We show that information in quantum memory can be erased and recovered perfectly if it is necessary. The fact that the final states of environment are completely determined by the initial states of the system allows an erasure operation to be realized by a swap operation between the system and an ancilla. Therefore, the erased information can be recovered. When there is an irreversible process, e.g. an irreversible operation or a decoherence process, in the erasure process, the information would be erased perpetually. We present that quantum erasure will also give heat dissipation in the environment. A classical limit of quantum erasure is given to coincide with Landauer's erasure principle.

By using the molecular orbit theory, we give a new model potential acting on the excited electron within a molecule. The potential is the total interaction energy of this electron with all the nuclei and other electrons. We find that the introduction of a new model potential results in an extreme increase of the number of closed orbits as compared to the hydrogen atom. Making use of the molecular closed-orbit theory (MCOT) and the new model potential, we calculate the recurrence spectra of H₂ molecules in parallel electric and magnetic fields for different quantum defects. The modulations in the spectra can be analysed in terms of the scattering of the excited electron on the molecular core. Our results are in good agreement with the quantum results.

We investigate the dense coding in the case of non-symmetric Hilbert spaces of the sender and receiver's particles sharing the quantum maximally entangled state. The efficiency of gaining classical information is also considered. We conclude that when a more level particle is with the sender, she can obtain a non-symmetric quantum channel from a symmetric one by entanglement transfer. Thus the efficiency of information transmission is improved.

The quantum scheduling algorithm proposed by Grover is generalized to extend its scope of applications. The generalized algorithm proposed here is realized on a nuclear magnetic resonance quantum computer. The experimental results show that the generalized algorithm can work efficiently in the case that Grover's scheduling algorithm is completely invalid, and represent the quantum advantages when qubits replace classical bits.

The functional integral approach (FIA) is introduced to study the transition temperature of an imperfect Bose gas in traps. An interacting model in quantum statistical mechanics is presented. With the model we study a Bose gas with attractive interaction trapped in an external potential. We obtain the result that the transition temperature of a trapped Bose gas will slightly shift upwards owing to the attractive interacting force. Successful application of the FIA to Bose systems is demonstrated.

A locally rotationally symmetric (LRS) Bianchi type-I string cosmological model with bulk viscosity is investigated. To obtain a determinate solution, it is assumed that the coefficient of bulk viscosity is a
power function of the energy density = ₀ρ^m and the scalar of expansion is proportional to the shear scalar θ ∝ σ, which leads to a relation between metric potentials R = ASⁿ, where R and S are only the functions of time. The physical and geometrical aspects of the model are also discussed. The solution includes some results previously given in the literature as special cases.

We discuss effects of the excitation frequency in an ac bridge differential capacitance transducer for the equivalence-principle test on the frequency-dependent characteristics of a practical operational amplifier, the thermal noise limitation, and stray-immune. Basic requirements of choosing the excitation frequency of the ac bridge capacitance transducer are given based on the three effects, which are significant for designing a capacitance transducer and choosing proper electric elements.

We propose a new technique to investigate the dynamical transitions among the traffic phases. A type of the control signals has been designated at a given site (signal point) of the single-lane highway. Under the effect of the control signal, the velocity of the vehicle that passes the signal point will be changed periodically. Our method is tested for the deterministic NaSch traffic model. The simulation results demonstrate that the disorder states in the deterministic NaSch traffic model can be suppressed, and the different types of periodic states would occur.

We introduce a simple asset migration model for the wealth redistribution in economical activities, in which a unit of asset migrates from one individual to another whenever they interact. By means of the mean-field rate equation, we have analysed the dynamic behaviour of the system. In the random migration case, the asset distribution of individuals takes the standard Gaussian form and consistently decreases to zero at the end. As for the system in which only the richer can gain assets from the poorer, it is found that the individual asset distribution is discontinuous at a critical point and only the individuals with asset absolute value less than a cutoff value have a uniform and non-zero distribution. Moreover, the result shows that for the system with migration bias the assets of the individuals may have a cutoff value at each given time, which is different from the system without migration bias.

