Exploring key sustainable development themes through learning activities

The Masters programme in Engineering for Sustainable Development at Cambridge University explores a number of key themes, including dealing with: complexity, uncertainty, change, other disciplines, people, environmental limits, whole life costs, and trade-offs. This paper examines how these concepts are introduced and analyses the range of exercises and assignments which are designed to encourage students to test their own assumptions and abilities to develop competencies in these areas. Student performance against these tasks is discussed and student feedback is also presented, with a focus on how their awareness of the themes are met through a range of activities.

Exploring key sustainable development themes through learning activities

Purpose: The paper examines how a number of key themes are introduced in the Masters programme in Engineering for Sustainable Development at Cambridge University through student centred activities. These themes include dealing with complexity, uncertainty, change, other disciplines, people, environmental limits, whole life costs, and trade-offs. Design/methodology/approach: The range of exercises and assignments designed to encourage students to test their own assumptions and abilities to develop competencies in these areas are analysed by mapping the key themes onto the formal activities which all students undertake throughout the core MPhil programme. The paper reviews the range of these activities that are designed to help support the formal delivery of the taught programme. These include residential field courses, role plays, change challenges, games, systems thinking, multi criteria decision making, awareness of literature from other disciplines and consultancy projects. An axial coding approach to the analysis of routine feedback questionnaires drawn from recent years has been used to identify how student’s own awareness develops. Also results of two surveys are presented which tests the students’ perceptions about whether or not the course is providing learning environments to develop awareness and skills in these areas. Findings: Students generally perform well against these tasks with a significant feature being the mutual support they give to each other in their learning. The paper concludes that for students from an engineering background it is an holistic approach to delivering a new way of thinking through a combination of lectures, class activities, assignments, interactions between class members, and access to material elsewhere in the University that enables participants to develop their skills in each of the key themes. Originality /value: The paper provides a reflection on different pedagogical approaches to exploring key sustainable themes and reports students own perceptions of the value of these kinds of activities. Experiences are shared of running a range of diverse learning activities within a professional practice Masters programme.

Device and circuit-level performance of carbon nanotube field-effect transistor with benchmarking against a nano-MOSFET

The performance of a semiconducting carbon nanotube (CNT) is assessed and tabulated for parameters against those of a metal-oxide-semiconductor field-effect transistor (MOSFET). Both CNT and MOSFET models considered agree well with the trends in the available experimental data. The results obtained show that nanotubes can significantly reduce the drain-induced barrier lowering effect and subthreshold swing in silicon channel replacement while sustaining smaller channel area at higher current density. Performance metrics of both devices such as current drive strength, current on-off ratio (Ion/Ioff), energy-delay product, and power-delay product for logic gates, namely NAND and NOR, are presented. Design rules used for carbon nanotube field-effect transistors (CNTFETs) are compatible with the 45-nm MOSFET technology. The parasitics associated with interconnects are also incorporated in the model. Interconnects can affect the propagation delay in a CNTFET. Smaller length interconnects result in higher cutoff frequency. © 2012 Tan et al.

Risk based lifetime costs assessment of a ground source heat pump (GSHP) system design: Methodology and case study

Space heating accounts for a large portion of the world's carbon dioxide emissions. Ground Source Heat Pumps (GSHPs) are a technology which can reduce carbon emissions from heating and cooling. GSHP system performance is however highly sensitive to deviation from design values of the actual annual energy extraction/rejection rates from/to the ground. In order to prevent failure and/or performance deterioration of GSHP systems it is possible to incorporate a safety factor in the design of the GSHP by over-sizing the ground heat exchanger (GHE). A methodology to evaluate the financial risk involved in over-sizing the GHE is proposed is this paper. A probability based approach is used to evaluate the economic feasibility of a hypothetical full-size GSHP system as compared to four alternative Heating Ventilation and Air Conditioning (HVAC) system configurations. The model of the GSHP system is developed in the TRNSYS energy simulation platform and calibrated with data from an actual hybrid GSHP system installed in the Department of Earth Science, University of Oxford, UK. Results of the analysis show that potential savings from a full-size GSHP system largely depend on projected HVAC system efficiencies and gas and electricity prices. Results of the risk analysis also suggest that a full-size GSHP with auxiliary back up is potentially the most economical system configuration. © 2012 Elsevier Ltd.

Mapping the global flow of aluminum: from liquid aluminum to end-use goods.

