Essays in Scheduling: Applications in Health Care and Manufacturing

The problem of finding an optimal schedule is ubiquitous in human endeavor. Airlines strive to find the best schedule for their aircrafts and flight-crews, academic scheduling offices at universities schedule classes, and business organizations prioritize their jobs or customers and schedule them accordingly. Even in our day to day lives, whether consciously or not, we decide on our daily schedule and go about our sequence of tasks, prioritizing certain tasks, and procrastinating on others. Not surprisingly, scheduling of people, tasks, and manufacturing jobs constitute a significant proportion of the operations management literature. Despite all the research that has been published on scheduling, we encounter scheduling problems that call for novel approaches, and when treated with appropriate tools and techniques, provide interesting managerial insights. The dissertation consists of three such scheduling problems, two from the health care industry, and one from manufacturing. The first health care paper (Ganguly et al. 2013) employs mixed-integer linear programming to schedule physicians for a medical emergency department (ED). The second paper (Ganguly and Samorani 2013) uses an analytical approach for making real time updates to patient schedules in outpatient clinics that primarily operate on an appointment basis. The paper on manufacturing (Ganguly and Laguna 2013) develops heuristic techniques for a particular type of job-sequencing problem that involves two types of setups

Software Approaches to Manage Resource Tradeoffs of Power and Energy Constrained Applications

Power and energy efficiency have become an increasingly important design metric for a wide spectrum of computing devices. Battery efficiency, which requires a mixture of energy and power efficiency, is exceedingly important especially since there have been no groundbreaking advances in battery capacity recently. The need for energy and power efficiency stretches from small embedded devices to portable computers to large scale data centers. The projected future of computing demand, referred to as exascale computing, demands that researchers find ways to perform exaFLOPs of computation at a power bound much lower than would be required by simply scaling today's standards. There is a large body of work on power and energy efficiency for a wide range of applications and at different levels of abstraction. However, there is a lack of work studying the nuances of different tradeoffs that arise when operating under a power/energy budget. Moreover, there is no work on constructing a generalized model of applications running under power/energy constraints, which allows the designer to optimize their resource consumption, be it power, energy, time, bandwidth, or space. There is need for an efficient model that can provide bounds on the optimality of an application's resource consumption, becoming a basis against which online resource management heuristics can be measured. In this thesis, we tackle the problem of managing resource tradeoffs of power/energy constrained applications. We begin by studying the nuances of power/energy tradeoffs with the response time and throughput of stream processing applications. We then study the power performance tradeoff of batch processing applications to identify a power configuration that maximizes performance under a power bound. Next, we study the tradeoff of power/energy with network bandwidth and precision. Finally, we study how to combine tradeoffs into a generalized model of applications running under resource constraints. The work in this thesis presents detailed studies of the power/energy tradeoff with response time, throughput, performance, network bandwidth, and precision of stream and batch processing applications. To that end, we present an adaptive algorithm that manages stream processing tradeoffs of response time and throughput at the CPU level. At the task-level, we present an online heuristic that adaptively distributes bounded power in a cluster to improve performance, as well as an offline approach to optimally bound performance. We demonstrate how power can be used to reduce bandwidth bottlenecks and extend our offline approach to model bandwidth tradeoffs. Moreover, we present a tool that identifies parts of a program that can be downgraded in precision with minimal impact on accuracy, and maximal impact on energy consumption. Finally, we combine all the above tradeoffs into a flexible model that is efficient to solve and allows for bounding and/or optimizing the consumption of different resources

Transactional data structures

Concurrent programming is difficult and the effort is rarely rewarded by faster execution. The concurrency problem arises because information cannot pass instantly between processors resulting in temporal uncertainty. This thesis explores the idea that immutable data and distributed concurrency control can be combined to allow scalable concurrent execution and make concurrent programming easier. A concurrent system that does not impose a global ordering on events lends itself to a scalable distributed implementation. A concurrent programming environment in which the ordering of events affecting an object is enforced locally has intuitive concurrent semantics. This thesis introduces Transactional Data Structures which are data structures that permit access to past versions, although not all accesses succeed. These data structures form the basis of a concurrent programming solution that supports database type transactions in memory. Transactional Data Structures permit non-blocking concurrent access to familiar abstract data types such as deques, maps, vectors and priority queues. Using these data structures a programmer can write a concurrent program in C without having to reason about locks. The solution is evaluated by comparing the performance of a concurrent algorithm to calculate the minimum spanning tree of a graph with that of a similar algorithm which uses Transactional Memory and by comparing a non-blocking Producer Consumer Queue with its blocking counterpart.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Uchronia: time at the intersection of design, chronosociology and chronobiology

