14 results on '"Pais, Cristobal"'
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2. Global scale coupling of pyromes and fire regimes
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Pais, Cristobal, Gonzalez-Olabarria, Jose Ramon, Elimbi Moudio, Pelagie, Garcia-Gonzalo, Jordi, González, Marta C., and Shen, Zuo-Jun Max
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- 2023
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3. A firebreak placement model for optimizing biodiversity protection at landscape scale
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Carrasco, Jaime, Mahaluf, Rodrigo, Lisón, Fulgencio, Pais, Cristobal, Miranda, Alejandro, de la Barra, Felipe, Palacios, David, and Weintraub, Andrés
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- 2023
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4. Stochastic forestry planning under market and growth uncertainty
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Pais, Cristobal, Weintraub, Andres, and Shen, Zuo-Jun Max
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- 2023
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5. Exploring the multidimensional effects of human activity and land cover on fire occurrence for territorial planning
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Carrasco, Jaime, Acuna, Mauricio, Miranda, Alejandro, Alfaro, Gabriela, Pais, Cristobal, and Weintraub, Andrés
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- 2021
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6. Stochastic forestry harvest planning under soil compaction conditions
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Rossit, Daniel, Pais, Cristóbal, Weintraub, Andrés, Broz, Diego, Frutos, Mariano, and Tohmé, Fernando
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- 2021
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7. Downstream protection value: Detecting critical zones for effective fuel-treatment under wildfire risk
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Pais, Cristobal, Carrasco, Jaime, Elimbi Moudio, Pelagie, and Shen, Zuo-Jun Max
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- 2021
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8. Quantifying the impact of ecosystem services for landscape management under wildfire hazard
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Elimbi Moudio, Pelagie, Pais, Cristobal, and Shen, Zuo-Jun Max
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- 2021
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9. A multicriteria stochastic optimization framework for sustainable forest decision making under uncertainty
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Álvarez-Miranda, Eduardo, Garcia-Gonzalo, Jordi, Pais, Cristobal, and Weintraub, Andrés
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- 2019
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10. Data-driven Applications and Decision Making Models in Natural Resources
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Pais, Cristobal
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Industrial engineering ,Applied mathematics ,Climate change ,Data-driven optimization ,Decision support system ,Deep learning ,Machine learning ,Optimization ,Wildfires - Abstract
The destructive potential of wildfires has been exacerbated by climate change, causing their frequencies and intensities to continuously increase globally. In this context, increasing wildfire activity across the globe has become an urgent issue with enormous ecological and social impacts. Wildfires have consumed important areas and forest resources, as a result, fire management expenditures have increased and thousands of homes and many lives have been lost. Moreover, they have significantly impacted biodiversity and greenhouse gas emissions on a global scale.The current incidents across the globe highlight the need for preemptive policy measures to reduce the risk of fire occurrence, managing the land in an effective way to protect natural forests, agricultural areas, and human lives. These concepts are included in what is known as FireSmart Forest Management (FSFM). This paradigm considers opportunities in three dimensions: i) decrease of the fire behavior potential of the landscape, ii) reduction of the potential for fire ignitions, and iii) increase in the fire suppression capability.This dissertation aims at advancing the theory, practice, and large-scale implementation of complex data-driven decision making and machine learning models in the context of landscape management under wildfire risk, integrating Operations Research, Computer Science, and Data Science techniques. We focus our efforts on the understanding, evaluation, and development of effective prevention and mitigation policies, with the potential of being implemented practice, as well as exploring and developing new FSFM techniques.We divided our study into three main aspects: Simulation, Decision-Making, and Machine Learning. In Chapter 1, we focus on the development and evaluation of an accurate, flexible, and efficient wildfire simulation model that can be integrated with data-driven decision-making models. Empirical results on thousands of simulations show the high performance of the model compared to existing solutions, highlighting its accuracy with real-life instances. We then focus our efforts on its generalization in Chapter 2, seeking to adjust its main parameters to mimic the fire spread behavior observed in different regions of the world where no empirical models are available. This, exploiting historical information for training purposes using derivative-free optimization techniques to adjust the parameters of the model, allowing us to capture current wildfire dynamics. Experiments performed on datasets located in different regions of the world show the potential of the proposed method.Second, in Chapters 3 and 4, we explore the integration of this model with landscape planning decision-making models to derive robust fuel treatment policies to mitigate expected losses due to future wildfire events, generating fire resilient landscapes. We study and compare complex network algorithms to develop a mathematical model denoted Downstream Protection Value, capturing the importance of the different components of the land to provide a natural prioritization of where mitigation actions should be implemented. An optimization framework incorporating multiple variables to analyze the inherent trade-offs involved in the planning process is developed, providing practitioners and researchers with an open-source decision support system implementation involving multiple and potentially, opposing objectives. We