Minimum stored energy

Key Words Nuclear magnetic resonance, Superconducting magnet, Minimum stored energy, Magnetic resonance imaging... 

Q. M. Tieng, V. Vegh and I. M. Brereton, Minimum stored energy high-field MRI superconducting magnets. IEEE Trans. Appl. Supercond., 2009,19,3645-3652. 

Minimum ignition energy (MIE) Lowest electrical energy stored in a capacitor which, upon discharge, is just sufficient to effect ignition of the most ignitable atmosphere under specified test conditions. 

Hie rationale in this case was that it. was considered feasible to determine the relative sensitivity or ranking of the expl tested among other expls despite the fact that an absolute minimum energy was not measured. This (approach has been followed in the tests conducted at PicArsn and at NOL, but none of these tests has been sufficiently evaluated to determine the fraction of stored energy actually delivered to the spark gaps or to det the delivery... 

Effects of S tze of Storage Capacitance. Regardless of the stored energy, no ignitions were observed for capacitances below a certain limit. The minimum energies for both contact and spark initiation were nearly, identical for a range of capacitance 100 to... 

The energy that can be stored by capacitance of an object can be compared with the minimum ignition energies of flammable gas-air mixtures and of dust-air mixtures... 

The point to notice is that a threshold level of stored energy in the bond is necessary before AG -> 0 and thus before the forward reaction can proceed. This stored energy is, of course, equal to AG and thus (when normalised) to the surface energy of the material. Thus we see that the kinetic model of fracture requires a minimum energy supply equal to the surface energy, which is the fracture criterion employed by Griffith. No contradiction therefore exists between the kinetic and Griffith theories. 

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