Two (2+1)-dimensional (3D) lattice systems are proposed in view of the compatibility of 2D lattice systems in the same hierarchy. Furthermore, the Darboux transformation (DT) method is generalized to the case of 3D lattice equations. As a consequence, some exact solutions for the resulting discrete systems are presented.

We study the pairwise entanglement and mixture of a three-qubit XXZ spin chain in the ground state in the presence of an external magnetic field B. The effects of the magnetic field, the anisotropy and the temperature on the entanglement and mixture are considered, and entanglement versus the mixture of all the two-spin states is investigated. We find that the maximal entangled mixed state can be obtained in the considered system by controlling the magnetic field. Our results provide another way to generate maximally entangled mixed states.

We investigate quantum decoherence of the multi-photon entangled state |ψN m> =Nm[cosγ|N-m>₁|m>₂ +e^iθmsinγ|m>₁|N-m>₂]. When the entangled channel |ψN m> is embedded in an environment, the channel decoheres and becomes a mixed state governed by a master equation. We calculate the linear entropy and the relative entropy of entanglement, which describe the mixedness and the amount of entanglement for the mixed state, respectively. We show that quantum decoherence weakens the amount of entanglement and enhances the mixedness with the time evolution. It is indicated that the relative entropy of entanglement depends on not only the initial entanglement angle and the decohering parameter, but also the number of photons in each mode. In particular, we find that the decohering speed depends on the number-difference of photons in the two modes. The larger the number-difference of photons is, the higher the decohering speed.

The dynamic behaviour of a modulated torsion pendulum used to test the weak equivalence principle (WEP) is studied in detail. Theoretical analysis shows that the pendulum will be driven by a force with double-frequency of the rotating turntable no matter whether the WEP is valid or not. This double-frequency effect should be considered for improving the sensitivity of the modulated pendulum in test of the WEP.

Simulations are performed on atom substitution behaviour in Ni₇₅Al_25-xCr_x alloys based on a microscopic phase-field model at 873K. The ordering of both the Al and Cr atoms takes place simultaneously, Cr occupies both the Al and Ni sites with a preference for the Al sites, and Cr and Al atoms together occupy the β -sites, and the complex γ’ Ni₃(Al_1-xCr_x) (L1₂ structure) phases are formed during the precipitation. At the ordering boundary of L1₂ phases, Cr atoms occupy the Al sites, then Ni₃Cr phases are formed.

The generalized Langevin equation is used to describe the motion of a charged particle interacting with a blackbody radiation field via dipole coupling. The exact expressions for the mean-square displacement and velocity of such a particle are obtained, which show a ballistic diffusion and a modified Kubo fluctuation--dissipation relation. In particular, a velocity-dependent coupling or force can induce this novel phenomenon.

The knot structure of three-dimensional flow has been constructed based on minimal braid assumption [Chin. Phys. Lett. 20(2003)1444]. Here we provide a new universal form of renormalizable knots. From this universal form an arbitrary renormalizable knot can be decomposed into a unique set of elementary templates.

A new algorithm for filtering highly noisy contaminated chaotic time series is proposed and realized. It is indicated by computer simulation that this algorithm can effectively reduce noise on chaotic signal no mater how parameter of chaos generator varies with time. In comparison with the extended-Kalman-filter-based method, this algorithm has a better filtering performance in the case of low signal-to-noise (SNR) ratios, and has the similar performance in the case of high SNR. In addition, a chaotic modulation communication system is also used to evaluate the performance of the algorithm, the result shows the effectiveness of the method.

We present both the bright and dark solitons of Bose--Einstein condensates with a time-dependent atomic scattering length in an expulsive parabolic potential. As a discussed example, we select the experimental parameter, i.e. the Feshbach-managed nonlinear coefficient reading a(t)=g₀exp(λt), and obtain the results which can be recovered in the literature [Phys. Rev. Lett. 94(2005)050402].

Using the language of jet bundles, we generalize the definitions of Euler--Lagrange one-form and the associated cohomology which were introduced by Guo et al. [Commun. Theor. Phys. 37(2002)1]. Continuous and discrete Lagrange mechanics and field theory are presented. Higher order Euler--Lagrange cohomology groups are also introduced.

At a very high temperature, the quark matter is a hot and dense matter under the colour deconfinement condition, and quarks can coalescent diquarks. Energy density of this system is figured out. A way to calculate baryon ratios produced from quark gluon plasma with diquarks in relativistic heavy ion collisions is presented.

We present an improved quark mass density-dependent model which includes the quark and non-linear scalar field coupling. The wavefunction of quark is given. The rms charge radius, the magnetic moment, and the ratio between the axial-vector and the vector β-decay coupling constants of the nucleon are calculated. We find that the results given the present model are in agreement with experiments.

The asymptotic normalization coefficient (ANC) of ⁹C = ⁸B+p deduced from ⁸Li(d,p)⁹Li reaction is used to obtain the root-mean-square (rms) radius of the loosely bound proton in the ⁹C ground state. We obtain (r²)^1/2 = 3.61fm for the valence proton, which is significantly larger than the matter radius of ⁹C. The probability of the valence proton outside the matter radius of ⁹C is greater than 60%. The present work supports the conclusion that ⁹C has a proton halo structure.

High-spin level structure of doubly odd nucleus ¹⁴⁰Pr has been investigated via the ¹³⁰Te(¹⁴N,4n)¹⁴⁰Pr reaction at beam energies from 55 to 65MeV. Measurements of γ-ray excitation functions, γ-ray singles and γ-γ-t coincidences were performed with twelve BGO(AC)HPGe detectors. The level scheme of ¹⁴⁰Pr, including 27 new levels and 42 new γ rays, has been established for the first time. The level structure is compared with those in the neighbouring odd--odd nuclei, and interpreted qualitatively.

Dynamical structures of collective excitation in continuum are studied by calculating the isoscalar and isovector strength as well as transition density of nuclei near the drip-line such as ²⁸O and ³⁴Ca. It is found that for some excited states in continuum the proton and neutron transition density calculated from isoscalar and isovector excitation at some given energies may be different, which will affect the calculation of the polarization for nuclei with N≠Z.

