Few-shot Adaptation for Manipulating Granular Materials Under Domain Shift

Autonomous lander missions on extraterrestrial bodies will need to sample granular material while coping with domain shift, no matter how well a sampling strategy is tuned on Earth. This paper proposes an adaptive scooping strategy that uses deep Gaussian process method trained with meta-learning to learn on-line from very limited experience on the target terrains. It introduces a novel meta-training approach, Deep Meta-Learning with Controlled Deployment Gaps (CoDeGa), that explicitly trains the deep kernel to predict scooping volume robustly under large domain shifts. Employed in a Bayesian Optimization sequential decision-making framework, the proposed method allows the robot to use vision and very little on-line experience to achieve high-quality scooping actions on out-of-distribution terrains, significantly outperforming non-adaptive methods proposed in the excavation literature as well as other state-of-the-art meta-learning methods. Moreover, a dataset of 6,700 executed scoops collected on a diverse set of materials, terrain topography, and compositions is made available for future research in granular material manipulation and meta-learning

Characterization and Generation of 3D Realistic Geological Particles with Metaball Descriptor based on X-Ray Computed Tomography

The morphology of geological particles is crucial in determining its granular characteristics and assembly responses. In this paper, Metaball-function based solutions are proposed for morphological characterization and generation of three-dimensional realistic particles according to the X-ray Computed Tomography (XRCT) images. For characterization, we develop a geometric-based Metaball-Imaging algorithm. This algorithm can capture the main contour of parental particles with a series of non-overlapping spheres and refine surface-texture details through gradient search. Four types of particles, hundreds of samples, are applied for evaluations. The result shows good matches on key morphological indicators(i.e., volume, surface area, sphericity, circularity, corey-shape factor, nominal diameter and surface-equivalent-sphere diameter), confirming its characterization precision. For generation, we propose the Metaball Variational Autoencoder. Assisted by deep neural networks, this method can generate 3D particles in Metaball form, while retaining coessential morphological features with parental particles. Additionally, this method allows for control over the generated shapes through an arithmetic pattern, enabling the generation of particles with specific shapes. Two sets of XRCT images different in sample number and geometric features are chosen as parental data. On each training set, one thousand particles are generated for validations. The generation fidelity is demonstrated through comparisons of morphologies and shape-feature distributions between generated and parental particles. Examples are also provided to demonstrate controllability on the generated shapes. With Metaball-based simulations frameworks previously proposed by the authors, these methods have the potential to provide valuable insights into the properties and behavior of actual geological particles

Deconstructing the glass transition through critical experiments on colloids

The glass transition is the most enduring grand-challenge problem in contemporary condensed matter physics. Here, we review the contribution of colloid experiments to our understanding of this problem. First, we briefly outline the success of colloidal systems in yielding microscopic insights into a wide range of condensed matter phenomena. In the context of the glass transition, we demonstrate their utility in revealing the nature of spatial and temporal dynamical heterogeneity. We then discuss the evidence from colloid experiments in favor of various theories of glass formation that has accumulated over the last two decades. In the next section, we expound on the recent paradigm shift in colloid experiments from an exploratory approach to a critical one aimed at distinguishing between predictions of competing frameworks. We demonstrate how this critical approach is aided by the discovery of novel dynamical crossovers within the range accessible to colloid experiments. We also highlight the impact of alternate routes to glass formation such as random pinning, trajectory space phase transitions and replica coupling on current and future research on the glass transition. We conclude our review by listing some key open challenges in glass physics such as the comparison of growing static lengthscales and the preparation of ultrastable glasses, that can be addressed using colloid experiments.Comment: 137 pages, 45 figure

Tunnel Magnetoresistance in Self-Assemblies of Exchange-Coupled Core/Shell Nanoparticles

We report the precise control of tunneling magnetoresistance (TMR) in devices of self-assembled core-shell Fe3O4/Co1-xZnxFe2O4 nanoparticles (0≤x≤1). Adjusting the magnetic anisotropy through the content of Co2+ in the shell, provides an accurate tool to control the switching field between the bistable states of the TMR. In this way, different combinations of soft-hard and hard-soft core/shell configurations can be envisaged for optimizing devices with the required magnetotransport response.Fil: Fabris, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Lima, Enio Junior. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Quinteros, Cynthia Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Neñer, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Granada, Mara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Sirena, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Zysler, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Leborán, Victor. Universidad de Santiago de Compostela; EspañaFil: Rivadulla, Francisco. Universidad de Santiago de Compostela; EspañaFil: Winkler, Elin Lilian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin

