26,013 research outputs found
A finite element solver for 3-D compressible viscous flows
Computation of the flow field inside a space shuttle main engine (SSME) requires the application of state of the art computational fluid dynamic (CFD) technology. Several computer codes are under development to solve 3-D flow through the hot gas manifold. Some algorithms were designed to solve the unsteady compressible Navier-Stokes equations, either by implicit or explicit factorization methods, using several hundred or thousands of time steps to reach a steady state solution. A new iterative algorithm is being developed for the solution of the implicit finite element equations without assembling global matrices. It is an efficient iteration scheme based on a modified nonlinear Gauss-Seidel iteration with symmetric sweeps. The algorithm is analyzed for a model equation and is shown to be unconditionally stable. Results from a series of test problems are presented. The finite element code was tested for couette flow, which is flow under a pressure gradient between two parallel plates in relative motion. Another problem that was solved is viscous laminar flow over a flat plate. The general 3-D finite element code was used to compute the flow in an axisymmetric turnaround duct at low Mach numbers
Magnoliopsida, Gamopetalae, Gentianales, Asclepiadaceae, <I>Heterostemma deccanense</i> (Talb.) Swarup & Mangaly: Distribution, extension and geographic distribution map
Blasim: A computational tool to assess ice impact damage on engine blades
A portable computer called BLASIM was developed at NASA LeRC to assess ice impact damage on aircraft engine blades. In addition to ice impact analyses, the code also contains static, dynamic, resonance margin, and supersonic flutter analysis capabilities. Solid, hollow, superhybrid, and composite blades are supported. An optional preprocessor (input generator) was also developed to interactively generate input for BLASIM. The blade geometry can be defined using a series of airfoils at discrete input stations or by a finite element grid. The code employs a coarse, fixed finite element mesh containing triangular plate finite elements to minimize program execution time. Ice piece is modeled using an equivalent spherical objective that has a high velocity opposite that of the aircraft and parallel to the engine axis. For local impact damage assessment, the impact load is considered as a distributed force acting over a region around the impact point. The average radial strain of the finite elements along the leading edge is used as a measure of the local damage. To estimate damage at the blade root, the impact is treated as an impulse and a combined stress failure criteria is employed. Parametric studies of local and root ice impact damage, and post-impact dynamics are discussed for solid and composite blades
Resistance of dent corn to Basisporium gallarum Moll.
Injury by Basisporium gallarum is associated with cessation of translocation within the corn plant. It occurs at the time of germination, after normal maturity, and when plants die prematurely from cold or other causes.
Basisporium-infected seed dies within a few days after it is planted in soils slightly below the temperature range for germination. The organism kills the germ before active translocation sets in. Active translocation, in this case, means germination and germination marks a change in the embryo from neutral to acid reaction. Acid reaction in the cob was shown to be correlated with resistance to Basisporium infection. Therefore, the fact that the germinating kernel becomes resistant at the same time that the embryo becomes acid may mean that there is a similar correlation between acidity and resistance in the seed as has been shown between the acidity of the cob and resistance to Basisporium ear infection. Therefore, good field stands are correlated with warm soil temperatures which promote rapid germination and poor field stands with cold soil temperatures which make germination slow.
Seed treatments are most beneficial under conditions suitable to greatest injury by the organisms, namely, cold soil at time of germination.
Seed corn strains which germinate readily at low temperatures (below 11°C.) . are injured little by Basisporium gallarum. Seed corn strains requiring high temperatures (above 11°C.) for germination are severely injured by B. gallarum.
Experiments on artificial inoculation of corn ears with Basisporium gallarum indicated that when natural inoculum was widespread the number of infected ears was not significantly increased by artificial wound inoculations. With or without artificial inoculation, susceptible ears became infected and the resistant ears did not. A similar experiment in a year when natural infection was much less (6 percent in check), gave an increase (9 percent in inoculated) following artificial inoculation.
The resistant ears are those having high hydrogen ion concentration in the cobs. The susceptible ones are those having low hydrogen ion concentration in the cobs.
Cob reaction is an inherited character and promises a means of more easily breeding strains of corn resistant to Basisporium ear-rot.
The correlation between the ability to germinate at low temperature and the resistance to injury by the organism is the basis for breeding strains of corn resistant to seed rotting by Basisporium gallarum at time of germination
Dispersion and decay of collective modes in neutron star cores
We calculate the frequencies of collective modes of neutrons, protons and
electrons in the outer core of neutron stars. The neutrons and protons are
treated in a hydrodynamic approximation and the electrons are regarded as
collisionless. The coupling of the nucleons to the electrons leads to Landau
damping of the collective modes and to significant dispersion of the low-lying
modes. We investigate the sensitivity of the mode frequencies to the strength
of entrainment between neutrons and protons, which is not well characterized.