The societal transformation from an agricultural to an urbanised 24/7 society, reflected in a move from natural time to the mechanical clock to the contemporary digital age, has significantly influenced our daily biological and social rhythms. Modern technology has fostered an increasing temporal fragmentation, heralding an era of flexible time with ever more complex processes of synchronisation. These inhumane rhythms conflict with the natural rhythmicity of the human biological clock. This thesis investigates the potential of new perceptions of time through the application of uchronia - a term derived from the Greek word ou-chronos meaning ‘ no time ’ or ‘ non-time’, and from utopia, from the Greek ou-topos. This research is situated within contemporary debates on the nature of temporality, often denoted as time crisis or dyschronia. It investigates uchronia as temporal utopia and in the way it generates insights about our knowledge of contemporary temporality. The research develops an original uchronian methodology and applications of uchronian thinking in practice-led design research, intertwining design, chronobiological and chronosociological research to propose a new area of chronodesign. Through design practice, I explore how scientific research can be translated into lived, aesthetic experience. The methods range from critical and speculative design ( thought experiments ), artistic research ( unlearning methods ), to methods drawn from chronobiological research ( zeitgeber method ). I investigate practical work which challenges thought patterns regarding the temporal structure of contemporary life, in which participants explore alternative time-givers or synchronisers, in order to think outside the boundaries of clocks and calendars. By providing a broadened definition of uchronianism, I aim to establish uchronia as a platform for critical thought and debate on the contemporary time crisis, with chronodesign as a practical design initiative

Hackers gonna hack: investigating the effect of group processes and social identities within online hacking communities.

Hacking is an ethically and legally ambiguous area, often associated with cybercrime and cyberattacks. This investigation examines the human side of hacking and the merits of understanding this community. This includes group processes regarding: the identification and adoption of a social identity within hacking, and the variations this may cause in behaviour; trust within in the social identity group; the impact of breaches of trust within the community. It is believed that this research could lead to constructive developments for cybersecurity practices and individuals involved with hacking communities by identifying significant or influencing elements of the social identity and group process within these communities. For cybersecurity, the positive influence on individual security approaches after the hacker social identity adoption, and the subsequent in-group or out-group behaviours, could be adapted to improve security in the work place context. For individuals involved in the communities, an increase in the awareness of the potential influences from their adopted social identities and from other members could help those otherwise vulnerable to manipulation, such as new or younger members. Further discussion on such information, as well as historical examples, will lead to informed behaviour by these communities. Whilst this may not cause the group behaviour to change, it would ensure there would be understanding and acceptance of consequences to unethical or illegal actions, which is hoped to discourage cybercriminal behaviour. The research employed a mixed methods approach, with online questionnaires and individual participant interviews. This approach primarily utilised the netnographic approach (Kozinets, 2015), with the results providing more qualitative information than originally anticipated. Informal data collection for this research included observation of relevant websites and forum discussions as well as observation at hacking related conferences; the subsequent surveys and interviews were conducted with volunteers from these communities. Formal data collection was initiated through a pilot study, carried out in early 2016, with 44 participants. This was followed by the first study survey in early 2017, completed by 155 participants. The second study was individual interviews, conducted with 14 participants throughout 2017. These interviews were analysed in the context of Social Identity Theory (Tajfel, 1974). The third and final study was another survey, conducted early 2018 with 197 participants. Thematic analysis was conducted on all data. There was limited evidence of manipulation of group process or trust observed in forums or reported by participants. The adoption of a specific social identity does have strong and influential behavioural norms; however, the adoption of a specific social identity category does not prevent individuals from identifying and confirming to multiple categories which may use or accept different behaviours. The majority of particiapnts in these studies appeared to position themselves as positive deviants, acknowledging past or minor “black-hat” behaviour. This work contributes to the development and improvement of methodologies in online environments: this research was exploratory in accessing a hard to reach demographic that is often untrusting of outsiders. Adaptions to ethical procedures ensured complete anonymity for the participants, improving the participant recruitment rate. Key findings from this research demonstrate that hacking communities can be very positive and supportive for their members, functioning primarily as meritocracies. This is regarded by the communities as an important positive trait, in conjunction with online anonymity. The conclusions of this research consistently support the findings of previous studies

Maritime expressions:a corpus based exploration of maritime metaphors

This study uses a purpose-built corpus to explore the linguistic legacy of Britain’s maritime history found in the form of hundreds of specialised ‘Maritime Expressions’ (MEs), such as TAKEN ABACK, ANCHOR and ALOOF, that permeate modern English. Selecting just those expressions commencing with ’A’, it analyses 61 MEs in detail and describes the processes by which these technical expressions, from a highly specialised occupational discourse community, have made their way into modern English. The Maritime Text Corpus (MTC) comprises 8.8 million words, encompassing a range of text types and registers, selected to provide a cross-section of ‘maritime’ writing. It is analysed using WordSmith analytical software (Scott, 2010), with the 100 million-word British National Corpus (BNC) as a reference corpus. Using the MTC, a list of keywords of specific salience within the maritime discourse has been compiled and, using frequency data, concordances and collocations, these MEs are described in detail and their use and form in the MTC and the BNC is compared. The study examines the transformation from ME to figurative use in the general discourse, in terms of form and metaphoricity. MEs are classified according to their metaphorical strength and their transference from maritime usage into new registers and domains such as those of business, politics, sports and reportage etc. A revised model of metaphoricity is developed and a new category of figurative expression, the ‘resonator’, is proposed. Additionally, developing the work of Lakov and Johnson, Kovesces and others on Conceptual Metaphor Theory (CMT), a number of Maritime Conceptual Metaphors are identified and their cultural significance is discussed