Cluster algebra structure on the finite dimensional representations of affine quantum group Uq(Â3)
Exact solutions and residual symmetries of the Ablowitz-Kaup-Newell-Segur system
The residual symmetries of the Ablowitz-Kaup-Newell-Segur (AKNS) equations are obtained by the truncated Painlevé analysis. The residual symmetries for the AKNS equations are proved to be nonlocal and the nonlocal residual symmetries are extended to the local Lie point symmetries of a prolonged AKNS system. The local Lie point symmetries of the prolonged AKNS equations are composed of the residual symmetries and the standard Lie point symmetries, which suggests that the residual symmetry method is a useful complement to the classical Lie group theory. The calculation on the symmetries shows that the enlarged equations are invariant under the scaling transformations, the space-time translations, and the shift translations. Three types of similarity solutions and the reduction equations are demonstrated. Furthermore, several types of exact solutions for the AKNS equations are obtained with the help of the symmetry method and the Bäcklund transformations between the AKNS equations and the Schwarzian AKNS equation.
Residual symmetry reductions and interaction solutions of the (2+1)-dimensional Burgers equation
Hybrid natural element method for viscoelasticity problems
A new optical field generated as an output of the displaced Fock state in an amplitude dissipative channel
We propose a new optical field and show that such an optical field can be generated as an output of a displaced Fock state in an amplitude dissipative channel. We derive new generating function formulas and binomial formula involving two-variable Hermite polynomials to reach this result. The photon number average in this new optical field is (m+|α|2)e-2κt, which indicates that controlling the photon number can be realized by adjusting the value of m or |α|2 or κ. The time evolution law of displaced Fock state in a thermo reservoir is thus revealed.
Efficient error estimation in quantum key distribution
In a quantum key distribution (QKD) system, the error rate needs to be estimated for determining the joint probability distribution between legitimate parties, and for improving the performance of key reconciliation. We propose an efficient error estimation scheme for QKD, which is called parity comparison method (PCM). In the proposed method, the parity of a group of sifted keys is practically analysed to estimate the quantum bit error rate instead of using the traditional key sampling. From the simulation results, the proposed method evidently improves the accuracy and decreases revealed information in most realistic application situations.
Disordered quantum walks in two-dimensional lattices
The properties of the two-dimensional quantum walk with point, line, and circle disorders in phase are reported. Localization is observed in the two-dimensional quantum walk with certain phase disorder and specific initial coin states. We give an explanation of the localization behavior via the localized stationary states of the unitary operator of the walker + coin system and the overlap between the initial state of the whole system and the localized stationary states.
Coherent spin dynamics in spin-imbalanced ferromagnetic spinor condensates
Neural adaptive chaotic control with constrained input using state and output feedback
Predictive control of a chaotic permanent magnet synchronous generator in a wind turbine system
Robust output feedback cruise control for high-speed train movement with uncertain parameters
Design and test of the microwave cavity in an optically-pumped Rubidium beam frequency standard
Thermal efficiency of the principal greenhouse gases
Atmospheric gases are ranked according to the efficiency with which they absorb and radiate longwave radiation. The open international HITRAN database of gaseous absorption lines of high resolution together with inverse Fourier transform were used. The autocorrelation functions of the total dipole moment of the basic greenhouse gases molecules such as H2O, CO2, O3, N2O, and CH4 were obtained. Absorption coefficient spectra and emission power spectra of infrared radiation of these gases were calculated. Analysis of the emissive ability of all gases under consideration was carried out. Compared to CO2, all the gases under investigation have more effective emission except ozone. An efficiency criterion of IR absorption and emission is defined and is calculated for each studied gas, and the gases are ranked accordingly as follows (from strong to weak): H2O, CH4, CO2, N2O, and O3.
