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We investigate the dynamics of rotating spin-orbit-coupled spin-1 Bose–Einstein condensates (BECs) in an in-plane gradient magnetic field, which is confined in an anharmonic trap. In the case of rotating spin-orbit-coupled spin-1 BECs with given parameters, the system evolves from initial disk-shaped condensates into drastic turbulent oscillations and ghost vortices on the surface of the component densities due to surface wave excitations and then into two final vortex necklaces along the azimuthal direction with an irregular density hole, in which the vortices differ by one quantum number in turn. For the case of rotating spin-orbit-coupled spin-1 BECs with in-plane gradient magnetic field, with the dynamic evolution, the system undergoes a transition from an initial central polar-core vortex to violent turbulent oscillations and then to a final vortex chain along the diagonal of BECs, with the remaining vortices symmetrically distributed on both sides in the individual component. In addition, the corresponding spin texture undergoes a transition from plane-wave phase to double half-antiskyrmion necklaces for the former case and a transition from a structure similar to a quadrupole magnetic field to a half-antiskyrmion chain with the rest of the half-antiskyrmions on both sides. During the dynamic evolution process, the angular momentum increases gradually and then approaches a convergent value.

Weak signal detection has been widely used in many fields such as military and national economy. Aiming at the problem that the traditional stochastic resonance (SR) method can’t obtain the signal amplitude when detecting weak signals, the frequency and amplitude of the weak signal are obtained by combining the SR and chaos characteristics of the two-dimensional Duffing system. Firstly, the effects of two-dimensional Duffing system parameters a, b, k, noise intensity D on the Kramers rate and signal-to-noise ratio (SNR) are analyzed under the Gaussian white noise environment. The results show that the damping ratio K can hinder the SR effect of the system to some extent. Secondly, to solve the misjudgment of the state method of the weak signal amplitude in the detection, the Lyapunov exponent is used to assure the threshold's range, and the threshold of the chaotic critical state is found. Finally, the paper gives the processes of frequency and amplitude detection of multiple high-frequency signals, which realizes the effective detection of the frequency and amplitude of multiple high-frequency signals in a Gaussian white noise environment, and successfully applies the method to the accurate detection of boundary voltage amplitude in electrical impedance tomography.

As a typical hole-doped cuprate superconductor, Bi 2 Sr 2 CaCu 2 O 8+{\delta} (Bi2212) carrier doping is mostly determined by its oxygen content. Traditional doping methods can regulate its doping level within the range of hole doping. Here we report the first application of CaH 2 annealing method in regulating the doping level of Bi2212. By continuously controlling the anneal time, a series of differently doped samples can be obtained. The combined experimental results of x-ray diffraction, scanning transmission electron microscopy, resistance and Hall measurements demonstrate that the CaH 2 induced topochemical reaction can effectively change the oxygen content of Bi2212 within a very wide range, even switching from hole doping to electron doping. We also found evidence of a low-T c superconducting phase in the electron doping side., Comment: 7pages,3 figures and Supplementary Material 3pages,3 figures

Revealing the atomistic mechanisms for the high-temperature mechanical behavior of materials is important for optimizing their properties for service at high-temperatures and their thermomechanical processing. However, due to materials microstructure’s dynamic recovery and the absence of available in situ techniques, the high-temperature deformation behavior and atomistic mechanisms of materials are difficult to evaluate. Here, we report the development of a microelectromechanical systems-based thermomechanical testing apparatus that enables mechanical testing at temperatures reaching 1556 K inside a transmission electron microscope for in situ investigation with atomic-resolution. With this unique technique, we first uncovered that tungsten fractures at 973 K in a ductile manner via a strain-induced multi-step body-centered cubic (BCC)-to-face-centered cubic (FCC) transformation and dislocation activities within the strain-induced FCC phase. Both events reduce the stress concentration at the crack tip and retard crack propagation. Our research provides an approach for timely and atomic-resolved high-temperature mechanical investigation of materials at high-temperatures., High-temperature deformation of materials is challenging to evaluate. Here the authors develop a novel device that allows atomic resolved in situ high temperature mechanical tests inside a transmission electron microscope and reveal ductile fracture of a single crystal tungsten deformed at 973 K.

It remains a daunting task to quantify the configurational entropy of a material from atom‐revolved electron microscopy images and correlate the results with the material's lattice thermal conductivity, which strides across statics, dynamics, and thermal transport of crystal lattice over orders of magnitudes in length and time. Here, a proof‐of‐principle study of atomic‐scale visualization and quantification of configurational entropy in relation to thermal conductivity in single crystalline trigonal GeSb2Te4 (aka t‐GeSb2Te4) with native atomic site disorder is reported. A concerted effort of large t‐GeSb2Te4 single crystal growth, in‐lab developed analysis procedure of atomic column intensity, the visualization and quantification of configurational entropy including corresponding modulation, and thermal transport measurements enable an entropic “bottom‐up” perspective to the lattice thermal conductivity of t‐GeSb2Te4. It is uncovered that the configurational entropy increases phonon scattering and reduces phonon mean free path as well as promotes anharmonicity, thereby giving rise to low lattice thermal conductivity and promising thermoelectric performance. The current study sheds lights on an atomic scale bottom‐up configurational entropy design in diverse regimes of structural and functional materials research and applications.

