Effects of H on Electronic Structure and Ideal Tensile Strength of W： A First-Principles Calculation

We investigate the structure, energetics, and the ideal tensile strength of tungsten （W） with hydrogen （H） using a first-principles method. Both density of states （DOS） and the electron localization function （ELF） reveal the underlying physical mechanism that the tetrahedral interstitial H is the most energetically favorable. The firstprinciples computational tensile test （FPCTT） shows that the ideal tensile strength is 29.1 GPa at the strain of 14% along the [001] direction for the intrinsic W, while it decreases to 27.1 GPa at the strain of 12% when one impurity H atom is embedded into the bulk W. These results provide a useful reference to understand W as a plasma facing material in the nuclear fusion Tokamak.

Effects of Grain Boundary Barrier in ZnO/Si Heterostructure

The influence of ZnO microstructure on electrical barriers is investigated using capacitance-voltage （C - V）, current-voltage （I- V） and deep level transient spectroscopy （DLTS） measurements. A deep level center located at Ec - 0.24 eV obtained by DLTS in the ZnO films is an intrinsic defect related to Zni. The surface states in the ZnO grains that have acceptor behavior of capturing electrons from Zni defects result in the formation of grain barriers. In addition, we find that the current transport is dominated by grain barriers after annealing at 600℃ at 02 ambient. With the increment of the annealing temperature, the current transport mechanism of ZnO/Si heterostructure is mainly dominated by thermo-emission.

Multifractal analysis of white matter structural changes on 3D magnetic resonance imaging between normal aging and early Alzheimer's disease

Applications of multifractal analysis to white matter structure changes on magnetic resonance imaging（MRI） have recently received increasing attentions. Although some progresses have been made, there is no evident study on applying multifractal analysis to evaluate the white matter structural changes on MRI for Alzheimer＇s disease（AD） research. In this paper, to explore multifractal analysis of white matter structural changes on 3D MRI volumes between normal aging and early AD, we not only extend the traditional box-counting multifractal analysis（BCMA） into the 3D case, but also propose a modified integer ratio based BCMA（IRBCMA） algorithm to compensate for the rigid division rule in BCMA. We verify multifractal characteristics in 3D white matter MRI volumes. In addition to the previously well studied multifractal feature,△α, we also demonstrated △ f as an alternative and effective multifractal feature to distinguish NC from AD subjects.Both △α and △ f are found to have strong positive correlation with the clinical MMSE scores with statistical significance.Moreover, the proposed IRBCMA can be an alternative and more accurate algorithm for 3D volume analysis. Our findings highlight the potential usefulness of multifractal analysis, which may contribute to clarify some aspects of the etiology of AD through detection of structural changes in white matter.

Effect of In Composition on Two-Dimensional Electron Gas in Wurtzite AlGaN/InGaN Heterostructures

The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction x, due to the increase in the polarization charge at the AlGaN/InGaN interface. The electron sheet density is enhanced with the doping in the AlGaN layer. The sheet carrier density is as high as 3.7×1013 cm^-2 at the donor density of 10×1018 cm^-3 for the HEMT structure with x=0.3. The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.

Effects of Rapid Thermal Processing on Microstructure and Optical Properties of As-Deposited Ag2O Films by Direct-Current Reactive Magnetron Sputtering

（111） preferentially oriented Ag2O film deposited by direct current reactive magnetron sputtering is annealed by rapid thermal processing at different annealing temperatures for 5 min. The film microstructure and optical properties are then characterized by x-ray diffractometry, scanning electron microscopy, and spectrophotometry, respectively. The results indicate that no clear Ag diffraction peak is discernable in the Ag2O film annealed below 200°C. In comparison, the Ag2O film annealed at 200°C begins to exhibit characteristic Ag diffraction peaks, and in particular the Ag2O film annealed at 250°C can demonstrate enhanced Ag diffraction peaks. This implies that the threshold of the thermal decomposition reaction to produce Ag particles is approximately 200°C for the Ag2O film. In addition, an evolution of the film surface morphology from compact and pyramid-like to a rough and porous structure clearly occurred with increasing annealing temperature. The porous structure might be attributable to the escape of the oxygen produced during annealing, while the rough surface might originate from the reconstruction of the surface. The dispersion of interference peak intensity in the reflectance and transmission spectra could be attributed to the Ag particles produced. The lowered crystallinity and Ag particles produced induce a lattice defect, which results in an enhanced transmissivity in the violet region and a weakened transmissivity in the infrared region.

