Magnetic gear dynamics for servo control

This paper considers the analysis and application of magnetic gearbox and magnetic coupling technologies and issues surrounding their use for motion control servo systems. Analysis of a prototype magnetic gear is used as a basis for demonstrating the underlying nonlinear torque transfer characteristic, nonlinear damping, and `pole-slipping' when subject to over-torque (overload) conditions. It is also shown how `pole-slipping' results in consequential loss of control. A theoretical investigation into the suppression of mechanical torsional resonances in transmission systems encompassing these highly-compliant magnetically-coupled components is included, along with experimental results, from a demonstrator drive-train. The automatic detection of pole-slipping, and recovery scenarios, is also presented

"Pseudo" Direct Drive Electrical Machines With Alternative Winding Configurations

The integration of a magnetic gear and a brushless permanent magnet machine to realize a “pseudo” direct drive (PDD) with alternative winding configurations is investigated. It is shown topologies which facilitate the winding process and achieve a more robust stator construction exist. Comparisons with conventional PDD topologies which are essentially equipped with concentric windings have shown that similar efficiencies can be achieved, albeit at the expense of reduced torque densities. Furthermore, analysis of the magnetic forces exhibited by a pole piece has shown that both the average and dynamic forces are significantly affected by the rated load condition, exacerbating the radial forces

Relative Booster Ideals of Distributive p-algebras

In this article, the definition and characterization of relative booster ideals in distributive p-algebras are given. The relationship between disjunctive relative booster ideals and normal relative booster ideals is established in the distributive p-algebras. A lattice congruence relation defined via the relative boosters is given and its quotient lattice structure is obtained

Can pervasive sensing address current challenges in global healthcare?

Important challenges facing global healthcare include the increase in the number of people affected by escalating healthcare costs, chronic and infectious diseases, the need for better and more affordable elderly care and expanding urbanisation combined with air and water pollution. Recent advances in pervasive sensing technologies have led to miniaturised sensor networks that can be worn or integrated within the living environment without affecting a person's daily patterns. These sensors promise to change healthcare from snapshot measurements of physiological parameters to continuous monitoring enabling clinicians to provide guidance on a daily basis. This article surveys several of the solutions provided by these sensor platforms from elderly care to neonatal monitoring and environmental mapping. Some of the opportunities available and the challenges facing the adoption of such technologies in large-scale epidemiological studies are also discussed

The second-generation Shifted Boundary Method and its numerical analysis

Recently, the Shifted Boundary Method (SBM) was proposed within the class of unfitted (or immersed, or embedded) finite element methods. By reformulating the original boundary value problem over a surrogate (approximate) computational domain, the SBM avoids integration over cut cells and the associated problematic issues regarding numerical stability and matrix conditioning. Accuracy is maintained by modifying the original boundary conditions using Taylor expansions. Hence the name of the method, that shifts the location and values of the boundary conditions. In this article, we present enhanced variational SBM formulations for the Poisson and Stokes problems with improved flexibility and robustness. These simplified variational forms allow to relax some of the assumptions required by the mathematical proofs of stability and convergence of earlier implementations. First, we show that these new SBM implementations can be proved asymptotically stable and convergent even without the rather restrictive assumption that the inner product between the normals to the true and surrogate boundaries is positive. Second, we show that it is not necessary to introduce a stabilization term involving the tangential derivatives of the solution at Dirichlet boundaries, therefore avoiding the calibration of an additional stabilization parameter. Finally, we prove enhanced L2-estimates without the cumbersome assumption – of earlier proofs – that the surrogate domain is convex. Instead we rely on a conventional assumption that the boundary of the true domain is smooth, which can also be replaced by requiring convexity of the true domain. The aforementioned improvements open the way to a more general and efficient implementation of the Shifted Boundary Method, particularly in complex three-dimensional geometries. We complement these theoretical developments with numerical experiments in two and three dimensions

Calcium supplementation to prevent pre-eclampsia - a systematic review

Background. Calcium supplementation during pregnancy may prevent high blood pressure and preterm labour. Objective. To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child adverse outcomes. Design. A systematic review of randomised trials that compared supplementation with at least 1 g calcium daily during pregnancy with placebo. Search strategy. The Cochrane Pregnancy and Childbirth Group trials register (October 2001) and the Cochrane Controlled Trials Register (Issue 3, 2001) were searched and study s were contacted. Data collection and analysis. Eligibility and trial quality were assessed. Data were extracted and analysed. Main results. There was a modest reduction in the risk of pre-eclampsia with calcium supplementation (relative risk (RR) 0.68, 95% confidence interval (CI): 0.57- 0.81). The effect was greatest for women at high risk of hypertension (RR 0.21, 95% CI: 0.11 - 0.39) and those with low baseline calcium intake (RR 0.32, 95% CI: 0.21 - 0.49). There was no overall effect on the risk of preterm delivery, although there was a reduction in risk among women at high risk of hypertension (RR 0.42, 95% CI: 0.23 - 0.78). There was no evidence of any effect of calcium supplementation on stillbirth or death before discharge from hospital. There were fewer babies with birthweight 95th percentile was reduced (RR 0.59, 95% CI: 0.39 - 0.91). Conclusions. Calcium supplementation appears to be beneficial for women at high risk of gestational hypertension and in communities with low dietary calcium intake. These benefits were confined to several rather small trials, and were not found in the largest trial to date, conducted in a low-risk population. Further research is required. (South African Medical Journal: 2003 93(3): 224-228