We study the ratchet model with both thermal and potential fluctuations, discussing analytically the coherence resonance of the particle moving in such a potential field. It is found that the correlation between the thermal and potential fluctuations has significant effect on the coherence of the system, i.e. negative correlation enhances the coherence of the system greatly, and with positive correlation, there appears the phenomenon that the coherence suppression and enhancement occur alternatively as the additive noise becomes larger.

We investigate the spiral wave control in the two-dimensional complex Ginzburg-Landau equation. External drivings which are not resonant with spiral waves but with intrinsic system modes are used to successfully annihilate spiral waves and direct the system to various target states. The novel control mechanism is intuitively explained and the richness and flexibility the control results are emphasized.

The effect of Lorentz invariance breaking on the production rate and the equation of state at finite temperature is investigated in the frame of Ф³ theory. The invariance breaking significantly changes the off-shell degree at high temperatures.

Based on the Dyson-Schwinger approach, a method for obtaining the chemical potential dependence of the dressed quark propagator in the ‘Nambu-Goldstone’ and the ‘Wigner’ phase is developed. The bag constant in the presence of the non-zero chemical potential is analysed.

By solving the Friedmann-Robertson-Walker (FRW) geodesic equations for a free test particle with finite mass, we extend the widely used time-of-flight delay expression, which is just valid locally in the neighbourhood of our Galaxy, to the cosmic distance scale. If neutrino masses are known, this may provide a potential method to determine a large scale geometry of the Universe.

By using the improved Zimanyi-Moszkowski (ZM) model including the freedom of nucleons, σ mesons, ω mesons and ρ mesons, we investigate the liquid-gas phase transition for asymmetric nuclear matter. It is found that the phase transition for asymmetric nuclear matter in the improved ZM model with the isospin vector ρ meson degree of freedom is well defined. The binodal surface, which is essential in the study of the phase transition process, is addressed.

A standard in-beam γ-spectroscopy experiment for ¹⁷⁹Au has been performed via the ¹⁴⁹Sm (³⁵Cl, 5n) reaction at beam energies of 164-180 MeV. Based on the analysis of the experimental results, a rotational band built on the 1/2 [660](πi_13/2) proton intruder orbital is established for ¹⁷⁹Au for the first time. Systematic properties of the 1/2 [660](i_13/2) band in odd-A Au nuclei are discussed, and the evolution of bandhead energy and deformation with changing neutron number are revealed.

We use density functional theory and the Green function formalism with charge energy effect included in the self-consistent calculation of the I-V characteristics of a single benzene ring with an appendage of cf₃, and identify some interesting properties of the I-V characteristics at low bias. The molecule picks up a fractional charge at zero bias, then the additional fractional charge produces a barrier on the junction of the molecule and contacts to perturb current flow on the molecule. This phenomenon may be useful for the design of future molecular devices.

Introducing a theoretical method to treat time-dependent wave-packet dynamics for atom collisions, we calculate the cross sections of proton impact excitation (2s - 2p) with a Li atom by directly numerically integrating the time-dependent Schrödinger equation on a three-dimensional Cartesian mesh. Our calculated results are in good agreement with the available experimental measurements.

An experimental test of ac Zeeman effect in an optically pumped caesium beam frequency standard is reported and analysed. An interference pattern of the atomic energy level shift as a function of the applied microwave field near the atomic transition frequency was observed. It was superimposed on the dispersion lineshape of a normal ac Zeeman effect. This effect was analysed with the atomic wavefunction phase analysing method.

With the help of the density operator, the angular differential cross-section for ionization of helium is calculated within the framework of the one-centre atomic-orbital close-coupling method. We consider a naked C⁶⁺ ion as projectile with an energy of 2.5 MeV/a.u. Our result agrees well with the experimental data and the other theoretical calculations such as the first Born approximation, various Distorted Wave models and the classical trajectory Monte Carlo simulation.

