Adaptively time stepping the stochastic Landau-Lifshitz-Gilbert equation at nonzero temperature: implementation and validation in MuMax3

Thermal fluctuations play an increasingly important role in micromagnetic research relevant for various biomedical and other technological applications. Until now, it was deemed necessary to use a time stepping algorithm with a fixed time step in order to perform micromagnetic simulations at nonzero temperatures. However, Berkov and Gorn have shown that the drift term which generally appears when solving stochastic differential equations can only influence the length of the magnetization. This quantity is however fixed in the case of the stochastic Landau-Lifshitz-Gilbert equation. In this paper, we exploit this fact to straightforwardly extend existing high order solvers with an adaptive time stepping algorithm. We implemented the presented methods in the freely available GPU-accelerated micromagnetic software package MuMax3 and used it to extensively validate the presented methods. Next to the advantage of having control over the error tolerance, we report a twenty fold speedup without a loss of accuracy, when using the presented methods as compared to the hereto best practice of using Heun's solver with a small fixed time step.Comment: 9 pages, 9 figure

Eddy-induced cross currents in the Westerschelde estuary: numerical simulation, physical driving mechanisms and navigation assistance

The Westerschelde estuary is located in The Netherlands and is a major shipping route connecting the North Sea to the Port of Antwerp (Belgium). Cross currents up to three knots occur at high water during extreme spring tides and are increasingly hampering navigation in the Westerschelde near Hansweert resulting in one major incident leaving a container vessel stranded on a nearby sand bank.This study aimed at the simulation, prediction and assessment of a large eddy (stretching over the complete navigation channel) which produces these cross currents. A numerical model was set up and a detailed calibration of the hydrodynamic model was executed. A good agreement was obtained between model and measured data on the location of the eddy and the strength of the cross currents. Flow fields produced by the numerical model subsequently have been implemented in a nautical simulator in which pilots are trained on sailing in these exceptional conditions.Currently, a warning is sent out to Traffic Control whenever at least one of two parameters is being foreseen to pass a critical value according to forecasting models (high water level and water level gradient). This system has been proven to yield false negatives in some cases. The simulation results and analysis have clarified the conditions in which the eddy grows sufficiently (2 km across) to cause cross currents in the navigation channel. A new criterion for sending out a navigation warning is proposed. It shows a better correlation with the occurrence of cross currents, hence pilots will have a higher probability to be warned in case of cross currents.</p

Quality of life in children surviving cancer: A personality and multi-informant perspective [IF: 1.5]

Objective: To describe quality of life (QoL) of children surviving cancer in relation to their personality, using self- and maternal reports and examining differences with healthy referents. Method: Sixty-seven children who survived childhood cancer were compared with eighty-one healthy children on QoL and personality characteristics. Results: Children who survived cancer reported higher QoL than healthy children, whereas there were no differences for personality. Two main effects emerged for informant with children rating themselves as less neurotic and more conscientious than their mothers. The correspondence between mothers and children was substantially higher for survivors for QoL and personality ratings. QoL and trait measures share substantial variance, and personality traits significantly predict QoL. Parental personality ratings explained child QoL beyond children's personality ratings. Conclusions: Personality traits contribute to quality of life, indicating that personality significantly influences child's quality of life beyond the experience of a negative life event such as surviving cancer and its treatment. From a diagnostic perspective, parental trait ratings are informative in addition to children's ratings of personality to understand children's QoL

An analysis of the inter-relationship between savings product usage and satisfaction using a SERVQUAL framework

The article maintains that improved participation in the financial services industries seems to be dependent on satisfaction levels regarding financial services product usage. Empirical evidence shows that higher usage and higher satisfaction regarding basic savings products such as savings accounts, money market investments and fixed deposits, as well as wealth management products such as home loan accounts, vehicle finance, endowment policies, retirement annuity policies, collective investment schemes and other specific needs savings products go hand in hand. Financial advisors, financial regulators as well as financial product providers should understand their role and responsibilities towards savers or potential savers in South Africa to ensure satisfaction levels, which would result in an increase in the use of financial products and could potentially lead to improved savings rates for South Africa.Key words: financial services, satisfaction, SERVQUAL, marginal utility, saving

A comparison of soil moisture relations between standing and clearfelled plots with burnt and unburnt harvest residue treatments of a clonal eucalypt plantation on the Zululand Coastal Plain, South Africa

The effects of clearfelling and subsequent residue retention or burning on water and nutrient balances needs to be understood and quantified on forest sites that are sensitive to loss, so that the long-term sustainable productivity of such sites can be maintained and promoted. An&nbsp; experimental site was established in a clonal eucalypt compartment on the Zululand Coastal Plain, to compare changes in water fluxes through the mature undisturbed eucalypt stand with those after felling and re-planting, under 2 conditions: burning, and retention of the harvesting residues. The study was located in an area of high rainfall and high stand productivity, with sandy soils and low soil carbon and nutrient status; chosen so that the effects of intensive demands on water and nutrient fluxes on a potentially sensitive site could be investigated. This paper presents only the hydrological component of the study. Data collection included weekly determination of rainfall, throughfall, stemflow and soil moisture fluxes from the surface to a depth of 1 m. Drainage rates through the profile were established using time domain reflectometry probes while water drainage volumes were assessed using shallow plate lysimeters. Despite slow growth in the unfelled crop during the monitoring period (attributed to a pest infestation), soil moisture depletion remained rapid and drainage below 1 m remained low. Soil moisture was recharged within a few months after clearfelling, but became rapidly depleted as the canopy of new crop developed and approached canopy closure. A decreased wetting-front velocity and a marginally higher field capacity were proposed as evidence of pore clogging that appeared to occur during the inter-rotation period. The soil profile under the unburnt residue maintained a marginally higher soil moisture status and lower drainage than the soil profile under the burnt residue. Although soil moisture and drainage in the burnt and unburnt residue treatments became similar to the unfelled crop from canopy closure onwards, rainfall additions to soil moisture were depleted faster under the new crop during the first few months after canopy closure. Small differences in soil moisture status between the burnt and unburnt residue treatments presented here may not be sufficient to influence residue management decisions. The length of the inter-rotation period and practice of residue burning may, however, need consideration where soil carbon and nutrient loss or displacement may negatively affect the sustainability of the site.Keywords: Soil moisture drainage, residue burning, post felling, inter-rotatio

From Design to Practice: How can large-scale household surveys better represent the complexities of the social units under investigation?

The way in which ‘the household’ is defined and operationalised in surveys and census data collection has long been criticised as unable to adequately capture the complexities of the social units within which people live. In a South African national survey on household wealth (HWS) a definition of the household was used to rep-resent the ways in which South African households arrange themselves financially. Here we report on a qualitative study in which 36 households originally included in the HWS were re-interviewed to collect detailed data on household financial links and dependencies. Households with more complex structures, which represent the majority of household types in South Africa, were very poorly represented, and possible reasons for this are explored. We analyse and discuss the HWS research process in the light of the findings of this study, and propose ways to improve large-scale survey design and data collection, drawing on perspectives from multiple disciplines.