This paper deals with off-diagonal operator matrices and their applications in elasticity theory. Two kinds of completeness of the system of eigenvectors are proven, in terms of those of the compositions of two block operators in the off-diagonal operator matrices. Using these results, the double eigenfunction expansion method for solving upper triangular matrix differential systems is proposed. Moreover, we apply the method to the two-dimensional elasticity problem and the problem of bending of rectangular thin plates on elastic foundation.

In this paper, a meshfree boundary integral equation (BIE) method, called the moving Kriging interpolation-based boundary node method (MKIBNM), is developed for solving two-dimensional potential problems. This study combines the BIE method with the moving Kriging interpolation to present a boundary-type meshfree method, and the corresponding formulae of the MKIBNM are derived. In the present method, the moving Kriging interpolation is applied instead of the traditional moving least-square approximation to overcome Kronecker's delta property, then the boundary conditions can be imposed directly and easily. To verify the accuracy and stability of the present formulation, three selected numerical examples are presented to demonstrate the efficiency of MKIBNM numerically.

This paper obtains Lagrange equations of nonholonomic systems with fractional derivatives. First, the exchanging relationships between the isochronous variation and the fractional derivatives are derived. Secondly, based on these exchanging relationships, the Hamilton's principle is presented for non-conservative systems with fractional derivatives. Thirdly, Lagrange equations of the systems are obtained. Furthermore, the d'Alembert–Lagrange principle with fractional derivatives is presented, and the Lagrange equations of nonholonomic systems with fractional derivatives are studied. An example is designed to illustrate these results.

The electromagnetic concentrative coils are indispensable in the functional magnetic stimulation and have potential applications in nondestructive testing. In this paper, we propose a figure-8-shaped coil being composed of two arbitrary oblique elliptical coils, which can change the electromagnetic concentrative region and the magnitude of eddy current density by changing the elliptical shape and/or spread angle between two elliptical coils. Pulsed current is usually the excitation source in the functional magnetic stimulation, so in this paper we derive the analytical solutions of transient pulsed eddy current field in the time domain due to the elliptical concentrative coil placed in an arbitrary position over a half-infinite plane conductor by making use of the scale-transformation, the Laplace transform and the Fourier transform are used in our derivation. Calculation results of field distributions produced by the figure-8-shaped elliptical coil show some behaviours as follows: 1) the eddy currents are focused on the conductor under the geometric symmetric centre of figure-8-shaped coil; 2) the greater the scale factor of ellipse is, the higher the eddy current density is and the wider the concentrative area of eddy current along y axis is; 3) the maximum magnitude of eddy current density increases with the increase of spread angle. When spread angle is 180o, there are two additional reverse concentrative areas on both sides of x axis.

We newly construct two mutually-conjugate tripartite entangled state representations, based on which we propose the formulation of three-mode entangled fractional Fourier transformation (EFFT) and derive the transformation kernel. The EFFT's additivity property is proved and the eigenmode of EFFT is derived. As an application, we calculate the EFFT of the three-mode squeezed vacuum state.

Considering the effects that the probability of traffic interruption and the friction between two lanes have on the car-following behaviour, this paper establishes a new two-lane microscopic car-following model. Based on this microscopic model, a new macroscopic model was deduced by the relevance relation of microscopic and macroscopic scale parameters for the two-lane traffic flow. Terms related to lane change are added into the continuity equations and velocity dynamic equations to investigate the lane change rate. Numerical results verify that the proposed model can be efficiently used to reflect the effect of the probability of traffic interruption on the shock, rarefaction wave and lane change behaviour on two-lane freeways. The model has also been applied in reproducing some complex traffic phenomena caused by traffic accident interruption.

We investigate a one-dimensional open Bose–Einstein condensate with attractive interaction, by considering the effect of feeding from nonequilibrium thermal cloud and applying the time-periodic inverted-harmonic potential. Using the direct perturbation method and the exact shock wave solution of the stationary Gross–Pitaevskii equation, we obtain the chaotic perturbed solution and the Melnikov chaotic regions. Based on the analytical and the numerical methods, the influence of the feeding strength on the chaotic motion is revealed. It is shown that the chaotic regions could be enlarged by reducing the feeding strength and the increase of feeding strength plays a role in suppressing chaos. In the case of "nonpropagated" shock wave with fixed boundary, the number of condensed atoms increases faster as the feeding strength increases. However, for the free boundary the metastable shock wave with fixed front density oscillates its front position and atomic number aperiodically, and their amplitudes decay with the increase of the feeding strength.

In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 (Internet Protocol version 4) addresses, this paper proposes a forecasting model by using S curve (logistic curve). The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions (i.e., Barabási–Albert method) is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabási–Albert method commonly used in current network research.

This paper deals with the problem of synchronization for a class of uncertain chaotic systems. The uncertainties under consideration are assumed to be Lipschitz-like nonlinearity in tracking error, with unknown growth rate. A logic-based switching mechanism is presented for tracking a smooth orbit that can be a limit cycle or a chaotic orbit of another system. Based on the Lyapunov approach, the adaptation law is determined to tune the controller gain vector online according to the possible nonlinearities. To demonstrate the efficiency of the proposed scheme, the well-known chaotic system namely Chua's circuit is considered as an illustrative example.

Based on the improved state observer and the pole placement technique, by adding a constant which extends the scope of use of the original system, a new design method of generalized projective synchronization is proposed. With this method, by changing the projective synchronization scale factor, one can achieve not only complete synchronization, but also anti-synchronization, as well as arbitrary percentage of projective synchronization, so that the system may attain arbitrary synchronization in a relatively short period of time, which makes this study more meaningful. By numerical simulation, and choosing appropriate scale factor, the results of repeated experiments verify that this method is highly effective and satisfactory. Finally, based on this method and the relevant feedback concept, a novel secure communication project is designed. Numerical simulation verifies that this secure communication project is very valid, and moreover, the experimental result has been greatly improved in decryption time.

This paper investigates the cluster consensus problem for second-order multi-agent systems by applying the pinning control method to a small collection of the agents. Consensus is attained independently for different agent clusters according to the community structure generated by the group partition of the underlying graph and sufficient conditions for both cluster and general consensus are obtained by using results from algebraic graph theory and the LaSalle Invariance Principle. Finally, some simple simulations are presented to illustrate the technique.