Using the growth rate method, we obtain the single-electron detachment (SED) cross-sections for 5-30 keV C^-+He, and double-electron detachment (DED) cross-sections for 5-15 keV C^--+He. The SED cross-sections first increase with the increasing incident ion energy, and then decrease with further increase of the energy. The DED cross-sections increase with the increasing incident energy in the 5-15 keV region.

A compact optical demultiplexer with etched diffraction grating (EDG) is designed and fabricated on a silicon-on-insulator (SOI) material. Several 90°turning mirrors are used to bend the waveguides, and the size of the EDG-based demultiplexer is minimized to only 16 x 1.7mm². The crosstalk is about 18 dB. The on-chip loss is about 18.2 dB, which is composed of about 16.9 dB excess loss and 1.3 dB diffraction loss. Measures to improve the performance are discussed.

It is shown that an anomaly of the spectrum takes place in the interference field when Young’s double-slit interference experiment is illuminated by spatially coherent polychromatic light. Specifically, drastic spectral changes (i.e. the spectral shifts exhibit a rapid transition) occur in the vicinity of the dark fringes. The potential applications of this spectral anomaly are also considered.

We propose a new scheme to guide cold atoms (or molecules) by using a one-dimensional (1D) array of focused hollow-beam pipes generated by the combination of a binary phase grating and a 1D array of micro-cylindrical lenses on the substrate surface. We also calculate the intensity distribution of the focused hollow-beam pipe array and its optical potential for ⁸⁵Rb atoms. The result shows that when the blue detuning of the incident beam and its intensity are 10 GHz and 7.0 x 10³W/m² respectively, the horizontal dark spot size of each focused hollow-beam pipe and the efficient optical potential are 4.4 μm and ~ 0.23 mK, which is high enough to guide cold ⁸⁵Rb atoms (~20 μK) from a standard optical molasses and then to realize the 1D array of surface atomic waveguides on an atom chip.

A simple technique for the generation of equal-amplitude high repetition rate pulses from a rational harmonic mode-locked fibre ring laser is demonstrated. The principle is based on the combination of the nonlinear characteristics of the modulator and the effect of rational harmonic mode-locking. The two sources act on each other and the integrated effect eventually leads to the pulse amplitude-equalization. We obtain amplitude-equalized short pulses up to the fifth-order rational harmonic mode-locking with an optimum bias level and modulation depth of the modulator, which demonstrates the efficiency of this method.

A tunable Yb-doped double-clad fibre (YDCF) laser by tuning the fibre Bragg grating (FBG) is successfully demonstrated. The FBG was fabricated in the YDCF directly, resulting in low splicing loss and compact configuration. A continuous tuning range of 15.6 nm from 1046.6 nm to 1062.2 nm is achieved. The laser linewidth is smaller than 0.1 nm in the whole tuning range. A maximum output power 117 mW is achieved when the pump power is 332 mW. The laser oscillation is quite stable in the whole operation.

We present a novel 800-nm Bragg-mirror-based semiconductor saturable absorption mirror with low temperature and surface state hybrid absorber, with which we can realize the passive soliton mode locking of a Ti:sapphire laser pumped by 532-nm green laser which produces pulses as short as 37 fs. The reflection bandwidth of the mirror is 30 nm and the pulse frequency is 107 MHz. The average output power is 1.1 W at the pump power of 7.6 W.

A design of a polarization beam splitter (PBS) in two-dimensional triangular photonic crystals is proposed and numerically demonstrated, for the first time to our knowledge. The principle of the model is based on the polarization dependence of the photonic band gaps in photonic crystals; the polarization extinction ratios for transverse-magnetic and transverse-electric modes are 11.5 dB and 46.7 dB at the centre of its operating frequency range, respectively. When the central wavelength is tuned at 1550 nm, the possible operation wavelength range of this structure can be as large as 28.5 nm, which almost covers the whole C band in modern optical communication systems. Furthermore, due to its small size and only one kind of material being involved, the PBS structure may have practical applications in the integrated optics field.