Three time scales of a fissioning nucleus starting from the ground state to the scission point are defined and calculated by the Monte Carlo method. The result shows that the time of oscillating around the saddle point is longer than both the mean first passage time from the ground state to the saddle point and the time of descent from the saddle to scission points. Thus it is suggested that more neutrons could be emitted from a hot heavy fissioning nucleus during the period of the stretching and contracting of the deformation process.

The relativistic multichannel theory has been extended to calculate both the eigen quantum defects μ_α, transformation matrix U_iα, and the eigen dipole matrix elements D_α of krypton. The Rydberg and autoionization spectra of krypton across the first ionization threshold are calculated within the framework of multichannel quantum defect theory. Our calculated spectra are in agreement with the absolute measurement data.

We propose a novel electrostatic guiding scheme for cold polar molecules in weak-field-seeking states using a single charged wire half embanked in a ceramic substrate (i.e., a chip) and a homogeneous bias electric field, which is produced by a capacitor composed of two large parallel metal plates. We calculate the spatial distribution of the electrostatic fields generated by the combination of the charged wire and the plate capacitor and the corresponding trapping potentials for CO molecules, and analyse the relationships between the electric field and the parameters of the charged-wire layout. Our study shows that the proposed scheme with a single charged-wire can be used to guide cold polar molecules in the weak-field-seeking states, and has some potential applications in construction of various molecule-optical elements.

We present a calculation scheme with significant modifications and improvements for determining the ionization balance and the ion temperature evolution in an electron beam ion trap (EBIT). The scheme is applied to uranium and nitrogen ions using a specific set of EBIT operating parameters. The calculation results are compared to the experimental data. Rates for the individual atomic processes in EBIT, especially single and multiple charge exchange processes, are discussed. The time evolution of the ion temperatures for uranium and its coolant nitrogen are also given.

We report the calculations of the elastic scattering differential cross section for positron--H₂ collisions with the impact energy below the positronium formation threshold. Our calculation is based on the static-exchange-optical model which has obtained great success in the case of electron scattering. The effective potential used here includes the static and optical potentials. The optical method can completely include the second-order effect arising from real and virtual excitation of target states, which is important for the scattering. A comparison is made with the available theoretical calculations.

Ultrathin films containing methaofullerene are prepared by electrostatic layer-by-layer self-assembly of a positively charged trifluoroacetic acid salt of monoamino-substituted methanofullerene (TMAF) derivative and a negatively charged poly (sodium 4-styrenesulfonate) (PSS). Absorptive optical nonlinearities of 30 bilayer TMAF/PSS films and TMAF in water solution are measured using the Z-scan technique at 532nm. Nonresonant saturation absorption is observed in the film sample, whereas reverse saturation absorption was for TMAF in water. The saturation-absorption behaviour is interpreted by a special formula. The saturation intensity is extracted to be 15.2±0.8MW/cm². The mechanism of saturation absorption in the TMAF/PSS film is discussed.

Laser frequency splitting generated by intracavity birefringence elements has been applied widely, but tuning characters of such lasers have not been successfully studied quantitatively. Based on the vectorial extension of Lamb's semi-classical theory, we study the intensity tuning of frequency splitting of He--Ne lasers. It is found that the intensity tuning curve is affected obviously by the compositive ratio of isotopes in the gain medium and the frequency difference of splitting modes. The threshold of locking is also quantitatively obtained. All the calculations are consistent with the experimental results.

A layer of 40nm-thick Ag--SiN film with Ag nano-particles embedded and distributed randomly in the SiN thin film were deposited by the method of radiant-frequency magnetron sputtering. Specimens orderly comprising a random Ag--SiN film and an optical phase change recording layer were exposed to a focused laser beam with wavelength of 690nm. It is shown that, with a random Ag--SiN layer deposited above the recording layer. Calculation by the finite difference time domain method of a 40nm-thick SiN film under a Gaussian beam irradiation has been carried out to simulate the near-field distribution in the film, which showed a huge local near-field intensity enhancement of about 200 times if small Ag particles with diameter of 6nm were modelled in the SiN film in the central region of the incident laser spot.

A two-phase shifting method is introduced to eliminate the strong autocorrelation noise inherent in spectral optical coherence tomography and to mitigate the unwanted auto- and cross-coherent terms introduced by the reflections from various optical interfaces present in the system. Furthermore, this method is also able to amplify the desired signal by a factor of 2. The feasibility of such a method is demonstrated using a mirror-like object. An intact porcine cornea tissue in vitro is also used to show the potential of this method for biological imaging.

We have experimentally studied the high order harmonic generation (HHG) in CO molecules by two femtosecond laser pulses using a pump--probe technique. The delay time between two pulses is longer than the pulse duration, and the pump intensity is about 6.2×10¹⁴ W/cm². It is found that the HHG signal is independent of the time delay in the picosecond region, but it is dependent on the distance between the centres of focuses of the two beams. The phase modulation induced by the pump pulse is regarded to be responsible for this.

A new method of phase determination is presented to directly measure the intensity and frequency temporal profiles of attosecond EUV pulses. The profiles can be reconstructed from the photoelectron energy spectra measured with two different laser intensities at 0°and 180° with respect to the linear laser polarization using a cross correlation between the femtosecond laser and the attosecond EUV. The method has a temporal measurement range from a quarter to about half of a laser oscillation period. The time resolution depends on the jitter and control precision of laser and EUV pulses. This method improves the time resolution in measuring attosecond EUV pulses.

We present a system to produce continuous and widely wavelength-tunable optical short pulses by use of a self-seeded Fabry-Pérot laser diode. The system exhibits a good sidemode suppression ratio of greater than 37dB over a large wavelength tuning range of 48nm. The system is also easy to operate and is convenient for continuous wavelength tuning.