The large aperture deuterated potassium dihydrogen phosphate (DKDP) is an important frequency conversion crystal in a large power laser device. There are many defects inside the DKDP bulk material, including the varying element impurities and electronic defects. Comparing with the defect-free material, these bulk defects can easily absorb incident laser energy and pose the risks of initiating damage sites when exposed to high-energy lasers. Beside bulk defects, there are surface defects originating from the DKDP machining process, including cracks, scratches and protuberances. These surface defects affect the damage performance of DKDP crystal by increasing light absorption and weakening local mechanical strength. Due to the defects from both bulk and surface, the actual damage threshold of DKDP crystal is much lower than the expected theoretical value. The lack of its laser damage resistance seriously restricts the laser output power. In this study, the off-line sub-nanosecond laser conditioning technology is proposed to effectively improve the laser damage performance of large aperture DKDP crystal. Its principle is to irradiate DKDP with a mild laser fluence in advance. Although the laser pretreatment cannot directly eliminate the impurities, dislocations, grain boundaries or other macro structural defects in crystals, it indeed changes the distribution and density of intrinsic point defects on a micro-scale. It suggests that the complicated reactions of electron-hole, atom-vacancy and the intrinsic point defect annihilation caused by the microstructural transformation of crystal materials under laser conditioning are the possible reasons for reducing absorption and improving the damage resistance. In this experiment, the result of the damage to high-power laser device shows that the mean surface damage density of DKDP crystal at 9 J/cm2 decreases from 5.02 pp/cm2 to 0.55 pp/cm2 after sub-nanosecond laser conditioning. The laser conditioning can remove the protuberance defects on the surface, thus reducing the surface damage density. In addition, the damage size probably decreases after laser conditioning. There is a leftward shift in the damage size curve after laser conditioning, and its peak decreases from 25 μm to 18 μm–20 μm. In addition, due to the removal effect of laser conditioning on defects, the spatial distribution of damage points after sub-nanosecond laser irradiation turns more uniform. This study provides a foundation for the applications of off-line sub-nanosecond laser conditioning technology in high-power laser facility.

Electrospinning technology is considered to be one of the efficient, convenient, and low-cost technologies for preparing nanofibers, which can be applied in various industries, including filtration, catalysis, and energy. Here, aiming at the performance requirements of the nanometer fiber filter membrane for filtering PM2.5, the preparation of the nanofiber filter membrane was realized based on multi-needle electrospinning equipment. Meanwhile, by adding silver nitrate to the spinning solution, a polyvinylidene fluoride antibacterial nanofiber filter layer with high filtration efficiency and low resistance was successfully prepared on the traditional air conditioning filter meshes. We found that four key factors affecting the filtration performance include ambient humidity, substrate meshes, voltage, and production rate. Among them, voltage and production rate are the key factors affecting the filtration performance. According to the development trend of multifunctional nanofiber membranes, the preparation of air conditioning filters with nanofibers as the main filter material was realized, producing air conditioning filter membranes with antibacterial and deodorizing functions. This article provides a reliable experimental basis and empirical reference for the preparation of nanofiber membranes based on multi-needle electrospinning technology.

The melting point of Ti:MgAl2O4 crystal is as high as 2130 °C, it is a challenge to obtain a large-sized and high-quality laser crystal. By optimizing the crystal growth process, Ti:MgAl2O4 crystal with a size of 30 mm× 70 mm is successfully grown by the Czochralski method under the condition of weak reducing atmosphere. The X-ray diffraction pattern is studied, and the x-ray rocking curve indicates that the grown crystal has a high crystalline quality in terms of the lower full width at half maximum(FWHM) intensity, which provides a material basis for the next laser output experiment. In a range of 100–1000 cm–1, there are four Raman vibration peaks located at 312, 410, 675 cm–1 and 771 cm–1 respectively. The grown crystal has an absorption cutoff range of 250–318 nm and two wide absorption bands of 395–495 nm and 550–1100 nm. Excited by 271 nm, the grown crystal shows a strong broadband emission ina range of 340–650 nm with a peak centered at 480 nm. After annealing in hydrogen atmosphere, shape of the transmittance spectrum and emission spectrum are both unchanged, but the fluorescent emission intensity is significantly reduced. After annealing in air atmosphere, the original two absorption bands disappear while none of the characteristics of fluorescence emission in a 340–650 nm range changes significantly. In addition, a new fluorescence emission peak near 725 nm is observed. Combining with the ESR spectrum, what we canconfirm is that the Ti:MgAl2O4 as-grown crystal contains Ti3+ and Ti4+ ions, and no ESR signal of Ti3+ is observed after annealing in air atmosphere. Moreover, excitationspectrum is also recorded. The fluorescence lifetime is 14 μs at room temperature, which is 4–5 times that of Ti:Al2O3 crystal and Ti:BeAl2O4 crystal. Furthermore, the emission cross section of the grown Ti:MgAl2O4 crystal is calculated from the Füchtbauer-Ladenburg (F-L) formula and its value is 2 × 10–20 cm2, large emission cross section which is beneficial for realizing laser oscillation. All the above results show that the Ti:MgAl2O4 crystal is a potential crystal material for realizing broadband tunable blue laser output.

Hierarchical NiO microspheres, composed of ultrathin nanosheets with porous structure, are prepared through a facile solvothermal route followed by a calcination process. First, the precursor Ni 3 (NO 3 ) 2 (OH) 4 hierarchical architectures assembled by irregular nanosheets were synthesized through urea assisted precipitation. Second, the NiO hierarchical architecture was obtained from the precursor by a simple calcination procedure without changing their morphologies. The resultant products were characterized by XRD, SEM, TEM, TG, FT-IR and BET analysis techniques. The XRD pattern showed that the sample exhibited a rocksalt cubic phase structure after calcined at 500 °C for 2 h. The SEM and TEM images demonstrated that the as-prepared NiO were microspheres composed of ultrathin nanosheets with porous structure. The catalytic efficiency of the NiO nanomaterials is evaluated by the photocatalytic degradation of methylene blue (MB). The obtained NiO displayed the excellent degradable ability and stable cyclability to MB dye, which may be attributed to its unique hierarchical characteristics: ultrathin-porous microstructure.

