Improved control of distributed parameter systems using wireless sensor and actuator networks: An observer-based method
Carlson iterating rational approximation and performance analysis of fractional operator with arbitrary order
Consensus of multiple autonomous underwater vehicles with double independent Markovian switching topologies and timevarying delays
Physical interpretation of Planck's constant based on the Maxwell theory
The discovery of the Planck relation is generally regarded as the starting point of quantum physics. Planck's constant h is now regarded as one of the most important universal constants. The physical nature of h, however, has not been well understood. It was originally suggested as a fitting constant to explain the black-body radiation. Although Planck had proposed a theoretical justification of h, he was never satisfied with that. To solve this outstanding problem, we use the Maxwell theory to directly calculate the energy and momentum of a radiation wave packet. We find that the energy of the wave packet is indeed proportional to its oscillation frequency. This allows us to derive the value of Planck's constant. Furthermore, we show that the emission and transmission of a photon follows the all-or-none principle. The “strength” of the wave packet can be characterized by ζ, which represents the integrated strength of the vector potential along a transverse axis. We reason that ζ should have a fixed cut-off value for all photons. Our results suggest that a wave packet can behave like a particle. This offers a simple explanation to the recent satellite observations that the cosmic microwave background follows closely the black-body radiation as predicted by Planck's law.
Experimentally testing Hardy's theorem on nonlocality with entangled mixed states
Hardy's theorem on nonlocality has been verified by a series of experiments with two-qubit entangled pure states. However, in this paper we demonstrate the experimental test of the theorem by using the two-photon entangled mixed states. We first investigate the generic logic in Hardy's proof of nonlocality, which can be applied for arbitrary two-qubit mixed polarization entangled states and can be reduced naturally to the well-known logic tested successfully by the previous pure state experiments. Then, the optimized violations of locality for various experimental parameters are delivered by the numerical method. Finally, the logic argued above for testing Hardy's theorem on nonlocality is demonstrated experimentally by using the mixed entangled-photon pairs generated via pumping two type-I BBO crystals. Our experimental results shows that Hardy's proof of nonlocality can also be verified with two-qubit polarization entangled mixed states, with a violation of about 3.4 standard deviations.
Spherical reconciliation for a continuous-variable quantum key distribution
Bidirectional multi-qubit quantum teleportation in noisy channel aided with weak measurement
Correction of cosine oscillation to the improved correlation method of estimating the amplitude of gravitational background signal
In the measurement of G with the angular acceleration method, the improved correlation method developed by Wu et al. (Wu W H, Tian Y, Luo J, Shao C G, Xu J H and Wang D H 2016 Rev. Sci. Instrum. 87 094501) is used to accurately estimate the amplitudes of the prominent harmonic components of the gravitational background signal with time-varying frequency. Except the quadratic slow drift, the angular frequency of the gravitational background signal also includes a cosine oscillation coming from the useful angular acceleration signal, which leads to a deviation from the estimated amplitude. We calculate the correction of the cosine oscillation to the amplitude estimation. The result shows that the corrections of the cosine oscillation to the amplitudes of the fundamental frequency and second harmonic components obtained by the improved correlation method are within respective errors.
Fiber-based multiple access timing signal synchronization technique
Noise analysis of grating-based x-ray differential phase-contrast imaging with angular signal radiography
X-ray phase-contrast imaging is one of the novel techniques, and has potential to enhance image quality and provide the details of inner structures nondestructively. In this work, we investigate quantitatively signal-to-noise ratio (SNR) of grating-based x-ray phase contrast imaging (GBPCI) system by employing angular signal radiography (ASR). Moreover, photon statistics and mechanical error that is a major source of noise are investigated in detail. Results show the dependence of SNR on the system parameters and the effects on the extracted absorption, refraction and scattering images. Our conclusions can be used to optimize the system design for upcoming practical applications in the areas such as material science and biomedical imaging.
