Beijing, China

Beijing University of Technology , also called Beijing Polytechnic University or Bei Gong Da , is recognized as one of the Project 211 universities. The University has established a multidisplinary academic structure, offering a variety of programs and is involved in diversified research in the fields of Science, Engineering, Economics, Management, Liberal Arts, and Law. Wikipedia.


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A method for improving resistance of a fusion reactor inner wall to plasma irradiation by using lamination structure comprises: making a material for facing plasma into multiple metal sheets, laminating the multiple metal sheets together according to a direction perpendicular to a wall surface, and combining the laminated multiple metal sheets with a copper substrate. The method relates to the field of nuclear applications, and is applicable to a plasma-facing surface on an inner wall of an apparatus for conducting a fusion reaction by using hydrogen isotopes. Not only does the method reduce aggregation of hydrogen, helium, and isotopes thereof, and the like, under a surface layer of a tungsten-based material, greatly reducing a blistering phenomenon on a surface thereof, but also reduces thermal fatigue cracking damages.


The present disclosure provides a full-duplex wireless communication method, an antenna device and a full-duplex wireless communication system. The method includes steps of: within a training period, acquiring a relevant parameter for cancelling a self-interference signal from an antenna itself as a first estimated value, and a relevant parameter for cancelling a cross-interference signal between the antenna and the other antenna as a second estimated value; and within a data transmission period, receiving and transmitting signals simultaneously by the antenna using an identical frequency, cancelling the self-interference signal from the antenna itself in accordance with the first estimated value, and cancelling the cross-interference signal between the antenna and the other antenna in accordance with the second estimated value.


Patent
Beijing University of Technology | Date: 2015-12-31

This invention disclosed a visual perception characteristics-combining hierarchical video coding method, comprising: setting priority of visual interest area and setting allocation scheme of video coding resource. The former one is about: due to the richness of video image and selective perception of human visual, visual characteristics saliency of video content has been analyzed from time and space, priority of visual interest area can be labeled. The later one is about improving real-time performance of video coding, while at the same time, quality of video coding and compression efficiency is guaranteed. According to the priority of visual interest area, macroblock coding resource of interest area should be satisfied firstly, to realize hierarchical coding. The video coding scheme of this paper can remit conflict between coding complexity and coding efficiency validly. Compare with H.264/AVC international video coding standard, it can improve 80% of average coding speed, and at the same time it can maintain better quality of video image and lower compression bit-Rate. The video coding performance can be improved dramatically.


Patent
Beijing University of Technology | Date: 2015-04-30

The present disclosure relates to a method of acquiring neighboring disparity vectors for multi-texture and multi-depth video (e.g., 3D-HEVC video). The method belongs to the area of 3D-HEVC video coding technology. The method includes changing the standard associated with a disparity vector that is first searched as a final disparity vector. By deleting location which is minimum searched in candidate space and time location of the coding unit next to current coding unit to divide candidate space and time location of the coding unit into groups, the method takes searched disparity vector that is combined based on the proportion of adoption rate as final disparity vector. The method improves coding quality and at the same time maintaining origin fast algorithm efficiency. The embodiments of the present disclosure improve coding quality at least 0.05% and at the same time maintain origin fast algorithm efficiency while the decoding time is decreased to 97.1%.


Zhang C.,Peking University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology
Journal of Physical Chemistry Letters | Year: 2016

Using global particle-swarm optimization method, we report, for the first time, a BeN2 sheet (h-BeN2) with a graphene-like honeycomb lattice but displaying a direct band gap. Symmetry group analysis indicates that the dipole transition is allowed between the conduction band minimum and the valence band maximum. Although the direct band gap of 2.23 eV is close to that (2.14 eV) of MoS2 sheet, the h-BeN2 sheet has additional advantages: the direct band gap feature of the h-BeN2 sheet is quite insensitive to the layer stacking pattern and layer number, in contrast to the well-known direct-to-indirect band gap transition observed in TMDs and h-BN sheets. When rolled up, all the resulting h-BeN2 nanotubes have direct band gaps independent of chirality and diameter. Furthermore, the intrinsic acoustic-phonon-limited carrier mobility of the h-BeN2 sheet can reach ∼105 cm2 V-1 s-1 for electron and ∼104 cm2 V-1 s-1 for hole, which are higher than that of MoS2 and black phosphorus. © 2016 American Chemical Society.


An L.,Peking University | Huang W.,Anhui University of Science and Technology | Zhang N.,Peking University | Chen X.,Beijing University of Technology | Xia D.,Peking University
Journal of Materials Chemistry A | Year: 2014

Carbon-supported CoN (CoN/C) nanoparticles have been synthesized by heating at reflux in the solution of o-xylene and subsequent thermal annealing under a NH3 reducing atmosphere. The as-prepared CoN/C composite exhibited high oxygen reduction reaction (ORR) activity and excellent stability as a new efficient non-precious metal electrocatalyst. © The Royal Society of Chemistry.


Chen H.-X.,Beijing University of Technology | Chen H.-X.,Beihang University | Chen W.,University of Saskatchewan | Liu X.,Lanzhou University | And 2 more authors.
Physics Reports | Year: 2016

In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like Zc states and bottomonium-like Zb states cannot be accommodated within the naive quark model. These charged Zc states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states. © 2016 Elsevier B.V..


Zhu H.X.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Li H.T.,Beijing University of Technology | And 3 more authors.
Physical Review Letters | Year: 2013

We develop a framework for a systematic resummation of the transverse momentum distribution of top-quark pairs produced at hadron colliders based on effective field theory. Compared to Drell-Yan and Higgs production, a novel soft function matrix is required to account for the soft gluon emissions from the final states. We calculate this soft function at the next-to-leading order, and perform the resummation at the next-to-next-to-leading logarithmic accuracy. We compare our results with parton shower programs and with the experimental data at the Tevatron and the LHC. We also discuss the implications for the top quark charge asymmetry. © 2013 American Physical Society.


Liang H.,Beijing University of Technology | Shen S.,Beijing University of Technology | Zhao P.,Beijing University of Technology | Meng J.,Beijing University of Technology | And 2 more authors.
Physical Review C - Nuclear Physics | Year: 2013

The origin of pseudospin symmetry (PSS) and its breaking mechanism are explored by combining supersymmetry (SUSY) quantum mechanics, perturbation theory, and the similarity renormalization group (SRG) method. The Schrödinger equation is taken as an example, corresponding to the lowest-order approximation in transforming a Dirac equation into a diagonal form by using the SRG. It is shown that while the spin-symmetry-conserving term appears in the single-particle Hamiltonian H, the PSS-conserving term appears naturally in its SUSY partner Hamiltonian H̃. The eigenstates of Hamiltonians H and H̃ are exactly one-to-one identical except for the so-called intruder states. In such a way, the origin of PSS deeply hidden in H can be traced in its SUSY partner Hamiltonian H̃. The perturbative nature of PSS in the present potential without a spin-orbit term is demonstrated by the perturbation calculations, and the PSS-breaking term can be regarded as a very small perturbation on the exact PSS limits. A general tendency that the pseudospin-orbit splittings become smaller with increasing single-particle energies can also be interpreted in an explicit way. © 2013 American Physical Society.


Gao J.,Southern Methodist University | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Zhu H.X.,SLAC
Physical Review Letters | Year: 2013

We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark mass and W boson width effects. In particular, we also show the first results of the fully differential decay rates for the top-quark semileptonic decay t→W+(l+ν)b at next-to-next-to-leading order in QCD. Our method is based on the understanding of the invariant mass distribution of the final-state jet in the singular limit from effective field theory. Our result can be used to study arbitrary infrared-safe observables of top-quark decay with the highest perturbative accuracy. © 2013 American Physical Society.


Zhao S.,Beijing University of Technology | Zhao S.,Peking University | Kang W.,Beijing University of Technology | Kang W.,Peking University | Xue J.,Beijing University of Technology
Journal of Materials Chemistry A | Year: 2014

The capacity and stability of the constituent electrodes critically determine the performance of Li-ion batteries (LIBs). In this study, density functional theory is employed to explore the potential application of the recently synthesized two dimensional phosphorene as an electrode material in LIBs. Our results show that Li atoms can bind strongly with the phosphorene monolayer and double layer with significant electron transfer. Besides, the structure of phosphorene is not influenced much by lithiation and the volume change is only 0.2%. After lithiation, a semiconductor-to-conductor transition is observed. The diffusion barrier values of Li are calculated to be 0.76 and 0.72 eV on monolayer and double layer phosphorene, respectively. We further demonstrate that the theoretical specific capacity of the phosphorene monolayer is 432.79 mA h g-1, which is larger than those of other commercial anode materials. The influence of Si and S implantation is also examined and our results indicate that Si-doped phosphorene greatly improves the binding of Li atoms, while the diffusion barrier is not affected. Our findings show that the high capacity, low open circuit voltage, small volume change and electrical conductivity of lithiated phosphorene make it a good candidate for application as an electrode material in batteries. © 2014 the Partner Organisations.


Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We propose simple forms of the neutrino mixing matrix in analogy with the Wolfenstein parametrization of the quark mixing matrix by adopting the smallest mixing angle θ13 as a measure of expansion parameters with the tribimaximal pattern as the base matrix. The triminimal parametrization technique is utilized to expand the mixing matrix under two schemes, i.e., the standard Chau-Keung scheme and the original Kobayashi-Maskawa scheme. The new parametrizations have their corresponding Wolfenstein-like parametrizations of the quark mixing matrix, and therefore they share the same intriguing features of the Wolfenstein parametrization. The newly introduced expansion parameters for neutrinos are connected to the Wolfenstein parameters for quarks via the quark-lepton complementarity. © 2013 American Physical Society.


Du M.-L.,Beijing University of Technology | Chen W.,Beijing University of Technology | Chen X.-L.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

After constructing the possible JP=0-, 0+, 1 -, and 1+ QQq̄q̄ tetraquark interpolating currents in a systematic way, we investigate the two-point correlation functions and extract the corresponding masses with the QCD sum rule approach. We study the QQq̄q̄, QQq̄s̄, and QQs̄s̄ systems with various isospins I=0, 1/2, 1. Our numerical analysis indicates that the masses of doubly bottomed tetraquark states are below the threshold of the two-bottom mesons, two-bottom baryons, and one doubly bottomed baryon plus one antinucleon. Very probably these doubly bottomed tetraquark states are stable. © 2013 American Physical Society.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Zhang J.-J.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The area law of Bekenstein-Hawking entropy of the black hole suggests that the black hole should have a lower-dimensional holographic description. It has been found recently that such holographic pictures could be set up from the study of the thermodynamics of both outer and inner horizons for a large class of rotating and charged black holes. For a four-dimensional dyonic Reissner-Nordström black hole, its thermodynamics indicates that it has multiple holographic pictures - not only the electric and magnetic ones corresponding to the conserved electric and magnetic charges carried by the black hole, but also the more generic ones generated by the SL(2,Z) transformations. We show that this SL(2,Z) group originates from the underlying electromagnetic duality symmetry in the Einstein-Maxwell theory. It turns out that the thermodynamics of the black hole not only encodes the information of holographic pictures; moreover, it could reflect the symmetries of the underlying theory. © 2013 American Physical Society.


Wang J.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Zhu H.X.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study the factorization and resummation of t-channel top quark transverse momentum distribution at large pT in the standard model at both the Tevatron and the LHC with soft-collinear effective theory. The cross section in the threshold region can be factorized into a convolution of hard, jet and soft functions. In particular, we first calculate the next-to-leading order soft functions for this process, and give a renormalization group improved cross section by evolving the different functions to a common scale. Our results show that the resummation effects increase the next-to-leading order results by about 9%∼13% and 4%∼9% when the top quark pT is larger than 50 and 70 GeV at the Tevatron and the 8 TeV LHC, respectively. Also, we discuss the scale independence of the cross section analytically, and show how to choose the proper scales at which the perturbative expansion can converge fast. © 2013 American Physical Society.


Lu Z.,Nanjing Southeast University | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The transverse momentum dependent helicity distributions of valence quarks are calculated in the light-cone diquark model by adopting two different approaches. We use the model results to analyze the P h⊥-dependent double spin asymmetries for π+, π-, and π0 productions in semi-inclusive deep inelastic scattering, and find that the asymmetries agree with the CLAS data in one of the approaches. By taking the Fourier transform of the transverse momentum dependent helicity distributions, we obtain the helicity distributions of valence quarks in the transverse coordinate space, and then apply them further to predict the Bessel-weighted double spin asymmetries of π+, π-, and π0 productions in semi-inclusive deep inelastic scattering at CLAS, COMPASS, and HERMES for the first time. The shape of the Bessel-weighted double spin asymmetry thereby provides a direct probe on the transverse structure of longitudinally polarized quarks. © 2013 American Physical Society.


Duan L.,Beijing University of Technology | Wu C.,Beijing University of Technology | Miao J.,CAS Institute of Computing Technology | Qing L.,University of Chinese Academy of Sciences | Fu Y.,University of Surrey
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2011

In this paper, a new visual saliency detection method is proposed based on the spatially weighted dissimilarity. We measured the saliency by integrating three elements as follows: the dissimilarities between image patches, which were evaluated in the reduced dimensional space, the spatial distance between image patches and the central bias. The dissimilarities were inversely weighted based on the corresponding spatial distance. A weighting mechanism, indicating a bias for human fixations to the center of the image, was employed. The principal component analysis (PCA) was the dimension reducing method used in our system. We extracted the principal components (PCs) by sampling the patches from the current image. Our method was compared with four saliency detection approaches using three image datasets. Experimental results show that our method outperforms current state-of-the-art methods on predicting human fixations. © 2011 IEEE.


Sun S.,Beijing University of Technology | Sun S.,Peking University | Jiang N.,Beijing University of Technology | Jiang N.,Peking University | And 2 more authors.
Journal of Physical Chemistry C | Year: 2011

In this paper, density functional theory is applied to study the electrochemical reduction of oxygen on iron phthalocyanine (FePc), iron porphyrin (FeP), cobalt phthalocyanine (CoPc), and cobalt porphyrin (CoP). According to the calculation results, for the four metal-macrocyclic complexes, O2 will not directly be cleaved without the cooperation of hydrogen. In the reduction process, on FePc or FeP, H2O2 does not form as an intermediate, and O2 is reduced to H2O, while on CoPc or CoP, O2 is just reduced to H2O2. The reason why the oxygen reduction ability of FePc or FeP is higher than that of CoPc or CoP, respectively, is that the energy level of the highest-occupied 3d orbital of the former is higher than that of the later. The high energy level of the metal 3d orbital leads to the strong ability of oxygen reduction. © 2011 American Chemical Society.


Huang F.P.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Wang J.,Beijing University of Technology | Shao D.Y.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study the signal of dark matter and photon associated production induced by the vector and axial-vector operators at the LHC, including the QCD next-to-leading order (NLO) effects. We find that the QCD NLO corrections reduce the dependence of the total cross sections on the factorization and renormalization scales, and the K factors increase with the increasing of the dark matter mass, which can be as large as about 1.3 for both the vector and axial-vector operators. Using our QCD NLO results, we improve the constraints on the new physics scale from the results of the recent CMS experiment. Moreover, we show the Monte Carlo simulation results for detecting the γ+EÌ̧T signal at the QCD NLO level, and present the integrated luminosity needed for a 5σ discovery at the 14 TeV LHC. If the signal is not observed, the lower limit on the new physics scale can be set. © 2013 American Physical Society.


Meng C.,Beijing University of Technology | Gao Y.-J.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

B→χc1(1P,2P)K decays are studied in QCD factorization by treating charmonia as nonrelativistic bound states. No infrared divergences exist in the vertex corrections, while the logarithmic end-point singularities in the hard spectator corrections can be regularized by a momentum cutoff. Within certain uncertainties, we find that the B→χc1(2P)K decay rate can be comparable to B→χc1(1P)K and get Br(B0→χc1′K0)=Br(B+→χc1′K +)≈(2-4)×10-4. This might imply a possible interpretation for the newly discovered X(3872): that this state has a dominant JPC=1++(2P) cc̄ component, but it is mixed with a substantial D0D̄*0+D*0D̄0 component. © 2013 American Physical Society.


Dou Z.,Beijing University of Technology | Song Y.,Beijing University of Technology | Tian J.,Beijing University of Technology | Liu J.,Beijing University of Technology | And 2 more authors.
Optics Express | Year: 2014

We demonstrated an all-normal-dispersion Yb-doped modelocked fiber laser based on Bi2Se3topological insulator (TI). Different from previous TI-mode-locked fiber lasers in which TIs were mixed with filmforming agent, we used a special way to paste a well-proportioned pure TI on a fiber end-facet. In this way, the effect of the film-forming agent could be removed, thus the heat deposition was relieved and damage threshold could be improved. The modulation depth of the Bi2Se3film was measured to be 5.2%. When we used the Bi2Se3film in the Yb-doped fiber laser, the mode locked pulses with pulse energy of 0.756 nJ, pulse width of 46 ps and the repetition rate of 44.6 MHz were obtained. The maximum average output power was 33.7 mW. When the pump power exceeded 270 mW, the laser can operate in multiple pulse state that six-pulse regime can be realized. This contribution indicates that Bi2Se3has an attractive optoelectronic property at 1μm waveband. ©2014 Optical Society of America.


Wang K.,Beijing University of Technology | Ma Y.-Q.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

With nonrelativistic QCD factorization, we calculate the Υ(1S) prompt production at hadron colliders at next-to-leading order in α s. In addition to the color-singlet contribution, color-octet channels (especially the P-wave channel) up to O(v4) are all considered. Aside from direct production, the feed-down contributions from higher excited S-wave and P-wave bb̄ states to Υ(1S) production are also included. We use the potential model estimates as input for color-singlet long-distance matrix elements (LDMEs). While for color-octet contributions, we find they can be approximately described by three LDMEs: 〈O(S1[8]3)〉, 〈O(S0[8]1)〉 and 〈O(P0[8]3)〉. By fitting the Tevatron data we can determine some linear combinations of these LDMEs, and then use them to predict Υ(1S) production at the LHC. Our predictions are consistent with the new experimental data of CMS and LHCb. © 2012 American Physical Society.


Zhang X.,Beijing University of Technology | Zheng Y.-J.,Beijing University of Technology | Zheng Y.-J.,Shandong University | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We reexamine the quark-lepton complementarity (QLC) in nine angle-phase parametrizations with the latest result of a large lepton mixing angle θ 13 from the T2K, MINOS, and Double-Chooz experiments. We find that there are still two QLC relations satisfied in P1, P4, and P6 parametrizations, whereas only one QLC relation holds in P2, P3, P5, and P9 parametrizations separately. We also work out the corresponding reparametrization-invariant forms of the QLC relations and check the resulting expressions with the experimental data. The results can be viewed as a check of the validity of the QLC relations, as well as a new perspective into the issue of seeking for the connection between quarks and leptons. © 2012 American Physical Society.


Hu X.,Peking University | Li Z.,Peking University | Zhang J.,Peking University | Yang H.,Peking University | And 2 more authors.
Advanced Functional Materials | Year: 2011

A novel nanoscale integrated all-optical diode is reported, realized by combining the strong plasmonic responses of gold nanoparticles with the all-optical tunable properties of polymeric photonic crystal microcavities. Non-reciprocal transmission properties are achieved based on the effect of surface-plasmon resonance enhancing the optical non-linearity and dynamic coupling of asymmetrical microcavity modes. An ultralow-threshold photon intensity of 2.1 MW cm-2 and an ultrahigh transmission contrast over 104 are realized simultaneously. Compared with previously reported all-optical diodes, the operating power is reduced by five orders of magnitude, while the transmission contrast is enlarged by three orders of magnitude. A nanoscale integrated all-optical diode is realized via nanocomposite photnic crystal microcavities. Excellent performance is achieved by combining the strong plasmonic responses of gold nanoparticles with the all-optical tunable properties of polymeric photonic crystal microcavities. The operating power is reduced by five orders of magnitude, while the transmission contrast is enlarged by three orders of magnitude. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Li Z.P.,Southwest University | Song B.Y.,Southwest University | Yao J.M.,Southwest University | Vretenar D.,University of Zagreb | And 4 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

The evolution of quadrupole and octupole shapes in Th isotopes is studied in the framework of nuclear Density Functional Theory. Constrained energy maps and observables calculated with microscopic collective Hamiltonians indicate the occurrence of a simultaneous quantum shape phase transition between spherical and quadrupole-deformed prolate shapes, and between non-octupole and octupole-deformed shapes, as functions of the neutron number. The nucleus 224Th is closest to the critical point of a double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation. © 2013 Elsevier B.V.


Chi Y.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We perform a study on the struck quark to the Λ-hyperon fragmentation processes by taking into account the anti-quark fragmentations and intermediate decays from other hyperons. We concentrate on how the longitudinally polarized quark fragments to the longitudinally polarized Λ, how unpolarized quark and anti-quark fragment to the unpolarized Λ, and how quark and anti-quark fragment to the Λ through the intermediate decay processes. We calculate the effective fragmentation functions in the light-cone SU(6) quark-spectator-diquark model via the Gribov-Lipatov relation, with the Melosh-Wigner rotation effect also included. The calculated results are in reasonable agreement with the HERMES semi-inclusive ep experimental data and the OPAL and ALEPH e+e- annihilation experimental data. © 2013 Elsevier B.V.


Yan K.,Beijing University of Technology | Wang J.,Beijing University of Technology | Shao D.Y.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We present the calculations of the complete next-to-leading order QCD corrections to the total cross section, invariant mass distribution, and the forward-backward asymmetry (A FB) of top quark pair production mediated by the W ′ boson. Our results show that in the best fit point in the parameter space allowed by data at the Tevatron, the next-to-leading order corrections change the new physics contributions to the total cross section slightly, but increase the A FB in the large invariant mass region by about 9%. Moreover, we evaluate the total cross section and charge asymmetry (A C) of top pair production at the LHC, and find that both total cross section and A C can be used to distinguish new physics from the standard model with the integrated luminosity increasing. © 2012 American Physical Society.


Zhang X.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

Inspired by a new relation θ13PMNS=θ C/√2 observed from the relatively large θ13PMNS, we find that the combination of this relation with the quark-lepton complementarity and the self-complementarity results in correlations of the lepton mixing angles with the quark mixing angles. We find that the three mixing angles in the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix are all related to the Wolfenstein parameter λ in the quark mixing, so they are also correlated. Consequently, the PMNS matrix can be parameterized by λ, A, and a Dirac CP-violating phase δ. Such parametrizations for the PMNS matrix have the same explicitly hierarchical structure as the Wolfenstein parametrization for the Cabibbo-Kobayashi-Maskawa matrix in the quark mixing, and the bimaximal mixing pattern is deduced at the leading order. We also discuss implications of these phenomenological relations in parametrizations. © 2012 American Physical Society.


Wang J.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Shao D.Y.,Beijing University of Technology | Zhang H.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We investigate the potential of the early LHC to discover the signal of monotops, which can be decay products of some resonances in models such as R-parity-violating supersymmetry or SU(5), etc. We show how to constrain the parameter space of the models by the present data of Z boson hadronic decay branching ratio, K0-K ̄0 mixing and dijet productions at the LHC. Then, we study the various cuts imposed on the events, reconstructed from the hadronic final states, to suppress backgrounds and increase the significance in detail. And we find that in the hadronic mode the information from the missing transverse energy and reconstructed resonance mass distributions can be used to specify the masses of the resonance and the missing particle. Finally, we study the sensitivities to the parameters at the LHC with √s=7TeV and an integrated luminosity of 1fb -1 in detail. Our results show that the early LHC may detect this signal at 5σ level for some regions of the parameter space allowed by the current data. © 2012 American Physical Society.


Li N.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We reinvestigate the possibility of X(3872) as a DD ̄* molecule with JPC=1 ++ within the framework of both the one-pion-exchange model and the one-boson-exchange model. After careful treatment of the S-D wave mixing, the mass difference between the neutral and charged D(D*) mesons and the coupling of the DD ̄* pair to D*D ̄*, a loosely bound molecular state X(3872) emerges quite naturally with large isospin violation in its flavor wave function. For example, the isovector component is 26.24% if the binding energy is 0.30 MeV, where the isospin breaking effect is amplified by the tiny binding energy. After taking into account the phase space difference and assuming the 3π and 2π come from a virtual omega and rho meson respectively, we obtain the ratio of these two hidden-charm decay modes: B(X(3872) →π +π -π0J/ψ)/B(X(3872) →π +π -J/ψ)=0.42 for the binding energy being 0.3 MeV, which is consistent with the experimental value. © 2012 American Physical Society.


Cao Q.-H.,Beijing University of Technology | Li Z.,Michigan State University | Yu J.-H.,Michigan State University | Yuan C.-P.,Michigan State University | Yuan C.-P.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We explore the discovery potential of W ′ and Z' boson searches for various SU(2) 1 - SU(2) 2 - U(1) X models at the Large Hadron Collider (LHC), after taking into account the constraints from low energy precision measurements and direct searches at both the Tevatron (1.96TeV) and the LHC (7TeV). In such models, the W' and Z' bosons emerge after the electroweak symmetry is spontaneously broken. Two patterns of the symmetry breaking are considered in this work: one is SU(2) L - SU(2) 2 - U(1) X→SU(2) L - U(1) Y (breaking pattern I), another is SU(2) 1 - SU(2) 2 - U(1) Y→SU(2) L - U(1) Y (breaking pattern II). Examining the single production channel of W' and Z' with their subsequent leptonic decays, we find that the probability of detecting W' and Z' bosons in the considered models at the LHC (with 14TeV) is highly limited by the low energy precision data constraints. We show that observing Z' alone, without seeing a W', does not rule out new physics models with non-Abelian gauge extension, such as the phobic models in breaking pattern I. Models in breaking pattern II would predict the discovery of degenerate W' and Z' bosons at the LHC. © 2012 American Physical Society.


Li N.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We investigate the possible molecules composed of two heavy flavor baryons such as "A QB Q" (Q=b, c) within the one-pion-exchange model (OPE). Our results indicate that the long-range π exchange force is strong enough to form molecules such as [Σ QΞQ′]S=1I=1/2 (Q=b, c), [Σ QΛ Q]S=1I=1 (Q=b, c), [Σ bΞb′]S=1I=3/2, and [Ξ bΞb′]S=1I=0 where the S-D mixing plays an important role. In contrast, the π exchange does not form the spin-singlet A QB Q bound states. If we consider the heavier scalar and vector meson exchanges as well as the pion exchange, some loosely bound spin-singlet S-wave states appear while results of the spin-triplet A QB Q system do not change significantly, which implies the pion exchange plays an dominant role in forming the spin-triplet molecules. Moreover, we perform an extensive coupled channel analysis of the Λ QΛ Q system within the OPE and one-boson-exchange framework and find that there exist loosely bound states of Λ QΛ Q (Q=b, c) with quantum numbers I(JP)=0(0 +), 0(0 -), and 0(1 -). The binding solutions of Λ QΛ Q system mainly come from the coupled-channel effect in the flavor space. Besides the OPE force, the medium- and short-range attractive force also plays a significant role in the formation of the loosely bound Λ cΛ c and Λ bΛ b states. Once produced, they will be very stable because such a system decays via weak interaction with a very long lifetime around 10 -13-10 -12s. © 2012 American Physical Society.


Zhang Y.,Beijing University of Technology | Zhang X.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

With the progress of increasingly precise measurements on the neutrino mixing angles, phenomenological relations such as quark-lepton complementarity (QLC) among mixing angles of quarks and leptons and self-complementarity (SC) among lepton mixing angles have been observed. Using the latest global fit results of the quark and lepton mixing angles in the standard Chau-Keung scheme, we calculate the mixing angles and CP-violating phases in the other eight different schemes. We check the dependence of these mixing angles on the CP-violating phases in different phase schemes. The dependence of QLC and SC relations on the CP phase in the other eight schemes is recognized and then analyzed, suggesting that measurements on CP-violating phases of the lepton sector are crucial to the explicit forms of QLC and SC in different schemes. © 2012 American Physical Society.


Han Z.,University of Oregon | Han Z.,Beijing University of Technology | Liu Y.,University of Oregon | Liu Y.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We propose a novel method for probing sleptons in compressed spectra at hadron colliders. The process under study is slepton pair production in R-parity conserving supersymmetry, where the slepton decays to a neutralino lightest supersymmetric particle of mass close to the slepton mass. In order to pass the trigger and obtain large missing energy, an energetic monojet is required. Both leptons need to be detected in order to suppress large standard model backgrounds with one charged lepton. We study variables that can be used to distinguish the signal from the remaining major backgrounds, which include tt¯, WW+jet, Z+jet, and single top production. We find that the dilepton mT2, bound by the mass difference, can be used as an upper bound to efficiently reduce the backgrounds. It is estimated that sleptons with masses up to about 150 GeV can be discovered at the 14 TeV LHC with 100fb-1 integrated luminosity. © 2015 American Physical Society.


Chen N.,Anhui University of Science and Technology | Li J.,University of Adelaide | Liu Y.,Beijing University of Technology | Liu Z.,Tsinghua University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The LHC searches for the CP-odd Higgs boson A are studied (with masses from 300 GeV to 1 TeV) in the context of the general two-Higgs-doublet model. With the discovery of the 125 GeV Higgs boson at the LHC, we highlight one promising discovery channel of A→hZ. This channel can become significant for a heavy CP-odd Higgs boson after the global signal fitting to the 125 GeV Higgs boson in the general two-Higgs-doublet model. It is particularly interesting in the scenario where two CP-even Higgs bosons in the two-Higgs-doublet model have the common mass of 125 GeV. Since the final states involve a standard-model-like Higgs boson, we apply the jet substructure analysis of tagging the fat Higgs jet in order to eliminate the standard-model background sufficiently. After performing the kinematic cuts, we present the LHC search sensitivities for the CP-odd Higgs boson with mass up to 1 TeV via this channel. © 2015 American Physical Society.


Ren X.-L.,Beihang University | Geng L.-S.,Beihang University | Meng J.,Beihang University | Meng J.,Beijing University of Technology | Meng J.,Stellenbosch University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The scalar strangeness content of the nucleon, characterized by the so-called strangeness-nucleon sigma term, is of fundamental importance in understanding its sea-quark flavor structure. We report a determination of the octet baryon sigma terms via the Feynman-Hellmann theorem by analyzing the latest high-statistics nf=2+1 lattice QCD simulations with covariant baryon chiral perturbation theory up to next-to-next-to-next-to-leading order. In particular, we predict σπN=55(1)(4)MeV and σsN=27(27)(4)MeV, while the first error is statistical and the second systematic due to different lattice scales. The predicted σsN is consistent with the latest LQCD results and the results based on the next-to-next-to-leading order chiral perturbation theory. Several key factors in determining the sigma terms are systematically taken into account and clarified for the first time, including the effects of lattice scale setting, systematic uncertainties originating from chiral expansion truncations, and constraint of strong-interaction isospin breaking effects. © 2015 American Physical Society.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Wu J.-Q.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Inspired by the holographic computation of large interval entanglement entropy of two-dimensional (2D) conformal field theory at high temperature, it was proposed that the thermal entropy is related to the entanglement entropy as Sth=liml→0(SEE(R-l)-SEE(l)). In this paper, we prove this relation for 2D CFT with a discrete spectrum in two different ways. Moreover, we discuss this relation for a 2D noncompact free scalar, which is a gapless CFT with continuous spectrum. We show that it could be recovered, after appropriately regularizing the theory. © 2015 American Physical Society.


Chen R.,Lanzhou University | Liu X.,Nankai University | Li X.-Q.,Beijing University of Technology | Li X.-Q.,Peking University | Zhu S.-L.,Lanzhou University
Physical Review Letters | Year: 2015

The LHCb Collaboration at the Large Hadron Collider at CERN discovered two pentaquark states Pc(4380) and Pc(4450). These two hidden-charm states are interpreted as the loosely bound Σc(2455)D∗ and Σc∗(2520)D∗ molecular states in the boson exchange interaction model, which provides an explanation for why the experimental width of Pc(4450) is much narrower than that of Pc(4380). The discovery of the new resonances Pc(4380) and Pc(4450), indeed, opens a new page for hadron physics. The partners of Pc(4380) and Pc(4450) should be pursued in future experiments. © 2015 American Physical Society.


Liu T.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We investigate the properties of octet and decuplet baryons in a light-front holographic model. By taking into account the effect of nonvanishing quark mass, we obtain the modified light-front wave functions which are applicable at both low and high energy scales. We calculate the spectra, form factors, magnetic moments and electromagnetic radii of octet and decuplet baryons with the results all matching the experiments well. The axial charge, which describes the contribution of quark helicity to the proton spin in the quark-parton model at the high energy scale, is also consistent with the experimental value. Therefore, the light-front holographic method is successful in studying hadronic physics at all energy scales, and the nonzero quark mass is essential to understand the spin structures together with other low energy properties. © 2015 American Physical Society.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Wu J.-Q.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In this paper, we study the holographic Rényi entropy of a large interval on a circle at high temperature for the two-dimensional conformal field theory (CFT) dual to pure AdS3 gravity. In the field theory, the Rényi entropy is encoded in the CFT partition function on n-sheeted torus connected with each other by a large branch cut. As proposed by Chen and Wu [Large interval limit of Rényi entropy at high temperature, arXiv:1412.0763], the effective way to read the entropy in the large interval limit is to insert a complete set of state bases of the twist sector at the branch cut. Then the calculation transforms into an expansion of four-point functions in the twist sector with respect to e-2πTRn. By using the operator product expansion of the twist operators at the branch points, we read the first few terms of the Rényi entropy, including the leading and next-to-leading contributions in the large central charge limit. Moreover, we show that the leading contribution is actually captured by the twist vacuum module. In this case by the Ward identity the four-point functions can be derived from the correlation function of four twist operators, which is related to double interval entanglement entropy. Holographically, we apply the recipe in [T. Faulkner, The entanglement Rényi entropies of disjoint intervals in AdS/CFT, arXiv:1303.7221] and [T. Barrella et al., Holographic entanglement beyond classical gravity, J. High Energy Phys. 09 (2013) 109] to compute the classical Rényi entropy and its one-loop quantum correction, after imposing a new set of monodromy conditions. The holographic classical result matches exactly with the leading contribution in the field theory up to e-4πTR and l6, while the holographical one-loop contribution is in exact agreement with next-to-leading results in field theory up to e-6πTRn and l4 as well. © 2015 American Physical Society.


Cao Q.-H.,Beijing University of Technology | Cao Q.-H.,Peking University | Yan B.,Beijing University of Technology | Zhang D.-M.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The ATLAS collaboration reported excesses at around 2 TeV in the diboson production decaying into hadronic final states. We consider the possibility of explaining the excesses with extra gauge bosons in two simple non-Abelian extensions of the standard model. One is the so-called G(221) models with a symmetry structure of SU(2)1 - SU(2)2 - U(1)X and the other is the G(331) models with an extended symmetry of SU(3)C - SU(3)L - U(1)X. The W′ and Z′ bosons emerge after the electroweak symmetry is spontaneously broken. Two patterns of symmetry breaking in the G(221) models are considered in this work: one is SU(2)L - SU(2)2 - U(1)X→SU(2)L - U(1)Y, the other is SU(2)1 - SU(2)2 - U(1)Y→SU(2)L - U(1)Y. The symmetry breaking of the G(331) model is SU(3)L - U(1)X→SU(2)L - U(1)Y. We perform a global analysis of W′ and Z′ phenomenology in ten new physics models, including all the channels of W′/Z′ decay. Our study shows that the leptonic mode and the dijet mode of W′/Z′ decays impose a very stringent bound on the parameter space in several new physics models. Such tight bounds provide a useful guide for building new physics models to address on the diboson anomalies. We also note that the left-right and leptophobic models can explain the 3.4σWZ excess if the 2.6σ deviation in the W+W- pair around 2 TeV were confirmed to be a fluctuation of the SM backgrounds. © 2015 American Physical Society.


