Simulation of Temperature Field of Oil Film in Super-High Speed Hybrid Journal Bearing Based on FLUENT

The hybrid journal bearing with the high rigidity and rotation accuracy has been used in super-high speed grinding machine in some cases. But the main shortcoming of hybrid journal bearing is the higher temperature rise in the oil film when bearing works, which can lower the bearing capacity and cause the bearing failure due to the drop of oil viscosity and the larger thermal deformation. Fluent is a special CFD soft to simulate and analyze the flow and the heat exchange of liquid in the complex geometrical field. In this paper, the simulations of the temperature field of the oil film in the super-high speed hybrid journal bearing were performed by Fluent based on the mathematical models. The simulation results can not only forecast the flow state and the thermal properties of the bearing oil, but also find the design limitation of the bearing for the more improvement of the bearing design.

A New Volume Warping Method for Surface Reconstruction

Volumetric models of 3D objects have recently been introduced into the reverse engineering (RE) process. Grid-based methods are considered as the major technique for reconstructing surfaces from these volumetric models. This is mainly due to the efficiency and simplicity of these methods. However, these grid-based methods suffer from a number of inherent drawbacks, resulting from the fact that the imposed Cartesian grid in general is not well adapted to the surface, neither in size nor in orientation. In order to overcome the above obstacles a new iso-surface extraction method is proposed for volumetric models. The main idea is first to construct a geometrical field that is induced by the object’s shape. This geometrical field represents the natural directions and a grid cell size for each point in the domain. Then, the imposed volumetric grid is deformed by the produced geometrical field toward the object’s shape. The iso-surface meshes can be extracted from the resulting adaptive grid by any conventional grid-based contouring technique. The proposed method provides better approximation of the unknown surface and exhibits anisotropy, which is present inherently in the surface. Moreover, since the produced meshes are quad-dominant, Catmull-Clark subdivision surfaces are directly constructed from these meshes.

Theory and Modelling of Field-Induced Electron Emission

ABSTRACTThis paper addresses issues in the theory of field-induced electron emission. First, it summarises our present understanding of the theory of Fowler-Nordheim (FN) plots, and shows the relationship between a recent precise (in standard FN theory) approach to the interpretation of the FN-plot intercept and older approximate approaches. Second, it comments on the interpretation of FN plots taken from semiconductor field emitters. Third, it summarises the main points of a recent hypothesis about the mechanism of field-induced emission from carbonbased films and other electrically nanostructured heterogeneous (ENH) materials. Weaknesses in previous hypotheses are noted. It is hypothesised that thin films of all ENH materials, when deposited on a conducting substrate, will emit electrons in appropriate circumstances. Such films emit electrons at low macroscopic fields because they contain conducting nanostructure inside them: this structure generates sufficient geometrical field enhancement near the film/vacuum interface that more-or-less normal Fowler-Nordheim emission can occur. In connection with experiments on amorphous carbon films carried out by a group in Fribourg, it is shown that nanostructure of the size measured by scanning probe techniques should be able to generate field enhancement of the size measured in field electron spectroscopy experiments. This result provides a quantitative corroboration of other work suggesting that emission from amorphous carbon films is primarily due to geometrical field enhancement by nanostructures inside the film. Some counter-arguments to the internal-field-enhancement hypothesis are considered and disposed of. Some advantages of ENH materials as broad-area field emission electron sources are noted; these include control of material design.

Analysis of Measured I(V) Relations for Electron Emission from Insulating Diamond Films on Various SI Substrates

ABSTRACTIn this work, we shall analyze the performance of a geometrical interface roughness model to estimate current from p-type silicon into insulating diamond and compare the performance of that model to experimental data. A minimum number of adjustable parameters are invoked. While the model qualitatively accounts for trends in the experimental data, in particular, the shift from negative to positive slope on a Fowler Nordheim plot of the I(V) data, it does so at the expense of demanding ellipsoid parameters that appear to be unreasonable. We therefore conclude that a simple geometrical field enhancement model of interface roughness is insufficient to account for the current observed, and thus the theory must be augmented by a more comprehensive electron transport model at the interface.

Emergence of Spinless and Spin-1/2 Particles from Higher-Dimensional Gravity with D-Dimensional Torus as a Compact Manifold

Using gravitational action for four-dimensional theory of R2-gravity, it has been shown earlier that, at high energy level, Ricci scalar R behaves like a physical field in addition to its usual nature as a geometrical field. The physical aspect of R is represented by spinless particles, called riccions. It is shown here that riccions can also be obtained from multi-dimensional R2-gravity. Further it is shown that these riccions disintegrate into fermion and anti-fermion pairs under certain conditions. Some physical properties of these fermions (here called riccinos) are discussed. On the basis of the results obtained here, one is tempted to speculate that our physical universe might have emerged through decay of riccions and riccinos.

An Electrochemical Study of Porous Silicon

ABSTRACTThe I-V and impedance characteristics of p and n-type silicon electrodes in HF solutions have been determined. Three different I-V regimes are observed, one of which is associated with the on-set of localized dissolution. The formation of porous silicon takes place via a surface state mediated charge transfer mechanism. The position of the main recombination-generation center is estimated at 400 mV above the valence band edge. Localized dissolution is initiated at or close to active adsorption sites. It is then favoured because of geometrical field enhancement effects. Porous silicon has a surface chemistry that can be significant in luminescence.