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Search Results: 1 - 10 of 42654 matches for " Xiang Zhu "
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A Regularity Criterion for the Navier-Stokes Equations in the Multiplier Spaces
Xiang'ou Zhu
Abstract and Applied Analysis , 2012, DOI: 10.1155/2012/682436
Abstract: We exhibit a regularity condition concerning the pressure gradientfor the Navier-Stokes equations in a special class. It is shown that if the pressuregradient belongs to 2/(2?)?((0,);?((?3?)→?(?3))), where ??((?3?)→?(?3)) is the multipliers between Sobolev spaces whosedefinition is given later for 0<<1, then the Leray-Hopf weak solution to theNavier-Stokes equations is actually regular.
Research of Blind Watermark Detection Algorithm Based on Generalized Gaussian Distribution
Xiang-wei Zhu
Journal of Software , 2010, DOI: 10.4304/jsw.5.4.413-420
Abstract: In digital management, multimedia content and data can easily be used in an illegal way-- being copied, modified and distributed again. Copyright protection, intellectual and material rights protection for authors, owners, buyers, distributors and the authenticity of content are crucial factors in solving an urgent and real problem. In such scenario, digital watermark techniques are emerging as a valid solution. Blind watermark detection is a modern digital watermark technology with outstanding feature. A novel algorithm of Blind Watermark Detection based on Generalized Gaussian Distribution is proposed in this paper. To start with, this paper carries on the statistical analysis to the high frequency sub-band coefficients of wavelet and contourlet transform, then knowing the high frequency sub-band coefficients of wavelet and contourlet transform can be characterized by Generalized Gaussian Distribution. So a blind watermark detection algorithm can be designed according to the method of maximum likelihood estimator. Experimental results demonstrate that the performance of watermark detector is good based on Generalized Gaussian Distribution. The scheme is robust against most attack, so it is very effective and practical.
Efficient Parallel Levenberg-Marquardt Model Fitting towards Real-Time Automated Parametric Imaging Microscopy
Xiang Zhu, Dianwen Zhang
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076665
Abstract: We present a fast, accurate and robust parallel Levenberg-Marquardt minimization optimizer, GPU-LMFit, which is implemented on graphics processing unit for high performance scalable parallel model fitting processing. GPU-LMFit can provide a dramatic speed-up in massive model fitting analyses to enable real-time automated pixel-wise parametric imaging microscopy. We demonstrate the performance of GPU-LMFit for the applications in superresolution localization microscopy and fluorescence lifetime imaging microscopy.
Entanglement in a Dimerized Antiferromagnetic Heisenberg Chain
Xiang Hao,Shiqun Zhu
Physics , 2008,
Abstract: The entanglement properties in an antiferromagnetic dimerized Heisenberg spin-1/2 chain are investigated. The entanglement gap, which is the difference between the ground-state energy and the minimal energy that any separable state can attain, is calculated to detect the entanglement. It is found that the entanglement gap can be increased by varying the alternation parameter. Through thermal energy, the witness of the entanglement can determine a characteristic temperature below that an entangled state can be obtained. The entanglement detected by the energy can provide a lower bound for that determined by the concurrence. If the alternation parameter is smaller than a critical value, there is always no inter-dimer entanglement in the chain.
Entanglement in a hardcore-boson Hubbard model
Xiang Hao,Shiqun Zhu
Physics , 2008,
Abstract: The entanglement in a Hubbard chain of hardcore bosons is investigated. The analytic expression of the global entanglement in ground state is derived. The divergence of the derivative of the global entanglement shows the quantum criticality of the ground state. For the thermal equilibrium state, the bipartite and the multipartite entanglement are evaluated. The entanglement decreases to zero at a certain temperature. The thermal entanglement is rapidly decreasing with the increase of the number of sites in the lattice. The bipartite thermal entanglement approaches a constant value at a certain number of sites while the multipartite entanglement eventually vanishes.