Progress on accurate measurement of the Planck constant: Watt balance and counting atoms
The Planck constant h is one of the most significant constants in quantum physics. Recently, the precision measurement of the value of h has been a hot issue due to its important role for the establishment of both a new SI and a revised fundamental physical constant system. Up to date, two approaches, the watt balance and counting atoms, have been employed to determine the Planck constant at a level of several parts in 108. In this paper, the principle and progress on precision measurement of the Planck constant using watt balance and counting atoms at national metrology institutes are reviewed. Further improvement in determining the Planck constant and possible developments of a revised physical constant system in future are discussed.
Accurate ab initio-based analytical potential energy function for S2 (ã1Δg) via extrapolation to the complete basis set limit
The potential energy curves (PECs) of the first electronic excited state of S2 (ã1Δg) are calculated employing a multi-reference configuration interaction method with the Davidson correction in combination with a series of correlation-consistent basis sets from Dunning: aug-cc-pVXZ (X=T, Q, 5, 6). In order to obtain PECs with high accuracy, PECs calculated with aug-cc-pV(Q, 5)Z basis sets are extrapolated to the complete basis set limit. The resulting PECs are then fitted to the analytical potential energy function (APEF) using the extended Hartree-Fock approximate correlation energy method. By utilizing the fitted APEF, accurate and reliable spectroscopic parameters are obtained, which are consistent with both experimental and theoretical results. By solving the Schrödinger equation numerically with the APEFs obtained at the AV6Z and the extrapolated AV(Q, 5)Z level of theory, we calculate the complete set of vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants.
Precision frequency measurement of 1S0-3P1 intercombination lines of Sr isotopes
Non-linear spectral splitting of Rydberg sodium in external fields
Lifetimes of Rydberg states of Eu atoms
The radiative lifetimes of the Eu 4f76snp (8PJ or 10PJ) Rydberg states with J=5/2 and 11/2 are investigated with a combination of multi-step laser excitation and pulsed electric field ionization, from which their dependence on the effective principal quantum number is observed. The lifetimes of 21 states are reported along with an evaluation of their experimental uncertainty. The influence of blackbody radiation, due to the oven temperature, on the lifetime of the higher-n states is detected. The non-hydrogen behavior of the investigated states is also observed.
Control of electron localization in the dissociation of H2+ and its isotopes with a THz pulse
Effect of pump-1 laser on Autler–Townes splitting in photoelectron spectrum of K2 molecule
We theoretically investigate the Autler-Townes (AT) splitting in the photoelectron spectrum of four-level ladder K2 molecule driven by a pump 1-pump 2-probe pulse via employing the time-dependent wave packet approach. The effects of the pump-1 laser intensity and wavelength on AT splitting are studied for the first time. The magnitude of AT splitting increases with increasing the pump-1 laser intensity. The triple splitting with asymmetric profile occurs due to the nonresonant excitation. The triple structure is transformed into a double structure (near-resonant region), and then becomes a peak (far-off resonant region) progressively as the pump-1 laser is detuned from the resonance wavelength, which can be explained in terms of the asymmetric excitation/population of dressed states. The splitting between adjacent peaks and the splitting between the two sideband peaks in the triplet do not change with the pump-1 pulse wavelength. The three peaks shift toward lower energy with the same shift 1/4*Δ1 as the pump-1 wavelength changes in near-resonant region. The asymptotic behaviors of AT splitting with the pump-1 laser intensity are interesting in the threshold points of the near-resonant region and the far-off resonant region.
Electron correlation in fast ion-impact single ionization of helium atoms
A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections (FDCS) for proton-impact single ionization of helium atoms in their ground states. The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically. Calculations are performed in the scattering and perpendicular planes. The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets. An illustrative computation is performed for 75-keV proton-helium collisions and the obtained results are compared with experimental data and other theoretical predictions. Although for small momentum transfers, the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes, some significant discrepancies are still present at large momentum transfers in these planes. However, our results are compatible and for some cases, better than those of the other sophisticated calculations.
