A class of inherently fault tolerant distributed programs

Software for industrial process-control systems, such as nuclear power plant safety control systems and robots, can be very complex because of the large number of cases that must be considered. A design approach is proposed that uses decentralized control concepts, and is based on E.W. Dijkstra's concept of self-stabilizing systems (1974). This method greatly simplifies the software, so that its correctness can be verified more easily. A simple control system is described for a simulated robot that is tolerant of partial failure of controllers and mechanisms, and permits online repair and enhancement of the control functions     

The segregation of phosphorus to the free surface of a ferritic iron alloy at 723 to 823 K

The isothermal segregation of phosphorus to the free surface of an annealed polycrystalline Fe-Ni-Cr-C alloy, containing 0.06 wt pct P, has been studied by Auger electron spectroscopy between 723 and 823 K using anin situ heating technique. It is found that after high temperature argon-ion bombardment the kinetics of isothermal segregation are consistent with bulk (lattice) diffusion of phosphorus as the rate determining mechanism. An approximate value for the adsorption isotherm constant is deduced to be 8×10² per wt pct by a limited analysis of the kinetic data in terms of linear bulk diffusion with a boundary condition given by an ideal adsorption isotherm.     

Analysis of cool storage for air conditioning

The paper investigates the thermal performance of ice-water cool storage systems theoretically and experimentally. Cool storage systems are used to shift electric demand from periods of high demand to those of low demand. A general lump model to determine the thermal storage characteristics is developed. The solution of the system equations is found through a Laplace transformation method. Experimental data of temperature profiles obtained for both single container and packet containers under the conditions of various flow rates and different inlet coolant temperatures confirm the validity of the theory. A closed form solution of the required time for latent-heat storage has also been established on the basis of the quasi-steady-state assumption of the coolant.     

A clinical phase I/II study of recombinant human interleukin-1 receptor in glucocorticoid-resistant graft-versus-host disease

Graft-versus-host disease (GVHD) is the major complication of allogeneic bone marrow transplantation. GVHD is accompanied by the release of inflammatory cytokines, including interleukin (IL)-1, and previous work has demonstrated that IL-1 participates in the pathogenesis of GVHD. The recombinant human IL-1 receptor (rhuIL-1R) is the soluble form of the type I IL-1 receptor that can bind to IL-1 and prevent cellular activation. We report a phase I/II trial utilizing the rhuIL-1R in the treatment of allogeneic bone narrow transplant patients not improving with glucocorticoid therapy. RhuIL-R was given at four dose levels for 21 days to 14 patients with progressive or persistent acute GVHD. The study drug had no clinical or persistent hematopoiesis and the treatment was tolerated by patients without toxicity at all dose levels. Eight of 14 patients (57%) had an improvement of GVHD after rhuIL-1R therapy. Improvement in GVHD was noted at each dose level, although a dose-response effect for rhuIL-1R treatment was not observed. This work supports the concept that IL-1 plays a role in the inflammation associated with acute GVHD. A controlled study of the rhuIL-1R for treatment of prophylaxis of GVHD is warranted.     

Two necessary conditions for a complex polynomial to be strictlyHurwitz and their applications in robust stability analysis

The necessary conditions for a complex polynomial to be strictly Hurwitz are reviewed and rigorously proved. Both necessary conditions have been extended to cover nonmonic polynomials instead of monic polynomials. Also, based on these two results, some necessary conditions for an interval polynomial to be stable in terms of being strictly Hurwitz are obtained. They can be used to quickly determine the instability of a complex interval polynomial family. Finally, their application to the study of robust stability, in the case where coefficient perturbation intervals are functions of a single parameter, is briefly discussed     

Microstructural examination of extended crystal defects in silicon selective epitaxial growth

Selective epitaxial growth has been used to produce electronically isolated devices. The oxide/silicon interfaces in such materials are often associated with regions of poor device performance. In this study, the extended defects in the bulk near interfacial regions are examined by transmission electron microscopy. Process modifications suggest a large portion of the defects were due to thermal expansion mismatch and can be avoided.     

Measurement and simulation of residual stress in type 304 weld overlay stainless steel pipe

Repair by welding overlay is a commonly used method mainly employed to rebuild piping systems suffering from intergranular stress corrosion cracking (IGSCC). It is desirable that the overlay welding technique, by attaching an overlay weld to the pipe and sustaining a heat sink of flowing water inside the pipe, induces a compressive residual stress at the inner surface of the welded pipe for prevention of IGSCC. A better understanding of the effect of a welding overlay repair on the residual stresses at the inner and outer surfaces of weld overlay is thus required. To obtain this understanding, it is necessary to investigate the distribution of residual stresses on the welded pipe.

In this study, the hole-drilling strain-gauge method was adopted to determine the residual stresses at the inner and outer surfaces of the weld overlay pipe. The incremental drilling technique was used on pipes with outside diameters of 267 mm. In addition, the Weld 3 code was applied to simulate the residual stress distribution for comparison and verification with the measured results.

The results obtained from the experimental and from the computational methods are in good agreement. The residual stress at the inner surface of the pipe is compressive with a magnitude approaching the yield stress of the material; that at the outer surface is tensile, also with a magnitude close to yield stress but smaller than the compressive stress. The experimental residual stress magnitude is generally greater than that from computation. This observation can be attributed to several factors including applied mechanics, temperature distribution, original residual stress, strain gauge location, mechanical grinding and the oxidation layer.     

The cydra 5 minisupercomputer: Architecture and implementation

The Cydra 5 exploited both fine-grained and coarse-grained parallelism for a broad class of compute-intensive tasks. It utilized a unique architecture designed for efficient compilation and execution of inner loops, as well as parallel execution of nonloop code. We discuss the architecture and implementation of the numeric processor and its associated high-bandwidth memory system as well as attributes of the overall system.