Parallel propagating modes and anomalous spatial damping in the ultra-relativistic electron plasma with arbitrary degeneracy
Simple and practical method of characterizing the parametric down-conversion source
Quantum coherence preservation of atom with a classical driving field under non-Markovian environment
Balancing four-state continuous-variable quantum key distribution with linear optics cloning machine
Performance optimization for quantum key distribution in lossy channel using entangled photons
Effect of plasma on combustion characteristics of boron
As it is very difficult to release boron energy completely, kinetic mechanism of boron is not clear, which leads to the lack of theoretical guidance for studying how to accelerate boron combustion. A new semi-empirical boron combustion model is built on the King combustion model, which contains a chemical reaction path; two new methods of plasma-assisted boron combustion based on kinetic and thermal effects respectively are built on the ZDPLASKIN zero-dimensional plasma model. A plasma-supporting system is constructed based on the planar flame, discharge characteristics and the spectral characteristics of plasma and boron combustion are analyzed. The results show that discharge power does not change the sorts of excited-particles, but which can change the concentration of excited-particles. Under this experimental condition, plasma kinetic effect will become the strongest at the discharge power of 40 W; when the discharge power is less than 40 W, plasma mainly has kinetic effect, otherwise plasma has thermal effect. Numerical simulation result based on plasma kinetic effect is consistent with the experimental result at the discharge power of 40 W, and boron ignition delay time is shortened by 53.8% at the discharge power of 40 W, which indicates that plasma accelerates boron combustion has reaction kinetic paths, while the ability to accelerate boron combustion based on thermal effect is limited.
Multi-scroll hidden attractors and multi-wing hidden attractors in a 5-dimensional memristive system
Free-matrix-based time-dependent discontinuous Lyapunov functional for synchronization of delayed neural networks with sampled-data control
Nonlinear density wave and energy consumption investigation of traffic flow on a curved road
Empirical topological investigation of practical supply chains based on complex networks
The industrial supply chain networks basically capture the circulation of social resource, dominating the stability and efficiency of the industrial system. In this paper, we provide an empirical study of the topology of smartphone supply chain network. The supply chain network is constructed using open online data. Our experimental results show that the smartphone supply chain network has small-world feature with scale-free degree distribution, in which a few high degree nodes play a key role in the function and can effectively reduce the communication cost. We also detect the community structure to find the basic functional unit. It shows that information communication between nodes is crucial to improve the resource utilization. We should pay attention to the global resource configuration for such electronic production management.
Rubidium-beam microwave clock pumped by distributed feedback diode lasers
A rubidium-beam microwave clock, optically pumped by a distributed feedback diode laser, is experimentally investigated. The clock is composed of a physical package, optical systems, and electric servo loops. The physical package realizes the microwave interrogation of a rubidium-atomic beam. The optical systems, equipped with two 780-nm distributed feedback laser diodes, yield light for pumping and detecting. The servo loops control the frequency of a local oscillator with respect to the microwave spectrum. With the experimental systems, the microwave spectrum, which has an amplitude of 4 nA and a line width of 700 Hz, is obtained. Preliminary tests show that the clock short-term frequency stability is 7×10-11 at 1 s, and 3×10-12 at 1000 s. These experimental results demonstrate the feasibility of the scheme for a manufactured clock.
Helium nano-bubble bursting near the nickel surface
We have investigated the expansion and bursting of a helium nano-bubble near the surface of a nickel matrix using a molecular dynamics simulation. The helium atoms erupt from the bubble in an instantaneous and volcano-like process, which leads to surface deformation consisting of cavity formation on the surface, along with modification and atomic rearrangement at the periphery of the cavity. During the kinetic releasing process, the channel may undergo the “open” and “close” states more than once due to the variation of the stress inside the nano-bubble. The ratio between the number of helium atoms and one of vacancies can directly reflect the releasing rate under different temperatures and crystallographic orientation conditions, respectively. Moreover, a special relationship between the stress and He-to-vacancy ratio is also determined. This model is tested to compare with the experimental result from Hastelloy N alloys implanted by helium ions and satisfactory agreement is obtained.
