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  • 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.
61

Uncertainty Analysis of Long Term Correction Methods for Annual Average Winds / Osäkerhetsanalys av beräkningsmetoder för normalårskorrigerad medelvind

Klinkert, Rickard January 2012 (has links)
For the construction of a wind farm, one needs to assess the wind resources of the considered site location. Using reference time series from numerical weather prediction models, global assimilation databases or observations close to the area considered, the on-site measured wind speeds and wind directions are corrected in order to represent the actual long-term wind conditions. This long-term correction (LTC) is in the typical case performed by making use of the linear regression within the Measure-Correlate-Predict (MCP) method. This method and two other methods, Sector-Bin (SB) and Synthetic Time Series (ST), respectively, are used for the determination of the uncertainties that are associated with LTC.The test area that has been chosen in this work, is located in the region of the North Sea, using 22 quality controlled meteorological (met) station observations from offshore or nearby shore locations in Denmark, Norway and Sweden. The time series that has been used cover the eight year period from 2002 to 2009 and the year with the largest variability in the wind speeds, 2007, is used as the short-term measurement period. The long-term reference datasets that have been used are the Weather Research and Forecast model, based on both ECMWF Interim Re-Analysis (ERA-Interim) and National Centers for Environmental Prediction Final Analysis (NCEP/FNL), respectively and additional reference datasets of Modern Era Re-Analysis (MERRA) and QuikSCAT satellite observations. The long-term period for all of the reference datasets despite QuikSCAT, correspond to the one of stations observations. The QuikSCAT period of observations used cover the period from November 1st, 1999 until October 31st, 2009.The analysis is divided into three parts. Initially, the uncertainty connected to the corresponding reference dataset, when used in LTC method, is investigated. Thereafter the uncertainty due to the concurrent length of the on-site measurements and reference dataset is analyzed. Finally, the uncertainty is approached using a re-sampling method of the Non-Parametric Bootstrap. The uncertainty of the LTC method SB, for a fixed concurrent length of the datasets is assessed by this methodology, in an effort to create a generic model for the estimation of uncertainty in the predicted values for SB.The results show that LTC with WRF model datasets based on NCEP/FNL and ERA-Interim, respectively, is slightly different, but does not deviate considerably in comparison when comparing with met station observations. The results also suggest the use of MERRA reference dataset in connection with long-term correction methods. However, the datasets of QuikSCAT does not provide much information regarding the overall quality of long-term correction, and a different approach than using station coordinates for the withdrawal of QuikSCAT time series is preferred. Additionally, the LTC model of Sector-Bin is found to be robust against variation in the correlation coefficient between the concurrent datasets. For the uncertainty dependence of concurrent time, the results show that an on-site measurement period of one consistent year or more, gives the lowest uncertainties compared to measurements of shorter time. An additional observation is that the standard deviation of long-term corrected means decreases with concurrent time. Despite the efforts of using the re-sampling method of Non-Parametric Bootstrap the estimation of the uncertainties is not fully determined. However, it does give promising results that are suggested for investigation in further work. / För att bygga en vindkraftspark är man i behov av att kartlägga vindresurserna i det aktuella området. Med hjälp av tidsserier från numeriska vädermodeller (NWP), globala assimileringsdatabaser och intilliggande observationer korrigeras de uppmätta vindhastigheterna och vindriktningarna för att motsvara långtidsvärdena av vindförhållandena. Dessa långtidskorrigeringsmetoder (LTC) genomförs generellt sett med hjälp av linjär regression i Mät-korrelera-predikera-metoden (MCP). Denna metod, och två andra metoder, Sektor-bin (SB) och Syntetiska tidsserier (ST), används i denna rapport för att utreda de osäkerheter som är knutna till långtidskorrigering.Det testområde som är valt för analys i denna rapport omfattas av Nordsjöregionen, med 22 meteorologiska väderobservationsstationer i Danmark, Norge och Sverige. Dessa stationer är till största del belägna till havs eller vid kusten. Tidsserierna som används täcker åttaårsperioden från 2002 till 2009, där det året med högst variabilitet i uppmätt vindhastighet, år 2007, används som den korta mätperiod som blir föremål för långtidskorrigeringen. De långa referensdataseten som använts är väderprediktionsmodellen WRF ( Weather Research and Forecast Model), baserad både på data från NCEP/FNL (National Centers for Environmental Prediciton Final Analysis) och ERA-Interim (ECMWF Interim Re-analysis). Dessutom används även data från MERRA (Modern Era Re-Analysis) och satellitobservationer från QuikSCAT. Långtidsperioden för alla dataset utom QuikSCAT omfattar samma period som observationsstationerna. QuikSCAT-datat som använts omfattar perioden 1 november 1999 till 31 oktober 2009.Analysen är indelad i tre delar. Inledningsvis behandlas osäkerheten som är kopplad till referensdatans ingående i långtidskorrigeringsmetoderna. Därefter analyseras osäkerhetens beroende av längden på den samtidiga datan i referens- och observationsdataseten. Slutligen utreds osäkerheten med hjälp av en icke-parametrisk metod, en s.k. Bootstrap: Osäkerheten i SB-metoden för en fast samtidig längd av tidsserierna från observationer och referensdatat uppskattas genom att skapa en generell modell som estimerar osäkerheten i estimatet.Resultatet visar att skillnaden när man använder WRF-modellen baserad både på NCEP/FNL och ERA-Interim i långtidskorrigeringen är marginell och avviker inte markant i förhållande till stationsobservationerna. Resultatet pekar också på att MERRA-datat kan användas som långtidsreferensdataset i långtidsdkorrigeringsmetoderna. Däremot ger inte QuikSCAT-datasetet tillräckligt med information för att avgöra om det går att använda i långtidskorrigeringsmetoderna. Därför föreslås ett annat tillvägagångssätt än stationsspecifika koordinater vid val av koordinater lämpliga för långtidskorrigering. Ytterligare ett resultat vid analys av långtidskorrigeringsmetoden SB, visar att metoden är robust mot variation i korrelationskoefficienten.Rörande osäkerhetens beroende av längden på samtidig data visar resultaten att en sammanhängande mätperiod på ett år eller mer ger den lägsta osäkerheten i årsmedelvindsestimatet, i förhållande till mätningar av kortare slag. Man kan även se att standardavvikelsen av de långtidskorrigerade medelvärdena avtar med längden på det samtidiga datat. Den implementerade ickeparametriska metoden Bootstrap, som innefattar sampling med återläggning, kan inte estimera osäkerheten till fullo. Däremot ger den lovande resultat som föreslås för vidare arbete.
62