High quality colloidal photonic crystals made from polystyrene spheres with diameter 240 nm are fabricated by the vertical deposition method. The scanning electron microscopy (SEM) and the transmittance spectrum are used to characterize the properties of the photonic crystal. The SEM images show that there are few lattice defects. The transmittance of the photonic crystal is above 75% in the pass band at 700 nm and is lower than 5% at the centre of the band gap, respectively. It is found that proper concentration is a very important factor to fabricate the photonic crystal when the diameter of the spheres is lower than 300 nm.

Based on the Raman spectrum measurement, we investigate the mechanism of proton exchange, by which the optical waveguides are formed in the LiNbO₃ crystal which are proton doped. The proton source is formed by a mixture of benzoic and adipic acids. The experimental results show that there is a Raman formant peak of optical waveguide at 650 cm^-1, and the higher the relative percentage of the mol ratio of adipic acid dilution, the higher the intensity of the Raman formant peak.

A two-dimensional theoretical model is used to analyse the acoustic field of cylindrical surface waves generated by a pulsed laser line source in the ablation regime. The complete dispersive curves for cylindrical Rayleigh wave are presented. The laser-generated transient acoustic field of cylindrical Rayleigh waves is calculated and the corresponding laser ultrasonic experiments are carried out. Both the numerical and experimental results are in good agreement.

Based on the lattice Boltzmann method and general theory of fluids flowing in porous media, a numerical model is presented for the diffusion-reaction-transport (DRT) processes in porous media. As a test, we simulate a DRT process in a two-dimensional horizontal heterogeneous porous medium. The influence of gravitation in this case can be neglected, and the DRT process can be described by a strongly heterogeneous diagnostic test strip or a thin confined piece of soil with stochastically distributing property in horizontal directions. The results obtained for the relations between reduced fluid saturation S, concentration c₁, and concentration c₂ are shown by using the visualization computing technique. The computational efficiency and stability of the model are satisfactory.

We propose a new method to increase the output power of a three-cavity transit-time oscillator (TC-TTO). Conventional transit-time effect oscillators, such as the split-cavity oscillator (SCO), super-Reltron, and TC-TTO (or double-foil SCO), etc., have a common feature that the span of any modulating cavity is uniform. The new method is to vary the three-cavity spans from uniform to nonuniform. Its configuration is called the nonuniform three-cavity transit-time oscillator (NTC-TTO). Numerical simulations show that the electron-beam is modulated more deeply in certain NTC-TTOs than that in the TC-TTO with the same whole modulating length, and the output microwave power in certain NTC-TTOs is higher than that in the TC-TTO. The experimental results are in agreement with those of the numerical simulations. The results show that the new method can increase the output power of a microwave tube based on the TC-TTO.

A 21/2-dimensional electromagnetic particle-in-cell (PIC) simulation code is used to investigate the wave phenomena in the plasma sheet of collisionless magnetic reconnection. The results show that these waves have the following characteristics: they are right-hand circularity polarized, with propagation direction nearly parallel to local magnetic field, and frequency between 0.07 and 0.17 times of local electron cyclotron frequency. Therefore we conclude that such waves are Whistler waves, and their possible excitation mechanisms are also discussed.

The normalized performance indicated by the product of β_NH₈₉ > 2 was achieved by a combination of the lower hybrid current driving (LHCD) and the ion Berstein wave (IBW) heating in the HT-7 tokamak. More than 80% of the plasma current was sustained by the LHCD and the bootstrap current. Large edge pressure gradients were observed. The magnetohydrodynamic (MHD) instabilities were often driven to terminate the discharge or reduce the discharge performance, when the IBW resonant layer was near the rational surface. The resonant layer of the safety factor q = 2 is located at 0.6a with a = 27 cm being the minor radius. The width of magnetic island (the poloidal mode number m = 2) was about 2 cm. The plasma energy was reduced quickly by 30% by MHD instabilities. The behaviour of MHD instabilities is reported. A large sawtooth activity (m = 1) was observed before inducing MHD (m = 2).

