The three essays in this dissertation progressively answer the following questions: (a) How important are constraints? (b) Who benefits from removing constraints? (c) When does a constraint for a single market predominantly affect closely related markets? These questions are applied in the context of time, weather, and minimum wage constraints, respectively. The first essay demonstrates that constraints matter. A data envelopment analysis capacity utilization methodology is used to measure impacts on sales from a sequential relaxation of the time and income constraints. Using a subsample bootstrap to estimate confidence intervals, results show that time matters more than income, particularly in fall and winter when other activities compete for gardening time. The second essay shows that the poor are least likely to gain from the relaxation of non-income constraints. A theory of demand is developed in which consumers face multiple constraints. Then, a structural model is used to econometrically estimate the effect of global warming on demand, using nursery data on flowering plants. The model shows that there exists a tipping point around 64 degrees Fahrenheit, above which demand ceases to be climate-constrained. The third essay shows that a constraint in a single market can sometimes have more profound consequences on other, more distantly related markets. First, it is proven that if a series of markets are structured like a chain-- where only own and neighboring prices matter--then a shock to one market decreases with distance. The case of minimum wages in Oregon is investigated using a large panel dataset for all workers in Oregon using a first difference econometric model. It is determined that the ripple effects of the minimum have even larger effects on higher-wage earners, disconfirming the chain pattern. High substitutions between low and high wage groups may explain the pattern. Altogether the essays further the understanding of constraints to demonstrate that (a) constraints significantly affect economic outcomes, (b) if one constraint is lifted, those individuals alternately-constrained are left behind from any benefits, and (c) constraints to a single market may have unintended and sometimes larger effects on 'farther' markets. / Graduation date: 2012

This thesis addresses the challenges in the efficient and robust generation and optimization of three-dimensional landing trajectories for fixed-wing aircraft subject to prescribed boundary conditions and constraints on maneuverability and collision avoidance. In particular, this thesis focuses on the airliner emergency landing scenario and the minimization of landing time. The main contribution of the thesis is two-fold. First, it provides a hierarchical scheme for integrating the complementary strength of a variety of methods in path planning and trajectory optimization for the improvement in efficiency and robustness of the overall landing trajectory optimization algorithm. The second contribution is the development of new techniques and results in mesh refinement for numerical optimal control, optimal path tracking, and smooth path generation, which are all integrated in a hierarchical scheme and applied to the landing trajectory optimization problem. A density function based grid generation method is developed for the mesh refinement process during numerical optimal control. A numerical algorithm is developed based on this technique for solving general optimal control problems, and is used for optimizing aircraft landing trajectories. A path smoothing technique is proposed for recovering feasibility of the path and improving the tracking performance by modifying the path geometry. The optimal aircraft path tracking problem is studied and analytical results are presented for both the minimum-time, and minimum-energy tracking with fixed time of arrival. The path smoothing and optimal path tracking methods work together with the geometric path planner to provide a set of feasible initial guess to the numerical optimal control algorithm. The trajectory optimization algorithm in this thesis was tested by simulation experiments using flight data from two previous airliner accidents under emergency landing scenarios.The real-time application of the landing trajectory optimization algorithm as part of the aircraft on-board automation avionics system has the potential to provide effective guidelines to the pilots for improving the fuel consumption during normal landing process, and help enhancing flight safety under emergency landing scenarios. The proposed algorithms can also help design optimal take-off and landing trajectories and procedures for airports.

Bien qu'il soit désormais établi que les institutions du travail (tel que la syndicalisation et le salaire minimum) aient eu pour effet de réduire l'inégalité des salaires entre les travailleurs au Canada et dans d'autres pays industrialisés, leur impact sur l'inégalité des revenus entre les familles ou les ménages reste incertain. Cette étude a pour but d'estimer l'impact de la densité syndicale et du salaire minimum réel sur l'évolution de l'inégalité des revenus de marché entre les ménages canadiens durant les années 1981 à 2008. À partir d'une base de données qui intègre des données annuelles agrégées par province, et en maintenant constant un ensemble de facteurs, les estimations par effets fixes indiquent que la densité syndicale a réduit l'inégalité des revenus mesurée au moyen du coefficient de Gini, alors que le salaire minimum réel a plutôt eu pour effet d'accroître celle-ci. Les résultats d'estimation indiquent également que le taux d'activité et la scolarité moyenne sont les principaux facteurs à avoir réduit l'inégalité des revenus, alors que le taux de chômage, le changement technologique (mesuré de différentes façons) et l'immigration récente ont contribué à l'accroître. / While some consensus exists that labor institutions (such as unionization and minimum wage) narrowed wages inequality among workers in Canada, as well as in other industrialized countries, there is little agreement about their outcome on income inequality among families or households. This study investigates how union density and real minimum wage affected the evolution of market income inequality among Canadian households between 1981 and 2008. Utilizing a dataset that incorporates annual data aggregated by province, and holding constant for a range of other factors, fix effects estimates indicate that union density narrowed income inequality as measured by the Gini coefficient, while real minimum wage widened it instead. Estimates further suggest that participation rate and educational attainment are the main factors to have dampened income inequality in recent years, whereas unemployment rate, technological change (measured in different ways) and recent immigration are found to have contributed to greater income inequality.