Based on the stability theory of the fractional order system, the dynamic behaviours of a new fractional order system are investigated theoretically. The lowest order we found to have chaos in the new three-dimensional system is 2.46, and the period routes to chaos in the new fractional order system are also found. The effectiveness of our analysis results is further verified by numerical simulations and positive largest Lyapunov exponent. Furthermore, a nonlinear feedback controller is designed to achieve the generalized projective synchronization of the fractional order chaotic system, and its validity is proved by Laplace transformation theory.

This paper demonstrates rigorous chaotic dynamics in nonlinear Bloch system by virtue of topological horseshoe and numerical method. It considers a properly chosen cross section and the corresponding Poincaré map, and shows the existence of horseshoe in the Poincaré map. In this way, a rigorous verification of chaos in the nonlinear Bloch system is presented.

In most earlier ferroresonance studies the traditional excitation characteristic of iron core, in which the traditional excitation characteristic contains harmonic voltages or currents, has been used as if it were made up of pure fundamental voltage or current. However, this is not always true. In comparison with traditional excitation characteristics, this paper introduces the power frequency excitation characteristic of the iron core, which contains no harmonics. The power frequency excitation characteristic of iron core has been obtained by Elector Magnetic Transient Program, resulting in discrete voltage and current pairs. Extensive simulations are carried out to analyse the effect of power frequency excitation characteristic on potential transformer ferroresonance. A detailed analysis of simulation results demonstrates that with power frequency excitation characteristic of iron core inclusion at certain excitation voltage the ferroresonance may happen, conversely it may not happen with traditional excitation characteristic inclusion.

A new four-dimensional chaotic system with a linear term and a 3-term cross product is reported. Some interesting figures of the system corresponding different parameters show rich dynamical structures.

This paper gives the definition of function projective synchronization with less conservative demand for a scaling function, and investigates the function projective synchronization in partially linear drive–response chaotic systems. Based on the Lyapunov stability theory, it has been shown that the function projective synchronization with desired scaling function can be realized by simple control law. Moreover it does not need scaling function to be differentiable, bounded and non-vanished. The numerical simulations are provided to verify the theoretical result.

This paper concerns the absolute stability problem of discrete-time descriptor systems with feedback connected ferromagnetic hysteresis nonlinearities. The ferromagnetic hysteresis model satisfies the passivity conditions of hysteresis operator, that is the input–output relation of the transformed operator is passive. The bound condition of the solution of the ferromagnetic hysteresis model is given. Through the framework of loop transformation, an augmented discrete-time descriptor system model is established for the stability analysis. A new extended Tsypkin criterion for the absolute stability of discrete-time descriptor systems with hysteresis is presented based on the linear matrix inequalities technique. A numerical example is given to illustrate the effectiveness of the extended criterion.

Scale-free networks and consensus behaviour among multiple agents have both attracted much attention. To investigate the consensus speed over scale-free networks is the major topic of the present work. A novel method is developed to construct scale-free networks due to their remarkable power-law degree distributions, while preserving the diversity of network topologies. The time cost or iterations for networks to reach a certain level of consensus is discussed, considering the influence from power-law parameters. They are both demonstrated to be reversed power-law functions of the algebraic connectivity, which is viewed as a measurement on convergence speed of the consensus behaviour. The attempts of tuning power-law parameters may speed up the consensus procedure, but it could also make the network less robust over time delay at the same time. Large scale of simulations are supportive to the conclusions.

This paper discusses the forward and inverse problem for cardiac magnetic fields and electric potentials. A torso-heart model established by boundary element method (BEM) is used for studying the distributions of cardiac magnetic fields and electric potentials. Because node-to-node and triangle-to-triangle BEM can lead to discrepant field distributions, their properties and influences are compared. Then based on constructed torso-heart model and supposed current source functional model–current dipole array, the magnetic and electric imaging by optimal constrained linear inverse method are applied at the same time. Through figure and reconstructing parameter comparison, though the magnetic current dipole array imaging possesses better reconstructing effect, however node-to-node BEM and triangle-to-triangle BEM make little difference to magnetic and electric imaging.

In this study, our vibrational spectroscopic analysis is made on hydrogen-bonding between dimethyl sulfoxide and water comprises both experimental Raman spectra and ab initio calculations on structures of various dimethyl sulfoxide/water clusters with increasing water content. The Raman peak position of the v(S=O) stretching mode of dimethyl sulfoxide serves as a probe for monitoring the degree of hydrogen-bonding between dimethyl sulfoxide and water. In addition, the two vibrational modes, namely, the CH_{3} symmetric stretching mode and the CH_{3} asymmetric stretching mode have been analysed under different concentrations. We relate the computational results to the experimental vibrational wavenumber trends that are observed in our concentration-dependent Raman study. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the nature of the hydrogen bonding and the structures of the hydrogen-bonded complexes studied.

This paper investigates the effect of basis sets through the potential energy curves (PECs) of six rare gas complexes He_{2}, Ne_{2}, Ar_{2}, He–Ne, He–Ar, and Ne–Ar. The coupled cluster singles and doubles method with perturbative treatment of triple excitations, doubly augmented basis sets of d-aug-cc-pVQZ, bond functions, and basis set superposition errors are employed. The diffuse function is more effective than the polarization function on describing the dissociation energy. The PECs are fitted into analytical potential energy functions (APEFs) using three expressions. It is found that all the expressions are suitable for describing the complexes of rare gases. Based on these APEFs, the spectroscopic parameters are calculated and the results are compared with the theoretical and experimental data available in the literature.

