Two-dimensional Planar Surface Research Articles

Stereo-imaging LSPIV (SI-LSPIV) for 3D water surface reconstruction and discharge measurement in mountain river flows

Large-Scale Particle Image Velocimetry (LSPIV) has been successfully applied for stream flow and flood measurements. In most LSPIV studies, the water surface has been approximated as a two-dimensional planar surface. Errors may arise due to this approximation for flows in steep channels and with complex riverbed topography, especially for small mountain rivers. In this study, a Stereo Imaging based LSPIV system (SI-LSPIV) is developed to reconstruct the three-dimensional topography and water surface distribution, in addition to surface velocity measurements. The SI-LSPIV system consists of two synchronized Raspberry Pi camera modules that can capture stereo images autonomously. Uncalibrated rectification and point cloud methods are implemented for surface reconstruction. Detailed three-dimensional surface topography as well as water level distribution can be obtained, which facilitates image ortho-rectification and wetted-area delineation for LSPIV calculation. Over the past years, an unattended SI-LSPIV system has been deployed in Longxi River, Sichuan, China. One major flow event was captured and the results were presented to demonstrate that LSPIV analysis aided with three-dimensional water surface distribution can improve velocity measurement and stream discharge estimation for torrential mountain river flows.

Edge effect in the oxidation of three-dimensional nano-structured silicon

Understanding and controlling the oxidation of 3D nano-structured Si is important for the three-dimensional (3D) nano-structured vertical metal–oxide–semiconductor (MOS) field-effect transistor. The retarded oxidation of Si in a corner (edge) has been widely considered since the 1980s to be due to the compressive stress from oxide and/or the slow diffusion of the oxidant in the oxide caused by compressive stress, although some problems remain unresolved. In the current work, a sharp angle in a simultaneously oxidized concave-structured adjacent two-dimensional planar surface was observed for the first time by using transmission electron microscope, for which the traditional consideration is difficult to interpret. We also found that the oxidation of Si near the edge is delayed (edge effect) irrespective of whether the edge is non-oxidized Si3N4 or a simultaneously oxidized convex- or concave-structured adjacent two-dimensional planar surface, widely exists in different Si planar surface of the observed 3D nano-structures (pillar, fin, and terrace) independent of grain orientation. We further developed a model for the formation of the edge effect and discussed its mechanism. The edge effect completely explains the residual Si and formed SiO2 in all Si nano-structures and also contributes in intrinsically understanding and precisely controlling the oxidation of 3D nano-structured Si for future device fabrications.

Scale effects in gas nano flows

Most previous studies on gas transport in nano-scale confinements assume dynamic similarity with rarefied gas flows, and employ kinetic theory based models. This approach is incomplete, since it neglects the van der Waals forces imposed on gas molecules by the surfaces. Using three-dimensional molecular dynamics (MD) simulations of force driven gas flows, we show the significance of wall force field in nano-scale confinements by defining a new dimensionless parameter (B) as the ratio of the wall force-penetration length to the channel height. Investigation of gas transport in different nano-channels at various Knudsen numbers show the importance of wall force field for finite B values, where the dynamic similarity between the rarefied and nano-scale gas flows break down. Comparison of MD results employing molecularly structured three-dimensional walls versus reflection of gas molecules from a two-dimensional planar surface with Maxwell distribution show that the nano-confinement effects cannot be resolved by the latter approach, frequently used in kinetic theory calculations. Molecularly structured walls determine the bulk flow physics by setting a proper tangential momentum accommodation coefficient, and they also determine the transport in the near wall region. Gas nano-flows with finite B exhibit significant differences in the local density and velocity profiles, affecting the mass flow rate and the formation of Knudsen's minimum in nano-channels.

Thanks for the memory: Cooperative autonomous agent search in uncertain environments

The effects of cooperation between autonomous electronic or physical agents are widely studied in computational science literature. We concentrate on a homogenous population of agents in a multi-agent system (MAS) to explore the effects of useful memory on goal achievement. We use simulations to consider two-dimensional planar surfaces upon which N targets are randomly scattered. N agents exist each with a maximal interest in one specific target. Agents may observe the positions of “uninteresting” targets in the environment and communicate this information to other agents encountered within the environment. The benefits of cooperation can be approximated by pure probabilistic analysis for theoretical search success, but the introduction of real-world cost factors (e.g. fuel, energy, transmission time) associated with movement within the environment renders these predictions unusable. In pure probabilistic terms, higher numbers of cooperative agents can greatly increase search effectiveness. In systems where positive costs are associated with search, internal agent memory factors can allow agent density to approximate pure probabilistic effectiveness. Practical applications for this research include real-time electronic document search, problems in robotic multi-agent systems (e.g. “foraging” or “consumption” problems), and network coverage for wireless communication devices.

Two-axis probing system for atomic force microscopy

A novel two-axis probing system is proposed for multiaxis atomic force microscopy (AFM). It employs a compliant manipulator that is optimally designed in terms of geometries and kinematics, and is actuated by multiple magnetic actuators to simultaneously control tip position and change tip orientation to achieve greater accessibility of the sample surface when imaging surfaces having large geometric variations. It leads to the creation of a multiaxis AFM system, which is a three-dimensional surface tool rather than a two-dimensional planar surface tool. The use of the system to scan the bottom corner of a grating step is reported.

Ordered ground-state structures in binary h.c.p. alloys using the configuration polyhedron method

Abstract Ground-state structures in binary h.c.p. (non-ideal axial ratio) alloys have been studied taking interactions up to third-neighbour distances. The configuration polyhedron method was adopted for this purpose. The procedure for deriving the structural inequalities used in this method has been generalized. Tetrahedral, octahedral and another larger motif have been used. 15 ground-state structures (corresponding to vertices and points on edges of the configuration polyhedron) with the stoichiometries A5B, A3B, A2B, A9B5 and AB have been identified. In addition, the A7B5 structure and a series of structures with stoichiometries An+3Bn+1(n>1) (with points on the two-dimensional planar surfaces of the configuration polyhedron) are also ground states. The structural details of the former group of ground-state structures, such as the lattice, the number of atoms per unit cell, the equivalent positions of atoms and their site symmetries have been worked out. The stability of all experimentally observed su...