24,486 research outputs found
Resource Management with Stochastic Recharge and Environmental Threats
Exploitation diminishes the capacity of renewable resources to with-stand environmental stress, increasing their vulnerability to extreme conditions that may trigger abrupt changes. The onset of such events depends on the coincidence of extreme environmental conditions (environmental threat) and the resource state (determining its resilience). When the former is uncertain and the latter evolves stochastically, the uncertainty regarding the event occurrence is the result of the combined effect of these two uncertain components. We analyzed optimal resource management in such a setting. Existence of an optimal stationary policy is established and long run properties are characterized. A numerical illustration based on actual data is presented.Stochastic stock dynamics, event uncertainty, Markov decision process, optimal stationary policy, Environmental Economics and Policy,
DYNAMIC-SPATIAL MANAGEMENT OF COASTAL AQUIFERS
We analyze the management of a coastal aquifer under seawater intrusion using distributed control methods. The aquifer's state is taken as the water head elevation, which varies with time and in space since extraction, natural recharge and lateral water flows vary with time and in space. The water head, in turn, induces a temporal-spatial seawater intrusion process, which changes the volume of fresh water in the aquifer. Under reasonable conditions we show that the optimal state converges to a steady state process that is constant in time. We characterize the optimal steady state process in terms of a standard control problem (in space) and offer a tractable algorithm to solve for it.distributed control, groundwater, optimal exploitation, seawater intrusion, Resource /Energy Economics and Policy, C61, C62, Q25,
Time Series Analysis
We provide a concise overview of time series analysis in the time and frequency domains, with lots of references for further reading.time series analysis, time domain, frequency domain, Research Methods/ Statistical Methods,
The resource theory of informational nonequilibrium in thermodynamics
We review recent work on the foundations of thermodynamics in the light of
quantum information theory. We adopt a resource-theoretic perspective, wherein
thermodynamics is formulated as a theory of what agents can achieve under a
particular restriction, namely, that the only state preparations and
transformations that they can implement for free are those that are thermal at
some fixed temperature. States that are out of thermal equilibrium are the
resources. We consider the special case of this theory wherein all systems have
trivial Hamiltonians (that is, all of their energy levels are degenerate). In
this case, the only free operations are those that add noise to the system (or
implement a reversible evolution) and the only nonequilibrium states are states
of informational nonequilibrium, that is, states that deviate from the
maximally mixed state. The degree of this deviation we call the state's
nonuniformity; it is the resource of interest here, the fuel that is consumed,
for instance, in an erasure operation. We consider the different types of state
conversion: exact and approximate, single-shot and asymptotic, catalytic and
noncatalytic. In each case, we present the necessary and sufficient conditions
for the conversion to be possible for any pair of states, emphasizing a
geometrical representation of the conditions in terms of Lorenz curves. We also
review the problem of quantifying the nonuniformity of a state, in particular
through the use of generalized entropies. Quantum state conversion problems in
this resource theory can be shown to be always reducible to their classical
counterparts, so that there are no inherently quantum-mechanical features
arising in such problems. This body of work also demonstrates that the standard
formulation of the second law of thermodynamics is inadequate as a criterion
for deciding whether or not a given state transition is possible.Comment: 51 pages, 9 figures, Revised Versio
An Efficient Monte Carlo-based Probabilistic Time-Dependent Routing Calculation Targeting a Server-Side Car Navigation System
Incorporating speed probability distribution to the computation of the route
planning in car navigation systems guarantees more accurate and precise
responses. In this paper, we propose a novel approach for dynamically selecting
the number of samples used for the Monte Carlo simulation to solve the
Probabilistic Time-Dependent Routing (PTDR) problem, thus improving the
computation efficiency. The proposed method is used to determine in a proactive
manner the number of simulations to be done to extract the travel-time
estimation for each specific request while respecting an error threshold as
output quality level. The methodology requires a reduced effort on the
application development side. We adopted an aspect-oriented programming
language (LARA) together with a flexible dynamic autotuning library (mARGOt)
respectively to instrument the code and to take tuning decisions on the number
of samples improving the execution efficiency. Experimental results demonstrate
that the proposed adaptive approach saves a large fraction of simulations
(between 36% and 81%) with respect to a static approach while considering
different traffic situations, paths and error requirements. Given the
negligible runtime overhead of the proposed approach, it results in an
execution-time speedup between 1.5x and 5.1x. This speedup is reflected at
infrastructure-level in terms of a reduction of around 36% of the computing
resources needed to support the whole navigation pipeline
Beyond the thermodynamic limit: finite-size corrections to state interconversion rates
Thermodynamics is traditionally constrained to the study of macroscopic
systems whose energy fluctuations are negligible compared to their average
energy. Here, we push beyond this thermodynamic limit by developing a
mathematical framework to rigorously address the problem of thermodynamic
transformations of finite-size systems. More formally, we analyse state
interconversion under thermal operations and between arbitrary
energy-incoherent states. We find precise relations between the optimal rate at
which interconversion can take place and the desired infidelity of the final
state when the system size is sufficiently large. These so-called second-order
asymptotics provide a bridge between the extreme cases of single-shot
thermodynamics and the asymptotic limit of infinitely large systems. We
illustrate the utility of our results with several examples. We first show how
thermodynamic cycles are affected by irreversibility due to finite-size
effects. We then provide a precise expression for the gap between the
distillable work and work of formation that opens away from the thermodynamic
limit. Finally, we explain how the performance of a heat engine gets affected
when one of the heat baths it operates between is finite. We find that while
perfect work cannot generally be extracted at Carnot efficiency, there are
conditions under which these finite-size effects vanish. In deriving our
results we also clarify relations between different notions of approximate
majorisation.Comment: 31 pages, 10 figures. Final version, to be published in Quantu
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