A Distributed Error Recovery Technique and Its Implementation and Application on UNIX

This paper presents a checkpoint setting technique to eliminate domino effect in backward recovery in distributed systems,which is very efficient,powerful,widely applicable and easy to be implememted.Besides theoretical analysis,an implementation on UNIX system and a package for software fault-tolerance are in- troduced.Then the problems of checkpoint management and process termination are discussed.

RECOVERY EXPERIMENTAL TECHNIQUES OF TENSILE IMPACT

Based on loading-unloading test, tensile impact recovery experimental techniques have been developed to obtain the isothermal stress-strain curves of materials under high strain rates. The thermal softening effect can be decoupled by comparing the isothermal stress-strain curves with the adiabatic stress-strain curves at the same strain rate. In the present paper, recovery experiments of brass have been carried out on a self-designed rotating disk tensile impact apparatus. According to the parabolic strain hardening power-law thermo-viscoplastic constitutive model, strain hardening parameter, strain rates strengthening parameter and thermal softening synthetical parameter have been decoupled from experimental results. Furthermore, from these parameters, one can determine the theoretical isothermal curves and adiabatic curves at high strain rates well-coinciding the experimental results respectively. It indicates that the recovery experimental techniques of tensile impact are effective and reliable and are important means for the study of thermo-mechanical coupling. The experimental results also reveals that brass is a typical thermo-viscoplastic material.

Pore-scale study of the effects of DTPA chelating agent flooding on oil recovery utilizing a clay-coated micromodel

The use of diethylenetriaminepentaacetic acid(DTPA)chelating agent has shown promising results for enhanced oil recovery(EOR)in prior research.Several mechanisms,mainly resulting from rock-fluid interaction,have been proposed for chelating agent flooding;however,little attention has been paid to fluid-fluid interaction thus far.The assessment of these mechanisms has primarily relied on macroscopic techniques such as core flooding.This paper aims to investigate the injection of DTPA brine and its dominant mechanisms at the pore scale using a clay-coated micromodel.The micromodel tests were performed under oil-wet and water-wet states.For a more precise examination of fluid/fluid interactions,the dynamic interfacial tension(IFT)and Zeta potential were measured.It was observed that the injection of DTPA brine in water-wet state changed the saturation distribution and increased oil recovery.Based on visual inspections,this change in saturation distribution could potentially be linked to the formation of micro-dispersions and viscoelastic interfacial phenomena.Micro-dispersions facilitate flow to unswept areas,and viscoelastic interface formation reshapes the interface between oil and brine,causing disconnected oil droplets to coalesce and thus increase recovery.Under the oil-wet state,the micro-dispersion formation and wettability alteration can be the dominant mechanisms,and the amount of recovered oil was higher than that observed in the water-wet state.Furthermore,Zeta potential measurements at the interface between brine and oil showed a more negative value for DTPA brine,which is effective in wettability alteration and micro-dispersions stability.The results indicate that IFT reduction was not significant enough to be considered the dominant mechanism,although it assists in DTPA brine penetration into the crude oil and subsequent micro-dispersion formation.