A typical problem in traffic control is the steering over a network of vehicles with different origins and destinations. In this report this scenario is formulated as a multi-commodity network flow problem, a linear programming problem whose objective is to transport, with minimum cost, different commodities from their respective sources to their sinks through a network, while respecting the capacity constraints of the roads. The dynamic network flow formulation of the problem is also presented, extending the network over time to incorporate the temporal dimension. Different algorithms for solving the multi-commodity network flow problem are examined. First, the simplex method, more precisely its revised version, is considered, and then the Dantzig-Wolfe decomposition is illustrated, an optimization algorithm which exploits specific block structures in the constraints. These methods are applied using state-of-the-art linear programming solvers and evaluated with a simulation based on the road network in central Stockholm. The results show that both methods allow for solving the traffic flow problem, with limitations given by the specifics of the solvers and by the space and time discretization of the problem. In particular, the revised simplex algorithm results the faster method.

This study aims to understand the impact of organizational learning on project portfolio success in a multinational Oil and Gas company operated in Indonesia. The Organizational Learning and Project Portfolio Success have been proven to have contribution to business performance and they might possess a relationship where enhancing one of them will strengthen the other. Exploring on this relationship might give beneficial input to the organization in order to maximize their success.  Thus, our research question is formulated as: To what extent does Organizational Learning impact the Project Portfolio Success? We developed the study’s conceptual model based on the relevant previous literature. The conceptual model depicted the aim of the study to test the potential positive impact of each Learning Stocks (Individual, Group, and Organizational) on Project Portfolio Success, as well as the aim to test the potential negative impact of the misalignment between Learning Stocks and Learning Flows on Project Portfolio Success in the studied company. We adopted quantitative research method due to the nature of research question and the ontological and epistemological assumptions we hold toward the studied phenomena. Accordingly, we used a questionnaire as an instrument to collect the required data to test the hypotheses. The questionnaire was subject to a pilot test to ensure the clarity of statements before it was distributed to the targeted respondents which are the managers and the Project Management Office personnel in the studied company. The research hypotheses were tested by applying single and multi-regression analyses using SPSS software. Our findings showed that, independently, each learning stock type (Individual, Group and organizational) has a significant positive impact to project portfolio success. When we looked for the best model that gives the highest explanatory power, the result showed that the combination of all three learning stocks in one model can explain project portfolio success construct the most. Lastly, the study proved that the misalignment between learning stocks and flows gives negative impact to the project portfolio success. We concluded the study by stating the theoretical contribution and practical recommendations based on the results such as the need to have a balanced investment in the individual, group and organizational learning stocks; ensure the alignment between the organizational units’ strategies and goals; develop an “Internal Strategy Awareness Index”; and conduct a revision of the alignment between the company’s strategy and the project portfolio.

While worker flow analysis has grown in importance in many countries, Austria still lacks a specific longitudinal dataset as a prerequisite to perform similar analyses. For this reason, this article provides a coherent procedure to construct a longitudinal dataset based on the rotational panel structure of the Austrian quarterly LFS from 2004 to 2014. The procedure, which is available for researcher, is grounded on the discussion of several related and important issues inherent in constructing this sort of longitudinal data: First, it deals with the construction of the quarterly-matched dataset and the quality-of-measurement of several labour market variables. Second, the paper analyses non-response as a sample selection process, and shows that the selected (quarterly-matched) dataset causes biased estimates of worker flows. Third, the article proposes an iterative raking procedure to obtain survey weights as a bias-correcting device for any future analysis. Based on these adjustments, we present unbiased time-series of worker flows and transition rates, and conclude that the employment-unemployment margin is highly sensitive to economic shocks and that the Austrian labour market is additionally shaped by large movements within the participation margin. (authors' abstract) / Series: Department of Economics Working Paper Series