A new chromatic dispersion profile of a single-mode optical fibre is proposed for generating a supercontinuum with a flatly broadened spectrum. The chromatic dispersion D(λ,z) is a convex function of wavelengths and has no zero-dispersion wavelengths over the whole part of the fibre as D(λ,z) is negative. It is shown that the flat supercontinuum spectrum is obtained when the pump wavelength is set in the vicinity of the wavelength at which the peak chromatic dispersion is near zero and the strong residual pump component is eliminated.

Solutions of dual-pump fibre-optical parametric amplifiers (DP-FOPAs) with dispersion fluctuations are derived by using a matrix operator. Based on these solutions and a hybrid genetic algorithm, we have optimized three-section DP-FOPAs to increase the signal band and improve the gain uniformity. The optimizations demonstrate that when dispersion fluctuations are taken into account, the 44-nm signal band with the 0.37-dB ripple and over 14.8-dB gain can be obtained from the three-section DP-FOPA, instead of the lowest gain of ～13dB with the ripple of more than 15dB from the single-section DP-FOPA.

The abnormal transmittance in the dielectric band edge of a polystyrene opal is observed and analysed. The transmittance is periodically modulated and the period of modulation varies with the wavelength, which destroys the perfect structure of the photonic band gap. The transmittance modulation originates from the propagation of the low order whispering-gallery mode excited in polystyrene spheres. These results indicate that the whispering-gallery mode has a great influence on practical applications of polystyrene opal.

We fabricated two-dimensional photonic crystal slab Y-branch waveguides with different intervals between the two output ports and measured their light guiding characteristics. The field intensity distributions of the TE polarized wave modes are also calculated by means of a transfer matrix method. Both the theoretical and experimental results show that the minimum interval between the two output ports is about 1.4 times the transport wavelength of 1.55μm. If the interval becomes smaller, light waves in the two branches will couple each other seriously. The result will be helpful for designs of ultracompact wave demultiplexers and all-optical integrated circuits.

By applying the dyadic Green function, the dispersion relation of two-dimensional photonic crystal can be expressed as the cylindrical wave expansions of eigenmodes. With the aid of Green’s theorem, the plane-wave coefficients of eigenmodes are reconstructed and employed to formulate the scattering matrix of finite-height two-dimensional photonic crystal. These operations make the convergence rate very rapid, and reduce the dimension of the scattering matrix. As a demonstration, we present the transmission and electromagnetic field distributions for an InGaAsIn photonic crystal, and investigate their convergence.

The transmission properties of quasiperiodic photonic crystals (QPCs) based on the random square-triangle tiling system are investigated by the multiple scattering method. The hollow cylinders are introduced in our calculation. It is found that QPCs with hollow cylinders also possess a complete band gap common to s- and p-polarized waves when the inner radius of hollow cylinders is larger than a certain value. The QPCs possessing the complete band gap can be applied to the fields of light emitting, wave-guides, optical filters, high-Q resonators and antennas.

We obtain the error-free transmission of an 8×10Gb/s signal over a 1500km G.652 fibre by means of significantly improving the quality of narrow-band chirped fibre Bragg gratings (FBGs). Asymmetric apodization is one of the powerful measures to improve the quality of gratings. Wavelength-dependent transmission performance is also observed. The experimental results indicate that the total in-band local dispersion deviation of the cascaded gratings in each channel could be a good indicator of the performance degradation tendency at different operating wavelengths, which further reveals the potential of local dispersion deviation as a performance evaluating indicator of chirped FBGs.

A simple, economical and applicable spectrum equalization method is implemented by employing a reshaping filter in the combined frequency-shift-keying/amplitude-shift-keying modulation scheme to improve the quality of amplitude-shift-keying optical signal. The 3-dB improvement for eye diagram height is experimentally demonstrated.

We design a new double-layer grating template, which has the advantages of period uniformity, period number adjustability and continuous period regulation. By studying the transmission spectrum under the new template, we also find some new characteristics different from traditional fibre gratings: the resonant wavelength is mainly determined by the grating period; the intensity of transmission peak loss lies in the external pressures; the bandwidth of transmission spectrum can be controlled by the period number. Therefore, various applications can be realized by optimizing the transmission spectrum by reasonably selecting the matched parameters.

We investigate the optical properties of ZIP49 and ZIP51. The thickness and the refractive index of the polymer film are measured using an ellipsometer to be from 2μm to 10μm and from 1.49 to 1.51, respectively. A 32×32 arrayed waveguide grating is fabricated using the reactive ion etching technique. The curing temperature is increased to 270°C in nitrogen atmosphere. The etching rate is about 0.067μm/min. Using re-solution technique, the surface roughness of polymer film was reduced to less than 0.4nm after spin coating. The insertion loss of the arrayed waveguide grating is about 10dB and the crosstalk is about -20dB.

We investigate the vibrational band gaps in a thin plate of two-dimensional phononic crystals with the locally resonant structure in theory and experiment. The experimental sample is optimized based on the simple analytical model. The experimental results are in good agreement with the theoretical calculation by the finite element method. The findings will be significant for applications of phononic crystals in the field of vibration isolation.

The kink formation in a vertical vibrated granular layer has been widely studied in three-dimensional systems, but there are few if any experimental reports on bidimensional granular layers. We report the kink formation newly found in a perfect bidimensional granular system. We measure the range of the driving frequencies and dimensionless accelerations for kinks. Furthermore, we observe a heaping process, which is caused by co-operative action of the kink-associated convection and the sidewall-associated convection.

A new high resolution approach based on spectral element method is proposed to analyse the complex global stability for the non-parallel flow passing a rotating and translating circular cylinder. The studies presented here predict the variation of Strouhal number S_t as the spin parameter α increases from 0.0 to 1.4, for the Reynolds number R_e=60. The direct numerical simulation shows a small increase of vortex shedding frequency at α<1.1, and a slight decrease as α approaches the critical spin parameter α=1.37. The trend of variation of eigen-frequency with α obtained by linear stability analysis is opposite to those obtained by direct numerical simulation for R_e=60, although they achieve the same frequency at the onset of vortex shedding.

