Analysing inaccurate artifact usages in workflow specifications

Although many workflow models have been proposed, analyses on artifacts are seldom discussed. A workflow application with well structured and adequate resources may still fail or yield unexpected results in execution due to inaccurate artifact manipulation, for example, inconsistency between data flow and control flow, or contradictions between artifact operations. Thus, artifact analysis is very important since activities cannot be executed properly without accurate information. This paper presents a three-layer workflow model for designing a workflow and characterises the behaviour of an artifact by its state transition diagram. By abstracting common usages of artifacts, six types of inaccurate artifact usage affecting workflow execution are identified and a set of algorithms to detect these inaccurate usages in workflow specifications is presented. An example is demonstrated and then related works are compared.     

Formation and retention of local melted films in AZ91 friction stir spot welds

The formation of local melted films during friction stir spot welding of as-cast AZ91D and thixomolded AZ91 material is investigated. The average temperatures close to the tip of the rotating pin vary from 438 to 454 °C during the dwell period in friction stir spot welding. These measured temperature values are higher than the melting temperature of α-Mg + Mg₁₇Al₁₂ eutectic (437 °C). It is suggested that the temperature in the stir zone during the dwell period is determined by the relative proportions of α-Mg and (α-Mg + Mg₁₇Al₁₂) eutectic material, which are incorporated during friction stir spot welding. Based on the stir zone temperature measurements and a detailed examination of material located at the root of the pin thread it is suggested that material is moved downwards via the pin thread and into the stir zone during the dwell period in friction stir spot welding. Evidence of local melted film formation is observed in the stir zone of AZ91 spot welds. It is suggested that melted films are retained since their dissolution rate is much slower in the high temperature stir zone than it is when melted films is formed in the stir zone during Al 7075-T6 friction stir spot welding. The spontaneous melting temperature, solute diffusion rate and the thermodynamic driving force for droplet dissolution are much higher during Al 7075-T6 friction stir spot welding.     

Problem on estimation of the content of <Superscript>131</Superscript>I in milk in the “iodine” period of the Chernobyl accident

Measurements of the beta-activity of milk, serving as the main source of information on the radioactive contamination of the environment by the iodine isotope ¹³¹I, carried out on a DP-100 radiometer in the early post-Chernobyl period (1986) in Belarus, have been mathematically simulated. The results obtained allow the conclusion that the indicated measurements should be analyzed again with consideration for all of the nuclides present in milk. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 102–108, November–December, 2007.     

Realization of high pressures and temperatures in the gas phase of a bubble liquid flowing through a nozzle

A steady flow of a bubble gas-liquid mixture in a nozzle having a circular cross section has been investigated. The possibility of realization of superhigh temperatures and pressures in the gas phase of the mixture in the region near the smallest cross section of the nozzle has been analyzed. The influence of the initial radius of the flow and the volume content of bubbles, determining the volumetric rate of flow of the liquid supplied to the nozzle, on the pattern of the flow has been considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 134–137, November–December, 2007.     

Mathematical Modeling of Heat and Mass Transfer in Evaporation of a Substance from a Porous Body in Vacuum

A problem of the Stefan type which describes heat and mass transfer in a porous body with the double phase transition liquid–ice–vapor has been formulated and solved.     

Internal nonlinear four-mode interactions of capillary oscillations of a charged drop

Analytical expressions for the shape of a charged drop of an incompressible liquid nonlinearly oscillating upon multimode initial deformation have been obtained for the first time to within the third order of smallness. The second-order corrections to oscillation frequencies are calculated depending on the spectrum of modes determining the initial deformation. The third-order calculations show that the fundamental mode amplitude may increase due to the energy exchange with higher modes in a large number of possible four-mode resonance interactions.     

Failure Analysis of Fuel System Assemblies

Fuel system assemblies used on recreational watercraft failed after a short time in service in a seawater environment. Examination of the assemblies revealed significant degradation of the polyacetal connectors of the wire subassemblies. Optical and microscopic evaluations indicated the complete loss of connector material implying decomposition of the resin, along with mud-cracking and a rough surface morphology signifying chemical attack. An elemental analysis performed on both an intact connector and degraded connector suggested a potential chemical agent in the form of zinc chloride. At elevated temperatures, concentrated zinc chloride solutions are known to decompose polyacetal resins. The source of the zinc chloride was established as corrosion products that resulted during the dezincification of the internal brass connector through exposure to saltwater in the application.