Demand for aluminum in final products has increased 30-fold since 1950 to 45 million tonnes per year, with forecasts predicting this exceptional growth to continue so that demand will reach 2-3 times today's levels by 2050. Aluminum production uses 3.5% of global electricity and causes 1% of global CO2 emissions, while meeting a 50% cut in emissions by 2050 against growing demand would require at least a 75% reduction in CO2 emissions per tonne of aluminum produced--a challenging prospect. In this paper we trace the global flows of aluminum from liquid metal to final products, revealing for the first time a complete map of the aluminum system and providing a basis for future study of the emissions abatement potential of material efficiency. The resulting Sankey diagram also draws attention to two key issues. First, around half of all liquid aluminum (~39 Mt) produced each year never reaches a final product, and a detailed discussion of these high yield losses shows significant opportunities for improvement. Second, aluminum recycling, which avoids the high energy costs and emissions of electrolysis, requires signification "dilution" (~ 8 Mt) and "cascade" (~ 6 Mt) flows of higher aluminum grades to make up for the shortfall in scrap supply and to obtain the desired alloy mix, increasing the energy required for recycling.

Biobjective optimisation of preliminary aircraft trajectories

The protection of the environment against pollutants produced by aviation is of great concern in the 21st century. Among the multiplicity of proposed solutions, modifying flight profiles for existing aircraft is a promising approach. The aim is to deliver and understand the trade-off between environmental impact and operating costs. This work will illustrate the optimisation process of aircraft trajectories by minimising fuel consumption and flight time for the climb phase of an aircraft that belongs to A320 category. To achieve this purpose a new variant of a multi-objective Tabu Search optimiser was evolved and integrated within a computational framework, called GATAC, that simulates flight profiles based on altitude and speed. © 2013 Springer-Verlag.

Nanobodies raised against monomeric α-synuclein distinguish between fibrils at different maturation stages.

Nanobodies are single-domain fragments of camelid antibodies that are emerging as versatile tools in biotechnology. We describe here the interactions of a specific nanobody, NbSyn87, with the monomeric and fibrillar forms of α-synuclein (αSyn), a 140-residue protein whose aggregation is associated with Parkinson's disease. We have characterized these interactions using a range of biophysical techniques, including nuclear magnetic resonance and circular dichroism spectroscopy, isothermal titration calorimetry and quartz crystal microbalance measurements. In addition, we have compared the results with those that we have reported previously for a different nanobody, NbSyn2, also raised against monomeric αSyn. This comparison indicates that NbSyn87 and NbSyn2 bind with nanomolar affinity to distinctive epitopes within the C-terminal domain of soluble αSyn, comprising approximately amino acids 118-131 and 137-140, respectively. The calorimetric and quartz crystal microbalance data indicate that the epitopes of both nanobodies are still accessible when αSyn converts into its fibrillar structure. The apparent affinities and other thermodynamic parameters defining the binding between the nanobody and the fibrils, however, vary significantly with the length of time that the process of fibril formation has been allowed to progress and with the conditions under which formation occurs, indicating that the environment of the C-terminal domain of αSyn changes as fibril assembly takes place. These results demonstrate that nanobodies are able to target forms of potentially pathogenic aggregates that differ from each other in relatively minor details of their structure, such as those associated with fibril maturation.

The potential use of 241Am as proliferation resistant burnable poison in PWRs

This paper discusses the use of 241Am as proliferation resistant burnable poison for light water reactors. Homogeneous addition of small (as little as 0.12%) amounts of 241Am to the conventional light water reactor fuel results in significant increase in 238Pu/Pu ratio in the discharged fuel improving its proliferation resistance. Moreover, 241Am, admixed to the fuel, acts as burnable absorber allowing for substantial reduction in conventional reactivity control means without a notable fuel cycle length penalty. This is possible due to favorable characteristics of 241Am transmutation chain. The fuel cycle length penalty of introducing 241Am into the core is evaluated and discussed, as well as the impact of He production in the fuel pins and degradation of reactivity feedback coefficients. Proliferation resistance and reactivity control features related to the use of 241Am are compared to those of using 237Np, which has also been suggested as an additive to the conventional fuel in order to improve its proliferation resistance. It was found that 241Am admixture is more favorable than 237Np admixture because of the smaller fuel cycle length penalty and higher burnable poison savings. Addition of either 237Np or 241Am would provide substantial but not ultimate protection from misuse of Pu originating in the spent fuel from the commercial power reactors. Therefore, the benefits from application of the concept would have to be carefully evaluated against the additional costs and proliferation risks associated with manufacturing of 237Np or 241Am doped fuel. Although this work concerns specifically with PWRs, the conclusions could also be applied to BWRs and, to some extent, to other thermal spectrum reactor types. © 2009 Elsevier Ltd. All rights reserved.

