Based on conservation of mass and momentum, a fluid dynamics model of debris motion from a near-space nuclear detonation is established. Many influence factors are considered, such as energy dissipation, air density as a function of height, gravity, increasing air temperature caused by X-ray deposition and radiation cooling. A computation program is developed. The expansion and upward motion of debris in TEAK and ORANGE tests are calculated. Evolution of typical parameters such as central height, maximum horizontal radius, ascending velocity, and shape of debris are given. They are in accordance with experimental data. The model provides delayed radiation source parameters for ionospheric effect and artificial radiation band effect.

With first-principles pseudo-potential plane-wave method, crystal structures, electronic structures and optical properties of sulvanite compounds:Cu₃VS₄, Cu₃NbS₄ and Cu₃TaS₄ are calculated to investigate their electrical conductivity and electrochromic performance. They are potentially applied in solar cells and electrochromic devices as transparent semiconductors. Electronic structures indicate that the secompounds are indirect band-gap semiconductors, with conduction band minimum and valence band maximum located at X and R points, respectively, in Brillouin zone. Electronic states of conduction band minimum and valence band maximum are dominated by d-orbitals of Cu and Ⅴ-group elements, respectively. From band structure, atomic charge population analysis, electron localization function and optical adsorption/reflectivity spectrum it is suggested that these sulvanite compounds are polar covalent semiconductors with high charge transport mobility and extraordinary electrochromic characteristics. They could be applied to electrochromic devices.

Lattice Boltzmann model with double distribution function is used to study fast phase-change heat transfer in single-pulse laser metal drilling process. Flow and heat transfer of the melted metal material is considered and an immersion moving boundary scheme was used to track solid-liquid interface in the process. Pure heat conduction model and heat transfer model considering convection are used to simulate the process and the results are compared with experimental data. It shows that flow of the melted material has a great impact on phase change heat transfer during laser drilling and results with model that considers flow heat transfer are closer to experimental data. Melting rate, melting depth and temperature field distribution were analyzed, and effects of laser parameters on phase transition process were discussed. It shows that at the end of a pulse, the larger the pulse width of laser, the smaller hole depth, the larger aperture, and the lower temperature of shorter pulse laser are found.

Natural convection problem in a deformable outlet cavity is studied with lattice Boltzmann method. Heated size at left wall are set to two conditions: The whole wall (H) and the middle wall (0.5H). The right wall is open to external environment. The upper and lower boundaries are adiabatic and their right end can be moved up and down to adjust size of the right outlet. Effects of Rayleigh number (10⁴ ≤ Ra ≤ 10⁶), the right exit size (1.0H ≤ L ≤ 2.0H), the left wall heating size (L_h=0.5H or L_h=H) on streamlines, isothermal lines, local Nusselt numbers and average Nusselt numbers are investigated. It shows that heat transfer in the cavity increases with the increase of Rayleigh number, which manifests as size of elliptical quasi-stationary region in the cavity increases and is closer to the upper and lower adiabatic boundaries. Thickness of thermal stratification is gradually reduced and average Nusselt number is increased. However, increase of the right outlet has a different degree of influence on heat transfer effect in the cavity. As the heating size is in the middle of the left wall surface, size of the right side opening does not significantly affect the heat exchange. In addition, at the left wall heating size of 0.5H it shows a higher average heat transfer efficiency. An empirical prediction of functional relation between average Nusselt number and control parameters is proposed. The fitting function satisfies practice and design in projects.

Phase change heat transfer of a gold particle irradiated by ulter-fast laser was studied. Position of solid-liquid interface was determined with coupling interface energy balance equation and interface tracking method for nucleation dynamics. In addition, effects of laser parameters on sintering process were studied. It showed that as laser irradiates gold particle vertically, melting phenomenon occurs mainly in poles of particle. Bottom of particle melts earlier than top and melting volume is smaller. As laser pulse width becomes shorter melting is earlier and melting volume increases. Melting degree of particle increases with laser heat source fluence.

An accurate equation of state (EOS) for carbon dioxide is coupled into an improved lattice Boltzmann equation (LBE) model. With the model continuous interfacial dynamics of carbon dioxide in two phase in a microchannel, including breaking up, coalescence, deformation, and mass exchange between gas and liquid phases, is studied. It is found that flows achieve a steady-state as balance of breaking up and coalescence is reached, and mass exchange occurs. Comprehensive results show that flow shape at steady-state depends mainly on surface tension, inertial force, wettability of channel surface, and initial volume fraction. Specially, formative bubbles or droplets are almost spherical as inertial force is smaller than surface tension. As surface tension overcomes inertial force, slug flow is formed since bubbles or droplets are easy to expand to contact with solid surface. On the other hand, it shows that influence of wettability on flow pattern is also important. Slug flow is observed if contact angle is small while annular flow is observed if contact angel is large. At different volume fraction slug flow and annular flow are obtained.

Fourier property of nonlinear weights and limiters in wave-space are analyzed. Firstly, a statistical method is designed to analyze Fourier property of nonlinear weights. Secondly, averaged values and deviations of nonlinear weights are shown, and values with change of wave-number are analyzed. It is helpful to comprehension of nonlinear schemes. The method is a guidance for designing shock-capture schemes.

