Forest management strategies directly affect landowner welfare, and factors ranging from natural disturbances to institutional environments play important roles in influencing the outcomes for both landowners and society. This dissertation, consisting of three essays, delves into the forest sectors in both developed and developing countries with an aim of uncovering the impacts of various factors in forest management, as well as resulting welfare changes felt by landowners and society. The first essay extends previous literature on natural disturbances and forest management, where a single disturbance and immediate clearcut after it are always assumed, through the introduction of multiple disturbances and flexible harvest timing. A Faustmann-type rotation model is developed and used to guide simulations of loblolly pine management in the southern United States. We show that failure to consider the possibility of multiple disturbances and the oversimplification of harvest rules after a single disturbance leads to suboptimal harvest decisions. The second essay further extends the natural disturbance literature by considering the amenity value of unharvested forests in addition to timber value. As before, multiple types of disturbances as well as flexible harvest timing are incorporated into a Hartmann-type framework. Alternative amenity functions are employed in the simulations in which socially optimal harvest strategies are derived. We further examine the discrepancies between optimal harvest decisions of the landowner and those of the social planner, and compute social costs of ignoring amenity value. Our results show that ignoring amenity value can generate social costs and render harvest decisions socially suboptimal. Forest production in developing countries also suffers from institutional weaknesses that distorts household decision making. The third essay therefore investigates impacts of village democracy on rural household welfare in China through changes in production efficiency in forestry and agriculture sectors using data collected from a household survey. A theoretical framework is first established, and based upon that framework stochastic production frontier models are estimated where democracy is incorporated as a potential factor affecting the variation of technical efficiency. We find that higher levels of village democracy significantly increase production efficiency. A first study on how village democracy affects rural household welfare, we provide policy lessons for other developing countries undergoing democratization. / Ph. D.

Aims: Quantitative research and clinical observations have long supported a link between the eating disorders and disturbances of self / identity. However, less is known about the process of how this comes about, and little qualitative research has been conducted in the area. The current study therefore aimed to gain an in-depth understanding of the experience of self and eating disorder, using a qualitative approach. The study focused upon the experiences of women, in order to keep the sample homogenous, and sought to explore the following: How women with an eating disorder view and describe themselves; their thoughts and experiences concerning why they view themselves this way; and their thoughts and experiences regarding whether they think there is a link between their view of themselves and their eating disorder. Method: Semi-structured interviews were carried out with four women who had been diagnosed with, and were undergoing treatment for, an eating disorder. Verbatim transcripts of the interviews were then analysed using Interpretative Phenomenological Analysis (IPA). Results: The analysis produced four master themes. These were, "I'm always questioning, who am I?": 'Experiencing a fragile sense of self'; 'The influences of others on self perception'; "Just made me feel better about myself": 'Strategies employed to manage the sense of self'; and "I can't rise above my childhood": 'The enduring influence of early experiences on self'. A description of these master themes and the related subordinate themes is presented. Conclusion: The results of the analysis are considered in light of existing theory and their clinical implications.

Thesis (M.S.)--University of Puerto Rico, Mayagüez Campus, 2004. / Tables. Printout. Abstract in English and Spanish. Includes bibliographical references (leaves 30-38).

Travelling Ionospheric Disturbances (TIDs) are said to be produced by atmospheric gravitational waves propagating through the neutral ionosphere. These are smaller in amplitude and period when compared to most ionospheric disturbances and hence more difficult to measure. Very little is known about the properties of the travelling ionospheric disturbances (TIDs) over the Southern Hemisphere regions since studies have been conducted mostly over the Northern Hemisphere regions. This study presents a framework, using a High Frequency (HF) Doppler radar to investigate the physical properties and the possible driving mechanisms of TIDs. This research focuses on studying the characteristics of the TIDs, such as period, velocity and temporal variations, using HF Doppler measurements taken in South Africa. By making use of a Wavelet Analysis technique, the TIDs’ characteristics were determined. A statistical summary on speed and direction of propagation of the observed TIDs was performed. The winter medium scale travelling ionospheric disturbances (MSTIDs) observed are generally faster than the summer MSTIDs. For all seasons, the MSTIDs had a preferred south-southwest direction of propagation. Most of the large scale travelling ionospheric disturbances (LSTIDs) were observed during the night and of these, the spring LSTIDs were fastest when compared to autumn and summer LSTIDs. The general direction of travel of the observed LSTIDs is south-southeast. Total Electron Content (TEC), derived from Global Positioning System (GPS) measurements, were used to validate some of the TID results obtained from the HF Doppler data. The Horizontal Wind Model (HWM07), magnetic K index, and solar terminators were used to determine the possible sources of the observed TIDs. Only 41% of the observed TIDs were successfully linked to their possible sources of excitation. The information gathered from this study will be valuable in future radio communications and will serve as means to improve the existing ionospheric models over the South African region.

