Shannon information capacity of time reversal wideband multiple-input multiple-output system based on correlated statistical channels
Controlling chaos based on a novel intelligent integral terminal sliding mode control in a rod-type plasma torch
An integral terminal sliding mode controller is proposed in order to control chaos in a rod-type plasma torch system. In this method, a new sliding surface is defined based on a combination of the conventional sliding surface in terminal sliding mode control and a nonlinear function of the integral of the system states. It is assumed that the dynamics of a chaotic system are unknown and also the system is exposed to disturbance and unstructured uncertainty. To achieve a chattering-free and high-speed response for such an unknown system, an adaptive neuro-fuzzy inference system is utilized in the next step to approximate the unknown part of the nonlinear dynamics. Then, the proposed integral terminal sliding mode controller stabilizes the approximated system based on Lyapunov's stability theory. In addition, a Bee algorithm is used to select the coefficients of integral terminal sliding mode controller to improve the performance of the proposed method. Simulation results demonstrate the improvement in the response speed, chattering rejection, transient response, and robustness against uncertainties.
Dynamics of cubic-quintic nonlinear Schrödinger equation with different parameters
We study the dynamics of the cubic-quintic nonlinear Schrödinger equation by the symplectic method. The behaviors of the equation are discussed with harmonically modulated initial conditions, and the contributions from the quintic term are discussed. We observe the elliptic orbit, homoclinic orbit crossing, quasirecurrence, and stochastic motion with different nonlinear parameters in this system. Numerical simulations show that the changing processes of the motion of the system and the trajectories in the phase space are various for different cubic nonlinear parameters with the increase of the quintic nonlinear parameter.
Tunable two-axis spin model and spin squeezing in two cavities
Multi-mode cavities have now attracted much attention both experimentally and theoretically. In this paper, inspired by recent experiments of cavity-assisted Raman transitions, we realize a two-axis spin Hamiltonian H=q(Jx2+χJy2)+ω0Jz in two cavities. This realized Hamiltonian has a distinct property that all parameters can be tuned independently. For proper parameters, the well-studied one- and two-axis twisting Hamiltonians are recovered, and the scaling of N-1 of the maximal squeezing factor can occur naturally. On the other hand, in the two-axis twisting Hamiltonian, spin squeezing is usually reduced when increasing the atomic resonant frequency ω0. Surprisingly, we find that by combining with the dimensionless parameter χ(>-1), this atomic resonant frequency ω0 can enhance spin squeezing greatly. These results are beneficial for achieving the required spin squeezing in experiments.
Quantum information entropy for one-dimensional system undergoing quantum phase transition
Path integral approach to electron scattering in classical electromagnetic potential
A hybrid-type quantum random number generator
Multi-hop teleportation based on W state and EPR pairs
Bianchi type I in f(T) gravitational theories
Modeling the capability of penetrating a jammed crowd to eliminate freezing transition
Frozen state from jammed state is one of the most interesting aspects produced when simulating the multidirectional pedestrian flow of high density crowds. Cases of real life situations for such a phenomenon are not exhaustively treated. Our observations in the Hajj crowd show that freezing transition does not occur very often. On the contrary, penetrating a jammed crowd is a common aspect. We believe the kindness of pedestrians facing others whose walking is blocked is a main factor in eliminating the frozen state as well as in relieving the jammed state. We refine the social force model by incorporating a new social force to enable the simulated pedestrians to mimic the real behavior observed in the Hajj area. Simulations are performed to validate the work qualitatively.
New data assimilation system DNDAS for high-dimensional models
A novel methodology for constructing a multi-wing chaotic and hyperchaotic system with a unified step function switching control
Two-point resistance of an m×n resistor network with an arbitrary boundary and its application in RLC network
A rectangular m×n resistor network with an arbitrary boundary is investigated, and a general resistance formula between two nodes on an arbitrary axis is derived by the Recursion-Transform (RT) method, a problem that has never been resolved before, for the Green's function technique and the Laplacian matrix approach are inapplicable to it. To have the exact solution of resistance is important but it is difficult to obtain under the condition of arbitrary boundary. Our result is directly expressed in a single summation and mainly composed of characteristic roots, which contain both finite and infinite cases. Further, the current distribution is given explicitly as a byproduct of the method. Our framework can be effectively applied to RLC networks. As an application to the LC network, we find that our formulation leads to the occurrence of resonances at h1 = 1-cosφi-sinφicotnφi. This somewhat curious result suggests the possibility of practical applications of our formulae to resonant circuits.
