Abstracts

Julian Müller – Empirically Relevant Roles in Multivariate Networks

Under the assumption that actors with the same social role develop and get influenced by their relations in similar ways, we can infer the roles of actors from those relations. We therefore define that two actors have the same role in a network if the patterns in their relations are similar enough.
In this talk, we propose a framework for the emergence of role relations in social networks. It generalizes known role concepts such as structural, regular and exact equivalence, but also allows for other more nuanced notions of roles. Furthermore, it is applicable to networks involving multiple actor and tie attributes and provides a micro-foundation for the evolution of roles. We apply this approach to a multivariate data set of friendship and social knowledge relations among recruits in a police academy. Non-trivial and hitherto undiscovered roles are found using comparisons in which network structure and actor attributes are combined.

Victor Leiva – A new approach to modeling of data with skew distributions

Data modeling based on skew distributions has received considerable attention in recent years. In this article, we introduce a new approach for the case of Birnbaum–Saunders regression models, which allows us to analyze data in their original scale and to model non-constant variance. In addition, we propose different types of residuals for these models and conduct a simulation study to establish which of them has a better performance. Furthermore, we develop diagnostic methods of influence under different perturbation schemes. Finally, we perform real data analytics by using the approach proposed in the article. This analysis shows its potential applications.

Felipe Feijoo – Mixed complementarity problems (MCP) for natural gas markets: Infrastructure development under domestic and international socio-economic conditions.

Changes in the United States (U.S.) natural gas market have spawned the need for inter-state pipeline infrastructure planning. Previous studies have analyzed natural gas infrastructure development largely independent of the interactions of the natural gas sector with the broader economy. However, natural gas infrastructure development is primarily driven by broader domestic and international socioeconomic conditions. We couple a global human-Earth system model with state-level detail in the U.S. (GCAM-USA) that provides the broader socioeconomic context for natural gas supply and demand with a natural gas infrastructure investment model (NANGAM) to examine inter-state natural gas pipeline infrastructure development in the U.S. under a range of socioeconomic scenarios. The study shows that existing pipeline infrastructure in the U.S. is insufficient to satisfy the increasing demand for natural gas and investments in pipeline capacity will be required. However, the geographic distribution of investments within the U.S. is heterogeneous and depends on the capacity of existing infrastructure as well as the magnitude of increase in demand.

Sebastián Cea – Essential equilibria in large square economies

Exchange economies are defined by a mapping between an atomless space of agents and a space of characteristics where the commodity space is a separable Banach space. We characterize equilibrium stability of economies relaying on the continuity of the equilibrium correspondence without differentiability assumptions.

Óscar Romero – On the salmon production and transport planning in a freshwater stage with mobile cages allocation

Fish consumption faces a significant and persistent increment worldwide, where the salmon production is essential to cover the projected demands. The salmon production cycle mainly comprises three stages: freshwater (fish cultivation and handling), seawater (weight gain) and plant processing. Each stage has its own characteristics related to the geographical location, service and raw material providers, and regulations, among other issues. This research focuses on the freshwater stage, which is compounded by a number of serial productive sub-stages. This work proposes new Mixed Integer Programming models for salmon production and transport planning between the freshwater sub-stages in a multi-period scenario. The main contribution relies on integrating cages mobility between the farming centers located at each fresh water sub-stage. The model allows to determine the required cages as well as their allocation to the farming centers for each period within the planning horizon. In addition, a Lagrangian Relaxation-based algorithm is proposed in order to efficiently solve the proposed model.

Eusebio Vargas – Positional-based selective strategy of key players: controlling complex networks

Gaining control on complex networks is expected to make a huge impact in our world as we live in an interconnected society where a large amount of important aspects in our daily life  relies on complex systems which can be naturally modeled by the network paradigm. For the goal to be achieved, the problem of finding the best set of key players is crucial for designing an efficient selective strategy of pinning control. Different approaches are based on the idea that ranking players or actors by the use of well know (or newly developed) graph-based centrality indices would lead to the best set of important actors, but this assumption presents serious drawbacks.

