Weld sequence optimization: the use of surrogate models for solving sequential combinatorial problems

The solution of combinatorial optimization problems usually involves the consideration of many possible design configurations. This often makes such approaches computationally expensive, especially when dealing with complex finite element models. Here a surrogate model is proposed that can be used to reduce substantially the computational expense of sequential combinatorial finite element problems. The model is illustrated by application to a weld path planning problem

Future aircraft cabins and design thinking: optimisation vs. win-win scenarios

With projections indicating an increase in mobility over the next few decades and annual flight departures expected to rise to over 16 billion by 2050 there is a demand for the aviation industry and associated stakeholders to consider new forms of aircraft and technology. Customer requirements are recognised as a key driver in business. The airline is the principal customer for the aircraft manufacture. The passenger is, in turn, the airline’s principal customer but they are just one of several stakeholders that include aviation authorities, airport operators, air-traffic control and security agencies. The passenger experience is a key differentiator used by airlines to attract and retain custom and the fuselage that defines the cabin envelope for the in-flight passenger experience and cabin design therefore receives significant attention for new aircraft, service updates and refurbishments. Decision making in design is crucial to arriving at viable and worthwhile cabin formats. Too little innovation will result in an aircraft manufacturer and airlines using its products falling behind its competitors. Too much may result in an over-extension with, for example, use of immature technologies that do not have the necessary reliability for a safety critical industry or sufficient value to justify the development effort. The multiple requirements associated with cabin design, can be viewed as an area for optimisation, accepting trade-offs between the various parameters. Good design, however, is often defined as developing a concept that resolves the contradictions and takes the solution towards a win-win scenario. Indeed our understanding and practice of design allows for behaviours that enhance design thinking through divergence and convergence, the use of abductive reasoning, experimentation and systems thinking. This paper explores the challenges of designing the aircraft cabin of the future that will deliver on the multiple requirements. In particular the paper explores the value of implementing design thinking insights in engineering practice and discusses the relative merits of decisions based on optimisation verses win-win scenarios for aircraft cabin design and wider applications in aerospace environments. The increasing densification of technological opportunities and shifting consumer demand coupled with highly complex systems may ultimately challenge our ability to make decisions based on optimisation balances. From an engineering design perspective optimisation tends to preclude certain strategies that deliver high quality results in consumer scenarios whereas win-win solutions may face challenges in complex technical environments

Mutli-objective optimisation of GENIE Earth system models

Overview:•GENIE Project•Multi-objective Optimisation•Surrogate Modelling•Grid Computing Infrastructure•Parameter Estimation for a new Ocean Mixing Scheme•Conclusion

Water and sanitation provision in a low carbon society: The need for a systems approach

In the face of climate change threatening to cause major alterations to hydrological cycles and taking into account the relationship between water, energy use, and food production, water management challenges today prove more complex than ever to address. This paper, recognising the progress made through science and engineering in the last century, reflects on the need to manage water resources more sustainably. It proposes that a change in mindsets is required in order to reconsider our approach in applying established solutions and utilising current technologies and tools to deliver them, with a renewed focus on re-assessing what the real problems are from a systems perspective. Focusing on the water-energy-food nexus, water reuse using desalination processes as a management option is revisited. Findings demonstrate that interdisciplinary, integrated and holistic solutions have the potential to deliver benefits across different sectors, disciplines, and systems, with a real potential for taking us a bit closer to sustainability

High salinity tolerance of the Red Sea coral Fungia granulosa under desalination concentrate discharge conditions: an in situ photophysiology experiment.