Combination of multiple tools for surface manipulation of polar molecules
Deterministic loading of an individual atom:Towards scalable implementation of multi-qubit
Tuning the velocity and flux of a low-velocity intense source of cold atomic beam
Velocity-selective spectroscopy measurements of Rydberg fine structure states in a hot vapor cell
A velocity-selective spectroscopy technique for studying the spectra of Rydberg gases is presented. This method provides high-resolution spectrum measurements. We present experimental results for a ladder system 6S1/2→6P3/2→nS(D) electromagnetically-induced transparency involving highly-excited Rydberg states. Based on a radio-frequency modulation technique, we measure the hyperfine structure splitting of intermediate states and the fine structure splitting of Rydberg states in a room temperature 133Cs vapor cell. The experimental data and theoretical predictions show excellent agreement.
Nano-infrared imaging of localized plasmons in graphene nano-resonators
We conduct in-situ near-field imaging of propagating and localized plasmons (cavity and dipole modes) in graphene nano-resonator. Compared with propagating graphene plasmons, the localized modes show twofold near-field amplitude and high volume confining ability (~106). The cavity resonance and dipole mode of graphene plasmons can be effectively controlled through optical method. Furthermore, our numerical simulation shows quantitative agreement with experimental measurements. The results provide insights into the nature of localized graphene plasmons and demonstrate a new way to study the localization of polaritons in Van der Waals materials.
Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis
An electrically tunable metasurface integrated with graphene for mid-infrared light modulation
We propose a low-cost plasmonic metasurface integrated with single-layer graphene for dynamic modulation of mid-infrared light. The plasmonic metasurface is composed of an array of split magnetic resonators (MRs) where a nano slit is included. Extraordinary optical transmission (EOT) through the deep subwavelength slit is observed by excitation of magnetic plasmons in the split MRs. Furthermore, the introduction of the slit provides strongly enhanced fields around the graphene layer, leading to a large tuning effect on the EOT by changing the Fermi energy of the graphene. The proposed metasurface can be utilized as an optical modulator with a broad modulation width (15 μm) or an optical switch with a high on/off ratio (>100). Meanwhile, the overall thickness of the metasurface is 430 nm, which is tens of times smaller than the operating wavelength. This work may have potential applications in mid-infrared optoelectrical devices and give insights into reconfigurable flat optics and optoelectronics.
Ultra-broadband and polarization-independent planar absorber based on multilayered graphene
Tunable coupling of a hybrid plasmonic waveguide consisting of two identical dielectric cylinders and a silver film
Characteristics of photonic nanojets from two-layer dielectric hemisphere
The properties of the photonic nanojet generated by a two-layer dielectric microsphere are studied. Simulation results indicate that this novel structure can generate a photonic nanojet outside its volume when the refractive index contrast relative to the background medium is higher than 2:1 in the condition of plane wave incidence. When the refractive index is smaller than 2, we show that an ultralong nanojet generated by the two-layer hemisphere has an extension of 28.2 wavelengths, and compared with the homogeneous dielectric hemisphere, it has superior performance in jet length and focal distance. Its dependence on the configuration and refractive index is investigated numerically. According to the simulation of the two-layer dielectric microsphere, a photonic nanojet with a full width at half maximum (FWHM) less than 1/2 wavelength is obtained and the tunable behaviors of the photonic nanojet are demonstrated by changing the reflective indices of the material or radius contrast ratio.
Quantum statistical properties of photon-added spin coherent states
Different influences of u-InGaN upper waveguide on the performance of GaN-based blue and green laser diodes
Performances of blue and green laser diodes (LDs) with different u-InGaN upper waveguides (UWGs) are investigated theoretically by using LASTIP. It is found that the slope efficiency (SE) of blue LD decreases due to great optical loss when the indium content of u-InGaN UWG is more than 0.02, although its leakage current decreases obviously. Meanwhile the SE of the green LD increases when the indium content of u-InGaN UWG is varied from 0 to 0.05, which is attributed to the reduction of leakage current and the small increase of optical loss. Therefore, a new blue LD structure with In0.05Ga0.95N lower waveguide (LWG) is designed to reduce the optical loss, and its slope efficiency is improved significantly.