A wear resistant Ti₅Si₃/NiTi composite coating was fabricated on a substrate of a titanium alloy by plasma jet cladding using Ni-Ti-Si elemental powder blends. The microstructure, microhardness and wear resistance of the coating were evaluated. The result shows that the plasma jet clad composite coating has a rapidly solidified microstructure consisting of blocky primary Ti₅Si₃ and the inter-blocky Ti₅Si₃/NiTi eutectics and is metallurgically bonded to the titanium substrate. The composite coating has high hardness and excellent wear resistance under the dry-sliding-wear test condition.

Emission spectra of XeI^* excimers and ultraviolet intensity at 253 nm from a dielectric barrier discharge (DBD) lamp excited by a pulsed voltage were measured as functions of pressure, electrical power, and frequency. In the DBD lamp driven by a higher frequency voltage, a more intense emission of XeI^* excimers with high efficiency at 253 nm was found. A diffuse discharge mode was observed at high xenon pressure (> 1 atm) with an excessive iodine concentration in the DBD driven by a high frequency (60 kHz) voltage.

Nanocrystalline silicon (nc-Si) thin films have been prepared by a helicon-wave plasma chemical vapour deposition technique on glass-Si substrates. The structural properties and the surface morphology are characterized by Raman spectroscopy, x-ray diffraction and atomic force microscopy. It is proven that the deposited films have the features of high crystalline fraction and large grain size compared with that in the normal plasma-enhanced chemical vapour deposition regime. The crystalline fraction of the deposited films varying from 0% to 72% can be obtained by adjusting the substrate temperature.

We investigate the structural and optical properties of InGaN-based multi-quantum wells grown on a-c plane sapphire substrates by atomic force microscopy, high-resolution x-ray diffraction and temperature-dependent photoluminescence measurements. The multi-quantum wells grown on a-plane sapphire substrate show stronger exciton localization effect compared with that grown on the c-plane substrate, although the threading dislocation densities in the two samples are almost the same. We attribute the results to the different in-plane strain of quantum well grown on different substrate orientations at the same growth temperature. Since the exciton localization effect plays a key role to obtain high efficiency InGaN-based optoelectronics devices, the presented result should be emphasized.

ZnO nanodots have been grown on Si (100) assisted by anodic aluminium oxide (AAO) template at low temperature (350°C). Regular arrangement to a certain extent in local for ZnO nanodots is observed, and the average diameter of nanodots is about 9.7 nm. Photoluminescence studies at room temperature for photon energy between 2.0 and 3.6 eV reveal a strong single exciton peak at 3.274 eV (378.8 nm) with the green emission fully quenched. Narrow full width at half maximum (FWHM) of the UV emission band (0.14 eV) suggests the as-grown ZnO nanodots have a narrow size distribution.

We used a rectangular waveguide system to measure the X-band (8-12 GHz) transmission of hexagon split ring resonators (SRRs) alone and the left-handed metamaterials (LHMs) consisting of hexagon SRR array and wire array. The experimental results show that for an individual SRR, the resonance frequency increases with the azimuthal gap, but decreases with the radial gap. For two identical SRRs, the resonance peak has a shift because of the electromagnetic interaction, and the resonance frequency and the strength decrease with the separation distance. Finally, we demonstrate the left-handed effect of the LHMs.

Er-doped silicon-rich SiO₂ thin films were prepared by an rf co-sputtering method, followed by thermal annealing at 700-1200°C for 30 min. The microstructure is studied by transmission electron microscopy (TEM) and x-ray diffraction (XRD). When the films are annealed at T > 900°C, silicon nanocrystals (nc-Si) enveloped by amorphous silicon (α-Si) can be observed. The thermal quenching behaviour at γ = 1.535 μm and its relation with the annealing temperature are also investigated. With the increasing annealing temperature, the portion of α-Si and the intensity quenching both decrease. Efficient luminescence from Er ions and weak intensity thermal quenching can be obtained from the sample annealed at 1100°C. The role of α-Si in the non-radiative processes at T > 100 K is discussed.

