A new conformal technique of inhomogeneous cells based on electric field strength weighted values
Application of group theory in the problem of electromagnetic scattering of symmetry structures
Investigation on the reconstruction of objects buried in layered media based on the equivalent current source
Diffraction barrier breakthrough in coherent anti-Stokes Raman scattering microscopy and detection limitanalysis
Resolution of coherent field imaging technique
Joint spectral and depth domain spectral domain phase microscopy
Influence of pump chirp on the purity of an all fiber source of correlated photon pairs
Generation of femtosecond pulsed quadrature phase squeezed light
Lasing without inversion with considering spontaneously generated coherence
Electron spin studies of nitrogen vacancy centers in nanodiamonds
Fluorescent nanodiamonds containing nitrogen vacancy centers are created by electron irradiation. The values of spin echo coherence time T2 of nitrogen vacancy centers in nanodiamonds are very small, which are between 0.86 μs and 5.6 μs. The results of Ramsey interference fringes show that the values of dephasing time T2* differ from each other and the T2* of nitrogen vacancy center NV1 is biggest (0.7 μs). Its inhomogeneous linewidth obtained from Fourier transform frequency spectrum of Ramsey interference fringes is 1.05 MHz. The hyperfine structure for the nitrogen vacancy center electron spin coupled to the host nitrogen-14 nuclear spin can be detected by the electron spin resonance spectrum in nitrogen vacancy center NV1. It is important for the realization of the manipulation of nuclear spins and quantum gates of multiqubit in nanodiamonds.
Dual-channel chaos synchronization and communication based on a vertical-cavity surface emitting laser with double optical feedback
Scintillation statistics of a retro-reflected wave from space
An overview of the method of high-precision measuring the aperture diaphragn area
A design of liquid crystal lens with low voltage driving
Perturbation to Noether symmetries and adiabatic invariants for nonconservative dynamic systems
Control of the fluctuation in the uniform granular flow by a random force field
Experimental study on the local equation of state for vibrated granular gases
Effects of grain size on the dynamic tensile damage of ductile polycrystalline metall
Composition analysis and mechanism approach of the electrorheological fluids based on the precursor of TO2
We synthesize the powder of the precursor of TiO2, which shows the giant electrorheological effect but does not include the component of CaC2O4·H2O. By use of X-ray diffraction, scanning electron microscope, inductively-coupled plasma spectrometer, themogravimetry-mass spectrum, etc, it is found that the precursor of TiO2 is amorphous powder with nanosize, and its components include TiOC2O4·2H2O and TiO(OH)2. The electrorheological fluid made by the powder shows a similar temperature characteristic to that made by the precursor of CaTiO3, i.e., when the powder is heated to the temperature above 160℃, the yield stress of the electrorheological fluid made by it decreases gradually, and when it is heated to 200℃, the giant electrorheological effect disappears completely. It is also found that the chemical reaction accompanies with the disappearance of the giant electrorheological effect is that the crystalized water in TiOC2O4·2H2O is volatilized in heating process. These characteristics can be observed in all electrorheological fluids made by the precursor of other titanate, so we conclude that TiOC2O4·2H2O is the key component for this series of giant electrorheological fluids.
