Proving termination of normalization functions for conditional expressions

Boyer and Moore have discussed a recursive function that puts conditional expressions into normal form [1]. It is difficult to prove that this function terminates on all inputs. Three termination proofs are compared: (1) using a measure function, (2) in domain theory using LCF, (3) showing that its recursion relation, defined by the pattern of recursive calls, is well-founded. The last two proofs are essentially the same though conducted in markedly different logical frameworks. An obviously total variant of the normalize function is presented as the `computational meaning' of those two proofs. A related function makes nested recursive calls. The three termination proofs become more complex: termination and correctness must be proved simultaneously. The recursion relation approach seems flexible enough to handle subtle termination proofs where previously domain theory seemed essential

On the termination of recursive algorithms in pure first-order functional languages with monomorphic inductive data types

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 121).by Kostas Arkoudas.M.S

A comparative study of three international construction firms : knowledge management infrastructures for optimising organisations' learning

Sendo a comunicação crescentemente crucial na sociedade contemporânea, e com o aumento do número de plataformas de redes sociais e ferramentas agregadas que vão surgindo, torna-se relevante compreender de que forma estas podem ser aproveitadas e utilizadas enquanto meios de comunicação estratégica para empresas e instituições. A tendência é a de as redes disponibilizarem cada vez mais recursos ao utilizador, fruto da adaptação às necessidades do mesmo, e os baixos custos que possuem são um incentivo à sua exploração. Como tal, através de dois estudos de casos que se tornam aqui relevantes analisar, este trabalho propõe-se compreender de que forma a parceria estratégica entre o YouTube e o Facebook pode funcionar para fortalecer e tornar eficaz a transmissão de mensagens audiovisuais de uma instituição, evidenciando assim a sua presença junto do público-alvo que se encontra cada vez mais presente nestas redes

Twinning and the dynamic behavior of magnesium and its alloys

With a density two-thirds that of aluminum, magnesium has great potential to become the most sought-after structural metal. Naturally, many applications for structural metals require them to remain resilient under extreme conditions of pressure, temperature and loading rates (some common scenarios being car crashes, high speed machining, ballistic impact and micrometeorite impact). Most materials behave very differently when subjected to these extreme conditions in comparison to conventional quasi-static isothermal loading. In the context of magnesium, its asymmetric hexagonal close packed crystal structure results in an anisotropy in plastic deformation which can be linked back to two major plastic deformation mechanisms at the crystal scale: dislocation slip and deformation twinning. In this thesis, we focus on a mechanism-based approach to understand plastic deformation in magnesium under high rates of loading. Special focus has been placed on understanding deformation twinning under these loading conditions. We first investigate the macroscopic strength and ductility of a textured polycrystalline AZ31B magnesium alloy across 8 decades of strain rate (10^-4-10^4 /s) under uniaxial compression along different loading orientations relative to the material texture. The macroscopic flow stress and strain hardening are found to be a function of both strain rate and loading orientation. Post-mortem microscopy reveals both dislocation slip and twin-dominant deformation, depending on the loading orientation relative to the sample texture. We find that deformation twinning is more active at high strain rates than at quasi-static rates. This tends to affect both material strength and ductility. The next part of this thesis examines deformation twinning in greater detail. Using high strain rate experiments combined with in-situ high speed microscopy, we capture the dynamic evolution of deformation twins in single crystal magnesium. The measurements reveal the competition between twin nucleation and growth and its relation to macroscopic material response. A theoretical framework to predict twin propagation speeds is developed with significant potential to explain twin-twin and dislocation-twin interactions. Finally, we end with a discussion of the crystallographic nature of twins nucleated under both quasi-static and dynamic loading. The interplay between the mechanics of twinning (i.e. twin nucleation and growth kinetics) and the crystallography offers unique insights and may help improve predictive capabilities for the dynamic behavior of hcp crystals

Exploring contingent employment policy in IT – impacts upon IT project management capabilities enhancement in large Hong Kong organisations

Large Hong Kong organisations rely heavily on IT projects to sharpen their competitiveness. Contingent IT project employment is a globally increasing trend that results in high staff turnover. This raises risks that organisational project knowledge is rarely retained when contingent workers leave organisations and as individual contingent workers become frustrated by employer’s lack of commitment to their future. Contingent employment policy has generally been assumed to impede IT project management’s organisational capability and competitiveness through knowledge leakage and inhibited organisational learning. Limited research has been undertaken on the impact of contingent IT project management employment on organisational capability though there have been numerous separate studies on: IT project management; general contingent employment; and enhancing IT project management capabilities. This thesis combines these themes to (i) explore the importance of continuous advancement of IT project management capabilities to business successes; (ii) identify and explain the contingent and permanent employment policies of IT professionals (including project managers) in large Hong Kong organisations; (iii) investigate and explain the impacts of contingent employment policies on enhancing IT project management capabilities; (iv) identify and explain the practices of advancing IT project management capabilities as an individual, as a group and as a large organisation; and (v) identify and present possible solutions to satisfy the needs to advance IT project management capabilities using contingent employment. A case study multiple-case, comparative research design was followed that relied on open-ended interviews supported by semi-structured interviews and using archival documentation. Three case study organisations typify large Hong Kong organisations that are major IT workforce employers. The first and second case study organisations are representative of a large IT users organisation and an IT and communications services organisation (the two key categories of IT employers) respectively employing a high percentage (over 50%) of contingent IT workers. The third case study organisation is a contrast case since it employs a low percentage (below 20%) of contingent IT workers and is a typical IT users organisation. Analysis concluded that the degree of projectisation, project resource strategies and investment on IT project management capabilities have to fit the organisation’s specific business dynamics. The business situation of organisations determines IT projects’ scale and complexity. This leads IT groups to be organised along a functional, balanced matrix or projectised structure spectrum. Organisations with greater projectisation are more likely to rely on contingent IT workers. Continuing to enhance IT project management capability while depending on an increasing percentage of mobile external resources (including contingent workers) may require an organisation to invest more in project governance and support structures, project management methodologies and tools. Alternatively, organisations may prefer retaining in-house staff to capture their tacit organisational knowledge and invest in cognitive and operational learning to retain codified organisational knowledge while avoiding weakness in reflective learning and social learning processes