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Kinematic analysis of an electric stair-climbing wheelchair
No full textThis paper presents the functional design and kinematic synthesis of a recent version of an electric stair-climbing wheelchair. The proposed device represents the latest evolution of the ‘Wheelchair.q' project and introduces several improvements over previous designs. This updated solution has greater stability during stair-climbing operation, and it satisfies the safety requirements introduced by ISO 7176-28:2012, "Requirements and test methods for stair-climbing devices". The main improvement presented concerns the regularity of the user trajectory during stair-climbing, which ensures a more comfortable perception. This result has been achieved by introducing a cam mechanism between the frame connected to the locomotion unit and the seat frame, which properly manages the seat orientation. With an appropriate cam profile, it is possible to compensate for the oscillations that are introduced on the wheelchair during the climbing sequence and allow the user to obtain a translational trajectory. The proposed design and its working principle are first described and illustrated through schematic and graphic representations. A brief explanation of the procedure for obtaining the cam profile is also given. Two different architectures for the cam mechanism are then compared, and the advantages and disadvantages for each solution are identified. Finally, the kinematic wheelchair performances are tested through a simulation conducted in the MSC-ADAMS multibody environment
Local and scientific knowledge integration for multi-risk assessment in rural Niger
No full textIn the rural Tropics, the participatory risk assessment, based on local knowledge only, is very widespread. This practice is appropriate for hazard identification and for raising the awareness of local communities in relation to the importance of risk reduction, but it is still imprecise in determining risk level, ranking and treatment in a context of climate change, activities in which technical knowledge is unavoidable. Integration of local and technical-scientific knowledge within the framework of an encoded risk assessment method (ISO 31010), could favour more effective decision making with regard to risk reduction. The aim of this chapter is to verify the applicability of a multi-risk local assessment-MLA which combines local knowledge (participatory workshop, transect walk, hazard and resource mapping, disaster historical profile) and scientific knowledge (climate downscaling modelling, hazard probability and scenarios, potential damages, residual risk). The test is carried out in two villages of the Western Niger, particu-larly exposed to flooding and agricultural drought. The risk (hazard probability * potential damages) is identified, analysed (level of risk) and evaluated (residual risk, adaptation measures compared with potential damage costs). The MLA is feasible. The two villages, while bordering on one another, have a different risk ranking. Depending on the village, the risk treatment could reduce the risk level to 17% and to 41% of the current risk, with costs equating to 34% and 28% of the respective potential damages
Infrastrutturazione e riciclo del territorio
No full textIl saggio intende proporre alcune riflessioni in merito all'estensione del concetto di riciclo, dalla scala degli beni di consumo e dei componenti edilizi - in cui esso si è consolidato e a cui continua genericamente ad essere riferito - a quella più estesa della città e delle componenti del territorio. Chiave di lettura privilegiata per questa riflessione è l'infrastrutturazione, intesa non soltanto come costruzione fisica dei sistemi infrastrutturali, ma più in generale come il processo di predisposizione morfologica del territorio
Pressure-activated microsyringe (PAM) fabrication of bioactive glass-poly(lactic-co-glycolic acid) composite scaffolds for bone tissue regeneration
No full textThe aim of this work was the fabrication and characterization of bioactive glass-poly(lactic-co-glycolic acid) (PLGA) composite scaffolds mimicking the topological features of cancellous bone. Porous multilayer PLGA-CEL2 composite scaffolds were innovatively produced by a pressure-activated microsyringe (PAM) method, a CAD/CAM processing technique originally developed at the University of Pisa. In order to select the optimal formulations to be extruded by PAM, CEL2-PLGA composite films (CEL2 is an experimental bioactive SiO2-P2O5-CaO-MgO-Na2O-K2O glass developed at Politecnico di Torino) were produced and mechanically tested. The elastic modulus of the films increased from 30 to>400 MPa, increasing the CEL2 amount (10-50 wt%) in the composite. The mixture containing 20wt% CEL2 was used to fabricate 2D and 3D bone-like scaffolds composed by layers with different topologies (square, hexagonal and octagonal pores). It was observed that the increase of complexity of 2D topological structures led to an increment of the elastic modulus from 3 to 9MPa in the composite porous monolayer. The elastic modulus of 3D multilayer scaffolds was intermediate (about 6.5 MPa) between the values of the monolayers with square and octagonal pores (corresponding to the lowest and highest complexity, respectively). MG63 osteoblast-like cells and periosteal-derived precursor cells (PDPCs) were used to assess the biocompatibility of the 3D bone-like scaffolds. A significant increase in cell proliferation between 48 h and 7 days of culture was observed for both cell phenotypes. Moreover, qRT-PCR analysis evidenced an induction of early genes of osteogenesis in PDPCs
Biocompatibility versus peritoneal mesothelial cells of polypropylene prostheses for hernia repair, coated with a thin silica/silver layer
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Comparing usability of user interfaces for robotic telepresence
No full textIn the last years, robotic telepresence solutions have received a significant attention from both the commercial and academic worlds, due to their ability to allow people to feel physically present at a remote place and move in it. Operating a mobile robot with some autonomous capabilities from distance can enable a wide range of mass-market applications, encompassing teleconferencing, virtual tourism, etc. In these scenarios, the possibility to interact with the robot in a natural way becomes of crucial importance. The aim of this paper is to investigate, through a comparative analysis, the usability of two major approaches used today for controlling telepresence robots, i.e., keyboard and point-and-click video navigation. A control system featuring the above interfaces plus a combination of the two has been developed, and applied to the operation of a prototype telepresence robot in an office scenario. The system additionally includes functionalities found in many research and industry solutions, like map-based localization and "augmented" navigation. Then, a user study has been performed to assess the usability of the various control modalities for the execution of some navigation tasks in the considered context. The study provided precious indications to be possibly exploited for guiding next developments in the field
Teachers' voicing and silence periods during continuous speech in classrooms with different reverberation times
No full textThe relationship between reverberation times and the voicing and silence accumulations of continuous speech was quantified in 22 primary-school teachers. Teachers were divided into a high and a low reverberation time groups based on their classroom reverberation time (higher and lower than 0.90 s). Reverberation times higher than 0.90 s implicate higher voicing accumulations and higher accumulations of the silences typical of turn taking in dialogue. These results suggest that vocal load, which can lead to vocal fatigue, is influenced by classroom reverberation time. Therefore, it may be considered a risk factor for occupational voice users