Buckling and Post-Buckling of Composite Shells with Asymmetric Meshing in Form of Axial Band in Numerical Model

Asymmetric meshing is a perturbation introduced in the numerical model without changing geometry, loading or boundary conditions. Asymmetric meshing is employed in the form of a band along axial direction of the shell model, the elements size in the axial band is reduced as compared with the rest of shell to produce asymmetry in the meshing and four amplitudes of asymmetry are used in a particular band. Asymmetric meshing affects predicted buckling load, buckling mode shape and post-buckling behaviour. The reduction in the buckling load using asymmetric meshing was observed to be about 18%, which depends mainly on area of asymmetric meshing and less on different magnitudes of asymmetry in the same area. The load-displacement curve behaviourusing asymmetric meshing technique is quite similar to the curve obtained by introducing geometric imperfection in the shell model.

A new species of Leiostracus from Bahia, Brazil (Gastropoda, Pulmonata, Orthalicidae)

A remarkable new species of pulmonate snail was recently collected in a small Atlantic Rainforest fragment near the city of Canavieiras, state of Bahia, Brazil, an area known for a high diversity of land snails. It is described herein as Leiostracus fetidus sp. nov. and can be easily identified by its color pattern of irregular brown to black axial stripes on a white to yellow background, a reddish axial band "separating" the white peristome from the rest of the shell and a broad brown spiral band surrounding the umbilical region. Other diagnostic features include a relatively small size, a proto columellar fold and two very weak folds delimiting the basal region of the aperture. This discovery is a reminder of how little this fauna is known and also an alarm for proper conservation of these forest fragments.

Natural Convection of a Liquid Metal in Vertical Circular Cylinders Heated Locally From the Side

An experimental study is made of natural convection in gallium melts enclosed by vertical circular cylinders with localized circumferential heating. Heating is done in an axial band at the mid-height, and both ends of the cylinder are cooled. In the present study, the cylinder aspect (Ar = height/diameter) ratio ranges from 2 to 10, and the Rayleigh number (Ra) ranges from 9.0 × 104 to 3.0 × 107. The Prandtl number is 0.021. Temperature measurements are made at six axial levels around the circumference of the cylinder to study thermal convection in the melt. A numerical analysis is also conducted to supplement the experimental information. When Ra is small, the melt is in steady toroidal motion. Above a certain Ra, the flow becomes nonaxisymmetric as a result of a thermal instability, in the case of Ar larger than 3. With increasing Ra, the motion becomes oscillatory, mainly in the upper half. When Ar is smaller than 3, the toroidal flow becomes nonaxisymmetric and oscillatory at the same time beyond a certain Ra. The conditions for the appearance of oscillations and the oscillation frequencies are investigated in detail.

Molecular Gas Band Radiation in Cylinders

The radiative heat flux in a molecular gas within a cylinder is formulated in terms of an axial band absorptance. The axial band absorptance function is used to reduce the two angular, one spatial, and one spectral integrals encountered to one angular and one spatial integral such as is encountered in radiative transfer problems with spherical symmetry. A closed form is obtained for the axial band absorptance for the exponential-winged band model. Illustrative results are presented for a cylindrical gas volume with trapezoidal, parabolic, or Gaussian temperature profile. Mean beam length, absorptivity, and emissivity of a cylinder of gas are obtained as a function of the optical depth at the band head.