Salt pile stability: a mathematical model

AbstractThe maximum height for the salt pile in a circular dome with a 4ft retaining wall was determined by two methods. The first method used rigid-body physics; in this model, the critical angel, the maximum angle of inclination allowed while maintaining static equilibrium, was determined using only the external coefficient of friction for salt. Because the static equilibrium also depended upon internal friction, a second model was developed. Development of the second model utilized particle physics, fluid mechanics and soil stress analysis. Mohr's circle, the internal coefficient of friction for salt and its angle of repose were used to determine the critical angle. These results were combined to form our solution model, Model II, which consisted of two submodels:Model II(a) provides a general solution where the front-end loader is allowed to freely travel to any location on the salt pile. This model yields a maximum height of 17.4ft for a symmetric cone with a critical angle of 14.6°.Model II(b) provides a volume-maximizing solution if the loader's travel is restricted. This model yields a maximum height of 23.7ft for a wedge shape with a ramp slope of 14.6° and a back edge slope of 35.9°, where the loader must not cross the peak.Therefore, the authors recommend that Model II(a) be used in the general situation, since the loader is allowed to drive anywhere on the salt pile in this case. When the maximum volume provided is insufficient, Model II(b) can be utilized to increase the capacity of the dome. (Note: The loader must not cross the peak in this model.

NLSEmagic: Nonlinear Schr\"odinger Equation Multidimensional Matlab-based GPU-accelerated Integrators using Compact High-order Schemes

We present a simple to use, yet powerful code package called NLSEmagic to numerically integrate the nonlinear Schr\"odinger equation in one, two, and three dimensions. NLSEmagic is a high-order finite-difference code package which utilizes graphic processing unit (GPU) parallel architectures. The codes running on the GPU are many times faster than their serial counterparts, and are much cheaper to run than on standard parallel clusters. The codes are developed with usability and portability in mind, and therefore are written to interface with MATLAB utilizing custom GPU-enabled C codes with the MEX-compiler interface. The packages are freely distributed, including user manuals and set-up files.Comment: 37 pages, 13 figure

Non-urgent emergency department attendances in children : a retrospective observational analysis

Introduction: A significant proportion of ED attendances in children may be non-urgent attendances (NUAs), which could be better managed elsewhere. This study aimed to quantify NUAs and urgent attendances (UAs) in children to ED and determine which children present in this way and when. Methods: Dataset extracted from the CUREd research database containing linked data on the provision of care in Yorkshire and Humber. Analysis focused on children’s ED attendances (April 2014–March 2017). Summary statistics and odds ratios (OR) comparing NUAs and UAs were examined by: age, mode and time of arrival and deprivation alongside comparing summary statistics for waiting, treatment and total department times. Results: NUAs were more likely in younger children: OR for NUA in children aged 1–4 years, 0.82 (95% CI: 0.80 to 0.83), age 15 years, 0.39 (95% CI: 0.38 to 0.40), when compared with those under 1 year. NUAs were more likely to arrive out of hours (OOHs) compared with in hours: OR 1.19 (95% CI 1.18 to 1.20), and OOHs arrivals were less common in older children compared with those under 1 year: age 1–4 years, 0.87 (95% CI: 0.84 to 0.89) age 15 years, 0.66 (95% CI: 0.63 to 0.69). NUAs also spent less total time in the ED, with a median (IQR) of 98 min (60–147) compared with 127 min (80–185) for UAs. Conclusion: A substantial proportion of ED attendances in children are NUAs. Our data suggest there are particular groups of children for whom targeted interventions would be most beneficial. Children under 5 years would be such a group, particularly in providing accessible, timely care outside of usual community care opening hours

The mechanical and material properties of elderly human articular cartilage subject to impact and slow loading

Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.Peer reviewedPostprin

Predictive runtime code scheduling for heterogeneous architectures

Heterogeneous architectures are currently widespread. With the advent of easy-to-program general purpose GPUs, virtually every re- cent desktop computer is a heterogeneous system. Combining the CPU and the GPU brings great amounts of processing power. However, such architectures are often used in a restricted way for domain-speci c appli- cations like scienti c applications and games, and they tend to be used by a single application at a time. We envision future heterogeneous com- puting systems where all their heterogeneous resources are continuously utilized by di erent applications with versioned critical parts to be able to better adapt their behavior and improve execution time, power con- sumption, response time and other constraints at runtime. Under such a model, adaptive scheduling becomes a critical component. In this paper, we propose a novel predictive user-level scheduler based on past performance history for heterogeneous systems. We developed sev- eral scheduling policies and present the study of their impact on system performance. We demonstrate that such scheduler allows multiple appli- cations to fully utilize all available processing resources in CPU/GPU- like systems and consistently achieve speedups ranging from 30% to 40% compared to just using the GPU in a single application mode.Postprint (published version

Urgent care axis for the older adult: where is best to target interventions?

