On Minimal Annuli with a Straight Line Boundary

Shiffman proved that if a minimal annulus A in a slab is bounded by two convex Jordan curves contained respectively in the two boundary planes P and Q of the slab, then A intersects all parallel planes between P and Q in strictly convex curves. We generalize Shiffman's result to the case that A is bounded by a strictly convex C² Jordan curve and a straight line. We show that in this case Shiffman's result is still true.     

Broadening of Cr nanostructures in laser-focused atomic deposition

This paper presents the experimental progress of laser-focused Cr atomic deposition and the experimental condition.The result is an accurate array of lines with a periodicity of 212.8±0.2 nm and mean full-width at half maximum as approximately 95 nm.Surface growth in laser-focused Cr atomic deposition is modeled and studied by kinetic Monte Carlo simulation including two events:the one is that atom trajectories in laser standing wave are simulated with the semiclassical equations of motion to obtain the deposition position;the other is that adatom diffuses by considering two major diffusion processes,namely,terrace diffusion and step-edge descending.Comparing with experimental results(Anderson W R,Bradley C C,McClelland J J and Celotta R J 1999 Phys.Rev.A 59 2476),it finds that the simulated trend of dependence on feature width is in agreement with the power of standing wave,the other two simulated trends are the same in the initial stage.These results demonstrate that some surface diffusion processes play important role in feature width broadening.Numerical result also shows that high incoming beam flux of atoms deposited redounds to decrease the distance between adatoms which can diffuse to minimize the feature width and enhance the contrast.     

Inelastic partial cross sections for scattering of HF by neon

An analytic expression of the potential energy surface (PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science, 2003, 21(3): 9–13 (in Chinese)], which have been computed using the augmented correlation-consistent polarized quadruple zeta basis set aug-cc-pVQZ at the theoretical level of CCSD (T). On the basis of the PES, the partial cross sections (PCSs) at the incident energies of 60, 75, 100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic PCSs are discussed in detail. The results show: (1) The long-range attractive well of the EPS makes the significant contribution to the lower excitation PCSs, especially the tail maximum for j = 0→j′ = 1 transitions, whereas no contribution is to the j′⩾3 inelastic transitions. (2) The short-range (the repulsive and attractive) interaction makes the significant contribution to the lower excitation PCSs, especially the main peak for j = 0→j′ = 1, 2. As for the transitions of j′⩾3, the short-range interaction plays a key role in the inelastic excitation. (3) Although the positions of the maximums and minimums of the inelastic PCSs are different at the collision energies, they correspond to almost the same impact parameter. Supported by the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096)     

Reaction mechanism of ammonia oxidation over RuO2(1 1 0): A combined theory/experiment approach

Combining state-of-the-art density functional theory (DFT) calculations with high resolution core level shift spectroscopy experiments we explored the reaction mechanism of the ammonia oxidation reaction over RuO₂(1 1 0). The high catalytic activity of RuO₂(1 1 0) is traced to the low activation energies for the successive hydrogen abstractions of ammonia by on-top O (less than 73 kJ/mol) and the low activation barrier for the recombination of adsorbed O and N (77 kJ/mol) to form adsorbed NO. The NO desorption is activated by 121 kJ/mol and represents therefore the rate determining step in the ammonia oxidation reaction over RuO₂ (1 1 0).     

Explicit models for elastic and piezoelastic surface waves

^** Email: julius.kaplunov{at}brunel.ac.uk Explicit models for the Rayleigh and Bleustein–Gulyaevsurface waves are extracted from the original 2D formulationswithin the general framework of linear elasticity and electroelasticity.The derivations are based on perturbing in slow time the self-similarsolutions for homogeneous surface wave. Both the proposed modelsinvolve hyperbolic equations on the surface along with ellipticequations over the interior, emphasizing the dual nature ofa surface wave. Comparisons with exact solutions are presented,including that for the plane Lamb problem.     

Three-dimensional multi-relaxation-time lattice Boltzmann front-tracking method for two-phase flow

We developed a three-dimensional multi-relaxation-time lattice Boltzmann method for incompressible and immiscible two-phase flow by coupling with a front-tracking technique. The flow field was simulated by using an Eulerian grid, an adaptive unstructured triangular Lagrangian grid was applied to track explicitly the motion of the two-fluid interface, and an indicator function was introduced to update accurately the fluid properties. The surface tension was computed directly on a triangular Lagrangian grid, and then the surface tension was distributed to the background Eulerian grid. Three benchmarks of two-phase flow, including the Laplace law for a stationary drop, the oscillation of a three-dimensional ellipsoidal drop,and the drop deformation in a shear flow, were simulated to validate the present model.     

3DSEM++: Adaptive and intelligent 3D SEM surface reconstruction

Structural analysis of microscopic objects is a longstanding topic in several scientific disciplines, such as biological, mechanical, and materials sciences. The scanning electron microscope (SEM), as a promising imaging equipment has been around for decades to determine the surface properties (e.g., compositions or geometries) of specimens by achieving increased magnification, contrast, and resolution greater than one nanometer. Whereas SEM micrographs still remain two-dimensional (2D), many research and educational questions truly require knowledge and facts about their three-dimensional (3D) structures. 3D surface reconstruction from SEM images leads to remarkable understanding of microscopic surfaces, allowing informative and qualitative visualization of the samples being investigated. In this contribution, we integrate several computational technologies including machine learning, contrario methodology, and epipolar geometry to design and develop a novel and efficient method called 3DSEM++ for multi-view 3D SEM surface reconstruction in an adaptive and intelligent fashion. The experiments which have been performed on real and synthetic data assert the approach is able to reach a significant precision to both SEM extrinsic calibration and its 3D surface modeling.     

Nonlinear force density method for the form-finding of minimal surface membrane structures

We develop an alternative approach for the form-finding of the minimal surface membranes (including cable membranes) using discrete models and nonlinear force density method. Two directed weighted graphs with 3 and 4-sided regional cycles, corresponding to triangular and quadrilateral finite element meshes are introduced as computational models for the form-finding problem. The triangular graph model is closely related to the triangular computational models available in the literature whilst the quadrilateral graph uses a novel averaging approach for the form-finding of membrane structures within the context of nonlinear force density method. The viability of the mentioned discrete models for form-finding are studied through two solution methods including a fixed-point iteration method and the Newton–Raphson method with backtracking. We suggest a hybrid version of these methods as an effective solution strategy. Examples of the formation of certain well-known minimal surfaces are presented whilst the results obtained are compared and contrasted with analytical solutions in order to verify the accuracy and viability of the suggested methods.     

拉脱法测液体表面张力系数的误差分析

对拉脱法测量液体表面张力系数实验的原理和仪器做了简要的介绍,并着重对该实验误差的来源进行了分析探讨。