This paper presents the experimental progress of laser-focused Cr atomic deposition and the experimental condition. The result is an accurate array of lines with a periodicity of 212.8±0.2 nm and mean full-width at half maximum as approximately 95 nm. Surface growth in laser-focused Cr atomic deposition is modeled and studied by kinetic Monte Carlo simulation including two events: the one is that atom trajectories in laser standing wave are simulated with the semiclassical equations of motion to obtain the deposition position; the other is that adatom diffuses by considering two major diffusion processes, namely, terrace diffusion and step-edge descending. Comparing with experimental results (Anderson W R, Bradley C C, McClelland J J and Celotta R J 1999 Phys. Rev. A59 2476), it finds that the simulated trend of dependence on feature width is in agreement with the power of standing wave, the other two simulated trends are the same in the initial stage. These results demonstrate that some surface diffusion processes play important role in feature width broadening. Numerical result also shows that high incoming beam flux of atoms deposited redounds to decrease the distance between adatoms which can diffuse to minimize the feature width and enhance the contrast.

We report the experimental results on measuring the isotope shifts and hyperfine splittings of all ytterbium isotopes for a 399-nm transition by using a quite simple and novel method. It benefits from the advantages of the modulation transfer spectroscopy in an ytterbium hollow cathode lamp and the Doppler-free spectroscopy in a collimated ytterbium atomic beam. The key technique in this experiment is simultaneously measuring the frequency separations of the two spectra twice, and the separation difference between two measurements is solely determined by the well-defined frequency of an acousto-optics modulator. Compared with the most of previously reported experimental results, ours are more accurate and completed, which will provide the useful information for developing a more accurate theoretical model to describe the interaction inside an ytterbium atom.

This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.

The time-dependent wave packet method is used to investigate the influence of laser-fields on the vibrational population of molecules. For a two-state system in laser fields, the populations on different vibrational levels of the upper and lower electronic states are given by wavefunctions obtained by solving the Schrödinger equation with the split-operator method. The calculation shows that the field parameters, such as intensity, wavelength, duration, and delay time etc. can have different influences on the vibrational population. By varying the laser parameters appropriately one can control the evolution of wave packet and so the vibrational population in each state, which will benefit the light manipulation of atomic and molecular processes.

The potential energy curve (PEC) of HI(X^{1}Σ^{+}) molecule is studied using the complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction approach at the correlation-consistent basis sets, aug-cc-pV6Z for H and aug-cc-pV5Z-pp for I atom. Using the PEC of HI(X^{1}Σ^{+}), the spectroscopic parameters of three isotopes, HI(X^{1}Σ^{+}), DI(X^{1}Σ^{+}) and TI(X^{1}Σ^{+}), are determined in the present work. For the HI(X^{1}Σ^{+}), the values of D_{0}, D_{e}, R_{e}, ω_{e}, ω_{e}χ_{e}, α_{e} and B_{e} are 3.1551 eV, 3.2958 eV, 0.16183 nm, 2290.60 cm^{-1}, 40.0703 cm^{-1}, 0.1699 cm^{-1} and 6.4373 cm^{-1}, respectively; for the DI (X^{1}Σ^{+}), the values of D_{0}, D_{e}, R_{e}, ω_{e}, ω_{e}χ_{e}, α_{e} and B_{e} are 3.1965 eV, 3.2967 eV, 0.16183 nm, 1626.8 cm^{-1}, 20.8581 cm^{-1}, 0.0611 cm^{-1} and 3.2468 cm^{-1}, respectively; for the TI (X^{1}Σ^{+}), the values of D_{0}, D_{e}, R_{e}, ω_{e}, ω_{e}χ_{e}, α_{e} and B_{e} are of 3.2144 eV, 3.2967 eV, 0.16183 nm, 1334.43 cm^{-1}, 14.0765 cm^{-1}, 0.0338 cm^{-1} and 2.1850 cm^{-1}, respectively. These results accord well with the available experimental results. With the PEC of HI(X^{1}Σ^{+}) molecule obtained at present, a total of 19 vibrational states are predicted for the HI, 26 for the DI, and 32 for the TI, when the rotational quantum number J is equal to zero (J = 0). For each vibrational state, vibrational level G(ν), inertial rotation constant B_{ν} and centrifugal distortion constant D_{ν} are determined when J = 0 for the first time, which are in excellent agreement with the experimental results.

The lowest-energy structures and the electronic properties of Mo_{2n}N_{n} (n=1–5) clusters have been studied by using the density functional theory (DFT) simulating package DMol^{3} in the generalized gradient approximation (GGA). The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mo_{n} (n=2, 4, 6, 8, 10) clusters and nitrogen atoms which surround these cores. The average binding energy, the adiabatic electron affinity (AEA), the vertical electron affinity (VEA), the adiabatic ionization potential (AIP) and the vertical ionization potential (VIP) of Mo_{2n}N_{n} (n=1–5) clusters have been estimated. The HOMO–LUMO gaps reveal that the clusters have strong chemical activities. An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.

This paper studies supersonic jet-cooled 1-fluoronaphthalene (1FN) clusters by ultraviolet (UV) laser ionization at 281 nm in a time-of-flight mass spectrometer. The (1FN)_{n}^{+} (n=1–3) series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first "shell" in geometric structure while the larger clusters are generated based on this fundamental unit.

Polarization singularities in the near-field of Gaussian vortex beams diffracted by a circular aperture are studied by a rigorous electromagnetic theory. It is shown that there exist C-points and L-lines, which depend on off-axis displacement parameters along the x and y directions, waist width, wavelength, and topological charge of the diffracted Gaussian vortex beam, as well as on propagation distance. The results are illustrated by numerical calculations.

This paper addresses the formulae and numerical issues related to the possibility that fast wave may be grown when a relativistic electron beam through an ion channel in a cylindrical metal waveguide. To derive the dispersion equations of the beam–wave interaction, it solves relativistic Lorentz equation and Maxwell's equations for appropriate boundary conditions. It has been found in this waveguide structure that the TM_{0m} modes are the rational operating modes of coupling between the electromagnetic modes and the betatron modes. The interaction of the dispersion curves of the electromagnetic TM_{0m} modes and the upper betatron modes is studied. The growth rates of the wave are obtained, and the effects of the beam radius, the beam energy, the plasma frequency, and the beam plasma frequency on the wave growth rate are numerically calculated and discussed.

