548 research outputs found
Paying the forest for electricity: A modelling framework to market forest conservation as payment for ecosystem services benefiting hydropower generation
Published in PESC Special issue: Payments for ecosystem services in conservation: performance and prospectsThe operation and longevity of hydropower dams are
often negatively impacted by sedimentation. Forest
conservation can reduce soil erosion, and therefore
efforts to maintain upstream forest cover within a
watershed contribute to the economic life span of a
hydropower facility. The cost of forest conservation
can be viewed as an investment in hydropower and
be financed via a payment for ecosystem services
(PES) scheme. A novel modelling framework is used
to estimate payments for forest conservation consisting
of: (1) land-use change projection; (2)watershed erosion
modelling; (3) reservoir sedimentation estimation; (4)
power generation loss calculation; and (5) PES scheme
design. The framework was applied to a proposed dam
in Cambodia (Pursat 1). The estimated net present
value of forest conservation was US 6.4 million when considering droughts every eight
years. This can be remunerated with annual payments
ofUS 5.78ha-1, respectively, covering
forest protection costs estimated at US$ 0.9 ha-1 yr-1.
The application of this type of PES represents a rational
option that allows for conservation and development
of hydropower watersheds susceptible to erosion and
sedimentation
Paying the forest for electricity: A modelling framework to market forest conservation as payment for ecosystem services benefiting hydropower generation
Published in PESC Special issue: Payments for ecosystem services in conservation: performance and prospectsThe operation and longevity of hydropower dams are
often negatively impacted by sedimentation. Forest
conservation can reduce soil erosion, and therefore
efforts to maintain upstream forest cover within a
watershed contribute to the economic life span of a
hydropower facility. The cost of forest conservation
can be viewed as an investment in hydropower and
be financed via a payment for ecosystem services
(PES) scheme. A novel modelling framework is used
to estimate payments for forest conservation consisting
of: (1) land-use change projection; (2)watershed erosion
modelling; (3) reservoir sedimentation estimation; (4)
power generation loss calculation; and (5) PES scheme
design. The framework was applied to a proposed dam
in Cambodia (Pursat 1). The estimated net present
value of forest conservation was US 6.4 million when considering droughts every eight
years. This can be remunerated with annual payments
ofUS 5.78ha-1, respectively, covering
forest protection costs estimated at US$ 0.9 ha-1 yr-1.
The application of this type of PES represents a rational
option that allows for conservation and development
of hydropower watersheds susceptible to erosion and
sedimentation
A Top-Down Approach for a Synthetic Autobiographical Memory System
Autobiographical memory (AM) refers to the organisation of oneâs experience into a coherent narrative. The exact neural mechanisms responsible for the manifestation of AM in humans are unknown. On the other hand, the field of psychology has provided us with useful understanding about the functionality of a bio-inspired synthetic AM (SAM) system, in a higher level of description. This paper is concerned with a top-down approach to SAM, where known components and organisation guide the architecture but the unknown details of each module are abstracted. By using Bayesian latent variable models we obtain a transparent SAM system with which we can interact in a structured way. This allows us to reveal the properties of specific sub-modules and map them to functionality observed in biological systems. The top-down approach can cope well with the high performance requirements of a bio-inspired cognitive system. This is demonstrated in experiments using faces data
Extracting finite structure from infinite language
This paper presents a novel connectionist memory-rule based model capable of learning the finite-state properties of an input language from a set of positive examples. The model is based upon an unsupervised recurrent self-organizing map [T. McQueen, A. Hopgood, J. Tepper, T. Allen, A recurrent self-organizing map for temporal sequence processing, in: Proceedings of Fourth International Conference in Recent Advances in Soft Computing (RASC2002), Nottingham, 2002] with laterally interconnected neurons. A derivation of functionalequivalence theory [J. Hopcroft, J. Ullman, Introduction to Automata Theory, Languages and Computation, vol. 1, Addison-Wesley, Reading, MA, 1979] is used that allows the model to exploit similarities between the future context of previously memorized sequences and the future context of the current input sequence. This bottom-up learning algorithm binds functionally related neurons together to form states. Results show that the model is able to learn the Reber grammar [A. Cleeremans, D. Schreiber, J. McClelland, Finite state automata and simple recurrent networks, Neural Computation, 1 (1989) 372â381] perfectly from a randomly generated training set and to generalize to sequences beyond the length of those found in the training set
A Primal-Dual Interior-Point Method for Nonlinear Programming with Strong Global and Local Convergence Properties
A scheme---inspired from an old idea due to Mayne and Polak (Math. Prog.,vol.~11, 1976, pp.~67--80)---is proposed for extending to general smoothconstrained optimization problems a previously proposed feasibleinterior-point method for inequality constrained problems.It is shown that the primal-dual interior point framework allows for asignificantly more effective implementation of the Mayne-Polak idea thanthat discussed an analyzed by the originators in the contextof first order methods of feasible direction. Strong global and localconvergence results are proved under mild assumptions. In particular,the proposed algorithm does not suffer the Wachter-Biegler effect
Quantifying the 3D structure and function of porosity and pore space in natural sediment flocs
Purpose: Flocculated cohesive suspended sediments (flocs) play an important role in all aquatic environments, facilitating the transport and deposition of sediment and associated contaminants with consequences for aquatic health, material fluxes, and morphological evolution. Accurate modelling of the transport and behaviour of these sediments is critical for a variety of activities including fisheries, aquaculture, shipping, and waste and pollution management and this requires accurate measurement of the physical properties of flocs including porosity.
