Managing the restoration of membranes in reverse osmosis desalination using a digital twin

This thesis studies degradation and restoration policies for a pressure vessel in a reverse osmosis (RO) desalination plant. In the study context, biofouling is the primary cause of the degradation of the RO membrane elements, amplified by seasonal algal blooms. This research developed a decision support system (DSS) for evaluating membrane restoration strategy. The engine of the DSS is a digital twin (DT), a virtual representation of wear (degradation) and restoration of membrane elements in a RO pressure vessel. The basis of the DT is a mathematical model that describes an RO pressure vessel as a novel multi-component system in which the hidden wear-states of individual elements (components) are quantified, and elements can be swapped or replaced. This contrasts with the contemporary presentation of a membrane system as a single system in the literature. The parameters of the model are estimated using statistical methods. The research approach is described in the context of a case study on the Carlsbad Desalination Plant in California. Results show a good fit between the observed and the modelled wear-states. Competing policies are compared based on risk, cost, downtime, and the number of stoppages. Projections indicate that a significant cost-saving can be achieved while not compromising the integrity of the plant. Alternative policies 11 and 12 showed better wear management than the current policy 10 of the maintenance company while reducing costs between $0.7 to$1.7 million for the next five years.The research in the thesis contributes toward maintenance modelling. New models of multivariate degradation and imperfect repair are presented. The research makes an important contribution to desalination and water treatment engineering, providing a unique membrane maintenance management approach currently absent from the literature. The thesis also contributes to the maintenance theory. It proposes a general approach for applying a decision support system (DSS) for maintenance requirements analysis, involving a digital twin (DT) for wear and repair projections when wear is stochastic, and repair effects are not immediately apparent. The essential elements of a DSS are discussed. This research encourages a dialogue between researchers of maintenance theory and modelling and practitioners of maintenance planning about decision support systems and digital twins that not only project the when but also evaluate the what in maintenance strategy. The presented concept of a DSS driven by a DT for maintenance requirement analysis has valuable practical implications, and the thesis, in discussing this concept, makes an essential contribution to the discussion about Industry 4.0, digital twins, and maintenance

Factories of the Future

Engineering; Industrial engineering; Production engineerin

Laser-based manufacturing routes for functionalizing surfaces

Robust functional surfaces are of a growing industrial interest for a range of optical, easy-to clean, anti-icing and non-fouling applications. At the same time, nature is a great source of inspiration for micro/nano-scale surface structures with tailored functional properties. There are a number of competing technologies for producing such structures but ultrashort laser processing is emerging as one of the most promising for fabricating bio-inspired surfaces. However, the technology has limitations and its capabilities have to be augmented to achieve the required high throughput in manufacturing products that incorporate functional surface topographies. Therefore, this research investigates a promising process chain that combines synergistically the capabilities of laser texturing with complementary surface engineering and replication technologies. Several large-area laser texturing techniques are investigated, namely Direct Laser Writing (DLW), Laser-Induced Periodic Surface Structures (LIPSS) and microlenses-induced Photonic Jet (PJ) texturing. The research advances the knowledge in laser-based surface functionalization and also in factors affecting the functional response and durability of laser structured surfaces

Staring down the lion: Uncertainty avoidance and operational risk culture in a tourism organisation

The academic literature is not clear about how uncertainty influences operational risk decision-making. This study, therefore, investigated operational risk-based decision-making in the face of uncertainty in a large African safari tourism organisation by exploring individual and perceived team member approaches to uncertainty. Convenience sampling was used to identify 15 managers across three African countries in three domains of work: safari camp; regional office; and head office. Semi-structured interviews were conducted in which vignettes were incorporated, to which participants responded with their own reactions and decisions to the situations described, as well as with ways they thought other managers would react to these specific operational contexts. The data were transcribed and qualitatively analysed through thematic coding processes. The findings indicated that approaches to uncertainty were influenced by factors including situational context, the availability and communication of information, the level of operational experience, and participants’ roles. Contextual factors alongside diverse individual emotional and cognitive influences were shown to require prudent consideration by safari tourism operators in understanding employee behavioural reactions to uncertain situations. A preliminary model drawn from the findings suggests that, in practice, decision-making in the face of uncertainty is more complex than existing theoretical studies propose. Specifically, the diverse responses anticipated by staff in response to the vignettes could guide safari tourism management towards better handling of risk under uncertainty in remote locations

Conceptual models for selecting and managing Early Contractor Involvement (ECI) delivery system by clients.

The traditional procurement methods and contractual models, in which the main contractor and its subcontractors are appointed only for the construction phase, remains the common approach within the construction industry. The use of a traditional procurement method may offer some benefits to the clients such as time and cost certainty, control over the project outcomes, and ability to demonstrate value for money. Nevertheless, it is unlikely to obtain the best contributions of all parties to a successful project due to exclusion of the main contractor and subcontractors from the early design and project planning. Acknowledged by the industry, the emerging project delivery methods increasingly rely on collaboration between the client , designer and contractor. These methods aim to develop longer-term positive relationships. Early Contractor Involvement procurement system is one of the new delivery methods. Originated in the UK in 1998 and adopted later in Australia in 2005, ECI strives to involve the contractor at the early stage of the project before the statutory procedures have been implemented and when the proposed project may be little more than a line on a plan. Given the growing use of ECI in public project in Australia, it is necessary to conduct more studies about different aspects of this novel procurement option in order to enhance the public sector ability to deliver high-quality capital projects. This research aims to develop a theoretical methodology for clients to select and manage ECI procurement method for a project. The main objectives of the research are to explore the circumstances when an ECI is suitable for a project and develop strategies to manage the client-contractor relationship effectively once ECI is adopted. The research employs a Grounded Theory methodology to facilitate generation of theory. In particular, from the epistemological and ontological stance, this study deviated from the classic grounded theory principles into a process-driven theory. The analytical procedure of the study,however, follows the original tenets of Straussian interpretation of Grounded Theory. Four Australian local government organisations and one leading private professional consultant organisation are selected for the purpose of this research. Fourteen professional practitioners at the senior management level who have been involved in ECI projects and played significant roles in the project process in the selected organisation are interviewed. This results in the development of two models. The first model identifies the ECI selection criteria as well as ECI selection approaches, and the second model formulates a cyclical client-contractor relationship managing process in the ECI. The outcomes of this research are twofold. The first outcome is to assist the decision making process within the client’s organisations about whether to adopt an ECI method for a specific project by assessing the project conditions and evaluating internal capabilities. The second outcome is to develop a process model for effectively managing the client-contractor relationship in an ECI project. The model also assists the clients to advance their awareness of their strengths and weaknesses from the outset to ensure that the relationship with the contractor is not contaminated by misjudgement of the contractor’s performance