An expansion method for stationary states is applied to obtain the eigenfunctions and the eigenenergies of the quarter stadium billiard, and its nearest energy-level spacing distribution is obtained. The histogram is consistent with the standard Wigner distribution, which indicates that the stadium billiard system is chaotic. Particular attention is paid to pursuing the quantum manifestations of such classical chaos. The correspondences between the Fourier transformation of quantum spectra and classical orbits are investigated by using the closed-orbit theory. The analytical and numerical results are in agreement with the required resolution, which corroborates that the semiclassical method provides a physically meaningful image to understand such chaotic systems.

We present a scheme for generating four pairs of two-atom Einstein--Podolsky--Rosen (EPR) states using the simultaneous interaction of the two atoms with a single-mode cavity field under a large detuning condition. The influence of cavity dissipation on the prepared EPR states is investigated by means of the superoperator method and the state fidelity. It is shown that some kinds of the prepared EPR states are robust against cavity dissipation and the intensity of the field, and maintain their entanglement invariance, and the others are fragile and completely destroyed by the action of cavity dissipation and the intensity of the field in the long-time limit. Decoherence time of the fragile entangled states is extremely small for a typical cavity-QED experimental data.

We extend the idea of entanglement concentration protocol for pure states (Phys. Rev. Lett. 88, 187903) to the case of entanglement distillation for mixed states. The scheme works only with particle statistics and local operations, without the need of any other interactions. We show that the maximally entangled state can be distilled out when the initial state is pure, otherwise the entanglement distilled depends on the off-diagonal element of density matrix of the initial state. Because of the requirement for density matrix, the entanglement distilled is always less than one, and this result is the same for both fermionic and bosonic particles. The distillation efficiency is a product of the diagonal elements of the initial state, it takes the maximum 50%, the same as that in the case for pure states.

In practical quantum key distribution (QKD), weak coherent states as the photon source have a limit in the secure key rate and transmission distance because of the existence of multi-photon pulses and heavy loss in transmission line. The decoy-state method and the nonorthogonal encoding protocol are two important methods to combat these effects. Here, we combine both the methods and propose an efficient method that can substantially improve the performance of QKD. We find a 78-km increase over the prior record using the decoy-state method and a 123-km increase over the result of the SARG04 protocol in transmission distance.

The quantum random walk is a possible approach to construct new quantum search algorithms. It has been shown by Shenvi et al. [Phys. Rev. A 67(2003)52307] that a kind of algorithm can perform an oracle search on a database of N items with O(√N) calling to the oracle, yielding a speedup similar to other quantum search algorithms. We study the effect of white or Gaussian noise on this algorithm. The algorithm loses efficiency when noise is added. We also show that noise on the target state plays a more important role than that on other states. Finally we compare the effects of similar types of noise in the quantum random walk search algorithm and Grover's search algorithm.

We use the Kruskal time coordinate T to define the initial time. By this way, the stability study naturally becomes the one connected with the two regions, i.e. the white-hole-connected region and the black-hole-connected region. The union of the two regions covers the Schwarzschild space-time (r≥2m). We also obtain the very reasonable conclusion: the white-hole-connected region is unstable and the black-hole-connected region is stable. If we take the instability with caution and seriousness, it is not unreasonable to regard that the Schwarzschild black hole might be unstable to some extent.

Partial synchronization (PaS) on regular networks with a few non-local couplings are studied. The criterion that PaS can emerge in any given network and some relevant phenomena about Lyapunov exponents are found. Theoretical and numerical analysis show that the non-local coupling is the key mechanism of the emergence of PaS.

We study the anti-phase synchronization (APS) in a system of two coupled chaotic oscillators. The necessary condition and the stability analysis for the APS are given theoretically. The APS state in specific systems such as Chua circuits and Lorenz oscillators are numerically studied. The different types of transitions to APS in both the systems are found.

A new method to measure the divergence of x-ray beams propagated out from several capillaries is introduced. This new method is based on Bragg's law and is proven efficiently by the experimental measurement with collimators and straight polycapillaries.

We investigate the new spinor field realizations of the W₃ algebra, making use of the fact that the W₃ algebra can be linearized by the addition of a spin-1 current. We then use these new realizations to build the nilpotent Becchi--Rouet--Stora--Tyutin charges of the spinor non-critical W₃ string.

We investigate hard photon production of the near-collinear bremsstrahlung and a new process called the inelastic pair annihilation, fully including the LPM effect, in a chemically equilibrating quark-gluon plasma at finite baryon density, and find that the effect of the system evolution on the photon production and large contribution of the bremsstrahlung make the total photon yield of the two processes as a strongly increasing function of the initial quark chemical potential.

The Skyrme energy density functional is applied to study the ground state properties of a series of finite nuclei. The charge rms radii, neutron rms radii, and the neutron skin thickness for some nuclei are calculated and compared with the experimental data. The constraint on the effective interactions, especially, the density dependence of the isospin-dependent part of Skyrme interactions is extracted by the data of neutron skin thicknesses of ²⁰⁸Pb and isotopes of Sn.

We investigate the β decay of very neutron-rich ¹¹⁸Rh isotope using on-line mass-separated sources which are produced by applying 25MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β--γ and γ--γ coincidence spectroscopy is employed to establish the level scheme of daughter nucleus ¹¹⁸Pd. Five low-lying new levels are identified for the first time with tentative spin and parity assignments based on the even-mass Pd systematics.

The distorted-wave Born approximation (DWBA) method is used to calculate the half-lives of spherical proton emitters. The calculated results are in agreement with the experimental data. The sensitivity of the half-lives to the depth of central potential V₀ is investigated by using the DWBA method. The half-lives of spherical proton emitters are insensitive to the detail of their nuclear potential.

We presents the analysis of ring-like and jet-like events in terms of Scaled Factorial Moments (SFMs) in one-dimensional space up to the sixth order of moments for ³²--AgBr interactions at 200AGeV energy. The study reveals a power law growth of SFMs with decreasing bin width of the azimuthal distribution in the ³²S--AgBr data at 200AGeV in both the cases. It is seen that strong intermittent pattern is revealed only in jet-like events.

