In many distributed real-time systems, the workload can be modeled as a set of periodic tasks, each of which consists of a chain of subtasks executing on different processors.Synchronization protocols are used to govern the release of subtasks so that the precedence constraints among subtasks are satisfied and the schedulability of the resultant system is analyzable. Tasks have diflerent worst-case and average end-to-end response times when different protocols are used. In this papel; we consider distributed real-time systems with independent, periodic tasks andfixed-priority scheduling algorithms. We propose three synchronization protocols and conduct simulation to compare their performance with respect to the two timing aspects.

We introduce a new complexity regularization method for image denoising and explore the use of sophisticated complexity penalties. We have found improvements of the order of 2 dB in reconstructed image mean-squared error over existing complexity-regularized estimators.

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Application of electron diffraction (ED) to poly(ethy1ene naphthalate) (PEN) crystallized isothermally from the melt at 260°C has permitted determination of the a -and p-form unit cells. While the a-form lattice parameters and cell agree well with those proposed in the literature, a different cell is proposed for the pform (monoclinic, P2,lnI 1 space group; 4 chains, with a = 1.304 nm, b = 0.926 nm, c = 1.300 nm, a = 13 1.47", p = y = 90", p = 1.368 glcm'). The p-form crystals were large, resembling hedrites (axialites). A number of different, singlelone ED patterns from at least one additional two-chain unit cell (7) were found, indicating a large degree of PEN polymorphism. The y unit cell has not yet been determined. Nascent melt-polymerized samples were also examined, giving rise to both p-and y-type patterns. The y-patterns arise from extended-chain single crystals of variable thickness.'Dedicated to the memory of Prof. H.

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