The crucible-free electrode induction melting gas atomization (EIGA) technology is an advanced technology for preparing ultra-clean nickel-based superalloy powders. One of the key issues for fabricating powders with high quality and yield is the consecutive induction melting of a superalloy electrode. The coupling of a superalloy electrode and coil, frequency, output power, and heat conduction are investigated to improve the controllable electrode induction melting process. Numerical simulation results show that when the coil frequency is 400 kHz, the output power is 100 kW, superalloy liquid flow with a diameter of about 5 mm is not consecutive. When the coil frequency is reduced to 40 kHz, the output power is 120 kW, superalloy liquid flow is consecutive, and its diameter is about 7 mm.

The square-well (SW) potential is one of the simplest pair potential models and its phase behavior has been clearly revealed, therefore it has become a benchmark for checking new theories or numerical methods. We introduce the generalized canonical ensemble (GCE) into the isobaric replica exchange Monte Carlo (REMC) algorithm to form a novel isobaric GCE-REMC method, and apply it to the study of vapor-liquid transition of SW particles. It is validated that this method can reproduce the vapor-liquid diagram of SW particles by comparing the estimated vapor-liquid binodals and the critical point with those from the literature. The notable advantage of this method is that the unstable vapor-liquid coexisting states, which cannot be detected using conventional sampling techniques, are accessed with a high sampling efficiency. Besides, the isobaric GCE-REMC method can visit all the possible states, including stable, metastable or unstable states during the phase transition over a wide pressure range, providing an effective pathway to understand complex phase transitions during the nucleation or crystallization process in physical or biological systems.

We use the Bethe ansatz method to investigate the Schrödinger equation for a class of PT-symmetric non-Hermitian Hamiltonians. Elementary exact solutions for the eigenvalues and the corresponding wave functions are obtained in terms of the roots of a set of algebraic equations. Also, it is shown that the problems possess sl(2) hidden symmetry and then the exact solutions of the problems are obtained by employing the representation theory of sl(2) Lie algebra. It is found that the results of the two methods are the same.

We solve the Schrödinger equation with a position-dependent mass (PDM) charged particle interacted via the superposition of the Morse-plus-Coulomb potentials and is under the influence of external magnetic and Aharonov-Bohm (AB) flux fields. The nonrelativistic bound state energies together with their wave functions are calculated for two spatially-dependent mass distribution functions. We also study the thermal quantities of such a system. Further, the canonical formalism is used to compute various thermodynamic variables for second choosing mass by using the Gibbs formalism. We give plots for energy states as a function of various physical parameters. The behavior of the internal energy, specific heat, and entropy as functions of temperature and mass density parameter in the inverse-square mass case for different values of magnetic field are shown.

Einstein-Podolski-Rosen (EPR) entanglement state is achievable by combining two single-mode position and momentum squeezed states at a 50:50 beam-splitter (BS). We investigate the generation of the EPR entangled state of two vibrating membranes in a ring resonator, where clockwise (CW) and counter-clockwise (CCW) travelling-wave modes are driven by lasers and finite-bandwidth squeezed lights. Since the optomechanical coupling depends on the location of the membranes, CW and CCW can couple to the symmetric and antisymmetric combination of mechanical modes for a suitable arrangement, which corresponds to a 50:50 BS mixing. Moreover, by employing the red-detuned driving laser and tuning the central frequency of squeezing field blue detuned from the driving laser with a mechanical frequency, the squeezing property of squeezed light can be perfectly transferred to the mechanical motion in the weak coupling regime. Thus, the BS mixing modes can be position and momentum squeezed by feeding the appropriate squeezed lights respectively, and the EPR entangled mechanical state is obtained. Moreover, cavity-induced mechanical cooling can further suppress the influence of thermal noise on the entangled state.

A quantum access network has been implemented by frequency division multiple access and time division multiple access, while code division multiple access is limited for its difficulty to realize the orthogonality of the code. Recently, the chaotic phase shifters were proposed to guarantee the orthogonality by different chaotic signals and spread the spectral content of the quantum states. In this letter, we propose to implement the code division multiple access quantum network by using chaotic phase shifters and synchronization. Due to the orthogonality of the different chaotic phase shifter, every pair of users can faithfully transmit quantum information through a common channel and have little crosstalk between different users. Meanwhile, the broadband spectra of chaotic signals efficiently help the quantum states to defend against channel loss and noise.

Quantum algorithms provide a more efficient way to solve computational tasks than classical algorithms. We experimentally realize quantum permutation algorithm using light's orbital angular momentum degree of freedom. By exploiting the spatial mode of photons, our scheme provides a more elegant way to understand the principle of quantum permutation algorithm and shows that the high dimension characteristic of light's orbital angular momentum may be useful in quantum algorithms. Our scheme can be extended to higher dimension by introducing more spatial modes and it paves the way to trace the source of quantum speedup.

We propose a scheme for a fast generating three-qubit W state in a superconducting system by using a technique of shortcuts to adiabaticity, Lewis-Riesenfeld invariants. Three identical superconducting qubits (SQs) are connected by two coplanar waveguide resonators (CPWRs) capacitively. Under a certain limit condition, we convert the complicated SQ system into a simple three-state system. By designing experimentally accessible harmonic pulses, a three-SQ W state is implemented with quite short operation time and high fidelity. Numerical simulations prove that the scheme is robust against the parameter deviation. In addition, we also give detailed discussion about the scheme robustness against decoherence.

Entanglement purification is to distill the high quality entanglement from the low quality entanglement with local operations and classical communications. It is one of the key technologies in long-distance quantum communication. We discuss an entanglement purification protocol (EPP) with spontaneous parametric down conversion (SPDC) sources, in contrast to previous EPP with multi-copy mixed states, which requires ideal entanglement sources. We show that the SPDC source is not an obstacle for purification, but can benefit the fidelity of the purified mixed state. This EPP works for linear optics and is feasible in current experiment technology.

We develop a fabrication process for the superconducting phase qubits in which Josephson junctions for both the qubit and superconducting quantum interference device (SQUID) detector are prepared by shadow evaporation with a suspended bridge. Al junctions with areas as small as 0.05 μ^{2} are fabricated for the qubit, in which the number of the decoherence-causing two-level systems (TLS) residing in the tunnel barrier and proportional to the junction area are greatly reduced. The measured energy spectrum shows no avoided crossing arising from coherent TLS in the experimentally reachable flux bias range of the phase qubit, which demonstrates the energy relaxation time T_{1} and dephasing time T_{φ} on the order of 100 ns and 50 ns, respectively. We discuss several possible origins of decoherence from incoherent or weakly-coupled coherent TLS and further improvements of the qubit performance.

In this paper, we study the gravitational quasi-normal modes (QNMs) for a static R^{2} black hole (BH) in Anti-de Sitter (AdS) spacetime. The corresponding master equation of odd parity is derived and the QNMs are evaluated by the Horowitz and Hubeny method. Meanwhile the stability of such BH is also discussed through the temporal evolution of the perturbation field. Here we mainly consider the coefficient λ, which is related to the radius of AdS black hole, on the QNMs of the R^{2} AdS BH. The results show that the Re(ω) and |Im(ω)| of the QNMs increase together as |λ| increases for a given angular momentum number l. That indicates with a larger value of |λ| the corresponding R^{2} AdS BH returns to stable much more quickly. The dynamic evolution of the perturbation field is consistent with the results derived by the Horowitz and Hubeny method. Since in the conformal field theory the QNMs can reflect its approach to equilibrium, so our related results could be referential to studies of the AdS/CFT conjecture. The relationship between λ and the properties of the static R^{2} BH might be helpful for the development of R^{2} gravitational theory.