Population inversion in fluorescing fragments of super-excited molecules inside an air filament
An original idea is reviewed. When a molecule is pumped into a super-excited state, one of its decay channels is neutral dissociation. One or more of the neutral fragments will fluoresce. Hence, if a lower state of such fluorescing fragments was populated through other channels but with a lower probability, population inversion of the fluorescing fragments would be naturally realized. This idea seems to be validated, so far, by comparing published work on three hydrocarbon molecules, CH4, C2H2, C2H4, and water vapor, H2O. After super-excitation in a femtosecond laser filament in air mixed with these molecules, the fluorescence from the CH or OH fragments exhibits population inversion, i.e., amplified spontaneous emission was observed in the backscattering direction of the filament.
Femtosecond filamentation induced fluorescence technique for atmospheric sensing
Recent progress in filament-induced atmospheric sensing is reviewed. Self-guided propagation of ultrashort laser pulses in air induces laser filamentation. All molecules in the path of a filament can be dissociated into highly excited fragments, resulting in emission of characteristic fluorescence spectra. The fluorescence spectra provide information about the various molecules in the filaments. By using a filament-induced “fingerprinting” fluorescence technique, molecules in the atmosphere can be identified.
Absorption of ultrashort intense lasers in laser-solid interactions
With the advent of ultrashort high intensity laser pulses, laser absorption during the laser-solid interactions has received significant attention over the last two decades since it is related to a variety of applications of high intensity lasers, including the hot electron production for fast ignition of fusion targets, table-top bright X-ray and gamma-ray sources, ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Normally, some absorption mechanisms found for nanosecond long laser pulses also appear for ultrashort laser pulses. The peculiar aspects with ultrashort laser pulses are that their absorption depends significantly on the preplasma condition and the initial target structures. Meanwhile, relativistic nonlinearity and ponderomotive force associated with the laser pulses lead to new mechanisms or phenomena, which are usually not found with nanosecond long pulses. In this paper, we present an overview of the recent progress on the major absorption mechanisms in intense laser-solid interactions, where emphasis is paid to our related theory and simulation studies.
Studies of collisionless shockwaves using high-power laser pulses in laboratories
The remarkable experimental progress in the studies of collisionless shockwave (CS) in laboratories employing high-power lasers is briefly reviewed. The results show that CS can be generated in laser-produced plasmas due to the micro-turbulence associated with instabilities. CS is one of the most important astronomical phenomena. It has been found in supernova remnants (SNRs), Sun-Earth space, etc. This paper focuses on CS in ways relevant to SNRs. Laboratory astrophysics (LA), a new interdisciplinary frontier of astrophysics, plasma and laser physics, has developed rapidly in recent years. As an accessory to the astronomical observation, LA experimenters can closely study some astronomical events scaled-down to controllable phenomena.
Developments in laser wakefield accelerators: From single-stage to two-stage
Laser wakefield accelerators (LWFAs) are compact accelerators which can produce femtosecond high-energy electron beams on a much smaller scale than the conventional radiofrequency accelerators. It is attributed to their high acceleration gradient which is about 3 orders of magnitude larger than the traditional ones. The past decade has witnessed the major breakthroughs and progress in developing the laser wakfield accelerators. To achieve the LWFAs suitable for applications, more and more attention has been paid to optimize the LWFAs for high-quality electron beams. A single-staged LWFA does not favor generating controllable electron beams beyond 1 GeV since electron injection and acceleration are coupled and cannot be independently controlled. Staged LWFAs provide a promising route to overcome this disadvantage by decoupling injection from acceleration and thus the electron-beam quality as well as the stability can be greatly improved. This paper provides an overview of the physical conceptions of the LWFA, as well as the major breakthroughs and progress in developing LWFAs from single-stage to two-stage LWFAs.