Dynamic properties of chasers in a moving queue based on a delayed chasing model
Daily variation of radon gas and its short-lived progeny concentration near ground level and estimation of aerosol residence time
Accurate double many-body expansion potential energy surface of HS2(A2A') by scaling the external correlation
A globally accurate single-sheeted double many-body expansion potential energy surface is reported for the first excited state of HS2 by fitting the accurate ab initio energies, which are calculated at the multireference configuration interaction level with the aug-cc-pV QZ basis set. By using the double many-body expansion-scaled external correlation method, such calculated ab initio energies are then slightly corrected by scaling their dynamical correlation. A grid of 2767 ab initio energies is used in the least-square fitting procedure with the total root-mean square deviation being 1.406 kcal· mol-1. The topographical features of the HS2(A2A') global potential energy surface are examined in detail. The attributes of the stationary points are presented and compared with the corresponding ab initio results as well as experimental and other theoretical data, showing good agreement. The resulting potential energy surface of HS2(A2A') can be used as a building block for constructing the global potential energy surfaces of larger m S/H molecular systems and recommended for dynamic studies on the title molecular system.
Comparing two iteration algorithms of Broyden electron density mixing through an atomic electronic structure computation
Laser frequency locking based on Rydberg electromagnetically induced transparency
Carrier envelope phase effect on the spatial distribution of high-order harmonic generation in asymmetric molecule
The spatial distribution in high-order harmonic generation (HHG) from the asymmetric diatomic molecule HeH2+ is investigated by numerically solving the non-Born-Oppenheimer time-dependent Schrödinger equation (TDSE). The spatial distribution of the HHG spectra shows that there is little contribution in HHG around the geometric center of two nuclei (z = 1.17 a.u.) and the equilibrium internuclear position of the H nucleus (z = 3.11 a.u.). We demonstrate the carrier envelope phase (CEP) effect on the spatial distribution of HHG in a few-cycle laser pulse. The HHG process is investigated by the time evolution of the electronic density distribution. The time-frequency analysis of HHG from two nuclei in HeH2+ is presented to further explain the underlying physical mechanism.
Carrier-envelope phase measurement using plasmonic-field-enhanced high-order harmonic generation of H atom in few-cycle laser pulses
Coulomb explosion of CS2 molecule under an intense femtosecond laser field
Structural optimization and segregation behavior of quaternary alloy nanoparticles based on simulated annealing algorithm
Microwave-mediated magneto-optical trap for polar molecules Hot!
Realizing a molecular magneto-optical trap has been a dream for cold molecular physicists for a long time. However, due to the complex energy levels and the small effective Lande g-factor of the excited states, the traditional magneto-optical trap (MOT) scheme does not work very well for polar molecules. One way to overcome this problem is the switching MOT, which requires very fast switching of both the magnetic field and the laser polarizations. Switching laser polarizations is relatively easy, but fast switching of the magnetic field is experimentally challenging. Here we propose an alternative approach, the microwave-mediated MOT, which requires a slight change of the current experimental setup to solve the problem. We calculate the MOT force and compare it with the traditional MOT and the switching MOT scheme. The results show that we can operate a good MOT with this simple setup.
