Power Sharing and Control Strategy for Provisionally Coupled Microgrid Clusters through an Isolated Power Exchange Network

The two common mechanisms of load-shedding and renewable curtailment can prevent provisional overloading and excessive generation and the subsequent unacceptable voltage and frequency deviation in standalone microgrids (MGs), which makes MGs less resilient and reliable. However, instead of enabling load-shedding or renewable curtailment, such overloading or over-generation problems can be alleviated more efficiently and cost-effectively by provisionally interconnecting the neighboring MGs to exchange power amongst themselves. In such a scheme, the interconnected MGs can supply their local demand, as well as a portion of the demand of the adjacent MGs. In order to implement this strategy, a three-phase ac link can be used as the power exchange network, while each MG is coupled to the link through a back-to-back power electronics converter, in order to maintain the autonomy of each MG if they are eachoperated under different standards. This paper proposes a suitable decentralized power management strategy without a communication link between the MGs to achieve power-sharing amongst them and alleviate unacceptable voltage and frequency deviation along with the required control technique for the power electronic converters, which can be implemented at the primary level based on the measurement of the local parameters only. To this end, one of the converters should always regulate the dc link voltage while the other converter should operate in droop control mode when the MG is healthy and in constant PQ mode when overloaded or over-generating. Suitable status detection and mode transition algorithms and controllers were also developed and are proposed in this paper. The performance of the proposed power exchange and control mechanisms were evaluated and verified via PSIM®-based numerical simulation studies. The stability and sensitivity of the proposed power exchange topology are also analyzed against several critical design and operational parameters.

Value chain of sweet potato: a sociological analysis

This study analyzes the existing value chain of sweet potatoes in the Partido District of Camarines Sur, the Philippines. A combination of surveys and participant observation was utilized in the study. Four sociological perspectives were used in the interpretation and analysis of the data, such as new economic sociology, symbolic interactionism, role theory, and exchange network theory. Six components of the value chain were evaluated, such as (a) agents, roles, and links; (b) inputs, outputs and activities that generate transformation; (c) value addition and value allocation; (d) final products or a group of final products; (e) power relations and governance mechanisms; and (f) problems and opportunities shared by all agents. The study found four major links involving five actors – farmers/producers, middlemen or wholesalers, retailers, processors, and end consumers. Analysis of the sweet potato value chain shows that sweet potato production has great potential to improve the well-being of participants. Sweet potato production gave farmers an 81% net profit margin and contributed to 39% of their livelihood. However, there remain general production and utilization challenges and post-harvest and by-product processing issues. The study established the significance of embeddedness and the wider social structure for the sweet potato agribusiness and provided policy inputs for the development of the sweet potato value chain in the district.

Quantifying the Robustness of Complex Networks with Heterogeneous Nodes

The robustness of a complex network measures its ability to withstand random or targeted attacks. Most network robustness measures operate under the assumption that the nodes in a network are homogeneous and abstract. However, most real-world networks consist of nodes that are heterogeneous in nature. In this work, we propose a robustness measure called fitness-incorporated average network efficiency, that attempts to capture the heterogeneity of nodes using the `fitness’ of nodes in measuring the robustness of a network. Further, we adopt the same measure to compare the robustness of networks with heterogeneous nodes under varying topologies, such as the scale-free topology or the Erdős–Rényi random topology. We apply the proposed robustness measure using a wireless sensor network simulator to show that it can be effectively used to measure the robustness of a network using a topological approach. We also apply the proposed robustness measure to two real-world networks; namely the CO2 exchange network and an air traffic network. We conclude that with the proposed measure, not only the topological structure, but also the fitness function and the fitness distribution among nodes, should be considered in evaluating the robustness of a complex network.