Colistin represents one of the few available drugs for treating infections caused by carbapenem-resistant Enterobacteriaceae. As such, the recent plasmid-mediated spread of the colistin resistance gene mcr-1 poses a significant public health threat, requiring global monitoring and surveillance. Here, we characterize the global distribution of mcr-1 using a data set of 457 mcr-1-positive sequenced isolates. We find mcr-1 in various plasmid types but identify an immediate background common to all mcr-1 sequences. Our analyses establish that all mcr-1 elements in circulation descend from the same initial mobilization of mcr-1 by an ISApl1 transposon in the mid 2000s (2002–2008; 95% highest posterior density), followed by a marked demographic expansion, which led to its current global distribution. Our results provide the first systematic phylogenetic analysis of the origin and spread of mcr-1, and emphasize the importance of understanding the movement of antibiotic resistance genes across multiple levels of genomic organization., The recent plasmid-mediated spread of the mobilized colistin resistance gene mcr-1 poses a significant public health threat, requiring worldwide monitoring and surveillance. Here, Wang et al. compile and analyze a data set of 457 mcr-1-positive sequenced isolates to investigate the origin and global distribution of mcr-1.

Liquid–liquid equilibrium (LLE) data for the ternary system water + 2-methyl-1-propanol + butyl acetate and water + 2-methyl-2-propanol + butyl acetate were measured at the temperature T = (298.15 and 323.15) K and under atmospheric pressure, respectively. Both the Othmer–Tobias and Bachman equations were used to test the reliability of the experimental data. Moreover, the NRTL and UNIQUAC activity coefficient models were applied to correlate the determined data, and the result showed that the UNIQUAC and the NRTL models both could correlate the two systems studied well at the same conditions. In addition, distribution ratios and separation factors in the two ternary systems were calculated using the equations from the experimental liquid liquid equilibrium data and discussed in detail.

Numerical simulation of a fractured-vuggy porous medium is a challenging problem. One reason is the coexistence of matrix, fractures and vugs on multiple scales that need to be coupled, and the other reason is that the high-resolution fractured-vuggy model may contain up to several millions of gridcells in applications, which brings severe computational challenges into the numerical methods. Therefore, the requirement for accurate and efficient technique is widely increasing. Fractured-vuggy porous medium is generally represented by triple-continuum model in which the matrix system, fracture system and vug system each are treated as a parallel continuous system. Although triple-continuum model is widely used because of its easy-implementation and high efficiency, it fails to capture the detailed flow patterns of reservoir with disconnected long fractures. Discrete fracture-vug network (DFVN) model can precisely model the fluid flow in fractures and vugs. However, the simulation of this model is deemed intractable even with the advent of supercomputers because of the large amount of calculation. In view of the fact that the multigrid method is now well known as one of the fastest method of solving elliptic problems, in this paper we introduce a nearly linear complexity multiresolution decomposition method for fluid flow in a fractured-vuggy reservoir. The detailed flow patterns are described by combing the advantages of continuum model and discrete model. That is, the homogenization theory is used to construct an equivalent permeability in each coarse grid block in which the vugs and small-scale fractures are represented by discrete fracture-vug network model. We decompose the solution space into several subspaces and then we compute the corresponding solutions of heterogeneous discrete fracture network model in each subspace. Gamblets are constructed and they are elementary solutions of hierarchical information games associated with the process of computing with partial information and limited resources. These gamblets have a natural Bayesian interpretation under the mixed strategy emerging from the game theoretic formulation. This method could realize its fast simulation by decomposing the solution space into a direct sum of linear subspaces that are orthogonal to each other. Finally, the pressure difference distribution of fractured-vuggy porous medium is obtained by combing the DFVN solutions of all subspaces. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed multiresolution decomposition method. The results show that this method is a promising method of numerically simulating the fractured-vuggy porous medium.

Superhydrophobic surfaces resulting from nanoarrays have good performance in anti-condensation. However, the study of droplet nucleation during water vapor condensation is a challenge because of the limitation of observation on a nanoscale, and therefore the fundamental understanding of the influence of geometrical parameters of nanoarrays on the condensation behavior is still less clear. In this work a three-dimensional (3D) multiphase lattice Boltzmann (LB) model is employed to simulate the phenomenon of droplet condensation on the superhydrophobic nanostructured surface. The model validation is carried out through the comparison of the simulations with the results from the Laplace's law and the intrinsic contact angle theory. The LB simulations accord well with the results from Laplace's law. The relative deviation between the simulated intrinsic contact angle and the theoretical value is less than 0.14%, demonstrating the validity of the LB model. Then, the 3D LB model is used to simulate the different preferential nucleation positions and final wetting states of condensate droplets by changing the geometrical parameters, including interpost space, post height and post width, and local wettability of the nanoarrays on superhydrophobic surfaces. It is found that for the nanostructured surfaces patterned with tall posts, the droplets nucleate in the upside interpost space and at the bottom of nanostructures simultaneously. By designing wider and thinner interpost spaces at the downside and upside of the tall nanostructures, respectively, the phenomenon of droplet nucleation at the bottom can be avoided. The simulation results show that the condensate droplets nucleated in the upside interpost space of tall nanostructures migrate upwards during growth, producing a Wenzel-to-Cassie wetting state transition. On the other hand, the condensate droplets nucleated at the bottom of nanostructured surface patterned with short posts produce the Wenzel state. However, by setting non-uniform hydrophilic and hydrophobic regions on the top of the short nanostructures, the condensate droplets are found to nucleate on the hydrophilic top and generate a Cassie state. The simulated final wetting states of condensate droplets on the nanostructures, having various geometrical parameters, compare reasonably well with the experimental observations reported in the literature. It is demonstrated that the migration of condensate droplets is correlated with the evolution of the statistical average force. If the direction of the statistical average force acting on the droplet is upward, the condensate droplets nucleated in the upside interpost space move upward during growth. The 3D LB simulations provide an insight into the physical mechanism of droplet nucleation, growth and wetting state transitions on superhydrophobic nanostructured surfaces.