Using the bosonic numerical renormalization group method, we studied the equilibrium dynamical correlation function C(ω) of the spin operator σ_{z} for the biased sub-Ohmic spin-boson model. The small-ω behavior C(ω)∝ω^{s} is found to be universal and independent of the bias ε and the coupling strength α (except at the quantum critical point α=α_{c} and ε=0). Our NRG data also show C(ω)∝χ^{2}ω^{s} for a wide range of parameters, including the biased strong coupling regime (ε≠0 and α > α_{c}), supporting the general validity of the Shiba relation. Close to the quantum critical point α_{c}, the dependence of C(ω) on α and ε is understood in terms of the competition between ε and the crossover energy scale ω_{0}^{*} of the unbiased case. C(ω) is stable with respect to ε for ε≪ε^{*}. For ε≫ε^{*}, it is suppressed by ε in the low frequency regime. We establish that ε^{*}∝(ω_{0}^{*})^{1/θ} holds for all sub-Ohmic regime 0≤s < 1, with θ=2/(3s) for 0 < s≤1/2 and θ=2/(1+s) for 1/2 < s < 1. The variation of C(ω) with α and ε is summarized into a crossover phase diagram on the α-ε plane.

The spin-boson model with quadratic coupling is studied using the bosonic numerical renormalization group method. We focus on the dynamical auto-correlation functions C_{O}(ω), with the operator Ô taken as σ_{x}, σ_{z}, and X, respectively. In the weak-coupling regime α < α_{c}, these functions show power law ω-dependence in the small frequency limit, with the powers 1+2s, 1+2s, and s, respectively. At the critical point α=α_{c} of the boson-unstable quantum phase transition, the critical exponents y_{O} of these correlation functions are obtained as y_{σx}=y_{σz}=1-2s and y_{X}=-s, respectively. Here s is the bath index and X is the boson displacement operator. Close to the spin flip point, the high frequency peak of C_{σx}(ω) is broadened significantly and the line shape changes qualitatively, showing enhanced dephasing at the spin flip point.

The complex derivative D^{α±jβ}, with α, β∈R+ is a generalization of the concept of integer derivative, where α=1, β=0. Fractional-order electric elements and circuits are becoming more and more attractive. In this paper, the complex-order electric elements concept is proposed for the first time, and the complex-order elements are modeled and analyzed. Some interesting phenomena are found that the real part of the order affects the phase of output signal, and the imaginary part affects the amplitude for both the complex-order capacitor and complex-order memristor. More interesting is that the complex-order capacitor can do well at the time of fitting electrochemistry impedance spectra. The complex-order memristor is also analyzed. The area inside the hysteresis loops increases with the increasing of the imaginary part of the order and decreases with the increasing of the real part. Some complex case of complex-order memristors hysteresis loops are analyzed at last, whose loop has touching points beyond the origin of the coordinate system.

In-line phase-contrast computed tomography (IL-PC-CT) imaging is a new physical and biochemical imaging method. IL-PC-CT has advantages compared to absorption CT when imaging soft tissues. In practical applications, ring artifacts which will reduce the image quality are commonly encountered in IL-PC-CT, and numerous correction methods exist to either pre-process the sinogram or post-process the reconstructed image. In this study, we develop an IL-PC-CT reconstruction method based on anisotropic total variation (TV) minimization. Using this method, the ring artifacts are corrected during the reconstruction process. This method is compared with two methods:a sinogram preprocessing correction technique based on wavelet-FFT filter and a reconstruction method based on isotropic TV. The correction results show that the proposed method can reduce visible ring artifacts while preserving the liver section details for real liver section synchrotron data.

We report an experimental demonstration of two-dimensional (2D) lensless ghost imaging with true thermal light. An electrodeless discharge lamp with a higher light intensity than the hollow cathode lamp used before is employed as a light source. The main problem encountered by the 2D lensless ghost imaging with true thermal light is that its coherence time is much shorter than the resolution time of the detection system. To overcome this difficulty we derive a method based on the relationship between the true and measured values of the second-order optical intensity correlation, by which means the visibility of the ghost image can be dramatically enhanced. This method would also be suitable for ghost imaging with natural sunlight.

Ternary M_{n+1}AX_{n} phases with layered hexagonal structures, as candidate materials used for next-generation nuclear reactors, have shown great potential in tolerating radiation damage due to their unique combination of ceramic and metallic properties. However, M_{n+1}AX_{n} materials behave differently in amorphization when exposed to energetic neutron and ion irradiations in experiment. We first analyze the irradiation tolerances of different M_{n+1}AX_{n} (MAX) phases in terms of electronic structure, including the density of states (DOS) and charge density map. Then a new method based on the Bader analysis with the first-principle calculation is used to estimate the stabilities of MAX phases under irradiation. Our calculations show that the substitution of Cr/V/Ta/Nb by Ti and Si/Ge/Ga by Al can increase the ionicities of the bonds, thus strengthening the radiation tolerance. It is also shown that there is no obvious difference in radiation tolerance between M_{n+1}AC_{n} and M_{n+1}AN_{n} due to the similar charge transfer values of C and N atoms. In addition, the improved radiation tolerance from Ti_{3}AlC_{2} to Ti_{2}AlC (Ti_{3}AlC_{2} and Ti_{2}AlC have the same chemical elements), can be understood in terms of the increased Al/TiC layer ratio. Criteria based on the quantified charge transfer can be further used to explore other M_{n+1}AX_{n} phases with respect to their radiation tolerance, playing a critical role in choosing appropriate MAX phases before they are subjected to irradiation in experimental test for future nuclear reactors.

In this study, solution processed composite films of nickel phthalocyanine (NiPc) and cobalt phthalocyanine (CoPc) are deposited by drop casting and under centrifugal force. The films are deposited on surface-type inter-digitated silver electrodes on ceramic alumina substrates. The effects of illumination on the impedance and capacitance of the NiPc-CoPc composite samples are investigated. The samples deposited under centrifugal force show better conductivity than the samples deposited by drop casting technique. In terms of impedance and capacitance sensitivities the samples fabricated under centrifugal force are more sensitive than the drop casting samples. The values of impedance sensitivity (S_{z}) are equal to (-1.83) MΩ·cm^{2}/mW and (-5.365) MΩ·cm^{2}/mW for the samples fabricated using drop casting and under centrifugal force, respectively. Similarly, the values of capacitance sensitivity (S_{c}) are equal to 0.083 pF·cm^{2}/mW and 0.185 pF·cm^{2}/mW for the samples fabricated by drop casting and under centrifugal force. The films deposited using the different procedures could potentially be viable for different operational modes (i.e., conductive or capacitive) of the optical sensors. Both experimental and simulated results are discussed.

In this paper, we present a three-dimensional (3D) vacuum packaging technique at a wafer level for a radio frequency micro-electromechanical system (RF MEMS) resonator, in which low-loss silicon vias is used to transmit RF signals. Au-Sn solder bonding is adopted to provide a vacuum encapsulation as well as electrical conductions. A RF model of the encapsulation cap is established to evaluate the parasitic effect of the packaging, which provides an effective design solution of 3D RF MEMS encapsulation. With the proposed packaging structure, the signal-to-background ratio (SBR) of 24 dB is achieved, as well as the quality factor (Q-factor) of the resonator increases from 8000 to 10400 after packaging. The packaged resonator has a linear frequency-temperature (f-T) characteristic in a temperature range between 0℃ and 100℃. And the package shows favorable long-term stability of the Q-factor over 200 days, which indicates that the package has excellent hermeticity. Furthermore, the average shear strength is measured to be 43.58 MPa among 10 samples.

In this paper, an active optics and co-focus experimental system of segmented mirror is built. Firstly, a support structure of segmented mirror is designed and it is verified by simulation to meet the requirement for the experimental system of segmented mirror. In this system, the large de-focus and tilt/tip errors of the segmented mirror are adjusted by observing the density and contrast of interference fringes based on isoclinic interference theory until the defocus and tilt/tip errors are in the detective range of the Shack-Hartmann. Then, the Shack-Hartmann is used to measure them and they are adjusted by actuators. The actuators are controlled by active optics to realize the closed-loop adjustment and maintenance for fine co-focus of segmented mirror. And the interference fringes are utilized to verify the detective precision of Shack-Hartmann. After the co-focus fine-tuning of the segmented mirror, the tilt/tip residual surface error is better than 0.01λ RMS; the defocus residual surface error is better than 0.01λ RMS.