Cao Q.-H.,Beijing University of Technology | Cao Q.-H.,Peking University | Yan B.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Verifying Vtb≃1 is critical to test the three generation assumption of the Standard Model. So far our best knowledge of Vtb is inferred either from the 3×3 unitarity of the Cabibbo-Kobayashi-Maskawa matrix or from single top-quark productions upon the assumption of universal weak couplings. The unitarity could be relaxed in new physics models with extra heavy quarks and the universality of weak couplings could also be broken if the Wtb coupling is modified in new physics models. In this paper we propose to measure Vtb in the process of e+e-→tt¯ without prior knowledge of the number of fermion generations or the strength of the Wtb coupling. Using an effective Lagrangian approach, we perform a model-independent analysis of the interactions among electroweak gauge bosons and the third generation quarks, i.e. the Wtb, Ztt¯ and Zbb¯ couplings. The electroweak symmetry of the Standard Model specifies a pattern of deviations of the Z-tL-tL and W-tL-bL couplings after one imposes the known experimental constraint on the Z-bL-bL coupling. We demonstrate that, making use of the predicted pattern and the accurate measurements of top-quark mass and width from the energy threshold scan experiments, one can determine Vtb from the cross section and the forward-backward asymmetry of top-quark pair production at an unpolarized electron-positron collider. © 2015 American Physical Society.


Chen H.-X.,Beihang University | Chen W.,University of Saskatchewan | Liu X.,Lanzhou University | Steele T.G.,University of Saskatchewan | And 2 more authors.
Physical Review Letters | Year: 2015

Inspired by Pc(4380) and Pc(4450) recently observed by LHCb, a QCD sum rule investigation is performed, by which they can be identified as exotic hidden-charm pentaquarks composed of an anticharmed meson and a charmed baryon. Our results suggest that Pc(4380) and Pc(4450) have quantum numbers JP=3/2- and 5/2+, respectively. Furthermore, two extra hidden-charm pentaqurks with configurations D¯Σc∗ and D¯∗Σc∗ are predicted, which have spin-parity quantum numbers JP=3/2- and JP=5/2+, respectively. As an important extension, the mass predictions of hidden-bottom pentaquarks are also given. Searches for these partners of Pc(4380) and Pc(4450) are especially accessible at future experiments like LHCb and BelleII. © 2015 American Physical Society.


Huang F.P.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We study the electroweak baryogenesis in the framework of the effective field theory. Our study shows that by introducing a light singlet scalar particle and a dimension-5 operator, it can provide the strong first order phase transition and the source of the CP-violation during the phase transition, and then produce abundant particle phenomenology at zero temperature. We also show the constraints on the new physics scale from the observed baryon-to-photon ratio, the low-energy experiments, and the LHC data. © 2015 American Physical Society. © 2015 American Physical Society.


Liu Y.,Beijing University of Technology | Zhao X.,Beijing University of Technology | Li F.,Beijing University of Technology | Xia D.,Peking University
Electrochimica Acta | Year: 2011

Cubic MnO with particle sizes of ∼200 nm and ∼600 nm was synthesized by decomposition of MnCO3. The corresponding MnO/C composite was obtained by thermal treatment of mixture of MnCO3 and sucrose. The structure and morphology of the products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical experiments showed that the as-prepared MnO/C exhibited promising electrochemical properties, and could potentially be used as anode material in lithium-ion batteries. MnO/C delivered a reversible capacity of about 470 mAh/g after cycling 50 times, when testing at 75 mA/g. The reversible capacity, when tested at 150, 375, 755 mA/g, reached 440, 320, 235 mAh/g, respectively. The good electrochemical performance was ascribed to the smaller particle size and the efficient carbon coating on MnO. © 2011 Elsevier Ltd. All rights reserved.


Liu T.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We investigate the quark Wigner distributions in a light-cone spectator model. The Wigner distribution, as a quasidistribution function, provides the most general one-parton information in a hadron. Combining the polarization configurations, unpolarized, longitudinal polarized, or transversal polarized, of the quark and the proton, we can define 16 independent Wigner distributions at leading twist. We calculate all these Wigner distributions for the u quark and the d quark, respectively. In our calculation, both the scalar and the axial-vector spectators are included, and the Melosh-Wigner rotation effects for both the quark and the axial-vector spectator are taken into account. The results provide us a very rich picture of the quark structure in the proton. © 2015 American Physical Society.


Liu T.,Beijing University of Technology | Liu T.,National Institute of Nuclear Physics, Italy | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We investigate the angular momentum decomposition with a quantum electrodynamics example to clarify the proton spin decomposition debates. We adopt the light-front formalism where the parton model is well defined. We prove that the sum of fermion and boson angular momenta is equal to half the sum of the two gravitational form factors A(0) and B(0), as is well known. However, the suggestion to make a separation of the above relation into the fermion and boson pieces, as a way to measure the orbital angular momentum of fermions or bosons, respectively, is not justified from our explicit calculation. © 2015 American Physical Society.


Zhao S.,Beijing University of Technology | Zhao S.,Peking University | Kang W.,Beijing University of Technology | Kang W.,Peking University | Xue J.,Beijing University of Technology
Applied Physics Letters | Year: 2014

Tuning the electronic and magnetic properties of a material through strain engineering is an effective strategy to enhance the performance of electronic and spintronic devices. In this paper, first-principles calculations based on density functional theory are carried out to investigate the electronic and magnetic properties of M2C(M=Hf, Nb, Sc, Ta, Ti, V, Zr, known as MXenes) subjected to biaxial symmetric mechanical strains. At the strain-free state, all these MXenes exhibit no spontaneous magnetism except for Ti 2C and Zr2C which show a magnetic moment of 1.92 and 1.25μB/unit, respectively. As the tensile strain increases, the magnetic moments of MXenes are greatly enhanced and a transition from nonmagnetism to ferromagnetism is observed for those nonmagnetic MXenes at zero strains. The most distinct transition is found in Hf2C, in which the magnetic moment is elevated to 1.5μB/unit at a strain of 1.80%. We further show that the magnetic properties of Hf2C are attributed to the band shift mainly composed of Hf(5d) states. © 2014 AIP Publishing LLC.


Zhao S.,Beijing University of Technology | Zhao S.,Peking University | Kang W.,Beijing University of Technology | Kang W.,Peking University | Xue J.,Beijing University of Technology
Journal of Materials Chemistry C | Year: 2015

Quasi-one-dimensional nanoribbons have great potential for applications in nanoelectronics and nanospintronics due to their unique quantum confinement effects. In this work, first-principles calculations are carried out to predict the stability as well as magnetic and electronic properties of MXene nanoribbons with either zigzag- or armchair-terminated edges. Three types of MXene recently realized experimentally, i.e. Ti2C, Ti3C2 and V2C, are considered to construct their corresponding MXene nanoribbons. In addition, the O-functionalized Ti2C and Ti3C2 nanoribbons are also investigated. The effect of functionalization is studied by comparing different functional groups including OH, F and O. Six zigzag and two armchair families are distinguished according to different ribbon edges. Our results show that all the investigated bare MXenes are metallic and exhibit certain magnetic moments in their ground states, irrespective of the ribbon width and ribbon type. Remarkable edge reconstructions are observed for all types of nanoribbon. We further show that hydrogen passivation can lead to the increase of the magnetic moments of Ti2C and V2C nanoribbons due to charge transfer. For O-functionalized Ti2C nanoribbons, our calculations indicate that some of them exhibit semiconducting properties dependent on edge configurations. In particular, the band gap of armchair Ti2CO2 nanoribbons with a width of 7.34 Å is found to be around 1.0 eV, which is significantly enhanced compared to the 0.4 eV of a pristine Ti2CO2 layer. The stabilities of these nanoribbons are evaluated by virtue of their binding energies, formation energies and edge energies and we show that functionalized MXene nanoribbons are more stable than bare ribbons. Our results thus provide strong evidence for the effectiveness of nanostructuring on the electronic and magnetic properties of MXenes. © The Royal Society of Chemistry 2015.


Li X.,Beijing University of Technology | Zhou J.,Peking University | Wang Q.,Beijing University of Technology | Wang Q.,Virginia Commonwealth University | And 2 more authors.
Journal of Physical Chemistry Letters | Year: 2013

We propose porous C-N-based structures for biocompatible magnetic materials that do not contain even a single metal ion. Using first-principles calculations based on density functional theory, we show that when patterned in the form of a kagome lattice, nonmagnetic g-C3N4 not only becomes ferromagnetic but also its magnetic properties can be further enhanced by applying external strain. Similarly, the magnetic moment per atom in ferromagnetic g-C4N3 is increased three fold when patterned into a kagome lattice. The Curie temperature of g-C3N 4 kagome lattice is 100 K, while that of g-C4N3 kagome lattice is much higher, namely, 520 K. To date, all of the synthesized two- and three-dimensional magnetic kagome structures contain metal ions and are toxic. The objective of our work is to stimulate an experimental effort to develop nanopatterning techniques for the synthesis of g-C3N 4- and g-C4N3-based kagome lattices. © 2012 American Chemical Society.


Kan M.,Peking University | Zhou J.,Peking University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology | And 3 more authors.
Journal of Physical Chemistry Letters | Year: 2013

The Mn atom, because of its special electronic configuration of 3d 54s2, has been widely used as a dopant in various two-dimensional (2D) monolayers such as graphene, BN, silicene and transition metal dichalcogenides (TMDs). The distributions of doped Mn atoms in these systems are highly sensitive to the synthesis process and conditions, thus suffering from problems of low solubility and surface clustering. Here we show for the first time that the MnO2 monolayer, synthetized 10 years ago, where Mn ions are individually held at specific sites, exhibits intrinsic ferromagnetism with a Curie temperature of 140 K, comparable to the highest TC value achieved experimentally for Mn-doped GaAs. The well-defined atomic configuration and the intrinsic ferromagnetism of the MnO2 monolayer suggest that it is superior to other magnetic monolayer materials. © 2013 American Chemical Society.


Kan M.,Peking University | Kan M.,Sungkyunkwan University | Adhikari S.,Sungkyunkwan University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology
Physical Chemistry Chemical Physics | Year: 2014

Using density functional theory combined with Monte Carlo (MC) simulations, we show that the two dimensional (2D) MnS2 and MnSe2 sheets are ideal magnetic semiconductors with long-range magnetic ordering and high magnetic moments (3 μB per unit cell), where all the Mn atoms are ferromagnetically coupled, and the Curie temperatures (TC) estimated for MnS2 and MnSe2 by the MC simulations are 225 and 250 K, respectively, which can be further increased to 330 K and 375 K by applying 5% biaxial tensile strains. © 2014 the Owner Societies.


Zhang Z.,Beijing University of Technology | Sun H.,Beijing Institute of Technology | Peng L.,University of Surrey
Differential Geometry and its Application | Year: 2013

In this paper, we use natural gradient algorithm to control the shape of the conditional output probability density function for the stochastic distribution systems from the viewpoint of information geometry. The considered system here is of multi-input and single output with an output feedback and a stochastic noise. Based on the assumption that the probability density function of the stochastic noise is known, we obtain the conditional output probability density function whose shape is only determined by the control input vector under the condition that the output feedback is known at any sample time. The set of all the conditional output probability density functions forms a statistical manifold (M), and the control input vector and the output feedback are considered as the coordinate system. The Kullback divergence acts as the distance between the conditional output probability density function and the target probability density function. Thus, an iterative formula for the control input vector is proposed in the sense of information geometry. Meanwhile, we consider the convergence of the presented algorithm. At last, an illustrative example is utilized to demonstrate the effectiveness of the algorithm. © 2013 Elsevier B.V.


Chen W.,Beijing University of Technology | Cai Z.-X.,Beijing University of Technology | Zhu S.-L.,Beijing University of Technology | Zhu S.-L.,Peking University
Nuclear Physics B | Year: 2014

We calculate the two-point correlation function using the interpolating current with JPC=2-. After performing the Borel sum rule analysis, the extracted masses of the 2-- tensor charmonium and bottomonium are 3.97±0.25GeV and 10.13±0.34GeV respectively. For comparison, we also perform the moment sum rule analysis for the charmonium and bottomonium systems. We extend the same analysis to study the qq,qs,ss,qc,sc,qb,sb and cb systems. Their masses are 1.78±0.12, 1.85±0.14, 2.00±0.16, 2.86±0.14, 3.01±0.21, 5.66±0.33, 6.40±0.25, and 7.08±0.34GeV respectively. © 2014 The Authors.


Li Y.P.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Nie S.L.,Beijing University of Technology | Chen X.,Xinjiang Institute of Ecology and Geography
Agricultural Water Management | Year: 2011

In regional water management systems, various uncertainties may be derived from random feature of resource conditions and natural processes, errors in estimated modeling parameters, as well as imprecision or fuzziness human-induced. This leads to difficulties in formulating and solving the resulting regional water management problems. In this study, a robust multistage interval-stochastic programming (RISP) method is developed for dealing with vague and random information in regional water management systems. The decision variables are useful for justifying and/or adjusting the decision schemes for agricultural activities through the incorporation of their implicit knowledge on regional water management. Different policies for agricultural water supply have been analyzed. The results can help to identify desired water-allocation schemes for agricultural sustainable development that the prerequisite water demand for supporting crops' survival can be guaranteed when the water resource is scarce. © 2011 Elsevier B.V.


Li H.T.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Shao D.Y.,Beijing University of Technology | And 3 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We investigate the transverse momentum resummation for top quark pair production at hadron colliders using the soft-collinear effective theory and the heavy-quark effective theory. We derive the factorization formula for tt̄ production at the small pair transverse momentum, and show in detail the procedure for calculating the key ingredient of the factorization formula: the next-to-leading order soft functions. We compare our numerical results with experimental data and find that they are consistent within theoretical and experimental uncertainties. To verify the correctness of our resummation formula, we expand it to the next-to-leading order and the next-to-next-to- leading order, and compare those expressions with the exact fixed-order results numerically. Finally, using the results of transverse momentum resummation, we discuss the transverse-momentum-dependent forward-backward asymmetry at the Tevatron. © 2013 American Physical Society.


Qu H.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We propose a new mixing pattern for neutrinos with a nonzero mixing angle θ13. Under a simple form, it agrees well with current neutrino oscillation data and displays a number of intriguing features including the μ-τ interchange symmetry |Uμi| = |Uτi|, (i = 1, 2, 3), the trimaximal mixing |Ue2| = |Uμ2| = |Uτ2| = 1/√3, the self-complementarity relation θ1 + θ3 = 45°, together with the maximal Dirac CP violation as a prediction. © 2013 American Physical Society.


Li J.-Z.,Beijing University of Technology | Ma Y.-Q.,Brookhaven National Laboratory | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We calculate the annihilation decay widths of spin-singlet heavy quarkonia hc, hb and ηb into light hadrons with both QCD and relativistic corrections at order O(αsv2) in nonrelativistic QCD. With appropriate estimates for the long-distance matrix elements by using the potential model and operator evolution method, we find that our predictions of these decay widths are consistent with recent experimental measurements. We also find that the O(αsv2) corrections are small for bb̄ states but substantial for cc̄ states. In particular, the negative contribution of O(αsv2) correction to the hc decay can lower the decay width, as compared with previous predictions without the O(αsv2) correction, and thus result in a good agreement with the recent BESIII measurement. © 2013 American Physical Society.


Ji Q.,CAS Beijing National Laboratory for Molecular | Zhang Y.,CAS Beijing National Laboratory for Molecular | Zhang Y.,Peking University | Gao T.,CAS Beijing National Laboratory for Molecular | And 10 more authors.
Nano Letters | Year: 2013

Molybdenum disulfide (MoS2) is back in the spotlight because of the indirect-to-direct bandgap tunability and valley related physics emerging in the monolayer regime. However, rigorous control of the monolayer thickness is still a huge challenge for commonly utilized physical exfoliation and chemical synthesis methods. Herein, we have successfully grown predominantly monolayer MoS2 on an inert and nearly lattice-matching mica substrate by using a low-pressure chemical vapor deposition method. The growth is proposed to be mediated by an epitaxial mechanism, and the epitaxial monolayer MoS2 is intrinsically strained on mica due to a small adlayer-substrate lattice mismatch (∼2.7%). Photoluminescence (PL) measurements indicate strong single-exciton emission in as-grown MoS2 and room-temperature PL helicity (circular polarization ∼0.35) on transferred samples, providing straightforward proof of the high quality of the prepared monolayer crystals. The homogeneously strained high-quality monolayer MoS2 prepared in this study could competitively be exploited for a variety of future applications. © 2013 American Chemical Society.


Gu X.,Peking University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology
Physical Chemistry Chemical Physics | Year: 2013

Using density functional theory (DFT) and time-dependent DFT in different levels, we have systematically studied new porphyrin-based dyes with A-π-D structures focusing on optical absorption, light harvest efficiency, ground state oxidation potential, excited state oxidation potential, and natural transition orbitals. Compared with existing dyes, we find that these new dyes have wide absorption regions (400-1000 nm) with high molar extinction coefficients, and display good energy level alignment for efficient injection of electrons and fast regeneration of the oxidized dyes. This journal is © 2013 the Owner Societies.


Zhao X.,Beijing University of Technology | Xia Z.,Beijing Institute of Technology | Xia D.,Peking University
Electrochimica Acta | Year: 2010

Sn/Cu nanowire composite film was electrodeposited on copper foil substrates and used as an anode material for lithium-ion batteries. The structure of the obtained composite film anode was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy. It was found that the Sn/Cu nanowire composite film anode showed a better cycle stability than Sn film anode, whereas the Sn/CNT composite film anode indicated poor capacity retention. It could be deduced that copper nanowire reinforced the Sn film anode due to the better wetting property of Sn on the surface of copper and reduced the loss of electric contact among tin particles in the Sn/Cu nanowire composite film anode. © 2010 Elsevier Ltd. All rights reserved.


Yan Y.,University of Manchester | Yan Y.,Beijing University of Technology | Li L.,University of Manchester | Feng C.,Beijing University of Technology | And 3 more authors.
ACS Nano | Year: 2014

We report a direct optical super-resolution imaging approach with 25 nm (∼λ/17) lateral resolution under 408 nm wavelength illumination by combining fused silica and polystyrene microspheres with a conventional scanning laser confocal microscope (SLCM). The microsphere deposited on the target surface generates a nanoscale central lobe illuminating a sub-diffraction- limited cross-section located on the target surface. The SLCM confocal pinhole isolates the reflected light from the near-field subdiffractive cross-section and suppresses the noises from the side lobe and the far-field paraxial focal point. The structural detail of the subdiffractive cross-section is therefore captured, and the 2D target surface near the bottom of microspheres can be imaged by intensity-based point scanning. © 2014 American Chemical Society.


Yue J.,Beijing University of Technology | Zhao X.,Beijing University of Technology | Xia D.,Peking University
Electrochemistry Communications | Year: 2012

A novel C/Co composite with Co nanoparticles embedded in carbon matrix is synthesized firstly by pyrolysis of polymeric cobalt phthalocyanine (PcCo) at 700 °C in argon atmosphere. This composite is investigated as an anode material for lithium ion batteries, indicating high tap density and excellent electrochemical performance. The C/Co electrode can retain a higher reversible capacity of over 600 mAh g - 1 at a current of 50 mA g - 1 after 40 cycles and shows better rate capability and less hysteresis in comparison to carbon not containing Co. The significant improvement is attributed to the Co nanoparticles grown in-situ reaction with catalytic activity and high electrical conductivity. © 2012 Elsevier B.V.


Wu B.,Frankfurt Institute for Advanced Studies | Wu B.,Beijing University of Technology | Wu B.,Bielefeld University
Journal of High Energy Physics | Year: 2011

We study the contributions from radiation to p⊥-broadening of a high energy parton traversing a QCD medium with a finite length L. The interaction between the parton and the medium is described by decorrelated static multiple scattering. Amplitudes of medium-induced gluon emission and parton self-energy diagrams are evaluated in the soft gluon limit in the BDMPS formalism. We find both the double-logarithmic correction from incoherent scattering, which is parametrically the same as that in single scattering, and the logarithmic correction from the LPM effect. Therefore, we expect a parametrically large correction from radiation to the medium-induced p⊥-broadening in perturbative QCD. © 2011 SISSA.


Shao L.,Beijing University of Technology | Ma B.-Q.,Peking University
Modern Physics Letters A | Year: 2010

Lorentz violation (LV) is predicted by some quantum gravity (QG) candidates, wherein the canonical energymomentum dispersion relation, E 2 = p2+m2, is modified. Consequently, new phenomena beyond the standard model are predicted. In particular, the presence of LV highly affects the propagation of astrophysical photons with very high energies from distant galaxies. In this paper, we review the updating theoretical and experimental results on this topic. We classify the effects into three categories: (i) time lags between photons with different energies; (ii) a cutoff of photon flux above the threshold energy of photon decay, γ→e++e-; (iii) new patterns in the spectra of multi-TeV photons and EeV photons, due to the absorption of background lights. As we can see, the details of LV effects on astrophysical photons depend heavily on the "phase space" of LV parameters. From observational aspects, available and upcoming instruments can study these phenomena hopefully, and shed light onto LV issues and QG theories. The most recent progresses and constraints on the ultra-high energy cosmic rays (UHECRs) are also discussed. © 2010 World Scientific Publishing Company.


Chen W.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We study the possible charmoniumlike states with JPC=0-, 0 -+ using the tetraquark interpolating currents with the QCD sum rules approach. The extracted masses are around 4.5 GeV for the 0 - charmoniumlike states and 4.6 GeV for the 0-+ charmoniumlike states, while their bottomoniumlike analogues lie around 10.6 GeV. We also discuss the possible decay, production, and experimental search of the 0- charmoniumlike state. © 2010 The American Physical Society.


Chen B.,Peking University | Long J.,Beijing University of Technology | Zhang J.-J.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We study the hidden conformal symmetry of extremal black holes. We introduce a new set of conformal coordinates to write the SL(2,R) generators. We find that the Laplacian of the scalar field in many extremal black holes, including Kerr(-Newman), Reissner-Nordstrom, warped AdS3, and null warped black holes, could be written in terms of the SL(2,R) quadratic Casimir. This suggests that there exist dual conformal field theory (CFT) descriptions of these black holes. From the conformal coordinates, the temperatures of the dual CFTs could be read directly. For the extremal black hole, the Hawking temperature is vanishing. Correspondingly, only the left (right) temperature of the dual CFT is nonvanishing, and the excitations of the other sector are suppressed. In the probe limit, we compute the scattering amplitudes of the scalar off the extremal black holes and find perfect agreement with the CFT prediction. © 2010 The American Physical Society.


Chen W.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

After constructing all the tetraquark interpolating currents with JPC=1-+, 1-, 1++ and 1 +- in a systematic way, we investigate the two-point correlation functions to extract the masses of the charmoniumlike states with QCD sum rule. For the 1- qcq̄c̄ charmoniumlike state, mX=4.6∼4.7GeV, which implies a possible tetraquark interpretation for the state Y(4660). The masses for both the 1++ qcq̄c̄ and scs̄c̄ charmoniumlike states are around 4.0∼4.2GeV, which are slightly above the mass of X(3872). For the 1-+ and 1 +- qcq̄c̄ charmoniumlike states, the extracted masses are around 4.5∼4.7GeV and 4.0∼4.2GeV, respectively. As a by-product, the bottomoniumlike states are also studied. We also discuss the possible decay modes and experimental search of the charmoniumlike states. © 2011 American Physical Society.


Qin N.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Recent works show that the original Kobayashi-Maskawa (KM) form of fermion mixing matrix exhibits some advantages, especially when discussing problems such as unitarity boomerangs and maximal CP violation hypothesis. Therefore, the KM form of fermion mixing matrix is systematically studied in this paper. Starting with a general triminimal expansion of the KM matrix, we discuss the triminimal and Wolfenstein-like parametrizations with different basis matrices in detail. The quark-lepton complementarity relations play an important role in our discussions on describing quark mixing and lepton mixing in a unified way. © 2011 American Physical Society.


She J.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We reexamine our previous calculation on the Collins effect in the semi-inclusive deeply inelastic scattering process with a He3 target, and find that our previous treatment on the dilution factors may cause the results to be larger than the realistic situation. We thus modify our calculation in an improved treatment with an updated prediction on the sin(h+ S) asymmetry for the JLab 12 GeV under the transverse momentum dependent factorization framework. Meanwhile, we also provide the prediction of such asymmetry for the JLab 6 GeV and the prediction of the sin(3 h-S) asymmetry related to pretzelosity. © 2011 American Physical Society.


Ma Y.-Q.,Beijing University of Technology | Wang K.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

To clarify the outstanding problem in charmonium production that existing theories cannot explain the observed cross sections of χcJ(J=0,1, 2) and ratio Rχc= σχc2/σχc1∼0.75 (in contrast to the spin counting value 5/3) at the Tevatron, we study the complete next-to-leading order radiative corrections in nonrelativistic QCD, and find next-to-leading order contributions of PJ[1]3 are more important than leading order at high pT, and P1[1]3 decreases slower than P2[1]3, implying a natural explanation for the Rχc puzzle. By fitting R χc, the predicted cross sections of χcJ are found to agree with data. The result indicates color-octet contribution is crucially needed, thus providing a unique test for heavy quarkonium production mechanisms. Feed-down contributions of χcJ to prompt J/ψ production are estimated to be substantial, about 30%-40% at pT=20GeV. Production of χcJ(J=0,1,2) at the LHC is also predicted. © 2011 American Physical Society.


Feng R.,Peking University | Liu K.,Peking University | Liu K.,Beijing University of Technology
Physica B: Condensed Matter | Year: 2012

The mechanism for the shift of the band-gap in two kinds of finite phononic crystals (PCs) (steel/epoxy and aluminum/epoxy) with different initial stresses is studied experimentally and theoretically. The experimental results and theoretical analysis simultaneously indicate that the initial stress will efficiently tune the location and width of the band-gap. The current work provides a basis for tuning the band-gap of phononic crystals in engineering applications. © 2012 Elsevier B.V. All rights reserved.


Li Q.,Paul Scherrer Institute | Spira M.,Paul Scherrer Institute | Gao J.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Higgs bosons can be produced copiously at the LHC via gluon fusion induced by top and bottom quark loops, and can be enhanced strongly if extra heavy quarks exist. We present results for Higgs+zero-, one- and two-jet production at the LHC operating at 7 and 14TeV collision energy, in both the standard model and the 4th generation model, by evaluating the corresponding heavy quark triangle, box, and pentagon Feynman diagrams. We compare the results by using the effective Higgs-gluon interactions in the limit of heavy quarks with the cross sections including the full mass dependences. NLO effects on Higgs+zero-jet production rate with full mass dependence are presented for the first time consistently in the 4th generation model. Our results improve the theoretical basis for fourth generation effects on the Higgs boson search at the LHC. © 2011 American Physical Society.


Wang K.,Beijing University of Technology | Ma Y.-Q.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We analytically calculate the cross sections of double charmonium production in e+e-→J/ψ(ψ(2S)) χcJ (J=0, 1, 2) at next-to-leading order (NLO) in αs in nonrelativistic QCD, and confirm factorization of these processes. In contrast to χc0 production, for which the NLO correction is large and positive, the NLO corrections for χc1,2 production can be negative, resulting in decreased K factors of 0.91 and 0.78 for J=1 and 2, respectively, when μ=2mc. Consequently, the NLO QCD corrections markedly enlarge the difference between cross sections of χc0 and χc1,2. This may explain why e +e-→J/ψ(ψ(2S))χc0 but not e+e-→J/ψ(ψ(2S))χc1,2 is observed experimentally. Moreover, for J/ψ(ψ(2S))χc1,2, the NLO QCD corrections substantially reduce the μ dependence and lead to predictions with small theoretical uncertainties. © 2011 American Physical Society.


Peng T.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

The tetramixing of pseudoscalar mesons π-η-η′- ηc and vector mesons ω-ρ- -J/ψ are studied in the light-cone constituent quark model, and such mixing of four mesons provides a natural source for the intrinsic charm cc̄ components of light mesons. By mixing with the light mesons, the charmonium states J/ψ and ηc could decay into light mesons more naturally, without introducing gluons or a virtual photon as intermediate states. Thus, the introduction of light quark components into J/ψ is helpful to reproduce the new experimental data of J/ψ decays. The mixing matrices and the Q2 behaviors of the transition form factors are also calculated and compared with experimental data. © 2011 American Physical Society.


Guo H.-K.,Beijing University of Technology | Ma Y.-Q.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We study O(αsv2) corrections to decays of S01 heavy quarkonium into light hadrons and two photons within the framework of nonrelativistic QCD and find these O(αsv2) corrections to have significant contributions especially for the decay into light hadrons. With these new results, experimental measurements of the hadronic width and the γγ width of ηc can be described more consistently. By fitting experimental data, we find the long-distance matrix elements of ηc to be |Rηc(0)|2=0.834-0.197+0.281GeV3 and v2ηc=0.232-0.098+0.121. Moreover, ηc(2S) is also discussed and the γγ decay width is predicted to be 3.34-2.10+2.06KeV. © 2011 American Physical Society.


Ma Y.-Q.,Beijing University of Technology | Wang K.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

A complete next-to-leading-order calculation in α s for the J/ψ and ψ ′ prompt production at the Tevatron, LHC, and RHIC in nonrelativistic QCD is presented. We argue that the next-to-next-to-leading-order color-singlet contribution may not be so important as to resolve the large discrepancy between theory and experiment in J/ψ large p T production cross sections. Therefore, a complete next-to-leading-order calculation, including both color-singlet and color-octet contribution, is necessary and essential to give a good description for J/ψ and ψ ′ production. We also study the methods to fit the long-distance matrix elements using either two linear combined matrix elements or three matrix elements, and find these two methods can give consistent results. Compared with the measurements at the LHC and RHIC for prompt J/ψ and ψ ′ production, our predictions are found to agree with all data. In particular, the recently released large p T data (up to 60-70 GeV) at the LHC are in good agreement with our predictions. Our results imply that the universality of color-octet matrix elements holds approximately in charmonium hadroproduction, when one uses fixed-order perturbative calculation to describe data (the data in small p T region are not included). Our work may provide a new test for the universality of color-octet matrix elements, and the color-octet mechanism in general. © 2011 American Physical Society.


Peng J.,Beijing Normal University | Zhao P.W.,Kyoto University | Zhao P.W.,Beijing University of Technology
Physical Review C - Nuclear Physics | Year: 2015

The self-consistent tilted axis cranking relativistic mean-field (TAC-RMF) theory based on a point-coupling interaction is applied to investigate the observed magnetic and antimagnetic rotations in the nucleus Cd110. The energy spectra, the relation between the spin and the rotational frequency, the deformation parameters, and the reduced M1 and E2 transition probabilities are studied with the various configurations. It is found that the configuration has to be changed to reproduce the energy spectra and the relations between the spin and the rotational frequency for both the magnetic and antimagnetic rotational bands. The shears mechanism for the magnetic rotation and the two-shears-like mechanism for the antimagnetic rotation are examined by investigating the orientation of the neutron and proton angular momenta. The calculated electromagnetic transitions B(M1) and B(E2) are in reasonable agreement with the data, and their tendencies are coincident with the typical characteristics of the magnetic and antimagnetic rotations. © 2015 American Physical Society.


Zhang Y.-J.,Beijing University of Technology | Zhang Y.-J.,CAS Institute of Theoretical Physics | Ma Y.-Q.,Beijing University of Technology | Wang K.,Beijing University of Technology | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

In nonrelativistic quantum chromodynamics (NRQCD), we study the next-to-leading order (NLO) QCD radiative correction to the color-octet J/ψ inclusive production at B1/2 factories. Compared with the leading-order (LO) result, the NLO QCD corrections are found to enhance the short-distance coefficients in the color-octet J/ψ production e+e -→cc̄(S0(8)1orPJ(8)3)g (with J=0, 1, 2) by a factor of about 1.9. Moreover, the peak at the end point in the J/ψ energy distribution predicted at LO can be smeared by the NLO corrections, but the major color-octet contribution still comes from the large energy region of J/ψ. By fitting the latest data of σ(e+e -→J/ψ+Xnon-cc̄) observed by Belle, we find that the values of color-octet matrix elements are much smaller than expected earlier by using the naive velocity scaling rules or extracted from fitting experimental data with LO calculations. As the most stringent constraint by setting the color-singlet contribution to be zero in e+e-→J/ ψ+Xnon-cc̄, we get an upper limit of the color-octet matrix element, 0|OJ/ψ[S0(8)1]|0+4.0 0|OJ/ψ[P0(8)3]|0 /mc2<(2.0±0.6)×10-2GeV3 at NLO in αs. © 2010 The American Physical Society.


Zhu J.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We show that the polarized proton-antiproton Drell-Yan process is ideal to probe the pretzelosity distribution (h1T?), which is one of the new transverse-momentum-dependent parton distributions of the nucleon. We present predictions of the cos(2π+π a-π b) asymmetry in the transversely polarized proton-antiproton Drell-Yan process at PAX kinematics and find that the results are significantly larger compared with those of the sin(3π h-π S) asymmetry in the semi-inclusive deep inelastic scattering process at HERMES, COMPASS, and JLab kinematics. We conclude that the cos(2π+π a-π b) asymmetry in the PAX experiment can probe the new physical quantity of the pretzelosity distribution. © 2010 The American Physical Society.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Zhang J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

Rényi entanglement entropy provides a new window to study the AdS/CFT correspondence. In this paper we consider the short interval expansion of Rényi entanglement entropy in two-dimensional conformal field theory. This amounts to do the operator product expansion of the twist operators. We focus on the vacuum Verma module and consider the quasiprimary operators constructed from the stress tensors. After obtaining the expansion coefficients of the twist operators to level 6 in vacuum Verma module, we compute the leading contributions to the Rényi entropy, to order 6 in the short interval expansion. In the case of one short interval on cylinder, we reproduce the first several leading contributions to the Rényi entropy. In the case of two short disjoint intervals with a small cross ratio x, we obtain not only the classical and 1-loop quantum contributions to the Rényi entropy to order x6, both of which are in perfect match with the ones found in gravity, but also the leading 1/c contributions, which corresponds to 2-loop corrections in the bulk. © SISSA 2013.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Zhang J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

Recent studies suggest that in the Kerr/CFT correspondence, much universal information of the dual CFT, including the central charges and the temperatures, is fully encoded in the thermodynamics of the outer and inner horizons of the Kerr(-Newman) black holes. In this paper, we study holographic descriptions of Reissner-Nordström (RN) black holes in arbitrary dimensions by using the thermodynamics method.We refine the thermodynamics method proposed in [20] by imposing the "quantization" condition so that we can fix the ambiguity in determining the central charges of the dual CFT of RN black holes. Using the refined thermodynamics method, we find the holographic CFT duals for the RN black holes, and confirm these pictures by using conventional analysis of asymptotic symmetry group and the hidden conformal symmetry in the low-frequency scattering. In particular, we revisit the four-dimensional dyonic RN black hole and find a novel magnetic picture, besides the known electric CFT dual picture. We show how to generate a class of dual dyonic pictures by SL(2, Z) transformations. © 2013 SISSA, Trieste, Italy.


Chao W.,Peking University | Zheng Y.-J.,Shandong University | Zheng Y.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

Inspired by the indication of a relatively large θ 13 from accelerator and reactor neutrino oscillation experiments, we provide a systematic study of general modifications to the three well-studied neutrino mixing patterns, i.e., tri-bimaximal, bimaximal and democratic lepton mixing matrices. The correlation between θ 13 and the other two neutrino mixing angles are derived for each types of additional rotations. Predictions on θ 12 and θ 23 are also studied. Our study shows that, although some types of additional rotations are already excluded by the current global fit data of neutrino mixing angles, several types of additional rotations still survive. Our results may provide a guideline for the model building in neutrino physics. © 2013 SISSA, Trieste, Italy.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Xue Z.,Beijing University of Technology | Zhang J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

In the paper we further refine the thermodynamics method of black hole/CFT correspondence. We show that one can derive the central charges of different holographic pictures directly from the entropy product S + S - if it is mass-independent, for a black hole in the Einstein gravity or the gravity without diffeomorphism anomaly. For a general black hole in the Einstein gravity that admits holographic descriptions, we show that the thermodynamics method and asymptotic symmetry group (ASG) analysis can always give consistent results in the extreme limit. Furthermore, we discuss the relation between black hole thermodynamics and the hidden conformal symmetry. We show that the condition T + A + = T - A -, with A ± being the outer and inner horizon areas, is the necessary, but not sufficient, condition for a black hole to have the hidden conformal symmetry. In particular, for the Einstein(-Maxwell) gravity T + A + = T - A - is just the condition T + S+ = T- S -, with S ± being the outer and inner horizon entropies, which is the condition for the entropy product S + S - being mass-dependent. When there exists the hidden conformal symmetry in the low-frequency scattering off the generic non-extremal black hole, it always leads to the same temperatures of dual CFT as the ones got from the thermodynamics method. © 2013 SISSA, Trieste, Italy.