Bond dissociation energies for removal of nitrogen dioxide groups in 10 aliphatic nitro compounds, including nitromethane, nitroethylene, nitroethane, dinitromethane, 1-nitropropane, 2-nitropropane, 1-nitrobutane, 2-methyl-2-nitropropane, nitropentane, and nitrohexane, are calculated using the highly accurate complete basis set (CBS-Q) and the three hybrid density functional theory (DFT) methods B3LYP, B3PW91 and B3P86 with 6-31G** basis set. By comparing the computed bond dissociation energies and experimental results, we find that the B3LYP/6-31G** and B3PW91/6-31G** methods are incapable of predicting the satisfactory bond dissociation energy (BDE). However, B3P86/6-31G** and CBS-Q computations are capable of giving the calculated BDEs, which are in extraordinary agreement with the experimental data. Nevertheless, since CBS-Q computational demands increase rapidly with the number of containing atoms in molecules, larger molecules soon become prohibitively expensive. Therefore, we suggest to take the B3P86/6-31G** method as a reliable method of computing the BDEs for removal of the NO₂ groups in the aliphatic nitro compounds.

We propose a novel gravito-optical surface trap (GOST) for neutral atoms based on one-dimensional intensity gradient cooling. The surface optical trap is composed of a blue-detuned reduced semi-Gaussian laser beam (SGB), a far-blue-detuned dark hollow beam and the gravity field. The SGB is produced by the diffraction of a collimated Gaussian laser beam passing through the straight edge of a semi-infinite opaque plate and then is reduced by an imaging lens. We calculate the intensity distribution of the reduced SGB, and study the dynamic process of the SGB intensity-gradient induced Sisyphus cooling for ⁸⁷Rb atoms by using Monte Carlo simulations. Our study shows that the proposed GOST can be used not only to trap cold atoms loaded from a standard magneto-optical trap, but also to cool the trapped atoms to an equilibrium temperature of 3.47μK from ～120μK, even to realize an all-optical two-dimensional Bose--Einstein condensation by using optical-potential evaporative cooling.

We report the observation of coincidence of three K-shell x-rays generated from the long-lived rhodium isomer excited by bremsstrahlung irradiation. Our previous report revealed that the E3 Mössbauer transition has anisotropic emission due to anisotropic gravitational acceleration [Chin. Phys. Lett. 22 (2005) 2530]. Now, from broader energy-resolved spectra, we further discover abnormal coincidences and abnormal sum energies of the three K-shell x-rays. The coincidence cannot be explained by currently understood photon statistics, since the measured tri-photon count and the pile-up estimate differ by three orders of magnitude.

A quasiclassical trajectory study with the sixth-order explicit symplectic algorithm for the N(⁴S)+O₂(X³Σ_g^-) → NO(X²II) +O(³P) reaction has been reported by employing a new ground potential energy surface. We have discussed the influence of the relative translational energy, the vibrational and rotational levels of O₂ molecules on the total reaction cross section. Thermal rate constants at temperatures 300, 600, and 1000K determined in this work for the reaction are 4.4×10⁷, 1.8×10¹⁰, and 3.1 10¹¹cm³mol^-1s^-1, respectively. It is found that they are in better agreement with the experimental data than previous theoretical values.

The dyadic Green function for a homogeneous electromagnetic medium inspired by the spatiotemporally nonhomogeneous constitutive equations of gravitationally affected vacuum is derived.

We investigate the shape-preserving propagation of N optical pulses in an (N+1)-level medium. We solve Maxwell-Schrödinger equations exactly and provide several types of explicit coupled soliton solutions, which are temporally amplitude- and group-velocity-matched multi-mode slow-optical pulses of the system.

Numerical simulations show that proper fundamental mode-locking repetition range of hybrid soliton pulse source where transform-limited pulses are obtained is extremely increased with the use of linearly chirped tanh apodized fibre Bragg grating. Near transform-limited pulses are generated over a frequency range of 1.6GHz (1.9--3.4GHz) around a system operating frequency of 2.5GHz.

We experimentally demonstrate an S-band double-pass (DP) discrete fibre Raman amplifier (FRA) gain-flattened by using a mechanically induced long-period fibre grating (LPFG). Due to a photo-elastic effect in the fibre and its peak loss, the wavelength and depth of the mechanically induced LPFG are continuously regulated by varying the pressures, the angle of the fibre on the graphite rods which are used to produce the periodical pressures along the fibre, the number and the diameter of the graphite rods. Using this gain flattening filter, the gain profile of the DP-FRA is flattened to within ±0.8dB in the wavelength range from 1485nm to 1525nm.

The frequency down-conversion of one-dimensional photonic crystals with the coupled cavity structure is investigated by the nonlinear finite-difference time-domain method. The efficient frequency conversion is obtained by utilizing the advantages of the broad eigenfrequency band, the strong localization and the Bloch phase matching of the coupled cavity structure. More importantly, the signal frequency could be tuned continuously within the whole band of the coupled cavity structure (with a bandwidth to central frequency ratio of 5.4%), and the gains are homogeneous in the band.

We report a high-power high-efficient continuous-wave (cw) diode-end-pumped Nd:YVO₄ 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671nm with a compact three-element cavity. At incident pump power of 20.6W, a maximum output power of 7W at 1342nm is obtained with a slope efficiency of 37.3%. By inserting a type-I critical phase-matched LBO crystal as intracavity frequency-doubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diode-pumped solid-state Nd:YVO₄ red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.

