4,389 research outputs found
Information-Theoretic Methods for Identifying Relationships among Climate Variables
Information-theoretic quantities, such as entropy, are used to quantify the
amount of information a given variable provides. Entropies can be used together
to compute the mutual information, which quantifies the amount of information
two variables share. However, accurately estimating these quantities from data
is extremely challenging. We have developed a set of computational techniques
that allow one to accurately compute marginal and joint entropies. These
algorithms are probabilistic in nature and thus provide information on the
uncertainty in our estimates, which enable us to establish statistical
significance of our findings. We demonstrate these methods by identifying
relations between cloud data from the International Satellite Cloud Climatology
Project (ISCCP) and data from other sources, such as equatorial pacific sea
surface temperatures (SST).Comment: Presented at the Earth-Sun System Technology Conference (ESTC 2008),
Adelphi, MD. http://esto.nasa.gov/conferences/estc2008/ 3 pages, 3 figures.
Appears in the Proceedings of the Earth-Sun System Technology Conference
(ESTC 2008), Adelphi, M
Sustainable investment in Turkey 2010
The main objectives of this report are as follows:
1 To understand and provide a review of the current state of the Sustainable Investment (SI) market in Turkey,
2 To identify the drivers and obstacles for sustainable investments, and assess the commercial feasibility of different approaches and initiatives that may stimulate the SI market in Turkey,
3 To analyze the institutional prerequisites and interventions that will fuel the development of investments, which would, in turn, encourage a betterallocation of local and international capital to sustainable enterprises and hence support sustainable development of the Turkish economy.
This study forms part of a series of assessments of Sustainable Investment (SI) in Brazil (2009), India (2009) and China (2009), and draws upon earlier reports published by IFC jointly with the Economist Intelligence Unit: Sustainable Invest ing in Emerging Markets: Unscathed by the Financial Crises (2010) and with Mercer; Gaining Ground, Integrating Environmental, Social and Governance (ESG) Factors into Investment Processes in Emerging Markets (2009)
Engineering nonlinear response of nanomaterials using Fano resonances
We show that, nonlinear optical processes of nanoparticles can be controlled
by the presence of interactions with a molecule or a quantum dot. By choosing
the appropriate level spacing for the quantum emitter, one can either suppress
or enhance the nonlinear frequency conversion. We reveal the underlying
mechanism for this effect, which is already observed in recent experiments: (i)
Suppression occurs simply because transparency induced by Fano resonance does
not allow an excitation at the converted frequency. (ii) Enhancement emerges
since nonlinear process can be brought to resonance. Path interference effect
cancels the nonresonant frequency terms. We demonstrate the underlying physics
using a simplified model, and we show that the predictions of the model are in
good agreement with the 3-dimensional boundary element method (MNPBEM toolbox)
simulations. Here, we consider the second harmonic generation in a plasmonic
converter as an example to demonstrate the control mechanism. The phenomenon is
the semi-classical analog of nonlinearity enhancement via electromagnetically
induced transparency.Comment: 10 pages, 6 figure
Connectivity-Driven Coherence in Complex Networks
We study the emergence of coherence in complex networks of mutually coupled
non-identical elements. We uncover the precise dependence of the dynamical
coherence on the network connectivity, on the isolated dynamics of the elements
and the coupling function. These findings predict that in random graphs, the
enhancement of coherence is proportional to the mean degree. In locally
connected networks, coherence is no longer controlled by the mean degree, but
rather on how the mean degree scales with the network size. In these networks,
even when the coherence is absent, adding a fraction s of random connections
leads to an enhancement of coherence proportional to s. Our results provide a
way to control the emergent properties by the manipulation of the dynamics of
the elements and the network connectivity.Comment: 4 pages, 2 figure
Velocity Correlations in Dense Gravity Driven Granular Chute Flow
We report numerical results for velocity correlations in dense,
gravity-driven granular flow down an inclined plane. For the grains on the
surface layer, our results are consistent with experimental measurements
reported by Pouliquen. We show that the correlation structure within planes
parallel to the surface persists in the bulk. The two-point velocity
correlation function exhibits exponential decay for small to intermediate
values of the separation between spheres. The correlation lengths identified by
exponential fits to the data show nontrivial dependence on the averaging time
\dt used to determine grain velocities. We discuss the correlation length
dependence on averaging time, incline angle, pile height, depth of the layer,
system size and grain stiffness, and relate the results to other length scales
associated with the rheology of the system. We find that correlation lengths
are typically quite small, of the order of a particle diameter, and increase
approximately logarithmically with a minimum pile height for which flow is
possible, \hstop, contrary to the theoretical expectation of a proportional
relationship between the two length scales.Comment: 21 pages, 16 figure
Determination of ontogenetic selection criteria for grain yield in spring barley (Hordeum vulgare) by pathcoefficient analysis
Path-coefficient analysis was performed to determine the interrelationships among grain yield, yield components (spike number per m-2, kernel number per spike, average kernel weight) and somephenological characteristics (duration and growing degree-days of vegetative and grain-filling periods) in spring barley genotypes in 2004-2005. Grain yield depended mainly on spike number per m-2 andkernel number per spike; average kernel weight had a negligible effect on grain yield in spring barley genotypes. Grain yield was significantly and positively associated with the spike number per m-2 andnegatively correlated with other characteristics studied. Spike number per m-2 had considerable negative effect on the average kernel weight. A lengthening of the grain-filling period induced an increase in the average kernel weight and a positive and significant correlation was found between the two characteristics. Spike number per m-2 and kernel number had positive direct effects on grain yield in spring barley genotypes. The growing degree-days (GDD) for vegetative period had significant positive direct effect on kernel number, and the GDD for grain-filling period had significant positive direct effect on kernel weight. The results indicated that spike number per m-2, kernel number per spike and the GDD for vegetative and grain filling period were the most reliable selection criteria for improving grain yield in spring barley in cool and short-season environments
Quantum Simulator Based on the Paraxial Wave Equation
We propose a paraxial quantum simulator that requires only widely available
optical fibers or metamaterials. Such a simulator would facilitate
cost-effective quantum simulation without specialized techniques. We show
theoretically that the method accurately simulates quantum dynamics and quantum
effects for an example system, which invites extension of the method to
many-body systems using nonlinear optical elements and implementation of the
paraxial quantum simulator to extend access to quantum computation and
prototype quantum parity-time reversal () symmetric technologies
A drift-diffusion model for robotic obstacle avoidance
We develop a stochastic framework for modeling and analysis of robot navigation in the presence of obstacles. We show that, with appropriate assumptions, the probability of a robot avoiding a given obstacle can be reduced to a function of a single dimensionless parameter which captures all relevant quantities of the problem. This parameter is analogous to the Peclet number considered in the literature on mass transport in advection-diffusion fluid flows. Using the framework we also compute statistics of the time required to escape an obstacle in an informative case. The results of the computation show that adding noise to the navigation strategy can improve performance. Finally, we present experimental results that illustrate these performance improvements on a robotic platform.
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