SPECIAL TOPIC—Non-equilibrium phenomena in soft matters

Due to the dependence of the chemical and physical properties of the bimetallic nanoparticles (NPs) on their structures, a fundamental understanding of their structural characteristics is crucial for their syntheses and wide applications. In this article, a systematical atomic-level investigation of Au-Pd bimetallic NPs is conducted by using the improved particle swarm optimization (IPSO) with quantum correction Sutton-Chen potentials (Q-SC) at different Au/Pd ratios and different sizes. In the IPSO, the simulated annealing is introduced into the classical particle swarm optimization (PSO) to improve the effectiveness and reliability. In addition, the influences of initial structure, particle size and composition on structural stability and structural features are also studied. The simulation results reveal that the initial structures have little effects on the stable structures, but influence the converging rate greatly, and the convergence rate of the mixing initial structure is clearly faster than those of the core-shell and phase structures. We find that the Au-Pd NPs prefer the structures with Au-rich in the outer layers while Pd-rich in the inner ones. Especially, when the Au/Pd ratio is 6:4, the structure of the nanoparticle (NP) presents a standardized Pd_{core}Au_{shell} structure.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Carlo method is used to solve the problem of the optical surface with roughness in the proposed scheme. Moreover, the defect particles are observed as periodic particles for a more complex situation. In order to obtain the scattering contribution of defects inside the optical surface, a difference radar cross section is added into the model to analyze the selected calculations on the effects of numbers, separation distances, different depths and different materials of defects. The effects of different incident angles are also discussed. The numerical results are analyzed in detail to demonstrate the best position to find the defects in the optical surface by detecting in steps of a fixed degree for the incident angle.

The entangled orbital angular momentum (OAM) three photons propagating in Kolmogorov weak turbulence are investigated. Here, the single phase screen model is used to study the entanglement evolution of OAM photons. The results indicate that the entangled OAM three-qubit state with higher OAM modes will be more robust against turbulence. Furthermore, it is found that the entangled OAM three-qubit state has a higher overall transmission for small OAM values.

The coherent population trapping (CPT) phenomenon has found widespread application in quantum precision measurements. Various designs based on the narrow resonant spectrum corresponding to the linear Zeeman effect have been demonstrated to achieve high performance. In this article, the nonlinear Zeeman split of the CPT spectrum of ^{87}Rb in the lin||lin setup is investigated. We observe re-split phenomenon for both magnetic sensitive and magnetic insensitive CPT resonant lines at a large magnetic field. The re-split in the magnetic sensitive lines raises a practical problem to magnetometers worked in the lin||lin setup while the other one shows a good potential for applications in large magnetic field. We propose a design based on the nonlinear split of the magnetic insensitive lines and test its performance. It provides a much larger measurement range compared to the linear one, offering an option for atomic magnetometers where a large dynamic range is preferred.

The thermal stability of a vertical-cavity surface-emitting laser (VCSEL) array is enhanced by redesigning the mesa arrangement. Based on a thermoelectric coupling three-dimensional (3D) finite-element model, an optimized VCSEL array is designed. The effects of this optimization are studied experimentally. Power density characteristics of VCSEL arrays with different mesa configuration are obtained under different thermal stress in which the optimized device shows improved performance. Optimized device also shows better stability from measured spectra and calculated thermal resistances. The experimental results prove that our simulation model and optimization is instructive for VCSEL array design.

Cascaded fiber geometry with the dispersion of each fiber decreasing is proposed to enhance the multiple four-wave mixing (FWM) generation. The first fiber with relatively large dispersion initiates and accelerates the expansion of multiple FWM, and the second fiber with small dispersion would allow the phase-matching process (thus the spectrum broadening) to keep going. Numerical and experimental results show that with this geometry not only multiple FWM expansion can be accelerated, but also the efficiency of multiple FWM products can be effectively improved with shorter fibers.

We investigate theoretically and numerically the evolutions of optical pulses in the time domain due to modulation instability (MI), where CW pump accompanied with a probe is used as the input of nonlinear fiber. As the fiber length increases, we show that it exhibits beat frequency between the pump and the probe first when the probe lies outside the MI resonance region, and then gradually transforms into a pulse train resulting from spontaneous MI rather than induced MI. However, the regular pulse train is easier to generate in the whole fiber if the probe exists in MI resonance region, and the period of the pulse train is inversely proportional to the frequency spacing between the pump and the probe. It is emphasized that the pulse period can be adjusted only when the probe is in MI resonance region. The numerical simulations are in agreement with the theoretical results. The obtained results are guidable for generating and manipulating the optical pulse train in the fiber.

A novel wavelength modulation spectroscopy sensor for studying gas properties near 1.4 μm is developed, validated and used in a direct-connect supersonic combustion test facility. In this sensor there are two H_{2}O transitions near 7185.60 cm^{-1} and 7454.45 cm^{-1} that are used to enable the measurements along the line-of-sight. According to an iterative algorithm, the gas pressure, temperature and species mole fraction can be measured simultaneously. The new sensor is used in the isolator and extender of the supersonic combustion test facility. In the isolator, the sensor resolves the transient and measured pressure, temperature and H_{2}O mole fraction with accuracies of 2.5%, 8.2%, and 7.2%, respectively. Due to the non-uniform characteristic in the extender, the measured results cannot precisely characterize gas properties, but they can qualitatively describe the distinctions of different zones or the changes or fluctuations of the gas parameters.

The third harmonic generation (THG) of a linear cavity Ti:sapphire regenerative amplifier by use of a K_{3}B_{6}O_{10}Cl (KBOC) crystal is studied for the first time. Output power up to 5.9 mW is obtained at a central wavelength of 263 nm, corresponding to a conversion efficiency of 4.5% to the second harmonic power. Our results show a tremendous potential for nonlinear frequency conversion into the deep ultraviolet range with the new crystal and the output laser power can be further improved.

With the method of replacing the surface layer of photonic crystal with tubes, a novel photonic crystal composite structure used as a tunable surface mode waveguide is designed. The tubes support tunable surface states. The tunable propagation capabilities of the structure are investigated by using the finite-difference time-domain. Simulation results show that the beam transmission distributions of the composite structure are sensitive to the frequency range of incident light and the surface morphology which can be modified by filling the tubes with different organic liquids. By adjusting the filler in tubes, the T-shaped, Y-shaped, and L-shaped propagations can be realized. The property can be applied to the tunable surface mode waveguide. Compared with a traditional single function photonic crystal waveguide, our designed structure not only has a small size, but also is a tunable device.

Hyperthermia has proven to be beneficial to treating superficial malignancies, particularly chest wall recurrences of breast cancer. During hyperthermia, monitoring the time-temperature profiles in the target and surrounding areas is of great significance for the effect of therapy. An ultrasound-based temperature imaging method has advantages over other approaches. When the temperature around the tumor is calculated by using the propagation speed of ultrasound, there always exist overshoot artifacts along the boundary between different tissues. In this paper, we present a new method combined with empirical mode decomposition (EDM), similarity constraint, and continuity constraint to optimize the temperature images. Simulation and phantom experiment results compared with those from our previously proposed method prove that the EMD-based method can build a better temperature field image, which can adaptively yield better temperature images with less computation for assistant medical treatment control.