Phase change memory has been considered as the next generation in non-volatile electronic data storage. The property modulation of such materials by the doping of rare-earth elements has drawn a lot of attention, which motivates us to search for the optimal dopants and reveal the underlying mechanisms. Here, we investigate the role of Gd as a dopant in Ge2Sb2Te5, which exhibits higher crystalline resistance and better thermal stability and antioxidant capacity than the undoped counterpart. Moreover, Gd dopants suppress both the processes of phase transition and grain growth. The crystalline structure remains unchanged with Gd dopants and vacancies are randomly distributed. Furthermore, the bonding mechanism was theoretically investigated. In the amorphous state, Gd atoms modify the local structures around Ge, Sb, and Te atoms. The large coordination number of Gd and the “Gd–Te distorted pentagonal bipyramidal-like” structure can be attributed to the good thermal stability. These microscopic findings figure out some of the key issues about the bonding mechanism, electrical properties, and crystallization behaviors of Gd doped phase change memory materials, which could be useful for storage devices.

We report on the observation of a superconducting gap of about 14-15 meV, significantly enlarged compared with the value of 2.2 meV for bulk FeSe, in monolayer FeSe film interfaced with MgO epitaxial on SrTiO3(001) substrate by using the scanning tunneling microscopy. While the MgO exhibits the same work function as SrTiO3 substrate, the gap magnitude is in coincidence with that of surface K-doped two-unit-cell FeSe film on SrTiO3(001), suggesting that the interface enhanced superconductivity might be attributed to cooperation of interface charge transfer driven by band bending with interface electron-phonon coupling as discovered at FeSe/TiO2 interfaces. On the other hand, the observation of such an enlarged superconducting gap, complementary to our previous transport observation of an onset superconducting transition temperature of 18 K in monolayer FeSe film on a bulk MgO substrate, implies that FeSe/MgO interface is likely to be a new interface high-temperature superconducting system, providing a new platform for investigating the mechanism of interface hightemperature superconductivity.

In this paper, solute concentration and precipitate content in A2024 aluminum alloy are adjusted by solution treatment (ST) at different temperatures and tensile experiments on these treated specimens are carried out. It is found that the temperature of solution treatment (ST temperature) has a remarkable influence on the amplitude of the serrated flow and the propagation characteristics of shear bands. These results are due to the effects of solute atoms and precipitates on dynamic strain aging (DSA). When ST temperature is higher than 300 °C, solute concentration is relatively high and solute cloud is a key factor of DSA. When ST temperature is lower than 300 °C, precipitate content is relatively high and the mechanism of DSA is determined by precipitates.

This paper proposes a new method of aperture synthetizing in digital holography based on the principle of holography. In the new method aperture synthetizing is achieved by reconstructing each sub-hologram respectively, firstly, moving each reconstructed wave field referred to the benchmark reconstructed wave field according to the relationship between spacial motion and frequency shift, and finally splicing them by using superposition. Two different recording ways, using plane wave to record and using spherical wave to record, are analyzed, and their moving formula is deduced, too. Simulation and experiment are done. The results show that in comparison with the traditional method of aperture synthetizing in digital holography, the new method can decrease calculation and save reconstructed time obviously which has better applicability.

We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd3+:Y3A15O12 (Nd:YAG) and Yb3+:Y3A15O12 (Yb:YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340 nm. The former is contributed due to Fe3+ impurity, the latter is due to Fe2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100Mrad gamma-ray In contrast, the same dose irradiation does not impair the fluorescent properties of Yb:YAG crystal. These results indicate that Yb:YAG crystal possesses the advantage over Nd:YAG crystal that has better reliability for applications in harsh radiant environment.

Density functional theory (DFT) with local density approximation (LDA) is employed to study the structural and electronic properties of the high explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) under high pressure compression up to 40 GPa. Pressure dependences of the cell volume, lattice constants, and molecular geometry of solid β-HMX are presented and discussed. It is found that N-N and N-C bonds are subject to significant change. This may implies that these bonds may be related to the sensitivity. The band gap is calculated and plotted as a function of pressure. Compared the experimental results with other theoretical works we find that LDA gives good results.

In this paper a parameter observer and a synchronization controller are designed to synchronize unknown chaotic systems with diverse structures. Based on stability theory the structures of the observer and the controller are presented. The unknown Coullet system and Rossler system are taken for examples to demonstrate that the method is effective and feasible. The artificial simulation results show that global synchronization between the unknown Coullet system and the Rossler system can be achieved by a single driving variable with co-operation of the observer and the controller, and all parameters of the Coullet system can be identified at the same time.

Transmission electron microscopy is applied to study the diamond film grown in a CH4 and H2 gaseous mixture by microwave plasma assisted chemical vapour deposition. Defects in the nanometre scale, dislocation loops, are first observed in diamond films. The dislocation loops are found to be of co-existence with planar defects and are next to the planar defects for {111} faceting grains. A possible mechanism is suggested to interpret the co-existence of dislocation loops with planar defects.

The dynamics of two confined colloidal particles is studied by means of Brownian dynamics simulation. The autocorrelation function and cross-correlation function of the two colloidal spheres are computed by utilizing the formulae of hydrodynamic diffusion matrix expanded to different orders, as well as the accurate tensor through numerical algorithm. Furthermore, the numerical results are compared with the experimental results and the theoretical approximation. It is found that the relatively simple theoretical approximation gives good predictions when two spheres are far away from each other, but fails when the two spheres are very close.

