A theoretical analysis of a Monte Carlo (MC) method for the simulation of the diffusion-growth of helium clusters in materials is presented. This analysis is based on an assumption that the diffusion-growth process consists of first stage, during which the clusters diffuse freely, and second stage in which the coalescence occurs with certain probability. Since the accuracy of MC simulation results is sensitive to the coalescence probability, the MC calculations in the second stage is studied in detail. Firstly, the coalescence probability is analytically formulated for the one-dimensional diffusion-growth case. Thereafter, the one-dimensional results are employed to justify the MC simulation. The choice of time step and the random number generator used in the MC simulation are discussed.

We investigate the interactions between components of various vector solitons in Bose-Einstein condensates by means of the least action principle, and derive the effective potentials for different vector solitons, which indicate that the interactions are of short range, and may be repulsive or attractive decided by the different intra- and inter-species interactions in such a system. In the case of attraction, the two solitons will oscillate about and pass through each other around the equilibrium state. The comparison of analytical results with mumertical simulation is presented.

We present a scheme for probabilistic dense coding via quantum channels of non-maximally entangled three-particle states. Quantum dense coding will succeed with a certain probability if the sender introduces an auxiliary particle and performs a collective unitary transformation. The average information transmitted in this scheme is calculated.

We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross-Pitaevskii equation. It is indicated that the atom-atom interaction will weaken the localization and broaden the wave function, and it will destroy the adiabaticity of the ramped loading process in both single lattice and incommensurate lattice due to the broadening effect. A band structure model can interpret the difference of the adiabatic condition with non-interacting BEC in these optical lattices.

We propose a protocol of remote information concentration achieved by a four-particle cluster state. To achieve the task, Bell state measurement and unitary operation are needed. The result shows a peculiar phenomenon that the remote information concentration is not always successful but with certain probability.

By using a two-component approach to the one-dimensional effective mass Dirac equation, bound states are investigated under the effect of two new non-PT-symmetric and non-Hermitian exponential type potentials. It is observed that the Dirac equation can be mapped into a Schrödinger-like equation by rescaling one of the two Dirac wave functions in the case of the position-dependent mass. The energy levels and the corresponding Dirac eigenfunctions are found analytically.

We discuss the quantum locality (non-transfer of information) for a pair of mutually interacting systems, and point out the relaxed locality. The models fulfilling the relaxed locality condition can serve as a guide for quantum engineers in designing quantum-information hardware.

By virtue of the technique of integration within an ordered product of operators, we present a new approach for deriving the generalized thermo vacuum state which is simpler in form than that obtained from the Takahashi-Umezawa method. using this new approach, the thermo field dynamics can be developed. Applications of the new state are discussed.

We discuss many interesting and attractive features of a higher-dimensional cosmology with a static traversable wormhole dominated by a variable effective cosmological constant depending on the scale factor a(t) as Λ_{effective} =Ca^{-2}+Λ_{0}, where C and Λ_{0} are positive constants.

Distribution of film thickness coated on the pendulum of measuring the Newton gravitational constant G is determined with a weighing method by means of a precision mass comparator. The experimental result shows that the gold film on the pendulum will contribute a correction of -24.3ppm to our G measurement with an uncertainty of 4.3ppm, which is significant for improving the G value with high precision.

We report on synchronization between two identical time delay chaotic systems under parameter mismatch. It overcomes some limitations of the previous work where synchronization and antisynchronization has been investigated only in finite-dimensional chaotic systems under parameter mismatch, so we can achieve synchronization and antisynchronization in infinite-dimensional chaotic systems under parameter mismatch. For infinite-dimensional systems modelled by delay differential equations, we find stable synchronization and antisynchronization in long-, moderate- and short-time delay regions, in particular for the hyperchaotic case.

Time series prediction methods based on conventional neural networks do not take into account the functional relations between the discrete observed values in the time series. This usually causes a low prediction accuracy. To solve this problem, a functional time series prediction model based on a process neural network is proposed in this paper. A Levenberg-Marquardt learning algorithm based on the expansion of the orthonormal basis functions is developed to train the proposed functional time series prediction model. The efficiency of the proposed functional time series prediction model and the corresponding learning algorithm is verified by the prediction of the monthly mean sunspot numbers. The comparative test results indicate that process neural network is a promising tool for functional time series prediction.

A new 3D four-wing smooth autonomous chaotic system in which each equation contains a cubic product term is presented and physically implemented. Spectral analysis shows that the four-wing chaotic attractor has extremely wide frequency bandwidth compared with that of the Lorenz system and other four-wing chaotic systems, which is important in some relevant engineering applications such as secure communications.

We investigate the soliton structure of a coupled dispersionless system describing a current-conducting string with infinite length within a magnetic field. Thus, following Hirota's method, we unwrap three typical localized waves with nonzero angular momentum depending strongly upon their angular velocities. Illustrating the soliton behavior of these waves, we focus our interests on breather-like waves and depict the elastic scattering amongst such waves.

Based on the LaSalle invariance principle, we propose a simple adaptive-feedback for controlling the unified chaotic system. We show explicitly with numerical proofs that our method can easily achieve the control of chaos in the unified chaotic system using only a single variable feedback. The present controller, to our knowledge, is the simplest control scheme for controlling a unified chaotic system.