The structural and luminescence properties of nanocrystalline ZrO₂:Er³⁺ films are reported. Transparent nano-ZrO₂ crystalline films doped with Er³⁺ have been prepared using a wet chemistry process. An intense room-temperature emission at 1527nm with a full width at half-maximum of 46nm has been observed, which is assigned to the ⁴I_13/2 → ⁴I_15/2 intra-4fⁿ electric transition of Er³⁺. Correlations between the luminescence properties and structures of the nanocrystalline ZrO₂:Er³⁺ films have been investigated. Infrared-to-visible upconversion occurs simultaneously upon excitation of a commercially available 980-nm laser diode and the involved mechanisms have also been explained. The results indicate that the nanocrystalline ZrO₂:Er³⁺ films might be suggested as promising materials for achieving broadband Er³⁺-doped waveguide amplifiers and upconversion waveguide lasers.

Image restoration phase-filtering lateral superresolution confocal microscopy, a new approach, is proposed to achieve lateral superresolution using a confocal microscope. This approach uses a lateral superresolution pupil filter to preliminarily improve its lateral resolution and uses a single-image superresolution restoration technique based on a maximum likelihood estimate to further improve its lateral resolution. The new approach has the advantages of a low cost and the remarkable superresolution effect without excessive system complexity. Experiments indicate that the proposed approach can improve the lateral resolution of a confocal microscope from 0.3μm to less than 0.1μm when λ=632.8nm and NA=0.85.

Effects of draw parameters, such as drawing temperature and feed speed, on the capillaries and the geometry of the final photonic crystal fibre (PCF) are investigated. Inert gas pressurization is introduced in the preform during the fibre drawing process to finely control the geometry of the PCF so that good uniform in transversal and longitudinal of the final PCF can be realized. Due to the introduction of a special method, the drawing temperature is increased over 1900°C and the strength of the PCF is enhanced.

We report on 160Gbit/s RZ (return-to-zero) code transmission experiments including a dynamic polarization mode dispersion (PMD) compensation. The 2.5-ps first-order and 15-ps² second-order PMD are compensated for. The PMD compensation time is within 24ms. The experimental results show that a significant improvement of system performance can be achieved by auto-correlative curves.

Modulation arms with different widths are introduced to Mach--Zehnder interferometers (MZIs) to obtain improved performance. Theoretical analysis and numerical simulation have shown that when the widths of the two arms are properly designed to achieve an inherent mπ/2 (m is an odd integer) optical phase difference between the arms, the asymmetric MZI presents higher modulation speed. Furthermore, the carrier-absorption induced divergence of insertion losses in silicon-on-insulator (SOI) based MZI optical switches can be obviously improved.

The propagation of longitudinal acoustic waves in weakly compressible elastic media permeated with air bubbles is investigated on the basis of the radial pulsation equation of a single bubble. The multiple scattering of waves in such media is rigorously described by using a self-consistent approach. Theoretical results show that there exists strong acoustic localization in a range of frequency slightly above the bubble resonance frequency, even for a very small volume fraction of bubbles. Further study reveals that the localization is in fact attributed to collection behaviour of bubbles, allowing for an efficient cancellation of propagating waves. This is essentially consistent with the known conclusions recently drawn for bubbly liquid by Kou et al. [2003 Appl. Phys. Lett. 83 4247]

The focused acoustic field generated by an annular array transducer and its reflection field on a solid--liquid interface are investigated theoretically and experimentally. Theoretically, the concise analytic expressions about the radiation and reflection acoustic fields of the annular phased array are obtained by the ray approach method (saddle-point method). In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experiments about the radiation acoustic field and its reflection on the liquid-solid interface are carried out. The experimental characteristics of the transducer are in good agreement with the numerical ones. It shows the correctness of the theoretical result and the feasibility of dynamic focusing of the experiment system. With the maximum amplitude and its emergence time of the reflection wave, we can acquire the information and the imaging of the reflection interface by the annular phased array dynamic focusing.

A new two-sided model of vapour--liquid layer system with a deformable interface is proposed. In this model, the vapour recoil effect on the Marangoni--Bénard instability of a thin evaporating liquid layer can be examined only when the interface deflexion is considered. The instability of a liquid layer undergoing steady evaporation induced by the coupling of vapour recoil effect and the Marangoni effect is analysed using a linear stability theory. We modify and develop the Chebyshev--Tau method to solve the instability problem of a deformable interface system by introducing a new equation at interface boundary. New instability behaviour of the system has been found and the self-amplification mechanism between the evaporation flux and the interface deflexion is discussed.

Lagrangian and Eulerian statistics are obtained from the direct numerical simulation of a turbulent channel flow. The Reynolds number is obtained to be Re_τ=100 (based on friction velocity and channel half-height). The Lagrangian time microscales are compared to their Eulerian equivalents. It is found that the Lagrangian time microscales equal the Eulerian time microscales at the wall, but they are consistently larger than the Eulerian away from the wall. The Eulerian time scales are also found to be scaled by the propagation velocity rather than the mean velocity. The ratio of the Lagrangian to the Eulerian time microscales is found to be nearly constant away from the wall (y⁺>40).

A variable coefficient Korteweg de Vries (VCKdV) system is derived by considering the time-dependent basic flow and boundary conditions from the well-known Euler equation with an earth rotation term. The analytical solution obtained from the VCKdV equation can be successfully used to explain fruitful phenomena in fluid and other physical fields, for instance, the atmospheric blocking phenomena. In particular, a diploe blocking case happened during 9 April 1973 to 18 April 1973 read out from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data is well described by the analytical solution.

A new criterion has been proposed to predict the major disruptions caused by tearing mode instabilities. According to the HL-2A experimental results, the statistical analyses are employed to investigate the relationships between MHD activities and the plasma disruptions. Two kinds of the tearing mode activities can finally cause the disruption on HL-2A operations. By introducing a new parameter, i.e. an integral of poloidal magnetic field over time, as the criterion of disruption precursor, almost all of the disruptions can be predicted.

The evolution of Rayleigh--Taylor mode in dusty plasma with vortex-flow is investigated. Based on fluid theory and Bayly’s method, we derive the coupling equations describing the Rayleigh--Taylor mode in the core of vortex, and research the evolution characteristics of the perturbation amplitude with time numerically. It is shown that the eccentric of vortex and the content of dust have considerable effects on the amplitude evolutions.