The open-circuit photovoltage is improved by adding 1-hexyl-3-methylimidazolium iodide (HMImI) into the electrolyte. To investigate the mechanisms of the increase of the open-circuit photovoltage, we take the Mott–Schottky analysis and time-resolved mid-infrared absorption spectroscopy to study the band edge movement of TiO2 and the rate of back electron transfer, respectively. The results indicate that the negative shift of the conduction band of TiO2 is a predominant factor to increase the open-circuit photovoltage for the electrolyte containing HMImI.

Elucidating the initial kinetics of folding pathways is critical to the understanding of the protein folding mechanism. Transient infrared spectroscopy has proved a powerful tool to probe the folding kinetics. Herein we report the construction of a nanosecond laser-induced temperature-jump (T-jump) technique coupled to a nanosecond time-resolved transient mid-infrared (mid-IR) spectrometer system capable of investigating the protein folding kinetics with a temporal resolution of 50 ns after deconvolution of the instrumental response function. The mid-IR source is a liquid N2 cooled CO laser covering a spectral range of 5.0?m (2000 cm?1)~ 6.5?m (1540 cm?1). The heating pulse was generated by a high pressure H2 Raman shifter at wavelength of 1.9?m. The maximum temperature-jump could reach as high as 26?1?C. The fast folding/unfolding dynamics of cytochrome C was investigated by the constructed system, providing an example.

We employ the semirigid vibrating rotor target (SVRT) model to study the influence of rotational and vibrational excitation of the reagent on reactivity for the reaction H+NH3. The excitation of the pseudo H–NH2 stretching vibration of the SVRT model gives significant enhancement of reaction probability. Detailed study of the influence of initial rotational states on reaction probability shows strong steric effect. The steric effect of polyatomic reactions, treated by the SVRT model, is more complex and richer than theoretical calculations involving linear molecular models.

Er-doped SiOx films were synthesized at 500 degrees C by ion beam assisted deposition technique and annealed at 800 and 1100 degrees C for 2h in the air atmosphere. The analysis by using energy dispersive x-ray spectroscopy showed that the ratio of Si to O decreased from 3 in the as-deposited films to about 1 in the annealed films. The investigation by using transmission electron microscopy and x-ray diffraction indicated that annealing induces a microstructure change from amorphous to crystalline. The grain sizes in the films were about 10 and 40nm when annealed at 800 and 1100 degrees C, respectively. The films annealed at temperatures of 800 and 1100 degrees C exhibited a sharp photoluminescence (PL) at 1.533μm from the Er centres when pumped by 980nm laser. The influence of microstructure and grain size on the PL from Er-doped SiOx films has been studied and discussed.

The Portevin–Le Chatelier (PLC) effect with typical temporal instabilities in the recorded stress is closely associated with local inhomogeneities of deformation. By employing the dynamic digital speckle pattern interferometry technology, the characterizations for the PLC deformation bands of type A (continuous propagation along the specimen), type B (``hopping'' propagation along the specimen) and type C (random nucleation in the sample) were distinctly clarified. The corresponding positions of deformation bands were traced throughout the whole tensile process. By systemic experiments, the range of the applied strain rates for each type of bands existing was investigated respectively. The evolution of the band velocity (for types A and B) was also statistically investigated and qualitatively interpreted.

The semirigid vibrating rotor target (SVRT) model has been applied to the study of the reaction of D+CH4→ CH3+HD using a time-dependent wave packet method. The energy dependence of the calculated reaction probability shows oscillatory structures similar to those observed in the abstraction reaction of H+H2, H+CH4 etc. We have also studied the influence of rotational and vibrational excitation of the reacting molecule (CH4) on reaction probability. The excitation of the H–CH3 stretching vibration gives significant enhancement of reaction probability, which rises significantly with the enhancement of rotational quantum number j. Finally, we have compared the cross section and the rate constant of the D+CH4 system with that of the H+CH4 system.

Reaction probability, cross section and rate constant are studied for polyatomic reaction T+CH4→ CH3+HT using the semirigid vibrating rotor target (SVRT) model. The numerical calculation for the reaction system is carried out using the time-dependent wavepacket method, and the wavepacket is propagated by the split-operator method. The calculation exhibits a variety of features that can be used for comparison with future experimental investigations. The reaction probability as a function of the translational energy shows slight oscillatory structures, similar to those observed in H abstraction reactions H+H2 and H+CH4. The comparisons with the H+CH4 reaction are described.

The semirigid vibrating rotor target (SVRT) model proposed by Zhang [J. Chem. Phys. 111 (1999) 3929] is applied to study the dynamics of dissociative adsorption for CH4 on a flat and static Ni(100) surface. The molecule CH4 is treated as a semirigid vibrating rotor CH3-H, and the London–Eyring–Polanyi–Sato potential energy surface is utilized. The numerical calculation for the reaction system is carried out by using the time-dependent wave packet approach, and the propagation of wave packets is obtained by the split-operator method. The results demonstrate many important properties of the CH4 molecule dissociation process on the metal Ni. The dissociation probability is a strongly increasing function of the incident kinetic energy, and is enhanced significantly when the molecule CH4 is excited, which denotes the clear vibration-excitation effect, as observed in the molecular beam studies of Holmblad et al. [J. Chem. Phys. 102 (1995) 8255] The isotopic effect is also studied for molecules CH4 and CD4 at the ground rovibrational states.