Prevalence and predictors of immunologic failure among HIV patients on HAART in southern Ethiopia

Kesetebirhan Delele Yirdaw 20 August 2015 (has links)
Immunologic monitoring is part of the standard care for patients on antiretroviral treatment. Yet, little is known about the routine implementation of immunologic monitoring in Ethiopia. This study assessed the pattern of immunologic monitoring, immunologic response, level of immunologic treatment failure and factors related to it among patients on antiretroviral therapy in selected hospitals in southern Ethiopia. A retrospective longitudinal analytic study was conducted using documents of patients started on antiretroviral therapy. A total of 1,321 documents of patients reviewed revealed timely immunologic monitoring were inadequate. Despite overall adequate immunologic response, the prevalence of immunologic failure was 11.5% (n=147). Having WHO Stage III/IV of the disease and a higher CD4 (cluster differentiation 4) cell count at baseline were identified as risks for immunologic failure. These findings highlight the magnitude of the problem of immunologic failure. Prioritizing monitoring for high risk patients may help in effective utilisation of meager resources / Health Studies / M.A. (Public Health)
63

Prevalence and predictors of immunologic failure among HIV patients on HAART in southern Ethiopia

Kesetebirhan Delele Yirdaw 20 August 2015 (has links)
Immunologic monitoring is part of the standard care for patients on antiretroviral treatment. Yet, little is known about the routine implementation of immunologic monitoring in Ethiopia. This study assessed the pattern of immunologic monitoring, immunologic response, level of immunologic treatment failure and factors related to it among patients on antiretroviral therapy in selected hospitals in southern Ethiopia. A retrospective longitudinal analytic study was conducted using documents of patients started on antiretroviral therapy. A total of 1,321 documents of patients reviewed revealed timely immunologic monitoring were inadequate. Despite overall adequate immunologic response, the prevalence of immunologic failure was 11.5% (n=147). Having WHO Stage III/IV of the disease and a higher CD4 (cluster differentiation 4) cell count at baseline were identified as risks for immunologic failure. These findings highlight the magnitude of the problem of immunologic failure. Prioritizing monitoring for high risk patients may help in effective utilisation of meager resources / Health Studies / M. A. (Public Health)
64

Finanční analýza a. s. Crystelex, Nový Bor / Financial analysis Crystalex, a.s.