This paper studies a small f-number metallic lens with depth-modulated slits. Slits filled with dielectric between silver plates are designed to produce desired optical phase retardations based on the particular propagation properties of surface plasmon polaritons in nanostructures. Numerical simulation of this structure is performed through the finite-difference time-domain method. Different from the conventional dielectric lens, the metallic lens can be used as a pure phase element without energy loss brought by the light refraction at curved surfaces and total internal reflection. The focusing performance is consequently improved, with larger diffraction efficiency than that of the same shaped dielectric lens.

Based on the Kirchhoff approximation and the theoretical analysis of the random light fields, the speckle intensity distributions in the extremely deep Fresnel diffraction region are simulated. The fractal property of the speckles as well as the relation between the speckle intensity distribution and the corresponding random surface is investigated. We design a microscope system to detect experimentally the speckles in the extremely deep Fresnel diffraction region, and the experimental results prove the conclusions drawn from our simulations.

We propose a scheme for the direct measurement of Wigner function in two-mode cavity QED. The atoms are sent to resonantly interact with two orthogonally polarized cavity modes in the presence of strong classical field. The probability of measuring the atom in the ground state directly gives the useful information of the cavity field. This method can be used for quantum non-demolition measurement of the photon number.

This paper proposes a novel form of multimode nonlinear interactions by using a near-resonantly dressed atomic ensemble in an optical cavity. Due to quantum interference, a pair of collective fields come into the bilinear interactions, whose strengths are proportional to the population difference between dressed states which are coupled to the collective fields. By such an interaction, it is possible to obtain perfect multimode squeezing and collective Einstein–Podolsky–Rosen (EPR) entanglement in the cavity output.

In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states |τ> in terms of the spin values of j in the Schwinger bosonic realization. The correctness of the above conclusions can be verified by virtue of the entangled state <η| representation of the state |τ>.

This paper considers a scheme for the preparation of two-qutrit entangled states via adiabatic passage in ion-trapped system. In the proposal, the two three-level V-type ions are initially cooled to the ground states and need not be separately addressed. Moreover, only the ionic states act as memory and the system evolves in the dark space during the whole procedure, which makes the system robust against the decoherence and the fluctuation of the laser pulse.

From the viewpoint of quantum information, this paper studies preparation and control of atomic optimal entropy squeezing states (AOESS) for a moving two-level atom under control of the two-mode squeezing vacuum fields. Necessary conditions of preparation of the AOESS are analysed, and numerical verification of the AOESS is finished. It shows that the AOESS can be prepared by controlling the time of the atom interaction with the field, cutting the entanglement between the atom and field, and adjusting squeezing factor of the field. An atomic optimal entropy squeezing sudden generation in different components can alternately be realized by controlling the field-mode structure parameter.

Under the condition of two different cases, the absorption of a pulsed probe field and its slow propagation in a triple semiconductor quantum well are investigated. The result shows that semiconductor medium becomes transparent due to the action of control field. Another result shows that by choosing appropriate physical parameters, the slow propagation of the input field can be achieved. The proposed scheme has some potential applications and may lead to the development of the controlled technique of optical buffers and optical delay lines.

This paper demonstrates the realization of an optical switch by optically manipulating a large number of polystyrene spheres contained in a capillary. The strong scattering force exerted on polystyrene spheres with a large diameter of 4.3 μm is employed to realize the switching operation. A transparent window is opened for the signal light when the polystyrene spheres originally located at the beam centre are driven out of the beam region by the strong scattering force induced by the control light. The switching dynamics under different incident powers is investigated and compared with that observed in the optical switch based on the formation of optical matter. It is found that a large extinction ratio of ～30dB and fast switching-on and switching-off times can be achieved in this type of switch.

This paper investigates experimentally high-order harmonic generation (HHG) of neon gas with 5-fs and 25-fs driving laser pulses. It has been demonstrated that the cutoff energy of the harmonic extreme ultraviolet photons is extended to 131 eV and the HHG spectrum near the cutoff region becomes continuum as the driving laser pulse duration is 5 fs; whereas much lower cutoff photon energy and discrete harmonic spectrum near the cutoff region are presented as the laser pulse duration is 25 fs. The results can be explained by the fact that neutral atoms can be exposed to more intense laser field before they are depleted by ionization because of the extremely short rising time of the few-cycle pulse. The 5-fs driving laser pulse paves the way of generation of coherent x-ray in the water window and single attosecond pulse.

This paper reports that a long delay between the beginning of pumping current pulse and the onset of optical pulse is observed in InGaN laser diodes. The delay time decreases as the pumping current increases, and the speed of the delay time reduction becomes slower as the current amplitude increases further. Such delay phenomena are remarkably less serious in laser diodes grown on GaN substrate than those on sapphire. It attributes the delay to the traps which cause a large optical loss by saturable absorption and retard the laser action. The traps can be bleached by capturing injected carriers. The effect of GaAs laser irradiation on InGaN laser action demonstrates that the traps responsible for the delay are deep centres which can be filled by the photo-assisted processes.

The propagation of hollow Gaussian beams in strongly nonlocal nonlinear media is studied in detail. Two analytical expressions are derived. For hollow Gaussian beams, the intensity distribution always evolves periodically. However the second-order moment beam width can keep invariant during propagation if the input power is equal to the critical power. The interaction of two hollow Gaussian beams and the vortical hollow Gaussian beams are also discussed. The vortical hollow Gaussian beams with an appropriate topological charge can keep their shapes invariant during propagation.

This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a broad bandwidth. The energy transfer efficiency and modulation of the fundamental spectrum are investigated.

A novel highly efficient grating coupler with large filling factor and deep etching is proposed in silicon-on-insulator for near vertical coupling between the rib waveguide and optical fibre. The deep slots acting as high efficient scattering centres are analysed and optimized. As high as 60% coupling efficiency at telecom wavelength of 1550-nm and 3-dB bandwidth of 61 nm are predicted by simulation. A peak coupling efficiency of 42.1% at wavelength 1546-nm and 3-dB bandwidth of 37.6 nm are obtained experimentally.

Electroabsorption modulators combining Franz–Keldysh effect and quantum confined Stark effect have been monolithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.

A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.