Multi-scale decomposition by wavelet transform has been performed to velocity time sequences obtained by fine measurements of turbulent boundary layer flow. A conditional sampling technique for detecting multi-scale coherent eddy structures in turbulent field is proposed by using multi-scale instantaneous intensity factor and flatness factor of wavelet coefficients. Although the number of coherent eddy structures in the turbulent boundary layer is very small, their energy percentage with respect to the turbulence kinetic energy is high. Especially in buffer layer, the energy percentages of coherent structures are significantly higher than those in the logarithmic layer, indicating that the buffer layer is the most active region in the turbulent boundary layer. These multi-scale coherent eddy structures share some common dynamical characteristics and are responsible for the anomalous scaling law in the turbulent boundary layer.

The strong x-ray line emission of n=4→n=3 and n=5→n=3 transitions of Ni-like Au has been investigated under a coronal plasma condition. A complete set of atomic data, including energy level, transition probability and collision strength, has been obtained to simulate the emission spectra. Under a typical coronal equilibrium (electron temperature of 2500eV and density of 1.0×10¹⁵), the predicted strongest line is due to the transition of (3d_3/2^-14f_5/2)₁ → (3d¹⁰)₀. Extensive studies show that the relative intensity is insensitive to temperature and density over a wide plasma condition.

We derive a linear dispersion relation in the presence of a constant uniform guiding magnetic field parallel to the beam velocity direction, which shows a strong background magnetic field suppresses or even stabilizes the Weibel instability produced by two counter streams in electron-ion plasmas. The simulation results are in good agreement with the analytical ones. Also observed in the simulations are the suppression of electrostatic field, a higher level of saturation of self-generated magnetic field, and the apparent difference in phase space compared with those in the absence of guiding magnetic field.

An atmospheric pressure plasma fluidized bed (APPFB) is designed to generate plasma using a dielectric barrier discharge (DBD) with one liquid electrode. In the APPFB system, the physical properties of DBD discharge and its application in plant-seed mutating are studied fundamentally. The results show that the generated plasma is a typical glow discharge free from filament and arc plasma, and the macro-temperature of the plasma fluidized bed is nearly at room temperature. There are no obvious changes in the pimientos when their seeds are treated by APPFB, but great changes are found for coxcombs.

Ga(In, Al)N alloys are used as an active layer or cladding layer in light emitting diodes and laser diodes. x-ray diffraction is extensively used to evaluate the crystalline quality, the chemical composition and the residual strain in Ga(Al,In)N thin films, which directly determine the emission wavelength and the device performance. Due to the minor mismatch in lattice parameters between Ga(Al, In)N alloy and a GaN virtual substrate, x-ray diffraction comes to a problem to separate the signal from Ga(Al,In)N alloy and GaN. We give a detailed comparison on different diffraction planes. In order to balance the intensity and peak separation between Ga(Al,In)N alloy and GaN, (0004) and $(10\bar 15)$ planes make the best choice for symmetric scan and asymmetric scan, respectively.

Ab initio molecular dynamics simulations on liquid In₂₀Sn₈₀ alloy are carried out at six different temperatures from 798K to 1193K. The temperature dependences of binding energy, volume, pair-correlation function and structure factor are studied. The first-peak position of our calculated pair correlation function is in agreement with the experimental data. A shoulder is reproduced in the high wave number side of the first peak in our calculated structure factor, implying the existence of the residual directional bonds of Sn atoms in liquid In₂₀Sn₈₀ alloy. The first-peak height of our calculated structure factor and the coordination number of Sn atom decrease more sharply in the low-temperature region from 798K to 986K than that in the high-temperature region from 986K to 1193K, suggesting that a discontinuous structural change may occur at around 986K in liquid In₂₀Sn₈₀ alloy.

We investigate the structural properties of liquid Sn. With the help of the internal friction (tanФ) method, it is found that a peak appears in the tan Ф-T curve, suggesting that an anomalous discontinuous temperature-induced structure change may take place in liquid Sn. From the experimental data of pair distribution functions, we calculate the viscosity η and the excess entropy S and it is found that there are a peak of viscosity in the η-T curve and a bend of excess entropy in the S-T curve, which give a positive support to the appearance of the internal-friction peak in the tan Ф-T curve.

Plastic deformation behaviour of Zr_52.5Al₁₀Ni₁₀Cu₁₅Be_12.5 and Mg₆₅Cu₂₅Gd₁₀ bulk metallic glasses (BMGs) is studied by using the depth-sensing nanoindentation and microindentation. The subsurface plastic deformation zone of the BMGs is investigated using the bonded interface technique. Both the BMGs exhibit the serrated flow depending on the loading rate in the loading process of indentation. Slow indentation rates promote more conspicuous serrations, and rapid indentations suppress the serrated flow. Mg-based BMG shows a much higher critical loading rate for the disappearance of the serration than that in Zr-based BMG. The significant difference in the shear band pattern in the subsurface plastic deformation zone is responsible for the different deformation behaviour between the two BMGs. Increase of the loading rate can lead to the increase of the density of shear bands. However, there is no distinct change in the character of shear bands at the loading rate of as high as 1000nm/s.

The trapping of positrons at vacancy site in some materials provide a new and sensitive method for the equilibrium determination of point defect migration enthalpy. Data are presented for commercial Al--Mg alloys and fitted to a model allowing presentation in the form of Arrhenius plots, hence the migration enthalpy H_iv^m can be determined by the positron annihilation lifetime technique. The results show that the value of H_iv^m increases as the concentration of Mg increases.

