Making of wing models by tangent-milling

Wings whose surfaces arc developable have been milled on a jig-borer at the National Aeronautical Laboratory, Bangalore, employing tangential milling. In this process, the Wing cross-section is approximated by a polygon which can be smoothened by hand-finish. The polygonal approximation itself is such that each side of the polygon is a tangent to the aerofoil. The aerofoil is defined by a finite set of points got from experiments or otherwise. These points are joined smoothly by using Spline approximation to achieve continuity of first and second13; derivatives. The splines and the settings of the jig-borer (for tangential milling) were obtained on the NAL SIRIUS Computer. Each setting of the jig-borer consists of the cutter-height and two turnings of the turnables one about the axis perpendicular to the turntable and the other about a fixed horizontal axis, so that the plane of milling becomes horizontal. The two angles of rotation and the cutter height depend upon the Wing geometry besides some of the machine parameters

Optical spectroscopy study on pressure-induced phase transitions in the three-dimensional Dirac semimetal Cd3_3As2_2

We report a room-temperature optical reflectivity study performed on [112]-oriented Cd$_3$As$_2$ single crystals over a broad energy range under external pressure up to 10 GPa. The abrupt drop of the band dispersion parameter ($z$-parameter) and the interruption of the gradual redshift of the bandgap at $\sim$4~GPa confirms the structural phase transition from a tetragonal to a monoclinic phase in this material. The pressure-induced increase of the overall optical conductivity at low energies and the continuous redshift of the high-energy bands indicate that the system evolves towards a topologically trivial metallic state, although a complete closing of the band gap could not be observed in the studied pressure range. Furthermore, a detailed investigation of the low-pressure regime suggests the possible existence of an intermediate state between 2 and 4~GPa , that might be a precursor of the structural phase transition or due to the lifted degeneracy of the Dirac nodes. Several optical parameters show yet another anomaly at 8~GPa, where low-temperature superconductivity was found in an earlier study.Comment: submitted to PR

Individual Morality in T. Janagraman's Novel 'Nalapagam'

T. Janagraman is of the opinion that they are responsible for his life. In the novel ‘Nalapagam’ the individual morality is explained as social morality through the character of Kameshwaran in this review article with relevant external and internal evidence. Man does not need to be touched on many occasions even one occasion creates a chance for a man to make a mistake. An example of this is illustrated in the Guru's life of Kameshwaran with nikanta introspection. Kameswaran, who has had a lifelong experience, is illustrated with appropriate acknowledgments that in his life, Rangamani avoids the life of sexual perversion caused by society's contempt for being childless by the way. Kameswaran's life events are explained with psychological evidence. The creativity of T. Janagraman is illustrated with relevant evidence from the point of view of the reviewer

Application of Navier-Stokes analysis to stall flutter

A solution procedure was developed to investigate the two-dimensional, one- or two-dimensional flutter characteristics of arbitrary airfoils. This procedure requires a simultaneous integration in time of the solid and fluid equations of motion. The fluid equations of motion are the unsteady compressible Navier-Stokes equations, solved in a body-fitted moving coordinate system using an approximate factorization scheme. The solid equations of motion are integrated in time using an Euler implicit scheme. Flutter is said to occur if small disturbances imposed on the airfoil attitude lead to divergent oscillatory motions at subsequent times. The flutter characteristics of airfoils in subsonic speed at high angles of attack and airfoils in high subsonic and transonic speeds at low angles of attack are investigated. The stall flutter characteristics are also predicted using the same procedure

Study of Trajectory of Spin-Stabilised Artillery Projectiles

Equations of motion for conventional spin-stabilised artillery projectile have been derived using a pseudo-stability axes system in addition to body-fixed and space-fixed axes systems. The aerodynamic forces and moments have been represented by their respective coefficients and the effects of Mach number and Reynolds number have been suitably accounted. The magnus terms which are significant at high rates of spin are estimated using a simple model. The set of equations have been partly linearised and solved numerically for a typical projectile using NAG system routines. Various trajectory parameters are computed and compared with the range-table data for the projectile. A parametric study had been carried out varying the aerodynamic coefficients to understand the sensitivity of the results obtained