We explain the functional projective lag synchronization of a hyperchaotic Rössler system with four unknown parameters, where the output of the master system lags behind the output of the slave system proportionally. Based on Lyapunov stability theory, an active control method and adaptive control law are employed to make the states of two hyperchaotic Rössler systems asymptotically synchronized. Finally, some numerical examples are provided to show the effectiveness of our results.

A scheme for a microwave atomic clock is proposed for Cs or Rb atoms trapped in a blue detuned optical lattice. The ac Stark shift of the clock transition due to a trapping laser is calculated. We analyze it at some specific laser wavelength. Compared with the case of the fountain clock, the cavity related shifts, the collision shift and the Doppler effect are eliminated or suppressed dramatically in an atomic lattice clock. By analyzing various sources of clock uncertainty, a microwave atomic lattice clock with a high accuracy and small volume is feasible.

TiO_{2} nanofibers are synthesized via a simple electrospinning method and coated on a silicon substrate with Pt electrodes to fabricate a micro-structure sensor. This sensor exhibits high ethanol sensing properties at 300°C. The sensitivity is up to 4 when the sensor is exposed to 1ppm ethanol, the response time is about 3s, and the recovery is about 5s.

Most transmission gratings in the x-ray region work with their first orders and dispersion is limited by the line density achievable with current fabrication technology. We present a novel design of a two-dimensional x-ray transmission grating. The grating works with higher dispersion using its second orders, and the influence from first and third orders can be suppressed. A grating according to the novel design is fabricated and its diffraction performance is tested in comparison with a traditional x-ray transmission grating with the same line density. The novel grating could be especially useful when high dispersion is desired while the fabrication of high-density gratings becomes more difficult.

The DK interaction is relevant to the interpretation of the D_{sJ}(2317). We dynamically investigate S-wave DK interactions in the chiral SU(3) quark model by solving the resonating group method equation. The numerical results show an attraction between D and K, which is from boson exchanges between light quarks. However, such an attraction is not strong enough to form a DK molecule. Meanwhile, S partial wave phase shifts of DK elastic scattering are obtained. The case of S-wave D*K is rather similar to that of DK. To draw a definite conclusion of whether a molecular state exists in DK or the D*K system, more details of dynamics should be considered in a future study.

High-spin states in ^{129}Cs are populated via the ^{122}Sn (^{11}B, 4n) reaction at beam energies of 55 and 60MeV. Two additional bands are placed in the level scheme and the previously known bands are extended to higher spins. The results are compared to the cranked shell model calculations and to the systematics of the adjacent Cs isotpoes. One of the new bands is interpreted as the γ-vibrational band built on the π h_{11/2} orbital. The possible configuration for another new band is discussed. Upbend caused by (ν h_{11/2})^{2 }alignment is observed both in the favored and unfavored sequences of the π h_{11/2} configuration. The band based on the π g_{7/2} configuration at low pins forks around spin 17/2, and the two different S-bands are attributed to (ν h_{11/2})^{2} and (π h_{11/2})^{2} rotational alignments, respectively.

The imaginary time step (ITS) method is applied to solve the Dirac equation with the nonlocal potential in coordinate space by the ITS evolution for the corresponding Schrödinger-like equation for the upper component. It is demonstrated that the ITS evolution can be equivalently performed for the Schrödinger-like equation with or without localization. The latter algorithm is recommended in the application for the reason of simplicity and efficiency. The feasibility and reliability of this algorithm are also illustrated by taking the nucleus ^{16}O as an example, where the same results as the shooting method for the Dirac equation with localized effective potentials are obtained.

Based on the GEANT4 toolkit, we study the transportation of nucleons and nuclei in tissue-like media. The fragmentation of projectile nuclei and secondary interactions of produced nuclear fragments are considered. Livermore data is used to calculate electromagnetic interaction of primary and secondary charged particles. We validate the models using experimental data of 200MeV/u and 400MeV/u carbon ions, interacting with tissue equivalent materials of water. The model can well describe the depth-dose distributions in water and the doses measured for secondary fragments of certain charge and certain mass number. The secondary beam fragments produced by 200MeV/u and 400MeV/u ^{12}C^{6+} ions in water are investigated using the model. When the primary nuclei are in water, several neutron production mechanisms are involved. The light charged particles (p, d, t, ^{3}He and ^{4}He) and fast neutrons contribute to the dose tail behind the Bragg peak. The ^{11}C fragments which may be the most suitable nuclei for monitoring the energy deposition in carbon-ion therapy are also discussed.

GU Long, ZHU Sheng-Jiang, J. H. Hamilton, A. V. Ramayya, J. K. Hwang, S. H. Liu, WANG Jian-Guo, Y. X. Luo, J. O. Rasmussen, I. Y. Lee, DINGHuai-Bo, K. Li, XU Qiang, YANG Yun-Yi

Chin. Phys. Lett. 2009, 26 (9):
092502
.
DOI: 10.1088/0256-307X/26/9/092502

The high spin states of a neutron-rich ^{107}Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of ^{252}Cf. The previous level scheme is updated. A collective band based on the π5/2^{-}[303] orbital is confirmed and extended. Inconsistencies in the configuration assignments for a type of positive parity bands of odd-A ^{105,107,109}Tc in the previous reports are clarified according to the g factor calculations. A new band based on the 1499.5keV level in ^{107}Tc is proposed as a two-phonon γ-vibrational band.