A preliminary experiment of sound velocity measurements for porous iron with initial average density of 6.275g/cm³ has been performed at pressures below 100GPa, in order to clarify a long-standing problem that the static melting temperature Tm, mostly below 100GPa due to its technical limitations, is notably lower than the extrapolated melting data inferred from the shock wave experiments made above 200GPa, for the sake of making a direct comparison between the experimental static and dynamic melting temperatures in the same pressure region. With the lately proposed Hugoniot sound velocity data analysis technique [Chin. Phys. Lett. 22 (2005) 863], the results deduced from this Hugoniot sound velocity measurement is T_m=3200K at 87GPa and T_m=3080K at 80GPa, which are in good agreement with the two latest static data of T_m=3510K at 105GPa and T_m=2750K at 58GPa, which utilized modern improved double-side laser heating and in situ accurate x-ray diffraction techniques in experiments. It can be concluded that consensus Tm data would be obtained from static and shock wave experiments in the case that the recently improved techniques are adopted in investigations.

The fluid variational free energy model is applied to calculate the equation of state (EOS) of the fluid (Ne/3,2He/3) mixtures at 296K. The pair potential is used to describe the He--Ne interaction. The calculated EOSs at 296K are compared with the experiments for solid Ne(He)₂. The validity of the potential and the calculated model is verified by comparison. The present model is extended to calculate the equation of state of the fluid He--Ne mixtures with different He:Ne compositions in the pressure 0--160GPa and temperature up to 10000K.

The product Jahn--Teller (JT) system with two doubly-degenerate electronic open shells coupling to a single e-mode is studied using an operatorization approach followed by unitary transformation. It is found that the structure of the adiabatic potential energy surface can give anyone of the two different troughs based on the coupling constants, and the symmetry of the product JT system EoplusE can be decomposed into EoplusA₁oplus A₂. The present approach is conceptually simple and can be extended to other product JT systems.

Aiming at understanding how a liquid film on a substrate affects the atomic force microscopic image in experiments, we present an analytical representation of the shape of liquid surface under van der Waals interaction induced by a non-contact probe tip. The analytical expression shows good consistence with the corresponding numerical results. According to the expression, we find that the vertical scale of the liquid dome is mainly governed by a combination of van der Waals force, surface tension and probe tip radius, and is weekly related to gravity. However, its horizontal extension is determined by the capillary length.

A novel integration technique has been developed using band-gap energy control of InGaAsP/InGaAsP multi-quantum-well (MQW) structures during simultaneous ultra-low-pressure (22 mbar) selective-area-growth (SAG) process in metal-organic chemical vapour deposition. A fundamental study of the controllability of band gap energy by the SAG method is performed. A large band-gap photoluminescence wavelength shift of 83nm is obtained with a small mask width variation (0--30μm). The method is then applied to fabricate an MQW distributed-feedback laser monolithically integrated with an electroabsorption modulator. The experimental results exhibit superior device characteristics with low threshold of 19mA, over 24dB extinction ratio when coupled into a single mode fibre. More than 10GHz modulation bandwidth is also achieved, which demonstrates that the ultra-low-pressure SAG technique is a promising approach for high-speed transmission photonic integrated circuits.

P-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with PtSi Schottky barrier source/drain, high-k gate dielectric and metal gate electrode were fabricated on a thin p-type silicon-on-insulator (SOI) substrate using a simplified low temperature process. The device works on a fully-depleted accumulation-mode and has an excellent electrical performance. It reaches I_on/I_off ratio of about 10⁷, subthreshold swing of 65mV/decade and saturation drain current of I_dx = 8.8μA/μm at |V_g- V_th|= |V_d| = 1V for devices with the channel length 4.0μm and the equivalent oxide thickness 2.0nm. Compared to the corresponding bulk-Si counterparts, SOI p-SBMOSFETs have smaller off-state current due to reduction of the PtSi/Si contact area.

We present an analytic result of the polaronic band structure by using the one-dimensional Holstein model on an infinite lattice. The single-phonon effect is used to investigate the ground state properties, such as the polaronic band structure, ground state energy, phonon distribution and effective mass, which agree with the numerical and analytic results obtained recently in the region from the weak coupling to the intermediate coupling.

A zone annealing process is adopted to improve the performance of pentacene organic thin film transistors. The process is completed in a glove box full of dry nitrogen gas and with a heating wire (Ф0.1mm tungsten wire) inside. The device have the structure of glass/ITO (150nm)/Ta₂O₅ (60nm)/pentacene (60nm)/Au (20nm). Under the gate--source voltage -60V and the drain--source voltage -60V, the source--drain current, the mobility, and the on/off current ratio increase from 4×10^-7A to 2.0×10^-6A, 2.9×10^-3cm²V^-1s^-1 to 1.6×10 ²cm²V^-1s^-1, and 2×10³ to 5.33×10³, respectively. It is found that the distance between the pentacene grain boundaries decreases and an obvious layer structure can be formed in grains after annealing. According to the transport of carriers in the polycrystalline film, these changes of the pentacene film can improve the source--drain current and the mobility.

ZnO thin films were prepared on p-type Si (100) substrates by the sol-gel process. The influence of Ag doping at a content of 0.002 % on the photoluminescence and current-voltage (I-V) characteristics of ZnO thin films has been investigated. It is found that Ag doping leads to a pronounced increase in the intensity of near band edge emission at 3.23eV and a remarkable red shift of the visible broadband at room temperature. The I-V characteristics of ZnO/p-Si heterojunctions are also changed. These results could be explained by Ag substituting for Zn in Ag doped ZnO thin films.

We investigate the spin polarized current through a quantum dot connected to ferromagnetic leads in the presence of a finite spin-dependent chemical potential. The effects of the spin polarization of the leads p and the external magnetic field B are studied. It is found that both the magnitude and the symmetry of the current are dependent on the spin polarization of the leads. When the two ferromagnetic leads are in parallel configuration, the spin polarization p has an insignificant effect on the spin current, and an accompanying charge current appears with the increase of p. When the leads are in antiparallel configuration, however, the effect of p is distinct. The charge current is always zero regardless of the variation of p in the absence of B. The peaks appearing in the pure spin current are greatly suppressed and become asymmetric as p is increased. The applied magnetic field B results in an accompanying charge current in both the parallel and antiparallel configurations of the leads. The characteristics of the currents are explained in terms of the density of states of the quantum dot.

