The effectiveness of a low-cost soil moisture sensor for domestic irrigation systems

Domestic garden irrigation often constitutes a considerable percentage of the total urban scheme water demand. Improvements in irrigation efficiency have the potential to contribute to substantial water savings within the community. Improper scheduling of irrigation systems is one of the key factors contributing to inefficient use of water in domestic irrigation systems. The application of soil moisture sensors that automate irrigation cycles can help negate the effects of poor scheduling which would otherwise lead to over irrigation, resulting in the wastage of water resources and other consequential environmental impacts. A low-cost capacitance soil moisture sensor has been developed and is currently the subject of a twelve month trial at the Environmental Technology Centre, Murdoch University, Perth, Western Australia. The sensor is being assessed to determine its ability to contribute to water savings when used with shrub sprinklers, microspray and drip line irrigation on sandy soils, in the Mediterranean type climate that Perth experiences

Electrometer system measures nanoamps at high voltage

Floating electrometer eliminates major source of error since any leakage from electrometer case, which is at high voltage, appears only as load on high voltage supply and not as part of current being measured. Commands to and data from floating electrometer are transferred across high voltage interface by means of optical channels

Transport and diffusion in the embedding map

We study the transport properties of passive inertial particles in a $2-d$ incompressible flows. Here the particle dynamics is represented by the $4-d$ dissipative embedding map of $2-d$ area-preserving standard map which models the incompressible flow. The system is a model for impurity dynamics in a fluid and is characterized by two parameters, the inertia parameter $\alpha$, and the dissipation parameter $\gamma$. We obtain the statistical characterisers of transport for this system in these dynamical regimes. These are, the recurrence time statistics, the diffusion constant, and the distribution of jump lengths. The recurrence time distribution shows a power law tail in the dynamical regimes where there is preferential concentration of particles in sticky regions of the phase space, and an exponential decay in mixing regimes. The diffusion constant shows behaviour of three types - normal, subdiffusive and superdiffusive, depending on the parameter regimes. Phase diagrams of the system are constructed to differentiate different types of diffusion behaviour, as well as the behaviour of the absolute drift. We correlate the dynamical regimes seen for the system at different parameter values with the transport properties observed at these regimes, and in the behaviour of the transients. This system also shows the existence of a crisis and unstable dimension variability at certain parameter values. The signature of the unstable dimension variability is seen in the statistical characterisers of transport. We discuss the implications of our results for realistic systems.Comment: 28 pages, 14 figures, To Appear in Phys. Rev. E; Vol. 79 (2009

Deceleration of one-dimensional mixing by discontinuous mappings

We present a computational study of a simple one-dimensional map with dynamics composed of stretching, permutations of equal sized cells, and diffusion. We observe that the combination of the aforementioned dynamics results in eigenmodes with long-time exponential decay rates. The decay rate of the eigenmodes is shown to be dependent on the choice of permutation and changes non-monotonically with the diffusion coefficient for many of the permutations. The global mixing rate of the map M in the limit of vanishing diffusivity approximates well the decay rates of the eigenmodes for small diffusivity, however this global mixing rate does not bound the rates for all values of the diffusion coefficient. This counter-intuitively predicts a deceleration in the asymptotic mixing rate with increasing diffusivity rate. The implication of the results on finite time mixing are discussed

Orbital mechanism of the circular photogalvanic effect in quantum wells

It is shown that the free-carrier (Drude) absorption of circularly polarized radiation in quantum well structures leads to an electric current flow. The photocurrent reverses its direction upon switching the light helicity. A pure orbital mechanism of such a circular photogalvanic effect is proposed that is based on interference of different pathways contributing to the light absorption. Calculation shows that the magnitude of the helicity dependent photocurrent in $n$-doped quantum well structures corresponds to recent experimental observations.Comment: 5 pages, 2 figures, to be published in JETP Letter

The average distance between item values: A novel approach for estimating internal consistency

This article presents a method for assessing the internal consistency of scales that works equally well with short and long scales, namely, the average proportional distance. The method provides information on the average distance between item scores for a particular scale. In this article, we sought to demonstrate how this relatively simple statistic could be calculated and present examples that show its advantage over traditional methods. Simulation and empirical tests were conducted to establish standards for the average proportional distance of scores. The implications for test construction are discussed with a particular emphasis on the advantages of developing shorter scales for psychological and educational research.Social Sciences and Humanities Research Council (SSHRC

Stochastic Energetics of Quantum Transport

We examine the stochastic energetics of directed quantum transport due to rectification of non-equilibrium thermal fluctuations. We calculate the quantum efficiency of a ratchet device both in presence and absence of an external load to characterize two quantifiers of efficiency. It has been shown that the quantum current as well as efficiency in absence of load (Stokes efficiency) is higher as compared to classical current and efficiency, respectively, at low temperature. The conventional efficiency of the device in presence of load on the other hand is higher for a classical system in contrast to its classical counterpart. The maximum conventional efficiency being independent of the nature of the bath and the potential remains the same for classical and quantum systems.Comment: To be published in Phys. Rev.

Quantum kinetic theory of shift current electron pumping in semiconductors

We develop a theory of laser beam generation of shift currents in non-centrosymmetric semiconductors. The currents originate when the excited electrons transfer between different bands or scatter inside these bands, and asymmetrically shift their centers of mass in elementary cells. Quantum kinetic equations for hot-carrier distributions and expressions for the induced currents are derived by nonequilibrium Green functions. In applications, we simplify the approach to the Boltzmann limit and use it to model laser-excited GaAs in the presence of LO phonon scattering. The shift currents are calculated in a steady-state regime.Comment: 23 pages, 5 figures (Latex

Opto-Electronic Characterization of Three Dimensional Topological Insulators

We demonstrate that the terahertz/infrared radiation induced photogalvanic effect, which is sensitive to the surface symmetry and scattering details, can be applied to study the high frequency conductivity of the surface states in (Bi1-xSbx)2Te3 based three dimensional (3D) topological insulators (TI). In particular, measuring the polarization dependence of the photogalvanic current and scanning with a micrometre sized beam spot across the sample, provides access to (i) topographical inhomogeneity's in the electronic properties of the surface states and (ii) the local domain orientation. An important advantage of the proposed method is that it can be applied to study TIs at room temperature and even in materials with a high electron density of bulk carriers.Comment: 6 pages, 4 figure

Entrances and exits: changing perceptions of primary teaching as a career for men

Original article can be found at: http://www.informaworld.com/smpp/title~content=t713640830~db=all Copyright Informa / Taylor and Francis. DOI: 10.1080/03004430802352087The number of men in teaching has always been small, particularly in early childhood, but those that do come into teaching usually do so for the same reasons as women, namely enjoyment of working with children, of wanting to teach and wanting to make a difference to children's lives. However, in two separate studies, the authors have shown that on beginning teacher training in 1998, and at the point of leaving the profession in 2005, men and women tend to emphasise different concerns. This article will explore those differences and seek possible explanations for how men's views of teaching might be changing over time.Peer reviewe