Modeling and analysis for the image mapping spectrometer
Continuous variable quantum key distribution
Quantum key distribution enables unconditionally secure key distribution between two legitimate users. The information-theoretic security is guaranteed by the fundamental laws of quantum physics. Initially, the quantum key distribution protocol was proposed based on the qubits. Later on, it was found that quantum continuous variables can also be exploited for this target. The continuous variable quantum key distribution can build upon standard telecommunication technology and exhibits a higher secret key rate per pulse at a relatively short distance due to the possibility of encoding more than 1 bit per pulse. In this article, we review the current status of the continuous variable quantum key distribution research, including its basic principle, experimental implementations, security and future directions; the experimental progress in this field made by our group is also presented.
Semiclassical investigation of Coulomb focusing effects in atomic above-threshold ionization with elliptically polarized laser fields
We investigate atomic above-threshold ionization in elliptically polarized strong laser fields with a semiclassical approach. With increasing laser intensity, the Coulomb focusing (CF) effects are found to become stronger in both parallel and perpendicular directions with respect to the polarization plane. The dependence of CF effects on tunnel exit, initial transverse momentum distribution and laser electric field is analyzed. It was revealed that the effects of tunnel exit are most prominent with variation of the laser intensity, and the other two factors both play non-negligible roles. Our results provide a deeper insight to the recent experiments of Coulomb asymmetry [Shafir D, et al., 2013 Phys. Rev. Lett. 111 023005 and Li M, et al., 2013 Phys. Rev. Lett. 111 023006].
The effect of field modulation on the vibrational population of the photoassociated NaK and its dynamics
This paper presents calculation results for the photoassociation of a NaK molecule with a two-color modulated laser and gives a detailed analysis about them. For the two-step photoassociation process in intense fields, the effect of two-color modulated laser parameters, such as relative phase, envelope period, and laser intensity, on the population of the molecular electronic state can be obtained by solving the time-dependent Schrödinger equation through the quantum wave packet method. The numerical simulation shows not only that the influence of laser parameters on the vibrational distribution presents some regularity, but also that a higher population in the ground electronic state can be realized through adjusting these laser parameters.
Off-site trimer superfluid on a one-dimensional optical lattice
Common-mode noise rejection using fringe-locking method in WEP test by simultaneous dual-species atom interferometers
Computational and experimental verification of a wide-angle metamaterial absorber
Compressing ultrafast electron pulse by radio frequency cavity
Investigation of three-pulse photon echo in thick crystal using finite-difference time-domain method
Tunable second harmonic generation from a Kerr-lens mode-locked Yb: YCa4O(BO3)3 femtosecond laser Hot!
We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond (fs) laser with a self-frequency doubling Yb:YCa4O(BO3)3 crystal. Sub-40 fs laser pulses were directly generated from the oscillator without extracavity compression. The central wavelength was tunable from 1039 nm to 1049 nm with a typical bandwidth of 35 nm and an average output power of 53 mW. For the first time, a self-frequency doubled second harmonic green laser with tunable range from 519 nm to 525 nm was observed.
1.5-MHz repetition rate passively Q-switched Nd: YVO4 laser based on WS2 saturable absorber
Autler-Townes spectroscopy of high-lying state by phase conjugate six-wave mixing
An Autler-Townes (AT) spectroscopy based on phase conjugate six-wave mixing (SWM) is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system. It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors. We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that, due the atomic motion, the atomic polarizations acquire different phases for atoms with different velocities as time evolves. The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.
Optical nonlinearities of tetracarbonyl-chromium triphenyl phosphine complex
Laser phase effect on asymmetric harmonic distribution in H2+
Optical properties of Mg2+, Yb3+, and Ho3+ tri-doped LiNbO3 crystals
Numerical study on characteristic of two-dimensional metal/dielectric photonic crystals
DEM simulation of granular segregation in two-compartment system under zero gravity Hot!
In this paper, granular segregation in a two-compartment cell in zero gravity is studied numerically by DEM simulation. In the simulation using a virtual window method we find a non-monotonic flux, a function which governs the segregation. A parameter is used to quantify the segregation. The effect of three parameters: the total number of particles N, the excitation strength Γ, and the position of the window coupling the two compartments, on the segregation and the waiting time τ are investigated. It is found that the segregation observed in zero gravity exists and does not depend on the excitation strength Γ. The waiting time τ, however, depends strongly on Γ: the higher the Γ, the lower the waiting time τ. The simulation results are important in guiding the SJ-10 satellite microgravity experiments.
