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Identifying the community structure of the food-trade international multi-network
Achieving international food security requires improved understanding of how international trade networks connect countries around the world through the import-export flows of food commodities. The properties of international food trade networks are still poorly documented, especially from a multi-network perspective. In particular, nothing is known about the multi-network's community structure. Here we find that the individual crop-specific layers of the multi-network have densely connected trading groups, a consistent characteristic over the period 2001–2011. Further, the multi-network is characterized by low variability over this period but with substantial heterogeneity across layers in each year. In particular, the layers are mostly assortative: more-intensively connected countries tend to import from and export to countries that are themselves more connected. We also fit econometric models to identify social, economic and geographic factors explaining the probability that any two countries are co-present in the same community. Our estimates indicate that the probability of country pairs belonging to the same food trade community depends more on geopolitical and economic factors—such as geographical proximity and trade-agreement co-membership—than on country economic size and/or income. These community-structure findings of the multi-network are especially valuable for efforts to understand past and emerging dynamics in the global food system, especially those that examine potential 'shocks' to global food trade
Identifying the community structure of the international food-trade multi network
Achieving international food security requires improved understanding of how
international trade networks connect countries around the world through the
import-export flows of food commodities. The properties of food trade networks
are still poorly documented, especially from a multi-network perspective. In
particular, nothing is known about the community structure of food networks,
which is key to understanding how major disruptions or 'shocks' would impact
the global food system. Here we find that the individual layers of this network
have densely connected trading groups, a consistent characteristic over the
period 2001 to 2011. We also fit econometric models to identify social,
economic and geographic factors explaining the probability that any two
countries are co-present in the same community. Our estimates indicate that the
probability of country pairs belonging to the same food trade community depends
more on geopolitical and economic factors -- such as geographical proximity and
trade agreements co-membership -- than on country economic size and/or income.
This is in sharp contrast with what we know about bilateral-trade determinants
and suggests that food country communities behave in ways that can be very
different from their non-food counterparts.Comment: 47 pages, 19 figure
Global Virtual Water Trade: integrating Structural Decomposition Analysis with Network Theory
The consideration of both the direct and the indirect effects of global production and trade is the first step in order to assess the sustainability of resource exploitation, in particular water usage. This paper
applies the Global Multi-Regional Input-Output model to quantify the interdependencies of different sectors
and to determine the overall water consumption of each country. This procedure allows the measurement of Virtual Water Trade, that is the volume of water embedded in traded goods. This paper introduces further extensions based on network analysis to overcome the limitations of I-O models. To the best of our knowledge, this is the first attempt to build a bridge between two different, but related, methodologies. Firstly, we assess the evolution of the structure of international trade in Virtual Water (VW). Secondly, we present the results from the Structural Decomposition Analysis. Finally, we introduce other measures
from Network Theory, in order to integrate the previous results. Community Detection assessment reveals
the emergence of regional VW systems composed by a limited set of countries. Thus our study confirms the need of elaborating and implementing transboundary policies for water management, especially in the European Union
Understanding Co-evolution in Large Multi-relational Social Networks
Understanding dynamics of evolution in large social networks is an important
problem. In this paper, we characterize evolution in large multi-relational
social networks. The proliferation of online media such as Twitter, Facebook,
Orkut and MMORPGs\footnote{Massively Multi-player Online Role Playing Games}
have created social networking data at an unprecedented scale. Sony's Everquest
2 is one such example. We used game multi-relational networks to reveal the
dynamics of evolution in a multi-relational setting by macroscopic study of the
game network. Macroscopic analysis involves fragmenting the network into
smaller portions for studying the dynamics within these sub-networks, referred
to as `communities'. From an evolutionary perspective of multi-relational
network analysis, we have made the following contributions. Specifically, we
formulated and analyzed various metrics to capture evolutionary properties of
networks. We find that co-evolution rates in trust based `communities' are
approximately higher than the trade based `communities'. We also find
that the trust and trade connections within the `communities' reduce as their
size increases. Finally, we study the interrelation between the dynamics of
trade and trust within `communities' and find interesting results about the
precursor relationship between the trade and the trust dynamics within the
`communities'
Management in the Gulf and Caribbean: mosaic or melting pot?
Does \u27\u27managing large pelagic fishes mean the same thing across the diversity of maritime jurisdictions, governance arrangements, economies, languages, cultures, scales of operation and other features of the Gulf and Caribbean region? It would be surprising if it did. Yet international fisheries management urges this mosaic of management to become a melting pot; at least integrated, even if differentiated. This paper examines some themes underlying whether a mosaic or melting pot is the most apt metaphor for where we are, and are headed, in attempts to manage large pelagic fishes in the region. We pay particular attention to the multi-dimensional concept of scale. Included are the scales of management units, fisheries authorities, management outcomes, harvest and postharvest enterprises, and the interdisciplinary perspectives that can be brought to bear on fishery problems and solutions. We are also interested in linkages, because linkage is connected to the scaling-up that is important in a region with many small countries and territories. Even if the management of large pelagics starts as a mosaic, coherent patterns of sub-regional and regional interactions can conceivably be nested and linked to improve the integration, and hence effectiveness, of management interventions ... at least in theory
Evolution of community structure in the world trade web
In this note we study the bilateral merchandise trade flows between 186
countries over the 1948-2005 period using data from the International Monetary
Fund. We use Pajek to identify network structure and behavior across thresholds
and over time. In particular, we focus on the evolution of trade "islands" in
the a world trade network in which countries are linked with directed edges
weighted according to fraction of total dollars sent from one country to
another. We find mixed evidence for globalization.Comment: To be submitted to APFA 6 Proceedings, 8 pages, 3 Figure
Identifying the Community Structure of the International-Trade Multi Network
We study the community structure of the multi-network of commodity-specific trade relations among world countries over the 1992-2003 period. We compare structures across commodities and time by means of the normalized mutual information index (NMI). We also compare them with exogenous community structures induced by geographical distances and regional trade agreements. We find that commodity-specific community structures are very heterogeneous and much more fragmented than that characterizing the aggregate ITN. This shows that the aggregate properties of the ITN may result (and be very different) from the aggregation of very diverse commodity-specific layers of the multi network. We also show that commodity-specific community structures, especially those related to the chemical sector, are becoming more and more similar to the aggregate one. Finally, our findings suggest that geographical distance is much more correlated with the observed community structure than RTAs. This result strengthens previous findings from the empirical literature on trade.Networks; Community structure; International-trade multi-network; Normalized mutual information
Peer-to-peer and community-based markets: A comprehensive review
The advent of more proactive consumers, the so-called "prosumers", with
production and storage capabilities, is empowering the consumers and bringing
new opportunities and challenges to the operation of power systems in a market
environment. Recently, a novel proposal for the design and operation of
electricity markets has emerged: these so-called peer-to-peer (P2P) electricity
markets conceptually allow the prosumers to directly share their electrical
energy and investment. Such P2P markets rely on a consumer-centric and
bottom-up perspective by giving the opportunity to consumers to freely choose
the way they are to source their electric energy. A community can also be
formed by prosumers who want to collaborate, or in terms of operational energy
management. This paper contributes with an overview of these new P2P markets
that starts with the motivation, challenges, market designs moving to the
potential future developments in this field, providing recommendations while
considering a test-case
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