Using Dynamic Programming to Obtain Efficient Kiln-drying Schedules

This paper outlines a method for determining kiln-drying schedules that is based on the optimization technique of dynamic programming. The method is described with reference to the kiln drying of cedar pencil slats, but could be extended, with appropriate adjustments, to the kiln drying of other wood materials

Scale and Unit Specification Influences in Harvest Scheduling with Maximum Area Restrictions

This article examines alternative approaches for representing a forest region to be scheduled for harvesting, where the primary concerns are maximizing return and imposing a maximum contiguous area of disturbance restriction. One approach assumes that any two adjacent management units exceed a regulated maximum area of disturbance. An alternative approach recognizes that management units may be substantially smaller than the maximum area restriction, so simultaneously disturbing two neighboring units does not necessarily represent a maximum area violation. The distinguishing feature of these two approaches is the way in which a forest is spatially represented. A single time period, 351 management unit harvest scheduling problem is utilized to investigate whether analysis results are subject to manipulation when forest representation, and associated modeling, is interpreted in different ways. Empirical results highlight significant economic and spatial variation in harvest schedules when maximum area restrictions are imposed using alternative approaches

Forestry harvest planning considering social impacts and soil compaction issues

Forest harvest planning implies great challenges for wood supply companies. This type of planning involves complex decision processes involving different stakeholders, as well as factors outside the stakeholders that directly affect the resolution of the problem. Within these factors that affect, one of special interest is the conditioning by risk of soil compaction. This factor can be decisive in planning since it functions as a restriction or prohibition on harvesting operations. This phenomenon depends on the hydrological balances of the soils, which in turn depends on the meteorological and climatic conditions. That is why to properly address these decision processes, stochastic approaches are required. On the other hand, there exists a large number of SMEs and micro-SMEs that are dedicated to forest harvesting operations, which work as contractors for industries and provide. These companies have a direct interference in the industrial matrix and in the labor offer in the regional economy of the Argentine Northwest. However, a purely utilitarian approach to forest harvesting would tend to prioritize the hiring of larger companies with superior technical capacity, which would allow production costs to be reduced. However, this would impede the possibility of growth of the regional economy, leaving out smaller companies, which do not have the resources for technological migration. This issue has gained relevance after United Nations included this topic in its Sustainable Development Goals agenda (ODS 8).To contribute to this line, an approach based on mathematical programming is proposed that allow addressing the stochastic complexity of the problem (due to the risk of soil compaction), but that balance the workload delivered to each contractor, ensuring compliance with the demand. For this, a goal programming model is developed, which contemplates the minimization of costs and the balancing of the workload among contractors.Fil: Rossit, Daniel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Matemática Bahía Blanca. Universidad Nacional del Sur. Departamento de Matemática. Instituto de Matemática Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Broz, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Forestales; ArgentinaFil: Pais, Cristóbal. University of California at Berkeley; Estados UnidosFil: Weintraub, Andrés. Universidad de Chile.; ChileXXI Latin Ibero-American Conference on Operations Research -CLAIO 2022Buenos AiresArgentinaUniversidad de Buenos Aires. Facultad de Ciencias Exactas y Naturale

Comparison of metaheuristics for the firebreak placement problem: a simulation-based optimization approach

The problem of firebreak placement is crucial for fire prevention, and its effectiveness at landscape scale will depend on their ability to impede the progress of future wildfires. To provide an adequate response, it is therefore necessary to consider the stochastic nature of fires, which are highly unpredictable from ignition to extinction. Thus, the placement of firebreaks can be considered a stochastic optimization problem where: (1) the objective function is to minimize the expected cells burnt of the landscape; (2) the decision variables being the location of firebreaks; and (3) the random variable being the spatial propagation/behavior of fires. In this paper, we propose a solution approach for the problem from the perspective of simulation-based optimization (SbO), where the objective function is not available (a black-box function), but can be computed (and/or approximated) by wildfire simulations. For this purpose, Genetic Algorithm and GRASP are implemented. The final implementation yielded favorable results for the Genetic Algorithm, demonstrating strong performance in scenarios with medium to high operational capacity, as well as medium levels of stochasticit

