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This paper presents a methodology for integrating a polygeneration network with an integrated renewable energy supply chain network and an interplant heat and mass exchange network using a centralized hub layout approach. The method involves developing a three-layered superstructure. The first layer consists of bio-based renewable energy sources connected to the second layer through various transport modes. The second layer, a centralized polygeneration hub, includes combined heat and power systems and resource subnetworks, featuring a boiler for generating high-pressure steam, turbines for power generation, process and utility heat exchangers, and a stripping column for regenerating solutes from mass separating agents. The third layer, connected to the second layer via pipelines, comprises co-located process plants where energy and resource demands are met through heat and mass exchanger network synthesis. The integrated superstructure, represented as a mixed-integer non-linear programming model, is applied to a hypothetical case study involving wood pulp, corn stover, and glycerine as renewable energy sources. It includes two turbines for generating a specified amount of power, hot and cold streams to be cooled and heated in three co-located plants, and gaseous streams from which ammonia is absorbed using mass separating agents in one of the plants. The solution, dominated by the cost of the supply chain, involves seven process heat exchangers (three of which are used for interplant heat exchange), six utility exchangers, and seven mass exchangers, including one stripping column. When the case study is compared to its equivalent non-integrated scenario, the proposed integrated model shows a 79% reduction in total annual cost for a case where the cost of fossil energy is $0.1/kg. Additionally, in terms of environmental impact, it releases 58% less carbon. The results demonstrate the benefits of adopting a centralized design approach using a polygeneration hub integrated with multiple resource networks.

This ethnographic study examines how and why Detroit-area credit-constrained members of the urban poor relied on owners/employees of corner convenience stores, known as \"party stores,\" for accessing short-term, interest-free informal credit services. Findings indicate that informal credit at party stores functioned as a low- or no-cost alternative to formal credit and high-cost fringe banking services such as payday loans, both of which were inaccessible and/or cost prohibitive for informants. These data contribute empirically to a growing body of research on \"credit invisibility\" by exploring these populations' use of informal credit mechanisms. Findings also make a theoretical contribution by highlighting the importance of resource exchange networks through which members of the urban poor build strong yet disposable social ties in order to respond to economic shocks, combat food insufficiency, and survive economic destitution.

Multistage Interconnection Networks (MINs) are an effective means of communication between multiple processors and memory modules in many parallel processing systems. Literature consists of numerous fault-tolerant MIN designs. However, due to the recent advances in the field of parallel processing, requiring large processing power, an increase in the demand to design and develop more reliable, cost-effective and fault-tolerant MINs is being observed. This work proposes two novel MIN designs, namely, Augmented-Shuffle Exchange Gamma Interconnection Network (A-SEGIN) and Enhanced A-SEGIN (EA-SEGIN). The proposed MINs utilize chaining of switches, and multiplexers & demultiplexers for providing a large number of alternative paths and thereby better fault tolerance. Different reliability measures, namely, 2-terminal, multi-source multi-destination, broadcast and network/global, respectively, of the proposed MINs have been evaluated with the help of all enumerated paths and well-known Sum-of-Disjoint Products approach. Further, overall performance, with respect to the number of paths, different reliability measures, hardware cost and cost per unit, of the proposed MINs has been compared with 19 other well-studied MIN layouts. The results suggest that the proposed MINs are very strong competitors of the preexisting MINs of their class owing to their better reliability and cost effectiveness.

A bark shield now in the British Museum can be identified from documentary and pictorial evidence as one collected by Captain Cook during his first voyage to Australia in 1770. Such shields often had special value to their Australian Aboriginal owners and hence might have been exchanged over considerable distances. This particular shield is known to have been collected in Kamay Botany Bay but analysis of the bark of which it is made revealed it to be of red mangrove, a tropical species found today more than 500km distant on the New South Wales north coast. It hence bears valuable testimony to the long-distance exchange networks operating in eastern Australia in the period before the disruption caused by European colonisation.

Large-scale online communities rely on computer-mediated communication between participants, enabling them to sustain interactions and exchange on a scale hitherto unknown. Yet little research has focused on how these online communities sustain themselves and how their interactions are structured. In this paper, we theorize and empirically measure the network exchange patterns of long-duration sustainable online communities. We propose that participation dynamics follow specific forms of social exchange: direct reciprocity, indirect reciprocity, and preferential attachment. We integrate diverse findings about individual participation motivations by identifying how individual behavior manifests in network-level structures of online communities. We studied five online communities over 27 months and analyzed 38,483 interactions using exponential random graph ( p * ) models and mixed-effects analysis of covariance. In a test of competing models, we found that network exchange patterns in online community communication networks are characterized by direct reciprocity and indirect reciprocity patterns and, surprisingly, a tendency away from preferential attachment. Our findings undermine previous explanations that online exchange follows a power law distribution based on people wanting to connect to \"popular\" others in online communities. Our work contributes to theories of new organizational forms by identifying network exchange patterns that regulate participation and sustain online communities.