Study of ignition process of boron particle with considering Stefan flow effects
Simulation study of effect of initial melt temperature on microstructure evolution of liquid metal Ni during solidfication process
A molecular dynamics simulation study is performed on the effect of the thermal history of initial melt temperature on the microstructure evolution in solidification process of liquid metal Ni by means of quantum Sutton-Chen n-body potential. The pair distribution function g(r) curves, the bond-type index method, the cluster-type index method and the three-dimensional (3D) visualization method are used to analyze the microstructure evolution in the solidification process. It is found that the initial melt temperature plays a critical role in the evolution of microstructures, but it is not obvious in liquid and supercooled states and the effects can be fully displayed only near the crystallization transition temperature Tc. The 1421 and 1422 bond-types or the FCC (12 0 0 0 12 0) and HCP (12 0 0 0 6 6) cluster in the system play the critical role in the microstructure evolution. The results show that at a cooling rate of 1×1012 K/s with different initial melt temperatures, the solidification structures of liquid metal Ni are always crystallized, but the numbers of the main bond-types and clusters have a vast varying range, and it does not vary linearly with the decrease of initial melt temperature. However, the system energy changes linearly with the decrease of initial melt temperature. Through the 3D visualization method, it is also found that atoms of the same cluster are gathered in the same layer when the system has a higher initial temperature, and these layers would be scattered when the initial melt temperature decreases. The 3D visualization method would help to deeply investigate the evolution mechanisms of microstructures in liquid metals during solidification.
The magnetism study of N-doped diamond
We perform the first-principles calculations to investigate the roles of C vacancy and nitrogen impurity in the magnetic properties of diamond. The coupling is ferromagnetic between the C vacancies in -2e charged state, whereas they prefer to interact antiferromagnetically in -e charged state. Substituting C with N atoms can manipulate the charge states of C vacancies and the magnetic interactions between them. Our work offers a possible route toward high Curie temperature ferromagnetism in metal-free diamond.
Effects of helium and deuterium on irradiation damage in pure iron
Productions of transmute elements (hydrogen and helium) have great influences on the resistance to irradiation damage in structural materials for fusion reactor. The evolution of irradiation damage in bcc iron is investigated with ion implantation and electron irradiation. Pure iron implanted by He+ or D+ ions at room temperature are aged at 500℃ for 1 h, then irradiated by electrons under high voltage electron microscope. The results show that interstitial loops (i-loop) and vacancy loops (v-loop) are formed in He+-implanted iron and D+-implanted iron respectively. Under electron irradiation, due to the absorption of interstitials atom, i-loop grows up while v-loop shrinks. According to the rate of variation of dislocation loop, v-loop absorbs more interstitial atoms, i.e., the dislocation bias of D+-implanted iron is larger than that of He+-implanted iron, which means that the v-loop has the more contributions to irradiation swelling than i-loop. The causes of the different natures of dislocation loops formed in D+-implanted iron and He+-implanted iron are analyzed by the structures of He-V and D-V complexes.
Effects of the concentration of heavily oxygen vacancy of rutile TiO2 on electric conductivity performance from first principles study
The band structures and the total densities of states of pure and the different concentrations of heavily oxygen vacancy of rutile TiO2-x (x=0, 0.125, 0.25) supercell are studied by using the plane-wave ultrasoft pseudopotential method based on the the density functional theory. Local density approximation +U is used to correct band gaps. The results show that the higher the concentration of heavy oxygen vacancy, the narrower the gap of rutile TiO2 is, the smaller the effective mass of electron is, the lower the electron mobility is, and the lower the electron conductivity is. The calculation results are in agreement with the experimental results.
Effects of intrachain disorder on polaron transport in conjugated polymer
Polaron transport process in conjugated polymer with intrachain disorder is simulated using a nonadiabatic evolution method. The simulations are performed within the framework of an extended version of the Su-Schrieffer-Heeger model modified to include intrachin disorder and an external electric field. It is found that the polaron transport mechanism is determined by both the electric field and the intrachain disorder. The effects of intrachin disorder are negative in most cases, but with the increase of the electric field, the influence of intrachin disorder on polaron transport decreases.
Numerical study of surface plasmon polariton coupling on the metal-insulator hybrid gratings
Surface plasmon polaritons can localize the photons near the metal surface, forming a strong near-field energy density, which affects the efficiency of illumination for molecules and the coefficient of utilization for optical-voltage materials near the metal surface. We analyze the absorption spectrum for the metal-insulator hybrid structure grating and give out the surface plasmon coupling condition according to structure and filling factor. We prove that when filling factor is high enough to form a tiny gap between grating elements, the efficiency for photons to be coupled into surface plasmon polaritons can reach above 94%.
