10,755 research outputs found
Evolution of topological order in Xe films on a quasicrystal surface
We report results of the first computer simulation studies of a physically
adsorbed gas on a quasicrystalline surface, Xe on decagonal Al-Ni-Co. The grand
canonical Monte Carlo method is employed, using a semi-empirical gas-surface
interaction, based on conventional combining rules, and the usual Lennard-Jones
Xe-Xe interaction. The resulting adsorption isotherms and calculated structures
are consistent with the results of LEED experimental data. The evolution of the
bulk film begins in the second layer, while the low coverage behavior is
epitaxial. This transition from 5-fold to 6-fold ordering is temperature
dependent, occurring earlier (at lower coverage) for the higher temperatures
POINTLESS SPACES IN GENERAL RELATIVITY
The new approach to quantize the gravity based on the notion of differential
algebra is suggested. It is shown that the differential geometry of this object
can not be described in terms of points. The spatialization procedure giving
rise to points by loosing a part of the entire structure is discussed. The
counterpart of the traditional objects of differential geometry are studied.Comment: 40 Kb, latex, no figures, paper accepted for publication in the
International Journal of Theoretical Physics (May 1995
Einfluss ökologischer Bewirtschaftung und verschiedener Kulturen auf die Regenwurmfauna
Problemstellung/Ziele:Vorkommen und Artenzusammensetzung der Regenwurmpopulation haben eine grosse Bedeutung im nachhaltigen Ackerbau. Als Architekten und Bauarbeiter des Bodens beeinflussen die RegenwĂŒrmer verschiedene Parameter der Bodenfruchtbarkeit und damit das Wachstums der Kulturpflanzen. Der Landwirt beeinflusst das Regenwurmvorkommen bei vorgegebenem Standort und Fruchtfolge vor allem durch Bewirtschaftungsmassnahmen wie DĂŒngung, Pflanzenschutz und Bodenbearbeitung. Um Richtung und Ausmass dieser EinflĂŒsse zu erkennen untersuchten wir von 1997 bis 2001 die Regenwurmpopulationen im ökologischen und den integrierten Anbausystemen des Vergleichsversuches Burgrain (D. Dubois, 1999).
Fazit: Ăkologische Bewirtschaftung förderte auf Burgrain spezifisch das Vorkommen von anözischen Lumbricus und endogĂ€ischen Arten; hingegen nicht das Vorkommen von anözischen Nicodrilus Arten. Letztere wurden hingegen sehr deutlich durch die kulturbedingten Bewirtschaftungsmassnahmen beeinflusst. Besonders das PflĂŒgen im Oktober vor Winterweizen wirkte sich negativ auf die tiefgrabenden anözischen Nicodrilus Arten aus. Hier gilt es Verbesserungsmöglichkeiten zu prĂŒfen
Solving multi-criteria decision problems under possibilistic uncertainty using optimistic and pessimistic utilities
International audienceThis paper proposes a qualitative approach to solve multi-criteria decision making problems under possibilistic uncertainty. De-pending on the decision maker attitude with respect to uncertainty (i.e. optimistic or pessimistic) and on her attitude with respect to criteria (i.e. conjunctive or disjunctive), four ex-ante and four ex-post decision rules are dened and investigated. In particular, their coherence w.r.t. the principle of monotonicity, that allows Dynamic Programming is studied
New variables, the gravitational action, and boosted quasilocal stress-energy-momentum
This paper presents a complete set of quasilocal densities which describe the
stress-energy-momentum content of the gravitational field and which are built
with Ashtekar variables. The densities are defined on a two-surface which
bounds a generic spacelike hypersurface of spacetime. The method used
to derive the set of quasilocal densities is a Hamilton-Jacobi analysis of a
suitable covariant action principle for the Ashtekar variables. As such, the
theory presented here is an Ashtekar-variable reformulation of the metric
theory of quasilocal stress-energy-momentum originally due to Brown and York.
This work also investigates how the quasilocal densities behave under
generalized boosts, i. e. switches of the slice spanning . It is
shown that under such boosts the densities behave in a manner which is similar
to the simple boost law for energy-momentum four-vectors in special relativity.
The developed formalism is used to obtain a collection of two-surface or boost
invariants. With these invariants, one may ``build" several different mass
definitions in general relativity, such as the Hawking expression. Also
discussed in detail in this paper is the canonical action principle as applied
to bounded spacetime regions with ``sharp corners."Comment: Revtex, 41 Pages, 4 figures added. Final version has been revised and
improved quite a bit. To appear in Classical and Quantum Gravit
Toward a General Framework for Information Fusion
National audienceDepending on the representation setting, different combination rules have been proposed for fusing information from distinct sources. Moreover in each setting, different sets of axioms that combination rules should satisfy have been advocated, thus justifying the existence of alternative rules (usually motivated by situations where the behavior of other rules was found unsatisfactory). These sets of axioms are usually purely considered in their own settings, without in-depth analysis of common properties essential for all the settings. This paper introduces core properties that, once properly instantiated, are meaningful in different representation settings ranging from logic to imprecise probabilities. The following representation settings are especially considered: classical set representation, possibility theory, and evidence theory, the latter encompassing the two other ones as special cases. This unified discussion of combination rules across different settings is expected to provide a fresh look on some old but basic issues in information fusion
Experimental investigation of eccentricity ratio, friction, and oil flow of long and short journal bearings with load-number charts
Experimental Investigation of Misaligning Couples and Eccentricity at Ends of Misaligned Plain Bearings
Mapping of toxic vapors on board of chemical tankers
During normal management of a chemical tanker, the crew will perform operations in the cargo part of the vessel, like entering tanks, cleaning lines, connecting and disconnecting of the manifold, sampling and maintenance of specific equipment. Under these circumstances there will be a higher risk of direct contact with the cargo and cargo vapors. These vapors can be taken up by ventilation intakes, bringing the cargo fumes into the accommodation and engine RadielloÂź passive samplers offer several advantages for this application, including no electricity use, small sizes, adjustable exposure times and especially a precise and selective measurement of air concentrations.Especially the benzene concentrations on board were relatively high. The cargo on board can explain a lot. During our stay on board benzene has been loaded in three tanks and later on these tanks have been cleaned and ventilated during our measurements. The International Maritime Organisation (IMO), recognized that chronic exposure to very low concentrations of benzene vapors in air, of the order of a few parts per million, may cause leukaemia. According to Madl, benzene exposure on board of crude oil and chemical tankers do not pose a health risk to deck crewman. interpretation of the results will soon demonstrate if we can confirm Madlâs statement on board of this type of vessels.On the other hand we measured the concentrations of toxic vapors over relatively short periods, during well specific operations on deck. Here the concentrations were measured with the âPAC IIIâ apparatus of DraegerÂź. The results of this investigation have to be compared with the TLV-TWA and TLV-STEL values. Conclusions here should encourage the optimization of the use of respiratory protection aids during cargo operations
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