This paper investigates the influences of a semiconductor laser with narrow linewidth on a fibre-optic distributed disturbance sensor based on Mach–Zehnder interferometer. It establishes an effective numerical model to describe the noises and linewidth of a semiconductor laser, taking into account their correlations. Simulation shows that frequency noise has great influences on location errors and their relationship is numerically investigated. Accordingly, there is need to determine the linewidth of the laser less than a threshold and obtain the least location errors. Furthermore, experiments are performed by a sensor prototype using three semiconductor lasers with different linewidths, respectively, with polarization maintaining optical fibres and couplers to eliminate the polarization induced noises and fading. The agreement of simulation with experimental results means that the proposed numerical model can make a comprehensive description of the noise behaviour of a semiconductor laser. The conclusion is useful for choosing a laser source for fibre-optic distributed disturbance sensor to achieve optimized location accuracy. What is more, the proposed numerical model can be widely used for analysing influences of semiconductor lasers on other sensing, communication and optical signal processing systems.

The performance of time-reversal focusing with a horizontal line array at different depths is investigated by normal mode modeling and computer simulation. It is observed that the focusing performance of a bottom-mounted horizontal time-reversal array is much better than that of a horizontal time-reversal array at other depths in shallow water. The normal mode modeling is used to explain this result. The absolute values of the modes at different depths are compared. It is shown that the number of modes whose absolute values close to zero is smaller at the bottom than that at other depths. It means that the horizontal time-reversal array deployed at the bottom can sample more modes，obtain more information of the probe source and achieve better focusing performance. The numerical simulations of time-reversal focusing performance under various conditions, such as different sound speed profiles, and different bottom parameters, lead to similar results.

The Noether symmetry, the Mei symmetry and the conserved quantities of discrete generalized Birkhoffian system are studied in this paper. Using the difference discrete variational approach, the difference discrete variational principle of discrete generalized Birkhoffian system is derived. The discrete equations of motion of the system are established. The criterion of Noether symmetry and Mei symmetry of the system is given. The discrete Noether and Mei conserved quantities and the conditions for their existence are obtained. Finally, an example is given to show the applications of the results.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

This paper reports that an experimental investigation of fast pitch angle scattering (FPAS) of runaway electrons in the EAST tokamak has been performed. From the newly developed infrared detector (HgCdTe) diagnostic system, the infrared synchrotron radiation emitted by relativistic electrons can be obtained as a function of time. The FPAS is analysed by means of the infrared detector diagnostic system and the other correlative diagnostic systems (including electron–cyclotron emission, hard x-ray, neutrons). It is found that the intensity of infrared synchrotron radiation and the electron–cyclotron emission signal increase rapidly at the time of FPAS because of the fast increase of pitch angle and the perpendicular velocity of the energetic runaway electrons. The Parail and Pogutse instability is a possible mechanism for the FPAS.

In order to produce millimeter-scale plasmas for the research of laser-plasma interactions (LPIs), gasbag target is designed and tested on Shenguang-III prototype laser facility. The x-ray pinhole images show that millimeter-scale plasmas are produced with the gasbag. The electron temperature inferred from the stimulated Raman scattering (SRS) spectrum is about 1.6 keV. The SRS spectrum also indicates that the electron density has a flat region within the duration of 200 ps. The obvious differences between the results of the gasbag and that of the void half hohlraum show the feasibility of the gasbag target in creating millimeter-scale plasmas. The LPIs in these millimeter-scale plasmas may partially mimic those in the ignition condition because the duration of the existence of a flat plasma density is much larger than the growth time of the two main instabilities, i.e., SRS and stimulated Brillouin scattering (SBS). So we make the conclusion that the gasbag target can be used to research the large-scale LPIs.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

This paper investigates the structural stability of intermetallics R_{3}Ni_{13-x}Co_{x}B_{2} (R=Y, Nd and Sm) with Nd_{3}Ni_{13}B_{2}-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials. The space group remains unchanged upon substitution of Co for Ni in R_{3}Ni_{13-x}Co_{x}B_{2} and the calculated lattice constants are found to agree with reports in literatures. The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g, 4h and 6i. Moreover, the total and partial phonon densities of states are first evaluated for the R_{3}Ni_{13}B_{2} compounds with the hexagonal Nd_{3}Ni_{13}B_{2}-type structure.

In this work, we present a feasible scheme based on framework of the sophisticated Voronoi tessellation method in order to evaluate what clusters should be preferred for building blocks in any given metallic glass, by analysing the fivefold-symmetry axes as well as the degree of structural regularity in various clusters. This scheme is well proved by a group of experiments and calculations, which may have broad implications for exploration of obtaining explicit and proper structural pictures, and understanding the structural origin of the unique properties and glass forming ability in these novel amorphous alloys.

This paper reports that carbon microcoils are grown through a chemical vapour deposit process, they are then embedded in silicone rubber, and manipulated to parallel with each other along their axes in the resulting composite. The impedance |Z| as well as phase angle θ of both the original carbon microcoil sheets and the aligned carbon microcoil/silicone rubber composites are measured. The results illustrate that carbon microcoils in different forms show different alternating current electric properties. The aligned carbon microcoils in the composites show stable parameters for f<10^{4} Hz but a sharp decrease in both |Z| and θ for frequencies >10^{4} Hz, which will also change as the carbon microcoils are extended. But, the original sheets have a pure resistance with their parameters stable throughout the entire alternating current frequency range investigated.

This paper reports that the film composed of flower-like ZnO micro-spheres, which consists of nano-sheets, is fabricated by chemical bath deposition. By adding hydrogen fluoride (HF) into the reaction solution, which contains zinc nitrate hexahydrate and hexamethylenetetramine, the ZnO crystal growth process is changed and the film composed by ZnO micro-spheres is obtained after keeping the reaction solution at 95 oC for 2 h. The morphology, crystal phase and wettability of the sample are characterized by scanning electron microscope, x-ray diffraction and contact angle meter, respectively. The results show that the film has the micro-nano compound structure. After modification with heptadecafluorodecyltrimethoxy-silane, the wettability of the film changed from superhydrophilicity to superhydrophobicity, on which water contact angle and the sliding angle are 154o and less than 5o for 8-μL water droplet, respectively. Additionally, the formation mechanism of the ZnO micro-sphere is also discussed.