Ultrafast solvation dynamics at internal sites of staphylococcal nuclease investigated by site-directed mutagenesis
Internal solvation of protein was studied by site-directed mutagenesis, with which an intrinsically fluorescent probe, tryptophan, is inserted into the desired position inside a protein molecule for ultrafast spectroscopic study. Here we review this unique method for protein dynamics research. We first introduce the frontiers of protein solvation, site-directed mutagenesis, protein stability and characteristics, and the spectroscopic methods. Then we present time-resolved spectroscopic dynamics of solvation dynamics inside cavities of active sites. The studies are carried out on a globular protein, staphylococcal nuclease. The solvation at sites inside the protein molecule's cavities clearly reveals characteristics of the local environment. These solvation behaviors are directly correlated to enzyme activity.
Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification
Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification (OPCPA) became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of fewoptical- cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively.
Experimental demonstration of an invisible cloak with irregular shape by using tensor transmission line metamaterials
Broadband perfect polarization conversion metasurfaces
Wide-band circular polarization-keeping reflection mediated by metasurface
s-parameterized Weyl transformation and the corresponding quantization scheme
Role of incoherent pumping and Er3+ ion concentration on subluminal and superluminal light propagation in Er3+-doped YAG crystal
We study the absorption-dispersion process and group index of weak probe field in a four-level Er3+:YAG crystal. We find that the Er3+ ion concentration and incoherent pumping field can influence the absorption-dispersion process and group index of weak probe field. Moreover, our results show that Er3+ ion concentration plays a major role in lasing without inversion and absorption with inversion.
Macroscopic effects in electromagnetically-induced transparency in a Doppler-broadened system
A quartz-enhanced photoacoustic spectroscopy sensor for measurement of water vapor concentration in the air
A 1.7-ps pulse mode-locked Yb3+:Sc2SiO5 laser with a reflective graphene oxide saturable absorber
By using a reflective graphene oxide as saturable absorber, a diode-pumped passively mode-locked Yb3+:Sc2SiO5 (Yb:SSO) laser has been demonstrated for the first time. Without extra negative dispersion compensation, the minimum pulse duration of 1.7 ps with a repetition rate of 94 MHz was obtained at the central wavelength of 1062.6 nm. The average output power amounts to 355 mW under the absorbed pump power of 15 W. The maximum peak power of the mode-locking laser is up to 2.2 kW, and the single pulse energy is 3.8 nJ.
Three-wavelength generation from cascaded wavelength conversion in monolithic periodically poled lithium niobate
Tunable coherent emission is generated in a single-pass, cascaded wavelength conversion process from mode-locked laser-pumped monolithic periodically poled lithium niobate (PPLN). Three ranges of wavelength, including visible output from 628 nm to 639 nm, near-infrared output from 797 nm to 816 nm, and mid-infrared output from 3167 nm to 3459 nm, were obtained from the monolithic PPLN, which consists of a 10-mm section for 532-nm-pumped optical parametric generation (OPG) and a 7-mm section for 1064-nm-pumped sum frequency generation (SFG). A pump-to-signal conversion efficiency of 23.4% for OPG at 50 ℃ and a quantum efficiency of 26.2% for SFG at 200 ℃ were obtained.
Fluctuations of optical phase of diffracted light for Raman-Nath diffraction in acousto-optic effect
Backward Raman amplification in plasmas with chirped wideband pump and seed pulses Hot!
Chirped wideband pump and seed pulses are usually considered for backward Raman amplification (BRA) in plasmas to achieve an extremely high-power laser pulse. However, current theoretical models only contain either a chirped pump or a chirped seed. In this paper, modified three-wave coupling equations are proposed for the BRA in the plasmas with both chirped wideband pump and seed. The simulation results can more precisely describe the experiments, such as the Princeton University experiment. The optimized chirp and bandwidth are determined based on the simulation to enhance the output intensity and efficiency.