An experimental system based on the background-oriented schlieren (BOS) technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient. The cross-correlation algorithm with sub-pixel accuracy is introduced and used to calculate the background-element displacement of a disturbed image and a fourth-order difference scheme is also developed to solve the Poisson equation. An experiment for a disturbed flow field caused by a burning candle is performed to validate the built BOS system and the results indicate that density and temperature distribution of the disturbed flow field can be reconstructed accurately. A notable conclusion is that in order to make the reconstructed results have a satisfactory accuracy, the inquiry step length should be less than the size of the interrogation window.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

The quantum molecular dynamics based on the density functional theory has been adopted to simulate the equation of state for the shock compressed lithium. In contrary to some earlier experimental measurement and theoretical simulation, there is not any evidence of the ‘kink’ in the Hugoniot curve in our accurate simulation. Throughout the shock compression process, only a simple solid-to-liquid melting behavior is demonstrated, instead of complicated solid-solid phase transitions. Moreover, the x-ray absorption near-edge spectroscopy has been predicted as a feasible way to diagnose the structural evolution of warm dense lithium in this density region.

Using the trans-neut module of the BOUT++ code, we study how the fueling penetration depth of supersonic molecular beam injection (SMBI) is affected by plasma density and temperature profiles. The plasma densities and temperatures in L-mode are initialized to be a set of linear profiles with different core plasma densities and temperatures. The plasma profiles are relaxed to a set of steady states with different core plasma densities or temperatures. For a fixed gradient, the steady profiles are characterized by the core plasma density and temperature. The SMBI is investigated based on the final steady profiles with different core plasma densities or temperatures. The simulated results suggest that the SMB injection will be blocked by dense core plasma and high-temperature plasma. Once the core plasma density is set to be N_{i0}=1.4N_{0} (N_{0}=1×10^{19} m^{-3}) it produces a deeper penetration depth. When N_{i0} is increased from 1.4N_{0} to 3.9N_{0} at intervals of 0.8N_{0}, keeping a constant core temperature of T_{e0}=725 eV at the radial position of ψ=0.65}, the penetration depth gradually decreases. Meanwhile, when the density is fixed at N_{i0}=1.4N_{0} and the core plasma temperature T_{e0} is set to 365 eV, the penetration depth increases. The penetration depth decreases as T_{e0} is increased from 365 eV to 2759 eV. Sufficiently large N_{i0} or T_{e0} causes most of the injected molecules to stay in the scrape-off-layer (SOL) region, lowering the fueling efficiency.

For the sake of investigating the drift coherent vortex structure in an inhomogeneous dense dusty magnetoplasma, using the quantum hydrodynamic model a nonlinear controlling equation is deduced when the collision effect is considered. New vortex solutions of the electrostatic potential are obtained by a special transformation method, and three evolutive cases of monopolar vortex chains with spatial and temporal distribution are analyzed by representative parameters. It is found that the collision frequency, particle density, drift velocity, dust charge number, electron Fermi wavelength, quantum correction, and quantum parameter are all influencing factors of the vortex evolution. Compared to the uniform dusty system, the vortex solutions of the inhomogeneous system present richer spatial evolution and physical meaning. These results may explain corresponding vortex phenomena and support beneficial references for the dense dusty plasma atmosphere.

In order to generate high quality ion beams through the stable radiation pressure acceleration (RPA) of the near critical density (NCD) target, we propose a new type of target where an ultra-thin high density (HD) layer is attached to the front surface of an NCD target, which has a preferable self-supporting property in the RPA experiments than the ultra-thin foil target. It is found that in one-dimensional particle-in-cell (PIC) simulation, by the block of the HD layer in the new target, there emerges the hole-boring process rather than propagation in the NCD layer when the intense laser pulse impinges on this target. As a result, a typical RPA structure that the compressed electron layer overlaps the ion layer as a whole is formed and a high quality ion beam is obtained, e.g., a circularly polarized laser pulse with normalized amplitude a_{0}=120 impinges on this new target and a 1.2 GeV monoenergetic ion beam is generated through the RPA of the NCD layer. Similar results are also found in the two-dimensional PIC simulation.

This paper reports a novel analytic model of this multichannel spark discharge, considering the delay time in the breakdown process, the electric transforming of the discharge channel from a capacitor to a resistor induced by the air breakdown, and the varying plasma resistance in the discharge process. The good agreement between the experimental and the simulated results validated the accuracy of this model. Based on this model, the influence of the circuit parameters on the maximum discharge channel number (MDCN) is investigated. Both the input voltage amplitude and the breakdown voltage threshold of each discharge channel play a critical role. With the increase of the input voltage and the decrease of the breakdown voltage, the MCDN increases almost linearly. With the increase of the discharge capacitance, the MDCN first rises and then remains almost constant. With the increase of the circuit inductance, the MDCN increases slowly but decreases quickly when the inductance increases over a certain value. There is an optimal value of the capacitor connected to the discharge channel corresponding to the MDCN. Finally, based on these results, to shorten the discharge time, a modified multichannel discharge circuit is developed and validated by the experiment. With only 6-kV input voltage, 31-channels discharge is achieved. The breakdown voltage of each electrode gap is larger than 3 kV. The modified discharge circuit is certain to be widely used in the PSJA flow control field.

Vertical displacement event (VDE) is a big challenge to the existing tokamak equipment and that being designed. As a Chinese next-step tokamak, the Chinese Fusion Engineering Test Reactor (CFETR) has to pay attention to the VDE study with full-fledged numerical codes during its conceptual design. The tokamak simulation code (TSC) is a free boundary time-dependent axisymmetric tokamak simulation code developed in PPPL, which advances the MHD equations describing the evolution of the plasma in a rectangular domain. The electromagnetic interactions between the surrounding conductor circuits and the plasma are solved self-consistently. The TokSys code is a generic modeling and simulation environment developed in GA. Its RZIP model treats the plasma as a fixed spatial distribution of currents which couple with the surrounding conductors through circuit equations. Both codes have been individually used for the VDE study on many tokamak devices, such as JT-60U, EAST, NSTX, DIII-D, and ITER. Considering the model differences, benchmark work is needed to answer whether they reproduce each other's results correctly. In this paper, the TSC and TokSys codes are used for analyzing the CFETR vertical instability passive and active controls design simultaneously. It is shown that with the same inputs, the results from these two codes conform with each other.

The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period-n discharge becomes more and more unstable with the increase of n. The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied. It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation.

The effect of driving frequency on the structure of silicon grown on Ag (111) film is investigated, which was prepared by using the very-high-frequency (VHF) (40.68 MHz and 60 MHz) magnetron sputtering. The energy and flux density of the ions impinging on the substrate are also analyzed. It is found that for the 60-MHz VHF magnetron sputtering, the surface of silicon on Ag (111) film exhibits a small cone structure, similar to that of Ag (111) film substrate, indicating a better microstructure continuity. However, for the 40.68-MHz VHF magnetron sputtering, the surface of silicon on Ag (111) film shows a hybrid structure of hollowed-cones and hollowed-particles, which is completely different from that of Ag (111) film. The change of silicon structure is closely related to the differences in the ion energy and flux density controlled by the driving frequency of sputtering.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Fe-based metallic glasses (MGs) with excellent soft magnetic properties are applicable in a wide range of electronic industry. We show that the cryogenic thermal cycle has a sensitive effect on soft magnetic properties of Fe_{78}Si_{9}B_{13} glassy ribbon. The values of magnetic induction (or magnetic flux density) B and coercivity H_{c} show fluctuation with increasing number of thermal cycles. This phenomenon is explained as thermal-cycle-induced stochastically structural aging or rejuvenation which randomly fluctuates magnetic anisotropy and, consequently, the magnetic induction and coercivity. Overall, increasing the number of thermal cycles improves the soft magnetic properties of the ribbon. The results could help understand the relationship between relaxation and magnetic property, and the thermal cycle could provide an effective approach to improving performances of metallic glasses in industry.

A fluorescent probe for the sensitive and selective determination of copper ion (Cu^{2+}) is presented. It is based on the use of tungsten disulfide quantum dots (WS_{2} QDs) which is independent of the pH of solution and emits strong blue fluorescence. Copper ions could cause aggregation of the WS_{2} QDs and lead to fluorescence quenching of WS_{2} QDs. The change of fluorescence intensity is proportional to the concentration of Cu^{2+}, and the limit of detection is 0.4 μM. The fluorescent probe is highly selective for Cu^{2+} over some potentially interfering ions. These results indicate that WS_{2} QDs, as a fluorescent sensing platform, can meet the selective requirements for biomedical and environmental application.