In the present paper, the problem of sidebranches in the binary dendritic growth with enforced flow is studied. The positions of the first sidebranch and spacing of dendritic sidebranches are presented. For the neutral stable mode of dendritic growth, effects of various parameters on sidebranches are analysed. Our result shows that sidebranches are produced behind a critical point ξ'_{C}.

The physical vapour deposition of Ni atoms on α-Fe(001) surface under different deposition temperatures were simulated by molecular dynamics to study the intermixing and microstructure of the interfacial region. The results indicate that Ni atoms hardly penetrate into Fe substrate while Fe atoms easily diffuse into Ni deposition layers. The thickness of the intermixing region is temperature-dependent, with high temperatures yielding larger thicknesses. The deposited layers are mainly composed of amorphous phase due to the abnormal deposition behaviour of Ni and Fe. In the deposited Ni-rich phase, the relatively stable metallic compound B_{2} structured FeNi is found under high deposition temperature conditions.

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

Using the first principle method based on density functional theory, this paper studies the electronic structure and the ferromagnetic stability in N-doped ZnO. The calculated results based on local density approximation (LDA) and LDA+U method show that ferromagnetism coupling between N atoms is more energetically favourable for eight geometrically distinct configurations. The dominant ferromagnetic interaction is due to the hybridization between O 2p and N 2p. The origin of the ferromagnetic state in N doped ZnO is discussed by analysing coupling between N 2p levels. We also analyse N dopant concentration and lattice strain effect on ferromagnetism.

This paper performs the density functional theory calculations to obtain some factors influencing the response of pyrochlores Gd_{2}B_{2}O_{7} (B= Ti, Sn, Zr) to ion irradiation-induced amorphization. The 48f oxygen position parameter x, cohesive energy, bond type and defect-formation energy are discussed. The results show that parameter x can be used to indicate the disordering tendencies within a given pyrochlore family. Bond type, cohesive energy and defect-formation energies can be used to explain some experimental observations, but they are not determined exclusively by radiation ''resistance'' for a different pyrochlore family.

The electronic structures and magnetocrystalline anisotropy (MA) of ordered hexagonal close-packed (hcp) Co_{1-x}Ni_{x} alloys are studied using the full-potential linear-augmented-plane-wave (FLAPW) method with generalized gradient approximation (GGA). Great changes of magnetocrystalline anisotropy energy (MAE) are gained with different Ni compositions. Also, in-plane magnetocrystalline anisotropy is obtained for Co_{15}Ni in which the Snoek's limit is exceeded. It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions, which plays an important role in modulating the magnetization direction, where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states. The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition, and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.

Using ab initio plane-wave pseudo-potential density functional theory method, the elastic constants and band structures of stishovite were calculated. The calculated elastic constants under ambient conditions agree well with previous experimental and theoretical data. C_{13}, C_{33}, C_{44}, and C_{66} increase nearly linearly with pressure while C_{11} and C_{12} show irregularly changes with pressure over 20 GPa. The shear modulus (C_{11}-C_{12})/2 was observed to decrease drastically between 40 GPa and 50 GPa, indicating acoustic mode softening in consistency with the phase transition to CaCl_{2}-type structure around 50 GPa. The calculated band structures show no obvious difference at 0 and 80 GPa, being consistent with the high incompressibility of stishovite. With a quasi-harmonic Debye model, thermodynamic properties of stishovite were also calculated and the results are in good agreement with available experimental data.

This paper studies in detail the electronic properties of the semimetallic single-walled carbon nanotubes by applying the symmetry-adapted tight-binding model. It is found that the hybridization of π–σ states caused by the curvature produces an energy gap at the vicinity of the Fermi level. Such effects are obvious for the small zigzag and chiral single-walled carbon nanotubes. The energy gaps decrease as the diameters and the chiral angles of the tubes increase, while the top of the valence band and the bottom of the conduction band of armchair tubes cross at the Fermi level. The numeral results agree well with the experimental results.

In the adiabatic and weak-modulation quantum pump, net electron flow is driven from one reservoir to another by absorbing or emitting an energy quantum hω from or to the reservoirs. This paper considers high-order dependence of the scattering matrix on the time. Non-sinusoidal behaviour of strong pumping is revealed. The relation between the pumped current and the ac driving amplitude varies from power of 2, 1 to 1/2 when stronger modulation is exerted. Open experimental observation can be interpreted by multi-energy-quantum-related processes.

In this paper the quantum transport in a dot-array coupled with an Aharonov–Bohm (AB) ring is investigated via single-band tight-binding Hamiltonian. It is shown that the output spin current is a periodic function of the magnetic flux in the quantum unit Φ_{0}. The resonance positions of the total transmission probability do not depend on the size of the AB ring but the electronic spectrum. Moreover, the persistent currents in the AB ring is also spin-polarization dependent and different from the isolated AB ring where the persistent current is independent of spin polarization.

GaAs-based planar Gunn diodes with AlGaAs hot electron injector have been successfully developed to be used as a local oscillator of 76 GHz in monolithic millimeter-wave integrated circuits. We designed two kinds of structure diode, one has a fixed distance between the anode and cathode, but has variational cathode area, the other has a fixed cathode area, but has different distances between two electrodes. The fabrication of Gunn diode is performed in accordance with the order of operations: cathode defining, mesa etching, anode defining, isolation, passivation, via hole and electroplating. A peak current density of 29.5 kA/cm^{2} is obtained. And the characteristics of negative differential resistance and the asymmetry of the current–voltage curve due to the AlGaAs hot electron injector are discussed in detail. It is demonstrated that the smaller size of active area corresponds to the smaller current, and the shorter distance between anode and cathode also corresponds to the lower threshold voltage and higher peak current, and hot electron injector can effectively enhance the radio frequency conversion efficiency and output power.

In order to fabricate AlSb polycrystalline thin films without post annealing, this paper studies a technology of magnetron co-sputtering onto intentionally heated substrate. It compares the structural characteristics and electrical properties of AlSb films which are deposited at different substrate temperatures. It finds that the films prepared at a substrate temperature of 450 oC exhibit an enhanced grain growth with an average grain size of 21 nm and the lattice constant is 0.61562 nm that goes well with unstained lattice constant (0.61355 nm). The ln(σ_{dark})～1/T curves show that the conductivity activation energy is about 0.38 eV when the film is deposited at 450 oC without an annealing. The transmittance and reflectance spectra show that the film deposited at 450 oC has an optical band gap of 1.6 eV. These results indicate that we have prepared AlSb polycrystalline films which do not need a post annealing.