Exploring analogies between granular materials and fluids

The direct application of fluid system approaches to granular materials oftentimes leads to spectacular failures, e.g. two miscible fluids shaken in a container rapidly become an homogeneous mixture, while vibrating a device containing two kinds of powders result in extreme segregation. Nevertheless, much can be learned through analogies between these disparate systems. The approach taken in this work is to focus on adapting concepts from fluid behavior and explore their application in relevant industrial processes involving granular materials---such as mixing/segregation, heat transfer and flowability. We use Particle Dynamics (PD)---a Discrete Element Method---to model transport and flow of granular materials.Adhesion, for example, is commonly found in operations involving fine powders where van der Waals forces start to play an important role. Our PD model, which is capable of simulating dry adhesive interactions, is used to study mixing/segregation. By introducing a characterization tool---the van der Waals Granular Bond Number---the asymptotic mixed/segregated state of the system is analytically predicted. These predictions are most easily summarized by phase-space diagrams which exhibit both mixed and segregated regions. The phase-space diagrams are computationally tested (with PD) by selecting granular materials of different properties so that we explore both mixed and segregated regions. Each of these materials is allowed to reach its asymptotic state in a mixing drum, and this final state is compared to the predictions.Beyond predicting the asymptotic state of a system, the next natural step is to explore the possibility of controlling it. With this purpose, we propose the addition of ``helper" particles that can either promote mixing or segregation. These amphiphilic helper particles---also called Janus particles---act as bridges between the base (non-helper) particles, alternatively promoting mixing in a system that would otherwise segregate (surfactant helpers) or separating a specific kind of particle from a mixture (extractant helpers). Phase space diagrams summarizing these trends are analytically built by comparing the interaction forces in the system: the final state of the system is determined by the interactions that predominate. Again, the predictions are then tested against results obtained by PD simulations of the system including Janus particles, which are further compared to the binary adhesive system that contain no helper particles.The presence of adhesive forces in granular materials can also affect the flowability of a granular material. Glidants---also known as flow aids or conditioners---are frequently added to dry cohesive powders to improve their flow properties and to facilitate their handling. These aids can reduce the inter-particle forces by imposing a physical barrier between host particles but are often identified on a trial-and-error or ad hoc basis. Using our PD model and characterization tools, glidant particles are engineered to improve the flowability properties of a dry cohesive powder.Finally, heat transfer within granular materials is studied by observing the dominant heat transfer mechanisms in the granular bed. Specifically, we examine the conditions necessary to achieve conduction-dominated versus convection-dominated heat transfer and introduce a granular analog of the Peclet number as a means of quantifying the transition. Our experiments consist of PD simulations of rotating tumblers where the granular material is being heated from the walls. When conduction is the dominant mechanism, increasing the mixing rate seems to have a positive impact in the rate of heat transfer; however, under convection-dominated conditions the opposite is often true. In order to further clarify the role of inter-particle mixing, the temperature profiles of the material in the drums are compared to a continuum model for mixing of cohesionless granular materials. Similarities between these two are most likely to be found when convection is the mechanism that dominates the heat transport. Dimensionless numbers are used to correlate the results obtained for multiple systems and surprising degree of similarity is found when compared to analogous fluid correlations

Composing Music for Acoustic Instruments and Electronics Mediated Through the Application of Microsound

This project seeks to extend, through a portfolio of compositions, the use of microsound to mixed works incorporating acoustic instrument and electronics. Issues relating to the notation of microsound when used with acoustic instruments are explored and the adoption of a clear and intuitive system of graphical notation is proposed. The design of the performance environment for the electroacoustic part is discussed and different models for the control of the electronics are considered. Issues relating to structure and form when applied to compositions that mix note-based material with texture-based material are also considered. A framework based on a pure sound/noise continuum, used in conjunction with a hierarchy of gestural archetypes, is adopted as a possible solution to the challenges of structuring mixed compositions. Gestural and textural relationships between different parts of the compositions are also explored and the use of extended instrumental techniques to create continua between the acoustic and the electroacoustic is adopted. The role of aleatoric techniques and improvisation in both the acoustic and the electroacoustic parts are explored through adoption of an interactive performance environment incorporating a pitch-tracking algorithm. Finally, the advantages and disadvantages of real time recording and processing of the electronic part when compared with live processing of pre-existing sound-files are discussed