A two-dimensional mathematical model is adopted to investigate the development of buoyancy driven circulation patterns and temperature contours inside a rectangular enclosure filled with a compressible fluid where one of the vertical walls of the enclosure is kept at a higher temperature than the opposite one. Fluid thermodynamic and transport properties are assumed to be functions of temperature. The governing equations are discretized using second order accurate differencing for spatial and temporal derivatives and then linearized using Newton's linearization method. The resulting set of algebraic equations is solved using the Coupled Modified Strongly Implicit Procedure for the unknowns of the problem. The results of this study show that the variable property model predicts lower values for wall heat fluxes and Nu number than the constant property one for Rayleigh numbers between 104 and 105.

Tax aggressiveness generates significant cash savings and information asymmetry. Combining these two consequences of tax aggressiveness, I suggest that tax aggressiveness is associated with higher agency costs of free cash flows that affect investment decisions. Using the conditional investment efficiency model, I find evidence that tax aggressiveness is associated with more investments in firms with high access to investable funds, thus suggesting tax aggressiveness is associated with overinvestment. I also provide evidence that stronger tax monitoring and a change in tax disclosures mitigate the relation between tax aggressiveness and overinvestment. Lastly, I find that the overinvestment is associated with lower future abnormal returns. Thus, my results suggest that poor managerial investment decision making is an unintended consequence to tax aggressiveness. Additionally, I further the need for shareholders and board of directors to exert influence to avoid compensating managers for aggressive tax strategies.

Thesis (M.M. (Finance & Investment))--University of the Witwatersrand, Faculty of Commerce, Law and Management, Graduate School of Business Administration, 2015. / e period 2000:q1 – 2014:q3 in South Africa. In addition, the paper examines the impact that the exchange rate volatility exerts on the different forms of capital flows. Consequently, the aim of the study is to examine whether the volatility in the exchange rate is a significant determinant of foreign investor capital into South African markets as well as to empirically establish the dynamic relationship that can be observed between capital flows and exchange rate volatility. A trade weighted exchange rate was constructed from which the conditional variance GARCH (1,1) model is applied to estimate exchange rate volatility. The findings from the multiple regression analysis reveal that exchange rate volatility has a statistically significant negative impact on the aggregated capital flows to South Africa. Using the bi-variate vector autoregressions (VARs), the Granger-causality test, impulse response and variance decomposition, the results show there is a dynamic interrelationship between exchange rate volatility and the aggregated and disaggregated capital flows. Furthermore, the VAR specifications results reveal that portfolio flows exhibits a strong bi-directional causality with exchange rate volatility as well as explaining a significant percentage of innovations in exchange rate volatility. This suggests that fluctuations in the exchange rate can be explained by portfolio flows into South Africa’s capital markets. The recommendations for authorities resulting from the findings include, a monetary policy that mitigates the rand exchange rate volatility in an effort to attenuate the adverse subduing effects it has on capital flows in South Africa. Further broadening financial instruments and derivatives available for investors to hedge against exchange rate volatility and a meticulous management of portfolio flows is imperative to ensure prevention of its destabilizing effect on the exchange rate.

Este trabalho objetiva propor diretrizes para a elaboração de um modelo de gestão de fluxo de informações como suporte à logística em empresas construtoras de edifícios. O foco da pesquisa limita-se especificamente à gestão de materiais, apesar da logística também abranger mão-de-obra, serviços e equipamentos. O objetivo da gestão de materiais é o de assegurar um fluxo continuo e sem interferências de materiais e componentes à obra, na quantidade requerida, com a qualidade especificada, no tempo e lugar certo, ao menor custo total. Estas diretrizes foram identificadas visando a uma integração funcional dentro da empresa construtora. Com base em um estudo de caso realizado em três empresas construtoras e em um levantamento e estudo bibliográfico, foram estudados os fluxos de informações ligados à gestão de materiais que ocorrem dentro das empresas construtoras. Desta maneira, identificaram-se os principais fatores que facilitam e que dificultam os fluxos de informações entre agentes relacionados com a gestão de materiais. Uma vez analisados estes fatores, foram identificadas as diretrizes objeto desta pesquisa e foi proposto um fluxo de informações modelo baseado exclusivamente nos casos estudados. Adicionalmente, foram discutidos alguns parâmetros a se levar em conta para avaliar o modelo proposto e conseguir uma melhoria continua dentro do processo. Também, foi brevemente discutida a forma como as parcerias com os fornecedores, o uso de produtos normalizados, a Internet e os códigos de barras poderiam inovar estes fluxos de informações e conseguir a integração tão almejada na cadeia de suprimentos. / This research aims to identify guidelines for developing an information flow management model to support materials management in building construction firms. The main purpose of building materials management is to have the required materials at the right place, at the right time, in the right quantity without prejudicing cost and quality. These guidelines were identified considering a functional integration within the construction firm. Based on three case studies developed in construction firms and a literature review, the materials management information flows inside the construction firm were studied. In this way, the principal factors that affect or enhance these information flows were analyzed. Once analyzed these factors, we were able to determine the best arrange for these flows and identify the guidelines and propose an information flow model based exclusively in the three cases studied. Besides this, we discussed the parameters that should be taken into account to guarantee a continuous improvement in the model proposed. Finally, we briefly discuss how partnering with suppliers, the use of normalized products, the Internet and the use of code bars could innovate traditional information flows and integrate the supply chain.