Six different solutions of 6M NaOH, containing different amounts of Na_{2}CO_{3} at 70°C were used for the revelation of latent damage trails in CR-39 plastic track detectors. These detectors were earlier exposed to fission fragments from ^{252}Cf source for 30min in vacuum and were then etched in the respective solutions for different etching time intervals of 5-20min starting from 5min up to 160min. The etch induction time in each detector was obtained by extrapolating the intersection of resulting curves of track lengths and track diameters with the time axis.

CHENG Cheng, LIAO Shu-Qing, ZHENG Shu-Xin, LIN Yu-Zheng, TANG Chuan-Xiang, JING Xiao-Bing, MU Fan, PAN Hai-Feng, ZHANG Kai-Zhi, SHI Jin-Shui, DENG Jian-Jun

Chin. Phys. Lett. 2009, 26 (9):
092902
.
DOI: 10.1088/0256-307X/26/9/092902

Mini-LIA is a miniature of a linear induction accelerator developed by China Academy of Engineering Physics and Tsinghua University in 2007. It has been constructed with a thermionic cathode in an electron injector and a metglas core in the induction accelerator cavities. A double-pulsed electron beam was produced for the first time in China on the Mini-LIA with a thermionic cathode in the electron gun and a metglas core in the induction accelerator cavities. A double-pulsed beam current of more than 1.1A was obtained on condition of 80kV double-pulsed high voltage produced by pulsed power system supplying to the injector and accelerating modules. Some primary experiments for measuring the parameters of Mini-LIA has been performed, and some beam characterizations of Mini-LIA are presented. Further improvement is underway.

The angular distribution of energy for synchrotron radiation in low frequency band (ω«ω_{c}) is obtained by rigorously solving the Nicolo Tartaglia equation. The result shows that the critical angle increases with decreasing frequency, but it cannot exceed 90°. The relation between critical angle θ_{c} and frequency is common covering all wavelengths. For the small angle case, it is consistent with the result obtained by Jackson. With the increase of emanative angle, the radiant intensity increases first, then decays.

Using the semiclassical closed orbit theory, we study the coherent control of the photodetachment of H^{-} by a single and double-pulse laser in perpendicular electric and magnetic fields. Theoretically, dependences of calculated cross section on laser pulse widths, time delays, relative phases and the classical detached electron's closed orbit period are presented and discussed in detail. The results suggest that for the single pulse laser, if the pulse width is shorter than the particular closed orbit period, then the contribution of that closed orbit to the photodetachment cross section is reduced. While for the double pulse laser, the cross section not only depends on the pulse width, but also depends on the time delay and the relative phase of the two pulses. If the pulse delay time equals to the period of one closed orbit, then the contribution of that orbit becomes significant. Therefore, we can use the pulse laser to control the photodetachment process of ion or atom in external fields.

We report the experimental realization of a ^{88}Sr magneto-optical trap (MOT) operating at the wavelength of 461nm. The MOT is loaded via a 32cm long spin-flip type Zeeman slower which enhances the MOT population by a factor of 22. The total laser power available in our experiment is about 300mW. We have trapped 1.6×10^{8}^{88}Sr atoms with a 679nm and 707nm repumping laser. The two repumping lasers enhance the trap population and trap lifetime by factors of 11 and 7, respectively. The ^{88}Sr cloud has a temperature of about 2.3mK, measured by recording the time evolution of the absorption signal.

We calculate the vibrational frequencies of nickel tetraphenyl porphyrin for 36 vibrational bands by using the U(2) algebraic approach. The algebraic parameters in the calculations are accurate with the experimental data.

FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)

We present a numerical investigation for steady laminar flow of a viscous incompressible electrically conducting fluid through a channel of a rectangular cross-section with a transverse magnetic field and suction or injection walls. Multiple solutions are presented for values of suction Reynolds number R and velocity coefficients of accelerating walls. Additionally, the associated transfer characteristics are discussed in detail.

Based on the double superimposition model, a sea slope model is obtained on the basis of the generated oceanic surface instead of being assumed as a Gaussian distribution model. Then, a summation formula of the backscattering coefficient is derived from the Bass-Fuks two-scale model and its application is extended to the non-Gaussian oceanic surface with the help of simulated sea slopes, which can adequately reflect the non-Gaussian configuration of the sea surface. Finally, this scattering model is employed to describe the backscattering configuration of sea surfaces in different sea states and wind directions, and is confirmed by several numerical examples.

We design high quality factor (Q) photonic crystal microcavities in diamond films for applications in quantum information based on color centers. A photonic microcavity made from a waveguide heterostructure with a mode gap is demonstrated to have a high Q factor over 1051400 and a modal volume V of 2.24 cubic wavelengths by modifying the mode gap width and the tapered region geometry. Besides its ultrahigh Q factor, the waveguide-like geometry of the cavity allows for easy on-chip transportation of quantum information between different cavities.

