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Browsing Centros UC by browse.metadata.fuente "WoS"

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    Active and legacy mining in an arid urban environment : challenges and perspectives for Copiapó, Northern Chile
    (Springer, 2016) Carkovic Aguilera, Athena Belen; Calcagni García, Magdalena Sol; Vega Contreras, Alejandra Soledad; Coquery, Marina; Moya Arias, Pablo Manuel; Bonilla Meléndez, Carlos Alberto; Pastén González, Pablo Arturo; CEDEUS (Chile)
    Urban expansion in areas of active and legacy mining imposes a sustainability challenge, especially in arid environments where cities compete for resources with agriculture and industry. The city of Copiapó, with 150,000 inhabitants in the Atacama Desert, reflects this challenge. More than 30 abandoned tailings from legacy mining are scattered throughout its urban and peri-urban area, which include an active copper smelter. Despite the public concern generated by the mining-related pollution, no geochemical information is currently available for Copiapó, particularly for metal concentration in environmental solid phases. A geochemical screening of soils (n = 42), street dusts (n = 71) and tailings (n = 68) was conducted in November 2014 and April 2015. Organic matter, pH and elemental composition measurements were taken. Notably, copper in soils (60–2120 mg/kg) and street dusts (110–10,200 mg/kg) consistently exceeded international guidelines for residential and industrial use, while a lower proportion of samples exceeded international guidelines for arsenic, zinc and lead. Metal enrichment occurred in residential, industrial and agricultural areas near tailings and the copper smelter. This first screening of metal contamination sets the basis for future risk assessments toward defining knowledge-based policies and urban planning. Challenges include developing: (1) adequate intervention guideline values; (2) appropriate geochemical background levels for key metals; (3) urban planning that considers contaminated areas; (4) cost-effective control strategies for abandoned tailings in water-scarce areas; and (5) scenarios and technologies for tailings reprocessing. Assessing urban geochemical risks is a critical endeavor for areas where extreme events triggered by climate change are likely, as the mud flooding that impacted Copiapó in late March 2015.
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    The impact of using a naive approach in the limited-stop bus service design problem
    (Pergamon, Elsevier Science Ltd, 2021) Kumar Suman, Hemant; Larraín Izquierdo, Homero; Muñoz Abogabir, Juan Carlos; CEDEUS (Chile)
    The proven benefits of limited-stop services have captured the attention of researchers, especially during the last decade. However, to solve the limited-stop service design problem many existing works directly impose a capacity constraint to a total social cost objective function. This "naive approach" implicitly assumes that passengers behave altruistically, basing their decisions on what is best for the whole system. Although this issue has been identified in earlier works, the magnitude of the error induced by this simplification has not been studied yet. The objective of this work is to measure this error and to understand how it misrepresents passenger flows and bus occupation rates. To measure this error gap, we optimize a set of test scenarios by applying a naive approach, and then take the resulting design and obtain a benchmark passenger assignment using a simple behavioral model. We propose two main indicators to compare both passenger assignment: the total passenger deviation, and the total capacity deficit. This comparison reveals that the assignment of the naive approach may indeed be unrealistic, and raises concerns that a network design based on the naive approach might have severe problems when implemented. Thus, the work highlights the importance of taking the results of the naive approach with caution and verify them with a passenger assignment model before their implementation.