3,127 research outputs found
Qualität des Weidefutters in der ökologischen Milchviehhaltung
Grazing of dairy cows is mandatory in organic farming. However, as in conventional farming there is a tendency to increase milk yield per cows by employing other feeding strategies than grazing. On-farm research was initiated on organic dairy farms in Lower Saxony to investigate the current practice of grassland utilization and dairy husbandry and to explore the potential of grazing for milk production. The results show that with an increased focus on grazing of dairy cows there is considerable room for more milk being produced from grazed grass. An in-depth analysis of the spatio-temporal pattern of the quality of the herbage on offer revealed steadily high net energy and protein concentrations almost irrespective of the sward botanical composition and the season of sampling. Research is needed to improve grazing management strategies in organic farming to make better use of the high potential of grazed grasslands and thereby increase the sustainability of milk production
Stable propagation of an ordered array of cracks during directional drying
We study the appearance and evolution of an array of parallel cracks in a
thin slab of material that is directionally dried, and show that the cracks
penetrate the material uniformly if the drying front is sufficiently sharp. We
also show that cracks have a tendency to become evenly spaced during the
penetration. The typical distance between cracks is mainly governed by the
typical distance of the pattern at the surface, and it is not modified during
the penetration. Our results agree with recent experimental work, and can be
extended to three dimensions to describe the properties of columnar polygonal
patterns observed in some geological formations.Comment: 8 pages, 4 figures, to appear in PR
Exploiting the Temporal Logic Hierarchy and the Non-Confluence Property for Efficient LTL Synthesis
The classic approaches to synthesize a reactive system from a linear temporal
logic (LTL) specification first translate the given LTL formula to an
equivalent omega-automaton and then compute a winning strategy for the
corresponding omega-regular game. To this end, the obtained omega-automata have
to be (pseudo)-determinized where typically a variant of Safra's
determinization procedure is used. In this paper, we show that this
determinization step can be significantly improved for tool implementations by
replacing Safra's determinization by simpler determinization procedures. In
particular, we exploit (1) the temporal logic hierarchy that corresponds to the
well-known automata hierarchy consisting of safety, liveness, Buechi, and
co-Buechi automata as well as their boolean closures, (2) the non-confluence
property of omega-automata that result from certain translations of LTL
formulas, and (3) symbolic implementations of determinization procedures for
the Rabin-Scott and the Miyano-Hayashi breakpoint construction. In particular,
we present convincing experimental results that demonstrate the practical
applicability of our new synthesis procedure
Technical Note: Description and assessment of a nudged version of the new dynamics Unified Model
International audienceWe present a "nudged" version of the Met Office general circulation model, the Unified Model. We constrain this global climate model using ERA-40 re-analysis data with the aim of reproducing the observed "weather" over a year from September 1999. Quantitative assessments are made of its performance, focusing on dynamical aspects of nudging and demonstrating that the "weather" is well simulated
Методи оцінки ризиків в інформаційній системі аналізу екологічного стану басейну малої ріки
В інформаційній системі аналізу стану басейну малої ріки запропоновано методи оцінки ризиків на основі імовірнісних та статистичних оцінок, формалізації моделі гри з природою, прогнозування процесів підтоплення земель з використанням ланцюгів Маркова, розглянуто багато критеріальні моделі ризиків.In informational and analytical system of the small rivers’ ecological condition estimation the methods of risks modelling on the basis of likelihood and statistical estimations, formalization of models of game with nature, risk modelling and forecasting processes flooded lands using Markov chains are offered, multicriteria models of risks are considered
Probing two topological surface bands of Sb2Te3 by spin-polarized photoemission spectroscopy
Using high resolution spin- and angle-resolved photoemission spectroscopy, we
map the electronic structure and spin texture of the surface states of the
topological insulator Sb2Te3. In combination with density functional
calculations (DFT), we directly show that Sb2Te3 exhibits a partially occupied,
single spin-Dirac cone around the Fermi energy, which is topologically
protected. DFT obtains a spin polarization of the occupied Dirac cone states of
80-90%, which is in reasonable agreement with the experimental data after
careful background subtraction. Furthermore, we observe a strongly spin-orbit
split surface band at lower energy. This state is found at 0.8eV below the
Fermi level at the gamma-point, disperses upwards, and disappears at about
0.4eV below the Fermi level into two different bulk bands. Along the gamma-K
direction, the band is located within a spin-orbit gap. According to an
argument given by Pendry and Gurman in 1975, such a gap must contain a surface
state, if it is located away from the high symmetry points of the Brillouin
zone. Thus, the novel spin-split state is protected by symmetry, too.Comment: 8 pages, 10 figure
Are Individuals Fickle-Minded?
Game theory has been used to model large-scale social events — such as constitutional law, democratic stability, standard setting, gender roles, social movements, communication, markets, the selection of officials by means of elections, coalition formation, resource allocation, distribution of goods, and war — as the aggregate result of individual choices in interdependent decision-making. Game theory in this way assumes methodological individualism. The widespread observation that game theory predictions do not in general match observation has led to many attempts to repair game theory by creating behavioral game theory, which adds corrective terms to the game theoretic predictions in the hope of making predictions that better match observations. But for game theory to be useful in making predictions, we must be able to generalize from an individual’s behavior in one situation to that individual’s behavior in very closely similar situations. In other words, behavioral game theory needs individuals to be reasonably consistent in action if the theory is to have predictive power. We argue on the basis of experimental evidence that the assumption of such consistency is unwarranted. More realistic models of individual agents must be developed that acknowledge the variance in behavior for a given individual
The Atomic Slide Puzzle: Self-Diffusion of an Impure Atom
In a series of recent papers van Gastel et al have presented first
experimental evidence that impure, Indium atoms, embedded into the first layer
of a Cu(001) surface, are not localized within the close-packed surface layers
but make concerted, long excursions visualized in a series of STM images. Such
excursions occur due to continuous reshuffling of the surface following the
position exchanges of both impure and host atoms with the naturally occuring
surface vacancies. Van Gastel et al have also formulated an original
lattice-gas type model with asymmetric exchange probabilities, whose numerical
solution is in a good agreement with the experimental data. In this paper we
propose an exact lattice solution of several versions of this model.Comment: Latex, 4 pages, 2 figures, to appear in Phys. Rev. E (RC
Effects of climate-induced changes in isoprene emissions after the eruption of Mount Pinatubo
In the 1990s the rates of increase of greenhouse gas concentrations, most notably of methane, were observed to change, for reasons that have yet to be fully determined. This period included the eruption of Mt. Pinatubo and an El Nino warm event, both of which affect biogeochemical processes, by changes in temperature, precipitation and radiation. We examine the impact of these changes in climate on global isoprene emissions and the effect these climate dependent emissions have on the hydroxy radical, OH, the dominant sink for methane. We model a reduction of isoprene emissions in the early 1990s, with a maximum decrease of 40 Tg(C)/yr in late 1992 and early 1993, a change of 9%. This reduction is caused by the cooler, drier conditions following the eruption of Mt. Pinatubo. Isoprene emissions are reduced both directly, by changes in temperature and a soil moisture dependent suppression factor, and indirectly, through reductions in the total biomass. The reduction in isoprene emissions causes increases of tropospheric OH which lead to an increased sink for methane of up to 5 Tg(CH4)/year, comparable to estimated source changes over the time period studied. There remain many uncertainties in the emission and oxidation of isoprene which may affect the exact size of this effect, but its magnitude is large enough that it should remain important
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