Truck Synchronizer Rings Recovery by Plastic Deformation Technology

A truck's gearbox friction rings restoring process by hot 3D stamping was developed and adopted for implementation. Using this recovery method in combination with subsequent synchronizer rings mechanical processing allows restoring up to 95% resource of worn parts. It was established that section of a stamp's deforming element for axisymmetrical parts restoring should be a one-way wedge with a sloping face facing the reconstructed surface. The most significant factors influencing the transmission gearbox synchronizer rings restoring process are: stamp deforming element thickness, plunging depth and distance to a recoverable surface. The energy and force parameters study of hot plastic deformation process serves as input data for automatic design systems of working elements of stamps for restoring synchronizer rings as well as for determination of a required deforming force during hot stamping.

New insight on the role of localisation in the electronic structure of the Si(111)(7 × 7) surfaces

New angle-resolved photoelectron spectroscopy (ARPES) data, recorded at several different photon energies from the Si(111)(7 × 7) surface, show that the well-known S1 and S2 surface states that lie in the bulk band gap are localised at specific (adatom and rest atom) sites on the reconstructed surface. The variations in the photoemission intensity from these states as a function of polar and azimuthal emission angle, and incident photon energy, are not consistent with Fermi surface mapping but are well-described by calculations of the multiple elastic scattering in the final state. This localisation of the most shallowly bound S1 state is consistent with the lack of significant dispersion, with no evidence of Fermi surface crossing, implying that the surface is not, as has been previously proposed, metallic in character. Our findings highlight the importance of final state scattering in interpreting ARPES data, an aspect that is routinely ignored and can lead to misleading conclusions.

A New Shape Adaptive Motion Control System

In recent years there is a growing trend on integrating Computer Aid Design (CAD), Computer Aid Manufacturing (CAM) and Computer Aided Inspection (CAI). This thesis presents a new shape adaptive motion control system that integrates part measurement with motion control. The proposed system consists of five blocks: surface measurement; surface reconstruction; tool trajectory planning; axis motion control and part alignment In this thesis, the key technology used in surface measurement and surface reconstruction is spatial spectral analysis. In the surface measurement block, a new special spectrum comparison method is proposed to find out an optimal digitizing frequency. In the surface reconstruction block, different interpolation methods are compared in the spatial spectral domain. A spatial spectral B-Spline method is presented. In the tool trajectory planning block, a method is developed to select the motion profile first and then determine the tool locations according to the reconstructed surface in order to improve the accuracy of the planned path. In the part alignment, a three-point alignment method is presented to align the part coordinates with the machine coordinates. Based on the proposed methods, a software package is developed and implemented on the polishing robot constructed at Ryerson University. The effectiveness of the proposed system has been demonstrated by the experiment on edge polishing. In this experiment, the shape of the part edges is measured first, and then constructed as a wire-frame CAD model, based on which tool trajectory is planned to control the tool to polish the edges.

A New Shape Adaptive Motion Control System

In recent years there is a growing trend on integrating Computer Aid Design (CAD), Computer Aid Manufacturing (CAM) and Computer Aided Inspection (CAI). This thesis presents a new shape adaptive motion control system that integrates part measurement with motion control. The proposed system consists of five blocks: surface measurement; surface reconstruction; tool trajectory planning; axis motion control and part alignment In this thesis, the key technology used in surface measurement and surface reconstruction is spatial spectral analysis. In the surface measurement block, a new special spectrum comparison method is proposed to find out an optimal digitizing frequency. In the surface reconstruction block, different interpolation methods are compared in the spatial spectral domain. A spatial spectral B-Spline method is presented. In the tool trajectory planning block, a method is developed to select the motion profile first and then determine the tool locations according to the reconstructed surface in order to improve the accuracy of the planned path. In the part alignment, a three-point alignment method is presented to align the part coordinates with the machine coordinates. Based on the proposed methods, a software package is developed and implemented on the polishing robot constructed at Ryerson University. The effectiveness of the proposed system has been demonstrated by the experiment on edge polishing. In this experiment, the shape of the part edges is measured first, and then constructed as a wire-frame CAD model, based on which tool trajectory is planned to control the tool to polish the edges.

A parallel dual marching cubes approach to quad only surface reconstruction

We present a novel method that reconstructs surfaces from volume data using a dual marching cubes approach without lookup tables. The method generates quad only meshes which are consistent across cell borders, i.e., they are manifold and watertight. Vertices are positioned exactly on the reconstructed surface almost everywhere, leading to higher accuracy than other reconstruction methods. A halfedge data structure is used for storing the meshes which is convenient for further processing. The method processes elements in parallel and therefore runs efficiently on GPU. Due to the transition between layers in volume data, meshes have numerous vertices with valence three. We use simplification patterns for eliminating quads containing these vertices wherever possible which reduces the number of elements and increases quality. We briefly describe a CUDA implementation of our method, which allows processing huge amounts of data on GPU at almost interactive time rates. Finally, we present runtime and quality results of our method on medical and synthetic data sets.

