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A Survey of Bitmap Index Compression Algorithms for Big Data

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Tsinghua Science and Technology 2015年第1期20卷 100-115页

作者： Zhen Chen Yuhao Wen Junwei Cao Wenxun Zheng Jiahui Chang Yinjun Wu Ge Ma Mourad Hakmaoui Guodong Peng the Research Institute of Information Technology Tsinghua University Tsinghua National Laboratory for Information Science and Technology (TNList) Tsinghua University department of Electronic engineering Tsinghua University department of physics Tsinghua University department of Aerospace engineering Tsinghua University department of Automation Tsinghua University department of Computer Science and Technology Tsinghua University department of Mechanical engineering Tsinghua University

With the growing popularity of Internet applications and the widespread use of mobile Internet, Internet traffic has maintained rapid growth over the past two decades. Internet Traffic Archival Systems（ITAS） for packets or flow records have become more and more widely used in network monitoring, network troubleshooting, and user behavior and experience analysis. Among the three key technologies in ITAS, we focus on bitmap index compression algorithm and give a detailed survey in this paper. The current state-of-the-art bitmap index encoding schemes include： BBC, WAH, PLWAH, EWAH, PWAH, CONCISE, COMPAX, VLC, DF-WAH, and VAL-WAH. Based on differences in segmentation, chunking, merge compress, and Near Identical（NI） features, we provide a thorough categorization of the state-of-the-art bitmap index compression algorithms. We also propose some new bitmap index encoding algorithms, such as SECOMPAX, ICX, MASC, and PLWAH＋, and present the state diagrams for their encoding algorithms. We then evaluate their CPU and GPU implementations with a real Internet trace from CAIDA. Finally, we summarize and discuss the future direction of bitmap index compression algorithms. Beyond the application in network security and network forensic, bitmap index compression with faster bitwise-logical operations and reduced search space is widely used in analysis in genome data, geographical information system, graph databases, image retrieval, Internet of things, etc. It is expected that bitmap index compression will thrive and be prosperous again in Big Data era since 1980s.

关键词： Internet traffic big data traffic archival network security bitmap index bitmap compression algorithm

Photonic phase transition in circuit quantum electrodynamics lattices coupled to superconducting phase qubits

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Science China(physics,Mechanics & Astronomy) 2014年第11期57卷 2092-2097页

作者： LIU YiMin JIN WuYin YOU JiaBin department of physics Shaoguan University School of Mechanical & Electronical engineering Lanzhou University of Technology Center for Quantum Technologies and physics department National University of Singapore3 Science Drive 2117543Singapore

A hybrid quantum architecture was proposed to engineer a localization-delocalization phase transition of light in a two-dimension square lattices of superconducting coplanar waveguide resonators,which are interconnected by current-biased Josephson junction phase *** find that the competition between the on-site repulsion and the nonlocal photonic hopping leads to the Mott insulator-superfluid *** using the mean-field approach and the quantum master equation,the phase boundary between these two different phases could be obtained when the dissipative effects of superconducting resonators and phase qubit are *** good tunability of the effective on-site repulsion and photon-hopping strengths enable quantum simulation on condensed matter physics and many-body models using such a superconducting resonator lattice *** experimental feasibility is discussed using the currently available technology in the circuit QED.

关键词： hopping resonator waveguide junction engineer currently insulator enable photonic condensed

Modeling development on the meso-scale reacting transport phenomena in proton exchange membrane fuel cells

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Acta Mechanica Sinica 2013年第3期29卷 370-378页

作者： Jianliang Yuan Yu Xiao department of Energy Sciences Lund University Fuel Cell System and engineering Laboratory Dalian Institute of Chemical Physics Chinese Academy of Science

The catalyst layer （CL） of proton exchange mem-brane fuel cell （PEMFC） involves various particles and pores in meso-scale, which has an important effect on the mass, charge （proton and electron） and heat transport coupled with the electrochemical reactions. The coarse-grained molecular dynamics （CG-MD） method is employed as a meso-scale structure reconstruction technique to mimic the self-organization phenomena in the fabrication steps of a CL. The meso-scale structure obtained at the equilibrium state is further analyzed by molecular dynamic （MD） software to provide the necessary microscopic parameters for understanding of multi-scale and-physics processes in CLs. The primary pore size distribution （PSD） and active platinum （Pt） surface areas are also calculated and then compared with the experiments. In addition, we also highlight the implementation method to combine microscopic elementary kinetic reaction schemes with the CG-MD approaches to provide insight into the reactions in CLs. The concepts from CG modeling with particle hydrodynamics （SPH） and the problems on coupling of SPH with finite element modeling （FEM） methods are further outlined and discussed to understand the effects of the meso-scale transport phenomena in fuel cells.