This thesis analyses and compares the performance, performance persistence and fund flows for UK equity unit trusts/OEICs and UK equity unit-linked personal pensions over the sample period January 1980 to December 2007. Unit-linked personal pension funds are an illiquid investment from the investor’s perspective since any invested capital is inaccessible until retirement whereas for unit trusts/OEICs capital invested can be withdrawn at any time. Since decreasing returns to scale from fund flows are the equilibrating mechanism in Berk and Green (2004) that results in no persistence in performance the illiquid nature of unit-linked personal pension funds should ensure more evidence of performance persistence in comparison to unit trusts/OEICs. I find significant evidence using performance ranked portfolio strategies that underlying portfolios that are only composed of unit-linked personal pension funds have greater performance persistence than unit-linked personal pension funds that have underlying portfolios that also include at least a unit trust/OEIC. This evidence is consistent with Berk and Green (2004) since the illiquid nature of personal pension funds results in an attenuated performance fund flow relationship restricting the equilibrating mechanism. However, there are anomalies in the performance persistence results in relation to Berk and Green (2004) but it could be due to the differential between the number of non-surviving unit trusts/OEICs and non-surviving unit-linked personal pension funds. I also find that the performance fund flow relationship based on abnormal returns from a Carhart four factor model for both UK equity unit trusts/OEICs and UK unit-linked personal pensions is convex but the performance fund flow relationship is more attenuated for the unit-linked personal pension funds. For the worst performing unit trusts/OEICs there are outflows on average whereas for unit-linked personal pensions there are fund inflows on average. For performance persistence tests conditional on underlying portfolio fund flows unit trusts/OEICs that have the worst performance but the lowest net fund flows in the ranking period have significantly greater subsequent performance in comparison to the unit trusts/OEICs that have the worst performance but the highest net fund flows in the ranking period. This empirical evidence provides support for Berk and Green (2004) but for the unit-linked personal pension funds the evidence is less convincing. There is very little evidence that UK equity unit-trusts/OEICs or UK equity unit-linked personal pensions produce abnormal returns. These results are robust across the single index (CAPM) model, the Fama and French three factor model and the Carhart four factor model for both conditional and unconditional models. There is also no evidence that unit trusts/OEICs or unit-linked personal pension funds can time the market. There is a significantly negative timing effect across unconditional factor models which becomes insignificant for the conditional models. There is also no evidence that unit trusts/OEICs have significantly different performance than unit-linked personal pension funds.

Downslope flows and regions of enhanced cooling have important impacts on society and the environment. Parameterisation of these often subgrid-scale phenomena in numerical models requires a sound understanding of the underlying physical processes, which has been the overarching aim of this work. A numerical model has been used to characterise the development of a region of enhanced cooling in an idealised alpine valley with width and depth of order 10 and 1 km, respectively, under stable, decoupled, poorly-drained conditions. A focus of this work has been to remove the uncertainty surrounding the forcing mechanisms behind the development of regions of enhanced cooling. The average valley-atmosphere cooling has been found to be almost equally partitioned between radiative and dynamics effects. Complex interactions between the downslope flows and the region of enhanced cooling have been quantified for the first time. For example, relatively large variations in the downslope flows are generally restricted to the region of enhanced cooling and cannot solely be attributed to the analytical model of [McNider, 1982a]. These flow variations generally coincide with return flows above the downslope flows, where a thin region of unstable air occurs, as well as coinciding with elongated downslope flow structures. The impact of these interactions on the dispersion of passive pollutants has been investigated. For example, pollutants are generally trapped within the region of enhanced cooling. The concentration of pollutants within the region of enhanced cooling, emitted over the lower half of the slopes, increase as the emission source moves away from the ground-based inversion that expands from the bottom of the valley. The concentration of pollutants within the region of enhanced cooling is very similar when varying the location of the emission source over the top half of the valley slopes. This work includes a test of the effects of varying the horizontal numerical grid resolution on average valley-atmosphere temperature changes.

