Papers by Andrés Weintraub
Interfaces, 2012
In this paper, we present a system that Compañía Sud Americana de Vapores (CSAV), one of the worl... more In this paper, we present a system that Compañía Sud Americana de Vapores (CSAV), one of the world's largest shipping companies, developed to support its decisions for repositioning and stocking empty containers. CSAV's main business is shipping cargo in containers to clients worldwide. It uses a fleet of about 700,000 TEU containers of different types, which are carried by both CSAV-owned and third-party ships. Managing the container fleet is complex; CSAV must make thousands of decisions each day. In particular, imbalances exist among the regions. For example, China often has a deficit of empty containers and is a net importer; Saudi Arabia often has a surplus and is a net exporter. CSAV and researchers from the University of Chile developed the Empty Container Logistics Optimization System (ECO) to manage this imbalance. ECO's multicommodity, multiperiod model manages the repositioning problem, whereas an inventory model determines the safety stock required at each lo...
Forest Science, Apr 1, 2009
We survey three integer-programming approaches for solving the area restriction model (ARM) for h... more We survey three integer-programming approaches for solving the area restriction model (ARM) for harvest scheduling. We describe and analyze each of these approaches in detail, comparing them both from a modeling and computational point of view. In our analysis of these formulations as modeling tools we show how each can be extended to incorporate additional harvest scheduling concerns. In our computational analysis we illustrate the strengths and weaknesses of each formulation as a practical optimization tool by studying harvest scheduling in four North American forests.
Frontiers in forests and global change, Feb 10, 2023
Preventive management of wildfire risk through traditional fuel reduction management practices or... more Preventive management of wildfire risk through traditional fuel reduction management practices or fire-adapted forest management (González-Olabarria and Pukkala, 2011) involves assessing the probability of a fire anywhere within the study area, in order to determine the potential damage to values at risk and evaluate the costs Frontiers in Forests and Global Change 01 frontiersin.org
Forest Policy and Economics, Jun 1, 2019
A core process in forestry planning corresponds to the design of optimal harvesting policies alon... more A core process in forestry planning corresponds to the design of optimal harvesting policies along with road network layouts. In the most common setting, decision makers seek for solutions that maximize the profit of the forest while respecting operative and market constraints. Due to the long-term nature of the industry, the inherent uncertainty in both forest growth and market conditions should be taken into account. Nowadays, forest planning must target towards a sustainable management; the maximization of carbon sequestration and the minimization of land erosion are two common environmental goals. The planning challenge addressed in this paper integrates uncertainty of future forest growth and timber prices with the need for considering three criteria; net-present value, carbon sequestration, and land erosion caused by the road construction within the forest. By using mathematical programming tools and stochastic optimization techniques, we develop a stochastic multicriteria model that enables decision makers to have not only one, but a pool of long term planning policies. Moreover, a risk-averse variant of the framework is also considered. To the best of our knowledge, this is the first time that this type of forestry planning setting, which responds to the new challenges of the industry, is addressed. The proposed tool is used on an eucalyptus forest located in Portugal; the obtained results show the benefit of the proposed framework for producing a pool of sustainable forest plans with efficient trade-offs among the three considered criteria.
Forests
This paper addresses a forest harvesting problem with adjacency constraints, including additional... more This paper addresses a forest harvesting problem with adjacency constraints, including additional environmental constraints to protect wildlife habitats and minimize infrastructure deployment costs. To this end, we propose an integer programming model to include those considerations during the optimization of the harvest regime of a Mexican forest. The model considered was based on the Unit Restriction Model, a benchmark approach that merges the management units before the optimization process. The resulting model, namely the Green Unit Restriction Model (GURM) and the benchmark model (URM) from the literature were tested with the forest Las Bayas, using information obtained from the SiPlaFor project from Universidad Juárez. The proposed model was solvable in all tested instances. Furthermore, a sensitivity analysis study over a core data set of test instances was carried out on the different parameters of the GURM model to determine optimal configurations for the specific case stud...
Forest Science, 2009
We survey three integer-programming approaches for solving the area restriction model (ARM) for h... more We survey three integer-programming approaches for solving the area restriction model (ARM) for harvest scheduling. We describe and analyze each of these approaches in detail, comparing them both from a modeling and computational point of view. In our analysis of these formulations as modeling tools we show how each can be extended to incorporate additional harvest scheduling concerns. In our computational analysis we illustrate the strengths and weaknesses of each formulation as a practical optimization tool by studying harvest scheduling in four North American forests.
Frontiers in Forests and Global Change, 2021
Cell2Fire is a new cell-based wildland fire growth simulator designed to integrate data-driven la... more Cell2Fire is a new cell-based wildland fire growth simulator designed to integrate data-driven landscape management planning models. The fire environment is modeled by partitioning the landscape into cells characterized by fuel, weather, moisture content, and topographic attributes. The model can use existing fire spread models such as the Canadian Forest Fire Behavior Prediction System to model fire growth. Cell2Fire is structured to facilitate its use for predicting the growth of individual fires or by embedding it in landscape management simulation models. Decision-making models such as fuel treatment/harvesting plans can be easily integrated and evaluated. It incorporates a series of out-of-the-box planning heuristics that provide benchmarks for comparison. We illustrate their use by applying and evaluating a series of harvesting plans for forest landscapes in Canada. We validated Cell2Fire by using it to predict the growth of both real and hypothetical fires, comparing our pred...
