Asymmetry of structural recovery

The glassy state is nonequilibrium in nature and exhibits a tendency to rmdergo structural relaxation toward equilibrium. This tendency of the glassy state to relax structurally toward equilibrium is often referred to as structural recovery. It was observed, however, that the progress towards structural recovery with time varies significantly between a down-quench and an up-quench. This is referred to as asymmetry of structural recovery. The norrlinearlty of the process is described by the following equation [16] ... 

Explain structural recovery and the asymmetry of structural recovery. 

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