Multipath amplifier theory: In this thesis it is proven that the theoretical minimum noise measure of a multipath amplifier (an amplifier which has multiple parallel amplifiers) is achieved by using the optimum source impedance for the amplifier and the optimum gain for each amplification path. This optimum source impedance and gain can be calculated by using the optimum–loaded input network, i.e. by replacing each amplifier with its optimum source impedance. The resulting noise measure is the same as the minimum noise measure of the amplifiers used in the amplification paths. Whereas single–path amplifiers can achieve this minimum noise measure over narrow bandwidths, multipath amplifiers are theoretically able to achieve the minimum noise measure over very broad bandwidths. The theory is demonstrated by applying it to distributed amplifiers. In an ideal distributed amplifier, the magnitude of the optimum gain of the amplification paths decreases and the phase delay increases the farther the stage is from the input, with the decrease in gain being faster for higher frequencies. The challenge in designing broadband, low–noise, distributed amplifiers is to achieve optimum gain matching over broad bandwidths. Multipath amplifier design procedure: Based on the theory, a three step design and optimisation procedure is introduced. Firstly, unconditionally stable amplification paths are designed to have small minimum noise measures, then an input network is designed for optimum source impedance matching and lastly an output network is designed for gain matching. Multipath amplifier prototype: The theory and design procedure is demonstrated by optimising a 0.5–2 GHz distributed amplifier. An average noise measure of 0.3 dB is achieved, which is only 0.1 dB higher than the minimum noise measure of the amplification stages used. This increase is mainly due to transmission line loss and gain mismatch. Radio telescope feasibility: Multipath amplifiers break the trade–off between noise temperature, bandwidth and source termination that a single–path amplifier has, because they have much more design freedom when designing the input network. In general, the more paths, the larger the low–noise bandwidth, but the larger and more complex the amplifier. Roughly two to three amplification paths are required per octave of bandwidth for LNAs around 1 GHz. When the bandwidth is very narrow, a single path is sufficient. Multipath amplifiers have similar trade–offs between linearity and power consumption, between noise temperature and noise resistance, and between noise temperature and size to a single–path amplifier. Multipath amplifiers are therefore a feasible alternative for use in radio telescopes. / Thesis (Ph.D. (Space Physics))--North-West University, Potchefstroom Campus, 2011.

Acoustic modeling in state-of-the-art speech recognition systems is commonly based on discriminative criteria. Different from the paradigm of the conventional distribution estimation such as maximum a posteriori (MAP) and maximum likelihood (ML), the most popular discriminative criteria such as MCE and MPE aim at direct minimization of the empirical error rate. As recent ASR applications become diverse, it has been increasingly recognized that realistic applications often require a model that can be optimized for a task-specific goal or a particular scenario beyond the general purposes of the current discriminative criteria. These specific requirements cannot be directly handled by the current discriminative criteria since the objective of the criteria is to minimize the overall empirical error rate. In this thesis, we propose novel objective-driven discriminative training and adaptation frameworks, which are generalized from the minimum classification error (MCE) criterion, for various tasks and scenarios of speech recognition and detection. The proposed frameworks are constructed to formulate new discriminative criteria which satisfy various requirements of the recent ASR applications. In this thesis, each objective required by an application or a developer is directly embedded into the learning criterion. Then, the objective-driven discriminative criterion is used to optimize an acoustic model in order to achieve the required objective. Three task-specific requirements that the recent ASR applications often require in practice are mainly taken into account in developing the objective-driven discriminative criteria. First, an issue of individual error minimization of speech recognition is addressed and we propose a direct minimization algorithm for each error type of speech recognition. Second, a rapid adaptation scenario is embedded into formulating discriminative linear transforms under the MCE criterion. A regularized MCE criterion is proposed to efficiently improve the generalization capability of the MCE estimate in a rapid adaptation scenario. Finally, the particular operating scenario that requires a system model optimized at a given specific operating point is discussed over the conventional receiver operating characteristic (ROC) optimization. A constrained discriminative training algorithm which can directly optimize a system model for any particular operating need is proposed. For each of the developed algorithms, we provide an analytical solution and an appropriate optimization procedure.

