• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1093
  • 920
  • 299
  • 125
  • 118
  • 34
  • 24
  • 19
  • 17
  • 15
  • 10
  • 10
  • 9
  • 7
  • 6
  • Tagged with
  • 3051
  • 732
  • 542
  • 499
  • 422
  • 306
  • 298
  • 250
  • 242
  • 237
  • 217
  • 184
  • 178
  • 150
  • 144
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Interdecadal Variability along 38°N in the North Atlantic

Lei, Ji Unknown Date
No description available.
102

Adolescent nonstutterers' preferences for stuttering control patterns as a function of socioeconomic and cultural variables

Lundgren, Cynthia Gail January 1977 (has links)
This thesis explored adolescent nonstutterers' preferences for the stuttering control patterns: bounce, prolongation, light contact, and conversational rate control. A videotape was produced of a black and white speaker imitating stuttering and portraying the four control patterns. Adolescents viewed the tape in small groups and rated the stuttering control patterns on a Likert seven point rating scale according to their degree of preference for each. The conversational rate control pattern was found to be the most preferred method of stuttering control for the adolescent viewer.Analyses of viewer race and socioeconomic status and the interactions between viewer race and speaker race were made also. The significant findings yielded a higher mean rating given to the black speaker by black and white viewers. This finding was interpreted in support of the hypothesis that adolescent peers expect and demand a return to increased fluency more so for a member of the black culture than of a white culture.
103

The Variability of Neuromuscular Control During Knee Extension Performance

Fung, Stephen 02 June 2014 (has links)
Movement variability that occurs while performing repetitions of any particular motion can be due to errors in one’s ability to select the required parameters for executing the movement. However, it has been suggested that an optimal amount of variability exists in a healthy system providing adaptability to varying situations while producing negligible errors. Investigation of the consistency of movement variability in a system may provide information regarding joint control and integrity since the functionality of a system can be disrupted by injury. Rupture of the anterior cruciate ligament is associated with deficits in knee joint stability and mobility, as well as altered movement patterns. There is value in developing a simple clinical test that can measure knee joint stability and evaluate the degree of knee damage and rate of progress during rehabilitation. The main objectives were to investigate the normal range of variability during repeated knee extensions in healthy subjects and subjects with a reconstructed anterior cruciate ligament, and to evaluate the reliability of the method. There were 30 participants in the control group and 8 in the subject group. All were physically active a minimum of 2-3 times per week for a total of 2-3 hours. Mean variance and mean correlation were used to evaluate variability in this study. Change in mean variance and mean correlation, standard error of measurement and intra-class correlation coefficient were used to evaluate reliability. The results showed the range of values for movement variability in control and subject groups. Standard error of measurement indicated mean correlation (1.31% to 2.38%) was more reliable than mean variance (21.80% to 54.87%). Mean variance and mean correlation significantly increased with speed, and mean correlation was significantly higher for dominant legs during trials at 70 beats per minute. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2014-06-02 12:18:42.802
104

Spatial structure of soil texture and its influence on spatial variability of nitrate leaching

Vivekananthan, Kokulan 06 January 2015 (has links)
Field scale variability of soil texture can influence crop yield and movement of soil water in the field. The objective of this study was to investigate the spatial structure of soil texture in relation to the variability of nitrate-N leaching using geostatistics. Soil textural fractions showed strong spatial autocorrelations from surface to 60 cm depth. Random variability of soil texture increased with depth. Soil water content, as well as total carbon, total nitrogen and soil organic carbon of top 15 cm, also showed spatial autocorrelations similar to soil texture. Elevation, relative slope position and vertical distance to channel network showed significant influence on the distribution of soil texture. Soil texture at 90 cm depth correlated best with cumulative percolated water and cumulative nitrate leached in field lysimeters. Our results showed that soil layers with low hydraulic conductivity control the water and nitrate movement through the soil profile.
105