The electronic structure and thermoelectric (TE) properties of Mg_{2}Ge_{x}Sn_{1-x} (x=0.25, 0.50, 0.75) solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure (SQS) is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results. The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor (PF) plays an important role. These values are higher than those of pure Mg_{2}Sn and Mg_{2}Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg_{2}Ge_{0.25}Sn_{0.75} at 800 K. The results suggest that the n-type Mg_{2}Ge_{x}Sn_{1-x} solid solutions are promising mid-temperature TE materials.

The first-principles methods have been employed to calculate the structural, electronic, and mechanical properties of the α, β, and γ phases of uranium under pressure up to 100 GPa. The electronic structure has been viewed in forms of density of states and band structure. The mechanical stability of metal U in the α, β, and γ phases have been examined. The independent elastic constants, polycrystalline elastic moduli, as well as Poisson's ratio have been obtained. Upon compression, the elastic constants, elastic moduli, elastic wave velocities, and Debye temperature of α phase are enhanced pronouncedly. The value of B/G illustrates that α and γ phases are brittle in ground state.

The systematic investigations of the mechanical, elastic, and electronic properties, and stability of the newly synthesized monoclinic C2/m-Ca_{2}C_{3} are performed, based on the first-principles calculations. Ca_{2}C_{3} is found to be mechanically and dynamically stable only from 0 GPa to 24 GPa. The elastic anisotropy studies show that Ca_{2}C_{3} exhibits the elastic anisotropy increasing with the augment of pressure. Furthermore, using the HSE06 hybrid functional, the electronic properties of Ca_{2}C_{3} under pressure are calculated. The structure can be regarded as a quasi-direct band gap semiconductor, and the pressure-induced direct-indirect band gap transition is studied in detail.

In this work, the effect of uniaxial strain on electronic and thermoelectric properties of magnesium silicide using density functional theory (DFT) and Boltzmann transport equations has been studied. We have found that the value of band gap increases with tensile strain and decreases with compressive strain. The variations of electrical conductivity, Seebeck coefficient, electronic thermal conductivity, and power factor with temperatures have been calculated. The Seebeck coefficient and power factor are observed to be modified strongly with strain. The value of power factor is found to be higher in comparison with the unstrained structure at 2% tensile strain. We have also calculated phonon dispersion, phonon density of states, specific heat at constant volume, and lattice thermal conductivity of material under uniaxial strain. The phonon properties and lattice thermal conductivity of Mg_{2}Si under uniaxial strain have been explored first time in this report.

We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO_{2}/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope (4P-STM). The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

The structural and magnetic properties of Fe_{80}P_{9}B_{11} amorphous alloy are investigated through ab initio molecular dynamic simulation. The structure evolution of Fe_{80}P_{9}B_{11} amorphous alloy can be described in the framework of topological fluctuation theory, and the fluctuation of atomic hydrostatic stress gradually decreases upon cooling. The left sub peak of the second peak of Fe-B partial pair distribution functions (PDFs) becomes pronounced below the glass transition temperature, which may be the major reason why B promotes the glass formation ability significantly. The magnetization mainly originates from Fe 3d states, while small contribution results from metalloid elements P and B. This work may be helpful for developing Fe-based metallic glasses with both high saturation flux density and glass formation ability.

We have systematically studied the behaviors of the resistivity and magnetization of CeSb_{2} single crystals as a function of temperature and external field. Four anomalies in the resistivity/magnetization-versus-temperature curves are observed at low magnetic field. They are located at 15.5 K, 11.5 K, 9.5 K, and 6.5 K, corresponding to the paramagnetic-magnetically ordered state (MO), MO-antiferromagnetic (AFM), AFM-AFM, and AFM-ferromagnetic (FM) transitions, respectively. The anomaly at 9.5 K is only visible with H||[010] by magnetic susceptibility measurements, indicating that the AFM-AFM transition only happens along[010] direction in ab-plane. The four magnetic transitions are strongly suppressed by high external field. Finally, the field-temperature phase diagrams of CeSb_{2} with different orientations of the applied field in ab-plane are constructed and indicate the highly anisotropic nature of the magnetization of CeSb_{2}.

Based on the density functional theory, the influences of strain on structural, elastic, thermal and optical properties of CuGaTe_{2} are discussed in detail. It is found that the tensile strain on CuGaTe_{2} is beneficial to the decrease of lattice thermal conductivity by reducing the mean sound velocity and Debye temperature. Moreover, all strained and unstrained CuGaTe_{2} exhibit rather similar optical characters. But the tensile strain improves the ability to absorb sunlight in the visible range. These research findings can give hints for designing thermoelectric and photovoltaic devices.

Using Fe, Co or Ni chains as electrodes, we designed several annulene-based molecular spintronic devices and investigated the quantum transport properties based on density functional theory and non-equilibrium Green's function method. Our results show that these devices have outstanding spin-filter capabilities and exhibit giant magnetoresistance effect, and that with Ni chains as electrodes, the device has the best transport properties. Furthermore, we investigated the spin-polarized optoelectronic properties of the device with Ni electrodes and found that the spin-polarized photocurrents can be directly generated by irradiating the device with infrared, visible or ultraviolet light. More importantly, if the magnetization directions of the two electrodes are antiparallel, the photocurrents with different spins are spatially separated, appearing at different electrodes. This phenomenon provides a new way to simultaneously generate two spin currents.

The transport study of graphene based junctions has become one of the focuses in graphene research. There are two stacking configurations for monolayer-bilayer-monolayer graphene planar junctions. One is the two monolayer graphene contacting the same side of the bilayer graphene, and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene. In this paper, according to the Landauer-Büttiker formula, we study the transport properties of these two configurations. The influences of the local gate potential in each part, the bias potential in bilayer graphene, the disorder and external magnetic field on conductance are obtained. We find the conductances of the two configurations can be manipulated by all of these effects. Especially, one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene. The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment.

Flexible electrically pumped random laser (RL) based on ZnO nanowires is demonstrated for the first time to our knowledge. The ZnO nanowires each with a length of 5 μm and an average diameter of 180 nm are synthesized on flexible substrate (ITO/PET) by a simple hydrothermal method. No obvious visible defect-related-emission band is observed in the photoluminescence (PL) spectrum, indicating that the ZnO nanowires grown on the flexible ITO/PET substrate have few defects. In order to achieve electrically pumped random lasing with a lower threshold, the metal-insulator-semiconductor (MIS) structure of Au/SiO_{2}/ZnO on ITO/PET substrate is fabricated by low temperature process. With sufficient forward bias, the as-fabricated flexible device exhibits random lasing, and a low threshold current of ~11.5 mA and high luminous intensity are obtained from the ZnO-based random laser. It is believed that this work offers a case study for developing the flexible electrically pumped random lasing from ZnO nanowires.

Recently, modifications of charge density wave (CDW) in two-dimensional (2D) show intriguing properties in quasi-2D materials such as layered transition metal dichalcogenides (TMDCs). Optical, electrical transport measurements and scanning tunneling microscopy uncover the enormous difference on the many-body states when the thickness is reduced down to monolayer. However, the CDW in quasi-one-dimensional (1D) materials like transition metal trichalcogenides (TMTCs) is yet to be explored in low dimension whose mechanism is likely distinct from their quasi-2D counterparts. Here, we report a systematic study on the CDW properties of titanium trisulfide (TiS_{3}). Two phase transition temperatures were observed to decrease from 53 K (103 K) to 46 K (85 K) for the bulk and <15-nm thick nanoribbon, respectively, which arises from the increased fluctuation effect across the chain in the nanoribbon structure, thereby destroying the CDW coherence. It also suggests a strong anisotropy of CDW states in quasi-1D TMTCs which is different from that in TMDCs. Remarkably, by using back gate of -30 V~70 V in 15-nm device, we can tune the second transition temperature from 110 K (at -30 V) to 93 K (at 70 V) owing to the altered electron concentration. Finally, the optical approach through the impinging of laser beams on the sample surface is exploited to manipulate the CDW transition, where the melting of the CDW states shows a strong dependence on the excitation energy. Our results demonstrate TiS_{3} as a promising quasi-1D CDW material and open up a new window for the study of collective phases in TMTCs.

