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Motivated by the popularity of marketplace applications over social net works, we study optimal recommendation algorithms for online exchange markets. Examples of such markets include peerflix. corn and readitswapit.co.uk. We model these markets as a social network in which each user has two as sociated lists: The item list, i.e, the set of items the user is willing to give away, and the wish list, i.e., the set of items the user is interested in receiv ing. A transaction involves a user giving an item to another user. Users are motivated to engage in transactions in expectation of realizing their wishes. Wishes may be realized by a pair of users swapping items corresponding to each other’s wishes, but more generally by means of users exchanging items through a cycle, where each user gives an item to the next user in a cycle, in accordance with the receiving user’s wishes. In this thesis, we first consider the problem of how to efficiently gener ate recommendations for item exchange cycles in an online market social network. We consider deterministic and probabilistic models and show that under both models, the problem of determining an optimal set of recommen dations that maximizes the expected value of items exchanged is NP-hard and develop efficient approximation algorithms for both models. Next, we study exchange markets over time and try to optimize users’ waiting times, and fairness whereby fairness we mean: give higher priority to users who contribute more to the system in addition to maximizing expected value. We show that by introducing the concept of points, average waiting time can be improved by a large factor. By designing a credit system, we try to maxi mize fairness in the system. We show not only is the fairness optimization problem NP-hard, but also inapproximable within any multiplicative factor. We propose two heuristic algorithms, one of which is based on rounding the solution to a linear programming relaxation and the other is a greedy algorithm. For both the one-shot market and the overtime market studied in this thesis, we conduct a comprehensive set of experiments, and explore the performance and also scalability of the proposed algorithms. Our experiments suggest that the performance of our algorithms in practice could be much better than the worst-case performance guarantee factors.

In order to increase the current efficiency in copper electrowinning tankhouses, iron can be removed from the electrolyte using ion exchange. While this is a proven technology, very little data is available for the application of this technology to copper electrowinning electrolytes containing antimony and bismuth. The feasibility of utilizing iron ion exchange for the removal of iron from copper electrowinning electrolytes containing antimony and bismuth was studied in the laboratory. A picolylamine, a sulphonated diphosphonic, an aminophosphonic and three sulphonated monophosphonic resins were tested. The picolylamine resin was found to be completely impractical as it loaded high levels of copper. All the phosphonic resins tested loaded an appreciable amount of antimony, however, only the aminophosponic resin loaded an appreciable amount of bismuth. Tests to determine whether or not the sulphonated monophosphonic Purolite 5957 resin would continue to load antimony with time and, hence, reduce the resin's ability to remove iron gave inconclusive results. In the event that the resin's ability to remove iron is hampered due to antimony loading, testing has shown that the resin performance may be restored via a regeneration with a solution containing sulphuric acid and sodium chloride. A case study for the application of this technology to the CVRD Inco CRED plant has shown that, while iron removal by ion exchange is technically feasible, it will upset the plant's acid balance in electrolyte. Therefore, an acid removal process would need to be implemented in tandem with an iron ion exchange system. Additionally, preliminary calculations suggest that a system with a single ion exchange column may have difficulty removing sufficient iron for the CRED design conditions. Therefore, consideration should be given to the possibility of utilizing a two column system (one column loading, one column stripping).

Examining the process of knowledge exchange and uptake (KEU) involved collaborating with a current decision-maker to determine what knowledge would be examined to increase the understanding why evidence is accepted or rejected as evidence for decision-making. The knowledge selected were the organizational values of a Regional Health Authority from a managerial perspective. The uptake was how the values informed decision-making. The secondary attributes were identified as the conditions and characteristics that enable or challenge using values. As decision-makers prefer usable tools as a research deliverable, a Continuous Improvement Model and Logic Model were populated with the results of a mixed method inquiry. The actionable recommendations are intended to counter challenges and encourage best practices, and provide evaluation indicators. This dissertation will add to the growing literature on how to influence the uptake of evidence through collaboration and effective knowledge transfer plans that aid in bridging the know-do gap.

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