Effect of Annealing on Microstructure and Electrical Characteristics of Doped Poly （3-Hexylthiophene） Films

The effect of annealing on the microstructure and electrical characteristics of poly （3-hexylthiophene） （P3HT） films doped with very small amounts of the electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane （F4-TCNQ） is studied. X-ray diffraction and UV-vis spectrum studies show that unlike the pure P3HT film, the thermal treatment on the doped fihns under an Ar atmosphere can effectively enhance the crystalline order of P3HT films, as well as successfully facilitate the orientation of the polymer chains. This improvement is attributed to the electrostatic force between P3HT and F4-TCNQ molecules. This force induces the polymer chains to crystallize and orient during the annealing process. As a result, annealing significantly improves performance, especially for the Ion/Ioff ratio of the TFTs based on the doped P3HT films.

In/Pd-Doped SnO2-Based CO Micro-Structure Sensor with High Sensitivity and Quick Response

In/Pd-doped SnO2 is synthesized via a sol-gel method and coated on a silicon substrate with Pt electrodes to fabricate a micro-structure sensor. The sensor can be used to detect CO down to l ppm （the sensitivity is about 3）, and the response time and recovery time are about 5 and 15 s, respectively. Excellent selectivity is also found based on our sensor. These results demonstrate a promising approach to fabricate high-performance CO sensors with high sensitivity and quick response.

The effect of dynamical quark mass on the calculation of a strange quark star's structure

We discuss the dynamical behavior of strange quark matter components, in particular the effects of density dependent quark mass on the equation of state of strange quark matter. The dynamical masses of quarks are computed within the Nambu-Jona-Lasinio model, then we perform strange quark matter calculations em- ploying the MIT bag model with these dynamical masses. For the sake of compar- ing dynamical mass interaction with QCD quark-quark interaction, we consider the one-gluon-exchange term as the effective interaction between quarks for the MIT bag model. Our dynamical approach illustrates an improvement in the obtained equation of state values. We also investigate the structure of the strange quark star using Tolman- Oppenheimer-Volkoff equations for all applied models. Our results show that dynamical mass interaction leads to lower values for gravitational mass.

The Three Postulates of the Theory of Everything

The three postulates of the posited dynamic and reversible theory of everything are: 1) the oscil-lating M-theory postulate for the oscillating matter structure, 2) the digital transitional Higgs-reversed Higgs fields postulate for the digital space structure, and 3) the reversible multiverse post-ulate for all physical laws and phenomena. The posited theory of everything based on the three postulates explains cosmology, the composition (baryonic matter, dark matter, and dark energy) in the universe, the periodic table of elementary particles (quarks, leptons, and bosons), the galaxy evolution, superconductivity, black hole, thermodynamic, and quantum mechanics. Oscillating M-theory is derived from oscillating membrane-string-particle whose space-time dimension number oscillates between 11D and 10D and between 10D and 4D. Space-time dimension number between 10 and 4 decreases with decreasing speed of light, decreasing vacuum energy, and in-creasing rest mass. The digital transitional Higgs-reversed Higgs fields are derived from digital attachment-detachment spaces which couple to particles. Under spontaneous symmetry breaking, the coupling of massless particle to zero-energy attachment space (the space for mass) produces the transitional nonzero-energy Higgs field-particle composite which under spontaneous symmetry restoring produces massive particle on zero-energy attachment space with the longitudinal component. The opposite of attachment space is detachment space as the space for kinetic energy and the nonzero-energy reverse Higgs field. The combination of n units of attachment space (de-noted as 1) and n units of detachment space (denoted as 0) brings about the three digital structures: binary partition space (1)n(0)n, miscible space (1 + 0)n, and binary lattice space (1 0)n to account for quantum mechanics, special relativity, and the force fields, respectively. In the third postulate, all physical laws and phenomena are permanently reversible in the multiverse, and temporary irreversible entropy increase is allowed. Our universe is an asymmetrical dual posi-tive-energy-negative-energy universe where the positive-energy universe on attachment space absorbed the interuniversal void on detachment space to result in the combination of attachment space and detachment space, while the negative-energy universe did not absorb the interuniversal void, resulting in temporary irreversible entropy increase through reversibility breaking, sym-metry violation, and low entropy beginning. Guided by the reversible negative-energy universe, our dual universe is a globally reversible cyclic dual universe.