Using the equation of motion, we investigate theoretically the dynamical ac conductance of a clean Luttinger-liquid quantum wire adiabatically coupled to Fermi liquid electron reservoirs in the presence of short-ranged electron-electron interactions. For a perfect single mode quantum wire, in the limit of zero-ranged interaction we conclude that the static dc conductance of ω→0 is e²/h, which is independent of the electron interactions. While in the dynamical case of ω≠0, the ac conductance oscillates with the amplitude e²/h and the period which depends on the interaction strength and the driving frequency as well as the position in the wire.

Magnetic tunnel junctions (MTJs) with structures of Ta(5nm)/Cu(30nm)/Ta(5nm)/Ni₇₉Fe₂₁(5nm)/Ir₂₂Mn₇₈ (12nm)/Co₆₂Fe₂₀B₁₈(4nm)/MgO(d)/Al(0.8nm)-oxide/Co₆₂Fe₂₀B₁₈(6nm)/Cu(30nm)/Ta(5nm) on a thermally oxidized Si wafer substrate were fabricated by magnetron sputtering and photolithographic patterning method. The tunnel magnetoresistance (TMR) and the bias dependence of TMR at room temperature for the MTJs with different thickness d of MgO are investigated. TMR values of over 50% as high as those of the MTJs with pure Al--O barrier and the TMR-voltage curve asymmetries, which vary with the increase of d, are observed in the MTJs with hybrid barriers after annealing at 265°C for an hour. The dependences of TMR, resistance and coercivity of the MTJs with composite barriers on temperature are also investigated.

The branch process of the skyrmions in the fractional quantum Hall effect is studied from the Ф-mapping topological current. It is shown that there exists a field zeta whose Hopf indices and Brouwer degrees characterize the topological structure of the skyrmions. Based on the bifurcation theory of the Ф-mapping theory, it is found that the skyrmions can be generated or annihilated at the limit points and they encounter, split or merge at the bifurcation points of the new field zeta.

Microwave-field responses of the surface intrinsic Josephson junctions (IJJs) of Bi₂Sr₂CaCu₂O_8+δ superconductors are investigated. The IJJs are fabricated using an in situ low-temperature cleavage technique, which leads to the well-characterized surface CuO₂ double layers and surface junctions. For the surface junctions in the large-junction limit, usually no Shapiro steps appear when a microwave field is applied. It is found that when the junctions are in a flux-trapped state, which is produced by a pulsed current and in which the critical current is significantly suppressed, clear Shapiro steps can be observed. These results are important for the study of the microwave-field properties of vortex-carrying IJJs and may find their use in device applications.

The electronic density of states, spin-splittings and atomic magnetic moments of SmCo_7-xCu_x are studied by means of the spin-polarized multi-scattering X_α method. The results show that a few of the electrons can transfer to the Sm $5d^{0}$ orbital due to orbital hybridization between Sm and Co. The exchange interactions between 3d and 5d electrons lead to the magnetic coupling between Sm and Co, and therefore result in the long-range ferromagnetic order in SmCo_7-xCu_x. The Curie temperature of SmCo_7-xCu_x is generally lower than that of the corresponding pure Co, which may be explained by the weaker average strength of coupling between Co lattices due to some negative exchange couplings mainly from the 2e site. The calculated results for the Sm₅Co₃₀Cu₄ cluster may lead to a better understanding of why SmCo_7-xCu_x is stable phase. Since the negative coupling of the 2e sites becomes small and the d bond at E_F becomes stronger in contrast to SmCo₇, which results in decrease of the free energy of the system, the stable ferromagnetic order forms in SmCo_7-xCu_x.

Metallocene intercalate compounds with iron oxychloride, FeOCl(FeCp₂)_0.16 and FeOCl(CoCp₂)_0.36 with Cp being cyclopentadienyl group, are synthesized and characterized. Magnetism and the structure--property relations are investigated by magnetic measurement and ⁵⁷Fe Mössbauer spectroscopy. The results show that the through-space dipolar interactions play a critical role in three-dimensional magnetic ordering of such layered compounds.

We calculate the resistivity of the insulating layer in a tunnelling-magnetoresistive (TMR) magnetic head by using the Landauer--Büttiker formula with a fast Green function method, where a recursive process with a faster simulation speed and higher accuracy is carried out to substitute the inversion of Green’s matrix. A tight-binding model with an energy barrier ΔE is utilized to simulate the magnetoresistive tunnelling junction in the TMR head. The resistivity of the insulating layer is 2.6×10⁵μΩcm with two oxygen-ion layers and ΔE=2.5eV, which agrees with the experimental data.

Effective medium theory is useful for designing optical elements with form birefringent subwavelength structures. Thin films fabricated by oblique deposition are similar to the two-dimensional surface relief subwavelength gratings. We use the effective medium theory to calculate the anisotropic optical properties of the thin films with oblique columnar structures. The effective refractive indices and the directions are calculated from effective medium theory. It is shown that optical thin films with predetermined refractive indices and birefringence may be engineered.

We investigate the refraction phenomena of extraordinary light at a planar interface associated with a uniaxial left-handed medium. It is found that the anomalous positive refraction can occur at the interface from an isotropic right-handed medium to a uniaxially anisotropic left-handed medium. When the optical axis of a uniaxial left-handed medium is not normal or parallel to the interface, the refraction of the Poynting vector for the extraordinary waves can be either positive or negative depending on the incident angles, while the refraction of the wave vector is always negative. The physical essential of the anomalous positive refraction results from the anisotropy of uniaxial crystals.

The verification and calculation of the negative refractive index of a meta-material is carried out by the finite-difference time-domain method. A slab and a prism of the meta-material are simulated. A genuine plane wave is generated by a two-direction periodic boundary condition (PBC) in the slab model. Based on an advanced phase extraction technique, the negative refractive index of the meta-material is verified by phase velocity measurement in the slab and prism measurement. From our results, not only the phenomenon of backward phase propagation but also the negative refraction is clearly observed. The index is also calculated precisely. The results from the two models are consistent.