Chen B.,Peking University | Chen B.,Beijing University of Technology | Long J.,Peking University | Long J.,Beijing University of Technology | Wang Y.-N.,Peking University
Journal of High Energy Physics | Year: 2013

In this paper, we investigate the phase structure of the black holes with one single higher spin hair, focusing specifically on the spin 3 and spin 4 black holes. Based on dimensional analysis and the requirement of thermodynamic consistency, we derive a universal formula relating the entropy with the conserved charges for arbitrary AdS 3 higher spin black holes. Then we use it to study the phase structure of the higher spin black holes. We find that there are six branches of solutions in the spin 3 gravity, eight branches of solutions in the spin 4 gravity and twelve branches of solutions in the G 2 gravity. In each case, all the branches are related by a simple angle shift in the entropy functions. In the spin 3 case, we reproduce all the results found before. In the spin 4 case, we find that at low temperature it lies in the BTZ branch while at high temperature it undergoes a phase transition to one of the two other branches, depending on the signature of the chemical potential, a reflection of charge conjugate asymmetry found before. © 2013 SISSA, Trieste, Italy.


Zhao X.-Y.,Beijing University of Technology | Sun D.,National University of Singapore | Toh K.-C.,National University of Singapore
SIAM Journal on Optimization | Year: 2010

We consider a Newton-CG augmented Lagrangian method for solving semidefinite programming (SDP) problems from the perspective of approximate semismooth Newton methods. In order to analyze the rate of convergence of our proposed method, we characterize the Lipschitz continuity of the corresponding solution mapping at the origin. For the inner problems, we show that the positive definiteness of the generalized Hessian of the objective function in these inner problems, a key property for ensuring the efficiency of using an inexact semismooth Newton-CG method to solve the inner problems, is equivalent to the constraint nondegeneracy of the corresponding dual problems. Numerical experiments on a variety of large-scale SDP problems with the matrix dimension n up to 4, 110 and the number of equality constraints m up to 2, 156, 544 show that the proposed method is very efficient. We are also able to solve the SDP problem fap36 (with n = 4, 110 and m = 1, 154, 467) in the Seventh DIMACS Implementation Challenge much more accurately than in previous attempts. Copyright © 2010, Society for Industrial and Applied Mathematics.


Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University | Ma Y.-Q.,Beijing University of Technology | Ma Y.-Q.,Brookhaven National Laboratory | And 3 more authors.
Physical Review Letters | Year: 2012

With nonrelativistic QCD factorization, we present a full next-to-leading order computation of the polarization observable for J/ψ production at hadron colliders including all important Fock states, i.e., S1[1,8]3, S0[8]1, and PJ[8]3. We find the PJ[8]3 channel contributes a positive longitudinal component and a negative transverse component, so the J/ψ polarization puzzle may be understood as the transverse components canceling between the S1[8]3 and PJ[8]3 channels, which results in mainly the unpolarized (even slightly longitudinally polarized) J/ψ. This may give a possible solution to the long-standing J/ψ polarization puzzle. Predictions for J/ψ polarization at the LHC are also presented. © 2012 American Physical Society.


Liang H.,Beijing University of Technology | Zhao P.,Beijing University of Technology | Meng J.,Beijing University of Technology | Meng J.,Beihang University | Meng J.,Stellenbosch University
Physical Review C - Nuclear Physics | Year: 2012

The charge-exchange spin-dipole (SD) excitations for both (p,n) and (n,p) channels in 16O are investigated in the fully self-consistent random phase approximation based on the covariant density functional theory. The fine structure of SD excitations in the most up-to-date 16O(p,n)16F experiment is excellently reproduced without any readjustment in the functional. The SD excitations are characterized by the delicate balance between the σ- and ω-meson fields via the exchange terms. The fine structure of SD excitations for the 16O(n,p)16N channel is predicted for future experiments. © 2012 American Physical Society.


Cao Q.-H.,Beijing University of Technology | Cao Q.-H.,Peking University | Yan B.,Beijing University of Technology | Zhang D.-M.,Beijing University of Technology | Zhang H.,University of California at Santa Barbara
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

The Higgs boson production can be affected by several anomalous couplings, e.g. ct and cg anomalous couplings. Precise measurement of gg→h production yields two degenerate parameter spaces of ct and cg; one parameter space exhibits the SM limit while the other does not. Such a degeneracy could be resolved by Higgs boson pair production. In this work we adapt the strategy suggested by the ATLAS collaboration to explore the potential of distinguishing the degeneracy at the 14 TeV LHC. If the ct anomalous coupling is induced only by the operator H†HQ-LH~tR, then the non-SM-like band could be excluded with an integrated luminosity of ~210 fb-1. Making use of the fact that the Higgs boson pair is mainly produced through an s-wave scattering, we propose an analytical function to describe the fraction of signal events surviving a series of experimental cuts for a given invariant mass of Higgs boson pair. The function is model independent and can be applied to estimate the discovery potential of various NP models. © 2015 The Authors.


Vretenar D.,University of Zagreb | Niu Y.F.,University of Zagreb | Niu Y.F.,Beijing University of Technology | Paar N.,University of Zagreb | And 3 more authors.
Physical Review C - Nuclear Physics | Year: 2012

The self-consistent random-phase approximation, based on the framework of relativistic energy density functionals, is employed in the study of isovector and isoscalar dipole response in 68Ni,132Sn, and 208Pb. The evolution of pygmy dipole states (PDSs) in the region of low excitation energies is analyzed as a function of the density dependence of the symmetry energy for a set of relativistic effective interactions. The occurrence of PDSs is predicted in the response to both the isovector and the isoscalar dipole operators, and its strength is enhanced with the increase in the symmetry energy at saturation and the slope of the symmetry energy. In both channels, the PDS exhausts a relatively small fraction of the energy-weighted sum rule but a much larger percentage of the inverse energy-weighted sum rule. For the isovector dipole operator, the reduced transition probability B(E1) of the PDSs is generally small because of pronounced cancellation of neutron and proton partial contributions. The isoscalar-reduced transition amplitude is predominantly determined by neutron particle-hole configurations, most of which add coherently, and this results in a collective response of the PDSs to the isoscalar dipole operator. © 2012 American Physical Society.


Li F.X.,Peking University | Li F.X.,Beijing University of Technology | Zhou X.L.,Peking University | Soh A.K.,University of Hong Kong
Applied Physics Letters | Year: 2010

An optimization-based computational model is proposed to study domain evolution in polycrystalline ferroelectrics composed of numerous grains, each of which consists of multiple domains. Domain switching is realized by an optimization process to minimize the free energy of each grain. Similar to phase field modeling, no priori domain-switching criterion is imposed in the proposed model. Moreover, by focusing on the volume fractions of domains only, the computational complexity of this model becomes much smaller and the domain textures evolution can be captured. Simulation results on both tetragonal and rhombohedral lead titanate zirconate ceramics illustrate the efficiency of this model. © 2010 American Institute of Physics.


Shao D.Y.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Li H.T.,Beijing University of Technology | Wang J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

We investigate the resummation effects in the Standard Model Higgs boson pair production through gluon-gluon fusion at the LHC with soft-collinear effective theory. We calculate the total cross section and the invariant mass distribution at Next-to-Next-to-Leading-Logarithmic level with π 2-enhanced terms resummed, which are matched to the QCD Next-to-Leading Order results. In the high order QCD predictions exact top quark mass effects are included in full form factors. Our results show that the resummation effects increase the Next-to-Leading Order results by about 20% ~ 30%, and the scale uncertainty is reduced to 8%, which leads to increased confidence on the theoretical predictions. The PDF+α s uncertainties are almost not changed after including resummation effects. We also study the sensitivities of the total cross section and the invariant mass distribution to the Higgs boson self-coupling. We find that the total cross section and the invariant mass distribution shape depend strongly on the Higgs boson self-coupling, and therefore it is possible to extract Higgs boson self-coupling from the total cross section and invariant mass distribution when the measurement precision increases at the LHC. © 2013 SISSA, Trieste, Italy.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Zhang J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

The recently proposed gravitational entropy generalize the usual black hole entropy to Euclidean solutions without U(1) symmetry in the framework of Einstein gravity. The entropy of such smooth configuration is given by the area of minimal surface, therefore explaining the Ryu-Takayanagi formula of holographic entanglement entropy. In this note we investigate the generalized gravitational entropy for general Lovelock gravity in arbitrary dimensions. We use the replica trick and consider the Euclidean bulk spacetime with conical singularity localized at a codimension two surface. We obtain a constraint equation for the surface by requiring the bulk equation of motion to be of good behavior. When the bulk spacetime is maximally symmetric, the constraints show that the traces of the extrinsic curvatures of the surface are vanishing, i.e. the surface has to be geometrically a minimal surface. However the constraint equation cannot be obtained by the variation of the known functional for holographic entanglement entropy in Lovelock gravity. © 2013 SISSA, Trieste, Italy.


Ferroglia A.,New York City College of Technology | Pecjak B.D.,Durham University | Yang L.L.,Beijing University of Technology | Yang L.L.,Peking University
Journal of High Energy Physics | Year: 2013

We obtain a soft plus virtual approximation to the NNLO QCD contributions to the top-pair invariant mass distribution at hadron colliders. It is valid up to corrections of order mt 2/M2, with M the pair invariant mass. This is currently the most complete QCD calculation for a differential cross section in top-quark pair production, and is useful for describing the high invariant mass region characteristic of boosted top quarks. We use our results to construct an improved NNLO approximation for the pair invariant mass distribution and compare it with previous, less complete approximations based on logarithmic terms from NNLL soft-gluon resummation alone. We find that the new NNLO approximation produces moderate enhancements of the differential cross section compared to previous ones, the effect being slightly more important at low values of invariant mass than at high ones. On the other hand, at high values of invariant mass the new NNLO corrections are dominated by even higher-order effects included in NNLL soft-gluon resummation, reaffirming the need for resummation in describing the highly boosted regime. © 2013 SISSA, Trieste, Italy.


Wang Z.,Beijing University of Technology | Guo Q.,Beijing University of Technology
Radiocarbon | Year: 2012

Specific activities of radiocarbon in annual tree rings corresponding to 1980-2009 are reported for a pine tree located 2 km from the Qinshan Nuclear Power Plant (Qinshan NPP), China. While a negligible enhanced 14C activity due to operation of the Qinshan NPP Plant I is evident, a relative increase (1.8-62.6 Bq/kg C) was observed in the specific activity after operation of the Qinshan NPP Plant II in 2002 and Plant III in 2003. The enhanced values were primarily affected by the 14C discharged from Plant III (CANDU-type reactor), and a good correlation was found between the 14C discharged from Plant III in the growing season and the 14C excess value. The excess 14C activities peaked in 2005 (at 302.0 Bq/kg C, which is 62.6 Bq/kg C above the "clean air" 14C level), and then declined due to the improvement in 14C discharge management of Plant III. In 2009, the 14C-specific activity was near the background level.


Zhou J.,Peking University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology
Nanoscale | Year: 2014

A two-dimensional sheet with long range ferromagnetic (FM) order has been hotly pursued currently. The recent success in synthesizing polymerized Fe-phthalocyanine (poly-FePc) porous sheets paves a possible way to achieve this goal. However, the poly-FePc and its analog poly-CrPc structure are intrinsically antiferromagnetic (AFM). Using first principles combined with Monte-Carlo simulations, we study systematically the carrier-induced magnetic coupling transitions in poly-CrPc and poly-FePc sheets. We show that electron doping can induce stable FM states with Curie temperatures of 130-140 K, while hole doping will enhance the stability of the AFM states. Such changes in magnetic couplings depend on the balance of AFM superexchange and FM p-d exchange. © 2014 The Royal Society of Chemistry.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Long J.,Beijing University of Technology | Wu J.-B.,CAS Institute of High Energy Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

In this Letter, we study the spin-3 topologically massive gravity (TMG), paying special attention to its properties at the chiral point. We propose an action describing the higher spin fields coupled to TMG. We discuss the traceless spin-3 fluctuations around the AdS3 vacuum and find that there is an extra local massive mode, besides the left-moving and right-moving boundary massless modes. At the chiral point, such extra mode becomes massless and degenerates with the left-moving mode. We show that at the chiral point the only degrees of freedom in the theory are the boundary right-moving graviton and spin-3 field. We conjecture that spin-3 chiral gravity with generalized Brown-Henneaux boundary condition is holographically dual to 2D chiral CFT with classical W3 algebra and central charge cR=3l/G. © 2011 Elsevier B.V.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Chen B.,CAS Institute of Theoretical Physics | Zhang J.-J.,Beijing University of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

In this Letter, we construct the quasi-normal modes of three-dimensional extremal black holes in an algebraic way. We show that the infinite towers of the quasi-normal modes of scalar, vector and tensor could be constructed as the descendents of the highest weight modes. Our investigation shows that the hidden conformal symmetry suggested in Chen et al. (2010) [5] is an intrinsic property of the extremal black hole. Moreover, we notice that we need to fix the freedom in defining the local vector fields and find the right hidden conformal symmetry to obtain the physical quasi-normal modes. © 2011 Elsevier B.V.


Qin N.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We propose a new relation between quark mixing matrix and lepton mixing matrix. Since the parameters in the quark sector are well determined, we employ them to describe the mixing of leptons. Phenomenologically, we study the neutrino oscillation probabilities for different channels, which can be measured precisely in forthcoming reactor and accelerator experiments. As an example of the applicability of our assumption, CP violation in the lepton sector is also discussed. In the latest T2K experiment, the range of the mixing angle θ13 is measured, and our prediction of θ13 is compatible with their result. © 2011 Elsevier B.V.


Chen N.,Anhui University of Science and Technology | Li J.,University of Adelaide | Liu Y.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We study the LHC searches for the heavy CP-odd Higgs boson A and CP-even Higgs boson H in the context of a general two-Higgs-doublet model. Specifically, we consider the decay mode of A/H→tt through the tt associated production channels. In the so-called "alignment limit" of the two-Higgs-doublet model, this decay mode can be the most dominant one. By employing the HEPTopTagger and the multivariate analysis method, we present the search sensitivities for both CP-odd Higgs boson A and CP-even Higgs boson H via this channel with multiple top quarks at the high-luminosity LHC runs. © 2016 American Physical Society.


Wang Z.,Beijing University of Technology | Guo Q.,Beijing University of Technology
Radiocarbon | Year: 2013

We used accelerator mass spectrometry (AMS) to study radiocarbon-specific activity levels in agricultural and botanical samples (moss and pine needles) distributed within a 6.5-km radius of the Qinshan Nuclear Power Plant (NPP). The 14C-specific activity in moss samples (ranging from 265.6 to 223.0 Bq/kg C) decreased with increased distance from the stacks of Plant III (heavy water reactor) and reached the background level (223.8 Bq/kg C) at 6.5 km distance. Compared to the pine needles, the moss was a better indicator for investigating the 14C distribution near Qinshan NPP. The 14C-specific activity distribution in moss samples showed that the diffusion of 14C discharged from the Qinshan NPP was affected by both geographical and meteorological factors. Excess 14C-specific activity in the food samples ranged from 8.5 to 13.0 Bq/kg C (except for rice samples), resulting in a minimal radiation dose of 0.5 μSv per year to the public. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.


Cao Q.-H.,Beijing University of Technology | Cao Q.-H.,Peking University | Liu Y.,Beijing University of Technology | Xie K.-P.,Beijing University of Technology | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We interpret the diphoton anomaly as a heavy scalar H3 in the so-called 331 model. The scalar is responsible for breaking the SU(3)C - SU(3)L - U(1)X gauge symmetry down to the standard model electroweak gauge group. It mainly couples to the standard model gluons and photons through quantum loops involving heavy quarks and leptons. Those quarks and leptons, together with the SM quarks and leptons, form the fundamental representation of the 331 model. We use the low energy theorem to calculate the effective couplings of H3gg, H3γγ, H3ZZ, H3WW and H3Zγ. The analytical results can be applied to new physics models satisfying the low energy theorem. We show that the heavy quark and lepton contribution cannot produce enough diphoton pairs. It is crucial to include the contribution of charged scalars to explain the diphoton excess. The extra neutral Z′ boson could also explain the 2 TeV diboson excess observed at the LHC Run-I. © 2016 American Physical Society.


Liu Y.-R.,Shandong University | Liu X.,Lanzhou University | Zhu S.-L.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

Stimulated by the recent observation of the X(5568), we study the X(5568) and its partners under the tetraquark scenario. In the framework of the color-magnetic interaction, we estimate the masses of the partner states of the X(5568) and discuss their decay pattern, which provides valuable information on the future experimental search of these states. © 2016 American Physical Society.


Qin N.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Although different parametrizations of quark mixing matrix are mathematically equivalent, the consequences of experimental analysis may be distinct. Based on the triminimal expansion of Kobayashi-Maskawa matrix around the unit matrix, we propose a new simple parametrization. Compared with the Wolfenstein parametrization, we find that the new form is not only consistent with the original one in the hierarchical structure, but also more convenient for numerical analysis and measurement of the CP-violating phase. By discussing the relation between our new form and the unitarity boomerang, we point out that along with the unitarity boomerang, this new parametrization is useful in hunting for new physics. © 2010 Elsevier B.V.


Zhu J.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We calculate g1T and h1L ⊥, two of the eight leading twist transverse momentum dependent parton distributions (TMDs), in the light-cone quark-diquark model. The new TMDs can be measured through semi-inclusive deep inelastic scattering (SIDIS). We present predictions of the single and double spin asymmetries related to g1T and h1L ⊥ in SIDIS at HERMES, COMPASS, and JLab kinematics respectively. © 2010 Elsevier B.V.


Ma Y.-Q.,Beijing University of Technology | Wang K.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review Letters | Year: 2011

We present a complete evaluation for J/ψ(ψ′) prompt production at the Tevatron and LHC at next-to-leading order in nonrelativistic QCD, including color-singlet, color-octet, and higher charmonia feeddown contributions. The short-distance coefficients of PJ[8]3 at next-to-leading order are found to be larger than leading order by more than an order of magnitude but with a minus sign at high transverse momentum pT. Two new linear combinations of color-octet matrix elements are obtained from the CDF data, and used to predict J/ψ production at the LHC, which agrees with the CMS data. The possibility of S0[8]1 dominance and the J/ψ polarization puzzle are also discussed. © 2011 American Physical Society.


Shao H.-S.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Based on a general form of the effective vertex functions for the decays of P-wave charmonia χcJ, angular distribution formulas for the subsequent decays χcJ→J/ψγ and J/ψ→μ+μ- are derived. The formulas are the same as those obtained in a different approach in the literature. Our formulas are expressed in a more general form, including parity violation effects and the full angular dependence of J/ψ and muon in the cascade decay χcJ→J/ψγ→μ+μ-γ. The χcJ polarization observables are expressed in terms of rational functions of the spin density matrix elements of χcJ production. Generalized rotation-invariant relations for arbitrary integer-spin particles are also derived and their expressions in terms of observable angular distribution parameters are given in the χc1 and χc2. To complement our previous direct-J/ψ polarization result, we also discuss the impact on the observable prompt-J/ψ polarization. As an illustrative application of our angular distribution formulas, we present the angular distributions in terms of the tree-level spin density matrix elements of χc1 and χc2 production in several different frames at the Large Hadron Collider. Moreover, a reweighting method is also proposed to determine the entire set of the production spin density matrix elements of the χc2, some of which disappear or are suppressed for vanishing higher-order multipole effects making the complete extraction difficult experimentally. © 2014 American Physical Society.


Li Q.,Beijing University of Technology | Yan Q.-S.,University of Chinese Academy of Sciences | Yan Q.-S.,Peking University | Zhao X.,University of Chinese Academy of Sciences
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Higgs pair production is crucial for measuring the Higgs boson self-coupling. The dominant channel at hadron colliders is gluon fusion via heavy-quark loops. We present the results of a fully exclusive simulation of gluon fusion Higgs pair production based on the matrix elements for hh+0, 1 partons including full heavy-quark loop dependence, matched to a parton shower. We examine and validate this new description by comparing it with (a) Higgs effective theory predictions, (b) exact hh+0-parton sample showered by Pythia, and (c) exact hh+1-parton distributions, by looking at the most relevant kinematic distributions, such as pTh, pThh, Mhh spectra, and the jet rate as well. We find that matched samples provide a state-of-the-art accurate exclusive description of the final state. © 2014 American Physical Society.


Song H.,Beijing University of Technology
Pramana - Journal of Physics | Year: 2015

In this article, we briefly review recent progress on hydrodynamic modelling and its implementations to relativistic heavy-ion collisions at RHIC and LHC. The related topics include: (1) initial-state fluctuations, final-state correlations and event-by-event hydrodynamics, (2) extracting the QGP shear viscosity from flow data, (3) flow and hydrodynamics in p+Pb collisions at √sNN = 5.02 TeV. © Indian Academy of Sciences.


Zhao X.,Beijing University of Technology | Xia D.,Peking University | Zheng K.,Beijing University of Technology
Journal of Alloys and Compounds | Year: 2012

An Fe 3O 4-FeO-Fe@C composite material has been successfully synthesized by a one-pot hydrothermal method without any templates and a sequential heat treatment process. X-ray diffraction, Raman spectrometry, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy and galvanostatic cell cycling have been used to characterize the structure and electrochemical performance of the as-prepared Fe 3O 4-FeO-Fe@C composite. The electrode shows a stable and reversible capacity of over 600 mAh g -1 at a current of 53 mA g -1 for up to 60 cycles, which could be ascribed to the unique double-layer core-shell and embedded structures. © 2011 Elsevier B.V. All rights reserved.


Sun T.,Peking University | Wang J.,Peking University | Kang W.,Beijing University of Technology
Nanoscale | Year: 2013

Interfaces usually impede heat transfer in heterogeneous structures. Recent experiments show that van der Waals (vdW) interactions can significantly enhance thermal conductivity parallel to the interface of a bundle of nanoribbons compared to a single layer of freestanding nanoribbon. In this paper, by simulating heat transfer in nanostructures based on a model of nonlinear one-dimensional lattices interacting via van der Waals interactions, we show that the vdW interface interaction can adjust the thermal conductivity parallel to the interface. The efficiency of the adjustment depends on the intensity of interactions and temperature. The nonlinear dependence of the conductivity on the intensity of interactions agrees well with experimental results for carbon nanotube bundles, multi-walled carbon nanotubes, multi-layer graphene, and nanoribbons. © 2013 The Royal Society of Chemistry.


Han M.,Beijing University of Technology | Zhang X.-S.,Beijing University of Technology | Meng B.,Beijing University of Technology | Liu W.,Beijing University of Technology | And 5 more authors.
ACS Nano | Year: 2013

Piezoelectric and triboelectric nanogenerators (NGs) have been proposed in the past few years to effectively harvest mechanical energy from the environment. Here, a polydimethylsiloxane (PDMS) layer is placed under the aluminum electrode of polyvinylidene fluoride (PVDF), thus forming an r-shaped hybrid NG. Micro/nanostructures have been fabricated on the PDMS surface and the aluminum electrodes of PVDF to enhance the output performance. Power densities of the piezoelectric part and the triboelectric part are 10.95 and 2.04 mW/cm3, respectively. Moreover, influence of the triboelectric charges on the piezoelectric output voltage is investigated. Both finite element method simulations and experimental measurements are conducted to verify this phenomenon. The novel hybrid NG is also demonstrated as a power source for consumer electronics. Through one cycle of electric generation, 10 light-emitting diodes are lighted up instantaneously, and a 4-bit liquid crystal display can display continuously for more than 15 s. Besides, the device is integrated into a keyboard to harvest energy in the typing process. © 2013 American Chemical Society.


Zhao X.,Beijing University of Technology | Xia D.,Peking University | Zheng K.,Beijing University of Technology
ACS Applied Materials and Interfaces | Year: 2012

A plum pudding-like Fe 3O 4/Fe/carbon composite was synthesized by a sol-gel polymerization followed by a heat-treatment process and characterized by X-ray diffraction, Raman spectroscopic analysis, thermogravimetric analysis, scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and electrochemical test. In this composite, uniform spherical Fe 3O 4/Fe nanoparticles of about 100 nm were embedded into carbon matrix with high monodispersion. As-prepared Fe 3O 4/Fe/carbon composite electrode exhibits a stable and reversible capacity of over 600 mA h g -1 at a current of 50 mA g -1 between 0.002 V and 3.0 V, as well as excellent rate capability. The plum pudding-like structure, in which trace Fe promotes conductivity and carbon matrix mediates the volume change, can enhance the cycling performance and rate capability of Fe 3O 4 electrode. This unique structure is valuable for the preparation of other electrode materials. © 2012 American Chemical Society.


Zhao P.W.,Beijing University of Technology | Peng J.,Beijing Normal University | Liang H.Z.,Beijing University of Technology | Ring P.,Beijing University of Technology | And 4 more authors.
Physical Review Letters | Year: 2011

Covariant density functional theory and the tilted axis cranking method are used to investigate antimagnetic rotation (AMR) in nuclei for the first time in a fully self-consistent and microscopic way. The experimental spectrum as well as the B(E2) values of the recently observed AMR band in Cd105 are reproduced very well. This gives a further strong hint that AMR is realized in specific bands in nuclei. © 2011 American Physical Society.


Liu H.L.,Xi'an Jiaotong University | Walker P.M.,University of Surrey | Xu F.R.,Beijing University of Technology
Physical Review C - Nuclear Physics | Year: 2014

Configuration-constrained potential-energy-surface calculations are performed including β6 deformation to investigate high-K isomeric states in nuclei around 254No and 270Ds, the heaviest nuclei where there have been some observations of two-quasiparticle isomers, while data for four-quasiparticle isomers are scarce. We predict the prevalent occurrence of four-quasiparticle isomeric states in these nuclei, together with their favored configurations. The most notable examples, among others, are Kπ=20+ states in 266,268Ds and 268,270Cn having very high K value, relatively low excitation energy, and well-deformed axially symmetric shape. The predicted isomeric states, with hindered spontaneous fission and α decay, could play a significant role in the future study of superheavy nuclei. © 2014 American Physical Society.


Song H.,Beijing University of Technology | Bass S.A.,Duke University | Heinz U.,Ohio State University
Physical Review C - Nuclear Physics | Year: 2014

Using the vishnu hybrid model that couples (2+1)-dimensional viscous hydrodynamics to a microscopic hadronic transport model, we calculate the multiplicity, pT spectra, and elliptic flow for pions, kaons, and protons in 2.76A TeV Pb+Pb collisions, using mc-kln initializations with smoothed initial conditions, obtained by averaging over a large number of events. The results from our calculations are compared to data from the ALICE Collaboration, showing nice agreement over several centrality bins. Using the same inputs, we predict the pT spectra and elliptic flow for Ï• mesons and explore their flow development in the strong and weak coupling limits through hydrodynamic calculations with different decoupling temperatures. In addition we study the influence of baryon and antibaryon annihilation processes on common observables and demonstrate that, by including annihilation processes below a switching temperature of 165 MeV, vishnu provides a good description of the multiplicity and pT spectra for pions, kaons, and protons measured by PHENIX and ALICE at both the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). © 2014 American Physical Society.


Lv P.,Peking University | Xue Y.,Peking University | Shi Y.,Peking University | Shi Y.,Beijing University of Technology | And 3 more authors.
Physical Review Letters | Year: 2014

Superhydrophobicity on structured surfaces is frequently achieved via the maintenance of liquid-air interfaces adjacent to the trapped air pockets. These interfaces, however, are subject to instabilities due to the Cassie-Baxter-to-Wenzel transition and total wetting. The current work examines in situ liquid-air interfaces on a submerged surface patterned with cylindrical micropores using confocal microscopy. Both the pinned Cassie-Baxter and depinned metastable states are directly observed and measured. The metastable state dynamically evolves, leading to a transition to the Wenzel state. This process is extensively quantified under different ambient pressure conditions, and the data are in good agreement with a diffusion-based model prediction. A similarity law along with a characteristic time scale is derived which governs the lifetime of the air pockets and which can be used to predict the longevity of underwater superhydrophobicity. © 2014 American Physical Society.


Liu T.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review C - Nuclear Physics | Year: 2014

We investigate the generalized form factors of the nucleon in a light-cone spectator-diquark model. Compared to the form factors, the generalized form factors contain some more information of the structure of the nucleon. In our calculation, both the scalar and the axial-vector spectator diquark are taken into account. As a relation between the spin in the instant form and that in the light-cone form, the Melosh-Wigner rotation effect is included for both the quark and the axial-vector diquark. We also provide numerical results from our model calculations, and the results are comparable with those from lattice QCD. © 2014 American Physical Society.


Shao H.-S.,Beijing University of Technology | Ma Y.-Q.,Brookhaven National Laboratory | Wang K.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review Letters | Year: 2014

Prompt χc production at hadron colliders may provide a unique test for the color-octet mechanism in nonrelativistic QCD. We present an analysis for the polarization observables of χc1 and χc2 at next-to-leading order in αS and propose to measure them at the LHC, which is expected to be important for testing the validity of nonrelativistic QCD. © 2014 American Physical Society.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Wu J.-Q.,Beijing University of Technology
Journal of High Energy Physics | Year: 2014

Abstract: In this paper, we calculate the Rényi entropy of one single interval on a circle at finite temperature in 2D CFT. In the low temperature limit, we expand the thermal density matrix level by level in the vacuum Verma module, and calculate the first few leading terms in e−π/T L explicitly. On the other hand, we compute the same Rényi entropy holographically. After considering the dependence of the Rényi entropy on the temperature, we manage to fix the interval-independent constant terms in the classical part of holographic Rényi entropy. We furthermore extend the analysis in [9] to higher orders and find exact agreement between the results from field theory and bulk computations in the large central charge limit. Our work provides another piece of evidence to support holographic computation of Rényi entropy in AdS3/CFT2 correspondence, even with thermal effect. © 2014, The Author(s).


Chen B.,Beijing University of Technology | Chen B.,Peking University | Long J.,Beijing University of Technology | Zhang J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2014

In this paper we investigate the holographic Rényi entropy of two disjoint intervals on complex plane with small cross ratio x for conformal field theory with W symmetry in the ground state, which could be dual to a higher spin AdS3 gravity. We focus on the cases of W 3 and W 4 symmetries. In order to see the nontrivial contributions from the W fields, we calculate the Rényi entropy in the expansion of x to order x 8 in both the gravity and the CFT sides. In the gravity side the classical contributions to the entanglement entropy is still given by the Ryu-Takayanagi area formula under the reasonable assumption, while the 1-loop quantum corrections have to take into account of the contributions not only from massless gravitons, but also from massless higher spin fields. In the CFT side we still use the operator product expansion of twist operators in the small interval limit, but now we need to consider the quasiprimary fields constructed from W fields, besides the ones from Virasoro Verma module. In the large central charge limit, we obtain the classical, 1-loop, 2-loop, and 3-loop parts of the Rényi entropy. The classical and 1-loop results in the gravity and the CFT sides are in exact match. This confirms the higher spin gravity/CFT correspondence, and also supports the holographic computation of Rényi entanglement entropy, including the quantum correction, in both the AdS 3 gravity and the higher spin AdS3 gravity. © 2014 The Author(s).


Shao D.Y.,Beijing University of Technology | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Li H.T.,Beijing University of Technology
Journal of High Energy Physics | Year: 2014

We investigate the resummation effects for the SM Higgs and vector boson associated production at the LHC with a jet veto in soft-collinear effective theory using "collinear anomalous" formalism. We calculate the jet vetoed invariant mass distribution and the cross section for this process at Next-to-Next-to-Leading-Logarithmic level, which are matched to the QCD Next-to-Leading Order results, and compare the differences of the resummation effects with different jet veto pveto Tand jet radius R. Our results show that both resummation enhancement effects and the scale uncertainties decrease with the increasing of jet veto pveto Tand jet radius R, respectively. When pveto T= 25GeV and R = 0.4 (0.5), the resummation effects reduce the scale uncertainties of the Next-to-Leading Order jet vetoed cross sections to about 7% (6%), which lead to increased confidence on the theoretical predictions. Besides, after including resummation effects, the PDF uncertainties of jet vetoed cross section are about 7%. © 2014 The Authors.


Zhao L.,Beijing University of Technology | Deng W.-Z.,Beijing University of Technology | Zhu S.-L.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Experimentally several charged axial-vector hidden-charm states were reported. Within the framework of the color-magnetic interaction, we have systematically considered the mass spectrum of the hidden-charm and hidden-bottom tetraquark states. It is impossible to accommodate all of the three charged states Zc(3900), Zc(4025), and Zc(4200) within the axial-vector tetraquark spectrum simultaneously. Not all of these three states are tetraquark candidates. Moreover, the eigenvector of the chromomagnetic interaction contains valuable information of the decay pattern of the tetraquark states. The dominant decay mode of the lowest axial-vector tetraquark state is J/ψπ while its D∗D¯ and D¯∗D∗ modes are strongly suppressed, which is in contrast with the fact that the dominant decay mode of Zc(3900) and Zc(4025) is D¯D∗ and D¯∗D∗, respectively. We emphasize that all the available experimental information indicates that Zc(4200) is a very promising candidate of the lowest axial-vector hidden-charm tetraquark state. © 2014 American Physical Society.


Zhao L.,Beijing University of Technology | Ma L.,Beijing University of Technology | Zhu S.-L.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

In the framework of the one-boson exchange model, we have calculated the effective potentials between two heavy mesons BB̄* and DD̄* from the t- and u-channel π-, η-, ρ-, ω-, and σ-meson exchanges with four kinds of quantum number: I=0, JPC=1++; I=0, JPC=1+-; I=1, JPC=1++; I=1, JPC=1+-. We keep the recoil corrections to the BB̄* and DD̄* systems up to O(1M2). The spin-orbit force appears at O(1M), which turns out to be important for the very loosely bound molecular states. Our numerical results show that the momentum-related corrections are unfavorable to the formation of the molecular states in the I=0, JPC=1++ and I=1, JPC=1+- channels in the DD̄* system. © 2014 American Physical Society.


Ke W.-Y.,Beijing University of Technology | Liu Y.-X.,Beijing University of Technology | Liu Y.-X.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We study the QCD phases and their transitions in the 2+1 flavor Nambu-Jona-Lasinio model, with a focus on the interface effects such as the interface tension, the interface entropy, and the critical bubble size in the coexistence region of the first-order phase transitions. Our results show that under the thin-wall approximation, the interface contribution to the total entropy density changes its discontinuity scale in the first-order phase transition. However, the entropy density of the dynamical chiral symmetry (DCS) phase is always greater than that of the dynamical chiral symmetry broken (DCSB) phase in both the heating and hadronization processes. To address this entropy puzzle, the thin-wall approximation is evaluated in the present work. We find that the puzzle can be attributed to an overestimate of the critical bubble size at low temperature in the hadronization process. With an improvement on the thin-wall approximation, the entropy puzzle is well solved with the total entropy density of the hadron-DCSB phase exceeding apparently that of the DCS-quark phase at low temperature. © 2014 American Physical Society.


Li Z.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We propose a model for baryons at a finite temperature using AdS/QCD correspondence. In this model, we modify the AdS spacetime into the AdS-Schwarzchild spacetime and consider a couple of bulk spinors in this background. Solving this model, we get an eigenvalue equation for the baryon masses. We then investigate the effects of temperature on the baryon masses numerically and find an interesting temperature dependence. Our result is consistent with the results from lattice QCD and other phenomenological models. © 2014 American Physical Society.


