National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Earth observation system incorporating an LCTF spectropolarimeter

Abstract: There is an emerging demand for remote sensing technologies that can determine the surface characteristics of objects from the properties of reflected light. In particular, hyperspectral analysis of solar rays reflected from the Earth's surface is expected to play an increasingly important role in Earth environment observation. The National Aerospace Laboratory (NAL) has developed a new type of imaging spectropolarimeter for such analysis that uses a liquid crystal tunable filter (LCTF), and efforts are now under way to develop it into a practical aircraft or spacecraft on-board sensor system for Earth environment sensing. This paper first presents the concept and architecture of an Earth observation system using an LCTF optical sensor which can sense radiation in the 400-720 nm wavelength band. The results of laboratory experiments to evaluate the performance characteristics of the observation system, e.g. hyperspectral resolution, optional selection of the plane of polarization, etc. are then presented, and the results of preliminary image acquisition experiments that demonstrate the feasibility of acquiring of spectral images is also shown. Finally, the applicability of the LCTF spectropolarimeter to Earth observation is summarized based on the results of the laboratory and field evaluation experiments.

CHARACTERIZATION AND HARDNESS OF Co–P COATINGS OBTAINED FROM DIRECT CURRENT ELECTRODEPOSITION USING GLUCONATE BATH

Abstract: Direct current electrodeposition of Co–P alloy coatings were carried out using gluconate bath and they were characterized by employing techniques like XRD, FESEM, DSC and XPS. Broad XRD lines demonstrate the amorphous nature of Co–P coatings. Spherical and rough nodules are observed on the surface of coatings as seen from FESEM images. Three exothermic peaks around 290, 342 and 390°C in DSC profiles of Co–P coatings could be attributed to the crystallization and formation of Co2P phase in the coatings. As-deposited coatings consist of Co metal and oxidized Co species as revealed by XPS studies. Bulk alloy P(Pδ-) as well as oxidized P(P5+) are present on the surface of coatings. Concentrations of Co metal and Pδ- increase with successive sputtering of the coating. Observed microhardness value is 1005 HK when Co–P coating obtained from 10 g L-1NaH2PO2 is heated at 400°C that is comparable with hard chromium coatings.

Oscillatory eddy structure in a container

Abstract: We consider the periodic, two-dimensional motion of a viscous, incompressible liquid which fills a rectangular container. The motion is due to the periodic motion of the13; lid which moves in its own plane. If the velocities are sufficiently small the motion will be governed by the linearized Navier-Stokes equations and consequently the13; dimensionless stream function V (x,z,t) = i/f(x,z)ett will satisfy the equation V4i/f x2014;irveV2^=0, where Re is the Reynolds number. If we then seek separable solutions13; for ^(.v, z) that satisfy the no-slip conditions on the sidewalls, it is easy to show that the problem reduces to the eigenvalue problem A tan iA = VA2 - iRe tan \ v/.2 - iRe where / is the eigenvalue. A detailed analysis is made of this eigenvalue problem. All the eigenvalues are complex; all eigenvalues with positive real part either belong to a set {/.quot;x201E;} in the upper half-plane or to another {/I',} in the lower half-plane. They satisfy13; the important relationship A', = A/A;;*quot; + iRe. We show by an asymptotic analysis that while the Aj, move to the neighbourhood of the real axis as Re -gt; GO, the Aquot; move away from the origin and approach the line A,- = Ar in the complex-A-plane. This fact has,an important bearing on the damping of gravity waves at high Reynolds numbers.13; The eigenfunctions derived above are used to write down a formal expansion for the stream function and the coefficients are determined from the boundary conditions13; using a least-squares procedure. An examination of the resulting streamline patterns reveals interesting inertial effects even at low Reynolds numbers. In particular we13; examine the mechanism by which the flow field reverses its direction when the lid stops and reverses its direction of motion. If inertial effects are completely negelected,13; as has been done till now, one would infer an immediate response of the fluid to the changes in the lid motion; for example, one would conclude, wrongly, that when the13; lid is at rest so is the fluid. Our analysis shows, in fact, a very intricate and beautiful mechanism, involving among other things an apparent engulfing of the corner eddy13; by the new primary eddy, by which the direction of the circulation is reversed in the fluid. These results should be of importance in the analysis of mixing, where such13; effects appear to have been ignored till now.

Institutional repositories in india: a case study of national aerospace laboratories

Abstract: This paper traces the history and developments in Open Archives Initiatives including open access journals, e-print archives and Institutional repositories The setting up of NAL's Institutional Repository using OSS GNU Eprints, document types with statistical analysis, country wise statistics of full text download, levels of accessibility and technologies used in building the Institutional Repository have been discussed at length