Low-repetition-rate, all-polarization-maintaining Yb-doped fiber laser mode-locked by a semiconductor saturable absorber
2-μm mode-locked nanosecond fiber laser based on MoS2 saturable absorber
Two-color laser wavelength effect on intense terahertz generation in air
A new method of calculating the orbital angular momentum spectra of Laguerre-Gaussian beams in channels with atmospheric turbulence
Intensities and spectral features of the 4I13/2-4I15/2 potential laser transition of Er3+ centers in CaF2-CeF3 disordered crystal
Photonic crystal fiber polarization filter with two large apertures coated with gold layers
Angular-modulated spatial distribution of ultrahigh-order modes assisted by random scattering
Gamma-radiation effects in pure-silica-core photonic crystal fiber
We investigated the steady state gamma-ray radiation response of pure-silica-core photonic crystal fibers (PSC-PCFs) under an accumulated dose of 500 Gy and a dose rate of 2.38 Gy/min. The radiation-induced attenuation (RIA) spectra in the near-infrared region from 800 nm to 1700 nm were obtained. We find that the RIA at 1550 nm is related with hydroxyl (OH-) absorption defects in addition to the identified self-trapped hole (STH) defects. Moreover, it is proposed and demonstrated that reduced OH- absorption defects can decrease the RIA at 1550 nm. The RIA at 1550 nm has effectively declined from 27.7 dB/km to 3.0 dB/km through fabrication improvement. Preliminary explanations based on the unique fabrication processes were given to interpret the RIA characteristics of PSC-PCFs. The results show that the PSC-PCFs, which offer great advantages over conventional fibers, are promising and applicable to fiber sensors in harsh environments.
Analysis of proton and γ-ray radiation effects on CMOS active pixel sensors
Radiation effects on complementary metal-oxide-semiconductor (CMOS) active pixel sensors (APS) induced by proton and γ-ray are presented. The samples are manufactured with the standards of 0.35 μm CMOS technology. Two samples have been irradiated un-biased by 23 MeV protons with fluences of 1.43×1011 protons/cm2 and 2.14×1011 protons/cm2, respectively, while another sample has been exposed un-biased to 65 krad(Si) 60Co γ-ray. The influences of radiation on the dark current, fixed-pattern noise under illumination, quantum efficiency, and conversion gain of the samples are investigated. The dark current, which increases drastically, is obtained by the theory based on thermal generation and the trap induced upon the irradiation. Both γ-ray and proton irradiation increase the non-uniformity of the signal, but the non-uniformity induced by protons is even worse. The degradation mechanisms of CMOS APS image sensors are analyzed, especially for the interaction induced by proton displacement damage and total ion dose (TID) damage.
Three-dimensional parabolic equation model for seismo-acoustic propagation:Theoretical development and preliminary numerical implementation
A three-dimensional (3D) parabolic equation (PE) model for sound propagation in a seismo-acoustic waveguide is developed in Cartesian coordinates, with x, y, and z representing the marching direction, the longitudinal direction, and the depth direction, respectively. Two sets of 3D PEs for horizontally homogenous media are derived by rewriting the 3D elastic motion equations and simultaneously choosing proper dependent variables. The numerical scheme is for now restricted to the y-independent bathymetry. Accuracy of the numerical scheme is validated, and its azimuthal limitation is analyzed. In addition, effects of horizontal refraction in a wedge-shaped waveguide and another waveguide with a polyline bottom are illustrated. Great efforts should be made in future to provide this model with the ability to handle arbitrarily irregular fluid-elastic interfaces.
Theoretical analysis of interaction between a particle and an oscillating bubble driven by ultrasound waves in liquid
A theoretical model is developed to describe the interaction of a particle and an oscillating bubble at arbitrary separation between them. The derivation of the model is based on the multipole expansion of the particle and bubble velocity potentials and the use of Lagrangian mechanics. The model consists of three coupled ordinary differential equations. One of them accounts for the pulsation of the bubble and the other two describe the translation of the bubble and particle in an infinite, incompressible liquid. The model here is accurate to order 1/d10, where d is the distance between the centers of the particle and bubble. The effects of the size and density of the particle are investigated, namely, the interaction between the particle and bubble changes from repulsion to attraction with the increment of the particle density, and the increment of the particle size makes the interaction between the particle and bubble stronger. It is demonstrated that the driving frequency and acoustic pressure amplitude can affect the interaction of the particle and bubble. It is shown that the correct modeling of the translational dynamics of the bubble and particle at small separation distances requires terms accurate up to the tenth order.
Broadband acoustic focusing by symmetric Airy beams with phased arrays comprised of different numbers of cavity structures
We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays, in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth (about 1.4 kHz), high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.