The 650-nm variable optical attenuator based on polymer/silica hybrid waveguide
Dynamic study of compressed electron layer driven by linearly polarized laser
Image encryption using random sequence generated from generalized information domain
Higher-order nonclassical effects generated by multiple-photon annihilation-then-creation and creation-then-annihilation coherent states
We explore two observable nonclassical properties of quantum states generated by repeatedly operating annihilation-then-creation (AC) and creation-then-annihilation (CA) on the coherent state, respectively, such as higher-order sub-Poissonian statistics and higher-order squeezing-enhanced effect. The corresponding analytical expressions are derived in detail depending on m. By numerically comparing those quantum properties, it is found that these states above have very different nonclassical properties and nonclassicality is exhibited more strongly after AC operation than after CA operation.
Triple optomechanical induced transparency in a two-cavity system
We theoretically investigate the optomechanical induced transparency (OMIT) phenomenon in a two-cavity system which is composed of two optomechanical cavities. Both of the cavities consist of a fixed mirror and a high-Q mechanical resonator, and they couple to each other via a common waveguide. We show that in the presence of a strong pump field applied to one cavity and a weak probe field applied to the other, a triple-OMIT can be observed in the output field at the probe frequency. The two mechanical resonators in the two cavities are identical, but they lead to different quantum interference pathways. The transparency windows are induced by the coupling of the two cavities and the optical pressure radiated to the mechanical resonators, which can be controlled via the power of the pump field and the coupling strength of the two cavities.
Control of microwave signals using bichromatic electromechanically induced transparency in multimode circuit electromechanical systems
A 12.1-W SESAM mode-locked Yb:YAG thin disk laser
Analysis of melt ejection during long pulsed laser drilling
In pulsed laser drilling, melt ejection greatly influences the keyhole shape and its quality as well, but its mechanism has not been well understood. In this paper, numerical simulation and experimental investigations based on 304 stainless steel and aluminum targets are performed to study the effects of material parameters on melt ejection. The numerical method is employed to predict the temperatures, velocity fields in the solid, liquid, and vapour front, and melt pool dynamics of targets as well. The experimental methods include the shadow-graphic technique, weight method, and optical microscope imaging, which are applied to real-time observations of melt ejection phenomena, measurements of collected melt and changes of target mass, observations of surface morphology and the cross-section of the keyhole, respectively. Numerical and experimental results show that the metallic material with high thermal diffusivity like aluminum is prone to have a thick liquid zone and a large quantity of melt ejection. Additionally, to the best of our knowledge, the liquid zone is used to illustrate the relations between melt ejection and material thermal diffusivity for the first time. The research result in this paper is useful for manufacturing optimization and quality control in laser-material interaction.
Lasing dynamics study by femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy
Optical bistability and multistability in a defect slab doped by GaAs/AlGaAs multiple quantum wells
We proposed a new model for controlling the optical bistability (OB) and optical multistability (OM) in a defect slab doped with four-level GaAs/AlGaAs multiple quantum wells with 15 periods of 17.5 nm GaAs wells and 15-nm Al0.3 Ga0.7As barriers. The effects of biexciton energy renormalization, exciton spin relaxation, and thickness of the slab on the OB and OM properties of the defect slab were theoretically investigated. We found that the transition from OB to OM or vice versa is possible by adjusting the controllable parameters in a lab. Moreover, the transmission, reflection, and absorption properties of the weak probe light through the slab were also discussed in detail.
A novel single-order diffraction grating: Random position rectangle grating
Spectral diagnosis of radiation from laser plasma interaction and monochromation of radiation source are hot and important topics recently. Grating is one of the primary optical elements to do this job. Although easy to fabricate, traditional diffraction grating suffers from multi-order diffraction contamination. On the other hand, sinusoidal amplitude grating has the nonharmonic diffraction property, but it is too difficult to fabricate, especially for x-ray application. A novel nonharmonic diffraction grating named random position rectangle grating (RPRG) is proposed in this paper. Theoretical analysis and experiment results show that the RPRG is both higher order diffraction suppressing and not difficult to fabricate. Additionally, it is highly efficient; its first order absolute theoretical diffraction efficiency reaches 4.1%. Our result shows that RPRG is a novel tool for radiation diagnosis and monochromation.
