This paper assesses the energy efficiency of a redundant actuation architecture combining Quasi-Direct Drive (QDD) motors and Series Elastic Actuators (SEAs) by comparing its energy consumption to ...Geared Motors (GMs) and SEAs alone. We consider this comparison for two robotic systems performing different tasks. Our results show that using the redundant actuation we can save up to 99% of energy with respect to SEA for sinusoidal movements. This efficiency is achieved by exploiting the coupled dynamics of the two actuators, resulting in a latching-like control strategy. We also show that these large energy savings are not straightforwardly extendable to nonsinusoidal movements, but smaller savings ( e.g. , 7%) are nonetheless possible. The presented results were obtained thanks to the framework of concurrent design (co-design), namely the simultaneous optimization of hardware parameters and control trajectories. This shows that the combination of complex hardware morphologies and advanced numerical co-design can lead to peak hardware performance that would be unattainable by human intuition alone.
Up to date, Dielectric Elastomer Actuators (DEA) have been mostly based on either silicone or acrylic elastomers, whereas the potential of DEAs based on inexpensive, wide-spread natural and synthetic ...rubbers has been scarcely investigated. In this paper, a DEA based on a styrene-based rubber is demonstrated for the first time. Using a Lozenge-Shaped DEA (LS-DEA) layout and following a design procedure previously proposed by the authors, we develop prototypes featuring nearly-zero mechanical stiffness, in spite of the large elastic modulus of styrenic rubber. Stiffness compensation is achieved by simply taking advantage of a biaxial pre-stretching of the rubber DE membrane, with no need for additional stiffness cancellation mechanical elements. In the paper, we present a characterization of the styrene rubber-based LS-DEA in different loading conditions (namely, isopotential, isometric, and isotonic), and we prove that actuation strokes of at least 18% the actuator side length can be achieved, thanks to the proposed stiffness-compensated design.
Environmental problems are among the most pressing issues in the modern world, including the shortage of clean drinking water partially caused by contamination from various industries and the ...excessive emission of CO2 primarily from the massive use of fossil fuels. Consequently, it is crucial to develop inexpensive, effective, and environmentally friendly methods for wastewater treatment and CO2 reduction, turning them into useful feedstocks. This study explores a unique method that addresses both challenges by utilizing ZnO, which is recognized as one of the most active semiconductors for photocatalysis, as well as a cost-effective electrocatalyst for the CO2 reduction reaction (CO2RR). Specifically, we investigate the influence of the morphology of various ZnO nanostructures synthesized via different low-cost routes on their photocatalytic properties for degrading the rhodamine-B dye (RhB) and on their electrocatalytic performance for the CO2RR. Our results show that the ZnO lamella morphology achieves the best performance compared to the nanorod and nanoparticle structures. This outcome is likely attributed to the lamella’s higher aspect ratio, which plays a critical role in determining the structural, optical, and electrical properties of ZnO.
Bimetallic copper-tin catalysts are considered cost-effective and suitable for large-scale electrochemical conversion of CO2 to valuable products. In this work, a class of tin (Sn) modified cuprous ...oxide (Cu2O) is simply synthesized through a one-pot microwave-assisted solvothermal method and thoroughly characterized by various techniques. Sn is uniformly distributed on the Cu2O crystals showing a cube-within-cube structure, and CuSn alloy phase emerges at high Sn contents. The atomic ratio of Cu to Sn is found to be crucially important for the selectivity of the CO2 reduction reaction, and a ratio of 11.6 leads to the optimal selectivity for CO. This electrode shows a high current density of 47.2 mA cm−2 for CO formation at −1.0 V vs. the reversible hydrogen electrode and also displays good CO selectivity of 80–90% in a wide potential range. In particular, considerable CO selectivity of 72–81% is achieved at relatively low overpotentials from 240 mV to 340 mV. During the long-term tests, satisfactory stability is observed for the optimal electrode in terms of both electrode activity and CO selectivity. The relatively low price, the fast and scalable synthesis, and the encouraging performance of the proposed material implies its good potential to be implemented in large-scale CO2 electrolyzers.