A comprehensive two-level numerical model is developed to describe carrier distribution in a quantum-dot laser. Light-emission spectra with different intraband relaxation rates (2ps, 7.5ps and 20ps) are calculated and analysed to investigate the influence of relaxation rates on performance of the quantum-dot laser. The results indicate that fast intraband relaxation favours not only the ground state single mode operation but also the higher injection efficiency.

Based on the results of the temperature-dependent photoluminescence (PL) measurements, the broad PL emission in the phase-separated GaNP alloys with P compositions of 0.03, 0.07, and 0.15 has investigated. The broad PL peaks at 2.18, 2.12 and 1.83eV are assigned to be an emission from the optical transitions from several trap levels, possibly the iso-electronic trap levels related to nitrogen. With the increasing P composition (from 0.03 to 0.15), these iso-electronic trap levels are shown to become resonant with the conduction band of the alloy and thus optically inactive, leading to the apparent red shift (80--160meV) of the PL peak energy and the trend of the red shift is strengthened. No PL emission peak is observed from the GaN-rich GaNP region, suggesting that the photogenerated carriers in the GaN-rich GaNP region may recombine with each other via non-radiation transitions.

ZnO nanostructures with different morphologies were fabricated by changing the partial oxygen pressure. The structures, morphologies and optical properties of ZnO nanostructures were investigated by x-ray diffraction, field emission scanning electron microscopy and photoluminescence (PL) spectra at room temperature. All the samples show preferred orientation along the c-axis. The oxygen partial pressure and the annealing atmosphere have important effect on the PL property of ZnO nanostructures. The high oxygen partial pressure during growth of samples and high-temperature annealing of the ZnO samples in oxygen can increase oxygen vacancies and can especially increase antisite oxygen (Oz_n) defects, which degraded the near band-edge emission. However, the annealing in H₂ can significantly modify the NBE emission.

Optical properties of highly strained GaInAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy with Sb assistance are investigated. The samples grown by Sb incorporation and Sb pre-deposition methods display high room-temperature photoluminescence (PL) intensity at extended long wavelength. This result is explained by the surfactant effects of Sb during the growth of GaInAs/GaAs QW systems. An abnormal S-shaped temperature dependence of the PL peak position is found in the In_0.42Ga_0.58As/GaAs triple QWs sample grown with Sb pre-deposition. By investigating the transmission electron microscope images and time-resolved PL spectra, it is found that the S-shaped temperature dependence of the PL peak position originates from the exciton localization effect brought by the Sb-rich clusters on the QW interface.

We investigate the decay process of photoelectrons from a luminescent material of ZnO:Zn using a microwave dielectric spectrometry. Electrons in the conduction band are found to decay exponentially and the lifetime is 781ns, while the time interval of decay from the maximum to half of this value is 470ns. ZnO:Zn is a green luminescent material at its central wavelength of 510nm. Compared to the decay of electrons in the conduction band, the decay process of the luminescence is faster, and the time interval of decay from the maximum to half of the maximum is about 100ns. We believe that the mechanism of the ZnO:Zn visible luminescence is recombination luminescence, and find that our theoretical simulation is in agreement with the experimental results.

Low-temperature photoluminescence measurement is performed on an undoped Al_xGa_1-xN/GaN heterostructure. Temperature-dependent Hall mobility confirms the formation of two-dimensional electron gas (2DEG) near the heterointerface. A weak photoluminescence (PL) peak with the energy of ～79meV lower than the free exciton (FE) emission of bulk GaN is related to the radiative recombination between electrons confined in the triangular well and the holes near the flat-band region of GaN. Its identification is supported by the solution of coupled one-dimensional Poisson and Schrödinger equations. When the temperature increases, the red shift of the 2DEG related emission peak is slower than that of the FE peak. The enhanced screening effect coming from the increasing 2DEG concentration and the varying electron distribution at two lowest subbands as a function of temperature account for such behaviour.

We propose a novel coupled quantum well structure, i.e. a quasi-symmetric coupled quantum well (QSCQW). Based on the demands of optical switching devices for quantum well materials, the QSCQW configuration is further optimized. Consequently, in the case of low applied electric field 25kV/cm and low absorption loss 100cm^-1, a large field-induced refractive index change (for TE mode, n=0.0106; for TM mode, n=0.0115) is obtained in the QSCQW structure at the operation wavelength 1550nm. The value is in one or two order of magnitude larger than that in a rectangular quantum well and about 50% larger than that of five-step asymmetric coupled quantum well structure under the same working conditions. The refractive index change obtained with the optimized QSCQW under so low absorption loss and applied electric field is very attractive for semiconductor optical switching devices. This manifests that the QSCQW structure has a great potential for applications in ultra-fast and low-voltage optical switches and in travelling wave modulators.

The composition-dependent thermoelectric properties of lead telluride (PbTe) doped with bismuth telluride (Bi₂Te₃), antimony telluride (Sb₂Te₃) and (BiSb)₂Te₃ have been studied at room temperature. All the samples exhibit small thermal conductivity. The figures of merit, 7.63, 1.03 and 8.97×10^-4, have been obtained in PbTe with these dopants, respectively. These values are several times higher than those of PbTe containing other dopants with small grain sizes. The high thermoelectric performance is explained by electronic topological transition induced by alloying. The results indicate that these dopants are effective to enhance the thermoelectric performance of PbTe.

Ni films are deposited by using ultra high vacuum dc magnetron sputtering onto silicon substrates at room temperature, and the high-quality and high-density films are prepared. The parameters, such as thickness, density and surface roughness, are obtained by using small-angle x-ray diffraction (XRD) analyses with the Marquardt gradient-expansion algorithm. The deposition rate is calculated and the Ni single layer can be fabricated precisely. Based on the fitting results, we can find that the surface roughness of the Ni films is about 0.7nm, the densities of Ni films are around 97% and the deposition rate is 0.26nm/s. The roughness of the surface is also characterized by using an atomic force microscope (AFM). The changing trend of the surface roughness in the simulation of XRD is in good agreement with the AFM measurement.