Schizophrenia is accompanied by distortion of all mental functions, including thinking, speech, motivation, perception or general experiencing of the world and oneself. Theoretical part of the thesis describes the process of schizophrenia and its symptoms with focus on auditory hallucinations, which roughly 70% of people with schizophrenia have some experience with. Main contribution of the theoretical part is the summary of the self- disturbances concept, which incorporates for instance loss of control over parts of mental experience, disruption of boundaries between the person and its surroundings and other similar aspects that are for a person who never experienced them almost unimaginable, and are difficult to explain even for an individual who does experience these disturbances of oneself. The thesis puts theoretical outcomes of self-disturbances into perspective, as well as current approaches and knowledge. First part of the research validates that the newly developed method for measurement of self-disturbances acquires sufficient internal consistency. Results of the next part confirm that the self-disturbances measure varies among patients with schizophrenia and healthy volunteers in all of the individual domains. Last research part presents relationships between currently experienced...

This study was conducted in the Afram Headwaters, Tain Tributaries Block II and Worobong South Forest Reserves. Satellite record of fire incidence for the country over 11 years (1997 to 2007) was modelled via binary logistic regression analysis, and correlations between fire incidence and the correlates of fire used to explain the observed trends. Fire incidence was found to be correlated with multiple variables which probably covary. Rainfall, vegetation type and geology showed the strongest correlations with fire incidence. Recurrent fire has impacted negatively on forest structure, ground cover biomass and species composition in two forest reserves, but more marked in the wetter Worobong South Forest Reserve than the drier Tain II Forest Reserve. Basal area has reduced from 40 m²ha^-1 in least-degraded to <1 m²ha^-1 in heavily-degraded stand in Worobong South Forest Reserve, along with tree density, whereas canopy openness has increased from 6% in least-degraded to 83% in heavily-degraded forest. In Tain II Forest Reserve, however, the heavily-degraded forest has lost close to 50% of its maximum value in terms of basal area, tree density and canopy cover, all in approximately 20 years. Early-burning, with maximum seedling height growth rates of 130 cm yr^-1 and 40 cm yr^-1 for Worobong South and Tain II Forest Reserves respectively, might help control the fires, and restore forest canopy in about 10 to 20 years if regularly maintained, but must be accompanied by green firebreaks. Complete protection from fire (during convalescence), on the other hand, would take between five and 15 years to restore forest canopy, but at huge resource cost. Implications for sustainable forest management are discussed.

The emerging consensus among investigators seems to be that bulimia is a multidetermined disorder with a number of contributing factors, including biological components, sociocultural factor, personality, and family characteristics (Garfinkel & Garner, 1982). An etiological model was examined in this study integrating two important theoretical perspectives in the bulimia literature: the stress-coping perspective (Cattanach & Rodin, 1988) and the family systems perspective (Minuchin et al., 1978). Five latent variables: Family Characteristics, Coping Resources, Psychological Disturbance, Environmental Stressors, and Bulimia were represented by twelve measured variables. Structural Equation Modeling analysis allowed for the simultaneous examination of the hypothesized interrelationships between model variables. Findings confirmed a direct impact of psychological disturbances on bulimic symptoms. Hypothesized indirect relationships of family characteristics, coping resources and environmental stressors to bulimia were confirmed. Treatment implications as well as directions for future research were discussed.

Modeling, system identification and controller design for a 16’ catamaran is described with the objective of enhanced operation in the presence of environmental disturbances including wind, waves and current. The vehicle is fully-actuated in surge, sway and yaw degrees of freedom. Analytical and experimental system identification is carried out to create a numerical model of the vehicle. A composite system of a Multiinput multi-output Proportional-Derivative (PD) controller and a nonlinear disturbance observer is used for station-keeping and transiting modes of operation. A waypoint transiting algorithm is developed to output heading and cross-track error from vehicle position and waypoints. A control allocation method is designed to lower azimuthing frequency and incorporate angle saturation and rate limits. Validation is achieved with improvement in simulation with the addition of the nonlinear observer. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