Flow control of micro-ramps on supersonic forward-facing step flow
Structural transitions of SWNT filled with C60 under high pressure
Stability of concentration-related self-interstitial atoms in fusion material tungsten
Effect of pressure on electronic and thermoelectric properties of magnesium silicide: A density functional theory study
Thermal effect on endurance performance of 3-dimensional RRAM crossbar array
Three-dimensional (3D) crossbar array architecture is one of the leading candidates for future ultra-high density nonvolatile memory applications. To realize the technological potential, understanding the reliability mechanisms of the 3D RRAM array has become a field of intense research. In this work, the endurance performance of the 3D 1D1R crossbar array under the thermal effect is investigated in terms of numerical simulation. It is revealed that the endurance performance of the 3D 1D1R array would be seriously deteriorated under thermal effects as the feature size scales down to a relatively small value. A possible method to alleviate the thermal effects is provided and verified by numerical simulation.
Thermodynamic behaviour of Rashba quantum dot in the presence of magnetic field
Topological phase boundary in a generalized Kitaev model
First-principles study of the elastic and thermodynamic properties of thorium hydrides at high pressure
First-principles study of strain effect on the formation and electronic structures of oxygen vacancy in SrFeO2
Pressure induced magnetic and semiconductor-metal phase transitions in Cr2MoO6
Homopolar bonds in Se-rich Ge—As—Se chalcogenide glasses
First-principles modeling hydrogenation of bilayered boron nitride
We have investigated the structural and electronic characteristics of hydrogenated boron-nitride bilayer (H-BNBN-H) using first-principles calculations. The results show that hydrogenation can significantly reduce the energy gap of the BN-BN into the visible-light region. Interestingly, the electric field induced by the interface dipoles helps to promote the formation of well-separated electron-hole pairs, as demonstrated by the charge distribution of the VBM and CBM. Moreover, the applied bias voltage on the vertical direction of the bilayer could modulate the band gap, resulting in transition from semiconductor to metal. We conclude that H-BNBN-H could improve the solar energy conversion efficiency, which may provide a new way for tuning the electronic devices to meet different environments and demands.
Electronic and magnetic properties at rough alloyed interfaces of Fe/Co on Au substrates: An augmented space study
We studied the interface electronic and magnetic properties of Fe/Co deposited on Au substrate and researched the effects of roughness at the interfaces within augmented space formalism (ASF). The full calculation is carried out by recursion and tight-binding linear muffin tin orbital (TB-LMTO) methods. The amount of roughness is different at different atomic layers. The formalism is also applied to sharp interface, when interdiffusion of atoms is negligible. Our results of one monolayer transition metal agree with other reported results. A realistic rough interface is also modeled with three and four monolayers of transition metals, deposited on Au substrates.
Tunable Fano resonances and plasmonic hybridization of gold triangle-rod dimer nanostructure
High-performance germanium n+/p junction by nickel-induced dopant activation of implanted phosphorus at low temperature
Magnetoresistance and exchange bias in high Mn content melt-spun Mn46Ni42Sn11Sb1 alloy ribbon
Contact resistance asymmetry of amorphous indium-gallium-zinc-oxide thin-film transistors by scanning Kelvin probe microscopy Hot!
In this work, a method based on scanning Kelvin probe microscopy is proposed to separately extract source/drain (S/D) series resistance in operating amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. The asymmetry behavior of S/D contact resistance is deduced and the underlying physics is discussed. The present results suggest that the asymmetry of S/D contact resistance is caused by the difference in bias conditions of the Schottky-like junction at the contact interface induced by the parasitic reaction between contact metal and a-IGZO. The overall contact resistance should be determined by both the bulk channel resistance of the contact region and the interface properties of the metal-semiconductor junction.