Picosecond pulses compression at 1053-nm center wavelength by using a gas-filled hollow-core fiber compressor
Crosstalk elimination in multi-view autostereoscopic display based on polarized lenticular lens array
All-fiber optical modulator based on no-core fiber and magnetic fluid as cladding
Sound field prediction of ultrasonic lithotripsy in water with spheroidal beam equations
Reception pattern influence on magnetoacoustic tomography with magnetic induction
Based on the acoustic radiation theory of a dipole source, the influence of the transducer reception pattern is studied for magnetoacoustic tomography with magnetic induction (MAT-MI). Numerical studies are conducted to simulate acoustic pressures, waveforms, and reconstructed images with unidirectional, omnidirectional, and strong directional transducers. With the analyses of equivalent and projection sources, the influences of the model dimension and the layer effect are qualitatively analyzed to evaluate the performance of MAT-MI. Three-dimensional simulation studies show that the strong directional transducer with a large radius can reduce the influences of equivalent sources, projection sources, and the layer effect effectively, resulting in enhanced pressure and improved image contrast, which is beneficial for boundary pressure extraction in conductivity reconstruction. The reconstructed conductivity contrast images present the conductivity boundaries as stripes with different contrasts and polarities, representing the values and directions of the conductivity changes of the scanned layer. The favorable results provide solid evidence for transducer selection and suggest potential practical applications of MAT-MI in biomedical imaging.
Near-field radiative heat transfer in mesoporous alumina
Stability and Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback
A measurement method for distinguishing the real contact area of rough surfaces of transparent solids using improved Otsu technique
An experimental method of measuring the real contact area of transparent blocks based on the principle of total internal reflection is presented, intending to support the investigation of friction characteristics, heat conduction, and energy dissipation at the contact interface. A laser sheet illuminates the contact interface, and the transmitted laser sheet is projected onto a screen. Then the contact information is acquired from the screen by a camera. An improved Otsu method is proposed to process the data of experimental images. It can compute the threshold of the overall image and filter out all the pixels one by one. Through analyzing the experimental results, we describe the relationship between the real contact area and the positive pressure during a continuous loading process, at different loading rates, with the polymethyl methacrylate (PMMA) material. A hysteresis phenomenon in the relationship between the real contact area and the positive pressure is found and explained.
Critical deflagration waves leading to detonation onset under different boundary conditions
Partial slip effect on non-aligned stagnation point nanofluid over a stretching convective surface
Lattice Boltzmann simulation of liquid–vapor system by incorporating a surface tension term
Thermodynamic study of fluid in terms of equation of state containing physical parameters
Cylindrical effects in weakly nonlinear Rayleigh–Taylor instability
Tunable terahertz plasmon in grating-gate coupled graphene with a resonant cavity
Plasmon modes in graphene can be tuned into resonance with an incident terahertz electromagnetic wave in the range of 1-4 THz by setting a proper gate voltage. By using the finite-difference-time-domain (FDTD) method, we simulate a graphene plasmon device comprising a single-layer graphene, a metallic grating, and a terahertz cavity. The simulations suggest that the terahertz electric field can be enhanced by several times due to the grating-cavity configuration. Due to this near-field enhancement, the maximal absorption of the incident terahertz wave reaches up to about 45%.
Growth of PbS nanoclusters on specific sites of programmed oligodeoxynucleotides
We develope a method to synthesize PbS nanoclusters (NCs) using guanine-containing oligodeoxynucleotides (ODNs) as templates. The NCs on the ODNs are ultra small (ranging from ～ 0.5 nm to 2.1 nm) and luminescent in the visible region. They are characterized by photoluminescence (PL) spectra, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). The ODN-NC complexes can be used as customer-designed fluorophores which do not have the problem of multiple conjugations. The same method enables us to fabricate PbS quantum dot molecules and connect them into nanowires, expanding their potential applications in molecule electronics and quantum computing.
