1,133 research outputs found
Atomistic origins of the phase transition mechanism in Ge2Sb2Te5
Combined static and molecular dynamics first-principles calculations are used
to identify a direct structural link between the metastable crystalline and
amorphous phases of Ge2Sb2Te5. We find that the phase transition is driven by
the displacement of Ge atoms along the rocksalt [111] direction from the
stable-octahedron to high-energy-unstable tetrahedron sites close to the
intrinsic vacancy regions, which give rise to the formation of local 4-fold
coordinated motifs. Our analyses suggest that the high figures of merit of
Ge2Sb2Te5 are achieved from the optimal combination of intrinsic vacancies
provided by Sb2Te3 and the instability of the tetrahedron sites provided by
GeTe
Implementation of an Intelligent Robotized GMAW Welding Cell, Part 2: Intuitive Visual Programming Tool for Trajectory Learning
Modeling the impact of dilution on the microbial degradation time of dispersed oil in marine environments
Dispersants aid the breakup of crude oil masses and increase the available
interfacial surface area for bacteria to degrade insoluble hydrocarbons in the
marine environment. However, this common view neglects key aspects of the
microscale interactions between bacteria and oil droplets, particularly the
encounters between these elements that are required for degradation to occur.
This chapter discusses a biophysical model for hydrocarbon consumption of
suspended oil droplets under conditions of rapid dilution that occur in natural
environments. Based on the model, which includes typical biological growth
parameters, dilution is found to produce an effective delay in the onset of
biodegradation by approximately a week. The steady and rapid reduction in oil
concertation, due to dilution, is found to outpace the production of
oil-degrading bacteria that result from colonization of degrading oil droplets,
maintaining the process in an encounter-limited state. This mechanistic model
provides a baseline for better understanding of microscale biodegradation in
dilute oil environments and can help inform the design of mitigation strategies
in marine systems
Assessing Earthquake-Induced Tree Mortality in Temperate Forest Ecosystems: A Case Study from Wenchuan, China
Earthquakes can produce significant tree mortality, and consequently affect regional carbon dynamics. Unfortunately, detailed studies quantifying the influence of earthquake on forest mortality are currently rare. The committed forest biomass carbon loss associated with the 2008 Wenchuan earthquake in China is assessed by a synthetic approach in this study that integrated field investigation, remote sensing analysis, empirical models and Monte Carlo simulation. The newly developed approach significantly improved the forest disturbance evaluation by quantitatively defining the earthquake impact boundary and detailed field survey to validate the mortality models. Based on our approach, a total biomass carbon of 10.9 Tg∙C was lost in Wenchuan earthquake, which offset 0.23% of the living biomass carbon stock in Chinese forests. Tree mortality was highly clustered at epicenter, and declined rapidly with distance away from the fault zone. It is suggested that earthquakes represent a significant driver to forest carbon dynamics, and the earthquake-induced biomass carbon loss should be included in estimating forest carbon budgets
Bribeproof mechanisms for two-values domains
Schummer (Journal of Economic Theory 2000) introduced the concept of
bribeproof mechanism which, in a context where monetary transfer between agents
is possible, requires that manipulations through bribes are ruled out.
Unfortunately, in many domains, the only bribeproof mechanisms are the trivial
ones which return a fixed outcome.
This work presents one of the few constructions of non-trivial bribeproof
mechanisms for these quasi-linear environments. Though the suggested
construction applies to rather restricted domains, the results obtained are
tight: For several natural problems, the method yields the only possible
bribeproof mechanism and no such mechanism is possible on more general domains.Comment: Extended abstract accepted to SAGT 2016. This ArXiv version corrects
typos in the proofs of Theorem 7 and Claims 28-29 of prior ArXiv versio
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