A validated computational framework to evaluate the stiffness of 3D printed ankle foot orthoses

The purpose of this study was to create and validate a standardized framework for the evaluation of the ankle stiffness of two designs of 3D printed ankle foot orthoses (AFOs). The creation of four finite element (FE) models allowed patient-specific quantification of the stiffness and stress distribution over their specific range of motion during the second rocker of the gait. Validation was performed by comparing the model outputs with the results obtained from a dedicated experimental setup, which showed an overall good agreement with a maximum relative error of 10.38% in plantarflexion and 10.66% in dorsiflexion. The combination of advanced computer modelling algorithms and 3D printing techniques clearly shows potential to further improve the manufacturing process of AFOs

Development and clinical evaluation of laser-sintered ankle foot orthoses

Ankle foot orthoses (AFOs) are traditionally manufactured using vacuum thermoforming as shaping technology. Additive manufacturing has the potential to disruptively change the way these orthopaedic devices are produced. In this study, AFOs are developed which are virtually designed and produced with laser sintering as shaping technology. The mechanical and clinical performances of these laser-sintered AFOs are compared with traditionally manufactured AFO by asking seven patients (both children and adults) to walk with each type of AFO

Solar sail science mission applications and advancement : solar sailing: concepts, technology, missions

Solar sailing has long been envisaged as an enabling or disruptive technology. The promise of open-ended missions allows consideration of radically new trajectories and the delivery of spacecraft to previously unreachable or unsustainable observation outposts. A mission catalogue is presented of an extensive range of potential solar sail applications, allowing identification of the key features of missions which are enabled, or significantly enhance, through solar sail propulsion. Through these considerations a solar sail application-pull technology development roadmap is established, using each mission as a technology stepping-stone to the next. Having identified and developed a solar sail application-pull technology development roadmap, this is incorporated into a new vision for solar sailing. The development of new technologies, especially for space applications, is high-risk. The advancement difficulty of low technology readiness level research is typically underestimated due to a lack of recognition of the advancement degree of difficulty scale. Recognising the currently low technology readiness level of traditional solar sailing concepts, along with their high advancement degree of difficulty and a lack of near-term applications a new vision for solar sailing is presented which increases the technology readiness level and reduces the advancement degree of difficulty of solar sailing. Just as the basic principles of solar sailing are not new, they have also been long proven and utilised in spacecraft as a low-risk, high-return limited-capability propulsion system. It is therefore proposed that this significant heritage be used to enable rapid, near-term solar sail future advancement through coupling currently mature solar sail, and other, technologies with current solar sail technology developments. As such the near-term technology readiness level of traditional solar sailing is increased, while simultaneously reducing the advancement degree of difficulty along the solar sail application-pull technology development roadmap

Survey of highly non-Keplerian orbits with low-thrust propulsion

Celestial mechanics has traditionally been concerned with orbital motion under the action of a conservative gravitational potential. In particular, the inverse square gravitational force due to the potential of a uniform, spherical mass leads to a family of conic section orbits, as determined by Isaac Newton, who showed that Kepler‟s laws were derivable from his theory of gravitation. While orbital motion under the action of a conservative gravitational potential leads to an array of problems with often complex and interesting solutions, the addition of non-conservative forces offers new avenues of investigation. In particular, non-conservative forces lead to a rich diversity of problems associated with the existence, stability and control of families of highly non-Keplerian orbits generated by a gravitational potential and a non-conservative force. Highly non-Keplerian orbits can potentially have a broad range of practical applications across a number of different disciplines. This review aims to summarize the combined wealth of literature concerned with the dynamics, stability and control of highly non-Keplerian orbits for various low thrust propulsion devices, and to demonstrate some of these potential applications

The effect of simulating weight gain on the energy cost of walking in unimpaired children and children with cerebral palsy

Objective: To examine the effect of simulating weight gain on the energy cost of walking in children with cerebral palsy (CP) compared with unimpaired children. Design: Repeated measures, matched subjects, controlled. Setting: University hospital clinical gait and movement analysis laboratory. Participants: Children (n=42) with CP and unimpaired children (n=42). Interventions: Addition of 10% of body mass in weight belt. Main Outcome Measures: Energy cost of walking parameters consisting of walking speed, Physiological Cost Index, Total Heart Beat Index, oxygen uptake ((V) over doto(2)), gross oxygen cost, nondimensional net oxygen cost, and net oxygen cost with speed normalized to height were measured by using a breath-by-breath gas analysis system (K4b(2)) and a light beam timing Gate system arranged around a figure 8 track. Two walking trials were performed in random order, with and the other without wearing a weighted belt. Results: Children with CP and their unimpaired counterparts responded in fundamentally different ways to weight gain. The unimpaired population maintained speed and (V) over doto(2) but the children with CP trended toward a drop in their speed and an increase in their (V) over doto(2) The oxygen consumption of children with CP showed a greater dependence on mass than the unimpaired group (P=.043). Conclusions: An increase of a relatively small percentage ill body mass began to significantly impact the energy cost of walking in children with CP. This result highlights the need for weight control to sustain the level of functional walking in these children

The clinical relevance of selecting resting data at different points in an energy cost of walking test in cerebral palsy

AIM Energy cost of walking (ECOW) is defined as 'walking oxygen consumption minus resting oxygen consumption divided by speed', where 'resting' data can be obtained either at the start or cessation of a test. This study aimed to ascertain when resting data should be taken during an ECOW test in children with cerebral palsy (CP). METHOD Resting oxygen consumption per unit mass (VO2) and heart rate were recorded in children without physical impairment (18 males, 13 females; mean age 11y [SD 2y 1mo]) and children with diplegic CP (18 males, 13 females; mean age 11y [SD 2y 6mo, Gross Motor Function Classification System levels I and II]) at three stages, namely pre- and posttest sitting and pretest standing before and after an 8-minute ECOW test using the Cosmed K4b. RESULTS Heart rate and VO2 differed significantly between groups and stages (p <= 0.05) except for heart rate in standing and posttest sitting in the unimpaired children and for VO2 during pretest sitting between groups. These differences impacted on the calculation of non-dimensional net oxygen cost (NDNOC) and physiological cost index (PCI) in CP but not in the unimpaired group. PCI was correlated with NDNOC in CP but not in the unimpaired cohort. INTERPRETATION Pretest sitting resting data appear to be the most appropriate for use in the calculation of NDNOC and PCI. PCI may still have relevance in pathology where walking efficiency is compromised