Xu H.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Astroparticle Physics | Year: 2016

The effect of quantum gravity can bring a tiny light speed variation which is detectable through energetic photons propagating from gamma ray bursts (GRBs) to an observer such as the space observatory. Through an analysis of the energetic photon data of the GRBs observed by the Fermi Gamma-ray Space Telescope (FGST), we reveal a surprising regularity of the observed time lags between photons of different energies with respect to the Lorentz violation factor due to the light speed energy dependence. Such regularity suggests a linear form correction of the light speed v(E)=c(1-E/ELV), where E is the photon energy and ELV=(3.60±0.26)×1017GeV is the Lorentz violation scale measured by the energetic photon data of GRBs. The results support an energy dependence of the light speed in cosmological space. © 2016 Elsevier B.V. All rights reserved.


Zhou L.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Astroparticle Physics | Year: 2012

The light speed anisotropy, i.e., the variation of the light speed with respect to the direction in an "absolute" reference frame, is a profound issue in physics. The one-way experiment, performed at the GRAAL facility of the European Synchrotron Radiation Facility (ESRF) in Grenoble, reported results on the light speed anisotropy by Compton scattering of laser photons on high-energy electrons. So far, most articles concerned with the GRAAL data have established only the upper bounds on the anisotropy parameters based on available theories. We use a new theory of the Lorentz invariance violation to analyse the available GRAAL data and obtain the stringent upper limit of the order 2.4×10 -14 on the Lorentz violation parameters. In the meantime, we also can reproduce the allowed light speed anisotropy appearing in the azimuthal distribution of the GRAAL experimental data, and find that the best-fit parameters are compatible with the competitive upper bounds.© 2012 Elsevier B.V. All rights reserved.


Liu T.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case. © 2014 The Authors.


Zhang S.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Astroparticle Physics | Year: 2015

The constancy of light speed is a basic assumption in Einstein's special relativity, and consequently the Lorentz invariance is a fundamental symmetry of space-time in modern physics. However, it is speculated that the speed of light becomes energy-dependent due to the Lorentz invariance violation (LV) in various new physics theories. We analyse the data of the energetic photons from the gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Space Telescope, and find more events to support the energy dependence in the light speed with both linear and quadratic form corrections. We provide two scenarios to understand all the new-released Pass 8 data of bright GRBs by the Fermi-LAT Collaboration, with predictions from such scenarios being testable by future detected GRBs. © 2014 Elsevier B.V. All rights reserved.


Chow C.L.,University of Cambridg | Li J.,Beijing University of Technology
Journal of Civil Engineering and Management | Year: 2010

Static smoke exhaust systems with natural vents are starting to be installed in big shopping complexes, warehouses and cargo terminals in the Far East. These systems are used for natural ventilation as well as for letting out smoke. This paper responds to concerns over the performance of static smoke exhaust systems, which remain less popular than dynamic smoke exhaust systems with mechanical fans. We propose a modification of a simple flow model found in the literature, adapting this to study smoke layer interface height with natural vents opened. We compare and justify our results, as generated by both Computational Fluid Dynamics and zone models, alongside reports of historical field tests. The model of smoke exhaust is applied in an illustrative example of a large hall, leading to the suggestion that a flow model could be used for designing natural vents. As the key driving force in removing smoke through natural vents is smoke's own buoyancy, the system might only be effective for bigger fires.


Hu X.,Beijing University of Technology | Xia D.,Peking University | Zhang L.,National Research Council Canada | Zhang J.,National Research Council Canada
Journal of Power Sources | Year: 2013

High crystallinity binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes (bi-FePc/MWNT), was synthesized. Transmission electron microscopy (TEM) confirms that the crystalline bi-FePc forms a uniform coating on the carbon nanotubes with a thickness of about 20 nm. The plane of the macrocyle is perpendicular to the surface of the nanotube and the stacking axis of the bi-FePc molecules, which is the direction of high electrical conductivity, is found to be parallel to the substrate. The bi-FePc/MWNT show activity of 1.43 mA cm-2 at 0.66 V versus NHE indicating good activity and the current is stable for 14 h as electrocatalyst in oxygen reduction reactions (ORR) indicating good stability; the oxygen reduction current does not change in the presence of methanol showing the binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes specifically catalyzes oxygen reduction and not methanol oxidation. © 2012 Elsevier B.V. All rights reserved.


Chen X.,Beijing University of Technology | Li F.,Beijing University of Technology | Wang X.,Beijing University of Technology | Sun S.,Beijing University of Technology | Xia D.,Peking University
Journal of Physical Chemistry C | Year: 2012

A theoretical study of the oxygen reduction mechanism catalyzed by cobalt-polypyrrole is investigated in detail by means of density functional theory method using the BLYP/DZP basis set. The calculations suggest that the cobalt-polypyrrole has a platinum-like catalytic behavior based on the adsorption energetics of the reaction intermediates. The di-cobalt-polypyrrole catalyst exhibits a higher catalytic activity than that of mono-cobalt- polypyrrole, due to the fact that the PPy chains in di-cobalt-polypyrrole have a regular structure. © 2012 American Chemical Society.


Chen X.,Beijing University of Technology | Sun S.,Beijing University of Technology | Wang X.,Beijing University of Technology | Li F.,Beijing University of Technology | Xia D.,Peking University
Journal of Physical Chemistry C | Year: 2012

A theoretical study on the oxygen reduction mechanism catalyzed by metal-polyaniline is investigated in detail by means of density functional theory. In the oxygen reduction process, we find that-OH, not H 2O 2, is the reaction intermediate. The catalytic activities for the studied models decrease in the sequence CoFe-PANI > Fe-PANI (FeFe-PANI) > Co-PANI. This is due to a synergistic effect between heterogeneous metal atoms in CoFe-PANI, which facilitates additional electron donation from the active sites to the adsorbed oxygen reduction intermediates. The doping with cobalt may also decrease the HOMO-LUMO gap in CoFe-PANI, making it more active. © 2012 American Chemical Society.


Chena B.,Beijing University of Technology | Chena B.,Peking University | Zhanga J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2012

In this paper, we investigate the holographic descriptions of two kinds of black rings, the neutral doubly rotating black ring and the dipole charged black ring. For generic nonextremal black rings, the information of holographic CFT duals, including the central charges and left- and right-moving temperatures, could be read from the thermodynamics at the outer and inner horizons, as suggested in [20]. To confirm these pictures, we study the extreme black rings in the well-established formalism. We compute the central charges of dual CFTs by doing asymptotic symmetry group analysis in the stretched horizon formalism, and find exact agreements. Moreover, we study the superradiant scattering of a scalar field off the near-extremal black rings and obtain the scattering amplitudes, which are in good match with the CFT predictions.© SISSA 2012.


Chen B.,Peking University | Chen B.,Beijing University of Technology | Liu S.,Peking University | Zhang J.-J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2012

In this paper we investigate the thermodynamics of the inner horizon and its implication on the holographic description of the black hole. We focus on the black holes with two physical horizons. Under reasonable assumption, we prove that the first law of thermodynamics of the outer horizon always indicates that of the inner horizon. As a result, the fact that the area product being mass-independent is equivalent to the relation T +S + = T -S -, with T± and S± being the Hawking temperatures and the entropies of the outer and inner horizons respectively. We find that the mass-independence of entropy product breaks down in general Myers-Perry black holes with spacetime dimension d ≥ 6 and Kerr-AdS black holes with d ≥ 4. Moreover we discuss the implication of the first laws of the outer and inner horizons on the thermodynamics of the right- and left-moving sectors of dual CFT in Kerr/CFT correspondence. We show that once the relation T +S + = T -S - is satisfied, the central charges of two sectors must be same. Furthermore from the thermodynamics relations, we read the dimensionless temperatures of microscopic CFT, which are in exact agreement with the ones obtained from hidden conformal symmetry in the low frequency scattering off the black holes, and then determine the central charges. This method works well in well-known cases in Kerr/CFT correspondence, and reproduce successfully the holographic pictures for 4D Kerr-Newman and 5D Kerr black holes. We go on to predict the central charges and temperatures of a possible holographic CFT description dual to 5D doubly rotating black ring. © SISSA 2012.


Zhang X.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

With the latest results of a large mixing angle ∴ 13 for neutrinos by the T2K, MINOS and Double Chooz experiments, we find that the self-complementarity (SC) relations agree with the data in some angle-phase parametrizations of the lepton mixing matrix. There are three kinds of self-complementarity relations: (1) ∴ i+∴ j=∴ k=45°; (2) ∴ i+∴ j=∴ k; (3) ∴ i+∴ j=45° (where i, j, k denote the mixing angles in the angle-phase parametrizations). We present a detailed study on the self-complementarity relations in nine different angle-phase parametrizations, and also examine the explicit expressions in reparametrization-invariant form, as well as their deviations from global fit. These self-complementarity relations may lead to new perspective on the mixing pattern of neutrinos. © 2012 Elsevier B.V.


Zhang X.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

The latest experimental progress has established three kinds of neutrino oscillations with three mixing angles measured to rather high precision. There is still one parameter, i.e., the CP violating phase, missing in the neutrino mixing matrix. It is shown that a replay between different parameterizations of the mixing matrix can determine the full neutrino mixing matrix together with the CP violating phase. From the maximal CP violation observed in the original Kobayashi-Maskawa (KM) scheme of quark mixing matrix, we make an Ansatz of maximal CP violation in the neutrino mixing matrix. This leads to the prediction of all nine elements of the neutrino mixing matrix and also a remarkable prediction of the CP violating phase δ CK=(85.48 -1.80(-4.90) +4.67(+12.87))° within 1. σ (3. σ) range from available experimental information. We also predict the three angles of the unitarity triangle corresponding to the quark sector for confronting with the CP violation related measurements. © 2012 Elsevier B.V.


Shao H.-S.,Beijing University of Technology | Zhang Y.-J.,Beihang University | Chao K.-T.,Peking University
Journal of High Energy Physics | Year: 2012

We present a new systematic method to evaluate one-loop tensor integrals in conventional ultraviolet cutoff regularization. By deriving a new recursive relation that describes the momentum translation variance of ultraviolet integrals, we implement this relation in the Passarino-Veltman reduction method. With this method, we recalculate the Higgs boson decay into two photons at one-loop level in the Standard Model. We reanalyze this process carefully and clarify some issues arisen recently in cutoff regularization. © SISSA 2012.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Zhang J.-J.,Beijing University of Technology
Nuclear Physics B | Year: 2012

In this paper, we study the CFT duals for extreme black holes in the stretched horizon formalism. We consider the extremal RN, Kerr-Newman-AdS-dS, as well as the higher dimensional Kerr-AdS-dS black holes. In all these cases, we reproduce the well-established CFT duals. Actually we show that for stationary extreme black holes, the stretched horizon formalism always gives rise to the same dual CFT pictures as the ones suggested by ASG of corresponding near horizon geometries. Furthermore, we propose new CFT duals for 4D Kerr-Newman-AdS-dS and higher dimensional Kerr-AdS-dS black holes. We find that every dual CFT is defined with respect to a rotation in certain angular direction, along which the translation defines a U(1) Killing symmetry. In the presence of two sets of U(1) symmetry, the novel CFT duals are generated by the modular group SL(2,Z), and for n sets of U(1) symmetry there are general CFT duals generated by T-duality group SL(n,Z). © 2011 Elsevier B.V.


Zhou J.,Peking University | Wang Q.,Beijing University of Technology | Sun Q.,Peking University | Sun Q.,Virginia Commonwealth University | And 2 more authors.
Journal of Physical Chemistry Letters | Year: 2012

Motivated by the recent success in synthesizing two-dimensional Fe-phthalocyanine (poly-FePc) porous sheets, we studied strain-induced spin crossover in poly-TMPc (TM = Mn, Fe, Co, and Ni) systems by using first-principle calculations based on density functional theory. A small amount of biaxial tensile strain is found to not only significantly enhance the magnetic moment of the central TM atoms by 2 μ B when the strain reaches a critical value, but also the systems undergo low-spin (LS) to high-spin (HS) transition. These systems, however, show different response to strain, namely, poly-FePc sheet becomes ferromagnetic (FM) while poly-MnPc and poly-NiPc sheets become antiferromagnetic (AFM). Poly-CoPc, on the other hand, remains AFM. These predicted results can be observed in suspended poly-TMPc sheets by using scanning tunneling microscope (STM) tips to manipulate strain. © 2012 American Chemical Society.


Chen B.,Peking University | Chen B.,Beijing University of Technology | Long J.,Peking University
Journal of High Energy Physics | Year: 2010

In this paper, we study the real-time correlators in Kerr/CFT, in the low frequency limit of generic non-extremal Kerr(-Newman) black holes. From the low frequency scattering off Kerr-Newman black holes, we show that for the uncharged scalar scattering, there exists hidden conformal symmetry on the solution space. Similar to Kerr case, this suggests that the Kerr-Newman black hole is dual to a two-dimensional CFT with central charges c l = c r = 12 J and temperatures T L =(r ++r -)-Q 2/M/4πa, T R= r +-r -/4πa Using the Minkowski prescription, we compute the real-time correlators of a charged scalar and find perfect match with CFT prediction. We further discuss the low-frequency scattering of photons and gravitons by a Kerr black hole and find that their retarded Green's functions are in good agreement with CFT prediction. Our study shows that hidden conformal symmetry in the solution space is essential to set up and check the Kerr/CFT correspondence. © SISSA 2010. © SISSA 2010.


Shao H.-S.,Beijing University of Technology | Zhang Y.-J.,Beihang University | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Journal of High Energy Physics | Year: 2011

We study Feynman rules for the rational part R of the Standard Model amplitudes at one-loop level in the 't Hooft-Veltman γ5 scheme. Comparing our results for quantum chromodynamics and electroweak 1-loop amplitudes with that obtained based on the Kreimer-Korner-Schilcher (KKS) γ5 scheme, we find the latter result can be recovered when our γ5 scheme becomes identical (by setting g5s = 1 in our expressions) with the KKS scheme. As an independent check, we also calculate Feynman rules obtained in the KKS scheme, finding our results in complete agreement with formulae presented in the literature. Our results, which are studied in two different γ5 schemes, may be useful for clarifying the γ5 problem in dimensional regularization. They are helpful to eliminate or find ambiguities arising from different dimensional regularization schemes. © SISSA 2011.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Zhang J.-J.,Peking University
Journal of High Energy Physics | Year: 2011

There are two known CFT duals, namely the J-picture and the Q-picture, for a four-dimensional Kerr-Newman black hole, corresponding to the angular momentum J and the electric charge Q respectively. In our recent study we found a one-parameter class of CFT duals for extremal Kerr-Newman black hole, connecting these two pictures. In this paper we study these novel CFT duals for the generic non-extremal Kerr-Newman black hole. We investigate the hidden conformal symmetry in the low frequency scattering off Kerr-Newman black hole, from which the dual temperatures could be read. We find that there still exists a hidden conformal symmetry for a general CFT dual. We reproduce the correct Bekenstein-Hawking entropy from the Cardy formula, assuming the form of the central charge being invariant. Moreover we compute the retarded Green's function in the general CFT dual picture and find it is in good match with the CFT prediction. Furthermore we discuss the hidden conformal symmetries of the five dimensional Kerr black hole and obtain the similar evidence to support the general dual CFT pictures. © 2011 SISSA.


Zhang X.,Beijing University of Technology | Shao L.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Astroparticle Physics | Year: 2011

Doubly special relativity (DSR), with both an invariant velocity and an invariant length scale, elegantly preserves the principle of relativity between moving observers, and appears as a promising candidate of the quantum theory of gravity. We study the modifications of photon gas thermodynamics in the framework of DSR with an invariant length λ, after properly taking into account the effects of modified dispersion relation, upper bounded energy-momentum space, and deformed integration measure. We show that with a positive λ, the grand partition function, the energy density, the specific heat, the entropy, and the pressure are smaller than those of special relativity (SR), while the velocity of photons and the ratio of pressure to energy are larger. In contrast, with a negative λ, the quantum gravity effects show up in the opposite direction. However, these effects only manifest themselves significantly when the temperature is larger than 10 -3EP. Thus, DSR can have considerable influence on the early universe in cosmological study. © 2011 Elsevier B.V. All rights reserved.


Xin X.-Y.,Beijing University of Technology | Qin S.-X.,Goethe University Frankfurt | Liu Y.-X.,Beijing University of Technology | Liu Y.-X.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We propose a simple scheme to improve the Polyakov-Nambu-Jona-Lasinio model by including an explicit chemical-potential dependence in the Polyakov-loop potential. In the improved model, both the dynamical chiral symmetry restoration and the deconfinement are crossovers at high temperature T and small chemical potential μ, while they are first-order phase transitions at low T and large μ. We locate the critical end points and chart the phase diagrams of the associated phase transitions on the T-μ plane. Our result suggests that the dynamical chiral symmetry restoration and the deconfinement phase transitions almost coincide with each other on the T-μ plane. © 2014 American Physical Society.


Gehrmann T.,University of Zürich | Lubbert T.,University of Zürich | Lubbert T.,University of Hamburg | Yang L.L.,Beijing University of Technology | Yang L.L.,Peking University
Journal of High Energy Physics | Year: 2014

We describe the perturbative calculation of the transverse parton distribution functions in all partonic channels up to next-to-next-to-leading order based on a gauge invariant operator definition. We demonstrate the cancellation of light-cone divergences and show that universal process-independent transverse parton distribution functions can be obtained through a refactorization. Our results serve as the first explicit higher-order calculation of these functions starting from first principles, and can be used to perform next-to-next-to-next-to-leading logarithmic q T resummation for a large class of processes at hadron colliders. © 2014 The Author(s).


Diao K.,University of Innsbruck | Diao K.,Beijing University of Technology | Zhou Y.,Beijing University of Technology | auch W.,University of Innsbruck
Journal of Water Resources Planning and Management | Year: 2013

Accounting for water in a distribution system can be improved by dividing systems into smaller, metered zones. This paper proposes an approach that could create boundaries for district metered areas (DMA) automatically on the basis of the community structure of water distribution systems. Community structure-the gathering of vertices into communities such that there is a higher density of edges within communities than between them-is a common property of many complex systems. For verification, the method was tested on a realworld distribution system, and the result was compared with a manually designed DMA layout. Although further improvements are necessary, because the achieved community structure is in excellent agreement with the zoning plan in reality, this approach is a new addition to the number of automated methods aimed at complementing and eventually substituting the empirical trial-and-error approach. © 2013 American Society of Civil Engineers.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Chen B.,CAS Institute of Theoretical Physics | Long J.,Beijing University of Technology
Journal of High Energy Physics | Year: 2011

We propose an action to describe high spin topologically massive gravity with a negative cosmological constant. With the frame-like fields and spin connections being combined into two gauge fields, the action includes two gauge field Chern-Simons actions with different levels, and also a linear term proportional to the difference of the gauge field strengths. Such linear term play the role of imposing the torsion free conditions for high spin fields. We discuss the gauge symmetry of this action and study the fluctuations around the AdS3 vacuum. We show how to relate the the fluctuations of the gauge field to the Frondal fields, using the gauge symmetry. For the gauge group SL(n, R) × SL(n, R), we find that the fluctuations of all high spin fields up to spin n satisfy third order differential equations, and hence there generically exist massive traceless and trace mode for every spin. © 2012 SISSA.


Chen B.,Beijing University of Technology | Chen B.,Peking University | Chen C.-M.,National Central University | Ning B.,Beijing University of Technology
Nuclear Physics B | Year: 2011

In this article, we show that a four-dimensional Kerr-Newman-AdS-dS black hole could be described by two different holographic two-dimensional conformal field theories. The first description, in view of the angular momentum, has been well discussed in Chen and Long (2010) [23]. The other alternative dual picture, however, is somehow overlooked. This new description, in view of the charge, provides another holographic correspondence. This picture again is supported not only by the match of the macroscopic entropy with the counting of microscopic degrees of freedom via the Cardy formula and also by the agreement on the real-time correlator in the superradiant scattering. © 2011 Elsevier B.V.


Yao C.,Beijing University of Technology | Li F.,Beijing University of Technology | Li X.,Beijing University of Technology | Xia D.,Peking University
Journal of Materials Chemistry | Year: 2012

We report on the successful synthesis of fiber-like nanostructured Ti 4O 7 (NS-Ti 4O 7) by multistep method. The specific surface area of this NS-Ti 4O 7 was 26 m 2 g -1. The synthesized NS-Ti 4O 7 was platinized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing. It was found that the monodispersed Pt nanoparticles supported on NS-Ti 4O 7 with a uniform size of 4.8 nm. The prepared Pt/NS-Ti 4O 7 catalysts exhibited superior durability as well as enhanced Pt mass activity in comparison to commercial Pt/XC-72 catalyst. After undergoing accelerated durability tests (ADT), the oxygen reduction reaction (ORR) mass activity of Pt/NS-Ti 4O 7 was nearly thirty times higher than that of Pt/XC-72. The superior durability of Pt/NS-Ti 4O 7 is attributed to the high stability of Ti 4O 7 and the strong metal-support interaction between Pt and Ti 4O 7. © The Royal Society of Chemistry 2012.


Zhou J.,Peking University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology
Journal of the American Chemical Society | Year: 2011

A two-dimensional (2D) periodic Fe phthalocyanine (FePc) single-layer sheet has very recently been synthesized experimentally (Abel, M.; et al. J. Am. Chem. Soc.2011, 133, 1203), providing a novel pathway for achieving 2D atomic sheets with regularly and separately distributed transition-metal atoms for unprecedented applications. Here we present first-principles calculations based on density functional theory to investigate systematically the electronic and magnetic properties of such novel organometallics (labeled as TMPc, TM = Cr-Zn) as free-standing sheets. Among them, we found that only the 2D MnPc framework is ferromagnetic, while 2D CrPc, FePc, CoPc, and CuPc are antiferromagnetic and 2D NiPc and ZnPc are nonmagnetic. The difference in magnetic couplings for the studied systems is related to the different orbital interactions. Only MnPc displays metallic d xz and d yz orbitals that can hybridize with p electrons of Pc, which mediates the long-range ferromagnetic coupling. Monte Carlo simulations based on the Ising model suggest that the Curie temperature (T C) of the 2D MnPc framework is ∼150 K, which is comparable to the highest T C achieved experimentally, that of Mn-doped GaAs. The present study provides theoretical insight leading to a better understanding of novel phthalocyanine-based 2D structures beyond graphene and BN sheets. © 2011 American Chemical Society.


Yang J.-J.,Tsinghua National Laboratory for Information Sciences and Technology | Yang J.-J.,Tsinghua University | Li J.-Q.,Beijing University of Technology | Niu Y.,Tsinghua University
Future Generation Computer Systems | Year: 2014

Storing and sharing of medical data in the cloud environment, where computing resources including storage is provided by a third party service provider, raise serious concern of individual privacy for the adoption of cloud computing technologies. Existing privacy protection researches can be classified into three categories, i.e., privacy by policy, privacy by statistics, and privacy by cryptography. However, the privacy concerns and data utilization requirements on different parts of the medical data may be quite different. The solution for medical dataset sharing in the cloud should support multiple data accessing paradigms with different privacy strengths. The statistics or cryptography technology alone cannot enforce the multiple privacy demands, which blocks their application in the real-world cloud. This paper proposes a practical solution for privacy preserving medical record sharing for cloud computing. Based on the classification of the attributes of medical records, we use vertical partition of medical dataset to achieve the consideration of different parts of medical data with different privacy concerns. It mainly includes four components, i.e., (1) vertical data partition for medical data publishing, (2) data merging for medical dataset accessing, (3) integrity checking, and (4) hybrid search across plaintext and ciphertext, where the statistical analysis and cryptography are innovatively combined together to provide multiple paradigms of balance between medical data utilization and privacy protection. A prototype system for the large scale medical data access and sharing is implemented. Extensive experiments show the effectiveness of our proposed solution. © 2014 Elsevier B.V.


Meng J.,Beijing University of Technology | Meng J.,Beihang University | Meng J.,Stellenbosch University | Peng J.,Beijing Normal University | And 2 more authors.
Frontiers of Physics | Year: 2013

Magnetic rotation and antimagnetic rotation are exotic rotational phenomena observed in weakly deformed or near-spherical nuclei, which are respectively interpreted in terms of the shears mechanism and two shearslike mechanism. Since their observations, magnetic rotation and antimagnetic rotation phenomena have been mainly investigated in the framework of tilted axis cranking based on the pairing plus quadrupole model. For the last decades, the covariant density functional theory and its extension have been proved to be successful in describing series of nuclear ground-states and excited states properties, including the binding energies, radii, single-particle spectra, resonance states, halo phenomena, magnetic moments, magnetic rotation, low-lying excitations, shape phase transitions, collective rotation and vibrations, etc. This review will mainly focus on the tilted axis cranking covariant density functional theory and its application for the magnetic rotation and antimagnetic rotation phenomena. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.


Sun L.,Henan Normal University | Sun L.,Beijing University of Technology | Xu J.,Henan Normal University | Tian Y.,Beijing Normal University
Knowledge-Based Systems | Year: 2012

Feature selection in large, incomplete decision systems is a challenging problem. To avoid exponential computation in exhaustive feature selection methods, many heuristic feature selection algorithms have been presented in rough set theory. However, these algorithms are still time-consuming to compute. It is therefore necessary to investigate effective and efficient heuristic algorithms. In this paper, rough entropy-based uncertainty measures are introduced to evaluate the roughness and accuracy of knowledge. Moreover, some of their properties are derived and the relationships among these measures are established. Furthermore, compared with several representative reducts, the proposed reduction method in incomplete decision systems can provide a mathematical quantitative measure of knowledge uncertainty. Then, a heuristic algorithm with low computational complexity is constructed to improve computational efficiency of feature selection in incomplete decision systems. Experimental results show that the proposed method is indeed efficient, and outperforms other available approaches for feature selection from incomplete and complete data sets. © 2012 Elsevier B.V. All rights reserved.


Wang J.,Beijing University of Technology | Tang S.,Illinois Institute of Technology | Yin B.,Beijing University of Technology | Li X.-Y.,Illinois Institute of Technology | Li X.-Y.,Tsinghua National Laboratory for Information Sciences and Technology
Proceedings - IEEE INFOCOM | Year: 2012

The recently emerged compressive sensing (CS) theory provides a whole new avenue for data gathering in wireless sensor networks with benefits of universal sampling and decentralized encoding. However, existing compressive sensing based data gathering approaches assume the sensed data has a known constant sparsity, ignoring that the sparsity of natural signals vary in temporal and spatial domain. In this paper, we present an adaptive data gathering scheme by compressive sensing for wireless sensor networks. By introducing autoregressive (AR) model into the reconstruction of the sensed data, the local correlation in sensed data is exploited and thus local adaptive sparsity is achieved. The recovered data at the sink is evaluated by utilizing successive reconstructions, the relation between error and measurements. Then the number of measurements is adjusted according to the variation of the sensed data. Furthermore, a novel abnormal readings detection and identification mechanism based on combinational sparsity reconstruction is proposed. Internal error and external event are distinguished by their specific features. We perform extensive testing of our scheme on the real data sets and experimental results validate the efficiency and efficacy of the proposed scheme. Up to about 8dB SNR gain can be achieved over conventional CS based method with moderate increase of complexity. © 2012 IEEE.


Li S.-W.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

The most popular way to present mixing matrices of quarks (CKM) and leptons (PMNS) is the parametrization with three mixing angles and one CP-violating phase. There are two major options in this kind of parametrizations, one is the original Kobayashi-Maskawa (KM) matrix, and the other is the Chau-Keung (CK) matrix. In a new proposal by Frampton and He, a unitarity boomerang is introduced to combine two unitarity triangles, and this new presentation displays all four independent parameters of the KM parametrization in the quark sector simultaneously. In this Letter, we study the relations between KM and CK parametrizations, and also consider the quark-lepton complementarity (QLC) in the KM parametrization. The unitarity boomerang is discussed in the situation of the CK parametrization for comparison with that in the KM parametrization in the quark sector. Then we extend the idea of unitarity boomerang to the lepton sector, and check the corresponding unitarity boomerangs in the two cases of parametrizations. © 2010 Elsevier B.V.


Shao L.,Beijing University of Technology | Zhang Y.-J.,LIAONING Technical University | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

The flavor asymmetry of the nucleon sea, i.e., the excess of d over(d, ̄) quark-antiquark pairs over u over(u, ̄) ones in the proton, can be explained by several different models; therefore, it is a challenge to discriminate these models from each other. We examine in this Letter three models: the balance model, the meson cloud model, and the chiral quark model, and we show that these models give quite different predictions on the sea quark contents of other octet baryons. New experiments aimed at measuring the flavor contents of other octet baryons are needed for a more profound understanding of the non-perturbative properties of quantum chromodynamics (QCD). © 2010 Elsevier B.V. All rights reserved.


Chen B.,Peking University | Chen B.,Beijing University of Technology | Long J.,Peking University
Journal of High Energy Physics | Year: 2010

In this paper, we study the holographic description of the generic four-dimensional non-extremal Kerr-Newman-AdS-dS black holes. We find that if focusing on the near-horizon region, for the massless scalar scattering in the low-frequency limit, there exists hidden conformal symmetry on the solution space. Similar to the Kerr case, this suggests that the Kerr-Newman-AdS-dS black hole is dual to a two-dimensional CFT with central charges c L = c R= 6a (r ++r */k and temperatures T L = k(r + 2+ r * 2 + 2a 2)/4πaΞ(r ++r *), T R = k (r +-r *) 4πaΞ . The macroscopic Bekenstein-Hawking entropy could be recovered from the microscopic counting in dual CFT via the Cardy formula. Using the Minkowski prescription, we compute the real-time correlators of the scalar, photon and graviton in near horizon geometry of near extremal Kerr-AdS-dS black hole. In all these cases, the retarded Green's functions and the corresponding absorption cross sections are in perfect match with CFT prediction. We further discuss the low-frequency scattering of a charged scalar by a Kerr-Newman-AdS-dS black hole and find the dual CFT description. © 2010 SISSA, Trieste, Italy.


Meng J.,Beihang University | Meng J.,Beijing University of Technology | Meng J.,Stellenbosch University | Zhang S.Q.,Beijing University of Technology
Journal of Physics G: Nuclear and Particle Physics | Year: 2010

Open problems in the interpretation of the observed pair of near-degenerate ΔI = 1 bands with the same parity as the chiral doublet bands are discussed. The ambiguities for the existing fingerprints of the chirality in atomic nuclei and problems in existing theory are discussed, including the description of quantum tunneling in the mean field approximation as well as the deformation, core polarization and configuration of the particle rotor model (PRM). Future developments of the theoretical approach are anticipated. © 2010 IOP Publishing Ltd.


Li X.,Beijing University of Technology | An L.,Beijing University of Technology | Wang X.,Beijing University of Technology | Li F.,Beijing University of Technology | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Supported chemically ordered Pt-Fe intermetallic compounds have been prepared through a straightforward two-stage approach. By taking advantage of this straightforward two-stage synthesis, we have for the first time successfully obtained supported Pt 3Fe 1 and Pt 1Fe 1 intermetallic nanoparticles with a mean size of less than 5 nm, a narrow size distribution and good dispersion. The nanoparticles of supported intermetallic Pt 3Fe 1 and Pt 1Fe 1 compounds showed superior electrocatalytic activities towards the oxygen reduction reaction (ORR). The ORR enhancement in supported electrocatalysts made from Pt-Fe intermetallic compounds may be attributed to their geometric and electronic structure. Accelerated durability tests (ADT) show that Pt 3Fe 1/C has better durability, the electrochemical surface area (ECSA) values of commercial Pt/C decreased by 49% after 5000 cycles, but Pt 1Fe 1/C showed a reduction in the ECSA value of 3% after 5000 cycles. This journal is © The Royal Society of Chemistry 2012.


Patent
Beijing University of Technology and Anhui Earth Panda Advance Magnetic Material Co. | Date: 2016-11-09

The present invention discloses a short process preparation technology of sintered NdFeB magnets from the NdFeB sludge, which relates to a field of recycle technology of NdFeB sludge. The present invention comprises the following steps: water bath distillation of organics in sludge, ultrasonic cleaning, calcium reduction and diffusion, ultrasonic rinsing in a magnetic field and drying, powders mixing and sintering. NdFeB sludge as raw materials was directly prepared from recycled sintered magnets with high magnetic properties. Most of the organics in the sludge could be removed by a vacuum distillation process with stepwise heating. The ultrasonic rinsing process in a magnetic field could effectively remove the remaining organics. The recycled sintered magnets exhibited good maximum energy product [(BH)_(max)] of 35.26 MGOe. The present invention has important features, such as the short processing time, efficient environmental protection, high recycling rate and effective utilization rate of rare earth metals.


Patent
Beijing University of Technology and Anhui Earth Panda Advance Magnetic Material Co. | Date: 2016-04-19

The present invention discloses a short process preparation technology of sintered NdFeB magnets from the NdFeB sludge, which relates to a field of recycle technology of NdFeB sludge. The present invention comprises the following steps: water bath distillation of organics in sludge, ultrasonic cleaning, calcium reduction and diffusion, ultrasonic rinsing in a magnetic field and drying, powders mixing and sintering. NdFeB sludge as raw materials was directly prepared from recycled sintered magnets with high magnetic properties. Most of the organics in the sludge could be removed by a vacuum distillation process with stepwise heating. The ultrasonic rinsing process in a magnetic field could effectively remove the remaining organics. The recycled sintered magnets exhibited good maximum energy product [(BH)_(max)] of 35.26 MGOe. The present invention has important features, such as the short processing time, efficient environmental protection, high recycling rate and effective utilization rate of rare earth metals.


Liang H.,Beijing University of Technology | Liang H.,RIKEN | Meng J.,Beijing University of Technology | Meng J.,Beihang University | And 3 more authors.
Physics Reports | Year: 2015

Symmetry plays a fundamental role in physics. The quasi-degeneracy between single-particle orbitals (n,l,j=l+1/2) and (n-1,l+2,j=l+3/2) indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry (PSS). Since the introduction of the concept of PSS in atomic nuclei, there have been comprehensive efforts to understand its origin. Both splittings of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with radioactive ion beam facilities. Since the PSS was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry (SS) for anti-nucleon, and many new concepts have been introduced. In the present Review, we focus on the recent progress on the PSS and SS in various systems and potentials, including extensions of the PSS study from stable to exotic nuclei, from non-confining to confining potentials, from local to non-local potentials, from central to tensor potentials, from bound to resonant states, from nucleon to anti-nucleon spectra, from nucleon to hyperon spectra, and from spherical to deformed nuclei. Open issues in this field are also discussed in detail, including the perturbative nature, the supersymmetric representation with similarity renormalization group, and the puzzle of intruder states. © 2015 Elsevier B.V.


Zhou J.,Peking University | Sun Q.,Peking University | Sun Q.,Beijing University of Technology
Applied Physics Letters | Year: 2012

There has been a long-standing dream to synthesize a semihydrogenated graphene sheet. Here, we propose a promising strategy based on physical method instead of chemical method to avoid the current problems in synthesizing. By applying pressure on a fluorinated BN sheet supported on a graphene sheet, we can induce a structural transition for H atoms jumping from the graphane sheet to fluorinated BN sheet, thus transforming the graphane sheet to a graphone sheet. Moreover, hole doping can reduce the pressure required for such structural transition. This strategy is more feasible and controllable as compared to the existing experimental techniques. © 2012 American Institute of Physics.


Grant
Agency: Cordis | Branch: FP7 | Program: CP-FP-SICA | Phase: ENV.2009.1.3.3.1 | Award Amount: 5.14M | Year: 2010

Collaborative research on flood resilience in urban areas (CORFU) is an interdisciplinary international project that will look at advanced and novel strategies and provide adequate measures for improved flood management in cities. The differences in urban flooding problems in Asia and in Europe range from levels of economic development, infrastructure age, social systems and decision making processes, to prevailing drainage methods, seasonality of rainfall patterns and climate change trends. Our vision is that this project will use these differences to create synergies that will bring new quality to flood management strategies globally. Through a 4-year collaborative research programme, the latest technological advances will be cross-fertilised with traditional and emerging approaches to living with floods. The overall aim of CORFU is to enable European and Asian institutions to learn from each other through joint investigation, development, implementation and dissemination of strategies that will enable more scientifically sound management of the consequences of urban flooding in the future. Flood impacts in urban areas potential deaths, damage to infrastructure and health problems and consequent effects on individuals and on communities and possible responses will be assessed by envisaging different scenarios of relevant drivers: urban development, socio-economic trends and climate changes. The cost-effectiveness of resilience measures and integrative and adaptable flood management plans for these scenarios will be quantified. CORFU is structured in six Work Packages. WP1 will look at drivers that impact on urban flooding. WP2 will enhance methodologies and tools for flood hazard assessment based on urban flood modelling. WP3 will improve, extend and integrate modern methods for flood impact assessment. WP4 will aim to assess and enhance existing flood risk management strategies. WP5 will disseminate the outputs. WP6 will co-ordinate the project.


