Study of composites as substrate materials in large space telescopes

Nonmetallic composites such as the graphite/epoxy system were investigated as possible substrates for the primary mirror of the large space telescope. The possible use of fiber reinforced metal matrix composites was reviewed in the literature. Problems arising out of the use of composites as substrate materials such as grinding, polishing, adherence of reflective coatings, rigidity of substrate, hygrospcopici tendency of the composites, thermal and temporal stability and other related problems were examined

On weak shock diffraction in real gases

Asymptotic solutions are obtained for the two-dimensional Euler system for real gases with appropriate boundary conditions which describe the diffraction of a weak shock at a right-angled wedge; the real gas effects are characterized by a van der Waals type equation of state. The behavior of the flow configuration influenced by the real gas effects, that includes the local structure near a singular point, is studied in detail.Comment: 14 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:1405.066

Thermodynamics of free Domain Wall fermions

Studying various thermodynamic quantities for the free domain wall fermions for both finite and infinite fifth dimensional extent N_5, we find that the lattice corrections are minimum for $N_T\geq10$ for both energy density and susceptibility, for its irrelevant parameter M in the range 1.45-1.50. The correction terms are, however, quite large for small lattice sizes of $N_T\leq8$. We propose modifications of the domain wall operator, as well as the overlap operator, to reduce the finite cut-off effects to within 10% of the continuum results of the thermodynamic quantities for the currently used N_T=6-8 lattices. Incorporating chemical potential, we show that \mu^2 divergences are absent for a large class of such domain wall fermion actions although the chiral symmetry is broken for $\mu\neq0$.Comment: 11 pages, 15 figures include