Theory as a source of software and system requirements

Requirements Engineering - Today, when undertaking requirements elicitation, engineers attend to the needs and wants of the user groups considered relevant for the software system. However, answers...     

Fine resolution mapping of population age-structures for health and development applications

The age-group composition of populations varies considerably across the world, and obtaining accurate, spatially detailed estimates of numbers of children under 5 years is important in designing vaccination strategies, educational planning or maternal healthcare delivery. Traditionally, such estimates are derived from population censuses, but these can often be unreliable, outdated and of coarse resolution for resource-poor settings. Focusing on Nigeria, we use nationally representative household surveys and their cluster locations to predict the proportion of the under-five population in 1 × 1 km using a Bayesian hierarchical spatio-temporal model. Results showed that land cover, travel time to major settlements, night-time lights and vegetation index were good predictors and that accounting for fine-scale variation, rather than assuming a uniform proportion of under 5 year olds can result in significant differences in health metrics. The largest gaps in estimated bednet and vaccination coverage were in Kano, Katsina and Jigawa. Geolocated household surveys are a valuable resource for providing detailed, contemporary and regularly updated population age-structure data in the absence of recent census data. By combining these with covariate layers, age-structure maps of unprecedented detail can be produced to guide the targeting of interventions in resource-poor settings.     

On building cyclic and shared structures in Haskell

We demonstrate how to build certain cyclic and other multi-linked structures in the lazy functional programming language Haskell. No explicit pointers are used in these constructions. Each task is accomplished by starting with a suitable specification and then calculating the required program.     

Short answers to deep questions: supporting teachers in large‐class settings

In large class settings, individualized student–teacher interaction is difficult. However, teaching interactions (e.g., formative feedback) are central to encouraging deep approaches to learning. While there has been progress in automatic short‐answer grading, analysing student responses to support formative feedback at scale is arguably some way from being widely applied in practice. However, analysing student written responses can provide insights into student conceptions, thus directly informing teacher actions. Indeed, we argue that analysing student responses to provide feedback directly to teachers is as worthy a goal as providing individualized feedback to students and is achievable given the current state‐of‐the‐art in natural language processing. In this paper, we analyse student written responses to short‐answer questions posed in the context of a large first year health sciences course. Each question was designed to elicit deep responses. Our qualitative analysis illustrates the variability in student responses and reveals multiple relationships between these responses, course materials and the questions posed. Such information can be invaluable for teacher praxis. We conclude with a conceptual ‘dashboard’ that categorizes student responses and reveals relationships between responses, course resources and the questions. Such a dashboard could provide timely, actionable insights for teachers and help foster deep learning approaches for students.     

Variational wave-scattering theory for a sinusoidal reflection grating

Abstract

Scattering calculations via the Schwinger variational principle are exemplified for the canonical model of E _∥ plane waves incident on a planarsinusoidal perfect-reflector surface. The complete solution is obtained in terms of a contour integral from which analytic limits are derived that agree with exact results. The contour integral is then evaluated by principal-value and asymptotic techniques, furnishing an explicit solution in Bessel and digamma functions. The variational solution is cast finally into the form of a linear algebraic system, whence we derive various analytic expansions that reproduce further exact results and confirm the efficacy of a simple form of our trial functions. Computations employing this trial function are compared with other approximations and the exact solution. Alternative variational solution representations involving incomplete Anger–Weber or half-range Anger functions are appended.     

Very Low Degree of Energetic Disorder as the Origin of High Mobility in an n‐channel Polymer Semiconductor

Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings.     

An experimental investigation into the pre-treatment of synthetic membranes using sodium hydroxide solutions

In this paper the effect of two pre-treatment methods are compared experimentally for the filtration of (i) a spent sulphite liquor (17.8 wt.% dry solids) using a 20 kg mol⁻¹ molar mass cut off (MMCO) fluoropolymer membrane and (ii) a molasses solution (45° Brix) using a polysulphone (Psf) membrane (1.5 μm pore size). Both feeds are industrially relevant, and subject to severe fouling issues when membranes are used in their subsequent processing. The pre-treatment methods evaluated were: (i) conditioning with water at 60 °C only [Protocol 1], and (ii) conditioning with water at 60 °C followed by cleaning with 0.5 wt.% NaOH [Protocol 2]. Results are presented that confirm the benefits of sodium hydroxide preconditioning upon performance, supporting the suggestion by some membrane manufacturers that this step be included as part of the pre-treatment protocol.     