We demonstrate the first quasi-three-level passively Q-switched Nd:GGG laser at 937nm using a Nd,Cr:YAG crystal as the saturable absorber. The dependences of the average output power, the repetition rate and the pulse width on the incident pump power are obtained. A maximum average output power of 1.18W with repetition rate of 35kHz and pulse width of 45ns is achieved at an incident pump power of 18.3W. The corresponding optical-to-optical and slope efficiencies are 6% and 10%, respectively.

We report the use of a large depth of focus Bessel beam in the fabrication of cell structures. Two axicon lenses are investigated in the formation of high aspect ratio line structures. A sol-gel resin, with good mechanical strength, is polymerised in a modified two-photon polymerisation system. Examples of different two-dimensional grids are presented to show that the lateral resolution can be maintained even in the rapid fabrication of high-sided structures.

Fiber Bragg gratings (FBGs) are successfully written in a non-photosensitive Tm-doped single-mode fiber by a 800nm fs laser and a 2.7μm period phase mask. The intra-core FBGs are written using the phase mask ±1 order interference, and have a period of 1.35μm, which responds to the second-order reflective central wavelength at 1946.4nm. Based on the magnification tuning writing technology, the tunable writing technology is also experimentally investigated. The distance between the phase mask and the fiber, between the phase mask and the tuning lens, and the focal length of the tuning lens all have an influence on the tunable characteristics. Four different FBGs tuning reflective central wavelengths located at 1958.7nm, 1970.8nm, 1882.5nm and 1899.7nm are obtained.

We investigate the generation of two-mode entangled light from cooperative three-level cascade emitters driven by two lasers inside an optical cavity. It is found that through collective coherent population trapping (CPT) to prepare the atomic states close to the coherent superposition state |1>-|3>√2 of the top and ground levels, the entanglement and mean photon number of the entangled light can be significantly enhanced in comparison to the case of independent atoms.

A flashlamp-pumped Cr:LiSAF laser system with a voltage controlled Q-switch structure in the cavity is designed. A dual-wavelength and dual-pulse tunable laser output is gained. The relation of laser output behavior with input energy is studied experimentally. The output is dual-pulsed with the energy of the 32mJ/pulse producing the total output energy of 64mJ and the pulse width is about 27ns at 850nm. Then, we use one LBO crystal as the frequency doubling crystal to obtain a dual wavelength (448.1nm and 449.15nm) and dual pulse laser. The output for one wavelength is about 10.3mJ and the line width is less than 0.02nm.

We report a high-efficiency Nd:YAG laser operating at 1064nm and 1319nm, respectively, thermally boosted pumped by an all-solid-state Q-switched Ti:sapphire laser at 885nm. The maximum outputs of 825.4mW and 459.4mW, at 1064nm and 1319nm respectively, are obtained in a 8-mm-thick 1.1at.% Nd:YAG crystal with 2.1W of incident pump power at 885nm, leading to a high slope efficiency with respect to the absorbed pump power of 68.5% and 42.0%. Comparative results obtained by the traditional pumping at 808nm are presented, showing that the slope efficiency and the threshold with respect to the absorbed pump power at 1064nm under the 885nm pumping are 12.2% higher and 7.3% lower than those of 808nm pumping. At 1319nm, the slope efficiency and the threshold with respect to the absorbed pump power under 885nm pumping are 9.9% higher and 3.5% lower than those of 808nm pumping. The heat generation operating at 1064nm and 1319nm is reduced by 19.8% and 11.1%, respectively.

A hybrid high quality factor (Q-factor) microwave photonic filter with a cascaded active filter and a passive filter is presented and experimentally demonstrated. The active infinite impulse response filter is realized by a recirculating delay line loop with a semiconductor optical amplifier, and a much narrower 3dB bandwidth of response peaks can be achieved. A passive finite impulse response filter is realized by an unbalance Mach-Zehnder interferometer, and it is cascaded to select the desired filter frequencies and to suppress the intermediate peaks. Compared with the purely active filter scheme, the free spectrum range and the Q-factor of the hybrid structure can be doubled. Stable operation and a high Q-factor of 362 are experimentally demonstrated.

Chirped mirrors (CMs) are designed and manufactured. The optimized CM provides a group delay dispersion (GDD) of around -60 fs^{2} and average reflectivity of 99.4% with bandwidth 200nm at a central wavelength of 800nm. The CM structure consists of 52 layers of alternating high refractive index Ta_{2}O_{5} and low refractive index SiO_{2}. Measurement results show that the control of CM manufacturing accuracy can meet our requirement through time control with ion beam sputtering. Because the GDD of CMs is highly sensitive to small discrepancies between the layer thickness of calculated design and those of the manufactured mirror, we analyze the error sources which result in thickness errors and refractive index inhomogeneities in film manufacture.

A simple and accurate method for calculating the optimal width of an annular spiral phase plate (SPP) to generate optical vortices with sidelobe suppression is proposed. The sidelobes can be sharply suppressed when the ratio of inner and outer radii of an annular SPP is equal to that of the principal ring and the first sidelobe diffracted by a circular SPP with the same topological charge n. Moreover, the ratio of the inner and outer radii of the optimal annular SPP depends only on the topological charge n and is not affected by the incident wavelength or the size of the SPP.