Phase H (MgSiO_{4}H_{2}), one of the dense hydrous magnesium silicates (DHMSs), is supposed to be vital to transporting water into the lower mantle. Here the crystal structure, elasticity and Raman vibrational properties of the two possible structures of phase H with Pm and P2/m symmetry under high pressures are evaluated by first-principles simulations. The cell parameters, elastic and Raman vibrational properties of the Pm symmetry become the same as the P2/m symmetry at~30 GPa. The symmetrization of hydrogen bonds of the Pm symmetry at~30 GPa results in this structural transformation from Pm to P2/m. Seismic wave velocities of phase H are calculated in a range from 0 GPa to 100 GPa and the results testify the existence and stability of phase H in the lower mantle. The azimuthal anisotropies for phase H are A_{P0}=14.7%, A_{S0}=21.2% (P2/m symmetry) and A_{P0}=16.4%, A_{S0}=27.1% (Pm symmetry) at 0 GPa, and increase to A_{P30}=17.9%, A_{S30}=40.0% (P2/m symmetry) and A_{P30}=19.2%, A_{S30}=37.8% (Pm symmetry) at 30 GPa. The maximum V_{P} direction for phase H is[101] and the minimum direction is[110]. The anisotropic results of seismic wave velocities imply that phase H might be a source of seismic anisotropy in the lower mantle. Furthermore, Raman vibrational modes are analyzed to figure out the effect of symmetrization of hydrogen bonds on Raman vibrational pattern and the dependence of Raman spectrum on pressure. Our results may lead to an in-depth understanding of the stability of phase H in the mantle.

Using scanning tunneling spectroscopy, we studied the transition from tunneling regime to local point contact on the iron-based superconductor Ba_{0.6}K_{0.4}Fe_{2}As_{2}. By gradually reducing the junction resistance, a series of spectra were obtained with the characteristics evolving from single-particle tunneling into Andreev reflection. The spectra can be well fitted to the modified Blonder-Tinkham-Klapwijk (BTK) model and exhibit significant changes of both spectral broadening and orbital selection due to the formation of point contact. The spatial resolution of the point contact was estimated to be several nanometers, providing a unique way to study the inhomogeneity of unconventional superconductors on such a scale.

By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz-Thouless (KT) transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin-1 Kondo effect is realized. While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the Rayleigh-Schrödinger perturbation theory is used.

In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La_{1-x}Pr_{x}Fe_{11.4}Si_{1.6}H_{y} hydrides. The powder x-ray diffraction patterns of the La_{1-x}Pr_{x}Fe_{11.4}Si_{1.6} and its hydrides show that each of the alloys is crystallized into the single phase of cubic NaZn_{13}-type structure. There are hydrogen-absorbing plateaus under 0.4938 MPa and 0.4882 MPa in the absorbing curves for the La_{0.8}Pr_{0.2}Fe_{11.4}Si_{1.6} and La_{0.6}Pr_{0.4}Fe_{11.4}Si_{1.6} compounds. The releasing processes lag behind the absorbing process, which is obviously different from the coincidence between absorbing and releasing curves of the LaFe_{11.4}Si_{1.6} compound. The remnant hydrogen content for La_{0.6}Pr_{0.4}Fe_{11.4}Si_{1.6} is significantly more than that for La_{0.8}Pr_{0.2}Fe_{11.4}Si_{1.6} after hydrogen desorption, indicating that more substitutions of Pr for La are beneficial to retaining more hydrogen atoms in the alloys. The values of maximum magnetic entropy change are 14.91 J/kg·K and 17.995 J/kg·K for La_{0.8}Pr_{0.2}Fe_{11.4}Si_{1.6}H_{0.13} and La_{0.6}Pr_{0.4}Fe_{11.4}Si_{1.6}H_{0.87}, respectively.

The magnetic property in a material is induced by the unpaired electrons. This can occur due to defect states which can enhance the magnetic moment and the spin polarization. In this report, CdS and CdTe thin films are grown on FTO glass substrates by chemical bath deposition and close-spaced sublimation, respectively. The magnetic properties, which are introduced from oxygen states, are found in CdS and CdTe thin films. From the hysteresis loop of magnetic moment it is revealed that CdS and CdTe thin films have different kinds of magnetic moments at different temperatures. The M-H curves indicate that from 100 K to 350 K, CdS and CdTe thin films show paramagnetism and diamagnetism, respectively. A superparamagnetic or a weakly ferromagnetic response is found at 5 K. It is also observed from ZFC/FC curves that magnetic moments decrease with temperature increasing. Spin polarized density functional calculation for spin magnetic moment is also carried out.

A comparative study of two kinds of oxidants (H_{2}O and O_{3}) with the combination of two metal precursors (TMA and La(^{i}PrCp)_{3}) for atomic layer deposition (ALD) La_{2}O_{3}/Al_{2}O_{3} nanolaminates is carried out. The effects of different oxidants on the physical properties and electrical characteristics of La_{2}O_{3}/Al_{2}O_{3} nanolaminates are studied. Initial testing results indicate that La_{2}O_{3}/Al_{2}O_{3} nanolaminates could avoid moisture absorption in the air after thermal annealing. However, moisture absorption occurs in H_{2}O-based La_{2}O_{3}/Al_{2}O_{3} nanolaminates due to the residue hydroxyl/hydrogen groups during annealing. As a result, roughness enhancement, band offset variation, low dielectric constant and poor electrical characteristics are measured because the properties of H_{2}O-based La_{2}O_{3}/Al_{2}O_{3} nanolaminates are deteriorated. Addition thermal annealing effects on the properties of O_{3}-based La_{2}O_{3}/Al_{2}O_{3} nanolaminates indicate that O_{3} is a more appropriate oxidant to deposit La_{2}O_{3}/Al_{2}O_{3} nanolaminates for electron devices application.

As a low-bandgap ferroelectric material, BiFeO_{3} has gained wide attention for the potential photovoltaic applications, since its photovoltaic effect in visible light range was reported in 2009. In the present work, Bi(Fe, Mn)O_{3} thin films are fabricated by pulsed laser deposition method, and the effects of Mn doping on the microstructure, optical, leakage, ferroelectric and photovoltaic characteristics of Bi(Fe, Mn)O_{3} thin films are systematically investigated. The x-ray diffraction data indicate that Bi(Fe, Mn)O_{3} thin films each have a rhombohedrally distorted perovskite structure. From the light absorption results, it follows that the band gap of Bi(Fe, Mn)O_{3} thin films can be tuned by doping different amounts of Mn content. More importantly, photovoltaic measurement demonstrates that the short-circuit photocurrent density and the open-circuit voltage can both be remarkably improved through doping an appropriate amount of Mn content, leading to the fascinating fact that the maximum power output of ITO/BiFe_{0.7}Mn_{0.3}O_{3}/Nb-STO capacitor is about 175 times higher than that of ITO/BiFeO_{3}/Nb-STO capacitor. The improvement of photovoltaic response in Bi(Fe, Mn)O_{3} thin film can be reasonably explained as being due to absorbing more visible light through bandgap engineering and maintaining the ferroelectric property at the same time.

