1,720,956 research outputs found
Developing a framework for an adaptive transtibial prosthetic socket using FEA-based tissue injury risk estimation and generalised predictive control
No full textTo perform daily activities, people with amputation depend on the socket for stability and proprioceptive feedback for control over their prosthetic. Sockets are bespokely fitted, rarely definitive, and require iterative, expensive replacement to accommodate residual limb changes. The socket is the primary load-bearing interface and user comfort is greatly linked to the quality of the socket fit. Poorly fitting sockets cause pain, limb tissue injuries, limited device usage, and potential rejection. Contact stresses at the socket-limb interface and strain of underlying soft tissues greatly determine user comfort and the risk of residuum tissue injury. Adjustable socket technologies exist, but are passive or semi-passive, entrusting responsibility of determining safe interface pressure levels solely on the user’s perception. This research entails a set of theoretical studies developing a framework for an automatically adjustable prosthetic socket system enabling estimation of residuum tissue injury risk for safe interface pressure modulation, within a control system structure. Candidate methods for functional interface actuation were identified, and their design specifications and theoretical models developed and described. A comparative Concept- Design Failure Mode and Effects Analysis was performed, considering the limitations of the different actuation options for the adaptive socket system. This revealed that the probability of detection of some potential design weaknesses largely determines overall failure risk criticality among the actuation options. Also, mitigation measures to address high scoring risks should consider users with compromised sensory perception of discomfort or injury. A study was performed using finite element modelling, to determine the effect of local socket stiffness changes on tissue strain and interface pressure, and between select anatomical regions. Minimal changes in compressive strain (< 2%) indicated negligible cross-effects between regions, and appropriate application of an uncoupled controller configuration for the multiple interface actuators. Application of representative prosthetic loading instances allowed estimation of interface pressure-tissue strain relationships at the actuator locations. These were used as training data to create surrogate models for each location for tissue injury risk assessment within the socket system control framework. Generalised Predictive Control (GPC) was simulated for active interface actuation within estimated safe and functional limits. Optimisation of a cost function to minimise tissue injury risk by adaptive interface pressure control showed adequate dynamic performance. Feasibility of the GPC formulation to satisfy operational requirements, and its influence on actuation performance of the different actuators for prosthetic device usage in several scenarios was demonstrated. This research provides a systematic development platform for designing an adjustable prosthetic socket integrating dynamic monitoring and minimisation of sub-dermal residuum tissue injury risk with active adaptation of the interface pressure. <br/
Predictive control for an active prosthetic socket informed by FEA-based tissue damage risk estimation
No full textThis paper presents an architecture for generalized predictive control for an active prosthetic socket system, based on a cost function performance index measure for minimization of residual limb tissue injury. Finite element analysis of a transtibial residuum model donned with a total surface bearing socket was used to provide controller training data and biomechanical rationale for deep tissue injury risk assessment, by estimating the internal deformation state of the soft tissues and the residuum-socket interface loading under a range of prosthetic loading instances. The results demonstrate the concept of this approach for interface actuation modelled as translational spring and damper systems
Developing a control framework for self-adjusting prosthetic sockets incorporating tissue injury risk estimation and generalized predictive control
No full textTo perform activities of daily living (ADL), people with lower limb amputation depend on the prosthetic socket for stability and proprioceptive feedback. Poorly fitting sockets can cause discomfort, pain, limb tissue injuries, limited device usage, and potential rejection. Semi-passively controlled adjustable socket technologies exist, but these depend upon the user’s perception to determine safe interfacial pressure levels. This paper presents a framework for automatic control of an adjustable transtibial prosthetic socket that enables active adaptation of residuum-socket interfacial loading through localized actuators, based on soft tissue injury risk estimation. Using finite element analysis, local interfacial pressure vs. compressive tissue strain relationships were estimated for three discrete anatomical actuator locations, for tissue injury risk assessment within a control structure. Generalized Predictive Control of multiple actuators was implemented to maintain interfacial pressure within estimated safe and functional limits. Controller simulation predicted satisfactory dynamic performance in several scenarios. Actuation rates of 0.06–1.51 kPa/s with 0.67% maximum overshoot, and 0.75–1.58 kPa/s were estimated for continuous walking, and for a demonstrative loading sequence of ADL, respectively. The developed platform could be useful for extending recent efforts in adjustable lower limb prosthetic socket design, particularly for individuals with residuum sensory impairment.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Design and Evaluation of a Propulsion System for Small, Compact, Low-Speed Maneuvering Underwater Vehicles
Full text linkUnderwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed via direct thrust measurement experiments and by use of an initial proof-of-concept test vehicle. Experiments are performed to enable the evaluation and modelling of the thrust output of the mechanism as well as the speed capability of a vehicle employing the propulsion system
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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