Grant
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2007.4.2 | Award Amount: 10.68M | Year: 2008

Current Semantic Web reasoning systems do not scale to the requirements of their hottest\napplications, such as analyzing data from millions of mobile devices, dealing with terabytes of\nscientific data, and content management in enterprises with thousands of knowledge workers.\nWe will build the Large Knowledge Collider (LarKC, for short, pronounced lark), a platform\nfor massive distributed incomplete reasoning that will remove these scalability barriers. This\nwill be achieved by:\n- Enriching the current logic-based Semantic Web reasoning methods with methods\nfrom information retrieval, machine learning, information theory, databases and\nprobabilistic reasoning,\n- Employing cognitively inspired approaches and techniques such as spreading activation,\nfocus of attention, reinforcement, habituation, relevance reasoning, and bounded\nrationality.\n- Building a distributed reasoning platform and realising it both on a high-performance\ncomputing cluster and via computing at home.\nThe consortium is an interdisciplinary team of engineers and researchers in Computing Science,\nWeb Science and Cognitive Science, well qualified to realize this ambitious vision. The Large\nKnowledge Collider will be an open architecture. Researchers and practitioners from outside the\nconsortium will be encouraged to develop and plug in their own components to drive parts of the\nsystem. This will make the Large Knowledge Collider a generic platform, and not just a single\nreasoning engine.\nThe success of the Large Knowledge Collider will be demonstrated in three end-user case\nstudies. The first case study is from the telecom sector. It aims at real-time aggregation and\nanalysis of location data obtained from mobile phones carried by the population of a city, in order\nto regulate city infrastructure functions such as public transport and to provide context-sensitive\nnavigation information. The other two case studies are in the life-sciences domain, related\nrespectively to dr


Zhao X.,Beijing Materials University | Xia D.,Beijing Materials University | Yue J.,Beijing University of Technology | Liu S.,Beijing University of Technology
Electrochimica Acta | Year: 2014

A novel C/Fe3C composite prepared by simple polymerization- pyrolysis of iron phthalocyanine (PcFe) at 700 C in an Ar atmosphere, exhibits a high reversible capacity, stable cyclability, excellent rate performance, improved initial efficiency and reduced hysteresis as an anode material for lithium ion batteries. In-situ embedded Fe3C nanoparticles and N doping can enhance electrical conductivity and facilitate the reaction of C/Fe3C electrode effectively. This work provides a new way for developing high performance non-graphitic carbon electrode materials in the future.© 2013 Published by Elsevier Ltd. All rights reserved.


Si P.,Beijing University of Technology | Ji H.,Beijing University of Posts and Telecommunications | Yu F.R.,Carleton University | Leung V.C.M.,University of British Columbia
IEEE Transactions on Vehicular Technology | Year: 2010

Spectrum pooling in cognitive radio systems is an approach to manage the available spectrum bands from different licensed networks. Most previous work on spectrum pooling concentrates on the system architecture and the design of flexible-access algorithms and schemes. In this paper, we present a cooperative scheme for internetwork spectrum sharing among multiple secondary systems, which takes into account the price and spectrum efficiency as the design criteria. Specifically, the spectrum-sharing problem is formulated as a stochastic bandit system; thus, the optimal spectrum-sharing scheme is simply allocating the new available band to the secondary network with the lowest index. Extensive simulation examples illustrate that the proposed scheme significantly improves the performance compared with the existing scheme that ignores optimal spectrum sharing. © 2006 IEEE.


Kelley R.,Harvard University | Schwartz M.D.,Harvard University | Schabinger R.M.,Autonomous University of Madrid | Zhu H.X.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We investigate the exclusive jet mass distribution in e +e - events, defined with a veto on the out-of-jet radiation, at two-loop order. In particular, we calculate the two-loop soft function, which is required to describe this distribution in the region of small jet mass. When combined with other ingredients using the soft-collinear effective theory, this generates the complete singular distribution for jet thrust, the sum of the jet masses, at two-loop order. The result is in excellent agreement with full quantum chromodynamics. The integrated jet thrust distribution is found to depend in an intricate way on both the finite jet cone size, R, and the jet veto scale. The result clarifies the structure of the potentially large logarithms (both global and nonglobal) which arise in jet observables for the first time at this order. Somewhat surprisingly, we find that, in the small R limit, there is a precise and simple correspondence between the nonglobal contribution to the integrated jet thrust distribution and the previously calculated nonglobal contribution to the integrated hemisphere soft function, including subleading terms. This suggests that the small R limit may provide a useful expansion for studying other exclusive jet substructure observables. © 2012 American Physical Society.


Qiu B.,Beijing University of Technology | Zhao X.,Beijing University of Technology | Xia D.,Beijing University of Technology | Xia D.,Beijing Materials University
Journal of Alloys and Compounds | Year: 2013

This study reports a novel strategy of preparing CoS2/reduced graphene oxides (RGO) nanocomposites by employing graphene oxides (GO) as an oxidizing agent and Na2S2O3 as a reducing agent. CoS2 can be in situ synthesized with GO being reduced. X-ray diffraction (XRD), Raman spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical test are used to characterize the nanocomposite. The CoS2 particles with the size of 150 nm are dispersed in the networks made from thin RGO nanosheets. The CoS 2/RGO nanocomposite as an anode material for lithium-ion batteries can deliver excellent reversible capacity retention (640 mA hg-1) after cycling 50 times when tested at 100 mA g-1 and rate performance. The enhanced electrochemical properties can be attributed to the nanoscale particles sizes of CoS2 in addition to the effects of RGO networks in preventing the agglomeration of CoS2 and absorbing lithium polysulfides during the charge-discharge processes. © 2013 Elsevier B.V. All rights reserved.


Ding W.,CAS Institute of Physics | Wang Y.-Y.,Beijing University of Technology
Optics Express | Year: 2015

We identify, for the first time to our best knowledge, a new type of transmission band having hybrid resonance nature in hollow-core anti-resonant fibers (ARF). We elucidate its unique phase-locking feature of the electric field at the outermost boundary. Exploiting this hybrid band, large birefringence in the order of 10-4 is obtained. Our analyses based on Kramer-Kronig relation and transverse field confinement interpret the link between the hybrid transmission band and the large birefringence. Guided by these analyses, an experimentally realizable polarization-maintaining ARF design is proposed by introducing multi-layered dielectric structure into a negative curvature core-surround. This multi-layered ARF possesses characteristics of low loss, broad transmission band and large birefringence simultaneously. © 2015 Optical Society of America.


Lansberg J.-P.,University Paris - Sud | Shao H.-S.,Beijing University of Technology | Shao H.-S.,CERN
Physical Review Letters | Year: 2013

We proceed for the first time to the evaluation of the Born cross section for J/ψ+ηc production, namely, via g+g→J/ ψ+ηc+g, and show that it has a harder PT spectrum than the J/ψ-pair yield at the Born level. If one stuck to a comparison at the Born level, one would conclude that J/ψ+ηc production would surpass that of J/ψ+J/ψ at large PT. This is nonetheless not the case since J/ψ-pair production, as for single J/ψ, receives leading-PT contributions at higher orders in αs. We also present the first evaluation of these leading-PT next-to-leading order contributions. These are indeed significant for increasing PT and are of essential relevance for comparison with forthcoming data. We also compute kinematic correlations relevant for double-parton-scattering studies. Finally, we evaluate the polarization of a J/ψ accompanied by either an ηc or a J/ψ and another light parton. These results may be of great help to understand the polarization of quarkonia produced at high energies. © 2013 American Physical Society.


Li W.-C.,Beijing University of Technology | Zeng C.-C.,Beijing University of Technology | Hu L.-M.,Beijing University of Technology | Tian H.-Y.,Beijing Technology and Business University | Little R.D.,University of California at Santa Barbara
Advanced Synthesis and Catalysis | Year: 2013

An electrochemical strategy for the effi-cient synthesis of 2-substituted benzoxazoles was de-veloped using a catalytic amount of sodium iodide (Nal) as a redox catalyst in a two-phase buffer system. © 2013 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.


Ding W.,CAS Institute of Physics | Wang Y.,Beijing University of Technology
Optics Express | Year: 2014

We report an analytic model for quantitatively calculating the transmission attenuation of single-wall hollow-core anti-resonant fibers. Our calculations unveil the light leakage dependences on azimuthal angle, polarization, and geometrical shape and have been examined in a variety of fiber geometries. Based on our model, a simple and clear picture about light guidance in hollow-core lattice fibers is presented. Formation of equiphase surface at fiber's outermost boundary and light emission ruled by Helmholtz equation in transverse plane constitute the basis of this picture. Using this picture, we explain how the geometrical shape of a single-wall hollow-core fiber influences its transmission properties. © 2014 Optical Society of America


Yang Y.-G.,Beijing University of Technology | Xia J.,Beijing University of Technology | Jia X.,Beijing University of Technology | Zhang H.,Beijing University of Posts and Telecommunications
Quantum Information Processing | Year: 2013

A novel gray-level image encryption/decryption scheme is proposed, which is based on quantum Fourier transform and double random-phase encoding technique. The biggest contribution of our work lies in that it is the first time that the double random-phase encoding technique is generalized to quantum scenarios. As the encryption keys, two phase coding operations are applied in the quantum image spatial domain and the Fourier transform domain respectively. Only applying the correct keys, the original image can be retrieved successfully. Because all operations in quantum computation must be invertible, decryption is the inverse of the encryption process. A detailed theoretical analysis is given to clarify its robustness, computational complexity and advantages over its classical counterparts. It paves the way for introducing more optical information processing techniques into quantum scenarios. © 2013 Springer Science+Business Media New York.


Yang Y.-G.,Beijing University of Technology | Yang Y.-G.,Xidian University | Xia J.,Beijing University of Technology | Jia X.,Beijing University of Technology | Zhang H.,Beijing University of Posts and Telecommunications
Quantum Information Processing | Year: 2013

As an important branch of quantum cryptography, quantum private comparison (QPC) has recently received a lot of attention. In this paper we study the security of previous QPC protocols with a semi-honest third party (TP) from the viewpoint of secure multi-party computation and show that the assumption of a semi-honest TP is unreasonable. Without the unreasonable assumption of a semi-honest TP, one can easily find that the QPC protocol (Tseng et al. in Quantum Inf Process, 2011, doi: 10.1007/s11128-011-0251-0) has an obvious security flaw. Some suggestions about the design of QPC protocols are also given. © 2012 Springer Science+Business Media, LLC.


Li Y.,Beijing University of Technology | Chen B.,Shanghai JiaoTong University
Construction and Building Materials | Year: 2013

Magnesium phosphate cement (MPC) was prepared with dead burned magnesia oxide (MgO), potassium di-hydrogen phosphate (KH2PO4) and some retarders in a given proportion used in the same manner as Portland cement. Factors such as the w/c ratio, casting temperature and fly ash contents that affect the properties of MPC were studied in this paper. The experimental results demonstrate that the setting time was significantly affected by the w/c ratio and casting temperature. Adding fly ash can increase the setting time and flowability of fresh MPC paste. The compressive strengths of MPC paste prepared using various w/c ratios were measured at ages of 3 h, 1 d, 7 d and 28 d. The 3-, 7- and 28-day compressive strengths of MPC mortar prepared using various fly ash contents were also measured. The compressive strength of MPC paste decreased with an increasing w/c ratio, and the aged compressive strengths of MPC mortar increased with increasing fly ash content. The results also indicate that adding fly ash can improve the water resistance and dry shrinkage of MPC mortar. Finally, the hydrate products were analyzed using XRD and SEM. © 2013 Elsevier B.V. All rights reserved.


Kelley R.,Harvard University | Schwartz M.D.,Harvard University | Schabinger R.M.,Autonomous University of Madrid | Zhu H.X.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

The hemisphere soft function is calculated to order αs2. This is the first multiscale soft function calculated to two loops. The renormalization scale dependence of the result agrees exactly with the prediction from effective field theory. This fixes the unknown coefficients of the singular parts of the two-loop thrust and heavy-jet mass distributions. There are four such coefficients, for 2 event shapes and 2 color structures, which are shown to be in excellent agreement with previous numerical extraction. The asymptotic behavior of the soft function has double logs in the CFCA color structure, which agree with nonglobal log calculations, but also has subleading single logs for both the CFCA and C FTFnf color structures. The general form of the soft function is complicated, does not factorize in a simple way, and disagrees with the Hoang-Kluth ansatz. The exact hemisphere soft function will remove one source of uncertainty on the αs fits from e+e - event shapes. © 2011 American Physical Society.


Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Institute of Physics | Liu X.,Lanzhou University | Zhu S.-L.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Inspired by the newly observed two charged bottomoniumlike states, we consider the possible contribution from the intermediate Zb(10610) and Zb(10650) states to the Υ(5S)→Υ(2S) π+π- decay process, which naturally explains Belle's previous observation of the anomalous Υ(2S)π+π - production near the peak of Υ(5S) at √s=10.87GeV. The resulting dΓ(Υ(5S)→Υ(2S)π+π-)/ dmπ+π- and dΓ(Υ(5S) →Υ(2S)π+π-)/dcosθ distributions agree with Belle's measurement after inclusion of these Zb states. This formalism also reproduces the Belle observation of the double-peak structure and its reflection in the Υ(2S)π+ invariant mass spectrum of the Υ(5S)→Υ(2S)π+π- decay. © 2011 American Physical Society.


Yan Y.,University of Notre Dame | Sheng Q.,Beijing University of Technology | Wang C.,Beijing University of Technology | Xue J.,Beijing University of Technology | Chang H.-C.,University of Notre Dame
Journal of Physical Chemistry C | Year: 2013

With asymptotic and numerical analyses, we systematically study the influence of slip length and access Ohmic resistance (due to pore-end field focusing and concentration polarization) on the energy conversion efficiency of pressure-driven electrolyte flow through a charged nanopore. Hydrodynamic slip reduces the percent of energy dissipated by viscous dissipation but, through electro-osmotic convective current, can also reduce the electrical resistance of the nanopore. Since the nanopore resistance is in parallel to the load-access serial resistance, the latter effect can actually reduce useful current through the load. These two opposing effects of slip produce specific and finite optimum values of surface charge density and ionic strength. The optimization offers explicit analytical estimates for the realistic parameters and suggests an upper bound of 50% conversion efficiency at the slip length of 90 nm and 35% for measured electro-osmotic flow slip lengths of about 30 nm for charged channels. © 2013 American Chemical Society.


Li Y.,Beijing University of Technology | Sun J.,Beijing University of Technology | Chen B.,Shanghai JiaoTong University
Construction and Building Materials | Year: 2014

Magnesium phosphate cement (MPC) is prepared by mixing MgO powder (M) with KH2PO4 powder (P) and borax powder (B). To investigate the influence of calcined magnesia on the compressive and flexural strength of MPC, two types of magnesia were calcinated under different temperatures, and the chemical and physical properties were analysed. The MPC was prepared by mixing calcinated magnesia with fly ash and retarder. The selection principle of magnesia was proposed to optimise the physical and chemical properties of the MPC. The experimental results demonstrate that the increasing calcination temperature led to the increasing particle size of the magnesia. The calcination temperature had a significant influence on the light magnesia and had no effect on its chemical composition. The compressive and flexural strength of the MPC was tested, and its microstructure was analysed using XRD and SEM methods. The testing results demonstrate that within a certain range, the compressive strength increased with an increasing calcination temperature. The compressive strength was the maximum when the mole ratio of phosphate to MgO was 1/4-1/5. In a certain range, as the P/M decreased, the flexural strength of the MPC increased and subsequently remained at a certain level. © 2014 Elsevier Ltd. All rights reserved.


Qin S.-X.,Beijing University of Technology | Qin S.-X.,Goethe University Frankfurt | Chang L.,Jülich Research Center | Liu Y.-X.,Beijing University of Technology | And 3 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

The gauge principle is fundamental in formulating the Standard Model. Fermion-gauge-boson couplings are the inescapable consequence and the primary determining factor for observable phenomena. Vertices describing such couplings are simple in perturbation theory and yet the existence of strong-interaction bound-states guarantees that many phenomena within the Model are nonperturbative. It is therefore crucial to understand how dynamics dresses the vertices and thereby fundamentally alters the appearance of fermion-gauge-boson interactions. We consider the coupling of a dressed-fermion to an Abelian gauge boson, and describe a unified treatment and solution of the familiar longitudinal Ward-Green-Takahashi identity and its less well known transverse counterparts. Novel consequences for the dressed-fermion-gauge-boson vertex are exposed. © 2013 Elsevier B.V.


Lansberg J.-P.,University Paris - Sud | Shao H.-S.,Beijing University of Technology | Shao H.-S.,CERN
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We demonstrate that the recent studies of J/ψ-pair production by CMS at the LHC and by D0 at the Tevatron reveal the presence of different production mechanisms in different kinematical regions. We find out that next-to-leading-order single parton scattering contributions at αs 5 dominate the yield at large transverse momenta of the pair. Our analysis further emphasises the importance of double parton scatterings - which are expected to dominate the yield at large J/ψ-rapidity differences - at large invariant masses of the pair in the CMS acceptance, and thereby solve a large discrepancy between the theory and the CMS data. In addition, we provide the first exact - gauge-invariant and infrared-safe - evaluation of a class of leading-PT (PT-4) next-to-next-to-leading-order contributions at αs 6, which can be relevant in the region of large values of PTmin=min(PT1, PT2). Finally, we derive simple relations for the feed-down fractions from the production of an excited charmonium state with a J/ψ in the case of the dominance of the double parton scatterings, which significantly deviate from those for single parton scatterings. Such relations can be used to discriminate these extreme scenarios, either DPS or SPS dominance. © 2015 The Authors.


Liu C.-F.,Hebei United University | Kong S.-S.,Beijing University of Technology | Yuan S.-J.,Hebei United University
Thermal Science | Year: 2013

A reconstructive scheme for variational iteration method using the Yang-Laplace transform is proposed and developed with the Yang-Laplace transform. The identification of fractal Lagrange multiplier is investigated by the Yang-Laplace transform. The method is exemplified by a fractal heat conduction equation with local fractional derivative. The results developed are valid for a compact solution domain with high accuracy.


Wang L.,South China University of Technology | Wang L.,Shanghai JiaoTong University | Zeng Y.,Beijing University of Technology
Neurological Sciences | Year: 2013

Firing properties of biological neurons have long been recognized to be determined by extrinsic synaptic afferents that neurons receive and intrinsic ionic mechanisms that neurons possess, however, previous researches have also demonstrated that firing behavior of single neurons can be modulated by the neurons themselves, realized by the autapses. Thus in this investigation, we argued that how autaptic modulations shape the bursting behavior of biological neurons. We considered the issue from the following two aspects: autaptic-excitation and -inhibition. Our results suggested that for autaptic-excitation, under the condition of relatively weak stimulus, regular bursting was more incline to occur when the autaptic strength was weak, while regular spiking was more likely to appear when the autaptic strength was strong. However, larger stimulus would diminish the portion of bursting, but increase the portion of spiking. For autaptic-inhibition, under relatively weak stimulus, a wide range of regular bursting emerges when the autaptic strength was small, but when stronger stimulus were applied, the range of regular bursting shrinked into a small region. Meanwhile, we observed that synaptic delays have no obvious effects in the case of autaptic-excitation, while a subtle effect of synaptic delays was observed in the case of autaptic-inhibition. These results showed that bursting behavior of neurons could be controlled and modulated by the autaptic mechanisms that biological neurons intrinsically possess, and the final results may further promote the understanding in the generation of various neuronal firing patterns. © 2013 Springer-Verlag Italia.


Zhang L.,Beijing University of Technology | Hu P.,Beijing University of Technology | Zhao X.,Beijing University of Technology | Tian R.,Beijing University of Technology | And 2 more authors.
Journal of Materials Chemistry | Year: 2011

The present study reports a straightforward template-free route for the synthesis of core-shell Co@CoO nanocomposites by the controlled reduction of Co3O4 nanospheres. The target Co@CoO nanoparticles consist of an unsealed hollow porous CoO shell with a metal Co core, in which the outer porous CoO shell as the active anode material can be fully in contact with the electrolyte. The void within the particles provides a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium. Most importantly, the inner nanosized metal Co core gives a new impetus to the reversible decomposition of Li2O due to its catalytic activity. Furthermore, the exposed metal Co portion outside the nanoshells provides a favorable electrical contact between adjacent particles and greatly improves the efficiency of the electronic connection between the active material and the current collector. The Co@CoO nanocomposite maintains an excellent reversible capacity over 800 mA h g-1 after 50 cycles with an initial coulombic efficiency of 74.2%, which is much higher than that of pure CoO (67.8%). This superior electrochemical performance is closely related to the unique composition and nanostructure of the electrode material. Notably, it is the first case of a hybrid-structured Co@CoO anode material derived from the reduction process from oxide precursors. Such a conclusion may be advantageously used to guide the design of a wide range of nanostructured metal oxides. © 2011 The Royal Society of Chemistry.


Hao X.,Beijing University of Technology | Hao X.,CAS Beijing Institute of Applied Physics And Computational Mathematics | Chen J.,Beijing University of Technology | Chen J.,CAS Beijing Institute of Applied Physics And Computational Mathematics | And 4 more authors.
Physical Review Letters | Year: 2014

So far, nonsequential double ionization (NSDI) of atoms can be well understood within a semiclassical or even classical picture. No quantum effect appears to be required to explain the data observed. We theoretically study electron correlation resulting from NSDI of argon in a low-intensity laser field using a quantum-mechanical S-matrix theory. We show that quantum interference between the contributions of different intermediate excited states of the singly charged argon ion produces a transition from back-to-back to side-by-side emission with increasing laser intensity, which is in close agreement with the experimental data. For higher intensities, this transition is enhanced by the consequences of depletion of the excited states. © 2014 American Physical Society.


Chen B.,Beijing University of Technology | Chu C.-S.,Durham University
Journal of High Energy Physics | Year: 2010

We study real-time correlators in the Kerr/CFT correspondence. The near-horizon geometry of extreme and near-extremal Kerr black holes could be taken as the warped AdS spacetimes with the warping factor being a function of angular variable θ We show that for the perturbations whose equations of motions could be decomposed into the angular part and radial part, their real-time correlation functions could be computed from warped AdS/CFT correspondence. We find that the retarded Green's functions, the cross sections and the quasi-normal modes are all in perfect match with the dual CFT predictions. The same analysis is also generalized to the charged Newman-Kerr black holes. © SISSA 2010.


Song X.,Beijing University of Technology | Sun Z.,Beijing University of Technology | Huang Q.,U.S. National Institute of Standards and Technology | Rettenmayr M.,Friedrich - Schiller University of Jena | And 5 more authors.
Advanced Materials | Year: 2011

A universal mechanism that controls the zero thermal expansion (ZTE) behavior of the antiperovskite manganese nitrides is discovered. Modulating the Mn occupancy at its lattice sites leads to a drastic change in the thermal expansion behavior. The Mn site occupancy can be reduced by nanostructuring the material, generating a form of "giant" ZTE. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Fu X.,Beijing University of Posts and Telecommunications | Qian J.,Beijing University of Posts and Telecommunications | Qian J.,Beijing University of Technology | Qiao X.,CAS Institute of Semiconductors | And 2 more authors.
Optics Letters | Year: 2014

We report the nonlinear optical (NLO) properties of vertically stood WS2 nanoplates excited by 532-nm picosecond laser light. The nanoplates were synthesized by a no-catalyst thermal evaporation process. Raman spectroscopy and x-ray diffraction pattern indicate that the nanoplates are of high crystal quality. The nanoplates exhibit large nonlinear saturable absorption but negligible nonlinear refraction. Mechanisms of the NLO response are proposed. © 2014 Optical Society of America.


Lei J.,Beijing University of Technology | Garcia-Sanchez F.,University of Malaga | Zhang C.,University of Siegen
International Journal of Solids and Structures | Year: 2013

In this paper, a universal matrix-form displacement extrapolation formula and the explicit form are derived to determine the dynamic intensity factors of an interface crack in general anisotropic piezoelectric bi-materials. It is very feasible for numerical methods, especially for boundary element method (BEM) which can directly present the unknown boundary values. Using the explicit extrapolation formula, the transient response of interfacial cracks in piezoelectric bi-materials under electro-mechanical impacts is studied by time-domain BEM together with a sub-domain technique. The present time-domain BEM uses a quadrature formula for the temporal discretization to approximate the convolution integrals and a collocation method for the spatial discretization. Quadratic quarter-point elements are implemented at the tips of the interface cracks. General cases for the poling axis of each piezoelectric component unparallel to the Cartesian coordinate axes are studied. Numerical examples are presented and discussed the effects of the poling direction, material combination and the load combination on dynamic intensity factors. © 2013 Elsevier Ltd. All rights reserved.


Jiang Y.,Shanghai JiaoTong University | Lu S.,Shanghai JiaoTong University | Zeng Y.,Beijing University of Technology
Journal of Tissue Engineering and Regenerative Medicine | Year: 2011

A major objective of scaffold fabrication for tissue-engineering applications in wound healing is to understand the relationship between scaffold topography and cell behaviour. Recently, researchers have focused on arrays of cell adhesion protein styled in linear-grid micropatterns; however, these linear-grid patterns hardly reflect the topographical features of a natural extracellular matrix (ECM). In order to clarify the relationship between substrate adhesion points and cell behaviour, changes of dermal fibroblasts cultured on triangular microdot arrays were investigated. Micropatterns were micro-printed by silicone substrate stamps with collagen, while regions outside of the microdots were functionalized to block cellular adhesion. Cell morphology, expression of α-SMA, cell viability and hydroxyproline levels were examined for dermal fibroblasts cultured on the microdot substrates and on non-patterned control substrates. On patterned substrates, the expression of α-SMA significantly decreased, cell vitality increased and hydroxyproline content decreased with increasing vertex angles of the triangular array. Significantly more hydroxyproline was observed in all experimental groups in comparison to the control group. The results indicate that small vertex angles of the triangular array were detrimental to cell survival, likely due to constraint of the cell to a small adhesion area. We hypothesize that cells actively adapt to this situation by attempting to remodel their microenvironments with secretion of hydroxyproline. This illustrates the existence of feedback between cells and their microenvironments, such that when surroundings are unfavourably altered, the cells attempt to reconstruct the environment with secretion of ECM. © 2010 John Wiley & Sons, Ltd.


Wang N.,Guangxi Normal University | Liu M.,Guangxi Normal University | Wu X.,China Institute of Atomic Energy | Meng J.,Beijing University of Technology | Meng J.,Beihang University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

By taking into account the surface diffuseness correction for unstable nuclei, the accuracy of the macroscopic-microscopic mass formula is further improved. The rms deviation with respect to essentially all the available mass data falls to 298 keV, crossing the 0.3 MeV accuracy threshold for the first time within the mean-field framework. Considering the surface effect of the symmetry potential which plays an important role in the evolution of the "neutron skin" toward the "neutron halo" of nuclei approaching the neutron drip line, we obtain an optimal value of the symmetry energy coefficient J = 30.16 MeV. With an accuracy of 258 keV for all the available neutron separation energies and of 237 keV for the α-decay Q-values of super-heavy nuclei, the proposed mass formula is particularly important not only for the reliable description of the r process of nucleosynthesis but also for the study of the synthesis of super-heavy nuclei. © 2014 The Authors.


Zheng H.,Beijing University of Technology | Liu Z.,CAS Wuhan Institute of Rock and Soil Mechanics | Ge X.,CAS Wuhan Institute of Rock and Soil Mechanics
International Journal for Numerical Methods in Engineering | Year: 2013

For second-order problems, where the behavior is described by second-order partial differential equations, the numerical manifold method (NMM) has gained great success. Because of difficulties in the construction of the H 2-regular Lagrangian partition of unity subordinate to the finite element cover; however, few applications of the NMM have been found to fourth-order problems such as Kirchhoff's thin plate problems. Parallel to the finite element methods, this study constructs the numerical manifold space of the Hermitian form to solve fourth-order problems. From the minimum potential principle, meanwhile, the mixed primal formulation and the penalized formulation fitted to the NMM for Kirchhoff's thin plate problems are derived. The typical examples indicate that by the proposed procedures, even those earliest developed elements in the finite element history, such as Zienkiewicz's plate element, regain their vigor. © 2013 John Wiley & Sons, Ltd.


Chen Y.J.,Shaanxi Normal University | Fu L.B.,CAS Beijing Institute of Applied Physics And Computational Mathematics | Fu L.B.,Beijing University of Technology | Liu J.,CAS Beijing Institute of Applied Physics And Computational Mathematics | Liu J.,Beijing University of Technology
Physical Review Letters | Year: 2013

The exquisite procedure for imaging a molecular orbital with high-order harmonics proposed by Itatani et al. encounters difficulty when extended to an asymmetric molecule because the wave function there usually does not have a definite parity. With the observation that the wave function can be decomposed into a sum of odd and even functions and that the ionization process in harmonic generation is usually not sensitive to the asymmetry of the molecular potential, we predict that asymmetric molecular orbital imaging can be implemented through decoding odd-even high-order harmonics. A generalized tomography procedure is proposed, which has been certified by analytic deduction and numerical simulation. The above finding greatly extends the molecular tomography procedure and will further stimulate related experiments. © 2013 American Physical Society.


Cao L.,Beijing University of Technology | Guo W.,CAS Beijing National Laboratory for Molecular | Wang Y.,Beijing University of Technology | Jiang L.,CAS Beijing National Laboratory for Molecular | Jiang L.,Beihang University
Langmuir | Year: 2012

Ion current rectification (ICR) in negatively charged conical nanopores is shown to be controlled by the electrolyte concentration gradient depending on the direction of ion diffusion. The degree of ICR is enhanced with the increasing forward concentration difference. An unusual rectification inversion is observed when the concentration gradient is reversely applied. A numerical simulation based on the coupled Poisson and Nernst-Planck (PNP) equations is proposed to solve the ion distribution and ionic flux in the charged and structurally asymmetric nanofluidic channel with diffusive ion flow. Simulation results qualitatively describe the diffusion-induced ICR behavior in conical nanopores suggested by the experimental data. The concentration-gradient- dependent ICR enhancement and inversion is attributed to the cooperation and competition between geometry-induced asymmetric ion transport and the diffusive ion flow. The present study improves our understanding of the ICR in asymmetric nanofluidic channels associated with the ion concentration difference and provides insight into the rectifying biological ion channels. © 2011 American Chemical Society.


Yue Y.,Beihang University | Zheng K.,Beijing University of Technology
Applied Physics Letters | Year: 2014

With electron-beam (e-beam) off, in-situ tensile experiments on amorphous silica nanowires (NWs) were performed inside a transmission electron microscope (TEM). By controlling the loading rates, the strain rate can be adjusted accurately in a wide range. The result shows a strong strain rate effect on the plasticity of amorphous silica NWs. At lower strain rate, the intrinsic brittle materials exhibit a pronounced elongation higher than 100% to failure with obvious necking near ambient temperature. At the strain rate higher than 5.23 × 10- 3/s, the elongation of the NW decreased dramatically, and a brittle fracture feature behavior was revealed. This ductile feature of the amorphous silica NWs has been further confirmed with the in-situ experiments under optical microscopy while the effect of e-beam irradiation could be eliminated. © 2014 AIP Publishing LLC.


Wang J.,Sichuan University | Xiao C.,Beijing University of Technology | Wang X.,Beijing University of Technology
Physics of Plasmas | Year: 2012

Effects of out-of-plane shear flows on fast magnetic reconnection in Hall magnetohydrodynamics approximation are studied in a slab model with an initial Harris sheet equilibrium. It is found that the out-of-plane shear flows can also generate a series of out-of-plane magnetic perturbations that significantly modify the out-of-plane quadrupolar magnetic perturbation induced by the Hall effect in magnetic reconnection. The modification to out-of-plane magnetic perturbations then considerably affects the magnetic reconnection process. Particularly, flows along the X-line can either enhance or reduce the reconnection rate, even altering the X-point to an O-point and resulting in a secondary island. The impact on satellite observations is also discussed. © 2012 American Institute of Physics.


Aleksandrov A.Yu.,Saint Petersburg State University | Chen Y.,Beijing University of Technology | Platonov A.V.,Saint Petersburg State University | Zhang L.,Beijing University of Technology
Automatica | Year: 2011

This paper addresses the stability analysis of a class of switched nonlinear systems. The switched systems have uncertain nonlinear functions constrained in a sector set, which are called admissible sector nonlinearities. A sufficient condition in terms of linear inequalities is presented to guarantee the existence of a common Lyapunov function, and thereby to ensure that the switched system is stable for an arbitrary switching signal and any admissible sector nonlinearities. A constructive algorithm based on the modified Gaussian elimination procedure is given to find the solutions of the linear inequalities. The obtained results are applied to a population model with switchings of parameter values and the conditions of ultimate boundedness of its solutions are investigated. Another example of an automatic control system is considered to demonstrate the effectiveness of the proposed approaches. © 2011 Elsevier Ltd. All rights reserved.


Zheng H.,Beijing University of Technology | Xu D.,CAS Wuhan Institute of Rock and Soil Mechanics
International Journal for Numerical Methods in Engineering | Year: 2014

Aiming to solve, in a unified way, continuous and discontinuous problems in geotechnical engineering, the numerical manifold method introduces two covers, namely, the mathematical cover and the physical cover. In order to reach the goal, some issues in the simulation of crack propagation have to be solved, among which are the four issues to be treated in this study: (1) to reduce the rank deficiency induced by high degree polynomials as local approximation, a new variational principle is formulated, which suppresses the gradient-dependent DOFs; (2) to evaluate the integrals with singularity of 1/r, a new numerical quadrature scheme is developed, which is simpler but more efficient than the existing Duffy transformation; (3) to analyze kinked cracks, a sign convention for argument in the polar system at the crack tip is specified, which leads to more accurate results in a simpler way than the existing mapping technique; and (4) to demonstrate the mesh independency of numerical manifold method in handling strong singularity, a mesh deployment scheme is advised, which can reproduce all singular locations of the crack with regard to the mesh. Corresponding to the four issues, typical examples are given to demonstrate the effectiveness of the proposed schemes. © 2014 John Wiley & Sons, Ltd.


Zheng H.,Beijing University of Technology | Liu F.,CAS Wuhan Institute of Rock and Soil Mechanics | Li C.,CAS Wuhan Institute of Rock and Soil Mechanics
International Journal of Fracture | Year: 2014

In order to solve problems, from a continuum point of view and in a unified way, involving continuum and discontinuum deformation, and small deformation and large movement, the numerical manifold method (NMM) introduces two covers, namely the mathematical cover (MC) and the physical cover (PC). This study generates the MC with the influence domains of nodes in the moving least squares (MLS) interpolation instead of commonly-used finite element meshes, significantly simplifying the generation of PCs and the simulation of crack growth. Advantageous over the conventional meshfree method, the MLS-based NMM can naturally treat complex geometry without recourse to those complicated but contrived criteria or operations. Moreover, the treatment of large movement caused by cracking is much easier with the MLS-based NMM than with the FE-based NMM. © 2014, Springer Science+Business Media Dordrecht.


