Learning the Dynamics of Compliant Tool-Environment Interaction for Visuo-Tactile Contact Servoing

Many manipulation tasks require the robot to control the contact between a grasped compliant tool and the environment, e.g. scraping a frying pan with a spatula. However, modeling tool-environment interaction is difficult, especially when the tool is compliant, and the robot cannot be expected to have the full geometry and physical properties (e.g., mass, stiffness, and friction) of all the tools it must use. We propose a framework that learns to predict the effects of a robot's actions on the contact between the tool and the environment given visuo-tactile perception. Key to our framework is a novel contact feature representation that consists of a binary contact value, the line of contact, and an end-effector wrench. We propose a method to learn the dynamics of these contact features from real world data that does not require predicting the geometry of the compliant tool. We then propose a controller that uses this dynamics model for visuo-tactile contact servoing and show that it is effective at performing scraping tasks with a spatula, even in scenarios where precise contact needs to be made to avoid obstacles.Comment: 6th Conference on Robotic Learning (CoRL 2022), Auckland, New Zealand. 8 pages + references + appendi

Time dependent properties of thermoplastic protein produced from bloodmeal with sodium sulphite as an anti-crosslinking agent

The aim of this research was to investigate how the time dependent mechanical behaviour of bloodmeal-based thermoplastic was affected by varying sodium sulphite content at two injection moulding temperatures (120°C at exit or 140°C at exit). Thermoplastic protein was prepared by extrusion with 2, 3 or 4g sodium sulphite (SS), 3g sodium dodecyl sulphate, 10 g urea, 20 g triethylene glycol and 40 g water per 100 g bloodmeal, then injection moulded into test specimens. Pull to break, creep and stress relaxation tests were performed on conditioned samples and glass transition temperature (Tg) was determined by dynamic mechanical analysis. Ultimate tensile strength was 7.9, 7.6 and 5.6 MPa for samples moulded at 120°C and 7.6, 6.3 and 5.7 MPa when moulded at 140°C with 2, 3 and 4 g SS respectively. Experimental creep data was modelled with a 4 element model, consisting of a spring and dashpot in parallel, in series with an additional spring and dashpot. Plotting creep compliance versus time showed increasing chain mobility as SS content increased. Relaxation was modelled with the Struik equation for short-time experiments. Relaxation times were 530, 360 and 250 s with 2, 3 and 4 g SS respectively when moulded at the lower temperature. At 140°C, relaxation times were 440, 430 and 190 s for these SS contents. Tg was in the range 57-65°C (1 Hz peak in tanδ) for all samples, but was lowest for samples with 4 g SS. These results show that both increased sodium sulphite and the higher moulding temperature increased chain mobility in the processed plastic

The Near-Ring of Lipschitz Functions on a Metric Space

This paper treats near-rings of zero-preserving Lipschitz functions on metric spaces that are also abelian groups, using pointwise addition of functions as addition and composition of functions as multiplication. We identify a condition on the metric ensuring that the set of all such Lipschitz functions is a near-ring, and we investigate the complications that arise from the lack of left distributivity in the resulting right near-ring. We study the behavior of the set of invertible Lipschitz functions, and we initiate an investigation into the ideal structure of normed near-rings of Lipschitz functions. Examples are given to illustrate the results and to demonstrate the limits of the theory

Investigation of a Microcystis aeruginosa cyanobacterial freshwater harmful algal bloom associated with acute microcystin toxicosis in a dog

