Numerical study on the performance of a twin-raft wave energy dissipator in a stilling basin

In this paper, a raft-typed wave energy dissipator is proposed, and a mathematical model for the hydrodynamics of such a dissipator is presented, based on Reynolds-averaged Navier–Stokes equations. The model is validated by a comparison of the numerical results with the results of other investigators. The validated model is then utilized to examine the effect of wave height, wave frequency, damping coefficient, flow velocity on wave energy dissipation ratio and wave transmission coefficient for a hinged twin-raft wave energy dissipator. Our results reveal that the differences in behaviour exhibited by an inviscid fluid and a viscous fluid can be large and vary considerably, depending on the flow velocity.     

Newton's method for solving heat transfer,fluid flow and interface shapes in a floating molten zone

Newton's method is applied to the finite volume approximation for the steady state heat transfer, fluid flow and unknown interfaces in a floating molten zone. The streamfunction/vorticity and temperature formulation of the Navier–Stokes and energy equations and their associated boundary conditions are written in generalized curvilinear co-ordinates and conservative law form with the Boussinesq approximation. During Newton iteration the ILU(0) preconditioned GMRES matrix solver is applied for solving the linear system, where the sparse Jacobian matrix is estimated by finite differences. Nearly quadratic convergence of the method is observed. Sample calculations are reported for sodium nitrate, a high-Prandtl-number material (Pr = 9.12). Both natural convection and thermocapillary flow as well as an overall mass balance constraint in the molten zone are considered. The effects of convection and heat input on the flow patterns, zone position and interface shapes are illustrated. After the lens effect due to the molten zone is considered, the calculated flow patterns and interface shapes are compared with the observed ones and are found to be in good agreement.     

The story of Sr2RuO4

This article reports on the experiments performed in the Sr–Ru–O system, the motivation behind them and their impact on basic research and device applications. It refers to the time from 1987 to 2003, with emphasis on the occurrences before the discovery of superconductivity in Sr₂RuO₄ in 1994. Apart from the title compound Sr₂RuO₄ itself and related ruthenates, it touches on many different topics like titanates, ferrates, high-T_c superconducting cuprates, crystal growth by floating zone melting and thin films as well as fundamental and applied research.     

FSGO calculations of octahydrotriborate anion and tetraborane

The FSGO quantum mechanical model is used to makeab initio calculations of the geometrical structures and energies of the ground state configurations of the octahydrotriborate anion, B₃H ₈ ⁻ , and tetraborane, B₄H₁₀. Both molecules are assumed to belong to theC _2v symmetry point group during these computations. Comparisons with available experimental data show good agreement. B₄H₁₀ calculations are also compared with results of SCF calculations.     

Large-size and high-quality Zn2TiO4 single crystal grown by the optical floating zone method

Crack-free and transparent Zn₂TiO₄ single crystals of 4–6 mm in diameter and 30 mm in length have been grown by the optical floating zone method. The powder X-ray diffraction (XRD) results show that the as-grown crystals have the spinel-type Zn₂TiO₄ structure. XRD² measurements on Zn₂TiO₄ wafers cut perpendicular to the growth direction display only one peak at 42.7°, which indicates that the Zn₂TiO₄ single crystals grow along the 〈4 0 0〉 direction (a-axis). The formation of bubble inclusions was effectively suppressed by lowering rotation rate. Transmission polarized-light microscopy results showed that as-grown crystals were free of low angle grain boundaries.     

A multistep attachment process: Transformation of titanate nanotubes into nanoribbons

The mechanism of the conversion of titanate nanotubes into nanoribbons is of considerable interest.The details of the transformation processes involved when nanoribbons are produced from a P25 TiO 2 powder precursor by alkaline hydrothermal treatment have been investigated systematically by transmission electron microscopy.A multistep attachment model is proposed for the growth at the early stage of coarsening.The treatment duration has a strong effect on the change in product morphology from hollow nanotubes into nanoribbons,since the nanotubes cannot retain their morphology in the strong alkaline solution for extended periods of time.Most of the nanotubes were etched and dissolved,providing the nutrients for subsequent nanoribbon growth.Some stable nanotubes grew spirally internally to form nanowires or became connected together to form rafts which acted as the grains for nanoribbon growth.With increasing hydrothermal time,a large number of nanotubes and other fragments became attached to the grains which began to grow larger and eventually formed the nanoribbons,in a process in which the stepped faces and kinked faces became fused and were eliminated while the flat faces were retained in the nanoribbon morphology.     

Computation of flow-induced motion of floating bodies

A computational procedure for the prediction of motion of rigid bodies floating in viscous fluids and subjected to currents and waves is presented. The procedure is based on a coupled iterative solution of equations of motion of a rigid body with up to six degrees of freedom and the Reynolds-averaged Navier–Stokes equations describing the two- or three-dimensional fluid flow. The fluid flow is predicted using a commercial CFD package which can use moving grids made of arbitrary polyhedral cells and allows sliding interfaces between fixed and moving grid blocks. The computation of body motion is coupled to the CFD code via user-coding interfaces. The method is used to compute the 2D motion of floating bodies subjected to large waves and the results are compared to available experimental data, showing favorable agreement.     

Bounds for in-progress floating-strike Asian options using symmetry

This paper studies symmetries between fixed and floating-strike Asian options and exploits this symmetry to derive an upper bound for the price of a floating-strike Asian. This bound only involves fixed-strike Asians and vanillas, and can be computed simply given one of the many efficient methods for pricing fixed-strike Asian options. The bound coincides with the true price until after the averaging has begun and again at maturity. The bound is compared to benchmark prices obtained via Monte Carlo simulation in numerical examples. D. Hobson is supported by an Advanced Fellowship from the EPSRC. V. Henderson is partially supported by the NSF under grant DMI 0447990.     

Bionanodot monolayer array fabrication for nonvolatile memory application

A polyelectrolyte thin film which was simply spin-coated on a substrate showed the high-density adsorption of bionanodot-accommodated ferritins through electrostatic interaction. Solution pH adjustment facilitated the control of adsorption density to a value grater than 80% of the theoretical maximum density. The formed polyelectrolyte film was very thin and vulnerable like protein, therefore, only the array with densely adsorbed bionanodot was left on the substrate after organic component removal. The floating nanodot gate type MOS capacitor fabricated with this bionanodot array showed a memory effect, and no negative influences of polymer such as carrier trapping on the capacitance-voltage characteristics was observed.     

火焰原子吸收光谱法测定铜镍矿浮选产品中铜、镍、镁

研究了用火焰原子吸收光谱法在同一溶液体系中直接快速测定金川铜镍矿浮选产品中铜、镍、镁含量新的新方法。考察了产品中高含量的SiO2对测定镁的干扰情况，并提出了排除这项干扰简便方法，根据各元素的标准溶液系列的测定数据，推算出了铜、镍、镁3元素的线性回归方程及线性相关系数，特征浓度铜为0．40mg.L^-1/1%，镍为0．48mg.L^-1／1％，Mg为0．018mg.L^-1／1％；线性浓度范围铜，镍均为0－10mg.L^-1，镁为0．2－1．2mg.L^-1。相对标准偏差铜为2．5％(n=6)，镍为2．3％（n＝6），镁为2．8％（n=6），加标回收率铜为96．5％－102．5％，镍为98．8％－103．5％，镁为98．2％－102．5％，这种方法操作简便，快速，实用，具有较好的精密度和准确度，实际产品分析结果与外检单位及金川公司测定的结果吻合。