A classic problem in circuit theory first studied by German physicist Kirchhoff more than 170 years ago is the computation of resistances in resistor networks. Nowadays, resistor network has been an important model in the fields of natural science and engineering technology, but it is very difficult to calculate the equivalent resistance between two arbitrary nodes in an arbitrary resistor network. In 2004, Wu F Y formulated a Laplacian matrix method and derived expressions for the two-point resistance in arbitrary finite and infinite lattices in terms of the eigenvalues and eigenvectors of the Laplacian matrix, and the resistance results obtained by Laplacian matrix method is composed of double sums. The weakness of the Laplacian matrix approach is that it depends on the two matrices along two orthogonal directions. In 2011, Tan Z Z created the recursion-transform (RT) method, which can resolve the resistor network with arbitrary boundary. Using the RT method to compute the equivalent resistance relies on just one matrix along one direction, and the resistance is expressed by single summation. In the present paper, we investigate the equivalent resistance and complex impedance of an arbitrary mn cylindrical network by the RT method. Firstly, based on the network analysis, a recursion relation between the current distributions on three successive vertical lines is established through a matrix equation. In order to obtain the eigenvalues and eigenvectors of the matrix, and the general solution of the matrix equation, we then perform a diagonalizing transformation on the driving matrix.Secondly, we derive a recursion relation between the current distributions on the boundary, and construct some particular solutions of the matrix equation. Finally by using the matrix equation of inverse transformation, we obtain the analytical solution of the branch current, and gain the equivalent resistance formula along the axis of the arbitrary mn cylindrical network, which consists of the characteristic root and expressed by only single summation. As applications, several new formulae of equivalent resistances in the semi-infinite and infinite cases are given. These formulae are compared with those in other literature, meanwhile an interesting new identity of trigonometric function is discovered. At the end of the article, the equivalent impedance of the mn cylindrical RLC network is also treated, where the equivalent impedance formula is also given.

A periodic potential system excited by multi-low frequency weak signals, the high frequency signal and additive stable noise is constructed. Based on this model, the vibrational resonance phenomenon under stable noise is investigated by taking the mean signal-noise-ratio gain (MSNRI) of output as a performance index. Then the influences of stability index (0 2), the skewness parameter (-1 1) of stable noise, the amplification factor D and the high frequency signal amplitude B, and frequency on the resonant output effect are explored. The results show that under the different distributions of stable noise, the multi-low frequency weak signals detection can be realized by adjusting the high frequency signal parameter B or to induce vibrational resonance within a certain range. When (or ) is given different values, the curve of MSNRI-B has multiple peaks with the increase of B for a certain frequency , and the values of MSNRI corresponding to peaks of the curve of MSNRI-B are equal. So the intervals of B which can induce vibrational resonances are multiple, and the multiple resonance phenomenon turns periodic with the increase of B. Similarly, the curve of MSNRI- also has multiple peaks with the increase of for a certain amplitude B, so the intervals of which can induce vibrational resonances are also multiple. The difference is that the multiple resonance phenomenon becomes irregular with the increase of . Besides, the resonance intervals of B and do not change with nor . Under the different values of amplitude factor D, the resonance intervals of B (or ) do not change with the increase of D, indicating that only the energy of the high frequency signal transfers toward the signals to be measured, and the energy of stable noise does not transfer toward the signals to be measured. Besides, when B and are fixed, it can still be realized to detect the weak signal with the increase of D, which shows that the weak signal detection method based on vibrational resonance can overcome the shortcoming that noise intensity in industrial sites cannot be regulated and controlled. The results provide a new method of detecting the weak signal, and have potential application value in signal processing.

Ferromagnetic structures such as pipes or vessels are widely used in petroleum, chemical and power generation industries. Periodical nondestructive testing (NDT) is vital for continued safe operation. As a NDT technology, pulsed eddy current testing (PECT) technology which is excited by a square-wave pulse rather than a sinusoidal waveform has been widely used for its advantages of non-contact and acquisition of information at various depths in one excitation process. In PECT, the analytical modeling is important because it gives a better understanding of the signal and benefits the inverse process of PECT in extracting information of structures. The foundation of theoretical model of PECT is the Dodd-Deeds model presented by Dodd and Deeds in 1968, Theodoulidis and Kriezis represented the integral solution of Dodd-Deeds model in the form of series by using the truncated region eigenfunction expansion (TREE) method. Using the Dodd-Deeds model and the TREE method, other analytical modelings have been solved. However, most modelings assume that the wall thinning of the specimen is uniform, and the analytical solution only contains the variables in the z direction (the direction perpendicular to the surface of the specimen), such as the thickness of the specimen. With the rapid development of PECT, problems such as the footprint of the probe, the quantitative analysis of local wall thinning also need to be solved. These problems are related to the variable in the r direction (the direction parallel to the surface of the specimen), so the analytical modelings mentioned above are not available any more. To solve these problems, the analytical modeling of the plate with a flat-bottom hole is proposed. Considering the fact that the boundary condition in the analytical modeling of the plate with a flat-bottom hole is complicated, the assumption that the transverse wave number and the longitudinal wave number in the layer where the flat-bottom hole located are the same is made in this paper, and the transverse wave number is set to be only related to the structure in the r direction. Firstly, the expressions of magnetic vector potential in all the layers are obtained by using the reflection and refraction theory of electromagnetic wave. Then the analytical solution is solved based on the extended Cheng's matrix method by introducing the construction coefficient Wn. Finally, the 16MnR specimen with the flat bottom holes is conducted as an example, and experiments are carried out. The good agreement between results calculated by the analytical model and the experimental results measured verifies the developed analytical model.

