Solution Strategies in Short-term Scheduling for Multitasking Multipurpose Plants

This thesis addresses challenges in short-term scheduling of multipurpose facilities using mathematical optimization. Such approach involves the formulation of a predictive model and an objective function, and the development of a solution strategy around such scheduling model formulation in order to obtain an operating schedule that achieves certain objectives, such as maximization of throughput or minimization of makespan. There are many choices that must be made in these aspects of short-term scheduling, and these choices often lead to a trade-off between the solution quality and computational time. This thesis presents two studies analyzing the quality-CPU time trade-off in two major aspects: time representations in model formulation, and the strategy for handling multiple conflicting objectives. The ultimate goal is to develop bi-objective short-term scheduling approaches to tackle industrial-sized problems for multitasking multipurpose plants that are computationally inexpensive, but provide practical schedules with a good balance between throughput and makespan. The first study addresses the first aspect of interest and compares two different time representation approaches: discrete-time and continuous-time approaches. This comparison is made considering maximization of throughput as the sole objective. We show that, for the modeling framework implemented in this work, the selected discrete-time formulation typically obtained higher quality solutions, and required less time to solve compared to the selected continuous-time formulation, as the continuous-time formulation exhibited detrimental trade-off between computational time and solution quality. We also show that within the scope of this study, non-uniform discretization schemes typically yielded solutions of similar quality compared to a fine uniform discretization scheme, but required only a fraction of the computational time. The second study builds on the first study and develops a strategy around an efficient non-uniform discretization approach to handle the conflicting objectives of throughput maximization and makespan minimization, focusing on a priori multi-objective methods. Two main contributions are presented in this regard. The first contribution is to propose a priori bi-objective methods based on the hybridization of compromise programming and the U+03B5-constraint method. The second is to present short-term operational objective functions, that can be used within short-term scheduling to optimize desired long term objectives of maximizing throughput and minimizing makespan. Two numerical case studies, one in a semiconductor processing plant and an analytical services facility, are presented using a rolling horizon framework, which demonstrate the potential for the proposed methods to improve solution quality over a traditional a priori approac

Scheduling process operations under uncertainty and integration with long term planning

This thesis centers upon the application of mathematical modelling, optimization theory and uncertainty analysis to the problem of scheduling batch operations for large scale industries. Over the years, decision making strategies such as scheduling, that deals with allocation of plant resources, has been widely adopted by industries to efficiently carry out their operations and achieve the desired targets. In this thesis, the focus is on planning and scheduling under endogenous uncertainty in the context of multijob, multitasking batch plants. This class of scheduling problems are of practical importance, specially in the analytical services sector, where effective scheduling models could increase the efficiency in carrying out the plant operations and may lead to increased throughput, or reduced makespan, resulting in greater profits or customer satisfaction

Parallel and Distributed Computing

The 14 chapters presented in this book cover a wide variety of representative works ranging from hardware design to application development. Particularly, the topics that are addressed are programmable and reconfigurable devices and systems, dependability of GPUs (General Purpose Units), network topologies, cache coherence protocols, resource allocation, scheduling algorithms, peertopeer networks, largescale network simulation, and parallel routines and algorithms. In this way, the articles included in this book constitute an excellent reference for engineers and researchers who have particular interests in each of these topics in parallel and distributed computing

An Optimisation-based Framework for Complex Business Process: Healthcare Application

The Irish healthcare system is currently facing major pressures due to rising demand, caused by population growth, ageing and high expectations of service quality. This pressure on the Irish healthcare system creates a need for support from research institutions in dealing with decision areas such as resource allocation and performance measurement. While approaches such as modelling, simulation, multi-criteria decision analysis, performance management, and optimisation can – when applied skilfully – improve healthcare performance, they represent just one part of the solution. Accordingly, to achieve significant and sustainable performance, this research aims to develop a practical, yet effective, optimisation-based framework for managing complex processes in the healthcare domain. Through an extensive review of the literature on the aforementioned solution techniques, limitations of using each technique on its own are identified in order to define a practical integrated approach toward developing the proposed framework. During the framework validation phase, real-time strategies have to be optimised to solve Emergency Department performance issues in a major hospital. Results show a potential of significant reduction in patients average length of stay (i.e. 48% of average patient throughput time) whilst reducing the over-reliance on overstretched nursing resources, that resulted in an increase of staff utilisation between 7% and 10%. Given the high uncertainty in healthcare service demand, using the integrated framework allows decision makers to find optimal staff schedules that improve emergency department performance. The proposed optimum staff schedule reduces the average waiting time of patients by 57% and also contributes to reduce number of patients left without treatment to 8% instead of 17%. The developed framework has been implemented by the hospital partner with a high level of success

