Pricing of Sorghum Irrigation Water: A Comparison between Gravity, Spate and Rain-fed Irrigations in Sudan

There is global consensus to use scientific approaches to value all natural resources including water resources. Valuation of water is one way of making users more aware of its value. The aims of this paper is to determine the value of water used in agriculture under gravity system in Gezira Scheme and spate irrigation systems in Gash Delta Agricultural Corporation in Sudan. CROPWAT model was used to determine the volume of water supplied for irrigation. Net revenue was calculated to determine the output from agriculture. The main results show that the net values of water are $0.005/m3 and$ 0.001/m3 under gravity and spate irrigation systems respectively. The value of water used in gravity irrigation system is greater than water used in spate irrigation system. These findings will help into setting real value and cost of water in agriculture as the major consumptive sector and hence will help policy makers in developing decisions on agricultural water

Numerical study of SQUID array responses due to asymmetric junction parameters

Superconducting quantum interference device arrays have been extensively studied for their high magnetic field sensitivity. The performance of these devices strongly depends on the characteristic parameters of their Josephson junctions, i.e. their critical currents and shunt resistances. Using a resistively shunted junction model and including thermal noise, we perform a numerical investigation of the effects of asymmetric Josephson junctions by independently studying variations in the critical currents and junction resistances. We compare the voltage response of a dc-SQUID with a 1D parallel SQUID array and study the maximum transfer function dependence on the number of junctions in parallel, the screening parameter and thermal noise strength. Our results show that the maximum transfer function and linearity increase with the number of junctions in parallel for arrays with different junction resistances, in contrast to SQUID arrays with identical junctions or with spreads in the critical currents

The effect of bias current configuration on the performance of SQUID arrays

Designing superconducting electronic devices involves a careful study of all the elements in the circuit, including the superconducting bias leads, however, the effect of the bias current leads on the performance of the device have not been previously addressed. In this work, we introduce a theoretical model for two-dimensional superconducting quantum interference device (SQUID) arrays capable of simulating the response of devices with different bias current configurations. First, we compare uniformly biased and centre biased SQUID arrays by investigating the voltage versus magnetic flux response, maximum transfer function and voltage modulation depth. Then, we calculate the time-averaged fluxoid distributions for 1D and 2D centre biased arrays. Finally, we study the performance of the two bias current configurations depending on array size, screening parameter, thermal noise strength and kinetic self-inductance fraction. Our calculations reveal: (i) centre biased 1D parallel SQUID arrays present an unusual voltage response caused by the asymmetric fluxoid distribution; (ii) the optimal transfer function of centre biased arrays strongly depends on the number of junctions in parallel; (iii) the performance of centre biased arrays approaches the uniform biased ones when the number of junctions in series exceeds those in parallel; (iv) while the screening parameter and the thermal noise strength clearly affect the device performance, the kinetic self-inductance fraction seems to play only a secondary role.Comment: 10 pages, 9 Figure

Characterization of the nitrogen split interstitial defect in wurtzite aluminum nitride using density functional theory

We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane wave supercell calculations in wurtzite aluminum nitride in order to characterize the geometry, formation energies, transition levels and hyperfine tensors of the nitrogen split interstitial defect. The calculated hyperfine tensors may provide useful fingerprint of this defect for electron paramagnetic resonance measurement.Comment: 5 pages, 3 figure

Modelling the transfer function of two-dimensional SQUID and SQIF arrays with thermal noise

We present a theoretical model for 2D SQUID and SQIF arrays with over-damped Josephson junctions for uniform bias current injection at 77 K. Our simulations demonstrate the importance of including Johnson thermal noise and reveal that the mutual inductive coupling between SQUID loops is of minor importance. Our numerical results establish the validity of a simple scaling behaviour between the voltages of 1D and 2D SQUID arrays and show that the same scaling behaviour applies to the maximum transfer functions. The maximum transfer function of a 2D SQUID array can be further optimised by applying the optimal bias current which depends on the SQUID loop self-inductance and the junction critical current. Our investigation further reveals that a scaling behaviour exits between the maximum transfer function of a 2D SQUID array and that of a single dc-SQUID. Finally, we investigate the voltage response of 1D and 2D SQIF arrays and illustrate the effects of adding spreads in the heights and widths of SQUID loops.Comment: 9 Figures Submitted to PR