On the Design of Pulse Detonation Engines

This report addresses some basic issues in the structural and performance aspects of Pulse Detonation Engines (PDEs). Performance parameters studied include thrust-specific-fuel-consumption (TSFC), frequency limits, and thrust-to-weight ratio. A design surface is developed that accounts for various design limits. The structural aspects deal with critical parameters, material properties, and phenomena such as engine geometry, mass, yield stress, structural resonance due to flexural wave excitation, critical flaw size, and fracture toughness. Four materials for PDEs were chosen for comparison: silicon nitride, inconel, steel, and aluminum. Estimates of wall thickness and thrust-to-weight ratio are given over a range of operating conditions. Key issues and areas for further work are identified for both propulsion and performance aspects

Effects of antimicrobial food additives on growth and ochratoxin A production by Aspergillus sulphureus and Pencillium viridicatum

The effects of antimicrobial food additives on growth and ochratoxin A production by strains of Aspergillus sulphurous NRRL 4077 and Penicillium viridicatum NRRL 3711 were investigated! At pH 4.5» in order to obtain 100^ inhibition of both mycelium and toxin production, 0.02, O.O67, 0.0667, and 0.2% of potassium sorbate, methyl paraben, sodium bisulfite, and sodium propionate were required, respectively. At pH 5-St 0.134^ of potassium sorbate and 0.067% of methyl paraben completely inhibited the growth and ochratoxin A production by both fungi. Sodium bisulfite at 0.1% and sodium propionate at 0»6k% were found to inhibit fungal growth by the following percentages, respectively: A. sulphureus NRRL 4077, 45.45^, P. viridicatum NRRL 3711. 89.38%-, A. sulphureus NRRL 4077-, 79-91^, P. viridicatum NRRL 3711, 88.^5%. For toxin inhibition, the following percentages were achieved according to their previous sequence: 97\u27l?. 99•89. 99=40, and 100^

Well-posedness of The Prandtl Equation in Sobolev Spaces

We develop a new approach to study the well-posedness theory of the Prandtl equation in Sobolev spaces by using a direct energy method under a monotonicity condition on the tangential velocity field instead of using the Crocco transformation. Precisely, we firstly investigate the linearized Prandtl equation in some weighted Sobolev spaces when the tangential velocity of the background state is monotonic in the normal variable. Then to cope with the loss of regularity of the perturbation with respect to the background state due to the degeneracy of the equation, we apply the Nash-Moser-Hormander iteration to obtain a well-posedness theory of classical solutions to the nonlinear Prandtl equation when the initial data is a small perturbation of a monotonic shear flow