The healthcare sector needs more operational research

Abstract. More efficient use of resources and improved quality of services is needed in the health care sector, in order to meet the challenges of aging populations coupled with rising quality expectations due to technological advances and desire to cap or reduce budgets. In healthcare, complex decisions at strategic, tactical, and operational levels are coupled across organizational boundaries, with interdependency between plans that share many of the same resources and infrastructure. Decision support tools from Operations Research have for decades been successfully applied to complex resource management problems in other industries. While such tools are needed in the health sector, they are no panacea but maybe one of the most promising approach to ease their strain. A wide-spread application of such tools will increased efficiency at hospitals and patients will experience more streamlined coordination of activities, improved predictability and regularity-getting a higher service levels and ultimately better quality of health care services

The effects of pushback delays on airport ground movement

With the constant increase in air traffic, airports are facing capacity problems. Optimisation methods for specific airport processes are starting to be increasingly utilised by many large airports. However, many processes do happen in parallel, and maximising the potential benefits will require a more complex optimisation model, which can consider multiple processes simultaneously and take into account the detailed complexities of the processes where necessary, rather than using more abstract models. This paper focuses on one of these complexities, which is usually ignored in ground movement planning; showing the importance of the pushback process in the routing process. It investigates whether taking the pushback process into consideration can result in the prediction of delays that would otherwise pass unnoticed. Having an accurate model for the pushback process is important for this and identifying all of the delays that may occur can lead to more accurate and realistic models that can then be used in the decision making process for ground movement operations. After testing two different routing methods with a more detailed pushback process, we found that many of the delays are not predicted if the pushback process is not explicitly modelled. Having a more precise model, with accurate movements of aircraft is very important for any integrated model and will allow ground movement models to be of use in more reliable integrated decision making systems at airports. Minimising these delays can help airports increase their capacity and become more environmentally friendly

The importance of considering pushback time and arrivals when routing departures on the ground at airports

With the constant increase in air traffic, airports are facing capacity problems. Many airports are increasingly interested in utilising optimisation methods for specific airport processes. However, many such processes do happen in parallel, and maximising the potential benefits will require a complex optimisation model. A model which considers multiple processes simultaneously and the detailed complexities of the processes, rather than using more abstract models. This paper investigates how the arriving aircraft can affect the routing process and whether the pushback process can result into different types of delays. Furthermore, aircraft are routed backwards, starting from the destination in order to be at the runway on time and to respect the departure sequence. After testing our model with and without the arriving aircraft we found that arriving aircraft can indeed produce a lot of delays. Such delays would otherwise pass unnoticed as they result to departing aircraft choose different paths or pushback earlier so they be at the runway on time. Having an accurate model for the pushback process is important in order to understand in depth how the pushback process affects the other processes that happen in parallel. Furthermore, it led to more accurate and realistic model, which may assist the decision making process for ground movement operations and thereby help airports increase their capacity and become more environmentally friendly

The importance of considering pushback time and arrivals when routing departures on the ground at airports

With the constant increase in air traffic, airports are facing capacity problems. Many airports are increasingly interested in utilising optimisation methods for specific airport processes. However, many such processes do happen in parallel, and maximising the potential benefits will require a complex optimisation model. A model which considers multiple processes simultaneously and the detailed complexities of the processes, rather than using more abstract models. This paper investigates how the arriving aircraft can affect the routing process and whether the pushback process can result into different types of delays. Furthermore, aircraft are routed backwards, starting from the destination in order to be at the runway on time and to respect the departure sequence. After testing our model with and without the arriving aircraft we found that arriving aircraft can indeed produce a lot of delays. Such delays would otherwise pass unnoticed as they result to departing aircraft choose different paths or pushback earlier so they be at the runway on time. Having an accurate model for the pushback process is important in order to understand in depth how the pushback process affects the other processes that happen in parallel. Furthermore, it led to more accurate and realistic model, which may assist the decision making process for ground movement operations and thereby help airports increase their capacity and become more environmentally friendly

