Self-assembly of Nanometer-scale Magnetic Dots with Narrow Size Distributions on an Insulating Substrate

The self-assembly of iron dots on the insulating surface of NaCl(001) is investigated experimentally and theoretically. Under proper growth conditions, nanometer-scale magnetic iron dots with remarkably narrow size distributions can be achieved in the absence of a wetting layer Furthermore, both the vertical and lateral sizes of the dots can be tuned with the iron dosage without introducing apparent size broadening, even though the clustering is clearly in the strong coarsening regime. These observations are interpreted using a phenomenological mean-field theory, in which a coverage-dependent optimal dot size is selected by strain-mediated dot-dot interactions.Comment: 5 pages, 4 figure

Improved Algebraic Algorithm On Point Projection For Bézier Curves

International audienceThis paper presents an improved algebraic pruning method for point projection for Bézier curves. It first turns the point projection into a root finding problem, and provides a simple but easily overlooked method to avoid finding invalid roots which is obviously irrelative to the closest point. The continued fraction method and its expansion are utilized to strengthen its robustness. Since NURBS curves can be easily turned into Bézier form, the new method also works with NURBS curves. Examples are presented to illustrate the efficiency and robustness of the new method

Propagation Path Loss Models in Forest Scenario at 605 MHz

When signals propagate through forest areas, they will be affected by environmental factors such as vegetation. Different types of environments have different influences on signal attenuation. This paper analyzes the existing classical propagation path loss models and the model with excess loss caused by forest areas and then proposes a new short-range wireless channel propagation model, which can be applied to different types of forest environments. We conducted continuous-wave measurements at a center frequency of 605 MHz on predetermined routes in distinct types of forest areas and recorded the reference signal received power. Then, we use various path loss models to fit the measured data based on different vegetation types and distributions. Simulation results show that the proposed model has substantially smaller fitting errors with reasonable computational complexity, as compared with representative traditional counterparts

RH20T: A Comprehensive Robotic Dataset for Learning Diverse Skills in One-Shot

A key challenge in robotic manipulation in open domains is how to acquire diverse and generalizable skills for robots. Recent research in one-shot imitation learning has shown promise in transferring trained policies to new tasks based on demonstrations. This feature is attractive for enabling robots to acquire new skills and improving task and motion planning. However, due to limitations in the training dataset, the current focus of the community has mainly been on simple cases, such as push or pick-place tasks, relying solely on visual guidance. In reality, there are many complex skills, some of which may even require both visual and tactile perception to solve. This paper aims to unlock the potential for an agent to generalize to hundreds of real-world skills with multi-modal perception. To achieve this, we have collected a dataset comprising over 110,000 contact-rich robot manipulation sequences across diverse skills, contexts, robots, and camera viewpoints, all collected in the real world. Each sequence in the dataset includes visual, force, audio, and action information. Moreover, we also provide a corresponding human demonstration video and a language description for each robot sequence. We have invested significant efforts in calibrating all the sensors and ensuring a high-quality dataset. The dataset is made publicly available at rh20t.github.ioComment: RSS 2023 workshop on LTAMP. The project page is at rh20t.github.i

Study on macromolecular structure of different types of contact metamorphic coals

Contact metamorphism occurs when magma intrudes into the coal seam, resulting in changes to the microfraction, grade, chemical composition, physico-chemical structure and process properties of the coal. Different types of contact metamorphic products are formed under different tectonic-thermal conditions. In order to reveal the variability of different types of contact metamorphic coals and their controlling factors from the macromolecular structure scale, a comparative study of natural coke series samples from the Tashan mine in Datong, Shanxi Province and coal-based graphite series samples from the Lutang mine in Hunan Province was carried out using industrial analysis, elemental analysis, reflectance determination, X-ray diffraction (XRD) and Raman spectroscopy (Raman) test methods, and combined with geological background analysis. The results show that the small shallow-formed rocks have a short thermal action time, poor thermal confinement conditions, belong to high temperature and low pressure condition, narrow contact metamorphic zone, and develop natural coke - thermal transformation coal sequence; the series is in the carbonation stage, and the coal macromolecular structure is dominated by chemical changes, with aromatization and ring condensation dominating. It shows carbon enrichment, dehydrogenation, deoxygenation, reduction of defects in the active sites such as side chains and functional groups, growth of aromatic structural units leading to an increase in defects within the aromatic level, and the aromatic lamellae are not ordered. The acidic and moderately acidic deep-formed rock bodies such as strains and bases intruded in a regional extrusive tectonic setting are well heated, thermally confined and under high temperature and pressure conditions, and the contact metamorphic width can exceed 1km, developing graphite-semi-graphite-anthracite metamorphic sequences; the chemical composition of the coal-based graphite series is highly mature and less variable, and the macromolecular structure is dominated by physical changes, mainly occurring as collagenesis and rank physicochemical interactions. The non-oriented aromatic lamellae are spliced and stacked and rotated and oriented by forces, with a continuous reduction of defects and a transition to a three-dimensional ordered crystal structure