First-Principles Study of Structural Stabilities, Electronic and Optical Properties of SrF2 under High Pressure

An investigation of structural stabilities, electronic and optical properties of SrF2 under high pressure is conducted using a first-principles calculation based on density functional theory （DFT） with the plane wave basis set as implemented in the CASTEP code. Our results predict that the second high-pressure phase of SrF2 is of a Ni2In- type structure, and demonstrate that the sequence of the pressure-induced phase transition of SrF2 is the fluorite structure （Fm3m） to the PbC12-type structure （Pnma）, and to the Ni2In-type phase （P63/mmc）. The first and second phase transition pressures are 5. 77 and 45.58 GPa, respectively. The energy gap increases initially with pressure in the Fm3m, and begins to decrease in the Pnma phases at 30 GPa. The band gap overlap metallization does not occur up to 210 GPa. The pressure effect on the optical properties is discussed.

New Discrete Element Models for Three-Dimensional Impact Problems

Two 3-D numerical models of the discrete element method （DEM） for impact problems are proposed. The models can calculate not only the impact problems of continuum and non-continuum, but also the transient process from continuum to non-continuum. The stress wave propagation in a concrete block and a dynamic splitting process of a marble disc under impact loading are numerically simulated with the proposed models. By comparing the numerical results with the corresponding results obtained by the finite element method （FEM） and the experiments, it is proved that the models are reliable for three-dimensional impact problems.

Existence of Shear Horizontal Surface Waves in a Magneto-Electro-Elastic Material

The existence of shear horizontal surface waves in a magneto-electro-elastic （MEE） half-space with hexagonal （6mm） symmetry is investigated. The surface of the MEE half-space is mechanically free, but subjected to four types of electromagnetic boundary conditions. These boundary conditions are electrically open/magnetically closed, electrically open/magnetically open, electrically closed/magnetically open and electrically closed/magnetically dosed. It is shown that except for the electrically open/magnetically closed condition, the three other sets of electromagnetic boundary conditions allow the propagation of shear horizontal surface waves.

Phase-Transition and Magnetic Moment of the Gd3＋ Ion in the Gd2Fe17 Compound

The structure and magnetic phase transitions of the Gd2Fe17 compound are investigated by using a differential thermal/thermogravimetric analyzer, x-ray diffraction, and magnetization measurements. The result shows that there are two phase structures for the Gd2Fe17 compound： the hexagonal Th2Nilr-type structure at high temperatures （above 1243℃）, and the rhombohedral Th2Zn17-type structure, respectively. A method to measure the magnetic moments of the Gd-sublattice and the Fe-sublattice in the Gd2Fe17 compound is presented. The moments of the Gd-sublattice and the Fe-sublattice in the Gd2Fe17 compound from 77 to 500 K are measured in this way with a vibrating sample magnetometer. A detailed discussion is presented.

Theoretical and Experimental Investigation of Flexural Wave Propagating in a Periodic Pipe with Fluid-Filled Loading

Based on the Bragg scattering mechanism of phononic crystals （PCs）, a periodic composite material pipe with fluid loading is designed and studied. The band structure of the flexural wave in the periodic pipe is calculated with the transfer matrix （TM） method. A periodic piping experimental system is designed, and the vibration experiment is performed to validate the attenuation ability of the periodic pipe structure. Finally, a finite-element pipe model is constructed using the MSC-Actran software, and the calculated results match well with the vibration experiment. The errors between the theoretical calculation results and the vibration experimental results are analyzed.