Zheng H.,Beijing University of Technology | Liu F.,CAS Wuhan Institute of Rock and Soil Mechanics | Du X.,Beijing University of Technology
Computer Methods in Applied Mechanics and Engineering | Year: 2015

The full response of a brittle structure containing multiple cracks to loading under the servo control is of vital importance in the evaluation of properties of the structure. During crack growth, the fracture toughness condition at all the crack tips as well as the equilibrium condition should be obeyed, leading to a nonlinear complementarity problem (NCP). The vector-valued function in the NCP depends implicitly on the cracking increments which in turn determine the stress field. The stress field can be obtained through solving a mixed variational problem. Since the degrees of freedom in the discrete variational problem vary with cracking not only in magnitude but also in number, the Jacobian matrix of the NCP is hard to compute and, it cannot be expected to be solved by the Newton methods that involve the calculation of Jacobian matrices. Therefore, a well-scaled projection-contraction algorithm is designed. The proposed procedure is able to simulate growth of multiple cracks in a natural way, allowing the crack tips to stop anywhere with no sensitivity to node configuration or cracking increments. Through the analysis of some examples that have been widely tested, many interesting and profound phenomena are found which have never been revealed. © 2015 Elsevier B.V.


Yan C.,CAS Wuhan Institute of Rock and Soil Mechanics | Zheng H.,Beijing University of Technology
International Journal of Rock Mechanics and Mining Sciences | Year: 2016

In this study, we propose a new coupled hydro-mechanical model considering porous media flow (FDEM-flow) for simulating hydraulic fracturing, which makes full use of the unique topological connection between joint elements and solid elements in the combined finite-discrete element method (FDEM). The joint elements form the flow channel for fluid, through which flow obeys the cubic law. In addition, viscous forces of fluid are taken into account in FDEM-flow. A simple example with analytical solution is given to verify the model. Then, the effects of fluid viscosity on hydraulic fracturing are investigated by this model. The simulated results show that when a low viscosity fluid is injected, the fluid infiltrates the fracture rapidly. The initiation pressure is lower than the theoretical value and the breakdown pressure is slightly larger than the initiation pressure. When high viscosity fluid is injected, fluid infiltrate into the cracks very slowly. The initiation pressure is close to the theoretical value and the breakdown pressure is much larger than the initiation pressure. © 2016


Zhang R.,Beihang University | Quan Q.,Beihang University | Quan Q.,Beijing University of Technology | Cai K.-Y.,Beihang University
IET Control Theory and Applications | Year: 2011

Here, the attitude control of a quadrotor aircraft subject to a class of disturbances is studied. Unlike disturbances mentioned in most of the existing literature, the disturbance considered here is time varying and non-vanished. An extended observer is designed to estimate the disturbance by treating it as a new unknown state. Based on the estimation, a feedback controller with a sliding mode term is designed to stabilise the attitude of the quadrotor. Furthermore, to avoid the discontinuity of the control law caused by the sliding mode term, a modified sliding mode term is designed. The resulting continuous feedback controller makes the attitude error uniformly ultimate bounded. Theoretical results are confirmed by numerical simulations. © 2011 The Institution of Engineering and Technology.


Chen H.-X.,Beijing University of Technology | Dmitrasinovic V.,University of Belgrade | Hosaka A.,Osaka University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Three-quark nucleon interpolating fields in QCD have well-defined SU L(3)×SUR(3) and UA(1) chiral transformation properties, viz. [(6,3)×(3,6)], [(3,3̄) ×(3̄,3)], [(8,1)×(1,8)], and their mirror images; see. It has been shown (phenomenologically) in that mixing of the [(6,3)×(3,6)] chiral multiplet with one ordinary (naive) and one mirror field belonging to the [(3,3̄)×(3̄,3)], [(8,1)×(1,8)] multiplets can be used to fit the values of the isovector (gA(3)) and the flavor-singlet (isoscalar) axial coupling (gA(0)) of the nucleon and then predict the axial F and D coefficients, or vice versa, in reasonable agreement with experiment. In an attempt to derive such mixing from an effective Lagrangian, we construct all SUL(3)×SUR(3) chirally invariant nonderivative one-meson-baryon interactions and then calculate the mixing angles in terms of baryons' masses. It turns out that there are (strong) selection rules: for example, there is only one nonderivative chirally symmetric interaction between J=12 fields belonging to the [(6,3)×(3,6)] and the [(3,3̄) ×(3̄,3)] chiral multiplets, that is also UA(1) symmetric. We also study the chiral interactions of the [(3,3̄)×(3̄,3)] and [(8,1)×(1,8)] nucleon fields. Again, there are selection rules that allow only one off-diagonal nonderivative chiral SUL(3)×SU R(3) interaction of this type, that also explicitly breaks the U A(1) symmetry. We use this interaction to calculate the corresponding mixing angles in terms of baryon masses and fit two lowest-lying observed nucleon (resonance) masses, thus predicting the third (J=12, I=32) Δ resonance, as well as one or two flavor-singlet Λ hyperon(s), depending on the type of mixing. The effective chiral Lagrangians derived here may be applied to high density matter calculations. © 2011 The American Physical Society.


Gu Z.,Nanjing Normal University | Xi X.,Beijing University of Technology | Yang J.,Beijing University of Technology | Xu J.,Nanjing Southeast University
Fuel | Year: 2012

In this paper, three rare earth tungsten (RE-W) electrostatic precipitation cathodes (cerium-tungsten (Ce-W), lanthanum-tungsten (La-W) and yttrium-tungsten (Y-W)) were prepared by powder metallurgy. The microstructure and the electron emission properties of the three cathodes were examined. The application of the Y-W cathode in high temperature electrostatic precipitation was investigated. Results show that the addition of the rare earth reduces the tungsten crystal size, with yttrium (Y) affecting the crystal size more significantly than lanthanum (La) and cerium (Ce). The rare earth (cerium, lanthanum or yttrium) exists, in the form of crystalline tungstates, at the tungsten (W) crystal boundary. The effective work function of the La-W cathode has the lowest value of 2.88 eV at vacuum condition, but the Y-W cathode shows the best emission properties at atmosphere pressure. The collection performance of an electrostatic precipitator (ESP) using the Y-W cathode was investigated by ash particles with various resistivity and size distribution at various temperatures. The particles with higher resistivity tend to be collected effectively at high ambient temperature, and the collection efficiency rise with the increase in temperature. If the resistivity of dusts is not high enough, corresponding to the highest collection efficiency, there exists an optimum temperature value. As in a conventional corona ESP, the larger particles are collected more effectively in an ESP with Y-W cathode. © 2012 Elsevier Ltd. All rights reserved.


Huang X.-L.,CAS Changchun Institute of Applied Chemistry | Huang X.-L.,University of Chinese Academy of Sciences | Wang R.-Z.,Beijing University of Technology | Xu D.,CAS Changchun Institute of Applied Chemistry | And 8 more authors.
Advanced Functional Materials | Year: 2013

Ultralong cycle life, high energy, and power density rechargeable lithium-ion batteries are crucial to the ever-increasing large-scale electric energy storage for renewable energy and sustainable road transport. However, the commercial graphite anode cannot perform this challenging task due to its low theoretical capacity and poor rate-capability performance. Metal oxides hold much higher capacity but still are plagued by low rate capability and serious capacity degradation. Here, a novel strategy is developed to prepare binder-free and mechanically robust CoO/graphene electrodes, wherein homogenous and full coating of β-Co(OH)2 nanosheets on graphene, through a novel electrostatic induced spread growth method, plays a key role. The combined advantages of large 2D surface and moderate inflexibility of the as-obtained β-Co(OH)2/graphene hybrid enables its easy coating on Cu foil by a simple layer-by-layer stacking process. Devices made with these electrodes exhibit high rate capability over a temperature range from 0 to 55 °C and, most importantly, maintain excellent cycle stability up to 5000 cycles even at a high current density. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Gehrlein J.,Karlsruhe Institute of Technology | Petcov S.T.,International School for Advanced Studies | Petcov S.T.,University of Tokyo | Petcov S.T.,Bulgarian Academy of Science | And 2 more authors.
Nuclear Physics B | Year: 2015

In this paper we discuss a minor modification of a previous SU(5)×A5 flavour model which exhibits at leading order golden ratio mixing and sum rules for the heavy and the light neutrino masses. Although this model could predict all mixing angles well it fails in generating a sufficient large baryon asymmetry via the leptogenesis mechanism. We repair this deficit here, discuss model building aspects and give analytical estimates for the generated baryon asymmetry before we perform a numerical parameter scan. Our setup has only a few parameters in the lepton sector. This leads to specific constraints and correlations between the neutrino observables. For instance, we find that in the model considered only the neutrino mass spectrum with normal mass ordering and values of the lightest neutrino mass in the interval 10-18 meV are compatible with the current data on the neutrino oscillation parameters. With the introduction of only one NLO operator, the model can accommodate successfully simultaneously even at 1σ level the current data on neutrino masses, on neutrino mixing and the observed value of the baryon asymmetry. © 2015 The Authors.


Shao H.-S.,Beijing University of Technology | Zhang Y.-J.,Beihang University
Journal of High Energy Physics | Year: 2012

The complete set of Feynman rules for the rational part R of QCD corrections in the MSSM are calculated at the one-loop level, which can be very useful in the next-to-leading order calculations in supersymmetric models. Our results are expressed in the 't Hooft-Veltman regularization scheme and in the Four Dimensional Helicity scheme with non-anticommutating and anticommutating γ 5 strategies. © 2012 SISSA.


Shi Z.,Beihang University | Zhang S.,Beijing University of Technology
Acta Physica Polonica B, Proceedings Supplement | Year: 2015

The low-lying structures of the even-even Gd isotopes, including the partial dynamical symmetry candidates 156-162Gd, are investigated in the framework of five-dimensional collective Hamiltonian based on the covariant density functional theory with the density functional PC-PK1. The available experimental data are reproduced by the microscopic calculations. A shape evolution from the γ-soft 150Gd to the well-deformed prolate 162Gd is presented. The ground states of the partial dynamical symmetry candidates 156-162Gd are all well-deformed prolate at β 0:35.


Yan C.Z.,CAS Wuhan Institute of Rock and Soil Mechanics | Zheng H.,Beijing University of Technology
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2016

Although the potential contact force proposed by Munjiza overcomes the difficulties inherent in the traditional discrete element methods, the physical meaning of the potential is not clear and the contact force derived from the original potential function is strongly dependent on the mesh configuration. In this study, we redefine a potential function and propose a new contact force calculation method based on a unified standard. Moreover, the new potential function retains all the advantages of the original potential function but has less mesh dependency. © 2016 John Wiley & Sons, Ltd.


Lu Z.,Nanjing Southeast University | Lu Z.,Federico Santa María Technical University | Ma B.-Q.,Beijing University of Technology | She J.,Beijing University of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We study the single spin asymmetries for the πp↑→μ+μ-X process. We consider the asymmetries contributed by the coupling of the Boer-Mulders function with the transversity distribution and the pretzelosity distribution, characterized by the sin(3φ+φS) and sin(3φ-φS) azimuthal angular dependence, respectively. We estimate the magnitude of these asymmetries at COMPASS by using proper weighting functions. We find that the sin(φ+φS) asymmetry is of the size of a few percent and can be measured through the experiment. The sin(3φ-φS) asymmetry is smaller than the sin(φ+φS) asymmetry. After a cut on qT, we succeed in enhancing the asymmetry. © 2011 Elsevier B.V.


Wang M.,Beijing University of Technology | Zan T.,Beijing University of Technology | Yang Y.,Beihang University | Fei R.,Beijing University of Technology
International Journal of Machine Tools and Manufacture | Year: 2010

A new-type nonlinear tuned mass damper (TMD) containing an additional element of elastic support dry friction compared with the common linear TMD is proposed to suppress machining chatter. The design and tuning process of this nonlinear TMD have used a combination of analytical modeling with experimentally measured frequency response function (FRF) of the machining system. Theoretical studies and experimental results show that the proposed nonlinear TMD can remarkably improve the machining stability by effectively suppressing the magnitude of the real part of the FRF of the damped machining system. © 2010 Elsevier Ltd. All rights reserved.


Li J.,Beihang University | Wang L.,Beijing University of Technology | Liu L.,Beihang University | Guo L.,Beihang University | And 2 more authors.
Chemical Communications | Year: 2010

Tetrahexahedral Au nanocrystals with exposed {520} facets have been prepared in high yield by facile seed-mediated growth and the as-synthesized tetrahexahedral Au nanocrystals possess enhanced electrocatalytic activity toward the oxidation of formic acid. © The Royal Society of Chemistry 2010.


BEIJING, October 28, 2016 /PRNewswire/ -- Phoenix New Media Limited (NYSE: FENG), a leading new media company in China ("Phoenix New Media", "ifeng" or the "Company"), today announced that it has appointed media veteran Mr. Tong Chen as Co-President of ifeng, effective October 31, 2016. Mr. Chen has also been appointed by Particle Inc. ("Yidian") as its President, effective the same date. Mr. Chen will be fully responsible for ifeng's content operations management and Yidian's content, product operations, and public relations. "We are extremely excited to have Tong, a seasoned media executive and pioneer of China's internet media ecosystem, join us at ifeng," stated Mr. Shuang Liu, CEO of ifeng. "Over the years, Tong has helped lead the media industry's content consumption evolution and spearheaded the development and success of China's portal, blog and weibo productions. He is a proven leader with significant media and content development expertise and a deep understanding of the changes and direction that are taking place, not only in our industry, but within China overall and recognizes the vast opportunities they present for ifeng. As we continue to improve our cutting-edge technology and provide our users with the highest quality, customized content across our mobile and PC platforms, we aim to leverage Tong's vision and track record of delivering results to lead us in the right direction. We look forward to working with him to build upon the Company's strong foundation and accelerate our success for years to come." Mr. Chen is a well-known, highly accomplished media executive with nearly 20 years of experience in the media and content development space. From November 2014 to October 2016, he served as Vice President of Xiaomi Inc., responsible for its content investment and operation. Prior to joining Xiaomi Inc., Mr. Chen spent 17 years at SINA Corporation and served as its Chief Editor and Executive Vice President from February 2007 to November 2014. Mr. Chen holds an M.B.A. from China-Europe International Business School, an M.A. in Journalism from Renmin University of China, an M.A. in Communications from Beijing Institute of Technology, and a B.S. in electronic engineering from Beijing University of Technology. Phoenix New Media Limited (NYSE: FENG) is a leading new media company providing premium content on an integrated platform across Internet, mobile and TV channels in China. Having originated from a leading global Chinese language TV network based in Hong Kong, Phoenix TV, the Company enables consumers to access professional news and other quality information and share user-generated content on the Internet and through their mobile devices. Phoenix New Media's platform includes its ifeng.com channel, consisting of its ifeng.com website and web-based game platform, its video channel, comprised of its dedicated video vertical and mobile video services, and its mobile channel, including its mobile Internet website, mobile applications and mobile value-added services. Yidian owns Yidian Zixun, which is an interest-oriented mobile App, which integrates cutting-edge search and recommendation technologies to provide its users with unique personalized content. Yidian is dedicated to building a next-generation, interest-based content engine. Yidian was co-founded by Mr. Xuyang Ren, who is the Chairman of Yidian and former vice president of Baidu, Dr. Zhaohui Zheng, who is the CEO of Yidian and former founding head of Yahoo! Labs in China, Dr. Xin Li and Mr. Rongqing Lu, both of whom are Internet technology veterans with years of experiences in top-notch Silicon Valley high-tech companies. This announcement contains forwarda??looking statements. These statements are made under the "safe harbor" provisions of the U.S. Private Securities Litigation Reform Act of 1995. These forwarda??looking statements can be identified by terminology such as "will," "expects," "anticipates," "future," "intends," "plans," "believes," "estimates" and similar statements. Among other things, the business outlook and quotations from management in this announcement, as well as Phoenix New Media's strategic and operational plans, contain forwarda??looking statements. Phoenix New Media may also make written or oral forwarda??looking statements in its periodic reports to the U.S. Securities and Exchange Commission ("SEC") on Forms 20a??F and 6a??K, in its annual report to shareholders, in press releases and other written materials and in oral statements made by its officers, directors or employees to third parties. Statements that are not historical facts, including statements about Phoenix New Media's beliefs and expectations, are forwarda??looking statements. Forwarda??looking statements involve inherent risks and uncertainties. A number of factors could cause actual results to differ materially from those contained in any forwarda??looking statement, including but not limited to the following: the Company's goals and strategies; the Company's future business development, financial condition and results of operations; the expected growth of online and mobile advertising, online video and mobile paid services markets in China; the Company's reliance on online and mobile advertising and MVAS for a majority of its total revenues; the Company's expectations regarding demand for and market acceptance of its services; the Company's expectations regarding maintaining and strengthening its relationships with advertisers, partners and customers; fluctuations in the Company's quarterly operating results; the Company's plans to enhance its user experience, infrastructure and services offerings; the Company's reliance on mobile operators in China to provide most of its MVAS; changes by mobile operators in China to their policies for MVAS; competition in its industry in China; and relevant government policies and regulations relating to the Company. Further information regarding these and other risks is included in the Company's filings with the SEC, including its registration statement on Form Fa??1, as amended, and its annual reports on Form 20a??F. All information provided in this press release and in the attachments is as of the date of this press release, and Phoenix New Media does not undertake any obligation to update any forwarda??looking statement, except as required under applicable law. For investor and media inquiries please contact: To view the original version on PR Newswire, visit:http://www.prnewswire.com/news-releases/phoenix-new-media-announces-appointments-of-tong-chen-as-co-president-of-ifeng-and-president-of-yidian-300353356.html


Yu C.,University of North Texas | Yan W.,Beijing University of Technology
Thin-Walled Structures | Year: 2011

This paper proposes a design method, based on the Effective Width Method, for determining the nominal distortional buckling strength of typical cold-formed steel C and Z sections subjected to bending. The method can be integrated into the classic effective width design provisions specified in AISI S100, and it allows the conventional design approach to cover more comprehensive limit states. The proposed method is calibrated by the flexural distortional buckling strength predicted by the Direct Strength Method. Comparison with experimental results indicates that the proposed method yields reasonable predictions for the flexural distortional buckling strength of industrial standard C and Z sections. The method offers the same level of accuracy and reliability as the Direct Strength Method. © 2010 Elsevier Ltd. All rights reserved.


Jin S.,Beijing University of Civil Engineering and Architecture | Jin S.,University of Tennessee at Knoxville | Zhang J.,Beijing University of Technology | Huang B.,University of Tennessee at Knoxville
Construction and Building Materials | Year: 2013

Pore structure is one of the major characteristics influencing the freeze-thaw resistance of concrete. Although the air-void spacing factor associated to the porosity features of concrete is known as a widely used parameter to assess the freeze-thaw resistance, controversies on the determination of critical values of air-void spacing factor still exist in many related studies. Moreover, it is reported that the pore-size distribution in concrete also significantly affects its freeze-thaw resistance. In this study, a fractal model was established to characterize the air voids size-distribution in concrete, and the corresponding fractal dimension obtained from the fractal model was validated for its effectiveness in describing the air voids size-distribution quantitatively. By comparison to a fractal model presented in a previous study, the fractal model proposed in this study was found more reasonable and reliable. Based on the theoretical principle, correlations between air voids size-distributions and the measured freeze-thaw resistances of concrete were established through laboratory experiments. The results revealed that air voids size-distribution exhibited more significant influence on the freeze-thaw resistance of concrete than the air-void spacing. Furthermore, a regression equation with fairly high correlation coefficient between the fractal dimension of air voids size-distribution and the durability factors of concrete was obtained from the results. © 2013 Elsevier Ltd. All rights reserved.


Liu Y.,Beijing University of Technology | Qin F.,Beijing University of Technology | Liu Y.,Tsinghua University | Cen Z.,Tsinghua University
Computational Mechanics | Year: 2010

In this paper, Daubechies (DB) wavelet is used for solution of 2D large deformation problems. Because the DB wavelet scaling functions are directly used as basis function, no meshes are needed in function approximation. Using the DB wavelet, the solution formulations based on total Lagrangian approach for two-dimensional large deformation problems are established. Due to the lack of Kroneker delta properties in wavelet scaling functions, Lagrange multipliers are used for imposition of boundary condition. Numerical examples of 2D large deformation problems illustrate that this method is effective and stable. © 2009 Springer-Verlag.


Fei H.,Rice University | Ye R.,Rice University | Ye G.,Rice University | Gong Y.,Rice University | And 6 more authors.
ACS Nano | Year: 2014

The scarcity and high cost of platinum-based electrocatalysts for the oxygen reduction reaction (ORR) has limited the commercial and scalable use of fuel cells. Heteroatom-doped nanocarbon materials have been demonstrated to be efficient alternative catalysts for ORR. Here, graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing. This hybrid material combined the advantages of both components, such as abundant edges and doping sites, high electrical conductivity, and high surface area, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media. © 2014 American Chemical Society.


Zheng M.-P.,Beijing University of Technology | Hou Y.-D.,Beijing University of Technology | Xie F.-Y.,Sun Yat Sen University | Chen J.,Sun Yat Sen University | And 2 more authors.
Acta Materialia | Year: 2013

A CoCO3-added Pb((Zn1/3Nb2/3) 0.20(Zr0.50Ti0.50)0.80)O 3 (0.2PZN-0.8PZT) system was prepared and investigated. The results reveal that Co ions are present in the mixed valence form of +2 and +3, and their relative mole ratio depends on doping content. Co doping induces a phase transformation from the MPB to the tetragonal phase side, and the corresponding domain size increases accordingly. The solubility limit of Co ions in the perovskite matrix is near 0.2 wt.% in CoCO3 form. Below the solubility limit, Co ions enter the B sites of the oxygenic octahedral center, and the charge-compensating oxygen vacancies accelerate mass transport, which assists in the densification of the specimens. Above the solubility limit, excess Co ions gather in the grain boundaries and triple junctions, which facilitate the formation of a liquid phase with excess PbO and lead to remarkable grain growth. The resulting size effect plays a dominant role in improving the piezoelectric properties, which compensates for the hardening effect of acceptor doping. The optimum piezoelectric parameters are obtained at 0.8 wt.% CoCO3-doped 0.2PZN-0.8PZT system: d33 = 310 pC N-1, kp = 0.66, and Zmax = 14,600. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Yang Y.,Rice University | Fan X.,Rice University | Fan X.,Beijing University of Technology | Casillas G.,University of Texas at San Antonio | And 5 more authors.
ACS Nano | Year: 2014

Three-dimensional self-organized nanoporous thin films integrated into a heterogeneous Fe2O3/Fe3C-graphene structure were fabricated using chemical vapor deposition. Few-layer graphene coated on the nanoporous thin film was used as a conductive passivation layer, and Fe 3C was introduced to improve capacity retention and stability of the nanoporous layer. A possible interfacial lithium storage effect was anticipated to provide additional charge storage in the electrode. These nanoporous layers, when used as an anode in lithium-ion batteries, deliver greatly enhanced cyclability and rate capacity compared with pristine Fe2O 3: a specific capacity of 356 μAh cm-2 μm -1 (3560 mAh cm-3 or ∼1118 mAh g-1) obtained at a discharge current density of 50 μA cm-2 (∼0.17 C) with 88% retention after 100 cycles and 165 μAh cm-2 μm -1 (1650 mAh cm-3 or ∼518 mAh g-1) obtained at a discharge current density of 1000 μA cm-2 (∼6.6 C) for 1000 cycles were achieved. Meanwhile an energy density of 294 μWh cm -2 μm-1 (2.94 Wh cm-3 or ∼924 Wh kg -1) and power density of 584 μW cm-2 μm-1 (5.84 W cm-3 or ∼1834 W kg-1) were also obtained, which may make these thin film anodes promising as a power supply for micro- or even nanosized portable electronic devices. © 2014 American Chemical Society.


Wei W.,Beijing University of Technology | Wei W.,Tsinghua University | Wang S.,Tsinghua University | Hao J.,Tsinghua University | Cheng S.,Beijing University of Technology
Atmospheric Environment | Year: 2011

The future (2010-2020) anthropogenic volatile organic compounds (VOCs) emissions in China were projected in this study using 2005 as the reference year. The projections are based on the assumptions of a lower population growth rate (less than 1%), continuous economic development with high GDP growth, and increased urbanization. The results show that the national VOCs emissions would continuously increase from 19.4 Tg in 2005 to 25.9 Tg in 2020, even if China's legislative standards for VOCs emissions are implemented effectively in the future (assumed as control scenario I). The contributions of various emission sources were found to differ greatly in the period of 2010-2020. Solvent utilization would become the largest contributor rising from 22% to 37%, along with an increase for industrial processes from 17% to 24%. However, road vehicle emissions would rapidly decrease from 25% to 11% due to the strict VOCs emission limit standards in China, along with the decrease for stationary fuel combustion from 23% to 16% caused by the reduction of domestic biofuel consumption. Additionally, there would be a notable divergence among provincial emissions. The developed eastern and coastal regions would emit more VOCs than the relatively underdeveloped western and inland regions. Moreover, this divergence grows in the future.When we assumed stricter control measures for solvent utilization and industrial processes (control scenario II) for that period, the projections revealed national VOCs emissions per year would remain at about 20 Tg, if exhaust after-treatment systems are installed in newly-built factories (after 2005) for the most important industrial sources, and the market shares of " low/zero-VOCs" products in paints, adhesives and printing ink raise to the present levels of developed countries. The emission abatements of the two types of measures were estimated to be similar. While scenario II indicates that the sectoral and provincial differences of VOCs emissions would still exist, they would be smaller than in scenario I. © 2011 Elsevier Ltd.


Wang E.H.,Beijing University of Technology | Zhang H.G.,Beijing University of Technology | Fan B.Y.,Beijing University of Technology | Ouyang M.G.,Tsinghua University | And 2 more authors.
Energy | Year: 2011

Organic Rankine Cycle (ORC) could be used to recover low-grade waste heat. When a vehicle is running, the engine exhaust gas states have a wide range of variance. Defining the operational conditions of the ORC that achieve the maximum utilization of waste heat is important. In this paper the performance of different working fluids operating in specific regions was analyzed using a thermodynamic model built in Matlab together with REFPROP. Nine different pure organic working fluids were selected according to their physical and chemical properties. The results were compared in the regions when net power outputs were fixed at 10. kW. Safety levels and environmental impacts were also evaluated. The outcomes indicate that R11, R141b, R113 and R123 manifest slightly higher thermodynamic performances than the others; however, R245fa and R245ca are the most environment-friendly working fluids for engine waste heat-recovery applications. The optimal control principle of ORC under the transient process is discussed based on the analytical results. © 2011 Elsevier Ltd.


Luo B.,Tsinghua University | Wang X.,Tsinghua University | Wang Y.,Beijing University of Technology | Li L.,Tsinghua University
Journal of Materials Chemistry A | Year: 2014

Calcium barium zirconate titanate (Ba0.95Ca 0.05Zr0.15Ti0.85O3, BCZT) ceramic particles were prepared by a conventional solid-state method. BCZT powders were modified by dopamine through a chemical coating method. The composite flexible films based on dopamine@BCZT and polyvinylidene fluoride were fabricated via a solution casting method. The microstructure and morphology were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, and field emission scanning electron microscopy. A precision impedance analyzer and a dielectric withstand voltage test were used to test the dielectric constant, loss tangent, and breakdown strength. TEM results showed that dopamine was uniformly coated on the surface of BCZT particles with an average thickness of 20 nm. SEM results showed that the ceramic particles were dispersed homogeneously in the matrix. The dielectric constant increased with the increase of BCZT contents, while the loss tangent remained constant in the frequency range of 103 to 105 Hz. Different theoretical models were employed to predict the effective dielectric constants of the composite films, and the estimated results were compared with the experimental data. Weibull distribution was used to analyze the dielectric breakdown strength, and the results showed that the breakdown strength decreased then stayed over 60 kV mm-1. © 2013 The Royal Society of Chemistry.


Cao J.,Henan Normal University | Hikasa K.-I.,Tohoku University | Wang W.,Beijing University of Technology | Yang J.M.,CAS Institute of Theoretical Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

For the experimental search of neutralino dark matter, it is important to know its allowed mass and scattering cross section with the nucleon. In order to figure out how light a neutralino dark matter can be predicted in low energy supersymmetry, we scan over the parameter space of the NMSSM (next-to-minimal supersymmetric model), assuming all the relevant soft mass parameters to be below TeV scale. We find that in the parameter space allowed by current experiments the neutralino dark matter can be as light as a few GeV and its scattering rate off the nucleon can reach the sensitivity of XENON100 and CoGeNT. As a result, a sizable parameter space is excluded by the current XENON100 and CoGeNT data (the plausible CoGeNT dark matter signal can also be explained). The future 6000 kg-days exposure of XENON100 will further explore (but cannot completely cover) the remained parameter space. Moreover, we find that in such a light dark matter scenario a light CP-even or CP-odd Higgs boson must be present to satisfy the measured dark matter relic density. Consequently, the SM-like Higgs boson hSM may decay predominantly into a pair of light Higgs bosons or a pair of neutralinos so that the conventional decays like hSM→γγ is much suppressed. © 2011 Elsevier B.V.


Hua J.,Beijing University of Technology | Fan H.,Beijing University of Technology | Wang X.,Tsinghua University | Zhang Y.,Tsinghua University
Building and Environment | Year: 2015

Because heating energy consumption is huge and it takes a large part of building energy consumption, techniques aiming at decreasing the heating energy demand are very important in today's world. While, there are few studies regarding the determination method of the optimal heating mode (i.e. convective, radiative or mixing) of a given house. A novel concept based on the inverse problem method to determine the optimal heating mode of residential rooms is put forward in this paper. By minimizing the additive heating energy consumption and keeping indoor thermal comfort simultaneously, the optimal heating mode of residential rooms is determined by the variation method. Some general conclusions are derived, such as the transition point of the convective and radiative heating mode and the influence of wall's thermophysical properties on the energy saving ratio. For illustrative purposes, a typical residential room in Beijing is analyzed. In addition, optimal heating modes of six typical room kinds in four representative cities in China are determined, which can guide the proper selection of the heating method in various places. The proposed method can be the first step to build the optimal indoor thermal network, and the new concepts can be used to deal with other similar problems in the built environment field. © 2014 Elsevier Ltd.


Yu J.,Tsinghua University | Li D.-P.,Beijing University of Technology | Liao Q.-M.,Tsinghua University
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2011

Imaging in the atmosphere is often degraded by scattering due to atmospheric particles such as haze, fog, and mist. In this paper, we propose a novel fast defogging method based on the atmospheric scattering model. The white balance is performed and the atmospheric scattering model is simplified prior to visibility restoration. In the inference process of the atmospheric veil, the coarser estimate is refined using a fast bilateral filtering approach that preserves edges. Finally, the scene albedo is recovered by inverting this simplified model. The complexity of the proposed method is only a linear function of the number of input image pixels and this allows a very fast implementation. Results on a variety of outdoor foggy images demonstrate that the proposed method achieves good restoration for contrast and color fidelity, resulting in a great improvement in image visibility. Copyright © 2011 Acta Automatica Sinica.


Li B.,Johns Hopkins University | Yan P.F.,CAS Shenyang Institute of Metal Research | Sui M.L.,Beijing University of Technology | Ma E.,Johns Hopkins University
Acta Materialia | Year: 2010

We present transmission electron microscopy (TEM) observations of stacking faults (SFs) and their interactions with pyramidal dislocations, in plastically deformed polycrystalline pure magnesium. We have observed well-defined fringes as well as streaking in diffraction patterns, typical of SFs. The basal SFs are decorated by a large number of dark speckles, which are created by the interaction with pyramidal dislocations that have both 〈c〉 and 〈a〉 components as revealed by our contrast analysis. The SFs do not appear to result from the splitting of unit dislocations, as the SFs are relatively wide and no dislocation nodes were observed. By tilting the specimen systematically inside TEM, the SFs and the associated dislocations in Mg are found to exhibit a rich variety of features in terms of their morphology and diffraction contrast. © 2009 Acta Materialia Inc.


Yan P.F.,CAS Shenyang Institute of Metal Research | Du K.,CAS Shenyang Institute of Metal Research | Sui M.L.,Beijing University of Technology
Acta Materialia | Year: 2010

A martensitic transformation from the α to the γ phase of aluminum oxide was observed by transmission electron microscopy (TEM) upon rapid heating induced by pulsed laser irradiation. Two variants possessing a twin relationship were found in the product. Highresolution TEM reveals that the transformation is achieved via the glide of quarter partial dislocations on every other basal plane of α-Al 2O 3. The high thermal stress caused by pulsed laser irradiation is believed to be the main driving force of the phase transformation. This martensitic transformation is associated with a positive volume change and substantial shear strain. The overall shear strain could be minimized by the self-accommodating variants. These characteristics suggest potential application of the martensitic transformation for transformation toughening in ceramic materials. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Wang F.,Zhengzhou University | Wang F.,CAS Institute of Theoretical Physics | Wang W.,Beijing University of Technology | Wang W.,CAS Institute of Theoretical Physics | Yang J.M.,CAS Institute of Theoretical Physics
European Physical Journal C | Year: 2014

We recalculate the two-loop beta functions for three gauge couplings taking into account all low energy threshold corrections in split supersymmetry (split-SUSY) which assumes a very high scalar mass scale (Formula presented.). We find that in split-SUSY with a gaugino mass unification assumption and with a large (Formula presented.) the gauge coupling unification requires a lower bound on the gaugino mass. Combined with the constraints from the dark matter relic density and direct detection limits, we find that split-SUSY is very restricted and for dark matter mass below 1 TeV the allowed parameter space can be fully covered by XENON-1T(2017). © 2014, The Author(s).


Li A.,Xiamen University | Xu R.-X.,Beijing University of Technology | Lu J.-F.,Xiamen University
Monthly Notices of the Royal Astronomical Society | Year: 2010

We investigate the stability of strange quark matter and the properties of the corresponding strange stars for a wide range of quark mass scalings. The calculations show that the resulting maximum mass always lies between 1.5 M⊙ and 1.8 M⊙ for all the scalings chosen here. Strange star sequences with a linear scaling support the lowest gravitational masses, and a change (increase or decrease) of the scaling around the linear scaling leads to a higher maximum mass. Radii always decrease with the mass scaling. Thus, the larger the scaling, the faster the star might spin. In addition, the variation of the scaling causes an order of magnitude change of the strong electric field on the quark surface. This field is essential to the support of possible crusts of strange stars against gravity and thus may have some astrophysical implications. © 2010 The Authors. Journal compilation © 2010 RAS.


Wang Z.-L.,Jilin University | Yan J.-M.,Jilin University | Zhang Y.-F.,Beijing University of Technology | Ping Y.,Jilin University | And 2 more authors.
Nanoscale | Year: 2014

AuPd-CeO2 nanocomposites directly nucleated and grown on nitrogen-doped reduced graphene oxide, exhibit excellent catalytic activity and 100% hydrogen selectivity toward formic acid decomposition for hydrogen generation without any additives at room temperature. This journal is © The Royal Society of Chemistry.


Qu Z.,Tsinghua University | Qu Z.,Beijing University of Technology | Wan C.,Tsinghua University | Pan W.,Tsinghua University
Acta Materialia | Year: 2012

Compounds with an A 2B 2O 7-type pyrochlore structure have been identified as a class of materials with low thermal conductivity. To ascertain the effect of the pyrochlore structure, the thermophysical properties of rare-earth stannates which constitute the longest isostructural series with this unique crystal structure were measured and the thermal conduction behavior was investigated by analyzing the variation in the inverse phonon mean free path with temperature in terms of the phonon-scattering theory. The results show that the contraction of rare-earth ions and the accompanying deviation from the ideal pyrochlore structure result in a simultaneous increase in the Young's modulus and the thermal expansion coefficient. Scattering due to the strain field fluctuation caused by the systemic displacement of 48f oxygen ions rather than scattering from the so-called 8a site "oxygen vacancies" and thermal defects predominates in reducing the phonon mean free path and consequently the thermal conductivity at relative low temperature. At a certain critical temperature, the thermal conduction behavior of the stannates undergoes a transition to a minimum phonon mean free path mechanism, which is responsible for the remarkable variation in temperature dependence of thermal conductivity across the compositions. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Wang C.,Beijing University of Technology | Wang Y.,Beijing University of Technology | Yuille A.L.,University of California at Los Angeles
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2013

We address action recognition in videos by modeling the spatial-temporal structures of human poses. We start by improving a state of the art method for estimating human joint locations from videos. More precisely, we obtain the K-best estimations output by the existing method and incorporate additional segmentation cues and temporal constraints to select the ''best'' one. Then we group the estimated joints into five body parts (e.g. the left arm) and apply data mining techniques to obtain a representation for the spatial-temporal structures of human actions. This representation captures the spatial configurations of body parts in one frame (by spatial-part-sets) as well as the body part movements(by temporal-part-sets) which are characteristic of human actions. It is interpretable, compact, and also robust to errors on joint estimations. Experimental results first show that our approach is able to localize body joints more accurately than existing methods. Next we show that it outperforms state of the art action recognizers on the UCF sport, the Keck Gesture and the MSR-Action3D datasets. © 2013 IEEE.