Timothy Matis – High Reliability Organizational Theory in Healthcare

High Reliability Organizational theory has been championed by the Joint Commission on Accreditation of Hospitals (JCAHO) as a means to reduce major medical error. The theory was developed through the empirical observation of organizations in industries whose system failure has a low probability of occurrence but would result in catastrophic consequences. This presentation explores the applicability of HRO theory in Healthcare, and proposes alternative interventive measures.

Felipe Feijoo – Climate and carbon budget implication of linked future changes CO2 and non-CO2 forcing

The approximate proportional relationship between cumulative carbon emissions and instantaneous global temperature rise (the carbon budget approximation) has proven to be a useful concept to translate policy-relevant temperature objectives into CO2 emissions pathways. However, when non-CO2 forcing is changing along with CO2 forcing, error in the approximation increases. Using the GCAM model to produce an ensemble of~ 3,000 scenarios,  I show that linked changes in CO2 forcing, aerosol forcing, and non-CO2 greenhouse gas forcing lead to an increase in total non-CO2 forcing over the 21st century across mitigation scenarios. This increase causes the relationship between instantaneous temperature and cumulative CO2 emissions to become more complex than the proportional approximation often assumed, particularly for low temperature objectives such as 1.5 C.

Armin Lüer – A multiple-allocation profit maximizing p-hub location problem considering hub congestion, time-sensitive demands and 1-stop paths – Diapositivas Presentación

Hub location models are used to design communication and transportation networks in different industries. Fundamental hub location models have been extended to consider profit maximization, hub congestion, price-sensitive demands and multiple stops in every origin-destination (OD) path, etc. We formulate and solve a problem where a profit-maximizing company wants to design a p-hub and spoke network. The transportation demands react to total travel time, which is the arc travel time plus hub processing time; hubs are congested by inbound flows; and every OD path includes at most one hub. This challenging model is solved using an ad-hoc solution method that integrates Lagrangian relaxation and column generation. Ongoing research includes extensive computational experiments to show properties and stability of our novel approach. Future lines of work are the extension of our model to include capacity selection at the hubs, and two or more hubs in OD paths and more sophisticated cost structures.

Pía Amigo – Financial markets for reaching energy targets: cap-and-trade strategies in the Chilean electric sector

In the Paris Agreement, Chile pledged to reduce Greenhouse Gases (GHG) in 30% and to phase out coal as energy generator. However, it is unclear how we will achieve that goal. So far, the only green policy implemented in Chile is an emission tax, first of its kind in Latin America. However, it has proven to be insufficient. In our work, we present an alternative approach for pricing carbon emissions: the cap and trade paradigm. We modelled the Chilean electric market as a two-stage capacity expansion equilibrium problem, where we allow future investment and trading of emission permits among agents. This presentation will show the applicability of our model and the current state of the project.

Germán Paredes – El problema de recolección de leche con mezclas graduales

En este artículo estudiamos un problema de recolección de leche considerando varios tipos o calidades de leche. Una planta procesadora recolecta leche desde un conjunto de predios utilizando una flota de camiones homogénea. Cada predio produce uno de tres posibles tipos de leche. Cada camión tiene un compartimiento, y se permite la mezcla de diferentes tipos de leche cuando esto maximiza el beneficio. La leche que llega a la planta en cada camión se clasifica en uno de los tres tipos. Los tipos de leche son definidos en función del conteo de células somáticas (CS) por mililitro de leche. Asimismo, el máximo contenido de CS por mililitro de leche para cada tipo es regulado por la ley vigente o por la compañía. El objetivo es maximizar el beneficio considerando el ingreso por la leche recibida en la planta y los costos de transporte. Presentamos resultados computacionales para un caso real en el sur de Chile.