Fault impact and fault tolerance in multiprocessor interconnection networks

Growing complexity of parallel machines coupled with increasing chip densities escalates the need for fault tolerance and recovery in these systems. In pursuit of the goal of fault-tolerant multiprocessors, many techniques have been proposed. Since methods for designing fault-tolerant processors and memories are relatively mature, the techniques considered in this paper focus on the interconnection network (ICN) linking the processors. The impact of faults on non-fault-tolerant ICNs is contrasted with that in fault-tolerant networks. Fault tolerance in ICNs is addressed at two levels, inter-node or switch level and system level. Inter-node or switch level pertains to data and control integrity and system level deals with maintaining network connectivity and adequate performance levels in the presence of faults. Fault-tolerant schemes at the switching element level warrant some form of concurrent error detection such as the use of codes usually combined with a full handshake protocol. Space–time trade-offs involved in the use of various codes and protocols are investigated. At the system level, several augmented multi-stage switching ICNs, tree and ring networks are studied. The combined provision for fault tolerance together with improved performance in the non-fault condition is emphasized. Finally, strategies for network reconfiguration and rerouting after system failure are presented.     

Atomic migration on ordering and diffusion in bulk and nanostructured FePt intermetallic

“Order-order” kinetics was studied by means of in situ and quasi-residual resistometry in bulk polycrystal stoichiometric L1₀-ordered FePt and in epitaxially deposited FePt thin film. In addition, Fe diffusion in FePt thin film was examined by means of a combination of nuclear resonant scattering and nuclear tracer techniques. In bulk FePt, a discontinuous drop of the activation energy for chemical ordering (from 2.7–15 eV) was detected below 850 K, definitely away from the Curie point (735 K). The activation energy for Fe radiotracer diffusion in the FePt thin film studied below 900 K was found to be equal to 1.7 eV (in view of the value higher than 3 eV measured above 1100 K). Kinetic Monte Carlo simulations of order-order processes in bulk and nanolayered FePt reproduced their experimentally observed multi-time-scale character. In simulated FePt nanolayers, a reorientation of the initial z-variant L1₀ superstructure into a mixture of x and y variants was definitely a dominating process.     

Morphology and properties of polylactide modified by thermal treatment, filling with layered silicates and plasticization

Polylactide (PLA) was modified physically by filling with inorganic additives—organomodified particles of clay, unmodified particles of clay as well as with a plasticizer—poly(ethylene glycol). The PLA-based systems were prepared by melt blending of PLA with other components. Combination of PLA with organomodified clay particles formed nanocomposite with intercalated nanostructure, while introducing microparticles led to microcomposite, respectively. The clay concentration was maintained at 3 wt% in the both systems. Additionally unfilled PLA, plasticized PLA and plasticized nanocomposite were prepared under the same blending conditions. For plasticization, 10 wt% of poly(ethylene glycol) was used. Two groups of the PLA samples and PLA-based systems featured by starting amorphous structure or semicrystalline structure were considered, respectively. The structure, thermal behavior, thermo-optical properties and dynamic mechanical response of the PLA-based systems were investigated and compared with unfilled PLA of the same thermo-mechanical history and with the neat (unprocessed) PLA. The influence of the composition and thermal treatment on the structure and physical properties of the considered samples was determined. The effect of aging on the structure and crystallization ability of the PLA material from its glassy amorphous state was evaluated as well. Temperature modulated differential scanning calorimetry, thermo-optical analysis, X-ray diffraction technique, dynamic mechanical analysis (DMTA) were used.