Learning Recursive Functions From Approximations

This article investigates algorithmic learning, in the limit, of correct programs for recursive functionsffrom both input/output examples offand several interesting varieties ofapproximateadditional (algorithmic) information aboutf. Specifically considered, as such approximate additional information aboutf, are Rose\u27s frequency computations forfand several natural generalizations from the literature, each generalization involving programs for restricted trees of recursive functions which havefas a branch. Considered as the types of trees are those with bounded variation, bounded width, and bounded rank. For the case of learning final correct programs for recursive functions, EX-learning, where the additional information involves frequency computations, an insightful and interestingly complex combinatorial characterization of learning power is presented as a function of the frequency parameters. For EX-learning (as well as for BC-learning, where a finalsequenceof correct programs is learned), for the cases of providing the types of additional information considered in this paper, the maximal probability is determined such that the entire class of recursive functions is learnable with that probability

Retrieval for Extremely Long Queries and Documents with RPRS: a Highly Efficient and Effective Transformer-based Re-Ranker

Retrieval with extremely long queries and documents is a well-known and challenging task in information retrieval and is commonly known as Query-by-Document (QBD) retrieval. Specifically designed Transformer models that can handle long input sequences have not shown high effectiveness in QBD tasks in previous work. We propose a Re-Ranker based on the novel Proportional Relevance Score (RPRS) to compute the relevance score between a query and the top-k candidate documents. Our extensive evaluation shows RPRS obtains significantly better results than the state-of-the-art models on five different datasets. Furthermore, RPRS is highly efficient since all documents can be pre-processed, embedded, and indexed before query time which gives our re-ranker the advantage of having a complexity of O(N) where N is the total number of sentences in the query and candidate documents. Furthermore, our method solves the problem of the low-resource training in QBD retrieval tasks as it does not need large amounts of training data, and has only three parameters with a limited range that can be optimized with a grid search even if a small amount of labeled data is available. Our detailed analysis shows that RPRS benefits from covering the full length of candidate documents and queries.Comment: Accepted at ACM Transactions on Information Systems (ACM TOIS journal

Full coverage displays for non-immersive applications

Full Coverage Displays (FCDs), which cover the interior surface of a room with display pixels, can create novel user interfaces taking advantage of natural aspects of human perception and memory which we make use of in our everyday lives. However, past research has generally focused on FCDs for immersive experiences, the required hardware is generally prohibitively expensive for the average potential user, configuration is complicated for developers and end users, and building applications which conform to the room layout is often difficult. The goals of this thesis are: to create an affordable, easy to use (for developers and end users) FCD toolkit for non-immersive applications; to establish efficient pointing techniques in FCD environments; and to explore suitable ways to direct attention to out-of-view targets in FCDs. In this thesis I initially present and evaluate my own "ASPECTA Toolkit" which was designed to meet the above requirements. Users during the main evaluation were generally positive about their experiences, all completing the task in less than three hours. Further evaluation was carried out through interviews with researchers who used ASPECTA in their own work. These revealed similarly positive results, with feedback from users driving improvements to the toolkit. For my exploration into pointing techniques, Mouse and Ray-Cast approaches were chosen as most appropriate for FCDs. An evaluation showed that the Ray-Cast approach was fastest overall, while a mouse-based approach showed a small advantage in the front hemisphere of the room. For attention redirection I implemented and evaluated a set of four visual techniques. The results suggest that techniques which are static and lead all the way to the target may have an advantage and that the cognitive processing time of a technique is an important consideration."This work was supported by the EPSRC (grant number EP/L505079/1) and SurfNet (NSERC)." - Acknowledgement

Essays on cultural and institutional dynamics in economic development using spatial analysis

This thesis seeks to research patterns of economic growth and development from a number of perspectives often resonated in the growth literature. By addressing themes about history, geography, institutions and culture the thesis is able to bring to bear a wide range of inter-related literatures and methodologies within a single content. Additionally, by targeting different administrative levels in its research design and approach, this thesis is also able to provide a comprehensive treatment of the economic growth dilemma from both cross-national and sub-national perspectives. The three chapters herein discuss economic development from two broad dimensions. The first of these chapters takes on the economic growth inquiry by attempting to incorporate cultural geography within a cross-country formal spatial econometric growth framework. By introducing the global cultural dynamics of languages and ethnic groups as spatial network mechanisms, this chapter is able to distinguish economic growth effects accruing from own-country productive efforts from those accruing from interconnections within a global productive network chain. From this, discussions and deductions about the implications for both developed and developing countries are made as regards potentials for gains and losses from such types and levels of productive integration. The second and third chapters take a different spin to the economic development inquiry. They both focus on economic activity in Africa, tackling the relevant issues from a geo-intersected dimension involving historic regional tribal homelands and modern national and subnational administrative territories. The second chapter specifically focuses on attempting to adopt historical channels to investigate the connection between national institutional quality and economic development in demarcated tribal homelands at the fringes of national African borders. The third chapter on the other hand focuses on looking closer at the effects of demarcations on economic activity. It particularly probes how different kinds of demarcation warranted by two different but very relevant classes of politico-economic players have affected economic activity quite distinguishably within the resulting subnational regions in Africa

Childbearing preferences and behaviour: Where are all the men?

Research shows a predominantly female orientated approach to the study of fertility and childbearing. Prior to the 1990s men were missing from this research by design. Women were asked to report their partner’s childbearing preferences and behaviours and thus the true attitudes and opinions of men were largely unknown. Although men are no longer missing from this research, their participation rates are disproportionally low compared to women. The aims of the studies to be presented in this thesis were to better understand the childbearing preferences and behaviours of men, establish reasons for why men have disproportionately low participation rates in the research on childbearing, identify who and what could be a target of behaviour change interventions aimed to increase participation in childbearing research and identify whether the implementation of such interventions increase male participation. The work presented in this thesis demonstrates that, as with women, a number of factors influence whether and when men begin parenthood. However, there is diversity between men and women in terms of what factors they consider to be important and influential in the preconception decision-making process. Men overall wanted to be fathers but did not want to be involved beyond being the breadwinner of the family.Therefore results highlight the need to consider the childbearing preferences and behaviours of men in order to understand contemporary fertility trends and identify unmet needs in policy and research that concern men. Notwithstanding this, the disproportionally low participation rates of men in the research on childbearing ultimately means that the research base is not providing a good account of male attitudes towards whether and when to have children. When given the opportunity to participate in childbearing research men participate significantly less than women actively excluding themselves from the research as a result of less favourable attitudes towards the behaviour. The modification of attitudes is thus identified to be the mechanism that would most likely elicit intention (and potentially behaviour) change. The implementation of persuasive messages aimed to modify attitudes towards participation in childbearing research increased the perceived relevance of the behaviour but had little effect on attitude, intention and research behaviour. Overall, the work presented in this thesis demonstrates that raising public awareness that childbearing is an issue that affects men as well as women is likely to be key to integrating men into family life and increasing their participation in childbearing research