Fu W.-J.,CAS Institute of Theoretical Physics | Liu Y.-X.,Beijing University of Technology | Liu Y.-X.,Accelerator Centre | Wu Y.-L.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We study fluctuations of conserved charges including baryon number, electric charge, and strangeness as well as the correlations among these conserved charges in the 2+1 flavor Polyakov-Nambu-Jona-Lasinio model at finite temperature. The calculated results are compared with those obtained from recent lattice calculations performed with an improved staggered fermion action at two values of the lattice cutoff with almost physical up and down quark masses and a physical value for the strange quark mass. We find that our calculated results are well consistent with those obtained in lattice calculations except for some quantitative differences for fluctuations related with strange quarks. Our calculations indicate that there is a pronounced cusp in the ratio of the quartic to quadratic fluctuations of baryon number, i.e. χ4B/χ2B, at the critical temperature during the phase transition, which confirms that χ4B/χ2B is a useful probe of the deconfinement and chiral phase transition. © 2010 The American Physical Society.


Wang W.,Beijing University of Technology | Yang J.M.,CAS Institute of Theoretical Physics | You L.L.,Beijing University of Technology
Journal of High Energy Physics | Year: 2013

In order to have massive neutrinos, the right-handed neutrino/sneutrino superfield (N) need to be introduced in supersymmetry. In the framework of NMSSM (the MSSM with a singlet S) such an extension will dynamically lead to a TeV-scale Majorana mass for the right-handed neutrino through the SN N coupling when S develops a vev (the free Majorana mass term is forbidden by the assumed Z 3 symmetry). Also, through the couplings SN N and SH u H d, the SM-like Higgs boson (a mixture of H u, H d and S) can naturally couple with the right-handed neutrino/sneutrino. As a result, the TeV-scale right-handed neutrino/sneutrino may significantly contribute to the Higgs boson mass. Through an explicit calculation, we find that the Higgs boson mass can indeed be sizably altered by the right-handed neutrino/sneutrino. Such new contribution can help to push up the SM-like Higgs boson mass and thus make the NMSSM more natural. © 2013 SISSA, Trieste, Italy.


Wang C.,Beijing University of Technology | Wang Y.,Beijing University of Technology | Yuille A.L.,University of California at Los Angeles
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2016

Recognizing an action from a sequence of 3D skeletal poses is a challenging task. First, different actors may perform the same action in various styles. Second, the estimated poses are sometimes inaccurate. These challenges can cause large variations between instances of the same class. Third, the datasets are usually small, with only a few actors performing few repetitions of each action. Hence training complex classifiers risks over-fitting the data. We address this task by mining a set of key-pose-motifs for each action class. A key-pose-motif contains a set of ordered poses, which are required to be close but not necessarily adjacent in the action sequences. The representation is robust to style variations. The key-pose-motifs are represented in terms of a dictionary using soft-quantization to deal with inaccuracies caused by quantization. We propose an efficient algorithm to mine key-pose-motifs taking into account of these probabilities. We classify a sequence by matching it to the motifs of each class and selecting the class that maximizes the matching score. This simple classifier obtains state-ofthe-art performance on two benchmark datasets.


Li B.Q.,CAS Shenyang Institute of Metal Research | Sui M.L.,Beijing University of Technology | Mao S.X.,University of Pittsburgh
Applied Physics Letters | Year: 2010

It is usually believed that the partial dislocation and deformation twin are the results of permanent plasticity in materials. Here, we present in situ atomic-scale observation of reversible stacking fault and deformation twin during loading and unloading in nanocrystalline Ni under high-resolution transmission electron microscopy. The high propensity for the reversibility of the stacking fault and deformation twin is due to the high stacking fault force and small grain size, and will provide an understanding at atomistic scale on the nature of the deformation in nanocrystalline materials. © 2010 American Institute of Physics.


Wang L.,CAS Institute of Computing Technology | Zhan J.,CAS Institute of Computing Technology | Shi W.,Wayne State University | Liang Y.,Beijing University of Technology
IEEE Transactions on Parallel and Distributed Systems | Year: 2012

The basic idea behind cloud computing is that resource providers offer elastic resources to end users. In this paper, we intend to answer one key question to the success of cloud computing: in cloud, can small-to-medium scale scientific communities benefit from the economies of scale? Our research contributions are threefold: first, we propose an innovative public cloud usage model for small-to-medium scale scientific communities to utilize elastic resources on a public cloud site while maintaining their flexible system controls, i.e., create, activate, suspend, resume, deactivate, and destroy their high-level management entitiesservice management layers without knowing the details of management. Second, we design and implement an innovative systemDawningCloud, at the core of which are lightweight service management layers running on top of a common management service framework. The common management service framework of DawningCloud not only facilitates building lightweight service management layers for heterogeneous workloads, but also makes their management tasks simple. Third, we evaluate the systems comprehensively using both emulation and real experiments. We found that for four traces of two typical scientific workloads: High-Throughput Computing (HTC) and Many-Task Computing (MTC), DawningCloud saves the resource consumption maximally by 59.5 and 72.6 percent for HTC and MTC service providers, respectively, and saves the total resource consumption maximally by 54 percent for the resource provider with respect to the previous two public cloud solutions. To this end, we conclude that small-to-medium scale scientific communities indeed can benefit from the economies of scale of public clouds with the support of the enabling system. © 2006 IEEE.


Cao J.,Henan Normal University | Wang W.,Beijing University of Technology | Yang J.M.,CAS Institute of Theoretical Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We examine the present and future XENON limits on the neutralino dark matter in split supersymmetry (split-SUSY). Through a scan over the parameter space under the current constraints from collider experiments and the WMAP measurement of the dark matter relic density, we find that in the allowed parameter space a large part has been excluded by the present XENON100 limits and a further largish part can be covered by the future exposure (6000 kgday). In case of unobservation of dark matter with such an exposure in the future, the lightest neutralino will remain bino-like and its annihilation is mainly through exchanging the SM-like Higgs boson in order to get the required relic density. © 2011 Elsevier B.V.


Peng Y.,Beijing University of Technology | Miao H.,Tsinghua University | Peng Z.,Beijing University of Technology
International Journal of Refractory Metals and Hard Materials | Year: 2013

In order to improve the performances of TiCN-based cermets, researchers have paid much attention directly towards developing various new spices of cermets. The present review will try to sum up the efforts in designing and tailing in compositions and microstructures of TiCN-based cermets in recent years aiming at enhanced cermet properties. The relationship between the cermet constituents and their mechanical properties and wear resistance, as well as the advances in the synthesis of TiCN powders and preparation of TiCN-based cermets were included. Special emphasis was paid on the preparation of ultrafine/nano TiCN-based cermets possessing enhanced hardness, mechanical strength, toughness and wear resistance, which has led to a very recent surge of interest in the development of TiCN-based cermets. In particular, it has been possible to obtain dense TiCN-based cermets with ultrafine- and/or nano-structures by means of fast sintering techniques, such as spark plasma sintering, microwave vacuum sintering and so on. © 2013 Elsevier Ltd. All rights reserved.


Frixione S.,CERN | Hirschi V.,SLAC | Pagani D.,Catholic University of Louvain | Shao H.-S.,Beijing University of Technology | Zaro M.,CNRS Theoretical and High Energy Physics
Journal of High Energy Physics | Year: 2014

Abstract: We present the calculation of the next-to-leading contribution of order αS2α2 to the production of a Standard Model Higgs boson in association with a top-quark pair at hadron colliders. All effects of weak and QCD origin are included, whereas those of QED origin are ignored. We work in the MadGraph5_aMC@NLO framework, and discuss sample phenomenological applications at a 8, 13, and 100 TeV pp collider, including the effects of the dominant next-to-leading QCD corrections of order αS3α. © 2014, The Author(s).


Han C.,CAS Institute of Theoretical Physics | Ji X.,CAS Institute of Theoretical Physics | Ji X.,Beijing University of Technology | Wu L.,University of Sydney | And 2 more authors.
Journal of High Energy Physics | Year: 2014

We consider the current experimental constraints on the parameter space of the MSSM and NMSSM. Then in the allowed parameter space we examine the Higgs pair production at the 14 TeV LHC via b̄b → hh (h is the 125 GeV SM-like Higg boson) with one-loop SUSY QCD correction and compare it with the production via gg → hh. We obtain the following observations: (i) For the MSSM the production rate of b̄b → hh can reach 50 fb and thus can be competitive with gg → hh, while for the NMSSM b̄b → hh has a much smaller rate than gg → hh due to the suppression of the hb̄b coupling; (ii) The SUSY-QCD correction to b̄b → hh is sizable, which can reach 45% for the MSSM and 15% for the NMSSM within the 1σ region of the Higgs data; (iii) In the heavy SUSY limit (all soft mass parameters become heavy), the SUSY effects decouple rather slowly from the Higgs pair production (especially the gg → hh process), which, for M SUSY = 5 TeV and m A < 1 TeV, can enhance the production rate by a factor of 1.5 and 1.3 for the MSSM and NMSSM, respectively. So, the Higgs pair production may be helpful for unraveling the effects of heavy SUSY. © 2014 The Author(s).


Alwall J.,National Taiwan University | Frederix R.,CERN | Frixione S.,CERN | Hirschi V.,SLAC | And 7 more authors.
Journal of High Energy Physics | Year: 2014

We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations - parton-level fixed order, shower-matched, merged - in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e - collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way. © 2014 The Author(s).


Wang F.,Zhengzhou University | Wang F.,CAS Institute of Theoretical Physics | Wang W.,Beijing University of Technology | Yang J.M.,CAS Institute of Theoretical Physics
Journal of High Energy Physics | Year: 2015

Abstract: From generalized gravity mediation we build a SUGRA scenario in which the gluino is much heavier than the electroweak gauginos at the GUT scale. We find that such a non-universal gaugino scenario with very heavy gluino at the GUT scale can be naturally obtained with proper high dimensional operators in the framework of SU(5) GUT. Then, due to the effects of heavy gluino, at the weak scale all colored sparticles are heavy while the uncolored sparticles are light, which can explain the Brookhaven muon g − 2 measurement while satisfying the collider constraints (both the 125 GeV Higgs mass and the direct search limits of sparticles) and dark matter requirements. We also find that, in order to explain the muon g − 2 measurement, the neutralino dark matter is lighter than 200 GeV in our scenario, which can be mostly covered by the future Xenon1T experiment. © 2015, The Author(s).


Wang F.,Zhengzhou University | Wang F.,CAS Institute of Theoretical Physics | Wang W.,Beijing University of Technology | Yang J.M.,CAS Institute of Theoretical Physics
Journal of High Energy Physics | Year: 2015

Abstract: We propose to split the sparticle spectrum from the hierarchy between the GUT scale and the Planck scale. A split supersymmetric model, which gives non-universal gaugino masses, is built with proper high dimensional operators in the framework of SO(10) GUT. Based on a calculation of two-loop beta functions for gauge couplings (taking into account all weak scale threshold corrections), we check the gauge coupling unification and dark matter constraints (relic density and direct detections). We find that our scenario can achieve the gauge coupling unification and satisfy the dark matter constraints in some part of parameter space. We also examine the sensitivity of the future XENON1T experiment and find that the currently allowed parameter space in our scenario can be covered for a neutralino dark matter below about 1.0 TeV. © 2015, The Author(s).


Li A.,Xiamen University | Huang F.,Xiamen University | Xu R.-X.,Beijing University of Technology
Astroparticle Physics | Year: 2012

The maximum mass of a neutron star is generally determined by the equation of state of the star material. In this study, we take into account dark matter particles, assumed to behave like fermions with a free parameter to account for the interaction strength among the particles, as a possible constituent of neutron stars. We find dark matter inside the star would soften the equation of state more strongly than that of hyperons, and reduce largely the maximum mass of the star. However, the neutron star maximum mass is sensitive to the particle mass of dark matter, and a very high neutron star mass larger than 2 Mȯ could be achieved when the particle mass is small enough, being Mȯ the mass of the sun. Such kind of dark-matter-admixed neutron stars could explain the recent measurement of the Shapiro delay in the radio pulsar PSR J1614-2230, which yielded a neutron star mass of 1.97 ± 0.04 Mȯ that may be hardly reached when hyperons are considered only, as in the case of the microscopic Brueckner theory. Furthermore, in this particular case, we point out that the dark matter around a neutron star should also contribute to the mass measurement due to its pure gravitational effect. However, our numerically calculation illustrates that such contribution could be safely ignored because of the usual diluted dark matter environment assumed. We conclude that a very high mass measurement of about 2 Mȯ requires a really stiff equation of state in neutron stars, and find a strong upper limit (≤0.64 GeV) for the particle mass of non-self-annihilating dark matter based on the present model. © 2012 Elsevier B.V. All rights reserved.


Zhong N.,Maebashi Institute of Technology | Zhong N.,Beijing University of Technology | Li Y.,Queensland University of Technology | Wu S.-T.,Asia University, Taiwan
IEEE Transactions on Knowledge and Data Engineering | Year: 2012

Many data mining techniques have been proposed for mining useful patterns in text documents. However, how to effectively use and update discovered patterns is still an open research issue, especially in the domain of text mining. Since most existing text mining methods adopted term-based approaches, they all suffer from the problems of polysemy and synonymy. Over the years, people have often held the hypothesis that pattern (or phrase)-based approaches should perform better than the term-based ones, but many experiments do not support this hypothesis. This paper presents an innovative and effective pattern discovery technique which includes the processes of pattern deploying and pattern evolving, to improve the effectiveness of using and updating discovered patterns for finding relevant and interesting information. Substantial experiments on RCV1 data collection and TREC topics demonstrate that the proposed solution achieves encouraging performance. © 2011 IEEE.


Jiang G.,Key Laboratory of Geo detection China University of Geosciences Beijing | Jiang G.,Beijing University of Technology | Zhao D.,Tohoku University | Zhang G.,Beijing University of Technology
Physics of the Earth and Planetary Interiors | Year: 2015

Seismic tomography and numerical simulations show that the western Pacific slab bends horizontally when it reaches the boundary between the upper mantle and lower mantle beneath northeast Asia. It is expected that a metastable olivine wedge (MOW) exists in the cold core of the slab because of a delayed phase transition from olivine to its high-pressure polymorphs. However, it is still debated whether the MOW actually exists or not, and even if it exists, its physical properties, such as seismic velocity and density, are still unclear. In this work we use high-quality arrival-time data of 17 deep earthquakes occurring within the Pacific slab under northeast Asia to study the detailed structure of the slab. The deep earthquakes are relocated precisely by applying a modified double-difference location method to arrival-time data recorded at both Chinese and Japanese stations. Based on the precise hypocentral locations, a forward modeling method and differential travel-time residuals data are used to estimate seismic velocity within the deep source zone, which can decrease or remove the influence of ambient velocity heterogeneities. Our results show that the MOW does exist within the Pacific slab under northeast Asia, and the MOW has a mean velocity anomaly of 7-9% lower than the iasp91 Earth model. The existence of MOW in the slab has important geodynamic implications. It can reduce the speed of slab subduction and affect the generation of deep earthquakes. © 2014 Elsevier B.V.


Mu C.-F.,Beijing University of Technology | He L.-Y.,Goethe University Frankfurt | Liu Y.-X.,Beijing University of Technology | Liu Y.-X.,Accelerator Centre
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We study the phase diagram of two-flavor dense QCD at finite isospin and baryon chemical potentials in the framework of the Nambu-Jona-Lasinio model. We focus on the case with arbitrary isospin chemical potential μI and small baryon chemical potential μB≤μBχ where μBχ is the critical chemical potential for the first-order chiral phase transition to happen at μI=0. The μI-μB phase diagram shows a rich phase structure since the system undergoes a crossover from a Bose-Einstein condensate of charged pions to a BCS superfluid with condensed quark-antiquark Cooper pairs when μI increases at μB=0, and a nonzero baryon chemical potential serves as a mismatch between the pairing species. We observe a gapless pion condensation phase near the quadruple point (μI,μB)=(mπ,M N-1.5mπ) where mπ, MN are the vacuum masses of pions and nucleons, respectively. The first-order chiral phase transition becomes a smooth crossover when μI>0.82m π. At very large isospin chemical potential, μI> 6.36mπ, an inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrell superfluid phase, appears in a window of μB, which should in principle exist for arbitrary large μI. Between the gapless and the Larkin-Ovchinnikov-Fulde-Ferrell phases, the pion superfluid phase and the normal quark matter phase are connected by a first-order phase transition. In the normal phase above the superfluid domain, we find that charged pions are still bound states even though μI becomes very large, which is quite different from that at finite temperature. Our phase diagram is in good agreement with that found in imbalanced cold atom systems. © 2010 The American Physical Society.


Zhang S.,Beijing University of Technology | Wang Q.,Beijing University of Technology | Wang Q.,Virginia Commonwealth University | Kawazoe Y.,Tohoku University | Jena P.,Virginia Commonwealth University
Journal of the American Chemical Society | Year: 2013

Boron nitride (BN) and carbon are chemical analogues of each other and share similar structures such as one-dimensional nanotubes, two-dimensional nanosheets characterized by sp2 bonding, and three-dimensional diamond structures characterized by sp3 bonding. However, unlike carbon which can be metallic in one, two, and three dimensions, BN is an insulator, irrespective of its structure and dimensionality. On the basis of state-of-the-art theoretical calculations, we propose a tetragonal phase of BN which is both dynamically stable and metallic. Analysis of its band structure, density of states, and electron localization function confirms the origin of the metallic behavior to be due to the delocalized B 2p electrons. The metallicity exhibited in the studied three-dimensional BN structures can lead to materials beyond conventional ceramics as well as to materials with potential for applications in electronic devices. © 2013 American Chemical Society.


Cao J.,Henan Normal University | Hikasa K.-I.,Tohoku University | Wang W.,Beijing University of Technology | Yang J.M.,CAS Institute of Theoretical Physics | Yu L.-X.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

Assuming the lightest neutralino solely composes the cosmic dark matter, we examine the constraints of the CDMS-II and XENON100 dark matter direct searches on the parameter space of the minimal supersymmetric standard model (MSSM) Higgs sector. We find that the current CDMS-II/XENON100 limits can exclude some of the parameter space which survive the constraints from the dark matter relic density and various collider experiments. We also find that in the currently allowed parameter space, the charged Higgs boson is hardly accessible at the LHC for an integrated luminosity of 30fb-1, while the neutral non-SM (standard model) Higgs bosons (H,A) may be accessible in some allowed region characterized by a large μ. The future XENON100 (6000 kg-days exposure) will significantly tighten the parameter space in case of nonobservation of dark matter. © 2010 The American Physical Society.


Fan X.,Beijing University of Technology | Fan X.,Rice University | Zhou H.,Rice University | Guo X.,Beijing University of Technology
ACS Nano | Year: 2015

Single nanocrystalline tungsten carbide (WC) was first synthesized on the tips of vertically aligned carbon nanotubes (VA-CNTs) with a hot filament chemical vapor deposition (HF-CVD) method through the directly reaction of tungsten metal with carbon source. The VA-CNTs with preservation of vertical structure integrity and alignment play an important role to support the nanocrystalline WC growth. With the high crystallinity, small size, and uniform distribution of WC particles on the carbon support, the formed WC-CNTs material exhibited an excellent catalytic activity for hydrogen evolution reaction (HER), giving a η10 (the overpotential for driving a current of 10 mA cm-2) of 145 mV, onset potential of 15 mV, exchange current density@ 300 mV of 117.6 mV and Tafel slope values of 72 mV dec-1 in acid solution, and η10 of 137 mV, onset potential of 16 mV, exchange current density@ 300 mV of 33.1 mV and Tafel slope values of 106 mV dec-1 in alkaline media, respectively. Electrochemical stability test further confirms the long-term operation of the catalyst in both acidic and alkaline media. © 2015 American Chemical Society.


Pan W.,Tsinghua University | Phillpot S.R.,University of Florida | Wan C.,Nagoya University | Chernatynskiy A.,University of Florida | Qu Z.,Beijing University of Technology
MRS Bulletin | Year: 2012

Oxides hold great promise as new and improved materials for thermal-barrier coating applications. The rich variety of structures and compositions of the materials in this class, and the ease with which they can be doped, allow the exploration of various mechanisms for lowering thermal conductivity. In this article, we review recent progress in identifying specific oxides with low thermal conductivity from both theoretical and experimental perspectives. We explore the mechanisms of lowering thermal conductivity, such as introducing structural/chemical disorder, increasing material density, increasing the number of atoms in the primitive cell, and exploiting the structural anisotropy. We conclude that further systematic exploration of oxide crystal structures and chemistries are likely to result in even further improved thermal-barrier coatings. © 2012 Materials Research Society.


Dey R.,New York University | Tang C.,Beijing University of Technology | Ross K.,New York University | Saxena N.,University of Alabama at Birmingham
Proceedings - IEEE INFOCOM | Year: 2012

We perform a large-scale study to quantify just how severe the privacy leakage problem is in Facebook. As a case study, we focus on estimating birth year, which is a fundamental human attribute and, for many people, a private one. Specifically, we attempt to estimate the birth year of over 1 million Facebook users in New York City. We examine the accuracy of estimation procedures for several classes of users: (i) highly private users, who do not make their friend lists public; (ii) users who hide their birth years but make their friend lists public. To estimate Facebook users' ages, we exploit the underlying social network structure to design an iterative algorithm, which derives age estimates based on friends' ages, friends of friends' ages, and so on. We find that for most users, including highly private users who hide their friend lists, it is possible to estimate ages with an error of only a few years. We also make a specific suggestion to Facebook which, if implemented, would greatly reduce privacy leakages in its service. © 2012 IEEE.


Su M.,Beijing University of Technology | Tan J.,Beijing University of Technology | Lin C.-Y.,Chang Gung University
Drug Discovery Today | Year: 2015

Of the three viral enzymes essential to HIV replication, HIV-1 integrase (IN) is gaining popularity as a target for the antiviral therapy of AIDS. Substantial work focusing on IN has been done over the past three decades, which has facilitated and led to the approval of three drugs. Here, we discuss in detail the development of IN inhibitors between January 2012 and May 2014, with a particular focus on molecular simulation. We highlight controversial aspects of computational drug design and refer to alternative practices where appropriate. The analysis of these computational approaches provides some useful clues to the possible future discovery of novel IN inhibitors. © 2015 Elsevier Ltd. All rights reserved.


Zhang Y.,Beijing University of Technology | Zhu J.,University of Technology, Sydney
IEEE Transactions on Power Electronics | Year: 2011

Conventional switching-table-based direct torque control (DTC) presents large torque and flux ripples as well as variable switching frequency. Many methods have been proposed to tackle the aforementioned problems, among which duty cycle control is a kind of very effective approach. It is known that by adjusting the duty ratio of the active vector selected from the switching table, the torque ripple can be reduced. However, most of the prior duty cycle control methods only focus on the torque performance improvement and fail to take the flux ripple reduction into account. Furthermore, the methods obtaining the duty ratio are usually complicated and relies heavily on the accuracy of machine parameters, which negates the merits of simplicity and robustness of conventional DTC. This paper proposes a unified switching table to select three vectors rather than two vectors in prior arts; hence, lower flux ripple and more sinusoidal stator current can be obtained while maintaining the torque performance. A very simple but effective method is proposed to obtain the durations of the three vectors. The influence of one-step delay caused by digital implementation is investigated. By arranging the switching sequence of the three vectors appropriately, the switching frequency can be significantly reduced. The superiority of the novel method is confirmed by a comparative study with its counterpart using two vectors only. Both simulation and experimental results obtained from a 1-kW permanent magnet synchronous motor (PMSM) DTC drive are presented to validate the effectiveness of the novel duty cycle control strategy. © 2006 IEEE.


Hou Z.-f.,Beijing University of Technology | Zhang Y.,Liaoning Normal University | Liu Y.-x.,Beijing University of Technology | Liu Y.-x.,Accelerator Centre
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

Implementing a shell model Hamiltonian with monopole-pair, quadrupole-pair and quadrupole-quadrupole interactions between nucleons, we study the shape phases of nuclei and their transitions, with the Dyson boson mapping approach. The investigation concentrates on the influence of each interaction on the nuclear shape phases. A correspondence between the strength of each of the interactions and the nuclear shape phases is obtained. The investigation also indicates that increasing the quadrupole-pair interaction strength can induce the vibrational to the axially prolate rotational shape phase transition and enhancing the quadrupole-quadrupole interaction can drive the phase transition from the axially oblate rotational to the axially prolate rotational, with the γ-soft rotational being the critical point. © 2010 Elsevier B.V. All rights reserved.


Chen B.,Beijing University of Technology | Chen B.,CAS Institute of Theoretical Physics | Huang Q.-G.,Korea Institute for Advanced Study | Huang Q.-G.,CAS Institute of Theoretical Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

We construct the general renormalizable actions for the scalar field and the gauge field at a Lifshitz point characterized by the dynamical critical exponent z. The Lorentz invariance is broken down in the UV region, but is recovered in the IR limit. Even though the theories are UV complete, the speed of light is related to the momentum by z (k / M)z - 1 which can go to infinity in the UV limit for z ≥ 2. Since the Lorentz invariance is broken down, the dispersion relation is modified and the time delays in gamma-ray bursts can be easily explained. In addition, we also discuss the thermal dynamics and the size of causal patch in a FRW universe for the field theory at a Lifshitz point. © 2009 Elsevier B.V. All rights reserved.


Qu Z.,Tsinghua University | Qu Z.,Beijing University of Technology | Sparks T.D.,Harvard University | Pan W.,Tsinghua University | Clarke D.R.,Harvard University
Acta Materialia | Year: 2011

The apatite crystal structure of the gadolinium calcium silicates can accommodate a wide range of point defects, including oxygen and cation vacancies, as well as anti-site defects, depending on the Gd/Ca ratio. Compositions having only cation or oxygen vacancies were identified and the thermal diffusivity and conductivity were measured up to 1000 °C. All the compositions, including the stoichiometric composition, exhibit low thermal conductivities from room temperature to high temperature with the defect-containing compositions having even lower thermal conductivities. The high-temperature thermal conductivity, at temperatures below the onset of significant radiative heat transport, decreases with the inverse square root of the cation and anion vacancy concentration, consistent with simple defect scattering models. Based on the data, it is concluded that the oxygen vacancies are slightly more effective in reducing thermal conductivity. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Li B.Q.,CAS Shenyang Institute of Metal Research | Li B.,Johns Hopkins University | Wang Y.B.,CAS Shenyang Institute of Metal Research | Sui M.L.,Beijing University of Technology | Ma E.,Johns Hopkins University
Scripta Materialia | Year: 2011

In situ straining in a high-resolution transmission electron microscope and molecular dynamics simulations reveal a new deformation twinning mechanism in the face-centered-cubic structure. A twin forms via the simultaneous and cooperative activation of different Shockley partial dislocations on three (1 1 1) layers. The synchronized slip produces a zero net Burgers vector; such twining relieves local stress concentration in a shear confined to adjacent atomic layers, but induces no macroscopic shape change of the surrounding crystal. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Seyring M.,Friedrich - Schiller University of Jena | Song X.,Beijing University of Technology | Rettenmayr M.,Friedrich - Schiller University of Jena
ACS Nano | Year: 2011

The special properties of nanocrystalline materials are generally accepted to be a consequence of the high density of planar defects (grain and twin boundaries) and their characteristics. However, until now, nanograin structures have not been characterized with similar detail and statistical relevance as coarse-grained materials, due to the lack of an appropriate method. In the present paper, a novel method based on quantitative nanobeam diffraction in transmission electron microscopy (TEM) is presented to determine the misorientation of adjacent nanograins and subgrains. Spatial resolution of <5 nm can be achieved. This method is applicable to characterize orientation relationships in wire, film, and bulk materials with nanocrystalline structures. As a model material, nanocrystalline Cu is used. Several important features of the nanograin structure are discovered utilizing quantitative analysis: the fraction of twin boundaries is substantially higher than that observed in bright-field images in the TEM; small angle grain boundaries are prominent; there is an obvious dependence of the grain boundary characteristics on grain size distribution and mean grain size. © 2011 American Chemical Society.


Li H.,China University of Geosciences | Li H.,Beijing University of Technology | Bernardi F.,Italian National Institute of Geophysics and Volcanology | Michelini A.,Italian National Institute of Geophysics and Volcanology
Geophysical Journal International | Year: 2010

We present the surface wave dispersion results of the application of the ambient noise method to broad-band data recorded at 114 stations from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) national broad-band network, some stations of the Mediterranean Very Broadband Seismographic Network (MedNet) and of the Austrian Central Institute for Meteorology and Geodynamics (ZAMG). Vertical-component ambient noise data from 2005 October to 2007 March have been cross-correlated for station-pairs to estimate fundamental mode Rayleigh wave Green's functions. Cross-correlations are calculated in 1-hr segments, stacked over periods varying between 3 months and 1.5 yr. Rayleigh wave group dispersion curves at periods from 8 to 44 s were determined using the multiple-filter analysis technique. The study region was divided into a 0.2°× 0.2° grid to invert for group velocity distributions. Checkerboard tests were first carried out, and the lateral resolution was estimated to be about 0.6°. The resulting group velocity maps from 8 to 36 s show the significant difference of the crustal structure and good correlations with known geological and tectonic features in the study region. The Po Plain and the Southern Alps evidence lower group velocities due to soft alluvial deposits, and thick terrigenous sediments. Our results also clearly showed that the Tyrrhenian Sea is characterized with much higher velocities below 8 km than the Italian peninsula and the Adriatic Sea which indicates a thin oceanic crust beneath the Tyrrhenian Sea. © 2010 The Authors Journal compilation © 2010 RAS.


Song Z.-G.,Harbin Institute of Technology | Li F.-M.,Harbin Institute of Technology | Li F.-M.,Beijing University of Technology
Composite Structures | Year: 2013

The aerothermoelastic characteristics of the supersonic laminated cylindrical shell are analyzed, and the active flutter control of the aeroelastic structure is also investigated using the piezoelectric material. In the structural modeling, the influences of the in-plane thermal load on the transverse deformation are taken into account. The aerodynamic pressure is evaluated using the supersonic piston theory. Hamilton's principle and the Galerkin's method are used to establish the equation of motion. The proportional feedback and LQG control methods are applied to design the controller. The aerothermoelastic analysis for the laminated cylindrical shell is carried out using the frequency- and time-domain methods. The influences of the ply angle on the flutter and thermal buckling properties are investigated. The active flutter control effects of different controllers are compared. Numerical simulation shows that the LQG controller is more accurate and effective than the LQR and proportional feedback controllers. © 2013 Elsevier Ltd.


Wang Y.-Z.,Harbin Institute of Technology | Li F.-M.,Beijing University of Technology
International Journal of Non-Linear Mechanics | Year: 2014

Based on the nonlocal continuum theory, the nonlinear primary resonance of nano beam with the axial initial load is investigated. The amplitude-frequency response for the primary resonance is derived with the multiple scale method and the stability is analyzed. The nonlinear primary resonance of nano beam is discussed with the influences of small scale effect, axial initial load, mode number, Winkler foundation modulus and the ratio of the length to the diameter. From the results, the typical hardening nonlinearity can be observed. Moreover, some significant and interesting nonlinear phenomena can be found for the primary resonance of nano beam. This work is expected to be useful for the design and analysis for the nonlinear dynamic behaviors of structures at nano scales. © 2014 Published by Elsevier Ltd. All rights reserved.


Gao D.,Harbin Institute of Technology | Gao D.,Northeast Forestry University | Peng Y.,Beijing University of Technology | Wu W.-M.,Stanford University
Environmental Science and Technology | Year: 2010

A kinetic model for shortcut nitrification-denitrification process with sequencing batch reactor (SBR) was developed. To test this model, the kinetic parameters of the model including maximum specific rates and half-maximum rate concentrations for shortcut nitrification and denitrification were estimated from the results obtained from a laboratory-scale SBR fed with a soybean curd processing wastewater (400-800 mg COD L-1, 50-65 mg NH 4 +-N L-1) at 26 °C. In the nitrification step, two DO levels (0.5 and 3.5 mg L-1) were tested and the predicated nitrification rates under different NH4 +-N concentrations using this model fit well with correlation coefficient R = 0.9902. In the denitrification step, the process of nitrite removal was close to a zero-order reaction if the concentration of electron donor was not so low (COD > 100 mg L-1), and concentrations of nitrite and organic matter (as COD) had limited effect on denitrification rate. The model can be used to predict nitrogen removal performance with different influent NH 4 +-N and COD concentrations and under various DO concentrations. © 2010 American Chemical Society.


Lai X.Y.,Xinjiang University | Lai X.Y.,Beijing University of Technology | Gao C.Y.,Beijing University of Technology | Xu R.X.,Beijing University of Technology
Monthly Notices of the Royal Astronomical Society | Year: 2013

The study of dense matter at ultrahigh density has a very long history, which is meaningful for us to understand not only cosmic events in extreme circumstances but also fundamental laws of physics. It is well known that the state of cold matter at supranuclear density depends on the non-perturbative nature of quantum chromodynamics (QCD) and is essential for modelling pulsars. A so-called H-cluster matter is proposed in this paper as the nature of dense matter in reality. In compact stars at only a few nuclear densities but low temperature, quarks could be interacting strongly with each other there. That might render quarks grouped in clusters, although the hypothetical quark clusters in cold dense matter have not been confirmed due to the lack of both theoretical and experimental evidence. Motivated by recent lattice QCD simulations of the H-dibaryons (with structure uuddss), we therefore consider here a possible kind of quark clusters, H-clusters, that could emerge inside compact stars during their initial cooling as the dominant components inside (the degree of freedom could then be H-clusters there). Taking into account the in-medium stiffening effect, we find that at baryon densities of compact stars H-cluster matter could be more stable than nuclear matter. We also find that for the H-cluster matter with lattice structure, the equation of state could be so stiff that it would seem to be 'superluminal' in the most dense region. However, the real sound speed for H-cluster matter is in fact difficult to calculate, so at this stage we do not put constraints on our model from the usual requirement of causality. We study the stars composed of H-clusters, i.e. H-cluster stars, and derive the dependence of their maximum mass on the in-medium stiffening effect, showing that the maximum mass could be well above 2 M. ⊙ as observed and that the resultant mass-radius relation fits the measurement of the rapid burster under reasonable parameters. Besides a general understanding of different manifestations of compact stars, we expect further observational and experimental tests for the H-cluster stars in the future. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Wei P.,Beijing University of Technology | Cheng S.,Beijing University of Technology | Li J.,University of Northern British Columbia | Su F.,Chinese Research Academy of Environmental Sciences
Atmospheric Environment | Year: 2011

Based on a Lagrangian particle dispersion model FLEXPART 3-D in conjunction with a Weather Research and Forecasting (WRF) model, this study analyzed the synoptic patterns of the three sections (i.e. front, center, and rear) of a slow-moving anticyclonic weather system that took place during April 22-30, 2002 in northern China. The impacts of anticyclone on regional air quality were also revealed through simulating the transport trajectories of PM10 particles in the anticyclone. The findings indicate that PM10 pollutant transport process within the anticyclone showed the following characteristics: (a) the frontal pressure field played a strong role in removing pollutants from a high concentration zone located before the front, (b) the central part of anticyclone with an evident isobaric pressure field tended to create a pollutant accumulation process, and (c) the rear of the anticyclone system with a southerly warmer advection in the pressure gradient zone formed a stable channel for transporting pollutants. By using air pressure data and PM10 concentration measurements, the quantitative relationship between pressure variability and PM10 variation in different sections of the anticyclone was established. A linear relationship was assumed between PM10 variation per unit area in the mixing layer and pressure variation within a time interval, and different sections of the anticyclone were associated with different linear regression equations. A parameter called PM10 variation rate was then put forward, which could be easily applied for regional air pollution control and management. © 2011 Elsevier Ltd.