Microcystin poisoning was diagnosed in a dog exposed to a Microcystis aeruginosa dominated freshwater harmful algal bloom at Milford Lake, Kansas, which occurred during the summer of 2011. Lake water microcystin concentrations were determined at intervals during the summer, using competitive enzyme-linked immunosorbent assays, and indicated extremely high, localized microcystin concentrations of up to 126,000 ng/ml. Multiple extraction and analysis techniques were utilized in the determination of free and total microcystins in vomitus and liver samples from the poisoned dog. Vomitus and liver contained microcystins, as determined by enzyme-linked immunosorbent assays, and the presence of microcystin LR was confirmed in vomitus and liver samples using liquid chromatography coupled with tandem mass spectrometry. Major toxic effects in a dog presented for treatment on the day following exposure included fulminant liver failure and coagulopathy. The patient deteriorated rapidly in spite of aggressive treatment, and was euthanized. Postmortem lesions included diffuse, acute, massive hepatic necrosis and hemorrhage, and acute necrosis of the renal tubular epithelium. A diagnosis of microcystin poisoning was based on the demonstration of M. aeruginosa and microcystin-LR in the lake water, as well as in vomitus produced early in the course of the poisoning, the presence of microcystin-LR in liver tissue, and on a typical clinical course

Presentation of the ISRM mine closure state of the art report

International audienceIn 2005, Prof. Nielen Van der Merwe, at that time President of the ISRM, initiated a commission to facilitate the constitution of an international network of experts involved in mine closure and post-mining management. Eight experts coming from different countries have been deeply involved in this ISRM 'mine closure commission', for four years. Closure of mining operations does not lead to the complete elimination of risks likely to affect the surface above old mine workings. Therefore, disorders potentially harmful for people and goods may develop, sometimes just after the closure but also, in some cases, long time after. The first mandate of the commission has been dedicated to the elaboration of a state-ofthe- art report presenting, at an international scale, the mine closure problem (context, main risks of disorders, major hazard assessment methods and treatment techniques). The present paper presents an outline of this ISRM report that members may download on the ISRM website

Seroprevalence survey of SARS-CoV-2, community behaviors, and practices in Kansanshi and Kalumbila mining towns

BackgroundCoronavirus disease 2019 (SARS-CoV-2) was declared a global pandemic by WHO after it spreads quickly around the world from its source city in Wuhan. Africa has some of the lowest documented SARS-CoV-2 incidences globally, with over 9 million confirmed cases as of December 2022. This may be due to efficient mitigation, outbreak response, or demographic traits. Surveillance capability may have suffered as nations changed funding, regulations, and testing plans. Therefore, this study was to document the prevalence of SARS-CoV-2, its characteristics, and the socio-economic characteristics in the two mining districts of Solwezi and Kalumbila of Zambia.MethodsBetween 28 March and 26 April 2021, a cross-sectional cluster-sample survey of households in two mining districts of Zambia was conducted. Twenty standard enumeration areas (SEAs) were randomly selected in Kansanshi (17 SEA) and Kalumbila (3 SEA) from a total of 67 SEA that encompass the two mines. Members of households aged <5 years were not eligible to participate in the survey. All participants that consented to participate in the interview were also asked to consent to test for SARS-CoV-2 infection using a rapid diagnostic test (RDT), which tested for recent infection and past exposure to the virus (IgM and IgG, respectively).ResultOut of the total sample of 3,047 that were present for the interview, 622 of them agreed to test for COVID-19. Of the total that tested for SARS-CoV-2, 2.6% were IgM positive while 9.0% were IgG positive. Despite the above results, 1,586 participants that agreed to the interview indicated a low self-risk assessment of getting COVID-19 (46.5%) or someone (45.5%). On the public health measures, participants who did handwashing more than usual (65.0%), not hand sanitizing more than usual (69.0%), not disinfecting surfaces in their households than usual (87.5%), not avoiding drinking from bars or nightclubs (90.6%), and not wearing a mask when out in public places (71.1%). In the logistic multivariable model, participants with age 24 years and above (AOR = 2.94; 95% CI = 1.10, 7.81) and having experienced symptoms of SARS-CoV-2 (AOR = 2.60; 95% CI: 1.33, 5.05) had a significant effect on testing positive for SARS-CoV-2.ConclusionAlthough the results showed that active COVID-19 prevalence in Solwezi and Kalumbila communities surrounding the two mines was low, exposure to infection was five times high. Government and mining firms should continue to sensitize the community members on the preventive measures of COVID-19 and continue with community testing so that all those positive but without symptoms can self-isolate and those with symptoms and sick can be admitted to the hospital