Electron transport in electrically biased inverse parabolic double-barrier structure
Length dependence of rectification in organic co-oligomer spin rectifiers
Developing Josephson junction array chips for microvolt applications
Effect of residual stress on nematic domains in BaFe2-xNixAs2 studied by angular magnetoresistance
We have studied the angular magnetoresistance of iron pnictides BaFe2-xNixAs2, which shows clear 180 degree periodicity as fitted by a cosine function. In the x = 0.065 sample, the phase of the two-fold symmetry changes 90 degrees above the tetragonal-to-orthorhombic structural transition temperature Ts. Since the phase at low temperature is associated with the rotation of orthorhombic domains by magnetic field, we show that even vacuum grease can push the presence of orthorhombic domains at temperatures much higher than Ts. Our results suggest that residual stress may have significant effects in studying the nematic orders and its fluctuations in iron pnictides.
First-principles investigation of electronic structure, effective carrier masses, and optical properties of ferromagnetic semiconductor CdCr2S4
The electronic structures, the effective masses, and optical properties of spinel CdCr2S4 are studied by using the full-potential linearized augmented planewave method and a modified Becke-Johnson exchange functional within the density-functional theory. Most importantly, the effects of the spin-orbit coupling (SOC) on the electronic structures and carrier effective masses are investigated. The calculated band structure shows a direct band gap. The electronic effective mass and the hole effective mass are analytically determined by reproducing the calculated band structures near the BZ center. SOC substantially changes the valence band top and the hole effective masses. In addition, we calculated the corresponding optical properties of the spinel structure CdCr2S4. These should be useful to deeply understand spinel CdCr2S4 as a ferromagnetic semiconductor for possible semiconductor spintronic applications.
Abnormal variation of magnetic properties with Ce content in (PrNdCe)2Fe14B sintered magnets prepared by dual alloy method
Dielectric and piezoelectric properties of (110) oriented Pb(Zr1-xTix)O3 thin films
Distribution of electron traps in SiO2/HfO2 nMOSFET
Observation of positive and small electron affinity of Si-doped AlN films grown by metalorganic chemical vapor deposition on n-type 6H-SiC
Field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method
Effect of size and indium-composition on linear and nonlinear optical absorption of InGaN/GaN lens-shaped quantum dot
Origin of strain-induced resonances in flexible terahertz metamaterials
Broadband tunability of surface plasmon resonance in graphene-coating silica nanoparticles Hot!
Graphene decorated nanomaterials and nanostructures can potentially be used in military and medical science applications. In this article, we study the optical properties of a graphene wrapping silica core-shell spherical nanoparticle under illumination of external light by using the Mie theory. We find that the nanoparticle can exhibit surface plasmon resonance (SPR) that can be broadly tuned from mid infrared to near infrared via simply changing the geometric parameters. A simplified equivalent dielectric permittivity model is developed to better understand the physics of SPR, and the calculation results agree well qualitatively with the rigorous Mie theory. Both calculations suggest that a small radius of graphene wrapping nanoparticle with high Fermi level could move the SPR wavelength of graphene into the near infrared regime.
Temperature dependent direct-bandgap light emission and optical gain of Ge
Optical study of charge dynamics in CaCo2As2
We present an infrared spectroscopy study of charge dynamics in CaCo2As2 single crystal. In this material, the optical conductivity can be described by two Drude components with different scattering rates (1/τ): a broad incoherent background and a narrow Drude component. By monitoring the temperature dependence, we find that only the narrow Drude component is temperature-dependent and determines the transport properties. Especially a Fermi liquid behavior of carriers is revealed by the T2 behavior in the dc resistivity ρn and scattering rate 1/τn, indicating a coherent nature of quasiparticles in the narrow Drude subsystem.
