A quantitative taxonomy of human hand grasps

Background: A proper modeling of human grasping and of hand movements is fundamental for robotics, prosthetics, physiology and rehabilitation. The taxonomies of hand grasps that have been proposed in scientific literature so far are based on qualitative analyses of the movements and thus they are usually not quantitatively justified. Methods: This paper presents to the best of our knowledge the first quantitative taxonomy of hand grasps based on biomedical data measurements. The taxonomy is based on electromyography and kinematic data recorded from 40 healthy subjects performing 20 unique hand grasps. For each subject, a set of hierarchical trees are computed for several signal features. Afterwards, the trees are combined, first into modality-specific (i.e. muscular and kinematic) taxonomies of hand grasps and then into a general quantitative taxonomy of hand movements. The modality-specific taxonomies provide similar results despite describing different parameters of hand movements, one being muscular and the other kinematic. Results: The general taxonomy merges the kinematic and muscular description into a comprehensive hierarchical structure. The obtained results clarify what has been proposed in the literature so far and they partially confirm the qualitative parameters used to create previous taxonomies of hand grasps. According to the results, hand movements can be divided into five movement categories defined based on the overall grasp shape, finger positioning and muscular activation. Part of the results appears qualitatively in accordance with previous results describing kinematic hand grasping synergies. Conclusions: The taxonomy of hand grasps proposed in this paper clarifies with quantitative measurements what has been proposed in the field on a qualitative basis, thus having a potential impact on several scientific fields

Designing, building, measuring, and testing a constant equivalent fall height terrain park jump

Previous work has presented both a theoretical foundation for designing terrain park jumps that control landing impact and computer software to accomplish this task. US ski resorts have been reluctant to adopt this more engineered approach to jump design, in part due to questions of feasibility. The present study demonstrates this feasibility. It describes the design, construction, measurement, and experimental testing of such a jump. It improves on the previous efforts with more complete instrumentation, a larger range of jump distances, and a new method for combining jumper- and board-mounted accelerometer data to estimate equivalent fall height, a measure of impact severity. It unequivocally demonstrates the efficacy of the engineering design approach, namely that it is possible and practical to design and build free style terrain park jumps with landing surface shapes that control for landing impact as predicted by the theory

Il derivato OTC come scommessa finanziaria sotto condizione di razionalità

Il contributo analizza il filone giurisprudenziale, inaugurato da A.. Milano n. 3459/2013, favorevole al recupero della figura della "scommessa finanziaria" al fine di inquadrare civilisticamente le operazioni derivative (specificamente, i contratti swap su tassi di interesse) e definirne le condizioni di validit\ue0 (in vista anche del vaglio di meritevolezza dell'operazione negoziale)

Contratti del consumatore e "diritto delle restituzioni" : secondo la Corte di Giustizia CE

L'articolo affronta il problema della disciplina delle restituzioni in dipendenza di fenomeni demolitori e/o caducatori del contratto, alla luce della pi\uf9 recente giurisprudenza comunitaria

Termini di esperibilità dei rimedi

L'elaborato ha analizzato i profili cronologici e procedimentali di esercizio dei rimedi conferiti al consumatore in collegamento con la "garanzia legale di conformit\ue0" (artt. 128 ss. cod. cons.). Tra i plurimi aspetti oggetto di approfondimento particolare attenzione \ue8 stata dedicata all'esatta qualificazione della "consegna" del bene, quale momento dal quale inizia a decorrere il termine prescrizionale, agli effetti dell'eventuale riconoscimento (ovvero occultamento) del difetto di conformit\ue0 e all'onere della denuncia del vizio da parte del consumatore. Ulteriore problema affrontato in occasione dello scritto \ue8 quello degli atti interruttivi del termine prescrizionale (nell'ottica della rilevanza, a tal fine, anche degli atti stragiudiziali di esercizio dei rimedi conformativi)

Quantification of the user-wheelchair system stability based on the CoP trajectory within the base of support

AbstractAim of the work was the introduction of a user-wheelchair Stability Index able to give objective information to find the most appropriate wheelchair settings both for daily and sports use. The Stability Index was introduced after asking two users to assume four pre-defined postures over a dynamometric force platform and measuring the centre of pressure (CoP) trajectory. After identifying the base of support centroid Ctd and the instantaneous CoP, the Stability Index expresses how far is the instantaneous CoP from the sides of the base of support outline: the index is calculated with respect to each direction (forward, rearward, right and left side) and referred to the centroid of the base of support. The Stability Index values increase proportionally with the stability: a zero value means that CoP is on the outline, a unit value corresponds to coincidence between CoP and Ctd. A preliminary evaluation of the Stability Index was performed by varying both back adjustment and user posture. The proposed method only requires a force plate or a stabilometric plate. The evaluation of user-wheelchair system stability can be performed in real time, merging this objective parameter with user subjective feeling in order to propose the most satisfactory solution to users, manufacturers and clinicians

Deep learning with convolutional neural networks applied to electromyography data: A resource for the classification of movements for prosthetic hands

Natural control methods based on surface electromyography (sEMG) and pattern recognition are promising for hand prosthetics. However, the control robustness offered by scientific research is still not sufficient for many real life applications, and commercial prostheses are capable of offering natural control for only a few movements. In recent years deep learning revolutionized several fields of machine learning, including computer vision and speech recognition. Our objective is to test its methods for natural control of robotic hands via sEMG using a large number of intact subjects and amputees. We tested convolutional networks for the classification of an average of 50 hand movements in 67 intact subjects and 11 transradial amputees. The simple architecture of the neural network allowed to make several tests in order to evaluate the effect of pre-processing, layer architecture, data augmentation and optimization. The classification results are compared with a set of classical classification methods applied on the same datasets. The classification accuracy obtained with convolutional neural networks using the proposed architecture is higher than the average results obtained with the classical classification methods, but lower than the results obtained with the best reference methods in our tests. The results show that convolutional neural networks with a very simple architecture can produce accurate results comparable to the average classical classification methods. They show that several factors (including pre-processing, the architecture of the net and the optimization parameters) can be fundamental for the analysis of sEMG data. Larger networks can achieve higher accuracy on computer vision and object recognition tasks. This fact suggests that it may be interesting to evaluate if larger networks can increase sEMG classification accuracy too