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.

Graphitic-carbon nitride support for the synthesis of shape-dependent ZnO and their application in visible light photocatalysts

Abstract: Shape-dependent synthesis of ZnO has been developed on the surface of g-C3N4 following a simple and reproducible strategy. Initially, graphitic-carbon nitride (g-C3N4) was synthesized by pyrolysis of urea which was further used to grow ZnO nanostructures via refluxing conditions. Different hydrolyzing agents, such as hexamethylenetetramine (HMT) and ammonia were used to synthesize dumbbell and cone structures, respectively. Apart from hydrolyzing agents, cetyltrimethylammoniumbromide (CTAB) was also used as a growth controlling agent. Structural, morphological and optical characterizations of the as-synthesized materials were performed by using FESEM, TEM, XRD, XPS, UV-vis etc. techniques. After successful synthesis, the as-synthesized heterostructures were explored as visible light driven photocatalysts towards organic pollutant (methylene blue and phenol) degradation. The photocatalytic performances of bare ZnO, dumbbell and cone structures of g-C3N4/ZnO as well as g-C3N4, have been examined thoroughly. Photocatalytic results revealed that g-C3N4/ZnO heterostructures exhibit a higher efficiency under the illumination of visible light as compared to pure g-C3N4. Superior photodegradation activity of the g-C3N4/ZnO heterostructure originated from the synergistic effect and high charge separation at the interface of g-C3N4 and ZnO has also been discussed.

Conceptual design of free flight with airborne separation assurance

Abstract: The study described in this paper originally only aimed at studying the human factors problems of airborne separation hi a Free Flight environment. However to define the Free Flight environment with sufficient detail, a concept was designed at NLR. This conceptual design includes rules-of-the-sky, a conflict resolution algorithm, conflict detection, cockpit display recommendations, system description as well as operational implications. The feasibility of the design has been evaluated in three sub-studies: (i) off-line traffic simulations with very high traffic densities and a total of up to 300 aircraft, (ii) a safety analysis comparing the resolution method with current day ATC and (iii) a man-in-the-loop simulator experiment hi traffic densities up to three times the average WestEuropean traffic density with eight air line crews. None of these studies could refute the feasibility of the Free Flight conceptual design.

Shockwave/Boundary-Layer Interaction Control on a Compression Ramp Using Steady Micro Jets

Abstract: An experimental investigation was conducted to control the amplitude of shock unsteadiness associated with a 24 deg compression-ramp-induced interaction in a Mach 2 flow.Two control configurations in the form of an array of 1) 16 90-deg-pitched steady micro-air-jet vortex-generating devices (AJVG1), and 2) eight pairs of 45-deg-pitched steady micro-air-jet vortex-generating devices (AJVG2) were studied. EachAJVGdevice was placed upstream of the interaction region at 12:5� from the compression corner. Both micro-AJVG configurations show a reduction in separation shock strength and help considerably reduce the height of the lambda-wave triple point with increase in Poj . Pitching the microjets at 45 deg, as in the AJVG2 configuration, prevents a stronger control-generated bow shock to form ahead of the injectors and, hence, reduces the obstruction component of the interaction significantly. A well defined separation line for no control is seen to get replaced by a highly corrugated separation line with control. Significant reduction (up to 67%) in the peak rms value is observed in the intermittent region of separation with AJVG1 for Poj � 208:5 kPa while the same is achieved with AJVG2 at a much higher Poj�>500 kPa�. The spectral content of the pressure fluctuations also indicate that, relative to the AJVG2 configuration, AJVG1 is successful in reducing the amplitude of fluctuations in the range of unsteadiness by an order of magnitude as soon as Poj exceeds 208.5 kPa. The amplitude of these fluctuations is seen to further decrease with increase in Poj.

Optical oxygen sensing based on luminescence quenching of platinum porphyrin dyes doped in ormosil coatings

Abstract: Organically modified sol–gel films (ormosils) doped with platinum porphyrin dyes were prepared by using acid-catalyzed hydrolysis and condensation of methyl triethoxysilane (MTEOS) as precursor. The process variables like water to precursor molar ratio, acid concentration and aging time of the acid-catalyzed MTEOS-based sol were controlled to obtain ormosil coatings with good sensor properties. The effect of dopant concentration on the oxygen sensitivity was studied. The photophysical properties and decay kinetics of the coatings were studied and compared. Stern–Volmer plots for both PtOEP- and PtTFPP-doped sensor coatings were linear. The oxygen sensitivities (I0/I100) of these sensor coatings were found to be about 28 and 50 for PtTFPP and PtOEP, respectively. The ormosil coatings doped with porphyrin dyes exhibited higher oxygen sensitivity and better photostability compared to other silicone-based sensor coatings. Hence they may have good potential for surface pressure measurements in aerodynamic applications.