Seawater reverse osmosis desalination concentrate may have chronic and/or acute impacts on the marine ecosystems in the near-field area of the discharge. Environmental impact of the desalination plant discharge is supposedly site- and volumetric- specific, and also depends on the salinity tolerance of the organisms inhabiting the water column in and around a discharge environment. Scientific studies that aim to understand possible impacts of elevated salinity levels are important to assess detrimental effects to organisms, especially for species with no mechanism of osmoregulation, e.g., presumably corals. Previous studies on corals indicate sensitivity toward hypo- and hyper-saline environments with small changes in salinity already affecting coral physiology. In order to evaluate sensitivity of Red Sea corals to increased salinity levels, we conducted a long-term (29 days) in situ salinity tolerance transect study at an offshore seawater reverse osmosis (SWRO) discharge on the coral Fungia granulosa. While we measured a pronounced increase in salinity and temperature at the direct outlet of the discharge structure, effects were indistinguishable from the surrounding environment at a distance of 5 m. Interestingly, corals were not affected by varying salinity levels as indicated by measurements of the photosynthetic efficiency. Similarly, cultured coral symbionts of the genus Symbiodinium displayed remarkable tolerance levels in regard to hypo- and hypersaline treatments. Our data suggest that increased salinity and temperature levels from discharge outlets wear off quickly in the surrounding environment. Furthermore, F. granulosa seem to tolerate levels of salinity that are distinctively higher than reported for other corals previously. It remains to be determined whether Red Sea corals in general display increased salinity tolerance, and whether this is related to prevailing levels of high(er) salinity in the Red Sea in comparison to other oceans.Research in this study was supported by King Abdullah University of Science and Technology (KAUST)

Seawater desalination concentrate—a new frontier for sustainable mining of valuable minerals

The ocean has often been announced as a sustainable source of important materials for civilization. Application of the same extraction processes to desalination concentrate, rather than to unconcentrated seawater, will necessarily be more energetically favorable, so the expansion of seawater desalination in recent decades brings this dream closer to reality. However, there is relatively little concrete commercial development of 'concentrate mining'. This review assesses the technical and economic prospects for utilization of commercially viable products from seawater. The most important technologies for economic use of products from desalination plant concentrate are technologies for more economic separation and technologies for more economic concentration. The most promising separation technologies are those, such as nanofiltration, which separate brine into streams enriched/depleted in entire classes of constituents with minimal input of energy and reagents. Concentration is becoming more economic due to rapid advances in Osmotically-Assisted RO technology. Despite very active research on many aspects of desalination concentrate utilization, it is likely that commercial development of the non-NaCl components of desalination brine will depend on the available market for NaCl, as the challenges and costs of extracting the other mineral components from bitterns in which they are highly enriched are so much less than those faced in direct treatment of brines

Choice function based hyper-heuristics for multi-objective optimization

A selection hyper-heuristic is a high level search methodology which operates over a fixed set of low level heuristics. During the iterative search process, a heuristic is selected and applied to a candidate solution in hand, producing a new solution which is then accepted or rejected at each step. Selection hyper-heuristics have been increasingly, and successfully, applied to single-objective optimization problems, while work on multi-objective selection hyper-heuristics is limited. This work presents one of the initial studies on selection hyper-heuristics combining a choice function heuristic selection methodology with great deluge and late acceptance as non-deterministic move acceptance methods for multi-objective optimization. A well-known hypervolume metric is integrated into the move acceptance methods to enable the approaches to deal with multi-objective problems. The performance of the proposed hyper-heuristics is investigated on the Walking Fish Group test suite which is a common benchmark for multi-objective optimization. Additionally, they are applied to the vehicle crashworthiness design problem as a real-world multi-objective problem. The experimental results demonstrate the effectiveness of the non-deterministic move acceptance, particularly great deluge when used as a component of a choice function based selection hyper-heuristic

Optimal design of water treatment processes

Predicted water shortages assign water treatment a leading role in improving water resources management. One of the main challenges associated with the processes remains early stage design of techno-economically optimised purification. This work addresses the current gap by undertaking a whole-system approach of flowsheet synthesis for the production of water at desired purity at minimum overall cost. The optimisation problem was formulated as a mixed-integer non-linear programming model. Two case studies were presented which incorporated the most common commercial technologies and the major pollution indicators, such as chemical oxygen demand, dissolved organic carbon, total suspended solids and total dissolved solids. The results were analysed and compared to existing guidelines in order to examine the applicability of the proposed approach