A theoretical study of the dynamical behaviors of the interaction between a two-level atom with a Morse potential in the framework of the Jaynes-Cummings model (JCM) is discussed. We show that this system is equivalent to an intensity-dependent coupling between the two-level atom and the non-deformed single-mode radiation field in the presence of an additional nonlinear interaction. We study the dynamical properties of the system such as, atomic population inversion, the probability distribution of cavity-field, the Mandel parameter and atomic dipole squeezing. It is shown how the depth of the Morse potential can be affected by non-classical properties of the system. Moreover, the temporal evolution of the Husimi-distribution function is explored.

Relationships among the signal coherence-time of matched-field processing (MFP), the acoustic frequency, the source-receiver range, and the sound speed standard deviation (STD) caused by internal waves in shallow water, are numerically investigated based on oceanographic data from two shallow water experiments. It is found that the coherence-time can be fitted with an inverse square-root power of range, a near inverse 1 power of frequency, and inverse 1.3 power of sound speed STD.

The transient thermoelastic stress fields of GaN films is analyzed by the finite element method for the laser lift-off (LLO) technique. Stress distributions in GaN films irradiated by pulse laser with different energy densities as functions of time and depth are simulated. The results show that the high thermoelastic stress distributions in GaN films localize within about 1μm below the GaN/Al_{2}O_{3} interface using proper laser parameters. It is also found that GaN films can avoid the thermal deformation because the maximum thermoelastic stress 4.28GPa is much smaller than the yield strength of GaN 15GPa. The effects of laser beam dimension and the thickness of GaN films on stress distribution are also analyzed. The variation range of laser beam dimension as a function of the thickness of GaN films is simulated to keep the GaN films free of thermal deformation. LLO experiments are also carried out. GaN-based light-emitting diodes (LEDs) are separated from sapphire substrates using the parameters obtained from the simulation. Compared with devices before LLO, P-I-V measurements of GaN-based LEDs after LLO show that the electrical and optical characteristics improve greatly, indicating that no stress damage is brought to GaN films using proper parameters obtained by calculation during LLO.

An approach which combines direct numerical simulation (DNS) with the Lighthill acoustic analogy theory is used to study the potential noise sources during the transition process of a Mach 2.25 flat plate boundary layer. The quadrupole sound sources due to the flow fluctuations and the dipole sound sources due to the fluctuating surface stress are obtained. Numerical results suggest that formation of the high shear layers leads to a dramatic amplification of amplitude of the fluctuating quadrupole sound sources. Compared with the quadrupole sound source, the energy of dipole sound source is concentrated in the relatively low frequency range.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

The filamentation mechanisms of prefocused and freely propagated femtosecond laser pulses are compared using the ray-tracing method. The dynamic spatial replenishment mechanism takes place in the filaments with high electron density, which is generally formed by prefocused laser pulses. The mechanism of long-range filamentation over 100m distance is analyzed to be the spatiotemporal moving focus.

Under optimized operating parameters, a wear and corrosion resistant Cr_{3}Si/γ-Fe composite coating is fabricated on a normalized 0.45% carbon steel substrate by using the plasma transferred arc (PTA) cladding technique with Fe-Cr-Si elemental powder blend as the precursor material. Microstructure, microhardness, dry-sliding wear resistance and electrochemical corrosion characteristic of the coating are evaluated. Test results show that the composite coating is mainly composed of primary Cr_{3}Si dendrites and the interdendritic supersaturated iron-base solid solution γ-Fe. Between the Cr_{3}Si/γ-Fe composite coating and the normalized 0.45% carbon steel substrate, there is a narrow metallurgical bonding zone. The Cr_{3}Si/γ-Fe composite coating exhibits high microhardness, excellent wear and corrosion resistance under test conditions.

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES

The generalized gradient approximation based on density functional theory is used to study the structural, electronic and magnetic properties of the endohedral complex of C_{80} with tetrahedral T_{d}-N_{4}. The most unstable I_{h}-C_{80} can most effectively stabilize the N_{4} molecule, similar to the case of I_{h}-N_{4}@C_{60} [Structural Chemistry 16(2005)567]. It is worth noting that the cage becomes nonmagnetic due to the encaging of N_{4}.

The behavior of an extended dislocation near an elliptical blunt crack is investigated. The equilibrium separation between Shockley partials and the critical value of stacking fault energy for the formation of extended dislocations by dissociation reaction as well as the extended dislocation emission criterion are developed. The results show that the equilibrium separation increases as the extended dislocation tends to the blunt crack. If the stacking fault energy is comparable to the critical energy for dissociation in a perfect medium, complete dislocations can dissociate to form extended dislocations near the blunt crack. The critical stress intensity factor (SIF) for extended dislocation emission increases with the stacking fault energy and the curvature radius of the blunt crack tip. Moreover, the critical SIF for extended dislocation emission is far lower than the critical SIF for edge dislocation emission.