Matušková, Petra January 2008 (has links)
The Financial analysis Crystalex a.s. examines a general financial situation of the company. I use classical methods for financial analysis. The significant part of my project is the application of creditworthy and bankruptcy models. The aim of my thesis is to find out if these models were able to predict the current situation for management in the past.
65

PREDICTION OF PREMIXED INTERNAL COMBUSTION ENGINE MASS FRACTON BURNED PROFILES USING A PHYSICAL FORM OF THE WIEBE FUNCTION AND THE THEORY OF TURBULENT FLAME BRUSH THICKNESS DYNAMICS

Aquino, Phillip A. January 2020 (has links)
No description available.
66

Predicting the Longevity of DVDR Media by Periodic Analysis of Parity, Jitter, and ECC Performance Parameters

Wells, Daniel Patrick 14 July 2008 (has links) (PDF)
For the last ten years, DVD-R media have played an important role in the storage of large amounts of digital data throughout the world. During this time it was assumed that the DVD-R was as long-lasting and stable as its predecessor, the CD-R. Several reports have surfaced over the last few years questioning the DVD-R's ability to maintain many of its claims regarding archival quality life spans. These reports have shown a wide range of longevity between the different brands. While some DVD-Rs may last a while, others may result in an early and unexpected failure. Compounding this problem is the lack of information available for consumers to know the quality of the media they own. While the industry works on devising a standard for labeling the quality of future media, it is currently up to the consumer to pay close attention to their own DVD-R archives and work diligently to prevent data loss. This research shows that through accelerated aging and the use of logistic regression analysis on data collected through periodic monitoring of disc read-back errors it is possible to accurately predict unrecoverable failures in the test discs. This study analyzed various measurements of PIE errors, PIE8 Sum errors, POF errors and jitter data from three areas of the disc: the whole disc, the region of the disc where it first failed as well as the last half of the disc. From this data five unique predictive equations were produced, each with the ability to predict disc failure. In conclusion, the relative value of these equations for end-of-life predictions is discussed.
67

An empirical statistical model relating winds and ocean surface currents : implications for short-term current forecasts

Zelenke, Brian Christopher 02 December 2005 (has links)
Graduation date: 2006 / Presented on 2005-12-02 / An empirical statistical model is developed that relates the non-tidal motion of the ocean surface currents off the Oregon coast to forecasts of the coastal winds. The empirical statistical model is then used to produce predictions of the surface currents that are evaluated for their agreement with measured currents. Measurements of the ocean surface currents were made at 6 km resolution using Long-Range CODAR SeaSonde high-frequency (HF) surface current mappers and wind forecasts were provided at 12 km resolution by the North American Mesoscale (NAM) model. First, the response of the surface currents to wind-forcing measured by five coastal National Data Buoy Center (NDBC) stations was evaluated using empirical orthogonal function (EOF) analysis. A significant correlation of approximately 0.8 was found between the majority of the variability in the seasonal anomalies of the low-pass filtered surface currents and the seasonal anomalies of the low-pass filtered wind stress measurements. The U and the V components of the measured surface currents were both shown to be forced by the zonal and meridional components of the wind-stress at the NDBC stations. Next, the NAM wind forecasts were tested for agreement with the measurements of the wind at the NDBC stations. Significant correlations of around 0.8 for meridional wind stress and 0.6 for zonal wind stress were found between the seasonal anomalies of the low-pass filtered wind stress measured by the NDBC stations and the seasonal anomalies of the low-pass filtered wind stress forecast by the NAM model. Given the amount of the variance in the winds captured by the NAM model and the response of the ocean surface currents to both components of the wind, bilinear regressions were formed relating the seasonal anomalies of the low-pass filtered NAM forecasts to the seasonal anomalies of the low-pass filtered surface currents. The regressions turned NAM wind forecasts into predictions of the seasonal anomalies of the low-pass filtered surface currents. Calculations of the seasonal cycle in the surface currents, added to these predicted seasonal anomalies, produced a non-tidal estimation of the surface currents that allowed a residual difference to be calculated from recent surface current measurements. The sum of the seasonal anomalies, the seasonal cycle, and the residual formed a prediction of the non-tidal surface currents. The average error in this prediction of the surface currents off the Oregon coast remained less than 4 cm/s out through 48 hours into the future.
68

Foreseeing Political Change. Structure, System and Agency in the Making of the Lebanese Intifadha al-Iqtad

QUARENGHI, ALESSANDRO 04 July 2007 (has links)
La tesi cerca di rispondere alla domanda: 'La libanese intifadha al-Iqtad poteva essere prevista?'. la tesi prima definisce l'evento politico, e. Successivamente esamina le condizioni epistemologiche in base alle quali una predizione del futuro possa essere considerata scientifica. In terzo luogo, propone uno schema di previsione organizzato in funzione del coinvolgimento degli agenti nella creazione della storia umana. Infine, analizza la intifadha al-Iqtad in base allo schema analitico proposto. / The thesis aims to answer the question 'could the Lebanese Intifadha al-Iqtad have been predicted?' In order to do so, it first of all tries to define the political event, in terms of features, dynamic, and outcome. Secondly, it outlines the epistemological assumptions on which a scientific prediction of the future could be based. Thirdly, it puts forward a framework for foreseeing the future organised on different levels and divided into macro-categories. Finally, it analyses the Lebanese Intifadha al-Iqtad according to the proposed framework.
69