Advances in Operations Research, 2020
Long time horizons, typical of forest management, make planning more difficult due to added expos... more Long time horizons, typical of forest management, make planning more difficult due to added exposure to climate uncertainty. Current methods for stochastic programming limit the incorporation of climate uncertainty in forest management planning. To account for climate uncertainty in forest harvest scheduling, we discretize the potential distribution of forest growth under different climate scenarios and solve the resulting stochastic mixed integer program. Increasing the number of scenarios allows for a better approximation of the entire probability space of future forest growth but at a computational expense. To address this shortcoming, we propose a new heuristic algorithm designed to work well with multistage stochastic harvest-scheduling problems. Starting from the root-node of the scenario tree that represents the discretized probability space, our progressive hedging algorithm sequentially fixes the values of decision variables associated with scenarios that share the same pat...
Annals of Operations Research, 2015
An introduction to the special volume on Operations Research in Forestry from the 14th Symposium ... more An introduction to the special volume on Operations Research in Forestry from the 14th Symposium for Systems Analysis in Forest Resources, held at the Marbella Resort, Maitencillo, Chile, March 8-11, 2011. This volume of the Annals of Operations Research contains some of the papers presented at the Symposium that were submitted for publication and passed the rigorous peer review process. In addition, manuscripts were solicited from the operations research and forest resources communities to enrich the contributions for this special volume. The 14th Symposium for Systems Analysis in Forest Resources was held at the Marbella Resort, Maitencillo, Chile, March 8-11, 2011. Seventeen keynote talks and 68 contributed papers were presented within the following general categories: forest environment, long range planning, transportation and logistics, tactical spatial planning, forest fire, stochastic models, and stand-level planning. Authors of papers came from 21 countries, making this the largest of the Systems Analysis in Forest Resources symposia held to date. This volume of the Annals of Operations Research contains some of the papers presented at the Symposium that were submitted for publication and passed the rigorous peer review process. In addition, manuscripts were solicited from the operations research and forest resources communities to enrich the contributions for this special volume. Some of the earliest applications of operations research to forest resource problems occurred in the late 1950s and early 1960s when linear programming (LP) was applied to a B B. Bruce Bare
Canadian Journal of Forest Research, 2015
When a company is integrated vertically, it can manage and plan its overall value chain in one di... more When a company is integrated vertically, it can manage and plan its overall value chain in one direct and integrated approach. However in many cases, companies follow a decoupled approach where forests and production plants optimize separately their processes in a supply-driven strategy. In Chile, the two largest forest companies are vertically integrated (i.e., they own forest and mills that produce logs, lumber, plywood, pulp, paper, and bioenergy, etc.). Historically, they have coordinated their value chains using a make-to-stock strategy, for which the forest is the main driver of the value chain activities. In this paper, we propose an integrated planning approach to show the impacts of a demand-driven integration of the value chain in the forest industry. To compare this strategy with the decoupled strategy, we propose a mixed integer programming (MIP) model for the integrated strategy. To illustrate our proposal, we use forest and production information from a Chilean forest ...
Annals of Operations Research, 2015
Forestry has contributed many problems to the Operations Research (OR) community. At the same tim... more Forestry has contributed many problems to the Operations Research (OR) community. At the same time, OR has developed many models and solution methods for use in forestry. In this article, we describe the current status of research on the application of OR methods to forestry and a number of research challenges or open questions that we believe will be of interest to both researchers and practitioners. The areas covered include strategic, tactical and operational planning, fire management, conservation and the use of OR to address environmental concerns. The paper also considers more general methodological areas that are important to forestry including uncertainty, multiple objectives and hierarchical planning.
PLANEX is a system that solves the road network construction together with the location of harves... more PLANEX is a system that solves the road network construction together with the location of harvesting machinery, skidders and towers, in planning the habilitation of up to a thousand hectares of terrain to harvest. The system is fed from digitalized information stored in geographic databases. This graphic tool automatically designs the road network, which is the third most important operational
Production and Operations Management, 2009
An important issue being discussed for Chilean pine plantation policies is the application of env... more An important issue being discussed for Chilean pine plantation policies is the application of environmental protection measures when managing its timber areas. Typical measures, already in place in more developed countries, include imposing riparian strips and protecting fragile soils from the use of heavy machinery. While environmental protection measures have been considered vital for decades, so far there has been almost no attempt to quantify both the benefits and costs of these measures. This paper attempts to measure the costs associated with the main measures which can help both the forestry firms and the government evaluate the cost impact of the new environmental protection regulations being studied. The analysis for different environmental scenarios is carried out by modifying a mixed integer LP, currently used for tactical planning by one forestry firm.
