Search

Inference systems Τ and search strategies E for T are distinguished from proof procedures β = (T,E) The completeness of procedures is studied by studying separately the completeness of inference systems and of search strategies. Completeness proofs for resolution systems are obtained by the construction of semantic trees. These systems include minimal α-restricted binary resolution, minimal α-restricted M-clash resolution and maximal pseudo-clash resolution. Certain refinements of hyper-resolution systems with equality axioms are shown to be complete and equivalent to refinements of the pararmodulation method for dealing with equality. The completeness and efficiency of search strategies for theorem-proving problems is studied in sufficient generality to include the case of search strategies for path-search problems in graphs. The notion of theorem-proving problem is defined abstractly so as to be dual to that of and" or tree. Special attention is given to resolution problems and to search strategies which generate simpler before more complex proofs. For efficiency, a proof procedure (T,E) requires an efficient search strategy E as well as an inference system T which admits both simple proofs and relatively few redundant and irrelevant derivations. The theory of efficient proof procedures outlined here is applied to proving the increased efficiency of the usual method for deleting tautologies and subsumed clauses. Counter-examples are exhibited for both the completeness and efficiency of alternative methods for deleting subsumed clauses. The efficiency of resolution procedures is improved by replacing the single operation of resolving a clash by the two operations of generating factors of clauses and of resolving a clash of factors. Several factoring methods are investigated for completeness. Of these the m-factoring method is shown to be always more efficient than the Wos-Robinson method.

Since the industrial revolution, the concentration of atmospheric CO2 has drastically risen. Currently, the CO2 reduction reaction (CO2RR) has been extensively studied to convert CO2 into higher values products like CO, formic acid, methane, etc. Industrially, the first step of the CO2RR is to capture the CO2 using some capture agent, typically an amine. However, as these chemicals bind CO2 quite strongly a large amount of thermal energy is required to liberate the CO2. Thus, it has been proposed to directly reduce the capture agent in the general captured CO2 reduction reaction (c-CO2RR). This work is a prospective on Ag that considers different capture agents, proton source effects, and facets. We show that the proton source chosen has a large effect on the reactivity, we show that methanol is predicted to be a competitive capture agent compared to NH3, and we show that steps and kinks sites hinder or do not improve the c-CO2RR. However, overall, we determine that on Ag the HER dominates and therefore, further catalyst development is necessary.

The “University” is under pressure to address both local and general requirements from society towards a phenomenon called globalisation. In Brazil, the Ministry of Education has tried, without success, to promote institutional change. Confronted by this situation a process initiated by an internal change agent and based upon the introduction of Action Research was itself the subject of this AR Study by the change agent. This thesis draws upon the findings of that AR and uses it to critically examine the potential to foster change within the higher education context in Brazil using AR. The research was designed in two synchronous processes taking place at two different levels. The first is the facilitation of the uptake of Action Research by a group of academic staff, and the second is the research into that process as a piece of Action Research in its own right by the change agent/facilitator. Facilitation of change has been described as taking place in three phases: a) Mobilization; b) Implementation; and c) Continuation. Throughout such phases in this case data were systematically gathered by the use of five instruments of data collection: 1) Observation; 2) Diary; 3) Questionnaires; 4) Interviews; and 5) Sociogram. Results show my personal learning in facilitating this process of change and two main contributions to knowledge. The first is one which, though local and specific, may nevertheless speak to the challenges faced by other practitioners. Exemplified in this study by the critical exploration of the ‘Daisy Model’ of introducing AR that led to its modification into the ‘Flower Model’. The second is that new knowledge which appears to be more generalisable and for which a case can be made for its wider applicability. Again exemplified in the continuous and disruptive process of change that unfolded to reveal a suitable framework for the use of Action Research as a vehicle of change in a rural university in Brazil where all actions were based on four central principles that emerged from the research: neutrality, voluntary participation, time and motivation. The future success and sustainability of the change processes begun are contingent upon the reaction of the current management of the institution. Five scenarios are examined and a second phase for this AR project is suggested that attempts to address the issues raised.

The current deficiencies of extension interventions in aquaculture in Bangladesh, in particular, in the North-west have been examined. The importance of the inclusion of a social dimension in development interventions has been reviewed. Aquaculture, extension, social development and poverty are defined in the context of the study and a model of their interactions is proposed and used to elucidate the role of aquaculture in poverty reduction. Research questions were generated to examine the contention that ‘Aquaculture Extension Approaches that fail to substantially address social development will lead to no more than a superficial reduction of poverty’. The study approach chosen was comparative case study (the first use of its' kind in this context). Within the study, communities representing four different aquaculture extension approaches and a, null-case, control were selected and then engaged in the research process. The findings that emerged from the study were matched and linked to the proposed model to establish patterns and linkages between aquaculture and poverty; extension and aquaculture; aquaculture and social development; social development and poverty; extension and poverty. The study suggests that all these aspects go hand in hand within communities, and that it is the degree of marginalisation that defines the success of any intervention as much as the intervention approach itself. The study indicates that aquaculture could be an entry point for a poverty alleviation strategy but the inclusion of a social dimension, together with the chosen technical intervention, is essential in achieving higher impacts on a sustainable basis. A number of recommendations for greater poverty impact through aquaculture intervention as an entry point are put forward, including the targeting of women as well as men, emphasise a learning approach, and the building of networks through forming community producers groups, fish clubs, Fry Traders and fingerling producers groups.