A parallel finite element solver is developed for simulation of the unsteady incompressible viscous flows. Implicit mid-point scheme is used to discretize time variable. Based on unstructured grid, velocity and pressure are discretized by classical P2-P1 Taylor-Hood mixed finite element. Resulting linear algebraic systems are large-scale, sparse, non-symmetric and ill-conditioned. Using a specially designed iterative strategy, it is solved by preconditioned GMRES method with modified pressure-convection-diffusion(PCD) preconditioner. A number of numerical experiments verify scability and validity of the solver. Especially, driven cavity flow simulation in 3D (Re=3200.0) clearly shows existence of primary eddy, downstream secondary eddy, upstream secondary eddy, end-wall vortices and T-G-like vortices. A parallel efficiency comparison with least-squares commutator(LSC) preconditioner is also given.

With principle of conformal transformation and mirror reflection, a mathematical model of flow field in a mixed injection production well pattern was established. Five point horizontal well and vertical well pattern are used for an example. Mathematical expressions of potential function and stream function are derived. Distribution maps of potential line and flow line in a mixed injection production well network with five point method are obtained. Influence of key parameters on internal flow field distribution of mixed injection production well network is analyzed. It shows that at both ends of horizontal well flow lines are relatively dense, and liquid producing capacity at both ends is stronger. The longer the horizontal section, the greater the discharge area of flow line control. As horizontal well is 45 degree angle with vertical wells connection line, displacement effect of horizontal well is relatively good. As horizontal well is perpendicular to direction of main permeability, streamlines are concentrated to production well. Linear displacement is formed and the displacement effect is good. As horizontal well is off center position greater, streamline distribution density differentiation is more obvious.

First-principles calculations are used to study alloy effects on configurations, stability and water adsorption of PtRu_n-1(n=2-14) and H₂O-PtRu_n-1 (n=2-14) systems. It shows that substitution energy of a Pt atom to a Ru atom is low which manifests that Pt is easy to form alloy with Ru clusters. Compared with pure Ru_n cluster, alloy effects enhance adsorption energy of H₂O molecule on PtRu_n cluster, and H₂O molecule is not easy to release in molecular form from PtRu_n cluster. Considering van de Waals force, adsorption energy of water on PtRu₇ increased and dissociation barrier decreased, making it possible to split water on PtRu₇. In conclusion, PtRu_n is suitable to be catalyst for spliting water and producing hydrogen.

Coefficients C₃ of hyperfine levels of excited states|6²P_3/2 F> (F=2, 3, 4, 5) of ¹³³Cs atom are calculated with irreducible tensor method and van der Waals (vdW) interaction between alkali atoms and perfect surface of a metal. C₃ of|6²P_3/2F>(F=2, 3, 4, 5) we obtained are 4.3385 kHz·μm³, 4.3619 kHz·μm³, 4.3680 kHz·μm³, and 4.3467 kHz·μm³. Our data are compared with other theoretical data and experimental data. It shows that they are reliable.

Based on a method combining coherent destruction of tunneling( CDT) theory and self-trapping effect,a scheme realized all-optical transform. In scalar field and paraxial approximation,and by using tight binding approximation,we derived coupled mode equations of optical signal propagation in periodic modulated optical fibers. Considering coupling effect of adjacent fibers,we realized all-optical transform function numerically and conditions required were obtained. With introduction of tunable filter at output side,broadcast transmitting,optical transformation and drop/on functions are realized with an 8×8 optical cross connector,which can be extended to N×N optical cross connector. It can be used to solve problems of signals delay and capacity requirements in WDM optical networks.

Transformation of dielectric properties in uniaxial anisotropic perfectly matched layer(UPML) regions is explored and unified modeling of UPML is proposed.Two condensing optimized algorithms for auxiliary variables,six regions' intersected method and parameter-compressed method,are proposed.In three cycles all initialization of medium parameters and iterative coefficients in three directions are completed with unified modeling method.Though the six regions' intersected method saves a lot of memory,it is the slowest.The parameter-compressed method saves space,which is programmed easily and runs the fastest.

Edge region of HL-2A tokamak with closed divertor configuration is divided into meshes by a code combined with 2D fluid edge modeling code B2.5. Postprocessing code is provided. HL-2A tokamak edge plasma with about 3 MW auxiliary heating power is modeled and analyzed. It indicates that the plasma in front of divertor target plate exhibits high density and low temperature, and the divertor runs in conduction-limited regime, i.e, in high recycling mode.

Combined with spectral band model, control volume method and discrete transfer (DT) method are employed to investigate numerical calculation dealing with the transient combined radiation-conduction heat transfer in three dimensional cylindrical semi-transparent medium. The first and the third nonlinear boundary conditions are both considered. Compared with Zone method and improved Monte-Carlo approach, the calculated results by this method are reliable and more precise.

A penalty upwind finite element method is adopted to deal with the thermohaline double-diffusive system.The method has good stability and second-order accuracy. Natural convection with lateral heating in a square rectangular enclosure can be examined by this way, and it's solutions approximate to the results obtained with velocity-pressure Method. Afterwards, the method is employed for a two-dimensional, laminar, with lateral heating, steady double-diffusive convection partitioned by an adiabatic baffle. Main computation is for Ra=10⁶ and thermal buoyancy ratio N= 1,3,5,7. Distinct flow results depend on the magnitude of the thermal buoyancy ratio N and the baffle.

This paper gives a class of parallel block predictor-corrector methods with a parameter θ for solving initial value problems in ordinary differential equations. The stability and convergence on iterative processes are discussed. It is proven that the methods not only have large stability intervals but also have large convergent regions, thus they are very suitable for par allel integration of ordinary differential equations.

In this paper, a class of polynomial collocation methods with the second deriva live is derived for efficient integration of stiff systems. The methods are of one-step type, and the numerical solutions at m-point can simultaneously be obtained for each application of the formulas. It is shown that this class of methods is of order 2m+1 and the stability is analysed.