approaches and techniques for implementing the services. On the basis of the analysis and by using a feature tree, we provide taxonomy of the features of WSN middleware and their relationships, and use the taxonomy to classify and evaluate existing work. We also discuss open problems in this important area of research.

关键词： middleware wireless sensor network pervasive computing

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

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

SAND: semi-automated adaptive network defense via programmable rule generation and deployment

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Science China(Information Sciences) 2022年第7期65卷 121-138页

作者： Haoyu CHEN Deqing ZOU Hai JIN Shouhuai XU Bin YUAN National Engineering research center for Big Data Technology and System Services Computing Technology and System LabCluster and Grid Computing Lab School of Computer Science and TechnologyHuazhong University of Science and Technology National Engineering research center for Big Data Technology and System Services Computing Technology and System LabHubei Engineering Research Center on Big Data Security School of Cyber Science and EngineeringHuazhong University of Science and Technology Department of Computer Science University of Colorado at Colorado Springs

Cyber security is dynamic as defenders often need to adapt their defense postures. The state-ofthe-art is that the adaptation of network defense is done manually(i.e., tedious and error-prone). The ideal solution is to automate adaptive network defense, which is however a difficult problem. As a first step towards automation, we propose investigating how to attain semi-automated adaptive network defense(SAND). We propose an approach extending the architecture of software-defined networking, which is centered on providing defenders with the capability to program the generation and deployment of dynamic defense rules enforced by network defense tools. We present the design and implementation of SAND, as well as the evaluation of the prototype implementation. Experimental results show that SAND can achieve agile and effective dynamic adaptations of defense rules(less than 15 ms on average for each operation), while only incurring a small performance overhead.

关键词： network defense adaptive defense automated defense programmable defense security services software-defined networking security management

Temporal enhanced sentence-level attention model for hashtag recommendation

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CAAI Transactions on Intelligence Technology 2018年第2期3卷 95-100页

作者： Jun Ma Chong Feng Ge Shi Xuewen Shi Heyang Huang Beijing Engineering research center of High Volume Language Information Processing and cloud computing Applications College of Computer Science Beijing Institute of Technology University 5 South Zhong Guan Cun Street of Haidian District Beijing People's Republic of China

Hashtags of microblogs can provide valuable information for many natural language processing tasks. How to recommend reliable hashtags automatically has attracted considerable attention. However, existing studies assumed that all the training corpus crawled from social networks are labelled correctly, while large sample statistics on real social media shows that there are 8.9% of microblogs with hashtags having wrong labels. The notable influence of noisy data to the classifier is ignored before. Meanwhile, recency also plays an important role in microblog hashtag, but the information is not used in the existing studies. Some temporal hashtags such as World Cup will ignite at a particular time, but at other times, the number of people talking about it will sharply decrease. To address the twofold shortcomings above, the authors propose an long short-term memory-based model, which uses temporal enhanced selective sentence-level attention to reduce the influence of wrong labelled microblogs to the classifier. Experimental results using a dataset of 1.7 million microblogs collected from SINA Weibo microblogs demonstrated that the proposed method could achieve significantly better performance than the state-of-the-art methods.

关键词：分类器数据集计算机技术智能技术

An Effective RAID Data Layout for Object-Based De-duplication Backup System

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Chinese Journal of Electronics 2016年第5期25卷 832-840页

作者： YAN Fang TAN Yu'an ZHANG Quanxin WU Fei CHENG Zijing ZHENG Jun School of Computer Science and Technology Beijing Institute of Technology School of Information Beijing Wuzi University Beijing Engineering research center of Massive Language Information Processing and cloud computing Application Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Space Star Technology CO. LtdChina Academy of Space Technology

We propose an alternative Redundant array of independent disks(RAID) data layout, Asymmetrical grouping data organization(AGDO), for object-based data de-duplication backup system. Object-based data deduplication is an effective solution for detecting duplicate data for compound files. We designed an asymmetrical grouping strategy, the disk in the array are partitioned into different groups, and in each group parallelism data access scheme is adopted, different types of objects are stored in different groups with maybe different group size, it can set and manage dynamic group size by using dynamic disk group adjustment algorithms. The performance of AGDO is evaluated and proved to be sufficient for the continuous storage application. The result is that disk accesses are concentrated in a part of the disks over a long time period and reduces the power consumption to 25% in a 10-disk configuration. Moreover, object-based de-duplication combined with AGDO has great potential in increasing data restoration speed for compound files. We have shown that this combination makes average restoration speed improved 11%.

关键词： Data layout Object-based deduplication Backup Energy aware Redundant array of independent disks(RAID)

Reinvent cloud Software Stacks for Resource Disagggiregation

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Journal of Computer Science & Technology 2023年第5期38卷 949-969页

作者：王晨曦单一舟左鹏飞崔慧敏 Institute of computing Technology Chinese Academy of SciencesBeijing 100190China University of the Chinese Academy of Sciences Beijing 101408China Huawei cloud Shenzhen 518129China

Due to the unprecedented development of low-latency interconnect technology,building large-scale disaggre-gated architecture is drawing more and more attention from both industry and *** disaggregation is a new way to organize the hardware resources of datacenters,and has the potential to overcome the limitations,e.g.,low re-source utilization and low reliability,of conventional ***,the emerging disaggregated architecture brings severe performance and latency problems to the existing cloud *** this paper,we take memory disaggregation as an example to demonstrate the unique challenges that the disaggregated datacenter poses to the existing cloud software stacks,e.g.,programming interface,language runtime,and operating system,and further discuss the possible ways to rein-vent the cloud systems.

关键词： cloud computing resource disaggregation datacenter program semantics

Studying the Equilibrium Points of the Modified Circular Restricted Three-body Problem: The Case of Sun–Haumea System

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research in Astronomy and Astrophysics 2023年第11期23卷 232-242页

作者： INurul Huda B.Dermawan M.B.Saputra R.Sadikin T.Hidayat research center for computing National Research and Innovation AgencyBogorIndonesia Department of Astronomy and Bosscha Observatory FMIPAInstitut Teknologi BandungBandungIndonesia

We intend to study a modified version of the planar Circular Restricted Three-Body Problem(CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radiation while the small primary has an elongated body. We also consider the perturbation from a disk-like structure encompassing this three-body system. First, we develop a mathematical model of this modified *** have found there exist five equilibrium points in this modified CRTBP model, where three of them are collinear and the other two are non-collinear. Second, we apply our modified CRTBP model to the Sun–Haumea system by considering several values of each perturbing parameter. Through our numerical investigation, we have discovered that the incorporation of perturbing parameters has resulted in a shift in the equilibrium point positions of the Sun–Haumea system compared to their positions in the classical CRTBP. The stability of equilibrium points is investigated. We have shown that the collinear equilibrium points are unstable and the stability of non-collinear equilibrium points depends on the mass parameter μ of the system. Unlike the classical case, non-collinear equilibrium points have both a maximum and minimum limit of μ for achieving stability. We remark that the stability range of μ in non-collinear equilibrium points depends on the perturbing parameters. In the context of the Sun–Haumea system, we have found that the non-collinear equilibrium points are stable.

关键词： celestial mechanics Kuiper Belt:general planets and satellites:dynamical evolution and stability