A mixed integer programming approach for multi-action planning for threat management

Planning for management actions that address threats to biodiversity is important for securing its long term persistence. However, systematic conservation planning (SCP) has traditionally overlooked this aspect and just focused on identiying priority areas without any recommendation on actions needed. This paper develops a mixed integer mathematical programming (MIP) approach for the multi-action management planning problem (MAMP), where the goal is to find an optimal combination of management actions that abate threats, in an efficent way while accounting for connectiivty. An extended version of the MAMP model (MAMP-E) is also proposed that adds an expression for minimizing fragmentation between different actions. To evaluate the efficiency of the two models, they were applied to a case study corresponding to a large area of the Mitchell River in Northern Asutralia, where 45 species of freshwater fish are exposed to the presence of four threats. The evaluation compares our exact MIP approach with the conservation planning software Marxan and the heuristic approach developed in Cattarino et al. (2015). The results obtained show that our MIP models have three advantages over their heuristic counterparts: shorter execution times, higher solutions quality, and a solution quality guarantee. Hence, the proposed MIP methodology provides a more effective framework for addressing the multi-action conservation problem.Peer ReviewedPostprint (published version

Algoritmos de optimización para la logística marítima y terrestre de una empresa salmonera de Chile

La industria salmonera es uno de los principales sectores de exportación de Chile. En la etapa de engorda en agua salada, los peces son cultivados en grandes jaulas flotantes agrupadas en centros de cultivo a lo largo de toda la Décima Región del sur de Chile. Al momento de la cosecha, cuando alcanzan un peso y volumen de venta, los peces deben ser transportados en barcos hasta los denominados centros de acopio, ubicados cerca de las plantas de faenado. Llegados al centro de acopio los peces son depositados en grandes jaulas en espera a ser enviados a las plantas de faenado. En estas plantas se realiza la faena y limpieza de los peces que luego son enviados hacia las plantas de proceso mediante transporte terrestre. Uno de los principales desafíos de las empresas salmoneras con este tipo de cadena de proceso es la planificación global de la logística marítima y terrestre, combinada con la planificación del stock en las jaulas en los centros de acopio y las líneas de producción en las plantas de faenado. En este trabajo, estudiamos este problema y presentamos un modelo de programación entera y un algoritmo heurístico para su resolución. Como resultado de este trabajo, se desarrolló un software de planificación que actualmente se utiliza en la empresa de mayor producción de salmones de Chile. Comparamos los resultados computacionales de ambos métodos y mostramos resultados sobre instancias reales de la empresa mencionada.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Cell cycle-regulated expression of the muscle determination factor Myf5 in proliferating myoblasts.

Myf5 is the earliest-known muscle-specific factor to be expressed in vivo and its expression is associated with determination of the myoblast lineage. In C2 cells, we show by immunocytolocalization that Myf5 disappears rapidly from cells in which the differentiation program has been initiated. In proliferating myoblasts, the levels of Myf5 and MyoD detected from cell to cell are very heterogeneous. We find that some of the heterogeneity of Myf5 expression arises from a posttranscriptional regulation of Myf5 by the cell cycle. Immunoblotting of extracts from synchronized cultures reveals that Myf5 undergoes periodic fluctuations during the cell cycle and is absent from cells blocked early in mitosis by use of nocodazole. The disappearance of Myf5 from mitotic cells involves proteolytic degradation of a phosphorylated form of Myf5 specific to this phase of the cell cycle. In contrast, MyoD levels are not depleted in mitotic C2 cells. The mitotic destruction of Myf5 is the first example of a transcription factor showing cell cycle-regulated degradation. These results may be significant in view of the possible role of Myf5 in maintaining the determination of proliferating cells and in timing the onset of differentiation

ERK1/2 MAP kinases promote cell cycle entry by rapid, kinase-independent disruption of retinoblastoma–lamin A complexes

When in the nucleus, ERK1/2 dislodges the retinoblastoma protein from lamin A, facilitating its rapid phosphorylation

Observational diagnostics of gas in protoplanetary disks

Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date manuscript: October 2008. 17 Pages, 6 graphics, 134 reference