Search Results - (Author, Cooperation:X. D. Li)

2014-12-20

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Adaptor Proteins, Signal Transducing/genetics/*immunology ; Animals ; Antibody Formation ; Antigens, T-Independent/*immunology ; B-Lymphocytes/*immunology ; Cytosol/immunology ; DNA/immunology ; Endogenous Retroviruses/genetics/*immunology ; Lymphocyte Activation ; Membrane Proteins/immunology ; Mice ; Mice, Inbred C57BL ; NF-kappa B/metabolism ; Nucleotides, Cyclic/immunology ; Nucleotidyltransferases/genetics/*immunology ; RNA, Viral/genetics/*immunology ; Transcription, Genetic

2013-08-31

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Antibodies, Viral/biosynthesis ; DNA, Viral/genetics/immunology ; Dendritic Cells/immunology ; Fibroblasts/immunology ; Herpes Simplex/*immunology ; *Herpesvirus 1, Human ; Interferon Regulatory Factor-3/genetics ; Interferon-beta/*biosynthesis/genetics ; Lymphocyte Activation ; Macrophages/immunology ; Mice ; Mice, Knockout ; Nucleotidyltransferases/genetics/*immunology ; Signal Transduction ; T-Lymphocytes/immunology ; Transfection

2014-08-15

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Amino Acid Sequence ; Animals ; Binding Sites ; Crystallography, X-Ray ; Mice ; Models, Molecular ; Molecular Sequence Data ; Neurotransmitter Agents/metabolism ; Protein Structure, Quaternary ; Protein Structure, Tertiary ; Protein Subunits/chemistry/metabolism ; Receptors, Serotonin, 5-HT3/*chemistry/metabolism

2018-10-02

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

1365-246X

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Splitting functions retrieved from spectra of the free oscillations are sensitive to the lateral variations in P velocity (α), S velocity (β), and density (ρ) simultaneously. In this study they are used to constrain the values of the ratios d ln α/d ln β and d ln ρ/d ln α for the lower mantle. Assuming that the upper mantle structure is obtainable from model M84A (this is not a crucial assumption as experiments indicate), the optimal value of d ln α/d ln β inferred from the modal data is 0.44 and d ln α/d ln β lies in the interval (0.39, 0.60) with 75 per cent confidence, strongly discriminating against the value (0.8) often used. The constraints on density structure of the current data are insufficient to yield new definitive results. The analysis demonstrates, however, that the value of d ln ρ/d ln α could be estimated from a larger set of modal data.

Electronic Resource

0021-9673

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

1435-5663

Discontinuous Galerkin ; Error estimation adaptivity ; Postprocessing ; Superconvergence

Springer Online Journal Archives 1860-2000

Computer Science

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Technology

Abstract The paper discusses error estimation and h-adaptive finite element procedures for elasticity and plasticity problems. For the spatial discretization error, an enhanced Superconvergent Patch Recovery (SPR) technique which improves the error estimation by including fulfillment of equilibrium and boundary conditions in the smoothing procedure is discussed. It is known that an accurate error estimation on an early stage of analysis results in a more rapid and optimal adaptive process. It is shown that node patches and element patches give similar quality of the postprocessed solution. For dynamic problems, a postprocessed type of error estimate and an adaptive procedure for the semidiscrete finite element method are discussed. It is shown that the procedure is able to update the spatial mesh and the time step size so that both spatial and time discretization errors are controlled within specified tolerances. A time-discontinuous Galerkin method for solving the second-order ordinary differential equations in structural dynamics is also presented. Many advantages of the new approach such as high order accuracy, possibility to filter effects of spurious modes and convenience to apply adaptive analysis are observed. For plasticity problems, some recent work that improved plastic strains and plastic localization is discussed.

Electronic Resource

1432-0800

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Medicine

Electronic Resource

1432-0495

Keywords China ; Geochemistry ; River ; Sediment ; Trace metals

Springer Online Journal Archives 1860-2000

Geosciences

Abstract  A total of 26 geographically and hydrologically diverse sediment samples were collected from 12 major rivers in eastern China. The 〈63-μm fraction of the sediments was analysed for both total concentrations of Cu, Zn, Pb and Cd, and their associations with various geochemical phases. The geographical variations of sediment-bound trace metals can be related to the bedrock types and weathering processes in the corresponding river basins. The rivers in southern China had notably higher concentrations of trace metals in sediments because of abundant non-ferrous mineral deposits and stronger weathering process in the region. A large proportion of trace metals in these sediments was associated with iron and manganese oxides and organic matter. Relative low levels of trace metals were found in river sediments in northern China, and a significant proportion of the metals was bound to organic matter, carbonates, and the residual fraction. The sediments in the Yellow River, originating from special loess, had the lowest concentrations of trace metals. Most of the trace metals were associated with the carbonates and residual phases.