Mechanism of single-event transient pulse quenching between dummy gate isolated logic nodes
Electron-acoustic phonon interaction and mobility in stressed rectangular silicon nanowires
Giant magnetic moment at open ends of multiwalled carbon nanotubes
The attractions of cantilevers made of multiwalled carbon nanotubes (MWNTs) and secured on one end are studied in the non-uniform magnetic field of a permanent magnet. Under an optical microscope, the positions and the corresponding deflections of the original cantilevers (with iron catalytic nanoparticles at the free end) and corresponding cut-off cantilevers (the free ends consisting of open ends of MWNTs) are studied. Both kinds of CNT cantilevers are found to be attracted by the magnet, and the point of application of force is proven to be at the tip of the cantilever. By measuring and comparing deflections between these two kinds of cantilevers, the magnetic moment at the open ends of the CNTs can be quantified. Due to the unexpectedly high value of the magnetic moment at the open ends of carbon nanotubes, it is called giant magnetic moment, and its possible mechanisms are proposed and discussed.
Effect of far-field flow on a columnar crystal in the convective undercooled melt
Tb doping induced enhancement of anomalous Hall effect in NiFe films Hot!
Tbx(Ni0.8Fe0.2)1-x films with x≤0.14 are fabricated and the anomalous Hall effect is studied. The intrinsic anomalous Hall conductivity and the extrinsic one from the impurity and phonon induced scattering both increase with increasing x. The enhancement of the intrinsic anomalous Hall conductivity is ascribed to both the weak spin-orbit coupling enhancement and the Fermi level shift. The enhancement of the extrinsic term comes from the changes of both Fermi level and impurity distribution. In contrast, the in-plane and the out-of-plane uniaxial anisotropies in the TbNiFe films change little with x. The enhancement of the Hall angle by Tb doping is helpful for practical applications of the Hall devices.
Tight-binding electron-phonon coupling and band renormalization in graphene
Influence of compressive strain on the incorporation of indium in InGaN and InAlN ternary alloys
In order to investigate the influence of compressive strain on indium incorporation in InAlN and InGaN ternary nitrides, InAlN/GaN heterostructures and InGaN films were grown by metal-organic chemical vapor deposition. For the heterostructures, different compressive strains are produced by GaN buffer layers grown on unpatterned and patterned sapphire substrates thanks to the distinct growth mode; while for the InGaN films, compressive strains are changed by employing AlGaN templates with different aluminum compositions. By various characterization methods, we find that the compressive strain will hamper the indium incorporation in both InAlN and InGaN. Furthermore, compressive strain is conducive to suppress the non-uniform distribution of indium in InGaN ternary alloys.
Degradation mechanism of enhancement-mode AlGaN/GaN HEMTs using fluorine ion implantation under the on-state gate overdrive stress
Fano-type resonances induced by a boson mode in Andreev conductance
We study spectroscopic signatures of a monochromatic boson mode interacting with a T-shape double quantum dot coupled between the metallic and superconducting leads. Focusing on a weak interdot coupling, we find that the proximity effect together with the bosonic mode are responsible for the series of Fano-type resonances appearing simultaneously at negative and positive energies. We investigate these interferometric features and discuss their influence on the subgap Andreev conductance taking into account the correlation effects driven by the Coulomb repulsion.
Different charging behaviors between electrons and holes in Si nanocrystals embedded in SiNx matrix by the influence of near-interface oxide traps
Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals (Si-NCs) embedded in SiNx floating gate MOS structures. The capacitance-voltage (C-V), current-voltage (I-V), and admittance-voltage (G-V) measurements are used to investigate the charging characteristics. It is found that the maximum flat band voltage shift (ΔVFB) due to full charged holes (～ 6.2 V) is much larger than that due to full charged electrons (～ 1 V). The charging displacement current peaks of electrons and holes can be also observed by the I-V measurements, respectively. From the G-V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the SiO2/Si-substrate interface. Combining the results of C-V and G-V measurements, we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism. The evolution of G-V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.
