Solid-state combustion synthesis of ceramics and alloys in reduced gravity

Possible microgravity effects are explored in the combustion synthesis of ceramics and alloys from their constituent elements. Molten intermediates are typically present during the combustion process, thereby offering the chance for natural convection to take place. Numerical simulations suggest that the combustion front in concert with gravity may act as a partial zone-refinement mechanism which is attempting to sweep out porosity in the sample. Contrary to suggestions by dimensional analysis, no effects on the combustion rate are seen. An analytical model of the combustion velocity as a function of the gravitational field and the spreading rate of molten material gives the correct order of magnitude of the gravity effect as measured by centrifuge experiments

Classification of boundary Lefschetz fibrations over the disc

We show that a four-manifold admits a boundary Lefschetz fibration over the disc if and only if it is diffeomorphic to $S^1 \times S^3\# n \overline{\mathbb{C} P^2}$, $\# m\mathbb{C} P^2 \#n\overline{\mathbb{C} P^2}$ or $\# m (S^2 \times S^2)$. Given the relation between boundary Lefschetz fibrations and stable generalized complex structures, we conclude that the manifolds $S^1 \times S^3\# n \overline{\mathbb{C} P^2}$, $\#(2m+1)\mathbb{C} P^2 \#n\overline{\mathbb{C} P^2}$ and $\# (2m+1) S^2 \times S^2$ admit stable structures whose type change locus has a single component and are the only four-manifolds whose stable structure arise from boundary Lefschetz fibrations over the disc.Comment: 18 pages, 8 figures. Paper for the proceedings of the conference in honour of Prof. Nigel Hitchin on the occasion of his 70th birthda

Testing the Home Market Effects in a Multi-country World: The Theory

We extend the two-country model by Krugman (1980) to a multi-country set-up and show that the `home-market effect' highlighted with two countries does not readily extend to such a more general setting. In particular, we prove that the most important result, namely the disproportionate causation from demand to supply, generalizes only under the fairly implausible assumption of pairwise symmetric trade costs between all countries. We argue, therefore, that the implications of product differentiation for the structure of world trade are better characterized in terms of spatial (`accessibility') and non-spatial (`attraction') effects, and we provide a theory-based specification that suggests how to test the home market effect in a more general settinghome market effect; hub effect; market potential; new trade theory; economic geography

Ballast Quarterly Review, v06n1, Autumn 1990

A journal devoted to wit, the contents of which are intended to be insightful, amusing, or thought provoking.https://scholarworks.uni.edu/ballast/1019/thumbnail.jp

Ballast Quarterly Review, v20n1, Autumn 2004

A journal devoted to wit, the contents of which are intended to be insightful, amusing, or thought provoking.https://scholarworks.uni.edu/ballast/1075/thumbnail.jp

Ballast Quarterly Review, v07n4, Summer 1992

A journal devoted to wit, the contents of which are intended to be insightful, amusing, or thought provoking.https://scholarworks.uni.edu/ballast/1026/thumbnail.jp

Ballast Quarterly Review, v05n4, Summer 1990

A journal devoted to wit, the contents of which are intended to be insightful, amusing, or thought provoking.https://scholarworks.uni.edu/ballast/1018/thumbnail.jp