We present the investigation on the reflex triode virtual cathode oscillator in which performances of carbon-fibre and stainless-steel cathodes are compared with each other. The experimental results and analyses show that surface tracking induces the electron emission of the carbon fibre cathode. There are electron emission phenomena observed not only from the top of the carbon fibre but also from its side surface. Compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fibre cathode is slower, and using the carbon fibre cathode can widen the pulse width of output microwave. The output microwave pulse width reaches an increase of about 20%. This mechanism is different from the conventional explosive emission of metal cathodes.

We optimize the room-temperature etching of InP using Cl₂N₂ and Cl₂/CH₄/H₂ inductively coupled plasma reactive ions. A design of experiment is used in the optimization. The results, in terms of etch rate, surface roughness and etched profile, are presented. These Cl₂-based recipes do not require substrate heating and thus can be more cost effectively and widely applied. The Cl₂/CH₄/H₂ process is able to give a higher etch rate (about 850nm/min) and cleaner surface with less polymer formation compared to the conventional CH₄/H₂ process. The Cl₂/N₂ process produces even higher etch rate (as high as 2μm/min), but rougher surface with slight sidewall undercut. The Cl₂/N₂ process also has no polymer formation due to the absence of methane gas. Both the processes give very good selectivity to the silicon dioxide (SiO₂) etch mask. The selectivity of InP to the oxide mask (up to 55:1) for the Cl₂/N₂ process is one of the highest reported so far. The etched structures possess reasonably good sidewall verticality and surface quality comparable to that obtained under elevated temperature condition (>200°C).

Zn_1-xNi_xO (x=0.001, 0.01, 0.02, 0.05 and 0.20) powders are prepared by sol-gel method. An extended x-ray absorption fine structure technique (EXAFS) for the Ni K-edge is employed to probe the local structures around Ni atoms doped in ZnO powders by fluorescence mode. The near edge EXAFS of the samples does not change in the range of Ni concentration from x=0.001 to 0.05, which is consistent with the results of x-ray diffraction of the samples. The simulation results for the first shell EXAFS signals indicated that Ni atoms are substituted in Zn sites.

The lattice parameters of AlB₂, MgB₂ and TiB₂ under pressures are determined with a high-energy synchrotron source in a diamond anvil cell. The experimental results indicate that these three compounds have different mechanical behaviour under pressures, TiB₂ is the hardest and MgB₂ is the softest among the three materials. The phenomena are explained in terms of bonding strength in the crystal. Our results may be helpful for understating the decrease of the superconducting transition temperature of MgB₂ under pressures.

Formation of icosahedral clusters in rapidly solidified binary amorphous Ni_xZr_100-x (x=15, 33.3, 50, 66.7, 85) is studied by using molecular dynamics simulation methods. A large number of icosahedral clusters with 13 atoms (Ih13) were observed in Ni_xZr_100-x alloys, and most of them, even those in Zr-rich alloys, are found to be Ni-centred. Studies on the structures of Ni_33.3Zr_66.7 obtained at different cooling rates demonstrate that most of iscosahedral clusters enhanced by decreasing cooling rates are also Ni-centred. The essentials of Ni atoms preferring to be the core of icosahedral clusters are illustrated with the criterion of energy minimization and the equilibrium interatomic distances between different atoms.

We investigate quantum well intermixing of a double-quantum-well structure caused by phosphorus ion implantation by means of photoluminescence (PL). The ion implantation is performed at the energy of 120keV with the dose ranging from 1×10¹¹ to 1×10¹⁴/cm². The rapid thermal annealing is performed at the temperature of 700°C for 30s under pure nitrogen protection. The PL measurement shows that the band gap blueshift is influenced by the depth of ion implantation. The blueshift of the upper well which is closer to the implanted vacancies is enhanced with the ion dose faster than that from a lower well under the lower dose implantation (<5×10¹¹/cm²). When the ion dose is over 10¹²/cm², the band gap blueshift from both the wells increases with the ion dose and finally the two peaks combine together as one peak, indicating that the ion implantation results in a total intermixing of both the quantum wells.

A planar optical waveguide is formed in monoclinic double rare-earth-tungstate laser crystal Yb:KLu(WO₄)₂ by 6.0MeV oxygen ion implantation with a dose of 2 10¹⁵ions/cm² at room temperature. Subsequently, annealing at 300°C for an hour in air is performed on the sample to decrease colour centres to improve the thermal stability of the waveguide. The refractive index profiles of the waveguide are reconstructed by an effective refractive index method. Dark modes of the waveguide are observed at wavelengths of 633nm and 1539nm. TRIM'98 is used to simulate the damage profile caused by the implantation process. It is found that the refractive index change may be mainly due to the damage induced by the nuclear energy loss.

We investigate the equilibrium lattice constant, bulk modulus, elastic constants and Debye temperature of Li₂O under pressure by using ab initio unrestricted Hartree--Fock (HF) linear combination of atomic orbital (LCAO) periodic approach. The obtained results at zero pressure are well consistent with the available experimental data and other theoretical results. It is found that the elastic constants C₁₁, C₁₂ and C₄₄ and bulk modulus B increase monotonously as pressure increases. Also, the anisotropy will weaken and the Debye temperature will rise with pressure increasing.

Organic light-emitting diodes (OLEDs) based on N,N’-bis(1-naphthyl)-N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine (NPB) and tris (8-hydroxyquinoline) aluminium (Alq₃) are improved by using a thin MgF₂ buffer layer sandwiched between the indium tin oxide (ITO) anode and hole transporting layer (HTL) of NPB. The current-voltage curves of the OLEDs with MgF₂ buffers shift to lower voltages, which can be explained by the tunnelling effect. Under 10V bias, the current density and brightness for the optimized OLED with a 1.0-nm MgF₂ are 196A/m² and 517cd/m², respectively, while for the OLED without anode buffer layer are only 109A/m² and 156cd/m². The atomic force microscopy shows that the rms roughness of NPB on ITO/MgF₂ is only 1/3 of NPB on bare ITO. The improved morphology of the HTL would lead to more robust OLEDs. The OLED with a 1.0-nm MgF₂ layer has a long lifetime of more than five times of the MgF₂-free reference device due to the combined electrical and morphological effects of the MgF₂ layer.

