A new-style four-wheeled driving (4WD) series-parallel hybrid electric vehicle (HEV) plus with a two speed transmission is presented in this paper. The system structure and operation principles are discussed systematically, and then the control strategy is proposed. Control strategy focus on the multi modes switch logic and power distribution. In addition, shifting strategy of the two speed transmission is researched. Simulation results indicate that the presented 4WD HEV can realize nice dynamic property; the presented control strategy is correct and effective.
In 4H-silicon carbide crystals, basal plane slip is the predominant deformation mechanism. However, prismatic slip is often observed in single crystals grown by the physical vapor transport method as the diameter expands to 6 inches or larger. Thermal modeling has shown that occurrence of prismatic slip is attributed to increased radial thermal gradients. While X-ray topography can be used to characterize the presence and extent of prismatic slip, the feasibility of using the chemical etching method to assess the extent of prismatic slip in an industrial setting is investigated. The distribution of scallop shaped etch pits oriented along the directions that correspond to prismatic dislocations, correlate well with the results of the thermal model that predicts the occurrence of prismatic slip dislocations. This capability of the etch pit method to characterize prismatic slip can be used to manage radial thermal gradients during PVT growth.
4H-SiC wafers with 12 um epilayer were implanted at the Tandem Van de Graaff facility at Brookhaven National Laboratory with tunable energy from 13 MeV up to 66 MeV. Lattice strains introduced by the implantation process were characterized in detail by synchrotron rocking curve X-ray topography (SXRCT) and reciprocal space maps (RSMs). It is observed that the strain levels correlate with the atomic mass and energy of acceleration of the dopant atoms.
Understanding the depth from which contrast from dislocations is still discernible (the effective penetration depth of the X-rays) in grazing-incidence synchrotron monochromatic beam X-ray topography is of great interest as it enables three-dimensional dislocation configuration analysis and accurate density calculations. To this end, systematic analysis has been performed of topographic and ray-tracing simulated contrast of basal plane dislocations with different Burgers vector and line direction combinations, and a universal method to determine the effective penetration depth based on ray tracing has been developed. This study reveals that the observable dislocation contrast depends on the effective misorientation associated with the dislocation modulated by the photoelectric absorption effect. The dislocations with larger effective misorientation tend to have longer projected length and correspondingly deeper effective penetration depths.
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