This thesis presents an investigation into the dynamics of vortex rings impacting a sharply-stratified density interface. This problem has a long history and is important for understanding how individual eddies in stratified turbulence mix the density field. We tackle this problem using a combination of experimental, numerical and modelling techniques to understand the flow instability and subsequent mixing induced by the impinging vortex ring. Our findings demonstrate that there exists a critical Richardson number, corresponding to a mixing transition, beyond which the mixing efficiency is constant. Using a novel Stereo Particle Image Velocimetry (Stereo-PIV) technique, we analyze a series of vortex ring experiments. By amalgamating an ensemble of these experiments, we measure the full, time-resolved, three-dimensional velocity field of the vortex-ring interaction. These measurements capture the instability that is produced on the baroclinically generated vorticity field. This instability is identified as a Crow-like instability. At low Richardson numbers, the timescale of the interface rebound is faster than that of the instability. As a result, there exists a critical Richardson number below which the Crow-like instability will not have sufficient time to grow to large amplitude. By generating a large number of vortex-ring interactions, we measure the incremental change to the stratification. After an initialization period, there is strong evidence to suggest that the mixing due to each vortex ring becomes constant over a moderate range of Richardson numbers. We suggest that the mixing efficiency of the vortex rings does drop at low Richardson numbers (below unity) in agreement with the analysis of the Stereo-PIV measurements. A model of the system accurately predicts the dependence of the mixing rate on the Richardson number. Based upon our study of the vortex-ring system, we construct a one-dimensional turbulence model that includes the energy advection from the vortex rings. This model is validated with both physical experiments and numerical simulations of repeated vortex-ring generations. The constant mixing efficiency regime is recovered in all three methodologies. Through examining the detailed dynamics of the flow, this work suggests that there exists a critical Richardson number corresponding to a transition between mixing regimes, and that this critical Richardson number is a result of the growth of a Crow-like instability. We have highlighted how to improve current mixing-models to capture this physics. New avenues of future research are currently underway to study the mixing produced by a stratified mixing-box experiment in light of these new developments.

The use of remotely sensed imagery (e.g. Landsat TM) for developing forest inventory strata has become increasingly more common in recent years as data have become more readily available. Errors are inherent with the use of this technology, either from user mis-classification of conditions represented in the imagery or due to flaws in the technology. Knowledge of these errors is important, as they can inflate the variance of inventory estimates. Forest inventory estimates from the Mississippi Institute for Forest Inventory (MIFI) were applied to determine the extent that classification errors affect volume and area estimates. Forest strata (e.g. hardwood, mixed, and pine) determined by the classification of imagery and used for inventory design were compared with field verification data obtained during the inventory. Mis-classified plots were reallocated to their correct strata and both area and volume estimates were obtained for both scenarios (i.e. mis-classified and correctly classified plots). The standard error estimates for mean and total volume decreased when plots were re-allocated to their correct strata. Mis-classification scenarios were then performed, introducing various levels of mis-classification in each stratum. When the scenarios were performed for the Doyle volume unit the statistical efficiencies were larger than for cubic foot volume. Care should be taken when utilizing moderate resolution satellite imagery such as Landsat TM as image mis-classification could lead to large losses in the precision of volume estimates. The increased efficiency obtained from a correct classification/forest stratification scheme, as demonstrated here, could lead to the exploration of additional image classification methods or the use of higher resolution satellite data. Knowledge of these errors in advance could be useful to investors seeking a minimum-risk area for a forest products mill location.

Although sampling techniques have been used effectively in education research and practice it is not clear how stratified random sampling techniques apply to high-stakes testing in the current educational environment. The present study focused on representative sampling as a possible means for reducing the quantity of state-administered tests in Texas public education. The purpose of this study was two-fold: (1) to determine if stratified random sampling is a viable option for reducing the number of students participating in Texas state assessments, and (2) to determine which sampling rate provides consistent estimates of the actual test results among the population of students. The study examined students’ scaled scores, percent of students passing, and student growth over a three-year period on state-mandated assessments in reading, mathematics, science, and social studies. Four sampling rates were considered (10%, 15%, 20%, & 25%) when analyzing student performance across demographic variables, including population estimates by socioeconomic status, limited English proficiency, and placement in special education classes. The data set for this study included five school districts and 68,641 students. Factorial ANOVAs were used initially to examine the effects of sampling rate on bias in reading and mathematics scores and bias in percentage of students passing these tests. Also 95% confidence intervals (CIs) and effect sizes for each model were examined to aid in the interpretation of the results. The results showed main effects for sampling rate and campus as well as a two-way interaction between these variables. The results indicated that a 20% sampling rate would closely approximate the parameter values regarding the mean TAKS reading and mathematics scale scores and the percentage of students passing these assessments. However, as population size decreases, sampling rate may have to be increased. For example, in populations with 30 or fewer students in a subgroup it is recommended that all students be included in the testing program. This study situated in one state contributes to the growing body of research being conducted on an international basis in sample-based educational assessments.