Energy audit and calculation strategies for energy flows in buildings: a case study of Vallongatan 1   This thesis involves an energy audit of a building with offices and laboratories in Uppsala, Sweden. The calculations are performed in Microsoft Excel and were later used as the basis for developing calculation strategies for similar, future, energy audits.   The building was erected in the early 1990s and the heating requirement of just above 700 MWh is covered by district heating from the city network. The total gross floor area is about 8400 m2 and is served by an air conditioning system consisting of seven ventilation units with rotary heat exchangers, heating and cooling coils, as well as water radiators throughout the building.   No significant improvement measures have been implemented since the construction, and the building therefore has a potential to improve its energy performance. The report addresses a number of measures that could be taken, as well as an evaluation of each one. The most economically viable of these would be to clean the rotary heat exchangers, which is deemed to have a potential to save about 70 MWh or 48 700 SEK annually. In comparison to the estimated cost of between 35 000 and 42 000 SEK this is likely to become profitable as early as the first year.   The calculation templates that were developed cover three different building standards, these are categorized as low, improved and advanced standard. Here, the desired areas and types of activities are typed in easily for either individual rooms or entire offices or buildings. The templates provide estimates regarding power and energy needs for heating and comfort cooling, recommended air flows, heat development and dissipation as well as carbon dioxide concentration in the room air.

A study of the use of solution adaptive grid (SAG) method for simulations of incompressible flows is carried out in this work. Both laminar and turbulent types of flows are chosen. Investigation on laminar flow simulation starts with mesh adaptation criteria that are based on strong changes of some selected flow parameters; pressure and velocity components. Three most common laminar types of flows are studied; flow in a circular pipe, flow in a channel with sudden expansion and flow in a cavity with a moving lid. It is found that with the use of SAG, a reduction in both computational grid nodes and CPU time can be obtained when compared to those of fixed grid while satisfactory solutions are also achievable. Nevertheless, the refinement criteria setup procedure reveals inconveniences and requirement for several judgments that have to be defined ‘ad hoc’. This hence, makes the refinement criteria dubious for real engineering applications. For the study of turbulent flows with large eddy simulation (LES) and implicit filtering, examination of literature reveals that the lack of connections between the filter width and a physical scale has made LES somewhat unclosed, i.e. in a physical sense. In addition, it is known that numerical and modelling errors are always combined and it is difficult to study each of them separately making the total error magnitude difficult to control. Since both error types are characterised by the grid size, LES users very often find cases where a finer mesh no longer provides better accuracy. An attempt to address this ‘physical’ enclosure property of LES and its complication to implement/setup in FLUENT begins with the construction of a new refinement variable as a function of the Taylor scale. Then a new SAG algorithm is formed. The requirement to satisfy a condition of the selected subgrid scale (SAG) model, the Smagorinsky model, is taken into consideration to minimize the modeling error. The construction of a new refinement algorithm is also aimed to be the key to studying the interaction between the two types of error and could lead to the means of controlling their total magnitude. The validation in terms of its effectiveness, efficiency and reliability of the algorithm are made based on several criteria corresponding to suitability for practical applications. This includes the simplicity to setup/employ, computational affordability, and the accuracy level. For this, two different turbulent flow types that represent different commonly found turbulent phenomena are chosen; plane free jet and the flow over a circular cylinder. The simulations of the two cases were carried out in two dimensions. It is found that there are two key factors that strongly determine the success of the algorithm. The first factor is the Taylor scale definition, with literature only available for the turbulent plane jet study, for which good level of accuracy is expected. Unfortunately, this is not true for the flow over a circular cylinder, indicating a need for further analytical work. The second encountered difficulty results from limited access to software codes, which makes it impossible to implement the proposed scheme. As a result, the algorithm formulation needs be modified with carful judgment. Nevertheless, overall results are in reasonably good agreement with their corresponding experimental data.

