It is very important to know how to allocate tolerances economically for parts in a CAD

[1] During fast fluid flows in Earth's magnetotail, the plasma distribution function often takes the form of one beam flowing through another, which raises the question of whether bursty bulk flows can reasonably be represented in terms of single-fluid magnetohydrodynamics, either in global MHD codes or in thin filament theory. An exact kinetic solution is compared with exact fluid solutions for a simplified case of cold, collisionless particles in a pipe, under conditions where there are counterstreaming beams similar to the ones that often occur in Earth's magnetotail. The results from kinetic theory differ from standard fluid theory but are exactly consistent with Chew-Goldberger-Low double-adiabatic fluid theory. Double-adiabatic MHD equations are derived for the motion of a thin filament through a medium. An initial simulation is presented of a doubleadiabatic filament that starts out with lower gas pressure than nearby flux tubes. As in earlier calculations for the isotropic case, the near-equatorial part of the filament moves rapidly earthward. A compressional shock wave forms in the filament near the equatorial plane and propagates earthward. The near-equatorial region of the filament exhibits characteristics similar to a flow burst, while the behavior far from the equatorial plane resembles that of earthward-streaming plasma sheet boundary layer. The double-adiabatic filament becomes firehose unstable after the shock wave reflects from the earthward boundary of the simulation and propagates back into the tail.

For deep-water Gulf of Mexico, accurate salt geometry is critical to subsalt imaging. This requires the definition of both external and internal salt geometries. In recent years, external salt geometry (i.e., boundaries between allochthonous salt and background sediment) has improved a great deal due to advances in acquisition, velocity model building, and migration algorithms. But when it comes to defining internal salt geometry (i.e., intrasalt inclusions or dirty salt), no efficient method has yet been developed. In common industry practices, intrasalt inclusions (and thus their velocity anomalies) are generally ignored during the model building stages. However, as external salt geometries reach higher levels of accuracy, it becomes more important to consider the once-ignored effects of dirty salt. We have developed a reflectivity-based approach for dirty salt velocity inversion. This method takes true-amplitude reverse time migration stack volumes as input, then estimates the dirty salt velocity based on reflectivity under a 1D assumption. Results from a 2D synthetic data set and a real 3D Wide Azimuth data set demonstrated that the reflectivity inversion scheme significantly improves the subsalt image for certain areas. In general, we believe that this method produces a better salt model than the traditional clean salt velocity approach.

In modern manufacturing engineering, tolerance synthesis is important because it directly e ects product quality and manufacturing cost. This paper introduces a new method for tolerance synthesis of machining parts. The new method consists of three steps. First, machining parts are evaluated using the second-order fuzzy comprehensive evaluation (FCE). Then, a mathematical model for tolerance allocation is formed based on the machinability of the parts. Finally, the model is solved using the genetic algorithm (GA). The feasibility of the method is validated using a practical gearbox design example.

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