Thesis (Ph. D.)--New York University, 1987. / Typescript. Includes bibliographical references (p. 402-407).

Thesis (Ph. D.)--University of Nevada, Reno, 1995. / Includes bibliographical references (leaves 283-306).

Thesis (Ph. D.)--University of Iowa, 1993. / Includes bibliographical references (leaves 124-127).

Thesis (master's)--Instituto de Economia da UNICAMP. / Includes bibliographical references (p. 203-214).

Thesis (Ph. D.)--University of Chicago, 1994. / Includes bibliographical references (leaves 148-152).

This dissertation looks at how African countries can mitigate the effects of external debt burden. African countries are enmeshed in unsustainable external debts that have led to debt overhang problems, declining output, escalating current account deficits and worsening human welfare indicators. These external debt burdens are further worsened by the structural weaknesses of these economies. The World Bank and the International Monetary Fund have initiated strategies aimed at trying to arrest the escalating debt burden such as rescheduling, structural adjustment programs and the highly indebted poor countries initiative. However, African countries continue to experience difficulties in servicing external debts. The objective of this study is to find ways by which African countries can effectively manage their debt burden and possibly come up with self pre-qualification schemes that would forestall future external debt problems. The questions the study seeks to answer are: how can African countries effectively manage their current debt burden? What can African countries do to forestall the pervasive external debt accumulation in the future? To address these questions, I develop a dynamic stochastic general equilibrium model of external debt burden for Africa. The model is estimated using the maximum likelihood method by applying the Kalman filter to the state space representation of the model. Empirical results of the model suggest that African countries need to refine their basket of imports and mainly import inputs that can be used in the production sector as opposed to importing consumption goods. Most importantly, these countries must re-think their export products and markets, and perhaps endeavor to export final goods as opposed to exporting primary commodities. Furthermore, simulations of the model show that an expansionary monetary shock and a favourable world commodity price shock leads to an increase in external debt. On the other hand, the world interest rate shock leads to a fall in external debt. An interesting result worth highlighting is that a favourable commodity price shock leads to an increase in imported investments but the increase in imported investments does not translate into increased output. On the other hand, an unfavourable world interest rate shock leads to a fall in imported investments. Generally, these findings suggest that African countries are vulnerable to external shocks. In pursuit of the second objective – possible ways of sourcing external debt and managing it sustainably – I find that the appropriate threshold level for debt sustainability is a ratio of external debt to gross domestic product of between 40%-60% for Africa compared to 120%-150% for Latin America. Surprisingly, East Asia has the lowest significant debt sustainability threshold of the three emerging market regions. On liquidity, which is captured by the short-term debt to reserves ratio, the threshold is 60%-80% for all the three regions. On governance, a stable political environment plays a crucial role in determining the external debt burden of African countries. An improvement in the legal system and a stable political environment leads to an increase in exports and a fall in consumption imports. These in turn reduce foreign debt. These findings suggest that African countries must pursue proper governance practices if they are to appropriately and effectively manage their external debt in ways that enhance economic progress instead of economic retardation.