Simulation and prediction of North Pacific sea surface temperature

Lienert, Fabian 24 June 2011 (has links)
The first part of this thesis is an assessment of the ability of global climate models to reproduce observed features of the leading Empirical Orthogonal Function (EOF) mode of North Pacific sea surface temperature (SST) anomalies known as the Pacific Decadal Oscillation (PDO). The simulations from 13 global climate models I am analyzing were performed under phase 3 of the coupled model intercomparison project (CMIP3). In particular, I am investigating whether these climate models capture tropical influences on the PDO, and the influences of the PDO on North American surface temperature and precipitation. My results are that 1) the models as group produce a realistic pattern of the PDO. The simulated variance of the PDO index is overestimated by roughly 30%. 2) The tropical influence on North Pacific SSTs is biased systematically in these models. The simulated response to El Niño-Southern Oscillation (ENSO) forcing is delayed compared to the observed response. This tendency is consistent with model biases toward deeper oceanic mixed layers in winter and spring and weaker air-sea feedbacks in the winter half-year. Model biases in mixed layer depths and air-sea feedbacks are also associated with a model mean ENSO-related signal in the North Pacific whose amplitude is overestimated by roughly 30%. Finally, model power spectra of the PDO signal and its ENSO-forced component are “redder” than observed due to errors originating in the tropics and extratropics. 3) The models are quite successful at capturing the influence of both the tropical Pacific related and the extratropical part of the PDO on North American surface temperature. 4) The models capture some of the influence of the PDO on North American precipitation mainly due to its tropical Pacific related part. In the second part of this thesis, I investigate the ability of one such coupled ocean- atmosphere climate model, carefully initialized with observations, to dynamically predict the future evolution of the PDO on seasonal to decadal time scales. I am using forecasts produced by the Canadian climate data assimilation and prediction system employing the Canadian climate model CanCM3 for seasonal (CHFP2) and CanCM4 for decadal (DHFP1) predictions. The skill of this system in predicting the future evolution of the PDO index is then inferred from a set of historical “forecasts” called hindcasts. In this manner, hindcasts are issued over the past 30 years (seasonal), or over the past 50 years (decadal) when they can be verified against the observed historical evolution of the PDO index. I find that 1) CHFP2 is successful at predicting the PDO at the seasonal time scale measured by mean-square skill score and correlation skill. Weather “noise” unpredictable at the seasonal time scale generated by substantial North Pacific storm track activity that coincides with a shallow oceanic mixed layer in May and June appear to pose a prediction barrier for the PDO. PDO skill therefore depends on the start season of the forecast. PDO skill also varies as a function of the target month. Variations in North Pacific storminess appear to impact PDO skill by means of a lagged response of the ocean mixed layer to weather “noise”. In CHFP2, times of increasing North Pacific storm track activity are followed by times of reduced PDO skill, while the North Pacific midwinter suppression of storm track activity with decreasing storminess is followed by a substantial recovery in PDO skill. 2) This system is capable of forecasting the leading 14 EOF modes of North Pacific SST departures, that explain roughly three quarters of the total SST variance. CHFP2 is less successful at predicting North Pacific SSTs, i.e., the combination of all the EOF modes, at the seasonal time scale. 3) Besides the skill in Pacific SST, CHFP2 skillfully predicts indices that measure the atmospheric circulation regime over the North Pacific and North America such as the Pacific/North American pattern (PNA) (skillful for three out of four start seasons) and the North Pacific index (NPI) (skillful for all four start seasons). 4) CHFP2 is successful at forecasting part of the influence of Pacific SST on North American climate at the seasonal time scale. Measured by 12-month average anomaly correlation skill, in this system the PDO is a better predictor for North American precipitation (skillful for all four start seasons) than temperature (skillful for one out of four start seasons). In CHFP2, ENSO is a better predictor for North American temperature (skillful for all four start seasons) than the PDO. Both ENSO and the PDO are, however, good predictors for North American precipitation (skillful for all four start seasons). Finally, DHFP1 is less successful at forecasting the PDO at the decadal time scale. Ten-year forecasts of the PDO index exhibit significantly positive correlation skill exclusively in the first year of the forecast. When the correlation skill of the predicted index averaged over lead years is considered, the PDO skill in this system stays significantly positive during the first three years of the decadal forecast. In other words, this climate data assimilation and prediction system is expected to skillfully predict the future three year averaged evolution of the PDO index, but not the evolution of the index in each year individually. / Graduate
106

The development and application of a normative framework for considering uncertainty and variability in economic evaluation