Gesture-level model : A modified Keystroke-level model for tasks on mobile touchscreen devices

Nyström, Anton January 2018 (has links)
The aim of this thesis was to develop a touchscreen-adapted version of the well established Keystroke-level model, which is a user performance model designed to be a quick and easy way to evaluate user interfaces prior to creating prototypes. A quantitative research method was chosen to measure general execution times for common touchscreen gestures on mobile devices. Over 1000 data points were collected from participants who partook in a observational experiment using a prototype specifically programmed for this study. The results of the thesis involves the analyzed measurements acquired from the experiment, as well as a four important aspect to consider when performing similar experiments, namely: (1) The individual speed of the participants; (2) The participants’ level of expertise; (3) The participants’ methods of performing the gestures; (4) Designing the experiment for medium difficulty. / Målet med denna uppsats var att utveckla en pekskärmsanpassad version av den välkända modellen Keystroke-level model, vilket är en modell som kan användas för att snabbt och enkelt utvärdera gränssnitt utan att behöva utveckla fungerande prototyper. En kvantitativ forskningsmetod användes för att mäta hur lång tid det tar för användare generellt att utföra de vanligaste fingergesterna på mobila pekskärmar. Över 1000 datapunkter samlades in från ett experiment där deltagarna fick använda en prototyp som automatiskt mätte den tid det tog för användarna att utföra de olika fingergesterna. Resultaten av studien består av de mätvärden som räknats ut samt fyra aspekter som är viktiga att ha i beaktning när liknande experiment ska utformas. Dessa är: (1) Varje deltagares individuella hastighet; (2) Deltagarnas pekskärmsvana; (3) Sättet de olika deltagarna utför fingergesterna; (4) Utforma experimentet för att representera en medium svårighetsgrad. / Le but de ce projet fut de créer une version du Keystroke-level model adaptée aux écrans tactiles. Ce modèle de performance utilisateur est une méthode d’évaluation simple et rapide d’interfaces utilisateur avant la création de prototypes. Une étude quantitative fut choisie pour mesurer le temps d’exécution général de mouvements spécifiques effectués sur des écrans tactiles de téléphones. Plus de 1000 points de données furent collectés auprès de participants ayant pris part à une étude observationnelle utilisant un prototype spécialement programmé pour l’occasion. Les résultats de ce projet incluent l’analyse des mesures acquises lors de cette étude ainsi que quatre aspects importants à considérer lors de la réalisation d’études similaires, à savoir: (1) La vitesse individuelle des participants; (2) Le niveau d’habitude d’utilisation d’écrans tactiles des participants; (3) Les méthodes utilisées par les participants lors de la réalisation des mouvements; (4) La conception d’étude pour des mouvements de difficulté dite moyenne.
70

The Relationship Of 10th-grade District Progress Monitoring Assessment Scores To Florida Comprehensive Assessment Test Scores In Reading And Mathematics For 2008-2009

Underwood, Marilyn 01 January 2010 (has links)
The focus of this research was to investigate the use of a district created formative benchmark assessment in reading to predict student achievement for 10th-grade students on the Florida Comprehensive Assessment Test (FCAT) in one county in north central Florida. The purpose of the study was to provide information to high school principals and teachers to better understand how students were performing and learning and to maximize use of the formative district benchmark assessment in order to modify instruction and positively impact student achievement. This study expanded a prior limited study which correlated district benchmark assessment scores to FCAT scores for students in grades three through five in five elementary schools in the targeted county. The high correlations suggested further study. This research focused on secondary reading, specifically in 10th grade where both state and targeted county FCAT scores were low in years preceding this research. Investigated were (a) the district formative assessment in reading as a predictor of FCAT Reading scores, (b) differences in strength of correlation and prediction among student subgroups and between high schools, and (c) any relationships between reading formative assessment scores and Mathematics FCAT scores. An additional focus of this study was to determine best leadership practices in schools where there were the highest correlations between the formative assessment and FCAT Reading scores. Research on best practices was reviewed, and principals were interviewed to determine trends and themes in practice. Tenth grade students in the seven Florida targeted district high schools were included in the study. The findings of the study supported the effective use of formative assessments both in instruction and as predictors of students' performance on the FCAT. The results of the study also showed a significant correlation between performance on the reading formative assessment and performance on FCAT Mathematics. The data indicated no significant differences in the strength of correlation between student subgroups or between the high schools included in the study. Additionally, the practices of effective principals in using formative assessment data to inform instruction, gathered through personal interviews, were documented and described.

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