Hubble, trouble, toil and space rubble: The management history of an object in space

This article tells the saga of the Hubble Space Telescope, and how the attempt to overcome the restrictions Earths atmosphere imposes upon astronomy, came to dominate the existence of NASA in the later part of the 20th century.This biography of an object is told over four stages fundamental to the order of management; development, failure, recovery and completion.With a failed mirror, what became hidden and forgotten, was once more revealed.With the wild and uncertain dimension of Hubble’s assemblage disclosing itself through malfunction, management was able to rescue through repair its prior unavailability. Eventually management has contended with Hubble’s demise as it fades out of view during the process of completion. Running in counterpart to the four stages of Hubble’s life will be an explication of the events using the work of Martin Heidegger, particularly his work and concepts of Being and Time (Heidegger, 1962)

Inverse and centreline segregation formation in twin roll cast AZ31 magnesium alloy

Two microstructure defects formed in the twin roll cast AZ31 strips were investigated: inverse and centreline segregations. A two-dimensional finite element thermal-fluid-stress model was employed to study the thermomechanical response of the AZ31 strip during twin roll casting process. The results showed that the key parameter for centreline segregation is the mushy zone thickness at centreline. For inverse segregation, the interaction between the yy peak stress at the centreline in the mushy zone and the solidified shell on the roll surface is the determinant parameter. The modelling results suggested increasing the setback distance decreases the risk of both defects. Moreover, scaling up the caster reduces the propensity to inverse segregation but appears to have a minor effect for centreline segregation formation