Thesis advisor: Fabio Ghironi / Thesis advisor: Susanto Basu / The present dissertation is composed by three essays. The first essay is titled ``Comparative Advantage, Service Trade, and Global Imbalances''. The large current account deficit of the U.S. is the result of a large deficit in the goods balance and a modest surplus in the service balance. The opposite is true for Japan, Germany and China. Moreover, I document the emergence from the mid-nineties of a strong negative relation between specialization in export of services and current account balances in a large sample of OECD and developing countries. Starting from these new stylized facts, I propose in this essay a ``service hypothesis'' for global imbalances, a new explanation based on the interplay between the U.S. comparative advantage in services and the asymmetric trade liberalization process in goods trade versus service trade that took place in the last 15 years. I use a structural gravity model to quantify the extent of this asymmetry. I show that a simple two-period model can rationalize the emergence of current account deficits in the presence of such asymmetric liberalization. The key inter-temporal mechanism is the asymmetric timing of trade policies, which affects savings decisions. Finally, I explore the quantitative relevance of this explanation for global imbalances. A multi-period version of the model, fed with the asymmetric trade liberalization path found in the data, generates a current account deficit of about 1% of GDP (roughly 20% of what was observed in the U.S. in 2006). The policy implications of the analysis proposed could be relevant for the evolution of the WTO DOHA Development Round. A major focus on services, in fact, could help expanding the ``policy space'' faced by the negotiators, possibly increasing the likelihood of a successful conclusion of the round. Moreover, this paper inform also the recent debate about the need of a revaluation of the yuan. Allowing the U.S. to increase its exports of services (not necessarily to China) might help alleviating global imbalances even without movements in the exchange rates. The second essay is titled ``Estimating Trade and Investment Flows: Partners and Volumes''. I present empirical evidence from a large sample of countries for the period 2000-2006. Bilateral foreign direct investment (FDI) flows are almost never observed in the absence of bilateral trade flows, thus configuring an order of trade and investment flows. I document a similar pattern using bilateral foreign affiliate sales (FAS), aggregating them up from a large firm level dataset (ORBIS), which includes over 45,000 firms. I propose a model where heterogeneous firms face a proximity-concentration tradeoff when they decide whether to serve foreign markets through export or FDI. I derive theory-based gravity-type equations for the aggregate bilateral trade and foreign affiliate sales (FAS) flows. I then suggest a two-stage estimation procedure. In the first stage, a ordered Probit model is used to retrieve consistent estimates of the terms needed to correct the flows equations for heterogeneity and selection. In the second stage, a maximum likelihood estimator is applied to the corrected trade and FAS equations. The main results of the analysis are as follows: 1) The impact of distance, border and regional trade agreements on bilateral foreign affiliate sales becomes substantially smaller after controlling for selection and firms' heterogeneity (hence separating the impact on the extensive versus the intensive margin). 2) The same ``attenuation'' result is found also for the trade equations, consistently with HMR. 3) When FAS are observed, failing to take this into account when correcting for heterogeneity and selection in the trade equations leads to differences in the estimated coefficients. The third essay is titled ``Some Evidence on the Importance of Sticky Wages'', and is co-authored with Susanto Basu and Peter Gottshalk. Nominal wage stickiness is an important component of recent medium-scale structural macroeconomic models, but to date there has been little microeconomic evidence supporting the assumption of sluggish nominal wage adjustment. We present evidence on the frequency of nominal wage adjustment using data from the Survey of Income and Program Participation (SIPP) for the period 1996-1999. The SIPP provides high-frequency information on wages, employment and demographic characteristics for a large and representative sample of the US population. The main results of the analysis are as follows. 1) After correcting for measurement error, wages appear to be very sticky. In the average quarter, the probability that an individual will experience a nominal wage change is between 5 and 18 percent, depending on the samples and assumptions used. 2) The frequency of wage adjustment does not display significant seasonal patterns. 3) There is little heterogeneity in the frequency of wage adjustment across industries and occupations 4) The hazard of a nominal wage change first increases and then decreases, with a peak at 12 months. 5) The probability of a wage change is positively correlated with the unemployment rate and with the consumer price inflation rate. To a certain extent, the three essays presented here are self-contained and deal with three different issues regarding international economics and macroeconomics. Going to a deeper level, however, the essays are linked by a common feature: they are three examples of economic research across fields. The first essay, in fact, is an example of the growing fields at the edge between international trade and international macroeconomics. While the trade of goods and services and the dynamics of macroeconomic variables such as the current account are highly interconnected in the real world, these two fields have been characterized by a large divide in the last thirty years in the economic literature. The second essay is an example of a joint study of international trade and investment flows. Also in this case, while conceptually clearly interconnected, these topics have been usually studied separately by the economic literature. Finally, the third essay is an example of research across fields (labor economics and macroeconomics) and techniques (micro-level analysis informing macroeconomic models). In this last case, macroeconomists were interested in estimating certain wage dynamics parameters highly used in macro models. However, they were largely unaware of the fact that labor economists had the data to answer those research questions. On the other hand, the labor economists had the data, but not the questions. I hope that these essays might help increasing further the awareness that more communication between economists working in different fields can bring to valuable insights. / Thesis (PhD) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Geophysical granular flows, such as snow avalanches, pyroclastic density currents, mudslides and debris flows, can be extremely hazardous to local populations, and understanding their complex behaviour remains an important challenge. This project aims to provide insight into these events by exploring different aspects in isolation, using a combination of mathematical theory, numerical simulations and small-scale experiments. Firstly, the effect of lateral confinement is examined by studying granular material moving in an inclined chute. This can have applications to natural releases flowing down confined valleys or conduits, and the relative simplicity of the geometry also provides a useful test case for new theoretical models. One such model is the recent depth-averaged μ(I)-rheology, which, because of the viscous terms introduced into the depth-averaged momentum balance, may be described as an intermediate approach between full constitutive laws and classical shallow-water-type equations for dense granular flows. Here, a generalisation of the new system to two spatial dimensions is described, and the resulting viscous equations are able to capture the cross-slope curvature of the downslope velocity profiles in steady uniform chute flows. This may be regarded as major progress compared to traditional hyperbolic models, which only admit constant velocity solutions. Particle size-segregation in geophysical granular flows is then investigated, which can cause important feedback on the overall bulk properties as it can lead to the development of regions with different frictional properties. A particularly striking example is segregation-induced 'finger' formation, where large particles are segregated to the flow surface and sheared to form a resistive coarse-rich front, which is unstable and spontaneously breaks down into a series of lobate structures. These travel both faster and further than one might anticipate. To model such segregation-mobility feedback effects, the depth-averaged μ(I)-rheology is extended to bidisperse flows by coupling with a depth-integrated model for size-segregation. The system of equations remains mathematically well-posed and is able to qualitatively capture finger formation, with the newly-introduced viscous terms controlling the characteristics of the leveed channels that develop. A more subtle segregation effect is studied in bidisperse roll waves, which form as small irregularities merge and coarsen as they move downslope, eventually growing into destructive large amplitude pulses. Experimental measurements show lateral, as well as vertical, segregation profiles, with the coarser grains accumulating at the fastest moving wave crests. The disturbances that form in mixtures with higher proportions of large particles grow more slowly, leading to smaller amplitude waves that travel at slower speeds, and the new coupled model predicts qualitatively similar behaviour. Finally, the influence of complex topography is investigated. A smooth two-dimensional bump is placed across the width of a chute, which, depending on the initial conditions, can lead to the formation of an airborne jet or granular shock at steady state. A simple depth-averaged model in a curvilinear coordinate system following the topography accurately captures both regimes, and represents a significant improvement on using an aligned Cartesian approach.