关键词： CG-MD · Meso-scale · Reaction · Catalyst layer · Fuel cell

Effect of single dead end entry inclination on DPM plume dispersion

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International Journal of Mining Science and Technology 2017年第3期27卷 401-406页

作者： Zheng Yi Lan Hai Thiruvengadam Magesh Tien Jerry C. Li Ying department of Mining & nuclear engineering Missouri University of Science and Technology (MST) Rolla MO 65401 USA Clean Air Power Inc. Poway CA 92064 USA Division of Mining and Resources engineering Department of Civil Engineering Monash University Clayton Campus Wellington Road Clayton VIC 3800 Australia

Diesel particulate matter(DPM) is a by-product from operating diesel engines. Since diesel powers are one of the major sources of energy for mobile underground mining equipment, the adverse health effects of DPM are of a great concern. This paper used computational fluid dynamics(CFD) method to study the effect of entry inclination on DPM plume distribution in a dead end entry. An upward mining face and a downward mining face were built with a truck and a loader in loading operation close to the face area. A species transport model with incorporated buoyancy effect was used to examine the DPM dispersion pattern for the above steady-state scenarios. High DPM and temperature regions were identified for the two different faces. The model was used to assess the role of auxiliary ventilation in reducing DPM exposures of underground miners working in those entries. In this study, it is suggested to provide local ventilation at least three times of the diesel exhaust rate to be able to lower the average DPM level for the mining upward face. The requirement for local ventilation is much less for the mining downward face. This can provide guidelines for good working practices and selection of diesel emission reduction technologies underground.

关键词： Entry inclination Diesel particulate matter Computational fluid dynamics Ventilation

Color-selective three-dimensional polarization structures

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Light(Science & Applications) 2022年第11期11卷 2706-2715页

作者： Yuttana Intaravanne Ruoxing Wang Hammad Ahmed Yang Ming Yaqin Zheng Zhang-Kai Zhou Zhancheng Li Shuqi Chen Shuang Zhang Xianzhong Chen Institute of Photonics and Quantum Sciences School of Engineering and Physical SciencesHeriot-Watt UniversityEdinburgh EH144ASUK department of Mathematics and physics North China Electric Power UniversityBaoding 071003China School of physics and Electronic engineering Changshu Institute of TechnologySuzhou 215000China State Key Laboratory of Optoelectronic Materials and Technologies School of PhysicsSun Yat-sen UniversityGuangzhou 510275China School of physics and TEDA Applied physics Institute Nankai University94 Weijin RoadTianjin 300071China department of physics University of Hong KongHong KongChina department of Electronic&Electrical engineering University of Hong KongHong KongChina

Polarization as an important degree of freedom for light plays a key role in *** beams with controlled polarization profles have diverse applications,such as information encoding,display,medical and biological imaging,and manipulation of ***,conventional polarization optics can only realize two-dimensional polarization structures in a transverse *** emergent ultrathin optical devices consisting of planar nanostructures,so-called metasurfaces,have shown much promise for polarization *** we propose and experimentally demonstrate color-selective three-dimensional(3D)polarization structures with a single *** geometric metasurfaces are designed based on color and phase multiplexing and polarization rotation,creating various 3D polarization ***,different 3D polarization knots in the same observation region can be achieved by controlling the incident wavelengths,providing unprecedented polarization control with color information in 3D *** research findings may be of interest to many practical applications such as vector beam generation,virtual reality,volumetric displays,security,and anti-counterfeiting.

关键词： polarization optics dimensional

Investigation of the fast magnetosonic wave excited by the Alfvén wave phase mixing by using the Hall–MHD model in inhomogeneous plasma

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Plasma Science and Technology 2021年第3期23卷 22-29页

作者： Zhongzheng LI Juanfang HAN Fangping WANG Zhengwu CHEN Wenshan DUAN College of physics and Electronic engineering Northwest Normal UniversityLanzhou 730070People's Republic of China department of physics Gansu Normal College For NationalitiesHezuo 747000People's Republic of China

The inhomogeneity is introduced by a nonzero density gradient which separates the plasma into two different regions where plasma density are *** Alfvén waves,the phase mixing and the fast magnetosonic wave are excited by the boundary condition in inhomogeneous magnetized *** using the Hall–magnetohydrodynamics(MHD)model,it is found that there are Alfvén waves in the homogeneous regions,while the phase mixing appears in the inhomogeneous *** interesting result is that a fast magnetosonic wave is excited in a different direction which has a nonzero angle between the wave propagation direction and the direction of the background magnetic *** dependence of the propagation direction of the excited fast magnetosonic wave and its strength of the magnetic field on the plasma parameters are given *** results show that increasing both the driving frequency and the ratio of magnetic pressure to thermal pressure will increase the acceleration of the *** electron acceleration also depends on the inhomogeneity parameters.

