Purchase Decision Making and the Increasing Significance of Family Types

Purpose The authors note the growing significance of different family types in the West and explore the relationship between the complexity of family relationships typified in single parent, blended and intact families and the involvement of children in purchase decisions. Originality Whilst social trends indicate that the composition of the family will continue to change, little research has been conducted on the impact of changing family structures on consumption behaviour. Methodology The quantitative research is a development based on earlier qualitative research on the three family types and large scale piloting of the questionnaire. Sampling A random sample of mothers with children aged 10-16 were contacted from the TNS Postal Access Panel. Questionnaires were only used where there were responses from both the mother and child. 524 fully completed questionnaires were used for the analysis. Findings The analysis supports the idea that where familial relationships are simpler such as in single parent homes (fewer relationships) then the involvement of the child is greater and in more complex relationships such as in blended homes (where there are step-parents and step children present) a child’s involvement may be less marked. Exceptions to the “rule” are discussed as are the theoretical and practical implications

Development and Validation of a Model for Centrifugal Compressors in Reversed Flow Regimes

Turbochargers are widely used to help reduce the environmental impact of automotive engines. However, a limiting factor for turbochargers is compressor surge. Surge is an instability that induces pressure and flow oscillations that often damages the turbocharger and its installation. Most predictions of the surge limit are based on low-order models, such as the Moore-Greitzer model. These models tend to rely on a characteristic curve for the compressor created by extrapolating the constant speed lines of a steady-state compressor map into the negative mass flow region. However, there is little validation of these assumptions in the public literature. In this article, we develop further the first-principles model for a compressor characteristic presented in Powers, K., Brace, C., Budd, C., Copeland, C., &amp; Milewski, P., 2020, "Modeling Axisymmetric Centrifugal Compressor Characteristics From First Principles," J. Turbomachinery, 142(9), with a particular emphasis on reverse flow. We then perform experiments using a 58 mm diameter centrifugal compressor provided by Cummins Turbo Technologies, where we feed air in the reverse direction though the compressor while the impeller is spinning in the forward direction to obtain data in the negative mass flow region of the compressor map. This demonstrated experimentally that there is a stable operating region in the reverse flow regime. The recorded data showed a good match with the theoretical model developed in this article. We also identified a change in characteristic behavior as the impeller speed is increased, which, to the authors' knowledge, has not been observed in any previously published experimental work.</p

Investigation into the benefits of reduced oil flows in internal combustion engines

The engine lubrication system is a vital element for engine health but causes a parasitic load on the engine which increases the fuel consumption: this load can be reduced by matching the oil flow to lubricating requirements using a variable displacement oil pump. In a first stage, two variable displacement oil pumps were installed on a 2.4-L diesel engine; experiments over the New European Drive cycle showed reductions in fuel consumption of up to 3.4% and up to 5.8% over the urban phase of the cycle. A variable displacement oil pump was subsequently installed on an instrumented engine capturing over 100 metal and fluid temperatures within the engine structure. This showed that reducing oil flows resulted in lower oil temperature by up to 4 °C during cold-start New European Drive cycle but hotter cylinder liner temperatures by up to 6 °C. The higher cylinder wall temperatures caused an increase of 3% in oxides of nitrogen emissions but a reduction of 3%−5% in carbon monoxide and hydrocarbon emissions. Finally, an energy flow analysis showed that the variable displacement oil pump can reduce oil pump energy consumption by 160 kJ (32%) but that this led to a 400-kJ reduction in friction and accessory work. These findings highlight the need for a system-level rather than a component-level approach to engine lubrication design to capture key thermal interactions. </jats:p

Coupling streaming AI and HPC ensembles to achieve 100-1000x faster biomolecular simulations

Machine learning (ML)-based steering can improve the performance of ensemble-based simulations by allowing for online selection of more scientifically meaningful computations. We present DeepDriveMD, a framework for ML-driven steering of scientific simulations that we have used to achieve orders-of-magnitude improvements in molecular dynamics (MD) performance via effective coupling of ML and HPC on large parallel computers. We discuss the design of DeepDriveMD and characterize its performance. We demonstrate that DeepDriveMD can achieve between 100-1000x acceleration for protein folding simulations relative to other methods, as measured by the amount of simulated time performed, while covering the same conformational landscape as quantified by the states sampled during a simulation. Experiments are performed on leadership-class platforms on up to 1020 nodes. The results establish DeepDriveMD as a high-performance framework for ML-driven HPC simulation scenarios, that supports diverse MD simulation and ML back-ends, and which enables new scientific insights by improving the length and time scales accessible with current computing capacity

The Small and the Dead: A Review of Ancient DNA Studies Analysing Micromammal Species

The file attached is the Published/publisher’s pdf version of the article

Systems optimisation of an active thermal management system during engine warm-up

Belgium Herbarium image of Meise Botanic Garden

Systems optimisation of an active thermal management system during engine warm-up

Active thermal management systems offer a potential for small improvements in fuel consumption that will contribute to upcoming legislation on carbon dioxide emissions. These systems offer new degrees of freedom for engine calibration; however, their full potential will only be exploited if a systems approach to their calibration is adopted, in conjunction with other engine controls. In this work, a design-of-experiments approach is extended to allow its application to transient drive cycles performed on a dynamic test stand. Experimental precision is of crucial importance in this technique since even small errors would obscure the effects of interest. The dynamic behaviour of the engine was represented mathematically in a manner that enabled conventional steady state modelling approaches to be employed in order to predict the thermal state of critical parts of the engine as a function of the actuator settings. A 17-point test matrix was undertaken, and subsequent modelling and optimisation procedures indicated potential 2–3% fuel consumption benefits under iso-nitrogen oxide conditions. Reductions in the thermal inertia appeared to be the most effective approach for reducing the engine warm-up time, which translated approximately to a 1.3% reduction in the fuel consumption per kilogram of coolant. A novel oil-cooled exhaust gas recirculation system showed the significant benefits of cooling the exhaust gases, thereby reducing the inlet gas temperature by 5 °C and subsequently the nitrogen oxide emissions by 6%, in addition to increasing the warm-up rate of the oil. This suggested that optimising the thermal management system for cooling the gases in the exhaust gas recirculation system can offer significant improvements. For the first time this paper presents a technique that allows simple predictive models of the thermal state of the engine to be integrated into the calibration process in order to deliver the optimum benefit. In particular, it is shown how the effect of the thermal management system on the nitrogen oxides can be traded off, by advancing the injection timing, to give significant improvements in the fuel consumption. </jats:p