The autocatalytic oxidation ofp-phenylenediamines with peroxydisulfate can be strongly enhanced by irradiation in the presence of tri-2,2'-bipyridylylruthenium(II). R~( b p y ) 3~+ acts as photosensitizer and photocatalyst.First, R~( b p y ) 3~+ is formed by quenching excited R~* ( b p y ) 3~+ with S 2 0~~-.Then the ruthenium(II1) complex oxidizesp-phenylenediamine. The resulting R~( b p y ) 3~+ can start the cycle again. The photocatalytic oxidation of N,N-diethyl-p-phenylenediamine as well as the dark reactions were studied with stopped-flow techniques.

Low-pressure die cast (LPDC) is widely used in high performance, precision aluminum alloy automobile wheel castings, where defects such as porosity voids are not permitted. The quality of LPDC parts is highly influenced by the casting process conditions. A need exists to optimize the process variables to improve the part quality against difficult defects such as gas and shrinkage porosity. To do this, process variable measurements need to be studied against occurrence rates of defects. In this paper, industry 4.0 cloud-based systems are used to extract data. With these data, supervised machine learning classification models are proposed to identify conditions that predict defectives in a real foundry Aluminum LPDC process. The root cause analysis is difficult, because the rate of defectives in this process occurred in small percentages and against many potential process measurement variables. A model based on the XGBoost classification algorithm was used to map the complex relationship between process conditions and the creation of defective wheel rims. Data were collected from a particular LPDC machine and die mold over three shifts and six continuous days. Porosity defect occurrence rates could be predicted using 36 features from 13 process variables collected from a considerably small sample (1077 wheels) which was highly skewed (62 defectives) with 87% accuracy for good parts and 74% accuracy for parts with porosity defects. This work was helpful in assisting process parameter tuning on new product pre-series production to lower defectives.

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