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In the past few decades the number of airplanes has increased dramatically and aircraft systems have become increasingly more complex. Under these conditions, the next generation of airplanes will undergo substantial changes and will make significant technical progress to improve operational safety. This vision is entirely consistent with the adoption of Integrated Vehicle Health Management (IVHM) technology which uses merging of interdisciplinary trends to carry out safe and effective vehicle operation. Hitherto, IVHM has made much progress in the realm of maintenance and operation, but little on safety assessment. This paper discusses the issues around how IVHM could be used to aid the operational safety assessment in the aviation industry. Special attention is paid to existing safety assessment methods, and some challenges and promising research directions are highlighted.

Selective Catalytic Reduction (SCR) is a leading aftertreatment technology for the removal of nitrogen oxide (NOx) from exhaust gases (DeNOx). It presents an interesting control challenge, especially at high conversion, because both reagents (NOx and ammonia) are toxic, and therefore an excess of either is highly undesirable. Numerous system layouts and control methods have been developed for SCR systems, driven by the need to meet future emission standards. This paper summarizes the current state-of-the-art control methods for the SCR aftertreatment systems, and provides a structured and comprehensive overview of the research on SCR control. The existing control techniques fall into three main categories: traditional SCR control methods, model-based SCR control methods, and advanced SCR control methods. For each category, the basic control technique is defined. Further techniques in the same category are then explained and appreciated for their relative advantages and disadvantages.