The temperature dependence of the thermal conductivity in Bi₂Sr₂Ca_1-xCe_xCu₂O_y x = 0.1, 0.2, 0.3, 0.4 is presented. With increasing Ce-doping level, the thermal conductivity peak under T_c is suppressed then disappears, while another peak appears at low temperatures for the non-superconducting compounds. The numerical analysis shows that the thermal conductivity peak under T_c can be well described by the normal electron relaxation-time contribution model, and the phonon-induced thermal conductivity peak could be well described within the Debye approximation of the phonon spectrum. The existence and variation of these two thermal conductivity peaks indicate the adjustability between the superconducting and insulating components in the samples with different Ce-doping levels.

We show a nonlinear materials equation of superconductors in the form of an extended power law which can be derived from the Ginzburg-Landau (GL) functional. The critical current J_c and ac susceptibility X are analysed by using this equation, and the puzzling question of the increasing height of the out-of-phase susceptibility peak X''_peak with increasing amplitude h_ac is explained.

Current density and local magnetic field of spontaneous magnetization states in one-dimensional superconducting connected corner-junction arrays have been analysed by solving the phase equation of the arrays. The solutions can be expressed by the Jacobian elliptic functions, which have been calculated numerically. Our results show that the corner fluxons with a fraction of half flux quantum are arranged in an antiferromagnetic fashion, which is in agreement with the recent experiments observed by Hilgenkamp et al. (Nature 422(2003)50). In addition, we present the magnetization flux of each corner junction in the array as a function of facet length.

The pressure dependence of the residual resistivity of the doped electron-type and hole-type Kondo insulators (KIs) are calculated within the framework of the slave-boson mean-field theory and the coherent potential approximation. It is shown that as the pressure increases, the resistivity increases and decreases for the dilute doping electron-type and hole-type KIs, respectively. These results are qualitatively in agreement with the experiments.

A comparative study of electrical transport and magnetoresistance (MR) is performed for sol-gel prepared samples of nominal composition La_2/3Ca_1/3MnO₃, La_2/3Ca_1/3Mn_1-xCu_xO₃ and La_2/3Ca_1/3Mn_1-xZn_xO₃ with x = 4%. Compared with La_2/3Ca_1/3MnO₃, the introduction of Cu or Zn causes a significant downward shift of insulator--metal transition and a sharp MR peak near the transition. The sharp MR peak becomes observable even upon the application of low magnetic fields. It is also shown that although the same behaviour of transport and MR is observed, the sample containing Cu stands out clearly from the sample containing Zn for a substantial enhancement in MR near the transition.

We present an image-intensified charge-coupled-device (ICCD) version of Z-scan by employing an ICCD detector and fixing the sample at the beam waist, and a measurement of the third-order nonlinear optical coefficient of single crystal zinc oxide (ZnO). The X⁽³⁾ value of -9.1 x 10^-15cm²/W measured is in agreement with the published result. Our Z-scan configuration of placing sample at beam waist and collecting the whole wavefront by an ICCD detector is simple and can be deployed in cryogenic research where the sample cannot be Z-scanned.

For characterization of semiconductor lasers, quasi-Fermi-level separation is a critical parameter due to its relationship with carrier density and gain. We suggest a new technique to determine the quasi-Fermi-level separation from amplified spontaneous emission measured from one facet.

We study the photoluminescence (PL) and the PL dynamics of Ir(PPY)₃-doped poly(N-vinylcarbazol) (PVK) under the modulation of an electric field. The results show that the electric-field-induced quenching of PL from Ir(PPY)₃-doped PVK mainly comes from the dissociation of excitons in the chains of PVK. There is no significant difference in the excited state lifetime of Ir(PPY)₃ to be observed under the different applied negative biases. Our experiments demonstrate that the excitons attached to the molecules of Ir(PPY)₃ are very stable.

