OpenMutt - 3D Printed Robotic Quadruped

The objective of the OpenMutt project is to build a modular, open-source quadruped as a multidisciplinary research testbed for students and faculty. The design is based on proven models, including the MIT Mini-Cheetah, NYU Open Dynamic Robot, and Bruton’s openDogV3, with modifications to decrease manufacturing time and cost. OpenMutt utilizes 12 brushless motors, each attached to a cycloidal gearbox for actuation. The quarter model has three degrees of freedom, translational and rotational. A remote control will be used for general movement with impedance and PID controllers for torque and joint control. The majority of parts were additively manufactured with Fused Deposition Modeling(FDM) printers using Polylactic Acid(PLA) and Thermoplastic Polyurethane(TPU). A power supply will be used for quarter model testing, while the full model will use an onboard battery with the battery-management system (BMS). Due to the 13:1 gear ratio of the cycloidal gearbox, motors like the ones selected are adaptable to the model. The purpose behind the application of these methods is to ensure a platform that is easy to construct, iterate and learn with

OpenMutt - 3D Printed Robotic Quadruped

Embry-Riddle Aeronautical University is seeking a robotic dog as a research avenue for different biomechanical designs, control systems, and robotic designs for experimentation and study. The quadruped is based on several open-source platforms including James Bruton’s openDogV3, the MIT Mini-Cheetah, and the NYU Open Dynamic Robot Initiative. The implementation of this research will begin with a quarter model, consisting of a singular leg from the hip to the foot. The leg will be mounted on a benchtop test stand that allows for controlled movement and accessible experimentation. The leg will be separate from the full-model quadruped strictly for experimentation and any full-model revisions. The OpenMutt’s quarter model uses 3 Brushless DC Electric Motors (BLDC) attached to 3 cycloidal gearboxes as its main form of actuation. The majority of parts were manufactured using Polylactic Acid (PLA). Some leg testing has already been completed, but a synchronized movement is yet to be completed

Chen-Ruan cohomology of ADE singularities

We study Ruan's \textit{cohomological crepant resolution conjecture} for orbifolds with transversal ADE singularities. In the $A_n$-case we compute both the Chen-Ruan cohomology ring $H^*_{\rm CR}([Y])$ and the quantum corrected cohomology ring $H^*(Z)(q_1,...,q_n)$. The former is achieved in general, the later up to some additional, technical assumptions. We construct an explicit isomorphism between $H^*_{\rm CR}([Y])$ and $H^*(Z)(-1)$ in the $A_1$-case, verifying Ruan's conjecture. In the $A_n$-case, the family $H^*(Z)(q_1,...,q_n)$ is not defined for $q_1=...=q_n=-1$. This implies that the conjecture should be slightly modified. We propose a new conjecture in the $A_n$-case which we prove in the $A_2$-case by constructing an explicit isomorphism.Comment: This is a short version of my Ph.D. Thesis math.AG/0510528. Version 2: chapters 2,3,4 and 5 has been rewritten using the language of groupoids; a link with the classical McKay correpondence is given. International Journal of Mathematics (to appear

Tensile Testing of 3D Printed TPU Samples for Pediatric Biomaterial Applications

Additive Manufacturing (AM) has, in recent years, become one of the most widespread and preferred prototyping methods. The most popular additive manufacturing method is Fused Deposition Modeling. FDM’s popularity is primarily attributed to its 3 major strengths of rapid prototyping, variability in material choice, and subject specific nature. The medical industry is one of the larger industries that has benefited from 3D printing especially in the terms of medical trainers. Unfortunately, most medical trainers that are developed (either being 3d printed or through traditional manufacturing processes) are poor substitutes for the human body. This can be attributed to either a poor design or poor material choice. FDM printing is the obvious solution to these issues, but one of the largest problems in 3D printing for engineers is that the properties of most filaments after extrusion are not well-known. Additionally, 3D prints are rarely 100% solid in FDM which makes assuming the material properties of the base materials inaccurate. This project seeks to test 3D printed samples at numerous different infills of a common 3D printing material known as Thermoplastic Polyurethane of TPU using ASTM D638. The test samples will be printed across numerous printers with the same settings to determine whether different printers influence the material properties after a print. Once tensile testing has been completed the curves will be imported into an FEA software to be tested on numerous bone geometries to determine if TPU is a suitable material to use to mimic pediatric bones