A polyvinylidene-fluoride (PVDF)-based magnetoelectric torque (MET) device is designed with elastic layer sandwiched by PVDF layers, and low-frequency MET effect is carefully studied. It is found that elastic modulus and thickness of the elastic layer have great influences on magnetoelectric (ME) voltage coefficient (α_{ME}) and working range of frequency in PVDF-based MET device. The decrease of the modulus and thickness can help increase the α_{ME}. However, it can also reduce the working range in the low frequency. By optimizing the parameters, the giant α_{ME} of 320 V/cm·Oe (1 Oe=79.5775 A·m^{-1}) at low frequency (1 Hz) can be obtained. The present results may help design PVDF-based MET low-frequency magnetic sensor with improved magnetic sensitivity in a relative large frequency range.

The quartz crystal microbalance (QCM) is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey's and Kanazawa's theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.

One of the peculiar phenomenons in non-zero magnetic resonance magnetometer is that, with the increase of the temperature, the magnetic resonance linewidth is narrowed at first instead of broadened due to the increasing collision rate. The magnetometer usually operates at the narrowest linewidth temperature to obtain the best sensitivity. Here, we explain this phenomenon quantitatively considering the nonlinear of the optical pumping in the cell and did experiments to verify this explanation. The magnetic resonance linewidth is measured using one amplitude-modulated pump laser and one continuous probe laser. The field is along the direction orthogonal to the plane of pump and probe beams. We change the temperature from 53℃ to 93℃ and the pumping light from 0.1 mW to 2 mW. The experimental results agree well with the theoretical calculations.

Angle-resolved polarized Raman (ARPR) spectroscopy can be utilized to assign the Raman modes based on crystal symmetry and Raman selection rules and also to characterize the crystallographic orientation of anisotropic materials. However, polarized Raman measurements can be implemented by several different configurations and thus lead to different results. In this work, we systematically analyze three typical polarization configurations:1) to change the polarization of the incident laser, 2) to rotate the sample, and 3) to set a half-wave plate in the common optical path of incident laser and scattered Raman signal to simultaneously vary their polarization directions. We provide a general approach of polarization analysis on the Raman intensity under the three polarization configurations and demonstrate that the latter two cases are equivalent to each other. Because the basal plane of highly ordered pyrolytic graphite (HOPG) exhibits isotropic feature and its edge plane is highly anisotropic, HOPG can be treated as a modelling system to study ARPR spectroscopy of two-dimensional materials on their basal and edge planes. Therefore, we verify the ARPR behaviors of HOPG on its basal and edge planes at three different polarization configurations. The orientation direction of HOPG edge plane can be accurately determined by the angle-resolved polarization-dependent G mode intensity without rotating sample, which shows potential application for orientation determination of other anisotropic and vertically standing two-dimensional materials and other materials.

Localized surface electromagnetic resonances in spherical nanoparticles with gain are investigated by using the Mie theory. Due to the coupling between the gain and resonances, super scattering phenomenon is raised and the total scattering efficiency is increased by over six orders of magnitude. The dual frequency resonance induced by the electric dipole term of the particle is observed. The distributions of electromagnetic field and the Poynting vector around nanoparticles are provided for better understanding different multipole resonances. Finally, the scattering properties of active spherical nanoparticles are investigated when the sizes of nanoparticles are beyond the quasi-static limit. It is noticed that more high-order multipole resonances can be excited with the increase of the radius. Besides, all resonances dominated by multipole magnetic terms can only appear in dielectric materials.

Colloidal ZnAgInSe (ZAISe) quantum dots (QDs) with different particle sizes were obtained by accommodating the reaction time. In the previous research, photoluminescence (PL) of ZAISe QDs only could be tuned by changing the composition. In this work the size-tunable photoluminescence was observed successfully. The red shift in the photoluminescence spectra was caused by the quantum confinement effect. The time-resolved photoluminescence indicated that the luminescence mechanisms of the ZAISe QDs were contributed by three recombination processes. Furthermore, the temperature-dependent PL spectra were investigated. We verified the regular change of temperature-dependent PL intensity, peak energy, and the emission linewidth of broadening for ZAISe QDs. According to these fitting data, the activation energy (ΔE) of ZAISe QDs with different nanocrystal sizes was obtained and the stability of luminescence was discussed.

Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo_{2}C heterostructure by using chemical vapor deposition (CVD). The composition and structure of the heterostructure are characterized through energy-dispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo_{2}C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

GaN micro-pyramids with AlGaN capping layer are grown by selective metal-organic-vapor phase epitaxy (MOVPE). Compared with bare GaN micro-pyramids, AlGaN/GaN micro-pyramids show wrinkling morphologies at the bottom of the structure. The formation of those special morphologies is associated with the spontaneously formed AlGaN polycrystalline particles on the dielectric mask, owing to the much higher bond energy of Al-N than that of Ga-N. When the sizes of the polycrystalline particles are larger than 50 nm, the uniform source supply behavior is disturbed, thereby leading to unsymmetrical surface morphology. Analysis reveals that the scale of surface wrinkling is related to the migration length of Ga adatoms along the AlGaN {1101} facet. The migration properties of Al and Ga further affect the distribution of Al composition along the sidewalls, characterized by the μ-PL measurement.

In order to synthesize high-quality type-IIa large diamond, the selection of catalyst is very important, in addition to the nitrogen getter. In this paper, type-IIa large diamonds are grown under high pressure and high temperature (HPHT) by using the temperature gradient method (TGM), with adopting Ti/Cu as the nitrogen getter in Ni_{70}Mn_{25}Co_{5} (abbreviated as NiMnCo) or Fe_{55}Ni_{29}Co_{16} (abbreviated FeNiCo) catalyst. The values of nitrogen concentration (N_{c}) in both synthesized high-quality diamonds are less than 1 ppm, when Ti/Cu (1.6 wt%) is added in the FeNiCo or Ti/Cu (1.8 wt%) is added in the NiMnCo. The difference in solubility of nitrogen between both catalysts at HPHT is the basic reason for the different effect of Ti/Cu on eliminating nitrogen. The nitrogen-removal efficiency of Ti/Cu in the NiMnCo catalyst is less than in the FeNiCo catalyst. Additionally, a high-quality type-IIa large diamond size of 5.0 mm is obtained by reducing the growth rate and keeping the nitrogen concentration of the diamond to be less than 1 ppm, when Ti/Cu (1.6 wt%) is added in the FeNiCo catalyst.

Two kinds of InAs/GaAs quantum dot (QD) structures are grown by molecular beam epitaxy in formation-dissolution-regrowth method with different in-situ annealing and regrowth processes. The densities and sizes of quantum dots are different for the two samples. The variation tendencies of PL peak energy, integrated intensity, and full width at half maximum versus temperature for the two samples are analyzed, respectively. We find the anomalous temperature dependence of the InAs/GaAs quantum dots and compare it with other previous reports. We propose a new energy band model to explain the phenomenon. We obtain the activation energy of the carrier through the linear fitting of the Arrhenius curve in a high temperature range. It is found that the GaAs barrier layer is the major quenching channel if there is no defect in the material. Otherwise, the defects become the major quenching channel when some defects exist around the QDs.

We investigate the magnesium (Mg) incorporation efficiencies in Mg_{x}Zn_{1-x}O films on c-plane Zn-face ZnO substrates by using metalorganic chemical vapor deposition (MOCVD) technique. In order to deposit high quality Mg_{x}Zn_{1-x}O films, atomically smooth epi-ready surfaces of the hydrothermal grown ZnO substrates are achieved by thermal annealing in O_{2} atmosphere and characterized by atomic force microscope (AFM). The AFM, scanning electron microscope (SEM), and x-ray diffraction (XRD) studies demonstrate that the Mg_{x}Zn_{1-x}O films each have flat surface and hexagonal wurtzite structure without phase segregation at up to Mg content of 34.4%. The effects of the growth parameters including substrate temperature, reactor pressure and VI/II ratio on Mg content in the films are investigated by XRD analysis based on Vegard's law, and confirmed by photo-luminescence spectra and x-ray photoelectron spectroscopy as well. It is indicated that high substrate temperature, low reactor pressure, and high VI/II ratio are good for obtaining high Mg content.