Magnetic tunnel junctions (MTJs) with one proper oxidized FeOx layer placed between the Al oxide barrier and the top CoFe pinned layer show large tunnelling-magnetoresistance (TMR) signals as high as 39% after anneal at 380°C. The increased TMR signal may originate from the as-deposited Fe/FeO_x (non-magnetic) layers changing to Fe+magnetic FeOy layer (some Fe₃O₄ and mostly other kind of magnetic Fe oxide) after high temperature anneal. The maximum TMR value (TMR_max) and the corresponding temperature T_s where the TMR_max occurs upon annealing are closely associated with the oxidation time of the AlO_x and FeO_x layers, too long oxidation for the Fe layers is detrimental for the TMR value. In addition to the enhanced AlO_x barrier quality upon anneal, the improved thermal stability is also attributed to the Mn diffusion retardation by the presence of the FeO_x layer which acts as an antidiffusion layer. For MTJs without the interposed FeO_x layer, the TMR signal reduction at 300°C originates from the MnIr/CoFe partially decoupling and CoFe/AlO_x interface polarization loss due to the significant Mn diffusion.

We experimentally studied the in-plane thermal and electrical properties of a suspended platinum nanofilm in thickness of 15nm. 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 28nm, 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.

Undoped and copper doped zinc oxide (ZnO) thin films have been prepared on glass substrates by spray pyrolysis technique. The films were doped with copper using the direct method by addition of a copper salt (CuCl₂) in the spray solution of ZnO. Variation of structural, electrical, optical and thermoluminescence (TL) properties with doping concentrations is investigated in detail.

We calculate the band structure of BaS using the local density approximation and the GW approximation (GWA), i.e. in combination of the Green function G and the screened Coulomb interaction W. The Ba 4d states are treated as valence states. We find that BaS is a direct band-gap semiconductor. The result shows that the GWA band gap (E_g-GW=3.921eV) agrees excellently with the experimental result (E_g-EXPT=3.88eV or 3.9eV).

We present a simple demonstration of the nonfeasibility of metal-insulator transition in an exactly two-dimensional (2D) system. The Hartree--Fock potential in the 3D system is suitably modified and presented for the 2D case. The many body effects are included in the screening function, and binding energies of a donor are obtained as a function of impurity concentration so as to find out the possible way leading metal-insulator transition in the 2D system. While solving for the binding energy for a shallow donor in an isolated well of a GaAs/Ga_1-x Al_s As superlattice system within the effective mass approximation, it leads to unphysical results for higher concentrations. It shows that the phase transition, the bound electron entering into the conduction band whereby _min= 0, is not possible beyond this concentration. The results suggest that a phase transition is impossible in 2D systems, supporting the scaling theory of localization. The results are compared with the existing data available and discussed in the light of existing literature.

Using the time-of-flight photocurrent measurements, we investigate the hole transport properties of polymer 2-methoxy, 5-(2’-ethyl-hexyloxy)-1, 4-phenylene vinylene (MEH-PPV). The change of hole transport properties from non-dispersive transport to a dispersive type is presented, with the increasing excitation wavelength near the MEH-PPV absorption edge. At room temperature, the effective mobility of MEH-PPV depends on the applied electric field as commonly seen in some organic materials.

We investigate the resistance and magnetoresistance (MR) of an entangled single-walled carbon nanotube (SWNT) network. The temperature dependence of conductance is fitted by formula G(T)=G₀exp[-(T₀/T)^1/2] with T₀=15.8K at a wide temperature range from 4K to 300K. The MR defined by [R(T,H)-R(T,0)]/R(T,0) as a function of temperature and magnetic field perpendicular to the tube axis is negative at low temperatures. The MR amplitude increases as the temperature decreases at relative high temperature, but becomes decrease when temperature below 4K. The results are explained in terms of the coherent hopping of carriers in the presence of a Coulomb gap at low temperature.

The deformation potential and piezoelectric field in nitride GaN/AlN quantum dots (QDs) are investigated in the framework of effective mass approximation (EMA) and finite element method (FEM). The strained fields and piezoelectric characteristics are studied by using FEM for GaN/AlN QDs (GaN embedded in AlN) in the shape of truncated hexagonal pyramids. We presented the calculated results of the electronic states, wave functions, QD strain field distribution and piezoelectric effects in the QDs. Effects of spontaneous and piezoelectric polarization are taken into account in the calculation. The theoretical results are dependent on QD shapes and sizes. Some of them make the GaN/AlN QDs interesting candidates in optoelectronic applications.

We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant-tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the bias step of the external bias voltage applied on the device has an important effect on the final current-voltage (I-V) curves. The results show that different bias step applied on the device can change the bistability, hysteresis and current plateau structure of the I-V curve. The current plateau occurs only in the case of small bias step. As the bias step increases, this plateau structure disappears.

Ag-Mg-V alloy is prepared and investigated to develop a new sheath alloy used for BSCCO tapes. Bi-2223 Ag/AgMgV and Bi-2223 AgMgV/AgMgV tapes are studied with the help of stress-strain measurement, optical microstructure and critical current I_c. The value of I_c at 77K and at magnetic field B=0 is obtained to be 90A/cm² for the samples of Bi-2223 Ag/AgMgV tapes, which is higher than that of Bi-2223 AgMgV/AgMgV tapes (72A/cm²). The resistance of AgMgV alloy, up to 0.37μΩ.cm at 77K, is higher than that of pure Ag (0.28μOmega.cm) after annealed at 840°C for 40h, which is studied for reducing the ac loss. The values of the fracture strength and the maximum strain are 86MPa and 0.50% for Bi-2223 Ag/AgMgV tapes and 108MPa and 0.33% for Bi-2223 AgMgV/AgMgV tapes, respectively.

