Semi-empirical model for prediction of unsteady forces on an airfoil with application to flutter

A semi-empirical model is described for predicting unsteady aerodynamic forces on arbitrary airfoils under mildly stalled and unstalled conditions. Aerodynamic forces are modeled using second order ordinary differential equations for lift and moment with airfoil motion as the input. This model is simultaneously integrated with structural dynamics equations to determine flutter characteristics for a two degrees-of-freedom system. Results for a number of cases are presented to demonstrate the suitability of this model to predict flutter. Comparison is made to the flutter characteristics determined by a Navier-Stokes solver and also the classical incompressible potential flow theory

Shock effects on electronic components within a projectile

Launching a projectile generates severe shocks, which can result in the malfunction of electronic components within the device. The reliability of these components is related to the mode shapes, natural frequencies and the dynamic deflection of the Printed Circuit Boards. Structural vibration analysis of Printed Circuit Boards and their electronic components can be performed using both Finite Element Methods and vibration test. This study presents the effect of shock and the structural response of the electronic components within the projectile. The results are verified by experimental and modal analysis

The Origin of X-shaped Radio Galaxies: Clues from the Z-symmetric Secondary Lobes

Existing radio images of a few X-shaped radio galaxies reveal Z-symmetric morphologies in their weaker secondary lobes which cannot be naturally explained by either the galactic merger or radio-lobe backflow scenarios, the two dominant models for these X-shaped radio sources. We show that the merger picture can explain these morphologies provided one takes into account that, prior to the coalescence of their supermassive black holes, the smaller galaxy releases significant amounts of gas into the ISM of the dominant active galaxy. This rotating gas, whose angular momentum axis will typically not be aligned with the original jets, is likely to provide sufficient ram pressure at a distance ~10 kpc from the nucleus to bend the extant jets emerging from the central engine, thus producing a Z-symmetry in the pair of radio lobes. Once the two black holes have coalesced some 10^7 yr later, a rapid reorientation of the jets along a direction close to that of the orbital angular momentum of the swallowed galaxy relative to the primary galaxy would create the younger primary lobes of the X-shaped radio galaxy. This picture naturally explains why such sources typically have powers close to the FR I/II break. We suggest that purely Z-symmetric radio sources are often en route to coalescence and the concomitant emission of substantial gravitational radiation, while X-shaped ones have already merged and radiated.Comment: 12 pages, 1 compressed figure; accepted for publication in ApJ Letter

Multispectral Quantum Dots-in-a-Well Infrared Detectors Using Plasmon Assisted Cavities

We present the design, fabrication, and characterization, of multi-spectral quantum dots-in-a-well (DWELL) infrared detectors, by the integration of a surface plasmon assisted resonant cavity with the infrared detector. A square lattice and rectangular lattice cavity, formed by modifying the square lattice have been used in this design. By confining the resonant mode of the cavity to detector active region, the detector responsivity and detectivity have been improved by a factor of 5. A spectral tuning of 5.5 to 7.2 μm has been observed in the peak response of the detectors, by tuning the lattice constant of the cavity. Simulations indicate the presence of two modes of absorption, which have been experimentally verified. The use of a rectangular lattice predicts highly polarization sensitive modes in x- and y-direction, which are observed in fabricated detectors. A peak detectivity of 3.1 x 10^9 cm √(Hz)/W was measured at 77 K. This design offers a cost-effective and simple method of encoding spectral and polarization information, in infrared focal plane arrays

The effects of transients on photospheric and chromospheric power distributions

We have observed a quiet Sun region with the Swedish 1-meter Solar Telescope (SST) equipped with CRISP Imaging SpectroPolarimeter. High-resolution, high-cadence, H$\alpha$ line scanning images were taken to observe different layers of the solar atmosphere from the photosphere to upper chromosphere. We study the distribution of power in different period-bands at different heights. Power maps of the upper photosphere and the lower chromosphere show suppressed power surrounding the magnetic-network elements, known as "magnetic shadows". These also show enhanced power close to the photosphere, traditionally referred to as "power halos". The interaction between acoustic waves and inclined magnetic fields is generally believed to be responsible for these two effects. In this study we explore if small-scale transients can influence the distribution of power at different heights. We show that the presence of transients, like mottles, Rapid Blueshifted Excursions (RBEs) and Rapid Redshifted Excursions (RREs), can strongly influence the power-maps. The short and finite lifetime of these events strongly affects all powermaps, potentially influencing the observed power distribution. We show that Doppler-shifted transients like RBEs and RREs that occur ubiquitously, can have a dominant effect on the formation of the power halos in the quiet Sun. For magnetic shadows, transients like mottles do not seem to have a significant effect in the power suppression around 3 minutes and wave interaction may play a key role here. Our high cadence observations reveal that flows, waves and shocks manifest in presence of magnetic fields to form a non-linear magnetohydrodynamic system.Comment: 11 pages, 11 Figures, 4 movies (will be available online in ApJ). ApJ (accepted

Algorithm for Solving Tri-diagonal Finite Volume Discretized Linear Systems

In this paper we present efficient computational algorithms for solving finite volume discretized tri-diagonal linear systems. The implementation of the algorithm for steady state finite volume structured grids linear system using MS Excel is presented. An example is given in order to illustrate the algorithms

Titrimetric Determination of α-Amino Acids via Formation of Dithiocarbamates

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Titrimetric Determination of a-Amino Acids via Formation of Dithiocarbamates

721-72

Nanoscale quantum dot infrared sensors with photonic crystal cavity

We report high performance infrared sensors that are based on intersubband transitions in nanoscale self-assembled quantum dots combined with a microcavity resonator made with a high-index-contrast two-dimensional photonic crystal. The addition of the photonic crystal cavity increases the photocurrent, conversion efficiency, and the signal to noise ratio (represented by the specific detectivity D*) by more than an order of magnitude. The conversion efficiency of the detector at Vb=–2.6 V increased from 7.5% for the control sample to 95% in the PhC detector. In principle, these photonic crystal resonators are technology agnostic and can be directly integrated into the manufacturing of present day infrared sensors using existing lithographic tools in the fabrication facility

GC-MS ANALYSES OF LEAF AND ROOT EXTRACTS OF DIDYMOCARPUS TOMENTOSA

Objective: Didymocarpus tomentosa Wight., is a traditional medicinal plant used in the treatment of fever and skin allergy and the present study were conducted to identify the phytochemical constituents in leaf and root extracts using gas chromatography and mass spectrometry (GC-MS).Methods: The methanolic leaf and root extracts were analyzed using Shimadzu GCMS-QP 2010 gas chromatography-mass spectrometer. The mass spectrum of GC-MS was interpreted using the database of the National Institute of Standards and Technology (NIST).Results: The GC-MS analyses of leaf and root extracts revealed the presence of twenty six and twenty three phytochemical constituents respectively. 5-Hydrxoymethylfurfural (15.1%), cis, cis, cis-7,10,13-Hexadecatrienal (12.5%), Hexadecanoic acid (11.8%), Lupenone (29.1%), γ-Sitosterol (21.3%) and Lupeol (12.0%) were the major constituents. Conclusion: The leaf and root extracts of D. tomentosa possess various phytochemical constituents, which are of high therapeutic values.Â