Mechanical design and friction modelling of a cable-driven upper-limb exoskeleton

This paper presents a lightweight and low-inertia cable-driven upper-limb exoskeleton powerful enough to meet the requirements for activities of daily living. It presents the mechanical design, kinematic structure,the underlying actuation system, sensors, other electronic components as well as the controller of the exoskeleton. The extensive effect of friction on cable-driven designs, such as the one presented in this paper, requires proper mathematical modelling for controller design. Thus, we propose a current actuator model that describes the relationship between the motor current, velocity, and external load. The model relies on an underlying Stribeck+Coulomb friction representation and an additional parameter that modifies its Coulomb friction representation with an offset to represent adhesion between a cable and sheath. The model has been validated based on experimental data collected with the exoskeleton. The results show that the proposed model better captures the non-linear behaviour of the exoskeleton’s actuation system, increasing overall descriptive performance by 15%. However, adding the adhesion offset to extend the relation of static friction, does not improve the model

Cyclic tests on two-leaf rubble stone masonry spandrels strengthened with CRM coating on one or both sides

The paper reports the results of an original experimental campaign carried out on full-scale, two-leaf rubble stone masonry spandrels retrofitted using the Composites Reinforced Mortar (CRM) technique, applied on one or both wall faces. The CRM system consisted of a mortar coating reinforced with Glass Fibre-Reinforced Polymer (GFRP) meshes and GFRP transverse connectors to promote the connection with the existing masonry. When the coating was applied on one side, additional transverse connectors, made of grout cores with embedded steel ties (artificial diatons), were also used. These elements further strengthened the connection between the coating and the masonry and connected the leaves of the multi-leaf stone masonry walls. The GFRP mesh in the mortar coating provided the walls with the capacity to resist tension: once the coating and the masonry cracked, the strengthened samples withstood higher distortions, exhibited increased ductility and developed very diffuse crack patterns before collapsing, yielding greater energy dissipation. Furthermore, the transverse connectors enabled the composite action of the CRM coating and the walls and, in the case of artificial diatons, prevented the separation of the masonry leaves. The resistance of the walls with the CRM coating on one and both sides was 2.8 and 3.4 times that of the plain samples, respectively; in both cases, the ultimate drift was more than five times larger than the reference, while the cumulative dissipated energy was more than 30 times. The equivalent hysteretic damping in the damaged state was 11–14% (for CRM on one side) and 8–9% (for both sides)

A new method of seismic strengthening stone masonry with CRM coatings on one side

The paper presents the results of a research study aimed at assessing the effectiveness of composite-reinforced mortar (CRM) for the seismic strengthening of existing stone masonry walls. The experimental research focused on the strengthening performance of a coating applied only on one side of the masonry wall. Such an application is interesting because it does not require the temporary relocation of residents. The historic two-wythe stone masonry used in the research represents Adriatic's coastal and surrounding regions. The coating was made of hydraulic lime mortar reinforced with a glass fibre–reinforced polymer mesh attached to the wall using two types of anchors. In-plane cyclic shear compression tests and cyclic out-of-plane tests were conducted, and the performances of the coating on one and both sides were compared. The results showed that the coating on one side was effective, improving all aspects of the seismic response, which was successfully simulated using existing design models

Fungicide resistance among Cladobotryum spp. – causal agents of cobweb disease of the edible mushroom Agaricus bisporus

A survey of fungicide resistance among isolates of the mushroom pathogens Cladobotryum mycophilum and C. dendroides Types I and II was undertaken, with respect to the active ingredients thiabendazole, carbendazim (benzimidazoles) and prochloraz manganese following an epidemic in Britain and Ireland in 1994/95. The majority of isolates (41/57) were strongly resistant to thiabendazole (ED50 > 200 ppm) and were exclusively C. dendroides Type II. All C. mycophilum and C. dendroides Type I isolates, and four C. dendroides Type II isolates, were weakly resistant to thiabendazole (ED50 1–10 ppm). Thiabendazole-resistant C. dendroides Type II isolates were only weakly resistant to carbendazim (ED50 2–10 ppm) and isolates which were weakly resistant to thiabendazole were carbendazim-sensitive (ED50 < 1 ppm), demonstrating a lack of complete cross resistance between these two benzimidazole fungicides. The ED50 values for all isolates with respect to prochloraz manganese ranged from 0.14 to 7.8 ppm. Benzimidazole resistance was considered to have been an important factor influencing the severity of the 1994/95 cobweb epidemic but 25% of isolates collected were benzimidazole sensitive

Differential Geometry applied to Acoustics : Non Linear Propagation in Reissner Beams