Background We explored the urgent care axis across EDs in Yorkshire and Humber (Y&H) for patients aged ≥75 years to identify where interventions could be targeted to prevent ED attendances and inpatient admissions. Methods Hospital Episode Statistics (HES) data for attendances across 18 EDs in Y&H from April 2011 to March 2014 were retrospectively analysed. HES A&E and Admitted Patient Care patient records data were linked to describe the entire patient pathway. The population studied was adult patients attending type 1 EDs, comparing those ≥75 years with those under 75. Data analysed included arrival mode, presentation time, time in ED, outcome (admitted/discharged), admission length of stay, International Classification of Diseases 10th Revision (ICD-10) and cause codes related to admission. Short-stay admissions and admissions with potentially avoidable conditions (identified by ICD-10 codes and cause codes) were identified. Comparative analysis was undertaken between sites. Results There were 3 736 541 ED attendances, of which 625 772 (16.7%) were ≥75 years. Older patients were significantly more likely to attend via ambulance than the younger cohort (OR 7.7, 95% CI 7.6 to 7.7), and had significantly longer median stays within ED (195 vs 136 min, p<0.001) and increased likelihood of admission (OR 4.5, 95% CI 4.5 to 4.6). Short-stay admissions accounted for 28.3% of older adult admissions. 37.3% of older adult admissions were with conditions that were potentially avoidable, accounting for 42.3% of short-stay admissions. There was regional variation in the proportions of older adults admitted (between 34.3% and 40.9%). Discussion Large numbers of older adults present to EDs mainly by ambulance. Significant proportions are admitted for short periods with conditions that might potentially be managed outside of hospital. Variation across the region warrants further study

HOx observations over West Africa during AMMA: impact of isoprene and NOx

Aircraft OH and HO2 measurements made over West Africa during the AMMA field campaign in summer 2006 have been investigated using a box model constrained to observations of long-lived species and physical parameters. "Good" agreement was found for HO2 (modelled to observed gradient of 1.23 ± 0.11). However, the model significantly overpredicts OH concentrations. The reasons for this are not clear, but may reflect instrumental instabilities affecting the OH measurements. Within the model, HOx concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O(1D) with water vapour, and loss processes dominated by HO2 + HO2 and HO2 + RO2. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NOx and high isoprene environments, we do not observe any dependence of model success for HO2 on isoprene and attribute this to efficient recycling of HOx through RO2 + NO reactions under the moderate NOx concentrations (5–300 ppt NO in the boundary layer, median 76 ppt) encountered during AMMA. This suggests that some of the problems with understanding the impact of isoprene on atmospheric composition may be limited to the extreme low range of NOx concentrations

Construction of markov processes from hitting distributions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47648/1/440_2004_Article_BF00538487.pd

Menus for Feeding Black Holes

Black holes are the ultimate prisons of the Universe, regions of spacetime where the enormous gravity prohibits matter or even light to escape to infinity. Yet, matter falling toward the black holes may shine spectacularly, generating the strongest source of radiation. These sources provide us with astrophysical laboratories of extreme physical conditions that cannot be realized on Earth. This chapter offers a review of the basic menus for feeding matter onto black holes and discusses their observational implications.Comment: 27 pages. Accepted for publication in Space Science Reviews. Also to appear in hard cover in the Space Sciences Series of ISSI "The Physics of Accretion onto Black Holes" (Springer Publisher

Gravity wave analogs of black holes

It is demonstrated that gravity waves of a flowing fluid in a shallow basin can be used to simulate phenomena around black holes in the laboratory. Since the speed of the gravity waves as well as their high-wavenumber dispersion (subluminal vs. superluminal) can be adjusted easily by varying the height of the fluid (and its surface tension) this scenario has certain advantages over the sonic and dielectric black hole analogs, for example, although its use in testing quantum effects is dubious. It can be used to investigate the various classical instabilities associated with black (and white) holes experimentally, including positive and negative norm mode mixing at horizons. PACS: 04.70.-s, 47.90.+a, 92.60.Dj, 04.80.-y.Comment: 14 pages RevTeX, 5 figures, section VI modifie