Sharif Digital Repository

Workflow management systems are responsible for modeling and execution of business processes that are widely used as workflow systems in different organizations. The main advantage of the workflow management systems is to improve the efficiency of organizations and control of the processes. However, one of the main drawbacks in the current workflow management systems is the way that they can deal with changes in the workflow systems. In the other words, their capability of dynamic handling of changes occurred. Since a workflow system may be affected by different changes while it is applied in an organization, handling these changes efficiently and during its execution through a dynamic... 

In this study, the influence of eutectic modification, grain refining and cooling rate on amount of shrinkage porosity in aluminium A356 alloy were investigated. Modification process for changing the morphology of eutectic silicon from needle like to fibrous like, use in aluminium – silicon alloys. This process often leads to increasing porosity in melt and affect harmfully on mechanical properties. For studying shrinkage porosity, the melt degassed completely to minimizing amount of gas in the melt. For modification, strontium in Al-10Sr master alloy and sodium in NaF salt used and for grain refining Al-10Ti and Al-5Ti-1B master alloys used. To study the effect of cooling rate, three mold... 

Studies have shown that use of crumb rubber additive can improve the mechanical and performance properties of hot mix asphalts. Nowadays, different methods are used for adding crumb rubber to asphalt mixtures. However, no comprehensive research has been done to investigate the effects of these different methods in cold mix asphalts. In this research, different crumb rubber modification methods were evaluated to compare their effects on cold mix asphalts’ performance. In this regard, various crumb rubber modification methods, such as pre blending crumb rubber into the asphalt before emulsification, post blending crumb rubber into the prepared asphalt emulsion and blending crumb rubber with... 

The magnetic MOF-based catalytic system has been reported here to be an efficient catalyst for synthesis of benzonitriles and diarylethers of aryl halides under optimal conditions. The MOF catalyst was built based on magnetic nanoparticles and UiO-66-NH2 which further modified with 2,4,6-trichloro-1,3,5-triazine and 5-phenyl tetrazole and the catalyst structure was confirmed by various techniques. Furthermore, the products’ yields were obtained in good to excellent for all reactions under mild conditions which result from superior activity of the synthesized heterogeneous catalyst containing palladium. Also, the magnetic property of the MOF-based catalyst makes it easy to separate from... 

The possibility of time travel in modern physics based on the theory of relativity has led to the study of this issue from various aspects. In this research, the metaphysical possibility of time travel will be examined and therefore its physical and technological possibility is out of the subject of this research. Metaphysical possibility is also considered to mean the compatibility of time travel with the laws of metaphysics. The metaphysical possibility of time travel is challenged by the paradoxes that arise from it. These paradoxes, despite their great diversity, fall into four general categories: Temporal Paradoxes, The paradoxes of freedom, The paradoxes of Causal, and The paradoxes of...