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

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

Backward whirl in a simple rotor supported on hydrodynamic bearings

The asymmetric nature of the fluid film stiffness and damping properties in rotors supported on fluid film bearings causes a forward or a backward whirl depending on the bearing parameters and the speed of the rotor. A rotor was designed to exhibit backward synchronous whirl. The rotor-bearing system exhibited split criticals, and a backward whirl was observed between the split criticals. The orbital diagrams show the whirl pattern

Development of Test Items for Technical and General English Language with Specific Reference to Knowledge Domain of Bloom\u27s Taxonomy

Taxonomy of educational objectives has always been providing an objective and scientific framework both for setting educational objectives and restructuring test items for evaluation. This paper is an attempt to describe various components of the knowledge domain of Blooms taxonomy and design different test items which could be included in a typical question paper. The test items are based on the explanation of terms provided by Benjamin Blooms and are confined only to the domain of knowledge. The questions are restricted to the course contents of the first year BE engineering students at PSG college of Technology, the researcher\u27s workplace and are pitched at the level of intermediate and advanced learners, who are familiarized with the basic nuances of style, grammar, USAge, syntax and other elements of language through the course. The design of questions presuppose that a certain level of mastery in the English language has been attained the learners