Methods: Despite the importance of understanding floc porosity, measurement approaches are indirect or inferential. Here, using ÎŒCT, a novel processing and analysis protocol, we directly quantify porosity in natural sediment flocs. For the first time, the complexity of floc pore spaces is observed in 3-dimensions, enabling the identification and quantification of important pore space and pore network characteristics, namely 3D pore diameter, volume, shape, tortuosity, and connectivity.
Results: We report on the complexity of floc pore space and differentiate effective and isolated pore space enabling new understanding of the hydraulic functioning of floc porosity. We demonstrate that current methodological approaches are overestimating floc porosity by c. 30%.
Conclusion: These new data have implications for our understanding of the controls on floc dynamics and the function of floc porosity and can improve the parameterisation of current cohesive sediment transport models
Topological mirror symmetry with fluxes
Motivated by SU(3) structure compactifications, we show explicitly how to
construct half--flat topological mirrors to Calabi--Yau manifolds with NS
fluxes. Units of flux are exchanged with torsion factors in the cohomology of
the mirror; this is the topological complement of previous
differential--geometric mirror rules. The construction modifies explicit SYZ
fibrations for compact Calabi--Yaus. The results are of independent interest
for SU(3) compactifications. For example one can exhibit explicitly which
massive forms should be used for Kaluza--Klein reduction, proving previous
conjectures. Formality shows that these forms carry no topological information;
this is also confirmed by infrared limits and old classification theorems.Comment: 35 pages, 5 figure
Effect of Hydrologic Restoration on the Habitat of the Cape Sable Seaside Sparrow, 2008 â Final Report
This document summarizes the activities that were accomplished in 2008, the sixth year of the research project âEffect of hydrologic restoration on the habitat of the Cape Sable seaside sparrowâ, a collaborative effort among the US Army Corps of Engineers, Everglades National Park, Florida International University, and the US Geological Survey (Florida Integrated Science Center). The major activities in 2008 included field work, data analysis, and presentations. Jay Sah presented the results of 6th year field work at the Cape Sable seaside sparrow (CSSS) Fire Meeting 2008, held on December 2-3 at the Krome Center, Homestead, Florida. In the same meeting, Mike Ross presented results from a related USFWS-funded project on encroachment pattern of woody plants in Cape Sable seaside sparrow habitat
Ultra-High Energy Cosmic Rays from Neutrino Emitting Acceleration Sources?
We demonstrate by numerical flux calculations that neutrino beams producing
the observed highest energy cosmic rays by weak interactions with the relic
neutrino background require a non-uniform distribution of sources. Such sources
have to accelerate protons at least up to 10^{23} eV, have to be opaque to
their primary protons, and should emit the secondary photons unavoidably
produced together with the neutrinos only in the sub-MeV region to avoid
conflict with the diffuse gamma-ray background measured by the EGRET
experiment. Even if such a source class exists, the resulting large
uncertainties in the parameters involved in this scenario does currently not
allow to extract any meaningful information on absolute neutrino masses.Comment: 6 pages, 4 figures, RevTeX styl
N=1* in 5 dimensions: Dijkgraaf-Vafa meets Polchinski-Strassler
One of the powerful techniques to analyze the 5 dimensional Super Yang Mills
theory with a massive hypermultiplet (N=1*) is provided by the AdS/CFT
correspondence. It predicts that, for certain special values of the
hypermultiplet mass, this theory develops nonperturbative branches of the
moduli space as well as new light degrees of freedom.
We use the higher dimensional generalization of the matrix model/gauge theory
correspondence and recover all the prediction of the supergravity analysis. We
construct the map between the four dimensional holomorphic superpotential and
the five dimensional action and explicitly show that the superpotential is flat
along the nonperturbative branches. This is the first instance in which the
Dijkgraaf-Vafa method is used to analyze intrinsically higher dimensional
phenomena.Comment: 28 pages, Late
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