For the necessity of measuring the small phase difference of internal friction, a detailed comparison is carried out among the fast Fourier transformation (FFT), correlation function and three-parameter sine wave curve-fit methods. The comparison shows that the three-parameter sine wave curve-fit method can obtain more precise phase angle difference than correlation methods. Compared with the FFT algorithm, the three-parameter sine wave curve-fit method can obtain more precise frequency values.

The images of manganese flowers (clusters) on the surface of the natural magnesium silicate substance are scanned and the pictures of them are transferred to computer atmosphere. By using these scanning parameters, the exponents of density correlation function and fractal dimension values are calculated. For all different groups between the least and the most dense in the samples, the correlation function exponents may range from 0.141 to 0.178 and the fractal dimension values may vary between 1.61 and 1.88. In addition, the manganese flowers are divided into seven different groups according to their smallest- and largest-density features. The formation of the natural manganese clusters (flowers, dendrites) on the surface of the magnesium silicate substance can be defined by using the deposition, diffusion and aggregation model.

We develop a novel and efficient quasi-solid-state electrolyte based on the mesoporous silica SBA-15 as a framework material for a dye sensitized nanocrystalline TiO₂ solar cell. A solar energy-to-electricity conversion efficiency of 4.34% is achieved under AM 1.5 illumination (100mW/cm²).

The Peclet number is a useful index to estimate the importance of sedimentation as compared to the Brownian motion. However, how to choose the characteristic length scale for the Peclet number evaluation is rather critical because the diffusion length increases as the square root of the time whereas the drifting length is linearly related to time. Our Brownian dynamics simulation shows that the degree of sedimentation influence on the coagulation decreases when the dispersion volume fraction increases. Therefore using a fixed length, such as the diameter of particle, as the characteristic length scale for Peclet number evaluation is not a good choice when dealing with the influence of sedimentation on coagulation. The simulations demonstrated that environmental factors in the coagulation process, such as dispersion volume fraction and size distribution, should be taken into account for more reasonable evaluation of the sedimentation influence.

THz emission spectroscopy is used to study the generation mechanism dependent behaviour of terahertz (THz) electromagnetic waves from the GaAs crystal under excitation by 400nm and 800nm femtosecond (fs) pulses, respectively. The wavelength dependence of the emission spectrum under two types of THz generation mechanisms is analysed. Under the optical rectification mechanism, a slight enhancement of the spectral amplitude in the high-frequency regime is observed in a GaAs(110) crystal by the excitation of a 400-nm optical pulse compared with that of 800nm. Whereas an obvious red shift of the amplitude spectrum occurs in the GaAs(100) sample under the transient photoconduction mechanism. These phenomena are explained in detail by the duration of the optical pump pulse and the band structure of GaAs, respectively.

Degradation of ultra-thin gate-oxide n-channel metal--oxide--semiconductor field-effect transistors with the halo structure has been studied under different stress modes with a reverse substrate bias. The device degradation under the same stress mode with different reverse substrate voltages has been characterized by monitoring the substrate current in a stressing process, which follows a simple power law. When the gate voltage is less than the critical value, the device degradation will first decrease and then increase with the increasing reverse substrate voltage, otherwise, the device degradation will increase continuously. The critical value can be obtained by measuring the substrate current variation with the increases of reverse substrate voltage and gate voltage. The experimental results indicate that the stress mode with enhanced injection efficiency and smaller device degradation can be obtained when the gate voltage is less than the critical value with a proper reverse substrate voltage chosen.

Using a two-dimensional thermal flow model, we calculate the thermal resistance and the temperature distribution of InGaAsP/InP multi-quantum-well superluminescent diodes. The influence of lateral chip size and composition are evaluated. The results reveal that when the injection power reaches 1W, temperatures in the active region rises up to almost 50K. The width and length of the chip also have strong influence on the thermal resistance that can reach two orders of magnitude. The thermal resistance will change from 290K/W to 68K/W when the chip width increases from 500μm to 2500μm, and a similar result exists for the length. There is small effect on thermal resistance for active width. In view of the characteristics of output power versus the input current under pulsed and continues currents, the fitted experimental thermal resistance matches well with the measured results.

In view of the bonding angle and the number of neighbouring sites, the hexagonal lattice model is preferred to investigate the designability of protein structures. Here we simulate the designable structures by the simplified HP model in a two-dimensional hexagonal lattice with an unrestricted boundary. The result shows that the structures with a large number of core sites correspond to the high designability and have circular-like profiles. The maximum and average designabilities for the hexagonal lattice model are much higher than those for the square lattice mode, and the maximum and average designabilities for the square lattice model are much higher than those for the triangle lattice model.

A strategic collective decision model is introduced to investigate the role of decision transmission mechanism and interaction networks in determining the collective decision dynamics. Assuming that agents are located in a scale-free network and their decisions are interdependent of each other. In our model, it is found that the effective decision transmission rate λ exists a threshold λ_c=1, which marks the transition between the two regimes, i.e. the decision spreading and the decision disappearing in the population. Furthermore, λ is mainly determined by the decision transmission mechanism and interaction network's topology.

The complex electrical properties of natural pyroxenite were measured over a frequency range from 0.01 to 10⁶Hz, at 3.0GPa and 1266--1504K, using the solid buffers (Mo--MoO₂) to control the oxygen fugacity. The frequency dependence of electrical properties for the natural pyroxenite is investigated. Two distinct conduction mechanisms of the natural pyroxenite are observed: grain interior and grain boundary conduction. Grain interior transport controls the response above 100Hz, whereas grain boundary transport dominates between ～ 100 and 0.01Hz. Electrical response of natural pyroxenite is modelled with an equivalent circuit in which parallel RC circuit elements representing grain interior and grain boundary responses act in series. The grain boundaries do not enhance the total conductivity of natural pryoxenite. The total electrical conductivity of natural pyroxenite is lower than either grain interior or grain boundary conductivity alone.