By means of mounting the specimen on a low-impedance buffer, reshock experiments were carried out on a 2A12 aluminum alloy up to shock stresses of 67.6GPa. Reshock wave profiles from the initial shock stresses of 60.9-67.6GPa were measured with a velocity interferometer, and it shows that the 2A12 aluminum alloy characterizes as quasi-elastic response during recompression process. The Lagrange longitudinal velocities along the reloading path from initial shock state were obtained from two shots of experiments, while the bulk velocities at corresponding shock stresses were determined via extrapolating from the public reported unloading plastic sound velocities. Combining the reshock and the release experimental results, the yield strength of 2A12 aluminum alloy at shock stress of 60.9GPa was estimated to be about 1.7GPa.

Hydrostaticity under high pressure of several materials from solid, fluid to gas, which are widely used as pressure media in modern high-pressure experiments, is investigated in diamond anvil cells. Judging from the R-line widths and R_{1}-R_{2} peak separation of Ruby fluorescence, the inert argon gas is hydrostatic up to about 30GPa. The behavior of silicon oil is found to be similar to argon at pressures less than 10GPa, while the widening of R-lines and increase of R_{1}-R_{2 }peak separation at higher pressure loads indicate a significant degradation of hydrostaticity. Therefore silicon oil is considered as a good pressure medium at pressures less than 10GPa but poor at higher pressures.

The structure of the vortex in a two-component Bose-Einstein condensate is studied by the method of Dirac δ function. The vortex can be characterized by the Brouwer degree and Hopf index, i.e., β_{1}η_{1}, β_{2}η_{2}. The circulation of the vortex can be a fraction, which is different from the usual result for a one-component condensate. The kinetic helicity of vortices is calculated.

Thick GaN films of high quality are directly grown on wet-etching patterned sapphire in a vertical hydride vapour phase epitaxy reactor. The optical and structural properties of GaN films are studied using scanning electronic microscopy and cathodoluminescence. Test results show that initial growth of hydride vapour phase epitaxy GaN occurs not only on the mesas but also on the two asymmetric sidewalls of the V-shaped grooves without selectivity. After the two-step coalescence near the interface, the GaN films near the surface keep on growing along the direction perpendicular to the long sidewall. Based on Raman results, GaN of the coalescence region in the grooves has the maximum residual stress and poor crystalline quality over the whole GaN film, and the coalescence process can release the stress. Therefore, stress-free thick GaN films are prepared with smooth and crack-free surfaces by this particular growth mode on wet-etching patterned sapphire substrates.

Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg_{2}SiO_{4} and MgF_{2} through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.

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

The pressure induced phase transitions of RuB_{2} from the OsB_{2}-type structure to the ReB_{2}-type structure are investigated by first-principles calculations based on the plane-wave basis set with the generalized gradient approximation for exchange and correlation. It is found that the phase transition occurs at 18.6GPa. We predict the phase transition from the OsB_{2}-type RuB_{2} to the ReB_{2}-type RuB_{2} at high temperatures for the first time. The dependences of the heat capacity, thermal expansion coefficient, and the Grüneisen parameter on pressure and temperature for OsB_{2}-type RuB_{2 }and ReB_{2}-type RuB_{2} are also investigated.

We present a theoretical study of the conductance in an Aharonov-Bohm interferometer containing two coupled quantum dots. The interdot tunneling divides the interferometer into two coupled subrings, where opposite magnetic fluxes are threaded separately while the net flux is kept zero. Using the Green function technique we derive the expression of the linear conductance. It is found that the Aharonov-Bohm effect still exists, and when the level of each dot is aligned, the exchange of the Fano and Breit-Wigner resonances in the conductance can be achieved by tuning the magnetic flux. When the two levels are mismatched the exchange may not happen. Further, for some specific asymmetric systems where the coupling strengths between the two dots and the leads are not equal, the flux can change the Fano resonance into an antiresonance, which is absent in symmetric systems.

We propose a spin-splitter composed of triple quantum dots that works due to the Coulomb blockade effect and the charge and spin biases applied on external electron source and drains. The spin biases are applied only on the two drains and give their spin-dependent chemical potentials, which act as the driving forces for electron spin-polarized transport. By tuning the biases and the dots' levels, spin-up and spin-down electrons can be simultaneously split or separated from the source into two different drains. We show that such a tunneling process is detectable in terms of the spin accumulations on the dots or the currents flowing through the external leads. The present device is quite simple and realizable within currently existing technologies.

We study the electron states on lateral double quantum dots coupled in parallel. The charge stability diagrams are given in terms of the gate voltages of both dots. We discover that the two electron states translate from separated states to coupled states continuously by increasing the inter-dot coupling strength. Our results demonstrate that the parallel-quantum-dot tunability bodes well for future quantum computing applications.

