A class of optimal fault tolerant Jacobian for minimal redundant manipulators based on symmetric geometries

Design of locally optimal fault tolerant manipulators has been recently addressed via using the constraints of the desired null space for the Jacobian matrix of the manipulators. In the present paper the Jacobian matrices for optimal fault tolerance are presented based on geometric properties of column vectors instead of the null space. They are equally fault tolerant to a single joint failure from the worst-case relative manipulability and worst-case dexterity points of view. The optimality is achieved through a symmetric distribution of points on spheres.

Organic ionic plastic crystal electrolytes; a new class of electrolyte for high efficiency solid state dye-sensitized solar cells

Dye-sensitized solar cells are an increasingly promising alternative to conventional silicon solar cells as a method of converting solar energy to electricity and thus providing an effectively inexhaustible energy source. However, the most efficient of these devices currently utilize liquid electrolytes, which suffer from the associated problems of leakage and evaporation. Hence, significant research is currently focused on the development of solid state alternatives. Here we report a new class of solid state electrolyte for these devices, organic ionic plastic crystal electrolytes, that allow relatively rapid diffusion of the redox couple through the matrix, which is critical to the cell performance. A range of different organic ionic plastic crystal materials, utilizing different cation and anion structures, have been investigated and the conductivities, diffusion rates and photovoltaic performance of the electrolytes are reported. The best material, utilizing the dicyanamide anion, achieves efficiencies of more than 5%.

William Wardell's 1859 St John's College - a rare realisation of Pugin's ideal Catholic College?

William Wardell’s St John’s College, Sydney, considered the grandest and architecturally most distinguished university college in New South Wales, is an exceptional example of 19th century Gothic Revival architecture.  The information board outside the college states that St John’s is ‘a rare realisation of Pugin’s ideal Catholic College’ and further that ‘it demonstrates [Pugin]’s profound influence on the work of Wardell’. This is but a small part of the story. The commission for St John’s College was far more complex.  The correspondence between the architects, William Wardell, Edmund Blacket and others, and St John’s Council indicates that right from the beginning there was a general lack of understanding of Wardell’s original design concept for the building. This has continued to the present day, as evidenced by the information on the board outside St John’s College, in which it is incorrectly assumed that Wardell’s proposal included a quadrangle as featured in Pugin’s ‘ideal College’. This paper, based largely on primary sources, investigates such claims about St John’s, considers William Wardell and the Gothic Revival, examines St John’s College within the University of Sydney – its design and its translation and posits a few conclusions leading to new understandings.

Scandium-doped AlN 1D hexagonal nanoprisms : a class of room-temperature ferromagnetic materials

Pretty vacancy: The formation energy of Al vacancies in aluminum nitride is decreased by doping with nonmagnetic scandium ions. These vacancies are shown to be the cause of the room-temperature ferromagnetism in the resulting 1D hexagonal nanoprisms of AlN:Sc, a result that is confirmed by first-principles calculations. The doping approach provides a new route to dilute magnetic semiconductor materials.

Adaptive fast finite-time multiple-surface sliding control for a class of uncertain non-linear systems

This paper concerns the adaptive fast finite-time multiple-surface sliding control (AFFTMSSC) problem for a class of high-order uncertain non-linear systems of which the upper bounds of the system uncertainties are unknown. By using the fast control Lyapunov function and the method of so-called adding a power integrator merging with adaptive technique, a recursive design procedure is provided, which guarantees the fast finite-time stability of the closed-loop system. Further, it is proved that the control input is bounded.

Is lithium in a class of its own? A brief profile of its clinical use

Lithium is a unique and effective psychotropic agent with a long-standing history of clinical use yet it is increasingly overlooked in lieu of newer agents. The purpose of the present paper was to succinctly review the therapeutic profile of lithium particularly with respect to the treatment of mood disorders and consider its unique properties and clinical utility. A comprehensive literature review pertaining to lithium was undertaken using electronic database search engines to identify relevant clinical trials, meta-analyses and Cochrane reviews. In addition articles and book chapters known to the authors were carefully reviewed, and the authors appraised published guidelines. The evidence from these sources was rated using National Health and Medical Research Council evidence levels and synthesized according to phenotype and mood states. In addition, the authors have drawn upon published guidelines and their own clinical experience. Lithium has specificity for mood disorders with proven efficacy in the treatment of both unipolar depression and bipolar disorder. The recommendations are based predominantly on Level I evidence, but its clinical use has to be tempered against potential side-effects and the need for ongoing monitoring. In practice, lithium should be considered a first-line option in bipolar disorder, especially in prophylaxis and when onset of action is not an imperative. Lithium has been in use in modern medicine for 60 years and as such has been tried and tested across the full range of mood disorders. Arguably, lithium is the only true mood stabilizer and because of its unique properties is in a class of its own.

On the feasibility of utilising gearing to extend the rotational workspace of a class of parallel robots

Parallel manipulators provide several benefits compared to serial manipulators of similar size. These advantages typically include higher speed and acceleration, improved position accuracy and increased stiffness. However, parallel manipulators also suffer from several disadvantages. These drawbacks commonly include a small ratio of the positional workspace relative to the manipulator footprint and a limited rotational capability of the manipulated platform. A few parallel manipulators featuring a large ratio of the positional workspace relative to the footprint have been proposed. This paper investigates the feasibility of employing gearing to extend the range of the end-effector rotation of such mechanisms. The objective is to achieve parallel manipulators where both the positional and rotational workspace are comparable to that of serial manipulators.

Global finite-time stabilisation for a class of stochastic nonlinear systems by output feedback

In this paper, the problem of global finite-time stabilisation by output feedback is considered for a class of stochastic nonlinear systems. First, based on homogeneous systems theory and the adding a power integrator technique, a homogeneous reduced order observer and control law are constructed in a recursive manner for the nominal system. Then, the homogeneous domination approach is used to deal with the nonlinearities in drift and diffusion terms; it is shown that the proposed output-feedback control law can guarantee that the closed-loop system is global finite-time stable in probability. Finally, simulation examples are carried out to demonstrate the effectiveness of the proposed control scheme.