The Sungai Batu Archaeological Complex: Re-assessing the Emergence of Ancient Kedah

This article proposes new historical perspectives arising from the findings in the Sungai Batu Archaeological Complex, Kedah, by the Centre for Global Archaeological Research, Universiti Sains Malaysia in 2009. Excavations in the complex unearthed the remains of iron smelting sites, wharves and other brick structures, dating back to the 2nd/3rd century AD. The discoveries of furnaces, tuyeres and iron slag attest to Sungai Batu’s role as the centre for primary iron production, employing the bloomery method. The study suggests that Ancient Kedah appeared as one of the hubs for the trans-Asiatic trade network with the rise of the iron industry, while its economic complexity grew steadily in successive centuries. The early emergence of Ancient Kedah was a development synchronous with the later phase of the Indian-Southeast Asian exchange network between the 2nd to the 4th century AD when inter and intra-regional trade intensified. Due to its favourable geological features, strategic location with a suitable ecozone, as well as being a thriving centre for primary iron production, Ancient Kedah emerged as an important harbour. It was this trading and industrial past, the article will argue, that contributed to the rise of other economic hubs within Ancient Kedah, such as Pengkalan Bujang and Kampung Sungai Mas, which eventually developed into entrepôts after the 5th century AD.

Linking Up: The Role of Institutions and Farmers in Forage Seed Exchange Networks of Southeast Asia

In Southeast Asia, access to improved forages remains a challenge for smallholder farmers and limits livestock production. We compared seed exchange networks supporting two contrasting livestock production systems to identify bottlenecks in seed availability and determine the influences of the market, institutions, and cultural context of seed exchange, using interview-based methods for ‘seed tracing’ and network analysis. Government agencies were the primary sources of high-quality genetic materials, with secondary diffusion in the Philippines dairy case being dominated by key individuals in active cooperatives. In the Vietnamese beef-oriented production context, farmer to farmer dissemination was more substantial. In both cases, formal actors dominated where botanical seed was exchanged, while farmers frequently exchanged vegetatively propagated materials among themselves. To improve access to forage seed in these contexts, government agencies and development actors should coordinate quality seed production upstream while supporting the creation of appropriate training, structures, and incentives for seed exchange network improvement downstream.

PatientMatcher: a customizable Python-based open-source tool for matching undiagnosed rare disease patients via the MatchMaker Exchange network

The amount of data available from genomic medicine has revolutionized the approach to identify the determinants underlying many rare diseases. The task of confirming a genotype-phenotype causality for a patient affected with a rare genetic disease is often challenging. In this context, the establishment of the MatchMaker Exchange (MME) network has assumed a pivotal role in bridging heterogeneous patient information stored on different medical and research servers. MME has made it possible to solve rare disease cases by “matching” the genotypic and phenotypic characteristics of a patient of interest with patient data available at other clinical facilities participating in the network. Here, we present PatientMatcher (https://github.com/Clinical-Genomics/patientMatcher), an open-source Python and MongoDB-based software solution developed by Clinical Genomics facility at the Science for Life Laboratory in Stockholm. PatientMatcher is designed as a standalone MME server, but can easily communicate via REST API with external applications managing genetic analyses and patient data. The MME node is being implemented in clinical production in collaboration with the Genomic Medicine Center Karolinska at the Karolinska University Hospital. PatientMatcher is written to implement the MME API and provides several customizable settings, including a custom-fit similarity score algorithm and adjustable matching results notifications.

Migration of the Zoques to the Mountain Region of Tabasco, Mexico

The mountain region of Tabasco was a significant area in the interregional exchange network in pre-Hispanic times and during the colonial period. Additionally, the exchange of various regional products followed the intricate network of trade routes within the coastal plain and Chiapas. Therefore, the role played by the settlements of the Sierra Tabasqueña within the commercial chain that existed between pre-Hispanic times and the first half of the last century was undoubtedly reflected among these territories. Trade was an important part of the economy of the Zoque settlements established in the Tabasqueña mountain range. Linguistic evidence suggests that the Proto-Mixe-Zoque speakers from several centuries BC were among the first foreign groups to migrate to Tabasco, merging with the local inhabitants. The documents written by Spaniards in the first half of the 16th century state that the Province of the Sierra de Tabasqueña was occupied by Zoque-speaking inhabitants. Based on the analysis of pre-Hispanic pottery recovered in this region, a chronology can be proposed from the Early Preclassic to the Protoclassic period, continuing into the Late-Terminal-Classic through the Late-Postclassic period.