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Showing papers by "Beihang University published in 2007"


Journal ArticleDOI
TL;DR: In this article, the Dzyaloshinski-Moriya (DM) anisotropic antisymmetric interaction and entanglement teleportation when using two independent Heisenberg chains as the quantum channel are investigated.
Abstract: Thermal entanglement of a two-qubit Heisenberg chain in the presence of the Dzyaloshinski-Moriya (DM) anisotropic antisymmetric interaction and entanglement teleportation when using two independent Heisenberg chains as the quantum channel are investigated. It is found that the DM interaction can excite entanglement and teleportation fidelity. The output entanglement increases linearly with increasing value of the input; its dependences on the temperature, DM interaction, and spin coupling constant are given in detail. Entanglement teleportation will be better realized via an antiferromagnetic spin chain when the DM interaction is turned off and the temperature is low. However, the introduction of the DM interaction can cause the ferromagnetic spin chain to be a better quantum channel for teleportation. A minimal entanglement of the thermal state in the model is needed to realize the entanglement teleportation regardless of whether the spin chains are antiferromagnetic or ferromagnetic.

260 citations


Journal ArticleDOI
TL;DR: A new method for the delay-dependent stability analysis and stabilization problems for continuous-time Takagi and Sugeno (T-S) fuzzy systems with a time-varying delay is suggested, which is less conservative than other existing ones.
Abstract: This paper is concerned with delay-dependent stability analysis and stabilization problems for continuous-time Takagi and Sugeno (T-S) fuzzy systems with a time-varying delay A new method for the delay-dependent stability analysis and stabilization is suggested, which is less conservative than other existing ones First, based on a fuzzy Lyapunov-Krasovskii functional (LKF), a delay-dependent stability criterion is derived for the open-loop fuzzy systems In the derivation process, some free fuzzy weighting matrices are introduced to express the relationships among the terms of the system equation, and among the terms in the Leibniz-Newton formula Then, a delay-dependent stabilization condition based on the so-called parallel distributed compensation (PDC) scheme is worked out for the closed-loop fuzzy systems The proposed stability criterion and stabilization condition are represented in terms of linear matrix inequalities (LMIs) and compared with the existing ones via two examples Finally, application to control of a truck-trailer is also given to illustrate the effectiveness of the proposed design method

244 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that the presence of nanoparticles enhances thermal conduction under macroscopically static conditions mainly due to nanoparticle structuring / networking, while the natural convective heat transfer coefficient decreases systematically with increasing nanoparticle concentration, and the deterioration is partially attributed to the high viscosity of nanofluids.
Abstract: This paper summarises some of our recent work on the heat transfer of nanofluids (dilute liquid suspensions of nanoparticles). It covers heat conduction, convective heat transfer under both natural and forced flow conditions, and boiling heat transfer in the nucleate regime. The results show that, despite considerable data scattering, the presence of nanoparticles enhances thermal conduction under macroscopically static conditions mainly due to nanoparticle structuring / networking. The natural convective heat transfer coefficient is observed to decrease systematically with increasing nanoparticle concentration, and the deterioration is partially attributed to the high viscosity of nanofluids. However, either enhancement or deterioration of convective heat transfer is observed under the forced flow conditions and particle migration is suggested to be an important mechanism. The results also show that the boiling heat transfer is enhanced in the nucleate regime for both alumina and titania nanofluids, and the enhancement is more sensitive to the concentration change for TiO(2) nanofluids. It is concluded that there is still some way to go before we can tailor-make nanofluids for any targeted applications.

233 citations


Journal ArticleDOI
TL;DR: In this article, a polyaniline-intercalated layered manganese oxide (PANI-MnO2) nanocomposite was synthesized via exchange reaction of PANI with n-octadecyltrimethylammonium (N-methyl-2-pyrrolidone) solvent.