A nano-scale $s$-wave superconducting grain, coupled to a normal metallic contact through a tunnelling junction, is placed in an external magnetic field. We suppose that effect of this quantum tunnelling on the Fourier transform of the order parameter is in the form of a small additive correction to the BCS order parameter. At the first order approximation in terms of this correction term and by using an instanton method, the related Green functions (in frequency space) are obtained. By establishing a self-consistent configuration an analytic formula for the order parameter is also found. We also show that a departure from superconductivity can be captured by this formula. This change of state is indeed a manifestation of a quantum transition induced by quantum fluctuations. In this sense, this is an advantage of our simple method which, like other more elaborate methods, can detect a quantum transition in the state of the grain.

Superconducting flux qubits with three Josephson junctions are promising candidates for the building blocks of a quantum computer. We have applied the imaginary time evolution method to study the model of this qubit accurately by calculating its wavefunctions and eigenenergies. Because such qubits are manipulated with magnetic flux microwave pulses, they might be irradiated into non-computational states, which is called the leakage effect. By the evolution of the density matrix of the qubit under either hard-shaped π-pulse or Gaussian-shaped π-pulse to carry out quantum NOT operation, it has been demonstrated that the leakage effect for a flux qubit is very small even for hard-shaped microwave pulses while Gaussian-shaped pulses may
suppress the leakage effect to a negligible level.

Temperature-dependent resistivity and magnetic susceptibility were studied for quaternary borocarbide intermetallic compounds Y_1-xHo_xNi₂B₂C (x=0, 0.25, 0.5, 0.75), which show coexistence of superconductivity with magnetism. In a normal state, the compounds exhibit conventional metallic behaviour. The Debye temperature θ_D is derived by fitting the temperature dependence of resistivity to the Bloch--Gruneisen expression, i.e. θ_D scales with M^-0.5 (M is the averaged atomic mass on the Y³⁺ site), which means that the acoustic mode of the lattice vibrating spectrum is influenced by the Y³⁺ site atoms. Fitting the temperature-dependent magnetic susceptibility above T_N to the Curie--Weiss law, effective magnetic moment μ_eff is deduced, and then de Gennes factor dG is calculated. It is found that as Ho content increases, μ_eff as well as dG increases and T_C decreases. Moreover, the decrease of T_C scales with dG, i.e., Δ T_C ∝ -nI² N(ε_F)dG, which is consistent with the prediction of the Abrikosov--Gor'kov theory. We suggest that the depression of T_C could be mainly ascribed to the magnetic pair-breaking effect of magnetic Ho³⁺ ions. The change of Debye temperature with Ho content may not have significant impact on T_C.

We investigate the structure and exchange coupling in TbFeCo/FePt bilayer films. It is found that FePt has the L1₀ structure and the easy axis of the FePt film is perpendicular to the film plane. Results of the vibrating sample magnetometer and the magneto-optical Kerr effect measurements show a strong perpendicular exchange coupling between the ferrimagnetic TbFeCo layer and the hard ferromagnetic FePt layer. The magnetization direction of each layer and the process of magnetization reversal are discussed in detail. The switching field dependence on the exchange coupling has been modelled by micromagnetic simulation and the interlayer coupling constant is about -0.9erg/cm² according to this simulation.

Good rectifying current--voltage characteristics and nanosecond photoelectric effects are observed in the p--n heterojunctions of La_0.9Sr_0.1MnO₃/SrNb_0.01Ti_0.99O₃ fabricated by laser molecular beam epitaxy. The rise time is about 26ns and the full width at half maximum is about 125ns for the open-circuit photovoltaic pulses when the La_0.9Sr_0.1MnO₃/ film in the heterojunction is irradiated by a laser operated at wavelength 308nm with pulse duration of about 25ns. A qualitative explanation is presented, based on an analysis of the photoelectric effect of p--n heterojunction.

The frequency dependence of the in-plane angular change of the antiferromagnetic resonance (AFMR) field of KCuF₃ is systematically measured at frequencies ranging from 3.8 to 10.6GHz at 4.2K. The effect of inequivalent g-tensors is found to gradually diminish with decreasing the frequency, and completely vanish when the frequency is decreased to the lower-frequency branch of C-band, while the effect of the effective anisotropy field is significantly enhanced with decreasing the frequency. The calculated AFMR field H_res based on the eight-sublattice model proposed by Yamada and Kato [J. Phys. Soc. Jpn. 63(1994)289] is in good agreement with the experimental data.

Impedance spectroscopy is performed to establish the electrical property and microstructure relations of the as-deposited and post-annealed polycrystalline CaCu₃Ti₄O₁₂ (CCTO) films. Our results show that the resistance and capacitance of the grains and grain boundaries could be tuned by changing the annealing atmosphere and temperature. The simple resistor--capacitor equivalent circuit and the modified constant phase element (CPE) circuit are used to describe the impedance spectroscopy, and excellent agreement between the calculated and measured curves is obtained in the CPE circuit. Based on the experimental results, it is suggested that the origin of the semiconductivity of the grains in CCTO polycrystalline films originates from their oxygen-loss, while the grain boundaries are close to oxygen- stoichiometry.

Imaging properties of a two-dimensional photonic crystal (PC) slab consisting of a triangular lattice of metallic cylinders immersed in a dielectric background are investigated by the finite-difference time-domain technique. With the calculated field patterns of a point source placed in the vicinity of the PC slab and the corresponding equifrequency-surface contours, we find that a high-quality image can form in the opposite side of the slab in the lowest TM-polarized photonic band, and this near-field image is formed mainly by the self-collimation effect.

Thermo-optic coefficient dn/dT as well as volume expansion coefficients β of different polymer systems are measured for both TE and TM polarizations in an attenuated total reflection (ATR) configuration. Experimental results indicate that cross-linked polymer systems exhibit the thermal expansion coefficients smaller than those of the original side-chain systems. Moreover, the anisotropies in thermo-optic coefficients of the polymer systems with small birefringence exhibit linear relationship with the anisotropies in volume expansion coefficients, but the polymer systems with larger birefringence exhibit more complicated relationship.