evaluate the performance of the proposed mathematical model compared to existing solutions, highlighting its superior performance with thousands of experiments involving uncertainty for landscapes located in North America. Several extensions are discussed providing future research directions in the field. We further expand this framework in Chapter 5, incorporating wildfire suppression strategies derived from a novel multi-agent decision-making model. In this application, a group of agents is deployed to the field once an ignition or active fire is detected with the aim of containing or stopping it as soon as possible. The sequential and temporal dimensions of the problem become a challenge to apply traditional modeling techniques. We develop a deep reinforcement learning algorithm focused on exploiting the collaboration and coordination between independent agents. Extensive computational results demonstrate the impact of including local rewards and the concept of sub-groups of agents in the context of centralized training and decentralized execution algorithms, leading to more complex and effective collaboration strategies between agents belonging to the same group and the environment in general.As part of our decision support system extensions, we build end-to-end machine learning models to understand the wildfire phenomenon from a large-scale perspective. For this, in Chapter 6, we explore the impact of different landscape compositions on the risk of wildfire ignition using remote sensing data to support challenging landscape planning decisions. Using a custom convolutional neural network model integrated with state-of-the-art visualization techniques, we highlight the main areas of interest for the deep learning model, focusing our efforts on the interpretability of the results. This, with the aim of opening the artificial intelligence black-box to fully understand the rationale behind the results and the different risk levels associated with characteristic spatial patterns observed in the land. We validate our results with previous studies using similar datasets, noting how the proposed model significantly surpasses their predictive performance while providing insights about the learning process of the model. Finally, in Chapter 7, we develop a global study of the main characteristics and drivers of wildfire regimes consolidating observations for almost two decades of wildfires. We classify and delineate regions of the world sharing similar fire activity as well as identifying their driving factors to support national or regional wildfire prevention/mitigation policies using a variety of machine learning techniques. To the best of our knowledge, this represents the first study that defines fire regimes spatially at a global scale bridging existing knowledge gaps between global and regional fire studies.Our results represent an attempt at improving the integration of multiple disciplines in the context of effective data-driven decision-making under natural hazards uncertainty. Several challenges are still open. We hope that this research can serve as a motivation to expand the field's perspective with high-impact applied projects involving mathematical, ecological, economic, data, and social sciences.
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- 2021
11. Accounting for climate change in a forest planning stochastic optimization model
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Garcia-Gonzalo, Jordi, Pais, Cristobal, Bachmatiuk, Joanna, and Weintraub, Andres
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Climatic changes -- Environmental aspects -- Models ,Learning models (Stochastic processes) -- Usage ,Forest management -- Models ,Earth sciences - Abstract
An approach is proposed for incorporating the variations in timber growth and yield due to climate change uncertainty into the forest harvesting decision process. A range of possible climate scenarios are transformed by a forest growth and yield model into tree growth scenarios, which in turn are integrated into a multistage stochastic model that determines the timber cut in each future period so as to maximize net present value over the planning horizon. For comparison purposes, a deterministic model using a single average climate scenario is also developed. The performance of the deterministic and stochastic formulations are tested in a case study of a medium-term forest planning problem for a Eucalyptus forest in Portugal where climate change is expected to severely impact production in the coming years. Experiments conducted using 32 climate scenarios demonstrate the stochastic model's superior results in terms of present value, particularly in cases of relatively high minimum timber demand. The model should therefore be useful in supporting forest planners' decisions under climate uncertainty. Key words: forestry, stochastic decision models, forest planning, climate change, uncertainty. Cet article propose une approche qui permet d'incorporer dans le processus de decision concernant la recolte de bois les variations de croissance et de rendement dues a l'incertitude engendree par le changement climatique. Une variete de scenarios climatiques potentiels sont transformes a l'aide d'un modele de croissance et de rendement de la foret en trois scenarios de croissance qui sont ensuite integres dans un modele stochastique multietape lequel determine le calendrier de recolte durant chaque periode future en maximisant la valeur actualisee nette sur l'horizon de planification. Un modele deterministe utilisant un seul scenario climatique moyen a aussi ete developpe pour servir de comparaison. La performance des formulations deterministe et stochastique a ete testee dans une etude de cas portant sur un probleme de planification forestiere a moyen terme pour une foret d'eucalyptus au Portugal oU le changement climatique devrait severement affecter la production dans les annees a venir. Des experiences realisees en utilisant 32 scenarios climatiques demontrent la superiorite des resultats du modele stochastique en termes de valeur actualisee, particulierement dans les cas oU la demande minimum de bois est relativement elevee. Le modele devrait par consequent etre utile pour aider les gestionnaires forestiers a prendre des decisions dans un contexte d'incertitude due au climat. [Traduit par la Redaction] Mots-cles : foresterie, modele decisionnel stochastique, planification forestiere, changement climatique, incertitude., 1. Introduction Uncertainty and risk play an important role in the development of forest management planning (Pasalodos et al. 2013; Yousefpour et al. 2012). Typical examples of these phenomena are [...]
