Sound Radiated by a Supercritical Airfoil Operating in the Incompressible Regime

Measurements of far-field sound radiated by two and three-dimensional supercritical airfoils (ONERA OAT 15A) placed in a low Mach number flow were performed in an anechoic open-jet facility. The chord-based Reynolds numbers were between 156,000 and 468,000, while the Mach numbers ranged between 0.04 and 0.13. For the three-dimensional airfoil, two different aspect ratios (span-to-chord ratio) of 1.0 and 1.5 were considered. For comparison, the sound radiated by a symmetric NACA 0012 and cambered NACA 2412 airfoil was also measured under the same conditions. The noise from the two-dimensional airfoil was found to scale on the fifth power of Mach number. The noise generated by the cross-flow across the tip was the dominant noise source for the three-dimensional airfoils, particularly under high-lift conditions where it exceeds the noise from the mid-span portion across the considered frequency range. The tip noise spectra for the supercritical airfoils exhibit a prominent peak that scales with the free-stream velocity, but its frequency is a weak function of the lift on the airfoil and the aspect ratio. No such peak was observed for the NACA profiles even for higher lift conditions. The beamformed source maps for NACA profiles reveal an intense high-frequency noise source near the tip leading-edge which is much weaker for the supercritical airfoil due to differences in the curvature of the profiles. The tip noise spectra for the supercritical airfoil can be scaled on the fourth power of Mach number and the length-scale associated with the spectral peak. The tip noise peak magnitude and frequencies were found to be nearly independent of the airfoil aspect ratio; however, a reduction in AR was found to shift the tip noise source region further inboard. Stereo particle image velocimetry (PIV) measurements performed in a cross-plane behind the three-dimensional airfoils show that this is because a reduction in AR also shifts vortex core towards the mid-span. The PIV results were also used to quantify the meander of the tip vortex and it is shown that the amplitude of vortex meandering is independent of the angle of attack and the aspect ratio with a value between 0.5 – 0.6% of the chord-length for all cases considered

Quantum Chessboards in the Deuterium Molecular Ion

We present a new algorithm for vibrational control in deuterium molecules that is feasible with current experimental technology. A pump mechanism is used to create a coherent superposition of the D2+ vibrations. A short, intense infrared control pulse is applied after a chosen delay time to create selective interferences. A `chessboard' pattern of states can be realized in which a set of even- or odd-numbered vibrational states can be selectively annihilated or enhanced. A technique is proposed for experimental realization and observation of this effect using 5 fs pulses of 790 nm radiation, with intermediate intensity (5e13 W/cm2)Comment: 12 pages, 5 figure

On Coloring Resilient Graphs

We introduce a new notion of resilience for constraint satisfaction problems, with the goal of more precisely determining the boundary between NP-hardness and the existence of efficient algorithms for resilient instances. In particular, we study $r$-resiliently $k$-colorable graphs, which are those $k$-colorable graphs that remain $k$-colorable even after the addition of any $r$ new edges. We prove lower bounds on the NP-hardness of coloring resiliently colorable graphs, and provide an algorithm that colors sufficiently resilient graphs. We also analyze the corresponding notion of resilience for $k$-SAT. This notion of resilience suggests an array of open questions for graph coloring and other combinatorial problems.Comment: Appearing in MFCS 201

Development of IPM Package with Safe Pesticide Residue: 1. Cabbage

An IPM module with safe pesticide residues on cabbage, with already proven treatments such as carbosulfan, dimethoate, cypermethrin + profenofos and mancozeb under chemical method of control; NSP, Bacillus thuringiensis and Trichogramma bactrae under non chemical method of control were revalidated individually and in combination. Six releases of parasitoid T. bactrae at weekly intervals starting from 12 days after transplanting or spray of NSP 4% at 10-15 days interval, 4 times, starting from 20 days after transplanting, foliar spray of dimethoate and mancozeb gave good control of aphids, leaf blight and black rot respectively. Based on the effectiveness of the treatment and pesticide residues below their permissible levels in cabbage at harvest, a module was developed and tested in the field. The IPM package thus developed was found to control the pests effectively and at the same time the residues on the crop were within the safe limits

Multi-wavelength Diagnostics of the Precursor and Main phases of an M1.8 Flare on 2011 April 22

We study the temporal, spatial and spectral evolution of the M1.8 flare, which occurred in NOAA AR 11195 (S17E31) on 22 April 2011, and explore the underlying physical processes during the precursors and their relation to the main phase. The study of the source morphology using the composite images in 131 {\deg}A wavelength observed by the SDO/AIA and 6-14 keV revealed a multiloop system that destabilized systematically during the precursor and main phases. In contrast, HXR emission (20-50 keV) was absent during the precursor phase, appearing only from the onset of the impulsive phase in the form of foot-points of emitting loop/s. This study has also revealed the heated loop-top prior to the loop emission, although no accompanying foot-point sources were observed during the precursor phase. We estimate the flare plasma parameters viz. T, EM, power-law index, and photon turn-over energy by forward fitting RHESSI spectral observations. The energy released in the precursor phase was thermal and constituted ~1 per cent of the total energy released during the flare. The study of morphological evolution of the filament in conjunction with synthesized T and EM maps has been carried out which reveals (a) Partial filament eruption prior to the onset of the precursor emission, (b) Heated dense plasma over the polarity inversion line and in the vicinity of the slowly rising filament during the precursor phase. Based on the implications from multi-wavelength observations, we propose a scheme to unify the energy release during the precursor and main phase emissions in which, the precursor phase emission has been originated via conduction front formed due to the partial filament eruption. Next, the heated leftover S-shaped filament has undergone slow rise and heating due to magnetic reconnection and finally erupted to produce emission during the impulsive and gradual phases.Comment: 16 Pages, 11 Figures, Accepted for Publication in MNRAS Main Journa