Preparation of High-Density Nanocrystalline Bulk Selenium by Rapid Compressing of Melt

The melt＇s solidification behavior of elemental selenium is investigated by a series of experiments including rapid compressing to 2.8 and 3.5 GPa within 20ms respectively, slow compressing to 2.8 GPa for 20 min and natural cooling at ambient pressure. Based on the x-ray diffraction, scanning electron microscope and transmission electron microscope results of the recovered samples, it is clearly shown that homogenous nanostructures are formed only by the rapid compression processes, and that the average crystal sizes are about 18.7 and 19.0 nm in the samples recovered from 2.8 and 3.5 GPa, respectively. The relative density of the nanocrystalline bulk reaches 98.17% of the theoretical value. It is suggested that rapid compression could induce pervasive nucleation and restrain grain growth during the solidification, which is related to fast supercooling, higher viscosity of the melt and lower diffusivity of atoms under high pressure.

AlGaN-Based Deep-Ultraviolet Light Emitting Diodes Fabricated on AlN/sapphire Template

We report on the growth and fabrication of deep ultraviolet （DUV） light emitting diodes （LEDs） on an AIN template which was grown on a pulsed atomic-layer epitaxial buffer layer. Threading dislocation densities in the AlN layer are greatly decreased with the introduction of this buffer layer. The crystalline quality of the AlGaN epilayer is further improved by using a low-temperature GaN interlayer between AlGaN and AlN. Electroluminescences of different DUV-LED devices at a wavelength of between 262 and 317nm are demonstrated. To improve the hole concentration of p-type AlGaN, Mg-doping with trimethylindium assistance approach is performed. It is found that the serial resistance of DUV-LED decreases and the performance of DUV-LED such as EL properties is improved.

Characterization and Magnetic Properties of Nickel Ferrite Nanoparticles Prepared by Ball Milling Technique

Nickel ferrite nanoparicles with various grain sizes are synthesized using annealing treatment followed by ball milling of its bulk component materials. Commercially available nickel and iron oxide powders are first mixed, and then annealed at 1100~C in an oxygen environment furnace and for 3h. The samples are then milled for different times in an SPEX mill. X-ray diffraction pattern indicates that in this stage the sample is single phase. The average grain size is estimated by scanning electron microscopy （SEM） and x-ray diffraction techniques. Magnetic behavior of the sample at room temperatm＇e is studied using a superconducting quantum interference device （SQUID）. The Curie temperature of the powders is measured by an LCR meter unit. The x-ray diffraction patterns clearly indicate that increasing the milling time leads to a decrease in the grain size and consequently leads to a decrease in the saturation magnetization as well as the Curie temperatures. This result is attributed to the spin-glass-like surface layer on the nanocrystalline nickel ferrite with a ferrimagnetically aligned core.

Synthesis and Properties of Magnetic Composites of Carbon Nanotubes/Fe Nanoparticle

Magnetic composites of carbon nanotubes （CNTs） are synthesized by the in situ catalytic decomposition of benzene at temperatures as low as 400℃ over Fe nanoparticles （mean grain size = 26 nm） produced by sol-gel fabrication and hydrogen reduction. The yield of CNT composite is up to about 3025% in a run of 6 h. FE- SEM and HRTEM investigations reveal that one-dimensional carbon species are produced in a large quantity. A relatively high value of magnetization is observed for the composite due to the encapsulation of ferromagnetic Fe3 C and/or α-Fe. The method is suitable for the mass-production of CNT composites that contain magnetic nanoparticles.

Equivalent Method of Solving Quantum Efficiency of Reflection-Mode Exponential Doping GaAs Photocathode

The mathematical expression of the electron diffusion and drift length LDE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reflection-mode uniform doping cathode, substituting LDE for LD, the equivalent quantum efficiency equation of the reflection-mode exponential doping cathode is obtained. By using the equivalent equation, theoretical simulation and experimental analysis shows that the equivalent index formula and formula-doped cathode quantum efficiency results in line. The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode.

Simulation of Light Intensification Induced by Defects of Polished Fused Silica

Light intensity distribution in the vicinity of inclusions and etched cracks in polished fused silica at wavelength scale are simulated by using the finite-difference time-domain algorithm. Light intensity enhancement factor as functions of diameter and refractive index of inclusions are investigated, more than 10 times that of incident beam is obtained in the simulation. We model the etched crack in close proximity to a real structure, which is characterized by AFM. We find that the peak light intensity of the crack is a function of its cross sectional breadth depth ratio, providing good hints for the effective processing of fused silica samples to improve the damage threshold.