Modified Maxwell model for predicting thermal conductivity of nanocomposites considering aggregation
Establishment of infinite dimensional Hamiltonian system of multilayer quasi-geostrophic flow & study on its linear stability
Aerodynamic measurement of a large aircraft modelin hypersonic flow
Instabilities of thermocapillary-buoyancy convection in open rectangular liquid layers
This article presents the experimental investigation on instabilities of thermocapillary-buoyancy convection in the transition process in an open rectangular liquid layer subject to a horizontal temperature gradient. In the experimental run, an infrared thermal imaging system was constructed to observe and record the surface wave of the rectangular liquid layer. It was found that there are distinct convection longitudinal rolls in the flow field in the thermocapillary-buoyancy convection transition process. There are different wave characterizations for liquid layers with different thicknesses. For sufficiently thin layers, oblique hydrothermal waves are observed, which was predicted by the linear-stability analysis of Smith & Davis in 1983. For thicker layers, the surface flow is distinct and intensified, which is because the buoyancy convection plays a dominant role and bulk fluid flow from hot wall to cold wall in the free surface of liquid layers. In addition, the spatiotemporal evolution analysis has been carried out to conclude the rule of the temperature field destabilization in the transition process.
Review on second-harmonic generation of ultrasonic guided waves in solid media (I):Theoretical analyses
Considering the high sensitivity of the nonlinear ultrasonic measurement technique and great advantages of the guided wave testing method, the use of nonlinear ultrasonic guided waves provides a promising means for evaluating and characterizing the hidden and/or inaccessible damage/degradation in solid media. Increasing attention on the development of the testing method based on nonlinear ultrasonic guided waves is largely attributed to the theoretical advances of nonlinear guided waves propagation in solid media. One of the typical acoustic nonlinear responses is the generation of second harmonics that can be used to effectively evaluate damage/degradation in materials/structures. In this paper, the theoretical progress of second-harmonic generation (SHG) of ultrasonic guided wave propagation in solid media is reviewed. The advances and developments of theoretical investigations on the effect of SHG of ultrasonic guided wave propagation in different structures are addressed. Some obscure understandings and the ideas in dispute are also discussed.
Effect of aperture field distribution on the maximum radiated power at atmospheric pressure
Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure
Tunneling dynamics of a few bosons with both two-and three-body interactions in a double-well potential
We investigate the tunneling dynamics of a few bosons with both two-and three-body interactions in a double-well potential. Uncorrelated tunneling of Rabi oscillation with the minimum period can happen only when the two-and three-body interactions satisfy a critical condition, i.e., the effective interaction energy is minimized. When the atomic interactions are slightly away from the critical condition in the weak interaction regime, the uncorrelated tunneling exhibits collapse-revival character. When the atomic interactions are strong and far away from the critical condition, the correlated tunneling with Rabi oscillation occurs. The tunneling period (the period of collapse-revival) increases (decreases) when the rate between the two-body and three-body interactions is away from the corresponding critical condition or when the number of bosons increases. Further, the tunneling properties are understood with the help of the energy spectrum of the system. Eventually, the effect of the initial configuration on the tunneling dynamics of a few bosons for both odd and even numbers of bosons is studied, which results in intriguing consequences.
Toroidal rotation induced by 4.6 GHz lower hybrid current drive on EAST tokamak
Using a tangentially viewing x-ray imaging crystal spectrometer, substantial co-current rotation driven by lower hybrid current drive (LHCD) at 4.6 GHz is observed on EAST tokamak. This study presents plasma rotation behaviors with 4.6 GHz LHCD injection. Typically, the 10-20 km/s co-current rotation change and the transport of rotation velocity from edge to core are observed. The relationship between plasma parameters and rotation is also investigated, indicating that rotation decreases with increasing internal inductance (li) and increases with increasing safety factor (q0). Hysteresis between rotation and Te plasma stored energy is observed, suggesting different response times between the electron heating and rotation acceleration by LHCD. A comparison between the rotations driven by 4.6 G LHCD and 2.45 G LHCD on EAST is also presented, in which higher frequency LHCD could induce more rotation changes.
