7,831 research outputs found
Lack of Hyperbolicity in Asymptotic Erd\"os--Renyi Sparse Random Graphs
In this work we prove that the giant component of the Erd\"os--Renyi random
graph for c a constant greater than 1 (sparse regime), is not Gromov
-hyperbolic for any positive with probability tending to one
as . As a corollary we provide an alternative proof that the giant
component of when c>1 has zero spectral gap almost surely as
.Comment: Updated version with improved results and narrativ
Load Shifting in the Smart Grid: To Participate or Not?
Demand-side management (DSM) has emerged as an important smart grid feature
that allows utility companies to maintain desirable grid loads. However, the
success of DSM is contingent on active customer participation. Indeed, most
existing DSM studies are based on game-theoretic models that assume customers
will act rationally and will voluntarily participate in DSM. In contrast, in
this paper, the impact of customers' subjective behavior on each other's DSM
decisions is explicitly accounted for. In particular, a noncooperative game is
formulated between grid customers in which each customer can decide on whether
to participate in DSM or not. In this game, customers seek to minimize a cost
function that reflects their total payment for electricity. Unlike classical
game-theoretic DSM studies which assume that customers are rational in their
decision-making, a novel approach is proposed, based on the framework of
prospect theory (PT), to explicitly incorporate the impact of customer behavior
on DSM decisions. To solve the proposed game under both conventional game
theory and PT, a new algorithm based on fictitious player is proposed using
which the game will reach an epsilon-mixed Nash equilibrium. Simulation results
assess the impact of customer behavior on demand-side management. In
particular, the overall participation level and grid load can depend
significantly on the rationality level of the players and their risk aversion
tendency.Comment: 9 pages, 7 figures, journal, accepte
Integrating Energy Storage into the Smart Grid: A Prospect Theoretic Approach
In this paper, the interactions and energy exchange decisions of a number of
geographically distributed storage units are studied under decision-making
involving end-users. In particular, a noncooperative game is formulated between
customer-owned storage units where each storage unit's owner can decide on
whether to charge or discharge energy with a given probability so as to
maximize a utility that reflects the tradeoff between the monetary transactions
from charging/discharging and the penalty from power regulation. Unlike
existing game-theoretic works which assume that players make their decisions
rationally and objectively, we use the new framework of prospect theory (PT) to
explicitly incorporate the users' subjective perceptions of their expected
utilities. For the two-player game, we show the existence of a proper mixed
Nash equilibrium for both the standard game-theoretic case and the case with PT
considerations. Simulation results show that incorporating user behavior via PT
reveals several important insights into load management as well as economics of
energy storage usage. For instance, the results show that deviations from
conventional game theory, as predicted by PT, can lead to undesirable grid
loads and revenues thus requiring the power company to revisit its pricing
schemes and the customers to reassess their energy storage usage choices.Comment: 5 pages, 4 figures, conferenc
Biodegradable and compostable alternatives to conventional plastics
This article is available open access through the publisher’s website at the link below. Copyright @ 2009 The Royal Society.Packaging waste forms a significant part of municipal solid waste and has caused increasing environmental concerns, resulting in a strengthening of various regulations aimed at reducing the amounts generated. Among other materials, a wide range of oil-based polymers is currently used in packaging applications. These are virtually all non-biodegradable, and some are difficult to recycle or reuse due to being complex composites having varying levels of contamination. Recently, significant progress has been made in the development of biodegradable plastics, largely from renewable natural resources, to produce biodegradable materials with similar functionality to that of oil-based polymers. The expansion in these bio-based materials has several potential benefits for greenhouse gas balances and other environmental impacts over whole life cycles and in the use of renewable, rather than finite resources. It is intended that use of biodegradable materials will contribute to sustainability and reduction in the environmental impact associated with disposal of oil-based polymers.
The diversity of biodegradable materials and their varying properties makes it difficult to make simple, generic assessments such as biodegradable products are all ‘good’ or petrochemical-based products are all ‘bad’. This paper discusses the potential impacts of biodegradable packaging materials and their waste management, particularly via composting. It presents the key issues that inform judgements of the benefits these materials have in relation to conventional, petrochemical-based counterparts. Specific examples are given from new research on biodegradability in simulated ‘home’ composting systems. It is the view of the authors that biodegradable packaging materials are most suitable for single-use disposable applications where the post-consumer waste can be locally composted.EPSR
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