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In recent years several high-profile building fires have highlighted shortcomings in the way we design for the complex interaction of structures and fire. These weaknesses appear to arise from a combination of gaps in knowledge of some of the more intricate aspects of compartment fire dynamics and from limitations in the engineering applications developed to date from hitherto established fundamentals. In particular the One Meridian Plaza Fire (1991), the Madrid Windsor Tower Fire (2005) and the Lakanal House Fire (2009) have emphasised the need for further study in the field of post-flashover compartment fires and the often consequent external fires that emerge from the compartment openings. External fire plumes impinge upon the structural façade, causing added structural stress, and often result in external fire spread and secondary ignition in upper level compartments. Hence a better understanding of the effect had by the internal compartment fire on the development of external flaming and the insult of the plume to its surroundings is beneficial for Structural Engineers, Fire Protection Engineers and Emergency Response Personnel alike. This research explores existing correlations, identifies their limitations and proposes a simplified methodology that links key parameters found to govern the internal post-flashover compartment fire to the heat flux potentially imposed on the exterior façade. Existing correlations addressing the effect of compartment fires on the insult to the external structure have largely been compiled by Law and are summarised in the form of a design manual for bare external structural steel [1]. Formulated in the 1970s, these correlations are based on the combined findings of several different experimental tests devised to investigate component phenomena of compartment fires and external flaming, forming an analytical model which is mostly empirical in nature. The methodology is convoluted and has several inherent assumptions which give rise to various limits of applicability however it is currently still used in structural-fire design, but best known as Annex B of both Eurocodes 1 and 3 [2,3]. As part of the present research, full-scale fire tests are conducted in situ, in a highly instrumented high-rise building, to provide high-resolution measurements of several internal compartment fire characteristics during a post-flashover fire in a modern, realistically-furnished compartment. External high resolution instrumentation in the main test also provides detailed measurements of the external flaming and distribution of heat flux incident on the façade. The tests provide realistic benchmark scenario data for comparing physical measurements against the analytical Law Model, the difference in which allows for an evaluation of the assumptions used in the model, which are often defined as ‘conservative’ in nature from the perspective of structural design. A detailed sensitivity study of the main input parameters in the Law Model allows for the identification of parameters of pivotal influence on the resultant heat flux incident on the plane of the external façade. Analysis of the Law Model and its underlying experimental basis also enables the identification of several limits of applicability of the model. Combined, these assessments show the analytical model can be stripped of unnecessary complexity and a Simplified Model is proposed with clear bounds of applicability. The proposed model describes the distribution of heat flux to the façade above a compartment opening and features only parameters of key importance, where low-dependency parameters are grouped into associated error bars. This results in a model that can be applied in the design of several building components that fall in the plane of the façade, such as structural elements, façade cladding and window arrangements. Its ease of implementation renders the model more widely accessible to different factions of the Fire Engineering Community. Furthermore, analysis of the Law Model identifies further parameters of potential importance that have, as of yet, not been addressed. A preliminary investigation conducted using Computational Fluid Dynamics (CFD) tools shows that variation in some parameters – that are not individually accounted for in the Law Model – may influence the compartment fire conditions, the consequent external flaming and the resultant external heat exposure. Therefore, it is recommended that further comprehensive experimental research be conducted into the potential influence of the identified parameters.

<p>The influence of environment in galaxy evolution has been observed in a wide range of environments, where in general red quiescent early-type galaxies preferentially reside in high-density regions. The aim of this thesis is to understand the role that galaxy groups, and in particular group dynamics, play in galaxy evolution.</p> <p>We examine substructure in rich groups at intermediate redshifts and find that 4/15 groups contain substructure, which is preferentially found on the group outskirts. Galaxies in groups with substructure have properties similar to the field, while the galaxies in groups with no substructure are similar to cluster populations. These results indicate that substructure galaxies do not feel the effects of the environment until well inside the group potential.</p> <p>We then study the evolution of group dynamics to z~1 and find that the fraction of non-Gaussian groups increases with redshift, while the fraction of groups with substructure remains constant. Additionally, we find that the quiescent fraction correlates with galaxy stellar mass, but has little or no dependence on group dynamical mass or state. However, we do observe some correlation between substructure and quiescent fraction for low mass galaxies.</p> <p>Finally, we investigate infalling subhalo galaxies to probe the importance of pre-processing in galaxy evolution. At r200 > 2, galaxies in subhaloes show enhanced quenching, when compared to non-subhalo galaxies. At these radii, the infall population dominates, indicating that enhanced quenching is due to the infalling subhalo population. Additionally, the fraction of groups with subhaloes is a function of halo mass, where more massive systems have a higher fraction of subhaloes. We conclude that for groups, pre-processing is insignificant; however, for the most massive clusters a significant fraction (∼ 25%) of the member galaxies have been pre-processed.</p> / Doctor of Philosophy (PhD)

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