The interaction between a screw dislocation and a wedge-shaped crack in one-dimensional hexagonal piezoelectric quasicrystals
Based on the fundamental equations of piezoelasticity of quasicrystal material, we investigated the interaction between a screw dislocation and a wedge-shaped crack in the piezoelectricity of one-dimensional hexagonal quasicrystals. Explicit analytical solutions are obtained for stress and electric displacement intensity factors of the crack, as well as the force on dislocation. The derivation is based on the conformal mapping method and the perturbation technique. The influences of the wedge angle and dislocation location on the image force are also discussed. The results obtained in this paper can be fully reduced to some special cases already available or deriving new ones.
Research on the jet characteristics of the deflector-jet mechanism of the servo valve
Variation of passivation behavior induced by sputtered energetic particles and thermal annealing for ITO/SiOx/Si system
Mode transition in dusty micro-plasma driven by pulsed radio-frequency source in C2H2/Ar mixture
Analysis of the Zeeman effect on Dα spectra on the EAST tokamak
Theoretical prediction of new C-Si alloys in C2/m-20 structure
Influence of high pulsed magnetic field on tensile properties of TC4 alloy
The tensile tests of TC4 alloy are carried on electronic universal testing machine in the synchronous presence of high pulsed magnetic field (HPMF) parallel to the axial direction. The effects of magnetic induction intensity (B=0, 1 T, 3 T, and 5 T) on elongation (δ) of TC4 alloy are investigated. At 3 T, the elongation arrives at a maximum value of 12.41%, which is enhanced by 23.98% in comparison with that of initial sample. The elongation curve shows that 3 T is a critical point. With B increasing, the volume fraction of α phase is enhanced from 49.7% to 55.9%, which demonstrates that the HPMF can induce the phase transformation from β phase to α phase. Furthermore, the magnetic field not only promotes the orientation preference of crystal plane along the slipping direction, but also has the effect on increasing the dislocation density. The dislocation density increases with the enhancement of magnetic induction intensity and the 3-T parameter is ascertained as a turning point from increase to decrease tendency. When B is larger than 3 T, the dislocation density decreases with the enhancement of B. The influence of magnetic field is analyzed on the basis of magneto-plasticity effect. The high magnetic field will enhance the dislocation strain energy and promote the state conversion of radical pair generated between the dislocation and obstacles from singlet into triplet state, in which is analyzed the phenomenon that the dislocation density is at an utmost with B=3 T. Finally, the inevitability of optimized 3-T parameter is further discussed on a quantum scale.
High-pressure dynamic, thermodynamic properties, and hardness of CdP2
Using a pseudopotential plane-waves method, we calculate the phonon dispersion curves, thermodynamic properties, and hardness values of α-CdP2 and β-CdP2 under high pressure. From the studies of the phonon property and enthalpy difference curves, we discuss a phase transform from β-CdP2 to α-CdP2 in a pressure range between 20 GPa and 25 GPa. Then, the thermodynamic properties, Debye temperatures, and heat capacities are investigated at high pressures. What is more, we employ a semiempirical method to evaluate the pressure effects on the hardness for these two crystals. The results show that the hardness values of both α-CdP2 and β-CdP2 increase as pressure is increased. The influence mechanism of the pressure effect on the hardness of CdP2 is also briefly discussed.