Hexagonal ZnO microrods and sub-microrods have been prepared through thermal decomposition of an equimolar (0.1 M) aqueous solution of Zn(NO₃)₂.4H₂O and (CH₂)₆N₄ at 90°C for different times (10-46 h). The microrods were transformed into hollow hexagonal ZnO microtubes when the growth time reached 46 h. The Raman spectra and the photoluminescent (PL) spectra were measured. The PL spectra of microrods consist of two strong narrow near-UV bands at 380 nm and 400 nm assigned to free exciton emission and exciton--exciton collision, respectively. The PL spectrum of ZnO microtubes show only one peak in the near-UV region with peak located at 380 nm with FWHM of about 20 nm assigned to free exciton emission. When the growth time increased, the peak intensity of near-UV band decreased.

The dependence of light intensities of organic light-emitting diodes (OLEDs) on the distance of emission zone to metal cathode is investigated numerically. The investigation is based on the half-space optical model that accounts for optical interference effects of metal cathode. We find that light intensities of OLEDs are functions of the distance of emission zone from the metal cathode because of the effect of interference of the metal cathode. This interference leads to an optimal location of emission zone in OLEDs for the maximum of light intensities. Optimal locations of emission zone are numerically shown in various emitting colour OLEDs with different metal cathodes and these results are expected to give insight into the preparation of high efficiency full colour or white light OLEDs.

SnO₂/SiO₂ nanocomposites have been prepared by the soaking-thermal-decomposing method, tin oxide nanoparticles are uniformly dispersed in the mesopores of silica. The optical absorption edge of the obtained nanocomposite presents a redshift compared with bulk tin oxide. With the increasing annealing temperature during the procedure of the sample preparation, the optical absorption edge of the sample moves to shorter wavelength (blueshift). These optical properties can be ascribed to the amorphous structure and band defects of surface layers of the tin oxide nanoparticles.

We investigate the capillary effect and the residual stress evolution in the wetting, drying and rewetting stages of porous silicon using x-ray diffraction and micro-Raman spectroscopy. A reversible capillary effect and an irreversible oxidation effect are the driving forces for the residual stress evolution. The lattice expansion of the porous-silicon layer is observed to decrease slightly by x-ray diffraction and the tensile residual stress increases rapidly by micro-Raman spectroscopy, with the change of about 82 MPa for the oxidation effect and the change of 2.78 GPa (enough for cracking) for the capillary effect. Therefore, the capillary effect plays a major role in the residual stress evolution in the stages. A simple microscopic liquid-bridge model is introduced to explain the capillary effect and its reversibility. The capillary emergence has a close relation with a great deal of the micro-pore structure of porous silicon.

ZnO thin films were successfully deposited on Si (100) substrates by chemical vapour deposition (CVD) at atmospheric pressure (1 atm). The only solid source used here is zinc acetate, (CH₃COO)₂Zn, and the carrier gas is nitrogen. The sample, which was prepared at 550°C during growth and then annealed in air at 900°C, has only a ZnO (002) diffraction peak at 34.6° with its FWHM of 0.23° in the XRD pattern. The room-temperature PL spectrum shows a strong ultraviolet emission with the peak centred at 380 nm. We analysed the effects of many factors, such as the source, substrates, growth and annealing temperatures, and annealing ambience, on the structural and optical properties of our prepared ZnO films.

In nanocrystalline dye-sensitized solar cells (DSSCs) the absorption of a large fraction of the incident solar radiation is important for achieving high efficiencies. We develop a model to include both the optical process and the electrochemical process. This model allows us to calculate the performance of the different optical designs (for example the different scattering layers and the different reflecting plane). It is found that appropriate optical designs can improve the performance of DSSCs greatly.

