12,215 research outputs found
Economic Analysis in the Pacific Northwest Land Resources Project: Theoretical Considerations and Preliminary Results
The Pacific Northwest Land Resources Inventory Demonstration Project i s an a ttempt to combine a whole spectrum of heterogeneous geographic, institutional and applications elements in a synergistic approach to the evaluation of remote sensing techniques. This diversity is the prime motivating factor behind a theoretical investigation of alternative economic analysis procedures. For a multitude of reasons--simplicity, ease of understanding, financial constraints and credibility, among others--cost-effectiveness emerges as the most practical tool for conducting such evaluation determinatIons in the Pacific Northwest. Preliminary findings in two water resource application areas suggest, in conformity with most published studies, that Lands at-aided data collection methods enjoy substantial cost advantages over alternative techniques. The pntential for sensitivity analysis based on cost/accuracy tradeoffs is considered on a theoretical plane in the absence of current accuracy figures concerning the Landsat-aided approach
Bounded Model Checking of State-Space Digital Systems: The Impact of Finite Word-Length Effects on the Implementation of Fixed-Point Digital Controllers Based on State-Space Modeling
The extensive use of digital controllers demands a growing effort to prevent
design errors that appear due to finite-word length (FWL) effects. However,
there is still a gap, regarding verification tools and methodologies to check
implementation aspects of control systems. Thus, the present paper describes an
approach, which employs bounded model checking (BMC) techniques, to verify
fixed-point digital controllers represented by state-space equations. The
experimental results demonstrate the sensitivity of such systems to FWL effects
and the effectiveness of the proposed approach to detect them. To the best of
my knowledge, this is the first contribution tackling formal verification
through BMC of fixed-point state-space digital controllers.Comment: International Symposium on the Foundations of Software Engineering
201
Force-extension relation of cross-linked anisotropic polymer networks
Cross-linked polymer networks with orientational order constitute a wide
class of soft materials and are relevant to biological systems (e.g., F-actin
bundles). We analytically study the nonlinear force-extension relation of an
array of parallel-aligned, strongly stretched semiflexible polymers with random
cross-links. In the strong stretching limit, the effect of the cross-links is
purely entropic, independent of the bending rigidity of the chains. Cross-links
enhance the differential stretching stiffness of the bundle. For hard
cross-links, the cross-link contribution to the force-extension relation scales
inversely proportional to the force. Its dependence on the cross-link density,
close to the gelation transition, is the same as that of the shear modulus. The
qualitative behavior is captured by a toy model of two chains with a single
cross-link in the middle.Comment: 7 pages, 4 figure
Nonlinear modes in the harmonic PT-symmetric potential
We study the families of nonlinear modes described by the nonlinear
Schr\"odinger equation with the PT-symmetric harmonic potential . The found nonlinear modes display a number of interesting features. In
particular, we have observed that the modes, bifurcating from the different
eigenstates of the underlying linear problem, can actually belong to the same
family of nonlinear modes. We also show that by proper adjustment of the
coefficient it is possible to enhance stability of small-amplitude and
strongly nonlinear modes comparing to the well-studied case of the real
harmonic potential.Comment: 7 pages, 2 figures; accepted to Phys. Rev.
Ion Trap Mass Spectrometers for Identity, Abundance and Behavior of Volatiles on the Moon
NASA GSFC and The Open University (UK) are collaborating to deploy an Ion Trap Mass Spectrometer on the Moon to investigate the lunar water cycle. The ITMS is flight-proven throughthe Rosetta Philae comet lander mission. It is also being developed under ESA funding to analyse samples drilled from beneath the lunar surface on the Roscosmos Luna-27 lander (2025).Now, GSFC and OU will now develop a compact ITMS instrument to study the near-surface lunar exosphere on board a CLPS Astrobotic lander at Lacus Mortis in 2021
High rate continuous synthesis of nanocrystalline materials in a colliding vapor stream of microdroplets
Progress in nanotechnology is driving the need of large scale synthesis of functional
nanomaterials. The lack of a workforce trained on process control and scale-up of nanomaterials
manufacturing, the gap between laboratories and economically practical nanofabrication and the
funding strain on the survivability of startup companies all contribute to the difficulties in scaling up
nanotechnologies and their commercialization [1,2]. We report here a high rate continuous synthesis of
functional inorganic nanomaterials using colliding vapor stream of reagents microdroplets
Capillary-gravity waves: The effect of viscosity on the wave resistance
The effect of viscosity on the wave resistance experienced by a 2d
perturbation moving at uniform velocity over the free surface of a fluid is
investigated. The analysis is based on Rayleigh's linearized theory of
capillary-gravity waves. It is shown in particular that the wave resistance
remains bounded as the velocity of the perturbation approches the minimun phase
speed, unlike what is predicted by the inviscid theory.Comment: Europhysics Letters, in pres
High rate continuous synthesis of nanocrystalline materials in a colliding vapor stream of microdroplets
Progress in nanotechnology is driving the need of large scale synthesis of functional
nanomaterials. The lack of a workforce trained on process control and scale-up of nanomaterials
manufacturing, the gap between laboratories and economically practical nanofabrication and the
funding strain on the survivability of startup companies all contribute to the difficulties in scaling up
nanotechnologies and their commercialization [1,2]. We report here a high rate continuous synthesis of
functional inorganic nanomaterials using colliding vapor stream of reagents microdroplets
A Modified Approach to Single-Spin Detection Using Magnetic Resonance Force Microscopy
The magnetic moment of a single spin interacting with a cantilever in
magnetic resonance force microscopy (MRFM) experiences quantum jumps in
orientation rather than smooth oscillations. These jumps cannot be detected by
a conventional MRFM based on observation of driven resonant oscillations of a
cantilever. In this paper, we propose a method which will allow detection of
the magnetic signal from a single spin using a modification of a conventional
MRFM. We estimate the opportunity to detect the magnetic signal from a single
proton.Comment: 4 pages LaTex, 4 figures in GIF forma
Collisionless Magnetic Reconnection via Alfven Eigenmodes
We propose an analytic approach to the problem of collisionless magnetic
reconnection formulated as a process of Alfven eigenmodes' generation and
dissipation. Alfven eigenmodes are confined by the current sheet in the same
way that quantum mechanical waves are confined by the tanh^2 potential. The
dynamical time scale of reconnection is the system scale divided by the
eigenvalue propagation velocity of the n=1 mode. The prediction of the n=1 mode
shows good agreement with the in situ measurement of the
reconnection-associated Hall fields
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