Effects of winglet on transonic flutter characteristics of a cantilevered twin-engine-transport wing model

A transonic model and a low-speed model were flutter tested in the Langley Transonic Dynamics Tunnel at Mach numbers up to 0.90. Transonic flutter boundaries were measured for 10 different model configurations, which included variations in wing fuel, nacelle pylon stiffness, and wingtip configuration. The winglet effects were evaluated by testing the transonic model, having a specific wing fuel and nacelle pylon stiffness, with each of three wingtips, a nonimal tip, a winglet, and a nominal tip ballasted to simulate the winglet mass. The addition of the winglet substantially reduced the flutter speed of the wing at transonic Mach numbers. The winglet effect was configuration-dependent and was primarily due to winglet aerodynamics rather than mass. Flutter analyses using modified strip-theory aerodynamics (experimentally weighted) correlated reasonably well with test results. The four transonic flutter mechanisms predicted by analysis were obtained experimentally. The analysis satisfactorily predicted the mass-density-ratio effects on subsonic flutter obtained using the low-speed model. Additional analyses were made to determine the flutter sensitivity to several parameters at transonic speeds

A Critique of Drexler Dark Matter

Drexler dark matter is an alternate approach to dark matter that assumes that highly relativistic protons trapped in the halo of the galaxies could account for the missing mass. We look at various energetics involved in such a scenario such as the energy required to produce such particles and the corresponding lifetimes. Also we look at the energy losses from synchrotron and inverse Compton scattering and their signatures. The Coulomb repulsive instability due to the excess charge around the galaxies is also calculated. The above results lead us to conclude that such a model for DM is unfeasible.Comment: 4 pages, 10 equation

The impacts of solar wind on the Martian upper atmosphere

Since the first in-situ measurements of the altitude profile of upper atmospheric density and composition were carried out by the Viking lander missions in 1976, similar data are continuously gathered by MAVEN and MOM spacecraft orbiting Mars since their launch in September 2014 with mass spectrometers and other related payloads. Using near-simultaneous observations by the two orbiters, it is seen that both data sets indicate significant day-to-day variations of Argon density profiles in the thermosphere-exosphere, 150-300 km region, during the period 1-15, June 2018, when the solar EUV radiation did not show any appreciable change but the solar wind energetic particle fluxes did so. Extending this study to include the other parent atmospheric constituents carbon dioxide, helium, nitrogen and their photochemical products atomic oxygen, and carbon monoxide during the same period it is found that the density profiles of carbon dioxide and atomic oxygen also show similar variations with carbon dioxide densities showing an increasing trend similar to Argon, but a reversal of this trend for atomic oxygen densities. Using insitu and near simultaneous measurements of solar EUV fluxes and the solar wind plasma velocities and densities near MAVEN periapsis it is noted that, unlike the solar EUV radiation, solar wind parameters showed a decrease by a factor of 2-3. Hence, it is inferred that the energetic and penetrating solar wind charged particle impact-driven dissociation, ionisation and ion-chemical processes could decrease the carbon dioxide densities leading to an increase in atomic oxygen densities. This result is also discussed from the considerations of the proton gyro radius effect, pickup ions, sputtering, energetic neutral atoms driven ionisation and ion losses. Further data and modelling efforts would be necessary to confirm this finding.Comment: 20 pages, 10 figure

Diversity and composition of riparian vegetation across forest and agroecosystem landscapes of river Cauvery, southern India

The study aims to examine tree species richness, and composition and diversity of riparian forests across forest and agro-ecosystem landscapes observed along the river Cauvery of southern India. Riparian forest was sampled in a belt transect of size 100 à 50 m, at each of the 80 sampling plots scattered over a 318 km length along the river Cauvery. Total of 177 tree species belonging to 52 families, representing 2930 individuals, were recorded. Differences occurred between the forest and agro ecosystem landscape in terms of species richness, family richness and number of individuals observed, with a decrease in agro-ecosystem compared to forest landscape. Species similarity was low between the forest and agro-ecosystem landscapes. The Shannon-Wiener diversity index was higher for forest landscape (5.6) with more evenness in distribution. In the forest landscape, high importance value indices (IVI) were obtained for Terminalia arjuna, Pongamia pinnata, Hopea parviflora. In the agro-ecosystem, species Pongamia pinnata, Ficus benghalensis, Salix tetraspermae exhibited high IVI. Expansion of agricultural activities and other biotic pressures might have led to the variation in species composition between the forest and agro-ecosystem. Also, it has led to the decline in ripicole and evergreen species such as Hydnocarpus pentandra, Elaeocarpus tuberculatus, Madhuca neriifolia, Palaquium ellipticum, Myristica dactyloides, etc., consequently affecting the associated biodiversity of the river in the agro-ecosystem. Country needs to enact a permanent policy to protect and conserve riparian buffers to avoid further degradation and loss of biodiversity in the unregulated areas along the river. © International Society for Tropical Ecology