The Protein-Le Chatelier (PLC) effects are investigated by using digital image correlation at a constant applied strain rate of 5.0010-3 s-1 and room temperature in Al-Mg alloys with Mg content values (wt.%) of 2.30, 4.57, 6.10 and 6.91 respectively in this study. Both the yield strength and the ultimate strength increase with increasing Mg content, which is generally called solution strengthening. Type of PLC band changes from A to B with increasing Mg content. In low Mg content (2.30%) alloy, the serration amplitude almost remains 1 MPa, while in each of high Mg content (4.57%, 6.10%, 6.91%) alloys it linearly increases with the strain increasing. The serration amplitude is found to increase with increasing Mg content and gradually reaches a saturated state. With the increase of Mg content, the period of PLC band for continuous propagation gradually reduces and the time when the PLC band location sudden jumps increases in the process of propagation. When the strain is small, the out-of-band deformation of alloy is inhomogeneous obviously. And the deformation inhomogeneity slightly decreases with increasing Mg content. DIC results indicate that the PLC bandwidth does not change with Mg content, while the maximum strain increment in the PLC band increases with increasing both Mg content and strain. Additionally, special periodic damped serrations are observed in the stress-time curve of the low Mg content (2.30%), the corresponding PLC band shows that the periodic changed serrations in the stress-time curve correspond to the transformation of the PLC band orientation. Besides, the PLC band propagates upward continuously both before and after the shift.

Pulsed actuation is one of the most fundamental control types to study regularity of flow structures in supersonic mixing layers, which helps to predict the aero-optical effects caused by the supersonic mixing layer where the different-sized vortices dominate the flow field. However, the knowledge about the evolution mechanism of vortices in the supersonic mixing layer which is controlled by the pulsed forcing is limited. Based on the large eddy simulation (LES), the visualized flow field of a supersonic mixing layer controlled by the pulsed forcing is presented and the unique growth mechanism of the vortices in such a case is revealed clearly. The method of position extraction of the vortex core in the supersonic mixing layer, which is a quantitative technique to obtain the instantaneous location of a vortex in flow field, is employed to calculate the dynamic characteristics (e.g., instantaneous convective speed and size) of the vortices quantitatively. The pulsed forcings of different frequencies are imposed on the same supersonic mixing layer respectively, and the instantaneous convective speed and size of the vortices for each pulse frequency considered in this study are then computed. By comparing the dynamic characteristics of the vortices between cases, the evolution mechanism of the vortices in the supersonic mixing layer controlled by the pulsed forcing is revealed.as follows. 1) Growth of the vortices in the supersonic mixing layer controlled by the pulsed forcing no longer depends on the pairing nor merging between adjacent vortices, which is just the growth mechanism of vortices in a free supersonic mixing layer. Actually, the size of a vortex in the controlled supersonic mixing layer is dominated by the imposed pulse frequency, so the size of each vortex in such a flow field is approximately identical. 2) The number of vortices in the controlled supersonic mixing layer is proportional to the pulse frequency, whereas the size of vortex is inversely proportional to the pulse frequency. That is, the higher the pulse frequency, the bigger the number of vortices in the controlled flow field is and the smaller the size of every vortex. 3) The average convective speed of vortices in the controlled supersonic mixing layer gradually decreases with pulse frequency increasing because the pulsed forcing essentially drags on the movement of vortices in flow field. Finally, an equation which describes the quantitative relationship between the dynamic characteristics of a vortex and the pulsed forcing frequency is derived, that is, the product of the average convective speed of vortices in the controlled supersonic mixing layer and the imposed pulse period is approximately equal to the mean diameter of vortices in the flow field.

We have studied the influence of incident atoms with low energy on the Pt(100) surface by molecular dynamics simulation. The interaction potential obtained by the embedded atom method (EAM) was used in the simulation. The incident energy changes from 0.1eV to 200eV and the target temperature ranges from 100 to 500 K. The target scales are 6×6×4 and 8×8×4 fcc cells for lower and higher incident energies, respectively. The adatom, sputtering, vacancy and backscattering yields are calculated. It was found that there is a sputtering threshold for the incident energy. When the incident energy is higher than the sputtering threshold, the sputtering yield increases with the increase of incident energy and the sputtering shows a symmetrical pattern. We found that the adatom and vacancy yields increase as the incident energy increases. The vacancy yields are much higher than those obtained by Monte Carlo simulation. The dependence of the adatom and sputtering yields on the incident energy and the relative atomistic mechanisms are discussed.

Partially oriented and highly textured diamond films on Si(111) substrates were achieved by hot-filament chemical vapor deposition(HFCVD). High nucleation density greater than 5 x 10(8) cm(-2) was realized in 3 min by near-surface glow discharge. The as-grown films were characterized. by scanning electron microscopy (SEM), X-ray diffraction(XRD) and Raman spectroscopy. It was found that by adding a small amount of oxygen to the mixture of CH4/H-2, the appearance of facet(111) was well controlled, and the secondary nucleation on the facet(111) was suppressed greatly. Growth feature of homoepitaxy on diamond(111) surface was demonstrated to be in Stranski-Krastanov model by SEM.

We present a scheme to realize the arbitrary control of the time evolution of an atom-cavity system via atomic feedback for the generation of an arbitrary quantum state. The scheme does not need to detect the atomic state, thus the uncontrollable measurement can be avoided.

The energetic atom deposition of thin Au/Au(100) film has been studied by molecular dynamics simulation using the Au-Au interatomic interaction potential with embedded atom method. By investigating the variation of coverage curves and Bragg diffraction intensities during the film growth, the transition of Stranski-Kranstanov growth mode to Frank-van der Merwe growth mode was observed with the increase of the incident energy of deposition atoms. The role of energetic atoms in the film growth is discussed by analyzing the transport properties of deposited atoms and the evolution of incident energy and substrate temperatures.

