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INTRINSIC FEATURES OF TURBULENT FLOW IN STRONGLY 3-D SKEW BLADE PASSAGE OF A FRANCIS TURBINE

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Journal of Hydrodynamics 2007年第1期19卷 92-99页

作者： ZHANG Li-xiang WANG wen-quan GUO Yakun Department of Engineering Mechanics Kunming University of Science and Technology Kunming 650051 China GUO Yakun Department of Engineering University of Aberdeen Aberdeen AB24 3UE UK.

The turbulent flow, with the Reynolds number of 5.9×10^5, in the strongly 3-D skew blade passage of a true Francis hydro turbine was simulated by the Large Eddy Simulation （LES） approach to investigate the spatial and temporal distributions of the fully developed turbulence in the passage with strongly 3-D complex geometry. The simulations show that the strong three-dimensionality of the passage has a great amplification effect on the turbulence in the passage, and the distributions of the turbulence are diversely nonuniform, for instance, the rise of turbulent kinetic energy in the lower 1/3 region of the passage is more than 45%, whereas its rise in the upper 1/3 region is less than 1%. With the LES approach, the details of the flow structures at the near-wall surfaces of the blades could be obtained. Several turbulent spots were captured.

关键词： turbulent flow Large Eddy Simulation (LES),hydro turbine

Adaptive ant-based routing in wireless sensor networks using Energy~* Delay metrics

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 531-538页

作者： Yao-feng wen Yu-quan CHEN Min PAN State Specialized Laboratory of Biomedical Sensors Zhejiang University Hangzhou 310027 China

To find the optimal routing is always an important topic in wireless sensor networks (WSNs). Considering a WSN where the nodes have limited energy, we propose a novel Energy*Delay model based on ant algorithms ("E&D ANTS" for short) to minimize the time delay in transferring a fixed number of data packets in an energy-constrained manner in one round. Our goal is not only to maximize the lifetime of the network but also to provide real-time data transmission services. However, because of the tradeoff of energy and delay in wireless network systems, the reinforcement learning (RL) algorithm is introduced to train the model. In this survey, the paradigm of E&D ANTS is explicated and compared to other ant-based routing algorithms like AntNet and AntChain about the issues of routing information, routing overhead and adaptation. Simulation results show that our method performs about seven times better than AntNet and also outperforms AntChain by more than 150% in terms of energy cost and delay per round.

关键词： Ant colony optimization (ACO) Pheromones Power consumption Wireless sensor networks (WSNs)

Superoscillation:from physics to optical applications

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Light(Science & Applications) 2019年第1期8卷 688-710页

作者： Gang Chen Zhong-quan wen Cheng-Wei Qiu College of Optoelectronic Engineering Chongqing University174 Shazheng StreetChongqing 400044China Department of Electrical and Computer Engineering National University of Singapore4 Engineering Drive 3Singapore 117583Singapore

The resolution of conventional optical elements and systems has long been perceived to satisfy the classic Rayleigh *** efforts have been made to develop different types of superresolution techniques to achieve optical resolution down to several nanometres,such as by using evanescent waves,fluorescence labelling,and *** imaging techniques,which are noncontact,far field and label free,are highly desirable but challenging to *** concept of superoscillation offers an alternative route to optical superresolution and enables the engineering of focal spots and point-spread functions of arbitrarily small size without theoretical *** paper reviews recent developments in optical superoscillation technologies,design approaches,methods of characterizing superoscillatory optical fields,and applications in noncontact,far-field and label-free superresolution *** work may promote the wider adoption and application of optical superresolution across different wave types and application domains.