Polarization properties of plasmonic color filters comprised of arrays of subwavelength size holes on Au films
Plasmonic color filters comprised of metal films can be adjusted easily. Periodic arrays of subwavelength size holes with circle, square and rectangular shape are fabricated on 200 nm thick Au films by using focused ion beam. The structures are utilized as plasmonic color filters for exhibiting color variation under the illumination of white light in different polarization directions. We find that for rectangular hole arrays, the color of the transmitted light changes greatly with polarization direction. However, for arrays of circle and square holes, color of the transmitted light is not sensitive to the polarization direction of incident light. We conclude that localized surface plasmon around a single hole is a key factor in influencing the color of transmission light, rather than surface plasmon polaritons induced by periodic arrays. If incident light does not excite the localized surface plasmon around the holes, the effect of surface plasmon polariton will disappear, Based on different display colors of transmitted light of the subwavelength holes with polarization, a composite color display sample is prepared, which will exhibit different color patterns as the polarization direction of incident light changes.
Optical Tamm state theory study on asymmetric DBR-metal-DBR structure
As a special metal surface state, optical Tamm state (OTS) has been widely used in designing the new generation of optical devices for its unique advantages in light control and operation. Based on distribute Bragg reflector (DBR)-metal-DBR (DMD)structure, asymmetric mechanism is introduced by mismatching central frequencies of the two DBRs to design and control the generation of OTS. Through the analysis of reflection spectrum and the electric field distribution characteristics, the interaction and variation rules of OTS on each side of metal are revealed. The results indicate that the DMD structure can support the presence of two OTSs with different intrinsic wavelengths. Besides, the mismatch δ will affect the strengths and intrinsic wavelengths of the two OTSs, i.e., the upper and lower branches of OTS appear with the variation of δ. In addition, polarization state and injection angle of incident light have a considerable influence on the strength and intrinsic wavelength of OTS.
Properties and mechanism analysis of metal/Ge ohmic contact
Large contact resistance due to Fermi level pinning effect at the interface between metal and n-type Ge strongly restricts the performance of Ge device on Si substrate. In this paper, the contacts of metal Al and Ni with n-type Ge and p-type Ge epitaxial layers grown by UHV/CVD are comparatively studied. It is found that the contact of NiGe/n-Ge is better than that of Al/n-Ge at the same dopant concentration. When the concentration of P is 2×1019 cm-3, the ohmic contact of NiGe/n-Ge with ρc down to 1.43×10-5 Ω·cm2 is demomstrated, which is about one order of magnitude lower than that of Al/n-Ge contact. The specific contact resistance of NiGe/p-Ge is 1.68×10-5 Ω·cm2 when the B concentration is 4.2×1018 cm-3, corresponding to that of Al/p-Ge. Compared with Al/n-Ge contact, P segregation at the interface between NiGe and Ge, rather than lowering Schottky barrier height, is the main reseaon for achieving the low specific contact resistance. NiGe/Ge contact should be a good choice for contact electrode for Ge devices at present.
Flat-roof of dynamic equilibrium phenomenon in static negative biase temperature instability effect on power metal-oxide-semiconductor field-effect transistor
The effect of static negative bias temperature instability stress on p-channel power metal-oxide-semiconductor field-effect transistor (MOSFET) is investigated by experiment and simulation. The time evolution of the negative bias temperature instability degradation presents the trend which follows the reaction-diffusion (R-D) theory on the exaggerated time scale. A flat-roof section is observed under the varying stress condition, which can be considered as the dynamic equilibrium phase through the simulation verification based on the R-D model. The analysis of the simulated results also provides the explanation for the difference in the time duration of the dynamic equilibrium phase under the condition of varying stress voltage.