Surface Chemistry of Ternary Nanocrystals: Engineering the Deposition of Conductive NaBiS2 Films

The ability to engineer the surface chemistry of complex ternary nanocrystals is critical to their successful application in photovoltaic, thermoelectric, and other energy conversion devices. For many years, several studies have shed light into the surface chemistry of unary and binary semiconductor nanocrystals, as well as their surface modification with monodentate and multidentate ligands in a variety of applications. In contrast, our understanding of the surface chemistry and ligand modification of ternary and other complex multinary nanocrystals remains relatively limited. Recently, our group reported the synthesis of colloidal NaBiS2 semiconductor nanocrystals with sizes tunable between 2–60 nm, and a light absorption edge of ca. 1.4 eV. Here, we use a combination of infrared and nuclear magnetic resonance spectroscopies to show that the as-made NaBiS2 nanocrystals are capped by oleylamine and neodecanoate ligands. We investigate biphasic liquid-liquid exchange as a means to replace these native ligands with either carboxylate-terminated lipoic acid or with small iodide ligands, leading in both cases to solubility in polar solvents—such as methanol, water, and dimethylformamide. We also investigate a layer-by-layer, biphasic solid-liquid exchange approach to prepare films of NaBiS2 nanocrystals capped with halide ligands—iodide, bromide, chloride. Upon exchange and removal of the native ligands, we show that the resistance of NaBiS2 nanocrystal films greatly decreases, with their measured conductivity being comparable to that of films made of isostructural PbS nanocrystals, which have been used in solar cells. Lastly, we report the first solar cell device made of NaBiS2 nanocrystal films with a limited power conversion efficiency (PCE) of 0.07. Further nanostructuring and ligand optimization may enable the preparation of much more efficient energy conversion devices based on NaBiS2 as well as other non-toxic and Earth-abundant, biocompatible multinary semiconductors

Pose Measurement Performance of the Argon Relative Navigation Sensor Suite in Simulated Flight Conditions

Argon is a flight-ready sensor suite with two visual cameras, a flash LIDAR, an on- board flight computer, and associated electronics. Argon was designed to provide sensing capabilities for relative navigation during proximity, rendezvous, and docking operations between spacecraft. A rigorous ground test campaign assessed the performance capability of the Argon navigation suite to measure the relative pose of high-fidelity satellite mock-ups during a variety of simulated rendezvous and proximity maneuvers facilitated by robot manipulators in a variety of lighting conditions representative of the orbital environment. A brief description of the Argon suite and test setup are given as well as an analysis of the performance of the system in simulated proximity and rendezvous operations

Swarm UAVs for Area Mapping in GPS-denied Locations

Utilizing small Unmanned Aerial Systems (SUAS) in mapping and cartography applications holds transformative potential, particularly in challenging and GPS-denied environments. Traditionally, mapping involved manual efforts using diverse tools, but there has been a fundamental shift towards autonomous vehicles capable of achieving efficient results in less time and with reduced human effort. Autonomous mapping typically relies on single a UAV employing Simultaneous Localization and Mapping (SLAM) or photogrammetry alongside GPS. This research project seeks to leverage swarm robotics to map intricate landscapes and rugged terrains using SUASs with a faster, more accurate, and precise approach, eliminating dependence on GPS for global positioning. The mapping scope encompasses hard-to-access locations like cliffs, abandoned structures, and forests, as well as areas impractical for manual surveying, such as construction sites and expansive indoor spaces like warehouses, factories, or historical buildings resistant to modifications for survey purposes. The swarm will exhibit an emergent-like behavior to map any location efficiently, ensuring collision-free navigation among sUAS and ground objects