Multipath amplifier theory: In this thesis it is proven that the theoretical minimum noise measure of a multipath amplifier (an amplifier which has multiple parallel amplifiers) is achieved by using the optimum source impedance for the amplifier and the optimum gain for each amplification path. This optimum source impedance and gain can be calculated by using the optimum–loaded input network, i.e. by replacing each amplifier with its optimum source impedance. The resulting noise measure is the same as the minimum noise measure of the amplifiers used in the amplification paths. Whereas single–path amplifiers can achieve this minimum noise measure over narrow bandwidths, multipath amplifiers are theoretically able to achieve the minimum noise measure over very broad bandwidths. The theory is demonstrated by applying it to distributed amplifiers. In an ideal distributed amplifier, the magnitude of the optimum gain of the amplification paths decreases and the phase delay increases the farther the stage is from the input, with the decrease in gain being faster for higher frequencies. The challenge in designing broadband, low–noise, distributed amplifiers is to achieve optimum gain matching over broad bandwidths. Multipath amplifier design procedure: Based on the theory, a three step design and optimisation procedure is introduced. Firstly, unconditionally stable amplification paths are designed to have small minimum noise measures, then an input network is designed for optimum source impedance matching and lastly an output network is designed for gain matching. Multipath amplifier prototype: The theory and design procedure is demonstrated by optimising a 0.5–2 GHz distributed amplifier. An average noise measure of 0.3 dB is achieved, which is only 0.1 dB higher than the minimum noise measure of the amplification stages used. This increase is mainly due to transmission line loss and gain mismatch. Radio telescope feasibility: Multipath amplifiers break the trade–off between noise temperature, bandwidth and source termination that a single–path amplifier has, because they have much more design freedom when designing the input network. In general, the more paths, the larger the low–noise bandwidth, but the larger and more complex the amplifier. Roughly two to three amplification paths are required per octave of bandwidth for LNAs around 1 GHz. When the bandwidth is very narrow, a single path is sufficient. Multipath amplifiers have similar trade–offs between linearity and power consumption, between noise temperature and noise resistance, and between noise temperature and size to a single–path amplifier. Multipath amplifiers are therefore a feasible alternative for use in radio telescopes. / Thesis (Ph.D. (Space Physics))--North-West University, Potchefstroom Campus, 2011.

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The theoretical portion of the work dealt with the state social support, its individual allowances and the current problems related to the situation in public funds. The first main objective of the work and its partial objectives identified opinions of beneficiaries and of the broader public regarding changes in the system of the state social support introduced by Act no. 261/2007 Coll. To test the hypotheses and to collect primary data the author used qualitative research {--} the interviewing method and the questionnaire technique. Three hypotheses were determined in the degree work. The performed research confirmed hypotheses 1 and 2, whereas it did not confirm hypothesis 3. The mapping of the experience gained by administrators of the state social support system in relation to changes arising from Act no. 261/2007 Coll. was the second main objective of the work. This objective was fulfilled by complementary qualitative research which identified the experience of administrators of the state social support system with the researched changes. The interviewing method, the technique of a free dialogue was used for this purpose. One hypothesis came out of this qualitative research. The work looks back at more than a year of effect of the Act on stabilization of public budgets and at the impact of changes which this Act introduced in the system of the state social support.

Several studies have shown that prices differ across regions and affect standards of living substantially. This thesis investigates whether they cause the differential impact of minimum wage on employment and hours of work across the European Union NUTS 2 regions. Based on the existing regional price estimates of 7 European Union countries and publicly available aggregate regional data, estimates of regional price levels for another 11 European Union countries with minimum wage are obtained. The method that was used for this purpose (multiple imputation) enables to use the resulting estimates as an explanatory variable in another regression as it takes into consideration using imputed instead of observed values by correcting the variances of parameter coefficients. The impacts of minimum wage are investigated for 3 groups of people who are at risk of being affected by its increase - young adults (15-19 years), low-educated individuals and low-skilled individuals. The results indicate that the minimum wage has a negative impact on employment that is higher in regions with higher price levels. The negative effect of minimum wage on hours of work was not confirmed.

In 2011, vertical and longitudinal gradients of temperature, oxygen, pH, conductivity and chlorophyll were measured in the Římov Reservoir. Relative distance model was employed to evaluate spatial heterogeneity of parameters measured along the longitudinal axis of the reservoir. The inflow part comprised 15 % of the overall reservoir length and was characterized with temperature, pH and chlorophyll values lower than the rest of the reservoir. Highest chlorophyll and dissolved oxygen concentrations along with pH were measured in the transition zone constituting 40 % of the reservoir length. Lacustrine zone with low chlorophyll concentration accounted for 45 % of the reservoir. It was characterized with pronounced metalimnetic and hypolimnetic oxygen minima during summer as well as the marked increase in conductivity towards bottom.