The effects of pushback delays on airport ground movement

With the constant increase in air traffic, airports are facing capacity problems. Optimisation methods for specific airport processes are starting to be increasingly utilised by many large airports. However, many processes do happen in parallel, and maximising the potential benefits will require a more complex optimisation model, which can consider multiple processes simultaneously and take into account the detailed complexities of the processes where necessary, rather than using more abstract models. This paper focuses on one of these complexities, which is usually ignored in ground movement planning; showing the importance of the pushback process in the routing process. It investigates whether taking the pushback process into consideration can result in the prediction of delays that would otherwise pass unnoticed. Having an accurate model for the pushback process is important for this and identifying all of the delays that may occur can lead to more accurate and realistic models that can then be used in the decision making process for ground movement operations. After testing two different routing methods with a more detailed pushback process, we found that many of the delays are not predicted if the pushback process is not explicitly modelled. Having a more precise model, with accurate movements of aircraft is very important for any integrated model and will allow ground movement models to be of use in more reliable integrated decision making systems at airports. Minimising these delays can help airports increase their capacity and become more environmentally friendly

The effects of pushback delays on airport ground movement

With the constant increase in air traffic, airports are facing capacity problems. Optimisation methods for specific airport processes are starting to be increasingly utilised by many large airports. However, many processes do happen in parallel, and maximising the potential benefits will require a more complex optimisation model, which can consider multiple processes simultaneously and take into account the detailed complexities of the processes where necessary, rather than using more abstract models. This paper focuses on one of these complexities, which is usually ignored in ground movement planning; showing the importance of the pushback process in the routing process. It investigates whether taking the pushback process into consideration can result in the prediction of delays that would otherwise pass unnoticed. Having an accurate model for the pushback process is important for this and identifying all of the delays that may occur can lead to more accurate and realistic models that can then be used in the decision making process for ground movement operations. After testing two different routing methods with a more detailed pushback process, we found that many of the delays are not predicted if the pushback process is not explicitly modelled. Having a more precise model, with accurate movements of aircraft is very important for any integrated model and will allow ground movement models to be of use in more reliable integrated decision making systems at airports. Minimising these delays can help airports increase their capacity and become more environmentally friendly

Constraint relaxation techniques & knowledge base reuse

Effective reuse of KBs often entails the expensive task of identifying plausible KB-combinations. This research assists the MUSKRAT-Advisor [133] to decide whether existing KBs could be reused for solving new problems. This research assists this process, by developing an aid based on constraint satisfaction techniques which identifies incompatible KB-combinations in the scheduling domain. Incompatible KBs can be discarded, thus leaving fewer combinations for the MUSKRAT-Advisor to examine in detail. I have used a constraint solver as the Problem Solver (PS) and have represented the existing scheduling KBs as Constraint Satisfaction Problems (CSPs) which can be combined to create a composite CSP. If the composite CSP is found to be inconsistent, the KB-combination will not fulfil the PS requirements and can be discarded. Proving a CSP inconsistent can be a lengthy process, so I propose a constraint relaxation approach to more quickly identify inconsistent KB-combinations. My approach relaxes the CSP by removing constraints and if the relaxed version is unsolvable then the original CSP will not have a solution either. However, it is not certain that relaxing a CSP will produce an easier problem; previous research has shown that random binary CSP are hardest to solve around the solution transition phase [25, 96]. Moreover, part of my research has shown that when constraints are removed randomly from an inconsistent CSP (binary and non-binary), the new relaxed CSP can be up to 10 times harder to solve. To investigate these issues, I created a Prolog test suite designed to generate test-beds of CSPs and to help identify useful relaxation strategies and analyse their results. The identified relaxation strategies are based on different constraint graph properties and are in most cases easy to implement. Empirical tests show that removing constraints of low tightness as well as high arity are efficient strategies which are also simple to implement and can create relaxed CSPs that verify that the original CSP is inconsistent, using less than half the search effort of the original CSP.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

ARTIFICIAL INTELLIGENCE IN BUSSINESS

I would like to acknowledge the kind assistance of the following persons in completing this thesis: Rod Thompson, who first sparked my interest in Artificial Intelligence, for his critical, yet always supportive, supervision, and for giving me the opportunity to look into a very interesting topic. Jean Geoppinger, a close friend and a brilliant lawyer, for proofreading and surviving my brutal abuse of the English language. Becky Jones, for proofreading the dissertation in the last minute. For providing me the information necessary to develop the different case studies