The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

By using a finite difference time domain (FDTD) method, the effects of a one-dimensional (1D) surface defect on designer surface plasmon polaritons (designer SPPs) supported by a 1D metallic grating in THz domain are investigated. When the size of the defect is in a special range which is not too large, the designer SPPs reflected and scattered by the defect are weak enough to be neglected. The defect only induces a disturbance in the energy distribution of the designer SPP supported by the whole defect grating. If the defect size exceeds the said range, the reflecting and scattering are dominant in the influences of the defect on designer SPPs. Our analysis opens opportunities to control and direct designer SPPs by introducing a 1D defect, especially in low frequency domain.

This paper investigates the electrical characteristics and temperature distribution of strained Si/SiGe n-type metal oxide semiconductor field effect transistor (nMOSFET) fabricated on silicon-on-aluminum nitride (SOAN) substrate. This novel structure is named SGSOAN nMOSFET. A comparative study of self-heating effect of nMOSFET fabricated on SGOI and SGSOAN is presented. Numerical results show that this novel SGSOAN structure can greatly eliminate excessive self-heating in devices, which gives a more promising application for silicon on insulator to work at high temperatures.

In contrast with Au/Ni/Al_{0.25}Ga_{0.75}N/GaN Schottky contacts, this paper systematically investigates the effect of thermal annealing of Au/Pt/Al_{0.25}Ga_{0.75}N/GaN structures on electrical properties of the two-dimensional electron gas in Al_{0.25}Ga_{0.75}N/GaN heterostructures by means of temperature-dependent Hall and temperature-dependent current–voltage measurements. The two-dimensional electron gas density of the samples with Pt cap layer increases after annealing in N_{2} ambience at 600 du while the annealing treatment has little effect on the two-dimensional electron gas mobility in comparison with the samples with Ni cap layer. The experimental results indicate that the Au/Pt/Al_{0.25}Ga_{0.75}N/GaN Schottky contacts reduce the reverse leakage current density at high annealing temperatures of 400–600 du. As a conclusion, the better thermal stability of the Au/Pt/Al_{0.25}Ga_{0.75}N/GaN Schottky contacts than the Au/Ni/Al_{0.25}Ga_{0.75}N/GaN Schottky contacts at high temperatures can be attributed to the inertness of the interface between Pt and Al_{x}Ga_{1-x}N.

Using a universal relation between electron filling factor and ground state energy, this paper studies the dependence of correlation exponents on the electron filling factor of one-dimensional extended Hubbard model in a strong coupling regime, and demonstrates that in contrast to the usual Hubbard model (g_{c}=1/2), the dimensionless coupling strength parameter g_{c} heavily depends on the electron filling, and it has a "particle–hole" symmetry about electron quarter filling point. As increasing the nearest neighbouring repulsive interaction, the single particle spectral weight is transferred from low energy to high energy regimes. Moreover, at electron quarter filling, there is a metal-Mott insulator transition at the strong coupling point g_{c}=1/4, and this transition is a continuous phase transition.

We theoretically studied the nonlocal Andreev reflection with Rashba spin–orbital interaction in a triple-quantum-dot (QD) ring, which is introduced as Rashba spin–orbital interaction to act locally on one component quantum dot. It is found that the electronic current and spin current are sensitive to the systematic parameters. The interdot spin-flip term does not play a leading role in causing electronic and spin currents. Otherwise the spin precessing term leads to shift of the peaks of the the spin-up and spin-down electronic currents in different directions and results in the spin current. Moreover, the spin–orbital interaction suppresses the nonlocal Andreev reflection, so we cannot obtain the pure spin current.

The effect of Dy substitution for La site in layered manganese oxides La_{1.3}Sr_{1.7}Mn_{2}O_{7} on the magnetic and electrical properties has been investigated. With the La^{3+} substituting by Dy^{3+}, the long range three-dimensional ferromagnetism transition and the insulator–metal transition disappear. These effects are attributed to the lattice distortion due to the substitution of the smaller Dy^{3+}. Addtionally, the small Dy^{3+} is inclined to occupy the R site which is in the rock-salt layer, then the distribution of La, Sr, Dy ions in Dy-doped sample should be more orderly than that in La_{1.3}Sr_{1.7}Mn_{2}O_{7}, so there is only one insulator–metal transition in the ρ–T curve of the sample with x=0.05 and x=0.1.

The quantum fluctuations of a three-layer Heisenberg model with six sublattices are studied by the retarded Green's function method and the spin-wave theory. The effects of anisotropy on the quantum fluctuations at zero temperature are discussed. The results show that the interlayer anisotropy plays an important role in balancing the quantum competitions.

By modifying the interchange interactions and the transverse fields on the epitaxy surface layer, this paper studies the phase transition properties of an n-layer ferroelectric thin film by the Fermi-type Green's function technique based on the transverse Ising model with a four-spin interaction. The special attention is given to the effect of the epitaxy surface layer on the first-order phase transition properties in the parameter space constructed by the ratios of the bulk transverse field and the bulk four-spin interaction to the bulk two-spin interaction with the framework of the higher-order decoupling approximation to the Fermi-type Green's function. The results show that the first-order phase transition properties will be changed significantly due to the modification of interchange interaction and transverse field parameters on the epitaxy surface layer. The dependence of the first-order phase transition properties on the thickness of ferroelectric thin films is also discussed.

Undoped and Si-doped AlGaN/AlN multiple quantum wells (MQWs) were grown on AlN/Sapphire templates by metalorganic phase vapor epitaxy. High-resolution x-ray diffraction measurements showed the high interface quality of the MQWs little affected by Si-doping. Room-temperature (RT) cathodoluminescence measurements demonstrated a significant enhancement of the RT deep ultraviolet emission at about 240 nm from the AlGaN/AlN MQWs by Si doping. The mechanism of the improved emission efficiency was that the Si-doping partially screens the internal electric field and thus leads to the increase of the overlap between electron and hole wavefunctions. Further theoretical simulation also supports the above results.

