10 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/
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
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
Design and Evaluation of a Propulsion System for Small, Compact, Low-Speed Maneuvering Underwater Vehicles
No full textUnderwater 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
Financing health services in Africa : an assessment of alternative approaches
No full textThis paper outlines a strategy for financing health services in sub-Saharan Africa. The individual components of the strategy are as follows: general tax revenues, international finance, a system of user charges, community finance, health insurance, and contributions from nongovernmental organizations, including the private sector. The author states that financial positions of public health care systems in sub-Saharan Africa would be greatly enhanced if governments in the region were to adopt policies that would use each of the above sources of finance. Since a strong financial base is a prerequisite for an effective health care system, such policies would considerably improve the health status of the population. It is important that for each country different policies be pursued at various levels of society, and in different sectors of the economy.Health Systems Development&Reform,Health Monitoring&Evaluation,Housing&Human Habitats,Health Economics&Finance,Pharmaceuticals&Pharmacoeconomics
Predictive Control for an Active Prosthetic Socket informed by FEA-based Tissue Damage Risk Estimation
No full textDo differences in the scale of irrigation projects generate different impacts on poverty and production?
No full textThis paper investigates differences in household production and consumption among small- and large-scale irrigators to assess whether the scale of an irrigation project increases household welfare in Mali. Much of the evidence of the impact of irrigation does not use counterfactual analysis to estimate such impact or distinguish between the scale of the irrigation projects to be evaluated. In the dataset collected by the author, both a large-scale irrigation project and small-scale projects are used to construct counterfactual groups. Propensity score matching is used to estimate the average treatment effect on the treated for small and large irrigators relative to nonirrigators on agricultural production, agricultural income, and consumption per capita. Small-scale irrigation has a larger effect on agricultural production and agricultural income than large-scale irrigation, but large-scale irrigation has a larger effect on consumption per capita. This suggests that market integration and nonfarm externalities are important in realizing gains in agricultural surplus from irrigation.Irrigation, program evaluation,
Characteristics and performance of settlement programs : a review
No full textThe studies and cases reviewed by the authors suggest that settlement programs are too often designed on the assumption that all settlers will or can succeed. This had led to too much centralized administration and rigid designs, rather than reliance on decentralized approaches, flexibility in implementation, support for spontaneous settlement, and reliance on the settler's own investment capacity. Collective forms of crop production have not worked. Cropland is best allocated to individual families whose land rights must be clearly defined as ownership or long-term leases. Farm sizes must be flexibly adjusted to skills, the availability of family labor, and the families'capital ownership. Settlers should therefore be allowed to sell or rent the land to other beneficiaries. If poor settlers are to benefit or succeed, settlement cannot be based on credit finance but must include grants. Paternalistic constraints on the choice of crops or technologies, marketing, or participation in the labor force have usually not been enforceable or have had negative effects.Agricultural Knowledge&Information Systems,Urban Housing,Banks&Banking Reform,Environmental Economics&Policies,Housing&Human Habitats
Uzbekistan’s self-reliance 1991-2010 : public politics and the impact of roles in shaping bilateral relationships
No full textThis thesis applies role theory to understand how Uzbekistan’s bilateral relationships became either conflicting or cooperative between 1991 and 2010. Roles are key elements of social interaction as they describe plausible lines of action in a particular subject-person. They are thus a helpful way of identifying actors and constructing narratives. Furthermore, if they are seen as metaphors for drama, one may argue that roles - as opposed to personal identities - encapsulate autonomous action, which, like a text, ascertains meaning beyond the author’s intent. In other words, by separating action from intent, one may regard politics in a different light - as interaction emplotted by roles -, thereby revealing how actions contradict a set of roles and lead to conflict and crises in public credibility. This manner of emplotting relationships divulges an alternative story that, rather than focusing on Tashkent’s strategic balancing and alignment, demonstrates how Uzbekistani leadership gradually developed an overarching self-reliant role set that shapes its actions. Moreover, Uzbekistan’s cooperative and conflicting relationships are described less in light of strategic survival rationale than as the outcome of gradual role compatibilities arising through time. Therefore, unlike some other accounts, this thesis argues that, throughout Uzbekistan’s first twenty years of independence, public disputes were crucial to understanding interaction and also that Tashkent was never actually aligned with Russia or the United States. To bring forth this argument, the following chapters expound the assumptions behind some scholarly research and develop the concepts of self-reliance, roles, action, public sphere, credibility and narrative. The discussion progresses toward self-reliance and how the concept captures President Karimov’s roles, which are used to emplot Uzbekistan’s interaction with the United States, Russia, Germany and Turkey. The first two are relevant for analyzing whether roles reveal more than the typical accounts based on security balancing. Germany is then included because its relationship with Tashkent was rarely conflicting in the public sphere, allowing it to increase bilateral trade and secure a military base in Uzbekistan after the 2005 Andijan Crisis. It was thus a relatively stable connection, unlike Tashkent’s relationships with Washington and Moscow. Lastly, to control Germany’s middle-power status, the case of Turkey is brought to the fore since Ankara’s willingness to engage with Tashkent was not enough to foster cooperation
Perception of, and adjustment to, drought hazard by farmers in southern SRI Lanka
No full textIn Sri Lanka, two thirds of the land mass lies within the Dry Zone where agriculture is the most important economic activity. In this climatic zone, rainfall is highly uncertain, seasonal, and limited to a few months. Consequently, the farmers in the area have to face drought as a natural hazard. This study focusses on how the farmers in the southern Dry Zone of Sri Lanka perceive drought as a hazard, the adjustments they make to reduce their vulnerability to droughts and how human behaviour affects the growing hazardousness of the study area. The results of this study show that the farmers in the study area have perceived drought as one of their major problems, and that the vulnerability to this natural phenomenon is growing as a result of the power abuse and environmental mismanagement of those high ranking people responsible. However, the farmers’ deeper understanding regarding their living environment (natural and man-made) has enhanced their power to combat the hazardous effects of droughts by way of a variety of adjustments. Considering and studying the above problems and issues the researcher has come to some conclusions and has put forward some suggestions, the most important of which, lie with changing the self-centered attitudes and activities of the powerful people in the direction of a socially and environmentally more sustainable and wholesome path