Chandra Smells a RRAT: X-ray Detection of a Rotating Radio Transient

"Rotating RAdio Transients" (RRATs) are a newly discovered astronomical phenomenon, characterised by occasional brief radio bursts, with average intervals between bursts ranging from minutes to hours. The burst spacings allow identification of periodicities, which fall in the range 0.4 to 7 seconds. The RRATs thus seem to be rotating neutron stars, albeit with properties very different from the rest of the population. We here present the serendipitous detection with the Chandra X-ray Observatory of a bright point-like X-ray source coincident with one of the RRATs. We discuss the temporal and spectral properties of this X-ray emission, consider counterparts in other wavebands, and interpret these results in the context of possible explanations for the RRAT population.Comment: 5 pages, 2 b/w figures, 1 color figure. To appear in the proceedings of "Isolated Neutron Stars", Astrophysics & Space Science, in pres

On Multifractal Structure in Non-Representational Art

Multifractal analysis techniques are applied to patterns in several abstract expressionist artworks, paintined by various artists. The analysis is carried out on two distinct types of structures: the physical patterns formed by a specific color (``blobs''), as well as patterns formed by the luminance gradient between adjacent colors (``edges''). It is found that the analysis method applied to ``blobs'' cannot distinguish between artists of the same movement, yielding a multifractal spectrum of dimensions between about 1.5-1.8. The method can distinguish between different types of images, however, as demonstrated by studying a radically different type of art. The data suggests that the ``edge'' method can distinguish between artists in the same movement, and is proposed to represent a toy model of visual discrimination. A ``fractal reconstruction'' analysis technique is also applied to the images, in order to determine whether or not a specific signature can be extracted which might serve as a type of fingerprint for the movement. However, these results are vague and no direct conclusions may be drawn.Comment: 53 pp LaTeX, 10 figures (ps/eps

Substrate stabilisation and small structures in coral restoration: State of knowledge, and considerations for management and implementation.

Coral reef ecosystems are under increasing pressure from local and regional stressors and a changing climate. Current management focuses on reducing stressors to allow for natural recovery, but in many areas where coral reefs are damaged, natural recovery can be restricted, delayed or interrupted because of unstable, unconsolidated coral fragments, or rubble. Rubble fields are a natural component of coral reefs, but repeated or high-magnitude disturbances can prevent natural cementation and consolidation processes, so that coral recruits fail to survive. A suite of interventions have been used to target this issue globally, such as using mesh to stabilise rubble, removing the rubble to reveal hard substrate and deploying rocks or other hard substrates over the rubble to facilitate recruit survival. Small, modular structures can be used at multiple scales, with or without attached coral fragments, to create structural complexity and settlement surfaces. However, these can introduce foreign materials to the reef, and a limited understanding of natural recovery processes exists for the potential of this type of active intervention to successfully restore local coral reef structure. This review synthesises available knowledge about the ecological role of coral rubble, natural coral recolonisation and recovery rates and the potential benefits and risks associated with active interventions in this rapidly evolving field. Fundamental knowledge gaps include baseline levels of rubble, the structural complexity of reef habitats in space and time, natural rubble consolidation processes and the risks associated with each intervention method. Any restoration intervention needs to be underpinned by risk assessment, and the decision to repair rubble fields must arise from an understanding of when and where unconsolidated substrate and lack of structure impair natural reef recovery and ecological function. Monitoring is necessary to ascertain the success or failure of the intervention and impacts of potential risks, but there is a strong need to specify desired outcomes, the spatial and temporal context and indicators to be measured. With a focus on the Great Barrier Reef, we synthesise the techniques, successes and failures associated with rubble stabilisation and the use of small structures, review monitoring methods and indicators, and provide recommendations to ensure that we learn from past projects