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A set of second-moment closure turbulence models are implemented for the study of wake evolution in an oceanic environment. The effects of density stratification are considered, and the models are validated against laboratory experiments mimicking the stratified ocean environment, and against previous experimental study of wakes subjected to a density stratification. The turbulence models are found to reproduce a number of important behaviors which differentiate stratified wakes from those in a homogeneous environment, including the appropriate decay rates in turbulence quantities, buoyant suppression of turbulence length scales, and canonical stages in wake evolution. The existence of background turbulence is considered both through the introduction of production terms to the turbulence model equations and the replication of scale-resolved simulations of wakes embedded in turbulence. It is found that the freestream turbulence causes accelerated wake growth and faster decay of wake momentum. Wakes are then simulated at a variety of Re and Fr representative of full-scale vehicles operating in an ocean environment, to downstream distances several orders of magnitude greater than existing RANS studies. The models are used to make some general predictions concerning the dependence of late-wake behavior on these parameters, and specific insights into expected behavior are gained. The wake turbulence is classified using "fossil turbulence" and stratification strength criteria from the literature. In keeping with experimentally observed behavior, the stratification is predicted to increase wake persistence. It is also predicted that, regardless of initial Re or F r, the wake turbulence quickly becomes a mixture of overturning eddies and internal waves. It is found that the high Re wakes eventually become strongly affected by the stratification, and enter the strongly-stratified or LAST regime. Additional model improvements are proposed based on the predicted late wake behavior. / Doctor of Philosophy / A set of advanced turbulence models are implemented and used to study ship wakes in an oceanic environment. The flows in the ocean are subject to a density stratification due to changes in temperature and salinity; the associated effects are included in the turbulence models. The models are validated against laboratory experiments mimicking the stratified ocean environment, and against previous experimental study of wakes subjected to a density stratification. The turbulence models are found to reproduce a number of important behaviors expected under such conditions based on experimental study. Additional modifications are made to the models to include the effect of pre-existing freestream turbulence. Wakes are then simulated under conditions representative of full-scale vehicles operating in an ocean environment. The models are used to make some general predictions concerning late-wake behavior. Specific insights into expected behavior are gained. The wake turbulence is classified using ``fossil turbulence'' and stratification strength criteria from the literature. In keeping with experimentally observed behavior, the stratification is predicted to increase wake persistence. Additional model improvements are proposed based on the predicted late wake behavior.

The speed and efficiency of stratified turbulent mixing in homogenising temperatures, chemical composition and flow speeds makes it one of farthest reaching fluid mechanical phenomenon for life on earth. It is an aesthetically beautiful phenomenon, rich in complex physical behaviours and extremely challenging to model mathematically. Laboratory experiments have a valuable role to play to guide theoretical and numerical work towards a better understanding of this phenomenon by providing insight into real flows under controlled conditions. This dissertation addresses some aspects of the laboratory buoyancy-driven exchange flows through an inclined duct connecting two reservoirs containing fluids of different densities. We employ a novel experimental technique to perform near-instantaneous, volumetric measurements of the three-component velocity field and density field simultaneously, providing an unprecedented quantitative picture of these sustained stratified shear flows. We start by characterising the variety of observed behaviours, or flow regimes, as we vary the density difference between the two reservoirs, the angle of inclination of the duct with respect to the horizontal, the way the density difference is achieved (solutions of salt/fresh water or cold/warm water) and the geometry of the duct. These empirical observations allow us to formulate a number of specific research questions, guiding the work of the next chapters. We then focus on the regime in which Holmboe waves are observed, and demonstrate that these well-known interfacial travelling disturbances have a distinct structure when confined by solid boundaries. We characterise this structure and identify the physical mechanisms at its origin by means of linear stability theory. Since Holmboe waves are found in the intermediate, transitional regime between laminar and turbulent flows, we conjecture that their structure may be relevant to more turbulent flows, where resembling structures are indeed observed. Next, we tackle the quantitative analysis of universal transition curves separating the observed flow regimes (laminar, waves, intermittently turbulent or fully turbulent) as well and the net mass flow rate exchanged by the reservoirs. We show that these long-lasting questions in the study of exchange flows can be addressed in the framework of frictional hydraulic theory, and we derive detailed scaling laws involving only a few nondimensional parameters. Finally, we overcome some of the limitations of hydraulic theory by performing a more detailed, time-resolved, three-dimensional analysis of the energetics of the wave, intermittent and turbulent regimes. We identify and quantify the sources and sinks of energy in each regime, and identify some of the structures responsible for viscous energy dissipation and mixing. We also suggest possible future directions for the present work given recent progress in the literature.