Many firms try to leverage consumers’ interactions on social platforms as part of their communication strategies. However, information on online social networks only propagates if it receives consumers’ attention. This paper proposes a seeding strategy to maximize information propagation while accounting for competition for attention. The theory of exchange networks serves as the framework for identifying the optimal seeding strategy and recommends seeding people that have many friends, who, in turn, have only a few friends. There is little competition for the attention of those seeds’ friends, and these friends are therefore responsive to the messages they receive. Using a game-theoretic model, we show that it is optimal to seed people with the highest Bonacich centrality. Importantly, in contrast to previous seeding literature that assumed a fixed and nonnegative connectivity parameter of the Bonacich measure, we demonstrate that this connectivity parameter is negative and needs to be estimated. Two independent empirical validations using a total of 34 social media campaigns on two different large online social networks show that the proposed seeding strategy can substantially increase a campaign’s reach. The second study uses the activity network of messages exchanged to confirm that the effects are driven by competition for attention. This paper was accepted by Anandhi Bharadwaj, information systems.

In this paper, a methodology for systematically integrating the synthesis of combined heat, mass, and regeneration exchange networks with solar thermal is presented. The process considered involves the removal of ammonia from ammonia-rich gaseous streams using water-based solvents as the mass separating agent (MSA) and subsequent regeneration of the ammonia-rich MSA stream using steam stripping. A composite superstructure, which comprises the stage-wise superstructure for the synthesis of the heat exchanger network subsystem, primary mass exchanger network subsystem, regeneration subsystem and integrated solar thermal with periodic heat storage, is developed. In order to simplify the modelling of the unpredictable availability of solar thermal energy within the composite superstructure, a multi-periodic synthesis approach is adopted. Sensitivity analysis was performed to establish the price at which solar thermal is favoured over fossil-derived energy as the hot utility source. The economics of the resulting solution is evaluated using net present value, and it was found that, to obtain a positive NPV, the stripping cost in the retrofitted network will have to be as low as possible, or annual operating cost of the non-retrofitted primary mass exchange network will have to be high.

Seed exchange is a major means for smallholder farmers to access seeds of both traditional and new crop varieties. This study explores how social and cultural norms influence farmers’ seed exchange and thereby shape the distribution of sorghum diversity among farmers from two ethnolinguistic groups in Northern Ethiopia. Network data on sorghum variety transactions for 300 households was analyzed to map the flow of seed and determine key characteristics of the farmers playing particularly important roles as nodes in the networks. Together with a household survey, ethnographic studies of cultural practices and norms informed the interpretation of the network data. We found that exchange with neighbors was the main seed transaction type and that exchange mainly happens within ethnolinguistic groups and villages. A norm saying that no one should be denied access to seeds underpins seed sharing within the communities. Sociocultural institutions like the labor exchange institutions Lifnti/Kowa, marriage, and religious institutions influence seed sharing within both ethnolinguistic groups. Seed sharing is common among all categories of farmers, and we found no significant association between farmers’ socioeconomic status and seed sharing. The dynamics of seed exchange can explain the sorghum diversity in the study areas, as the most exchanged sorghum varieties within each ethnolinguistic group are also the most cultivated. We discuss the implications of our findings for the conservation of sorghum diversity and seed system development and conclude that policies and extension programs should leverage farmers’ seed exchange networks for the management of crop diversity and in efforts to strengthen farmers’ access to seeds of both local and improved seeds.

We examine the informal exchange of favors in societies such that any two individuals interact too infrequently to sustain exchange, but such that the social pressure of the possible loss of multiple relationships can sustain exchange. Patterns of exchange that are locally enforceable and renegotiation-proof necessitate that all links are \"supported\": any two individuals exchanging favors have a common friend. In symmetric settings, such robust networks are \"social quilts\": tree-like unions of completely connected subnetworks. Examining favor exchange networks in 75 villages in rural India, we find high levels of support and identify characteristics that correlate with support.

The Big Exchange project investigates large-scale exchange systems in Eurasia and Africa (8000–1 BC). We concentrate on raw materials of known origin (‘sourced finds’). Network analysis of tools and artificial intelligence methods are used to analyse the combined data sets. We invite broad collaboration on bimodal exchange networks.