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- 2016
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12. Adjusting Rate of Spread Factors through Derivative-Free Optimization: A New Methodology to Improve the Performance of Forest Fire Simulators
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Carrasco, Jaime, Pais, Cristobal, Shen, Zuo-Jun Max, and Weintraub, Andres
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FOS: Computer and information sciences ,Computer Science - Machine Learning ,Optimization and Control (math.OC) ,FOS: Mathematics ,Mathematics - Optimization and Control ,Machine Learning (cs.LG) - Abstract
In practical applications, it is common that wildfire simulators do not correctly predict the evolution of the fire scar. Usually, this is caused due to multiple factors including inaccuracy in the input data such as land cover classification, moisture, improperly represented local winds, cumulative errors in the fire growth simulation model, high level of discontinuity/heterogeneity within the landscape, among many others. Therefore in practice, it is necessary to adjust the propagation of the fire to obtain better results, either to support suppression activities or to improve the performance of the simulator considering new default parameters for future events, best representing the current fire spread growth phenomenon. In this article, we address this problem through a new methodology using Derivative-Free Optimization (DFO) algorithms for adjusting the Rate of Spread (ROS) factors in a fire simulation growth model called Cell2Fire. To achieve this, we solve an error minimization optimization problem that captures the difference between the simulated and observed fire, which involves the evaluation of the simulator output in each iteration as part of a DFO framework, allowing us to find the best possible factors for each fuel present on the landscape. Numerical results for different objective functions are shown and discussed, including a performance comparison of alternative DFO algorithms., 8 figures, 35 pages
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- 2019
13. Item Assignment Problem in a Robotic Mobile Fulfillment System.
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Kim, Hyun-Jung, Pais, Cristobal, and Shen, Zuo-Jun Max
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HEURISTIC algorithms , *ASSIGNMENT problems (Programming) , *ALGORITHMS , *ROBOTICS , *WAREHOUSE automation , *ORDER picking systems , *CARTONS - Abstract
A robotic mobile fulfillment system (RMFS) performs the order fulfillment process by bringing inventory to workers at pick-pack-and-ship warehouses. In the RMFS, robots lift and carry shelving units, called inventory pods, from storage locations to picking stations where workers pick items off the pods and put them into shipping cartons. The robots then return the pods to the storage area and transport other pods. In this article, we consider an item assignment problem in the RMFS in order to maximize the sum of similarity values of items in each pod. We especially focus on a reoptimization heuristic to address the situation where the similarity values are altered so that a good assignment solution can be obtained quickly with the changed similarity values. A constructive heuristic algorithm for the item assignment problem is developed, and then, a reoptimization heuristic is proposed based on the constructive heuristic algorithm. Then, computational results for several instances of the problem with 10–500 items are presented. We further analyze the case for which an item type can be placed into two pods. Note to Practitioners—This article proposes an efficient heuristic algorithm for assigning items to pods in a robotic mobile fulfillment system (RMFS) so that items ordered together frequently are put into the same pod. Computational results with 10–500 items show that the gaps from upper bounds are very small on average. For cases where the similarity values between items change or their estimation is not accurate due to the fluctuations in demand, a reoptimization heuristic algorithm that alters the original assignment is developed. The experimental results show that the reoptimization algorithm is robust when perturbation levels are approximately 40%–50% of the original similarity values with much less computation times. We believe that this research work can be very helpful for operating the RMFS efficiently. [ABSTRACT FROM AUTHOR]
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- 2020
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14. Deep fire topology: Understanding the role of landscape spatial patterns in wildfire occurrence using artificial intelligence.
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Pais, Cristobal, Miranda, Alejandro, Carrasco, Jaime, and Shen, Zuo-Jun Max
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ARTIFICIAL intelligence , *FIRE management , *COMPUTER vision , *WILDFIRE prevention , *WILDFIRES , *DEEP learning , *TOPOLOGY , *LANDSCAPES - Abstract
Increasing wildfire activity globally has become an urgent issue with enormous ecological and social impacts. In this work, we focus on analyzing and quantifying the influence of landscape topology, understood as the spatial structure and interaction of multiple land-covers in an area, on fire ignition. We propose a deep learning framework, Deep Fire Topology, to estimate and predict wildfire ignition risk. We focus on understanding the impact of these topological attributes and the rationale behind the results to provide interpretable knowledge for territorial planning considering wildfire ignition uncertainty. We demonstrate the high performance and interpretability of the framework in a case study, accurately detecting risky areas by exploiting spatial patterns. This work reveals the strong potential of landscape topology in wildfire occurrence prediction and its implications to develop robust landscape management plans. We discuss potential extensions and applications of the proposed method, available as an open-source software. • We show the impact of different landscape topologies on wildfire ignitions. • We develop a novel and interpretable deep learning framework. • The model detects and highlights low/high-risk land-cover topological patterns. • We obtain accurate fire occurrence predictions only using land-cover data. • Our framework can be applied in any field exploiting computer vision. [ABSTRACT FROM AUTHOR]
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- 2021
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