Although acoustics is one of the disciplines of mechanics, its "geometrization" is still limited to a few areas. As shown in the work on nonlinear propagation in Reissner beams, it seems that an interpretation of the theories of acoustics through the concepts of differential geometry can help to address the non-linear phenomena in their intrinsic qualities. This results in a field of research aimed at establishing and solving dynamic models purged of any artificial nonlinearity by taking advantage of symmetry properties underlying the use of Lie groups. The geometric constructions needed for reduction are presented in the context of the "covariant" approach.Comment: Submitted to GSI2013 - Geometric Science of Informatio

Improved understanding of dynamic water and mass budgets of high‐alpine karst systems obtained from studying a well‐defined catchment area

Large areas of Europe, especially in the Alps, are covered by carbonate rocks and in many alpine regions, karst springs are important sources for drinking water supply. Because of their high variability and heterogeneity, the understanding of the hydrogeological functioning of karst aquifers is of particular importance for their protection and utilisation. Climate change and heavy rainfall events are major challenges in managing alpine karst aquifers which possess an enormous potential for future drinking water supply. In this study, we present research from a high‐alpine karst system in the UNESCO Biosphere Reserve Großes Walsertal in Austria, which has a clearly defined catchment and is drained by only one spring system. Results show that (a) the investigated system is a highly dynamic karst aquifer with distinct reactions to rainfall events in discharge and electrical conductivity; (b) the estimated transient atmospheric CO2 sink is about 270 t/a; (c) the calculated carbonate rock denudation rate is between 23 and 47 mm/1000a and (d) the rainfall‐discharge behaviour and the internal flow dynamics can be successfully simulated using the modelling package KarstMod. The modelling results indicate the relevance of matrix storage in determining the discharge behaviour of the spring, particularly during low‐flow periods. This research and the consequent results can contribute and initiate a better understanding and management of alpine karst aquifers considering climate change with more heavy rainfall events and also longer dry periods.The investigated karst system contributes to the transient atmospheric CO2 sink with about 270 t/a. Carbonate denudation rates vary between 23 and 47 mm/1000a. Rainfall‐discharge modelling results indicate the importance of matrix storage particularly during low‐flow periods. imageBundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347FP7 People: Marie‐Curie Actions http://dx.doi.org/10.13039/10001126

Strain-Based Analysis for Geometrically Nonlinear Beams: A Modal Approach

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97066/1/AIAA2012-1713.pd

Prioritizing Stream Barrier Removal to Maximize Connected Aquatic Habitat and Minimize Water Scarcity

Instream barriers, such as dams, culverts, and diversions, alter hydrologic processes and aquatic habitat. Removing uneconomical and aging instream barriers is increasingly used for river restoration. Historically, selection of barrier removal projects used score‐and‐rank techniques, ignoring cumulative change and the spatial structure of stream networks. Likewise, most water supply models prioritize either human water uses or aquatic habitat, failing to incorporate both human and environmental water use benefits. Here, a dual‐objective optimization model identifies barriers to remove that maximize connected aquatic habitat and minimize water scarcity. Aquatic habitat is measured using monthly average streamflow, temperature, channel gradient, and geomorphic condition as indicators of aquatic habitat suitability. Water scarcity costs are minimized using economic penalty functions while a budget constraint specifies the money available to remove barriers. We demonstrate the approach using a case study in Utah\u27s Weber Basin to prioritize removal of instream barriers for Bonneville cutthroat trout, while maintaining human water uses. Removing 54 instream barriers reconnects about 160 km of quality‐weighted habitat and costs approximately US$10 M. After this point, the cost‐effectiveness of removing barriers to connect river habitat decreases. The modeling approach expands barrier removal optimization methods by explicitly including both economic and environmental water uses

Methods and approaches for blind test predictions of out-of-plane behavior of masonry walls: a numerical comparative study

Earthquakes cause severe damage to masonry structures due to inertial forces acting in the normal direction to the plane of the walls. The out-of-plane behavior of masonry walls is complex and depends on several parameters, such as material and geometric properties of walls, connections between structural elements, the characteristics of the input motions, among others. Different analytical methods and advanced numerical modeling are usually used for evaluating the out-of-plane behavior of masonry structures. Furthermore, different types of structural analysis can be adopted for this complex behavior, such as limit analysis, pushover, or nonlinear dynamic analysis.Aiming to evaluate the capabilities of different approaches to similar problems, blind predictions were made using different approaches. For this purpose, two idealized structures were tested on a shaking table and several experts on masonry structures were invited to present blind predictions on the response of the structures, aiming at evaluating the available tools for the out-of-plane assessment of masonry structures. This article presents the results of the blind test predictions and the comparison with the experimental results, namely in terms of formed collapsed mechanisms and control outputs (PGA or maximum displacements), taking into account the selected tools to perform the analysis.info:eu-repo/semantics/publishedVersio