Lattice dynamics properties of chalcopyrite ZnSnP2: Density-functional calculations by using a linear response theory
The electronic, optical, and thermodynamical properties of tetragonal, monoclinic, and orthorhombic M3N4 (M=Si, Ge, Sn): A first-principles study
High pressure electrical transport behavior in SrF2 nanoplates
Low-temperature phase transformation of CZTS thin films
Superfluidity of coherent light in self-focusing nonlinear waveguides
Superexchange-mediated magnetization dynamics with ultracold alkaline-earth atoms in an optical lattice
Superexchange and inter-orbital spin-exchange interactions are key ingredients for understanding (orbital) quantum magnetism in strongly correlated systems and have been realized in ultracold atomic gases. Here we study the spin dynamics of ultracold alkaline-earth atoms in an optical lattice when the two exchange interactions coexist. In the superexchange interaction dominating regime, we find that the time-resolved spin imbalance shows a remarkable modulated oscillation, which can be attributed to the interplay between local and nonlocal quantum mechanical exchange mechanisms. Moreover, the filling of the long-lived excited atoms affects the collapse and revival of the magnetization dynamics. These observations can be realized in state-dependent optical lattices combined with the state-of-the-art advances in optical lattice clock spectroscopy.
Icephobic performance on the aluminum foil-based micro-/nanostructured surface
Effect of deposited temperatures of the buffer layer on the band offset of CZTS/In2S3 heterostructure and its solar cell performance
Ab initio study on the anisotropy of mechanical behavior and deformation mechanism for boron carbide
First principles investigation of protactinium-based oxide-perovskites for flexible opto—electronic devices
Electric current-induced giant electroresistance in La0.36Pr0.265Ca0.375MnO3 thin films
The electroresistance (ER) of La0.36Pr0.265Ca0.375MnO3 (LPCMO) epitaxial thin film was studied under various dc currents. The current effect was compared for the unpatterned film and patterned microbridge with a width of 50 μm. The value of ER in the unpatterned LPCMO film could reach 0.54 under a 1-mA current, which is much higher than ER under 1 mA for the patterned weak phase-separated La0.67Ca0.33MnO3 and La0.85Sr0.15MnO3 microbridges with 50-μm width. More interestingly, for the patterned LPCMO microbridge, the maximum of ER can reach 0.6 under a small current of 100 μA. The results were explained by considering the coexistence of ferromagnetic metallic phase with the charge-ordered phase, and the variation of the phase separation with electric current.
Investigation of the surface orientation influence on 10-nm double gate GaSb nMOSFETs
The origin of spin current in YIG/nonmagnetic metal multilayers at ferromagnetic resonance
Decoupling technique of patch antenna arrays with shared substrate by suppressing near-field magnetic coupling using magnetic metamaterials
Enhancement of Förster energy transfer from thermally activated delayed fluorophores layer to ultrathin phosphor layer for high color stability in non-doped hybrid white organic light-emitting devices
Etching mask optimization of InAs/GaSb superlattice mid-wavelength infared 640×512 focal plane array
Quantum transport through a Z-shaped silicene nanoribbon
A novel enhancement mode AlGaN/GaN high electron mobility transistor with split floating gates
Improvement of reverse blocking performance in vertical power MOSFETs with Schottky-drain-connected semisuperjunctions
Structural, electronic, and optical properties of hexagonal and triangular SiC NWs with different diameters
Density-functional theory study on the electronic properties of laves phase superconductor CaIr2
Macroscopic resonant tunneling in an rf-SQUID flux qubit under a single-cycle sinusoidal driving
We experimentally demonstrate the observation of macroscopic resonant tunneling (MRT) phenomenon of the macroscopic distinct flux states in a radio frequency superconducting quantum interference device (rf-SQUID) under a single-cycle sinusoidal driving. The population of the qubit exhibits interference patterns corresponding to resonant tunneling peaks between states in the adjacent potential wells. The dynamics of the qubit depends significantly on the amplitude, frequency, and initial phase of the driving signal. We do the numerical simulations considering the intra-well and inter-well relaxation mechanism, which agree well with the experimental results. This approach provides an effective way to manipulate the qubit population by adjusting the parameters of the external driving field.
