8,226 research outputs found
Large wind energy converter: Growian 3 MW
The main features of the Growian wind energy converter are presented. Energy yield, environmental impact, and construction of the energy converter are discussed. Reliability of the windpowered system is assessed
Understanding climate: A strategy for climate modeling and predictability research, 1985-1995
The emphasis of the NASA strategy for climate modeling and predictability research is on the utilization of space technology to understand the processes which control the Earth's climate system and it's sensitivity to natural and man-induced changes and to assess the possibilities for climate prediction on time scales of from about two weeks to several decades. Because the climate is a complex multi-phenomena system, which interacts on a wide range of space and time scales, the diversity of scientific problems addressed requires a hierarchy of models along with the application of modern empirical and statistical techniques which exploit the extensive current and potential future global data sets afforded by space observations. Observing system simulation experiments, exploiting these models and data, will also provide the foundation for the future climate space observing system, e.g., Earth observing system (EOS), 1985; Tropical Rainfall Measuring Mission (TRMM) North, et al. NASA, 1984
Effect of the orientational relaxation on the collective motion of patterns formed by self-propelled particles
We investigate the collective behavior of self-propelled particles (SPPs)
undergoing competitive processes of pattern formation and rotational relaxation
of their self-propulsion velocities. In full accordance with previous work, we
observe transitions between different steady states of the SPPs caused by the
intricate interplay among the involved effects of pattern formation,
orientational order, and coupling between the SPP density and orientation
fields. Based on rigorous analytical and numerical calculations, we prove that
the rate of the orientational relaxation of the SPP velocity field is the main
factor determining the steady states of the SPP system. Further, we determine
the boundaries between domains in the parameter plane that delineate
qualitatively different resting and moving states. In addition, we analytically
calculate the collective velocity of the SPPs and show that it
perfectly agrees with our numerical results. We quantitatively demonstrate that
does not vanish upon approaching the transition boundary between the
moving pattern and homogeneous steady states.Comment: 3 Figure
Stability analysis of polarized domains
Polarized ferrofluids, lipid monolayers and magnetic bubbles form domains
with deformable boundaries. Stability analysis of these domains depends on a
family of nontrivial integrals. We present a closed form evaluation of these
integrals as a combination of Legendre functions. This result allows exact and
explicit formulae for stability thresholds and growth rates of individual
modes. We also evaluate asymptotic behavior in several interesting limits.Comment: 12 pages, 3 figures, Late
Thin film evolution equations from (evaporating) dewetting liquid layers to epitaxial growth
In the present contribution we review basic mathematical results for three
physical systems involving self-organising solid or liquid films at solid
surfaces. The films may undergo a structuring process by dewetting,
evaporation/condensation or epitaxial growth, respectively. We highlight
similarities and differences of the three systems based on the observation that
in certain limits all of them may be described using models of similar form,
i.e., time evolution equations for the film thickness profile. Those equations
represent gradient dynamics characterized by mobility functions and an
underlying energy functional.
Two basic steps of mathematical analysis are used to compare the different
system. First, we discuss the linear stability of homogeneous steady states,
i.e., flat films; and second the systematics of non-trivial steady states,
i.e., drop/hole states for dewetting films and quantum dot states in epitaxial
growth, respectively. Our aim is to illustrate that the underlying solution
structure might be very complex as in the case of epitaxial growth but can be
better understood when comparing to the much simpler results for the dewetting
liquid film. We furthermore show that the numerical continuation techniques
employed can shed some light on this structure in a more convenient way than
time-stepping methods.
Finally we discuss that the usage of the employed general formulation does
not only relate seemingly not related physical systems mathematically, but does
as well allow to discuss model extensions in a more unified way
Modelling the evaporation of thin films of colloidal suspensions using Dynamical Density Functional Theory
Recent experiments have shown that various structures may be formed during
the evaporative dewetting of thin films of colloidal suspensions. Nano-particle
deposits of strongly branched `flower-like', labyrinthine and network
structures are observed. They are caused by the different transport processes
and the rich phase behaviour of the system. We develop a model for the system,
based on a dynamical density functional theory, which reproduces these
structures. The model is employed to determine the influences of the solvent
evaporation and of the diffusion of the colloidal particles and of the liquid
over the surface. Finally, we investigate the conditions needed for
`liquid-particle' phase separation to occur and discuss its effect on the
self-organised nano-structures
Interrogatives in Yanomam
This thesis is a general linguistic description of yes-no and information questions in Yanom&m (a member of the Yanomami language family of Brazil and Venezuela) in the descriptive/typological tradition, including morphosyntax and semantics, appropriate responses, certain discourse-pragmatic conditions of their use (such as bias and focus), and intonation patterns.
Some things in the Yanomam language that are typologically unusual are an information question system that utilizes just one interrogative word, interaction of temporal-evidential particles with questions, and the occurrence of hortative constructions in questions.
My sources of information include the limited published works and articles on the language, previously unpublished materials, and my own field notes
The World Council of Churches
The World Council of Churches represents the confluence of previous ecumenical movements. The two most important streams of activity that merged in this broader and deeper endeavor are the Faith and Order Movement (Conference) and the Life and Work Conference. Each of these deserves our attention
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