Investigating the Comprehensive Inventory of Thriving (CIT) as a rehabilitation outcome measure

Reliable and valid outcome measures are needed in community rehabilitation settings following acquired neurological injury. The Comprehensive Inventory of Thriving (CIT) (Su, Tay and Diener, 2013) was investigated for this purpose. The CIT is a 54 item self-report measure that provides 18 subscales and seven main scales of thriving: Relationships, Engagement, Mastery, Autonomy, Meaning, Optimism and Subjective Well-being. Participants (n=76) were administered the CIT on admission to a community rehabilitation service. The mean age of participants was 54.8 (SD = 17.7), with 43% being male. The main diagnostic groups were cerebrovascular disease (28%), traumatic brain injury (17%) and Parkinson's disease (12%). Internal consistency was moderate to high (α =.6 to .9) for all subscales with the exception of Support (Relationships) and Skills (Mastery); and high (α=.79-.93) for all indexes with the exception of Subjective Wellbeing. Correlational analyses supported the scale groupings. However, the subscales of Support (Relationships) and Skills (Mastery) did not correlate significantly with any subscales. Additionally the Subjective Well-being scale should not be calculated, but instead its three subscales (Negative Feelings, Life Satisfaction, Positive Feelings) used individually. In terms of demographic variables, there were no significant gender differences on CIT scales. Age had low correlations with two Relationships subscales only (Trust r=.23, p=.04; Loneliness r=-.25, p=.03). Diagnostic group minimally influenced CIT scores. Significant between-group differences were only found for Accomplishment (Mastery), with post-hoc analyses indicating higher levels for the cerebrovascular group. The CIT shows considerable promise in rehabilitation outcomes as a reliable and valid multi-component measure of wellbeing

Modelling the Interactions between Information and Communication Technologies and Travel Behaviour

The growing capabilities and widespread proliferation of information and communication technologies (ICT) into virtually every aspect of lifestyle, combined with the continuing challenges faced by transport systems, has ensured ongoing interest in the interactions between ICT and travel behaviour. Yet, despite more than three decades of efforts to understand these relationships, few point of consensus have so far emerged, partly due to the rapidly evolving character of ICT, and partly due to the inherent complexity of such interactions. This thesis seeks to develop novel understandings of such interactions by introducing a number of extensions to the existing modelling frameworks. This is achieved through three interrelated research objectives which seek to explore the topic from macro, micro, and temporal perspectives. The macro perspective takes the form of a structural equation analysis of the relationships between ICT use and travel behaviour across four countries: Canada, the United States, the United Kingdom, and Norway, with the data for the latter three obtained by pooling separate datasets on ICT use and travel behaviour. The micro perspective seeks to develop a microeconomic model of an individual maximising utility through joint choice of activities, including in-travel activities, ICT use, as well as the choice of travel mode, timing and route, with the decisions motivated by contribution towards satisfaction, productivity, and consumption. The model is subsequently tested in the empirical contexts of rail business travel time, business travel time valuation, and conceptualisation of the ICT and travel behaviour interaction scenarios reported elsewhere in the literature. The final, temporal perspective analyses the comparatively least explored topic of evolution in the relationships between ICT use and travel behaviour over time. This is achieved by analysing repeated cross-sectional data using structural equation modelling, and interpreted with reference to the theory of diffusion of innovations. The thesis also discusses a number of potential research, policy and industrial applications of its empirical and theoretical contributions.Open Acces

Challenges and opportunities of introducing Internet of Things and Artificial Intelligence applications into Supply Chain Management

The study examines the challenges and opportunities of introducing Artificial Intelligence (AI) and the Internet of Things (IoT) into the Supply Chain Management (SCM). This research focuses on the Logistic Management. The central research question is “What are the key challenges and opportunities of introducing AI and IoT applications into the Supply Chain Management?” The goal of this research is to collect the most appropriate literature to help create a conceptual framework, which involves the integration of the IoT and AI applications into contemporary supply chain management with the emphasis on the logistics management. Additionally, the role of 5G Network is closely studied in order to indicate its capabilities and the processing capacity that it can provide to the AI and IoT operations. In addition, the semi-structured online interview with the top managers from several companies was conducted in order to identify the degree of readiness of the companies for the AI and IoT applications in SCM. From the retrieved results, the major challenges of integrating the IoT into SCM are the security and privacy issues, the sensitivity of the data and high costs of the implementation at an initial stage. Moreover, the research results have shown that the IoT applications can positively affect the SCM activities, in particular, the high visibility across the SC, an effective traceability and an automated data collection. Furthermore, the predictive analysis of AI programs can help the SCM to eliminate the potential errors and failures in the processes.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Formal techniques for the procedural control of industrial processes

Imperial Users onl