Swap Action in a Solid-State Controllable Anisotropic Heisenberg Model
Xiang Hao,Shiqun Zhu
Physics , 2008, DOI: 10.1016/j.physleta.2007.09.004
Abstract: Correct swap action can be realized via the control of the anisotropic Heisenberg interaction in solid-state quantum systems. The conditions of performing a swap are derived by the dynamics of arbitrary bipartite pure state. It is found that swap errors can be eliminated in the presence of symmetric anisotropy. In realistic quantum computers with unavoidable fluctuations, the gate fidelity of swap action is estimated. The scheme of quantum computation via the anisotropic Heisenberg interaction is implemented in a one dimensional quantum dots. The slanting and static magnetic field can be used to adjust the anisotropy.
Quantum computation in semiconductor quantum dots of electron-spin asymmetric anisotropic exchange
Xiang Hao,Shiqun Zhu
Physics , 2008, DOI: 10.1103/PhysRevA.76.044306
Abstract: The universal quantum computation is obtained when there exists asymmetric anisotropic exchange between electron spins in coupled semiconductor quantum dots. The asymmetric Heisenberg model can be transformed into the isotropic model through the control of two local unitary rotations for the realization of essential quantum gates. The rotations on each qubit are symmetrical and depend on the strength and orientation of asymmetric exchange. The implementation of the axially symmetric local magnetic fields can assist the construction of quantum logic gates in anisotropic coupled quantum dots. This proposal can efficiently use each physical electron spin as a logical qubit in the universal quantum computation.
Quantum information processing in a spin-bus system of coupled chains
Xiang Hao,Shiqun Zhu
Physics , 2008, DOI: 10.1103/PhysRevA.78.044302
Abstract: The effective Heisenberg interaction of long distance is constructed in spin qubits connected to a bus of two strongly coupled chains. Universal quantum computation can be realized on the basis of the bus which always keeps frozen at the ground state. It is found that the effective interaction is primarily determined by the energy spectra of the bus. With the variation of the distance between two connecting nodes, the interaction alternately occurs between antiferromagnetic and ferromagnetic ones. The long range interaction can also be attained in coupled infinite chains. The quantum gate operations with the high precision are implemented in the condition of quantum fluctuations.
A continuum model for dislocation dynamics in three dimensions using the dislocation density potential functions and its application in understanding the micro-pillar size effect
Yichao Zhu,Yang Xiang
Physics , 2015, DOI: 10.1016/j.jmps.2015.07.015
Abstract: In this paper, we present a dislocation-density-based three-dimensional continuum model, where the dislocation substructures are represented by pairs of dislocation density potential functions (DDPFs), denoted by $\phi$ and $\psi$. The slip plane distribution is characterized by the contour surfaces of $\psi$, while the distribution of dislocation curves on each slip plane is identified by the contour curves of $\phi$ which represents the plastic slip on the slip plane. By using DDPFs, we can explicitly write down an evolution equation system, which is shown consistent with the underlying discrete dislocation dynamics. The system includes i) A constitutive stress rule, which describes how the total stress field is determined in the presence of dislocation networks and applied loads; ii) A plastic flow rule, which describes how dislocation ensembles evolve. The proposed continuum model is validated through comparisons with discrete dislocation dynamics simulation results and experimental data. As an application of the proposed model, the "smaller-being-stronger" size effect observed in single-crystal micro-pillars is studied. A scaling law for the pillar flow stress $\sigma_{\text{flow}}$ against its (non-dimensionalized) size $D$ is derived to be $\sigma_{\text{flow}}\sim\log(D)/D$.
Entanglement in a Quantum Mixed-Spin Chain
Xiang Hao,Shiqun Zhu
Physics , 2006, DOI: 10.1016/j.physleta.2007.01.053
Abstract: The entanglement in a general mixed spin chain with arbitrary spin $S$ and 1/2 is investigated in the thermodynamical limit. The entanglement is witnessed by the magnetic susceptibility which decides a characteristic temperature for an entangled thermal state. The characteristic temperature is nearly proportional to the interaction $J$ and the mixed spin $S$. The bound of negativity is obtained on the basis of the magnetic susceptibility. It is found that the macroscopic magnetic properties are affected by the quantum entanglement in the real solids. Meanwhile, the entanglement can be quantitatively evaluated by the thermodynamical observable.
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