Applicability of the vortex-glass model for the single crystal Tl0.4K0.41Fe1.71Se2
We measure the current-voltage (I-V) characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2 with the superconducting transition temperature (TC) around 30.5 K, under a 10 T magnetic field applied perpendicular and parallel to the ab plane. We find that the shapes of the I-V isotherms are very different from the description by the vortex-glass (VG) model. Combining theoretical calculations and analysis of the ρH⊥ab-T and ρH||ab-T data, we give an explicit discussion over the suitability of the VG model for the A0.8Fe2Se2 superconductors, and point out the possibility of the material acting as a convenient platform for re-examination and further study of the complex vortex behaviors in the layered superconductors.
Field-dependent resistive transitions in Yba2Cu3O7-δ thin films: Influence of the pseudogap on vortex dynamics
Effects of pressure and/or magnetism on superconductivity of δ-MoN single crystal
Effects of pressure and/or magnetism on the critical superconducting temperature (Tc) of δ-MoN single crystal were investigated using a Maglab system. The δ-MoN single crystal was synthesized at extreme conditions of high pressure and high temperature. The carrier density of δ-MoN single crystal as a function of applied pressure was determined using Hall coefficient measurement.
Electronic, optical properties, surface energies and work functions of Ag8SnS6: First-principles method
Effect of CoSi2 buffer layer on structure and magnetic properties of Co films grown on Si (001) substrate
Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films. In this paper, Co films with different thickness of CoSi2 buffer layers were grown on Si (001) substrates. In order to investigate morphology, structure, and magnetic properties of films, scanning tunneling microscope (STM), low energy electron diffraction (LEED), high resolution transmission electron microscopy (HRTEM), and surface magneto-optical Kerr effect (SMOKE) were used. The results show that the crystal quality and magnetic anisotropies of the Co films are strongly affected by the thickness of CoSi2 buffer layers. Few CoSi2 monolayers can prevent the interdiffusion of Si substrate and Co film and enhance the Co film quality. Furthermore, the in-plane magnetic anisotropy of Co film with optimal buffer layer shows four-fold symmetry and exhibits the two-jumps of magnetization reversal process, which is the typical phenomenon in cubic (001) films.
High-pressure synthesis, characterization, and equation of state of double perovskite Sr2CoFeO6
Fine-grained NdFeB magnets prepared by low temperature pre-sintering and subsequent hot pressing
Ferroelectricity in hexagonal YFeO3 film at room temperature
Temperature-dependent Raman spectroscopic study of bismuth borate Bi2ZnOB2O6
A temperature-dependent Raman spectroscopic study on Bi2ZnOB2O6 crystal was carried out to investigate the structure change of the crystal with the increase of temperature. Raman spectra of crystal Bi2ZnOB2O6 were recorded in the spectral range 10-1600 cm-1 at room temperature first. Compared with the vibrational spectra of the referred compounds, satisfactory assignment of most of the high-energy modes to vibrations of Bi-O, B-O, and Zn-O bonds was achieved. In particular, the Raman high-frequency peak located at 1344 cm-1 was attributed to the B-O vibration in the BO3 triangle. This temperature-dependent Raman spectroscopic study was carried out up to 600 ℃. It was found that all the Raman lines exhibit decreases in frequency and the widths of the Raman peaks increase with increasing temperature. No phase transition was observed under 600 ℃.
Ordered silicon nanorod arrays with controllable geometry and robust hydrophobicity
Highly ordered silicon nanorod (SiNR) arrays with controllable geometry are fabricated via nanosphere lithography and metal-assisted chemical etching. It is demonstrated that the key to achieving a high-quality metal mask is to construct a non-close-packed template that can be removed with negligible damage to the mask. Hydrophobicity of SiNR arrays of different geometries is also studied. It is shown that the nanorod structures are effectively quasi-hydrophobic with a contact angle as high as 142°, which would be useful in self-cleaning nanorod-based device applications.
Variational Monte Carlo study of the nematic state in iron-pnictide superconductors with a five-orbital model Hot!