Coeliac disease in primary care: case finding study

OBJECTIVES: To provide evidence of underdiagnosis of coeliac disease and to describe the main presenting symptoms of coeliac disease in primary care. DESIGN: Case finding in a primary care setting by testing for coeliac disease by using the endomysial antibody test. SETTING: Nine surgeries in and around a market town in central England, serving a population of 70 000. PARTICIPANTS: First 1000 patients screened from October 1996 to October 1997. OUTCOME MEASURES: Determination of endomysial antibody titre of patients fulfilling the study criteria, followed by small intestine biopsy of those with positive results. RESULTS: The 30 patients (out of 1000 samples) with positive results on the endomysial antibody test all had histological confirmation on small intestine biopsy. The commonest mode of presentation (15/30) was anaemia of varying severity. Most patients (25/30) presented with non-gastrointestinal symptoms. Specificity of the endomysial antibody test was 30/30. CONCLUSIONS: Underdiagnosis and misdiagnosis of coeliac disease are common in general practice and often result in protracted and unnecessary morbidity. Serological screening in primary care will uncover a large proportion of patients with this condition and should be made widely available and publicised. Coeliac disease should be considered in patients who have anaemia or are tired all the time, especially when there is a family history of the disease.     

Use of Numerical Calculations to Simulate the Sampling Efficiency Performance of a Personal Aerosol Sampler

Numerical calculations were conducted to simulate air and particle behavior near and into the inlet of an aerosol sampler in order to determine sampling efficiency performance. This was done with the pre-verified commercial computational fluid dynamics (CFD) software package, FLUENT (Fluent, Inc., Lebanon, NH, US). Air flow behavior was calculated for steady-state conditions approaching and flowing into 3D geometries of an aerosol sampler free in the air that was similar in dimension to two commercial samplers, namely the Gesamtstaubprobenahme sampler (GSP) and the conical inhalable sampler (CIS). Particle trajectories were calculated in a Lagrangian reference frame on the resulting velocity fields. Based on the particle trajectories, sampling efficiencies were calculated and compared to those reported in the literature for a CIS aerosol sampler. They were found to have similar overall trends for particle sizes up to 21 μ m. Using a correction factor, agreement was observed to be very good for smaller particles, but less so for larger particles.     

Temperature-dependent mechanical and long crack behavior of zirconium diboride–silicon carbide composite

Hot pressed ZrB2–20 vol.% SiC ultra-high temperature ceramic composites have been prepared for strength and fracture investigations. Two composites fabricated under differing hot pressing temperatures with (ZSB) and without (ZS) B4C sintering aids were selected for room temperature modulus of rupture (MOR) strength and single-edge-notch bend (SENB) fracture toughness experiments. Structure property relationships were examined for both composites. MOR and stiffness temperature dependence was also investigated up to 1500 °C. Long crack propagation studies were conducted up to 1400 °C using the double cantilevered beam geometry with half-chevron-notch initiation zones. Residual Boron-rich carbide maximum particle sizes were found to be strength limiting in ZSB billets while SiC controlled strength in ZS billets. Flexure strength decreased linearly with temperature from 1000 to 1500 °C with no visible plastic deformation prior to fracture. Similar stiffness decreases were observed with a transition temperature range of 1100–1200 °C. Long crack studies produced R-curves that show no significant toughening behavior at room temperature with some modest rising R-curve behavior appearing at higher temperatures. These studies also show the plateau toughness increases with temperature up to 1200 °C. This is supported by an observed transition from primarily transgranular fracture at room temperature to primarily intergranular fracture at high temperatures. Wake zone toughening is evident up to 1000 °C with K_R rise from 0.1 to 0.5 MPa√m. Beyond 1000 °C fracture mechanism transitions to include creep zone development ahead of crack tip with wake zone toughening vanishing.