Nanobodies raised against monomeric α-synuclein distinguish between fibrils at different maturation stages

Nanobodies are single-domain fragments of camelid antibodies that are emerging as versatile tools in biotechnology. We describe here the interactions of a specific nanobody, NbSyn87, with the monomeric and fibrillar forms of α-synuclein (αSyn), a 140-residue protein whose aggregation is associated with Parkinson's disease. We have characterized these interactions using a range of biophysical techniques, including nuclear magnetic resonance and circular dichroism spectroscopy, isothermal titration calorimetry and quartz crystal microbalance measurements. In addition, we have compared the results with those that we have reported previously for a different nanobody, NbSyn2, also raised against monomeric αSyn. This comparison indicates that NbSyn87 and NbSyn2 bind with nanomolar affinity to distinctive epitopes within the C-terminal domain of soluble αSyn, comprising approximately amino acids 118-131 and 137-140, respectively. The calorimetric and quartz crystal microbalance data indicate that the epitopes of both nanobodies are still accessible when αSyn converts into its fibrillar structure. The apparent affinities and other thermodynamic parameters defining the binding between the nanobody and the fibrils, however, vary significantly with the length of time that the process of fibril formation has been allowed to progress and with the conditions under which formation occurs, indicating that the environment of the C-terminal domain of αSyn changes as fibril assembly takes place. These results demonstrate that nanobodies are able to target forms of potentially pathogenic aggregates that differ from each other in relatively minor details of their structure, such as those associated with fibril maturation. © 2013 Elsevier Ltd.

The impact of sand slugs against beams and plates: Coupled discrete particle/finite element simulations

The impact of a slug of dry sand particles against a metallic sandwich beam or circular sandwich plate is analysed in order to aid the design of sandwich panels for shock mitigation. The sand particles interact via a combined linear-spring-and-dashpot law whereas the face sheets and compressible core of the sandwich beam and plate are treated as rate-sensitive, elastic-plastic solids. The majority of the calculations are performed in two dimensions and entail the transverse impact of end-clamped monolithic and sandwich beams, with plane strain conditions imposed. The sand slug is of rectangular shape and comprises a random loose packing of identical, circular cylindrical particles. These calculations reveal that loading due to the sand is primarily inertial in nature with negligible fluid-structure interaction: the momentum transmitted to the beam is approximately equal to that of the incoming sand slug. For a slug of given incoming momentum, the dynamic deflection of the beam increases with decreasing duration of sand-loading until the impulsive limit is attained. Sandwich beams with thick, strong cores significantly outperform monolithic beams of equal areal mass. This performance enhancement is traced to the "sandwich effect" whereby the sandwich beams have a higher bending strength than that of the monolithic beams. Three-dimensional (3D) calculations are also performed such that the sand slug has the shape of a circular cylindrical column of finite height, and contains spherical sand particles. The 3D slug impacts a circular monolithic plate or sandwich plate and we show that sandwich plates with thick strong cores again outperform monolithic plates of equal areal mass. Finally, we demonstrate that impact by sand particles is equivalent to impact by a crushable foam projectile. The calculations on the equivalent projectile are significantly less intensive computationally, yet give predictions to within 5% of the full discrete particle calculations for the monolithic and sandwich beams and plates. These foam projectile calculations suggest that metallic foam projectiles can be used to simulate the loading by sand particles within a laboratory setting. © 2013 Elsevier Ltd.

Remediation against floatation of underground structures

Underground structures located in liquefiable soil deposits are susceptible to floatation following an earthquake event due to their lower unit weight relative to the surrounding saturated soil. Centrifuge tests have been carried out to assess the effectiveness of existing remediation techniques in reducing the uplift of underground structures, namely in situ densification and the use of coarse sand backfill. The centrifuge test results showed that these methods do reduce the uplift displacement of buoyant structures. Their performance was thereafter linked to the theoretical mechanism of floatation of underground structures. Based on the understanding from preceding tests, a further improvement on the use of the coarse sand backfill was carried out, which produced a greater reduction in the uplift displacement of the structure. Each of these techniques, however, does pose issues when applied in the field, such as possible damage to surrounding structures, construction issues and maintenance problems.

Comparison of ilities for protection against uncertainty in system design

The concepts of reliability, robustness, adaptability, versatility, resilience and flexibility have been used to describe how a system design can mitigate the likely impact of uncertainties without removing their sources. With the increasing number of publications on designing systems to have such ilities, there is a need to clarify the relationships between the different ideas. This short article introduces a framework to compare these different ways in which a system can be insensitive to uncertainty, clarifying their meaning in the context of complex system design. We focus on relationships between the ilities listed above and do not discuss in detail methods to design-for-ilities. © 2013 The Author(s). Published by Taylor & Francis.