A linearized instability analysis of Taylor-Couette flow between two rotating concentric cylinders of an electrorheological (ER) fluid is carried out. The ER fluid exhibits a yield stress in addition to the plastic viscosity when an extra electric-field is applied. It can be found that the yield stress plays a dual role in the flow instability. The possibility of the yield surface falling between the cylinders is analysed. Although small waves appeared on the yielded surface is considered, the yielded surface, which has been treated as a free surface, has little effect on the flow instability. The effects of axisymmetric perturbation on the flow instability are presented due to the axisymmetric of the basic flow. The parameter β in the yield stress formula of the ER fluid is shown to have distinct effects on the flow instability characteristics.

We report a new cosensitization utilizing quantum dot (QD) PbS and Cis-(SCN)₂Bis(2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (N3) dye on the nanoporous TiO₂ film. Solid-state Grätzel solar cells with the cosensitized films show an improved overall efficiency by 200% relative to the cells assembled with only N3 sensitization and an extremely high open-circuit voltage of 840 mV, and a fill factor of 70.5%. Back reaction characteristics of the above cells are also investigated, demonstrating a great suppression of recombination due to cosensitization. It seems that the cosensitization also facilitates the electron injection into the conduction band of TiO₂.

In the driven reconnection process with various scales, the effect of Hall current is studied numerically using a Hall magnetohydrodynamics (MHD) code derived from a multi-step implicit scheme. In the cases with L_c/d_i ≤ 1.0 (L_c is the half-thickness of initial current layer, d_i is the ion inertial length), the features of Hall MHD reconnection are shown as follows: a quasi-steady single X-line reconnection is obtained, the B_y component with a quadrupolar structure is generated and the maximum reconnection rate is larger than 0.11. In the cases with L_c/d_i > 1.0, the effect of Hall current on the reconnection dynamics weakens and Hall MHD reconnection is gradually transformed into resistive MHD reconnection as L_c/d_i increases.

We study the circumstellar interaction around SN 1993J by its intermediate-band light curves obtained by the 60/90 cm Schmidt telescope at Xinglong station. The optical emission showed a slow decay of 0.05±0.02 mag/100 d in the period from 1995 to 2003, invoking a main energy contribution from SN-circumstellar interaction at late times. The relatively flat power law SN density model fits better with the observations. In particular, the line ratio of [O III]λλ4959, 5007 and Na I D relative to H_α are well reproduced by the model. Moreover, the H_α light curve displayed obvious bump structures at some epochs, which is probably attributed to the density fluctuations in the ambient material that surrounds the reverse shockwave.

Using the hybrid model and the neutrino jet rocket model, we calculate the magnetic fields and the initial periods of 72 pulsars. We probe into the possible connection among magnetic field, initial period, and initial quantum number.

The correlation of screw-instability in black hole magnetosphere with pairs of high-frequency quasi-periodic oscillations (HFQPOs) is discussed in the coexistence of the Blandford-Znajek (BZ) and magnetic coupling (MC) processes. It turns out that screw-instability can result in HFQPOs. Such an HFQPO can be regarded as the transient process in an equivalent circuit with resistor and inductor in series (R-L circuit), and its period can be estimated by the relaxation time of this process. When the BZ process and the MC process coexist, the screw-instability can occur both in the BZ region and in the MC region, and the pairs of HFQPOs can be generated. Calculations show that such pairs of HFQPOs are likely to show frequencies in a 3:2 ratio. The frequencies of pairs of HFQPOs in our model scale inversely with the mass of central black hole, which is consistent with the observations.

Assuming that baryons within a galactic halo have the same specific angular momentum as the dark matter where they locate initially and a disc forms due to the gas cooling and condensation with the conservation of angular momentum, we investigate the angular momentum distribution in a resulting galactic disc under the new preheated galaxy formation model suggested by Mo and Mao (Mon. Not. R. Astron. Soc. 333 (2002) 768). Compared with the observational results, it can be concluded that the preheated galaxy formation model can match current observations. This model can be a good approach to solve the problems of both the angular momentum catastrophe and the mismatch of angular-momentum profiles in current disc galaxy formation models.