In this paper the fabrication technique of amorphous SnO_{2}:(Zn,In) film is presented. The transmittance and gap-states distribution of the film are given. The experimental results of gap-states distribution are compared with the calculated results by using the facts of short range order and lattice vacancy defect of the gap states theory. The distribution of gap state has been proved to be discontinuous due to the short-range order of amorphous structure.

This paper reports that heat insulating property of infrared reflective coatings is obtained through the use of pigments which diffuse near-infrared thermal radiation. Suitable structure and size distribution of pigments would attain maximum diffuse infrared radiation and reduce the pigment volume concentration required. The optimum structure and size range of pigments for reflective infrared coatings are studied by using Kubelka–Munk theory, Mie model and independent scattering approximation. Taking titania particle as the pigment embedded in an inorganic coating, the computational results show that core-shell particles present excellent scattering ability, more so than solid and hollow spherical particles. The optimum radius range of core-shell particles is around 0.3～1.6μm. Furthermore, the influence of shell thickness on optical parameters of the coating is also obvious and the optimal thickness of shell is 100–300 nm.

Yb^{3+}:Er^{3+} co-doped oxy-fluoride ceramics glass has been prepared. The mechanism of up-conversion emissions about Er^{3+} was discussed, and the temperature properties of green up-conversion fluorescence between 303 and 823 K were investigated. The results show that the sensitivity of this sample reaches its maximum value, about 0.0047 K^{-1}, when the temperature is 383 K, indicating that this kind of sample can be used as high temperature and high sensitivity optical temperature sensor.

Interconnect power and repeater area are important in the interconnect optimization of nanometer scale integrated circuits. Based on the RLC interconnect delay model, by wire sizing, wire spacing and adopting low-swing interconnect technology, this paper proposed a power-area optimization model considering delay and bandwidth constraints simultaneously. The optimized model is verified based on 65-nm and 90-nm complementary metal-oxide semiconductor (CMOS) interconnect parameters. The verified results show that averages of 36% of interconnect power and 26% of repeater area can be saved under 65-nm CMOS process. The proposed model is especially suitable for the computer-aided design of nanometer scale systems-on-chip.

Based on the finite difference time domain method, we investigated theoretically the optical properties and the plasmonic interactions between a gold film perforated with periodic sub-wavelength holes and a thin gold film. We showed that the plasmon resonant energies and intensities depend strongly on the thicknesses of the two films and the lattice constant. Based on the distributions of normal electric field component E_{z}, tangential electric field component E_{y} and total energy, we showed that the optical transmission is due to the collaboration of the localized waveguide resonance, the surface plasmon resonance and the coupling of the flat-surface plasmon of the two layers.

The luminescence properties of lanthanum silicon oxynitride (La-Si-O-N) series doped by trivalent Ce ions have been investigated to seek for tunable wavelength-conversion phosphor for white light emitting diode applications. Four compound hosts of LaSiO_{2}N, La_{4}Si_{2}O_{7}N_{2}, La_{5}Si_{3}O_{12}N, and La_{2}Si_{6}O_{3}N_{8} were synthesized and examined in this work. Crystallographic examination for the equal amount of Ce^{3+} substitution indicated that the covalency degree decreased in a sequence LaSiO_{2}N > La_{2}Si_{6}O_{3}N_{8} > La_{4}Si_{2}O_{7}N_{2} > La_{5}Si_{3}O_{12}N, not simply in correlation to the ratio of N^{3}/O^{2}. Excitation and emission spectrum measurements showed the main features of Ce^{3+} luminescence in the series: the centre of gravity of 5d bands depends on crystal-field splitting more strongly than that on covalency of Ce–N bonding; nephelauxetic effect could not be observed clearly for the investigated series; to some extent Stokes shift was dominated by crystal-field splitting rather than Ce–N covalency degree.

Sr_{2}ScAlO_{5}:Eu^{2+}, a red oxide phosphor with a perovskite-type structure, has been synthesized through a solid-state reaction and its luminescence properties have been investigated. An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra, indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes. A broad red emission band at 620 nm is found from the emission spectra, originating from the 4f^{6}5d–4f^{7} transition of the Eu^{2+} ions. The best doping content of Eu in this material is about 5%. Sr_{2}ScAlO_{5}:Eu^{2+} is a highly promising red phosphor for use in white light-emitting diodes.

This paper reports that the green phosphor BaAl_{11.9}O_{19}:0.1Mn^{2+} is prepared by a flux assisted solid state reaction method. The effect of flux systems on the crystal structure, morphology and luminescent properties of the phosphor are studied in detail. The samples are characterized by the application of x-ray diffraction patterns, scanning electron microscopy patterns, luminescent spectra and decay curves. The results show that a pure phase BaAl_{12}O_{19} can be achieved at the firing temperature above 1300 du by adding the proper flux system, the firing temperature is reduced at least 200 du in comparison with the conventional solid state reaction method. Maximum photoluminescence emission intensity is observed at 517 nm for (AlF_{3}+Li_{2}CO_{3}) flux system under vacuum ultraviolet region (147 nm) excitation. The photoluminescence emission intensity and the decay time of these phosphor is found to be more superior to that of the corresponding sample prepared by the conventional solid state reaction method implying the suitability of this route for the preparation of display device worthy phosphor materials.

According to the one-dimensional tight-binding SuSchrieffer–Heeger model, we have investigated the effects of charged polarons on the static polarizability, α_{xx}, and the second order hyperpolarizabilities, γ_{xxxx}, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su–Schrieffer–Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron–electron interactions on α_{xx} and γ_{xxxx} of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of α_{xx} and γ_{xxxx} increase as the on-site Coulomb interaction U increases for Uc and decrease with U for U >U_{c}, where U_{c} is a critical value of U at which the static polarizability or the second order hyperpolarizability reaches a maximal value of α_{max} or γ_{max}. It is found that the effect of the e–e interaction on the value of α_{xx} is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γ_{xxxx} is sensitive both to the ratio of U to V and to the size of the molecule.

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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