Temperature dependence of the upper critical magnetic field (H_{c2}) near T_{c} of 20K in a BaFe_{1.9}Ni_{0.1}As_{2} single crystal is determined via magneto-resistance measurements, for the out-plane (H⊥ab) and in-plane (H || ab) directions in magnetic fields of up to 8T. The upper critical fields at zero temperature estimated by the Werthamer-Helfand-Hohenberg (WHH) formula are μ_{0 }H_{c2}^{||}(0)= 137T and μ_{0} H_{c2}^{⊥}(0) = 51T, both exceeding the weak-coupling Pauli paramagnetic limit (μ_{0}H_{p}=1.84T_{c}). However, the WHH formula could overestimate the μ_{0}H_{c2}^{||} (0) value. The anisotropy of upper critical fields is around 3 in the temperature range close to T_{c}. The result is very similar to the Co-doped 122 superconductor BaFe_{2-x}Co_{x}As_{2}, indicating that electron-doped 122 superconductors exhibit similar superconducting properties.

We study the electronic Raman scattering in the cuprates to distinguish the two possible scenarios of the pseudogap normal state. In one scenario, the pseudogap is assumed to be caused by phase fluctuations of the preformed Cooper pairs. We find that pair-breaking peaks appear in both the B_{1g} and B_{2g} Raman channels, and they are smeared and tend to shift to the same energy with the increasing strength of phase fluctuations. Thus both channels reflect the same pairing energy scale, irrespectively of the doping level. In another scenario, the pseudogap is assumed to be caused by a hidden order that competes with the superconducting order. As an example, we assume that the hidden order is the d-density-wave (DDW) order. We find analytically and numerically that in the DDW normal state there is no Raman peak in the B_{2g} channel in a tight-binding model up to the second nearest-neighbor hopping, while the Raman peak in the B_{1g }channel reflects the energy gap caused by the DDW order. This behavior is in agreement with experiments in the pseudogap normal state. To gain further insights, we also calculate the Raman spectra in the DDW+SC state. We study the doping and temperature dependence of the peak energy in both channels and find a two-gap behavior, which is in agreement with recent Raman experiments. Therefore, our results shed light on the hidden order scenario for the pseudogap.

We present a theory of orbital ordering in orbital-degenerate itinerant electron systems. The orbital instability in a two-orbital degenerate Hubbard model is investigated in the random phase approximation (RPA). After demonstrating the criteria for the formation of orbital ordering or the orbital density wave ordering, we find that the orbital and the spin-orbital collective excitation spectra in the ferro-orbital ordered phase exhibit finite gaps. The possible application of the present theory in orbital-ordered 4d compounds is also discussed.

Structural and magnetic properties of Fe-doped anatase TiO_{2} films fabricated by sol-gel spin coating are investigated. X-ray diffraction measurements reveal that Fe^{3+} ions are incorporated into the TiO_{2} lattice. No ferromagnetism-related secondary phases and magnetic nanoparticles are observed in the films. The presence of electron paramagnetic resonance signals at g ~ 2.0 supports oxygen vacancies and/or defects generated in the films after annealing in vacuum. Magnetic measurements indicate that Fe-doped anatase TiO_{2} films are ferromagnetic at room temperature. These observations suggest that oxygen vacancies and/or defects are energetically favorable for the long range Fe^{3+}-Fe^{3+} ferromagnetic coupling in Fe-doped anatase TiO_{2} films.

This work focuses on the crystal structure and magnetic properties of the hard magnetic Sm_{2}Fe_{17}N_{δ} films prepared by dc magnetron sputtering and the subsequent nitriding process. The XRD, EDS, M-H and M-T data show that N enters the cell structure and the films with the single Th_{2}Zn_{17} phase are obtained when the nitriding temperature varies from 300 to 400°C, thus the maximum value of the coercivity H_{C} reaches 2561.7Oe. However, the Sm_{2}Fe_{17} phase decomposes to the SmN nonmagnetic phase and the α-Fe soft magnetic phase with further increasing nitriding temperature, which corresponds to the decreasing H_{C}. Furthermore, the easy magnetization direction (EMD) is found to locate randomly in the film plane. This texture can not give an excellent M_{R}/M_{S} higher than the Stoner-Wohlfarth limitation (M_{R}/M_{S}=0.5), which agrees well with the observed low M_{R}/M_{S} (0.58). It is suggested that the magnetization reversal process is dominated by the nucleation mechanism according to the initial magnetization curve and the dependence of H_{C} on the field H.

The enhancement of electroluminescent (EL) performance of polymer light emitting diodes (PLEDs) with electron transport emitter poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) through thermal annealing treatment is investigated. Post-annealing of the PLEDs at temperature 120°C over the glass transition temperature of F8BT (99°C) could bring about an improvement of EL efficiency to more than twice that of the untreated devices, up to 6.02cd/A. The improvement of the EL efficiency is due to the balance of electron and hole carriers in the exciton recombination zone, because the dominative electron current in the PLEDs could be reduced by post-annealing in terms of both issues of electron transport limited in the F8BT film and electron injection decreased by the interface between F8BT/cathode.

We present the characteristics of bulk damage induced by the third harmonic of Nd:YAG laser irradiation in KDP and DKDP crystals. Bulk damage occurs as a few or a series of pinpoints consisting of a core and the deforming zone. The results of a 1-on-1 test reveal that the pinpoint size increases with incvreasing fluence, and the pinpoint density increases exponentially with increasing fluence. The results of an s-on-1 test indicate that the pinpoint density increases gradually with laser pulse number, but the size does not grow. These results are consistent with a model in which nanoabsorbers are assumed to exist in the crystal and the initiation of damage is determined by heating them to the critical temperature.

