We search for Riemannian metrics whose Levi-Civita connection belongs to a given projective class. Following Sinjukov and Mikeš, we show that such metrics correspond precisely to suitably positive solutions of a certain projectively invariant finite-type linear system of partial differential equations. Prolonging this system, we may reformulate these equations as defining covariant constant sec...

This paper addresses the problem of tracing intruders who obscure their identity by logging through a chain of multiple machines. After discussing previous approaches to this problem, we introduce thumbprints which are short summaries of the content of a connection. These can be compared to determine whether two connections contain the same text and are therefore likely to be part of the same c...

OBGYN.net is pleased to announce a new interview section with Advisory Board member Lesa Childers. Childers is a PCOSupport Chapter Development Coordinator and is the founder of WNC PCOSupport. A great advocate for PCOS education,, Childers meets many doctors and medical professionals in her work with PCOSupport. This section will highlight different health professionals discussing their work r...

We characterize the models of Asher and Vieu’s first-order mereotopology RT0 in terms of mathematical structures with well-defined properties: topological spaces, lattices, and graphs. We give a full representation theorem for the models of the subtheory RT− (RT0 without existential axioms) as p-ortholattices (pseudocomplemented, orthocomplemented). We further prove that the finite models of RT...

In the paper “On the foundations of combinatorial theory III. Theory of binomial enumeration” [7-j, Mullin and Rota developed the theory of polynomials of binomial type (definitiou below). They observed that in many cases these sequences of polynomials and the linear relations between them, given by the so-called connection constants, could be treated set-theoretically. But the problem of exten...

Some considerable damage to steel structures during the Hyogo-ken Nanbu Earthquake occurred. Among them, many exposed-type column bases failed in several consistent patterns, such as brittle base plate fracture, excessive bolt elongation, unexpected early bolt failure, and inferior construction work, etc. The lessons from these phenomena led to the need for improved understanding of column base...

Moment-resisting frames have extensive usage in earthquake-prone areas and high ability in energy dissipation.After the earthquake in Northridge 1994,Kobe 1995 fixed connections of steel structures have shown poor performance and generally they were caught brittle fracture of beam flange weld to the column.In order to remedy to avoid similar situations in future earthquakes,researchers introduc...

Dual systems of steel moment frame and reinforced concrete shear wall have combined the advantages of steel frames and reinforced concrete shear wall. These walls have increased the lateral stiffness of steel frames and have reduced seismic demands on steel frames thus providing opportunities to use such system. In this research intermediate dual system of steel moment frame was chosen with int...

We study numerically how the intercellular conductance affects the process of spiral breakup in an array of coupled excitable cells. The cell dynamics are described by the Aliev-Panfilov model, and the intercellular connection is made via Ohmic elements. We find that decreasing intercellular conductance can prevent the breaking up of a spiral wave into a complex spatiotemporal pattern. We study...