Electronic Resource

1572-9540

Springer Online Journal Archives 1860-2000

Physics

Abstract The hyperfine fieldsH f(T), center shifts δ(T) and relative recoilless fractionsf a(T) at different lattice sites of barium ferrite were determined by Mössbauer spectroscopy of57Fe over a temperature range from 12 to 723 K. For ferric iron in the crystalline site (2b), the recoilless fractionf a(T) decreases most with increasing temperature in comparison with that of other sites, corresponding to a characteristic temperature {ie219-1}. These results indicate that the ferric iron in the site (2b) oscillates between two equivalent positions (4e) on either side of the symmetry plane normal to thec-axis.

Electronic Resource

1573-4811

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

1069-8299

Engineering ; Engineering General

Wiley InterScience Backfile Collection 1832-2000

Mathematics

Technology

In the paper we present a superconvergent patch recovery technique for obtaining higher-order-accurate finite-element solutions and thus a postprocessed type of L2 norm error estimate. Two modifications make our procedure different from the one proposed by Zienkiewicz and Zhu (1992), in which higher-order-accurate derivatives of the finite-element solution at nodes are determined. Firstly, the recovery process is made for element, not for nodes. An ‘element patch’, which represents the union of an element under consideration and the surrounding elements, is introduced. Secondly, the local error estimate is calculated directly from the improved solution for this element. Numerical tests on both 1D and 2D model problems show that this method can provide an asymptotically exact a posteriori L2 norm error estimate if the used element possesses superconvergent points for the solutions.

7 Ill.

Electronic Resource

1069-8299

Engineering ; Engineering General

Wiley InterScience Backfile Collection 1832-2000

Mathematics

Technology

A simple a posteriori local error estimator for time discretization in structural dynamic analysis is presented. It is derived from the difference of the solutions between an ordinary integration method (the Newmark scheme) and another higher-order one which assumes that the derivatives of accelerations vary linearly within each time step. It may be obtained directly without resolving new equations, so the additional computational cost is small and the implementation is convenient. Furthermore, it is shown that this error estimator may also be obtained by Taylor expansion or by a post-processing technique. Accordingly, an adaptive time-stepping procedure, which automatically adjusts the time-step size so that the local error at each time step is within a prescribed accuracy, is described. Numerical examples, including two single-DOF problems, a two-DOF problem and a multi-DOF model, are presented. The results show that the presented local error estimator is simple, reliable and accurate.

9 Ill.

Electronic Resource

0029-5981

Engineering ; Engineering General

Wiley InterScience Backfile Collection 1832-2000

Mathematics

Technology

In the paper we present a postprocessed type of a posteriori error estimate and a h-version adaptive procedure for the semidiscrete finite element method in dynamic analysis. In space the super-convergent patch recovery technique is used for determining higher-order accurate stresses and, thus, a spatial error estimate. In time a postprocessing technique is developed for obtaining a local error estimate for one step time integration schemes (the HHT-α method). Coupling the error estimate with a mesh generator, a h-version adaptive finite element procedure is presented for two-dimensional dynamic analysis. It updates the spatial mesh and time step automatically so that the discretization errors are controlled within specified tolerances. Numerical studies on different problems are presented for demonstrating the performances of the proposed adaptive procedure.

19 Ill.

Electronic Resource

0029-5981

discontinuous Galerkin finite element method ; predictor-multicorrector ; adaptive time integration ; structural dynamics ; Engineering ; Engineering General

Wiley InterScience Backfile Collection 1832-2000

Mathematics

Technology

This paper studies a time-discontinuous Galerkin finite element method for structural dynamic problems, by which both displacements and velocities are approximated as piecewise linear functions in the time domain and may be discontinuous at the discrete time levels. A new iterative solution algorithm which involves only one factorization for each fixed time step size and a few iterations at each step is presented for solving the resulted system of coupled equations. By using the jumps of the displacements and the velocities in the total energy norm as error indicators, an adaptive time-stepping procedure for selecting the proper time step size is described. Numerical examples including both single-DOF and multi-DOF problems are used to illustrate the performance of these algorithms. Comparisons with the exact results and/or the results by the Newmark integration scheme are given. It is shown that the time-discontinuous Galerkin finite element method discussed in this study possesses good accuracy (third order) and stability properties, its numerical implementation is not difficult, and the higher computational cost needed in each time step is compensated by use of a larger time step size.

20 Ill.

Electronic Resource