Effects of Mg doping in the quantum barriers on the efficiency droop of GaN based light emitting diodes
First-principles study of the structural, electronic, and magnetic properties of double perovskite Sr2FeReO6 containing various imperfections
Enhanced circular dichroism based on the dual-chiral metamaterial in terahertz regime
Characterization of atomic-layer MoS2 synthesized using a hot filament chemical vapor deposition method
Structural and photoluminescence studies on europium-doped lithium tetraborate (Eu:Li2B4O7) single crystal grown by microtube Czochralski (μT-Cz) technique
Rare earth europium (Eu3+)-doped lithium tetraborate (Eu:Li2B4O7) crystal is grown from its stoichiometric melt by microtube Czochralski pulling technique (μT-Cz) for the first time. The grown crystals are subjected to powder x-ray diffraction (PXRD) analysis which reveals the tetragonal crystal structure of the crystals. UV-vis-NIR spectral analysis is carried out to study the optical characteristics of the grown crystals. The crystal is transparent in the entire visible region, and the lower cutoff is observed to be at 304 nm. The existence of BO3 and BO4 bonding structure and the molecular associations are analyzed by Fourier transform infrared (FTIR) spectroscopy. The results of excitation and emission-photoluminescence spectra of europium ion incorporated in lithium tetraborate (LTB) single crystal reveal that the observations of peaks at 258, 297, and 318 nm in the excitation spectra and peaks at 579, 591, 597, 613, and 651 nm are observed in the emission spectra. The chromaticity coordinates are calculated from the emission spectra, and the emission intensity of the grown crystal is characterized through a CIE 1931 (Commission International d'Eclairage) color chromaticity diagram.
Influences of different structures on the characteristics of H2O-based and O3-based LaxAlyO films deposited by atomic layer deposition
A nano-scale mirror-like surface of Ti-6Al-4V attained by chemical mechanical polishing
A G-band terahertz monolithic integrated amplifier in 0.5-μm InP double heterojunction bipolar transistor technology
Design and characterization of a G-band (140-220 GHz) terahertz monolithic integrated circuit (TMIC) amplifier in eight-stage common-emitter topology are performed based on the 0.5-μm InGaAs/InP double heterojunction bipolar transistor (DHBT). An inverted microstrip line is implemented to avoid a parasitic mode between the ground plane and the InP substrate. The on-wafer measurement results show that peak gains are 20 dB at 140 GHz and more than 15-dB gain at 140-190 GHz respectively. The saturation output powers are -2.688 dBm at 210 GHz and -2.88 dBm at 220 GHz, respectively. It is the first report on an amplifier operating at the G-band based on 0.5-μm InP DHBT technology. Compared with the hybrid integrated circuit of vacuum electronic devices, the monolithic integrated circuit has the advantage of reliability and consistency. This TMIC demonstrates the feasibility of the 0.5-μm InGaAs/InP DHBT amplifier in G-band frequencies applications.
Levitation and lateral forces between a point magnetic dipole and a superconducting sphere
Increasing energy relaxation time of superconducting qubits with nonmagnetic infrared filter and shield
One of the primary origins of the energy relaxation in superconducting qubits is the quasiparticle loss. The quasiparticles can be excited remarkably by infrared radiation. In order to minimize the density of quasiparticle and increase the qubit relaxation time, we design and fabricate the infrared filter and shield for superconducting qubits. In comparison with previous filters and shields, a nonmagnetic dielectric is used as the infrared absorbing material, greatly suppressing the background magnetic fluctuations. The filters can be made to impedance-match with other microwave devices. Using the as-fabricated infrared filter and shield, we increased the relaxation time of a transmon qubit from 519 ns to 1125 ns.
A novel circuit design for complementary resistive switch-based stateful logic operations
High-speed waveguide-integrated Ge/Si avalanche photodetector
Two-color light-emitting diodes with polarization-sensitive high extraction efficiency based on graphene
Stability of weighted spectral distribution in a pseudo tree-like network model
The comparison of networks with different orders strongly depends on the stability analysis of graph features in evolving systems. In this paper, we rigorously investigate the stability of the weighted spectral distribution (i.e., a spectral graph feature) as the network order increases. First, we use deterministic scale-free networks generated by a pseudo tree-like model to derive the precise formula of the spectral feature, and then analyze the stability of the spectral feature based on the precise formula. Except for the scale-free feature, the pseudo tree-like model exhibits the hierarchical and small-world structures of complex networks. The stability analysis is useful for the classification of networks with different orders and the similarity analysis of networks that may belong to the same evolving system.
Distributed event-triggered consensus tracking of second-order multi-agent systems with a virtual leader