There are four chapters in my dissertation. Chapter one gives a brief introduction of the three essays. Chapter two studies the choice of exchange rate regimes in East Asia using a business-cycle approach. My results suggest that countries in East Asia are driven mainly by country-specific shocks, making more rigid exchange rate regimes less desirable. Neither a yen bloc nor a dollar bloc has been identified in East Asia. However, Japan seems more influential to countries such as Korea and Taiwan. An optimum currency area does not seem feasible for East Asia, at least in the short run. Chapter three applies the cointegration and causality analyses to the real effective exchange rates to study the degree of monetary integration in East Asia. I find that the ASEAN and the NIE countries, respectively, have achieved some degree of integration, but not East Asia as a whole. The yen is found to move closely with the NIE currencies. However, neither the yen nor the dollar imposes a dominant driving force on the East Asian currencies. My results suggest that East Asia is not an optimum currency area. Chapter four expands the traditional monetary model of exchange rate determination into a structural VAR model incorporating various capital flows and the balance of trade in addition to the macroeconomic fundamentals. The model is then applied to the Australian dollar (AUD), the Canadian dollar (CAD), and the US dollar (USD) exchange rates over 19802004. I find that capital flows, especially portfolio investments, explain a major portion of the exchange rate fluctuations in the relatively small and open economies such as Australia and Canada in the short-to-medium run. The impacts of capital flows are limited to the US dollar exchange rates. Among the macroeconomic fundamentals, the interest rate plays an important role in exchange rate determination for all three currencies. The results imply that different capital flows do influence exchange rates differently and are important determinants of exchange rates.

Plasma synthetic jet actuators are investigated experimentally, in which the geometrical design of single dielectric barrier discharge (SDBD) plasma actuators is modified to produce zero-mass flux jets similar to those created by mechanical devices. The SDBD plasma actuator consists of two rectangular electrodes oriented asymmetrically and separated by a layer of dielectric material. Under an input of high voltage, high frequency AC or pulsed DC, a region of plasma is created in the interfacial air gap on account of electrical breakdown of the ambient air. A coupling between the electric field in the plasma and the neutral air near the actuator is introduced, such that the latter experiences a net force which results in a horizontal wall jet. This effect of the actuator has been demonstrated to be useful in mitigating boundary layer separation in aerodynamic flows. To increase the impact that a plasma actuator may have on the flow field, this research investigates the development and characterization of a novel flow control device, the plasma synthetic jet actuator, which tailors the residual air in the form of a vertical jet resembling conventional continuous and synthetic jets. This jet can be either three dimensional using annular electrode arrays, or nearly two dimensional using two rectangular strip exposed electrodes and one embedded electrode. Detailed measurements on the isolated plasma synthetic jet reveal that pulsed operation of the actuator results in the formation of multiple counterrotating vortical structures in the flow field. The output jet velocity and momentum are found to be higher for unsteady pulsing as compared to steady operation. In the case of flow over a flat plate, the actuator is observed to create a localized interaction region within which the baseline flow direction and boundary layer characteristics are modified. The efficiency of the actuator in coupling momentum to the neutral air is found to be related to the plasma morphology, pulsing frequency, actuator dimension, and input power. An analytical scaling model is proposed to describe the effects of varying the above variables on the output jet characteristics and actuator efficiency, and the experimental data is used for model validation.

A new approach to large-eddy simulation (LES) based on the use of explicit spatial filtering combined with backscatter forcing is presented. The forcing uses a discrete dynamical system (DDS) called the compressible ``poor man's'' Navier--Stokes (CPMNS) equations. This DDS is derived from the governing equations and is shown to exhibit good spectral and dynamical properties for use in a turbulence model. An overview and critique of existing turbulence theory and turbulence models is given. A comprehensive theoretical case is presented arguing that traditional LES equations contain unresolved scales in terms generally thought to be resolved, and that this can only be solved with explicit filtering. The CPMNS equations are then incorporated into a simple forcing in the OVERFLOW compressible flow code, and tests are done on homogeneous, isotropic, decaying turbulence, a Mach 3 compression ramp, and a Mach 0.8 open cavity. The numerical results validate the general filter-forcing approach, although they also reveal inadequacies in OVERFLOW and that the current approach is likely too simple to be universally applicable. Two new proposals for constructing better forcing models are presented at the end of the work.