Operations Research, 2005
We consider a spatial problem arising in forest harvesting. For regulatory reasons, blocks harves... more We consider a spatial problem arising in forest harvesting. For regulatory reasons, blocks harvested should not exceed a certain total area, typically 49 hectares. Traditionally, this problem, called the adjacency problem, has been approached by forming a priori blocks from basic cells of 5 to 25 hectares and solving the resulting mixed-integer program. Superior solutions can be obtained by including the construction of blocks in the decision process. The resulting problem is far more complex combinatorially. We present an exact algorithmic approach that has yielded good results in computational tests. This solution approach is based on determining a strong formulation of the linear programming problem through a clique representation of a projected problem.
Operations Research, 2013
Connectivity requirements are a common component of forest planning models, with important exampl... more Connectivity requirements are a common component of forest planning models, with important examples arising in wildlife habitat protection. In harvest scheduling models, one way of addressing preservation concerns consists of requiring that large contiguous patches of mature forest are maintained. In the context of nature reserve design, it is common practice to select a connected region of forest, as a reserve, in such a way as to maximize the number of species and habitats protected. Although a number of integer programming formulations have been proposed for these forest planning problems, most are impractical in that they fail to solve reasonably sized scheduling instances. We present a new integer programming methodology and test an implementation of it on five medium-sized forest instances publicly available in the Forest Management Optimization Site repository. Our approach allows us to obtain near-optimal solutions for multiple time-period instances in fewer than four hours.
Natural Hazards, 2014
This paper proposes a multi-criteria approach that accounts for the risk of fire when determining... more This paper proposes a multi-criteria approach that accounts for the risk of fire when determining the optimal rotation of a forest stand that is being managed for both timber production and carbon sequestration purposes. The multi-criteria framework uses in a combined way, multi-objective optimization and compromise programming methods. The proposed approach is computationally simple and allows for the quantification of conflicts between the criteria considered through the elicitation of the corresponding Pareto frontiers. Once the best portion or compromise sets of the Pareto frontiers are determined, then some indications of the increase in social welfare due to a potential reduction in the risk of fire are obtained. We illustrate the use of our methodology by applying it to an example that has previously been investigated in the forestry literature. Finally, some potential policy implications derived from the results obtained are highlighted.
Journal of Multi-Criteria Decision Analysis, 2006
In this paper a decision-making process is applied to a Chilean forestry firm that must deal with... more In this paper a decision-making process is applied to a Chilean forestry firm that must deal with a host of environmental variables as well as profit making. At the core of this process is a 'dynamic objective-subjective structure' founded on the approach that decision making is about comprehending the preferences of the various parties involved and expanding the set of alternatives open to the decision makers. This is in contrast to many models that aim at finding the 'best alternative' and to decision analysis approaches that focus on presenting preferences via value functions. The paper describes in chronological order, following the sessions of a decisionmaking process, how the various components of the structure emerged. In doing so it demonstrates how the process led to an understanding of the real effects of dealing with the environment and how comprehending the preferences led to the introduction of new decision variables.
International Transactions in Operational Research, 2011
Operations research is becoming increasingly prevalent in the natural resource sector, specifical... more Operations research is becoming increasingly prevalent in the natural resource sector, specifically in agriculture, fisheries, forestry and mining. While there are similar research questions in these areas, e.g., how to harvest and/or extract the resources and how to account for environmental impacts, there are also differences, e.g., the length of time associated with a growth and harvesting or extraction cycle, and whether or not the resource is renewable. Research in all four areas is at different levels of advancement in terms of the methodology currently developed and the acceptance of implementable plans and policies. In this paper, we review the most recent and seminal work in all four areas, considering modeling, algorithmic developments and application.
Interfaces, 2006
Operations research (OR) has helped people to understand and manage agricultural and forestry res... more Operations research (OR) has helped people to understand and manage agricultural and forestry resources during the last 40 years. We analyzed its use to assess the past performance of OR models in this field and to highlight current problems and future directions of research and applications. Thus, in the agriculture part, we concentrate on planning problems at the farm and regional-sector level, environmental implications, risk and uncertainty issues, multiple criteria, and the formulation of livestock rations and feeding stuffs. In the forestry part, we concentrate on planning problems at the strategic, tactical, and operational levels, implementation issues, environmental implications, as well as the treatment of uncertainty and multiple objectives. Finally we made a comparison between the two areas in terms of problem types, problem-solving approaches, and reported applications.
Interfaces, 1999
The Chilean forestry sector is composed of private firms that combine large timber-land holdings ... more The Chilean forestry sector is composed of private firms that combine large timber-land holdings of mostly pine plantations and some eucalyptus with sawmills and pulp plants. Since 1988, to compete in the world market, the main Chilean forest firms, which have sales of about $1 billion, have started implementing OR models developed jointly with academics from the University of Chile. These systems support decisions on daily truck scheduling, short-term harvesting, location of harvesting machinery and access roads, and medium- and long-term forest planning. Approaches used in solving these complex problems include simulation, linear programming with column generation, mixed-integer LP formulations, and heuristic methods. The systems have led to a change in organizational decision making and to estimated gains of at least US $20 million per year.
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Papers by Andrés Weintraub