The composite quasi solid state electrolytes (CQSE) is firstly synthesized with quasi solid state electrolytes (QSE) and lithium-ion-conducting material Li_{1.4}Al_{0.4}Ti_{1.6}(PO_{4})_{3} (LATP), and the QSE consists of[LiG4][TFSI] with fumed silica nanoparticles. Compared with LATP, CQSE greatly improves the interface conductance of solid electrolytes. In addition,it has lower liquid volume relative to QSE. Although the liquid volume fraction of CQSE drops to 60%, its conductivity can also reach 1.39×10^{-4} s/cm at 20℃. Linear sweep voltammetry (LSV) is conducted on each composite electrolyte. The results show the possibility that CQSE has superior electrochemical stability up to 5.0 V versus Li/Li^{+1}. TG curves also show that composite electrolytes have higher thermal stability. In addition, the performance of Li/QSE/LiMn_{2}O_{4} cells and Li/CQSE/LiMn_{2}O_{4} is evaluated and shows good electrochemical characteristics at 60℃.

The high pressure and high temperature (HPHT) method is successfully used to synthesize jadeite in a temperature range of 1000℃-1400℃ under a pressure of 3.5 GPa. The initial raw materials are Na_{2}SiO_{3}·9H_{2}O and Al_{2}(SiO_{3})_{3}. Through the HPHT method, the amorphous glass material is entirely converted into crystalline jadeite. We can obtain the good-quality jadeite by optimizing the reaction pressure and temperature. The measurements of x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) and Raman scattering indicate that the properties of synthesized jadeite at 1260℃ under 3.5 GPa are extremely similar to those of the natural jadeite. What is more, the results will be valuable for understanding the formation process of natural jadeite. This work also reveals the mechanism for metamorphism of magma in the earth.

In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.

In this paper a non-iterative technique is developed for the correction of faulty antenna array based on matrix pencil technique (MPT). The failure of a sensor in antenna array can damage the radiation power pattern in terms of sidelobes level and nulls. In the developed technique, the radiation pattern of the array is sampled to form discrete power pattern information set. Then this information set can be arranged in the form of Hankel matrix (HM) and execute the singular value decomposition (SVD). By removing nonprincipal values, we obtain an optimum lower rank estimation of HM. This lower rank matrix corresponds to the corrected pattern. Then the proposed technique is employed to recover the weight excitation and position allocations from the estimated matrix. Numerical simulations confirm the efficiency of the proposed technique, which is compared with the available techniques in terms of sidelobes level and nulls.

RecQ5β is an essential DNA helicase in humans, playing important roles in DNA replication, repair, recombination and transcription. The unwinding activity and substrate specificity of RecQ5β is still elusive. Here, we used stopped-flow kinetic method to measure the unwinding and dissociation kinetics of RecQ5β with several kinds of DNA substrates, and found that RecQ5β could well unwind ss/dsDNA, forked DNA and Holiday junction, but was compromised in unwinding blunt DNA and G-quadruplex. Rec5β has the preferred unwinding specificity for certain DNA substrates containing the junction point, which may improve the binding affinity and unwinding activity of RecQ5β. Moreover, from a comparison with the truncated RecQ5β^{1-467}, we discovered that the C-terminal domain might strongly influence the unwinding activity and binding affinity of RecQ5β. These results may shed light on the physiological functions and working mechanisms of RecQ5β helicase.

The minimization of spurious wave reflection is a challenge in multiscale coupling due to the difference of spatial resolution between atomistic and continuum regions. In this study, a new damping condition is presented for eliminating spurious wave reflection at the interface between atomistic and continuum regions. This damping method starts by a coarse-fine decomposition of the atomic velocity based on the bridging scale method. The fine scale velocity of the atoms in the damping region is reduced by applying nonlinear damping coefficients. The effectiveness of this damping method is verified by one-and two-dimensional simulations.

This paper investigates the cooperative formation problem via impulsive control for a class of networked Euler-Lagrange systems. To reduce the energy consumption and communication frequency, the impulsive control method and cooperative formation control approach are combined. With the consideration of system uncertainties and communication delays among agents, neural networks-based adaptive technique is used for the controller design. Firstly, under the constraint that each agent interacts with its neighbors only at some sampling moments, an adaptive neural-networks impulsive formation control algorithm is proposed for the networked uncertain Euler-Lagrange systems without communication delays. Using Lyapunov stability theory and Laplacian potential function in the graph theory, we conclude that the formation can be achieved by properly choosing the constant control gains. Further, when considering communication delays, a modified impulsive formation control algorithm is proposed, in which the extended Halanay differential inequality is used to analyze the stability of the impulsive delayed dynamical systems. Finally, numerical examples and performance comparisons with continuous algorithm are provided to illustrate the effectiveness of the proposed methods.

The dissociation of H_{2} molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to determine the kinetics of the regeneration of the storage material. In this paper, we investigate the hydrogen adsorption and dissociation on Mg-coated B_{12}C_{6}N_{6}. The B_{12}C_{6}N_{6} is an electron deficient fullerene, and Mg atoms can be strongly bound to this cage by donating their valance electrons to the virtual 2p orbitals of carbon in the cluster. The preferred binding sites for Mg atoms are the B_{2}C_{2} tetragonal rings. The positive charge quantity on the Mg atom is 1.50 when a single Mg atom is coated on a B_{2}C_{2} ring. The stable dissociation products are determined and the dissociation processes are traced. Strong orbital interaction between the hydrogen and the cluster occurs in the process of dissociation, and H_{2} molecule can be easily dissociated. We present four dissociation paths, and the lowest energy barrier is only 0.11 eV, which means that the dissociation can take place at ambient temperature.

P-type silicon heterojunction (SHJ) solar cells with a-SiC:H(n) emitters were studied by numerical computer simulation in this paper. The influence of interface states, conduction band offset, and front contact on the performance of a-SiC:H(n)/c-Si(p) SHJ solar cells was investigated systematically. It is shown that the open circuit voltage (V_{oc}) and fill factor (FF) are very sensitive to these parameters. In addition, by analyzing equilibrium energy band diagram and electric field distribution, the influence mechanisms that interface states, conduction band offset, and front contact impact on the carrier transport, interface recombination and cell performance were studied in detail. Finally, the optimum parameters for the a-SiC:H(n)/c-Si(p) SHJ solar cells were provided. By employing these optimum parameters, the efficiency of SHJ solar cell based on p-type c-Si was significantly improved.

We demonstrate a simple and fast post-deposition treatment with high process compatibility on the hole transport material (HTM) Spiro-MeOTAD in vapor-assisted solution processed methylammonium lead triiodide (CH_{3}NH_{3}PbI_{3})-based solar cells. The prepared Co-doped p-type Spiro-MeOTAD films are treated by O_{3} at room temperature for 5 min, 10 min, and 20 min, respectively, prior to the deposition of the metal electrodes. Compared with the traditional oxidation of Spiro-MeOTAD films overnight in dry air, our fast O_{3} treatment of HTM at room temperature only needs just 10 min, and a relative 40.3% increment in the power conversion efficiency is observed with respect to the result of without-treated perovskite solar cells. This improvement of efficiency is mainly attributed to the obvious increase of the fill factor and short-circuit current density, despite a slight decrease in the open-circuit voltage. Ultraviolet photoelectron spectroscopy (UPS) and Hall effect measurement method are employed in our study to determine the changes of properties after O_{3} treatment in HTM. It is found that after the HTM is exposed to O_{3}, its p-type doping level is enhanced. The enhancement of conductivity and Hall mobility of the film, resulting from the improvement in p-doping level of HTM, leads to better performances of perovskite solar cells. Best power conversion efficiencies (PCEs) of 13.05% and 16.39% are achieved with most properly optimized HTM via CH_{3}NH_{3}I vapor-assisted method and traditional single-step method respectively.

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