Coyle, Douglas January 2004 (has links)
The focus of this thesis is in the development and application of a normative framework for handling both variability and uncertainty in making decisions using economic evaluation. The framework builds on the recent work which takes an intuitive Bayesian approach to handling uncertainty as well as adding a similar approach for the handling of variability. The technique of stratified cost effectiveness analysis is introduced as an innovative, intuitive and theoretically sound basis for consideration of variability with respect to cost effectiveness. The technique requires the identification of patient strata where there are differences between strata but individual strata are relatively homogenous. For handling uncertainty, the normative framework requires a twofold approach. First, the cost effectiveness of therapies within each patient stratum must be assessed using probabilistic analysis. Secondly, techniques for estimation of the expected value of perfect information should be applied to determine an efficient research plan for the disease of interest. For the latter, a new technique for estimating EVPI based on quadrature is described which is both accurate and allows simpler calculation of the expected value of sample information. In addition the unit normal loss integral method previously ignored as a method of estimating EVPPI is shown to be appropriate in specific circumstances. The normative framework is applied to decisions relating to the public funding of the treatment of osteoporosis in the province of Ontario. The optimal limited use criteria would be to fund treatment with alendronate for women aged 75 years and over with previous fracture and 77 years and over with no previous fracture. An efficient research plan would fund a randomised controlled trial comparing etidronate to no therapy with a sample size of 640. Certain other research studies are of lesser value. Subsequent to the analysis contained in this thesis, the province of Ontario revised there limited use criteria to be broadly in line with the conclusions of this analysis. Thus, the application of the framework to this area demonstrates both its feasibility and acceptability. The normative framework developed in this thesis provides an optimal solution for decision makers in terms of handling uncertainty and variability in economic evaluation. Further research refining methods for estimating information value and considering other forms of uncertainty within models will enhance the framework.
107

Hydrologic risk assessment framework for Alberta's green zone

Wagner, Michael Johann 11 1900 (has links)
In this dissertation, a hydrologic classification approach was tested using the shape factor of hydrographs to represent variation in streamflow regimes across Alberta. Hydrograph shape factor was effective at separating the forested landbase into 6 spatially distinct regions. Further statistical analysis of hydrometric data showed each region to have unique streamflow characteristics. Differences in physiography between regions were evident and strong associations were found between physical catchment characteristics and hydrologic variables describing streamflow magnitude and timing. In a case study, findings were used to define the regional natural range of hydrologic variation and applied into a watershed assessment tool evaluating the potential changes to streamflow regimes as a result of forest disturbance. This analysis showed that because of hydrologic variability among regions, spatial variation in sensitivity to harvest likely exists within the forested landbase, highlighting the need for development of regional criteria and indicators for sustainable management of water resources. / Forest Biology and Management
108

Interdecadal Variability along 38N in the North Atlantic

Lei, Ji 06 1900 (has links)
Hydrographic data, in the time range from 1908 to 2006, extracted from the International Council for the Exploration of the Sea (ICES) database, are used to examine variability of water masses in the North Atlantic ocean along 38N. All the data are interpolated in an ideal isopycnal framework, which has a longitudinal resolution of 1/3 degree and 50 isopycnal layers of variable thickness, to 38N by using an objective analysis approach. A 5 year-running mean triad analysis is performed from 1950 to 2004 for further variability study. Extensive decadal to inter-decadal variability is observed, in both shallow and deep layers. In the deep layers, a signal of westward phase propagating is detected, coincided with the time scale of a first mode baroclinic Rossby wave transporting at this latitude. Strong negative correlations (maximum at a lag of 7 years) are seen between the variability in the DWBC and the North Atlantic Oscillation. A similar correlation at the same lag is also detected in the basin interior, suggesting the Labrador Sea Water (LSW) pathway is not only restrained to the DWBC.
109

Examining nonlinear changes of coefficients in time-varying dynamic factor models

Zu, Jiyun. January 2008 (has links)
Thesis (M.A.)--University of Notre Dame, 2008. / Thesis directed by Ke-Hai Yuan for the Department of Psychology. "April 2008." Includes bibliographical references (leaves 101-107).
110

Variations in Northern Hemisphere snowfall an analysis of historical trends and the projected response to anthropogenic forcing in the twenty-first century.

Krasting, John P. January 2008 (has links)
Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Atmospheric Science." Includes bibliographical references (p. 98-108).

Page generated in 0.0674 seconds