We perform a variational Monte Carlo study of the nematic state in iron-pnictide superconductors within a realistic five-orbital model. Our numerical results show that the nematic state, formed by introducing an anisotropic hopping order into the projected wave function, is not stable unless the off-site Coulomb interaction V exceeds a critical value. This demonstrates that V plays a key role in forming the nematic state in iron-pnictide superconductors. In the nematic state, the orbital order and the anisotropic spin correlations are consistent with the experimental observations. We argue that the experimentally observed anisotropic magnetic couplings and structural transition are associated with the nematic state and can be understood in a unified framework.
High-crystalline GaSb epitaxial films grown on GaAs(001) substrates by low-pressure metal-organic chemical vapor deposition
Orthogonal experiments of GaSb films growth on GaAs(001) substrates have been designed and performed by using a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters. It was demonstrated that the optimized GaSb thin film has a narrow full width at half maximum (358 arc sec) of the (004) ω-rocking curve, and a smooth surface with a low root-mean-square roughness of about 6 nm, which is typical in the case of the heteroepitaxial single-crystal films. In addition, we studied the effects of layer thickness of GaSb thin film on the density of dislocations by Raman spectra. It is believed that our research can provide valuable information for the fabrication of high-crystalline GaSb films and can promote the integration probability of mid-infrared devices fabricated on mainstream performance electronic devices.
Fluctuations of electrical and mechanical properties of diamond induced by interstitial hydrogen
Measurement of micro weld joint position based on magneto-optical imaging
GaSb p-channel metal-oxide-semiconductor field-effect transistor and its temperature dependent characteristics
GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with an atomic layer deposited Al2O3 gate dielectric and a self-aligned Si-implanted source/drain are experimentally demonstrated. Temperature dependent electrical characteristics are investigated. Different electrical behaviors are observed in two temperature regions, and the underlying mechanisms are discussed. It is found that the reverse-bias pn junction leakage of the drain/substrate is the main component of the off-state drain leakage current, which is generation-current dominated in the low temperature regions and is diffusion-current dominated in the high temperature regions. Methods to further reduce the off-state drain leakage current are given.
Preparation of graphene on Cu foils by ion implantation with negative carbon clusters
Excellent acetone sensing properties of porous ZnO
Mechanisms of ultrasonic modulation of multiply scattered incoherent light based on diffusion theory
An analytic equation interpreting the intensity of ultrasound-modulated scattering light is derived, based on diffusion theory and previous explanations of the intensity modulation mechanism. Furthermore, an experiment of ultrasonic modulation of incoherent light in a scattering medium is developed. This analytical model agrees well with experimental results, which confirms the validity of the proposed intensity modulation mechanism. The model supplements the existing research on the ultrasonic modulation mechanism of scattering light.
PET image reconstruction with a system matrix containing point spread function derived from single photon incidence response
A point spread function (PSF) for the blurring component in positron emission tomography (PET) is studied. The PSF matrix is derived from the single photon incidence response function. A statistical iterative reconstruction (IR) method based on the system matrix containing the PSF is developed. More specifically, the gamma photon incidence upon a crystal array is simulated by Monte Carlo (MC) simulation, and then the single photon incidence response functions are calculated. Subsequently, the single photon incidence response functions are used to compute the coincidence blurring factor according to the physical process of PET coincidence detection. Through weighting the ordinary system matrix response by the coincidence blurring factors, the IR system matrix containing the PSF is finally established. By using this system matrix, the image is reconstructed by an ordered subset expectation maximization (OSEM) algorithm. The experimental results show that the proposed system matrix can substantially improve the image radial resolution, contrast, and noise property. Furthermore, the simulated single gamma-ray incidence response function depends only on the crystal configuration, so the method could be extended to any PET scanners with the same detector crystal configuration.
Detecting overlapping communities in networks via dominant label propagation
Novel pressure and displacement sensors based on carbon nanotubes