[pt] Neste trabalho é apresentado um estudo teórico-experimental da propagação de perturbações acústicas num escoamento de ar, em regime turbulento e subsônico, no interior de um duto circular (comprimento 3000mm, diâmetro 50,8mm). Introduziram-se perturbações senoidais no escoamento, por intermédio de um alto-falante colocado na parede de uma câmara de estabilização, situada a montante do tubo de teste. Estudou-se a propagação da onda ao longo do escoamento e os efeitos da mesma nas distribuições de pressão, de velocidade e de intensidade de turbulência. Realizaram-se experimentos, em regime hidrodinâmico caracterizado por um número de Reynolds 70000, introduzindo perturbações acústicas no escoamento correspondentes à primeira e segunda frequências de ressonância do tubo, respectivamente, 56Hz e 112Hz (números de Strouhal 0,13 e 0,26). A 56Hz, a intensidade da perturbação acústica foi 3 por cento (valor eficaz da onda de velocidade, na frequência de perturbação, na entrada do tubo, normalizada na velocidade média na seção de entrada no centro do tubo); a 112Hz aplicaram-se duas intensidades de perturbação, 3 por cento e 18 por cento. Em várias posições ao longo do tubo, foram medidos, entre r/R=0 e r/R=0,96, os perfis transversais da velocidade média temporal, da intensidade da turbulência e do componente de onda. A distribuição de pressão foi medida por intermédio de tomadas de pressão posicionadas ao longo da parede do tubo. Foi estudada, teoricamente, a propagação da onda ao longo do tubo, considerando um modelo sem dissipação e, outro, com dissipação. Os resultados experimentais confirmaram as estimativas de dissipação baseadas no modelo, segundo as quais, nas condições do caso estudado (designadamente para a faixa de frequências de perturbação consideradas, e comprimento do tubo da ordem do comprimento de onda), a dissipação tem um efeito bastante moderado na propagação da onda. Nestas condições, grande parte dos aspectos do comportamento da onda é interpretada a partir do modelo sem dissipação, que mostrou boa concordância com os resultados experimentais. O modelo com dissipação permitiu interpretar alguns aspectos essencialmente ligados à dissipação, designadamente o comportamento da onda na vizinhança da ressonância e os perfis transversais da onda de velocidade, e interpretar as razões da validade aproximada, no caso estudado, no modelo sem dissipação. As diferenças entre o comportamento previsto pelos modelos apresentados e os resultados experimentais foram da ordem de grandeza dos erros de medida. Com base na análise efetuada, afigura-se que, para as condições estudadas, nem as estruturas de turbulência afetam significativamente a onda acústica, nem as perturbações acústicas impostas afetam significamente as características do escoamento turbulento (velocidade média temporal, intensidade de turbulência e distribuição de pressão estatística). Afigura-se, assim, que uma aproximação linear, baseada na técnica da superposição, usada nos modelos teóricos apresentados, é apropriada para descrever o escoamento turbulento resultante da aplicação da perturbação acústica. / [en] In this work, it is presented a theoretical-experimental study of acoustic perturbations propagation, in turbulent, subsonic, air flow in a circular pipe (lenght: 3000mmm; diameter: 50,8mm). Sinusoidal perturbations were introduced in the flow, by means of a loud-speaker, placed at the wall of a settling chamber, upstream of the test pipe. The wave propagation along the flow was studied, as well as its effects on pressure, velocity and turbulance intensity distributions. The experiments were conducted at flow Reynolds Number 70000, introducing acoustic perturbations corresponding to the first and second resonant frequencies of the pipe, namely 56Hz and 112Hz (Strouhal Numbers 0.13 and 0.26). At 56Hz the intensity of the acoustic perturbation was 3 percent (r.m.s. value of the wave component of the velocity, at the perturbation frequency, at the pipe entrance, normalized by the pipe entrance centerline mean velocity); at 112Hz two perturbation intensities were applied: 3 percent and 18 percent. The mean velocity, turbulance intensity and wave component profiles were measured at several stations along the pipe, between r/R=0 and r/R=0,96. The wave propagation along the pipe was theoretically studied. Two models were considered, a model without dissipation and a model with dissipation. The experimental results confirmed the dissipation estimates based on the model, and have shown that, for the studied case conditions (namely for the frequency range considered, and pipe lenght of the order of the wave lenght), the dissipation has a moderate effect on the wave propagation. So, a great part of the wave behavior is a interpreted on the basis of the model without dissipation, that has shown good agreement with the experimental results. The model with dissipation allows to intepret some aspects strongly connected with dissipation, namely the wave behavior in the vicinity of the ressonance and the transversal profiles of the wave component of the velocity, in the studied case, of the model without dissipation. The differences between the behavior forseen by the presented models, and the experimental results, were of the order of magnitude of the measurement errors. According to the analysis performed, it appears that, for the studied conditions, neither the turbulance structure significantly affects the acoustic wave, nor the acoustic perturbations significantly affect the turbulent flow characteristics (mean velocity, turbulance intensity and pressura distribution). So, it appears that, a linear approach, based on a superposition technique, used in the presented theoretical models, is adequate to describe the overall disturbed turbulent flow.