208 citations


Journal ArticleDOI
TL;DR: In this article, the equations of motion of an insect with flapping wings were derived and then simplified to that of a flying body using the "rigid body" assumption, and the longitudinal dynamic flight stability of four insects (hoverfly, cranefly, dronefly and hawkmoth) in hovering flight was studied.
Abstract: The equations of motion of an insect with flapping wings are derived and then simplified to that of a flying body using the “rigid body” assumption. On the basis of the simplified equations of motion, the longitudinal dynamic flight stability of four insects (hoverfly, cranefly, dronefly and hawkmoth) in hovering flight is studied (the mass of the insects ranging from 11 to 1,648 mg and wingbeat frequency from 26 to 157 Hz). The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. The validity of the “rigid body” assumption is tested and how differences in size and wing kinematics influence the applicability of the “rigid body” assumption is investigated. The primary findings are: (1) For insects considered in the present study and those with relatively high wingbeat frequency (hoverfly, drone fly and bumblebee), the “rigid body” assumption is reasonable, and for those with relatively low wingbeat frequency (cranefly and howkmoth), the applicability of the “rigid body” assumption is questionable. (2) The same three natural modes of motion as those reported recently for a bumblebee are identified, i.e., one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. (3) Approximate analytical expressions of the eigenvalues, which give physical insight into the genesis of the natural modes of motion, are derived. The expressions identify the speed derivative Mu (pitching moment produced by unit horizontal speed) as the primary source of the unstable oscillatory mode and the stable fast subsidence mode and Zw (vertical force produced by unit vertical speed) as the primary source of the stable slow subsidence mode.

201 citations


Journal ArticleDOI
TL;DR: Magnetic chains up to 10 μm in length formed of hollow cobalt mesospheres (480-850 nm) with a 60 nm thick shell are synthesized by a new soft-assembly protocol.
Abstract: Magnetic chains up to 10 μm in length formed of hollow cobalt mesospheres (480-850 nm) with a 60 nm thick shell are synthesized by a new soft-assembly protocol. The obtained chains show a saturation magnetization of 37.5 emug -1 , a remnant magnetization of 1.55 emu g -1 , and a coercivity of ca. 66 Oe at 300 K. A possible mechanism for the formation of the chainlike hollow structures is proposed.

193 citations


Journal ArticleDOI
TL;DR: A formal analysis shows that it is possible to generate forced satisfiable instances whose hardness is similar to unforced satisfiable ones.

180 citations


Journal ArticleDOI
TL;DR: This paper starts from a classical method that uses interval arithmetic to check whether trajectories can move over the boundaries in a rectangular grid and improves it by developing an additional refinement step that employs interval-constraint propagation to add information to the abstraction without introducing new grid elements.
Abstract: This paper deals with the problem of safety verification of nonlinear hybrid systems. We start from a classical method that uses interval arithmetic to check whether trajectories can move over the boundaries in a rectangular grid. We put this method into an abstraction refinement framework and improve it by developing an additional refinement step that employs interval-constraint propagation to add information to the abstraction without introducing new grid elements. Moreover, the resulting method allows switching conditions, initial states, and unsafe states to be described by complex constraints, instead of sets that correspond to grid elements. Nevertheless, the method can be easily implemented, since it is based on a well-defined set of constraints, on which one can run any constraint propagation-based solver. Tests of such an implementation are promising.

178 citations


Journal ArticleDOI
TL;DR: This paper compares the predictive performance of ARIMA, artificial neural network and the linear combination models for forecasting wheat price in Chinese market and concludes that the ANN model is overall the best model, and can be used as an alternative method to model Chinese future food grain price.

171 citations



Journal ArticleDOI
TL;DR: An integrated bibliometric analysis of the knowledge base of nanoscience and nanotechnology in the Chinese research community is provided and it is found that China is productive in nanos science as far as publication activity is concerned.

Journal ArticleDOI
TL;DR: In this paper, the glass-formation range of bulk metallic glasses (BMGs) based on lanthanum and cerium was pinpointed in the La-Ce, Ce-Al-Co and pseudo-ternary (La−Ce)-AlCo systems, respectively, by copper mold casting.

Journal ArticleDOI
01 Jan 2007-EPL
TL;DR: In this article, a (3+1)-dimensional spherical Kadomtsev-Petviashvili model is constructed with symbolic computation, 4th-ordered and with variable coefficients, in spherical geometry with both azimuthal and zenith perturbations existing.
Abstract: Dust-ion-acoustic waves in a cosmic dusty plasma is investigated, in spherical geometry with both azimuthal and zenith perturbations existing. (3+1)-dimensional spherical Kadomtsev-Petviashvili ((3+1)DsKP) model is constructed with symbolic computation, 4th-ordered and with variable coefficients. Auto-Backlund transformation and (3+1)DsKP nebulons are analytically obtained for such a generic model. Astromechanical and physical implications are discussed, of the supernova-shell-type expanding bright and Saturn-F-ring-type expanding dark (3+1)DsKP nebulons. Possibly observable nebulonic effects are proposed for future cosmic experiments.