My dissertation consists of two essays on mutual funds. The first essay examines the role of extreme positive returns on future fund flows using maximum style-adjusted daily returns (hereafter MAX) over the previous month. My results suggest that there is a positive and significant relation between MAX and future fund flows. The results are robust to controls for fund performance, fund size, age, turnover, fund fees, volatility, and skewness of fund returns. Of particular interest, this relation exits only in retail funds. Moreover, MAX is persistent from one month to the next, but MAX-based investment strategies are associated with lower risk-adjusted returns than investors could have achieved in otherwise similar funds. Overall, my analysis suggests that mutual fund investors are attracted to maximum style-adjusted daily returns, which is in line with the theoretical argument that investors exhibit a preference for lottery-like payoffs. These investors are successful in achieving a lottery-like return profile, but this strategy is costly in terms of expected returns The second essay studies the effect of recent and long-term mutual fund performance on future fund flows. I document that investors' response to recent performance depends on average long-term performance. In particular, a recent loser fund experiences outflows only if its longer-term performance is also poor. Similarly, recent good performance leads to more inflows only if the fund has also good long-run performance. In contrast, investors ignore recent performance if it provides a signal that conflicts with the longer-term signal. This implies that good fund managers with a longer-term focus will find it easier to attract future inflows than managers with a short-term horizon.