Au(100) as a Template for Pentacene Monolayer

The surface of quasi-hexagonal reconstructed Au(100) is used as the template for monolayer pentacene (PEN) self-assembly. The system is characterized by means of scanning tunneling microscopy at room temperature and under an ultra-high vacuum. A new modulated pattern of molecules with long molecular axes (MA) arranged along hex stripes is found. The characteristic features of the hex reconstruction are preserved herein. The assembly with MA across the hex rows leads to an unmodulated structure, where the molecular layer does not recreate the buckled hex phase. The presence of the molecules partly lifts the reconstruction—i.e., the gold hex phase is transformed into a (1×1) phase. The arrangement of PEN on the gold (1×1) structure is the same as that of the surrounding molecular domain on the reconstructed surface. The apparent height difference between phases allows for the distinction of the state of the underlying gold surface.

Initial atomic-scale oxidation pathways on a Ni–15Cr(100) alloy surface

To understand the atomistic phenomenon behind initial oxidation processes, we have studied the nanoscale evolution of oxide growth prior to the formation of a complete layer on a Ni–15 wt%Cr(100) alloy surface using scanning tunneling microscopy/spectroscopy (STM/STS). At the onset of oxidation, a NiO superlattice forms oxide wedges across the step edges, eventually growing across the terraces. The completion of the NiO layer is followed by nucleation of the next layer, which always commences at the groove site of the superlattice. The Cr-oxide formation initiates as disk-shaped oxide particles early in the oxidation process, which Monte Carlo simulations reveal are likely caused by Cr clustering across the alloy surface. Upon further oxidation, a Cr(100)-p(2 × 2)O reconstructed surface is observed, indicating phase separation of Cr predicates the formation of the passive Cr-oxide film. The STS results vary across the oxide–alloy interface and between each oxide, providing greater insight into the origins of electronic heterogeneity and their effect on oxide growth. Using these data, we propose an oxidation model that highlights the growth of partial oxide layers on Ni–Cr(100) alloys within the pre-Cabrera–Mott regime.

Winter upper-ocean thermohaline variability observed from drifting ice platforms in the Amundsen Basin, Arctic Ocean

<p>We analyzed hydrographic data from several autonomous oceanographic buoys within the MOSAiC Distributed Network together with regular CTD casts from the MOSAiC Central Observatory during the 2019/20 winter in the Amundsen Basin. These drifting platforms can yield as small as ~300 m (or 10 min) horizontal resolution, providing unprecedented perspectives for the (sub)mesoscale dynamics. Full-depth CTD profiles yielded the first baroclinic Rossby radii (R<sub>1</sub>) of ~7.5 km, which is consistent with previous studies based on climatology. Near-surface layers shallower than the halocline were not always mixed. Restratification was commonly observed, suggesting the onset of baroclinic instabilities and/or eddies emanating from the lateral fronts. A surface-layer eddy with estimated radius of ~5 km was fortuitously observed and coincident with the surrounding mixed geostrophic shear in the vertical, that is, oppositely-sloping isopycnals within the depth range of ~20 – 200 m. This structure is reminiscent of the Charney-type baroclinic instability, resulting from a difference in the sign of the vertical gradient of the interior quasigeostrophic potential vorticity and that of the surface buoyancy forcing. A reconstructed surface dynamic height field supports this argument, showing that submesoscale to mesoscale surface lateral buoyancy gradients are ubiquitous. This result implies that the study domain could be inherently unstable and prone to generate baroclinic eddies. We also observed that the slopes of the density horizontal wavenumber spectra changed at the halocline depths (~40 – 75 m) after a ~3-day storm event with peak speeds ~ 20 m s<sup>-1</sup>. We hypothesize that such change could be related to the Ekman pumping due to large ice drift (~50 cm s<sup>-1</sup>) and its resultant stress curl during the storm. Our analyses underline that thinning Arctic sea ice and increasing ice drift could together trigger more oceanic heat flux into the cold halocline by storms, further deteriorating winter ice growth in the Amundsen Basin.</p>

Atom-vacancy hopping in ultra-high vacuum at room temperature in SrTiO3 (001)

The diffusion at atomic scale is of considerable interest as one of the critical processes in growth and evaporation as well as a probe of the forces at an atomically flat reconstructed surface. This atomic-scale migration is critical to investigate in strontium titanate (SrTiO3) as it possesses the same status in oxide electronics as does silicon in ordinary electronics based on elemental semiconductors. Here we show that (001) terminated SrTiO3 reconstructed surface is atomically unstable enough to allow atom-vacancy hopping at room temperature. In this work, SrTiO3 (001) single crystal (7 × 2 × 0.5 mm) was sputtered (0.5 keV, 2.5 µA, 10 min) and annealed multiple times in ultra-high vacuum (UHV) and imaged using scanning tunneling microscope (STM). A relatively unstable surface was observed at low-temperature annealing and tip–surface interactions caused dislocation of mass at the surface. Both square and zig-zag nanolines were observed with atomic resolution where an atom-vacancy hopping was observed in a square diline while imaging at room temperature. The hopping was ceased when sample was annealed at higher temperature and a more compact network of nanolines was achieved. Graphic abstract