This action research project with district health councils (DHCs) in Ontario, Canada, took place between 1976 and 1980. The purpose of the research was to identify the most effective forms of organization for DHCs, bodies set up to provide a local focus for planning and coordination of health services in the Province. The research method was based on social analysis, a method developed over thelast thirty years through applications in industrial, commercial, health, education and social service settings. The first DHC was created in 1974 to serve the Ottawa-Carleton Region and there are now 25 DHCs covering 88% of the provincial population. Councils are generally regarded as community bodies, consisting of interested local citizens who serve on a voluntary, unpaid basis. The members comprise a mixture of 'providers', 'consumers' and local government representatives. The intensive research work was carried out in collaboration with three DHCs (Hamilton-Wentworth, Kenora-Rainy River and Ottawa-Carleton) and the emerging research findings were tested in a wide variety of settings including a number of the other DHCs. The first two chapters attempt to set the DHCs in an organizational and political context. Chapter 1 looks at the development of DHCs vis a vis other social developments, particularly regionalisation and decentralisation. Chapter 2 examines the political context in which DHCs emerged and identifies the policy tensions that are inherent in their work. In Chapter 3 a detailed account is given of the three intensive research settings and the organizational developments that took place during the course of the research. This chapter is in effect a summary of the whole research project. Chapter 4 is concerned with the nature and composition of councils, the roles of DHC member and chairman, and relationships among the DHCs. The research findings on alternative models of DHC structure are in Chapter 5 and 6, respectively concentrating on the Council and its committees and on the executive staff of council. The focus lengthens again in the concluding chapter to examine the potential for making overall judgements about the effectiveness of DHCs and the implications of this organizational study for other experiments in community-based health planning.

Management writers have emphasised that both new product development and innovation need to be stimulated in corporations if they are to prosper (Kanter, 1983; Lawrence and Dyer, 1983; Ouchi, 1981; Pascale and Athos, 1981) and they have focused mainly on issues of marketing and organisational behaviour and only to a limited extent on job autonomy. In the thesis aspects of team leader autonomy in new product development companies are investigated critically and empirically. The empirical study is based on data obtained from fifteen semi-structured interviews and two questionnaire surveys. The problems of managing and monitoring team leaders is discussed and conceptually represented in an improved definition of 'autonomy' originally proposed by Bailyn (1985). Autonomy is characterized in multi-dimensional terms and provides a new approach to understanding the complexity of team leader autonomy. Following a review of the literature and a grounded theory analysis of the pilot interview data, a number of common manifestations of autonomy were identified and subdivided into 'operational' and 'strategic' components. The findings of the pilot and main questionnaire studies into the level of team leader autonomy granted by top management are reported and analysed using correspondence analysis. 'Strategic' autonomy is found to reside primarily with senior management whilst team leaders are delegated more 'operational' autonomy. The literature on innovation cautions against too much hierarchical control but also draws attention to the top management dilemma of exercising responsibility and control of strategic tasks without stifling employees' technical competence and entrepreneurialism. A major finding from the main study is that in high technology types of company, management shares 'strategic" responsibilities with the team leader more than in other types of company. Top management cannot abrogate responsibility for directing and managing the company but, it is argued, a number of the strategic tasks could become more the responsibility of the team leader.

This thesis is concerned with some features of natural language in sociological argument and the implications of the presence of such features in such arguments for the satisfaction of the arguments. Part I describes some 'troubles' that natural language can occasion scientific methodology in research settings. It looks specifically at the damage to finality and uniqueness in questionnaire and interview interpretation. Part II describes four ways in which natural language may facilitate sociological arguments! by presentation devices; in display of author as credible; in transfer of materials in citation and in the invocation of common sense. It is suggested, then that natural language acts as a 'trouble' and a resource, the resource possibly repairing the trouble.

This essay is constructed around an empirical relationship which it attempts to interpret in terms of concepts and propositions of economic theory. This interpretation is necessary because the conceptual variables which enter the relationship as well as the method of their empirical measurement and the hypothesis of "causal" relation between them were not originally derived from economics, theoretical or applied. The principal concepts involved are called 'time-span of discretion1 (TSD), 'felt fair pay1 (FFP) and 'capacity1 (C). They are an original discovery, in a field where concepts and theory are scarce, of Elliott Jaques and the team of researchers who subsequently formed the Glacier Institute of Management. These three concepts are the principal elements of the structure for a theory of the evolution of organisational institutions. It is inside these institutions that the reality of work and payis found in present industrial society . . .