The recent notable increase in refugees' flows, with refugee children and adolescents relocating worldwide, posed severe challenges to the different national healthcare systems. Social groups such as ...refugees fleeing from their countries because of persecution, wars and violence are considered at high risk of developing mental health-related problems. Despite international and national policies legally regulating the reception process and protecting health-related rights, including the mental well-being of refugee migrants, there is a theoretical and applied need for evidence-based instruments and procedures to support mental health within this population. Recent evidence refers to the Refugee Health Screener-15 (RHS-15) as a reliable and valid instrument for the early detection of trauma-related mental health problems. In this scenario, this study aimed to test the RHS screening process within a multidisciplinary first intervention reception context for unaccompanied refugee minors.
The RHS-15 was administered with the support of cultural-linguistic mediators to 81 unaccompanied minor residents in a first intervention facility in Milan, Italy. This study aimed to assess psychometric characteristics, such as reliability, sensitivity and specificity feasibility and its implementation within a first intervention reception process.
The analysis resulted in the validation of the RHS in its 13-item format. The results highlighted and confirmed an efficient delivery, excellent reliability and a positive predictive and convergent validity of the 13-item version. Further analysis showed an excellent ability to avoid false negatives, although there was a clear tendency to identify false positives.
The early identification of vulnerabilities among refugee minors is recommended to promote their long-term overall well-being. Integrating the screening results with additional observational elements and more specific diagnostic tools is recommended to gain a comprehensive perspective of the minors’ well-being.
We report the details of the construction and calibration of a sensitive surface rheometer, inspired by an instrument described in the literature, adapted to the study of photosensitive polymeric ...materials. By high resolution video tracking of the motion of a floating magnetized needle we are able to measure the viscoelastic complex shear modulus G of a Langmuir monolayer with an accuracy of 5*10
−
6
N/m. This instrument is then employed for the rheological characterization of a Langmuir monolayer of a photosensitive azobenzene polymer, which can be brought out of equilibrium by a suitable photoperturbation. The shear modulus is measured as a function of temperature, illumination power and wavelength. The reversible rheological changes induced in the film by photo-perturbation are monitored during time, observing a transition from a predominantly elastic (G mainly real) to a viscoelastic regime (real and imaginary parts of G comparable). These results are confirmed by a comparison with independent measurements performed using other rheological techniques. Finally a discussion is made, taking into account the results of a recent X-ray photon correlation spectroscopy (XPCS) experiment on the same polymer in equilibrium and out of equilibrium.
Graphene is a 2D carbon material with peculiar features such as high electrical conductivity, high thermal conductivity, mechanical stability, and a high ratio between surface and thickness. ...Applications are continuously growing, and the possibility of dispersing graphene in low-boiling green solvents could reduce its global environmental impact. Pristine graphene can be dispersed in high concentration only in polar aprotic solvents that usually have high boiling points and high toxicity. For this reason, the oxidized form of graphene is always used, as it is easier to disperse and to subsequently reduce to reduced graphene oxide. However, compared to pristine graphene, reduced graphene oxide has more defects and has inferior properties respect to graphene. In this work, the polymerization of (diethyl maleate derivate) on graphene obtained by sonication was performed in a microwave reactor. The obtained material has good stability in ethanol even after a long period of time, therefore, it can be used to deposit graphene by mass production of inks or by casting and easy removal of the solvent. The thermal annealing by heating at 300–400 °C in inert atmosphere allows the removal of the polymer to obtain pristine graphene with a low number of defects.
Lignins have shown remarkable antioxidant properties; acting as “scavengers” of free radicals physiologically produced by cell metabolisms; and exerting a protective action caused by the strong ...ability of these molecules to absorb UV radiation. Through preliminary Molecular Modeling studies and experimental studies in vivo and in vitro, a lignin hydrolysate compound has been shown to be an extremely versatile active ingredient, presenting soothing, anti-inflammatory, anti-itch, anti-oxidant, anti-aging and anti-pollution properties. The possible fields of application are therefore multiple; making this lignin hydrolysate a particularly interesting ingredient for topical dermatological compositions in the treatment of various skin disorders such as inflammation, edema, swelling, rash, redness, itching, chrono- and photo-induced skin aging. These manifestations are also the basis of more or less serious skin problems, making lignin hydrolysate capable of being used in cosmetic products for the eternal challenge of fighting skin aging, but also in medical devices that can be used to fight more painful and annoying symptoms, like those caused by dermatitis or psoriasis.
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