Composition dependence of quaternary CuIn_1-xGa_xSe₂ films on Ga content has been systematically investigated by Raman scattering. The dominant A₁ mode shifts from 174cm^-1 for CuInSe₂ to 185cm^-1 for CuGaSe₂ in an approximately polynomial curve other than a linear curve, indicating existence of asymmetric distribution of Ga and In on a microscopic scale in films. With Ga content x>0.3, the significantly broadening and intensity decrease of A₁ modes suggest the degradation of crystalline quality of chalcopyrite phase. Additionally, the quenching of additional Raman band at 183cm^-1 for the Ga-rich films reveals that CuAu-ordered phase can coexist in nominal chalcopyrite CuInSe₂ films but not in CuGaSe₂, due to Ga inhibition effect.

High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3μm to 1.5μm range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N₂ flow rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54μm GaInNAs/GaAs QWs was kept as comparable as that in 1.31μm.

Permeability is one of the most important properties of porous media. It is considerably difficult to calculate reservoir permeability precisely by using single well-logging response and simple formula because reservoir is of serious heterogeneity, and well-logging response curves are badly affected by many complicated factors underground. We propose a neural network method to calculate permeability of porous media. By improving the algorithm of the back-propagation neural network, convergence speed is enhanced and better results can be achieved. A four-layer back-propagation network is constructed to effectively calculate permeability from well log data. Spontaneous potential, resistivity of deep lateral log, resistivity of micro-gradient log, resistivity of micro-normal log, Interval transit time of acoustic log and resistivity of shallow lateral log are selected as the inputs, and permeability is selected as the output. There are 35 and 40 units used in the two hidden layers, respectively. During the training course, the correlation coefficient between the calculated permeability and the standard pattern is as high as 0.9937, the average absolute error between them is 0.046μm² and the average relative error is only 1.93%. For practical applications, the average relative error between the calculated permeability and actual permeability is also as low as about 10.0%.

We report on a white organic light emitting device (OLED) with a single light emitting layer consisting of a greenish-white emitting host bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)₂) and an orange-red dopant 5,6,11,12-tetraphenylnaphthacene (rubrene). The Commission Internationale De L'Eclairage (CIE) coordinates, external quantum efficiency, and brightness of the white OLED are (0.341, 0.334), 0.63% and 4000Cd/m² at the bias of 20V, respectively. Pure red-green-blue (RGB) emissions have been successfully achieved from the white OLED combined well with several built-in optical colour filters (CFs). The CIE coordinates of the white mixture calculated in theory are very close to the coordinates of the white mixture which recorded with spectrophotometer in practice.

High-efficient saturated red light-emitting diodes are realized based on a bilayer of phenyl-substituted poly [p-phenylene vinylene] derivative (P-PPV) and {copolymer (PFO-DBT15) of 9,9-dioctylfluorene (DOF) and 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DBT)}. External electroluminescent (EL) quantum efficiency of PFO-DBT15 is increased from 1.6% for a single-layer device to 4.7% for the bilayer device by insertion of a P-PPV layer between PEDOT (polyethylene dioxythiophene-polystyrene sulfonic acid) and PFO-DBT15 at the current density of 35mA/cm². The luminescence efficiency reaches 0.83cd/A, and the Commission Internationale de I'Eclairage coordinates (CIE) become nearly x=0.700 and y=0.300. In comparison with the devices from PFO-DBT15 and P-PPV blend films, the P-PPV/PFO-DBT15 bilayer device shows higher EL quantum efficiency and better stability under high current density. The improved device performance can be attributed to the charge-confinement effect at the interface of the P-PPV/PFO-DBT15 bilayer structure.

Considering the vapour effects, we calculate the shape instability of single-bubble sonoluminescence (SBSL) in the phase diagram of the amplitude of driving pressure versus ambient radius, i.e. the p_a-R₀ diagram. The numerical calculation shows that the results calculated by the present model are reliable, even some parameters, such as the binary diffusion constant and the thermal conductivity of the mixture of argon and water vapour inside the bubble, are roughly evaluated. It is found by numerical calculation that the shape stable area of a single argon bubble in those viscous liquids with low vapour pressure, such as oil of vitriol, glycerol and 1,2-propanediol, can be extended to a wider region. Combining with the calculation of the maximum temperature inside the bubble, we may predict that these areas are probably the stable region of SBSL.

Epitaxial ZnO films are grown on Al₂O₃ (0001) by the MOCVD method. These films are high quality wurtzite crystals with (0001) orientation. Big hexagonal crystallites (diameter from several decades to 100μm) are found on the surface. Inside these crystallites, a stronger luminescence is observed compared with the plain area. Transmission electronic microscopy reveals that the film is thicker inside the hexagonal crystallites than the plain area, and some crystallites are not connected with each other and are slightly rotated with respect to their neighbours.

Tin dioxide (SnO₂) nanobelts have been successfully synthesized in bulk quantity by the CVD process based on the thermal evaporation of tin powders. The x-ray diffraction analysis indicates that the nanobelts are the tetragonal rutile structure of SnO₂. Scanning electron microscopy and transmission electron microscopy observations reveal that the nanobelts are uniform. The selected-area electron diffraction analysis demonstrates that the nanobelts are single crystals. The energy dispersive x-ray analysis of the nanobelt shows that the nanobelts are composed of Sn and O. Gas-sensing components have been manufactured with prepared SnO₂ nanobelts. Their performance indicates that SnO₂ nanobelts have high sensitivity and selectivity to liquefied petroleum gas with fairly good response-recovery characteristic and stability at 220 °C.

