The complex-shift method is applied to the Kuzmin-Toomre family of discs to generate a family of non-axisymmetric flat distributions of matter. These are then superposed to construct non-axisymmetric flat rings. We also consider triaxial potential-density pairs obtained from these non-axisymmetric flat systems by means of suitable transformations. The use of the imaginary part of complex-shifte...

In the Lake Tanganyika cichlid Lamprologus callipterus, males were >12 times heavier than females, the most extreme sexual size dimorphism in this direction among animals. L. callipterus males construct nests of empty snail shells in which the females breed. If the ancestors of L. callipterus were small cichlids, both sexes may have used shells for shelter. If the ancestors were larger, snail s...

There are 509 expanding neutral hydrogen shells catalogued in the Small Magellanic Cloud (SMC), all apparently very young, with dynamical ages of a few Myr. To examine their relationship with young stellar objects we cross-correlated the shell catalogue with various catalogues of OB associations, super giants, Cepheids, WR stars, supernova remnants, and star clusters. The incidence of chance li...

The high efficiency of circular monocoque cylindrical shells in carrying axial loads is impaired by their extreme sensitivity to imperfections and there is an extensive body of literature that addresses this behavior. Instead of following this classical path, focused on circular cross-sections, this paper presents a novel approach that adopts optimal symmetry-breaking wavy cross-sections (wavy ...

Large crystalline molecular shells, such as some viruses and fullerenes, buckle spontaneously into icosahedra. Meanwhile multicomponent microscopic shells buckle into various polyhedra, as observed in many organelles. Although elastic theory explains one-component icosahedral faceting, the possibility of buckling into other polyhedra has not been explored. We show here that irregular and regula...

Elastic stability of ring and stringer-stiffened cylindrical shells under axial, internal and external pressures is studied using Ritz method. The stiffeners are rings, stringers and their different arrangements at the inner and outer surfaces of the shell. Critical buckling loads are obtained using Ritz method. It has been found that the cylindrical shells with outside rings are more stable th...

In the present research, the elastic buckling of composite cross-ply elliptical cylindrical shells under axial compression is studied through finite element approach. The formulation is based on shear deformation theory and the serendipity quadrilateral eight-node element is used to study the elastic behavior of elliptical cylindrical shells. The strain-displacement relations are accurately acc...

This paper develops a methodology for benchmarking knowledge-based systems that practitioners may use to perform a comparative analysis of expert system shells. A program utilizing a deliberate instructional mix was found to be the most suitable and accurate way to measure the value of shells. The benchmark is intended for rule-based shells, such as CLIPS, VP-Expert and Ibis. The methodology fo...

Unmodified versions of common computer programs such as MODFLOW, MT3DMS, and SEAWAT that use Cartesian geometry can accurately simulate axially symmetric ground water flow and solute transport. Axisymmetric flow and transport are simulated by adjusting several input parameters to account for the increase in flow area with radial distance from the injection or extraction well. Logarithmic weight...