10 research outputs found
The 3-dimensional cellular automata for HIV infection
China National Funds for Distinguished Young Scientists [11125419, 10925525]; Fujian Province Funds for Leading Scientist in UniversitiesThe HIV infection dynamics is discussed in detail with a 3-dimensional cellular automata model in this paper. The model can reproduce the three-phase development, i.e., the acute period, the asymptotic period and the AIDS period, observed in the HIV-infected patients in a clinic. We show that the 3D HIV model performs a better robustness on the model parameters than the 2D cellular automata. Furthermore, we reveal that the occurrence of a perpetual source to successively generate infectious waves to spread to the whole system drives the model from the asymptotic state to the AIDS state. (C) 2013 Elsevier B.V. All rights reserved
A mechanically and electrically self-healing supercapacitor
The first mechanically and electrically self-healing supercapacitor has been successfully fabricated. It exhibits excellent self-healing performance with the restoration of the specific capacitance up to 85.7% of its original value even after the 5th mechanical cutting. This achievement may provide a way to expand the lifetime of future energy storage devices and endow them with desirable economic and human safety attributes, as well as promote the development of next-generation self-healing electronics
Defect suppression in AlN epilayer using hierarchical growth units
Growing AlN layers remains a significant challenge because it is subject to a large volume fraction of grain boundaries. In this study, the nature and formation of the AlN growth mechanism is examined by ab initio simulations and experimental demonstration. The calculated formation enthalpies of the constituent elements, including the Al/N atom, Al-N molecule, and Al-N 3 cluster, vary with growth conditions in N-rich and Al-rich environments. Using the calculation results as bases, we develop a three-step metalorganic vapor-phase epitaxy, which involves the periodic growth sequence of (i) trimethylaluminum (TMAl), (ii) ammonia (NH3), and (iii) TMAl+NH3 supply, bringing in hierarchical growth units to improve AlN layer compactness. A series of AlN samples were grown, and their morphological and luminescent evolutions were evaluated by atomic force microscopy and cathodoluminescence, respectively. The proposed technique is advantageous because the boundaries and defect-related luminescence derived are highly depressed, serving as a productive platform from which to further optimize the properties of AlGaN semiconductors. ? 2013 American Chemical Society
Defect Suppression in AlN Epilayer Using Hierarchical Growth Units
Growing AlN layers
remains a significant challenge because it is
subject to a large volume fraction of grain boundaries. In this study,
the nature and formation of the AlN growth mechanism is examined by
ab initio simulations and experimental demonstration. The calculated
formation enthalpies of the constituent elements, including the Al/N
atom, Al–N molecule, and Al–N<sub>3</sub> cluster, vary
with growth conditions in N-rich and Al-rich environments. Using the
calculation results as bases, we develop a three-step metalorganic
vapor-phase epitaxy, which involves the periodic growth sequence of
(i) trimethylaluminum (TMAl), (ii) ammonia (NH<sub>3</sub>), and (iii)
TMAl+NH<sub>3</sub> supply, bringing in hierarchical growth units
to improve AlN layer compactness. A series of AlN samples were grown,
and their morphological and luminescent evolutions were evaluated
by atomic force microscopy and cathodoluminescence, respectively.
The proposed technique is advantageous because the boundaries and
defect-related luminescence derived are highly depressed, serving
as a productive platform from which to further optimize the properties
of AlGaN semiconductors
Stoichiomery control and electronic and transport properties of pyrochlore Bi2Ir2O7 thin films
Synthesizing stoichiometric and epitaxial thin films of pyrochlore iridates is an essential step toward the experimental realization of unusual topological and magnetic states that are theoretically predicted in this unique spin-orbit coupled material system. Here, we report on the stoichiometry control and electronic and transport properties of pyrochlore iridate BiIrO thin films grown by pulsed laser deposition. The as-grown films form a bilayerlike structure, in which the top surface is highly Ir deficient while the bottom layer is mainly composed of iridium metal. By postannealing the as-deposited films in IrO + O atmosphere, we improved the stoichiometry and homogeneity through the film thickness with the lattice constant close to the bulk value. Density functional theory calculation in the bulk limit shows a fourfold degenerate Dirac node slightly below the Fermi energy at the X point, along with trivial bands around the point. The projected partial density of states suggests that the states in the vicinity of the Fermi energy (−3 to 0 eV) mainly consist of highly hybridized Ir 5 and O 2 with minor contributions from Bi 6 and 6, while those far below the Fermi energy (−9 to –3 eV) are contributed primarily by the O bands. Transport measurements revealed a weakly metallic behavior at higher temperatures transitioning to a weakly insulating behavior below 150 K, and a low-temperature magnetoresistance qualitatively ascribed to multicarrier and band-structural effects. The transport features are influenced by a density of states sharply peaked at the Fermi energy, and by the coexistence of trivial bands with the Dirac node, as revealed by the density functional theory calculations
High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms
The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. The experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. We conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup can be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. The use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved
High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms
The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. The experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. We conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup can be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. The use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.RST/Fundamental Aspects of Materials and Energ