关键词： optical oscillation resolution

Synthesis of Polybutadienes with Controllable Microstructure by a Novel Binary Nd(3-NBSO_3)_3/Alkylaluminum Catalyst System

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Chinese Journal of Polymer Science 2015年第3期33卷 475-480页

作者： Ji-qin wen Xue-quan Zhang 代全权 Key Laboratory of Synthetic Rubber Changchun Institute of Applied ChemistryChinese Academy of Sciences jiangsu Province Institute for Medical Equipment Testing

The polymerization of 1,3-butadiene was examined by using a novel halogen-free neodymium m-nitrobenzenesulfonate （Nd（3-NBSOa）3·donors）/alkylaluminum binary catalyst system. The catalyst showed fairly high activity and controllable selectivity. The microstructure of the resultant polymer was adjustable by variation of electron donor and/or the alkylaluminum. ^13C-NMR and thermal analysis demonstrate that the produced polybutadienes have stereo-block chain structures of cis-1,4 and trans-1,4 segments with adjustable Tm and To. The neodymium sulfonate-based catalyst is believed to be significant in regulating the chain structure of polydienes and in exploring 1,3-diene polymerization mechanism.

关键词： Polybutadiene Microstructure Ziegler-Natta polymerization.

Effect of electromechanical the properties of epitaxial boundary conditions on ferroelectric thin films

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Chinese Physics B 2011年第10期20卷 407-412页

作者： Zhou Zhi-Dong Zhang Chun-Zu jiang quan Department of Materials Science and Engineering College of Materials Xiamen University Xiamen 361005 China Department of Civil Engineering School of Architecture and Civil Engineering Xiamen University Xiamen 361005 China College of Civil Engineering Nantong University Nantong 226019 China

The effects of internal stresses and depolarization fields on the properties of epitaxial ferroelectric perovskite thin films are discussed by employing the dynamic Ginzbur~Landau equation （DCLE）. The numerical solution for BaTiO3 film shows that internal stress and the depolarization field have the most effects on ferroelectric properties such as polarization, Curie temperature and susceptibility. With the increase of the thickness of the film, the polarization of epitaxia] ferroelectric thin film is enhanced rapidly under high internal compressively stress. With the thickness exceeding the critical thickness for dislocation formation, the polarization increases slowly and even weakens due to relaxed internal stresses and a weak electrical boundary condition. This indicates that the effects of mechanical and electrical boundary conditions both diminish for ferroelectric thick films. Consequently, our thermodynamic method is a full scale model that can predict the properties of ferroelectric perovskite films in a wide range of film thickness.

关键词： ferroelectric film internal stresses thermodynamic equations polarizations

General formalism for dirty extreme-mass-ratio inspirals

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 22-29页

作者： Ye jiang wen-Biao Han Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China Shanghai Frontiers Science Center for Gravitational Wave Detection Shanghai 200240China

Detecting the environment around the supermassive black holes and tests of general relativity are important applications of extreme-mass-ratio inspirals(EMRIs).There is still a challenge to efficiently describe various“dirty”impacts on the inspirals,such as dark matter,gas,dipole radiation,and electromagnetic *** this study,we find the inherent linearity of the asymptotic solution of the inhomogeneous Teukolsky *** the basis of this property,we completely decouple the factors of the perturber and the background spacetime in the energy fluxes and *** the new decoupling form,the waveforms of EMRIs with non-geodesic motion in Kerr spacetime can be conveniently *** will help to resolve the environment(including gas,field,dark matter,electromagnetic interaction)around supermassive black holes and test general relativity.

关键词： gravitational wave Teukolsky equation extreme-mass-ratio inspirals

Metadata Feedback and Utilization for Data Deduplication Across WAN

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Journal of Computer Science & Technology 2016年第3期31卷 604-623页