Design and study of the active frequency selective surface based on the complementary screen
Separating the load impedance of the resonant frequency selective surface (FSS) can form the complementary frequency selective surface (CFSS), whose filtering feature is based on the coupling mechanism. The resonance of CFSS can be tuned by controlling the rotation angle α of the element on the capacitive surface. Taking tripole element for example, the frequency response of the CFSS is calculated by using the coupled integral equation method. A 250 mm×250 mm prototype is tested via free space method. Calculation and test results show that the resonance of the CFSS can be tuned actively as the rotation angle α changes. This study provides reference to the active FSS design.
Design and study of the dual-band frequency-selective surface operation at Ku/Ka-band
In order to make the dual-band frequency-selective surface (FSS) used in the engineering conditions of thick substrate, wide band spacing and large incident angle, an FSS structure with dual-band at Ku-band and Ka-band is presented. The stable filtering condition of the FSS is analyzed by using the grating lobe diagram, and the transmission of the FSS with combination or fractal elements is calculated using the vector modal matching method. The design method of the dual-band FSS with thick substrate is obtained by analyzing the resonance mode of the element and the transmission of the FSS. By using those methods, an FSS with combination elements of the square and “Y” loops is designed. The simulated and tested results show that the dual-bands of the structure at Ku-band and Ka-band are stable and the transmissions of the two pass-bands are larger than 75% when the incident angle is varied from normal to 45°. This paper provides some theoretical and experimental references for the design of the dual-band FSS with thick substrate, wide band spacing and large incident angle.
Proximity-effect-induced superconductivity by granular Pb film on the surface of Bi2Te3 topological insulator
The appearance of topological insulators provides us with a chance of finding topological superconductors and Majorana fermions. To pursue these findings one might need to induce large areas of proximity superconductivity on the surface of Bi2Te3 by depositing granular and discrete Pb film. In this experiment, a superconducting state over a distance of 9.5 μrm is observed below 0.25 K on a Bi2Te3 crystal whose surface is deposited with Pb grains with a thickness of less than 20 nm and separated at a distance of 20-30 nm.
Magnetic properties and magnetocaloric effect in Mn42Al50-xFe8+x alloys
The structure, magnetism and magnetocaloric effect in Mn42Al50-xFe8+x are studied in this paper. The Curie temperature (TC) is tunable in a wide temperature range around the ambient temperature by varying the Fe and Al concentration. The values of TC are 270 K, 341 K and 370 K, respectively corresponding to the values of x of 8, 10 and 12. The magnetization has a sharp drop around the respective phase transition temperature and no obvious thermal or magnetic hysteresis is found, suggesting that a typical reversible second order phase transition occurs. The maxima of the magnetic entropy change (ΔSm) under an applied field change of 0-5 T are 2.48 (Mn42Al42Fe16), 2.52 (Mn42Al40Fe18) and 2.40 J·kg-1·K-1 (Mn42Al38Fe20), which are almost independent of composition. The simple and easy preparation process, the good corrosion resistance and ductility, the reversible second order phase transition, and the low cost of raw material make them attractive candidate for the magnetic refrigerant, although their values of ΔSm are not very large compared those that of the rare earth based compounds.
Influences of strain on electronic structure and magnetic properties of CoFe2O4 from first-principles study
Spinel ferrites, such as CoFe2O4, can be used in various fields such as computer technology, aerospace, and medical biotechnology due to their good electromagnetic properties. Although, CoFe2O4 thin films have good application prospects in the magnetoelectric composites, the effects of strain on the electronic structure and magnetic properties of cobalt ferrite film have not been reported. Through the use of two-dimensional strain model closer to the epitaxial growth experiments, the films of Cobalt ferrite are simulated on various substrates with a realistic biaxial strain model by first-principles plane-wave pseudopotential method based on density functional theory, and combined with the generalized gradient approximation in the paper. And the structural stabilities, electronic structures and magnetic properties of CoFe2O4 films are studied. The results show that the inverse spinel is still energetically favored under strain, but the energy difference decreases, thus Fe3+ions in the tetrahedral sites and Co2+ ions in the octahedral sites are easier to exchange their positions. As the strain increases, the band gap of cobalt ferrite becomes narrower, and the magnetic moment of atom in the lattice changes, while the net magnetic moment changes little.