Numerical investigation of the electronic structure of a small closed quantum system fabricated on the two-dimensional electron gas forming on the interference between GaAs and AlxGa1-xAs is reported. The Kohn-Sham spin-density-functional theory is applied. Self-consistent results show that the quantum system assumes unequal numbers of electrons for spin up and spin down because of the existence of bound states. The profiles of effective potential energies for spin up and spin down electrons are then found to be very different, which will result in different transmission coefficients. It is notable that this spin polarization is caused by the geometry of the nanostructure.

We present a new substrate-free bimaterial cantilever array made of SiNx and Au for an uncooled micro-optomechanical infrared imaging device. Each cantilever element has an optimized deformation magnification structure. A 160 × 160 array with a 120 μm × 120 μm pitch is fabricated and an optical readout is used to collectively measure deflections of all microcantilevers in the array. Thermal images of room-temperature objects with higher spatial resolution have been obtained and the noise-equivalent temperature difference of the fabricated focal plane arrays is given statistically and is measured to be about 270 mK.

A new conserved quantity is deduced from Mei symmetry of Tzenoff equations for holonomic systems. The expression of this new conserved quantity is given, and the determining equation to induce this new conserved quantity is presented. The results exhibit that this new method is easier to find more conserved quantities than the previously reported ones. Finally, application of this new result is presented by a practical example.

We study the Raman spectra of Bi4Ge3O12 crystal at different temperatures, as well as its melt. The structure characters of the single crystal, melt and growth solid–liquid boundary layer of BGO are investigated by their high-temperature Raman spectra for the first time. The rule of structure change of BGO crystal with increasing temperature is analysed. The results show that there exists [GeO4] polyhedral structure and Bi ion independently in BGO melt. The bridge bonds Bi–O–Bi and Bi–O–Ge appear in the crystal and at the boundary layer, but disappear in the melt. The structure of the growth solid–liquid boundary layer is similar to that of BGO crystal. In the melt, the long-range order structure of the crystal disappears. The thickness of the growth solid–liquid boundary layer of BGO crystal is about 50 μm.

A new one-dimensional phenomenological model based on the dynamic strain aging mechanism is developed. In order to account for the elastic shrinkage induced by the Portevin–Le Chatelier effect, elastic deformation is considered under the boundary conditions of the present model. The simulated results are found to be in good agreement with the experimental observations.

Mg63Ni22Pr15 metallic glasses are produced by a single roller melt-spinning technique. The hydrogen absorption and desorption capacities are respectively 0.38 and 0.14 wt.% at 313 K obtained by pressure-composition isotherm. The amorphous structure is found to be retained after gaseous hydrogenation. The glass transition temperature, the onset crystallization temperature, and the crystallization temperature of the hydrogenated Mg63Ni22Pr15 metallic glass are 550, 570 and 577 K, respectively, much higher than the corresponding values of 440, 470 and 499 K of the as-quenched sample. This means that dramatic enhancement of thermal stability occurs in Mg63Ni22Pr15 metallic glass due to hydrogenation.

The nonlinear interaction in the coherent structure in the CT-6B tokamak plasma turbulence is studied by using the wavelet bicoherence technique. The results show that the coherent structure mainly results from the nonlinear interaction between waves.

We experimentally studied the in-plane thermal and electrical properties of a suspended platinum nanofilm in thickness of 15 nm. The measured results show that the in-plane thermal conductivity, the electrical conductivity and the resistance-temperature coefficient of the studied nanofilm are much less than those of the bulk material, while the Lorenz number is greater than the bulk value. Comparing with the results reported previously for the platinum nanofilm in thickness of 28 nm, we further find that the in-plane thermal conductivity, the electrical conductivity and the resistance-temperature coefficient decrease with the decreasing thickness of the nanofilm, while the Lorenz number increases with the decreasing thickness of the nanofilm. These results indicate that strong size effects exist on the in-plane thermal and electrical properties of platinum nanofilms.

Nanocrystalline TiO2 powder was prepared by sol-gel process. The structures of the as-prepared and the TiO2 powder heat-treated at different temperatures were studied by thermogravimetric analyzer, differential thermal analysis, x-ray diffraction, and Raman spectra. As the powder was heat-treated at 350°C, it turned into tetragonal anatase structure. A structural transformation from anatase to rutile type occurred and the grains of the powder grew drastically when the powder was heat-treated at above 550°C. The structural transformation from anatase to rutile type completed at 750°C. The Raman spectra of TiO2 nanocrystalline powder were also studied.

The energy levels and the E2 transition probabilities B(E2) of uranium isotopes 232-238U are calculated by the 1/N expansion technique with the consistent Q framework in sdIBM1. The energy spectra for the five isotopes and B(E2) of 236U can be reproduced quite well with a few number of parameters only.

High resolution electron energy loss spectroscopy, low energy electron diffraction and quadrupole mass spectrometer (QMS) have been employed to study the effect of atomic hydrogen on the acetylene-saturated pre-adsorbed Si(100)(2 × 1) surface and the surface phase transition at room temperature. It is evident that the atomic hydrogen has a strong effect on the adsorbed C2H2 and the underlying surface structure of Si. The experimental results show that CH and CH2 radicals co-exist on the Si surface after the dosing of atomic hydrogen; meanwhile, the surface structure changes from Si(100)(2 × 1) to a dominant of (1 × 1). These results indicate that the atomic hydrogen can open C=C double bonds and change them into C-C single bonds, transfer the adsorbed C2H2 to C2Hx(x = 3,4) and break the underlying Si-Si dimer, but it cannot break the C-C bond intensively. The QMS results show that some C4 species are formed during the dosing of atomic hydrogen. It may be the result of atomic hydrogen abstraction from C2Hx which leads to carbon catenation between two adjacent C-C dimers. The C4 species formed are stable on Si(100) surfaces up to 1100 K, and can be regarded as the potential host of diamond nucleation.