Dynamics of vortex-antivortex pair in a superconducting thin strip with narrow slits
Control of spins in a nano-sized magnet using electric-current
Study on the dielectric properties of Mg-doped NaBiTi6O14 ceramics
Structural characterization of Al0.55Ga0.45N epitaxial layer determined by high resolution x-ray diffraction and transmission electron microscopy
Structural characteristics of Al0.55Ga0.45N epilayer were investigated by high resolution x-ray diffraction (HRXRD) and transmission electron microscopy (TEM); the epilayer was grown on GaN/sapphire substrates using a high-temperature AlN interlayer by metal organic chemical vapor deposition technique. The mosaic characteristics including tilt, twist, heterogeneous strain, and correlation lengths were extracted by symmetric and asymmetric XRD rocking curves as well as reciprocal space map (RSM). According to Williamson-Hall plots, the vertical coherence length of AlGaN epilayer was calculated, which is consistent with the thickness of AlGaN layer measured by cross section TEM. Besides, the lateral coherence length was determined from RSM as well. Deducing from the tilt and twist results, the screw-type and edge-type dislocation densities are 1.0×108 cm-2 and 1.8×1010 cm-2, which agree with the results observed from TEM.
Review of flexible and transparent thin-film transistors based on zinc oxide and related materials
Flexible and transparent electronics enters into a new era of electronic technologies. Ubiquitous applications involve wearable electronics, biosensors, flexible transparent displays, radio-frequency identifications (RFIDs), etc. Zinc oxide (ZnO) and relevant materials are the most commonly used inorganic semiconductors in flexible and transparent devices, owing to their high electrical performances, together with low processing temperatures and good optical transparencies. In this paper, we review recent advances in flexible and transparent thin-film transistors (TFTs) based on ZnO and relevant materials. After a brief introduction, the main progress of the preparation of each component (substrate, electrodes, channel and dielectrics) is summarized and discussed. Then, the effect of mechanical bending on electrical performance is highlighted. Finally, we suggest the challenges and opportunities in future investigations.
Recent progress of ZnMgO ultraviolet photodetector
The ultra-violet (UV) detection has a wide application in both civil and military fields. ZnO is recognized as one of ideal materials for fabricating the UV photodetectors due to its plenty of advantages, such as wide bandgap, low cost, being environment-friendly, high radiation hardness, etc. Moreover, the alloying of ZnO with MgO to make ZnMgO could continually increase the band gap from ~3.3 eV to ~7.8 eV, which allows both solar blind and visible blind UV radiation to be detected. As is well known, ZnO is stabilized in the wurtzite structure, while MgO is stabilized in the rock salt structure. As a result, with increasing the Mg content, the crystal structure of ZnMgO alloy will change from wurtzite structure to rock salt structure. Therefore, ZnMgO photodetectors can be divided into three types based on the structures of alloys, namely, wurtzite-phase, cubic-phase and mixed-phase devices. In this paper, we review recent development and make the prospect of three types of ZnMgO UV photodetectors.
Recent progress of the native defects and p-type doping of zinc oxide
Zinc oxide (ZnO) is a compound semiconductor with a direct band gap and high exciton binding energy. The unique property, i.e., high efficient light emission at ultraviolet band, makes ZnO potentially applied to the short-wavelength light emitting devices. However, efficient p-type doping is extremely hard for ZnO. Due to the wide band gap and low valence band energy, the self-compensation from donors and high ionization energy of acceptors are the two main problems hindering the enhancement of free hole concentration. Native defects in ZnO can be divided into donor-like and acceptor-like ones. The self-compensation has been found mainly to originate from zinc interstitial and oxygen vacancy related donors. While the acceptor-like defect, zinc vacancy, is thought to be linked to complex shallow acceptors in group-VA doped ZnO. Therefore, the understanding of the behaviors of the native defects is critical to the realization of high-efficient p-type conduction. Meanwhile, some novel ideas have been extensively proposed, like double-acceptor co-doping, acceptor doping in iso-valent element alloyed ZnO, etc., and have opened new directions for p-type doping. Some of the approaches have been positively judged. In this article, we thus review the recent (2011-now) research progress of the native defects and p-type doping approaches globally. We hope to provide a comprehensive overview and describe a complete picture of the research status of the p-type doping in ZnO for the reference of the researchers in a similar area.