关键词： Hall–MHD Alfvén wave phase mixing numerical simulations fast magnetosonic wave

Giant magneto field effect in up-conversion amplified spontaneous emission via spatially extended states in organic-inorganic hybrid perovskites

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Opto-Electronic Advances 2022年第2期5卷 33-41页

作者： Tangyao Shen Jiajun Qin Yujie Bai Jia Zhang Lei Shi Xiaoyuan Hou Jian Zi Bin Hu department of physics Fudan UniversityShanghai 200433China department of physics Chemistry and Biology(IFM)Linköping UniversityLinköping 58183Sweden department of Materials Science and engineering University of TennesseeKnoxvilleTennessee 37996USA

Up-conversion lasing actions are normally difficult to realize in light-emitting materials due to small multi-photon absorp-tion cross section and fast dephasing of excited states during multi-photon *** paper reports an easily ac-cessible up-conversion amplified spontaneous emission(ASE)in organic-inorganic hybrid perovskites(MAPbBr3)films by optically exciting broad gap states with sub-bandgap laser *** broad absorption was optimized by adjust-ing the grain sizes in the MAPbBr3 *** low sub-bandgap pumping intensities,directly exciting the gap states leads to 2-photon,3-photon,and 4-photon up-conversion spontaneous emission,revealing a large optical cross section of multi-photon excitation occurring in such hybrid perovskite *** moderate pumping intensity(1.19 mJ/cm2)of 700 nm laser excitation,a significant spectral narrowing phenomenon was observed with the full width at half maximum(FWHM)de-creasing from 18 nm to 4 nm at the peak wavelength of 550 nm,simultaneously with a nonlinear increase on spectral peak intensity,showing an up-conversion ASE realized at low threshold pumping *** interestingly,the up-con-version ASE demonstrated a giant magnetic field effect,leading to a magneto-ASE reaching 120%.In contrast,the up-conversion photoluminescence(PL)showed a negligible magnetic field effect(<1%).This observation provides an evid-ence to indicate that the light-emitting states responsible for up-conversion ASE are essentially formed as spatially exten-ded *** angular dependent spectrum results further verify the existence of spatially extended states which are polarized to develop coherent in-phase ***,using broad gap states with spatially extended light-emitting states presents a new approach to develop up-conversion ASE in organic-inorganic hybrid perovskites.

关键词： organic-inorganic hybrid perovskite orbital order magneto-ASE spatially extended states

OBSERVATIONS OF PERCOLATION STRUCTURES INDUCED IN THIN SOLID FILMS BY ION IRRADIATION

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Chinese physics Letters 1988年第7期5卷 321-324页

作者： DING Juren HUANG Liji LIU Baixin department of engineering physics Tsinghua UniversityBeijing Center of Theoretical physics CCAST(Wor1d Lab)Beijing and Department of Engineering PhysicsTsinghua UniversityBeijing

Percolation structures of precipitated new phases were observed in Au-Ti and Ni-A1 amorphous films upon ion *** experimental evidences showed that the observed structures were formed in the surface layer,ca 20nm *** was revealed that the formation of percolation clusters was sensitive to alloy composition as well as irradiation dose.

关键词： alloy formed amorphous

Linear optimal control of transient growth in turbulent channel flows

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Acta Mechanica Sinica 2019年第4期35卷 729-739页

作者： Yang Song Chunxiao Xu Weixi Huang Institute of Applied physics and Computational Mathematics Beijing 100094 China AML Department of Engineering MechanicsTsinghua University Beijing 100084 China

The suppression of linear transient growth in turbulent channel flows via linear optimal controls is investigated. The control algorithms are the LQR control based on full information of flow fields and the LQG control based on the information measured at walls. The influence of these controls on the development of small-scale and large-scale perturbations are considered respectively. It is found that the energy amplification of large-scale perturbations is suppressed significantly by both LQR and LQG control, while small-scale perturbations can be only affect by LQR control. Effects of the weighting parameters and control price on the control performance of both controls are analysed. It turns out that the different weighting parameters in cost function do not qualitatively change the evalution of control performance. As control price raises, the effectiveness of both controls decreases distinctly. For small-scale perturbations, the upper limit of the effective range of control price is lower than that for large-scale perturbations. As Reynolds number increases, it indicates that both LQR and LQG control get more effective on suppressing the energy amplification of large-scale perturbations.

关键词： Linear optimal control Turbulent channel flow Optimal transient growth