Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Towards visual assessment of succulent valley bushveld.

Visual vegetation assessment was tested for repeatability and accuracy and compared with an objective survey technique for time and cost efficiency. Eighteen operators first inspected a range of sites where ecological status was known. Using these for reference, they then visually inspected and independently estimated the ecological status of 15 other sitesLanguage: EnglishKeywords: Accuracy; Efficiency; Field procedures; Range monitoring; Repeatability; Vegetation assessment; Veld conditions; ecological status; monitoring; precision; relationships; veld condition; valley bushveld; vegetation; survey technique; technique; kirkwood district; eastern cape; south afric

An alternative approach to veld condition assessment in the non-grassveld regions of South Africa.

Briefly reviews techniques of assessing veld in each of three non-grassveld regions of South Africa. Evaluates the concept of veld condition as presently used and end by discussing the theory of an alternative approach; Traditional veld condition assessment methods score veld either in terms of its 'state of health' or its value for a specific land-use objective. This is problematic and we propose that 'veld condition' should simply be a descriptive index, devoid of value judgement. The index should convey multivariate information about the current state of the vegetation at a site in the same way that a cow's breed, sex or age (all descriptive indices) convey multivariate information about that cow, to which different people can attach a value. We propose that the position which a sample site occupies in multivariate space (from ordination analysis) should be its descriptive index (or condition). Different land-users can then all use the same descriptive index, but may interpret it differently, depending on their objectives. It should be noted that simply using multivariate statistics to analyse floristic data does not mean that the vegetation is being assessed according to the approach outlined in this paper.Language: EnglishKeywords: Condition assessments; Ecological status; Karoo; Non-grassveld regions; Savanna; South Africa; Thicket; Vegetation assessment; Veld; condition; ordination; veld condition assessment; method; land-use; index; vegetation; botan

Browse and herbage production in the Eastern Cape Thornveld in response to tree size and defoliation frequency.

Grass yields in this semi-arid savanna declined as the size of Acacia karroo increased. Browse yields, however, did not increase as trees grew out beyond 1, 8 m in height and it follows that if bush thinning is required, then the taller trees should be selectively removed from these savannas. Simulated browsing of A. karroo trees was found to stimulate browse production, provided it was not too intense. As a consequence, the competitive ability of the trees increased and grass yields were adversely affected. Conversely, simulated grazing reduced the competitiveness of the grass and, thereby, resulted in an increase in browse production. It is argued that residual soil moisture levels remain relatively high when grass growth is poor, so that water penetrates to greater depths after rain than when grass growth is vigorous and this favours the deep rooted trees. Livestock programmes in Thornveld should take account of the interacting effects of grazing and browsing on grass and browse yield in determining the stocking rates of grazers and browsers.Keywords: acacia karroo; browse; browse production; browsers; browsing; competition; competitive ability; defoliation; eastern cape; grasses; grazers; grazing; herbage; herbage production; production; semi-arid savanna; soil moisture; south africa; stocking rate; stocking rates; thornveld; yiel

The effect of severe drought and management after drought on the mortality and recovery of semi-arid grassveld.

The False Thornveld of the Eastern Cape experienced a particularly intense drought during the 1982/1983 growing season. Extensive grass mortality took place during the drought. After the drought, recovery was particularly sensitive to the post-drought management treatment applied. Veld that was grazed immediately after the drought recovered far more slowly than veld that was rested. This effect was still evident three years later, illustrating the considerable importance of resting semi-arid grassveld after a drought. Increaser I grass species present were apparently more capable of surviving drought than the decreaser species, which in turn were more stable than the increaser II species. Their ability to recover after the drought followed an opposite trend. On this basis, the desirability of decreaser dominated veld, in situations that are likely to be poorly managed, is questioned.Keywords: decreaser species; drought; eastern cape; false thornveld; grasses; grazing capacity; increaser i species; increaser ii species; management; mortality; recovery; semi-arid grassveld; south africa; species composition; tillers; tufts; veld conditio

Use of multivariate techniques to identify vegetation units and monitor change on a livestock production system in a semi-arid savanna of the eastern Cape.

Species composition data of the grass layer were determined from point surveys along permanently demarcated transects. These data were separated into vegetation units using multivariate techniques. The repeatability of this classification was tested on data collected over a period of time. The results indicate that classification based on composition data collected from a single sampling period was adequate for practical purposes provided certain precautions were taken. Change in vegetation was assessed by ordering sites from repeated measurements and tracing site trajectories through ordination space. The trends along the axes were strongly correlated with assessed condition score.Keywords: adelaide research station; benchmarks; botany; eastern cape; grasses; livestock; ordination; point surveys; repeatability; sampling; savanna; site trajectories; south africa; species composition; techniques; transects; trends; vegetation units; veld conditio

The influence of an Acacia karroo tree on grass production in its vicinity.

The investigation was concerned with the impact of an Acacia karroo tree on the productivity of the surrounding herbaceous layer. It was established that a consistent pattern of grass production occurs around isolated A. karroo trees. This is characterised by high yields under and immediately south of the tree canopy, and low yields immediately to the north of the canopy. The former is attributed to favourable influences by the tree (e.g. shade and tree leaf litter), whereas the latter is probably a result of reduced water input associated with physical redistribution of rainfall by the tree and competition from the tree for soil water. It is argued that the net effect of the favourable or unfavourable influences of A. karroo on grass production is dependent on tree density. This explains why grass production is greater where there are a few A. karroo trees than where there are no trees and why grass production declines as tree density increases beyond a critical level.Language: EnglishKeywords: acacia karroo; Acacia karroo trees; adelaide experimental farm; Competition; eastern cape; false thornveld; Grass production; grasses; herbaceous layer; leaf litter; leaves; litter; nutrient pump; Nutrient pumps; production; productivity; Rainfall redistribution; Shade; soil water; south africa; tree density; trees; Water utilization; yiel