The language Esterel has found success in many safety-critical applications, such as fly-by-wire systems and nuclear power plant control software. Its imperative style is natural to programmers building such systems and its precise semantics makes it work well for reasoning about programs. Existing semantics of Esterel generally fall into two categories: translation to Boolean circuits, or operational semantics that give a procedure for running a whole program. In contrast, equational theories enable reasoning about program behavior via equational rewrites at the source level. Such theories form the basis for proofs of transformations inside compilers or for program refactorings, and defining program evaluation syntactically. This paper presents the first such equational calculus for Esterel. It also illustrates the calculus's usefulness with a series of example equivalences and discuss how it enabled us to find bugs in Esterel implementations.
The feasibility of a newly proposed method for the removal of cutter marks in die finishing operations has been investigated. The method is based on the superposition of a tertiary motion onto the conventional cutter motions. Path equations that consider motion and geometric variables have been derived and used as a basis for the development of a computer simulation model for generating three-dimensional surface representations. It has been shown that the tertiary motion results in a considerable reduction in the volume of the material in the scallops or blend marks left on the surface.
Calculation of REV (representative elementary volume) properties of geological porous media refers to the process of creating a 3D digital representation of a rock sample, typically obtained from imaging techniques such as X-ray microtomography. This technique allows for a detailed analysis of the internal structure and the properties of rocks, as well as precise calculation of various flow parameters. However, one major challenge with calculation of REV properties of geological porous media is the high computational cost required to generate accurate results, especially for large and complex samples. In this study, we constructed 3D digital cores of dune sand and fractured shale using CT scanning technology, and then used two image processing techniques, namely digital core image resampling and cutting, to reduce the computational cost of calculating digital core permeability. Next, a fast permeability calculation method is employed to reduce the complexity of permeability calculation. Finally, we summarized the applicability of different image processing methods to different rock samples, and provided prerequisites for high computational cost digital core permeability calculation.
The permeability of porous materials determines the fluid flow rate and aids in the prediction of their mechanical properties. This study developed a novel approach that combines the discrete cosine transform (DCT) and artificial neural networks (ANN) for permeability analysis and prediction in digital rock images, focusing on nanoscale porous materials in shale formations. The DCT effectively captured the morphology and spatial distribution of material structure at the nanoscale and enhanced the computational efficiency, which was crucial for handling the complexity and high dimensionality of the digital rock images. The ANN model, trained using the Levenberg–Marquardt algorithm, preserved essential features and demonstrated exceptional accuracy for permeability prediction from the DCT-processed rock images. Our approach offers versatility and efficiency in handling diverse rock samples, from nanoscale shale to microscale sandstone. This work contributes to the comprehension and exploitation of unconventional resources, especially those preserved in nanoscale pore structures.
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