The contribution of collective modes to the thermal conductivity is evaluated.Comment: 10 pages, 4 figure
Ethnomedicinal Observations Among the Kondareddis of Khammam District, Andhra Pradesh, India
Ethnomedicinal information of Kondareddis has been collected from Khammam district of Andhra Pradesh, India during 2006-2008. A total of 40 plant species belonging to 39 genera and 31 families were used in traditional medicine to heal different diseases. The present work is an attempt to identify and conserve the medicinal plants in Khammam district. The study shows a high degree of ethnobotanical novelty and the use of plants among the Kondareddis reflects the revival of interest in traditional folk culture
Trust Based Participant Driven Privacy Control in Participatory Sensing
Widespread use of sensors and multisensory personal devices generate a lot of
personal information. Sharing this information with others could help in
various ways. However, this information may be misused when shared with all.
Sharing of information between trusted parties overcomes this problem. This
paper describes a model to share information based on interactions and opinions
to build trust among peers. It also considers institutional and other controls,
which influence the behaviour of the peers. The trust and control build
confidence. The computed confidence bespeaks whether to reveal information or
not thereby increasing trusted cooperation among peers.Comment: 14 page
Ethnobotanical Survey on Respiratory Disorders in Eastern Ghats of Andhra Pradesh, India
An Ethnopharmacological survey of the Eastern Ghats region of Andhra Pradesh, comprising Chittoor, Cuddapah, East Godavari, Guntur, Khammam, Krishna, Kurnool, Srikakulam, Visakhapatnam, Vijayanagaram and the West Godavari districts, was conducted during 2000-2005. Eighty-four species of folk drug plants belonging to 72 genera and 41 families were found to be used as a remedy for respiratory disorders by the rural people and forest ethnic people (Chenchus, Erukulas, Lambadas, Koyas, Kondareddies, Nukadoras, Yanadis). The scientific, vernacular and family names of these medicinal plants, along with the parts used and the mode of their administration are enumerated
X-ray properties of UV-selected star forming galaxies at z~1 in the Hubble Deep Field North
We present an analysis of the X-ray emission from a large sample of
ultraviolet (UV) selected, star forming galaxies with 0.74<z<1.32 in the Hubble
Deep Field North (HDF-N) region. By excluding all sources with significant
detected X-ray emission in the 2 Ms Chandra observation we are able to examine
the properties of galaxies for which the emission in both UV and X-ray is
expected to be predominantly due to star formation. Stacking the X-ray flux
from 216 galaxies in the soft and hard bands produces significant detections.
The derived mean 2-10 keV rest-frame luminosity is 2.97+/-0.26x10^(40) erg/s,
corresponding to an X-ray derived star formation rate (SFR) of 6.0+/-0.6
Msolar/yr. Comparing the X-ray value with the mean UV derived SFR, uncorrected
for attenuation, we find that the average UV attenuation correction factor is
\~3. By binning the galaxy sample according to UV magnitude and colour,
correlations between UV and X-ray emission are also examined. We find a strong
positive correlation between X-ray emission and rest-frame UV emission. A
correlation between the ratio of X-ray-to-UV emission and UV colour is also
seen, such that L(X)/L(UV) increases for redder galaxies. Given that X-ray
emission offers a view of star formation regions that is relatively unaffected
by extinction, results such as these can be used to evaluate the effects of
dust on the UV emission from high-z galaxies. For instance we derive a
relationship for estimating UV attenuation corrections as a function of colour
excess. The observed relation is inconsistent with the Calzetti et al. (2000)
reddening law which over predicts the range in UV attenuation corrections by a
factor of ~100 for the UV selected z~1 galaxies in this sample (abridged).Comment: 10 pages, 7 figures, accepted for publication in MNRA
The dynamics and control of large flexible space structures, 8
A development of the in plane open loop rotational equations of motion for the proposed Spacecraft Control Laboratory Experiment (SCOLE) in orbit configuration is presented based on an Eulerian formulation. The mast is considered to be a flexible beam connected to the (rigid) shuttle and the reflector. Frequencies and mode shapes are obtained for the mast vibrational appendage modes (assumed to be decoupled) for different boundary conditions based on continuum approaches and also preliminary results are obtained using a finite element representation of the mast reflector system. The linearized rotational in plane equation is characterized by periodic coefficients and open loop system stability can be examined with an application of the Floquet theorem. Numerical results are presented to illustrate the potential instability associated with actuator time delays even for delays which represent only a small fraction of the natural period of oscillation of the modes contained in the open loop model of the system. When plant and measurement noise effects are added to the previously designed deterministic model of the hoop column system, it is seen that both the system transient and steady state performance are degraded. Mission requirements can be satisfied by appropriate assignment of cost function weighting elements and changes in the ratio of plant noise to measurement noise
- …