Journal ArticleDOI
TL;DR: In this article, the complex dynamics of a Holling type II prey-predator system with impulsive state feedback control were studied in both theoretical and numerical ways, and sufficient conditions for the existence and stability of semi-trivial and positive periodic solutions were obtained by using the Poincare map and the analogue of the poincare criterion.
Abstract: The complex dynamics of a Holling type II prey–predator system with impulsive state feedback control is studied in both theoretical and numerical ways. The sufficient conditions for the existence and stability of semi-trivial and positive periodic solutions are obtained by using the Poincare map and the analogue of the Poincare criterion. The qualitative analysis shows that the positive periodic solution bifurcates from the semi-trivial solution through a fold bifurcation. The bifurcation diagrams, Lyapunov exponents, and phase portraits are illustrated by an example, in which the chaotic solutions appear via a cascade of period-doubling bifurcations. The superiority of the state feedback control strategy is also discussed.

Journal ArticleDOI
TL;DR: In this article, the martensitic transformation peak temperatures of Ni50+xMn25Ga25� x (x = 2-11) alloys were studied as high-temperature shape-memory alloys.

Journal ArticleDOI
TL;DR: In this article, a cylindrical modified Kadomtsev-Petviashvili (CMKP) model is constructed by virtue of symbolic computation, with three families of exact analytic solutions obtained as well.

Journal ArticleDOI
TL;DR: In this article, molecular dynamics simulations are carried out to analyze the diffusion bonding at the Cu/Al interfaces, and the results indicate that the thickness of the interfacial layer is temperature-dependent, with higher temperatures yielding larger thicknesses.

Journal ArticleDOI
TL;DR: In this paper, the dynamics of a predator-prey model with impulsive state feedback control, which is described by an autonomous system with impulses, was studied, and the sufficient conditions of existence and stability of semi-trivial solution and positive period-1 solution were obtained by using the Poincare map and analogue of the poincare criterion.

Journal ArticleDOI
TL;DR: Tian et al. as mentioned in this paper obtained an auto-Backlund transformation on the TE and more general nebulons, and addressed that there are cosmic plasma systems for which the TE is valid, and removed a constraint set in that Comment so that the TE can be useful for the Saturn-Fring-typed dusty plasmas as well.

Journal ArticleDOI
TL;DR: In this paper, a multiclass, multicriteria (cost versus time) logit-based traffic equilibrium assignment model was proposed for road networks served by advanced traveler information systems (ATIS).

Journal ArticleDOI
TL;DR: In this paper, the vertex solution theorem is used to determine the supremum and the infimum of the static responses of structures with bounded uncertainties in terms of the vertex notation in interval analysis.

Journal ArticleDOI
TL;DR: In this article, a 3D cellular silicon-based anode was prepared by casting milled silicon powders into the "valley-ridge" copper architecture, then its electrochemical property and failure mechanism were studied by means of charging-discharging (C-D) test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Journal ArticleDOI
TL;DR: In this paper, a transient thermal structural finite element solution was employed to analyze the stress distribution in the nanostructured yttria stabilized zirconia (YSZ) ceramic layer.
Abstract: Nanostructured and traditional thermal barrier coatings have been prepared by atmospherical plasma spraying (APS) on NiCrAlY-coated superalloy substrates. Nanostructured thermal barrier coating has relatively longer lifetime than the common coating after cyclic testing at 1050, 1100 and 1150 °C. A transient thermal structural finite element solution was employed to analyze the stress distribution in the coatings. The reasons why the two kinds of the coatings have different lifetimes have been explored. The results indicate that the stresses ( S x ) within the nanostructured yttria stabilized zirconia (YSZ) ceramic layer in the axial ( x ) direction is about 67% that of the traditional YSZ. The stress ( S y ) in the radial ( y ) direction at the vicinity of the interface between the thermally grown oxide scale (TGO) and the YSZ topcoat at the edge of the sample is only about 73% that of the traditional YSZ. So it could be concluded that the decrease of the stress in the nanostructured ceramic layers is a fundamental reason, resulting in longer thermal cycling lifetime of the nanostructured thermal barrier coating.