This thesis was concerned with investigating a visual-illusionary phenomenon that co-occurs with post-traumatic anxiety symptoms. More specifically, individuals who report recurring specific memories of a fearful event (RSM) also tend to report a persistent illusion of movement (PIM) upon prolonged visual fixation (Tym, Dyck & McGrath, 2000). The development of a visual test (i-Test) designed to reliably elicit PIM has enabled research to be conducted on the nature and correlates of this type of visual disturbance. The present research aimed: 1) To develop a standard protocol for assessment of PIM and RSM; 2) to test the reliability of the i-Test in eliciting PIM in a student sample 3) to test the predictive relationship between dissociation and anxiety symptoms with PIM and RSM 4) to formulate and test a hypothesis regarding a mechanism underlying PIM. The first study screened 142 participants for RSM and PIM using self-administered questionnaires designed by Tym (personal communication, 2001). There was an unexpectedly high rate (54.2%) of PIM and RSM (37.3%) in the sample, which appeared to be the product of questionnaire design limitations. Two semi-structured interviews were developed and subsequently tested on a new sample of 50 participants in Study 2. Study 2 documented intra-rater and inter-rater reliability co-efficient of sufficient strength to indicate good reliability for the semi-structured interviews. The results of Study 2 indicate that PIM is a relatively stable symptom over a 30-minute and one-week test-retest time frame. / The onset time for PIM was relatively consistent between participants, with a mean latency of approximately 7 seconds. The oscillation rate of PIM was relatively consistent between individuals, with a mean average oscillation of approximately 0.8Hz. The third study tested a sample of 148 participants using the revised assessment protocols. The base rate for PIM (16.2%) and RSM (18.9%), and the concordance rates (46% to 54%) were slightly stronger than the Tym et al. (2000) community based study (33%). In addition to this, 11 other illusionary phenomena were documented, however none of these visual symptoms significantly correlated with RSM. The average oscillation rate is comparable to the rate documented in Study 2, further establishing the consistency of the reported rate of PIM oscillations between individuals. In Study 3, each participant was assessed for levels of dissociation (Dissociative Experiences Scale), somatic arousal (Mood and Anxiety Symptoms Questionnaire – Anxious Arousal Scale) and anxiety sensitivity (Anxiety Sensitivity Index). The results indicate that gender and dissociation significantly predict RSM status, and self-reported levels of anxious-arousal significantly predict PIM status. A multiway frequency analysis between the sub-components of RSM and PIM revealed that the physiological arousal inducing properties of the recurring memory is the only significant predictor of PIM. / The observed relationship between RSM and PIM may reflect the broader relationship between anxiety and dissociation. A pulsatile hypothesis was proposed as a feasible mechanism underlying PIM, due to the rhythmical nature of the visual disturbance, the range of the documented oscillations, and its specificity to psychological disorders characterised by cardiovascular sensitivities. All participants were administered the i-Test prior to and following aerobic exercise aimed at increasing pulse rate to 80% of maximum load. An increase in physical exertion significantly increased the latency of PIM onset, but did not impact on the rate of PIM. PIM rate appeared relatively consistent between individuals at 0.6Hz to 0.8Hz at the pre-exercise condition. Several participants who reported PIM also displayed obvious nystagmoid-like movements during the i-Test perceptual task. The role of eye-movements in PIM requires further investigation by future ophthalmological research. The final aim of Study 3 was to investigate the relationship between RSM/PIM and flicker sensitivity. Through the use of a Critical Flicker Frequency/Fusion task (CFF), each participant’s sensitivity to flicker was determined. In addition to detecting sensitivity thresholds, CFF is also considered to be a reliable indicator of the level of cortical arousal. / The results of this study suggest that individuals with RSM have a higher sensitivity to flicker than other participants, however there was a non-significant relationship between CFF and PIM. The lack of relationship between PIM and CFF may be due to issues concerning statistical power and effect-size. Future research is required to investigate this link in more detail. The overall results of this thesis suggest that i-Test elicited PIM is a reliable phenomenon that is associated with higher rates of traumatic memories when compared with persons who do not report this visual symptom. The strength of the association between RSM and PIM, however, does not support the use of the i-Test as a marker for the presence of RSM outside a clinical sample. The reliability of PIM as a phenomenon and its association with anxiety symptoms may be of theoretical importance in enabling future research to investigate the relationship between visual symptoms and anxiety-related pathology.