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Redesign of the gStore system

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Frontiers of Computer Science 2018年第4期12卷 623-641页

作者： li zeng Lei ZOU School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Beijing Institute of Big Data Research Beijing 100871 China

gStore is an open-source native Resource Description Framework （RDF） triple store that answers SPARQL queries by subgraph matching over RDF graphs. However, there are some deficiencies in the original system design, such as answering simple queries （including one-triple pattern queries）. To improve the efficiency of the system, we reconsider the system design in this paper. Specifically, we propose a new query plan generation module that generates different query plans according to the structures of query graphs. Furthermore, we re-design our vertex encoding strategy to achieve more pruning power and a new multi-join algorithm to speed up the subgraph matching process. Extensive experiments on synthetic and real RDF datasets show that our method outperforms the state-of-the-art algorithms significantly.

关键词： graph database subgraph matching RDF management SPARQL query

Kinematics of the high-excitation HH 890 jet in the Rosette Nebula

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Chinese Journal of Astronomy and Astrophysics 2009年第5期9卷 577-584页

作者： Jin-zeng li National Astronomical Observatory Chinese Academy of Sciences Beijing 100012 China

Photoionized jets immersed in HII regions display special properties, which made them a distinctive category of Herbig-Haro （HH） flows. Detailed studies of such jet systems became one of the key issues in our understanding of jet production and evolution. HH 890, initially called the Rosette HH2 jet, is the second photoionized jet discovered in the spectacular HII region of the Rosette Nebula. Contrary to conventional impressions of a jet, its discrete components are found to be unexpectedly broad and spatially detached from the proposed energy source. The jet displays additional unusual features which point to the disputable nature of the system. Here, we investigate the kinematics of the jet through high-quality echelle spectrograms. It is distinctively resolved into a fast component with a mean approaching velocity of-39 km s^-1 with respect to the systemic rest frame and a slow component with radial velocity centered at -9 km s^-1. The slow component indicates an apparently larger dispersion in radial velocity in various emission lines and is likely dissolving at roughly the speed of sound, which favors a photoevaporated origin. The [SII] doublet ratios indicate an electron density of -1.1×10^3 cm^-3 in the collimated jet and ,-9×10^2 cm^-3 in the HII region. This, along with the diffuse appearance of the extensive part of the jet, leads to a dissipation of the jet in the fully ionized medium of Rosette. In addition, time series of photometric observations provide evidence for remarkable light variations of the energy source. Its amplitudes of variation amount to 〉 1 mag in both R and I, which is commensurate with the young evolutionary status of the source as indicated by a red, late type optical spectrum.

关键词： accretion disks -- ISM jets and outflows -- stars formation -- stars premain-sequence

Tcn and Tcn@C70 Endohedral Metalofullerenes: ab initio Spin-density-functional Calculations

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Chinese Journal of Chemical Physics 2015年第4期28卷 -页

作者： li-jing zeng Ke Deng CAS Key Laboratory of Standardization and Measurement for Nanotechnology National Center for Nanoscience and Technology (NCNST) Beijing 100190 China

Ab initio spin-density-functional calculations have been performed to study the equilibrium structural, electronic, and magnetic properties of Tcn and Tcn@C70 endohedral metalofullerenes. Our results indicate that C70 can encapsulate Tcn clusters with up to n=9 atoms. Except n=2, the formation of Tcn@C70 endohedral metalofullerenes is predicted to be exothermic when n≤5, while the encapsulation process becomes increasingly endothermic beyond n=5. When encapsulating into the C70 cage, the geometries as well as electronic structures of the Tc cluster undergo comparative changes. Especially, compared to the isolated Tcn clusters, the total magnetic moments of Tcn@C70 reduce significantly. The analyses of the orbital population, Hirshfeld population and density of states show that electrons transfer from the Tc cluster to the carbon cage through the Tc–C efficient hybridization, which is responsible for such reduction of the whole magnetism.

关键词： Density functional theory Endohedral metalofullerenes Tcn@C70 Vienna ab initio simulation package

Vibration Analysis of a Drillstring in Horizontal Well

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Computer Modeling in Engineering & Sciences 2019年第11期121卷 631-660页

作者： Xiaohua Zhu li zeng Bo li School of Mechanical Engineering Southwest Petroleum University ChengduChengdu610500China

The complicated geological conditions will bring great challenges to the drillstring of horizontal wells for the reason that the increase of the well depth in Sichuan-Chongqing *** drillstring failure and friction during drilling are generally caused by drillstring vibration,great importance must be attached to computer simulation methods for the prediction of drillstring vibration.A finite element model considering axial,lateral and torsional vibration is *** order to verify the established numerical model,an indoor experimental device based on the similarity principle was *** vibration characteristics of three shale gas horizontal wells drillstrings are *** reasons for the large difference in vibration characteristics between the three wells were discussed by changing the well structure,BHA(bottom hole assembly)and drilling *** simulation results show that the depth of ultra-deep well 3 is only 1.27 times of that of medium-deep well 2,but the fluctuation of WOB(weight on bit)is 2.8 *** primary factor for the great difference of WOB fluctuation is the change of vertical section depth,the secondary factor is the change of the horizontal section ***,the reasonable range of speeds has been proposed and applied in the *** advantage of this numerical analysis method is that it can judge the vibration and friction torque of drillstring in horizontal wells with arbitrary structure,drilling parameters and *** method has certain guiding significance to the field practice.

