An efficient TDMA start-up and restart synchronization approach for distributed embedded systems

A desired attribute in safety-critical embedded real-time systems is a system time and event synchronization capability on which predictable communication can be established. Focusing on bus-based communication protocols, we present a novel, efficient, and low-cost start-up and restart synchronization approach for TDMA environments. This approach utilizes information about a node's message length that forms a unique sequence to achieve synchronization such that communication overhead can be avoided. We present a fault-tolerant initial synchronization protocol with a bounded start-up time. The protocol avoids start-up collisions by deterministically postponing retries after a collision. We also present a resynchronization strategy that incorporates recovering nodes into synchronization.     

Entropy Based Approach to Data Loss Reparation Through the Indeterminate Fine-Grained Parallel Computation

The new method of a gap recovery in symbol sequences is presented. A covering is combined from the suitable reasonably short strings of the parts of a sequence available for observation. Two criteria are introduced to choose the best covering. It must yield the maximum of entropy of a frequency dictionary developed over the sequence obtained due to the recovery, if an overlapping combined from the copies of strings from the available parts of the sequence exists. The second criterion identifies the best covering in case when one has to use any string to cover the gap; here the best covering must yield the minimum of specific entropy of the frequency dictionary developed over the available parts of the sequence against the one developed over the entire sequence obtained due to the recovery. Kirdin kinetic machine which is the ideal fine-grained structureless computer has been used to resolve the problem of the reconstruction of a gap in symbol sequence.     

Ionizing-Radiation Response of the GaAs/(Al, Ga)As PHEMT: A Comparison of Gamma- and X-ray Results

An experiment is reported on the effect of ⁶⁰Co gamma rays or 45-keV x-ray photons on the GaAs/(Al, Ga)As PHEMT. It is shown that x-ray treatment can improve the dc performance of the device in some cases. This finding is attributed in part to the annealing or modification of DX centers.     

Effect of proton radiation on the kinetics of phosphorescence decay in the ceramic material ZnS-Cu

The results of studying the dose dependences of the decay kinetics of phosphorescence excited by X-ray radiation in luminescent ZnS-Cu ceramic material before and after irradiation with 50-MeV protons are considered. An anomalous variation in the exponent of the hyperbolic phosphorescence curves was observed experimentally as the accumulated light sum increased. It is found from an analysis of the data obtained that two processes are involved in the decay: one of these is monomolecular and corresponds to the first-order kinetics; the other is bimolecular and corresponds to the second-order kinetics. Transitions of charge carriers delocalized from traps occur at the nonradiative-recombination centers induced by proton radiation. Recombination of these charge carriers at the emission centers in the course of decay is described by the second-order kinetics.     

Thermodynamics of Chemical Interactions in the CdTe–ZnTe–O2–C System during Melt Growth of Cd1 – x Zn x Te Crystals

Thermodynamic analysis is used to identify the possible chemical reactions of CdTe and ZnTe with the container material and gaseous atmosphere during Bridgman growth. Thermodynamic parameters of carbide and oxycarbide formation in the growth system are evaluated. The calculation results are consistent with the well-known fact that oxygen-containing impurities can be removed from the growth charge by calcination in hydrogen. Moreover, as shown in experiment, the removal of oxygen from the charge ensures a substantial decrease in the carbon content of the crystals.     

High-power 1320-nm wafer-bonded VCSELs with tunnel junctions

A new long-wavelength vertical-cavity surface-emitting laser structure is described that utilizes AlGaAs-GaAs mirrors bonded to AlInGaAs-InP quantum wells with an intracavity buried tunnel junction. This structure offers complete wavelength flexibility in the 1250-1650 nm fiber communication bands and reduces the high free-carrier losses and bonded junction voltage drops in previous devices. The intracavity contacts electrically bypass the bonded junctions to reduce threshold voltage. N-type current spreading layers and undoped AlGaAs mirrors minimize optical losses. This has enabled 134/spl deg/C maximum continuous-wave lasing temperature, 2-mW room-temperature continuous-wave single-mode power, and 1-mW single-mode power at 80/spl deg/C, in various devices in the 1310-1340 nm wavelength range.     

A new form of the Green function for a transversely isotropic body

Summary. The well known solutions for the Green function have a form which cannot be used directly in the degenerate case of equal roots. A simple algebraic procedure is described which allows us to derive new formulae for the Green function, which are valid in the case of equal roots. The case of an annular loading is considered in some detail. It is shown that the derived results are valid for z positive as well as z negative.