Journal ArticleDOI
TL;DR: Subtle and spatially complex deformation patterns of hippocampus between patients with AD and healthy control subjects can be detected by machine learning methods.
Abstract: RESULTS: Patients with AD showed significant deformations in the CA1 region of bilateral hippocampi, as well as the subiculum of the left hippocampus. There were also some changes in the CA2–4 subregions of the left hippocampus among patients with AD. Moreover, the left hippocampal surface showed greater variations than the right compared with those in healthy control subjects. The accuracies of leave-1-out cross-validation and 3-fold cross-validation experiments for assessing the reliability of these subregions were more than 80% in bilateral hippocampi. CONCLUSION: Subtle and spatially complex deformation patterns of hippocampus between patients with AD and healthy control subjects can be detected by machine learning methods.

Journal ArticleDOI
TL;DR: In this article, magnetic hollow spheres of low density were prepared by plating Fe 3 O 4 magnetic films on hollow glass spheres using ferrite plating, and the complex permeability and permittivity of spheres-wax composites were measured in the range of 2-18 GHz.

Journal ArticleDOI
TL;DR: In this paper, a 3D progressive damage model was developed to study the tensile behavior of open-hole composite plates bonded with external composite patches, and the effects of several repair parameters on the failure initiation strength, ultimate strength and failure mechanism of these repaired structures were investigated.

Journal ArticleDOI
TL;DR: This paper proposes a new and efficient imputation method for a kind of missing data: semi-parametric data, and demonstrates that it is much better than existing deterministic semi- parametric regression imputation in efficiency and effectiveness.
Abstract: Missing data imputation is an important issue in machine learning and data mining. In this paper, we propose a new and efficient imputation method for a kind of missing data: semi-parametric data. Our imputation method aims at making an optimal evaluation about Root Mean Square Error (RMSE), distribution function and quantile after missing-data are imputed. We evaluate our approaches using both simulated data and real data experimentally, and demonstrate that our stochastic semi-parametric regression imputation is much better than existing deterministic semi-parametric regression imputation in efficiency and effectiveness.

Journal ArticleDOI
TL;DR: This paper analyzes the equilibrium properties of the morning peak-period commuting pattern on a many-to-one transit system with in-vehicle crowding effect and schedule delay cost in a monocentric city to characterize the equilibrium state.
Abstract: This paper analyzes the equilibrium properties of the morning peak-period commuting pattern on a many-to-one transit system with in-vehicle crowding effect and schedule delay cost in a monocentric city. Commuters are assumed to choose their optimal time-of-use decision from various stations/home locations to a single destination/workplace by trading off the travel time and crowding cost against the schedule delay cost. An equivalent mathematical programming model is proposed to characterize the equilibrium state, in which no commuter can reduce his/her total commuting cost by unilaterally changing his/her departure time or train service. Solution of the model yields many insights including the following: (1) commuters living closer to the destination choose trains also chosen by those living farther from the destination; (2) the train arriving at the time desired by everyone is utilized by commuters from all stations; (3) the farther a station is from the workplace, the longer is the peak-period departure duration from that station; (4) finally, a ‘saturated’ time period exists for each station during which the departure rate of commuters is identical and maximal.

Journal ArticleDOI
TL;DR: In this paper, a surface modification-induced hydrophilicity to super-hydrophobicity transition on well-aligned single-crystalline ZnO nanorod array films (ZnO-NAFs) was reported.

Journal ArticleDOI
TL;DR: In this article, the effect of fiber orientation and aspect ratio distribution on the overall elastic properties of composites using the Mori-Tanaka's method was discussed, and the results showed that using an average aspect ratio of the fibers to estimate overall elastic property is not appropriate under some conditions.
Abstract: A composite’s microstructure significantly influences its overall properties. Orientation and aspect ratio of the fiber are two key parameters that describe the microstructures of a composite with straight short fibers. This paper discusses the effects of fiber orientation and aspect ratio distribution on the overall elastic properties of composites using the Mori–Tanaka’s method in this paper. The results show that using an average aspect ratio of the fibers to estimate overall elastic properties is not appropriate under some conditions. When the aspect ratio of the fibers does not follow a symmetric distribution, the overall elastic properties obtained by the average aspect ratio of the fibers may differ by more than 30% from those obtained by the method considering the aspect ratio distribution. This paper presents a model used to predict the properties of nanotube-reinforced composites. The results obtained by the model were compared with experimental results.