Wo, Weifeng. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 99-102). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

This investigation studies the leakage flows over the high pressure turbine blade tip at high speed flow conditions. There is an unavoidable gap between the un-shrouded blade tip and the engine casing in a turbine stage, where the pressure difference between the pressure and the suction surfaces of the blade gives rise to the development of leakage flows through this gap. These flows contribute to about one third of the aerodynamic losses in a turbine stage. In addition they expose the blade tip to a very high temperature and result in thermal damages which reduce the blade‟s operational life. Therefore any improvement on the tip design to reduce these flows has a significant impact on the engine‟s efficiency and turbine blade‟s operational life. At the engine operational condition, the leakage flows over the high pressure turbine blade tip are mostly transonic. On the other hand literature survey has shown that most of the studies on the tip leakage flows have been performed at low speed conditions and there are only a few experimental works on the transonic tip flows. This project aims to explore the tip leakage flows at high speed condition which is the real engine condition, both experimentally and computationally and establish a comprehensive understanding of these flows on different tip geometries. The effect of tip geometry was studied using the flat tip and the cavity tip models and the effect of in-service burnout on these two tip models was established using the radius-edge flat tip and the radius-edge cavity tip models. The experimental work was carried out in the transonic wind tunnel of Queen Mary University of London and the computational simulations were performed using RANS and URANS. As the flow approached each tip model it turned and accelerated around its leading edge in the same way as the flow turns around the leading edge of an aerofoil. In the case of the tip models with sharp edges the tip flow separated at the inlet to the tip gap. For the flat tip model the flow reattachment occurred further downstream whereas in the case of the cavity tip model the length of the pressure side rim was not sufficient for the reattachment to occur and the separated flow left the rim as a free shear layer. The cavity tip model was found to have a smaller effective tip gap and hence smaller discharge coefficient in comparison to the flat tip model. For the radius-edge tip models, no separation occurred at the inlet to the tip gap and the effective tip gap was found to be the same as the geometrical tip gap. Therefore it was concluded that the tip model with radius-edges had a larger effective tip gap and hence a greater discharge coefficient than the tip geometry with sharp edges. It was observed that in the case of the supersonic tip leakage flows, decreasing the pressure ratio PR (i.e. the ratio of the static pressure at the tip gap exit to the stagnation pressure at the inlet to the tip gap) increased the discharge coefficient Cd for the tip models with sharp edges but it decreased the Cd value in the case of the tip models with radius edges. The cavity tip model with sharp edges was found to have the smallest discharge coefficient and thus the best performance in reducing the tip leakage flows as compared to all the other tip models studied in this investigation.

Effusive volcanic eruptions repave landscapes rapidly with lava flows, resetting the underlying landscape and ecosystem. The unique physical properties of lava pose interesting challenges for recovery, as lava flows can be highly permeable while lava itself is dense, sterile, and generally inhospitable towards life. This dissertation examines two aspects of landscape recovery following lava flow emplacement: (1) hydrologic adaptation of surface and groundwater to recent volcanism and (2) plant colonization of young lava flows. I examine two sites in the central Oregon Cascades: the c. 3 ka Sand Mountain volcanic field (SMVF), located in the headwaters of the McKenzie River, a critical water resource for the state of Oregon, and the c. 1.5 ka Collier Cone lava flow, originating on the north flanks of North Sister volcano. My investigation of the SMVF and upper McKenzie River watershed reveals a complex volcanic history with profound impacts on the configuration and short-term discharge of the McKenzie River: lava flows from the SMVF and other Holocene vents have buried, dammed, and altered the path of the McKenzie River. Moreover, given the large groundwater contribution from the SMVF to the McKenzie River, I estimate that SMVF activity caused McKenzie River discharge in present-day Eugene, Oregon to decrease by up to 20% for days to months at a time; future regional mafic volcanic activity could have a similar impact. The SMVF and the Collier Cone lava flow are notable for the juxtaposition of barren exposed lava and mature forests on the same or similarly aged lava flows. I use a combination of LiDAR analysis, field observations, and soil characterization to examine soil and vegetation at these two sites and find that the presence of an external soil source greatly facilitates plant establishment, growth, and survival. Here, external soil sources are syn- or post-eruptive tephra (SMVF) or flood-borne deposits (Collier Cone lava flow). External soil appears to provide a substrate for plants to grow in along with key nutrients and sufficient moisture; overall, external soil sources are key for the initial recovery following an effusive volcanic disturbance. This dissertation includes co-authored material submitted for publication.