作者： Bing Zhou jiang-Tao wen State Key Laboratory on Intelligent Technology and Systems Tsinghua University Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Data deduplication for file communication across wide area network （WAN） in the applications such as file synchronization and mirroring of cloud environments usually achieves significant bandwidth saving at the cost of significant time overheads of data deduplication. The time overheads include the time required for data deduplication at two geographi- cally distributed nodes （e.g., disk access bottleneck） and the duplication query/answer operations between the sender and the receiver, since each query or answer introduces at least one round-trip time （RTT） of latency. In this paper, we present a data deduplication system across WAN with metadata feedback and metadata utilization （MFMU）, in order to harness the data deduplication related time overheads. In the proposed MFMU system, selective metadata feedbacks from the receiver to the sender are introduced to reduce the number of duplication query/answer operations. In addition, to harness the metadata related disk I/O operations at the receiver, as well as the bandwidth overhead introduced by the metadata feedbacks, a hysteresis hash re-chunking mechanism based metadata utilization component is introduced. Our experimental results demonstrated that MFMU achieved an average of 20%~40% deduplication acceleration with the bandwidth saving ratio not reduced by the metadata feedbacks, as compared with the ＂baseline＂ content defined chunking （CDC） used in LBFS （Low-bandwith Network File system） and exiting state-of-the-art Bimodal chunking algorithms based data deduplication solutions.

关键词： data deduplication wide area network (WAN) metadata feedback metadata utilization

A Data Deduplication Framework of Disk Images with Adaptive Block Skipping

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Journal of Computer Science & Technology 2016年第4期31卷 820-835页

作者： Bing Zhou jiang-Tao wen State Key Laboratory on Intelligent Technology and Systems Tsinghua University Beijing 100084 China

We describe an efficient and easily applicable data deduplication framework with heuristic prediction based adaptive block skipping for the real-world dataset such as disk images to save deduplication related overheads and improve deduplication throughput with good deduplication efficiency maintained. Under the framework, deduplication operations are skipped for data chunks determined as likely non-duplicates via heuristic prediction, in conjunction with a hit and matching extension process for duplication identification within skipped blocks and a hysteresis mechanism based hash indexing process to update the hash indices for the re-encountered skipped chunks. For performance evaluation, the proposed framework was integrated and implemented in the existing data domain and sparse indexing deduplication algorithms. The experimental results based on a real-world dataset of 1.0 TB disk images showed that the deduplication related overheads were significantly reduced with adaptive block skipping, leading to a 30%-80% improvement in deduplication throughput when deduplieation mctadata were stored on the disk for data domain, and 25%-40% RAM space saving with a 15%-20% improvement in deduplication throughput when an in-RAM sparse index was used in sparse indexing. In both cases, the corresponding deduplication ratios reduced were below 5%.

关键词： data deduplication metadata adaptive block skipping

Improving Metadata Caching Efficiency for Data Deduplication via In-RAM Metadata Utilization

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Journal of Computer Science & Technology 2016年第4期31卷 805-819页

We describe a data deduplication system for backup storage of PC disk images, named in-RAM metadata utilizing deduplication （IRwMUD）. In-RAM hash granularity adaptation and miniLZO based data compression are firstly proposed to reduce the in-RAM metadata size and thereby reduce the space overheads required by the in-RAM metadata caches. Secondly, an in-RAM metadata write cache, as opposed to the traditional metadata read cache, is proposed for further reducing metadata-related disk I/O operations and improving deduplication throughput. During deduplication, the metadata write cache is managed following the LRU caching policy. For each manifest that is hit in the metadata write cache, an expensive manifest reloading operation from the disk is avoided. After deduplieation, all the manifests in the metadata write cache are cleared and stored on the disk. Our experimental results using 1.5 TB real-world disk image dataset show that I） IR-MUD achieved about 95% size reduction for the deduplication metadata, with a small time overhead introduced, 2） when the metadata write cache was not utilized, with the same RAM space size for the metadata read cache, IR-MUD achieved a 400% higher RAM hit ratio and a 50% higher deduplication throughput, as compared with the classic Sparse Indexing deduplication system where no metadata utilization approaches are utilized, and 3） when the metadata write cache was utilized and enough RAM space was available, IR-MUD achieved a 500% higher RAM hit ratio compared with Sparse Indexing and a 70% higher deduplication throughput compared with IR-MUD with only a single metadata read cache. The in-RAM metadata harnessing and metadata write caching approaches of IR-MUD can be applied in most parallel deduplication systems for improving metadata caching efficiency.

关键词： data deduplication cache metadata utilization