Gaussian type inhomogeneous stress and strain effects on the magnetic properties in ferromagnetic thin films
The effects of Gaussian type inhomogeneous stress and strain on the magnetic properties in ferromagnetic thin films are studied by Monte-Carlo simulation. The results show that the coercive field could be enhanced by the strain parallel to the easy axis and stress perpendicular to the easy axis, on the other hand, it could also be weakened by the stress parallel to the easy axis and strain perpendicular to the easy axis. The coercive field increases (or decreases) in the system, meanwhile, the remanent magnetization and squareness increase (or decrease) as well. More interestingly, the easy axis will rotate within the centralized region under stress parallel to the initial easy axis and strain perpendicular to the initial easy axis. The range of centralized region with easy axis rotation is strongly dependent on the magnitude of stress or strain and the width of its distribution.
First-principles study of Ag-N dual-doped p-type ZnO
The formation energies and ionization energies of Ag-N dual-doped ZnO and interstitial N and H monodoped ZnO:(Ag,N) are investigated from the firstprinciples pseudo-potential approach based on density functional theory. It is found that AgZn-NO accepter pair has lower formation energy and ionization energy than Ag-N related to acceptor clusters, which demonstrates that the p-type conductivity of Ag-N dual-doped ZnO system is mainly attributed to the formation of the accepter pairs. Moreover, when ZnO:(Ag,N) system has additional N atoms in some interstitial sites of ZnO crystal, interstitial N atom and AgZn-NO accepter pair prefer to bind together to form AgZn-(N2)O donor complex which lowers doping efficiency, which is not conducive to p-type conductivity. For H doping in the ZnO:(Ag,N) system, the interstitial H atoms also prefer to bind to the AgZn-NO accepter pair, forming acceptor-donor-acceptor (AgZn-H#em/em#-NO) triplet, which not only enhances the incorporation of acceptors (AgZn-NO) but also gives rise to a shallower acceptor level in the band gap in p-type ZnO crystal. Thus, it is suggested that H-assisted Ag-N codoping is an effective method of p-type doping in ZnO.
Piezoelectric and acoustic behavior of polypropylene piezoelectret films
Piezoelectrets are made from cellular polypropylene(pp)foam sheets by using a pressed-gas expansion followed by corona charging process. The elastic modulus, piezoelectricity and the acoustic response of such fabricated films are investigated. The results show that the Young’s modulus in the thickness direction is more than two orders of magnitude higher than those in the transverse directions. The d33 coefficient remains linear in an applied pressure range from 15 to 35 kPa. As measuring frequency increases from 2 to 300 Hz, d33 coefficient decreases to 81%, which is probably associated with the enhancement of elastic modulus of the film with pressure increasing. In a range from 100 Hz to 100 kHz, the PP piezoelectric films exhibit flat frequency response curves. The open circuit voltage sensitivity and d33 coefficient at 1 kHz are 0.84 mV/Pa and 164 pC/N, respectively.
Nano surface two-dimensional periodic half-round grooves enhanced light absorption in silicon film solar cell
The influence of nano surface two-dimensional periodic half-round grooves on the enhancement of light absorption in silicon film solar cell is studied with the finite-difference time-domain method. The result shows that the broadband solar spectrum absorption is enhanced. The light optical absorption in Si thin-film cell is enhanced by optimizing the thickness of SiO2 anti-reflection film and the radius of half-round grooves, and the total integrated absorption of solar spectrum wavelength in a range from 300 nm to 1000 nm is about 117% greater than that of single silicon thin film.
