Virtual prototyping of a semi-active transfemoral prosthetic leg

This article presents a virtual prototyping study of a semi-active lower limb prosthesis to improve the functionality of an amputee during prosthesis–environment interaction for level ground walking. Articulated ankle–foot prosthesis and a single-axis semi-active prosthetic knee with active and passive operating modes were considered. Data for level ground walking were collected using a photogrammetric method in order to develop a base-line simulation model and with the hip kinematics input to verify the proposed design. The simulated results show that the semi-active lower limb prosthesis is able to move efficiently in passive mode, and the activation time of the knee actuator can be reduced by approximately 50%. Therefore, this semi-active system has the potential to reduce the energy consumption of the actuators required during level ground walking and requires less compensation from the amputee due to lower deviation of the vertical excursion of body centre of mass

Review on the influence of process parameters in incremental sheet forming

Incremental sheet forming (ISF) is a relatively new flexible forming process. ISF has excellent adaptability to conventional milling machines and requires minimum use of complex tooling, dies and forming press, which makes the process cost-effective and easy to automate for various applications. In the past two decades, extensive research on ISF has resulted in significant advances being made in fundamental understanding and development of new processing and tooling solutions. However, ISF has yet to be fully implemented to mainstream high-value manufacturing industries due to a number of technical challenges, all of which are directly related to ISF process parameters. This paper aims to provide a detailed review of the current state-of-the-art of ISF processes in terms of its technological capabilities and specific limitations with discussions on the ISF process parameters and their effects on ISF processes. Particular attention is given to the ISF process parameters on the formability, deformation and failure mechanics, springback and accuracy and surface roughness. This leads to a number of recommendations that are considered essential for future research effort

Measuring Multi-Joint Stiffness during Single Movements: Numerical Validation of a Novel Time-Frequency Approach

This study presents and validates a Time-Frequency technique for measuring 2-dimensional multijoint arm stiffness throughout a single planar movement as well as during static posture. It is proposed as an alternative to current regressive methods which require numerous repetitions to obtain average stiffness on a small segment of the hand trajectory. The method is based on the analysis of the reassigned spectrogram of the arm's response to impulsive perturbations and can estimate arm stiffness on a trial-by-trial basis. Analytic and empirical methods are first derived and tested through modal analysis on synthetic data. The technique's accuracy and robustness are assessed by modeling the estimation of stiffness time profiles changing at different rates and affected by different noise levels. Our method obtains results comparable with two well-known regressive techniques. We also test how the technique can identify the viscoelastic component of non-linear and higher than second order systems with a non-parametrical approach. The technique proposed here is very impervious to noise and can be used easily for both postural and movement tasks. Estimations of stiffness profiles are possible with only one perturbation, making our method a useful tool for estimating limb stiffness during motor learning and adaptation tasks, and for understanding the modulation of stiffness in individuals with neurodegenerative diseases

Demographic and angioarchitectural features associated with seizures presentation in patients with brain arteriovenous malformations in Durban, KwaZulu-Natal, South Africa

Background: Brain arteriovenous malformations (AVMs) often present with epileptic seizures which carry standard mortality rate two to three folds higher than in the general population, yet preventative eradication of these lesions remains controversial. The aim of this study was to determine the demographic and angioarchitectural features associated with clinical presentation of seizures in patients with brain AVMs. Methods: We conducted a retrospective chart review of all consecutive patients who presented to three interventional neuroradiology hospitals, with brain AVMs in Kwazulu-Natal, South Africa, over a period of 10years. The demographic and clinical presentations were derived from patient's electronic medical records. Radiological features were determined using axial Computerized Topography (CT) or Magnetic Resonance Imaging (MRI) Scan. Angioarchitectural features were determined from Digital Subtraction Angiography (DSA). Simple and multiple logistic regression models were used to identify factors associated with the risk of seizure as initial presentation in brain AVMs. Results: The analysis identified race/ethnicity, nidus size and location as the predictors of seizure presentation. By multiple logistic regression analysis, African-black race (OR=4.7; 95%CI: 1.15–19.60), brain AVM nidus >3cm in diameter, (OR=4.4; 95%CI: 1.7−11.42) and cortical lobar location (OR=13.6; 95%CI: 2.80−65.14) were found to be significant predictors of brain AVM-associated seizures. Conclusion: Improved knowledge of specific morphological factors associated with brain AVM epilepsy could aid in the formulation of appropriate therapeutic strategies for control and/or cure of these brain AVM-associated seizures. Keywords: Angioarchitecture, Arteriovenous malformations, Brain, Demographics, Seizure