Wang L.,Harbin Institute of Technology | Wang L.,Beijing University of Technology | Wang Y.,National School in Computer Science | Gao W.,National School in Computer Science
International Journal of Computer Vision | Year: 2011

We propose a layered-grammar model to represent actions. Using this model, an action is represented by a set of grammar rules. The bottom layer of an action instance's parse tree contains action primitives such as spatiotemporal (ST) interest points. At each layer above, we iteratively mine grammar rules and "super rules" that account for the high-order compositional feature structures. The grammar rules are categorized into three classes according to three different ST-relations of their action components, namely the strong relation, weak relation and stochastic relation. These ST-relations characterize different action styles (degree of stiffness), and they are pursued in terms of grammar rules for the purpose of action recognition. By adopting the Emerging Pattern (EP) mining algorithm for relation pursuit, the learned production rules are statistically significant and discriminative. Using the learned rules, the parse tree of an action video is constructed by combining a bottom-up rule detection step and a top-down ambiguous rule pruning step. An action instance is recognized based on the discriminative configurations generated by the production rules of its parse tree. Experiments confirm that by incorporating the high-order feature statistics, the proposed method largely improves the recognition performance over the bag-of-words models. © 2010 Springer Science+Business Media, LLC.


Wang Y.-Z.,Harbin Institute of Technology | Li F.-M.,Beijing University of Technology
JVC/Journal of Vibration and Control | Year: 2015

In this paper, the nonlinear dynamical characteristics of the Duffing-van der Pol oscillator subject to both external and parametric excitations with time delayed feedback control are analyzed. Using the multiple scale method, the primary and principal parametric resonances are discussed. Both the periodic and chaos dynamical behaviors are presented by numerical solutions. From the results, it can be seen that the frequency and amplitude responses for the primary and principal parametric resonances can be affected by the time delayed control. Moreover, it is not only the external and parametric excitations that have an influence on the periodic and chaotic motions, but also the control parameters. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.


Tan M.,China University of Geosciences | Tan M.,Beijing University of Technology | Zou Y.,Beijing University of Technology | Zhou C.,Petrochina
Computers and Geosciences | Year: 2013

One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail. © 2012.


Wu C.-Y.,Harbin Institute of Technology | Peng Y.-Z.,Harbin Institute of Technology | Peng Y.-Z.,Beijing University of Technology | Wang S.-Y.,Beijing University of Technology | Ma Y.,Beijing University of Technology
Water Research | Year: 2010

In this study, phosphorus accumulating microbial granules were successfully cultivated in a sequencing batch reactor (SBR) using synthetic wastewater. The average diameter of the granules was 0.74 mm and the diameter distribution fitted well with normal distribution with a correlation coefficient of 0.989. Good performance of biological phosphorus removal (BPR) was obtained in the granular system. The average phosphorus removal efficiency was over 94.3% and the level of phosphorus in the effluent was below 0.50 mg/L during 300 days of operation. Particle analysis showed that positive charged particles were formed with the release of phosphorus in the anaerobic stage. These particles served as the cores of granules and stimulate the granulation. The maturated granules had a well-formed micro-pore structure with an average pore width between 291.5 nm and 446.5 nm. The spatial distribution of phosphorus decreased gradually from the surface to the center of the granules. Smaller granules had a higher specific area, pore width and phosphorus removal activity than bigger granules. © 2009.


Tian J.-y.,Harbin Institute of Technology | Chen Z.-l.,Harbin Institute of Technology | Yang Y.-l.,Beijing University of Technology | Liang H.,Harbin Institute of Technology | And 2 more authors.
Water Research | Year: 2010

Chemical cleaning of fouled hollow-fiber polyvinyl chloride (PVC) membrane with the consecutive use of NaOH and ethanol during ultrafiltration of river water was investigated in the study. Results showed that through the chemical cleaning with 1% NaOH for 30 min, a negative cleaning efficiency of -14.6% was observed for the PVC membrane. This might be due to the increase of membrane hydrophobicity, which was reflected by the increase of contact angle from 69.7° to 87.6°. On the other hand, the cleaning efficiency of 85.1% was obtained by the consecutive cleaning with 30 min of 1% NaOH and 30 min of ethanol. Individual ethanol cleaning could remove 48.5% of the irreversible resistance, indicating that NaOH cleaning also made its contribution (36.6%) to the removal of membrane foulants. Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) analyses demonstrated that both NaOH and ethanol were not only able to eliminate the foulants on membrane surface, but also able to remove the in-pore fouling of the PVC membrane. The synergetic effects for removing membrane foulants were observed between the NaOH and ethanol. Furthermore, ethanol could also restore the hydrophilicity of the membrane by decreasing the contact angle from 87.6° to 71.4°. Considering that ethanol is easy to be used and reclaimed, the consecutive chemical cleaning by alkali and ethanol is recommended for PVC membrane in filtration of surface water. © 2009 Elsevier Ltd. All rights reserved.


Zhang W.,Beijing University of Technology | Peng Y.,Beijing University of Technology | Ren N.,Harbin Institute of Technology | Liu Q.,Beijing University of Technology | Chen Y.,Beijing University of Technology
Chemosphere | Year: 2013

A two-sludge system, combining anaerobic/anoxic/aerobic process with biological aerated filter (AAO-BAF), is used to treat domestic wastewater with low COD/N ratio (around 3.6). The volume ratio of anoxic to aerobic zone (Vano/Vaer) of the AAO reactor gradually increased from 2:5 to 6:1, during which the nutrient removal was improved. However, phosphorous removal began to deteriorate noticeably while Vano/Vaer increased to 7:0. The favorable Vano/Vaer was between 2.5:1 and 6:1. When Vano/Vaer was 6:1, the average removal efficiencies of COD, TN and PO43- were 89±4%, 83±3% and 99±1%, respectively. This study suggested the AAO-BAF system could achieve efficient nitrogen and phosphorous removal with limited carbon source. © 2013 Elsevier Ltd.


Wei X.-L.,Xiangtan University | Fang H.,Beijing University of Technology | Wang R.-Z.,Beijing University of Technology | Chen Y.-P.,Xiangtan University | Zhong J.-X.,Xiangtan University
Applied Physics Letters | Year: 2011

First-principles calculations are performed to study the modulation of energy gaps in nitrogen delta-doping (N Δ-doping) graphene and armchair-edge graphene nanoribbons (AGNRs). The energy gap of graphene only opens at a large nitrogen doping content. For AGNRs, the energy gaps tend to decrease with the N Δ-doping, and an interesting transition from direct to indirect bandgap is observed. Moreover, the effects of N Δ-doping on energy gaps incline to decease with the reduction of the doping content. Our results may help to design novel graphene-based nanoelectronics devices by controlling N Δ-doping of graphene. © 2011 American Institute of Physics.


Liu L.,Beijing University of Technology | Kafui K.D.,University of Birmingham | Thornton C.,University of Birmingham
Powder Technology | Year: 2010

A numerical study of the micro-mechanics of breakage of agglomerates impacting with a target wall has been carried out using discrete element simulations. Three agglomerates of different shapes are examined, namely spherical, cuboidal and cylindrical. Each agglomerate consists of 10,000 polydisperse auto-adhesive elastic spheres with a normal size distribution. The effect of agglomerate shape and impact site on the damage of the agglomerates under an impact velocity of 1.0 m/s for an interface energy of 1.0 J/m2 is reported. It is found from the simulations that cuboidal edge, cylindrical rim and cuboidal corner impacts generate less damage than spherical agglomerate impacts. The cuboidal face, cylindrical side and cylindrical end impacts fracture the agglomerates into several fragments. Detailed examinations of the evolutions of damage ratio, number of wall contacts and total wall force indicate that the size of the contact area and the rate of change of the contact area play important roles in agglomerate breakage behaviour. Internal damage to the agglomerate is closely related to the particle deceleration adjacent to the impact site. However, the local microstructure may not be a decisive factor in terms of the breakage mode for non-spherical agglomerates. © 2010 Elsevier B.V. All rights reserved.


Li F.-M.,Harbin Institute of Technology | Li F.-M.,Beijing University of Technology | Song Z.-G.,Harbin Institute of Technology
Journal of Sound and Vibration | Year: 2013

Aerothermoelastic analysis for composite laminated panels in supersonic flow is carried out. The flutter and thermal buckling control for the panels are also investigated. In the modeling for the equation of motion, the influences of in-plane thermal load on the transverse bending deflection are taken into account, and the unsteady aerodynamic pressure in supersonic flow is evaluated by the linear piston theory. The governing equation of the structural system is developed applying the Hamilton's principle. In order to study the influences of aerodynamic pressure on the vibration mode shape of the panel, both the assumed mode method (AMM) and the finite element method (FEM) are used to derive the equation of motion. The proportional feedback control method and the linear quadratic regulator (LQR) are used to design the controller. The aeroelastic stability of the structural system is analyzed using the frequency-domain method. The effects of ply angle of the laminated panel on the critical flutter aerodynamic pressure and the critical buckling temperature change are researched. The flutter and thermal buckling control effects using the proportional feedback control and the LQR are compared. An effective method which can suppress the flutter and thermal buckling simultaneously is proposed. © 2013 Elsevier Ltd. All rights reserved.


Jie W.,Harbin Institute of Technology | Jie W.,Heilongjiang East University | Peng Y.,Harbin Institute of Technology | Peng Y.,Beijing University of Technology | And 2 more authors.
Bioresource Technology | Year: 2014

This study aimed at exploring the potential of volatile fatty acids (VFAs) produced from excess sludge (ES) as a new cost-effective internal carbon source in wastewater treatment processes. The optimal condition for VFA accumulation and the bacterial community structure in the bio-production of VFAs from ES were investigated at different pH conditions. Denaturing gradient gel electrophoresis (DGGE) was performed to characterize the bacterial community structure of ES. The results showed that the optimal pH was 10.0 for VFA production, and acetic and propionic acids were the dominant acid species. Pseudomonas sp. was identified as the major bacteria capable of utilizing organic carbon at all pHs. Uncultured bacterium (AB658278) adapted well at high pH. Uncultured bacteria (KC633537 and JN596370) were mainly responsible for anaerobic degradation of ES. The study demonstrated the variation of bacterial community structures at pHs and the close correlation with the VFA accumulation. © 2013 Elsevier Ltd.


Tang X.,Beijing University of Technology | Ren N.,Harbin Institute of Technology | Xu J.,Inner Mongolia University
International Journal of Hydrogen Energy | Year: 2013

Corn cob is a promising hydrogen fermentation substrate, not only because of its abundant and low cost, but also because of its high cellulose and hemicellulose content. However, little information is available on the use of corn cob as a feedstock for hydrogen production. In this study, corn cob was hydrolyzed by cellulase after acid steam-explosion, alkali soaking, or steam-explosion pretreatment. The liquid products of pretreatment and the enzymatic hydrolysates were then used as carbon sources for hydrogen production by Clostridium hydrogeniproducens HR-1. Pretreatment followed by enzymatic hydrolysis yielded 720, 670, and 530 mg reducing sugars/g corn cob, and the hydrogen yield from corn cob reached 119, 100, and 83 ml H2/g corn cob, which is 55.9%, 46.7%, and 38.8% of the theoretical hydrogen yield from corn cob using C. hydrogeniproducens HR-1, respectively. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Chen D.,Beijing University of Technology | Fan J.,Beijing University of Technology | Zhang F.,Harbin Institute of Technology
Measurement: Journal of the International Measurement Confederation | Year: 2013

Identification of the spindle unbalance is very important for the ultra-precision machining tools. In the first part, the frequency information for the spindle system is computed by two methods. In the second part, the results between the modal information of the spindle and the error frequency of the measured workpiece surface which processed by wavelet transform and power spectral density is compared, the signal feature in the waviness which is consistent with the spindle unbalance frequency is extracted. In the last part, the identified result is compared, it proves the extraction and identification method for the spindle unbalance of the machine tool is correctness and validity. © 2012 Elsevier Ltd. All rights reserved.


Chen B.,Beijing University of Technology | Wu J.-B.,International School for Advanced Studies | Wu J.-B.,National Institute of Nuclear Physics, Italy
Nuclear Physics B | Year: 2010

We study supersymmetric Wilson loop operators in ABJM theory from both sides of the AdS4 / CFT3 correspondence. We first construct some supersymmetric Wilson loops. The perturbative computations are performed in the field theory side at the first two orders. A fundamental string solution ending on a circular loop is also studied. © 2009 Elsevier B.V. All rights reserved.


Song Z.-G.,Harbin Institute of Technology | Li F.-M.,Harbin Institute of Technology | Li F.-M.,Beijing University of Technology
Composites Part B: Engineering | Year: 2014

Aero-thermal-elastic characteristics of hypersonic nonlinear laminated panels considering the shock wave (SW) as well as the aerodynamic heating are studied in this paper. The linear and third order piston theories are used to evaluate the aerodynamic pressure. Hamilton's principle is employed to establish the aeroelastic model of the laminated panel. In the aerothermal model, the heat flux in the aerodynamic heating is computed using the reference temperature method, and the finite element method (FEM) is applied to solve the transient heat transfer in the panel. After solving the aeroelastic and aerothermal models separately, the solutions are substituted into each other. Then performing the procedure of iteration, the coupling effects among the structure, fluid and thermal are realized. Time domain responses of the laminated panel are obtained. The influences of the shock wave on the aeroleastic characteristics of the panel are also investigated. From the numerical simulation, it can be observed that the aeroelastic stability is weakened with the increase of the temperature change. It is also noted that in the calculation of the airflow parameters for the aerothermoelastic analysis in the hypersonic flow, the influences of the shock wave should be taken into account. © 2013 Elsevier Ltd. All rights reserved.


Wang Y.-Z.,Harbin Institute of Technology | Li F.-M.,Beijing University of Technology
Mechanics Research Communications | Year: 2014

In this paper, the nonlinear free vibration of the nanotube with damping effects is studied. Based on the nonlocal elastic theory and Hamilton principle, the governing equation of the nonlinear free vibration for the nanotube is obtained. The Galerkin method is employed to reduce the nonlinear equation with the integral and partial differential characteristics into a nonlinear ordinary differential equation. Then the relation is solved by the multiple scale method and the approximate analytical solution is derived. The nonlinear vibration behaviors are discussed with the effects of damping, elastic matrix stiffness, small scales and initial displacements. From the results, it can be observed that the nonlinear vibration can be reduced by the matrix damping. The elastic matrix stiffness has significant influences on the nonlinear vibration properties. The nonlinear behaviors can be changed by the small scale effects, especially for the structure with large initial displacement. © 2014 Elsevier Ltd.


Chen D.,Beijing University of Technology | Bonis M.,University of Technology of Compigne | Zhang F.,Harbin Institute of Technology | Dong S.,Harbin Institute of Technology
Precision Engineering | Year: 2011

This paper proposes a thermo-mechanical error model of a hydrostatic spindle for a high precision machine tool. By predicting the variation of motion error induced by thermal effects on a machine worktable during machining, this model allows deeper insights into the underlying mechanisms that result in evolutions of the spindle accuracy. The heat power generated in the spindle elements and the coefficients of convection heat transfer over its outer surface have been evaluated. Then, the distribution of temperature and deformation of the spindle have been simulated by a finite element coupled thermo-elastic model, from which the influence on notably spindle stiffness variation was deduced. Experimental measurement of the thrust plate axial displacement under thermal expansion is in close agreement with the computed axial thermal expansion. © 2011 Elsevier Inc.


Ge S.,Beijing University of Technology | Peng Y.,Beijing University of Technology | Qiu S.,New York University | Zhu A.,Beijing University of Technology | Ren N.,Harbin Institute of Technology
Water Research | Year: 2014

This study assessed the technical feasibility of removing nitrogen from municipal wastewater by partial nitrification (nitritation) in a continuous plug-flow step feed process. Nitrite in the effluent accumulated to over 81.5±9.2% but disappeared with the transition of process operation from anoxic/oxic mode to the anaerobic/anoxic/oxic mode. Batch tests showed obvious ammonia oxidizing bacteria (AOB) stimulation (advanced ammonia oxidation rate) and nitrite (NOB) oxidizing bacteria inhibition (reduced nitrite oxidation rate) under transient anoxic conditions. Two main factors contributed to nitritation in this continuous plug-flow process: One was the alternating anoxic and oxic operational condition; the step feed strategy guaranteed timely denitrification in anoxic zones, allowing a reduction in energy supply (nitrite) to NOB. Fluorescence in Situ Hybridization and quantitative real-time polymerase chain reaction analysis indicated that NOB population gradually decreased to 1.0±0.1% of the total bacterial population (dominant Nitrospira spp., 1.55×109 copies/L) while AOB increased approximately two-fold (7.4±0.9%, 1.25×1010 copies/L) during the above anoxic to anaerobic transition. Most importantly, without addition of external carbon sources, the above wastewater treatment process reached 86.0±4.2% of total nitrogen (TN) removal with only 7.23±2.31mg/L of TN in the effluent, which met the discharge requirements. © 2014 Elsevier Ltd.


Goertz F.,ETH Zurich | Papaefstathiou A.,University of Zürich | Yang L.L.,Beijing University of Technology | Zurita J.,Johannes Gutenberg University Mainz
Journal of High Energy Physics | Year: 2013

We consider the ratio of cross sections of double-to-single Higgs boson production at the Large Hadron Collider at 14 TeV. Since both processes possess similar higherorder corrections, leading to a cancellation of uncertainties in the ratio, this observable is well-suited to constrain the trilinear Higgs boson self-coupling. We consider the scale variation, parton density function uncertainties and conservative estimates of experimental uncertainties, applied to the viable decay channels, to construct expected exclusion regions. We show that the trilinear self-coupling can be constrained to be positive with a 600 fb-1 LHC dataset at 95% confidence level. Moreover, we demonstrate that we expect to obtain a ∼ +30% and ∼ -20% uncertainty on the self-coupling at 3000fb-1 without statistical fitting of differential distributions. The present article outlines the most precise method of determination of the Higgs trilinear coupling to date. © 2013 SISSA, Trieste, Italy.


Wu C.,Beijing University of Technology | Deng S.,Beijing University of Technology | Wang H.,Beijing University of Technology | Wang H.,Chengdu Green Energy And Green Manufacturing Technology | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2014

A new type of three-dimensional (3D) NiO/ultrathin derived graphene (UDG) hybrid on commercial Ni foam (NF) for a binder-free pseudocapacitor electrode is presented. NiO nanoflakes are in situ grown by a chemical bath deposition (CBD) technique on the free-standing 3D UDG/NF scaffold, which is first prepared by a simple nanocasting process consisting of hydrothermal reaction and subsequent thermal transformation. The 3D UDG/NF scaffold with interconnected network affords a high conductivity due to the high graphitization degree and efficiently facilitates the electron transport to NiO. Moreover, the 3D NiO/UDG/NF hybrid allows for a thinner 3D active material layer under the same loading density, which could shorten the diffusion paths of ions. The NiO/UDG/NF hybrid is directly used as a binder-free supercapacitor electrode, which exhibited significantly improved supercapacitor performance compared to the bare CBD prepared NiO/NF electrode. © 2014 American Chemical Society.


Liu Y.,Beijing University of Chemical Technology | Dai H.,Beijing University of Chemical Technology | Du Y.,Beijing University of Technology | Deng J.,Beijing University of Chemical Technology | And 3 more authors.
Journal of Catalysis | Year: 2012

Three-dimensionally ordered macroporous (3DOM) single-phase rhombohedral perovskite-type oxide LaMnO 3 materials with nanovoid skeletons were prepared using the poly(methyl methacrylate)-templating methods with the assistance of surfactant (poly(ethylene glycol) (PEG) or triblock copolymer (Pluronic P123)). The nature of surfactant influenced the pore structure of the LaMnO 3 sample. The use of PEG400 alone led to a 3DOM-structured LaMnO 3 without nanovoid skeletons; with the addition of PEG400 and P123, however, one could prepare LaMnO 3 samples with high-quality 3DOM structures, nanovoid skeletons, and high surface areas (37-39 m 2/g). Under the conditions of toluene concentration = 1000 ppm, toluene/O 2 molar ratio = 1:400, and space velocity = 20,000 mL/(g h), the porous LaMnO 3 samples were superior to the bulk counterpart in catalytic performance, with the nanovoid-containing 3DOM-structured LaMnO 3 catalyst performing the best (the temperatures for toluene conversions of 50% and 90% were 222-232 and 243-253 °C, respectively). The apparent activation energies (57-62 kJ/mol) over the 3DOM-structured LaMnO 3 catalysts were much lower than that (97 kJ/mol) over the bulk LaMnO 3 catalyst. We believe that the excellent performance of the 3D macroporous LaMnO 3 materials in catalyzing the combustion of toluene might be due to factors such as large surface area, high oxygen adspecies concentration, good low-temperature reducibility, and unique nanovoid-containing 3DOM structure of the materials. © 2011 Elsevier Inc. All rights reserved.


Zhang D.-Y.,University of Waterloo | Li X.,Beijing University of Technology | Yan W.-M.,Beijing University of Technology | Xie W.-C.,University of Waterloo | Pandey M.D.,University of Waterloo
Engineering Structures | Year: 2013

This paper presents a comprehensive theoretical analysis of a concrete-filled steel tubular (CFST) arch bridge under tridirectional spatial seismic motions using the pseudo-excitation method. Formulations for modelling tridirectional spatial ground motions at varying site conditions are first derived. A site response analysis is presented for the tridirectional motions based on deterministic wave propagation theory, assuming that the base rock motions consist of out-of-plane SH wave or in-plane combined P and SV waves propagating into the multiple layered site with an assumed incident angle. Integration between the structural health monitoring (SHM) technique and the structural seismic analysis is proposed and conducted for the finite element (FE) model calibration of the CFST arch bridge through the model updating approach. Using the calibrated FE model, stochastic seismic analysis of the CFST arch bridge is conducted in a comprehensive and systematic way, by considering the dimensionality, incoherence effect, wave-path effect of ground motions, and local site effects with different and irregular site conditions. Critical conclusions are drawn and can be applied in the actual seismic design of the half-through CFST arch bridges under tridirectional multiple excitations. © 2013 Elsevier Ltd.


Wang X.B.,University of Jyväskylä | Dong G.X.,Beijing University of Technology | Xu F.R.,Beijing University of Technology
EPJ Web of Conferences | Year: 2014

The spin-tensor decomposition method has been used to analyse the shell model effective interactions in sd shell systematically. Almost all the interactions have been studied, including the microscopic interactions and phenomenological ones. It can be noticed that the discrepancies between the central force of microscopic interactions with the ones of empirical interactions are remarkable. © Owned by the authors, published by EDP Sciences, 2014.


Chen H.,Nanchang University | Zhao Y.,Beijing University of Technology
International Journal of Systems Science | Year: 2014

This paper is mainly concerned with the problem for the robustly exponential stability in mean square moment of uncertain neutral stochastic neural networks with interval time-varying delay. With an appropriate augmented Lyapunov-Krasovskii functional (LKF) formulated, the convex combination method is utilised to estimate the derivative of the LKF. Some new delay-dependent exponential stability criteria for such systems are obtained in terms of linear matrix inequalities, which involve fewer matrix variables and have less conservatism. Finally, two illustrative numerical examples are given to show the effectiveness of our obtained results. © 2014 © 2014 Taylor & Francis.


Hao B.,Beijing University of Technology | Yan Y.,Beijing University of Technology | Yan Y.,TU Ilmenau | Wang X.,Beijing University of Technology | Chen G.,Beijing University of Technology
Nanoscale | Year: 2013

We fabricated a sandwich-like branched-polyethyleneimine (b-PEI)/TiO 2/Au/graphene oxide (GO) nanocomposite through a biomimetic layer-by-layer co-mineralization approach, and the polymer b-PEI was believed to act as both an inducing agent for the hydrolysis of titanium bis(ammonium lactato)-dihydroxide (Ti-BALDH) and a reducing agent for the reduction of HAuCl4 in the synthetic procedure. Upon organic pyrolysis in air at 500°C, a TiO2/Au nanosheet was formed; and gold nanocrystals were observed uniformly dispersed on TiO2 nanosheet. Moreover, the obtained TiO2/Au nanosheets demonstrated an enhanced lithium storage performance when they are used as anode materials for lithium ion batteries (LIBs), particularly, a high capacity of 205 mA h g-1 and 189 mA h g-1 was obtained at 5 C and 10 C rate, respectively, indicating the high rate capability of the material. The greatly improved rate performance might be attributed from both the sheet-like nanostructure and the existence of uniformly dispersed gold nanocrystals, which facilitate electron transfer and lithium ions diffusion in the material. The result suggests that the TiO 2 electrode performance can be improved through a design of sheet-like nanocomposites using a bio-inspired route, which is desirable for both "green synthesis" and application for high power LIBs, moreover, such a benign bio-inspired route can be developed into a general pathway to synthesize many other TiO2 based nanocomposites for broad applications in the fields of batteries, photoelectrochemistry, photocatalysis and dye-sensitized solar cells. © 2013 The Royal Society of Chemistry.


Gong L.,Beijing University of Technology | Jun L.,Zhejiang University of Technology | Yang Q.,Beijing University of Technology | Wang S.,Beijing University of Technology | And 2 more authors.
Bioresource Technology | Year: 2012

In this work, a novel integrated reactor incorporating anoxic fixed bed biofilm reactor (FBBR), oxic moving bed biofilm reactor (MBBR) and settler sequentially was proposed for nitrogen removal from rural domestic sewage. For purposes of achieving high efficiency, low costs and easy maintenance, biomass characteristics and simultaneous nitrification-denitrification (SND) were investigated under long sludge retention time during a 149-day period. The results showed that enhanced SND with proportions of 37.7-42.2% tapped the reactor potentials of efficiency and economy both, despite of C/N ratio of 2.5-4.0 in influent. TN was removed averagely by 69.3% at least, even under internal recycling ratio of 200% and less proportions of biomass assimilation (<3%). Consequently, lower internal recycle and intermittent wasted sludge discharge were feasible to save costs, together with cancellations of sludge return and anoxic stir. Furthermore, biomass with low observed heterotrophic yields (0.053 ± 0.035g. VSS/g. COD) and VSS/TSS ratio (<0.55) in MBBR, simplified wasted sludge disposal. © 2012 Elsevier Ltd.


Ji J.,Beijing University of Technology | Zhang A.,Beijing University of Technology | Liu C.,State University of New York at Buffalo | Quan X.,Beijing University of Technology | Liu Z.,Beijing University of Technology
IEEE Transactions on Knowledge and Data Engineering | Year: 2014

A protein-protein interaction (PPI) network is a biomolecule relationship network that plays an important role in biological activities. Studies of functional modules in a PPI network contribute greatly to the understanding of biological mechanism. With the development of life science and computing science, a great amount of PPI data has been acquired by various experimental and computational approaches, which presents a significant challenge of detecting functional modules in a PPI network. To address this challenge, many functional module detecting methods have been developed. In this survey, we first analyze the existing problems in detecting functional modules and discuss the countermeasures in the data preprocess and postprocess. Second, we introduce some special metrics for distance or graph developed in clustering process of proteins. Third, we give a classification system of functional module detecting methods and describe some existing detection methods in each category. Fourth, we list databases in common use and conduct performance comparisons of several typical algorithms by popular measurements. Finally, we present the prospects and references for researchers engaged in analyzing PPI networks. © 1989-2012 IEEE.


Liu H.L.,Xi'an Jiaotong University | Xu F.R.,Beijing University of Technology
Physical Review C - Nuclear Physics | Year: 2013

Configuration-constrained potential-energy-surface calculations with reflection asymmetry show enhanced octupole correlations in the Kπ=6 - states with configuration ν5/2+[633]⊠- ν7/2-[743] in N=142,144 isotones, where a 33.5-μs isomer has been observed in 234U. High-K isomeric states in other nuclei around 240Pu are calculated to have reflection-symmetric deformations with excitation energies, in agreement with available data. © 2013 American Physical Society.


Waltz R.E.,General Atomics | Deng Z.,Beijing University of Technology
Physics of Plasmas | Year: 2013

A nonlinear theory of drift-cyclotron kinetics (termed cyclo-kinetics here) is formulated to test the breakdown of the gyro-kinetic approximations. Six dimensional cyclo-kinetics can be regarded as an extension of five dimensional gyro-kinetics to include high-frequency cyclotron waves, which can interrupt the low-frequency gyro-averaging in the (sixth velocity grid) gyro-phase angle. Nonlinear cyclo-kinetics has no limit on the amplitude of the perturbations. Formally, there is no gyro-averaging when all cyclotron (gyro-phase angle) harmonics of the perturbed distribution function (delta-f) are retained. Retaining only the (low frequency) zeroth cyclotron harmonic in cyclo-kinetics recovers both linear and nonlinear gyro-kinetics. Simple recipes are given for converting continuum nonlinear delta-fgyro- kinetic transport simulation codes to cyclo-kinetics codes by retaining (at least some) higher cyclotron harmonics. © 2013 American Institute of Physics.


Wang W.,Beijing University of Technology | Wang W.,Wright State University | Shan G.,University of Nevada, Las Vegas
Biometrics | Year: 2015

For comparison of proportions, there are three commonly used measurements: the difference, the relative risk, and the odds ratio. Significant effort has been spent on exact confidence intervals for the difference. In this article, we focus on the relative risk and the odds ratio when data are collected from a matched-pairs design or a two-arm independent binomial experiment. Exact one-sided and two-sided confidence intervals are proposed for each configuration of two measurements and two types of data. The one-sided intervals are constructed using an inductive order, they are the smallest under the order, and are admissible under the set inclusion criterion. The two-sided intervals are the intersection of two one-sided intervals. R codes are developed to implement the intervals. Supplementary materials for this article are available online. © 2015, The International Biometric Society.


Liu H.,Xi'an Jiaotong University | Xu F.,Beijing University of Technology
Science China: Physics, Mechanics and Astronomy | Year: 2013

Configuration-constrained potential-energy-surface calculations are performed to investigate high-K isomers in 97Y, 130Ba, 176Yb, 177Lu, and 178Hf that were observed to have increased electric quadrupole moments but decreased charge radii relative to the states on which they are built. Taking into account the effects of deformation change and unpaired protons, our calculations can reproduce the enhancement of electric quadrupole moments for the isomers in 97Y, 130Ba, 176Yb, 177Lu and the K π = 8- isomer in 178Hf, and can reproduce the reduction of charge radii for the K π = 27/2- isomer in 97Y and the K π = 16+ isomer in 178Hf. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg.


Deng Z.,Beijing University of Technology | Waltz R.E.,General Atomics
Physics of Plasmas | Year: 2015

This paper presents numerical simulations of the nonlinear cyclokinetic equations in the cyclotron harmonic representation [R. E. Waltz and Zhao Deng, Phys. Plasmas 20, 012507 (2013)]. Simulations are done with a local flux-tube geometry and with the parallel motion and variation suppressed using a newly developed rCYCLO code. Cyclokinetic simulations dynamically follow the high-frequency ion gyro-phase motion which is nonlinearly coupled into the low-frequency drift-waves possibly interrupting and suppressing gyro-averaging and increasing the transport over gyrokinetic levels. By comparing the more fundamental cyclokinetic simulations with the corresponding gyrokinetic simulations, the breakdown of gyrokinetics at high turbulence levels is quantitatively tested over a range of relative ion cyclotron frequency 10 < Ω∗< 100 where Ω∗= 1/ρ∗, and ρ∗ is the relative ion gyroradius. The gyrokinetic linear mode rates closely match the cyclokinetic low-frequency rates for Ω∗> 5. Gyrokinetic transport recovers cyclokinetic transport at high relative ion cyclotron frequency (Ω∗≥ 50) and low turbulence level as required. Cyclokinetic transport is found to be lower than gyrokinetic transport at high turbulence levels and low-Ω∗ values with stable ion cyclotron (IC) modes. The gyrokinetic approximation is found to break down when the density perturbations exceed 20%. For cyclokinetic simulations with sufficiently unstable IC modes and sufficiently low Ω∗∼ 10, the high-frequency component of cyclokinetic transport level can exceed the gyrokinetic transport level. However, the low-frequency component of the cyclokinetic transport and turbulence level does not exceed that of gyrokinetics. At higher and more physically relevant Ω∗≥ 50 values and physically realistic IC driving rates, the low-frequency component of the cyclokinetic transport and turbulence level is still smaller than that of gyrokinetics. Thus, the cyclokinetic simulations do not account for the so-called "L-mode near edge short fall" seen in some low-frequency gyrokinetic transport and turbulence simulations. © 2015 AIP Publishing LLC.


Wang L.,Beijing University of Technology | Han X.,Beijing University of Technology | Liu P.,Beijing University of Technology | Yue Y.,Beijing University of Technology | And 3 more authors.
Physical Review Letters | Year: 2010

Using a newly developed nanoscale deformation device, atomic scale and time-resolved dislocation dynamics have been captured in situ under a transmission electron microscope during the deformation of a Pt ultrathin film with truly nanometer grains (diameter d<∼10nm). We demonstrate that dislocations are highly active even in such tiny grains. For the larger grains (d∼10nm), full dislocations dominate and their evolution sometimes leads to the formation, destruction, and reformation of Lomer locks. In smaller grains, partial dislocations generating stacking faults are prevalent. © 2010 The American Physical Society.


Draper P.,University of Chicago | Liu T.,University of Chicago | Liu T.,University of California at Santa Barbara | Wagner C.E.M.,University of Chicago | And 4 more authors.
Physical Review Letters | Year: 2011

We study a limit of the nearly Peccei-Quinn-symmetric next-to-minimal supersymmetric standard model possessing novel Higgs and dark matter (DM) properties. In this scenario, there naturally coexist three light singletlike particles: a scalar, a pseudoscalar, and a singlinolike DM candidate, all with masses of order 0.1-10 GeV. The decay of a standard model-like Higgs boson to pairs of the light scalars or pseudoscalars is generically suppressed, avoiding constraints from collider searches for these channels. For a certain parameter window annihilation into the light pseudoscalar and exchange of the light scalar with nucleons allow the singlino to achieve the correct relic density and a large direct-detection cross section consistent with the DM direct-detection experiments, CoGeNT and DAMA/LIBRA, preferred region simultaneously. This parameter space is consistent with experimental constraints from LEP, the Tevatron, Υ, and flavor physics. © 2011 American Physical Society.


Yue Y.,Beijing University of Technology | Liu P.,Beijing University of Technology | Deng Q.,Beijing University of Technology | Ma E.,Johns Hopkins University | And 3 more authors.
Nano Letters | Year: 2012

In situ tensile tests of Cu single crystalline nanowires in a high-resolution transmission electron microscope reveal a novel effect of sample dimensions on plasticity mechanisms. When the single crystalline nanowire size was reduced to <∼150 nm, the normal full dislocation slip was taken over by partial dislocation mediated plasticity (PDMP). For the first time, we demonstrate this transition in a quantitative manner by assessing the relative contributions to plastic strain from PDMP and full dislocations. The crossover sample size is consistent, well within model predictions. This discovery represents yet another "sample size effect", beyond other reported influence of sample dimensions on the mechanical behavior of metals, such as dislocation starvation or source truncation, and the "smaller is stronger" trend. © 2012 American Chemical Society.


Yu J.,Henan Polytechnic University | Wu B.,Beijing University of Technology | He C.,Beijing University of Technology
International Journal of Engineering Science | Year: 2010

Functionally graded material (FGM) is a promising heat insulation material. Wave propagation in FGM structures has received much attention for the purpose of non-destructive testing and evaluation. Few literatures dealt with the thermoelastic wave in FGM structures although the thermal effect would cause attenuations of elastic waves. In this paper, guided thermoelastic waves in FGM plates subjected to stress-free, isothermal boundary conditions are investigated in the context of the Green-Lindsay (GL) generalized thermoelastic theories (with two relaxation times). Coupled wave equations and heat conduction equation are solved by the Legendre polynomial approach. Dispersion curves for a pure elastic graded plate are calculated to make a compar