ZnO-based deep-ultraviolet light-emitting devices
Deep-ultraviolet (DUV) light-emitting devices (LEDs) have a variety of potential applications. Zinc-oxide-based materials, which have wide bandgap and large exciton binding energy, have potential applications in high-performance DUV LEDs. To realize such optoelectronic devices, the modulation of the bandgap is required. This has been demonstrated by the developments of MgxZn1-xO and BexZn1-xO alloys for the larger bandgap materials. Many efforts have been made to obtain DUV LEDs, and promising successes have been achieved continuously. In this article, we review the recent progress of and problems encountered in the research of ZnO-based DUV LEDs.
Fabrication of crystalline selenium microwire
Two-dimensional polyaniline nanosheets via liquid-phase exfoliation Hot!
Two-dimensional (2D) organic nanomaterials are fascinating because of their unique properties and pentential applications in future optoelectronic devices. Polyaniline (PANI) has attracted much attention for its high conductivity, good environmental stability and unusual doping chemistry. We report on liquid-phase exfoliation of layered PANI films grown by electrochemical polymerization. Atomic force microscopy images demonstrate that few- or even mono-layer PANI nanosheets can be fabricated. The PANI nanosheets can be transferred onto a variety of surfaces, providing a promising route to their incorporation into a variety of devices for further studies and various applications.
Large scale and controllable preparation of W2C nanorods or WC nanodots with peroxidase-like catalytic activity
Interface states study of intrinsic amorphous silicon for crystalline silicon surface passivation in HIT solar cell
Combined effects of headgroup charge and tail unsaturation of lipids on lateral organization and diffusion of lipids in model biomembranes
Lateral organization and dynamics of lipids in plasma membranes are crucial for several cellular processes such as signal transduction across the membrane and still remain elusive. In this paper, using coarse-grained molecular dynamics simulation, we theoretically study the combined effects of headgroup charge and tail unsaturation of lipids on the lateral organization and diffusion of lipids in ternary lipid bilayers. In neutral ternary lipid bilayers composed of saturated lipids, unsaturated lipids, and cholesterols, under the conditions of given temperature and components, the main factor for the phase separation is the unsaturation of unsaturated lipids and the bilayers can be separated into liquid-ordered domains enriched in saturated lipids and cholesterols and liquid-disordered domains enriched in unsaturated lipids. Once the headgroup charge is introduced, the electrostatic repulsion between the negatively charged lipid headgroups will increase the distance between the charged lipids. We find that the lateral organization and diffusion of the lipids in the (partially) charged ternary lipid bilayers are determined by the competition between the headgroup charge and the unsaturation of the unsaturated lipids. In the bilayers containing unsaturated lipids with lower unsaturation, the headgroup charge plays a crucial role in the lateral organization and diffusion of lipids. The headgroup charge may make the lipid domains unstable and even can suppress phase separation of the lipids in some systems. However, in the bilayers containing highly unsaturated lipids, the lateral organization and diffusion of lipids are mainly dominated by the unsaturation of the unsaturated lipids. This work may provide some theoretical insights into understanding the formation of nanosized domains and lateral diffusion of lipids in plasma membranes.
Design and optimization of carbon nanotube/polymer actuator by using finite element analysis
In recent years, actuators based on carbon nanotube (CNT) or graphene demonstrate great potential applications in the fields of artificial muscles, smart switches, robotics, and so on. The electrothermal and photothermal bending actuators based on CNT/graphene and polymer composites show large bending actuations, which are superior to traditional thermal-driven actuators. However, the influence of material parameters (thickness, temperature change, etc.) on the actuation performance needs to be further studied, because it is a critical point to the design and fabrication of high-performance actuators. In this work, finite element analysis (FEA) is employed to simulate the actuation performance of CNT/polymer actuator, which has a bilayer structure. The main focus of this work is to design and to optimize material parameters by using computational method. FEA simulation results show that each layer thickness of actuator has an important influence on the actuation deformation. A maximum curvature of 2.7 cm-1 is obtained by simulation, which is much larger than most of the actuator curvature reported in previous experiments. What is more, larger temperature change and larger difference of coefficient of thermal expansion (CTE) between two layers will result in larger bending actuation. This study is expected to provide valuable theoretical reference for the design and realization of CNT-based thermal actuator with ultra-large actuation performance.
A simulation study on p-doping level of polymer host material in P3HT: PCBM bulk heterojunction solar cells