10,820 research outputs found
F100(3) parallel compressor computer code and user's manual
The Pratt & Whitney Aircraft multiple segment parallel compressor model has been modified to include the influence of variable compressor vane geometry on the sensitivity to circumferential flow distortion. Further, performance characteristics of the F100 (3) compression system have been incorporated into the model on a blade row basis. In this modified form, the distortion's circumferential location is referenced relative to the variable vane controlling sensors of the F100 (3) engine so that the proper solution can be obtained regardless of distortion orientation. This feature is particularly important for the analysis of inlet temperature distortion. Compatibility with fixed geometry compressor applications has been maintained in the model
Microwave device investigations Semiannual progress report, 1 Apr. - 1 Oct. 1968
Beam-plasma interactions, cyclotron harmonic instabilities, harmonic generation in beam-plasma system, relativistic electron beam studies, and materials test
Frequency multiplication in high-energy electron beams Semiannual progress report, 1 Oct. 1967 - 31 Mar. 1968
Electron beam-plasma interactions, cyclotron harmonic instabilities, paramagnetic and semiconductor materials, and harmonic current generatio
Conceptual-level evaluation of a variable stiffness skin for a morphing wing leading edge
A morphing leading edge produces a continuous aerodynamic surface that has no gaps between the moving and fixed parts. The continuous seamless shape has the potential to reduce drag, compared to conventional devices, such as slats that produce a discrete aerofoil shape change. However, the morphing leading edge has to achieve the required target shape by deforming from the baseline shape under the aerodynamic loads. In this paper, a conceptual-level method is proposed to evaluate the morphing leading edge structure. The feasibility of the skin design is validated by checking the failure index of the composite when the morphing leading edge undergoes the shape change. The stiffness of the morphing leading edge skin is spatially varied using variable lamina angles, and comparisons to the skin with constant stiffness are made to highlight its potential to reduce the actuation forces. The structural analysis is performed using a two-level structural optimisation scheme. The first level optimisation is applied to find the optimised structural proper- ties of the leading edge skin and the associated actuation forces. The structural properties of the skin are given as a stiffness distribution, which is controlled by a B spline interpolation function. In the second level, the design solution of the skin is investigated. The skin is assumed to be made of variable stiffness composite. The stack sequence of the composite is optimised element-by-element to match the target stiffness. A failure criterion is employed to obtain the failure index when the leading edge is actuated from the baseline shape to the target shape. Test cases are given to demonstrate that the optimisation scheme is able to provide the stiffness distribution of the leading edge skin and the actuation forces can be reduced by using a spatially variable stiffness skin
Fusarium wilt of banana in Brazil: current state and research advances at Embrapa towards sustainable disease management.
Fusarium wilt (FW) impairs banana production in large areas of Brazil, affecting mainly the most profitable cultivars: \'Maçã\' (Silk, AAB) and ‘Prata’ (Pomme, AAB). Plant nutrition is frequently associated with disease severity, but little is known about the banana-FW pathosystem in Brazil. In this work we samples 18 farms in four different production systems in SP. In each farm areas with low (FOC-) and high (FOC+) incidence of FW were selected for plant analysis. Lamina of the third leaf were sampled and analyzed for nutrient content. The main differences between FOC- and FOC+ areas were related to N, K and Ca contents. The most outstanding effect of FW on plant nutrition was the reduction of K and Ca. This might be explained by the fact K and Ca are highly linked to water transport and FW causes severe damages in the vascular system. Interestingly, a relative increase of N content was also observed in some FOC+ plants. This may be due to a concentration effect as a result of growth reduction caused by FW. Our data suggest FW triggers a feedback mechanism towards destabilization in banana. The significant reduction of Ca and K detected on infected plants and the documented role of these nutrients on plant resistance, open opportunities to better understand soil-based management strategies of FW in banana
Predicting Intermediate Storage Performance for Workflow Applications
Configuring a storage system to better serve an application is a challenging
task complicated by a multidimensional, discrete configuration space and the
high cost of space exploration (e.g., by running the application with different
storage configurations). To enable selecting the best configuration in a
reasonable time, we design an end-to-end performance prediction mechanism that
estimates the turn-around time of an application using storage system under a
given configuration. This approach focuses on a generic object-based storage
system design, supports exploring the impact of optimizations targeting
workflow applications (e.g., various data placement schemes) in addition to
other, more traditional, configuration knobs (e.g., stripe size or replication
level), and models the system operation at data-chunk and control message
level.
This paper presents our experience to date with designing and using this
prediction mechanism. We evaluate this mechanism using micro- as well as
synthetic benchmarks mimicking real workflow applications, and a real
application.. A preliminary evaluation shows that we are on a good track to
meet our objectives: it can scale to model a workflow application run on an
entire cluster while offering an over 200x speedup factor (normalized by
resource) compared to running the actual application, and can achieve, in the
limited number of scenarios we study, a prediction accuracy that enables
identifying the best storage system configuration
Tungsten nuclear rocket, phase I, part 1 Final report
Tungsten water moderated nuclear rocket reactor experiments and analyse
Applicability of Modified Effective-Range Theory to positron-atom and positron-molecule scattering
We analyze low-energy scattering of positrons on Ar atoms and N2 molecules
using Modified Effective-Range Theory (MERT) developped by O'Malley, Spruch and
Rosenberg [Journal of Math. Phys. 2, 491 (1961)]. We use formulation of MERT
based on exact solutions of Schroedinger equation with polarization potential
rather than low-energy expansions of phase shifts into momentum series. We show
that MERT describes well experimental data, provided that effective-range
expansion is performed both for s- and p-wave scattering, which dominate in the
considered regime of positron energies (0.4 - 2 eV). We estimate the values of
the s-wave scattering lenght and the effective range for e+ - Ar and e+ - N2
collisions.Comment: RevTeX, 4 pages, 2 figure
Isotopic Production Cross Sections in Proton-Nucleus Collisions at 200 MeV
Intermediate mass fragments (IMF) from the interaction of Al,
Co and Au with 200 MeV protons were measured in an angular range
from 20 degree to 120 degree in the laboratory system. The fragments, ranging
from isotopes of helium up to isotopes of carbon, were isotopically resolved.
Double differential cross sections, energy differential cross sections and
total cross sections were extracted.Comment: accepted by Phys. Rev.
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