Solar magnetic field reversal as seen at Ulysses

The rapid motion of the Ulysses spacecraft from high southern to high northern latitudes in 2000–2001 provided an excellent opportunity to make inferences regarding the solar magnetic dipole's behaviour around solar maximum. A simple dipole model is fitted to Ulysses measurements of the polarity of the heliospheric magnetic field mapped back to the solar wind source surface. Although higher order components of the field are ignored, the gradual reversal in orientation of the dipole field component can be followed during solar maximum, with the dipole axis crossing the solar equator during early 2000–early 2001. The dipole appears to exhibit a rotation at a slower rate than the Carrington frame of reference, similar to previous measurements made around solar maximum in the solar equatorial regions

Development of methods for optimisation of complex 3D weave geometries

The development of 3D weaves has resulted in the ability to produce near net shaped preforms, with the additional advantage over unidirectional lay-ups and 2D weaves of greater delamination resistance provided by through-thickness reinforcement. 3D weaving can allow the post-weave formation of bifurcations to form the web and flange of structural components. The mechanical properties of 3D woven components are highly dependent on the weave architecture, allowing the mechanical performance of the component to be tailored to its specific application. Given the number of design parameters to be varied, the design space is potentially infinite. This work focuses on the development of methods to find the optimum weave geometry of a unit cell based on the numerical evaluation of objective functions.This work demonstrates the development of methods to optimise 3D woven textile geometry, using the University of Nottingham’s open-source software TexGen [1] to automatically generate each weave based on the input from a global optimisation algorithm. Methods of varying a number of the parameters will be reported alongside their geometric and physical constraints. Finally, the facility to automatically generate a wide range of weaves, with the ability to vary parameters as desired for input either directly into an optimisation algorithm or for further pre-processing is demonstrated

Development of methods for optimisation of complex 3D weave geometries

The development of 3D weaves has resulted in the ability to produce near net shaped preforms, with the additional advantage over unidirectional lay-ups and 2D weaves of greater delamination resistance provided by through-thickness reinforcement. 3D weaving can allow the post-weave formation of bifurcations to form the web and flange of structural components. The mechanical properties of 3D woven components are highly dependent on the weave architecture, allowing the mechanical performance of the component to be tailored to its specific application. Given the number of design parameters to be varied, the design space is potentially infinite. This work focuses on the development of methods to find the optimum weave geometry of a unit cell based on the numerical evaluation of objective functions. This work demonstrates the development of methods to optimise 3D woven textile geometry, using the University of Nottingham’s open-source software TexGen [1] to automatically generate each weave based on the input from a global optimisation algorithm. Methods of varying a number of the parameters will be reported alongside their geometric and physical constraints. Finally, the facility to automatically generate a wide range of weaves, with the ability to vary parameters as desired for input either directly into an optimisation algorithm or for further pre-processing is demonstrated

Geometric phases for non-degenerate and degenerate mixed states

This paper focuses on the geometric phase of general mixed states under unitary evolution. Here we analyze both non-degenerate as well as degenerate states. Starting with the non-degenerate case, we show that the usual procedure of subtracting the dynamical phase from the total phase to yield the geometric phase for pure states, does not hold for mixed states. To this end, we furnish an expression for the geometric phase that is gauge invariant. The parallelity conditions are shown to be easily derivable from this expression. We also extend our formalism to states that exhibit degeneracies. Here with the holonomy taking on a non-abelian character, we provide an expression for the geometric phase that is manifestly gauge invariant. As in the case of the non-degenerate case, the form also displays the parallelity conditions clearly. Finally, we furnish explicit examples of the geometric phases for both the non-degenerate as well as degenerate mixed states.Comment: 23 page

Quantitative transformation for implementation of adder circuits in physical systems

© 2015 Elsevier Ireland Ltd. Computing devices are composed of spatial arrangements of simple fundamental logic gates. These gates may be combined to form more complex adding circuits and, ultimately, complete computer systems. Implementing classical adding circuits using unconventional, or even living substrates such as slime mould Physarum polycephalum, is made difficult and often impractical by the challenges of branching fan-out of inputs and regions where circuit lines must cross without interference. In this report we explore whether it is possible to avoid spatial propagation, branching and crossing completely in the design of adding circuits. We analyse the input and output patterns of a single-bit full adder circuit. A simple quantitative transformation of the input patterns which considers the total number of bits in the input string allows us to map the respective input combinations to the correct outputs patterns of the full adder circuit, reducing the circuit combinations from a 2:1 mapping to a 1:1 mapping. The mapping of inputs to outputs also shows an incremental linear progression, suggesting its implementation in a range of physical systems. We demonstrate an example implementation, first in simulation, inspired by self-oscillatory dynamics of the acellular slime mould P. polycephalum. We then assess the potential implementation using plasmodium of slime mould itself. This simple transformation may enrich the potential for using unconventional computing substrates to implement digital circuits

Tkachenko waves, glitches and precession in neutron star

Here I discuss possible relations between free precession of neutron stars, Tkachenko waves inside them and glitches. I note that the proposed precession period of the isolated neutron star RX J0720.4-3125 (Haberl et al. 2006) is consistent with the period of Tkachenko waves for the spin period 8.4s. Based on a possible observation of a glitch in RX J0720.4-3125 (van Kerkwijk et al. 2007), I propose a simple model, in which long period precession is powered by Tkachenko waves generated by a glitch. The period of free precession, determined by a NS oblateness, should be equal to the standing Tkachenko wave period for effective energy transfer from the standing wave to the precession motion. A similar scenario can be applicable also in the case of the PSR B1828-11.Comment: 6 pages, no figures, accepted to Ap&S