We consider the problem of feasible trajectory generation of an underactuated axi-symmetric spacecraft subject to two external torques acting on the plane normal to the symmetry axis. We derive the condition that must be satissed by an attitude history in order to be a feasible trajectory. W e then propose a methodology to generate trajectories satisfying this condition. Our approach makes use ...

It is well-known that the Einstein-Rosen solutions to the 3+1 dimensional vacuum Einstein's equations are in one to one correspondence with solutions of 2+1 dimensional general relativity coupled to axi-symmetric, zero rest mass scalar fields. We first reexamine the quantization of this midi-superspace paying special attention to the asymptotically flat boundary conditions and to certain functi...

An axi{symmetric problem for a penny{shaped crack bridged by bres is considered. The study is reduced to the analysis of a hy-persingular integral equation with respect to the relative crack{face separation over a circular domain occupied by crack. The special case of a large crack subjected to Mode{I loading is examined. A matched asymptotic expansions technique is used in order to estimate th...

The surface diffusion of an axi-symmetric solid, a whisker, subject to applied uniaxial stress, is studied numerically based on a new boundary integral formulation for periodic stress configurations. An efficient semi-implicit time-stepping scheme is developed to treat the serve stiffness due to high-order derivatives. When the initial perturbation is small the effect of the stress on the motio...

premixed combustion is widely used for reducing pollutant emission from combustion chambers. however, these systems may be sensitive to complex phenomena such as flashback. in the present study flame, flashback and structure of premixed laminar flames are investigated theoretically. the mathematical model includes the axi-symmetric continuity, navier stocks, energy, and species equations. combu...

We investigate the formation of acoustic horizons for an inviscid fluid moving in a pipe in the case of stationary and axi-symmetric flow. We show that, differently from what is generally believed, the acoustic horizon forms in correspondence of either a local minimum or maximum of the flux tube cross-section. Similarly, the external potential is required to have either a maximum or a minimum a...

We report the discovery of two symmetric spiral arms in the near-infrared (NIR) images of the starburst galaxy M 82. The spiral arms are recovered when an axi-symmetric exponential disk is subtracted from the NIR images. The arms emerge from the ends of the NIR bar and can be traced up to three disk scalelengths. The winding of the arms is consistent with an m = 2 logarithmic spiral mode of pit...

In this paper, we consider a vertically positioned cylindrical filtering element. Filtering occurs in the radial direction, therefore, direction of velocities liquid and suspended particles coincide with direction. The flow can be considered to one-dimensional radially axisymmetric. To describe such process, axisymmetric Stefan problem will formulated. mass balance formalism Darcy’s law are uti...