A thermal model is considered in order to better understand the mechanism of laser induced damage in KDP and DKDP crystals. We demonstrate that the expressions of pinpoint density and damage probability, predicted by the thermal model, are consistent with the experimental data. We also discuss the effect of particle interaction on the thermal model.

A simple method for synthesis of well dispersed cadmium sulphide nanoparticles embedded in a polyethylene glycol matrix (PEG 400) in thin film form is presented. The large blue shift of the band gap energy of the CdS nanoparticles compared to the bulk semiconductors is observed via UV-vis absorption spectra. Photoluminescence spectra of CdS nanocomposite films show that the emission peaks shift towards the longer wavelength with the increase of annealing temperature. Transmission electron microscopic images as well as Raman scattering studies confirm the CdS nanometer size particle formation within the polymer matrix. The particle size is about 8 nm. Selected area electron diffraction (SAED) shows the cubic zinc blende polycrystalline rings. Third-order optical nonlinearity of the CdS nanoparticles embedded in polymer thin films is studied with the Z-scan technique under 1064 nm excitation. The results show that the CdS nanocomposite film exhibits negative nonlinear refraction index and positive absorption coefficient. The film shows large optical nonlinearity, and the magnitude of the third-order nonlinear susceptibility of the film is calculated to be 1.73×10^{-9 }esu. The corresponding mechanism is discussed.

Laser-induced damage is a key lifetime limiter for optics in large laser facilities. Fused silica is tested to find the damage threshold on two different laser facilities of different apertures. The damage threshold shows that the corners of the component are less damage resistant. The acid etch on a corner does not effectively increase the damage threshold. A statistics-based model is presented to extrapolate the threshold data in a small-aperture test to predict the damage threshold under functional conditions.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

Reproducible p-type phosphorus-doped ZnO (p-ZnO:P) films are prepared on semi-insulating InP substrates by metal-organic chemical vapour deposition technology. The electrical properties of these films show a hole concentration of 9.02×1017cm^{-3}, a mobility of 1.05cm^{2}/V s, and a resistivity of 6.6 Ω・cm. Obvious acceptor-bound-exciton-related emission and P-induced zinc vacancy (V_{Zn}) emission are observed by low-temperature photoluminescence spectra of the films, and the acceptor binding energy is estimated to be about 125meV. The local chemical bonding environments of the phosphorus atoms in the ZnO are also identified by x-ray photoelectron spectra. Our results show direct experimental evidence that P_{Zn}-2V_{Zn} shallow acceptor complex most likely contributes to the p-type conductivity of ZnO:P films.

A patterned Au/Pt/In_{0.2}Ga_{0.8}N/GaN heterostructure Schottky prototype solar cell is fabricated. The forward current-voltage characteristics indicate that thermionic emission is a dominant current transport mechanism at the Pt/InGaN interface in our fabricated cell. The Schottky solar cell has an open-circuit voltage of 0.91V, short-circuit current density of 7mA/cm^{2}, and fill factor of 0.45 when illuminated by a Xe lamp with a power density of 300mW/cm^{2}. It exhibits a higher short-circuit current density of 30mA/cm^{2} and an external quantum efficiency of over 25% when illuminated by a 20-mW-power He-Cd laser.

A kinetic model of the interactions between operators and regulators is developed to study the stabilities of genetic states and lysogeny/lysis switch in Escherichia coli infected by bacteriophage lambda. Using adiabatic approximation, the kinetic evolutions of mRNA and regulator concentrations can be deduced from operators' equations. Furthermore, the stability of each state of the system is studied. The results show that the lysogenic state switches to the lytic state through two bifurcations: one from a single stable state to a three-point state, and the other from a three-point state to a single stable state. Then we indicate that the property of the lysogeny/lysis switch satisfies the topological characteristics theorem. Finally, the influence of the left operators on the lysogeny/lysis switch is briefly discussed. The results show that the cooperativity of the CI_{2} bound to left and right operators makes the lysogenic state more stable.

A three-company econophysics model for competing multi-agent systems in a triangular lattice is analyzed using mean field theory for its phase diagram. Interpretations for the temperature, spin density and lattice structures are presented. Suggestions for the use of this model for econophysics in the context of multi-agent systems are made.

In the global economic system, each economy stimulates the growth of its gross domestic products (GDP) by increasing its international trade. Using a fluctuation analysis of the flux data of GDP and foreign trade, we find that both GDP and foreign trade are dominated by external force and driven by each other. By excluding the impact of the associated trade dependency degree, GDP and the total volume of foreign trade collapse well into a power-law function. The economy's total trade volume scales with the number of trade partners, and it is distributed among its trade partners in an exponential form. The model which incorporated these empirical results can integrate the growth dynamics of GDP and the interplay dynamics between GDP and weighted international trade networks simultaneously.

Inspiring Newton's law of universal gravitation and empirical studies, we propose a concept of virtual network mass and network gravitational force in complex networks. Then a network gravitational model for complex networks is presented. In the model, each node in the network is described with its position, edges (links) and virtual network mass. The proposed model is examined by experiments to show its potential applications.