Acceleration and radiation of externally injected electrons in laser plasma wakefield driven by a Laguerre-Gaussian pulse
Measurement of iron characteristics under ramp compression
Novel conductance step in carbon nanotube with wing-like zigzag graphene nanoribbons
Slip on the surface of silicon wafers under laser irradiation:Scale effect
Ab-initio investigation of AGeO3 (A=Ca, Sr) compounds via Tran–Blaha-modified Becke–Johnson exchange potential
Ce–Co-doped BiFeO3 multiferroic for optoelectronic and photovoltaic applications
Exploring the compression behavior of HP-BiNbO4 under high pressure
First-principles calculations of structural and thermodynamic properties of β-PbO
High-temperature thermodynamics of silver:Semi-empirical approach
Thermal transport in twisted few-layer graphene
Twisted graphene possesses unique electronic properties and applications, which have been studied extensively. Recently, the phonon properties of twisted graphene have received a great deal of attention. To the best of our knowledge, thermal transports in twisted graphene have been investigated little to date. Here, we study perpendicular and parallel transports in twisted few-layer graphene (T-FLG). It is found that perpendicular and parallel transports are both sensitive to the rotation angle θ between layers. When θ increases from 0° to 60°, perpendicular thermal conductivity κ⊥ first decreases and then increases, and the transition angle is θ=30°. For the parallel transport, the relation between thermal conductivity κ|| and θ is complicated, because intra-layer thermal transport is more sensitive to the edge of layer than their stacking forms. However, the dependence of interlayer scattering on θ is similar to that of κ⊥. In addition, the effect of layer number on the thermal transport is discussed. Our results may provide references for designing the devices of thermal insulation and thermal management based on graphene.
Temperature-induced effect on refractive index of graphene based on coated in-fiber Mach-Zehnder interferometer
Structural characterization of indium-rich nanoprecipitate in InGaN V-pits formed by annealing
InGaN layers capped with GaN were annealed at 550℃ for 1 hour. During annealing, cracks appeared and dissolved InGaN penetrated through the microcracks into the V-pits to form indium-rich nanoprecipitates. Some precipitates, in-situ annealed under nitrogen ion irradiation by MBE, were confirmed to be cubic GaN on the tops of precipitates, formed by nitriding the pre-existing Ga droplets under nitrogen ions irradiation.
Formation of high-Sn content polycrystalline GeSn films by pulsed laser annealing on co-sputtered amorphous GeSn on Ge substrate
Polycrystalline Ge1-xSnx (poly-Ge1-xSnx) alloy thin films with high Sn content (> 10%) were fabricated by co-sputtering amorphous GeSn (a-GeSn) on Ge (100) wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm2 to 550 mJ/cm2. High quality poly-crystal Ge0.90Sn0.10 and Ge0.82Sn0.18 films with average grain sizes of 94 nm and 54 nm were obtained, respectively. Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn. The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers. The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution, strain, and disorder. The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum (FWHM) is well quantified by a linear relationship, which provides an effective method to evaluate the quality of poly-Ge1-xSnx by Raman spectra.
Improvement of sensitivity of graphene photodetectorby creating bandgap structure
Graphene has aroused large interest in optoelectronic applications because of its broad band absorption and ultrahigh electron mobility. However, the low absorption of 2.3% seriously limits its photoresponsivity and restricts the relevant applications. In this paper, a method to enhance the sensitivity of graphene photodetector is demonstrated by introducing electron trapping centers and creating a bandgap structure in graphene. The carrier lifetime obviously increases, and more carriers are collected by the electrodes. Compared with intrinsic graphene detector, the defective graphene photodetector possesses high photocurrent and low-driving-voltage, which gives rise to great potential applications in photodetector area.
Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye
Uncertainties of clock and shift operators for an electron in one-dimensional nonuniform lattice systems
Biaxial strain-induced enhancement in the thermoelectric performance of monolayer WSe2
The effects of biaxial strain on the electronic structure and thermoelectric properties of monolayer WSe2 have been investigated by using first-principles calculations and the semi-classical Boltzmann transport theory. The electronic band gap decreases under strain, and the band structure near the Fermi level of monolayer WSe2 is modified by the applied biaxial strain. Furthermore, the doping dependence of the thermoelectric properties of n-and p-doped monolayer WSe2 under biaxial strain is estimated. The obtained results show that the power factor of n-doped monolayer WSe2 can be increased by compressive strain while that of p-doping can be increased with tensile strain. Strain engineering thus provides a direct method to control the electronic and thermoelectric properties in these two-dimensional transition metal dichalcogenides materials.
