Enhancing decision support for solutions of packing problem in additive manufacturing: features, datasets and experimental studies

Additive manufacturing (AM) encompasses a set of technological advancements that enable objects to be produced in an incremental layer-by-layer material deposition process. The advantages of such techniques include a more flexible production chain and the capacity to manufacture highly customised products. The manufacturing process takes place within an enclosed build container, referred to as a `build volume', which should be fully utilised to achieve more efficient production times and reduce costs. This requirement is at the core of cutting and packing problems, which are well-known combinatorial problems that have been algorithmically addressed by the operations research community. This study devotes particular attention to the understanding of three-dimensional irregular packing (3DIP) problems, i.e., the task of arranging arbitrary three-dimensional geometries. It is motivated by the necessity for more precise and well-informed terminology and categorisation criteria in this problem domain. The thesis also investigates the properties of existing 3DIP algorithms and the performance patterns with respect to build volume utilisation and the feature space. These topics have been scarcely addressed in the literature due to the amount of available data and relevant features on this problem domain. The primary objective of this work is to contribute to more efficient AM processes by assessing how volume utilisation can be maximised within the machine at every build. First, the research assists in the characterisation of 3DIP problems by introducing new measurements for assessing part complexity. Experiment results demonstrate that such metrics are suitable for describing entrant geometric features in non-convex three-dimensional objects. Second, this study extends the existing taxonomy for cutting and packing and provides the most significant benchmark for 3DIP in the literature, which is aligned with the challenging requirements observed in the AM environment. Third, it evaluates some of the most commonly used packing approaches based on the deepest bottom left with fill heuristic. Lastly, this thesis presents one of the first reported applications of algorithm selection to 3DIP problems, mapping the problem instance features, including the newly proposed ones, to the best packing algorithm. The results confirm the potential of the algorithm selection approach to deliver increased build volume utilisation in AM processes

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset

Enhancing decision support for solutions of packing problem in additive manufacturing: features, datasets and experimental studies

Additive manufacturing (AM) encompasses a set of technological advancements that enable objects to be produced in an incremental layer-by-layer material deposition process. The advantages of such techniques include a more flexible production chain and the capacity to manufacture highly customised products. The manufacturing process takes place within an enclosed build container, referred to as a `build volume', which should be fully utilised to achieve more efficient production times and reduce costs. This requirement is at the core of cutting and packing problems, which are well-known combinatorial problems that have been algorithmically addressed by the operations research community. This study devotes particular attention to the understanding of three-dimensional irregular packing (3DIP) problems, i.e., the task of arranging arbitrary three-dimensional geometries. It is motivated by the necessity for more precise and well-informed terminology and categorisation criteria in this problem domain. The thesis also investigates the properties of existing 3DIP algorithms and the performance patterns with respect to build volume utilisation and the feature space. These topics have been scarcely addressed in the literature due to the amount of available data and relevant features on this problem domain. The primary objective of this work is to contribute to more efficient AM processes by assessing how volume utilisation can be maximised within the machine at every build. First, the research assists in the characterisation of 3DIP problems by introducing new measurements for assessing part complexity. Experiment results demonstrate that such metrics are suitable for describing entrant geometric features in non-convex three-dimensional objects. Second, this study extends the existing taxonomy for cutting and packing and provides the most significant benchmark for 3DIP in the literature, which is aligned with the challenging requirements observed in the AM environment. Third, it evaluates some of the most commonly used packing approaches based on the deepest bottom left with fill heuristic. Lastly, this thesis presents one of the first reported applications of algorithm selection to 3DIP problems, mapping the problem instance features, including the newly proposed ones, to the best packing algorithm. The results confirm the potential of the algorithm selection approach to deliver increased build volume utilisation in AM processes

Atributos químicos e físicos de latossolos e sua relação com os rendimentos de milho e feijão irrigados Chemical and physical attributes of oxisols and their relation with irrigated corn and common bean yields

Em sistemas de produção agrícola que utilizam a irrigação, uma das principais causas da variabilidade dos rendimentos, a disponibilidade de água para as culturas, é controlada. Nesse caso, outros fatores limitantes ao rendimento, relacionados a atributos de solo, passam a ter sua importância aumentada. Com o objetivo de investigar a variabilidade espacial dos principais atributos químicos e do rendimento de culturas, além de determinar os atributos químicos e físico-hídricos do solo em diferentes zonas de rendimento, foram analisadas duas áreas comerciais irrigadas por pivô central, com 51,8 e 58,2 ha, localizadas, respectivamente, em Trindade do Sul (TS) e Palmeira das Missões (PM), no Rio Grande do Sul (RS). As amostragens para caracterização dos atributos químicos foram georreferenciadas seguindo uma malha regular de 100 x 100 m, na camada de 0-0,10 m. Já para investigar a relação entre os atributos químicos e físico-hídricos do solo com os rendimentos obtidos, dada a extensão das áreas, três zonas com distinto potencial produtivo foram estabelecidas, utilizando os mapas de rendimento disponíveis (safras de feijão-preto de 2005/2006 e safrinha de 2006 em TS, e de milho de 2002/2003 e 2003/2004 em PM), obtidos por colhedoras equipadas com sensores de rendimento. Nessas zonas, quinze pontos amostrais foram investigados em cada área nas camadas de 0-0,05, 0,05-0,10 e 0,10-0,20 m. Os atributos químicos do solo foram submetidos à análise de estatística descritiva e geoestatística. Eles apresentaram dependência espacial classificada como forte e moderada, com modelo ajustado à semivariância predominantemente esférico. O P apresentou a maior variabilidade espacial e o pH a menor. Embora manejadas sob irrigação, ambas as áreas apresentaram variabilidade espacial de rendimento. Na zona de baixo rendimento de TS, foram constatadas acidez no solo, baixa saturação de bases e menor capacidade de água disponível, e na de PM foram observadas limitações físicas representadas por compactação por meio dos indicadores densidade, resistência à penetração e macroporosidade. A ocorrência de zonas com menor rendimento das culturas irrigadas nas duas áreas foi associada a limitações químicas e físicas do solo, especialmente em subsuperfície.<br>Under irrigated agriculture one of the main causes of yield variability, which is the plant-available water, is controlled. In this case, other yield limitations caused by soil attributes become more relevant. To investigate the spatial variability of soil attributes and crop yields, besides the relation between chemical and physical-hydric soil attributes and crop yields of two irrigated commercial plantations (51.8 and 58.2 ha) were studied in Trindade do Sul (TS) and Palmeira das Missões (PM) respectively, in the state of Rio Grande do Sul, Brazil. The soil was sampled from a regular grid of 100 x 100 m in the 0-0.10 m layer for chemical analysis. To investigate the relation between chemical and physical-hydric soil attributes and yields, due to the large area of the plantations, three soil management zones were established based on yield maps available (common bean in 2005/06 and 2006, in TS, and corn in 2002/03 and 2003/04, in PM) recorded by harvesters equipped with yield sensors. In these zones, 15 grid points were sampled in the layers 0-0.05, 0.05-0.10 and 0.10-0.20 m to analyze soil attributes. These underlying soil data, analyzed by descriptive statistics and geostatistics, classified the spatial dependence as strong and moderate, with predominance of the spherical model. Spatial variability was highest for P and lowest for pH. Although both plantations were irrigated there was spatial variability in the yields. In the low-yield zone in TS soil acidity, low base saturation and lower available soil water capacity was diagnosed, while in PM the yield constraints were associated to soil compaction, expressed in the bulk density, soil resistance and macroporosity. The low yield zones of irrigated crops, in both croplands, were linked mainly to chemical and physical limitations in the subsurface