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

Structural transitions and magnetocaloric properties of low-cost MnNiSi-based intermetallics

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Control of Structural and Magnetic Properties of Polycrystalline Co2FeGe Films via Deposition and Annealing Temperatures

: Thin polycrystalline Co2FeGe films with composition close to stoichiometry have been fabricated using magnetron co-sputtering technique. Effects of substrate temperature (TS) and postdeposition annealing (Ta) on structure, static and dynamic magnetic properties were systematically studied. It is shown that elevated TS (Ta) promote formation of ordered L21 crystal structure. Variation of TS (Ta) allow modification of magnetic properties in a broad range. Saturation magnetization ~920 emu/cm3 and low magnetization damping parameter α ~ 0.004 were achieved for TS = 573 K. This in combination with soft ferromagnetic properties (coercivity below 6 Oe) makes the films attractive candidates for spin-transfer torque and magnonic devices

Electronic structure and ferroelectricity in SrBi2Ta2O9

The electronic structure of SrBi2Ta2O9 is investigated from first-principles, within the local density approximation, using the full-potential linearized augmented plane wave (LAPW) method. The results show that, besides the large Ta(5d)-O(2p) hybridization which is a common feature of the ferroelectric perovskites, there is an important hybridization between bismuth and oxygen states. The underlying static potential for the ferroelectric distortion and the primary source for ferroelectricity is investigated by a lattice-dynamics study using the Frozen Phonon approach.Comment: 17 pages, 7 figures. Phys. Rev. B, in pres

Multilayer design of CrN/MoN protective coatings for enhanced hardness and toughness

We report on CrN/MoN multilayer coatings, their structure, elemental and phase composition, residual stresses, mechanical properties and their dependence on deposition conditions. The hardness and toughness were considered as main parameters for improvement of the protective properties of coatings. Multilayers with varying bilayer periods, ranging from 40 nm to 2.2 mm, were obtained by using cathodic arc physical vapour deposition (Arc-PVD) on stainless steel substrate. The elemental analysis was performed using wavelength-dispersive X-ray spectroscopy (WDS). The surface morphology and cross-sections were analysed with scanning electron microscopy (SEM). The X-ray diffraction (XRD) measurements, including grazing incidence X-ray diffraction (GIXRD), in-plane diffraction analysis and electron backscatter diffraction (EBSD), were used for microstructure characterisation. Mechanical properties of deposited films were studied by measuring hardness (H) and Young's modulus (E) with micro-indentation, H/E and H3/E2 ratios were calculated. The dependences of internal structure and, hence, mechanical properties, on layer thickness of films have been found. Significant enhancement of hardness and toughness was observed with decreasing individual layer thickness to 20 nm: H = 38-42 GPa, H/E = 0.11The study was partly financed by the Foundation of Science and Technology (FCT) of Portugal, project UID/NAN/50024/2013, budget project of Ministry of Education and Science of Ukraine “Physical basics of forming the composition and properties of transition metals boride, nitride and boride-nitride films for application in machine-building” (number 0116U002621) and Erasmus Mundus scholarship from European Commission (grant number 2013-2526/001-001). B.O. Postolnyi is also grateful to Arlete Apolinário from LEPABE, Department of Chemical Engineering, Faculty of Engineering of the University of Porto, and to João H. Belo from IFIMUP and IN - Institute of Nanoscience and Nanotechnology, Physics and Astronomy Department, Faculty of Sciences of the University of Porto, for help and useful discussion.info:eu-repo/semantics/publishedVersio

Magnetic field strength and orientation effects on co-fe discontinuous multilayers close to percolation

International audienceMagnetization and magnetoresistance in function of the magnitude and orientation of applied magnetic field were studied in Co-Fe discontinuous multilayers close to their structural percolation. The high pulsed magnetic fields up to 33 T were used in the 120–310 K temperature range. Comparison between longitudinal and transverse with respect to the film plane field configurations was made in the low-field and high-field regimes in order to clarify the nature of the measured negative magnetoresistance. Coexistence of two distinct magnetic fractions, superparamagnetic SPM, consisting of small spherical Co-Fe granules and superferromagnetic SFM, by bigger Co-Fe clusters, was established in this system. These fractions were shown to have different relevance for the system magnetization and magnetotransport. While the magnetization is almost completely up to 97% defined by the SFM contribution and practically independent of temperature in this range, the magnetoresistance experiences a crossover from a regime dominated by Langevin correlations suppressed with temperature between neighbor SPM and SFM moments at low fields, to that dominated by spin scattering enhanced with temperature of charge carriers within SFM clusters at high fields. Also, the demagnetizing effects, sensitive to the field orientation, were found to essentially define the low-field behavior and characteristic crossover field

Challenges in Complex Systems Science

FuturICT foundations are social science, complex systems science, and ICT. The main concerns and challenges in the science of complex systems in the context of FuturICT are laid out in this paper with special emphasis on the Complex Systems route to Social Sciences. This include complex systems having: many heterogeneous interacting parts; multiple scales; complicated transition laws; unexpected or unpredicted emergence; sensitive dependence on initial conditions; path-dependent dynamics; networked hierarchical connectivities; interaction of autonomous agents; self-organisation; non-equilibrium dynamics; combinatorial explosion; adaptivity to changing environments; co-evolving subsystems; ill-defined boundaries; and multilevel dynamics. In this context, science is seen as the process of abstracting the dynamics of systems from data. This presents many challenges including: data gathering by large-scale experiment, participatory sensing and social computation, managing huge distributed dynamic and heterogeneous databases; moving from data to dynamical models, going beyond correlations to cause-effect relationships, understanding the relationship between simple and comprehensive models with appropriate choices of variables, ensemble modeling and data assimilation, modeling systems of systems of systems with many levels between micro and macro; and formulating new approaches to prediction, forecasting, and risk, especially in systems that can reflect on and change their behaviour in response to predictions, and systems whose apparently predictable behaviour is disrupted by apparently unpredictable rare or extreme events. These challenges are part of the FuturICT agenda