Spin transport in a chain of polygonal quantum rings with Dresselhaus spin-orbit coupling
Band structure and edge states of star-like zigzag graphene nanoribbons
Photon-assisted electronic and spin transport through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm interferometer
We investigate the time-modulated electronic and spin transport properties through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm (A-B) interferometer. By using the Keldysh non-equilibrium Green's function technique, the photon-assisted spin-dependent average current is analyzed. The T-shaped three-quantum-dot molecule A-B interferometer exhibits excellent controllability in the average current resonance spectra by adjusting the interdot coupling strength, Rashba spin-orbit coupling strength, magnetic flux, and amplitude of the time-dependent external field. Efficient spin filtering and multiple electron-photon pump functions are exploited in the multi-quantum-dot molecule A-B interferometer by a time-modulated external field.
Fluctuating specific heat in two-band superconductors Hot!
Theory of thermal fluctuations in two-band superconductors under an essentially homogeneous magnetic field is developed within the framework of the two-band Ginzburg-Landau theory. The fluctuating specific heat is calculated by using the optimized self-consistent perturbation approach and the results are applied to analyze the thermodynamic data of the iron-based superconductors Ba1-xKxFe2As2 with x~0.4, which have been suggested to have a two-band structure by recent experiments. We estimate the fluctuation strength in this material and find that the specific heat is described well with the Ginzburg number Gi=4·10-4. The influence of interband coupling strength is investigated and the result of the two-band Gaussian approximation approach is compared.
Observation of giant magnetocaloric effect under low magnetic fields in EuTi1-xCoxO3
Effects of dipolar interactions on magnetic properties of Co nanowire arrays
On the parameters for electrocaloric effect predicted by indirect method
Resonant magneto-optical Kerr effect induced by hybrid plasma modes in ferromagnetic nanovoids
The p-type ZnO thin films obtained by a reversed substitution doping method of thermal oxidation of Zn3N2 precursors
P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device applications. In this paper, we introduce an alternative route to stabilizing N in the oxidation process, the thermal stability of p-ZnO is significantly improved. Finally, we discuss the limitations of the alternative doping method and provide some prospective outlook of the method.
One-dimensional ZnO nanostructure-based optoelectronics
Semiconductor nanowires, with their unique capability to bridge the nanoscopic and macroscopic worlds, have been demonstrated to have potential applications in energy conversion, electronics, optoelectronics, and biosensing devices. One-dimensional (1D) ZnO nanostructures, with coupled semiconducting and piezoelectric properties, have been extensively investigated and widely used to fabricate nanoscale optoelectronic devices. In this article, we review recent developments in 1D ZnO nanostructure based photodetectors and device performance enhancement by strain engineering piezoelectric polarization and interface modulation. The emphasis is on a fundamental understanding of electrical and optical phenomena, interfacial and contact behaviors, and device characteristics. Finally, the prospects of 1D ZnO nanostructure devices and new challenges are proposed.
Anisotropic nanocomposite soft/hard multilayer magnets
Experimental and theoretical researches on nanostructured exchange coupled magnets have been carried out since about 1988.Here,we review the structure and magnetic properties of the anisotropic nanocomposite soft/hard multilayer magnets including some new results and phenomena from an experimental point of view.According to the different component of the oriented hard phase in the nanocomposite soft/hard multilayer magnets,three types of magnets will be discussed:1) anisotropic Nd2Fe14B based nanocomposite multilayer magnets,2) anisotropic SmCo5 based nanocomposite multilayer magnets,and 3) anisotropic rare-earth free based nanocomposite multilayer magnets.For each of them,the formation of the oriented hard phase,exchange coupling,coercivity mechanism,and magnetic properties of the corresponding anisotropic nanocomposite multilayer magnets are briefly reviewed,and then the prospect of realization of bulk magnets on new results of anisotropic nanocomposite multilayer magnets will be carried out.
Effects of Al particles and thin layer on thermal expansion and conductivity of Al-Y2Mo3O12 cermets
An easy way to controllably synthesize one-dimensional SmB6 topological insulator nanostructures and exploration of their field emission applications Hot!
A convenient fabrication technique for samarium hexaboride (SmB6) nanostructures (nanowires and nanopencils) is developed, combining magnetron-sputtering and chemical vapor deposition. Both nanostructures are proven to be single crystals with cubic structure, and they both grow along the direction. Formation of both nanostructures is attributed to the vapor-liquid-solid (VLS) mechanism, and the content of boron vapor is proposed to be the reason for their different morphologies at various evaporation distances. Field emission (FE) measurements show that the maximum current density of both the as-grown nanowires and nanopencils can be several hundred μA/cm2, and their FN plots deviate only slightly from a straight line. Moreover, we prefer the generalized Schottky-Nordheim (SN) model to comprehend the difference in FE properties between the nanowires and nanopencils. The results reveal that the nonlinearity of FN plots is attributable to the effect of image potential on the FE process, which is almost independent of the morphology of the nanostructures. All the research results suggest that the SmB6 nanostructures would have a more promising future in the FE area if their surface oxide layer was eliminated in advance.
Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching Hot!
Polished fused silica samples were etched for different durations by using hydrofluoric (HF) acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared (IR) spectrometer, respectively. The laser induced damage thresholds (LIDTs) of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.
Sampled-data modeling and dynamical effect of output-capacitor time-constant for valley voltage-mode controlled ewline buck-boost converter
By analyzing the output voltage ripple of a buck-boost converter with large equivalent series resistance (ESR) of output capacitor, one valley voltage-mode controller for buck-boost converter is proposed. Considering the fact that the increasing and decreasing slopes of the inductor current are assumed to be constant during each switching cycle, an especial sampled-data model of valley voltage-mode controlled buck-boost converter is established. Based on this model, the dynamical effect of an output-capacitor time-constant on the valley voltage-mode controlled buck-boost converter is revealed and analyzed via the bifurcation diagrams, the movements of eigenvalues, the Lyapunov exponent spectra, the boundary equations, and the operating-state regions. It is found that with gradual reduction of output-capacitor time-constant, the buck-boost converter in continuous conduction mode (CCM) shows the evolutive dynamic behavior from period-1 to period-2, period-4, period-8, chaos, and invalid state. The stability boundary and the invalidated boundary are derived theoretically by stability analysis, where the stable state of valley voltage-mode controlled buck-boost converter can enter into an unstable state, and the converter can shift from the operation region to a forbidden region. These results verified by time-domain waveforms and phase portraits of both simulation and experiment indicate that the sampled-data model is correct and the time constant of the output capacitor is a critical factor for valley voltage-mode controlled buck-boost converter, which has a significant effect on the dynamics as well as control stability.
A phenomenological memristor model for synaptic memory and learning behaviors
An improved memristor model for brain-inspired computing
Luminescent properties of thermally activated delayed fluorescence molecule with intramolecular π-π interaction betweendonor and acceptor
Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence (TADF) molecule (3, 5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-phenyl)(pyridin-4-yl) methanone (DTCBPY) is theoretically studied by using the density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Four conformations (named as A, B, C, and D) of the DTCBPY can be found by relax scanning, and the configuration C corresponds to the luminescent molecule detected experimentally. Besides, we calculate the proportion of each conformation by Boltzmann distribution, high configuration ratios (44% and 52%) can be found for C and D. Moreover, C and D are found to exist with an intramolecular π-π interaction between one donor and the acceptor; the intramolecular interaction brings a smaller Huang-Rhys factor and reduced reorganization energy. Our work presents a rational explanation for the experimental results and demonstrates the importance of the intramolecular π-π interaction to the photophysical properties of TADF molecules.
Improved simultaneous multislice magnetic resonance imaging using total variation regularization
Wavelet optimization for applying continuous wavelet transform to maternal electrocardiogram component enhancing
In the procedure of non-invasive fetal electrocardiogram (ECG) extraction, high-quality maternal R wave peak detection demands enhancing the maternal ECG component firstly. Among all the enhancing algorithms, the one based on the continuous wavelet transform (CWT) is very important and its effectiveness depends on the optimization of the used wavelet. However, up to now, there is still no clear conclusion on the optimal wavelet (including type and scale) for CWT to enhance the maternal ECG component of an abdominal ECG signal. To solve this problem, in this paper, we select several common used types of wavelets to carry out our research on what the optimal wavelets are. We first establish big-enough training datasets with different sampling rates and make a maternal QRS template for each signal in the training datasets. Second, for each type of selected wavelets, we find its optimal scale corresponding to each QRS template in a training dataset based on the principle of maximal correlation. Then calculating the average of all optimized wavelet scales results in the mean optimal wavelet of this type for the dataset. We use two original abdominal ECG databases to train and test the optimized mean optimal wavelets. The test results show that, as a whole, the mean optimal wavelets obtained are superior to the wavelets used in other publications for applying CWT to maternal ECG component enhancing.
Image of local energy anomaly during a heavy rainfall event