KrF excimer laser annealing on ultrathin hydrogenated amorphous Si films with various initial Si thicknesses is carried out to obtain a single layer of nanocrystalline Si structures. It is found that Si nanograins can be obtained with the area density as high as 10¹¹cm^-2 under the irradiation with suitable laser fluence. Raman and planar transmission electron microscopy are used to characterize the formation process of Si nanocrystals from amorphous phase. Moreover, a strong photoluminescence is observed at room temperature from well-relaxed nanocrystalline Si structures.

Oblique-incidence reflectivity difference (OI-RD) analysis is applied to detect the immunoglobulin-G and cytochrome biomolecules on standard glass substrates without fluorescence labelling. The OI-RD intensities not only depend on the protein structure, but also vary with the protein concentration. The results indicate that this method should have potential applications in detection of biochemical processes.

The CO--NO reaction on a catalytic surface is studied by using Langmuir--Hinshelwood thermal mechanism with Monte Carlo computer simulation. In this model, a novel concept of CO--CO repulsion is introduced, which has experimental evidence due to the formation of dipoles when these molecules are chemisorbed on the surface. The system is investigated by applying two approaches of NO dissociation. In the first case, NO always decomposes into N and O before adsorption on the surface. In the second case, NO adsorbs on the surface molecularly and then dissociates into N and O if a vacancy is present in its adjacent neighbourhood. The steady state reactive window (i.e. the continuous production of CO₂ and N₂) is obtained only with the diffusion of N-atoms on the surface, which extends with CO--CO repulsion in the first case. However, in the second case, reactive window is obtained with CO--CO repulsion alone. The reactive window width in this case is reasonably large. The first-order phase transition is eliminated in both the cases with CO--CO repulsion.

According to the acceptance ratio method, the influences on the depletion interactions between a large sphere and a plate from another closely placed large sphere are studied by Monte Carlo simulation. The numerical results show that both the depletion potential and depletion force are affected by the presence of the closely placed large sphere; the closer the large sphere are placed to them, the larger the influence will be. Furthermore, the influences on the depletion interactions from another large sphere are more sensitive to the angle than to the distance.

Pb(Zr_0.4Ti_0.6)O₃ film prepared by sol-gel spin coating on a Pt/Ti/SiO₂/Si substrate is applied to ferroelectric capacitors with Pt or Ru as the top electrode. For the Pt/PZT/Pt and Ru/PZT/Pt ferroelectric capacitors, although with the same ferroelectric film, different top electrode materials incur different properties of PZT capacitors, such as fatigue, leakage, remanent and saturated polarization, except the similar crystal orientations of the PZT film. After 10¹⁰ switch cycles, the remanent polarizations of the Ru/PZT/Pt and Pt/PZT/Pt capacitors decrease to 70% and 84%, respectively. The leakage current density of the latter increases obviously at positive bias after 10⁸ switch cycles, compared with the former. Different materials for the top electrode bring different conditions at the PZT/top electrode interface. The influence of oxygen-vacancy concentration at the PZT/electrode interface and the influence of oxides of the electrode material at the PZT/electrode interface to charge injection can explain the difference of properties of the PZT capacitors with Pt or Ru as the top electrodes.

We consider the effect of clustering coefficient on the synchronizability of coupled oscillators located on scale-free networks. The analytic result for the value of clustering coefficient aiming at a highly clustered scale-free network model, the Holme--Kim model is obtained, and the relationship between network synchronizability and clustering coefficient is reported. The simulation results strongly suggest that the more clustered the network, the poorer the synchronizability.

How the microscopic structure of complex network takes influence on the epidemic propagation is investigated. Special attention is paid to the growing network where its average degree changes with time. A formula for the final density of infected individuals is given and is confirmed by numerical simulations. Our results show that the final density of refractory increases nonlinearly with both the average degree of nodes and the adjustable random parameter of network structure.

We analyse the vertical structure of the magnetotail current sheet for two time intervals during which the Cluster spacecrafts crossed the neutral sheet in a quiet time. In the intervals, the current sheet moved slowly, and the value of the AE index was relatively small, about 40--130nT. We find two examples of current sheets, with the current density maximum at the magnetic equator (B_x = 0), as well as an example of off-centre or bifurcated current sheets. In the quiet time, without any fast plasma flow and without significant flapping motion, we also directly observed the bifurcated current sheet. The bifurcated current sheet is probably associated with instabilities in the current sheet. These may be important for researching the mechanism of current sheet bifurcation.

Growing observations reveal that soft gamma-ray repeaters and anomalous x-ray pulsars are magnetars. Their magnetic fields may achieve 10¹⁴-10¹⁵G. We explore the origin of the superstrong magnetic field by considering the magnetization of the ³P₂ superfluid neutrons inside neutron stars (NSs). By solving the Tolman--Oppenheimer--Volkov equations together with the equation of state adopted by Elgaroy it et al. [Phys. Rev. Lett. 77(1996)1428] in the calculation of the neutron pairing gap, we specifically calculate the NS internal structure, the permissible region for ³P₂ superfluid neutrons inside the NS, and the total magnetic moment contributed by the orderly arranged neutron vortexes. The result shows that the induced magnetic field may cover a wide range, which is consistent with the magnetic field predicted by the standard magnetic dipole radiation for pulsar spindown.

Adopting the observational distributions of star formation rates and half-light radii of Lyman break galaxies (LBGs) in the rest frame UV, we investigate empirically the predicted stellar mass function for LBGs. It is found that a peak exists at mass around 1.5 × 10¹⁰M_⊙ for their stellar mass function and there have been significant amount of LBGs with stellar masses higher than 10¹¹ M_⊙ at z～ 3. There should be two families for LBG population observed by the Infrared Array Camera (IRAC) (which is a key instrument in the infrared space telescope Spitzer), one is red and the other is blue, which are consistent with recent works. Moreover, the predicted comoving correlation lengths for LBGs with different stellar masses, i.e., with different 8μm magnitudes, are also discussed. The red LBGs should be clustered in space more strongly than the blue LBGs. These predictions can and will be tested by the observations of IRAC, and will provide strong constraints on the current hierarchical galaxy formation model.