Dislocation motion during rapid thermal processing of single-crystalline silicon wafers
The fabrication of the antireflective periodic nano-arrary structure on Si surface using nanoimprint lithography and the study on its properties
Analysis on steady plasma process of high-rate microcrystalline silicon by optical emission spectroscopy
Output short-circuit spark discharging energy and output intrinsic safety criterion of Buck converters
Optimal design of high-power microwave source based on particle simulation and genetic algorithms
A construction method of biorthogonal heart sound wavelet
An efficient reconstruction algorithm for flat object based on backprojection filtration method in circular half-cover computed tomography
A pair of high resolution magnetic tweezers with illumination of total reflection evanescent field and its application in the study of DNA helicases
The resolution of conventional magnetic tweezers is limited by the Brown motion of magnetic beads. When the force is lower than ～10 pN, the resolution of magnetic tweezers decreases significantly because of the increased Brown motion. To improve the resolution of magnetic tweezers under low forces, we combine the total internal reflection fluorescence techniques with magnetic tweezers, and design a novel single molecule connection: “magnetic bead-DNA linker-fluorescent bead-single molecule”. With the improved magnetic tweezers, we study the folding dynamics of a DNA hairpin. The results reveal that a nanometer-scale resolution is obtained. By analyzing these results, we calibrate the penetration depth of the total internal reflection field. Finally, we investigate the unwinding dynamics of a BLM helicase core protein. Some preliminary results of the helicase unwinding experiments confirm the practicability of the improved magnetic tweezers in the field of single molecular research.
A detailed study of the effect of Schottky barrier on the dark current density-voltage characteristics of CdS/CdTe solar cells
Performance of polycrystal silicon color solar cells
Modeling and analysis of vehicle behavior at bottlenecks
Advisor-advisee relationship identification based on maximum entropy model
Epidemic spreading on multi-relational networks
The measurement of complex network based on motif
Conformal invariance and conserved quantity of Mei symmetry for Appell equations in holonomic system
Hopf bifurcation and the problem of periodic solutions in a recharge-discharge oscillator model for El Niño and southern oscillation with time delay
Symmetries, reductions and exact solutions of Broer-Kau-Kupershmidt system
Photon squeezing of the Rabi model
Quantum voting protocols based on the non-symmetric quantum channel with controlled quantum operation teleportation
The periodic modulation of a Bose-Fermi mixture in double-well trap
Magnetic charge constrained the mass-radius ratio of neutron star
Dynamics of current controlled quadratic boost converters
Spiral-wave dynamics in an excitable medium with many excitability obstacles
Fault tracking of rotating machinery under variable operation based on phase space warping
Effect of apparatus polarization efficiency on quantification analysis in polarized neutron imaging
Accurate Rutherford backscattering spectrocsopy measurement of aluminium composition in AlxGa1-xN crystal film
Application of mean value theorem of integrals in the efficiency callibration technology of radioactive xeon sample
Interactional potential of helium atom and hydrogen halide molecules
First-principles study on the electronic structure and optical properties of RDX
Spectroscopic properties and molecular constants of the ground and excited states of SF molecule
Infrared absorption spectrum of solid deuterium at near-triple point temperature
Resonance enhanced multiphoton ionization spectra of HCl：analysis of F1Δ2 spectral perturbation
A theoretical study on non-first-order effects of double differential cross sections
A theoretical study on impulse approximation of (e, 2e) reactions
Origin of energetic carbon ions with different charge states in ultrashort laser-thin foil interactions
Effect of laser-induced zinc micro-spheres on enhanced absorption of subsequent pulse laser
Molecular dynamics study of interaction between the H atoms and Si surface
A diagnosis of gas-phase processes in a high pressure DC CH4/H2 plasma
Investigation on the characteristics of dielectric barrier discharge with fairly large volume generated in air at atmospheric pressure
Analysis of modal tomography for three-dimensional wavefront sensing of atmosphere turbulence