关键词： Horizontal well drillstring vibration friction torque fatigue life

New chaos-based encryption scheme for digital sequence

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Journal of Systems Engineering and Electronics 2007年第4期18卷 698-703,709页

作者： Zhang Zhengwei Fan Yangyu zeng li School of Electronics and Information Northwestern Polytechnical Univ. Xi'an 710072 P. R. China

To enhance the anti-breaking performance of privacy information, this article proposes a new encryption method utilizing the leaping peculiarity of the periodic orbits of chaos systems. This method maps the secret sequence to several chaos periodic orbits, and a short sequence obtained by evolving the system parameters of the periodic orbits in another nonlinear system will be the key to reconstruct these periodic orbits. In the decryption end, the shadowing method of chaos trajectory based on the modified Newton-Raphson algorithm is adopted to restore these system parameters. Through deciding which orbit each pair coordinate falls on, the original digital sequence can be decrypted.

关键词： encryption scheme LPO (leaping periodic orbits) chaos initial conditions parameter estimation nonlinear system

Research of Mechanism of Inductive Maglev Spherical Driving Joint

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Chinese Journal of Electronics 2016年第1期25卷 26-32页

作者： zeng li CHEN Qiuyue ZHANG Xiaohong College of Mechanical Engineering Yangzhou University

The multi-degree-of-freedom inductive spherical driving joint owns high mechanical integrity and has advantages such as control and trajectory *** of its limit of rotor pose, instant stepping angle and inability to spin around any axis through center of sphere, the suspension and rotation precision of spherical reluctance driving joint isn't high and the response speed can't reach the best. Based on mechanism of rotation and suspension, due to distribution of air gap magnetic induction intensity, a novel inductive maglev spherical driving joint was presented, and electromagnetic suspending force and electromagnetic torque were established. Analyze the magnetic induction intensity, electromagnetic suspending force and electromagnetic torque through finite element simulation, build a bench test of maglev spherical driving joint, and do testing research on displacement characters and suspension and rotation characters of joint rotor.

关键词： Magnetic levitation spherical reluctance driving joint Displacement character Suspending force character Electromagnetic torque character

Breast cancer animal models and applications

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Zoological Research 2020年第5期41卷 477-494页

作者： li zeng Wei li Ce-Shi Chen Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province Kunming Institute of ZoologyChinese Academy of SciencesKunmingYunnan 650223China Kunming College of life Science University of the Chinese Academy of SciencesKunmingYunnan 650204China KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases Kunming Institute of ZoologyChinese Academy of SciencesKunmingYunnan 650223China

Breast cancer is the most common malignancy in women. Basic and translational breast cancer research relies heavily on experimental animal models. Ideally, such models for breast cancer should have commonality with human breast cancer in terms of tumor etiology, biological behavior,pathology, and response to therapeutics. This review introduces current progress in different breast cancer experimental animal models and analyzes their characteristics, advantages, disadvantages, and potential applications. Finally, we propose future research directions for breast cancer animal models.

关键词： Breast cancer Animal models Metastasis Drug development

Multiwavelength Doppler factors for Fermi-detected gamma-ray loud blazars

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Research in Astronomy and Astrophysics 2011年第4期11卷 391-400页

作者： Hou-Dun zeng li Zhang Department of Physics Yunnan University Kunming 650091 China

We collect a sample of 51 Fermi-detected gamma-ray loud blazars with known radio Doppler factors and study properties of the Doppler factors of blazars at optical, X-ray and gamma-ray bands. A basic assumption is that the emission from the radio to gamma-ray bands of the blazars are produced by the nonthermal radiation of accelerated particles in a jet. Our results show that （1） the Doppler factors of blazars are a function of frequency, with the Doppler factor decreasing with frequency from the radio to X-ray regions, and then increasing from the X-ray to ,y-ray regions which are similar to results given by Zhang et al., and （2） there are marginal correlations between the Doppler factors at radio and X-ray bands and the synchrotron peak fre- quency, and a strong correlation between the Doppler factor in the gamma-ray band and the synchrotron peak frequency, but no correlation in the optical band.

关键词： galaxies active -- galaxies nuclei - galaxies jets -- radiation mecha-nisms non-thermal

Modified precoding strategy over MIMO double-correlated channels

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The Journal of China Universities of Posts and Telecommunications 2009年第2期16卷 35-38页

作者： JIN li-biao li Jian-zeng School of Information Engineering Communication University of China Beijing 100024 China

Double-correlated channels commonly occur due to insufficient scattering around both the transmitting and receiving antennas. In this article, the authors propose a linear precoding strategy with a modified system model over double-correlated channels. In this system model, an inner decorrelation strategy is added combined with precoding. First, a linear precoder that achieves minimum bit error rate （MBER） is proposed and analyzed based on the modified system model. The simulation results show that the bit error rate （BER） performance can be improved by decorrelation. Second, the influence of double correlation on multiple input and multiple output （MIMO） capacity is analyzed and simulated.

关键词： MIMO precoding decorrelation capacity